Scattering and absorption coefficients of silica-doped alumina aerogels.
Fu, Tairan; Tang, Jiaqi; Chen, Kai; Zhang, Fan
2016-02-01
Alumina-based aerogels are especially useful in many applications due to their excellent stability at high temperatures. This study experimentally analyzed the radiative properties of silica-doped alumina aerogels through spectral directional-hemispherical measurements for wavelengths of 0.38-25 μm. The silica-doped alumina aerogel samples were prepared with a 1.4∶1 molar ratio of silica to alumina. A two-flux model was used to describe the radiation propagation in a 1D scattering absorbing sample to derive expressions for the normal-hemispherical transmittances and reflectances based on the transport approximation. The normal-hemispherical transmittances and reflectances were measured at various spectral wavelengths and sample thicknesses using the integrating sphere method. The spectral absorption and transport scattering coefficients of silica-doped alumina aerogels were then determined from the measured normal-hemispherical data. The absorption and transport scattering coefficients of silica-doped alumina aerogels are (0.1 cm-1, 36 cm-1) and (0.1 cm-1, 112 cm-1) for wavelengths of 0.38-8.0 μm. The spectral transport scattering coefficient varies in the opposite direction from the spectral absorption coefficient for various wavelengths. The radiative properties for silica and alumina aerogels were quite different for the absorption coefficient for wavelengths of 2.5-8.0 μm and for the transport scattering coefficient for wavelengths of 0.38-2.5 and 3.5-6.0 μm. The measured radiative properties were used to predict the spectral normal-hemispherical reflectance and transmittance of the silica-doped alumina aerogels for various sample thicknesses and wavelengths. The predicted values do not change for the sample thicknesses greater than a critical value. The analysis provides valuable reference data for alumina aerogels for high-temperature applications. PMID:26836071
NASA Astrophysics Data System (ADS)
Li, Xiaoqi; Jiang, Huabei
2013-02-01
We present a study through extensive simulation that considers the impact of inhomogeneous optical scattering coefficient distribution on recovery of optical absorption coefficient maps using tomographic photoacoustic data collected from media mimicking breast tissue. We found that while the impact of scattering heterogeneities/targets is modest on photoacoustic recovery of optical absorption coefficients, the impact of scattering contrast caused by adipose tissue, a layer of normal tissue along the boundary of the breast, is dramatic on reconstruction of optical absorption coefficients using photoacoustic data—up to 25.8% relative error in recovering the absorption coefficient is estimated in such cases. To overcome this problem, we propose a new method to enhance photoacoustic recovery of the optical absorption coefficient in heterogeneous media by considering inhomogeneous scattering coefficient distribution provided by diffuse optical tomography (DOT). Results from extensive simulations show that photoacoustic recovery of absorption coefficient maps can be improved considerably with a priori scattering information from DOT.
A method for determination mass absorption coefficient of gamma rays by Compton scattering.
El Abd, A
2014-12-01
A method was proposed for determination mass absorption coefficient of gamma rays for compounds, alloys and mixtures. It is based on simulating interaction processes of gamma rays with target elements having atomic numbers from Z=1 to Z=92 using the MCSHAPE software. Intensities of Compton scattered gamma rays at saturation thicknesses and at a scattering angle of 90° were calculated for incident gamma rays of different energies. The obtained results showed that the intensity of Compton scattered gamma rays at saturations and mass absorption coefficients can be described by mathematical formulas. These were used to determine mass absorption coefficients for compound, alloys and mixtures with the knowledge of their Compton scattered intensities. The method was tested by calculating mass absorption coefficients for some compounds, alloys and mixtures. There is a good agreement between obtained results and calculated ones using WinXom software. The advantages and limitations of the method were discussed. PMID:25241360
NASA Astrophysics Data System (ADS)
Wex, Heike; Neusüß, Christian; Wendisch, Manfred; Stratmann, Frank; Koziar, Christian; Keil, Andreas; Wiedensohler, Alfred; Ebert, Martin
2002-11-01
Comparisons between measured and calculated aerosol scattering, backscattering, and absorption coefficients were made based on in situ, ground-based measurements during the Melpitz INTensive (MINT) and Lindenberg Aerosol Characterization Experiment 1998 (LACE 98) field studies. Furthermore, airborne measurements made with the same type of instruments are reviewed and compared with the ground-based measurements. Agreement between measured and calculated values is on the order of ±20% for scattering and backscattering coefficients. A sensitivity analysis showed a large influence on the calculated particle scattering and backscattering coefficients resulting from sizing uncertainties in the measured number size distributions. Measured absorption coefficients were significantly smaller than the corresponding calculated values. The largest uncertainty for the calculated absorption coefficients resulted from the size-dependent fraction of elemental carbon (EC) of the aerosol. A correction for the measured fractions of EC could significantly improve the agreement between measured and calculated absorption coefficients. The overall uncertainty of the calculated values was investigated with a Monte Carlo method by simultaneously and randomly varying the input parameters of the calculations, where the variation of each parameter was bounded by its uncertainty. The measurements were mostly found to be within the range of uncertainties of the calculations, with uncertainties for the calculated scattering and backscattering coefficients of about ±20% and for the absorption coefficients of about ±30%. Thus, to increase the accuracy of calculated scattering, backscattering, and absorption coefficients, it is crucial to further reduce the error in particle number size distribution measurement techniques. In addition, further improvement of the techniques for measuring absorption coefficients and further investigation of the measurement of the fraction of EC of the aerosol is
ERIC Educational Resources Information Center
Cordon, Gabriela B.; Lagorio, M. Gabriela
2007-01-01
A biophysical-chemistry experiment, based on the reflectance spectroscopy for calculating the absorption and scattering coefficients of leaves is described. The results show that different plants species exhibit different values for both the coefficients because of their different pigment composition.
Measuring absorption coefficient of scattering liquids using a tube inside an integrating sphere.
Villanueva, Yolanda; Veenstra, Colin; Steenbergen, Wiendelt
2016-04-10
A method for measuring the absorption coefficient μ_{a} of absorbing and scattering liquid samples is presented. The sample is injected into a small transparent tube mounted through an integrating sphere. Two models for determining the absorption coefficient using the relative optical output signal are described and validated using aqueous ink absorbers of 0.5 vol.% (0.3 mm^{-1}<μ_{a}<1.55 mm^{-1}) and 1.0 vol.% (1.0 mm^{-1}<μ_{a}<4.0 mm^{-1}) concentrations with 1 vol.% (μs'≈1.4 mm^{-1}) and 10 vol.% (μs'≈14 mm^{-1}) Intralipid dilutions. The low concentrations give μ_{a} and μ_{s} values, which are comparable with those of biological tissues. One model assumes a uniform light distribution within the sample, which is valid for low absorption. Another model considers light attenuation that obeys Lambert-Beer's law, which may be used for relatively high absorption. Measurements with low and high scattering samples are done for the wavelength range of 400-900 nm. Measured spectra of purely absorbing samples are within 15% agreement with measurements using standard transmission spectrophotometry. For 0.5 vol.% ink absorbers and at wavelengths below 700 nm, measured μ_{a} values are higher for samples with low scattering and lower for those with high scattering. At wavelengths above 700 nm, measured μ_{a} values do not vary significantly with amount of scattering. For 1.0 vol.% ink absorbers, measured spectra do not change with low scattering. These results indicate that the method can be used for measuring absorption spectra of scattering liquid samples with optical properties similar to biological absorbers, particularly at wavelengths above 700 nm, which is difficult to accomplish with standard transmission spectrophotometry. PMID:27139871
NASA Astrophysics Data System (ADS)
Yoshida, Kenichiro
2016-08-01
We derived the absorption coefficient ( μ a) and the reduced scattering coefficient ( μ s') using the edge-loss method (ELM) and the video reflectometry method (VRM), and compared the results. In a previous study, we developed the ELM to easily evaluate the lateral spread in the skin; the VRM is a conventional method. The ELM measures the translucency index, which is correlated with μ a and μ s'. To obtain a precise estimation of these parameters, we improved the treatment of a white standard and the surface reflection. For both skin phantoms and actual skin, the values for μ a and μ s' that we obtained using the ELM were similar to those obtained using the VRM, when μ a/ μ s' was less than or equal to 0.05 and the diffusion approximation was applicable. Under this condition, the spectral reflectivity is greater than 0.4. In this study, we considered wavelengths longer than 600 nm for Types III and IV of the Fitzpatrick scale. For skin, the repeatability errors of the parameters obtained with the ELM were smaller than those obtained with the VRM; this can be an advantage in field tests.
NASA Astrophysics Data System (ADS)
Yoshida, Kenichiro
2016-07-01
We derived the absorption coefficient (μ a) and the reduced scattering coefficient (μ s') using the edge-loss method (ELM) and the video reflectometry method (VRM), and compared the results. In a previous study, we developed the ELM to easily evaluate the lateral spread in the skin; the VRM is a conventional method. The ELM measures the translucency index, which is correlated with μ a and μ s'. To obtain a precise estimation of these parameters, we improved the treatment of a white standard and the surface reflection. For both skin phantoms and actual skin, the values for μ a and μ s' that we obtained using the ELM were similar to those obtained using the VRM, when μ a/μ s' was less than or equal to 0.05 and the diffusion approximation was applicable. Under this condition, the spectral reflectivity is greater than 0.4. In this study, we considered wavelengths longer than 600 nm for Types III and IV of the Fitzpatrick scale. For skin, the repeatability errors of the parameters obtained with the ELM were smaller than those obtained with the VRM; this can be an advantage in field tests.
NASA Technical Reports Server (NTRS)
Eldridge, Jeffrey I.; Spuckler, Charles M.; Markham, James R.
2009-01-01
The temperature dependence of the scattering and absorption coefficients for a set of freestanding plasma-sprayed 8 wt% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) was determined at temperatures up to 1360 C in a wavelength range from 1.2 micrometers up to the 8YSZ absorption edge. The scattering and absorption coefficients were determined by fitting the directional-hemispherical reflectance and transmittance values calculated by a four-flux Kubelka Munk method to the experimentally measured hemispherical-directional reflectance and transmittance values obtained for five 8YSZ thicknesses. The scattering coefficient exhibited a continuous decrease with increasing wavelength and showed no significant temperature dependence. The scattering is primarily attributed to the relatively temperature-insensitive refractive index mismatch between the 8YSZ and its internal voids. The absorption coefficient was very low (less than 1 per centimeter) at wavelengths between 2 micrometers and the absorption edge and showed a definite temperature dependence that consisted of a shift of the absorption edge to shorter wavelengths and an increase in the weak absorption below the absorption edge with increasing temperature. The shift in the absorption edge with temperature is attributed to strongly temperature-dependent multiphonon absorption. While TBC hemispherical transmittance beyond the absorption edge can be predicted by a simple exponential decrease with thickness, below the absorption edge, typical TBC thicknesses are well below the thickness range where a simple exponential decrease in hemispherical transmittance with TBC thickness is expected. [Correction added after online publication August 11, 2009: "edge to a shorter wavelengths" has been updated as edge to shorter wavelengths."
Effects of combined scattering and absorption coefficients on laser speckle contrast imaging values
NASA Astrophysics Data System (ADS)
Khaksari, Kosar; Kirkpatrick, Sean J.
2015-03-01
Laser Speckle contrast imaging (LSCI) is a non-invasive or minimally invasive method for visualizing blood flow and perfusion in biological tissues. In LSCI the motion of scattering particles results in a reduction in global and regional speckle contrast. A variety of parameters can affect the calculated contrast values in LSCI techniques, including the optical properties of the fluid and surrounding tissue. In typical LSCI where the motion of blood is of interests, optical properties are influenced by hematocrit levels. In this work we considered the combined effects of both the scattering and absorption coefficients on LSCI measurements on a flow phantom. Fluid phantoms consisting of various concentrations of neutrally buoyant ~10 micron microspheres and India ink mixed with DI water were formulated to mimic the optical properties of whole blood with various levels of hematocrit. In these flow studies, it was found that an increase in μa and/or μs led to a decrease in contrast values when all other experimental parameters were held constant. The observed reduction in contrast due to optical property changes could easily be confused with a contrast reduction due to increased flow velocity. These results suggest that optical properties need to be considered when using LSCI to make flow estimates.
NASA Astrophysics Data System (ADS)
Dombrovsky, Leonid A.
2016-03-01
A significant uncertainty in the absorption coefficient of highly scattering dispersed materials is typical in the spectral ranges of very weak absorption. The traditional way to identify the main absorption and scattering characteristics of semi-transparent materials is based on spectral measurements of normal-hemispherical reflectance and transmittance for the material sample. Unfortunately this way cannot be used in the case of in vivo measurements of optical properties of biological tissues. A method suggested in the present paper is based on thermal response to the periodic radiative heating of the open surface of a semi-transparent material. It is shown that the period of a variation of the surface temperature is sensitive to the value of an average absorption coefficient in the surface layer. As a result, the monochromatic external irradiation combined with the surface temperature measurements can be used to retrieve the spectral values of absorption coefficient. Possible application of this method to porous semi-transparent ceramics is considered. An example problem is also solved to illustrate the applicability of this method to human skin. The approach suggested enables one to estimate an average absorption coefficient of human skin of a patient just before the thermal processing.
NASA Astrophysics Data System (ADS)
Fukutomi, D.; Ishii, K.; Awazu, K.
2015-12-01
Anisotropy factor g, one of the optical properties of biological tissues, is the most important parameter to accurately determine scattering coefficient μs in the inverse Monte Carlo (iMC) simulation. It has been reported that g has wavelength and absorption dependence, however, there are few attempts in order to calculate μs of biological tissue considering the wavelength and absorption dependence of g. In this study, the scattering angular distributions of biological tissue phantoms were measured in order to determine g by using goniometric measurements with three polarization conditions at strongly and weakly absorbing wavelengths of hemoglobin. Then, optical properties, especially, μs were measured by integrating sphere measurements and iMC simulation in order to confirm the influence of measured g on optical properties in comparison of with general value of g (0.9) for soft biological tissue. Consequently, it was found that μs was overestimated at strongly absorbing wavelength, however, μs was underestimated at weakly absorbing wavelength if the g was not considered its wavelength and absorption dependence.
NASA Astrophysics Data System (ADS)
Fukutomi, Daichi; Ishii, Katsunori; Awazu, Kunio
2016-04-01
The anisotropy factor g, one of the optical properties of biological tissues, has a strong influence on the calculation of the scattering coefficient μ s in inverse Monte Carlo (iMC) simulations. It has been reported that g has the wavelength and absorption dependence; however, few attempts have been made to calculate μ s using g values by taking the wavelength and absorption dependence into account. In this study, the angular distributions of scattered light for biological tissue phantoms containing hemoglobin as a light absorber were measured by a goniometric optical setup at strongly (405 nm) and weakly (664 nm) absorbing wavelengths to obtain g. Subsequently, the optical properties were calculated with the measured values of g by integrating sphere measurements and an iMC simulation, and compared with the results obtained with a conventional g value of 0.9. The μ s values with measured g were overestimated at the strongly absorbing wavelength, but underestimated at the weakly absorbing wavelength if 0.9 was used in the iMC simulation.
Shortell, Matthew P; Hewins, Rodney A; Fernando, Joseph F S; Walden, Sarah L; Waclawik, Eric R; Jaatinen, Esa A
2016-07-25
A thorough analysis of the resonance light scattering (RLS) technique for quantitative scattering measurements of subwavelength nanoparticles is reported. The systematic error associated with using a measurement at a single angle to represent all of the scattered light is investigated. In-depth analysis of the reference material was performed to identify and minimize the error associated with the reference material. Semiconductor ZnO nanobullets and spherical Au nanoparticles of various sizes were used to verify the approach. A simple and inexpensive modification to standard fluorometers is demonstrated using a glass prism allowing scattering measurements in the slightly forward and backwards directions. This allows quantification of the systematic error associated with RLS which is consistently overlooked. PMID:27464160
NASA Astrophysics Data System (ADS)
Kim, J. H.; Kim, S. W.; Yoon, S. C.; Park, R.; Ogren, J. A.
2014-12-01
Filter-based instrument, such as aethalometer, is being widely used to measure equivalent black carbon(EBC) mass concentration and aerosol absorption coefficient(AAC). However, many other previous studies have poited that AAC and its aerosol absorption angstrom exponent(AAE) are strongly affected by the multi-scattering correction factor(C) when we retrieve AAC from aethalometer EBC mass concentration measurement(Weingartner et al., 2003; Arnott et al., 2005; Schmid et al., 2006; Coen et al., 2010). We determined the C value using the method given in Weingartner et al. (2003) by comparing 7-wavelngth aethalometer (AE-31, Magee sci.) to 3-wavelength Photo-Acoustic Soot Spectrometer (PASS-3, DMT) at Gosan climate observatory, Korea(GCO) during Cheju ABC plume-asian monsoon experiment(CAPMEX) campaign(August and September, 2008). In this study, C was estimated to be 4.04 ± 1.68 at 532 nm and AAC retrieved with this value was decreased as approximately 100% as than that retrieved with soot case value from Weingartner et al (2003). We compared the AAC determined from aethalomter measurements to that from collocated Continuous Light Absorption Photometer (CLAP) measurements from January 2012 to December 2013 at GCO and found good agreement in both AAC and AAE. This result suggests the determination of site-specific C is crucially needed when we calculate AAC from aethalometer measurements.
NASA Astrophysics Data System (ADS)
sharma, N.; Arnold, I. J.; Moosmuller, H.; Arnott, P.; Mazzoleni, C.
2012-12-01
the Desert Research Institute, measuring absorption and scattering coefficients of kerosene soot and sodium chloride aerosols. As a reference system we used a commercial three-wavelength photoacoustic-nephelometer instrument (DMT Inc.). Here, we present the results of this laboratory intercomparison.
Radiometer gives true absorption and emission coefficients
NASA Technical Reports Server (NTRS)
Fymat, A. L.
1977-01-01
Novel radiometer, unaffected by scattering and polarization, measures true absorption and emmission coefficients for arbitrary mixture of gases and polluting particles. It has potential astronomical, meteorological, and environmental applications, such as determination of radiative heat budget, aerosol relative concentration, and morphology of cloud, haze, and fog formations. Data and temperature can be coupled directly to small computer for online calculation of radiation coefficients.
NASA Astrophysics Data System (ADS)
Pei, Yaling; Graber, Harry L.; Barbour, Randall L.
2001-06-01
In this report, we present a method to reduce the cross-talk problem in optical tomography. The method described is an extension of a previously reported perturbation formulation related to relative detector values, and employs a weight matrix scaling technique together with a constrained CGD method for imaging reconstruction. Results from numerical and experimental studies using DC measurement data demonstrate that the approach can effectively isolate absorption and scattering heterogeneities, even for complex combinations of perturbations in optical properties. The derive method is remarkably stable to errors originating from an insufficiently accurate estimate of properties of the reference medium.
Baba, Justin S; Koju, Vijay; John, Dwayne O
2016-01-01
The modulation of the state of polarization of photons due to scatter generates associated geometric phase that is being investigated as a means for decreasing the degree of uncertainty in back-projecting the paths traversed by photons detected in backscattered geometry. In our previous work, we established that polarimetrically detected Berry phase correlates with the mean photon penetration depth of the backscattered photons collected for image formation. In this work, we report on the impact of state-of-linear-polarization (SOLP) filtering on both the magnitude and population distributions of image forming detected photons as a function of the absorption coefficient of the scattering sample. The results, based on Berry phase tracking implemented Polarized Monte Carlo Code, indicate that sample absorption plays a significant role in the mean depth attained by the image forming backscattered detected photons.
NASA Astrophysics Data System (ADS)
DeMilo, Charles; Brukilacchio, Thomas; Soller, Babs R.; Soyemi, Olusola
2004-06-01
A visible-near IR (500-1,000nm) fiber optic sensor is under development that is intended to non-invasively assess muscle metabolism through the measurement of tissue pH and oxygen partial pressure. These parameters are calculated from the spectra of hemoglobin and myoglobin in muscle. The sensor consists of transmit (illumination) fibers and receive (detection) fibers that are coupled to a spectrometer. Light from the probe must penetrate below the surface of the skin and into a 5-10mm thick layer of muscle. A study was conducted to quantify the relationship between transmit and receive fiber separation and sensor penetration depth below the surface of the skin. A liquid phantom was created to replicate the absorption (μa) and reduced scatter coefficient (μs') profiles typically found in human blood and tissue. The phantom consisted of a solution of Intralipid and India ink in the appropriate concentrations to achieve desired reduced scatter coefficient and absorption profiles. The reduced scatter coefficient of the liquid phantom was achieved to an accuracy of +/-10% compared to previously published data. A fixed illumination fiber and translatable detector fiber were placed in the liquid phantom, and the fiber separation was varied from 3-40mm. Values of μa and μs' varied from 0.03-0.40 cm-1 and 5.0-15.0 cm-1 respectively. Results from the experiment demonstrate a strong correlation between penetration depth and fiber separation. Additionally, it was found that penetration depth was not substantially influenced by absorption and scatter concentration. As signal-to-noise is an important parameter in many non-invasive biomedical applications, the relative signal as a function of fiber separation was determined to follow an exponential relationship.
Ashoor, Mansour; Asgari, Afrouz; Khorshidi, Abdollah; Rezaei, Ali
2015-01-01
Purpose: Estimation of Compton attenuation and the photoelectric absorption coefficients were explored at various depths. Methods: A new method was proposed for estimating the depth based on the convolution of two exponential functions, namely convolution of scattering and primary functions (CSPF), which the convolved result will conform to the photopeak region of energy spectrum with the variable energy-window widths (EWWs) and a theory on the scattering cross-section. The triple energy-windows (TEW) and extended triple energy-windows scatter correction (ETEW) methods were used to estimate the scattered and primary photons according to the energy spectra at various depths due to a better performance than the other methods in nuclear medicine. For this purpose, the energy spectra were employed, and a distinct phantom along with a technetium-99 m source was simulated by Monte Carlo method. Results: The simulated results indicate that the EWW, used to calculate the scattered and primary counts in terms of the integral operators on the functions, was proportional to the depth as an exponential function. The depth will be calculated by the combination of either TEW or ETEW and proposed method resulting in the distinct energy-window. The EWWs for primary photons were in good agreement with those of scattered photons at the same as depths. The average errors between these windows for both methods TEW, and ETEW were 7.25% and 6.03% at different depths, respectively. The EWW value for functions of scattered and primary photons was reduced by increasing the depth in the CSPF method. Conclusions: This coefficient may be an index for the scattering cross-section. PMID:26170567
NASA Astrophysics Data System (ADS)
Rosati, B.; Weingartner, E.; Gysel, M.; Tillmann, R.; Mentel, T. F.; Decesari, S.; Marinoni, A.; Gobbi, G. P.; Fierli, F.; Cairo, F.; Bucci, S.; Zanatta, M.; Größ, J.; Baltensperger, U.
2014-12-01
Aerosol particles influence the Earth's radiation budget by interacting with the incoming sunlight. The chemical composition and size of aerosol particles determine their potential to scatter and absorb radiation as well as their capability to take up water (Zieger et al., 2011). If particles are hygroscopic their optical properties will be altered at enhanced relative humidities (RH) due to the increase in size and change in index of refraction. It is known that RH but also the chemical composition of aerosols change with altitude (Morgan et al., 2010) which makes it very important to investigate optical properties at different heights. Within the Pan-European Gas-Aerosols-climate interaction Study (PEGASOS) a set of instruments was installed on a Zeppelin to investigate changes of light scattering and absorption in the planetary boundary layer. In order to obtain the scattering properties, Mie calculations were performed for size distributions recorded with SMPS (scanning mobility particle sizer) and WELAS (optical size spectrometer). The index of refraction and the hygroscopicity of the aerosol particles were measured with the white-light humidified optical particle spectrometer (WHOPS). These measurements further allowed studying the RH-dependence of the optical properties. Moreover, a seven wavelength portable aethalometer was employed to determine the light absorption properties of the aerosol. In this work we will present vertical profiles of scattering and absorption coefficients measured during Zeppelin flights of the PEGASOS campaigns in Italy in 2012. Additionally comparisons with ground based measurements from nephelometers and aethalometers, as well as remote sensing results will be shown. W.T. Morgan et al., Enhancement of the aerosol direct radiative effect by semi-volatile aerosol components: Airborne measurements in North-Western Europe, Atmospheric Chemistry and Physics 10(2010), pp. 8151-8171.P. Zieger et al., Comparison of ambient aerosol
Greening, Gage J; Istfan, Raeef; Higgins, Laura M; Balachandran, Kartik; Roblyer, Darren; Pierce, Mark C; Muldoon, Timothy J
2014-01-01
Optical phantoms are used in the development of various imaging systems. For certain applications, the development of thin phantoms that simulate the physical size and optical properties of tissue is important. Here, we demonstrate a method for producing thin phantom layers with tunable optical properties using poly(dimethylsiloxane) (PDMS) as a substrate material. The thickness of each layer (between 115 and 880 μm) was controlled using a spin coater. The reduced scattering and absorption coefficients were controlled using titanium dioxide and alcohol-soluble nigrosin, respectively. These optical coefficients were quantified at six discrete wavelengths (591, 631, 659, 691, 731, and 851 nm) at varying concentrations of titanium dioxide and nigrosin using spatial frequency domain imaging. From the presented data, we provide lookup tables to determine the appropriate concentrations of scattering and absorbing agents to be used in the design of PDMS-based phantoms with specific optical coefficients. In addition, heterogeneous phantoms mimicking the layered features of certain tissue types may be fabricated from multiple stacked layers, each with custom optical properties. These thin, tunable PDMS optical phantoms can simulate many tissue types and have broad imaging calibration applications in endoscopy, diffuse optical spectroscopic imaging, and optical coherence tomography, etc. PMID:25387084
Scattering with absorptive interaction
NASA Astrophysics Data System (ADS)
Cassing, W.; Stingl, M.; Weiguny, A.
1982-07-01
The S matrix for a wide class of complex and nonlocal potentials is studied, with special attention given to the motion of singularities in the complex k plane as a function of the imaginary coupling strength. Modifications of Levinson's theorem are obtained and discussed. Analytic approximations to the S matrix in the vicinity of narrow resonances are exhibited and compared to numerical results of resonating-group calculations. The problem of defining resonances in the case of complex interactions is discussed, making contact with the usual analysis of scattering in terms of Argand diagrams. NUCLEAR REACTIONS Scattering theory, S matrix for absorptive potentials.
Nondestructive Method For Measuring The Scattering Coefficient Of Bulk Material
NASA Astrophysics Data System (ADS)
Groenhuis, R. A. J.; ten Bosch, J. J.
1981-05-01
During demineralization and remineralization of dental enamel its structure changes resulting in a change of the absorption and scattering coefficients of the enamel. By measuring these coefficients during demineralization and remineralization these processes can be monitored in a non-destructive way. For this purpose an experimental arrangement was made: a fibre illuminates a spot on the sample with monochromatic light with a wave-length between 400 nm and 700 nm; a photomultiplier measures the luminance of the light back-scattered by the sample as a function of the distance from the measuring snot to the spot of illumination. In a Monte Carlo-model this luminance is simulated using the same geometry given the scattering and absorption coefficients in a sample. Then the scattering and absorption coefficients in the sample are determined by selecting the theoretical curve fitting the experimental one. Scattering coefficients below 10 mm-1 and absorption coefficients obtained with this method on calibration samples correspond well with those obtained with another method. Scattering coefficients above 10 mm-1 (paper samples) were measured ton low. This perhaps is caused by the anisotropic structure of paper sheets. The method is very suitable to measure the scattering and absorption coefficients of bulk materials.
Aerosol Angstrom Absorption Coefficient Comparisons during MILAGRO.
NASA Astrophysics Data System (ADS)
Marley, N. A.; Marchany-Rivera, A.; Kelley, K. L.; Mangu, A.; Gaffney, J. S.
2007-12-01
aerosol Angstrom absorption exponents by linear regression over the entire UV-visible spectral range. These results are compared to results obtained from the absorbance measurements obtained in the field. The differences in calculated Angstrom absorption exponents between the field and laboratory measurements are attributed partly to the differences in time resolution of the sample collection resulting in heavier particle pileup on the filter surface of the 12-hour samples. Some differences in calculated results can also be attributed to the presence of narrow band absorbers below 400 nm that do not fall in the wavelengths covered by the 7 wavelengths of the aethalometer. 1. Marley, N.A., J.S. Gaffney, J.C. Baird, C.A. Blazer, P.J. Drayton, and J.E. Frederick, "The determination of scattering and absorption coefficients of size-fractionated aerosols for radiative transfer calculations." Aerosol Sci. Technol., 34, 535-549, (2001). This work was conducted as part of the Department of Energy's Atmospheric Science Program as part of the Megacity Aerosol Experiment - Mexico City during MILAGRO. This research was supported by the Office of Science (BER), U.S. Department of Energy Grant No. DE-FG02-07ER64329. We also wish to thank Mexican Scientists and students for their assistance from the Instituto Mexicano de Petroleo (IMP) and CENICA.
Sensitivity of room acoustic parameters to changes in scattering coefficients
NASA Astrophysics Data System (ADS)
Rathsam, Jonathan; Wang, Lily M.
2001-05-01
This project uses the room acoustics computer modeling program, ODEON, to investigate the sensitivity of room acoustic parameters to changes in scattering coefficients. Particularly, the study is interested in determining if the results from certain room models are more sensitive to scattering coefficients than from other models, due to their geometry or absorption characteristics. If so, how can one quantify a model's susceptibility to being sensitive to scattering? Various models of three real spaces in Omaha, Nebraska are tested. The predicted reverberation, clarity, and spaciousness parameters are compared at various receiver locations, while the scattering coefficient of all surfaces is varied from 0 to 0.1, 0.3, 0.5, and 0.8. The resulting data are analyzed by frequency according to the (1) average absorption of the room; (2) magnitude variation of absorption within the room; (3) spatial distribution of absorption within the room; and (4) level of model detail. Initial results indicate that parameters studied may show more sensitivity to scattering coefficients in models that have a wider range of absorption values, more disparate distribution of absorption, and lower detail level. Various schemes that include these aspects are proposed for computing a model's sensitivity to changes in scattering.
Allegood, M.S.; Baba, J.S.
2008-01-01
Light interaction with biological tissue can be described using three parameters: the scattering and absorption coeffi cients (μs and μa), as well as the anisotropy (g) which describes the directional dependence of the scattered photons. Accurately determining these optical properties for different tissue types at specifi c wavelengths simultaneously would be benefi cial for a variety of different biomedical applications. The goal of this project was to take a user defi ned g-value and determine the remaining two parameters for a specifi ed wavelength range. A fully automated computer program and process was developed to collect data for all wavelengths in a timely and accurate manner. LabVIEW® was used to write programs to automate raw intensity data collection from a spectrometer equipped integrating sphere, conversion of the data into a format for analysis via Scott Prahl’s Inverse Adding-Doubling (IAD) C code execution, and fi nally computation of the optical properties based on the output from the IAD code. To allow data to be passed effi ciently between LabVIEW® and C code program modules, the two were combined into a single program (OPT 3.1). OPT 3.1 was tested using tissue mimicking phantoms. Determination of the absorption and scattering coeffi cients showed excellent agreement with theory for wavelengths where the user inputted single g-value was suffi ciently precise. Future improvements entail providing for multi-wavelength g-value entry to extend the accuracy of results to encompass the complete multispectral range. Ultimately, the data collection process and algorithms developed through this effort will be used to examine actual biological tissues for the purpose of building and refi ning models for light-tissue interactions.
Determination of absorption coefficients of thin films
Lodenquai, J.F. )
1994-08-01
The equations that are usually presented as those used to determine the absorption coefficients of materials in film form based on measurements of transmission and reflection coefficients are fundamentally incorrect. These equations omit a multiplicative factor arising from the complex nature of the refractive indices of the materials. This factor enters explicitly into the relationship between the transmission and reflection coefficients for such materials and is not necessarily close to unity, although in practice this factor can be approximated by unity at least in the infrared through the optical range of wavelengths.
Inversion of instantaneous equivalent absorption coefficient and its application
Weihua, W. )
1992-01-01
Absorption coefficient is an important parameter for reservoir description. The major troubles in extracting absorption coefficient from seismic data are amplitude and waveform distortions; they greatly restrict the inversion which is based on reflection amplitude variation or reflection frequency variation. This paper presents a new method which avoids amplitude and uses waveform variation gradient in wave propagation to make the inversion of absorption coefficient. Apparent absorption coefficient and pseudo absorption coefficient are adopted so as to remove the influence which the waveform distortion due to thin bed tuning brings to absorption coefficient extraction. The final instantaneous equivalent absorption coefficient, a true absorption coefficient which reflects real absorptive character of a seismic medium, can be obtained by subtracting the pseudo absorption coefficient (inversely calculated using maximum entropy) from the apparent absorption coefficient the authors have calculated.
[Influencing factors in measuring absorption coefficient of suspended particulate matters].
Yu, Xiao-long; Shen, Fang; Zhang, Jin-fang
2013-05-01
Absorption coefficient of suspended particulate matters in natural water is one of the key parameters in ocean color remote sensing. In order to study the influencing factors that affect the measurement, a series of experiments were designed to measure samples using transmittance method (T method), transmittance-reflectance method (T-R method) and absorptance method (A method). The results shows that absorption coefficient measured by the A method has a much lower error compared to the T method and T-R method due to influencing factors,such as filter-to-filter variations, water content of the filter, and homogeneity of filter load and so on. Another factor influence absorption coefficient is path-length amplification induced by multiple scattering inside the filter. To determine the path-length amplification, the true absorption was measured by AC-s (WetLabs). The linear fitting result shows that the mean path-length amplification is much higher for the A method than that of the T-R method and the T method (4.01 versus 2.20 and 2.32), and the corresponding correlation coefficient are 0.90, 0.87 and 0.80. For the A method and the T-R method, higher correlation coefficients are calculated when using polynomial fitting, and the value are 0.95 and 0.94. Analysis of the mean relative error caused by different influencing factors indicates that path-length amplification is the largest error source in measuring the absorption coefficient. PMID:23914523
Measurements of the absorption coefficient of stratospheric aerosols
NASA Technical Reports Server (NTRS)
Ogren, J. A.; Ahlquist, N. C.; Clarke, A. D.; Charlson, R. J.
1981-01-01
The absorption coefficients of stratospheric aerosols are measured using a variation on the integrating plate method. The technique is based on the decrease in the transparency of a substrate when an absorbing aerosol is deposited on it. A Lambert scatterer is placed behind the substrate to integrate forward scattered light and minimize the effect of scattering on the measurement. The low pressure in the stratosphere is used for the direct impaction of particles onto a narrow strip of opal glass. The eight samples collected had a median value of 4 x 10 to the -9th m with an uncertainty of + or - 5 x 10 to the -9th m. If this absorption is due to graphitic carbon, then its concentration is estimated at about 0.4 ng/cu m, or about 0.25% of the total aerosol mass concentration. Estimates of the aerosol scattering coefficients based on satellite extinction inversions result in an aerosol single-scattering albedo in the range of 0.96-1.0.
NASA Astrophysics Data System (ADS)
Tanifuji, T.
2016-03-01
Time-resolved multi-distance measurements are studied to retrieve absorption and reduced scattering coefficients of adult heads, which have enough depth sensitivity to determine the optical parameters in superficial tissues and brain separately. Measurements were performed by putting the injection and collection fibers on the left semi-sphere of the forehead, with the injection fiber placed toward the temporal region, and by moving the collection fiber between 10 and 60 mm from the central sulcus. It became clear that optical parameters of the forehead at all collection fibers were reasonably determined by selecting the appropriate visibility length of the geometrical head models, which is related to head surface curvature at each position.
Neutron scattering and absorption properties
Holden, N.E.
1993-12-01
The Table in this report presents an evaluated set of values for the experimental quantities, which characterize the properties for scattering and absorption of neutrons. The neutron cross section is given for room temperature neutrons, 20.43{degree}C, corresponds to a thermal neutron energy of 0.0253 electron volts (eV) or a neutron velocity of 2200 meters/second. The neutron resonance integral is defined over the energy range from 0.5 eV to 0.1 {times} 10{sup 6} eV, or 0.1 MeV. A list of the major references used is given below. The literature cutoff data is October 1993. Uncertainties are given in parentheses. Parentheses with two or more numbers indicate values to the excited states(s) and to the ground state of the product nucleus.
Linear and nonlinear optical absorption coefficients of spherical dome shells
NASA Astrophysics Data System (ADS)
Guo, Kangxian; Liu, Guanghui; Huang, Lu; Zheng, Xianyi
2015-08-01
Linear and nonlinear optical absorption coefficients of spherical dome shells are theoretically investigated within analytical wave functions and numerical quantized energy levels. Our results show that the inner radius, the outer radius and the cut-off angle of spherical dome shells have great influences on linear and nonlinear optical absorption coefficients as well as the total optical absorption coefficients. It is found that with the increase of the inner radius and the outer radius, linear and nonlinear optical absorption coefficients exhibit a blueshift and a redshift, respectively. However, with the increase of the cut-off angle, linear and nonlinear optical absorption coefficients do not shift. Besides, the resonant peaks of linear and nonlinear optical absorption coefficients climb up and then decrease with increasing the cut-off angle. The influences of the incident optical intensity on the total optical absorption coefficients are studied. It is found that the bleaching effect occurs at higher incident optical intensity.
NASA Astrophysics Data System (ADS)
Samatham, Ravikant; Jacques, Steven L.
2013-02-01
Different techniques have been developed to determine the optical properties of turbid media, which include collimated transmission, diffuse reflectance, adding-doubling and goniometry. While goniometry can be used to determine the anisotropy of scattering (g), other techniques are used to measure the absorption coefficient and reduced scattering coefficient (μs(1-g)). But separating scattering coefficient (μs) and anisotropy of scattering from reduced scattering coefficient has been tricky. We developed an algorithm to determine anisotropy of scattering from the depth dependent decay of reflectance-mode confocal scanning laser microscopy (rCSLM) data. This report presents the testing of the algorithm on tissue phantoms with different anisotropies (g = 0.127 to 0.868, at 488 nm wavelength). Tissue phantoms were made from polystyrene microspheres (6 sizes 0.1-0.5 μm dia.) dispersed in both aqueous solutions and agarose gels. Three dimensional images were captured. The rCSLM-signal followed an exponential decay as a function of depth of the focal volume, R(z)ρexp(-μz) where ρ (dimensionless, ρ = 1 for a mirror) is the local reflectivity and μ [cm-1] is the exponential decay constant. The theory was developed to uniquely map the experimentally determined μ and ρ into the optical scattering properties μs and g. The values of μs and g depend on the composition and microstructure of tissues, and allow characterization of a tissue.
Scattering and Absorption Properties of Biomaterials for Dental Restorative Applications
NASA Astrophysics Data System (ADS)
Fernandez-Oliveras, A.; Rubiño, M.; Pérez, M. M.
2013-08-01
The physical understanding of the optical properties of dental biomaterials is mandatory for their final success in restorative applications.Light propagation in biological media is characterized by the absorption coefficient, the scattering coefficient, the scattering phase function,the refractive index, and the surface conditions (roughness). We have employed the inverse adding-doubling (IAD) method to combine transmittance and reflectance measurements performed using an integrating-sphere setup with the results of the previous scattering-anisotropygoniometric measurements. This has led to the determination of the absorption and the scattering coefficients. The aim was to optically characterize two different dental-resin composites (nanocomposite and hybrid) and one type of zirconia ceramic, and comparatively study them. The experimental procedure was conducted under repeatability conditions of measurement in order to determine the uncertainty associated to the optical properties of the biomaterials. Spectral variations of the refraction index and the scattering anisotropy factor were also considered. The whole experimental procedure fulfilled all the necessary requirements to provide optical-property values with lower associated uncertainties. The effective transport coefficient presented a similar spectral behavior for the two composites but completely different for the zirconia ceramic. The results demonstrated that the scattering anisotropy exerted a clearly distinct impact on the optical properties of the zirconia ceramic compared with those of the dental-resin composites.
Optical absorption and scattering spectra of pathological stomach tissues
NASA Astrophysics Data System (ADS)
Giraev, K. M.; Ashurbekov, N. A.; Lakhina, M. A.
2011-03-01
Diffuse reflection spectra of biotissues in vivo and transmission and reflection coefficients for biotissues in vitro are measured over 300-800 nm. These data are used to determine the spectral absorption and scattering indices and the scattering anisotropy factor for stomach mucous membranes under normal and various pathological conditions (chronic atrophic and ulcerous defects, malignant neoplasms). The most importan tphysiological (hemodynamic and oxygenation levels) and structural-morphological (scatterer size and density) parameters are also determined. The results of a morphofunctional study correlate well with the optical properties and are consistent with data from a histomorphological analysis of the corresponding tissues.
Su, Jing-Wei; Lin, Yang-Hsien; Chiang, Chun-Ping; Lee, Jang-Ming; Hsieh, Chao-Mao; Hsieh, Min-Shu; Yang, Pei-Wen; Wang, Chen-Ping; Tseng, Ping-Huei; Lee, Yi-Chia; Sung, Kung-Bin
2015-01-01
The progression of epithelial precancers into cancer is accompanied by changes of tissue and cellular structures in the epithelium. Correlations between the structural changes and scattering coefficients of esophageal epithelia were investigated using quantitative phase images and the scattering-phase theorem. An ex vivo study of 14 patients demonstrated that the average scattering coefficient of precancerous epithelia was 37.8% higher than that of normal epithelia from the same patient. The scattering coefficients were highly correlated with morphological features including the cell density and the nuclear-to-cytoplasmic ratio. A high interpatient variability in scattering coefficients was observed and suggests identifying precancerous lesions based on the relative change in scattering coefficients. PMID:26504630
Su, Jing-Wei; Lin, Yang-Hsien; Chiang, Chun-Ping; Lee, Jang-Ming; Hsieh, Chao-Mao; Hsieh, Min-Shu; Yang, Pei-Wen; Wang, Chen-Ping; Tseng, Ping-Huei; Lee, Yi-Chia; Sung, Kung-Bin
2015-10-01
The progression of epithelial precancers into cancer is accompanied by changes of tissue and cellular structures in the epithelium. Correlations between the structural changes and scattering coefficients of esophageal epithelia were investigated using quantitative phase images and the scattering-phase theorem. An ex vivo study of 14 patients demonstrated that the average scattering coefficient of precancerous epithelia was 37.8% higher than that of normal epithelia from the same patient. The scattering coefficients were highly correlated with morphological features including the cell density and the nuclear-to-cytoplasmic ratio. A high interpatient variability in scattering coefficients was observed and suggests identifying precancerous lesions based on the relative change in scattering coefficients. PMID:26504630
Technology Transfer Automated Retrieval System (TEKTRAN)
Optical absorption and scattering properties are useful for quantifying light interaction with plant tissue, as well as for quality assessment of horticultural products. The aim of this research was to measure the absorption and reduced scattering coefficient spectra of two cultivars of apple (Malus...
Effect of applied mechanical stress on absorption coefficient of compounds
Gupta, Manoj Kumar; Singh, Gurinderjeet; Dhaliwal, A. S.; Kahlon, K. S.
2015-08-28
The absorption coefficient of given materials is the parameter required for the basic information. The measurement of absorption coefficient of compounds Al{sub 2}O{sub 3}, CaCO{sub 3}, ZnO{sub 2}, SmO{sub 2} and PbO has been taken at different incident photon energies 26, 59.54, 112, 1173, 1332keV. The studies involve the measurements of absorption coefficient of the self supporting samples prepared under different mechanical stress. This mechanical stress is render in terms of pressure up to 0-6 ton by using hydraulic press. Measurements shows that absorption coefficient of a material is directly proportional to applied mechanical stress on it up to some extent then become independent. Experimentally measured results are in fairly good agreement with in theoretical values obtained from WinXCOM.
Effect of applied mechanical stress on absorption coefficient of compounds
NASA Astrophysics Data System (ADS)
Gupta, Manoj Kumar; Singh, Gurinderjeet; Dhaliwal, A. S.; Kahlon, K. S.
2015-08-01
The absorption coefficient of given materials is the parameter required for the basic information. The measurement of absorption coefficient of compounds Al2O3, CaCO3, ZnO2, SmO2 and PbO has been taken at different incident photon energies 26, 59.54, 112, 1173, 1332keV. The studies involve the measurements of absorption coefficient of the self supporting samples prepared under different mechanical stress. This mechanical stress is render in terms of pressure up to 0-6 ton by using hydraulic press. Measurements shows that absorption coefficient of a material is directly proportional to applied mechanical stress on it up to some extent then become independent. Experimentally measured results are in fairly good agreement with in theoretical values obtained from WinXCOM.
Measurements of Soot Mass Absorption Coefficients from 300 to 660 nm
NASA Astrophysics Data System (ADS)
Renbaum-Wolff, Lindsay; Fisher, Al; Helgestad, Taylor; Lambe, Andrew; Sedlacek, Arthur; Smith, Geoffrey; Cappa, Christopher; Davidovits, Paul; Onasch, Timothy; Freedman, Andrew
2016-04-01
Soot, a product of incomplete combustion, plays an important role in the earth's climate system through the absorption and scattering of solar radiation. In particular, the assumed mass absorption coefficient (MAC) of soot and its variation with wavelength presents a significant uncertainty in the calculation of radiative forcing in global climate change models. As part of the fourth Boston College/Aerodyne soot properties measurement campaign, we have measured the mass absorption coefficient of soot produced by an inverted methane diffusion flame over a spectral range of 300-660 nm using a variety of optical absorption techniques. Extinction and absorption were measured using a dual cavity ringdown photoacoustic spectrometer (CRD-PAS, UC Davis) at 405 nm and 532 nm. Scattering and extinction were measured using a CAPS PMssa single scattering albedo monitor (Aerodyne) at 630 nm; the absorption coefficient was determined by subtraction. In addition, the absorption coefficients in 8 wavelength bands from 300 to 660 nm were measured using a new broadband photoacoustic absorption monitor (UGA). Soot particle mass was quantified using a centrifugal particle mass analyzer (CPMA, Cambustion), mobility size with a scanning mobility particle sizer (SMPS, TSI) and soot concentration with a CPC (Brechtel). The contribution of doubly charged particles to the sample mass was determined using a Single Particle Soot Photometer (DMT). Over a mass range of 1-8 fg, corresponding to differential mobility diameters of ~150 nm to 550 nm, the value of the soot MAC proved to be independent of mass for all wavelengths. The wavelength dependence of the MAC was best fit to a power law with an Absorption Ångstrom Coefficient slightly greater than 1.
Continuum Absorption Coefficient of Atoms and Ions
NASA Technical Reports Server (NTRS)
Armaly, B. F.
1979-01-01
The rate of heat transfer to the heat shield of a Jupiter probe has been estimated to be one order of magnitude higher than any previously experienced in an outer space exploration program. More than one-third of this heat load is due to an emission of continuum radiation from atoms and ions. The existing computer code for calculating the continuum contribution to the total load utilizes a modified version of Biberman's approximate method. The continuum radiation absorption cross sections of a C - H - O - N ablation system were examined in detail. The present computer code was evaluated and updated by being compared with available exact and approximate calculations and correlations of experimental data. A detailed calculation procedure, which can be applied to other atomic species, is presented. The approximate correlations can be made to agree with the available exact and experimental data.
Measurements of Scattering and Absorption Changes in Muscle and Brain
NASA Astrophysics Data System (ADS)
Gratton, Enrico; Fantini, Sergio; Franceschini, Maria Angela; Gratton, Gabriele; Fabiani, Monica
1997-06-01
Non-invasive techniques for the study of human brain function based on changes of the haemoglobin content or on changes of haemoglobin saturation have recently been proposed. Among the new methods, near-infrared transmission and reflection measurements may have significant advantages and complement well-established methods such as functional magnetic resonance imaging and positron emission tomography. Near-infrared measurements can be very fast, comparable in speed to electrophysiological measurements, but are better localized. We will present the demonstration of measurements of millisecond signals due to brain activity in humans following stimulation of the visual cortex. However, major unresolved questions remain about the origin of the signals observed. Optical measurements on exposed cortex in animals show that both the absorption and the scattering coefficient are affected by neural activity. Model calculations show that the signals we detected may originate from rapid changes of the scattering coefficient in a region about 1 to 2 cm below the scalp. We discuss our measurement protocol, which is based on a frequency-domain instrument, and the algorithm to separate the absorption from the scattering contribution in the overall optical response. Our method produces excellent separation between scattering and absorption in relatively homogeneous masses such as large muscles. The extrapolation of our measurement protocol to a complex structure such as the human head is critically evaluated.
NASA Astrophysics Data System (ADS)
Brochu, Frederic M.; Joseph, James; Tomaszewski, Michal R.; Bohndiek, Sarah E.
2016-03-01
Optoacoustic Tomography is a fast developing imaging modality, combining the high resolution and penetration depth of ultrasound detection with the high contrast available from optical absorption in tissue. The spectral profile of near infrared excitation light used in optoacoustic tomography instruments is modified by absorption and scattering as it propagates deep into biological tissue. The resulting images therefore provide only qualitative insight into the distribution of tissue chromophores. Knowledge of the spectral profile of excitation light across the mouse is needed for accurate determination of the absorption coefficient in vivo. Under the conditions of constant Grueneisen parameter and accurate knowledge of the light fluence, a linear relationship should exist between the initial optoacoustic pressure amplitude and the tissue absorption coefficient. Using data from a commercial optoacoustic tomography system, we implemented an iterative optimization based on the σ-Eddington approximation to the Radiative Transfer Equation to derive a light fluence map within a given object. We segmented the images based on the positions of phantom inclusions, or mouse organs, and used known scattering coefficients for initialization. Performing the fluence correction in simple phantoms allowed the expected linear relationship between recorded and independently measured absorption coefficients to be retrieved and spectral coloring to be compensated. For in vivo data, the correction resulted in an enhancement of signal intensities in deep tissues. This improved our ability to visualize organs at depth (> 5mm). Future work will aim to perform the optimization without data normalization and explore the need for methodology that enables routine implementation for in vivo imaging.
Absorption coefficients of a hydrogen plasma for laser radiation
NASA Technical Reports Server (NTRS)
Stallcop, J. R.
1974-01-01
The formalism for the calculation of the absorption of radiation by a hydrogen plasma at common laboratory conditions is summarized. The hydrogen plasma absorption coefficient for laser radiation has been computed for a wide range of electron densities and temperatures (10,000-40,000 K). The results of this computation are presented in a graphical form that permits a determination of the absorption coefficient for the following laser wavelengths: 0.176, 0.325, 0.337, 0.442, 0.488, 0.515, 0.633, 0.694, 1.06, 1.15, 2.36, 3.39, 5.40 and 10.6 microns. The application of these results and laser radiation absorption measurements to plasma diagnostics is discussed briefly.
NASA Astrophysics Data System (ADS)
Nishidate, Izumi; Yoshida, Keiichiro; Kawauchi, Satoko; Sato, Shunichi; Sato, Manabu
2014-03-01
We investigate a method to estimate the spectral images of reduced scattering coefficients and the absorption coefficients of in vivo exposed brain tissues in the range from visible to near-infrared wavelength (500-760 nm) based on diffuse reflectance spectroscopy using a digital RGB camera. In the proposed method, the multi-spectral reflectance images of in vivo exposed brain are reconstructed from the digital red, green blue images using the Wiener estimation algorithm. The Monte Carlo simulation-based multiple regression analysis for the absorbance spectra is then used to specify the absorption and scattering parameters of brain tissue. In this analysis, the concentration of oxygenated hemoglobin and that of deoxygenated hemoglobin are estimated as the absorption parameters whereas the scattering amplitude a and the scattering power b in the expression of μs'=aλ-b as the scattering parameters, respectively. The spectra of absorption and reduced scattering coefficients are reconstructed from the absorption and scattering parameters, and finally, the spectral images of absorption and reduced scattering coefficients are estimated. The estimated images of absorption coefficients were dominated by the spectral characteristics of hemoglobin. The estimated spectral images of reduced scattering coefficients showed a broad scattering spectrum, exhibiting larger magnitude at shorter wavelengths, corresponding to the typical spectrum of brain tissue published in the literature. In vivo experiments with exposed brain of rats during CSD confirmed the possibility of the method to evaluate both hemodynamics and changes in tissue morphology due to electrical depolarization.
Ottink, Marco; Brunskog, Jonas; Jeong, Cheol-Ho; Fernandez-Grande, Efren; Trojgaard, Per; Tiana-Roig, Elisabet
2016-01-01
Absorption coefficients are mostly measured in reverberation rooms or with impedance tubes. Since these methods are only suitable for measuring the random incidence and the normal incidence absorption coefficient, there exists an increasing need for absorption coefficient measurement of finite absorbers at oblique incidence in situ. Due to the edge diffraction effect, oblique incidence methods considering an infinite sample fail to measure the absorption coefficient at large incidence angles of finite samples. This paper aims for the development of a measurement method that accounts for the finiteness of the absorber. A sound field model, which accounts for scattering from the finite absorber edges, assuming plane wave incidence is derived. A significant influence of the finiteness on the radiation impedance and the corresponding absorption coefficient is found. A finite surface method, which combines microphone array measurements over a finite sample with the sound field model in an inverse manner, is proposed. Besides, a temporal subtraction method, a microphone array method, impedance tube measurements, and an equivalent fluid model are used for validation. The finite surface method gives promising agreement with theory, especially at near grazing incidence. Thus, the finite surface method is proposed for further measurements at large incidence angles. PMID:26827003
Reciprocity in the scattering coefficients of acoustic waveguide modes.
Tong, Yuhui; Pan, Jie
2013-09-01
In this Letter, a proof is provided for the reciprocity between modal scattering coefficients of the acoustic waveguides connected by a junction enclosure. The result holds for all waveguide modes and for junction enclosures with locally reactive boundary conditions away from the interfaces between the junction and waveguides. Also provided is a physical interpretation of the reciprocity of the modal scattering coefficients. The scattering of two-dimensional waveguide modes by a right-angled bend in a rectangular duct is used as an illustrating example. PMID:23967907
Prediction of apple internal quality using spectral absorption and scattering properties
Technology Transfer Automated Retrieval System (TEKTRAN)
This paper reports on the measurement of the absorption and reduced scattering coefficients of apples via a new spatially-resolved hyperspectral imaging technique and their correlation with fruit firmness and soluble solids content (SSC). Spatially-resolved hyperspectral scattering profiles were acq...
NASA Astrophysics Data System (ADS)
Kim, B.; Eun, S.; Seo, W.; Park, J.; Ahn, J.; Moon, K.
2013-12-01
Aerosols in the atmosphere can scatter and absorb solar radiation and their spatial/temporal distributions are highly inhomogeneous due to short lifetimes (about a few weeks or less). Through scattering and absorption of solar radiation, aerosols directly affect visibility and climate through the modification of the Earth's energy budget (Charlson et al., 1992; Yan, 2007; Wang, 2012). This study investigates long-term trends and characteristics of aerosol light scattering coefficient at Seoul and Baengnyeongdo, 100 km upstream of Seoul, in Korea. Aerosol scattering coefficients were measured continuously with nephelometers. The analysis period is limited to one year of 2011. For the relationship analysis of extinction coefficients (σext) to visibility and aerosol optical depth, σsp observed at 3 p.m. have been used with help of aerosol absorption coefficients (σap) in order to remove its dependence upon relative humidity (RH), and also those of rainy period have been excluded. As expected, σext estimated are inversely proportional to visibility observation by eye. Aerosol extinction coefficients have been vertically integrated with an assumption of nearly well-mixed within an e-folding height to determine aerosol optical depth (τa), and compared with those retrieved from sunphotometer. The results show a reasonable agreement in spite of an inherent difference of each definition. We expect these findings would help to eventually understand aerosol radiative forcing and its effect on the regional climate change around Korea.
Absorption-coefficient-determination method for particulate materials.
Lindberg, J D; Douglass, R E; Garvey, D M
1994-07-01
A method is presented for determining the optical absorption coefficient, or the imaginary refractive index, of particulate material that has been collected from aerosols or hydrosols by means of filtration. The method, based on the Kubelka-Munk theory of diffuse reflectance, is nondestructive and requires no other knowledge of the sample than the amount present, the specific gravity, and an estimate of the real index of refraction. The theoretical development of the method is discussed along with an analysis of photometric and gravimetric errors. We test the method by comparing results obtained for powdered didymium glass with measurements made before the glass was crushed. An example of the method's application to the determination of the absorption coefficient of atmospheric dust at UV, visible, and near-IR wavelengths is also presented. PMID:20935789
A high absorption coefficient DL-MPP imitating owl skin
NASA Astrophysics Data System (ADS)
Guo, Lijun; Zhao, Zhan; Kong, Deyi; Wu, Shaohua; Du, Lidong; Fang, Zhen
2012-11-01
This paper proposes a high absorption coefficient micro-perforated panel (MPP) imitating owl skin structure for acoustic noise reduction. Compared to the traditional micro-perforated panel, this device has two unique characteristics-simulating the owl skin structure, its radius of perforated apertures even can be as small as 55μ, and its material is silicon and fabricated by micro-electrical mechanical system (MEMS) technology; So that its absorption coefficients of acoustic noise for normal incidence sound wave whose frequencies arrange from 1.5 kHz to 6.0 kHz are all above 0.8 which is the owl's hunts sensitivity frequency band. Double leaf MPP fabricated by MEMS technology is an absolutely bionic success in functional-imitation.
Gas in scattering media absorption spectroscopy - GASMAS
NASA Astrophysics Data System (ADS)
Svanberg, Sune
2008-09-01
An overview of the new field of Gas in Scattering Media Absorption Spectroscopy (GASMAS) is presented. GASMAS combines narrow-band diode-laser spectroscopy with diffuse media optical propagation. While solids and liquids have broad absorption features, free gas in pores and cavities in the material is characterized by sharp spectral signatures, typically 10,000 times sharper than those of the host material. Many applications in materials science, food packaging, pharmaceutics and medicine have been demonstrated. So far molecular oxygen and water vapour have been studied around 760 and 935 nm, respectively. Liquid water, an important constituent in many natural materials, such as tissue, has a low absorption at such wavelengths, allowing propagation. Polystyrene foam, wood, fruits, food-stuffs, pharmaceutical tablets, and human sinus cavities have been studied. Transport of gas in porous media can readily be studied by first immersing the material in, e.g., pure nitrogen, and then observing the rate at which normal air, containing oxygen, reinvades the material. The conductance of the sinus connective passages can be measured in this way by flushing the nasal cavity with nitrogen. Also other dynamic processes such as drying of materials can be studied. The techniques have also been extended to remote-sensing applications (LIDAR-GASMAS).
NASA Astrophysics Data System (ADS)
del Mar Pérez, Maria; Ghinea, Razvan; Ionescu, Ana-Maria; de la Cruz Cardona, Juan
2011-05-01
Photocured polymers are widely used in dental applications. The optical properties of the dental composites change during curing; the appearance of the composites also changes. Recently, a new silorane-based composite resin and dental nanocomposite have been introduced. However, research regarding the effect of the silorane monomers or the size filler on appearance after curing of the resin composite is limited. This work aims to examine the optical properties of silorane-based composite and nanocomposite, in terms of scattering and absorption during curing. Six dimethacrylate-based dental resin composite (five universal and one nanocomposite) and one silorane-based dental resin composite (all shades A2 and T) were studied. The curing irradiance was 1100mW/cm2. The spectral reflectance of 1mm thick composite samples against white and black backgrounds were measured both before and after curing, and were converted to scattering and absorption coefficients using the Kubelka-Munk Theory. Both for pre and post-curing dental resin composites, the Albedo coefficient (K/S) shows that absorption prevails over the scattering for short wavelengths while for medium and large wavelengths, the scattering becomes more important, except for the T shade of the nanocomposite. After curing, the scattering and absorption values decreased for both types of materials. Changes in the absorption coefficient values should be caused by changes in the camphorquinone (CQ) absorption, whereas the scattering changes found should be directly attributable to index of refraction changes of the resin during curing.
Optimization of the acoustic absorption coefficients of certain functional absorbents
NASA Technical Reports Server (NTRS)
Pocsa, V.; Biborosch, L.; Veres, A.; Halpert, E.; Lorian, R.; Botos, T.
1974-01-01
The sound absorption coefficients of some functional absorbents (mineral wool plates) are determined by the reverberation chamber method. The influence of the angle of inclination of the sound absorbing material with respect to the surface to be treated is analyzed as well as the influence of the covering index, defined as the ratio of the designed area of a plate and the area of the treated surface belonging to another plate. As compared with the conventional method of applying sound-absorbing plates, the analyzed structures have a higher technological and economical efficiency. The optimum structure corresponds to an angle of inclination of 15 deg and a covering index of 0.8.
A method for monitoring nuclear absorption coefficients of aviation fuels
NASA Technical Reports Server (NTRS)
Sprinkle, Danny R.; Shen, Chih-Ping
1989-01-01
A technique for monitoring variability in the nuclear absorption characteristics of aviation fuels has been developed. It is based on a highly collimated low energy gamma radiation source and a sodium iodide counter. The source and the counter assembly are separated by a geometrically well-defined test fuel cell. A computer program for determining the mass attenuation coefficient of the test fuel sample, based on the data acquired for a preset counting period, has been developed and tested on several types of aviation fuel.
Ren, Yatao; Qi, Hong; Zhao, Fangzhou; Ruan, Liming; Tan, Heping
2016-01-01
A secondary optimization technique was proposed to estimate the temperature-dependent thermal conductivity and absorption coefficient. In the proposed method, the stochastic particle swarm optimization was applied to solve the inverse problem. The coupled radiation and conduction problem was solved in a 1D absorbing, emitting, but non-scattering slab exposed to a pulse laser. It is found that in the coupled radiation and conduction problem, the temperature response is highly sensitive to conductivity but slightly sensitive to the optical properties. On the contrary, the radiative intensity is highly sensitive to optical properties but slightly sensitive to thermal conductivity. Therefore, the optical and thermal signals should both be considered in the inverse problem to estimate the temperature-dependent properties of the transparent media. On this basis, the temperature-dependent thermal conductivity and absorption coefficient were both estimated accurately by measuring the time-dependent temperature, and radiative response at the boundary of the slab. PMID:26912418
NASA Astrophysics Data System (ADS)
Ren, Yatao; Qi, Hong; Zhao, Fangzhou; Ruan, Liming; Tan, Heping
2016-02-01
A secondary optimization technique was proposed to estimate the temperature-dependent thermal conductivity and absorption coefficient. In the proposed method, the stochastic particle swarm optimization was applied to solve the inverse problem. The coupled radiation and conduction problem was solved in a 1D absorbing, emitting, but non-scattering slab exposed to a pulse laser. It is found that in the coupled radiation and conduction problem, the temperature response is highly sensitive to conductivity but slightly sensitive to the optical properties. On the contrary, the radiative intensity is highly sensitive to optical properties but slightly sensitive to thermal conductivity. Therefore, the optical and thermal signals should both be considered in the inverse problem to estimate the temperature-dependent properties of the transparent media. On this basis, the temperature-dependent thermal conductivity and absorption coefficient were both estimated accurately by measuring the time-dependent temperature, and radiative response at the boundary of the slab.
Ren, Yatao; Qi, Hong; Zhao, Fangzhou; Ruan, Liming; Tan, Heping
2016-01-01
A secondary optimization technique was proposed to estimate the temperature-dependent thermal conductivity and absorption coefficient. In the proposed method, the stochastic particle swarm optimization was applied to solve the inverse problem. The coupled radiation and conduction problem was solved in a 1D absorbing, emitting, but non-scattering slab exposed to a pulse laser. It is found that in the coupled radiation and conduction problem, the temperature response is highly sensitive to conductivity but slightly sensitive to the optical properties. On the contrary, the radiative intensity is highly sensitive to optical properties but slightly sensitive to thermal conductivity. Therefore, the optical and thermal signals should both be considered in the inverse problem to estimate the temperature-dependent properties of the transparent media. On this basis, the temperature-dependent thermal conductivity and absorption coefficient were both estimated accurately by measuring the time-dependent temperature, and radiative response at the boundary of the slab. PMID:26912418
NASA Astrophysics Data System (ADS)
Brochu, Frederic M.; Joseph, James; Tomaszewski, Michal; Bohndiek, Sarah E.
2015-07-01
MultiSpectral Optoacoustic Tomography (MSOT) is a fast developing imaging modality, combining the high resolution and penetration depth of ultrasound with the excellent contrast from optical imaging of tissue. Absorption and scattering of the near infrared excitation light modulates the spectral profile of light as it propagates deep into biological tissue, meaning the images obtained provide only qualitative insight into the distribution of tissue chromophores. The goal of this work is to accurately recover the spectral profile of excitation light by modelling light fluence in the data reconstruction, to enable quantitative imaging. We worked with a commercial small animal MSOT scanner and developed our light fluence correction for its' cylindrical geometry. Optoacoustic image reconstruction pinpoints the sources of acoustic waves detected by the transducers and returns the initial pressure amplitude at these points. This pressure is the product of the dimensionless Grüneisen parameter, the absorption coefficient and the light fluence. Under the condition of constant Grüneisen parameter and well modelled light fluence, there is a linear relationship between the initial pressure amplitude measured in the optoacoustic image and the absorption coefficient. We were able to reproduce this linear relationship in different physical regions of an agarose gel phantom containing targets of known optical absorption coefficient, demonstrating that our light fluence model was working. We also demonstrate promising results of light fluence correction effects on in vivo data.
Measurements of scattering and absorption in mammalian cell suspensions
Mourant, J.R.; Johnson, T.M.; Freyer, J.P.
1996-03-01
During the past several years a range of spectroscopies, including fluorescence and elastic-scatter spectroscopy, have been investigated for optically based detection of cancer and other tissue pathologies. Both elastic-scatter and fluorescence signals depend, in part, on scattering and absorption properties of the cells in the tissue. Therefore an understanding of the scattering and absorption properties of cells is a necessary prerequisite for understanding and developing these techniques. Cell suspensions provide a simple model with which to begin studying the absorption and scattering properties of cells. In this study we have made preliminary measurements of the scattering and absorption properties of suspensions of mouse mammary carcinoma cells (EMT6) over a broad wavelength range (380 nm to 800 nm).
NASA Astrophysics Data System (ADS)
Arnott, W. P.; Lewis, K.; Paredes-Miranda, G.; Winter, S.; Day, D.; Chakrabarty, R.; Moosmuller, H.; Jimenez, J. L.; Ulbrich, I.; Huffman, A.; Onasch, T.; Trimborn, A.; Kreidenweis, S.; Carrico, C.; Wold, C.; Lincoln, E.; Freeborn, P.; Hao, W.; McMeeking, G.
2006-12-01
A very interesting case of smoke aerosol with very low single scattering albedo, yet very large hygroscopic growth for scattering is presented. Several samples of chamise (Adenostoma fasciculatum), a common and often dominant species in California chaparral, were recently burned at the USFS Fire Science Laboratory in Missoula Montana, and aerosol optics and chemistry were observed, along with humidity-dependent light scattering, absorption, and particle morphology. Photoacoustic measurements of light absorption by two instruments at 870 nm, one on the dry channel, one on the humidified channel, showed strong reduction of aerosol light absorption with RH above 65 percent, and yet a strong increase in light scattering was observed both at 870 nm and 550 nm with nephelometers. Multispectral measurements of aerosol light absorption indicated an Angstrom coefficient for absorption near unity for the aerosols from chamise combustion. It is argued that the hygroscopic growth of scattering is due to uptake of water by the sulfur bearing aerosol. Furthermore, the reduction of aerosol light absorption is argued to be due to the collapse of chain aggregate aerosol as the RH increases wherein the interior of aerosol does no longer contribute to absorption. Implications for biomass burning in general are that humidity processing of aerosols from this source and others like it tends to substantially increase its single scattering albedo, probably in a non-reversible manner. The chemical pathway to hygroscopicity will be addressed.
Townsend coefficients for electron scattering over dielectric surfaces
NASA Technical Reports Server (NTRS)
Peck, Timothy L.; Kushner, Mark J.
1988-01-01
A method for describing the probability of initiating flashover discharges across dielectric surfaces is presented in which a transport coefficient for electron multiplication similar to the Townsend coefficient used for gas discharges is defined. The coefficient is a function of the scaling parameter (charge released from the cathode)/(cathode-anode separation) and is also a measure of the growth of the sheath on the dielectric surface resulting from electron scattering. Results are discussed as to when the source of seed electrons does not necessarily depend upon field emission at the cathode-vacuum-dielectric triple point. For these conditions, there is a different functional dependence of flashover probability on voltage and geometry than when field emission provides the seed electrons. As a result, criteria previously used to predict flashover discharges may not apply.
Bremmer, Rolf H; van Gemert, Martin J C; Faber, Dirk J; van Leeuwen, Ton G; Aalders, Maurice C G
2013-08-01
Diffuse reflectance spectra are used to determine the optical properties of biological samples. In medicine and forensic science, the turbid objects under study often possess large absorption and/or scattering properties. However, data analysis is frequently based on the diffusion approximation to the radiative transfer equation, implying that it is limited to tissues where the reduced scattering coefficient dominates over the absorption coefficient. Nevertheless, up to absorption coefficients of 20 mm-1 at reduced scattering coefficients of 1 and 11.5 mm-1, we observed excellent agreement (r2=0.994) between reflectance measurements of phantoms and the diffuse reflectance equation proposed by Zonios et al. [Appl. Opt.38, 6628-6637 (1999)], derived as an approximation to one of the diffusion dipole equations of Farrell et al. [Med. Phys.19, 879-888 (1992)]. However, two parameters were fitted to all phantom experiments, including strongly absorbing samples, implying that the reflectance equation differs from diffusion theory. Yet, the exact diffusion dipole approximation at high reduced scattering and absorption also showed agreement with the phantom measurements. The mathematical structure of the diffuse reflectance relation used, derived by Zonios et al. [Appl. Opt.38, 6628-6637 (1999)], explains this observation. In conclusion, diffuse reflectance relations derived as an approximation to the diffusion dipole theory of Farrell et al. can analyze reflectance ratios accurately, even for much larger absorption than reduced scattering coefficients. This allows calibration of fiber-probe set-ups so that the object's diffuse reflectance can be related to its absorption even when large. These findings will greatly expand the application of diffuse reflection spectroscopy. In medicine, it may allow the use of blue/green wavelengths and measurements on whole blood, and in forensic science, it may allow inclusion of objects such as blood stains and cloth at crime
NASA Astrophysics Data System (ADS)
Bremmer, Rolf H.; van Gemert, Martin J. C.; Faber, Dirk J.; van Leeuwen, Ton G.; Aalders, Maurice C. G.
2013-08-01
Diffuse reflectance spectra are used to determine the optical properties of biological samples. In medicine and forensic science, the turbid objects under study often possess large absorption and/or scattering properties. However, data analysis is frequently based on the diffusion approximation to the radiative transfer equation, implying that it is limited to tissues where the reduced scattering coefficient dominates over the absorption coefficient. Nevertheless, up to absorption coefficients of 20 m at reduced scattering coefficients of 1 and 11.5 mm-1, we observed excellent agreement (r2=0.994) between reflectance measurements of phantoms and the diffuse reflectance equation proposed by Zonios et al. [Appl. Opt.
Internal quality evaluation of apples using spectral absorption and scattering properties
Technology Transfer Automated Retrieval System (TEKTRAN)
The objective of this research was to measure the absorption and reduced scattering coefficients of apples via a spatially-resolved hyperspectral imaging technique and relate them to fruit firmness and soluble solids content (SSC). Spatially-resolved hyperspectral images were acquired from 600 ‘Gold...
Assessing multiple quality attributes of peaches using spectral absorption and scattering properties
Technology Transfer Automated Retrieval System (TEKTRAN)
The objective of this research was to measure the spectral absorption and reduced scattering coefficients of peaches, using a hyperspectral imaging-based spatially-resolved method, for maturity/quality assessment. A newly developed optical property measuring instrument was used for acquiring hypersp...
Khalifah, Peter
2015-02-01
The problem of numerically evaluating absorption correction factors for cylindrical samples has been revisited using a treatment that fully takes advantage of the sample symmetry. It is shown that the path lengths for all points within the sample at all possible diffraction angles can be trivially determined once the angle-dependent distance distribution for a single line of points is calculated. This provides advantages in both computational efficiency and in gaining an intuitive understanding of the effects of absorption on diffraction data. A matrix of absorption coefficients calculated for µR products between 0 and 20 for diffraction angles θ_{D} of 0° to 90° were used to examine the influence of (1) capillary diameter and of (2) sample density on the overall scattered intensity as a function of diffraction angle, where µ is the linear absorption coefficient for the sample and R is the capillary radius. Based on this analysis, the optimal sample loading for a capillary experiment to maximize diffraction at angles of 0 – 50° is in general expected to be achieved when the maximum radius capillary compatible with the beam is used, and when the sample density is adjusted to be 3/(4µR) of its original density.
Khalifah, Peter
2015-02-01
The problem of numerically evaluating absorption correction factors for cylindrical samples has been revisited using a treatment that fully takes advantage of the sample symmetry. It is shown that the path lengths for all points within the sample at all possible diffraction angles can be trivially determined once the angle-dependent distance distribution for a single line of points is calculated. This provides advantages in both computational efficiency and in gaining an intuitive understanding of the effects of absorption on diffraction data. A matrix of absorption coefficients calculated for µR products between 0 and 20 for diffraction angles θD of 0°more » to 90° were used to examine the influence of (1) capillary diameter and of (2) sample density on the overall scattered intensity as a function of diffraction angle, where µ is the linear absorption coefficient for the sample and R is the capillary radius. Based on this analysis, the optimal sample loading for a capillary experiment to maximize diffraction at angles of 0 – 50° is in general expected to be achieved when the maximum radius capillary compatible with the beam is used, and when the sample density is adjusted to be 3/(4µR) of its original density.« less
Two-photon interband absorption coefficients in tungstate and molybdate crystals
NASA Astrophysics Data System (ADS)
Lukanin, V. I.; Karasik, A. Ya.
2015-02-01
Two-photon absorption (TPA) coefficients were measured in tungstate and molybdate crystals - BaWO4, KGW, CaMoO4, BaMoO4, CaWO4, PbWO4 and ZnWO4 upon different orientations of excitation polarization with respect to the crystallographic axes. Trains of 25 ps pulses with variable radiation intensities of third (349 nm) harmonics of passively mode-locked 1047 nm Nd:YLF laser were used for interband two-photon excitation of the crystals. It was suggested that in the case, when 349 nm radiation pumping energy exceeds the bandgap width (hν>Eg), the nonlinear excitation process can be considered as two-step absorption. The interband two-photon absorption in all the studied crystals induces the following one-photon absorption from the exited states, which affects the nonlinear process dynamics and leads to a hysteresis in the dependence of the transmission on the excitation intensity. This fact was taken into account under analysis of the experimental dependences of the reciprocal transmission on the excitation intensity. Laser excitation in the transparency region of the crystals caused stimulated Raman scattering (SRS) not for all the crystals studied. The measured nonlinear coefficients allowed us to explain the suppression of SRS in crystals as a result of competition between the SRS and TPA.
Photosensitizer absorption coefficient modeling and necrosis prediction during Photodynamic Therapy.
Salas-García, Irene; Fanjul-Vélez, Félix; Arce-Diego, José Luis
2012-09-01
The development of accurate predictive models for Photodynamic Therapy (PDT) has emerged as a valuable tool to adjust the current therapy dosimetry to get an optimal treatment response, and definitely to establish new personal protocols. Several attempts have been made in this way, although the influence of the photosensitizer depletion on the optical parameters has not been taken into account so far. We present a first approach to predict the spatio-temporal variation of the photosensitizer absorption coefficient during PDT applied to dermatological diseases, taking into account the photobleaching of a topical photosensitizer. This permits us to obtain the photons density absorbed by the photosensitizer molecules as the treatment progresses and to determine necrosis maps to estimate the short term therapeutic effects in the target tissue. The model presented also takes into account an inhomogeneous initial photosensitizer distribution, light propagation in biological media and the evolution of the molecular concentrations of different components involved in the photochemical reactions. The obtained results allow to investigate how the photosensitizer depletion during the photochemical reactions affects light absorption by the photosensitizer molecules as the optical radiation propagates through the target tissue, and estimate the necrotic tumor area progression under different treatment conditions. PMID:22704663
Correction of optical absorption and scattering variations in laser speckle rheology measurements
Hajjarian, Zeinab; Nadkarni, Seemantini K.
2014-01-01
Laser Speckle Rheology (LSR) is an optical technique to evaluate the viscoelastic properties by analyzing the temporal fluctuations of backscattered speckle patterns. Variations of optical absorption and reduced scattering coefficients further modulate speckle fluctuations, posing a critical challenge for quantitative evaluation of viscoelasticity. We compare and contrast two different approaches applicable for correcting and isolating the collective influence of absorption and scattering, to accurately measure mechanical properties. Our results indicate that the numerical approach of Monte-Carlo ray tracing (MCRT) reliably compensates for any arbitrary optical variations. When scattering dominates absorption, yet absorption is non-negligible, diffusing wave spectroscopy (DWS) formalisms perform similar to MCRT, superseding other analytical compensation approaches such as Telegrapher equation. The computational convenience of DWS greatly simplifies the extraction of viscoelastic properties from LSR measurements in a number of chemical, industrial, and biomedical applications. PMID:24663983
Correction of optical absorption and scattering variations in Laser Speckle Rheology measurements.
Hajjarian, Zeinab; Nadkarni, Seemantini K
2014-03-24
Laser Speckle Rheology (LSR) is an optical technique to evaluate the viscoelastic properties by analyzing the temporal fluctuations of backscattered speckle patterns. Variations of optical absorption and reduced scattering coefficients further modulate speckle fluctuations, posing a critical challenge for quantitative evaluation of viscoelasticity. We compare and contrast two different approaches applicable for correcting and isolating the collective influence of absorption and scattering, to accurately measure mechanical properties. Our results indicate that the numerical approach of Monte-Carlo ray tracing (MCRT) reliably compensates for any arbitrary optical variations. When scattering dominates absorption, yet absorption is non-negligible, diffusing wave spectroscopy (DWS) formalisms perform similar to MCRT, superseding other analytical compensation approaches such as Telegrapher equation. The computational convenience of DWS greatly simplifies the extraction of viscoelastic properties from LSR measurements in a number of chemical, industrial, and biomedical applications. PMID:24663983
NASA Astrophysics Data System (ADS)
Fishkin, Joshua B.; So, Peter T. C.; Cerussi, Albert E.; Gratton, Enrico; Fantini, Sergio; Franceschini, Maria Angela
1995-03-01
We have measured the optical absorption and scattering coefficient spectra of a multiple-scattering medium (i.e., a biological tissue-simulating phantom comprising a lipid colloid) containing methemoglobin by using frequency-domain techniques. The methemoglobin absorption spectrum determined in the multiple-scattering medium is in excellent agreement with a corrected methemoglobin absorption spectrum obtained from a steady-state spectrophotometer measurement of the optical density of a minimally scattering medium. The determination of the corrected methemoglobin absorption spectrum takes into account the scattering from impurities in the methemoglobin solution containing no lipid colloid. Frequency-domain techniques allow for the separation of the absorbing from the scattering properties of multiple-scattering media, and these techniques thus provide an absolute
Combined effects of scattering and absorption on laser speckle contrast imaging
NASA Astrophysics Data System (ADS)
Khaksari, Kosar; Kirkpatrick, Sean J.
2016-07-01
Several variables may affect the local contrast values in laser speckle contrast imaging (LSCI), irrespective of relative motion. It has been suggested that the optical properties of the moving fluid and surrounding tissues can affect LSCI values. However, a detailed study of this has yet to be presented. In this work, we examined the combined effects of the reduced scattering and absorption coefficients on LSCI. This study employs fluid phantoms with different optical properties that were developed to mimic whole blood with varying hematocrit levels. These flow phantoms were imaged with an LSCI system developed for this study. The only variable parameter was the optical properties of the flowing fluid. A negative linear relationship was seen between the changes in contrast and changes in reduced scattering coefficient, absorption coefficient, and total attenuation coefficient. The change in contrast observed due to an increase in the scattering coefficient was greater than what was observed with an increase in the absorption coefficient. The results indicate that optical properties affect contrast values and that they should be considered in the interpretation of LSCI data.
Spectroscopic method for determination of the absorption coefficient in brain tissue
NASA Astrophysics Data System (ADS)
Johansson, Johannes D.
2010-09-01
I use Monte Carlo simulations and phantom measurements to characterize a probe with adjacent optical fibres for diffuse reflectance spectroscopy during stereotactic surgery in the brain. Simulations and measurements have been fitted to a modified Beer-Lambert model for light transport in order to be able to quantify chromophore content based on clinically measured spectra in brain tissue. It was found that it is important to take the impact of the light absorption into account when calculating the apparent optical path length, lp, for the photons in order to get good estimates of the absorption coefficient, μa. The optical path length was found to be well fitted to the equation lp=a+b ln(Is)+c ln(μa)+d ln(Is)ln(μa), where Is is the reflected light intensity for scattering alone (i.e., zero absorption). Although coefficients a-d calculated in this study are specific to the probe used here, the general form of the equation should be applicable to similar probes.
Nonlinear bleaching, absorption, and scattering of 532-nm-irradiated plasmonic nanoparticles
Liberman, V.; Sworin, M.; Kingsborough, R. P.; Geurtsen, G. P.; Rothschild, M.
2013-02-07
Single-pulse irradiation of Au and Ag suspensions of nanospheres and nanodisks with 532-nm 4-ns pulses has identified complex optical nonlinearities while minimizing material damage. For all materials tested, we observe competition between saturable absorption (SA) and reverse SA (RSA), with RSA behavior dominating for intensities above {approx}50 MW/cm{sup 2}. Due to reduced laser damage in single-pulse experiments, the observed intrinsic nonlinear absorption coefficients are the highest reported to date for Au nanoparticles. We find size dependence to the nonlinear absorption enhancement for Au nanoparticles, peaking in magnitude for 80-nm nanospheres and falling off at larger sizes. The nonlinear absorption coefficients for Au and Ag spheres are comparable in magnitude. On the other hand, the nonlinear absorption for Ag disks, when corrected for volume fraction, is several times higher. These trends in nonlinear absorption are correlated to local electric field enhancement through quasi-static mean-field theory. Through variable size aperture measurements, we also separate nonlinear scattering from nonlinear absorption. For all materials tested, we find that nonlinear scattering is highly directional and that its magnitude is comparable to that of nonlinear absorption. These results indicate methods to improve the efficacy of plasmonic nanoparticles as optical limiters in pulsed laser systems.
Nonlinear bleaching, absorption, and scattering of 532-nm-irradiated plasmonic nanoparticles
NASA Astrophysics Data System (ADS)
Liberman, V.; Sworin, M.; Kingsborough, R. P.; Geurtsen, G. P.; Rothschild, M.
2013-02-01
Single-pulse irradiation of Au and Ag suspensions of nanospheres and nanodisks with 532-nm 4-ns pulses has identified complex optical nonlinearities while minimizing material damage. For all materials tested, we observe competition between saturable absorption (SA) and reverse SA (RSA), with RSA behavior dominating for intensities above ˜50 MW/cm2. Due to reduced laser damage in single-pulse experiments, the observed intrinsic nonlinear absorption coefficients are the highest reported to date for Au nanoparticles. We find size dependence to the nonlinear absorption enhancement for Au nanoparticles, peaking in magnitude for 80-nm nanospheres and falling off at larger sizes. The nonlinear absorption coefficients for Au and Ag spheres are comparable in magnitude. On the other hand, the nonlinear absorption for Ag disks, when corrected for volume fraction, is several times higher. These trends in nonlinear absorption are correlated to local electric field enhancement through quasi-static mean-field theory. Through variable size aperture measurements, we also separate nonlinear scattering from nonlinear absorption. For all materials tested, we find that nonlinear scattering is highly directional and that its magnitude is comparable to that of nonlinear absorption. These results indicate methods to improve the efficacy of plasmonic nanoparticles as optical limiters in pulsed laser systems.
NASA Astrophysics Data System (ADS)
Yoshida, Keiichiro; Ishizuka, Tomohiro; Mizushima, Chiharu; Nishidate, Izumi; Kawauchi, Satoko; Sato, Shunichi; Sato, Manabu
2015-04-01
To evaluate multi-spectral images of the absorption and scattering properties in the cerebral cortex of rat brain, we investigated spectral reflectance images estimated by the Wiener estimation method using a digital red-green-blue camera. A Monte Carlo simulation-based multiple regression analysis for the corresponding spectral absorbance images at nine wavelengths (500, 520, 540, 560, 570, 580, 600, 730, and 760 nm) was then used to specify the absorption and scattering parameters. The spectral images of absorption and reduced scattering coefficients were reconstructed from the absorption and scattering parameters. We performed in vivo experiments on exposed rat brain to confirm the feasibility of this method. The estimated images of the absorption coefficients were dominated by hemoglobin spectra. The estimated images of the reduced scattering coefficients had a broad scattering spectrum, exhibiting a larger magnitude at shorter wavelengths, corresponding to the typical spectrum of brain tissue published in the literature.
Uzhegov, V.N.; Kozlov, V.S.; Panchenko, M.V.; Pkhalagov, Yu.A.; Pol'kin, V.V.; Terpugova, S.A.; Shmargunov, V.P.; Yausheva, E.P.
2005-03-18
The problem of the choice of the aerosol optical constants and, in particular, imaginary part of the refractive index of particles in visible and infrared (IR) wavelength ranges is very important for calculation of the global albedo of the atmosphere in climatic models. The available models of the aerosol optical constants obtained for the prescribed chemical composition of particles (see, for example, Ivlev et al. 1973; Ivlev 1982; Volz 1972), often are far from real aerosol. It is shown in (Krekov et al. 1982) that model estimates of the optical characteristics of the atmosphere depending on the correctness of real and imaginary parts of the aerosol complex refractive index can differ by some hundreds percent. It is known that the aerosol extinction coefficient {alpha}({lambda}) obtained from measurements on a long horizontal path can be represented as {alpha}({lambda})={sigma}({lambda})+{beta}({lambda}), where {sigma} is the directed light scattering coefficient, and {beta} is the aerosol absorption coefficient. The coefficient {sigma}({lambda}) is measured by means of a nephelometer. Seemingly, if measure the values {alpha}({lambda}) and {sigma}({lambda}), it is easy to determine the value {beta}({lambda}). However, in practice it is almost impossible for a number of reasons. Firstly, the real values {alpha}({lambda}) and {sigma}({lambda}) are very close to each other, and the estimate of the parameter {beta}({lambda}) is concealed by the errors of measurements. Secondly, the aerosol optical characteristics on the long path and in the local volume of nephelometer can be different, that also leads to the errors in estimating {beta}({lambda}). Besides, there are serious difficulties in performing spectral measurements of {sigma}({lambda}) in infrared wavelength range. Taking into account these circumstances, in this paper we consider the statistical technique, which makes it possible to estimate the absorption coefficient of real aerosol on the basis of analysis
NASA Astrophysics Data System (ADS)
Lyamani, H.; Olmo, F. J.; Alados-Arboledas, L.
Surface measurements of optical and physical aerosol properties were made at an urban site, Granada (Spain) (37.18°N, 3.58°W, 680 m a.s.l), during winter 2005-2006. Measurements included the aerosol scattering, σsca, and backscattering coefficients, σbsca, at three wavelengths (450, 550 and 700 nm) measured at low relative humidity (RH<50%) by an integrating nephelometer, the absorption coefficient at 670 nm, σabs, measured with a multi-angle absorption photometer, and aerosol size distribution in the 0.5-20 μm aerodynamic diameter range registered by an aerodynamic aerosol sizer (APS-3321, TSI). The hourly average of σsca (550 nm) ranged from 2 to 424 M m -1 with an average value of 84±62 M m -1 (±S.D.). The Angstrom exponent presented an average value of 1.8±0.3, suggesting a large fraction of fine particles at the site, an observation confirmed by aerosol size distribution measurements. The hourly average of σabs (670 nm) ranged from 1.7 to 120.5 M m -1 with an average value of 28±20 M m -1. The results indicate that the aerosol absorption coefficient in Granada was relatively large. The largest σsca value was associated with air masses that passed over heavily polluted European areas and local stagnation conditions. High absorbing aerosol level was obtained during dust transport from North Africa probably due to the presence of hematite. Based on the measured scattering and absorption coefficients, a very low average value of the single scattering albedo of 0.66±0.11 at 670 nm was calculated, suggesting that urban aerosols in this region contain a large fraction of absorbing material. A clear diurnal pattern was observed in scattering and absorption coefficients and particle concentrations with two local maxima occurring in early morning and late evening. This behavior can be explained in terms of local conditions that control the particle sources associated with traffic and upward mixing of the aerosol during the daytime development of a
NASA Astrophysics Data System (ADS)
Jacques, S. L.; Samatham, R.; Phillips, K. G.
2011-03-01
Optical clearing of mouse dermis by glycerol was tested by reflectance-mode confocal microscopy (rCSLM) using 488- nm light. The reflectance signal R(z) was acquired as a function of the depth of the focus (z) within the upper 100 μm of freshly excised mouse dermis. The results specify the scattering coefficient (μs [cm-1]) and the anisotropy of scattering (g [dimensionless]). The absorption is too low to exert an effect. The results, published in Samatham et al., Journal of Innovative Optical Health Sciences 2010, 3(3):183-188, described how the clearing effect of glycerol was to increase g toward nearly 1.0, while having only a modest effect on μs. In other words, glycerol caused light scattering to become very forward-directed, but did not strongly alter the number of scattering events per unit length of photon path. This paper discusses the possible mechanism of action that is responsible for this clearing effect.
NASA Astrophysics Data System (ADS)
Thomas, S. M.
2015-12-01
Minor and trace element chemistry, phase relations, rheology, thermal structure and the role of volatiles and their abundance in the deep Earth mantle are still far from fully explored, but fundamental to understanding the processes involved in Earth formation and evolution. Theory and high pressure experiments imply a significant water storage capacity of nominally anhydrous minerals, such as majoritic garnet, olivine, wadsleyite and ringwoodite, composing the Earth's upper mantle and transition zone to a depth of 660 km. Studying the effect of water incorporation on chemical and physical mineral properties is of importance, because the presence of trace amounts of water, incorporated as OH through charge-coupled chemical substitutions into such nominally anhydrous high-pressure silicates, notably influences phase relations, melting behavior, conductivity, elasticity, viscosity and rheology. Knowledge of absolute water contents in nominally anhydrous minerals is essential for modeling the Earth's interior water cycle. One of the most common and sensitive tools for water quantification is IR spectroscopy for which mineral-specific absorption coefficients are required. Such calibration constants can be derived from hydrogen concentrations determined by independent techniques, such as secondary ion mass spectrometry, Raman spectroscopy or proton-proton(pp)-scattering. Here, analytical advances and mineral-specific IR absorption coefficients for the quantification of H2O in major phases of the Earth's mantle will be discussed. Furthermore, new data from optical absorption measurements in resistively heated diamond-anvil cells at high pressures and temperatures up to 1000 K will be presented. Experiments were performed on synthetic single-crystals of olivine, ringwoodite, majoritic garnet, and Al-bearing phase D with varying iron, aluminum and OH contents to calculate radiative thermal conductivities and study their contribution to heat transfer in the Earth's interior
Majaron, Boris; Verkruysse, Wim; Tanenbaum, B Samuel; Milner, Thomas E; Nelson, J Stuart
2002-06-01
Pulsed photothermal radiometry can be used for non-invasive depth profiling of optically scattering samples, including biological tissues such as human skin. Computational reconstruction of the laser-induced temperature profile from recorded radiometric signals is sensitive to the value of the tissue absorption coefficient in the infrared detection band (muIR). While assumed constant in reported reconstruction algorithms, muIR of human skin varies by two orders of magnitude in the commonly used 3-5 microm detection band. We analyse the problem of selecting the effective absorption coefficient value to be used with such algorithms. In a numerical simulation of photothermal profiling we demonstrate that results can be markedly impaired, unless the reconstruction algorithm is augmented by accounting for spectral variation muIR(lambda). Alternatively, narrowing the detection band to 4.5-5 microm reduces the spectral variation muIR(lambda) to a level that permits the use of the simpler, unaugmented algorithm. Implementation of the latter approach for depth profiling of port wine stain birthmarks in vivo is presented and discussed. PMID:12108776
NASA Technical Reports Server (NTRS)
Mcpeters, R. D.; Bass, A. M.
1982-01-01
Real structure is revealed, by an analysis of continuous scan data from the solar backscattered UV instrument on Nimbus 7, in the backscattered atmospheric albedo region between 300 and 310 nm where spectral anomalies have been reported in ground-based observation. The spectral anomalies are explainable as structure at the 1-5% level in the ozone absorption coefficient, as measured by Bass and Paur (1981). The new absorption coefficient measurements are judged to approach the 1%-level of accuracy in atmospheric radiation calculation, which should resolve discrepancies between different Dobson wavelength pairs and between different instruments and permit the more accurate analysis of such second-order effects as NO emission, SO2 absorption in polluted atmospheres, and Raman scattering effects.
Absorption and elastic scattering of light by particle aggregates.
Quinten, M; Kreibig, U
1993-10-20
Light scattering and absorption by spherical particles is extended to aggregates of spheres with arbitrary shape and size. We applied the theory of G6rardy and Ausloos [Phys. Rev. B 25, 4204-4229 (1082)] to compute the total extinction loss spectra of several aggregates of nanometer-sized silver spheres from the near IR to the near UV. Silver was best suited to provide quantitative comparison with experiments concerning the scattering and absorption in the visible spectral region. Additional resonant extinction was obtained besides the resonant extinction of the single silver sphere. The spectra were discussed in detail to give general results that are independent of the particle material. PMID:20856447
Absorption coefficient at 10.6 microm in CdTe modulator crystals.
Tucker, A W; Birnbaum, M; Montes, H; Fincher, C L
1982-08-15
The bulk and surface absorption coefficients of CdTe modulator crystals at 10.6 microm were compared with those of single-crystal KC1 and NaCl which served to calibrate the laser calorimeter. High-resistivity (>10(7) ohm/cm) CdTe crystals exhibited a bulk absorption coefficient of 0.0014 cm(-1). PMID:20396150
Scattering with absorptive interaction: Energy-dependent potentials
NASA Astrophysics Data System (ADS)
Cassing, W.; Stingl, M.; Weiguny, A.
1983-05-01
The energy dependence and analytic structure of the effective interaction for elastic scattering of composite particles are investigated using Feshbach's projection technique. A generalized Levinson theorem is established for complex, nonlocal, and energy-dependent interactions. The analytical results are illustrated by means of Argand diagrams for a solvable model and the effect of energy averaging is discussed. NUCLEAR REACTIONS Scattering theory, S matrix for absorptive, energy-dependent potentials, Levinson theorem.
NASA Technical Reports Server (NTRS)
Molina, L. T.; Grant, W. B.
1984-01-01
The absorption spectra of three hydrazines and four of their air-oxidation products were measured in the 9-12-micron spectral region with a Fourier transform infrared (FTIR) spectrometer with a 0.05-kayser resolution to determine absorption coefficients at CO2 and tunable diode laser wavelengths. The measurements agreed well with published CO2 laser determinations for many of the absorption coefficients, except where the published values are thought to be in error. The coefficients were then used to estimate the sensitivity for remote detection of these gases using CO2 and tunable diode lasers in long-path differential absorption measurements.
Measurement of the absorption coefficient of acoustical materials using the sound intensity method
NASA Technical Reports Server (NTRS)
Atwal, Mahabir S.; Crocker, Malcolm J.
1987-01-01
In this study the possibility of using the two-microphone sound intensity technique to measure the normal incidence and the random incidence sound absorption coefficient was investigated. The normal incidence absorption coefficient was determined by measuring the intensity incidence on the sample and the intensity reflected by the sample placed in an anechoic chamber. The random incidence absorption coefficient was determined by measuring the intensity incident on the sample and the intensity reflected by the sample placed in a reverberation chamber. Absorption coefficient results obtained by the sound intensity technique were compared with standard techniques, namely the reverberation chamber and the standing wave tube. The major advantages of using the sound intensity technique are that it permits 'in situ' measurements and the absorption coefficient for a large range of frequencies can be obtained from a single measurement.
Dynamic absorption coefficients of CAR and non-CAR resists at EUV
NASA Astrophysics Data System (ADS)
Fallica, Roberto; Stowers, Jason K.; Grenville, Andrew; Frommhold, Andreas; Robinson, Alex P. G.; Ekinci, Yasin
2016-03-01
The dynamic absorption coefficients of several CAR and non-CAR EUV photoresists are measured experimentally using a specifically developed setup in transmission mode at the XIL beamline of the Swiss Light Source. The absorption coefficient α and the Dill parameters ABC were measured with unprecedented accuracy. In general the α of resists match very closely with the theoretical value calculated from elemental densities and absorption coefficients, whereas exceptions are observed. In addition, through the direct measurements of the absorption coefficients and dose-to-clear values, we introduce a new figure of merit called Chemical Sensitivity to account for all the post-absorption chemical reaction ongoing in the resist, which is also predicts a quantitative clearing volume, and respectively clearing radius, due to the photon absorption in the resist. These parameters may help in deeper insight into the underlying mechanisms of EUV concept of clearing volume and clearing radius are then defined and quantitatively calculated.
Tromberg, Bruce J.; Berger, Andrew J.; Cerussi, Albert E.; Bevilacqua, Frederic; Jakubowski, Dorota
2008-09-23
A technique for measuring broadband near-infrared absorption spectra of turbid media that uses a combination of frequency-domain and steady-state reflectance methods. Most of the wavelength coverage is provided by a white-light steady-state measurement, whereas the frequency-domain data are acquired at a few selected wavelengths. Coefficients of absorption and reduced scattering derived from the frequency-domain data are used to calibrate the intensity of the steady-state measurements and to determine the reduced scattering coefficient at all wavelengths in the spectral window of interest. The absorption coefficient spectrum is determined by comparing the steady-state reflectance values with the predictions of diffusion theory, wavelength by wavelength. Absorption spectra of a turbid phantom and of human breast tissue in vivo, derived with the combined frequency-domain and steady-state technique, agree well with expected reference values.
Measurement of the absorption coefficient using the sound-intensity technique
NASA Technical Reports Server (NTRS)
Atwal, M.; Bernhard, R.
1984-01-01
The possibility of using the sound intensity technique to measure the absorption coefficient of a material is investigated. This technique measures the absorption coefficient by measuring the intensity incident on the sample and the net intensity reflected by the sample. Results obtained by this technique are compared with the standard techniques of measuring the change in the reverberation time and the standing wave ratio in a tube, thereby, calculating the random incident and the normal incident adsorption coefficient.
Incorporating tissue absorption and scattering in rapid ultrasound beam modeling
NASA Astrophysics Data System (ADS)
Christensen, Douglas; Almquist, Scott
2013-02-01
We have developed a new approach for modeling the propagation of an ultrasound beam in inhomogeneous tissues such as encountered with high-intensity focused ultrasound (HIFU) for treatment of various diseases. This method, called the hybrid angular spectrum (HAS) approach, alternates propagation steps between the space and the spatial frequency domains throughout the inhomogeneous regions of the body; the use of spatial Fourier transforms makes this technique considerably faster than other modeling approaches (about 10 sec for a 141 x 141 x 121 model). In HIFU thermal treatments, the acoustic absorption property of the tissues is of prime importance since it leads to temperature rise and the achievement of desired thermal dose at the treatment site. We have recently added to the HAS method the capability of independently modeling tissue absorption and scattering, the two components of acoustic attenuation. These additions improve the predictive value of the beam modeling and more accurately describes the thermal conditions expected during a therapeutic ultrasound exposure. Two approaches to explicitly model scattering were developed: one for scattering sizes smaller than a voxel, and one when the scattering scale is several voxels wide. Some anatomically realistic examples that demonstrate the importance of independently modeling absorption and scattering are given, including propagation through the human skull for noninvasive brain therapy and in the human breast for treatment of breast lesions.
Absorption and Scattering 2D Volcano Images from Numerically Calculated Space-weighting functions
NASA Astrophysics Data System (ADS)
Del Pezzo, Edoardo; Ibañez, Jesus; Prudencio, Janire; Bianco, Francesca; De Siena, Luca
2016-04-01
Short period small magnitude seismograms mainly comprise scattered waves in the form of coda waves (the tail part of the seismogram, starting after S-waves and ending when the noise prevails), spanning more than 70% of the whole seismogram duration. Corresponding coda envelopes provide important information about the earth inhomogeneity, which can be stochastically modeled in terms of distribution of scatterers in a random medium. In suitable experimental conditions (i.e. high earth heterogeneity) either the two parameters describing heterogeneity (scattering coefficient), intrinsic energy dissipation (coefficient of intrinsic attenuation) or a combination of them (extinction length and seismic albedo) can be used to image Earth structures. Once a set of such parameter couples has been measured in a given area and for a number of sources and receivers, imaging their space distribution with standard methods is straightforward. However, as for finite-frequency and full-waveform tomography, the essential problem for a correct imaging is the determination of the weighting function describing the spatial sensitivity of observable data to scattering and absorption anomalies. Due to the nature of coda waves, the measured parameter-couple can be seen as a weighted space average of the real parameters characterizing the rock volumes illuminated by the scattered waves. This paper uses the Monte Carlo numerical solution of the Energy Transport Equation to find approximate but realistic 2D space-weighting functions for coda waves. Separate images for scattering and absorption based on these sensitivity functions are then compared with those obtained with commonly-used sensitivity functions in an application to data from an active seismic experiment carried out at Deception Island (Antarctica). Results show the that these novel functions are based on a reliable and physically grounded method to image magnitude and shape of scattering and absorption anomalies. Their extension to
Absorption and scattering 2-D volcano images from numerically calculated space-weighting functions
NASA Astrophysics Data System (ADS)
Del Pezzo, Edoardo; Ibañez, Jesus; Prudencio, Janire; Bianco, Francesca; De Siena, Luca
2016-08-01
Short-period small magnitude seismograms mainly comprise scattered waves in the form of coda waves (the tail part of the seismogram, starting after S waves and ending when the noise prevails), spanning more than 70 per cent of the whole seismogram duration. Corresponding coda envelopes provide important information about the earth inhomogeneity, which can be stochastically modeled in terms of distribution of scatterers in a random medium. In suitable experimental conditions (i.e. high earth heterogeneity), either the two parameters describing heterogeneity (scattering coefficient), intrinsic energy dissipation (coefficient of intrinsic attenuation) or a combination of them (extinction length and seismic albedo) can be used to image Earth structures. Once a set of such parameter couples has been measured in a given area and for a number of sources and receivers, imaging their space distribution with standard methods is straightforward. However, as for finite-frequency and full-waveform tomography, the essential problem for a correct imaging is the determination of the weighting function describing the spatial sensitivity of observable data to scattering and absorption anomalies. Due to the nature of coda waves, the measured parameter couple can be seen as a weighted space average of the real parameters characterizing the rock volumes illuminated by the scattered waves. This paper uses the Monte Carlo numerical solution of the Energy Transport Equation to find approximate but realistic 2-D space-weighting functions for coda waves. Separate images for scattering and absorption based on these sensitivity functions are then compared with those obtained with commonly used sensitivity functions in an application to data from an active seismic experiment carried out at Deception Island (Antarctica). Results show that these novel functions are based on a reliable and physically grounded method to image magnitude and shape of scattering and absorption anomalies. Their
NASA Astrophysics Data System (ADS)
Müller, T.; Schladitz, A.; Massling, A.; Kaaden, N.; Kandler, K.; Wiedensohler, A.
2009-02-01
ABSTRACT During the SAMUM-1 experiment, absorption coefficients and imaginary parts of refractive indices of mineral dust particles were investigated in southern Morocco. Main absorbing constituents of airborne samples were identified to be iron oxide and soot. Spectral absorption coefficients were measured using a spectral optical absorption photometer (SOAP) in the wavelength range from 300 to 800 nm with a resolution of 50 nm. A new method that accounts for a loading-dependent correction of fibre filter based absorption photometers, was developed. The imaginary part of the refractive index was determined using Mie calculations from 350 to 800 nm. The spectral absorption coefficient allowed a separation between dust and soot absorption. A correlation analysis showed that the dust absorption coefficient is correlated (R2 up to 0.55) with the particle number concentration for particle diameters larger than 0.5 μm, whereas the coefficient of determination R2 for smaller particles is below 0.1. Refractive indices were derived for both the total aerosol and a dust aerosol that was corrected for soot absorption. Average imaginary parts of refractive indices of the entire aerosol are 7.4 × 10-3, 3.4 × 10-3 and 2.0 × 10-3 at wavelengths of 450, 550 and 650 nm. After a correction for the soot absorption, imaginary parts of refractive indices are 5.1 × 10-3, 1.6 × 10-3 and 4.5 × 10-4.
NASA Technical Reports Server (NTRS)
Stallcop, J. R.
1974-01-01
The theory for calculating the absorption of laser radiation by hydrogen is outlined for the temperatures and pressures of common laboratory plasmas. Nonhydrogenic corrections for determining the absorption by helium are also included. The coefficients for the absorption of He-Ne laser radiation at the wavelengths of 0.633, 1.15, and 3.39 microns in a H plasma is presented for temperatures in the range from 10,000 to 40,000 K and electron number densities in the range from 10 to the 15th power to 10 to the 18th power per cu cm. The total absorption of a H-He plasma calculated from this theory is compared with the measured absorption. The theoretical composition of the H-He absorption is analyzed with respect to the significant absorption processes, inverse bremsstrahlung, photoionization, resonance excitation, and photodetachment.
NASA Astrophysics Data System (ADS)
Yoshida, Keiichiro; Nishidate, Izumi; Ishizuka, Tomohiro; Kawauchi, Satoko; Sato, Shunichi; Sato, Manabu
2015-05-01
In order to estimate multispectral images of the absorption and scattering properties in the cerebral cortex of in vivo rat brain, we investigated spectral reflectance images estimated by the Wiener estimation method using a digital RGB camera. A Monte Carlo simulation-based multiple regression analysis for the corresponding spectral absorbance images at nine wavelengths (500, 520, 540, 560, 570, 580, 600, 730, and 760 nm) was then used to specify the absorption and scattering parameters of brain tissue. In this analysis, the concentrations of oxygenated hemoglobin and that of deoxygenated hemoglobin were estimated as the absorption parameters, whereas the coefficient a and the exponent b of the reduced scattering coefficient spectrum approximated by a power law function were estimated as the scattering parameters. The spectra of absorption and reduced scattering coefficients were reconstructed from the absorption and scattering parameters, and the spectral images of absorption and reduced scattering coefficients were then estimated. In order to confirm the feasibility of this method, we performed in vivo experiments on exposed rat brain. The estimated images of the absorption coefficients were dominated by the spectral characteristics of hemoglobin. The estimated spectral images of the reduced scattering coefficients had a broad scattering spectrum, exhibiting a larger magnitude at shorter wavelengths, corresponding to the typical spectrum of brain tissue published in the literature. The changes in the estimated absorption and scattering parameters during normoxia, hyperoxia, and anoxia indicate the potential applicability of the method by which to evaluate the pathophysiological conditions of in vivo brain due to the loss of tissue viability.
Absorption Coefficient Imaging by Near-Field Scanning Optical Microscopy in Bacteria
NASA Astrophysics Data System (ADS)
de Paula, Ana M.; Chaves, Claudilene R.; Silva, Haroldo B.; Weber, Gerald
2003-06-01
We present a method for obtaining a position-dependent absorption coefficient from near-field scanning optical transmission microscopy. We show that the optical transmission intensity can be combined with the topography, resulting into an absorption coefficient that simplifies the analysis of different materials within a sample. The method is tested with the dye rhodamine 6G, and we show some analysis in biological samples such as bacteria Klebsiella pneumoniae and Pseudomonas aeruginosa . The calculated absorption coefficient images show important details of the bacteria, in particular for P. aeruginosa , in which membrane vesicles are clearly seen.
Binary TLBO algorithm assisted for designing plasmonic nano bi-pyramids-based absorption coefficient
NASA Astrophysics Data System (ADS)
Akhlaghi, Majid; Emami, Farzin; Nozhat, Najmeh
2014-07-01
A new efficient binary optimization method based on Teaching-Learning-Based Optimization (TLBO) algorithm is proposed to design an array of plasmonic nano bi-pyramids in order to achieve maximum absorption coefficient spectrum. In binary TLBO, a group of learners consisting of a matrix with binary entries controls the presence ('1') or the absence ('0') of nanoparticles in the array. Simulation results show that absorption coefficient strongly depends on the localized position of plasmonic nanoparticles. Non-periodic structures have more appropriate response in term of absorption coefficient. This approach is useful in optical applications such as solar cells and plasmonic nano antenna.
Pathlength determination for gas in scattering media absorption spectroscopy.
Mei, Liang; Somesfalean, Gabriel; Svanberg, Sune
2014-01-01
Gas in scattering media absorption spectroscopy (GASMAS) has been extensively studied and applied during recent years in, e.g., food packaging, human sinus monitoring, gas diffusion studies, and pharmaceutical tablet characterization. The focus has been on the evaluation of the gas absorption pathlength in porous media, which a priori is unknown due to heavy light scattering. In this paper, three different approaches are summarized. One possibility is to simultaneously monitor another gas with known concentration (e.g., water vapor), the pathlength of which can then be obtained and used for the target gas (e.g., oxygen) to retrieve its concentration. The second approach is to measure the mean optical pathlength or physical pathlength with other methods, including time-of-flight spectroscopy, frequency-modulated light scattering interferometry and the frequency domain photon migration method. By utilizing these methods, an average concentration can be obtained and the porosities of the material are studied. The last method retrieves the gas concentration without knowing its pathlength by analyzing the gas absorption line shape, which depends upon the concentration of buffer gases due to intermolecular collisions. The pathlength enhancement effect due to multiple scattering enables also the use of porous media as multipass gas cells for trace gas monitoring. All these efforts open up a multitude of different applications for the GASMAS technique. PMID:24573311
Pathlength Determination for Gas in Scattering Media Absorption Spectroscopy
Mei, Liang; Somesfalean, Gabriel; Svanberg, Sune
2014-01-01
Gas in scattering media absorption spectroscopy (GASMAS) has been extensively studied and applied during recent years in, e.g., food packaging, human sinus monitoring, gas diffusion studies, and pharmaceutical tablet characterization. The focus has been on the evaluation of the gas absorption pathlength in porous media, which a priori is unknown due to heavy light scattering. In this paper, three different approaches are summarized. One possibility is to simultaneously monitor another gas with known concentration (e.g., water vapor), the pathlength of which can then be obtained and used for the target gas (e.g., oxygen) to retrieve its concentration. The second approach is to measure the mean optical pathlength or physical pathlength with other methods, including time-of-flight spectroscopy, frequency-modulated light scattering interferometry and the frequency domain photon migration method. By utilizing these methods, an average concentration can be obtained and the porosities of the material are studied. The last method retrieves the gas concentration without knowing its pathlength by analyzing the gas absorption line shape, which depends upon the concentration of buffer gases due to intermolecular collisions. The pathlength enhancement effect due to multiple scattering enables also the use of porous media as multipass gas cells for trace gas monitoring. All these efforts open up a multitude of different applications for the GASMAS technique. PMID:24573311
Absorption coefficients for water vapor at 193 nm from 300 to 1073 K
NASA Technical Reports Server (NTRS)
Kessler, W. J.; Carleton, K. L.; Marinelli, W. J.
1993-01-01
Measurements of the water absorption coefficient at 193 nm from 300 to 1073 K are reported. The measurements were made using broadband VUV radiation and a monochromator-based detection system. The water vapor was generated by a saturator and metered into a flowing, 99 cm absorption cell via a water vapor mass flow meter. The 193 nm absorption coefficient measurements are compared to room temperature and high temperature shock tube measurements with good agreement. The absorption can be parameterized by a nu3 vibrational mode reaction coordinate and the thermal population of the nu3 mode.
Lawniczak, Michał; Hul, Oleh; Bauch, Szymon; Seba, Petr; Sirko, Leszek
2008-05-01
We present the results of an experimental and numerical study of the distribution of the reflection coefficient P(R) and the distributions of the imaginary P(v) and the real P(u) parts of the Wigner reaction K matrix for irregular fully connected hexagon networks (graphs) in the presence of strong absorption. In the experiment we used microwave networks, which were built of coaxial cables and attenuators connected by joints. In the numerical calculations experimental networks were described by quantum fully connected hexagon graphs. The presence of absorption introduced by attenuators was modeled by optical potentials. The distribution of the reflection coefficient P(R) and the distributions of the reaction K matrix were obtained from measurements and numerical calculations of the scattering matrix S of the networks and graphs, respectively. We show that the experimental and numerical results are in good agreement with the exact analytic ones obtained within the framework of random matrix theory. PMID:18643145
The scattering phase function coefficients of pulverized-coal particles in flames
Manickavasagam, S.; Menguec, M.P.
1992-12-31
The most significant mode of heat transfer in large-scale combustion systems is radiative transfer. To model such systems, radiation heat transfer should be accounted for correctly, which requires a thorough knowledge of the radiative properties of combustion products (Viskanta and Menguec, 1987; Menguec and Webb, 1992). It is usually difficult to calculate the properties of coal/char particles and soot agglomerates from theory, as they are non-homogeneous and irregularly shaped. Therefore, it is desirable to determine the effective radiative properties of these particles directly from experiments. The information available for the optical and radiative properties of burning coal/char particles in the infrared region of the wavelength spectrum is scarce. It is more desirable to estimate the effective parameters required in the solution of the radiative transfer equation (RTE), i.e., the absorption and scattering coefficients and the scattering phase function of coal and char particles. In the present study, we determined the scattering characteristics of pulverized-coal particles heated in a premixed flame directly from experiments. The details of the theoretical models considered for data reduction were already reported in another paper (Menguec, et al., 1991). In the following sections, first we will briefly discuss the experimental system used. After that the results will be presented and compared against those obtained from the Lorenz-Mie theory for spherical particles.
Martelli, Fabrizio; Zaccanti, Giovanni
2007-01-22
In spite of many progresses achieved both with theories and with experiments in studying light propagation through diffusive media, a reliable method for accurate measurements of the optical properties of diffusive media at NIR wavelengths is, in our opinion, still missing. It is therefore difficult to create a diffusive medium with well known optical properties to be used as a reference. In this paper we describe a method to calibrate the reduced scattering coefficient, mu'(s) , of a liquid diffusive medium and the absorption coefficient, mu(a), of an absorbing medium with a standard error smaller than 2% both on mu'(s) and on mu(a). The method is based on multidistance measurements of fluence into an infinite medium illuminated by a CW source. The optical properties are retrieved with simple inversion procedures (linear fits) exploiting the knowledge of the absorption coefficient of the liquid into which the diffuser and the absorber are dispersed. In this study Intralipid diluted in water has been used as diffusive medium and Indian ink as absorber. For a full characterization of these media measurements of collimated transmittance have also been carried out, from which the asymmetry factor of the scattering function of Intralipid and the single scattering albedo of Indian ink have been determined. PMID:19532267
Absorption and scattering of laser radiation by the diffusion flame of aviation kerosene
Gvozdev, S V; Glova, A F; Dubrovskii, V Yu; Durmanov, S T; Krasyukov, A G; Lysikov, A Yu; Smirnov, G V; Solomakhin, V B
2012-04-30
The absorption coefficient of the radiation of a repetitively pulsed Nd : YAG laser with an average output power up to 6 W and of a cw ytterbium optical fibre laser with an output power up to 3 kW was measured in the diffusion flame of aviation kerosene burning on a free surface in the atmospheric air. The absorption coefficient as a function of flame length, radiation power, and radiation intensity, which was varied in the {approx}10{sup 3} - 5 Multiplication-Sign 10{sup 4} W cm{sup -2} range, was obtained for two distances (1 and 2 cm) between the laser beam axis and the surface. The coefficient of radiation absorption by kerosene flame was compared with that in ethanol and kerosene - ethanol mixture flames. The radiation power scattered by a small segment of the kerosene flame irradiated by Nd : YAG laser radiation was measured as a function of longitudinal and azimuthal coordinates. An estimate was made of the total scattered radiation power.
Moore, Travis J; Jones, Matthew R
2015-02-20
Knowledge of the spectral absorption coefficient of fused silica optical fibers is important in modeling heat transfer in the processes and applications in which these fibers are used. An experimental method used to measure the spectral absorption coefficient of optical fibers is presented. Radiative energy from a blackbody radiator set at different temperatures is directed through the optical fibers and into an FTIR spectrometer. Spectral instrument response functions are calculated for different fiber lengths. The ratios of the slopes of the instrument response functions for the different lengths of fibers are used to solve for the spectral absorption coefficient of the fibers. The spectral absorption coefficient of low OH pure fused silica optical fibers is measured between the wavelengths 1.5 and 2.5 μm. PMID:25968202
NASA Technical Reports Server (NTRS)
Billman, K. W.; Rowley, P. D.; Stallcop, J. R.; Presley, L.
1974-01-01
The absorption coefficients of 0.633-, 1.15-, and 3.39-micron laser radiation for a homogeneous H-He plasma have been measured in the temperature range from 12.2 to 21.7 (x 1000 K) and in the electron number density range 0.45 to 6.5 (x 10 to the 17th power per cu cm). Good agreement is found between the experimentally determined total absorption for each of the wavelengths and that calculated from theory. Furthermore, because the 3.39-micron absorption is dominated by inverse bremsstrahlung, while the 0.633-micron absorption is dominated by photoionization and resonance absorption, the experiment indicates a correct assessment by the theory of these individual absorption mechanisms.
Levine, Zachary H.; Grantham, Steven; Tarrio, Charles; Paterson, David J.; McNulty, Ian; Levin, T. M.; Ankudinov, Alexei L.; Rehr, John J.
2003-01-01
The mass absorption coefficients of tungsten and tantalum were measured with soft x-ray photons from 1450 eV to 2350 eV using an undulator source. This region includes the M3, M4, and M5 absorption edges. X-ray absorption fine structure was calculated within a real-space multiple scattering formalism; the predicted structure was observed for tungsten and to a lesser degree tantalum as well. Separately, the effects of dynamic screening were observed as shown by an atomic calculation within the relativistic time-dependent local-density approximation. Dynamic screening effects influence the spectra at the 25 % level and are observed for both tungsten and tantalum. We applied these results to characterize spatially-resolved spectra of a tungsten integrated circuit interconnect obtained using a scanning transmission x-ray microscope. The results indicate tungsten fiducial markers were deposited into silica trenches with a depths of 50 % and 60 % of the markers’ heights.
Hoge, F E; Wright, C W; Lyon, P E; Swift, R N; Yungel, J K
1999-12-20
Oceanic radiance model inversion methods are used to develop a comprehensive algorithm for retrieval of the absorption coefficients of phycourobilin (PUB) pigment, type I phycoerythrobilin (PEB) pigment rich in PUB, and type II PEB deficient in PUB pigment (together with the usual "big three" inherent optical properties: the total backscattering coefficient and the absorption coefficients of chromophoric dissolved organic matter (CDOM)-detritus and phytoplankton). This fully modeled inversion algorithm is then simplified to yield a hybrid modeled-unmodeled inversion algorithm in which the phycoerythrin (PE) absorption coefficient is retrieved as unmodeled 488-nm absorption (which exceeds the modeled phytoplankton and the CDOM-detritus absorption coefficients). Each algorithm was applied to water-leaving radiances, but only hybrid modeled-unmodeled inversions yielded viable retrievals of the PE absorption coefficient. Validation of the PE absorption coefficient retrieval was achieved by relative comparison with airborne laser-induced PEB fluorescence. The modeled-unmodeled retrieval of four inherent optical properties by direct matrix inversion is rapid and well conditioned, but the accuracy is strongly limited by the accuracy of the three principal inherent optical property models across all four spectral bands. Several research areas are identified to enhance the radiance-model-based retrievals: (a) improved PEB and PUB absorption coefficient models, (b) PE spectral shifts induced by PUB chromophore substitution at chromophore binding sites, (c) specific absorption-sensitive phytoplankton absorption modeling, (d) total constituent backscattering modeling, (e) unmodeled carotinoid and phycocyanin absorption that are not now accounted for in the chlorophyll-dominated phytoplankton absorption coefficient model, and (f) iterative inversion techniques to solve for six constituents with only five radiances. Although considerable progress has been made toward the
NASA Astrophysics Data System (ADS)
Hoge, Frank E.; Wright, C. Wayne; Lyon, Paul E.; Swift, Robert N.; Yungel, James K.
1999-12-01
Oceanic radiance model inversion methods are used to develop a comprehensive algorithm for retrieval of the absorption coefficients of phycourobilin (PUB) pigment, type I phycoerythrobilin (PEB) pigment rich in PUB, and type II PEB deficient in PUB pigment (together with the usual big three inherent optical properties: the total backscattering coefficient and the absorption coefficients of chromophoric dissolved organic matter (CDOM) detritus and phytoplankton). This fully modeled inversion algorithm is then simplified to yield a hybrid modeled unmodeled inversion algorithm in which the phycoerythrin (PE) absorption coefficient is retrieved as unmodeled 488-nm absorption (which exceeds the modeled phytoplankton and the CDOM detritus absorption coefficients). Each algorithm was applied to water-leaving radiances, but only hybrid modeled unmodeled inversions yielded viable retrievals of the PE absorption coefficient. Validation of the PE absorption coefficient retrieval was achieved by relative comparison with airborne laser-induced PEB fluorescence. The modeled unmodeled retrieval of four inherent optical properties by direct matrix inversion is rapid and well conditioned, but the accuracy is strongly limited by the accuracy of the three principal inherent optical property models across all four spectral bands. Several research areas are identified to enhance the radiance-model-based retrievals: (a) improved PEB and PUB absorption coefficient models, (b) PE spectral shifts induced by PUB chromophore substitution at chromophore binding sites, (c) specific absorption-sensitive phytoplankton absorption modeling, (d) total constituent backscattering modeling, (e) unmodeled carotinoid and phycocyanin absorption that are not now accounted for in the chlorophyll-dominated phytoplankton absorption coefficient model, and (f) iterative inversion techniques to solve for six constituents with only five radiances. Although considerable progress has been made toward the satellite
Fang, Zhen-Huan; Fu, Xia-Ping; He, Xue-Ming
2016-06-01
For a quantitative understanding of light interaction with fruit tissue, it is critical to obtain two fundamental parameters: the absorption coefficient and the scattering coefficient of the tissue. This study was to investigate the optical properties of kiwifruit tissue at the wavelength of 632.8 nm. The total reflectance and total transmittance of kiwifruit tissue from three parts (including the flesh part, the seed part, and the seed-base part) were measured using a single integrating sphere system. Based on the measured spectral signals, the absorption coefficient μa and the reduced scattering coefficient μs' of kiwifruit tissue were calculated using the inverse adding-doubling (IAD) method. Phantoms made from Intralipid 20% and India ink as well as a Biomimic solid phantom were used for system validation. The mean values of μa and μs' of different parts of the kiwifruit were 0.031-0.308 mm(-1) and 0.120-0.946 mm(-1), respectively. The results showed significant differences among the μa and μs' of the three parts of the kiwifruit. The results of this study confirmed the importance of studying the optical properties for a quantitative understanding of light interaction with fruit tissue. Further investigation of fruit optical properties will be extended to a broader spectral region and different kinds of fruits. PMID:27256682
Fang, Zhen-huan; Fu, Xia-ping; He, Xue-ming
2016-01-01
For a quantitative understanding of light interaction with fruit tissue, it is critical to obtain two fundamental parameters: the absorption coefficient and the scattering coefficient of the tissue. This study was to investigate the optical properties of kiwifruit tissue at the wavelength of 632.8 nm. The total reflectance and total transmittance of kiwifruit tissue from three parts (including the flesh part, the seed part, and the seed-base part) were measured using a single integrating sphere system. Based on the measured spectral signals, the absorption coefficient μ a and the reduced scattering coefficient μ s' of kiwifruit tissue were calculated using the inverse adding-doubling (IAD) method. Phantoms made from Intralipid 20% and India ink as well as a Biomimic solid phantom were used for system validation. The mean values of μ a and μ s' of different parts of the kiwifruit were 0.031–0.308 mm−1 and 0.120–0.946 mm−1, respectively. The results showed significant differences among the μ a and μ s' of the three parts of the kiwifruit. The results of this study confirmed the importance of studying the optical properties for a quantitative understanding of light interaction with fruit tissue. Further investigation of fruit optical properties will be extended to a broader spectral region and different kinds of fruits. PMID:27256682
Zerrad, M; Soriano, G; Ghabbach, A; Amra, C
2013-02-11
We show how disordered media allow to increase the local degree of polarization (DOP) of an arbitrary (partial) polarized incident beam. The role of cross-scattering coefficients is emphasized, together with the probability density functions (PDF) of the scattering DOP. The average DOP of scattering is calculated versus the incident illumination DOP. PMID:23481735
NASA Astrophysics Data System (ADS)
Hirasawa, T.; Ishihara, M.; Tsujita, K.; Hirota, K.; Irisawa, K.; Kitagaki, M.; Fujita, M.; Kikuchi, M.
2012-02-01
In photo-acoustic (PA) imaging, valuable medical applications based on optical absorption spectrum such as contrast agent imaging and blood oxygen saturation measurement have been investigated. In these applications, there is an essential requirement to determine optical absorption coefficients accurately. In present, PA signal intensities have been commonly used to determine optical absorption coefficients. This method achieves practical accuracy by combining with radiative transfer analysis. However, time consumption of radiative transfer analysis and effects of signal generation efficiencies were problems of this method. In this research, we propose a new method to determine optical absorption coefficients using continuous wavelet transform (CWT). We used CWT to estimate instantaneous frequencies of PA signals which reflects optical absorption distribution. We validated the effectiveness of CWT in determination of optical absorption coefficients through an experiment. In the experiment, planar shaped samples were illuminated to generate PA signal. The PA signal was measured by our fabricated PA probe in which an optical fiber and a ring shaped P(VDFTrFE) ultrasound sensor were coaxially aligned. Optical properties of samples were adjusted by changing the concentration of dye solution. Tunable Ti:Sapphire laser (690 - 1000 nm) was used as illumination source. As a result, we confirmed strong correlation between optical absorption coefficients of samples and the instantaneous frequency of PA signal obtained by CWT. Advantages of this method were less interference of light transfer and signal generation efficiency.
Experiment to Determine the Absorption Coefficient of Gamma Rays as a Function of Energy.
ERIC Educational Resources Information Center
Ouseph, P. J.; And Others
1982-01-01
Simpler than x-ray diffractometer experiments, the experiment described illustrates certain concepts regarding the interaction of electromagnetic rays with matter such as the exponential decrease in the intensity with absorber thickness, variation of the coefficient of absorption with energy, and the effect of the K-absorption edge on the…
Tunable diode laser measurements of HO2NO2 absorption coefficients near 12.5 microns
NASA Technical Reports Server (NTRS)
May, R. D.; Molina, L. T.; Webster, C. R.
1988-01-01
A tunable diode laser spectrometer has been used to measure absorption coefficients of peroxynitric acid (HO2NO2) near the 803/cm Q branch. HO2NO2 concentrations in a low-pressure flowing gas mixture were determined from chemical titration procedures and UV absorption spectroscopy. The diode laser measured absorption coefficients, at a spectral resolution of better than 0.001/cm, are about 10 percent larger than previous Fourier transform infrared measurements made at a spectral resolution of 0.06/cm.
Hessler, J.P.; Ogren, P.J.
1992-08-31
A technique was developed for determining relative importance and correlation between reactions making up a complex kinetic system. This technique was used to investigate measurements of optical absorption cross sections and the correlation between cross sections and measured rate coefficients. It is concluded that (1) species, initial conditions, and temporal regions may be identified where cross sections may be measured without interference from the kinetic behavior of the observed species and (2) experiments designed to measure rate coefficients will always be correlated with the absorption cross section of the observed species. This correlation may reduce the accuracy of rate coefficient measurements.
A reverberation room round robin on the determination of absorption coefficients
NASA Astrophysics Data System (ADS)
Kath, U.
In ten reverberation rooms with very different volumes and different room shapes, the absorption coefficients for mineral fiber mat were measured. The particular feature of this round robin was that the absorption material was much thicker than in other similar experiments and that it was measured not only with an area of 12 sq m on the floor, but also as a complete surface covering of a small wall in order to avoid the edge effect. The decay curves were evaluated in at least two institutions and the absorption coefficients were calculated using the Eyring equation. The absorption coefficients were quite dispersed from one room to another and also from one-third octave band to the adjacent ones. Errors due to change are small, thus one is dealing with systematic errors.
NASA Technical Reports Server (NTRS)
Wan, Zhengming; Dozier, Jeff
1992-01-01
The effect of temperature-dependent molecular absorption coefficients on thermal infrared spectral signatures measured from satellite sensors is investigated by comparing results from the atmospheric transmission and radiance codes LOWTRAN and MODTRAN and the accurate multiple scattering radiative transfer model ATRAD for different atmospheric profiles. The sensors considered include the operational NOAA AVHRR and two research instruments planned for NASA's Earth Observing System (EOS): MODIS-N (Moderate Resolution Imaging Spectrometer-Nadir-Mode) and ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer). The difference in band transmittance is as large as 6 percent for some thermal bands within atmospheric windows and more than 30 percent near the edges of these atmospheric windows. The effect of temperature-dependent molecular absorption coefficients on satellite measurements of sea-surface temperature can exceed 0.6 K. Quantitative comparison and factor analysis indicate that more accurate measurements of molecular absorption coefficients and better radiative transfer simulation methods are needed to achieve SST accuracy of 0.3 K, as required for global numerical models of climate, and to develop land-surface temperature algorithms at the 1-K accuracy level.
Nonlinear absorption coefficient of pulsed laser deposited MgZnO thin film
Agrawal, Arpana Dar, Tanveer A.; Solanki, Ravi; Sen, Pratima; Phase, D. M.
2015-06-24
We report the imaginary part of 3{sup rd} order nonlinear susceptibility and the nonlinear absorption coefficient of Mg doped ZnO thin film using standard Z-scan technique. The origin of nonlinear absorption is attributed to the two photon absorption followed by the free carrier absorption because of the presence of oxygen vacancy defects. We have also confirmed the experimental results with the theoretical results obtained by considering the steady state response of a two level atom with the monochromatic field models.
Finlay, Jarod C.; Zhu, Timothy C; Dimofte, Andreea; Stripp, Diana; Malkowicz, S. Bruce; Whittington, Richard; Miles, Jeremy; Glatstein, Eli; Hahn, Stephen M.
2015-01-01
A continuing challenge in photodynamic therapy is the accurate in vivo determination of the optical properties of the tissue being treated. We have developed a method for characterizing the absorption and scattering spectra of prostate tissue undergoing PDT treatment. Our current prostate treatment protocol involves interstitial illumination of the organ via cylindrical diffusing optical fibers (CDFs) inserted into the prostate through clear catheters. We employ one of these catheters to insert an isotropic white light point source into the prostate. An isotropic detection fiber connected to a spectrograph is inserted into a second catheter a known distance away. The detector is moved along the catheter by a computer-controlled step motor, acquiring diffuse light spectra at 2 mm intervals along its path. We model the fluence rate as a function of wavelength and distance along the detector’s path using an infinite medium diffusion theory model whose free parameters are the absorption coefficient µa at each wavelength and two variables A and b which characterize the reduced scattering spectrum of the form µ’s = Aλ−b. We analyze our spectroscopic data using a nonlinear fitting algorithm to determine A, b, and µa at each wavelength independently; no prior knowledge of the absorption spectrum or of the sample’s constituent absorbers is required. We have tested this method in tissue simulating phantoms composed of intralipid and the photosensitizer motexafin lutetium (MLu). The MLu absorption spectrum recovered from the phantoms agrees with that measured in clear solution, and µa at the MLu absorption peak varies linearly with concentration. The µ’s spectrum reported by the fit is in agreement with the known scattering coefficient of intralipid. We have applied this algorithm to spectroscopic data from human patients sensitized with MLu (2 mg kg−1) acquired before and after PDT. Before PDT, the absorption spectra we measure include the characteristic
Velocity space scattering coefficients with applications in antihydrogen recombination studies
Chang; Ordonez
2000-12-01
An approach for calculating velocity space friction and diffusion coefficients with Maxwellian field particles is developed based on a kernel function derived in a previous paper [Y. Chang and C. A. Ordonez, Phys. Plasmas 6, 2947 (1999)]. The original fivefold integral expressions for the coefficients are reduced to onefold integrals, which can be used for any value of the Coulomb logarithm. The onefold integrals can be further reduced to standard analytical expressions by using a weak coupling approximation. The integral expression for the friction coefficient is used to predict a time scale that describes the rate at which a reflecting antiproton beam slows down within a positron plasma, while both species are simultaneously confined by a nested Penning trap. The time scale is used to consider the possibility of achieving antihydrogen recombination within the trap. The friction and diffusion coefficients are then used to derive an expression for calculating the energy transfer rate between antiprotons and positrons. The expression is employed to illustrate achieving antihydrogen recombination while taking into account positron heating by the antiprotons. The effect of the presence of an electric field on recombination is discussed. PMID:11138156
Compton scattering from nuclei and photo-absorption sum rules
NASA Astrophysics Data System (ADS)
Gorchtein, Mikhail; Hobbs, Timothy; Londergan, J. Timothy; Szczepaniak, Adam P.
2011-12-01
We revisit the photo-absorption sum rule for real Compton scattering from the proton and from nuclear targets. In analogy with the Thomas-Reiche-Kuhn sum rule appropriate at low energies, we propose a new “constituent quark model” sum rule that relates the integrated strength of hadronic resonances to the scattering amplitude on constituent quarks. We study the constituent quark model sum rule for several nuclear targets. In addition, we extract the α=0 pole contribution for both proton and nuclei. Using the modern high-energy proton data, we find that the α=0 pole contribution differs significantly from the Thomson term, in contrast with the original findings by Damashek and Gilman.
Scattering coefficients and gray-body factor for 1D BEC acoustic black holes: Exact results
NASA Astrophysics Data System (ADS)
Fabbri, Alessandro; Balbinot, Roberto; Anderson, Paul R.
2016-03-01
A complete set of exact analytic solutions to the mode equation is found in the region exterior to the acoustic horizon for a class of 1D Bose-Einstein condensate acoustic black holes. From these, analytic expressions for the scattering coefficients and gray-body factor are obtained. The results are used to verify previous predictions regarding the behaviors of the scattering coefficients and gray-body factor in the low-frequency limit.
NASA Astrophysics Data System (ADS)
Liu, Qiang; Huang, Hong-Hua; Wang, Yao; Wang, Gui-Shi; Cao, Zhen-Song; Liu, Kun; Chen, Wei-Dong; Gao, Xiao-Ming
2014-06-01
The atmospheric aerosol absorption capacity is a critical parameter determining its direct and indirect effects on climate. Accurate measurement is highly desired for the study of the radiative budget of the Earth. A multi-wavelength (405 nm, 532 nm, 780 nm) aerosol absorption meter based on photoacoustic spectroscopy (PAS) invovling a single cylindrical acoustic resonator is developed for measuring the aerosol optical absorption coefficients (OACs). A sensitivity of 1.3 Mm-1 (at 532 nm) is demonstrated. The aerosol absorption meter is successfully tested through measuring the OACs of atmospheric nigrosin and ambient aerosols in the suburbs of Hefei city. The absorption cross section and absorption Ångström exponent (AAE) for ambient aerosol are determined for characterizing the component of the ambient aerosol.
Minority carrier diffusion lengths and absorption coefficients in silicon sheet material
NASA Technical Reports Server (NTRS)
Dumas, K. A.; Swimm, R. T.
1980-01-01
Most of the methods which have been developed for the measurement of the minority carrier diffusion length of silicon wafers require that the material have either a Schottky or an ohmic contact. The surface photovoltage (SPV) technique is an exception. The SPV technique could, therefore, become a valuable diagnostic tool in connection with current efforts to develop low-cost processes for the production of solar cells. The technique depends on a knowledge of the optical absorption coefficient. The considered investigation is concerned with a reevaluation of the absorption coefficient as a function of silicon processing. A comparison of absorption coefficient values showed these values to be relatively consistent from sample to sample, and independent of the sample growth method.
NASA Astrophysics Data System (ADS)
O'Brien, J. J.
2002-09-01
The absorption spectrum of methane has been recorded in the visible to near-IR region using the intracavity laser spectroscopy technique. Spectra are recorded at high spectral resolution for narrow overlapping intervals in the region for room and 77 K temperature methane samples. After spectra are deconvolved for the instrument function, absorption coefficients are derived. These will be presented (750-940 nm for room temperature methane; 850-920 nm for 77 K methane) and compared with results reported by other workers. Future work in this area also will be indicated. Support from NASA's Planetary Atmospheres Program (NAG5-6091 and a Major Equipment Grant) is gratefully acknowledged.
Measurement of nanofluids absorption coefficient by Moiré deflectometry technique
NASA Astrophysics Data System (ADS)
Madanipour, Khosro; Koohian, Ataollah; Shahrabi Farahani, Shahrzad
2015-05-01
Nanoparticles exhibit many unique and interesting optical properties which make them very useful in biomedical applications. In order to employ NPs for disease treatment, comprehensive knowledge of their important properties is crucial. One of these parameters is absorption coefficient. In this work, absorption coefficient of a nanofluid (Au nanoparticles in water) is measured by using Moiré deflectometry technique. Two laser beams are used: a comparatively high intensity laser beam as interacting beam and a low intensity as a probe beam. This method is fast, easy and nonscanning, also insensitive to vibrations.
[Obtaining aerosol backscattering coefficient using pure rotational Raman-Mie scattering spectrum].
Rong, Wei; Chen, Si-Ying; Zhang, Yin-Chao; Chen, He; Guo, Pan
2012-11-01
Both the traditional Klett and Fernald methods used to obtain atmospheric aerosol backscattering coefficient require the hypothesis of relationship between the extinction coefficient and backscattering coefficient, and this will bring error. According to the theory that the pure rotational Raman backscattering coefficient is only related to atmospheric temperature and pressure, a new method is presented for inverting aerosol backscattering coefficient, which needed the intensity of elastic scattering and rotational Raman combined with atmospheric temperature and pressure obtained with the sounding balloons in this article. This method can not only eliminate the errors of the traditional Klett and Fernald methods caused by the hypothesis, but also avoid the error caused by the correction of the overlap. Finally, the aerosol backscattering coefficient was acquired by using this method and the data obtained via the Raman-Mie scattering Lidar of our lab. And the result was compared with that of Klett and Fernald. PMID:23387171
NASA Astrophysics Data System (ADS)
Yahya, I.; Kusuma, J. I.; Harjana; Kristiani, R.; Hanina, R.
2016-02-01
This paper emphasizes the influence of tubular shaped microresonators phononic crystal insertion on the sound absorption coefficient of profiled sound absorber. A simple cubic and two different bodies centered cubic phononic crystal lattice model were analyzed in a laboratory test procedure. The experiment was conducted by using transfer function based two microphone impedance tube method refer to ASTM E-1050-98. The results show that sound absorption coefficient increase significantly at the mid and high-frequency band (600 - 700 Hz) and (1 - 1.6 kHz) when tubular shaped microresonator phononic crystal inserted into the tested sound absorber element. The increment phenomena related to multi-resonance effect that occurs when sound waves propagate through the phononic crystal lattice model that produce multiple reflections and scattering in mid and high-frequency band which increases the sound absorption coefficient accordingly
NASA Astrophysics Data System (ADS)
Paredes-Miranda, G.; Arnott, W. P.; Gaffney, J. S.; Marley, N. A.; Campbell, D.; Fujita, E.
2007-12-01
Aerosol light scattering and absorption measurements were deployed in and near Mexico City in March 2006 as part of the Megacity Impacts on Regional and Global Environments (MIRAGE). The primary site in Mexico City was an urban site at Instituto Mexicano del Petroleo (Mexican Oil Institute, denoted by IMP). Similar campaigns were held in Las Vegas, NV in January-February, 2003; and Los Angeles, CA at numerous sites during all seasons from 2003 through 2007. The IMP site gave in-situ characterization of the Mexico City plume under favorable wind conditions. The photoacoustic instrument (PAS) used at IMP operates at 532 nm, and conveniently allowed for characterization of gaseous absorption at this wavelength as well. Light scattering measurements are accomplished within the PAS by the reciprocal nephelometery method. In Mexico City the aerosol absorption coefficient typically varies between 20 and 180 Mm-1 during the course of the day and significant diurnal variation of the aerosol single scattering albedo was observed probably as a consequence of secondary aerosol formation. We will present the diurnal variation of the scattering and absorption as well as the single scattering albedo and fraction of absorption due to gases at the IMP site and compare with Las Vegas diurnal variation. Mexico City 'breaths' more during the course of the day than Las Vegas, Nevada in part because the latitude of Mexico City resulted in more direct solar radiation. Further insight on the meteorological connections and population dynamics will be discussed.
NASA Astrophysics Data System (ADS)
Ladhaf, Bibifatima M.; Pawar, Pravina P.
2015-04-01
We measured here the mass attenuation coefficients (μ/ρ) of carbohydrates, Esculine (C15H16O9), Sucrose (C12H22O11), Sorbitol (C6H14O6), D-Galactose (C6H12O6), Inositol (C6H12O6), D-Xylose (C5H10O5) covering the energy range from 122 keV up to 1330 keV photon energies by using gamma ray transmission method in a narrow beam good geometry set-up. The gamma-rays were detected using NaI(Tl) scintillation detection system with a resolution of 8.2% at 662 keV. The attenuation coefficient data were then used to obtain the total attenuation cross-section (σtot), molar extinction coefficients (ε), mass-energy absorption coefficients (μen/ρ) and effective (average) atomic energy-absorption cross section (σa,en) of the compounds. These values are found to be in good agreement with the theoretical values calculated based on XCOM data.
Photoacoustic measurements of black carbon light absorption coefficients in Irbid city, Jordan.
Hamasha, Khadeejeh M; Arnott, W Patrick
2010-07-01
There is a need to recognize air pollution levels by particles, especially in developing countries such as Jordan where data are scarce due to the absence of routine monitoring of ambient air quality. This study aims at studying the air quality in different locations at Irbid, Jordan through the measurement and analysis of the time series of black carbon light absorption coefficients (B (abs)). Black carbon light absorption coefficients were measured with a photoacoustic instrument at a wavelength of 870 nm. The measurements were conducted during July 2007 at six sites in Irbid city, Jordan. Comparisons of black carbon concentrations at various locations were conducted to understand where values tend to be largest. The average value of B (abs) of all sites was 40.4 Mm(-1). The largest value of B (abs) was 61.2 Mm(-1) at Palestine Street which is located at a very crowded street in a highly populated region in the city center. The lowest value was 14.1 Mm(-1) at Thirtieth Street which is located at a main street in an open plain region in the east of the city. The black carbon light absorption coefficients fluctuate above a background level (transported black carbon from the neighboring states), which are almost identical at all sampling sites. The light absorption coefficients will be used as a benchmark in later years as combustion efficiencies and population patterns change. PMID:19479334
The average ion model. Computation of the absorption and emission coefficients in hot plasmas
NASA Astrophysics Data System (ADS)
Gauthier, Jean-Claude; Geindre, Jean-Paul
1988-06-01
A program was developed to evaluate the emission and absorption plasma coefficient variations as a function of the density, temperature and the atomic number of the specimen. The treatment is simplified because of the reduced number of characteristic frequencies which are necessary for the hydrodynamic code. The approach is less efficient when applied to high Z atoms.
NASA Astrophysics Data System (ADS)
Costabile, F.; Barnaba, F.; Angelini, F.; Gobbi, G. P.
2013-03-01
Characterizing chemical and physical aerosol properties is important to understand their sources, effects, and feedback mechanisms in the atmosphere. This study proposes a scheme to classify aerosol populations based on their spectral optical properties (absorption and scattering). The scheme is obtained thanks to the outstanding set of information on particle size and composition these properties contain. The spectral variability of the aerosol single scattering albedo (dSSA), and the extinction, scattering and absorption Angstrom exponents (EAE, SAE and AAE, respectively) were observed on the basis of two-year measurements of aerosol optical properties (scattering and absorption coefficients at blue, green and red wavelengths) performed in the suburbs of Rome (Italy). Optical measurements of various aerosol types were coupled to measurements of particle number size distributions and relevant optical properties simulations (Mie theory). These latter allowed the investigation of the role of the particle size and composition in the bulk aerosol properties observed. The combination of simulations and measurements suggested a general "paradigm" built on dSSA, SAE and AAE to optically classify aerosols. The paradigm proved suitable to identify the presence of key aerosol populations, including soot, biomass burning, organics, dust and marine particles. The work highlights that (i) aerosol populations show distinctive combinations of SAE and dSSA times AAE, these variables being linked by a linear inverse relation varying with varying SSA; (ii) fine particles show EAE > 1.5, whilst EAE < 2 is found for both coarse particles and ultrafine soot-rich aerosols; (iii) fine and coarse particles both show SSA > 0.8, whilst ultrafine urban Aitken mode and soot particles show SSA < 0.8. The proposed paradigm agrees with aerosol observations performed during past major field campaigns, this indicating that relations concerning the paradigm have a general validity.
NASA Astrophysics Data System (ADS)
Danan, Yossef; Ilovitsh, Tali; Liu, Danping; Pinhas, Hadar; Sinvani, Moshe; Ramon, Yehonatan; Azougi, Jonathan; Douplik, Alexandre; Zalevsky, Zeev
2016-03-01
In this paper we present gold nanoparticles coated with silicon that switch the order between the scattering and the absorption magnitude at the resonance peak and tune the plasmon resonance over the spectrum. This is obtained by modifying the refractive index of the silicon coating of the nanoparticle by illuminating it with a pumping light due to the plasma dispersion effect in silicon. We also report how changing the diffraction limited point spread function through the utilization of plasma dispersion effect of the above mentioned silicon coated nanoparticles allows doing imaging with sub wavelength resolution. The plasma dispersion effect can increase the absorption coefficient of the silicon, when illuminated with a focused laser beam and as explained above it can also tune the absorption versus scattering properties of the nanoparticle. Due to the Gaussian nature of the laser illumination which has higher intensity at its peak, the plasma dispersion effect is more significant at the center of the illumination. As a consequence, the reflected light from probe beam at the near infra-red region has a sub wavelength dip that overlaps with the location of the pump illumination peak. This dip has a higher spatial frequency than an ordinary Gaussian, which enables to achieve super resolution.
Liu, Qiang; Niu, Ming-Sheng; Wang, Gui-Shi; Cao, Zhen-Song; Liu, Kun; Chen, Wei-Dong; Gao, Xiao-Ming
2013-07-01
In the present paper, the authors focus on the effect of the resonance frequency shift due to the changes in temperature and humidity on the PA signal, present several methods to control the noise derived form gas flow and vibration from the sampling pump. Based on the efforts mentioned above, a detection limit of 1.4 x 10(-8) W x cm(-1) x Hz(-1/2) was achieved for the measurement of atmospheric aerosols absorption coefficient. During the experiments, the PA cell was calibrated with the absorption of standard NO2 gas at 532 nm and the atmospheric aerosols were measured continuously. The measurement results show that the PAS is suitable for the real-time measurement of the absorption coefficient of atmospheric aerosols in their natural suspended state. PMID:24059163
NASA Astrophysics Data System (ADS)
Utry, N.; Ajtai, T.; Pintér, M.; Tombácz, E.; Illés, E.; Bozóki, Z.; Szabó, G.
2014-09-01
Mass specific optical absorption coefficients of various mineral dust components including silicate clays (illite, kaolin and bentonite), oxides (quartz, hematite and rutile), and carbonate (limestone) were determined at wavelengths of 1064, 532, 355 and 266 nm. These values were calculated from aerosol optical absorption coefficients measured by a multi-wavelength photoacoustic (PA) instrument, the mass concentration and the number size distribution of the generated aerosol samples as well as the size transfer functions of the measuring instruments. These results are expected to have considerable importance in global radiative forcing calculations. They can also serve as reference for validating calculated wavelength dependent imaginary parts (κ) of complex refractive indices which up to now have been typically deduced from bulk phase measurements by using indirect measurement methods. Accordingly, the presented comparison of the measured and calculated aerosol optical absorption spectra revealed the strong need for standardized sample preparation and measurement methodology in case of bulk phase measurements.
Correction of radiation absorption on biological samples using Rayleigh to Compton scattering ratio
NASA Astrophysics Data System (ADS)
Pereira, Marcelo O.; Conti, Claudio de Carvalho; dos Anjos, Marcelino J.; Lopes, Ricardo T.
2012-06-01
The aim of this work was to develop a method to correct the absorbed radiation (the mass attenuation coefficient curve) in low energy (E < 30 keV) applied to a biological matrix based on the Rayleigh to Compton scattering ratio and the effective atomic number. For calibration, scattering measurements were performed on standard samples of radiation produced by a gamma-ray source of 241Am (59.54 keV) also applied to certified biological samples of milk powder, hay powder and bovine liver (NIST 1557B). In addition, six methods of effective atomic number determination were used as described in literature to determinate the Rayleigh to Compton scattering ratio (R/C), in order to calculate the mass attenuation coefficient. The results obtained by the proposed method were compared with those obtained using the transmission method. The experimental results were in good agreement with transmission values suggesting that the method to correct radiation absorption presented in this paper is adequate for biological samples.
Light Scattering and Absorption Studies of Sickle Cell Hemoglobin
NASA Astrophysics Data System (ADS)
Kim-Shapiro, Daniel
1997-11-01
The use of physical techniques has been very important in understanding the pathophysiology of sickle cell disease. In particular, light scattering and absorption studies have been used to measure the kinetics of sickle cell hemoglobin polymerization and depolymerization (melting). The theory of sickle cell polymerization that has been derived and tested by these methods has not only led to an increased understanding of the pathophysiology of the disease but has also led to improved treatment strategies. Sickle cell disease effects about 1 out of 600 people of African descent born in the United States. The disease is caused by a mutant form of hemoglobin (the oxygen transporting molecule in the blood), hemoglobin S (HbS), which differs from normal adult hemoglobin by the substitution of a single amino acid for another. The polymerization of HbS, which occurs under conditions of low oxygen pressure, causes distortion and increased rigidity of the sickle red blood cell that leads to blockage of the capillaries and a host of resulting complications. The disease is associated with tissue damage, severe painful crises and a high degree of mortality. Light scattering studies of purified HbS and whole cells (conducted by F.A. Ferrone, J. Hofrichter, W.A. Eaton, and their associates) have been used to determine the mechanism of HbS polymerization. Polymerization will generally not occur when the hemoglobin is in an oxygen-rich environment. The question is, when HbS is rapidly deoxygenated (as it is when going from the lungs to the tissues) what is the kinetics of polymerization? Photolysis methods were used to rapidly deoxygenate HbS and light scattering was used as a function of time to measure the kinetics of polymerization. Polarized light scattering may be a more effective way to measure polymer content than total intensity light scattering. It was found that no polymerization occurs during a period of time called the delay time and subsequent polymerization occurs
Spectra Aerosol Light Scattering and Absorption for Laboratory and Urban Aerosol
NASA Astrophysics Data System (ADS)
Gyawali, Madhu S.
Atmospheric aerosols considerably influence the climate, reduce visibility, and cause problems in human health. Aerosol light absorption and scattering are the important factors in the radiation transfer models. However, these properties are associated with large uncertainties in climate modeling. In addition, atmospheric aerosols widely vary in composition and size; their optical properties are highly wavelength dependent. This work presents the spectral dependence of aerosol light absorption and scattering throughout the ultraviolet to near-infrared regions. Data were collected in Reno, NV from 2008 to 2010. Also presented in this study are the aerosol optical and physical properties during carbonaceous aerosols and radiative effects study (CARES) conducted in Sacramento area during 2010. Measurements were made using photoacoustic instruments (PA), including a novel UV 355 nm PA of our design and manufacture. Comparative analyses are presented for three main categories: (1) aerosols produced by wildfires and traffic emissions, (2) laboratory-generated and wintertime ambient urban aerosols, and (3) urban plume and biogenic emissions. In these categories, key questions regarding the light absorption by secondary organic aerosols (SOA), so-called brown carbon (BrC), and black carbon (BC) will be discussed. An effort is made to model the emission and aging of urban and biomass burning aerosol by applying shell-core calculations. Multispectral PA measurements of aerosols light absorption and scattering coefficients were used to calculate the Angstrom exponent of absorption (AEA) and single scattering albedo (SSA). The AEA and SSA values were analyzed to differentiate the aerosol sources. The California wildfire aerosols exhibited strong wavelength dependence of aerosol light absorption with AEA as lambda -1 for 405 and 870 nm, in contrast to the relatively weak wavelength dependence of traffic emissions aerosols for which AEA varied approximately as lambda-1. By using
Absorption and Scattering Behavior of Nanofluids in the Visible Range
NASA Astrophysics Data System (ADS)
Eggers, Jan Rudolf; Kabelac, Stephan
2015-11-01
The use of plasmonic nanofluids in photothermal applications, such as solar thermal receivers, is a strong subject in current research. Additionally, other fields show interests in basefluids, of which the optical properties are tuned by adding nanoparticles. Exemplary research activities are plasmonic hyperthermia or nanoparticle-based sunscreen products. However, chosing the appropriate nanoparticle material is of great importance for the efficiency of such systems. The `classical' approach is to measure the absorption or scattering behavior of known nanofluids, followed by an estimation whether or not this fluid is suitable for the designated application. This paper shows up a different approach: a method is presented to be used as a guided search for a global optimal nanoparticle material for a certain task.
NASA Astrophysics Data System (ADS)
Chantler, C. T.
2000-07-01
Reliable knowledge of the complex x-ray form factor [Re(f ) and f″] and the photoelectric attenuation coefficient (σPE) is required for crystallography, medical diagnosis, radiation safety, and XAFS studies. Discrepancies between currently used theoretical approaches of 200% exist for numerous elements from 1 to 3 keV x-ray energies. The key discrepancies are due to the smoothing of edge structure, the use of nonrelativistic wave functions, and the lack of appropriate convergence of wave functions. This paper addresses these key discrepancies and derives new theoretical results of substantially higher accuracy in near-edge soft x-ray regions. The high-energy limitations of the current approach are also illustrated. The energy range covered is 0.1 to 10 keV. The associated figures and tabulation demonstrate the current comparison with alternate theory and with available experimental data. In general, experimental data are not sufficiently accurate to establish the errors and inadequacies of theory at this level. However, the best experimental data and the observed experimental structure as a function of energy are strong indicators of the validity of the current approach. New developments in experimental measurement hold great promise in making critical comparisons with theory in the near future.
Aerosol Light Absorption and Scattering Assessments and the Impact of City Size on Air Pollution
NASA Astrophysics Data System (ADS)
Paredes-Miranda, Guadalupe
The general problem of urban pollution and its relation to the city population is examined in this dissertation. A simple model suggests that pollutant concentrations should scale approximately with the square root of city population. This model and its experimental evaluation presented here serve as important guidelines for urban planning and attainment of air quality standards including the limits that air pollution places on city population. The model was evaluated using measurements of air pollution. Optical properties of aerosol pollutants such as light absorption and scattering plus chemical species mass concentrations were measured with a photoacoustic spectrometer, a reciprocal nephelometer, and an aerosol mass spectrometer in Mexico City in the context of the multinational project "Megacity Initiative: Local And Global Research Observations (MILAGRO)" in March 2006. Aerosol light absorption and scattering measurements were also obtained for Reno and Las Vegas, NV USA in December 2008-March 2009 and January-February 2003, respectively. In all three cities, the morning scattering peak occurs a few hours later than the absorption peak due to the formation of secondary photochemically produced aerosols. In particular, for Mexico City we determined the fraction of photochemically generated secondary aerosols to be about 75% of total aerosol mass concentration at its peak near midday. The simple 2-d box model suggests that commonly emitted primary air pollutant (e.g., black carbon) mass concentrations scale approximately as the square root of the urban population. This argument extends to the absorption coefficient, as it is approximately proportional to the black carbon mass concentration. Since urban secondary pollutants form through photochemical reactions involving primary precursors, in linear approximation their mass concentration also should scale with the square root of population. Therefore, the scattering coefficient, a proxy for particulate matter
Mitigation of scattering defect and absorption of DKDP crystals by laser conditioning.
Wang, Yueliang; Zhao, Yuanan; Hu, Guohang; Peng, Xiaocong; Chang, Junxiu; Xie, Xiaoyi; He, Jun; Guo, Meng; Shao, Jianda
2015-06-15
The variation of scattering and absorption in DKDP crystals by laser conditioning was investigated by combining light scattering technique and on-site transmittance measurement technique. Laser-induced disappearance of scattering defects was observed, and variation of transmittance was achieved. Using Mie theory, a kind of absorbing defects, aside from scattering defect, was discovered. Moreover, the experimental results demonstrated that the absorption of crystal could be mitigated by laser conditioning. PMID:26193600
NASA Astrophysics Data System (ADS)
Donnelly, Vincent M.; Belostotskiy, Sergey G.; Economou, Demetre J.; Sadeghi, Nader
2010-05-01
Laser scattering experiments were performed in high pressure (100s of Torr) parallel-plate, slot-type DC microdischarges operating in argon or nitrogen. Laser Thomson Scattering (LTS) and Rotational Raman Scattering were employed in a novel, backscattering, confocal configuration. LTS allows direct and simultaneous measurement of both electron density (ne) and electron temperature (Te). For 50 mA current and over the pressure range of 300 - 700 Torr, LTS yielded Te = 0.9 ± 0.3 eV and ne = (6 ± 3)·1013 cm-3, in reasonable agreement with the predictions of a mathematical model. Rotational Raman spectroscopy (RRS) was employed for absolute calibration of the LTS signal. RRS was also applied to measure the 3D gas temperature (Tg) in nitrogen DC microdischarges. In addition, diode laser absorption spectroscopy was employed to measure the density of argon metastables (1s5 in Paschen notations) in argon microdischarges. The gas temperature, extracted from the width of the absorption profile, was compared with Tg values obtained by optical emission spectroscopy.
Temperature- and pressure-dependent absorption coefficients for CO2 and O2 at 193 nm
NASA Astrophysics Data System (ADS)
Hartinger, K. T.; Nord, S.; Monkhouse, P. B.
Absorption of laser radiation at 193 nm by CO2 and O2 was studied at a series of different temperatures up to 1273 K and pressures up to 1 bar. The spectrum for CO2 was found to be broadband, so that absorption could be fitted to a Beer-Lambert law. On the other hand, the corresponding O2 spectrum is strongly structured and parameterisation requires a more complex relation, depending on both temperature and the product (pressure × absorption path length). In this context, the influence of spectral structure on the resulting spectrally integrated absorption coefficients is discussed. Using the fitting parameters obtained, effective transmissions at 193 nm can be calculated for a wide range of experimental conditions. As an illustration of the practical application of these data, the calculation of effective transmission for a typical industrial flue gas is described.
NASA Astrophysics Data System (ADS)
Goela, P.; Icely, J.; Cristina, S.; Newton, A.
2010-12-01
Variability of particulate absorption coefficients was studied off the south-west coast of Portugal, as part of a validation exercise for the Medium Resolution Image Spectrometer Sensor. Regular sampling campaigns occurred at three stations on a transect from inshore to offshore to compare fluctuations in these coefficients at the local scale. Transmittance-reflectance method with sodium hypochlorite bleaching was used to determine absorption coefficients for phytoplankton and non-algal particles. Photosynthetic pigment concentrations were determined by High Performance Liquid Chromatography. Results show that the absorption of light by particulate matter is almost totally dependent on the phytoplankton, with no significant contribution from non-algal particles, both in coastal and oceanic waters. Specific phytoplankton coefficients show significant fluctuations between seasons and stations, ranging from 0.012 to 0.038 at 678 nm. Particulate absorption is dominant over dissolved absorption. The variations in the coefficients of absorption are analysed as a function of species assemblages.
NASA Astrophysics Data System (ADS)
Wichmann, Janine; Janssen, Nicole A. H.; van der Zee, Saskia; Brunekreef, Bert
Population studies indicate that study participants living near major roads are more prone to chronic respiratory symptoms, lung function decrements and hospital admissions for asthma. The majority of the studies used proxy measures, such as distance to major roads or traffic intensity in the surroundings of the home. Few studies have communicated findings of concurrently performed measurements of outdoor, indoor and personal air pollution in urban streets with high- and low-traffic density. Measuring light absorption or reflectance of particulate matter (PM) collected on filters is an alternative method to determine elemental carbon, a marker for particles produced by incomplete combustion, compared to expensive and destructive analytical methods. This study sets out to test the null hypothesis that there is no difference in personal and indoor filter absorption coefficients for participants living along busy and quiet roads in Amsterdam. In one study we measured personal and indoor absorption coefficients in a sample of adults (50-70 years) and, in another study, the indoor levels in a population of adults (50-70 years) and school children (10-12 years). In the first study, the ratios of personal and indoor absorption coefficients in homes along busy roads compared with homes on quiet streets were significantly higher by 29% for personal measurements ( n=16 days, p<0.001), and by 19% for indoor measurements ( n=20, p<0.001), while in the second study, the ratio for the indoor measurements was higher by 26% ( n=25 days, p<0.05). Exposure differences between homes along busy compared to homes along quiet streets remained and significant after adjustment for potential indoor sources (such as cooking and use of unvented heating appliances). This study therefore provides tentative support for the use of the type of road as proxy measure for indoor and personal absorption coefficient measurements in epidemiological studies due to the limitations of the study.
View From a Megacity: Aerosol Light Absorption and Scattering at Four Sites in and Near Mexico City.
NASA Astrophysics Data System (ADS)
Paredes-Miranda, G.; Arnott, W. P.; Gaffney, J. S.; Marley, N. A.
2006-12-01
As part of the Megacity Impacts on Regional and Global Environments, MIRAGE-Mex deployment to Mexico City in the period of 30 days, March 2006, a suite of photoacoustic spectrometers (PAS) were installed to measure at ground level the light absorption and scattering by aerosols at four sites: an urban site at Instituto Mexicano del Petroleo (Mexican Oil Institute, denoted by IMP), a suburban site at the Technological University of Tecamac, a rural site at "La Biznaga" ranch, and a site at the Paseo de Cortes (altitude 3,810 meters ASL) in the rural area above Amecameca in the State of Mexico, on the saddle between the volcanoes Popocatepetl and Iztaccihuatl. The IMP site gave in-situ characterization of the Mexico City plume under favorable wind conditions while the other sites provided characterization of the plume, mixed in with any local sources. The second and third sites are north of Mexico City, and the fourth site is south. The PAS used at IMP operates at 532 nm, and conveniently allowed for characterization of gaseous absorption at this wavelength as well. Instruments at the second and third sites operate at 870 nm, and the one at the fourth site at 780 nm. Light scattering measurements are accomplished within the PAS by the reciprocal nephelometery method. In the urban site the aerosol absorption coefficient typically varies between 40 and 250 Mm-1 during the course of the day and significant diurnal variation of the aerosol single scattering albedo was observed. Comparisons with TSI nephelometer scattering and Aetholemeter absorption measurements at the T0 site will be presented. We will present a broad overview of the diurnal variation of the scattering and absorption as well as the single scattering albedo and fraction of absorption due to gases at the IMP site. Insight on the dynamical connections will be discussed.
A new photoacoustic method based on the modulation of the light induced absorption coefficient
NASA Astrophysics Data System (ADS)
Engel, S.; Wenisch, C.; Müller, F. A.; Gräf, S.
2016-04-01
The present study reports on a new photoacoustic (PA) measurement method that is suitable for the investigation of light induced absorption effects including e.g. excited state absorption. Contrary to the modulation of the radiation intensity used in conventional PA-methods, the key principle of this novel setup is based on the modulation of the induced absorption coefficient by light. For this purpose, a pump-probe setup with a pulsed pump laser beam and a continuous probe laser beam is utilized. In this regime, the potential influence of heat on the PA-signal is much smaller when compared to arrangements with pulsed probe beam and continuous pump beam. Beyond that, the negative effect of thermal lenses can be neglected. Thus, the measurement technique is well-suited for materials exhibiting a strong absorption at the pump wavelength. The quantitative analysis of the induced absorption coefficient was achieved by the calibration of the additional PA-signal caused by the continuous probe laser to the PA-signal resulting from the pulsed pump laser using thallium bromoiodide (KRS-5) as sample material.
NASA Astrophysics Data System (ADS)
Yang, Yi; Wang, Tianheng; Biswal, Nrusingh C.; Wang, Xiaohong; Sanders, Melinda; Brewer, Molly; Zhu, Quing
2011-09-01
Optical scattering coefficient from ex vivo unfixed normal and malignant ovarian tissue was quantitatively extracted by fitting optical coherence tomography (OCT) A-line signals to a single scattering model. 1097 average A-line measurements at a wavelength of 1310 nm were performed at 108 sites obtained from 18 ovaries. The average scattering coefficient obtained from the normal tissue group consisted of 833 measurements from 88 sites was 2.41 mm-1 (+/-0.59), while the average coefficient obtained from the malignant tissue group consisted of 264 measurements from 20 sites was 1.55 mm-1 (+/-0.46). The malignant ovarian tissue showed significant lower scattering than the normal group (p < 0.001). The amount of collagen within OCT imaging depth was analyzed from the tissue histological section stained with Sirius Red. The average collagen area fraction (CAF) obtained from the normal tissue group was 48.4% (+/-12.3%), while the average CAF obtained from the malignant tissue group was 11.4% (+/-4.7%). A statistical significance of the collagen content was found between the two groups (p < 0.001). These results demonstrated that quantitative measurements of optical scattering coefficient from OCT images could be a potential powerful method for ovarian cancer detection.
NASA Astrophysics Data System (ADS)
Chrobak, Ł.; Maliński, M.; Pawlak, M.
2014-11-01
This paper presents a method of the measurement of the optical absorption coefficient of the Ar8+ ions implanted layers in the p-type silicon substrate. The absorption coefficient is calculated using a value of the attenuation of amplitudes of a photothermal radiometry (PTR) and/or a modulation free carrier absorption (MFCA) signals and the implanted layer thickness calculated by means of the TRIM program. The proposed method can be used to indicate the amorphization of the ions implanted layers.
Absorption coefficients of GeSn extracted from PIN photodetector response
NASA Astrophysics Data System (ADS)
Ye, Kaiheng; Zhang, Wogong; Oehme, Michael; Schmid, Marc; Gollhofer, Martin; Kostecki, Konrad; Widmann, Daniel; Körner, Roman; Kasper, Erich; Schulze, Jörg
2015-08-01
In this paper the optical absorption of the GeSn PIN photodetector was investigated. The vertical GeSn PIN photodetectors were fabricated by molecular beam epitaxy (MBE) and dry etching. By means of current density-voltage (J-V) and capacity-voltage (C-V) measurements the photodetector device was characterized. The absorption coefficients of GeSn material were finally extracted from the optical response of PIN structure. With further direct bandgap analysis the influences of device structure was proved negligible.
NASA Technical Reports Server (NTRS)
Bergstrom, Robert W.; Russell, Philip B.; Hignett, Phillip
2002-01-01
Measurements are presented of the wavelength dependence of the aerosol absorption coefficient taken during the Tropical Aerosol Radiative Forcing Observational Experiment (TARFOX) over the northern Atlantic. The data show an approximate lamda(exp -1) variation between 0.40 and 1.0 micrometers. The theoretical basis of the wavelength variation of the absorption of solar radiation by elemental carbon [or black carbon (BC)] is explored. For a wavelength independent refractive index the small particle absorption limit simplifies to a lambda(exp -1) variation in relatively good agreement with the data. This result implies that the refractive indices of BC were relatively constant in this wavelength region, in agreement with much of the data on refractive indices of BC. However, the result does not indicate the magnitude of the refractive indices. The implications of the wavelength dependence of BC absorption for the spectral behavior of the aerosol single scattering albedo are discussed. It is shown that the single scattering albedo for a mixture of BC and nonabsorbing material decreases with wavelength in the solar spectrum (i.e., the percentage amount of absorption increases). This decease in the single scattering albedo with wavelength for black carbon mixtures is different from the increase in single scattering allied for most mineral aerosols (dusts). This indicates that, if generally true, the spectral variation of the single- scattering albedo can be used to distinguish aerosol types. It also highlights the importance of measurements of the spectral variation of the aerosol absorption coefficient and single scattering albedo.
Heat/Mass Transfer Coefficients of an Absorber in Absorption Refrigeration System
NASA Astrophysics Data System (ADS)
Fujita, Isamu; Hihara, Eiji
This paper presents a new method to calculate heat and mass transfer coefficients applicable to the vertical tube or plate type absorber of absorption refrigeration system. Conventional method for calculating the coefficients using logarithmic mean temperature/ concentration differences is criticized for its lacking in the theoretical rationality and usually giving untrue values except some limited situations such that temperature of the solution can be assumed to change linearly along the heat transfer surface. The newly introduced method, which is intended to overcome this difficulty, is verified by numerical simulation and is accompanied by an example applied to the experimental results.
NASA Technical Reports Server (NTRS)
Lacis, Andrew A.; Oinas, Valdar
1991-01-01
A radiative transfer method for treating nongray gaseous absorption and thermal emission in vertically inhomogeneous multiple scattering atmospheres is described. Probability density distributions of absorption coefficient strength are derived from line-by-line calculations to construct line-by-line and band model based k distributions. The monotonic ordering of absorption coefficient strengths in these k distributions implicitly preserves the monochromatic structure of the atmosphere at different pressure levels, thus simulating monochromatic spectral integration at a fraction of the line-by-line computing cost. The k distribution approach also permits accurate modeling of overlapping absorption by different atmospheric gases and accurate treatment of nongray absorption in multiple scattering media. It is shown that the correlated k distribution method is capable of achieving numerical accuracy to within 1 percent of cooling rates obtained with line-by-line calculations throughout the troposphere and most of the stratosphere.
NASA Astrophysics Data System (ADS)
Grabtchak, Serge; Montgomery, Logan G.; Whelan, William M.
2014-05-01
We demonstrated the application of relative radiance-based continuous wave (cw) measurements for recovering absorption and scattering properties (the effective attenuation coefficient, the diffusion coefficient, the absorption coefficient and the reduced scattering coefficient) of bulk porcine muscle phantoms in the 650-900 nm spectral range. Both the side-firing fiber (the detector) and the fiber with a spherical diffuser at the end (the source) were inserted interstitially at predetermined locations in the phantom. The porcine phantoms were prostate-shaped with ˜4 cm in diameter and ˜3 cm thickness and made from porcine loin or tenderloin muscles. The described method was previously validated using the diffusion approximation on simulated and experimental radiance data obtained for homogenous Intralipid-1% liquid phantom. The approach required performing measurements in two locations in the tissue with different distances to the source. Measurements were performed on 21 porcine phantoms. Spectral dependences of the effective attenuation and absorption coefficients for the loin phantom deviated from corresponding dependences for the tenderloin phantom for wavelengths <750 nm. The diffusion constant and the reduced scattering coefficient were very close for both phantom types. To quantify chromophore presence, the plot for the absorption coefficient was matched with a synthetic absorption spectrum constructed from deoxyhemoglobin, oxyhemoglobin and water. The closest match for the porcine loin spectrum was obtained with the following concentrations: 15.5 µM (±30% s.d.) Hb, 21 µM (±30% s.d.) HbO2 and 0.3 (±30% s.d.) fractional volume of water. The tenderloin absorption spectrum was best described by 30 µM Hb (±30% s.d), 19 µM (±30% s.d.) HbO2 and 0.3 (±30% s.d.) fractional volume of water. The higher concentration of Hb in tenderloin was consistent with a dark-red appearance of the tenderloin phantom. The method can be applied to a number of biological
Index of Refraction and Absorption Coefficient Spectra of Paratellurite in the Terahertz Region
NASA Astrophysics Data System (ADS)
Unferdorben, Márta; Buzády, Andrea; Hebling, János; Kiss, Krisztián; Hajdara, Ivett; Kovács, László; Péter, Ágnes; Pálfalvi, László
2016-07-01
Index of refraction and absorption coefficient spectra of pure paratellurite (α-TeO2) crystal as a potential material for terahertz (THz) applications were determined in the 0.25-2 THz frequency range at room temperature by THz time domain spectroscopy (THz-TDS). The investigation was performed with beam polarization both parallel (extraordinary polarization) and perpendicular (ordinary polarization) to the optical axis [001] of the crystal. Similarly to the visible spectral range, positive birefringence was observed in the THz range as well. It was shown that the values of the refractive index for extraordinary polarization are higher and show significantly larger dispersion than for the ordinary one. The absorption coefficient values are also larger for extraordinary polarization. The measured values were fitted by theoretical curves derived from the complex dielectric function containing independent terms of Lorentz oscillators due to phonon-polariton resonances. The results are compared with earlier publications, and the observed significant discrepancies are discussed.
Majaron, Boris; Milanic, Matija
2008-01-01
Although photothermal radiometric (PTR) measurements commonly employ broad-band signal acquisition to increase the signal-to-noise ratio, all reported studies apply a fixed infrared (IR) absorption coefficient to simplify the involved signal analysis. In samples with large spectral variation of micro(lambda) in mid-IR, which includes most biological tissues, the selection of the effective IR absorption coefficient value (micro(eff)) can strongly affect the accuracy of the result. We present a novel analytical approach for the determination of optimal micro(eff) from spectral properties of the sample and radiation detector. In extensive numerical simulations of pulsed PTR temperature profiling in human skin using three common IR radiation detectors and several acquisition spectral bands, we demonstrate that our approach produces viable values micro(eff). Two previously used analytical estimations perform much worse in the same comparison. PMID:18182701
Determination of RW3-to-water mass-energy absorption coefficient ratio for absolute dosimetry.
Seet, Katrina Y T; Hanlon, Peta M; Charles, Paul H
2011-12-01
The measurement of absorbed dose to water in a solid-phantom may require a conversion factor because it may not be radiologically equivalent to water. One phantom developed for the use of dosimetry is a solid water, RW3 white-polystyrene material by IBA. This has a lower mass-energy absorption coefficient than water due to high bremsstrahlung yield, which affects the accuracy of absolute dosimetry measurements. In this paper, we demonstrate the calculation of mass-energy absorption coefficient ratios, relative to water, from measurements in plastic water and RW3 with an Elekta Synergy linear accelerator (6 and 10 MV photon beams) as well as Monte Carlo modeling in BEAMnrc and DOSXYZnrc. From this, the solid-phantom-to-water correction factor was determined for plastic water and RW3. PMID:21960410
NASA Astrophysics Data System (ADS)
Salazar, Agustín; Fuente, Raquel; Apiñaniz, Estibaliz; Mendioroz, Arantza; Celorrio, R.
2011-08-01
The aim of this work is to analyze the ability of modulated photothermal radiometry to retrieve the thermal diffusivity and the optical absorption coefficient of layered materials simultaneously. First, we extend the thermal quadrupole method to calculate the surface temperature of semitransparent multilayered materials. Then, this matrix method is used to evaluate the influence of heat losses by convection and radiation, the influence of the use of thin paint layers on the accuracy of thermal diffusivity measurements, and the effect of lateral heat diffusion due to the use of Gaussian laser beams. Finally, we apply the quadrupole method to retrieve (a) the thermal contact resistance in glass stacks and (b) the thermal diffusivity and optical absorption coefficient depth profiles in heterogeneous materials with continuously varying physical properties, as is the case of functionally graded materials and partially cured dental resins.
Measurement and calculation of the sound absorption coefficient of pine wood charcoal
NASA Astrophysics Data System (ADS)
Suh, Jae Gap; Baik, Kyung min; Kim, Yong Tae; Jung, Sung Soo
2013-10-01
Although charcoal has been widely utilized for physical therapy and as a deodorant, water purifier, etc. due to its porous features, research on its role as a sound-absorbing material is rarely found. Thus, the sound absorption coefficients of pine wood charcoal were measured using an impedance tube and were compared with the theoretical predictions in the frequency range of 500˜ 5000 Hz. The theory developed in the current study only considers the lowest possible mode propagating along the air channels of the charcoal and shows good agreements with the measurements. As the frequency is increased, the sound absorption coefficients of pine wood charcoals also increase, but are lower than those of other commonly-used sound-absorbing materials.
Sadler, M.; Charlson, R.J.; Rosen, H.; Novakov, T.
1980-07-01
The absorption coefficients determined by the integrating plate method and the laser transmission method are found to be comparable and highly correlated. Furthermore, a high correlation is found between these absorption coefficients and the carbon content of the aerosol in urbanized regions.
Infrared absorption-coefficient data on SF6 applicable to atmospheric remote sensing
NASA Technical Reports Server (NTRS)
Varanasi, P.; Gopalan, A.; Brannon, J. F., Jr.
1992-01-01
Spectral absorption coefficients, k(nu)/cm per atm, of SF6 have been measured in the central Q-branches of the nu(3)-fundamental at 947/cm at various temperature-pressure combinations representing tangent heights in solar-occultation experiments or layers in the atmosphere. The data obtained with the Doppler-limited spectral resolution (about 0.0001/cm) of a tunable-diode laser spectrometer are useful in the atmospheric remote sensing of this trace gas.
NASA Astrophysics Data System (ADS)
Lovesey, Stephen W.
1996-12-01
Previous work with the resonant scattering length that is based on an atomic model and dipolar absorption events is extended to encompass quadrupolar absorption events. The scattering length is the common element in calculations of the attenuation coefficient, dichroism and the cross-sections for elastic and inelastic resonance-enhanced scattering of x-rays by magnetic materials. Both jj-coupling and Russell - Saunders coupling schemes for the atomic electrons are utilized; included are tables of relevant Racah unit-tensor operators for the valence shell 0953-8984/8/50/025/img1.
Ripeness of 'Sun Bright' tomato using the optical absorption and scattering properties
Technology Transfer Automated Retrieval System (TEKTRAN)
Maturity is one of the most important factors in determining the processing and eating quality of tomato. The objective of this research was to test the suitability of optical absorption and scattering properties for evaluating the maturity of tomatoes. Optical absorption and reduced scattering coef...
Water vapor absorption coefficients in the 8-13-micron spectral region - A critical review
NASA Technical Reports Server (NTRS)
Grant, William B.
1990-01-01
Measurements of water vapor absorption coefficients in the thermal IR atmospheric window (8-13 microns) during the past 20 years obtained by a variety of techniques are reviewed for consistency and compared with computed values based on the AFGL spectral data tapes. The methods of data collection considered were atmospheric long path absorption with a CO2 laser or a broadband source and filters, a White cell and a CO2 laser or a broadband source and a spectrometer, and a spectrophone with a CO2 laser. Advantages and disadvantages of each measurement approach are given as a guide to further research. Continuum absorption has apparently been measured accurately to about the 5-10 percent level in five of the measurements reported.
NASA Astrophysics Data System (ADS)
Yang, Yi; Wang, Tianheng; Biswal, Nrusingh; Wang, Xiaohong; Sanders, Melinda; Brewer, Molly; Zhu, Quing
2012-01-01
Optical scattering coefficient from ex-vivo unfixed normal and malignant ovarian tissue was quantitatively extracted by fitting optical coherence tomography (OCT) A-line signals to a single scattering model. 1097 average A-line measurements at a wavelength of 1310nm were performed at 108 sites obtained from 18 ovaries. The average scattering coefficient obtained from normal group consisted of 833 measurements from 88 sites was 2.41 mm-1 (+/-0.59), while the average coefficient obtained from malignant group consisted of 264 measurements from 20 sites was 1.55 mm-1 (+/-0.46). Using a threshold of 2 mm-1 for each ovary, a sensitivity of 100% and a specificity of 100% were achieved. The amount of collagen within OCT imaging depth was analyzed from the tissue histological section stained with Sirius Red. The average collagen area fraction (CAF) obtained from normal group was 48.4% (+/-12.3%), while the average CAF obtained from malignant group was 11.4% (+/-4.7%). Statistical significance of the collagen content was found between the two groups (p < 0.001). The preliminary data demonstrated that quantitative extraction of optical scattering coefficient from OCT images could be a potential powerful method for ovarian cancer detection and diagnosis.
The dependence of the nephelometer scattering coefficient of atmospheric air on the relative humidity at the RTP is discussed for four different meteorological examples. These examples feature (1) the passage of a low pressure system with thunderstorms, (2) the passage of a cold,...
A simple method for finding the scattering coefficients of quantum graphs
Cottrell, Seth S.
2015-09-15
Quantum walks are roughly analogous to classical random walks, and similar to classical walks they have been used to find new (quantum) algorithms. When studying the behavior of large graphs or combinations of graphs, it is useful to find the response of a subgraph to signals of different frequencies. In doing so, we can replace an entire subgraph with a single vertex with variable scattering coefficients. In this paper, a simple technique for quickly finding the scattering coefficients of any discrete-time quantum graph will be presented. These scattering coefficients can be expressed entirely in terms of the characteristic polynomial of the graph’s time step operator. This is a marked improvement over previous techniques which have traditionally required finding eigenstates for a given eigenvalue, which is far more computationally costly. With the scattering coefficients we can easily derive the “impulse response” which is the key to predicting the response of a graph to any signal. This gives us a powerful set of tools for rapidly understanding the behavior of graphs or for reducing a large graph into its constituent subgraphs regardless of how they are connected.
Bénilan, Y; Bruston, P; Raulin, F; Courtin, R; Guillemin, J C
1995-01-01
The interpretation of mid-UV albedo spectra of planetary atmospheres, especially that of Titan, is the main goal of the SIPAT (Spectroscopie uv d'Interet Prebiologique dans l'Atmosphere de Titan) research program. This laboratory experiment has been developed in order to systematically determine the absorption coefficients of molecular compounds which are potential absorbers of scattered sunlight in planetary atmospheres, with high spectral resolution, and at various temperatures below room temperature. From photochemical modelling and experimental simulations, we may expect triacetylene (C6H2) to be present in the atmosphere of Titan, even though it has not yet been detected. We present here the first determination of the absolute absorption coefficient of that compound in the 200-300 nm range and at two temperatures (296 K and 233 K). The temperature dependence of the C6H2 absorption coefficient in that wavelength range is compared to that previously observed in the case of cyanoacetylene (HC3N). We then discuss the implications of the present results for the interpretation of Titan UV spectra, where it appears that large uncertainities can be introduced either by the presence of trace impurities in laboratory samples or by the variations of absorption coefficients with temperature. PMID:11538441
Parthasarathy, Ranganathan; Misra, Anil; Park, Jonggu; Ye, Qiang; Spencer, Paulette
2012-01-01
The diffusion of water into dentin adhesive polymers and leaching of unpolymerized monomer from the adhesive are linked to their mechanical softening and hydrolytic degradation. Therefore, diffusion coefficient data are critical for the mechanical design of these polymeric adhesives. In this study, diffusion coefficients of water and leachables were obtained for sixteen methacrylate-based crosslinked polymers using absorption experiments. The experimental mass change data was interpreted using numerical solution of the two-dimensional diffusion equations. The calculated diffusion coefficients varied from 1.05 × 10−8 cm2/sec (co-monomer TMTMA) to 3.15 × 10−8 cm2/sec (co-monomer T4EGDMA). Correlation of the diffusion coefficients with crosslink density and hydrophilicity showed an inverse trend (R2 = 0.41). The correlation of diffusion coefficient with crosslink density and hydrophilicity are closer for molecules differing by simple repeat units (R2 = 0.95). These differences in the trends reveal mechanisms of interaction of the diffusing water with the polymer structure. PMID:22430592
Microwave Resonator Measurements of Atmospheric Absorption Coefficients: A Preliminary Design Study
NASA Technical Reports Server (NTRS)
Walter, Steven J.; Spilker, Thomas R.
1995-01-01
A preliminary design study examined the feasibility of using microwave resonator measurements to improve the accuracy of atmospheric absorption coefficients and refractivity between 18 and 35 GHz. Increased accuracies would improve the capability of water vapor radiometers to correct for radio signal delays caused by Earth's atmosphere. Calibration of delays incurred by radio signals traversing the atmosphere has applications to both deep space tracking and planetary radio science experiments. Currently, the Cassini gravity wave search requires 0.8-1.0% absorption coefficient accuracy. This study examined current atmospheric absorption models and estimated that current model accuracy ranges from 5% to 7%. The refractivity of water vapor is known to 1% accuracy, while the refractivity of many dry gases (oxygen, nitrogen, etc.) are known to better than 0.1%. Improvements to the current generation of models will require that both the functional form and absolute absorption of the water vapor spectrum be calibrated and validated. Several laboratory techniques for measuring atmospheric absorption and refractivity were investigated, including absorption cells, single and multimode rectangular cavity resonators, and Fabry-Perot resonators. Semi-confocal Fabry-Perot resonators were shown to provide the most cost-effective and accurate method of measuring atmospheric gas refractivity. The need for accurate environmental measurement and control was also addressed. A preliminary design for the environmental control and measurement system was developed to aid in identifying significant design issues. The analysis indicated that overall measurement accuracy will be limited by measurement errors and imprecise control of the gas sample's thermodynamic state, thermal expansion and vibration- induced deformation of the resonator structure, and electronic measurement error. The central problem is to identify systematic errors because random errors can be reduced by averaging
Sound absorption coefficient in situ: an alternative for estimating soil loss factors.
Freire, Rosane; Meletti de Abreu, Marco Henrique; Okada, Rafael Yuri; Soares, Paulo Fernando; GranhenTavares, Célia Regina
2015-01-01
The relationship between the sound absorption coefficient and factors of the Universal Soil Loss Equation (USLE) was determined in a section of the Maringá Stream basin, Paraná State, by using erosion plots. In the field, four erosion plots were built on a reduced scale, with dimensions of 2.0×12.5m. With respect to plot coverage, one was kept with bare soil and the others contained forage grass (Brachiaria), corn and wheat crops, respectively. Planting was performed without any type of conservation practice in an area with a 9% slope. A sedimentation tank was placed at the end of each plot to collect the material transported. For the acoustic system, pink noise was used in the measurement of the proposed monitoring, for collecting information on incident and reflected sound pressure levels. In general, obtained values of soil loss confirmed that 94.3% of material exported to the basin water came from the bare soil plot, 2.8% from the corn plot, 1.8% from the wheat plot, and 1.1% from the forage grass plot. With respect to the acoustic monitoring, results indicated that at 16kHz erosion plot coverage type had a significant influence on the sound absorption coefficient. High correlation coefficients were found in estimations of the A and C factors of the USLE, confirming that the acoustic technique is feasible for the determination of soil loss directly in the field. PMID:24972796
NASA Astrophysics Data System (ADS)
Wang, Lihong; Jacques, Steven L.
1995-05-01
A simple and quick approach is used to measure the reduced scattering coefficient ( mu s `) of a semi-infinite turbid medium having a much smaller absorption coefficient than mu s`. A laser beam with an oblique angle of incidence to the medium causes the center of the diffuse reflectance that is several transport mean-free paths away from the incident point to shift away from the point of incidence by an amount Delta x. This amount is used to compute mu s` by mu s` = sin( alpha i)/(n Delta x), where n is the refractive index of the turbid medium divided by that of the incident medium and alpha i is the angle of incidence measured from the surface normal. For a turbid medium having an absorption coefficient comparable with mu s `, a revision to the above formula is made. This method is tested theoretically by Monte Carlo simulations and experimentally by a video reflectometer.
Zheng, Xiaobing; Dickey, Tommy; Chang, Grace
2002-10-20
In situ time-series measurements of spectral diffuse downwelling irradiance from the Bermuda Testbed Mooring are presented. Averaged diffuse attenuation coefficients of downwelling irradiance, Kd,and their elastic and inelastic components are investigated at seven wavelengths. At shorter wavelengths (<510 nm), Kd is weakly dependent on the solar zenith angle owing to the prevailing scattering effect and therefore can be considered a quasi-inherent optical property. At longer wavelengths (>510 nm), Kd shows a strong dependence on the solar zenith angle. As depth increases, inelastic scattering plays a greater role for the underwater light field at red wavelengths. PMID:12396201
Pressure-induced absorption coefficients for radiative transfer calculations in Titan's atmosphere
NASA Technical Reports Server (NTRS)
Courtin, Regis
1988-01-01
The semiempirical theory of Birnbaum and Cohen (1976) is used to calculate the FIR pressure-induced absorption (PIA) spectra of N2, CH4, N2 + Ar, N2 + CH4, and N2 + H2 under conditions like those in the Titan troposphere. The results are presented graphically and compared with published data from laboratory measurements of PIA in the same gases and mixtures (Dagg et al., 1986; Dore et al., 1986). Good agreement is obtained, with only a slight underestimation of PIA at 300-400/cm in the case of CH4. The absorption coefficients are presented in tables, and it is suggested that the present findings are of value for evaluating the effects of tropospheric clouds on the Titan FIR spectrum and studying the greenhouse effect near the Titan surface.
Weber, Jessie R.; Cuccia, David J.; Johnson, William R.; Bearman, Gregory H.; Durkin, Anthony J.; Hsu, Mike; Lin, Alexander; Binder, Devin K.; Wilson, Dan; Tromberg, Bruce J.
2011-01-01
We present an approach for rapidly and quantitatively mapping tissue absorption and scattering spectra in a wide-field, noncontact imaging geometry by combining multifrequency spatial frequency domain imaging (SFDI) with a computed-tomography imaging spectrometer (CTIS). SFDI overcomes the need to spatially scan a source, and is based on the projection and analysis of periodic structured illumination patterns. CTIS provides a throughput advantage by simultaneously diffracting multiple spectral images onto a single CCD chip to gather spectra at every pixel of the image, thus providing spatial and spectral information in a single snapshot. The spatial-spectral data set was acquired 30 times faster than with our wavelength-scanning liquid crystal tunable filter camera, even though it is not yet optimized for speed. Here we demonstrate that the combined SFDI-CTIS is capable of rapid, multispectral imaging of tissue absorption and scattering in a noncontact, nonscanning platform. The combined system was validated for 36 wavelengths between 650–1000 nm in tissue simulating phantoms over a range of tissue-like absorption and scattering properties. The average percent error for the range of absorption coefficients (μa) was less than 10% from 650–800 nm, and less than 20% from 800–1000 nm. The average percent error in reduced scattering coefficients (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}\\mu_{\\rm s}^{\\prime}\\end{equation*} \\end{document}μs′) was less than 5% from 650–700 nm and less than 3% from 700–1000 nm. The SFDI-CTIS platform was applied to a mouse model of brain injury in order to demonstrate the utility of this approach in characterizing spatially and spectrally varying tissue optical properties. PMID:21280902
A comparison of methods for the measurement of the absorption coefficient in natural waters
NASA Technical Reports Server (NTRS)
Pegau, W. Scott; Cleveland, Joan S.; Doss, W.; Kennedy, C. Dan; Maffione, Robert A.; Mueller, James L.; Stone, R.; Trees, Charles C.; Weidemann, Alan D.; Wells, Willard H.
1995-01-01
In the spring of 1992 an optical closure experiment was conducted at Lake Pend Orielle, Idaho. A primary objective of the experiment was to compare techniques for the measurement of the spectral absorption coefficent and other inherent optical properties of natural waters. Daily averages of absorption coefficents measured using six methods are compared at wavelengths of 456, 488, and 532 nm. Overall agreement was within 40% at 456 nm and improved with increasing wavelength to 25% at 532 nm. These absorption measurements were distributed over the final 9 days of the experiement, when bio-optical conditions in Lake Pend Oreille (as indexed by the beam attenuation coefficent c(sub p)(660) and chlorophyll a fluorescence profiles) were representative of those observed throughout the experiment. However, profiles of stimulated chlorophyll a fluorescence and beam transmission showed that bio-optical properties in the lake varied strongly on all time and space scales. Therefore environmental variabilty contributed significantly to deviations between daily mean absorption coefficients measured using the different techniques.
Mesure de coefficients d'absorption de plasmas créés par laser nanoseconde
NASA Astrophysics Data System (ADS)
Thais, F.; Chenais-Popovics, C.; Eidmann, K.; Bastiani, S.; Blenski, T.; Gilleron, F.
2005-06-01
La mesure des coefficients d'absorption dans les plasmas chauds est particulièrement utile dans le domaine de la fusion par confinement inertiel ainsi que dans divers contextes en astrophysique. Le développement des calculs de physique atomique qui y sont associés repose sur des hypothèses qu'il est nécessaire de vérifier dans la plus large gamme possible de conditions physiques. Nous présentons ici la méthode de mesure et d'analyse employée en nous appuyant sur l'exemple des cibles multicouches nickel/aluminium.
Determination of Absorption Coefficient of a Solution by a Simple Experimental Setup
NASA Astrophysics Data System (ADS)
Gopalakrishnan, Deepak; Akhildev, C.; Sreenivasan, P. V.; Leelamma, K. K.; Joseph, Lyjo K.; Anila, E. I.
2011-10-01
The absorption coefficients of aqueous potassium permanganate (KMnO4) solution at 638.8 nm for various concentrations are determined using a simple experimental set up. The setup consists of He-Ne laser source (Red, 638.8 nm, 10 mW), a glass jar in which the KMnO4 sample is taken, a mirror strip inclined at 45° to direct the laser beam towards the bottom of the glass jar, a traveling microscope to adjust the position of light dependent resistor (LDR) and a digital multimeter to measure the resistance.
Theoretical calculations of nonlinear refraction and absorption coefficients of doped graphene
NASA Astrophysics Data System (ADS)
Margulis, Vl A.; Muryumin, E. E.; Gaiduk, E. A.
2014-12-01
In this study, we present the first theoretical predictions concerning the nonlinear refractive and absorptive properties of the doped graphene in which the Fermi energy {{E}F} of charge carriers (noninteracting massless Dirac fermions) is controlled by an external gate voltage. We base our study on the original perturbation theory technique developed by Genkin and Mednis (1968 Sov. Phys. JETP 27 609) for calculating the nonlinear-optical (NLO) response coefficients of bulk crystalline semiconductors with partially filled bands. Using a simple tight-binding model for the π-electron energy bands of graphene, we obtain analytic expressions for the nonlinear refractive index {{n}2}(ω ) and the nonlinear absorption coefficient {{α }2}(ω ) of the doped graphene at photon energies above twice the value of the Fermi energy (\\hbar ω \\gt 2{{E}F}). We show that in this spectral region, both the nonlinear refraction ant the nonlinear absorption are determined predominantly by the combined processes which simultaneously involve intraband and interband motion of π-electrons. Our calculations indicate that extremely large negative values of n2 (of the order of -{{10}-6} cm2 W-1) can be achieved in the graphene at a relatively low doping level (of about 1012 cm-2) provided that the excitation frequency slightly exceeds the threshold frequency corresponding to the onset of interband transitions. With a further increase of the radiation frequency, the {{n}2}(ω ) becomes positive and begins to decrease in its absolute magnitude. The peculiar frequency dispersion of n2 and a negative sign of the {{α }2} (absorption bleaching), as predicted by our theory, suggest that the doped graphene is a prospective NLO material to be used in practical optical switching applications.
Assessment of the differential linear coherent scattering coefficient of biological samples
NASA Astrophysics Data System (ADS)
Conceição, A. L. C.; Antoniassi, M.; Poletti, M. E.
2010-07-01
New differential linear coherent scattering coefficient, μ CS, data for four biological tissue types (fat pork, tendon chicken, adipose and fibroglandular human breast tissues) covering a large momentum transfer interval (0.07≤ q≤70.5 nm -1), resulted from combining WAXS and SAXS data, are presented in order to emphasize the need to update the default data-base by including the molecular interference and the large-scale arrangements effect. The results showed that the differential linear coherent scattering coefficient demonstrates influence of the large-scale arrangement, mainly due to collagen fibrils for tendon chicken and fibroglandular breast samples, and triacylglycerides for fat pork and adipose breast samples at low momentum transfer region. While, at high momentum transfer, the μ CS reflects effects of molecular interference related to water for tendon chicken and fibroglandular samples and, fatty acids for fat pork and adipose samples.
Griffing, G.W.
1981-01-01
The dependence of the nephelometer scattering coefficient of atmospheric air on the relative humidity at the RTP is discussed for four different meteorological examples. These examples feature (1) the passage of a low pressure system with thunderstorms, (2) the passage of a cold, dry front, (3) a nocturnal weather disturbance due to an unknown source, and (4) wood smoke aerosols from burning tree piles. Nephelometer scattering coefficient data were obtained by the use of two nephelometers. One nephelometer was operated at the ambient outside relative humidity and the other nephelometer at a different relative humidity. Using this operational mode of data acquisition, qualitative temporal information was deduced on the variations of aerosol size and number density as various meteorological parameters vary. The temporal trend of the visibility is also discussed for each example.
Orbit Optimization and Scattering Coefficient Analysis for the Proposed GLORIA System
NASA Technical Reports Server (NTRS)
Welch, Bryan
2004-01-01
This paper investigates the optimization of an orbit for a Low-Earth Orbiting (LEO) satellite for coastal coverage over Antarctic and United States shorelines as part of the Geostationary/Low-Earth Orbiting Radar Image Acquisition (GLORIA) System. Simulations over a range of orbital parameters are performed to determine the optimal orbit. Scattering coefficients are computed for the optimal orbit throughout the day and characterized to compare various scenarios for which link budget comparisons could then be made.
NASA Technical Reports Server (NTRS)
Harward, C. N.
1977-01-01
Measurements were performed to determine the pressure and temperature dependence of CFM-12 absorption coefficients for CO2 waveguide laser radiation. The absorption coefficients of CFM-12 for CO2 waveguide laser radiation were found to have no spectral structure within small spectral bandwidths around the CO2 waveguide laser lines in the CO2 spectral band for pressures above 20 torr. All of the absorption coefficients for the CO2 laser lines studied are independent of pressure above 100 torr, except for the P(36) laser CO2 spectral band. The absorption coefficients associated with the P(42) line in the same band showed the greatest change with temperature, and it also has the largest value of all the lines studied.
NASA Astrophysics Data System (ADS)
Zamani, N.; Keshavarz, A.; Nadgaran, H.
2016-06-01
In this paper, we investigate the optical absorption coefficient of hybrid structure consisting of metal nano particle (MNP) coupled to multi-layer spherical quantum dot (MSQD). Energy eigenvalues and eigenfunctions of Schrödinger equation in this structure are obtained by using numerical solution (by the fourth-order Runge-Kutta method). The effect of MNP in the vicinity of MSQD is calculated by considering local field theory. Then the variation of optical absorption coefficient hybrid structure is calculated. The results show that the presence of MNP near MSQD enhances the optical absorption coefficient. Also, by changing the distance between MNP and MSQD and radius of MNP, variation of optical absorption coefficient and refractive index changes are introduced.
NASA Astrophysics Data System (ADS)
Boss, Emmanuel; Pegau, W. Scott
2001-10-01
We revisit the problem of computing the backscattering coefficient based on the measurement of scattering at one angle in the back direction. Our approach uses theory and new observations of the volume scattering function (VSF) to evaluate the choice of angle used to estimate bb . We add to previous studies by explicitly treating the molecular backscattering of water (bbw ) and its contribution to the VSF shape and to bb . We find that there are two reasons for the tight correlation between observed scattering near 120 and the backscattering coefficient reported by Oishi [Appl. Opt. 29, 4658, (1990) , namely, that (1) the shape] of the VSF of particles (normalized to the backscattering) does not vary much near that angle for particle assemblages of differing optical properties and size, and (2) the ratio of the VSF to the backscattering is not sensitive to the contribution by water near this angle. We provide a method to correct for the water contribution to backscattering when single-angle measurements are used in the back direction (for angles spanning from near 90 to 160 ) that should provide improved estimates of the backscattering coefficient.
Spectral absorption coefficients of argon and silicon and spectral reflectivity of aluminum
NASA Technical Reports Server (NTRS)
Krascella, N. L.
1972-01-01
A theoretical investigation was conducted to estimate the spectral properties of argon as a function of pressure, temperature, and wave number. The spectral characteristics of the argon buffer gas exert a strong influence on radiative energy transfer in the in-reactor test configuration of the nuclear light bulb engine. An existing computer program was modified and used to calculate the spectral absorption coefficients of argon at total pressures of 50, 100, 250, 500, 750 and 1000 atm in the temperature interval between 1000 and 30,000 K. At each pressure and temperature, spectral properties were calculated for forty-seven wave numbers in the interval between 1000 and 1,000,000 cm/1. Estimates of the spectral absorption coefficients of silicon were made as part of an evaluation of silicon vapor as a possible buffer-gas seeding agent for the reference nuclear light bulb engine. Existing cross-section data were used to calculate the spectral characteristics of silicon at twenty-four temperatures in the interval between 2000 and 10,000 K.
NASA Astrophysics Data System (ADS)
Markushev, D. D.; Ordonez-Miranda, J.; Rabasović, M. D.; Galović, S.; Todorović, D. M.; Bialkowski, S. E.
2015-06-01
The open-cell photoacoustic signal measured in the transmission configuration for aluminum thin plates with thicknesses of 280 μm, 197 μm, and 112 μm is experimentally and theoretically analyzed, in the 20 Hz-7 kHz modulation frequency range. It is shown that the observed differences between the predictions of the standard thermoelastic model and the experiment data of both the amplitude and phase of the photoacoustic signal can be overcome by considering the aluminum samples coated with a thin layer of black paint as volume-absorber materials. This new approach provides a quite good agreement with the obtained experimental data, in the whole frequency range, and yields an effective absorption coefficient of (16 ± 2) mm-1, for a 280 μm-thick sample. The introduction of the finite absorption coefficient led to the correct ratio between the thermal diffusion and thermoelastic components of the photoacoustic signal. Furthermore, it is found that the "volume-absorber" approach accurately describes the behavior of the amplitude, but not that of the phase recorded for a 112 μm-thick sample, due to its relatively strong thermoelastic bending, which is not considered by this theory. Within the approximation of the small bending, the proposed "volume-absorber" model provides a reliable description of the photoacoustic signal for Al samples thicker than 112 μm, and extends the applicability of the classical "opaque" approach.
NASA Astrophysics Data System (ADS)
Guo, Kangxian; Zhang, Zhongmin; Mou, Sen; Xiao, Bo
2015-05-01
The analytical expressions of linear and nonlinear optical absorption coefficients and refractive index changes in a quantum dot with a hydrogenic impurity are obtained by using the compact-density-matrix approach and iterative method. The wave functions and the energy levels are obtained by using the variational method. Numerical results show that the optical absorption coefficients and refractive index changes are strongly affected by the hydrogenic impurity.
Granot, Er'el
2005-01-15
We calculate the exact transmission coefficients of a quantum wire in the presence of a single point defect at the wire's cutoff frequencies. We show that at these frequencies while the conductance pattern (i.e., the scattering) is strongly affected by the presence of the defect, the pattern is totally independent of the defect's characteristics (i.e., the defect that caused the scattering cannot be identified from that pattern). The change in the conduction pattern can cause universal attraction and/or repulsion forces between two parallel conducting wires.
Aerosol particle absorption spectroscopy by photothermal modulation of Mie scattered light
Campillo, A.J.; Dodge, C.J.; Lin, H.B.
1981-09-15
Absorption spectroscopy of suspended submicron-sized aqueous ammonium-sulfate aerosol droplets has been performed by employing a CO/sub 2/ laser to photothermally modulate visible Mie scattered light. (AIP)
NASA Astrophysics Data System (ADS)
O'Brien, J. J.; Cao, H.
2000-10-01
Methane spectral features are prominent in the reflected sunlight spectra from the outer planets and some of their major satellites and can provide useful information on the atmospheres of those bodies. Methane bands occurring in the visible to near-IR region are particularly important because for many of these planetary bodies, methane bands occurring in the IR are saturated. Spectral observations of these bodies also are being made at increasingly higher resolution. In order to interpret the planetary spectra, laboratory data for methane obtained at appropriate sample conditions and spectral resolution are required. Since the visible to near-IR spectrum of methane is intrinsically weak, sensitive techniques are required to perform the laboratory measurements. We have employed the intracavity laser spectroscopy (ILS) technique to record methane spectrum in the visible to near-IR region. New results for room temperature methane in the 10,635 - 13,300 cm-1 region and for liquid nitrogen temperature (77 K) methane in the 10,860 - 11,605 cm-1 region will be presented. Spectra throughout the more strongly absorbing sections will be shown. These spectra are acquired at a resolution of 400,000 - 500,000 and are calibrated using iodine reference spectra acquired from an extra-cavity cell at nearly the same time as when the methane data are recorded. From the spectra, absorption coefficients are determined and these are presented as averages over 1 Å and 1 cm-1 intervals. In order to obtain the results, spectra are deconvolved for the instrument function using a Fourier transform technique. The validity of the approach is verified from studies of isolated oxygen lines in the A band occurring around 760 nm. Good agreement is observed between the intensity values determined from the FT deconvolution and integration method and those derived by fitting the observed line profiles to Voigt line-shapes convoluted with the instrument function. The methane results are compared
Hoche, S; Hussein, M A; Becker, T
2015-03-01
The accuracy of density, reflection coefficient, and acoustic impedance determination via multiple reflection method was validated experimentally. The ternary system water-maltose-ethanol was used to execute a systematic, temperature dependent study over a wide range of densities and viscosities aiming an application as inline sensor in beverage industries. The validation results of the presented method and setup show root mean square errors of: 1.201E-3 g cm(-3) (±0.12%) density, 0.515E-3 (0.15%) reflection coefficient and 1.851E+3 kg s(-1) m(-2) (0.12%) specific acoustic impedance. The results of the diffraction corrected absorption showed an average standard deviation of only 0.12%. It was found that the absorption change shows a good correlation to concentration variations and may be useful for laboratory analysis of sufficiently pure liquids. The main part of the observed errors can be explained by the observed noise, temperature variation and the low signal resolution of 50 MHz. In particular, the poor signal-to-noise ratio of the second reflector echo was found to be a main accuracy limitation. Concerning the investigation of liquids the unstable properties of the reference material PMMA, due to hygroscopicity, were identified to be an additional, unpredictable source of uncertainty. While dimensional changes can be considered by adequate methodology, the impact of the time and temperature dependent water absorption on relevant reference properties like the buffer's sound velocity and density could not be considered and may explain part of the observed deviations. PMID:25465962
Determination of absorption coefficient based on laser beam thermal blooming in gas-filled tube.
Hafizi, B; Peñano, J; Fischer, R; DiComo, G; Ting, A
2014-08-01
Thermal blooming of a laser beam propagating in a gas-filled tube is investigated both analytically and experimentally. A self-consistent formulation taking into account heating of the gas and the resultant laser beam spreading (including diffraction) is presented. The heat equation is used to determine the temperature variation while the paraxial wave equation is solved in the eikonal approximation to determine the temporal and spatial variation of the Gaussian laser spot radius, Gouy phase (longitudinal phase delay), and wavefront curvature. The analysis is benchmarked against a thermal blooming experiment in the literature using a CO₂ laser beam propagating in a tube filled with air and propane. New experimental results are presented in which a CW fiber laser (1 μm) propagates in a tube filled with nitrogen and water vapor. By matching laboratory and theoretical results, the absorption coefficient of water vapor is found to agree with calculations using MODTRAN (the MODerate-resolution atmospheric TRANsmission molecular absorption database) and HITRAN (the HIgh-resolution atmospheric TRANsmission molecular absorption database). PMID:25090334
The Optical Absorption Coefficient of Bean Seeds Investigated Using Photoacoustic Spectroscopy
NASA Astrophysics Data System (ADS)
Sanchez-Hernandez, G.; Hernandez-Aguilar, C.; Dominguez-Pacheco, A.; Cruz-Orea, A.; Perez-Reyes, M. C. J.; Martinez, E. Moreno
2015-06-01
A knowledge about seed optical parameters is of great relevance in seed technology practice. Such parameters provide information about its absorption and reflectance, which could be useful for biostimulation processes, by light sources, in early stages of seed germination. In the present research photoacoustic spectroscopy (PAS) and the Rosencwaig and Gersho model were used to determine the optical absorption coefficient () of five varieties of bean seeds ( Phaseolus vulgaris L.), of different productive cycles; the seeds were biostimulated by laser treatment to evaluate the effects of biostimulation pre-sowing. It was found that the bean varieties V1, V2, V4, and V5 were optically opaque in the visible spectrum; in the case of the V3 variety, this sample was optically transparent from 680 nm. The varieties of the studied bean seeds showed significant statistical differences in sizes and also in their optical absorption spectra. The biostimulation effects showed that the seed samples with a higher optical penetration length had a positive biostimulation, in the percentage of germination, obtaining an enhancement of 47 % compared to the control sample. The utility of PAS for the optical characterization of seeds has been demonstrated in this study of the laser biostimulation process of this kind of samples.
Jacques, S L; McAuliffe, D J
1991-06-01
The explosive vaporization of melanosomes in situ in skin during pulsed laser irradiation (pulse duration less than 1 microsecond) is observed as a visible whitening of the superficial epidermal layer due to stratum corneum disruption. In this study, the ruby laser (694 nm) was used to determine the threshold radiant exposure, H0 (J/cm2), required to elicit whitening for in vitro black (Negroid) human skin samples which were pre-equilibrated at an initial temperature, Ti, of 0, 20, or 50 degrees C. A plot of H0 vs Ti yields a straight line whose x-intercept indicates the threshold temperature of explosive vaporization to be 112 +/- 7 degrees C (SD, N = 3). The slope, delta H0/delta Ti, specifies the internal absorption coefficient, mua, within the melanosome: mua = -rho C/(slope(1 + 7.1 Rd)), where rho C is the product of density and specific heat, and Rd is the total diffuse reflectance from the skin. A summary of the absorption spectrum (mua) for the melanosome interior (351-1064 nm) is presented based on H0 data from this study and the literature. The in vivo absorption spectrum (380-820 nm) for human epidermal melanin was measured by an optical fiber spectrophotometer and is compared with the melanosome spectrum. PMID:1886936
De Roo, Jonathan; Ibáñez, Maria; Geiregat, Pieter; Nedelcu, Georgian; Walravens, Willem; Maes, Jorick; Martins, Jose C; Van Driessche, Isabel; Kovalenko, Maksym V; Hens, Zeger
2016-02-23
Lead halide perovskite materials have attracted significant attention in the context of photovoltaics and other optoelectronic applications, and recently, research efforts have been directed to nanostructured lead halide perovskites. Collodial nanocrystals (NCs) of cesium lead halides (CsPbX3, X = Cl, Br, I) exhibit bright photoluminescence, with emission tunable over the entire visible spectral region. However, previous studies on CsPbX3 NCs did not address key aspects of their chemistry and photophysics such as surface chemistry and quantitative light absorption. Here, we elaborate on the synthesis of CsPbBr3 NCs and their surface chemistry. In addition, the intrinsic absorption coefficient was determined experimentally by combining elemental analysis with accurate optical absorption measurements. (1)H solution nuclear magnetic resonance spectroscopy was used to characterize sample purity, elucidate the surface chemistry, and evaluate the influence of purification methods on the surface composition. We find that ligand binding to the NC surface is highly dynamic, and therefore, ligands are easily lost during the isolation and purification procedures. However, when a small amount of both oleic acid and oleylamine is added, the NCs can be purified, maintaining optical, colloidal, and material integrity. In addition, we find that a high amine content in the ligand shell increases the quantum yield due to the improved binding of the carboxylic acid. PMID:26786064
Absorption coefficients of selected explosives and related compounds in the range of 0.1-2.8 THz.
Chen, Jian; Chen, Yunqing; Zhao, Hongwei; Bastiaans, Glenn J; Zhang, X-C
2007-09-17
We have investigated the absorption spectra of seventeen explosives and related compounds (ERCs) by using terahertz time-domain spectroscopy in the 0.1-2.8 THz region. Most of these substances show characteristic absorption features in this frequency range. The measured absorption coefficients of these ERCs form a database, which is of great importance for biochemical, defense and security related applications. PMID:19547570
NASA Technical Reports Server (NTRS)
Linsky, J. L.; Mount, G. H.
1972-01-01
The relationship of directional hemispherical reflectivity to emissivity is investigated for a nonisothermal medium with isotropic coherent scattering and absorption. Departures from a generalized Kirchhoff's Law occur due to the long range nature of the scattering process. Such departures occur in lunar thermal emission at microwave but not at infrared frequencies.
Bondarenko, S V; Garanin, Sergey G; Zhidkov, N V; Pinegin, A V; Suslov, N A
2012-01-31
We set forth the data of experimental investigation of X-ray spectral absorption coefficients in the 1.1 - 1.6 keV photon energy range for Al and Ge specimens bulk heated by soft X-ray radiation. Two experimental techniques are described: with the use of one facility channel and the heating of specimens by the X-ray radiation from a plane burnthrough target, as well as with the use of four channels and the heating by the radiation from two cylindrical targets with internal input of laser radiation. The X-ray radiation absorption coefficients were studied by way of transmission absorption spectroscopy using backlighting X-ray radiation from a point source. The results of investigation of X-ray spectral absorption coefficients on the 1s - 2p transitions in Al atoms and the 2p - 3d transitions in Ge atoms are presented.
The measurement of self-diffusion coefficients in liquid metals with quasielastic neutron scattering
NASA Astrophysics Data System (ADS)
Meyer, Andreas
2015-01-01
Quasielastic incoherent neutron scattering (QENS) has proven to be a versatile tool to study self diffusion of atoms in liquid metals. Here it is shown, that coherent contributions to the signal in the small q limit appear as a flat and energy independent constant to the QENS signal in single-component liquid metals even for systems with a small incoherent scattering cross section, like aluminum. Container-less processing via electromagnetic or electrostatic levitation devices, especially designed for QENS, enables the in-situ measurement on liquid metallic droplets of sizes between 5 mm to 10 mm in diameter. This gives access to the study of chemically reactive, refractory metallic melts and extends the accessible temperature range to undercoolings of several hundred Kelvin below the respective melting point. Compared to experiments using a thin-walled crucible giving hollow-cylindrical sample geometry it is shown that multiple scattering on levitated droplets is negligible for the analysis of the self-diffusion coefficient. QENS results of liquid germanium and 73germanium isotope mixtures, titanium, nickel, copper and aluminum are reviewed. The self-diffusion coefficients of these systems are best described by an Arrhenius-type temperature dependence around their respective melting points.
Spectral absorption-coefficient data on HCFC-22 and SF6 for remote-sensing applications
NASA Technical Reports Server (NTRS)
Varanasi, P.; Li, Z.; Nemtchinov, V.; Cherukuri, A.
1994-01-01
Spectral absorption-coefficients (cross-sections) kappa(sub nu) (/cm/atm) have been measured in the 7.62, 8.97, and 12.3 micrometer bands of HCFC-22 (CHClF2) and the 10.6 micrometer bands of SF6 employing a high-resolution Fourier-transform spectrometer. Temperature and total pressure have been varied to simulate conditions corresponding to tropospheric and stratospheric layers in the atmosphere. The kappa(sub nu) are compared with values measured by us previously using a tunable diode laser spectrometer and with the appropriate entries in HITRAN and GEISA, two of the databases known to the atmospheric scientist. The measured absolute intensities of the bands are compared with previously published values.
Madelin, Guillaume; Grucker, Daniel; Franconi, Jean-Michel; Thiaudiere, Eric
2006-07-01
In this study, magnetic resonance imaging (MRI) is used to visualize acoustic streaming in liquids. A single-shot spin echo sequence (HASTE) with a saturation band perpendicular to the acoustic beam permits the acquisition of an instantaneous image of the flow due to the application of ultrasound. An average acoustic streaming velocity can be estimated from the MR images, from which the ultrasonic absorption coefficient and the bulk viscosity of different glycerol-water mixtures can be deduced. In the same way, this MRI method could be used to assess the acoustic field and time-average power of ultrasonic transducers in water (or other liquids with known physical properties), after calibration of a geometrical parameter that is dependent on the experimental setup. PMID:16650447
NASA Technical Reports Server (NTRS)
Senior, T. B. A.; Weil, H.
1977-01-01
Important in the atmospheric heat balance are the reflection, transmission, and absorption of visible and infrared radiation by clouds and polluted atmospheres. Integral equations are derived to evaluate the scattering and absorption of electromagnetic radiation from thin cylindrical dielectric shells of arbitrary cross section when irradiated by a plane wave of any polarization incident in a plane perpendicular to the generators. Application of the method to infinitely long hexagonal cylinders has yielded numerical scattering and absorption data which simulate columnar sheath ice crystals. It is found that the numerical procedures are economical for cylinders having perimeters less than approximately fifteen free-space wavelengths.
NASA Astrophysics Data System (ADS)
Sierau, B.; Covert, D. S.; Coffman, D. J.; Quinn, P. K.; Bates, T. S.
2006-12-01
In-situ, three wavelength-measurements of aerosol scattering and absorption of the regional aerosol near the coast of Texas, i.e. Houston and the Houston ship channel, as well as the Gulf of Mexico were carried out onboard the NOAA research vessel Ronald H. Brown during the 2006 TEXAQS/GoMACCS field campaign in July through September 2006. Aerosol scattering, hemispheric backscattering and absorption-coefficients were measured for particles with diameters dp<10μm and dp<1μm using multiwavelength integrating nephelometers and filter-based absorption photometers (PSAPs) at 60% RH (nephelometers). Light scattering was measured as a function of RH at two additional humidities, (ca. 25%, and 85% RH). Together with the 60% RH data, this enabled determination of the hygroscopic growth curve of scattering. The extensive and intensive optical properties were used to characterize the aerosol in the Houston, TX area and the Coastal Gulf of Mexico region and to provide information critical to understanding the climatic and air quality impacts of those aerosols. Analysis focuses on how these properties change during the chemical processing of sources within the project area and how they are affected by changes in atmospheric relative humidity that accompany transport, diurnal cycles and vertical mixing. The results are relevant to radiation transfer, visibility, air quality, and interpretation of remote sensing data from lidar and satellite. The results will be presented based on a regional classification of the sampled air masses to identify distinct aerosol populations and sources and to show the temporal and spatial variability of the measured parameters. Special emphasize will be given to the physico-chemical properties of aerosols measured during extensive Saharan dust periods encountered during the cruise and several air pollution episodes and industrial plumes. Scattering hygroscopic growth will be analyzed along with the chemical composition of the aerosol and its
Chemical and size effects of hygroscopic aerosols on light scattering coefficients
NASA Astrophysics Data System (ADS)
Tang, Ignatius N.
1996-08-01
The extensive thermodynamic and optical properties recently reported [Tang and Munkelwitz, 1994a] for sulfate and nitrate solution droplets are incorporated into a visibility model for computing light scattering by hygroscopic aerosols. The following aerosol systems are considered: NH4HSO4, (NH4)2SO4, (NH4)3H(SO4), NaHSO4, Na2SO4, NH4NO3, and NaNO3. In addition, H2SO4 and NaCl are included to represent freshly formed sulfate and background sea-salt aerosols, respectively. Scattering coefficients, based on 1 μg dry salt per cubic meter of air, are calculated as a function of relative humidity for aerosols of various chemical compositions and lognormal size distributions. For a given size distribution the light scattered by aerosol particles per unit dry-salt mass concentration is only weakly dependent on chemical constituents of the hygroscopic sulfate and nitrate aerosols. Sulfuric acid and sodium chloride aerosols, however, are exceptions and scatter light more efficiently than all other inorganic salt aerosols considered in this study. Both internal and external mixtures exhibit similar light-scattering properties. Thus for common sulfate and nitrate aerosols, since the chemical effect is outweighed by the size effect, it follows that observed light scattering by the ambient aerosol can be approximated, within practical measurement uncertainties, by assuming the aerosol being an external mixture. This has a definite advantage for either visibility degradation or climatic impact modeling calculations, because relevant data are now available for external mixtures but only very scarce for internal mixtures.
Study of the absorption coefficient of alpha particles to lower hybrid waves in tokamak
Wang, Jianbing Zhang, Xianmei Yu, Limin Zhao, Xiang
2014-02-12
Part of the energy of the Lower Hybrid (LH) waves may be absorbed by the α particles via the so-called perpendicular landau damping mechanism, which depends on various parameters of fusion reactors and the LH waves. In this article, we calculate the absorption coefficient γ{sub α} of LH waves due to α particles. Results show that, the γ{sub α} increases with the parallel refraction index n{sub ∥} while deceases with increasing the frequency of LH waves ω{sub LH} over a wide range. Higher background plasma temperature and toroidal magnetic field will increase the absorption, and there is a peak value of γ{sub α} when n{sub e}≈8×10{sup 19}m{sup −3} for ITER-like scenario. The thermal corrections to the cold plasma dispersion relation will change the damping rate to a certain extent under some specific conditions. We have also evaluated the fraction of LH power absorbed by the alpha particles, η ≈ 0.47% and 4.1% for an LH frequency of 5 GHz and 3.7 GHz respectively for ITER-like scenario. This work gives the effective reference for the choice of parameters of future fusion reactors.
Correction for multiple scattering of unpolarized photons in attenuation coefficient measurements
Fernandez, J.E.; Sumini, M.; Satori, R.
1995-01-01
Calculations of the diffusion of unpolarized photons in thin thickness targets have been performed with recourse to a vector transport model taking rigorously into account the polarization introduced by the scattering interactions. An order-of-interactions solution of the Boltzmann transport equation for photons was used to describe the multiple scattering terms due to the prevailing effects in the X-ray regime. An analytical expression for the correction factor to the attenuation coefficient is given in term of the solid angle subtended by the detector and the energy interval characterizing the detection response. Although the main corrections are due to the influence of the pure Rayleigh effect, first- and second-order chains involving the Rayleigh and Compton effects have been considered as possible sources of overlapping contributions to the transmitted intensity. The extent of the corrections is estimated and some examples are given for pure element targets.
Derivation of the chemical-equilibrium rate coefficient using scattering theory
NASA Technical Reports Server (NTRS)
Mickens, R. E.
1977-01-01
Scattering theory is applied to derive the equilibrium rate coefficient for a general homogeneous chemical reaction involving ideal gases. The reaction rate is expressed in terms of the product of a number of normalized momentum distribution functions, the product of the number of molecules with a given internal energy state, and the spin-averaged T-matrix elements. An expression for momentum distribution at equilibrium for an arbitrary molecule is presented, and the number of molecules with a given internal-energy state is represented by an expression which includes the partition function.
NASA Astrophysics Data System (ADS)
Sung, Kung-Bin; Chen, Hsi-Hsun
2012-10-01
Diffuse reflectance spectroscopy has been applied to detect tissue absorption and scattering properties associated with dysplasia, which is a potential precursor of epithelial cancers. The ability of DRS techniques to detect dysplasia could be improved by enhancing the detection of optical properties of the thin epithelial layer where dysplasia occurs. We propose a beveled fiber bundle probe consisting of a source fiber and multiple detection fibers parallel to each other and oriented obliquely to the tissue surface and investigate the sensitivity of reflectance measured with the probe to optical properties of a two-layered normal oral mucosa model. A scalable Monte Carlo method is employed to speed up analyzing spatially resolved reflectance spectra. Results reveal that the oblique probe is more sensitive to epithelial scattering and less sensitive to both stromal absorption and scattering than conventional perpendicular fiber configuration. The clinical relevance of the enhanced sensitivity to epithelial scattering by the proposed probe is demonstrated by quantifying optical properties of the two-layered tissue model from simulated data. The average error of extracted epithelial scattering coefficient is 1.5% and 32% using the oblique and perpendicular probe, respectively. The errors in other optical properties are all below 10% using the oblique probe.
NASA Astrophysics Data System (ADS)
Arnott, W. P.; Miranda, G. P.; Gaffney, J. S.; Marley, N. A.
2007-05-01
Four photoacoustic spectrometers (PAS) for aerosol light scattering and absorption measurements were deployed in and near Mexico City in March 2006 as part of the Megacity Impacts on Regional and Global Environments (MIRAGE). The four sites included: an urban site at Instituto Mexicano del Petroleo (Mexican Oil Institute, denoted by IMP); a suburban site at the Technological University of Tecamac; a rural site at "La Biznaga" ranch; and a site at the Paseo de Cortes (altitude 3,810 meters ASL) in the rural area above Amecameca in the State of Mexico, on the saddle between the volcanoes Popocatepetl and Iztaccihuatl. A similar campaign was held in Las Vegas, Nevada, USA in January-February, 2003. The IMP site gave in-situ characterization of the Mexico City plume under favorable wind conditions while the other sites provided characterization of the plume, mixed in with any local sources. The second and third sites are north of Mexico City, and the fourth site is south. The PAS used at IMP operates at 532 nm, and conveniently allowed for characterization of gaseous absorption at this wavelength as well. Instruments at the second and third sites operate at 870 nm, and the one at the fourth site at 780 nm. Light scattering measurements are accomplished within the PAS by the reciprocal nephelometery method. In the urban site the aerosol absorption coefficient typically varies between 20 and 180 Mm-1 during the course of the day and significant diurnal variation of the aerosol single scattering albedo was observed probably as a consequence of secondary aerosol formation. Comparisons with TSI nephelometer scattering at the T0 site will be presented. We will present the diurnal variation of the scattering and absorption as well as the single scattering albedo and fraction of absorption due to gases at the IMP site and compare with Las Vegas diurnal variation. Mexico City 'breaths' more during the course of the day than Las Vegas, Nevada in part because the latitude of
NASA Astrophysics Data System (ADS)
Giraev, K. M.; Ashurbekov, N. A.; Magomedov, M. A.; Murtazaeva, A. A.; Medzhidov, R. T.
2015-07-01
Spectra of optical transmission coefficients and optical reflectance for bile and pancreatic juice samples were measured experimentally for different forms of pathologies of the pancreas within the range of 250-2500 nm. The absorption and scattering spectra, as well as the spectrum of the anisotropy factor of scattering, were determined based on the results obtained using the reverse Monte Carlo method. The surface morphology for the corresponding samples of the biological media was studied employing electron microscopy. The dynamics of the optical properties of the biological media was determined depending on the stage of the pathology. It has been demonstrated that the results of the study presented are in a good agreement with pathophysiological data and could supplement and broaden the results of conventional methods for diagnostics of the pancreas.
Assessing blood vessel abnormality via extracting scattering coefficients from OCT images
NASA Astrophysics Data System (ADS)
Levitz, David; Andersen, Claus B.; Frosz, Michael H.; Thrane, Lars; Hansen, Peter R.; Jorgensen, Thomas M.; Andersen, Peter E.
2003-10-01
Background: Coronary artery disease (CAD) is the leading cause of mortality and morbidity in the industrialized world. Optical coherence tomography (OCT) is a high-resolution intravascular imaging technology with a potential for in vivo plaque characterization. Although structural remodeling of the arterial vessel wall during plaque development can change tissue optical scattering properties, very limited evidence is available on the exact optical scattering properties of plaques. The scattering coefficient, μs, and the anisotropy factor, g, can be derived from OCT images by fitting a theoretical model to individual depth-scans. The aim of the current study was to use this method to examine by OCT the scattering properties of human arteries with different stages of atherosclerotic lesion development. Methods: Normal (n=4), lipid-rich (n=4), and fibrous (n=3) aortic blocks as classified by parallel histopathologic examination were obtained within 24 hours of death and imaged by OCT. The intima was located in the OCT images, and then further split into 115 blocks (41 normal, 40 lipid-rich, and 34 fibrous) of adjacent OCT depth-scans transversely spanning ~200-300 μm. Scattering signals from each block were averaged and fit to the theoretical model. From these fittings, μs and g were extracted. Results and Discussion: The optical scattering properties of normal aortic intima were quite different from lipid-rich and fibrous lesions, respectively. We discovered that the normal intima was generally highly forward scattering, i.e., with 0.917
Wei, Jianwei; Lee, Zhongping
2015-02-01
The light absorption of phytoplankton and colored detrital matter (CDM), which includes contribution of gelbstoff and detrital matters, has distinctive yet overlapping features in the ultraviolet (UV) and visible domain. The CDM absorption (a(dg)) increases exponentially with decreasing wavelength while the absorption coefficient of phytoplankton (a(ph)) generally decreases toward the shorter bands for the range of 350-450 nm. It has long been envisioned that including ocean color measurements in the UV range may help the separation of these two components from the remotely sensed ocean color spectrum. An attempt is made in this study to provide an analytical assessment of this expectation. We started with the development of an absorption decomposition model [quasi-analytical algorithm (QAA)-UV], analogous to the QAA, that partitions the total absorption coefficient using information at bands 380 and 440 nm. Compared to the retrieval results relying on the absorption information at 410 and 440 nm of the original QAA, our analyses indicate that QAA-UV can improve the retrieval of a(ph) and a(dg), although the improvement in accuracy is not significant for values at 440 nm. The performance of the UV-based algorithm is further evaluated with in situ measurements. The limited improvement observed with the field measurements highlights that the separation of a(dg) and a(ph) is highly dependent on the accuracy of the ocean color measurements and the estimated total absorption coefficient. PMID:25967770
NASA Astrophysics Data System (ADS)
Wu, J.; Hong, H.; Shang, S.; Dai, M.; Lee, Z.
2007-05-01
We examined the temporal and spatial variabilities of phytoplankton absorption coefficients (αphλ)) and their relationships with physical processes in the northern South China Sea from two cruise surveys during spring (May 2001) and late autumn (November 2002). A large river plume induced by heavy precipitation in May stimulated a phytoplankton bloom on the inner shelf, causing significant changes in the surface water in αph values and B/R ratios (αph(440)/αph(675)). This was consistent with the observed one order of magnitude elevation of chlorophyll α and a shift from a pico/nano dominated phytoplankton community to one dominated by micro-algae. At the seasonal level, enhanced vertical mixing due to strengthened northeast monsoon in November has been observed to result in higher surface αph(675) (0.002-0.006 m-1 higher) and less pronounced subsurface maximum on the outer shelf/slope in November as compared that in May. Measurements of αph and B/R ratios from three transects in November revealed a highest surface αph(675) immediately outside the mouth of the Pearl River Estuary, whereas lower αph(675) and higher B/R ratios were featured in the outer shelf/slope waters, demonstrating the respective influence of the Pearl River plume and the oligotrophic nature of South China Sea water. The difference in spectral shapes of phytoplankton absorption (measured by B/R ratios and bathochromic shifts) on these three transects infers that picoprocaryotes are the major component of the phytoplankton community on the outer shelf/slope rather than on the inner shelf. In addition, a regional tuning of the phytoplankton absorption spectral model (Carder et al., 1999) demonstrated a greater spatial variation than seasonal variation in the lead parameter a0(λ). These results suggest that phytoplankton absorption properties in a coastal region such as the northern South China Sea are complex and region-based parameterization is mandatory in order for remote sensing
Gaigalas, A. K.; He, Hua-Jun; Wang, Lili
2009-01-01
A spectrometer with an integrating sphere (IS) detector was used to measure the absorbance due to scattering and absorption. Analysis of the measurement process showed that two measurements of the absorbance, one with the cuvette placed in the normal spectrometer position, and the second with the cuvette placed next to the entrance aperture of the IS detector, provide enough information to separate the contributions from scattering and molecular absorption. Measurements were carried out with mixtures of microsphere and chromophore solutions. Two cases were examined: microspheres suspended in an aqueous fluorescein solution, and microspheres suspended in an aqueous holmium oxide solution. In both cases, the proposed measurement model gave results which were in good agreement with the expected response. Measurements on microalgae suspensions yielded a molecular absorption contribution and a scattering contribution. The scattering contribution had significant spectral structure which was inversely related to the molecular absorption contribution. The absorption and scattering contributions may provide independent information on the status of chlorophyll molecules and the structure of chloroplasts in microalgae. PMID:27504214
NASA Astrophysics Data System (ADS)
Sierau, B.; Covert, D. S.; Coffman, D. J.; Quinn, P. K.; Bates, T. S.
2007-12-01
In-situ, three wavelength-measurements of optical properties of the aerosol near the coast of Texas, i.e. in the region of Houston and the Houston ship channel, as well as in the Gulf of Mexico were carried out onboard the NOAA research vessel Ronald H. Brown during the 2006 TEXAQS/GoMACCS field campaign in July through September 2006. Aerosol scattering, hemispheric backscattering and absorption-coefficients were measured for particles with diameters dp<10μm and dp<1μm using integrating nephelometers and filter-based absorption photometers (PSAPs) at 60% RH (nephelometers). Submicrometric light scattering coefficient was measured at two additional humidities, ca. 25%, and 85% RH. Together with the 60% RH data, this enabled determination of the effect of aerosol hygroscopic growth on light scattering and an empirical light scattering growth factor. The results are relevant to radiation transfer, visibility, air quality, and interpretation of remote sensing data from lidar and satellite. The extensive and intensive optical properties along with meteorological analysis are used to characterize the aerosol in the Houston, TX region and the Coastal Gulf of Mexico and to provide information critical to understanding the climatic and air quality impacts of those aerosols. Further analysis focuses on the changes that these properties undergo during chemical processing of emissions within the project area and how they are affected by changes in atmospheric relative humidity that accompany transport, diurnal cycles and vertical mixing. The results are classified by source region and flow regime of the sampled air masses to identify distinct aerosol populations. Special emphasis is given to the physico-chemical properties of aerosols measured during two periods when Saharan dust was encountered during the cruise as well as to several air pollution episodes and plumes from industrial complexes. The combination of hygroscopic growth, light scattering and absorption
A Guide to Electronic Multipoles in Photon Scattering and Absorption
NASA Astrophysics Data System (ADS)
Lovesey, Stephen William; Balcar, Ewald
2013-02-01
The practice of replacing matrix elements in atomic calculations by those of convenient operators with strong physical appeal has a long history, and in condensed matter physics it is perhaps best known through use of operator equivalents in electron resonance by Elliott and Stevens. Likewise, electronic multipoles, created with irreducible spherical-tensors, to represent charge-like and magnetic-like quantities are widespread in modern physics. Examples in recent headlines include a magnetic charge (a monopole), an anapole (a dipole) and a triakontadipole (a magnetic-like atomic multipole of rank 5). In this communication, we aim to guide the reader through use of atomic, spherical multipoles in photon scattering, and resonant Bragg diffraction and dichroic signals in particular. Applications to copper oxide CuO and neptunium dioxide (NpO2) are described. In keeping with it being a simple guide, there is sparse use in the communication of algebra and expressions are gathered from the published literature and not derived, even when central to the exposition. An exception is a thorough grounding, contained in an Appendix, for an appropriate version of the photon scattering length based on quantum electrodynamics. A theme of the guide is application of symmetry in scattering, in particular constraints imposed on results by symmetry in crystals. To this end, a second Appendix catalogues constraints on multipoles imposed by symmetry in crystal point-groups.
NASA Astrophysics Data System (ADS)
Vivacqua, Marco; Espinosa, Daniel; Martins Figueiredo Neto, Antônio
2012-06-01
We investigate the occurrence of the optical Kerr effect and two-photon absorption when an oil-based magnetic Fe3O4 nanoparticles colloidal suspension is illuminated with high intensity femtosecond laser pulses. The frequency of the pulses is controlled and the Z-scan technique is employed in our measurements of the nonlinear optical Kerr coefficient (n2) and two-photon absorption coefficient (β). From these values it was possible to calculate the real and imaginary parts of the third-order susceptibility. We observed that increasing the pulse frequency, additional physical processes take place, increasing artificially the absolute values of n2 and β. The experimental conditions are discussed to assure the obtention of reliable values of these nonlinear optical parameters, which may be useful in all-optical switching and optical power limiting applications.
NASA Astrophysics Data System (ADS)
Cacciani, Marco; Disarra, Alcide; Fiocco, Giorgio
1987-06-01
Instrumentation for the absolute measurement of the ozone absorption coefficient in the Huggins bands at different temperatures was set up. Ozone is produced with an electrical discharge and stored cryogenically; differential absorption measurements are carried out in a slowly evolving mixture of ozone and molecular oxygen. Results in the region 339 to 362 nm at temperatures between minus 30 and plus 40 C are reported. Results support Katayama's (1979) model of the transitions giving rise to the Huggins absorption bands of ozone. For measurements of atmospheric ozone profiles by DIAL techniques, the results on the temperature dependence of the absorption coefficient at the wavelength corresponding to the third harmonic of an NdYAG laser are stressed.
Dimofte, Andreea; Finlay, Jarod C; Zhu, Timothy C
2005-05-21
We have developed a method to quickly determine tissue optical properties (absorption coefficient mu(a) and transport scattering coefficient mu'(s)) by measuring the ratio of light fluence rate to source power along a linear channel at a fixed distance (5 mm) from an isotropic point source. Diffuse light is collected by an isotropic detector whose position is determined by a computer-controlled step motor, with a positioning accuracy of better than 0.1 mm. The system automatically records and plots the light fluence rate per unit source power as a function of position. The result is fitted with a diffusion equation to determine mu(a) and mu'(s). We use an integrating sphere to calibrate each source-detector pair, thus reducing uncertainty of individual calibrations. To test the ability of this algorithm to accurately recover the optical properties of the tissue, we made measurements in tissue simulating phantoms consisting of Liposyn at concentrations of 0.23, 0.53 and 1.14% (mu'(s) = 1.7-9.1 cm(-1)) in the presence of Higgins black India ink at concentrations of 0.002, 0.012 and 0.023% (mu(a) = 0.1-1 cm(-1)). For comparison, the optical properties of each phantom are determined independently using broad-beam illumination. We find that mu(a) and mu'(s) can be determined by this method with a standard (maximum) deviation of 8% (15%) and 18% (32%) for mu(a) and mu'(s), respectively. The current method is effective for samples whose optical properties satisfy the requirement of the diffusion approximation. The error caused by the air cavity introduced by the catheter is small, except when mu(a) is large (mu(a) > 1 cm(-1)). We presented in vivo data measured in human prostate using this method. PMID:15876668
Instruments and methods for measuring the backward-scattering coefficient of ocean waters.
Maffione, R A; Dana, D R
1997-08-20
The backward-scattering coefficient bb is an important optical property that plays a central role in studies of ocean-color remote sensing, suspended particle distributions, water clarity, and underwater visibility. We investigate the fixed-angle backscattering sensor approach for the application of measuring bb . Analysis shows that the sensor response to volume scattering can be expressed as the integral of the volume scattering function (VSF) over the backward angles (90 -180 degrees ) weighted by the sensor-response function. We present a procedure for determining the sensor-response function that contains all the information necessary to calibrate the sensor fully to measure the VSF at a nominal backscattering angle. It is shown that, for fixed-angle backscattering sensors,bb is most accurately estimated when the sensor-response function covers the middle range of backscattering angles, roughly 110 -160 degrees , where the shape of the VSF has the least variability. Backscattering at and near the end angles, namely, 90 degrees and 180 degrees , are least correlated with bb . We describe a variety of spectral backscattering sensors that we have developed, and we present their sensor-response functions. PMID:18259450
Recent measurements of the spectral backward-scattering coefficient in coastal waters
NASA Astrophysics Data System (ADS)
Maffione, Robert A.; Dana, David R.
1997-02-01
The backward scattering coefficient bb was measured in various coastal waters with fixed-angle backscattering sensors developed by the authors. Measurements were made at four discrete wavelengths covering the spectral range 440 to 675 nm. A power law spectral dependence of bb due to scattering by particles was investigated of the form bbp((lambda) ) equals bbp ((lambda) 0) ((lambda) 0/(lambda) )(gamma , where the superscript p denotes particle scattering and (lambda) is the wavelength. The exponent (gamma) depends on the particle size distribution and composition of particles. Extensive measurements in Monterey Bay, California, showed that 0.1
Mass-energy absorption coefficient and backscatter factor ratios for kilovoltage x-ray beams
NASA Astrophysics Data System (ADS)
Ma, C.-M.; Seuntjens, J. P.
1999-01-01
For low-energy (up to 150 kV) x-rays, the ratio of mass-energy absorption coefficients for water to air, , and the backscatter factor B are used in the conversion of air kerma, measured free-in-air, to water kerma on the surface of a water phantom. For clinical radiotherapy, similar conversion factors are needed for the determination of the absorbed dose to biological tissues on (or near) the surface of a human body. We have computed the ratios and B factor ratios for different biological tissues including muscle, soft tissue, lung, skin and bone relative to water. The ratios were obtained by integrating the respective mass-energy absorption coefficients over the in-air primary photon spectra. We have also calculated the ratios at different depths in a water phantom in order to convert the measured in-phantom water kerma to the absorbed dose to various biological tissues. The EGS4/DOSIMETER Monte Carlo code system has been used for the simulation of the energy fluence at different depths in a water phantom irradiated by a kilovoltage x-ray beam of variable beam quality (HVL: 0.1 mm Al-5 mm Cu), field size and source-surface distance (SSD). The same code was also used in the calculation of the B factor ratios, soft tissue to water and bone to water. The results show that the B factor for bone differs from the B factor for water by up to 20% for a 100 kV beam (HVL: 2.65 mm Al) with a 100 field. On the other hand, the difference in the B factor between water and soft tissue is insignificant (well within 1% generally). This means that the B factors for water may be directly used to
NASA Technical Reports Server (NTRS)
Smith, Wm. Hayden; Conner, Charles P.; Baines, Kevin H.
1990-01-01
A novel laser intracavity photoacoustic spectroscopy method allowing high sample control accuracy due to the small sample volume required has been used to obtain absorption coefficients for the CH4 6190 A band as a function of temperature, from 290 to 100 K. The peak absorption coefficient is found to increase from 0.6 to 1.0/cm, and to be accompanied by significant band shape changes. When used to further constrain the Baines and Bergstrahl (1986) standard model of the Uranus atmosphere, the low-temperature data yield an excellent fit to the bandshape near the 6190 A band's minimum.
Smith, WM.H.; Conner, C.P.; Baines, K.H. JPL, Pasadena, CA )
1990-05-01
A novel laser intracavity photoacoustic spectroscopy method allowing high sample control accuracy due to the small sample volume required has been used to obtain absorption coefficients for the CH{sub 4} 6190 A band as a function of temperature, from 290 to 100 K. The peak absorption coefficient is found to increase from 0.6 to 1.0/cm, and to be accompanied by significant band shape changes. When used to further constrain the Baines and Bergstrahl (1986) standard model of the Uranus atmosphere, the low-temperature data yield an excellent fit to the bandshape near the 6190 A band's minimum. 18 refs.
Rowley, R.L.; Adams, M.E.; Marshall, T.L.; Oscarson, J.L.; Wilding, W.V.; Anderson, D.J.
1997-03-01
Natural gas processors use amine treating processes to remove the acid gases H{sub 2}S and CO{sub 2} from gas streams. Absorption rates of gaseous CO{sub 2} into aqueous N-methyldiethanolamine (MDEA) solutions were measured in a quiescent, inverted-tube diffusiometer by monitoring the rate of pressure drop. The absorption rate was found to be insensitive to the diffusion coefficient of CO{sub 2} in solution but very sensitive to the diffusion rate of bicarbonate and protonated MDEA ions. Evidence also suggested that chemical reaction equilibrium is rapid relative to diffusion. A numerical model was developed on the basis of these observations. The model was used to regress diffusion coefficients of bicarbonate and protonated amine, which must be equivalent by electroneutrality arguments, from measured absorption rates. Complete modeling of the absorption process also required data for the diffusion coefficient of MDEA in water. These were measured using a Taylor dispersion apparatus. CO{sub 2} absorption rates and diffusion coefficients of bicarbonate and protonated MDEA were obtained at 298.2 K and 318.2 K in solutions containing 20, 35, and 50 mass % MDEA in water.
Reflection and Scattering of Acoustical Waves from a Discontinuity in Absorption
NASA Astrophysics Data System (ADS)
Jones, J. P.; Leeman, S.; Nolan, E.; Lee, D.
The reflection and transmission of a plane acoustical wave from a planar boundary at the interface between two homogeneous media of different acoustical properties is a classical problem in acoustics that has served as a basis for many developments in acoustics for over 100 years. This problem, detailed in virtually every textbook on acoustics, provides us with the acoustical analogue to Snell's Law in optics and gives us correspondingly simple results. Classical acoustics predicts that a reflection from a boundary occurs only if the characteristic acoustical impedances of the two media are different. Here we show that a reflection also occurs if the media have the same impedances but different absorption coefficients. Our analysis yields some surprising results. For example, a reflection will occur at a discontinuity in absorption even if the impedance is uniform and continuous across the interface. In addition, a discontinuity in impedance at an interface between two media that have constant and equal, but non-zero absorption, results in a reflection coefficient that is dependent on absorption as well as impedance. In general, reflection coefficients now become frequency dependent. To experimentally test our results, we measured the reflection at the interface between water and castor oil, two liquids with similar impedances but very different absorption coefficients. Measurement of the reflection coefficient between 1 and 50 MHz demonstrated a frequency dependence that was in good agreement with our analysis.
NASA Astrophysics Data System (ADS)
Lim, S.; Lee, M.; Kim, S.-W.; Yoon, S.-C.; Lee, G.; Lee, Y.
2013-12-01
Carbonaceous and soluble ionic species of PM1.0 and PM10 were measured along with the absorption and scattering properties and aerosol number size distributions at Gosan climate observatory (GCO) from January to September 2008. The daily averaged equivalent black carbon (EBC) measured as aerosol absorption exhibited two types of spectral dependence with a distinct maximum (peak) at either 370 nm or 880 nm, by which two subsets were extracted and classified into the respective groups (370 nm and 880 nm). The 370 nm group was distinguished by high organic carbon (OC) concentrations relative to elemental carbon (EC) and sulfate, but sulfate was predominant for the 880 nm group. The PM1.0 OC of the 370 nm group was mainly composed of refractory and pyrolized components that correlated well with PM1.0 EC1, referred to as char EC, which suggests biofuel and biomass combustion as the source of these OC fractions, particularly during winter. The scanning electron microscope (SEM) images and the number size distributions implied that aerosols of the 370 nm group were externally mixed upon transport in fast-moving air masses that passed through the Beijing area in about one day. In contrast, the aerosols of the 880 nm group were characterized by high sulfate concentrations, and seemed to be internally mixed during slow transport over the Yellow Sea region over approximately two to four days. The absorption and scattering coefficients of the 880 nm group were noticeably higher compared to those of the 370 nm group. The average absorption ångström exponent (AAE) was estimated to be 1.29 and 1.0 for the 370 nm and 880 nm groups, respectively, in the range 370-950 nm. These results demonstrated that the optical properties of aerosols were intimately linked to chemical composition and mixing state, characteristics determined both by source and atmospheric aging processes. In OC dominant aerosols, absorption was enhanced in the UV region, which was possibly due to refractory and
NASA Astrophysics Data System (ADS)
Lim, S.; Lee, M.; Kim, S.-W.; Yoon, S.-C.; Lee, G.; Lee, Y. J.
2014-08-01
Carbonaceous and soluble ionic species of PM1.0 and PM10 were measured along with the absorption and scattering properties and aerosol number size distributions at Gosan Climate Observatory (GCO) from January to September 2008. The daily averaged equivalent black carbon (EBC) measured as aerosol absorption exhibited two types of spectral dependence with a distinct maximum (peak) at either 370 nm or 880 nm, by which two subsets were extracted and classified into the respective groups (370 and 880 nm). The 370 nm group was distinguished by high organic carbon (OC) concentrations relative to elemental carbon (EC) and sulfate, but sulfate was predominant for the 880 nm group. The PM1.0 OC of the 370 nm group was mainly composed of refractory and pyrolized components that correlated well with PM1.0 EC1, referred to as char EC, which suggests biofuel and biomass combustion as the source of these OC fractions, particularly during winter. The scanning electron microscope (SEM) images and the number size distributions implied that aerosols of the 370 nm group were externally mixed upon transport in fast-moving air masses that passed through the Beijing area in about one day. In contrast, the aerosols of the 880 nm group were characterized by high sulfate concentrations, and seemed to be internally mixed during slow transport over the Yellow Sea region over approximately 2 to 4 days. The absorption and scattering coefficients of the 880 nm group were noticeably higher compared to those of the 370 nm group. The average absorption ångström exponent (AAE) was estimated to be 1.29 and 1.0 for the 370 and 880 nm groups, respectively, in the range 370-950 nm. These results demonstrated that the optical properties of aerosols were intimately linked to chemical composition and mixing state, characteristics determined both by source and atmospheric aging processes. In OC dominant aerosols, absorption was enhanced in the UV region, which was possibly due to refractory and pyrolized
Tissue characterization with ballistic photons: counting scattering and/or absorption centres
NASA Astrophysics Data System (ADS)
Corral, F.; Strojnik, M.; Paez, G.
2015-03-01
We describe a new method to separate ballistic from the scattered photons for optical tissue characterization. It is based on the hypothesis that the scattered photons acquire a phase delay. The photons passing through the sample without scattering or absorption preserve their coherence so they may participate in interference. We implement a Mach-Zehnder experimental setup where the ballistic photons pass through the sample with the delay caused uniquely by the sample indices of refraction. We incorporate a movable mirror on the piezoelectric actuator in the sample arm to detect the amplitude of the modulation term. We present the theory that predicts the path-integrated (or total) concentration of the scattering and absorption centres. The proposed technique may characterize samples with transmission attenuation of ballistic photons by a factor of 10-14.
Scattering and Absorption by Nonspherical Particles in Planetary Atmospheres
NASA Technical Reports Server (NTRS)
West, Robert A.
2005-01-01
The atmospheres of Mars, the giant planets, and Titan all support populations of nonspherical particles. Analyses of observations of these atmospheres therefore rely on an understanding of the optical properties of nonspherical particles. We can glean information on particle size and composition from the wavelength dependence of the optical depth and from the shape of the forward peak of the scattering phase function. Additional information comes from polarization measurements which have been especially fruitful for Titan's haze. The Mars atmosphere contains mineral dust particles with effective radii near 1.6 micro meters, and water ice particles with radii between about 1 and 4 micro meters. The uppermost tropospheric hazes in Jupiter and Saturn are composed of ice crystals of ammonia, water and possibly traces of ammonium hydrosulfide, Methane ice and hydrogen sulfide ice are present in the atmospheres of Uranus and Neptune. Size estimation for these hazes in the giant planets is difficult, and even the expected spectral signatures are elusive, Titan's haze is both forward scattering and strongly polarized - a combination which points toward a fractal aggregate struc1.ure of 10 - 100 or more organic monomers whose radius is about 0.06 micro meters. Polar stratospheric hazes on Jupiter and Saturn also display this characteristic.
Multiple-scattering calculations of the uranium L3-edge x-ray-absorption near-edge structure
NASA Astrophysics Data System (ADS)
Hudson, E. A.; Rehr, J. J.; Bucher, J. J.
1995-11-01
A theoretical study of the uranium L3-edge x-ray absorption near-edge structure (XANES) is presented for several uranium compounds, including oxides, intermetallics, uranyl fluoride, and α-uranium. Calculations were performed using feff6, an ab initio multiple-scattering (MS) code that includes the most important features of current theories. The results, which account for both the fine structure χ and the atomiclike background μ0 of the absorption coefficient μ, are compared to new and previously measured experimental spectra, reavealing very good agreement for most systems. For several compounds, a more detailed theoretical analysis determined the influence of cluster size and scattering order upon the calculated spectra. Results indicate that MS paths and scattering paths that include rather distant atoms make significant contributions for UO2, whereas XANES for crystals with lower symmetry and density can be modeled using only shorter single-scattering paths. In most cases, assumption of a screened final state in the calculation gives better agreement with experiment than use of an unscreened final state. The successful modeling of spectra for a variety of different uranium compounds, with differing spectral features, indicates that the semirelativistic treatment of XANES used here is adequate even for heavy elements. The well-known resonance, observed experimentally for uranyl (UO2+2) compounds ~=15 eV above the white line, is successfully modeled here for the first time, using multiple-scattering paths within the O-U-O axial bonds. Overlapping muffin-tin spheres were required in the calculation, probably as a result of the short uranyl axial bonds.
NASA Astrophysics Data System (ADS)
Artaxo, P.; Brito, J. F.; Rizzo, L. V.
2012-12-01
The megacity of São Paulo with its 19 million people and 7 million cars is a challenge from the point of view of air pollution. High levels of organic aerosols, PM10, black carbon and ozone and the peculiar situation of the large scale use of ethanol fuel makes it a special case. Little is known about the impact of ethanol on air quality and human health and the increase of ethanol as vehicle fuel is rising worldwide An experiment was designed to physico-chemical properties of aerosols in São Paulo, as well as their optical properties. Aerosol size distribution in the size range of 1nm to 10 micrometers is being measured with a Helsinki University SMPS (Scanning Mobility Particle Sizer), an NAIS (Neutral ion Spectrometer) and a GRIMM OPC (Optical Particle Counter). Optical properties are being measured with a TSI Nephelometer and a Thermo MAAP (Multi Angle Absorption Photometer). A CIMEL sunphotometer from the AERONET network measure the aerosol optical depth. Furthermore, a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) and an Aerosol Chemical Speciation Monitor (ACSM) are used to real-time VOC analysis and aerosol composition, respectively. The ACSM was operated for 3 months continuosly during teh wintertime of 2012. The measured total particle concentration typically varies between 10,000 and 30,000 cm-3 being the lowest late in the night and highest around noon and frequently exceeding 50,000 cm-3. Clear diurnal patterns in aerosol optical properties were observed. Scattering and absorption coefficients typically range between 20 and 100 Mm-1 at 450 nm, and between 10 to 40 Mm-1 at 637 nm, respectively, both of them peaking at 7:00 local time, the morning rush hour. The corresponding single scattering albedo varies between 0.50 and 0.85, indicating a significant contribution of primary absorbing particles to the aerosol population. During the first month a total of seven new particle formation events were observed with growth rates ranging from 9 to 25
Domené, Esteban A; Balzarotti, Francisco; Bragas, Andrea V; Martínez, Oscar E
2009-12-15
We present a novel noncontact, photothermal technique, based on the focus error signal of a commercial CD pickup head that allows direct determination of absorption in thin films. Combined with extinction methods, this technique yields the scattering contribution to the losses. Surface plasmon polaritons are excited using the Kretschmann configuration in thin Au films of varying thickness. By measuring the extinction and absorption simultaneously, it is shown that dielectric constants and thickness retrieval leads to inconsistencies if the model does not account for scattering. PMID:20016617
Vittoria, Fabio A. Diemoz, Paul C.; Endrizzi, Marco; Olivo, Alessandro; Wagner, Ulrich H.; Rau, Christoph; Robinson, Ian K.
2014-03-31
We propose two different approaches to retrieve x-ray absorption, refraction, and scattering signals using a one dimensional scan and a high resolution detector. The first method can be easily implemented in existing procedures developed for edge illumination to retrieve absorption and refraction signals, giving comparable image quality while reducing exposure time and delivered dose. The second method tracks the variations of the beam intensity profile on the detector through a multi-Gaussian interpolation, allowing the additional retrieval of the scattering signal.
Method for measuring changes in light absorption of highly scattering media
Bigio, Irving J.; Johnson, Tamara M.; Mourant, Judith R.
2002-01-01
The noninvasive measurement of variations in absorption that are due to changes in concentrations of biochemically relevant compounds in tissue is important in many clinical settings. One problem with such measurements is that the pathlength traveled by the collected light through the tissue depends on the scattering properties of the tissue. It is demonstrated, using both Monte Carlo simulations and experimental measurements, that for an appropriate separation between light-delivery and light-collection fibers, the pathlength of the collected photons is insensitive to scattering parameters for the range of parameters typically found in tissue. This is important for developing rapid, noninvasive, inexpensive, and accurate methods for measuring absorption changes in tissue.
Majaron, Boris; Milanic, Matija
2007-02-21
Spectral variation of the sample absorption coefficient in mid-infrared (muIR) demands caution in photothermal radiometric measurements, because a constant muIR is regularly assumed in inverse analysis of the acquired signals. Adverse effects of such approximation were recently demonstrated in numerical simulations of pulsed photothermal radiometric (PPTR) temperature profiling in soft biological tissues, utilizing a general-purpose optimization code in the reconstruction process. We present here an original reconstruction code, which combines a conjugate gradient minimization algorithm with non-negativity constraint to the sought temperature vector. For the same test examples as in the former report (hyper-Gaussian temperature profiles, InSb detector with 3-5 microm acquisition band, signal-to-noise ratio SNR=300) we obtain markedly improved reconstruction results, both when using a constant value mueff and when the spectral variation muIR(lambda) is accounted for in the analysis. By comparing the results, we find that the former approach introduces observable artefacts, especially in the superficial part of the profile (z<100 microm). However, the artefacts are much less severe than previously reported and are almost absent in the case of a deeper, single-lobed test profile. We demonstrate that the observed artefacts do not result from sub-optimal selection of mueff, and that they vary with specific realizations of white noise added to the simulated signals. The same holds also for a two-lobed test profile. PMID:17264372
NASA Astrophysics Data System (ADS)
Fuente, Raquel; Apiñaniz, Estibaliz; Mendioroz, Arantza; Salazar, Agustín
2011-08-01
Modulated photothermal radiometry (PTR) has been widely used to measure the thermal diffusivity of bulk materials. The method is based on illuminating the sample with a plane light beam and measuring the infrared emission with an infrared detector. The amplitude and phase of the PTR voltage is recorded as a function of the modulation frequency and then fitted to the theoretical model. In this work, we test the ability of modulated PTR to retrieve simultaneously the thermal diffusivity and the optical absorption coefficient of homogeneous slabs. In order to eliminate the instrumental factor, self-normalization is used, i.e., the ratio of the PTR signal recorded at the rear and front surfaces. The influence of the multiple reflections of the light beam, the heat losses, and the transparency to infrared wavelengths are analyzed. Measurements performed on a wide variety of homogeneous materials, covering the whole range from transparent to opaque, confirm the validity of the method. In Part II of this work, the method is extended to multilayered materials.
Noise-driven optical absorption coefficients of impurity doped quantum dots
NASA Astrophysics Data System (ADS)
Ganguly, Jayanta; Saha, Surajit; Pal, Suvajit; Ghosh, Manas
2016-01-01
We make an extensive investigation of linear, third-order nonlinear, and total optical absorption coefficients (ACs) of impurity doped quantum dots (QDs) in presence and absence of noise. The noise invoked in the present study is a Gaussian white noise. The quantum dot is doped with repulsive Gaussian impurity. Noise has been introduced to the system additively and multiplicatively. A perpendicular magnetic field acts as a source of confinement and a static external electric field has been applied. The AC profiles have been studied as a function of incident photon energy when several important parameters such as optical intensity, electric field strength, magnetic field strength, confinement energy, dopant location, relaxation time, Al concentration, dopant potential, and noise strength take on different values. In addition, the role of mode of application of noise (additive/multiplicative) on the AC profiles has also been analyzed meticulously. The AC profiles often consist of a number of interesting observations such as one photon resonance enhancement, shift of AC peak position, variation of AC peak intensity, and bleaching of AC peak. However, presence of noise alters the features of AC profiles and leads to some interesting manifestations. Multiplicative noise brings about more complexity in the AC profiles than its additive counterpart. The observations indeed illuminate several useful aspects in the study of linear and nonlinear optical properties of doped QD systems, specially in presence of noise. The findings are expected to be quite relevant from a technological perspective.
NASA Astrophysics Data System (ADS)
Clark, Christopher J. R.; Schofield, Simon P.; Gomez, Haley L.; Davies, Jonathan I.
2016-06-01
We use the published photometry and spectroscopy of 22 galaxies in the Herschel Reference Survey to determine that the value of the dust mass absorption coefficient κd at a wavelength of 500 μm is kappa _{500} = 0.051^{+0.070}_{-0.026} m^{2 kg^{-1}}. We do so by taking advantage of the fact that the dust-to-metals ratio in the interstellar medium of galaxies appears to be constant. We argue that our value for κd supersedes that of James et al. - who pioneered this approach for determining κd - because we take advantage of superior data, and account for a number of significant systematic effects that they did not consider. We comprehensively incorporate all methodological and observational contributions to establish the uncertainty on our value, which represents a marked improvement on the oft-quoted `order-of-magnitude' uncertainty on κd. We find no evidence that the value of κd differs significantly between galaxies, or that it correlates with any other measured or derived galaxy properties. We note, however, that the availability of data limits our sample to relatively massive (109.7 < M⋆ < 1011.0 M⊙), high metallicity (8.61 < [ 12 + log_{10} fracOH ] < 8.86) galaxies; future work will allow us to investigate a wider range of systems.
NASA Astrophysics Data System (ADS)
Vuye, Cedric; Vanlanduit, Steve; Guillaume, Patrick
2009-06-01
When using optical measurements of the sound fields inside a glass tube, near the material under test, to estimate the reflection and absorption coefficients, not only these acoustical parameters but also confidence intervals can be determined. The sound fields are visualized using a scanning laser Doppler vibrometer (SLDV). In this paper the influence of different test signals on the quality of the results, obtained with this technique, is examined. The amount of data gathered during one measurement scan makes a thorough statistical analysis possible leading to the knowledge of confidence intervals. The use of a multi-sine, constructed on the resonance frequencies of the test tube, shows to be a very good alternative for the traditional periodic chirp. This signal offers the ability to obtain data for multiple frequencies in one measurement, without the danger of a low signal-to-noise ratio. The variability analysis in this paper clearly shows the advantages of the proposed multi-sine compared to the periodic chirp. The measurement procedure and the statistical analysis are validated by measuring the reflection ratio at a closed end and comparing the results with the theoretical value. Results of the testing of two building materials (an acoustic ceiling tile and linoleum) are presented and compared to supplier data.
Effects of nanosilver on sound absorption coefficients in solid wood species.
Taghiyari, Hamid Reza; Esmailpour, Ayoub; Zolfaghari, Habib
2016-06-01
Sound absorption coefficients (ACs) were determined in five solid woods (poplar, beech, walnut, mulberry, and fir) in the longitudinal and tangential directions at four different frequencies of 800, 1000, 2000, and 4000 Hz. The length of the longitudinal and tangential specimens was 50-mm and 10-mm, respectively. Separate sets of specimens were impregnated with either nanosilver suspension or water. The size range of nanoparticles was 30-80 nm. Results showed that sound ACs were lower in longitudinal specimens because sound waves could penetrate the open ends of vessels more easily, being trapped and damped there. Impregnation with both nanosilver suspension and water resulted in a significant decrease in the sound ACs. The decrease in the ACs was due to the collapsing and accumulation of perforation plates and cell parts, blocking the way through which waves could pass through the vessels. This caused higher damping due to a phenomenon called vibration decay. Correlation between gas permeability versus sound AC is significantly dependant on the porous structure of individual specimens. PMID:27256895
Determination of the diffusion length and the optical self absorption coefficient using EBIC model
NASA Astrophysics Data System (ADS)
Guermazi, S.; Guermazi, H.; Mlik, Y.; El Jani, B.; Grill, C.; Toureille, A.
2001-10-01
We have developed a model of calculation of the induced current due to an electron beam. The expression for the electron beam induced current (EBIC) with an extended generation profile is obtained via the resolution of a steady state continuity equation by the Green function method, satisfying appropriated boundary conditions to the physical model. The generation profile takes into account the lateral diffusion, the effect of defects, dislocations and recombination surfaces besides the number of absorbed electrons and that of diffuse electrons as a function of the depth. In the case of a Schottky diode Au/GaAs obtained by metalorganic vapour phase epitaxy (MOVPE) method, the theoretical induced current profile is compared to the experimental one and to theoretical profiles whose analytical expressions are given by van Roosbroeck and Bresse. The minority carriers diffusion length L_n = 2 μm and the optical self-absorption coefficient a=0.034 μm^{-1} can be deduced from the experimental current profile, measured by scanning electron microscopy. The theoretical curve, obtained from the proposed model is in a good agreement with the experimental one for surface recombination velocity 10^6 cm s^{-1} except for distances far from the depletion layer (x_0 > 2.3 μm) where the photocurrent produced by the multiple process of the reabsorbed recombination radiation is preponderant. Our results are in agreement with those obtained by other experimental techniques on the same samples.
Control of acoustic absorption in one-dimensional scattering by resonant scatterers
NASA Astrophysics Data System (ADS)
Merkel, A.; Theocharis, G.; Richoux, O.; Romero-García, V.; Pagneux, V.
2015-12-01
We experimentally report perfect acoustic absorption through the interplay of the inherent losses and transparent modes with high Q factor. These modes are generated in a two-port, one-dimensional waveguide, which is side-loaded by isolated resonators of moderate Q factor. In symmetric structures, we show that in the presence of small inherent losses, these modes lead to coherent perfect absorption associated with one-sided absorption slightly larger than 0.5. In asymmetric structures, near perfect one-sided absorption is possible (96%) with a deep sub-wavelength sample ( λ / 28 , where λ is the wavelength of the sound wave in the air). The control of strong absorption by the proper tuning of the radiation leakage of few resonators with weak losses will open possibilities in various wave-control devices.
Design data for radars based on 13.9 GHz Skylab scattering coefficient measurements
NASA Technical Reports Server (NTRS)
Moore, R. K. (Principal Investigator)
1974-01-01
The author has identified the following significant results. Measurements made at 13.9 GHz with the radar scatterometer on Skylab have been combined to produce median curves of the variation of scattering coefficient with angle of incidence out to 45 deg. Because of the large number of observations, and the large area averaged for each measured data point, these curves may be used as a new design base for radars. A reasonably good fit at larger angles is obtained using the theoretical expression based on an exponential height correlation function and also using Lambert's law. For angles under 10 deg, a different fit based on the exponential correlation function, and a fit based on geometric optics expressions are both reasonably valid.
Chazel, V; Houpert, P; Paquet, F; Ansoborlo, E
2001-01-01
In the Human Respiratory Tract Model (HRTM) described in ICRP Publication 66, time-dependent dissolution is described by three parameters: the fraction dissolved rapidly, fr, and the rapid and slow dissolution rates sr and ss. The effect of these parameters on the dose coefficient has been studied. A theoretical analysis was carried out to determine the sensitivity of the dose coefficient to variations in the values of these absorption parameters. Experimental values of the absorption parameters and the doses per unit intake (DPUI) were obtained from in vitro dissolution tests, or from in vivo experiments with rats, for five industrial uranium compounds UO2, U3O8, UO4, UF4 and a mixture of uranium oxides. These compounds were classified in terms of absorption types (F, M or S) according to ICRP. The overall result was that the factor which has the greatest influence on the dose coefficient was the slow dissolution rate ss. This was verified experimentally, with a variation of 20% to 55% for the DPUI according to the absorption type of the compound. In contrast, the rapid dissolution rate sr had little effect on the dose coefficient, excepted for Type F compounds. PMID:11487809
Several important optical terms such as "absorbance" and "absorption coefficient" are frequently used ambiguously in the current peer-reviewed literature. Since they are important terms that are required to derive other quantities such as the "apparent quantum yield" of photoprod...
NASA Technical Reports Server (NTRS)
Barstow, M. A.; Lewis, M.; Petre, R.
1983-01-01
Transmittances of thin-film filters fabricated for an extreme-UV astronomy sounding-rocket experiment yield values for the linear absorption coefficient of beryllium in the 50-300-A wavelength range, in which previous measurements are sparse. The inferred values are consistent with the lowest data previously published and may have important consequences for extreme-UV astronomers.
NASA Astrophysics Data System (ADS)
Ebrahimipour, Bahareh Alsadat; Askari, Hassan Ranjbar; Ramezani, Ali Behjat
2016-09-01
The interlevel absorption coefficient of CdSe/ZnS and ZnS/CdSe core-shell Quantum Dot (QD) in luminescent solar concentrators (LSCs) is reported. By considering the quantum confinement effects, the wave functions and eigenenergies of electrons in the nonperturebative system consists of a core-shell QD have been numerically calculated under the frame work of effective-mass approximation by solving a three-dimensional Schrӧdinger equation. And then the absorption coefficient is obtained under density matrix approximation considering in the polymer sheets of the concentrator including the core-shell QDs. The effect of the hetero-structure geometry upon the energy spectrum and absorption coefficient associated to interlevel transitions was also considered. The results show that the core-shell QDs can absorb the photons with higher energy in solar spectrum as compared to the inverted core-shell. And with a small shell layer diameter, the core-shell QDs produce larger linear absorption coefficients and consequently higher efficiency values, however it is inversed for inverted core-shell QDs. The work described here gives a detailed insight into the promise of QD-based LSCs and the optoelectronic devices applications.
NASA Astrophysics Data System (ADS)
Kassianov, E.; Barnard, J.; Pekour, M. S.; Berg, L. K.; Shilling, J.; Flynn, C. J.; Mei, F.; Jefferson, A.
2014-12-01
Scattering and backscattering coefficients of atmospheric aerosol are crucial parameters for numerous climate-relevant applications, including studies related to the Earth's radiation budget. Due to their strong connection to aerosol chemical and microphysical characteristics, in situ measurements have been commonly used for evaluating optical properties routines in global and regional scale models. However, these in situ measurements, including size distribution and chemical composition data, can be subject to uncertainties. Techniques for obtaining these data depend on particle size (submicron versus supermicron) and relative humidity range (dry versus wet conditions). In this study, we examine how the data uncertainties can impact the level of agreement between the calculated and measured optical properties (commonly known as optical closure). Moreover, we put forth a novel technique for inferring in parallel the effective density and real refractive index of weakly absorbing aerosols from simultaneously measured size distributions (with mobility and aerodynamic sizes), and two optical properties, namely the scattering coefficient and hemispheric backscatter fraction, measured by integrating nephelometer. We demonstrate the performance of our technique, which permits discrimination between the retrieved aerosol characteristics of sub-micron and sub-10-micron particles, using both a sensitivity study with synthetically generated inputs with random noise and a six-week case study with real measurements. These measurements cover a wide range of coastal summertime conditions observed during the recent Two-Column Aerosol Project (TCAP, http://campaign.arm.gov/tcap/) and include periods with a wide range of aerosol loading and relative humidity. Finally, we discuss how in situ data and retrievals of aerosol characteristics can be applied for model evaluation.
Wang, J.; Zhang, X. Yu, L.; Zhao, X.
2014-12-15
In tokamaks, fusion generated α particles may absorb lower hybrid (LH) wave energy, thus reducing the LH current drive efficiency. The absorption coefficient γ{sub α} of LH waves due to α particles changing with some typical parameters is calculated in this paper. Results show that γ{sub α} increases with the parallel refraction index n{sub ‖}, while decreases with the frequency of LH waves ω over a wide range. Higher background plasma temperature and toroidal magnetic field will increase the absorption. The absorption coefficient γ{sub α} increases with n{sub e} when n{sub e} ≤ 8 × 10{sup 19} m{sup −3}, while decreases with n{sub e} when n{sub e} becomes larger, and there is a peak value of γ{sub α} when n{sub e} ≈ 8 × 10{sup 19} m{sup −1} for the ITER-like scenario. The influence of spectral broadening in parametric decay instabilities on the absorption coefficient is evaluated. The value of γ{sub α} with n{sub ‖} being 2.5 is almost two times larger than that with n{sub ‖} being 2.0 and is even lager in the case of 2.9, which will obviously increase the absorption of the LH power by alpha particles.
Effects of absorption on high-latitude meteor scatter communication systems
Ostergaard, J.C.; Weitzen, J.A.; Kossey, P.A.; Bailey, A.D.; Bench, P.M. USAF, Geophysics Laboratory, Hanscom AFB, MA )
1991-08-01
Propagation data covering the solar disturbances of March and August 1989, acquired with the Geophysical Laboratory's High-Latitude Meteor Scatter Test-Bed, are presented and are examined as a function of frequency. It was found that the two solar-disturbance events were very different. The August event was dominated by ionospheric absorption which affected meteor arrival rates and duty cycles primarily at 35 and 45 MHz, while the March event combined weak ionospheric absorption with large solar noise burst. The absorption was frequency dependent during both events. 21 refs.
NASA Astrophysics Data System (ADS)
Alvarado, Matthew J.; Lonsdale, Chantelle R.; Macintyre, Helen L.; Bian, Huisheng; Chin, Mian; Ridley, David A.; Heald, Colette L.; Thornhill, Kenneth L.; Anderson, Bruce E.; Cubison, Michael J.; Jimenez, Jose L.; Kondo, Yutaka; Sahu, Lokesh K.; Dibb, Jack E.; Wang, Chien
2016-07-01
Accurate modeling of the scattering and absorption of ultraviolet and visible radiation by aerosols is essential for accurate simulations of atmospheric chemistry and climate. Closure studies using in situ measurements of aerosol scattering and absorption can be used to evaluate and improve models of aerosol optical properties without interference from model errors in aerosol emissions, transport, chemistry, or deposition rates. Here we evaluate the ability of four externally mixed, fixed size distribution parameterizations used in global models to simulate submicron aerosol scattering and absorption at three wavelengths using in situ data gathered during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. The four models are the NASA Global Modeling Initiative (GMI) Combo model, GEOS-Chem v9-02, the baseline configuration of a version of GEOS-Chem with online radiative transfer calculations (called GC-RT), and the Optical Properties of Aerosol and Clouds (OPAC v3.1) package. We also use the ARCTAS data to perform the first evaluation of the ability of the Aerosol Simulation Program (ASP v2.1) to simulate submicron aerosol scattering and absorption when in situ data on the aerosol size distribution are used, and examine the impact of different mixing rules for black carbon (BC) on the results. We find that the GMI model tends to overestimate submicron scattering and absorption at shorter wavelengths by 10-23 %, and that GMI has smaller absolute mean biases for submicron absorption than OPAC v3.1, GEOS-Chem v9-02, or GC-RT. However, the changes to the density and refractive index of BC in GC-RT improve the simulation of submicron aerosol absorption at all wavelengths relative to GEOS-Chem v9-02. Adding a variable size distribution, as in ASP v2.1, improves model performance for scattering but not for absorption, likely due to the assumption in ASP v2.1 that BC is present at a constant mass fraction
Absorption coefficient of urban aerosol in Nanjing, west Yangtze River Delta, China
NASA Astrophysics Data System (ADS)
Zhuang, B. L.; Wang, T. J.; Liu, J.; Ma, Y.; Yin, C. Q.; Li, S.; Xie, M.; Han, Y.; Zhu, J. L.; Yang, X. Q.; Fu, C. B.
2015-12-01
Absorbing aerosols can significantly modulate short-wave solar radiation in the atmosphere, affecting regional and global climate. The aerosol absorption coefficient (AAC) is an indicator that assesses the impact of absorbing aerosols on radiative forcing. In this study, the near-surface AAC and absorption Ångström exponent (AAE) in the urban area of Nanjing, China, are characterized on the basis of measurements in 2012 and 2013 using the seven-channel Aethalometer (model AE-31, Magee Scientific, USA). The AAC is estimated with direct and indirect corrections, which result in consistent temporal variations and magnitudes of AAC at 532 nm. The mean AAC at 532 nm is about 43.23 ± 28.13 M m-1 in the urban area of Nanjing, which is much lower than that in Pearl River Delta and the same as in rural areas (Lin'an) in Yangtze River Delta. The AAC in the urban area of Nanjing shows strong seasonality (diurnal variations); it is high in cold seasons (at rush hour) and low in summer (in the afternoon). It also shows synoptic and quasi-2-week cycles in response to weather systems. Its frequency distribution follows a typical log-normal pattern. The 532 nm AAC ranging from 15 to 65 M m-1 dominates, accounting for more than 72 % of the total data samples in the entire study period. Frequent high pollution episodes, such as those observed in June 2012 and in winter 2013, greatly enhanced AAC and altered its temporal variations and frequency distributions. These episodes are mostly due to local emissions and regional pollution. Air masses flowing from northern China to Nanjing can sometimes be highly polluted and lead to high AAC at the site. AAE at 660/470 nm from the Schmid correction (Schmid et al., 2006) is about 1.56, which might be more reasonable than from the Weingartner correction (Weingartner et al., 2003). Low AAEs mainly occur in summer, likely due to high relative humidity (RH) in the season. AAC increases with increasing AAE at a fixed aerosol loading. The RH
Absorption coefficient of urban aerosol in Nanjing, west Yangtze River Delta of China
NASA Astrophysics Data System (ADS)
Zhuang, B. L.; Wang, T. J.; Liu, J.; Ma, Y.; Yin, C. Q.; Li, S.; Xie, M.; Han, Y.; Zhu, J. L.; Yang, X. Q.; Fu, C. B.
2015-06-01
Absorbing aerosols can significantly modulate shortwave solar radiation in the atmosphere, affecting regional and global climate. Aerosol absorption coefficient (AAC) is an indicator to assess the impact of absorbing aerosols on radiative forcing. In this study, the near-surface AAC and absorption angstrom exponent (AAE) in urban Nanjing, China, are characterized on the basis of measurements in 2012 and 2013 using the 7-channel Aethalometer (model AE-31, Magee Scientific, USA). The AAC is estimated with direct and indirect corrections, which show consistent temporal variations and magnitudes of AAC at 532 nm. The mean AAC at 532 nm is about 43.23 ± 28.13 M m-1 in urban Nanjing, which is much lower than that in Pearl River Delta and as the same as that in rural areas (Lin'an) in Yangtze River Delta. The AAC in urban Nanjing shows strong seasonality (diurnal variations), high in cold seasons (at rush hours) and low in summer (in afternoon). It also show synoptic and quasi-two-week cycles in response to weather systems. Its frequency distribution follows a typical lognormal pattern. The 532 nm-AAC ranging from 15 to 65 M m-1 dominates, accounting for more than 72% of the total data samples in the entire study period. Frequent high pollution episodes, such as those observed in June 2012 and in winter 2013, greatly enhanced AAC and altered its temporal variations and frequency distributions. These episodes are mostly due to local emissions and regional pollutions. Air masses from northern China to Nanjing can sometimes be highly polluted and lead to high AAC at the site. AAE at 660/470 nm from the Schmid correction (Schmid et al., 2006) is about 1.56, which might be more reasonable compared to that from the Weingartner correction (Weingartner et al., 2003). Low AAEs mainly appear in summer in response to the relative humidity (RH). AAC increases with increasing AAE at a fixed aerosol loading. The RH-AAC relationship is more complex. Overall, AAC peaks around RH values
NASA Astrophysics Data System (ADS)
Difilippo, Felix C.
2012-09-01
Within the context of general relativity theory we calculate, analytically, scattering signatures around a gravitational singularity: angular and time distributions of scattered massive objects and photons and the time and space modulation of Doppler effects. Additionally, the scattering and absorption cross sections for the gravitational interactions are calculated. The results of numerical simulations of the trajectories are compared with the analytical results.
Yang, Defu; Chen, Xueli; Peng, Zhen; Wang, Xiaorui; Ripoll, Jorge; Wang, Jing; Liang, Jimin
2013-01-01
Modeling light propagation in the whole body is essential and necessary for optical imaging. However, non-scattering, low-scattering and high absorption regions commonly exist in biological tissues, which lead to inaccuracy of the existing light transport models. In this paper, a novel hybrid light transport model that couples the simplified spherical harmonics approximation (SPN) with the radiosity theory (HSRM) was presented, to accurately describe light transport in turbid media with non-scattering, low-scattering and high absorption heterogeneities. In the model, the radiosity theory was used to characterize the light transport in non-scattering regions and the SPN was employed to handle the scattering problems, including subsets of low-scattering and high absorption. A Neumann source constructed by the light transport in the non-scattering region and formed at the interface between the non-scattering and scattering regions was superposed into the original light source, to couple the SPN with the radiosity theory. The accuracy and effectiveness of the HSRM was first verified with both regular and digital mouse model based simulations and a physical phantom based experiment. The feasibility and applicability of the HSRM was then investigated by a broad range of optical properties. Lastly, the influence of depth of the light source on the model was also discussed. Primary results showed that the proposed model provided high performance for light transport in turbid media with non-scattering, low-scattering and high absorption heterogeneities. PMID:24156077
Yang, Defu; Chen, Xueli; Peng, Zhen; Wang, Xiaorui; Ripoll, Jorge; Wang, Jing; Liang, Jimin
2013-01-01
Modeling light propagation in the whole body is essential and necessary for optical imaging. However, non-scattering, low-scattering and high absorption regions commonly exist in biological tissues, which lead to inaccuracy of the existing light transport models. In this paper, a novel hybrid light transport model that couples the simplified spherical harmonics approximation (SPN) with the radiosity theory (HSRM) was presented, to accurately describe light transport in turbid media with non-scattering, low-scattering and high absorption heterogeneities. In the model, the radiosity theory was used to characterize the light transport in non-scattering regions and the SPN was employed to handle the scattering problems, including subsets of low-scattering and high absorption. A Neumann source constructed by the light transport in the non-scattering region and formed at the interface between the non-scattering and scattering regions was superposed into the original light source, to couple the SPN with the radiosity theory. The accuracy and effectiveness of the HSRM was first verified with both regular and digital mouse model based simulations and a physical phantom based experiment. The feasibility and applicability of the HSRM was then investigated by a broad range of optical properties. Lastly, the influence of depth of the light source on the model was also discussed. Primary results showed that the proposed model provided high performance for light transport in turbid media with non-scattering, low-scattering and high absorption heterogeneities. PMID:24156077
Jain, Prashant K; Lee, Kyeong Seok; El-Sayed, Ivan H; El-Sayed, Mostafa A
2006-04-13
the nanoshell size or decreasing the ratio of the core/shell radius. Gold nanorods show optical cross-sections comparable to nanospheres and nanoshells, however, at much smaller effective size. Their optical resonance can be linearly tuned across the near-infrared region by changing either the effective size or the aspect ratio of the nanorods. The total extinction as well as the relative scattering contribution increases rapidly with the effective size, however, they are independent of the aspect ratio. To compare the effectiveness of nanoparticles of different sizes for real biomedical applications, size-normalized optical cross-sections or per micron coefficients are calculated. Gold nanorods show per micron absorption and scattering coefficients that are an order of magnitude higher than those for nanoshells and nanospheres. While nanorods with a higher aspect ratio along with a smaller effective radius are the best photoabsorbing nanoparticles, the highest scattering contrast for imaging applications is obtained from nanorods of high aspect ratio with a larger effective radius. PMID:16599493
Technology Transfer Automated Retrieval System (TEKTRAN)
Optical absorption and scattering properties of fruit change with the physiological and biochemical activities in the tissue during ripening and postharvest storage. But it has not been well understood on how these changes are related to the structural and mechanical properties of fruit. This resear...
Scalar waves in regular Bardeen black holes: Scattering, absorption and quasinormal modes
NASA Astrophysics Data System (ADS)
Macedo, Caio F. B.; Crispino, Luís C. B.; de Oliveira, Ednilton S.
2016-05-01
We discuss the phenomenology of massless scalar fields around a regular Bardeen black hole, namely absorption cross-section, scattering cross-section and quasinormal modes. We compare the Bardeen and Reissner-Nordström black holes, showing limiting cases for which their properties are similar.
Spectral Absorption and Scattering Properties of Normal and Bruised Apple Tissue
Technology Transfer Automated Retrieval System (TEKTRAN)
Knowledge of the spectral absorption and scattering properties of apple tissue, especially bruised tissue, can help us develop an effective method for detecting bruises during postharvest sorting and grading. This research was intended to determine the optical properties of normal and bruised apple ...
On-road measurement of black carbon mass, absorption, and single-scattering albedo
Absorption and scattering of solar radiation by aerosols emitted from combustion sources can affect the earth’s radiative balance and may potentially affect local and regional climate. Optical properties of aerosols emitted from mobile sources have not been thoroughly characteri...
Technology Transfer Automated Retrieval System (TEKTRAN)
This paper reports on the development of a hyperspectral imaging technique for rapid determination of the absorption and scattering properties of turbid liquid foods over the visible and near-infrared region of 530-900 nm. A hyperspectral imaging system in line scanning mode was first tested and val...
How to measure and predict the molar absorption coefficient of a protein.
Pace, C. N.; Vajdos, F.; Fee, L.; Grimsley, G.; Gray, T.
1995-01-01
The molar absorption coefficient, epsilon, of a protein is usually based on concentrations measured by dry weight, nitrogen, or amino acid analysis. The studies reported here suggest that the Edelhoch method is the best method for measuring epsilon for a protein. (This method is described by Gill and von Hippel [1989, Anal Biochem 182:319-326] and is based on data from Edelhoch [1967, Biochemistry 6:1948-1954]). The absorbance of a protein at 280 nm depends on the content of Trp, Tyr, and cystine (disulfide bonds). The average epsilon values for these chromophores in a sample of 18 well-characterized proteins have been estimated, and the epsilon values in water, propanol, 6 M guanidine hydrochloride (GdnHCl), and 8 M urea have been measured. For Trp, the average epsilon values for the proteins are less than the epsilon values measured in any of the solvents. For Tyr, the average epsilon values for the proteins are intermediate between those measured in 6 M GdnHCl and those measured in propanol. Based on a sample of 116 measured epsilon values for 80 proteins, the epsilon at 280 nm of a folded protein in water, epsilon (280), can best be predicted with this equation: epsilon (280) (M-1 cm-1) = (#Trp)(5,500) + (#Tyr)(1,490) + (#cystine)(125) These epsilon (280) values are quite reliable for proteins containing Trp residues, and less reliable for proteins that do not. However, the Edelhoch method is convenient and accurate, and the best approach is to measure rather than predict epsilon. PMID:8563639
NASA Astrophysics Data System (ADS)
Aruna, K.; Lakshmi Kumar, T. V.; Rao, D. Narayana; Krishna Murthy, B. V.; Babu, S. Suresh; Krishnamoorthy, K.
2014-11-01
The scattering and absorption components of Aerosol Optical Depth (AOD) over a semi-urban coastal location (12.81°N, 80.03°E) near the mega city Chennai in peninsular India are separated using the collocated measurements of Black Carbon concentration and Atmospheric Boundary Layer Height (ABLH) from ERA Interim Reanalysis data assuming that most of the BC is contained and homogeneously mixed in the ABL. It is found that the absorption component to scattering component ratio has a strong seasonal variation with a pronounced maximum in the South West (SW) monsoon season. This is indicative of more effective wet removal of scattering aerosols than absorbing (BC) aerosols. There could also be an effect due to preferential removal of large particles which would have a lower content of BC. The Angstrom wavelength exponent shows a minimum in the SW monsoon season, the minimum being more pronounced for the scattering aerosols implying relative dominance of coarse mode particles. Investigation of the effect of Relative Humidity on scattering and absorption components of AOD revealed that the BC (absorbing) aerosols are non-hydrophilic/not coated with hydrophilic substance.
Zhang, Yanni; Huang, Hai; Zheng, Jing; Pan, Jie
2015-11-01
This paper extends previous work of Zhang and Pan [J. Acoust. Soc. Am. 133(4), 2082-2096 (2013)] on sound scattering and absorption by an underwater coated plate with a single attached distributed-inhomogeneity to that with periodically located distributed-inhomogeneities. A comparison is made among cases of a plate without inhomogeneities, a plate with inhomogeneities, and one with inhomogeneities ignoring the mutual coupling. Results show that coupling of the structural waves scattered by the inhomogeneities plays an important role in modifying the sound absorption and scattering of surface sound pressure, especially at low frequencies and/or the resonance frequencies of the trapped modes of the plate. The sound absorption of the plate is dependent on the distance between the adjacent inhomogeneities, the length of the inhomogeneity, and the angle of the incident sound. On the surface of the inhomogeneities, the scattered/total sound pressure is generally enhanced. On the surface in between the inhomogeneities, the pressure is also enhanced at low frequencies but is nearly unchanged at higher frequencies. Results also show that the coupling-induced variation of scattered/total pressure is significant only at the resonance frequencies of the global modes and trapped modes. The surface normal velocity is presented to explain the coupling-induced variations in the vibration and pressure fields. PMID:26627747
Grabtchak, Serge; Montgomery, Logan G; Whelan, William M
2014-05-21
We demonstrated the application of relative radiance-based continuous wave (cw) measurements for recovering absorption and scattering properties (the effective attenuation coefficient, the diffusion coefficient, the absorption coefficient and the reduced scattering coefficient) of bulk porcine muscle phantoms in the 650-900 nm spectral range. Both the side-firing fiber (the detector) and the fiber with a spherical diffuser at the end (the source) were inserted interstitially at predetermined locations in the phantom. The porcine phantoms were prostate-shaped with ∼4 cm in diameter and ∼3 cm thickness and made from porcine loin or tenderloin muscles. The described method was previously validated using the diffusion approximation on simulated and experimental radiance data obtained for homogenous Intralipid-1% liquid phantom. The approach required performing measurements in two locations in the tissue with different distances to the source. Measurements were performed on 21 porcine phantoms. Spectral dependences of the effective attenuation and absorption coefficients for the loin phantom deviated from corresponding dependences for the tenderloin phantom for wavelengths <750 nm. The diffusion constant and the reduced scattering coefficient were very close for both phantom types. To quantify chromophore presence, the plot for the absorption coefficient was matched with a synthetic absorption spectrum constructed from deoxyhemoglobin, oxyhemoglobin and water. The closest match for the porcine loin spectrum was obtained with the following concentrations: 15.5 µM (±30% s.d.) Hb, 21 µM (±30% s.d.) HbO2 and 0.3 (±30% s.d.) fractional volume of water. The tenderloin absorption spectrum was best described by 30 µM Hb (±30% s.d), 19 µM (±30% s.d.) HbO2 and 0.3 (±30% s.d.) fractional volume of water. The higher concentration of Hb in tenderloin was consistent with a dark-red appearance of the tenderloin phantom. The method can be applied to a number of
Enhanced light absorption and scattering by carbon soot aerosol internally mixed with sulfuric acid.
Khalizov, Alexei F; Xue, Huaxin; Wang, Lin; Zheng, Jun; Zhang, Renyi
2009-02-12
Light absorption by carbon soot increases when the particles are internally mixed with nonabsorbing materials, leading to increased radiative forcing, but the magnitude of this enhancement is a subject of great uncertainty. We have performed laboratory experiments of the optical properties of fresh and internally mixed carbon soot aerosols with a known particle size, morphology, and the mixing state. Flame-generated soot aerosol is size-selected with a double-differential mobility analyzer (DMA) setup to eliminate multiply charged particle modes and then exposed to gaseous sulfuric acid (10(9)-10(10) molecule cm(-3)) and water vapor (5-80% relative humidity, RH). Light extinction and scattering by fresh and internally mixed soot aerosol are measured at 532 nm wavelength using a cavity ring-down spectrometer and an integrating nephelometer, respectively, and the absorption is derived as the difference between extinction and scattering. The optical properties of fresh soot are independent of RH, whereas soot internally mixed with sulfuric acid exhibits significant enhancement in light absorption and scattering, increasing with the mass fraction of sulfuric acid coating and relative humidity. For soot particles with an initial mobility diameter of 320 nm and a 40% H(2)SO(4) mass coating fraction, absorption and scattering are increased by 1.4- and 13-fold at 80% RH, respectively. Also, the single scattering albedo of soot aerosol increases from 0.1 to 0.5 after coating and humidification. Additional measurements with soot particles that are first coated with sulfuric acid and then heated to remove the coating show that both scattering and absorption are enhanced by irreversible restructuring of soot aggregates to more compact globules. Depending on the initial size and density of soot aggregates, restructuring acts to increase or decrease the absorption cross-section, but the combination of restructuring and encapsulation always results in an increased absorption for
Measurements and Modeling of Aerosol Absorption and Single Scattering Albedo at Ambient Relative Hum
NASA Technical Reports Server (NTRS)
Redemann, J.; Russell, P. B.; Hamill, P.
2000-01-01
Uncertainties in the aerosol single scattering albedo have been identified to be an important source of errors in current large-scale model estimates of the direct aerosol radiative forcing of climate. A number of investigators have obtained estimates of the single scattering albedo from a variety of remote sensing and in situ measurements during aerosol field experiments. During the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX, 1996) for example, estimates of the aerosol single scattering albedo were obtained (1) as a best-fit parameter in comparing radiative flux changes measured by airborne pyranometer to those computed from independently measured aerosol properties; (2) from estimates of the aerosol complex index of refraction derived using a combination of airborne sunphotometer, lidar backscatter and in situ size distribution measurements; and (3) from airborne measurements of aerosol scattering and absorption using nephelometers and absorption photometers. In this paper, we briefly compare the results of the latter two methods for two TARFOX case studies, since those techniques provide height-resolved information about the aerosol single scattering albedo. Estimates of the aerosol single scattering albedo from nephelometer and absorption photometer measurements require knowledge of the scattering and absorption humidification (i.e., the increase in these properties in response to an increase in ambient relative humidity), since both measurements are usually carried out at a relative humidity different from the ambient atmosphere. In principle, the scattering humidification factor can be measured, but there is currently no technique widely available to measure the absorption of an aerosol sample as a function of relative humidity. Frequently, for lack of better knowledge, the absorption humidification is assumed to be unity (meaning that there is no change in aerosol absorption due to an increase in ambient relative humidity). This
Wandinger, U
1998-01-20
A formalism describing the influence of multiple scattering on cloud measurements with Raman and high-spectral-resolution lidars is presented. Model calculations including both particulate and molecular scattering processes are performed to describe the general effects of multiple scattering on both particulate and molecular lidar backscatter signals. It is found that, for typical measurement geometries of ground-based lidars, as many as five scattering orders contribute significantly to the backscattered light. The relative intensity of multiple-scattered light is generally larger in signals backscattered from molecules than in signals backscattered from particles. The multiple-scattering formalism is applied to measurements of water and ice clouds taken with a Raman lidar. Multiple-scattering errors of measured extinction coefficients are typically of the order of 50% at the bases of both water and ice clouds and decrease with increasing penetration depth to below 20%. In contrast, the multiple-scattering errors of backscatter coefficients are negligible in ice clouds and below 20% in water clouds. PMID:18268599
NASA Astrophysics Data System (ADS)
Draine, Bruce T.; Flatau, Piotr J.
2000-08-01
DDSCAT is a freely available software package which applies the "discrete dipole approximation" (DDA) to calculate scattering and absorption of electromagnetic waves by targets with arbitrary geometries and complex refractive index. The DDA approximates the target by an array of polarizable points. DDSCAT.5a requires that these polarizable points be located on a cubic lattice. DDSCAT allows accurate calculations of electromagnetic scattering from targets with "size parameters" 2 pi a/lambda < 15 provided the refractive index m is not large compared to unity (|m-1| < 1). The DDSCAT package is written in Fortran and is highly portable. The program supports calculations for a variety of target geometries (e.g., ellipsoids, regular tetrahedra, rectangular solids, finite cylinders, hexagonal prisms, etc.). Target materials may be both inhomogeneous and anisotropic. It is straightforward for the user to import arbitrary target geometries into the code, and relatively straightforward to add new target generation capability to the package. DDSCAT automatically calculates total cross sections for absorption and scattering and selected elements of the Mueller scattering intensity matrix for specified orientation of the target relative to the incident wave, and for specified scattering directions. This User Guide explains how to use DDSCAT to carry out EM scattering calculations. CPU and memory requirements are described.
NASA Astrophysics Data System (ADS)
Hunt, Arlon J.; Quinby-Hunt, Mary S.; Shapiro, Daniel B.
1990-09-01
This paper investigates the wavelength dependence of the polarization characteristics of light scattered from laboratory cultures of marine Clzlorella. Scattering measurements were obtained using a scanning polarization-modulation nephelometer at wavelengths of 457 and 514 nm. The experimental data are corrected for non-spherical contributions and the resulting curves compared to Mie calculations of coated spheres with a Gaussian size distribution. Although the absorption of Chiorella has been reported to be strongly wavelength-dependent in the blue to green region of the spectrum, the scattering behavior changes very little. To verify the sensitivity of the scattering technique to changes in the imaginary refractive index, measurements were performed on absorbing and non-absorbing suspensions of wellcharacterized, coated copolymer particles. In all cases, the angle-dependent measurements and calculations were compared for four elements of the 16 element Mueller scattering matrix at two wavelengths. In the past, comparison of scattering models and measurements were generally performed for only the total intensity (one element of the scattering matrix). The use of four elements provides a much more stringent test of scattering calculations than those based on a single element. Using this method we are able to infer information about the internal structure and refractive indices of microscopic single cell organisms in vivo.
The absorption coefficient of the liquid N2 2.15-micron band and application to Triton
NASA Technical Reports Server (NTRS)
Grundy, William M.; Fink, Uwe
1991-01-01
The present measurements of the temperature dependence exhibited by the liquid N2 2.15-micron 2-0 collision-induced band's absorption coefficient and integrated absorption show the latter to be smaller than that of the N2 gas, and to decrease with decreasing temperature. Extrapolating this behavior to Triton's nominal surface temperature yields a new estimate of the N2-ice grain size on the Triton south polar cap; a mean N2 grain size of 0.7-3.0 cm is consistent with grain growth rate calculation results.
NASA Astrophysics Data System (ADS)
Genkina, Dina; Aycock, Lauren; Stuhl, Benjamin; Lu, Hsin-I.; Williams, Ross; Spielman, Ian
2016-05-01
We directly measured the normalized s-wave scattering cross-section of ultracold 40 K atoms across a magnetic-field Feshbach resonance by colliding pairs of degenerate Fermi gases (DFGs) and imaging the scattered atoms. We extracted the scattered fraction for a range of bias magnetic fields, and measured the resonance location to be B 0 = 20.206(15) mT with width Δ = 1.0(5) mT. To optimize the signal-to-noise ratio (SNR) of atom number in scattering images, we developed techniques to interpret absorption images in a regime where recoil induced detuning corrections are significant. These imaging techniques are generally applicable to experiments with lighter alkalis that would benefit from maximizing SNR on atom number counting at the expense of spatial imaging resolution.
NASA Astrophysics Data System (ADS)
Tian, Jing; Zhang, Qiqi; Liu, Shaopu; Yang, Jidong; Teng, Ping; Zhu, Jinghui; Qiao, Man; Shi, Ying; Duan, Ruilin; Hu, Xiaoli
2015-04-01
In pH 7.0-8.0 KH2PO4-Na2HPO4 buffer solution, Cd(II) reacted with 1,10-phenanthroline to form chelate cation [Cd(phen)3]2+, which further reacted with anion of erythrosine to form ternary ion-association complex through electrostatic attraction and hydrophobic effect. This process could result in remarkable absorption spectra change and produce obvious fading reaction at 528 nm. Absorbance change (ΔA) of system was directly proportional to the concentration of Cd(II). Hereby, a highly sensitive spectrophotometric method for the determination of Cd(II) was established. The molar absorption coefficient was 2.29 × 105 L mol-1 cm-1 and the detection limit of Cd(II) was 26.5 ng mL-1. Furthermore, the resonance Rayleigh scattering (RRS) of this system with two peaks located at 371 and 590 nm enhanced significantly, and second-order scattering (SOS) and frequence doubling scattering (FDS) of this system changed notably at 640 and 350 nm, respectively. Under the optimum conditions, the scattering intensities (ΔIRRS, ΔIDWO-RRS, ΔISOS and ΔIFDS) had good linear relationship with the concentration of Cd(II) in certain ranges. The detection limits of Cd(II) were 1.27 ng mL-1, 1.39 ng mL-1, 4.03 ng mL-1, 5.92 ng mL-1 and 14.7 ng mL-1 for dual-wavelength overlapping resonance Rayleigh scattering (DWO-RRS), RRS (371 nm), RRS (590 nm), SOS and FDS, respectively. In addition, the suitable reaction conditions and effects of coexisting substances were investigated. The methods had been successfully applied to the determination of Cd(II) in environmental water samples. The recovery range was between 93.0% and 103.0% and the relative standard deviation (RSD) was between 2.5% and 4.3%. The results were in agreement with those obtained from atomic absorption spectroscopy.
NASA Astrophysics Data System (ADS)
Andreo, Pedro; Burns, David T.; Salvat, Francesc
2012-04-01
A systematic analysis of the available data has been carried out for mass energy-absorption coefficients and their ratios for air, graphite and water for photon energies between 1 keV and 2 MeV, using representative kilovoltage x-ray spectra for mammography and diagnostic radiology below 100 kV, and for 192Ir and 60Co gamma-ray spectra. The aim of this work was to establish ‘an envelope of uncertainty’ based on the spread of the available data. Type A uncertainties were determined from the results of Monte Carlo (MC) calculations with the PENELOPE and EGSnrc systems, yielding mean values for µen/ρ with a given statistical standard uncertainty. Type B estimates were based on two groupings. The first grouping consisted of MC calculations based on a similar implementation but using different data and/or approximations. The second grouping was formed by various datasets, obtained by different authors or methods using the same or different basic data, and with different implementations (analytical, MC-based, or a combination of the two); these datasets were the compilations of NIST, Hubbell, Johns-Cunningham, Attix and Higgins, plus MC calculations with PENELOPE and EGSnrc. The combined standard uncertainty, uc, for the µen/ρ values for the mammography x-ray spectra is 2.5%, decreasing gradually to 1.6% for kilovoltage x-ray spectra up to 100 kV. For 60Co and 192Ir, uc is approximately 0.1%. The Type B uncertainty analysis for the ratios of µen/ρ values includes four methods of analysis and concludes that for the present data the assumption that the data interval represents 95% confidence limits is a good compromise. For the mammography x-ray spectra, the combined standard uncertainties of (µen/ρ)graphite,air and (µen/ρ)graphite,water are 1.5%, and 0.5% for (µen/ρ)water,air, decreasing gradually down to uc = 0.1% for the three µen/ρ ratios for the gamma-ray spectra. The present estimates are shown to coincide well with those of Hubbell (1977 Rad. Res
NASA Astrophysics Data System (ADS)
Li, Meng; Jiang, Li-Hui; Xiong, Xing-Long; Ma, Yu-Zhao; Liu, Jie-Sheng
2016-08-01
Layer boundaries detection with LIDAR is of great significance for the meteorological and environmental research. Apart from the background noise, multiple scattering can also seriously affect the detection results in LIDAR signal processing. To alleviate these issues, a novel approach was proposed based upon morphological filtering and multiple scattering correction with multiple iterations, which essentially acts as a weighted algorithm with multiple scattering factors in different filtering scales, and applies integral extinction coefficients as media to perform correction. Simulations on artificial signals and real LIDAR signals support this approach.
NASA Astrophysics Data System (ADS)
Li, Meng; Jiang, Li-Hui; Xiong, Xing-Long; Ma, Yu-Zhao; Liu, Jie-Sheng
2016-05-01
Layer boundaries detection with LIDAR is of great significance for the meteorological and environmental research. Apart from the background noise, multiple scattering can also seriously affect the detection results in LIDAR signal processing. To alleviate these issues, a novel approach was proposed based upon morphological filtering and multiple scattering correction with multiple iterations, which essentially acts as a weighted algorithm with multiple scattering factors in different filtering scales, and applies integral extinction coefficients as media to perform correction. Simulations on artificial signals and real LIDAR signals support this approach.
Marcano, Aristides; Alvarado, Salvador; Meng, Junwei; Caballero, Daniel; Moares, Ernesto Marín; Edziah, Raymond
2014-01-01
We developed a pump-probe photothermal lens spectrophotometer that uses a broadband arc-lamp and a set of interference filters to provide tunable, nearly monochromatic radiation between 370 and 730 nm as the pump light source. This light is focused onto an absorbing sample, generating a photothermal lens of millimeter dimensions. A highly collimated monochromatic probe light from a low-power He-Ne laser interrogates the generated lens, yielding a photothermal signal proportional to the absorption of light. We measure the absorption spectra of scattering dye solutions using the device. We show that the spectra are not affected by the presence of scattering, confirming that the method only measures the absorption of light that results in generation of heat. By comparing the photothermal spectra with the usual absorption spectra determined using commercial transmission spectrophotometers, we estimate the quantum yield of scattering of the sample. We discuss applications of the device for spectroscopic characterization of samples such as blood and gold nanoparticles that exhibit a complex behavior upon interaction with light. PMID:25014724
NASA Technical Reports Server (NTRS)
Ohi, Nobuaki; Makinen, Carla P.; Mitchell, Richard; Moisan, Tiffany A.
2008-01-01
Ocean color algorithms are based on the parameterization of apparent optical properties as a function of inherent optical properties. WET Labs underwater absorption and attenuation meters (ac-9 and ac-s) measure both the spectral beam attenuation [c (lambda)] and absorption coefficient [a (lambda)]. The ac-s reports in a continuous range of 390-750 nm with a band pass of 4 nm, totaling approximately 83 distinct wavelengths, while the ac-9 reports at 9 wavelengths. We performed the ac-s field measurements at nine stations in the Mid-Atlantic Bight from water calibrations to data analysis. Onboard the ship, the ac-s was calibrated daily using Milli Q-water. Corrections for the in situ temperature and salinity effects on optical properties of water were applied. Corrections for incomplete recovery of the scattered light in the ac-s absorption tube were performed. The fine scale of spectral and vertical distributions of c (lambda) and a (lambda) were described from the ac-s. The significant relationships between a (674) and that of spectrophotometric analysis and chlorophyll a concentration of discrete water samples were observed.
NASA Technical Reports Server (NTRS)
Goldstein, M. L.; Klimas, A. J.; Sandri, G.
1975-01-01
The Fokker-Planck coefficient for pitch-angle scattering, appropriate for cosmic rays in homogeneous stationary magnetic turbulence is computed without making any specific assumptions concerning the statistical symmetries of the random field. The Fokker-Planck coefficient obtained can be used to compute the parallel diffusion coefficient for high-energy cosmic rays propagating in the presence of strong turbulence, or for low-energy cosmic rays in the presence of weak turbulence. Because of the generality of magnetic turbulence allowed for in the analysis, special interplanetary magnetic field features, such as discontinuities or particular wave modes, can be included rigorously.
I-scan thermal lens experiment in the pulse regime for measuring two-photon absorption coefficient
NASA Astrophysics Data System (ADS)
Rodríguez, L.; Echevarria, L.; Fernandez, A.
2007-09-01
We present a new pump-probe mode-mismatched thermal lens method for pulse excitation aimed to the measurement of nonlinear absorption coefficient in optical materials. We develop a theoretical model based on the Fresnel diffraction approximation and their predictions are verified experimentally with samples of Rhodamine 6G and Rhodamine B in ethanol solution. The principal advantage of this technique is that it does not require any mechanical movement during measurement. Below we perform the new type of thermal lens experiment in the pulse regime for the measurement of nonlinear absorption coefficient in transparent samples and we demonstrate the validity of theoretical predictions using an alternative method to the classical thermal lens technique.
NASA Technical Reports Server (NTRS)
Wang, Qinglin; Gogineni, S. P.
1991-01-01
A numerical procedure for estimating the true scattering coefficient, sigma(sup 0), from measurements made using wide-beam antennas. The use of wide-beam antennas results in an inaccurate estimate of sigma(sup 0) if the narrow-beam approximation is used in the retrieval process for sigma(sup 0). To reduce this error, a correction procedure was proposed that estimates the error resulting from the narrow-beam approximation and uses the error to obtain a more accurate estimate of sigma(sup 0). An exponential model was assumed to take into account the variation of sigma(sup 0) with incidence angles, and the model parameters are estimated from measured data. Based on the model and knowledge of the antenna pattern, the procedure calculates the error due to the narrow-beam approximation. The procedure is shown to provide a significant improvement in estimation of sigma(sup 0) obtained with wide-beam antennas. The proposed procedure is also shown insensitive to the assumed sigma(sup 0) model.
NASA Technical Reports Server (NTRS)
Varanasi, Prasad
1992-01-01
Spectral absorption coefficients k(v) in the atmospheric window are reported for CFC-11 and CFC-12. Data obtained with a grating spectrometer are compared with NCAR cross sections and measurements of k(v) made with a tunable diode laser spectrometer at various temperature-pressure combinations representing tangent heights or layers in the atmosphere are presented. The results are suitable for atmospheric remote sensing and global warming studies.
NASA Technical Reports Server (NTRS)
Starr, W. L.
1976-01-01
Absorption cross sections for O2, N2, CO2, CH4, N2O, and CO have been measured at each of the lines of the atomic oxygen triplet at 1302, 1305, and 1306 A. Radiation resonantly scattered from oxygen atoms at a temperature of about 300 K was used for the line source. Absorber temperatures were also near 300 K. Direct application of the Lambert-Beer absorption equation yielded pressure-dependent cross sections for carbon monoxide at each line of the O I triplet. Reasons for this apparent dependence are presented and discussed.
Yue, Jian-Hua; Tao, Jun; Lin, Ze-Jian; Zhu, Li-Hua; Cao, Jun-Ji; Luo, Lei
2012-07-01
Aerosol samples for PM2.5 were collected from 19 April to 17 May in 2009 at Chengdu. The concentrations of organic carbon, element carbon, water-solubility ions, crustal elements and levoglucosan of all particle samples were determined by thermal/ optical carbon analyzer,ion chromatography, X-ray fluorescence spectrometer and high performance anion exchange chromatography, respectively. In-situ scattering coefficients (b(sp)) and meteorological parameters for this period were also conducted. Ambient scattering coefficients were reconstructed by IMPROVE formula and compared with measured scattering coefficients. The results showed that the average mass concentration of PM2.5 and measured b(sp) were 133.2 microg x m(-3) and 530 Mm(-1), respectively. Levoglucosan and crustal elements were good traces for biomass burning and dust storm events, respectively. The calculated b'sp was 504 Mm(-1) during campaigning period. The major contributors to scattering coefficients included: (NH4)2SO4 (26%), NH4NO3 (15%), OM (53%), FS (4%) and CM (2%), respectively. The calculated b'sp was 575 Mm(-1) and the dominant species were FS (17%) and CM (21%) during dust storm period (DS). The calculated b'sp was 635 Mm(-1) and OM contributed 62% during biomass burning (BB) period. PMID:23002585
NASA Astrophysics Data System (ADS)
Zhevstovskikh, I. V.; Okulov, V. I.; Gudkov, V. V.; Mayakin, V. Yu.; Sarychev, M. N.; Andriichuk, M. D.; Paranchich, L. D.
2015-05-01
The effects of the interaction of ultrasound with donor d electrons of cobalt impurity atoms at low concentrations in mercury selenide crystals have been investigated. The temperature dependences of the electronic contribution to the absorption coefficient at a frequency of 53 MHz in crystals with cobalt concentrations from 1018 to 1020 cm-3 and in the undoped crystal have been observed experimentally. It has been found that crystals with impurities are characterized by an anomalous nonmonotonic temperature dependence of the absorption coefficient of the slow transverse wave in a narrow temperature range near 10 K. A smooth monotonic temperature dependence has been observed for longitudinal and fast transverse waves. Based on the developed theoretical interpretation, it has been established that the anomaly in the temperature dependence of the absorption coefficient of a slow transverse wave is associated with the hybridization of impurity d states in the conduction band of the crystal. A comparison of the theoretical and experimental dependences has made it possible to determine the parameters characterizing the hybridized electronic states.
Study of the nanosurface properties by analyzing its absorption and scattering cross-section
NASA Astrophysics Data System (ADS)
Bariakhtar, Irina
The interest to study the nanoparticles absorbed on the dielectric or semiconductor substrate is caused by the multiple practical applications of these systems such as nanosensors, electronic devices and lately in PV elements for improving of their efficiency. The author suggests a method of examining the properties of the nanosurface with the absorbed nanoparticle by calculating the absorption and scattering of the electromagnetic field by such system based on construction of its effective electric susceptibility. It was built based on the Green's function approach. The computer simulations show good correspondence with the theory. It was shown that this approach can be applied to investigate the optical absorption and scattering on the nanoparticles on the substrate to be used in PV engineering.
2011-01-01
In the present work, we investigated the scattering and spectrally resolved absorption properties of nanofluids consisting in aqueous and glycol suspensions of single-wall carbon nanohorns. The characteristics of these nanofluids were evaluated in view of their use as sunlight absorber fluids in a solar device. The observed nanoparticle-induced differences in optical properties appeared promising, leading to a considerably higher sunlight absorption with respect to the pure base fluids. Scattered light was found to be not more than about 5% with respect to the total attenuation of light. Both these effects, together with the possible chemical functionalization of carbon nanohorns, make this new kind of nanofluids very interesting for increasing the overall efficiency of the sunlight exploiting device. PACS 78.40.Ri, 78.35.+c, 78.67.Bf, 88.40.fh, 88.40.fr, 81.05.U. PMID:21711795
Radiation Force Caused by Scattering, Absorption, and Emission of Light by Nonspherical Particles
NASA Technical Reports Server (NTRS)
Mishchenko, Michael I.; Hansen, James E. (Technical Monitor)
2001-01-01
General formulas for computing the radiation force exerted on arbitrarily oriented and arbitrarily shaped nonspherical particles due to scattering, absorption, and emission of electromagnetic radiation are derived. For randomly oriented particles with a plane of symmetry, the formula for the average radiation force caused by the particle response to external illumination reduces to the standard Debye formula derived from the Lorenz-Mie theory, whereas the average radiation force caused by emission vanishes.
Polarization and absorption effects in electron-helium scattering at 30--400 eV
Thirumalai, D.; Truhlar, D.G.; Brandt, M.A.; Eades, R.A.; Dixon, D.A.
1982-06-01
We report several calculations of the differential, integral, and momentum-transfer cross sections for elastic scattering, and of the absorption cross sections (for the sum of all electronically inelastic and ionization processes) for electron-He collisions at 30--400 eV. We consider two basically different approaches to include the effect of absorption, i.e., loss of flux from the initial channel. The first is the matrix effective potential (MEP) based on a variational calculation of the polarization potential; this models absorption by including a pseudochannel whose properties are based on a variational adiabatic polarization potential. This method predicts both the absorption and elastic cross sections. The second method involves phenomenological absorption (A) potentials, calibrated against experimental absorption cross sections. These potentials, when combined with static (S), exchange (E), and real polarization (P) potentials form an SEPA optical model potential that is used to predict the elastic cross sections. The MEP model based on the variational polarization potential predicts the absorption cross sections with an average absolute error of 28% at 30 and 50 eV and 5% at 100--400 eV. It predicts the elastic integral cross sections with an average absolute error of 8% over the whole energy range. The SEPA models, including a nonadiabatic polarization potential, predict the elastic integral cross sections with average absolute errors of 12 or 6%, depending on the shape function (i.e., r dependence) of the absorption potential. The adiabatic approximation for polarization is less accurate than the nonadiabatic one, even when absorption effects are included. Five new calculations of the differential cross sections at each of five impact energies are compared to experimental results in detail.
Polarization and absorption effects in electron-helium scattering at 30-400 eV
NASA Astrophysics Data System (ADS)
Thirumalai, Devarajan; Truhlar, Donald G.; Brandt, Maynard A.; Eades, Robert A.; Dixon, David A.
1982-06-01
We report several calculations of the differential, integral, and momentum-transfer cross sections for elastic scattering, and of the absorption cross sections (for the sum of all electronically inelastic and ionization processes) for electron-He collisions at 30-400 eV. We consider two basically different approaches to include the effect of absorption, i.e., loss of flux from the initial channel. The first is the matrix effective potential (MEP) based on a variational calculation of the polarization potential; this models absorption by including a pseudochannel whose properties are based on a variational adiabatic polarization potential. This method predicts both the absorption and elastic cross sections. The second method involves phenomenological absorption (A) potentials, calibrated against experimental absorption cross sections. These potentials, when combined with static (S), exchange (E), and real polarization (P) potentials form an SEPA optical model potential that is used to predict the elastic cross sections. The MEP model based on the variational polarization potential predicts the absorption cross sections with an average absolute error of 28% at 30 and 50 eV, and 5% at 100-400 eV. It predicts the elastic integral cross sections with an average absolute error of 8% over the whole energy range. The SEPA models, including a nonadiabatic polarization potential, predict the elastic integral cross sections with average absolute errors of 12 or 6%, depending on the shape function (i.e., r dependence) of the absorption potential. The adiabatic approximation for polarization is less accurate than the nonadiabatic one, even when absorption effects are included. Five new calculations of the differential cross sections at each of five impact energies are compared to experimental results in detail.
Absorption and scattering cross-section extinction values of silver nanoparticles
NASA Astrophysics Data System (ADS)
Hlaing, May; Gebear-Eigzabher, Bellsabel; Roa, Azael; Marcano, Aristides; Radu, Daniela; Lai, Cheng-Yu
2016-08-01
We determine the extinction values of silver nanoparticles as a function of their diameter for three different wavelengths (405 nm, 532 nm, and 671 nm) from the values of absorbance and their photothermal lens response. We show that for particles of small diameters (<50 nm) the extinction grows as the cube of the diameter for all three wavelengths. For larger particles the extinction determined from absorbance exhibits a sixth order dependence on the diameters for 532 nm and 671 nm. This kind of behavior is typical of scattering processes that should dominate for large particles. For 405 nm the plasmonic resonant absorption dominates over scattering making difficult the observation of the sixth order dependence even for particles larger than 50 nm. The absorption cross-section measured by the photothermal method does not show the sixth order dependence. It depends on the cube of the particle's diameter for all nanoparticles confirming the scattering free character of this absorption technique and validating the results of the absorbance experiment.
Absorption and scattering cross-section extinction values of silver nanoparticles
NASA Astrophysics Data System (ADS)
Hlaing, May; Gebear-Eigzabher, Bellsabel; Roa, Azael; Marcano, Aristides; Radu, Daniela; Lai, Cheng-Yu
2016-08-01
We determine the extinction values of silver nanoparticles as a function of their diameter for three different wavelengths (405 nm, 532 nm, and 671 nm) from the values of absorbance and their photothermal lens response. We show that for particles of small diameters (<50 nm) the extinction grows as the cube of the diameter for all three wavelengths. For larger particles the extinction determined from absorbance exhibits a sixth order dependence on the diameters for 532 nm and 671 nm. This kind of behavior is typical of scattering processes that should dominate for large particles. For 405 nm the plasmonic resonant absorption dominates over scattering making difficult the observation of the sixth order dependence even for particles larger than 50 nm. The absorption cross-section measured by the photothermal method does not show the sixth order dependence. It depends on the cube of the particle's diameter for all nanoparticles confirming the scattering free character of this absorption technique and validating the results of the absorbance experiment.
NASA Technical Reports Server (NTRS)
Gasso, B. S.; Hegg, D. A.; Covert, D. S.; Collins, D.; Noone, K.; Oestroem, E.; Schmid, B.; Russell, P. B.; Livingston, J. M.; Durkee, P. A.; Jonsson, H.
2000-01-01
Aerosol scattering coefficients (sigma(sub sp)) have been measured over the ocean at different relative humidities (RH) as a function of attitude in the region surrounding the Canary Islands during the Second Aerosol Characterization Experiment (ACE-2) in June and July 1997. The data were collected by the University of Washington passive humidigraph (UWPH) mounted on the Pelican research aircraft. Concurrently, particle size distributions absorption coefficients and aerosol optical depth were measured throughout 17 flights. A parameterization of sigma(sub sp) as a function of RH was utilized to assess the impact of aerosol hydration on the upwelling radiance (normalized to the solar constant and cosine of zenith angle). The top of the atmosphere radiance signal was simulated at wavelengths corresponding to visible and near-infrared bands or the EOS-AM ("Terra") detectors, MODIS and MISR. The UWPH measured (sigma(sub sp)) at 2 RHs, one below and the other above ambient conditions. Ambient (sigma(sub sp)) was obtained by interpolation of these 2 measurements. The data were stratified in terms of 3 types of aerosols: Saharan dust, clean marine (marine boundary layer background) and polluted marine aerosols (i.e., 2- or 1-day old polluted aerosols advected from Europe). An empirical relation for the dependence of (sigma(sub sp)) on RH, defined by (sigma(sub sp))(RH) = k. ((1 - RH/100)(exp -gamma), was used with the hygroscopic exponent gamma derived from the data. The following gamma values were obtained for the 3 aerosol types: gamma(dust) = 0.23 +/- 0.05, gamma(clean marine) = 0.69 +/- 0.06 and gamma(polluted marine) = 0.57 + 0.06. Based on the measured (gamma)(s), the above equation was utilized to derive aerosol models with different hygroscopicities. The satellite simulation signal code 6S was used to compute the upwelling radiance corresponding to each of those aerosol models at several ambient humidities. For the pre-launch estimated precision of the sensors and
NASA Technical Reports Server (NTRS)
Gasso, S.; Hegg, D. A.; Covert, D. S.; Collins, D.; Noone, K. J.; Oestroem, E.; Schmid, B.; Russell, P. B.; Livingston, J. M.; Durkee, P. A.
2000-01-01
Aerosol scattering coefficients (sigma(sub sp)) have been measured over the ocean at different relative humidities (RH) as a function of altitude in the region surrounding the Canary Islands during the Second Aerosol Characterization Experiment (ACE-2) in June and July 1997. The data were collected by the University of Washington passive humidigraph (UWPH) mounted on the Pelican research aircraft. Concurrently, particle size distributions, absorption coefficients and aerosol optical depth were measured throughout 17 flights. A parameterization of sigma(sub sp) as a function of RH was utilized to assess the impact of aerosol hydration on the upwelling radiance (normalized to the solar constant and cosine of zenith angle). The top of the atmosphere radiance signal was simulated at wavelengths corresponding to visible and near-infrared bands of the EOS (Earth Observing System) AM-1 (Terra) detectors, MODIS (Moderate Resolution Imaging Spectroradiometer) and MISR (Multi-angle Imaging Spectroradiometer). The UWPH measured sigma(sub sp) at two RHs, one below and the other above ambient conditions. Ambient sigma(sub sp) was obtained by interpolation of these two measurements. The data were stratified in terms of three types of aerosols: Saharan dust, clean marine (marine boundary layer background) and polluted marine aerosols (i.e., two- or one-day old polluted aerosols advected from Europe). An empirical relation for the dependence of sigma(sub sp) on RH, defined by sigma(sub sp)(RH) = k.(1 - RH/100)(sup gamma), was used with the hygroscopic exponent gamma derived from the data. The following gamma values were obtained for the 3 aerosol types: gamma(dust) = 0.23 +/- 0.05, gamma(clean marine) = 0.69 +/- 0.06 and gamma(polluted marine) = 0.57 +/- 0.06. Based on the measured gammas, the above equation was utilized to derive aerosol models with different hygroscopicities. The satellite simulation signal code 6S was used to compute the upwelling radiance corresponding to each
Measurement of the depolarization ratio of Rayleigh scattering at absorption bands
NASA Astrophysics Data System (ADS)
Anglister, J.; Steinberg, I. Z.
1981-01-01
Measurements of the depolarization ratio ρv of light scattered by the pigments lycopene and β-carotene at the red part of their absorption bands yielded values which are very close to the theoretical value 1/3 of a fully anisotropic molecular polarizability, i.e., that due to an electric dipole moment. Measurements of ρv at the blue edge of the visible absorption band of pinacyanol chloride yielded a value of 0.75 at 472.2 nm, which is the maximum value that a depolarization ratio can assume, and is attained if the average molecular polarizability is zero. This is possible only if the diagonalized polarizability tensor has at least one negative element to counterbalance the positive ones. A negative refractive index at the blue edge of the absorption band is thus experimentally demonstrated.
NASA Astrophysics Data System (ADS)
Titos, G.; Cazorla, A.; Zieger, P.; Andrews, E.; Lyamani, H.; Granados-Muñoz, M. J.; Olmo, F. J.; Alados-Arboledas, L.
2016-09-01
Knowledge of the scattering enhancement factor, f(RH), is important for an accurate description of direct aerosol radiative forcing. This factor is defined as the ratio between the scattering coefficient at enhanced relative humidity, RH, to a reference (dry) scattering coefficient. Here, we review the different experimental designs used to measure the scattering coefficient at dry and humidified conditions as well as the procedures followed to analyze the measurements. Several empirical parameterizations for the relationship between f(RH) and RH have been proposed in the literature. These parameterizations have been reviewed and tested using experimental data representative of different hygroscopic growth behavior and a new parameterization is presented. The potential sources of error in f(RH) are discussed. A Monte Carlo method is used to investigate the overall measurement uncertainty, which is found to be around 20-40% for moderately hygroscopic aerosols. The main factors contributing to this uncertainty are the uncertainty in RH measurement, the dry reference state and the nephelometer uncertainty. A literature survey of nephelometry-based f(RH) measurements is presented as a function of aerosol type. In general, the highest f(RH) values were measured in clean marine environments, with pollution having a major influence on f(RH). Dust aerosol tended to have the lowest reported hygroscopicity of any of the aerosol types studied. Major open questions and suggestions for future research priorities are outlined.
Figueroa, C.; Brizuela, H.; Heluani, S. P.
2014-05-21
The backscattering coefficient is a magnitude whose measurement is fundamental for the characterization of materials with techniques that make use of particle beams and particularly when performing microanalysis. In this work, we report the results of an analytic method to calculate the backscattering and absorption coefficients of electrons in similar conditions to those of electron probe microanalysis. Starting on a five level states ladder model in 3D, we deduced a set of integro-differential coupled equations of the coefficients with a method know as invariant embedding. By means of a procedure proposed by authors, called method of convergence, two types of approximate solutions for the set of equations, namely complete and simple solutions, can be obtained. Although the simple solutions were initially proposed as auxiliary forms to solve higher rank equations, they turned out to be also useful for the estimation of the aforementioned coefficients. In previous reports, we have presented results obtained with the complete solutions. In this paper, we present results obtained with the simple solutions of the coefficients, which exhibit a good degree of fit with the experimental data. Both the model and the calculation method presented here can be generalized to other techniques that make use of different sorts of particle beams.
NASA Astrophysics Data System (ADS)
Huffman, H. Dale
Using the IMPROVE network aerosol data from rural or remote sites across the United States, the ratio of the optically measured light absorption coefficient ( σa) to the elemental carbon measured by Thermal/Optical Reflectance (TOR) analysis consistently indicates an absorption efficiency that is twice the accepted value of 10m 2g -1. Correlations between σa and the TOR carbon strongly suggest that the discrepancy is due to an underevaluation of light-absorbing carbon rather than to an overestimation of σa or a real, higher value of the absorption efficiency. In particular, past doubts about the accuracy and precision of the IMPROVE σa measurement are here shown to be unsupported by the IMPROVE data. The large empirical correction that is applied to this σa measurement, for multiple scattering effects due to filter mass loading, is given a new explanation as the effect of an increasing forward scattering fraction as sample thickness increases. The old explanation of shadowing by overlying particles in the sample is rejected as having just the opposite effect to that needed to explain the correction. The use of a diffuse source rather than a laser beam is indicated as a way to avoid the large empirical correction of σa. Modelling of the light absorption by TOR carbon measurements, at twelve remote sites over a wide portion of the western United States, suggests the following errors in the current interpretation of TOR analysis for these sites: (1) The pyrolysis correction, based upon optical reflectance monitoring, appears to be largely wrong; and (2) The carbon evolving between 450 and 550°C in a pure helium atmosphere, currently interpreted as organic and therefore non-light-absorbing, appears to be as strongly light-absorbing as elemental carbon. However, the present analysis indicates that for a large majority (˜90%) of samples the light-absorbing carbons, as reinterpreted herein, are not only measured accurately by TOR, they are also reasonably well
Bendib, A.; Tahraoui, A.; Bendib, K.; Mohammed El Hadj, K.; Hueller, S.
2005-03-01
The transport coefficients of fully ionized plasmas under the influence of a high-frequency electric field are derived solving numerically the electron Fokker-Planck equation using a perturbation method, parametrized as a function of the electron mean-free-path {lambda}{sub ei} compared to the spatial scales L. The isotropic and anisotropic contributions of the inverse bremsstrahlung heating are considered. Electron-electron collision terms are kept in the analysis, which allows us to consider with sufficient accuracy to describe plasmas with arbitrary atomic number Z. Practical numerical fits of the transport coefficients are proposed as functions of Z and the collisionality parameter {lambda}{sub ei}/L.
NASA Astrophysics Data System (ADS)
Riddick, Caitlin A. L.; Hunter, Peter D.; Tyler, Andrew N.; Martinez-Vicente, Victor; Horváth, Hajnalka; Kovács, Attila W.; Vörös, Lajos; Preston, Tom; Présing, Mátyás.
2015-10-01
In order to improve robustness of remote sensing algorithms for lakes, it is vital to understand the variability of inherent optical properties (IOPs) and their mass-specific representations (SIOPs). In this study, absorption coefficients for particulate and dissolved constituents were measured at 38 stations distributed over a biogeochemical gradient in Lake Balaton, Hungary. There was a large range of phytoplankton absorption (aph(λ)) over blue and red wavelengths (aph(440) = 0.11-4.39 m-1, aph(675) = 0.048-2.52 m-1), while there was less variability in chlorophyll-specific phytoplankton absorption (a*ph(λ)) in the lake (a*ph(440) = 0.022 ± 0.0046 m2 mg-1, a*ph(675) = 0.010 ± 0.0020 m2 mg-1) and adjoining wetland system, Kis-Balaton (a*ph(440) = 0.017 ± 0.0015 m2 mg-1, a*ph(675) = 0.0088 ± 0.0017 m2 mg-1). However, in the UV, a*ph(350) significantly increased with increasing distance from the main inflow (Zala River). This was likely due to variable production of photoprotective pigments (e.g., MAAs) in response to the decreasing gradient of colored dissolved organic matter (CDOM). The slope of CDOM absorption (SCDOM) also increased from west to east due to larger terrestrial CDOM input in the western basins. Absorption by nonalgal particles (aNAP(λ)) was highly influenced by inorganic particulates, as a result of the largely mineral sediments in Balaton. The relative contributions to the absorption budget varied more widely than oceans with a greater contribution from NAP (up to 30%), and wind speed affected the proportion attributed to NAP, phytoplankton, or CDOM. Ultimately, these data provide knowledge of the heterogeneity of (S)IOPs in Lake Balaton, suggesting the full range of variability must be considered for future improvement of analytical algorithms for constituent retrieval in inland waters.
Liquid water absorption and scattering effects in DOAS retrievals over oceans
NASA Astrophysics Data System (ADS)
Peters, E.; Wittrock, F.; Richter, A.; Alvarado, L. M. A.; Rozanov, V. V.; Burrows, J. P.
2014-12-01
Spectral effects of liquid water are present in absorption (differential optical absorption spectroscopy - DOAS) measurements above the ocean and, if insufficiently removed, may interfere with trace gas absorptions, leading to wrong results. Currently available literature cross sections of liquid water absorption are provided in coarser resolution than DOAS applications require, and vibrational Raman scattering (VRS) is mostly not considered, or is compensated for using simulated pseudo cross sections from radiative transfer modeling. During the ship-based TransBrom campaign across the western Pacific in October 2009, MAX-DOAS (Multi-AXis differential optical absorption spectroscopy) measurements of light penetrating very clear natural waters were performed, achieving average underwater light paths of up to 50 m. From these measurements, the retrieval of a correction spectrum (H2Ocorr) is presented, compensating simultaneously for insufficiencies in the liquid water absorption cross section and broad-banded VRS structures. Small-banded structures caused by VRS were found to be very efficiently compensated for by the intensity offset correction included in the DOAS fit. No interference between the H2Ocorr spectrum and phytoplankton absorption was found. In the MAX-DOAS tropospheric NO2 retrieval, this method was able to compensate entirely for all liquid water effects that decrease the fit quality, and performed better than using a liquid water cross section in combination with a simulated VRS spectrum. The decrease in the residual root mean square (rms) of the DOAS fit depends on the measurement's contamination with liquid water structures, and ranges from ≈ 30% for measurements slightly towards the water surface to several percent in small angles above the horizon. Furthermore, the H2Ocorr spectrum was found to prevent misfits of NO2 slant columns, especially for very low NO2 scenarios, and thus increases the reliability of the fit. In test fits on OMI satellite
NASA Astrophysics Data System (ADS)
Smagin, N. V.; Krutyansky, L. M.; Zelenova, Z. V.; Brysev, A. P.
2014-03-01
Acoustic absorption has been measured in a series of biological tissue specimens—porcine muscle, renal and fat tissues—by the standard insert-substitution method, as well as by ultrasonic phase conjugation. Comparison of the experimental results and revealed differences confirm the promise of using phase conjugate waves to measure acoustic losses in biological objects. It is demonstrated that in inhomogeneous tissues, the phase conjugation method makes it possible to obtain a more reliable estimate of dissipative losses.
NASA Astrophysics Data System (ADS)
Pérez Reyes, Ma. C.; Hernandez-Aguilar, C.; Dominguez-Pacheco, A.; Cruz-Orea, A.; Moreno Martínez, E.
2015-09-01
Laser light as a biostimulator has been applied in agriculture, and some scientific reports evidence its usefulness. A knowledge about seed optical parameters is of great relevance in the biostimulation process, because information can be provided about the light absorption of seeds. Thus, the objective of the present study was to determine the optical absorption coefficient (β ) of barley ( Hordeum vulgare L.) seeds by means of photoacoustic spectroscopy; these seeds were studied in two conditions: seeds in their natural color and seeds dyed with methylene blue. The seeds were biostimulated by a laser beam (650 nm wavelength) to evaluate the effects of pre-sowing biostimulation in natural mycobiota associated with different laser irradiation times (0 s, 60 s, 120 s, 240 s, and 480 s). The results of this research demonstrated changes in the optical parameters (absorption and penetration) that occur in the seeds by changing the natural condition to a dyed condition. The dyed seeds, by the methylene blue photosensitizer, become optically opaque, producing greater optical absorption at 650 nm which causes an increase in the effect of laser stimulation. The experimental results showed that the biggest mycobiota reduction (52 %) corresponded to dyed seeds irradiated with a laser for 120 s.
Absorption coefficients and band strengths for the 703 nm and 727 bands of methane at 77 K
O`Brien, J.J.; Singh, K.
1996-12-31
The technique of intracavity laser spectroscopy has been used to obtain methane absorption spectra for the vibrational overtone bands that occur around 703 nm and 727 nm. Absorption coefficients for the 690-742 nm range have been obtained for a sample temperature of 77 K at a spectral resolution of <0.02 cm{sup -1}. A new method of data analysis is utilized in obtaining the results. It involves deconvolving the many ILS spectral profiles that comprise the absorption bands and summing the results. Values averaged over 1 cm{sup -1} and 1 {Angstrom} intervals are provided. Band strengths also are obtained. The total intensities of the 703 and 727 nm bands are in reasonable agreement with previous laboratory determinations which were obtained for relatively high pressures of methane at room temperature using lower spectral resolution. The methane bands appear in the reflected sunlight spectra from the outer planets. Results averaged over 1 nm intervals are compared with other laboratory studies and with those derived from observations of the outer planets. The band profiles differ considerably from other laboratory results but are in good accord with the planetary observations. Laboratory spectra of methane at appropriate conditions are required for the proper interpretation of the observational data. Absorption spectra can provide some of the most sensitive diagnostic data on the atmospheres of those bodies.
Okubo; Suda
1999-05-15
zeta-Potential and the effective diameter of the colloidal spheres absorbed with the macro-cations and macro-anions are studied by the electrophoretic light-scattering and dynamic light-scattering measurements. Colloidal spheres used are monodispersed polystyrene (220 nm in diameter) and colloidal silica spheres (110 nm). Macro-ions used are sodium polyacrylate, sodium polymethylacrylate, sodium poly(styrene sulfonate), and poly-4-vinyl pyridines quaternized with ethyl bromide, n-butyl bromide, benzyl chloride, and 5% hexadecyl bromide and 95% benzyl chloride. Reversal of colloidal surface charges from negative to positive occurs abruptly above the critical concentration of macro-ions by the excess absorption of the macro-cations onto the anionic colloidal spheres, i.e., avalanche-type absorption. The effective diameter of colloidal spheres including the absorbed layers increases substantially by four- to tenfold. In the presence of large amount of macro-cations aggregation of colloidal spheres mediated by the layers of absorbed macro-cations may occur. Absorption also occurs on the anionic colloidal spheres in the presence of an excess amount of macro-anions by the dipole-dipole-type attractive interactions. Copyright 1999 Academic Press. PMID:10222098
The effects of dust scattering on high-resolution X-ray absorption edge structure
NASA Astrophysics Data System (ADS)
Corrales, L.; García, J.; Wilms, J.; Baganoff, F.
2016-06-01
High energy studies of astrophysical dust complement observations of dusty interstellar gas at other wavelengths. With high resolution X-ray spectroscopy, dust scattering significantly enhances the total extinction optical depth and alters the shape of photoelectric absorption edges. This effect is modulated by the dust grain size distribution, spatial location along the line of sight, and the imaging resolution of the X-ray telescope. At soft energies, the spectrum of scattered light is likely to have significant features at the 0.3 keV (C-K), 0.5 keV (O-K), and 0.7 keV (Fe-L) photoelectric absorption edges. This direct probe of ISM dust grain elements will be important for (i) understanding the relative abundances of graphitic grains or PAHs versus silicates, and (ii) measuring the depletion of gas phase elements into solid form. We focus in particular on the Fe-L edge, fitting a template for the total extinction to the high resolution spectrum of three X-ray binaries from the Chandra archive: GX 9+9, XTE J1817-330, and Cyg X-1. We discuss ways in which spectroscopy with XMM can yield insight into dust obscured objects such as stars, binaries, AGN, and foreground quasar absorption line systems.
Fu, Q.; Sun, W.B.; Yang, P.
1999-08-15
This paper examines a number of commonly used methods for the calculation of the scattering and absorption properties of nonspherical ice crystals at thermal infrared wavelengths. It is found that, for randomly oriented nonspherical particles, Mie theory using equivalent ice spheres tends to overestimate the absorption efficiency while the anomalous diffraction theory (ADT) and the geometric optics method (GOM) tend to underestimate it. The absorption efficiency is not sensitive to the particle shape when the size parameter is large. Herein a composite scheme is used that is valid for nonspherical particles with a wide range of size parameters. This scheme is a composite of Mie theory, GOM, and ADT to fit the single-scattering properties of hexagonal particles derived from the GOM for large size parameters and the finite-difference time domain technique for small size parameters. Applying this composite technique, errors in the broadband emissivity of cirrus clouds associated with conventional approaches are examined. It is shown that, when the projected area is preserved, Mie results overestimate the emissivity of cirrus clouds while, when the volume is preserved, Mie results underestimate the emissivity. Mie theory yields the best results when both projected area and volume are preserved (the relative errors are less than 10%). It is also shown that the ADT underestimates cirrus cloud emissivity. In some cases, the relative errors can be as large as 20%. The errors in the GOM are also significant and are largely a result of nonspherical particles with size parameters smaller than 40.
NASA Astrophysics Data System (ADS)
Leid, Terrence Vincent
The emission of electron cyclotron radiation parallel to the magnetic field direction near the fundamental frequency from a fully ionized, multi-component plasma, is investigated for finite (omega)(,p)/(omega)(,c) within the Klimontovich formalism. Each species may have T(,(PARLL)) different from T(,(PERP)) and may possess a loss cone. We use a bi- maxwellian with an analytic loss cone for each component. In addition, the source function for a multi-component plasma is calculated. We find that for a Maxwellian distribution function the emission coefficient is that of a system of shielded charges. It is shown that only in the case of a tenuous Maxwellian plasma is the source function the Rayleigh-Jeans blackbody intensity. For the case of the Maxwellian we present experimental evidence for finite density emission, (omega)('2)(,p)/(omega)('2) >> (beta). We have constructed a computer code that solves the radiative transfer equation. The resulting power spectra are used as an aid in extracting from experimental data the temperature and density of the various components of the TMX-Upgrade end cell plasma. The code compares both the Ellis-Tsakiris scheme for computing the emission coefficient for a multi-component plasma and the finite density multi -component emission coefficient. The Ellis- Tsakiris scheme estimates the emission coefficient by assuming. that each species radiates independently of each other.('1) Results are presented for the case of the TMX -Upgrade tandem mirror device. ('1)R. F. Ellis and G. D. Tsakiris, Nucl. Fusion 23, 1115 (1984).
NASA Astrophysics Data System (ADS)
Post, Anouk L.; Zhang, Xu; Bosschaart, Nienke; Van Leeuwen, Ton G.; Sterenborg, Henricus J. C. M.; Faber, Dirk J.
2016-03-01
Both Optical Coherence Tomography (OCT) and Single Fiber Reflectance Spectroscopy (SFR) are used to determine various optical properties of tissue. We developed a method combining these two techniques to measure the scattering anisotropy (g1) and γ (=1-g2/1-g1), related to the 1st and 2nd order moments of the phase function. The phase function is intimately associated with the cellular organization and ultrastructure of tissue, physical parameters that may change during disease onset and progression. Quantification of these parameters may therefore allow for improved non-invasive, in vivo discrimination between healthy and diseased tissue. With SFR the reduced scattering coefficient and γ can be extracted from the reflectance spectrum (Kanick et al., Biomedical Optics Express 2(6), 2011). With OCT the scattering coefficient can be extracted from the signal as a function of depth (Faber et al., Optics Express 12(19), 2004). Consequently, by combining SFR and OCT measurements at the same wavelengths, the scattering anisotropy (g) can be resolved using µs'= µs*(1-g). We performed measurements on a suspension of silica spheres as a proof of principle. The SFR model for the reflectance as a function of the reduced scattering coefficient and γ is based on semi-empirical modelling. These models feature Monte-Carlo (MC) based model constants. The validity of these constants - and thus the accuracy of the estimated parameters - depends on the phase function employed in the MC simulations. Since the phase function is not known when measuring in tissue, we will investigate the influence of assuming an incorrect phase function on the accuracy of the derived parameters.
Almasian, Mitra; Bosschaart, Nienke; van Leeuwen, Ton G; Faber, Dirk J
2015-12-01
Optical coherence tomography (OCT) has the potential to quantitatively measure optical properties of tissue such as the attenuation coefficient and backscattering coefficient. However, to obtain reliable values for strong scattering tissues, accurate consideration of the effects of multiple scattering and the nonlinear relation between the scattering coefficient and scatterer concentration (concentration-dependent scattering) is required. We present a comprehensive model for the OCT signal in which we quantitatively account for both effects, as well as our system parameters (confocal point spread function and sensitivity roll-off). We verify our model with experimental data from controlled phantoms of monodisperse silica beads (scattering coefficients between 1 and 30 mm(−1) and scattering anisotropy between 0.4 and 0.9). The optical properties of the phantoms are calculated using Mie theory combined with the Percus–Yevick structure factor to account for concentration-dependent scattering. We demonstrate excellent agreement between the OCT attenuation and backscattering coefficient predicted by our model and experimentally derived values. We conclude that this model enables us to accurately model OCT-derived parameters (i.e., attenuation and backscattering coefficients) in the concentration-dependent and multiple scattering regime for spherical monodisperse samples. PMID:26720868
The effects of dust scattering on high-resolution X-ray absorption edge structure
NASA Astrophysics Data System (ADS)
Corrales, Lia; Garcia, Javier; Wilms, Joern; Baganoff, Frederick K.
2016-04-01
In high resolution X-ray spectroscopy, dust scattering significantly enhances the total extinction optical depth and alters the shape of photoelectric absorption edges. This effect is modulated by the dust grain size distribution, spatial location along the line of sight, and the imaging resolution of the X-ray telescope. We focus in particular on the Fe L-edge at 0.7 keV, fitting a template for the total extinction to the high resolution spectrum of three X-ray binaries from the Chandra archive: GX 9+9, XTE J1817-330, and Cyg X-1. In cases where dust is intrinsic to the source, a covering factor based on the angular extent of the dusty material must be applied to the extinction curve, regardless of imaging resolution. We discuss the various astrophysical cases in which scattering effects need to be taken into account.
Attenuation studies near K-absorption edges using Compton scattered 241 Am gamma rays
NASA Astrophysics Data System (ADS)
Abdullah, K. K.; Ramachandran, N.; Karunakaran Nair, K.; Babu, B. R. S.; Joseph, Antony; Thomas, Rajive; Varier, K. M.
2008-04-01
We have carried out photon attenuation measurements at several energies in the range from 49.38 keV to 57.96 keV around the K-absorption edges of the rare earth elements Sm, Eu, Gd, Tb, Dy and Er using 59.54 keV gamma rays from ^{241}Am source after Compton scattering from an aluminium target. Pellets of oxides of the rare earth elements were chosen as mixture absorbers in these investigations. A narrow beam good geometry set-up was used for the attenuation measurements. The scattered gamma rays were detected by an HPGe detector. The results are consistent with theoretical values derived from the XCOM package.
THE INFLUENCE OF ATMOSPHERIC SCATTERING AND ABSORPTION ON OHMIC DISSIPATION IN HOT JUPITERS
Heng, Kevin
2012-03-20
Using semi-analytical, one-dimensional models, we elucidate the influence of scattering and absorption on the degree of Ohmic dissipation in hot Jovian atmospheres. With the assumption of Saha equilibrium, the variation in temperature is the main driver of the variations in the electrical conductivity, induced current, and Ohmic power dissipated. Atmospheres possessing temperature inversions tend to dissipate most of the Ohmic power superficially, at high altitudes, whereas those without temperature inversions are capable of greater dissipation deeper down. Scattering in the optical range of wavelengths tends to cool the lower atmosphere, thus reducing the degree of dissipation at depth. Purely absorbing cloud decks (in the infrared), of a finite extent in height, allow for localized reductions in dissipation and may reverse a temperature inversion if they are dense and thick enough, thus greatly enhancing the dissipation at depth. If Ohmic dissipation is the mechanism for inflating hot Jupiters, then variations in the atmospheric opacity (which may be interpreted as arising from variations in metallicity and cloud/haze properties) and magnetic field strength naturally produce a scatter in the measured radii at a given strength of irradiation. Future work will determine if these effects are dominant over evolutionary effects, which also contribute a scatter to the measured radii.
Ugalde, A.; Pujades, L.G.; Canas, J.A.; Villasenor, A.
1998-01-01
Northeastern Venezuela has been studied in terms of coda wave attenuation using seismograms from local earthquakes recorded by a temporary short-period seismic network. The studied area has been separated into two subregions in order to investigate lateral variations in the attenuation parameters. Coda-Q-1 (Q(c)-1) has been obtained using the single-scattering theory. The contribution of the intrinsic absorption (Q(i)-1) and scattering (Q(s)-1) to total attenuation (Q(t)-1) has been estimated by means of a multiple lapse time window method, based on the hypothesis of multiple isotropic scattering with uniform distribution of scatterers. Results show significant spatial variations of attenuation: the estimates for intermediate depth events and for shallow events present major differences. This fact may be related to different tectonic characteristics that may be due to the presence of the Lesser Antilles subduction zone, because the intermediate depth seismic zone may be coincident with the southern continuation of the subducting slab under the arc.
NASA Technical Reports Server (NTRS)
Fisk, L. A.; Goldstein, M. L.; Klimas, A. J.; Sandri, G.
1973-01-01
For the case of homogeneous, isotropic magnetic field fluctuations, it is shown that most theories which are based on the quasi-linear and adiabatic approximation yield the same integral for the Fokker-Planck coefficient for the pitch angle scattering of cosmic rays. For example, despite apparent differences, the theories due to Jokipii and to Klimas and Sandri yield the same integral. It is also shown, however, that this integral in most cases has been evaluated incorrectly in the past. For large pitch angles these errors become significant, and for pitch angles of 90 deg the actual Fokker-Planck coefficient contains a delta function. The implications for these corrections relating cosmic ray diffusion coefficients to observed properties of the interplanetary magnetic field are discussed.
NASA Astrophysics Data System (ADS)
Tao, Zongming; Liu, Dong; Ma, Xiaomin; Shi, Bo; Shan, Huihui; Zhao, Ming; Xie, Chenbo; Wang, Yingjian
2015-09-01
The near-ground aerosols have the most impact on the human beings. Its fine spatial and temporal distribution, with which the environmental and meteorological departments concern themselves most, has not been elaborated very well due to the unavailable measurement tools. We present the continuous observations of the vertical profile of near-ground aerosol backscattering coefficients by employing our self-developed side-scattering lidar system based on charge-coupled device camera. During the experimental period from April 2013 to August 2014, four catalogs of aerosol backscattering coefficient profiles are found in the near ground. The continuous measurement is revealed by the contour plots measured during the whole night. These experimental results indicate that the aerosol backscattering coefficients in near ground are inhomogeneous and vary with altitude and time, which are very useful for the model researchers to study the regional air pollution and its climate impact.
X-ray scattering and absorption studies of MnAs/GaAs heterostructures
NASA Astrophysics Data System (ADS)
Huang, S.; Ming, Z. H.; Soo, Y. L.; Kao, Y. H.; Tanaka, M.; Munekata, H.
1996-02-01
Ferromagnetic MnAs thin films grown on GaAs (001) substrates by molecular-beam epitaxy have been studied by the methods of grazing incidence x-ray scattering, x-ray diffraction, and extended x-ray-absorption fine structure. Microstructures in two films prepared with different first-layer growth conditions (template effects) are compared in terms of the interfacial roughness in the layer structure, lattice constants, epilayer thickness, local environment surrounding the Mn atoms, coordination number, and local disorder. Our results indicate that the template effects can cause significant differences in the local structures and crystallinity of the MnAs epitaxial layers.
NASA Astrophysics Data System (ADS)
Thomas, S.; Koch-Mueller, M.; Reichart, P.; Rhede, D.; Thomas, R.
2007-12-01
Conventionally applied Infrared (IR) calibrations [1, 2] for quantitative water analyses in solids are established on hydrous minerals and glasses with several wt% water. These calibrations are based on a negative correlation between the IR molar absorption coefficient (ɛ) for water and the mean wavenumber of the corresponding OH pattern. The correlation reflects the dependence of the OH band position on the appropriate O- H...O distances and thereby the magnitude of the dipole momentum which is proportional to the band intensity. However, it has been observed that these calibrations can not be adopted to nominally anhydrous minerals (NAMs) [3].To study the potential dependence of ɛ on structure and chemistry in NAMs we synthesized olivine and SiO2 polymorphs with specific isolated hydroxyl point defects, e.g. quartz, coesite and stishovite with B3++H+=Si4+ and/or Al3++H+=Si4+ substitutions. Experiments were performed with water in excess in piston cylinder and multi-anvil presses. Single crystal IR spectra demonstrate that we successfully managed to seperate generally complex OH patterns as e.g. observed in natural quartz and synthetic coesite. We quantified sample water contents of both natural samples and our run products by applying proton-proton-scattering [4], confocal microRaman spectroscopy [5] and Secondary Ion mass spectrometry. Resulting water concentrations were used to calculate new mineral specific ɛs. For olivine with the mean wavenumber of 3517 cm-1 we determined an ɛ value of 41,000±5,000 lmol-1H2Ocm-2. Quantification of olivine with the mean wavenumber of 3550 cm-1 in contrast resulted in an ɛ value of 47,000±1,000 lmol-1H2Ocm-2. Taking into account previous studies [6, 7] there is evidence to suggest a linear wavenumber dependent correlation for olivine, where ɛ increases with decreasing wavenumber. In case of the SiO2 system it turns out that the magnitude of ɛ within one structure type is independent of the liable OH point defect and
Kabi, Sanjib; Perera, A. G. Unil
2015-03-28
The intersublevel absorption peak energy and absorption coefficient of non-uniform quantum dot (QD) ensembles are calculated analytically. The effect of size variations and size distribution of QDs on their energy states is analyzed. The dots are considered as a quantum box with finite potential at the barriers and the size distribution described by a Gaussian function. The influence of the aspect ratio (base to height ratio) of the QDs on the optical transitions is studied. Our model predicts the dot size (height and base) accurately to determine the absorption peaks and corresponding absorption coefficient. We also compute the absorption coefficient of the QD with different size distributions to verify the results calculated using this model with the reported experimental and other theoretical results.
NASA Astrophysics Data System (ADS)
Stevens, Michael H.
1995-08-01
The fluorescent scattering of UV sunlight and self-absorption by the nitric oxide (NO) γ bands between 2000-2500 Å are quantified for the purpose of inferring NO density profiles as a function of altitude in the mesosphere and above. Rotational line emission rate factors and cross sections are calculated at a variety of temperatures. The observed variation of the solar spectrum across the γ bands and its effect on emission rate factors are explored by using irradiance measurements that resolve features down to 0.1 Å. The model also includes quenching by O2 and N2, multiple scattering, temperature effects, attenuation of the solar irradiance by O2 and ozone, and self-absorption with the summation of adjacent rotational features. Results indicate that for resonant γ bands, the rotational structure in emission is not symmetric to that in absorption so that as self-absorption increases the shape of the observed emission envelope changes. For γ(1,0) this is largely characterized by an increase in the integrated emission observed longward of 2151 Å compared to shortward. It is found that solar irradiances measured at 0.1 Å resolution decrease the calculated γ(1,0) and γ(0,0) band emission rate factors by less than 3% compared to those measured at 2 Å resolution. However, more Fraunhofer structure included in the calculation is reflected in the relative intensities of the rotational features. It is also found that extinction of the solar irradiance by ozone and quenching by O2 rapidly reduce the γ(1,0) emission rate factor with decreasing altitude below 60 km.
Wang, Kangpeng; Ju, Yongfeng; He, Jin; Zhang, Long E-mail: lzhang@siom.ac.cn; Wang, Jun E-mail: lzhang@siom.ac.cn; Chen, Yu; Blau, Werner J.
2014-01-13
Laser propagation in a tandem structure comprising carbon nanotubes and phthalocyanines is studied by Z-scan method. Due to the different mechanisms of the two materials, the laser beam can be attenuated with different absorptivities, by changing the sequence of light passing through each material. Numerical simulations considering the effect of path length and the change of nonlinear coefficient within each material are conducted for understanding the distribution of laser intensity in the tandem system and hence, fitting of the asymmetric Z-scan curves. The results are helpful for the design of nonlinear optical devices comprising multiple nonlinear materials and mechanisms.
Inverse Bremsstrahlung in Astrophysical Plasmas: The Absorption Coefficients and Gaunt Factors
NASA Astrophysics Data System (ADS)
Mihajlov, A. A.; Srećković, V. A.; Sakan, N. M.
2015-12-01
The electron-ion inverse Bremsstrahlung is considered here as a factor of the influence on the opacity of the different stellar atmospheres and other astrophysical plasmas. It is shown that this process can be successfully described in the frames of cut-off Coulomb potential model within the regions of the electron densities and temperatures. The relevant quantum mechanical method of the calculation of the corresponding spectral coefficient processes is described and discussed. The results obtained for the plasmas with the electron densities from 1014 c m -3 to 2ṡ1019 c m -3 and temperatures from 5ṡ103 K to 3ṡ104 K in the wavelength region 100 nm< λ<3000 nm are presented. Also, these results can be of interest for different laboratory plasmas.
Dimitriadis, Alexandros I.; Kantartzis, Nikolaos V.; Tsiboukis, Theodoros D.; Hafner, Christian
2015-01-15
Highlights: •Formulas for E/M fields radiated by continuous surface polarization distributions. •Non-local effective surface susceptibility model for periodic metafilms. •Generalized reflection and transmission coefficients for an arbitrary metafilm. •Successful treatment of non-planar scatterer arrays and spatial dispersion effects. -- Abstract: A non-local surface susceptibility model for the consistent description of periodic metafilms formed by arbitrarily-shaped, electrically-small, bianisotropic scatterers is developed in this paper. The rigorous scheme is based on the point-dipole approximation technique and is valid for any polarization and propagation direction of an electromagnetic wave impinging upon the metafilm, unlike existing approaches whose applicability is practically confined to very specific cases of incidence. Next, the universal form of the resulting surface susceptibility matrix is employed for the derivation of the generalized Fresnel coefficients for such surfaces, which enable the comprehensive interpretation of several significant, yet relatively unexamined, physical interactions. Essentially, these coefficients include eight distinct terms, corresponding to the co-polarized and cross-polarized reflection and transmission coefficients for the two orthogonal eigenpolarizations of a linearly-polarized incident plane wave. The above formulas are, then, utilized for the prediction of the scattering properties of metafilms with different planar and non-planar resonators, which are characterized via the featured model and two previously reported local ones. Their comparison with numerical simulation outcomes substantiates the merits of the proposed method, reveals important aspects of the underlying physics, and highlights the differences between the various modeling procedures.
NASA Technical Reports Server (NTRS)
Sun, W.; Loeb, N. G.; Fu, Q.
2002-01-01
The three-dimensional (3-D) finite-difference time-domain (FDTD) technique has been extended to simulate light scattering and absorption by nonspherical particles embedded in an absorbing dielectric medium. A uniaxial perfectly matched layer (UPML) absorbing boundary condition is used to truncate the computational domain. When computing the single-scattering properties of a particle in an absorbing dielectric medium, we derive the single-scattering properties including scattering phase functions, extinction, and absorption efficiencies using a volume integration of the internal field. A Mie solution for light scattering and absorption by spherical particles in an absorbing medium is used to examine the accuracy of the 3-D UPML FDTD code. It is found that the errors in the extinction and absorption efficiencies from the 3-D UPML FDTD are less than similar to 2%. The errors in the scattering phase functions are typically less than similar to 5%. The errors in the asymmetry factors are less than similar to 0.l%. For light scattering by particles in free space, the accuracy of the 3-D UPML FDTD scheme is similar to a previous model.
Wu, R.S.; Xie, X.B.
1994-12-31
The theory of spatial distribution of seismic energy density in one dimensional (1D) random media derived in part 1 (Wu, 1993) is tested by numerical experiments using a full wave propagation matrix method. The geometry of numerical experiment mimics the configuration of zero-offset VSP (Vertical Seismic Profiling) along a borehole. A procedure of octave-band frequency averaging is applied to the measured data to reduce fluctuation of spatial energy distribution, so that stable estimations of medium parameters can be achieved without resorting to ensemble averaging. Results from Monte-Carlo numerical experiments for both infinite random media and finite random slabs with or without bottom reflections show good agreement for dark-to-gray (weak to intermediate scattering compared with absorption) media. When scattering is very strong (when backscattering-absorption ratio S{sub b} > 3), results from single realization fluctuate substantially. However, most the practical situations of sedimentary rocks in the crust fall into the validity region of the energy transfer theory.
Absorption coefficients of the methane-nitrogen binary ice system: Implications for Pluto
NASA Astrophysics Data System (ADS)
Protopapa, S.; Grundy, W. M.; Tegler, S. C.; Bergonio, J. M.
2015-06-01
The methane-nitrogen phase diagram of Prokhvatilov and Yantsevich (1983. Sov. J. Low Temp. Phys. 9, 94-98) indicates that at temperatures relevant to the surfaces of icy dwarf planets like Pluto, two phases contribute to the methane absorptions: nitrogen saturated with methane N2 ‾ :CH4 and methane saturated with nitrogen CH4 ‾ :N2 . No optical constants are available so far for the latter component limiting construction of a proper model, in compliance with thermodynamic equilibrium considerations. New optical constants for solid solutions of methane diluted in nitrogen (N2 :CH4) and nitrogen diluted in methane (CH4 :N2) are presented at temperatures between 40 and 90 K, in the wavelength range 1.1-2.7 μm at different mixing ratios. These optical constants are derived from transmission measurements of crystals grown from the liquid phase in closed cells. A systematic study of the changes of methane and nitrogen solid mixtures spectral behavior with mixing ratio and temperature is presented.
Optical analysis of trapped Gas—Gas in Scattering Media Absorption Spectroscopy
NASA Astrophysics Data System (ADS)
Svanberg, S.
2010-01-01
An overview of the new field of Gas in Scattering Media Absorption Spectroscopy (GASMAS) is presented. The technique investigates sharp gas spectral signatures, typically 10000 times sharper than those of the host material, in which the gas is trapped in pores or cavities. The presence of pores causes strong multiple scattering. GASMAS combines narrow-band diode-laser spectroscopy, developed for atmospheric gas monitoring, with diffuse media optical propagation, well-known from biomedical optics. Several applications in materials science, food packaging, pharmaceutics and medicine have been demonstrated. So far molecular oxygen and water vapour have been studied around 760 and 935 nm, respectively. Liquid water, an important constituent in many natural materials, such as tissue, has a low absorption at such wavelengths, and this is also true for haemoglobin, making propagation possible in many natural materials. Polystyrene foam, wood, fruits, food-stuffs, pharmaceutical tablets, and human sinus cavities (frontal, maxillary and mastoideal) have been studied, demonstrating new possibilities for characterization and diagnostics. Transport of gas in porous media (diffusion) can be studied by first subjecting the material to, e.g., pure nitrogen, and then observing the rate at which normal, oxygen-containing air, reinvades the material. The conductance of the passages connecting a sinus with the nasal cavity can be objectively assessed by observing the oxygen gas dynamics when flushing the nose with nitrogen. Drying of materials, when liquid water is replaced by air and water vapour, is another example of dynamic processes which can be studied. The technique has also been extended to remote-sensing applications (LIDAR-GASMAS or Multiple-Scattering LIDAR).
Gas in Scattering Media Absorption Spectroscopy -- Laser Spectroscopy in Unconventional Environments
NASA Astrophysics Data System (ADS)
Svanberg, Sune
2010-02-01
An overview of the new field of Gas in Scattering Media Absorption Spectroscopy (GASMAS) is presented. The GASMAS technique combines narrow-band diode-laser spectroscopy with optical propagation in diffuse media. Whereas solids and liquids have broad absorption features, free gas in pores and cavities in the material is characterized by sharp spectral signatures. These are typically 10,000 times sharper than those of the host material. Many applications in materials science, food packaging, pharmaceutics and medicine have been demonstrated. Molecular oxygen and water vapor have been studied around 760 and 935 nm, respectively. Liquid water, an important constituent in many natural materials, such as tissue, has a low absorption at such wavelengths, allowing propagation. Polystyrene foam, wood, fruits, food-stuffs, pharmaceutical tablets, and human sinus cavities have been studied, demonstrating new possibilities for characterization and diagnostics. Transport of gas in porous media can readily be studied by first immersing the material in, e.g., pure nitrogen gas, and then observing the rate at which normal air, containing oxygen, reinvades the material. The conductance of the human sinus connective passages can be measured in this way by flushing the nasal cavity with nitrogen, while breathing normally through the mouth. A clinical study comprising 40 patients has been concluded.
NASA Astrophysics Data System (ADS)
Tran, Huong; Du, Wei; Ghetmiri, Seyed A.; Mosleh, Aboozar; Sun, Greg; Soref, Richard A.; Margetis, Joe; Tolle, John; Li, Baohua; Naseem, Hameed A.; Yu, Shui-Qing
2016-03-01
The absorption coefficient and refractive index of Ge1-xSnx alloys (x from 0% to 10%) were characterized for the wavelength range from 1500 to 2500 nm via spectroscopic ellipsometry at room temperature. By applying physical models to fit the obtained data, two empirical formulae with extracted constants and coefficients were developed: (1) Absorption coefficient. The absorption regarding Urbach tail, indirect and direct bandgap transitions were comprehensively taken into account; (2) refractive index. The Sellmeier coefficients associated with dispersion relationship were extracted. In these formulae, the Sn composition and strain percentage were the input parameters, by inputting which the spectral absorption coefficient and spectral refractive index can be obtained. Since the absorption coefficient is key information to determine the performance of the photodetectors including operation wavelength range, responsivity, and specific detectivity, and the refractive index is very useful for the design of the anti-reflection coating for photodetectors and the layer structure for waveguides, the developed formulae could simplify the optoelectronic device design process due to their parameter-based expressions.
NASA Astrophysics Data System (ADS)
Xie, Hong-Yi; Foster, Matthew S.
2016-05-01
We study the electric and thermal transport of the Dirac carriers in monolayer graphene using the Boltzmann-equation approach. Motivated by recent thermopower measurements [F. Ghahari, H.-Y. Xie, T. Taniguchi, K. Watanabe, M. S. Foster, and P. Kim, Phys. Rev. Lett. 116, 136802 (2016), 10.1103/PhysRevLett.116.136802], we consider the effects of quenched disorder, Coulomb interactions, and electron-optical-phonon scattering. Via an unbiased numerical solution to the Boltzmann equation we calculate the electrical conductivity, thermopower, and electronic component of the thermal conductivity, and discuss the validity of Mott's formula and of the Wiedemann-Franz law. An analytical solution for the disorder-only case shows that screened Coulomb impurity scattering, although elastic, violates the Wiedemann-Franz law even at low temperature. For the combination of carrier-carrier Coulomb and short-ranged impurity scattering, we observe the crossover from the interaction-limited (hydrodynamic) regime to the disorder-limited (Fermi-liquid) regime. In the former, the thermopower and the thermal conductivity follow the results anticipated by the relativistic hydrodynamic theory. On the other hand, we find that optical phonons become non-negligible at relatively low temperatures and that the induced electron thermopower violates Mott's formula. Combining all of these scattering mechanisms, we obtain the thermopower that quantitatively coincides with the experimental data.
Falcao-Filho, E.L.; Araujo, Cid B. de; Bosco, C.A.C.; Maciel, G.S.; Acioli, L.H.; Nalin, M.; Messaddeq, Y.
2005-01-01
Antimony glasses based on the composition Sb{sub 2}O{sub 3}-SbPO{sub 4} were prepared and characterized. The samples present high refractive index, good transmission from 380 to 2000 nm, and high thermal stability. The nonlinear refractive index, n{sub 2}, of the samples was studied using the optical Kerr shutter technique at 800 nm. The third-order correlation signals between pump and probe pulses indicate ultrafast response (<100 fs) for all compositions. Enhancement of n{sub 2} was observed by adding lead oxide to the Sb{sub 2}O{sub 3}-SbPO{sub 4} composition. Large values of n{sub 2}{approx_equal}10{sup -14} cm{sup 2}/W and negligible two-photon absorption coefficients (smaller than 0.01 cm/GW) were determined for all samples. The glass compositions studied present appropriate figure-of-merit for all-optical switching applications.
Berdnik, Vladimir V; Loiko, Valery A
2011-08-01
Scattering of light by an ensemble of nonabsorbing spherical concentric two-layered particles is considered. It has been shown that exponent of the power function describing the wavelength dependence of the extinction coefficient of the medium with subwavelength-sized particles can exceed considerably the value of 4, which takes place for the Rayleigh scattering. Spatial correlation of particles enhances this "anomalous" dependence on the wavelength. Bleaching and darkening effects can be implemented. In the first case transmittance increases, while in the second case transmittance decreases with increased volume concentration. These effects can be used to get a sharp spectral dependence of transmittance. Comparison with the data for spatially correlated homogeneous particles is carried out. PMID:21833095
Kanick, S. C.; Gamm, U. A.; Schouten, M.; Sterenborg, H. J. C. M.; Robinson, D. J.; Amelink, A.
2011-01-01
This paper presents a relationship between the intensity collected by a single fiber reflectance device (RSF) and the fiber diameter (dfib) and the reduced scattering coefficient ( μs′) and phase function (p(θ)) of a turbid medium. Monte Carlo simulations are used to identify and model a relationship between RSF and dimensionless scattering ( μs′dfib). For μs′dfib > 10 we find that RSF is insensitive to p(θ). A solid optical phantom is constructed with μs′ ≈ 220 mm−1 and is used to convert RSF of any turbid medium to an absolute scale. This calibrated technique provides accurate estimates of μs′ over a wide range ([0.05 – 8] mm−1) for a range of dfib ([0.2 – 1] mm). PMID:21698029
NASA Astrophysics Data System (ADS)
Foschum, F.; Jäger, M.; Kienle, A.
2011-10-01
We describe a fully automated setup which is based on measurements of the spatially resolved reflectance for the determination of the reduced scattering and absorption coefficients in semi-infinite turbid media. The sample is illuminated with a xenon light source in combination with a monochromator enabling the scan of the wavelength from 450 nm to 950 nm. Reflected light from the sample is detected with a CCD camera providing a high spatial resolution. The essential steps for signal processing including, e.g., the consideration of the optical transfer function and the correct treatment of the background subtraction, are presented. The solutions of the diffusion theory and of the radiative transfer theory are investigated regarding the exact detection and illumination geometry. Systematic errors caused by using the different theories for fitting the optical parameters are characterized. The system was validated using liquid phantoms which contain Intralipid 20% and ink, and the measurement range of the system is specified. Further, we carefully characterized the optical properties of Intralipid 20% in the wavelength range between 450 nm and 950 nm.
LeClair, Robert J.; Boileau, Michel M.; Wang Yinkun
2006-04-15
The goal of this work is to develop a technique to measure the x-ray diffraction signals of breast biopsy specimens. A biomedical x-ray diffraction technology capable of measuring such signals may prove to be of diagnostic use to the medical field. Energy dispersive x-ray diffraction measurements coupled with a semianalytical model were used to extract the differential linear scattering coefficients [{mu}{sub s}(x)] of breast tissues on absolute scales. The coefficients describe the probabilities of scatter events occurring per unit length of tissue per unit solid angle of detection. They are a function of the momentum transfer argument, x=sin({theta}/2)/{lambda}, where {theta}=scatter angle and {lambda}=incident wavelength. The technique was validated by using a 3 mm diameter 50 kV polychromatic x-ray beam incident on a 5 mm diameter 5 mm thick sample of water. Water was used because good x-ray diffraction data are available in the literature. The scatter profiles from 6 deg. to 15 deg. in increments of 1 deg. were measured with a 3 mmx3 mmx2 mm thick cadmium zinc telluride detector. A 2 mm diameter Pb aperture was placed on top of the detector. The target to detector distance was 29 cm and the duration of each measurement was 10 min. Ensemble averages of the results compare well with the gold standard data of A. H. Narten [''X-ray diffraction data on liquid water in the temperature range 4 deg. C-200 deg. C, ORNL Report No. 4578 (1970)]. An average 7.68% difference for which most of the discrepancies can be attributed to the background noise at low angles was obtained. The preliminary measurements of breast tissue are also encouraging.
Liquid water absorption and scattering effects in DOAS retrievals over oceans
NASA Astrophysics Data System (ADS)
Peters, E.; Wittrock, F.; Richter, A.; Alvarado, L. M. A.; Rozanov, V. V.; Burrows, J. P.
2014-05-01
It is well-known that spectral effects of liquid water are present in absorption (DOAS) measurements above the ocean and insufficiently removed liquid water structures may interfere with trace gas absorptions leading to wrong (sometimes even non-physical) results. Currently available literature cross-sections of liquid water absorption are provided in coarser resolution than hyperspectral DOAS applications require and Vibrational Raman Scattering (VRS) is mostly unconsidered or compensated for using simulated pseudo cross-sections from radiative transfer modelling. During the ship-based TransBrom campaign across the western Pacific in October 2009, MAX-DOAS measurements were performed into very clear natural waters achieving underwater light paths of up to 50 m. From these measurements, the retrieval of a residual (H2Ores) spectrum is presented compensating simultaneously for insufficiencies of the liquid water absorption cross-section and broad-banded VRS structures. Small-banded (Ring) structures caused by VRS were found to be very efficiently compensated for by the intensity offset (straylight) correction included in the DOAS fit. In the MAX-DOAS tropospheric NO2 retrieval, this method was able to compensate entirely for all liquid water effects that decrease the fit quality. This was not achieved using a liquid water cross-section in combination with a simulated VRS spectrum. Typical values of improvement depend on the measurement's contamination with liquid water structures and range from ≈ 30% for measurements slightly towards the water surface to several percent in small angles above the horizon. Furthermore, the H2Ores spectrum was found to prevent misfits of NO2 slant columns especially for very low NO2 scenarios and thus increase the reliability of the fit. In test fits on OMI satellite data, the H2Ores spectrum was found selectively above ocean surfaces where it leads to fit quality improvements of up to 6-18%.
NASA Astrophysics Data System (ADS)
Ansari, Rafat R.; Suh, Kwang I.; Sebag, J.
2006-02-01
PURPOSE: Pharmacologic vitreolysis is a new approach to improve vitreo-retinal surgery. Ultimately, the development of drugs to liquefy and detach vitreous from retina should prevent disease by mitigating the contribution of vitreous to retinopathy and eliminate the need for surgery. However, the mechanism of action of pharmacologic vitreolysis remains unclear. The technique of Dynamic light scattering (DLS) was used to evaluate the effects of microplasmin by following the diffusion coefficients of spherical polystyrene nano-particles injected with microplasmin into the vitreous. METHODS: Diffusion coefficients in dissected (n=9) porcine eyes were measured in vitro. DLS was performed on all specimens at 37°C as often as every 10 minutes for up to 6 hours following injections of human recombinant microplasmin at doses ranging from 0.125 mg to 0.8 mg, with 20 nm diameter tracer nanospheres. RESULTS: DLS findings in untreated porcine vitreous were similar to the previously described findings in bovine and human vitreous, demonstrating a fast (early) component, resulting from the flexible hyaluronan molecules, and a slow (late) component, resulting form the stiff collagen molecules. Microplasmin increased porcine vitreous diffusion coefficients. A new approach was developed to use DLS measurements of vitreous diffusion coefficients to evaluate the effects of microplasmin in intact eyes. CONCLUSIONS: Pharmacologic vitreolysis with human recombinant microplasmin increases vitreous diffusion coefficients in vitro. The results of these studies indicate that this new approach using DLS to measure vitreous diffusion coefficients can be used to study the effects of pharmacologic vitreolysis using microplasmin and other agents in intact eyes and ultimately in vivo.
NASA Astrophysics Data System (ADS)
McGillen, Max R.; Bernard, François; Fleming, Eric L.; Burkholder, James B.
2015-07-01
HCFC-133a (CF3CH2Cl), an ozone-depleting substance, is primarily removed from the atmosphere by gas-phase reaction with OH radicals and by UV photolysis. The rate coefficient, k, for the OH + HCFC-133a reaction was measured between 233 and 379 K and is given by k(T) = (9.32 ± 0.8) × 10-13 exp(-(1296 ± 28)/T), where k(296 K) was measured to be (1.10 ± 0.02) × 10-14 (cm3 molecule-1 s-1) (2σ precision uncertainty). The HCFC-133a UV absorption spectrum was measured between 184.95 and 240 nm at 213-323 K, and a spectrum parameterization is presented. The HCFC-133a atmospheric loss processes, lifetime, ozone depletion potential, and uncertainties were evaluated using a 2-D atmospheric model. The global annually averaged steady state lifetime and ozone depletion potential (ODP) were determined to be 4.45 (4.04-4.90) years and 0.017 (±0.001), respectively, where the ranges are based solely on the 2σ uncertainty in the kinetic and photochemical parameters. The infrared absorption spectrum of HCFC-133a was measured, and its global warming potential was determined to be 380 on the 100 year time horizon.
NASA Astrophysics Data System (ADS)
Villanueva, Yolanda; Hondebrink, Erwin; Petersen, Wilma; Steenbergen, Wiendelt
2015-03-01
A method for simultaneously measuring the absorption coefficient μa and Grüneisen parameter Γ of biological absorbers in photoacoustics is designed and implemented using a coupled-integrating sphere system. A soft transparent tube with inner diameter of 0.58mm is used to mount the liquid absorbing sample horizontally through the cavity of two similar and adjacent integrating spheres. One sphere is used for measuring the sample's μa using a continuous halogen light source and a spectrometer fiber coupled to the input and output ports, respectively. The other sphere is used for simultaneous photoacoustic measurement of the sample's Γ using an incident pulsed light with wavelength of 750nm and a flat transducer with central frequency of 5MHz. Absolute optical energy and pressure measurements are not necessary. However, the derived equations for determining the sample's μa and Γ require calibration of the setup using aqueous ink dilutions. Initial measurements are done with biological samples relevant to biomedical imaging such as human whole blood, joint and cyst fluids. Absorption of joint and cyst fluids is enhanced using a contrast agent like aqueous indocyanine green dye solution. For blood sample, measured values of μa = 0.580 +/- 0.016 mm-1 and Γ = 0.166 +/- 0.006 are within the range of values reported in literature. Measurements with the absorbing joint and cyst fluid samples give Γ values close to 0.12, which is similar to that of water and plasma.
NASA Astrophysics Data System (ADS)
Wei, Jianwei; Lee, Zhongping; Ondrusek, Michael; Mannino, Antonio; Tzortziou, Maria; Armstrong, Roy
2016-03-01
The spectral slope of the absorption coefficient of colored dissolved and detrital material (CDM), Scdm (units: nm-1), is an important optical parameter for characterizing the absorption spectral shape of CDM. Although highly variable in natural waters, in most remote sensing algorithms, this slope is either kept as a constant or empirically modeled with multiband ocean color in the visible domain. In this study, we explore the potential of semianalytically retrieving Scdm with added ocean color information in the ultraviolet (UV) range between 360 and 400 nm. Unique features of hyperspectral remote sensing reflectance in the UV-visible wavelengths (360-500 nm) have been observed in various waters across a range of coastal and open ocean environments. Our data and analyses indicate that ocean color in the UV domain is particularly sensitive to the variation of the CDM spectral slope. Here, we used a synthesized dataset to show that adding UV wavelengths to the ocean color measurements will improve the retrieval of Scdm from remote sensing reflectance considerably, while the spectral band settings of past and current satellite ocean color sensors cannot fully account for the spectral variation of remote sensing reflectance. Results of this effort support the concept to include UV wavelengths in the next generation of satellite ocean color sensors.
NASA Astrophysics Data System (ADS)
Bililign, Solomon; Singh, Sujeeta; Fiddler, Marc; Smith, Damon
2015-03-01
The phenomena of scattering, absorption, and emission of light and other electromagnetic radiation by small particles are central to many science and engineering disciplines. Absorption of solar radiation by black carbon aerosols has a significant impact on the atmospheric energy distribution and hydrologic processes. By intercepting incoming solar radiation before it reaches the surface, aerosols heat the atmosphere and, in turn, cool the surface. The magnitude of the atmospheric forcing induced by anthropogenic absorbing aerosols, mainly black carbon (BC) emitted from biomass burning and combustion processes has been suggested to be comparable to the atmospheric forcing by all greenhouse gases (GHGs). Despite the global abundance of biomass burning for cooking, forests clearing for agriculture and wild fires, the optical properties of these aerosols have not been characterized at wide range of wavelengths. Our laboratory uses a combination of Cavity ring down spectroscopy and integrating nephelometry to measure optical properties of (extinction, absorption and scattering coefficients) of biomass aerosols. Preliminary results will be presented. Supported by the Department of Defense under Grant #W911NF-11-1-0188.
NASA Astrophysics Data System (ADS)
Zhong, Min; Jang, Myoseon
2011-08-01
A method for measuring an aerosol light absorption coefficient ( B a) has been developed using a conventional UV-visible spectrometer equipped with an integrating sphere covering a wide range of wavelengths (280-800 nm). The feasibility of the proposed method was evaluated in both the transmittance mode (TUV-IS) and the reflective mode (RUV-IS) using the reference aerosol known for the cross-sectional area. The aerosol was collected on a conventional filter and measured for B a values. The resulting RUV-IS method was applied to measure light absorption of secondary organic aerosol (SOA). SOA was produced through photooxidation of different precursor hydrocarbons such as toluene, d-limonene and α-pinene in the presence of NO x (60-70 ppb) and inorganic seed aerosol using a 2-m 3 indoor Teflon film chamber. Of the three precursor hydrocarbons, the B a value of toluene SOA (0.574 m 2 g -1 at 350 nm) was the highest compared with B a values for α-pinene SOA (0.029 m 2 g -1) and d-limonene SOA (0.038 m 2 g -1). When d-limonene SOA or toluene SOA was internally mixed with neutral [(NH 4) 2SO 4] or acidic inorganic seed (NH 4HSO 4:H 2SO 4 = 1:1 by mole), the SOA showed 2-3 times greater B a values at 350 nm than the SOA with no seed. Aerosol aging with a light source for this study reduced B a values of SOA (e.g., on average 10% for toluene SOA and 30% for d-limonene SOA within 4 h). Overall, weak absorption appeared for chamber-generated SOA over wavelengths ranging from 280 to 550 nm, which fall into the sunlight spectrum.
Petoukhoff, Christopher E.; O'Carroll, Deirdre M.
2015-01-01
Interactions between absorbers and plasmonic metasurfaces can give rise to unique optical properties not present for either of the individual materials and can influence the performance of a host of optical sensing and thin-film optoelectronic applications. Here we identify three distinct mode types of absorber-coated plasmonic metasurfaces: localized and propagating surface plasmons and a previously unidentified optical mode type called absorption-induced scattering. The extinction of the latter mode type can be tuned by controlling the morphology of the absorber coating and the spectral overlap of the absorber with the plasmonic modes. Furthermore, we show that surface plasmons are backscattered when the crystallinity of the absorber is low but are absorbed for more crystalline absorber coatings. This work furthers our understanding of light–matter interactions between absorbers and surface plasmons to enable practical optoelectronic applications of metasurfaces. PMID:26271900
NASA Technical Reports Server (NTRS)
Dlugach, Jana M.; Mishchenko, Michael I.; Mackowski, Daniel W.
2012-01-01
Using the results of direct, numerically exact computer solutions of the Maxwell equations, we analyze scattering and absorption characteristics of polydisperse compound particles in the form of wavelength-sized spheres covered with a large number of much smaller spherical grains.The results pertain to the complex refractive indices1.55 + i0.0003,1.55 + i0.3, and 3 + i0.1. We show that the optical effects of dusting wavelength-sized hosts by microscopic grains can vary depending on the number and size of the grains as well as on the complex refractive index. Our computations also demonstrate the high efficiency of the new superposition T-matrix code developed for use on distributed memory computer clusters.
Hudson, E.A.; Rehr, J.J.; Bucher, J.J.
1995-11-15
A theoretical study of the uranium {ital L}{sub 3}-edge x-ray absorption near-edge structure (XANES) is presented for several uranium compounds, including oxides, intermetallics, uranyl fluoride, and {alpha}-uranium. Calculations were performed using FEFF6, an {ital ab} {ital initio} multiple-scattering (MS) code that includes the most important features of current theories. The results, which account for both the fine structure {chi} and the atomiclike background {mu}{sub 0} of the absorption coefficient {mu}, are compared to new and previously measured experimental spectra, reavealing very good agreement for most systems. For several compounds, a more detailed theoretical analysis determined the influence of cluster size and scattering order upon the calculated spectra. Results indicate that MS paths and scattering paths that include rather distant atoms make significant contributions for UO{sub 2}, whereas XANES for crystals with lower symmetry and density can be modeled using only shorter single-scattering paths. In most cases, assumption of a screened final state in the calculation gives better agreement with experiment than use of an unscreened final state. The successful modeling of spectra for a variety of different uranium compounds, with differing spectral features, indicates that the semirelativistic treatment of XANES used here is adequate even for heavy elements. The well-known resonance, observed experimentally for uranyl (UO{sub 2}{sup 2+}) compounds {approx}15 eV above the white line, is successfully modeled here for the first time, using multiple-scattering paths within the O-U-O axial bonds. Overlapping muffin-tin spheres were required in the calculation, probably as a result of the short uranyl axial bonds.
NASA Astrophysics Data System (ADS)
Sierau, B.; Covert, D.; Coffman, D.; Quinn, P.; Bates, T.
2005-12-01
In-situ, three wavelength measurements of aerosol scattering and absorption of the New York and Boston urban pollution outflow were carried out aboard the NOAA research vessel Ronald H. Brown during the NEAQS-ITCT 2004 (New England Air Quality Study-Intercontinental Transport and Chemical Transformation Study) field campaign during July 2004 in the Gulf of Maine. Aerosol scattering, backscattering and absorption-coefficients were measured using integrating nephelometers and multiwavelength, filter-based absorption photometers (PSAPs) at ~55-60% RH (nephelometers). Two data sets were collected, one for particles with diameters dp<10μm and one for particles <1μm. The purpose of the latter was to focus on the largely pollution related accumulation mode and to minimize the uncertainty due to highly variable near-surface sea salt aerosol. Combining the aerosol scattering and absorption coefficients σsp and σap yields the derived, intensive parameters, single-scattering albedo, ω=σsp/(σsp+σap), Ångström exponents, å, for σsp, and σap, the hemispheric backscattering ratio, and the fine mode fraction of the aerosol, FMF =σsp(dp<1μm)/σsp(dp<10μm). These are key parameters in estimating aerosol direct radiative forcing and they provide constraints on model building and closure studies with physical and chemical aerosol properties. They are important for relating in-situ optical properties to those sensed remotely, e.g., optical depth from ground- or aircraft-based sun photometry or optical depth from satellite, and to the FMF retrieved from satellite data. The measured and derived data will be classified based on a trajectory analysis of the sampled air masses to identify distinct aerosol populations and sources. Case studies describing the aging of pollution plumes are calculated and analyzed in context of other measurements and the prevailing meteorology and the upwind sources. The obtained relationship between in-situ Ångström and FMF will be compared
Kotova, S P; Maiorov, I V; Maiorova, A M
2007-01-31
We analyse the possibilities of simultaneous measuring three optical parameters of scattering media, namely, the scattering and absorption coefficients and the scattering anisotropy parameter by the intensity profile of backscattered radiation by using the neural network inversion method and the method of adaptive-network-based fuzzy inference system. The measurement errors of the absorption and scattering coefficients and the scattering anisotropy parameter are 20%, 5%, and 10%, respectively. (special issue devoted to multiple radiation scattering in random media)
NASA Astrophysics Data System (ADS)
Qiu, Le
Light scattering spectroscopy (LSS), an optical technique that relates the spectroscopic properties of light elastically scattered by small particles to their size, refractive index and shape, has been recently successfully employed for sensing morphological and biochemical properties of epithelial tissues and cells in vivo. LSS does not require exogenous markers, is non-invasive, and, due to its multispectral nature, can sense biological structures well beyond the diffraction limit. All that makes LSS be a very good candidate to be used both in clinical medicine for in vivo detection of disease and in cell biology to monitor cell function on the organelle scale. Recently we developed two LSS-based imaging modalities: clinical Polarized LSS (PLSS) Endoscopic Technique for locating early pre-cancerous changes in GI tract and Confocal Light Absorption and Scattering Spectroscopic (CLASS) Microscopy for studying cells in vivo without exogenous markers. One important application of the clinical PLSS endoscopic instrument, a noncontact scanning imaging device compatible with the standard clinical endoscopes and capable of detecting dysplastic changes, is to serve as a guide for biopsy in Barrett's esophagus (BE). The instrument detects parallel and perpendicular components of the polarized light, backscattered from epithelial tissues, and determines characteristics of epithelial nuclei from the residual spectra. It also can find tissue oxygenation, hemoglobin content and other properties from the diffuse light component. By rapidly scanning esophagus the PLSS endoscopic instrument makes sure the entire BE portion is scanned and examined for the presence of dysplasia. CLASS microscopy, on the other hand, combines principles of light scattering spectroscopy (LSS) with confocal microscopy. Its main purpose is to image cells on organelle scale in vivo without the use of exogenous labels which may affect the cell function. The confocal geometry selects specific region and
NASA Astrophysics Data System (ADS)
Qiu, Le; Vitkin, Edward; Fang, Hui; Zaman, Munir M.; Andersson, Charlotte; Salahuddin, Saira; Modell, Mark D.; Freedman, Steven D.; Hanlon, Eugene B.; Itzkan, Irving; Perelman, Lev T.
2007-02-01
We recently developed a new microscopic optical technique capable of noninvasive analysis of cell structure and cell dynamics on the submicron scale [1]. It combines confocal microscopy, a well-established high-resolution microscopic technique, with light scattering spectroscopy (LSS) and is called confocal light absorption and scattering spectroscopic (CLASS) microscopy. CLASS microscopy requires no exogenous labels and is capable of imaging and continuously monitoring individual viable cells, enabling the observation of cell and organelle functioning at scales on the order of 100 nm. To test the ability of CLASS microscopy to monitor cellular dynamics in vivo we performed experiments with human bronchial epithelial cells treated with DHA and undergoing apoptosis. The treated and untreated cells show not only clear differences in organelle spatial distribution but time sequencing experiments on a single cell show disappearance of certain types of organelles and change of the nuclear shape and density with the progression of apoptosis. In summary, CLASS microscopy provides an insight into metabolic processes within the cell and opens doors for the noninvasive real-time assessment of cellular dynamics. Noninvasive monitoring of cellular dynamics with CLASS microscopy can be used for a real-time dosimetry in a wide variety of medical and environmental applications that have no immediate observable outcome, such as photodynamic therapy, drug screening, and monitoring of toxins.
Heng, Ri-Liang; Sy, Ki Cheong; Pilon, Laurent
2015-01-01
This study demonstrates that the absorption and scattering cross sections and asymmetry factor of randomly oriented and optically soft bispheres, quadspheres, and circular rings of spheres, with either monodisperse or polydisperse monomers, can be approximated by an equivalent coated sphere with identical volume and average projected area. This approximation could also apply to the angle-dependent scattering matrix elements for monomer size parameter less than 0.1. However, it quickly deteriorated with increasing monomer number and/or size parameter. It was shown to be superior to previously proposed approximations considering a volume equivalent homogeneous sphere and a coated sphere with identical volume and surface area. These results provide a rapid and accurate way of predicting the radiation characteristics of bispheres, quadspheres, and rings of spheres representative of various unicellular and multicellular cyanobacteria considered for producing food supplements, biofuels, and fertilizers. They could also be used in inverse methods for retrieving the monomers' optical properties, morphology, and/or concentration. PMID:26366489
X-ray absorption spectroscopy of hemes and hemeproteins in solution: multiple scattering analysis.
D'Angelo, Paola; Lapi, Andrea; Migliorati, Valentina; Arcovito, Alessandro; Benfatto, Maurizio; Roscioni, Otello Maria; Meyer-Klaucke, Wolfram; Della-Longa, Stefano
2008-11-01
A full quantitative analysis of Fe K-edge X-ray absorption spectra has been performed for hemes in two porphynato complexes, that is, iron(III) tetraphenylporphyrin chloride (Fe(III)TPPCl) and iron(III) tetraphenylporphyrin bis(imidazole) (Fe(III)TPP(Imid)2), in two protein complexes whose X-ray structure is known at atomic resolution (1.0 A), that is, ferrous deoxy-myoglobin (Fe(II)Mb) and ferric aquo-myoglobin (Fe(III)MbH2O), and in ferric cyano-myoglobin (Fe(III)MbCN), whose X-ray structure is known at lower resolution (1.4 A). The analysis has been performed via the multiple scattering approach, starting from a muffin tin approximation of the molecular potential. The Fe-heme structure has been obtained by analyzing independently the Extended X-ray Absorption Fine Structure (EXAFS) region and the X-ray Absorption Near Edge Structure (XANES) region. The EXAFS structural results are in full agreement with the crystallographic values of the models, with an accuracy of +/- 0.02 A for Fe-ligand distances, and +/-6 degrees for angular parameters. All the XANES features above the theoretical zero energy (in the lower rising edge) are well accounted for by single-channel calculations, for both Fe(II) and Fe(III) hemes, and the Fe-N p distance is determined with the same accuracy as EXAFS. XANES evaluations of Fe-5th and Fe-6th ligand distances are determined with 0.04-0.07 A accuracy; a small discrepancy with EXAFS (0.01 to 0.05 A beyond the statistical error), is found for protein compounds. Concerns from statistical correlation among parameters and multiple minima in the parameter space are discussed. As expected, the XANES accuracy is slightly lower than what was found for polarized XANES on Fe(III)MbCN single crystal (0.03-0.04 A), and states the actual state-of-the-art of XANES analysis when used to extract heme-normal parameters in a solution spectrum dominated by heme-plane scattering. PMID:18837548
DOE R&D Accomplishments Database
Sibener, S. J.; Lee, Y. T.
1978-05-01
An experiment was performed which confirms the existence of an internal mode dependence of molecular sticking probabilities for collisions of molecules with a cold surface. The scattering of a velocity selected effusive beam of CCl{sub 4} from a 90 K CC1{sub 4} ice surface has been studied at five translational velocities and for two different internal temperatures. At a surface temperature of 90 K (approx. 99% sticking probability) a four fold increase in reflected intensity was observed for the internally excited (560 K) CC1{sub 4} relative to the room temperature (298 K) CC1{sub 4} at a translational velocity of 2.5 X 10{sup 4} cm/sec. For a surface temperature of 90 K all angular distributions were found to peak 15{sup 0} superspecularly independent of incident velocity.
NASA Astrophysics Data System (ADS)
Shatsky, A. V.
2016-08-01
We consider the problem of the influence of diffraction effects on the result of measuring the absorption coefficient of ultrasound in weakly absorbing liquids by the pulse method. Diffraction attenuation of an ultrasonic signal in a measuring cell using solid-state delay lines is calculated. It is shown that the use of delay lines of the ultrasonic signal leads to a considerable distortion of the measured absorption coefficient in the low-frequency range from the true value and can either overestimate or underestimate the results.
Prisutova, Jevgenija; Horoshenkov, Kirill; Groby, Jean-Philippe; Brouard, Bruno
2014-12-01
The measurement of acoustic material characteristics using a standard impedance tube method is generally limited to the plane wave regime below the tube cut-on frequency. This implies that the size of the tube and, consequently, the size of the material specimen must remain smaller than a half of the wavelength. This paper presents a method that enables the extension of the frequency range beyond the plane wave regime by at least a factor of 3, so that the size of the material specimen can be much larger than the wavelength. The proposed method is based on measuring of the sound pressure at different axial locations and applying the spatial Fourier transform. A normal mode decomposition approach is used together with an optimization algorithm to minimize the discrepancy between the measured and predicted sound pressure spectra. This allows the frequency and angle dependent reflection and absorption coefficients of the material specimen to be calculated in an extended frequency range. The method has been tested successfully on samples of melamine foam and wood fiber. The measured data are in close agreement with the predictions by the equivalent fluid model for the acoustical properties of porous media. PMID:25480044
NASA Astrophysics Data System (ADS)
Okawa, Shinpei; Hirasawa, Takeshi; Kushibiki, Toshihiro; Ishihara, Miya
2015-03-01
Quantification of the optical properties of the tissues and blood by noninvasive photoacoustic (PA) imaging may provide useful information for screening and early diagnosis of diseases. Linearized 2D image reconstruction algorithm based on PA wave equation and the photon diffusion equation (PDE) can reconstruct the image with computational cost smaller than a method based on 3D radiative transfer equation. However, the reconstructed image is affected by the differences between the actual and assumed light propagations. A quantitative capability of a linearized 2D image reconstruction was investigated and discussed by the numerical simulations and the phantom experiment in this study. The numerical simulations with the 3D Monte Carlo (MC) simulation and the 2D finite element calculation of the PDE were carried out. The phantom experiment was also conducted. In the phantom experiment, the PA pressures were acquired by a probe which had an optical fiber for illumination and the ring shaped P(VDF-TrFE) ultrasound transducer. The measured object was made of Intralipid and Indocyanine green. In the numerical simulations, it was shown that the linearized image reconstruction method recovered the absorption coefficients with alleviating the dependency of the PA amplitude on the depth of the photon absorber. The linearized image reconstruction method worked effectively under the light propagation calculated by 3D MC simulation, although some errors occurred. The phantom experiments validated the result of the numerical simulations.
NASA Astrophysics Data System (ADS)
Fuente, R.; Mendioroz, A.; Apiñaniz, E.; Salazar, A.
2012-11-01
Modulated photothermal radiometry (PTR) and a modulated photopyroelectric (PPE) technique have been widely used to measure the thermal diffusivity of bulk materials. The method is based on illuminating the sample with a plane light beam and measuring the infrared emission with an infrared detector (PTR) or the electric voltage produced by a pyroelectric sensor in contact with the sample (PPE). The amplitude and phase of both photothermal signals are recorded as a function of the modulation frequency and then fitted to the theoretical model. In this work, we compare the ability of modulated PTR and PPE to retrieve simultaneously the thermal diffusivity and the optical absorption coefficient of homogeneous slabs. In order to eliminate the instrumental factor, self-normalization is used, i.e., the ratio of the photothermal signal recorded at the rear and front surfaces. The influence of the multiple reflections of the light beam and the transparency to infrared wavelengths are analyzed. Measurements performed on a wide variety of homogeneous materials, transparent and opaque, good and bad thermal conductors, confirm the validity of the method. The advantages and disadvantages of both techniques are discussed.
NASA Technical Reports Server (NTRS)
Fahr, A.; Braun, W.; Kurylo, M. J.
1993-01-01
Ultraviolet absorption cross sections of CH3CFCl2(HCFC-141b) were determined in the gas phase (190-260 nm) and liquid phase (230-260 mm) at 298 K. The liquid phase absorption cross sections were then converted into accurate gas phase values using a previously described procedure. It has been demonstrated that scattered light from the shorter-wavelength region (as little as several parts per thousand) can seriously compromise the absorption cross-section measurement, particularly at longer wavelengths where cross sections are low, and can be a source of discrepancies in the cross sections of weakly absorbing halocarbons reported in the literature. A modeling procedure was developed to assess the effect of scattered light on the measured absorption cross section in our experiments, thereby permitting appropriate corrections to be made on the experimental values. Modeled and experimental results were found to be in good agreement. Experimental results from this study were compared with other available determinations and provide accurate input for calculating the atmospheric lifetime of HCFC-141b.
Enomoto, K.; Kitagawa, M.; Kasa, K.; Tojo, S.; Takahashi, Y.
2007-05-18
We report photoassociation spectroscopy of {sup 174}Yb for the {sup 1}S{sub 0}-{sup 1}P{sub 1} transition at 1 {mu}K, where only the s-wave scattering state contributes to the spectra. The wave function of the s-wave scattering state is obtained from the photoassociation efficiency, and we determine that the C{sub 6} potential coefficient is 2300{+-}250 a.u. and the s-wave scattering length is 5.53{+-}0.11 nm. Based on these parameters, we discuss the scattering properties of s- and d-wave states.
Enomoto, K; Kitagawa, M; Kasa, K; Tojo, S; Takahashi, Y
2007-05-18
We report photoassociation spectroscopy of 174Yb for the 1S(0)-1P1 transition at 1 microK, where only the s-wave scattering state contributes to the spectra. The wave function of the s-wave scattering state is obtained from the photoassociation efficiency, and we determine that the C6 potential coefficient is 2300+/-250 a.u. and the s-wave scattering length is 5.53+/-0.11 nm. Based on these parameters, we discuss the scattering properties of s- and d-wave states. PMID:17677695
NASA Astrophysics Data System (ADS)
De Siena, Luca; Calvet, Marie; Watson, Keira J.; Jonkers, Art R. D.; Thomas, Christine
2016-04-01
Frequency-dependent peak-delay times and coda quality factors have been used jointly to separate seismic absorption from scattering quantitatively in Earth media at regional and lithospheric scale; to this end, we measure and map these two quantities at Mount St. Helens volcano. The results show that we can locate and characterise volcanic and geological structures using their unique contribution to seismic attenuation. At 3 Hz a single high-scattering and high-absorption anomaly outlines the debris flows that followed the 1980 explosive eruption, as deduced by comparison with remote sensing imagery. The flows overlay a NNW-SSE interface, separating rocks of significant varying properties down to 2-4 km, and coinciding with the Saint Helens Seismic Zone. High-scattering and high-absorption anomalies corresponding to known locations of magma emplacement follow this signature under the volcano, showing the important interconnections between its feeding systems and the regional tectonic boundaries. With frequency increasing from 6 to 18 Hz the NNW-SSE tectonic/feeding trends rotate around an axis centered on the volcano in the direction of the regional-scale magmatic arc (SW-NE). While the aseismic high-scattering region WSW of the volcano shows no evidence of high absorption, the regions of highest-scattering and absorption are consistently located at all frequencies under either the eastern or the south-eastern flank of the volcanic edifice. From the comparison with the available geological and geophysical information we infer that these anomalies mark both the location and the trend of the main feeding systems at depths greater than 4 km.
NASA Astrophysics Data System (ADS)
De Siena, L.; Calvet, M.; Watson, K. J.; Jonkers, A. R. T.; Thomas, C.
2016-05-01
Frequency-dependent peak-delay times and coda quality factors have been used jointly to separate seismic absorption from scattering quantitatively in Earth media at regional and continental scale; to this end, we measure and map these two quantities at Mount St. Helens volcano. The results show that we can locate and characterize volcanic and geological structures using their unique contribution to seismic attenuation. At 3 Hz a single high-scattering and high-absorption anomaly outlines the debris flows that followed the 1980 explosive eruption, as deduced by comparison with remote sensing imagery. The flows overlay a NNW-SSE interface, separating rocks of significant varying properties down to 2-4 km, and coinciding with the St. Helens Seismic Zone. High-scattering and high-absorption anomalies corresponding to known locations of magma emplacement follow this signature under the volcano, showing the important interconnections between its feeding systems and the regional tectonic boundaries. With frequency increasing from 6 to 18 Hz the NNW-SSE tectonic/feeding trends rotate around an axis centered on the volcano in the direction of the regional-scale magmatic arc (SW-NE). While the aseismic high-scattering region WSW of the volcano shows no evidence of high absorption, the regions of highest-scattering and absorption are consistently located at all frequencies under either the eastern or the south-eastern flank of the volcanic edifice. From the comparison with the available geological and geophysical information we infer that these anomalies mark both the location and the trend of the main feeding systems at depths greater than 4 km.
Customized three-dimensional printed optical phantoms with user defined absorption and scattering
NASA Astrophysics Data System (ADS)
Pannem, Sanjana; Sweer, Jordan; Diep, Phuong; Lo, Justine; Snyder, Michael; Stueber, Gabriella; Zhao, Yanyu; Tabassum, Syeda; Istfan, Raeef; Wu, Junjie; Erramilli, Shyamsunder; Roblyer, Darren M.
2016-03-01
The use of reliable tissue-simulating phantoms spans multiple applications in spectroscopic imaging including device calibration and testing of new imaging procedures. Three-dimensional (3D) printing allows for the possibility of optical phantoms with arbitrary geometries and spatially varying optical properties. We recently demonstrated the ability to 3D print tissue-simulating phantoms with customized absorption (μa) and reduced scattering (μs`) by incorporating nigrosin, an absorbing dye, and titanium dioxide (TiO2), a scattering agent, to acrylonitrile butadiene styrene (ABS) during filament extrusion. A physiologically relevant range of μa and μs` was demonstrated with high repeatability. We expand our prior work here by evaluating the effect of two important 3D-printing parameters, percent infill and layer height, on both μa and μs`. 2 cm3 cubes were printed with percent infill ranging from 10% to 100% and layer height ranging from 0.15 to 0.40 mm. The range in μa and μs` was 27.3% and 19.5% respectively for different percent infills at 471 nm. For varying layer height, the range in μa and μs` was 27.8% and 15.4% respectively at 471 nm. These results indicate that percent infill and layer height substantially alter optical properties and should be carefully controlled during phantom fabrication. Through the use of inexpensive hobby-level printers, the fabrication of optical phantoms may advance the complexity and availability of fully customizable phantoms over multiple spatial scales. This technique exhibits a wider range of adaptability than other common methods of fabricating optical phantoms and may lead to improved instrument characterization and calibration.
Nakazato, Masahisa; Nagai, Tomohiro; Sakai, Tetsu; Hirose, Yasuo
2007-04-20
A UV ozone differential-absorption lidar (DIAL) utilizing a Nd:YAG laser and a single Raman cell filled with carbon dioxide (CO(2)) is designed, developed, and evaluated. The generated wavelengths are 276, 287, and 299 nm, comprising the first to third Stokes lines of the stimulated Raman scattering technique. The correction terms originated from the aerosol extinction, the backscatter, and the absorption by other gases are estimated using a model atmosphere. The experimental results demonstrate that the emitted output energies were 13 mJ/pulse at 276 nm and 287 nm and 5 mJ/pulse at 299 nm, with pump energy of 91 mJ/pulse and a CO(2) pressure of 0.7 MPa. The three Stokes lines account for 44.0% of the available energy. The use of argon or helium as a buffer gas in the Raman cell was also investigated, but this leads to a dramatic decrease in the third Stokes line, which makes this wavelength practically unusable. Our observations confirmed that 30 min of integration were sufficient to observe ozone concentration profiles up to 10 km. Aerosol extinction and backscatter correction are estimated and applied. The aerosol backscatter correction profile using 287 and 299 nm as reference wavelengths is compared with that using 355 nm. The estimated statistical error is less than 5% at 1.5 km and 10% at 2.6 km. Comparisons with the operational carbon-iodine type chemical ozonesondes demonstrate 20% overestimation of the ozone profiles by the DIAL technique. PMID:17415396
NASA Astrophysics Data System (ADS)
Zhao, Hui; Chou, Dean-Yi
2016-05-01
The solar acoustic waves are modified by the interaction with sunspots. The interaction can be treated as a scattering problem: an incident wave propagating toward a sunspot is scattered by the sunspot into different modes. The absorption cross section and scattering cross section are two important parameters in the scattering problem. In this study, we use the wavefunction of the scattered wave, measured with a deconvolution method, to compute the absorption cross section σ ab and the scattering cross section σ sc for the radial order n = 0–5 for two sunspots, NOAA 11084 and NOAA 11092. In the computation of the cross sections, the random noise and dissipation in the measured acoustic power are corrected. For both σ ab and σ sc, the value of NOAA 11092 is greater than that of NOAA 11084, but their overall n dependence is similar: decreasing with n. The ratio of σ ab of NOAA 11092 to that of NOAA 11084 approximately equals the ratio of sunspot radii for all n, while the ratio of σ sc of the two sunspots is greater than the ratio of sunspot radii and increases with n. This suggests that σ ab is approximately proportional to the sunspot radius, while the dependence of σ sc on radius is faster than the linear increase.
NASA Astrophysics Data System (ADS)
Lovesey, Stephen W.; Balcar, Ewald
1996-12-01
The scattering length common to the attenuation coefficient and cross-sections for the resonance-enhanced scattering of x-rays suffers from a dependence on a spectrum of virtual, intermediate states which contain next to no useful information about the environment of the atoms. It is the dependence of the scattering length on intermediate states that sets the x-ray techniques apart from neutron scattering and other techniques which directly probe properties of magnetic materials, and limits the usefulness of physical intuition in the interpretation of empirical x-ray data. As a step toward a legible interpretation, in a language of standard atomic variables, an investigation is reported of a modified scattering length constructed to possess a structure similar to the scattering length for magnetic neutron scattering, namely, it has the mathematical structure of a spherical tensor operator, to which all Racah's methods for electrons in an open valence shell can be applied. In the process of reaching this goal, the influence of the intermediate states on the scattering length is reduced by summing over a limited set of quantum numbers for the intermediate states. Topics covered in the investigation include the attenuation coefficient for x-rays passing through a foil of magnetic material, dichroism, and the cross-sections for resonance-enhanced elastic (Bragg) and inelastic scattering of x-rays by magnetic materials. The treatment of polarization in the primary beam admits states of partial polarization, described by a Stokes vector. Both jj-coupling and Russell - Saunders coupling schemes for the valence states are explored.
NASA Astrophysics Data System (ADS)
Trainoff, Steven
2009-03-01
Many modern pharmaceuticals and naturally occurring biomolecules consist of complexes of proteins and polyethylene glycol or carbohydrates. In the case of vaccine development, these complexes are often used to induce or amplify immune responses. For protein therapeutics they are used to modify solubility and function, or to control the rate of degradation and elimination of a drug from the body. Characterizing the stoichiometry of these complexes is an important industrial problem that presents a formidable challenge to analytical instrument designers. Traditional analytical methods, such as using florescent tagging, chemical assays, and mass spectrometry perturb the system so dramatically that the complexes are often destroyed or uncontrollably modified by the measurement. A solution to this problem consists of fractionating the samples and then measuring the fractions using sequential non-invasive detectors that are sensitive to different components of the complex. We present results using UV absorption, which is primarily sensitive to the protein fraction, Light Scattering, which measures the total weight average molar mass, and Refractive Index detection, which measures the net concentration. We also present a solution of the problem inter-detector band-broadening problem that has heretofore made this approach impractical. Presented will be instrumentation and an analysis method that overcome these obstacles and make this technique a reliable and robust way of non-invasively characterizing these industrially important compounds.
Three-dimensional printed optical phantoms with customized absorption and scattering properties.
Diep, Phuong; Pannem, Sanjana; Sweer, Jordan; Lo, Justine; Snyder, Michael; Stueber, Gabriella; Zhao, Yanyu; Tabassum, Syeda; Istfan, Raeef; Wu, Junjie; Erramilli, Shyamsunder; Roblyer, Darren
2015-11-01
Three-dimensional (3D) printing offers the promise of fabricating optical phantoms with arbitrary geometry, but commercially available thermoplastics provide only a small range of physiologically relevant absorption (µa) and reduced scattering (µs`) values. Here we demonstrate customizable acrylonitrile butadiene styrene (ABS) filaments for dual extrusion 3D printing of tissue mimicking optical phantoms. µa and µs` values were adjusted by incorporating nigrosin and titanium dioxide (TiO2) in the filament extrusion process. A wide range of physiologically relevant optical properties was demonstrated with an average repeatability within 11.5% for µa and 7.71% for µs`. Additionally, a mouse-simulating phantom, which mimicked both the geometry and optical properties of a hairless mouse with an implanted xenograft tumor, was printed using dual extrusion methods. 3D printed tumor optical properties matched the live tumor with less than 3% error at a wavelength of 659 nm. 3D printing with user defined optical properties may provide a viable method for durable optically diffusive phantoms for instrument characterization and calibration. PMID:26600987
Three-dimensional printed optical phantoms with customized absorption and scattering properties
Diep, Phuong; Pannem, Sanjana; Sweer, Jordan; Lo, Justine; Snyder, Michael; Stueber, Gabriella; Zhao, Yanyu; Tabassum, Syeda; Istfan, Raeef; Wu, Junjie; Erramilli, Shyamsunder; Roblyer, Darren
2015-01-01
Three-dimensional (3D) printing offers the promise of fabricating optical phantoms with arbitrary geometry, but commercially available thermoplastics provide only a small range of physiologically relevant absorption (µa) and reduced scattering (µs`) values. Here we demonstrate customizable acrylonitrile butadiene styrene (ABS) filaments for dual extrusion 3D printing of tissue mimicking optical phantoms. µa and µs` values were adjusted by incorporating nigrosin and titanium dioxide (TiO2) in the filament extrusion process. A wide range of physiologically relevant optical properties was demonstrated with an average repeatability within 11.5% for µa and 7.71% for µs`. Additionally, a mouse-simulating phantom, which mimicked both the geometry and optical properties of a hairless mouse with an implanted xenograft tumor, was printed using dual extrusion methods. 3D printed tumor optical properties matched the live tumor with less than 3% error at a wavelength of 659 nm. 3D printing with user defined optical properties may provide a viable method for durable optically diffusive phantoms for instrument characterization and calibration. PMID:26600987
Light tracking through ice and water—Scattering and absorption in heterogeneous media with PHOTONICS
NASA Astrophysics Data System (ADS)
Lundberg, J.; Miočinović, P.; Woschnagg, K.; Burgess, T.; Adams, J.; Hundertmark, S.; Desiati, P.; Niessen, P.
2007-11-01
In the field of neutrino astronomy, large volumes of optically transparent matter like glacial ice, lake water, or deep ocean water are used as detector media. Elementary particle interactions are studied using in situ detectors recording time distributions and fluxes of the faint photon fields of Cherenkov radiation generated by ultra-relativistic charged particles, typically muons or electrons. The PHOTONICS software package was developed to determine photon flux and time distributions throughout a volume containing a light source through Monte Carlo simulation. Photons are propagated and time distributions are recorded throughout a cellular grid constituting the simulation volume, and Mie scattering and absorption are realised using wavelength and position dependent parameterisations. The photon tracking results are stored in binary tables for transparent access through ANSI-C and C++ interfaces. For higher-level physics applications, like simulation or reconstruction of particle events, it is then possible to quickly acquire the light yield and time distributions for a pre-specified set of light source and detector properties and geometries without real-time photon propagation. In this paper the PHOTONICS light propagation routines and methodology are presented and applied to the IceCube and ANTARES neutrino telescopes. The way in which inhomogeneities of the Antarctic glacial ice distort the signatures of elementary particle interactions, and how PHOTONICS can be used to account for these effects, is described.
NASA Technical Reports Server (NTRS)
Wilkerson, T. D.; Schwemmer, G.; Gentry, B.; Giver, L. P.
1979-01-01
Intensities and N2 collision-broadening coefficients are measured for 62 water vapor absorption lines between 715 and 732 nm potentially applicable to laser remote sensing of atmospheric water vapor. Absolute line strengths and widths were determined from spectra corrected for instrument resolution, air-path absorption and Lorentz and Doppler broadening for pure water vapor and water vapor-nitrogen mixtures in a multipass absorption cell with a base path length of 25 m (White cell). Line strengths are observed to range from 4 x 10 to the -25th to 4 x 10 to the -23rd kayser/molecule per sq cm, and collision broadening coefficients are found to be approximately equal to 0.1 kayser/atm.
NASA Technical Reports Server (NTRS)
Peters, Kenneth J.
1992-01-01
Previous theoretical work on the coherent-backscatter effect in the context of speckle time autocorrelation has gone beyond the diffusion approximation and the assumption of isotropic (point) scatterers. This paper extends the theory to include the effects of polarization and absorption, and to give the angular line shape. The results are expressions for angular variations valid for small and large scatterers and linear and circular polarizations, in lossless or lossy media. Calculations show that multiple anisotropic scattering results in the preservation of incident polarization. Application to a problem in radar astronomy is considered. It is shown that the unusual radar measurements (high reflectivity and polarization ratios) of Jupiter's icy Galilean satellites can be explained by coherent backscatter from anisotropic (forward) scatterers.
NASA Technical Reports Server (NTRS)
Seasholtz, Richard G.; Buggele, Alvin E
1997-01-01
Filtered Rayleigh scattering using iodine absorption cells is an effective technique for obtaining density, temperature, and velocity measurements in high speed confined flows. By tuning a single frequency laser to a strong iodine absorption line, stray scattered laser light can be greatly suppressed. For example, the minimum transmission predicted by an iodine absorption model calculation is less than 10(exp -5) at the 18788.44/cm line using a 200 mm absorption cell containing iodine vapor at 0.46 T. Measurements obtained by other researches using a CW Nd:YAG laser agree with the model calculations. However, measurements made by us and by others using Q-switched, injection-seeded, frequency doubled Nd:YAG lasers only show minimum transmission of about 3 x 10(exp -3). This greatly reduces the applicability of the filtered Rayleigh scattering technique using these lasers in experiments having large amounts of stray scattered laser light. The purposes of the present study are to characterize the spectrum of the excess light transmitted by the iodine cell and to make changes to the laser to reduce the transmitted laser light. Transmission data as a function of laser frequency for the iodine absorption line at 18788.44/cm are presented. A planar mirror Fabry-Perot interferometer was used to characterize the frequency spectrum of the light passed through the cell. Measurements taken with the laser tuned to the center of the iodine absorption line show the light transmitted through the iodine cell to have a component with a bandwidth of about 40 GHz. This is probably caused by other modes in the laser that exist in spite of the single frequency injection beam. A second broadband component was also observed, possibly caused by the laser flash lamps or by fluorescence. An intracavity etalon was installed in the laser oscillator cavity to suppress the 40 GHz component. Measurements taken with the etalon tuned to the injection frequency showed a reduction in the transmitted
Mourant, J.R.; Boyer, J.; Johnson, T.M.; Lacey, J.; Bigio, I.J.; Bohorfoush, A.; Mellow, M.
1995-03-01
The Los Alamos National Laboratory has continued the development of the Optical Biopsy System (OBS) for noninvasive, real-time in situ diagnosis of tissue pathologies. In proceedings of earlier SPIE conferences we reported on clinical measurements in the bladder, and we report here on recent results of clinical tests in the gastrointestinal tract. With the OBS, tissue pathologies are detected/diagnosed using spectral measurements of the elastic optical transport properties (scattering and absorption) of the tissue over a wide range of wavelengths. The use of elastic scattering as the key to optical tissue diagnostics in the OBS is based on the fact that many tissue pathologies, including a majority of cancer forms, exhibit significant architectural changes at the cellular and sub-cellular level. Since the cellular components that cause elastic scattering have dimensions typically on the order of visible to near-IR wavelengths, the elastic (Mie) scattering properties will be wavelength dependent. Thus, morphology and size changes can be expected to cause significant changes m an optical signature that is derived from the wavelength-dependence of elastic scattering. Additionally, the optical geometry of the OBS beneficially enhances its sensitivity for measuring absorption bands. The OBS employs a small fiber-optic probe that is amenable to use with any endoscope or catheter, or to direct surface examination, as well as interstitial needle insertion. Data acquistion/display time is <1 second.
Miettunen, R; Korhola, O; Savikurki, S
1991-01-01
Some scatter studies have previously been conducted using film as a detector. The serious limitations caused by the narrow latitude, the non-linear density response, and the required optical densitometric measurements of film can be avoided by computed radiography (CR) which provides linear numeric data over a wide dynamic range. The imaging plate is used as a large-area detector and the data is analyzed from the computer memory. Variation in the scatter-to-primary ratio within an image caused by absorption differences was simulated in a water-aluminum phantom. The measurement technique showed repeatable results, being comparable to the values expected on the basis of previous studies. A multiple pencil-beam (MPB) imaging device was also compared to a standard 1:12 grid by this technique. The maximal scatter-to-primary ratio in our model was up to 7.9 with no scatter reduction, 1.5 with grid, and 0.4 with the MPB device. The variation caused by the absorption of primary radiation was much less in the MPB modality, and the MPB system was also less sensitive to an increase in the used tube voltage from 60 to 120 kVp. The benefits of multiple pencil-beam imaging in scatter reduction are briefly discussed. PMID:1743195
NASA Astrophysics Data System (ADS)
Aptowicz, Kevin B.; Pan, Yong-Le; Chang, Richard K.; Pinnick, Ronald G.; Hill, Steven C.; Tober, Richard L.; Goyal, Anish; Jeys, Thomas; Bronk, Burt V.
2004-09-01
Two-dimensional angular optical scattering (TAOS) patterns of droplets composed of a mixture of H2O and D2O are detected in the mid infrared. First, a lens is used in the Abbé sine condition to collect a small solid angle of light, where the scattering pattern matches well numerical simulations based on Mie theory. Next, TAOS patterns from droplets spanning a large (almost equal to 2pi sr) solid angle are captured simultaneously at two wavelengths. The effects of absorption are evident in the patterns and are discernible without the need for curve matching by Mie theory.
NASA Astrophysics Data System (ADS)
Zhong, Jie; Wen, Ji-Hong; Zhao, Hong-Gang; Yin, Jian-Fei; Yang, Hai-Bin
2015-08-01
Locally resonant sonic materials, due to their ability to control the propagation of low-frequency elastic waves, have become a promising option for underwater sound absorption materials. In this paper, the finite element method is used to investigate the absorption characteristics of a viscoelastic panel periodically embedded with a type of infinite-long non-coaxially cylindrical locally resonant scatterers (LRSs). The effect of the core position in the coating layer of the LRS on the low-frequency (500 Hz-3000 Hz) sound absorption property is investigated. With increasing the longitudinal core eccentricity e, there occur few changes in the absorptance at the frequencies below 1500 Hz, however, the absorptance above 1500 Hz becomes gradually better and the valid absorption (with absorptance above 0.8) frequency band (VAFB) of the viscoelastic panel becomes accordingly broader. The absorption mechanism is revealed by using the displacement field maps of the viscoelastic panel and the steel slab. The results show two typical resonance modes. One is the overall resonance mode (ORM) caused by steel backing, and the other is the core resonance mode (CRM) caused by LRS. The absorptance of the viscoelastic panel by ORM is induced mainly by the vibration of the steel slab and affected little by core position. On the contrary, with increasing the core eccentricity, the CRM shifts toward high frequency band and decouples with the ORM, leading to two separate absorption peaks and the broadened VAFB of the panel. Project supported by the National Natural Science Foundation of China (Grant No. 51275519).
NASA Astrophysics Data System (ADS)
More, Chaitali V.; Lokhande, Rajkumar M.; Pawar, Pravina. P.
2016-05-01
Mass attenuation coefficients of amino acids such as n-acetyl-l-tryptophan, n-acetyl-l-tyrosine and d-tryptophan were measured in the energy range 0.122-1.330 MeV. NaI (Tl) scintillation detection system was used to detect gamma rays with a resolution of 8.2% at 0.662 MeV. The measured attenuation coefficient values were then used to determine the mass energy-absorption coefficients (σa,en) and average atomic energy-absorption cross sections (μen/ρ) of the amino acids. Theoretical values were calculated based on XCOM data. Theoretical and experimental values are found to be in good agreement.
NASA Astrophysics Data System (ADS)
Paredes-Miranda, G.; Arnott, W. P.; Jimenez, J. L.; Aiken, A. C.; Gaffney, J. S.; Marley, N. A.
2009-06-01
A photoacoustic spectrometer, a nephelometer, an aethalometer, and an aerosol mass spectrometer were used to measure at ground level real-time aerosol light absorption, scattering, and chemistry at an urban site located in North East Mexico City (Instituto Mexicano del Petroleo, Mexican Petroleum Institute, denoted by IMP), as part of the Megacity Impact on Regional and Global Environments field experiment, MILAGRO, in March 2006. Photoacoustic and reciprocal nephelometer measurements at 532 nm accomplished with a single instrument compare favorably with conventional measurements made with an aethalometer and a TSI nephelometer. The diurnally averaged single scattering albedo at 532 nm was found to vary from 0.60 to 0.85 with the peak value at midday and the minimum value at 07:00 a.m. local time, indicating that the Mexico City plume is likely to have a net warming effect on local climate. The peak value is associated with strong photochemical generation of secondary aerosol. It is estimated that the photochemical production of secondary aerosol (inorganic and organic) is approximately 75% of the aerosol mass concentration and light scattering in association with the peak single scattering albedo. A strong correlation of aerosol scattering at 532 nm and total aerosol mass concentration was found, and an average mass scattering efficiency factor of 3.8 m2/g was determined. Comparisons of photoacoustic and aethalometer light absorption with oxygenated organic aerosol concentration (OOA) indicate a very small systematic bias of the filter based measurement associated with OOA and the peak aerosol single scattering albedo.
NASA Astrophysics Data System (ADS)
Paredes-Miranda, G.; Arnott, W. P.; Jimenez, J. L.; Aiken, A. C.; Gaffney, J. S.; Marley, N. A.
2008-09-01
A photoacoustic spectrometer, a nephelometer, an aetholemeter, and an aerosol mass spectrometer were used to measure at ground level real-time aerosol light absorption, scattering, and chemistry at an urban site located in north east Mexico City (Instituto Mexicano del Petroleo, Mexican Petroleum Institute, denoted by IMP), as part of the Megacity Impact on Regional and Global Environments field experiment, MILAGRO, in March 2006. Photoacoustic and reciprocal nephelometer measurements at 532 nm accomplished with a single instrument compare favorably with conventional measurements made with an aethelometer and a TSI nephelometer. The diurnally averaged single scattering albedo at 532 nm was found to vary from 0.60 to 0.85 with the peak value at midday and the minimum value at 7 a.m. local time, indicating that the Mexico City plume is likely to have a net warming effect on local climate. The peak value is associated with strong photochemical generation of secondary aerosol. It is estimated that the same-day photochemical production of secondary aerosol (inorganic and organic) is approximately 40 percent of the aerosol mass concentration and light scattering in association with the peak single scattering albedo. A strong correlation of aerosol scattering at 532 nm and total aerosol mass concentration was found, and an average mass scattering efficiency factor of 3.8 m2/g was determined. Comparisons of photoacoustic and aethalometer light absorption with oxygenated organic aerosol concentration (OOA) indicate a very small systematic bias of the filter based measurement associated with OOA and the peak aerosol single scattering albedo.
Tang, Robert Y.; Laamanen, Curtis McDonald, Nancy; LeClair, Robert J.
2014-05-15
Purpose: Develop a method to subtract fat tissue contributions to wide-angle x-ray scatter (WAXS) signals of breast biopsies in order to estimate the differential linear scattering coefficients μ{sub s} of fatless tissue. Cancerous and fibroglandular tissue can then be compared independent of fat content. In this work phantom materials with known compositions were used to test the efficacy of the WAXS subtraction model. Methods: Each sample 5 mm in diameter and 5 mm thick was interrogated by a 50 kV 2.7 mm diameter beam for 3 min. A 25 mm{sup 2} by 1 mm thick CdTe detector allowed measurements of a portion of the θ = 6° scattered field. A scatter technique provided means to estimate the incident spectrum N{sub 0}(E) needed in the calculations of μ{sub s}[x(E, θ)] where x is the momentum transfer argument. Values of μ{sup ¯}{sub s} for composite phantoms consisting of three plastic layers were estimated and compared to the values obtained via the sum μ{sup ¯}{sub s}{sup ∑}(x)=ν{sub 1}μ{sub s1}(x)+ν{sub 2}μ{sub s2}(x)+ν{sub 3}μ{sub s3}(x), where ν{sub i} is the fractional volume of the ith plastic component. Water, polystyrene, and a volume mixture of 0.6 water + 0.4 polystyrene labelled as fibphan were chosen to mimic cancer, fat, and fibroglandular tissue, respectively. A WAXS subtraction model was used to remove the polystyrene signal from tissue composite phantoms so that the μ{sub s} of water and fibphan could be estimated. Although the composite samples were layered, simulations were performed to test the models under nonlayered conditions. Results: The well known μ{sub s} signal of water was reproduced effectively between 0.5 < x < 1.6 nm{sup −1}. The μ{sup ¯}{sub s} obtained for the heterogeneous samples agreed with μ{sup ¯}{sub s}{sup ∑}. Polystyrene signals were subtracted successfully from composite phantoms. The simulations validated the usefulness of the WAXS models for nonlayered biopsies. Conclusions: The methodology to
NASA Astrophysics Data System (ADS)
Wang, Jian; Liu, Zhongfang; Liu, Jiangtao; Liu, Shaopu; Shen, Wei
2008-03-01
In pH 4.4-4.5 Britton-Robinson (BR) buffer solution, fluoroquinolone antibiotics (FLQs) including ciprofloxacin (CIP), norfloxacin (NOR), levofloxacin (LEV) and lomefloxacin (LOM) could react with erythrosine (Ery) to form 1:1 ion-association complexes, which not only resulted in the changes of the absorption spectra and the quenching of fluorescence, but also resulted in the great enhancement of resonance Rayleigh scattering (RRS). These offered some indications of the determination of fluoroquinolone antibiotics by spectrophotometric, fluorescence and resonance Rayleigh scattering methods. The detection limits for fluoroquinolone antibiotics were in the range of 0.097-0.265 μg/mL for absorption methods, 0.022-0.100 μg/mL for fluorophotometry and 0.014-0.027 μg/mL for RRS method, respectively. Among them, the RRS method had the highest sensitivity. In this work, the spectral characteristics of the absorption, fluorescence and RRS, the optimum conditions of the reactions and the properties of the analytical chemistry were investigated. The methods have been successfully applied to determination of some fluoroquinolone antibiotics in human urine samples and tablets. Taking CIP-Ery system as an example, the charge distribution, the enthalpy of formation and the mean polarizability were calculated by density function theory (DFT) method. In addition, the reasons for the enhancement of scattering spectra were discussed.
Arteaga, Oriol; Canillas, Adolf; El-Hachemi, Zoubir; Crusats, Joaquim; Ribó, Josep M
2015-12-28
The optical properties of diprotonated meso-tetrakis(4-sulphonatophenyl)porphyrin (TPPS(4)) J-aggregates of elongated thin particles (nanotubes in solution and ribbons when deposited on solid interfaces) are studied by different polarimetric techniques. The selective light extinction in these structures, which depends on the alignment of the nanoparticle with respect to the polarization of light, is contributed by excitonic absorption bands and by resonance light scattering. The optical response as a function of the polarization of light is complex because, although the quasi-one-dimensional structure confines the local fields along the nanotube axis, there are two orthogonal excitonic bands, of H- and J-character, that can work in favor of or against the field confinement. Results suggest that resonance light scattering is the dominant effect in solid state preparations, i.e. in collective groups (bundles) of ribbons but in diluted solutions, i.e. with isolated nanotubes, the absorption at the excitonic transitions remains dominant and linear dichroism spectra can be a direct probe of the exciton orientations. Therefore, by analyzing scattering and absorption data we can determine the alignment of the excitonic bands within the nanoparticle, i.e. of the orientation of the basic 2D porphyrin architecture in the nanoparticle. This is a necessary first step for understanding the directions of energy transport, charge polarization and non-linear optical properties in these materials. PMID:26584333
NASA Technical Reports Server (NTRS)
Giver, L. P.; Gentry, B.; Schwemmer, G.; Wilkerson, T. D.
1982-01-01
Intensities were measured for 97 lines of H2O vapor between 932 and 961 nm. The lines were selected for their potential usefulness for remote laser measurements of H2O vapor in the earth's atmosphere. The spectra were obtained with several different H2O vapor abundances and N2 broadening gas pressures; the spectral resolution was 0.046/cm FWHM. Measured H2O line intensities range from 7 x 10 to the -25th to 7 x 10 to the -22nd/cm per (molecules/sq cm). H2O self-broadening coefficients were measured for 13 of these strongest lines; the mean value was 0.5/cm per atm. N2-collision-broadening coefficients were measured for 73 lines, and the average was 0.11 cm per atm HWHM. Pressure shifts in air were determined for a sample of six lines between 948 and 950 nm; these lines shift to lower frequency by an amount comparable to 0.1 of the collision-broadened widths measured in air or N2. The measured intensities of many lines of 300-000 band are much larger than expected from prior computations, in some cases by over an order of magnitude. Coriolis interactions with the stronger 201-000 band appear to be the primary cause of the enhancement of these line intensities.
NASA Astrophysics Data System (ADS)
Orlov, Yu. V.; Irgaziev, B. F.; Nikitina, L. I.
2016-01-01
Recently we have published a paper [Irgaziev, Phys. Rev. C 91, 024002 (2015), 10.1103/PhysRevC.91.024002] where the S -matrix pole method (SMP), which is only valid for resonances, has been developed to derive an explicit expression for the asymptotic normalization coefficient (ANC) and is applied to the low-energy resonant states of nucleon +α and α +12C systems. The SMP results are compared with the effective-range expansion method (EFE) results. In the present paper the SMP and EFE plus the Padé approximation are applied to study the excited 2+ resonant states of 9Be. A contradiction is found between descriptions of the experimental phase shift data for α α scattering and of the 9Be resonant energy for 2+ state. Using the EFE method, we also calculate the ANC for the 9Be ground 0+ state with a very small width. This ANC agrees well with the value calculated using the known analytical expression for narrow resonances. In addition, for the α +12C states 1- and 3- the SMP results are compared with the Padé approximation results. We find that the Padé approximation improves a resonance width description compared with the EFE results. The EFE method is also used to calculate the ANCs for the bound 0mml:mprescripts>O ground 0+ state and for the excited 1- and 2+ levels, which are situated near the threshold of α +12C channel.
Electron back-scattering coefficient below 5 keV: Analytical expressions and surface-barrier effects
NASA Astrophysics Data System (ADS)
Cazaux, J.
2012-10-01
Simple analytical expressions for the electron backscattering coefficient, η, are established from published data obtained in the ˜0.4-5 keV range for 21 elements ranging from Be to Au. They take into account the decline in η with a decrease in energy E° for high-Z elements and the reverse behavior for low-Z elements. The proposed expressions for η (E°) lead to crossing energies situated in the 0.4-1 keV range and they may be reasonably extended to any of the other elements—via an interpolation procedure—to metallic alloys and probably to compounds. The influence of the surface barrier on the escape probability of the back-scattered electrons is next evaluated. This evaluation provides a theoretical basis to explain the observed deviation between various published data as a consequence of surface contamination or oxidation. Various practical applications and strategies are deduced for the η-measurements in dedicated instruments as well for the image interpretation in low voltage scanning electron microscopy based on the backscattered electron detection. In this microscopy, the present investigation allows to generalize the scarce contrast changes and contrast reversals previously observed on multi elemental samples and it suggests the possibility of a new type of contrast: the work function contrast.
NASA Technical Reports Server (NTRS)
Moore, R. K. (Principal Investigator); Ulaby, F. T.; Sobti, A.; Burton, T.
1974-01-01
The author has identified the following significant results. The Skylab S-193 radiometer/scatterometer collected thousands of measurements of scattering coefficient and brightness temperature over various parts of the United States during the summer of 1973 at angles of incidence between vertical and about 45 deg. These measurements have been combined to produce histograms of the response at each of several angles within this range, and to establish average scattering coefficient vs angle curves with 10% and 90% exceedance levels as well. The variation of the radiometric measurements is primarily in the region from 255 K to 285 K, with very few measurements giving higher values, but a significant, though small, number giving values down to and even below 200 K. The scattering coefficient varies, for the mean, from about 0 db at 1 deg off vertical to a low in the neighborhood of -10 db at 45 deg. The variability of the scattering coefficient measurements with this coarse resolution sensor is surprisingly small. The number of distinguishable levels is slightly more for the scatterometer than for the radiometer, but the amount of variation in brightness temperature caused by the physical temperature of the ground is enough so that the scatterometer can be used to distinguish significantly more meaningful levels than the radiometer.
NASA Astrophysics Data System (ADS)
Pawlak, M.
2015-01-01
In this paper, a non-contact method that allows to determine the carrier concentration in CdSe crystals is presented. The method relies on the measurement of the effective infrared absorption coefficient by means of the photothermal infrared radiometry (PTR). In order to obtain the effective infrared absorption coefficient and thermal diffusivity, the frequency characteristics of the PTR signal were analyzed in the frame of a one-dimensional heat transport model for infrared semitransparent crystals. The carrier concentrations were estimated using a theory introduced by Ruda and a recently proposed normalization procedure for the PTR signal. The deduced carrier concentrations of the investigated CdSe crystals are in reasonable agreement with those obtained using Hall measurements and infrared spectroscopy. The method presented in this paper can also be applied to other semiconductors with the carrier concentration in the range of 1014-1017 cm-3.
Yuan, Liu; Lu, Kun; Xia, Benzheng; Zhang, Jianqi; Wang, Zhen; Wang, Zaiyu; Deng, Dan; Fang, Jin; Zhu, Lingyun; Wei, Zhixiang
2016-07-01
Acceptor end-capping of oligomeric conjugated molecules is found to be an effective strategy for simultaneous spectral broadening, extinction coefficient enhancement, and energy level optimization, resulting in profoundly enhanced power conversion efficiencies (of 9.25% and 8.91%) compared to the original oligomers. This strategy is effective in overcoming the absorption disadvantage of oligomers and small molecules due to conjugation limitation. PMID:27172541
Abbas Ghaleb, Khalil; Georges, Joseph
2006-01-01
Two-photon absorption of the solvent under pulsed-laser excitation at 266 nm produces a high background thermal lens signal interfering with the analyte signal. Discrimination of both solvent and analyte signals along with calibration of the photothermal response has allowed the determination of the two-photon absorption coefficient of ethanol. The obtained value, 3.0x10(-10) cm W-1, is close to the literature values obtained from transmittance measurements using picosecond or femtosecond laser pulses. PMID:16454917
NASA Technical Reports Server (NTRS)
Pan, Xiaoju; Mannino, Antonio; Russ, Mary E.; Hooker, Stanford B.
2008-01-01
At present, satellite remote sensing of coastal water quality and constituent concentration is subject to large errors as compared to the capability of satellite sensors in oceanic waters. In this study, field measurements collected on a series of cruises within U.S. southern Middle Atlantic Bight (SMAB) were applied to improve retrievals of satellite ocean color products in order to examine the factors that regulate the bio-optical properties within the continental shelf waters of the SMAB. The first objective was to develop improvements in satellite retrievals of absorption coefficients of phytoplankton (a(sub ph)), colored dissolved organic matter (CDOM) (a(sub g)), non-pigmented particles (a(sub d)), and non-pigmented particles plus CDOM (a(sub dg)), and chlorophyll a concentration ([Chl_a]). Several algorithms were compared to derive constituent absorption coefficients from remote sensing reflectance (R(sub rs)) ratios. The validation match-ups showed that the mean absolute percent differences (MAPD) were typically less than 35%, although higher errors were found for a(sub d) retrievals. Seasonal and spatial variability of satellite-derived absorption coefficients and [Chl_a] was apparent and consistent with field data. CDOM is a major contributor to the bio-optical properties of the SMAB, accounting for 35-70% of total light absorption by particles plus CDOM at 443 nm, as compared to 30-45% for phytoplankton and 0-20% for non-pigmented particles. The overestimation of [Chl_a] from the operational satellite algorithms may be attributed to the strong CDOM absorption in this region. River discharge is important in controlling the bio-optical environment, but cannot explain all of the regional and seasonal variability of biogeochemical constituents in the SMAB.
Kulp, T.J.; Shinn, J.
1995-04-01
The accurate characterization of the latent infrared (IR) absorption in the atmospheric window regions continues to be an area of research interest for the global climate modeling community. In the window between 8 and 14 {mu}m, this absorption can be attributed primarily to water vapor. It consists of (1) weak lines originating from the edge of the water vapor pure rotational band (at low wavenumbers) and the trailing P-branch of the v{sub 2} rovibrational band (at the high-wavenumber boundary of the window); and (2) the water vapor continuum absorption. The goal of our project has been to improve our quantitative and physical understanding of both of these absorption processes. Specifically, our immediate aims are to fill gaps in the experimental radiative transfer databases pertaining to the line parameters (i.e., line intensities and broadening coefficients) and to the self- and foreign-broadened water vapor continuum. To accomplish our goals, we have made long-pathlength absorption measurements using a Fourier transform infrared spectrometer (FTIR) (for the continuum and line measurements, at low resolution) and a tunable diode laser absorption spectrometer (TDLAS) (for the line measurements, at high resolution). These measurements were made on gas samples contained in a 400-m maximum pathlength Horn Pimentel multipass cell designed and constructed for this project.
NASA Technical Reports Server (NTRS)
Temma, T.; Baines, K. H.; Butler, R. A. H.; Brown, L. R.; Sagui, L.; Kleiner, I.
2006-01-01
PH3 exponential sum k coefficients were computed between 2750 and 3550/cm (2.82-3.64 (microns), in view of future application to radiative transfer analyses of Jupiter and Saturn in a phosphine absorption band near 3 microns. The temperature and pressure of this data set cover the ranges from 80 to 350 K and from 10 (exp -3)to 10(exp 1) bars, respectively. Transmission uncertainty incurred by the use of the k coefficients is smaller than a few percent as long as the radiation is confined above an altitude of a few bars in the giant planets. In spectral regions of weak absorption at high pressures close to 10 bars, contributions from far wings of strong absorption lines must be carefully taken into account. Our data set helps map the three-dimensional distribution of PH3 on the giant planets, revealing their global atmospheric dynamics extending down to the deep interior. The complete k coefficient data set of this work is available at the Web site of the NASA Planetary Data System Atmospheres Node.
NASA Astrophysics Data System (ADS)
Fairuz Budiman, Mohd; Hu, Weiguo; Igarashi, Makoto; Tsukamoto, Rikako; Isoda, Taiga; Itoh, Kohei M.; Yamashita, Ichiro; Murayama, Akihiro; Okada, Yoshitaka; Samukawa, Seiji
2012-02-01
A sub-10 nm, high-density, periodic silicon-nanodisc (Si-ND) array has been fabricated using a new top-down process, which involves a 2D array bio-template etching mask made of Listeria-Dps with a 4.5 nm diameter iron oxide core and damage-free neutral-beam etching (Si-ND diameter: 6.4 nm). An Si-ND array with an SiO2 matrix demonstrated more controllable optical bandgap energy due to the fine tunability of the Si-ND thickness and diameter. Unlike the case of shrinking Si-ND thickness, the case of shrinking Si-ND diameter simultaneously increased the optical absorption coefficient and the optical bandgap energy. The optical absorption coefficient became higher due to the decrease in the center-to-center distance of NDs to enhance wavefunction coupling. This means that our 6 nm diameter Si-ND structure can satisfy the strict requirements of optical bandgap energy control and high absorption coefficient for achieving realistic Si quantum dot solar cells.
NASA Astrophysics Data System (ADS)
Disney, Claire E. R.; Pillai, Supriya; Green, Martin A.
2015-12-01
Rear reflectors for solar cells comprised of metal films with periodic arrays of nanoscale features on their surface can provide significantly enhanced light trapping in the absorber layer. However these structures can also result in significantly increased parasitic absorption into the metal layer at various wavelengths of light. Conversely these highly absorbing resonances can also coincide with the wavelengths which display the largest enhancement to the cell's photocurrent. As such it is important to understand the underlying causes for such photocurrent enhancements and losses in the metal in order to design the optimum structure for use. 3D Finite-difference-time-domain simulations have been used to model a variety of structures and analyze the spatial distribution of absorption within different materials which make up the structure, the angles at which light will be scattered from the rear surface, as well as the idealized short circuit current from each structure integrated across the AM1.5 spectrum. These reveal the properties of these modes at resonant wavelengths at which absorption into both materials is enhanced. Despite the enhanced coupling of light into the metal at these wavelengths, the amount of light scattered back into the absorber at large angles is also significantly boosted. For a large variety of geometries, the impact of this large angle scattering dominates leading to significant increases to a cell's photocurrent. Our simulations allow us to understand the contributions of multiple plasmonic effects occurring in such structures, allowing selection of the most suitable geometries to achieve large-angle scattering in a desired wavelength range.
NASA Technical Reports Server (NTRS)
Surinov, Y. A.; Sosnovyy, N. V.
1975-01-01
Local and average radiation functions, which represent purely geometric characteristics of the radiating system, are used to determine the absorptivity in a system of bodies separated by an attenuating medium.
NASA Technical Reports Server (NTRS)
Baines, Kevin H.; West, Robert A.; Giver, Lawrence P.; Moreno, Fernando
1993-01-01
Near-infrared 10/cm resolution spectra of methane obtained at various temperatures, pressures, and abundances are fit to a quasi-random narrow-band model. Exponential-sum absorption coefficients for three temperatures (112, 188, and 295 K), and 20 pressures from 0.0001 to 5.6 bars, applicable to the cold environments of the major planets, are then derived from the band model for the 230 wavelengths measured from 1.6 to 2.5 microns. RMS deviations between the laboratory and the exponential-sum synthetic transmissions are reported for the best fitting 50 wavelengths. Deviations relevant to broadband, 1-percent spectral resolution observations are also presented. The validity of exponential-sum coefficients derived from broadband (10/cm) transmission data is demonstrated via direct comparison with line-by-line calculations. The complete atlas of coefficients is available from the Planetary Data System-Planetary Atmospheres Discipline Node.
NASA Astrophysics Data System (ADS)
Gaebler, Peter J.; Eulenfeld, Tom; Wegler, Ulrich
2015-12-01
In this study, frequency-dependent seismic scattering and intrinsic attenuation parameters for the crustal structure beneath the W-Bohemia/Vogtland swarm earthquake region close to the border of Czech Republic and Germany are estimated. Synthetic seismogram envelopes are modelled using elastic and acoustic radiative transfer theory. Scattering and absorption parameters are determined by fitting these synthetic envelopes to observed seismogram envelopes from 14 shallow local events from the October 2008 W-Bohemia/Vogtland earthquake swarm. The two different simulation approaches yield similar results for the estimated crustal parameters and show a comparable frequency dependence of both transport mean free path and intrinsic absorption path length. Both methods suggest that intrinsic attenuation is dominant over scattering attenuation in the W-Bohemia/Vogtland region for the investigated epicentral distance range and frequency bands from 3 to 24 Hz. Elastic simulations of seismogram envelopes suggest that forward scattering is required to explain the data, however, the degree of forward scattering is not resolvable. Errors in the parameter estimation are smaller in the elastic case compared to results from the acoustic simulations. The frequency decay of the transport mean free path suggests a random medium described by a nearly exponential autocorrelation function. The fluctuation strength and correlation length of the random medium cannot be estimated independently, but only a combination of the parameters related to the transport mean free path of the medium can be computed. Furthermore, our elastic simulations show, that using our numerical method, it is not possible to resolve the value of the mean free path of the random medium.
NASA Astrophysics Data System (ADS)
De Siena, Luca; Calvet, Marie; Thomas, Christine
2015-04-01
Knowing how seismic waves lose their energy in space and frequency is both critical for understating volcanic structures and important to detect eventual changes in their seismic and volcanic activity. We measure both the peak-delay time and the coda quality factor on seismic envelopes recorded at Mount St. Helens volcano between 2000 and 2003, just before its 2004 explosive eruption. By the 2D mapping of these two frequency-dependent quantities we obtain S-wave scattering and absorption maps in the pre-eruptive phase of the volcano. We use a 2D K-means cluster analysis to highlight correlations in the frequency-dependent spatial patterns and interpret the results in terms of tectonic and feeding structures. The transition between the high-velocity and high-scattering Siletz terrane and the low-velocity and high-absorption Cascade arc crust is a persistent signature in the entire frequency range. At high frequencies, we observe strong correlation between high-scattering, high-absorption, and high P-wave heterogeneity (this last tomographically derived between depths of 0 and 10 km). In our interpretation, this correlation is a direct consequence of resonance effects, induced by the presence of melt and fluid inclusions as well as residuals of previous eruptions. The area of maximum heterogeneity is located south-south-west of the central crater: the region shows selective high absorption characteristics at 6 Hz only. If this supports the presence of a previously-inferred aseismic magma chamber intersecting the south-south-western flank of the volcano, the selectivity suggests a depth extension of the magma chamber lower than 1 km. The most important high-scattering and high-absorption signature at high frequencies remains a NNW-SSE suture crossing the volcanic cone and parallel to the St. Helens Seismic Zone. The trend confirms the persistent major role of the main direction of regional structural stress in the uprise of magma/fluid filled materials in the first
NASA Astrophysics Data System (ADS)
Akter, Sharmin; Maejima, Satoshi; Kawauchi, Satoko; Sato, Shunichi; Hinoki, Akinari; Aosasa, Suefumi; Yamamoto, Junji; Nishidate, Izumi
2015-07-01
Diffuse reflectance spectroscopy (DRS) has been extensively used for characterization of biological tissues as a noninvasive optical technique to evaluate the optical properties of tissue. We investigated a method for evaluating the reduced scattering coefficient , the absorption coefficient μa, the tissue oxygen saturation StO2, and the reduction of heme aa3 in cytochrome c oxidase CcO of in vivo liver tissue using a single-reflectance fiber probe with two source-collector geometries. We performed in vivo recordings of diffuse reflectance spectra for exposed rat liver during the ischemia-reperfusion induced by the hepatic portal (hepatic artery, portal vein, and bile duct) occlusion. The time courses of μa at 500, 530, 570, and 584 nm indicated the hemodynamic change in liver tissue as well as StO2. Significant increase in μa(605)/μa(620) during ischemia and after euthanasia induced by nitrogen breathing was observed, which indicates the reduction of heme aa3, representing a sign of mitochondrial energy failure. The time courses of at 500, 530, 570, and 584 nm were well correlated with those of μa, which also reflect the scattering by red blood cells. On the other hand, at 700 and 800 nm, a temporary increase in and an irreversible decrease in were observed during ischemia-reperfusion and after euthanasia induced by nitrogen breathing, respectively. The change in in the near-infrared wavelength region during ischemia is indicative of the morphological changes in the cellular and subcellular structures induced by the ischemia, whereas that after euthanasia implies the hepatocyte vacuolation. The results of the present study indicate the potential application of the current DRS system for evaluating the pathophysiological conditions of in vivo liver tissue.
NASA Astrophysics Data System (ADS)
Pokhrel, Rudra P.; Wagner, Nick L.; Langridge, Justin M.; Lack, Daniel A.; Jayarathne, Thilina; Stone, Elizabeth A.; Stockwell, Chelsea E.; Yokelson, Robert J.; Murphy, Shane M.
2016-08-01
Single-scattering albedo (SSA) and absorption Ångström exponent (AAE) are two critical parameters in determining the impact of absorbing aerosol on the Earth's radiative balance. Aerosol emitted by biomass burning represent a significant fraction of absorbing aerosol globally, but it remains difficult to accurately predict SSA and AAE for biomass burning aerosol. Black carbon (BC), brown carbon (BrC), and non-absorbing coatings all make substantial contributions to the absorption coefficient of biomass burning aerosol. SSA and AAE cannot be directly predicted based on fuel type because they depend strongly on burn conditions. It has been suggested that SSA can be effectively parameterized via the modified combustion efficiency (MCE) of a biomass burning event and that this would be useful because emission factors for CO and CO2, from which MCE can be calculated, are available for a large number of fuels. Here we demonstrate, with data from the FLAME-4 experiment, that for a wide variety of globally relevant biomass fuels, over a range of combustion conditions, parameterizations of SSA and AAE based on the elemental carbon (EC) to organic carbon (OC) mass ratio are quantitatively superior to parameterizations based on MCE. We show that the EC / OC ratio and the ratio of EC / (EC + OC) both have significantly better correlations with SSA than MCE. Furthermore, the relationship of EC / (EC + OC) with SSA is linear. These improved parameterizations are significant because, similar to MCE, emission factors for EC (or black carbon) and OC are available for a wide range of biomass fuels. Fitting SSA with MCE yields correlation coefficients (Pearson's r) of ˜ 0.65 at the visible wavelengths of 405, 532, and 660 nm while fitting SSA with EC / OC or EC / (EC + OC) yields a Pearson's r of 0.94-0.97 at these same wavelengths. The strong correlation coefficient at 405 nm (r = 0.97) suggests that parameterizations based on EC / OC or EC / (EC + OC) have good predictive
NASA Astrophysics Data System (ADS)
Arteaga, Oriol; Canillas, Adolf; El-Hachemi, Zoubir; Crusats, Joaquim; Ribó, Josep M.
2015-12-01
The optical properties of diprotonated meso-tetrakis(4-sulphonatophenyl)porphyrin (TPPS4) J-aggregates of elongated thin particles (nanotubes in solution and ribbons when deposited on solid interfaces) are studied by different polarimetric techniques. The selective light extinction in these structures, which depends on the alignment of the nanoparticle with respect to the polarization of light, is contributed by excitonic absorption bands and by resonance light scattering. The optical response as a function of the polarization of light is complex because, although the quasi-one-dimensional structure confines the local fields along the nanotube axis, there are two orthogonal excitonic bands, of H- and J-character, that can work in favor of or against the field confinement. Results suggest that resonance light scattering is the dominant effect in solid state preparations, i.e. in collective groups (bundles) of ribbons but in diluted solutions, i.e. with isolated nanotubes, the absorption at the excitonic transitions remains dominant and linear dichroism spectra can be a direct probe of the exciton orientations. Therefore, by analyzing scattering and absorption data we can determine the alignment of the excitonic bands within the nanoparticle, i.e. of the orientation of the basic 2D porphyrin architecture in the nanoparticle. This is a necessary first step for understanding the directions of energy transport, charge polarization and non-linear optical properties in these materials.The optical properties of diprotonated meso-tetrakis(4-sulphonatophenyl)porphyrin (TPPS4) J-aggregates of elongated thin particles (nanotubes in solution and ribbons when deposited on solid interfaces) are studied by different polarimetric techniques. The selective light extinction in these structures, which depends on the alignment of the nanoparticle with respect to the polarization of light, is contributed by excitonic absorption bands and by resonance light scattering. The optical
Validity criterion of the radiative Fourier law for an absorbing and scattering medium.
Gomart, Hector; Taine, Jean
2011-02-01
For radiative heat transfer applications, in particular in homogenized phases of porous media, an exhaustive and accurate validity criterion of the radiative Fourier law, depending only on the logarithmic derivative of the temperature field and an effective absorption coefficient, accounting for possible multiple scattering phenomena, has been established for a semitransparent medium. This effective absorption coefficient is expressed as a function of the absorption coefficient, the albedo, and the scattering asymmetry parameter. The criterion can be applied to semitransparent media that do not follow Beer's laws related to extinction, absorption, and scattering. PMID:21405835
Yang, Yimin E-mail: tqiu@seu.edu.cn; Du, Deyang; Fan, Jiyang; Qiu, Teng E-mail: tqiu@seu.edu.cn; Kong, Fan
2015-06-28
Indium-tin-oxide (ITO) nanoparticles were annealed in vacuum or reducing atmosphere to obtain different surface structures and investigate their influence on the adsorptive character and conformation of cytochrome c (Cyt c) molecule. Annealing-induced morphometric or structural changes of ITO nanoparticles were characterized by instruments of transmission electron microscopy, x-ray diffraction, and Raman scattering. Semiconductor ITO nanoparticle-enhanced Raman scattering of Cyt c was observed and the enhanced efficiency was found to closely depend on the surface structures which control the adsorbance of buffer anions needed for Cyt c loading. Direct electron transfer between Cyt c and ITO surface at the moment of molecular elastic collision was found and a reverse electron transfer process for O-terminated surface and metal-terminated surface was observed, according to absorption spectroscopic measurement on the residual solution.
NASA Astrophysics Data System (ADS)
Utry, N.; Ajtai, T.; Pintér, M.; Tombácz, E.; Illés, E.; Bozóki, Z.; Szabó, G.
2015-01-01
Mass-specific optical absorption coefficients (MACs) and the imaginary part (κ) of the refractive indices of various mineral dust components including silicate clays (illite, kaolin and bentonite), oxides (quartz, hematite and rutile), and carbonate (limestone) were determined at the wavelengths of 1064, 532, 355 and 266 nm. The MAC values were calculated from aerosol optical absorption coefficients measured by a multi-wavelength photoacoustic (PA) instrument, the mass concentration and the number size distribution of the generated aerosol samples as well as the size transfer functions of the measuring instruments. Values of κ were calculated from the measured and particle-loss-corrected data by using a Mie-theory-based retrieval algorithm. The determined values could be used for comparisons with calculated wavelength-dependent κ values typically deduced from bulk-phase measurements by using indirect measurement methods. Accordingly, the presented comparison of the measured and calculated aerosol optical absorption spectra revealed the strong need for standardized sample preparation and measurement methodology in case of bulk-phase measurements.
Ivascu, I R; Matei, C E; Patachia, M; Bratu, A M; Dumitras, D C
2016-06-15
Absorption coefficients of the ethanol vapors at atmospheric pressure and room temperature were measured by photoacoustic technique using a cw, line-tunable, frequency-stabilized CO2 laser as radiation source. The spectrum of the employed CO2 laser includes 54 lines with wavelengths in the infrared region of 9.2-10.8μm and power levels up to 4.7W. Measurements revealed a predominant absorption for ethanol within 9.4μm band of the CO2 laser spectrum, where the highest values of the absorption coefficients were recorded: 3.68cm(-1)atm(-1) at 9R(20) line and 3.65cm(-1)atm(-1) at 9R(22) line. The estimated detection range covers six orders of magnitude, from a minimum of 30ppbV to a maximum of 4% concentration of ethanol in nitrogen, which proves the suitability of the photoacoustic technique for accurate measurements of the ethanol concentration in various applications. PMID:27045783
NASA Astrophysics Data System (ADS)
Ivascu, I. R.; Matei, C. E.; Patachia, M.; Bratu, A. M.; Dumitras, D. C.
2016-06-01
Absorption coefficients of the ethanol vapors at atmospheric pressure and room temperature were measured by photoacoustic technique using a cw, line-tunable, frequency-stabilized CO2 laser as radiation source. The spectrum of the employed CO2 laser includes 54 lines with wavelengths in the infrared region of 9.2-10.8 μm and power levels up to 4.7 W. Measurements revealed a predominant absorption for ethanol within 9.4 μm band of the CO2 laser spectrum, where the highest values of the absorption coefficients were recorded: 3.68 cm- 1 atm- 1 at 9R(20) line and 3.65 cm- 1 atm- 1 at 9R(22) line. The estimated detection range covers six orders of magnitude, from a minimum of 30 ppbV to a maximum of 4% concentration of ethanol in nitrogen, which proves the suitability of the photoacoustic technique for accurate measurements of the ethanol concentration in various applications.
NASA Astrophysics Data System (ADS)
Zinenko, Tatiana L.
2015-05-01
The plane wave scattering and absorption by an infinite flat graphene strip grating in the free space are studied in the THz range in the H- and E-polarization regimes. Accurate numerical treatment is based on the dual series equations and the analytical regularization technique. The resulting numerical algorithm possesses guaranteed convergence and controlled accuracy of computations. Reflectance, transmittance and absorbance by the graphene-strip gratings are studied as a function of various parameters. In the H-polarization case, the dominant feature is the excitation of the surface plasmon resonances on each strip. In the E-polarization case, Rayleigh anomalies are the only observable features.
NASA Technical Reports Server (NTRS)
Yang, Ping; Bi, Lei; Baum, Bryan A.; Liou, Kuo-Nan; Kattawar, George W.; Mishchenko, Michael I.; Cole, Benjamin
2013-01-01
A data library is developed containing the scattering, absorption, and polarization properties of ice particles in the spectral range from 0.2 to 100 microns. The properties are computed based on a combination of the Amsterdam discrete dipole approximation (ADDA), the T-matrix method, and the improved geometric optics method (IGOM). The electromagnetic edge effect is incorporated into the extinction and absorption efficiencies computed from the IGOM. A full set of single-scattering properties is provided by considering three-dimensional random orientations for 11 ice crystal habits: droxtals, prolate spheroids, oblate spheroids, solid and hollow columns, compact aggregates composed of eight solid columns, hexagonal plates, small spatial aggregates composed of 5 plates, large spatial aggregates composed of 10 plates, and solid and hollow bullet rosettes. The maximum dimension of each habit ranges from 2 to 10,000 microns in 189 discrete sizes. For each ice crystal habit, three surface roughness conditions (i.e., smooth, moderately roughened, and severely roughened) are considered to account for the surface texture of large particles in the IGOM applicable domain. The data library contains the extinction efficiency, single-scattering albedo, asymmetry parameter, six independent nonzero elements of the phase matrix (P11, P12, P22, P33, P43, and P44), particle projected area, and particle volume to provide the basic single-scattering properties for remote sensing applications and radiative transfer simulations involving ice clouds. Furthermore, a comparison of satellite observations and theoretical simulations for the polarization characteristics of ice clouds demonstrates that ice cloud optical models assuming severely roughened ice crystals significantly outperform their counterparts assuming smooth ice crystals.
Radiative properties of the background aerosol: absorption component of extinction.
Clarke, A D; Charlson, R J
1985-07-19
The light-scattering and light-absorption coefficients of the global background aerosol define its single-scatter albedo. Continuous, simultaneous measurements of these optical coefficients were made on a daily basis for the remote marine mid-troposphere; such measurements are essential for assessment of the effects of aerosol on atmospheric radiative transfer. Measurements of light-absorption coefficients made at the Mauna Loa Observatory in Hawaii were higher than expected, and the single-scatter albedo was lower than the value often used in radiative transfer models. Soot appears to be the most likely primary absorber, and hemispheric dispersal of this combustion-derived material is suggested. PMID:17759145
NASA Astrophysics Data System (ADS)
Montejo, Ludguier D.; Jia, Jingfei; Kim, Hyun K.; Hielscher, Andreas H.
2013-03-01
We apply the Fourier Transform to absorption and scattering coefficient images of proximal interphalangeal (PIP) joints and evaluate the performance of these coefficients as classifiers using receiver operator characteristic (ROC) curve analysis. We find 25 features that yield a Youden index over 0.7, 3 features that yield a Youden index over 0.8, and 1 feature that yields a Youden index over 0.9 (90.0% sensitivity and 100% specificity). In general, scattering coefficient images yield better one-dimensional classifiers compared to absorption coefficient images. Using features derived from scattering coefficient images we obtain an average Youden index of 0.58 +/- 0.16, and an average Youden index of 0.45 +/- 0.15 when using features from absorption coefficient images.
NASA Technical Reports Server (NTRS)
Joseph, Rose M.; Hagness, Susan C.; Taflove, Allen
1991-01-01
The initial results for femtosecond pulse propagation and scattering interactions for a Lorentz medium obtained by a direct time integration of Maxwell's equations are reported. The computational approach provides reflection coefficients accurate to better than 6 parts in 10,000 over the frequency range of dc to 3 x 10 to the 16th Hz for a single 0.2-fs Gaussian pulse incident upon a Lorentz-medium half-space. New results for Sommerfeld and Brillouin precursors are shown and compared with previous analyses. The present approach is robust and permits 2D and 3D electromagnetic pulse propagation directly from the full-vector Maxwell's equations.
NASA Technical Reports Server (NTRS)
Lee, Zhong-Ping; Carder, Kendall L.
2001-01-01
A multi-band analytical (MBA) algorithm is developed to retrieve absorption and backscattering coefficients for optically deep waters, which can be applied to data from past and current satellite sensors, as well as data from hyperspectral sensors. This MBA algorithm applies a remote-sensing reflectance model derived from the Radiative Transfer Equation, and values of absorption and backscattering coefficients are analytically calculated from values of remote-sensing reflectance. There are only limited empirical relationships involved in the algorithm, which implies that this MBA algorithm could be applied to a wide dynamic range of waters. Applying the algorithm to a simulated non-"Case 1" data set, which has no relation to the development of the algorithm, the percentage error for the total absorption coefficient at 440 nm a (sub 440) is approximately 12% for a range of 0.012 - 2.1 per meter (approximately 6% for a (sub 440) less than approximately 0.3 per meter), while a traditional band-ratio approach returns a percentage error of approximately 30%. Applying it to a field data set ranging from 0.025 to 2.0 per meter, the result for a (sub 440) is very close to that using a full spectrum optimization technique (9.6% difference). Compared to the optimization approach, the MBA algorithm cuts the computation time dramatically with only a small sacrifice in accuracy, making it suitable for processing large data sets such as satellite images. Significant improvements over empirical algorithms have also been achieved in retrieving the optical properties of optically deep waters.
NASA Astrophysics Data System (ADS)
Degrelle, D.; Mavon, C.; Groetz, J.-E.
2016-04-01
This study presents a numerical method in order to determine the mass attenuation coefficient of a sample with an unknown chemical composition at low energy. It is compared with two experimental methods: a graphic method and a transmission method. The method proposes to realise a numerical absorption calibration curve to process experimental results. Demineralised water with known mass attenuation coefficient (0.2066cm2g-1 at 59.54 keV) is chosen to confirm the method. 0.1964 ± 0.0350cm2g-1 is the average value determined by the numerical method, that is to say less than 5% relative deviation compared to more than 47% for the experimental methods.
Curiel, Fernando; Vargas, William E; Barrera, Rubén G
2002-10-01
A spectral-projected gradient method and an extension of the Kubelka-Munk theory are applied to obtain the relevant parameters of the theory from measured diffuse reflectance spectra of pigmented samples illuminated with visible diffuse radiation. The initial estimate of the spectral dependence of the parameters, required by a recursive spectral-projected gradient method, was obtained by use of direct measurements and up-to-date theoretical estimates. We then tested the consistency of the Kubelka-Munk theory by repeating the procedure with samples of different thicknesses. PMID:12371558
NASA Astrophysics Data System (ADS)
Deckers, Elke; Claeys, Claus; Atak, Onur; Groby, Jean-Philippe; Dazel, Olivier; Desmet, Wim
2016-05-01
This paper presents an extension to the Wave Based Method to predict the absorption, reflection and transmission coefficients of a porous material with an embedded periodic set of inclusions. The porous unit cell is described using the Multi-Level methodology and by embedding Bloch-Floquet periodicity conditions in the weighted residual scheme. The dynamic pressure field in the semi-infinite acoustic domains is approximated using a novel wave function set that fulfils the Helmholtz equation, the Bloch-Floquet periodicity conditions and the Sommerfeld radiation condition. The method is meshless and computationally efficient, which makes it well suited for optimisation studies.
NASA Astrophysics Data System (ADS)
Bernhard, G.; Evans, R. D.; Labow, G. J.; Oltmans, S. J.
2005-05-01
The Dobson spectrophotometer is the primary standard instrument for ground-based measurements of total column ozone. The accuracy of its data depends on the knowledge of ozone absorption coefficients used for data reduction. We document an error in the calculations that led to the set of absorption coefficients currently recommended by the World Meteorological Organisation (WMO). This error has little effect because an empirical adjustment was applied to the original calculations before the coefficients were adopted by WMO. We provide evidence that this adjustment was physically sound. The coefficients recommended by WMO are applied in the Dobson network without correction for the temperature dependence of the ozone absorption cross sections. On the basis of data measured by Dobson numbers 80 and 82, which were operated by the National Oceanic and Atmospheric Administration (NOAA) Climate Monitoring and Diagnostics Laboratory at the South Pole, we find that omission of temperature corrections may lead to systematic errors in Dobson ozone data of up to 4%. The standard Dobson ozone retrieval method further assumes that the ozone layer is located at a fixed height. This approximation leads to errors in air mass calculations, which are particularly relevant at high latitudes where ozone measurements are performed at large solar zenith angles (SZA). At the South Pole, systematic errors caused by this approximation may exceed 2% for SZAs larger than 80°. The bias is largest when the vertical ozone distribution is distorted by the "ozone hole" and may lead to underestimation of total ozone by 4% at SZA = 85° (air mass 9). Dobson measurements at the South Pole were compared with ozone data from a collocated SUV-100 UV spectroradiometer and Version 8 overpass data from NASA's Total Ozone Mapping Spectrometer (TOMS). Uncorrected Dobson ozone values tend to be lower than data from the two other instruments when total ozone is below 170 Dobson units or SZAs are larger than
Adhesion of Mineral and Soot Aerosols can Strongly Affect their Scattering and Absorption Properties
NASA Technical Reports Server (NTRS)
Mishchenko, Michael I.; Dlugach, Jana M.
2012-01-01
We use the numerically exact superposition T-matrix method to compute the optical cross sections and the Stokes scattering matrix for polydisperse mineral aerosols (modeled as homogeneous spheres) covered with a large number of much smaller soot particles. These results are compared with the Lorenz-Mie results for a uniform external mixture of mineral and soot aerosols. We show that the effect of soot particles adhering to large mineral particles can be to change the extinction and scattering cross sections and the asymmetry parameter quite substantially. The effect on the phase function and degree of linear polarization can be equally significant.
Phase diagram for passive electromagnetic scatterers.
Lee, Jeng Yi; Lee, Ray-Kuang
2016-03-21
With the conservation of power, a phase diagram defined by amplitude square and phase of scattering coefficients for each spherical harmonic channel is introduced as a universal map for any passive electromagnetic scatterers. Physically allowable solutions for scattering coefficients in this diagram clearly show power competitions among scattering and absorption. It also illustrates a variety of exotic scattering or absorption phenomena, from resonant scattering, invisible cloaking, to coherent perfect absorber. With electrically small core-shell scatterers as an example, we demonstrate a systematic method to design field-controllable structures based on the allowed trajectories in this diagram. The proposed phase diagram and inverse design can provide tools to design functional electromagnetic devices. PMID:27136839
NASA Astrophysics Data System (ADS)
Sipelgas, Liis; Raudsepp, Urmas
2015-11-01
The spectral variations in the attenuation and scattering coefficients measured with a hyperspectral ac-spectra (Wetlabs) instrument were analyzed from a dataset collected in the vicinity of commercial harbors on the Estonian coast of the Gulf of Finland, Baltic Sea. In total, the measured TSM concentration varied from 0.4 to 30 mg L-1 and the concentration of Chl a varied from values below the detection limit (0.05) to 23 mg m-3. The reliability of the power law describing the particle attenuation cp (λ) and scattering bp(λ) coefficients was evaluated by means of a determination coefficient (R2). The power law described the particle attenuation spectra with high accuracy (R2 > 0.67), giving the dataset an average cp (λ) slope of 1.3. In the case of particle scattering coefficients, the power law did not represent the whole dataset. Depending on a particular spectrum, the R2 varied from 0 to 1.0 and the slope varied from 1.15 to -0.56. Decomposition of bp(λ) into dominant modes using principal component analyses resulted in the first principal mode accounting for the power law dependence of bp(λ), i.e. the "mineral-type" spectrum, and the second and third mode representing the characteristic bp(λ) of dominant algal particles, i.e. the "algae-type" spectrum. From our dataset we estimated that if Chl a concentration is above 10 mg m-3 or below 5 mg m-3 then most likely the "algae-type" or the "mineral-type" spectrum is dominant, respectively. There was strong linear relationship (R2 > 0.92) between TSM concentration and cp(555) and bp(555),irrespective of the dominant shape of the particle scattering spectra. The estimated TSM-specific attenuation and scattering coefficients at 555 nm were 0.8 m2 g-1 and 0.68 m2 g-1, respectively. Corresponding values for water samples with a dominant "mineral-type" spectrum were 0.85 m2 g-1 and 0.73 m2 g-1, respectively and for water samples with a dominant "algae-type" spectrum were 0.64 m2 g-1 and 0.52 m2 g-1, respectively.
Hughes, Nicole M.; Vogelmann, Thomas C.; Smith, William K.
2008-01-01
A red/purple coloration of lower (abaxial) leaf surfaces is commonly observed in deeply-shaded understorey plants, especially in the tropics. However, the functional significance of red abaxial coloration, including its role in photosynthetic adaptation, remains unclear. The objective of this study was to test the back-scatter hypothesis for abaxial leaf coloration, which posits that red pigments internally reflect/scatter red light transmitted by the upper leaf surface back into the mesophyll, thereby enhancing photon capture in light-limited environments. Abaxially red/non-red variegated leaves of Begonia heracleifolia (Cham. & Schltdl.) were used to compare reflectance spectra and chlorophyll fluorescence profiles of abaxially anthocyanic (red) and acyanic (non-red) tissues under red light. Photosynthetic gas exchange in response to red light was also compared for abaxially red/non-red leaf sections. The results did not support a back-scattering function, as anthocyanic leaf surfaces were not more reflective of red light than acyanic surfaces. Anthocyanic tissues also did not exhibit any increases in the mesophyll absorbance of red light, or increased photosynthetic gas exchange under red light at any intensity, relative to acyanic tissues. These results suggest that abaxial anthocyanins do not significantly enhance the absorption of red light in the species tested, and alternative functions are discussed. PMID:18653695
2012-01-01
The linear and nonlinear intraband optical absorption coefficients in GaAs three-dimensional single quantum rings are investigated. Taking into account the combined effects of hydrostatic pressure and electric field, applied along the growth direction of the heterostructure, the energies of the ground and first excited states of a donor impurity have been found using the effective mass approximation and a variational method. The energies of these states are examined as functions of the dimensions of the structure, electric field, and hydrostatic pressure. We have also investigated the dependencies of the linear, nonlinear, and total optical absorption coefficients as a function of incident photon energy for several configurations of the system. It is found that the variation of distinct sizes of the structure leads to either a redshift and/or a blueshift of the resonant peaks of the intraband optical spectrum. In addition, we have found that the application of an electric field leads to a redshift, whereas the influence of hydrostatic pressure leads to a blueshift (in the case of on-ring-center donor impurity position) of the resonant peaks of the intraband optical spectrum. PMID:23021497
NASA Astrophysics Data System (ADS)
Martínez-Orozco, J. C.; Rodríguez-Magdaleno, K. A.; Suárez-López, J. R.; Duque, C. A.; Restrepo, R. L.
2016-04-01
In this work we present theoretical results for the electronic structure as well as for the absorption coefficient and relative refractive index change for an asymmetric double δ-doped like confining potential in the active region of a Multiple Independent Gate Field Effect Transistor (MIGFET) system. We model the potential profile as a double δ-doped like potential profile between two Schottky (parabolic) potential barriers that are just the main characteristics of the MIGFET configuration. We investigate the effect of external electromagnetic fields in this kind of quantum structures, in particular we applied a homogeneous constant electric field in the growth direction z as well as a homogeneous constant magnetic field in the x-direction. In general we conclude that by applying electromagnetic fields we can modulate the resonant peaks of the absorption coefficient as well as their energy position. Also with such probes it is possible to control the nodes and amplitude of the relative refractive index changes related to resonant intersubband optical transitions.
Barseghyan, Manuk G; Restrepo, Ricardo L; Mora-Ramos, Miguel E; Kirakosyan, Albert A; Duque, Carlos A
2012-01-01
: The linear and nonlinear intraband optical absorption coefficients in GaAs three-dimensional single quantum rings are investigated. Taking into account the combined effects of hydrostatic pressure and electric field, applied along the growth direction of the heterostructure, the energies of the ground and first excited states of a donor impurity have been found using the effective mass approximation and a variational method. The energies of these states are examined as functions of the dimensions of the structure, electric field, and hydrostatic pressure. We have also investigated the dependencies of the linear, nonlinear, and total optical absorption coefficients as a function of incident photon energy for several configurations of the system. It is found that the variation of distinct sizes of the structure leads to either a redshift and/or a blueshift of the resonant peaks of the intraband optical spectrum. In addition, we have found that the application of an electric field leads to a redshift, whereas the influence of hydrostatic pressure leads to a blueshift (in the case of on-ring-center donor impurity position) of the resonant peaks of the intraband optical spectrum. PMID:23021497
NASA Astrophysics Data System (ADS)
Consalvi, J. L.; Nmira, F.
2016-03-01
The main objective of this article is to quantify the influence of the soot absorption coefficient-Planck function correlation on radiative loss and flame structure in an oxygen-enhanced propane turbulent diffusion flame. Calculations were run with and without accounting for this correlation by using a standard k-ε model and the steady laminar flamelet model (SLF) coupled to a joint Probability Density Function (PDF) of mixture fraction, enthalpy defect, scalar dissipation rate, and soot quantities. The PDF transport equation is solved by using a Stochastic Eulerian Field (SEF) method. The modeling of soot production is carried out by using a flamelet-based semi-empirical acetylene/benzene soot model. Radiative heat transfer is modeled by using a wide band correlated-k model and turbulent radiation interactions (TRI) are accounted for by using the Optically-Thin Fluctuation Approximation (OTFA). Predicted soot volume fraction, radiant wall heat flux distribution and radiant fraction are in good agreement with the available experimental data. Model results show that soot absorption coefficient and Planck function are negatively correlated in the region of intense soot emission. Neglecting this correlation is found to increase significantly the radiative loss leading to a substantial impact on flame structure in terms of mean and rms values of temperature. In addition mean and rms values of soot volume fraction are found to be less sensitive to the correlation than temperature since soot formation occurs mainly in a region where its influence is low.
Anisotropy-assisted non-scattering coherent absorption of surface plasmon-polaritons
NASA Astrophysics Data System (ADS)
Ignatov, Anton I.; Nechepurenko, Igor A.; Baranov, Denis G.
2016-08-01
The ability to control propagation of electromagnetic guided modes lies at the heart of integrated nanophotonics. Surface plasmon-polaritons are a class of guided modes which can be employed in integrated optical systems. Here, we present a theoretical design of a coherent surface plasmon absorber which can perfectly harvest energy of coherently incident surface plasmons without parasitic scattering into free space modes. Excitation of free space modes which usually accompanies scattering of a surface plasmon by an interface boundary is avoided due to specially tailored anisotropy of the absorber. The concept of coherent SPP absorber is analyzed numerically for spatially non-uniform and finite-size structures. We believe that our results will be important for the development of integrated nanoplasmonic systems.
Werfelli, Ghofran; Halvick, Philippe; Honvault, Pascal; Kerkeni, Boutheïna; Stoecklin, Thierry
2015-09-21
The observed abundances of the methylidyne cation, CH(+), in diffuse molecular clouds can be two orders of magnitude higher than the prediction of the standard gas-phase models which, in turn, predict rather well the abundances of neutral CH. It is therefore necessary to investigate all the possible formation and destruction processes of CH(+) in the interstellar medium with the most abundant species H, H2, and e(-). In this work, we address the destruction process of CH(+) by hydrogen abstraction. We report a new calculation of the low temperature rate coefficients for the abstraction reaction, using accurate time-independent quantum scattering and a new high-level ab initio global potential energy surface including a realistic model of the long-range interaction between the reactants H and CH(+). The calculated thermal rate coefficient is in good agreement with the experimental data in the range 50 K-800 K. However, at lower temperatures, the experimental rate coefficient takes exceedingly small values which are not reproduced by the calculated rate coefficient. Instead, the latter rate coefficient is close to the one given by the Langevin capture model, as expected for a reaction involving an ion and a neutral species. Several recent theoretical works have reported a seemingly good agreement with the experiment below 50 K, but an analysis of these works show that they are based on potential energy surfaces with incorrect long-range behavior. The experimental results were explained by a loss of reactivity of the lowest rotational states of the reactant; however, the quantum scattering calculations show the opposite, namely, a reactivity enhancement with rotational excitation. PMID:26395702
NASA Technical Reports Server (NTRS)
King, Michael D.; Nakajima, Teruyuki; Radke, Lawrence F.; Hobbs, Peter V.
1990-01-01
Researchers briefly review the diffusion domain method for deriving the cloud similarity parameter and present preliminary analyses of the results thus far obtained. The presentation concentrates on the following points: (1) intercomparison of calibrated reflected intensities between the cloud absorption radiometer and the U.K. multispectral cloud radiometer; (2) quality control tests required to select those portions of an aircraft flight for which measurements are obtained within the diffusion domain; (3) case studies of the spectral similarity parameter of marine stratocumulus clouds; and comparisons of the experimentally-derived similarity parameter spectrum with that expected theoretically from the cloud droplet size distribution obtained from in situ observations.
Fasano, William J; Baer, Kevin N
2006-01-01
Vinyl toluene is one of several methylstyrene monomers that provide improved performance in resins for specialty paints, hydrocarbon resins for adhesives, specialty polymers, and unsaturated polyester resins. The purpose of this study was to determine a permeability coefficient (Kp) and short-term absorption rate for vinyl toluene using human cadaver skin mounted in an in vitro static diffusion cell model with an exposure area of 0.64 cm2. For the Kp determination, vinyl toluene was applied at a rate of 100 microL/cm2 to 6 skin replicates representing 4 human subjects. Serial receptor fluid samples were collected at 1, 2, 4, 8, 12, 24, 36, and 48 h postapplication and analyzed for vinyl toluene by HPLC-UV. Based on the slope at steady-state (203.3 microg cm(-2) h(-1) +/- 120.0 microg cm(-2) h(-1)) and the concentration of the applied dose of vinyl toluene, taken as its density (894,600 microg/cm3), the Kp was calculated to be 2.27 x 10(-4) cm/h (+/-1.34 x 10(-4) cm/h). For the short-term absorption experiments, 12 skin replicates representing 3 human subjects were employed. Following 10- and 60-min exposures to a finite dose of vinyl toluene (10 microL/cm2), the respective short-term absorption rates were calculated to be 66.0 (+/-29.9) and 104.2 (+/-63.0) microg cm(-2) h(-1). These data provide industrial hygienists and safety personnel values to estimate the amount of vinyl toluene that may be absorbed via the dermal exposure route, given a variety of exposure scenarios, and the time it takes (skin absorption time) to reach a body burden equal to the Occupational Safety and Health Administrative permissible exposure level (OSHA PEL) or ACGIH TLV. PMID:16455589
Lee, Ik-Jae; Yu, Chung-Jong; Yun, Young-Duck; Lee, Chae-Soon; Seo, In Deuk; Kim, Hyo-Yun; Lee, Woul-Woo; Chae, Keun Hwa
2010-02-15
A new hard x-ray beamline, 10B KIST-PAL beamline (BL10B), has been designed and constructed at the Pohang Light Source (PLS) in Korea. The beamline, operated by Pohang Accelerator Laboratory-Korean Institute of Science and Technology consortium, is dedicated to x-ray scattering (XRS) and x-ray absorption fine structure (XAFS) experiments. X rays with photon energies from 4.0 to 16.0 keV are delivered to the experimental station passing a collimating mirror, a fixed-exit double-crystal Si(111) monochromator, and a toroidal mirror. Basic experimental equipments for XAFS measurement, a high resolution diffractometry, an image plate detector system, and a hot stage have been prepared for the station. From our initial commissioning and performance testing of the beamline, it is observed that BL10B beamline can perform XRS and XAFS measurements successfully.
Stark, Peter C.; Zurek, Eduardo; Wheat, Jeffrey V.; Dunbar, John M.; Olivares, Jose A.; Garcia-Rubio, Luis H.; Ward, Michael D.
2011-07-26
There is provided a method and device for remote sampling, preparation and optical interrogation of a sample using light scattering and light absorption methods. The portable device is a filtration-based device that removes interfering background particle material from the sample matrix by segregating or filtering the chosen analyte from the sample solution or matrix while allowing the interfering background particles to be pumped out of the device. The segregated analyte is then suspended in a diluent for analysis. The device is capable of calculating an initial concentration of the analyte, as well as diluting the analyte such that reliable optical measurements can be made. Suitable analytes include cells, microorganisms, bioparticles, pathogens and diseases. Sample matrixes include biological fluids such as blood and urine, as well as environmental samples including waste water.
NASA Astrophysics Data System (ADS)
Tan, Hairen; Sivec, Laura; Yan, Baojie; Santbergen, Rudi; Zeman, Miro; Smets, Arno H. M.
2013-04-01
We show experimentally that the photocurrent of thin-film hydrogenated microcrystalline silicon (μc-Si:H) solar cells can be enhanced by 4.5 mA/cm2 with a plasmonic back reflector (BR). The light trapping performance is improved using plasmonic BR with broader angular scattering and lower parasitic absorption loss through tuning the size of silver nanoparticles. The μc-Si:H solar cells deposited on the improved plasmonic BR demonstrate a high photocurrent of 26.3 mA/cm2 which is comparable to the state-of-the-art textured Ag/ZnO BR. The commonly observed deterioration of fill factor is avoided by using μc-SiOx:H as the n-layer for solar cells deposited on plasmonic BR.
Zimnyakov, D A; Yuvchenko, S A; Pravdin, A B; Kochubey, V I; Gorokhovsky, A V; Tretyachenko, E V; Kunitsky, A I
2014-07-31
The results of experimental studies of depolarising properties of disperse systems on the basis of potassium polytitanate nanoplatelets and nanoribbons in the visible and near-UV spectral regions are presented. It is shown that in the fundamental absorption band of the nanoparticle material the increase in the depolarisation factor takes place for the radiation scattered perpendicularly to the direction of the probing beam. For nanoribbons a pronounced peak of depolarisation is observed, which is caused by the essential anisotropy of the particles shape and the peculiarities of the behaviour of the material dielectric function. The empirical data are compared with the theoretical results for 'nanodiscs' and 'nanoneedles' with the model dielectric function, corresponding to that obtained from optical constants of the titanium dioxide dielectric function. (laser biophotonics)
Le, Fei; Brandl, Daniel W; Urzhumov, Yaroslav A; Wang, Hui; Kundu, Janardan; Halas, Naomi J; Aizpurua, Javier; Nordlander, Peter
2008-04-01
Nanoshell arrays have recently been found to possess ideal properties as a substrate for combining surface enhanced raman scattering (SERS) and surface enhanced infrared absorption (SEIRA) spectroscopies, with large field enhancements at the same spatial locations on the structure. For small interparticle distances, the multipolar plasmon resonances of individual nanoshells hybridize and form red-shifted bands, a relatively narrow band in the near-infrared (NIR) originating from quadrupolar nanoshell resonances enhancing SERS, and a very broadband in the mid-infrared (MIR) arising from dipolar resonances enhancing SEIRA. The large field enhancements in the MIR and at longer wavelengths are due to the lightning-rod effect and are well described with an electrostatic model. PMID:19206602
Absorption and scattering properties of the Martian dust in the solar wavelengths.
Ockert-Bell, M E; Bell JF 3rd; Pollack, J B; McKay, C P; Forget, F
1997-04-25
A new wavelength-dependent model of the single-scattering properties of the Martian dust is presented. The model encompasses the solar wavelengths (0.3 to 4.3 micrometers at 0.02 micrometer resolution) and does not assume a particular mineralogical composition of the particles. We use the particle size distribution, shape, and single-scattering properties at Viking Lander wavelengths presented by Pollack et al. [1995]. We expand the wavelength range of the aerosol model by assuming that the atmospheric dust complex index of refraction is the same as that of dust particles in the bright surface geologic units. The new wavelength-dependent model is compared to observations taken by the Viking Orbiter Infrared Thermal Mapper solar channel instrument during two dust storms. The model accurately matches afternoon observations and some morning observations. Some of the early morning observations are much brighter than the model results. The increased reflectance can be ascribed to the formation of a water ice shell around the dust particles, thus creating the water ice clouds which Colburn et al. [1989], among others, have predicted. PMID:11541455
Optical inhomogeneity of dust-like aerosols and its effects on scattering and absorption
NASA Astrophysics Data System (ADS)
Mishchenko, M. I.; Dlugach, Z.; Liu, L.
2015-12-01
The use of the very concept of effective refractive index has been implicit in virtually all computations of electromagnetic scattering by dust-like aerosols since the nanometer-scale heterogeneity of such particles has been essentially ignored. Therefore, the failure of this concept in application to dust-like aerosols would create a highly problematic situation. It is thus imperative to perform a comprehensive analysis of the actual physical origin of the heuristic effective-medium approximations (EMAs) and the range and conditions of their practical applicability. In this talk, we will identify the true place of the EMAs in the framework of statistical electrodynamics. We will validate the outcome of this analysis by superposition T-matrix computer calculations and will perform a detailed quantitative assessment of the actual accuracy of the EMAs when they are applied to less-than-ideal types of heterogeneity encountered in nature. It is expected that the accuracy of an EMA will depend on many factors: on type of mixing; on refractive indices and size parameters of the host and the inclusions; on number, spatial distribution, and packing density of the inclusions; on whether one computes monodisperse or polydisperse optical characteristics; on whether one computes only integral radiometric characteristics or also the elements of the scattering matrix; etc. If so, the actual practical suitability of an EMA will vary widely depending on the specific type of application, e.g., lidar remote sensing, polarimetric remote sensing, radiometric remote sensing, or integral radiation-budget computations.
Mean absorption coefficient of H2O-air-MgCl2/CaCl2/NaCl thermal plasmas
NASA Astrophysics Data System (ADS)
Hannachi, R.; Cressault, Y.; Salem, D.; Teulet, Ph; Béji, L.; Ben Lakhdar, Z.
2012-12-01
Under the local thermodynamic equilibrium hypothesis, the mean absorption coefficients (MACs) were calculated for H2O-air-MgCl2/CaCl2/NaCl thermal plasmas in a temperature range from 300 to 30 000 K and at atmospheric pressure. The MACs were computed under the hypothesis of isothermal plasmas which allows a good description of the radiation absorbed in cold regions. In this study, we took into account the absorption radiation resulting from the atomic continuum, molecular continuum, atomic lines and some molecular bands. Free-free transitions (bremsstrahlung) and free-bound (electron-ion recombination and electron attachment) or bound-free transitions in terms of absorption were considered for the calculation of atomic continuum. For bound-bound transitions, natural, resonance, van der Waals, Stark and Doppler effects were taken into account for the line broadenings while the escape factors were used to treat the self-absorption of the resonance lines. Molecular continuum was considered for the main molecules (H2, O2, N2, OH, NO, H2O, N2O, NO2, O3, NO3 and N2O5) whereas we studied only diatomic systems O2, N2, NO and N_2^+ for the absorption of molecular bands. The influence of the proportion of MgCl2, CaCl2 or NaCl in a water-air mixture was analysed as the effect of the strong self-absorbed resonance lines of the alkaline salts (Ca, Ca+, Na, Na+, Mg, Mg+, Cl and Cl+). Our results show that a low concentration of alkaline salts (less than 1% in molar proportions) in the plasma increased the MACs at low temperatures (T < 10 000 K) due to the resonance lines mainly localized in the near-UV and visible spectral regions in opposition to hydrogen, oxygen or nitrogen species for which 90% of them exist in ultraviolet. In addition to the atomic and molecular continuum, the absorption radiation of molecular bands is important at low temperatures.
NASA Astrophysics Data System (ADS)
Marley, N. A.; Gaffney, J. S.; Castro, T.; Salcido, A.; Frederick, J.
2008-07-01
Measurements of aerosol absorption and scattering were obtained in Mexico City during the MILAGRO (Megacity Initiative: Local and Global Research Observations) field campaign in March 2006. A comparison of aerosol absorption and scattering was obtained in Mexico City at site T0 located in the northern part of Mexico City at the Instituto Mexicano del Petróleo Laboratories and at site T1 located at the Universidad Tecnológica de Tecamac, 18 miles northwest of T0. Hourly averages of aerosol absorption were similar at both sites, ranging from 6 93 Mm-1 with an average of 31 Mm-1 at T0; and from 2 104 Mm-1 with an average of 19 Mm-1 at T1. Aerosol scattering at T0 ranged from 16 344 Mm-1 with an average of 105 Mm-1; while the scattering values at T1 were lower than T0 ranging from 2 136 with an average of 53 Mm-1. Aerosol single scattering albedos (SSAs) were determined at both sites using these data. SSAs at T1 ranged from 0.44 0.90 with an average 0.75 as compared to hose at T0, range 0.51 0.93 with an average of 0.77. Broadband UV-B intensity was found to be higher at site T0, with an average of 64 μW/cm2 at solar noon, than at site T1, which had an average of 54 μW/cm2 at solar noon. Comparisons of clear-sky modeled UV-B intensities with the simultaneous UV-B measurements obtained at site T0 and at site T1 for cloudless days indicate a larger diffuse radiation field at site T0 than at site T1. The determination of aerosol scattering Ångstrom coefficient at T0 suggests the larger diffuse radiation is due to the predominance of submicron aerosols at T0 with aerosol scattering of UV-B radiation peaked in the forward direction, leading to the enhancement observed at ground level.
NASA Astrophysics Data System (ADS)
Jones, A. P.; Köhler, M.; Ysard, N.; Dartois, E.; Godard, M.; Gavilan, L.
2016-04-01
Context. The observed cloudshine and coreshine (C-shine) have been explained in terms of grain growth leading to enhanced scattering from clouds in the J, H, and K photometric bands and the Spitzer IRAC 3.6 and 4.5 μm bands. Aims: Using our global dust-modelling approach THEMIS (The Heterogeneous dust Evolution Model at the IaS), we explore the effects of dust evolution in dense clouds, through aliphatic-rich carbonaceous mantle formation and grain-grain coagulation. Methods: We model the effects of wide band gap a-C:H mantle formation and the low-level aggregation of diffuse interstellar medium dust in the moderately-extinguished outer regions of molecular clouds. Results: The formation of wide band gap a-C:H mantles on amorphous silicate and amorphous carbon (a-C) grains leads to a decrease in their absorption cross-sections but no change in their scattering cross-sections at near-infrared wavelengths, resulting in higher albedos. Conclusions: The evolution of dust, with increasing density and extinction in the diffuse-to-dense molecular cloud transition, through mantle formation and grain aggregation, appears to be a likely explanation for the observed C-shine.
Oliéric, V; Ennifar, E; Meents, A; Fleurant, M; Besnard, C; Pattison, P; Schiltz, M; Schulze-Briese, C; Dumas, P
2007-07-01
Radiation damage in macromolecular crystals is not suppressed even at 90 K. This is particularly true for covalent bonds involving an anomalous scatterer (such as bromine) at the 'peak wavelength'. It is shown that a series of absorption spectra recorded on a brominated RNA faithfully monitor the extent of cleavage. The continuous spectral changes during irradiation preserve an 'isosbestic point', each spectrum being a linear combination of 'zero' and 'infinite' dose spectra. This easily yields a good estimate of the partial occupancy of bromine at any intermediate dose. The considerable effect on the near-edge features in the spectra of the crystal orientation versus the beam polarization has also been examined and found to be in good agreement with a previous study. Any significant influence of the (C-Br bond/beam polarization) angle on the cleavage kinetics of bromine was also searched for, but was not detected. These results will be useful for standard SAD/MAD experiments and for the emerging 'radiation-damage-induced phasing' method exploiting both the anomalous signal of an anomalous scatterer and the 'isomorphous' signal resulting from its cleavage. PMID:17582167
NASA Technical Reports Server (NTRS)
Egan, W. G.; Fischbein, W. L.
1975-01-01
The Braslau-Dave atmospheric model which calculates the upward monochromatic light fluxes leaving the top of the atmosphere as a function of viewing angle, sun angle, and ground reflectance was employed to study the effect of atmospheric scattering and attenuation on universal apparent contrast for two EOS remote sensors operated at very large offset or pointing angles: the Thematic Mapper (TM) and the High Resolution Pointable Imager (HRPI). The TM offset off nadir could be plus or minus 20 degrees with an 11 degree scan angle and the HRPI pointing angle off nadir could be plus or minus 45 degrees with a 3 degree scan angle. The reduction of universal apparent contrast of EOS imagery is studied as a function of sun elevation angle, atmospheric aerosol loading, radiation wavelength and sensor look angles.
NASA Technical Reports Server (NTRS)
Redemann, Jens; Russell, Philip B.; Hamill, Patrick
2001-01-01
Atmospheric aerosols frequently contain hygroscopic sulfate species and black carbon (soot) inclusions. In this paper we report results of a modeling study to determine the change in aerosol absorption due to increases in ambient relative humidity (RH), for three common sulfate species, assuming that the soot mass fraction is present as a single concentric core within each particle. Because of the lack of detailed knowledge about various input parameters to models describing internally mixed aerosol particle optics, we focus on results that were aimed at determining the maximum effect that particle humidification may have on aerosol light absorption. In the wavelength range from 450 to 750 nm, maximum absorption humidification factors (ratio of wet to 'dry=30% RH' absorption) for single aerosol particles are found to be as large as 1.75 when the RH changes from 30 to 99.5%. Upon lesser humidification from 30 to 80% RH, absorption humidification for single particles is only as much as 1.2, even for the most favorable combination of initial ('dry') soot mass fraction and particle size. Integrated over monomodal lognormal particle size distributions, maximum absorption humidification factors range between 1.07 and 1.15 for humidification from 30 to 80% and between 1.1 and 1.35 for humidification from 30 to 95% RH for all species considered. The largest humidification factors at a wavelength of 450 nm are obtained for 'dry' particle size distributions that peak at a radius of 0.05 microns, while the absorption humidification factors at 700 nm are largest for 'dry' size distributions that are dominated by particles in the radius range of 0.06 to 0.08 microns. Single-scattering albedo estimates at ambient conditions are often based on absorption measurements at low RH (approx. 30%) and the assumption that aerosol absorption does not change upon humidification (i.e., absorption humidification equal to unity). Our modeling study suggests that this assumption alone can
NASA Astrophysics Data System (ADS)
Hoge, Frank E.; Vodacek, Anthony; Swift, Robert N.; Yungel, James K.; Blough, Neil V.
1995-10-01
The absorption coefficient of chromophoric dissolved organic matter (CDOM) at 355 nm has been retrieved from airborne laser-induced and water Raman-normalized CDOM fluorescence. Four combined airborne and ship field experiments have demonstrated that (1) the airborne CDOM fluorescence-to--water Raman ratio is linearly related to concurrent quinine-sulfate-standardized CDOM shipboard fluorescence measurements over a wide range of water masses (coastal to blue water); (2) the vicarious calibration of the airborne fluorosensor in units traceable to a fluorescence standard can be established and then maintained over an extended time period by tungsten lamp calibration; (3) the vicariously calibrated airborne CDOM fluorescence-to-water Raman ratio can be directly applied to previously developed
NASA Astrophysics Data System (ADS)
Mandal, Arkajit; Sarkar, Sucharita; Ghosh, Arghya Pratim; Ghosh, Manas
2015-12-01
We make an extensive investigation of total optical absorption coefficient (TOAC) of impurity doped quantum dots (QDs) in presence and absence of Gaussian white noise. The TOAC profiles have been monitored against incident photon energy with special emphasis on the roles played by the electric field, magnetic field, and the dot confinement potential. Presence of impurity also influences the TOAC profile. In general, presence of noise causes enhancement of TOAC over that of noise-free condition. However, the interplay between the noise and the quantities like electric field, magnetic field, confinement potential and impurity potential bring about rich subtleties in the TOAC profiles. The said subtleties are often manifested by the alterations in TOAC peak intensity, extent of TOAC peak bleaching, and value of saturation intensity. The findings reveal some technologically relevant aspects of TOAC for the doped QD systems, specially in presence of noise.
Qu, Bin; Ouyang, Qiuyun; Yu, Xianbo; Luo, Wenhe; Qi, Lihong; Chen, Yujin
2015-02-28
MoS2-ZnO composites were synthesized using a solution-based method. The scanning electron microscopy and transmission electron microscopy analysis demonstrated that ZnO nanoparticles with a size of about 4.5 nm were coated on the basal surface of MoS2 nanosheets with an expanded spacing of the (002) plane. The MoS2-ZnO composite-based poly(methyl methacrylate) (PMMA) organic glasses (MoS2-ZnO-PMMA organic glasses) were prepared through a polymerization process. The nonlinear absorption (NLA), nonlinear scattering (NLS), and optical limiting (OL) properties of the MoS2-ZnO-PMMA organic glasses with different amounts of MoS2-ZnO were investigated using a modified Z-scan technique. Compared to MoS2-PMMA and ZnO-PMMA organic glasses, the MoS2-ZnO-PMMA organic glasses exhibited enhanced NLA, NLS, and OL properties, which were attributed to the interfacial charge transfer between MoS2 nanosheets and ZnO nanoparticles, the layered structure of MoS2 nanosheets, the small size effect of ZnO nanoparticles, and the local field effect. In addition, a changeover from saturable absorption (SA) to reverse saturable absorption (RSA) could be realized in the MoS2-ZnO-PMMA organic glasses by adjusting the input energy. The total nonlinear extinction coefficient and response time of the MoS2-ZnO-PMMA organic glasses could be up to 2380 cm GW(-1) and several hundred picoseconds, respectively. Compared to the MoS2 films, the MoS2-ZnO-PMMA organic glasses have higher optical damage threshold, better mechanical strength and flexibility. Thus the MoS2-ZnO-PMMA organic glasses are very promising for optical devices such as optical limiters, optical shutters, ultrafast lasers, and ultrafast optical switches. PMID:25642471
NASA Astrophysics Data System (ADS)
Puķīte, Jānis; Wagner, Thomas
2016-05-01
We address the application of differential optical absorption spectroscopy (DOAS) of scattered light observations in the presence of strong absorbers (in particular ozone), for which the absorption optical depth is a non-linear function of the trace gas concentration. This is the case because Beer-Lambert law generally does not hold for scattered light measurements due to many light paths contributing to the measurement. While in many cases linear approximation can be made, for scenarios with strong absorptions non-linear effects cannot always be neglected. This is especially the case for observation geometries, for which the light contributing to the measurement is crossing the atmosphere under spatially well-separated paths differing strongly in length and location, like in limb geometry. In these cases, often full retrieval algorithms are applied to address the non-linearities, requiring iterative forward modelling of absorption spectra involving time-consuming wavelength-by-wavelength radiative transfer modelling. In this study, we propose to describe the non-linear effects by additional sensitivity parameters that can be used e.g. to build up a lookup table. Together with widely used box air mass factors (effective light paths) describing the linear response to the increase in the trace gas amount, the higher-order sensitivity parameters eliminate the need for repeating the radiative transfer modelling when modifying the absorption scenario even in the presence of a strong absorption background. While the higher-order absorption structures can be described as separate fit parameters in the spectral analysis (so-called DOAS fit), in practice their quantitative evaluation requires good measurement quality (typically better than that available from current measurements). Therefore, we introduce an iterative retrieval algorithm correcting for the higher-order absorption structures not yet considered in the DOAS fit as well as the absorption dependence on
NASA Astrophysics Data System (ADS)
Montes-Hugo, Martin; Xie, Huxiang
2015-10-01
The inversion of individual inherent optical properties (IOPs) is very challenging in optically complex waters and within the violet spectral range (i.e., 380-450 nm) due to the strong light attenuation caused by chromophoric dissolved organic matter, nonalgal particulates, and phytoplankton. Here we present a technique to better discriminate light absorption contributions due to phytoplankton based on a hybrid model (QAA-hybrid) that combines regional Saint Lawrence System estimates of IOPs derived from a quasi-analytical algorithm (hereafter QAA-SLE) and empirical relationships between salinity and IOPs. Preliminary results in the Saint Lawrence System during May 2000 and April 2001 showed that QAA-hybrid estimates of phytoplankton absorption coefficient at 443 nm have a smaller bias with respect to in situ measurements (root-mean-square deviation, RMSD = 0.156) than those derived from QAA-SLE (RMSD = 0.341). These results were valid for surface waters (i.e., 0-5 m depth) of the lower estuary with a salinity and chlorophyll-a concentration range of 22-28 psu and 2.1-13.8 mg m-3, respectively.
Optical phantoms with adjustable subdiffusive scattering parameters.
Krauter, Philipp; Nothelfer, Steffen; Bodenschatz, Nico; Simon, Emanuel; Stocker, Sabrina; Foschum, Florian; Kienle, Alwin
2015-10-01
A new epoxy-resin-based optical phantom system with adjustable subdiffusive scattering parameters is presented along with measurements of the intrinsic absorption, scattering, fluorescence, and refractive index of the matrix material. Both an aluminium oxide powder and a titanium dioxide dispersion were used as scattering agents and we present measurements of their scattering and reduced scattering coefficients. A method is theoretically described for a mixture of both scattering agents to obtain continuously adjustable anisotropy values g between 0.65 and 0.9 and values of the phase function parameter γ in the range of 1.4 to 2.2. Furthermore, we show absorption spectra for a set of pigments that can be added to achieve particular absorption characteristics. By additional analysis of the aging, a fully characterized phantom system is obtained with the novelty of g and γ parameter adjustment. PMID:26473589
Optical phantoms with adjustable subdiffusive scattering parameters
NASA Astrophysics Data System (ADS)
Krauter, Philipp; Nothelfer, Steffen; Bodenschatz, Nico; Simon, Emanuel; Stocker, Sabrina; Foschum, Florian; Kienle, Alwin
2015-10-01
A new epoxy-resin-based optical phantom system with adjustable subdiffusive scattering parameters is presented along with measurements of the intrinsic absorption, scattering, fluorescence, and refractive index of the matrix material. Both an aluminium oxide powder and a titanium dioxide dispersion were used as scattering agents and we present measurements of their scattering and reduced scattering coefficients. A method is theoretically described for a mixture of both scattering agents to obtain continuously adjustable anisotropy values g between 0.65 and 0.9 and values of the phase function parameter γ in the range of 1.4 to 2.2. Furthermore, we show absorption spectra for a set of pigments that can be added to achieve particular absorption characteristics. By additional analysis of the aging, a fully characterized phantom system is obtained with the novelty of g and γ parameter adjustment.
NASA Astrophysics Data System (ADS)
Turgut, U.; Simsek, O.; Büyükkasap, E.
2007-08-01
The total mass attenuation coefficients for elements Cr, Co and Fe and compounds CrCl_{2}, CrCl_{3}, Cr_{2}(SO_{4})_{3}K_{2}SO_{4}\\cdot24H_{2}O, CoO, CoCl_{2}, Co(CH_{3}COO)_{2}, FePO_{4}, FeCl_{3}\\cdot6H_{2}O, Fe(SO_{4})_{2}NH_{4}\\cdot12H_{2}O were measured at different energies between 4.508 and 14.142 keV using secondary excitation method. Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr were chosen as secondary exciters. 59.5 keV γ-rays emitted from a ^{241}Am annular source were used to excite a secondary exciter and K_{α}(K-L_{3}, L_{2}) lines emitted by the secondary exciter were counted by a Si(Li) detector with a resolution of 160 eV at 5.9 keV. It was observed that mixture rule method is not a suitable method for determination of the mass attenuation coefficients of compounds, especially at an energy that is near the absorption edge. The obtained values were compared with theoretical values.
Webb, S.M.; Fuller, C.C.; Tebo, B.M.; Bargar, J.R.
2006-01-01
Biogenic manganese oxides are common and an important source of reactive mineral surfaces in the environment that may be potentially enhanced in bioremediation cases to improve natural attenuation. Experiments were performed in which the uranyl ion, UO22+ (U(VI)), at various concentrations was present during manganese oxide biogenesis. At all concentrations, there was strong uptake of U onto the oxides. Synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray diffraction (XRD) studies were carried out to determine the molecular-scale mechanism by which uranyl is incorporated into the oxide and how this incorporation affects the resulting manganese oxide structure and mineralogy. The EXAFS experiments show that at low concentrations (2 mol % U, >4 ??M U(VI) in solution), the presence of U(VI) affects the stability and structure of the Mn oxide to form poorly ordered Mn oxide tunnel structures, similar to todorokite. EXAFS modeling shows that uranyl is present in these oxides predominantly in the tunnels of the Mn oxide structure in a tridentate complex. Observations by XRD corroborate these results. Structural incorporation may lead to more stable U(VI) sequestration that may be suitable for remediation uses. These observations, combined with the very high uptake capacity of the Mn oxides, imply that Mn-oxidizing bacteria may significantly influence dissolved U(VI) concentrations in impacted waters via sorption and incorporation into Mn oxide biominerals. ?? 2006 American Chemical Society.
NASA Astrophysics Data System (ADS)
Giles, D. M.; Holben, B. N.; Eck, T. F.; Schafer, J.; Crawford, J. H.; Kim, J.; Sano, I.; Liew, S.; Salinas Cortijo, S. V.; Chew, B. N.; Lim, H.; Smirnov, A.; Sorokin, M.; Kenny, P.; Slutsker, I.
2013-12-01
Aerosols can have major implications on human health by inducing respiratory diseases due to inhalation of fine particles from biomass burning smoke or industrial pollution and on radiative forcing whereby the presence of absorbing aerosol particles (e.g., black carbon) increases atmospheric heating. Aerosol classification techniques have utilized aerosol loading and aerosol properties derived from multi-spectral and multi-angle observations by ground-based (e.g., AERONET) and satellite instrumentation (e.g., MISR). Aerosol Robotic Network (AERONET) data have been utilized to determine aerosol types by implementing various combinations of measured aerosol optical depth or retrieved size and absorption aerosol properties (e.g., Gobbi et al., 2007; Russell et al., 2010). Giles et al. [2012] showed single scattering albedo (SSA) relationship with extinction Angstrom exponent (EAE) can provide an estimate of the general classification of dominant aerosol types (i.e., desert dust, urban/industrial pollution, biomass burning smoke, and mixtures) based on data from ~20 AERONET sites located in known aerosol source regions. In addition, the absorption Angstrom exponent relationship with EAE can provide an indication of the dominant absorbing aerosol type such as dust, black carbon, brown carbon, or mixtures of them. These classification techniques are applied to the AERONET Level 2.0 quality assured data sets collected during Distributed Regional Aerosol Gridded Observational Network (DRAGON) campaigns in Maryland (USA), Japan, South Korea, Singapore, Penang (Malaysia), and California (USA). An analysis of aerosol type classification for DRAGON sites is performed as well as an assessment of the spatial variability of the aerosol types for selected DRAGON campaigns. Giles, D. M., B. N. Holben, T. F. Eck, A. Sinyuk, A. Smirnov, I. Slutsker, R. R. Dickerson, A. M. Thompson, and J. S. Schafer (2012), An analysis of AERONET aerosol absorption properties and classifications
NASA Astrophysics Data System (ADS)
Ko, J. H.; Roleder, K.; Bussmann-Holder, A.
2014-03-01
The temperature dependence of the three independent elastic constants of antiferroelectric lead zirconate single crystals was determined in the cubic, paraelectric phase by Brillouin light scattering spectroscopy. Two longitudinal elastic moduli of C11 and (C11 + C12+2 C44)/2 showed softening upon cooling toward the phase transition temperature, indicating the coupling of the acoustic waves to the polarization fluctuations of the precursor polar clusters. Among the two transverse acoustic modes, C44 was almost constant while (C11-C12)/2 showed a noticeable softening in the paraelectric phase. This was attributed to the acoustic instability of lead zirconate toward the orthorhombic ground state.
A three-wavelength differential-absorption lidar (DIAL) technique for the UV spectral region is presented that reduces the influence of aerosol differential scattering on measured O3-concentration profiles. The principal advantage of this approach is that, to a good first approxi...
Absorption of visible radiation by aerosols in the volcanic plume of mount st. Helens.
Ogren, J A; Charlson, R J; Radke, L F; Domonkos, S K
1981-02-20
Samples of particles from Mount St. Helens were collected in both the stratosphere and troposphere for measurement of the light absorption coefficient. Results indicate that the stratospheric dust had a small but finite absorption coefficient ranging up to 2 x 10(-7) per meter at a wavelength of 0.55 micrometer, which is estimated to yield an albedo for single scatter of 0.98 or greater. Tropospheric results showed similar high values of an albedo for single scatter. PMID:17740397
Absorption of visible radiation by aerosols in the volcanic plume of Mount St. Helens
NASA Technical Reports Server (NTRS)
Ogren, J. A.; Charlson, R. J.; Radke, L. F.; Domonkos, S. K.
1981-01-01
Samples of particles from Mount St. Helens were collected in both the stratosphere and troposphere for measurement of the light absorption coefficient. Results indicate that the stratospheric dust had a small but finite absorption coefficient ranging up to 2 x 10 to the minus 7 per meter at a wavelength of 0.55 micron, which is estimated to yield an albedo for single scatter of 0.98 or greater. Tropospheric results showed similar high values of an albedo for single scatter
Absorption of visible radiation by aerosols in the volcanic plume of Mount St. Helens
Ogren, J.A.; Charlson, R.J.; Radke, L.F.; Domonkos, S.K.
1981-01-01
Samples of particles from Mount St. Helens were collected in both the stratosphere and troposhere for measurement of the light absorption coefficient. Results indicate that the stratospheric dust had a small but finite absorption coefficient ranging up to 2 x 10-7 per meter at a wavelength of 0.55 micrometer, which is estimated to yield an albedo for single scatter of 0.98 or greater. Tropospheric results showed similar high values of an albedo for single scatter.
Bulat, Lev P.; Osvenskii, Vladimir B.; Parkhomenko, Yurii N.; Pshenay-Severin, Dmitry A.
2012-09-15
One of the possible ways to increase the thermoelectric figure of merit is the use of bulk nanostructured materials fabricated by melt spinning with subsequent hot pressing or spark plasma sintering. Among a variety of nanostructure types these materials contain regions of initial solid solution with nanometer sized inclusions of different compositions. In the present work the scattering of holes and phonons on nanoinclusions in such p-Bi{sub x}Sb{sub 1-x}Te{sub 3} based materials is considered. The change of transport coefficients due to this scattering mechanism is theoretically estimated. The estimations showed that the reduction of lattice thermal conductivity (about 12-13%) for nanoinclusions of Bi{sub 2}Te{sub 3}-Sb{sub 2}Te{sub 3} solid solution with different compositions is much greater than the change in power factor. Therefore the corresponding increase of the thermoelectric figure of merit for this case is determined mainly by phonon scattering. Also it is shown that the results of estimations depend on phonon spectrum approximation, e.g. in the case of sine-shaped instead of linear phonon spectrum the estimations give two times higher thermal conductivity reduction. - Graphical abstract: Relative phonon thermal conductivity {kappa}{sub ph} change (black line) due to nanoinclusion scattering versus nanoinclusion radius a, and relative thermoelectric power factor change (red line) due to nanoinclusion scattering versus chemical potential {mu} at nanoinclusion size a=1.5 nm and U{sub 0}=-0.146 eV. Highlights: Black-Right-Pointing-Pointer p-Bi{sub x}Sb{sub 1-x}Te{sub 3} solid solutions with nanosized inclusions were considered. Black-Right-Pointing-Pointer Selective hole scattering can increase power factor at high carrier concentrations. Black-Right-Pointing-Pointer Lattice thermal conductivity estimations depend on phonon spectrum approximation. Black-Right-Pointing-Pointer Phonon scattering can reduce lattice thermal conductivity by about 12-13%. Black
Adams, M.E.; Marshall, T.L.; Rowley, R.L.
1998-07-01
Absorption rates of gaseous CO{sub 2} into aqueous blends of N-methyldiethanolamine (MDEA) and diethanolamine (DEA) and of gaseous H{sub 2}S into aqueous MDEA were measured in a quiescent, inverted-tube diffusiometer by monitoring the rate of pressure drop. A numerical model for absorption, diffusion, and reaction of CO{sub 2} and H{sub 2}S in blends of MDEA, DEA, and water was developed. The model was used to regress diffusion coefficients of bicarbonate, carbamate, and MDEAH{sub 2}CO{sub 3} for the case of CO{sub 2} absorption and of bisulfide ion for the case of H{sub 2}S absorption from measured absorption rates. CO{sub 2} absorption rates and diffusion coefficients of bicarbonate, carbamate, and MDEAH{sub 2}CO{sub 3} were obtained at 298.2 K and 318.2 K in aqueous solutions containing 50 mass % total amine at DEA:MDEA mole ratios of 1:20, 1:4, 1L3, and 2:3. H{sub 2}S absorption rates and diffusion coefficients of bisulfide ion were obtained at 298.2 K and 318.2 K in aqueous solutions containing 20, 35, and 50 mass % MDEA.
NASA Astrophysics Data System (ADS)
Perico, Angelo; La Ferla, Roberto; Freed, Karl F.
1987-05-01
Numerical calculations are presented for the frequency dependent Huggins coefficient based on the formal derivation provided in paper I using the dynamical multiple scattering theory for discrete Gaussian chains. The calculations employ fast Fourier transform methods and confirm the analytic complexity of this frequency dependence as previously anticipated from our calculations of the concentration dependence of the normal mode autocorrelation function. The harmonic spring model is considered because this simple limit is amenable to closed form solution, displaying the frequency dependence of the relaxation rates and providing a useful check on the difficult numerical computations for higher numbers n of beads. The steady state Huggins coefficient is also calculated with carefully optimized Gauss-Laguerre quadrature methods which permit extrapolation to n→∞. The calculated steady state value of 0.33 lies below experimental data for theta solutions, and an extensive discussion of the experimental data is provided to understand the discrepancy. One major factor, suggested by Schrag, arises from a strong concentration dependence of the individual bead friction coefficient.
Giachini, Lisa; Francia, Francesco; Mallardi, Antonia; Palazzo, Gerardo; Carpenè, Emilio; Boscherini, Federico; Venturoli, Giovanni
2005-01-01
Binding of transition metal ions to the reaction center (RC) protein of the photosynthetic bacterium Rhodobacter sphaeroides has been previously shown to slow light-induced electron and proton transfer to the secondary quinone acceptor molecule, QB. On the basis of x-ray diffraction at 2.5 Å resolution a site, formed by AspH124, HisH126, and HisH128, has been identified at the protein surface which binds Cd2+ or Zn2+. Using Zn K-edge x-ray absorption fine structure spectroscopy we report here on the local structure of Zn2+ ions bound to purified RC complexes embedded into polyvinyl alcohol films. X-ray absorption fine structure data were analyzed by combining ab initio simulations and multiparameter fitting; structural contributions up to the fourth coordination shell and multiple scattering paths (involving three atoms) have been included. Results for complexes characterized by a Zn to RC stoichiometry close to one indicate that Zn2+ binds two O and two N atoms in the first coordination shell. Higher shell contributions are consistent with a binding cluster formed by two His, one Asp residue, and a water molecule. Analysis of complexes characterized by ∼2 Zn ions per RC reveals a second structurally distinct binding site, involving one O and three N atoms, not belonging to a His residue. The local structure obtained for the higher affinity site nicely fits the coordination geometry proposed on the basis of x-ray diffraction data, but detects a significant contraction of the first shell. Two possible locations of the second new binding site at the cytoplasmic surface of the RC are proposed. PMID:15613631
NASA Astrophysics Data System (ADS)
Eleftheriadis, Konstantinos; Kalogridis, Athina-Cerise; Vratolis, Sterios; Fiebig, Markus
2016-04-01
Light absorbing carbon in atmospheric aerosol plays a critical role in radiative forcing and climate change. Despite the long term measurements across the Arctic, comparing data obtained by a variety of methods across stations requires caution. A method for extracting the aerosol absorption coefficient from data obtained over the decades by filter based instrument is still under development. An IASOA Aerosol working group has been initiated to address this and other cross-site aerosol comparison opportunities. Continuous ambient measurements of EBC/light attenuation by means of a Magee Sci. AE-31 aethalometer operating at the Zeppelinfjellet station (474 m asl; 78°54'N, 11°53'E), Ny Ålesund, Svalbard, have been available since 2001 (Eleftheriadis et al, 2009), while a new aethalometer model (AE33, Drinovec et al, 2014) has been installed to operate in parallel from the same inlet since June 2015. Measurements are recorded by a Labview routine collecting all available parameters reported by the two instrument via RS232 protocol. Data are reported at 1 and 10 minute intervals as averages for EBC (μg m-3) and aerosol absorption coefficients (Mm-1) by means of routine designed to report Near Real Time NRT data at the EBAS WDCA database (ebas.nilu.no) Results for the first 6 month period are reported here in an attempt to evaluate comparative performance of the two instruments in terms of their response with respect to the variable aerosol load of light absorbing carbon during the warm and cold seasons found in the high arctic. The application of available conversion schemes for obtaining the absorption coefficient by the two instruments is found to demonstrate a marked difference in their output. During clean periods of low aerosol load (EBC < 30 ng m-3), the two instruments display a better agreement with regression slope for the 880 nm signal between the two at ~ 0.9 compared to a slope at ~ 0.6 during the period of higher absorbing carbon loads (400< EBC<30 ng m
NASA Astrophysics Data System (ADS)
Kugeiko, M. M.; Lisenko, S. A.
2008-04-01
An easily automated method for the determination of the hematocrit C V of human blood from the extinction and small-angle scattering coefficients measured at radiation wavelengths of 0.37, 0.76, and 0.98 μm of semiconductor laser sources is proposed. The method does not require the solution of inverse problems and a priori information on the refractive index of erythrocytes. The effects that the measurement errors of the optical characteristics of blood, the dispersion of the refractive index, and the variations in the parameters of the distribution function of erythrocytes have on the determination accuracy of C V are estimated. The possibility of determining C V of whole blood is demonstrated.
Protasenko, Vladimir; Bacinello, Daniel; Kuno, Masaru
2006-12-21
Absorption cross-sections and corresponding molar extinction coefficients of solution-based CdSe and CdTe nanowires (NWs) are determined. Chemically grown semiconductor NWs are made via a recently developed solution-liquid-solid (SLS) synthesis, employing low melting Au/Bi bimetallic nanoparticle "catalysts" to induce one-dimensional (1D) growth. Resulting wires are highly crystalline and have diameters between 5 and 12 nm as well as lengths exceeding 10 microm. Narrow diameters, below twice the corresponding bulk exciton Bohr radius of each material, place CdSe and CdTe NWs within their respective intermediate to weak confinement regimes. Supporting this are solution linear absorption spectra of NW ensembles showing blue shifts relative to the bulk band gap as well as structure at higher energies. In the case of CdSe, the wires exhibit band edge emission as well as strong absorption/emission polarization anisotropies at the ensemble and single-wire levels. Analogous photocurrent polarization anisotropies have been measured in recently developed CdSe NW photodetectors. To further support fundamental NW optical/electrical studies as well as to promote their use in device applications, experimental absorption cross-sections are determined using correlated transmission electron microscopy, UV/visible extinction spectroscopy, and inductively coupled plasma atomic emission spectroscopy. Measured CdSe NW cross-sections for 1 microm long wires (diameters, 6-42 nm) range from 6.93 x 10(-13) to 3.91 x 10(-11) cm2 at the band edge (692-715 nm, 1.73-1.79 eV) and between 3.38 x 10(-12) and 5.50 x 10(-11) cm2 at 488 nm (2.54 eV). Similar values are obtained for 1 microm long CdTe NWs (diameters, 7.5-11.5 nm) ranging from 4.32 x 10(-13) to 5.10 x 10(-12) cm2 at the band edge (689-752 nm, 1.65-1.80 eV) and between 1.80 x 10(-12) and 1.99 x 10(-11) cm2 at 2.54 eV. These numbers compare well with previous theoretical estimates of CdSe/CdTe NW cross-sections far to the blue of the
NASA Astrophysics Data System (ADS)
Kaya, Necati; Tıraşoğlu, Engin; Apaydın, Gökhan; Aylıkcı, Volkan; Cengiz, Erhan
2007-08-01
The K-shell absorption jump factors and jump ratios were derived from new mass attenuation coefficients measured using an energy dispersive X-ray fluorescence (EDXRF) spectrometer for Tm, Yb elements being Tm 2O 3, Yb 2O 3 compounds and pure Lu, Hf, Ta, W, Re and Os. The measurements, in the region 56-77 keV, were done in a transmission geometry utilizing the K α1 , K α2 , K β1 and K β2 X- rays from different secondary source targets (Yb, Ta, Os, W, Re and Ir, etc.) excited by the 123.6 keV γ-photons from an 57Co annular source and detected by an Ultra-LEGe solid state detector with a resolution of 150 eV at 5.9 keV. Experimental results have been compared with theoretically calculated values. The measured values of Tm, Yb, Lu, Hf, Ta, W, Re and Os are reported here for the first time.
NASA Astrophysics Data System (ADS)
Corrales, L. R.; García, J.; Wilms, J.; Baganoff, F.
2016-05-01
Small angle scattering by dust grains causes a significant contribution to the total interstellar extinction for any X-ray instrument with sub-arcminute resolution (Chandra, Swift, XMM-Newton). However, the dust-scattering component is not included in the current absorption models: phabs, TBabs, and TBnew. We simulate a large number of Chandra spectra to explore the bias in the spectral fit and NH measurements obtained without including extinction from dust scattering. We find that without incorporating dust scattering, the measured NH will be too large by a baseline level of 25 per cent. This effect is modulated by the imaging resolution of the telescope, because some amount of unresolved scattered light will be captured within the aperture used to extract point source information. In high-resolution spectroscopy, dust scattering significantly enhances the total extinction optical depth and the shape of the photoelectric absorption edges. We focus in particular on the Fe-L edge at 0.7 keV, showing that the total extinction template fits well to the high-resolution spectrum of three X-ray binaries from the Chandra archive: GX 9+9, XTE J1817-330, and Cyg X-1. In cases where dust is intrinsic to the source, a covering factor based on the angular extent of the dusty material must be applied to the extinction curve, regardless of angular imaging resolution. This approach will be particularly relevant for dust in quasar absorption line systems and might constrain clump sizes in active galactic nuclei.
NASA Astrophysics Data System (ADS)
Kozlov, Valerii S.; Rakhimov, Rustam F.; Shmargunov, Vladimir P.
2015-11-01
The possibility of determining the Black Carbon (BC) concentration and its size distribution in submicron aerosol from data of polarization spectronephelometric measurements of angular aerosol scattering is demonstrated for the first time. The data of simultaneous nephelometric and aethalometric measurements of BC concentration in wood smoke are compared. The inverse problem is solved from measurements of 40 polarization components of spectral coefficients of angular scattering, and aerosol filling factors and the imaginary part of the complex refractive indexes are determined for subfractions of ultrafine- (radii of 30-100 nm), fine- (100-430 nm), and coarse-disperse (430-770 nm) particles. Then the total BC concentration, its size distribution, and BC fraction are estimated in the approximation of homogeneous volume internal mixture of BC and nonabsorbing matter. The analysis shows that at the long evolution of smoke aerosol, nephelometric and aethalometric estimates of the BC concentrations are in a good agreement. The discrepancy averages about 16% for concentrations varying in a range 30-1000 μg/m3.
NASA Astrophysics Data System (ADS)
Jiang, Yuanyuan; McKeirnan, Kelci; Piao, Daqing; Bartels, Kenneth E.
2011-03-01
Extrusion or protrusion of an intervertebral disc is a common, frequently debilitating, painful, and sometimes fatal neurologic disease in the chondrodystrophic dog (dachshund, Pekingese, etc.). A similar condition of intervertebral disc degeneration with extrusion/protrusion is also a relatively common neurologic condition in human patients. Degeneration of the relatively avascular chondrodystrophoid intervertebral disc is associated with loss of water content, increased collagen, and deposits of calcified mineral in the nucleus pulposus. Current diagnostic methods have many limitations for providing accurate information regarding disc composition in situ prior to surgical intervention. Disc composition (i.e., mineralization), can influence the type of treatment regime and potentially prognosis and recurrence rates. The objective of this study is to investigate the feasibility of using a fiber-needle spectroscopy sensor to analyze the changes of tissue compositions involved in the chondrodystrophoid condition of the canine intervertebral disc. The nucleous pulposus, in which the metaplastic process / degeneration develops, is approximately 2mm thick and 5mm in diameter in the dachshund-sized dog. It lies in the center of the disc, surrounded by the annulus fibrosis and is enclosed by cartilaginous vertebral endplates cranially and caudally. This "shallow-and-small-slab" geometry limits the configuration of a fiber probe to sense the disc tissue volume without interference from the vertebrae. A single-fiber sensor is inserted into a 20 gauge myelographic spinal needle for insertion into the disc in situ and connected via a bifurcated fiber to the light source and a spectrometer. A tungsten light source and a 940nm light-emitting-diode are combined for spectral illumination covering VIS/NIR with expected improved sensitivity to water. Analysis of the reflectance spectra is expected to provide information of scattering and absorption compositions of tissue in
NASA Technical Reports Server (NTRS)
Nelson, David D., Jr.; Schiffman, Aram; Nesbitt, David J.; Orlando, John J.; Burkholder, James B.
1990-01-01
FTIR emission/absorption spectroscopy is used to measure the relative intensities of 88 pairs of rovibrational transitions of OH(X2Pi) distributed over 16 vibrational bands. The experimental technique used to obtain the Einstein A ratios is discussed. The dipole moment function which follows from the intensity ratios along with Einstein A coefficients calculated from mu(r) is presented.
Paper area density measurement from forward transmitted scattered light
Koo, Jackson C.
2001-01-01
A method whereby the average paper fiber area density (weight per unit area) can be directly calculated from the intensity of transmitted, scattered light at two different wavelengths, one being a non-absorpted wavelength. Also, the method makes it possible to derive the water percentage per fiber area density from a two-wavelength measurement. In the optical measuring technique optical transmitted intensity, for example, at 2.1 microns cellulose absorption line is measured and compared with another scattered, optical transmitted intensity reference in the nearby spectrum region, such as 1.68 microns, where there is no absorption. From the ratio of these two intensities, one can calculate the scattering absorption coefficient at 2.1 microns. This absorption coefficient at this wavelength is, then, experimentally correlated to the paper fiber area density. The water percentage per fiber area density can be derived from this two-wavelength measurement approach.
Ultraviolet (250-550 nm) absorption spectrum of pure water.
Mason, John D; Cone, Michael T; Fry, Edward S
2016-09-01
Data for the spectral light absorption of pure water from 250 to 550 nm have been obtained using an integrating cavity made from a newly developed diffuse reflector with a very high UV reflectivity. The data provide the first scattering-independent measurements of absorption coefficients in the spectral gap between well-established literature values for the absorption coefficients in the visible (>400 nm) and UV (<200 nm). A minimum in the absorption coefficient has been observed in the UV at 344 nm; the value is 0.000811±0.000227 m^{-1}. PMID:27607297
NASA Astrophysics Data System (ADS)
Aptowicz, Kevin B.; Pan, Yong-Le; Pinnick, Ronald G.; Hill, Steven C.; Tober, Richard L.; Chang, Richard K.; Bronk, Burt V.
2004-03-01
Real-time and in-situ detection and discrimination of aerosol particles, especially bio-aerosols, continues to be an important challenge. The technique labeled TAOS (Two-dimensional Angular Optical Scattering) characterizes particles based upon the angular distribution of elastically scattered light. The detected angular distribution of light, labeled the TAOS pattern, depends upon the particle"s shape, size, surface features, and its complex refractive index. Thus, the absorptive properties of a particle affect the TAOS pattern. Furthermore, we expect to use this change in the TAOS pattern, which occurs when the particle absorption band includes the input wavelength, to characterize the strength of the absorption. Thus, by illuminating a particle in the mid-infrared wavelength range, high frequency vibrational modes that are unique to the aerosol can be reached and quantified. Spherical aerosol particles (in the diameter range of 50-60 micrometers) were generated via a droplet generator and illuminated by an Interband Cascade (IC) laser designed to emit in the 3-5 micrometers wavelength range. The TAOS pattern of the elastically scattered light was detected with an InSb-focal-plane-array infrared camera.
NASA Astrophysics Data System (ADS)
Al-Hawat, Sharif
2013-02-01
Infrared (IR) absorption in the spectral range of (1071.88-1084.62 cm-1) vs. pressure in chlorodifluoromethane (CFC-22, F-22, and CHClF2) was studied using a tunable continuous wave (CW) CO2 laser radiation on 9R branch lines with a maximum output power of about 2.12 W, provided with an absorber cell located outside the laser cavity. The absorption coefficients were determined vs. the gas pressure between 0.2 mbar and 170 mbar at lines from 9R branch for CFC-22. The frequency shifts of the absorption lines of CFC-22 in relative to the central frequencies of laser lines were calculated vs. the pressure on the basis of these absorption coefficients. The chosen lines were selected according to IR spectrum of the studied gas given by HITRAN cross section database. So the absorption was achieved for CFC-22 at the spectral lines of 9R branch situated from 9R (10) to 9R (30) emitted by a tunable CW CO2 laser. The absorption cross sections of CFC-22 determined in this work were compared with the relevant data given by HITRAN cross section database and a reasonable agreement was observed.
NASA Astrophysics Data System (ADS)
Chen, Jun; Cui, Tingwei; Quan, Wenting
2015-01-01
this study, a neural network-based four-band model (NNFM) for the global oceanic and coastal waters has been developed in order to retrieve the total absorption coefficients a(λ). The applicability of the quasi-analytical algorithm (QAA) and NNFM models is evaluated by five independent data sets. Based on the comparison of a(λ) predicted by these two models with the field measurements taken from the global oceanic and coastal waters, it was found that both the QAA and NNFM models had good performances in deriving a(λ), but that the NNFM model works better than the QAA model. The results of the QAA model-derived a(λ), especially in highly turbid waters with strong backscattering properties of optical activity, was found to be lower than the field measurements. The QAA and NNFM models-derived a(λ) could be obtained from the MODIS data after atmospheric corrections. When compared with the field measurements, the NNFM model decreased by a 0.86-24.15% uncertainty (root-mean-square relative error) of the estimation from the QAA model in deriving a(λ) from the Bohai, Yellow, and East China seas. Finally, the NNFM model was applied to map the global climatological seasonal mean a(443) for the time range of July 2002 to May 2014. As expected, the a(443) value around the coastal regions was always larger than the open ocean around the equator. Viewed on a global scale, the oceans at a high latitude exhibited higher a(443) values than those at a low latitude.
Stadler, H; Klock, E; Skritek, P; Mach, R L; Zerobin, W; Farnleitner, A H
2010-01-01
Because spring water quality from alpine karst aquifers can change very rapidly during event situations, water abstraction management has to be performed in near real-time. Four summer events (2005-2008) at alpine karst springs were investigated in detail in order to evaluate the spectral absorption coefficient at 254 nm (SAC254) as a real-time early warning proxy for faecal pollution. For the investigation Low-Earth-Orbit (LEO) Satellite-based data communication between portable hydrometeorological measuring stations and an automated microbiological sampling device was used. The method for event triggered microbial sampling and analyzing was already established and described in a previous paper. Data analysis including on-line event characterisation (i.e. precipitation, discharge, turbidity, SAC254) and comprehensive E. coli determination (n>800) indicated that SAC254 is a useful early warning proxy. Irrespective of the studied event situations SAC254 always increased 3 to 6 hours earlier than the onset of faecal pollution, featuring different correlation phases. Furthermore, it seems also possible to use SAC254 as a real-time proxy parameter for estimating the extent of faecal pollution after establishing specific spring and event-type calibrations that take into consideration the variability of the occurrence and the transferability of faecal material It should be highlighted that diffuse faecal pollution from wildlife and live stock sources was responsible for spring water contamination at the investigated catchments. In this respect, the SAC254 can also provide useful information to support microbial source tracking efforts where different situations of infiltration have to be investigated. PMID:20962406
NASA Astrophysics Data System (ADS)
Du Le, Vinh Nguyen; Patterson, Michael S.; Farrell, Thomas J.; Hayward, Joseph E.; Fang, Qiyin
2015-12-01
The ability to recover the intrinsic fluorescence of biological fluorophores is crucial to accurately identify the fluorophores and quantify their concentrations in the media. Although some studies have successfully retrieved the fluorescence spectral shape of known fluorophores, the techniques usually came with heavy computation costs and did not apply for strongly absorptive media, and the intrinsic fluorescence intensity and fluorophore concentration were not recovered. In this communication, an experimental approach was presented to recover intrinsic fluorescence and concentration of fluorescein in the presence of hemoglobin (Hb). The results indicated that the method was efficient in recovering the intrinsic fluorescence peak and fluorophore concentration with an error of 3% and 10%, respectively. The results also suggested that chromophores with irregular absorption spectra (e.g., Hb) have more profound effects on fluorescence spectral shape than chromophores with monotonic absorption and scattering spectra (e.g., black India ink and polystyrene microspheres).
NASA Technical Reports Server (NTRS)
Magi, Brian I.; Hobbs, Peter V.; Schmid, Beat; Redermann, Jens
2003-01-01
Airborne in situ measurements of vertical profiles of aerosol light scattering, light absorption, and single scattering albedo (omega (sub 0)) are presented for a number of locations in southern Africa during the dry, biomass burning season. Features of the profiles include haze layers, clean air slots, and marked decreases in light scattering in passing from the boundary layer into the free troposphere. Frequency distributions of omega (sub 0) reflect the strong influence of smoke from biomass burning. For example, during a period when heavy smoke was advected into the region from the north, the mean value of omega (sub 0) in the boundary layer was 0.81 +/- 0.02 compared to 0.89 +/- 0.03 prior to this intrusion. Comparisons of layer aerosol optical depths derived from the in situ measurements with those measured by a Sun photometer aboard the aircraft show excellent agreement.
NASA Astrophysics Data System (ADS)
Tao, Jiangchuan; Zhao, Chunsheng
2016-04-01
Hygroscopic growth of aerosol particles can significantly affect their single-scattering albedo (ω), and consequently alters the aerosol effect on tropospheric photochemistry. In this study, the impact of aerosol hygroscopic growth on ω and its application to the NO2 photolysis rate coefficient (JNO2) are investigated for a typical aerosol particle population in the North China Plain (NCP). The variations of aerosol optical properties with relative humidity (RH) are calculated using a Mie theory aerosol optical model, on the basis of field measurements of number-size distribution and hygroscopic growth factor (at RH values above 90 %) from the 2009 HaChi (Haze in China) project. Results demonstrate that ambient ω has pronouncedly different diurnal patterns from ω measured at dry state, and is highly sensitive to the ambient RHs. Ambient ω in the NCP can be described by a dry state ω value of 0.863, increasing with the RH following a characteristic RH dependence curve. A Monte Carlo simulation shows that the uncertainty ofω from the propagation of uncertainties in the input parameters decreases from 0.03 (at dry state) to 0.015 (RHs > 90 %). The impact of hygroscopic growth on ω is further applied in the calculation of the radiative transfer process. Hygroscopic growth of the studied aerosol particle population generally inhibits the photolysis of NO2 at the ground level, whereas accelerates it above the moist planetary boundary layer. Compared with dry state, the calculated JNO2 at RH of 98 % at the height of 1 km increases by 30.4 %, because of the enhancement of ultraviolet radiation by the humidified scattering-dominant aerosol particles. The increase of JNO2 due to the aerosol hygroscopic growth above the upper boundary layer may affect the tropospheric photochemical processes and this needs to be taken into account in the atmospheric chemical models.
NASA Astrophysics Data System (ADS)
Loria Salazar, S.; Arnott, W. P.; Moosmuller, H.; Colucci, D.
2012-12-01
Reno, Nevada, USA is subject to typical urban aerosol, wind-blown dust, and occasional biomass burning smoke from anthropogenic and natural fires. Reno has complex air flow at levels relevant for aerosol transport. At times recirculating mountain and urban flow arrives from the Sierra Nevada, San Francisco, CA and Sacramento, CA. The urban plumes are further modified by biogenic forest emissions and secondary aerosol formation during transport over the Sierra Nevada Mountains to Reno. This complicates the use of MODIS aerosol optical depth (AOD) for air quality measurements in Reno. Our laboratory at the University of Nevada Reno has collocated multispectral photoacoustic instruments and reciprocal nephelometers to measure light absorption and light scattering coefficients as well as an AERONET operated CIMEL CE-318 ground-based sunphotometer. Preliminary measurements from August 2011 indicate substantially larger Cimel AOD than could be accounted for by use of the in situ aerosol extinction measurements combined with mixing height estimate. This poster presents new results comparing AERONET AOD and single scattering albedo and MODIS AOD with in situ measurements for summer and fall 2012, along with extensive back trajectory analysis, to evaluate conditions when satellite measurement may be useful for air pollution applications in Reno.
NASA Astrophysics Data System (ADS)
Orlov, Yu. V.; Nikitina, L. I.
2014-04-01
The properties of the first excited state of the 8Be* nucleus (2+) are studied. This state corresponds to the resonance in αα scattering at the energy of E α = E 2 ≈ 3 MeV. Use is made of an expansion of the effective-range function K( k 2). The function K( k 2) is sensitive to the value of E 2. A fit to experimental data on the dependence of the Coulomb-nuclear phase shift δ {2/C} on the energy E α leads to an E 2 value that is smaller than the average value obtained from an analysis of various reactions. The experimental behavior of δ {2/C} ( E α) cannot be described satisfactorily by fixing the average value of E 2. The renormalized nuclear vertex function for the process α + α → 8Be*(2+) and the asymptotic normalization coefficient for the respectiveGamow wave function are calculated by using the set of parameter values found in the present study.
NASA Technical Reports Server (NTRS)
Siegman, A. E.; Wang, S. C.
1970-01-01
Absorptivity, transition probability and collision broadening frequency of dimethylether at 3.51 micron He-Xe laser wavelength, noting pressure dependence, transition lifetime and saturation intensity
NASA Astrophysics Data System (ADS)
Penilla, E. H.; Hardin, C. L.; Kodera, Y.; Basun, S. A.; Evans, D. R.; Garay, J. E.
2016-01-01
Light scattering due to birefringence has prevented the use of polycrystalline ceramics with anisotropic optical properties in applications such as laser gain media. However, continued development of processing technology has allowed for very low porosity and fine grains, significantly improving transparency and is paving the way for polycrystalline ceramics to be used in demanding optical applications. We present a method for producing highly transparent Cr3+ doped Al2O3 (ruby) using current activated pressure assisted densification. The one-step doping/densification process produces fine grained ceramics with well integrated (doped) Cr, resulting in good absorption and emission. In order to explain the light transmission properties, we extend the analytical model based on the Rayleigh-Gans-Debye approximation that has been previously used for undoped alumina to include absorption. The model presented captures reflection, scattering, and absorption phenomena in the ceramics. Comparison with measured transmission confirms that the model adequately describes the properties of polycrystalline ruby. In addition the measured emission spectra and emission lifetime are found to be similar to single crystals, confirming the high optical quality of the ceramics.
NASA Astrophysics Data System (ADS)
El-Kader, M. S. A.; Mostafa, S. I.; Bancewicz, T.; Maroulis, G.
2014-08-01
The rototranslational collision-induced absorption (CIA) at different temperatures and collision-induced light scattering (CILS) at room temperature of nitrogen gas are analyzed in terms of new isotropic intermolecular potential, multipole-induced dipole functions and interaction-induced pair polarizability models, using quantum spectral lineshape computations. The irreducible spherical form for the induced operator of light scattering mechanisms was determined. The high frequency wings are discussed in terms of the collision-induced rotational Rayleigh effect and estimates for the dipole-octopole polarizability E4, is obtained and checked with the ab initio theoretical value. The quality of the present potential has been checked by comparing between calculated and experimental thermo-physical and transport properties over a wide temperature range, which are found to be in good agreement.
NASA Astrophysics Data System (ADS)
Pan, Wenbo; Huang, Cheng; Pu, Mingbo; Ma, Xiaoliang; Cui, Jianhua; Zhao, Bo; Luo, Xiangang
2016-02-01
The absorptive and radiative losses are two fundamental aspects of the electromagnetic responses, which are widely occurring in many different systems such as waveguides, solar cells, and antennas. Here we proposed a metasurface to realize the control of the absorptive and radiative loss and to reduce the radar cross section (RCS) in multi-frequency bands. The anti-phase gradient and absorptive metasurfaces were designed that consists of metallic square patch and square loop structure inserted with resistors, acting as an phase gradient material in the X and Ku band, while behaving as an absorber in the S band. The simulation and experiment results verified the double-band, wideband and polarization-independent RCS reduction by the absorptive and anti-phase gradient metasurfaces.