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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.
Assemblages of living organisms that occur together in an area. The nature of the forces that knit these assemblages into organized systems and those properties of assemblages that manifest this organization have been topics of intense debate among ecologists since the early years of this century.
On the one hand, there are those who view a community as simply consisting of species with similar physical requirements, such as temperature, soil type, or light regime. The similarity of requirements dictates that these species be found together, but interactions between the species are of secondary importance and the level of organization is low.
On the other hand, there are those who conceive of the community as a highly organized, holistic entity, with species inextricably and complexly linked to one another and to the physical environment, so that characteristic patterns recur, and properties arise that one can neither understand nor predict from a knowledge of the component species. In this view, the ecosystem (physical environment plus its community) is as well organized as a living organism, and constitutes a superorganism. Between these extremes are those who perceive some community organization but not nearly enough to invoke images of holistic superorganisms.
Industry:Science
Equipment used for determining the direction from which a received signal is being radiated. Direction finders serve a variety of applications. Direction finders can be used for navigation purposes to determine the heading of a vehicle relative to a transmitter at a known location, and to determine the location of the vehicle when the range to that transmitter is known, as in the case of VOR/DME instrumentation. Direction finding may also be used to determine vehicle heading for guidance along a desired route toward a given destination.
Surveillance uses of direction finders include discovering and locating covert transmitters used for espionage, locating the emitter in search-and-rescue missions, and tracking crewless objects in scientific missions. A direction finder may be implemented either as a ground station used to track a moving source or on a moving vehicle. Bearing information obtained by the ground station can also be passed to a moving vehicle that is equipped with a transmitter that can be tracked by the ground station. As mentioned above, a direction finder may also be found on a moving vehicle, such as an aircraft or a ship, to determine the vehicle's heading relative to a transmitter or the transmitter's bearing relative to the known track of the vehicle.
Industry:Science
C<i>andida</i> species are fungi that cause important human diseases collectively referred to as candidiasis. The diseases are usually endogenous in origin, meaning that the source of the pathogen is within the host. <i>Candida albicans</i> is a common, usually harmless inhabitant of mucosal surfaces of the oral cavity, gut, and vaginal canal along with a variety of other microorganisms that are collectively called the normal flora. Most often, candidiasis occurs in the immunocompromised host; cancer, transplant, diabetic, AIDS, and surgical patients as well as premature infants are especially susceptible to infections.
The reason for susceptibility varies. For the AIDS patient, a depletion in T-lymphocyte numbers triggers mucosal disease. The premature infant may develop candidiasis because of an underdeveloped immune system or because bacteria that are part of the normal flora of the human oral cavity or gut are not as protective. It is believed that competition among members of the normal flora of mucosal surfaces (oral cavity, vaginal system, gut) protects the host against the transgression of <i>C. albicans.</i> Consequently, if the competing bacteria at these locations are reduced in number by the prolonged use of antibiotics, an overgrowth of <i>C. albicans</i> can result in disease.
Industry:Science
Forensic science has never been more popular or more popularized. From documentary TV shows such as <i>Forensic Files</i>, to their more fictionalized offspring such as the <i>CSI</i> series, forensic science has gained a solid foothold in the public's perception of its practitioners and methods. Belying that perception, however, is the reality of what it takes currently to become a forensic scientist, namely, a strong science education.
The educational foundation for a forensic science degree has changed over the years in response to the increasing recognition that forensic science is a separate discipline in its own right and not merely applied chemistry, biology, or other science. The development of forensic science and the growth in the number of educational programs offering forensic science degrees have contributed to the need for accreditation of these programs. With this accreditation comes a level of assurance for students and employers of what the degree entails and what can be expected of graduates from accredited programs. A recent report from the National Academy of Sciences recommends an increased emphasis on graduate education in forensic science and, with that, additional research to improve the reliability of the science used in investigations, laboratories, and courtrooms.
Industry:Science
Chemical microreactors are characterized by the extremely small dimensions of the reaction devices and related unit operation elements. In comparison to macroscale devices, large temperature and concentration gradients are feasible in microreactors, resulting in correspondingly high heat and mass transfer rates. Since the boundary conditions concerning flow, temperature, pressure, and other parameters can be precisely adjusted, and since the thermal mass of such microsystems is small, an exact setting of the residence time in the reaction volume is easily obtained. This leads to a novel approach for process control. Usually a number of microreactors are operated in parallel, with all devoted to either different or identical reactions. In the first case, microreactors may be regarded as devices generating information like miniaturized analytical laboratories; in the second case, they work as production units for chemical substances which achieve the required throughput by parallel operation.
The unique characteristics of microreactors open up novel approaches for utilizing a wide variety of reaction pathways, for improving safety aspects, for a faster transfer of laboratory results into production, and, evidently, for cost-saving innovations in many fields of modern chemistry and biotechnology.
Industry:Science
Ecology of prehistoric times, extending from about 10,000 to about 3.5 × 10<sup>9</sup> years ago. Although the principles of paleoecology are the same as those underlying modern ecology, the two fields actually differ greatly. Paleoecology is a historical science that must rely on empirical data from fossils and their enclosing sedimentary rocks to make inferences about past conditions.
Experimental approaches and direct measurement of environmental parameters, which are critical components of modern ecology, are generally impossible in paleoecology. Furthermore, distortion and loss of information during fossilization means that fossil assemblages and distributions are rarely congruent with living communities. Hence, the resolution of ancient ecosystems must remain relatively imprecise. The lack of precision is compensated for by the fact that paleoecology deals with processes occurring over vast spans of time that are unavailable to modern ecology. Long-term changes in communities (replacement) may be discerned and related to patterns of environmental change. More significantly, overall patterns of ecological change in the global biosphere may be documented; evolutionary paleoecology focuses on recognition and interpretation of long-term ecological trends that have been critical in shaping evolution.
Industry:Science
Failure of two or more genes to recombine at random as a result of their location on the same chromosome pair. Among the haploid products of a cell which has gone through meiosis, two genes located in the same chromosome pair remain in their two original combinations of alleles (parental) unless an odd number of exchanges of homologous segments occurred within the interval bounded by their loci. The incidence of exchanges of homologous segments at meiosis is roughly proportional to the length of the chromosome segment between two loci. The percentage of recombinants thus provides an estimate of this length and a basis for constructing gene maps on which linked loci are arranged in linear order and spaced out in proportion to the recombination percentages between them. The analogy is with a linear map of the stations along a railway line spaced out according to the time of travel between any two or more of them.
By extension of the meaning of linkage to bacterial transduction or transformation, two bacterial genes are said to be linked when both are incorporated together in the chromosome of recipient cells more often than would be expected from mere coincidence of two separate incorporations. This is the consequence of their being frequently carried on the same transducing or transforming DNA fragment.
Industry:Science
Each copy of the human genome is made up of just over 3.2 billion pairs of nucleotides (the structural units of nucleic acids), comprising the individual “letters” that make up all deoxyribonucleic acid (DNA) sequences. The sequence is housed on 23 chromosomes, containing approximately 22,000 genes as well as the regulatory switches that turn those genes on and off. Every person carries two copies of the genome, one inherited from each parent, in each cell in the body (excluding the gametes). As the genome is passed from one generation to the next, changes occur in the DNA sequence at a very low rate; over time, some of these changes are lost, while others remain.
As a result, the genomes carried by present-day humans contain a large number of genetic variants that arose as new mutations many generations ago. These old genetic variants are now shared across many genomes, making them common in the human population. These common variants may influence the risk of common human diseases and other traits, an idea that is referred to as the <i>common disease–common variant</i> (CDCV) hypothesis. <i>Whole genome</i> (or genome-wide) association studies (WGAS) are designed to test the CDCV hypothesis by examining the effect of common genetic variants on the risk of human disease, response to drug treatment, and other human traits.
Industry:Science
Economic deposits of minerals (ore deposits) in the Earth's crust are commonly formed by the transport of dissolved ore-forming materials in fluids (hydrothermal fluids or magmas), with ore deposition occurring at sites of fluid cooling or chemical change. Because of this dependence on fluid mobility, ore deposits are commonly located in areas of relatively high permeability, where fluid flow has been focused. Such zones may be formed by high-permeability sedimentary or volcanic horizons or layers (such as conglomerates, sandstones, or vesicular lavas) or by faulting (that is, fracturing) of otherwise impermeable rocks.
Major fault zones and permeable stratigraphic horizons are large-scale crustal features that can be recognized over wide areas, and may even be extrapolated beneath areas where younger geological materials have covered their traces. This geologic evidence provides a powerful tool for mineral exploration, particularly in areas of poor exposure or in covered terrains. Because much of the world's easily accessible land area has now been explored, and easily identified (that is, exposed) ore deposits have already been discovered, modern mineral explorers seek to locate previously hidden deposits. Extrapolation of regional-scale prospective zones beneath cover is one method for selecting early exploration targets.
Industry:Science
High-temperature superconductor (HTS) wires are so efficient that they can carry up to 140 times the power of conventional copper wires of the same size. The potential uses for HTS wires in electric power applications include underground transmission cables, oil-free transformers, superconducting magnetic-energy storage (SMES) units, fault-current limiters, high-efficiency motors, and compact generators. Electricity grid losses have grown to be more than 10% of all electricity generated due to resistance and other losses in conventional equipment, and blackouts highlighted transmission bottlenecks in the United States in 2003.
Efficiency and reliability will be enhanced when new transmission technologies are used that have reduced line losses and the capability to carry more current for a given size of conductor. Superconductors have virtually no electrical resistance; therefore, they can carry current with no electrical energy loss. Superconductors are of two types: low- and high-temperature. Low-temperature superconductors (LTS) work at only very frigid temperatures, near 4 K (−452°F). Equipment made with LTS wires can be expensive to operate because they need to be chilled with liquid helium. Equipment with HTS wires, however, works at relatively warmer temperatures, near 77 K (−320°F), and requires liquid nitrogen to operate.
Industry:Science
