- 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.
Each of the giant planets (Jupiter, Saturn, Uranus, and Neptune) hosts three types of natural satellites: regular satellites, collisional remnants, and irregular satellites. The regular satellites follow prograde orbits (in which they move in the same direction as the planets about the Sun) that are nearly circular and lie in the equatorial plane of their host at a distance of a few tens of planetary radii. Their sizes (about 1000 km or 600 mi) rival or exceed that of the Earth's Moon. The smaller (about 10–100 km or 6–60 mi) collisional remnants also trace nearly circular, equatorial orbits, but they inhabit regions only a few planetary radii in extent and are often associated with planetary rings.
At these distances, the more intense meteoroid flux, gravitationally focused by the planet, has collisionally disrupted presumably once-larger bodies. The sizes of the known irregular satellites overlap those of the collisional remnants, but the irregular satellites follow extended (hundreds of planetary radii) orbits with significant eccentricities and inclinations. These distinct orbital characteristics suggest different formation mechanisms: The regular satellites and the progenitors of the collisional remnant satellites are believed to have formed in a circumplanetary accretion disk, while the irregular satellites are generally thought to have been captured from heliocentric orbits.
Although the regular satellites and collisional remnants have been and continue to be well studied by spacecraft missions, investigations of irregular satellites have been hampered by the small number of them that are known. However, in the past few years dozens more have been discovered, enlarging the known number from 11 to nearly 50. The larger number of examples of such bodies enables more detailed study of the mechanisms of their capture.
Industry:Science
Electric power system breakdown is a rather rare event. However, when it occurs the influence on society and the costs are tremendous. The electric power system is the most complex, widespread, and powerful interconnected process ever designed and constructed by humankind. Power systems normally cover many countries in synchronous operation, which means that changes of the operational conditions in one part of the system affect those in the rest of the system.
In normal stable operation these changes are small, coordinated, and well planned for, and do not affect the stability or the integrity of the system. Power systems will always be exposed to faults, such as earth faults and short circuits, caused by lightning strokes or insulation breakdown. Ever since the beginning of the electrification era, protection has been used to rapidly disconnect a power system element, such as a line, transformer, or generator, if it is faulted or overloaded, in order to save the element from total destruction and to continue the power supply to the healthy part of the system. However, power systems may, slowly or more rapidly, slide towards instability. Such a transition, from stable operational conditions, can be triggered by a very severe disturbance (such as the loss of a number of lines or of a whole substation) in a stressed operational situation (high load level and large power transfers). It could also be a result of a very rapid load growth, where the corresponding increase in generation cannot be achieved.
To preserve the integrity of the power system and avoid a widespread system breakdown, wide-area protection systems are now being introduced. Other names of systems aimed at taking actions to preserve the power system operation, even though no specific element is overloaded or faulted, are remedial action schemes (RAS); system protection schemes (SPS); and wide-area monitoring, protection, and control systems (WAMPAC).
Industry:Science
Fungi are eukaryotic organisms known to inhabit almost all ecological niches of the Earth and have the ability to utilize various solid substrates as a consequence of diversity of their biological and biochemical evolution. Some of the solid substrates utilized by fungi are dead and decaying material, including herbivore dung (saprophytic and coprophilous fungi), live plants (endophytic, parasitic, and mycorrhizal fungi), lichens (lichenicolous and endolichenic fungi), and insects (entomopathogenic fungi).
A characteristic feature of many of these fungi, especially those that exhibit filamentous growth and have a relatively complex morphology, is their ability to produce secondary metabolites. Soilborne, parasitic, and saprophytic fungal sources are relatively well investigated with regard to their secondary metabolites, and currently there is intense interest in secondary metabolites of symbiotic fungi that live in association with land plants, insects, lichens, and marine organisms. In contrast to primary metabolites such as proteins, DNA, RNA, polysaccharides, and so on, which occur universally, secondary metabolites are small-molecule organic compounds found restricted to a particular species, genus, or family. Thus, the presence or absence of certain secondary metabolites has been used successfully in the classification (chemotaxonomy) of large ascomycete genera (including <i>Alternaria</i>, <i>Aspergillus</i>, <i>Fusarium</i>, <i>Hypoxylon</i>, <i>Penicillium</i>, <i>Stachybotrys</i>, and <i>Xylaria</i>) and in a few genera of basidiomycetes.
Many secondary metabolites are not involved directly in the normal growth, development, or reproduction of the fungus in which they occur, but they may play an important role in ecological interactions with other organisms. For this reason, many fungal secondary metabolites exhibit useful biological activities and are of interest to the pharmaceutical, food, and agrochemical industries. Production of secondary metabolites often occurs after fungal growth has ceased as a result of nutrient limitations but with an excess carbon source available, making it possible to manipulate their formation. It is intriguing that some endophytic fungi are capable of producing secondary metabolites previously known from plants. Noteworthy examples include production of two clinically important anticancer drugs, paclitaxel (Taxol<sup>®</sup>) and camptothecin, by <i>Taxomyces andreanae</i> and <i>Nothapodytes foetida</i>, respectively, and a synthetic precursor of an anticancer drug, podophyllotoxin, by <i>Phialocephala fortinii</i>.
Industry:Science
Methods that make use of the behavior of physical quantities under coordinate transformations.
Industry:Science
Recent advances in printing technology involve digital platemaking and digital color proofing.
Industry:Science
Interruption of fuel flow to an engine due to blockage of passages in the fuel system by fuel vapor.
Industry:Science
One of the more common minerals of the borate group (in which boron is chemically bonded to oxygen).
Industry:Science
Printing on demand uses digital content and reproduction technology to print a digital page on paper.
Industry:Science
Quantum states for which certain variables can be measured more accurately than is normally possible.
Industry:Science
In quantum mechanics, a state that is not truly stationary but is almost stationary, as defined below.
Industry:Science
