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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 pigmented structure found in many animals, generally in the integument. The term is usually restricted to those structures that bring about changes in color or brightness. A majority of chromatophores are single cells that are highly branched and contain pigment granules that can disperse or aggregate within the cell. However, in coleoid cephalopod mollusks (all mollusks except <i>Nautilus</i>), the chromatophores function as miniature organs, and changes in the dispersion of pigment are brought about by muscles. Although the mode of action of the two types of chromatophore is completely different, the effect is the same: pigment either is spread out over a large area of the body or is retracted into a small area.
Industry:Science
A place or containment area where water is stored. Where large volumes of water are to be stored, reservoirs usually are created by the construction of a dam across a flowing stream. When water occurs naturally in streams, it is sometimes not available when needed. Reservoirs solve this problem by capturing water and making it available at later times.
Industry:Science
A place where groundwater discharges upon the land surface because the natural flow of ground water to the place exceeds the flow from it. Springs are ephemeral, discharging intermittently, or permanent, discharging constantly.
Industry:Science
A plagioclase feldspar with composition Ab<sub>50</sub>An<sub>50</sub> to Ab<sub>30</sub>An<sub>70</sub> (Ab = NaAlSi<sub>3</sub>O<sub>8</sub>; An = CaAl<sub>2</sub>Si<sub>2</sub>O<sub>8</sub>), occurring in basic igneous rocks, that is, basalts, gabbros and anorthosites. Its hardness is 6–6.5; mean refractive index, 1.56; and specific gravity, 2.70. Labradorite crystals are translucent to dark or cloudy (from inclusions) but often display brilliant colors like those in peristerites and Huttenlocher intergrowths. In nature, most plagioclases throughout the composition range Ab<sub>54</sub>An<sub>46</sub> to Ab<sub>40</sub>An<sub>60</sub> are exsolved into two e-plagioclases that have compositions Ab<sub>56±4</sub>An<sub>44∓4</sub> and Ab<sub>42±6</sub>An<sub>58∓6</sub> and are coherently intergrown as somewhat irregular lamellar slabs 50 to 20 nanometers thick and known as Boggild intergrowths (see <b>illus.</b>). Intense colors may result from constructive interference of selected wavelengths of light reflected at successive interfaces between the alternating Ab- and An-rich lamellae. In fact, interference colors are so commonly observed in this composition range that the phenomenon has been called labradorescence. Gemologists often use the nonmineralogical term spectrolite in describing them. Iridescent colors in hummingbird feathers and the wings of <i>Morpho</i> butterflies are physically similar phenomena.
Industry:Science
A plagioclase feldspar with composition Ab<sub>70</sub>An<sub>30</sub> to Ab<sub>50</sub>An<sub>50</sub> (Ab = NaAlSi<sub>3</sub>O<sub>8</sub>; An = CaAl<sub>2</sub>Si<sub>2</sub>O<sub>8</sub>). Andesine occurs primarily in igneous rocks, often in a glassy matrix as small, chemically zoned, lathlike crystals known as microlites. The rock types may be called andesinites (if dominantly feldspar), andesites (see <b>illus.</b>), andesitic basalts (or olivine-bearing andesites, as in Hawaiian lava flows), or pyroxene-, hornblende- or biotite-andesites (depending on the second most dominant mineral—all are volcanic).
Industry:Science
A plagioclase feldspar with composition in the range Ab<sub>90</sub>An<sub>10</sub> to Ab<sub>70</sub>An<sub>30</sub>, where Ab represents the composition of albite, NaAlSi<sub>3</sub>O<sub>8</sub>, and An represents the composition of anorthite, CaAl<sub>2</sub>Si<sub>2</sub>O<sub>8</sub>. The diagnostic properties are hardness on Mohs scale, 6–6.5; density, 2.65 g/cm<sup>3</sup>; two good cleavages that intersect at approximately 90°; and color usually white or colorless, transparent to translucent. The presence of minute, mutually parallel inclusions of hematite (Fe<sub>2</sub>O<sub>3</sub>) causes a golden play of color in the variety of oligoclase called aventurine or sunstone. Repeated twinning is common and results in closely spaced striations visible with a hand-held magnifier. Mean refractive index is 1.545; the mineral may be optically positive or negative, depending on composition. Oligoclase is triclinic. The mineral is common in both plutonic and volcanic silicic igneous rocks, as well as in quartzofeldspathic and pelitic metamorphic rocks.
Industry:Science
A plane surface inclined at an angle with the line of action of the force that is to be exerted or overcome. The usual application is diagrammed in the <b>illustration</b>. A relatively small force acting parallel to the surface holds an object in place, or moves it at a constant speed.
Industry:Science
A plant (<i>Humulus lupulus</i>) belonging to the family Cannabaceae, also including nettles and hemp. The plant is a rough-stemmed, tall-twining dioecious perennial herb. It is propagated by cuttings of underground stems. The male flowers are borne on loose stalks. The anthers burst to produce large quantities of pollen, which is wind-borne. The female flowers occur in a cluster consisting of a compressed central axis that holds many flowers. As the clusters mature, the central axis elongates and papery leaves replace each flower, growing into a conelike structure, which is thehop of commerce (see <b>illus.</b>).
Industry:Science
A plant (<i>Psophocarpus tetragonolobus</i>), also known as four-cornered bean, asparagus pea, goa bean, and manila bean, in the family Leguminosae. It is a climbing perennial that is usually grown as an annual. It has been suggested that it originated either in East Africa or Southeast Asia, but there is more evidence to support an African origin. However, Southeast Asia and the highlands of Papua New Guinea represent two foci of its domestication.
Industry:Science
A plant community consisting predominantly of trees and other woody vegetation, growing closely together, is a forest. Forests cover about one-fourth of the land area on Earth. The trees can be large and densely packed, as they are in the coastal forests of the Pacific Northwest, or they can be relatively small and sparsely scattered, as they are in the dry tropical forests of sub-Saharan Africa.
Industry:Science
