06413_20 - T 2,4,5-T 2,4,5-trichlorophenoxyacetic acid

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T 2,4,5-T 2,4,5-trichlorophenoxyacetic acid (2,4,5-trichlorophenoxyethanoic acid): a synthetic * auxin formerly widely used as a herbicide and defoliant. It is now banned in many countries as it tends to become contaminated with the toxic chemical * dioxin. tachometer An instrument for measur- ing angular speed, especially the number of revolutions made by a rotating shaft in unit time. Various types of instrument are used, including mechanical, electri- cal, and electronic devices. The widely used electrical-generator tachometer con- sists of a small generator in which the output voltage is a measure of the rate of rotation of the shaft that drives it. tachyon A hypothetical particle that has a speed in excess of the * speed of light. According to electromagnetic theory, a charged particle travelling through a medium at a speed in excess of the speed of light in that medium emits * Cerenkov radiation. A charged tachyon would emit Cerenkov radiation even in a vacuum. No such particle has yet been de- tected. According to the special theory of * relativity, it is impossible to accelerate a particle up to the speed of light because its energy E , given by E = mc 2 / (1 – v 2 / c 2 ), would have to become in Ü nite. The theory, however, does not forbid the exis- tence of particles with v > c (where c is the speed of light). In such cases the expres- sion in the brackets becomes negative and the energy would be imaginary. tactic movement See taxis . tactic polymer See polymer . taiga A terrestrial * biome consisting mainly of evergreen coniferous forests (mainly pine, Ü r, and spruce), which oc- curs across subarctic North America and Eurasia. In certain parts, such as north- eastern Siberia, deciduous conifers and broadleaved trees, such as larch and birch, are dominant. Over most of the taiga the ground is permanently frozen within about one metre of the surface, which prevents water from Ü ltering down to deeper levels in the soil. This means that bogs may form in depres- sions. For at least six months of the year temperatures are below freezing but there is a short growing season lasting 3–5 months. The soil in taiga areas is acidic and infertile. Compare tundra . talc A white or pale-green mineral form of magnesium silicate, Mg 3 Si 4 O 10 (OH) 2 , crystallizing in the triclinic system. It forms as a secondary mineral by alter- ation of magnesium-rich olivines, pyrox- enes, and amphiboles of ultrabasic rocks. It is soaplike to touch and very soft, hav- ing a hardness of 1 on the Mohs’ scale. Massive Ü ne-grained talc is known as soapstone or steatite . Talc in powdered form is used as a lubricant, as a Ü ller in paper, paints, and rubber, and in cosmet- ics, ceramics, and French chalk. It occurs chie Û y in the USA, Russia, France, and Japan. Tamm, Igor
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This note was uploaded on 05/29/2009 for the course CIVIL ENG 12345 taught by Professor Xhfxfh during the Spring '09 term at Amirkabir University of Technology.

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06413_20 - T 2,4,5-T 2,4,5-trichlorophenoxyacetic acid

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