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diode

(Encyclopedia)diode dīˈōd [key], two-terminal electronic device that permits current flow predominantly in only one direction. Most diodes are semiconductor devices; diode electron tubes are now used only for a ...

superconductivity

(Encyclopedia)superconductivity, abnormally high electrical conductivity of certain substances. The phenomenon was discovered in 1911 by Heike Kamerlingh Onnes, who found that the resistance of mercury dropped sudd...

butane

(Encyclopedia)butane byo͞oˈtān [key], C4H10, gaseous alkane, a hydrocarbon that is obtained from natural gas or by refining petroleum. It can be liquefied at room temperature by compression. There are two struct...

chronometer

(Encyclopedia)chronometer krənŏmˈətər [key], instrument for keeping highly accurate time, used especially in navigation. Before the advent of radio time signals it was the only device that provided the time ac...

Matanzas, city, Cuba

(Encyclopedia)Matanzas, city (1994 est. pop. 115,000), capital of Matanzas prov., W central Cuba. A port with a large, deep harbor, it exports sugar, fruits, and sisal. Industries in the city include sugar refineri...

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...

centrifuge

(Encyclopedia)centrifuge sĕnˈtrəfyo͞oj [key], device using centrifugal force to separate two or more substances of different density, e.g., two liquids or a liquid and a solid. The centrifuge consists of a fixe...

galena

(Encyclopedia)galena gəlēˈnə [key] or lead glance, lustrous, blue-gray mineral crystallizing usually in cubes, sometimes in octahedrons. It is the most important ore and the principal source of lead. It consist...

Ohm, Georg Simon

(Encyclopedia)Ohm, Georg Simon gāˈôrkh zēˈmôn ōm [key], 1787–1854, German physicist. He was professor at Munich from 1852. His study of electric current led to his formulation of the law now known as Ohm's...

Sumner, James Batcheller

(Encyclopedia)Sumner, James Batcheller, 1887–1955, American biochemist, b. Canton, Mass., Ph.D. Harvard Medical School, 1914. He was a professor at Cornell from 1914 until his death in 1955. In 1946 Sumner was a ...