- 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.
The second subdivision of the Tertiary Period (Eocene, Miocene, and Pliocene) by Charles Lyell in 1833; the fourth in a more modern sevenfold subdivision (epochs) of the Cenozoic Era; and the first epoch of the Neogene Period (which includes in successive order the Miocene, Pliocene, Pleistocene, and Holocene). The Miocene represents the interval of time from the end of the Oligocene to the beginning of the Pliocene and the rocks (series) formed during this epoch. The Miocene was originally considered as a biostratigraphic (rather than temporal) entity, to unite rocks containing 20–40% extant molluscan species. Lyell based his concept of the Miocene primarily on the shallow marine sediments and associated molluscan faunas in the Superga Hill of northern Italy (near Turin), as well as other Piedmont localities and outcrops in southwestern France (Aquitaine Basin), Touraine, and the Vienna Basin.
Industry:Science
The study of the structure of the atom, its dynamical properties, including energy states, and its interactions with particles and fields. These are almost completely determined by the laws of quantum mechanics, with very refined corrections required by quantum electrodynamics. Despite the enormous complexity of most atomic systems, in which each electron interacts with both the nucleus and all the other orbiting electrons, the wavelike nature of particles, combined with the Pauli exclusion principle, results in an amazingly orderly array of atomic properties. These are systematized by the Mendeleev periodic table. In addition to their classification by chemical activity and atomic weight, the various elements of this table are characterized by a wide variety of observable properties. These include electron affinity, polarizability, angular momentum, multiple electric moments, and magnetism.
Industry:Science
The techniques, equipment, and organization for providing the memory capability required by computers in order to store instructions and data for processing at high electronic speeds. In early computer systems, memory technology was very limited in speed and high in cost. Since the mid-1970s, the advent of high-density, high-speed random-access memory (RAM) chips has reduced the cost of computer main memory by more than two orders of magnitude. Chips are no larger than ¼ in. (6 mm) square and contain all the essential electronics to store tens to hundreds of thousands of bits of data or instructions. An analogous increase in magnetic recording density has increased the capacity and reduced the cost per bit of secondary memory. Traditionally, computer storage has consisted of a hierarchy of three or more types of memory storage devices (for example, RAM chips, disks, and magnetic tape units).
Industry:Science
The most familiar flowers of the angiosperms (flowering plants) are colorful, with the colors serving to attract insect or other animal pollinators. However, many plants, including grasses and many broad-leaved trees of the Northern Temperate Zone, have inconspicuous flowers. These are pollinated by wind, so colorful structures are not needed and are not produced. The essential features that define a flower are the reproductive structures at the center of the flower, not colorful petals. Stamens are the male structures of flowers. Stamens surround the female structures, the carpels. Stamens and carpels have many technical features that distinguish them from the reproductive organs of nonflowering plants. The nonflowering plants include the gymnosperms, which make seeds but do not make flowers, and the ferns, lycopods, mosses, and liverworts, which reproduce by means of tiny spores rather than by seeds.
Industry:Science
The quantity that measures the relationship between the strength of an information-carrying signal in an electrical communications system and the random fluctuations in amplitude, phase, and frequency superimposed on that signal and collectively referred to as noise. For analog signals, the ratio, denoted <i>S</i>/<i>N</i>, is usually stated in terms of the relative amounts of electrical power contained in the signal and noise. For digital signals the ratio is defined as the amount of energy in the signal per bit of information carried by the signal, relative to the amount of noise power per hertz of signal bandwidth (the noise power spectral density), and is denoted <i>E<sub>b</sub></i>/<i>N</i><sub>0</sub>. Since both signal and noise fluctuate randomly with time, <i>S</i>/<i>N</i> and <i>E<sub>b</sub></i>/<i>N</i><sub>0</sub> are specified in terms of statistical or time averages of these quantities.
Industry:Science
The main vessel of the systemic arterial circulation arising from the left ventricle of the heart; it is divided into three parts for convenience only. The first portion, the ascending aorta, passes upward under the pulmonary artery; the coronary arteries arise at the base of the ascending aorta behind the aortic valves. The second part, or aortic arch, curves over the hilum of the left lung, giving off the innominate, left carotid, and left subclavian arteries, which supply the neck, head, and forelimbs. The third portion, or descending aorta, continues downward in the thorax on the left side of the vertebral column to the diaphragm, giving off small arteries to the bronchi, esophagus, and other adjacent tissues. Below the diaphragm this vessel, known as the abdominal aorta, descends to the level of the fourth lumbar vertabra where it bifurcates into the two common iliac arteries supplying the hindlimbs.
Industry:Science
The reaction that occurs when tissue (usually skin) receives more energy (heat, chemical energy, electrical energy, or radiation) than it can absorb without injury. Factors such as the duration of contact, temperature, volume of chemical, and voltage influence the severity of the injury. The notable pathologic changes are denaturation of protein and coagulation of blood vessels. Local destruction of tissue leads to bacterial invasion and infection; loss of fluid, electrolytes, and protein; loss of temperature control; and pain. Systemic reactions include altered blood flow and temperature regulation, fluid and electrolyte imbalances, shock, infections, and catabolism. Associated problems—other illnesses (particularly cardiopulmonary), trauma, and injuries caused by inhaling carbon monoxide, smoke, and occasionally heat—may be lethal or contribute significantly to mortality and morbidity from burn injuries.
Industry:Science
The process by which a document is scanned and converted into electrical signals which are transmitted over a communications channel and recorded on a printed page or displayed on a computer screen. The scanner may be compared with a camcorder, and the recorder is similar to an office copier or a computer printer. As an alternative to scanning, a document stored in computer memory can be transmitted. As an alternative to recording, a text facsimile (fax) image can be captured in computer memory and converted into computer-processable text by optical character recognition (OCR) software. Telephone lines or satellites provide the communication channel. More than 99% of facsimile units are International Telegraph and Telephone Consultative Committee Group 3, used for sending business documents. The remainder have specialized designs tailored for a number of important applications that cannot be fulfilled by Group 3.
Industry:Science
The science dealing with the description of the positions of objects in space under the action of forces as a function of time. Some of the laws of mechanics were recognized at least as early as the time of Archimedes (287?–212 <small>b.c.</small>). In 1638, Galileo stated some of the fundamental concepts of mechanics, and in 1687, Isaac Newton published his <i>Principia</i>, which presents the basic laws of motion, the law of gravitation, the theory of tides, and the theory of the solar system. This monumental work and the writings of J. d'Alembert, J. L. Lagrange, P. S. Laplace, and others in the eighteenth century are recognized as classic works in the field of mechanics. Jointly they serve as the base of the broad field of study known as classical mechanics, or Newtonian mechanics. This field does not encompass the more recent developments in mechanics, such as statistical, relativistic, or quantum mechanics.
Industry:Science
The principle of conservation of energy states that energy cannot be created or destroyed, although it can be changed from one form to another. Thus in any isolated or closed system, the sum of all forms of energy remains constant. The energy of the system may be interconverted among many different forms—mechanical, electrical, magnetic, thermal, chemical, nuclear, and so on—and as time progresses, it tends to become less and less available; but within the limits of small experimental uncertainty, no change in total amount of energy has been observed in any situation in which it has been possible to ensure that energy has not entered or left the system in the form of work or heat. For a system that is both gaining and losing energy in the form of work and heat, as is true of any machine in operation, the energy principle asserts that the net gain of energy is equal to the total change of the system's internal energy.
Industry:Science
