- 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.
The tissues of a plant are organized into three systems: the dermal tissue system, the ground tissue system, and the vascular tissue system. Most plants are composed of coherent masses of cells called tissues. Large units of tissues having some features in common are called tissue systems. In actual usage, however, the terms tissue and tissue system are not strictly separated. A given tissue or a combination of tissues may be continuous throughout the plant or large parts of it. “Simple tissues” refer to tissues composed of one cell type. However, different cell types may be contained within a tissue, often referred to as a “complex tissue,” and the same cell type may be part of different tissues.
Industry:Science
The process of imparting a force to a flying vehicle, such as a missile or a spacecraft, by the momentum of ejected matter. This matter, called propellant, is stored in the vehicle and ejected at high velocity. In chemical rockets the propellants are chemical compounds that undergo a chemical combustion reaction, releasing the energy for thermodynamically accelerating and ejecting the gaseous reaction products at high velocities. Chemical rocket propulsion is thus differentiated from other types of rocket propulsion, which use nuclear, solar, or electrical energy as their power source and which may use mechanisms other than the adiabatic expansion of a gas for achieving a high ejection velocity.
Industry:Science
The pump is the most widely used turbomachine and is the subject of intensive research and development. It is believed to be the second most frequently built machine of modern times, next to the electric motor. Pumps reach efficiency levels above 90% and are built with powers ranging from a few watts to megawatts. As pumps have evolved to handle a wider range of liquids at higher pressures and temperatures, whole industries have become dependent on them. The complex flow in pumps makes them among the most complicated fluid machines ever built. Although the most rapid development of pumps has occurred since around 1940, the pump has a long history that parallels the rise of modern engineering itself.
Industry:Science
The prophylactic use of vaccines has contributed significantly to the decrease in morbidity and mortality associated with many common infections. Diseases such as measles, polio, and tetanus have been largely eliminated from most developed countries, and since about 1950 their incidence has been declining globally because of widespread vaccination programs. However, with the AIDS pandemic and the appearance of antibiotic-resistant bacteria, humankind is once again challenged with developing vaccines to combat both human and veterinary pathogens. Recently a new class of vaccines has been developed, composed not of living organisms or purified proteins as are conventional vaccines, but of nucleic acids.
Industry:Science
The safety of meat—pork, beef, and lamb—begins at the farm, the feed lot, and the ranch. Yet, little is known about how to prevent apparently healthy livestock from leaving the farm with food-transmissible hazards outside or inside their bodies. Admittedly, brucellosis in cattle and swine and tuberculosis in cattle have been practically eradicated from the United States, resulting in the disappearance of these human infections acquired through milk or meat. Brucellosis and tuberculosis are serious diseases in both livestock and humans. Currently, about 15 bacterial diseases, 7 parasitic diseases, and 4 viral diseases may be meat-borne to people but cause little or no illness in the livestock carriers.
Industry:Science
The study of the structure and dynamics of atoms and their associated electron clouds in the vicinity of a surface, usually at the boundary between a solid and a low-density gas. Surface physics deals with those regions of large and rapid variations of atomic and electron density that occur in the vicinity of an interface between the two “bulk” components of a two-phase system. In conventional usage, surface physics is distinguished from interface physics by the restriction of the scope of the former to interfaces between a solid (or liquid) and a low-density gas, often at ultrahigh-vacuum pressures <i>p</i> = 10<sup>−10</sup> torr (1.33 × 10<sup>−8</sup> newton/m<sup>2</sup> or 10<sup>−13</sup> atm).
Industry:Science
The science dealing with the chemical changes accompanying the passage of an electric current, or the reverse process in which a chemical reaction is used as the source of energy to produce an electric current, as in a battery or fuel cell. Electric conduction occurs through the motion of charged particles. The charged particles may be electrons (as in metals or semiconductors) or ions, which are electrically charged atoms, molecules, or molecular aggregates. Ionic conduction in electrolytes (liquid solutions, molten salts, and certain ionically conductive solids) is a phase of electrochemistry, as is corrosion. Conduction in metals, semiconductors, and gases is generally considered a portion of physics.
Industry:Science
The scientific discipline that studies the origin, evolution, distribution, and future of life in the universe. It is an interdisciplinary science integrating contributions from biology, geology, astronomy, paleontology, and planetary science, among others. The first use of the term appears to have been in 1941 when it was defined as the subject of life in the universe other than on Earth. The U.S. National Aeronautics and Space Administration (NASA) adopted the term in 1996 and expanded the meaning to include the origin and history of life on Earth, and the future of life in the universe. In 1998, the NASA Astrobiology Institute was established, solidifying this new discipline within the science community.
Industry:Science
The study of the physical properties of solids, such as electrical, dielectric, elastic, and thermal properties, and their understanding in terms of fundamental physical laws. Most problems in solid-state physics would be called solid-state chemistry if studied by scientists with chemical training, and vice versa. Solid-state physics emphasizes the properties common to large classes of compounds rather than the dependence of properties upon compositions, the latter receiving greater emphasis in solid-state chemistry. In addition, solid-state chemistry tends to be more descriptive, while solid-state physics focuses upon quantitative relationships between properties and the underlying electronic structure.
Industry:Science
The older major subdivision (period) of the Cenozoic Era, extending from the Cretaceous (top of the Mesozoic Era) to the beginning of the Quaternary (younger Cenozoic Period). The term Tertiary corresponds to all the rocks and fossils formed during this period. Although the International Commission on Stratigraphy uses the terms Paleogene and Neogene (pre-Quaternary part) instead, Tertiary is still widely used in the geologic literature. Typical sedimentary rocks include widespread limestones, sandstones, mudstones, marls, and conglomerates deposited in both marine and terrestrial environments; igneous rocks include extrusive and intrusive volcanics as well as rocks formed deep in the Earth's crust (plutonic).
Industry:Science
