Barn (redirected from Barns)

barn, abbr. b, in physics, unit of nuclear cross section, i.e., the effective target presented by a nucleus for collisions leading to nuclear reactions; it is equal to 10⁻²⁴ square centimeters. The barn is approximately the size of the geometric cross section of an atomic nucleus; the term was coined because an effective cross section that large would present a target "as big as a barn," i.e., an easy target for nuclear bombardment. In practice, effective cross sections of nuclei for many reactions are measured in millibarns (10⁻³ barn) because, for most interactions, only a small fraction of collisions cause reactions.

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barn

Farm building used for sheltering animals, their feed and other supplies, farm machinery, and farm products. Barns are named according to their purpose (e.g., hog barns, dairy barns, tobacco barns, and tractor barns). The principal type in the U.S. is the general-purpose barn, used for housing livestock and for storing hay and grain. Most North American and European farms have one or more barns. They usually consist of two stories, though one-story barns gained in popularity in the late 20th century.

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barn¹

US and Canadian a large shed for sheltering railroad cars, trucks, etc.

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barn²

a unit of nuclear cross section equal to 10^--28 square metre.

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barn [′bärn]

(agriculture)

A farm building used for storage of agricultural products and equipment or for housing farm animals.

(nuclear physics)

A unit of area equal to 10^-24square centimeter; used in specifying nuclear cross sections. Symbolized b.

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barn

A farm building, most often rectangular (but occasionally circular or polygonal), for housing farm animals, storing farm equipment, threshing grain, and storing grain, hay, and other agricultural produce. Barn construction usually depends on such factors as the local climate and traditions, building materials available, the skills and time required for construction, and the cost. For some examples, see bank barn, basement barn, circular barn, connected barn, Connecticut barn, crib barn, double barn, Dutch barn, English barn, forebay barn, four-crib barn, German barn, hex barn, New England connected barn, octagon barn, Pennsylvania barn, Pennsylvania Dutch barn, potato barn, raised barn, round barn, side-hill barn, Sweitzer barn, Swiss barn, three-bay barn, tobacco barn, Yankee barn.

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Barn 

a unit of effective cross-sectional area of nuclear processes. One barn = 10^–24 cm² = 10^–28 m². Selection of this unit is related to the fact that the geometric cross sections of atomic nuclei are on the order of 10^–24 cm² in size. The magnitudes of the majority of cross sections of nuclear reactions usually lie in the range between 10^–22 cm² and 10^–27cm². For this reason fractional and multiple barn units are used, such as millibarn (10^–27 cm²), microbarn (10^–30 cm²), and megabarn (10^–18 cm²).