- 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.
During the first 500–600 million years of the Earth's history, the crust was continuously destroyed by convection within the very hot young planet and by meteorite bombardment. This turbulent period is known as the Hadean Era, which is defined as the period from which no geological record exists (no rocks were preserved). The oldest rocks known on the Earth occur in Canada and West Greenland and appeared between 4000 and 3800 million years ago (Ma). They define the beginning of the Archean Era, which gave way to the Proterozoic (“earlier life”) Era 2500 Ma. Until recently, no fossils were known from the Archean.
Industry:Science
Electrophilic reagents are chemical species which, in the course of chemical reactions, acquire electrons, or a share in electrons, from other molecules or ions. Although this definition embraces all oxidizing agents and all Lewis acids, electrophilic reagents are ordinarily thought of as cationic species, such as H<sup>+</sup>, NO<sub>2</sub><sup>+</sup>, Br<sup>+</sup>, or SO<sub>3</sub> (or carriers of these species such as HCl, CH<sub>3</sub> COONO<sub>2</sub>, or Br<sub>2</sub>), which can form stable covalent bonds with carbon atoms. Electrophilic reagents frequently are positively charged ions (cations).
Industry:Science
Application of the systems sciences has facilitated remarkable technological achievements, ranging from the International Space Station to our household computers. Both are tremendously complex and involve the orchestration of engineers, scientists, and technicians from a variety of disciplines. The relatively new discipline of systems engineering focuses on pulling together, or integration, of the efforts of mechanical engineers, electrical engineers, software engineers, scientists, and technicians for team achievements. The master plan or “blueprint” that guides this common work effort is a systems architecture.
Industry:Science
Hybrid vehicles use two or more sources of energy for propulsion. Typically, one source is a liquid or gaseous fuel and the other is energy stored in an energy storage system such as batteries or ultracapacitors. Other options for energy storage include compressed gas, pressurized liquids (hydraulics), and mechanical energy stored in a flywheel. The most common type of hybrid vehicle is the hybrid-electric vehicle (HEV), which typically uses a liquid fuel (gasoline, diesel, or a gasoline/ethanol blend) to power an internal combustion engine that works with batteries, or ultracapacitors, to power an electric motor.
Industry:Science
Auxin is a plant hormone involved in regulating growth and development throughout the life cycle of the plant. Auxin plays an essential role in a diverse range of processes, including pattern formation in embryogenesis, organ development, apical dominance (inhibition of lateral bud growth by the apical bud of a shoot), shoot and root growth, lateral root initiation, leaf formation, and tropisms (directional growth in response to environmental stimuli). Auxin itself is a very simple molecule; yet despite over 100 years of research, the mechanisms of auxin biosynthesis, signaling, and action are not fully understood.
Industry:Science
Biological diversity is being depleted worldwide through habitat loss, introduced species, overexploitation, and pollution. These conditions reduce population sizes and increase susceptibility to chance fluctuations (environmental, catastrophic, demographic, and genetic), and so increase the risk of extinction. Human intervention is required to ensure the survival of many species: 11.7% of mammals and 10.6% of birds are categorized as threatened species by the World Conservation Union (IUCN). A recent assessment from the Conservation Breeding Specialist Group of the IUCN classified 38% of vertebrates as threatened.
Industry:Science
Electromagnetic radiation emitted by relativistic charged particles following a curved path in magnetic or electric fields. Synchrotron radiation is generally produced in laboratories by a beam of relativistic (moving near the speed of light) electrons or positrons in a generally circular path in a specialized synchrotron called a storage ring. A storage ring produces electromagnetic radiation with high flux, brightness, and coherent power levels. Synchrotron radiation is used for a wide variety of basic and applied research in biology, chemistry, and physics, as well as for applications in medicine and technology.
Industry:Science
High-speed rail (HSR) is currently regarded as one of the most significant technological breakthroughs in passenger transportation developed in the second half of the twentieth century. According to the definition of the International Union of Railways (UIC), high-speed rail is a type of passenger rail transportation capable of operating at speeds of 200 km/h (124 mi/h) for upgraded track and 250 km/h (155 mi/h) or faster for new track. During the past 50 years, the high-speed rail has developed rapidly to meet the increasing demand for passenger rail travel. The development process can be divided into three stages.
Industry:Science
Any of a group of organic compounds which, when applied in low concentration, are able to promote elongation growth of plant shoots excised from a growing region of a young seedling. These substances were the first plant hormones to be studied, and were given the generic name auxins, indicating an increase, by F. Kögl and A. J. Haagen-Smit in 1931. The ability to increase the rate of shoot elongation is a key to the designation of a synthetic or naturally occurring compound as an auxin. However, auxins, and the other plant hormones, influence a variety of plant processes during various stages of plant development.
Industry:Science
Commercial trucks in the United States vary significantly in size and load-carrying capacity. These vehicles are classified by the United States Department of Transportation (DOT) based upon their gross vehicle weight rating (GVWR). The classes range from 1 to 8, with categories of light-duty (1–3), medium-duty (4–6), and heavy-duty (7–8). The 2007 statistics for combination trucks on the highway show that there are over 2 million trucks, each traveling an average of 65,000 mi per year (105,000 km per year) and consuming 12,800 gal (48,600 L) of fuel per year to give an average fuel economy of 5.1 mi/gal (46 L/100 km).
Industry:Science
