entomology Branch of zoology dealing with the scientific study of INSECTS, including their taxonomy, morphology, physiology, and ecology. Applied aspects of entomology, such as the harmful and beneficial impact of insects on humans, are also studied.
entropy \'en-tro-pe\ Measure of a system’s energy that is unavailable for work, or of the degree of a system’s disorder. When heat is added to a system held at constant temperature, the change in entropy is related to the change in energy, the pressure, the temperature, and the change in vol¬ ume. Its magnitude varies from zero to the total amount of energy in a system. The concept, first proposed in 1850 by the German physicist Rudolf Clausius (1822-1888), is sometimes presented as the second law of thermodynamics, which states that entropy increases during irreversible processes such as spontaneous mixing of hot and cold gases, uncontrolled expansion of a gas into a vacuum, and combustion of fuel. In popular, nontechnical use, entropy is regarded as a measure of the chaos or ran¬ domness of a system.
enuresis \,en-yu-'re-s3s\ Repeated urination into bedding or clothing, usually at night, in a normal child old enough to have completed toilet training. Enuresis may be voluntary or involuntary. It may run in fami¬ lies. Stressful life events, poor toilet training, and chronic social disad¬ vantage increase its likelihood. It usually resolves with time. Treatment includes family education, reassurance, and behaviour therapy. An alarm to wake the child when urination begins has proved highly effective but takes time to achieve complete success. Drug treatment, though not the treatment of choice, is sometimes effective.
Enver Pasha \en-'ver-pa-'sha\ (b. Nov. 22, 1881, Constantinople, Otto¬ man Empire—d. Aug. 4, 1922, Baldzhuan, Turkistan) Soldier and poli¬ tician in the Ottoman Empire. He was one of the Young Turks who deposed the Ottoman sultan Abdulhamid II in 1908. He later served as governor of BanghazI, Libya (1912), chief of staff of the Ottoman army in the Sec¬ ond Balkan War (1913), and minister of war during World War I (1914— 18). A rival of Mustafa Kemal AtatOrk in the postwar period, he unsuccessfully sought Soviet help to overthrow him (1920). The Soviets permitted him to help organize the Turkic and Muslim Central Asian republics, but he joined Basmachi rebels against the Soviet Union and was killed fighting the Red Army.
environmental geology Scientific field concerned with applying the findings of geologic research to the problems of land use and civil engi¬ neering. It is closely allied with urban geology and deals with the impact of human activities on the physical environment. Other important con¬ cerns of environmental geology include reclaiming mined lands; identi¬ fying geologically stable sites for constructing buildings, nuclear power plants, and other facilities; and locating sources of building materials, such as sand and gravel.
Environmental Protection Agency (EPA) U.S. government agency that sets and enforces national pollution-control standards. It was established by Pres. Richard Nixon (1970) to supersede a welter of con¬ fusing and ineffective state environmental laws. Its early accomplishments include banning the use of DDT (1972), setting deadlines for the removal of lead from gasoline (1973), establishing health standards for drinking water (1974), and monitoring fuel efficiency in automobiles (1975). The EPA’s enforcement was in large part responsible for a decline of one- third to one-half in most air-pollution emissions in the U.S. from 1970 to 1990, and during the 1980s the pollution standards index improved by half in major cities; water quality and waste disposal also improved sig¬ nificantly. The EPA also oversees the cleanup of abandoned waste sites through Superfund. Its existence has resulted in heightened awareness and concern for the environment worldwide.
environmental sculpture Art form, developed in the 20th century, that involves or encompasses the spectator. The environmental sculptor can use any medium, from mud and stone to light and sound. Indoor envi¬ ronmental works often incorporate sculptural figures in detailed settings in gallery or museum spaces. Outdoor works in natural or urban settings include “earthworks” (large-scale alterations of the Earth’s surface effected by earth-moving equipment) such as Robert Smithson’s Spiral Jetty (1970), a rock-and-dirt spiral 1,500 feet long in the Great Salt Lake. The wrapped buildings of Christo are notable urban environmental works.
environmentalism Advocacy of the preservation or improvement of the natural environment, especially the social and political movement to control environmental pollution. Other specific goals of environmental¬ ism include control of human population growth, conservation of natural resources, restriction of the negative effects of modem technology, and the adoption of environmentally benign forms of political and economic organization. Environmental advocacy at the international level by non¬ governmental organizations and some states has resulted in treaties, con¬ ventions, and other instruments of environmental law addressing problems such as global warming, the depletion of the ozone layer, and the danger of transboundary pollution from nuclear accidents. Influential U.S. and British environmentalists have included Thomas Robert Malthus, John Muir, Rachel Carson, Barry Commoner, Paul R. Ehrlich, and Edward O. Wilson. In the social sciences, the term refers to any theory that empha¬ sizes the importance of environmental factors in the development of cul¬ ture and society.
enzyme Substance that acts as a catalyst in living organisms, regulat¬ ing the rate at which life’s chemical reactions proceed without being altered in the process. Enzymes reduce the activation energy needed to start these reactions; without them, most such reactions would not take place at a
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useful rate. Because enzymes are not consumed, only tiny amounts of them are needed. Enzymes catalyze all aspects of cell metabolism, includ¬ ing the digestion of food, in which large nutrient molecules (including proteins, carbohydrates, and fats) are broken down into smaller molecules; the conservation and transformation of chemical energy; and the con¬ struction of cellular materials and components. Almost all enzymes are proteins; many depend on a nonprotein cofactor, either a loosely associ¬ ated organic compound (e.g., a vitamin; see coenzyme) or a tightly bound metal ion (e.g., iron, zinc) or organic (often metal-containing) group. The enzyme-cofactor combination provides an active configuration, usually including an active site into which the substance (substrate) involved in the reaction can fit. Many enzymes are specific to one substrate. If a com¬ peting molecule blocks the active site or changes its shape, the enzyme’s activity is inhibited. If the enzyme’s configuration is destroyed (see dena- turation), its activity is lost. Enzymes are classified by the type of reac¬ tion they catalyze: (1) oxidation-reduction, (2) transfer of a chemical group, (3) hydrolysis, (4) removal or addition of a chemical group, (5) isomerization (see isomer; isomerism), and (6) binding together of substrate units (polymerization). Most enzyme names end in -ase. Enzymes are chiral catalysts, producing mostly or only one of the possible stereoisomeric products (see optical activity). The fermentation of wine, leavening of bread, curdling of milk into cheese, and brewing of beer are all enzymatic reactions. The uses of enzymes in medicine include killing disease- causing microorganisms, promoting wound healing, and diagnosing cer¬ tain diseases.