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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 physiologic mechanisms by which one nerve cell (neuron) influences the activity of an anatomically adjacent neuron with which it is functionally coupled. Brain function depends on interactions of nerve cells with each other and with the gland cells and muscle cells they innervate. The interactions take place at specific sites of contact between cells known as synapses. The synapse is the smallest and most fundamental information-processing unit in the nervous system. By means of different patterns of synaptic connections between neurons, synaptic circuits are constructed during development to carry out the different functional operations of the nervous system. In order to understand nervous function, it is first necessary to understand the mechanism of transmission at a single synapse, and then the varieties of synapses out of which synaptic circuits are formed.
Industry:Science
The scientific study of volcanic phenomena, especially the processes, products, and hazards associated with active or potentially active volcanoes. It focuses on eruptive activity that has occurred within the past 10,000 years of the Earth's history, particularly eruptions during recorded history. Strictly speaking, it emphasizes the surface eruption of magmas and related gases, and the structures, deposits, and other effects produced thereby. Broadly speaking, however, volcanology includes all studies germane to the generation, storage, and transport of magma, because the surface eruption of magma represents the culmination of diverse physicochemical processes at depth. This article considers the activity of erupting volcanoes and the nature of erupting lavas. For a discussion of the distribution of volcanoes and the surface structures and deposits produced by them
Industry:Science
The term “transit” is used in several ways in astronomy. A hundred years ago its most common usage referred to the image of a star, planet, or other celestial body traversing the cross-hairs of a telescope that was fixed to move only in a north-south direction, and was essential to the determination of time and celestial coordinates. A second common usage of transit refers to a satellite passing in front of its parent planet as seen from the Earth. It was suggested as early as Galileo that the timing of such transits across the face of Jupiter by its four largest satellites would provide a solution to the age-old problem of navigation at sea—a solution which, however, never proved satisfactory. A third usage of transit refers to the passing of either Mercury or Venus in front of the Sun as seen from Earth. It is this phenomenon that will be examined in this article.
Industry:Science
The phytohormone (plant hormone) ethylene is an important signaling molecule that is involved in many plant processes including, but not limited to, abscission (the physiological process promoted by abscisic acid whereby plants shed a part), leaf and flower senescence, germination, sex determination, and fruit ripening. Ethylene also functions in both biotic and abiotic stress responses. Exposure to environmental stresses—such as flooding, wounding, herbivory (the consumption of plants without killing them), chilling, or pathogen attack—can enhance ethylene production. This ethylene then slows growth until the stress is removed. Interest in ethylene's importance as a plant hormone has resulted in thousands of peer-reviewed publications in the last 100 years and has laid the foundation for a real understanding of ethylene's involvement in plant growth and development.
Industry:Science
The study of primate phylogeny and human evolution through the genetic information in the DNA of genomes and in the proteins that genes encode. The first studies in molecular anthropology used immunological and biochemical methods to obtain information from proteins on the degrees of genetic similarity of humans and other primates. These results not only placed chimpanzees and gorillas closest to humans rather than to orangutans, but also indicated that the very close kinship between chimpanzees and gorillas was not any closer than the kinship of each to humans. Subsequent studies that extracted genetic information directly from DNA extended this original finding. Indeed, the accumulating comparative DNA sequence data provide extensive, commanding evidence that the closest genetic kinship is between chimpanzees and humans rather than between chimpanzees and gorillas.
Industry:Science
The term “spintronics” usually refers to the branch of physics concerned with the manipulation, storage, and transfer of information by means of electron spins in addition to or in place of the electron charge as in conventional electronics. Introduced in 1996, spintronics (the word coined by S. Wolf) was originally the name for a Defense Advanced Research Projects Agency (DARPA) program managed by Wolf. In conventional electronics, only the charge of the electrons is of consequence for device operation, but using the electron's other fundamental property, its spin, has opened up the new field of spintronics. Major advances in electron spin transport started in 1979–1980 with the discovery of large low-temperature magnetoresistance in metallic superlattices. Later demonstrations of the “giant” effect at room temperature evolved toward application in practical devices.
Industry:Science
The study of the relations between electrical, magnetic, and mechanical phenomena. This includes considerations of the magnetic fields produced by currents, the electromotive forces induced by changing magnetic fields, the forces on currents in magnetic fields, the propagation of electromagnetic waves, and the behavior of charged particles in electric and magnetic fields. Classical electrodynamics deals with fields and charged particles in the manner first systematically described by J. C. Maxwell, whereas quantum electrodynamics applies the principles of quantum mechanics to electrical and magnetic phenomena. Relativistic electrodynamics is concerned with the behavior of charged particles and fields when the velocities of the particles approach that of light. Cosmic electrodynamics is concerned with electromagnetic phenomena occurring on celestial bodies and in space.
Industry:Science
The order of teleost fishes collectively called dories. The order has representatives in all seas of the world from the tropics to Antarctica; however, they are most common in tropical and temperate zones, in waters of moderate depth to at least 1800 m. Most species are mesopelagic or bathypelagic. Structurally intermediary to the beryciform and the perciform fishes, zeiforms are characterized by a body varying from moderately elongate to very deep and compressed; jaws usually greatly protractile; colors predominantly silvery or silver gray; absence of an orbitosphenoid bone; a simple posttemporal bone rigidly united to the skull; a pelvic fin each with one spine or none and from two to ten soft rays; a first dorsal fin with five to ten spines, usually strong; and an anal fin with one to four spines. Most species are of small size and of minor economic importance.
Industry:Science
The movement of cells, changes in cell shape including cell division, and the movement of materials within cells. Many free-living protozoa are capable of movement, as are sperm and ameboid cells of higher organisms. Coordinated movement of cells occurs during embryogenesis, wound healing, and muscle contraction in higher organisms. Cell division is observed in all organisms and is a requirement for reproduction, growth, and development. Many cells also undergo structural changes as they differentiate, such as the outgrowth of axonal and dendritic processes during nerve cell differentiation. A more subtle form of cell motility involves the active transport of membranous organelles within the cytoplasm. This form of movement is required for proper organization of the cytoplasmic contents, and the redistribution of metabolites, hormones, and other materials within the cell.
Industry:Science
The law that a given chemical compound always contains the same elements in the same fixed proportions by weight. Thus, whatever its source, silver chloride always contains 108 g (3.81 oz) of silver to every 35.45 g (1.251 oz) of chlorine. If a compound is formed by the union of <i>m</i> atoms of one element, each weighing <i>a</i>, with <i>n</i> atoms of another element, each weighing <i>b</i>, the composition by weight of one molecule of the compound is in the ratio <i>ma</i>:<i>nb</i>. This must be the composition of any mass of the compound, provided that all atoms of the same kind have the same weight. It is now known that this is not usually the case but that the atoms of an element may consist of a number of isotopes, having different masses. However, as long as any sample of the element always contains the same relative proportions of the isotopes, the law still holds.
Industry:Science
