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Kellogg, John Harvey

(Encyclopedia)Kellogg, John Harvey, 1852–1943, American physician, health-food advocate, and breakfast cereal developer, b. Tyrone, N.Y., grad. New York Univ. (M.D., 1875) and continued his medical studies in Eur...

Simon, Herbert Alexander

(Encyclopedia)Simon, Herbert Alexander, 1916–2001, American social scientist and economist, b. Milwaukee, grad. Univ. of Chicago (B.A., 1936, Ph.D., 1943). A professor of computer science and psychology at Carneg...

phenylketonuria

(Encyclopedia)phenylketonuria fĕnˌəlkētˌəno͝orˈēə [key] (PKU), inherited metabolic disorder caused by a deficiency in a specific enzyme (phenylalanine hydroxylase). The absence of this enzyme, a recessive...

wind shear

(Encyclopedia)wind shear, a sudden, drastic change in wind direction or speed over a comparatively short distance. Most winds travel horizontally, as does most wind shear, but under certain conditions, including th...

waveguide

(Encyclopedia)waveguide, device that controls the propagation of an electromagnetic wave so that the wave is forced to follow a path defined by the physical structure of the guide. Waveguides, which are useful chie...

cataract

(Encyclopedia)cataract, in medicine, opacity of the lens of the eye, which impairs vision. In the young, cataracts are generally congenital or hereditary; later they are usually the result of degenerative changes b...

biennial

(Encyclopedia)biennial, plant requiring two years to complete its life cycle, as distinguished from an annual or a perennial. In the first year a biennial usually produces a rosette of leaves (e.g., the cabbage) an...

blood substitute

(Encyclopedia)blood substitute, substance that mimics the function of blood. Blood substitutes typically concentrate only on reproducing the function of hemoglobin, the molecule that carries oxygen through the body...

bluebird

(Encyclopedia)bluebird, common name for a North American migratory bird of the family Turdidae (thrush family). The eastern bluebird, Sialia sialis, is among the first spring arrivals in the North. It is about 7 in...

nationality

(Encyclopedia)nationality, in political theory, the quality of belonging to a nation, in the sense of a group united by various strong ties. Among the usual ties are membership in the same general community, common...