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The bow and arrow is a projectile weapon system (a bow with arrows) that predates recorded history and is common to most cultures. Archery is the art, practice, or skill of applying it.
A bow is a flexible length of material which shoots aerodynamic projectiles called arrows. A string joins the two ends and when the string is drawn back, the ends of the stick are flexed. When the string is released, the potential energy of the flexed stick is transformed into the velocity of the arrow. Archery is the art or sport of shooting arrows from bows.
Today, bows and arrows are used primarily for hunting and for the sport of archery. Though they are still occasionally used as weapons of war, the development of gunpowder and muskets, and the growing size of armies, led to their replacement in warfare several centuries ago in much of the world.
Someone who makes bows is known as a bowyer, and one who makes arrows is a fletcher —or in the case of the manufacture of metal arrow heads, an arrowsmith.
The bow and arrow was not the first composite projectile weapon to be invented. It was preceded by the sling and by spear throwers such as the atlatl of the Americas and the woomera of Australia. A
A sensor (also called detector) is a converter that measures a physical quantity and converts it into a signal which can be read by an observer or by an (today mostly electronic) instrument. For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated glass tube. A thermocouple converts temperature to an output voltage which can be read by a voltmeter. For accuracy, most sensors are calibrated against known standards.
Sensors are used in everyday objects such as touch-sensitive elevator buttons (tactile sensor) and lamps which dim or brighten by touching the base. There are also innumerable applications for sensors of which most people are never aware. Applications include cars, machines, aerospace, medicine, manufacturing and robotics.
A sensor is a device which receives and responds to a signal when touched. A sensor's sensitivity indicates how much the sensor's output changes when the measured quantity changes. For instance, if the mercury in a thermometer moves 1 cm when the temperature changes by 1 °C, the sensitivity is 1 cm/°C (it is basically the slope Dy/Dx assuming a linear
A ballistic knife is a specialized combat knife with a detachable, self-propelled blade that can be ejected to a distance of several meters by pressing a trigger or operating a lever or switch on the handle. Originally developed as a weapon for Soviet and Eastern Bloc military special forces, the ballistic knife was not adopted by the military forces of other nations. Spring-powered ballistic knives briefly gained notoriety in the United States in the mid-1980s after commercial examples were marketed and sold in the United States and other Western countries. Since then, the marketing and/or sale of ballistic knives to civilians has been restricted or prohibited by law in several countries.
Ballistic or 'firing knives' are believed to have first appeared as part of the equipment issued to Soviet and Eastern Bloc special forces formations, such as the Soviet Voyska spetsialnogo naznacheniya, or Spetsnaz. By 1985, spring-powered ballistic knives were being advertised for sale in the United States in the Shotgun News, Soldier of Fortune, and other publications.
Ballistic knives were originally intended by Soviet military planners to be an improvement on teaching the skill of knife
A phenomenon (Greek: φαινόμενoν, from the Greek word ‘phainomenon’, from the verb ‘phanein’, to show, shine, appear, to be manifest (or manifest itself)), plural phenomena, is any observable occurrence. Phenomena are often, but not always, understood as 'appearances' or 'experiences'. These are themselves sometimes understood as involving qualia.
The term came into its modern philosophical usage through Immanuel Kant, who contrasted it with the noumenon (for which he used the term Ding an sich, or "thing-in-itself"). In contrast to a phenomenon, a noumenon is not directly accessible to observation. Kant was heavily influenced by Leibniz in this part of his philosophy, in which phenomenon and noumenon serve as interrelated technical terms.
In modern philosophical use, the term ‘phenomena’ has come to mean what is experienced as given. In Immanuel Kant’s Inaugural Dissertation, On the Form and Principles of the Sensible and Intelligible World (1770), Kant theorizes that the human mind is restricted to the logical world and thus can only interpret and understand occurrences according to their physical appearances. He wrote that humans could infer only as much as their senses allowed,
A loudspeaker (or "speaker") is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful. The most common form of loudspeaker uses a paper cone supporting a voice coil electromagnet acting on a permanent magnet, but many other types exist. Where accurate reproduction of sound is required, multiple loudspeakers may be used, each reproducing a part of the audible frequency range. Miniature loudspeakers are found in devices such as radio and TV receivers, and many forms of music players. Larger loudspeaker systems are used for music, sound reinforcement in theatres and concerts, and in public address systems.
The term "loudspeaker" may refer to individual transducers (known as "drivers") or to complete speaker systems consisting of an enclosure including one or more drivers. To adequately reproduce a wide range of frequencies, most loudspeaker systems employ more than one driver, particularly for higher sound pressure level or maximum accuracy. Individual drivers are used to
Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station. Nylon is one of the most commonly used polymers.
Nylon is a thermoplastic, silky material, first used commercially in a nylon-bristled toothbrush (1938), followed more famously by women's stockings ("nylons"; 1940). Nylon is made of repeating units linked by amide bonds and is frequently referred to as polyamide (PA). Nylon was the first commercially successful synthetic polymer. There are two common methods of making nylon for fiber applications. In one approach, molecules with an acid (-COOH) group on each end are reacted with molecules containing amine (-NH2) groups on each end. The resulting nylon is named on the basis of the number of carbon atoms separating the two acid groups and the two amines. These are formed into monomers of intermediate molecular weight, which are then reacted to form long polymer chains.
Nylon was intended to be a synthetic replacement for silk and substituted for it in many different products after silk became scarce during World
A periscope is an instrument for observation from a concealed position. In its simplest form it consists of an outer case with mirrors at each end set parallel to each other at a 45-degree angle. This form of periscope, with the addition of two simple lenses, served for observation purposes in the trenches during World War I. Military personnel also use periscopes in some gun turrets and in armoured vehicles.
More complex periscopes, using prisms instead of mirrors, and providing magnification, operate on submarines. The overall design of the classical submarine periscope is very simple: two telescopes pointed into each other. If the two telescopes have different individual magnification, the difference between them causes an overall magnification or reduction.
In 1854 Hippolyte Marié-Davy invented the first naval periscope, consisting of a vertical tube with two small mirrors fixed at each end at 45°. Simon Lake used periscopes in his submarines in 1902. Sir Howard Grubb perfected the device in World War I. Morgan Robertson (1861–1915) claimed to have tried to patent the periscope: he described a submarine using a periscope in his fictional works.
Periscopes, in some cases fixed
A desktop computer is a personal computer (PC) in a form intended for regular use at a single location, as opposed to a mobile laptop or portable computer. Early desktop computers are designed to lay flat on the desk, while modern towers stand upright. Most modern desktop computers have separate screens and keyboards.
Prior to the widespread use of microprocessors, a computer that could fit on a desk was considered remarkably small. Early personal computers, like the IBM PC, were "desktop" machines, with a horizontally oriented computer case, usually intended to have the display screen placed on top to save space on the desktop. In modern usage the word "desktop" usually refers to tower cases that are in fact more often located on the floor under the desk than on a desk.
Technically speaking desktop and tower computers are two different styles of computer case that use desk space in varying ways. Cases intended for home theater PC systems are usually considered to be desktop cases in both senses, regardless of orientation and placement.
Early computers took up the space of a room. Minicomputers generally fit into one or a few refrigerator sized racks. It was not until the 1970s
The ballista (Latin, from Greek βαλλίστρα - ballistra and that from - βάλλω ballō, "throw"), plural ballistas, was an ancient missile weapon which launched a large projectile at a distant target.
Developed from earlier Greek weapons, it relied upon different mechanics, using two levers with torsion springs instead of a prod, the springs consisting of several loops of twisted skeins. Early versions ejected heavy darts or spherical stone projectiles of various sizes for siege warfare. It developed into a smaller sniper weapon, the Scorpio, and possibly the polybolos.
The early ballista in Ancient Rome was developed from two weapons called oxybeles and gastraphetes. The gastraphetes ('belly-bow') was a hand held crossbow. It had a composite prod and was spanned by bracing the front end of the weapon against the ground while placing the end of a slider mechanism against the stomach. The operator would then walk forward to arm the weapon while a ratchet prevented it from shooting during loading. This produced a weapon which, it was claimed, could be operated by a person of average strength but which had a power that allowed it to be successfully used against armoured troops. The
The falconet or falcon was a light cannon developed in the late 15th century. During the Middle Ages guns were decorated with engravings of reptiles, birds or beasts depending on their size. For example, a culverin would often feature snakes, as the handles on the early cannons were often decorated to resemble serpents. The falconet fired small yet lethal shot of similar weight and size to a bird of prey, and so was decorated with a falcon. Similarly, the musket was associated with the sparrowhawk.
Its barrel was approximately 4 feet (1.2 m) long, had a caliber of 2 inches (5 cm) and weighed 80 kilograms (176 lb)~200 kilograms (441 lb). The falconet used 0.5 pounds (0.23 kg) of black powder to fire a 1 pound (0.5 kg) round shot approximately 5,000 feet (1,524 m). They could also be used to fire grapeshot.
The falconet resembled an oversized matchlock musket with two wheels attached to improve mobility. In 1620s Germany a breechloading version was invented, seeing action in the Thirty Years War. Many falconets were in use during the English Civil War as they were lighter and cheaper than the culverins, sakers and minions. During times of unrest they were used by the nobility to
Polybolos was an ancient Greek repeating ballista reputedly invented by Dionysius of Alexandria, a 3rd century BC Greek engineer at the Rhodes arsenal and used in antiquity. Philo of Byzantium encountered and described the polybolos, a catapult that like a modern machine gun could fire again and again without a need to reload. Philo left a detailed description of the gears that powered its chain drive, the oldest known application of such a mechanism, and that placed bolt after bolt into its firing slot.
The polybolos would have differed from an ordinary ballista in that it had a wooden magazine over the mensa (the cradle that holds the bolt prior to firing) capable of holding several dozen bolts. The mechanism is unique in that it is driven by a flat-link chain connected to a windlass; the flat-link chain is an invention more often attributed to Leonardo da Vinci.
When loading a new bolt, the windlass is rotated counter-clockwise with the trigger claw raised; this drives the mensa forward towards the bow string, where a metal lug pushes the trigger under the trigger claw, which is closed over the string.
Once the string is locked into the trigger mechanism, the windlass is then
An anchor is a device, normally made of metal, that is used to connect a vessel to the bed of a body of water to prevent the vessel from drifting due to wind or current. The word derives from Latin ancora, which itself comes from the Greek ἄγκυρα (ankura ).
Anchors can either be temporary or permanent. A permanent anchor is used in the creation of a mooring, and is rarely moved; a specialist service is normally needed to move or maintain it. Vessels carry one or more temporary anchors, which may be of different designs and weights.
A sea anchor is a drogue, not in contact with the seabed, used to control a drifting vessel.
Anchors achieve holding power either by "hooking" into the seabed, or via sheer mass, or a combination of the two. Permanent moorings use large masses (commonly a block or slab of concrete) resting on this seabed. Semi-permanent mooring anchors (such as mushroom anchors) and large ship's anchors derive a significant portion of their holding power from their mass, while also hooking or embedding in the bottom. Modern anchors for smaller vessels have metal flukes which hook on to rocks on the bottom or bury themselves in soft bottoms.
The vessel is attached to the
An art car is a vehicle that has had its appearance modified as an act of personal artistic expression. Art cars are often driven and owned by their creators, who are sometimes referred to as "Cartists".
Most car artists are ordinary people with no artistic training. Artists are largely self-taught and self funded, though some mainstream trained artists have also worked in the art car medium. Most others agree that creating and driving an art car daily is its own reward. Artists like Roy Lichtenstein, Andy Warhol and others have designed BMW Art Cars and their work has been reflected in racing cars like the BMW V12 LMR.
There is some disagreement as to what precisely led to the growth of the art car world. It can be seen as a twining together of several influences - the hippie-themed VWs of the late 1960s, the lowrider, as well as a Merry Pranksters' creation, the decorated schoolbus known as Further.
During the late 1960s, singer Janis Joplin had a psychedelically-painted Porsche 356 and John Lennon, a paisley Rolls Royce. Partly in imitation, the late 1960s/early 1970s counterculture featured many painted VW Buses and customized vehicles (e.g. a customized 1977 Cadillac
The supercritical water reactor (SCWR) is a Generation IV reactor concept that uses supercritical water (referring to the critical point of water, not the critical mass of the nuclear fuel) as the working fluid. SCWRs resemble light water reactors (LWRs) but operating at higher pressure and temperature, with a direct once-through cycle like a boiling water reactor (BWR), and the water always in a single, fluid state like the pressurized water reactor (PWR). The BWR, PWR and the supercritical boiler are all proven technologies. The SCWR is a promising advanced nuclear system because of its high thermal efficiency (~45% vs. ~33% for current LWRs) and simpler design, and is being investigated by 32 organizations in 13 countries.
The SCWR uses supercritical water as a neutron moderator and coolant. Above the critical point, steam and liquid become the same density and are indistinguishable, eliminating the need for pressurizers and steam generators (PWR), or jet/recirculation pumps, steam separators and dryers (BWR). Also by avoiding boiling, SCWR does not generate chaotic voids (bubbles) with less density and moderating effect. In a LWR this can affect heat transfer and water flow,
A golf club is used to hit a golf ball in a game of golf. Each club is composed of a shaft with a grip and a clubhead. Woods are mainly used for long-distance fairway or tee shots; irons, the most versatile class, are used for a variety of shots; Hybrids that combine design elements of woods and irons are becoming increasingly popular; putters are used mainly on the green to roll the ball into the cup. A standard set consists of 14 golf clubs, and while there are traditional combinations sold at retail as matched sets, players are free to bring any combination of 14 or fewer legal clubs.
An important variation in different clubs is loft, or the angle between the club's face and the vertical plane. It is loft that is the primary determinant of the ascending trajectory of the golf ball, with the tangential angle of the clubhead's swing arc at impact being a secondary and relatively minor consideration (though these small changes in swing angle can nevertheless have a significant influence on launch angle when using low-lofted clubs). The impact of the club compresses the ball, while grooves on the clubface give the ball backspin (which would appear as a clockwise spin on the ball
Discounts and allowances are reductions to a basic price of goods or services.
They can occur anywhere in the distribution channel, modifying either the manufacturer's list price (determined by the manufacturer and often printed on the package), the retail price (set by the retailer and often attached to the product with a sticker), or the list price (which is quoted to a potential buyer, usually in written form).
There are many purposes for discounting, including; to increase short-term sales, to move out-of-date stock, to reward valuable customers, to encourage distribution channel members to perform a function, or to otherwise reward behaviors that benefit the discount issuer. Some discounts and allowances are forms of sales promotion.
The most common types of discounts and allowances are listed below.
Deduction in price given by the wholesaler/manufacturer to the retailer at the list price or catalogue price.
Reduction in price given by the creditor to the debitor is known as cash discount. This discount is intended to speed payment and thereby provide liquidity to the firm. They are sometimes used as a promotional device. we also explain that
A handheld video game console is a lightweight, portable electronic device with a built-in screen, game controls, speakers and replaceable and/or rechargeable batteries or battery pack. Handheld game consoles are smaller than home video game consoles and contain the console, screen, speakers, and controls in one unit, allowing people to carry them and play them at any time or place.
In 1976, Mattel introduced the first handheld electronic game with the release of Auto Race. Later, several companies—including Coleco and Milton Bradley—made their own single-game, lightweight table-top or handheld electronic game devices. The oldest true handheld game console with interchangeable cartridges is the Milton Bradley Microvision in 1979.
Nintendo is credited with popularizing the handheld console concept with the release of the Game Boy in 1989 and as of 2011 continues to dominate the handheld console market with their Nintendo DS and DSi systems. However, Nintendo's latest handheld, the Nintendo 3DS, has been their largest handheld or video game console investment success in 30 years.
The origins of handheld game consoles are found in handheld and tabletop electronic game devices of the
A room is any distinguishable space within a structure. Usually, a room is separated from other spaces or passageways by interior walls; moreover, it is separated from outdoor areas by an exterior wall, sometimes with a door. Historically the use of rooms dates at least to early Minoan cultures about 2200 BC, where excavations on Santorini, Greece at Akrotiri reveal clearly defined rooms within certain structures.
In early structures, diverse room types could be identified to include bedrooms, kitchens, bathing rooms, reception rooms, and other specialized uses. The aforementioned Akrotiri excavations reveal rooms sometimes built above other rooms connected by staircases, bathrooms with alabaster appliances such as washbasins, bathing tubs, and toilets, all connected to an elaborate twin plumbing systems of ceramic pipes for cold and hot water separately. Ancient Rome manifested very complex building forms with a variety of room types, including some of the earliest examples of rooms for indoor bathing. The Anasazi civilization also had an early complex development of room structures, probably the oldest in North America, while the Maya of Central America had very advanced room
A rifle is a firearm designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves ("rifling") cut into the barrel walls. The raised areas of the rifling are called "lands," which make contact with the projectile (for small arms usage, called a bullet), imparting spin around an axis corresponding to the orientation of the weapon. When the projectile leaves the barrel, this spin lends gyroscopic stability to the projectile and prevents tumbling, in the same way that a properly thrown American football or rugby ball behaves. This allows the use of aerodynamically-efficient pointed bullets (as opposed to the spherical balls used in muskets) and thus improves range and accuracy. The word "rifle" originally referred to the grooving, and a rifle was called a "rifled gun." Rifles are used in warfare, hunting and shooting sports.
Typically, a bullet is propelled by the contained deflagration of an explosive compound (originally black powder, later cordite, and now nitrocellulose), although other means such as compressed air are used in air rifles, which are popular for vermin control, hunting small game, formal target shooting and casual shooting
A throwing axe is an axe that is used primarily as a missile weapon. Usually, they are thrown in an overhand motion (much like throwing a baseball) in a manner that causes the axe to rotate as it travels through the air. Throwing axes have been used since prehistoric times and were developed into the Francisca by the Franks in the third century AD. A skilled axe thrower will rotate the axe exactly once throughout the flight so that the sharpened edge of the head will penetrate the target.
Unlike knives, most small axes can be thrown reasonably well, even if they weren't designed to be thrown. Furthermore, if an axe is thrown, it may rotate faster than a knife thrown in the same way, owing to the greater part of weight in the head of the weapon.
A cotyledon ( /kɒtɨˈliːdən/; "seed leaf" from Greek: κοτυληδών kotylēdōn, gen.: κοτυληδόνος kotylēdonos, from κοτύλη kotýlē "cup, bowl"), is a significant part of the embryo within the seed of a plant. Upon germination, the cotyledon may become the embryonic first leaves of a seedling. The number of cotyledons present is one characteristic used by botanists to classify the flowering plants (angiosperms). Species with one cotyledon are called monocotyledonous ("monocots"). Plants with two embryonic leaves are termed dicotyledonous ("dicots") and placed in the class Magnoliopsida.
In the case of dicot seedlings whose cotyledons are photosynthetic, the cotyledons are functionally similar to leaves. However, true leaves and cotyledons are developmentally distinct. Cotyledons are formed during embryogenesis, along with the root and shoot meristems, and are therefore present in the seed prior to germination. True leaves, however, are formed post-embryonically (i.e. after germination) from the shoot apical meristem, which is responsible for generating subsequent aerial portions of the plant.
The cotyledon of grasses and many other monocotyledons is a highly modified leaf composed of a
A personal digital assistant (PDA), also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. PDAs are largely considered obsolete with the widespread adoption of smartphones.
Nearly all current PDAs have the ability to connect to the Internet. A PDA has an electronic visual display, enabling it to include a web browser, all current models also have audio capabilities enabling use as a portable media player, and also enabling most of them to be used as mobile phones. Most PDAs can access the Internet, intranets or extranets via Wi-Fi or Wireless Wide Area Networks. Most PDAs employ touchscreen technology.
The first "PDA" was released in 1984 by Psion, the Organizer II. Followed by Psion's Series 3, in 1991, which began to resemble the more familiar PDA style. It also had a full keyboard.
The term PDA was first used on January 7, 1992 by Apple Computer CEO John Sculley at the Consumer Electronics Show in Las Vegas, Nevada, referring to the Apple Newton.
In 1996, Nokia introduced the first PDA with full mobile phone functionality, the 9000 Communicator, which became the world's best-selling PDA. The Communicator
In standard Western musical notation, the staff, or stave, is a set of five horizontal lines and four spaces that each represent a different musical pitch—or, in the case of a percussion staff, different percussion instruments. Appropriate music symbols, depending upon the intended effect, are placed on the staff according to their corresponding pitch or function. Musical notes are placed by pitch, percussion notes are placed by instrument, and rests and other symbols are placed by convention.
A single vertical line drawn to the left of multiple staffs creates a "system", indicating that the music on all the staffs is to be played simultaneously. A "bracket" is an additional straight line joining staffs, to show groupings of instruments that function as a unit, such as the string section of an orchestra. A "brace" is used to join multiple staffs that represent a single instrument, such as a piano, organ, harp, or marimba. Sometimes, a second bracket is used to show instruments grouped in pairs, such as the first and second oboes, or the first and second violins in an orchestra. In some cases, a brace is used for this purpose instead of a bracket.
The absolute pitch of each line for
A notebook (notepad, writing pad, drawing pad, legal pad) is a book or binder composed of pages, often ruled, made out of paper, used for purposes including recording notes or memoranda, writing, drawing, and scrapbooking.
Paper notebooks can be distinguished by:
According to legend, Thomas W. Holley of Holyoke, Massachusetts invented the legal pad around the year 1888 when he innovated the idea to collect all the sortings, various sort of substandard paper scraps from various factories, and stitch them together in order to sell them as pads at an affordable and fair price. In about 1900, the latter then evolved into the modern legal pad when a local judge requested for a margin to be drawn on the left side of the paper. This was the first legal pad.
The only technical requirement for this type of stationery to be considered a true "legal pad" is that it must have margins of 1.25 inches (3.17 centimeters) from the left edge of legal pad. Here, the margin, also known as down lines, is room used to write notes or comments. Legal pads usually have a gum binding at the top as opposed to a spiral or stitched binding.
Principal types of binding are padding, perfect, spiral, comb, sewn,
An Ambassador is an official envoy; especially, a highest ranking diplomat who represents a State and is usually accredited to another sovereign State (country), or to an international organization as the resident representative of his or her own government or sovereign or appointed for a special and often temporary diplomatic assignment.
In its most common use, the term usually applies to the ranking government representative stationed in a foreign capital. The host country typically allows the ambassador control of specific territory called an embassy, whose territory, staff, and even vehicles are generally afforded diplomatic immunity in the host country.
The equivalent to an Ambassador exchanged among members of the Commonwealth of Nations are known as High Commissioners. The "Ambassadors" of the Holy See are known as Papal or Apostolic Nuncios.
As formally defined and recognized at the Congress of Vienna (1815), ambassadors were originally regarded as personal representatives of their country's chief executive rather than of the whole country, and their rank entitled them to meet personally with the head of state of the host country. Originally, only the principal monarchies
Humanitarian aid is material or logistical assistance provided for humanitarian purposes, typically in response to humanitarian crises including natural disaster and man-made disaster. The primary objective of humanitarian aid is to save lives, alleviate suffering, and maintain human dignity. It may therefore be distinguished from development aid, which seeks to address the underlying socioeconomic factors which may have led to a crisis or emergency.
According to The Overseas Development Institute, a London-based research establishment, whose findings were released in April 2009 in the paper 'Providing aid in insecure environments:2009 Update', the most lethal year in the history of humanitarianism was 2008, in which 122 aid workers were murdered and 260 assaulted. Those countries deemed least safe were Somalia and Afghanistan.
Aid is funded by donations from individuals, corporations, governments and other organizations. The funding and delivery of humanitarian aid is increasingly international, making it much faster, more responsive, and more effective in coping with to major emergencies affecting large numbers of people (e.g. see Central Emergency Response Fund). The United
Gunpowder, also known since the late 19th century as black powder, was the first chemical explosive and the only one known until the mid-1800s. It is a mixture of sulfur, charcoal, and potassium nitrate (saltpetre)—with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer. Because of its burning properties and the amount of heat and gas volume that it generates, gunpowder has been widely used as a propellant in firearms and as a pyrotechnic composition in fireworks.
Gunpowder was, according to prevailing academic consensus, discovered in the 9th century in China, attributed to Chinese alchemists searching for an elixir of immortality. This discovery led to the invention of fireworks and the earliest gunpowder weapons in China. In the centuries following the Chinese discovery, gunpowder weapons began appearing in the Arab world, Europe, and India. The consensus is that this was spread from China, through the Middle East, and then into Europe.
Gunpowder is classified as a low explosive because of its relatively slow decomposition rate and consequently low brisance. Low explosives deflagrate at subsonic speeds, whereas high explosives detonate, producing a
A personal computer (PC) is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator. This contrasted with the batch processing or time-sharing models which allowed larger, more expensive minicomputer and mainframe systems to be used by many people, usually at the same time. Large data processing systems require a full-time staff to operate efficiently.
Software applications for personal computers include, but are not limited to, word processing, spreadsheets, databases, Web browsers and e-mail clients, digital media playback, games, and myriad personal productivity and special-purpose software applications. Modern personal computers often have connections to the Internet, allowing access to the World Wide Web and a wide range of other resources. Personal computers may be connected to a local area network (LAN), either by a cable or a wireless connection. A personal computer may be a desktop computer or a laptop, tablet, or a handheld PC.
Early PC owners usually had to write their own programs to do anything useful with the
Pressurized water reactors (PWRs) constitute the large majority of all Western nuclear power plants and are one of three types of light water reactor (LWR), the other types being boiling water reactors (BWRs) and supercritical water reactors (SCWRs). In a PWR, the primary coolant (water) is pumped under high pressure to the reactor core where it is heated by the energy generated by the fission of atoms. The heated water then flows to a steam generator where it transfers its thermal energy to a secondary system where steam is generated and flows to turbines which, in turn, spin an electric generator. In contrast to a boiling water reactor, pressure in the primary coolant loop prevents the water from boiling within the reactor. All LWRs use ordinary light water as both coolant and neutron moderator.
PWRs were originally designed to serve as nuclear propulsion for nuclear submarines and were used in the original design of the second commercial power plant at Shippingport Atomic Power Station.
PWRs currently operating in the United States are considered Generation II reactors. Russia's VVER reactors are similar to U.S. PWRs. France operates many PWRs to generate the bulk of its
A prime minister is the most senior minister of cabinet in the executive branch of government in a parliamentary system. In many systems, the prime minister selects and may dismiss other members of the cabinet, and allocates posts to members within the government. In most systems, the prime minister is the presiding member and chairman of the cabinet. In a minority of systems, notably in semi-presidential systems of government, a prime minister is the official who is appointed to manage the civil service and execute the directives of the head of state.
In parliamentary systems fashioned after the Westminster system, the prime minister is the presiding and actual head of the government and head of the executive branch. In such systems, the head of state or the head of state's official representative (i.e. the monarch, president, or governor-general) usually holds a largely ceremonial position, although often with reserve powers.
The prime minister is often, but not always, a member of parliament and is expected with other ministers to ensure the passage of bills through the legislature. In some monarchies the monarch may also exercise executive powers (known as the royal
SWOT analysis (alternately SWOT Matrix) is a strategic planning method used to evaluate the Strengths, Weaknesses/Limitations, Opportunities, and Threats involved in a project or in a business venture. It involves specifying the objective of the business venture or project and identifying the internal and external factors that are favorable and unfavorable to achieve that objective. The technique is credited to Albert Humphrey, who led a convention at the Stanford Research Institute (now SRI International) in the 1960s and 1970s using data from Fortune 500 companies.
Setting the objective should be done after the SWOT analysis has been performed. This would allow achievable goals or objectives to be set for the organization.
Identification of SWOTs is essential because subsequent steps in the process of planning for achievement of the selected objective may be derived from the SWOTs.
First, the decision makers have to determine whether the objective is attainable, given the SWOTs. If the objective is NOT attainable a different objective must be selected and the process repeated.
Users of SWOT analysis need to ask and answer questions that generate meaningful information for each
Easter eggs are special eggs that are often given to celebrate Easter or springtime. Easter eggs are common during Eastertide as they symbolize the empty tomb of Jesus. Though an egg appears to be like the stone of a tomb, a bird hatches from it with life; similarly, the Easter egg, for Christians, is a reminder that Jesus rose from the grave, and that those who believe will also experience eternal life.
The custom of the Easter egg originated amongst the early Christians of Mesopotamia, who stained eggs red in memory of the blood of Christ, shed at his crucifixion. The Christian Church officially adopted the custom, regarding the eggs as a symbol of the resurrection; in A.D. 1610, Pope Paul V proclaimed the following prayer:
Bless, O Lord! we beseech thee, this thy creature of eggs, that it may become a wholesome sustenance to thy faithful servants, eating it in thankfulness to thee on account of the resurrection of the Lord.
Although the tradition is to use dyed or painted chicken eggs, a modern custom is to substitute chocolate eggs, or plastic eggs filled with confectionery such as jelly beans. These eggs can be hidden for children to find on Easter morning, which may be left
An optical instrument either processes light waves to enhance an image for viewing, or analyzes light waves (or photons) to determine one of a number of characteristic properties.
The first optical instruments were telescopes used for magnification of distant images, and microscopes used for magnifying very tiny images. Since the days of Galileo and Van Leeuwenhoek, these instruments have been greatly improved and extended into other portions of the electromagnetic spectrum. The binocular device is a generally compact instrument for both eyes designed for mobile use. A camera could be considered a type of optical instrument, with the pinhole camera and camera obscura being very simple examples of such devices.
Another class of optical instrument is used to analyze the properties of light or optical materials. They include:
DNA sequencers can be considered optical instruments as they analyse the color and intensity of the light emitted by a fluorochrome attached to a specific nucleotide of a DNA strand.
Surface plasmon resonance-based instruments use refractometry to measure and analyze biomolecular interactions.
Sport (or, in the United States, sports) is all forms of competitive physical activity which, through casual or organised participation, aim to use, maintain or improve physical ability and provide entertainment to participants. Hundreds of sports exist, from those requiring only two participants, through to those with hundreds of simultaneous participants, either in teams or competing as individuals.
Sport is generally recognised as activities which are based in physical athleticism or physical dexterity, with the largest major competitions such as the Olympic Games admitting only sports meeting this definition, and other organisations such as the Council of Europe using definitions precluding activities without a physical element from classification as sports. However, a number of competitive, but non-physical, activities claim recognition as mind sports. The International Olympic Committee (through ARISF) recognises both chess and bridge as bona fide sports, and SportAccord, the international sports federation association, recognises five non-physical sports, although limits the amount of mind games which can be admitted as sports.
Sports are usually governed by a set of rules
A weapon, arm, or armament is a tool or instrument used in order to inflict damage or harm to living beings—physical or mental—artificial structures, or systems. In human society, weapons are used to increase the efficacy and efficiency of activities such as hunting, crime, law enforcement, and warfare.
Weapons are employed individually or collectively. A weapon can be either expressly designed as such or be an item re-purposed through use (for example, hitting someone with a hammer). Their form can range from simple implements such as clubs to complicated modern implementations such as intercontinental ballistic missiles and biological weapons. Weapon development has progressed from early wood or stone clubs through revolutions in metalworking (swords, maces, etc.) and gunpowder (guns, cannon), electronics and nuclear technology.
In a broader context, weapons may be construed to include anything used to gain a strategic, material or mental advantage over an adversary on land, sea, air, or even outer space or virtual space.
Very simple weapon use has been observed among chimpanzees, leading to speculation that early hominids began their first use of weapons as early as five million
Cosmetics (colloquially known as makeup or make-up) are care substances used to enhance the appearance or odor of the human body. They are generally mixtures of chemical compounds, some being derived from natural sources, many being synthetic.
In the U.S., the Food and Drug Administration (FDA) which regulates cosmetics, defines cosmetics as "intended to be applied to the human body for cleansing, beautifying, promoting attractiveness, or altering the appearance without affecting the body's structure or functions." This broad definition includes, as well, any material intended for use as a component of a cosmetic product. The FDA specifically excludes soap from this category.
The word cosmetics derives from the Greek κοσμητική τέχνη (kosmetikē tekhnē), meaning "technique of dress and ornament", from κοσμητικός (kosmētikos), "skilled in ordering or arranging" and that from κόσμος (kosmos), meaning amongst others "order" and "ornament".
Archaeological evidence of cosmetics dates at least from ancient Egypt and Greece. According to one source, early major developments include:
The Ancient Greeks also used cosmetics. Cosmetics are mentioned in the Old Testament—2 Kings 9:30 where
A playing field is a field used for playing sports or games. They are generally outdoors, but many large structures exist to enclose playing fields from bad weather or to provide seating stands for watching the sports. Generally, playing fields are wide expanses of grass, dirt or sand without many obstructions. More recently, some types of field have begun using a synthetic grass-like material called AstroTurf, some fields are also covered with snow, but its use is often controversial. Today a lot of fields have Next Turf, ProGreen or Field Turf. These Turfs are filled with rubber and/or sand.
There are a variety of different commonly used fields, including:
In other sports, the field of play is called a "court":
A spear is a pole weapon consisting of a shaft, usually of wood, with a pointed head.
The head may be simply the sharpened end of the shaft itself, as is the case with bamboo spears, or it may be made of a more durable material fastened to the shaft, such as flint, obsidian, iron, steel or bronze.
The most common design for hunting or combat spears since ancient times has incorporated a metal spearhead shaped like a triangle, lozenge or leaf. The heads of fishing spears usually feature barbs or serrated edges.
Spears can be divided into two broad categories: those designed for thrusting in melee combat and those designed for throwing (usually referred to as javelins).
Spear manufacture and use is not confined to human beings. It is also practised by the western chimpanzee. Chimpanzees near Kédougou, Senegal have been observed to create spears by breaking straight limbs off trees, stripping them of their bark and side branches, and sharpening one end with their teeth. They then used the weapons to hunt galagos sleeping in hollows. Orangutans also have used spears to fish, presumably after observing humans fishing in a similar manner.
Archeological evidence found in Germany documents
A push-button (also spelled pushbutton) (press-button in the UK) or simply button is a simple switch mechanism for controlling some aspect of a machine or a process. Buttons are typically made out of hard material, usually plastic or metal. The surface is usually flat or shaped to accommodate the human finger or hand, so as to be easily depressed or pushed. Buttons are most often biased switches, though even many un-biased buttons (due to their physical nature) require a spring to return to their un-pushed state. Different people use different terms for the "pushing" of the button, such as press, depress, mash, and punch.
The "push-button" has been utilized in calculators, push-button telephones, kitchen appliances, and various other mechanical and electronic devices, home and commercial.
In industrial and commercial applications, push buttons can be linked together by a mechanical linkage so that the act of pushing one button causes the other button to be released. In this way, a stop button can "force" a start button to be released. This method of linkage is used in simple manual operations in which the machine or process have no electrical circuits for control.
In rail terminology, a spike is a large nail with an offset head that is used to secure rails or tie plates (or baseplates) to ties in the track. Spikes are driven into wooden ties either by hammering them with a spike hammer by hand, or in an automated fashion with a spiker.
Many railways use large wood screws, also called lag screws, to fasten the tie plates (or baseplates) to the railroad ties. Machine screws (or bolts) are also used to hold fishplates on jointed rail.
The presence of the letters HC (high carbon) on a spike's head indicates that the spike contains about 0.40% carbon.
The American Railway Engineering and Maintenance of Way Association sets the technical standards for the proper manufacture and use of this part by U.S. railroads.
The demi-cannon was a medium sized cannon, similar to but slightly larger than a culverin and smaller than a regular 42lb (19kg) cannon, developed in the early 17th century. A full cannon fired a 42-pound shot but these were discontinued in the 18th century as they were seen as too unwieldy. The lower tier of 17th Century English warships were usually equipped with demi-cannons. Ships featuring demi-cannons included HMS Sovereign of the Seas, HMS Resolutionand HMS James, which fought in the Anglo-Dutch naval wars.
The barrels of demi-cannon were typically 11ft (3.4m) long, had a calibre of 6 inches (15.4cm) and could weigh up to 5600lb (2540kg). It required 18lb (8kg) of black powder to fire a 32lb (14.5kg) round shot. The demi-cannon had an effective range of 1600ft (490m).
These 32-pounders were used during the 18th century on first-rate three-decker ships of the line which carried up to 100 guns. Though powerful, the naval demi-cannons were inaccurate except at close range so opposing warships would try to get as close as possible before firing their broadside in order to cause as much damage as possible; sometimes a single broadside was enough to cripple the enemy vessel.
A cheeseburger is a hamburger with cheese. Traditionally, the slice of cheese is placed on top of the meat patty, but the burger can include many variations in structure, ingredients and composition. The term itself is a portmanteau of the words "cheese" and "hamburger". The cheese is usually sliced, and then added to the cooking hamburger patty shortly before the patty is completely cooked which allows the cheese to melt. Cheeseburgers are often served with lettuce, tomato, onion, pickles, mustard, mayonnaise, or ketchup.
In fast food restaurants, the cheese used is typically processed cheese, but there are variations, such as cheddar, Swiss cheese, mozzarella, blue cheese and pepper jack. When cheese is added to a burger the nutritional value of the burger can be changed substantially. For example, a slice of Cheddar cheese can add 95 calories and 4.5 grams of saturated fat to a burger. Other types and amounts of cheese would have varying effects, depending on their nutritional content.
Adding cheese to hamburgers became popular in the late-1920s to mid-1930s, and there are several competing claims as to who created the first cheeseburger. Lionel Sternberger is reputed to have
A firearm is a weapon that launches one or more projectile(s) at high velocity through confined burning of a propellant. This subsonic burning process is technically known as deflagration, as opposed to supersonic combustion known as a detonation. In older firearms, the propellant was typically black powder, but modern firearms use smokeless powder or other propellants. Most modern firearms (with the notable exception of smoothbore firearms) have rifled barrels to impart spin to the projectile for improved flight stability.
Beginning around 700 A.D., scientists and inventors in Ancient China developed different grades of gunpowder and different types of firearms, including single-shot smooth-bore fire lances, multi-barreled guns, multiple-launch artillery rockets and the first cannon in the world made from cast bronze. Several centuries later, in late Dark Age Europe, the term "firearm" was used in Old English to denote the arm in which the match was held that was used to light the touch hole on the hand cannon. The term was a variation on the contemporary terms of bow arm and drawing arm still used in archery. Due to the effects of firing the ordnance (barrel) at the time, the
A loudspeaker driver that produces the frequency range from approximately 300–5000 Hz is known as a midrange (rarely, but sometimes, called a "squawker", in an attempt to match the phraseology of the words "woofer" and "tweeter").
Midrange drivers are usually cone types or, less commonly, dome types, or compression horn drivers. The radiating diaphragm of a cone midrange unit is a truncated cone, with a voice coil attached at the neck, along with the spider portion of the suspension, and with the cone surround at the wide end. Cone midranges typically resemble small woofers. The most common material used for midrange cones is paper, occasionally impregnated and/or surface-treated with polymers or resins in order to improve vibrational damping. Other midrange cone materials include plastics such as polypropylene, Cobex, Bextrene, woven Kevlar, fiberglass, carbon fiber, or light metal alloys based on aluminium, magnesium, titanium, or other alloys. The radiating surface of a dome midrange is typically a 90-degree section of a sphere, made from cloth, metal, or plastic film, with its suspension and voice coil co-located at the outer edge of the dome. Most professional concert midrange
A hamburger (also called a hamburger sandwich, burger or hamburg) is a sandwich consisting of a cooked patty of ground meat usually placed inside a sliced bread roll. Hamburgers are often served with lettuce, bacon, tomato, onion, pickles, cheese and condiments such as mustard, mayonnaise, ketchup and relish.
The term "burger", can also be applied to the meat patty on its own, especially in the UK where the term "patty" is rarely used. The term may be prefixed with the type of meat as in "beef burger".
The term hamburger originally derives from Hamburg, Germany's second largest city, from which many people emigrated to the United States. In High German, Burg means fortified settlement or fortified refuge; and is a widespread component of place names. Hamburger can be a descriptive noun in German, referring to someone from Hamburg (compare London → Londoner) or an adjective describing something from Hamburg. Similarly, frankfurter and wiener, names for other meat-based foods, are also used in Germany and Austria as descriptive nouns for people and as adjectives for things from the cities of Frankfurt and Wien (Vienna), respectively. The term "burger" is associated with many
A magazine is an ammunition storage and feeding device within or attached to a repeating firearm. Magazines may be integral to the firearm (fixed) or removable (detachable). The magazine functions by moving the cartridges stored in the magazine into a position where they may be loaded into the chamber by the action of the firearm. The detachable magazine is often controversially referred to as a clip.
Magazines come in many shapes and sizes, from bolt action express rifles that hold only a few rounds to machine guns that hold hundreds of rounds. Since the magazine is an essential part of most repeating firearms, they are sometimes subject to regulation by gun control laws seeking to limit the number of cartridges they hold.
The earliest firearms were loaded with loose powder and a lead ball, and to fire more than a single shot without reloading required multiple barrels, such as pepper-box guns and double-barreled shotguns, or multiple chambers, such as in revolvers. Both of these add bulk and weight over a single barrel and a single chamber, however, and many attempts were made to get multiple shots from a single loading of a single barrel through the use of superposed loads.
A microcomputer is a computer with a microprocessor as its central processing unit (CPU). It includes a microprocessor, memory, and input/output (I/O) facilities. Such computers are physically small compared to mainframes and minicomputers, although present-day mainframes such as the IBM System z machines use one or more custom microprocessors as their CPUs. Many microcomputers (when equipped with a keyboard and screen for input and output) are also personal computers (in the generic sense).
The abbreviation "micro" was common during the 1970s and 1980s, but has now fallen out of common usage.
The term "Microcomputer" came into popular use after the introduction of the minicomputer, although Isaac Asimov used the term microcomputer in his short story "The Dying Night" as early as 1956 (published in The Magazine of Fantasy and Science Fiction in July that year). Most notably, the microcomputer replaced the many separate components that made up the minicomputer's CPU with one integrated microprocessor chip. The earliest models such as the Altair 8800 were often sold as kits to be assembled by the user, and came with as little as 256 bytes of RAM, and no input/output devices other
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Murder is the unlawful killing, with malice aforethought, of another human, and generally this state of mind distinguishes murder from other forms of unlawful homicide (such as manslaughter). As the loss of a human being inflicts enormous grief upon the individuals close to the victim, as well as the fact that the commission of a murder is highly detrimental to the good order within society, most societies both present and in antiquity have considered it a most serious crime worthy of the harshest of punishment. In most countries, a person convicted of murder is typically given a long prison sentence, possibly a life sentence where permitted, and in some countries, the death penalty may be imposed for such an act — though this practice is becoming less common. In most countries, there is no statute of limitations for murder (no time limit for prosecuting someone for murder). A person who commits murder is called a murderer.
William Blackstone (citing Edward Coke), in his Commentaries on the Laws of England set out the common law definition of murder, which by this definition occurs
The elements of common law murder are:
The Unlawful—This distinguishes murder from killings that are
Dreams are successions of images, ideas, emotions, and sensations that occur involuntarily in the mind during certain stages of sleep. The content and purpose of dreams are not definitively understood, though they have been a topic of scientific speculation, as well as a subject of philosophical and religious interest, throughout recorded history. The scientific study of dreams is called oneirology. Scientists believe that, in addition to humans, certain birds and the majority of mammals also dream.
Dreams mainly occur in the rapid-eye movement (REM) stage of sleep—when brain activity is high and resembles that of being awake. REM sleep is revealed by continuous movements of the eyes during sleep. At times, dreams may occur during other stages of sleep. However, these dreams tend to be much less vivid or memorable.
Dreams can last for a few seconds, or as long as twenty minutes. People are more likely to remember the dream if they are awakened during the REM phase. The average person has about 3 to 5 dreams per night, but some may have up to 7 dreams in one night. The dreams tend to last longer as the night progresses. During a full 8-hour night sleep, two hours of it is spent
A drive shaft, driveshaft, driving shaft, propeller shaft (prop shaft), or Cardan shaft is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement between them.
Drive shafts are carriers of torque: they are subject to torsion and shear stress, equivalent to the difference between the input torque and the load. They must therefore be strong enough to bear the stress, whilst avoiding too much additional weight as that would in turn increase their inertia.
To allow for variations in the alignment and distance between the driving and driven components, drive shafts frequently incorporate one or more universal joints, jaw couplings, or rag joints, and sometimes a splined joint or prismatic joint.
The term drive shaft first appeared during the mid 19th century. In Storer's 1861 patent reissue for a planing and matching machine, the term is used to refer to the belt-driven shaft by which the machine is driven. The term is not used in his original patent. Another early use of the term occurs in the 1861 patent reissue for the
The Apollo Lunar Module (LM), also known as the Lunar Excursion Module (LEM), was the lander portion of the Apollo spacecraft built for the US Apollo program by Grumman to carry a crew of two from lunar orbit to the surface and back. Six such craft successfully landed on the Moon between 1969–1972.
The LM, consisting of an ascent stage and descent stage, was ferried to lunar orbit by its companion Command/Service Module (CSM), a separate spacecraft of approximately twice its mass, which also took the astronauts home to Earth. After completing its mission, the LM was discarded. In one sense it was the world's first true spacecraft in that it was capable of operation only in outer space, structurally and aerodynamically incapable of flight through the Earth's atmosphere.
Its development was also plagued with several hurdles which delayed its first unmanned flight by about ten months, and its first manned flight by about three months. Despite this, the LM eventually became the most reliable component of the Apollo/Saturn system, the only one never to suffer any failure that significantly impacted a mission, and in at least one instance (Apollo 13's LM-7 Aquarius) greatly exceeded its
A borescope (occasionally called a boroscope) is an optical device consisting of a rigid or flexible tube with an eyepiece on one end, an objective lens on the other linked together by a relay optical system in between. The optical system is usually surrounded by optical fibers used for illumination of the remote object. An internal image of the illuminated object is formed by the objective lens and magnified by the eyepiece which presents it to the viewer's eye.
Rigid or flexible borescopes may be fitted with an imaging or video device.
Borescopes are used for inspection work where the area to be inspected is inaccessible by other means. Similar devices for use inside the human body are referred to as endoscopes. Borescopes are mostly used in non destructive testing techniques for recognizing defects or imperfections. Borescopes are used to perform a type of visual inspection.
Borescopes are commonly used in the visual inspection of aircraft engines, aeroderivative industrial gas turbines, steam turbines, diesel engines, and automotive and truck engines. Gas and steam turbines require particular attention because of safety and maintenance requirements. Borescope inspection of
Microfiber or microfibre refers to synthetic fibers that measure less than one denier. The most common types of microfibers are made from polyesters, polyamides (e.g., nylon, kevlar, nomex, trogamide), and or a conjugation of polyester and polyamide and of polypropylene prolen.
Microfiber is used to make non-woven, woven and knitted textiles. The shape, size and combinations of synthetic fibers are selected for specific characteristics, including: softness, durability, absorption, wicking abilities, water repellency, electrodynamics, and filtering capabilities.
Microfiber is commonly used for apparel, upholstery, industrial filters and cleaning products.
Microfiber is a fiber with less than 1 Decitex per filament. Decitex is a measure of linear density and is commonly used to describe the size of a fiber or filament. Ten thousand meters of a 1-decitex fiber weighs one gram. Some commercial producers may use a value of less than 1.3 Decitex to define microfibers. Fibers are combined to create yarns which are knitted or woven in a variety of constructions. While many microfibers are made of polyester, they can also be composed of polyamide or other polymers polypropylene.
In clothing, a collar is the part of a shirt, dress, coat or blouse that fastens around or frames the neck. Among clothing construction professionals, a collar is differentiated from other necklines such as revers and lapels, by being made from a separate piece of fabric, rather than a folded or cut part of the same piece of fabric used for the main body of the garment.
A collar may be permanently attached to the main body of the garment (e.g. by stitching) or detachable.
The Oxford English Dictionary traces collar in its modern meaning to c. 1300. Today's shirt collars descend from the ruffle created by the drawstring at the neck of the medieval chemise, through the Elizabethan ruff and its successors, the whisk collar and falling band. Separate collars exist alongside attached collars since the mid-16th century, usually to allow starching and other fine finishing.
During the Edwardian period and sporadically thereafter, ornamental collars were worn as a form of jewelry.
Collars can be categorized as:
Collars may also be stiffened, traditionally with starch; modern wash-and-wear shirt collars may be stiffened with interfacing or may include metal or plastic collar stays. Shirt
An optical illusion (also called a visual illusion) is characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a perception that does not tally with a physical measurement of the stimulus source. There are three main types: literal optical illusions that create images that are different from the objects that make them, physiological ones that are the effects on the eyes and brain of excessive stimulation of a specific type (brightness, colour, size, position, tilt, movement), and cognitive illusions, the result of unconscious inferences.
Physiological illusions, such as the afterimages following bright lights, or adapting stimuli of excessively longer alternating patterns (contingent perceptual aftereffect), are presumed to be the effects on the eyes or brain of excessive stimulation or interaction with contextual or competing stimuli of a specific type—brightness, colour, position, tile, size, movement, etc. The theory is that a stimulus follows its individual dedicated neural path in the early stages of visual processing, and that intense or repetitive activity in that or interaction with
A diacritical mark ( /daɪ.əˈkrɪtɨk/; also diacritical point, diacritical sign from ancient Greek διά (dia, through) and κρίνω (krinein, to separate) is a glyph added to a letter, or basic glyph. The term derives from the Greek διακριτικός (diakritikós, "distinguishing"). Diacritic is primarily an adjective, though sometimes used as a noun, whereas diacritical is always and only an adjective. Some diacritical marks, such as the acute ( ´ ) and grave ( ` ) are often called accents. Diacritical marks may appear above or below a letter, or in some other position such as within the letter or between two letters.
The main use of diacritical marks in the Latin alphabet is to change the sound value of the letter to which they are added. Examples from English are the diaeresis in naïve and Noël, which show that the vowel with the diaeresis mark is pronounced separately from the preceding vowel; the acute and grave accents, which can indicate that a final vowel is to be pronounced, as in saké and poetic breathèd, and the cedilla under the "c" in the borrowed French word façade, which shows it is pronounced /s/ rather than /k/. In other Latin alphabets, they may distinguish between homonyms,
A mineral is a naturally occurring substance that is solid and stable at room temperature, representable by a chemical formula, usually abiogenic, and has an ordered atomic structure. It is different from a rock, which can be an aggregate of minerals or non-minerals, and does not have a specific chemical composition. The exact definition of a mineral is under debate, especially with respect to the requirement a valid species be abiogenic, and to a lesser extent with regards to it having an ordered atomic structure. The study of minerals is called mineralogy.
There are over 4,900 known mineral species; over 4,660 of these have been approved by the International Mineralogical Association (IMA). The silicate minerals compose over 90% of the Earth's crust. The diversity and abundance of mineral species is controlled by the Earth's chemistry. Silicon and oxygen constitute approximately 75% of the Earth's crust, which translates directly into the predominance of silicate minerals. Minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish various species, and these properties in turn are influenced by the
An autopilot is a mechanical, electrical, or hydraulic system used to guide a vehicle without assistance from a human being. An autopilot can refer specifically to aircraft, self-steering gear for boats, or auto guidance of space craft and missiles. The autopilot of an aircraft is sometimes referred to as "George", after one of the key contributors to its development.
In the early days of aviation, aircraft required the continuous attention of a pilot in order to fly safely. As aircraft range increased allowing flights of many hours, the constant attention led to serious fatigue. An autopilot is designed to perform some of the tasks of the pilot.
The first aircraft autopilot was developed by Sperry Corporation in 1912. The autopilot connected a gyroscopic Heading indicator and attitude indicator to hydraulically operated elevators and rudder (ailerons were not connected as wing dihedral was counted upon to produce the necessary roll stability.) It permitted the aircraft to fly straight and level on a compass course without a pilot's attention, greatly reducing the pilot's workload.
Lawrence Sperry (the son of famous inventor Elmer Sperry) demonstrated it two years later in 1914 at
A cartridge, also called a round, packages the bullet, propellant (usually either smokeless powder or gunpowder) and primer into a single unit within a containing metallic case that is precisely made to fit within the firing chamber of a firearm. The primer is a small charge of an impact-sensitive chemical mixture that can be located at the center of the case head (centerfire ammunition) or inside a rim (rimfire ammunition). Remington also makes electrically fired cartridges and many larger military cartridges are electrically fired. Military and commercial producers have made Caseless ammunition. A cartridge without a bullet is called a blank; one that is completely inert (contains no primer and no propellant) is called a dummy.
In popular use, the term "bullet" is often misused to refer to complete cartridges.
The cartridge case seals a firing chamber in all directions excepting the bore. A firing pin strikes the primer and ignites it; the primer compound deflagrates (that is, it rapidly burns), it does not detonate. A jet of burning gas from the primer ignites the propellant powder.
Gases from the burning powder pressurize and expand the case to seal it against the chamber wall.
A catapult is a device used to throw or hurl a projectile a great distance without the aid of explosive devices—particularly various types of ancient and medieval siege engines. Although the catapult has been used since ancient times, it has proven to be one of the most effective mechanisms during warfare. The word 'catapult' comes from the Latin 'catapulta', which in turn comes from the Greek καταπέλτης (katapeltēs), itself from (kata), "downwards" + πάλλω (pallō), "to toss, to hurl". Catapults were invented by the ancient Greeks.
The early history of the catapult and the crossbow in Greece are closely intertwined. Primitive catapults were essentially “the product of relatively straightforward attempts to increase the range and penetrating power of missiles by strengthening the bow which propelled them”. The historian Diodorus Siculus (fl. 1st century BC), described the invention of a mechanical arrow firing catapult (katapeltikon) by a Greek task force in 399 BC. The weapon was soon after employed against Motya (397 BC), a key Carthaginian stronghold in Sicily. Diodorus is assumed to have drawn his description from the highly rated history of Philistus, a contemporary of the
The Grand Staff using both bass clef on the bottom and treble clef on top allows for four octaves of notation, counting the two high leger lines for Soprano C and two leger lines below bass clef for Deep C. Note, however, that more than two leger lines may be used.
It is known as the grand staff because the two-clef notation allows the notation of nearly all musical notes without many ledger lines or octave shifts such as 8va. 8va basso (8vb), or 15ma. The grand staff uses a brace to show that the treble clef and bass clef are used together. It is for this reason that the staves can be said as being "braced together." Nearly all keyboard music is written on the grand staff, as is some choral music. When the grand staff is used in choral music, however, a bracket is normally used instead of a brace.
Middle C (on the grand staff) is named so because it appears exactly in the middle between the bass and treble clefs. Middle C is not exactly in the middle of any keyboard instrument, including the piano. Middle C is usually the splitting point between the two staves on the grand staff, and can be shared between the staves.
A handgun is a firearm designed to be handheld, in either one or both hands. This characteristic differentiates handguns as a general class of firearms from long guns such as rifles and shotguns (which are mounted against the shoulder).
Major handgun subtypes are the revolver and pistol; other subtypes include derringers, single-shot pistols, semi-automatic pistols, pepperboxes, and machine pistols.
The overlapping variations in meaning of the words "pistol" and "handgun" are discussed below.
Although handgun use often includes bracing with a second hand, the essential distinguishing characteristic of a handgun is its facility for one-handed operation.
The word "pistol" is often synonymous with the word "handgun". Some handgun experts make a technical distinction that views pistols as a subset of handguns. Sometimes in American usage, the term "pistol" refers to a handgun having one chamber integral with the barrel, making pistols distinct from the other main type of handgun, the revolver, which has a revolving cylinder containing multiple chambers. But UK/Commonwealth usage often does not make this distinction. For example, the official designation of the Webley Mk VI was "Pistol,
A mortar is an indirect fire weapon that fires explosive projectiles known as (mortar) bombs at low velocities, short ranges, and high-arcing ballistic trajectories. It is typically muzzle-loading and has a barrel length less than 15 times its caliber.
A mortar is relatively simple and easy to operate. A modern mortar consists of a tube into which assistant gunners drop a purpose-designed bomb. The tube is generally set at between 45 and 85 degrees angle to the ground, with the higher angle giving shorter firing distances. The bomb has no cartridge case; the propellant is attached to the bomb's fins. When it reaches the base of the tube it hits a firing pin, which detonates the propellant and fires the projectile. Some larger caliber mortars have a string-operated firing pin.
These attributes contrast with the mortar's larger siblings, howitzers and field guns, that fire shells at higher velocities, longer ranges, flatter arcs, and sometimes using direct fire. These weapons are also breech-loaded while mortars are muzzle-loaded.
From the 18th to the early 20th century very heavy, relatively immobile siege mortars were used, of up to one metre calibre, often made of cast iron and
Radio-controlled helicopters (also RC helicopters) are model aircraft which are distinct from RC airplanes because of the differences in construction, aerodynamics, and flight training. Several basic designs of RC helicopters exist, of which some (such as those with collective pitch, meaning blades which rotate on their longitudinal axis to vary or reverse lift) are more maneuverable than others. The more maneuverable designs are often harder to fly, but benefit from greater aerobatic capabilities.
Flight controls allow pilots to control the collective and throttle (usually linked together), the cyclic controls (pitch and roll), and the tail rotor (yaw). Controlling these in unison enables the helicopter to perform most of the same maneuvres as full-sized helicopters, such as hovering and backwards flight, and many that full-sized helicopters cannot, such as inverted flight (where collective pitch control provides negative blade pitch to hold heli up inverted, and pitch/yaw controls must be reversed by pilot).
The various helicopter controls are effected by means of small servo motors, commonly known as servos. A piezoelectric gyroscope is typically used on the tail rotor (yaw)
Smoked fish are fish that have been cured by smoking.
Foods have been smoked by humans throughout history. Originally this was done as a preservative. In more recent times fish is readily preserved by refrigeration and freezing and the smoking of fish is generally done for the unique taste and flavour imparted by the smoking process.
According to Jeffrey J. Rozum "The process of smoking fish occurs through the use of fire. Wood contains three major components that are broken down in the burning process to form smoke. The burning process is called pyrolysis, which is simply defined as the chemical decomposition by heat. The major wood components are cellulose, hemicellulose and lignin."
"The major steps in the preparation of smoked fish are salting (bath or injection of liquid brine or dry salt mixture), cold smoking, cooling, packaging (air/vacuum or modified), and storage. Smoking, one of the oldest preservation methods, combines the effects of salting, drying, heating and smoking. Typical smoking of fish is either cold (28–32°C) or hot (70–80°C). Cold smoking does not cook the flesh, coagulate the proteins, inactivate food spoilage enzymes, or eliminate the food pathogens, and
A tennis court is where the game of tennis is played. It is a firm rectangular surface with a low net stretched across the center. The same surface can be used to play both doubles and singles.
Tennis is played on a rectangular flat surface, usually of grass, clay, concrete (hard court) or a synthetic suspended court. The court is 23.78 meters (78 feet) long, 10.97 meters (36 feet) wide. Its width is 8.23 meters (27 feet) for singles matches and 10.97 meters (36 feet) for doubles matches. The service line is 6.40 meters (21 feet) from the net. Additional clear space around the court is needed in order for players to reach overrun balls for a total of 18.3 meters (60 feet) wide and 36.7 meters (120 feet) long. A net is stretched across the full width of the court, parallel with the baselines, dividing it into two equal ends. The net is 1.07 meters (3 feet 6 inches) high at the posts, and 0.914 meters (3 feet) high in the center.
A North/South orientation is generally desirable for outdoor courts to avoid background glare at dawn or dusk. Orientation also should take into consideration other structures and features on the site, neighbouring property, vehicle and pedestrian traffic
An idea is a concept or mental impression. Very often, ideas are construed as representational images; i.e. images of some object. In other contexts, ideas are taken to be concepts, although abstract concepts do not necessarily appear as images. Many philosophers consider ideas to be a fundamental ontological category of being. The capacity to create and understand the meaning of ideas is considered to be an essential and defining feature of human beings. In a popular sense, an idea arises in a reflex, spontaneous manner, even without thinking or serious reflection, for example, when we talk about the idea of a person or a place.
One view on the nature of ideas is that there exist some ideas (called innate ideas) which are so general and abstract, that they could not have arisen as a representation of any object of our perception, but rather were, in some sense, always in the mind before we could learn them. These are distinguished from adventitious ideas which are images or concepts which are accompanied by the judgment that they are caused by some object outside of the mind.
Another view holds that we only discover ideas in the same way that we discover the real world, from
Installation art describes an artistic genre of three-dimensional works that are often site-specific and designed to transform the perception of a space. Generally, the term is applied to interior spaces, whereas exterior interventions are often called Land art; however, the boundaries between these terms overlap.
Installation art can be either temporary or permanent. Installation artworks have been constructed in exhibition spaces such as museums and galleries, as well as public and private spaces. The genre incorporates a broad range of everyday and natural materials, which are often chosen for their "evocative" qualities, as well as new media such as video, sound, performance, immersive virtual reality and the internet. Many installations are site-specific in that they are designed to exist only in the space for which they were created. A number of institutions focusing on Installation art were created from the 1980s onwards, suggesting the need for Installation to be seen as a separate discipline. These included the Mattress Factory, Pittsburgh, the Museum of Installation in London, and the Fairy Doors of Ann Arbor, MI, among others.
Installation art came to prominence in the
PDCA (plan–do–check–act or plan–do–check–adjust) is an iterative four-step management method used in business for the control and continuous improvement of processes and products. It is also known as the Deming circle/cycle/wheel, Shewhart cycle, control circle/cycle, or plan–do–study–act (PDSA). Another version of this PDCA cycle is OPDCA. The added "O" stands for observation or as some versions say "Grasp the current condition." This emphasis on observation and current condition has currency with Lean/TPS literature.
The steps in each successive PDCA cycle are :
PDCA was made popular by Dr. W. Edwards Deming, who is considered by many to be the father of modern quality control; however he always referred to it as the "Shewhart cycle". Later in Deming's career, he modified PDCA to "Plan, Do, Study, Act" (PDSA) because he felt that "check" emphasized inspection over analysis.
The concept of PDCA is based on the scientific method, as developed from the work of Francis Bacon (Novum Organum, 1620). The scientific method can be written as "hypothesis"–"experiment"–"evaluation" or plan, do and check. Shewhart described manufacture under "control"—under statistical control—as a three
A spotting scope is a small portable telescope with added optics to present an erect image, optimized for the observation of terrestrial objects. They are used for birdwatching and other naturalist activities, for hunting, verifying a marksman's shots, surveillance, and for any other application that requires more magnification than a pair of binoculars, typically on the order of 20× to 60×.
The light-gathering power and resolution of a spotting scope is determined by the diameter of the objective lens, typically between 50 and 80 mm (2.0 and 3.1 in). The larger the objective, the more massive and expensive the telescope.
The optical assembly has a small refracting objective lens, an image erecting system that uses either image erecting relay lenses or prisms (porro prisms or roof prisms), and an eyepiece that is usually removable and interchangeable to give different magnifications. Other telescope designs are used such as Schmidt and Maksutov optical assemblies. They may have a ruggedised design, a mounting for attaching to a tripod, and an ergonomically designed and located knob for focus control.
Eyepieces are usually interchangeable to give different magnifications, or may
Duty-free shops (or stores) are retail outlets that are exempt from the payment of certain local or national taxes and duties, on the requirement that the goods sold will be sold to travelers who will take them out of the country. Which products can be sold duty-free vary by jurisdiction, as well as how they can be sold, and the process of calculating the duty or refund the duty component.
However, some countries impose duty on goods brought into the country, though they had been bought duty-free in another country, or when the value or quantity of such goods exceed an allowed limit. Duty-free shops are often found in the international zone of international airports and sea ports, but goods can be also bought duty-free on board airplanes and passenger ships. They are not as commonly available for road or train travelers, although several border crossings between the United States and Canada have duty-free shops for car travelers.
These outlets were abolished for intra-EU travellers in 1999, but are retained for travelers whose final destination is outside the EU. They also sell to intra-EU travelers but with appropriate taxes. Some special member state territories such as Åland,
The optical microscope, often referred to as the "light microscope", is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest design of microscope and were possibly designed in their present compound form in the 17th century. Basic optical microscopes can be very simple, although there are many complex designs which aim to improve resolution and sample contrast. Historically optical microscopes were easy to develop and are popular because they use visible light so that samples may be directly observed by eye.
The image from an optical microscope can be captured by normal light-sensitive cameras to generate a micrograph. Originally images were captured by photographic film but modern developments in CMOS and charge-coupled device (CCD) cameras allow the capture of digital images. Purely digital microscopes are now available which use a CCD camera to examine a sample, showing the resulting image directly on a computer screen without the need for eyepieces.
Alternatives to optical microscopy which do not use visible light include scanning electron microscopy and transmission electron
A projectile is any object projected into space (empty or not) by the exertion of a force. Although any object in motion through space (for example a thrown baseball) may be referred to as a projectile, the term more commonly refers to a weapon.
For details of the mathematics surrounding projectile trajectory, see equations of motion.
Arrows, darts, spears, and similar weapons are fired using pure mechanical force applied by another object; apart from throwing without tools, mechanisms include the catapult, slingshot, and bow.
Other weapons use the compression or expansion of gases as their motive force.
Blowguns and pneumatic rifles use compressed gases, while most other guns and firearms utilize expanding gases liberated by sudden chemical reactions. Light gas guns use a combination of these mechanisms.
Railguns utilize electromagnetic fields to provide a constant acceleration along the entire length of the device, greatly increasing the muzzle velocity.
Some projectiles provide propulsion during flight by means of a rocket engine or jet engine. In military terminology, a rocket is unguided, while a missile is guided. Note the two meanings of "rocket" (weapon and engine): an ICBM
The light water reactor (LWR) is a type of thermal reactor that uses normal water as its coolant and neutron moderator. Thermal reactors are the most common type of nuclear reactor, and light water reactors are the most common type of thermal reactor. There are three varieties of light water reactors: the pressurized water reactor (PWR), the boiling water reactor (BWR), and (most designs of) the supercritical water reactor (SCWR).
The family of nuclear reactors known as light water reactors (LWR), cooled and moderated using ordinary water, tend to be simpler and cheaper to build than other types of nuclear reactor; due to these factors, they make up the vast majority of civil nuclear reactors and naval propulsion reactors in service throughout the world as of 2009. LWRs can be subdivided into three categories - pressurized water reactors (PWRs), boiling water reactors (BWRs), and supercritical water reactors (SWRs). Various agencies of the United States Federal Government were responsible for the initial development of the PWR and BWR. An effort by the United States Navy, starting immediately after the end of World War II, and led by (then) Captain Hyman Rickover, developed the
Long-distance trails (or long-distance tracks, paths, footpaths or greenways) are the longer recreational trails mainly through rural areas, used for non-motorized recreational travelling (walking, backpacking, cycling or horse riding).
Any route named as a "trail" (or "way", in the UK) will probably be marked, or identified on a map, but it will usually only be described as "long-distance" if it takes the average user more than one day to travel from end to end. Typically, a "long-distance" trail, way or path will be at least 50 km (31 mi) long, but some in Britain are several hundred miles long, and many in the US are much longer.
In some countries, official "trails" will have the surface specially prepared to make the going easier.
In the UK long-distance paths are simply existing rights of way (over private land) "joined together" (perhaps with specially negotiated linking sections) to make a named route. Generally the surface is not especially prepared (which can come as a surprise to walkers from abroad, who find their distance-covering estimates need to be rethought to take rough ground into account) except in special places such as converted rail tracks, or some "busy"
A longsword (also spelled long sword, long-sword) is a type of European sword characterized as having a cruciform hilt with a grip for two handed use and a straight double-edged blade of around 100–122 cm (39–48 in) Current during the late medieval and Renaissance periods, approximately 1350 to 1550 (with early and late use reaching into the 13th and 17th centuries).
Historical (15th to 16th century) terms for this type of sword included Spanish espadón, montante or mandoble, Italian spadone or spada longa (lunga), Portuguese montante and French passot. The Gaelic claidheamh mòr means "great sword"; anglicized as claymore it came to refer to the Scottish type of longsword with V-shaped crossguard. Historical terminology overlaps with that applied to the Zweihänder sword in the 16th century: French espadon, Spanish espadón or Portuguese montante may also be used more narrowly to refer to these large swords. The French épée de passot may also refer to a medieval single-handed sword optimized for thrusting.
The French épée bâtarde as well as the English bastard sword originates in the 15th or 16th century, originally in the general sense of "irregular sword, sword of uncertain
A loudspeaker enclosure is a purpose-engineered cabinet in which speaker drivers and associated electronic hardware, such as crossover circuits and amplifiers, are mounted. Enclosures may range in design from simple, rectangular particle-board boxes to very complex cabinets that incorporate composite materials, internal baffles, ports and acoustic insulation.
The primary role of the enclosure is to prevent sound waves generated by the rearward-facing surface of the diaphragm of an open driver interacting with sound waves generated at the front of the driver. Because the forward- and rearward-generated sounds are out of phase with each other, any interaction between the two in the listening space creates a distortion of the original signal as it was intended to be reproduced. Additionally, because they would travel different paths through the listening space, the sound waves would arrive at the listener's position at slightly different times, introducing echo and reverberation effects not part of the original sound.
The enclosure also plays a role in managing vibration induced by the driver frame and moving airmass within the enclosure, as well as heat generated by driver voice
Pottery is the material from which the potteryware is made, of which major types include earthenware, stoneware and porcelain. The place where such wares are made is also called a pottery (plural "potteries"). Pottery also refers to the art or craft of the potter or the manufacture of pottery.
The definition of pottery used by ASTM is "all fired ceramic wares that contain clay when formed, except technical, structural, and refractory products." Some archaeologists use a different understanding by excluding ceramic objects such as figurines which are made by similar processes, materials and the same people but are not vessels.
Pottery is made by forming a clay body into objects of a required shape and heating them to high temperatures in a kiln which removes all water from the clay, which induces reactions that lead to permanent changes including increasing their strength and hardening and setting their shape. A clay body can be decorated before or after firing. Prior to some shaping processes, clay must be prepared. kneading helps to ensure an even moisture content throughout the body. Air trapped within the clay body needs to be removed. This is called de-airing and can be
The bow ( /ˈbaʊ/) is a nautical term for the forward part of the hull of a ship or boat, the point that is most forward when the vessel is underway. Both of the adjectives fore and forward mean towards the bow. The other end of the boat is called the stern.
The bow is designed to reduce the resistance of the hull cutting through water and should be tall enough to prevent water from easily washing over the top of it. On slower ships like tankers, a fuller bow shape is used to maximise the volume of the ship for a given length.
A "wet bow" results from seawater washing over the top of the hull. A raked stem can help to reduce the wetness of the bow. Aside from making the deck slippery, water can corrode the metal of the ship. If the temperature is low enough this water can also freeze on the deck, rails, turrets, and other exposed surfaces, increasing the topside weight.
The forward part of the bow, usually on the ship's centreline, is called the stem. Traditionally, the stem was an upright timber or metal bar into which side planks or plates were joined.
Several types of bows exist. These include :
A mind map is a diagram used to visually outline information. A mind map is often created around a single word or text, placed in the center, to which associated ideas, words and concepts are added. Major categories radiate from a central node, and lesser categories are sub-branches of larger branches. Categories can represent words, ideas, tasks, or other items related to a central key word or idea.
Mindmaps can be drawn by hand, either as "rough notes" during a lecture or meeting, for example, or as higher quality pictures when more time is available. An example of a rough mind map is illustrated.
Other terms for this diagramming style are: "spider diagrams," "spidergrams," "spidergraphs," "webs", "mind webs", or "webbing", and "idea sun bursting". (A "spider diagram" used in mathematics and logic is different.)
Diagrams that visually map information using branching and radial maps trace back centuries. These pictorial methods record knowledge and model systems, and a long history in learning, brainstorming, memory, visual thinking, and problem solving by educators, engineers, psychologists, and others. Some of the earliest examples of such graphical records were developed by
A refracting or refractor telescope is a type of optical telescope that uses a lens as its objective to form an image (also referred to a dioptric telescope). The refracting telescope design was originally used in spy glasses and astronomical telescopes but is also used for long focus camera lenses. Although large refracting telescopes were very popular in the second half of the 19th century, for most research purposes the refracting telescope has been superseded by the reflecting telescope.
Refractors were the earliest type of optical telescope. The first practical refracting telescopes appeared in the Netherlands about 1608, and were credited to three individuals, Hans Lippershey and Zacharias Janssen, spectacle-makers in Middelburg, and Jacob Metius of Alkmaar. Galileo Galilei, happening to be in Venice in about the month of May 1609, heard of the invention and constructed a version of his own. Galileo then communicated the details of his invention to the public, and presented the instrument itself to the Doge Leonardo Donato, sitting in full council.
All refracting telescopes use the same principles. The combination of an objective lens 1 and some type of eyepiece 2 is used to
A semi-automatic, or self-loading firearm is a weapon which performs all steps necessary to prepare the weapon to fire again after firing—assuming cartridges remain in the weapon's feed device or magazine. Typically, this includes extracting and ejecting the spent cartridge case from the weapon's firing chamber, re-cocking the firing mechanism, and loading a new cartridge into the firing chamber. Although automatic weapons and selective fire firearms do the same tasks, semi-automatic firearms do not automatically fire an additional round until the trigger is released and re-pressed by the person firing the weapon.
While all basic firearm actions require the action to be cycled manually before the first shot, semi-automatic as well as automatic and selective fire actions are differentiated from other forms such as single-action or double-action revolvers, pump-action, bolt-action, or lever-action firearms by eliminating the need to manually cycle the weapon after each shot. For example, to fire ten rounds from a semi-automatic firearm or a selective fire weapon set to fire semi-automatically, the action would initially be cycled to load the first round and the trigger would need to
Six Thinking Hats is the title and subject of a book by Edward De Bono, published in 1985.
De Bono considered human cognition and thought to be of several types, approaches, or orientations. He theorized that of these approaches, most people used only one or two of the approaches and that people developed thinking habits which in turn limited people to those approaches. De Bono believed that if the various approaches could be identified and a system of their use developed which could be taught, that people could be more productive in meetings and in collaborating within groups and teams by deliberately using the approaches.
As a result of his investigations, De Bono was able to describe a process of deliberately adopting a particular approach to a problem as an implementation of Parallel Thinking￢ﾄﾢ as well as an aid to lateral thinking. Six different approaches are described, and each is symbol by the act of putting on a coloured hat, either actually or imaginatively. This he suggests can be done either by individuals working alone or in groups.
De Bono's six hats are:
The main purposes of using Six Thinking Hats are:
De Bono believed that the key to a successful use of
An electron microscope uses a beam of electrons to illuminate a specimen and produce a magnified image. An electron microscope (EM) has greater resolving power than a light-powered optical microscope because electrons have wavelengths about 100,000 times shorter than visible light (photons). They can achieve better than 50 pm resolution and magnifications of up to about 10,000,000x whereas ordinary, non-confocal light microscopes are limited by diffraction to about 200 nm resolution and useful magnifications below 2000x.
The electron microscope uses electrostatic and electromagnetic "lenses" to control the electron beam and focus it to form an image. These lenses are analogous to but different from the glass lenses of an optical microscope that form a magnified image by focusing light on or through the specimen. Electron microscopes are used to observe a wide range of biological and inorganic specimens including microorganisms, cells, large molecules, biopsy samples, metals, and crystals. Industrially, the electron microscope is often used for quality control and failure analysis. Modern electron microscopes produce electron micrographs, using specialised digital cameras or frame
An autocannon or automatic cannon is a rapid-fire projectile weapon firing a shell as opposed to the bullet fired by a machine gun. Autocannons often have a larger caliber than a machine gun (i.e., 20 mm or greater). Usually, autocannons are smaller than a field gun or other artillery, and are mechanically loaded for a faster rate of fire. They can use a variety of ammunition: common shells include high-explosive dual-purpose types (HEDP), any variety of armour-piercing (AP) types, such as composite rigid (APCR) or discarding sabot types (APDS).
Although capable of generating a high rate of fire, autocannons overheat if used for sustained fire, and are limited by the amount of ammunition that can be carried by the weapons systems mounting them. Both the U.S. 25 mm Bushmaster and the British 30 mm Rarden have relatively slow rates of fire so as not to use ammunition too fast. The rate of fire of a modern autocannon ranges from 90 rounds per minute (British RARDEN) to 2,500 rounds per minute (GIAT 30). Systems with multiple barrels can have rates of fire over 9,000 (GSh-6-23) rounds per minute. Such extremely high rates of fire are effectively employed by aircraft in air-to-air
A blade is that portion of a tool, weapon, or machine with an edge that is designed to cut and/or puncture, stab, slash, chop, slice, thrust, or scrape animate or inanimate surfaces or materials. A blade may be made from a flaking stone, such as flint, metal (usually steel), ceramic, or other material.
Stone blades were among the first human inventions, dating to the Oldowan culture in human prehistory - see stone tool - and fundamentally changed human existence by aiding the transition from a prey species on Earth to a predator species, as well as giving humanity a cutting tool that could be used to shape other tools.
Since then, blades have been used for utility purposes (food preparation, craftwork, outdoors sport, etc.) and for combat for millions of years.
When used for food preparation, the main uses are slicing (cutting by drawing the blade across the object, applying light pressure) and chopping (cutting by pushing the blade through object), with some piercing (using the tip to cut through the surface).
In combat, a blade may be used to slash (i.e. to cut with the edge, generally in a swinging motion), puncture or stab (the blade is plunged into the opponent, starting with
In modern clothing and fashion design, a button is a small fastener, most commonly made of plastic, but also frequently of seashell, which secures two pieces of fabric together. In archaeology, a button can be a significant artifact. In the applied arts and in craft, a button can be an example of folk art, studio craft, or even a miniature work of art.
Buttons are most often attached to articles of clothing but can also be used on containers such as wallets and bags. However, buttons may be sewn onto garments and similar items exclusively for purposes of ornamentation. Buttons serving as fasteners work by slipping through a fabric or thread loop, or by sliding through a buttonhole.
Some museums and art galleries hold culturally, historically, politically, and/or artistically significant buttons in their collections. The Victoria & Albert Museum has many buttons, particularly in its jewellery collection, as does the Smithsonian Institution.
Hammond Turner & Sons, a button-making company in Birmingham, hosts an online museum with an image gallery and historical button-related articles, including an 1852 article on button-making by Charles Dickens. In the USA, large button collections
The term derringer is a genericized misspelling of the last name of Henry Deringer, a famous 19th-century maker of small pocket pistols. Many copies of the original Philadelphia Deringer pistol were made by other gun makers worldwide, and the name was often misspelled; this misspelling soon became an alternate generic term for any pocket pistol, along with the generic phrase palm pistol Deringer's competitors invented and used in their advertising. The original Deringer pistol was a single-shot muzzleloading pistol; with the advent of cartridge firearms, pistols began to be produced in the modern form still known as a derringer.
A derringer is generally the smallest usable handgun of a given caliber. They were frequently used by women, because they are easily concealable in a purse or as a stocking gun. Such weapons designed specifically for women were called "muff pistols", due to their compact size enabling them to be carried in a muff. Derringers are not repeating firearms—repeating mechanisms such as used on semi-automatic handguns or revolvers would add significant bulk to the gun, defeating the purpose. The original cartridge derringers held only a single round, usually a
A fastener is a hardware device that mechanically joins or affixes two or more objects together.
Fasteners can also be used to close a container such as a bag, a box, or an envelope; or they may involve keeping together the sides of an opening of flexible material, attaching a lid to a container, etc. There are also special-purpose closing devices, e.g. a bread clip. Fasteners used in these manners are often temporary, in that they may be fastened and unfastened repeatedly.
Some types of woodworking joints make use of separate internal reinforcements, such as dowels or biscuits, which in a sense can be considered fasteners within the scope of the joint system, although on their own they are not general purpose fasteners.
Furniture supplied in flat-pack form often uses cam dowels locked by cam locks, also known as conformat fasteners.
Items like a rope, string, wire (e.g. metal wire, possibly coated with plastic, or multiple parallel wires kept together by a plastic strip coating), cable, chain, or plastic wrap may be used to mechanically join objects; but are not generally categorized as fasteners because they have additional common uses. Likewise, hinges and springs may join
In computer science, a sorting algorithm is an algorithm that puts elements of a list in a certain order. The most-used orders are numerical order and lexicographical order. Efficient sorting is important for optimizing the use of other algorithms (such as search and merge algorithms) that require sorted lists to work correctly; it is also often useful for canonicalizing data and for producing human-readable output. More formally, the output must satisfy two conditions:
Since the dawn of computing, the sorting problem has attracted a great deal of research, perhaps due to the complexity of solving it efficiently despite its simple, familiar statement. For example, bubble sort was analyzed as early as 1956. Although many consider it a solved problem, useful new sorting algorithms are still being invented (for example, library sort was first published in 2006). Sorting algorithms are prevalent in introductory computer science classes, where the abundance of algorithms for the problem provides a gentle introduction to a variety of core algorithm concepts, such as big O notation, divide and conquer algorithms, data structures, randomized algorithms, best, worst and average case
The stern is the rear or aft-most part of a ship or boat, technically defined as the area built up over the sternpost, extending upwards from the counter rail to the taffrail. The stern lies opposite of the bow, the foremost part of a ship. Originally, the term only referred to the aft port section of the ship, but eventually came to refer to the entire back of a vessel. The stern end of a ship is indicated with a white navigation light at night.
Sterns on European and American wooden sailing ships began with two principal forms: the square or transom stern and the elliptical, fantail, or merchant stern, and were developed in that order. The hull sections of a sailing ship located before the stern are composed of a series of U-shaped rib-like frames set in a sloped or "cant" arrangement, with the last frame before the stern being called the fashion timber(s) or fashion piece(s), so called for "fashioning" the after part of the ship. This frame is designed to support the various beams that make up the stern.
In 1817 the British naval architect Sir Robert Seppings first introduced the concept of the round or circular stern. The square stern had been an easy target for enemy cannon,
A swing bridge is a movable bridge that has as its primary structural support a vertical locating pin and support ring, usually at or near to its centre of gravity, about which the turning span can then pivot horizontally as shown in the animated illustration to the right. Small swing bridges as found over canals may be pivoted only at one end, opening as would a gate, but require substantial underground structure to support the pivot.
In its closed position, a swing bridge carrying a road or railway over a river or canal, for example, allows traffic to cross. When a water vessel needs to pass the bridge, road traffic is stopped (usually by traffic signals and barriers), and then motors rotate the bridge approximately 90 degrees horizontally about its pivot point.
The "Abtsewoudsebrug" in Delft, close to the Technische Universiteit Delft, is a bridge of this type. 52°0′5.71″N 4°21′50.10″E / 52.0015861°N 4.363917°E / 52.0015861; 4.363917
(n.b. "swing bridge" in New Zealand refers to a flexible walking track bridge which "swings" as you walk across)
The largest double swing span bridge in the United States is the 3,250 feet (990 m) long, 450 feet (140 m) navigable span, 60 feet
An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is so named because it is usually the lens that is closest to the eye when someone looks through the device. The objective lens or mirror collects light and brings it to focus creating an image. The eyepiece is placed near the focal point of the objective to magnify this image. The amount of magnification depends on the focal length of the eyepiece.
An eyepiece consists of several "lens elements" in a housing, with a "barrel" on one end. The barrel is shaped to fit in a special opening of the instrument to which it is attached. The image can be focused by moving the eyepiece nearer and further from the objective. Most instruments have a focusing mechanism to allow movement of the shaft in which the eyepiece is mounted, without needing to manipulate the eyepiece directly.
The eyepieces of binoculars are usually permanently mounted in the binoculars, causing them to have a pre-determined magnification and field of view. With telescopes and microscopes, however, eyepieces are usually interchangeable. By switching the eyepiece, the user can adjust what
Golf is a precision club and ball sport, in which competing players (or golfers) use many types of clubs to hit balls into a series of holes on a golf course using the fewest number of strokes. Golf is defined, in the rules of golf, as "playing a ball with a club from the teeing ground into the hole by a stroke or successive strokes in accordance with the Rules."
It is one of the few ball games that does not require a standardized playing area. Instead, the game is played on a "course", generally consisting of an arranged progression of either 9 or 18 "holes". Each hole on the course must contain a "tee box" and a "putting green" with the actual hole, and there are various other standardized forms of terrain in between such as the fairway, rough, and hazards, but each hole on a course and indeed among virtually all courses is unique in its specific layout and arrangement.
Golf competition is generally played for the lowest number of strokes by an individual, known simply as stroke play, or the lowest score on the most individual holes during a complete round by an individual or team, known as match play. Stroke play is the most commonly-seen format at virtually all levels of play,
An electronic calculator is a small, portable, often inexpensive electronic device used to perform both basic and complex operations of arithmetic. Modern calculators are more portable than most computers, though most PDAs or mobile phones are comparable in size to handheld calculators and may soon replace them.
The first solid state electronic calculator was created in the 1960s, building on the extensive history of tools such as the abacus, developed around 2000 BC; and the mechanical calculator, developed in the 17th century. It was developed in parallel with the analog computers of the day.
Pocket sized devices became available in the 1970s, especially after the invention of the microprocessor developed by Intel for the Japanese calculator company Busicom.
Modern electronic calculators vary from cheap, give-away, credit-card sized models to sturdy desktop models with built-in printers. They became popular in the mid-1970s as integrated circuits made their size and cost small. By the end of that decade, calculator prices had reduced to a point where a basic calculator was affordable to most and they became common in schools.
Computer operating systems as far back as early Unix
An essay is a piece of writing which is often written from an author's personal point of view. Essays can consist of a number of elements, including: literary criticism, political manifestos, learned arguments, observations of daily life, recollections, and reflections of the author. The definition of an essay is vague, overlapping with those of an article and a short story. Almost all modern essays are written in prose, but works in verse have been dubbed essays (e.g. Alexander Pope's An Essay on Criticism and An Essay on Man). While brevity usually defines an essay, voluminous works like John Locke's An Essay Concerning Human Understanding and Thomas Malthus's An Essay on the Principle of Population are counterexamples.
In some countries (e.g., the United States and Canada), essays have become a major part of formal education. Secondary students are taught structured essay formats to improve their writing skills, and admission essays are often used by universities in selecting applicants and, in the humanities and social sciences, as a way of assessing the performance of students during final exams. The concept of an "essay" has been extended to other mediums beyond writing. A
In botany, the radicle is the first part of a seedling (a growing plant embryo) to emerge from the seed during the process of germination. The radicle is the embryonic root of the plant, and grows downward in the soil (the shoot emerges from the plumule). Above the radicle is the embryonic stem or hypocotyl, supporting the cotyledon(s).
The radicle emerges from a seed through the micropyle. Radicles in seedlings are classified into two main types. Those pointing away from the seed coat scar or hilum are classified as antitropous, and those pointing towards the hilum are syntropous.
If the radicle begins to decay, the seedling undergoes preemergence damping-off. This disease appears on the radicle as darkened spots. Eventually, it causes death of the seedling.
The plumule is the baby shoot. It grows after the radicle.
the lower part of the axis of an embryo; the primary root.
It's the embryonic root inside the seed. It's the first thing to emerge out of a seed and down into the ground to allow the seed to suck up water and send out its leaves so that it can start photosynthesizing.
A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft or other conveyance that moves through a medium (generally air or water). On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane. A rudder operates by redirecting the fluid past the hull or fuselage, thus imparting a turning or yawing motion to the craft. In basic form, a rudder is a flat plane or sheet of material attached with hinges to the craft's stern, tail or after end. Often rudders are shaped so as to minimize hydrodynamic or aerodynamic drag. On simple watercraft, a tiller -- essentially, a stick or pole acting as a lever arm—may be attached to the top of the rudder to allow it to be turned by a helmsman. In larger vessels, cables, pushrods, or hydraulics may be used to link rudders to steering wheels. In typical aircraft, the rudder is operated by pedals via mechanical linkages or hydraulics.
Generally, a rudder is "part of the steering apparatus of a boat or ship that is fastened outside the hull", that is denoting all different types of oars, paddles and rudders. More specifically, the steering gear of ancient
Home computers were a class of microcomputers entering the market in 1977, and becoming common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a single nontechnical user. These computers typically cost much less than business, scientific or engineering-oriented computers of the time, and were generally less powerful in terms of memory and expandability. However, a home computer often had better graphics and sound than contemporary business computers and, by far, their most common use was playing video games.
Advertisements for early home computers were rife with possibilities for their practical use in the home, from cataloging recipes to personal finance to home automation, but these were seldom realized in practice. For example, using a typical 1980s home computer as a home automation appliance would require the computer to be kept powered on at all times and dedicated to this task. Personal finance and database use required tedious data entry. If no packaged software was available for a particular application, the home computer user was required to learn computer programming; a
A knife (plural knives) is a cutting tool with an exposed cutting edge or blade, hand-held or otherwise, with or without a handle. Knife-like tools were used at least two-and-a-half million years ago, as evidenced by the Oldowan tools. Originally made of rock, flint, and obsidian, knives have evolved in construction as technology has, with blades being made from bronze, copper, iron, steel, ceramics, and titanium. Many cultures have their unique version of the knife. Due to its role as humankind's first tool, certain cultures have attached spiritual and religious significance to the knife.
Most modern-day knives follow either a fixed-blade or a folding construction style, with blade patterns and styles as varied as their makers and countries of origin.
Today, knives come in many forms but can be generally categorized between two broad types: fixed blade knives and folding, or pocket knives.
Modern knives consist of a blade (1) and handle (2). The blade edge can be plain or serrated or a combination of both. The handle, used to grip and manipulate the blade safely, may include the tang, a portion of the blade that extends into the handle. Knives are made with partial tangs
Mathematics (from Greek μάθημα máthēma, “knowledge, study, learning”) is the abstract study of topics encompassing quantity, structure, space, change, and others; it has no generally accepted definition.
Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proof. The research required to solve mathematical problems can take years or even centuries of sustained inquiry. Since the pioneering work of Giuseppe Peano (1858–1932), David Hilbert (1862–1943), and others on axiomatic systems in the late 19th century, it has become customary to view mathematical research as establishing truth by rigorous deduction from appropriately chosen axioms and definitions. When those mathematical structures are good models of real phenomena, then mathematical reasoning can provide insight or predictions about nature.
Through the use of abstraction and logical reasoning, mathematics developed from counting, calculation, measurement, and the systematic study of the shapes and motions of physical objects. Practical mathematics has been a human activity for as far back as written records exist. Rigorous arguments first
In geology, a rock is a naturally occurring solid aggregate of one or more minerals or mineraloids. For example, the common rock, granite, is a combination of the quartz, feldspar and biotite minerals. The Earth's outer solid layer, the lithosphere, is made of rock.
Rocks have been used by mankind through out history. From the Stone Age rocks have been used for tools. The minerals and metals we find in rocks have been essential to human civilization.
Three major groups of rocks are defined: igneous, sedimentary, and metamorphic. The scientific study of rocks is called petrology, which is an essential component of geology.
Rocks are generally classified by mineral and chemical composition, by the texture of the constituent particles and by the processes that formed them. These indicators separate rocks into three types: igneous, sedimentary, and metamorphic. They are further classified according to particle size. The transformation of one rock type to another is described by the geological model called the rock cycle.
Igneous rocks are formed when molten magma cools and are divided into two main categories: plutonic rock and volcanic. Plutonic or intrusive rocks result when magma
Rye (Secale cereale) is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe (Triticeae) and is closely related to barley (Hordeum) and wheat (Triticum). Rye grain is used for flour, rye bread, rye beer, some whiskeys, some vodkas, and animal fodder. It can also be eaten whole, either as boiled rye berries, or by being rolled, similar to rolled oats.
Rye is a cereal grain and should not be confused with ryegrass, which is used for lawns, pasture, and hay for livestock.
Rye is one of a number of species that grow wild in central and eastern Turkey, and in adjacent areas. Domesticated rye occurs in small quantities at a number of Neolithic sites in Turkey, such as PPNB Can Hasan III, but is otherwise virtually absent from the archaeological record until the Bronze Age of central Europe, c. 1800-1500 BC. It is possible that rye traveled west from Turkey as a minor admixture in wheat (possibly as a result of Vavilovian mimicry), and was only later cultivated in its own right. Although archeological evidence of this grain has been found in Roman contexts along the Rhine, Danube, and in the British Isles, Pliny the Elder was dismissive of rye,
The sabre or saber (see spelling differences) is a kind of backsword that usually has a curved, single-edged blade and a rather large hand guard, covering the knuckles of the hand as well as the thumb and forefinger. Although sabres are typically thought of as curved-bladed slashing weapons, those used by the world's heavy cavalry often had straight and even double-edged blades more suitable for thrusting. The length of sabres varied, and most were carried in a scabbard hanging from a shoulder belt known as a baldric or from a waist-mounted sword belt, usually with slings of differing lengths to permit the scabbard to hang below the rider's waist level . Exceptions not intended for personal carry include the Patton saber adopted by the United States Army in 1913 and always mounted to the cavalryman's saddle.
The English word sabre derives from the French sabre which is akin to the Hungarian szablya, Polish szabla, and Russian сабля (sablya). Owing to contamination with Hungarian verb szab, which means "to cut" (cognate with the English "stab"), the term is believed to originate from the Kipchak Turkic selebe.
Sabre-like curved backswords have been in use in Europe since the
A school is an institution designed for the teaching of students (or "pupils") under the direction of teachers. Most countries have systems of formal education, which is commonly compulsory. In these systems, students progress through a series of schools. The names for these schools vary by country (discussed in the Regional section below), but generally include primary school for young children and secondary school for teenagers who have completed primary education. An institution where higher education is taught, is commonly called a university college or university.
In addition to these core schools, students in a given country may also attend schools before and after primary and secondary education. Kindergarten or pre-school provide some schooling to very young children (typically ages 3–5). University, vocational school, college or seminary may be available after secondary school. A school may also be dedicated to one particular field, such as a school of economics or a school of dance. Alternative schools may provide nontraditional curriculum and methods.
There are also non-government schools, called private schools. Private schools may be required when the government does
A turbine is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. A turbine is a turbomachine with at least one moving part called a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades so that they move and impart rotational energy to the rotor. Early turbine examples are windmills and water wheels.
Gas, steam, and water turbines usually have a casing around the blades that contains and controls the working fluid. Credit for invention of the steam turbine is given both to the British engineer Sir Charles Parsons (1854–1931), for invention of the reaction turbine and to Swedish engineer Gustaf de Laval (1845–1913), for invention of the impulse turbine. Modern steam turbines frequently employ both reaction and impulse in the same unit, typically varying the degree of reaction and impulse from the blade root to its periphery.
The word "turbine" was coined in 1822 by the French mining engineer Claude Burdin from the Latin turbo, or vortex, in a memoir, "Des turbines hydrauliques ou machines rotatoires à grande vitesse", which he submitted to the Académie royale des sciences in Paris. Benoit
A handle is a part of, or attachment to, an object that can be moved or used by hand. The design of each type of handle involves substantial ergonomic issues, even where these are dealt with intuitively or by following tradition. Handles for tools are an important part of their function, enabling the user to exploit the tools to maximum effect.
The three nearly universal requirements of are:
Other requirements may apply to specific handles:
One major category of handles are pull handles, where one or more hands grip the handle or handles, and exert force to shorten the distance between the hands and their corresponding shoulders. The three criteria stated above are universal for pull handles.
Many pull handles are for lifting, mostly on objects to be carried.
Horizontal pull handles are widespread, including drawer pulls, handles on latchless doors and the outside of car doors. The inside controls for opening car doors from inside are usually pull handles, although their function of permitting the door to be pushed open is accomplished by an internal unlatching linkage.
Two kinds of pull handles may involve motion in addition to the hand-focused motions described:
A laptop computer is a personal computer for mobile use. A laptop has most of the same components as a desktop computer, including a display, a keyboard, a pointing device such as a touchpad (also known as a trackpad) and/or a pointing stick, and speakers into a single unit. A laptop is powered by mains electricity via an AC adapter, and can be used away from an outlet using a rechargeable battery. Laptops are also sometimes called notebook computers, notebooks or netbooks.
Portable computers, originally monochrome CRT-based and developed into the modern laptops, were originally considered to be a small niche market, mostly for specialized field applications such as the military, accountants and sales representatives. As portable computers became smaller, lighter, cheaper, more powerful and as screens became larger and of better quality, laptops became very widely used for all sorts of purposes.
As the personal computer became feasible in the 1970s, the idea of a portable personal computer followed. A "personal, portable information manipulator" was imagined by Alan Kay at Xerox PARC in 1968, and described in his 1972 paper as the "Dynabook".
The IBM Special Computer APL Machine
The acute accent ( ´ ) is a diacritic used in many modern written languages with alphabets based on the Latin, Cyrillic, and Greek scripts.
An early precursor of the acute accent was the apex, used in Latin inscriptions to mark long vowels.
The acute accent was first used in the polytonic orthography of Ancient Greek, where it indicated a syllable with a high pitch. In Modern Greek, a stress accent has replaced the pitch accent, and the acute marks the stressed syllable of a word. The Greek name of the accent was oxeîa (Modern Greek oxía) "sharp" or "high", which was calqued into Latin as acūta "sharpened".
The acute accent marks the stressed vowel of a word in several languages:
The acute accent marks the height of some stressed vowels in various Romance languages.
The acute accent marks long vowels in several languages:
The acute accent marks short vowels in:
A graphically similar, but not identical, mark is indicative of a palatalized sound in several languages.
In Polish, such a mark is known as a kreska (English: stroke) and is an integral part of several letters: four consonants and one vowel. When appearing in consonants, it indicates palatalization, similar to the use of
A belt or ammunition belt is a device used to retain and feed cartridges into a firearm. Belts and the associated feed systems are typically employed to feed machine guns or other automatic weapons. Belt-fed systems minimize the proportional weight of the ammunition to the feeding device along with allowing high rates of continuous fire.
Belts were originally composed of canvas or cloth with pockets spaced evenly to allow the belt to be mechanically fed into the gun. These designs were prone to malfunctions due to the effects of oil and other contaminants altering the belt. Later belt designs used permanently connected metal links to retain the cartridges during feeding. These belts were more tolerant to exposure to solvents and oil. Many weapons designed to use non-disintegrating or canvas belts are provided with machines to automatically reload these belts with loose rounds or rounds held in stripper clips. In use during World War I, reloaders allowed ammunition belts to be recycled quickly to allow practically continuous fire.
Many modern ammunition belts use disintegrating links. Disintegrating links retain a single round and are articulated with the round ahead of it in the
A boardwalk (board walk, boarded path) is a constructed pedestrian walkway along or overlooking beaches; or as walking paths and trails over bogs and wetlands and above fragile ecosystems, usually built with wood.
Boardwalks along intertidal zones are known as foreshoreways in Australia. A boardwalk along a river is often known as a riverwalk and a boardwalk along an oceanfront is often known as an oceanway. Aside from their obvious pedestrian usage, boardwalks have been used to create commercial districts and enable commerce along waterfronts where conventional streets would have been more expensive because of a beach or other waterfront feature. Although boardwalks can be found around the world, they are especially common along the East Coast of the United States in North America.
Many of the original boardwalks in the United States have developed to be so successful as commercial districts and tourist attractions that the simple wooden pathways have been replaced by esplanades made of concrete, brick or other construction, sometimes with a wooden facade on the surface and sometimes not. Indeed in many parts of the U.S. today the term boardwalk often carries more the connotation
Carbon fiber, alternatively graphite fiber, carbon graphite or CF, is a material consisting of fibers about 5–10 μm in diameter and composed mostly of carbon atoms. The carbon atoms are bonded together in crystals that are more or less aligned parallel to the long axis of the fiber. The crystal alignment gives the fiber high strength-to-volume ratio (makes it strong for its size). Several thousand carbon fibers are bundled together to form a tow, which may be used by itself or woven into a fabric.
The properties of carbon fibers, such as high stiffness, high tensile strength, low weight, high chemical resistance, high temperature tolerance and low thermal expansion, make them very popular in aerospace, civil engineering, military, and motorsports, along with other competition sports. However, they are relatively expensive when compared to similar fibers, such as glass fibers or plastic fibers.
Carbon fibers are usually combined with other materials to form a composite. When combined with a plastic resin and wound or molded it forms carbon fiber reinforced plastic (often referred to as carbon fiber) which has a very high strength-to-weight ratio, and is extremely rigid although
A fiberscope is a flexible fiber optic bundle with an eyepiece at one end, and a lens at the other. It is used for inspection work, often to examine small components in tightly packed equipment, when the inspector cannot easily access the part requiring inspection.
The lens is often a wide-angle lens, and the eyepiece is occasionally instead connected to a camera. Some fiberscopes use an additional fiber to carry light from an external source to illuminate the material being inspected, for clearer viewing.
All fiberscopes introduce a certain amount of image distortion; much of this is similar to the distortion of modern night vision equipment.
Quartz fiberscopes can reach lengths of up to about 90 m (300 ft)
Fiberscopes are used in medicine, machining, computer repair, espionage, locksmithing, safecracking, and computer forensics, among many other uses.
A judge is a person who presides over court proceedings, either alone or as part of a panel of judges. The powers, functions, method of appointment, discipline, and training of judges vary widely across different jurisdictions. The judge is supposed to conduct the trial impartially and in an open court. The judge hears all the witnesses and any other evidence presented by the parties of the case, assesses the credibility and arguments of the parties, and then issues a ruling on the matter at hand based on his or her interpretation of the law and his or her own personal judgment. In some jurisdictions, the judge's powers may be shared with a jury. In inquisitorial systems of criminal investigation, a judge might also be an examining magistrate.
A variety of traditions have become associated with the rank or occupation.
In many parts of the world, judges wear long robes (usually in black or red) and sit on an elevated platform during trials (known as the bench).
In some countries, especially in the Commonwealth of Nations, judges sometimes wear wigs. The long wig often associated with judges is now reserved for ceremonial occasions, although it was part of the standard attire in
A slingshot, shanghai, flip, bean shooter, Wrist-Rocket or catapult (primarily British English) is a small hand-powered projectile weapon. The classic form consists of a Y-shaped frame held in the off hand, with two rubber strips attached to the uprights. The other ends of the strips lead back to a pocket which holds the projectile. The pocket is grasped by the dominant hand and drawn back to the desired extent to provide power for the projectile (up to a full span of the arms with sufficiently long bands).
Slingshots depend on strong elastic materials, typically vulcanized natural rubber or the equivalent, and thus date back no further than the invention of vulcanized rubber by Charles Goodyear in 1839 (patented in 1844). By 1860, this "new engine" had already established a reputation for juvenile use in vandalism, as well as at least one human death.
For much of their early history, slingshots were a "do it yourself" item, typically made from a forked branch to form the "Y" shaped handle, with rubber strips sliced from items as inner tubes or other sources of good vulcanized rubber and firing suitably sized stones.
While early slingshots were most associated with young vandals,
A toy is any object that can be used to play. Toys are associated commonly with children and pets. Playing with toys is often thought to be an enjoyable pastime. Different materials are used to make toys enjoyable to both young and old. Many items are designed to serve as toys, but goods produced for other purposes can also be used. For instance, a small child may pick up a household item and "fly" it through the air as to pretend that it is an airplane. Another consideration is interactive digital entertainment, such as a video game. Some toys are produced primarily as collector's items and are intended for display only.
The origin of toys is prehistoric; dolls representing infants, animals, and soldiers, as well as representations of tools used by adults are readily found at archaeological sites. The origin of the word "toy" is unknown, but it is believed that it was first used in the 14th century.
Toys, and play in general, are important when it comes to growing up and learning about the world around us. The young use toys and play to discover their identity, help their bodies grow strong, learn cause and effect, explore relationships, and practice skills they will need as
Track racing is a form of motorcycle racing where teams or individuals race opponents around an oval track. There are differing variants, with each variant racing on a different surface type.
The most common variant is Speedway which has many professional domestic and international competitions in a number of countries.
Administered internationally by the Fédération Internationale de Motocyclisme (FIM), the sport became popular in the 1920s and remains so today.
Track racing involves between 4 and 6 sometimes 8 competitors riding around an oval track in a counter-clockwise direction over a set amount of laps - usually 4 to 6 sometimes 8 - with points being awarded to all but the last finisher on a sliding scale.
These points are accumulated over a number of heats, with the winner being the team or individual who has scored the most overall.
The machines used are customised motorcycles, these have no brakes and are fuelled with methanol. Speedway also uses motorcycles with no gears or rear suspension. The use of methanol provides an increased compression ratio to the engine resulting in higher speeds (approx 80mph when cornering) although the skill of Track Racing lies in the
The atom probe is a microscope used in material science that was invented in 1967 by Erwin Wilhelm Müller, J. A. Panitz, and S. Brooks McLane. The atom probe is closely related to the method of Field Ion Microscopy, which is the first microscopic method to achieve atomic resolution, occurring in 1951.
Atom probes are unlike conventional optical or electron microscopes, in that the magnification effect comes from the magnification provided by a highly curved electric field, rather than by the manipulation of radiation paths. Technically, the method is destructive in nature removing ions from a sample surface in order to image and identify them, generating magnifications sufficient to observe individual atoms as they are removed from the sample surface. Through coupling of this magnification method with time of flight mass spectrometry, ions evaporated by application of electric pulses can have their mass-to-charge ratio computed.
Through successive evaporation of material, layers of atoms are removed from a specimen, allowing for probing not only of the surface, but also through the material itself. Computer methods are utilised to rebuild a three dimensional view of the sample,
In electricity, a battery is a device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery (or "voltaic pile") in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power source for many household and industrial applications. According to a 2005 estimate, the worldwide battery industry generates US$48 billion in sales each year, with 6% annual growth.
There are two types of batteries: primary batteries (disposable batteries), which are designed to be used once and discarded, and secondary batteries (rechargeable batteries), which are designed to be recharged and used multiple times. Batteries come in many sizes, from miniature cells used to power hearing aids and wristwatches to battery banks the size of rooms that provide standby power for telephone exchanges and computer data centers.
In strict terms, a battery is a collection of multiple electrochemical cells, but in popular usage battery often refers to a single cell. For example, a 1.5-volt AAA battery is a single 1.5-volt cell, and a 9-volt battery has six
In physics and all science, dimensional analysis is a tool to find or check relations among physical quantities by using their dimensions. The dimension of a physical quantity is the combination of the basic physical dimensions (usually length, mass, time, electric current, temperature, amount of substance and luminous intensity) which describe it; for example, speed has the dimension length per time, and may be measured in meters per second, miles per hour, or other units. Dimensional analysis is based on the fact that a physical law must be independent of the units used to measure the physical variables. A straightforward practical consequence is that any meaningful equation (and any inequality and inequation) must have the same dimensions in the left and right sides. Checking this is the basic way of performing dimensional analysis.
Dimensional analysis is routinely used to check the plausibility of derived equations and computations. It is also used to form reasonable hypotheses about complex physical situations that can be tested by experiment or by more developed theories of the phenomena, and to categorize types of physical quantities and units based on their relations to or
A field gun is an artillery piece. Originally the term referred to smaller guns that could accompany a field army on the march and when in combat could be moved about the battlefield in response to changing circumstances (field artillery), as to opposed guns installed in a fort (garrison artillery/coastal artillery), or to siege cannon or mortars which were too large to be moved quickly, and would be used only in a prolonged siege.
Perhaps the most famous use of the field gun in terms of advanced tactics was Napoleon's use of very large wheels on the guns that allowed them to be moved quickly even during a battle. By moving the guns from point to point during the battle, enemy formations could be broken up to be handled by the infantry wherever they were massing, dramatically increasing the overall effectiveness of the infantry.
As the evolution of artillery continued, almost all guns of any size became capable of being moved at some speed. With few exceptions, even the largest siege weapons had become mobile by road or rail by the start of World War I, and evolution after that point tended to be towards smaller weapons with increased mobility. Even the German super-heavy guns in
A siege engine is a device that is designed to break or circumvent city walls and other fortifications in siege warfare. Some have been operated close to the fortifications, while others have been used to attack from a distance. From antiquity, siege engines were constructed largely of wood and tended to use mechanical advantage to fling stones and similar missiles. With the development of gunpowder and improved metallurgical techniques, siege engines became artillery. Collectively, siege engines or artillery together with the necessary troops and transport vehicles to conduct a siege are referred to as a siege-train.
The earliest engine was the battering ram, developed by the Assyrians, followed by the catapult in ancient Greece. The Spartans used battering rams in the Siege of Plataea in 429 BC, but it seems that the Greeks limited their use of siege engines to assault ladders, though Peloponnesian forces used something resembling flamethrowers.
The first Mediterranean people to use advanced siege machinery were the Carthaginians, who used siege towers and battering rams against the Greek colonies of Sicily. These engines influenced the ruler of Syracuse, Dionysius I, who
The modern torpedo is a self-propelled weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with its target or in proximity to it.
Historically, it was called an automotive, automobile, locomotive or fish torpedo; colloquially called a fish. The term torpedo was originally employed for a variety of devices, most of which would today be called mines. From about 1900, torpedo has been used strictly to designate an underwater self-propelled weapon. The original torpedo is a kind of fish: an electric ray.
While the battleship had evolved primarily around engagements between armoured ships with large-caliber guns, the torpedo allowed torpedo boats and other lighter surface ships, submersibles, even ordinary fishing boats or frogmen, and later, aircraft, to destroy large armoured ships without the need of large guns, though sometimes at the risk of being hit by longer-range shellfire.
Today's torpedoes can be divided into lightweight and heavyweight classes; and into straight-running, autonomous homers, and wire-guided. They can be launched from a variety of platforms.
A workstation is a high-end microcomputer designed for technical or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems. The term workstation has also been used to refer to a mainframe computer terminal or a PC connected to a network.
Both being microcomputers, workstations had offered higher performance than desktop computers, especially with respect to CPU and graphics, memory capacity, and multitasking capability. They are optimized for the visualization and manipulation of different types of complex data such as 3D mechanical design, engineering simulation (e.g. computational fluid dynamics), animation and rendering of images, and mathematical plots. Typically, consoles consist of a high resolution display, a keyboard and a mouse at a minimum, but also offer multiple displays, graphics tablets, 3D mice (devices for manipulating 3D objects and navigating scenes), etc. Workstations are the first segment of the computer market to present advanced accessories and collaboration tools.
Presently, the workstation market is highly commoditized and is dominated by large
The boiling water reactor (BWR) is a type of light water nuclear reactor used for the generation of electrical power. It is the second most common type of electricity-generating nuclear reactor after the pressurized water reactor (PWR), also a type of light water nuclear reactor. The main difference between a BWR and PWR is that in a BWR, the reactor core heats water, which turns to steam and then drives a steam turbine. In a PWR, the reactor core heats water, which does not boil. This hot water then exchanges heat with a lower pressure water system, which turns to steam and drives the turbine. The BWR was developed by the Idaho National Laboratory and General Electric in the mid-1950s. The main present manufacturer is GE Hitachi Nuclear Energy, which specializes in the design and construction of this type of reactor.
The BWR uses demineralized water as a coolant and neutron moderator. Heat is produced by nuclear fission in the reactor core, and this causes the cooling water to boil, producing steam. The steam is directly used to drive a turbine, after which it is cooled in a condenser and converted back to liquid water. This water is then returned to the reactor core, completing
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light). The first known practical telescopes were invented in the Netherlands at the beginning of the 17th century, using glass lenses. They found use in terrestrial applications and astronomy.
Within a few decades, the reflecting telescope was invented, which used mirrors. In the 20th century many new types of telescopes were invented, including radio telescopes in the 1930s and infrared telescopes in the 1960s. The word telescope now refers to a wide range of instruments detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors.
The word "telescope" (from the Greek τῆλε, tele "far" and σκοπεῖν, skopein "to look or see"; τηλεσκόπος, teleskopos "far-seeing") was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galilei's instruments presented at a banquet at the Accademia dei Lincei. In the Starry Messenger Galileo had used the term "perspicillum".
The earliest recorded working telescopes were the refracting telescopes that appeared in the Netherlands in 1608. Their
A bowling green is a finely-laid, close-mown and rolled stretch of lawn for playing the game of lawn bowls.
Before 1830, when Edwin Beard Budding invented the lawnmower, lawns were often kept cropped by grazing sheep on them. The world's oldest surviving bowling green is the Southampton Old Bowling Green, which was first used in 1299.
When the French adopted "boulingrin" in the 17th century, it was understood to mean a sunk geometrically shaped piece of perfect grass, framed in gravel walks, which often formed the center of a regularly planted wood called a bosquet, somewhat like a highly formalized glade; it might have a central pool or fountain.
The diarist Samuel Pepys relates a conversation he had with the architect Hugh May:
Bowling green specifications are stipulated in the Laws of the Sport of Bowls.
Several games of bowls can be played on a bowling green at the same time. The number of games depends on the dimensions of the green. Each game is played on its own portion of the green. These divided portions of the green are called rinks.
The length of a green in the direction of play will be between 31 metres and 40 metres. The green should have a suitable level playing
Neuro-linguistic programming (NLP) is an approach to communication, personal development, and psychotherapy created in the 1970s. The title refers to a stated connection between the neurological processes ("neuro"), language ("linguistic"), and behavioral patterns that have been learned through experience ("programming") and can be organized to achieve specific goals in life. According to certain neuroscientists, psychologists, and linguists, NLP is unsupported by current scientific evidence, and is accused of using incorrect and misleading terms and concepts.
The founders of NLP, Richard Bandler and John Grinder, say that NLP is capable of addressing problems such as phobias, depression, habit disorder, psychosomatic illnesses, and learning disorders. Their stated aim was in "finding ways to help people have better, fuller and richer lives." Bandler and Grinder claimed that if the effective patterns of behaviour of exceptional people could be modeled then these patterns could be acquired by others. NLP has been adopted by private therapists, including hypnotherapists, and in management workshops and seminars marketed to business and government.
Reviews of empirical research on NLP
A shotgun (also known as a scattergun and peppergun, or historically as a fowling piece) is a firearm that is usually designed to be fired from the shoulder, which uses the energy of a fixed shell to fire a number of small spherical pellets called shot, or a solid projectile called a slug. Shotguns come in a wide variety of sizes, ranging from 5.5 mm (.22 inch) bore up to 5 cm (2 inch) bore, and in a range of firearm operating mechanisms, including breech loading, single-barreled, double or combination gun, pump-action, bolt-, and lever-action, semi-automatic, and even fully automatic variants.
A shotgun is generally a smoothbore firearm, which means that the inside of the barrel is not rifled. Preceding smoothbore firearms, such as the musket, were widely used by armies in the 18th century. The direct ancestor to the shotgun, the blunderbuss, was also used in a similar variety of roles from self defence to riot control. It was often used by cavalry troops due to its generally shorter length and ease of use, as well as by coachmen for its substantial power. However, in the 19th century, these weapons were largely replaced on the battlefield with breechloading rifled firearms, which
The teddy bear is a stuffed toy bear. They are usually stuffed with soft, white cotton and have smooth and soft fur. It is an enduring form of a stuffed animal in many countries, often serving the purpose of entertaining children. In recent times, some teddy bears have become collector's items. Now, teddy bears come in various styles and people can dress them up in many different articles of clothing. Teddy bears are also among the most popular gifts for children and significant others on Valentine's Day, birthdays, Christmas and other holidays.
The name Teddy Bear comes from former United States President Theodore Roosevelt, whose nickname was "Teddy". The name originated from an incident on a bear hunting trip in Mississippi in November 1902, to which Roosevelt was invited by Mississippi Governor Andrew H. Longino. There were several other hunters competing, and most of them had already killed an animal. A suite of Roosevelt's attendants, led by Holt Collier, cornered, clubbed, and tied an American Black Bear to a willow tree after a long exhausting chase with hounds. They called Roosevelt to the site and suggested that he should shoot it. He refused to shoot the bear himself,
An arrow is a shafted projectile that is shot with a bow. It predates recorded history and is common to most cultures. An arrow usually consists of a shaft with an arrowhead attached to the front end, with fletchings and a nock at the other.
In 2010, during an excavation at the Sibudu Cave in South Africa, led by Professor Lyn Wadley from the University of the Witwatersrand, researchers discovered the earliest direct evidence of human-made arrowheads: 64,000-year-old stone points which may have been shot from a bow. These had remnants of blood and bone, confirming their use in hunting.
Arrow sizes vary greatly across cultures, ranging from eighteen inches to five feet (45 cm to 150 cm). However, most modern arrows are 75 centimetres (30 in) to 96 centimetres (38 in); most war arrows from an English ship sunk in 1545 were 76 centimetres (30 in). Very short arrows have been used, shot through a guide attached either to the bow (an "overdraw") or to the archer's wrist (the Turkish "siper"). These may fly farther than heavier arrows, and an enemy without suitable equipment may find himself unable to return them.
The shaft is the primary structural element of the arrow, to which the
A blowgun (also called a blowpipe or blow tube) is a simple weapon consisting of a small tube for firing light projectiles or darts.
The weapon is used by inserting the projectile inside the pipe (known as a blowgun) and using the force created by one's breath to give the projectile momentum. Its propulsive power is limited by the user's respiratory muscles.
Many cultures have used this weapon, but various indigenous peoples of South East Asia, the Amazon and Guiana regions of South America, and Guatemala in Central America are best known for its use. Projectiles include seeds, clay pellets, and darts. Some cultures dip the tip of the darts in curare or other poisons in order to paralyze the target. Blowguns were very rarely used by these tribes as anti-personnel weapons, but primarily to hunt small game such as monkeys. North American Cherokees were known for making blowguns out of river cane to supplement their diet with rabbits and other small creatures.
Blowguns are depicted in paintings on pre-Columbian pottery and are mentioned in many Mesoamerican myths. Back then and today, the Maya use a blowgun to hunt birds and small animals with spherical dry seeds and clay pellets. The
The brown bear (Ursus arctos) is a large bear distributed across much of northern Eurasia and North America. Adult bears generally weigh between 100 and 635 kg (220 and 1,400 lb) and its largest subspecies, the Kodiak bear, rivals the polar bear as the largest member of the bear family and as the largest land-based predator.
There are several recognized subspecies within the brown bear species. In North America, two types are generally recognized, the coastal brown bear and the inland grizzly bear, and the two types could broadly define all brown bear subspecies. An adult grizzly living inland in Yukon may weigh as little as 80 kg (180 lb), while an adult brown bear in nearby coastal Alaska living on a steady, nutritious diet of spawning salmon may weigh as much as 680 kg (1,500 lb). The exact number of overall brown subspecies remains in debate.
While the brown bear's range has shrunk and it has faced local extinctions, it remains listed as a least concern species by the IUCN with a total population of approximately 200,000. As of 2012, this and the American black bear are the only bear species not classified as threatened by the IUCN. However, the Californian, North African
Ishikawa diagrams (also called fishbone diagrams, herringbone diagrams, cause-and-effect diagrams, or Fishikawa) are causal diagrams created by Kaoru Ishikawa (1968) that show the causes of a specific event. Common uses of the Ishikawa diagram are product design and quality defect prevention, to identify potential factors causing an overall effect. Each cause or reason for imperfection is a source of variation. Causes are usually grouped into major categories to identify these sources of variation. The categories typically include:
Ishikawa diagrams were proposed by Kaoru Ishikawa in the 1960s, who pioneered quality management processes in the Kawasaki shipyards, and in the process became one of the founding fathers of modern management.
It was first used in the 1940s, and is considered one of the seven basic tools of quality control. It is known as a fishbone diagram because of its shape, similar to the side view of a fish skeleton.
Mazda Motors famously used an Ishikawa diagram in the development of the Miata sports car, where the required result was "Jinba Ittai" (Horse and Rider as One — jap. 人馬一体). The main causes included such aspects as "touch" and "braking" with the lesser
The term outsider art was coined by art critic Roger Cardinal in 1972 as an English synonym for art brut (French: [aʁ bʁyt], "raw art" or "rough art"), a label created by French artist Jean Dubuffet to describe art created outside the boundaries of official culture; Dubuffet focused particularly on art by those on the outsides of the established art scene such as insane-asylum inmates and children.
While Dubuffet's term is quite specific, the English term "outsider art" is often applied more broadly, to include certain self-taught or naïve art makers who were never institutionalized. Typically, those labeled as outsider artists have little or no contact with the mainstream art world or art institutions. In many cases, their work is discovered only after their deaths. Often, outsider art illustrates extreme mental states, unconventional ideas, or elaborate fantasy worlds.
Outsider art has emerged as a successful art marketing category (an annual Outsider Art Fair has taken place in New York since 1993). The term is sometimes misapplied as a catch-all marketing label for art created by people outside the mainstream "art world," regardless of their circumstances or the content of
A semi-automatic rifle is a type of rifle that fires a single bullet each time the trigger is pulled, automatically ejects the spent cartridge, chambers a fresh cartridge from its magazine, and is immediately ready to fire another shot. They may be operated by a number of mechanisms, all of which derive their power from the explosion of the powder in the cartridge that also fires the bullet. Historically, the self-loading design was the successor to the repeating rifle, which stored a number of cartridges within the weapon, but required manual action to load a fresh cartridge before each shot. Automatically loading the next round more easily allows for rapid fire. These rifles are also commonly known as self-loading rifles ('SLR') or auto-loading rifles.
A semi-automatic rifle is distinguished from a fully automatic rifle or machine gun in that it can only fire once each time the trigger is pulled. In some contexts, the term "automatic rifle" may refer to a semi-automatic/self-loading rifle, not a fully automatic rifle. The magazine in a semi-automatic rifle is usually of a box-type which protrudes underneath the receiver and feeds cartridges vertically into the action. These may
The track on a railway or railroad, also known as the permanent way, is the structure consisting of the rails, fasteners, sleepers and ballast (or slab track), plus the underlying subgrade. For clarity it is often referred to as railway track (British English and UIC terminology) or railroad track (predominantly in the United States).
The term permanent way also refers to the track in addition to lineside structures such as fences etc.
Notwithstanding modern technical developments, the overwhelmingly dominant track form worldwide consists of flat-bottom steel rails supported on timber or pre-stressed concrete sleepers (railroad ties in the US), which are themselves laid on crushed stone ballast.
Most railroads with heavy traffic use continuously welded rails supported by sleepers (ties) attached via baseplates which spread the load. A plastic or rubber pad is usually placed between the rail and the tieplate where concrete sleepers (ties) are used. The rail is usually held down to the sleeper (tie) with resilient fastenings, although cut spikes are widely used in North American practice. For much of the 20th century, rail track used softwood timber ties and jointed rails, and
Agroforestry is an integrated approach of using the interactive benefits from combining trees and shrubs with crops and/or livestock. It combines agricultural and forestry technologies to create more diverse, productive, profitable, healthy, and sustainable land-use systems. A narrow definition of agroforestry is "trees on farms."
The theoretical base for agroforestry comes from ecology, via agroecology. From this perspective, agroforestry is one of the three principal land-use sciences. The other two are agriculture and forestry.
Agroforestry has a lot on common with intercropping. Both have two or more plant species in close interaction, both provide multiple outputs, as a consequence, higher overall yields and, because a single application or input is shared, costs are reduced. Beyond these, there are gains specific to agroforestry.
Agroforestry systems can be advantageous over conventional agricultural and forest production methods. They can offer increased productivity, economic benefits, and more diversity in the ecological goods and services provided.
Biodiversity in agroforestry systems is typically higher than in conventional agricultural systems. With two or more
A club (also known as cudgel, baton, truncheon, nightstick, or bludgeon) is among the simplest of all weapons. A club is essentially a short staff, or stick, usually made of wood, and wielded as a weapon since prehistoric times.
Most clubs are small enough to be swung in one hand although two-handed variants are known. Various kinds of clubs are used in martial arts and other specialized fields, including the law-enforcement baton. The military mace is a more sophisticated descendant of the club, typically made of metal and featuring a spiked, knobbed or flanged head attached to a haft.
The wounds inflicted by a club are generally known as bludgeoning or blunt-force trauma injuries.
Police forces and their predecessors have traditionally favored the use, whenever possible, of less-lethal weapons than guns or blades to impose public order or to subdue and arrest law-violators. Until recent times, when alternatives such as tasers and capsicum spray became available, this category of policing weapon has generally been filled by some form of wooden club variously termed a truncheon, baton, nightstick or lathi.
Conversely, criminals have been known to arm themselves with an array of
DNA sequencing is the process of reading the nucleotide bases in a DNA molecule. It includes any method or technology that is used to determine the order of the four bases—adenine, guanine, cytosine, and thymine—in a strand of DNA.
Knowledge of DNA sequences has become indispensable for basic biological research, and in numerous applied fields such as diagnostic, biotechnology, forensic biology, and biological systematics. The advent of DNA sequencing has significantly accelerated biological research and discovery. The rapid speed of sequencing attained with modern DNA sequencing technology has been instrumental in the sequencing of complete DNA sequences, or genomes of numerous types and species of life, including the human genome. Related projects have generated the complete DNA sequences of many animal, plant, and microbial genomes.
The first DNA sequences were obtained in the early 1970s by academic researchers using laborious methods based on two-dimensional chromatography. Following the development of dye-based sequencing methods with automated analysis, DNA sequencing has become easier and orders of magnitude faster.
DNA sequencing may be used to determine the sequence of
An electron gun (also called electron emitter) is an electrical component that produces an electron beam that has a precise kinetic energy and is most often used in television sets and computer displays which use cathode ray tube (CRT) technology, as well as in other instruments, such as electron microscopes and particle accelerators. Electron guns may be classified in several ways:
A direct current, electrostatic thermionic electron gun is formed from several parts: a hot cathode, which is heated to create a stream of electrons via thermionic emission, electrodes generating an electric field which focus the beam (such as a Wehnelt cylinder), and one or more anode electrodes which accelerate and further focus the electrons. A large voltage between the cathode and anode accelerates the electrons. A repulsive ring placed between them focuses the electrons onto a small spot on the anode at the expense of a lower extraction field strength on the cathode surface. Often at this spot is a hole so that the electrons that pass through the anode form a collimated beam and finally reach a second anode called a collector. This arrangement is similar to an Einzel lens.
An ion gun consists of a
Fashion dolls are dolls primarily designed to be dressed to reflect fashion trends. They are manufactured both as toys for children to play with and as collectibles for adult collectors. The dolls are usually modeled after teen girls or adult women, though child, male, and even some non-human variants exist. Contemporary fashion dolls are typically made of vinyl or another plastic.
The earliest fashion dolls were French bisque dolls from the mid-19th century. Barbie was released by the American toy-company Mattel in 1959, and was followed by many similar vinyl fashion dolls intended as children's toys. The size of the Barbie, 11.5 inches (290 mm) set the standard often used by other manufacturers. But fashion dolls have been made in many different sizes varying from 10.5 inches (270 mm) to 36 inches (900 mm).
Costumers and seamstresses use fashion dolls as a canvas for their work. Customizers repaint faces, reroot hair, or do other alterations to the dolls themselves. Many of these works are one-of-a-kind. These artists are usually not connected to the original manufacturers and sell their work to collectors.
The earliest bisque dolls from French companies were fashion dolls. These
A gun barrel is the tube, usually metal, through which a controlled explosion or rapid expansion of gases are released in order to propel a projectile out of the end at a high velocity.
The first guns were made in a time where metallurgy was not advanced enough to cast tubes able to withstand the explosive forces of early cannon, so the pipe (often actually built from staves of metal) needed to be braced periodically along its length, producing an appearance somewhat reminiscent of a storage barrel.
Another explanation, tied to etymology, states that many very first firearms barrels were in fact realized, during the 12th and 13th centuries, using small storage barrels with their usual metal rings reinforced by leather, hence the barrel name. In fact a set of old French words, some of them staying in modern French, were used as root words for various English terms related to firearms (and storage barrels). The old French gonne (pronounced by a French speaker it sounds approximately as gun does when pronounced by an English speaker) was a small barrel used on merchant and military ships. Likewise a baril was, as early as 1323 (used in Du Chevalier au barisel), and remains now, a big
A nightstand, alternatively night table or bedside table, is a small table or cabinet designed to stand beside a bed or elsewhere in a bedroom. It serves the role of a coffee table during nighttime hours, at a person's bedside.
Before indoor flushing toilets became commonplace, the main function of a nightstand was to contain a chamber pot. As a result, early nightstands were often small cabinets, sometimes fitted with a drawer, and usually containing an enclosed storage space below covered by one or more doors. Another term sometimes given to such cabinets was commode.
Modern nightstands are usually small bedside tables, often with a drawer. They are often used to support items that might be useful during the night, such as a lamp, alarm clock, mobile phone, reading matter, a glass of water, medication, or condoms.
French, Italian and Spanish antique nightstands usually have one drawer and an enclosed storage space with one door. They can be embellished with gold leaf finish, bronze or parquetry inlaid.
The first known use of the word nightstand was in 1892.
An organization (or organisation – see spelling differences) is a social entity that has a collective goal and is linked to an external environment. The word is derived from the Greek word organon, itself derived from the better-known word ergon which means "organ" – a compartment for a particular task.
There are a variety of legal types of organizations, including corporations, governments, non-governmental organizations, international organizations, armed forces, charities, not-for-profit corporations, partnerships, cooperatives, and universities. A hybrid organization is a body that operates in both the public sector and the private sector simultaneously, fulfilling public duties and developing commercial market activities.
In the social sciences, organizations are the object of analysis for a number of disciplines, such as sociology, economics, political science, psychology, management, and organizational communication. The broader analysis of organizations is commonly referred to as organizational structure, organizational studies, organizational behavior, or organization analysis. A number of different perspectives exist, some of which are compatible:
Sociology can be
A rosé (From French: rosé, also known as rosado in Spanish-speaking countries or rosato in Italy) is a type of wine that has some of the color typical of a red wine, but only enough to turn it pink. The pink color can range from a pale "onion"-skin orange to a vivid near-purple, depending on the grape varieties used and winemaking techniques. There are three major ways to produce rosé wine: skin contact, saignée and blending. Rosé wines can be made still, semi-sparkling or sparkling and with a wide range of sweetness levels from bone-dry Provençal rosé to sweet White Zinfandels and blushes. Rosé are made from a wide variety of grapes and can be found all across the globe.
When rosé wine is the primary product, it is produced with the skin contact method. Black-skinned grapes are crushed and the skins are allowed to remain in contact with the juice for a short period, typically one to three days. The must is then pressed, and the skins are discarded rather than left in contact throughout fermentation (as with red wine making). The longer that the skins are left in contact with the juice, the more intense the color of the final wine.
When a winemaker desires to impart more tannin and
A video game console is an interactive entertainment computer or customized computer system that produces a video display signal which can be used with a display device (a television, monitor, etc.) to display a video game. The term "video game console" is used to distinguish a machine designed for people to buy and use primarily for playing video games on a TV. As of 2007, it is estimated that video game consoles have made up 75% of the world's gaming market. They have been banned in China since June 2000.
Although the first computer games appeared in the 1950s, they were based around vector displays, not analog video. It was not until 1972 that Magnavox released the first home video game console which could be connected to a TV set—the Magnavox Odyssey, invented by Ralph H. Baer. The Odyssey was initially only moderately successful, and it was not until Atari's arcade game Pong popularized video games, that the public began to take more notice of the emerging industry. By the autumn of 1975 Magnavox, bowing to the popularity of Pong, cancelled the Odyssey and released a scaled down version that played only Pong and hockey, the Odyssey 100. A second, "higher end" console, the
Wheat (Triticum spp.) is a cereal grain, originally from the Levant region of the Near East and Ethiopian Highlands, but now cultivated worldwide. In 2010 world production of wheat was 651 million tons, making it the third most-produced cereal after maize (844 million tons) and rice (672 million tons). In 2009, world production of wheat was 682 million tons, making it the second most-produced cereal after maize (817 million tons), and with rice as close third (679 million tons).
This grain is grown on more land area than any other commercial crop and is the most important staple food for humans. World trade in wheat is greater than for all other crops combined. Globally, wheat is the leading source of vegetable protein in human food, having a higher protein content than either maize (corn) or rice, the other major cereals. In terms of total production tonnages used for food, it is currently second to rice as the main human food crop and ahead of maize, after allowing for maize's more extensive use in animal feeds.
Wheat was a key factor enabling the emergence of city-based societies at the start of civilization because it was one of the first crops that could be easily cultivated
The cheiroballistra (Greek) or manuballista (Latin), which translates in all its forms to 'hand ballista', was a late Roman siege engine. Designed by Hero of Alexandria around the year 100 and mostly composed of metal (the spring mechanism and the skeins), it fired bolts that were smaller than those in other forms of ballistae and generally made of metal. It was the next major improvement after the scorpio.
The name of the weapon implies that portable versions might also have existed, similar to crossbows.
Drawing is a form of visual art that makes use of any number of drawing instruments to mark a two-dimensional medium. Common instruments include graphite pencils, pen and ink, inked brushes, wax color pencils, crayons, charcoal, chalk, pastels, various kinds of erasers, markers, styluses, and various metals (such as silverpoint). An artist who practices or works in drawing may be called a draftsman or draughtsman.
A small amount of material is released onto the two dimensional medium, leaving a visible mark. The most common support for drawing is paper, although other materials, such as cardboard, plastic, leather, canvas, and board, may be used. Temporary drawings may be made on a blackboard or whiteboard or indeed almost anything. The medium has been a popular and fundamental means of public expression throughout human history. It is one of the simplest and most efficient means of communicating visual ideas. The relatively easy availability of basic drawing instruments makes drawing more universal than most other media.
Drawing is a form of visual expression and is one of the major forms within the visual arts. There are several categories of drawing, including cartooning.
A cantilever bridge is a bridge built using cantilevers, structures that project horizontally into space, supported on only one end. For small footbridges, the cantilevers may be simple beams; however, large cantilever bridges designed to handle road or rail traffic use trusses built from structural steel, or box girders built from prestressed concrete. The steel truss cantilever bridge was a major engineering breakthrough when first put into practice, as it can span distances of over 1,500 feet (460 m), and can be more easily constructed at difficult crossings by virtue of using little or no falsework.
Engineers in the nineteenth century understood that a bridge which was continuous across multiple supports would distribute the loads among them. This would result in lower stresses in the girder or truss and meant that longer spans could be built. Several nineteenth century engineers patented continuous bridges with hinge points mid-span. The use of a hinge in the multi-span system presented the advantages of a statically determinate system and of a bridge that could handle differential settlement of the foundations. Engineers could more easily calculate the forces and stresses
A condiment is an edible substance, such as sauce, added to food to impart a particular flavor, enhance its flavor, or in some cultures, to complement the dish. The term originally described pickled or preserved foods, but has shifted meaning over time. Many condiments are available packaged in single-serving sachets (packets), like mustard or ketchup, particularly when supplied with take-out or fast-food meals. Condiments are usually applied by the diner. Condiments are sometimes added prior to serving, for example a sandwich made with ketchup or mustard. Some condiments are used during cooking to add flavor or texture to the food; barbecue sauce, teriyaki sauce, soy sauce, marmite are examples.
In cultures around the world, dessert or pudding is a course that typically comes at the end of a meal, usually consisting of sweet food. The word comes from the French language as dessert and this from Old French desservir, "to clear the table" and "to serve." The etymology is linked to the medieval practice of a two part meal. During the first, nobles (at a high) and servants (separate) would eat together in the same room. During the second - dessert, the noble family would retreat in separate private quarters for an intimate part of the meal without servants. The food consumed during dessert included but was not limited to sweets.
Common Western desserts include cakes, cookies, biscuits, gelatin dessert, pastries, ice cream, pies, pudding, and candies. Fruit may also be eaten with or as a dessert. Variations of desserts can be found all around the world, such as in Russia, where breakfast foods such as bliny, oladi, and syrniki served with honey and jam are also popular as desserts. Desserts are sometimes eaten with a dessert spoon, intermediate in size between a teaspoon and a tablespoon, or a "fruit spoon".
The first desserts were candies, made from raw honeycomb and dried
A howitzer is a type of artillery piece characterized by a relatively short barrel and the use of comparatively small propellant charges to propel projectiles at relatively high trajectories, with a steep angle of descent. Until fairly recently, about the end of the Second World War, such weapons were characterized by a barrel length 15 to 25 times the caliber of the gun.
In the taxonomies of artillery pieces used by European (and European-style) armies in the eighteenth, 19th, and 20th centuries, the howitzer stood between the "gun" (characterized by a longer barrel, larger propelling charges, smaller shells, higher velocities, and flatter trajectories) and the "mortar" (which was meant to fire at even higher angles of ascent and descent). Howitzers, like other artillery pieces, are usually organized in groups called batteries.
The English word howitzer originates ultimately from the Czech word houfnice. Czech houfnice is derived, through the addition of the suffix -nice, from the word houf, "crowd", suggesting the cannon's use against massed enemies, and houf is in turn a borrowing from the Middle High German word Hūfe or Houfe (modern German Haufen), meaning "heap". Haufen,
The movie camera is a type of photographic camera which takes a rapid sequence of photographs on strips of film which was very popular for private use in the last century until its successor, the video camera, replaced it. Many of these cameras today have become collectors items and there is a small but well organized group of fans of these devices who still use and maintain these cameras as hobby or a special interest, even if they went out of productions a long time ago. For professional purposes however, movie cameras are used and produced today, especially for the production of full feature movies. In contrast to a still camera, which captures a single snapshot at a time, the movie camera takes a series of images; "frame". This is accomplished through an intermittent mechanism. The frames are later played back in a movie projector at a specific speed, called the "frame rate" (number of frames per second). While viewing, a person's eyes and brain merge the separate pictures together to create the illusion of motion.
One of the first patented motion-picture film cameras was designed by Louis Le Prince in 1888. It still exists with the National Media Museum, England. Le Prince
A reflecting telescope (also called a reflector) is an optical telescope which uses a single or combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century as an alternative to the refracting telescope which, at that time, was a design that suffered from severe chromatic aberration. Although reflecting telescopes produce other types of optical aberrations, it is a design that allows for very large diameter objectives. Almost all of the major telescopes used in astronomy research are reflectors. Reflecting telescopes come in many design variations and may employ extra optical elements to improve image quality or place the image in a mechanically advantageous position. Since reflecting telescopes use mirrors, the design is sometimes referred to as a "catoptric" telescope.
The idea that curved mirrors behave like lenses dates back at least to Alhazen's 11th century treatise on optics, works that had been widely disseminated in Latin translations in early modern Europe. Soon after the invention of the refracting telescope, Galileo, Giovanni Francesco Sagredo, and others, spurred on by their knowledge of the principles of
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing, entertainment, public safety, and warfare. Historically, a "ship" was a vessel with sails rigged in a specific manner.
Ships and boats have developed alongside mankind. In armed conflict and in daily life they have become an integral part of modern commercial and military systems. Fishing boats are used by millions of fishermen throughout the world. Military forces operate vessels for combat and to transport and support forces ashore. Commercial vessels, nearly 35,000 in number, carried 7.4 billion tons of cargo in 2007.
Ships were key in history's great explorations and scientific and technological development. Navigators such as Zheng He spread such inventions as the compass and gunpowder. Ships have been used for such purposes as colonization and the slave trade, and have served scientific, cultural, and humanitarian needs. After the 16th century, new crops that had come from and to the
Agriculture also called farming or husbandry is the cultivation of animals, plants, fungi, and other life forms for food, fiber, biofuel and other products used to sustain life. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the development of civilization. The study of agriculture is known as agricultural science. Agriculture generally speaking refers to human activities, although it is also observed in certain species of ant and termite. The word agriculture is the English adaptation of Latin agricultūra, from ager, "a field", and cultūra, "cultivation" in the strict sense of "tillage of the soil". Thus, a literal reading of the word yields "tillage of fields".
The history of agriculture dates back thousands of years, and its development has been driven and defined by greatly different climates, cultures, and technologies. However, all farming generally relies on techniques to expand and maintain the lands that are suitable for raising domesticated species. For plants, this usually requires some form of irrigation, although there are methods of dryland farming; pastoral
Ammunition is a generic term derived from the French language la munition which embraced all material used for war (from the Latin munire, to provide), but which in time came to refer specifically to gunpowder and artillery. The collective term for all types of ammunition is munitions. In the widest sense of the word it covers anything that can be used in combat that includes bombs, missiles, warheads, and mines (landmines, naval mines, and anti-personnel mines)—that munitions factories manufacture. The purpose of ammunition is predominantly to project force against a selected target. However, the nature of ammunition use also includes delivery or combat supporting munitions such as pyrotechnic or incendiary compounds. Since the design of the cartridge, the meaning has been transferred to the assembly of a projectile and its propellant in a single package.
The subject of ammunition is a complex one which covers application of fire to targets, general use of weapons by personnel, explosives and propellants, cartridge systems, high explosive projectiles (HE), warheads, shaped charge forms of attack on armour and aircraft, carrier projectiles, fuzes, mortar ammunition, small arms
Auto racing (also known as automobile racing or car racing) is a motorsport involving the racing of cars for competition.
Racing began soon after the construction of the first successful gasoline-fueled automobiles. The first organized race was on April 28, 1887 by the chief editor of Paris publication Le Vélocipède, Monsieur Fossier. It ran 2 kilometres (1.2 mi) from Neuilly Bridge to the Bois de Boulogne. It was won by Georges Bouton of the De Dion-Bouton Company, in a car he had constructed with Albert, the Comte de Dion, but as he was the only competitor to show up it is rather difficult to call it a race.
On July 23, 1894, the Parisian magazine Le Petit Journal organized what is considered to be the world's first motoring competition from Paris to Rouen. Sporting events were a tried and tested form of publicity stunt and circulation booster. Pierre Giffard, the paper's editor, promoted it as a Competition for Horseless Carriages (Concours des Voitures sans Chevaux) that were not dangerous, easy to drive, and cheap during the journey. Thus it blurred the distinctions between a reliability trial, a general event and a race. One hundred two competitors paid the 10 franc entrance
A bead is a small, decorative object that is usually pierced for threading or stringing. Beads range in size from under 1 millimetre (0.039 in) to over 1 centimetre (0.39 in) in diameter. A pair of beads made from Nassarius sea snail shells, approximately 100,000 years old, are thought to be the earliest known examples of jewellery. Beadwork is the art or craft of making things with beads. Beads can be woven together with specialized thread, strung onto thread or soft, flexible wire, or adhered to a surface (e.g. fabric, clay).
Beads may be divided into several types of overlapping categories, based on different criteria such as component materials, manufacturing process, place or period of origin, surface patterning, or general shape. In some cases, such as millefiori and cloisonné beads, multiple categories may overlap in an inseparably interdependent fashion.
Beads can be made of many types of materials. The earliest beads were made of convenient natural materials; when found, these could be readily drilled and shaped. As human technology became capable of obtaining or working with more difficult natural materials, those were added to the range of available substances. The same
A beer bottle is a bottle made to contain beer, usually made of glass and come in various sizes, shapes and colours. Dark amber or brown glass greatly reduces UV light from spoiling the beer. However, lighter colored bottles are often used for marketing reasons.
The common alternative to glass bottles are beverage cans and aluminum bottles.
Bottling lines are production lines that fill beer into bottles on a large scale.
This typically involves drawing beer from a holding tank and filling it into bottles in a filling machine (filler), which are then capped, labeled and packed into cases or cartons. Many smaller breweries send their bulk beer to large facilities for contract bottling—though some will bottle by hand.
The first step in bottling beer is depalletising, where the empty bottles are removed from the original pallet packaging delivered from the manufacturer, so that individual bottles may be handled. The bottles may then be rinsed with filtered water or air, and may have carbon dioxide injected into them in attempt to reduce the level of oxygen within the bottle. The bottle then enters a "filler" which fills the bottle with beer and may also inject a small amount of inert
A breech-loading weapon is a firearm in which the cartridge or shell is inserted or loaded into a chamber integral to the rear portion of a barrel.
Modern mass production firearms are breech-loading (though mortars are generally muzzle-loaded). Early firearms were almost entirely muzzle-loading. The main advantage of breech-loading is a reduction in reloading time - it is much quicker to load the projectile and charge into the breech than to force them down a long tube, especially when the tube has spiral ridges from rifling. In field artillery, breech loading allows the crew to reload the weapon without exposing themselves to enemy fire or repositioning the piece (as was required for muzzle-loaded weapons) and allows turrets and emplacements to be smaller (since breech loaded weapons do not need to be retracted for loading).
Although breech-loading weapons were developed as far back as the late 14th century in Burgundy, breech-loading became more successful with improvements in precision engineering and machining in the 19th century.
The main challenge for developers of breech-loading weapons was sealing the breech. This was eventually solved for smaller weapons by the development
A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle. Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed, the material used to make it and the funds available to build it.
The Oxford English Dictionary traces the origin of the word bridge to an Old English word brycg, of the same meaning, derived from the hypothetical Proto-Germanic root brugjō. There are cognates in other Germanic languages.
The first bridges were made by nature itself — as simple as a log fallen across a stream or stones in the river. The first bridges made by humans were probably spans of cut wooden logs or planks and eventually stones, using a simple support and crossbeam arrangement. Some early Americans used trees or bamboo poles to cross small caverns or wells to get from one place to another. A common form of lashing sticks, logs, and deciduous branches together involved the use of long reeds or other harvested fibers woven together to form a connective rope capable of binding and holding together the materials used in early bridges.
A bullet is a projectile propelled by a firearm, sling, or air gun. Bullets do not normally contain explosives, but damage the intended target by impact and penetration. The word "bullet" is sometimes colloquially used to refer to ammunition in general, or to a cartridge, which is a combination of the bullet, case/shell, powder, and primer. This incorrect use of 'bullet' when 'cartridge' is intended, leads to confusion when the components of a cartridge are discussed or intended. See the reference section for more detail.
The history of bullets far predates the history of firearms. Originally, bullets were metallic, stone or purpose-made clay balls used as sling ammunition, as weapons and for hunting. Eventually as firearms were developed, these same items were placed in front of a propellant charge of gun powder at the end of a closed tube. As firearms became more technologically advanced, from 1500 to 1800, bullets changed very little. They remained simple round (spherical) lead balls, called rounds, differing only in their diameter.
The development of the hand culverin and matchlock arquebus brought about the use of cast lead balls as projectiles. "Bullet" is derived from the
Stockfish is unsalted fish, especially cod, dried by cold air and wind on wooden racks on the foreshore, called "hjell". The drying of food is the world's oldest known preservation method, and dried fish has a storage life of several years. The method is cheap and effective in suitable climates; the work can be done by the fisherman and family, and the resulting product is easily transported to market.
Cod is the most common fish used in stockfish production, while other whitefish, such as pollock, haddock, ling and tusk, are used to a lesser degree.
Over the centuries, several variants of dried fish have evolved. The Stockfish (fresh dried (not salted)) category is often wrongly mixed with the Clipfish or salt cod category, where the fish is salted before drying. After 2–3 weeks in salt the fish has saltmatured, and is transformed from wet salted fish to Clipfish through a drying process. The salted fish was earlier dried on rocks (clips) on the foreshore. The production method of Clipfish (or Bacalhau in Portuguese) was developed by the Portuguese who first mined salt near the brackish water of Aveiro, and brought it to Newfoundland where cod was available in massive quantities.
A covered bridge is a timber-truss bridge with a roof and siding which, in most covered bridges, create an almost complete enclosure. The purpose of the covering is to protect the wooden structural members from the weather. Uncovered wooden bridges have a life span of only 10 to 15 years because of the effects of rain and sun.
Bridges having covers for reasons other than protecting wood trusses, such are for protecting pedestrians, are also sometimes called covered bridges.
Early timber covered bridges consisted of horizontal beams laid on top of piles driven into the riverbed. The problem is that the length between spans is limited by the maximum length of each beam. The development of the timber truss allowed bridges to span greater distances than those with beam-only structures or of arch structures, whether of stone, masonry, or timber.
Early European truss bridges used on King post and Queen post configurations. Some early German bridges included diagonal panel bracing in trusses with parallel top and bottom chords.
Possibly the first covered bridge in the United States was built in Philadelphia in the early 1800s. The investors asked to have it covered in the hopes of
Food preservation is the process of treating and handling food to stop or slow down Food spoilage, loss of quality, edibility or nutritional value and thus allow for longer food storage.
Preservation usually involves preventing the growth of bacteria, fungi (such as yeasts), and other micro-organisms (although some methods work by introducing benign bacteria, or fungi to the food), as well as retarding the oxidation of fats which cause rancidity. Food preservation can also include processes which inhibit visual deterioration, such as the enzymatic browning reaction in apples after they are cut, which can occur during food preparation.
Many processes designed to preserve food will involve a number of food preservation methods. Preserving fruit by turning it into jam, for example, involves boiling (to reduce the fruit’s moisture content and to kill bacteria, yeasts, etc.), sugaring (to prevent their re-growth) and sealing within an airtight jar (to prevent recontamination). There are many traditional methods of preserving food that limit the energy inputs and reduce carbon footprint.
Maintaining or creating nutritional value, texture and flavour is an important aspect of food
In general terms, an information appliance or information device is any machine or device that is usable for the purposes of computing, telecommunicating, reproducing, and presenting encoded information in myriad forms and applications. The common technical usage of "information appliance" (IA) is more specific — i.e., an appliance that is specially designed to perform a specific user-friendly function —such as playing music, photography, or editing text.
Typical examples are smartphones and personal digital assistants (PDAs). Information appliances partially overlap in definition with, or are sometimes referred to as smart devices, embedded systems, mobile devices or wireless devices.
The term information appliance was coined by Jef Raskin around 1979. As later explained by Donald Norman in his influential The Invisible Computer, the main characteristics of IA, as opposed to any normal computer, were:
This definition of IA was different from today's. Jef Raskin initially tried to include such features in the Apple Macintosh, which he designed, but eventually the project went a quite different way. For a short while during the mid- and late 1980s, there were a few models of simple
A microscope (from the Ancient Greek: μικρός, mikrós, "small" and σκοπεῖν, skopeîn, "to look" or "see") is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy. Microscopic means invisible to the eye unless aided by a microscope.
There are many types of microscopes, the most common and first to be invented is the optical microscope which uses light to image the sample. Other major types of microscopes are the electron microscope (both the transmission electron microscope and the scanning electron microscope) and the various types of scanning probe microscope.
The first microscope to be developed was the optical microscope, although the original inventor is not easy to identify. An early microscope was made in 1590 in Middelburg, Netherlands. Two eyeglass makers are variously given credit: Hans Lippershey (who developed an early telescope) and Zacharias Janssen. Giovanni Faber coined the name microscope for Galileo Galilei's compound microscope in 1625 (Galileo had called it the "occhiolino" or "little eye").
The first detailed account of the interior construction of living
The naginata (なぎなた, 薙刀) is one of several varieties of traditionally made Japanese swords (nihonto) in the form of a pole weapon. Naginata were originally used by the samurai class of feudal Japan, and naginata were also used by ashigaru (foot soldiers) and sōhei (warrior monks).
A naginata consists of a wooden shaft with a curved blade on the end, it is similar to the Chinese guan dao or the European glaive. Naginata often have a sword-like hand guard (tsuba) between the blade and shaft when mounted in a koshirae. The 30 cm to 60 cm long naginata blade is forged in the same manner as traditional Japanese swords. The blade has a long tang (nakago) which is inserted in the shaft (nagaye or ebu), the blade is removable and is secured by means of a wood peg (mekugi) that passes through a hole (mekugi-ana) in both the nakago and the nagaye (ebu). The nagaye (ebu) ranges from 120 cm to 240 cm in length and is oval shaped. The area of the nagaye (ebu) were the naginata nakago sits is the tachiuchi or tachiuke. The tachiuchi (tachiuke) would be re-enforced with metal rings (naginata dogane or semegane), and or metal sleeves (sakawa) and wrapped with cord (san-dan maki), the end of the
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant. The formation of the seed completes the process of reproduction in seed plants (started with the development of flowers and pollination), with the embryo developed from the zygote and the seed coat from the integuments of the ovule.
Seeds have been an important development in the reproduction and spread of flowering plants, relative to more primitive plants such as mosses, ferns and liverworts, which do not have seeds and use other means to propagate themselves. This can be seen by the success of seed plants (both gymnosperms and angiosperms) in dominating biological niches on land, from forests to grasslands both in hot and cold climates.
The term "seed" also has a general meaning that antedates the above — anything that can be sown, e.g. "seed" potatoes, "seeds" of corn or sunflower "seeds". In the case of sunflower and corn "seeds", what is sown is the seed enclosed in a shell or husk, whereas the potato is a tuber.
TRIZ ( /ˈtriːz/; Russian: теория решения изобретательских задач, teoriya resheniya izobretatelskikh zadatch) is "a problem-solving, analysis and forecasting tool derived from the study of patterns of invention in the global patent literature". It was developed by the Soviet inventor and science fiction author Genrich Altshuller and his colleagues, beginning in 1946. In English the name is typically rendered as "the theory of inventive problem solving", and occasionally goes by the English acronym TIPS.
Following Altshuller's insight, the theory developed on a foundation of extensive research covering hundreds of thousands of inventions across many different fields to produce a theory which defines generalisable patterns in the nature of inventive solutions and the distinguishing characteristics of the problems that these inventions have overcome.
An important part of the theory has been devoted to revealing patterns of evolution and one of the objectives which has been pursued by leading practitioners of TRIZ has been the development of an algorithmic approach to the invention of new systems, and the refinement of existing ones.
The theory includes a practical methodology, tool
A baseball field, also called a ball field or a baseball diamond, is the field upon which the game of baseball is played. The term is also used as a metonym for baseball park.
The starting point for much of the action on the field is home plate, which is a five-sided slab of whitened rubber, 17-inches square with two of the corners removed so that one edge is 17 inches long, two adjacent sides are 8½ inches and the remaining two sides are 12 inches and set at an angle to make a point. Adjacent to each of the two parallel 8½-inch sides is a batter's box. The point of home plate where the two 12-inch sides meet at right angles, is at one corner of a ninety-foot square. The other three corners of the square, in counterclockwise order from home plate, are called first base, second base, and third base. Three canvas bags fifteen inches (38 cm) square mark the three bases. These three bags along with home plate form the four bases at the corners of the infield.
All the bases, including home plate, lie entirely within fair territory. Thus, any batted ball that touches those bases must necessarily be in fair territory. While the first and third base bags are placed so that they lie inside
A billiard ball is a small, hard ball used in cue sports, such as carom billiards, pool, and snooker. The number, type, diameter, color, and pattern of the balls differ depending upon the specific game being played. Various particular ball properties such as hardness, friction coefficient and resilience are very important to the finer points of gameplay.
The earliest balls were made of wood and then later clay (the latter remaining in use well into the 20th century). Although affordable ox-bone balls were in common use in Europe, ivory was favored since at least 1627 until the early 20th century; the earliest known written reference to ivory billiard balls is in the 1588 inventory of the Duke of Norfolk. By the mid-19th century, elephants were being slaughtered for their ivory at an alarming rate, just to keep up with the demand for high-end billiard balls – no more than eight balls could be made from a single elephant's tusks. The billiard industry realized that the supply of elephants (their primary source of ivory) was endangered, as well as dangerous to obtain (the latter an issue of notable public concern at the turn of the 19th century). Inventors were challenged to come up
Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container. Canning provides a typical shelf life ranging from one to five years, although under specific circumstances a freeze-dried canned product, such as canned, dried lentils, can last as long as 30 years in an edible state. In 1795 the French military offered a cash prize of 12,000 francs for a new method to preserve food. Nicolas Appert suggested canning and the process was first proven in 1806 in test with the French navy and the prize awarded in 1809 or 1810. The packaging prevents microorganisms from entering and proliferating inside.
To prevent the food from being spoiled before and during containment, a number of methods are used: pasteurisation, boiling (and other applications of high temperature over a period of time), refrigeration, freezing, drying, vacuum treatment, antimicrobial agents that are natural to the recipe of the foods being preserved, a sufficient dose of ionizing radiation, submersion in a strong saline solution, acid, base, osmotically extreme (for example very sugary) or other microbially-challenging environments.
Other than sterilization, no
A chain gun is a type of machine gun or autocannon that uses an external source of power, rather than diverting energy from the cartridge, to cycle the weapon, and does so via a continuous loop of chain similar to that used on a motorcycle or bicycle. "Chain gun" is a registered trademark of Alliant Techsystems Inc. for a chain-powered weapon.
Reliability and controllability are the advantages of chain-driven weapons over their recoil-actuated counterparts. Instead of depending upon the sometimes unreliable firing of a cartridge to power the cycle of action, a chain gun uses an electric motor to drive the chain that moves in a rectangular circuit via four sprockets that apply tension to it. One link of the chain is connected to the bolt assembly, moving it back and forth to load, fire, extract, and eject cartridges.
As with all guns that do not use energy from a fired cartridge to load the next round, a misfired round does not stop the functioning of the weapon; it is simply ejected.
During each full cycle of four periods, two periods (passage along the "long" sides of the rectangle) control the time the bolt takes to drive forward and load a round into the chamber, and how quickly
A classroom is a room in which teaching or learning activities can take place. Classrooms are found in educational institutions of all kinds, including public and private schools, home schools, corporations, and religious and humanitarian organizations. The classroom attempts to provide a safe space where learning can take place uninterrupted by other distractions.
Most classrooms have a large writing surface where the instructor or students can share notes with other members of the class. Traditionally, this was in the form of a blackboard but these are becoming less common in well-equipped schools, and are replaced by flipcharts, whiteboards and interactive whiteboards. Many classrooms also have TVs, maps, charts, Pencils, books, monographs and LCD projectors for presenting information and images from a computer.
The layout, design and decor of the classroom has a significant effect upon the quality of education. Attention to the acoustics and colour scheme may reduce distractions and aid concentration. The lighting and furniture likewise influence study and learning.
For lessons that require specific resources or a vocational approach different types of classrooms both indoors
An electric organizer is a small calculator-sized computer, often with an in-built diary application but few other functions such as an address book and calendar. It normally has a small alphanumeric keypad and an LCD screen of one, two or three lines.
A glyph ( /ˈɡlɪf/) is an element of writing: an individual mark on a written medium that contributes to the meaning of what is written.
For example, in most languages written in any variety of the Latin alphabet the dot on a lower-case "i" is not a glyph because it does not convey any distinction, and an i in which the dot has been accidentally omitted is still likely to be read as an "i". In Turkish however, it is a glyph, because that language has two distinct versions of the letter "i", with and without a dot.
In Japanese syllabaries, a number of the characters are made up of more than one separate mark, but in general these separate marks are not glyphs because they have no meaning by themselves. However, in some cases, additional marks fulfill the role of diacritics, to differentiate distinct characters. Such additional marks constitute glyphs.
In general, a diacritic is a glyph, even if (like a cedilla in Spanish, the ogonek in several languages or the stroke on a Polish L) it is "joined up" with the rest of the character.
Some characters, such as ⟨æ⟩ in Icelandic and the ⟨ß⟩ in German, would probably be regarded as glyphs: they were originally ligatures but over time have
An optical phenomenon is any observable event that results from the interaction of light and matter. See also list of optical topics and optics. A mirage is an example of an optical phenomenon.
Common optical phenomena are often due to the interaction of light from the sun or moon with the atmosphere, clouds, water, dust, and other particulates. One common example is the rainbow, when light from the sun is reflected and refracted by water droplets. Some, such as the green ray, are so rare they are sometimes thought to be mythical. Others, such as Fata Morganas, are commonplace in favored locations.
Other phenomena are simply interesting aspects of optics, or optical effects. The colors generated by a prism are often shown in classrooms, for instance.
Optical phenomena include those arising from the optical properties of the atmosphere; the rest of nature (other phenomena); of objects, whether natural or human-made (optical effects); and of our eyes (Entoptic phenomena). Also listed here are unexplained phenomena that could have an optical explanation and "optical illusions" for which optical explanations have been excluded.
There are many phenomena that result from either the
A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning over it with a focused beam of electrons. The electrons interact with electrons in the sample, producing various signals that can be detected and that contain information about the sample's surface topography and composition. The electron beam is generally scanned in a raster scan pattern, and the beam's position is combined with the detected signal to produce an image.SEM can achieve resolution better than 1 nanometer; specimens can be observed in high vacuum, low vacuum and in Environmental SEM specimens can be observed in wet condition.
The first SEM image was obtained by Max Knoll, who in 1935 obtained an image of silicon steel showing electron channeling contrast. Further pioneering work on the physical principles of the SEM and beam specimen interactions was performed by Manfred von Ardenne in 1937, who produced a British patent but never made a practical instrument. The SEM was further developed by Professor Sir Charles Oatley and his postgraduate student Gary Stewart and was first marketed in 1965 by the Cambridge Scientific Instrument Company as the
A trail (also track, byway) is a path with a rough beaten or dirt/stone surface used for travel. Trails may be for use only by walkers and in some places are the main access route to remote settlements. Some trails can also be used for hiking, cycling, or cross-country skiing and less often for moving cattle herds and other livestock.
Trail often denotes a hiking trail. Historically the term was used for a route into or through wild territory used by emigrants (e.g. the Oregon Trail). In the early years of the 20th century the term auto trail was used for a marked highway route, and trail is now also used to designate routes, including highway routes, designated for tourist interest (e.g. National Historic Trails, the Cabot Trail and Quilt Trail). The term trail has also been used by developers and urban planners for a variety of modern paved roads, highways, and boulevards. A particularly unusual use of the term is in the province of Alberta, Canada, which has multi-lane freeways called "trails".
In Australia, the term track can be used interchangeably with trail, and can refer to anything from a dirt road to an unpaved pedestrian path. The term trail gained popularity during
Chunking, in psychology, is a phenomenon whereby individuals group responses when performing a memory task. Tests where individuals can demonstrate "chunking" commonly include serial and free recall tasks. All three tasks require the individual to reproduce items that he or she had previously been instructed to study. Test items generally include words, syllables, digits/numbers, or lists of letters. Presumably, individuals that exhibit the "chunking" process in their responses are forming clusters of responses based on the items' semantic relatedness or perceptual features. The chunks are often meaningful to the participant. It is believed that the assimilation of different items according to their properties occurs due to individuals creating higher order cognitive representations of the items on the list that are more easily remembered as a group than as individual items, themselves. Representations of these groupings are highly subjective, as they depend critically on the individual's perception of the features of the items and the individual’s semantic network. The size of the chunks generally range anywhere from two to six items, but differs based on language and culture. For
A clay court is one of the four different types of tennis court. Clay courts are made of crushed shale, stone or brick. The red clay is slower than the green, or Har-Tru "American" clay. The French Open uses clay courts, making it unique among the Grand Slam tournaments.
Clay courts are more common in Continental Europe and Latin America than in the United States, Canada or Britain. In the United States, courts made of green clay, also known as "rubico", are often called "clay", but are not made of the same clay used in most European and Latin American countries. Although cheaper to construct than other types of tennis courts, the maintenance costs of clay are high as the surface must be rolled to preserve flatness. The water content must also be balanced; green courts are often sloped in order to allow water run-off.
Clay courts favor the "full western grip" for more topspin. Clay courters generally play in a semi circle about 1.5 to 3 metres behind the baseline.
Clay courts are considered "slow", because the balls bounce relatively high and more slowly, making it more difficult for a player to hit an unreturnable shot. Points are usually longer as there are fewer winners.
Enduro is a form of motorcycle sport run on courses that are predominantly off-road. Enduro consists of many different obstacles and challenges. The main type of enduro event, and the format to which the World Enduro Championship is run, is a time-card enduro, whereby a number of stages are raced in a time trial against the clock.
In a traditional time-keeping enduro, riders leave together in groups or rows, and each row starts at a certain minute. The object of the event is to arrive at pre-defined locations according to a strict schedule. Early or late arrivals result in the riders' scores being penalized. Throughout a day there will also be allocated periods for refuelling and servicing the machine. Penalties apply for not meeting defined times or for outside-assistance when not permitted.
A world championship course must be at least 200 km and a maximum of 30% of its length can be on asphalt roads. American Motorcycle Association (AMA) rules are different with respect to course length and other variables (i.e. average speed, terrain type, etc.). The rules of the regional sanctioning body can also affect the rules for a particular enduro course.
Casual observers often confuse
Enzymes ( /ˈɛnzaɪmz/) are biological molecules that catalyze (i.e., increase the rates of) chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates sufficient for life. Since enzymes are selective for their substrates and speed up only a few reactions from among many possibilities, the set of enzymes made in a cell determines which metabolic pathways occur in that cell.
Like all catalysts, enzymes work by lowering the activation energy (Ea) for a reaction, thus dramatically increasing the rate of the reaction. As a result, products are formed faster and reactions reach their equilibrium state more rapidly. Most enzyme reaction rates are millions of times faster than those of comparable un-catalyzed reactions. As with all catalysts, enzymes are not consumed by the reactions they catalyze, nor do they alter the equilibrium of these reactions. However, enzymes do differ from most other catalysts in that they are highly specific for their substrates. Enzymes are known to catalyze about
A flowchart is a type of diagram that represents an algorithm or process, showing the steps as boxes of various kinds, and their order by connecting these with arrows. This diagrammatic representation can give a step-by-step solution to a given problem. Process operations are represented in these boxes, and arrows connecting them represent flow of control. Data flows are not typically represented in a flowchart, in contrast with data flow diagrams; rather, they are implied by the sequencing of operations. Flowcharts are used in analyzing, designing, documenting or managing a process or program in various fields.
A flowchart is a picture of the separate steps of a process in sequential order. This is a generic tool that can be adapted for a wide variety of purposes. Flowchart are being used:
Elements that may be included are: sequence of actions, materials or services entering or leaving the process (inputs and outputs), decisions that must be made, people who become involved, time involved at each step and/or process measurements. The process described can be anything: a manufacturing process, an administrative or service process, a project plan.
Flowcharts are used in designing
In music, a fugue ( /ˈfjuːɡ/ FEWG) is a compositional technique (in classical music) in two or more voices, built on a subject (theme) that is introduced at the beginning in imitation (repetition at different pitches) and recurs frequently in the course of the composition.
The English term fugue originated in the 16th century and is derived from the French word fugue or the Italian fuga. This in turn comes from Latin, also fuga, which is itself related to both fugere ('to flee') and fugare ('to chase'). The adjectival form is fugal. Variants include fughetta (literally, 'a small fugue') and fugato (a passage in fugal style within another work that is not a fugue).
A fugue usually has three sections: an exposition, a development, and a recapitulation containing the return of the subject in the fugue's tonic key, though not all fugues have a recapitulation. In the Middle Ages, the term was widely used to denote any works in canonic style; by the Renaissance, it had come to denote specifically imitative works. Since the 17th century, the term fugue has described what is commonly regarded as the most fully developed procedure of imitative counterpoint.
Most fugues open with a short
Humans (Homo sapiens) are primates of the family Hominidae, and the only living species of the genus Homo. They originated in Africa, where they reached anatomical modernity about 200,000 years ago and began to exhibit full behavioral modernity around 50,000 years ago.
The human lineage diverged from the last common ancestor with its closest living relative, the chimpanzee, some five million years ago, evolving into the Australopithecines and eventually the genus Homo. The first Homo species to move out of Africa was Homo erectus, the African variety of which, together with Homo heidelbergensis, is considered to be the immediate ancestor of modern humans. Homo sapiens proceeded to colonize the continents, arriving in Eurasia 125,000-60,000 years ago, Australia around 40,000 years ago, the Americas around 15,000 years ago, and remote islands such as Hawaii, Easter Island, Madagascar, and New Zealand between the years AD 300 and 1280.
As early as 12,000 years ago, humans began to practice sedentary agriculture, domesticating plants and animals which allowed for the growth of civilization. Humans subsequently established various forms of government, religion, and culture
Loyalty programs are structured marketing efforts that reward, and therefore encourage, loyal buying behavior — behavior which is potentially beneficial to the firm.
In marketing generally and in retailing more specifically, a loyalty card, rewards card, points card, advantage card, or club card is a plastic or paper card, visually similar to a credit card or debit card, that identifies the card holder as a member in a loyalty program. Loyalty cards are a system of the loyalty business model. In the United Kingdom it is typically called a loyalty card, in Canada a rewards card or a points card, and in the United States either a discount card, a club card or a rewards card. Cards typically have a barcode or magstripe that can be easily scanned, and some are even chip cards. Small keyring cards (also known as keytags) which serve as key fobs are often used for convenience in carrying and ease of access.
By presenting the card, the purchaser is typically entitled to either a discount on the current purchase, or an allotment of points that can be used for future purchases. Hence, the card is the visible means of implementing a type of what economists call a two-part tariff.
Pickling, also known as brining or corning, is the process of preserving food by anaerobic fermentation in brine to produce lactic acid, or marinating and storing it in an acid solution, usually vinegar (acetic acid). The resulting food is called a pickle. This procedure gives the food a salty or sour taste. In South Asia, edible oils are used as the pickling medium with vinegar.
Another distinguishing characteristic is a pH less than 4.6, which is sufficient to kill most bacteria. Pickling can preserve perishable foods for months. Antimicrobial herbs and spices, such as mustard seed, garlic, cinnamon or cloves, are often added. If the food contains sufficient moisture, a pickling brine may be produced simply by adding dry salt. For example, sauerkraut and Korean kimchi are produced by salting the vegetables to draw out excess water. Natural fermentation at room temperature, by lactic acid bacteria, produces the required acidity. Other pickles are made by placing vegetables in vinegar. Unlike the canning process, pickling (which includes fermentation) does not require that the food be completely sterile before it is sealed. The acidity or salinity of the solution, the temperature
The demi-culverin was a medium cannon similar to but slightly larger than a saker and smaller than a regular culverin developed in the late 16th century. Barrels of demi-culverins were typically about 11 feet (3.4 m) long, had a calibre of 4 inches (10 cm) and could weigh up to 3,400 pounds (1,500 kg). It required 6 pounds (2.7 kg) of black powder to fire an 8-pound (3.6 kg) round shot (though there were heavier variants firing 9-pound (4.1 kg) or 10-pound (4.5 kg) round shot). The demi-culverin had an effective range of 1,800 feet (550 m).
Demi-culverins were valued by generals for their range, accuracy and effectiveness. They were often used in sieges for wall and building demolition.
Landcare Research (Māori: Manaaki Whenua) is one of New Zealand's Crown Research Institutes. The focus of the research at this company is the environment, biodiversity, and sustainability.
Landcare Research was originally part of the Department of Scientific and Industrial Research (DSIR), but was established as an independent organisation when the Crown Research Institutes were created in 1992. As part of that process, it was semi-commercialised, and now operates as a government-owned company rather than as a government department. The commercialisation has led to greater emphasis on financial viability, and Landcare Research is employed by various private groups to provide advice and information.
The main site is in Lincoln, near Christchurch. There are also other sites at Auckland on the Tamaki campus of Auckland University, Hamilton, Gisborne, Havelock North, Palmerston North, Wellington, Nelson, Alexandra, and Dunedin.
Landcare Research holds several collections of organisms that are of significant national importance to New Zealand. Detailed information on all the specimens can be found though the Systematics Collections Data (SCD) website: http://scd.landcareresearch.co.nz/
Measurement is the process or the result of determining the ratio of a physical quantity, such as a length, time, temperature etc., to a unit of measurement, such as the meter, second or degree Celsius. The science of measurement is called metrology.
The English word measurement originates from the Latin mēnsūra and the verb metiri through the Middle French mesure.
With the exception of a few seemingly fundamental quantum constants, units of measurement are essentially arbitrary; in other words, people make them up and then agree to use them. Nothing inherent in nature dictates that an inch has to be a certain length, or that a mile is a better measure of distance than a kilometre. Over the course of human history, however, first for convenience and then for necessity, standards of measurement evolved so that communities would have certain common benchmarks. Laws regulating measurement were originally developed to prevent fraud in commerce.
Today, units of measurement are generally defined on a scientific basis, overseen by governmental or supra-governmental agencies, and established in international treaties, pre-eminent of which is the General Conference on Weights and Measures
Brainstorming is a group or individual creativity technique by which efforts are made to find a conclusion for a specific problem by gathering a list of ideas spontaneously contributed by its member(s). The term was popularized by Alex Faickney Osborn in the 1953 book Applied Imagination. Osborn claimed that brainstorming was more effective than individuals working alone in generating ideas, although more recent research has questioned this conclusion.
Advertising executive Alex F. Osborn began developing methods for creative problem solving in 1939. He was frustrated by employees’ inability to develop creative ideas individually for ad campaigns. In response, he began hosting group-thinking sessions and discovered a significant improvement in the quality and quantity of ideas produced by employees. Osborn outlined the method in his 1953 book Applied Imagination.
Osborn claimed that two principles contribute to "ideative efficacy," these being "1. Defer judgment," and "2. Reach for quantity." Following these principles were his four general rules of brainstorming, established with intention to reduce social inhibitions among group members, stimulate idea generation, and increase
In many countries, a mayor (from the Latin māior, meaning "greater") is the highest-ranking officer in the municipal government of a town or a large urban city.
In many municipal systems the mayor serves as chief executive officer and/or ceremonial official of many types of municipalities. Worldwide, there is a wide variance in local laws and customs regarding the powers and responsibilities of a mayor, as well as the means by which a mayor is elected or otherwise mandated.
In England, the mayor is the later descendant of the feudal lord's bailiff or reeve (see borough). The chief magistrate of London bore the title of portreeve for considerably more than a century after the Norman Conquest. This official was elected by popular choice, a privilege secured from King John. By the beginning of the 12th century, the title of portreeve gave way to that of mayor as the designation of the chief officer of London. The adoption of the title by other boroughs followed at various intervals. In the 19th century, in the United Kingdom, the Municipal Corporations Act 1882, Section 15, regulated the election of mayors. He was to be a fit person elected annually on 9 November by the council of the
A portable computer is a computer that is designed to be moved from one place to another and includes a display and keyboard. Portable computers, by their nature, are generally microcomputers. Portable computers, because of their size, are also commonly known as 'Lunchbox' or 'Luggable' computers. They can also be called a 'Portable Workstation' or 'Portable PC'.
The principal advantage of a portable computer versus a laptop or other mobile computing device is the use of standard motherboards or backplanes providing plug-in slots for add-in cards. This allows mission specific cards such as test, A/D, or communication protocol (IEEE-488, 1553) to be installed. Portable computers also provide for more disk storage by using standard 3-1/2" drives and providing for multiple drives.
The IBM 5100 Portable Computer, introduced in September 1975, was perhaps the first portable computer. IBM referred to its PALM processor as a microprocessor, though they used that term to mean a processor that executes microcode to implement a higher-level instruction set, rather than its conventional definition of a complete processor on a single silicon integrated circuit.
Xerox NoteTaker, developed in
A submarine is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term submarine most commonly refers to a large crewed autonomous vessel. However, historically or colloquially, submarine can also refer to medium-sized or smaller vessels (midget submarines, wet subs), remotely operated vehicles or robots.
The adjective submarine, in terms such as submarine cable, means "under the sea". The noun submarine evolved as a shortened form of submarine boat (and is often further shortened to sub). For reasons of naval tradition submarines are usually referred to as "boats" rather than as "ships", regardless of their size.
Although experimental submarines had been built before, submarine design took off during the 19th century, and they were adopted by several different navies. Submarines were first widely used during World War I (1914–1918) and now figure in many large navies. Military usage includes attacking enemy surface ships or submarines, aircraft carrier protection, blockade running, ballistic missile submarines as part of a nuclear strike force, reconnaissance, conventional land attack (for
Bears are mammals of the family Ursidae. Bears are classified as caniforms, or doglike carnivorans, with the pinnipeds being their closest living relatives. Although there are only eight living species of bear, they are widespread, appearing in a wide variety of habitats throughout the Northern Hemisphere and partially in the Southern Hemisphere. Bears are found in the continents of North America, South America, Europe, and Asia.
Common characteristics of modern bears include a large body with stocky legs, a long snout, shaggy hair, plantigrade paws with five nonretractile claws, and a short tail. While the polar bear is mostly carnivorous and the giant panda feeds almost entirely on bamboo, the remaining six species are omnivorous, with varied diets.
With the exceptions of courting individuals and mothers with their young, bears are typically solitary animals. They are generally diurnal, but may be active during the night (nocturnal) or twilight (crepuscular), particularly around humans. Bears are aided by an excellent sense of smell, and despite their heavy build and awkward gait, they can run quickly and are adept climbers and swimmers. In autumn, some bear species forage large
A cannon is any piece of artillery that uses gunpowder or other usually explosive-based propellents to launch a projectile. Cannon vary in caliber, range, mobility, rate of fire, angle of fire, and firepower; different forms of cannon combine and balance these attributes in varying degrees, depending on their intended use on the battlefield. The word cannon is derived from several languages, in which the original definition can usually be translated as tube, cane, or reed. The plural of cannon is also cannon, though more commonly in America, cannons. In the modern era, the term cannon has fallen out of common usage, replaced by "guns" or "artillery" if not a more specific term such as "mortar" or "howitzer". In aviation, cannon generally describes weapons firing bullets larger than 0.5 inches (12.7 mm) in diameter.
First used in China, cannon were among the earliest forms of gunpowder artillery, and over time replaced siege engines—among other forms of aging weaponry—on the battlefield. In the Middle East, the first use of the hand cannon is argued to be during the 1260 Battle of Ain Jalut between the Mamluks and Mongols. The first cannon in Europe were probably used in Iberia in
A culverin was a relatively simple ancestor of the musket, and later a medieval cannon, adapted for use by the French in the 15th century, and later adapted for naval use by the English in the late 16th century. The culverin was used to bombard targets from a distance. The weapon had a relatively long barrel and a light construction. The culverin fired solid round shot projectiles with a high muzzle velocity, producing a relatively long range and flat trajectory. Round shot refers to the classic solid spherical cannonball.
The term "culverin" is derived from the Latin, colubrinus, or "of the nature of a snake". It was originally the name of a medieval ancestor of the musket, used in the 15th and 16th centuries.
The hand culverin consisted in a simple smoothbore tube, closed at one end except for a small hole designed to allow ignition of the gunpowder. The tube was held in place by a wooden piece which could be held under the arm. The tube was loaded with gunpowder and lead bullets. The culverin was fired by inserting a burning slow match into the hole.
These hand culverins soon evolved into heavier portable culverins, around 40 kg (88 lb) in weight, which required a swivel for
A dagger is a fighting knife with a sharp point designed or capable of being used as a thrusting or stabbing weapon. The design dates to human prehistory, and daggers have been used throughout human experience to the modern day in close combat confrontations. Many ancient cultures used adorned daggers in ritual and ceremonial purposes, a trend which continues to the present time in the form of art knives. The distinctive shape and historic usage of the dagger have made it iconic and symbolic.
Over the years, the term 'dagger' has been used to describe a wide variety of thrusting knives, including knives that feature only a single cutting edge, such as the European rondel dagger or the Persian pesh-kabz, or, in some instances, no cutting edge at all, such as the stiletto of the Renaissance. However, over the last hundred years or so, authorities have recognized that the dagger, in its contemporary or mature form, has come to incorporate certain definable characteristics, including a short blade with a sharply-tapered point, a central spine or fuller, and (usually) two cutting edges sharpened the full length of the blade, or nearly so. Most daggers also feature a full crossguard to
Jewellery or jewelry ( /ˈdʒuːəlᵊri/) is a form of personal adornment, such as brooches, rings, necklaces, earrings, and bracelets.
With some exceptions, such as medical alert bracelets or military dog tags, jewellery normally differs from other items of personal adornment in that it has no other purpose than to look appealing, but humans have been producing and wearing it for a long time – with 100,000-year-old beads made from Nassarius shells thought to be the oldest known jewellery.
Jewellery may be made from a wide range of materials, but gemstones, precious metals, beads and shells have been widely used. Depending on the culture and times jewellery may be appreciated as a status symbol, for its material properties, its patterns, or for meaningful symbols. Jewellery has been made to adorn nearly every body part, from hairpins to toe rings.
The word jewellery itself is derived from the word jewel, which was anglicized from the Old French "jouel", and beyond that, to the Latin word "jocale", meaning plaything. In British English the spelling can be written as jewelery or jewellery, while in U.S. English the spelling is jewelry.
Jewellery has been used for a number of reasons:
The Kodiak bear (Ursus arctos middendorffi), also known as the Kodiak brown bear or the Alaskan grizzly bear or American brown bear, occupies the islands of the Kodiak Archipelago in South-Western Alaska. Its name in the Alutiiq language is Taquka-aq. It is the largest subspecies of brown bear.
Taxonomist C.H. Merriam was the first to recognize Kodiak bears as unique and he named the species "Ursus middendorffi" in honor of the celebrated Baltic naturalist Dr. A. Th. von Middendorff. Subsequent taxonomic revisions merged most North American brown bears into a single subspecies (Ursus arctos horribilis), but Kodiak bears are still considered to be a unique subspecies (Ursus arctos middendorffi). Recent investigations of genetic samples from bears on Kodiak have shown that they are closely related to brown bears on the Alaska Peninsula and Kamchatka, Russia. It appears that Kodiak bears have been genetically isolated since at least the last ice age (10,000 to 12,000 years ago) and there is very little genetic diversity within the population. Although the current population is healthy and productive, and has shown no overt adverse signs of inbreeding, it may be more susceptible to new
Perfume /ˈpɜr.fjuːm/ or parfum is a mixture of fragrant essential oils or aroma compounds, fixatives, and solvents used to give the human body, animals, objects, and living spaces "a pleasant scent." The odoriferous compounds that make up a perfume can be manufactured synthetically or extracted from plant or animal sources.
Perfumes have been known to exist in some of the earliest human civilizations, either through ancient texts or from archaeological digs. Modern perfumery began in the late 19th century with the commercial synthesis of aroma compounds such as vanillin or coumarin, which allowed for the composition of perfumes with smells previously unattainable solely from natural aromatics alone.
The word perfume used today derives from the Latin per fumum, meaning "through smoke." Perfumery, or the art of making perfumes, began in ancient Mesopotamia and Egypt and was further refined by the Romans and Persians.
The world's first recorded chemist is considered to be a woman named Tapputi, a perfume maker who was mentioned in a cuneiform tablet from the 2nd millennium BC in Mesopotamia. She distilled flowers, oil, and calamus with other aromatics then filtered and put them back
A Pocket PC (P/PC, PPC) is also known by Microsoft as a 'Windows Mobile Classic device'. It is a hardware specification for a handheld-sized computer, personal digital assistant (PDA), that runs the Microsoft 'Windows Mobile Classic' operating system. It has some of the abilities of modern desktop PCs.
As of 2010, thousands of applications exist for handhelds adhering to the Microsoft Pocket PC specification, many of which are freeware. Some of these devices are also mobile phones. Microsoft-compliant Pocket PCs can be used with many add-ons such as GPS receivers, barcode readers, RFID readers, and cameras.
In 2007, with the advent of Windows Mobile 6, Microsoft dropped the name Pocket PC in favor of a new naming scheme. Devices without an integrated phone are called Windows Mobile Classic devices instead of Pocket PCs. Devices with an integrated phone and a touch screen are called Windows Mobile Professional devices and devices without a touch screen are called Windows Mobile Standard devices.
The Pocket PC is an evolution from prior calculator-sized computers. Keystroke-programmable calculators which could do simple business and scientific applications were available by the
A cabinet is usually a box-shaped piece of furniture with doors or drawers for storing miscellaneous items. Some cabinets stand alone while others are built into a wall or are attached to it like a medicine cabinet. Cabinets are typically made of wood or, now increasingly, of synthetic materials.
Cabinets are manufactured in two basic box constructions: frameless or face frame. In face frame cabinets, supporting frames attach to the front of the cabinet box. This frame is usually 1 1/2 inches wide and made from wood. Mounted on this face frame is the door. Frameless cabinets, on the other hand, have no supporting front frame. The doors attach directly to the insides of the cabinet box.
Cabinets usually have one or more doors on the front, which are mounted with door hardware, and occasionally a lock. Many cabinets have doors and drawers or only drawers. Short cabinets often have a finished surface on top that can be used for display, or as a working surface such as the countertops found in kitchens.
A cabinet intended for clothing storage is usually called a wardrobe or an armoire (or a closet if built in). In previous centuries, such a cabinet was also known as a linen-press. In
A Fabergé egg (Russian: Яйца Фаберже; Yaĭtsa Faberzhe) is any one of the thousands of jeweled eggs made by the House of Fabergé from 1885 to 1917. Most were miniature eggs that were popular gifts at Easter. They were worn on a neck chain either singly or in groups.
The most famous eggs produced by the House were the larger ones made for Alexander III and Nicholas II of Russia; these are often referred to as the 'Imperial' Fabergé eggs. Approximately 50 eggs were made; 42 have survived. Another two eggs, the Constellation and Karelian Birch eggs, were planned for 1918 but not delivered, as Nicholas II and his family were executed that year, and Nicholas had abdicated the crown the year before.
Seven large eggs were made for the Kelch family of Moscow.
The eggs are made of precious metals or hard stones decorated with combinations of enamel and gem stones. The Fabergé egg has become a symbol of luxury, and the eggs are regarded as masterpieces of the jeweler's art.
'Fabergé egg' typically refers to products made by the company before the 1917 Revolution, but use of the Fabergé name has occasionally been disputed, and the trademark has been sold several times since the Fabergé family
Smoking is the process of flavoring, cooking, or preserving food by exposing it to the smoke from burning or smoldering plant materials, most often wood. Meats and fish are the most common smoked foods, though cheeses, vegetables, and ingredients used to make beverages such as whisky, smoked beer, and lapsang souchong tea are also smoked.
In Europe, alder is the traditional smoking wood, but oak is more often used now, and beech to a lesser extent. In North America, hickory, mesquite, oak, pecan, alder, maple, and fruit-tree woods, such as apple, cherry, and plum, are commonly used for smoking. Other fuels besides wood can also be employed, sometimes with the addition of flavoring ingredients. Chinese tea-smoking uses a mixture of uncooked rice, sugar, and tea, heated at the base of a wok. Some North American ham and bacon makers smoke their products over burning corncobs. Peat is burned to dry and smoke the barley malt used to make whisky and some beers. In New Zealand, sawdust from the native manuka (tea tree) is commonly used for hot smoking fish. In Iceland, dried sheep dung is used to cold-smoke fish, lamb, mutton, and whale.
Historically, farms in the Western world included a
A wedding dress or wedding gown is the clothing worn by a bride during a wedding ceremony. Color, style and ceremonial importance of the gown can depend on the religion and culture of the wedding participants. In Western cultures, brides often choose a white wedding dress, which was made popular by Queen Victoria in the 19th century. In eastern cultures, brides often choose red to symbolize auspiciousness.
Weddings performed during and immediately following the Middle Ages were often more than just a union between two people. They could be a union between two families, two businesses or even two countries. Many weddings were more a matter of politics than love, particularly among the nobility and the higher social classes. Brides were therefore expected to dress in a manner that cast their families in the most favorable light and befitted their social status, for they were not representing only themselves during the ceremony. Brides from wealthy families often wore rich colors and exclusive fabrics. It was common to see them wearing bold colors and layers of furs, velvet and silk. Brides dressed in the height of current fashion, with the richest materials money could buy. The
Leather is a durable and flexible material created by the tanning of animal rawhide and skin, often cattle hide. It can be produced through manufacturing processes ranging from cottage industry to heavy industry.
Several tanning processes transform hides and skins into leather:
Leather—usually vegetable-tanned—can be oiled to improve its water resistance. This supplements the natural oils remaining in the leather itself, which can be washed out through repeated exposure to water. Frequent oiling of leather, with mink oil, neatsfoot oil, or a similar material keeps it supple and improves its lifespan dramatically.
Leather with the hair still attached is called hair-on.
In general, leather is sold in four forms:
Less-common leathers include:
There are two other types of leather commonly used in specialty products, such as briefcases, wallets, and luggage:
The following are not "true" leathers, but contain leather material. Depending on jurisdiction, they may still be labeled as "Genuine Leather":
Today most leather is made of cattle skin but many exceptions exist. Lamb and deerskin are used for soft leather in more expensive apparel. Deer and elkskin are widely used in work gloves
A business (also known as enterprise or firm) is an organization engaged in the trade of goods, services, or both to consumers. Businesses are predominant in capitalist economies, where most of them are privately owned and administered to earn profit to increase the wealth of their owners. Businesses may also be not-for-profit or state-owned. A business owned by multiple individuals may be referred to as a company, although that term also has a more precise meaning.
The etymology of "business" relates to the state of being busy either as an individual or society as a whole, doing commercially viable and profitable work. The term "business" has at least three usages, depending on the scope — the singular usage to mean a particular organization; the generalized usage to refer to a particular market sector, "the music business" and compound forms such as agribusiness; and the broadest meaning, which encompasses all activity by the community of suppliers of goods and services. However, the exact definition of business, like much else in the philosophy of business, is a matter of debate and complexity of meanings.
Although forms of business ownership vary by jurisdiction, several common
Casing, sausage casing, or sausage skin is the material that encloses the filling of a sausage. Casings are divided into two categories, natural and artificial. Artificial casings, such as collagen, cellulose, plastic, and extruded casings, are relatively new to the field, mainly borne of market demand during the technological advances of the early 20th century.
It is often assumed that sausages were invented by the Sumerians in the region that is Iraq today, around 4000 BC. Reference to a cooked meat product stuffed in a goat stomach like a sausage was known in Babylon and described as a recipe in the world’s oldest cooking book 3,750 years ago (Yale Babylonian collection, New Haven Connecticut, USA).
The Chinese sausage làcháng, which consists of goat and lamb meat, was first mentioned in 589 BC. The Greek poet Homer mentioned a kind of blood sausage in his Odyssey (book 20, poem 25); Epicharmus (ca. 550 BC — ca. 460 BC) wrote a comedy entitled The Sausage. Numerous books report that sausages were already popular among the ancient Greeks and Romans.
Natural sausage casings (“casings”) are made from the sub-mucosa, a layer of the intestine that consists mainly of naturally
A crossbow is a weapon consisting of a bow mounted on a stock that shoots projectiles, often called bolts or quarrels. The medieval crossbow was called by many names, most of which derived from the word ballista, a torsion engine resembling a crossbow in appearance.
Historically, crossbows played a significant role in the warfare of East Asia, Europe and the Mediterranean. Today, they are used primarily for shooting sports, hunting, and when shooting in silence is an important consideration.
A crossbow is a weapon bow mounted on a stick (called a tiller or stock) with a mechanism in it which holds the drawn bow string. The earliest designs featured a slot in the stock, down into which the string was placed. To shoot this design, a vertical rod is thrust up through a hole in the bottom of the notch, forcing the string out. This rod is usually attached perpendicular to a rear-facing lever called a trigger or "tickler". A later design implemented a rolling cylindrical pawl called a "nut" to retain the string. This nut has a perpendicular center slot for the bolt, and an intersecting axial slot for the string, along with a lower face or slot against which the internal trigger sits.
A drawbridge is a type of movable bridge typically associated with the entrance of a castle surrounded by a moat. The term is often used to describe all different types of movable bridges, like bascule bridges and lift bridges.
Medieval castles were usually defended by a ditch or moat, crossed by wooden bridge. In early castles the bridge might be designed to be destroyed or removed in the event of an attack, but drawbridges became very common. A typical arrangement would have the drawbridge immediately outside a gatehouse, consisting of a wooden deck with one edge hinged or pivoting at the gatehouse threshold, so that in the raised position the bridge would be flush against the gate, forming an additional barrier to entry. It would be backed by one or more portcullises and gates. Access to the bridge could be resisted with missiles from machicolations above or arrow slits in flanking towers.
The bridge would be raised or lowered using ropes or chains attached to a windlass in a chamber in the gatehouse above the gate-passage. Only a very light bridge could be raised in this way without any form of counterweight, so some form of bascule arrangement is normally found. The bridge may
A gun is a device which acts at a distance through the discharge of a separate projectile. The projectile may be solid, liquid, gas or energy and may be free, as with bullets and artillery shells, or captive as with Taser probes and whaling harpoons. The means of projection varies according to design but is usually effected by the action of gas pressure, either produced through the rapid combustion of a propellant or compressed and stored by mechanical means, operating on the projectile inside an open-ended tube in the fashion of a piston. The confined gas accelerates the the movable projectile down the length of the tube imparting sufficient velocity to sustain the projectile's travel once the action of the gas ceases at the end of the tube or muzzle. Alternatively, acceleration via electromagnetic field generation may be employed in which case the tube may be dispensed with and a guide rail substituted.
In ordinary speech the term gun may refer to any sort of firearm including those that are usually hand-held (handgun). The word gun is also commonly used to describe objects which, while they are not themselves weapons, produce an effect or possess a form which is in some way
A mobile device (also known as a handheld device, handheld computer or simply handheld) is a small, hand-held computing device, typically having a display screen with touch input and/or a miniature keyboard and weighing less than 2 pounds (0.91 kg). Apple, HTC, Samsung, LG, Research in Motion (RIM) and Motorola are just a few examples of the many manufacturers that produce these types of devices.
A handheld computing device has an operating system (OS), and can run various types of application software, known as apps. Most hand held devices can also be equipped with WI-FI, Bluetooth and GPS capabilities that can allow connections to the Internet and other Bluetooth capable devices such as an automobile or a microphone headset. A camera or media player feature for video or music files can also be typically found on these devices along with a stable battery power source such as a lithium battery.
Early pocket sized ones were joined in the late 2000s by larger but otherwise similar tablet computers. As in a personal digital assistant (PDA), the input and output are often combined into a touch-screen interface.
Smartphones and PDAs are popular amongst those who wish to use some of the
A mace is a blunt weapon, a type of club or virge—that uses a heavy head on the end of a handle to deliver powerful blows. A mace typically consists of a strong, heavy, wooden or metal shaft, often reinforced with metal, featuring a head made of stone, copper, bronze, iron, or steel.
The head of a military mace can be shaped with flanges or knobs to allow greater penetration of plate armour. The length of maces can vary considerably. The maces of foot soldiers were usually quite short (two or three feet, or 70 to 90 cm). The maces of cavalrymen were longer and thus better suited for blows delivered from horseback. Two-handed maces could be even larger.
Maces are rarely used today for actual combat, but a large number of government bodies (for instance the British House of Commons, the U.S. Congress), universities and other institutions have ceremonial maces and continue to display them as symbols of authority. They are often paraded in academic, parliamentary or civic rituals and processions.
The mace was developed during the Upper Paleolithic from the simple club, by adding sharp spikes of flint or obsidian. It was the first weapon designed specifically for killing humans (as
A revolver or six-shooter (as most revolvers have a maximum capacity of six rounds) is a repeating firearm that has a cylinder containing multiple chambers and at least one barrel for firing. The first true revolver—a flintlock—was made by Elisha Collier in 1814. The percussion cap revolver was invented by Samuel Colt in 1836. This weapon became known as the Colt Paterson. The first cartridge revolvers were produced around 1856 by Smith and Wesson. Though the original name was "revolving gun", the short-form "revolver" is universally used.
As the user cocks the hammer, the cylinder revolves to align the next chamber and round with the hammer and barrel, which gives this type of firearm its name. The hammer-cocking happens either directly (via the shooter pulling it back) or indirectly (via the first portion of the trigger pull in double-action revolvers.) In modern revolvers, the revolving cylinder typically chambers five or six rounds, but some models hold ten rounds or more. Revolvers are most often handguns, but other weapons may also have a revolving chamber. These include some models of grenade launchers, shotguns, and some rifles.
Revolvers have been largely replaced by
A shirt stud is a decorative fastener that fits onto a buttonhole on the front of a pleated shirt, or onto the starched bib of a stiff-front shirt. Such shirts have special buttonholes solely for shirt studs.
A shirt stud may be fashioned from alloys, precious metals, and gemstones—materials uncommon to buttons sewn on shirts. The stud may have an inlay, such as of pearl or onyx.
Dress code of the modern western world reserves shirt studs for men's formal wear and some semi-formal occasions.
In the western world, shirt studs were first used in the mid-19th century, when some shirt fronts were too stiff to close with buttons. So remains the case for the heavily starched, modern full dress shirts worn with white tie.
A stuffed toy is a toy sewn from a textile, and stuffed with a soft material. They are also known as plush toys, plushies, or stuffed animals (U.S. English), and soft toys or cuddly toys (British English).
Textiles commonly used include plain cloth and pile textiles like plush or terrycloth. Common stuffing materials are synthetic fiber batting, cotton, straw, wood wool, plastic pellets or beans. Stuffed toys are made in many different forms, often resembling animals, legendary creatures, cartoon characters or inanimate objects. They are often used as comfort objects, for display or collecting and given as gifts, such as for graduation, Valentine's Day or birthdays.
The first commercial concern to create stuffed toys was the German Steiff company in 1880. Steiff used new technology developed for upholstery to make their stuffed toys. In 1903 Richard Steiff designed a soft bear that differed from earlier traditional rag dolls because it was made of plush furlike fabric. At the same time in the USA, Morris Michtom created the first teddy bear, after being inspired by a drawing of Theodore "Teddy" Roosevelt with a bear cub. The character Peter Rabbit from English author Beatrix Potter
Tar is modified pitch produced primarily from the wood and roots of pine by destructive distillation under pyrolysis. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America, particularly North Carolina. Its main use was in preserving wooden vessels against rot. The largest user was the Royal Navy. Demand for tar declined with the advent of iron and steel ships.
Tar-like products can also be produced from other forms of organic matter such as peat. Mineral products resembling tar can be produced from fossil hydrocarbons including petroleum. Coal tar is produced from coal as a byproduct of coke production. Bitumen is a term used for natural deposits of oil "tar" – such as at the La Brea Tar Pits.
In Northern Europe, the word "tar" refers primarily to a substance that is derived from the wood and roots of pine. In earlier times it was often used as a water repellent coating for boats, ships, and roofs. It is still used as an additive in the flavoring of candy, alcohol and other foods. Wood tar is microbicidal and has a pleasant odor – a sweet musky scent much like that of barbecue. Producing tar from wood was known in ancient
Feathered war bonnets (also called warbonnets or headdresses) are worn by honored Plains Indian men. In the past they were sometimes worn into battle, but most often worn for ceremonial occasions as is the case today. They are seen as items of great spiritual and magical importance. The eagle is considered by Plains tribes as the greatest and most powerful of all birds, and thus the finest bonnets are made out of its feathers.
Its beauty was considered of secondary importance; the bonnet's real value was in its supposed power to protect the wearer. The bonnet is still only to be worn on special occasions and is highly symbolic.
The bonnet had to be earned through brave deeds in battle because the feathers signified the deeds themselves. Some warriors might have obtained only two or three honor feathers in their whole lifetime, so difficult were they to earn. The bonnet was also a mark of highest respect because it could never be worn without the consent of the leaders of the tribe. A high honor, for example, was received by the warrior who was the first to touch an enemy fallen in battle, for this meant the warrior was at the very front of fighting. Feathers were notched and
A fuller is a rounded or beveled groove or slot in the flat side of a blade (e.g. a sword, knife, or bayonet). A fuller is often used to lighten the blade, much in the way that an I-beam shape allows a given amount of strength to be achieved with less material. Longer knives or bayonets intended as offensive weapons may employ fullers (also incorrectly known as 'blood grooves') to lighten the blade while maintaining its strength. When combined with proper distal tapers, heat treatment and blade tempering, a fullered blade can be 20% to 35% lighter than a non-fullered blade without any sacrifice of strength or blade integrity. This effect lessens as the blade is reduced in length. Short bladed knives may employ fullers simply for their aesthetic effect.
The basic design principle is that bending causes more stress in material near the edge or back of the blade than material in the middle, due to leverage. The diagram at right shows stress distribution in an ideal blade with a rectangular section, with only a small amount of normal stress present at the neutral axis. Fullers remove material from near this neutral axis, which is closer to the blade's spine if only one edge is
Wine is an alcoholic beverage made from fermented grapes or other fruits. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, water, or other nutrients. Yeast consumes the sugars in the grapes and converts them into alcohol. Different varieties of grapes and strains of yeasts produce different types of wine. The well-known variations result from the very complex interactions between the biochemical development of the fruit, reactions involved in fermentation, and human intervention in the overall process. The final product may contain tens of thousands of chemical compounds in amounts varying from a few percent to a few parts per billion.
Wines made from other fruits are usually named after the fruit from which they are produced (for example, apple wine and elderberry wine) and are generically called fruit wine. The term "wine" can also refer to the higher alcohol content of starch-fermented or fortified beverages such as barley wine, sake, and ginger wine.
Wine has a rich history dating back thousands of years, with the earliest known production occurring around 6000 BC in Georgia. It first appeared in the Balkans about 4500 BC
Automatic rifle is a term generally used to describe a firearm chambered for a rifle cartridge, which may or may not be of intermediate designation, capable of delivering both semi- and full automatic fire. This "select-fire" capability, as well as the (general) use of magazine-fed rifle ammunition, differentiate it from other classes of automatic firearm such as the machine gun and submachine gun.
In many cases, however, it simply describes a rifle capable of self-loading, but not capable of automatic fire (i.e., semiautomatic). Depending on the expert and point in history, full-automatic carbines, assault rifles and battle rifles are sometimes considered to be a type of automatic rifle, and at other times separated into their own categories.
As an example of the confusion, or at least differences in usage, there are books which feature a section for automatic rifles listing several semi-automatic rifles, but not a single full-automatic weapon. On the other hand, soldiers of the United States Army carrying the M249 SAW are designated automatic riflemen, and the weapon itself an automatic rifle — even though it is a full-automatic firearm, normally classified as a squad automatic
Blues is the name given to both a musical form and a music genre that originated in African-American communities of primarily the "Deep South" of the United States around the end of the 19th century from spirituals, work songs, field hollers, shouts and chants, and rhymed simple narrative ballads. The blues form, ubiquitous in jazz, rhythm and blues, and rock and roll is characterized by specific chord progressions, of which the twelve-bar blues chord progression is the most common. The blue notes that, for expressive purposes are sung or played flattened or gradually bent (minor 3rd to major 3rd) in relation to the pitch of the major scale, are also an important part of the sound.
The blues genre is based on the blues form but possesses other characteristics such as specific lyrics, bass lines and instruments. Blues can be subdivided into several subgenres ranging from country to urban blues that were more or less popular during different periods of the 20th century. Best known are the Delta, Piedmont, Jump and Chicago blues styles. World War II marked the transition from acoustic to electric blues and the progressive opening of blues music to a wider audience, especially white
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They are among the characteristics that distinguish the extant Aves from other living groups. Feathers have also been noticed in those Theropoda which have been termed feathered dinosaurs. Although feathers cover most parts of the body of birds, they arise only from certain well-defined tracts on the skin. They aid in flight, thermal insulation, waterproofing and coloration that helps in communication and protection.
Feathers are among the most complex integumentary appendages found in vertebrates and are formed in tiny follicles in the epidermis, or outer skin layer, that produce keratin proteins. The β-keratins in feathers, beaks and claws — and the claws, scales and shells of reptiles — are composed of protein strands hydrogen-bonded into β-pleated sheets, which are then further twisted and crosslinked by disulfide bridges into structures even tougher than the α-keratins of mammalian hair,
Quicksort(Hoare Sort) is a sorting algorithm developed by Tony Hoare that, on average, makes O(n log n) comparisons to sort n items. In the worst case, it makes O(n) comparisons, though this behavior is rare. Quicksort is often faster in practice than other O(n log n) algorithms. Additionally, quicksort's sequential and localized memory references work well with a cache. Quicksort can be implemented with an in-place partitioning algorithm, so the entire sort can be done with only O(log n) additional space.
Quicksort (also known as "partition-exchange sort") is a comparison sort and, in efficient implementations, is not a stable sort.
The quicksort algorithm was developed in 1960 by Tony Hoare while in the Soviet Union, as a visiting student at Moscow State University. At that time, Hoare worked in a project on machine translation for the National Physical Laboratory. He developed the algorithm in order to sort the words to be translated, to make them more easily matched to an already-sorted Russian-to-English dictionary that was stored on magnetic tape.
Quicksort is a divide and conquer algorithm. Quicksort first divides a large list into two smaller sub-lists: the low elements and
A railroad tie/railway tie/crosstie (North America), or railway sleeper (Europe) is a rectangular support for the rails in railroad tracks. Generally laid perpendicular to the rails, ties transfer loads to the track ballast and subgrade, hold the rails upright, and keep them spaced to the correct gauge.
Railroad ties were traditionally made of wood, but pre-stressed concrete is now widely used especially in Europe and Asia. Steel ties are common on secondary lines in the UK; plastic composite ties are also employed, although far less than wood or concrete. As of January 2008, the approximate market share in North America for traditional and wood ties was 91.5%, the remainder being concrete, steel, azobé (red ironwood) and plastic composite.
Coarse aggregate is the standard material for track ballast, which provides drainage and resilience. On lines with lower speeds and axle-weights, sand, gravel, and even coal ash from the fires of steam locomotives have been used.
Up to 3000 ties are used per mile of railroad track in the USA, 2640 per mile (30 per 60ft rail) on main lines in the UK. Rails in the USA may be fastened to the tie by a railroad spike; iron/steel baseplates screwed to
Salting is the preservation of food with dry edible salt. It is related to pickling (preparing food with brine, i.e. salty water). It is one of the oldest methods of preserving food, and two historically significant salt-cured foods are dried and salted cod (usually referred to as salt fish) and salt-cured meat.
Salting is used because most bacteria, fungi and other potentially pathogenic organisms cannot survive in a highly salty environment, due to the hypertonic nature of salt. Any living cell in such an environment will become dehydrated through osmosis and die or become temporarily inactivated.
It was discovered in the 19th century that salt mixed with nitrites (saltpeter) would color meats red, rather than grey, and consumers at that time then strongly preferred the red-colored meat.
Jewish and Muslim dietary laws require the removal of blood from freshly slaughtered meat. Salt and brine are used for the purpose in both traditions, but salting is more common in Kosher Shechita (where it is all but required) than in Halal Dhabiha (as in most cases, draining alone will suffice).
A sidewalk, or pavement, footpath, footway, and sometimes platform, is a path along the side of a road. A sidewalk may accommodate moderate changes in grade (height) and is normally separated from the vehicular section by a curb (British English: kerb). There may also be a road verge (a strip of vegetation, grass or bushes or trees or a combination of these) either between sidewalk and the roadway (British English: carriageway) or between the sidewalk and the boundary.
In some places, the same term may also be used for a paved path, trail or footpath that is not next to a road, for example, a path through a park.
The term Sidewalk is used for the pedestrian path beside a road. Shared-use path and multi-use path is reserved for use for ones available for use by both pedestrians and bicyclists.
Walkway is a more comprehensive term that includes stairs, ramps, passageways, and related structures that facilitate the use of a path as well as the sidewalk. The term pathway is used for pedestrian paths that are not next to a road.
The most common term in everyday usage is pavement. The professional, civil engineering and legal term for this is footway. Legally the term footpath is only
Soft systems methodology (SSM) is a systemic approach for tackling real-world problematic situations. Soft Systems Methodology is the result of the continuing action research that Peter Checkland, Brian Wilson, and many others have conducted over 30 years, to provide a framework for users to deal with the kind of messy problem situations that lack a formal problem definition.
It is a common misunderstanding that SSM is a methodology for dealing solely with ‘soft problems’ (i.e., problems which involve psychological, social, and cultural elements). SSM does not differentiate between ‘soft’ and ‘hard’ problems, it merely provides a different way of dealing with situations perceived as problematic. The ‘hardness’ or ‘softness’ is not the intrinsic quality of the problem situation to be addressed, it is an aspect of the way those involved address the situation. Each situation perceived as problematic has both ‘hard’ and ‘soft’ elements. The very notion of a problem is contingent on a human being perceiving it as such. e.g. One man's terrorist is another man's freedom fighter.
SSM distinguishes itself from hard systems approaches in the way it deals with the notion of ‘system.’ Common
AC power plugs and sockets are devices that allow electrically operated devices to be connected to the primary alternating current (AC) power supply in a building. Electrical plugs and sockets differ in voltage and current rating, shape, size and type of connectors. The types used in each country are set by national standards.
Generally the plug is the movable connector attached to an electrically operated device's mains cable, and the socket is fixed on equipment or a building structure. Plugs have male circuit contacts, while sockets have female contacts. The plug has protruding prongs, blades, or pins that fit into matching slots or holes in the socket. A socket is also called a receptacle, outlet, or power point (British English). It may be surrounded by a cover called a wall plate, face plate, outlet cover, socket cover, or wall cover.
To reduce the risk of electric shock, plug and socket systems can incorporate safety features. These may include socket design intended to accept only compatible plugs inserted in the correct orientation; plugs with insulated sleeves on contact pin shanks so a partially inserted plug does not bear exposed live pins that could be touched; or
Aramid fibers are a class of heat-resistant and strong synthetic fibers. They are used in aerospace and military applications, for ballistic rated body armor fabric and ballistic composites, in bicycle tires, and as an asbestos substitute. The name is a portmanteau of "aromatic polyamide". They are fibers in which the chain molecules are highly oriented along the fiber axis, so the strength of the chemical bond can be exploited.
Aromatic polyamides were first introduced in commercial applications in the early 1960s, with a meta-aramid fiber produced by DuPont as HT-1 and then under the trade name Nomex. This fiber, which handles similarly to normal textile apparel fibers, is characterized by its excellent resistance to heat, as it neither melts nor ignites in normal levels of oxygen. It is used extensively in the production of protective apparel, air filtration, thermal and electrical insulation as well as a substitute for asbestos. Meta-aramid is also produced in the Netherlands and Japan by Teijin under the trade name Conex, in China by Yantai Tayho under the trade name New Star, by SRO Group (China) under the trade name X-Fiper, and a variant of meta-aramid in France by Kermel
The axe, or ax, is an implement that has been used for millennia to shape, split and cut wood; to harvest timber; as a weapon; and as a ceremonial or heraldic symbol. The axe has many forms and specialized uses but generally consists of an axe head with a handle, or helve.
The earliest examples of axes have heads of stone with some form of wooden handle attached (hafted) in a method to suit the available materials and use. Axes made of copper, bronze, iron, steel appeared as these technologies developed.
The axe is an example of a simple machine, as it is a type of wedge, or dual inclined plane. This reduces the effort needed by the wood chopper. It splits the wood into two parts by the pressure concentration at the blade. The handle of the axe also acts as a lever allowing the user to increase the force at the cutting edge—not using the full length of the handle is known as choking the axe. For fine chopping using a side axe this sometimes is a positive effect, but for felling with a double bitted axe it reduces efficiency.
Generally, cutting axes have a shallow wedge angle, whereas splitting axes have a deeper angle. Most axes are double bevelled, i.e. symmetrical about the axis
A battering ram is a siege engine originating in ancient times and designed to break open the masonry walls of fortifications or splinter their wooden gates. It was used, too, in ancient Roman mines and quarries to attack hard rocks.
In its simplest form, a battering ram is just a large, heavy log carried by several people and propelled with force against an obstacle; the ram would be sufficient to damage the target if the log was massive enough and/or it were moved quickly enough (that is, if it had enough momentum). Later rams encased the log in an arrow-proof, fire-resistant canopy mounted on wheels. Inside the canopy, the log was swung from suspensory chains or ropes.
Rams proved effective weapons of war because old fashioned wall-building materials such as stone and brick were weak in tension, and therefore prone to cracking when impacted with sufficient force. With repeated blows, the cracks would grow steadily until a hole was created. Eventually, a breach would appear in the fabric of the wall—enabling armed attackers to force their way through the gap and engage the inhabitants of the citadel.
The introduction in the later Middle Ages of siege cannons, which harnessed the
A compass is a navigational instrument that measures directions in a frame of reference that is stationary relative to the surface of the earth. The frame of reference defines the four cardinal directions (or points) – north, south, east, and west. Intermediate directions are also defined. Usually, a diagram called a compass rose, which shows the directions (with their names usually abbreviated to initials), is marked on the compass. When the compass is in use, the rose is aligned with the real directions in the frame of reference, so, for example, the "N" mark on the rose really points to the north. Frequently, in addition to the rose or sometimes instead of it, angle markings in degrees are shown on the compass. North corresponds to zero degrees, and the angles increase clockwise, so east is 90 degrees, south is 180, and west is 270. These numbers allow the compass to show azimuths or bearings, which are commonly stated in this notation.
There are two widely used and radically different types of compass. The magnetic compass contains a magnet that interacts with the earth's magnetic field and aligns itself to point to the magnetic poles. The gyrocompass (sometimes spelled with a
Тhe cubicle, cubicle desk, office cubicle or cubicle workstation is a partially enclosed workspace, separated from neighboring workspaces by partitions that are usually 5–6 feet (1.5–1.8 m) tall. Its purpose is to isolate office workers from the sights and noises of an open workspace, the theory being that this allows workers more privacy, and personalization, and helps them to concentrate without distractions. Horizontal work surfaces are usually suspended from the vertical partitions of cubicles, as is shelving, overhead storage, and other amenities. The office cubicle was created by designer Robert Propst for Herman Miller, and released in 1967 under the name "Action Office II".
Although cubicles are often seen as being symbolic of work in a modern office setting due to their uniformity and blandness, they afford the employee a greater degree of privacy and personalization than in previous work environments, which often consisted of desks lined up in rows within an open room.
The term cubicle comes from the Latin cubiculum, for bed chamber. It was used in English as early as the 15th century. It eventually came to be used for small chambers of all sorts, and for small rooms or
A custom car is a passenger vehicle that has been modified in either of the following two ways. First, a custom car may be altered to improve its performance, often by altering or replacing the engine and transmission. Second, a custom car may be a personal "styling" statement, making the car look unlike any car as delivered from the factory. Although the two are related, custom cars are distinct from hot rods. The extent of this difference has been the subject of debate among customizers and rodders for decades. Additionally, a street rod can be considered a custom.
A development of hot rodding, the change in name corresponded to the change in the design of the cars being modified. The first hot rods were pre-World War II cars, with running boards and simple fenders over the wheels. Early model cars (1929 to 1934) were modified by removing the running boards and either removing the fenders entirely or replacing them with very light "cycle fenders". Later models usually had "fender skirts" installed on the rear fenders. Many cars were "hopped up" with engine modifications such as adding additional carburetors, high compression heads and dual exhausts. "Engine swaps" were done, the
A glass bottle is a bottle created from glass. Glass bottles can vary in size considerably, but are most commonly found in sizes ranging between about 10ml and 5 litres.
The history of glass can be traced back to at least 12,000 BC where glass coated objects have been found.
Millions of glass bottles are created worldwide every day. In the US, there is an average of at least two bottle-making factories in each county. It is a highly mechanized process, and bottles in use today are no longer hand blown as they were in the past.
A glass bottle is 100% recyclable with many new bottles containing glass which was created over 20 years ago. Less energy is used in recycling a glass bottle than creating the glass from raw materials, helping the environment.
When a glass bottle filled with liquid is dropped or subjected to shock, the water hammer effect may cause hydrodynamic stress, breaking the bottle.
Glass bottle manufacturing takes place over several stages. To briefly outline the processes from beginning to end: raw material, melting, forming, annealing, physical inspection, machine & laser inspection, secondary physical inspection, quality control, and finally packing.
A hot water bottle (or hottie or Dutch wife) is a container filled with hot water and sealed with a stopper, used to provide warmth, typically whilst in bed, but also for the application of heat to a specific part of the body.
Containers for warmth in bed were in use as early as the 16th century. The earliest versions contained hot coals from the dying embers of the fire, and these bed warmers were used to warm the bed before getting into it.
Containers using hot water were soon also used, with the advantage that they could remain in the bed with the sleeper. Prior to the invention of rubber that could withstand sufficient heat, these early hot water bottles were made of a variety of materials, such as zinc, copper, glass, earthenware or wood. To prevent burning, the metal hot water flasks were wrapped in a soft cloth bag.
Modern day conventional hot water bottles are manufactured in natural rubber or PVC, to a design patented by the Croatian inventor Eduard Penkala. They are now commonly covered in fabric, often with a novelty design.
By the late 20th century, the use of hot water bottles had markedly declined around most of the world. Not only were homes better heated, but newer
The hypocotyl (short for "hypocotyledonous stem", meaning "below seed leaf") is the stem of a germinating seedling, found below the cotyledons (seed leaves) and above the radicle (root).
As the plant embryo grows at germination, it sends out a shoot called a radicle that becomes the primary root and penetrates down into the soil. After emergence of the radicle, the hypocotyl emerges and lifts the growing tip (usually including the seed coat) above the ground, bearing the embryonic leaves (called cotyledons) and the plumule that gives rise to the first true leaves. The hypocotyl is the primary organ of extension of the young plant and develops into the stem.
The early development of a monocot seedling like cereals and other grasses is somewhat different. A structure called the coleoptile, essentially a part of the cotyledon, protects the young stem and plumule as growth pushes them up through the soil. A mesocotyl—that part of the young plant that lies between the seed (which remains buried) and the plumule—extends the shoot up to the soil surface, where secondary roots develop from just beneath the plumule. The primary root from the radicle may then fail to develop further. The
Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate (PET). Polyesters include naturally occurring chemicals, such as in the cutin of plant cuticles, as well as synthetics through step-growth polymerization such as polycarbonate and polybutyrate. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not.
Depending on the chemical structure, polyester can be a thermoplastic or thermoset; however, the most common polyesters are thermoplastics.
Fabrics woven or knitted from polyester thread or yarn are used extensively in apparel and home furnishings, from shirts and pants to jackets and hats, bed sheets, blankets, upholstered furniture and computer mouse mats. Industrial polyester fibers, yarns and ropes are used in tyre reinforcements, fabrics for conveyor belts, safety belts, coated fabrics and plastic reinforcements with high-energy absorption. Polyester fiber is used as cushioning and insulating material in pillows, comforters and upholstery padding. Polyesters are
Polyethylene (abbreviated PE) or polythene (IUPAC name polyethene or poly(methylene)) is the most common plastic. The annual production is approximately 80 million metric tons. Its primary use is within packaging (plastic bag, plastic films, geomembranes, containers including bottles, etc.). Many kinds of polyethylene are known, but they almost always have the chemical formula (C2H4)nH2. Thus PE is usually a mixture of similar organic compounds that differ in terms of the value of n.
Polyethylene is a thermoplastic polymer consisting of long hydrocarbon chains. Depending on the crystallinity and molecular weight, a melting point and glass transition may or may not be observable. The temperature at which these occur varies strongly with the type of polyethylene. For common commercial grades of medium- and high-density polyethylene the melting point is typically in the range 120 to 130 °C (248 to 266 °F). The melting point for average, commercial, low-density polyethylene is typically 105 to 115 °C (221 to 239 °F).
Most LDPE, MDPE and HDPE grades have excellent chemical resistance, meaning that it is not attacked by strong acids or strong bases. It is also resistant to gentle
A profession is a vocation founded upon specialized educational training, the purpose of which is to supply objective counsel and service to others, for a direct and definite compensation, wholly apart from expectation of other business gain.
Classically, there were only three : divinity, medicine, and law—the so-called "learned professions." The main milestones which mark an occupation being identified as a profession are:
With the rise of technology and occupational specialization in the 19th century, other bodies began to claim professional status: pharmacy, veterinary medicine, nursing, teaching, librarianship, optometry and social work, all of which could claim, using these milestones, to be professions by 1900.
Just as some professions rise in status and power through various stages, so others may decline. This is characterized by the red cloaks of bishops giving way to the black cloaks of lawyers and then to the white cloaks of doctors. More recently formalized disciplines, such as architecture, now have equally long periods of study associated with them.
Although professions enjoy high status and public prestige, not all professionals earn high salaries, and even within
A scimitar ( /ˈsɪmɨtər/ or /ˈsɪmɨtɑr/) is a backsword or sabre with a curved blade, originating in Southwest Asia (Middle East). The Arabic term saif (سيف) translates to "sword" in general, but is normally taken to refer to the scimitar type of curved backsword in particular.
The curved sword or "scimitar" was widespread throughout the Muslim world from at least the Ottoman period, with early examples dating to Abbasid era (9th century) Khurasan. The type harks back to the makhaira type of antiquity, but the Arabic term saif is a loan from Greek xiphos (the straight, double-edged sword of Greek antiquity). The Persian sword now called "shamshir" appears by the 12th century and was popularized in Persia by the early 16th century, and had "relatives" in Turkey (the kilij), the Mughal Empire (the talwar).
The name is thought to be derived from the Persian word shafsher which means “lion’s claw,” due to its long, curved design. The word has been translated through many languages to end at scimitar. Varieties of Persian shamshir have been created, including the Turkish kilij, Indian tulwar, Moroccan nimcha, Afghan pulwar, and Arabian saif.
The term saif in Arabic can refer to any Middle
Sonar (originally an acronym for SOund Navigation And Ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels. Two types of technology share the name "sonar": passive sonar is essentially listening for the sound made by vessels; active sonar is emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. Acoustic location in air was used before the introduction of radar. Sonar may also be used in air for robot navigation, and SODAR (an upward looking in-air sonar) is used for atmospheric investigations. The term sonar is also used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from very low (infrasonic) to extremely high (ultrasonic). The study of underwater sound is known as underwater acoustics or hydroacoustics.
Although some animals (dolphins and bats) have used sound for communication and object detection for millions of years, use by humans in the
A sword is a bladed weapon (edged weapon) used primarily for cutting or thrusting. The precise definition of the term varies with the historical epoch or the geographical region under consideration.
In the most narrow sense, a sword consists of a straight blade with two edges and a hilt. However, in some cases the term may also refer to weapons with a single edge (backsword).
The word sword comes from the Old English sweord, cognate to Old High German swert, Old Norse sverð, from a Proto-Indo-European root *swer- "to wound, to cut". Non-European weapons called "sword" include single-edged weapons such as the Middle Eastern saif, the Chinese dao and the related Japanese katana. The Chinese jian is an example of a non-European double-edged sword, like the European models derived from the double-edged Iron Age sword.
Historically, the sword developed in the Bronze Age, evolving from the dagger; the earliest specimens date to ca. 1600 BC. The Iron Age sword remained fairly short and without a crossguard. The spatha as it developed in the Late Roman army became the predecessor of the European sword of the Middle Ages, at first adopted as the Migration period sword, and only in the High