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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.
Superconducting fault-current limiters use the transition of superconductors from zero to finite resistance to limit the fault currents that result from short circuits in electric power systems. Such short circuits can be caused by aged or accidentally damaged insulation, by lightning striking an overhead line, or by other unforeseen faults. If not deliberately checked, the subsequent fault current is limited only by the impedance of the system between the location of the fault and the power sources. This current can reach as much as 100 times the nominal current of the system (the largest current in normal operation), and leads to high mechanical and thermal stresses, both of which are proportional to the square of the current's value.
Industry:Science
The feeding methods of invertebrates are as diverse as the invertebrates themselves, which are adapted to all kinds of habitats, in freshwater, in the sea, and on land. The feeding mechanisms are best classified by the method used: browsing, suspension feeding, deposit feeding, carnivorous, and phytophagous (plant-eating). An alternative classification often adopted, but perhaps less satisfactory, may be based on the size of particles ingested. Thus, the same invertebrate may be described either as microphagous (feeding on minute organisms) or as dependent on substances in solution. Both classification schemes may be further subdivided. Carnivorous feeders, for example, include predators and animal parasites; both share dependence on other (living) animals as a food source. Some methods will be restricted to particular habitats. Suspension feeders, for example, can only be aquatic, while the phytophagous habit may be found wherever edible plants occur. The feeding mechanisms employed will depend, at least partly, on the habit and habitat of the plants utilized.
Industry:Science
The application of mathematical theory and technique to ecology. The earliest studies in ecology were by naturalists interested in organisms and their relationships to the environment. Such investigations continue to this day as an active and central part of the subject, and have focused attention on understanding the ecological and evolutionary relationships among species. A large mathematical literature has arisen as an aid to the formalization of concepts and ideas; the underlying goal has been to understand patterns of nature. For the most part, such approaches are retrospective, designed to help in understanding how current ecological relationships developed, and to place that development within appropriate evolutionary context.
Industry:Science
The era of modern molecular biology began in the 1950s when James Watson and Francis Crick discovered the double helical structure of deoxyribonucleic acid (DNA). This discovery established the “central dogma” of molecular biology. Genetic information is codified in DNA. This information is copied to a messenger ribonucleic acid (mRNA). The genetic code in the mRNA is then used to generate a protein. Recent work by many individuals has culminated in the sequence determination of the entire human genome. The genome sequence has been immensely valuable for the identification of genes that contribute to disease, but it also has raised new questions. For example, most of the DNA in the genome does not seem to code for proteins. These regions were sometimes termed “junk DNA” because they did not have an obvious purpose. It is now known that important genes are hidden in these uncharacterized regions of DNA. These include genes that do not code for protein but instead generate biologically active RNAs. One very important type of these “noncoding RNAs” is the microRNA.
Industry:Science
The collapse of the World Trade Center (WTC) in New York provided television viewers worldwide with a firsthand view of the structural phenomenon known as progressive collapse. Although this phenomenon is not new (for example, the Ronan Point apartment building in London collapsed some 40 years previously), the dramatic impact raised questions within the structural engineering community about exactly how the collapse happened, what was the governing mechanism, and how greater robustness might be provided to potentially vulnerable structures. The result has been heightened interest at the fundamental level, considerable research, and the prospect of more realistic representations of the key features of the phenomenon in design procedures.
Industry:Science
The largest and most diversified class of the Crustacea; includes the shrimps, lobsters, crabs, sow bugs, beach hoppers, and their allies. The shell or carapace may be large, small, vestigial, or absent; the tail or abdomen is long or short; the eyes are generally set on movable stalks but may be sessile or even coalesced. Despite this diversity, the unity of the group is demonstrated by the following characteristics which all share. The maximum number of appendages is 19 pairs, even where there is an additional body segment such as is found in the Phyllocarida and embryonic Mysidacea. The trunk limbs are sharply differentiated into a thoracic series of eight pairs and an abdominal series of six pairs. The female genital duct always opens at the level of the sixth thoracic segment, whereas those of the male open at the level of the eighth. Additionally, the frontal organs of malacostracans differ significantly from nonmalacostracans. Even greater, more fundamental differences between malacostracans and nonmalacostracans have been found in their compound eyes.
Industry:Science
The cultivation of plants, primarily trees, that produce nuts. The term nut is used loosely. Generally, a nut is defined as any edible fruit or seed enclosed in a hard shell. Botanically, a nut is a hard, indehiscent, one-seeded (nut), pericarp (shell) generally resulting from a compound ovary of a flower. Indehiscent means the shell does not split open spontaneously when ripe. Examples are chestnuts, filberts, and acorns. Technically, a nut is a dry edible fruit consisting of a kernel or seed enclosed in a woody shell. Only a fraction of the 80 fruits and seeds designated as nuts fit this description. The peanut is notable because the plant is a herbaceous annual legume in which the nuts are analogous to peapods that mature underground.
Industry:Science
The expression of a trait in both the homozygous and the heterozygous condition. In experiments with the garden pea, the Austrian botanist Gregor Mendel crossed plants from true-breeding strains containing contrasting sets of characters. For seed shape, round and wrinkled strains were used. When plants with round seeds were crossed to plants with wrinkled seeds (P<sub>1</sub> generation), all offspring had round seeds. When the offspring (F<sub>1</sub> generation) were self-crossed, 5474 of the resulting F<sub>2</sub> offspring were round and 1850 were wrinkled. Thus, the round trait is expressed in both the F<sub>1</sub> and F<sub>2</sub> generations, while the wrinkled trait is not expressed in the F<sub>1</sub> but is reexpressed in the F<sub>2</sub> in about one-fourth of the offspring. In reporting these results in a paper published in 1866, Mendel called the trait which is expressed in the F<sub>1</sub> generation a dominant trait, while the trait which is unexpressed in the F<sub>1</sub> but reappears in the F<sub>2</sub> generation was called a recessive trait.
Industry:Science
The fleshy root of the plant <i>Ipomoea batatas</i>. The sweet potato was mentioned as being grown in Virginia as early as 1648. In 1930 the selection of outstanding strains of the Porto Rico variety, which was introduced into Florida in 1908, was begun in Louisiana, and the best strain, Unit I Porto Rico, was released in 1934. The Unit I Porto Rico is now being replaced by the Centennial, a yam type which has three times its vitamin A content. More than 70% of the commercial crop in the United States is of the Centennial variety. Another variety, Nemagold, is used largely in the Virginia area because of its resistance to nematodes. Most varieties released now have multiple disease resistance, particularly resistance to wilt and soil rot.
Industry:Science
The Earth is divided into crust, mantle, and core, with the core further divided into the inner and outer portions. The inner core, discovered by Inge Lehmann in 1936, has a radius of 1220 km (758 mi) and a density about 13 g/cm<sup>3</sup>. It represents about 1.7% of the mass of the Earth. The inner-core boundary represents a phase transition from liquid iron in the outer core to solid iron in the inner core. Despite its size, the inner core plays an important role in the Earth's dynamical system. For example, scientists believe the solidification of the outer-core materials, that is, the growth of the inner core, drives the convection in the outer core and powers the geodynamo, a physical process that generates the Earth's magnetic field. Most knowledge about the inner core (its discovery, radius, and density) has come from the study of seismic waves, or seismology. Recently, much has been learned by studying variations in seismic waves due to the direction in which they are propagated (anisotropy) and the part of the inner core in which they travel (hemisphericity).
Industry:Science
