seismic Vslz-mik\ wave Vibration generated by an earthquake, explo¬ sion, or similar phenomenon and propagated within the Earth or along its surface. Earthquakes generate two principal types of waves: body waves, which travel within the Earth, and surface waves, which travel along the surface. Seismograms (recorded traces of the amplitude and frequency of seismic waves) yield information about the Earth and its subsurface struc¬ ture; artificially generated seismic waves are used in oil and gas pros¬ pecting.
seismology \slz-'ma-l9-je\ Scientific discipline concerned with the study of earthquakes and of the propagation of seismic waves. A branch of geophysics, it has provided much information about the composition and state of the planet’s interior. Recent work has focused on predicting earth¬ quakes in hopes of minimizing the risk to humans. Seismologists have also studied quakes induced by human activities—such as impounding water behind high dams, injecting fluids into deep wells, and detonating underground nuclear explosions—in an effort to find ways of controlling natural earthquakes.
Seistan See Sistan Seiyukai See Rikken Seiyukai
Sejanus \si-'ja-n3s\, Lucius Aelius (d. ad 31) Administrator of the Roman empire for Tiberius. In ad 14 he became prefect of the Praetorian Guard and gained the emperor’s confidence. After the suspicious death of Tiberius’s son Drusus in 23, Sejanus sought to discredit Agrippina the Elder, mother of Tiberius’s probable heirs. Forbidden to marry Drusus’s widow, Sejanus moved the emperor to Capri (27) and had Agrippina and her son Nero exiled (29). The emperor suspected Sejanus of plotting a coup and had him executed, to widespread relief.
Sejong Vse-'j6q\ (b. 1397— d. 1450) Monarch of the Choson dynasty in Korea during whose reign (1419-50) Korean cultural achievements reached a high point. Sejong oversaw the creation of hangul, the Korean alphabet (see Korean language), and banned Buddhist monks from Seoul, thereby reducing the power and wealth of the Buddhist hierarchy.
Seki Takakazu also called Seki Kowa (b. c. 1640, Fujioka, Japan—d. Oct. 24, 1708, Edo) The most important figure of the wasan (“Japanese calculation”) tradition that flourished from the early 17th cen¬ tury until the opening of Japan to the West in the mid-19th century. He was adopted at an early age by Seki Gorozaemon, a samurai official with the Bureau of Supply in Edo, to carry on the Seki family name. He assumed various positions as an examiner of accounts for the lord of Kofu, Tokugawa Tsunashige (until 1678), and then his son, the future shogun Tokugawa Ienobu (see Tokugawa period). Seki’s most productive research was in algebra, a field in which he created powerful new tools and pro¬ vided many definitive solutions. He was instrumental in recovering math¬ ematical knowledge from ancient Chinese sources. He substituted a tabular notational system for the cumbersome Chinese method of count¬ ing rods, thereby simplifying the handling of equations with more than one unknown.
Seku, Ahmadu See Ahmadu Seku Selassie, Haile See Haile Selassie
Seldes Vsel-dosV George (b. Nov. 16, 1890, Alliance, N.J., U.S.—d. July 2, 1995, Hartland Four Comers, Vt.) U.S. journalist. He became a reporter in 1909. From 1918 to 1928 he worked for the Chicago Tribune, then quit to pursue independent journalism. In You Can’t Print That (1928) he criticized censorship and strictures on journalists, a continuing theme in his career. He reported on the rise of fascism in Italy and Spain in the 1930s,
and he and his wife published In Fact, a journal devoted to press criticism, in the years 1940-50. His other targets included the tobacco industry and J. Edgar Hoover. He published his memoirs, Witness to a Century, in 1987. His brother, the critic Gilbert Seldes (1893-1970), was managing editor of The Dial during the 1920s. George Seldes’s best-known book was The Seven Lively Arts (1924). He was a columnist for the New York Evening Journal and the Saturday Evening Post, film critic for The New Republic, first director of television for CBS News, and first dean of the University of Pennsylvania’s Annenberg School for Communication.
selection In biology, the preferential survival and reproduction or pref¬ erential elimination of individuals with certain genotypes, by means of natu¬ ral or artificial controlling factors. The theory of evolution by natural selection was proposed by Charles Darwin and Alfred Russel Wallace in 1858. Artificial selection differs from natural selection in that inherited variations in a species are manipulated by humans through controlled breed¬ ing in order to create qualities economically or aesthetically desirable to humans, rather than useful to the organism in its natural environment.
Selene \so-'le-ne\ Latin Luna In Greek and Roman religion, the goddess that personified the Moon. Her parents were the Titans Hyperion and Theia; her siblings were Helios and Eos, the goddess of dawn. Selene fell in love with Endymion, a handsome young shepherd; Zeus cast Endymion into eternal sleep, but Selene visited him in the cave where he slept, and he fathered her 50 daughters (one for each lunar month between Olym¬ piads) and, according to some accounts, Narcissus. In art Selene is often represented as a woman with the crescent moon on her head. As Luna she had temples in Rome on the Aventine and Palatine hills.
Selenga \,si-liq-'ga\ River River, Mongolia and east-central Russia. It is formed by the confluence of the Ider and Delger rivers and receives the Orhon River at Suhbaatar. It continues north into Russia, eventually flowing into Lake Baikal after a course of 920 mi (1,480 km). It is navigable from its mouth to beyond Suhbaatar from May to October, when it is free of ice.
selenium \s9-'le-ne-9m\ Semimetallic chemical element, chemical sym¬ bol Se, atomic number 34. It is widely distributed, usually in small amounts, occasionally uncombined but more often as selenides of iron, lead, silver, or copper. Selenium has several allotropes; the gray metallic crystalline form is the most stable at room temperature. Its electrical con¬ ductivity increases when light strikes it, and it can convert light directly into electricity, so selenium is used in photocells (e.g., in light meters and security alarms), solar cells, and photocopiers. It also has been used in rec¬ tifiers to convert alternating to direct electric current. It serves as a red colorant for glass and glazes. Selenium has valence 2, 4, and 6 in its com¬ pounds, many of which are toxic though the element is not. Selenium dioxide is an important reagent in organic chemistry. Vital to living cells, it works as an antioxidant in the body and is being studied for a variety of possible beneficial health effects; it is used in nutritional supplements and animal feeds.
Seles Vse-losV Monica (b. Dec. 2, 1973, Novi Sad, Yugos.) Yugoslav- U.S. tennis player. She went to the U.S. to train in 1985. She developed quickly and became one of the dominant women stars of the 1990s, achieving multiple wins in all grand-slam tournaments (French Open, 1990-92; Australian Open, 1991-93, 1996; U.S. Open, 1991-92) except Wimbledon, which she lost in 1991 and 1992 to her rival Steffi Graf. In 1993 she stopped competing temporarily after being stabbed by a Graf fan on a court in Hamburg, Ger.
Seleucia \sa-1u-sh3\ on the Tigris Ancient city, on the Tigris River, central Iraq. Founded by Seleucus I Nicator in the late 4th century bc as his eastern capital, it replaced Babylon as Mesopotamia’s leading city. The population, which Pliny the Elder estimated at 600,000, was composed largely of Macedonians and Greeks and also included Jews and Syrians. During the Parthian domination of the Tigris-Euphrates valley that began in the 2nd century bc, it maintained its position and trade despite its Greek sympathies. In ad 165 the Romans burned the city, marking the end of Hellenism in Mesopotamia. See also Seleucid dynasty.
Seleucid dynasty \s3-'lu-s3d\ Macedonian Greek dynasty (312-64 bc) founded by Seleucus I Nicator. Carved from the empire of Alexander the Great, the Seleucid domain stretched from Thrace to the border of India and included Babylonia, Syria, and Anatolia. Seleucus was suc¬ ceeded in 281 by Antiochus I Soter, who reigned until 261. He was fol¬ lowed by Antiochus II (r. 261-246), Seleucus II Calunicus (r. 246-225), Seleucus III (r. 225-223), and Antiochus III (the Great; r. 223-187). Under