- 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.
Different states of matter are distinguished by their internal structures or orders. For many years, all the orders were thought to be associated with symmetries (or rather, the breaking of symmetries). For example, when a gas changes into a crystal, the continuous translation symmetry of the gas is reduced to a discrete translation symmetry of the crystal. Based on the relation between orders and symmetries, a general theory of ordering was developed by L. Landau. The success of Landau's theory gave rise to a widespread belief that, at least in principle, all the kinds of order that matter can display were understood.
Industry:Science
Equations of motion of a mechanical system for which a classical (nonquantum-mechanical) description is suitable, and which relate the kinetic energy of the system to the generalized coordinates, the generalized forces, and the time. If the configuration of the system is specified by giving the values of <i>f</i> independent quantities <i>q</i><sub>1</sub>, …, <i>q</i><sub><i>f</i></sub>, there are <i>f</i> such equations of motion. In their usual form, these equations are equivalent to Newton's second law of motion and are differential equations of the second order for the <i>q</i>'s as functions of the time <i>t</i>.
Industry:Science
Human influence on the weather and, ultimately, climate. This can be either intentional, as with cloud seeding to clear fog from airports or to increase precipitation, or unintentional, as with air pollution, which increases aerosol concentrations and reduces sunlight. Weather is considered to be the day-to-day variations of the environment—temperature, cloudiness, relative humidity, wind-speed, visibility, and precipitation. Climate, on the other hand, reflects the average and extremes of these variables, changing on a seasonal basis. Weather change may lead to climate change, which is assessed over a period of years.
Industry:Science
For many years, experiments studying the scattering of electrons, muons, and neutrinos on nucleons have provided abundant information on the structure of the nucleon and on the properties of the basic forces acting between elementary constituents. With the opening of the electron-proton collider HERA (Hadron-Electron-Ring Accelerator) at DESY (Deutsches Elektronen-Synchrotron) in Hamburg, Germany, the available center-of-mass energy in the lepton-nucleon system increased by more than an order of magnitude, corresponding to a tenfold improvement in spatial resolution compared to that provided in fixed-target experiments.
Industry:Science
Fungal (or mold) spores are commonly dispersed in air, and on some days 10,000 or more fungal spores can be found in a cubic meter of air. With every breath humans take, there is a high potential that fungal spores will be inhaled. Usually this is not a problem, but if the number of spores inhaled is high enough, susceptible and sensitized individuals may develop adverse effects, such as an allergic response. Recently it has been suggested that the spores of some fungi may contain toxins and that inhalation leads to deleterious effects when the toxins are released in the lungs. However, this conclusion is controversial.
Industry:Science
High throughput screening (HTS) is used in the identification of small molecules that may lead to new therapeutic or commercial developments. Utilizing robotics, miniaturization, computer-aided molecular design (CAMD), combinatorial organic synthesis (COS), and screening information managing systems (SIMS), it provides a rapid, cost-effective method to screen potential sources for novel molecules often used in drug development. Unlike conventional screening, high throughput screening deals with a wide variety of input samples. Each sample has its own set of data and tracking issues, and produces new experimental results.
Industry:Science
Any of the viruses that infect bacterial cells. They are discrete particles with dimensions from about 20 to about 200 nanometers. A given bacterial virus can infect only one or a few related species of bacteria; these constitute its host range. Bacteriophages consist of two essential components: nucleic acid, in which genetic information is encoded (this may be either ribonucleic acid, in the RNA phages, or deoxyribonucleic acid, in the DNA phages), and a protein coat (capsid), which serves as a protective shell containing the nucleic acid and is involved in the efficiency of infection and the host range of the virus.
Industry:Science
Electrospinning is a fiber-forming process capable of producing continuous nanoscale-diameter fibers using electrostatic forces. The combination of high specific surface area, flexibility, and superior directional strength makes fiber a preferred material for many applications, ranging from clothing to reinforcements for aerospace structures. Although the effect of fiber diameter on the performance and processability of fibrous structures has long been recognized, the practical generation of nanoscale fibers was not realized until the rediscovery and popularization of electrospinning technology by D. Reneker in the 1990s.
Industry:Science
Cholesterol is an essential component of all animal cell membranes, especially the limiting plasma membrane. It must be made available in sufficient amount either by synthesis in situ or by acquisition from the diet. Yet, the accumulation of excess cholesterol in cells and tissues can be toxic. Thus, a highly regulated system has evolved for the synthesis and distribution of cholesterol within and between cells. This is particularly important in the brain, which by far has the highest concentration of cholesterol in the body. Indeed, the central nervous system has about 25% of the total body cholesterol of an adult animal.
Industry:Science
Cosmic high-energy gamma rays are produced by a diverse array of sources in the universe that signal the presence of natural particle accelerators. Among these are distant cores of active galaxies and the mysterious gamma-ray bursts, pulsars and cosmic-ray interactions in our Galaxy, and the Sun and Moon in our solar system. The recently launched <i>Fermi Gamma-ray Space Telescope</i>, with unprecedented sensitivity and angular resolution, is discovering hundreds of new sources of cosmic gamma rays with the hope of probing the inner workings of the high-energy accelerators and possibly uncovering the nature of dark matter.
Industry:Science
