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semiconductor

(Encyclopedia)CE5 N-type and P-type crystals: In a pure silicon crystal each silicon atom (Si) is surrounded by four valence electrons. In the N-doped semiconductor, illustrated in the left-hand figure, some sil...

alkali metals

(Encyclopedia)alkali metals, metals found in Group 1 of the periodic table. Compared to other metals they are soft and have low melting points and densities. Alkali metals are powerful reducing agents and form univ...

Cohen, Samuel Theodore

(Encyclopedia)Cohen, Samuel Theodore, 1921–2010, American physicist known as the “father of the neutron bomb,” b. Brooklyn, N.Y., grad. Univ. of California, Los Angeles, 1943. He worked on the Manhattan Proje...

Mira

(Encyclopedia)Mira mīˈrə [key], [Lat.,=marvelous], variable star in the constellation Cetus; Bayer designation Omicron Ceti; 1992 position R.A. 2h19.0m, Dec. −3°05′. The most famous long-period variable, Mi...

benzaldehyde

(Encyclopedia)benzaldehyde bĕnˌzēnkärˈbənəl [key], C6H5CHO, colorless liquid aldehyde with a characteristic almond odor. It boils at 180℃, is soluble in ethanol, but is insoluble in water. It is formed by ...

Strauss, Lewis Lichtenstein

(Encyclopedia)Strauss, Lewis Lichtenstein strôz [key], 1896–1974, American financier, chairman of the Atomic Energy Commission (1953–58), b. Charleston, W.Va. In World War I he served under Herbert Hoover on t...

surface chemistry

(Encyclopedia)surface chemistry, study of chemical reactions in which the reactants are first adsorbed onto a surface medium (see adsorption) that then acts as a catalyst for the reaction; after the reaction the pr...

Three Mile Island

(Encyclopedia)Three Mile Island, site of a nuclear power plant 10 mi (16 km) south of Harrisburg, Pa. On Mar. 28, 1979, failure of the cooling system of the No. 2 nuclear reactor led to overheating and partial melt...

pyridine

(Encyclopedia)pyridine ăzˈēn [key], C5H5N, colorless, flammable, toxic liquid with a putrid odor. It melts at −42℃ and boils at 115.5℃. Chemically, it is a heterocyclic aromatic tertiary amine (see under a...

dictator

(Encyclopedia)dictator, originally a Roman magistrate appointed to rule the state in times of emergency; in modern usage, an absolutist or autocratic ruler who assumes extraconstitutional powers. From 501 b.c. unti...