- 行业: Printing & publishing
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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.
The production of a permanent two-dimensional record of a scene of interest to astronomy. In direct imaging, the scene is a section of the sky optically imaged with a telescope. In other types of imaging, the scene is the output of an instrument, often a spectroscope. Although astronomical images can be produced using light from any part of the electromagnetic spectrum, this article mainly concerns images made in the optical and near-infrared regions (wavelengths of 320–1000 nanometers). The overriding concerns in astronomical imaging are resolution, wavelength sensitivity, and above all, detective quantum efficiency.
Industry:Science
The process of recording signals on a medium through the use of light, so that the signals may be reproduced at a subsequent time. Photographic film has been widely used as the medium, but in the late 1970s development of another medium, the optical disk, was undertaken. The introduction of the laser as a light source greatly improves the quality of reproduced signals. Digital storage techniques make it possible to obtain extremely high-fidelity reproduction of sound signals in optical disk recording systems. This article first describes optical film recording and then some of the more modern optical recording methods.
Industry:Science
The study of the interaction of electromagnetic waves in the optical range with material systems. The optical range of wavelengths may be taken as the range from about 1 nanometer (4 × 10<sup>−8</sup> in.) to about 1 millimeter (0.04 in.). More narrowly, physical optics deals with the relationship between the atomic structure of a system and the manner in which the system affects light sent into it. The chief founder of this branch of science was Michael Faraday, who in 1845 provided the first clue to the electromagnetic nature of light by showing the optical properties of glass could be altered by a magnetic field.
Industry:Science
The separation of a dilute suspension of solid particles into a supernatant liquid and a concentrated slurry. If the purpose of the process is to concentrate the solids, it is termed thickening; and if the goal is the removal of the solid particles to produce clear liquid, it is called clarification. Thickening is the common operation for separating fine solids from slurries. Examples are magnesia, alumina red mud, copper middlings and concentrates, china clay (kaolin), coal tailings, phosphate slimes, and pulp-mill and other industrial wastes. Clarification is prominent in the treatment of municipal water supplies.
Industry:Science
The study of the adverse effects of chemical and physical agents on living organisms. Toxicology has also been referred to as the science of poisons. Since about 1970, there has been a substantial increase in the understanding of biological systems and the way in which chemicals can interfere with the proper functioning of such systems. At the same time, there has been a tremendous increase in the number and volume of chemicals that are in everyday use. Therefore, despite intensive research efforts, knowledge of fundamental toxicological principles and the specific effects of many individual compounds is incomplete.
Industry:Science
The phylum comprising the multisegmented, invertebrate wormlike animals, of which the most numerous are the marine bristle worms and the most familiar the terrestrial earthworms. The Annelida (meaning little annuli or rings) include the Polychaeta (meaning many setae); the earthworms and fresh-water worms, or Oligochaeta (meaning few setae); the marine and fresh-water Hirudinea or leeches; and two other marine classes having affinities with the Polychaeta: the Archiannelida (meaning primitive annelids) are small heteromorphic marine worms, and the Myzostomaria (meaning sucker mouths) are parasites of crinoid echinoderms.
Industry:Science
The physical laws which are expressions of symmetries. The term symmetry, as it is used in mathematics and the exact sciences, refers to a special property of bodies or of physical laws, namely that they are left unchanged by transformations which, in general, might have changed them. For example, the geometric form of a sphere is not changed by any rotation of the sphere around its center, and so a sphere can be said to be symmetric under rotations. Symmetry can be very powerful in constraining form. Indeed, referring to the same example, the only sort of surface which is symmetric under arbitrary rotations is a sphere.
Industry:Science
The process of recovering mineral wealth from seawater and from deposits on and under the seabed. While the world's demand for mineral commodities is increasing at a rapid rate, most of the developed countries have been thoroughly explored for surface outcroppings of mineral deposits. The mining industry has needed to improve its capabilities for exploring and exploiting low-grade and unconventional sources of ore. Corresponding advances in oceanography have highlighted the importance of the ocean as a source of minerals and indicated that the technology required for their exploitation is in some cases already available.
Industry:Science
The reestablishment of forest cover either naturally or artificially. Given enough time, natural regeneration will usually occur in areas where temperatures and rainfall are adequate and when grazing and wildfires are not too frequent. For example, Canada was basically treeless 16,000 years ago (during the last glacial period). During that time, spruce trees probably dominated much of present Illinois and Missouri. Due to global warming, spruce forests gradually spread north and now cover much of Canada. Within 16,000 years, more than 1 billion acres (400 million hectares) of forests in Canada were regenerated naturally.
Industry:Science
The part of the upper atmosphere that is sufficiently ionized that the concentration of free electrons affects the propagation of radio waves. Existence of the ionosphere was suggested simultaneously in 1902 by O. Heaviside in England and A. E. Kennelly in the United States to explain the transatlantic radio communication that was demonstrated the previous year by G. Marconi; and for many years it was commonly referred to as the Kennelly-Heaviside layer. The existence of the ionosphere as an electronically conducting region had been postulated earlier by B. Steward to explain the daily variations in the geomagnetic field.
Industry:Science
