- 行业: Printing & publishing
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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.
An extraembryonic membrane which extends through the umbilicus in vertebrates. In some elasmobranchs, birds, and reptiles, it is laden with yolk which serves as the nutritive source of embryonic development. Developed in the splanchnopleure, it is composed of an endodermal layer and a mesodermal layer in which blood vessels are formed.
Industry:Science
An extremely complex nuclear reaction representing a cataclysmic division of an atomic nucleus into two nuclei of comparable mass. This rearrangement or division of a heavy nucleus may take place naturally (spontaneous fission) or under bombardment with neutrons, charged particles, gamma rays, or other carriers of energy (induced fission). Although nuclei with mass number <i>A</i> of approximately 100 or greater are energetically unstable against division into two lighter nuclei, the fission process has a small probability of occurring, except with the very heavy elements. Even for these elements, in which the energy release is of the order of 2 × 10<sup>8</sup> eV, the lifetimes against spontaneous fission are reasonably long.
Industry:Science
An extremely diverse, species-rich group of arthropods that have inhabited marine environments since the beginning of the Cambrian Period. In some ways, they may be thought of as the marine equivalents of the insects. Within the marine realm the crustaceans occupy as varied a spectrum of habitats as the insects inhabit on land. The Crustacea currently are regarded as a subphylum in the monophyletic phylum Arthropoda, although debate about this rank continues among carcinologists.
Industry:Science
An extremely strong container, usually made of metal and sometimes built into a wall or vault, designed to protect money or other valuables. A bank safe is fireproof, strongly built, and equipped with a well-locked door. A furrier's safe provides, in addition, cooling, ventilation, and protection against insects. A safe or vault is a complete structure, the walls, floor, and ceiling being as much a part of the protective features as the more conspicuous door. For utmost protection, a vault is so large and heavy that it cannot be removed. Combination locks eliminate the keyhole as a weakness, and eliminate the key, which could be stolen or duplicated. A time clock built into the locking mechanism unlocks the vault entirely from the inside. The time lock operates only after the elapsed time, set when the vault was closed. Walk-in vaults are furnished with shelves, locked drawers, and cabinets for systematic and compact storage of valuables. The vault may be air conditioned and may have a telephone extension inside.
Industry:Science
An hallucination can be defined as a sensory experience that occurs in the absence of corresponding external stimulation of the relevant sensory organ(s). In addition, the experience has a sufficient sense of reality to resemble a veridical (genuine) perception and occurs when one is awake; furthermore, one does not feel that one has direct and voluntary control over it. Thus, an hallucinating person sees things that are not there or hears voices while nobody in the vicinity is speaking, for example. Although visual and auditory hallucinations are most common, hallucinations of taste, smell, and touch can also occur. The exact mechanisms underlying the experience of hallucination remain elusive, but significant strides have been made in recent years to uncover processes in the mind and brain that are associated with hallucinations.
Industry:Science
An herb, also known as wild marjoram. The dried leaves of several species of aromatic plants are known as oregano; thus oregano is a common name for a general flavor and aroma rather than the name of a specific plant.
Industry:Science
An ideal energy radiator, which at any specified temperature emits in each part of the electromagnetic spectrum the maximum energy obtainable per unit time from any radiator due to its temperature alone. A blackbody also absorbs all the energy which falls upon it. The radiation properties of real radiators are limited by two extreme cases—a radiator which reflects all incident radiation, and a radiator which absorbs all incident radiation. Neither case is completely realized in nature. Carbon and soot are examples of radiators which, for practical purposes, absorb all radiation. Both appear black to the eye at room temperature, hence the name blackbody. Often a blackbody is also referred to as a total absorber. Such a total absorber constitutes a standard for the radiation of nonblackbodies, since Kirchhoff's law demands that the blackbody radiate the maximum amount of energy possible in any wavelength interval. For an extended discussion of blackbody radiation and Kirchhoff's law
Industry:Science
An idealized extended solid whose size and shape are definitely fixed and remain unaltered when forces are applied. Treatment of the motion of a rigid body in terms of Newton's laws of motion leads to an understanding of certain important aspects of the translational and rotational motion of real bodies without the necessity of considering the complications involved when changes in size and shape occur. Many of the principles used to treat the motion of rigid bodies apply in good approximation to the motion of real elastic solids.
Industry:Science
An igneous rock characterized by porphyritic texture, in which large crystals (phenocrysts) are enclosed in a matrix of very fine-grained to aphanitic (not visibly crystalline) material.
Industry:Science
An igneous rock characterized by small grain size (less than about 0.2 in. or 5 mm) and approximately equal proportions of calcium-rich plagioclase feldspar and calcium-rich pyroxene, with less than about 20% by volume of other minerals. Olivine, calcium-poor pyroxene, and iron-titanium oxide minerals are the most prevelant other minerals. Certain rare varieties of basalts are poor in SiO<sub>2</sub> and rich in melilite, olivine, and nepheline and may be poor in calcium-rich plagioclase and pyroxene. Most basalts are dark gray or black, but some are light gray. Various structures and textures of basalts are useful in inferring both their igneous origin and their environment of emplacement. Basalts are the predominant surficial igneous rocks on the Earth, Moon, and probably other bodies in the solar system. Several chemical-mineralogical types of basalts are recognized. The nature of basaltic rocks provides helpful clues about the composition and temperature within the Earth and Moon. The magnetic properties of basalts are responsible in large part for present knowledge of the past behavior of the Earth's magnetic field and of the rate of sea-floor spreading.
Industry:Science
