- 行业: Printing & publishing
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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.
The mass number <i>A</i> of an atom is the total number of its nuclear constituents, or nucleons, as the protons and neutrons are collectively called. The mass number is placed before and above the elemental symbol, as in <sup>238</sup>U. Because of the approximate equality of the proton and neutron masses, and the relative insignificance of that of the electron, the mass number gives a useful rough figure for the atomic mass; for example, <sup>1</sup>H = 1.00783 atomic mass units (amu), <sup>238</sup>U = 238.051 amu, and so on. The mass number is reduced by four during alpha emission, but is not altered during beta decay or electron capture.
Industry:Science
The thermodynamic modeling of liquids and liquid mixtures is important to both the chemist and the chemical engineer. The chemist is interested in the physical forces that influence the behavior of liquid mixtures. The chemical engineer is interested in modeling the behavior of liquids and liquid mixtures for use in industrial applications, for example to predict the properties of multicomponent mixtures in the petrochemical, pharmaceutical, and refrigeration and air-conditioning industries. Testing the models against experimentally measured properties makes it possible to determine whether the ideas on which the models are based are correct.
Industry:Science
The process of quantitatively determining one or more properties of acoustic noise. In noise assessment and control studies, knowledge of the physical properties of the undesirable sound is the initial step toward understanding the situation and what should be done to reduce or eliminate a noise problem. The instruments and techniques used for measuring noise are of fundamental importance in noise assessment and control. Many measurements may be required to characterize noise adequately because generally it is possible to make a noise measurement only at a particular point in space, while a noise field often has significant spatial variations.
Industry:Science
The red to red-violet variety of the gem mineral tourmaline. Perhaps the most sought-for of the many colors in which tourmaline occurs, it was named for its resemblance to ruby. The color is thought to be caused by the presence of lithium. Fine gem-quality material is found in Brazil, Madagascar, Maine, southern California, the Ural Mountains, and elsewhere. Gem material is almost exclusively a product of pegmatite dikes. Although rubellite is relatively inexpensive, it is regarded by many as one of the loveliest of gemstones. It has a hardness of 7–7.5 on Mohs scale, a specific gravity near 3.04, and refractive indices of 1.624 and 1.644.
Industry:Science
The region between two electrodes in which a disruptive electrical spark may take place. The gap should be taken to mean the electrodes as well as the intervening space. Such devices may have many uses. The ignition system in a gasoline engine furnishes a very important example. Another important case is the use of a spark gap as a protective device in electrical equipment. Here, surges in potential may be made to break down such a gap so that expensive equipment will not be damaged. The dependence of spark-gap operation on such factors as pressure, length, electrode characteristics, and time dependence of potential is quite complicated.
Industry:Science
The phenomenon or process involving the ascending motion of water in the ocean. Vertical motions are an integral part of ocean circulation, but they are a thousand to a million times smaller than the horizontal currents. Vertical motions are inhibited by the density stratification of the ocean because with increasing depth, as the temperature decreases, the density increases, and energy must be expended to displace water vertically. The ocean is also stratified in other properties; for example, nutrient concentration generally increases with depth. Thus even weak vertical flow may cause a significant effect by advecting nutrients to a new level.
Industry:Science
The phenomenon known as wing drop is experienced by an air vehicle during maneuvers at moderate to high angles of attack (AoA). It is caused by an abrupt reduction of lift from one side of the vehicle prior to the other side. This sudden asymmetric loss of lift creates a rolling moment, which causes loss of control of the airplane's roll attitude. Though typically an abrupt and momentary loss of control, these disturbances may be quite severe (up to 60–90°), resulting in abandonment of the task being performed in order to regain control. In operations at low altitudes, even a momentary loss of roll control could result in the loss of the aircraft.
Industry:Science
The mechanism by which the immune system destroys or damages foreign or abnormal cells. Immunologic cytotoxicity may lead to complete loss of viability of the target cells (cytolysis) or an inhibition of the ability of the cells to continue growing (cytostasis). Immunologic cytotoxicity can be manifested against a wide variety of target cells, including malignant cells, normal cells from individuals unrelated to the responding host, and normal cells of the host that are infected with viruses or other microorganisms. In addition, the immune system can cause direct cytotoxic effects on some microorganisms, including bacteria, parasites, and fungi.
Industry:Science
The product of a force and its perpendicular distance to a point of turning; also called the moment of the force. Torque produces torsion and tends to produce rotation. Torque arises from a force or forces acting tangentially to a cylinder or from any force or force system acting about a point. A couple, consisting of two equal, parallel, and oppositely directed forces, produces a torque or moment about the central point. A prime mover such as a turbine exerts a twisting effort on its output shaft, measured as torque. In structures, torque appears as the sum of moments of torsional shear forces acting on a transverse section of a shaft or beam.
Industry:Science
The plutonic equivalent of its more abundant extrusive equivalent, basalt. Because it crystallized from a magma intruded deep within the crust, gabbro has a grain size visible to the naked eye with approximately equal amounts of calcic plagioclase (with 50% or more anorthite, the calcium aluminium feldspar) and pyroxene. Olivine is common as an early crystallized mineral, but either nepheline or quartz could be a late-stage crystallization product found in the matrix. Hornblende or biotite is commonly formed as an alteration product of pyroxene during the late stages of the magmatic crystallization, when water becomes enriched in the residual magma.
Industry:Science
