Angevin \'an-ja-van\ dynasty Descendants of a 10th-century count of Anjou (the source of the adjective Angevin). The Angevin dynasty over¬ laps with the house of Plantagenet but is usually said to consist of only the English kings Henry II, Richard I, and John. Henry established the Angevin empire in the 1150s when he took control of Normandy, Anjou, Maine, and, through his marriage to Eleanor, Aquitaine. When he became the king of England in 1154, Henry extended the Angevin holdings from Scotland to the Pyrenees. English claims to French territory led to the Hundred Years' War; by 1558 the English had lost all their former French lands.
Angilbert Vaq-gsl-.bsrtV Saint (b. c. 740, Aachen, kingdom of the Franks—d. Feb. 18, 814, Centula, Picardy) Frankish poet and prelate at the court of Charlemagne. Of a noble family, he was educated at the pal¬ ace school at Aachen and was a student of Alcuin. In 800 he accompa¬ nied Charlemagne to Rome. He was made lay abbot of Centula (St.- Riquier), Picardy, in 794. His graceful and sophisticated Latin poems offer a picture of life in the imperial circle. Charlemagne’s daughter Bertha and Angilbert were the parents of the historian Nithard.
angina pectoris Van-'jl-ns-'pek-ts-rssV Spasm of chest pain, caused when the heart’s oxygen demand temporarily outpaces its blood supply, usually because of coronary heart disease. A deep, viselike pain in the heart and stomach area commonly spreads to the left arm. Exertion or emo¬ tional stress can bring on angina, obliging the victim to rest until the pain subsides. If rest does not help, drugs can dilate the blood vessels. As heart disease worsens, angina recurs with less exertion.
angiocardiography \ 1 an-je-o- 1 kar-de- , ag-r3-fe\ Method of diagnostic imaging that shows the flow of blood through the heart and great vessels. It is used to evaluate patients for surgery on the cardiovascular system. A contrast medium is introduced through a catheter into a heart chamber. A series of X-ray images shows where the flow narrows, signaling block¬ age of a blood vessel by atherosclerosis.
angiography \,an-je-'ag-r3-fe\ or arteriography \ar-,tir-e-'ag-ra- fe\ X-ray examination of arteries and veins with a contrast medium to dif¬ ferentiate them from surrounding organs. The contrast medium is intro¬ duced through a catheter to show the blood vessels and the structures they supply, including organs. Angiography of diseased leg, brain, or heart arteries is necessary before corrective surgery. See also angiocardiography.
Angiolini V.an-ja-'le-neV, Gasparo or Angelo Gasparini (b. Feb. 9, 1731, Florence—d. Feb. 6, 1803, Milan) Italian choreographer. In 1757 he became ballet master of the Vienna court opera house; in 1761 he col¬ laborated with the composer Christoph Willibald Gluck to produce Don Juan, and he later choreographed other ballets to Gluck’s music. In 1765 Angiolini became ballet master of the Imperial Theatre in St. Petersburg. He was among the first to integrate dance, music, and plot in dramatic ballets, developing the form known as ballet d’action. He maintained a rivalry with Jean-Georges Noverre and disagreed with his interpretation of the ballet d’action.
angioplasty \'an-je-3-,plas-te\ Therapeutic opening of a blocked blood vessel. Usually a balloon is inflated near the end of a catheter (see cath¬ eterization) to flatten plaques (see atherosclerosis) against an artery’s wall. Performed on a coronary artery, angioplasty is a less invasive alternative to coronary bypass surgery in the treatment of coronary heart disease. Com¬ plications, including embolisms and tearing, are rare and results are excel¬ lent, but plaques tend to build up again after the procedure. Angioplasty is also used to expand a severely obstructed heart valve.
angiosperm See flowering plant
Angkor Archaeological site, northwestern Cambodia. Located 4 mi (6 km) north of the modem town of Siem Reap, it was the capital of the Khmer (Cambodian) empire from the 9th to the 15th century. Its most imposing monuments are Angkor Wat, a temple complex built in the 12th century by King Suryavarman II, and Angkor Thom, a temple complex
Angel Falls (Salto Angel), La Gran Sabana region of Bolivar state, Ven¬ ezuela.
G. DE STEINHEIL/SHOSTAL ASSOCIATES
An aquarium angelfish ( Pterophyllum )
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Angkor Wat ► Angola I 73
built c. 1200 by King Jayavarman VII. During the period of great construc¬ tion that lasted more than 300 years, there were many changes in archi¬ tecture as the religious focus changed from Hindu to Buddhist cults. After the Siamese conquest of the Khmer in the 15th century, the ruined city and its temples were buried in the jungle. When the French colonial regime was established in 1863, the entire site became the focus of schol¬ arly interest. During Cambodia’s political upheavals of the late 20th cen¬ tury there was some war damage, but the major problem was one of neglect. Angkor was added to the World Heritage site list in 1992.
Angkor Wat Vaq-kor-'watX Temple complex in Angkor (now in north¬ western Cambodia), the crowning work of Khmer architecture. About 1,700 yards (1,550 m) long by 1,500 yards (1,400 m) wide, it is the world’s largest religious structure. Dedicated to Vishnu, it was built in the 12th cen¬ tury by Suryavarman II. The Wat, an artificial mountain originally sur¬ rounded by a vast external wall and moat, rises in three enclosures toward a flat summit. The five remaining towers (shrines) at the summit are com¬ posed of the repetitive diminishing tiers typical of Asian architecture.
Angle Any member of a Germanic people who, with the Jutes and Sax¬ ons, invaded England in the 5th century ad. According to Bede, their homeland was Angulus, traditionally identified as the Angeln district in Schleswig. They abandoned this area when they invaded Britain, where they settled in the kingdoms of Mercia, Northumbria, East Anglia, and Middle Anglia. Their language was known, even then, as Englisc, and they gave their name to England.
angle In geometry, a pair of rays (see line) sharing a common endpoint (the vertex). An angle may be thought of as the rotation of a single ray from an initial to a terminal position. Clockwise rotation is considered negative and counterclockwise rotation positive. Either may be measured in degrees (one full rotation = 360°) or radians (one full rotation = 2k rad). A 90° angle is called a right angle. Any angle less than 90° is an acute angle. Any angle more than 90° but less than 180° is an obtuse angle.
anglerfish Any of about 210 species of marine fishes (order Lophii- formes) named for their method of “fishing” for prey. The foremost spine of the dorsal fin is located on the head and is modified into a “fishing rod” tipped with a fleshy “bait.” Prey fishes attracted to this lure stray close enough for the anglerfish to swallow them. Often bizarre in form, angler¬ fishes are also characterized by small gill openings and by limblike pec¬ toral and (in some species) pelvic fins. Most species inhabit the sea bottom. In some species the small male bites into the larger female’s body, his mouth fuses with the skin, and the bloodstreams of the two become permanently connected.
Anglesey Vaq-gal-seV Isle of ancient Mona County (pop., 2001: 66,828), Wales. It encompasses Anglesey island, the largest island in England and Wales (276 sq mi [715 sq kmj), and Holy Island. Anglesey island is known for its ancient history and its prehistoric and Celtic remains. By 100 bc the Celts had colonized the island, which became a famous Druid centre and later a stronghold of resistance to the Romans. It finally fell to Agricola in ad 78. It was ruled by the princes of Wales in the 7th-13th centuries, until it was taken by Edward I. Tourism is now an important part of the county’s economy.