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nucleus, in physics

(Encyclopedia)nucleus, in physics, the extremely dense central core of an atom. Following the discovery of radioactivity by A. H. Becquerel in 1896, Ernest Rutherford identified two types of radiation given off b...

Mitchell, William

(Encyclopedia)Mitchell, William (Billy Mitchell), 1879–1936, American army officer and pilot, b. Nice, France. He enlisted (1898) in the U.S. army in the Spanish-American War and received a commission in the regu...

glacier

(Encyclopedia)glacier, moving mass of ice that survives year to year, formed by the compacting of snow into névé and then into granular ice and set in motion outward and downward by the force of gravity and the s...

aviation

(Encyclopedia)aviation, operation of heavier-than-air aircraft and related activities. Aviation can be conveniently divided into military aviation, air transport, and general aviation. Military aviation includes al...

mother-of-pearl

(Encyclopedia)mother-of-pearl or nacre nāˈkər [key], the iridescent substance that forms the lining of the shells of some fresh-water and some salt-water mollusks. Like the pearl it is a secretion of the mantle,...

Cliburn, Van

(Encyclopedia)Cliburn, Van (Harvey Lavan Cliburn) klīˈbərn [key], 1934–2013, American pianist, b. Shreveport, La. Until 1951, Cliburn studied with his mother, a concert pianist; he later was a pupil of Rosina ...

pampas grass

(Encyclopedia)pampas grass, any species of the genus Cortaderia, tall South American plants of the family Poaceae (grass family) cultivated in warm climates for ornament. The common pampas grass (C. argentea or sel...

yungas

(Encyclopedia)yungas yo͞ongˈgäs [key], region of lowland valleys in the eastern piedmont of the Andes Mts., 5,000–8,000 ft (1,524–2,438 m) high, extending from the Peru-Bolivia border SE into central Bolivia...

Deerfield, river, United States

(Encyclopedia)Deerfield, river, 70 mi (113 km) long, rising in S Vt. and flowing S into NW Mass., then SE to the Connecticut River at Greenfield, Mass. The river has extensive hydroelectric facilities but is also a...

aviation medicine

(Encyclopedia)aviation medicine, scientific study of the biological effects of aviation, especially on human beings. Although aviation medicine is concerned with such problems as the spread of diseases by persons t...