barn

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barn,

abbr. b, in physics, unit of nuclear cross section, i.e., the effective target presented by a nucleusnucleus,
in physics, the extremely dense central core of an atom. The Nature of the Nucleus
Composition

Atomic nuclei are composed of two types of particles, protons and neutrons, which are collectively known as nucleons.
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 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.

Barn

A building for housing animals and storing farm equipment, hay, and other agricultural produce.

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).

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 10-24 square centimeter; used in specifying nuclear cross sections. Symbolized b.

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.

barn

1
US and Canadian a large shed for sheltering railroad cars, trucks, etc.

barn

2
a unit of nuclear cross section equal to 10--28 square metre.
References in classic literature ?
From the open doorway came a flash of electric light, like a tiny searchlight, which quested about the barn and came to rest on her and Billy.
Greater plenty, likewise, was nowhere to be seen than what flourished in this barn.
While his majesty was thus discoursing with Jones, a sudden uproar arose in the barn, and as it seems upon this occasion:--the courtesy of these people had by degrees removed all the apprehensions of Partridge, and he was prevailed upon not only to stuff himself with their food, but to taste some of their liquors, which by degrees entirely expelled all fear from his composition, and in its stead introduced much more agreeable sensations.
Now, when they were alone together in a remote part of the barn, whether it proceeded from the strong liquor, which is never so apt to inflame inordinate desire as after moderate fatigue; or whether the fair gypsy herself threw aside the delicacy and decency of her sex, and tempted the youth Partridge with express solicitations; but they were discovered in a very improper manner by the husband of the gypsy, who, from jealousy it seems, had kept a watchful eye over his wife, and had dogged her to the place, where he found her in the arms of her gallant.
Instead, he bought a patented litter-carrier that made the job of removing manure from the barn an easy task.
However, she was so overcome that she consented to lie down awhile, and reclined on a heap of pull-tails--the refuse after the straight straw had been drawn--thrown up at the further side of the barn.
The dim light in the barn grew dimmer, and they could see to work no longer.
He had a long sleep in the barn and then a big breakfast of coffee and bread and oatmeal and stewed cherries, for which the man charged him only fifteen cents, perhaps having been influenced by his arguments.
When it rained he would find a deserted building, if he could, and if not, he would wait until after dark and then, with his stick ready, begin a stealthy approach upon a barn.
Twice he even managed to capture a chicken, and had a feast, once in a deserted barn and the other time in a lonely spot alongside of a stream.
In "The Historic Barns of Southeastern Pennsylvania: Architecture & Preservation, Built 1750-1900" he draws upon his years of experience and expertise to present an informed, informative, and beautifully illustrated volume for anyone who has ever admired a barn on an old country lane.
uk Tower Hill Barns | Where: Wrexham Their original two-storey barn has been opened out and glazed with large windows to bring natural daylight and scenery.