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rent
rent in law, periodic payment by a tenant for the use of another's property. In economics, its meaning is more complex, but since the word rent means any income or yield from an object capable of producing wealth, its limitation to a more special sense is somewhat arbitrary and justified only by ...
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Thomas Tooke
Thomas Tooke 1774-1858, British economist, b. St. Petersburg, Russia. A successful businessman, he began to speak on behalf of free trade before Parliamentary committees and was one of the founders of the Political Economy Club (1821). His History of Prices (6 vol., 1838-57) is a classic expositi...
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variable star
variable star star that varies, either periodically or irregularly, in the intensity of the light it emits. Other physical changes are usually correlated with the fluctuations in brightness, such as pulsations in size, ejection of matter, and changes in spectral type, color, or temperature. The cla...
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polynomial
polynomial mathematical expression which is a finite sum, each term being a constant times a product of one or more variables raised to powers. With only one variable the general form of a polynomial is a0xn + a1xn-1 + a2xn-2 +…+ an-1x + an where n is a positive integer and a0 , a1 , ...
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chi-square test
chi-square test (ky-skwair) n. (in statistics) a test to determine if the difference between two groups of observations is statistically significant (see significance), used in controlled trials and other studies. It measures the differences between theoretical and observed frequencies (see frequen...
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equation
equation in mathematics, a statement, usually written in symbols, that states the equality of two quantities or algebraic expressions, e.g., x +3=5. The quantity x +3, to the left of the equals sign (=), is called the left-hand, or first, member of the equation, that to the right (5) the right-ha...
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period
period unit of time on the geologic timescale . Periods are shorter than an era and longer than an epoch. Periods are of variable length, generally lasting tens of millions of years, with characteristic fossils found preserved in the sediments deposited during the period. It is also used to design...
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tensor
tensor in mathematics, quantity that depends linearly on several vector variables and that varies covariantly with respect to some variables and contravariantly with respect to others when the coordinate axes are rotated (see Cartesian coordinates ). Tensors appear throughout mathematics, though...
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Cepheid variables
Cepheid variables , class of variable stars that brighten and dim in an extremely regular fashion. The periods of the fluctuations (the time to complete one cycle from bright to dim and back to bright) last several days, although they range from 1 to 50 days. These stars are important because the pe...
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Annie Jump Cannon
Annie Jump Cannon 1863-1941, American astronomer, b. Dover, Del. In 1897 she became an assistant in the Harvard College Observatory, where (1911-38) she was astronomer and curator of astronomical photographs. Recognizing that spectra of many stars had been photographed in the second half of the 19t...
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