ouzel or ousel Vii-zolX Species ( Turdus torquatus) of songbird in the thrush family, characterized by a white crescent on the breast. A black¬ ish bird, about 10 in. (25 cm) long, it breeds locally in uplands from Britain and Norway to the Middle East. The name was formerly applied to a closely related European black¬ bird ( T. merula). The dipper is often called water ouzel.
ovarian cancer Malignant tumour of the ovaries. Risk factors include early age of first menstrua¬ tion (before age 12), late onset of menopause (after age 52), absence of pregnancy, presence of specific genetic mutations, use of fertility drugs, and personal history of breast cancer. Symptoms such as abdomi¬ nal swelling, pelvic pressure or pain, and unusual vaginal bleeding often do not appear until ovarian cancer is advanced. Surgery, sometimes fol¬ lowed by chemotherapy or radiation therapy, is an effective treatment for most ovarian cancers.
Ring-ouzel (Turdus torquatus).
DRAWING BY JOHN P. O'NEILl/EB INC.
ovary Vo-vo-reX In zoology, the female reproductive organ (see repro¬ ductive system) that produces eggs and sex hormones (estrogen and proges¬ terone). Human females have two ovaries, almond-shaped organs about 1.5 in. (4 cm) long. They contain hollow balls of cells (follicles) that hold immature eggs. About 150,000-500,000 follicles usually are present at birth; by young adulthood, only about 34,000 remain. The number con¬ tinues to decrease until menopause, when the few remaining follicles decay and the ovaries shrink and produce far less estrogen. Only 300-400 fol¬ licles mature and release an egg, which develops into an embryo if fertil¬ ized or, if not, passes from the body with menstruation. In botany, an ovary is the enlarged base of a flower’s female organ (pistil). It contains ovules, which develop into seeds when fertilized, and matures into a fruit.
over-the-counter market Trading in stocks and bonds that does not take place on stock exchanges. Such trading occurs most often in the U.S., where requirements for listing stocks on the exchanges are strict. Sched¬ ules of fees for buying and selling securities are not fixed in the over-the- counter market, and dealers derive their profits from the markup of their selling price over the price they paid. Many bond issues and preferred- stock issues, including U.S. government bonds, are listed on the New York Stock Exchange but have their chief market over-the-counter. Other U.S. government securities, as well as state and municipal bonds, are traded over-the-counter exclusively. Institutional investors such as mutual funds often trade over-the-counter because they are given volume discounts not offered on the exchanges. The regulation of the over-the-counter market is carried out largely by the National Association of Securities Dealers,
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1426 I overpopulation ► owl
created by Congress in 1939 to establish rules of conduct and protect members and investors from abuses. See also NASDAQ.
overpopulation Situation in which the number of individuals of a given species exceeds the number that its environment can sustain. Pos¬ sible consequences are environmental deterioration, impaired quality of life, and a population crash (sudden reduction in numbers caused by high mortality and failure to produce viable offspring).
overtone In acoustics, a faint higher tone contained within almost any musical tone. A body producing a musical pitch—such as a taut string or a column of air within the tubular body of a wind instrument—vibrates not only as a unit but simultaneously also in sections, resulting in the presence of a series of overtones within the fundamental tone (i.e., the one identified as the actual pitch). Harmonics are a series of overtones resulting when the partial vibrations are of equal sections (e.g., halves, thirds, fourths). Partials are nonharmonic overtones—that is, tones the frequencies of which lie outside the harmonic series. Overtones contrib¬ ute greatly to the timbre of a given sound source, even though few listen¬ ers are aware of hearing any pitch except the fundamental. There are a few rare examples of the human voice creating overtones, notably in the chants of the Tibetan monks and the songs of the Tuvan throat singers. The latter can sometimes produce two overtones.
overture Musical introduction to a larger, often dramatic, work. Origi¬ nating with Claudio Monteverdi’s Orfeo (1607), overtures served as open¬ ings for operas. The large-scale two- or three-part “French overture” invented by Jean-Baptiste Lully (1658) for his operas and ballets was widely imitated for a century. The sinfonia, the standard Italian overture form in the late 17th and 18th centuries, was a principal precursor of the three- part sonata form and thus provided the model for the earliest symphonies, which consisted of three movements. In the 19th century, overtures inde¬ pendent of any larger work usually illustrated a literary or historical theme (see symphonic poem). Overtures to operettas and musicals have tradition¬ ally been medleys of their themes.
Ovett \o-'vet\, Steve in full Stephen Michael Ovett (b. Oct. 9, 1955, Brighton, Sussex, Eng.) British runner. He was the winner of gold (in the 800-m race) and bronze medals at the 1980 Olympic Games. In the course of his career, Ovett set six world records; however, his best- known races were those that pitted him against his countryman and rival Sebastian Coe.
Ovid Va-vid\ Latin Publius Ovidius Naso (b. March 20, 43 bc, Sulmo, Roman Empire—d. ad 17, Tomis, Moesia) Roman poet. A mem¬ ber of Rome’s knightly class, Ovid dutifully started an official career but soon abandoned it for poetry. His first work, The Loves, was an imme¬ diate success. It was followed by Epistles of the Heroines', The Art of Beauty', The Art of Love, one of his best-known works; and Remedies for Love, all reflecting the sophisticated, pleasure-seeking society in which he moved. He was a well-established poet when he undertook perhaps his greatest work. Metamorphoses, on legends of transformations of human beings into nonhuman forms by gods; and Fasti (“Calendar”), an account of the Roman year and its religious festivals. His verse had immense influence because of its imaginative interpretations of classical myth and its supreme technical accomplishment. For unclear reasons, in ad 8 Augus¬ tus banished him to Tomis on the Black Sea; despite Ovid’s many pleas, he was never allowed to return. He described his life in an autobiographi¬ cal poem in Sorrows. He was extensively read and imitated in the Renais¬ sance, and his influence was felt into modern times.
Oviedo \o-'vya-tho\ ancient Asturias City (pop., 2001: 201,154), capital of Asturias, northwestern Spain. Oviedo lies on a hill surrounded by mountains and a fertile plain. Founded as a monastery in ad 757, it became the capital of the kingdom of Asturias in 810. It was one of the few Spanish towns never conquered by the Moors and contains many medieval landmarks, including a 14th-century cathedral. The cathedral was badly damaged during the Spanish Civil War. Oviedo is the centre of a mining region that produces coal and iron.
Ovimbundu \,o-vim-'bun-du\ Bantu-speaking people of central Angola. Numbering about 4 million, the Ovimbundu provided the major popular support for Jonas M. Savimbi and the National Union for the Total Independence of Angola (UNITA). They were formerly traders; today they farm, hunt, and raise livestock. About half the 22 Ovimbundu chief- doms were tributary to a larger chiefdom before Portuguese intervention in the 20th century.
ovum See egg
Owen, Robert (b. May 14, 1771, Newtown, Montgomeryshire, Wales—d. Nov. 17, 1858, Newtown) Welsh manufacturer and philanthro¬ pist. At his New Lanark cotton mills (Lanarkshire, Scot.), in partnership with Jeremy Bentham, he set up innovative social and industrial welfare programs, including improved housing and schools for young children. In A New View of Society (1813) he contended that character is wholly formed by one’s environment. By 1817 his work had evolved into ideas presaging socialism and the cooperative movement, ideas he would spend much of his life preaching. He sponsored several experimental utopian communities of “Owenites” in Britain and the U.S., including one at New Harmony, Ind. (1825-28)—where Owen lost some 80% of his fortune— all of which proved short-lived. He strongly supported early labour unions, but opposition and repression swiftly dissolved them, and it was two generations before socialism again influenced unionism. He was the father of Robert Dale Owen.