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attenuation
attenuation
1. (in medicine) A process of reducing the disease-producing ability of a microorganism. It can be achieved by chemical treatment, heating, drying, irradiation, by growing the organism under adverse conditions, or by serial passage through another organism. Attenuated bacteria or viruses are used for some vaccines. 2. (in mycology) The conversion by yeasts of carbohydrates to alcohol, as in brewing and wine and spirit production. 3. (in genetics) A mechanism for regulating gene expression in prokaryotes, observed especially in functional gene clusters (operons), such as the trp genes that encode enzymes responsible for synthesizing tryptophan in E. coli bacteria. Attenuation comes into play when the product of the enzymes (in this case tryptophan) is present to excess in the medium; transcription of the operon is drastically reduced, perhaps by as much as 90% of the maximum rate. This attenuation is thought to be caused by interaction of tryptophan in the medium with the initial part of the RNA transcript, encoded by an attenuator region upstream of the structural genes. |
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"attenuation." A Dictionary of Biology. 2004. Encyclopedia.com. 31 May. 2012 <http://www.encyclopedia.com>. "attenuation." A Dictionary of Biology. 2004. Encyclopedia.com. (May 31, 2012). http://www.encyclopedia.com/doc/1O6-attenuation.html "attenuation." A Dictionary of Biology. 2004. Retrieved May 31, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O6-attenuation.html |
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attenuation
attenuation
1. The reduction in strength of an electromagnetic wave by absorption or scattering in the medium through which it passes; for example, the extinction of starlight by interstellar dust. 2. The deliberate reduction of the signal strength in a radio receiver to prevent following stages of amplification being overloaded. |
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"attenuation." A Dictionary of Astronomy. 1997. Encyclopedia.com. 31 May. 2012 <http://www.encyclopedia.com>. "attenuation." A Dictionary of Astronomy. 1997. Encyclopedia.com. (May 31, 2012). http://www.encyclopedia.com/doc/1O80-attenuation.html "attenuation." A Dictionary of Astronomy. 1997. Retrieved May 31, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O80-attenuation.html |
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attenuation
attenuation The reduction in amplitude or energy of a signal. Attenuation of seismic waves (seismic attenuation) occurs as a result of spherical divergence, absorption, energy losses at interfaces through reflection and refraction, and by internal scatterers. For electromagnetic waves see SKIN DEPTH.
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AILSA ALLABY and MICHAEL ALLABY. "attenuation." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 31 May. 2012 <http://www.encyclopedia.com>. AILSA ALLABY and MICHAEL ALLABY. "attenuation." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (May 31, 2012). http://www.encyclopedia.com/doc/1O13-attenuation.html AILSA ALLABY and MICHAEL ALLABY. "attenuation." A Dictionary of Earth Sciences. 1999. Retrieved May 31, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-attenuation.html |
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attenuation
attenuation The loss of energy as a signal travels down a TRANSMISSION LINE. As a signal becomes more and more attenuated it becomes more and more difficult to read and process. The solution to attenuation problems is the use of AMPLIFIERS or REPEATERS.
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DARREL INCE. "attenuation." A Dictionary of the Internet. 2001. Encyclopedia.com. 31 May. 2012 <http://www.encyclopedia.com>. DARREL INCE. "attenuation." A Dictionary of the Internet. 2001. Encyclopedia.com. (May 31, 2012). http://www.encyclopedia.com/doc/1O12-attenuation.html DARREL INCE. "attenuation." A Dictionary of the Internet. 2001. Retrieved May 31, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O12-attenuation.html |
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attenuation
attenuation The reduction in amplitude of a signal when it passes through a medium that dissipates its energy. It is usually measured in decibels (attenuation then being negative while gain is positive).
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JOHN DAINTITH. "attenuation." A Dictionary of Computing. 2004. Encyclopedia.com. 31 May. 2012 <http://www.encyclopedia.com>. JOHN DAINTITH. "attenuation." A Dictionary of Computing. 2004. Encyclopedia.com. (May 31, 2012). http://www.encyclopedia.com/doc/1O11-attenuation.html JOHN DAINTITH. "attenuation." A Dictionary of Computing. 2004. Retrieved May 31, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O11-attenuation.html |
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attenuation
attenuation (ă-ten-yoo-ay-shŏn) n. reduction of the disease-producing ability (virulence) of a bacterium or virus so that it may be used for immunization.
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"attenuation." A Dictionary of Nursing. 2008. Encyclopedia.com. 31 May. 2012 <http://www.encyclopedia.com>. "attenuation." A Dictionary of Nursing. 2008. Encyclopedia.com. (May 31, 2012). http://www.encyclopedia.com/doc/1O62-attenuation.html "attenuation." A Dictionary of Nursing. 2008. Retrieved May 31, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O62-attenuation.html |
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