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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 term used in elementary particle physics to describe a class of elementary particles.
Industry:Science
A term used in serology and immunology to refer to a substance that enhances the phagocytosis of bacteria by leukocytes. As originally proposed by A. E. Wright and E. R. Douglas, the term denoted a thermolabile, relatively nonspecific substance present in normal sera. In modern usages, opsonin is more generally synonymous with the bacteriotropin of F. Neufeld and coworkers, a relatively thermostable antibody, increased in amount during specific immunization, that renders the corresponding bacterium more susceptible to phagocytosis. There is evidence that this action can be promoted to some extent by antibody alone, but that it is substantially increased by the further addition of the thermolabile complement system. Opsonic activity can be displayed by antibodies that also give precipitation, agglutination, lytic, and neutralization reactions.
Industry:Science
A term used in serology to describe a reaction that leads to the disruption or lysis of a cell. The best example is the lysis of sheep red blood cells by specific antibody and complement in the presence of Ca<sup>2+</sup> (calcium ion) and Mg<sup>2+</sup> (magnesium ion), a reaction that forms the indicator system of the standard Wassermann test for syphilis, as well as other complement-fixation reactions. In this example, lysis results in the release of cellular hemoglobin into the medium; the reaction may be followed by visual or instrumental estimation of the decreased cell turbidity or the increased color of the medium due to the free hemoglobin. The initiation of lysis by complement can apparently proceed after the attachment of only one molecule of IgM or two molecules of IgG antibody to the red blood cell. IgM and IgG are both immunoglobulins.
Industry:Science
A term used in serology to describe the completion or enhancement of an incomplete agglutinating system by the addition of certain substances. Some bacteria or erythrocyte suspensions do not exhibit the visible agglutination ordinarily expected after they have been coated with their specific antibodies and complement. Further addition of a conglutinating agent—normal bovine serum—however, initiates visible agglutination. Complement is an essential component of the system.
The conglutination reagent is itself without effect in the absence of antibody and complement. Similar overall actions, such as agglutination of Rh<sup>+</sup> cells, occur when human serum, gelatin, or bovine serum albumin are added to the incomplete Rh antibodies found in some sera, but since this enhancing effect occurs also in the absence of complement, these reactions probably are to be distinguished in mechanism from that of the traditional conglutination.
Industry:Science
A term used in spectroscopy to designate the set of spectra produced by different chemical elements ionized in such a way that their atoms or ions contain the same number of electrons. An atom or ion with the same number of electrons will generally have spectra with similar features, as the number of electrons determines most atomic properties.
Industry:Science
A term used to denote the geometry of the physical universe as suggested by the theory of relativity. It is also called space-time continuum. Whereas in newtonian physics space and time had been considered quite separate entities, A. Einstein and H. Minkowski showed that they are actually intimately intertwined. I. Newton's ideas on space and time are summarized in the following list: <ol style="FONT-SIZE: 12px; FONT-FAMILY: Verdana, Arial, Helvetica, sans-serif;" start="1"><li>Given two events, each of which is clearly localized in space and lasts only for an instant in time, such as two strokes of lightning striking small targets, all observers of the events will be in agreement as to which of the two events took place earlier in time, or whether they were actually simultaneous.</li><li>If the events were not simultaneous, the interval of time between them is an absolute entity, agreed on by all competent observers.</li><li>The spatial distance between two simultaneous events is an absolute entity, agreed on by all competent observers.</li></ol>
Industry:Science
A term used to describe a quantum number carried by the quarks which make up the strongly interacting elementary particles, such as the proton and neutron of the atomic nucleus. It has nothing to do with the ordinary, visual use of the word color.
Industry:Science
A term used to describe a technique and an instrument or combination of instruments which utilize x-radiation for chemical analysis and for magnification of 100–1000 diameters. The resolution possible is about 0.25 micrometer. X-ray microscopy is a relatively recent development among the microscopic techniques. The contrast in the x-ray microscopic image is caused by varying x-ray attenuation in the specimen. The advantage of x-ray microscopy is that it yields quantitative chemical information, besides structural information, about objects, including those which are opaque to light. It is a reliable ultramicrochemical analytical technique by which amounts of elements and weights of samples as small as 10<sup>−12</sup> to 10<sup>−14</sup> g can be analyzed with an error of only a few percent.
Industry:Science
A term used to describe the genes that influence acceptance or rejection of grafts. When grafts of tissue are exchanged between genetically dissimilar individuals, profound immunological rejection generally takes place. In contrast, grafts between genetically similar individuals, such as identical twins, are normally tolerated; they are histocompatible. Most known examples of histocompatibility (or H) genes encode polymorphic (that is, tending to differ between individuals) cell-surface proteins. The major histocompatibility complex (MHC) contains a set of histocompatibility genes, termed major because mismatching at these genes invokes rapid rejection. Other, minor antigens are revealed after precise matching of the major antigens.
Industry:Science
A term used to designate naturally occurring or pyrolytically obtained substances of dark to black color consisting almost entirely of carbon and hydrogen with very little oxygen, nitrogen, and sulfur. Bitumen may be of variable hardness and volatility, ranging from crude oil to asphaltites, and is largely soluble in carbon disulfide.
Industry:Science
