- 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.
Hypersonic speed commonly refers to travel at five times the speed of sound or faster, although there is no sharp boundary between supersonic flight—defined precisely as traveling faster than the speed of sound (Mach 1)—and hypersonic flight. Instead, hypersonic speed is more nebulously defined as traveling fast enough so that strong shock waves and friction in the gas through which a body travels raise the gas temperature high enough that it begins to chemically react (for example, oxygen and nitrogen dissociate from naturally occurring diatomic molecules into atomic species), and at higher speeds even to ionize (when electrons are stripped from gas molecules) and emit significant radiation. At hypersonic speed the heating of vehicle body surfaces due to air friction also becomes significant and can heat those surfaces to extreme temperatures.
Industry:Science
Coronary heart disease is the major cause of death and disability among women in the developed world. Several observational clinical studies have reported that postmenopausal women who take hormone replacement therapy have lower incidence of coronary heart disease; therefore, hormone replacement therapy has been recommended for secondary prevention of heart disease (which aims to decrease risk of disease recurrence) in postmenopausal women. Initially, estrogen alone was prescribed as hormone replacement therapy. However, progestins (natural or synthetic forms of progesterone) are now added to estrogen for women with an intact uterus in order to reduce, or eliminate, the excess risk for endometrial cancer observed with estrogen alone (unopposed estrogen); this treatment modality is now commonly referred to as combined hormone replacement therapy.
Industry:Science
Diagnosis employing equipment that can be used clinically to measure the intrinsic electrical activity of the heart (electrocardiography), the brain (electroencephalography), peripheral nerves (nerve conduction), and skeletal muscles (electromyography). Electrodiagnostic procedures depend upon the difference in electrical potential between the interior and external surfaces of living cells. This potential difference is created by use of cellular metabolic energy to establish and maintain the concentration gradient of ions across the cell membrane. A discharge of the electrical potential (depolarization) by stimulation or injury occurs in a wave proceeding from cell to cell. The ensuing electrical currents are conducted through the tissues to the surface of the body where electrodiagnostic equipment amplifies and records the changes in potential.
Industry:Science
For many years, seismic exploration techniques have been used by geophysicists for imaging underground structures (identifying their general shapes) and, consequently, locating oil and gas reservoirs (hydrocarbon-bearing formations). This exploration was achieved first in two dimensions, using acoustic sensor arrays, and evolved to three dimensions (3D seismic) in the 1980s as computing power increased. Over the past 15 years, 3D seismic data have been used to characterize hydrocarbon-bearing formations in terms of thickness, porosity, fluid content, and so on. In the late 1990s, a new technique for reservoir monitoring and management called time-lapse seismic or 4D seismic was developed (the four dimensions being the three geometrical dimensions plus time). By mid-2001, about 70 time-lapse seismic operations were under way throughout the world.
Industry:Science
For over a decade, molecular biology methods have been used to resolve identity issues in violent crimes, acts of terrorism, missing persons cases, mass disasters, and paternity testing. One very sensitive method is the direct sequencing of mitochondrial DNA (mtDNA). A mitochondrion contains 2–10 copies of mtDNA, and there can be up to 1000 mitochondria per somatic cell. Because of the large number of copies of mtDNA, tissues such as hair, bones, and teeth can be typed more readily than with nuclear-based DNA markers. mtDNA sequencing is the primary genetic analysis used to identify individuals from bones recovered from American war casualties. Victim remains from the World Trade Center tragedy have had their mtDNA sequenced. In addition, mtDNA analysis has been used in evolutionary and anthropological studies, including analyses of ancient DNA.
Industry:Science
Electromagnetic phenomena and electric currents, mostly of natural origin, that are associated with the Earth. Geophysical methods utilize natural and artificial electric currents to explore the properties of the Earth's interior and to search for natural resources (for example, petroleum, water, and minerals). Geoelectricity is sometimes known as terrestrial electricity. All electric currents (natural or artificial, local or worldwide) in the solid Earth are characterized as earth currents. The term telluric currents is reserved for the natural, worldwide electric currents whose origins are almost entirely outside the atmosphere. Geoelectromagnetism is a more comprehensive term than geoelectricity. Time variations of any magnetic field are associated with an electric field that induces electric currents in conducting media such as the Earth.
Industry:Science
Hepatitis C is a disease of the liver caused by the hepatitis C virus (HCV). Although the incidence of new HCV cases is declining, the number of patients with complications of chronic HCV continues to rise. The prevalence of HCV infection worldwide is 3% (170 million people), with infection rates in North America ranging from 1 to 2% of the population. The impact of HCV is being felt in the offices of primary care physicians, hepatologists (specialists in liver disease), and liver transplant programs. A simulation analysis estimated that in the period from 1998 to 2008 there will be an increase of 92% in the incidence of cirrhosis of the liver, resulting in a 126% increase in the incidence of liver failures and a 102% increase in the incidence of hepatocellular carcinoma (HCC), all attributed to HCV, placing an increasing burden on the health care system.
Industry:Science
Centuries ago, phrenologists studied the conformation of the human skull in an attempt to learn about variation in brain structure and mental function. They viewed the brain as a collection of parts, just as the body can be described as a collection of organs, each with a particular function and a characteristic location. While neuroscientists doubt the details of the phrenological view, the search for the cerebral basis of conceptual knowledge remains a project of functional localization, supported by theories of cognition and behavior. In 1929, it was proposed that brain function depends upon the allocation of fairly homogeneous neural resources to particular tasks. This uniformity of functional capability was called equipotentiality. Extreme localization and equipotentiality lie at two ends of a continuum describing functional organization in the brain.
Industry:Science
Fungi constitute one of the major branches of the tree of life. There are about 100,000 described species in the Fungi, but it has been estimated that there are as many as 1.5 million extant fungal species. Fungi have evolved a remarkable diversity of forms and lifestyles. Some produce mushrooms, which are sexual reproductive structures, but most fungal species are very inconspicuous and generally go unnoticed. Single-celled forms called yeasts occur in multiple fungal groups, but most species grow as a network of microscopic filaments (hyphae), termed a mycelium, by which the fungus explores its environment and captures resources. Some fungi are aquatic and produce swimming cells with typical eukaryotic flagella. However, most fungi are terrestrial and lack flagellated cells, which appear to have been lost, perhaps multiple times, during fungal evolution.
Industry:Science
Any of a class of yellow, orange, red, and purple pigments that are widely distributed in nature, including vegetables, fruits, insects, fishes, and birds. Most of these pigments are carotenoids, which are generally fat-soluble unless they are complexed with proteins. In plants, carotenoids are usually located in quantity in the grana of chloroplasts in the form of carotenoprotein complexes. Carotenoprotein complexes give blue, green, purple, red, or other colors to the outer surfaces or eggs of crustaceans, such as the lobster and crab. Echinoderms, nudibranch mollusks, and other invertebrate animals also contain carotenoproteins. Some coral coelenterates exhibit purple, pink, orange, or other colors due to carotenoids in the calcareous skeletal material. Cooked or denatured lobster, crab, and shrimp show the modified colors of their carotenoproteins.
Industry:Science
