- 行业: Printing & publishing
- Number of terms: 178089
- Number of blossaries: 0
- 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.
Even as we continue to destroy vast amounts of natural habitat, we are attempting to restore areas of degraded habitat to their past conditions. Unfortunately it is often unclear what the past conditions of the area were and, therefore, what the goal of habitat restoration should be. Historical ecology explores what a region or ecosystem looked like during different points in history. It can therefore aid us in setting goals for restoration projects and help us predict how our actions will affect the ultimate appearance of the land.
Industry:Science
From an information technology perspective, ontologies are hierarchical structuring of knowledge about things by subcategorizing them according to their essential or relevant qualities. An ontology can be considered a conceptualization of a domain or subject area typically captured in an abstract model of how people think about things in the domain. Humans have produced ontologies for millennia, from Plato's philosophical framework to modern-day classification systems, for understanding and explaining their rationale and environment.
Industry:Science
Elementary modes of oscillation of the whole nucleus, closely related to the normal modes of oscillation of coupled mechanical systems. Giant nuclear resonances occur systematically in most, if not all, nuclei, with oscillation energies typically in the range of 10–30 MeV. Among the best-known examples is the giant electric dipole (E1) resonance, in which all the protons and all the neutrons oscillate with opposite phase, producing a large time-varying electric dipole moment which acts as an effective antenna for radiating gamma rays.
Industry:Science
Genetic engineering is the use of molecular techniques to transfer genes from one organism to another, with the transfer usually occurring across species. This process allows scientists to create new crop varieties with novel combinations of traits. The resulting plants may confer enormous benefits or risks on both humanity and the environment at large. Worldwide, almost 70 million acres of farmland were sown with genetically engineered crops in 1998, and the acreage devoted to these “high-tech” crop varieties is continuing to expand.
Industry:Science
Directed evolution is an attempt to replicate in the laboratory nature's method of developing protein catalysts (enzymes) with desirable properties or for particular reactions. In this technology, the amino acid sequence of a known enzyme is randomly mutated to create millions of different versions; the variants are then screened to reveal which has particular attributes or is best suited to perform a specific task. Over the last decade, directed evolution has become an important tool for enzyme discovery in both academia and industry.
Industry:Science
Extinct, armored, jawless vertebrates with a single pair of external gill openings. Heterostraci first appeared in the Ordovician, according to some authorities, and became common in the Silurian and Devonian. Their bony dermal armor consists mainly of aspidine (bone with apparent growth layers, lacking cavities for bone cells) and is composed of three structural layers: a basal layer of lamellar bone, a middle layer usually with a honeycomb arrangement of cavities and partitions, and a superficial layer of dentine tubercles or ridges.
Industry:Science
Flow in which density changes are not negligible. Pressure changes normally occur throughout a fluid flow, and these pressure changes, in general, induce a change in the fluid density. In a compressible flow, the density changes that result from these pressure changes have a significant influence on the flow. The changes in the flow that result from the density changes are often termed compressibility effects. All fluids are compressible. However, compressibility effects are more frequently encountered in gas flows than in liquid flows.
Industry:Science
Halogenated hydrocarbons such as chlorinated ethylenes are commonly found in the environment. For many years it was believed that most of these compounds originated from anthropogenic (human-made) sources. However, it was recently discovered that over 3500 organohalides are naturally occurring. For instance, some researchers have found that organohalides are sometimes used as a part of microbial defense mechanisms against predators. It is now an accepted fact that these compounds are generated from both anthropogenic and biogenic sources.
Industry:Science
Any of a group of secondary metabolites produced by the common molds <i>Aspergillus flavus</i> and <i>A. parasiticus</i> that cause a toxic response in vertebrates when introduced in low concentration by a natural route. The group constitutes a type of mycotoxin. Discovered in 1960 after a massive poisoning of turkey poults fed moldy peanut meal, aflatoxin has become the focus of a highly interdisciplinary research field involving chemists, mycologists, veterinarians, agriculturalists, toxicologists, and other basic and applied scientists.
Industry:Science
Any of the substances containing esters of higher fatty acids and long-chain monohydric alcohols. From a practical standpoint, this definition is inadequate because it allows liquids such as sperm whale oil and jojoba oil to be called waxes, and it fails to indicate the complexity of waxes. While waxes do contain wax esters, they are seldom if ever pure. They are usually mixtures that may contain high-molecular-weight acids, alcohols, esters, ketones, hydrocarbons, sterols, diesters, hydroxyacids, and so forth, as well as the wax esters.
Industry:Science
