- 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.
Criteria air pollutants, including particulate matter, sulfur dioxide, nitrogen oxides, volatile organic compounds (precursors of ground-level ozone), carbon monoxide, and lead, and toxic air pollutants are a global concern. Historically, the Clean Air Act was concerned only with criteria air pollutants, the six common air pollutants for which the U.S. Environmental Protection Agency (EPA) had set standards. In 1990, the Clean Air Act was amended to address 188 chemical classes of air toxics.
A particular scenario that is receiving increased attention in the research and regulatory community is exposure to these compounds in near-road settings. Mobile source air toxics (MSATs) are emitted by vehicles either directly from exhaust systems or indirectly, such as from reentrainment of particle matter from roads. Addressing MSATs requires the combined expertise of engineering (for example, civil and mechanical engineering as applied to highway design and vehicle performance, respectively), the physical sciences (for example, particulate and gas phase partitioning of chemical compounds), and the social sciences (for example, decision theory as applied to selecting sites for representative samples from which to infer possible exposures).
Industry:Science
Eukaryotic chromosomes are divided into independent domains with distinct chromatin structures (euchromatin and heterochromatin). Most genes reside within euchromatic domains that are associated with irregular nucleosomal arrays enriched in histones (basic proteins of cell nuclei) that are hyperacetylated and methylated at lysine 4 of histone H3. Such nucleosomal modifications establish chromatin structures that are generally permissive to transcription factor association and gene transcription.
Within a given euchromatic domain, neighboring genes often display different expression patterns, indicating that distinct functional domains exist within large euchromatic regions. Transcriptionally active euchromatic domains are interspersed with hetero-chromatic regions that are gene-poor and organized into regular arrays of hypoacetylated nucleosomes that are methylated at lysine 9 of histone H3. Heterochromatic histone modifications generate a platform for interaction with proteins that spread in <i>cis</i> direction along the chromosome and limit transcription factor access to target sequences. A class of deoxyribonucleic acid (DNA) elements known as insulators defines the junctions between structural and functional chromatin domains.
Industry:Science
Brachiopods form one of very few phyla that have been present on Earth for over 550 million years, since early Cambrian times, when the first widespread appearance of animals with mineralized skeletons occurred. They were the most abundant filter-feeding group for much of that time, and dominate fossiliferous deposits in many localities.
Brachiopods are still present in all of the oceans, but are common and abundant only in restricted areas, such as the deep sea, fiords, polar seas, some parts of New Zealand, and the west coast of North America. They also are often found in cryptic habitats (areas which provide protection from physical disturbance and include crevices, underwater caves, and deep rocky overhangs). Many of the temperate and tropical shallow sea localities where they were formerly dominant are now occupied by bivalve mollusks. Whether this replacement is due to competition or whether bivalves more successfully colonized space made available after the dramatic decline of the brachiopods, during the mass extinction event at the end of the Permian period 150 million years ago, is strongly debated. In some areas, however, they still dominate local sites, with densities sometimes exceeding 1000 individuals per square meter.
Industry:Science
Celiac disease (CD) is an autoimmune condition of the small intestine that is believed to be T-cell–mediated and triggered by the consumption of gluten proteins found in foods containing wheat, rye, and barley. Symptoms can be overt and related to abdominal pain, diarrhea, weight loss, and other signs of intestinal malabsorption, or they can be subtle and present later in life as osteoporosis or iron-deficiency anemia. Conservative estimates place celiac disease at a prevalence of about 1 in 150 people in the United States, meaning that the majority of individuals remain undiagnosed.
Screening is now simple with assays that detect autoantibodies against tissue transglutaminase (tTG) in patient serum. Diagnosis is confirmed by an intestinal biopsy showing villous atrophy, with implications of a life-long condition that can be treated only by eliminating dietary gluten. Once gluten is removed from the diet, the autoantibodies, intestinal injury, and symptoms resolve over time. If the patient is rechallenged with gluten, disease and symptoms will recur. Celiac disease is associated with other autoimmune diseases, notably type 1 diabetes and autoimmune thyroid disease, because of shared human leukocyte antigen (HLA) gene predisposition.
Industry:Science
Any of the six different varieties of quarks. All hadronic matter is composed of quarks, the most elementary constituents of matter. The six different flavors are labeled <i>u</i>, <i>d</i>, <i>s</i>, <i>c</i>, <i>b</i>, and <i>t</i>, corresponding to up, down, strange, charmed, bottom, and top. Quarks are all spin-½ fermions. The <i>u</i>, <i>c</i>, and <i>t</i> flavors carry a positive electric charge equal in magnitude to two-thirds that of the electron; the <i>d, s</i>, and <i>b</i> flavors have a negative charge one-third that of the electron.
Different flavored quarks have vastly different masses ranging from the lightest, the <i>u</i> quark, with a mass around 5 MeV/<i>c</i><sup>2</sup> (where <i>c</i> is the speed of light), equal to the mass of about 10 electrons, to the top quark, with a mass 35,000 times greater, or 175 GeV/<i>c</i><sup>2</sup>, about the mass of a gold atom. Because of its large mass, only in 1994 was evidence presented for existence of the top quark. Quarks of any flavor are further characterized by three additional quantum numbers called color: red, green, and blue. Each quark has an antiquark counterpart carrying the corresponding anticolor. All of these properties have been well established by experiment.
Industry:Science
Forensic dentistry, or forensic odontology, can be defined as the use of dental knowledge in the judicial process. Forensic dentistry is best known for its usefulness in linking an identifying name to unknown human remains. This may be accomplished in single instances, such as when a body is discovered along a lake or river shore having presumably drowned. More than one victim may be involved, such as in a house fire or automobile accident. In some cases, referred to as multiple-fatality incidents (or mass fatalities, disaster victim identification), large numbers of deceased individuals may require identification.
Recent examples include Hurricane Katrina in 2005, the Sumatra–Andaman earthquake and tsunami in 2004, the World Trade Center attack in 2001, or any of a number of common carrier incidents, including the 2009 crash of Continental Connection Flight 3704 in Buffalo, New York. Forensic dentists also assist in law enforcement cases involving suspected biting activity (animal or human) and in abuse cases involving head and neck injury. In addition, many forensic dentists act as expert witnesses in litigation involving professional liability claims against dentists and in personal injury cases involving the jaws or other oral structures.
Industry:Science
Digital imaging is a mature technology that involves the acquisition, indexing, compression, storage, authentication, transmission, retrieval, and display of entire pages of documents by means of computers. Document image analysis attempts to go a step further, to extract the content of the digitized documents and convert it into a form suitable for digital processing. Document image analysis includes the processing of graphic documents such as engineering drawings, circuit schematics, and organization charts and maps, but this discussion is restricted to mostly-text documents.
The extraction of content from the digital image requires two major phases. The first phase, identification of the logical or functional components of a document, is called layout analysis. The second phase, encoding of the glyphs (letters, numerals, mathematical symbols, and punctuation) into a computer representation such as the American Standard Code for Information Interchange (ASCII), rich-text format (RTF), or UNICODE (a new international standard) is called optical character recognition. Both of these steps require prior knowledge of the underlying script. Furthermore, the accuracy of text recognition can be improved by postprocessing that applies linguistic constraints.
Industry:Science
Electromagnetic radiation emitted from the Earth and its atmosphere. Terrestrial radiation, also called thermal infrared radiation or outgoing longwave radiation, is determined by the temperature and composition of the Earth's atmosphere and surface. The atmosphere is composed of two groups of gases, one with a nearly permanent concentration, consisting principally of nitrogen (N<sub>2</sub>) and oxygen (O<sub>2</sub>) molecules, and another with variable concentrations of other gases. Although considered to be permanent constituents, carbon dioxide (CO<sub>2</sub>), methane (CH<sub>4</sub>), nitrous oxide (N<sub>2</sub>O), and carbon monoxide (CO) have been observed to increase in association with anthropogenic activities. One of the principal variable gases is water (H<sub>2</sub>O) vapor, the major compound that modulates the hydrological cycle involving evaporation, cloud formation, and precipitation.
Water vapor concentration decreases rapidly with latitude, almost following an exponential function. Ozone (O<sub>3</sub>) concentration also varies significantly with space and time and occurs principally at altitudes of about 15–30 km (10–20 mi). A significant variable gas is a mixture of chlorofluorocarbons (CFCs) produced by industrial activities.
Industry:Science
Chemists long assumed that all matter existed in one of three states (gaseous, liquid, or solid) depending on the temperature and pressure. However, during the nineteenth century it was recognized that many chemical systems did not fall into these categories. For example, fine clay suspensions can be considered neither true solids nor true solutions. Gels and smoke are other examples of states of matter that are difficult to define. Since many of these apparently anomalous systems are amorphous, they were called colloid, which means glue.
As knowledge of these systems progressed, they were divided into two categories: hydrophilic (water-loving) colloids, which are stabilized by strong solute-solvent interactions; and hydrophobic (water-hating) colloids, which are stabilized kinetically. Polymer solutions and gels are typical examples of the first category, and hydrosols of the second. While these terms are still used, they are not representative of the large number of systems now considered colloids. This is particularly true for self-assembly systems, recognized as part of the colloid domain in the midtwentieth century only. Furthermore, these terms can in some cases be misleading since, for example, the so-called hydrophobic colloids are not really hydrophobic.
Industry:Science
Freezing is a major environmental stress that inflicts injury to plant tissues and limits the productivity and geographic distribution of wild and crop species. Most tropical and subtropical species have little to no freezing tolerance. However, plants from temperate regions not only have some “constitutive” freezing tolerance (which is present all the time, typically at low levels), but they also have the genetic ability to increase this tolerance significantly when exposed to environmental cues that signal the arrival of winter, such as a period of low temperatures and/or short days. In temperate climates, such conditions are typically encountered by overwintering perennials in autumn, resulting in a seasonal increase in freezing tolerance.
The ability of plants to increase freezing tolerance in response to changing environment is called cold acclimation. The term deacclimation refers to reduction/loss of freezing tolerance originally attained through cold acclimation and, in nature, happens typically in early spring with the rise of temperatures. Depending on the depth of deacclimation, it may be either irreversible or reversed by subsequent exposure to low temperatures that may cause reacclimation, that is, restoration of at least a portion of the lost tolerance.
Industry:Science
