- 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.
A subphylum of the phylum Chordata comprising the lancelets, including <i>Branchiostoma</i> (amphioxus). They are also known as the Leptocardii. Lancelets are small fishlike animals, not exceeding 3.2 in. (80 mm) in length. They burrow in sand on the ocean bed or in estuaries in tropical and temperate regions throughout the world. Only two genera are recognized, <i>Branchiostoma</i> with 23 species and <i>Asymmetron</i> with 6 species.
Industry:Science
A subphylum of the Protozoa. The ciliates are a fairly homogeneous group of highly differentiated, unicellular organisms. Over 5000 species have been described, and many more surely exist but remain to be discovered. Typically, ciliates are larger than most other protozoa, ranging from 10 to 3000 micrometers or about 0.004 to 0.12 in. Some larger species are easily visible to the naked eye. The majority of them are free-living forms, found abundantly in a variety of fresh- and salt-water habitats, although a few entire groups live in association with other organisms, generally as harmless ecto- or endocommensals. Their principal value to humans is as experimental animals in a host of investigations concerned with fundamental problems of biology.
Industry:Science
A subspecialty in medicine that deals with problems specific to the activities of dancers, musicians, and vocalists. It is an outgrowth of the fields of sports medicine and occupational medicine.
Industry:Science
A subspecialty of medicine based on the use of radioactive substances in medical diagnosis, treatment, and research. Cyclotron-produced radioactive materials were introduced in the early 1930s, but the invention of the nuclear reactor during World War II made carbon-14, hydrogen-3, iodine-131, and later technetium-99m available in large quantities. Today most biomedical research and the care of many patients depend on the use of radioactive materials.
Industry:Science
A substance composed of two or more elements that do not vary in composition from sample to sample, and that have fixed and definite physical properties, such as density and refractive index. The elements in compounds cannot be separated by simple physical or mechanical means, but only by chemical treatment. When compounds are formed from their elements, heat is generated or absorbed. These properties distinguish them from mixtures.
Industry:Science
A substance containing a large amount of stored energy that can be released suddenly, thereby converting the substance into compressed gases or numerous fragments that expand with great force or velocity. An explosion is a sudden expansion of matter into a much larger volume than it formerly occupied, or a sudden increase in the pressure exerted by confined matter.
Industry:Science
A substance produced primarily from the dewaxing of lubricating-oil fractions of petroleum. It may be of either the crystalline or microcrystalline type. The crystalline wax is produced from distillate lubricating fractions, whereas the microcrystalline wax is obtained from the residual lubricating fractions of the crude oil. The melting-point range for refined crystalline waxes is 120–150°F (48–65°C) while the petrolatum or microcrystalline waxes have melting points in the range of 150–175°F (65–79°C).
Industry:Science
A substance that acts as a molecular messenger, transmitting information from one member of a species to another member of the same species. The first pheromone to be characterized chemically was bombykol, an unsaturated, straight-chain alcohol that is secreted in microgram amounts by females of the silkworm moth (<i>Bombyx mori</i>) and is capable of attracting male silkworm moths at large distances. The electroantennogram (EAG) technique was developed in connection with this work; the electrical signals that are generated by the pheromone stimulation of an insect's chemoreceptor cells are recorded and analyzed.
Industry:Science
A substance that can transfer ions from a hydrophilic medium such as water into a hydrophobic medium, such as hexane or a biological membrane, where the ions typically would not be soluble, also known as an ion carrier. The ions transferred are usually metal ions (for example, lithium (Li<sup>+</sup>), sodium (Na<sup>+</sup>), potassium (K<sup>+</sup>), magnesium (Mg<sup>2+</sup>), or calcium (Ca<sup>2+</sup>)); but there are ionophores that promote the transfer of other ions, such as ammonium ion (NH<sub>4</sub><sup>+</sup>) or amines of biological interest.
Industry:Science
A substance that reveals, through characteristic color changes, the degree of acidity or basicity of solutions. Indicators are weak organic acids or bases which exist in more than one structural form (tautomers) of which at least one form is colored. Intense color is desirable so that very little indicator is needed; the indicator itself will thus not affect the acidity of the solution.
Industry:Science
