- 行业: Printing & publishing
- Number of terms: 178089
- Number of blossaries: 0
- 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.
The study of chemical changes resulting from the absorption of high-energy, ionizing radiation. Such radiation includes alpha particles, electrons, gamma rays, fission fragments, protons, deuterons, helium nuclei, and heavier charged projectiles. X-rays are distinguished from gamma rays only as being extranuclear in origin. In absorbing materials of low and intermediate atomic weight such as aqueous systems and most biological systems, these radiations deposit energy in a largely indiscriminate manner, leaving behind a complex mixture of short-lived ions, free radicals, and electronically excited molecules. This contrasts with the absorption of visible and ultraviolet radiation, in which one or a few specific electronically excited species are formed. Radiation chemical change results from the further reaction of these intermediates.
Industry:Science
The scattering of x-rays by matter with accompanying variation in intensity in different directions due to interference effects. X-ray diffraction is one of the most important tools of solid-state chemistry, since it constitutes a powerful and readily available method for determining atomic arrangements in matter. X-ray diffraction methods depend upon the fact that x-ray wavelengths of the order of 1 nanometer are readily available and that this is the order of magnitude of atomic dimensions. When an x-ray beam falls on matter, scattered x-radiation is produced by all the atoms. These scattered waves spread out spherically from all the atoms in the sample, and the interference effects of the scattered radiation from the different atoms cause the intensity of the scattered radiation to exhibit maxima and minima in various directions.
Industry:Science
The study of small-scale meteorological processes associated with the interaction of the atmosphere and the Earth's surface. The lower boundary condition for the atmosphere and the upper boundary condition for the underlying soil or water are determined by interactions occurring in the lowest atmospheric layers. Momentum, heat, water vapor, various gases, and particulate matter are transported vertically by turbulence in the atmospheric boundary layer and thus establish the environment of plants and animals at the surface. These exchanges are important in supplying energy and water vapor to the atmosphere, which ultimately determine large-scale weather and climate patterns. Micrometeorology also includes the study of how air pollutants are diffused and transported within the boundary layer and the deposition of pollutants at the surface.
Industry:Science
The plant <i>Toxicodendron vernicifluum</i> (previously known as <i>Rhus vernicifera</i>), also called lacquer tree, a member of the sumac family (Anacardiaceae). It is a native of China, but has long been cultivated in Japan. When the bark is cut, it exudes a milky juice which darkens and thickens on exposure. This is the lacquer long used in China and Japan. When properly applied, the thin transparent film becomes a varnish of extreme hardness. Lacquer is a remarkably protective coating as it is not altered by acids, alkalies, alcohol, or heat up to 160°F (71°C). Nut galls, iron in solution, and gold or other metals are mixed with the lacquer before drying to make the various kinds of lacquers. The process of lacquering is technical and tedious, sometimes requiring 300–400 coats and several years to complete the finish of one item.
Industry:Science
The study of atmospheric structure and behavior in the areas astride the Equator, roughly between 30° north and south latitude. The weather and climate of the tropics involve phenomena such as trade winds, hurricanes, intertropical convergence zones, jet streams, monsoons, and the El Niño Southern Oscillation. More energy is received from the Sun over the tropical latitudes than is lost to outer space (infrared radiation). The reverse is true at higher latitudes, poleward of 30°. The excess energy from the tropics is transported by winds to the higher latitudes, largely by vertical circulations that span roughly 30° in latitudinal extent. These circulations are known as Hadley cells, after George Hadley who first drew attention to the phenomenon in 1735. This type of circulation is an important ingredient of the tropical general circulation.
Industry:Science
The marine environment has proven to be a rich source of both biological and chemical diversity and has, therefore, become the focus of a major research effort in natural products drug discovery. A natural product is a chemical that is produced by a plant, animal, or microorganism. Terrestrial plants and microorganisms have traditionally been an important source of natural products for the development of new drugs. Over 80% of the medicines most commonly prescribed in hospitals have their roots in natural products. These include compounds such as aspirin, which is a stable derivative of a compound present in the bark of the willow tree; numerous antibacterial drugs, such as penicillin, streptomycin, and erythromycin, which are produced by microorganisms; and the anticancer drug Taxol<sup>®</sup>, derived from the bark of the Pacific yew tree.
Industry:Science
The study of specific responses that take place in the ear or in the associated central (neural) auditory pathways. The ear is the receptor organ of mechanoacoustic energy, which occurs in the form of sound pressure waves. The responses are elicited by appropriate stimuli of well-defined parameters presented at any level of the auditory system. Such responses may be registered with the aid of various, usually invasive, recording techniques which make use of mechanical, electrical, optical, radiological, or biochemical phenomena, or their combinations. The approach employed by physiological acoustics therefore is purely analytical. This is in contrast to the noninvasive, holistic approach employed by psychoacoustics, which lends itself well to experiments on human subjects. Systematic physiological experiments can be performed only in animals.
Industry:Science
The study of interrelationships between microorganisms and their living and nonliving environments. Microbial populations are able to tolerate and to grow under varying environmental conditions, including habitats with extreme environmental conditions such as hot springs, salt lakes, and deep-sea thermal vents. Some microorganisms, referred to as extremophiles, grow only under conditions usually considered hostile to life. The archaebacteria (Archaea) have many extremophiles that grow at high temperatures, high salinities, and low pH. Understanding the environmental factors controlling microbial growth and survival offers insight into the distribution of microorganisms in nature, and many studies in microbial ecology are concerned with examining the adaptive features that permit particular microbial species to function in particular habitats.
Industry:Science
The relatively smooth sections of the continental surfaces, occupied largely by gentle rather than steep slopes and exhibiting only small local differences in elevation. Because of their smoothness, plains lands, if other conditions are favorable, are especially amenable to many human activities. Thus it is not surprising that the majority of the world's principal agricultural regions, close-meshed transportation networks, and concentrations of population are found on plains. Large parts of the Earth's plains, however, are hindered for human use by dryness, shortness of frost-free season, infertile soils, or poor drainage. Because of the absence of major differences in elevation or exposure or of obstacles to the free movement of air masses, extensive plains usually exhibit broad uniformity or gradual transition of climatic characteristics.
Industry:Science
The study of the structure of feeding relationships among organisms in an ecosystem. Researchers focus on the interplay between feeding relationships and ecosystem attributes such as nutrient cycling, physical disturbance, or the rate of tissue production by plants and the accrual of detritus (dead organic material). Feeding or trophic relationships can be represented as a food web or as a food chain. Food webs depict trophic links between all species sampled in a habitat, whereas food chains simplify this complexity into linear arrays of interactions among trophic levels. Thus, trophic levels (for example, plants, herbivores, detritivores, and carnivores) are amalgamations of species that have similar feeding habits. (However, not all species consume prey on a single trophic level. Omnivores are species that feed on more than one trophic level.)
Industry:Science
