turboprop Hybrid engine that provides jet thrust and also drives a pro¬ peller. It is similar to the turbojet except that an added turbine, behind the combustion chamber, works through a shaft and speed-reducing gears to turn a propeller at the front of the engine. Because of improvements in turbojet design, the turboprop, which is less efficient at high speeds, lost much of its importance in the 1960s, though it is still used for relatively short-range aircraft.
turbot Vtor-botN Species (Scophthalmus maximus, family Scophthalmi- dae or Bothidae) of broad-bodied European flatfish, a highly valued food fish. It lives along sand and gravel shores. It is left-sided (with eyes nor¬ mally on the left side of the head) and scaleless; the head and body are
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1950 I turbulence ► Turing machine
studded with numerous bony knobs. Turbots grow to, at most, 40 in. (1 m) long and weigh about 55 lb (25 kg). Colour varies with the surround¬ ings but is usually gray-brown or light brown with darker markings. A related species is the Black Sea turbot (S. maeoticus). Certain right-sided Pacific flatfish (genus Pleuronichthys, family Pleuronectidae) are also called turbot.
turbulence In fluid mechanics, a flow condition (see turbulent flow) in which local speed and pressure change unpredictably as an average flow is maintained. Common examples are wind and water swirling around obstructions, or fast flow (Reynolds number greater than 2,100) of any sort. Eddies, vortices, and a reduction in drag are characteristics of turbulence. Lowered drag enables golf balls to travel farther than they would do oth¬ erwise, and the dimpled surface of golf balls is meant to encourage tur¬ bulence in the boundary layer. If swimsuits with rough surfaces help swimmers to move faster, as has been claimed, the same explanation may apply.
Turcoman See Turkmen
Turenne \tu-'ren\, Henri de La Tour d'Auvergne, viscount de orig. Henri de La Tour d'Auvergne (b. Sept. 11, 1611,
Sedan, France—d. July 27, 1675,
Sasbach, Baden-Baden) French mili¬ tary leader. He earned his reputation as a military leader in the Thirty Years' War, especially with the cap¬ ture of Turin (1640). Made a marshal of France (1643), he commanded the French army in Germany and joined the Swedish army in conquering Bavaria (1648). In France he joined the aristocrats in the Fronde (1649), but later he skillfully commanded the royal army to defeat the forces led by the prince de Conde, who had allied himself with Spain, and to bring about the Peace of the Pyrenees (1659), which ended France’s war with Spain. Appointed marshal- general (1660), Turenne marched alongside Louis XIV in joint com¬ mand of the French armies in the War of Devolution (1667-68). His bold strategies won numerous victories against the imperial army in Germany (1672-75), but he was killed in action at Sasbach. He was buried with the kings of France at Saint-Denis and later moved to the Invalides by Napo¬ leon, who esteemed Turenne as the greatest military leader in history.
turf In horticulture, the surface layer of soil with its matted, dense veg¬ etation, usually grasses grown for ornamental or recreational use. Such turf grasses include Kentucky bluegrass, creeping bent grass, fine or red fescue, and perennial ryegrass among the popular cool-season types, and Bermuda grass, zoysia grass, and St. Augustine grass among the warm- season types. Turf grasses are often grown on turf, or sod, farms. Plugs, blocks, squares, or strips are cut and transplanted to areas where they quickly establish and grow. Lawns are fine-textured turfs that are mowed regularly and closely to develop into dense, uniformly green coverings that beautify open spaces and provide sports playing surfaces (e.g., tennis lawns, golf and bowling greens, and racing turfs).
Turgenev \tur-'g y a-n y if\, Ivan (Sergeyevich) (b. Nov. 9, 1818,
Oryol, Russia—d. Sept. 3, 1883,
Bougival, near Paris, France) Rus¬ sian novelist, poet, and playwright.
His years at the University of Berlin convinced him of the West’s superi¬ ority and the need for Russia to Westernize. He lived in Europe after c. 1862. He is known for realistic, affectionate portrayals of the Russian
peasantry and for penetrating studies of the Russian intelligentsia who were attempting to move the country into a new age. His most famous early work is “The Diary of a Superfluous Man” (1850), which supplied the epithet “superfluous man” for the weak-willed intellectual protagonist common in 19th-century Russian literature. He gained fame with the short-story cycle A Sportman’s Sketches (1852), which criticizes serfdom. His dramatic masterpiece, A Month in the Country (1855), and the novel Rudin (1856) followed. His interest in change and intergenerational dif¬ ferences is reflected in the controversial Fathers and Sons (1862), his greatest novel. Turgenev’s work is distinguished from that of his contem¬ poraries by its sophisticated lack of hyperbole, its balance, and its con¬ cern for artistic values. His greatest work was always topical, committed literature, having universal appeal in the elegance of the love story and the psychological acuity of the portraiture.
turgor Vtor-gorV Pressure exerted by fluid in a cell that presses the cell membrane against the cell wall. Turgor is what makes living plant tissue rigid. Loss of turgor, resulting from the loss of water from plant cells, causes flowers and leaves to wilt. Turgor plays a key role in the opening and closing of stomata (see stoma) in leaves.
Turgot \tur-'go\, Anne-Robert-Jacques, baron de I'Aulne (b.
May 10, 1727, Paris, France—d. March 18, 1781, Paris) French adminis¬ trator and economist. He entered the royal administrative branch of the magistracy in 1753, then became intendant (governor) of Limoges (1761— 74), where he instituted economic and administrative reforms. A physiocrat, in 1766 he wrote his best-known work, Reflections on the Formation and Distribution of Wealth. In 1774 he was appointed comptroller general by Louis XVI and introduced his Six Edicts to expand economic reforms. His effort to abolish the corvee (unpaid forced labour by peasants) was opposed by the privileged classes, and he was dismissed in 1776.
Turin Italian Torino City (pop., 2001 prelim.: 857,433), Piedmont region, northwestern Italy. Located on the Po River, it was founded by the Taurini. It was partly destroyed by Hannibal in 218 bc. It was made a Roman military colony under Emperor Augustus. A part of the Lombard duchy in the 6th century ad, it became the seat of government under Charlemagne (742-814). It passed to the house of Savoy in 1046. The capital of the kingdom of Sardinia in 1720, Turin was occupied by the French during the Napoleonic Wars. The political and intellectual centre of the Risorgimento movement, it served as the first capital of united Italy (1861-65). During World War II Turin sustained heavy damage from Allied air raids but was rebuilt. It is the focus of Italy’s automotive indus¬ try and an international fashion centre. The Shroud of Turin has been housed in the 15th-century cathedral there since the 16th century.
Turin, Shroud of Linen fragment said to be the burial garment of Jesus. It has been preserved since 1578 in the royal chapel of the Cathedral of San Giovanni Battista in Turin, Italy. Measuring 14.5 by 3.7 ft (4.42 by 1.13 m), it appears to portray images of the back and front of a gaunt, sunken-eyed man. The images contain markings that correspond to the stigmata and stains presumed to be blood. The cloth emerged historically in 1354 and went on exhibition in 1389, first as a representation of the shroud and eventually as the shroud itself. In 1988 independent tests using radiocarbon dating techniques indicated that the cloth had been made c. 1260-1390. Subsequent chemical analyses and other tests, however, sug¬ gested a much older date, possibly even the 1st century.
Turing Vtur-iqV Alan (Mathison) (b. June 23, 1912, London, Eng.—d. June 7, 1954, Wilmslow, Cheshire) English mathematician and logician. He studied at the University of Cambridge and at Princeton’s Institute for Advanced Study. In his seminal 1936 paper “On Computable Numbers,” he proved that there cannot exist any universal algorithmic method of determining truth in mathematics and that mathematics will always contain undecidable (as opposed to unknown) propositions. That paper also introduced the Turing machine. He believed that computers even¬ tually would be capable of thought indistinguishable from that of a human and proposed a simple test (see Turing test) to assess this capability. He did valuable work in cryptography during World War II, playing an impor¬ tant role in breaking the Enigma code used by Germany for radio com¬ munications. After the war he taught at the University of Manchester and began work on what is now known as artificial intelligence.