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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 nuclear reactions that involve the interaction of protons (nuclei of hydrogen atoms, designated by <sup>1</sup>H) with carbon, nitrogen, and oxygen nuclei. The cycle involving only isotopes of carbon and nitrogen is well known as the carbon-nitrogen (CN) cycle. These cycles are thought to be the main source of energy in main-sequence stars with mass 40% or more in excess of that of the Sun. Completion of any one of the cycles results in consumption of four protons (4 <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 with two electrons (<i>e</i><sup>-</sup>), and the total energy release is 26.73 MeV. Approximately 1.7 MeV is released as neutrino energy and is not available as thermal energy in the star. 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. Completion of a chain can be thought of as conversion of four hydrogen atoms into a helium atom. Because the nuclear fuel that is consumed in these processes is hydrogen, they are referred to as hydrogen-burning processes by means of the carbon-nitrogen-oxygen (CNO) cycles.
Industry:Science
A group of parasitic flatworms or flukes constituting a subclass or order of the class Trematoda, in the phylum Platyhelminthes. The name Digenea refers to the two types of generations in the life cycle: (1) the germinal sacs which parasitize the intermediate host (a mollusk or rarely an annelid) and reproduce asexually; and (2) the adult which is primarily endoparasitic in vertebrates and reproduces sexually. The adult usually is hermaphroditic, but many of the blood flukes and a few others are dioecious. Vertebrates of all classes, except the Cyclostomata, serve as definitive hosts. Those feeding on aquatic plants and animals harbor the greatest variety of digenetic trematodes, but several species occur in strictly terrestrial hosts. Effects on the vertebrate vary from no apparent harm to severe and even fatal injury. Control of flukes is by preventive measures, including interruption of their life cycles and treatment with drugs.
Industry:Science
A group of parts arranged to perform a useful function. Normally some of the parts are capable of motion; others are stationary and provide a frame for the moving parts. The terms machine and machinery are so closely related as to be almost synonymous; however, machinery has a plural implication, suggesting more than one machine. Common examples of machinery include automobiles, clothes washers, and airplanes; machinery differs greatly in number of parts and complexity.
Industry:Science
A group of plant hormones (phytohormones) that, together with other plant hormones, induces plant growth and development. The presence of an unknown compound in the phloem that stimulated cell proliferation of potato tubers was demonstrated in the early 1900s by G. Haberlandt. In the 1940s J. van Overbeek found that the milky endosperm from immature coconuts is rich in compounds that promote cell proliferation. Then, in 1954, during investigations of the nutritional requirements of tobacco callus tissue cultures, F. Skoog and C. O. Miller discovered a very active substance that stimulated cell division and was formed by the partial breakdown of aged or autoclaved herring sperm deoxyribonucleic acid (DNA). The compound was named kinetin because it induced cytokinesis of cultured tobacco cells. Kinetin has not been found in plants, and it can be formed from a mixture of autoclaved furfuryl alcohol and adenine. In 1961 Miller obtained an active substance that stimulates cell division from the milky endosperm of corn (<i>Zea mays</i>) seeds; in 1964 D. S. Letham, identified this active compound and named it zeatin. Cytokinin is now the accepted term for those naturally occurring and synthetic compounds that promote the cell division (cytokinesis) and growth of various plant tissues.
Industry:Science
A group of polysaccharides occurring in the cell walls and intercellular layers of all land plants. They are extractable with hot water, dilute acid, or ammonium oxalate solutions. Pectins are precipitated from aqueous solution by alcohol and are commercially used for their excellent gel-forming ability.
Industry:Science
A group of proteins in the blood and body fluids that are sequentially activated by limited proteolysis and play an important role in humoral immunity and the generation of inflammation. When activated by antigen–antibody complexes, or by other agents such as proteolytic enzymes (for example, plasmin), complement kills bacteria and other microorganisms. In addition, complement activation results in the release of peptides that enhance vascular permeability, release histamine, and attract white blood cells (chemotaxis). The binding of complement to target cells also enhances their phagocytosis by white blood cells. The most important step in complement system function is the activation of the third component of complement (C3), which is the most abundant of these proteins in the blood.
Industry:Science
A group of psychiatric conditions, also known as mood disorders, that are characterized by disturbances of affect, emotion, thinking, and behavior. Depression is the most common of these disorders; about 10–20% of those affected by depression also experience manic episodes (hence this condition is known as manic-depression or bipolar affective disorder). The affective disorders are not distinct diseases but psychiatric syndromes that likely have multiple or complex etiologies.
Industry:Science
A group of radio broadcast stations interconnected by leased channels on wire, fiber, microwave, or satellite to one or more central feed points for the purpose of receiving and rebroadcasting program material of a timely nature to a geographically diverse audience; or alternatively, an organization which provides programming for, but does not actually own or operate any, broadcast stations. The terms “radio broadcasting network” and “radio network” are often used interchangeably.
Industry:Science
A group of silicate minerals whose physical properties resemble those of pyroxenes. In contrast with the two-tetrahedra periodicity of pyroxene single silicate chains, the pyroxenoid crystal structures contain single chains of (SiO<sub>4</sub>)<sup>4-</sup> silicate tetrahedra having repeat periodicities ranging from three to nine (see <b>illus.</b>). The tetrahedron is a widely used geometric representation for the basic building block of most silicate minerals, in which all silicon cations (Si<sup>4+</sup>) are bonded to four oxygen anions arranged as if they were at the corners of a tetrahedron. In pyroxenoids, as in other single-chain silicates, two of the four oxygen anions in each tetrahedron are shared between two Si<sup>4+</sup> cations to form the single chains, and the other two oxygen anions of each tetrahedron are bonded to divalent cations, such as calcium (Ca<sup>2+</sup>), iron (Fe<sup>2+</sup>), or manganese (Mn<sup>2+</sup>). These divalent cations bond to six (or sometimes seven or eight) oxygen anions, forming octahedral (or irregular seven- or eight-cornered) coordination polyhedra.
Industry:Science
A group of small sessile hemichordates that may be colonial (<i>Rhabdopleura</i>), pseudocolonial (<i>Cephalodiscus</i>), or solitary (<i>Atubaria</i>). Each individual, or zooid, lives inside a nonchitinous tube secreted by the protosome, except for <i>Atubaria</i>; an aggregation of zooids is called a coenecium and can vary in shape. The protosome, or oral shield, is disciform, closes the mouth ventrally, and secretes the tube. The protocoel has symmetrical pores at the base of the first pair of arms. The mesosome, or collar, has an anteroventral mouth and one to nine pairs of dorsally ciliated tentaculated arms, which are used to collect small organisms for food. The mesocoels extend into both arms and tentacles.
Industry:Science
