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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.
Bound states of quarks, in which at least one of these constituents is of the strange (<i>s</i>) type. Strange quarks are heavier than the up (<i>u</i>) and down (<i>d</i> ) quarks, which form the neutrons and protons in the atomic nucleus. Neutrons (<i>udd</i> ) and protons (<i>uud</i> ) are the lightest examples of a family of particles composed of three quarks, known as baryons. These and other composite particles which interact dominantly through the strong (nuclear) force are known as hadrons.
The first strange hadron discovered (in cosmic rays in 1947) was named the lambda baryon, Λ; it is made of the three-quark combination <i>uds</i>. A baryon containing a strange quark is also called a hyperon. Although strange particles interact through the strong (nuclear) force, the strange quark itself can decay only by conversion to a quark of different type (such as <i>u</i> or <i>d</i> ) through the weak interaction. For this reason, strange particles have very long lifetimes, of the order of 10<sup>−10</sup> s, compared to the lifetimes of the order of 10<sup>−23</sup> s for particles which decay directly through the strong interaction. This long lifetime was the origin of the term strange particles. This stability was an important clue for the presence of quarks inside strongly interacting particles, and was one motivation for the development of the quark model in 1964. The quark model predicted a triply strange (<i>sss</i>) baryon which was named the Ω<sup>−</sup>, and its subsequent observation effectively confirmed the basic correctness of the quark model.
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Chemical compounds in which the relative number of atoms is not expressible as the ratio of small whole numbers, hence compounds for which the subscripts in the chemical formula are not rational (for example, Cu<sub>1.987</sub>S). Sometimes they are called berthollide compounds to distinguish them from daltonides, in which the ratio of atoms is generally simple.
Nonstoichiometry is a property of the solid state and arises because a fraction of the atoms of a given kind may be (1) missing from the regular structure (for example, Fe<sub>1 − δ</sub>O), (2) present in excess over the requirements of the structure (for example, Zn<sub>1 + δ</sub>O), or (3) substituted by atoms of another kind (for example, Bi<sub>2</sub>Te<sub>3 ± δ</sub>). The resulting materials are generally of variable composition, intensely colored, metallic or semiconducting, and different in chemical reactivity from the parent stoichiometric compounds from which they are derived.
Nonstoichiometry is best known in the binary compounds of the transition elements, particularly the hydrides, oxides, chalcogenides, pnictides, carbides, and borides. It is also well represented in the so-called insertion or intercalation compounds, in which a metallic element or neutral molecule has been inserted in a stoichiometric host. Nonstoichiometric compounds are important in some solid-state devices (such as rectifiers, thermoelectric generators, and photodetectors) and are probably formed as chemical intermediates in many reactions involving solids (for example, heterogeneous catalysis and metal corrosion).
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Formerly, one of the two classes of the phylum Brachiopoda. The phylum comprises solitary, exclusively marine, coelomate (having a true coelom or mesodermally lined body cavity), lophophorate (having a lophophore, a food-gathering ciliated organ), bivalved animals, with the two valves symmetrical about a median longitudinal plane. Now the former Inarticulata comprises two of the three subphyla currently recognized, Linguliformea and Craniiformea, together with a few taxa considered to be basal rhynchonelliform brachiopods. These two subphyla encompass approximately 6% of the generic diversity of the Recent (Holocene, from 10,000 years ago to the present day) and fossil brachiopods.
The name Inarticulata refers to the lack of tooth-and-socket articulatory structures on the two valves of these brachiopods. The name was abandoned because of recent changes made in the classification thought to reflect a better understanding of phylogenetic relationships among several groups of Cambrian brachiopods. Because some linguliform and craniiform species have primitive forms of articulation that may or may not be homologous with articulated brachiopods, and because some early rhynchonelliforms lack articulation, the term Inarticulata no longer accurately characterizes this group of brachiopods. However, molecular and morphological evidence suggests that Linguliformea and Craniiformea are each likely to be monophyletic (evolved from a single interbreeding population), are sister groups to one another, and may form a clade, together with Phoronida at the base, that is the sister group to Rhynchonelliformea.
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From instrumental records, we know that the Earth has warmed by 0.5°C (0.9°F) since 1860. Only through the study of the climate history over the past several centuries and millennia can we truly assess whether this warming should be expected in a naturally changing climate or if it is being caused by human activities. Paleoclimatology is the reconstruction of past climate changes. In order to accurately identify the causes and mechanisms of climatic change, it is necessary to develop high-resolution paleoclimate records which tell us about past climate changes on seasonal, annual, and decadal time scales. In addition to helping us understand the natural spatial and temporal patterns of climate variability, these high-resolution records provide an important means of testing the results of general circulation models, which are used to predict future climate changes that may result from anthropogenic carbon dioxide (CO<sub>2</sub>) emissions.
As historical and instrumental climate records cover only the very recent past, it is necessary to use indirect (proxy) records for a longer-term perspective on climatic variability. Paleoclimate records may be derived from natural archives, which incorporate climate-dependent physical or chemical proxy variables in their structure. The most complete and robust paleoclimate proxy records to date are ice-core records, marine-sediment records, and the Chinese loess record. While these records have provided key information about the Earth's climate history, they often are limited by low temporal resolution, uncertain chronologies, and poor geographic coverage.
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Discrete analytic functions, also known as circle-packing maps, are mappings between circle packings whose properties faithfully reflect the properties that are characteristic of classical analytic functions. A circle packing is nothing more than a collection of circles with prescribed tangencies that lie on a surface. The tangency information may be encoded in a graph in which each circle is represented by a vertex, and each point of tangency at which two circles meet is represented by an edge connecting the vertices that correspond to those two circles.
A discrete analytic function then may be represented by a mapping between two circle-packing graphs of this type. Though discrete analytic functions may be used to build discrete approximations of classical analytic functions of both planar domains and surfaces, their real importance derives from the discovery that their properties mark them as true analogs in the discrete setting of the familiar analytic mappings of classical complex analysis. As such, discrete analytic functions offer both the rigidity and versatility of their classical counterparts and, in particular, offer a range of manipulations of planar domains that makes them valuable for flat two-dimensional representations of surfaces in three dimensions.
The theory of discrete analytic functions has been developed to the point that it stands alone as a part of a general movement in the recent development of mathematics—that of the discretization of geometry. Before presenting a more detailed description of these functions, it will be instructive to place the subject in its proper context within the recent development of mathematics.
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Deception, whether intentional or unintentional, adds an important dimension to social interaction. Given the theoretical as well as practical benefits of detecting deceptive behavior, much effort has been devoted to developing methods of measurement that can accurately depict the act of deception. In the past, the only possible ways to detect deception relied on indirect measurement of physiological indicators that are linked to the acts of deception—for example, involuntary arousal of the autonomic nervous system during lying. Based on this connection, the polygraph was developed; it detects deception by measuring changes in skin conductivity and variations in the heart rate and respiration rate.
Other methods of physiological measurement, such as biofeedback and electroencephalography, psychological instruments (pencil and paper tests), analysis of facial expressions and other body movements, and evaluation of handwriting and voice, have been developed with the hope that they could accurately detect the act of deception. Much effort has been made to examine the psychometric properties of these methods. The validity of these indices remains a matter of constant debate. The main limitation of these instruments is that they can provide only an indirect measure of the acts of deception—that is, measurement of the changes in bodily status that result from lying.
Also, many liars are skillful in applying countermeasures to avoid detection once they have learned the design and aim of such instruments. However, recent advances in imaging technology have enabled direct observation of the activities of the human brain during various cognitive operations, including lying.
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Elevated blood lead levels (EBLLs) are one of the major environmental problems presently facing children in the United States and elsewhere. In 1991, the Centers for Disease Control and Prevention (CDC) identified 10 μg/dL as an EBLL that should prompt public health actions to identify and manage exposure to lead. (A commonly referenced unit of measure is the blood lead value in μg/dL (micrograms per deciliter); 10 μg/dL is equivalent to 0.48 μmol/L (micromoles per liter); the conversion factor of 0.04826 is multiplied by the lead value in μg/dL to give the lead value in μmol/L.) The level had been reduced from 40 in 1971 to 10 in 1991. It has also been termed a “level of concern,” which is an unfortunate wording because there has been concern about harmful effects below this level since before 1991. In addition, this level was never seen as a threshold level (a level below which adverse effects would not occur). Older terms, lead toxicity and lead poisoning, were less specific, and generally referred to adverse or toxic effects from lead exposure that were not specific to a particular blood lead level (BLL).
The prevalence of EBLLs has decreased dramatically for the entire population and for children aged 1–5 years in the United States. Data from the National Health and Nutrition Examination Surveys (NHANES) show a decline in the geometric mean (average) BLLs from 15.2 (1976–1980) to 1.9 (1999–2002), with a similar decline in the prevalence (or percentage) of children with BLLs of 10 μg/dL or higher from 88.2% to 1.6% over the same time periods. Although the numbers have decreased significantly, this still represents an estimated 310,000 children with BLLs in this category.
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Hypersonic flight is considered flight at Mach 5 (five times the speed of sound) or greater. The aerodynamic flow and characteristics of a flight vehicle as it accelerates from Mach 4.99 to Mach 5.01 do not markedly change. In contrast, when it accelerates from Mach 0.99 (subsonic) to Mach 1.01 (supersonic), there is a dramatic change in the physics of the flow, including the generation of shock waves at supersonic speeds. Hypersonic flight may be regarded as that portion of the high-speed flight regime where certain physical phenomena become important that are not so important at lower speeds.
At hypersonic speeds, shock waves lie very close to the surface of the vehicle, and there is a major thickening of that portion of the flow immediately adjacent to the surface that is affected by friction (the boundary layer), causing an interaction between the shocks and the boundary layer. Moreover, at high Mach numbers, the tremendous kinetic energy of the freestream flow ahead of the vehicle is dissipated through the shock waves and in the boundary layers, and it is converted into heat which creates high temperatures in the flow around the hypersonic vehicle—temperatures that are frequently high enough to chemically dissociate and ionize the gas in the flowfield. Under these conditions, extreme aerodynamic heating becomes a driving consideration in the design of a hypersonic vehicle.
All of this and more comprise the aerodynamic characteristics of hypersonic flight, making it perhaps the most challenging flight regime to conquer. However, the quest to fly faster and higher historically has been a major driving force in the advancement of flight, and hypersonic flight is the next objective in this quest.
Industry:Science
As the European Union and the United States are evolving into knowledge societies, the ability to generate, use, diffuse, and absorb new knowledge is increasingly being viewed as critical for economic success. Consequently, conventional wisdom regards high-tech, research-intensive, and science-based industries as the key drivers of future economic prosperity. The policy conclusion is that high-cost industrialized countries should concentrate their efforts on promoting these industries.
In this scenario, low- and medium-tech (LMT) industries are deemed to offer very limited prospects for future growth in comparison to high-tech ones and, as a result, receive less explicit policy attention and support. The statistical basis of this perspective is the internationally accepted research and development (R&D) intensity indicator (developed by the Organization for Economic Co-operation and Development (OECD) in the 1960s), which measures the ratio of the R&D expenditure to the turnover of a company or to the output value of a whole sector. Sectors with an R&D intensity of more than 3% are characterized as high-tech or medium-high-tech. Sectors with a R&D intensity below 3% are classified as low- or medium-tech. Mainly “mature” industries, such as the manufacture of household appliances; the food industry; the paper, publishing, and print industry; the wood and furniture industry; and the manufacturing of metal and plastic products, are regarded as low- or medium-tech. In contrast, pharmaceuticals, the electronics industry, medical engineering, vehicle construction, the aerospace industry, large parts of mechanical engineering, and the electrical industries are categorized as high-tech or medium-high-tech.
Industry:Science
Despite the large degree of success of many vaccines, humans are still plagued by diseases such as AIDS, chronic hepatitis, and cancer. Together these three diseases are responsible for over 530,000 deaths per year in the United States, 94% of this number being attributed to cancer alone. Without an effective vaccine, education is one of the few ways available for controlling disease. For example, education about high-risk behavior has helped bring the 78,000 reported cases of AIDS in the United States in 1993 down to 43,000 reported cases in 1999. Alterations in diet and lifestyle and having regular checkups can aid in lowering the reported cases of certain cancers. Nevertheless, the development of an effective vaccine would be the optimal solution to lowering incidence of AIDS and cancer.
Increasing knowledge of the human immune system, together with understanding of the mechanism by which vaccines provide immunity and how pathogens infect and evade the host defenses, allows for a focused approach on the development of effective vaccines. In the search for a vaccine, the cost of manufacture, ease of delivery and transport, and effectiveness at directing the immune response toward the pathogen with little negative impact on the host are taken into account. The effectiveness of a vaccine depends on the type of vaccine as well as the characteristics of the target pathogen. A large variety of vaccine strategies are available, and new delivery systems are being developed. Since different pathogens exhibit a variety of mechanisms for evading the human immune response, defining the immune response that would be most effective against a particular pathogen is also an important step in vaccine development.
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