Britannica Concise 2005

Avery, Oswald (Theodore) (b. Oct. 21, 1877, Halifax, N.S., Can.—d. Feb. 20, 1955, Nashville, Tenn., U.S.) Canadian-born U.S. bac¬ teriologist. He studied at Colgate University before taking a post at New York’s Rockefeller Institute Hospital. There he discovered transformation, a process by which a change could be introduced into bacteria and passed on to later generations of transformed cells. He and his coworkers reported in 1944 that the substance that caused the transformation was DNA, the cell’s genetic material. The discovery thus opened the door to decipher¬ ing the GENETIC CODE.

Avesta \o-'ves-t3\ or Zend-Avesta Sacred book of Zoroastrianism. It contains hymns, prayers, and appeals to righteousness ascribed to Zoro¬ aster. The present text was assembled in the 3rd-7th century ad from the remains of a larger body of scripture that was destroyed when Alexander the Great conquered Persia. It has five parts: the Gathas, hymns in what are thought to be Zoroaster’s own words; Visp-rat, containing homages

Avalokitesvara, bronze figure from Kurkihar, Bihar, 9th century; in Patna Museum, Patna, Bihar

BY COURTESY OF PATNA MUSEUM, PATNA (BIHAR); PHOTOGRAPH, ROYAL ACADEMY OF ARTS, LONDON

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Avestan ► Avon I 139

to spiritual leaders; Vendidad, the main source for Zoroastrian law; the Yashts, 21 hymns to angels and ancient heroes; and the Khurda avesta, composed of minor texts.

Avestan \3-'ves-t3n\ language Eastern Iranian language of the Avesta, the sacred book of Zoroastrianism. The oldest portion of the Avesta, the Gathas, are now commonly thought to date from around the end of the 2nd millennium bc and are thus contemporary with Vedic San¬ skrit. Not until the mid-SASANiAN period (5 th—6th century ad) was the Avesta committed to writing, in an alphabetic script invented for the pur¬ pose on the basis of existing Middle Persian scripts. The oldest manu¬ scripts date only from the 13th century.

aviary Structure for keeping captive birds, usually spacious enough for the aviculturist to enter. Aviaries range from small enclosures to large flight cages 100 ft (30 m) or more long and up to 50 ft (15 m) high. Enclosures for birds that fly only little or weakly (e.g., rails, pheasants) may be only about 3 ft (1 m) high. In cold climates the aviary is usually enclosed and heated. Most aviculturists prefer to place birds in natural, planted surroundings. Many aviaries are maintained for pleasure by pri¬ vate aviculturists; others, especially large ones, are found in zoos or research institutions.

aviation Development and operation of aircraft. In 1783 the balloon became the first aircraft to carry humans. Production of a successful glider in 1891 and refinement of the internal-combustion engine led to the first successful engine-powered airplane flight by Wilbur and Orville Wright in 1903. World War I accelerated the expansion of aviation, and in the 1920s the first small airlines began carrying mail and passengers. World War II was another period of innovation in aircraft size, speed, and range. In the late 1940s the jet engine made possible the subsequent development of commercial airlines throughout the world. See also airship; helicopter; sea¬ plane.

Avicenna V.a-vo-'se-noV Arabic Ibn Sina \'ib-3n-'se-na\ in full Abu ’All al-Husayn ibn *Abd Allah ibn STna (b. 980, Bukhara, Iran—d. 1037, Hamadan) Islamic philosopher and scientist. He became physician to several sultans and also twice served as vizier. His Canon of Medicine was long a standard work in the field. He is known for his great encyclopaedia of philosophy, The Book of Healing. His other writings include The Book of Salvation and The Book of Directives and Remarks. His interpretations of Aristotle influenced European Scholasticism. His sys¬ tem rests on a conception of God as the necessary existent: only in God do essence (what God is) and existence (that God is) coincide.

Avignon \,a-ve-'ny6 n \ ancient Avennio City (pop., 2004 prelim.: 89,400), southeastern France. Founded by the Gallic tribe of Cavares, it later fell under Roman rule and was a much-fought-over prize in its early days. Its status grew tremendously as the capital of the papacy (1309-77) and seat of the Avignonese popes during the Western Schism. France annexed the city in 1791. Landmarks include a Romanesque cathedral, the papal palace, and Saint-Benezet bridge, made famous by the song “Sur le pont d’Avignon.” The city’s historic centre was designated a World Heritage site in 1995.

Avignon papacy Roman Catholic papacy during the period 1309-77, when the popes resided at Avignon, France. Elected pope through the machinations of Philip IV of France, Clement V moved the papal capital to Avignon four years later primarily for political reasons. All seven popes of this period were French, as were most of the cardinals, which aroused English and German animosity. During the Avignon papacy the cardinals began to play a stronger role in church government, church and clergy were reformed, missionary efforts were expanded, and popes tried to settle royal rivalries and establish peace. The heavy French influence damaged the prestige of the papacy, however, and in 1377 Gregory XI returned to Rome. The cardinals elected a new pope who took the Avignon seat, becoming the first of a line of antipopes and beginning the Western Schism.

Avignon school School of late Gothic painting associated with the city of Avignon, Fr., during the Avignon papacy, when many Italian artists worked there. This “school” represents a body of late Gothic painting and not necessarily a single stylistic evolution. Under the direction of Simone Martini, the papal palace of Avignon and secular buildings in nearby towns were decorated with frescoes. The city was one of the channels by which Italian 14th-century art reached France. By the early 15th century Flem¬ ish influences had reached the city, consolidating the Italian and northern styles. The Avignon Pieta (c. 1460), attributed to Enguerrand Charonton,

is the masterpiece of the school. The artistic activity at Avignon greatly influenced French painting in the late 15th and 16th centuries. See also Gothic art.

Aviles, Pedro Menendez de See Pedro Menendez de Aviles

Avogadro's number Number of units in one mole of any substance (defined as its molecular weight in grams), equal to 6.0221367 x 10 23 . The units may be electrons, atoms, ions, or molecules, depending on the nature of the substance and the character of the reaction (if any). See also Avogadro's law; law of mass action; stoichiometry.

avoidance, zone of Region of apparent absence of galaxies near the plane of the Milky Way Galaxy. Millions of external galaxies are in this region of the sky but are obscured by interstellar dust within the Milky Way. The zone’s obscuration can be penetrated at the infrared portion of the ELECTROMAGNETIC SPECTRUM. See also INFRARED ASTRONOMY.

avoidance behaviour Type of activity, exhibited by animals exposed to adverse stimuli, in which the tendency to flee or to act defen¬ sively is stronger than the tendency to attack. Vision is the sense that most often produces avoidance behaviour (e.g., small birds react to the sight of an owl), but sound (e.g., a warning cry) may do so as well.

Avon, River or Lower Avon River, southwestern England. Rising in Gloucestershire, it flows 75 mi (121 km) southwest through Bristol and into the Bristol Channel at Avonmouth, Bristol’s port. Below Bristol it has cut through a limestone ridge to form Clifton Gorge, noted for its sus¬ pension bridge.

Avon, River or Upper Avon River, central England. Rising in Northamptonshire, it flows 96 mi (154 km) southwest into the River Sev¬ ern at Tewkesbury. It is known for its scenic beauty, notably in the Vale of Evesham. Important towns along it include Stratford, where William Shakespeare was born.

of the laurel family, a tree native

avocado Fruit of Persea americana, to the Western Hemisphere from Mexico south to the Andean regions.

Avocados are extremely variable in shape, size, and colour (green to dark purple). The outer skin may be thin, or coarse and woody. The greenish or yellowish flesh has a buttery consis¬ tency and a rich, nutty flavour. In some varieties the flesh contains as much as 25% unsaturated oil. Avo¬ cados are the principal ingredient of the Mexican sauce guacamole. They provide thiamine, riboflavin, and vitamin A.

avocet Va-v9-,set\ Any of several large shorebirds (genus Recurviros- tra ) with boldly contrasting plum¬ age, long bluish legs, and a long black bill upturned at the tip. Avocets inhabit fresh and salt marshes that have areas of open shallow water and mudflats, and feed by sweeping the partly open bill in the shallows. They often wade together to corral min¬ nows and crustaceans. Four avocet species are found in temperate and tropical regions worldwide. The American avocet is about 18 in. (45 cm) long, including the bill.

Avogadro's law ^a-vo-'ga-drozX Statement that, under the same con¬ ditions of TEMPERATURE and PRESSURE, equal volumes of different GASes

contain an equal number of molecules (see Avogadro's number). First pro¬ posed by the Italian scientist Amedeo Avogadro (1776-1856) in 1811, it became accepted c. 1860. From the law, it follows that the volume occu¬ pied by one mole of gas (at standard conditions of 32 °F [0 °C] and 1 atmosphere of pressure) is the same for all gases (0.791 cubic feet [22.4 litres]).

Avocado (Persea americana).

S.A. SCIBOR-SHOSTAL

American avocet (Recurvirostra ameri¬ cana)

MILDRED GLUECK FROM ROOT RESOURCES-EB INC.

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140 I AWAC5 ► Ayers

AWACS Va-waks\ (Airborne Warning and Control System)

Mobile, long-range radar surveillance-and-control centre for air defense. Used by the U.S. Air Force since 1977, AWACS is mounted in a specially modified Boeing 707 aircraft, with its main radar antenna affixed to a rotat¬ ing dome. It can detect, track, and identify low-flying aircraft at a distance of 200 nautical mi (370 km) and high-level targets at much greater dis¬ tances. It can also track maritime traffic and operate in any weather. The computer system can assess enemy action and track the location and avail¬ ability of any aircraft within range. Operators of its secure communications system can guide friendly aircraft against enemy planes.

Awakening, Great See Great Awakening

Awolowo Va-'wii-lo-.woV Obafemi (b. March 6, 1909, Ikenne, Colony and Protectorate of Southern Nigeria—d. May 9, 1987, Ikenne) Nigerian nationalist politician and leader of the Yoruba ethnic group. While studying law in London, he wrote the influential Path to Nigerian Freedom (1947) and laid the basis for the first Yoruba political party, the Action Group. As premier of Nigeria’s Western Region (1954-59), he worked to improve education, social services, and agriculture. He remained a major figure in national politics but never won high elective office.

ax Hand tool used for chopping, splitting, chipping, and piercing. Stone Age hand axes originated in simple stone implements that acquired wooden hafts, or handles, about 30,000 bc. Copper-bladed axes appeared in Egypt about 4000 bc and were followed by axes with blades of bronze and eventually iron. The development of the iron-bladed felling ax in the Middle Ages made possible the vast forest clearances of Europe, North and South America, and elsewhere. Though the ax has lost much of its historic role to powered saws and other machinery, it remains a widely used tool with many uses.

axiology or value theory Philosophical theory of value. Axiology is the study of value, or goodness, in its widest sense. The distinction is commonly made between intrinsic and extrinsic value—i.e., between that which is valuable for its own sake and that which is valuable only as a means to something else, which itself may be extrinsically or intrinsically valuable. Many different answers have been given to the question “What is intrinsically valuable?” For hedonists, it is pleasure; for pragmatists, it is satisfaction, growth, or adjustment; for Kantians, it is a good will. Plu- ralists such as G.E. Moore and William David Ross assert that there are any number of intrinsically valuable things. According to subjective theories of value, things are valuable only insofar as they are desired; objective theories hold that there are at least some things that are valuable inde¬ pendently of people’s interest in or desire for them. Cognitive theories of value assert that ascriptions of value function logically as statements of fact, whereas noncognitive theories assert that they are merely expres¬ sions of feeling (see emotivism) or prescriptions or commendations (see prescriptivism). According to naturalists, expressions such as “intrinsically good” can be analyzed as referring to natural, or non-ethical, properties, such as being pleasant. Moore famously denied this, holding that “good” refers to a simple (unanalyzable) non-natural property. See also fact-value distinction; naturalistic fallacy.

axiom In mathematics or logic, an unprovable rule or first principle accepted as true because it is self-evident or particularly useful (e.g., “Nothing can both be and not be at the same time and in the same respect”). The term is often used interchangeably with postulate, though the latter term is sometimes reserved for mathematical applications (such as the postulates of Euclidean geometry). It should be contrasted with a theorem, which requires a rigorous proof.

axiomatic method In logic, the procedure by which an entire science or system of theorems is deduced in accordance with specified rules by logical deduction from certain basic propositions (axioms), which in turn are constructed from a few terms taken as primitive. These terms may be either arbitrarily defined or conceived according to a model in which some intuitive warrant for their truth is felt to exist. The oldest examples of axiomatized systems are Aristotle’s syllogistic and Euclidean geometry. Early in the 20th century, Bertrand Russell and Alfred North Whitehead attempted to formalize all of mathematics in an axiomatic manner. Schol¬ ars have even subjected the empirical sciences to this method, as in J. H. Woodger’s The Axiomatic Method in Biology (1937) and Clark Hull’s Principles of Behavior (1943).

Axis Powers Coalition headed by Germany, Italy, and Japan that opposed the Allied Powers in World War II. The alliance originated in a

series of agreements between Germany and Italy, followed in 1936 by the Rome-Berlin Axis declaration and the German-Japanese Anti-Comintern Pact. The connection was strengthened by the formal Pact of Steel (1939) between Germany and Italy and by the Tripartite Pact signed by all three powers in 1940. Several other countries, including Hungary, Romania, Bulgaria, Croatia, and Slovakia, later allied themselves with the original Axis Powers.

axle Pin or shaft on or with which wheels revolve; with fixed wheels, one of the basic simple machines for amplifying force. Combined with the wheel, in its earliest form it was probably used for raising weights or water buckets from wells. Its principle of operation can be illustrated in the attachment of large and small gears to the same shaft; the tendency of a force applied at the radius on the large gear to turn the shaft is sufficient to overcome a larger force at the radius on the small gear. The mechanical advantage is equal to the ratio of the two forces and also equal to the ratio of the radii of the two gears.

Axminster carpet Floor covering produced in a factory founded at Axminster, England, in 1755 by the cloth weaver Thomas Whitty. The carpets were knotted in wool on woolen warps, with wefts of flax or hemp, and featured Renaissance architectural or floral patterns. The factory closed in 1835 with the advent of industrial weaving machines. The name survives as a generic term for all machine-made carpets with pile similar to velvet or chenille.

Axum See Aksum

ayatollah V.I-o-'to-loV In the Shiite branch of Islam, a high-ranking reli¬ gious authority regarded by his followers as the most learned person of his age. The ayatollah’s authority rests on the infallible imam. His legal decisions are accepted as binding by his personal followers and (in the present day) by the wider community.

Ayckbourn Vak-.bonA, Sir Alan (b. April 12, 1939, London, Eng.) British playwright. He began acting with the Stephen Joseph Co. in Scar¬ borough, Yorkshire, where he also wrote his earliest plays under the pseudonym Roland Allen (1959-61). Most of his plays premiered at the company’s theatre, where he was artistic director beginning in 1970. He has written over 50 plays, mostly farces and comedies that deal with marital and class conflicts, including Relatively Speaking (1967), Absurd Person Singular (1972), the trilogy The Norman Conquests (1973), Inti¬ mate Exchanges (1982), and Communicating Doors (1995).

Aydid \l-'ded\, Muhammad Farah orig. Muhammad Farah Hassan (b. c. 1930, Beledweyne, Italian Somaliland—d. Aug. 1, 1996, Mogadishu, Somalia) Somali faction leader. He received military training in Italy and the U.S.S.R. and served in posts under Mohamed Siad Barre (1978-89) before overthrowing him in 1991. He became the dominant clan leader at the centre of the Somalian civil war. Losing the interim presidency to another factional leader, Aydid continued warring on rival clans. When UN and U.S. troops arrived in Somalia (1992), Aydid ambushed a UN contingent and was declared an outlaw. The attempt to capture him led to many deaths, and foreign troops were withdrawn. He then intensified his campaign against his rivals, but he reportedly died of a heart attack after being wounded in battle.

Ayer \'a(o)r, 'e(o)r\, Sir A(lfred) J(ules) (b. Oct. 29, 1910, London, Eng.—d. June 27, 1989, London) British philosopher. He taught at Uni¬ versity College London (1946-59) and later at Oxford (1959-78). He gained international notice in 1936 with the publication of his first book, Language, Truth and Logic, a manifesto of logical positivism that drew on the ideas of the Vienna Circle and the tradition of British empiricism as rep¬ resented by David Hume and Bertrand Russell. He is also remembered for his contributions to epistemology and his writings on the history of Anglo- American philosophy (see also analytic philosophy). His other works include The Foundations of Empirical Knowledge (1940), The Problem of Knowledge (1956), The Origins of Pragmatism (1968), Russell and Moore (1971), The Central Questions of Philosophy (1973), and Wittgen¬ stein (1985).

Ayers \'arz\ Rock Rock outcrop, southwestern Northern Territory, Aus¬ tralia. Called Uluru by the Australian Aborigines and located in Uluru-Kata Tjuta National Park, it is 1,100 ft (335 m) high and may be the world’s largest monolith. Its arkosic sandstone changes colour according to the height of the sun. Shallow caves at the base of the rock are sacred to sev¬ eral Aboriginal tribes and contain carvings and paintings. In 1985 own¬ ership of Ayers Rock was officially returned to the Aborigines.

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Aying ► Azerbaijan I 141

Aying or A Ying Va-'yigX orig. Qian Xingcun (b. Feb. 6, 1900—d. June 17, 1977) Chinese critic and historian of modem Chinese literature. A member of the Communist Party and of the standing committee of the League of Left-Wing Writers, he began c. 1930 to gather and study mate¬ rials on the literature of modern times and of the Ming and Qing dynas¬ ties. His published works, including Women Writers in Modern China (1933) and Two Talks on the Novel (1958), contributed greatly to the record of modern culture in China.

Aylesbury Valz-b9-re\ Town (pop., 1995 est.: 61,000), south-central England. The county seat of Buckinghamshire, it lies northwest of London in the Thames valley known as the Vale of Aylesbury, noted for its rich clay. Once an important market town, it is now an industrial centre. Its historic buildings include an 18th-century county hall and a 15th-century inn.

Aymara \,I-m3- , ra\ Large South American Indian group living on the Titicaca plateau of the central Andes Mountains in present-day Peru and Bolivia. The Aymara were conquered by the Inca and the Spanish, though they rebelled against both. Traditional Aymara now live in an area of poor soil and harsh climate, where they herd llamas and alpacas, grow crops, and fish using boats made of large reeds. Poverty rates within the group are among the highest in the hemisphere.

Ayme Ve-'maV Marcel (b. March 29, 1902, Joigny, Fr.—d. Oct. 14, 1967, Paris) French novelist, essayist, and playwright. His novels include The Hollow Field (1929), The Fable and the Flesh (1943), and The Tran¬ sient Hour (1946). He delighted a vast public with witty tales of talking farm animals (reflecting his own farm upbringing), some of which were published in English as The Wonderful Farm (1951). Though his extrava¬ gant creations mingling fantasy and reality were long dismissed as minor, he was belatedly recognized as a master of light irony and storytelling.

Ayodhya \9-'yod-y9\ or Oudh Town (pop., 2001: 49,417), Uttar Pradesh state, northern India. Lying on the banks of the Ghaghara River just east of Faizabad, of which it is now a suburb, Ayodhya in ancient times was one of India’s greatest cities; today, it is one of the seven holy cities of Hinduism. It was the capital of Kosala, as described in the Ramay- ana. It became an important Buddhist centre in Buddhism’s early years (6th-4th century bc), and the Buddha is said to have lived there. In the 16th century the Mughal emperor Babur built a mosque on a site tradi¬ tionally associated with an ancient Hindu temple marking the birthplace of the god Rama. The storming of the mosque by Hindus in 1990, amid religious tensions, was followed by riots, and the ensuing crisis brought down the government. In 1992 the mosque was demolished by Hindu fundamentalists, and hundreds of people died in the rioting that subse¬ quently swept through India.

Ayrshire \'er-,shir\ Breed of hardy dairy cattle (see dairy farming) that originated in the county of Ayr, Scotland, in the late 18th century. It is considered the only special dairy breed to have originated in the British Isles. Its body colour varies from almost pure white to nearly all cherry red or brown. Exported widely to other countries, it is especially common in Great Britain, the U.S., and Canada.

Ayub Khan \a-'ub-'kan\, Mohammad (b. May 14, 1907, Hazara, India—d. April 19, 1974, near Islamabad, Pak.) President of Pakistan (1958-69). After studies at Aligarh Muslim University and at the British Royal Military College, he became an officer in the Indian army (1928). He fought in Burma (Myanmar) in World War II, and afterward he rose through the ranks in the military in newly independent Pakistan. In 1958 Pakistan’s Pres. Iskander Mirza abrogated the country’s constitution, and Ayub became chief martial-law administrator. He declared himself presi¬ dent the same year, exiling Mirza. He established close ties with China and in 1965 went to war with India over control of the Kashmir region. The failure to take Kashmir, combined with unrest over suffrage restric¬ tions, led to riots, and Ayub resigned in 1969.

Ayurveda Va-yor-.va-doV or Ayurvedic medicine Traditional sys¬ tem of Indian medicine. It is attributed to Dhanvantari, the physician to the gods in Hindu mythology, who received it from Brahma. Its earliest concepts were set out in the portion of the Vedas known as the Athar- vaveda (c. 2nd millennium bc). The most important Ayurvedic texts are the Caraka samhita and Susruta samhita (1st—4th century ad). These texts analyze the human body in terms of earth, water, fire, air, and ether as well as the three bodily humours (wind, bile, and phlegm). To prevent illness, Ayurvedic medicine emphasizes hygiene, exercise, herbal prepa¬ rations, and yoga. To cure ailments, it relies on herbal medicines, phys¬

iotherapy, and diet. Ayurvedic medicine is still a popular form of health care in India, where it is taught in roughly 100 colleges, and it has gained currency in the West as a form of alternative medicine.

Ayutthaya \,a-yu-'tI-9\ in full Phra Nakhon Si Ayutthaya. Town (pop., 2000 prelim.: 75,898), former capital city of the Thai kingdom of Ayutthaya. It is located northeast of present-day Bangkok. Modern-day Thailand (then called Siam) is said to date from its founding (between 1347 and 1351). The kingdom of Ayutthaya was once one of the most powerful in Southeast Asia, and its capital city flourished for more than 400 years. Much of the ancient city’s architecture, art, and literature was destroyed in 1767 when it was sacked by Hsinbyushin of the Alaungpaya dynasty. The modern town of Ayutthaya is set among the ruins of the ancient city. There is some manufacturing, and tourism is important. The area was designated a UNESCO World Heritage site in 1991.

Ayyubid \a-'yu-bid\ dynasty (1173-1250) Kurdish dynasty founded by Saladin that ruled over Egypt, most of Syria, upper Iraq, and Yemen. After overthrowing the Fajimid dynasty, Saladin defended Palestine during the Crusades and made Egypt the most powerful Muslim state in the world. After Saladin’s death the Ayyubid regime became decentralized. In 1250 a group of mamluks (military slaves) exploited a lapse in Ayyubid suc¬ cession to take over the government in Egypt and to found the MamlOk dynasty. Minor Ayyubid princes continued to rule in parts of the Syria for some years afterward.

azalea Any plant of certain species of the genus Rhododendron (heath family), formerly given the generic name Azalea. Though some gardeners consider azaleas distinct from rhododendrons, distinguishing characteris¬ tics of the two groups are not consistent enough to separate them into two genera. Azaleas typically are deciduous (see deciduous tree), with flowers that are funnel-shaped, somewhat two-lipped, and often fragrant. Culti¬ vated varieties have been bred from species native to the hilly regions of Asia and North America. Well-known North American kinds include the smooth, or sweet, azalea ( R. arborescensf, the flame azalea (R. calen- dulaceum ); and the pinxter flower (R. periclymenoides ).

Azall \a-za-'le\ Any member of the Bab! movement who remained faith¬ ful to the teachings of the Bab and his chosen successor, Mirza Yahya, known as Sobh-e Azal, after the movement split in 1863. For 13 years after the Bab’s execution, followers recognized Sobh-e Azal as their leader. Then Sobh-e Azal’s half-brother, Baha’ Ullah, privately declared himself to be the prophet whose coming the Bab had foretold. The Aza- lls rejected him, but most Babls followed him, establishing the BahaI faith in 1867. Now located almost exclusively in Iran, the Azalls probably number no more than a few thousand.

Azana \3-'than-yo\ (y Diaz), Manuel (b. Jan. 10, 1880, Alcala de Henares, Spain—<1. Nov. 4, 1940, Montauban, France) Spanish prime minister and president. As prime minister from 1931 to 1933, he attempted to fashion a moderately liberal government. Elected president in May 1936, he was able to accomplish little before the Spanish Civil War broke out in July. He lost control of policy and remained in office as only a fig¬ urehead until 1939, when he went into exile following the victory of the Nationalist forces of Francisco Franco.

Azande See Zande

Azerbaijan \,a-z9r-bl-'jan\ officially Republic of Azerbaijan

Country, Transcaucasia, western Asia. Area: 33,400 sq mi (86,600 sq km). Population (2005 est.): 8,381,000. Capital: Baku. Most residents are of Turkic origin, dating from the 11th century ad. Later migrations during the SeuOq period brought further groups, including some speaking Per¬ sian; Russians are a decreasing minority. Languages: Azerbaijanian (offi¬ cial), Russian. Religion: Islam (mostly Shl'ite). Currency: manat. Azerbaijan is characterized by a variety of landscapes. More than two- fifths of its territory is lowlands, while areas above 5,000 ft (1,500 m) occupy some one-tenth of the total area. The central part of the country is a plain through which flows the Kura River and its tributaries, includ¬ ing the Aras, whose upper course forms part of the boundary with Iran. The Caspian Sea serves Baku as a trade outlet. Agriculture, petroleum refining, and light manufacturing are economically important. Azerbaijan is a republic with one legislative body; its head of state and government is the president, assisted by the prime minister. Azerbaijan adjoins the Ira¬ nian region of the same name, and the origin of their respective inhabit¬ ants is the same. By the 9th century ad it had come under Turkish influence, and in ensuing centuries it was fought over by Arabs, Mongols,

© 2006 Encyclopaedia Britannica, Inc.

142 I Azhar ► azulejo

Turks, and Iranians. Russia acquired what is now independent Azerbaijan in the early 19th century. After the Russian Revolution of 1917, Azerbaijan declared its indepen¬ dence; it was subdued by the Red Army in 1920 and was incorporated into the Soviet Union. It declared indepen¬ dence from the collapsing Soviet Union in 1991. Azerbaijan has two geo¬ graphic peculiarities. The exclave Naxgivan (Nakhichevan) is separated from the rest of Azerbaijan by Armenian territory. Nagorno-Karabakh, which lies within Azerbaijan and is administered by it, has a Christian Armenian majority. Azerbaijan and Armenia went to war over both ter¬ ritories in the 1990s, causing many deaths and great economic disruption. Though attempts at mediation were made, the political situation remained unresolved.

Azhar \'az-,har\ University, al- Chief school of Islamic and Arabic learning in the world, centred on the al-Azhar Mosque in the medieval quarter of Cairo. It was founded by the Fatimid dynasty in 970. The basic program has always focused on Islamic law, theology, and the Arabic lan¬ guage. Philosophy and medical studies were added during the Middle Ages but were eventually dropped from the curriculum. Philosophy was restored at the end of the 19th century, and social sciences were added at a branch campus in the early 1960s. Women were first admitted in 1962.

Azikiwe \o-'zik-wa\, Nnamdi (b. Nov. 16, 1904, Zungeru, Nigeria—d. May 11, 1996, Enugu) First president (1963-66) of indepen¬ dent Nigeria. Azikiwe’s National Council party won the important 1959 federal elections and helped stimulate Nigerian independence. In the con¬ flict over Biafra (1967-70), Azikiwe first backed his fellow Igbo but then threw his support to the federal government. Thereafter he was a leading opponent of the ruling party.

azimuth See altitude and azimuth

azo \'a-zo\ dye Any of a large class of synthetic organic compounds, dyes containing two nitrogen atoms joined by a double bond (see bond¬ ing, covalent bond) in the form —N=N— as part of their molecular structure. More than half the dyes in commercial use are azo dyes. They are usually classed according to the fibres for which they are useful or the methods by which they are applied; direct dyes are absorbed from solu¬ tion by the fibres, but others require a second solution (a mordant) or a second step before the colour is fast.

Azores \o-'zorz\ Portuguese Acores \9-'so-rish\ Archipelago (pop., 2001: 242,073), northern Atlantic Ocean, constituting an autonomous region of Portugal. Its islands are Flores, Corvo, Terceira, Sao Jorge, Pico,

Faial, Graciosa, Sao Miguel, and Santa Maria; the capital is Ponta Del- gada (on Sao Miguel). It covers an area of 901 sq mi (2,333 sq km). Sub¬ ject to earthquakes and volcanic eruptions, the islands lie some 1,000 mi (1,600 km) west of mainland Europe. The uninhabited Azores were reput¬ edly discovered c. 1427 by Portuguese pilot Diogo de Sevilha. Settlement began c. 1432; by the end of the 15th century, all the islands were inhab¬ ited and trade with Portugal was well established. They were subject to Spain in 1580-1640, and a famous sea battle between the British and Spanish occurred off Flores in 1591. The Portuguese installed a governor and captain general for the whole group in 1766; the islands were given limited autonomy in 1895. Important air and naval bases were set up there during World War II; in 1951 the U.S. established a NATO base on Lajes.

Azov \3-'zof, 'a-.zoA, Sea of Inland sea in Europe between Ukraine and Russia. It is connected to the Black Sea by Kerch Strait. About 210 mi (340 km) long and 85 mi (135 km) wide, it occupies an area of 14,500 sq mi (37,600 sq km). With a maximum depth of only about 46 ft (14 m), it is the world’s shallowest sea. It is fed by the Don and Kuban rivers, and at their entrance in the Taganrog Gulf, its depth is 3 ft (1 m) or less. In the west lies the Arabat Spit, a 70-mi- (113-km-) long sandbar that sepa¬ rates the Sea of Azov from the Sy vash, a system of marshy inlets divid¬ ing the Crimean Peninsula from the Ukrainian mainland.

AZT in full azidothymidine also known as zidovudine Drug that has had success in delaying the development of AIDS in patients with HIV. Since its introduction in the mid 1980s, it has prolonged the lives of mil¬ lions of patients. It is particularly effective in preventing transmission of HIV from infected pregnant women to their fetuses. Since it has a greater effect on the replication of viRUSes than of body cells, it has fewer side effects than most other AIDS drugs, though many patients nevertheless cannot tolerate it. Because HIV rapidly becomes resistant to any single antiretroviral drug, AZT is usually given in combination with other drugs.

Aztec NAHUATL-speaking people who in the 15th and early 16th centu¬ ries ruled a large empire in what is now central and southern Mexico. They may have originated on the northern Mexican plateau before migrat¬ ing to their later location. Their migration may have been linked to the collapse of the Toltec civilization. The Aztec empire, which at its height comprised roughly five to six million people spread over some 80,000 sq mi (200,000 sq km), was made possible by their successful agricultural methods, including intensive cultivation, irrigation, and reclamation of wetlands. The Aztec state was despotic, militaristic, and sharply stratified according to class and caste. Aztec religion was syncretic, drawing espe¬ cially on the beliefs of the Maya. The Aztec practiced human sacrifice, an activity that sometimes reached mass proportions. The empire came to an end when the Spanish conquistador Hernan Cortes took the emperor Mon¬ tezuma II prisoner and conquered the great city Tenochtitlan (modem Mexico City). See also Nahua.

Aztec Ruins National Monument Archaeological site, northwest¬ ern New Mexico, U.S. Located on the Animas River just north of the town of Aztec, it was established in 1923 and has an area of 0.5 sq mi (1.3 sq km). Mistakenly named by early settlers, the site actually contains the excavated ruins of a 12th-century Pueblo town. It was designated a World Heritage site in 1987.