ischemia (reduced blood supply), must be distinguished from those due to hemorrhage (bleeding), which are usually severe and often fatal. Depending on its site in the brain, a stroke’s effects may include aphasia, ataxia, local paralysis, and/or disorders of one or more senses. A massive stroke can produce one-sided paralysis, inability to speak, coma, or death within hours or days. Anticoagulants can arrest strokes caused by clots but worsen those caused by bleeding. If the cause is closure of the major artery to the brain, surgery may clear or bypass the obstruction. Reha¬ bilitation and speech therapy should begin within two days to retain and restore as much function as possible, since survivors may live many more years. Transient ischemic attacks (“mini strokes”), with short-term loss of function, result from blockage of blood flow to small areas. They tend to recur and may worsen, leading to multi-infarct dementia or stroke.
stromatolite \stro- , ma-t 3 l-,It\ Layered deposit, mainly of limestone, formed by the growth of blue-green algae (see cyanobacteria). These struc¬ tures are usually characterized by thin, alternating light and dark layers that may be flat, hummocky, or dome-shaped. Stromatolites were com¬ mon in Precambrian time (more than 543 million years ago). Some of the first forms of life on Earth are recorded in stromatolites in rocks 3.5 bil¬ lion years old. Stromatolites continue to form in certain areas today, most abundantly in Shark Bay in western Australia.
Stromboli \ , stram-bo-( l )le\ Volcano, Stromboli Island, off northeastern Sicily, Italy. One of Europe’s most active volcanoes, it is 3,038 ft (926 m) high. Though the last serious eruption was in 1921, lava flows continu¬ ously from its crater to the sea. Tourists are attracted to the island by its volcano, climate, and beaches.
Strong, William (b. May 6, 1808, Somers, Conn., U.S.—d. Aug. 19, 1895, Lake Minnewaska, N.Y.) U.S. jurist. He served in the U.S. House of Representatives (1847-51) and on the Pennsylvania state supreme court (1857-68). In 1870 he was appointed to the U.S. Supreme Court by Ulysses S. Grant. In 1871 he spoke for the majority as the court overturned the Hepburn decision of the previous year, a reversal that allowed Congress the power to issue paper money as legal tender, a position favoured by Grant. Strong retired from the court in 1880.
strong force or strong nuclear force Fundamental force acting between elementary particles of matter, mainly quarks. The strong force binds quarks together in clusters to form protons and neutrons and heavier short-lived particles. It holds together the atomic nucleus and underlies interactions among all particles containing quarks. In strong interactions, quarks exchange gluons, carriers of the strong force, which are massless particles with one unit of intrinsic spin. Within its short range (about 10 -15 m), the strong force appears to become stronger with distance. At such distances, the strong interaction between quarks is about 100 times greater than the electromagnetic force.
strontium \'stran(t)-she-3m, 'stran-te-omN Chemical element, one of the alkaline earth metals, chemical symbol Sr, atomic number 38. A soft metal, it has a silvery lustre when freshly cut but reacts rapidly with air. In both the metal and the compounds (in which it has valence 2), strontium resembles calcium and barium so closely that it has few uses that the other two elements cannot supply more cheaply. The nitrate and chlorate, very volatile, give off brilliant crimson flames and are used in flares, fireworks, and tracer bullets. The radioactive isotope strontium-90 (see radioactivity), produced in nuclear explosions, is the principal health hazard in fallout; it can replace some of the calcium in foods, concentrate in bones and teeth, and cause radiation injury.
structural geology Scientific discipline concerned with rock defor¬ mation on both small and large scales. Its scope ranges from submicro- scopic lattice defects in crystals to fault structures and fold systems of the Earth’s crust. Depending on the scale, the general techniques used are the same as those used in petrology, field geology, and geophysics. Further¬ more, since the processes that cause rocks to deform can rarely be observed directly, computer models are also used.
structural system In building construction, the particular method of assembling and constructing structural elements of a building so that they support and transmit applied loads safely to the ground without exceed¬ ing the allowable stresses in the members. Basic types of systems include bearing-wall, post-and-beam, frame, membrane, and suspension. They fall into three major categories: low-rise, high-rise, and long-span. Systems for long-span buildings (column-free spaces of over 100 ft, or 30 m) include tension and compression systems (subject to bending) and funic-
"SS. Boris and Gleb," icon by a fol¬ lower of Prokopy Chirin, Stroganov school, 17th century; in the State Trety¬ akov Gallery, Moscow NOVOSTI PRESS AGENCY, MOSCOW
Erich von Stroheim in Foolish Wives,
BROWN BROTHERS
© 2006 Encyclopaedia Britannica, Inc.
1834 I structuralism ► Stubbs
ular systems, which are shaped to experience either pure tension or pure compression. Bending structures include the girder and two-way grids and slabs. Funicular structures include cable structures, membrane structures, and vaults and domes. See also framed structure; post-and-beam system; shell
STRUCTURE.
structuralism European critical movement of the mid-20th century. It is based on the linguistic theories of Ferdinand de Saussure, which hold that language is a self-contained system of signs, and the cultural theo¬ ries of Claude Levi-Strauss, which hold that cultures, like languages, can be viewed as systems of signs and analyzed in terms of the structural rela¬ tions among their elements. Central to structuralism is the notion that binary oppositions (e.g., male/female, public/private, cooked/raw) reveal the unconscious logic or “grammar” of a system. Literary structuralism views literary texts as systems of interrelated signs and seeks to make explicit their hidden logic. Prominent figures in the structuralist move¬ ment are Michel Foucault, Jacques Lacan, Roman Jakobson, and Roland Barthes. Areas of study that have adopted and developed structuralist pre¬ mises and methodologies include semiotics and narratology. See also DECONSTRUCTION.
Structured Query Language See SQL
Struma River River, western Bulgaria and northeastern Greece. Ris¬ ing in the Rhodope Mountains southwest of Sofia, Bulg., it courses 258 mi (415 km) southeast to the Aegean Sea. Its upper valley is a major source of brown coal for Bulgaria, and its lower course flows through a wide agricultural valley.
Struve Yshtru-vsV Friedrich Georg Wilhelm von (b. April 15, 1793, Altona, Den.—d. Nov. 23, 1864, St. Petersburg, Russia) German- bom Russian astronomer. He left Germany for Russia in 1808 to avoid conscription in the Napoleonic armies; he subsequently joined the faculty at the University of Dorpat and became director of its observatory. The founder of the modern study of binary stars, he measured some 3,000 binaries in his survey of more than 120,000 stars. He was also among the first to measure stellar parallax. In 1835, at the request of Tsar Nicholas I, he went to Pulkovo to supervise construction of a new observatory, becoming its director in 1839. His son, Otto Struve (1819-1905), served as director of Pulkovo Observatory (1862-89); his grandson Gustav Wil¬ helm Ludwig Struve (1858-1920) was director of University of Kharkov observatory; Otto Struve was his great-grandson.
Struve \ English Vstru-ve\, Otto (b. Aug. 12, 1897, Kharkov, Ukraine, Russian Empire—d. April 6, 1963, Berkeley, Calif., U.S.) Russian-bom U.S. astronomer. The great-grandson of Friedrich G.W. von Struve, he sus¬ pended his studies to serve in the Russian army in World War I before immigrating to the U.S. On the staff of Yerkes Observatory, he made important contributions to stellar spectroscopy and astrophysics, notably the discovery of the widespread distribution of hydrogen and other ele¬ ments in space. He served as director of Yerkes (beginning 1932) and later of McDonald Observatory in Texas, which he organized. He later taught at the University of Chicago (beginning 1947) and UC-Berkeley, and he directed the National Radio Astronomy Observatory in Green Bank, W.V. (1959-62). A prolific writer, he published about 700 papers and several books.