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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.
A class of Cnidospora characterized by the production of minute spores with a single intrasporal or one or two intracapsular filaments and a single sporoplasm. The spore membrane of these protozoa is usually a single piece. Microsporidians are mainly intracellular parasites of arthropods and fishes. Microsporida is the only order of this class.
Industry:Science
A class of Crustacea whose application is gaining moderately widespread use, despite the fact that its validity is not universally accepted by researchers. The constituent subclasses of the Maxillopoda also remain unsettled: before 1956, all major subclasses of the Crustacea were regarded as distinct taxa of equal rank. In addition to the Malacostraca, these included the Cephalocarida, Branchiopoda, Cirripedia, Copepoda, Mystacocarida, Branchiura, and Ostracoda. Use of cladistics, or phylogenetic analysis, has rekindled interest in phylogenetic relationships and hierarchy among the nonmalacostracan taxa.
Industry:Science
A class of crustaceans. Formerly, four extant orders were recognized: Anostraca, Notostraca, Conchostraca, and Cladocera, the first two of which are well defined. The Conchostraca consist of two groups which, although superficially similar, differ in so many fundamental features that they have been placed in separate orders, Laevicaudata and Spinicaudata. The Cladocera are in fact a heterogeneous assemblage of organisms that have now been split into four orders: Anomopoda, Ctenopoda, Onychopoda, and Haplopoda. Although the name Cladocera has to be abandoned as a taxonomic unit, it will doubtless continue to be used as a convenient descriptive term for members of these four orders. There are also two extinct orders, Lipostraca and Kazacharthra. Branchiopods have a long history. Both the Lipostraca and Spinicaudata were differentiated by Devonian times, and their ancestors doubtless originated even earlier.
Industry:Science
A class of crystals in which the lattice-site occupants are charged ions held together primarily by their electrostatic interaction. Such binding is called ionic binding. Empirically, ionic crystals are distinguished by strong absorption of infrared radiation, good ionic conductivity at high temperatures, and the existence of planes along which the crystals cleave easily.
Industry:Science
A class of drugs, also called psychedelic or hallucinogenic drugs, that induce transient states of altered perception resembling or mimicking the symptoms of psychosis and are characterized by profound alterations in mood. The term psychotomimetic was originally coined to reflect the similarities between the mind-altering effects of certain psychoactive drugs and some of the symptoms of schizophrenia.
Industry:Science
A class of Echinozoa characterized by a cylindrical body and smooth leathery skin, and known as sea cucumbers. There are no arms, but a ring of five or more tentacles may surround the mouth, which is usually at one end of the body. There are no pedicellariae. Tube feet may be present or lacking. There are no ambulacral grooves, although they are represented by internal epineural canals overlying the radial nerves. E. Deichmann (1957) regards them as the most aberrant group of extant echinoderms.
Industry:Science
A class of electronic systems containing both analog and digital subsystems whose most common application is to the conversion of analog signals to digital form and vice versa. The device is also known as a delta-sigma converter. The main advantage of the sigma-delta approach to signal conversion is its minimal reliance on the quality of the analog components required. To achieve this end, the system uses pulse density modulation to create a high-rate stream of single-amplitude pulses. For analog-to-digital conversion, the rate at which the pulses are generated depends on the amplitude of the analog voltage being sensed. For digital-to-analog conversion, the pulse density depends on the numeric digital quantity applied at the converter input.
Industry:Science
A class of energy transducers capable of receiving alternating current and generating acoustic waves resembling very closely the characteristics of that current. The movement of an element (diaphragm) is accomplished by magnetic attraction, electrostatic attraction, or the piezoelectric effect (the expansion or contraction of certain crystalline substances in response to electric charges). Earphone systems include the driver element with its diaphragm and arrangements for magnetic flux, or electrostatic or direct electric charge, plus a casing, one or more acoustic cavities and ports, acoustic damping and insulation, and some arrangement for coupling the driver to the human ear. The wiring connecting the precedent amplifier to the driver, which may be incorporated into the earphone system, may in modern systems be a complicated circuit which feeds, for each of two stereophonic channels, some part of the current to each ear. The time delays and energy ratios at the two earphones (each of which may contain two drivers) can be appropriately adjusted so that the listener is given the illusion that the sound sources are not “within the head” but are externalized appropriately in all three planes of space. The various types of earphones are described below.
Industry:Science
A class of extinct Echinozoa which arose early in Cambrian times and died out before the end of the Carboniferous Period. They resemble the other Echinozoa in having the ambulacral radial areas bordered by tube feet which emerge through pores in or between the ambulacral plates. In this feature they differ from Crinozoa, to which they were once thought to be related. They differ from extant Echinozoa in having the mouth and anus on the upper side of the theca. Hinged ambulacral plates bordered the groove on either side and could be erected over it to convert it into a tube (see <b>illus.</b>). The theca shows strong pentamerous symmetry and is more or less discoidal; it bears no stem. The animals in some cases were cemented to the substrate by the lower surface; in other cases they were free and rested upon the sea bed. Brachioles are lacking. About 30 genera have been described and grouped into more than a dozen families.
Industry:Science
A class of extinct Pelmatozoa in the subphylum Blastozoa which arose in the Ordovician and flourished in the Carboniferous and Permian. Blastoids did not survive the Permo-Triassic mass extinction event. Historically, two orders of the Blastoidea have been recognized: the Fissiculata with exposed hydrospire slits and the Spiraculata with concealed hydrospires. In recognition of their polyphyletic origins, the Spiraculata are now subdivided into the Troosticrinida, Nucleocrinida, Granatocrinida, and Pentremitida.
Industry:Science
