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  • spinet (harpsichord)

    Spinet, small form of the harpsichord, generally wing-shaped, with a single set of strings placed at an oblique angle to the keyboard. The wing-shaped spinet may have originated in Italy during the 16th century; later it became known in France and England. Spinets were popular substitutes for the

  • spinet (piano)

    upright piano: …heights; the shortest are called spinets or consoles, and these are generally considered to have an inferior tone resulting from the shortness of their strings and their relatively small soundboards. The larger upright pianos were quite popular in the later 19th and early 20th centuries. The action (hammer and damper…

  • Spinetti, Victor (Welsh actor)

    Victor Spinetti, (Vittorio Georgio Andrea Spinetti), Welsh actor (born Sept. 2, 1929, Cwm, Ebbw Vale, Wales—died June 19, 2012, Monmouth, Wales), had numerous theatrical roles but was best known for his parts in the Beatles’ movies and his friendship with members of the band. George Harrison asked

  • Spinetti, Vittorio Georgio Andrea (Welsh actor)

    Victor Spinetti, (Vittorio Georgio Andrea Spinetti), Welsh actor (born Sept. 2, 1929, Cwm, Ebbw Vale, Wales—died June 19, 2012, Monmouth, Wales), had numerous theatrical roles but was best known for his parts in the Beatles’ movies and his friendship with members of the band. George Harrison asked

  • Spingarn Medal

    Spingarn Medal, gold medal awarded annually by the National Association for the Advancement of Colored People (NAACP) since 1915 to honour “the man or woman of African descent and American citizenship who shall have made the highest achievement during the preceding year or years in any honorable

  • Spingarn, Joel Elias (American writer, literary critic, educator, and civil rights activist)

    Spingarn Medal: …29, 1914, is named for Joel Elias Spingarn, a white writer, literary critic, educator, and civil rights activist who served as chairman of the Board of Directors (1913–19), treasurer (1919–30), and president (1930–39) of the NAACP.

  • Spinicaudata (crustacean)

    branchiopod: Size range and diversity of structure: In the Spinicaudata, however, the number of paired trunk segments varies among its members from 12 up to 32 in some species. A carapace is present in the infraorders Ctenopoda and Anomopoda, but it encloses only the trunk, leaving the head free. In the infraorders Onychopoda and…

  • Spink, Alfred H. (American author)

    baseball: Baseball and the arts: Both Alfred H. Spink’s The National Game (1910) and A.G. Spalding’s America’s National Game (1911), generally regarded as the first attempts at writing a standard history of baseball, cite “Casey at the Bat” as the best baseball poem ever written. Spalding goes so far as to…

  • Spinks, Leon (American boxer)

    Leon Spinks, American boxer who won an Olympic gold medal in 1976 and was the world heavyweight champion in 1978. He and Michael Spinks became the first brothers to win gold medals in the same sport at the same Olympics and, as professional champions, the first brothers in boxing history to win

  • Spinks, Michael (American boxer)

    Michael Spinks, American boxer who was both the light heavyweight (1981–85) and heavyweight (1985–88) world champion and an Olympic gold medalist (1976). He and Leon Spinks became the first brothers to win gold medals in the same sport at the same Olympics and the first brothers to win world titles

  • spinner (game piece)

    Teetotum, form of top having usually 4, 6, 8, or 12 sides marked with distinctive symbols. A teetotum is used for playing games, mostly of the gambling variety, and serves in place of dice. The hexagonal (six-sided) teetotum was known to the ancient Greeks and Romans. A common gambling game with a

  • spinner shark

    carcharhinid: …somewhat larger large blacktip, or spinner shark (C. maculipinnis). One small species, C. melanopterus, is found in shallow Indo-Pacific waters.

  • spinneret (zoology)

    sericulture: …the insect emerge from the spinneret, a single exit tube in the head, hardening upon exposure to air and forming twin filaments composed of fibroin, a protein material. A second pair of glands secretes sericin, a gummy substance that cements the two filaments together. Because an emerging moth would break…

  • spinneret (fibre manufacturing)

    Spinneret, in the spinning of man-made fibre, small, thimble-shaped, metal nozzle having fine holes through which a spinning solution is forced to form a filament. The viscous or syrupy solution, prepared by melting or chemically dissolving raw material, emerges from the spinneret as long fibres t

  • spinnerette (fibre manufacturing)

    Spinneret, in the spinning of man-made fibre, small, thimble-shaped, metal nozzle having fine holes through which a spinning solution is forced to form a filament. The viscous or syrupy solution, prepared by melting or chemically dissolving raw material, emerges from the spinneret as long fibres t

  • Spinners; or, The Fable of Arachne, The (painting by Velázquez)

    Diego Velázquez: Last years: The Spinners; or, The Fable of Arachne (1655–60), a genre scene in a tapestry factory, is at the same time an illustration of the ancient Greek fable of the spinning contest between Pallas Athena and Arachne. Here the mythological subject—like the religious scene in some…

  • Spinners; or, The Fable of Arachne, The (painting by Velázquez)

    Diego Velázquez: Last years: The Spinners; or, The Fable of Arachne (1655–60), a genre scene in a tapestry factory, is at the same time an illustration of the ancient Greek fable of the spinning contest between Pallas Athena and Arachne. Here the mythological subject—like the religious scene in some…

  • Spinney, Caroll (American actor and puppeteer)

    Big Bird: …created by actor and puppeteer Caroll Spinney, who at the program’s inception and until his retirement in 2018 was the sole performer in the Big Bird role.

  • spinning (yarn manufacturing)

    Spinning, in textiles, process of drawing out fibres from a mass and twisting them together to form a continuous thread or yarn. In man-made fibre production the name is applied to the extrusion of a solution to form a fibre, a process similar to the method by which silkworms and similar insect

  • spinning (fishing)

    fishing: Methods: spin casting differ essentially in the type of reel, the rod length, and the strength of the line used. Bait casting usually employs a reel with heavier line, often in the 10- to 20-pound (4,500- to 9,000-gram) test range. Most spinning reels are usually spooled…

  • spinning (metalwork)

    Spinning, In metalwork, a technique for making hollow metal utensils and artifacts. Developed in the 19th century, the method can be used for most metals. A metal disk is set on a lathe behind an appropriately shaped metal or wooden chuck; while the lathe is rotating, the metal is pressed onto the

  • spinning frame (textiles)

    Drawing frame, Machine for drawing, twisting, and winding yarn. Invented in the 1730s by Lewis Paul and John Wyatt, the spinning machine operated by drawing cotton or wool through pairs of successively faster rollers. It was eventually superseded by R. Arkwright’s water

  • spinning jenny (textiles)

    Spinning jenny, early multiple-spindle machine for spinning wool or cotton. The hand-powered spinning jenny was patented by James Hargreaves in 1770. The development of the spinning wheel into the spinning jenny was a significant factor in the industrialization of the textile industry, though its

  • spinning mule (textiles)

    Spinning mule, Multiple-spindle spinning machine invented by Samuel Crompton (1779), which permitted large-scale manufacture of high-quality thread for the textile industry. Crompton’s machine made it possible for a single operator to work more than 1,000 spindles simultaneously, and was capable of

  • spinning reel (fishing)

    fishing: Early history: …patent on the fixed-spool, or spinning, reel. In this kind of reel, the spool permanently faces toward the tip of the rod, and the line peels off during the cast. The increased casting distance afforded by the spinning reel—and facilitated by new lines with smaller diameters—revolutionized freshwater fishing.

  • spinning top (toy)

    Top, a toy having a body of conical, circular, or oval shape, often hollow, with a point or peg on which it turns or is made to whirl. If given a knock, a spinning top will go around in a circle at a slant; if spun with a slant at the start, it will quickly stand upright until halted by friction.

  • spinning tower (textiles)

    man-made fibre: Solution spinning: …a heated column called the spinning tower, where the solvent evaporates, leaving a fibre. The emerging fibre may contain solvent that may have to be removed by further heating or by washing. This operation is followed by stretching, application of finish, and either take-up on a spindle or cutting to…

  • spinning wheel (textiles)

    Spinning wheel, early machine for turning fibre into thread or yarn, which was then woven into cloth on a loom. The spinning wheel was probably invented in India, though its origins are obscure. It reached Europe via the Middle East in the European Middle Ages. It replaced the earlier method of

  • spinocerebellar degeneration (pathology)

    nervous system disease: Spinocerebellar degenerations: Spinocerebellar degenerations are genetically determined conditions characterized by dysfunction of the dorsal columns or of the corticospinal and spinocerebellar tracts of the spinal cord. These conditions usually appear in the first 20 years of life and cause position sensation, gait, limb power, balance, and coordination…

  • spinocerebellar tract (anatomy)

    human nervous system: Spinocerebellar tracts: Impulses from stretch receptors are carried by fibres that synapse upon cells in deep laminae of the dorsal horn or in lamina VII. The posterior spinocerebellar tract arises from the dorsal nucleus of Clarke and ascends peripherally in the dorsal part of the…

  • spinochrome (biochemistry)

    coloration: Naphthoquinones: These are the echinochromes and spinochromes, so named because they are conspicuous in tissues and in the calcareous tests (shells) of echinoids, or sea urchins.

  • spinodal mechanism (chemistry)

    industrial glass: Phase separation: …the nucleated droplet and the spinodal; the microstructures produced by these two mechanisms, as revealed by electron microscopy, are shown in Figure 4. In Figure 4A the interface between the droplets and the matrix is sharp, owing to a sharp change in composition. With time the droplets increase in size…

  • Spinola family (Italian family)

    Spinola Family, one of the noble families that dominated the history of Genoa, Italy, during the city-state’s great period, from the 12th to the 14th century. They were descended from a younger son of Ido, the viscount who ruled Genoa in the 10th century as the representative of its feudal lord,

  • Spinola, Ambrogio di Filippo, marqués de los Balbases (Spanish military officer)

    Ambrogio di Filippo Spinola, marquis de los Balbases, an outstanding military commander in the service of Spain and one of the ablest soldiers of his time. Though he won fame in the wars against the Dutch Republic in the early 17th century, he was ultimately unable to break Dutch military power.

  • Spínola, António Sebasti?o Ribeiro de (president of Portugal)

    António Sebasti?o Ribeiro de Spínola, Portuguese military officer who briefly served as his country’s president following the military coup that toppled dictator Marcelo Caetano and set Portugal on the road to democracy (b. April 11, 1910--d. Aug. 13,

  • Spinola, Oberto (Italian noble)

    Doria Family: …Oberto Doria (died 1295) and Oberto Spinola, member of another great Genoese family, inaugurated a series of two-man governments headed by their families, with dictatorial powers as captains of the people. Ruling for 15 years during what has been termed the golden age of the Genoese medieval commune, Oberto Doria…

  • spinor (mathematics)

    élie-Joseph Cartan: …year later he discovered the spinors, complex vectors that are used to transform three-dimensional rotations into two-dimensional representations.

  • spinoreticular tract (anatomy)

    pain: Physiology of pain: …sensation of pain, and the spinoreticular tract is thought to effect the arousal and emotional aspects of pain.

  • Spinosaurus (dinosaur)

    Spinosaurus, a genus of theropod dinosaurs belonging to the family Spinosauridae, known from incomplete North African fossils that date to Cenomanian times (roughly 100 to 94 million years ago). Spinosaurus, or “spined reptile,” was named for its “sail-back” feature, created by tall vertebral

  • spinothalamic tract (anatomy)

    human nervous system: Spinothalamic tracts: Fibres concerned with pain, thermal sense, and light touch enter the lateral-root entry zone and then ascend or descend near the periphery of the spinal cord before entering superficial laminae of the dorsal horn—largely parts of laminae I, IV, and V. Cells in…

  • Spinout (film by Taurog [1966])

    Norman Taurog: Elvis movies: …Presley musicals completed Taurog’s career: Spinout (1966), Double Trouble (1967), Speedway (1968), and Live a Little, Love a Little (1968).

  • Spinoza of Market Street, The (short stories by Singer)

    The Spinoza of Market Street, title story of a short-story collection by Isaac Bashevis Singer, published in Yiddish in 1944 as “Der Spinozist.” The collection was published in English in 1961. The story is set in Warsaw on the brink of World War I. There Dr. Nahum Fischelson lives a meagre,

  • Spinoza, Baruch (Dutch-Jewish philosopher)

    Benedict de Spinoza, Dutch Jewish philosopher, one of the foremost exponents of 17th-century Rationalism and one of the early and seminal figures of the Enlightenment. His masterwork is the treatise Ethics (1677). Spinoza’s Portuguese parents were among many Jews who were forcibly converted to

  • Spinoza, Bendictus (Dutch-Jewish philosopher)

    Benedict de Spinoza, Dutch Jewish philosopher, one of the foremost exponents of 17th-century Rationalism and one of the early and seminal figures of the Enlightenment. His masterwork is the treatise Ethics (1677). Spinoza’s Portuguese parents were among many Jews who were forcibly converted to

  • Spinoza, Benedict de (Dutch-Jewish philosopher)

    Benedict de Spinoza, Dutch Jewish philosopher, one of the foremost exponents of 17th-century Rationalism and one of the early and seminal figures of the Enlightenment. His masterwork is the treatise Ethics (1677). Spinoza’s Portuguese parents were among many Jews who were forcibly converted to

  • Spinozist, Der (short stories by Singer)

    The Spinoza of Market Street, title story of a short-story collection by Isaac Bashevis Singer, published in Yiddish in 1944 as “Der Spinozist.” The collection was published in English in 1961. The story is set in Warsaw on the brink of World War I. There Dr. Nahum Fischelson lives a meagre,

  • Spinther (polychaete genus)

    annelid: Annotated classification: …on sponges; small; single genus, Spinther. Order Phyllodocida Free-moving; a large group characterized by a protrusible proboscis that may or may not be armed with chitinous jaws, teeth, or papillae; prostomium with 1 to 5 antennae, with palpi, and with 0 to 3 pairs of eyes; parapodia well developed into…

  • Spintherida (polychaete order)

    annelid: Annotated classification: Order Spintherida Body oval; median antenna on prostomium; pharynx retractable; dorsal surface with membranous ridges; ventral setae strongly curved; found on sponges; small; single genus, Spinther. Order Phyllodocida Free-moving; a large group characterized by a protrusible proboscis that may or may not be armed with

  • spintronics (electronics)

    nanotechnology: Spintronics: Spintronics refers to electronic devices that perform logic operations based on not just the electrical charge of carriers but also their spin. For example, information could be transported or stored through the spin-up or spin-down states of electrons. This is a new area of…

  • Spinulosa (invertebrate)

    sea star: Spiny sea stars, order Spinulosa, typically have clusters of spines; they have suction-tube feet but rarely pedicellariae. A common example in stony-bottomed European waters is the gibbous starlet (Asterina gibbosa). The sea bat (Patiria miniata) usually has webbed arms; it is common from Alaska to…

  • Spinus psaltria (bird)

    goldfinch: The 10-cm (4-inch) dark-backed goldfinch (C. psaltria) ranges from the western U.S. (where it is called lesser goldfinch) to Peru.

  • Spinus tristis (bird)

    goldfinch: The 13-cm (5-inch) American goldfinch (C. tristis), also called wild canary, is found across North America; the male is bright yellow, with black cap, wings, and tail. The 10-cm (4-inch) dark-backed goldfinch (C. psaltria) ranges from the western U.S. (where it is called lesser goldfinch) to Peru.

  • spiny amaranth (plant)

    pigweed: …stems rising at the tips; spiny pigweed, or spiny amaranth (A. spinosus), has spines at the base of the leafstalks; and rough pigweed, or redroot (A. retroflexus), is a stout plant up to 3 metres (about 10 feet) tall.

  • spiny anteater (monotreme)

    Echidna, (family Tachyglossidae), any of four species of peculiar egg-laying mammals from Australia, Tasmania, and New Guinea that eat and breathe through a bald tubular beak protruding from a dome-shaped body covered in spines. Echidnas have beady eyes and mere slits for ears, and at the end of

  • spiny dogfish (fish)

    dogfish: The spiny dogfishes of the family Squalidae possess a sharp spine in front of each of their two dorsal fins. The most widely known species is Squalus acanthias, called the spiny dogfish, spurdog, or skittle dog. It is abundant along northern Atlantic and Pacific coasts; a…

  • spiny dwarf catfish (fish)

    ostariophysan: Annotated classification: Family Scoloplacidae (spiny dwarf catfishes) Body with 2 bilateral series of teethlike-bearing plates, 1 midventral series of plates. Maximum length about 20 mm (less than 1 inch). South America. 1 genus, 4 species. Family Astroblepidae (climbing catfishes) Mouth and fins modified for adhesion to rocks in mountain…

  • spiny eel (fish)

    Spiny eel, any of two groups of fishes, those of the freshwater family Mastacembelidae (order Perciformes) and of the deep-sea family Notacanthidae (order Notacanthiformes). Members of both groups are elongated and eel-like but are not related to true eels. The freshwater spiny eels comprise about

  • spiny elm caterpillar (insect)

    brush-footed butterfly: The larvae, often known as spiny elm caterpillars, are gregarious in habit and feed principally on elm, willow, and poplar foliage.

  • spiny flathead (fish)

    scorpaeniform: Annotated classification: Family Hoplichthyidae (ghost flatheads or spiny flatheads) Small fishes with very depressed bodies. Scaleless; body with bony plates. Head with heavy spiny ridges. Vertebrae 26. Size to 43 cm (17 inches). Found in moderately deep water in Indo-Pacific region. 1 genus, Hoplichthys, with about 11 species. Family…

  • spiny lobster (crustacean)

    lobster: Unlike true lobsters, spiny lobsters (Palinuridae), so called because of their very spiny bodies, do not have large claws. People eat the abdomen, which is marketed as lobster tail. The antennae are long. Most species live in tropical waters; Palinurus elephas, however, is found from Great Britain to…

  • spiny pigweed (plant)

    pigweed: …stems rising at the tips; spiny pigweed, or spiny amaranth (A. spinosus), has spines at the base of the leafstalks; and rough pigweed, or redroot (A. retroflexus), is a stout plant up to 3 metres (about 10 feet) tall.

  • spiny pocket mouse (rodent)

    pocket mouse: Natural history: The five species of spiny pocket mice (genus Liomys) are found in extreme southern Texas, but they live mostly in Mexico southward to Panama in semiarid brushy and rocky habitats. These pocket mice weigh 34 to 50 grams and have a body length of 10 to 14 cm and…

  • spiny saltbush (plant)

    saltbush: canescens), and spiny saltbush (A. confertifolia).

  • spiny sea star (invertebrate)

    sea star: Spiny sea stars, order Spinulosa, typically have clusters of spines; they have suction-tube feet but rarely pedicellariae. A common example in stony-bottomed European waters is the gibbous starlet (Asterina gibbosa). The sea bat (Patiria miniata) usually has webbed arms; it is common from Alaska to…

  • spiny shark (fossil fish)

    Spiny shark, any of a class (Acanthodii) of small extinct fishes, the earliest known jawed vertebrates, possessing features found in both sharks and bony fishes. Acanthodians appeared first in the Silurian Period and lasted into the Early Permian (from about 438 to 258 million years ago). Among t

  • spiny striatal neuron (anatomy)

    human nervous system: Basal ganglia: Spiny striatal neurons are medium-size cells with radiating dendrites that are studded with spines. Axons of these cells project beyond the boundaries of the caudate nucleus and putamen. All nerves providing input to the caudate nucleus and the putamen terminate upon the dendritic spines of…

  • spiny sun star (sea star)

    sea star: …cm across; the very common spiny sun star (Crossaster papposus) has as many as 15 arms. Cushion stars, of the circumboreal genus Pteraster, are plump five-rayed forms with raised tufts of spines and webbed, short, blunt arms.

  • spiny tree mouse (rodent)

    Asian tree mouse: The Malabar spiny tree mouse (Platacanthomys lasiurus) lives only in the old-growth rainforests of southwestern India. Nocturnal and arboreal, it builds nests in tree cavities and eats fruits and nuts. The animal is named for its flat, grooved spines and bristles, which are tipped with white and…

  • spiny water flea (crustacean)

    Great Lakes: Plant and animal life: …the 1980s two nonindigenous creatures—the spiny water flea (a crustacean) and the zebra mussel (a mollusk)—gained access to the lakes and established large populations. Both have threatened the food web of native species, and the zebra mussel has become a nuisance by clogging water-intake pipes, covering spawning reefs, and fouling…

  • spiny-finned fish (animal)

    Spiny-finned fish, any member of the superorder Acanthopterygii, including four orders of marine and freshwater fishes having fins with some spiny (as opposed to soft) rays—Atheriniformes, Beryciformes, Zeiformes, and Lampridiformes. The atheriniform is the best known of the spiny-finned group,

  • spiny-furred mouse (rodent)

    mouse: General features: At one extreme are the spiny-furred species in the subgenus Pyromys, whose upperparts and undersides are covered with flat, channeled spines nestled in soft underfur (juveniles are not spiny). At the other extreme are the shrew-mice from Sumatra (M. crociduroides) and Java (M. vulcani), whose soft, short, and dense coat…

  • spiny-headed worm (invertebrate)

    Spiny-headed worm, any animal of the invertebrate phylum Acanthocephala. A proboscis, or snout, which bears hooks, gives the group its name. There are about 1,150 recorded species, all of which parasitize vertebrates (usually fish) as adults and arthropods (usually insects or crustaceans) as

  • spiny-rayed fish (animal)

    Spiny-finned fish, any member of the superorder Acanthopterygii, including four orders of marine and freshwater fishes having fins with some spiny (as opposed to soft) rays—Atheriniformes, Beryciformes, Zeiformes, and Lampridiformes. The atheriniform is the best known of the spiny-finned group,

  • spiny-tailed lizard (reptile)

    Spiny-tailed lizard, (Uromastyx), any of more than a dozen species belonging to the lizard family Agamidae. Spiny-tailed lizards live in arid and semiarid habitats from northern Africa to India. They are limbed lizards with broad heads and stout bodies, and most adults grow up to about 25 to 30 cm

  • Spio (polychaete genus)

    annelid: Annotated classification: …25 cm; examples of genera: Spio, Polydora. Order Chaetopterida Two to 3 distinct body regions; prostomium with palpi; modified setae on segment 4; tube dweller; examples of genera: Chaetopterus (parchment worm), Spiochaetopterus. Order

  • Spiochaetopterus (polychaete genus)

    annelid: Annotated classification: …of genera: Chaetopterus (parchment worm), Spiochaetopterus. Order Magelonida Long, slender bodies divided into 2 regions; prostomium flattened with 2 long palpi arising from the ventral surface at the junction of the prostomium and next segment; capillary and hooded hooks; single genus, Magelona. Order Psammodrilida

  • Spionida (polychaete order)

    annelid: Annotated classification: Order Spionida Sedentary; at least 2 long feeding tentacles adapted for grasping and arising from prostomium; size, 0.5 to 25 cm; examples of genera: Spio, Polydora. Order Chaetopterida Two to 3 distinct body regions; prostomium with palpi; modified setae on segment 4; tube

  • Spira, Johann da (German printer)

    typography: Italy: The brothers Johann and Wendelin von Speyer (sometimes called da Spira and sometimes of Spire) opened the first press in Venice in 1469 and, until Johann died in 1470, had a one-year monopoly on all printing in that city. They used a clear and legible typeface that…

  • Spira, Wendelin da (German printer)

    typography: Italy: Wendelin von Speyer (sometimes called da Spira and sometimes of Spire) opened the first press in Venice in 1469 and, until Johann died in 1470, had a one-year monopoly on all printing in that city. They used a clear and legible typeface that represented another…

  • spiracle (anatomy)

    Spiracle, in arthropods, the small external opening of a trachea (respiratory tube) or a book lung (breathing organ with thin folds of membrane resembling book leaves). Spiracles are usually found on certain thoracic and abdominal segments. In elasmobranch and ganoid fishes a pair of spiracles,

  • Spiraea (plant)

    Spirea, (genus Spiraea), genus of nearly 100 species of flowering shrubs in the rose family (Rosaceae). Native to the north temperate zone, many spirea species are commonly cultivated for their pleasing growth habit and attractive flower clusters. Members of the genus Spiraea are hardy deciduous

  • Spiraeoideae (plant subfamily)

    Rosales: Evolution: …genus Spiraea, of the subfamily Spiraeoideae, is known from fossil fruits and leaves, and the related genus Physocarpus is represented in fossils dating to the middle of the Cenozoic Era. In the subfamily Maloideae, fruit and seed remains have been recognized from the genera Crataegus and Pyrus. Leaf fossils are…

  • Spiral (missile)

    rocket and missile system: Antitank and guided assault: The AT-6 Spiral, a Soviet version of TOW and Hellfire, became the principal antiarmour munition of Soviet attack helicopters.

  • Spiral (American artists group)

    Norman Lewis: …was a founding member of Spiral, a group of black artists, including Hale Woodruff, Bearden, and Alston, who committed to the civil rights movement visually, through their art. From 1965 through 1971 he taught art at Harlem Youth in Action, an antipoverty organization. Lewis was active in the protest against…

  • spiral (mathematics)

    Spiral, plane curve that, in general, winds around a point while moving ever farther from the point. Many kinds of spiral are known, the first dating from the days of ancient Greece. The curves are observed in nature, and human beings have used them in machines and in ornament, notably

  • spiral arm (astronomy)

    nebula: …galaxy’s mass, but within a spiral arm its mass fraction increases to about 20 percent. About 1 percent of the mass of the interstellar medium is in the form of “dust”—small solid particles that are efficient in absorbing and scattering radiation. Much of the rest of the mass within a…

  • spiral coiling (basketry)

    basketry: Spiral coiling: The most common form is spiral coiling, in which the nature of the standard introduces two main subvariations: when it is solid, made up of a single whole stem, the thread must squeeze the two coils together binding each to the preceding one…

  • spiral dislocation (crystallography)

    electrochemical reaction: Electrocrystallization: Mechanisms associated with screw dislocations, or twinning edges, can provide for a continuous growth of crystals. The screw dislocation mechanism, shown in Figure 3B, is made possible by a specific fault often found in the crystal lattice that may be called a dislocation originating from a shift of…

  • spiral fracture (pathology)

    fracture: A spiral fracture, characterized by a helical break, commonly results from a twisting injury.

  • spiral freezer

    frozen prepared food: Freezing: …more compact arrangement employs a spiral belt. The spiral arrangement maximizes the belt surface area for a given floor space. A popular type of spiral freezer uses self-stacking belts. In the self-stacking arrangement, each tier rests on the vertical side flanges of the tier beneath. Several configurations of air flow…

  • spiral galaxy (astronomy)

    galaxy: Spiral galaxies: Spirals are characterized by circular symmetry, a bright nucleus surrounded by a thin outer disk, and a superimposed spiral structure. They are divided into two parallel classes: normal spirals and barred spirals. The normal spirals have arms that emanate from the nucleus, while…

  • spiral ganglion (anatomy)

    human ear: Transduction of mechanical vibrations: …endings, which lead to the spiral ganglion of Corti in the modiolus of the cochlea. The spiral ganglion sends axons into the cochlear nerve. At the top of the hair cell is a hair bundle containing stereocilia, or sensory hairs, that project upward into the tectorial membrane, which lies above…

  • spiral ganglion of Corti (anatomy)

    human ear: Transduction of mechanical vibrations: …endings, which lead to the spiral ganglion of Corti in the modiolus of the cochlea. The spiral ganglion sends axons into the cochlear nerve. At the top of the hair cell is a hair bundle containing stereocilia, or sensory hairs, that project upward into the tectorial membrane, which lies above…

  • spiral grain (botany)

    angiosperm: Secondary vascular system: …spiral pattern, sometimes called the spiral grain of a tree. The angle of the spiral arrangement usually changes from year to year; the path of water up a tree stem may therefore be very complicated if more than one growth layer acts as a conducting tissue. Functionally, the effect of…

  • Spiral Jetty (sculpture by Smithson)

    environmental sculpture: …extend a rock and dirt spiral, 1,500 feet (460 m) long, into Great Salt Lake in Utah (Spiral Jetty; 1970). The Bulgarian-born artist Christo has involved large numbers of people in the planning and construction of such mammoth alfresco art projects as Valley Curtain (1972; Rifle Gap, Colo.). Christo’s numerous…

  • spiral ligament (anatomy)

    human ear: Structure of the cochlea: The spiral ligament extends above the attachment of the Reissner membrane and is in contact with the perilymph in the scala vestibuli. Extending below the insertion of the basilar membrane, it is in contact with the perilymph of the scala tympani. It contains many stout fibres…

  • spiral nebula (astronomy)

    galaxy: Spiral galaxies: Spirals are characterized by circular symmetry, a bright nucleus surrounded by a thin outer disk, and a superimposed spiral structure. They are divided into two parallel classes: normal spirals and barred spirals. The normal spirals have arms that emanate from the nucleus, while…

  • spiral of silence (sociology)

    Spiral of silence, in the study of human communication and public opinion, the theory that people’s willingness to express their opinions on controversial public issues is affected by their largely unconscious perception of those opinions as being either popular or unpopular. Specifically, the

  • spiral prominence (anatomy)

    human ear: Structure of the cochlea: …of the stria is the spiral prominence, a low ridge parallel to the basilar membrane that contains its own set of longitudinally directed capillary vessels. Below the prominence is the outer sulcus. The floor of the outer sulcus is lined by cells of epithelial origin, some of which send long…

  • spiral separator (metallurgy)

    mineral processing: Gravity separation: …forces—for example, centrifugal force on spirals or impact forces on shaking tables. Spirals consist of a vertical spiral channel with an oval cross section. As the pulp flows from the top to the bottom of the channel, heavier particles concentrate on the inner side of the stream, where they can…

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