became its capital. Its modem development was furthered by the inde¬ pendence of Transjordan in 1946. Along with the rest of Jordan (the country’s name from 1949), Amman has had to absorb a large number of Arab refugees that fled Palestine during the Arab-Israeli wars.
Ammannati \,am-an-'na-te\ / Bartolommeo or Bartolommeo Ammanati (b. June 18, 1511, Settignano, near Florence—d. April 22, 1592, Florence ) Italian sculptor and architect active chiefly in Florence. He trained under Baccio Bandinelli in Florence and Jacopo Sansovino in Venice. In 1550 he went to Rome, where he collaborated with Giorgio Vasari and Giacomo da Vignola on the Villa Giulia. In 1555 he returned to Florence, where he spent the rest of his career working for the Medicis. He finished the Laurentian Library, begun by Michelangelo, but is best known for the Bridge of Santa Trinita and his additions to Filippo Brunelle¬ schi’s Pitti Palace, including the courtyard. His buildings mark the tran¬ sition from the Classicizing Renaissance to the more exuberant Baroque style.
ammonia Vo-'mo-nysX Colourless, pungent gas composed of nitrogen and hydrogen, chemical formula NH 3 . Easily liquefied by compression or cooling for use in refrigerating and air-conditioning equipment, it is manu¬ factured in huge quantities. Ammonia is made by the Haber-Bosch process (see Fritz Haber). Its major use is as a fertilizer, applied directly to soil from tanks of the liquefied gas. Also employed as fertilizers are salts of ammo¬ nia, including ammonium phosphate and ammonium nitrate (the latter used in high explosives as well). Ammonia has many other industrial uses as a raw material, catalyst, and alkali. It dissolves readily in water to form ammonium hydroxide, an alkaline solution (see base) familiar as a house¬ hold cleaner.
ammonia-soda process See Solvay process
ammonoid Vam-o-.nokL Any of a group of extinct shelled cephalopods, related to the modern pearly nautilus, that are commonly found as fossils in marine rocks of the Devonian through Cretaceous periods (410-65 mil¬ lion years ago). Most ammonoids were predators. The shells, either straight or coiled, served as protective and supportive structures and enabled the animals to compensate for varying water depths. Ammonoids are important index fossils because of their wide geographic distribution in shallow marine waters, rapid evolution, and easily recognizable fea¬ tures. See also belemnoid.
amnesia \am-'ne-zh9\ Loss of memory as a result of brain injury or deterioration, shock, fatigue, senility, drug use, alcoholism, anesthesia, illness, or neurotic reaction. Amnesia may be anterograde (in which events following the causative trauma or disease are forgotten) or retrograde (in which events preceding the trauma or disease are forgotten). It can often be traced to a severe emotional shock, in which case personal memories (in effect, identity) rather than such abilities as language skills are affected. Such amnesia seems to represent an escape from disturbing memories and is thus an example of repression; these memories can generally be recov¬ ered through psychotherapy or after the amnesic state has ended. Amnesia may occasionally last for weeks, months, or even years, a condition known as fugue.
amnesty In criminal law, a sovereign act of oblivion or forgetfulness (from Greek amnestia, “forgetfulness”) granted by a government, espe¬ cially to a group of persons who are guilty of (usually political) crimes in the past. It is often conditional upon the group’s return to obedience and duty within a prescribed period. See also pardon.
Amnesty International (Al) International human-rights organiza¬ tion. It was founded in 1961 by Peter Benenson, a London lawyer who organized a letter-writing campaign calling for amnesty for “prisoners of conscience.” AI seeks to inform the public about violations of human rights, especially abridgments of freedom of speech and religion and the imprisonment and torture of political dissidents. It actively seeks the release of political prisoners and support of their families when neces¬ sary. Its members and supporters are said to number one million people in some 140 countries. Its first director, Sean MacBride, won the 1974 Nobel Prize for Peace; AI itself won the award in 1977.
amniocentesis V.am-ne-o-sen-'te-sosN Surgical insertion of a hollow needle through the abdominal wall into the uterus of a pregnant female to extract fluid from the amniotic sac for analysis of fluid and fetal cells. This can reveal the fetus’s sex (important when sex-linked genetic dis¬ ease is possible), chromosomal disorders, and other problems. First per-
Great bronze Amida (Daibutsu) at Kamakura, Japan, 1252.
GAVIN HELUER—ROBERT HARDING PICTURE UBRARY/GETTY IMAGES
© 2006 Encyclopaedia Britannica, Inc.
amoeba ► Amphion and Zethus I 63
formed in the 1930s, amniocentesis is generally done under local anesthesia in the 15th—17th week of gestation.
amoeba Vo-'me-boN One-celled protozoan that can form temporary extensions of cytoplasm (pseudopo¬ dia) in order to move about. Some amoebas are found on the bottom of freshwater streams and ponds. Oth¬ ers live in the human digestive sys¬ tem; one type causes amebic dysentery in humans. Each amoeba contains a small mass of jellylike cytoplasm with vacuoles and a nucleus. Food is taken in and mate¬ rial is excreted at any point on the cell surface. Amoebas are used extensively in cell research for deter¬ mining the relative functions and interactions of the nucleus and the cyto¬ plasm.
Amon \'a-,man\ or Amen Egyptian deity revered as king of the gods. Amon may have originated as a local deity at Khmun in Middle Egypt. His cult spread to Thebes, where he became patron of the pharaohs by Mentuhotep I’s reign (2008-1957 bc) and was identified with the sun god Re. Represented as a human, a ram, or both, Amon-Re was worshiped with the goddess Mut and the youthful god Khons. Akhenaton directed his reforms against the cult of Amon, but with little success, and Amon’s status was restored in the 14th—13th century bc. In the New Kingdom, Amon came to be seen as one of a triad with Ptah and Re, and in the 11th-10th century bc as a universal god who intervened in affairs of state by speaking through oracles.
amortization V.am-or-ti-'za-shonV In finance, the systematic repayment of a debt; in accounting, the systematic writing off of some account over a period of years. An example of the first meaning is a home mortgage, which may be repaid in monthly installments that include interest and a gradual reduction of the principal. Such systematic reduction is safer for the lender, since it is easier for the borrower to repay a series of small amounts than a single lump sum. In the second sense, a firm may gradu¬ ally reduce the balance-sheet valuation of a depreciable asset such as a building, machine, or mine. The U.S. government has sometimes permit¬ ted accelerated amortization of assets, which encourages industrial devel¬ opment by decreasing a company’s tax burden in the years immediately after a purchase.
Amos (fl. 8th century bc) Earliest Hebrew prophet (one of the 12 Minor Prophets) to have a biblical book named for him. Born in Tekoa in Judah, he was a shepherd. According to the book of Amos, he traveled to the richer and more powerful northern kingdom of Israel to preach his visions of divine destruction and the message that God’s absolute sovereignty required justice for rich and poor alike and that God’s chosen people were not exempt from the moral order. He foretold the destruction of the north¬ ern kingdom and Judah and anticipated the predictions of doom by later biblical prophets.