“attenuation”的概念、定义、翻译、参考文献-科学参考

attenuation

Physics

1. A loss of intensity suffered by sound, radiation, etc., as it passes through a medium. It may be caused by absorption or scattering.

2. The drop in voltage or current experienced by a signal as it passes through a circuit.

Astronomy

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.

Statistics

The sample correlation coefficient between two variables that are subject to measurement error will be reduced by such errors—this is referred to as attenuation.

Computer

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).

Internet

A term that describes the loss of a signal as it travels through a network.

Electronics and Electrical Engineering

The reduction in magnitude of any electrical parameter of a signal, particularly electromagnetic radiation, on passing along any transmission path. The amount of attenuation is given by the ratio of the value of the parameter at the output to the corresponding value at the input under specified conditions. Attenuation results from the resistance present in the transmission path. It can be deliberately introduced into a transmission channel in order to reduce the magnitude of unwanted components of the parameter under consideration (see attenuator). Attenuation can also result from unwanted dissipation in the transmission path. See also absorption.

Biology

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 caused by formation of stem-loop structures in the initial part of the RNA transcript, encoded by the trpL gene upstream of the structural genes. These RNA structures either allow transcription to proceed past the trpL gene or cause termination, depending on available concentrations of tryptophan transfer RNA, and hence tryptophan.

Geology and Earth Sciences

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.

单词	attenuation
释义	attenuation Physics 1. A loss of intensity suffered by sound, radiation, etc., as it passes through a medium. It may be caused by absorption or scattering. 2. The drop in voltage or current experienced by a signal as it passes through a circuit. Astronomy 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. Statistics The sample correlation coefficient between two variables that are subject to measurement error will be reduced by such errors—this is referred to as attenuation. Computer 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). Internet A term that describes the loss of a signal as it travels through a network. Electronics and Electrical Engineering The reduction in magnitude of any electrical parameter of a signal, particularly electromagnetic radiation, on passing along any transmission path. The amount of attenuation is given by the ratio of the value of the parameter at the output to the corresponding value at the input under specified conditions. Attenuation results from the resistance present in the transmission path. It can be deliberately introduced into a transmission channel in order to reduce the magnitude of unwanted components of the parameter under consideration (see attenuator). Attenuation can also result from unwanted dissipation in the transmission path. See also absorption. Biology 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 caused by formation of stem-loop structures in the initial part of the RNA transcript, encoded by the trpL gene upstream of the structural genes. These RNA structures either allow transcription to proceed past the trpL gene or cause termination, depending on available concentrations of tryptophan transfer RNA, and hence tryptophan. Geology and Earth Sciences 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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