a paleoanthropological site in northern Malawi known for the discovery of a jawbone of an ancient human (genus Homo) dating to 2.4 million years ago (mya). It is similar to specimens dating to between 1.9 and 1.8 mya from Koobi ...
mountain range forming a rugged spine in west-central Russia and the major part of the traditional physiographic boundary between Europe and Asia. Extending some 1,550 miles (2,500 kilometres) from the bend of the Ural River in the south to the ...
river in Russia and Kazakstan. The Ural is 1,509 miles (2,428 km) long and drains an area of 91,500 square miles (237,000 square km). It rises in the Ural Mountains near Mount Kruglaya and flows south along their eastern flank ...
hypothetical language grouping that includes all the languages of the Uralic and Altaic language families. Most of the evidence for including the Uralic and Altaic languages in one language family is based on similarities of language structure rather than on ...
a 3,500-kilometre- (2,175-mile-) long elongate mountain system that extends from the Aral Sea to the islands of Novaya Zemlya. It is 500 km wide in the south but only 100-150 km wide in the north. The belt formed as a ...
family of more than 20 related languages, all descended from a Proto-Uralic language that existed 7,000 to 10,000 years ago. At its earliest stages, Uralic most probably included the ancestors of the Yukaghir language. The Uralic languages are spoken by ...
in Greek religion, one of the nine Muses, patron of astronomy. In some accounts she was the mother of Linus the musician (in other versions, his mother is the Muse Calliope); the father was either Hermes or Amphimarus, son of ...
observatory established in 1576 by the Danish astronomer Tycho Brahe. It was the last of the primitive observatories in that it antedated the invention of the telescope (c. 1608); and it was the first of the modern observatories in that ...
a major ore mineral of uranium, uranium dioxide (UO2). Uraninite usually forms black, gray, or brown crystals that are moderately hard and generally opaque. A variety of uraninite ore that is dense and found in granular masses with a greasy ...
municipal corporation, centre of the Beaverlodge Lake mining region in extreme northwestern Saskatchewan, Canada. It lies near the north shore of Lake Athabasca. The discovery in the early 1950s and the subsequent mining of uranium ore there by the Eldorado ...
method of age determination that makes use of the radioactive decay of uranium-238 to uranium-234; the method can be used for dating of sediments from either a marine or a playa lake environment. Because this method is useful for the ...
method of establishing the time of origin of a rock by means of the amount of common lead it contains; common lead is any lead from a rock or mineral that contains a large amount of lead and a small ...
seventh planet in order of distance from the Sun. Its low density (1.285 grams per cubic centimetre) and large size (radius four times that of the Earth) place it among the four giant planets, all of which are composed primarily ...
in Greek mythology, the personification of heaven. According to Hesiod's Theogony, Gaea (Earth), emerging from primeval Chaos, produced Uranus, the Mountains, and the Sea. From Gaea's subsequent union with Uranus were born the Titans, the Cyclopes, and the Hecatoncheires.
ancient language spoken in northeastern Anatolia and used as the official language of Urartu in the 9th-6th century BC. Non-Indo-European in origin, it is thought to be descended from the same parent language as the older, Hurrian language. Surviving texts ...
ancient country of southwest Asia centred in the mountainous region southeast of the Black Sea and southwest of the Caspian Sea. Today the region is divided among Armenia, eastern Turkey, and northwestern Iran. Mentioned in Assyrian sources from the early ...
city, northwestern Chiba ken (prefecture), east-central Honshu, Japan. Lying on a flat plain along Tokyo Bay, it is separated from the city of Tokyo to the west by the Edo River. Urayasu was a thriving fishing village ...
musical genre of the 1980s and '90s defined by recordings by rhythm-and-blues or soul artists with broad crossover appeal. Urban contemporary began as an American radio format designed to appeal to advertisers who felt that "black radio" would not reach ...
pope from 222 to 230. Succeeding that of St. Calixtus I, his pontificate occurred within the reign of the Roman emperor Severus Alexander, a time of peace for the church. His baptism of St. Cecilia's husband, St. Valerian, is fictitious. ...
head of the Roman Catholic church (1088-99) who developed ecclesiastical reforms begun by Pope Gregory VII, launched the Crusade movement, and strengthened the papacy as a political entity.
the programs pursued in most industrialized countries in an attempt to achieve certain social and economic objectives, in particular to shape and improve the urban environment in which increasing proportions of the world's population spend their lives.
comprehensive scheme to redress a complex of urban problems, including unsanitary, deficient, or obsolete housing; inadequate transportation, sanitation, and other services and facilities; haphazard land use; traffic congestion; and the sociological correlates of urban decay, such as crime. Early efforts ...
in anthropology and archaeology, the process by which small, kin-based, nonliterate agricultural villages are transformed into large, socially complex, civilized urban centres. The term urban revolution was introduced by V. Gordon Childe, an Australian archaeologist.
city, Champaign county, west-central Ohio, U.S., in a stock-raising and farming area, 40 miles (64 km) northeast of Dayton. Laid out in 1805 by Colonel William Ward of Virginia, it became the county seat in the same year and grew ...
city, seat (1833) of Champaign county, east-central Illinois, U.S. Urbana is contiguous with Champaign (west), about 135 miles (220 km) southwest of Chicago. The two cities are often called Champaign-Urbana. The area was first settled in 1822, and in 1833 ...
town, Pesaro e Urbino provincia, Marche (The Marches) regione, central Italy. Founded by the Umbrians, an ancient people of Italy, it was subsequently occupied by the Etruscans, Celts, and Gauls, and, in the 3rd century BC, by the Romans. It ...
Italian tin-glazed earthenware made in the city of Urbino, which from around 1520 dominated the market. Early wares, mostly dishes, are decorated with narrative scenes that typically cover the entire surface. The narrative scenes are taken from the Bible, from ...
Indo-Aryan language originating in the region between the Ganges and Jamuna rivers near Delhi, now the official language of Pakistan. Numbering some 48,980,000 speakers in the late 20th century, Urdu is the primary language of the Muslims of both Pakistan ...
writings in the Urdu language of the Muslims of Pakistan and northern India. It is written in the Perso-Arabic script, and, with a few major exceptions, the literature is the work of Muslim writers who take their themes from the ...
the diamide of carbonic acid. Its formula is H2NCONH2. Urea has important uses as a fertilizer and feed supplement, as well as a starting material for the manufacture of plastics and drugs. It is a colourless, crystalline substance that melts ...
any of a class of substances belonging to the family of organic polymers, prepared by heating urea and formaldehyde in the presence of mild alkalies, such as pyridine or ammonia. The urea and formaldehyde undergo a condensation reaction in which ...
an enzyme that catalyzes the hydrolysis of urea, forming ammonia and carbon dioxide. Found in large quantities in jack beans, soybeans, and other plant seeds, it also occurs in some animal tissues and intestinal microorganisms. Urease is significant in the ...
toxic effects of abnormally high concentrations of nitrogenous substances in the blood as a result of the kidney's failure to expel these waste products by way of the urine. The end products of protein metabolism accumulate in the blood but ...
plant of the family Malvaceae and its fibre, one of the bast fibre (q.v.) group. The plant, probably of Old World origin, grows wild in tropical and subtropical areas throughout the world. The name urena apparently derives from the name ...
one of two ducts that transmit urine from each kidney to the bladder. Each ureter is a narrow tube that is about 12 inches (30 cm) long. A ureter has thick, contractile walls, and its diameter varies considerably at different ...
