- 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.
Proton radioactivity is a process by which an unstable nucleus spontaneously decays by the emission of a proton. Other common types of radioactivity include beta decay (the emission of electrons or positrons), alpha decay (the emission of a helium-4 nucleus), and gamma decay (the emission of high-energy photons). Proton decay is simpler than other forms of radioactivity since the proton is one of the constituents of the nucleus, and thus provides an opportunity to study details of nuclear structure.
Industry:Science
Narrowly, the science of light and vision; broadly, the study of the phenomena associated with the generation, transmission, and detection of electromagnetic radiation in the spectral range extending from the long-wave edge of the x-ray region to the short-wave edge of the radio region. This range, often called the optical region or the optical spectrum, extends in wavelength from about 1 nanometer (4 × 10<sup>−8</sup> in.) to about 1 mm (0.04 in.). For information on the various branches of optics
Industry:Science
Molecules that undergo rapid intramolecular rearrangements among equivalent structures in which the component atoms are interchanged. The rearrangement process is usually detected by nuclear magnetic resonance (NMR) spectroscopy, which can measure rearrangement rates from 0.5 to 10,000 s<sup>-1</sup>. With sufficiently rapid rates, a single resonance is observed in the NMR spectrum for a molecule that might be expected to have several nonequivalent nuclei on the basis of its instantaneous structure.
Industry:Science
One of the major types of objects that move in closed orbits around the Sun. Compared to the orbits of planets and asteroids, comet orbits are more eccentric and have a much greater range of inclinations to the ecliptic (the plane of the Earth's orbit). Physically, a comet is a small, solid body which is roughly 2 mi (3 km) in diameter, contains a high fraction of icy substances, and shows a complex morphology, often including the production of an extensive atmosphere and tail, as it approaches the Sun.
Industry:Science
One of two orders in the class Pentastomida of the phylum Arthropoda. This order includes primitive pentastomids with six-legged larvae. The hooks are simple, lacking a fulcrum, and disposed in trapeziform pattern, with the anterior pair internal to the posterior pair. The mouth is anterior to the hooks. In both sexes the genital pores are located anteriorly on the abdomen. There is no cirrus sac; the cirrus is short and united with the gubernaculum. In the female the uterus is straight or saccate.
Industry:Science
Over the last decade, academic and industrial scientists and engineers have become increasingly interested in tuning the properties of polymers by adding small quantities of nanoparticles. Polymers include plastics, rubbers, adhesives, and epoxies, and when nanoparticles are incorporated in them, these materials are called polymer nanocomposites. There is a vast array of nanoparticles available that can be sorted by shape into plates, spheres, and rods, where their smallest dimension is 1–100 nanometers.
Industry:Science
Preparation of biologically active compounds with high optical purity is very important in the pharmaceutical sciences, as different enantiomers or diastereomers exhibit different biological activity. For example, <small>l</small>-DOPA (3,4-dihydroxy-<small>l</small>-phenylalanine) is used in the management of Parkinson's disease, while the <small>d</small>–isomer does not exhibit such activity. The control of the chirality is also important in the field of material sciences, such as for liquid crystals.
Industry:Science
Poultry production comprises two major categories, meat production and egg production. Most poultry produced in North America is grown under close control on highly specialized farms. The evolution from small flocks to large commercial units after World War II was facilitated by rapid advances in the knowledge of nutrition, breeding, housing, disease control, and processing of poultry and eggs, and by improvements in transportation and refrigeration which made possible distant marketing of fresh products.
Industry:Science
Pain is an intensely unpleasant sensory and emotional awareness that signals threat or damage to the body or that is experienced as bodily injury. Pain is acute if it accompanies an injury or a disease of limited duration. Acute pain disappears with healing. Pain is chronic when it lasts beyond the healing of damaged tissue, is associated with a chronic disease, or persists indefinitely with no apparent cause. Acute pain sometimes provides a protective function, but chronic pain serves no apparent purpose.
Industry:Science
In the petroleum industry, a chemical process in which an olefin (ethylene, propylene, and so forth) and a hydrocarbon, usually 2-methylpropane, are combined to produce a higher-molecular-weight and higher-carbon-number product. The product has a higher octane rating and is used to improve the quality of gasoline-range fuels. The process was originally developed during World War II to produce high-octane aviation gasoline. Its current main application is in the production of unleaded automotive gasoline.
Industry:Science
