Anti-Slavery Society, American See American Anti-Slavery Society
antiaircraft gun Artillery piece fired from the ground or shipboard in defense against aerial attack. They were first used in combat in World War I, when field artillery were converted to antiaircraft use by mount¬ ings that enabled them to fire nearly vertically. Range finders and search¬ lights, developed in the 1920s and ’30s, increased their effectiveness. Advances in World War II included rapid-firing and automatic weapons, radar for target tracking, and radio-operated fuses. British and U.S. forces used a 40-mm gun that fired ammunition to a height of 2 mi (3.2 km). Heavier guns, up to 120 mm, were used against high-flying bombers. For most of the war, the most effective was the German 88-mm Fliegerabwe- hrkanone\ its abbreviated name, flak, became a universal term for anti¬ aircraft fire. With the introduction of guided missiles in the 1950s and ’60s, heavy antiaircraft guns were phased out, though lighter radar-guided auto¬ matic guns remained effective against low-flying aircraft and helicopters.
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82 I antiballistic missile ► Antigone
antiballistic missile (ABM) Weapon designed to intercept and destroy ballistic missiles. Effective ABM systems have been sought since the Cold War, when the nuclear arms race raised the spectre of complete destruction by unstoppable ballistic missiles. In the late 1960s both the U.S. and the Soviet Union developed nuclear-armed ABM systems that combined a high-altitude interceptor missile (the U.S. Spartan and Soviet Galosh) with a terminal-phase interceptor (the U.S. Sprint and Soviet Gazelle). Both sides were limited by the 1972 Treaty on Antiballistic Missile Systems to one ABM location each; the U.S. dismantled its sys¬ tem, while the Soviet Union deployed one around Moscow. During the 1980s the U.S. began research on an ambitious Strategic Defense Initiative against an all-out Soviet attack, but this effort proved expensive and tech¬ nically difficult, and it lost urgency with the collapse of the Soviet Union. Attention shifted to “theatre” systems such as the U.S. Patriot missile, which was used with limited effect against conventionally armed Iraqi Scud missiles during the Persian Gulf War (1990-91). In 2002 the U.S. formally withdrew from the ABM treaty in order to develop a defense against limited missile attack by smaller powers or “rogue” states.
Antibes \a n -'teb\ ancient Antipolis Seaport (pop., 1999: 72,412), southeastern France. Located on the Mediterranean coast southwest of Nice, it was a Greek trading post established by Phocaeans c. 340 bc. It became a Roman town and eventually a fief of the Grimaldi family (see Monaco) from 1384 to 1608. It is noted as a winter resort and for its Roman ruins.
antibiotic Chemical substance that in dilute solutions can inhibit the growth of microorganisms or destroy them with little or no harm to the infected host. Early antibiotics were natural microbial products, but chem¬ ists have modified the structures of many to produce semisynthetic and even wholly synthetic ones. Since the discovery of penicillin (1928), anti¬ biotics have revolutionized the treatment of bacterial, fungal, and some other diseases. They are produced by many actinomycetes (e.g., streptomy¬ cin, tetracycline) and other bacteria (e.g., polypeptides such as bacitracin) and by fungi (e.g., penicillin). Antibiotics may be broad-spectrum (active against a wide range of pathogens) or specific (active against one, or one class). Drawbacks include activity against beneficial microorganisms, often causing diarrhea; allergies; and development of drug-resistant strains of the targeted microorganisms.
antibody Molecule in the immune system that circulates in blood and lymph in response to invasion by an antigen. Antibodies are globulins formed in lymphoid tissues by B cells, whose receptors are specialized to bind to a specific antigen. These receptors are copied as antibodies that attack the target antigens by binding to them, either neutralizing them or triggering a complement reaction. Antibodies have widely varying binding sites, providing protection from a wide range of infectious agents and toxic substances. Antibodies derived from the blood serum of infected people or animals are often given in an antiserum for quick immuniza¬ tion against fast-acting toxins or microbes. In 1975 Cesar Milstein and col¬ leagues developed a process for producing specific antibodies in virtually limitless amounts; these monoclonal antibodies can deliver radiation or drugs directly to specific antigens. See also antitoxin; reticuloendothelial SYSTEM.
Antichrist Chief enemy of Christ who would reign at the end of time, first mentioned in the epistles of St. John. The idea of a mighty ruler who will appear at the end of time to fight against the forces of good was adapted from Judaism; the Jewish concept in turn had been influenced by Iranian and Babylonian myths of the battle of God and the devil at the end of time. In the Book of Daniel the evil one is a military leader modeled on Antiochus IV Epiphanes, who persecuted the Jews. In several books of the New Testament, the Antichrist is a tempter who works by signs and wonders and seeks divine honors. It was a potent concept in medieval Christianity that received the attention of many commentators including Adso of Montier-en-Der, whose work became the basic medieval treatise on the Antichrist. During the Middle Ages, popes and emperors strug¬ gling for power often denounced each other as the Antichrist, and during the Reformation, Martin Luther and other Protestant leaders identified the papacy itself as the Antichrist.
anticoagulant Substance that prevents blood from clotting by sup¬ pressing the synthesis or function of various clotting factors (see coagu¬ lation). Anticoagulants are given to prevent thrombosis and used in drawing and storing blood. There are two main types of anticoagulants: heparin and vitamin K antagonists (e.g., warfarin). The latter have longer-
lasting effects, interfering in the liver’s metabolism of vitamin K to cause production of defective clotting factors. Anticoagulant therapy carries a high risk of uncontrollable hemorrhage.
Anticosti Island Island, Gulf of St. Lawrence. Lying at the mouth of the St. Lawrence River in southeastern Quebec, it is 140 mi (225 km) long; its greatest width is 35 mi (56 km). Visited by Jacques Cartier in 1534, it became part of Quebec province in 1774. Port-Menier is its present-day— and only—settlement. It is now primarily a recreation area.
antidepressant Any drug used to treat depression. The three main types inhibit the metabolism of serotonin and norepinephrine in the brain. The aim is to keep these monoamine neurotransmitters from dropping to levels associated with depression. The drugs may take a few weeks to show any effect. Tricyclic antidepressants, which inhibit inactivation of norepinephrine and serotonin, help more than 70% of patients. Monoam¬ ine oxidase (MAO) inhibitors apparently block the action of MAO, an enzyme that helps break down norepinephrine, serotonin, and dopamine in neurons. They have unpredictable side effects and are usually given only when tricyclic drugs do not help. Selective serotonin reuptake inhibitors (SSRIs) apparently block reabsorption only of serotonin, allowing its lev¬ els to build up in the brain. SSRIs, which include fluoxetine (trade name Prozac), often help with depression unrelieved by tricyclics or MAO inhibitors and have milder side effects.