- 行业: Printing & publishing
- Number of terms: 178089
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- 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.
Submarine hydrothermal vent environments span the temperature range from 2°C (36°F) for ambient deep seawater to over 400°C (750°F) for some hydrothermal fluids. These high-temperature fluids remain liquid because of the hydrostatic pressure at deep-sea vent depths (2–4 km or 1–2.5 mi). The microbial world at hydrothermal vents includes organisms capable of growing at 2°C (36°F) or lower to above the boiling point of water (100°C or 212°F at atmospheric pressure). The ability to grow above 60°C (140°F) is confined to prokaryotes (cells that lack a nucleus) divided into two groups: moderate thermophiles that have maximal growth temperatures of 50–60°C (122–140°F), and hyperthermophiles that grow optimally at 80°C (176°F) or higher with maximal growth temperatures of 90°C (194°F) or higher. The highest temperature for growth by a pure culture (<i>Pyrolobus fumaris</i>) is 113°C (235°F), although there is some evidence that deep-sea vent hyperthermophiles may grow and survive at higher temperatures under elevated pressures.
Industry:Science
The entire outer surface of the body and the principal boundary between the external environment and the body's internal environment of cells and fluids. Skin serves as the primary barrier against the intrusion of foreign elements and organisms into the body, and also as a large and complex sense organ through which animals explore and learn about the external world. In addition, skin functions to maintain the homeostasis of the body's constituents, acting as a barrier to the loss of various ions and nutrients by diffusion. For terrestrial animals, it also serves as an effective barrier to water loss, without which most land animals would rapidly become desiccated and die.
Industry:Science
The alteration of rocks or crystallization of minerals by gases or supercritical fluids (generically termed magmatic fluids) derived from solidifying magma. At surface conditions, magmatic fluids sampled from active volcanoes contain steam with lesser amounts of carbon dioxide, sulfur dioxide, hydrogen sulfide, hydrogen chloride, and hydrogen fluoride, and trace amounts of many other volatile constituents. Magmatic fluids may contain relatively high concentrations of light and heavy elements, particularly metals, that do not crystallize readily in common rockforming silicates constituting most of the solidifying magma; thus, valuable rare minerals and ores are sometimes deposited in rocks subjected to pneumatolysis. Magmatic fluids are acidic and may react extensively with rocks in the volcanic edifice or with wall rocks surrounding intrusions. Penetration of magmatic fluids into adjacent rocks is greatly aided by faults, fractures, and cracks developed during intrusion and eruption or created by earlier geologic events.
Industry:Science
The act of interrupting an electric current, beam of light, or beam of infrared radiation at regular intervals. This can be accomplished mechanically by rotating a vibrating mirror in the path of the beam to deflect it away from its intended source at regular intervals. A current can be chopped with an electromagnetic vibrator having contacts on its moving armature. A current can also be chopped electronically by passing it through a multivibrator or other switching circuit. Chopping is generally used to change a direct-current signal into an alternating-current signal that can more readily be amplified. Control systems for guided missiles make extensive use of chopping.
Industry:Science
The condition in which more than one genetically distinct population of cells coexists within one individual. The term mosaic is used for an individual composed of two or more cell lines of different genetic or chromosomal constitutions, where the cell lines originate from one zygote. Individuals derived from more than one zygote or from more than two gametes are called chimeras. However, because the etiology of mosaicism cannot always be established, the term mosaic often is used to refer to any kind of genetic multiplicity within an individual. Mosaicism is a common phenomenon in both the plant and animal kingdoms; it may originate at any state in the course of ontogeny, and in any tissue in which cells proliferate. Cells with a particular genetic constitution form a clone, and this may appear as a mosaic spot embedded in a background containing cells of different genotype. The several types of mosaicism include chromosomal mosaicism, mosiacism due to mitotic recombination or gene mutation, and functional mosaicism.
Industry:Science
The chief mineral constituent in the ornamental stone lapis lazuli. It crystallizes in the isometric system, but well-formed crystals, usually dodecahedral, are rare. Most commonly, it is granular or in compact masses. There is imperfect dodecahedral cleavage. The hardness is 5–5.5 on Mohs scale, and the specific gravity is 2.4–2.5. There is vitreous luster and the color is a deep azure, more rarely a greenish-blue. Lazurite is a tectosilicate, the composition of which is expressed by the formula Na<sub>4</sub>Al<sub>3</sub>Si<sub>3</sub>O<sub>12</sub>S, but some S may be replaced by SO<sub>4</sub> or Cl. Lazurite is soluble in HCl with the evolution of hydrogen sulfide.
Industry:Science
The development of the aboveground portion of seed plants, also called the shoot, is characterized by four phases: embryonic, juvenile vegetative, adult vegetative, and reproductive. The embryonic stage includes the period between the fertilization of an egg and the formation of a mature embryo within a seed. In contrast to animal embryos, plant embryos do not contain precursors of all of the organs found in an adult plant. Instead, the embryonic phase establishes the basic axes of growth, and new organs are continually formed throughout the life of the plant from a pool of stem cells at each end of the shoot-root axis. These stores of stem cells are called the shoot apical meristem (SAM) and the root apical meristem (RAM), respectively. Thus, while the apical end of an angiosperm embryo includes only one or two cotyledons, one or more immature true leaves, and the SAM, upon germination the plant repeatedly initiates new organs from the SAM—first vegetative organs (leaves, stems, and branches) and then reproductive ones (flowers).
Industry:Science
The control and management of hazardous wastes are truly among the most important challenges of our times. Environmental engineers play crucial roles in reducing the amount of hazardous substances produced, treating hazardous wastes to reduce their toxicity, and applying sound engineering controls to reduce or eliminate exposures to these wastes. Engineers design the facilities that generate the chemicals that, under the wrong circumstances, become hazards. The engineers also design and operate the containment and treatment facilities to deal with the wastes after they have been released, and are frequently called upon to address these wastes once they are in the environment.
Industry:Science
The determination and specification of the parts of a product and their interrelationship so that they become a unified whole. The design must satisfy a broad array of requirements in a condition of balanced effectiveness. A product is designed to perform a particular function or set of functions effectively and reliably, to be economically manufacturable, to be profitably salable, to suit the purposes and the attitudes of the consumer, and to be durable, safe, and economical to operate. For instance, the design must take into consideration the particular manufacturing facilities, available materials, know-how, and economic resources of the manufacturer. The product may need to be packaged; usually it will also need to be shipped so that it should be light in weight and sturdy of construction. The product should appear significant, effective, compatible with the culture, and appear to be worth more than the price. The emphasis may differ with the instance. Durability in a paper napkin is different from durability in a power shovel.
Industry:Science
The harvest of animals and plants from the ocean to provide food and recreation for people, food for animals, and a variety of organic materials for industry. Important products in marine capture fisheries include fish; mollusks such as oysters, clams, and squid; and crustaceans such as crabs and shrimps. Marine mammals (whales) and reptiles (turtles) have been important historically in marine landings (the weight of the catch landed at the wharf); and some plants, mostly seaweeds, are harvested in significant amounts. World landings began to increase substantially during the industrial revolution and rose at a rapid rate after World War II before leveling off in recent years.
Industry:Science
