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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 class of vermiform marine mollusks covered by a cuticle invested with innumerable calcareous spicules; also known as solenogasters. There are 277 named species. Most species are less than 0.4 in. (10 mm) in length, but a few attain 12 in. (300 mm). The head with a mouth is poorly differentiated; there is a small posterior mantle cavity, or cloaca. Despite their specialized shape (see <b>illus.</b>),Aplacophora retain a primitive molluscan condition in the radula, integument, gonad-pericardium, muscles, and nervous system. There are two distinct subclasses, the creeping neomenioids (Neomeniomorpha) with a narrow foot within a ventral groove, and the burrowing chaetoderms (Chaetodermomorpha) without either a groove or foot, and with a cuticular shield around the mouth. Aplacophora are continental-shelf and deep-sea forms found from subtidal depths to hadal depths (30,000 ft or 9000 m), and in some rare localities may be dominant organisms.
Industry:Science
A class or subclass (depending on the classification system used) of worms, including the earthworms, within the phylum Annelida. These animals exhibit both external and internal segmentation—that is, furrows in the body wall and transverse partitions (septa) dividing the coelom into chambers. They usually possess chaetae (setae), or bristles, made of chitin, which are not borne on parapodia and are few in number (compared to the Polychaeta). Oligochaetes are hermaphroditic. The gonads are few in number and situated in the anterior part of the body, the male gonads being anterior to the female gonads. The gametes are discharged through the oviducts and sperm ducts. At maturity, a portion of the body wall is swollen into a secretory area called the clitellum (<b>illus.</b> <i>a</i>). There is no larval stage during the development of oligochaetes.
Industry:Science
A class within the phylum Mollusca whose members are popularly called chitons, coat-of-mail shells, or sea cradles. Polyplacophora, or Loricata, was formerly combined with Aplacophora in the class Amphineura. All chitons are marine, and they typically live in the intertidal zone, although some live in deeper waters. They are found from subarctic to tropical latitudes but are most abundant in warmer waters. There are roughly 750 chiton species living today.
Industry:Science
A clastic rock composed of angular gravel-size fragments; the consolidated equivalent of rubble. The designation gravel-size refers to a mean particle diameter greater than 0.08 in. (2 mm), which means that 50% or more of the particles (by volume) are this size or larger. Various classifications specify different values for the degree of angularity. One system specifies angular or subangular fragments (roundness ≤ 0.25), whereas another restricts the term breccia to aggregates with angular fragments (roundness ≤0.10).
Industry:Science
A clastic sedimentary rock comprising an aggregate of sand-sized (0.06–2.0-mm) fragments of minerals, rocks, or fossils held together by a mineral cement. Sandstone forms when sand is buried under successive layers of sediment. During burial the sand is compacted, and a binding agent such as quartz, calcite, or iron oxide is precipitated from ground water which moves through passageways between grains. Sandstones grade upward in grain size into conglomerates and breccias; they grade downward in size into siltstones and shales. When the proportion of fossil fragments or carbonate grains is greater than 50%, sandstones grade into clastic limestones.
Industry:Science
A clay mineral similar in structure to kaolinite, having a 1:1 structure in which a silica tetrahedral sheet is joined to an alumina octahedral sheet. Unlike kaolinite, however, the structure is disordered in both the <i>a</i> and the <i>b</i> axis directions in successive layers, and it frequently contains water between the layers.
Industry:Science
A clay-size, micaceous mineral; a common component of soil, sediments, sedimentary rocks, and hydrothermal deposits. Generally, the term refers to any relatively nonexpanding clay that possesses a <i>c</i> dimension of approximately 1.0 nanometer. Specifically, illite is considered to possess a smaller layer charge and potassium (K) content than muscovite, its potassium (K) content generally being about 0.8 equivalent per half-unit cell as opposed to a content of −1.0 equivalent for muscovite. It is characterized by the ideal formula Al<sub>2</sub>(Si<sub>3.2</sub>Al<sub>0.8</sub>)O<sub>10</sub>(OH)<sub>2</sub>K<sub>0.8</sub>.
Industry:Science
A clear, flexible film made from cellulose. It first appeared commercially in the United States in 1924, and it revolutionized the packaging industry, which had been using opaque waxed paper or glassine as wrapping materials. Cellophane was also the first transparent mending tape. By 1960, petrochemical-based polymers (polyolefins) such as polyethylene had surpassed cellophane for use as a packaging film. Nevertheless, 50,000 tons (45,000 metric tons) of cellophane are used in the United States each year for packaging because cellophane gives a material that is stiffer and more easily imprinted than are polyolefin films.
Industry:Science
A clinical condition caused by widespread impairment of blood flow resulting in an inadequate supply of oxygen to the body's tissues. Shock is a sudden and progressive condition that, if not reversed, can lead to death. Shock affects the entire body, as opposed to other conditions where blood flow is reduced to only a portion of a single organ, such as stroke or heart attack. It is typically, but not always, associated with a low blood pressure that can be felt as a weak pulse.
Industry:Science
A clinical syndrome characterized by acute infectious gastroenteritis with watery diarrhea, vomiting, malaise, and abdominal cramps with a relatively short incubation period (12–36 h) and duration (24–48 h). A viral etiology is suspected when bacterial and parasitic agents are not found. In the United States, no etiologic agent can be found in 70% of the outbreaks of gastroenteritis. Most of these may be due to viral agents, such as the Norwalk, Snow Mountain, and Hawaii agents, astroviruses, caliciviruses, adenoviruses, nongroup A rotaviruses, and paroviruses. Epidemics are common worldwide, and have occurred following the consumption of fecally contaminated raw shellfish, food, or water, although the virus may be spread by airborne droplets as well. Epidemics are most frequent in residential homes, camps, institutions, and cruise ships. Many individual cases of mild diarrhea may in fact occur in epidemics for which the source of the infection cannot be found. Epidemic viral gastroenteritis is distinct from rotavirus diarrhea, a seasonal disease in winter that is the most common cause of diarrhea in young children, and affects virtually all children in the first 4 years of life.
Industry:Science
