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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.
Flowering plants (angiosperms), with about 300,000–400,000 living species, are the largest and most diverse assemblage of land plants on our planet. They include many familiar and economically important plant groups such as the cereal grasses, legumes, and most fruits and vegetables. One of the major goals of systematic botany is to reconstruct the evolutionary history of this diverse lineage. Traditionally, hypotheses of evolutionary relationships have been based largely on morphological traits (for example, flower structure, stem anatomy), but current approaches also consider genetic evidence from one or a combination of the three genomes found in plants (plastid, mitochondrial, and nuclear). This type of work has provided many important insights into flowering plant evolution, and there has been substantial progress in reconstructing the plant tree of life. This knowledge has necessitated the production of a new classification scheme because some families and higher taxa were found not to be natural, and this framework now provides a solid evolutionary basis by which all aspects of comparative flowering plant biology can be focused.
Industry:Science
Changes in a preexisting rock's mineralogy, texture, and/or composition that occur predominantly in the solid state when the rock is exposed to a physical or chemical environment that is significantly different from that in which it initially formed. Any parameter that can effect such a change is one that could cause metamorphism. These include temperature, pressure, the nature of the fluid phase, and the state of stress. Although the processes of weathering and diagenesis (changes in sediments) are essentially identical to those of metamorphism, and solid metamorphic rock masses can coexist with melts during partial melting, metamorphism is rather arbitrarily confined to conditions between those of diagenesis and large-scale melting. Given that weathering and diagenesis occur only in the thin uppermost veneer of sediments, and that large-scale melting is an exceptional process with respect to normal conditions at depth, metamorphism is considered the dominant process taking place throughout most of the Earth's crust and mantle. Significant uplift and erosion typically is required to expose metamorphic rocks at the surface of the earth.
Industry:Science
In algebra, the term field is used to designate an algebraic system or structure containing at least two elements and having two binary rules of composition: addition and multiplication (that is, if <i>a</i> and <i>b</i> are any two elements of the field, then <i>a</i> + <i>b</i> and <i>ab</i> are defined and are elements of the field). The structure rules are as follows: The elements form an abelian (commutative) group under addition with the additive identity denoted by 0; that is, <i>a</i> + 0 = <i>a</i> for all elements <i>a</i>. The set of nonzero elements (and there are some since the field has at least two elements) form an abelian group under multiplication with the multiplicative identity denoted by 1. It follows that all nonzero elements have a multiplicative inverse or reciprocal. The two rules of composition are related by the distributive law: (<i>a</i> + <i>b</i>)<i>c</i> = <i>ac</i> + <i>bc</i> for all elements <i>a</i>, <i>b</i>, <i>c</i>. It follows from the distributive law that <i>a</i> · 0 = 0 for all elements <i>a</i>, since 1 · <i>a</i> = (1 + 0)<i>a</i> = 1 · <i>a</i> + 0 · <i>a</i>, whence 0 = 0 · <i>a</i>.
Industry:Science
Any mineral belonging to the zeolite family of minerals and synthetic compounds characterized by an aluminosilicate tetrahedral framework, ion-exchangeable large cations, and loosely held water molecules permitting reversible dehydration. The general formula can be expressed as ·<i>n</i>H<sub>2</sub>O. Since the oxygen atoms in the framework are each shared by two tetrahedrons, the (Si,Al):O ratio is exactly 1:2. The amount of large cations (X) present is conditioned by the aluminum/silicon (Al:Si) ratio and the formal charge of these large cations. Typical large cations are the alkalies and alkaline earths such as sodium (Na<sup>+</sup>), potassium (K<sup>+</sup>), calcium (Ca<sup>2+</sup>), strontium (Sr<sup>2+</sup>), and barium (Ba<sup>2+</sup>). The large cations, coordinated by framework oxygens and water molecules, reside in large cavities in the crystal structure; these cavities and channels may even permit the selective passage of organic molecules. Thus, zeolites are extensively studied from theoretical and technical standpoints because of their potential and actual use as molecular sieves, catalysts, and water softeners.
Industry:Science
Construction as a whole accounts for approximately 13% of the gross domestic product (GDP) of the United States. Recognizing the recyclability and other characteristics of steel, this paper will focus on the leading role of the steel industry in a large number of sustainability efforts in the United States. The efficiency of steel as a primary construction material especially recognizes the changes that have taken place in steelmaking processes over the past 15–20 years. Thus, the industry has now formulated an aggressive program for energy-efficient and economical construction. Most of the mills use electric-arc furnaces, which are fed steel scrap in lieu of iron ore and coke, and continuous casting of shapes, plates, and sheet is used instead of the processing of large ingots into blooms and shapes and other products. This has led to significantly increased production efficiency and economies, with approximately 0.5 worker-hours now being used to produce 1 ton of steel. At the same time, the consumption of energy has been reduced by more than 60%, and the level of environmental pollutants and waste materials has been cut by nearly 70%.
Industry:Science
Dinosaurs are not completely extinct, as many might believe. It has been widely accepted for more than 30 years that birds are direct descendants of small theropods (meat-eating dinosaurs) called maniraptorans. This followed the discovery of a dromaeosaurid (of the family Dromaeosauridae) maniraptoran called <i>Deinonychus</i>, which showed a novel feature in the hand skeleton: a half-moon shaped wrist bone that allowed a wide range of hand movement and folding. This feature, which facilitated the wrist rotation and hand folding regarded as the precursor to the flight stroke, is shared uniquely with the earliest known bird, <i>Archaeopteryx</i>, discovered more than 150 years ago from 147-million-year-old latest Jurassic rocks in Germany. Many other skeletal features of <i>Archaeopteryx</i> and maniraptorans show a close resemblance. More impressive still are the impressions of wing and tail feathers, almost identical with those in modern birds, present in the fine-grained rock surrounding the skeletons of <i>Archaeopteryx</i>. The wings bear asymmetric primary and secondary feathers that confer aerodynamic properties necessary for flight.
Industry:Science
Cancer remains one of the principal threats to human health. More than 7 million people die of cancer worldwide each year. The high cancer mortality is due mainly to the lack of early detection modalities, especially for internal organs. Computerized tomography (CT), magnetic resonance imaging (MRI), and ultrasound imaging are commonly used diagnostic tools, but they have issues of relatively low resolution, low contrast, radiation risk, or high cost. These imaging modalities typically provide resolutions of 0.1–1 mm. On the other hand, several optical imaging techniques, such as confocal microcopy, nonlinear optical (NLO) microscopy, and optical coherence tomography (OCT), provide much higher resolutions. Confocal and NLO microscopy can achieve submicrometer resolutions while OCT's resolution ranges from 1 to 15 micrometers depending on the light source employed. These high resolutions are achieved by spatial gating of a pinhole for confocal microscopy, spectral gating of harmonic generation or multiphoton absorption for NLO imaging, and coherence gating for OCT. With such cellular or even subcellular resolutions, early cancers can be detected.
Industry:Science
Despite the extreme level of human-induced habitat destruction on Earth, which has resulted in more than 16,000 species worldwide being threatened with extinction, the last decade has seen a dramatic boom in the discovery of new vertebrate species. Such unprecedented taxonomic discoveries are the result of increased use of molecular biology in taxonomic studies and, most importantly, of increased numbers of scientific expeditions in regions (such as the Amazon and the Congo) that have been rarely, or never, surveyed previously.
Although many of the newly described species are small and cryptic (appearing identical but genetically quite distinct), some very large and unlikely animals, such as petrels, cats, elephants, pandas, and whales, are being newly described. In the present article, the state-of-the-knowledge in species and subspecies discoveries is discussed, and information is compiled from published taxonomic revisions—essentially a reinterpretation of the taxonomy of known animals—and from new field discoveries of animals. In particular, special attention is paid to tetrapod vertebrates, that is, amphibians, reptiles, mammals, and birds.
Industry:Science
Biological control (biocontrol) is the use of living organisms to reduce pest abundance and damage. Biocontrol agents are often consumers of pests; thus herbivores are used to reduce weeds, while predators or parasites are used to reduce insect and other animal pests. Pathogens and competitors that interact with pests are also used in biocontrol. Biologically based pest management includes biocontrol and other techniques, such as the use of pheromones to disrupt mating by pests. Agricultural and forest pests are the main targets of biocontrol, although biocontrol is also used against threats to human health (such as mosquitoes) and the environment (such as certain weeds). Biocontrol may operate as an alternative to pesticides and other control techniques or may be included in an integrated pest management system. The successful practice of biocontrol typically requires knowledge of the ecology of pests and their biocontrol agents and may also involve techniques based on other scientific disciplines, including physiology, animal behavior, genetics, and biochemistry. The three major methods of biocontrol are importation, augmentation, and conservation.
Industry:Science
Einstein's mass–energy equivalence principle, <i>E</i> = <i>mc</i><sup>2</sup>, where <i>E</i> is energy, <i>m</i> is mass, and <i>c</i> is the speed of light, is probably the best-known formula in science. Despite its algebraic simplicity, however, it demonstrates an inherent fundamental difficulty for direct experimental verification: The comparison between energy and mass is realized by a factor of <i>c</i><sup>2</sup>, which magnifies any mass variation by 17 orders of magnitude. Accordingly, the energy equivalent of 1 kg (2.2 lb) of mass is comparable to the energy released by the largest nuclear explosion achieved so far. Therefore, the choice of physical system for experimental verification of Einstein's formula is limited to microscopic masses. Here the thermal neutron capture reaction appears to be the best candidate: A thermal neutron with a kinetic energy of a few millielectronvolts (meV) induces a nuclear reaction in which a new isotope with excitation energy of the order of 10 MeV is formed. The relative energy uncertainty of this reaction is therefore of the order of 10<sup>−9</sup>, which would allow carrying out very precise experiments.
Industry:Science
