- 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.
Either of two fat-soluble sterol-like compounds, ergocalciferol (vitamin D<sub>2</sub>) and activated cholecalciferol (vitamin D<sub>3</sub>). Vitamin D<sub>2</sub> is formed from the irradiation of ergosterol, a plant sterol. However, vitamin D<sub>3</sub> is normally manufactured in the skin, where ultraviolet light activates the compound 7-dehydrocholesterol. Vitamins D<sub>3</sub> and D<sub>2</sub> are about equal in activity in all mammals except New World monkeys and birds, in which vitamin D<sub>2</sub> is approximately one-tenth as active as vitamin D<sub>3</sub>.
Industry:Science
Grasses that were once almost exclusively for pasture and meadow and now furnish ground cover for lawns, sportsfields, industrial parks and roadsides. Acreage of such mowed turf in the United States is reckoned in the tens of millions; in many states the turfgrass industry ranks among the top two or three “agricultural” pursuits. The same species important for grazing are also important for lawns. Grass is well adapted to repeated defoliation (grazing or mowing) because its meristem or growing point is basal, and for the most part only foliage tip growth is sacrificed.
Industry:Science
Harnessing the precision and efficiency of enzymes for catalysis of chemical reactions holds great promise for many industries. Enzymes are proteins, linear chains of amino acids that fold into complex three-dimensional structures. They catalyze the myriad chemical reactions in all living organisms. Because enzymes have a strong preference for acting on one particular substrate, they require less starting material and produce less waste than many conventional catalytic processes. In addition, they can catalyze intricate reactions which are inaccessible by any other method.
Industry:Science
Atherosclerosis, or hardening of the arteries, is an inflammatory process that may cause a number of diseases. The diseases stem from the loss of normal function of the blood vessels caused by the presence of the atheromatous mass or plaque that progressively encroaches on the lumen of the artery. The ensuing loss of function results in the inability to provide an adequate flow of blood to a particular downstream organ, a circumstance called ischemia. The discomfort associated with intermittent and recurrent ischemia of the heart is called angina pectoris, or simply angina.
Industry:Science
Diseases of both shade and forest trees have the same pathogens, but the trees differ in value, esthetics, and utility. In forests, disease is significant only when large numbers of trees are seriously affected. Diseases with such visible symptoms as leaf spots may be alarming on shade trees but hardly noticed on forest trees. Shade trees with substantial rot may be ornamentals with high value, whereas these trees would be worthless in the forest. Emphasis on disease control for the same tree species thus requires a different approach, depending on location of the tree.
Industry:Science
Electrons and the nuclei of atoms—largely hydrogen—that impinge upon Earth from all directions of space with nearly the speed of light. Before they enter the atmosphere they are typically referred to as primary cosmic rays, to distinguish them from the particles generated by their interaction with the terrestrial atmosphere. Secondary cosmic rays, comprising a large variety of species of charged and neutral particles, cascade down through the atmosphere all the way to the ground and below. Study of cosmic rays at high energy now is often referred to as particle astrophysics.
Industry:Science
Atmospheric clouds are dynamic systems consisting of cloud and precipitation particles falling at some terminal speed. Updrafts in the air reduce this downward descent and sometimes even reverse the direction of certain-sized cloud and precipitation particles. This dynamical nature plays a decisive role in the processes involving phase transitions and particle growth (such as melting, freezing, and evaporation), growth due to water vapor diffusion, growth arising out of collision-coalescence, as well as gas and aerosol particle scavenging by cloud and precipitation particles.
Industry:Science
Conditions in which there are recurrent seizures. Such conditions are also known as epilepsy; the isolated occurrence of a seizure, however, is not designated as epilepsy. A seizure (ictus) is an event in which there is a sudden alteration in function of nerve cells, most commonly involving excessive electrical activity of the cells. This sudden change in nerve cell function is usually relatively brief, lasting seconds to minutes. Soon after a seizure, the brain may function quite normally. The manifestation of a seizure varies depending on which area of the brain is involved.
Industry:Science
Covering some 71% of the Earth and absorbing about twice as much of the Sun's radiation as the atmosphere or the land surface, the oceans are a major component of the climate system. With their huge heat capacity, the oceans not only moderate temperature fluctuations but also play a dynamic role in transporting heat. Ocean currents move vast amounts of heat across the planet—roughly the same amount as the atmosphere does. But in contrast to the atmosphere, the oceans are confined by landmasses, so that their heat transport is more localized and channeled into specific regions.
Industry:Science
Hundreds of thousands of chemicals in current or past use are present in the environment, leaving human populations and ecosystems potentially at risk of exposure to them. The large number and various forms of chemicals preclude regulators from evaluating every chemical with the most rigorous testing strategies. Instead, standard toxicity tests have been limited to only a small number of chemicals, with the hope that the “worst” chemicals will receive specific attention. The chemicals that are tested may represent large classes of compounds, such as certain types of pesticides.
Industry:Science
