altitude and azimuth Vaz-motLA Two coordinates describing the position of an object above Earth in a coordinate system called the altaz¬ imuth, or horizon, system, and used in astronomy, gunnery, navigation, surveying, and other fields. Altitude in this sense is expressed as angle of elevation (up to 90°) above the horizon. Azimuth, in astronomical mea¬ surement, is the number of degrees clockwise from due north to the point on the horizon directly below the object.
altitude sickness or mountain sickness Acute reaction to a change from low altitudes to altitudes above 8,000 ft (2,400 m). Most people gradually adapt, but some have a severe reaction that can be fatal unless they return to low altitude. Normal adaptations to the reduced oxy¬ gen at high altitude (e.g., breathlessness, racing heartbeat) are exagger¬ ated; other manifestations include headache, gastrointestinal upsets, and weakness. Pulmonary edema is quickly reversed with oxygen and evacu¬ ation to a lower area.
Altman Volt-monV Robert (B.) (b. Feb. 20, 1925, Kansas City, Mo., U.S.) U.S. film director. He learned filmmaking by directing industrial films, then directed several television series before making his first fea¬ ture film, Countdown (1967). The successful antiwar comedy MAS*/7 (1970) established his reputation as an independent director whose work emphasizes character and atmosphere over plot. His most acclaimed films
include McCabe and Mrs. Miller (1971), Nashville (1976), The Player (1992), and Short Cuts (1993).
Altman, Sidney (b. May 7, 1939, Montreal, Que., Can.) Canadian- born U.S. molecular biologist. He studied at MIT and the University of Colorado and has taught at Yale University since 1971. Working inde¬ pendently, Altman and Thomas Cech discovered that RNA, previously believed to be simply a passive carrier of genetic codes between differ¬ ent parts of the living cell, could also initiate and carry out (i.e., catalyze) some reactions, opening up new fields of research and biotechnology. The two shared a 1989 Nobel Prize.
alto or contralto Voice or register that extends approximately from the F below middle C to the second D above it. The second-highest part in four-part music, it is normally sung by women. The name derives from contratenor altus , the part above the tenor part. It is used for some instru¬ ments that play principally in the alto range (alto saxophone, alto flute, etc.). See also countertenor.
Altria Group, Inc. U.S. holding company with interests in tobacco, foods, and financial services. Formerly called Philip Morris Cos., Inc., the group changed its name to Altria in January 2003. Its holdings include Kraft Foods, Inc. (including Nabisco), Philip Morris International Inc., and Philip Morris USA Inc. (see Philip Morris tobacco companies), and an interest in SABMiller PLC, which was created in 2002 from the merger of South African Breweries PLC and Miller Brewing Co. Philip Morris had acquired the Miller Brewing Co. in 1969. It continued to reduce its dependence on tobacco by acquiring General Foods (1985), Kraft Foods (1988), and Nabisco (2000), among others. In 1998, as part of the settle¬ ment of a suit brought against it and other cigarette manufacturers by 46 U.S. states, the company agreed to participate in paying more than $200 billion to the states for smoking-related health-care costs.
altruism Ethical theory that regards the good of others as the end of moral action; by extension, the disposition to take the good of others as an end in itself. The term (French, altruisme, derived from Latin alter: “other”) was coined in the 19th century by Auguste Comte and adopted generally as a convenient antithesis to egoism. Most altruists have held that each person has an obligation to further the pleasures and alleviate the pains of other people. The same argument holds if happiness, rather than pleasure, is taken as the end of life.
alum \'a-lom\ Inorganic compound, any of a class of hydrated double salts, usually consisting of aluminum sulfate, water of hydration (an essen¬ tial part of the crystal makeup), and the sulfate of another element. The most important alums are those of potassium sulfate (potassium alum, or potash alum, ^SO^Al^SO^^T^O), ammonium sulfate, and sodium sulfate. Alums occur naturally in various minerals and can be prepared and purified by crystallization from their solutions. Most are white crys¬ tals with an astringent, acid taste. They are used as paper-sizing agents, flocculating agents in water treatment, mordants in dyeing, and in pick¬ les, baking powder, fire extinguishers, and medicines.
aluminum Metallic chemical element, chemical symbol Al, atomic num¬ ber 13. A lightweight, silvery white metal, it is so reactive chemically that it always occurs in compounds. It is the most abundant metallic element in Earth’s crust, chiefly in bauxite (its principal ore), feldspars, micas, clay minerals, and laterite. It also occurs in gemstones, such as topaz, garnet, and chrysoberyl; emery, corundum, ruby, and sapphire are crystalline alumi¬ num oxide. Aluminum was first isolated in 1825, became commercially available in the late 19th century, and is now the most widely used metal after iron. Its surface oxidizes at once to a hard, tough film, deterring fur¬ ther corrosion. Uses include building and construction, corrosion-resistant chemical equipment, auto and aircraft parts, power transmission lines, photoengraving plates, cookware and other consumer goods, and tubes for ointments and pastes. Important compounds include alums; alumina (aluminum oxide), useful as corundum and as a carrier for many cata¬ lysts; aluminum chloride, a widely used catalyst for organic syntheses; and aluminum hydroxide, used to waterproof fabrics.
Alvarado \,al-va-'ra-tho\, Pedro de (b. c. 1485, Badajoz, Castile—d. 1541, in or near Guadalajara, New Spain) Spanish soldier and colonial administrator. In 1519 he accompanied the army led by HernAn Cortes that conquered Mexico. In 1522 he became the first mayor of Tenochti- tlan (Mexico City). In 1523 he conquered the native peoples of Guate¬ mala and founded the city (modern Antigua) that became the first capital of the Guatemala region, which later included much of Central America.
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Alvarez ► Amar Das I 55
He was governor of Guatemala in 1527-31. In 1539 he began an explo¬ ration of central Mexico, but died while quelling an Indian uprising.
Alvarez Val-v3- l rez\, Luis W(alter) (b. June 13, 1911, San Francisco, Calif., U.S.—d. Sept. 1,1988, Berke¬ ley, Calif.) U.S. experimental physi¬ cist. He joined the faculty of the University of California at Berkeley in 1936, where he would remain until 1978. In 1938 he discovered that some radioactive elements decay when an orbital electron merges with the atom’s nucleus, producing an ele¬ ment with an atomic number smaller by one, a form of beta decay. In 1939 he and Felix Bloch (1905-83) made the first measurement of the magnetic moment of the neutron. During World War II he developed a radar guidance system for landing aircraft and participated in the Manhattan Project to develop the atomic bomb.
He later helped construct the first proton linear accelerator and constructed the liquid hydrogen bubble cham¬ ber. With his son, the geologist Walter Alvarez (b. 1940), he helped develop the theory that links the dinosaurs’ extinction with a giant asteroid or comet impact. For work that included the discovery of many subatomic particles, he received the Nobel Prize for Physics in 1968.
alveolus See pulmonary alveolus
Alzheimer Valts-.hl-morN disease Degenerative brain disorder. It occurs in middle to late adult life, destroying neurons and connections in the cerebral cortex and resulting in significant loss of brain mass. The most common form of dementia, Alzheimer disease progresses from short-term memory impairment to further memory loss; deterioration of language, perceptual, and motor skills; mood instability; and, in advanced stages, unresponsiveness, with loss of mobility and control of body functions; death typically ensues in 5-10 years. Originally described in 1906 by the German neuropathologist Alois Alzheimer (1864-1915) with reference to a 55-year-old person and regarded as a presenile dementia, Alzheimer disease is now recognized as accounting for much of the senile dementia once thought normal with aging. The 10% of cases that begin before age 60 result from an inherited mutation. Neuritic plaques and neurofibrillary tangles in the brain on autopsy are the primary features used for diagno¬ sis. No cure has been found. Most treatment targets the depression, behav¬ ioral problems, and sleeplessness that often accompany the disease.