- 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.
The science of nourishment, including the study of the nutrients that each organism must obtain from its environment to maintain life and health and to reproduce. Although each kind of organism has its distinctive needs, which can be studied separately, a far-reaching biochemical unity in nature has been discovered which gives vastly more coherence to the whole subject. Many nutrients, such as amino acids, minerals, and vitamins, needed by higher organisms may also be needed by the simplest forms of life—single-celled bacteria and protozoa. The recognition of this fact has made possible highly important developments in biochemistry.
Industry:Science
The plant cell wall consists of a multilayer structure in which cellulose and hemicellulose are intimately associated with lignin. Lignin provides strength and impermeability, and serves as a barrier against microbial attack across the cell wall. In contrast to other natural polymers composed of regularly interlinked, repetitive monomers, lignin is an amorphous polymer made of randomly distributed phenylpropanoid monomers. Lignin production is estimated at 20 × 10<sup>6</sup> megatons annually; lignin therefore plays a central role in the global renewable carbon cycle. Its structure imposes unusual restrictions on its biodegradability.
Industry:Science
The physical character and distribution of natural resources at the face of the Earth. No section of the Earth is exactly like any other in its resource endowment. Combinations of land and ocean, latitudinal differences in insolation, variations in receipt of precipitation, patterns of geology, and deformation of the Earth's crust all converge to create different resources in various regions of the world. Nevertheless, there is some repetition in these natural features and forces of nature across the Earth. These similarities that exist from place to place distinguish regional patterns in the availability of resources on a global scale.
Industry:Science
The study of the composition and chemical properties of soil. Soil chemistry involves the detailed investigation of the nature of the solid matter from which soil is constituted and of the chemical processes that occur as a result of the action of hydrological, geological, and biological agents on the solid matter. Because of the broad diversity among soil components and the complexity of soil chemical processes, the application of concepts and methods employed in the chemistry of aqueous solutions, of amorphous and crystalline solids, and of solid surfaces is required. For a general discussion of the origin and classification of soils.
Industry:Science
The process of changing energy from one form to another. There are many conversion processes that appear as routine phenomena in nature, such as the evaporation of water by solar energy or the storage of solar energy in fossil fuels. In the world of technology the term is more generally applied to operations in which the energy is made more usable, for instance, the burning of coal in power plants to convert chemical energy into electricity, the burning of gasoline in automobile engines to convert chemical energy into propulsive energy of a moving vehicle, or the burning of a propellant for ion rockets and plasma jets to provide thrust.
Industry:Science
The optical analog of radar. The term lidar is an acronym for light detection and ranging. Lidar systems employ intense pulses of light, typically generated by lasers, and large telescopes and sensitive optical detectors to receive the reflected pulses. They are most commonly used to measure the composition and structure of the atmosphere. The very narrow beamwidth, narrow linewidth, and ultrashort pulses of the laser make it possible to optically probe the atmosphere with exceptional sensitivity and resolution. When used to measure the range and velocity of hard targets, lidars are usually called laser ranging systems or laser radars.
Industry:Science
The study of the development of an organism, commencing with the union of male and female gametes. Embryology literally means the study of embryos, but this definition is restrictive. An embryo is an immature organism contained within the coverings of an egg or within the body of the mother. Strictly speaking, the embryonic period ends at metamorphosis, hatching, or birth. Since developmental processes continue beyond these events, the scope of embryology is customarily broadened to encompass the entire life history of an organism. Embryology may, in this wider context, consider the mechanisms of both asexual reproduction and regeneration.
Industry:Science
The name traditionally applied to three hydrated magnesium silicate minerals, antigorite, chrysotile, and lizardite. All have similar chemical compositions (ideally ) but with three different but closely related layered crystal structures. Serpentine also has been used as a group name for minerals with the same layered structures but with a variety of compositions. The general formula is , where M may be magnesium (Mg), ferrous iron (Fe<sup>2+</sup>), ferric iron (Fe<sup>3+</sup>), aluminum (Al), nickel (Ni), manganese (Mn), cobalt (Co), chromium (Cr), zinc (Zn), or lithium (Li); and T may be silicon (Si), Al, Fe<sup>3+</sup>, or boron (B).
Industry:Science
The third largest continent, extending from the narrow isthmus of Central America to the Arctic Archipelago. The physical environments of North America, like the rest of the world, are a reflection of specific combinations of the natural factors such as climate, vegetation, soils, and landforms. While the distribution of life-giving solar heat and water seemingly should determine the character and distribution of the natural regions, in reality the landforms modify the expected environmental patterns. In addition, human activities affect the quality of some environments, and natural hazards alter some regions permanently or semipermanently.
Industry:Science
The term applied to heavier-than-air craft that cannot take off and land vertically but can operate within areas substantially more confined than those normally required by aircraft of the same size. A pure STOL aircraft is a fixed-wing vehicle that derives lift primarily from free-stream airflow over the wing and its high lift system, sometimes with significant augmentation from the propulsion system. Although all vertical takeoff and landing (VTOL) machines, including helicopters, can lift greater loads by developing forward speed on the ground before liftoff, they are still regarded as VTOL (or V/STOL craft), operating in the STOL mode.
Industry:Science
