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glass

(Encyclopedia)glass, hard substance, usually brittle and transparent, composed chiefly of silicates and an alkali fused at high temperature. Glass has become invaluable in modern architecture, illumination, elect...

quantum theory

(Encyclopedia)quantum theory, modern physical theory concerned with the emission and absorption of energy by matter and with the motion of material particles; the quantum theory and the theory of relativity togethe...

atom

(Encyclopedia)CE5 Bohr-Rutherford atom CE5 Probability distribution of the electron in the hydrogen atom: A. Ground state B. Highly excited state atom [Gr.,=uncuttable (indivisible)], basic unit of matte...

copernicium

(Encyclopedia)copernicium, artificially produced radioactive chemical element; symbol Cn; at. no. 112; mass number of most stable isotope 285; m.p., b.p., sp. gr., and valence unknown. Situated in Group 12 of the p...

alfalfa

(Encyclopedia)alfalfa lo͞osûnˈ [key], perennial leguminous plant (Medicago sativa) of the family Leguminosae (pulse family), the most important pasture and hay plant in North America, also grown extensively in A...

contour

(Encyclopedia)contour or contour line, line on a topographic map connecting points of equal elevation above or below mean sea level. It is thus a kind of isopleth, or line of equal quantity. Contour lines are drawn...

combinatorics

(Encyclopedia)combinatorics kŏmˌbĭnətôrˈēəl [key], sometimes called the science of counting, the branch of mathematics concerned with the selection, arrangement, and operation of elements within sets. Combi...

fatigue, in physiology

(Encyclopedia)fatigue, in physiology, inability to perform reasonable and necessary physical or mental activity. Muscle fatigue, for example, results when the contractile properties of muscle are reduced, and conti...

alumina

(Encyclopedia)alumina əlo͞oˈmĭnə [key] or aluminum oxide, Al2O3, chemical compound with m.p. about 2,000℃ and sp. gr. about 4.0. It is insoluble in water and organic liquids and very slightly soluble in stro...

interferon

(Encyclopedia)interferon ĭnˌtərfērˈŏn [key], any of a group of proteins produced by cells in the body in response to an attack by a virus. A cell infected by a virus releases minute amounts of interferons, wh...