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In Ireland the AK-47 is associated with The Troubles due to its extensive use by republican paramilitaries during this period. In 2013, a decommissioned AK-47 was included in the "A History of Ireland in 100 Objects" collection. The AK-47 made an appearance in U.S. popular culture as a recurring focus in the Nicolas Cage film "Lord of War" (2005). Numerous monologues in the movie focus on the weapon, and its effects on global conflict and the gun running market. In Iraq and Afghanistan, private military company contractors from the U.K. and other countries used the AK-47 and its variants along with Western firearms such as the AR-15. In 2006, the Colombian musician and peace activist César López devised the "escopetarra", an AK converted into a guitar. One sold for US$17,000 in a fundraiser held to benefit the victims of anti-personnel mines, while another was exhibited at the United Nations' Conference on Disarmament. In Mexico, the AK-47 is known as "Cuerno de Chivo" (literally "Goat's Horn") because of its curved magazine design. It is one of the weapons of choice of Mexican drug cartels. It is sometimes mentioned in Mexican folk music lyrics.
Atanasoff–Berry computer The Atanasoff–Berry computer (ABC) was the first automatic electronic digital computer. The device was limited by the technology of the day. The ABC's priority is debated among historians of computer technology, because it was neither programmable, nor Turing-complete. Conventionally, the ABC would be considered the first electronic ALU (arithmetic logic unit) which is integrated into every modern processor's design. Its unique contribution was to make computing faster by being the first to use vacuum tubes to do arithmetic calculations. Prior to this, slower electro-mechanical methods were used by Konrad Zuse's Z1 computer, and the simultaneously developed Harvard Mark I. The first electronic, programmable, digital machine, the Colossus computer from 1943 to 1945, used similar tube-based technology as ABC. Overview. Conceived in 1937, the machine was built by Iowa State College mathematics and physics professor John Vincent Atanasoff with the help of graduate student Clifford Berry. It was designed only to solve systems of linear equations and was successfully tested in 1942. However, its intermediate result storage mechanism, a paper card writer/reader, was not perfected, and when John Vincent Atanasoff left Iowa State College for World War II assignments, work on the machine was discontinued. The ABC pioneered important elements of modern computing, including binary arithmetic and electronic switching elements, but its special-purpose nature and lack of a changeable, stored program distinguish it from modern computers. The computer was designated an IEEE Milestone in 1990.
Atanasoff and Berry's computer work was not widely known until it was rediscovered in the 1960s, amid patent disputes over the first instance of an electronic computer. At that time ENIAC, that had been created by John Mauchly and J. Presper Eckert, was considered to be the first computer in the modern sense, but in 1973 a U.S. District Court invalidated the ENIAC patent and concluded that the ENIAC inventors had derived the subject matter of the electronic digital computer from Atanasoff. When, in the mid-1970s, the secrecy surrounding the British World War II development of the Colossus computers that pre-dated ENIAC, was lifted and Colossus was described at a conference in Los Alamos, New Mexico, in June 1976, John Mauchly and Konrad Zuse were reported to have been astonished. Design and construction. According to Atanasoff's account, several key principles of the Atanasoff–Berry computer were conceived in a sudden insight after a long nighttime drive to Rock Island, Illinois, during the winter of 1937–38. The ABC innovations included electronic computation, binary arithmetic, parallel processing, regenerative capacitor memory, and a separation of memory and computing functions. The mechanical and logic design was worked out by Atanasoff over the next year. A grant application to build a proof of concept prototype was submitted in March 1939 to the Agronomy department, which was also interested in speeding up computation for economic and research analysis. $5,000 of further funding () to complete the machine came from the nonprofit Research Corporation of New York City.
The ABC was built by Atanasoff and Berry in the basement of the physics building at Iowa State College from 1939 to 1942. The initial funds were released in September, and the 11-tube prototype was first demonstrated in October 1939. A December demonstration prompted a grant for construction of the full-scale machine. The ABC was built and tested over the next two years. A January 15, 1941, story in the "Des Moines Register" announced the ABC as "an electrical computing machine" with more than 300 vacuum tubes that would "compute complicated algebraic equations" (but gave no precise technical description of the computer). The system weighed more than . It contained approximately of wire, 280 dual-triode vacuum tubes, 31 thyratrons, and was about the size of a desk. It was not programmable, which distinguishes it from more general machines of the same era, such as Konrad Zuse's 1941 Z3 (or earlier iterations) and the Colossus computers of 1943–1945. Nor did it implement the stored-program architecture, first implemented in the Manchester Baby of 1948, required for fully general-purpose practical computing machines.
The machine was, however, the first to implement: The memory of the Atanasoff–Berry computer was a system called "regenerative capacitor memory", which consisted of a pair of drums, each containing 1600 capacitors that rotated on a common shaft once per second. The capacitors on each drum were organized into 32 "bands" of 50 (30 active bands and two spares in case a capacitor failed), giving the machine a speed of 30 additions/subtractions per second. Data was represented as 50-bit binary fixed-point numbers. The electronics of the memory and arithmetic units could store and operate on 60 such numbers at a time (3000 bits). The alternating current power-line frequency of 60 Hz was the primary clock rate for the lowest-level operations. The arithmetic logic functions were fully electronic, implemented with vacuum tubes. The family of logic gates ranged from inverters to two- and three-input gates. The input and output levels and operating voltages were compatible between the different gates. Each gate consisted of one inverting vacuum-tube amplifier, preceded by a resistor divider input network that defined the logical function. The control logic functions, which only needed to operate once per drum rotation and therefore did not require electronic speed, were electromechanical, implemented with relays.
The ALU operated on only one bit of each number at a time; it kept the carry/borrow bit in a capacitor for use in the next AC cycle. Although the Atanasoff–Berry computer was an important step up from earlier calculating machines, it was not able to run entirely automatically through an entire problem. An operator was needed to operate the control switches to set up its functions, much like the electro-mechanical calculators and unit record equipment of the time. Selection of the operation to be performed, reading, writing, converting to or from binary to decimal, or reducing a set of equations was made by front-panel switches and, in some cases, jumpers. There were two forms of input and output: primary user input and output and an intermediate results output and input. The intermediate results storage allowed operation on problems too large to be handled entirely within the electronic memory. (The largest problem that could be solved without the use of the intermediate output and input was two simultaneous equations, a trivial problem.)
Intermediate results were binary, written onto paper sheets by electrostatically modifying the resistance at 1500 locations to represent 30 of the 50-bit numbers (one equation). Each sheet could be written or read in one second. The reliability of the system was limited to about 1 error in 100,000 calculations by these units, primarily attributed to lack of control of the sheets' material characteristics. In retrospect, a solution could have been to add a parity bit to each number as written. This problem was not solved by the time Atanasoff left the university for war-related work. Primary user input was decimal, via standard IBM 80-column punched cards, and output was decimal, via a front-panel display. Function. The ABC was designed for a specific purpose the solution of systems of simultaneous linear equations. It could handle systems with up to 29 equations, a difficult problem for the time. Problems of this scale were becoming common in physics, the department in which John Atanasoff worked. The machine could be fed two linear equations with up to 29 variables and a constant term and eliminate one of the variables. This process would be repeated manually for each of the equations, which would result in a system of equations with one fewer variable. Then the whole process would be repeated to eliminate another variable.
George W. Snedecor, the head of Iowa State's Statistics Department, was very likely the first user of an electronic digital computer to solve real-world mathematics problems. He submitted many of these problems to Atanasoff. Patent dispute. On June 26, 1947, J. Presper Eckert and John Mauchly were the first to file for patent on a digital computing device (ENIAC), much to the surprise of Atanasoff. The ABC had been examined by John Mauchly in June 1941, and Isaac Auerbach, a former student of Mauchly's, alleged that it influenced his later work on ENIAC, although Mauchly denied this. The ENIAC patent did not issue until 1964, and by 1967 Honeywell sued Sperry Rand in an attempt to break the ENIAC patents, arguing that the ABC constituted prior art. The United States District Court for the District of Minnesota released its judgement on October 19, 1973, finding in "Honeywell v. Sperry Rand" that the ENIAC patent was a derivative of John Atanasoff's invention. Campbell-Kelly and Aspray conclude: The case was legally resolved on October 19, 1973, when U.S. District Judge Earl R. Larson held the ENIAC patent invalid, ruling that the ENIAC derived many basic ideas from the Atanasoff–Berry computer. Judge Larson explicitly stated:
Herman Goldstine, one of the original developers of ENIAC wrote: Replica. The original ABC was eventually dismantled in 1948, when the university converted the basement to classrooms, and all of its pieces except for one memory drum were discarded. In 1997, a team of researchers led by Delwyn Bluhm and John Gustafson from Ames Laboratory (located on the Iowa State University campus) finished building a working replica of the Atanasoff–Berry computer at a cost of $350,000 (equivalent to $ in ). The replica ABC was on display in the first floor lobby of the Durham Center for Computation and Communication at Iowa State University and was subsequently exhibited at the Computer History Museum.
Andes The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long and wide (widest between 18°S and 20°S latitude) and has an average height of about . The Andes extend from South to North through seven South American countries: Argentina, Chile, Bolivia, Peru, Ecuador, Colombia, and Venezuela. Along their length, the Andes are split into several ranges, separated by intermediate depressions. The Andes are the location of several high plateaus—some of which host major cities such as Quito, Bogotá, Cali, Arequipa, Medellín, Bucaramanga, Sucre, Mérida, El Alto, and La Paz. The Altiplano Plateau is the world's second highest after the Tibetan Plateau. These ranges are in turn grouped into three major divisions based on climate: the Tropical Andes, the Dry Andes, and the Wet Andes. The Andes are the highest mountain range outside of Asia. The range's highest peak, Argentina's Aconcagua, rises to an elevation of about above sea level. The peak of Chimborazo in the Ecuadorian Andes is farther from the Earth's center than any other location on the Earth's surface, due to the equatorial bulge resulting from the Earth's rotation. The world's highest volcanoes are in the Andes, including Ojos del Salado on the Chile-Argentina border, which rises to .
The Andes are also part of the American Cordillera, a chain of mountain ranges (cordillera) that consists of an almost continuous sequence of mountain ranges that form the western "backbone" of the Americas and Antarctica. Etymology. The etymology of the word "Andes" has been debated. The majority consensus is that it derives from the Quechua word "east" as in "Antisuyu" (Quechua for "east region"), one of the four regions of the Inca Empire. The term "cordillera" comes from the Spanish word "cordel" "rope" and is used as a descriptive name for several contiguous sections of the Andes, as well as the entire Andean range, and the combined mountain chain along the western part of the North and South American continents. Geography. The Andes can be divided into three sections: At the northern end of the Andes, the separate Sierra Nevada de Santa Marta range is often, but not always, treated as part of the Northern Andes. The Leeward Antilles islands Aruba, Bonaire, and Curaçao, which lie in the Caribbean Sea off the coast of Venezuela, were formerly thought to represent the submerged peaks of the extreme northern edge of the Andes range, but ongoing geological studies indicate that such a simplification does not do justice to the complex tectonic boundary between the South American and Caribbean plates.
Geology. The Andes are an orogenic belt of mountains along the Pacific Ring of Fire, a zone of volcanic activity that encompasses the Pacific rim of the Americas as well as the Asia-Pacific region. The Andes are the result of tectonic plate processes extending during the Mesozoic and Tertiary eras, caused by the subduction of oceanic crust beneath the South American Plate as the Nazca Plate and South American Plate converge. These processes were accelerated by the effects of climate. As the uplift of the Andes created a rain shadow on the western fringes of Chile, ocean currents and prevailing winds carried moisture away from the Chilean coast. This caused some areas of the subduction zone to be sediment-starved, which in turn prevented the subducting plate from having a well lubricated surface. These factors increased the rate of contractional coastal uplift in the Andes. The main cause of the rise of the Andes is the contraction of the western rim of the South American Plate due to the subduction of the Nazca Plate and the Antarctic Plate. To the east, the Andes range is bounded by several sedimentary basins, such as the Orinoco Basin, the Amazon Basin, the Madre de Dios Basin, and the Gran Chaco, that separate the Andes from the ancient cratons in eastern South America. In the south, the Andes share a long boundary with the former Patagonia Terrane. To the west, the Andes end at the Pacific Ocean, although the Peru-Chile trench can be considered their ultimate western limit. From a geographical approach, the Andes are considered to have their western boundaries marked by the appearance of coastal lowlands and less-rugged topography. The Andes also contain large quantities of iron ore located in many mountains within the range.
The Andean orogen has a series of bends or oroclines. The Bolivian Orocline is a seaward-concave bending in the coast of South America and the Andes Mountains at about 18° S. At this point, the orientation of the Andes turns from northwest in Peru to south in Chile and Argentina. The Andean segments north and south of the Orocline have been rotated 15° counter-clockwise to 20° clockwise respectively. The Bolivian Orocline area overlaps with the area of the maximum width of the Altiplano Plateau, and according to Isacks (1988) the Orocline is related to crustal shortening. The specific point at 18° S where the coastline bends is known as the Arica Elbow. Further south lies the Maipo Orocline, a more subtle orocline between 30° S and 38°S with a seaward-concave break in the trend at 33° S. Near the southern tip of the Andes lies the Patagonian Orocline. Orogeny. The western rim of the South American Plate has been the place of several pre-Andean orogenies since at least the late Proterozoic and early Paleozoic, when several terranes and microcontinents collided and amalgamated with the ancient cratons of eastern South America, by then the South American part of Gondwana.
The formation of the modern Andes began with the events of the Triassic, when Pangaea began the breakup that resulted in developing several rifts. The development continued through the Jurassic Period. It was during the Cretaceous Period that the Andes began to take their present form, by the uplifting, faulting, and folding of sedimentary and metamorphic rocks of the ancient cratons to the east. The rise of the Andes has not been constant, as different regions have had different degrees of tectonic stress, uplift, and erosion. Across the Drake Passage lie the mountains of the Antarctic Peninsula south of the Scotia Plate, which appear to be a continuation of the Andes chain. The far east regions of the Andes experience a series of changes resulting from the Andean orogeny. Parts of the Sunsás Orogen in Amazonian craton disappeared from the surface of the earth, being overridden by the Andes. The Sierras de Córdoba, where the effects of the ancient Pampean orogeny can be observed, owe their modern uplift and relief to the Andean orogeny in the Tertiary. Further south in southern Patagonia, the onset of the Andean orogeny caused the Magallanes Basin to evolve from being an extensional back-arc basin in the Mesozoic to being a contractional foreland basin in the Cenozoic.
Seismic activity. Tectonic forces above the subduction zone along the entire west coast of South America where the Nazca Plate and a part of the Antarctic Plate are sliding beneath the South American Plate continue to produce an ongoing orogenic event resulting in minor to major earthquakes and volcanic eruptions to this day. Many high-magnitude earthquakes have been recorded in the region, such as the 2010 Maule earthquake (M8.8), the 2015 Illapel earthquake (M8.2), and the 1960 Valdivia earthquake (M9.5), which as of 2024 was the strongest ever recorded on seismometers. The amount, magnitude, and type of seismic activity varies greatly along the subduction zone. These differences are due to a wide range of factors, including friction between the plates, angle of subduction, buoyancy of the subducting plate, rate of subduction, and hydration value of the mantle material. The highest rate of seismic activity is observed in the central portion of the boundary, between 33°S and 35°S. In this area, the angle of subduction is very low, meaning the subducting plate is nearly horizontal. Studies of mantle hydration across the subduction zone have shown a correlation between increased material hydration and lower-magnitude, more-frequent seismic activity. Zones exhibiting dehydration instead are thought to have a higher potential for larger, high-magnitude earthquakes in the future.
The mountain range is also a source of shallow intraplate earthquakes within the South American Plate. The largest such earthquake (as of 2024) struck Peru in 1947 and measured 7.5. In the Peruvian Andes, these earthquakes display normal (1946), strike-slip (1976), and reverse (1969, 1983) mechanisms. The Amazonian Craton is actively underthrusted beneath the sub-Andes region of Peru, producing thrust faults. In Colombia, Ecuador, and Peru, thrust faulting occurs along the sub-Andes due in response to contraction brought on by subduction, while in the high Andes, normal faulting occurs in response to gravitational forces. In the extreme south, a major transform fault separates Tierra del Fuego from the small Scotia Plate. Volcanism. The Andes range has many active volcanoes distributed in four volcanic zones separated by areas of inactivity. The Andean volcanism is a result of the subduction of the Nazca Plate and Antarctic Plate underneath the South American Plate. The belt is subdivided into four main volcanic zones that are separated from each other by volcanic gaps. The volcanoes of the belt are diverse in terms of activity style, products, and morphology. Although some differences can be explained by which volcanic zone a volcano belongs to, there are significant differences inside volcanic zones and even between neighboring volcanoes. Despite being a typical location for calc-alkalic and subduction volcanism, the Andean Volcanic Belt has a large range of volcano-tectonic settings, such as rift systems, extensional zones, transpressional faults, subduction of mid-ocean ridges, and seamount chains apart from a large range of crustal thicknesses and magma ascent paths, and different amount of crustal assimilations.
Ore deposits and evaporites. The Andes Mountains host large ore and salt deposits, and some of their eastern fold and thrust belts act as traps for commercially exploitable amounts of hydrocarbons. In the forelands of the Atacama Desert, some of the largest porphyry copper mineralizations occur, making Chile and Peru the first- and second-largest exporters of copper in the world. Porphyry copper in the western slopes of the Andes has been generated by hydrothermal fluids (mostly water) during the cooling of plutons or volcanic systems. The porphyry mineralization further benefited from the dry climate that reduced the disturbing actions of meteoric water. The dry climate in the central western Andes has also led to the creation of extensive saltpeter deposits that were extensively mined until the invention of synthetic nitrates. Yet another result of the dry climate are the salars of Atacama and Uyuni, the former being the largest source of lithium and the latter the world's largest reserve of the element. Early Mesozoic and Neogene plutonism in Bolivia's Cordillera Central created the Bolivian tin belt as well as the famous, now mostly depleted, silver deposits of Cerro Rico de Potosí.
Climate. The Andes Mountains is connected connection to the climate of South America, particularly through the hyper-arid conditions of the adjacent Atacama Desert. The Atacama Bench, a prominent low-relief feature along the Pacific seaboard, serves as a key geomorphological record of the long-term interplay between Andean tectonics and Cenozoic climate. While the initial uplift and shortening of the Andes were driven by the subduction of the Nazca Plate beneath the South American Plate, arid climate acted as an important feedback mechanism. Reduced erosion rates in the increasingly arid Atacama region may have effectively stopped tectonic activity in certain parts of the mountain range. This lack of erosion could have facilitated the eastward propagation of deformation, leading to the widening of the Andean orogen over time. Thus, the Atacama Desert and its geological features, like the Atacama Bench, offer critical insights into the coupled evolution of the Andes Mountains and the changing regional climate.
History. The Andes Mountains, initially inhabited by hunter-gatherers, experienced the development of agriculture and the rise of politically centralized civilizations, which culminated in the establishment of the century-long Inca Empire. This all changed in the 16th century, when the Spanish conquistadors colonized the mountains in advance of the mining economy. In the tide of anti-imperialist nationalism, the Andes became the scene of a series of independence wars in the 19th century, when rebel forces swept through the region to overthrow Spanish colonial rule. Since then, many former Spanish territories have become five independent Andean states. Climate and hydrology. The climate in the Andes varies greatly depending on latitude, altitude, and proximity to the sea. Temperature, atmospheric pressure, and humidity decrease in higher elevations. The southern section is rainy and cool, while the central section is dry. The northern Andes are typically rainy and warm, with an average temperature of in Colombia. The climate is known to change drastically in rather short distances. Rainforests exist just kilometers away from the snow-covered peak of Cotopaxi. The mountains have a large effect on the temperatures of nearby areas. The snow line depends on the location. It is between in the tropical Ecuadorian, Colombian, Venezuelan, and northern Peruvian Andes, rising to in the drier mountains of southern Peru and northern Chile south to about 30°S before descending to on Aconcagua at 32°S, at 40°S, at 50°S, and only in Tierra del Fuego at 55°S; from 50°S, several of the larger glaciers descend to sea level.
The Andes of Chile and Argentina can be divided into two climatic and glaciological zones: the Dry Andes and the Wet Andes. Since the Dry Andes extend from the latitudes of the Atacama Desert to the area of the Maule River, precipitation is more sporadic, and there are strong temperature oscillations. The line of equilibrium may shift drastically over short periods of time, leaving a whole glacier in the ablation area or in the accumulation area. In the high Andes of Central Chile and Mendoza Province, rock glaciers are larger and more common than glaciers; this is due to the high exposure to solar radiation. In these regions, glaciers occur typically at higher altitudes than rock glaciers. The lowest active rock glaciers occur at 900 m a.s.l. in Aconcagua. Though precipitation increases with height, there are semiarid conditions in the nearly highest mountains of the Andes. This dry steppe climate is considered to be typical of the subtropical position at 32–34° S. The valley bottoms have no woods, just dwarf scrub. The largest glaciers, for example the Plomo Glacier and the Horcones Glaciers, do not even reach in length and have only insignificant ice thickness. At glacial times, however, 20,000 years ago, the glaciers were over ten times longer. On the east side of this section of the Mendozina Andes, they flowed down to and on the west side to about above sea level. The massifs of Aconcagua (), Tupungato (), and Nevado Juncal () are tens of kilometres away from each other and were connected by a joint ice stream network. The Andes' dendritic glacier arms, components of valley glaciers, were up to long and over thick, and spanned a vertical distance of . The climatic glacier snowline (ELA) was lowered from to at glacial times.
Flora. The Andean region cuts across several natural and floristic regions, due to its extension, from Caribbean Venezuela to cold, windy, and wet Cape Horn passing through the hyperarid Atacama Desert. Rainforests and tropical dry forests used to encircle much of the northern Andes but are now greatly diminished, especially in the Chocó and inter-Andean valleys of Colombia. Opposite the humid Andean slopes are the relatively dry Andean slopes in most of western Peru, Chile, and Argentina. Along with several Interandean Valles, they are typically dominated by deciduous woodland, shrub and xeric vegetation, reaching the extreme in the slopes near the virtually lifeless Atacama Desert. About 30,000 species of vascular plants live in the Andes, with roughly half being endemic to the region, surpassing the diversity of any other hotspot. The small tree "Cinchona pubescens", a source of quinine that is used to treat malaria, is found widely in the Andes as far south as Bolivia. Other important crops that originated from the Andes are tobacco and potatoes. The high-altitude "Polylepis" forests and woodlands are found in the Andean areas of Colombia, Ecuador, Peru, Bolivia, and Chile. These trees, by locals referred to as Queñua, Yagual, and other names, can be found at altitudes of above sea level. It remains unclear if the patchy distribution of these forests and woodlands is natural, or the result of clearing that began during the Incan period. Regardless, in modern times, the clearance has accelerated, and the trees are now considered highly endangered, with some believing that as little as 10% of the original woodland remains.
Fauna. The Andes are rich in fauna: With almost 1,000 species, of which roughly 2/3 are endemic to the region, the Andes are the most important region in the world for amphibians. The diversity of animals in the Andes is high, with almost 600 species of mammals (13% endemic), more than 1,700 species of birds (about 1/3 endemic), more than 600 species of reptiles (about 45% endemic), and almost 400 species of fish (about 1/3 endemic). The vicuña and guanaco can be found living in the Altiplano, while the closely related domesticated llama and alpaca are widely kept by locals as pack animals and for their meat and wool. The crepuscular (active during dawn and dusk) chinchillas, two threatened members of the rodent order, inhabit the Andes' alpine regions. The Andean condor, the largest bird of its kind in the Western Hemisphere, occurs throughout much of the Andes but generally in very low densities. Other animals found in the relatively open habitats of the high Andes include the huemul, cougar, foxes in the genus "Pseudalopex", and, for birds, certain species of tinamous (notably members of the genus "Nothoprocta"), Andean goose, giant coot, flamingos (mainly associated with hypersaline lakes), lesser rhea, Andean flicker, diademed sandpiper-plover, miners, sierra-finches and diuca-finches.
Lake Titicaca hosts several endemics, among them the highly endangered Titicaca flightless grebe and Titicaca water frog. A few species of hummingbirds, notably some hillstars, can be seen at altitudes above , but far higher diversities can be found at lower altitudes, especially in the humid Andean forests ("cloud forests") growing on slopes in Colombia, Ecuador, Peru, Bolivia, and far northwestern Argentina. These forest-types, which includes the Yungas and parts of the Chocó, are very rich in flora and fauna, although few large mammals exist, exceptions being the threatened mountain tapir, spectacled bear, and yellow-tailed woolly monkey. Birds of humid Andean forests include mountain toucans, quetzals, and the Andean cock-of-the-rock, while mixed-species flocks dominated by tanagers and furnariids are commonly seen—in contrast to several vocal but typically cryptic species of wrens, tapaculos, and antpittas. A number of species such as the royal cinclodes and white-browed tit-spinetail are associated with "Polylepis", and consequently also threatened.
Human activity. The Andes Mountains form a north–south axis of cultural influences. A long series of cultural development culminated in the expansion of the Inca civilization and Inca Empire in the central Andes during the 15th century. The Incas formed this civilization through imperialistic militarism as well as careful and meticulous governmental management. The government sponsored the construction of aqueducts and roads in addition to pre-existing installations. Some of these constructions still exist today. Devastated by European diseases and by civil war, the Incas were defeated in 1532 by an alliance composed of tens of thousands of allies from nations they had subjugated (e.g. Huancas, Chachapoyas, Cañaris) and a small army of 180 Spaniards led by Francisco Pizarro. One of the few Inca sites the Spanish never found in their conquest was Machu Picchu, which lay hidden on a peak on the eastern edge of the Andes where they descend to the Amazon. The main surviving languages of the Andean peoples are those of the Quechua and Aymara language families. Woodbine Parish and Joseph Barclay Pentland surveyed a large part of the Bolivian Andes from 1826 to 1827.
Cities. In modern times, the largest cities in the Andes are Bogotá, with a metropolitan population of over ten million, and Santiago, Medellín, Cali, and Quito. Lima is a coastal city adjacent to the Andes and is the largest city of all Andean countries. It is the seat of the Andean Community of Nations. La Paz, Bolivia's seat of government, is the highest capital city in the world, at an elevation of approximately . Parts of the La Paz conurbation, including the city of El Alto, extend up to . Other cities in or near the Andes include Bariloche, Catamarca, Jujuy, Mendoza, Salta, San Juan, Tucumán, and Ushuaia in Argentina; Calama and Rancagua in Chile; Cochabamba, Oruro, Potosí, Sucre, Tarija, and Yacuiba in Bolivia; Arequipa, Cajamarca, Cusco, Huancayo, Huánuco, Huaraz, Juliaca, and Puno in Peru; Ambato, Cuenca, Ibarra, Latacunga, Loja, Riobamba, and Tulcán in Ecuador; Armenia, Cúcuta, Bucaramanga, Duitama, Ibagué, Ipiales, Manizales, Palmira, Pasto, Pereira, Popayán, Rionegro, Sogamoso, Tunja, and Villavicencio in Colombia; and Barquisimeto, La Grita, Mérida, San Cristóbal, Tovar, Trujillo, and Valera in Venezuela. The cities of Caracas, Valencia, and Maracay are in the Venezuelan Coastal Range, which is a debatable extension of the Andes at the northern extremity of South America.
Transportation. Cities and large towns are connected with asphalt-paved roads, while smaller towns are often connected by dirt roads, which may require a four-wheel-drive vehicle. The rough terrain has historically put the costs of building highways and railroads that cross the Andes out of reach of most neighboring countries, even with modern civil engineering practices. For example, the main crossover of the Andes between Argentina and Chile is still accomplished through the Paso Internacional Los Libertadores. Only recently have the ends of some highways that came rather close to one another from the east and the west been connected. Much of the transportation of passengers is done via aircraft. There is one railroad that connects Chile with Peru via the Andes, however, and there are others that make the same connection via southern Bolivia. There are multiple highways in Bolivia that cross the Andes. Some of these were built during a period of war between Bolivia and Paraguay, in order to transport Bolivian troops and their supplies to the war front in the lowlands of southeastern Bolivia and western Paraguay.
For decades, Chile claimed ownership of land on the eastern side of the Andes. These claims were given up in about 1870 during the War of the Pacific between Chile and the allied Bolivia and Peru, in a diplomatic deal to keep Peru out of the war. The Chilean Army and Chilean Navy defeated the combined forces of Bolivia and Peru, and Chile took over Bolivia's only province on the Pacific Coast, some land from Peru that was returned to Peru decades later. Bolivia has been completely landlocked ever since. It mostly uses seaports in eastern Argentina and Uruguay for international trade because its diplomatic relations with Chile have been suspended since 1978. Because of the tortuous terrain in places, villages and towns in the mountains—to which travel via motorized vehicles is of little use—are still located in the high Andes of Chile, Bolivia, Peru, and Ecuador. Locally, the relatives of the camel, the llama, and the alpaca continue to carry out important uses as pack animals, but this use has generally diminished in modern times. Donkeys, mules, and horses are also useful.
Agriculture. The ancient peoples of the Andes such as the Incas have practiced irrigation techniques for over 6,000 years. Because of the mountain slopes, terracing has been a common practice. Terracing, however, was only extensively employed after Incan imperial expansions to fuel their expanding realm. The potato holds a very important role as an internally consumed staple crop. Maize was also an important crop for these people, and was used for the production of chicha, important to Andean native people. Currently, tobacco, cotton, and coffee are the main export crops. Coca, despite eradication programs in some countries, remains an important crop for legal local use in a mildly stimulating herbal tea, and illegally for the production of cocaine. Irrigation. In unirrigated land, pasture is the most common type of land use. In the rainy season (summer), part of the rangeland is used for cropping (mainly potatoes, barley, broad beans, and wheat). Irrigation is helpful in advancing the sowing data of the summer crops, which guarantees an early yield in periods of food shortage. Also, by early sowing, maize can be cultivated higher up in the mountains (up to ). In addition, it makes cropping in the dry season (winter) possible and allows the cultivation of frost-resistant vegetable crops like onion and carrot.
Mining. The Andes rose to fame for their mineral wealth during the Spanish conquest of South America. Although Andean Amerindian peoples crafted ceremonial jewelry of gold and other metals, the mineralizations of the Andes were first mined on a large scale after the Spanish arrival. Potosí in present-day Bolivia and Cerro de Pasco in Peru were among the principal mines of the Spanish Empire in the New World. Río de la Plata and Argentina derive their names from the silver of Potosí. Currently, mining in the Andes of Chile and Peru places these countries as the first and second major producers of copper in the world. Peru also contains the 4th-largest goldmine in the world: the Yanacocha. The Bolivian Andes principally produce tin, although historically silver mining had a huge impact on the economy of 17th-century Europe. There is a long history of mining in the Andes, from the Spanish silver mines in Potosí in the 16th century to the vast current porphyry copper deposits of Chuquicamata and Escondida in Chile and Toquepala in Peru. Other metals, including iron, gold, and tin, in addition to non-metallic resources are important. The Andes have a vast supply of lithium; Argentina, Bolivia, and Chile have the three largest reserves in the world respectively.
Accion Andina's reforestation plan. Depending on the country, this species goes by different names. In Peru, it is known as queñual, queuña, or queñoa; in Bolivia, as kewiña; in Ecuador, as yagual; and in Argentina, tabaquillo. Regardless of the name, "Polylepis" is a high-Andean genus encompassing up to 45 species of trees and shrubs distributed across the South American Andes, from Venezuela to Patagonia, found up to 5,000 meters above sea level. In 2000, biologist Constantino Aucca founded Ecoan, an NGO promoting conservation of threatened species and endangered Andean ecosystems. Since then, the organization has reforested 4.5 million plants across 16 protected areas, involving 37 Andean communities in the process. Aucca's efforts caught the attention of Florent Kaiser, a Franco-German forest engineer. During a visit to Peru in 2018, Aucca invited Kaiser to the Queuña Raymi festival, where Cusco communities engage in queñual reforestation. Peaks. This list contains some of the major peaks in the Andes mountain range. The highest peak is Aconcagua of Argentina.
Ancylopoda Ancylopoda is a group of browsing, herbivorous, mammals in the Perissodactyla that show long, curved and cleft claws. Morphological evidence indicates the Ancylopoda diverged from the tapirs, rhinoceroses and horses (Euperissodactyla) after the Brontotheria; however, earlier authorities such as Osborn sometimes considered the Ancylopoda to be outside Perissodactyla or, as was popular more recently, to be related to Brontotheriidae. "Macrotherium", which is typically from the middle Miocene of Sansan, in Gers, France, may indicate a distinct genus. Limb-bones resembling those of "Macrotherium", but relatively stouter, have been described from the Pliocene beds of Attica and Samos as "Ancylotherium". In the Americas, the names "Morothorium" and "Moropus" have been applied to similar bones, in the belief that they indicated xenarthrans. "Macrotherium magnum" must have been an animal of about in length.
Anchor An anchor is a device, normally made of metal, used to secure a vessel to the bed of a body of water to prevent the craft from drifting due to wind or current. The word derives from Latin "", which itself comes from the Greek (). Anchors can either be temporary or permanent. Permanent anchors are used in the creation of a mooring, and are rarely moved; a specialist service is normally needed to move or maintain them. Vessels carry one or more temporary anchors, which may be of different designs and weights. A sea anchor is a drag device, not in contact with the seabed, used to minimize drift of a vessel relative to the water. A drogue is a drag device used to slow or help steer a vessel running before a storm in a following or overtaking sea, or when crossing a bar in a breaking sea. Anchoring. Anchors achieve holding power either by "hooking" into the seabed, or weight, or a combination of the two. The weight of the anchor chain can be more than that of the anchor and is critical to proper holding. Permanent moorings use large masses (commonly a block or slab of concrete) resting on the seabed. Semi-permanent mooring anchors (such as mushroom anchors) and large ship's anchors derive a significant portion of their holding power from their weight, while also hooking or embedding in the bottom. Modern anchors for smaller vessels have metal "flukes" that hook on to rocks on the bottom or bury themselves in soft seabed.
The vessel is attached to the anchor by the "rode" (also called a "cable" or a "warp"). It can be made of rope, chain or a combination of rope and chain. The ratio of the length of rode to the water depth is known as the scope. Holding ground is the area of sea floor that holds an anchor, and thus the attached ship or boat. Different types of anchor are designed to hold in different types of holding ground. Some bottom materials hold better than others; for instance, hard sand holds well, shell holds poorly. Holding ground may be fouled with obstacles. An anchorage location may be chosen for its holding ground. In poor holding ground, only the weight of an anchor and chain matters; in good holding ground, it is able to dig in, and the holding power can be significantly higher. The basic anchoring consists of determining the location, dropping the anchor, laying out the scope, setting the hook, and assessing where the vessel ends up. The ship seeks a location that is sufficiently protected; has suitable holding ground, enough depth at low tide and enough room for the boat to swing.
The location to drop the anchor should be approached from down wind or down current, whichever is stronger. As the chosen spot is approached, the vessel should be stopped or even beginning to drift back. The anchor should initially be lowered quickly but under control until it is on the bottom (see anchor windlass). The vessel should continue to drift back, and the cable should be veered out under control (slowly) so it is relatively straight. Once the desired scope is laid out, the vessel should be gently forced astern, usually using the auxiliary motor but possibly by backing a sail. A hand on the anchor line may telegraph a series of jerks and jolts, indicating the anchor is dragging, or a smooth tension indicative of digging in. As the anchor begins to dig in and resist backward force, the engine may be throttled up to get a thorough set. If the anchor continues to drag, or sets after having dragged too far, it should be retrieved and moved back to the desired position (or another location chosen.) Using an anchor weight, kellet or sentinel.
Lowering a concentrated, heavy weight down the anchor line – rope or chain – directly in front of the bow to the seabed behaves like a heavy chain rode and lowers the angle of pull on the anchor. If the weight is suspended off the seabed it acts as a spring or shock absorber to dampen the sudden actions that are normally transmitted to the anchor and can cause it to dislodge and drag. In light conditions, a kellet reduces the swing of the vessel considerably. In heavier conditions these effects disappear as the rode becomes straightened and the weight ineffective. Known as an "anchor chum weight" or "angel" in the UK. Forked moor. Using two anchors set approximately 45° apart, or wider angles up to 90°, from the bow is a strong mooring for facing into strong winds. To set anchors in this way, first one anchor is set in the normal fashion. Then, taking in on the first cable as the boat is motored into the wind and letting slack while drifting back, a second anchor is set approximately a half-scope away from the first on a line perpendicular to the wind. After this second anchor is set, the scope on the first is taken up until the vessel is lying between the two anchors and the load is taken equally on each cable.
This moor also to some degree limits the range of a vessel's swing to a narrower oval. Care should be taken that other vessels do not swing down on the boat due to the limited swing range. Bow and stern. (Not to be mistaken with the "Bahamian moor", below.) In the "bow and stern" technique, an anchor is set off each the bow and the stern, which can severely limit a vessel's swing range and also align it to steady wind, current or wave conditions. One method of accomplishing this moor is to set a bow anchor normally, then drop back to the limit of the bow cable (or to double the desired scope, e.g. 8:1 if the eventual scope should be 4:1, 10:1 if the eventual scope should be 5:1, etc.) to lower a stern anchor. By taking up on the bow cable the stern anchor can be set. After both anchors are set, tension is taken up on both cables to limit the swing or to align the vessel. Bahamian moor. Similar to the above, a "Bahamian moor" is used to sharply limit the swing range of a vessel, but allows it to swing to a current. One of the primary characteristics of this technique is the use of a swivel as follows: the first anchor is set normally, and the vessel drops back to the limit of anchor cable. A second anchor is attached to the end of the anchor cable, and is dropped and set. A swivel is attached to the middle of the anchor cable, and the vessel connected to that.
The vessel now swings in the middle of two anchors, which is acceptable in strong reversing currents, but a wind perpendicular to the current may break out the anchors, as they are not aligned for this load. Backing an anchor. Also known as "tandem anchoring", in this technique two anchors are deployed in line with each other, on the same rode. With the foremost anchor reducing the load on the aft-most, this technique can develop great holding power and may be appropriate in "ultimate storm" circumstances. It does not limit swinging range, and might not be suitable in some circumstances. There are complications, and the technique requires careful preparation and a level of skill and experience above that required for a single anchor. Kedging. "Kedging" or "warping" is a technique for moving or turning a ship by using a relatively light anchor. In yachts, a kedge anchor is an anchor carried in addition to the main, or bower, anchor, and usually stowed aft. Every yacht should carry at least two anchors – the main or "bower" anchor and a second lighter "kedge" anchor. It is used occasionally when it is necessary to limit the turning circle as the yacht swings when it is anchored, such as in a narrow river or a deep pool in an otherwise shallow area. Kedge anchors are sometimes used to recover vessels that have run aground.
For ships, a kedge may be dropped while a ship is underway, or carried out in a suitable direction by a tender or ship's boat to enable the ship to be winched off if aground or swung into a particular heading, or even to be held steady against a tidal or other stream. Historically, it was of particular relevance to sailing warships that used them to outmaneuver opponents when the wind had dropped but might be used by any vessel in confined, shoal water to place it in a more desirable position, provided she had enough manpower. Club hauling. Club hauling is an archaic technique. When a vessel is in a narrow channel or on a lee shore so that there is no room to tack the vessel in a conventional manner, an anchor attached to the lee quarter may be dropped from the lee bow. This is deployed when the vessel is head to wind and has lost headway. As the vessel gathers sternway the strain on the cable pivots the vessel around what is now the weather quarter turning the vessel onto the other tack. The anchor is then normally cut away (the ship's momentum prevents recovery without aborting the maneuver).
Multiple anchor patterns. When it is necessary to moor a ship or floating platform with precise positioning and alignment, such as when drilling the seabed, for some types of salvage work, and for some types of diving operation, several anchors are set in a pattern which allows the vessel to be positioned by shortening and lengthening the scope of the anchors, and adjusting the tension on the rodes. The anchors are usually laid in prearranged positions by an anchor tender, and the moored vessel uses its own winches to adjust position and tension. Similar arrangements are used for some types of single buoy moorings, like the catenary anchor leg mooring (CALM) used for loading and unloading liquid cargoes. Weighing anchor. Since all anchors that embed themselves in the bottom require the strain to be along the seabed, anchors can be broken out of the bottom by shortening the rope until the vessel is directly above the anchor; at this point the anchor chain is "up and down", in naval parlance. If necessary, motoring slowly around the location of the anchor also helps dislodge it. Anchors are sometimes fitted with a trip line attached to the crown, by which they can be unhooked from underwater hazards.
The term "aweigh" describes an anchor when it is hanging on the rope and not resting on the bottom. This is linked to the term "to weigh anchor", meaning to lift the anchor from the sea bed, allowing the ship or boat to move. An anchor is described as "aweigh" when it has been broken out of the bottom and is being hauled up to be "stowed". "Aweigh" should not be confused with "under way", which describes a vessel that is not "moored" to a dock or "anchored", whether or not the vessel is moving through the water. "Aweigh" is also often confused with "away", which is incorrect. History. Evolution of the anchor. The earliest anchors were probably rocks, and many rock anchors have been found dating from at least the Bronze Age. Pre-European Māori waka (canoes) used one or more hollowed stones, tied with flax ropes, as anchors. Many modern moorings still rely on a large rock as the primary element of their design. However, using pure weight to resist the forces of a storm works well only as a permanent mooring; a large enough rock would be nearly impossible to move to a new location.
The ancient Greeks used baskets of stones, large sacks filled with sand, and wooden logs filled with lead. According to Apollonius Rhodius and Stephen of Byzantium, anchors were formed of stone, and Athenaeus states that they were also sometimes made of wood. Such anchors held the vessel merely by their weight and by their friction along the bottom. Fluked anchors. Iron was afterwards introduced for the construction of anchors, and an improvement was made by forming them with teeth, or "flukes", to fasten themselves into the bottom. This is the iconic anchor shape most familiar to non-sailors. This form has been used since antiquity. The Roman Nemi ships of the 1st century AD used this form. The Viking Ladby ship (probably 10th century) used a fluked anchor of this type, made of iron, which would have had a wooden stock mounted perpendicular to the shank and flukes to make the flukes contact the bottom at a suitable angle to hook or penetrate. Admiralty anchor. The Admiralty Pattern anchor, or simply "Admiralty", also known as a "Fisherman", consists of a central shank with a ring or shackle for attaching the rode (the rope, chain, or cable connecting the ship and the anchor). At the other end of the shank there are two arms, carrying the flukes, while the stock is mounted to the shackle end, at ninety degrees to the arms. When the anchor lands on the bottom, it generally falls over with the arms parallel to the seabed. As a strain comes onto the rope, the stock digs into the bottom, canting the anchor until one of the flukes catches and digs into the bottom.
The Admiralty Anchor is an entirely independent reinvention of a classical design, as seen in one of the Nemi ship anchors. This basic design remained unchanged for centuries, with the most significant changes being to the overall proportions, and a move from stocks made of wood to iron stocks in the late 1830s and early 1840s. Since one fluke always protrudes up from the set anchor, there is a great tendency of the rode to foul the anchor as the vessel swings due to wind or current shifts. When this happens, the anchor may be pulled out of the bottom, and in some cases may need to be hauled up to be re-set. In the mid-19th century, numerous modifications were attempted to alleviate these problems, as well as improve holding power, including one-armed mooring anchors. The most successful of these "patent anchors", the Trotman Anchor, introduced a pivot at the centre of the crown where the arms join the shank, allowing the "idle" upper arm to fold against the shank. When deployed the lower arm may fold against the shank tilting the tip of the fluke upwards, so each fluke has a tripping palm at its base, to hook on the bottom as the folded arm drags along the seabed, which unfolds the downward oriented arm until the tip of the fluke can engage the bottom.
Handling and storage of these anchors requires special equipment and procedures. Once the anchor is hauled up to the hawsepipe, the ring end is hoisted up to the end of a timber projecting from the bow known as the cathead. The crown of the anchor is then hauled up with a heavy tackle until one fluke can be hooked over the rail. This is known as "catting and fishing" the anchor. Before dropping the anchor, the fishing process is reversed, and the anchor is dropped from the end of the cathead. Stockless anchor. The stockless anchor, patented in England in 1821, represented the first significant departure in anchor design in centuries. Although their holding-power-to-weight ratio is significantly lower than admiralty pattern anchors, their ease of handling and stowage aboard large ships led to almost universal adoption. In contrast to the elaborate stowage procedures for earlier anchors, stockless anchors are simply hauled up until they rest with the shank inside the hawsepipes, and the flukes against the hull (or inside a recess in the hull called the anchor box).
While there are numerous variations, stockless anchors consist of a set of heavy flukes connected by a pivot or ball and socket joint to a shank. Cast into the crown of the anchor is a set of tripping palms, projections that drag on the bottom, forcing the main flukes to dig in. Small boat anchors. Until the mid-20th century, anchors for smaller vessels were either scaled-down versions of admiralty anchors, or simple grapnels. As new designs with greater holding-power-to-weight ratios were sought, a great variety of anchor designs have emerged. Many of these designs are still under patent, and other types are best known by their original trademarked names. Grapnel anchor / drag. A traditional design, the grapnel is merely a shank (no stock) with four or more tines, also known as a "drag". It has a benefit in that, no matter how it reaches the bottom, one or more tines are aimed to set. In coral, or rock, it is often able to set quickly by hooking into the structure, but may be more difficult to retrieve. A grapnel is often quite light, and may have additional uses as a tool to recover gear lost overboard. Its weight also makes it relatively easy to move and carry, however its shape is generally not compact and it may be awkward to stow unless a collapsing model is used.
Grapnels rarely have enough fluke area to develop much hold in sand, clay, or mud. It is not unknown for the anchor to foul on its own rode, or to foul the tines with refuse from the bottom, preventing it from digging in. On the other hand, it is quite possible for this anchor to find such a good hook that, without a trip line from the crown, it is impossible to retrieve. Herreshoff anchor. Designed by yacht designer L. Francis Herreshoff, this is essentially the same pattern as an admiralty anchor, albeit with small diamond-shaped flukes or palms. The novelty of the design lay in the means by which it could be broken down into three pieces for stowage. In use, it still presents all the issues of the admiralty pattern anchor. Northill anchor. Originally designed as a lightweight anchor for seaplanes, this design consists of two plough-like blades mounted to a shank, with a folding stock crossing through the crown of the anchor. CQR plough anchor. Many manufacturers produce a plough-type anchor, so-named after its resemblance to an agricultural plough. All such anchors are copied from the original CQR ("Coastal Quick Release", or "Clyde Quick Release", later rebranded as 'secure' by Lewmar), a 1933 design patented in the UK by mathematician Geoffrey Ingram Taylor.
Plough anchors stow conveniently in a roller at the bow, and have been popular with cruising sailors and private boaters. Ploughs can be moderately good in all types of seafloor, though not exceptional in any. Contrary to popular belief, the CQR's hinged shank is not to allow the anchor to turn with direction changes rather than breaking out, but actually to prevent the shank's weight from disrupting the fluke's orientation while setting. The hinge can wear out and may trap a sailor's fingers. Some later plough anchors have a rigid shank, such as the Lewmar's "Delta". A plough anchor has a fundamental flaw: like its namesake, the agricultural plough, it digs in but then tends to break out back to the surface. Plough anchors sometimes have difficulty setting at all, and instead skip across the seafloor. By contrast, modern efficient anchors tend to be "scoop" types that dig ever deeper. Delta anchor. The Delta anchor was derived from the CQR. It was patented by Philip McCarron, James Stewart, and Gordon Lyall of British marine manufacturer Simpson-Lawrence Ltd in 1992. It was designed as an advance over the anchors used for floating systems such as oil rigs. It retains the weighted tip of the CQR but has a much higher fluke area to weight ratio than its predecessor. The designers also eliminated the sometimes troublesome hinge. It is a plough anchor with a rigid, arched shank. It is described as "self-launching" because it can be dropped from a bow roller simply by paying out the rode, without manual assistance. This is an oft copied design with the European Brake and Australian Sarca Excel being two of the more notable ones. Although it is a plough type anchor, it sets and holds reasonably well in hard bottoms.
Danforth anchor. American Richard Danforth invented the Danforth Anchor in the 1940s for use aboard landing craft. It uses a stock at the crown to which two large flat triangular flukes are attached. The stock is hinged so the flukes can orient toward the bottom (and on some designs may be adjusted for an optimal angle depending on the bottom type). Tripping palms at the crown act to tip the flukes into the seabed. The design is a burying variety, and once well set can develop high resistance. Its lightweight and compact flat design make it easy to retrieve and relatively easy to store; some anchor rollers and hawsepipes can accommodate a fluke-style anchor. A Danforth does not usually penetrate or hold in gravel or weeds. In boulders and coral it may hold by acting as a hook. If there is much current, or if the vessel is moving while dropping the anchor, it may "kite" or "skate" over the bottom due to the large fluke area acting as a sail or wing. The FOB HP anchor designed in Brittany in the 1970s is a Danforth variant designed to give increased holding through its use of rounded flukes setting at a 30° angle.
The Fortress is an American aluminum alloy Danforth variant that can be disassembled for storage and it features an adjustable 32° and 45° shank/fluke angle to improve holding capability in common sea bottoms such as hard sand and soft mud. This anchor performed well in a 1989 US Naval Sea Systems Command (NAVSEA) test and in an August 2014 holding power test that was conducted in the soft mud bottoms of the Chesapeake Bay. Bruce or claw anchor. This claw-shaped anchor was designed by Peter Bruce from Scotland in the 1970s. Bruce gained his early reputation from the production of large-scale commercial anchors for ships and fixed installations such as oil rigs. It was later scaled down for small boats, and copies of this popular design abound. The Bruce and its copies, known generically as "claw type anchors", have been adopted on smaller boats (partly because they stow easily on a bow roller) but they are most effective in larger sizes. Claw anchors are quite popular on charter fleets as they have a high chance to set on the first try in many bottoms. They have the reputation of not breaking out with tide or wind changes, instead slowly turning in the bottom to align with the force.
Bruce anchors can have difficulty penetrating weedy bottoms and grass. They offer a fairly low holding-power-to-weight ratio and generally have to be oversized to compete with newer types. Scoop type anchors. Three time circumnavigator German Rolf Kaczirek invented the Bügel Anker in the 1980s. Kaczirek wanted an anchor that was self-righting without necessitating a ballasted tip. Instead, he added a roll bar and switched out the plough share for a flat blade design. As none of the innovations of this anchor were patented, copies of it abound. Alain Poiraud of France introduced the scoop type anchor in 1996. Similar in design to the Bügel anchor, Poiraud's design features a concave fluke shaped like the blade of a shovel, with a shank attached parallel to the fluke, and the load applied toward the digging end. It is designed to dig into the bottom like a shovel, and dig deeper as more pressure is applied. The common challenge with all the scoop type anchors is that they set so well, they can be difficult to weigh.
Permanent anchors. These are used where the vessel is permanently or semi-permanently sited, for example in the case of lightvessels or channel marker buoys. The anchor needs to hold the vessel in all weathers, including the most severe storm, but needs to be lifted only occasionally, at most – for example, only if the vessel is to be towed into port for maintenance. An alternative to using an anchor under these circumstances, especially if the anchor need never be lifted at all, may be to use a pile that is driven into the seabed. Permanent anchors come in a wide range of types and have no standard form. A slab of rock with an iron staple in it to attach a chain to would serve the purpose, as would any dense object of appropriate weight (for instance, an engine block). Modern moorings may be anchored by augers, which look and act like oversized screws drilled into the seabed, or by barbed metal beams pounded in (or even driven in with explosives) like pilings, or by a variety of other non-mass means of getting a grip on the bottom. One method of building a mooring is to use three or more conventional anchors laid out with short lengths of chain attached to a swivel, so no matter which direction the vessel moves, one or more anchors are aligned to resist the force.
Mushroom. The mushroom anchor is suitable where the seabed is composed of silt or fine sand. It was invented by Robert Stevenson, for use by an 82-ton converted fishing boat, "Pharos", which was used as a lightvessel between 1807 and 1810 near to Bell Rock whilst the lighthouse was being constructed. It was equipped with a 1.5-ton example. It is shaped like an inverted mushroom, the head becoming buried in the silt. A counterweight is often provided at the other end of the shank to lay it down before it becomes buried. A mushroom anchor normally sinks in the silt to the point where it has displaced its own weight in bottom material, thus greatly increasing its holding power. These anchors are suitable only for a silt or mud bottom, since they rely upon suction and cohesion of the bottom material, which rocky or coarse sand bottoms lack. The holding power of this anchor is at best about twice its weight until it becomes buried, when it can be as much as ten times its weight. They are available in sizes from about 5 kg up to several tons.
Deadweight. A deadweight is an anchor that relies solely on being a heavy weight. It is usually just a large block of concrete or stone at the end of the chain. Its holding power is defined by its weight underwater (i.e., taking its buoyancy into account) regardless of the type of seabed, although suction can increase this if it becomes buried. Consequently, deadweight anchors are used where mushroom anchors are unsuitable, for example in rock, gravel or coarse sand. An advantage of a deadweight anchor over a mushroom is that if it does drag, it continues to provide its original holding force. The disadvantage of using deadweight anchors in conditions where a mushroom anchor could be used is that it needs to be around ten times the weight of the equivalent mushroom anchor. Auger. Auger anchors can be used to anchor permanent moorings, floating docks, fish farms, etc. These anchors, which have one or more slightly pitched self-drilling threads, must be screwed into the seabed with the use of a tool, so require access to the bottom, either at low tide or by use of a diver. Hence they can be difficult to install in deep water without special equipment.
Weight for weight, augers have a higher holding than other permanent designs, and so can be cheap and relatively easily installed, although difficult to set in extremely soft mud. High-holding-types. There is a need in the oil-and-gas industry to resist large anchoring forces when laying pipelines and for drilling vessels. These anchors are installed and removed using a support tug and pennant/pendant wire. Some examples are the Stevin range supplied by Vrijhof Ankers. Large plate anchors such as the Stevmanta are used for permanent moorings. Anchoring gear. The elements of anchoring gear include the anchor, the cable (also called a "rode"), the method of attaching the two together, the method of attaching the cable to the ship, charts, and a method of learning the depth of the water. Vessels may carry a number of anchors: "bower anchors" are the main anchors used by a vessel and normally carried at the bow of the vessel. A "kedge anchor" is a light anchor used for warping an anchor, also known as "kedging", or more commonly on yachts for mooring quickly or in benign conditions. A "stream anchor", which is usually heavier than a "kedge anchor", can be used for kedging or warping in addition to temporary mooring and restraining stern movement in tidal conditions or in waters where vessel movement needs to be restricted, such as rivers and channels.
Charts are vital to good anchoring. Knowing the location of potential dangers, as well as being useful in estimating the effects of weather and tide in the anchorage, is essential in choosing a good place to drop the hook. One can get by without referring to charts, but they are an important tool and a part of good anchoring gear, and a skilled mariner would not choose to anchor without them. Anchor rode. The anchor rode (or "cable" or "warp") that connects the anchor to the vessel is usually made up of chain, rope, or a combination of those. Large ships use only chain rode. Smaller craft might use a rope/chain combination or an all chain rode. All rodes should have some chain; chain is heavy but it resists abrasion from coral, sharp rocks, or shellfish beds, whereas a rope warp is susceptible to abrasion and can fail in a short time when stretched against an abrasive surface. The weight of the chain also helps keep the direction of pull on the anchor closer to horizontal, which improves holding, and absorbs part of snubbing loads. Where weight is not an issue, a heavier chain provides better holding by forming a catenary curve through the water and resting as much of its length on the bottom as would not be lifted by tension of the mooring load. Any changes to the tension are accommodated by additional chain being lifted or settling on the bottom, and this absorbs shock loads until the chain is straight, at which point the full load is taken by the anchor. Additional dissipation of shock loads can be achieved by fitting a snubber between the chain and a bollard or cleat on deck. This also reduces shock loads on the deck fittings, and the vessel usually lies more comfortably and quietly.
Being strong and elastic, nylon rope is the most suitable as an anchor rode. Polyester (terylene) is stronger but less elastic than nylon. Both materials sink, so they avoid fouling other craft in crowded anchorages and do not absorb much water. Neither breaks down quickly in sunlight. Elasticity helps absorb shock loading, but causes faster abrasive wear when the rope stretches over an abrasive surface, like a coral bottom or a poorly designed chock. Polypropylene ("polyprop") is not suited to rodes because it floats and is much weaker than nylon, being barely stronger than natural fibres. Some grades of polypropylene break down in sunlight and become hard, weak, and unpleasant to handle. Natural fibres such as manila or hemp are still used in developing nations but absorb a lot of water, are relatively weak, and rot, although they do give good handling grip and are often relatively cheap. Ropes that have little or no elasticity are not suitable as anchor rodes. Elasticity is partly a function of the fibre material and partly of the rope structure.
All anchors should have chain at least equal to the boat's length. Some skippers prefer an all chain warp for greater security on coral or sharp edged rock bottoms. The chain should be shackled to the warp through a steel eye or spliced to the chain using a chain splice. The shackle pin should be securely wired or moused. Either galvanized or stainless steel is suitable for eyes and shackles, galvanized steel being the stronger of the two. Some skippers prefer to add a swivel to the rode. There is a school of thought that says these should not be connected to the anchor itself, but should be somewhere in the chain. However, most skippers connect the swivel directly to the anchor. Scope. Scope is the ratio of length of the rode to the depth of the water measured from the highest point (usually the anchor roller or bow chock) to the seabed, making allowance for the highest expected tide. When making this ratio large enough, one can ensure that the pull on the anchor is as horizontal as possible. This will make it unlikely for the anchor to break out of the bottom and drag, if it was properly embedded in the seabed to begin with. When deploying chain, a large enough scope leads to a load that is entirely horizontal, whilst an anchor rode made only of rope will never achieve a strictly horizontal pull.
In moderate conditions, the ratio of rode to water depth should be 4:1 – where there is sufficient swing-room, a greater scope is always better. In rougher conditions it should be up to twice this with the extra length giving more stretch and a smaller angle to the bottom to resist the anchor breaking out. For example, if the water is deep, and the anchor roller is above the water, then the 'depth' is 9 meters (~30 feet). The amount of rode to let out in moderate conditions is thus 36 meters (120 feet). (For this reason, it is important to have a reliable and accurate method of measuring the depth of water.) When using a rope rode, there is a simple way to estimate the scope: The ratio of bow height of the rode to length of rode above the water while lying back hard on the anchor is the same or less than the scope ratio. The basis for this is simple geometry (Intercept Theorem): The ratio between two sides of a triangle stays the same regardless of the size of the triangle as long as the angles do not change.
Generally, the rode should be between 5 and 10 times the depth to the seabed, giving a scope of 5:1 or 10:1; the larger the number, the shallower the angle is between the cable and the seafloor, and the less upwards force is acting on the anchor. A 10:1 scope gives the greatest holding power, but also allows for much more drifting about due to the longer amount of cable paid out. Anchoring with sufficient scope and/or heavy chain rode brings the direction of strain close to parallel with the seabed. This is particularly important for light, modern anchors designed to bury in the bottom, where scopes of 5:1 to 7:1 are common, whereas heavy anchors and moorings can use a scope of 3:1, or less. Some modern anchors, such as the Ultra holds with a scope of 3:1; but, unless the anchorage is crowded, a longer scope always reduces shock stresses. A major disadvantage of the concept of scope is that it does not take into account the fact that a chain is forming a catenary when hanging between two points (i.e., bow roller and the point where the chain hits the seabed), and thus is a non-linear curve (in fact, a cosh() function), whereas scope is a linear function. As a consequence, in deep water the scope needed will be less, whilst in very shallow water the scope must be chosen much larger to achieve the same pulling angle at the anchor shank. For this reason, the British Admiralty does not use a linear scope formula, but a square root formula instead.
A couple of online calculators exist to work out the amount of chain and rope needed to achieve a (possibly nearly) horizontal pull at the anchor shank, and the associated anchor load. As symbol. An anchor frequently appears on the flags and coats of arms of institutions involved with the sea, as well as of port cities and seacoast regions and provinces in various countries. There also exists in heraldry the "Anchored Cross", or Mariner's Cross, a stylized cross in the shape of an anchor. The symbol can be used to signify 'fresh start' or 'hope'. The Mariner's Cross is also referred to as St. Clement's Cross, in reference to the way this saint was killed (being tied to an anchor and thrown from a boat into the Black Sea in 102). Anchored crosses are occasionally a feature of coats of arms in which context they are referred to by the heraldic terms "anchry" or "ancre". The Unicode anchor (Miscellaneous Symbols) is represented by: .
Anbar (town) Anbar (, ) was an ancient and medieval town in central Iraq. It played a role in the Roman–Persian Wars of the 3rd–4th centuries, and briefly became the capital of the Abbasid Caliphate before the founding of Baghdad in 762. It remained a moderately prosperous town through the 10th century, but quickly declined thereafter. As a local administrative centre, it survived until the 14th century, but was later abandoned. Its ruins are near modern Fallujah. The city gives its name to the Al-Anbar Governorate. History. Origins. The city is located on the left bank of the Middle Euphrates, at the junction with the Nahr Isa canal, the first of the navigable canals that link the Euphrates to the River Tigris to the east. The origins of the city are unknown, but ancient, perhaps dating to the Babylonian era and even earlier: the local artificial mound of Tell Aswad dates to . Sasanian period. The town was originally known as Misiche (Greek: ), Mesiche (), or Massice ( mšyk; mšyk). As a major crossing point of the Euphrates, and occupying the northernmost point of the complex irrigation network of the Sawad, the town was of considerable strategic significance. As the western gate to central Mesopotamia, it was fortified by the Sasanian ruler Shapur I () to shield his capital, Ctesiphon, from the Roman Empire. After his decisive victory over the Roman emperor Gordian III at the Battle of Misiche in 244, Shapur renamed the town to Peroz-Shapur ("Pērōz-Šāpūr" or "Pērōz-Šābuhr", from , meaning "victorious Shapur"; in ; in ). It became known as Pirisapora or Bersabora () to the Greeks and Romans.
The city was fortified by a double wall, possibly through the use of Roman prisoner labour; it was sacked and burned after an agreement with its garrison in March 363 by the Roman emperor Julian during his invasion of the Sasanian Empire. It was rebuilt by Shapur II. By 420, it is attested as a bishopric, both for the Church of the East and for the Syriac Orthodox Church. The town's garrison was Persian, but it also contained sizeable Arab and Jewish populations. Anbar was adjacent or identical to the Babylonian Jewish center of Nehardea (), and lies a short distance from the present-day town of Fallujah, formerly the Babylonian Jewish center of Pumbedita (). Islamic period. The city fell to the Rashidun Caliphate in July 633, after a fiercely fought siege. When Ali ibn Abi Talib (r. 656–661) passed through the city, he was warmly welcomed by ninety-thousand Jews who then lived there, and he "received them with great friendliness." The Arabs retained the name ("Fīrūz Shābūr") for the surrounding district, but the town itself became known as Anbar (Middle Persian word for "granary" or "storehouse") from the granaries in its citadel, a name that had appeared already during the 6th century. According to Baladhuri, the third mosque to be built in Iraq was erected in the city by Sa'd ibn Abi Waqqas. Ibn Abi Waqqas initially considered Anbar as a candidate for the location of one of the first Muslim garrison towns, but the fever and fleas endemic in the area persuaded him otherwise.
According to medieval Arabic sources, most of the inhabitants of the town migrated north to found the city of Hdatta south of Mosul. The famous governor al-Hajjaj ibn Yusuf cleared the canals of the city. Abu'l-Abbas as-Saffah (), the founder of the Abbasid Caliphate, made it his capital in 752, constructing a new town half a "farsakh" () to the north for his Khurasani troops. There he died and was buried at the palace he had built. His successor, al-Mansur (), remained in the city until the founding of Baghdad in 762. The Abbasids also dug the great Nahr Isa canal to the south of the city, which carried water and commerce east to Baghdad. The Nahr al-Saqlawiyya or Nahr al-Qarma canal, which branches off from the Euphrates to the west of the city, is sometimes erroneously held to be the Nahr Isa, but it is more likely that it is to be identified with the pre-Islamic Nahr al-Rufayl. It continued to be a place of much importance throughout the Abbasid period. Caliph Harun al-Rashid () stayed at the town in 799 and in 803. The town's prosperity was founded on agricultural activities, but also on trade between Iraq and Syria. The town was still prosperous in the early 9th century, but the decline of Abbasid authority during the later 9th century exposed it to Bedouin attacks in 882 and 899. In 927, the Qarmatians under Abu Tahir al-Jannabi sacked the city during their invasion of Iraq, and the devastation was compounded by another Bedouin attack two years later. The town's decline accelerated after that: while the early 10th-century geographer Istakhri still calls the town modest but populous, with the ruins of the buildings of as-Saffah still visible, Ibn Hawqal and al-Maqdisi, who wrote a generation later, attest to its decline, and the diminution of its population.
The town was sacked again in 1262 by the Mongols under Kerboka. The Ilkhanids retained Anbar as an administrative centre, a role it retained until the first half of the 14th century; the Ilkhanid minister Shams al-Din Juvayni had a canal dug from the city to Najaf, and the city was surrounded by a wall of sun-dried bricks. Ecclesiastical history. Anbar used to host an Assyrian community from the fifth century: the town was the seat of a bishopric of the Church of the East. The names of fourteen of its bishops of the period 486–1074 are known, three of whom became Chaldean Patriarchs of Babylon. Titular see. Anbar is listed by the Catholic Church as a titular see of the Chaldean Catholic Church, established as titular bishopric in 1980. It has had the following incumbents: Today. It is now entirely deserted, occupied only by mounds of ruins, whose great number indicate the city's former importance. Its ruins are northwest of Fallujah, with a circumference of some . The remains include traces of the late medieval wall, a square fortification, and the early Islamic mosque.
Anazarbus Anazarbus, also known as Justinopolis (, medieval Ain Zarba; modern Anavarza; ), was an ancient Cilician city. Under the late Roman Empire, it was the capital of Cilicia Secunda. Roman emperor Justinian I rebuilt the city in 527 after a strong earthquake hit it. It was destroyed in 1374 by the forces of the Mamluk Empire, after their conquest of Cilician Armenia. Location. It was situated in Anatolia in modern Turkey, in the present Çukurova (or classical Aleian plain) about 15 km west of the main stream of the present Ceyhan River (or classical Pyramus river) and near its tributary the Sempas Su. A lofty isolated ridge formed its acropolis. Though some of the masonry in the ruins is certainly pre-Roman, the Suda's identification of it with Cyinda, famous as a treasure city in the wars of Eumenes of Cardia, cannot be accepted in the face of Strabo's express location of Cyinda in western Cilicia. History.
Its great natural strength and situation, not far from the mouth of the Sis pass, and near the great road which debouched from the Cilician Gates, made Anazarbus play a considerable part in the struggles between the Eastern Roman Empire and the early Muslim invaders. It had been rebuilt by Harun al-Rashid in 796, refortified at great expense by the Hamdanid Sayf al-Dawla (mid-10th century) and again destroyed in 962 by Nikephoros II Phokas. In the 11th century it was again a major fortress, comparable to Tarsos and Marash, and belonged to the realm of Philaretos Brachamios before it was captured around 1084 by the Seljuk Turks. In late 1097 or early 1098 it was captured by the armies of the First Crusade and after the conquest of Antioch it was incorporated into Bohemond of Taranto's Principality of Antioch. The site briefly exchanged hands between the Byzantine Empire and Armenians, until it was formally part of the Armenian Kingdom of Cilicia. Anazarbus was one of a chain of Armenian fortifications stretching through Cilicia. The castle of Sis (modern Kozan, Adana) lies to the north while Tumlu Castle and Yilankale are to the south, and the fortresses of Amouda and Sarvandikar are to the east. The Mamluk Empire of Egypt finally destroyed the city in 1374.
Remains. The Crusaders are probably responsible for the construction of an impressive donjon atop the center of the outcrop. Most of the remaining fortifications, including the curtain walls, massive horseshoe-shaped towers, undercrofts, cisterns, and free-standing structures date from the Armenian periods of occupation, which began with the arrival of the Rubenid Baron T‛oros I, . Within the fortress are two Armenian chapels and the magnificent (but severely damaged) three-aisle church built by T‛oros I to celebrate his conquests. The church was once surrounded by a continuous, well-executed dedicatory inscription in Armenian. The present wall of the lower city is of late construction. It encloses a mass of ruins conspicuous in which are a fine triumphal arch, the colonnades of two streets, a gymnasium, etc. A stadium and a theatre lie outside the walls to the south. The remains of the acropolis fortifications are very interesting, including roads and ditches hewn in the rock. There are no notable structures in the upper town. For picturesqueness the site is not equaled in Cilicia, and it is worthwhile to trace the three fine aqueducts to their sources. A necropolis on the escarpment to the south of the curtain wall can also be seen complete with signs of illegal modern excavations.
A modest Turkish farming village (Dilekkaya) lies to the southwest of the ancient city. A small outdoor museum with some of the artifacts collected in the area can be viewed for a small fee. Also nearby are some beautiful mosaics discovered in a farmers field. A visit in December 2002 showed that the three aqueducts mentioned above have been nearly completely destroyed. Only small, isolated sections are left standing with the largest portion lying in a pile of rubble that stretches the length of where the aqueducts once stood. A powerful earthquake that struck the area in 1945 is thought to be responsible for the destruction. In 2013, excavations uncovered the first known colonnaded double-lane road of the ancient world, 34 meters wide and 2700 meters long, also uncovered the ruins of a church and a bathhouse. In 2017, archaeologists discovered a limestone statue of the goddess Hygieia and the god Eros. The statue is thought to date to the third or fourth century B.C. Ecclesiastical history. Anazarbus was the capital and so also from 553 (the date of the Second Council of Constantinople) the metropolitan see of the Late Roman province of Cilicia Secunda.
In the 4th century, one of the bishops of Anazarbus was Athanasius, a "consistent expounder of the theology of Arius." His theological opponent, Athanasius of Alexandria, in "De Synodis" 17, 1 refers to Anazarbus as Ναζαρβῶν. Maximin of Anazarbus attended the Council of Chalcedon. A 6th century "Notitia Episcopatuum" indicates that it had as suffragan sees Epiphania, Alexandria Minor, Irenopolis, Flavias, Castabala and Aegeae. Rhosus was also subject to Anazarbus, but after the 6th century was made exempt, and Mopsuestia was raised to the rank of autocephalous metropolitan see, though without suffragans. Latin Catholic titular see. The titular archbishopric was revived in the 18th century as a see of the Latin Catholic church, Anazarbus. It is vacant, having had the following incumbents, generally of the highest (Metropolitan) rank, "with an episcopal (lowest rank) exception:" Armenian Catholic titular see. In the 19th century, an Armenian Catholic titular bishopric of Anazarbus (of the Armenians) (Anazarbus degli Armeni in Curiate Italian) was established. It was a suppressed in 1933, having had a single incumbent, of the intermediary (archiepiscopal) rank :
Anagram An anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once. For example, the word "anagram" itself can be rearranged into the phrase "nag a ram"; which is an Easter egg suggestion in Google after searching for the word "anagram". The original word or phrase is known as the "subject" of the anagram. Any word or phrase that exactly reproduces the letters in another order is an anagram. Someone who creates anagrams may be called an "anagrammatist", and the goal of a serious or skilled anagrammatist is to produce anagrams that reflect or comment on their subject. Examples. Anagrams may be created as a commentary on the subject. They may be a parody, a criticism or satire. For example: An anagram may also be a synonym of the original word or phrase. For example: An anagram that has a meaning opposed to that of the original word or phrase is called an "antigram". For example: They can sometimes change from a proper noun or personal name into an appropriate sentence:
They can change part of speech, such as the adjective "silent" to the verb "listen". "Anagrams" itself can be anagrammatized as "Ars magna" (Latin, 'the great art'). History. Anagrams can be traced back to the time of the ancient Greeks, and were used to find the hidden and mystical meaning in names. They were popular throughout Europe during the Middle Ages, for example with the poet and composer Guillaume de Machaut. They are said to date back at least to the Greek poet Lycophron, in the third century BCE; but this relies on an account of Lycophron given by John Tzetzes in the 12th century. In the Talmudic and Midrashic literature, anagrams were used to interpret the Hebrew Bible, notably by Eleazar of Modi'im. Later, Kabbalists took this up with enthusiasm, calling anagrams "temurah". Anagrams in Latin were considered witty over many centuries. "Est vir qui adest", explained below, was cited as the example in Samuel Johnson's "A Dictionary of the English Language". They became hugely popular in the early modern period, especially in Germany.
Any historical material on anagrams must always be interpreted in terms of the assumptions and spellings that were current for the language in question. In particular, spelling in English only slowly became fixed. There were attempts to regulate anagram formation, an important one in English being that of George Puttenham's "Of the Anagram or Posy Transposed" in "The Art of English Poesie" (1589). Influence of Latin. As a literary game when Latin was the common property of the literate, Latin anagrams were prominent. Two examples are the change of "Ave Maria, gratia plena, Dominus tecum" (Latin: Hail Mary, full of grace, the Lord [is] with you) into "Virgo serena, pia, munda et immaculata" (Latin: Serene virgin, pious, clean and spotless), and the anagrammatic answer to Pilate's question, "Quid est veritas?" (Latin: What is truth?), namely, "Est vir qui adest" (Latin: It is the man who is here). The origins of these are not documented. Latin continued to influence letter values (such as I = J, U = V and W = VV). There was an ongoing tradition of allowing anagrams to be "perfect" if the letters were all used once, but allowing for these interchanges. This can be seen in a popular Latin anagram against the Jesuits: "Societas Jesu" turned into "Vitiosa seces" (Latin: Cut off the wicked things). Puttenham, in the time of Elizabeth I, wished to start from "Elissabet Anglorum Regina" (Latin: Elizabeth Queen of the English), to obtain "Multa regnabis ense gloria" (Latin: By thy sword shalt thou reign in great renown); he explains carefully that H is "a note of aspiration only and no letter", and that Z in Greek or Hebrew is a mere SS. The rules were not completely fixed in the 17th century. William Camden in his "Remains" commented, singling out some letters—Æ, K, W, and Z—not found in the classical Roman alphabet:
Early modern period. When it comes to the 17th century and anagrams in English or other languages, there is a great deal of documented evidence of learned interest. The lawyer Thomas Egerton was praised through the anagram "gestat honorem" ('he carries honor'); the physician George Ent took the anagrammatic motto "genio surget" ('he rises through spirit/genius'), which requires his first name as "Georgius". James I's courtiers discovered in "James Stuart" "a just master", and converted "Charles James Stuart" into "Claims Arthur's seat" (even at that point in time, the letters I and J were more-or-less interchangeable). Walter Quin, tutor to the future Charles I, worked hard on multilingual anagrams on the name of father James. A notorious murder scandal, the Overbury case, threw up two imperfect anagrams that were aided by typically loose spelling and were recorded by Simonds D'Ewes: "Francis Howard" (for Frances Carr, Countess of Somerset, her maiden name spelled in a variant) became "Car findes a whore", with the letters E hardly counted, and the victim Thomas Overbury, as "Thomas Overburie", was written as "O! O! a busie murther" (an old form of "murder"), with a V counted as U.
William Drummond of Hawthornden, in an essay "On the Character of a Perfect Anagram", tried to lay down rules for permissible substitutions (such as S standing for Z) and letter omissions. William Camden provided a definition of "Anagrammatisme" as "a dissolution of a name truly written into his letters, as his elements, and a new connection of it by artificial transposition, without addition, subtraction or change of any letter, into different words, making some perfect sense appliable (i.e., applicable) to the person named." Dryden in "MacFlecknoe" disdainfully called the pastime the "torturing of one poor word ten thousand ways". "Eleanor Audeley", wife of Sir John Davies, is said to have been brought before the High Commission in 1634 for extravagances, stimulated by the discovery that her name could be transposed to "Reveale, O Daniel", and to have been laughed out of court by another anagram submitted by Sir John Lambe, the dean of the Arches, "Dame Eleanor Davies", "Never soe mad a ladie". An example from France was a flattering anagram for Cardinal Richelieu, comparing him to Hercules or at least one of his hands (Hercules being a kingly symbol), where "Armand de Richelieu" became "Ardue main d'Hercule" ("difficult hand of Hercules").
Modern period. Examples from the 19th century are the transposition of "Horatio Nelson" into "Honor est a Nilo" (Latin: Honor is from the Nile); and of "Florence Nightingale" into "Flit on, cheering angel". The Victorian love of anagramming as recreation is alluded to by the mathematician Augustus De Morgan using his own name as an example; "Great Gun, do us a sum!" is attributed to his son William De Morgan, but a family friend John Thomas Graves was prolific, and a manuscript with over 2,800 has been preserved. With the advent of surrealism as a poetic movement, anagrams regained the artistic respect they had had in the Baroque period. The German poet Unica Zürn, who made extensive use of anagram techniques, came to regard obsession with anagrams as a "dangerous fever", because it created isolation of the author. The surrealist leader André Breton coined the anagram "Avida Dollars" for Salvador Dalí, to tarnish his reputation by the implication of commercialism. Applications. While anagramming is certainly a recreation first, there are ways in which anagrams are put to use, and these can be more serious, or at least not quite frivolous and formless. For example, psychologists use anagram-oriented tests, often called "anagram solution tasks", to assess the implicit memory of young adults and adults alike.
Establishment of priority. Natural philosophers (astronomers and others) of the 17th century transposed their discoveries into Latin anagrams, to establish their priority. In this way they laid claim to new discoveries before their results were ready for publication. Galileo used ' for ' (Latin: I have observed the most distant planet to have a triple form) for discovering the rings of Saturn in 1610. Galileo announced his discovery that Venus had phases like the Moon in the form ' (Latin: These immature ones have already been read in vain by me -oy), that is, when rearranged, ' (Latin: The Mother of Loves [= Venus] imitates the figures of Cynthia [= the moon]). In both cases, Johannes Kepler had solved the anagrams incorrectly, assuming they were talking about the Moons of Mars (') and a red spot on Jupiter ('), respectively. By coincidence, he turned out to be right about the actual objects existing. In 1656, Christiaan Huygens, using a better telescope than those available to Galileo, figured that Galileo's earlier observations of Saturn actually meant it had a ring (Galileo's tools were only sufficient to see it as bumps) and, like Galileo, had published an anagram, '. Upon confirming his observations, three years later he revealed it to mean ' (Latin: It [Saturn] is surrounded by a thin, flat, ring, nowhere touching, inclined to the ecliptic).
When Robert Hooke discovered Hooke's law in 1660, he first published it in anagram form, ', for ' (Latin: as the extension, so the force). Pseudonyms. Anagrams are connected to pseudonyms, by the fact that they may conceal or reveal, or operate somewhere in between like a mask that can establish identity. For example, Jim Morrison used an anagram of his name in the Doors song "L.A. Woman", calling himself "Mr. Mojo Risin'". The use of anagrams and fabricated personal names may be to circumvent restrictions on the use of real names, as happened in the 18th century when Edward Cave wanted to get around restrictions imposed on the reporting of the House of Commons. In a genre such as farce or parody, anagrams as names may be used for pointed and satiric effect. Pseudonyms adopted by authors are sometimes transposed forms of their names; thus "Calvinus" becomes "Alcuinus" (here V = U) or "François Rabelais" = "Alcofribas Nasier". The name "Voltaire" of François Marie Arouet fits this pattern, and is allowed to be an anagram of "Arouet, l[e] j[eune]" (U = V, J = I) that is, "Arouet the younger". Other examples include:
Several of these are "imperfect anagrams", letters having been left out in some cases for the sake of easy pronunciation. Titles. Anagrams used for titles afford scope for some types of wit. Examples: Coincidences. In Hebrew, the name "Gernot Zippe" (גרנוט ציפה), the inventor of the Zippe-type centrifuge, is an anagram of the word "centrifuge" (צנטריפוגה). The sentence "Name is Anu Garg", referring to anagrammer and founder of wordsmith.org Anu Garg, can be rearranged to spell "Anagram genius". Games and puzzles. Anagrams are in themselves a recreational activity, but they also make up part of many other games, puzzles and game shows. The Jumble is a puzzle found in many newspapers in the United States requiring the unscrambling of letters to find the solution. Cryptic crossword puzzles frequently use anagrammatic clues, usually indicating that they are anagrams by the inclusion of a descriptive term like "confused" or "in disarray". An example would be "Businessman burst into tears (9 letters)". The solution, "stationer", is an anagram of "into tears", the letters of which have "burst" out of their original arrangement to form the name of a type of "businessman".
Numerous other games and contests involve some element of anagram formation as a basic skill. Some examples: Ciphers. Multiple anagramming is a technique used to solve some kinds of cryptograms, such as a permutation cipher, a transposition cipher, and the Jefferson disk. Solutions may be computationally found using a Jumble algorithm. Methods of construction. Sometimes, it is possible to "see" anagrams in words, unaided by tools, though the more letters involved the more difficult this becomes. The difficulty is that for a word of different letters, there are (factorial of ) different permutations and so different anagrams of the word. Anagram dictionaries can also be used. Computer programs, known as "anagram search", "anagram servers", and "anagram solvers", among other names, offer a much faster route to creating anagrams, and a large number of these programs are available on the Internet. Some programs use the Anatree algorithm to compute anagrams efficiently.
Some anagrammatists indicate the method they used. Anagrams constructed without the aid of a computer are noted as having been done "manually" or "by hand"; those made by utilizing a computer may be noted "by machine" or "by computer", or may indicate the name of the computer program (using "Anagram Genius"). There are also a few "natural" instances: English words unconsciously created by switching letters around. The French "chaise longue" ("long chair") became the American "chaise lounge" by metathesis (transposition of letters and/or sounds). It has also been speculated that the English "curd" comes from the Latin "crudus" ("raw"). Similarly, the ancient English word for bird was "brid". Notable anagrammatists. The French king Louis XIII had a man named Thomas Billon appointed as his Royal Anagrammatist with an annual salary of 1,200 livres. Among contemporary anagrammers, Anu Garg, created an Internet Anagram Server in 1994 together with the satirical anagram-based newspaper "The Anagram Times". Mike Keith has anagrammed the complete text of "Moby Dick". He, along with Richard Brodie, has published "The Anagrammed Bible" that includes anagrammed version of many books of the Bible. Popular television personality Dick Cavett is known for his anagrams of famous celebrities such as Alec Guinness and Spiro Agnew.
Anadyr (river) The Anadyr (; Yukaghir: Онандырь; ) is a river in the far northeast of Siberia which flows into the Gulf of Anadyr of the Bering Sea and drains much of the interior of Chukotka Autonomous Okrug. Its basin corresponds to the Anadyrsky District of Chukotka. Geography. The Anadyr is long and has a basin of . It is frozen from October to late May and has a maximum flow in June with the snowmelt. It is navigable in small boats for about to near Markovo. West of Markovo it is in the Anadyr Highlands (moderate mountains and valleys with a few trees) and east of Markovo it moves into the Anadyr Lowlands (very flat treeless tundra with lakes and bogs). The drop from Markovo to the sea is less than . It rises at about 67°N latitude and 171°E longitude in the Anadyr Highlands, near the headwaters of the Maly Anyuy, flows southwest receiving the waters of the rivers Yablon and Yeropol, turns east around the Shchuchy Range and passes Markvovo and the old site of Anadyrsk, turns north and east and receives the Mayn from the south, thereby encircling the Lebediny Zakaznik, turns northeast to receive the Belaya from the north in the Parapol-Belsky Lowlands, then past Ust-Belaya it turns southeast into the Anadyr Lowlands past the Ust-Tanyurer Zakaznik and receives the Tanyurer from the north. At Lake Krasnoye, it turns east and flows into the Onemen Bay of the Anadyr Estuary. If the Onemen Bay is considered part of the river, it also receives the Velikaya from the south and the Kanchalan from the north. Other important tributaries are the Yablon, Yeropol and Mamolina from the right and the Chineyveyem and Ubiyenka from the left.
Its basin is surrounded by the Amguema and Palyavaam basins to the north, the Bolshoy Anyuy, Oloy and Kolyma basins to the northwest, and the Penzhina basin to the southwest. History. In 1648, Semyon Dezhnev reached the mouth of the Anadyr after being shipwrecked on the coast. In 1649, he went upriver and built winter quarters at Anadyrsk. For the next 100 years, the Anadyr was the main route from the Arctic to the Pacific and Kamchatka. In the 18th century, the Anadyr was described by the polar explorer Dmitry Laptev. Ecology. The country through which it passes is thinly populated, and is dominated by tundra, with a rich variety of plant life. Much of the region's landscapes are dominated by rugged mountains. For nine months of the year the ground is covered with snow, and the frozen rivers become navigable roads. George Kennan, an American working on the Western Union Telegraph Expedition in the late 1860s, found that dog sled travel on the lower Anadyr was limited by lack of firewood. Reindeer, upon which the local inhabitants subsisted, were once found in considerable numbers, but the domestic reindeer population has collapsed dramatically since the reorganization and privatization of state-run collective farms beginning in 1992. As herds of domestic reindeer have declined, herds of wild caribou have increased. There are ten species of salmon inhabiting the Anadyr river basin. Every year, on the last Sunday in April, there is an ice fishing competition in the frozen estuarine waters of the Anadyr's mouth. This festival is locally known as Korfest. The area is a summering place for a number of migratory birds including brent geese, Eurasian wigeons, and the pintails of California.
André-Marie Ampère André-Marie Ampère (, ; ; 20 January 177510 June 1836) was a French physicist and mathematician who was one of the founders of the science of classical electromagnetism, which he referred to as "electrodynamics". He is also the inventor of numerous applications, such as the solenoid (a term coined by him) and the electrical telegraph. As an autodidact, Ampère was a member of the French Academy of Sciences and professor at the École polytechnique and the Collège de France. The SI unit of electric current, the ampere (A), is named after him. His name is also one of the 72 names inscribed on the Eiffel Tower. The term "kinematic" is the English version of his "cinématique", which he constructed from the Greek "kinema" ("movement, motion"), itself derived from "kinein" ("to move"). Biography. Early life. André-Marie Ampère was born on 20 January 1775 in Lyon to Jean-Jacques Ampère, a prosperous businessman, and Jeanne Antoinette Desutières-Sarcey Ampère, during the height of the French Enlightenment. He spent his childhood and adolescence at the family property at Poleymieux-au-Mont-d'Or near Lyon. Jean-Jacques Ampère, a successful merchant, was an admirer of the philosophy of Jean-Jacques Rousseau, whose theories of education (as outlined in his treatise "Émile") were the basis of Ampère's education. Rousseau believed that young boys should avoid formal schooling and pursue instead a "direct education from nature." Ampère's father actualized this ideal by allowing his son to educate himself within the walls of his well-stocked library. French Enlightenment masterpieces such as Georges-Louis Leclerc, comte de Buffon's "Histoire naturelle, générale et particulière" (begun in 1749) and Denis Diderot and Jean le Rond d'Alembert's "Encyclopédie" (volumes added between 1751 and 1772) thus became Ampère's schoolmasters. The young Ampère, however, soon resumed his Latin lessons, which enabled him to master the works of Leonhard Euler and Daniel Bernoulli.
French Revolution. In addition, Ampère used his access to the latest books to begin teaching himself advanced mathematics at age 12. In later life Ampère claimed that he knew as much about mathematics and science when he was eighteen as ever he knew, but as a polymath, his reading embraced history, travels, poetry, philosophy, and the natural sciences. His mother was a devout Catholic, so Ampère was also initiated into the Catholic faith along with Enlightenment science. The French Revolution (1789–99) that began during his youth was also influential: Ampère's father was called into public service by the new revolutionary government, becoming a local judge ("juge de paix") in a small town near Lyon. When the Jacobin faction seized control of the Revolutionary government in 1792, his father Jean-Jacques Ampère resisted the new political tides, and he was guillotined on 24 November 1793, as part of the Jacobin purges of the period. In 1796, Ampère met Julie Carron and, in 1799, they were married. Ampère took his first regular job in 1799 as a mathematics teacher, which gave him the financial security to marry Carron and father his first child, Jean-Jacques (named after his father), the next year. (Jean-Jacques Ampère eventually achieved his own fame as a scholar of languages.) Ampère's maturation corresponded with the transition to the Napoleonic regime in France, and the young father and teacher found new opportunities for success within the technocratic structures favoured by the new French First Consul. In 1802, Ampère was appointed a professor of physics and chemistry at the École Centrale in Bourg-en-Bresse, leaving his ailing wife and infant son in Lyon. He used his time in Bourg to research mathematics, producing "Considérations sur la théorie mathématique du jeu" (1802; "Considerations on the Mathematical Theory of Games"), a treatise on mathematical probability that he sent to the Paris Academy of Sciences in 1803.
Teaching career. After the death of his wife in July 1803, Ampère moved to Paris, where he began a tutoring post at the new École Polytechnique in 1804. Despite his lack of formal qualifications, Ampère was appointed a professor of mathematics at the school in 1809. As well as holding positions at this school until 1828, in 1819 and 1820 Ampère offered courses in philosophy and astronomy, respectively, at the University of Paris, and in 1824 he was elected to the prestigious chair in experimental physics at the Collège de France. In 1814, Ampère was invited to join the class of mathematicians in the new "Institut Impérial", the umbrella under which the reformed state Academy of Sciences would sit. Ampère engaged in a diverse array of scientific inquiries during the years leading up to his election to the academy—writing papers and engaging in topics from mathematics and philosophy to chemistry and astronomy, which was customary among the leading scientific intellectuals of the day. Ampère claimed that "at eighteen years he found three culminating points in his life, his First Communion, the reading of Antoine Leonard Thomas's "Eulogy of Descartes", and the Taking of the Bastille. On the day of his wife's death he wrote two verses from the Psalms, and the prayer, 'O Lord, God of Mercy, unite me in Heaven with those whom you have permitted me to love on earth.' In times of duress he would take refuge in the reading of the Bible and the Fathers of the Church."
A lay Catholic, he took for a time into his family the young student Frédéric Ozanam (1813–1853), one of the founders of the Conference of Charity, later known as the Society of Saint Vincent de Paul. Ozanam would much later be beatified by Pope John Paul II in 1998. Through Ampère, Ozanam had contact with leaders of the neo-Catholic movement, such as François-René de Chateaubriand, Jean-Baptiste Henri Lacordaire, and Charles Forbes René de Montalembert. Work in electromagnetism. In September 1820, Ampère's friend and eventual eulogist François Arago showed the members of the French Academy of Sciences the surprising discovery by Danish physicist Hans Christian Ørsted that a magnetic needle is deflected by an adjacent electric current. Ampère began developing a mathematical and physical theory to understand the relationship between electricity and magnetism. Furthering Ørsted's experimental work, Ampère showed that two parallel wires carrying electric currents attract or repel each other, depending on whether the currents flow in the same or opposite directions, respectively - this laid the foundation of electrodynamics. He also applied mathematics in generalizing physical laws from these experimental results. The most important of these was the principle that came to be called Ampère's law, which states that the mutual action of two lengths of current-carrying wire is proportional to their lengths and to the intensities of their currents. Ampère also applied this same principle to magnetism, showing the harmony between his law and French physicist Charles Augustin de Coulomb's law of electric action. Ampère's devotion to, and skill with, experimental techniques anchored his science within the emerging fields of experimental physics.
Ampère also provided a physical understanding of the electromagnetic relationship, theorizing the existence of an "electrodynamic molecule" (the forerunner of the idea of the electron) that served as the component element of both electricity and magnetism. Using this physical explanation of electromagnetic motion, Ampère developed a physical account of electromagnetic phenomena that was both empirically demonstrable and mathematically predictive. Almost 100 years later, in 1915, Albert Einstein together with Wander Johannes de Haas made the proof of the correctness of Ampère's hypothesis through the Einstein–de Haas effect. In 1827, Ampère published his magnum opus, "Mémoire sur la théorie mathématique des phénomènes électrodynamiques uniquement déduite de l'experience" (Memoir on the Mathematical Theory of Electrodynamic Phenomena, Uniquely Deduced from Experience), the work that coined the name of his new science, "electrodynamics", and became known ever after as its founding treatise. In 1827, Ampère was elected a Foreign Member of the Royal Society and in 1828, a foreign member of the Royal Swedish Academy of Science. Probably the highest recognition came from James Clerk Maxwell, who in his "Treatise on Electricity and Magnetism" named Ampère "the Newton of electricity".
Honours. Legacy. An international convention, signed at the 1881 International Exposition of Electricity, established the ampere as one of the standard units of electrical measurement, in recognition of his contribution to the creation of modern electrical science and along with the coulomb, volt, ohm, watt and farad, which are named, respectively, after Ampère's contemporaries Charles-Augustin de Coulomb of France, Alessandro Volta of Italy, Georg Ohm of Germany, James Watt of Scotland and Michael Faraday of England. Ampère's name is one of the 72 names inscribed on the Eiffel Tower. Many streets and squares are named after Ampère, as are schools, a Lyon metro station, a graphics processing unit microarchitecture, a mountain on the moon and an electric ferry in Norway. Writings. Partial translations: Complete translations:
Ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the formula . A stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pungent smell. Biologically, it is a common nitrogenous waste, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to fertilisers. Around 70% of ammonia produced industrially is used to make fertilisers in various forms and composition, such as urea and diammonium phosphate. Ammonia in pure form is also applied directly into the soil. Ammonia, either directly or indirectly, is also a building block for the synthesis of many chemicals. Ammonia occurs in nature and has been detected in the interstellar medium. In many countries, it is classified as an extremely hazardous substance. Ammonia is toxic, causing damage to cells and tissues. For this reason it is excreted by most animals in the urine, in the form of dissolved urea. Ammonia is produced biologically in a process called nitrogen fixation, but even more is generated industrially by the Haber process. The process helped revolutionize agriculture by providing cheap fertilizers. The global industrial production of ammonia in 2021 was 235 million tonnes. Industrial ammonia is transported by road in tankers, by rail in tank wagons, by sea in gas carriers, or in cylinders.
Ammonia boils at at a pressure of one atmosphere, but the liquid can often be handled in the laboratory without external cooling. Household ammonia or ammonium hydroxide is a solution of ammonia in water. Etymology. Pliny, in Book XXXI of his Natural History, refers to a salt named "hammoniacum", so called because of the proximity of its source to the Temple of Jupiter Amun (Greek Ἄμμων "Ammon") in the Roman province of Cyrenaica. However, the description Pliny gives of the salt does not conform to the properties of ammonium chloride. According to Herbert Hoover's commentary in his English translation of Georgius Agricola's "De re metallica", it is likely to have been common sea salt. In any case, that salt ultimately gave ammonia and ammonium compounds their name. Natural occurrence (abiological). Traces of ammonia/ammonium are found in rainwater. Ammonium chloride (sal ammoniac), and ammonium sulfate are found in volcanic districts. Crystals of ammonium bicarbonate have been found in Patagonia guano. Ammonia is found throughout the Solar System on Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto, among other places: on smaller, icy bodies such as Pluto, ammonia can act as a geologically important antifreeze, as a mixture of water and ammonia can have a melting point as low as if the ammonia concentration is high enough and thus allow such bodies to retain internal oceans and active geology at a far lower temperature than would be possible with water alone. Substances containing ammonia, or those that are similar to it, are called "ammoniacal".
Properties. Ammonia is a colourless gas with a characteristically pungent smell. It is lighter than air, its density being 0.589 times that of air. It is easily liquefied due to the strong hydrogen bonding between molecules. Gaseous ammonia turns to a colourless liquid, which boils at , and freezes to colourless crystals at . Little data is available at very high temperatures and pressures, but the liquid-vapor critical point occurs at 405 K and 11.35 MPa. Solid. The crystal symmetry is cubic, Pearson symbol cP16, space group P213 No.198, lattice constant 0.5125 nm. Liquid. Liquid ammonia possesses strong ionising powers reflecting its high "ε" of 22 at . Liquid ammonia has a very high standard enthalpy change of vapourization (23.5 kJ/mol; for comparison, water's is 40.65 kJ/mol, methane 8.19 kJ/mol and phosphine 14.6 kJ/mol) and can be transported in pressurized or refrigerated vessels; however, at standard temperature and pressure liquid anhydrous ammonia will vaporize. Solvent properties. Ammonia readily dissolves in water. In an aqueous solution, it can be expelled by boiling. The aqueous solution of ammonia is basic, and may be described as aqueous ammonia or ammonium hydroxide. The maximum concentration of ammonia in water (a saturated solution) has a specific gravity of 0.880 and is often known as '.880 ammonia'.
Liquid ammonia is a widely studied nonaqueous ionising solvent. Its most conspicuous property is its ability to dissolve alkali metals to form highly coloured, electrically conductive solutions containing solvated electrons. Apart from these remarkable solutions, much of the chemistry in liquid ammonia can be classified by analogy with related reactions in aqueous solutions. Comparison of the physical properties of with those of water shows has the lower melting point, boiling point, density, viscosity, dielectric constant and electrical conductivity. These differences are attributed at least in part to the weaker hydrogen bonding in . The ionic self-dissociation constant of liquid at −50 °C is about 10−33. Liquid ammonia is an ionising solvent, although less so than water, and dissolves a range of ionic compounds, including many nitrates, nitrites, cyanides, thiocyanates, metal cyclopentadienyl complexes and metal bis(trimethylsilyl)amides. Most ammonium salts are soluble and act as acids in liquid ammonia solutions. The solubility of halide salts increases from fluoride to iodide. A saturated solution of ammonium nitrate (Divers' solution, named after Edward Divers) contains 0.83 mol solute per mole of ammonia and has a vapour pressure of less than 1 bar even at . However, few oxyanion salts with other cations dissolve.
Liquid ammonia will dissolve all of the alkali metals and other electropositive metals such as Ca, Sr, Ba, Eu and Yb (also Mg using an electrolytic process). At low concentrations (<0.06 mol/L), deep blue solutions are formed: these contain metal cations and solvated electrons, free electrons that are surrounded by a cage of ammonia molecules. These solutions are strong reducing agents. At higher concentrations, the solutions are metallic in appearance and in electrical conductivity. At low temperatures, the two types of solution can coexist as phases. Redox properties of liquid ammonia. The range of thermodynamic stability of liquid ammonia solutions is very narrow, as the potential for oxidation to dinitrogen, "E"° (), is only +0.04 V. In practice, both oxidation to dinitrogen and reduction to dihydrogen are slow. This is particularly true of reducing solutions: the solutions of the alkali metals mentioned above are stable for several days, slowly decomposing to the metal amide and dihydrogen. Most studies involving liquid ammonia solutions are done in reducing conditions; although oxidation of liquid ammonia is usually slow, there is still a risk of explosion, particularly if transition metal ions are present as possible catalysts.
Structure. The ammonia molecule has a trigonal pyramidal shape, as predicted by the valence shell electron pair repulsion theory (VSEPR theory) with an experimentally determined bond angle of 106.7°. The central nitrogen atom has five outer electrons with an additional electron from each hydrogen atom. This gives a total of eight electrons, or four electron pairs that are arranged tetrahedrally. Three of these electron pairs are used as bond pairs, which leaves one lone pair of electrons. The lone pair repels more strongly than bond pairs; therefore, the bond angle is not 109.5°, as expected for a regular tetrahedral arrangement, but 106.7°. This shape gives the molecule a dipole moment and makes it polar. The molecule's polarity, and especially its ability to form hydrogen bonds, makes ammonia highly miscible with water. The lone pair makes ammonia a base, a proton acceptor. Ammonia is moderately basic; a 1.0 M aqueous solution has a pH of 11.6, and if a strong acid is added to such a solution until the solution is neutral (), 99.4% of the ammonia molecules are protonated. Temperature and salinity also affect the proportion of ammonium . The latter has the shape of a regular tetrahedron and is isoelectronic with methane.
The ammonia molecule readily undergoes nitrogen inversion at room temperature; a useful analogy is an umbrella turning itself inside out in a strong wind. The energy barrier to this inversion is 24.7 kJ/mol, and the resonance frequency is 23.79 GHz, corresponding to microwave radiation of a wavelength of 1.260 cm. The absorption at this frequency was the first microwave spectrum to be observed and was used in the first maser. Amphotericity. One of the most characteristic properties of ammonia is its basicity. Ammonia is considered to be a weak base. It combines with acids to form ammonium salts; thus, with hydrochloric acid it forms ammonium chloride (sal ammoniac); with nitric acid, ammonium nitrate, etc. Perfectly dry ammonia gas will not combine with perfectly dry hydrogen chloride gas; moisture is necessary to bring about the reaction. As a demonstration experiment under air with ambient moisture, opened bottles of concentrated ammonia and hydrochloric acid solutions produce a cloud of ammonium chloride, which seems to appear 'out of nothing' as the salt aerosol forms where the two diffusing clouds of reagents meet between the two bottles.
The salts produced by the action of ammonia on acids are known as the and all contain the ammonium ion (). Although ammonia is well known as a weak base, it can also act as an extremely weak acid. It is a protic substance and is capable of formation of amides (which contain the ion). For example, lithium dissolves in liquid ammonia to give a blue solution (solvated electron) of lithium amide: Self-dissociation. Like water, liquid ammonia undergoes molecular autoionisation to form its acid and base conjugates: Ammonia often functions as a weak base, so it has some buffering ability. Shifts in pH will cause more or fewer ammonium cations () and amide anions () to be present in solution. At standard pressure and temperature, Combustion. Ammonia does not burn readily or sustain combustion, except under narrow fuel-to-air mixtures of 15–28% ammonia by volume in air. When mixed with oxygen, it burns with a pale yellowish-green flame. Ignition occurs when chlorine is passed into ammonia, forming nitrogen and hydrogen chloride; if chlorine is present in excess, then the highly explosive nitrogen trichloride () is also formed.
The combustion of ammonia to form nitrogen and water is exothermic: The standard enthalpy change of combustion, Δ"H"°c, expressed per mole of ammonia and with condensation of the water formed, is −382.81 kJ/mol. Dinitrogen is the thermodynamic product of combustion: all nitrogen oxides are unstable with respect to and , which is the principle behind the catalytic converter. Nitrogen oxides can be formed as kinetic products in the presence of appropriate catalysts, a reaction of great industrial importance in the production of nitric acid: A subsequent reaction leads to : The combustion of ammonia in air is very difficult in the absence of a catalyst (such as platinum gauze or warm chromium(III) oxide), due to the relatively low heat of combustion, a lower laminar burning velocity, high auto-ignition temperature, high heat of vapourization, and a narrow flammability range. However, recent studies have shown that efficient and stable combustion of ammonia can be achieved using swirl combustors, thereby rekindling research interest in ammonia as a fuel for thermal power production. The flammable range of ammonia in dry air is 15.15–27.35% and in 100% relative humidity air is 15.95–26.55%. For studying the kinetics of ammonia combustion, knowledge of a detailed reliable reaction mechanism is required, but this has been challenging to obtain.
Precursor to organonitrogen compounds. Ammonia is a direct or indirect precursor to most manufactured nitrogen-containing compounds. It is the precursor to nitric acid, which is the source for most N-substituted aromatic compounds. Amines can be formed by the reaction of ammonia with alkyl halides or, more commonly, with alcohols: Its ring-opening reaction with ethylene oxide give ethanolamine, diethanolamine, and triethanolamine. Amides can be prepared by the reaction of ammonia with carboxylic acid and their derivatives. For example, ammonia reacts with formic acid (HCOOH) to yield formamide () when heated. Acyl chlorides are the most reactive, but the ammonia must be present in at least a twofold excess to neutralise the hydrogen chloride formed. Esters and anhydrides also react with ammonia to form amides. Ammonium salts of carboxylic acids can be dehydrated to amides by heating to 150–200 °C as long as no thermally sensitive groups are present. Other organonitrogen compounds include alprazolam, ethanolamine, ethyl carbamate and hexamethylenetetramine.
Precursor to inorganic nitrogenous compounds. Nitric acid is generated via the Ostwald process by oxidation of ammonia with air over a platinum catalyst at , ≈9 atm. Nitric oxide and nitrogen dioxide are intermediate in this conversion: Nitric acid is used for the production of fertilisers, explosives, and many organonitrogen compounds. The hydrogen in ammonia is susceptible to replacement by a myriad substituents. Ammonia gas reacts with metallic sodium to give sodamide, . With chlorine, monochloramine is formed. Pentavalent ammonia is known as λ5-amine, nitrogen pentahydride decomposes spontaneously into trivalent ammonia (λ3-amine) and hydrogen gas at normal conditions. This substance was once investigated as a possible solid rocket fuel in 1966. Ammonia is also used to make the following compounds: Ammonia is a ligand forming metal ammine complexes. For historical reasons, ammonia is named ammine in the nomenclature of coordination compounds. One notable ammine complex is cisplatin (, a widely used anticancer drug. Ammine complexes of chromium(III) formed the basis of Alfred Werner's revolutionary theory on the structure of coordination compounds. Werner noted only two isomers ("fac"- and "mer"-) of the complex could be formed, and concluded the ligands must be arranged around the metal ion at the vertices of an octahedron.
Ammonia forms 1:1 adducts with a variety of Lewis acids such as , phenol, and . Ammonia is a hard base (HSAB theory) and its E & C parameters are EB = 2.31 and CB = 2.04. Its relative donor strength toward a series of acids, versus other Lewis bases, can be illustrated by C-B plots. Detection and determination. Ammonia in solution. Ammonia and ammonium salts can be readily detected, in very minute traces, by the addition of Nessler's solution, which gives a distinct yellow colouration in the presence of the slightest trace of ammonia or ammonium salts. The amount of ammonia in ammonium salts can be estimated quantitatively by distillation of the salts with sodium (NaOH) or potassium hydroxide (KOH), the ammonia evolved being absorbed in a known volume of standard sulfuric acid and the excess of acid then determined volumetrically; or the ammonia may be absorbed in hydrochloric acid and the ammonium chloride so formed precipitated as ammonium hexachloroplatinate, . Gaseous ammonia. Sulfur sticks are burnt to detect small leaks in industrial ammonia refrigeration systems. Larger quantities can be detected by warming the salts with a caustic alkali or with quicklime, when the characteristic smell of ammonia will be at once apparent. Ammonia is an irritant and irritation increases with concentration; the permissible exposure limit is 25 ppm, and lethal above 500 ppm by volume. Higher concentrations are hardly detected by conventional detectors, the type of detector is chosen according to the sensitivity required (e.g. semiconductor, catalytic, electrochemical). Holographic sensors have been proposed for detecting concentrations up to 12.5% in volume.
In a laboratorial setting, gaseous ammonia can be detected by using concentrated hydrochloric acid or gaseous hydrogen chloride. A dense white fume (which is ammonium chloride vapor) arises from the reaction between ammonia and HCl(g). Ammoniacal nitrogen (NH3–N). Ammoniacal nitrogen (NH3–N) is a measure commonly used for testing the quantity of ammonium ions, derived naturally from ammonia, and returned to ammonia via organic processes, in water or waste liquids. It is a measure used mainly for quantifying values in waste treatment and water purification systems, as well as a measure of the health of natural and man-made water reserves. It is measured in units of mg/L (milligram per litre). History. The ancient Greek historian Herodotus mentioned that there were outcrops of salt in an area of Libya that was inhabited by a people called the 'Ammonians' (now the Siwa oasis in northwestern Egypt, where salt lakes still exist). The Greek geographer Strabo also mentioned the salt from this region. However, the ancient authors Dioscorides, Apicius, Arrian, Synesius, and Aëtius of Amida described this salt as forming clear crystals that could be used for cooking and that were essentially rock salt. "Hammoniacus sal" appears in the writings of Pliny, although it is not known whether the term is equivalent to the more modern sal ammoniac (ammonium chloride).

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