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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 soil of the past, that is, a fossil soil. Paleosols are most easily recognized when they are buried by sediments. They also include surface profiles that are thought to have formed under very different conditions from those now prevailing, such as the deeply weathered tropical soils of Tertiary geological age that are widely exposed in desert regions of Africa and Australia. Such profiles are generally known as relict paleosols. Those that can be shown to have been buried and then uncovered by erosion are known as exhumed paleosols. The main problem in defining the term paleosol comes not so much from complications such as these arising from its fossil nature, but from defining what is meant by soil, a term that has very different meanings for agronomists, engineers, geologists, and soil scientists. Considering research on soils of Antarctica and Mars and on paleosols in a variety of rocks ranging back to 3.5 × 10<sup>9</sup> years old, soil can be considered distinct from sediment in that it forms in place, but soil need not necessarily include traces of life. At its most general level, soil is material forming the surface of a planet or similar body and altered in place from its parent material by physical, chemical, or biological processes.
Industry:Science
A soil that is mineralogically an impure limestone. Such soils are also known as duricrust, kunkar, nari, kafkalla, Omdurman lime, croute, and race. Many soil profiles in semiarid climates (that is, those characterized by a rainfall of 4–20 in. or 10–50 cm per year) contain concentrations of calcium carbonate (CaCO<sub>3</sub>). This calcium carbonate is not an original feature of the soils but has been added to the C horizon during soil formation either by direct precipitation in soil pores or by replacement of preexisting material. Fossil analogs of caliche, which are widely reported in ancient sedimentary sequences, are referred to as calcrete or cornstone.
Industry:Science
A solid crystalline material whose electrical conductivity is intermediate between that of a metal and an insulator. Semiconductors exhibit conduction properties that may be temperature-dependent, permitting their use as thermistors (temperature-dependent resistors), or voltage-dependent, as in varistors. By making suitable contacts to a semiconductor or by making the material suitably inhomogeneous, electrical rectification and amplification can be obtained. Semiconductor devices, rectifiers, and transistors have replaced vacuum tubes almost completely in low-power electronics, making it possible to save volume and power consumption by orders of magnitude. In the form of integrated circuits, they are vital for complicated systems. The optical properties of a semiconductor are important for the understanding and the application of the material. Photodiodes, photoconductive detectors of radiation, injection lasers, light-emitting diodes, solar-energy conversion cells, and so forth are examples of the wide variety of optoelectronic devices.
Industry:Science
A solid dielectric with a quasipermanent electric moment. Electrets may be classified as real-charge electrets and dipolar-charge electrets. Real-charge electrets of present importance are either solid dielectrics with charges of one polarity at or near one side of the dielectric and charges of opposite polarity at or near the other side, or cellular dielectrics with charges of opposite polarity on the two sides of the voids. The dipolar-charge electrets are dielectrics with aligned dipolar charges. Some dielectrics are capable of storing both real and dipolar charges. Examples of charge arrangements in electrets are shown in the <b>illustration</b>.
Industry:Science
A solid form of carbon dioxide, CO<sub>2</sub>, which finds its largest application as a cooling agent in the transportation of perishables. It is nontoxic and noncorrosive and sublimes directly from a solid to a gas, leaving no residue. At atmospheric pressure it sublimes at −109.6°F (−78.7°C), absorbing its latent heat of 246.4 Btu/lb (573.1 kilojoules/kg). Including sensible heat absorption, the cooling effect per pound (kilogram) of dry ice is approximately 270 Btu (628.0 kJ) at storage temperatures above 15°F (−9°C) and 250 Btu (581.5 kJ) at lower temperatures. Slabs of dry ice can easily be cut and used in shipping containers for frozen foods, in refrigerated trucks, and as a supplemental cooling agent in refrigerator cars.
Industry:Science
A solid in which the atoms or molecules are arranged periodically. Within a crystal, many identical parallelepiped unit cells, each containing a group of atoms, are packed together to fill all space (see <b>illus.</b> ). In scientific nomenclature, the term crystal is usually short for single crystal, a single periodic arrangement of atoms. Most gems are single crystals. However, many materials are polycrystalline, consisting of many small grains, each of which is a single crystal. For example, most metals are polycrystalline.
Industry:Science
A solid or liquid (molten), opaque material with a lustrous surface and good electrical and thermal conductivities. Solid metal is usually crystalline and ductile and can be permanently deformed by shear on crystal planes; permanent deformation is accompanied by an increase in strength (work hardening). Metallic properties are related to the arrangements of positively charged ions bonded through a surrounding field (sea) of free electrons that draw the ions into a close-packed crystalline structure with planes appropriate for slip. Liquids are nearly close packed, noncrystalline, with a thermal energy great enough to activate random, free movements of atoms.
Industry:Science
A solid rock body that formed by cooling and crystallization of molten rock (magma) within the Earth. Most plutons, or plutonic bodies, are regarded as the product of crystallization of magma intruded into surrounding “country rocks” within the Earth (principally within the crust). During the middle part of the twentieth century some geologists believed that many igneous or plutonic rock bodies were the result of ultrametamorphism (granitization). However, that model has largely been abandoned.
Industry:Science
A solid state device involved in amplifying small electrical signals and in processing of digital information. Transistors act as the key element in amplification, detection, and switching of electrical voltages and currents. They are the active electronic component in all electronic systems which convert battery power to signal power. Almost every type of transistor is produced in some form of semiconductor, often single-crystal materials, with silicon being the most prevalent. There are several different types of transistors, classified by how the internal mobile charges (electrons and holes) function. The main categories are bipolar junction transistors (BJTs) and field-effect transistors (FETs).
Industry:Science
A solid whose boundary consists of a finite number of polygonal faces, that is, planar regions that are bounded by polygons. The sides of the faces are edges of the polyhedron; the vertices of the faces also are vertices of the polyhedron.
Industry:Science
