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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 area of study focusing on the development of a classification system, or taxonomy, for plants based on their evolutionary relationships (phylogeny). The assumption is that if classification reflects phylogeny, reference to the classification will help researchers focus their work in a more accurate manner. This principle is illustrated by the example of a mother and daughter, with a great deal being known about the genetic traits of the mother. The genetic traits exhibited by the daughter can be largely predicted in this case, whereas for two people of unknown relationships no conjecture is possible regarding their genetic similarity. The task is to make phylogeny reconstruction as accurate as possible. How this phylogenetic system of classification is to be constructed has been subject to varying opinions over time. The basic unit of classification is generally accepted to be the species, but how a species should be recognized has been intensely debated. A historical perspective is useful in explaining the nature of this controversy.
Industry:Science
Tetrapods may be defined as vertebrates with four limbs and digits (that is, arms and legs bearing fingers and toes). The term includes not only the extinct forms described here, but all their relatives and descendants, including dinosaurs, snakes, frogs and salamanders, and even mammals like ourselves. It has, however, become increasingly difficult to draw a line between some of the earliest fossil tetrapods and their closest relatives with fins, in part as a result of the increase in the number of transitional fossils that are being discovered. Thus, the definition of the word “tetrapod” has become almost as murky as the swamps from which the first four-legged animals emerged.
Industry:Science
The first division under the subkingdom Embryobionta, in the classificatory system of A. Cronquist, A. Takhtajan, and W. Zimmermann. The bryophytes and vascular plants are included in this subkingdom. The category Rhyniophyta was devised for the relatively simple Silurian-Devonian vascular plants long held to be ancestral to other groups of vascular plants and usually referred to as Psilophytales. These plants have leafless stems and lack roots; their general morphological structure is not complex. Nevertheless, studies have shown that they fall into distinct groups on the basis of such characteristics as maturation of primary xylem, complexity of primary xylem in the stem, position of sporangia (terminal versus lateral), shape of sporangia (fusiform versus reniform), dehiscence of sporangia (longitudinal versus distal), and presence or absence of extensive lateral branch systems bearing large masses of terminal sporangia. The three classes of Rhyniophyta currently recognized are Rhyniopsida, Zosterophyllopsida, and Trimerophytopsida.
Industry:Science
The impedance or admittance of an alternating-current circuit. It is sometimes convenient to use the term immittance when referring to a complex number which may be either the impedance (ratio of voltage to current) or the admittance (ratio of current to voltage) of an electrical circuit. The units of impedance and admittance are, of course, different and so units cannot be assigned to an immittance. However, in certain theoretical work it may be necessary to deal with general functions which afterward will be specialized to become either an impedance or an admittance by the assignment of suitable units; in such cases it is convenient to refer to the functions as immittances.
Industry:Science
The hydride of fluorine and the first member of the family of halogen acids. Anhydrous hydrogen fluoride is a mobile, colorless liquid that fumes strongly in air. It has the empirical formula HF, melts at −83°C (−117°F) and boils at 19.8°C (67.6°F). The vapor is highly aggregated, and gaseous hydrogen fluoride deviates from perfect gas behavior to a greater extent than any other gaseous substance known. Aggregate formation in both the vapor and liquid phase arises from unusually strong hydrogen-bond interactions. Hydrogen fluoride is prepared on the large industrial scale by treating fluorspar (calcium fluoride, CaF<sub>2</sub>) with concentrated sulfuric acid. The crude product is purified by fractional distillation to yield a product containing more than 99.5% HF; the remaining impurities are principally water and small amounts of sulfur dioxide, silicon tetrafluoride, and boron trifluoride. Very dry hydrogen fluoride can be obtained by electrolysis or by treatment with reagents such as fluorine or cobaltic fluoride that react with water.
Industry:Science
The branch of medicine concerned with the resolution of legal issues by the application of scientific medical knowledge. The issues may be of criminal or civil nature. The specialty of forensic medicine is often referred to as legal medicine in Europe and in Spanish-speaking countries. The development of forensic medicine began in Europe in the early nineteenth century. Although forensic medicine has its basis in the specialty of pathology, physicians in other specialties, such as psychiatry, orthopedics, cardiology, and neurology as well as specialists in other disciplines, may be called on to resolve legal questions posed by judges, attorneys, investigators, and hearing boards.
Industry:Science
Spiders are among the most abundant and important of all insect predators, whose numbers often exceed 100 per square meter, or one million spiders per hectare (10,000 m<sup>2</sup>). The ecological success of spiders has been attributed to key innovations in how spiders use silk to capture insects, mainly with different kinds of webs. Spider webs have diverse, intricate architecture resulting from complex adaptations that evolved under various selection pressures. Primitive orb-weavers of the Deinopoidea, for example, produce dry cribellar threads made of thousands of silks (cribellar threads are produced from the cribellum, a specialized, flattened spinning organ), while modern Araneoidea orb-weavers produce viscous adhesive threads with droplets. Both kinds of threads are very elastic and have among the greatest tensile strength of any substance in nature. The stickiness of adhesive thread is more effective, though, which may have contributed among other factors to the dominance in modern environments of araneoids with respect to the deinopoids.
Industry:Science
The applied science of textile materials, consisting of the application of the principles of the many basic fields of chemistry to the understanding of textile materials and to their functional and esthetic modification into useful and desirable items. Textile chemistry includes the study of the chemical and physical properties of the various textile fibers, both natural and synthetic. Included also is the application of the principles of surface chemistry to the many cleaning operations and modifications of the textile material. Finally, there is the application of organic chemistry to the synthesis and formulation of the chemical products necessary for achieving these objectives.
Industry:Science
The application of engineering principles to conceive, design, develop, operate, and/or use processes and products based on biological and biochemical phenomena. Biochemical engineering (also known as biomolecular engineering because of the emphasis on the molecular basis of biological phenomena) influences a broad range of industries, including health care, agriculture, food, enzymes, chemicals, waste treatment, and energy, among others. Historically, biochemical engineering has been distinguished from biomedical engineering by its emphasis on biochemistry and microbiology and by the lack of a health care focus. This is no longer the case. There is increasing participation of biochemical engineers in the direct development of pharmaceuticals and other therapeutic products. Biochemical engineering has been central to the development of the biotechnology industry, given the need to generate prospective products (often using genetically engineered microorganisms and cells) on scales sufficient for testing, regulatory evaluation, and subsequent sale.
Industry:Science
The arboviral encephalitides comprise several different families of arthropod-borne viruses (arboviruses) that cause encephalitis, an inflammation of the brain tissue in humans and vertebrate animals. They are transmitted from one vertebrate host to another by insects, ticks, or other arthropods. The biology and behavior of the arthropod and vertebrate hosts greatly influence the ecology and epidemiology of these viruses. Surveillance for arboviral encephalitis involves the organized monitoring of levels of virus activity, vector populations, infections in vertebrate hosts, human cases, weather, and other factors to detect or predict changes in the transmission dynamics of the infection.
Industry:Science
