- 行业: Printing & publishing
- Number of terms: 178089
- Number of blossaries: 0
- Company Profile:
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 nesosilicate mineral of composition Al<sub>2</sub>O(SiO<sub>4</sub>), crystallizing in the orthorhombic system, space group Pbnm, <i>a</i> = 0.744, <i>b</i> = 0.760, and <i>c</i> = 0.575 nanometers, with four formula units in the cell. Sillimanite commonly occurs in slender crystals or parallel groups, and is frequently fibrous, hence the synonym fibrolite (see <b>illus.</b>). There is one perfect cleavage, luster is vitreous, color is brown, pale green, or white, hardness is 6–7 on Mohs scale, and the specific gravity is 3.23.
Industry:Science
A nesosilicate mineral with composition Al<sub>7</sub>(BO)<sub>3</sub>(SiO<sub>4</sub>)<sub>3</sub>O<sub>3</sub>. Dumortierite crystallizes in the orthorhombic system but well-formed crystals are rare; the mineral usually occurs in parallel or radiating fibrous aggregates. There is one direction of poor cleavage. The hardness is 7 on Mohs scale, and the specific gravity is 3.26–3.36. The mineral has a vitreous luster and a color that varies not only from one locality to another but in a single specimen. It may be pink, green, blue, or violet. Dumortierite is found in schists and gneisses and more rarely in pegmatites. In the United States it occurs at Dehesa, California, and at Rochester, Nevada, where it has been mined for the manufacture of high-grade porcelain.
Industry:Science
A nesosilicate mineral, composition Zn<sub>2</sub>SiO<sub>4</sub>, crystallizing in the hexagonal system. It is usually massive or granular with a vitreous luster; crystals are rare. The mineral has a basal cleavage and may be variously colored, most commonly green, red, or brown. Hardness is 5½ on Mohs scale; specific gravity is 3.9–4.2. Willemite forms a valuable ore of zinc at Franklin, New Jersey. At this famous zinc deposit willemite fluoresces a yellow-green and is found in crystalline limestone associated with franklinite, zincite, and many other rarer minerals. With the exception of the occurrence in New Jersey, willemite is a rare mineral.
Industry:Science
A network of interconnected glaciers or ice streams, with common source area or areas, in contrast to ice sheets and ice caps. The German word <i>Eisstromnetz</i>, which translates literally to ice-stream net, is sometimes used for glacial systems of moderate size (such as less than 3000 mi<sup>2</sup> or 8000 km<sup>2</sup>) and is most applicable to mountainous regions. Being generally associated with terrane of substantial relief, ice-field glaciers are mostly of the broad-basin, cirque, and mountain-valley type. Thus, different sections of an ice field are often separated by linear ranges, bedrock ridges, and nunataks.
Industry:Science
A neurobehavioral disorder that is characterized by frequent, recurrent motor and vocal tics (described in 1885 by the French neurologist Gilles de la Tourette). The motor tics of Tourette's syndrome include brief, rapid, and darting movements of almost any muscle group, and can include eye blinking, eye rolling or deviations, nose wrinkling, facial grimacing, and head shaking. Some motor tics are more complex, are slow, and appear purposeful such as head turning, shoulder shrugging, touching, hopping, or twirling. Vocal tics are brief guttural sounds such as recurrent sniffing, throat clearing, coughing, and grunting or barking sounds. Complex vocal tics can be more meaningful and include expressions such as "No," "Stop," or "Some other time." Infrequently, persons with Tourette's syndrome repeat what they have said (palilalia), repeat what others have said (echolalia), or bark or grunt profane language (coprolalia). Tourette's syndrome has been described in nearly every country and ethnic group, with an estimated prevalence of one or two occurrences per 2000 people.
Industry:Science
A neurodevelopmental condition that impairs the way that a person relates to and communicates with other people. Persons with autism also can have unusual behaviors, such as insistence on sameness, obsessions, or stereotypic (purposeless and repetitive) behaviors such as hand flapping, spinning, and toe walking. The condition varies greatly in the presenting symptoms, the timing of presentation, the range and severity of symptoms, and its association with other conditions. While recognition of autism is increasingly common, the cause and the reason for its increase remain unknown. With intensive early intervention, significant improvements in a large percentage of children with autism can be achieved.
Industry:Science
A neuromuscular disorder that characteristically involves the destruction of myelin, the insulating material around nerve fibers. The onset of the disease is unusual in persons under 15 or over 60 years of age, and peak incidence is found in people in their 20s and 30s. Multiple sclerosis affects females more frequently than males by approximately 2:1. Distribution is worldwide, but there is an unusual relationship to latitude, with a much higher incidence at northern latitudes than near the Equator.
Industry:Science
A neuronal system that is responsible for the synthesis, storage, and release of the neurotransmitter norepinephrine. Norepinephrine, also known as noradrenalin, consists of a single amine group and a catechol nucleus (a benzene ring with two hydroxyl groups) and is therefore referred to as a monoamine or catecholamine. It exists in both the central and peripheral nervous systems. In the autonomic system in the periphery, norepinephrine is the primary neurotransmitter released by the sympathetic nervous system. The sympathetic nervous system mediates the “fight or flight” reaction, preparing the body for action by affecting cardiovascular function, gastrointestinal motility and secretion, bronchiole dilation, glucose metabolism, and so on. Within the central nervous system, norepinephrine has been associated with several brain functions, including sleep, memory, learning, and emotions. The major clustering of norepinephrine-producing neuron cell bodies in the central nervous system is in the locus coeruleus. This center, located in the pons with extensive projections throughout the brain, produces more than 70% of all brain norepinephrine.
Industry:Science
A neutron emitted spontaneously from a nucleus as a consequence of excitation remaining from a preceding radioactive decay event. Analogously, delayed emission of protons and alpha particles is observed, but the known delayed-neutron emitters are more numerous, and some of them have practical implications. In particular, they are important in the control of nuclear chain reactors.
Industry:Science
A new class of sensors is based on environmentally responsive hydrogels. These sensors are made by spatially modulating the chemical nature of gels or by depositing a different material onto certain gel surface areas selected with a mask. These novel gels can change their shape or surface pattern in response to environmental stimuli such as temperature and pH. The gels' controlled sensitivity to a variety of environmental stimuli offers new opportunities in the development of sensor technology.
Industry:Science
