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codeine
codeine , alkaloid found in opium . It is a narcotic whose effects, though less potent, resemble those of morphine . An effective cough suppressant, it is mainly used in cough medicines. Like other narcotics, codeine is addictive. See drug addiction and drug abuse .
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toxicology
toxicology study of poisons, or toxins, from the standpoint of detection, isolation, identification, and determination of their effects on the human body. Toxicology may be considered the branch of pharmacology devoted to the study of the poisonous effects of drugs. It is also a division of foren...
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‘greenhouse effect’
‘greenhouse effect’ The effect of heat retention in the lower atmosphere as a result of absorption and reradiation of long-wave (more than 4 μm) terrestrial radiation by clouds and gases (e.g. water vapour and carbon dioxide). The insulating effect is not strictly analogous to th...
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Zeeman effect
Zeeman effect splitting of a single spectral line (see spectrum ) into a group of closely spaced lines when the substance producing the single line is subjected to a uniform magnetic field. The effect was discovered in 1896 by the Dutch physicist Pieter Zeeman. In the so-called normal Zeeman effec...
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Compton effect
Compton effect [for A. H. Compton ], increase in the wavelengths of X rays and gamma rays when they collide with and are scattered from loosely bound electrons in matter. This effect provides strong verification of the quantum theory since the theoretical explanation of the effect requires that on...
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barn
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 c...
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Raman effect
Raman effect , appearance of additional lines in the spectrum of monochromatic light that has been scattered by a transparent material medium. The effect was discovered by C. V. Raman in 1928. The energy and thus the frequency and wavelength of the scattered light is changed as the light either im...
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garlic
garlic The bulb of Allium sativum with a pungent odour when crushed, widely used to flavour foods. There is some evidence that garlic has a beneficial effect in lowering blood cholesterol....
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paregoric
paregoric , alcoholic solution of opium and camphor first prepared in the 18th cent. Because of the constipating effect of opium, paregoric has been used to control diarrhea. It was formerly a constituent of many cough elixirs.
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photon
photon , the particle composing light and other forms of electromagnetic radiation , sometimes called light quantum. The photon has no charge and no mass. About the beginning of the 20th cent., the classical theory that light is emitted and absorbed by matter in a continuous stream came under criti...
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