Ackermann, Konrad Ernst (baptized Feb. 4, 1712, Schwerin, Mecklenburg—d. Nov. 13, 1771, Hamburg) German actor-manager. After training with a theatre company that specialized in German adaptations of French plays, he led a troupe on tour throughout Europe in the 1750s. He became known for domestic drama and for playing roles that com¬ bined the comic and the sentimental. In 1765 he opened a theatre in Ham¬ burg, considered the first German national theatre, and later turned its management over to his stepson, Friedrich L. Schroder (1744-1816), who brought Shakespeare to the German stage. See also actor-manager system.
ACLU See American Civil Liberties Union
acne \'ak-ne\ Inflammatory disease of the oil glands of the skin. Acne vulgaris, probably the most frequent chronic skin disorder, results from an interplay of hereditary factors, hormones, and bacteria, beginning in the teen years when overactive sebaceous glands are stimulated by high levels of androgens. Its primary lesion, the blackhead, may be open or closed; it consists of a plug of skin oil (sebum), cell debris, and micro¬ organisms in a hair follicle. Acne has four grades of severity, with increas¬ ing degrees of spread, inflammation, pustule formation, and scarring. Methods of treatment vary from skin medication to antibiotics and hor¬ mones; many cases eventually resolve spontaneously.
Acoma Va-ko-moX Indian pueblo, west-central New Mexico, U.S. It is located on a reservation west of Albuquerque and is known as the “Sky City.” Its people live in terraced dwellings made of stone and adobe atop a sandstone butte 357 ft (109 m) high. Settled in the 10th century, it is believed to be the oldest continuously inhabited place in the U.S. In 1540 Spanish explorer Francisco Vazquez de Coronado described it as the strongest defensive position in the world.
Aconcagua X.a-kon-'ka-gwaX, Mount Mountain, western Argentina, on the Chilean border. Located in the Andes Mountains at an elevation of 22,834 ft (6,960 m), it is widely considered the highest peak in the West¬ ern Hemisphere. It is of volcanic origin but is not itself an active volcano. The summit was first reached in 1897.
aconite X'a-ka-.nltX Any member of two genera of perennial herbaceous plants of the buttercup family: Aconitum (monkshood or wolfsbane), con¬ sisting of summer-flowering poisonous plants, and Eranthis (winter aco¬ nite), consisting of spring-flowering ornamentals. The dried tuberous root of A. napellus was formerly used as a sedative and a painkiller.
acorn Nut of the oak. Acorns are usually seated in or surrounded by a woody cupule. They mature within one to two seasons, and their appear¬ ance varies depending on the species of oak. Acorns provide food for wildlife and are used to fatten swine and poultry.
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12 I Acosta ► acting
Acosta \a-'k6-sta\, Uriel orig. Gabriel da Costa (b. c. 1585, Oporto, Port.—d. April 1640, Amsterdam, Neth.) Portuguese Jewish free¬ thinker. Born into a Marrano family, he came to feel that there was no salvation through the Roman Catholic church and converted to Judaism. His mother and brother also converted, and he and his family fled to Amsterdam. In 1616 he attacked rabbinic Judaism as nonbiblical and was excommunicated. When he enlarged on his criticisms in 1623-24, deny¬ ing the immortality of the soul, he was arrested and fined. He recanted but was later excommunicated again. He recanted publicly in 1640, after which he wrote a short autobiography. Example of a Human Life , and shot himself.
acoustics \3-'ku-stiks\ Science of production, control, transmission, reception, and effects of sound. Its principal branches are architectural, environmental, musical, and engineering acoustics, and ultrasonics. Envi¬ ronmental acoustics focuses on controlling noise produced by aircraft engines, factories, construction machinery, and general traffic. Musical acoustics deals with the design and use of musical instruments and how musical sounds affect listeners. Engineering acoustics concerns sound recording and reproduction systems. Ultrasonics deals with ultrasonic waves, which have frequencies above the audible range, and their appli¬ cations in industry and medicine.
acoustics, architectural Relationship between sound produced in a space and its listeners, of particular concern in the design of concert halls and auditoriums. Good acoustic design takes into account such issues as reverberation time; sound absorption of the finish materials; echoes; acoustic shadows; sound intimacy, texture, and blend; and external noise. Architectural modifications (e.g., orchestral shells, canopies, and undu¬ lating or angled ceilings and walls) may act as focusing elements to improve sound quality.
acquired immunodeficiency syndrome See AIDS Acre See 'Akko
acrobatics Art of jumping, tumbling, and balancing. The art is of ancient origin; acrobats performed leaps, somersaults, and vaults at Egyp¬ tian and Greek events. Acrobatic feats were featured in the commedia dell'arte theatre in Europe and in jingxi (“Peking opera”) in China. The later use of apparatuses such as poles, tightropes, and flying trapezes made acrobatics a major attraction in circus performances. Its popularity increased in the 20th century with such performers as the Flying Wallen- das (see Karl Wallenda).
acromegaly V.a-kro-'me-go-leN Growth and metabolic disorder in which the skeletal extremities enlarge when a pituitary gland tumor causes over¬ production of growth hormone after maturity. It is often associated with pituitary gigantism. Acromegaly is characterized by gradual enlargement of hands and feet, exaggeration of facial features, skin thickening, and enlargement of most internal organs, along with headaches, excessive sweating, and high blood pressure. Acromegalic individuals are likely to develop congestive heart failure, muscle weakness, joint pain, osteoporo¬ sis, and often diabetes mellitus and visual problems, including blindness. If treatment with surgery and/or radiation fails, then hormone therapy is used. Treatment can cause hormone deficiency, necessitating hormone replace¬ ment therapy; spontaneous events may also cause hormone deficiency.
acropolis (Greek: “city at the top”) Central, defensively oriented dis¬ trict in ancient Greek cities, located on the highest ground and contain¬ ing the chief municipal and religious buildings. The renowned Athens Acropolis (5th century bc), atop a craggy walled hill, is home to four main edifices—the Propylaea (see propylaeum), Parthenon, Erechtheum (Ionic temple noted for its caryatid porch), and Temple of Athena Nike—all built from white marble plentiful in the region. See photograph opposite.
acrostic Originally, a short verse composition, constructed so that one or more sets of letters (such as the initial, middle, or final letters of the lines), taken consecutively, form words. An acrostic in which the initial letters form the alphabet is called an abecedarius. Ancient Greek and Latin writers, medieval monks, and Renaissance poets are among those who devised acrostics. Today the term is used for a type of word puzzle uti¬ lizing the acrostic principle. A popular form is double acrostics, puzzles constructed so that the middle or last, as well as initial, letters of lines may form words.
acrylic compound Any of a class of synthetic plastics, resins, and oils used to manufacture many products. By varying the starting reagents
(such as acrylic acid, C 3 H 4 0 2 , or acrylonitrile, C 3 H 3 N) and the process of forming, a material may be produced that is hard and transparent, soft and resilient, or a viscous liquid. Acrylic compounds are used to make molded structural and optical parts, jewelry, adhesives, coating com¬ pounds, and textile fibres. Lucite and Plexiglas are trademarks used for glasslike acrylic materials.