Rub< ol-Kholi Vriib-al-'ka-leV Vast desert, south-central Arabian Penin¬ sula. It covers about 250,000 sq mi (650,000 sq km), mainly in south¬ eastern Saudi Arabia, and has lesser portions in Yemen, Oman, and the United Arab Emirates. It is the largest area of continuous sand in the world
and occupies more than one-fourth of Saudi Arabia. It is virtually unin¬ habited and largely unexplored. In 1948 Al-Ghawar, the world’s largest oil field, was discovered there.
rubber Flexible material that can recover its shape after considerable deformation.The best-known rubber is natural rubber, made from the milky latex of the rubber tree (Hevea brasiliensis). Natural rubber is still important industrially, but it now competes with synthetic alternatives (e.g., neoprene, silicone) derived from petroleum, natural gas, and other source materials. Rubber’s usefulness is based on the unique elasticity of its constituent polymer molecules (built of thousands of isoprene mono¬ mers; see isoprenoid), which are capable of returning to their original coiled shape after being stretched to great extents; it is made more durable by vulcanization with sulfur or another agent that establishes chemical cross¬ links between the polymers. Fillers and other additives allow tailoring of properties to the desired use (e.g., by foaming, shaping, and curing). More than half of all rubber goes into making tires; the rest is used principally in belts, hoses, gaskets, shoes, clothing, furniture, and toys.
rubber plant or India rubber plant Tropical tree ( Ficus elastica) of the mulberry family. The rubber plant is large in its native Southeast Asia and other warm areas; elsewhere it is commonly grown indoors as a pot¬ ted plant. The plant has large, thick, oblong leaves and pairs of figlike fruits along its branches. The milky sap, or latex, was once an important source of an inferior natural rubber. Young plants available in the florist’s trade are durable and grow well under less-than-ideal indoor conditions. Some cultivated varieties have broader, darker green leaves; others are variegated. See also rubber tree.
rubber tree South American tropical tree (Hevea brasiliensis ) of the spurge family. Cultivated on plantations in the tropics and subtropics, especially in Southeast Asia and western Africa, it replaced the rubber plant in the early 20th century as the chief source of natural rubber. It has soft wood, high, branching limbs, and a large area of bark. The milky liquid (latex) that oozes from any wound to the tree bark contains about 30% rubber, which can be coagulated and processed into solid products such as tires. Latex can also be concentrated for producing dipped goods such as surgical gloves.
rubella \rii-'be-l3\ or German measles Viral disease with a usually mild course, except in women in the first 20 weeks of pregnancy, in whom it can cause fetal birth defects (of eyes, heart, brain, and large arteries) or death. Sore throat and fever are followed by swollen glands and a rash. Up to 30% of infections may have no symptoms. Lifelong immunity fol¬ lows infection. Encephalitis is a rare complication. Rubella was not distin¬ guished from measles (rubeola) until the early 19th century and was not known to be dangerous until 1941. The virus was isolated in 1962, and a vaccine became available in 1969.
Rubens, Peter Paul (b. June 28, 1577, Siegen, Westphalia—d. May 30, 1640, Antwerp, Spanish Neth.) Flemish painter and diplomat. After apprenticeships in Antwerp, he was admitted to its painters’ guild in 1598. He went to Italy in 1600 and until 1608 worked for the duke of Mantua, who in 1603 sent him to Spain to present paintings and other gifts to Philip III, the first of many diplomatic missions he would perform for various courts over three decades. The enormous fame he would achieve made him welcome at royal courts, and sovereigns often discussed affairs of state while they sat for portraits. Returning to the Spanish Netherlands (now Belgium) in 1608, he was appointed court painter to the Spanish Habsburg regents, and over the next decade produced numerous altar- pieces. A devout Catholic, he became the Counter-Reformation’s chief artistic proponent in northern Europe. In 1620 he contracted to design 39 ceiling paintings for the Jesuit church, to be completed by assistants, including the young Anthony Van Dyck. In France he did 21 large can¬ vases for Marie de Medicis and a tapestry cycle for Louis XIII; for Britain his Allegory of Peace and War (1629-30) commemorated the success of his own diplomatic efforts to end hostilities between Britain and Spain, and he decorated the royal Banqueting House for Charles I; in Spain he did more than 60 oil sketches for Philip IV’ s hunting lodge. Both Charles and Philip knighted him. His output was prodigious. He was the greatest exponent of Baroque painting’s dynamism, vitality, and sensual exuber¬ ance. His profound stylistic influence extended over three centuries.
rubeola See measles
Rubicon \ , rii-bi- l kan\ Small stream that separated Cisalpine Gaul from Italy in the era of the Roman republic. The movement of Julius Caesar’s
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1650 I rubidium-strontium dating ► Rudolph
forces over the Rubicon into Italy in 49 bc violated the law that forbade a general to lead an army out of the province to which he was assigned. Caesar’s act thus amounted to a declaration of war against the Roman Senate and resulted in the three-year civil war that left Caesar ruler of the Roman world. “Crossing the Rubicon” became a popular phrase describ¬ ing a step that irrevocably commits a person to a given course of action.
rubidium-strontium Nru-'bi-de-om-'stran-she-onA dating Method of estimating the age of rocks, minerals, and meteorites from measure¬ ments of the amount of the stable isotope strontium-87 formed by the decay of the unstable isotope rubidium-87 that was present in the rock at the time of its formation. The method is applicable to very old rocks because the transformation is extremely slow: the half-life, or time required for half the initial quantity of rubidium-87 to disappear, is approximately 48.8 billion years. See also dating.
Rubinstein, Anton (Grigoryevich) (b. Nov. 28, 1829, Vykhvati- nets, Podolia province, Russia—d.
Nov. 20, 1894, Peterhof) Russian composer and pianist. Touring as a piano virtuoso, he met Frederic Chopin and Franz Liszt in Paris and Giacomo Meyerbeer in Berlin. After several years of study, in 1848 he settled in St. Petersburg, where in 1862 he founded the St. Petersburg Conservatory and thereafter devoted much energy to improving the qual¬ ity of Russian musical education. His once popular compositions, includ¬ ing six symphonies, five piano con¬ certos, and many chamber works and piano pieces (including “Melody in F”) have largely disappeared from the repertoire. His brother Nicolay (1835-81), also a famous pianist and teacher, founded the Moscow Con¬ servatory in the 1860s.
Rubinstein, Artur (b. Jan. 28, 1887, Lodz, Pol.—d. Dec. 20, 1982, Geneva, Switz.) Polish-U.S. pianist. His studies with Joseph Joachim led to a debut in Berlin in 1900. He later studied with Ignacy Jan Paderewski as well and performed with moderate success. After some years accompany¬ ing the violinist Eugene Ysaye (1858-1931), he stopped performing for five years (1932-37) to improve his technique and reemerged as a giant of 20th-century music. Moving to the U.S., he became equally noted as soloist and chamber musician, with such partners as Jascha Heifetz and Gregor Piatigorsky (1903-76). Active through his 80s, his repertoire ranged from Johann Sebastian Bach to 20th-century Spanish composers; his playing of
W Frederic Chopin and Johannes Brahms was particularly admired.
■s Rubinstein, Helena (b. Dec. 25, 1870, Krakow, Pol., Austria-
M Hungary—d. April 1, 1965, New York, N.Y., U.S.) Polish-U.S. cosmeti¬