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OCHA (international organization)
agency of the United Nations (UN) Secretariat originally established in 1972 to coordinate international relief activities to countries struck by natural or other disasters. It is headed by a disaster relief coordinator who reports directly to the UN secretary-general and works closely w...
ocher (earth pigment)
Paint and painting were thought to animate sculpture—often literally, in religiosymbolic terms, as paint was considered to have magical, vivifying powers. Paints were generally ochres, with some vegetable-derived pigments. Water was the usual medium, occasionally supplemented with sap. Brushes were the fibrous ends of chewed or frayed sticks, small feather bundles, pieces of wood, and......
Ocherki russkoy smuty (work by Denikin)
...the remainder of his army was then evacuated to the Crimea (March 1920). In April Denikin turned over his command to General Pyotr N. Wrangel and settled in France, where he wrote his memoirs, Ocherki russkoy smuty, 5 vol. (1923–27; “History of the Civil Strife in Russia”). He immigrated to the United States in 1945....
ochetus (music)
in medieval polyphonic (multipart) music, the device of alternating between parts, single notes, or groups of notes. The result is a more or less continuous flow with one voice resting while the other voice sounds....
Óchi Mountain (mountain, Euboea, Greece)
...(3,182 feet [970 metres]). From Teléthrion the range trends eastward to the coast. In the centre of the island rises Dhírfis Mountain (5,715 feet [1,742 metres]), while in the south Óchi Mountain reaches 4,587 feet (1,398 metres). The east coast is rocky and harbourless; in ancient times the main traffic from the north Aegean to Athens used the inshore channels because of.....
Ochiba (painting by Hishida)
...Japanese line drawing with a Western Impressionistic style (pejoratively known as mōrōtai, or “vague,” “indistinct”). Among his best-known works are “Ochiba” (1909; “Fallen Leaves”) and “Kuroi neko” (1910; “A Black Cat”)....
Ochikubo monogatari (Japanese novel)
Japanese novel of the late 10th century, one of the world’s earliest extant novels. Its unknown author is thought to have been a man, one of the Heian court’s literate elite, writing for an audience of female readers. It was translated into English as Ochikubo monogatari; or, The Tale of the Lady Ochikubo....
Ochino, Bernardino (Italian religious reformer)
Protestant convert from Roman Catholicism who became an itinerant Reformer and influenced other radical Reformers by his controversial anti-Catholic views....
Ochna (plant genus)
Protestant convert from Roman Catholicism who became an itinerant Reformer and influenced other radical Reformers by his controversial anti-Catholic views.......
Ochna multiflora (plant)
...has nearly 90 species. Members of the family usually have alternate, simple leaves with closely parallel lateral veins and obvious stipules. Their flowers usually have five petals and sepals. Fun shrub, or carnival bush (Ochna multiflora), reaches 1.5 metres (5 feet) and has evergreen leaves. Its yellow, buttercup-like flowers have sepals that turn scarlet and remain after the......
Ochnaceae (plant family)
a family of the order Malpighiales, comprising 27 genera and some 495 species of tropical trees and shrubs, with a few genera of herbs. Many species are native to Brazil. The largest genus is Ouratea (including Gomphia), with about 200 species. The tropical African and Asian genus Ochna has nearly 90 species. Members of the family usually have alternate, simple leaves with clo...
Ocho comedias, y ocho entremeses nuevos (work by Cervantes)
...(1580s; “The Traffic of Algiers”). He names nine plays, the titles of a few of which sound like the originals of plays reworked and published years later in the collection Ocho comedias, y ocho entremeses nuevos (1615; “Eight Plays and Eight New Interludes”). Fixed theatre sites were just becoming established in the major cities of Spain, and there......
Ocho Rios (Jamaica)
town and Caribbean port on the north coast of Jamaica, northwest of Kingston. The Spanish name means “eight rivers,” in reference to the number of rivers in the area. The 600-foot (180-metre) cataracts of Dunns River Falls make Ocho Rios a popular tourist resort, and the town has numerous hotels as well as cruise ship...
Ochoa, Ellen (American engineer and astronaut)
American engineer and the first Hispanic female astronaut....
Ochoa, Lorena (Mexican golfer)
Mexican golfer who was one of the leading players in the Ladies Professional Golf Association (LPGA) in the early 2000s....
Ochoa, Severo (Spanish-American biochemist)
biochemist and molecular biologist who received (with the American biochemist Arthur Kornberg) the 1959 Nobel Prize for Physiology or Medicine for discovery of an enzyme in bacteria that enabled him to synthesize ribonucleic acid (RNA), a substance of central importance to the synthesis ...
Ochoan Stage (geology)
...of Petroleum Geologists in 1939 established North American standard reference sections for the Permian consisting of four series—namely, the Wolfcampian, Leonardian, Guadalupian, and Ochoan—on the basis of the succession in West Texas and New Mexico....
Ochotona (mammal)
small short-legged and virtually tailless egg-shaped mammal found in the mountains of western North America and much of Asia. Despite their small size, body shape, and round ears, pikas are not rodents but the smallest representatives of the l...
Ochotona collaris (mammal)
...roughly half of the Asian species live in rocky habitats and do not make burrows. Rather, their nests are made deep in a labyrinth of talus adjoining alpine meadows or other suitable vegetation. The collared pika (O. collaris) of Alaska and northern Canada has been found on the isolated nunataks (crags or peaks surrounded by glaciers) in Kluane National Park, and......
Ochotona hyperborea (mammal)
...in Kluane National Park, and O. macrotis has been recorded at 6,130 metres (20,113 feet) on the slopes of the Himalayas. The pika with the largest distribution, the northern pika (O. hyperborea), ranges from the Ural Mountains to the east coast of Russia and Hokkaido Island of northern Japan. Although the northern pika is considered......
Ochotona koslowi (mammal)
...as the pika is a keystone species for biodiversity in this region. Four Asian pikas—three in China and one in Russia and Kazakhstan—are listed as endangered species. One of these, Koslov’s pika (O. koslowi) from China, was originally collected by the Russian explorer Nikolai Przewalski in 1884, and approximately 100 years passed before it was se...
Ochotona macrotis (mammal)
...O. collaris) of Alaska and northern Canada has been found on the isolated nunataks (crags or peaks surrounded by glaciers) in Kluane National Park, and O. macrotis has been recorded at 6,130 metres (20,113 feet) on the slopes of the Himalayas. The pika with the largest distribution, the northern pika (O.......
Ochotona princeps (mammal)
...O. collaris) of Alaska and northern Canada has been found on the isolated nunataks (crags or peaks surrounded by glaciers) in Kluane National Park, and O. macrotis has been recorded at 6,130 metres (20,113 feet) on the slopes of the Himalayas. The pika with the largest distribution, the northern pika (O..........
Ochotona pusilla (mammal)
...is successful only when the first offspring are lost early in the breeding season. Litter size of most rock dwellers is low, but burrowing pikas may produce multiple large litters each season. The steppe pika (O. pusilla) has been reported to have litters of as many as 13 young and breed up to five times in a year....
Ochotonidae (mammal family)
...term pika comes from the vernacular piika of the Tunguses, a tribe from northeastern Siberia. Ochotona is the sole living genus of the family Ochotonidae, and its members lack several special skeletal modifications present in hares and rabbits (family Leporidae), such as a highly arched skull, relatively upright posture of the head, strong....
Ochotskoje More (sea, Pacific Ocean)
northwestern arm of the Pacific Ocean, bounded on the west and north by the east coast of Asia from Cape Lazarev to the mouth of the Penzhina River, on the east and southeast by the Kamchatka Peninsula and the Kuril Islands, on the s...
ochre (earth pigment)
Paint and painting were thought to animate sculpture—often literally, in religiosymbolic terms, as paint was considered to have magical, vivifying powers. Paints were generally ochres, with some vegetable-derived pigments. Water was the usual medium, occasionally supplemented with sap. Brushes were the fibrous ends of chewed or frayed sticks, small feather bundles, pieces of wood, and......
Ochrida (Macedonia)
town, Macedonia, on the northeastern shore of Lake Ohrid (Ohridsko Jezero). The chief resort of Macedonia, Ohrid is linked by rail, road, and air to Skopje. Agriculture, fishing, and tourism provide a livelihood for the population....
Ochroma lagopus (tree)
common, fast-growing tropical tree, occurring from southern Mexico to Bolivia, that is noted for its extremely lightweight and light-coloured wood. Balsa has pale bark and, like many tropical trees, has no annual growth rings. It can grow more than 5 metres (16.5 feet) per year in full sun, reaching a maximum height of about 30 metres (100 feet). The large leaves, generally concentrated at the end...
Ochroma pyramidale (tree)
common, fast-growing tropical tree, occurring from southern Mexico to Bolivia, that is noted for its extremely lightweight and light-coloured wood. Balsa has pale bark and, like many tropical trees, has no annual growth rings. It can grow more than 5 metres (16.5 feet) per year in full sun, reaching a maximum height of about 30 metres (100 feet). The large leaves, generally concentrated at the end...
Ochromonas (algae genus)
Annotated classification...
ochronosis (pathology)
...and oxidation, it imparts a black colour. The remainder is deposited in cartilage and, to a lesser degree, in the skin and sclerae. The resultant darkening of these tissues by this pigment is termed ochronosis and is accompanied by gradual erosion of cartilage and progressive joint disease....
ochronotic arthropathy (pathology)
Ochronotic arthropathy results from another, rarer inborn error of metabolism. It is characterized by pigmentation and degeneration of hyaline cartilage and by defective breakdown of the amino acids tyrosine and phenylalanine, causing large amounts of homogentisic acid to accumulate in body fluids and the urine. The urine turns black when exposed to air, a phenomenon called alkaptonuria. After......
Ochs, Adolph Simon (American newspaper publisher)
American newspaper publisher under whose ownership (from 1896) The New York Times became one of the world’s outstanding newspapers. Despising “yellow [sensational] journalism,” he emphasized comprehensive and trustworthy news gathering....
Ochs, Peter (Swiss revolutionary)
Swiss revolutionary who wrote most of the constitution of the unitary Helvetic Republic (1798)....
Ochs, Phil (American folksinger and songwriter)
American folksinger and songwriter best remembered for the protest songs he wrote in the 1960s on topics ranging from the Vietnam War to civil rights....
Ochsenbein, Johann Ulrich (Swiss politician)
Swiss politician and military leader who headed the confederation government during the Sonderbund War (1847) and presided over the constitutional reform committee of 1848....
Ochsenbein, Ulrich (Swiss politician)
Swiss politician and military leader who headed the confederation government during the Sonderbund War (1847) and presided over the constitutional reform committee of 1848....
Ochsenfeld, R. (German physicist)
...temperature, called the transition temperature, usually close to absolute zero. The Meissner effect, a property of all superconductors, was discovered by the German physicists W. Meissner and R. Ochsenfeld in 1933....
“ochsenfurter Männerquartett, Das” (work by Frank)
...of capitalism and the establishment of socialism was expressed in his novel Der Bürger (1924; A Middle-Class Man) and in Das ochsenfurter Männerquartett (1927; The Singers). During the same period he wrote his masterpiece, Karl und Anna (1926; Carl and Anna), a realistic, if sentimental, account of a soldier who seduces his comrade’...
Ochteridae (insect)
any insect of the family Ochteridae (order Heteroptera), which numbers about 25 species. These insects resemble tiny toads, are about 4 or 5 mm (almost 0.2 inch) long, and live among plants near streams and ponds. As indicated by their common name, the body surface is smooth and velvetlike. The front legs are slender and are developed for running....
Ochus (king of Persia)
Achaemenid king of Persia (reigned 359/358–338 bc)....
Ocimum (plant genus)
Of the 150 tropical species of Ocimum, one sacred to Hindus is basil, or tulsī (Ocimum basilicum); this plant is native in Africa and Asia but is cultivated as a culinary herb in other regions (see basil). The genus Origanum, native in Europe, includes 15 to 20 species, chief among them being marjoram (Origanum......
Ocimum basilicum (spice)
spice consisting of the dried leaves of Ocimum basilicum, an annual herb of the family Lamiaceae (Labiatae) native to India and Iran. A number of varieties are used in commerce including the small-leaf common basil, the larger leaf Italian basil, and the large lettuce-leaf basil. The dried large-leaf...
Ockeghem, Jean de (Flemish composer)
composer of sacred and secular music, one of the great masters of the Franco-Flemish style that dominated European music of the Renaissance....
Ockels, Wubbo (Dutch physicist and astronaut)
Dutch physicist and astronaut, the first Dutch citizen to travel into space....
Ockels, Wubbo Johannes (Dutch physicist and astronaut)
Dutch physicist and astronaut, the first Dutch citizen to travel into space....
ocker (film genre)
...agency charged with helping the film industry create commercial films for audiences at home and abroad. The success of Stork (1971) gave birth to a rash of “ocker” comedies, a genre that centred on boorish male characters and their antisocial behaviours. The AFDC was replaced by the Australian Film Commission (AFC) in 1975, and a more culturally......
Ockham, William (English philosopher)
Franciscan philosopher, theologian, and political writer, a late scholastic thinker regarded as the founder of a form of nominalism—the school of thought that denies that universal concepts such as “father” have any reality apart from the individual things signified by the universal or general term....
Ockham, William of (English philosopher)
Franciscan philosopher, theologian, and political writer, a late scholastic thinker regarded as the founder of a form of nominalism—the school of thought that denies that universal concepts such as “father” have any reality apart from the individual things signified by the universal or general term....
Ockham’s razor (philosophy)
principle stated by William of Ockham (1285–1347/49), a scholastic, that Pluralitas non est ponenda sine necessitate; “Plurality should not be posited without necessity.” The principle gives precedence to simplicity; of two competing theories, the simplest explanation of an entity is to be preferred. The principle is also expressed “Entities ar...
Ockrent, Michael Robert (British director)
British theatre director best known for his deft touch with comedies and musicals, notably the 1985 smash hit revival of the 1937 musical Me and My Girl and Crazy for You (1992), the Tony Award-winning reworking of George and Ira Gershwin’s Girl Crazy; other Ockrent successes included Once a Catholic (1976), Educating Rita (1980), the West End debut of Ste...
OCLC Online Computer Library Center
A number of important organizations facilitating library cooperation have been established to store and retrieve catalog records. In the United States, a library cooperative in Ohio grew into the OCLC Online Computer Library Center, a not-for-profit company with a database of millions of catalog records to which libraries can purchase access. Other organizations that store catalog records for......
O’Clery, Michael (Irish historian)
Irish chronicler who directed the compilation of the Annála Ríoghachta Éireann (1636; Annals of the Four Masters), a chronicle of Irish history from antiquity to 1616 and a work of incalculable importance to Irish scholarship....
O’Clery, Tadhg (Irish historian)
Irish chronicler who directed the compilation of the Annála Ríoghachta Éireann (1636; Annals of the Four Masters), a chronicle of Irish history from antiquity to 1616 and a work of incalculable importance to Irish scholarship....
Ocloo, Esther Afua (Ghanaian businesswoman)
Ghanaian entrepreneur (b. April 18, 1919, Peki-Dzake, Gold Coast (now in Ghana)—d. Feb. 8, 2002, Accra, Ghana), as cofounder (1979) and head of Women’s World Banking, pioneered the practice of microlending, providing tiny loans (often as little as $50) to small home-based businesses, usually those run by women in less-developed countries. Ocloo began as a street vendor of homemade or...
Ocmulgee National Monument (national monument, Georgia, United States)
village site containing earthwork structures built by farming peoples of the Mississippian culture. The monument is located in central Georgia, U.S., on the Ocmulgee River in the eastern outskirts of Macon. The monument was authorized in 1934 and established in 1936, with boundary changes occurring in 1941 and 1992. It occupies about 700 acr...
Ocoee River (river, United States)
river rising in the Blue Ridge Mountains, 9 mi (14 km) southeast of Blue Ridge city, Ga., U.S., and flowing northwest through Fannin County into Tennessee, past Copperhill, through Polk County, and north to the Hiwassee River, just north of Benton. Alo...
OCOG
When the IOC awards the Olympic Games to a city, an organizing committee for the Olympic Games (OCOG) replaces the successful bid committee, often including many of that committee’s members. Although the IOC retains ultimate authority over all aspects of an Olympiad, the local OCOG has full responsibility for the festival, including finance, facilities, staffing, and accommodations....
Oconee (county, South Carolina, United States)
county, extreme northwestern South Carolina, U.S. It is bordered by North Carolina to the north and Georgia to the west. Its most northerly portion lies within the rugged Blue Ridge Mountains of the Appalachian chain, and the remainder is in high piedmont hills. Much of the region is covered in upland hardwood forest. The ...
O’Connell, Arthur (American actor)
James Stewart ((Paul Biegler)Lee Remick (Laura Manion)Ben Gazzara (Lt. Frederick Manion)Arthur O’Connell (Parnell Emmett McCarthy)Eve Arden (Maida Rutledge)Kathryn Grant (Mary Pilant)George C. Scott (Claude Dancer)...
O’Connell, Daniel (Irish leader)
lawyer who became the first great 19th-century Irish nationalist leader....
O’Connell, David (Irish political activist)
Irish political activist and a cofounder of the Provisional (“Provo”) wing of the Irish Republican Army (IRA)....
O’Connell, Helen (American singer)
U.S. singer (b. May 23, 1920, Lima, Ohio--d. Sept. 9, 1993, San Diego, Calif.), was still a teenager when she joined (1939) Jimmy Dorsey’s big band, and she became an overnight sensation after recording “Green Eyes” with crooner Bob Eberly. O’Connell’s cool renditions of such other songs as...
O’Connell Street (street, Dublin, Ireland)
O’Connell Street—first called Drogheda and then Sackville Street—is a stretch of shops, cinemas, and snack bars. The only building of any distinction to survive the warfare that swept the street in 1916 and again in 1922 was the General Post Office, seized as headquarters of the 1916 rebellion. Badly damaged, it was reconstructed behind its surviving 1815 classical facade in 1...
O’Connor, Carroll (American actor)
American character actor (b. Aug. 2, 1924, New York, N.Y.—d. June 21, 2001, Culver City, Calif.), was classically trained and appeared in scores of movies and television programs, but to the majority of the viewing public, he was the irascible but lovable bigot Ar...
O’Connor, Donald (American actor)
multitalented American entertainer, best known for his comedic and dancing skills....
O’Connor, Donald David Dixon Ronald (American actor)
multitalented American entertainer, best known for his comedic and dancing skills....
O’Connor, Feargus Edward (Irish leader)
prominent Chartist leader who succeeded in making Chartism the first specifically working class national movement in Great Britain....
O’Connor, Flannery (American writer)
American novelist and short-story writer whose works, usually set in the rural American South and often treating of alienation, are concerned with the relationship between the individual and God....
O’Connor, Frank (Irish author)
Irish playwright, novelist, and short-story writer who, as a critic and as a translator of Gaelic works from the 9th to the 20th century, served as an interpreter of Irish life and literature to the English-speaking world....
O’Connor, Gordon (Canadian government official)
Defense Minister Gordon O’Connor found himself embroiled in a scandal in April when the national media reported claims of torture from prisoners who were detained by Canadian forces and were being held by Afghan security forces. Speaking to MPs in the House of Commons in May 2006, O’Connor had stated that the International Committee of the Red Cross had signed an agreement with Canad...
O’Connor, John Joseph Cardinal (American religious leader)
American Roman Catholic prelate, who served as the archbishop of New York (1984–2000) and was regarded as the Vatican’s leading spokesman in the United States....
O’Connor, Mary Flannery (American writer)
American novelist and short-story writer whose works, usually set in the rural American South and often treating of alienation, are concerned with the relationship between the individual and God....
O’Connor, Richard Nugent (British military officer)
Wavell, whose command included not only Egypt but also the East African fronts against the Italians, decided to strike first in North Africa. On Dec. 7, 1940, some 30,000 men, under Major General Richard Nugent O’Connor, advanced westward, from Mersa Matruh, against 80,000 Italians; but, whereas the Italians at Sīdī Barrānī had only 120 tanks, O’Connor had...
O’Connor, Sandra Day (United States jurist)
associate justice of the Supreme Court of the United States from 1981 to 2006. She was the first woman to serve on the Supreme Court. A moderate conservative, she was known for her dispassionate and meticulously researched opinions....
O’Connor, Sinead (Irish singer)
associate justice of the Supreme Court of the United States from 1981 to 2006. She was the first woman to serve on the Supreme Court. A moderate conservative, she was known for her dispassionate and meticulously researched opinions.......
O’Connor, William (American journalist)
...secretary of the Interior thought that Leaves of Grass was indecent. Whitman then obtained a post in the attorney general’s office, largely through the efforts of his friend, the journalist William O’Connor, who wrote a vindication of Whitman in The Good Gray Poet (published in 1866), which aroused sympathy for the victim of injustice....
Oconto (Wisconsin, United States)
city, seat (1854) of Oconto county, northeastern Wisconsin, U.S. It lies on the western shore of Green Bay, at the mouth of the Oconto River, about 30 miles (50 km) north of the city of Green Bay. The earliest inhabitants of the region, known as the Old Copper culture, lived there some 5,000 years ago. Fur traders arrived ...
Ocós phase (Mesoamerican history)
...of early village cultures. The Barra phase appears to have been transitional from earlier preagricultural phases and may not have been primarily dependent upon corn farming; but people of the Ocós and Cuadros phases raised a small-eared corn known as nal-tel, which was ground on metates and manos and cooked in globular jars. From the rich lagoons and estuaries in this area,......
Ocotal (Nicaragua)
city, northwestern Nicaragua. It lies on a sandy plain near the Cordillera Entre Ríos and the Coco River, at an elevation of 1,987 feet (606 m). Ocotal serves as a manufacturing and commercial centre. Shoes, furniture, and beverages are among its manufactures. Ocotal is accessible by roads leading s...
Ocotea (tree genus)
...Lauraceae is distributed throughout tropical and subtropical regions; principally Southeast Asia and tropical America, particularly Brazil. Some 66 percent of the species occur in only 6 genera: Ocotea has about 350 species in tropical America, South Africa, and the Mascarene Islands; Litsea has more than 400 species in Asia, Australasia, and America; Cryptocarya and......
Ocotea rodiei (Chlorocardium rodiei)
valuable South American timber tree of the laurel family (Lauraceae). A large tree, it grows to a height of 40 metres (130 feet) and is native to the Guianas. The bark and fruits contain bebeerine, an alkaloid formerly used to reduce fever....
Ocotea venenosa (tree)
...such as boats and wharf pilings. Bebeerine, a highly poisonous alkaloid produced as a secondary compound, has been extracted from several species of Ocotea, as well as from greenheart. Ocotea venenosa is a source of a poison used for the tips of arrows by Brazilian natives. Because alkaloids are present in many woods of Lauraceae, timber workers who process them are susceptible......
Ocotepeque (Honduras)
town, western Honduras. It lies along the Lempa River at 2,641 feet (805 m) above sea level. The town was originally situated just to the northeast, at the site of Ocotepeque, but it was relocated after the Marchala River, a tributary of the Lempa, overflowed in 1935. Nueva Ocotepeque is...
ocotillo (plant)
flowering spiny shrub characteristic of rocky deserts from western Texas to southern California and southward into Mexico. It is a member of the candlewood family (Fouquieriaceae), which belongs to the order Ericales. Near the plant’s base the stem divides into several slender, erect, widespreading, intensely spiny branches, usually abo...
ocotillo family (plant family)
Fouquieriaceae, or the ocotillo family, are shrubs that grow in drier parts of western North America. There is a single genus, Fouquieria (including Idria), with 11 species. They are often little-branched shrubs with spirally arranged leaves. Leaves on some shoots are borne close together (short shoots), while those on others are well separated (long shoots) and......
Ocotlán (Mexico)
city, east-central Jalisco estado (state), west-central Mexico. It lies near the northeastern shore of Lake Chapala, at the confluence of the Zula (or Atotonilco) and Santiago rivers, and is most important as a transportation hub. As the gateway to the Chapala resort district, it has c...
OCR (technology)
Scanning and comparison technique intended to identify printed text or numerical data. It avoids the need to retype already printed material for data entry. OCR software attempts to identify characters by comparing shapes to those stored in the software library. The software tries to identify words using character proximity and will try to reconstruct the original page layout. High accuracy can be...
Ocracoke Island (island, North Carolina, United States)
scenic coastal area situated on Bodie, Hatteras, and Ocracoke islands along the Outer Banks, eastern North Carolina, U.S. The park, the country’s first national seashore, was authorized in 1937 and established in 1953. It has a total area of 47 square miles (122 square km). The three narrow barrier islands lie between the Atlantic Ocean to the east and Pamlico Sound to the west; together wi...
octacarbonyldicobalt (chemical compound)
Many other metal carbonyls contain two or more metal atoms, such as decacarbonyldimanganese and octacarbonyldicobalt, shown here....
octachlor (chemical compound)
a chlorinated cyclodiene that is the principal isomer formed in the preparation of a contact insecticide of the same name. Chlordane is a thick, odourless, amber liquid with a molecular formula of C10H6Cl8. The compound’s accepted name is octachloro...
octadecanoic acid (chemical compound)
one of the most common long-chain fatty acids, found in combined form in natural animal and vegetable fats. Commercial “stearic acid” is a mixture of approximately equal amounts of stearic and palmitic acids...
octadecenoic acid (chemical compound)
...unsaturated fatty acids and glycerides to higher-melting saturated products. The process consists of the addition of hydrogen in the presence of a catalyst to the double (unsaturated) bonds. Thus oleic or linoleic acid (or their acid radicals in glycerides), which are normally liquid at room temperature, can be converted to stearic acid or the acid radical by the addition of hydrogen....
octadecyl alcohol (chemical compound)
waxy solid alcohol formerly obtained from whale or dolphin oil and used as a lubricant and antifoam agent and to retard evaporation of water from reservoirs. It is now manufactured by chemical reduction of stearic acid....
octaëteris (chronology)
The main use of cycles was to try to find some commensurable basis for lunar and solar calendars, and the best known of all the early attempts was the octaëteris, usually attributed to Cleostratus of Tenedos (c. 500 bce) and Eudoxus of Cnidus (390–c. 340 bce). The cycle covered eight years, as its name im...
Octagon (chapel, Aachen, Germany)
private chapel associated with a residence, especially of an emperor. Many of the early Christian emperors built private churches in their palaces—often more than one—as described in literary sources of the Byzantine period. Such structures in Constantinople (now Istanbul, Tur.) inspired the impressive 12th-century Palatine Chapel (Cappella Palatina) of the Sicilia...
Octagon Building (building, Washington, District of Columbia, United States)
...though Benjamin H. Latrobe completely redesigned the interiors. From 1794 to 1802 Thornton was a commissioner of the city of Washington. He designed several residences in the city, including the Octagon (1798–1800), which was used in 1814 by President James Madison after the White House was burned. The Octagon is now the national headquarters of the American Institute of Architects....
octahedral arrangement (molecular shape)
...is predicted and found to be a trigonal bipyramid. The XeF4 (xenon tetrafluoride) molecule is hypervalent with six electron pairs around the central xenon (Xe) atom. These pairs adopt an octahedral arrangement. Four of the pairs are bonding pairs, and two are lone pairs. According to VSEPR theory, the repulsion between the lone pairs is minimized if they lie on opposite sides of the....
octahedrite (meteorite)
...according to their crystal structure, which can be revealed through etching a polished cross section of the meteorite with dilute acid. There are three groups grading into one another: hexahedrites, octahedrites, and ataxites. Hexahedrites are usually made up entirely of kamacite and lack the Widmanstätten pattern. Octahedrites contain both kamacite and taenite and constitute the largest...