- 行业: Printing & publishing
- Number of terms: 178089
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- Company Profile:
McGraw Hill Financial, Inc. is an American publicly traded corporation headquartered in Rockefeller Center in New York City. Its primary areas of business are financial, publishing, and business services.
A loosely defined term used for a sedimentary mineral segregation that may range in size from inches to many feet. Concretions are usually distinguished from the sedimentary matrix enclosing them by a difference in mineralogy, color, hardness, and weathering characteristics. Some concretions show definite sharp boundaries with the matrix, while others have gradational boundaries. Most concretions are composed dominantly of calcium carbonate, with or without an admixture of various amounts of silt, clay, or organic material. Less common are the clay-ironstone concretions characteristic of the Carboniferous coal measures in many parts of the world. The latter are mixtures of iron carbonate minerals and iron silicate minerals. Coal balls are calcareous concretions, found in or immediately above coal beds, in which there may be a high percentage of original plant organic matter, showing wonderfully preserved plant fossils in a noncompressed condition. Concretions are normally spherical or ellipsoidal; some are flattened to disklike shapes. Frequently a concretion is dumbbell-shaped, indicating that two separate concretionary centers have grown together.
Industry:Science
A loose-to-consolidated sandstone or a porous carbonate rock, impregnated with bitumen, a heavy asphaltic crude oil with a viscosity under reservoir conditions greater than 10,000 millipascal seconds (10,000 centipoise); also known as tar sand or bituminous sand.
Industry:Science
A loss of muscle function or sensation in humans or certain animals following the prolonged feeding of female ticks. Paralysis, of Landry's type, usually begins in the legs and spreads upward to involve the arms and other parts of the body. Evidence suggests that paralysis is due to a neurotoxin formed by the feeding ticks rather than the result of infection with microorganisms.
Industry:Science
A low, perennial shrub or half-shrub of the tropical forest in Brazil and Colombia. Several species are used, but the dried roots and rhizomes of <i>Cephaelis ipecacuanha</i> (Rubiaceae) constitute the material recognized as the official drug ipecac (see <b>illus.</b>). Medically the principal use is as an emetic and an expectorant.
Industry:Science
A low-growing perennial plant, indigenous to the Americas. The cultivated varieties (cultivars) belong to the species <i>Ananas sativus</i> of the plant order Bromeliales.
Industry:Science
A low-lying area which is wholly or largely surrounded by higher land. An example is the Hudson Bay in northeastern Canada, which was formed by depression beneath the center of a continental ice sheet 18,000 years ago. Another example, the Qattara depression, is 150 mi (240 km) long and the largest of several wind-excavated basins of northern Egypt. Depressions in the ocean floor are also basins, as the Canary Basin, west of northern Africa, or the Argentine Basin, east of Argentina. These basins occur in regions where cold, dense oceanic crust lies between the topographically elevated ocean ridges and the continental margins.
Industry:Science
A low-mass main-sequence star of spectral classes M and L. Red dwarf stars range from about 0.6 solar mass at class M0 down to 0.08 solar mass in cool M and warm L, below which the proton-proton chain cannot run. Lower-mass bodies are termed brown dwarfs. At the transition, within class L, the two are difficult to distinguish. Effective temperatures range from 3800 K (6400<sup>°</sup>F) at class M0 down to 2000 K (3100<sup>°</sup>F) at class L0, and absolute visual magnitudes from +9 to +20. Downward along the main sequence, red dwarfs produce progressively more radiation in the infrared. Bolometric corrections (which account for invisible radiation) range from −1.2 magnitudes to around −6, so luminosities range from about 0.05 down to 2 × 10<sup>−4</sup> the solar luminosity. Radii range from about 0.5 to down 0.1 solar. Spectra become increasingly complex, with titanium oxide and neutral metals appearing at the warm end of class M, these and vanadium oxide appearing toward the cool end, and neutral metals and metal hydrides appearing in class L.
Industry:Science
A low-pass amplifier having a bandwidth in the range from 2 to 100 MHz. Typical applications are in television receivers, cathode-ray-tube computer terminals, and pulse amplifiers. The function of a video amplifier is to amplify a signal containing high-frequency components without introducing distortion.
Industry:Science
A low-pressure polymorph of carbon, the common high-pressure polymorph being diamond. Several other rare polymorphs have been synthesized or discovered in meteorites. The contrast in physical properties between these two polymorphs is remarkable: Graphite is metallic in appearance and very soft, whereas diamond is transparent and one of the hardest substances known.
Industry:Science
A low-speed generator driven by water turbines. Hydrogenerators may have a horizontal or vertical shaft. The horizontal units are usually small with speeds of 300–1200 revolutions per minute (rpm). The vertical units are usually larger and more easily adapted to small hydraulic heads. The rotor diameters range from 2 to 62 ft (0.6 to 19 m) and capacities from 50 to 900,000 kVA. The generators are rated in kVA (kilovolts times amperes). The kilowatt output is the product of kVA and power factor. The normal power- factor rating of small synchronous generators is between 0.8 and 1.0 with 0.9 being common. For large generators a rating of 0.9–0.95 is common with the machines able to operate up to 1.0 when the load requires. The generators may also supply reactive power.
Industry:Science
