- 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.
Red and near-infrared light with wavelengths between 700 and 1550 nanometers can penetrate a few millimeters into the human body before it is either absorbed by the tissue or scattered (that is, reflected in a different direction). Scattering occurs at locations in the tissue where boundaries between materials, such as vessel walls, give rise to a change in the index of refraction. As a result, some of this light is backscattered (reflected 180°) and exits the tissue in the same place it entered. Optical coherence tomography (OCT) is a system for delivering light and collecting backscattered light to produce images with micrometer resolution.
Industry:Science
Soil nutrients taken up by plants are conveyed to animals and humans in food; thus soil chemistry has significant effects on the quality of life. At times, levels of mineral nutrients or soil conditions (such as pH, which affects removal of the nutrients from the soil) are not optimal, and difficulties ensue. Thus, there may be deficiency disorders at one end of the supply spectrum or toxicities at the other. The soil relationships of the micronutrient element selenium are a case in point. Selenium is recognized, at levels of less than 1 part per million (ppm) in the diet, to be an essential nutrient, yet in excess quantities a potent poison.
Industry:Science
On-board assemblages of equipment to generate, store, and distribute electrical energy on satellites and spacecraft. A reliable source of electrical power is required for supplying energy to the spacecraft and its payloads during launch and through several years of operational lifetime in a space environment. Present-generation spacecraft fly power systems from tens of watts to several kilowatts. Each of the three fuel cells on the space shuttle delivers 12 kW continuous power and 16 kW peak power. The <i>International Space Station</i>'s solar arrays will generate 110 kW total power, with approximately 46 kW available for research activities.
Industry:Science
Medical mycology is the study of fungi that are pathogens of humans and animals. Most fungi are filamentous, growing as tubelike structures or hyphae, but one important group are single celled and are referred to as the yeasts. The fungi are classified in a separate kingdom; they are eukaryotic like mammalian cells but different from bacteria, which are prokaryotic. Most fungi form spores asexually and reproduce sexually, although some lack a mechanism for sexual reproduction. They are very diverse in appearance microscopically. Therefore, the diagnostic laboratory technician is often confronted with problems in identification of fungal samples.
Industry:Science
Plant scientists use carbon isotope discrimination (Δ) to express the relative abundances in plant carbon of the isotopes carbon-12 (<sup>12</sup>C) and carbon-13 (<sup>13</sup>C). These stable isotopes are present in carbon dioxide (CO<sub>2</sub>) in ambient air. They are incorporated by photosynthetic CO<sub>2</sub> assimilation into plant organic matter, but the two isotopes do not appear in plants in the same proportions as in the air. Carbon isotope discrimination by plants has been studied extensively in agricultural and native species (such as wheat, rice, and crested wheatgrass), often together with plant water-use efficiency and yield.
Industry:Science
Optical character recognition (OCR) systems convert digital images of text into symbolic strings (for example, ASCII). Digital images of text are typically created by scanning paper documents containing printed or handwritten text, from video images of scenes with text, or by digital pens. The OCR-generated symbolic form of the paper documents allows multiple users to simultaneously access, search, edit, and transmit the contents of these pages. In fact, with the help of machine translation and speech synthesis systems, the information in paper documents can now be accessed by people across language boundaries and by those with visual impairment.
Industry:Science
Production of beryllium and its compounds uses 4000–10,000 tons (3600–9000 metric tons) per year of the mineral beryl. The variant amounts of raw materials reflect wide differences in production rates for the beryllium industry. Beryl, a beryllium-aluminum silicate containing (in commercial grades) about 11–13% beryllium oxide (BeO), 17–19% aluminum oxide (Al<sub>2</sub>O<sub>3</sub>), 64–70% silicon dioxide (SiO<sub>2</sub>), and 1–2% alkali metal oxides, is the only mineral used as a raw material for beryllium. Although beryl ore is widely dispersed throughout the world, it is not concentrated in deposits sufficient to justify direct mining.
Industry:Science
Insects flap and twist their wings to stay aloft, to dart forward, to turn, and to hover. It is the swirls of air stirred by a flapping wing that generate an insect's lift and thrust. To understand how insects fly, it is necessary to understand the dynamics of unsteady airflows created by a flapping wing, which is significantly different from the steady airflows around a classical airfoil. Although the aerodynamics of a steady airfoil has been well understood for almost a century, it is only recently, with the advance of new experiments, computations, and analyses, that scientists have began to unravel some of the mysteries of unsteady aerodynamics.
Industry:Science
Literally, the synthesis of chemical compounds using light. The term photosynthesis, however, is used almost exclusively to designate one particularly important natural process: the use of light in the manufacture of organic compounds (primarily certain carbohydrates) from inorganic materials by chlorophyll- or bacteriochlorophyll-containing cells. This process requires a supply of energy in the form of light, since its products contain much more chemical energy than its raw materials. This is clearly shown by the liberation of energy in the reverse process, namely the combustion of organic material with oxygen, which takes place during respiration.
Industry:Science
Radionavigation systems using artificial satellites as sources of radio signals and position references. Development of satellite-based systems for global positioning and navigation began almost immediately after the launch of <i>Sputnik I</i> by the Soviet Union in 1957. The U.S. Navy Navigation Satellite System, better known as <i>Transit</i>, became operational in 1964. The Soviet Union responded with its own satellite navigation systems, <i>Parus</i> and <i>Tsikada</i>. All three systems were based on measurement of Doppler shift in signals received from a satellite, and were aimed mainly at offering navigational guidance to ships and submarines.
Industry:Science
