Opie, Eugene Lindsay (b. July 5, 1873, Staunton, Va., U.S.—d. March 12, 1971, Bryn Mawr, Pa.) U.S. pathologist. He received his M.D. from Johns Hopkins University. Early in his career, he correctly deduced that degenerative changes in the islets of Langerhans caused diabetes mel- litus and theorized that blockage of the junction of the bile and pancre¬ atic ducts caused acute pancreatitis. He later showed that tuberculosis (TB) was spread by contact, including from one family member to another. His work led to use of X-ray films to detect asymptomatic TB, the sputum test to predict the chance of its spread, and injection of heat-killed tubercle bacilli to prevent infection.
opium Organic compound, a narcotic drug known since ancient Greek times, obtained from exuded juice of immature fruit capsules of the opium poppy. Opium has legitimate medical uses, as the source of the alkaloids codeine and morphine and their derivatives. It is also used illicitly, either raw or purified as alkaloids and their derivatives (including heroin). Opium alkaloids of one type (e.g., morphine, codeine) act on the nervous system, mimicking the effects of endorphins; they are analgesic, narcotic, and potentially addicting (see drug addiction). Those of a second type, including papaverine and noscapine, relieve smooth muscle spasms and are not analgesic, narcotic, or addicting. Habitual opium use produces physical and mental deterioration and shortens life. Overdose can cause death by depressing respiration.
opium poppy Flowering plant ( Papaver somniferum) of the family Papaveraceae, native to Turkey. Opium, morphine, codeine, and heroin are
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1412 I Opium Wars ► opuntia
all derived from the milky fluid found in its unripe seed capsule. A com¬ mon garden annual in the U.S., the opium poppy bears blue-purple or white flowers 5 in. (13 cm) wide on plants about 3-16 ft (1-5 m) tall, with lobed or toothed silver-green foliage. It is also grown for its tiny nonnarcotic ripe seeds, which are kidney-shaped and grayish blue to dark blue; the seeds are used in bakery products and for seasoning, oil, and birdseed.
Opium Wars Two trading wars of the mid-19th century in China. The first (1839-42 was between China and Britain, and the second (1856-60; also called the Arrow War or Anglo-French War) was between China and a British-French alliance. Trade developed between China and Western countries from the late 16th century. The Chinese, accustomed to tribu¬ tary relationships with others, required that Westerners pay for Chinese goods with silver currency. To offset a growing negative flow of silver at home, the British created a market for opium in China and began import¬ ing it there illegally. As demand for opium grew, China tried to stop the practice, and hostilities broke out. Britain quickly triumphed, and the resultant Treaty of Nanjing (Nanking; 1842; the first of a series of unequal treaties between China and Western countries and, eventually, Japan) was a blow to China. The outbreak of the second war resulted in the Treaty of Tianjin (Tientsin; 1858), which required further Chinese concessions. When China refused to sign subsequent treaties, Beijing (Peking) was captured and the emperor’s summer palace burned. The overall result of these conflicts was to weaken the Chinese imperial system, greatly expand Western influence in China, and pave the way for such uprisings as the Taiping and Boxer rebellions. See also Canton system; British East India Company; Lin Zexu.
Oporto See Porto
opossum Any of about 66 species (family Didelphidae) of New World, mostly arboreal, nocturnal marsupi¬ als. Highly adaptable and prolific, opossums have changed little in mil¬ lions of years. The North American species, the stout-bodied common, or Virginia, opossum (Didelphis marsupialis), grows to 40 in. (100 cm) long. It is largely white and has an opposable clawless toe on each hind foot; with its long, hairless, pre¬ hensile tail, it resembles a large rat.
Up to 25 grublike, 0.07-oz (2-g) newborns compete for the 13 nipples in the pouch, where the survivors spend four or five weeks; they spend the following eight to nine weeks clinging to the mother’s back. The common opossum may feign death (“play possum”) if surprised. It eats small animals, insects, and fruit, and sometimes domestic poultry and cul¬ tivated grain. See also possum.
Oppenheimer, J(ulius) Rob¬ ert (b. April 22, 1904, New York, N.Y., U.S.—d. Feb. 18, 1967, Prince¬ ton, N.J.) U.S. theoretical physicist. He graduated from Harvard University, did research at Cambridge University, and earned a doctorate from Gottingen University. He returned to the U.S. to teach at the Cali¬ fornia Institute of Technology (1929^47). His research focused on energy processes of subatomic particles, and he trained a generation of Ameri¬ can physicists. In World War II he was named director of the army’s atomic-bomb project, later known as the Manhattan Project, and set up the laboratory in Los Alamos, N.M., that remains a principal weapons- research laboratory. He directed the Institute for Advanced Study in Prince¬ ton (1947-66). He strongly opposed the development of the hydrogen bomb, and in 1953 he was suspended from secret nuclear research as an alleged communist sympathizer and a security risk; the case, which pit¬ ted him against Edward Teller, became a worldwide cause celebre. In 1963 he was reinstated and awarded the Enrico Fermi Award.
opportunity cost In economic terms, the opportunities forgone in the choice of one expenditure over others. For a consumer with a fixed income, the opportunity cost of buying a new dishwasher might be the value of a vacation trip never taken or several suits of clothes unbought.
The concept of opportunity cost allows economists to examine the rela¬ tive monetary values of various goods and services.
opposition, square of Geometrical representation of the traditional logical relations of opposition (contradictories, contraries, subalterns) among the four types of propositions (universal affirmative or A-proposition, universal negative or E, particular affirmative or I, particu¬ lar negative or O) in the Aristotelian doctrine of the syllogism. At the top left is the A; at the top right is the E; below the A is the I; and below the E is the O. The A and the O, like the E and I, are contradictories (diago¬ nal relations); the A and the E are contraries; and the I is subaltern to (hence implied by) the A, the O subaltern to the E. Whereas contradic¬ tories have opposite truth-values (one true, the other false), contraries cannot both be true but can both be false.
optical activity Ability of a substance to rotate the plane of polarization of a beam of light passed through it, either as crystals or in solution. Clock¬ wise rotation as one faces the light source is “positive,” or dextrorotary; counterclockwise rotation “negative,” or levorotary. Louis Pasteur was the first to recognize that molecules with optical activity are stereoisomers (see isomerism). Optical isomers occur in pairs that are nonsuperimposable mirror images of one another. They have the same physical properties except for their effect on polarized light; in chemical properties they differ only in their interactions with other stereoisomers (see asymmetric synthesis).
optical character recognition See OCR optical scanner See optical scanner
optics Science concerned with the production and propagation of light, the changes it undergoes and produces, and closely related phenomena. Physical optics deals with the nature and properties of light; geometric optics deals with the formation of images by mirrors, lenses, and other devices that use light. Optical data processing involves manipulation of the information content of an image formed by coherent (one-wavelength) optical systems. The study of optics has led to the development of devices such as EYEGLASSES and CONTACT LENSeS, TELESCOPES, MICROSCOPES, CAMERAS, BIN¬ OCULARS, lasers, and optical fibres (see fibre optics).