- 行业: Printing & publishing
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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.
Biological invasion is the process by which species (or genetically distinct populations), with no historical record in an area, breach biogeographic barriers and extend their range. Invasions occur as a natural ecological process. For example, after North and South America collided 3 million years ago, numerous mammals (deer, rodents, cats, skunks, weasels, llamas) extended their ranges south, and a few (armadillo, porcupine, oppossum) extended their ranges north. However, over the course of human history, the pace of biological invasions has accelerated because, through their travels and trade, humans tend to move other species. The immediate consequence of biological invasion is a local increase in the number of introduced species, also called alien, invasive, exotic, or nonindigenous species.
Industry:Science
Flight at speeds well above the local velocity of sound. In the span of a few years speeds of aircraft, missiles, and spacecraft increased tremendously, from far less than the speed of sound (subsonic) to speeds required for orbiting or escape from the Earth. By convention, hypersonic flight starts at about Mach 5 (five times the speed of sound) and extends upward in speed indefinitely.
A more precise definition, attributed to T. von Kármán, states that hypersonic flight starts when the cross-flow Mach number (or Mach-number component perpendicular to the longitudinal axis) becomes 1 or greater. In any case, hypersonic flight refers to atmospheric flight at hypersonic speed when the characteristics of the flow field about the body are sensibly unchanged as the speed of the body increases further.
Industry:Science
Fundamental principles governing the transmission of genetic traits, discovered by an Augustinian monk Gregor Mendel. In 1856, Mendel performed his first set of hybridization experiments with pea plants in the monastery garden at Brno, Moravia.
Although the pea plant is normally self-fertilizing, it can be easily crossbred, and grows to maturity in a single season. True breeding strains, each with distinct characteristics, were available from local seed merchants. For his experiments, Mendel chose seven sets of contrasting characters or traits. For stem height, the true breeding strains tall (7 ft or 2.1 m) and dwarf (18 in. or 45 cm) were used. He also selected six other sets of traits, involving the shape and color of seeds, pod shape and color and the location of flowers on the plant stem.
Industry:Science
Diamond is the crystalline form of carbon with a wide range of unique and desirable properties. Diamond is the hardest substance known; it is the best conductor of heat at room temperatures; it expands or contracts less than nearly all other materials when exposed to temperature changes; and it is optically transparent to a very wide range of visible light and other electromagnetic radiation. Such properties have made diamond a useful material for precise and durable cutting and grinding tools, for optical windows for various sensor technologies, and for heat sinks to help draw away the energy and heat generated by closely packed electronic components. As such markets for diamond products have developed, considerable interest has been generated in finding and perfecting methods to synthesize diamond.
Industry:Science
Caves remain one of the last unexplored frontiers on Earth. Yet, unlike space or the deep ocean, cave exploration is available to the common man or woman; with training and minimal equipment (a helmet and three sources of light), it is possible to walk where no human has walked before. Nonetheless, the dangers of cave exploration are very real, and not every individual looks forward to the idea of 100-m (330-ft) pits, or crawls so tight that one must exhale to fit. Therefore, the exploration of these passages, as both a human and scientific endeavor, is well behind that of the other terrestrial areas of our planet. As scientists begin to examine this environment, they are making discoveries that are changing our ideas on how caves form and the role that microbial species play in this unique environment.
Industry:Science
Diamond is a very versatile material. Although it has remarkable characteristics, for example, high thermal conductivity, very low electric conductivity, and extreme hardness, its other properties have limited its use. Since the first production of high-pressure synthetic diamond in 1955, industrial diamond has been manufactured in large amounts, and it is now widely used.
In 1976, a film of diamond was formed for the first time by chemical vapor deposition. It is now possible to make thin films with sizes larger than those made by high-pressure synthesis. Consequently, diamond can be used in new applications, such as surface coating. The techniques for using diamond, like those for using silicon, have rapidly progressed as diamond has been transformed from a bulk material into a high-quality thin film.
Industry:Science
Despite being bilaterally symmetric from an external viewpoint, vertebrates exhibit a significant degree of internal asymmetry, particularly regarding the formation and location of internal organs. While some of the internal organs are paired, such as the kidneys and gonads, the majority are unpaired and localized in a conserved position within the body. For example, the heart, spleen, and stomach are located on the left side of the body, while the bulk of the liver is on the right side. Even organs which appear paired, such as the lungs, are actually asymmetric; for example, in humans the right lung consists of three lobes, while the left lung has two. The organization of the internal organs allows for their efficient packing within the body cavity; it is also important for their functional development.
Industry:Science
Feeling depressed is a common human experience, occurring most often as a normal response to external events or personal loss. However, a major depressive episode, whether of unknown origin or a part of a defined neurological disorder, is a pathological condition. Depression is characterized as one of the major affective disorders, all of which share a primary dysregulation in mood. It is diagnosed not only by the presence of persistent negative mood but also by pronounced and unrelenting disturbances in attention, motivation, motor and mental speed, sleep, appetite, and libido. These symptoms occur in combination with sustained anhedonia (that is, the inability to experience pleasure), excessive or inappropriate guilt, recurrent thoughts of death with suicidal ideations, and in some cases suicide attempts.
Industry:Science
Engineering activities involved in the creation and operation of the technical and economic processes that convert raw materials, energy, and purchased items into components for sale to other manufacturers or into end products for sale to the public. Defined in this way, manufacturing engineering includes product design and manufacturing system design as well as operation of the factory.
More specifically, manufacturing engineering involves the analysis and modification of product designs so as to assure manufacturability; the design, selection, specification, and optimization of the required equipment, tooling, processes, and operations; and the determination of other technical matters required to make a given product according to the desired volume, timetable, cost, quality level, and other specifications.
Industry:Science
Changes in technology, particularly information technology, are having an increasing impact on transportation systems and how we travel. Many automobile manufacturers now install car navigation systems. Personal communications service (PCS, or cell phones) and personal digital assistants (PDAs) affect urban locational and travel behavior. Location-based systems (LBS) will soon be able to use a combination of such technologies to advise travelers of the best route from point A to point B. Using PCS and PDAs, location-based systems will guide travelers to geographic locations, restaurants, gas stations, museums, and other objectives. Information technology also affects us in that any one or more of these telecommunication means may be substituted for face-to-face contact, making travel unnecessary in some cases.
Industry:Science
