synchrotron radiation Electromagnetic radiation emitted by charged particles that are moving at speeds close to that of light when their paths are altered. It is so called because it is produced by high-speed particles in a synchrotron. Such radiation is highly polarized (see polarization) and continuous. Its intensity and frequency depend on the strength of the mag¬ netic field that alters the path of the particles, as well as on the energy of those particles. Synchrotron radiation at radio frequencies is emitted by high-energy electrons as they spiral through magnetic fields in space, such as those around Jupiter. Synchrotron radiation is emitted by a variety of astronomical objects, from planets to supernova remnants to quasars.
syncope Vsiq-k3-pe\ Effect of temporary impairment of blood circula¬ tion to a part of the body. It is often used as a synonym for fainting, which is loss of consciousness due to inadequate blood flow to the brain. Pale¬ ness, nausea, sweating, and then pupil dilation, yawning, deep rapid breathing, and rapid heartbeat usually precede it. It lasts from under a minute to several minutes and may be followed by headache, confusion, and a weak feeling. The cause may be physical (e.g., heart failure, low blood sugar) or emotional (e.g., fear, anxiety). Abnormal vagus or auto¬ nomic nerve response can cause fainting (without preceding symptoms) triggered by ordinary activities such as urination, swallowing, coughing, or standing up or by pressure on the pulse point in the neck. Local syn¬ cope is coldness and numbness in a small area, especially the fingers, from diminished blood flow.
syndicalism Vsin-di-ko-.li-zomN Movement advocating direct action by the working class to abolish the capitalist order, including the state, and to replace it with a social order based on the syndicat, a free association of self-governing producers. Developed as a doctrine by leaders of the French trade union movement at the end of the 19th century, syndicalism was strongly influenced by the traditional anarchism and antiparliamen- tarianism of the French working class. Syndicalists looked forward to victory in a class war, after which society would be organized around the syndicats. These bodies would coordinate their activities through a labour exchange, which would function as an employment and economic plan¬ ning agency. At the peak of its influence, before World War I, the move¬ ment had in excess of one million members in Europe, Latin America,
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1858 I Synge ► Syria
and the U.S. After the war, syndicalists tended to drift toward the Soviet model of communism or to be lured by the ostensible benefits offered by labour unions and democratic reforms. See also corporatism.
Synge VsiqX, John Millington (b. April 16, 1871, Rathfarnham, near Dublin, Ire.—d. March 24, 1909, Dublin) Irish playwright. After study¬ ing languages and music in Dublin and France, he met William Butler Yeats, who advised Synge to go to the west coast of Ireland to draw material from life. From 1899 to 1902 he spent his summers on the Aran Islands, observing the people and learning their language; he based his first plays, In the Shadow of the Glen (1903) and Riders to the Sea (1904), on island¬ ers’ stories. His travels on the Irish west coast inspired his most famous play. The Playboy of the Western World (1907); its unsentimental treat¬ ment of Irish character traits caused riots at its opening at the Abbey The¬ atre. His unfinished Deirdre of the Sorrows was performed in 1910. A poetic dramatist of great power, he was a leading figure of the Irish liter¬ ary RENAISSANCE.
synodic \so-'na-dik\ period Time required for a body in the solar sys¬ tem to return to the same or about the same position relative to the Sun as seen from Earth. The Moon’s synodic period is the time between succes¬ sive recurrences of the same phase (e.g., the period between one full moon and the next). A planet’s synodic period is the time required for Earth to overtake it as both go around the Sun or (in the case of fast-moving Mer¬ cury or Venus) for the other planet to overtake Earth. See also sidereal PERIOD.
syntax Arrangement of words in sentences, clauses, and phrases, and the study of the formation of sentences and the relationship of their com¬ ponent parts. In English, the main device for showing this relationship is word order; for example, “The boy loves his dog” follows standard subject-verb-object word order, and switching the order of such a sen¬ tence would change the meaning or make the sentence meaningless. Word order is much more flexible in languages such as Latin, in which word endings indicate the case of a noun or adjective; such inflections make it unnecessary to rely on word order to indicate a word’s function in the sentence.
synthesizer Machine that electronically generates and modifies sounds, frequently with the use of a digital computer, for use in the composition of electronic music and in live performance. The synthesizer generates wave forms and then subjects them to alteration in intensity, duration, frequency, and timbre. It may use subtractive synthesis (removing unwanted compo¬ nents from a signal containing a fundamental and all related overtones), additive synthesis (building tones from signals for pure sine-wave tones), or other techniques, most importantly whole-sound sampling (digital recording of sounds, usually from acoustic instruments). The first synthe¬ sizer was developed c. 1955 by RCA. Compact, commercially viable syn¬ thesizers, generally with pianolike keyboards, were produced in the 1960s by Robert Moog (born 1934), Donald Buchla (born 1937), and others. With transistor technology, these soon became portable and cheap enough for practical performance use, and such instruments became fixtures in rock bands, often displacing electric pianos and organs. See also MIDI.
synthetic ammonia process See Haber-Bosch process
syphilis \'si-fa-bs\ Sexually transmitted disease caused by the spirochete Treponema pallidum. Without treatment, it may progress through three stages: primary, characterized by a chancre and low fever; secondary (weeks to months later; only half of those infected display symptoms), with a skin and mucous-membrane rash, lymph node swelling, and bone, joint, eye, and nervous system involvement; and tertiary. The tertiary stage follows a latency period that can last years, and only one-fourth of those infected display tertiary symptoms. These can be benign or incapacitat¬ ing and even fatal; almost any part of the body may be attacked. Syphilis can spread to a fetus from an infected mother. Other species of Treponema cause similar but milder, nonsexually transmitted forms of syphilis (see yaws). Several blood tests can detect syphilis, even during latency. Anti¬ biotic treatment is effective.
Syr Darya \,sir-d3r-'ya\ ancient Jaxartes River River, Central Asia, in Uzbekistan, Tajikistan, and Kazakhstan. Formed by the confluence of two headstreams in the fertile Fergana Valley, it flows west-northwest for 1,374 mi (2,212 km) to empty into the Aral Sea. Its lower course is on the eastern edge of the Kyzylkum desert. It is the longest river in Central Asia but carries less water than does the Amu Darya. It is used extensively for hydroelectric power and irrigation.
Syracuse Italian Siracusa ancient Syracusae Seaport city (pop., 2001 prelim.: 121,000), eastern coast of Sicily, Italy. Founded in 734 bc by Greeks from Corinth, it was seized by Hippocrates of Gela in 485 bc and ruled by tyrants until a revolution established a democratic govern¬ ment c. 465 bc. In 413 bc, during the Peloponnesian War, Syracuse defeated an Athenian invasion force. Under the rule of Dionysius I the Elder (405-367 bc), it became the most powerful of the Greek cities, fighting three wars against rival Carthage. Syracuse fell to Rome in 211 bc. It was sacked by Frankish invaders in ad 280 and captured by Arabs in 878; its importance waned in medieval times. Now the commercial centre for an agricultural district, it also supports the fishing and tourist industries. It has many examples of medieval and Renaissance architecture as well as Greek and Roman ruins. It is the birthplace of Theocritus and Archimedes.