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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.
A group of Mesozoic plants first recognized in 1925. The remains consist of palmately compound leaves with 3–6 lanceolate leaflets previously known as <i>Sagenopteris phillipsi</i>, pinnately branched microsporophylls (named <i>Caytonanthus arberi</i>) that bore winged pollen in four-chambered microsporangia, and fruit-bearing inflorescences, <i>Caytonia</i> (with two species), which bore a dozen or more globular, short-stalked fruits in subopposite rows. Each fruit was 0.2 in. (5 mm) or less in diameter. Near the attachment stalk at the lower part of the fruit was a small transverse lip beneath which was a minute depression marking the place where a small opening formed at pollination time. This opening admitted the pollen into the interior, where small orthotropous ovules were attached to the surface. The inflorescence thus resembled a simply pinnate frond, of which the individual pinnules were curved so as to enclose the seeds. When first discovered, it was believed that the flap served as a stigmatic surface to receive the pollen in a manner similar to the stigma of a modern flower. Later it was found that the pollen actually entered the young fruit through the small opening and germinated on the nucellus of the ovule after the manner in gymnosperms (Pinopsida). The Caytoniales appear related to the pteridosperms. They range from the Triassic to the Cretaceous.
Industry:Science
A group of metallic materials that can return to some previously defined shape or size when subjected to the appropriate thermal procedure. That is, shape memory alloys can be plastically deformed at some relatively low temperature and, upon exposure to some higher temperature, will return to their original shape. Materials that exhibit shape memory only upon heating are said to have a one-way shape memory, while those which also undergo a change in shape upon recooling have a two-way memory. Typical materials that exhibit the shape memory effect include a number of copper alloy systems and the alloys of gold-cadmium, nickel-aluminum, and iron-platinum.
Industry:Science
A group of minerals common in some soils and clays and belonging to the family of minerals called layer silicates. Species within the vermiculite group are denoted as either dioctahedral vermiculite or trioctahedral vermiculite, with two or three octahedral cation sites occupied per formula unit,respectively.
Industry:Science
A group of minerals having the general chemical formula XYSi<sub>2</sub>O<sub>6</sub>, in which the Y site contains iron (Fe) or magnesium (Mg) and the X site contains Fe, Mg, manganese (Mn), or a small amount of calcium (Ca; up to about 3%). They are characterized by orthorhombic crystal symmetry, which makes it impossible for significant amounts of larger cations such as Ca or sodium (Na) to enter the X position. The most important compositional variation in the orthopyroxene series is variation in the Fe-Mg ratio, leading to a solid solution series bounded by the end members enstatite (Mg<sub>2</sub>Si<sub>2</sub>O<sub>6</sub>; abbreviated En) and ferrosilite (Fe<sub>2</sub>Si<sub>2</sub>O<sub>6</sub>; Fs). Names that are used for intermediate members of the series are enstatite (Fs<sub>0-50</sub>) and ferrosilite (Fs<sub>50-100</sub>). More Fs-rich enstatite may be called ferroan enstatite, and more enstatite-rich ferrosilite may be called magnesian ferrosilite. In addition to the major elements noted above, minor components in orthopyroxene may include aluminum (Al), titanium (Ti), chromium (Cr), nickel (Ni), and ferric iron (Fe<sup>3+</sup>), although only Al occurs in substantial amounts. Conditions of formation may be important in determining orthopyroxene compositions: for example, Al content is greater at higher temperatures, and the most Fe-rich compositions are stable only at very high pressures. Further, there is a limited solid solution of orthopyroxene toward calcic clinopyroxene, noted above, which increases with increasing temperature.
Industry:Science
A group of monoclinic calcic pyroxenes which have the general chemical formula (Ca,Mg,Fe)(Mg,Fe)-Si<sub>2</sub>O<sub>6</sub>, in which calcium is the dominant cation in the first cation position. Monoclinic pyroxene with substantial iron or magnesium in place of calcium is called pigeonite, and has a different crystal structure from augite. Augite is generally considered to be a combination of the four end members, diopside (CaMgSi<sub>2</sub>O<sub>6</sub>), hedenbergite (CaFe<sup>2+</sup>Si<sub>2</sub>O<sub>6</sub>), enstatite (Mg<sub>2</sub>Si<sub>2</sub>O<sub>6</sub>), and ferrosilite (Fe<sub>2</sub><sup>2+</sup>Si<sub>2</sub>O<sub>6</sub>), but it almost always has substantial aluminum and minor to substantial amounts of sodium, ferric iron, chromium, and titanium. These minor constituents enter as solid solutions of augite toward acmite (NaFe<sup>3+</sup>Si<sub>2</sub>O<sub>6</sub>), jadeite (NaAlSi<sub>2</sub>O<sub>6</sub>), calcium Tschermak's molecule (CaAl<sub>2</sub>SiO<sub>6</sub>), ureyite (NaCrSi<sub>2</sub>O<sub>6</sub>), and CaTiAl<sub>2</sub>O<sub>6</sub>. The amount of substitution by any of these minor components depends upon the bulk composition of the rock as well as the conditions of formation. Four common varieties of augite are omphacite, which has about 50% substitution of jadeite; aegerine augite, which has substantial acmite substitution; fassaite, which has a considerable amount of calcium Tschermak's molecule in solution; and titanaugite, which is rich in titanium and has a characteristic purple color.
Industry:Science
A group of muscle diseases that are hereditary and characterized by progressive muscle weakness and wasting.
Industry:Science
A group of naturally occurring, organic substances that influence plant physiological processes at low concentrations. The processes consist mainly of growth, differentiation, and development, although other processes, such as stomatal movement, may also be affected. Typical effective concentrations (in the range of 1 μM externally, or about 1–100 nM internally (about one part per billion), depending on the compound) are far below those where either nutrients or vitamins would be effective.
Industry:Science
A group of nerve cell bodies, usually located outside the brain and spinal cord. A ganglion located inside the central nervous system is called a nucleus.
Industry:Science
A group of nerve fibers coursing together as a bundle in the peripheral nervous system. The individual fibers are covered by Schwann cells, many of which contain large amounts of myelin, which makes the nerve appear shiny white. The nerve fibers with their Schwann cell sheaths are held together by connective tissue. In most nerves, some of the fibers are sensory (carrying information to the central nervous system) and some are motor (carrying information from the central nervous system to peripheral glands and muscles). When both sensory and motor fibers are in a nerve, it is called a mixed nerve.
Industry:Science
A group of nuclear reactions involving fusion of light nuclei that converts hydrogen into helium. It is believed to be the principal source of energy in main sequence stars of a little more than a solar mass and of less massive stars. Completion of a chain results in the consumption of four protons (hydrogen-1 nuclei, designated <sup>1</sup>H), and the production of a helium (<sup>4</sup>He) nucleus plus two positrons (<i>e</i><sup>+</sup>) and two neutrinos (ν). The two positrons are annihilated along with two electrons (<i>e</i><sup>−</sup>), and the total energy release is 26.73 MeV. Approximately 0.58 MeV is released as neutrino energy and is not available as thermal energy in a star. The chain can be thought of as the conversion of four hydrogen atoms into a helium atom plus energy in the form of photons or neutrinos, or the kinetic energy of particles. The energy <i>E</i> = 26.73 MeV arises from the mass difference between four hydrogen atoms and the helium atom, and is calculated from the Einstein mass-energy equation <i>E</i> = Δ<i>mc</i><sup>2</sup>, where Δ<i>m</i> is the mass difference and <i>c</i><sup>2</sup> is the square of the velocity of light. Because hydrogen is the fuel consumed in the process, it is referred to as hydrogen burning by means of the proton-proton chain.
Industry:Science
