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.
azulejo \,a-zu-'la-ho\ Spanish and Portuguese glazed, polychromed tile produced from the 14th century.
Introduced into Spain by the Arabs during the Moorish occupation, azu- lejos were used in Islamic architec¬ ture for facing walls and paving floors. Early designs were geometric and 5-6 in. (13-15 cm) square. In the 15 th—16 th centuries Portugal imported the tiles from Spain for use in religious and private buildings.
The Portuguese exported them in the 17th century to the Azores, Madeira, and Brazil, and the Spaniards intro¬ duced them to their American colo¬ nies. In the 18th century, interiors and exteriors in Puebla, Mex., were covered with azulejos in brilliant colours on a scale unequaled elsewhere.
Azulejos from Seville, late 16th cen¬ tury; in the Museum Boymans-van Beuningen, Rotterdam
BY COURTESY OF MUSEUM BOYMANS-VAN BEUNINGEN, ROTTERDAM
© 2006 Encyclopaedia Britannica, Inc.
B-17 ► Babbitt I 143
B-17 or Flying Fortress U.S. heavy bomber used in World War II. Designed by the Boeing Aircraft Co. in 1934, it cruised at 35,000 ft (10,700 m) at a maximum speed of 287 mph (462 kph). It was called the Flying Fortress because of the .50-caliber machine guns, 13 in all, at every comer. It could carry 3 tons (2.7 metric tons) of bombs in its bays and more on racks under its wings. More than 12,000 B-17s were produced during World War II, and most were used for high-level bombing over Europe.
B-52 or Stratofortress U.S. long-range heavy bomber, designed in 1948 by the Boeing Company and first flown in 1952. Originally intended as an atomic-bomb carrier capable of reaching the Soviet Union, it has proved highly adaptable and has remained in service as a conventional bomber, cruise-missile carrier, and maritime reconnaissance platform. It has a wingspan of 185 ft (56 m) and a length of more than 160 ft (49 m).
Powered by eight jet engines, its maximum speed at 55,000 ft (17,000 m) is 595 mph (960 kph).
B cell One of the two types of lymphocytes (the others being T cells). All lymphocytes begin their development in the bone marrow. B cells are involved in so-called humoral immunity; on encountering a foreign substance (antigen), the B lymphocyte differentiates into a plasma cell, which secretes immunoglobulin (see antibody).
Baader-Meinhof Gang Vba-dor-'min-.hoA or Red Army Faction West German leftist terrorist group formed in 1968 and popularly named after two of its early leaders, Andreas Baader (1943-1977) and Ulrike Meinhof (1934-1976). The members initially sup¬ ported themselves by bank robberies and engaged in terrorist bombings and arson, especially of West German and U.S. targets in West Germany. Baader, Meinhof, and 18 others were arrested in 1972; Meinhof eventually hanged herself, and Baader apparently also died a suicide. By the mid-1970s the group had turned to international terrorism; two members took part in the 1976 Palestinian airplane hijacking in the Entebbe incident. After the collapse of communism in East Germany (1989— 90), it was discovered that East Germany’s secret police had provided training and supplies to the gang. The group announced an end to its ter¬ rorist campaign in 1992.