- 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.
Compounds containing the dinitrogen molecule, N<sub>2</sub>, bound to a metal (also called dinitrogen complexes). While it was long known that molecular nitrogen avidly binds to the surface atoms of many metallic phases, no reaction of molecular nitrogen has been observed under the conditions of ordinary solution chemistry. Indeed, chemists had been so accustomed to regard nitrogen as a completely inert gas at ordinary temperatures that the formation of coordination compounds with molecular nitrogen aroused general surprise when first reported in the mid-1960s. Since then the interaction of molecular nitrogen with coordination compounds has been the subject of intensive research. Today the capability of molecular nitrogen to enter into coordination compounds as a ligand is established beyond any doubt, and it is at least partly understood under which conditions the dinitrogen molecule can lose its customary inertness.
Industry:Science
As late as the nineteenth century, it was commonly believed that climate represented a kind of averaged weather over time at a geographical location and hardly changed, at least for the period comparable to the length of human history. It has been demonstrated that climate changes at millennial, centennial, and even decadal scales, as many studies in the twentieth century have revealed. Such studies were largely done by examining environmental data such as tree rings, pollen assemblages, lake sediment, and ice cores. These data are objective and usually continuous, but they are often difficult to interpret. For example, a narrow tree ring could mean either a dry spell or cold spring, or both. Consequently, conclusions obtained this way are often associated with considerable uncertainties or ambiguities. Furthermore, environmental data usually have low time resolution and hence are not suitable for high-resolution analysis.
Industry:Science
Any of several processes by which liquid mixtures containing azeotropes may be separated into their pure components with the aid of an additional substance (called the entrainer, the solvent, or the mass separating agent) to facilitate the distillation. Distillation is a separation technique that exploits the fact that when a liquid is partially vaporized the compositions of the two phases are different. By separating the phases, and repeating the procedure, it is often possible to separate the original mixture completely. However, many mixtures exhibit special states, known as azeotropes, at which the composition, temperature, and pressure of the liquid phase become equal to those of the vapor phase. Thus, further separation by conventional distillation is no longer possible. By adding a carefully selected entrainer to the mixture, it is often possible to “break” the azeotrope and thereby achieve the desired separation.
Industry:Science
In applying biotechnology to agriculture, the principal areas involve manipulation of crop plants and manipulation of microbial or invertebrate associates of crop plants and weeds. Technological objectives may be achieved by conventional selection and breeding or by genetic engineering of plants, microbes, or invertebrates, or via manipulation of the environment. Such technologies can be combined in various agronomic systems with traditional practices such as chemical pesticides or fertilizers. Fungi play an expanding role in agribiotechnology as biological control agents, as mycorrhizal associates of plant roots, as agents for the degradation of lignocellulose and other forms of bioremediation (the application of microorganisms to biodegrade pollutants), or as food crops which utilize agricultural waste as a substrate. In food and beverage processing, fungi supply an array of enzymes plus natural flavor and color additives.
Industry:Science
Criminalistics is the science and profession dealing with the recognition, collection, identification, individualization, and interpretation of physical evidence, and the application of the natural sciences to law-science matters. The term originated from the book <i>Handbuch für Untersuchungsrichter als System der Kriminalistik</i> (3d ed., 1898) by Hans Gross, an investigating magistrate and professor of criminology at the University of Prague. He described the need for a scientifically trained investigator who could undertake certain technical aspects of an investigation and could also serve as liaison between scientific specialists who might assist in the investigation of criminal activity. This concept was popular in Europe, where a number of forensic science institutes were developed to apply the tools and techniques of the natural sciences to the investigation of crime and, generally, in official governmental inquiries.
Industry:Science
Because of advancements in the analytical methods used for detecting chemicals in the environment, trace levels of prescription and over-the-counter drugs have been found in waterways. The frequent detection of many pharmaceutical compounds in the environment has been an increasing concern because of their potential to cause undesirable ecological effects, which may range from endocrine disruption in fish and wildlife to antibiotic resistance in pathogenic bacteria. Residues of human and veterinary pharmaceuticals (such as antibiotics, estrogens, and active ingredients of drugs) are introduced into the environment via a number of pathways, but primarily from discharges of wastewater treatment plants or land application of sewage sludge and animal manure. Most active ingredients of pharmaceuticals are transformed only partially in the body and thus are excreted as a mixture of metabolites and bioactive forms into sewage systems.
Industry:Science
Electricity, or electric polarity, resulting from the application of mechanical pressure on a dielectric crystal. The application of a mechanical stress produces in certain dielectric (electrically nonconducting) crystals an electric polarization (electric dipole moment per cubic meter) which is proportional to this stress. If the crystal is isolated, this polarization manifests itself as a voltage across the crystal, and if the crystal is short-circuited, a flow of charge can be observed during loading. Conversely, application of a voltage between certain faces of the crystal produces a mechanical distortion of the material. This reciprocal relationship is referred to as the piezoelectric effect. The phenomenon of generation of a voltage under mechanical stress is referred to as the direct piezoelectric effect, and the mechanical strain produced in the crystal under electric stress is called the converse piezoelectric effect.
Industry:Science
Immunoselective adsorption processes exploit biospecific interactions between antibodies and their corresponding antigens in order to separate pure high-value bioactive products from biological sources (for example, blood, food materials, and products of genetically engineering organisms). Enzymes, hormones, vaccines, interferons, and antibodies have been purified by using immunoselective adsorption processes. The purified products find applications in therapeutics, diagnostic tests, drug targeting, food immunoassays, research, and clinical examinations, and as ligands for the preparation of highly selective immunoadsorbents. Immunoassays are rapidly becoming important for the detection and quantification of components in foods such as additives, fungal and bacterial contaminants, antinutritional factors, pesticide residues, and hormones. Purified antibodies have potential use in infant formulas to prevent intestinal infections.
Industry:Science
Fast response can be the key to saving lives in an emergency. In the 1960s, the U.S. government reserved 911 as the telephone number to be used for requesting emergency assistance, because this number can be easily memorized and dialed quickly. Since that time, public safety agencies in the United States have invested heavily in Enhanced 911 (E911) service, which provides for automatic display of the calling party's address and phone number on the public safety operator's console. However, in recent years wireless communication networks, such as cellular and personal communication services (PCS), which cannot locate emergency callers, have been deployed throughout the United States. This is a growing concern because nearly 100,000 wireless 911 calls are placed each day and that number continues to increase. Unfortunately, public safety officials report that many wireless emergency callers cannot accurately describe their location.
Industry:Science
Humans evolved in Africa and were confined to that continent for much of their early history. Just what triggered the first dispersals from Africa is poorly understood, but it is clear that people began to colonize Eurasia shortly after 2 million years ago (Ma). These migrants were probably representatives of <i>Homo erectus</i> (sometimes called <i>H. ergaster</i>). This extinct species was the first to attain a body size (stature) equal to that of modern humans, although the brain remained low in volume and thus smaller relative to body size than our own. Archeological traces left by these people have been recovered from the Jordan Valley in Israel and the Georgian Caucasus. Such early occupations were likely transitory and did not result in permanent settlements. However, groups of <i>H. erectus</i> were able to travel across southern Asia to the Far East, where they established themselves in both Java and China by about 1.6 Ma.
Industry:Science
