obsidian Natural glass of volcanic origin that is formed by the rapid cooling of viscous lava. It has a glassy lustre and is slightly harder than window glass. It is typically jet black, but the presence of hematite (iron oxide) produces red and brown varieties, and tiny gas bubbles may cre¬ ate a golden sheen. It is sometimes used as a semiprecious stone. Obsid¬ ian was used by American Indians and others for weapons, implements, tools, and ornaments, and by the ancient Aztecs and Greeks for mirrors.
obstetrics and gynecology \,gl-n9-'ka-l3-je\ Medical and surgical specialty concerned with the management of pregnancy and childbirth and with the health of the female reproductive system. Obstetrics, first practiced by midwives, developed as a medical discipline in the 17th-19th centu¬ ries, adopting the use of forceps in delivery, anesthetics, and antiseptic methods. The last two made cesarean section possible. Obstetricians con¬ firm pregnancy, diagnose ectopic pregnancy, conduct prenatal care, per¬ form amniocentesis, deliver babies, and perform abortions. In the late 20th century a backlash against the excessive medicalization of birth led to a revival of midwifery and encouragement of natural childbirth. Gynecolo¬ gists do routine pelvic exams, take samples for Pap smears, advise on and prescribe birth control, and treat reproductive system disorders (e.g., endometriosis, hormonal imbalances, problems with menstruation and menopause). They perform surgery to prevent conception (tubal ligation), repair pelvic injuries, and remove cysts and tumours from the uterus, cer¬ vix, and ovaries. Both specialties are involved in diagnosis and treatment of INFERTILITY. See also HYSTERECTOMY.
Obuchi Vo-bu-cheV Keizo (b. June 25, 1937, Nakanojo, Japan—d. May 14, 2000, Tokyo) Japanese politician. A graduate of Waseda Uni¬ versity, he was first elected to the Diet (legislature) in 1963, where he spent 12 terms, serving as chairman of the finance committee (1976) and min¬ ister for foreign affairs (1997). As Japan’s prime minister (1998-2000), Obuchi had to deal with Japan’s flagging economy and the related Asian economic crisis.
O'Casey, Sean orig. John Casey (b. March 30, 1880, Dublin, Ire.—d. Sept. 18, 1964, Torquay, Devon, Eng.) Irish playwright. Born to
a poor Protestant family, he educated himself and worked from age 14 at manual labour. He embraced the Irish nationalist cause, changed his name to its Irish form, and became active in the labour movement and its paramilitary Irish Citizen Army.
By 1915 he had turned from politics to writing realistic tragicomedies about Dublin slum dwellers in war and revolution. The Abbey Theatre produced three of his earliest and best plays— The Shadow of a Gun¬ man (1923), Juno and the Paycock (1924), and The Plough and the Stars (1926)—which caused riots by Irish patriots. When his antiwar play The Silver Tassie was rejected by the Abbey, O’Casey moved to England, where it was produced in 1929. His later plays include Red Roses for Me (1946); he also published a six-volume autobiography (1939-56).
Occam, William of See William of Ockham Occam's razor See Ockham's razor
occasionalism Type of mind-body dualism that maintains that appar¬ ent interactions between mental and physical events are in reality the result of God’s constant causal action. Starting from Descartes’s mind- body dualism, the occasionalists, whose most prominent exponents were Nicolas de Malebranche and Arnold Geulincx, drew the conclusions that there can be no interaction between mind and body, and that all causality is immanent, within one order or the other, and any appearance of mind affecting body or of body affecting mind must be explained as the result of a special intervention by God, who, on the occasion of changes in one substance, produces corresponding changes in the other.
Occitan Vak-s9-,tan\ language or Provencal V.pro-.van-'sal, ,pra-v3n-'sal\ language Romance language spoken in Occitania, a region of southern France. The 1.5 million people of this region use Occi¬ tan dialects in everyday life and French as their official and cultural lan¬ guage. The term langue d’oc is based on the use of the word oc for “yes.” The name Provengal originally referred to the dialects of the Provence region, used by medieval troubadours and as a standard and literary lan¬ guage in France and northern Spain in the 12th— 14th centuries. Today’s major dialects are those of Limousin, Auvergnat, Provence, and Langue¬ doc. Gascon, spoken in southwestern France and usually classified as an Occitan dialect, is sometimes considered a distinct language. Occitan is closely related to Catalan and, despite recent French influences, has more in common with Spanish than with French.
occultism Theories, practices, and rituals based on esoteric knowledge of the world of spirits and unknown forces. The wide range of occult beliefs and practices includes astrology, alchemy, divination, magic, and witchcraft and sorcery. Devotees of occultism seek to explore spiritual mysteries through what they regard as higher powers of the mind. The Western tradition of occultism has its roots in Hellenistic magic and alchemy (especially the Hermetic writings ascribed to Thoth) and in the Jewish mysticism associated with the Kabbala.
Occupation (of Japan) (1945-52) Military occupation of Japan by the Allied Powers after its defeat in World War II. Theoretically an inter¬ national occupation, in fact it was carried out almost entirely by the U.S. under Gen. Douglas MacArthur. During the Occupation period, Japanese soldiers and civilians from abroad were repatriated to Japan, arms indus¬ tries were dismantled, and political prisoners were released. Wartime lead¬ ers stood trial for war crimes, and seven were executed. A new constitution, vesting power in the people, replaced the Meiji Constitution; in it Japan renounced its right to wage war, the emperor was reduced to ceremonial status, and women were given the right to vote. The Occupation admin¬ istration also carried out land reform, reducing the number of farmers who were tenants from 46% to 10%, and began the breakup of the zaibatsu (business conglomerates). Labour unions were initially encouraged, but as fears of leftist organizations grew with the advent of the Cold War, stronger governmental control of labour was supported. The education system, seen as elitist, was revised to resemble the U.S. system. Though
O'Casey, photograph byJ. Bown
CAMERA PRESS
© 2006 Encyclopaedia Britannica, Inc.
occupational disease ► Oceanic arts I 1395
the U.S. wanted to end the Occupation in 1947, the Soviet Union vetoed a peace treaty with Japan; a treaty was signed in 1951, and the Occupa¬ tion ended the following year.
occupational disease Illness associated with a particular occupation. The Industrial Revolution’s long working hours, dim light, lack of fresh air, and dangerous machinery fostered illness and injury in general, but certain occupations (e.g., mining) carry particular risks (e.g., black lung, a type of pneumoconiosis). Twentieth-century innovations (including use of new chemicals and radioactive materials) caused an increase in certain cancers (e.g.. leukemia and bone cancer in workers exposed to radiation) and injuries. So-called “sick buildings” (in which pathogens grow in air circulation systems) contribute to health problems among office workers. Occupational medicine also covers work-related emotional stresses. See also ASBESTOSIS; INDUSTRIAL MEDICINE.
occupational medicine See industrial medicine
occupational therapy Use of activities to promote health and inde¬ pendence, particularly after the acute phase of illness. Such therapy is often vital for reorienting patients unable to work for long periods. Occupational therapists assess patients’ abilities, tailor programs to restore physical function, and devise ways to help those with permanent limitations carry out everyday functions. See also physical medicine and rehabilitation.