Urartu \u-'rar-,tu\ Ancient kingdom around Lake Van, southwestern Asia. Today the region is divided among Armenia, eastern Turkey, and northwestern Iran. The kingdom flourished c. 13th—7th century bc, enjoy¬ ing considerable power in the Middle East in the 9th-8th century. Archaeological finds date from the time of King Shalmaneser I (c. 1274- 45) of Assyria. Repeatedly attacked by Assyrian kings, Urartu declined in the late 8th century. It ceased to exist after invasions by Cimmerians, Scythians, and Medes in the 7th century bc.
Urban II orig. Odo of Chatillon-sur-Marne (b. c. 1035, Chatillon- sur-Marne, or Lagery, or Lagny, Champagne, France—d. July 29, 1099, Rome) Pope (1088-99). The prior of a Cluniac monastery, he was made
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Urban VI ► urination I 1975
cardinal by Pope Gregory VII, whose reforms he furthered. Elected pope in 1088, Urban secured his authority against the antipope Clement 111 and strengthened the role of the papacy in the reform movement. He called for the First Crusade at the Council of Clermont (1095) in response to the appeal of Alexius I Comnenus, promoted the union of the Eastern and Western churches, and supported the Christian reconquest of Spain from the Moors.
Urban VI orig. Bartolomeo Prignano (b. 1318, Naples—d. Oct. 15, 1289, Rome) Pope (1378-89). Archbishop of Acerenza (1363) and Bari (1377), he became papal chancellor for Gregory XI, whom he was chosen to succeed. This election of an Italian appeased the Romans, who wanted to end the French-dominated Avignon papacy, but his harsh reforms soon angered the French cardinals, prompting them to elect the antipope Clement VII, beginning the Western Schism (1378). Europe was divided in its loyalties, and Urban warred with Naples when its queen backed Clement. Strife over the schism reduced the Papal States to anar¬ chy, and Urban’s death may have been from poisoning.
urban climate Any set of climatic conditions that prevails in a large metropolitan area and that differs from the climate of its rural surround¬ ings. Urban climates are distinguished from those of less built-up areas by differences of air temperature, humidity, wind speed and direction, and amount of precipitation. These differences are attributable in large part to the altering of the natural terrain through the construction of artificial structures and surfaces. For example, tall buildings, paved streets, and parking lots affect wind flow, precipitation runoff, and the local energy balance.
urban planning Programs pursued as a means of improving the urban environment and achieving certain social and economic objectives. Evi¬ dence of urban planning can be found in the ruins of ancient cities, includ¬ ing orderly street systems and conduits for water and sewage. During the Renaissance, European city areas were consciously planned to achieve circulation of the populace and provide fortification against invasion. Such concepts were exported to the New World, where William Penn, in founding the city of Philadelphia, developed the standard gridiron plan— the laying out of streets and plots of land adaptable to rapid change in land use. Modem urban planning and redevelopment arose in response to the disorder and squalor of the slums created by the Industrial Revolution. The urban planner best known for his transformation of Paris was Georges-Eugene Haussmann. City planners imposed regulatory laws estab¬ lishing standards for housing, sanitation, water supply, sewage, and pub¬ lic health conditions, and introduced parks and playgrounds into congested city neighbourhoods. In the 20th century, zoning—the regula¬ tion of building activity according to use and location—came to be a key tool for city planners. See also Pierre-Charles V Enfant.
Urbino majolica Vmo-'ja-li-koX Italian tin-glazed earthenware made in the city of Urbino, which dominated the market from c. 1520. Early wares, mostly dishes, are painted in a range of colours, dominated by brilliant yellow, orange, and brown, and decorated with narrative scenes typically covering the entire surface, a style known as istoriato. Scenes are taken from the Bible, mythology. Classical and contemporary history, and poetry. Later wares were decorated in a style called grotesque, adapted from motifs found in Roman excavations. Production declined in the late 17th century. See also majolica.
Urdu \'ur-du\ language Indo-Aryan language used by Muslims in India and Pakistan. In the sociopolitical realm, Urdu and Hindi are differ¬ ent languages, but the colloquial basis of both is identical, and as a writ¬ ten language Urdu differs from Hindi principally in its greater acceptance of Persian-Arabic vocabulary and in some syntactic features. It is written in the Arabic alphabet with modification of some letters to denote specifi¬ cally Indo-Aryan sounds. As Pakistan’s official language, Urdu has been promoted as a token of national unity, though less than 8% of Pakistanis— mainly immigrants and descendants of immigrants from India after the 1947 partition—speak it as a first language.
urea \yu-'re-o\ or carbamide One of the simplest organic compounds and the first synthesized from inorganic raw materials (see inorganic com¬ pound), by Friedrich Wohler (1800-82) in 1828. It is the diamide of car¬ bonic acid (H 2 NCONH 2 ; see amide; carbon dioxide). The chief nitrogenous end product of protein breakdown in mammals and some fishes, it occurs not only in urine but also in blood, bile, milk, and perspiration. It is one of the industrial chemicals produced in vast amounts. With its high nitrogen content and low price, it is a major agricultural fertilizer and animal-feed
ingredient. It is also used to make urea-formaldehyde plastics (including foamed plastics; see polyurethanes), to synthesize barbiturates, as a stabi¬ lizer in explosives, and in adhesives, hydrocarbon processing, and flame¬ proofing.
uremia \yu-'re-me-3\ Excess nitrogenous waste products in the blood and their toxic effects. Kidney impairment (see Bright disease; diabetes mel- utus; hypertension; kidney failure; nephritis) or disorders that hinder urine excretion (e.g., prostatic disorders) allow urea and other protein waste products to accumulate. Symptoms usually start with fatigue and loss of concentration. They may include itching and muscle twitches; dry, flaky, yellowish skin; dry mouth, metallic taste, and ammonia breath; and nau¬ sea, vomiting, diarrhea, and constipation. Advanced stages affect the ner¬ vous, cardiovascular, and respiratory systems and can lead to hypertension, seizures, heart failure, and death. If the underlying disorder cannot be treated, dialysis or kidney transplant may be required.
Urey \'yur-e\, Harold C(layton) (b. April 29, 1893, Walkerton, Ind., U.S.—d. Jan. 5, 1981, La Jolla, Calif.) U.S. scientist. He received his doctorate from the University of California at Berkeley and thereafter taught at various universities. He was awarded a Nobel Prize in 1934 for discovering deuterium and heavy water. He was a key figure in the devel¬ opment of the atomic bomb; his group worked on the gaseous diffusion pro¬ cess for separation of uranium-235. He devised methods for estimating the temperature of ancient oceans, theorized on the compositions of pri¬ mordial atmospheres, and studied the relative abundances of the elements, making fundamental contributions to a widely accepted theory of the ori¬ gin of the Earth and other planets in The Planets, (1952).