- 行业: Printing & publishing
- Number of terms: 178089
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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.
Epilepsy refers to the medical condition of recurrent, unprovoked seizures. Epilepsy and seizures are the most common neurologic disorder. Up to 10% of the population will experience a seizure at some point in their life, with most not being diagnosed with epilepsy. A seizure is a sudden change in behavior accompanied by an abnormal discharge of electricity in the brain. A seizure is typically brief and can present in many different ways, including motor changes, sensory phenomena, and alterations in consciousness. Seizures are a symptom of a neurological problem; thus, just as with a symptom such as headache, there are many reasons why a seizure may occur. High fever, meningitis, toxins, chemical imbalances of glucose or electrolytes, stimulant overdose, massive sleep deprivation, and alcoholic withdrawal are all examples of external events that can provoke a seizure.
Industry:Science
Colored, metal-containing proteins that combine reversibly with oxygen, found in the body fluids or tissues of multicellular invertebrate animals and microorganisms. The role of these pigments is primarily to aid in the transport of molecular oxygen. Thus they are distinguished from respiratory enzymes, which are concerned with the metabolic consumption of oxygen. Four distinctly colored groups of respiratory pigments exist among invertebrates: hemoglobins (purple, become orange-red with oxygen), chlorocruorins (green, become red with oxygen), hemocyanins (colorless, become blue with oxygen), and hemerythrins (colorless, become red with oxygen). Formerly, invertebrate hemoglobins were called erythrocruorins to distinguish them from functionally similar yet structurally distinct pigments of vertebrate bloods. Those hemoglobins confined to muscle cells are called myoglobins.
Industry:Science
Electrochemistry is emerging as an important technique for selective and sensitive detection in ultrasmall environments. The growth in use of electrochemical techniques can be attributed to improvements in instrumentation as well as miniaturization of the electrodes. Individual microelectrodes are being used to conduct cellular investigations in vitro and in vivo that require detection of minute amounts of material. Analyzing a sample released upon stimulation of a single cell is extremely difficult because of the sample's small volume and the femtomole (10<sup>−18</sup>) to zeptomole (10<sup>−21</sup>) levels of analyte present. To realize the full potential of electrochemical techniques, further developments in small-volume sample handling are needed to prevent dilution by restricting the low analyte levels present in single cells to picoliter (10<sup>−12</sup>) volumes.
Industry:Science
Idiopathic thrombocytopenic purpura (ITP) is a hematologic disorder of unknown origin (that is, idiopathic) in which the blood does not clot properly due to a decreased number of platelets (thrombocytopenia). It is characterized by the presence of purpura, small hemorrhages of capillaries that appear as purple bruises on the skin or mucous membranes. There are two forms of the disorder: adult (or chronic) ITP and childhood (or acute) ITP. Adult ITP generally lasts 6 months or longer and usually results from the development of an autoantibody (an antibody formed by an individual against the individual's own tissues) directed against a structural platelet antigen. Childhood ITP generally lasts less than 6 months and is thought to be caused by a viral infection that triggers the synthesis of an antibody that may react with a viral antigen associated with the platelet surface.
Industry:Science
Devices that employ surface acoustic waves in the analog processing of electronic signals in the frequency range 10<sup>7</sup>–10<sup>9</sup> Hz. Surface acoustic waves are mechanical vibrations that propagate along the surfaces of solids. In 1885, Lord Rayleigh discovered a type of surface acoustic wave that contains both compressional and transverse components 90° out of phase with one another. Since that time, other types of surface acoustic waves have been discovered and are an active area of intense research. A few notable examples include a wave propagating along a layer on a surface (Love wave), a wave propagating along an interface between two solids (Stoneley wave), and transverse guided waves on solids (Bleustein-Gulyaev-Shimizu waves). Love waves are shear-horizontal (SH) waves that have displacement only in a direction perpendicular to the plane of propagation.
Industry:Science
Human civilization would not have been possible without the domestication of plants and animals. Domestication is responsible for our clothes, food, and pets, and was also a necessary prerequisite for the development of written language, mathematics, architecture, and every technological breakthrough since stone tools. The study of domestication is therefore the study of the development of humankind over the past 10,000 years. Thus, by understanding how, when, and where animals were domesticated, we gain deeper insights into the foundations of modern society. In addition, domestication is an ideal model for understanding the process of change within evolutionary biology and for understanding the relationship between differences at the DNA level, and the ramifications those differences have on the physical, behavioral, and developmental characteristics of the organism itself.
Industry:Science
Any elevated area of relatively smooth land. Usually the term is used more specifically to denote an upland of subdued relief that on at least one side drops off abruptly to adjacent lower lands. In most instances the upland is cut by deep but widely separated valleys or canyons. Small plateaus that stand above their surroundings on all sides are often called tables, tablelands, or mesas. The abrupt edge of a plateau is an escarpment or, especially in the western United States, a rim. In the study of landform development the word plateau is commonly used to refer to any elevated area, especially one underlain by nearly horizontal rock strata, that once had a smooth surface at high level, even though that surface may since have been largely destroyed by valley cutting. An example is the now-hilly Appalachian Plateau of western Pennsylvania, West Virginia, and eastern Kentucky.
Industry:Science
For the last 2 decades, the origin of cetaceans (whales, dolphins, and porpoises) has become one of the best case studies in mammalian evolution. A rich collection of fossil cetaceans, mostly from Asia, Africa, and North America, traces the transition of cetaceans from a terrestrial to a completely aquatic environment. Cetaceans initially took to the seas about 50 million years ago in an ancient shallow seaway, the Tethys Sea, which was located between the Indian subcontinent and Asia. Within about 10 million years in the aquatic environment, cetaceans evolved specialized ears for hearing underwater, reduced the size of their hindlimbs, and evolved tail flukes for propulsion. The cetacean body plan has so radically evolved from terrestrial artiodactyls (even-toed hoofed mammals) that modern cetaceans are no longer able to bear their weight on land and are obligatorily aquatic.
Industry:Science
Complex systems that comprise both humans and machines. Human-machine systems engineering is the analysis, modeling, and design of such systems. It is distinguished from the more general field of human factors and from the related fields of human-computer interaction, engineering psychology, and sociotechnical systems theory in three general ways. First, human-machine systems engineering focuses on large, complex, dynamic control systems that often are partially automated (such as flying an airplane, monitoring a nuclear power plant, or supervising a flexible manufacturing system). Second, human-machine systems engineers build quantitative or computational models of the human-machine interaction as tools for analysis and frameworks for design. Finally, human-machine systems engineers study human problem-solving in naturalistic settings or in high-fidelity simulation environments.
Industry:Science
Deoxyribonucleic acid (DNA) has long been envisioned as a drug for both therapeutic (gene therapy) and prophylactic (vaccination) use. The idea of gene-based medicine is simple and appealing: If a disease is caused by a deficient gene, delivery of a good copy of the gene should correct the defect, making DNA a therapeutic drug. Similarly, delivery of an antigen gene should elicit a specific immune response against the protein encoded by the delivered gene, making DNA a prophylactic vaccine. (Note that delivery of genes is much safer than delivery of proteins because DNA molecules themselves do not elicit immune reactions.) However, after more than a decade of intense research and more than 600 clinical trials, no truly successful gene therapy protocol has been reported, and no DNA vaccination has been approved. The reason is the lack of an efficient and safe gene delivery system.
Industry:Science
