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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.
In upcoming years aviation technology could begin to change dramatically to achieve the benefits of reduced pollutants emission and decreased dependence on hydrocarbon fuels. To accommodate a switch to hydrogen power, for example, future aircraft designs, propulsion, and power systems will look much different from the systems of today. Hydrogen fuel will enable a number of new aircraft capabilities, from high-altitude long-endurance remotely operated aircraft (HALE ROA) that will fly weeks to months without refueling, to clean, zero-emissions transport aircraft. However, the transition will require decades of research and new technology breakthroughs to fulfill the vision. Additionally, there are a number of design and development challenges that must be overcome before such systems can become operational.
Industry:Science
Most studies of soil erosion have focused on cultivated lands. From such studies, much is known about the erosional characteristics of cultivated soils and about the erosional effects of different crops and cultivation practices, especially in countries such as the United States where soil erosion research has been extensive. The research has also been beneficial because a better understanding of the processes of soil erosion has aided the development of more effective soil conservation measures. However, serious problems involving soil erosion continue to threaten such key activities as food and hydroelectric power production throughout the world. As reservoirs fill with sediment, it becomes apparent that patterns of soil erosion in entire watersheds, not just the cultivated portions, need to be examined.
Industry:Science
Porous materials have been studied for years and are widely used in many industrial applications. More recently, they have become relevant in the field of nanotechnology as well as in fundamental studies of the new physics occurring in confined geometries. In particular, anodized porous alumina has a broad range of applications as a filter, gas and biological sensor, photonic crystal, and nanotemplate for the synthesis of various functional nanostructures, among others. Porous alumina has also been proposed as a model system for the understanding of capillary condensation and related effects. This broad interest originated from the discovery of self-organization of the porous structure in anodized alumina under certain conditions, leading to a hexagonal-close-packed array of nearly ideal cylindrical pores.
Industry:Science
Length, mass, time, or combinations of these quantities serving as an indication of the nature of a physical quantity. Quantities with the same dimensions can be expressed in the same units. For example, although speed can be expressed in various units such as miles/hour, feet/second, and meters/second, all these speed units involve the ratio of a length unit to a time unit; hence, the dimensions of speed are the ratio of length <i>L</i> to time <i>T</i>, usually stated as <i>LT</i><sup>-1</sup>. The dimensions of all mechanical quantities can be expressed in terms of <i>L</i>, <i>T</i>, and mass <i>M</i>. The validity of algebraic equations involving physical quantities can be tested by a process called dimensional analysis; the terms on the two sides of any valid equation must have the same dimensions.
Industry:Science
Perfluorooctanoic acid (PFOA; CF<sub>3</sub>(CF<sub>2</sub>)<sub>6</sub>COOH) is a member of the perfluoroalkyl acids (PFAA) family of chemicals, which consist of a carbon backbone typically four to fourteen carbons in length and a charged functional moiety (primarily carboxylate, sulfonate, or phosphonate). Many chemical intermediates (such as alcohols and amides) can be derived for commercial uses, but these intermediates ultimately break down to PFOA or its sister compound, perfluorooctane sulfontate (PFOS). PFAA are distinguishable from another class of perfluorocarbons, the perfluoroalkanes, primarily used clinically for oxygenation and respiratory ventilation. PFAA are relatively contemporary chemicals, in use only in the past 50 years, and until recently have been considered as biologically inactive.
Industry:Science
Nuclear radiations are used in biology because of their common property of ionizing matter. This makes their detection relatively simple, or makes possible the production of biological effects in any living cell. Nuclear radiations originate in atomic nuclei, either spontaneously, as in radioactive substances, or through interactions with neutrons, photons, and so on. Gamma radiation originates in atomic nuclei and constitutes one kind of nuclear radiation, but it is otherwise indistinguishable in its effects from x-radiation produced by extranuclear reactions. Because x-rays have been readily available for many years, they have been used more extensively in biology and medicine than gamma rays. Therefore, x-rays must be included in any discussion of the biological and medical uses of nuclear radiations.
Industry:Science
Mineral phases containing only oxide or hydroxide anions in their structures. By volume, oxide and hydroxide minerals comprise only a small fraction of the Earth's crust. However, their geochemical and petrologic importance cannot be overstated. Oxide and hydroxide minerals are important ores of metals such as iron, aluminum, titanium, uranium, and manganese. Oxide and hydroxide minerals occur in all geological environments. Some form as primary minerals in igneous rocks, while others form as secondary phases during the weathering and alteration of silicate and sulfide minerals. Some oxide and hydroxide minerals are biogenic; for example, iron(III) and manganese(IV) hydroxides and oxides often result from bacterial oxidation of dissolved Fe<sup>2+</sup> and Mn<sup>2+</sup> in low-temperature aqueous solutions.
Industry:Science
No two electrons may simultaneously occupy the same quantum state. This principle, often called the Pauli principle, was first formulated by Wolfgang Pauli in 1925 and, for time-independent quantum states, it means that no two electrons may be described by state functions which are characterized by exactly the same quantum numbers. In addition to electrons, all known particles having half-integer intrinsic angular momentum, or spin, obey the exclusion principle. It plays a central role in the understanding of many diverse phenomena, including the periodic table of the elements and their chemical activities, the electron contribution to the specific heat of metals, the shell structure in the atomic nucleus analogous to that of electrons in atoms, and certain symmetries in the scattering of identical particles.
Industry:Science
In the western interior of the United States, more than 73 million acres of national forests are at risk from insect attack and catastrophic fire because of the major change over the years in their vegetative structure and composition. Some of this change has been caused by 50 years of successful fire suppression that has created forests with significantly overstocked stands of small-diameter trees. This dense understory in the forest creates a ladder-type fuel (allowing fire to grow from ground level into the canopy fueled by vegetation at different heights) that can lead to high-intensity crown fires, which spread fast and can cause catastrophic alterations to forested landscapes and watersheds. The western wildfires of 2000 demonstrated the devastating impact these dense, overstocked stands can have on forests.
Industry:Science
Nuclear reactors for shipboard propulsion can be of any type used for the production of useful heat. Nuclear power is particularly suitable for vessels which need to be at sea for long periods without refueling or for powerful submarine propulsion. Only the pressurized water reactor (PWR) and the liquid metal reactor (LMR) have actually been applied to operating vessels. The pressurized water reactor has been most widely applied since it uses a readily available coolant and has a relatively simple cycle and control system and a large industrial and technical base. The supposed advantages of a liquid metal reactor (compactness, fast response, and higher propulsion plant efficiency) have not been proven in application, and liquid metal reactors are not now in marine service. For basic information on fission reactors
Industry:Science
