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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 forward portion of a spacecraft that is designed for atmospheric entry. Nose cones are utilized for intercontinental ballistic missiles and crewed spacecraft such as Apollo and space shuttles. The nose cone is required to withstand heating encountered during atmospheric entry, maintain the structural integrity of the spacecraft, prevent overheating of the payload, and usually maintain the aerodynamic characteristics of the spacecraft. The requirements for a safe entry pose many challenging problems to the designer. Nature provides a dramatic demonstration of the scope of the problem in the form of so-called shooting stars. These bodies are meteoroids which are heated to incandescence as they enter the Earth's atmosphere and which, with few exceptions, destroy themselves prior to Earth impact.
Industry:Science
Structurally modern terrestrial ecosystems originated approximately 380–340 million years ago (Ma) from the Middle Devonian Period through the earliest Carboniferous. Although on different temporal and spatial scales, the evolutionary assembly of these ecosystems parallels the assembly of modern ecosystems following major disturbances or recovery from widespread physical and climatic disruptions, such as the end of the last glaciation. The deep evolutionary history of terrestrial ecosystems documents the emergence of constraints that would affect all subsequent ecological dynamics and dictate the nature of smaller-scale landscape and successional patterns. The fossil record is the sole source of information about the establishment of these basic patterns of species interaction and resource partitioning.
Industry:Science
The field of biomechanics has undergone revolutionary changes in recent years. Early developments in the field focused mainly on phenomena at the level of the body, organs, and tissues, whereas recent technological developments make it possible to measure forces and displacements at cellular and molecular levels. In parallel with biochemical processes, mechanical or physical forces play important roles in biology at every level of organization: organism, organ, tissue, cell, and molecule. For example, the strength of skeletal muscles increases with regular physical exercise; heart and blood vessels are remodeled by elevated blood pressure; bone remodels in response to applied forces; cell migration depends on adhesion forces; and the cell cytoskeleton structure adjusts to the forces applied to the cell.
Industry:Science
The detection, identification, and separation of aerosols have potential applications in a wide variety of fields ranging from environmental science to homeland security. Information about airborne particle sizes, particle distribution, and particle composition is important, and sometimes even critical, to researchers studying the environmental impact of industrial smog, or to military specialists and emergency responders trying to detect chemical or biological agents in the air. To aid in the detection and classification of aerosols, many researchers have turned to acoustics to help concentrate and position aerosol particles in flowing airstreams. This article describes a new class of acoustic concentration and particle manipulation devices that has been developed for use in aerosol sampling applications.
Industry:Science
The first diverse assemblages of unquestionable animal fossils at the Proterozoic-Phanerozoic transition, which marks the change from a predominantly microbial biosphere to a modern type of biosphere abundant with multicellular life. The name derives from the Early Cambrian Tommotian Stage in Siberia, where the significance of this fauna of early skeletal fossils (often referred to as “small shelly fossils”) was first realized. However, the concept goes beyond the geographical and temporal boundaries of the Tommotian Stage. It can be traced back to the low-diversity assemblages of skeletal animal fossils appearing near the end of the Neoproterozoic, continuing into the Cambrian, in Siberia first in moderate diversity in the Manykaian (Nemakit-Daldynian) Stage, then burgeoning in the Tommotian Stage itself.
Industry:Science
That portion of living cells bordered externally by the plasma membrane (cell membrane) and internally by the nuclear envelope. In the terminology of classical cytology, the substance in living cells and in living organisms not compartmentalized into cells was called protoplasm. It was assumed at the time that the protoplasm of various cells was similar in structure and chemistry. Results of research on cell chemistry and ultrastructure after about 1960 showed that each cell type had a recognizably different “protoplasm.” Primarily for that reason, the term protoplasm gradually fell into disuse in contemporary biology. The terms cytoplasm and nucleoplasm have been retained and are used descriptively; they are used almost synonymously with the terms cytosome (body of cytoplasm) and nucleus, respectively.
Industry:Science
That branch of magnetism which treats of diamagnetic phenomena and of the properties of diamagnetic bodies. Diamagnetism is a property exhibited by substances with a negative magnetic susceptibility, that is, by substances which magnetize in a direction opposite to that of an applied magnetic field. A diamagnetic substance has a magnetic permeability less than 1, and is repelled when placed near a magnet. The magnetization of diamagnetic substances is associated with the currents induced on application of a magnetic field. According to Lenz's law, the flow of an induced current is in such a direction as to oppose the change of flux of the inducing field; this accounts for the negative susceptibility. The diamagnetic susceptibility is invariably small, of the order of −10<sup>-5</sup> cm<sup>3</sup>/mole.
Industry:Science
The completion of the human genome and the genomes of several model organisms is fundamentally changing how biological discovery takes place. More than any specific benefit, it has already changed how biological questions can be addressed. This is best illustrated in the application of deoxyribonucleic acid (DNA) microarray technology, by which thousands of gene segments are deposited on a glass slide or chip and then used to simultaneously analyze the expression levels of the corresponding genes. Thus, instead of testing the changes in expression of only a few genes at a time, it is now possible to measure changes in tens of thousands of genes in a single experiment. Having the complete blueprint of an organism in its DNA sequence is opening up possibilities at almost every level, including protein function.
Industry:Science
The device that controls the power output and fuel feed of internal combustion spark-ignition engines generally used for automotive, aircraft, and auxiliary services. Its duties include control of the engine power by the air throttle; metering, delivery, and mixing of fuel in the airstream; and graduating the fuel-air ratio according to engine requirements in starting, idling, and load and altitude changes. The fuel is usually gasoline or similar liquid hydrocarbon compounds, although some engines with a carburetor may also operate on a gaseous fuel such as propane or compressed natural gas. A carburetor may be classified as having either a fixed venturi, in which the diameter of the air opening ahead of the throttle valve remains constant, or a variable venturi, which changes area to meet the changing demand.
Industry:Science
Superconductors strongly repel a magnetic field. This phenomenon, known as the Meissner effect, is the scientific basis for the magnetically levitated (maglev) superconducting trains, which can move at a speed of 500 km/h (310 mi/h). According to electromagnetic theory, electric and magnetic fields are intricately related. Thus, the interaction between superconductors and an electric field is of great interest. Fritz London first studied the issue in 1935 and proposed that superconductors and conventional conductors might react to electric fields differently. However, due to the difficulties associated with these types of experiments, this issue remains controversial and unresolved. The recent discovery of the formation of superconducting balls in a strong electric field illustrates the rich physics of this area.
Industry:Science
