- 行业: Printing & publishing
- Number of terms: 178089
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- 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 peculiar arthropod, evidently related to the Pycnogonida and represented by a number of well-preserved fossils from the Devonian Hunsruck shales. It was formerly considered by a number of paleontologists to have an anterior jointed proboscis and a bulbous terminal abdomen, but studies of material under ultraviolet light have demonstrated that the bulbous abdomen is in fact a pair of robust, well-developed chelae (see <b>illus.</b>). Furthermore, additional appendages (palps and ovigers) not apparent in previously studied material have been discerned, bringing its complement of anterior appendages into agreement with that of the Pycnogonida. As reoriented, <i>Palaeoisopus</i> has anterior flattened appendages that separate it from extant families of Pycnogonida.
Industry:Science
A pendulum or swinging weight, supported by a long wire, by which J. B. L. Foucault demonstrated in 1851 the rotation of Earth on its axis. Foucault used a 62-lb (28-kg) iron ball suspended on about a 200-ft (60-m) wire in the Pantheon in Paris. The upper support of the wire restrains the wire only in the vertical direction. The bob is set swinging along a meridian in pure translation (no lateral or circular motion). In the Northern Hemisphere the plane of swing appears to turn clockwise; in the Southern Hemisphere it appears to turn counterclockwise, the rate being 15 degrees times the sine of the local latitude per sidereal hour. Thus, at the Equator the plane of swing is carried around by Earth and the pendulum shows no apparent rotation; at either pole the plane of swing remains fixed in space while Earth completes one rotation each sidereal day.
Industry:Science
A perennial herb, <i>Cichorium intybus</i> (Asteraceae), with a long taproot, a coarse branching stem, and a basal rosette of numerous leaves. Although the plant is a native of Europe, it has become a common weed in the United States. It is used as a salad plant or for greens. The roasted root is also used as an adulterant of coffee.
Industry:Science
A perennial woody plant at least 20 ft (6 m) in height at maturity, having an erect stem or trunk and a well-defined crown or leaf canopy. However, no sharp lines can be drawn between trees, shrubs, and lianas (woody vines). For example, the strangler fig (<i>Ficus aurea</i>) is a climbing liana which may develop into a self-supporting tree if the host around which it twines is removed. Many large trees, such as paper birch (<i>Betula papyrifera</i>) or Alaska cedar (<i>Chamaecyparis nootkatensis</i>), become prostrate shrubs at the northern limits of their range in the boreal region or at their altitudinal limits near timberline.
Industry:Science
A period of geologic time from about 3.8 to 2.5 billion years ago (Ga). During the Archean Eon a large percentage of the Earth's continental crust formed, plate tectonics began, very warm climates and oceans existed, and life appeared on Earth in the form of unicellular organisms.
Industry:Science
A period that encompasses at least the last 3 × 10<sup>6</sup> years of the Cenozoic Era, and is concerned with major worldwide glaciations and their effect on land and sea, on worldwide climate, and on the plants and animals that lived then. The Quaternary is divided into the Pleistocene and Holocene. The term Pleistocene is gradually replacing Quaternary; Holocene involves the last 7000 years since the Pleistocene.
Industry:Science
A periodic motion that is a sinusoidal function of time. It is often called simple harmonic motion. It is the simplest possible type of vibratory motion. The motion is symmetric about its midpoint, at which the velocity is greatest and the acceleration is zero. At the extreme displacements or turning points, the velocity is zero, and the acceleration is a maximum. The motion is characterized by a unique frequency (without overtones).
Industry:Science
A periodic waveform upon which an information-bearing signal is impressed. This process is known as modulation and comprises a variety of forms such as amplitude, phase, and frequency modulation. The most common type of carrier is the sinusoidal carrier (<b>illus. <i>a</i></b>), but in reality, any periodic waveform followed by a band-pass filter can serve as a carrier.
Industry:Science
A permanent substructure that, while being sunk into position, permits excavation to proceed inside and also provides protection for the workers against water pressure and collapse of soil. The term caisson covers a wide range of foundation structures. Caissons may be open, pneumatic, or floating type; deep or shallow; large or small; and of circular, square, or rectangular cross section. The walls may consist of timber, temporary or permanent steel shells, or thin or massive concrete. Large caissons are used as foundations for bridge piers, deep-water wharves, and other structures. Small caissons are used singly or in groups to carry such loads as building columns. Caissons are used where they provide the most feasible method of passing obstructions, where soil cannot otherwise be kept out of the bottom or where cofferdams cannot be used.
Industry:Science
A pesticidal chemical or chemical formulation that functions in a gaseous state. Chemical formulations are designed to increase toxicity, reduce flammability, give off warning odors, and provide for sorption at different rates.
Industry:Science
