- 行业: Printing & publishing
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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.
The study of gene structure and function in bacteria. Genetics itself is concerned with determining the number, location, and character of the genes of an organism. The classical way to investigate genes is to mate two organisms with different genotypes and compare the observable properties (phenotypes) of the parents with those of the progeny. Bacteria do not mate (in the usual way), so there is no way of getting all the chromosomes of two different bacteria into the same cell. However, there are a number of ways in which a part of the chromosome or genome from one bacterium can be inserted into another bacterium so that the outcome can be studied.
Industry:Science
The name “micromachined ultrasonic transducer (MUT)” is used for devices that are made using microfabrication techniques to generate and detect ultrasound. Although this general term also applies to transducers made by shaping bulk piezoelectric materials using micromachining techniques, the more specific definition refers to devices with tiny membranes that are driven by either capacitive or piezoelectric actuation. The advent of both capacitive and piezoelectric micromachined ultrasonic transducers, cMUTs and pMUTs, respectively, has been made possible by advances in integrated circuit fabrication technology. This article focuses particularly on cMUTs.
Industry:Science
The perceptual intensity of sound. Loudness depends importantly on the physical intensity of sound, increasing when physical intensity increases and decreasing when physical intensity decreases. But loudness also depends on other physical properties of sound, such as frequency and duration. Sound waves with frequencies between 1000 and 5000 Hz are louder than sound waves that have the same intensity but lower or higher frequencies. Very brief bursts of sound are less loud than are longer bursts, loudness increasing regularly as duration increases up to about 0.1–0.2 s, beyond which point in time, loudness no longer increases with increasing duration.
Industry:Science
The luminous streak lasting seconds or fractions of a second and seen at night when a solid, natural body plunges into the Earth's (or another planet's) atmosphere. The entering object is called a meteoroid and, if any of it survives atmospheric passage, the remainder is called a meteorite. Cosmic dust particles (with masses of micrograms) entering the atmosphere and leaving very brief, faint trails are called micrometeors, with the surviving pieces known as micrometeorites. If the apparent brightness of a meteor exceeds that of the planet Venus as seen from Earth, it is called a fireball; and when a bright meteor is seen to explode, it is called a bolide.
Industry:Science
The occurrence, circulation, distribution, and properties of any liquid water residing beneath the surface of the earth. This article excludes any water molecules which constitute mineral species such as clays. Generally, ground water is that fraction of precipitation which infiltrates the land surface and subsequently moves, in response to various hydrodynamic forces, to reappear once again as seeps or in a more obvious fashion as springs. Most of ground-water discharge is not evident because it occurs through the bottoms of surface water bodies; in fact, large fresh-water springs are relatively common on the ocean bottom off the eastern coast of Florida.
Industry:Science
The quantity of heat required to raise a unit mass of homogeneous material one unit in temperature along a specified path, provided that during the process no phase or chemical changes occur is known as the heat capacity of the material in question. The unit mass may be 1 g, 1 lb, or 1 gram-molecular weight (1 mole). Moreover, the path is so restricted that the only work effects are those necessarily done on the surroundings to cause the change to conform to the specified path. The path, except as noted later, is at either constant pressure or constant volume. This definition conforms to an average heat capacity for the chosen unit change in temperature.
Industry:Science
The science of measuring and describing the physical features and conditions of navigable waters and adjoining coastal areas. Hydrography is an applied science involving the study of marine areas, including oceans, rivers, and lakes. It involves geodesy, physical oceanography, marine geology, geophysics, photogrammetry (in coastal areas), remote sensing, and marine cartography. Basic parameters observed during a hydrographic survey are time, geographic position, depth of water, and bottom type. However, observation, analysis, and prediction of tides and currents area are also normally included in order to reduce depth measurements to a common vertical datum.
Industry:Science
The physical separation of different isotopes of an element from one another. The different isotopes of an element as it occurs in nature may have similar chemical properties but completely different nuclear reaction properties. Therefore, nuclear physics and nuclear energy applications often require that the different isotopes be separated. However, similar physical and chemical properties make isotope separation by conventional techniques unusually difficult. Fortunately, the slight mass difference of isotopes of the same element makes separation possible by using especially developed processes, some of which involve chemical industry distillation concepts.
Industry:Science
The principal food-conducting tissue in vascular plants. Its conducting cells are known as sieve elements, but phloem may also include companion cells, parenchyma cells, fibers, sclereids, rays, and certain other cells. As a vascular tissue, phloem is spatially associated with xylem, and the two together form the vascular system. Less is known of phloem than of xylem, partly because of its lesser direct economic importance and partly because the sieve elements function for a short time (usually one season) and then undergo marked structural and functional changes, such as crushing or sloughing off as a result of periderm formation in the case of woody plants.
Industry:Science
The measurement of the pressure on the surface of an object with fluid flow present is important in determining the behavior of fluid flow and calculating the forces imposed by the flow on an object. For example, the shock wave that forms on the upper surface of a commercial transport wing in cruise conditions can be located by knowing the surface pressure distribution. By knowing the pressure distribution over the surface of an automobile, ventilation inlets can be appropriately placed. Aircraft designers determine expected loads by measuring surface pressures on wind-tunnel models and integrating the corresponding forces over the entire surface of the model.
Industry:Science
