line
Basic element of Euclidean geometry. Euclid defined a line as an interval between two points and claimed it could be extended indefinitely in either direction. Such an extension in both directions is now thought of as a line, while Euclid's original definition is considered a line segment. A ray is part of a line extending indefinitely from a point on the line in only one direction. In a coordinate system on a plane, a line can be represented by the linear equation ax + by + c = 0. This is often written in the slope-intercept form as y = mx + b, in which m is the slope and b is the value where the line crosses the y-axis. Because geometrical objects whose edges are line segments are completely understood, mathematicians frequently try to reduce more complex structures into simpler ones made up of connected line segments.
(2) In text-based systems, a row of characters.
(3) In graphics-based systems, a row of pixels.
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line
line [līn]
LINE
| line - 1. By extension, a (usually physical) medium such as an optical fibre which carries a signal. |
Line
(the Central Polynesian Sporades), an archipelago in the equatorial part of the Pacific Ocean, in Polynesia. It consists of 11 islands and reefs, with a total area of about 600 sq km. Population, about 1,300 (1970). The number of inhabitants rises and falls sharply because of the reliance of the economy on seasonal labor. Some of the islands are uninhabited. Palmyra and Jarvis islands and Kingman Reef belong to the USA, the rest to Great Britain; of the latter, Christmas, Washington, and Fanning islands belong to the British colony of Gilbert and Ellice Islands. All the islands are coral atolls; Christmas Island is the largest atoll in the Pacific Ocean (area, 575 sq km.). The predominant vegetation is coconut groves. Copra and breadfruit are harvested, and there is fishing. There are airports on Palmyra and Christmas islands and an important transoceanic cable station on Fanning Island on the California-Fiji-New Zealand line. The Line Islands were discovered in 1777 by the British navigator J. Cook, and Vostok Island in 1820 by the First Russian Antarctic Expedition. In the first half of the 1950’s nuclear tests were conducted on Christmas and Maiden islands.
A. E. SUZIUMOV
Line
a hemp cable up to 25 mm in circumference, made by twisting or weaving individual threads, usually from high-quality vegetable fiber. Lines are used on ships for rigging and tackling operations. Lines have various names—logline, leadline, schiemansgaren (spun twine), or huizing —depending on their function, means of production, and number of threads and strands.
Line
(in genetics), related sexually reproducing organisms that are descended, as a rule, from a single ancestor or a single pair of common ancestors and that reproduce the same genetically stable characters in a number of generations.
Distinctive characters of a line are artificially maintained by means of selection and breeding together of closely related individuals. There are pure lines—the genotypically homogeneous offspring of self-pollinating plants in which almost all the genes are in a homozygous state—and inbred lines—the offspring of cross-pollinating plants obtained by forced self-pollination or a group of animals obtained by breeding together of closely related individuals (inbreeding). The more closely the parents are related, the higher the degree of homozygosis of the offspring. In both pure and inbred lines, constantly arising mutations disrupt homozygosis. Therefore, it is necessary to perform selection to preserve homozygosis of the genes that determine the basic properties of a line. In livestock breeding, a distinction is made between a genealogical line, a group of animals descended from a common ancestor, and a trade line, a homogeneous, qualitatively unique group maintained by selection with the use of inbreeding and consisting of highly productive animals descended from an outstanding forefather and similar to him in constitution and productivity.
Pure and inbred lines serve as the basis for obtaining highly productive hybrids in horticulture and livestock breeding. Lines of laboratory animals that preserve constancy in certain traits play an important role in biomedical research.
REFERENCES
Johannsen, W. L. O nasledovanii v populiatsiiakh i chistykh liniiakh. Moscow-Leningrad, 1935. (Translated from German.)Medvedev, N. N. Prakticheskaia genetika. Moscow, 1966.
IU. S. DEMIN and E. IA. BORISENKO
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