Arthurian legend Body of stories and medieval romances centring on the legendary English king Arthur. The stories chronicle Arthur’s life, the adventures of his knights, and the adulterous love between his knight Sir Lancelot and his queen, Guinevere. The legend was popular in Wales before the 11th century, was brought into literature by Geoffrey of Mon¬ mouth, and was adapted by other medieval writers, including Chretien de Troyes, Wace, Layamon, and Sir Thomas Malory, becoming entwined with legends of the Holy Grail. From Victorian times, when interest in the leg¬ end revived, it has figured in major works by Alfred Tennyson (Idylls of the King) and T.H. White (The Once and Future King). It is uncertain whether Arthur was a historical figure. Medieval sources say he was a 6th-century warrior and champion of Christianity who united the British tribes against the Saxon invaders, died in battle at Camlann c. 539, and was buried at Glastonbury. See also Galahad; Merlin; Tristan and Isolde.
Arthur's Pass or Arthur Pass Mountain pass. Southern Alps, New Zealand. It lies at an elevation of 3,020 ft (920 m) at the northern end of the mountain range and provides the main railway and highway passage.
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112 I Artibonite River ► Aruba
with the rail line passing through the Otira Tunnel (5.3 mi [8.6 km]). Arthur’s Pass National Park was created in 1929.
Artibonite River \,ar-te-b6-'net\ River, Hispaniola Island. Rising in the Cordillera Central of the Dominican Republic, it flows along the Haitian border and then west and northwest into and through Haiti’s Artibonite Plain to enter the Gulf of Gonaives after a course of some 150 mi (240 km). It is the island’s longest river.
artichoke Large, coarse, herbaceous, thistlelike perennial plant {Cynara scolymus) of the composite family. The thick edible scales and bottom part (heart) of the immature flower heads are a culinary delicacy. The artichoke is native to the Mediterranean and is cultivated extensively in other regions with rich soil and a mild, humid climate. The Jerusalem artichoke is a tuber and does not resemble the artichoke.
Articles of Confederation Early U.S. constitution (1781-89) under the government by the Continental Congress, replaced in 1787 by the U.S. Constitution. It provided for a confederation of sovereign states and gave the Congress power to regulate foreign affairs, war, and the postal ser¬ vice, to control Indian affairs, and to borrow money. Under the Articles, Congress settled state claims to western lands and established the North¬ west Ordinances. But Congress had no power to enforce its requests to the states for money or troops, and by late 1786 the government had ceased to be effective, as was demonstrated by Shays's Rebellion (1786-87) against courts that had been enforcing seizures of property for debt. Delegates to the Annapolis Convention called a meeting of all the states to amend the Articles.
articulation In phonetics, the shaping of the vocal tract (larynx, phar¬ ynx, and oral and nasal cavities) by positioning mobile organs (such as the tongue) relative to other parts that may be rigid (such as the hard palate) and thus modifying the airstream to produce speech sounds. Articulators include the tongue, lips, teeth and upper gum ridge, hard and soft palate, uvula, pharyngeal wall, and glottis. Primary articulation refers either to where or how the vocal tract is narrowed or blocked to produce a con¬ sonant, or to the tongue contour, lip shape, and larynx height that deter¬ mine the sound of a vowel. Other articulators may be used to produce a secondary articulation such as palatalization (the front of the tongue approaching the hard palate), glottalization (complete or partial closure of the vocal cords), or nasalization (simultaneous passage of air through the nasal and oral tracts).
artificial heart Machine or mechanical pump that maintains blood cir¬ culation in the human body. The heart-lung machine, a mechanical pump, can maintain circulation for a few hours while the heart is stopped for surgery. It shunts blood away from the heart, oxygenates it, and returns it to the body. No device has yet been developed for total, long-term replace¬ ment of the heart; existing artificial hearts reduce the heart’s workload by pumping between beats or acting as an auxiliary ventricle and are suit¬ able only as temporary replacements in patients awaiting transplant. See also PACEMAKER.
artificial insemination Introduction of semen into a female’s vagina or cervix by means other than sexual intercourse. First developed for ani¬ mal breeding in the early 20th century in Russia, it is now also used to induce pregnancy in women whose partners cannot impregnate them. The partner’s (or other donor’s) semen is inserted with a syringe. Though rea¬ sonably successful, artificial insemination in humans raises moral issues that are not yet fully resolved. In livestock, deep-frozen semen from a male animal can be stored for long periods without losing its fertility, thus allowing a single bull to sire as many as 10,000 calves a year.
artificial intelligence (Al) Ability of a machine to perform tasks thought to require human intelligence. Typical applications include game playing, language translation, expert systems, and robotics. Although pseudo-intelligent machinery dates back to antiquity, the first glimmer¬ ings of true intelligence awaited the development of digital computers in the 1940s. AI, or at least the semblance of intelligence, has developed in parallel with computer processing power, which appears to be the main limiting factor. Early AI projects, such as playing chess and solving math¬ ematical problems, are now seen as trivial compared to visual pattern rec¬ ognition, complex decision making, and the use of natural language. See also Turing test.
artificial respiration Breathing induced by any of several techniques in a person who has stopped or is having difficulty breathing. It consists chiefly of keeping the air passage open and inducing inhalation and exha¬
lation. It does not include chest compressions to maintain circulation (see cardiopulmonary resuscitation). The primary method is mouth-to-mouth breathing, in which the rescuer breathes into the victim’s mouth, with pauses to allow exhalation.
Artigas \ar-'te-gas\, Jose Gervasio (b. June 19, 1764, probably Montevideo [Uru.]—d. Sept. 23, 1850, Ibiray, near Asuncion, Para.) Sol¬ dier and revolutionary leader regarded as the father of Uruguayan inde¬ pendence. In his youth Artigas was a gaucho in what is now Uruguay. Allied with the Buenos Aires junta, he fought for independence from Spain and won a brilliant victory at Las Piedras. His insistence on fed¬ eralism against the efforts of Buenos Aires to assert control over the entire region led to civil war. He ruled over a portion of what is now Uruguay and central Argentina until a Portuguese invasion forced him into exile in 1820. Uruguay achieved independence in 1828.
artillery In modern military science, big guns such as cannons, howit¬ zers, or mortars operated by crews and of a calibre greater than 15 mm. The earliest artillery, introduced in the 14th century, were cannons and mortars of bronze, brass, or iron mounted on two-wheeled carriages. Mod¬ ern artillery dates from the second half of the 19th century, when advances included steel gun barrels, more powerful gunpowders, and piston mount¬ ings that held artillery carriages steady during recoil. Both powder and projectile were encased in a shell, which allowed for faster loading. Since World War II, artillery has been ranked as light (up to 105 mm, for support of ground troops), medium (106-155 mm, for bombardment), and heavy (over 155 mm, for attacking rear installations). See also antiaircraft gun.
Arts and Crafts movement English social and aesthetic movement of the second half of the 19th century, dedicated to reestablishing the importance of craftsmanship in an era of mechanization and mass pro¬ duction. The name derives from the Arts and Crafts Exhibition Society (1888). Inspired by John Ruskin and other writers who deplored the effects of industrialization, William Morris founded a firm of interior designers and manufacturers to produce handcrafted textiles, printed books, wall¬ paper, furniture, jewelry, and metalwork. The movement was criticized as elitist and impractical in an industrial society, but in the 1890s its appeal widened and spread to other countries, including the U.S. See also Art Nouveau.