Omdurman V.am-dor-'manN City (pop., 1993 est.: 1,267,000), east- central Sudan. It is situated on the left bank of the Nile River just below the confluence of the Blue and White Niles. It was an insignificant village until the victory of al-MAHDi over the British in 1885. It grew rapidly after al-Mahdl and his successor, c Abd Allah, made it their capital. It was captured by Anglo-Egyptian forces in 1898 but continued to develop into the cultural, religious, and commer¬ cial centre of The Sudan. Sites of interest include c Abd Allah’s house (now a museum) and the tomb of al-Mahdl.
Omega Centauri \o-'ma-g9-sen- 'tor-I\ Brightest globular cluster, located in the constellation Centau- rus. It has a magnitude of 3.7 and is visible to the unaided eye as a faint luminous patch. One of the nearer globular clusters (about 17,000 light- years away), it is estimated to con¬ tain hundreds of thousands of stars, including several hundred variable stars. John Herschel (see Herschel family) was the first to recognize it as a star cluster and not a nebula.
omen Observed phenomenon that is interpreted as signifying good or bad fortune. The many and varied omens that the ancients noted included lightning, cloud movements, the flights of birds, and the paths of sacred animals. Each type of omen was gauged according to specific meaning¬ ful characteristics, such as the kinds of bird in flight or the direction of flight in relation to the observer.
Ometecuhtli V.o-ma-'ta-.kut-leX Aztec deity, the Lord of Duality or Lord of Life. With his female counterpart, Omecihuatl (Lady of Duality), he lived in Omeyocan, the 13th and highest Aztec heaven. He was repre¬ sented by symbols of fertility, and his image was adorned with ears of
com. He was the only Aztec god to have neither a temple nor a formal cult. Seeing him as remote in the heavens, the Aztecs assumed he would never interact with them directly, but they felt his presence in rituals and in the rhythms of nature.
omnivore Vam-ns-.voiA Animal that eats both plant and animal matter. Most omnivorous species do not have highly specialized food-processing structures or food-gathering behaviour. Many animals generally consid¬ ered carnivores are actually omnivorous; for example, the red fox eats fruits and berries as well as mammals and birds. See also herbivore.
Omsk \'6msk\ City (pop., 2002: 1,133,900), west-central Russia. It is located in southwestern Siberia at the confluence of the Irtysh and Om riv¬ ers. Founded in 1716 as a military stronghold, Omsk became a city in 1804. It remained the headquarters of the Siberian Cossacks until the late 19th century. In 1918-19 it was the seat of the anti-Bolshevik govern¬ ment of Adm. Aleksandr Kolchak. Its growth was spurred by the building of the Trans-Siberian Railroad in the 1890s and the onset of World War II. Pipelines from the Volga-Urals and western Siberian oil fields supply the refinery, and the petrochemical industry is also is important.
On See Heliopolis
Onassis, Aristotle (Socrates) (b. Jan. 20, 1906, Smyrna, Tur.—d. March 15, 1975, Neuilly-sur-Seine, near Paris, France) Greek shipping magnate and international businessman. The son of a tobacco dealer, he started a tobacco-importing business in Buenos Aires, Arg. He was made consul general after negotiating a trade agreement for the Greek govern¬ ment. A millionaire by age 25, he bought his first freight ships in 1932. In the 1940s and ’50s his fleet grew until it was larger than the navies of many countries. He acquired business interests in Monte Carlo, and from 1957 to 1974 he owned and operated Olympic Airways, the Greek national airline. He conducted a long affair with Maria Callas, and in 1968 married Jacqueline Kennedy (see Jacqueline Kennedy Onassis).
Onassis, Jacqueline Kennedy orig. Jacqueline Bouvier (b.
July 28, 1929, Southampton, N.Y., U.S.—d. May 19, 1994, New York, N.Y.) U.S. first lady, socialite, and editor. After graduating from George Washington University in 1951 she took a job as a reporter-photographer at the Washington Times-Herald. In 1953 she married Sen. John F. Kennedy, who became president in 1961. As first lady, she restored the White House to its original Federal style and conducted a televised tour of the residence. Her graciousness, elegance, and beauty endeared her to the American public, and her broad culture and ease in speaking Spanish and French impressed foreign leaders. After her husband’s assassination in 1963 she moved to New York with their children, Caroline (b. 1957) and John, Jr. (1960-99). In 1968 she married Aristotle Onassis. After his death in 1975, she returned to New York, where she became a book editor.
Onate \on-'ya-ta\, Juan de (b. 15507, New Spain—d. 1630) Spanish conquistador. The son of wealthy parents in Zacatecas, New Spain, he married a granddaughter of Hernan Cortes. He received permission to govern the colony of New Mexico, which he founded in 1598. He sent exploring parties throughout the American Southwest to search for gold and led an expedition into present-day Kansas in 1601. Still searching for gold, he explored the region west to the Colorado River and south to the Gulf of California (1604). He resigned in 1607. Tried for his brutal treat¬ ment of Indians and settlers while governor, he was found guilty and exiled from the colony in 1614.
onchocerciasis See river blindness
oncogene \'aq-ko-Jen\ Gene that can cause cancer. It is a sequence of DNA that has been altered or mutated from its original form, the proto¬ oncogene (see mutation). Proto-oncogenes promote the specialization and division of normal cells. A change in their genetic sequence can result in uncontrolled cell growth, ultimately causing the formation of a cancerous tumour. In humans, proto-oncogenes can be transformed into oncogenes in three ways: point mutation (alteration of a single nucleotide base pair), translocation (in which a segment of the chromosome breaks off and attaches to another chromosome), or amplification (increase in the num¬ ber of copies of the proto-oncogene). Oncogenes were first discovered in certain RETROViRUSes and were later identified as cancer-causing agents in many animals. See also J. Michael Bishop; Harold Varmus.
Ondaatje \an-'da-cha\, (Philip) Michael (b. Sept. 12, 1943, Colombo, Ceylon) Sri Lankan-born Canadian novelist and poet. He immi¬ grated to Montreal at age 19 and attended the University of Toronto and
The tomb of al-Mahdl in Omdurman, The Sudan.
CHARLES BEERY/SHOSTAL ASSOCIATES
© 2006 Encyclopaedia Britannica, Inc.
Onega ► ontology I 1409
Queen’s University. His fascination with the American West led to one of his most celebrated works, the pastiche The Collected Works of Billy the Kid (1970). His novel The English Patient (1992, Booker Prize; film, 1996) won him international recognition; it was followed by Anil’s Ghost (2000). His musical poetry and prose are a blend of myth, history, jazz, memoirs, and other forms.
Onega \3-'nye-g3\, Lake Lake, northwestern Russia. Located between Lake Ladoga and the White Sea, it is the second-largest lake in Europe. It has an area of 3,753 sq mi (9,720 sq km) and is 154 mi (248 km) long. It empties into the Svir River and is frozen for about half of each year. It is connected with the Baltic and White seas by canal and with the Volga River basin by a waterway, enabling it to play an important part in inter¬ national trade and transport.
Oneida \o-'nI-d3\ North American Indian people living mainly in what is now central New York and Wisconsin, U.S., and Canada. They consti¬ tute one of the original five nations of the Iroquois Confederacy. Their language is Iroquoian. They call themselves Oneyoteaka, meaning “People of the Standing Stone.” The Oneida were semisedentary and practiced com agriculture. Longhouses sheltered families related through maternal descent and belonging to one of three clans. Bear, Turtle, or Wolf. Each community had a local council that guided the chief or chiefs. The Oneida supported the colonist cause in the American Revolution and were attacked by the pro-British Iroquois under Joseph Brant. By the mid- 19th century most Oneida had dispersed. They number some 12,000.