AM in full amplitude modulation Variation of the amplitude of a carrier wave (commonly a radio wave) in correspondence to fluctuations in the audio or video signal being transmitted. AM is the oldest method of broadcasting radio programs. Commercial AM stations operate in the frequency range of 535 to 1605 kHz. Because radio waves of these fre¬ quencies are reflected back to the Earth’s surface by the ionosphere, they can be detected by receivers hundreds of miles away. In addition to com¬ mercial radio broadcasting, AM is also employed in short-wave radio broadcasts, and in transmitting the video portion of television programs. See also FM.
AMA See American Medical Association
Amadeus V.am-o-'da-osX VI known as Amadeus the Green Count
(b. 1334, Chambery, Savoy [France]—d. March 1, 1383, Castropignano [Italy]) Count of Savoy (1343-83). Ruler of Savoy from age 9, he sig¬ nificantly extended his kingdom’s territory and power. By the 1350s, after adding lands on the Italian side, he held nearly the entire western Alps. He joined a Crusade against the Turks (1366) and restored John V Palae- ologus to the Byzantine throne. A mediator of quarrels among Italian powers, he set out to rescue Queen Joan I of Naples from her enemies (1382) but died of plague during the expedition.
Amado \a-'ma-du\, Jorge (b. Aug. 10, 1912, Ferradas, near Ilheus, Braz.—d. Aug. 6, 2001, Salvador, Bahia) Brazilian novelist. Amado was born and reared on a cacao plantation. He published his first novel at age 20. His early works, including The Violent Land (1942), explore the exploitation and suffering of plantation workers. Despite imprisonment and exile for leftist activities, he continued to produce novels, many of
which have been banned in Brazil and Portugal. Later works such as Gabriela, Clove and Cinnamon (1958), Dona Flor and Her Two Hus¬ bands (1966), and The War of the Saints (1993) preserve Amado’s politi¬ cal attitude in their more subtle satire; many of his books were adapted for film and television.
Amalfi \a-'mal-fe\ Town (pop., 2000: commune, 5,527), southern Italy, on the Gulf of Salerno. It was of little importance until the mid-6th cen¬ tury, when it fell under Byzantine control. It grew into one of the first Italian maritime republics in the 9th century, becoming a rival of Venice and Genoa. Annexed by Roger II of Sicily in 1131, it was sacked by Pisa in 1135 and 1137 and rapidly declined in importance, though its maritime code, the Tavola Amalfitana, was recognized in the Mediterranean until 1570. Amalfi is now a notable tourist resort.
amalgam \3-'mal-g3m\ Alloy of mercury and one or more other metals. Those of silver, gold, and palladium occur naturally. Those with a very high mercury content are liquid; others are crystalline. Amalgams of sil¬ ver and tin, with minor amounts of copper and zinc, are used in dentistry to fill teeth. Sodium amalgam is used in manufacturing chlorine and sodium hydroxide by electrolysis of brine. Amalgams are used to recover silver and gold from their ores: The ore is shaken with mercury, the amal¬ gam is separated and heated until the mercury distills off (see distillation), and the precious metal is the residue. Amalgams are also used to silver mirrors and apply other metal coatings.
Amalric Va-'mal-rik, 'am-3l-rik\ I (b. 1136—d. July 11, 1174) King of Jerusalem (1163-74). Amalric was a strong ruler who helped break the unity of Muslims surrounding the Holy Land. He passed a law giving vas¬ sals the right to appeal to the High Court against unjust treatment by their lords. His invasion of Egypt (1163) led to a war with Nureddin of Syria, which Amalric lost despite help from Manuel I Comnenus. Though the effort to conquer Egypt failed, the Palestinian-Byzantine alliance continued.
Amalric II (b. c. 1155—d. April 1, 1205) King of Cyprus (1194-1205) and of Jerusalem (1197-1205). Amalric inherited the kingdom of Cyprus on the death of his brother, Guy of Lusignan, and formed a close alliance with the ruler of Palestine. He also became the vassal of Holy Roman Emperor Henry VI. When the ruler of Palestine died, Amalric married his widow and became king of Jerusalem. He administered Jerusalem sepa¬ rately from his other lands and made peace with his Muslim neighbours after Saladin’s death (1193).
amanita \,am-3- , ne-t3\ Any mushroom of the genus Amanita, contain¬ ing about 100 species, some of which are poisonous to humans.
Among the deadliest of all mush¬ rooms are the large, white destroying angels (A. bispongera, A. ocreata, A. verna, and A. virosa ), which are found in forests during wet periods in summer and autumn. The green or brown death cap (A. phalloides), also deadly, is found in woods in summer or early autumn. The poisonous fly agaric (A. muscaria ), found in pas¬ tures and fields in summer, was once used as a fly poison. Common edible species include A. caesarea, A. rube- scens, and A. vaginata.
Amar Das Vom-ar-'dasV (b. 1479,
Khadur?, India—d. 1574, Goindwal)
Third Sikh Guru. Much revered for his wisdom and piety, he became Guru at age 73. He was noted for his missionary efforts to spread Sikhism and for the division of the Punjab into 22 dioceses. To strengthen the faith, he ordered three great Sikh festivals each year, and he made the city of Goindwal a centre of Sikh learning. He extended the casteless langar (“free kitchen”) and required that any¬ one wanting to see him must first eat there. Advocating a middle way between the extremes of asceticism and sensuous pleasure, he purified Sikhism of Hindu practices, encouraged intercaste marriages, allowed widows to remarry, and prohibited suttee (self-immolation of a widow on her husband’s funeral pyre).
Luis Alvarez
BY COURTESY OF THE LAWRENCE RADIATION LABORATORY, THE UNIVERSITY OF CALIFORNIA, BERKELEY
Fly agaric (Amanita muscaria)
LARRY C. MOON-TOM STACK & ASSOCIATES
© 2006 Encyclopaedia Britannica, Inc.
56 I amaranth ► amberjack
amaranth Va-m3- l ranth\ family Family Amaranthaceae, which con¬ tains about 60 genera and more than 800 species of herbaceous plants and a few shrubs, trees, and vines, native to tropical America and Africa. Globe amaranth ( Gomphrena ) and cockscomb ( Celosia ) are cultivated as ornamentals. The large genus Amaranthus contains the ornamentals love- lies-bleeding (A. caudatus) and Joseph’s-coat (A. tricolor ), as well as many weedy plants known as pigweed, especially A. retroflexus. Some Amaranthus species are tumbleweeds, and some are potential high-protein grain crops.
Amaravati \,a-m9-'ra-v9-te\ sculpture Style of sculpture found in the Andhra region of southeastern India. It flourished there from about the 2nd century bc to the end of the 3rd century ad, during the rule of the Satavahana dynasty. Carved in relief on greenish-white limestone, these sculptures depict events in the life of the Buddha. The compositions are dynamic, sensuous, and dramatic, with overlapping figures and diagonals suggesting depth. The style spread from the Amaravati ruins west to Maharashtra Pradesh, to Sri Lanka (Ceylon), and to much of South Asia. The Amaravati stupa was one of the largest in Buddhist India; it was largely destroyed in the 19th century by building contractors to make lime mortar.
Amarillo City (pop., 2000: 173,627), northern Texas, U.S. The chief city of the Texas Panhandle, it originated in 1887 with the coming of the railroad. After it grew to become one of the world’s busiest cattle-shipping sites in the 1890s, agriculture became important in the region. The dis¬ covery of petroleum and natural gas in the 1920s further promoted Ama¬ rillo’s development.