- 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.
Optical microscopy remains one of the most powerful research tools in the biological and material sciences. The main advantage of optical techniques is that they enable noninvasive studies on micrometer length scales under native environmental conditions. Their major drawback is that the diffraction of light limits the spatial resolution to about 100 nanometers, preventing visualization of smaller species such as single molecules and molecular assemblies. For many years, scientists searched for a complementary technique with the high resolution of electron microscopy that would operate in a physiologically relevant environment. With the development of scanning probe or proximal probe techniques, and in particular atomic force microscopy (AFM) in 1986, a new era of microscopy began.
Industry:Science
Short cosmic blasts of very high energy electromagnetic radiation (gamma radiation) that are recorded at an average of about once per day by detectors placed above the Earth's atmosphere. At distances of billions of light-years, the energy emitted in a gamma-ray burst (GRB) is more than a billion billion (10<sup>18</sup>) times the energy emitted each second by the Sun. The mechanism for the origin of gamma-ray bursts remains a focus of current research. Gamma-ray bursts longer than 2 seconds appear to be associated with the supernova explosions of massive stars in distant galaxies. Recent evidence suggests that shorter gamma-ray bursts are the result of merging neutron stars or black holes. There are indications that both types of gamma-ray bursts lead to the birth of black holes.
Industry:Science
One of a class of compounds which contains long-chain aliphatic hydrocarbons (cyclic or acyclic) and their derivatives, such as acids (fatty acids), alcohols, amines, amino alcohols, and aldehydes. The presence of the long aliphatic chain as the characteristic component of lipids confers distinct solubility properties on the simpler members of this class of naturally occurring compounds. This led to the traditional definition of lipids as substances which are insoluble in water but soluble in fat solvents such as ether, chloroform, and benzene. However, those lipids (particularly glycolipids and phospholipids) which contain polar components in the molecule may be insoluble in these solvents, and some are even soluble in water. Most of the phosphatides are good emulsifying agents.
Industry:Science
Loran is a ground-based radionavigation system, with signals that propagate along the surface of the Earth (groundwaves) and reflect off the ionosphere to return to the Earth's surface (skywaves). Groundwaves and skywaves impinge on a receiver, together with other noise present in the spectrum at frequencies around 100 kHz (such as noise from nearby power lines or lightning). In general, groundwaves are useful for navigation purposes, but skywaves contribute unwanted noise and distort groundwaves. In order to resolve the most useful groundwaves accurately and to reduce noise introduced by skywaves, less useful groundwaves, and other interference sources, a modern Loran receiver must track, separate, and process all these signals simultaneously to achieve the performance now possible.
Industry:Science
In the inner solar system, Mercury, Venus, and Mars are similar in size to the Earth, so the four are collectively called terrestrial planets. Their small masses and sizes are in marked contrast to those of the giant planets—Jupiter, Saturn, Uranus, and Neptune—at far greater distances from the Sun. The four terrestrial planets and Earth's Moon offer a rich variety in physical makeup and environment. Traditionally, Mercury and the Moon were described as airless bodies, classic cases of objects too small in mass to hold on to gases to form a permanent atmosphere. With advances in modern technology for ground-based remote sensing and space-flight opportunities for direct samplings, both Mercury and the Moon are now known to have transient atmospheres, continuously being formed and lost.
Industry:Science
Liquid and gaseous hydrocarbons remain the primary energy sources of the industrialized economies; in the United States, more than 700 million gallons of oil products and 51 billion cubic feet of natural gas are used every day. Pipelining is the primary means of delivering these hydrocarbons to the consumer. While less developed economies still rely heavily on batch mode such as trucks and rails as the primary means of distributing energy, the more developed economies rely more on the continuous mode of transport afforded by pipelines. In addition to being economic and very efficient, an underground pipeline network is an environmental and safety imperative. Burying pipelines preserves the esthetics of the environment while protecting the pipelines from accidental damage and sabotage.
Industry:Science
Proteins are polymers of amino acid building blocks that are joined by covalent peptide bonds (proteins are also known as polypeptides). They play critical roles in all organisms, from acting as channels through which metabolites enter cells to converting nutrients into energy or regulating production of other proteins. Until recently, each polypeptide prescribed by a genetic message was thought to have a single purpose or function. As more amino acid sequences of proteins were determined in various organisms, and as more experiments were done with specific proteins, the one-protein–one-function assumption was called into question because it underestimated the ingenuity at work in the cell. Geneticists and biochemists continue to discover that many proteins have more than one purpose.
Industry:Science
Severe acute respiratory syndrome was first recognized in November 2002. An international outbreak involving 26 countries, 8098 cases, and 774 deaths subsequently developed, ending in July 2003. Since then, two isolated cases of SARS and one cluster of 11 cases including one death have been identified, resulting from the “escape” of SARS-associated coronavirus (CoV) from research laboratories. In addition, four isolated cases of SARS with no secondary cases were identified in December 2003 and January 2004. Aside from these scenarios, to date there has been no evidence of a large-scale reemergence of SARS. Regardless, much interest and research continues into better understanding SARS in order to be prepared for its possible reemergence and/or the emergence of other similar pathogens.
Industry:Science
Neutrinos are elementary, subatomic particles, first postulated by W. Pauli in 1930 and first detected by F. Reines and C. L. Cowan in 1956. They carry no electric charge and interact with other particles only via the weak force. Neutrinos come in three flavors, as distinguished by the weak force. The three flavors are electron neutrino, muon neutrino, and tau neutrino. Other known elementary particles, such as quarks and charged leptons, also come in three flavors that are successively heavier in mass; however, the situation for neutrinos is less definitive. Until recently, all that was known about neutrino mass was that neutrinos must be very light if they had any mass at all. Theoretically, within the standard model of particle physics, neutrinos were even considered to be massless.
Industry:Science
In the broadest sense of the term, that part of mechanics which deals with the relation between force and deformation in material bodies. The nature of this relation depends on the material of which the body is constituted. It is customary to represent the deformation behavior of metals and other solids by a model called the linear or hookean elastic solid (displaying the property known as elasticity) and that of fluids by the model of the linear viscous or newtonian fluid (displaying the property known as viscosity). These classical models are, however, inadequate to depict certain nonlinear and time-dependent deformation behavior that is sometimes observed. It is these nonclassical behaviors which are the chief interest of rheologists and hence referred to as rheological behavior.
Industry:Science
