- 行业: Printing & publishing
- Number of terms: 178089
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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.
All motion is relative to some frame of reference. The simplest laboratory frame of reference is three mutually perpendicular axes at rest with respect to an observer. Such a system is commonly used in the laboratory when various types of motion are being studied. The general effects of other motions to which the system as a whole is subjected are then neglected and the system is said to be isolated. In terms of the frame of reference of an observer some distance from Earth, the laboratory frame of reference would be moving with Earth as it rotates on its axis and as it revolves about the Sun. A simple form of motion in the laboratory frame of reference would appear to be a much more complicated motion in the frame of reference of the distant observer.
Industry:Science
All multicellular organisms have a nervous system, which may be defined as assemblages of cells specialized by their shape and function to act as the major coordinating organ of the body. Nervous tissue underlies the ability to sense the environment, to move and react to stimuli, and to generate and control all behavior of the organism. Compared to vertebrate nervous systems, invertebrate systems are somewhat simpler and can be more easily analyzed. Invertebrate nerve cells tend to be much larger and fewer in number than those of vertebrates. They are also easily accessible and less complexly organized; and they are hardy and amenable to revealing experimental manipulations, such as changes in the composition and temperature of the fluids surrounding them. However, the rules governing the structure, chemistry, organization, and function of nervous tissue have been strongly conserved phylogenetically. Therefore, although humans and the higher vertebrates have unique behavioral and intellectual capabilities, the underlying physical-chemical principles of nerve cell activity and the strategies for organizing higher nervous systems are already present in the lower forms. Thus neuroscientists have taken advantage of the simpler nervous systems of invertebrates to acquire further understanding of those processes by which all brains function.
Industry:Science
All of the Earth beneath the land surface and the ocean bottom, including the crust, the mantle, and the core. The interior is not accessible to direct observation. Nevertheless, a rather detailed model has been constructed on the basis of measurements made at or above the surface. Measurements of gravity, the geomagnetic field, surface heat flow, and surface deformation can all be used to put constraints on the Earth model, but the most detailed information about the interior is provided by seismic measurements. To the nonspecialist, seismic methods are perhaps best known for their application to the oil exploration industry, where seismic data are used to map the subsurface structure of sedimentary basins. In the exploration of the Earth's interior, the seismic waves being analyzed are usually generated by earthquakes, and measurements are made of waves propagating through the interior of the body (body waves), waves propagating along the surface (surface waves), and standing waves bringing the whole Earth into a state of oscillation (free oscillations). Such measurements, when properly interpreted, provide information about seismic-wave velocities in the Earth. On the other hand, seismic-wave velocities can also be measured in laboratory experiments where rock samples are subjected to the high pressures and temperatures typical of conditions in the deep interior. Meteorites provide rock samples of materials that are probably abundant in the solar system. The comparison of laboratory and field measurements thus leads, by inference, to a model where the composition and temperature distribution can be specified to some extent. What emerges from these studies is a picture not only of the structure but also of the evolution and dynamics of the Earth's interior.
Industry:Science
All of the living marine resources that we enjoy, whether as food or for their intrinsic appeal, depend ultimately on the base of the food chain, the plankton. Scientists have long recognized that the open ocean is not an unchanging environment. Currents, topography, and climate combine to create variabilities in time and space in the physical, chemical, and biological characteristics of the oceans. Plankton have limited control over their movements and thus are subjected to the local conditions that prevail. These conditions, in turn, determine where various types of planktonic organisms occur and how fast and abundantly they grow. In this way, ocean climate changes are transferred up the food chain to the fish, marine mammals, and seabirds that are, to us, the most prominent product of the marine ecosystem. To understand and predict changes in living marine resources under future climate-change and ocean-use scenarios, we need information about the physical environment and the plankton. The question is how best to measure and monitor these properties over thousands of kilometers. Satellites have gone a long way toward enabling a wide view of surface ocean characteristics such as temperature, ocean color, sea-surface height, and the amount of phytoplankton (plant plankton), but zooplankton (animal plankton) cannot yet be viewed from space. Research ships cost a significant amount of money to operate, and any kind of comprehensive spatial coverage of the North Pacific Ocean plankton would be prohibitively expensive and time-consuming. When scientists at the North Pacific Marine Science Organization (PICES) were considering this problem, they turned to the Sir Alister Hardy Foundation for Ocean Science (SAHFOS) and the continuous plankton recorder (CPR) survey for help.
Industry:Science
All of the psychological interactions between humans (and animals) and the world of sound. It encompasses all studies of the perception of sound, as well as the production of speech.
Industry:Science
All organisms interact with their environments, whether acquiring the resources needed for survival, sensing other organisms or physical surfaces, protecting themselves from various threats, or disposing of their waste products. With their high biomass and large populations worldwide, microorganisms interact with their nonliving and living environments to have effects that extend far beyond their individual cells, even at the global scale. These interactions also shape the microbes themselves, physically and physiologically, through genetic and epigenetic processes. (Epigenetic processes, in contrast to genetic processes, involve changes in gene expression that are not due to changes in DNA sequence.)
Industry:Science
All particles and radiations emanating from an atomic nucleus due to radioactive decay and nuclear reactions. Thus the criterion for nuclear radiations is that a nuclear process is involved in their production. The term was originally used to denote the ionizing radiations observed from naturally occurring radioactive materials. These radiations were alpha particles (energetic helium nuclei), beta particles (negative electrons), and gamma rays (electromagnetic radiation with wavelength much shorter than visible light).
Industry:Science
All prehistoric skeletal remains of humans that are archeologically earlier than the Neolithic (necessarily an imprecise limit), regardless of degree of mineralization or fossilization of bone, and regardless of whether the remains may be classed as <i>Homo sapiens sapiens</i> (anatomically modern humans). In this sense, the term “humans” is used broadly to mean all primates related to living people since the last common ancestor of people and African apes, thus all species currently included in the genera <i>Homo</i>, <i>Australopithecus</i>, <i>Ardipithecus</i>, and <i>Paranthropus</i> (and potentially others discussed below).
Industry:Science
All silicates are built of a fundamental structural unit, the so-called SiO<sub>4</sub> tetrahedron. The crystal structure may be based on isolated SiO<sub>4</sub> groups or, since each of the four oxygen ions can bond to either one or two silicon (Si) ions, on SiO<sub>4</sub> groups shared to form complex isolated groups or indefinitely extending chains, sheets, or three-dimensional networks. Mixed structures in which more than one type of shared tetrahedra are present are also known.
Industry:Science
All substances used in the construction of devices or instruments whose function is to alter or control electromagnetic radiation in the ultraviolet, visible, or infrared spectral regions. Optical materials are fabricated into optical elements such as lenses, mirrors, windows, prisms, polarizers, detectors, and modulators. These materials serve to refract, reflect, transmit, disperse, polarize, detect, and transform light. The term “light” refers here not only to visible light but also to radiation in the adjoining ultraviolet and infrared spectral regions. At the microscopic level, atoms and their electronic configurations in the material interact with the electromagnetic radiation (photons) to determine the material's macroscopic optical properties such as transmission and refraction. These optical properties are functions of the wavelength of the incident light, the temperature of the material, the applied pressure on the material, and in certain instances the external electric and magnetic fields applied to the material.
Industry:Science
