吸収係数

WordNet

(chemistry) a process in which one substance permeates another; a fluid permeates or is dissolved by a liquid or solid (同)soaking up
(physics) the process in which incident radiated energy is retained without reflection or transmission on passing through a medium; "the absorption of photons by atoms or molecules"
a constant number that serves as a measure of some property or characteristic

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吸収,併合 / (…に)夢中になること,専心すること《+『in』+『名』》
(数学で)係数,(物理で)係数,率

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/10/22 12:49:07」(JST)

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For "attenuation coefficient" as it applies to electromagnetic theory and telecommunications see propagation constant. For the "mass attenuation coefficient", see the article mass attenuation coefficient.

The attenuation coefficient is a quantity that characterizes how easily a material or medium can be penetrated by a beam of light, sound, particles, or other energy or matter. A large attenuation coefficient means that the beam is quickly "attenuated" (weakened) as it passes through the medium, and a small attenuation coefficient means that the medium is relatively transparent to the beam. Attenuation coefficient is measured using units of reciprocal length.

The attenuation coefficient is also called linear attenuation coefficient, narrow beam attenuation coefficient. Although all four terms are often used interchangeably, they can occasionally have a subtle distinction, as explained below.

Overview

The attenuation coefficient describes the extent to which the intensity of an energy beam is reduced as it passes through a specific material. This might be a beam of electromagnetic radiation or sound.

It is used in the context of X-rays or Gamma rays, where it is represented using the symbol , and measured in cm⁻¹.
It is used in the context of neutrons and nuclear reactors, where it called macroscopic cross section (although actually it is not a section dimensionally speaking) being represented using the symbol , and measured in m⁻¹.
It is also used for modeling solar and infrared radiative transfer in the atmosphere, albeit usually denoted with another symbol (given the standard use of for slant paths).
In the case of ultrasound attenuation it is usually denoted as and measured in dB/cm/MHz.^[1]^[2]
The attenuation coefficient is widely used in acoustics for characterizing particle size distribution.^[1]^[2] A common unit in this contexts is inverse metres, and the most common symbol is the Greek letter .
It is also used in acoustics for quantifying how well a wall in a building absorbs sound. Wallace Sabine was a pioneer of this concept. A unit named in his honor is the sabin: the absorption by a 1-square-metre (11 sq ft) slab of perfectly absorptive material (the same amount of sound loss as if there were a 1-square-metre window).^[3] Note that the sabin is not a unit of attenuation coefficient; rather, it is the unit of a related quantity.

A small linear attenuation coefficient indicates that the material in question is relatively transparent, while a larger value indicates greater degrees of opacity. The linear attenuation coefficient is dependent upon the type of material and the energy of the radiation. Generally, for electromagnetic radiation, the higher the energy of the incident photons and the less dense the material in question, the lower the corresponding linear attenuation coefficient will be.

Definitions and formulae

The measured intensity of transmitted through a layer of material with thickness is related to the incident intensity according to the inverse exponential power law that is usually referred to as Beer–Lambert law:

where denotes the path length. The attenuation coefficient is . If it is uniform, the situation is referred to as linear attenuation and the law simplifies:

The Half Value Layer (HVL) signifies the thickness of a material required to reduce the intensity of the emergent radiation to half its incident magnitude. It is from these equations that engineers decide how much protection is needed for "safety" from potentially harmful radiation. The attenuation factor of a material is obtained by the ratio of the emergent and incident radiation intensities .

The linear attenuation coefficient and mass attenuation coefficient are related such that the mass attenuation coefficient is simply , where is the density in g/cm³. When this coefficient is used in the Beer-Lambert law, then "mass thickness" (defined as the mass per unit area) replaces the product of length times density.

The linear attenuation coefficient is also inversely related to mean free path. Moreover, it is very closely related to the absorption cross section.

Attenuation versus absorption

The terms "attenuation coefficient" and "absorption coefficient" are generally used interchangeably. However, in certain situations they are distinguished, as follows.^[4]

When a narrow (collimated) beam of light passes through a substance, the beam will lose intensity due to two processes: The light can be absorbed by the substance, or the light can be scattered (i.e., the photons can change direction) by the substance. Just looking at the narrow beam itself, the two processes cannot be distinguished. However, if a detector is set up to measure light leaving in different directions, or conversely using a non-narrow beam, one can measure how much of the lost intensity was scattered, and how much was absorbed.

In this context, the "absorption coefficient" measures how quickly the beam would lose intensity due to the absorption alone, while "attenuation coefficient" measures the total loss of narrow-beam intensity, including scattering as well. "Narrow-beam attenuation coefficient" always unambiguously refers to the latter. The attenuation coefficient is always larger than the absorption coefficient, although they are equal in the idealized case of no scattering.

References

^ ^a ^b ISO 20998-1:2006 "Measurement and characterization of particles by acoustic methods"
^ ^a ^b Dukhin, A.S. and Goetz, P.J. "Ultrasound for characterizing colloids", Elsevier, 2002
^ "Wallace Clement Sabine". Acoustics Engineering. Retrieved 2011-11-08.
^ Bohren,C. F. and Huffman, D.R. "Absorption and Scattering of Light by Small Particles", Wiley, (1983), isbn= 0-471-29340-7

External links

Absorption Coefficients α of Building Materials and Finishes
Sound Absorption Coefficients for Some Common Materials
Computations for Radio Wave Propagation
Tables of X-Ray Mass Attenuation Coefficients and Mass Energy-Absorption Coefficients from 1 keV to 20 MeV for Elements Z = 1 to 92 and 48 Additional Substances of Dosimetric Interest

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English Journal

Skin sensitization risk assessment model using artificial neural network analysis of data from multiple in vitro assays.

Tsujita-Inoue K1, Hirota M2, Ashikaga T1, Atobe T1, Kouzuki H1, Aiba S3.Author information 1Shiseido Research Center, Shiseido Co. Ltd., 2-2-1 Hayabuchi, Tsuzuki-ku, Yokohama-shi, Kanagawa 224-8558, Japan.2Shiseido Research Center, Shiseido Co. Ltd., 2-2-1 Hayabuchi, Tsuzuki-ku, Yokohama-shi, Kanagawa 224-8558, Japan. Electronic address: morihiko.hirota@to.shiseido.co.jp.3Department of Dermatology, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8574, Japan.AbstractThe sensitizing potential of chemicals is usually identified and characterized using in vivo methods such as the murine local lymph node assay (LLNA). Due to regulatory constraints and ethical concerns, alternatives to animal testing are needed to predict skin sensitization potential of chemicals. For this purpose, combined evaluation using multiple in vitro and in silico parameters that reflect different aspects of the sensitization process seems promising. We previously reported that LLNA thresholds could be well predicted by using an artificial neural network (ANN) model, designated iSENS ver.1 (integrating in vitro sensitization tests version 1), to analyze data obtained from two in vitro tests: the human Cell Line Activation Test (h-CLAT) and the SH test. Here, we present a more advanced ANN model, iSENS ver.2, which additionally utilizes the results of antioxidant response element (ARE) assay and the octanol-water partition coefficient (LogP, reflecting lipid solubility and skin absorption). We found a good correlation between predicted LLNA thresholds calculated by iSENS ver.2 and reported values. The predictive performance of iSENS ver.2 was superior to that of iSENS ver.1. We conclude that ANN analysis of data from multiple in vitro assays is a useful approach for risk assessment of chemicals for skin sensitization.
Toxicology in vitro : an international journal published in association with BIBRA.Toxicol In Vitro.2014 Jun;28(4):626-39. doi: 10.1016/j.tiv.2014.01.003. Epub 2014 Jan 18.
The sensitizing potential of chemicals is usually identified and characterized using in vivo methods such as the murine local lymph node assay (LLNA). Due to regulatory constraints and ethical concerns, alternatives to animal testing are needed to predict skin sensitization potential of chemicals. F
PMID 24444449

Intra-/inter-laboratory validation study on reactive oxygen species assay for chemical photosafety evaluation using two different solar simulators.

Onoue S1, Hosoi K2, Toda T3, Takagi H4, Osaki N4, Matsumoto Y5, Kawakami S6, Wakuri S7, Iwase Y8, Yamamoto T9, Nakamura K10, Ohno Y11, Kojima H12.Author information 1Department of Pharmacokinetics and Pharmacodynamics, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan. Electronic address: onoue@u-shizuoka-ken.ac.jp.2Non-Clinical Research Group, Ophthalmic Research and Development Center, Santen Pharmaceutical Co., Ltd., 8916-16 Takayama-cho, Ikoma, Nara 630-0101, Japan.3Drug Developmental Research Laboratories, Shionogi & Co., Ltd., 3-1-1 Futaba-cho, Toyonaka, Osaka 561-0825, Japan.4Research Center, Taisho Pharmaceutical Co., Ltd., 1-403, Yoshino-cho, Kita-ku, Saitama 331-9530, Japan.5Safety Research Department, ASKA Pharmaceutical Co., Ltd., 5-36-1, Shimosakunobe, Takatsu-ku, Kawasaki, Kanagawa 213-8522, Japan.6Pharmaceuticals Research Center, Asahi Kasei Pharma Corporation, 632-1 Mifuku Izunokuni-shi, Shizuoka 410-2321, Japan.7Laboratory of Cell Toxicology, Hatano Research Institute, Food and Drug Safety Center, 729-5 Ochiai, Hadano, Kanagawa 257-8523, Japan.8Safety Research Laboratories, Mitsubishi Tanabe Pharma Corporation, 1-1-1, Kazusakamatari, Kisarazu, Chiba 292-0818, Japan.9Safety Research Laboratories, Mitsubishi Tanabe Pharma Corporation, 2-2-50, Kawaguchi, Toda-shi, Saitama 335-8505, Japan.10Product Development Regulatory Affairs Department, Shionogi & Co., Ltd., 2-17-5 Shibuya, Shibuya-ku, Tokyo 150-8673, Japan.11National Institute of Health Sciences (NIHS), 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan.12Japanese Center for the Validation of Alternative Methods (JaCVAM), National Institute of Health Sciences (NIHS), 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan.AbstractA previous multi-center validation study demonstrated high transferability and reliability of reactive oxygen species (ROS) assay for photosafety evaluation. The present validation study was undertaken to verify further the applicability of different solar simulators and assay performance. In 7 participating laboratories, 2 standards and 42 coded chemicals, including 23 phototoxins and 19 non-phototoxic drugs/chemicals, were assessed by the ROS assay using two different solar simulators (Atlas Suntest CPS series, 3 labs; and Seric SXL-2500V2, 4 labs). Irradiation conditions could be optimized using quinine and sulisobenzone as positive and negative standards to offer consistent assay outcomes. In both solar simulators, the intra- and inter-day precisions (coefficient of variation; CV) for quinine were found to be below 10%. The inter-laboratory CV for quinine averaged 15.4% (Atlas Suntest CPS) and 13.2% (Seric SXL-2500V2) for singlet oxygen and 17.0% (Atlas Suntest CPS) and 7.1% (Seric SXL-2500V2) for superoxide, suggesting high inter-laboratory reproducibility even though different solar simulators were employed for the ROS assay. In the ROS assay on 42 coded chemicals, some chemicals (ca. 19-29%) were unevaluable because of limited solubility and spectral interference. Although several false positives appeared with positive predictivity of ca. 76-92% (Atlas Suntest CPS) and ca. 75-84% (Seric SXL-2500V2), there were no false negative predictions in both solar simulators. A multi-center validation study on the ROS assay demonstrated satisfactory transferability, accuracy, precision, and predictivity, as well as the availability of other solar simulators.
Toxicology in vitro : an international journal published in association with BIBRA.Toxicol In Vitro.2014 Jun;28(4):515-23. doi: 10.1016/j.tiv.2013.11.014. Epub 2013 Dec 30.
A previous multi-center validation study demonstrated high transferability and reliability of reactive oxygen species (ROS) assay for photosafety evaluation. The present validation study was undertaken to verify further the applicability of different solar simulators and assay performance. In 7 part
PMID 24384453

Broadband near-infrared emission property in Er(3+)/Ce(3+) co-doped silica-germanate glass for fiber amplifier.

Wei T1, Chen F1, Tian Y2, Xu S3.Author information 1College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018, PR China.2College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018, PR China. Electronic address: tianyingcjlu@163.com.3College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018, PR China. Electronic address: sxucjlu@hotmail.com.AbstractEr(3+) doped and Er(3+)/Ce(3+) co-doped silica-germanate glasses were synthesized by high-temperature melt-quenching technique. A detailed study of the 1.53μm spectroscopic properties and thermal stability was presented in this work. The absorption spectra, 1.53μm emission spectra and fluorescence lifetimes were measured and investigated, along with the quantitative calculations and analyses of Judd-Ofelt intensity parameters, stimulated absorption and emission cross-sections and the product of FWHM×σem(p). It was found that the prepared samples have outstanding thermal stability (Tg=585°C), large FWHM (77nm and 108nm) and high stimulated emission cross-sections (9.55×10(-28)cm(3) and 8.72×10(-28)cm(3)) of Er(3+). The 1.53μm fluorescence intensity improved significantly with the introduction of Ce(3+). Furthermore, the wavelength dependent gain coefficient G(λ) of (4)I13/2→(4)I15/2 transition of Er(3+) was determined by means of the absorption and emission cross-sections. The results indicate that the developed glass co-doped with Er(3+)/Ce(3+) is a promising gain medium applied for broadband amplifier pumped with a 980nm laser diode.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy.Spectrochim Acta A Mol Biomol Spectrosc.2014 May 21;126:53-8. doi: 10.1016/j.saa.2014.01.134. Epub 2014 Feb 12.
Er(3+) doped and Er(3+)/Ce(3+) co-doped silica-germanate glasses were synthesized by high-temperature melt-quenching technique. A detailed study of the 1.53μm spectroscopic properties and thermal stability was presented in this work. The absorption spectra, 1.53μm emission spectra and fluorescence
PMID 24583472

Japanese Journal

一般の飲用容器の音響共鳴の周波数や吸音率について

公益社団法人日本騒音制御工学会秋季研究発表会講演論文集 = Proceedings of the autumn meeting, the Institute of Noise Control Engineering of Japan, 165-168, 2017-11
NAID 40021387805