- 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 process in which energy is removed from a beam of electromagnetic radiation and reemitted with a change in direction, phase, or wavelength. All electromagnetic radiation is subject to scattering by the medium (gas, liquid, or solid) through which it passes. In the short-wavelength, high-energy regime in which electromagnetic radiation is most easily discussed by means of a particle description, these processes are termed photon scattering. At slightly longer wavelengths, the scattering of x-rays provides the most effective means of determining the structure of crystalline solids. In the visible wavelength region, scattering of light produces the blue sky, red sunsets, and white clouds. At longer wavelengths, scattering of radio waves determines their characteristics as they pass through the atmosphere.
Industry:Science
The male organ of copulation, or phallus. In mammals the penis consists basically of three elongated masses of erectile tissue. The central corpus spongiosum (corpus urethrae) lies ventral to the paired corpora cavernosa. The urethra runs along the underside of the spongiosum and then normally rises to open at the expanded, cone-shaped tip, the glans penis, which fits like a cap over the end of the penis. Loose skin encloses the penis and also forms the retractable foreskin, or prepuce. The organ is held firmly in place by fibrous tissue and ligaments that bind it to the posterior surface of the pubic arch. In some mammals, although not in man, there may be spines on the glans penis, or there may be a bone (the baculum) within the penis; both of these characters are useful in classifying certain types of mammals.
Industry:Science
The miniaturization of analytical instrumentation has been a driving force in analytical chemistry for several decades. Miniaturization brings about many advantages for chemical analysis, including decreased analysis time, sample consumption, and reagent consumption; increased sample throughput; and the ability to analyze very small samples. Miniaturized analytical systems are less expensive to manufacture, and therefore cost less. An additional benefit of miniaturization is the ability to include more functions on a single device, with the objective of integrating a chemical laboratory on a chip (lab-on-a-chip). One outcome of lab-on-a-chip technology will be portable devices for point-of-care medical diagnostics, environmental monitoring, and the detection of chemical and biological warfare agents in real time.
Industry:Science
The perpendicular intersection of two curves or two lines, one relatively horizontal and the other relatively vertical, is the basis for finding and describing terrestrial location. The Earth's graticule, consisting of an imaginary grid of east-to-west-bearing lines of latitude and north-to-south bearing lines of longitude, is derived from the Earth's shape and rotation, and is rooted in spherical geometry. The development of latitude and longitude likely originated during the classical period in Greece in the second century B.C. Hipparchus of Rhodes is thought to have been instrumental in its development. Plane coordinate systems, equivalent to horizontal X and vertical Y coordinates, are based upon cartesian geometry and differ from the graticule in that they have no natural origin or beginning for their grids.
Industry:Science
The signals for conventional magnetic resonance imaging (MRI) come from the nuclei of ordinary hydrogen (<sup>1</sup>H) atoms in the human body. It is difficult to image body parts such as the lungs which contain relatively few hydrogen atoms. However, excellent magnetic resonance images of the lungs can be obtained if the patient first takes a deep breath of the gases helium-3 (<sup>3</sup>He) or xenon-129 (<sup>129</sup>Xe) which have had their nuclear spin polarizations increased to tens of percent by laser optical pumping. The magnetic resonance images from the hyperpolarized nuclei of these gases are as good as, and often better than, conventional images from hydrogen in tissue. Because of its high solubility in human tissue, hyperpolarized xenon-129 is useful for imaging other body parts as well as the lungs.
Industry:Science
The study of the physical properties of molecules. Molecules possess a far richer variety of physical and chemical properties than do isolated atoms. This is attributable primarily to the greater complexity of molecular structure, as compared to that of the constituent atoms. Molecules also possess additional energy modes because they can vibrate; that is, the constituent nuclei oscillate about their equilibrium positions and rotate when unhindered. These modes give rise to additional spectroscopic properties, as compared to those of an atom; molecular spectroscopy in the optical, infrared, and microwave regions is one of the physical chemist's most powerful means of identifying and understanding molecular structure. Molecular spectroscopy has also given rise to the rapidly growing field of molecular astronomy.
Industry:Science
The propagation in a liquid of an acoustic wave that is caused by a rapid change in fluid velocity. Such relatively sudden changes in the liquid velocity are due to events such as the operation of pumps or valves in pipelines, the collapse of vapor bubbles within the liquid, underwater explosions, or the impact of water following the rapid expulsion of air from a vent or a partially open valve. Alternative terms such as pressure transients, pressure surge, hydraulic transients, and hydraulic shock are often employed. Although the physics and mathematical characterization of water hammer and underwater acoustics (employed in sonar) are identical, underwater sound is always associated with very small pressure changes compared to the potential of moderate to very large pressure differences associated with water hammer.
Industry:Science
The property of a thermodynamical system which satisfies certain conditions and whose thermodynamically defined absolute temperature is negative. The essential requirements for a thermodynamical system to be capable of negative absolute temperature are that (1) the elements of the thermodynamical system must be in thermodynamical equilibrium among themselves in order for the system to be described by a temperature at all; (2) there must be an upper limit to the possible energy of the allowed states of the system; and (3) the system must be thermally isolated from all systems which do not satisfy both of the first two requirements, that is, the internal thermal equilibrium time among the elements of the system must be short compared to the time during which appreciable energy is lost to or gained from other systems.
Industry:Science
The synthesis of hydrocarbons and, to a lesser extent, of aliphatic oxygenated compounds by the catalytic hydrogenation of carbon monoxide. The synthesis was discovered in 1923 by F. Fischer and H. Tropsch at the Kaiser Wilhelm Institute for Coal Research in Mülheim, Germany. The reaction is highly exothermic, and the reactor must be designed for adequate heat removal to control the temperature and avoid catalyst deterioration and carbon formation. The sulfur content of the synthesis gas must be extremely low to avoid poisoning the catalyst. The first commercial plant was built in Germany in 1935 with cobalt catalyst, and at the start of World War II there were six plants in Germany producing more than 4,000,000 bbl (6,000,000 m<sup>3</sup>) per year of primary products. Iron catalysts later replaced the cobalt.
Industry:Science
The quantum-mechanical theory of physical systems whose dynamical variables are local functions of space and time. As distinguished from the quantum mechanics of atoms, quantum field theories describe systems with an infinite number of degrees of freedom. Such theories provide the natural language for describing the interactions and properties of elementary particles, and have proved to be successful in providing the basis for the fundamental theories of the interactions of matter. The present understanding of the basic forces of nature is based on quantum field theories of the strong, weak, electromagnetic, and gravitational interactions. Quantum field theory is also useful in the study of many-body systems, especially in situations where the characteristic length of a system is large compared to its microscopic scale.
Industry:Science
