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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 structure built to provide ready passage over natural or artificial obstacles, or under another passageway. Bridges serve highways, railways, canals, aqueducts, utility pipelines, and pedestrian walkways. In many jurisdictions, bridges are defined as those structures spanning an arbitrary minimum distance, generally about 10–20 ft (3–6 m); shorter structures are classified as culverts or tunnels. In addition, natural formations eroded into bridgelike form are often called bridges. This article covers only bridges providing conventional transportation passageways.
Industry:Science
A structure erected to aid in the construction of a permanent project. Temporary structures are used to facilitate the construction of buildings, bridges, tunnels, and other above- and below-ground facilities by providing access, support, and protection for the facility under construction, as well as assuring the safety of the workers and the public. Temporary structures either are dismantled and removed when the permanent works become self-supporting or completed, or are incorporated into the finished work. Temporary structures are also used in inspection, repair, and maintenance work.
Industry:Science
A structure in which the nuclei of two atoms approach each other closely and their electrons are arranged in atomic orbitals characteristic of a single atom of atomic number equal to the sum of the nuclear charges. Quasiatoms can be formed for short times in atom-atom and ion-atom collisions when the nuclei are much closer than the mean orbital radius of the innermost K-shell electrons. The electrons are then bound in the electric field of both nuclear charges <i>Z</i><sub>1</sub> and <i>Z</i><sub>2</sub>, which resembles the spherically symmetric 1/<i>r</i><sup>2</sup> Coulomb field of a single united atom having charge <i>Z</i><sub>ua</sub> = <i>Z</i><sub>1</sub> + <i>Z</i><sub>2</sub>.
Industry:Science
A structure of logic used for synthesizing and analyzing processing schemes in the chemical and allied industries, in which the basic underlying concept is that all processing schemes can be composed from and decomposed into a series of individual, or unit, steps. If a step involves a chemical change, it is called a unit process; if physical change, a unit operation. These unit operations are utilized for certain definite functions wherever they are employed, and their use cuts across widely different processing applications, including industries as diverse as manufacture of chemicals, fuels, pharmaceuticals, pulp and paper, processed foods, and primary metals.
The unit operations approach thereby serves as a very powerful form of morphological analysis, which systematizes process design, and greatly reduces both the number of concepts that must be taught and the number of possibilities that should be considered in synthesizing a particular process.
Industry:Science
A structure which is a receptor for external or internal stimulation. A sense organ is often referred to as a receptor organ. External stimuli affect the sensory structures which make up the general cutaneous surface of the body, the exteroceptive area, and the tissues of the body wall or the proprioceptive area. These somatic area receptors are known under the general term of exteroceptors. Internal stimuli which originate in various visceral organs such as the intestinal tract or heart affect the visceral sense organs or interoceptors. A receptor structure is not necessarily an organ; in many unicellular animals it is a specialized structure within the organism. Receptors are named on the basis of the stimulus which affects them, permitting the organism to be sensitive to changes in its environment.
Industry:Science
A structure which produces a substance or substances essential and vital to the existence of the organism and species. Glands are classified according to (1) the nature of the product; (2) the structure; (3) the manner by which the secretion is delivered to the area of use; and (4) the manner of cell activity in forming secretion. A commonly used scheme for the classification of glands follows. <ul class="articlebody"><ul class="articlebody"><li>I. Morphological criteria</li><ul class="articlebody"><li><i>A.</i> Unicellular (mucous goblet cells)</li><li><i>B.</i> Multicellular</li></ul></ul><ul class="articlebody"><li>1. Sheets of gland cells (choroid plexus)</li><li>2. Restricted nests of gland cells (urethral</li><ul class="articlebody"><li>glands) </li></ul><li>3. Invaginations of varying degrees of com-</li><ul class="articlebody"><li>plexity</li></ul><ul class="articlebody"><li><i>a.</i> Simple or branched tubular (intestinal and gastric glands)—no duct interposed between surface and glandular portion</li><li><i>b.</i> Simple coiled (sweat gland)—duct interposed between glandular portion and surface</li><li><i>c.</i> Simple, branched, acinous (sebaceous gland)—andular portion spherical or ovoid, connected to surface by duct</li><li><i>d.</i> Compound, tubular glands (gastric cardia, renal tubules)—branched ducts between surface and glandular portion</li><li><i>e.</i> Compound tubular-acinous glands (pancreas, parotid gland)—branched ducts, terminating in secretory portion which may be tubular or acinar</li></ul></ul><ul class="articlebody"><li>II. Mode of secretion</li><ul class="articlebody"><li><i>A.</i> Exocrine—the secretion is passed directly or by ducts to the exterior surface (sweat glands) or to another surface which is continuous with the external surface (intestinal glands, liver, pancreas, submaxillary gland)</li><li><i>B.</i> Endocrine—the secretion is passed into adjacent tissue or area and then into the bloodstream directly or by way of the lymphatics; these organs are usually circumscribed, highly vascularized, and usually have no connection to an external surface (adrenal, thyroid, parathyroid, islets of Langerhans, parts of the ovary and testis, anterior lobe of the hypophysis, intermediate lobe of the hypophysis, groups of nerve cells of the hypothalamus, and the neural portion of the hypophysis)</li><li><i>C.</i> Mixed exocrine and endocrine glands (liver, testis, pancreas)</li><li><i>D.</i> Cytocrine—passage of a secretion from one cell directly to another (melanin granules from melanocytes in the connective tissue of the skin to epithelial cells of the skin)</li></ul></ul><ul class="articlebody"><li>III. Nature of secretion</li><ul class="articlebody"><li><i>A.</i> Cytogenous (testis, perhaps spleen, lymph node, and bone marrow)—gland “secretes” cells</li><li><i>B.</i> Acellular (intestinal glands, pancreas, parotid gland)—gland secretes noncellular product</li></ul></ul><ul class="articlebody"><li>IV. Cytological changes of glandular portion dur-</li><ul class="articlebody"><li>ing secretion</li></ul><ul class="articlebody"><li><i>A.</i> Merocrine (sweat glands, choroid plexus)—no loss of cytoplasm</li><li><i>B.</i> Holocrine (sebaceous glands)—and cells undergo dissolution and are entirely extruded, together with the secretory product</li><li><i>C.</i> Apocrine (mammary gland, axillary sweat gland)—only part of the cytoplasm is extruded with the secretory product</li></ul></ul><ul class="articlebody"><li>V. Chemical nature of the product</li><ul class="articlebody"><li><i>A.</i> Mucous goblet cells (submaxillary glands, urethral glands)—the secretion contains mucin</li><li><i>B.</i> Serous (parotid gland, pancreas)—secretion does not contain mucin</li></ul></ul></ul>
Industry:Science
A structure, usually curved, that when subjected to vertical loads causes its two end supports to develop reactions with inwardly directed horizontal components. The commonest uses for an arch are as a bridge, supporting a roadway, railroad track, or footpath, and as part of a building, where it provides a large open space unobstructed by columns. Arches are usually built of steel, reinforced concrete, or timber.
Industry:Science
A structure's ability to resist compressive stress without compromising its load-carrying capacity. When a structure is subjected to a sufficiently high compressive force (or stress), it has a tendency to lose its stiffness, experience a noticeable change in geometry, and become unstable. Examples of structural instability include the buckling of a column under a compressive axial force, the lateral torsional buckling of a beam under a transverse load, the sideways buckling of an unbraced frame under a set of concentric column forces, and the buckling of a plate under a set of in-plane forces.
Industry:Science
A study of the physical and thermodynamic properties of the atmosphere. The properties of primary concern in air conditioning are (1) dry-bulb temperature, (2) wet-bulb temperature, (3) dew-point temperature, (4) absolute humidity, (5) percent humidity, (6) sensible heat, (7) latent heat, (8) total heat, (9) density, and (10) pressure.
Industry:Science
A subclass in the class Gastropoda containing about 4000 living species, arranged in nine orders, including the herbivorous Aplysiomorpha (sea hares) and Sacoglossa and the carnivorous Thecosomata (sea butterflies); Nudibranchia (sea slugs); Cephalaspidea (or Bullomorpha); Gymnosomata; Pleurobranchomorpha (or Notaspidea); Acochlidiacea; and Runciniodea. Primitive members of many of the orders show adaptations for burrowing beneath sand or mud; more advanced members are always active surface-living or pelagic forms. This trend is accompanied by a decrease in the importance of the shell and operculum for passive defense. These are replaced by more dynamic chemical (some species secrete decinormal sulfuric acid through the skin if annoyed), physical (daggerlike calcareous epidermal spicules), or biological (redirected nematocysts derived from coelenterate prey) defensive mechanisms.
Industry:Science
