Rio de Oro Southern region. Western Sahara. Its principal town, Al-Dakhla (formerly Villa Cisneros), has a small port and must rely on imported drinking water. The narrow inlet of the Atlantic Ocean at Al-Dakhla was called Rio de Oro (“River of Gold”) by the Portuguese because of the trade in gold dust from western Africa that they engaged in there. From the 1880s until 1976 it was ruled by Spain. In 1979 it was occu¬ pied by Morocco. The indigenous inhabitants are Muslim and largely nomadic Berbers.
Rio Grande \ , re-o- , grand\ in Mexico Rio Bravo River, North America. One of the longest rivers of North America, it flows 1,900 mi
(3,000 km) from its sources in the Rocky Mountains of southwestern Colo¬ rado, U.S., to the Gulf of Mexico. It rises high in the San Juan Mountains and flows generally south, passing southeast and forming the entire bor¬ der between Texas and Mexico. The earliest European settlements were along the lower course of the river in the 16th century, but many of the Pueblo Indian settlements of New Mexico date from before the Spanish conquest. During the Spanish period, the middle and upper portions were called the Rio del Norte, and the lower course was called the Rio Bravo. It is a major source of irrigation. At the U.S.-Mexican border, it defines the edge of Big Bend National Park, Texas.
Rio Treaty officially Convention on Biological Diversity Inter¬ national environmental agreement approved at the 1992 Earth Suaamit in Rio de Janeiro. Negotiations began in 1988 under the auspices of the United Nations Environment Program. Its goals are the conservation of the planet’s biodiversity and the fair use of its resources. By the early 21st century, more than 185 governments were party to the agreement.
Riopelle \re-o-'pel\, Jean-Paul (b. Oct. 7, 1923, Montreal, Que., Can.—d. March 12, 2002, Ile-aux-Grues, near Quebec City) Canadian painter and sculptor. He moved to Paris in 1947 and, with Paul-Emile Bor- duas, became associated with the group of Canadian painters known as Les Automatistes, who practiced automatism. His early lyrical, abstract paintings evolved into a denser, more powerful impasto style. He is renowned for his use of various media (including watercolour, ink, oils, crayon, and chalk), and he also produced large collage murals. He achieved international acclaim with the huge triptych Pavane (1954) and is the leading Canadian abstract painter of his generation.
rip current or riptide Narrow, jetlike stream of water that flows spo¬ radically seaward for several minutes, in a direction perpendicular to a beach. The term riptide is a misnomer because the currents are in no way related to tides. Rip currents form at long coasts that are approached by wave trains that are nearly parallel to the shoreline. In shallow water, nor¬ mal wave motion displaces the water small distances shoreward with each passing wave. During periods of large waves, water builds up at the beach and cannot escape as longshore currents, which require oblique wave approach. The buildup continues until water can escape by surging for several minutes through a low point in a breaker, creating an undertow that can be dangerous for swimmers.
riparian right \ri-'par-e-on\ In law, the right of one who owns ripar¬ ian land (land abutting or including a stream or river) to have access to and use of the shore and water. These rights are a form of real property (see real and personal property) and are inherited with the land. A land- owner whose property abuts an ocean, sea, lake, or pond is said to pos¬ sess littoral rights. Specific water-use laws vary from state to state.
Ripken, Cal(vin Edwin), Jr, (b. Aug. 24, 1960, Havre de Grace, Md., U.S.) U.S. baseball player. Ripken was born into a baseball family; his father and brother both played professionally. He played for the Balti¬ more Orioles from 1981. In 1990 he set single-season records for highest fielding percentage by a shortstop (.996) and fewest errors by a shortstop (3), and in 1993 he broke the home-run record for a shortstop. On Sept. 6, 1995, he broke Lou Gehrig’s long-standing record of consecutive games played (2,130), eventually running his streak to 2,632 games before tak¬ ing a day off in 1998. Ripken retired at the end of the 2001 season.
Ripley, George (b. Oct. 3, 1802, Greenfield, Mass., U.S.—d. July 4, 1880, New York, N.Y.) U.S. journalist and reformer. He became a Uni¬ tarian minister after graduating from Harvard Divinity School. A mem¬ ber of the Transcendental Club and an editor of The Dial , its literary magazine, he founded the utopian community Brook Farm in 1841 and served as its director and leading promoter. When it closed in 1847, he took a job with the New York Tribune to pay off its debts. His own finan¬ cial position did not become secure until he published The Cyclopedia (1862), a popular reference book.
ripple mark One of a series of small marine, lake, or riverine features, consisting of repeating wavelike forms with symmetric slopes, sharp peaks, and rounded troughs. Ripple marks are formed in sandy bottoms by oscillation waves, in which only the wave form advances rapidly, the actual water-particle motion consisting of almost closed vertical orbits. The presence of the bottom restricts the lowermost orbits into nearly flat ellipses, and the bottom water moves back and forth rhythmically. If the maximum horizontal velocity of this motion is capable of moving the grains composing the bed, ripple marks develop. See also wave.
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RISC * Riyadh I 1625
RISC VriskA in full Reduced Instruction Set Computing Computer architecture that uses a limited number of instructions. RISC became popu¬ lar in microprocessors in the 1980s. The traditional CISC (Complex Instruction Set Computing) architecture uses many instructions that do long, complex operations. Each RISC instruction is executed much more quickly than a CISC instruction, and most computational tasks can be processed faster. Modern instruction sets combine attributes of CISC and RISC.
risk In economics and finance, an allowance for the hazard (risk) in an investment or loan. Default risk refers to the chance that a borrower will not repay a loan. If a banker believes that a borrower may not repay a loan, the banker will charge the true interest plus a premium for the default risk, the premium depending on the degree of presumed risk. All stock investment carries an implicit risk since there is no guarantee of return on investment. Trading or variability risk is the amount that the return may vary, up or down, from the expected return on investment.
Risorgimento Vre-.zor-ji-'men-toX Italian "Rising Again" Nineteenth-century movement for Italian unification. Reforms introduced by France into its Italian states in the Napoleonic period remained after the states were restored to their former rulers in 1815 and provided an impetus for the movement. Secret groups such as Young Italy advocated Italian unity, and leaders such as Camillo Cavour, who founded the jour¬ nal II Risorgimento (1847), Giuseppe Garibaldi, and Giuseppe Mazzini called for liberal reforms and a united Italy. After the failure of the Revolutions of 1848, leadership passed to Cavour and Piedmont, which formed an alliance with France against Austria (1859). The unification of most of Italy in 1861, followed by the annexation of Venetia (1866) and papal Rome (1870), marked the end of the Risorgimento.