COURTESY OF THE WALTERS ART GALLERY, BALTIMORE
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clone ► clown I 421
ern climates, the open-arcaded cloister remained standard. An especially fine example is Donato Bramante’s two-story open arcade at Santa Maria della Pace, Rome (1500^4).
clone Population of genetically identical cells or organisms that origi¬ nated from a single cell or organism by nonsexual methods. Cloning is fundamental to most living things, since the body cells of plants and ani¬ mals are clones that come ultimately from a single fertilized egg. More narrowly, the term refers to an individual organism grown from a single body cell of its parent that is genetically identical to the parent. Cloning has been commonplace in horticulture since ancient times; many variet¬ ies of plants are cloned simply by obtaining cuttings of their leaves, stems, or roots and replanting them. The body cells of adult humans and other animals are routinely cultured as clones in the laboratory. Entire frogs and mice have been successfully cloned from embryonic cells. British researchers led by Ian Wilmut achieved the first success in cloning an adult mammal in 1996. Having already produced clones from sheep embryos, they were able to produce a lamb (Dolly) using DNA from an adult sheep. The practical applications of cloning are economically prom¬ ising but philosophically unsettling.
Close, Chuck (b. July 5, 1940, Monroe, Wash., U.S.) U.S. artist. After early Abstract Expressionist experiments, in his first solo exhibition Close showed a series of enormous black-and-white portraits that he had pains¬ takingly transformed from small photographs to colossal. Photorealist paintings. Throughout his career, he concentrated on portraits—from the neck up—based on photographs he had taken. In addition to self-portraits, the paintings were usually of friends, many of whom were prominent in the art world. He experimented with a variety of media and techniques, including using fingerprints and colourful tiles that, seen from a distance, combined into an illusionistic whole. In 1988 a spinal blood clot left Close almost completely paralyzed and confined to a wheelchair. A brush¬ holding device strapped to his wrist and forearm, however, allowed him to continue working.
Close YklosV Glenn (b. March 19, 1947, Greenwich, Conn., U.S.) U.S. actress. She made her Broadway debut in 1974 and later starred in Bar- num (1980), The Real Thing (1984, Tony Award), and Death and the Maiden (1992, Tony Award). Her film debut in The World According to Garp (1982) was followed by roles in films such as The Natural (1984), Fatal Attraction (1987), and Dangerous Liaisons (1989). She also starred in the acclaimed television film Sarah, Plain and Tall (1991) and later returned to Broadway in Sunset Boulevard (1995, Tony Award).
closed-end trust See investment trust
closed shop Arrangement whereby a company employs only workers who are members in good standing of a specified labour union. It is the most rigid of the various schemes for protecting labour unions (more flexible arrangements include the union shop). Closed shops were declared illegal in the U.S. under the Taf-Hartley Act of 1947, but in practice they continue to exist in some industries, such as construction.
clostridium \klas-'trid-e-3m\ Any of the rod-shaped, usually gram¬ positive bacteria (see gram stain) that make up the genus Clostridium. They are found in soil, water, and the intestinal tracts of humans and other ani¬ mals. Some species grow only in the complete absence of oxygen. Dor¬ mant cells are highly resistant to heat, drying, toxic chemicals, and detergents. The toxins produced by C. botulinum, which causes botulism, are the strongest poisons known. The toxin of C. tetani causes tetanus; other species can cause gangrene.
Cloth of Gold, Field of See Field of Cloth of Gold
cloud Any visible mass of water droplets, ice crystals, or a mixture of the two that is suspended in the air, usually at a considerable height. Clouds are usually created and sustained by upward-moving air currents. Meteorologists classify clouds primarily by their appearance. The 10 main cloud families are divided into three groups on the basis of altitude. High clouds, which are found at mean heights of 45,000-16,500 ft (13-5 km), are, from highest to lowest, cirrus, cirrocumulus, and cirrostratus. Middle clouds, at 23,000-6,500 ft (7-2 km), are altocumulus, altostratus, and nimbostratus. Low clouds, at 6,500-0 ft (2-0 km), are stratocumulus, stratus, cumulus, and cumulonimbus. A shallow layer of cloud at or near ground level is called fog.
cloud chamber Radiation detector developed by C.T.R. Wilson. Its detecting medium is a supersaturated vapour (see saturation) that con¬
denses around ions produced by the passage of energetic charged particles, such as alpha particles, beta particles, or protons. In a Wilson cloud cham¬ ber, supersaturation is caused by the cooling induced by a sudden expan¬ sion of the saturated vapour by the motion of a piston or an elastic membrane. In a diffusion chamber, the saturated vapour is cooled to super¬ saturation as it diffuses into a region kept cold by a coolant such as solid carbon dioxide or liquid helium.
Clouet \klii-'e\, Jean (b. c. 1485—d. c. 1540, Paris, Fr.) French painter. He was chief painter to Francis I and produced many pastel portraits of members of the French court. Clouet was one of the best 16th-century portrait painters, both incisive and delicate in the psychological charac¬ terization of sitters. His drawings are simple, broad, and subtle; his paint¬ ings are fresh in colour, subdued in modeling, and minute in execution. He was celebrated in his lifetime as the equal of Michelangelo. His son Francois Clouet (c. 1515-72) took his place as official painter to Francis I in 1540.
clove Small, reddish brown flower bud of the tropical evergreen tree Syzygium aromaticum (sometimes called Eugenia caryophyllata ), of the myrtle family. The tree is believed to be native to the Moluccas of Indo¬ nesia. Cloves were important in the earliest spice trade. With a strong aroma and hot and pungent taste, they are used to flavour many foods. Clove oil is sometimes used as a local anesthetic for toothaches. Eugenol, its principal ingredient, is used in germicides, perfumes, and mouth¬ washes, in the synthesis of vanillin, and as a sweetener or flavour inten- sifier.
clover Any legume of the genus Trifolium, composed of 300 or more annual and perennial species, found in most temperate and subtropical regions. The alternate, compound leaves usually have three toothed leaflets. The very small, fragrant flowers are crowded into dense heads. Clovers are highly palatable to livestock and high in protein, phos¬ phorus, and calcium, thus providing valuable nourishment in the form of hay, pasture, and silage. They also improve and conserve soil by adding nitrogen and increasing the availabil¬ ity of other nutrients for crops that follow. The most important agricul¬ tural species are red clover (T. prat- ense), white clover (T. repens), and alsike clover (T. hybridum).
Clovis Vklo-v9s\ I German Chlodweg (b. c. 466—d. Nov. 27, 511, Paris, Fr.) Merovingian founder of the Frankish kingdom. The son of Childeric I, king of the Salian Franks, Clovis was still a pagan when he conquered the last Roman ruler in Gaul at Soissons (486). He extended his rule as far south as Paris by 494. His wife, Clotilda, was a Catholic princess later recognized as a saint. She sought to convert Clovis to her faith. According to Gregory of Tours, during a faltering campaign against the Alamanni in 496, Clovis invoked his wife’s god and saw defeat turned to victory. He was baptized at Reims two years later, and he credited St. Martin of Tours for his victory over the Visigoths. Although he was the first Germanic king to accept Catholic Christianity, Clovis expressed inter¬ est in Arian Christianity before converting to his wife’s religion. He pro¬ mulgated the legal code known as the Lex Salica. He is traditionally regarded as the founder of the French monarchy and the original French champion of the Christian faith.