Tonoue, Ryota; Katsura, Makoto; Hamamoto, Mai; Bessho, Hiroki; Nakashima, Satoru
2014-01-01
A method was developed to obtain the absorption coefficient spectrum of a grain of coal (as small as 10(-7)) in the region of aliphatic and aromatic C-H stretching bands (2700-3200 cm(-1)) using infrared transflection microspectroscopy. In this method, the complex refractive index n - ik was determined using an optimization algorithm with the Kramers-Kronig transform so that the calculated transflection spectrum from the Fresnel equation corresponded to the measured one. The obtained absorption coefficients were compared with the bulk values determined from the potassium bromide (KBr) pellet measurement method.
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.
Absorption Coefficient of Alkaline Earth Halides.
1980-04-01
levels . As a natural consequence, the magnitude of the absorption coefficient is the key parameter in selecting laser window materials. Over the past...of as can be achieved through improved crystal growing techniques and surface polishing. 2.5. Urbach’s Rule A central question for the development of...high absorption levels , inaccuracies progressively increasing with decreasing absorption level , a natural consequence of decreasing in instrumental
[Experimental determination of the absorption coefficients of biological tissues].
Kovtun, A V; Kondrat'ev, V S; Terekhov, D V
1980-01-01
Procedure is presented for studying the coefficient of biological tissue absorption of radiation with the wavelength lambda = 1.06 mkm. The absorption coefficient is determined by the temperature values of biological tissue experimentally measured with thermopairs. The coherent radiation current falls on the surface of biological tissue. A mathematical model is formulated for biological tissue heating with radiation. Solution of Furier equation obtained by means of Green function is given. Using the relationship found, the energy absorbed by the biological tissue was calculated and the absorption coefficient of radiation with lambda - 1.06 mkm was determined. The results were analysed and the error of the obtained values of absorption coefficients of biological tissues under study were determined.
Absorption coefficient instrument for turbid natural waters.
Friedman, E; Poole, L; Cherdak, A; Houghton, W
1980-05-15
An instrument has been developed that directly measures the multispectral absorption coefficient of turbid natural water. The design incorporates methods for compensation of variation in the internal light source intensity, correction of the spectrally dependent nature of the optical elements, and correction for variation in background light level. When used in conjunction with a spectrally matched total attenuation instrument, the spectrally dependent scattering coefficient can also be derived. Systematic errors associated with multiple scattering have been estimated using Monte Carlo techniques.
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.
Optical absorption coefficients of pure water
NASA Astrophysics Data System (ADS)
Lu, Zheng; Zhao, Xianzhen; Fry, Edward S.
2002-10-01
The integrating cavity absorption meter(ICAM), which is independent of scattering effect, is used to measure the absolute values of small optical absorption coefficients of liquid. A modified ICAM is being used to measure the absorption of water in the wavelength range 300 to 700 nm. The ultrapure water produced by a two-stages water purification system reaches Type I quality. This is equal to or better than ASTM,CAP and NCCLS water quality standards. To avoid the fact that dissolved oxygen absorbs ultraviolet light due to the photochemical effect, the water sample is delivered through a nitrogen sealed system which will prevent the sample from contacting with oxygen. A compassion of our absorption spectrum with other existing data is given.
Absorption coefficient instrument for turbid natural waters
NASA Astrophysics Data System (ADS)
Friedman, E.; Cherdak, A.; Poole, L.; Houghton, W.
1980-05-01
The paper presents an instrument that directly measures multispectral absorption coefficient of turbid natural water. Attention is given to the design, which is shown to incorporate methods for the compensation of variation in the internal light source intensity, correction of the spectrally dependent nature of the optical elements, and correction for variation in the background light level. In addition, when used in conjunction with a spectrally matched total attenuation instrument, the spectrally dependent scattering coefficient can also be derived. Finally, it is reported that systematic errors associated with multiple scattering have been estimated using Monte Carlo techniques.
Absorption coefficient instrument for turbid natural waters
NASA Technical Reports Server (NTRS)
Friedman, E.; Cherdak, A.; Poole, L.; Houghton, W.
1980-01-01
The paper presents an instrument that directly measures multispectral absorption coefficient of turbid natural water. Attention is given to the design, which is shown to incorporate methods for the compensation of variation in the internal light source intensity, correction of the spectrally dependent nature of the optical elements, and correction for variation in the background light level. In addition, when used in conjunction with a spectrally matched total attenuation instrument, the spectrally dependent scattering coefficient can also be derived. Finally, it is reported that systematic errors associated with multiple scattering have been estimated using Monte Carlo techniques.
Prediction of absorption coefficients by pulsed laser induced photoacoustic measurements.
Priya, Mallika; Satish Rao, B S; Ray, Satadru; Mahato, K K
2014-06-05
In the current study, a pulsed laser induced photoacoustic spectroscopy setup was designed and developed, aiming its application in clinical diagnostics. The setup was optimized with carbon black samples in water and with various tryptophan concentrations at 281nm excitations. The sensitivity of the setup was estimated by determining minimum detectable concentration of tryptophan in water at the same excitation, and was found to be 0.035mM. The photoacoustic experiments were also performed with various tryptophan concentrations at 281nm excitation for predicting optical absorption coefficients in them and for comparing the outcomes with the spectrophotometrically-determined absorption coefficients for the same samples. Absorption coefficients for a few serum samples, obtained from some healthy female volunteers, were also determined through photoacoustic and spectrophotometric measurements at the same excitations, which showed good agreement between them, indicating its clinical implications.
Methane Absorption Coefficients for the Jovian Planets and Titan
NASA Astrophysics Data System (ADS)
Karkoschka, Erich; Tomasko, M. G.
2009-09-01
We combined 11 data sets of methane transmission measurements within 0.4-5.5 micrometer wavelength in order to better understand the variation of methane absorption with temperature and pressure for conditions in the atmospheres of the Jovian planets and Titan. Eight data sets are based on published laboratory measurements. Another two data sets come from two spectrometers onboard the Huygens probe that measured methane absorption inside Titan's atmosphere (Tomasko et al. 2008, PSS 56, 624). We present the data with a refined analysis. The last data set consists of Hubble Space Telescope images of Jupiter taken in 2005 and 2007 as Ganymede started to be occulted by Jupiter. Using Ganymede as a light source, we probed Jupiter's stratosphere with large methane pathlengths. Below 1000 nm wavelength, we find methane absorption coefficients generally similar to those by Karkoschka (1998, Icarus 133, 134). We added descriptions of temperature and pressure dependence, which are typically small in this wavelength range. Data in this wavelength range are consistent with each other, except between 882 and 902 nm wavelength where laboratory data predict larger absorptions in the Jovian atmospheres than observed. We present possible explanations. Above 1000 nm, our analysis of the Huygens data confirms methane absorption coefficients by Irwin et al. (2006, Icarus 181, 309) at their laboratory temperatures. Huygens data are consistent with Irwin's model of the pressure dependence of methane absorption. However, when large extrapolations were needed, such as from laboratory data above 200 K to Titan's temperatures near 80 K, Irwin's model of temperature dependence predicts absorption coefficients up to 100 times lower than measured by Huygens. We combined Irwin's and Huygens' data to obtain more reliable methane absorption coefficients for the temperatures in the atmospheres of the Jovian planets and Titan. This research was supported by NASA grants NAG5-12014 and NNX08AE74G.
Determination of optical absorption coefficient with focusing photoacoustic imaging.
Li, Zhifang; Li, Hui; Zeng, Zhiping; Xie, Wenming; Chen, Wei R
2012-06-01
Absorption coefficient of biological tissue is an important factor for photothermal therapy and photoacoustic imaging. However, its determination remains a challenge. In this paper, we propose a method using focusing photoacoustic imaging technique to quantify the target optical absorption coefficient. It utilizes the ratio of the amplitude of the peak signal from the top boundary of the target to that from the bottom boundary based on wavelet transform. This method is self-calibrating. Factors, such as absolute optical fluence, ultrasound parameters, and Grüneisen parameter, can be canceled by dividing the amplitudes of the two peaks. To demonstrate this method, we quantified the optical absorption coefficient of a target with various concentrations of an absorbing dye. This method is particularly useful to provide accurate absorption coefficient for predicting the outcomes of photothermal interaction for cancer treatment with absorption enhancement.
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.
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.
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.
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.
Photon absorption potential coefficient as a tool for materials engineering
NASA Astrophysics Data System (ADS)
Akande, Raphael Oluwole; Oyewande, Emmanuel Oluwole
2016-09-01
Different atoms achieve ionizations at different energies. Therefore, atoms are characterized by different responses to photon absorption in this study. That means there exists a coefficient for their potential for photon absorption from a photon source. In this study, we consider the manner in which molecular constituents (atoms) absorb photon from a photon source. We observe that there seems to be a common pattern of variation in the absorption of photon among the electrons in all atoms on the periodic table. We assume that the electrons closest to the nucleus (En) and the electrons closest to the outside of the atom (Eo) do not have as much potential for photon absorption as the electrons at the middle of the atom (Em). The explanation we give to this effect is that the En electrons are embedded within the nuclear influence, and similarly, Eo electrons are embedded within the influence of energies outside the atom that there exists a low potential for photon absorption for them. Unlike En and Eo, Em electrons are conditioned, such that there is a quest for balance between being influenced either by the nuclear force or forces external to the atom. Therefore, there exists a higher potential for photon absorption for Em electrons than for En and Eo electrons. The results of our derivations and analysis always produce a bell-shaped curve, instead of an increasing curve as in the ionization energies, for all elements in the periodic table. We obtained a huge data of PAPC for each of the several materials considered. The point at which two or more PAPC values cross one another is termed to be a region of conflicting order of ionization, where all the atoms absorb equal portion of the photon source at the same time. At this point, a greater fraction of the photon source is pumped into the material which could lead to an explosive response from the material. In fact, an unimaginable and unreported phenomenon (in physics) could occur, when two or more PAPCs cross, and
NUMERICAL CALCULATION OF MAGNETOBREMSSTRAHLUNG EMISSION AND ABSORPTION COEFFICIENTS
Leung, Po Kin; Gammie, Charles F.; Noble, Scott C. E-mail: gammie@illinois.edu
2011-08-10
Magnetobremsstrahlung (MBS) emission and absorption play a role in many astronomical systems. We describe a general numerical scheme for evaluating MBS emission and absorption coefficients for both polarized and unpolarized light in a plasma with a general distribution function. Along the way we provide an accurate scheme for evaluating Bessel functions of high order. We use our scheme to evaluate the accuracy of earlier fitting formulae and approximations. We also provide an accurate fitting formula for mildly relativistic (kT/(m{sub e}c{sup 2}) {approx}> 0.5) thermal electron emission (and therefore absorption). Our scheme is too slow, at present, for direct use in radiative transfer calculations but will be useful for anyone seeking to fit emission or absorption coefficients in a particular regime.
Vapor-Phase Infrared Absorptivity Coefficient of HN1
2013-08-01
infrared spectrometer GC gas chromatography HD sulfur mustard HeNe helium–neon (laser) HgCdTe mercury–cadmium–telluride detector HN1, HN2, HN3...coefficient of the compound. 15. SUBJECT TERMS Vapor phase Saturator cell Infrared (IR) HN1 Vapor pressure Nitrogen mustard Vesicant...9 1 VAPOR-PHASE INFRARED ABSORPTIVITY COEFFICIENT OF HN1 1. INTRODUCTION The nitrogen mustards (HN1, HN2, and HN3) are similar to
NASA Astrophysics Data System (ADS)
Presser, Cary
2012-05-01
A laser-heating technique, referred as the laser-driven thermal reactor, was used in conjunction with laser transmissivity measurements to determine the absorption coefficient of particle-laden substrates (e.g., quartz-fiber filters). The novelty of this approach is that it analyzes a wide variety of specific samples (not just filtered samples) and overcomes measurement issues (e.g., absorption enhancement) associated with other filter-based particle absorption techniques. The absorption coefficient was determined for nigrosin-laden, quartz-fiber filters and the effect of the filter on the absorption measurements was estimated when compared to the isolated nigrosin results. The isolated nigrosin absorption coefficient compared favorably with Lorenz-Mie calculations for an idealized polydispersion of spherical particles (based on a measured nigronsin/de-ionized water suspension size distribution) dispersed throughout a volume equivalent to that of the nigrosin-laden filter. To validate the approach, the absorption coefficient of a nigrosin/de-ionized water suspension was in good agreement with results obtained from an ultraviolet/visible spectrometer. In addition, the estimated imaginary part of the refractive index from the Lorenz-Mie calculations compared well with literature values and was used to estimate the absorption coefficient of optically opaque packed nigrosin.
Ozone absorption coefficients' role in Dobson instrument ozone measurement accuracy
NASA Astrophysics Data System (ADS)
Basher, R. E.
1982-11-01
The differences of 10% or more between the laboratory measurements of UV absorption coefficients by different investigators indicate accuracies that are quite inadequate for current needs in the measurement of atmospheric ozone. The standard band-integrated set of coefficients now used with the Dobson instrument are mutually consistent to about 2%, but their absolute accuracy is still in question. The accurate calculation of band-integrated coefficients must take account of their dependence on source spectral irradiance, atmospheric spectral transmittance, mean ozone temperature, and instrument spectral transmittance. A careful examination shows that Komhyr's (1980) case for an error of about +5% in the standard Dobson AD ozone estimation is subject to large uncertainties and certain lacks of independence. The obvious solution to this accuracy problem lies in better laboratory measurements of ozone absorption.
Li, Xiaoqi; Jiang, Huabei
2013-02-21
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.
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.
Field testing of sound absorption coefficients in a classroom
NASA Astrophysics Data System (ADS)
Pettyjohn, Steve
2005-09-01
Formal procedures for determining the sound absorption coefficients of materials installed in the field do not exist. However, the U.S. Air Force requested such tests to prove that the sound-absorbing material used in classrooms at Beale AFB in Marysville, CA, met the specified NRC of 0.80. They permitted the use of two layers of 0.5-in. fiberboard or 1-in.-thick fiberglass panels to meet the specified NRC rating. Post-construction tests showed reverberation times longer than expected. Unrealistic sound-absorption coefficients for room finish materials had to be used with the Sabine equation to achieve agreement between the measured and predicted reverberation time. By employing the Fitzroy equation and generally published absorption coefficients for ceiling tile, carpet, and fiberboard, the model provided excellent agreement with the measured reverberation times. The NRC of the fiberboard was computed to be 0.35, agreeing with published data. Since this did not meet project specifications, the Fitzroy model was used to learn the type and quantity of material needed to meet design goals. Follow-up tests showed good agreement between the predicted and measured reverberation times with material added, and project specifications were met. Results are also compared with the requirements of ANSI 12.60.
NASA Astrophysics Data System (ADS)
Fry, Patrick M.; Sromovsky, L. A.
2009-09-01
Using new methane absorption coefficients from Karkoschka and Tomasko (2009, submitted to Icarus, "Methane Absorption Coefficients for the Jovian Planets from Laboratory, Huygens, and HST Data"), we fit Uranus near-IR spectra previously analyzed in Sromovsky et al. (2006, Icarus 182, 577-593, Fink and Larson, 1979 J- and H-band), Sromovsky and Fry (2008, Icarus 193, 252-266, 2006 NIRC2 J- and H-band, 2006 SpeX) using Irwin et al. (2006, Icarus 181, 309-319) methane absorption coefficients. Because the new absorption coefficients usually result in higher opacities at the low temperatures seen in Uranus' upper troposphere, our previously derived cloud altitudes are expected to generally rise to higher altitudes. For example, using Lindal et al. (1987, JGR 92, 14987-15001) model D temperature and methane abundance profiles, we are better able to fit the J-band 43-deg. south bright band with the new coefficients (chi-square=205, vs. 315 for Irwin), with the pressure of the upper tropospheric cloud decreasing to 1.6 bars (from 2.4 bars using Irwin coefficients). Improvements in fitting H-band spectra from the same latitude are not as readily obtained. Derived upper tropospheric cloud pressures are very similar using the two absorption datasets (1.6-1.7 bars), but the character of the fits differs. New Karkoschka and Tomasko coefficients better fit some details in the 1.5-1.58 micron region, but Irwin fits the broad absorption band wing at 1.61-1.62 microns better, and the fit chi-square values are similar (K&T: 243, Irwin: 220). Results for a higher methane concentration (Lindal et al. model F) were similar. Whether the new coefficients will simply raise derived altitudes across the planet or will result in fundamental changes in structure is as yet unclear. This work was suported by NASA planetary astronomy and planetary atmospheres programs.
IR absorption spectra of cellulose obtained from ozonated wood
NASA Astrophysics Data System (ADS)
Mamleeva, N. A.; Autlov, S. A.; Kharlanov, A. N.; Bazarnova, N. G.; Lunin, V. V.
2015-08-01
The kinetic curves of ozone absorption by aspen wood were obtained. Processing of wood with peracetic acid gave cellulose samples. The yields of ozonated wood, water-soluble compounds, and cellulose were determined for the samples corresponding to different consumptions of ozone. The IR absorption spectra of wood and cellulose isolated from ozonated wood were analyzed. The supramolecular structure of cellulose can be changed by varying the conditions of wood ozonation.
Mehnati, Parinaz; Jafari Tirtash, Maede; Zakerhamidi, Mohammad Sadegh; Mehnati, Parisa
2016-01-01
Background Blood concentrations and oxygen saturation levels are important biomarkers for breast cancer diagnosis. Objectives In this study, the absorption coefficient of hemoglobin (Hb) was used to distinguish between normal and abnormal breast tissue. Materials and Methods A near-infrared source (637 nm) was transmitted from major and minor vessels of a breast phantom containing 2×, 4× concentrations of oxy- and deoxy-Hb. The absorption coefficients were determined from spectrometer (SM) and powermeter (PM) data. Results The absorption coefficients were 0.075 ± 0.026 cm-1 for oxygenated Hb (normal) in major vessels and 0.141 ± 0.023 cm-1 at 4× concentration (abnormal) with SM, whereas the breast absorption coefficients were 0.099 ± 0.017 cm-1 for oxygenated Hb (normal) in minor vessels and 0.171 ± 0.005 cm-1 at 4× concentrations with SM. A comparison of the data obtained using a SM and a PM was not significant statistically. Conclusion The study of the absorption coefficient data of different concentrations of Hb in normal and abnormal breasts via the diffusion of near-infrared light is a valuable method and has the potential to aid in early detection of breast abnormalities with SM and PM in major and minor vessels. PMID:27895869
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.
Measurement of Acoustic Attenuation and Absorption Coefficients using Thermometry
NASA Astrophysics Data System (ADS)
Morris, Hugh; Rivens, Ian; Shaw, Adam; ter Haar, Gail
2007-05-01
Accurate knowledge of both the attenuation and the absorption coefficient of tissue are required when planning an optimal high intensity focused ultrasound treatment. A novel technique for simple measurement of this parameters has been developed in which a thin-film thermocouple (TFT) is placed between two layers of tissue of different thicknesses. The sample can be rotated about an axis through the junction of the TFT so that it can be insonated from either side leaving the tissue adjacent to the junction unchanged, but changing the overlying thickness. The attenuation and absorption coefficients can be calculated from the heating curves measured in the two orientations. Experiments have been carried out in both tissue mimicking material (TMM) and in ex vivo liver tissue. Weakly focused transducers, resonant at 1.05 MHz, 2.4 MHz and 3.55 MHz were used at free-field spatial peak intensities of 9-14 W/cm2. The temperature rise was measured as a function of time using a TFT. These thermocouples are not subject to the viscous heating artefact that is common to other thermocouple devices and so are advantageous for this purpose. Alignment was achieved with a 3D automated gantry system, which was controlled with specialised software. Timing and data acquisition were also controlled with this software. All experiments were carried out in degassed water. Results for TMM and degassed excised bovine liver are presented.
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.
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)
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.
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.
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)
Moseev, D.; Laqua, H. P.; Marsen, S.; Marushchenko, N.; Stange, T.; Braune, H.; Gellert, F.; Hirsch, M.; Hoefel, U.; Knauer, J.; Oosterbeek, J. W.; Turkin, Y.; The Wendelstein 7-X Team
2017-03-01
The efficiency of electron cyclotron heating is determined by the microwave absorption of the plasma. Good microwave absorption is also crucial for the machine safety. In this paper we present a method of evaluating the microwave absorption coefficient from stray radiation measurements. The discussed method is computationally simple and can be applied potentially in real time. Evolution of the second harmonic extraordinary mode (X2) microwave absorption coefficient in Wendelstein 7-X during the start-up phase is presented, as well as an estimate of the absorption coefficient for the second harmonic ordinary mode (O2) wave.
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."
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.
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.
NASA Astrophysics Data System (ADS)
Tamandani, Shahryar; Darvish, Ghafar
2017-02-01
We present an analytical method to calculate photon absorption coefficient in mono and bilayer circular graphene quantum dots (CGQDs). We use kobo equation to extract new closed relation as the main goal. First, we calculate real and imaginary part of optical conductance separately. Then, joint density of states is obtained using a new relation that was extracted for the energy levels of mono and bilayer circular grapheme quantum dots. In this work we use closed equations to calculate energy levels in CGQDs. Next we obtain a new closed formula to calculate the photon absorption coefficient. The results show that the absorption coefficient is related to the size of CGQDs and number of layers. The photon absorption coefficient becomes lower with larger size of CGQDs. It is seen that the results of our method is compatible with the results of practical works. We also compare photon absorption in biased and unbiased bilayer CGQDs and investigate the effect of external magnetic field on photon absorption. rights reserved
Study of the absorption coefficient in layers of a semiconductor laser heterostructure
Veselov, D A; Pikhtin, N A; Lyutetskiy, A V; Nikolaev, D N; Slipchenko, S O; Sokolova, Z N; Shamakhov, V V; Shashkin, I S; Voronkova, N V; Tarasov, I S
2015-07-31
A method of studying the absorption coefficient in layers of semiconductor lasers is proposed. Using lasers based on MOVPE-grown separate-confinement heterostructures with a broadened waveguide, the absorption coefficient is investigated under pulsed current pumping. It is found that when the pump current flows through the laser in question, an additional internal optical absorption arises in the heterostructure layers. It is shown that an increase in the pump current density up to 20 kA cm{sup -2} leads to an increase in absorption up to 2.5 cm{sup -1}. The feasibility of studying free-carrier absorption in the active region is demonstrated. (lasers)
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
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.
The coefficient of bond thermal expansion measured by extended x-ray absorption fine structure.
Fornasini, P; Grisenti, R
2014-10-28
The bond thermal expansion is in principle different from the lattice expansion and can be measured by correlation sensitive probes such as extended x-ray absorption fine structure (EXAFS) and diffuse scattering. The temperature dependence of the coefficient α(bond)(T) of bond thermal expansion has been obtained from EXAFS for CdTe and for Cu. A coefficient α(tens)(T) of negative expansion due to tension effects has been calculated from the comparison of bond and lattice expansions. Negative lattice expansion is present in temperature intervals where α(bond) prevails over α(tens); this real-space approach is complementary but not equivalent to the Grüneisen theory. The relevance of taking into account the asymmetry of the nearest-neighbours distribution of distances in order to get reliable bond expansion values and the physical meaning of the third cumulant are thoroughly discussed.
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.
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.
Visible and Near Infrared Absorption Coefficients of Kaolinite and Related Clays.
propagation of light. This work is intended to provide a quantitative estimate of the absorption coefficient of kaolinite clays by application of a method based on the Kubelka - Munk theory of diffuse reflectance.
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)
André, Frédéric; Solovjov, Vladimir; Vaillon, Rodolphe; Lemonnier, Denis
2013-07-01
The generalized k-moment method is formulated in terms of Cutteridge-Devyatov polynomials (CDP). In this novel approach, the moments involved are spectral averages of integer powers of the logarithm of the absorption coefficient. The technique to obtain k-distributions from those generalized moments is detailed both theoretically and from a practical point of view. Its outputs are afterward assessed against reference data in several test cases of increasing complexity. Indeed, the first ones involve single lines in the Lorentz, Doppler and Voigt regimes. The most sophisticated situations investigated in this work concern applications of the method to high resolution LBL data for pure CO2 at temperatures between 300K and 2300K and at atmospheric pressure. In any case, the CDP solution to the generalized k-moment problem is found to provide very accurate results. The present technique outperforms our previous approach to k-moment modeling of the cumulative distribution of absorption coefficients of gases that were based on first, second, first inverse and logarithmic moments, in all the situations investigated. Equations required to apply the model are provided in the paper, both over narrow bands and the full spectrum.
Interpreting measurements obtained with the cloud absorption radiometer
NASA Technical Reports Server (NTRS)
1988-01-01
The software developed for the analysis of data from the Cloud Absorption Radiometer (CAR) is discussed. The CAR is a multichannel radiometer designed to measure the radiation field in the middle of an optically thick cloud (the diffusion domain). It can also measure the surface albedo and escape function. The instrument currently flies on a C-131A aircraft operated by the University of Washington. Most of this data was collected during the First International satellite cloud climatology project Regional Experiment (FIRE) Marine Stratocumulus Intensive Field Observation program off San Diego during July 1987. Earlier flights of the CAR have also been studied.
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…
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.
Determination of absorption coefficients in AlInP lattice matched to GaAs
NASA Astrophysics Data System (ADS)
Cheong, J. S.; Ng, J. S.; Krysa, A. B.; Ong, J. S. L.; David, J. P. R.
2015-10-01
The absorption properties of Al0.52In0.48P have been investigated near the fundamental absorption edge by measuring the photocurrent as a function of wavelength in a series of PIN and NIP diodes. Modelling of the photocurrent in these structures enables the absorption coefficients to be determined accurately over a wide dynamic range, which allows the direct and indirect band-gap to be determined.
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.
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.
Determination of molar absorption coefficients of organic compounds adsorbed in porous media.
Ciani, Andrea; Goss, Kai-Uwe; Schwarzenbach, René P
2005-12-01
The kinetics of direct photochemical transformations of organic compounds in light absorbing and scattering media has been sparsely investigated. This is mostly due to the experimental difficulties to assess the major parameters: light intensity in porous media, the reaction quantum yield and the molar absorption coefficient of the adsorbed compound, epsilon(i) (lambda). Here, we propose a method for the determination of the molar absorption coefficient of compounds adsorbed to air-dry surfaces using the Kubelka-Munk model for the description of radiative transfer. To illustrate the method, the molar absorption coefficients of three compounds, i.e. 4-nitroanisole (PNA), the herbicide trifluralin and the flame retardant decabromodiphenyl ether (DecaBDE), were determined on air-dry kaolinite. The measured diffuse reflectance spectra were evaluated with the Kubelka-Munk model and with previously determined Kubelka-Munk absorption and scattering coefficients (k and s), for kaolinite. For all compounds the maximum absorption band was found to be red shifted and the corresponding epsilon(i) (lambda) values were significantly greater than those determined in solvents. Together with the absorption and scattering coefficient of the medium, the measured epsilon(i) (lambda) can be used to determine the quantum yield of the photochemical reaction in this medium from experimentally determined reaction kinetics.
Li, Zhi; Zhang, Zhao-hui; Zhao, Xiao-yan; Su, Hai-xia; Yan, Fang
2012-04-01
Extracting absorption spectrum in THz band is one of the important aspects in THz applications. Sample's absorption coefficient has a complex nonlinear relationship with its thickness. However, as it is not convenient to measure the thickness directly, absorption spectrum is usually determined incorrectly. Based on the method proposed by Duvillaret which was used to precisely determine the thickness of LiNbO3, the approach to measuring the absorption coefficient spectra of glutamine and histidine in frequency range from 0.3 to 2.6 THz(1 THz = 10(12) Hz) was improved in this paper. In order to validate the correctness of this absorption spectrum, we designed a series of experiments to compare the linearity of absorption coefficient belonging to one kind amino acid in different concentrations. The results indicate that as agreed by Lambert-Beer's Law, absorption coefficient spectrum of amino acid from the improved algorithm performs better linearity with its concentration than that from the common algorithm, which can be the basis of quantitative analysis in further researches.
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.
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.
NASA Astrophysics Data System (ADS)
Dumitras, D. C.; Dutu, D. C.; Matei, C.; Cernat, R.; Banita, S.; Patachia, M.; Bratu, A. M.; Petrus, M.; Popa, C.
2011-04-01
Photoacoustic spectroscopy represents a powerful technique for measuring extremely low absorptions independent of the path length and offers a degree of parameter control that cannot be attained by other methods. We report precise measurements of the ammonia absorption coefficients at the CO2 laser wavelengths by using a photoacoustic (PA) cell in an extracavity configuration and we compare our results with other values reported in the literature. Ammonia presents a clear fingerprint spectrum and high absorption strengths in the CO2 wavelengths region. Because more than 250 molecular gases of environmental concern for atmospheric, industrial, medical, military, and scientific spheres exhibit strong absorption bands in the region 9.2-10.8 μm, we have chosen a frequency tunable CO2 laser. In the present work, ammonia absorption coefficients were measured at both branches of the CO2 laser lines by using a calibrated mixture of 10 ppm NH3 in N2. We found the maximum absorption in the 9 μm region, at 9R(30) line of the CO2 laser. One of the applications based on the ammonia absorption coefficients is used to measure the ammonia levels in exhaled human breath. This can be used to determine the exact time necessary at every session for an optimal degree of dialysis at patients with end-stage renal disease.
Danilov, A A; Masloboev, Iu P; Selishchev, S V; Tereshchenko, S A
2006-01-01
A method for experimental determination of optical characteristics of a highly-dispersive medium (radiation scattering and absorption coefficients) is described. The method is based on two mathematical models of ultrashort laser pulse propagation through a highly-dispersive medium (HDM), an axial model and a diffusion model. Milk dissolved in water was used as HDM. Dependences of optical characteristics of HDM on the concentration of milk in water are obtained. The limits of applicability of the axial and diffusion models to media with different scattering and absorption characteristics are determined.
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.
Measurement of acoustic absorption coefficient with phase-conjugate ultrasonic waves
NASA Astrophysics Data System (ADS)
Smagin, N. V.; Krutyansky, L. M.; Brysev, A. P.; Bunkin, F. V.
2011-07-01
Experimental results on measurements of the acoustic absorption coefficient in test objects that were obtained with two methods, i.e., a standard insert-substitution method and a modification thereof using phase-conjugate waves, are given. Samples of gelatin and biological tissue in vitro (porcine muscle fibers) were used as test objects. Gelatin objects were manufactured that were both homogeneous and with inhomogeneities in the form of a rough surface or inclusions (air bubbles) distributed over the volume. A rough surface leads mainly to phase distortions of a probe beam, while bubble inclusions cause additional field scattering. For all homogeneous samples, both compared methods produce identical results. In the case of inhomogeneous samples including biological tissues, absorption measurement by a standard method may lead to significant errors. It is demonstrated that the use of properties of phase-conjugate waves provides an opportunity to eliminate almost completely the measurement error connected with phase distortions and reduce the error in the case of a medium with scatterers.
Lee, Joong Seok; Kim, Yoon Young; Kim, Jung Soo; Kang, Yeon June
2008-04-01
Optimal shape design of a two-dimensional poroelastic acoustical foam is formulated as a topology optimization problem. For a poroelastic acoustical system consisting of an air region and a poroelastic foam region, two different physical regions are continuously changed in an iterative design process. To automatically account for the moving interfaces between two regions, we propose a new unified model to analyze the whole poroelastic acoustical foam system with one set of governing equations; Biot's equations are modified with a material property interpolation from a topology optimization method. With the unified analysis model, we carry out two-dimensional optimal shape design of a poroelastic acoustical foam by a gradient-based topology optimization setting. The specific objective is the maximization of the absorption coefficient in low and middle ranges of frequencies with different amounts of a poroelastic material. The performances of the obtained shapes are compared with those of well-known wedge shapes, and the improvement of absorption is physically interpreted.
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)
Orlova, K. N.; Borovikov, I. F.; Gaidamak, M. A.
2016-08-01
The paper presents background value equivalent dose of gamma-radiation investigation in different weather: clear cloudy and overcast. The change of the dose rate of gamma radiation, depending on the weather and the ability cloudiness to shield gamma rays is shown. A new method for eliminating the consequences of accidents at nuclear power plants or plants using radioactive elements is proposed. A calculation method of cloudiness coefficient absorption and cloudiness gamma-radiation multiplicity attenuation is developed. The gamma- radiation multiplicity attenuation and the absorption coefficient of gamma radiation were calculated.
A numerical study of a method for measuring the effective in situ sound absorption coefficient.
Kuipers, Erwin R; Wijnant, Ysbrand H; de Boer, André
2012-09-01
The accuracy of a method [Wijnant et al., Proc. of ISMA 31, Leuven, Belgium (2010), Vol. 31] for measurement of the effective area-averaged in situ sound absorption coefficient is investigated. Based on a local plane wave assumption, this method can be applied to sound fields for which a model is not available. Investigations were carried out by means of finite element simulations for a typical case. The results show that the method is a promising method for determining the effective area-averaged in situ sound absorption coefficient in complex sound fields.
Measurement of optical absorption coefficient of bio-tissue at 532nm wavelength
NASA Astrophysics Data System (ADS)
Huang, Chuyun; Li, Zhengjia; Yao, Yucheng; He, Yanyan
2007-05-01
Laser technology has succeeded in medical application. High power 532nm laser has applied in prostate ablation and other clinic application. To understand optical property of bio-tissue at 532nm wavelength, a method of monitoring surface temperature was used to measure absorption coefficient of gall-stone, porcine liver and canine prostate. The absorption coefficient of gall-stone is about 62cm -1 at 532nm wavelength, and those of porcine liver and canine prostate are about 13cm -1 and 5.4cm -1, respectively. These results help to understand the optical property of bio-tissue and offer theoretic reference for optical dosimetry in clinic application.
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.
NASA Astrophysics Data System (ADS)
Fallica, Roberto; Stowers, Jason K.; Grenville, Andrew; Frommhold, Andreas; Robinson, Alex P. G.; Ekinci, Yasin
2016-07-01
The dynamic absorption coefficients of several chemically amplified resists (CAR) and non-CAR extreme ultraviolet (EUV) photoresists are measured experimentally using a specifically developed setup in transmission mode at the x-ray interference lithography 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 postabsorption chemical reaction ongoing in the resist, which also predicts a quantitative clearing volume and clearing radius, due to the photon absorption in the resist. These parameters may help provide deeper insight into the underlying mechanisms of the EUV concepts of clearing volume and clearing radius, which are then defined and quantitatively calculated.
NASA Technical Reports Server (NTRS)
Mogro-Campero, A.; Fillius, W.
1976-01-01
The process of trapped particle absorption by the inner Jovian satellites is considered in detail taking into account both the particle and satellite motions in a magnetic dipole field which is displaced from the center of the planet and tilted with respect to the planetary rotation axis. An expression is derived for computing the sweeping time at a given satellite, defined as the time required for the satellite to sweep up a given fraction of the trapped particles within its sweeping region. By making use of the sweeping time and the radial diffusion equation of particle transport approximate expressions for the diffusion coefficient are derived. Measurements obtained by Pioneer 10 are then used to obtain estimates of the diffusion coefficient at the orbits of Io and Europa. We find that the diffusion coefficient is a function of energy and magnetic latitude for electrons in the energy range 0.7-14 MeV.
Determination of Absorption and Scattering Coefficients for Nonhomogeneous Media: II. Experiment.
prepared from a glass of known absorption coefficient variation. The new model produces an accuracy inprovement up to a factor of 2.5 over the Kubelka ... Munk theory. Off-axis scattering measurements were made with improved instrumentation between 0.33 and 2.7 micrometers. The model was then applied to
Nelson, N B; Prézelin, B B
1993-11-20
Measuring the absolute absorption of suspensions of absorbing particles with unknown scattering characteristics is not possible in conventional spectrophotometers or in integrating spheres that have the sample located outside the sphere. A method for the calibration and use of an integrating sphere with a centrally located sample to measure absolute absorption coefficients of scattering suspensions is presented. Under the tested conditions the integrating sphere used in this study was insensitive to changes in the scattering coefficient of the sample but had a nonlinear response to increasing absorption of the sample, which could be corrected with an empirically derived function. This response was analyzed by using a Monte Carlo simulation, and results indicated that amplification of the absorption signal was primarily due to photons reflected from the sphere surface and the baffle reentering the cuvette. The calibration procedure described here may be generally applicable to spheres of different configurati n. An example of the use of the sphere for determining the absorption and scattering coefficients of marine phytoplankton samples is presented.
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.
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.
Guo, Zijian; Favazza, Christopher; Garcia-Uribe, Alejandro; Wang, Lihong V
2012-06-01
Photoacoustic (PA) microscopy (PAM) can image optical absorption contrast with ultrasonic spatial resolution in the optical diffusive regime. Conventionally, accurate quantification in PAM requires knowledge of the optical fluence attenuation, acoustic pressure attenuation, and detection bandwidth. We circumvent this requirement by quantifying the optical absorption coefficients from the acoustic spectra of PA signals acquired at multiple optical wavelengths. With the acoustic spectral method, the absorption coefficients of an oxygenated bovine blood phantom at 560, 565, 570, and 575 nm were quantified with errors of <3%. We also quantified the total hemoglobin concentration and hemoglobin oxygen saturation in a live mouse. Compared with the conventional amplitude method, the acoustic spectral method provides greater quantification accuracy in the optical diffusive regime. The limitations of the acoustic spectral method was also discussed.
NASA Technical Reports Server (NTRS)
Calvin, Wendy M.
1990-01-01
Reflectance spectra of carbon dioxide frosts were calculated using the optical constants provided by Warren (1986) for the wavelength region 2-6 microns. In comparing these calculated spectra to spectra of frosts observed in the laboratory and on the surface of Mars, problems in the optical constants presented by Warren (1986) became apparent. Absorption coefficients for CO2 ice have been derived using laboratory reflectance measurements and the Hapke (1981) model for calculating diffuse reflectance. This provides approximate values in regions where no data were previously available and indicates where corrections to the compilation by Warren (1986) are required. Using these coefficients to calculate the reflectance of CO2 ice at varying grain sizes indicates that a typical Mariner polar cap spectrum is dominated by absorptions due to CO2 frost or ice at grain sizes that are quite large, probably of the order of millimeters to centimeters. There are indications of contamination of water frost or dust, but confirmation will require more precise absorption coefficients for solid CO2 than can be obtained from the method used here.
Karsten, A E; Singh, A; Karsten, P A; Braun, M W H
2013-02-01
An individualised laser skin treatment may enhance the treatment and reduces risks and side-effects. The optical properties (absorption and scattering coefficients) are important parameters in the propagation of laser light in skin tissue. The differences in the melanin content of different skin phototypes influence the absorption of the light. The absorption coefficient at the treatment wavelength for an individual can be determined by diffuse reflectance spectroscopy, using a probe containing seven fibres. Six of the fibres deliver the light to the measurement site and the central fibre collects the diffused reflected light. This is an in vivo technique, offering benefits for near-real-time results. Such a probe, with an effective wavelength band from 450 to 800 nm, was used to calibrate skin-simulating phantoms consisting of intralipid and ink. The calibration constants were used to calculate the absorption coefficients from the diffuse reflectance measurements of three volunteers (skin phototypes, II, IV and V) for sun-exposed and non-exposed areas on the arm.
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.
Parameterization of the Mie Extinction and Absorption Coefficients for Water Clouds.
NASA Astrophysics Data System (ADS)
Mitchell, David L.
2000-05-01
It was found that the anomalous diffraction approximation (ADA) could be made to approximate Mie theory for absorption and extinction in water clouds by parameterizing the missing physics: 1) internal reflection/refraction, 2) photon tunneling, and 3) edge diffraction. Tunneling here refers to processes by which tangential or grazing photons beyond the physical cross section of a spherical particle may be absorbed. Contributions of the above processes to extinction and/or absorption were approximated in terms of particle size, index of refraction, and wavelength. It was found that tunneling can explain most of the difference between ADA and Mie theory for water clouds in the thermal IR.The modified ADA yielded analytical expressions for the absorption and extinction efficiencies, Qabs and Qext, which were integrated over a gamma size distribution to yield expressions for the absorption and extinction coefficients, abs and ext. These coefficients were expressed in terms of the three gamma distribution parameters, which were related to measured properties of the size distribution: liquid water content, mean, and mass-median diameter. Errors relative to Mie theory for abs and ext were generally 10% for the effective radius range in water clouds of 5-30 m, for any wavelength in the solar or terrestrial spectrum. For broadband emissivities and absorptivities regarding terrestrial and solar radiation, the errors were less than 1.2% and 4%, respectively. The modified ADA dramatically reduces computation times relative to Mie theory while yielding reasonably accurate results.
Thin-film absorption coefficients by attenuated-total-reflection spectroscopy.
Holm, R T; Palik, E D
1978-02-01
The application of attenuated-total-reflection spectroscopy to the measurement of the absorption coefficient of thin films is presented. For low absorption the sensitivity of ATR is discussed in terms of the concept of an effective thickness. Both the case in which the refractive index of the film is higher and the case in which it is lower than that of the ATR trapezoid are considered. Experimental ATR data for antireflection-coating materials for laser windows is analyzed and compared with calorimetric data.
Determining Spectral Reflectance Coefficients from Hyperspectral Images Obtained from Low Altitudes
NASA Astrophysics Data System (ADS)
Walczykowski, P.; Jenerowicz, A.; Orych, A.; Siok, K.
2016-06-01
Remote Sensing plays very important role in many different study fields, like hydrology, crop management, environmental and ecosystem studies. For all mentioned areas of interest different remote sensing and image processing techniques, such as: image classification (object and pixel- based), object identification, change detection, etc. can be applied. Most of this techniques use spectral reflectance coefficients as the basis for the identification and distinction of different objects and materials, e.g. monitoring of vegetation stress, identification of water pollutants, yield identification, etc. Spectral characteristics are usually acquired using discrete methods such as spectrometric measurements in both laboratory and field conditions. Such measurements however can be very time consuming, which has led many international researchers to investigate the reliability and accuracy of using image-based methods. According to published and ongoing studies, in order to acquire these spectral characteristics from images, it is necessary to have hyperspectral data. The presented article describes a series of experiments conducted using the push-broom Headwall MicroHyperspec A-series VNIR. This hyperspectral scanner allows for registration of images with more than 300 spectral channels with a 1.9 nm spectral bandwidth in the 380- 1000 nm range. The aim of these experiments was to establish a methodology for acquiring spectral reflectance characteristics of different forms of land cover using such sensor. All research work was conducted in controlled conditions from low altitudes. Hyperspectral images obtained with this specific type of sensor requires a unique approach in terms of post-processing, especially radiometric correction. Large amounts of acquired imagery data allowed the authors to establish a new post- processing approach. The developed methodology allowed the authors to obtain spectral reflectance coefficients from a hyperspectral sensor mounted on an
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.
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
Methane absorption coefficients for the jovian planets from laboratory, Huygens, and HST data
NASA Astrophysics Data System (ADS)
Karkoschka, Erich; Tomasko, Martin G.
2010-02-01
We use 11 data sets of methane transmission measurements within 0.4-5.5 μm wavelength to model the methane transmission for temperature and pressure conditions in the jovian planets. Eight data sets are based on published laboratory measurements. Another two data sets come from two spectrometers onboard the Huygens probe that measured methane absorption inside Titan's atmosphere ( Tomasko et al., 2008b, PSS 56, 624), and we provide a refined analysis. The last data set is a set of new Jupiter images by the Hubble Space Telescope to measure atmospheric transmission with Ganymede as the light source. Below 1000 nm wavelength, our resulting methane absorption coefficients are generally close to those by Karkoschka (1998, Icarus 133, 134), but we add descriptions of temperature and pressure dependence. One remaining inconsistency occurs between 882 and 902 nm wavelength where laboratory data predict larger absorptions in the jovian atmospheres than observed. We present possible explanations. Above 1000 nm, our analysis of the Huygens data confirms methane absorption coefficients by Irwin et al. (2006, Icarus 181, 309) at their laboratory temperatures. Huygens data also confirm Irwin's model of extrapolation to Titan's lower pressures. However, their model of extrapolation to Titan's lower temperatures predicts absorption coefficients up to 100 times lower than measured by Huygens. For each of ˜3700 wavelengths, we present a temperature dependence that is consistent with all laboratory data and the Huygens data. Since the Huygens data probe similar temperatures as many observations of Saturn, Uranus, Neptune, and Titan, our methane model will allow more reliable radiative transfer models for their atmospheres.
The influence of surface preparation on the absorption coefficient of laser radiation
NASA Astrophysics Data System (ADS)
Kurp, Piotr; Mucha, Zygmunt; Mulczyk, Krystian; Gradoń, Ryszard; Trela, Paweł
2016-12-01
The absorption coefficient of the surface of a workpiece is of importance in laser treatment, particularly in the treatment where the temperature of an element must be strictly controlled. Laser surface treatment (such as hardening, metallic glazing) and laser forming can be primarily included in this type of technology. In another case, surface temperature must be precisely controlled, especially if structural changes are to be avoided. There are a number of ways to increase the absorption coefficient of the surface of an element. Since the laser forming is the research subject of the authors of the presented paper, it was necessary to determine the absorption coefficient for the different surfaces preparation of workpieces. Raw surface, oxidized surface, sandblasted surface, black enamel covered surface and waterglass covered surface were examined, respectively. The experiment was performed using a CO2 laser with a head for a surface treatment which generates a rectangular beam of dimensions 2x20 mm, and the samples were made of X5CrNi18-10 stainless steel.
Dependence of dose coefficients for inhaled 239Pu on absorption parameters.
Suzuki, K; Sekimoto, H; Ishigure, N
2001-01-01
With regard to dissolution of particles in the respiratory tract after inhalation, the International Commission on Radiological Protection (ICRP) has classified all radionuclides into only three types according to the chemical form of compounds, and default values of absorption parameters are proposed for each type. However, it is just a simplification to estimate doses for practical use, and there is a possibility of unfitness in such an assortment. A code has been developed to reproduce the ICRP's dose coefficients for 239Pu, which is one of the most important elements for occupational exposure. By using this code, the respective absorption parameters were modified, and the effect owing to these changes evaluated. It was shown consequently that changes of absorption parameters do not greatly influence the effective doses of 239Pu for workers.
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.
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.
Benmakhlouf, Hamza; Bouchard, Hugo; Fransson, Annette; Andreo, Pedro
2011-11-21
Backscatter factors, B, and mass energy-absorption coefficient ratios, (μ(en)/ρ)(w, air), for the determination of the surface dose in diagnostic radiology were calculated using Monte Carlo simulations. The main purpose was to extend the range of available data to qualities used in modern x-ray techniques, particularly for interventional radiology. A comprehensive database for mono-energetic photons between 4 and 150 keV and different field sizes was created for a 15 cm thick water phantom. Backscattered spectra were calculated with the PENELOPE Monte Carlo system, scoring track-length fluence differential in energy with negligible statistical uncertainty; using the Monte Carlo computed spectra, B factors and (μ(en)/ρ)(w, air) were then calculated numerically for each energy. Weighted averaging procedures were subsequently used to convolve incident clinical spectra with mono-energetic data. The method was benchmarked against full Monte Carlo calculations of incident clinical spectra obtaining differences within 0.3-0.6%. The technique used enables the calculation of B and (μ(en)/ρ)(w, air) for any incident spectrum without further time-consuming Monte Carlo simulations. The adequacy of the extended dosimetry data to a broader range of clinical qualities than those currently available, while keeping consistency with existing data, was confirmed through detailed comparisons. Mono-energetic and spectra-averaged values were compared with published data, including those in ICRU Report 74 and IAEA TRS-457, finding average differences of 0.6%. Results are provided in comprehensive tables appropriated for clinical use. Additional qualities can easily be calculated using a designed GUI interface in conjunction with software to generate incident photon spectra.
Parameterization of the Mie extinction and absorption coefficients for water clouds
Mitchell, D.L.
2000-05-01
It was found that the anomalous diffraction approximation (ADA) could be made to approximate Mie theory for absorption and extinction in water clouds by parameterizing the missing physics: (1) internal reflection/refraction, (2) photon tunneling, and (3) edge diffraction. Tunneling here refers to processes by which tangential or grazing photons beyond the physical cross section of a spherical particle may be absorbed. Contributions of the above processes to extinction and/or absorption were approximated in terms of particle size, index of refraction, and wavelength. It was found that tunneling can explain most of the difference between ADA and Mie theory for water clouds in the thermal IR. The modified ADA yielded analytical expressions for the absorption and extinction efficiencies, Q{sub abs} and Q{sub ext}, which were integrated over a gamma size distribution to yield expressions for the absorption and extinction coefficients, {beta}{sub abs} and {beta}{sub ext}. These coefficients were expressed in terms of the three gamma distribution parameters, which were related to measured properties of the size distribution: liquid water content, mean, and mass-median diameter. Errors relative to Mie theory for {beta}{sub abs} and {beta}{sub ext} were generally {le}10% for the effective radius range in water clouds of 5--30 {micro}m, for any wavelength in the solar or terrestrial spectrum. For broadband emissivities and absorptivities regarding terrestrial and solar radiation, the errors were less than 1.2% and 4%, respectively. The modified ADA dramatically reduces computation times relative to Mie theory while yielding reasonably accurate results.
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
Parker, K; Morrison, G
2016-08-01
Occupants of former methamphetamine laboratories, often residences, may experience increased exposure through the accumulation of the methamphetamine in the organic films that coat skin and indoor surfaces. The objectives of this study were to determine equilibrium partition coefficients of vapor-phase methamphetamine with artificial sebum (AS-1), artificial sebum without fatty acids (AS-2), and real skin surface films, herein called skin oils. Sebum and skin oil-coated filters were exposed to vapor-phase methamphetamine at concentrations ranging from 8 to 159 ppb, and samples were analyzed for exposure time periods from 2 h to 60 days. For a low vapor-phase methamphetamine concentration range of ~8-22 ppb, the equilibrium partition coefficient for AS-1 was 1500 ± 195 μg/g/ppb. For a high concentration range of 98-112 ppb, the partition coefficient was lower, 459 ± 80 μg/g/ppb, suggesting saturation of the available absorption capacity. The low partition coefficient for AS-2 (33 ± 6 μg/g/ppb) suggests that the fatty acids in AS-1 and skin oil are responsible for much high partition coefficients. We predict that the methamphetamine concentration in skin lipids coating indoor surfaces can exceed recommended surface remediation standards even for air concentrations well below 1 ppb.
NASA Astrophysics Data System (ADS)
Yin, Yan; Chen, Yu; Wang, Weiwei; Yan, Jiade; Qian, Ling; Tong, Yaoqing; Lin, Zhenyi
2008-08-01
The absorption and scattering coefficients of atmospheric aerosols were continuously measured with a Photoacoustic Soot Spectrometer (PASS, DMT Inc. USA) at a suburb site of Nanjing, one of the regions experiencing rapid industrialization in China. The measurements were carried out during autumn and winter 2007. A preliminary analysis of the data shows that, the scattering coefficient, Bscat, is two to ten times larger than the absorption coefficient, Babs, implying that the aerosols formed/emitted in this area are more scattering than previous assumed, and can be more important in cooling the Earth-atmosphere system. The results also indicate that the absolute values of both parameters are very much dependent on the meteorological conditions, such as wind speed and direction, fog, rain, etc. as well as the time of the day. Higher values often appear at nighttimes when wind is weak, especially when a temperature inverse layer is present near the surface. Higher values of Bscat and Babs were also observed under hazy and foggy weather conditions or when wind is blown from east, where a large industrial zone is located. Simultaneous measurements of the number concentrations, chemical compositions, and size distributions of aerosol particles are used to explain the characteristics of the changes in Bscat and Babs.
NASA Technical Reports Server (NTRS)
Miyamoto, M.; Mikouchi, T.; Mckay, G. A.
1994-01-01
We report the partition coefficients for Ca, Al, Ti, Cr, and Ni in olivine obtained through a series of melting experiments on an LL6 chondrite under varying conditions of temperature and oxygen fugacity. It is necessary to examine the variation of partition coefficients up to extremely reducing conditions in order to study meteoritic olivines. For Ca, Al, and Cr, the partition coefficients tend to decrease as temperature increases, but do not change even under extremely reducing conditions.
NASA Astrophysics Data System (ADS)
Singh, Manjeet; Singh, Jaswant; Singh, Baljit; Ghanshyam, C.
2016-11-01
The aim of this study is to quantify the finite spectral bandwidth effect on laser absorption spectroscopy for a wide-band laser source. Experimental analysis reveals that the extinction coefficient of an analyte is affected by the bandwidth of the spectral source, which may result in the erroneous conclusions. An approximate mathematical model has been developed for optical intensities having Gaussian line shape, which includes the impact of source's spectral bandwidth in the equation for spectroscopic absorption. This is done by introducing a suitable first order and second order bandwidth approximation in the Beer-Lambert law equation for finite bandwidth case. The derived expressions were validated using spectroscopic analysis with higher SBW on a test sample, Rhodamine B. The concentrations calculated using proposed approximation, were in significant agreement with the true values when compared with those calculated with conventional approach.
Effect of sealants of the sound absorption coefficients of acoustical friable insulating materials
NASA Astrophysics Data System (ADS)
Wayman, J. L.; Lory, M. K.
1984-10-01
Acoustical friable insulating materials (AFIM), which often in the past contained asbestos, have been used for sound control since the mid 1930's. Because of their widespread use and the ease of fiber dissemination, friable asbestos materials are considered to be the major source of asbestos fiber contamination in the indoor environment. Encapsulation of asbestos materials with a commercial sealant product is one of several methods used to control potential asbestos exposure in rooms. A sealant product that preserves most of the acoustical properties of the material is preferred in this usage. AFIM sample materials were treated with 6 types of sealants and the effects on normally incident absorption coefficients from 100 to 2500 Hz were measured using a fixed, dual-microphone technique. Penetrating type sealants were found to have a less detrimental effect on sound absorption than those of a bridging type.
Excited state absorption spectrum of chlorophyll a obtained with white-light continuum.
De Boni, L; Correa, D S; Pavinatto, F J; dos Santos, D S; Mendonça, C R
2007-04-28
The study of excited state properties of chlorophyll a is a subject of foremost interest, given that it plays important roles in biological process and has also been proposed for applications in photonics. This work reports on the excited state absorption spectrum of chlorophyll a solution from 460 to 700 nm, obtained through the white-light continuum Z-scan technique. Saturation of absorption was observed due to the ground state depletion, induced by the white-light continuum region that is resonant with the Q band of chlorophyll a. The authors also observed reverse saturation of absorption related to the excitation from the first excited state to a higher energy level for wavelengths below 640 nm. An energy-level diagram, based on the electronic states of chlorophyll a, was employed to interpret their results, revealing that more states than the ones related to the Q and B bands participate in the excited state absorption of this molecule.
The effective air absorption coefficient for predicting reverberation time in full octave bands.
Wenmaekers, R H C; Hak, C C J M; Hornikx, M C J
2014-12-01
A substantial amount of research has been devoted to producing a calculation model for air absorption for pure tones. However, most statistical and geometrical room acoustic prediction models calculate the reverberation time in full octave bands in accordance with ISO 3382-1 (International Organization for Standardization, 2009). So far, the available methods that allow calculation of air absorption in octave bands have not been investigated for room acoustic applications. In this paper, the effect of air absorption on octave band reverberation time calculations is investigated based on calculations. It is found that the approximation method, as described in the standard ANSI S1.26 (American National Standards Institute, 1995), fails to estimate accurate decay curves for full octave bands. In this paper, a method is used to calculate the energy decay curve in rooms based on a summation of pure tones within the band. From this decay curve, which is found to be slightly concave upwards, T20 and T30 can be determined. For different conditions, an effective intensity attenuation coefficient mB ;eff for the full octave bands has been calculated. This mB ;eff can be used for reverberation time calculations, if results are to be compared with T20 or T30 measurements. Also, guidelines are given for the air absorption correction of decay curves, measured in a scale model.
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
2007-05-21
samples were collected with 1.7 L Niskin bottles mounted on a rosette equipped with a SBE19 CTD which provides temperature and salinity data. Samples were...21 November is 2002) on board R/V Yanping I1. Figure 1 shows the stations for CTD surveys and ab- sorption sampling . The 2001 cruise involved one...were sampled in both cruise legs for absorption coefficients (the second sampling is annotated as Sta. 6’ and Sta. 2’, respectively). 1559 Our sample
Two-photon absorption and Kerr coefficients of silicon for 850-2200 nm
NASA Astrophysics Data System (ADS)
Bristow, Alan D.; Rotenberg, Nir; van Driel, Henry M.
2007-05-01
The degenerate two-photon absorption coefficient β and Kerr nonlinearity n2 are measured for bulk Si at 300K using 200fs pulses with carrier wavelength of 850<λ<2200nm for which indirect gap transitions occur. With a broad peak near the indirect gap and maximum value of 2±0.5cm/GW, the dispersion of β compares favorably with theoretical calculations of Garcia and Kalyanaraman [J. Phys. B 39, 2737 (2006)]. Within our wavelength range, n2 varies by a factor of 4 with a peak value of 1.2×10-13cm2/W at λ =1800nm.
Vapor-Phase Absorptivity Coefficient of Ethyl N,N-Dimethylphosphoramidocyanidate
2010-01-01
diluted in solvent by gas chromotography -mass spectrometry (GC-MS) indicated 3.4% triethyl phosphate (TEPO), as well ə% each of 0-ethyl-N,N-dimethyl...absorptivity coefficient of the chemical warfare agent ethyl N,N-dimethyl- phosphoramidocyanidate ( GA ) in the mid-infrared (4000-550 cm"’) at a...spectral resolution of 0.125 cm"’. The GA used in the feedstock was purified by fractional distillation and analyzed by nuclear magnetic resonance and
Using molecular dynamics to obtain Maxwell-Stefan diffusion coefficients in liquid systems
NASA Astrophysics Data System (ADS)
van de Ven-Lucassen Thijs, Irma M. J. J.; Vlugt Antonius, J. H.; van der Zanden Piet, J. J.; Kerkhof, J. A. M.
Two methods are compared for the calculation of Maxwell-Stefan diffusion coefficients. The first method is a non-equilibrium molecular dynamics (NEMD) algorithm, in which the system is driven away from equilibrium and the system response is monitored. The second method is the equilibrium molecular dynamics (EMD) calculation of the appropriate GreenKubo equation. Simulations were performed for systems of 250 and 300 Lennard-Jones particles at various densities and temperatures. The systems were divided into two or three components by attaching a colour label to the particles. Since a colour label plays no role in the dynamics, the Maxwell-Stefan diffusion coefficients of the binary and ternary systems are equal to the self-diffusion coefficient. In dense fluids, the system response to an external perturbation is not a first-order process, and the diffusion coefficients cannot be determined from the short term response in the NEMD method. Only the long term response can be used, after a steady state has been reached. In binary systems the Maxwell-Stefan diffusion coefficients, determined by the Green-Kubo (EMD) method, are more accurate than the NEMD coefficients. Since in the NEMD method only the long term response can be used, the GreenKubo method is also less time consuming and is therefore preferred for the calculation of the Maxwell-Stefan diffusion coefficients. In ternary systems the Green-Kubo method is tested for the 250 particle system. The Maxwell-Stefan diffusion coefficients agree well with the selfdiffusion coefficient. For low mole fractions of the coloured components the diffusion coefficients were less accurate.
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)
Gaudette, Richard J.; Brooks, Dana H.; Di Marzio, Charles A.; Kilmer, Misha E.; Miller, Eric L.; Gaudette, Thomas; Boas, David A.
2000-04-01
We compare, through simulations, the performance of four linear algorithms for diffuse optical tomographic reconstruction of the three-dimensional distribution of absorption coefficient within a highly scattering medium using the diffuse photon density wave approximation. The simulation geometry consisted of a coplanar array of sources and detectors at the boundary of a half-space medium. The forward solution matrix is both underdetermined, because we estimate many more absorption coefficient voxels than we have measurements, and ill-conditioned, due to the ill-posedness of the inverse problem. We compare two algebraic techniques, ART and SIRT, and two subspace techniques, the truncated SVD and CG algorithms. We compare three-dimensional reconstructions with two-dimensional reconstructions which assume all inhomogeneities are confined to a known horizontal slab, and we consider two `object-based' error metrics in addition to mean square reconstruction error. We include a comparison using simulated data generated using a different FDFD method with the same inversion algorithms to indicate how our conclusions are affected in a somewhat more realistic scenario. Our results show that the subspace techniques are superior to the algebraic techniques in localization of inhomogeneities and estimation of their amplitude, that two-dimensional reconstructions are sensitive to underestimation of the object depth, and that an error measure based on a location parameter can be a useful complement to mean squared error.
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.
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.
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.
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.
NASA Astrophysics Data System (ADS)
Akimoto, Takuma; Yamamoto, Eiji
2016-12-01
Local diffusion coefficients in disordered systems such as spin glass systems and living cells are highly heterogeneous and may change over time. Such a time-dependent and spatially heterogeneous environment results in irreproducibility of single-particle-tracking measurements. Irreproducibility of time-averaged observables has been theoretically studied in the context of weak ergodicity breaking in stochastic processes. Here, we provide rigorous descriptions of equilibrium and non-equilibrium diffusion processes for the annealed transit time model, which is a heterogeneous diffusion model in living cells. We give analytical solutions for the mean square displacement (MSD) and the relative standard deviation of the time-averaged MSD for equilibrium and non-equilibrium situations. We find that the time-averaged MSD grows linearly with time and that the time-averaged diffusion coefficients are intrinsically random (irreproducible) even in the long-time measurements in non-equilibrium situations. Furthermore, the distribution of the time-averaged diffusion coefficients converges to a universal distribution in the sense that it does not depend on initial conditions. Our findings pave the way for a theoretical understanding of distributional behavior of the time-averaged diffusion coefficients in disordered systems.
Yin, Lu; Wang, Qiang; Zhang, Qizhi; Jiang, Huabei
2007-09-01
We present a new method that can provide high resolution images of absolute optical absorption coefficient in heterogeneous turbid media. In this method, acoustic measurements in conventional photoacoustic tomography are combined with diffusing light measurements to separate the product of absorption coefficient and optical fluence or photon density. We validate this method using a series of tissuelike phantom experiments. The experimental results show that targets as small as 0.5 mm in diameter with optical absorption contrasts as low as 1.5 relative to a 50 mm diameter scattering background medium can be clearly detected.
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.
Remote-Sensing Technique for Determination of the Volume Absorption Coefficient of Turbid Water
NASA Astrophysics Data System (ADS)
Sydor, Michael; Arnone, Robert A.; Gould, Richard W., Jr.; Terrie, Gregory E.; Ladner, Sherwin D.; Wood, Christoper G.
1998-07-01
We use remote-sensing reflectance from particulate R rs to determine the volume absorption coefficient a of turbid water in the 400 700-nm spectral region. The calculated and measured values of a ( ) show good agreement for 0 . 5 a 10 (m 1 ). To determine R rs from a particulate, we needed to make corrections for remote-sensing reflectance owing to surface roughness S rs . We determined the average spectral distribution of S rs from the difference in total remote-sensing reflectance measured with and without polarization. The spectral shape of S rs showed an excellent fit to theoretical formulas for glare based on Rayleigh and aerosol scattering from the atmosphere.
The Optical Absorption Coefficient of Maize Grains Investigated by Photoacoustic Spectroscopy
NASA Astrophysics Data System (ADS)
Rodríguez-Páez, C. L.; Carballo-Carballo, A.; Rico-Molina, R.; Hernández-Aguilar, C.; Domínguez-Pacheco, A.; Cruz-Orea, A.; Moreno-Martínez, E.
2017-01-01
In the maize and tortilla industry, it is important to characterize the color of maize ( Zea mays L.) grain, as it is one of the attributes that directly affect the quality of the tortillas consumed by the population. For this reason, the availability of alternative techniques for assessing and improving the quality of grain is valued. Photoacoustic spectroscopy has proven to be a useful tool for characterizing maize grain. So, the objective of the present study was to determine the optical absorption coefficient β of the maize grain used to make tortillas from two regions of Mexico: (a) Valles Altos, 2012-2013 production cycle and (b) Guasave, Sinaloa, 2013-2014 production cycle. Traditional reflectance measurements, physical characteristics of the grain and nutrient content were also calculated. The experimental results show different characteristics for maize grains.
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.
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.
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.
Approximating the near-edge mass absorption coefficients for Ni using an ultra-thin bimetal foil
Alkire, Randall W.
2016-11-01
In an effort to improve the characteristics of a fluorescing metal-foil-based beam position monitor, a new bimetal ultra-thin (0.98/0.67 µm) Ti–Ni foil was introduced to replace an existing single-element ultra-thin 0.5 µm thick Cr foil. During characterization it was determined that absorption measurements on the bimetal foil could be used to fit the Ni mass absorption coefficients accurately in the vicinity of the NiKedge. Comparison with experimental results from the literature demonstrated that the fitting procedure produced coefficients with uncertainties of the order of ±1%. Once determined, these fit coefficients allowed the thickness of an independently mounted 8 µm thickmore » Ni foil to be computed from absorption measurements instead of relying on a tool-based measurement of the foil thickness. Using the 8 µm thick foil, a continuous map of Ni mass absorption coefficients was produced at 1 eV resolution throughout the near-edge region. Lastly, this high-resolution map marks a significant improvement over the existing NIST XCOM or FFAST database mass absorption coefficients, which have estimated errors of 10–20% for the near-edge region.« less
Approximating the near-edge mass absorption coefficients for Ni using an ultra-thin bimetal foil
Alkire, Randall W.
2016-11-01
In an effort to improve the characteristics of a fluorescing metal-foil-based beam position monitor, a new bimetal ultra-thin (0.98/0.67 µm) Ti–Ni foil was introduced to replace an existing single-element ultra-thin 0.5 µm thick Cr foil. During characterization it was determined that absorption measurements on the bimetal foil could be used to fit the Ni mass absorption coefficients accurately in the vicinity of the Ni
IR Absorption Coefficients for the Quantification of Water in Hydrous Ringwoodite
NASA Astrophysics Data System (ADS)
Thomas, S.; Jacobsen, S. D.; Bina, C. R.; Smyth, J. R.; Frost, D. J.
2009-12-01
Raman spectroscopy, combined with the ‘Comparator technique’ has been developed to determine water contents ranging from a few wt ppm to wt% in glasses and nominally anhydrous minerals including garnets, olivine, and SiO2 polymorphs (Thomas et al. 2009). The routine is one promising example of quantification tools to determine mineral specific molar absorption coefficients (ɛ) for IR spectroscopy. Mineral specific absorption coefficients are required because general IR calibrations do not necessarily apply to minerals with water incorporated as hydroxyl point defects. Here we utilize the ‘Comparator technique’ to provide ɛ-values for a set of synthetic Fe-free and Fe-bearing (Fo90) ringwoodites, as well as for γ-Mg2GeO4. Ringwoodite is considered one of the major phases of the Earth’s lower transition zone (520-660 km depth) and the knowledge of its absolute water storage capacity is essential for modeling the Earth’s deep water cycle. Samples were synthesized at variable P-T conditions in a multi-anvil press and cover a range of OH contents. Single-crystals were characterized using X-ray diffraction and IR spectroscopy. Mineral specific IR absorption coefficients were calculated from independently determined water contents from Raman spectroscopy. Unpolarized IR spectra of Mg-ringwoodite show broad absorption features in the OH region with band maxima at ~2350, 2538, 3127, 3172, 3598 and 3688 cm-1. In the spectra of Fe-bearing ringwoodite and γ-Mg2GeO4 the maxima of the main OH band are shifted to 3172 cm-1 and 3207 cm-1, respectively. For Mg-ringwoodite with the mean wavenumber (area-weighted average of the peak position) of 3109 cm-1 an ɛ-value of 170000 ± 51000 L cm-2 / molH2O was determined. For a Fo90 sample with the mean wavenumber of 3132 cm-1 the value was calculated to be 123000 ± 37000 L cm-2 / molH2O. The latter two values are in good agreement with the data from the linear calibration of ~159000 L cm-2 / molH2O and ~153000 L cm-2
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)
Kienle, Alwin; Lilge, Lothar; Patterson, Michael S.; Hibst, Raimund; Steiner, Rudolf; Wilson, Brian C.
1996-05-01
The absorption and transport scattering coefficients of biological tissues determine the radial dependence of the diffuse reflectance that is due to a point source. A system is described for making remote measurements of spatially resolved absolute diffuse reflectance and hence noninvasive, noncontact estimates of the tissue optical properties. The system incorporated a laser source and a CCD camera. Deflection of the incident beam into the camera allowed characterization of the source for absolute reflectance measurements. It is shown that an often used solution of the diffusion equation cannot be applied for these measurements. Instead, a neural network, trained on the results of Monte Carlo simulations, was used to estimate the absorption and scattering coefficients from the reflectance data. Tests on tissue-simulating phantoms with transport scattering coefficients between 0.5 and 2.0 mm-1 and absorption coefficients between 0.002 and 0.1 mm -1 showed the rms errors of this technique to be 2.6% for the transport scattering coefficient and 14% for the absorption coefficients. The optical properties of bovine muscle, adipose, and liver tissue, as well as chicken muscle (breast), were also measured ex vivo at 633 and 751 nm. For muscle tissue it was found that the Monte Carlo simulation did not agree with experimental measurements of reflectance at distances less than 2 mm from the incident beam. Carlo, neural network.
NASA Astrophysics Data System (ADS)
Lee, H. J.; Aiona, P. K.; Nizkorodov, S.; Laskin, J.; Laskin, A.
2014-12-01
Atmospheric aerosols that absorb solar radiation have a direct effect on climate. Brown carbon (BrC) represents the type of carbonaceous aerosols characterized by large absorption coefficients in the near-UV range of the spectrum. BrC can be either directly emitted into the atmosphere from combustion sources, or be formed in the atmosphere through multi-phase reactions, such as aging of secondary organic aerosols (SOA) mediated by ammonium sulfate (AS). Under the conditions of exposure to solar radiation, both primary and secondary BrC can potentially change their molecular composition and optical properties as a result of photodegradation of chromophoric compounds. This presentation will discuss the molecular level composition, the absorption and fluorescence spectra, and the mechanism of photodegradation among several representative types of BrC. The primary BrC samples include aerosol produced by smoldering wood combustion. The secondary BrC samples include AS aged products of chamber-generated SOA, products of reaction between methylglyoxal and AS, and SOA produced by the hogh-NOx photooxdiation of aromatic compounds, such as naphthalene. This presentation will also include preliminary data on the absorption and fluorescence spectra of photo-degraded bioaerosols. In all cases, absorption spectra of extracted bulk samples are measured during irradiation by a known flux of UV or visible light. The molecular level composition of the fresh and photobleached samples are characterized by high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). Photobleaching of BrC is found to occur over a range of atmospherically relevant time scales. In many cases, the molecular level composition of photobleached BrC exhibits only subtle changes suggesting that the optical and fluorescence properties of BrC are controlled by a few compounds present in low quantities. The observed fluorescence from non-biological BrC indicates potential issues in using fluorescence
Specific absorption and backscatter coefficient signatures in southeastern Atlantic coastal waters
NASA Astrophysics Data System (ADS)
Bostater, Charles R., Jr.
1998-12-01
Measurements of natural water samples in the field and laboratory of hyperspectral signatures of total absorption and reflectance were obtained using long pathlength absorption systems (50 cm pathlength). Water was sampled in Indian River Lagoon, Banana River and Port Canaveral, Florida. Stations were also occupied in near coastal waters out to the edge of the Gulf Stream in the vicinity of Kennedy Space Center, Florida and estuarine waters along Port Royal Sound and along the Beaufort River tidal area in South Carolina. The measurements were utilized to calculate natural water specific absorption, total backscatter and specific backscatter optical signatures. The resulting optical cross section signatures suggest different models are needed for the different water types and that the common linear model may only appropriate for coastal and oceanic water types. Mean particle size estimates based on the optical cross section, suggest as expected, that particle size of oceanic particles are smaller than more turbid water types. The data discussed and presented are necessary for remote sensing applications of sensors as well as for development and inversion of remote sensing algorithms.
2012-09-01
bandwidth of the pulse. Using the standard laboratory and analysis methods of Sheik- Bahae et al., we obtain a two-photon absorption coefficient, β, of...organic thin-film materials deposited on various substrates. 15 6. References 1. Sheik- Bahae , M.; Said, A. A.; Van Stryland, E. W. High...sensitivity, Single-beam n2 Measurements. Optics Letters 1989, 14 (17). 2. Sheik- Bahae , M.; Said, A. A.; Van Stryland, E. W.; Wei, T-H; Hagan, D. J
Goodman, W A; Goorsky, M S
1995-06-20
We engineered a factor-of-4 reduction in the bulk absorption coefficient over the 2.6-to-3.0-µm bandwidth in single-crystal Czochralski silicon optics for high-energy infrared lasers with high-temperature annealing treatments. Defect engineering adapted from the integrated circuit industry has been used to reduce the absorption coefficient across the 1.5-to-5-µm bandwidth for substrates up to 5 cm thick. A high-temperature oxygen-dispersion anneal dissolves precipitates and thermal donors that are present in the as-grown material. The process has been verified experimentally with Fourier transform infrared spectroscopy, infrared laser calorimetry, and Hall measurements. Reduction of the absorption coefficient results in less substrate heating and thermal distortion of the optical surface. The process is appropriate for other silicon infrared optics applications such as thermal-imaging systems, infrared windows, and spectrophotometers.
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.
Optoelectronic properties of Mg{sub 2}Si semiconducting layers with high absorption coefficients
Kato, Takashi; Sago, Yuichiro; Fujiwara, Hiroyuki
2011-09-15
In an attempt to develop a low-cost material for solar cell devices, polycrystalline magnesium silicide (poly-Mg{sub 2}Si) semiconducting layers have been prepared by applying rf magnetron sputtering using a Mg{sub 2}Si target. The optimum substrate temperature for the poly-Mg{sub 2}Si growth was found to be T{sub s} = 200 deg. C; the film deposition at higher temperatures leads to desorption of Mg atoms from the growing surface, while the amorphous phase formation occurs at room temperature. The poly-Mg{sub 2}Si layer deposited at T{sub s} = 200 deg. C shows the (111) preferential orientation with a uniform grain size of {approx}50 nm. The dielectric function of the poly-Mg{sub 2}Si layer has been determined accurately by spectroscopic ellipsometry. From the analysis, quite high absorption coefficients and an indirect gap of 0.77 eV in the poly-Mg{sub 2}Si layer have been confirmed. The above poly-Mg{sub 2}Si layer shows clear photoconductivity and can be applied as a narrow-gap bottom layer in multi-junction solar cell devices.
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.
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.
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.
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...
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.
NASA Astrophysics Data System (ADS)
Millán-Núñez, Eduardo; Sieracki, Michael E.; Millán-Núñez, Roberto; Lara-Lara, José Rubén; Gaxiola-Castro, Gilberto; Trees, Charles C.
2004-03-01
In recent years, experts of optical hydrology have shown great interest in the variability of the specific absorption coefficient of light by phytoplankton (aph*). This parameter is important and necessary for comparing in situ bio-optical and satellite optical measurements. Such comparisons are needed for detecting primary productivity at a mesoscale level. At present, however, the parameters used in algorithms for predicting productivity are global averages. To avoid this bias, we measured the spatial-temporal variability of aph* as part of the Jan-01 Investigaciones Mexicanas de la Corriente de California cruise along the southern California Current. We observed median values of 0.041 m2 (mg chlorophyll a (Chl a))-1 at 440 nm and 0.015 at 674 nm, with significant differences between inshore and offshore stations. In general, the stations located in the area of Bahía Vizcaíno, with oceanographic conditions favorable for the growth of phytoplankton, showed lower values of the aph* . The nano-microphytoplankton (>5 μm) community comprised of 26 diatom genera with mean abundance values of the 19.5×103 cells l-1. Nitzschia closterium, a pennate diatom, was almost uniform throughout the study region. Flow cytometry measurements indicated that the picoplankton (<5 μm) community consisted of two prokaryotes, Prochlorococcus (mean 3.6×106 cells l-1) and Synechococcus (mean 10.4×106 cells l-1), and a mixture of picoeukaryotes (mean 6.5×106 cells l-1). Analyses of Chl and carotenoid pigments determined by high-performance liquid chromatographic confirmed the presence of the divinyl Chl a characteristic of Prochlorococcus. The nano-micro- and picoplankton were 82% and 18% of total phytoplankton biomass (μg C l-1), respectively. In general, we concluded that the phytoplankton community structure and biomass on this cruise showed conditions similar to oligotrophic systems.
NASA Astrophysics Data System (ADS)
Busch, T. A.; Nugent, R. E.
2003-10-01
In situ testing determined the insertion loss ( IL) and absorption coefficients of a candidate absorptive noise barrier (soundwall) to abate railway noise for residents of Anaheim, CA. A 4000 m barrier is proposed south of the tracks, but residential areas to the north have expressed concerns that barrier reflections will increase their noise exposure. To address these concerns, a 3.66 m high by 14.6 m long demonstration barrier was built in the parking lot of Edison Field, Anaheim, as part of a public open house, thereby allowing for acoustical measurements. Insertion loss ( IL) was measured in third-octave bands assuming 1/2-scale construction. The IL for three, scaled railway noise sub-sources (rail/wheel interface, locomotive, and train horn) was measured at six, scaled distances. The highest total, A-weighted IL, after corrections for finite-barrier and point-source speaker effects was 22 dB(A) for rail/wheel noise, 18 dB(A) for locomotive noise, and 20 dB(A) for train horn noise. These results can be compared favourably to IL predictions made using algorithms from the US Federal Rail Administration (FRA) noise assessment guidelines. For the actual barrier installation, shielded residential receivers located south of the project are expected to see their future noise exposures reduced from an unmitigated 78 CNEL to 65 CNEL. Absorption coefficients were measured using time delay spectrometry. At lower frequencies, measured absorption coefficients were notably less than the reverberation room results advertised in the manufacturer's literature, but generally conformed with impedance tube results. At higher frequencies the correspondence between measured absorption coefficients and reverberation room results was much improved. For the actual barrier installation, unshielded residential receivers to the north are expected to experience noise exposure increases of less than 1 dB(A). This factor of increase is consistent with a finding of no impact when assessed
NASA Astrophysics Data System (ADS)
Khoa, Doan Quoc; Phuong, Le Thi Thu; Hoi, Bui Dinh
2017-03-01
A quantum kinetic equation for electrons interacting with confined phonons is used to investigate the nonlinear absorption of an intense electromagnetic wave by electrons in cylindrical GaAs/AlAs quantum wires. The analytic expression for absorption coefficient is calculated for three models of confined optical phonons: the dielectric continuum (DC), hydrodynamic continuum (HC), and Huang-Zhu (HZ) models. The absorption coefficient depends on the square of the electromagnetic wave amplitude. The electrophonon resonance and optically detected electrophonon resonance (ODEPR) are observed through the absorption spectrum. The full width at half maximum (the line-width) of the ODEPR peaks is obtained by a computational method. The line-width is found to increase with increasing temperature and decrease with increasing the quantum wire radius. In particular, numerical results show that the DC and HZ models lead to a similar behaviour of electron - confined phonon interaction whereas the HC model results in a quite different one, especially at small quantum wire radius. For large quantum wire radii, above mentioned phonon models have equivalent contributions to the ODEPR line-width.
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.
Navarro, Juan M; Escolano, José; Cobos, Maximo; López, José J
2013-03-01
The diffusion equation model was used for room acoustic simulations to predict the sound pressure level and the reverberation time. The technical literature states that the diffusion equation method accurately models the late portion of the room impulse response if the energy is sufficiently scattered. This work provides conclusions on the validity of the diffusion equation model for rooms with homogeneous dimensions in relation to the scattering coefficients of the boundaries. A systematic evaluation was conducted out to determine the ranges of the absorption and scattering coefficient values that result in low noticeable differences between the predictions from a geometrical acoustic model and those from the diffusion equation model.
Effects of suspended sediment concentration on the absorption and scattering coefficients
NASA Astrophysics Data System (ADS)
Terrie, Gregory E.; Ladner, Sherwin; Gould, Richard A., Jr.
1997-02-01
The scattering coefficient (b) for the nearshore waters off the coast of North Carolina near Camp Lejeune is strongly influenced by suspended sediment concentration and total particulate cross-sectional area (xg). In-situ measurements of a and b were made using a WET Labs AC9 meter. Estimates of suspended sediment concentration and total particulate cross-sectional area were determined from laser particle size analyses of surface water samples. The SeaWiFS bio-optical algorithm was modified for Case II waters and used to estimate a and bb from remote sensing reflectance (Rrs). After conversion from backscattering (bb) to total scattering (b), modeled a and b values from the modified SeaWiFS algorithm were compared to the measured values. The differences between the measured and estimated values appear to be directly related to increases in suspended sediment concentration and xg. Correlations of about 0.90 were obtained for b vs xg and bb vs xg.
NASA Astrophysics Data System (ADS)
Dowell, M.
2006-12-01
Chlorophyll-a specific absorption (aph*) is a parameter used in bio-optical and primary production models and its coefficients are usually assumed to be constant. However, it has been documented in previous studies that these coefficients vary significantly due to pigmentation and "the package effect" which are a function of the taxonomic composition and the physiological state of the algal population. As part of the Coastal Ocean Observing Center (COOC) at the University of New Hampshire, HPLC pigments and phytoplankton absorption measurements were taken from water samples collected within the Gulf of Maine from 2004-2006. These data were then partitioned spatially, temporally, seasonally, and by other classification criteria. Spectral aph* means were generated for all partitions within each classification method. The results were used to parameterize province-specific bio-optical models for a regional algorithm. The separation of aph* means into different classes captured the effects of taxonomy and the package effect by reducing aph* variability.
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)
Sheng, Wang; Yun, Kang; Xianli, Li
2016-11-01
Within the quasi-one-dimensional effective potential model and effective mass approximation, we obtain the wavefunctions and energy eigenvalues of the ground (j = 1) and first 2 excited states (j = 2 and 3) of a donor impurity in a rectangular GaAs quantum dot in the presence of electric field. The donor impurity-related linear and nonlinear optical absorption as well as refractive index changes for the transitions j = 1-2 and j = 2-3 are investigated. The results show that the impurity position, incident optical intensity and electric field play important roles in the optical absorption coefficients and refractive index changes. We find that the impurity effect induces the blueshift for j = 1-2 and redshift for j = 3-2 in the absence of the electric field, but it leads to redshift for j = 1-2 and blueshift for j = 3-2 in the existence of the field. Also, the optical coefficient for the higher energy transitions j = 2-3 is insensitive to variation of impurity positions, while that for the low energy transition j = 1-2 depends significantly on the positions of impurity. In addition, the saturation and splitting phenomenon of the optical absorption are observed as the incident optical intensity increases. Project supported by the Science and Technology Project of Education Department of Heilongjiang Province of China (No. 12541070).
Chen, Sheng-Hui; Wang, Hsuan-Wen; Chang, Ting-Wei
2012-03-12
Considering the Mott-Davis density of state model and Rayleigh scattering effect, we present an approach to model the absorption profile of microcrystalline silicon thin films in this paper. Maxwell-Garnett effective medium theory was applied to analyze the absorption curves. To validate the model, several experimental profiles have been established and compared with those results from the model. With the assistance of the genetic algorithm, our results show that the absorption curves from the model are in good agreement with the experiments. Our findings also indicate that, as the crystal volume fraction increases, not only do the defects in amorphous silicon reduce, but the bulk scattering effect is gradually enhanced as well.
Ritter, André; Anton, Gisela; Weber, Thomas
2016-01-01
A maximum-likelihood reconstruction technique for X-ray Talbot-Lau tomography is presented. This technique allows the iterative simultaneous reconstruction of discrete distributions of absorption coefficient, refractive index and a dark-field scattering coefficient. This technique avoids prior phase retrieval in the tomographic projection images and thus in principle allows reconstruction from tomographic data with less than three phase steps per projection. A numerical phantom is defined which is used to evaluate convergence of the technique with regard to photon statistics and with regard to the number of projection angles and phase steps used. It is shown that the use of a random phase sampling pattern allows the reconstruction even for the extreme case of only one single phase step per projection. The technique is successfully applied to measured tomographic data of a mouse. In future, this reconstruction technique might also be used to implement enhanced imaging models for X-ray Talbot-Lau tomography. These enhancements might be suited to correct for example beam hardening and dispersion artifacts and improve overall image quality of X-ray Talbot-Lau tomography. PMID:27695126
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.
Uranyl ion: A convenient standard for transient molar absorption coefficient measurements
Bakac, A.; Burrows, H.D.
1997-12-01
Transient absorption spectra of an aqueous solution of uranyl sulfate have been measured in the ultraviolet and visible spectra. The excited uranyl ion may be a convenient standard for actinometry and photoacoustic calorimetry. (AIP) {copyright} {ital 1997} {ital Society for Applied Spectroscopy}
Park, Seoung-Hwan; Ahn, Doyeol; Park, Chan-Yong
2017-02-20
Intersubband absorption properties of lattice-matched BGaN/AlN quantum well (QW) structures grown on AlN substrate are theoretically investigated using an effective mass theory considering the nonparabolicity of the conduction band. These results are compared with those of GaN/AlN QW structures. The intersubband absorption coefficient of the BGaN/AlN QW structure is shown to be enhanced significantly, compared to that of the conventional GaN/AlN QW structure. This can be explained by the fact that the BGaN/AlN QW structure exhibits larger intersuband dipole moment and quasi-Fermi-level separation than the GaN/AlN QW structure, due to the increase in the carrier confinement by a larger internal field. We expect that the BGaN/AlN QW structure with a high absorption coefficient can be used for telecommunication applications at 1.55 µm under the lattice-matched condition, instead of the conventional GaN/AlN QW structure with the large strain.
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.
NASA Astrophysics Data System (ADS)
Nelson, David D., Jr.; Schiffman, Aram; Nesbitt, David J.; Orlando, John J.; Burkholder, James B.
1990-11-01
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.
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.
Vollbrecht, Joachim; Bock, Harald; Wiebeler, Christian; Schumacher, Stefan; Kitzerow, Heinz
2014-09-15
Bilaterally extended perylenes were synthesized, characterized, and used to create organic light-emitting devices. A detailed investigation of the electronic and optical properties, and a comparison of perylene derivatives and compounds with unilaterally and bilaterally extended aromatic cores, reveal unexpected changes of the absorption spectrum, which are in agreement with simulations based on DFT.
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.
NASA Astrophysics Data System (ADS)
Montilla, E.; Mogo, S.; Cachorro, V.; Lopez, J.; de Frutos, A.
2011-01-01
In situ measurements of aerosol optical properties were made in summer 2008 at the ALOMAR station facility (69°16 N, 16°00 E), located at a rural site in the North of the island of Andøya (Vesterålen archipelago), about 300 km north of the Arctic Circle. The extended three months campaign was part of the POLAR-CAT Project of the International Polar Year (IPY-2007-2008), and its goal was to characterize the aerosols of this sub-Arctic area which frequently transporte to the Arctic region. The ambient light-scattering coefficient, σs(550 nm), at ALOMAR had a hourly mean value of 5.412 Mm-1 (StD = 3.545 Mm-1) and the light-absorption coefficient, σa(550 nm), had an hourly mean value of 0.400 Mm-1 (StD = 0.273 Mm-1). The scattering/absorption Ångström exponents, αs,a, are used for detailed analysis of the variations of the spectral shape of σs,a. The single scattering albedo, &omega0, ranges from 0.622 to 0.985 (mean = 0.913, StD = 0.052) and the relation of this property to the absorption/scattering coefficients and the Ångström exponents is presented. The relationships between all the parameters analyzed, mainly those related to the single scattering albedo, allow us to describe the local atmosphere as extremely clean.
NASA Astrophysics Data System (ADS)
Mendonca, J.; Strong, K.; Sung, K.; Devi, V. M.; Toon, G. C.; Wunch, D.; Franklin, J. E.
2017-03-01
A quadratic-speed-dependent Voigt line shape (qSDV) with line mixing (qSDV+LM), together with spectroscopic line parameters from Devi et al. [1,2] for the 2v3 band of CH4, was used to retrieve total columns of CH4 from atmospheric solar absorption spectra. The qSDV line shape (Tran et al., 2013) [3] with line mixing (Lévy et al., 1992) [4] was implemented into the forward model of GFIT (the retrieval algorithm that is at the heart of the GGG software (Wunch et al., 2015) [5]) to calculate CH4 absorption coefficients. High-resolution laboratory spectra of CH4 were used to assess absorption coefficients calculated using a Voigt line shape and spectroscopic parameters from the atm line list (Toon, 2014) [6]. The same laboratory spectra were used to test absorption coefficients calculated using the qSDV+LM line shape with spectroscopic line parameters from Devi et al. [1,2] for the 2v3 band of CH4 and a Voigt line shape for lines that don't belong to the 2v3 band. The spectral line list for lines that don't belong to the 2v3 band is an amalgamation of multiple spectral line lists. We found that for the P, Q, and R branches of the 2v3 band, the qSDV+LM simulated the laboratory spectra better than the Voigt line shape. The qSDV+LM was also used in the spectral fitting of high-resolution solar absorption spectra from four ground-based remote sensing sites and compared to spectra fitted with a Voigt line shape. The average root mean square (RMS) residual for 131,124 solar absorption spectra fitted with absorption coefficients calculated using the qSDV+LM for the 2v3 band of CH4 and the new spectral line list for lines for lines that don't belong to the 2v3 band, was reduced in the P, Q, and R branches by 5%, 13%, and 3%, respectively when compared with spectra fitted using a Voigt line shape and the atm line list. We found that the average total column of CH4 retrieved from these 131,124 spectra, with the qSDV+LM was 1.1±0.3% higher than the retrievals performed using a
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)
Minimala, N. S.; Peter, A. John
2013-02-01
Effects of magnetic field strength and the built-in electric fields on the exciton binding energy and the non-linear optical property such as absorption coefficients in a GaN/AlGaN wide band gap heterostructure are investigated. The internal fields due to spontaneous and piezo-electric polarizations are included in the Hamiltonian. Our results show that the optical absorption coefficients strongly depend on the internal fields and the applied magnetic field.
NASA Astrophysics Data System (ADS)
Demkin, Artem S.; Nikitin, Dmitriy G.; Ryabushkin, Oleg A.
2016-04-01
In current work optical properties of LiB3O5 (LBO) crystal with ultraviolet (UV) (λ= 266 nm) induced volume macroscopic defect (track) are investigated using novel piezoelectric resonance laser calorimetry technique. Pulsed laser radiation of 10 W average power at 532 nm wavelength, is consecutively focused into spatial regions with and without optical defect. For these cases exponential fitting of crystal temperature kinetics measured during its irradiation gives different optical absorption coefficients α1 = 8.1 • 10-4 cm-1 (region with defect) and α =3.9ṡ10-4 cm-1 (non-defected region). Optical scattering coefficient is determined as the difference between optical absorption coefficients measured for opaque and transparent lateral facets of the crystal respectively. Measurements reveal that scattering coefficient of LBO in the region with defect is three times higher than the optical absorption coefficient.
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)
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.
Ishimatsu, Naoki; Matsumoto, Ken; Maruyama, Hiroshi; Kawamura, Naomi; Mizumaki, Masaichiro; Sumiya, Hitoshi; Irifune, Tetsuo
2012-09-01
Nano-polycrystalline diamond (NPD) [Irifune et al. (2003), Nature (London), 421, 599] has been used to obtain a glitch-free X-ray absorption spectrum under high pressure. In the case of conventional single-crystal diamond (SCD) anvils, glitches owing to Bragg diffraction from the anvils are superimposed on X-ray absorption spectra. The glitch has long been a serious problem for high-pressure research activities using X-ray spectroscopy because of the difficulties of its complete removal. It is demonstrated that NPD is one of the best candidate materials to overcome this problem. Here a glitch-free absorption spectrum using the NPD anvils over a wide energy range is shown. The advantage and capability of NPD anvils is discussed by a comparison of the glitch map with that of SCD anvils.
NASA Astrophysics Data System (ADS)
Barik, A. R.; Adarsh, K. V.; Naik, Ramakanta; Sandeep, C. S. Suchand; Philip, Reji; Zhao, Donghui; Jain, Himanshu
2011-05-01
We report a dramatic change in effective three-photon absorption coefficient of amorphous Ge16As29Se55 thin films, when its optical band gap decreases by 10 meV with 532 nm light illumination. This large change provides valuable information on the higher excited states, which are otherwise inaccessible via normal optical absorption. The results also indicate that photodarkening in chalcogenide glasses can serve as an effective tool to tune the multiphoton absorption in a rather simple way.
NASA Astrophysics Data System (ADS)
McKee, David; Röttgers, Rüdiger; Neukermans, Griet; Calzado, Violeta Sanjuan; Trees, Charles; Ampolo-Rella, Marina; Neil, Claire; Cunningham, Alex
2014-12-01
Understanding variability in the chlorophyll-specific absorption of marine phytoplankton, aph*Chl (λ), is essential for primary production modelling, calculation of underwater light field characteristics, and development of algorithms for remote sensing of chlorophyll concentrations. Previous field and laboratory studies have demonstrated significant apparent variability in aph*Chl (λ) for natural samples and algal cultures. However, the potential impact of measurement uncertainties on derived values of aph*Chl (λ) has received insufficient study. This study presents an analysis of measurement uncertainties for a data set collected in the Ligurian Sea in Spring and assesses the impact on estimates of aph*Chl (λ). It is found that a large proportion of apparent variability in this set of aph*Chl (λ) can be attributed to measurement errors. Application of the same analysis to the global NOMAD data set suggests that a significant fraction of variability in aph*Chl (λ) may also be due to measurement errors. The copyright line for this article was changed on 16 JAN 2015 after original online publication.
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.
On PAHs as interstellar grains - Infrared absorption coefficients. [polycyclic aromatic hydrocarbons
NASA Technical Reports Server (NTRS)
Salisbury, D. W.; Allen, J. E., Jr.; Donn, B.; Khanna, R. K.; Moore, W. J.
1988-01-01
Consideration is given to the proposal that PAHs are the source of IR continuum and emission features and the visible diffuse bands. Absolute IR cross-sections have been obtained for eight PAHs. The results show that a thermal continuum is not consistent with the spectra obtained, and that an array of normal molecules shows a spectrum that is more complex than the observed spectrum. The cross-sections of the UV spectra are 2-3 orders of magnitude larger than those of the IR spectra. It is suggested that, to account for these observations, structure must be produced in the UV extinction curve.
Li, Jun; Zhou, Xianming; Li, Jiabo
2008-12-01
An experimental method was developed to perform time-resolved, single-pass optical absorption measurements and to determine absorption coefficients of window materials under strong shock compression up to approximately 200 GPa. Experimental details are described of (i) a configuration to generate an in situ dynamic, bright, optical source and (ii) a sample assembly with a lithium fluoride plate to essentially eliminate heat transfer from the hot radiator into the specimen and to maintain a constant optical source within the duration of the experiment. Examples of measurements of optical absorption coefficients of several initially transparent single crystal materials at high shock pressures are presented.
Cuppo, F L S; Gómez, S L; Figueiredo Neto, A M
2004-04-01
In this paper is reported a systematic experimental study of the linear-optical-absorption coefficient of ferrofluid-doped isotropic lyotropic mixtures as a function of the magnetic-grains concentration. The linear optical absorption of ferrolyomesophases increases in a nonlinear manner with the concentration of magnetic grains, deviating from the usual Beer-Lambert law. This behavior is associated to the presence of correlated micelles in the mixture which favors the formation of small-scale aggregates of magnetic grains (dimers), which have a higher absorption coefficient with respect to that of isolated grains. We propose that the indirect heating of the micelles via the ferrofluid grains (hyperthermia) could account for this nonlinear increase of the linear-optical-absorption coefficient as a function of the grains concentration.
Sato, Chie; Shimada, Miho; Tanikawa, Yukari; Hoshi, Yoko
2013-09-01
Expanding our previously proposed "time segment analysis" for a two-layered turbid medium, this study attempted to selectively determine the absorption coefficient (μa) of the bottom layer in a four-layered human head model with time-domain near-infrared measurements. The difference curve in the temporal profiles of the light attenuation between an object and a reference medium, which are obtained from Monte Carlo simulations, is divided into segments along the time axis, and a slope for each segment is calculated to obtain the depth-dependent μa(μaseg). The reduced scattering coefficient (μs') of the reference is determined by curve fitting with the temporal point spread function derived from the analytical solution of the diffusion equation to the time-resolved reflectance of the object. The deviation of μaseg from the actual μa is expressed by a function of the ratio of μaseg in an earlier time segment to that in a later segment for mediums with different optical properties and thicknesses of the upper layers. Using this function, it is possible to determine the μa of the bottom layer in a four-layered epoxy resin-based phantom. These results suggest that the method reported here has potential for determining the μa of the cerebral tissue in humans.
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.
Gaonkar, Harshavardhan Ashok; Kumar, Dinesh; Ramasubramaniam, Rajagopal; Roy, Arindam
2014-05-01
Efforts are underway to better understand the absorption properties of micro- and nano-sized particles due to their potential in various photonic applications. However, most of these particles exhibit strong scattering in the spectral regions of interest in addition to absorption. Due to strong interference from scattering, the absorption of these turbid samples cannot be directly measured using conventional spectroscopy techniques. The optical properties of these particles are also different from that of the bulk due to quantum confinement and plasmon resonance effects and cannot be inferred from their bulk properties. By measuring the total transmittance and total reflectance (diffuse and collimated) of turbid samples and using an empirical relation between the coefficients of the Kubelka-Munk and radiative transfer theories, we have demonstrated a method to calculate the absorption and reduced scattering coefficients of turbid samples. This method is capable of extracting the absorption coefficient of turbid samples with an error of 2%. Using this method, we have decoupled the specific absorption and specific reduced scattering coefficients of commercially available micro-sized iron oxide particles. The current method can be used to measure the optical properties of irregularly shaped particle dispersions, which are otherwise difficult to estimate theoretically.
NASA Astrophysics Data System (ADS)
de Bruyn, W. J.; Swartz, E.; Hu, J. H.; Shorter, Jeffrey A.; Davidovits, P.; Worsnop, D. R.; Zahniser, M. S.; Kolb, C. E.
1995-04-01
Biogenically produced reduced sulfur compounds, including dimethylsulfide (DMS, CH3SCH3), hydrogen sulfide (H2S), carbon disulfide (CS2), methyl mercaptan (CH3SH), and carbonyl sulfide (OCS), are a major source of sulfur in the marine atmosphere. This source is estimated to contribute 25-40% of global sulfur emissions. These species and their oxidation products, dimethyl sulfoxide (DMSO), dimethyl sulfone (DMSO2), and methane sulfonic acid (MSA), dominate the production of aerosol and cloud condensation nuclei (CCN) in the clean marine atmosphere. The multiphase chemical processes for these species must be understood in order to study the evolving role of combustion-produced sulfur oxides over the oceans. Using a newly developed bubble column apparatus, a series of aqueous phase uptake studies have been completed for the reduced sulfur species DMS, H2S, CS2, CH3SH, and OCS. Aqueous phase uptake has been studied as a function of temperature (278-298 K), pH (1-14), H2O2 concentration (0-1 M), NaCl concentration (0-5 M), and (NH4)2SO4 concentration (0-4 M). The Henry's law coefficients for CH3SH and CS2 were determined for the first time, as were the Setchenow coefficients for all the species studied.
Mean absorption coefficients of He/Ar/N2/(C1-x-y , Ni x , Co y ) thermal plasmas for CNT synthesis
NASA Astrophysics Data System (ADS)
Salem, D.; Hannachi, R.; Cressault, Y.; Teulet, Ph; Béji, L.
2017-01-01
In this paper, we present the mean absorption coefficients (MACs) calculated for plasma mixtures of argon-helium-nitrogen-carbon-nickel-cobalt at 60 kPa and in a temperature range from 1 kK to 20 kK. These coefficients have been computed under the assumption of a local thermodynamic equilibrium (LTE), isothermal plasma, including atomic and molecular continuum, molecular bands and lines radiation splitted into nine spectral intervals. The results show that the continuum absorption coefficients strongly depend on photodissociation and photoionization processes of the molecular species N2, CN and C2, with a significant effect on photodetachment processes of C- in a frequency interval lower than 1 × 1015 Hz and for low temperature (<6 kK). While at high temperature, the main contribution in continuum absorption coefficient comes from radiative recombination processes except in the infrared region (<0.5 × 1015 Hz) where the inverse bremsstrahlung represents the most important component in continuum processes for all temperature values. On the other hand, the calculation of MAC shows that the role of molecular continuum, molecular bands and line absorption of the neutral catalysis species Ni/Co are only important in a small range of temperature and in a few spectral bands located in visible and infrared regions, while at high temperature and in UV and visible regions, the foremost contributions to MAC come from atomic continuum and line absorption.
NASA Astrophysics Data System (ADS)
Shori, Ramesh K.
The interaction of high-intensity, short-pulsed radiation with liquid water results in dynamic changes in the optical absorption coefficient of water. These changes and their implications, as related to mid-infrared laser ablation of tissue, were not investigated until the late 1980's and early 1990's. Classical models of absorption and heating do not explain the dynamic, non-linear changes in water. The objective of the present work was to quantify the dynamic changes in the absorption coefficient of liquid water as a function of incident energy at three clinically relevant infrared wavelengths (λ = 2.94, 9.6, 10.6 μm). To investigate the changes in the absorption spectrum of water in the 3-μm band, a stable, high-energy Q- switched Er:YAG laser emitting 2.94-μm radiation in a near-perfect TEMoo spatial beam profile was developed. Key to the development of this laser was careful attention to the gain medium, optical pump system, system optics, and the thermal system. The final system design was capable of emitting 110 mJ/pulse at of 2-4 Hz with a lamp lifetime exceeding 12 million pulses The laser was used in two sets of experiments in order to quantify the above changes. First, the laser was used to measure the velocity of the shock front produced by vaporizing a gelatin-based tissue phantom. The measured shock velocity was related to the optical energy absorbed by the tissue phantom and the absorption coefficient, based on the pressure relationships derived using a 1-D piston model for an expanding plume. The shock front velocity measurements indicate that the absorption coefficient is constant for incident fluences less than 20 J/cm2, a result consistent with transmission data. For higher fluences, the data indicate a decrease in the absorption coefficient, which is again consistent with transmission data. Quantification of the absorption coefficient can, however, not be made without violating assumptions that form the basis for the 1-D piston model. Second
De Bruyn, W.J.; Swartz, E.; Hu, J.H.
1995-04-20
Biogenically produced reduced sulfur compounds, including dimethylsulfide (DMS, CH{sub 3}SCH{sub 3}), hydrogen sulfide (H{sub 2}S), carbon disulfide (CS{sub 2}), methyl mercaptan (CH{sub 3}SH), and carbonyl sulfide (OCS), are a major source of sulfur in the marine atmosphere. This source is estimated to contribute 25-40% of global sulfur emissions. These species and their oxidation products, dimethyl sulfoxide (DMSO), dimethyl sulfone (DMSO{sub 2}), and methane sulfonic acid (MSA), dominate the production of aerosol and cloud condensation nuclei (CCN) in the clean marine atmosphere. The multiphase chemical processes for these species must be understood in order to study the evolving role of combustion-produced sulfur oxides over the oceans. Using a newly developed bubble column apparatus, a series of aqueous phase uptake studies have been completed for the reduced sulfur species DMS, H{sub 2}S, CS{sub 2}, CH{sub 3}SH, and OCS. Aqueous phase uptake has been studied as a function of temperature (278-298 K), pH (1-14), H{sub 2}O{sub 2} concentration (0-1 M), NaCl concentration (0-5 M), and (NH{sub 4}){sub 2}SO{sub 4} concentration (0-4 M). The Henry`s law coefficients for CH{sub 3}SH and CS{sub 2} were determined for the first time, as were the Setchenow coefficients for all the species studied. 33 refs., 8 figs., 2 tabs.
Krska, Rudolf; Schubert-Ullrich, Patricia; Josephs, Ralf D; Emteborg, Håkan; Buttinger, Gerhard; Pettersson, Hans; van Egmond, Hans P; Schothorst, Ronald C; Macdonald, Susan; Chan, Danny
2007-07-01
This paper presents results from the European Commission-funded project Doncalibrant, the objective of which was to produce calibrators with certified mass fractions of the Fusarium toxins deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-Ac-DON), 15-acetyldeoxynivalenol (15-Ac-DON), and nivalenol (NIV), in acetonitrile. The calibrators, available in ampoules, were sufficiently homogeneous, with between-bottle variations (s (bb)) of less than 2%. Long-term stability studies performed at four different temperatures between -18 and 40 degrees C revealed no significant negative trends (at a confidence level of 95%). Molar absorptivity coefficients (in L mol(-1) cm(-1)) were determined for all four toxins (DON: 6805 +/- 126, NIV: 6955 +/- 205, 3-Ac-DON: 6983 +/- 141, 15-Ac-DON: 6935 +/- 142) on the basis of a mini-interlaboratory exercise. The overall uncertainty of the calibrators' target values for DON and NIV were evaluated on the basis of gravimetric preparation data and include uncertainty contributions from possible heterogeneity, storage, and transport. The Doncalibrant project resulted in the production of calibrators for DON (IRMM-315) and NIV (IRMM-316) in acetonitrile with certified mass fractions of 25.1 +/- 1.2 microg g(-1) and 24.0 +/- 1.1 microg g(-1), respectively. Both CRMs became commercially available from the Institute for Reference Materials and Measurements (IRMM, Geel, Belgium) at the beginning of 2007.
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 Technical Reports Server (NTRS)
Guiot, R.; Wunnenberg, H.
1980-01-01
The methods by which aerodynamic coefficients are determined and discussed. These include: calculations, wind tunnel experiments and experiments in flight for various prototypes of the Alpha Jet. A comparison of obtained results shows good correlation between expectations and in-flight test results.
NASA Technical Reports Server (NTRS)
Mallet, M.; Dubovik, O.; Nabat, P.; Dulac, F.; Kahn, R.; Sciare, J.; Paronis, D.; Leon, J. F.
2013-01-01
Aerosol absorption properties are of high importance to assess aerosol impact on regional climate. This study presents an analysis of aerosol absorption products obtained over the Mediterranean Basin or land stations in the region from multi-year ground-based AERONET and satellite observations with a focus on the Absorbing Aerosol Optical Depth (AAOD), Single Scattering Albedo (SSA) and their spectral dependence. The AAOD and Absorption Angstrom Exponent (AAE) data set is composed of daily averaged AERONET level 2 data from a total of 22 Mediterranean stations having long time series, mainly under the influence of urban-industrial aerosols and/or soil dust. This data set covers the 17 yr period 1996-2012 with most data being from 2003-2011 (approximately 89 percent of level-2 AAOD data). Since AERONET level-2 absorption products require a high aerosol load (AOD at 440 nm greater than 0.4), which is most often related to the presence of desert dust, we also consider level-1.5 SSA data, despite their higher uncertainty, and filter out data with an Angstrom exponent less than 1.0 in order to study absorption by carbonaceous aerosols. The SSA data set includes both AERONET level-2 and satellite level-3 products. Satellite-derived SSA data considered are monthly level 3 products mapped at the regional scale for the spring and summer seasons that exhibit the largest aerosol loads. The satellite SSA dataset includes the following products: (i) Multi-angle Imaging SpectroRadiometer (MISR) over 2000-2011, (ii) Ozone Monitoring Instrument (OMI) near-UV algorithm over 2004-2010, and (iii) MODerate resolution Imaging Spectroradiometer (MODIS) Deep-Blue algorithm over 2005-2011, derived only over land in dusty conditions. Sun-photometer observations show that values of AAOD at 440 nm vary between 0.024 +/- 0.01 (resp. 0.040 +/- 0.01) and 0.050 +/- 0.01 (0.055 +/- 0.01) for urban (dusty) sites. Analysis shows that the Mediterranean urban-industrial aerosols appear "moderately
Zogka, Antonia G; Mellouki, Abdelwahid; Romanias, Manolis N; Bedjanian, Yuri; Idir, Mahmoud; Grosselin, Benoit; Daële, Véronique
2016-11-17
The rate coefficients for the reactions of OH and Cl with 1-methoxy 2-propyl acetate (MPA) in the gas phase were measured using absolute and relative methods. The kinetic study on the OH reaction was conducted in the temperature (263-373) K and pressure (1-760) Torr ranges using the pulsed laser photolysis-laser-induced fluorescence technique, a low pressure fast flow tube reactor-quadrupole mass spectrometer, and an atmospheric simulation chamber/GC-FID. The derived Arrhenius expression is kMPA+OH(T) = (2.01 ± 0.02) × 10(-12) exp[(588 ± 123/T)] cm(3) molecule(-1) s(-1). The absolute and relative rate coefficients for the reaction of Cl with MPA were measured at room temperature in the flow reactor and the atmospheric simulation chamber, which led to k(Cl+MPA) = (1.98 ± 0.31) × 10(-10) cm(3) molecule(-1) s(-1). GC-FID, GC-MS, and FT-IR techniques were used to investigate the reaction mechanism in the presence of NO. The products formed from the reaction of MPA with OH and their yields were methyl formate (80 ± 7.3%), acetic acid (50 ± 4.8%), and acetic anhydride (22 ± 2.4%), while for Cl reaction, the obtained yields were 60 ± 5.4, 41 ± 3.8, and 11 ± 1.2%, respectively, for the same products. The UV absorption cross section spectrum of MPA was determined in the wavelength range 210-370 nm. The study has shown no photolysis of MPA under atmospheric conditions. The obtained results are used to derive the atmospheric implication.
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
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.
Sánchez-Castaño, G; Ruíz-García, A; Bañón, N; Bermejo, M; Merino, V; Freixas, J; Garriguesx, T M; Plá-Delfina, J M
2000-11-01
A preliminary study attempting to predict the intrinsic absolute bioavailability of a group of antibacterial 6-fluoroquinolones-including true and imperfect homologues as well as heterologues-was carried out. The intrinsic absolute bioavailability of the test compounds, F, was assessed on permanently cannulated conscious rats by comparing the trapezoidal normalized areas under the plasma concentration-time curves obtained by intravenous and oral routes (n = 8-12). The high-performance liquid chromatography analytical methods used for plasma samples are described. Prediction of the absolute bioavailability of the compounds was based on their intrinsic rat gut in situ absorption rate constant, k(a). The working equation was: where T represents the mean absorbing time. A T value of 0.93 (+/-0.06) h provides the best correlation between predicted and experimentally obtained bioavailabilities (F' and F, respectively) when k(a) values are used (slope a = 1.10; intercept b = -0.05; r = 0.991). The k(a) values can also be expressed in function of the in vitro partition coefficients, P, between n-octanol and a phosphate buffer. In this case, theoretical k(a) values can be determined with the parameters of a standard k(a)/P correlation previously established for a group of model compounds. When P values are taken instead of k(a) values, reliable bioavailability predictions can also be made. These and other relevant features of the method are discussed.
Electronic structure of d{sup 0} vanadates obtained by x-ray absorption and emission spectroscopies
Herrera, G.; Jimenez-Mier, J.; Chavira, E.; Moewes, A.; Wilks, R.
2009-01-29
We present experimental results for x-ray absorption at the L{sub 2,3}-edge of vanadium in V{sub 2}O{sub 5}, YVO{sub 4} and LaVO{sub 4} compounds and at the M{sub 4,5}-edge of lanthanum in LaVO{sub 4} compound. The data are interpreted in terms of the multiplet structure of the transition metal ion V{sup 5+} (d{sup 0}) and rare earth ion La{sup 3+} (d{sup 10}). The data are compared with calculations in the free-ion approximation for La and including the effects of the D{sub 4h} ligand field and charge transfer for V. These calculations allow a direct interpretation of the absorption spectra. Good overall agreement between experiment and theory is found. We also show resonant x-ray emission (XES) data for these compounds obtained at the top of the L{sub 2} excitation.
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)
Allali, Karima; Bricaud, Annick; Claustre, Hervé
1997-01-01
Chlorophyll-specific absorption coefficients of particles, a*p(λ), and of phytoplankton, a*ph(λ), were determined using the glass-fiber filter technique along 150°W in the equatorial Pacific (13°S-1°N). A site-specific algorithm for correcting the path length amplification effect was derived from field measurements. Then a decomposition technique using the high-performance liquid chromatography pigment information and taking into account the package effect was used to partition a*ph into the contributions of photosynthetic pigments (a*ps) and nonphotosynthetic pigments (a*nps). Both a*ph and a*nps values were observed to decrease from the oligotrophic waters of the subequatorial area (13°-1°S) to the mesotrophic waters of the equatorial area (1°S-1°N) and from the surface to deep waters. The a*ph variations were primarily, but not exclusively, caused by changes in the concentrations of nonphotosynthetic pigments. The level of pigment packaging was also variable both horizontally and vertically, as a result of changes in populations and photoacclimation. In comparison with a*ph, a*ps exhibited a reduced range of variation with depth and along the latitudinal gradient. The variations in a*ps originating from the package effect were partly compensated by variations in the concentrations of photosynthetic pigments. We extended this analysis to include data collected in other areas with different trophic states. The a*ps values varied over a factor of 4 at 440 nm, instead of 8 for a*ph, for chlorophyll a concentrations covering 2 orders of magnitude (0.02-2 mg m-3). In agreement with a previous study performed off California with a different method [Sosik and Mitchell, 1995], we conclude that a*ps is less dependent on environmental parameters than a*ph. In addition, our results provide evidence that the variability in a*ps cannot be neglected. The use of a*ps instead of a*ph in light-photosynthesis models (in conjunction with a quantum yield for carbon fixation
NASA Astrophysics Data System (ADS)
Singer, W.; Latteck, R.; Friedrich, M.; Dalin, P.; Kirkwood, S.; Engler, N.; Holdsworth, D.
2005-08-01
A Doppler radar at 3.17 MHz has been installed close to the Andøya Rocket Range as part of the ALOMAR observatory at Andenes, Norway (69.3°N, 16.0°E) in summer 2002 to improve the ground based capabilities for measurements of small scale features and electron number densities in the mesosphere. The main feature of the new radar is the transmitting/receiving antenna which is arranged as a Mills Cross of 29 crossed half-wave dipoles with a minimum beam width of about 7°. The modular transceiver system provides high flexibility in beam forming and pointing as well as in switching of the polarisation between ordinary and extraordinary mode on transmission and reception. Doppler winds and electron number densities can be measured between about 55 km and 90 km with a time resolution of 9 minutes. The electron number density profiles derived with differential absorption (DAE) and differential phase (DPE) measurements are in remarkable good agreement. We discuss the diurnal and seasonal variability of electron densities obtained at Andenes in 2004/2005, the response of D-region electron densities to geomagnetic disturbances and solar proton events. The results are compared with rocket measurements from Andenes and with observations from EISCAT VHF radar at Tromsø.
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.
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.
Nader, Christelle Abou; Nassif, Rana; Pellen, Fabrice; Le Jeune, Bernard; Le Brun, Guy; Abboud, Marie
2015-12-10
In this paper, we present the evolution of speckle pattern polarimetric parameters in response to controlled changes in scatterer sizes, proportions, and the absorption coefficient in media. The experimental study was performed on mixtures of polystyrene microspheres with dye in order to ensure biological medium-like properties. The speckle grain sizes and degrees of polarization for linear and circular light were monitored. We observed helicity flipping in the degree of circular polarization for small scatterer proportion around 25%. Furthermore, linear depolarization decreased slightly for media containing more small particles. Good agreement was shown with numerical results computed using a Monte Carlo simulation of polarized light taking into account our experimental configuration. Speckle grain size also evolves with the increase of small scatterers as well as the media absorption coefficient. Such variations of properties are encountered during fruit maturation, in tissues in precancerous stages, and any transformation that causes a modification in particle proportions and absorption coefficient in biological media. The computed parameters proved to be sensitive to these changes.
Buhr, H; Büermann, L; Gerlach, M; Krumrey, M; Rabus, H
2012-12-21
For the first time the absolute photon mass energy-absorption coefficient of air in the energy range of 10 to 60 keV has been measured with relative standard uncertainties below 1%, considerably smaller than those of up to 2% assumed for calculated data. For monochromatized synchrotron radiation from the electron storage ring BESSY II both the radiant power and the fraction of power deposited in dry air were measured using a cryogenic electrical substitution radiometer and a free air ionization chamber, respectively. The measured absorption coefficients were compared with state-of-the art calculations and showed an average deviation of 2% from calculations by Seltzer. However, they agree within 1% with data calculated earlier by Hubbell. In the course of this work, an improvement of the data analysis of a previous experimental determination of the mass energy-absorption coefficient of air in the range of 3 to 10 keV was found to be possible and corrected values of this preceding study are given.
1975-07-01
coefficient. Diffuse reflectance spectroscopy, and in particular the Kubelka - Munk (K-M) theory, can provide such information. A convenient method for...34Uber Den Streukoeffizienten Der Kubelka - Munk -Theorie," Z. Naturforsch, 19a, 28. 3. J. B. Gillespie, J. D. Lindberg and L. S. Laude, 1975 " Kubelka ... Munk Optical Coefficients for a Barium Sulfate White Reflectance Standard," Appl. Opt. 14, 807. 4. F. Grum and G. W. Lucky, 1968, "Optical Sphere
Dakhlaoui, Hassen
2015-04-07
In the present paper, the linear and nonlinear optical absorption coefficients and refractive index changes between the ground and the first excited states in double GaN/Al{sub x}Ga{sub (1−x)}N quantum wells are studied theoretically. The electronic energy levels and their corresponding wave functions are obtained by solving Schrödinger-Poisson equations self-consistently within the effective mass approximation. The obtained results show that the optical absorption coefficients and refractive index changes can be red- and blue-shifted through varying the left quantum well width and the aluminum concentration x{sub b2} of the central barrier, respectively. These structural parameters are found to present optimum values for carrying out the transition of 0.8 eV (1.55 μm). Furthermore, we show that the desired transition can also be achieved by replacing the GaN in the left quantum well with Al{sub y}Ga{sub (1−y)}N and by varying the aluminum concentration y{sub Al}. The obtained results give a new degree of freedom in optoelectronic device applications such as optical fiber telecommunications operating at (1.55 μm)
NASA Astrophysics Data System (ADS)
Budilova, O. V.; Ionin, A. A.; Kinyaevskiy, I. O.; Klimachev, Yu M.; Kotkov, A. A.; Kozlov, A. Yu
2016-11-01
The broadband laser system based on multi-line Q-switched CO laser was experimentally studied in a nonlinear crystal AgGaSe2. The internal efficiency of sum frequency generation reached 1%. Test experiments on measurement of the absorption of the CO-laser sum frequency radiation by such gaseous substances as nitrous oxide and carbon dioxide were realized. A comparison of the experimental data with the theoretically calculated absorption spectrum of radiation was obtained.
Guo, Zijian; Hu, Song; Wang, Lihong V
2010-06-15
Optical absorption is closely associated with many physiological important parameters, such as the concentration and oxygen saturation of hemoglobin, and it can be used to quantify the concentrations of nonfluorescent molecules. We propose a method to use acoustic spectra of photoacoustic signals to quantify the absolute optical absorption. This method is self-calibrating and thus insensitive to variations in the optical fluence. Factors such as system bandwidth and acoustic attenuation can affect the quantification but can be canceled by dividing the acoustic spectra measured at two optical wavelengths. Using optical-resolution photoacoustic microscopy, we quantified the absolute optical absorption of black ink samples with various concentrations. We also quantified both the concentration and oxygen saturation of hemoglobin in a live mouse in absolute units.
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.
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.
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.
Zhao, Lei; Yu, Yiqun; Delzanno, Gian Luca; Jordanova, Vania K.
2015-04-01
Local acceleration via whistler wave and particle interaction plays a significant role in particle dynamics in the radiation belt. In this work we explore gyro-resonant wave-particle interaction and quasi-linear diffusion in different magnetic field configurations related to the March 17 2013 storm. We consider the Earth's magnetic dipole field as a reference and compare the results against non-dipole field configurations corresponding to quiet and stormy conditions. The latter are obtained with the ring current-atmosphere interactions model with a self-consistent magnetic field RAM-SCB, a code that models the Earth's ring current and provides a realistic modeling of the Earth's magnetic field. By applying quasi-linear theory, the bounce- and MLT-averaged electron pitch angle, mixed term, and energy diffusion coefficients are calculated for each magnetic field configuration. For radiation belt (~1 MeV) and ring current (~100 keV) electrons, it is shown that at some MLTs the bounce-averaged diffusion coefficients become rather insensitive to the details of the magnetic field configuration, while at other MLTs storm conditions can expand the range of equatorial pitch angles where gyro-resonant diffusion occurs and significantly enhance the diffusion rates. When MLT average is performed at drift shell L = 4.25 (a good approximation to drift average), the diffusion coefficients become quite independent of the magnetic field configuration for relativistic electrons, while the opposite is true for lower energy electrons. These results suggest that, at least for the March 17 2013 storm and for L ≲ 4.25, the commonly adopted dipole approximation of the Earth's magnetic field can be safely used for radiation belt electrons, while a realistic modeling of the magnetic field configuration is necessary to describe adequately the diffusion rates of ring current electrons.
Zhao, Lei; Yu, Yiqun; Delzanno, Gian Luca; ...
2015-04-01
Local acceleration via whistler wave and particle interaction plays a significant role in particle dynamics in the radiation belt. In this work we explore gyro-resonant wave-particle interaction and quasi-linear diffusion in different magnetic field configurations related to the March 17 2013 storm. We consider the Earth's magnetic dipole field as a reference and compare the results against non-dipole field configurations corresponding to quiet and stormy conditions. The latter are obtained with the ring current-atmosphere interactions model with a self-consistent magnetic field RAM-SCB, a code that models the Earth's ring current and provides a realistic modeling of the Earth's magnetic field.more » By applying quasi-linear theory, the bounce- and MLT-averaged electron pitch angle, mixed term, and energy diffusion coefficients are calculated for each magnetic field configuration. For radiation belt (~1 MeV) and ring current (~100 keV) electrons, it is shown that at some MLTs the bounce-averaged diffusion coefficients become rather insensitive to the details of the magnetic field configuration, while at other MLTs storm conditions can expand the range of equatorial pitch angles where gyro-resonant diffusion occurs and significantly enhance the diffusion rates. When MLT average is performed at drift shell L = 4.25 (a good approximation to drift average), the diffusion coefficients become quite independent of the magnetic field configuration for relativistic electrons, while the opposite is true for lower energy electrons. These results suggest that, at least for the March 17 2013 storm and for L ≲ 4.25, the commonly adopted dipole approximation of the Earth's magnetic field can be safely used for radiation belt electrons, while a realistic modeling of the magnetic field configuration is necessary to describe adequately the diffusion rates of ring current electrons.« less
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.
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.
Ghysels, M; Durry, G; Amarouche, N
2013-04-15
By using a tunable diode laser absorption spectrometer in conjunction with a cryogenically cooled multipath cell, we have revisited the air-induced pressure-broadening coefficients and the narrowing coefficients related to the Dicke effect, as well as the temperature dependences, for the R(18) and R(20) lines of the (10°1)I←(00°0) vibrational band at 2.68 μm of carbon dioxide. The selected transitions are used to probe in situ CO2 in the troposphere and the lower stratosphere by using balloon-borne laser sensors. The achieved measurements are thoroughly compared to existing former determinations. The impact of processing the in situ atmospheric CO2 spectra with this new set of molecular data is reported.
Kitamura, Ryunosuke; Inagaki, Tetsuya; Tsuchikawa, Satoru
2016-02-22
The true absorption coefficient (μa) and reduced scattering coefficient (μ´s) of the cell wall substance in Douglas fir were determined using time-of-flight near infrared spectroscopy. Samples were saturated with hexane, toluene or quinolone to minimize the multiple reflections of light on the boundary between pore-cell wall substance in wood. μ´s exhibited its minimum value when the wood was saturated with toluene because the refractive index of toluene is close to that of the wood cell wall substance. The optical parameters of the wood cell wall substance calculated were μa = 0.030 mm(-1) and μ´s= 18.4 mm(-1). Monte Carlo simulations using these values were in good agreement with the measured time-resolved transmittance profiles.
Park, Hyunjin; Green, Michael H
2014-03-28
In the existing compartmental models of human vitamin A metabolism, parameters related to the absorption of the isotopic oral dose have not been well identified. We hypothesised that fixing some poorly identified parameters related to vitamin A absorption would improve parameter identifiability and add statistical certainty to such models. In the present study, data for serum vitamin A kinetics in nine subjects given [2H8]retinyl acetate orally and a model with absorption fixed at 75 % were used to test this hypothesis. In addition to absorption efficiency, we fixed two other fractional transfer coefficients: one representing the initial processing of the ingested dose and the other representing the direct secretion of retinol bound to retinol-binding protein (RBP) from enterocytes into the plasma. The Windows version of Simulation, Analysis and Modeling software (WinSAAM) was used to fit serum tracer data v. time for each subject. Then, a population model was generated by WinSAAM's Extended Multiple Studies Analysis. All the parameters had fractional standard deviations < 0·5, and none of the pairs of parameters had a correlation coefficient >0·8 (accepted criteria for well-identified parameters). Similar to the values predicted by the original model, total traced mass for retinol was 1160 (sd 468) μmol, and the time for retinol to appear in the plasma bound to RBP was 31·3 (sd 4·4) h. In conclusion, we suggest that this approach holds promise for advancing compartmental modelling of vitamin A kinetics in humans when the dose must be administered orally.
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)
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.
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)
Vartanian, A. L.; Asatryan, A. L.; Vardanyan, L. A.
2017-03-01
We have investigated the influence of an image charge effect (ICE) on the energies of the ground and first few excited states of a hydrogen-like impurity in a spherical quantum dot (QD) in the presence of an external electric field. The oscillator strengths of transitions from the 1 s -like state to excited states of 2px and 2pz symmetries are calculated as the functions of the strengths of the confinement potential and the electric field. Also, we have studied the effect of image charges on linear and third-order nonlinear optical absorption coefficients and refractive index changes (RICs). The results show that image charges lead to the decrease of energies for all the hydrogen-like states, to the significant enhancement of the oscillator strengths of transitions between the impurity states, and to comparatively large blue shifts in linear, nonlinear, and total absorption coefficients and refractive index changes. Our results indicate that the total optical characteristics can be controlled by the strength of the confinement and the electric field.
Büermann, L; Grosswendt, B; Kramer, H-M; Selbach, H-J; Gerlach, M; Hoffmann, M; Krumrey, M
2006-10-21
For the first time absolute photon mass energy-absorption coefficients of air in the energy range 3 keV to 10 keV have been measured with relative standard uncertainties less than 1%, significantly smaller than those of up to 5% assumed hitherto for calculated data. Monochromatized synchrotron radiation was used to measure both the total radiant energy by means of silicon photodiodes calibrated against a cryogenic radiometer and the fraction of radiant energy that is deposited in dry air by means of a free air ionization chamber. The measured ionization charge was converted into energy absorbed in air by calculated effective W values of photons as a function of their energy based on new measurements of the W values in dry air for electron kinetic energies between 1 keV and 7 keV, also presented in this work. The measured absorption coefficients were compared with state-of-the art calculations and found to agree within 0.7% with data calculated earlier by Hubbell at energies above 4 keV but were found to differ by values up to 2.1% at 10 keV from more recent calculations of Seltzer.
NASA Astrophysics Data System (ADS)
Conny, J. M.; Norris, G.
2007-12-01
In thermal-optical transmission analysis (TOT), laser light passing through a particle-laden filter is monitored while carbonaceous material is removed in several heating steps and measured by flame ionization detection. In a helium atmosphere, the laser signal is attenuated by the pyrolysis of organic carbon (OC). Later, while carbon is removed in an oxidizing atmosphere, the laser signal returns to its value prior to pyrolysis (split point), whereupon the amount of carbon equivalent to the native BC is measured. Since pyrolyzed OC may actually evolve beyond the split point, the specific absorption cross sections of pyrolyzed OC and native BC must be equivalent. Moreover, OC pyrolysis must be sufficient so that unpyrolyzed OC is not measured as BC beyond the split point. Using response surfaces models of the apparent specific absorption cross sections for pyrolyzed OC and what the instrument measures as native BC, we determined the thermal conditions for establishing the equivalence of the apparent cross sections while insuring sufficient pyrolysis of OC. In this way, we have optimized TOT for BC mass based on the Beer-Lambert Law but without the need for an absolute mass absorption coefficient (or an absolute attenuation coefficient) for BC. Optimal thermal conditions for the equivalence of the cross sections were indicated by the intersection of the response surfaces. Concurrently, optimal conditions for sufficient pyrolysis of OC were indicated by a plateau in the response surface for the BC cross section. Modeling was based on extensive analyses of PM2.5 samples collected from Atlanta, Los Angeles, and Seattle. Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.
NASA Astrophysics Data System (ADS)
Liang, Yufeng; Vinson, John; Pemmaraju, Sri; Shirley, Eric; Prendergast, David
Transition metal oxides are an important class of materials featured with strongly correlated effects. Most interesting and yet to-be-unveiled physics is associated with the metal 3d orbitals, which can be probed by X-ray absorption near-edge spectroscopy. A thorough interpretation of the x-ray spectroscopy is often accompanied with first-principles simulations of structures, electronic properties and the corresponding x-ray spectra. However, the simulation for TMOs is particularly challenging with the localized 3d orbitals. Most previous studies relied on the ground-state calculations without the core-hole as a compromise. Other treated the excited atom as a charged impurity but the calculated spectra turn out to be even more deviated from experiments. Here, we present the first study for the O K-edge for several typical TMOs via solving the Bethe-Salpeter equation (BSE). We have found that electron-core-hole interactions can alter the absorption spectra significantly. Our study helps to disentangle core-hole effects from the intrinsic electron correlations and hence facilitates the development of more advanced many-electron theories.
Esteves, Freddy; Moutinho, Carla; Matos, Carla
2013-06-01
Absorption and consequent therapeutic action are key issues in the development of new drugs by the pharmaceutical industry. In this sense, different models can be used to simulate biological membranes to predict the absorption of a drug. This work compared the octanol/water and the liposome/water models. The parameters used to relate the two models were the distribution coefficients between liposomes and water and octanol and water and the fraction of drug orally absorbed. For this study, 66 drugs were collected from literature sources and divided into four groups according to charge and ionization degree: neutral; positively charged; negatively charged; and partially ionized/zwitterionic. The results show a satisfactory linear correlation between the octanol and liposome systems for the neutral (R²= 0.9324) and partially ionized compounds (R²= 0.9367), contrary to the positive (R²= 0.4684) and negatively charged compounds (R²= 0.1487). In the case of neutral drugs, results were similar in both models because of the high fraction orally absorbed. However, for the charged drugs (positively, negatively, and partially ionized/zwitterionic), the liposomal model has a more-appropriate correlation with absorption than the octanol model. These results show that the neutral compounds only interact with membranes through hydrophobic bonds, whereas charged drugs favor electrostatic interactions established with the liposomes. With this work, we concluded that liposomes may be a more-appropriate biomembrane model than octanol for charged compounds.
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.
Karki, K; Hugo, G; Ford, J; Saraiya, S; Weiss, E; Olsen, K; Groves, R
2014-06-15
Purpose: Diffusion-weighted MRI (DW-MRI) is increasingly being investigated for radiotherapy planning and response assessment. Selection of a limited number of b-values in DW-MRI is important to keep geometrical variations low and imaging time short. We investigated various b-value sets to determine an optimal set for obtaining monoexponential apparent diffusion coefficient (ADC) close to perfusion-insensitive intravoxel incoherent motion (IVIM) model ADC (ADC_{IVIM}) in nonsmall cell lung cancer. Methods: Seven patients had 27 DW-MRI scans before and during radiotherapy in a 1.5T scanner. Respiratory triggering was applied to the echo-planar DW-MRI with TR=4500ms approximately, TE=74ms, pixel size=1.98X1.98mm{sub 2}, slice thickness=4–6mm and 7 axial slices. Diffusion gradients were applied to all three axes producing traceweighted images with eight b-values of 0–1000μs/μm{sup 2}. Monoexponential model ADC values using various b-value sets were compared to ADC_{IVIM} using all b-values. To compare the relative noise in ADC maps, intra-scan coefficient of variation (CV) of active tumor volumes was computed. Results: ADC_{IVIM}, perfusion coefficient and perfusion fraction for tumor volumes were in the range of 880-1622 μm{sup 2}/s, 8119-33834 μm{sup 2}/s and 0.104–0.349, respectively. ADC values using sets of 250, 800 and 1000; 250, 650 and 1000; and 250–1000μs/μm{sup 2} only were not significantly different from ADC_{IVIM}(p>0.05, paired t-test). Error in ADC values for 0–1000, 50–1000, 100–1000, 250–1000, 500–1000, and three b-value sets- 250, 500 and 1000; 250, 650 and 1000; and 250, 800 and 1000μs/μm{sup 2} were 15.0, 9.4, 5.6, 1.4, 11.7, 3.7, 2.0 and 0.2% relative to the reference-standard ADC_{IVIM}, respectively. Mean intrascan CV was 20.2, 20.9, 21.9, 24.9, 32.6, 25.8, 25.4 and 24.8%, respectively, whereas that for ADC_{IVIM} was 23.3%. Conclusion: ADC values of two 3 b-value sets
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.
Crowe, Iain F; Clark, Nicholas; Hussein, Siham; Towlson, Brian; Whittaker, Eric; Milosevic, Milan M; Gardes, Frederic Y; Mashanovich, Goran Z; Halsall, Matthew P; Vijayaraghaven, Aravind
2014-07-28
We examine the near-IR light-matter interaction for graphene integrated cavity ring resonators based on silicon-on-insulator (SOI) race-track waveguides. Fitting of the cavity resonances from quasi-TE mode transmission spectra reveal the real part of the effective refractive index for graphene, n(eff) = 2.23 ± 0.02 and linear absorption coefficient, α(gTE) = 0.11 ± 0.01dBμm(-1). The evanescent nature of the guided mode coupling to graphene at resonance depends strongly on the height of the graphene above the cavity, which places limits on the cavity length for optical sensing applications.
NASA Astrophysics Data System (ADS)
Różańska, A.; Nikołajuk, M.; Czerny, B.; Dobrzycki, A.; Hryniewicz, K.; Bechtold, J.; Ebeling, H.
2014-04-01
We present the photoionisation modelling of the intrinsic absorber in the bright quasar HS 1603 + 3820. We constructed the broad-band spectral energy distribution using the optical/UV/X-ray observations from different instruments as inputs for the photoionisation calculations. The spectra from the Keck telescope show extremely high CIV to HI ratios, for the first absorber in system A, named A1. This value, together with high column density of CIV ion, place strong constraints on the photoionisation model. We used two photoionisation codes to derive the hydrogen number density at the cloud illuminated surface. By estimating bolometric luminosity of HS 1603 + 3820 using the typical formula for quasars, we calculated the distance to A1. We could find one photoionization solution, by assuming either a constant density cloud (which was modelled using CLOUDY), or a stratified cloud (which was modelled using TITAN), as well as the solar abundances. This model explained both the ionic column density of CIV and the high CIV to HI ratio. The location of A1 is 0.1 pc, and it is situated even closer to the nucleus than the possible location of the Broad Line Region in this object. The upper limit of the distance is sensitive to the adopted covering factor and the carbon abundance. Photoionisation modelling always prefers dense clouds with the number density n0 = 1010 - 1012 cm-3, which explains intrinsic absorption in HS 1603 + 3820. This number density is of the same order as that in the disk atmosphere at the implied distance of A1. Therefore, our results show that the disk wind that escapes from the outermost accretion disk atmosphere can build up dense absorber in quasars.
Baba, Justin S; Allegood, Marcus S
2008-01-01
Light interaction with biological tissue can be described using three parameters: the scattering and absorption coefficients (us and ua), 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 specific wavelengths, and simultaneously, would be beneficial for a variety of different biomedical applications. The goal of this project was to take a user-defined g-value and determine the remaining two parameters for a specified wavelength range for an integrating sphere with a collimated white light input source system. 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 computation of the optical properties based on the output from the IAD code. To allow data to be passed efficiently 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 and determination of the absorption and scattering coefficients showed excellent agreement with theory for wavelengths were the user inputted single g-value was sufficiently precise. Future improvements entail providing for multi-wavelength g-value entry to extend the accuracy of results to encompass the complete system multispectral range. Ultimately, the data collection process and algorithms developed through this effort will be used to study actual biological tissues for the purpose of deriving and refining models for light-tissue interactions.
Gao, Feifei; Wang, Yuan; Shi, Dong; Zhang, Jing; Wang, Mingkui; Jing, Xiaoyan; Humphry-Baker, Robin; Wang, Peng; Zakeeruddin, Shaik M; Grätzel, Michael
2008-08-13
We report two new heteroleptic polypyridyl ruthenium complexes, coded C101 and C102, with high molar extinction coefficients by extending the pi-conjugation of spectator ligands, with a motivation to enhance the optical absorptivity of mesoporous titania film and charge collection yield in a dye-sensitized solar cell. On the basis of this C101 sensitizer, several DSC benchmarks measured under the air mass 1.5 global sunlight have been reached. Along with an acetonitrile-based electrolyte, the C101 sensitizer has already achieved a strikingly high efficiency of 11.0-11.3%, even under a preliminary testing. More importantly, based on a low volatility 3-methoxypropionitrile electrolyte and a solvent-free ionic liquid electrolyte, cells have corresponding >9.0% and approximately 7.4% efficiencies retained over 95% of their initial performances after 1000 h full sunlight soaking at 60 degrees C. With the aid of electrical impedance measurements, we further disclose that, compared to the cell with an acetonitrile-based electrolyte, a dye-sensitized solar cell with an ionic liquid electrolyte shows a feature of much shorter effective electron diffusion lengths due to the lower electron diffusion coefficients and shorter electron lifetimes in the mesoporous titania film, explaining the photocurrent difference between these two type devices. This highlights the next necessary efforts to further improve the efficiency of cells with ionic liquid electrolytes, facilitating the large-scale production and application of flexible thin film mesoscopic solar cells.
Karki, Kishor; Hugo, Geoffrey D; Ford, John C; Olsen, Kathryn M; Saraiya, Siddharth; Groves, Robert; Weiss, Elisabeth
2015-10-21
The purpose of this study was to determine optimal sets of b-values in diffusion-weighted MRI (DW-MRI) for obtaining monoexponential apparent diffusion coefficient (ADC) close to perfusion-insensitive intravoxel incoherent motion (IVIM) model ADC (ADCIVIM) in non-small cell lung cancer. Ten subjects had 40 DW-MRI scans before and during radiotherapy in a 1.5 T MRI scanner. Respiratory triggering was applied to the echo-planar DW-MRI with TR ≈ 4500 ms, TE = 74 ms, eight b-values of 0-1000 μs μm(-2), pixel size = 1.98 × 1.98 mm(2), slice thickness = 6 mm, interslice gap = 1.2 mm, 7 axial slices and total acquisition time ≈6 min. One or more DW-MRI scans together covered the whole tumour volume. Monoexponential model ADC values using various b-value sets were compared to reference-standard ADCIVIM values using all eight b-values. Intra-scan coefficient of variation (CV) of active tumour volumes was computed to compare the relative noise in ADC maps. ADC values for one pre-treatment DW-MRI scan of each of the 10 subjects were computed using b-value pairs from DW-MRI images synthesized for b-values of 0-2000 μs μm(-2) from the estimated IVIM parametric maps and corrupted by various Rician noise levels. The square root of mean of squared error percentage (RMSE) of the ADC value relative to the corresponding ADCIVIM for the tumour volume of the scan was computed. Monoexponential ADC values for the b-value sets of 250 and 1000; 250, 500 and 1000; 250, 650 and 1000; 250, 800 and 1000; and 250-1000 μs μm(-2) were not significantly different from ADCIVIM values (p > 0.05, paired t-test). Mean error in ADC values for these sets relative to ADCIVIM were within 3.5%. Intra-scan CVs for these sets were comparable to that for ADCIVIM. The monoexponential ADC values for other sets-0-1000; 50-1000; 100-1000; 500-1000; and 250 and 800 μs μm(-2) were significantly different from the ADCIVIM values. From Rician noise
NASA Astrophysics Data System (ADS)
Karki, Kishor; Hugo, Geoffrey D.; Ford, John C.; Olsen, Kathryn M.; Saraiya, Siddharth; Groves, Robert; Weiss, Elisabeth
2015-10-01
The purpose of this study was to determine optimal sets of b-values in diffusion-weighted MRI (DW-MRI) for obtaining monoexponential apparent diffusion coefficient (ADC) close to perfusion-insensitive intravoxel incoherent motion (IVIM) model ADC (ADCIVIM) in non-small cell lung cancer. Ten subjects had 40 DW-MRI scans before and during radiotherapy in a 1.5 T MRI scanner. Respiratory triggering was applied to the echo-planar DW-MRI with \\text{TR}≈ 4500 ms, TE = 74 ms, eight b-values of 0-1000 μs μm-2, pixel size = 1.98× 1.98 mm2, slice thickness = 6 mm, interslice gap = 1.2 mm, 7 axial slices and total acquisition time ≈6 min. One or more DW-MRI scans together covered the whole tumour volume. Monoexponential model ADC values using various b-value sets were compared to reference-standard ADCIVIM values using all eight b-values. Intra-scan coefficient of variation (CV) of active tumour volumes was computed to compare the relative noise in ADC maps. ADC values for one pre-treatment DW-MRI scan of each of the 10 subjects were computed using b-value pairs from DW-MRI images synthesized for b-values of 0-2000 μs μm-2 from the estimated IVIM parametric maps and corrupted by various Rician noise levels. The square root of mean of squared error percentage (RMSE) of the ADC value relative to the corresponding ADCIVIM for the tumour volume of the scan was computed. Monoexponential ADC values for the b-value sets of 250 and 1000; 250, 500 and 1000; 250, 650 and 1000; 250, 800 and 1000; and 250-1000 μs μm-2 were not significantly different from ADCIVIM values (p>0.05 , paired t-test). Mean error in ADC values for these sets relative to ADCIVIM were within 3.5%. Intra-scan CVs for these sets were comparable to that for ADCIVIM. The monoexponential ADC values for other sets—0-1000 50-1000 100-1000 500-1000 and 250 and 800 μs μm-2 were significantly different from the ADCIVIM values. From Rician noise simulation
Makita, Hiroki; Hastings, Gary
2016-06-01
Time-resolved visible and infrared absorption difference spectroscopy data at both 298 and 77 K were obtained using cyanobacterial menB (-) mutant photosystem I particles with several non-native quinones incorporated into the A1 binding site. Data was obtained for photosystem I particles with phylloquinone (2-methyl-3-phytyl-1,4-naphthoquinone), 2-bromo-1,4-naphthoquinone, 2-chloro-1,4-naphthoquinone, 2-methyl-1,4-naphthoquinone, 2,3-dibromo-1,4-naphthoquinone, 2,3-dichloro-1,4-naphthoquinone, and 9,10-anthraquinone incorporated. Transient absorption data were obtained at 487 and 703 nm in the visible spectral range, and 1950-1100 cm(-1) in the infrared region. Time constants obtained from fitting the time-resolved infrared and visible data are in good agreement. The measured time constants are crucial for the development of appropriate kinetic models that can describe electron transfer processes in photosystem I, "Modeling Electron Transfer in Photosystem I" Makita and Hastings (2016) [1].
Pelivanov, Ivan M; Barskaya, M I; Podymova, N B; Khokhlova, Tanya D; Karabutov, Aleksander A
2009-09-30
A new method for measuring the local light absorption coefficient in turbid media, for example, biological tissues, is proposed. The method is based on the fact that the amplitude of the excited opto-acoustic (OA) signal is proportional to the absorbed laser power density (the product of the light absorption coefficient and the laser fluence) at the medium interface. In the first part of the paper, the influence of the laser beam diameter, the light absorption and reduced scattering coefficients on the maximal amplitude of the laser fluence at the laser beam axis in the near-surface layer of the turbid medium is studied by using the Monte-Carlo simulation. The conditions are predicted under which the amplitude of the OA signal detected in a transparent medium in contact with the scattering medium should remain proportional to the light absorption coefficient of the medium under study, when the scattering coefficient in it changes more than twice. The results of the numerical simulation are used for the theoretical substantiation of the OA method being proposed. (measurement of parametrs of laser radiation)
Ultraviolet absorption cross sections of hydrogen peroxide
NASA Technical Reports Server (NTRS)
Lin, C. L.; Rohatgi, N. K.; Demore, W. B.
1978-01-01
Absorption cross-sections of hydrogen peroxide vapor and of neutral aqueous solutions of hydrogen peroxide were measured in the wavelength range from 195 to 350 nm at 296 K. The spectrophotometric procedure is described, and the reported cross-sections are compared with values obtained by other researchers. Photodissociation coefficients of atmospheric H2O2 were calculated for direct absorption of unscattered solar radiation, and the vertical distributions of these coefficients are shown for various solar zenith angles.
Reflective-tube absorption meter
NASA Astrophysics Data System (ADS)
Zaneveld, J. Ronald V.; Bartz, Robert; Kitchen, James C.
1990-09-01
The design and calibration of a proposed in situ spectral absorption meter is evaluated using a laboratory prototype. The design includes a silver coated (second-surface) glass tube, a tungsten light source (stabilized by means of optical feedback), a monochromator, and a solid state detector. The device measures the absorption coefficient plus a portion of the volume scattering function. Theoretical analyses and laboratory experiments which explore the magnitude and variation of the errors due to scattering and internal reflections are described. Similar analyses are performed on the Cary 1 18 Spectrophotometer to allow cross calibration. Algorithms to yield the abscrption coefficient and the zenith-sun diffuse attenuation coefficient are presented and evaluated. Simultaneous measurement of the beam attenuation or backscattering coefficient allows use of algoriThms with much narrower error bands. The various methods of obtaining absorption and diffuse attenuation values are compared. Procedures for using reverse osmosis filtration to produce a clean water calibration standard are described. An absorption spectrum for pure water is obtained. Development of the absorption meter is proceeding along two lines: 1) a two-wavelength side-by-side LED is being fabricated to allow an in situ chlorophyll a absorption meter to be constructed, and 2) scientific projects using a shipboard or laboratory flow.-through pumping system are being planned.
Monitoring spacecraft atmosphere contaminants by laser absorption spectroscopy
NASA Technical Reports Server (NTRS)
Steinfeld, J. I.
1975-01-01
Data were obtained which will provide a test of the accuracy of the differential absorption method for trace contaminant detection in many-component gas mixtures. The necessary accurate absorption coefficient determinations were carried out for several gases; acetonitrile, 1,2-dichloroethane, Freon-113, furan, methyl ethyl ketone, and t-butyl alcohol. The absorption coefficients are displayed graphically. An opto-acoustic method was tested for measuring absorbance, similar to the system described by Dewey.
NASA Astrophysics Data System (ADS)
Kir'yanov, Alexander V.; Barmenkov, Yuri O.
2006-07-01
We reply to the comment [R. Paschotta and A.C. Tropper, Opt. Express, to be published (2006)] on our recent work reporting a study of the cooperative absorption and emission in heavily-doped Ytterbium silica fibers and mechanisms of the fiber nonlinear transmission coefficient reduction due to the Ytterbium ion-pairs’ effect [A.V. Kir’yanov et al., Opt. Express, 14 (9), 3981 (2006)]. We provide some additional evidences for that our work hypotheses and conclusions.
Improved input parameters for diffusion models of skin absorption.
Hansen, Steffi; Lehr, Claus-Michael; Schaefer, Ulrich F
2013-02-01
To use a diffusion model for predicting skin absorption requires accurate estimates of input parameters on model geometry, affinity and transport characteristics. This review summarizes methods to obtain input parameters for diffusion models of skin absorption focusing on partition and diffusion coefficients. These include experimental methods, extrapolation approaches, and correlations that relate partition and diffusion coefficients to tabulated physico-chemical solute properties. Exhaustive databases on lipid-water and corneocyte protein-water partition coefficients are presented and analyzed to provide improved approximations to estimate lipid-water and corneocyte protein-water partition coefficients. The most commonly used estimates of lipid and corneocyte diffusion coefficients are also reviewed. In order to improve modeling of skin absorption in the future diffusion models should include the vertical stratum corneum heterogeneity, slow equilibration processes, the absorption from complex non-aqueous formulations, and an improved representation of dermal absorption processes. This will require input parameters for which no suitable estimates are yet available.
NASA Astrophysics Data System (ADS)
Daneshvar, L.; Földes, T.; Buldyreva, J.; Vander Auwera, J.
2014-12-01
High resolution Fourier transform spectra of the 21102-00001 band of 12C16O2 near 3340 cm-1 have been recorded and analyzed to extract isolated-line intensities and collisional parameters, and first-order line-mixing coefficients. Voigt, hard-collision Rautian and Sobel'man, and quadratic-speed-dependent Voigt profiles have been used. The line-mixing coefficients measured for the three branches have also been evaluated using an Energy-Corrected Sudden approach employing a symmetric metric in the Liouville space. These coefficients compare very favorably with the experimental results and estimations with an algorithm available in the literature. Results of straightforward ECS-modeling of complete band shapes have been compared to the recorded spectra and future improvements of this model required at subatmospheric pressures have been outlined.
Gajardo, Francisco; Barrera, Mauricio; Vargas, Ricardo; Crivelli, Irma; Loeb, Barbara
2011-07-04
When tested in solar cells, ruthenium polypyridinic dyes with extended π systems show an enhanced light-harvesting capacity that is not necessarily reflected by a high (collected electrons)/(absorbed photons) ratio. Provided that metal-to-ligand charge transfer bands, MLCT, are more effective, due to their directionality, than intraligand (IL) π-π* bands for the electron injection process in the solar cell, it seems important to explore and clarify the nature of the absorption bands present in these types of dyes. This article aims to elucidate if all the absorbed photons of these dyes are potentially useful in the generation of electric current. In other words, their potentiality as dyes must also be analyzed from the point of view of their contribution to the generation of excited states potentially useful for direct injection. Focusing on the assignment of the absorption bands and the nature of the emitting state, a systematic study for a series of ruthenium complexes with 4,4'-distyryl-2,2'-dipyridine (LH) and 4,4'-bis[p-(dimethylamino)-α-styryl]-2,2'-bipyridine (LNMe(2)) "chromophoric" ligands was undertaken. The observed experimental results were complemented with TDDFT calculations to elucidate the nature of the absorption bands, and a theoretical model was proposed to predict the available energy that could be injected from a singlet or a triplet excited state. For the series studied, the results indicate that the percentage of MLCT character to the anchored ligand for the lower energy absorption band follows the order [Ru(deebpy)(2)(LNMe(2))](PF(6))(2) > [Ru(deebpy)(2)(LH)](PF(6))(2) > [Ru(deebpy)(LH)(2)](PF(6))(2), where deebpy is 4,4'-bis(ethoxycarbonyl)-2,2'-bipyridine, predicting that, at least from this point of view, their efficiency as dyes should follow the same trend.
Gasoline-Water Distribution Coefficients of Xylidines
1943-06-01
sample calculated. The extinction (absorption) of light is related to the concentration of the absorbing group by the Beer - Lambert law. It was neceaaar...the use of a Beckman quartz spectrophotometer . Data obtained 1dth the spectzrograph were checzed with the spectrophotom- eter and were reproducible to...within 5 percent of the value of the distribution coefficient given, The use of the spectrophotometer greatly enhanced the speed with which the
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.
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.
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}.
Absorption of 9.6-micron CO2 laser radiation by CO2 at elevated temperatures
NASA Astrophysics Data System (ADS)
Robinson, A. M.
1983-03-01
Transitions in CO2 gas induced by the absorption of 9.6 micron laser radiation at higher temperatures were examined. Several lines of the 9.6 micron 0011-0012 transition at temperatures between 296-625 K were studied, and the absorption coefficient was determined as a function of temperature. Additional trials were run to define the relative optical broadening coefficients due to He and N2 for the R16-R22 and P16-P22 transitions. The values obtained for the coefficients and the percentage contribution to calculated absorption coefficient at 620 K are provided.
Modified Biserial Correlation Coefficients.
ERIC Educational Resources Information Center
Kraemer, Helena Chmura
1981-01-01
Asymptotic distribution theory of Brogden's form of biserial correlation coefficient is derived and large sample estimates of its standard error obtained. Its relative efficiency to the biserial correlation coefficient is examined. Recommendations for choice of estimator of biserial correlation are presented. (Author/JKS)
The emission coefficient of uranium plasmas
NASA Technical Reports Server (NTRS)
Schneider, R. T.; Campbell, H. D.; Mack, J. M.
1973-01-01
The emission coefficient for uranium plasmas (Temperature: 8000 K) was measured for the wavelength range (200 A - 6000 A). The results are compared to theory and other measurements. The absorption coefficient for the same wavelength interval is also given.
Time-dependent oral absorption models
NASA Technical Reports Server (NTRS)
Higaki, K.; Yamashita, S.; Amidon, G. L.
2001-01-01
The plasma concentration-time profiles following oral administration of drugs are often irregular and cannot be interpreted easily with conventional models based on first- or zero-order absorption kinetics and lag time. Six new models were developed using a time-dependent absorption rate coefficient, ka(t), wherein the time dependency was varied to account for the dynamic processes such as changes in fluid absorption or secretion, in absorption surface area, and in motility with time, in the gastrointestinal tract. In the present study, the plasma concentration profiles of propranolol obtained in human subjects following oral dosing were analyzed using the newly derived models based on mass balance and compared with the conventional models. Nonlinear regression analysis indicated that the conventional compartment model including lag time (CLAG model) could not predict the rapid initial increase in plasma concentration after dosing and the predicted Cmax values were much lower than that observed. On the other hand, all models with the time-dependent absorption rate coefficient, ka(t), were superior to the CLAG model in predicting plasma concentration profiles. Based on Akaike's Information Criterion (AIC), the fluid absorption model without lag time (FA model) exhibited the best overall fit to the data. The two-phase model including lag time, TPLAG model was also found to be a good model judging from the values of sum of squares. This model also described the irregular profiles of plasma concentration with time and frequently predicted Cmax values satisfactorily. A comparison of the absorption rate profiles also suggested that the TPLAG model is better at prediction of irregular absorption kinetics than the FA model. In conclusion, the incorporation of a time-dependent absorption rate coefficient ka(t) allows the prediction of nonlinear absorption characteristics in a more reliable manner.
González, Sergio; Jiménez, Elena; Ballesteros, Bernabé; Martínez, Ernesto; Albaladejo, José
2015-04-01
CF3CH=CH2 (hydrofluoroolefin, HFO-1243zf) is a potential replacement of high global-warming potential (GWP) hydrofluorocarbon (HFC-134a, CF3CFH2). Both the atmospheric lifetime and the radiative efficiency of HFO-1243zf are parameters needed for estimating the GWP of this species. Therefore, the aim of this work is (i) to estimate the atmospheric lifetime of HFO-1243zf from the reported OH rate coefficients, k OH, determined under tropospheric conditions and (ii) to calculate its radiative efficiency from the reported IR absorption cross sections. The OH rate coefficient at 298 K also allows the estimation of the photochemical ozone creation potential (ε(POCP)). The pulsed laser photolysis coupled to a laser-induced fluorescence technique was used to determine k OH for the reaction of OH radicals with HFO-1243zf as a function of pressure (50-650 Torr of He) and temperature (263-358 K). Gas-phase IR spectra of HFO-1243zf were recorded at room temperature using a Fourier transform IR spectrometer between 500 and 4,000 cm(-1). At all temperatures, k OH did not depend on bath gas concentration (i.e., on the total pressure between 50 and 650 Torr of He). A slight but noticeable T dependence of k OH was observed in the temperature range investigated. The observed behavior is well described by the following Arrhenius expression: k OH(T) = (7.65 ± 0.26) × 10(-13) exp [(165 ± 10) / T] cm(3) molecule(-1) s(-1). Negligible IR absorption of HFO-1243zf was observed at wavenumbers greater than 1,700 cm(-1). Therefore, IR absorption cross sections, [Formula: see text], were determined in the 500-1,700 cm(-1) range. Integrated [Formula: see text] were determined between 650 and 1,800 cm(-1) for comparison purposes. The main diurnal removal pathway for HFO-1243zf is the reaction with OH radicals, which accounts for 64% of the overall loss by homogeneous reactions at 298 K. Globally, the lifetime due to OH reaction (τ OH) was estimated to be 8.7 days under
Absorption Coefficient of Alkali Halides. Part I.
1979-03-01
442 LIAY OF ~:S42.~SON T111 ALiSON ,’FlON CU12rCIUNT OF .l~i~ FLUORIVIl: (iviunLvr Iiepcndcncu) (cort .i.j) S’t .~Ue Rne uhr~) ~clo Wvna,br n rt...al. [134j reported their results for the region from 0.170 to 0.197 um and Handi et al. [24] reported results for the range of 35 to 770 pm. Li (331...lection Spectra of Pure and Doped Potassium Iodide at Low Temperatures," Appl. Opt., 7(1), 161-5 (1968). L, __ 243 26. Vergnat, P., Claudel, J., Handi
Acoustic Absorption Characteristics of People.
ERIC Educational Resources Information Center
Kingsbury, H. F.; Wallace, W. J.
1968-01-01
The acoustic absorption characteristics of informally dressed college students in typical classroom seating are shown to differ substantially from data for formally dressed audiences in upholstered seating. Absorption data, expressed as sabins per person or absorption coefficient per square foot, shows that there is considerable variation between…
Triplet extinction coefficients of some laser dyes. II
Pavlopoulos, T.G.; Golich, D.J.
1990-01-01
We measured the triplet extinction coefficients over the laser action spectral region of DODC, DMC, Sulforhodamine B, Rhodamine 575, Coumarin 523, Coumarin 521, Coumarin 504, Coumarin 498, Coumarin 490, LD466, bis-MSB, and BBO. We employed the different lines from an argon and a krypton ion cw laser for excitation. McClure's method was again employed to measure the triplet extinction coefficients. We provide a simplified derivation of McClure's equation. The triplet extinction coefficient of Rhodamine 575 was also measured by using the depletion method and improving it by reconstructing for true triplet-triplet (T-T) absorption. The ET value obtained is in good agreement with the one obtained by McClure's method.
JKTLD: Limb darkening coefficients
NASA Astrophysics Data System (ADS)
Southworth, John
2015-11-01
JKTLD outputs theoretically-calculated limb darkening (LD) strengths for equations (LD laws) which predict the amount of LD as a function of the part of the star being observed. The coefficients of these laws are obtained by bilinear interpolation (in effective temperature and surface gravity) in published tables of coefficients calculated from stellar model atmospheres by several researchers. Many observations of stars require the strength of limb darkening (LD) to be estimated, which can be done using theoretical models of stellar atmospheres; JKTLD can help in these circumstances.
Near-infrared optical coefficients of tumors and adjacent normal tissue
NASA Astrophysics Data System (ADS)
Laufer, Jan G.
2001-06-01
The absorption and reduced scattering coefficients of tumours of the human breast, liver and kidney and their normal surrounding tissue have been measured in vitro for the near-infrared wavelengths between 600 and 1000 nm as well as 1064 nm. The Monte Carlo inversion technique (Simpson et al) was used to determine the optical coefficients of tissue samples from measurements of the diffuse transmittance and reflectance. The measurements of the diffusely transmitted and reflected intensities were performed using a single integrating sphere 'comparison' method. Four post-mortem samples of both liver adenocarcinoma and normal liver tissue were obtained from one subject and four samples of both tumour and normal kidney tissue were obtained from another subject. Four samples of both breast tumour and normal tissue were obtained from two patients. The scattering coefficient of tumours was found in each case to be significantly higher than that of nondiseased tissue. The absorption coefficient of tumours was generally much smaller than those of normal tissue. The scattering coefficient of tumours was 20% to 200% higher depending on the type of cancer and the wavelength, while the absorption coefficient of tumours was as much as twenty times smaller compared to normal tissue.
Leidinger, M; Fieberg, S; Waasem, N; Kühnemann, F; Buse, K; Breunig, I
2015-08-24
We employ three highly sensitive spectrometers: a photoacoustic spectrometer, a photothermal common-path interferometer and a whispering-gallery-resonator-based absorption spectrometer, for a comparative study of measuring the absorption coefficient of nominally transparent undoped, congruently grown lithium niobate for ordinarily and extraordinarily polarized light in the wavelength range from 390 to 3800 nm. The absorption coefficient ranges from below 10(-4) cm(-1) up to 2 cm(-1). Furthermore, we measure the absorption at the Urbach tail as well as the multiphonon edge of the material by a standard grating spectrometer and a Fourier-transform infrared spectrometer, providing for the first time an absorption spectrum of the whole transparency window of lithium niobate. The absorption coefficients obtained by the three highly sensitive and independent methods show good agreement.
Models of filter-based particle light absorption measurements
NASA Astrophysics Data System (ADS)
Hamasha, Khadeejeh M.
Light absorption by aerosol is very important in the visible, near UN, and near I.R region of the electromagnetic spectrum. Aerosol particles in the atmosphere have a great influence on the flux of solar energy, and also impact health in a negative sense when they are breathed into lungs. Aerosol absorption measurements are usually performed by filter-based methods that are derived from the change in light transmission through a filter where particles have been deposited. These methods suffer from interference between light-absorbing and light-scattering aerosol components. The Aethalometer is the most commonly used filter-based instrument for aerosol light absorption measurement. This dissertation describes new understanding of aerosol light absorption obtained by the filter method. The theory uses a multiple scattering model for the combination of filter and particle optics. The theory is evaluated using Aethalometer data from laboratory and ambient measurements in comparison with photoacoustic measurements of aerosol light absorption. Two models were developed to calculate aerosol light absorption coefficients from the Aethalometer data, and were compared to the in-situ aerosol light absorption coefficients. The first is an approximate model and the second is a "full" model. In the approximate model two extreme cases of aerosol optics were used to develop a model-based calibration scheme for the 7-wavelength Aethalometer. These cases include those of very strong scattering aerosols (Ammonium sulfate sample) and very absorbing aerosols (kerosene soot sample). The exponential behavior of light absorption in the strong multiple scattering limit is shown to be the square root of the total absorption optical depth rather than linear with optical depth as is commonly assumed with Beer's law. 2-stream radiative transfer theory was used to develop the full model to calculate the aerosol light absorption coefficients from the Aethalometer data. This comprehensive model
Experimental determination of terahertz atmospheric absorption parameters
NASA Astrophysics Data System (ADS)
Slocum, David M.; Goyette, Thomas M.; Giles, Robert H.; Nixon, William E.
2015-05-01
The terahertz frequency regime is often used as the `chemical fingerprint' region of the electromagnetic spectrum since many molecules exhibit a dense selection of rotational and vibrational transitions. Water is a major component of the atmosphere and since it has a large dipole moment the propagation of terahertz radiation will be dominated by atmospheric effects. This study will present the results of high--resolution broadband measurements of the terahertz atmospheric absorption and detail the technique for directly measuring the pressure broadening coefficients, absolute absorption coefficients, line positions, and continuum effects. Differences between these measured parameters and those tabulated in HITRAN will be discussed. Once the water vapor absorption was characterized, the same technique was used to measure the line parameters for methanol, a trace gas of interest within Earth's atmosphere. Methanol has a dense absorption spectrum in the terahertz frequency region and is an important molecule in fields such as environmental monitoring, security, and astrophysics. The data obtained in the present study will be of immediate use for the remote sensing community, as it is uncommon to measure this many independent parameters as well as to measure the absolute absorption of the transitions. Current models rely on tabulated databases of calculated values for the line parameters measured in this study. Differences between the measured data and those in the databases will be highlighted and discussed.
Optical absorption measurement system
Draggoo, Vaughn G.; Morton, Richard G.; Sawicki, Richard H.; Bissinger, Horst D.
1989-01-01
The system of the present invention contemplates a non-intrusive method for measuring the temperature rise of optical elements under high laser power optical loading to determine the absorption coefficient. The method comprises irradiating the optical element with a high average power laser beam, viewing the optical element with an infrared camera to determine the temperature across the optical element and calculating the absorption of the optical element from the temperature.
Rubenchik, Alexander M.; Wu, Sheldon S. Q.; Kanz, V. Keith; LeBlanc, Mary M.; Lowdermilk, W. Howard; Rotter, Mark D.; Stanley, Joel R.
2014-07-17
When modeling laser interaction with metals for various applications it requires a knowledge of absorption coefficients for real, commercially available materials with engineering grade (unpolished, oxidized) surfaces. But, most currently available absorptivity data pertain to pure metals with polished surfaces or vacuum-deposited thin films in controlled atmospheres. A simple laboratory setup is developed for the direct calorimetric absorptivity measurements using a diode-array laser emitting at 780 nm. A scheme eliminating the effect of convective and radiative losses is implemented. Futhermore, the obtained absorptivity results differ considerably from existing data for polished pure metals and are essential for the development of predictive laser-material interaction models.
NASA Technical Reports Server (NTRS)
Rinsland, C. P.; Boughner, R. E.; Larsen, J. C.; Goldman, A.; Murcray, F. J.; Murcray, D. G.
1984-01-01
Simultaneous stratospheric vertical profiles of NO and NO2 at sunset were derived from an analysis of infrared solar absorption spectra recorded from a float altitude of 33 km with an interferometer system during a balloon flight. A nonlinear least squares procedure was used to analyze the spectral data in regions of absorption by NO and NO2 lines. Normalized factors, determined from calculations of time dependent altitude profiles with a detailed photochemical model, were included in the onion peeling analysis to correct for the rapid diurnal changes in NO and NO2 concentrations with time near sunset. The CO2 profile was also derived from the analysis and is reported.
A study of sound absorption by street canyon boundaries and asphalt rubber concrete pavement
NASA Astrophysics Data System (ADS)
Drysdale, Graeme Robert
A sound field model, based on a classical diffusion equation, is extended to account for sound absorption in a diffusion parameter used to model sound energy in a narrow street canyon. The model accounts for a single sound absorption coefficient, separate accommodation coefficients and a combination of separate absorption and accommodation coefficients from parallel canyon walls. The new expressions are compared to the original formula through numerical simulations to reveal the effect of absorption on sound diffusion. The newly established analytical formulae demonstrate satisfactory agreement with their predecessor under perfect reflection. As well, the influence of the extended diffusion parameter on normalized sound pressure levels in a narrow street canyon is in agreement with experimental data. The diffusion parameters are used to model sound energy density in a street canyon as a function of the sound absorption coefficient of the street canyon walls. The acoustic and material properties of conventional and asphalt rubber concrete (ARC) pavement are also studied to assess how the crumb rubber content influences sound absorption in street canyons. The porosity and absolute permeability of compacted specimens of asphalt rubber concrete are measured and compared to their normal and random incidence sound absorption coefficients as a function of crumb rubber content in the modified binder. Nonlinear trends are found between the sound absorption coefficients, porosity and absolute permeability of the compacted specimens and the percentage of crumb rubber in the modified binders. The cross-sectional areas of the air voids on the surfaces of the compacted specimens are measured using digital image processing techniques and a linear relationship is obtained between the average void area and crumb rubber content. The measured material properties are used to construct an empirical formula relating the average porosity, normal incidence noise reduction coefficients and
Balderas-López, J A; Díaz-Reyes, J; Zelaya-Angel, O
2011-12-01
A photoacoustic (PA) methodology, in the transmission configuration, for simultaneous measurements of thermal effusivity and molar absorption coefficient (absorptivity) for pigments in liquid solution is introduced. The analytical treatment involves a self-normalization procedure for the PA signal, as a function of the modulation frequency, for a strong absorbing material in the thermally thin regime, when the light travels across the sample under study. Two fitted parameters are obtained from the analysis of the self-normalized PA amplitude and phase, one of them proportional to the sample's optical absorption coefficient and from which, taking it for a series of samples at different concentrations, the pigment's absorptivity in liquid solution can be measured, the other one yields the sample's thermal effusivity. Methylene blue's absorptivity in distilled water was measured with this methodology at 658 nm, finding good agreement with the corresponding one reported in the literature.
Quantum efficiency coefficient for photogeneration of carriers in SbSI nanowires
NASA Astrophysics Data System (ADS)
Nowak, M.; Bober, Ł.; Borkowski, B.; Kępińska, M.; Szperlich, P.; Stróż, D.; Sozańska, M.
2013-10-01
This paper presents investigations of the quantum efficiency coefficient for the photogeneration of carriers in aligned antimony sulfoiodide (SbSI) nanowires. Therefore the spectral dependences (between 488 and 700 nm) of photoconductivity current (IPC) were measured for temperatures from 263 to 323 K and for different light intensities. The least squares method was applied to fit the experimental IPC data with appropriate theoretical dependence. From this fitting, diffusion length and surface recombination velocity of carriers as well as spectral dependences of quantum efficiency coefficients for different temperatures and different light intensities were obtained. A comparison of the values of absorption coefficient obtained from the measurements of optical diffusive reflectance and from evaluation of the quantum efficiency coefficient is presented.
Hydration shell parameters of aqueous alcohols: THz excess absorption and packing density.
Matvejev, V; Zizi, M; Stiens, J
2012-12-06
Solvation in water requires minimizing the perturbations in its hydrogen bonded network. Hence solutes distort water molecular motions in a surrounding domain, forming a molecule-specific hydration shell. The properties of those hydration shells impact the structure and function of the solubilized molecules, both at the single molecule and at higher order levels. The size of the hydration shell and the picoseconds time-scale water dynamics retardation are revealed by terahertz (THz) absorption coefficient measurements. Room-temperature absorption coefficient at f = 0.28 [THz] is measured as a function of alcohol concentration in aqueous methanol, ethanol, 1,2-propanol, and 1-butanol solutions. Highly diluted alcohol measurements and enhanced overall measurement accuracy are achieved with a THz absorption measurement technique of nL-volume liquids in a capillary tube. In the absorption analysis, bulk and interfacial molecular domains of water and alcohol are considered. THz ideal and excess absorption coefficients are defined in accordance with thermodynamics mixing formulations. The parameter extraction method is developed based on a THz excess absorption model and hydrated solute molecule packing density representation. First, the hydration shell size is deduced from the hydrated solute packing densities at two specific THz excess absorption nonlinearity points: at infinite alcohol dilution (IAD) and at the THz excess absorption extremum (EAE). Consequently, interfacial water and alcohol molecular domain absorptions are deduced from the THz excess absorption model. The hydration shell sizes obtained at the THz excess absorption extremum are in excellent agreement with other reports. The hydration shells of methanol, ethanol, 1- and 2-propanol consist of 13.97, 22.94, 22.99, and 31.10 water molecules, respectively. The hydration shell water absorption is on average 0.774 ± 0.028 times the bulk water absorption. The hydration shell parameters might shed light on
Kinetics and modeling of carbon dioxide absorption into aqueous solutions of diethanolamine
Rinker, E.B.; Ashour, S.S.; Sandall, O.C.
1996-04-01
Absorption of acid gases such as CO{sub 2} and H{sub 2}S from natural and process gases is of great industrial importance. The kinetics of the reaction between CO{sub 2} and aqueous diethanolamine (DEA) were estimated over the temperature range of 293--343 K from absorption data obtained in a laminar-liquid jet absorber. The absorption data were obtained over a wide range of DEA concentrations and for CO{sub 2} partial pressures near atmospheric. A rigorous numerical mass-transfer model based on penetration theory in which all chemical reactions are considered to be reversible was developed and used to estimate kinetic rate coefficients from the experimental absorption data. The kinetic data were found to be consistent with the zwitterion mechanism. The scarce zwitterion rate coefficient estimates reported in the literature are in fair agreement with the results of this work.
Peles, Dana N; Simon, John D
2012-01-01
Photoemission electron microscopy is used to measure the absorption coefficients, εc, of intact iridal stroma melanosomes isolated from dark brown and blue-green human irides for the spectral range λ=244-310 nm. These iridal stroma melanosomes were chosen because different colored irides produce organelles of varying eumelanin:pheomelanin ratios with similar size and morphology. Similar absorption spectra are found for the two types of melanosomes. The experimental spectra measured within are compared with both the extinction coefficient spectra obtained on soluble synthetic model systems and the monomeric precursors to each pigment.
Determining the Gruneisen coefficient for liquids using the PAZ-scan technique
NASA Astrophysics Data System (ADS)
Dantiste, Olivier A.
Measurement of Gruneisen coefficient is utterly important in developing efficient molecular photoacoustic (PA) contrast agents. It is one of the two parameters that describes how efficient a molecule is in transforming optical energy into sound, the other being absorption coefficient. Using the PAZ-scan technique, the Gruneisen coefficient was obtained for various samples and the values are compared with standard techniques. In a PAZ-scan, the sample is translated through the path of a focused laser beam in small steps while the generated PA signal is recorded. The incident intensity is optimum at the focal point and decreases gradually on either side of the focus. As such, the absorption and the PA signal varies according to the sample properties. Therefore at positions away from the focal point, the incident intensities are weak and the PA signal varies linearly with intensity. A plot of the PA signal versus the intensity is used to obtain the Gruneisen coefficient. Using this technique, the Gruneisen coefficients for crystal violet in two different solvents, food coloring dyes that are dissolved in water were determined. Results show that the linear part of the PAZ-scan can be used to determine the Gruneisen coefficient for liquids.
Optical absorption of sodium copper chlorophyllin thin films in UV-vis-NIR region.
Farag, A A M
2006-11-01
The optical absorption studies of sodium copper chlorophyllin thin films (SCC), prepared by spray pyrolysis, in the UV-vis-NIR region was reported for the first time. Several new discrete transitions are observed in the UV-vis region of the spectra in addition to a strong continuum component in the IR region. The spectra of the infrared absorption allow characterization of vibration modes for the powder and thin films of SCC. The absorption spectrum recorded in the UV-vis region showed different absorption bands, namely the Soret (B) in the region 340-450 nm and Q-band in the region 600-700 nm and other band labeled N in the 240-320 region. Some important spectral parameters namely optical absorption coefficient (alpha), molar extinction coefficient (epsilon(molar)), oscillator strength (f), electric dipole strength (q(2)) and absorption half bandwidth (Deltalambda) of the principle optical transitions were evaluated. The analysis of the absorption coefficient in the absorption region revealed direct transitions and the energy gap was estimated as 1.63 eV. Discussion of the obtained results and their comparison with the previous published data are also given.
Results of measurement of radio wave absorption in the ionosphere by the AI method
NASA Technical Reports Server (NTRS)
Korinevskaya, N. A.
1972-01-01
Median noon absorption values for each month from 1964 through 1967, the diurnal variations of absorption on the regular world days, and the seasonal variations of absorption are given. The dependence of the absorption coefficient on sunspot number is analyzed.
Factor Scores, Structure Coefficients, and Communality Coefficients
ERIC Educational Resources Information Center
Goodwyn, Fara
2012-01-01
This paper presents heuristic explanations of factor scores, structure coefficients, and communality coefficients. Common misconceptions regarding these topics are clarified. In addition, (a) the regression (b) Bartlett, (c) Anderson-Rubin, and (d) Thompson methods for calculating factor scores are reviewed. Syntax necessary to execute all four…
UV laser long-path absorption spectroscopy
NASA Technical Reports Server (NTRS)
Dorn, Hans-Peter; Brauers, Theo; Neuroth, Rudolf
1994-01-01
Long path Differential Optical Absorption Spectroscopy (DOAS) using a picosecond UV laser as a light source was developed in our institute. Tropospheric OH radicals are measured by their rotational absorption lines around 308 nm. The spectra are obtained using a high resolution spectrograph. The detection system has been improved over the formerly used optomechanical scanning device by application of a photodiode array which increased the observed spectral range by a factor of 6 and which utilizes the light much more effectively leading to a considerable reduction of the measurement time. This technique provides direct measurements of OH because the signal is given by the product of the absorption coefficient and the OH concentration along the light path according to Lambert-Beers law. No calibration is needed. Since the integrated absorption coefficient is well known the accuracy of the measurement essentially depends on the extent to which the OH absorption pattern can be detected in the spectra. No interference by self generated OH radicals in the detection lightpath has been observed. The large bandwidth (greater than 0.15 nm) and the high spectral resolution (1.5 pm) allows absolute determination of interferences by other trace gas absorptions. The measurement error is directly accessible from the absorption-signal to baseline-noise ratio in the spectra. The applicability of the method strongly depends on visibility. Elevated concentrations of aerosols lead to considerable attenuation of the laser light which reduces the S/N-ratio. In the moderately polluted air of Julich, where we performed a number of OH measurement spectra. In addition absorption features of unidentified species were frequently detected. A quantitative deconvolution even of the known species is not easy to achieve and can leave residual structures in the spectra. Thus interferences usually increase the noise and deteriorate the OH detection sensitivity. Using diode arrays for sensitive
Aerosol Absorption Measurements in MILAGRO.
NASA Astrophysics Data System (ADS)
Gaffney, J. S.; Marley, N. A.; Arnott, W. P.; Paredes-Miranda, L.; Barnard, J. C.
2007-12-01
to carbonyl- and nitro- functional groups on conjugated and aromatic organic structures (e.g. PAH, and terpene derived products). Using 12-hour fine (0.1-1.0 micron) aerosol samples collected in the field on quartz filters, uv/vis and infrared spectra were obtained in the laboratory using integrating spheres and diffuse reflectance spectroscopy, respectively. An inter-comparison of the "real-time" measurements made by the photo-acoustic, aethalometer and MAAP techniques have been described. In addition, the in situ aethalometer (seven-channel) results are compared with continuous integrating sphere uv-visible spectra to examine the angstrom absorption coefficient variance. These results will be briefly overviewed and the specific posters detailing these results will be highlighted highlighted. This work was performed as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City under the support of the Atmospheric Science Program. "This researchwas supported by the Office of Science (BER), U. S. Department of Energy, Grant No. DE-FG02-07ER64329.
Free-free absorption of infrared radiation in collisions of electrons with neutral rare-gas atoms
NASA Technical Reports Server (NTRS)
Stallcop, J. R.
1974-01-01
A relationship between the inverse bremsstrahlung absorption cross section and the electron neutral momentum transfer cross section has been utilized to determine the infrared free-free continuum absorption coefficient for the negative ions of helium, neon, argon, krypton, and xenon. The values of the momentum transfer cross section for this calculation have been obtained from experimental measurements. Analytical expressions for the absorption coefficient have also been developed. From the results of this calculation, it is possible to determine the absorption coefficient per unit electron density per neutral atom for temperatures in the range from 2500 to 25,000 K. The results are compared with those from tabulations of previous calculations and those computed from theoretical values of the phase shifts for the elastic scattering of electrons by neutral atoms.
NASA Astrophysics Data System (ADS)
Dreischuh, Tanja N.; Gurdev, Ljuan L.; Vankov, Orlin I.; Avramov, Lachezar A.; Stoyanov, Dimitar V.
2015-01-01
The experimental investigations on different aspects of optical tomography require the knowledge of the optical parameters of tissues and tissue-like phantoms in order to unambiguously interpret the experimental data and specify characteristic inhomogeneities in tissue diagnostics. The main optical parameters of interest are the absorption coefficient, the scattering, backscattering, and reduced-scattering coefficients, the total attenuation (extinction) coefficient and the anisotropy factor. In this work, we extend our investigations of the optical properties of tissuemimicking phantoms, such as Intralipid-20% fat emulsion, using an approach we have developed recently based on the peculiarities of laser radiation beams propagating through semi-infinite turbid media. The dependence of the total attenuation coefficient on the Intralipid concentration, for laser radiation wavelengths λ=405, 672, 850, and 1314 nm, is studied, by using a set of phantoms consisting of different dilutions of Intralipid in distilled water. The experimental results for the extinction are in agreement with our previous results and with empiric formulae found by other authors concerning the wavelength dependence of the scattering coefficient of Intralipid -10% and Intralipid - 20%. They are also in agreement with known data of the water absorptance. As a whole, the results obtained in this work confirm the consideration of the experimental phantoms as semi-infinite media. They also confirm and extend theoretical and experimental results obtained previously, and reveal advantages of using longer wavelengths for deeper diagnostics of tissues and mimic turbid media.
On the emission coefficient of uranium plasmas.
NASA Technical Reports Server (NTRS)
Schneider, R. T.; Campbell, H. D.; Mack, J. M.
1973-01-01
The emission coefficient for uranium plasmas (temperature: 8000 K) was measured for the wavelength range from 1200 to 6000 A. The results were compared to theoretical calculations and other measurements. Reasonable agreement between theoretical predictions and our measurements was found in the region from 1200 to 2000 A. Although it was difficult to make absolute comparisons among the different reported measurements, considerable disagreement was found for the higher wavelength region. A short discussion regarding the overall comparisons is given, and final suggestions are made as to the most appropriate emission coefficient values to be used in future design calculations. The absorption coefficient for the same wavelength interval is also reported.
Effective photons in weakly absorptive dielectric media and the Beer-Lambert-Bouguer law
NASA Astrophysics Data System (ADS)
Judge, A. C.; Brownless, J. S.; Bhat, N. A. R.; Sipe, J. E.; Steel, M. J.; de Sterke, C. Martijn
2014-04-01
We derive effective photon modes that facilitate an intuitive and convenient picture of photon dynamics in a structured Kramers-Kronig dielectric in the limit of weak absorption. Each mode is associated with a mode field distribution that includes the effects of both material and structural dispersion, and an effective line-width that determines the temporal decay rate of the photon. These results are then applied to obtain an expression for the Beer-Lambert-Bouguer law absorption coefficient for unidirectional propagation in structured media consisting of dispersive, weakly absorptive dielectric materials.
NASA Astrophysics Data System (ADS)
Roy, Arindam; Ramasubramaniam, Rajagopal; Gaonkar, Harshavardhan A.
2012-11-01
Kubelka-Munk (K-M) theory is a phenomenological light transport theory that provides analytical expressions for reflectance and transmittance of diffusive substrates such as tissues. Many authors have derived relations between coefficients of K-M theory and that of the more fundamental radiative transfer equations. These relations are valid only in diffusive light transport regime where scattering dominates over absorption. They also fail near boundaries where incident beams are not diffusive. By measuring total transmittance and total reflectance of tissue phantoms with varying optical parameters, we have obtained empirical relations between K-M coefficients and the radiative transport coefficients for integrating sphere-based spectrophotometers that use uniform, nondiffusive incident beams. Our empirical relations show that the K-M scattering coefficients depend only on reduced scattering coefficient (μs‧), whereas the K-M absorption coefficient depends on both absorption (μa) and reduced scattering (μs‧) coefficients of radiative transfer theory. We have shown that these empirical relations are valid in both the diffusive and nondiffusive regimes and can predict total reflectance within an error of 10%. They also can be used to solve the inverse problem of obtaining multiple optical parameters such as chromophore concentration and tissue thickness from the measured reflectance spectra with a maximum accuracy of 90% to 95%.
Roy, Arindam; Ramasubramaniam, Rajagopal; Gaonkar, Harshavardhan A
2012-11-01
Kubelka–Munk (K-M) theory is a phenomenological light transport theory that provides analytical expressions for reflectance and transmittance of diffusive substrates such as tissues. Many authors have derived relations between coefficients of K-M theory and that of the more fundamental radiative transfer equations. These relations are valid only in diffusive light transport regime where scattering dominates over absorption. They also fail near boundaries where incident beams are not diffusive. By measuring total transmittance and total reflectance of tissue phantoms with varying optical parameters, we have obtained empirical relations between K-M coefficients and the radiative transport coefficients for integrating sphere-based spectrophotometers that use uniform, nondiffusive incident beams. Our empirical relations show that the K-M scattering coefficients depend only on reduced scattering coefficient (μ's), whereas the K-M absorption coefficient depends on both absorption (μa ) and reduced scattering (μs' ) coefficients of radiative transfer theory. We have shown that these empirical relations are valid in both the diffusive and nondiffusive regimes and can predict total reflectance within an error of 10%. They also can be used to solve the inverse problem of obtaining multiple optical parameters such as chromophore concentration and tissue thickness from the measured reflectance spectra with a maximum accuracy of 90% to 95%.
Triplet extinction coefficients of some laser dyes. II. Interim technical report
Pavlopoulos, T.G.; Golich, D.J.
1989-04-19
The authors measured the triplet extinction coefficients T over the laser action spectral region of DODC, DMC, Sulforhodamine B, Rhodamine 575, Coumarin 523, Coumarine 521 Coumarin 504, Coumarin 498, Coumarin 490, LD466, bis-MSB, BBO, and OLIG0415. The different lines from an argon- and a krypton-ion cw laser were employed for excitation. McClure's method was again employed to measure the triplet extinction coefficients. The authors provide a simplified derivation of McClure's equation. The triplet extinction coefficient of Rhodamine 575 was also measured by using the depletion method and improving it by reconstructing for true triplet-triplet absorption. The value obtained is in good agreement with the one obtained by McClure's method.
Second virial coefficients for chain molecules
Bokis, C.P.; Donohue, M.D. . Dept. of Chemical Engineering); Hall, C.K. . Dept. of Chemical Engineering)
1994-01-01
The importance of having accurate second virial coefficients in phase equilibrium calculations, especially for the calculation of dew points, is discussed. The square-well potentials results in a simple but inaccurate equation for the second virial coefficient for small, spherical molecules such as argon. Here, the authors present a new equation for the second virial coefficient of both spherical molecules and chain molecules which is written in a form similar to that for the square-well potential. This new equation is accurate in comparison to Monte Carlo simulation data on second virial coefficients for square-well chain molecules and with second virial coefficients obtained from experiments on n-alkanes.
NASA Technical Reports Server (NTRS)
Lenoble, J.; Pruvost, P.
1983-01-01
SAGE four-channel transmission profiles are inverted to retrieve the extinction profiles from which the aerosol Angstrom coefficient alpha is obtained. The procedure allows one to check the influence of the NO2 absorption profile, which is small below 25 km. The results compare well with those obtained by a completely different procedure at NASA Langley Research Center, and the main features of the alpha profiles seem to be significant, even considering the rather large error bars. The relation between the retrieved Angstrom coefficient, the particle effective radius and the asymmetry factor is considered.
Transport coefficients of gluonic fluid
Das, Santosh K.; Alam, Jan-e
2011-06-01
The shear ({eta}) and bulk ({zeta}) viscous coefficients have been evaluated for a gluonic fluid. The elastic, gg{yields}gg and the inelastic, number nonconserving, gg{yields}ggg processes have been considered as the dominant perturbative processes in evaluating the viscous coefficients to entropy density (s) ratios. Recently the processes: gg{yields}ggg has been revisited and a correction to the widely used Gunion-Bertsch (GB) formula has been obtained. The {eta} and {zeta} have been evaluated for gluonic fluid with the formula recently derived. At large {alpha}{sub s} the value of {eta}/s approaches its lower bound, {approx}1/4{pi}.
Subgap Absorption in Conjugated Polymers
DOE R&D Accomplishments Database
Sinclair, M.; Seager, C. H.; McBranch, D.; Heeger, A. J; Baker, G. L.
1991-01-01
Along with X{sup (3)}, the magnitude of the optical absorption in the transparent window below the principal absorption edge is an important parameter which will ultimately determine the utility of conjugated polymers in active integrated optical devices. With an absorptance sensitivity of < 10{sup {minus}5}, Photothermal Deflection Spectroscopy (PDS) is ideal for determining the absorption coefficients of thin films of transparent'' materials. We have used PDS to measure the optical absorption spectra of the conjugated polymers poly(1,4-phenylene-vinylene) (and derivitives) and polydiacetylene-4BCMU in the spectral region from 0.55 eV to 3 eV. Our spectra show that the shape of the absorption edge varies considerably from polymer to polymer, with polydiacetylene-4BCMU having the steepest absorption edge. The minimum absorption coefficients measured varied somewhat with sample age and quality, but were typically in the range 1 cm{sup {minus}1} to 10 cm{sup {minus}1}. In the region below 1 eV, overtones of C-H stretching modes were observed, indicating that further improvements in transparency in this spectral region might be achieved via deuteration of fluorination.
Orthogonality of spherical harmonic coefficients
NASA Technical Reports Server (NTRS)
Mcleod, M. G.
1980-01-01
Orthogonality relations are obtained for the spherical harmonic coefficients of functions defined on the surface of a sphere. Following a brief discussion of the orthogonality of Fourier series coefficients, consideration is given to the values averaged over all orientations of the coordinate system of the spherical harmonic coefficients of a function defined on the surface of a sphere that can be expressed in terms of Legendre polynomials for the special case where the function is the sum of two delta functions located at two different points on the sphere, and for the case of an essentially arbitrary function. It is noted that the orthogonality relations derived have found applications in statistical studies of the geomagnetic field.
Optical absorption in semiconductor quantum dots coupling to dispersive phonons of infinite modes
NASA Astrophysics Data System (ADS)
Ding, Zhiwen; Wang, Qin; Zheng, Hang
2012-10-01
Optical absorption spectrum of semiconductor quantum dot is investigated by means of an analytical approach based on the Green's function for different forms of coupling strength in an unified method by using the standard model with valence and conduction band levels coupled to dispersive quantum phonons of infinite modes. The analytical expression of the optical absorption coefficient in semiconductor quantum dots is obtained and by this expression the line shape and the peak position of the absorption spectrum are procured. The relation between the properties of absorption spectrum and the forms of coupling strength is clarified, which can be referenced for choosing the proper form of the coupling strength or spectral density to control the features of absorption spectrum of quantum dot. The coupling and confinement induced energy shift and intensity decrease in the absorption spectrum are determined precisely for a wide range of parameters. The results show that the activation energy of the optical absorption is reduced by the effect of exciton-phonon coupling and photons with lower frequencies could also be absorbed in absorption process. With increase of the coupling constant, the line shape of optical absorption spectrum broadens and the peak position moves to lower photon energy with a rapid decrease in intensity at the same time. Both the coupling induced red shift and the confinement induced blue shift conduce to decrease in the intensity of absorption spectrum. Furthermore, this method may have application potential to other confined quantum systems.
Computed survey spectra of 2-5 micron atmospheric absorption
NASA Astrophysics Data System (ADS)
Leslie, D. H.; Lebow, P. S.
1983-08-01
Computed high resolution survey spectra of atmospheric absorption coefficient vs wavenumber are presented covering the wavelength region 2-5 micrometers. The 1980 AFGL atmospheric absorption parameter compilation was employed with a mid-latitude, sea-level atmospheric model.
Stochastic Approach to Phonon-Assisted Optical Absorption
NASA Astrophysics Data System (ADS)
Zacharias, Marios; Patrick, Christopher E.; Giustino, Feliciano
2015-10-01
We develop a first-principles theory of phonon-assisted optical absorption in semiconductors and insulators which incorporates the temperature dependence of the electronic structure. We show that the Hall-Bardeen-Blatt theory of indirect optical absorption and the Allen-Heine theory of temperature-dependent band structures can be derived from the present formalism by retaining only one-phonon processes. We demonstrate this method by calculating the optical absorption coefficient of silicon using an importance sampling Monte Carlo scheme, and we obtain temperature-dependent line shapes and band gaps in good agreement with experiment. The present approach opens the way to predictive calculations of the optical properties of solids at finite temperature.
Grossman, Gershon; Perez-Blanco, Horacio
1984-01-01
An improvement in an absorption heat pump cycle is obtained by adding adiabatic absorption and desorption steps to the absorber and desorber of the system. The adiabatic processes make it possible to obtain the highest temperature in the absorber before any heat is removed from it and the lowest temperature in the desorber before heat is added to it, allowing for efficient utilization of the thermodynamic availability of the heat supply stream. The improved system can operate with a larger difference between high and low working fluid concentrations, less circulation losses, and more efficient heat exchange than a conventional system.
Soliton absorption spectroscopy
Kalashnikov, V. L.; Sorokin, E.
2010-01-01
We analyze optical soliton propagation in the presence of weak absorption lines with much narrower linewidths as compared to the soliton spectrum width using the novel perturbation analysis technique based on an integral representation in the spectral domain. The stable soliton acquires spectral modulation that follows the associated index of refraction of the absorber. The model can be applied to ordinary soliton propagation and to an absorber inside a passively modelocked laser. In the latter case, a comparison with water vapor absorption in a femtosecond Cr:ZnSe laser yields a very good agreement with experiment. Compared to the conventional absorption measurement in a cell of the same length, the signal is increased by an order of magnitude. The obtained analytical expressions allow further improving of the sensitivity and spectroscopic accuracy making the soliton absorption spectroscopy a promising novel measurement technique. PMID:21151755
Microwave absorption characteristics of the clouds of Venus from Mariner 10 radio occultation
NASA Technical Reports Server (NTRS)
Kliore, A. J.; Elachi, C.; Patel, I. R.; Way, J. B.
1977-01-01
Measurements of received signal strength at S-band (13 cm) and X-band (4.8 cm) wavelengths during the radio occultation of Mariner 10 by Venus on February 5, 1974, are examined in order to study the structure and composition of the absorbing medium. The frequency excursions of the signals are determined and used to obtain the structure of the refractive index in the lower atmosphere. Profiles of excess signal attenuation due to atmospheric scattering and absorption are presented which indicate that the X-band signal experienced much more absorption and was extinguished at about 50 km, while the S-band signal penetrated to about 42 km. The optical-depth data are inverted by means of a discrete inversion method to obtain the absorption coefficient for each band as a function of height, and the resulting absorption-coefficient profiles are compared with the attenuation at vertical incidence modeled from planetary radar and passive microwave observations of Venus. The absorption coefficients at the two wavelengths are employed to estimate the liquid content and composition of the microwave-absorbing cloud particles.
Sarkissian, Raymond O'Brien, John
2015-01-21
Cross two photon absorption in silicon is characterized using a tapered fiber photonic crystal silicon waveguide coupler. There is a physical junction between the tapered fiber and the waveguide constituting a stand-alone device. This device is used to obtain the spectrum for cross two photon absorption coefficient per unit volume of interaction between photons of nondegenerate energy. The corresponding Kerr coefficient per unit volume of interaction is also experimentally extracted. The thermal resistance of the device is also experimentally determined and the response time of the device is estimated for on-chip all-optical signal processing and data transfer between optical signals of different photon energies.
NASA Astrophysics Data System (ADS)
Moazzami, K.; Phillips, J.; Lee, D.; Edwall, D.; Carmody, M.; Piquette, E.; Zandian, M.; Arias, J.
2004-06-01
Accurate knowledge of the optical-absorption coefficient in HgCdTe is important for infrared (IR) detector design, production process (layer screening), and interpretation of detector performance. Measurements of the optical-absorption coefficient of HgCdTe layers with uniform composition are presented with the goal of developing a revised model in the interest of IR detector technology. Existing methods of determining HgCdTe alloy composition from IR transmission measurements are compared, where one self-consistent method is suggested and shown to agree with experimental detector data. An exponential Urbach and hyperbolic model are presented to represent band tail and above-bandgap absorption regions, respectively. Parameters associated with these models are extracted for Hg1-xCdxTe compositions of x=0.22-0.60 and temperatures of T=40-300 K using samples of varying thickness to obtain accurate data for varying spectral regions of the absorption coefficient. An initial analytical expression for the absorption coefficient is presented and compared to experimental detector-response data. Detector-response simulations indicate that accurate optical-absorption models are needed, where detector structures with thin layers and arbitrary composition profiles in current and future IR detectors will be the most demanding.
Near-infrared absorptions of monomethylhydrazine
NASA Technical Reports Server (NTRS)
Murray, Mark; Kurtz, Joe
1993-01-01
The peak absorption coefficients for two near-infrared absorptions of monomethylhydrazine, CH3-N2H3, (MMH) were measured. Absorption bands located at 1.524 micrometers (6560/cm), 1.557 micrometers (6423/cm), and 1.583 micrometers (6316/cm) are assigned to the Delta upsilon = 2 overtones of the infared N-H stretching fundamentals at 3317, 3245 and 3177/cm. An absorption band located at 1.04 micrometers (9620 +/- 100/cm) is assigned to the Delta upsilon = 3 overtone of one of these fundamentals. The peak absorption coefficients (alpha(sub 10)) at 1.524 micrometers (6560 +/- 20/cm) and 1.04 micrometers (9620 +/- 100/cm) are 31 x 10(exp -3) and 0.97 x 10(exp -3)/(cm atm), respectively. Uncertainties in these coefficients were estimated to be less than +/- 20% due primarily to uncertainties in the partial vapor pressure of MMH.
The influence of water mixtures on the dermal absorption of glycol ethers
Traynor, Matthew J.; Wilkinson, Simon C.; Williams, Faith M. . E-mail: F.M.Williams@ncl.ac.uk
2007-01-15
Glycol ethers are solvents widely used alone and as mixtures in industrial and household products. Some glycol ethers have been shown to have a range of toxic effects in humans following absorption and metabolism to their aldehyde and acid metabolites. This study assessed the influence of water mixtures on the dermal absorption of butoxyethanol and ethoxyethanol in vitro through human skin. Butoxyethanol penetrated human skin up to sixfold more rapidly from aqueous solution (50%, 450 mg/ml) than from the neat solvent. Similarly penetration of ethoxyethanol was increased threefold in the presence of water (50%, 697 mg/ml). There was a corresponding increase in apparent permeability coefficient as the glycol ether concentration in water decreased. The maximum penetration rate of water also increased in the presence of both glycol ethers. Absorption through a synthetic membrane obeyed Fick's Law and absorption through rat skin showed a similar profile to human skin but with a lesser effect. The mechanisms for this phenomenon involves disruption of the stratum corneum lipid bilayer by desiccation by neat glycol ether micelles, hydration with water mixtures and the physicochemical properties of the glycol ether-water mixtures. Full elucidation of the profile of absorption of glycol ethers from mixtures is required for risk assessment of dermal exposure. This work supports the view that risk assessments for dermal contact scenarios should ideally be based on absorption data obtained for the relevant formulation or mixture and exposure scenario and that absorption derived from permeability coefficients may be inappropriate for water-miscible solvents.
Total and Partial Absorption Coefficients for a Nitrogen Plasma
2014-09-26
Boulder, CO 80309 ATTN: Dr. Arthur V. Phelps 43 0 - . .. > . v- . - . -, . . " )h A’ I , U’ C ’ -- o. • p Lawrence Berkeley Laboratory University of...Gerald N. Hays Dr. James Chang Dr. Michael G. Mazerakis RiJ University of California Physics Department Irvine, CA 92664 -ATTN: Dr. Gregory Benford Air
Absorption of CO laser radiation by NO
NASA Technical Reports Server (NTRS)
Hanson, R. K.; Monat, J. P.; Kruger, C. H.
1976-01-01
The paper describes absorption calculations and measurements at selected infrared CO laser wavelengths which are nearly coincident with absorption lines in the fundamental vibration-rotation band of NO near 5.3 microns. Initial work was directed towards establishing the optimal CO laser-NO absorption line coincidence for high temperature applications. Measurements of the absorption coefficient at this optimal laser wavelength were carried out, first using a room-temperature absorption cell for high-temperature calculations and then using a shock tube, for the temperature range 630-4000 K, to validate the high temperature calculations.
Influence of two-photon absorption on the dynamic behaviors of microring resonators.
Li, Qiliang; Chen, Haowen; Xu, Jie; Hu, Miao; Zeng, Ran; Zhou, Xuefang; Li, Shuqin
2017-04-01
In this paper, we have investigated the influence of two-photon absorption (TPA) on the dynamic behaviors of all-pass and add-drop microring resonators by using two iterative methods along with the linear stability analysis method. While the incident field is above a certain value, the TPA coefficient has greater influence on the steady state for all-pass and add-drop microring resonators. We use the linear stability analysis method to analyze the stability of the steady state solutions and obtain stability conditions. Results obtained have shown that the change of TPA coefficient will lead to different dynamic behaviors; in addition, while the TPA coefficient is small and its change is slight, the dynamic behaviors of the microring resonators will not change much for most regions. At last, we observe the period windows and route from chaotic to period-N in some original chaotic regions due to the fluctuation of the TPA coefficient.
Coefficients of Effective Length.
ERIC Educational Resources Information Center
Edwards, Roger H.
1981-01-01
Under certain conditions, a validity Coefficient of Effective Length (CEL) can produce highly misleading results. A modified coefficent is suggested for use when empirical studies indicate that underlying assumptions have been violated. (Author/BW)
Hahn, P. F.; Miller, L. L.; Robscheit-Robbins, F. S.; Bale, W. F.; Whipple, G. H.
1944-01-01
The absorption of red cells from the normal peritoneum of the dog can be demonstrated by means of red cells labeled with radio-iron incorporated in the hemoglobin of these red cells. Absorption in normal dogs runs from 20 to 100 per cent of the amount given within 24 hours. Dogs rendered anemic by bleeding absorb red cells a little less rapidly—ranging from 5 to 80 per cent of the injected red cells. Doubly depleted dogs (anemic and hypoproteinemic) absorb even less in the three experiments recorded. This peritoneal absorption varies widely in different dogs and even in the same dog at different times. We do not know the factors responsible for these variations but there is no question about active peritoneal absorption. The intact red cells pass readily from the peritoneal cavity into lymph spaces in diaphragm and other areas of the peritoneum. The red cells move along the lymphatics and through the lymph glands with little or no phagocytosis and eventually into the large veins through the thoracic ducts. PMID:19871404
Rubin, Deborah C
2004-03-01
Our understanding of nutrient absorption continues to grow, from the development of unique animal models and from studies in which cutting-edge molecular and cellular biologic approaches have been used to analyze the structure and function of relevant molecules. Studies of the molecular genetics of inherited disorders have also provided many new insights into these processes. A major advance in lipid absorption has been the cloning and characterization of several intestinal acyl CoA:monoacylglycerol acyltransferases; these may provide new targets for antiobesity drug therapy. Studies of intestinal cholesterol absorption and reverse cholesterol transport have encouraged the development of novel potential treatments for hyperlipidemia. Observations in genetically modified mice and in humans with mutations in glucose transporter 2 suggest the importance of a separate microsomal membrane transport pathway for glucose transport. The study of iron metabolism has advanced greatly with the identification of the hemochromatosis gene and the continued examination of the genetic regulation of iron absorptive pathways. Several human thiamine transporters have been identified, and their specific roles in different tissues are being explored.
Presser, Cary; Nazarian, Ashot; Conny, Joseph M.; Chand, Duli; Sedlacek, Arthur; Hubbe, John M.
2016-12-02
Absorptivity measurements with a laser-heating approach, referred to as the laser-driven thermal reactor (LDTR), were carried out in the infrared and applied at ambient (laboratory) nonreacting conditions to particle-laden filters from a three-wavelength (visible) particle/soot absorption photometer (PSAP). Here, the particles were obtained during the Biomass Burning Observation Project (BBOP) field campaign. The focus of this study was to determine the particle absorption coefficient from field-campaign filter samples using the LDTR approach, and compare results with other commercially available instrumentation (in this case with the PSAP, which has been compared with numerous other optical techniques).
Absorption heat pump for space applications
NASA Technical Reports Server (NTRS)
Nguyen, Tuan; Simon, William E.; Warrier, Gopinath R.; Woramontri, Woranun
1993-01-01
In the first part, the performance of the Absorption Heat Pump (AHP) with water-sulfuric acid and water-magnesium chloride as two new refrigerant-absorbent fluid pairs was investigated. A model was proposed for the analysis of the new working pairs in a heat pump system, subject to different temperature lifts. Computer codes were developed to calculate the Coefficient of Performance (COP) of the system with the thermodynamic properties of the working fluids obtained from the literature. The study shows the potential of water-sulfuric acid as a satisfactory replacement for water-lithium bromide in the targeted temperature range. The performance of the AHP using water-magnesium chloride as refrigerant-absorbent pair does not compare well with those obtained using water-lithium bromide. The second part concentrated on the design and testing of a simple ElectroHydrodynamic (EHD) Pump. A theoretical design model based on continuum electromechanics was analyzed to predict the performance characteristics of the EHD pump to circulate the fluid in the absorption heat pump. A numerical method of solving the governing equations was established to predict the velocity profile, pressure - flow rate relationship and efficiency of the pump. The predicted operational characteristics of the EHD pump is comparable to that of turbomachinery hardware; however, the overall efficiency of the electromagnetic pump is much lower. An experimental investigation to verify the numerical results was conducted. The pressure - flow rate performance characteristics and overall efficiency of the pump obtained experimentally agree well with the theoretical model.
NASA Technical Reports Server (NTRS)
Wu, J.; Yu, K. M.; Walukiewicz, W.; Shan, W.; Ager, J. W., III; Haller, E. E.; Miotkowski, I.; Ramdas, A. K.; Su, Ching-Hua
2003-01-01
Optical absorption experiments have been performed using diamond anvil cells to measure the hydrostatic pressure dependence of the fundamental bandgap of ZnSe(sub 1-xTe(sub x) alloys over the entire composition range. The first and second-order pressure coefficients are obtained as a function of composition. Starting from the ZnSe side, the magnitude of both coefficients increases slowly until x approx. 0.7, where the ambient-pressure bandgap reaches a minimum. For larger values of x the coefficients rapidly approach the values of ZnTe. The large deviations of the pressure coefficients from the linear interpolation between ZnSe and ZnTe are explained in terms of the band anticrossing model.
Consistent transport coefficients in astrophysics
NASA Technical Reports Server (NTRS)
Fontenla, Juan M.; Rovira, M.; Ferrofontan, C.
1986-01-01
A consistent theory for dealing with transport phenomena in stellar atmospheres starting with the kinetic equations and introducing three cases (LTE, partial LTE, and non-LTE) was developed. The consistent hydrodynamical equations were presented for partial-LTE, the transport coefficients defined, and a method shown to calculate them. The method is based on the numerical solution of kinetic equations considering Landau, Boltzmann, and Focker-Planck collision terms. Finally a set of results for the transport coefficients derived for a partially ionized hydrogen gas with radiation was shown, considering ionization and recombination as well as elastic collisions. The results obtained imply major changes is some types of theoretical model calculations and can resolve some important current problems concerning energy and mass balance in the solar atmosphere. It is shown that energy balance in the lower solar transition region can be fully explained by means of radiation losses and conductive flux.
Measurement of the absorption rate of carbon dioxide into aqueous diethanolamine
Rowley, R.L.; Adams, M.E.; Marshall, T.L.; Oscarson, J.L.; Wilding, W.V.; Anderson, D.J.
1998-05-01
Aqueous alkanolamine solutions are commonly used in natural gas sweetening processes to remove the acid gases CO{sub 2} and H{sub 2}S. Absorption rates of gaseous CO{sub 2} into aqueous diethanolamine (DEA) 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, protonated DEA, and carbamate ions. Evidence also suggested that chemical reaction equilibrium is rapid relative to diffusion. The diffusion coefficient of DEA in water was also measured using a Taylor dispersion apparatus. A numerical model was developed and used to regress diffusion coefficients of bicarbonate, carbamate, and protonated amine from measured absorption rates. CO{sub 2} absorption rates and diffusion coefficients of bicarbonate, carbamate, and protonated DEA were obtained at 298.2 K and 318.2 K in solutions containing 20, 35, and 50 mass % DEA in water.
Performance analysis of solar powered absorption refrigeration system
NASA Astrophysics Data System (ADS)
Abu-Ein, Suleiman Qaseem; Fayyad, Sayel M.; Momani, Waleed; Al-Bousoul, Mamdouh
2009-12-01
The present work provides a detailed thermodynamic analysis of a 10 kW solar absorption refrigeration system using ammonia-water mixtures as a working medium. This analysis includes both first law and second law of thermodynamics. The coefficient of performance (COP), exergetic coefficient of performance (ECOP) and the exergy losses (Δ E) through each component of the system at different operating conditions are obtained. The minimum and maximum values of COP and ECOP were found to be at 110 and 200°C generator temperatures respectively. About 40% of the system exergy losses were found to be in the generator. The maximum exergy losses in the absorber occur at generator temperature of 130°C for all evaporator temperatures. A computer simulation model is developed to carry out the calculations and to obtain the results of the present study.
Measurement of attenuation coefficients of the fundamental and second harmonic waves in water
NASA Astrophysics Data System (ADS)
Zhang, Shuzeng; Jeong, Hyunjo; Cho, Sungjong; Li, Xiongbing
2016-02-01
Attenuation corrections in nonlinear acoustics play an important role in the study of nonlinear fluids, biomedical imaging, or solid material characterization. The measurement of attenuation coefficients in a nonlinear regime is not easy because they depend on the source pressure and requires accurate diffraction corrections. In this work, the attenuation coefficients of the fundamental and second harmonic waves which come from the absorption of water are measured in nonlinear ultrasonic experiments. Based on the quasilinear theory of the KZK equation, the nonlinear sound field equations are derived and the diffraction correction terms are extracted. The measured sound pressure amplitudes are adjusted first for diffraction corrections in order to reduce the impact on the measurement of attenuation coefficients from diffractions. The attenuation coefficients of the fundamental and second harmonics are calculated precisely from a nonlinear least squares curve-fitting process of the experiment data. The results show that attenuation coefficients in a nonlinear condition depend on both frequency and source pressure, which are much different from a linear regime. In a relatively lower drive pressure, the attenuation coefficients increase linearly with frequency. However, they present the characteristic of nonlinear growth in a high drive pressure. As the diffraction corrections are obtained based on the quasilinear theory, it is important to use an appropriate source pressure for accurate attenuation measurements.
NASA Astrophysics Data System (ADS)
Tang, Hong; Lin, Jian-Zhong
2011-12-01
The extinction coefficient of atmospheric aerosol particles influences the earth's radiation balance directly or indirectly, and it can be determined by the scattering and absorption characteristics of aerosol particles. The problem of estimating the change of extinction coefficient due to time evolution of bimodal particle size distribution is studied, and two improved methods for calculating the Brownian coagulation coefficient and the condensation growth rate are proposed, respectively. Through the improved method based on Otto kernel, the Brownian coagulation coefficient can be expressed simply in powers of particle volume for the entire particle size regime based on the fitted polynomials of the mean enhancement function. Meanwhile, the improved method based on Fuchs-Sutugin kernel is developed to obtain the condensation growth rate for the entire particle size regime. And then, the change of the overall extinction coefficient of bimodal distributions undergoing Brownian coagulation and condensation can be estimated comprehensively for the entire particle size regime. Simulation experiments indicate that the extinction coefficients obtained with the improved methods coincide fairly well with the true values, which provide a simple, reliable, and general method to estimate the change of extinction coefficient for the entire particle size regime during the bimodal particle dynamic processes.
Hernández, Sergio E; Rodríguez, Vicente D; Pérez, Justo; Martín, Felipe A; Castellano, Miguel A; Gonzalez-Mora, Jose Luis
2009-01-01
Absorption and scattering processes in biological tissues are studied through reflectance spectroscopy in tissue-like phantoms. For this aim, an experimental setup is designed to independently control both processes in hemoglobin and intralipid solutions. From the analysis of the obtained spectra, a simple empirical power law equation is found that relates absorbance with scattering and absorption coefficients. This relationship includes three wavelength independent parameters, which can be determined geometry from in vitro measurements for each particular optical optode. The dependence of the optical path length on the absorption and scattering coefficients is also analyzed, and estimations of this parameter for physiological conditions are presented. This study is useful to better understand the scattering phenomena in biological tissue, and to obtain absolute concentration of absorber particles when a homogeneous medium can be assumed.
Transonic Blunt Body Aerodynamic Coefficients Computation
NASA Astrophysics Data System (ADS)
Sancho, Jorge; Vargas, M.; Gonzalez, Ezequiel; Rodriguez, Manuel
2011-05-01
In the framework of EXPERT (European Experimental Re-entry Test-bed) accurate transonic aerodynamic coefficients are of paramount importance for the correct trajectory assessment and parachute deployment. A combined CFD (Computational Fluid Dynamics) modelling and experimental campaign strategy was selected to obtain accurate coefficients. A preliminary set of coefficients were obtained by CFD Euler inviscid computation. Then experimental campaign was performed at DNW facilities at NLR. A profound review of the CFD modelling was done lighten up by WTT results, aimed to obtain reliable values of the coefficients in the future (specially the pitching moment). Study includes different turbulence modelling and mesh sensitivity analysis. Comparison with the WTT results is explored, and lessons learnt are collected.
NASA Technical Reports Server (NTRS)
Snyder, G. Jeffrey (Inventor)
2015-01-01
A high temperature Seebeck coefficient measurement apparatus and method with various features to minimize typical sources of errors is described. Common sources of temperature and voltage measurement errors which may impact accurate measurement are identified and reduced. Applying the identified principles, a high temperature Seebeck measurement apparatus and method employing a uniaxial, four-point geometry is described to operate from room temperature up to 1300K. These techniques for non-destructive Seebeck coefficient measurements are simple to operate, and are suitable for bulk samples with a broad range of physical types and shapes.
NASA Astrophysics Data System (ADS)
Mondelain, D.; Vasilchenko, S.; Čermák, P.; Kassi, S.; Campargue, A.
2017-01-01
The CO2 absorption continuum near 2.3 μm is determined for a series of sub atmospheric pressures (250-750 Torr) by high sensitivity Cavity Ring Down Spectroscopy. An experimental procedure consisting in injecting successively a gas flow of CO2 and synthetic air, keeping constant the gas pressure in the CRDS cell, has been developed. This procedure insures a high stability of the spectra baseline by avoiding changes of the optical alignment due to pressure changes. The CO2 continuum was obtained as the difference between the CO2 absorption coefficient and a local lines simulation using a Voigt profile truncated at ±25 cm-1. Following the results of the preceding analysis of the CO2 rovibrational lines (Vasilchenko S et al. J Quant Spectrosc Radiat Transfer 10.1016/j.jqsrt.2016.07.002, a CO2 line list with intensities obtained by variational calculations and empirical line positions was preferred to the HITRAN line list. A quadratic pressure dependence of the absorption continuum is observed, with an average binary absorption coefficient increasing from 2 to 4×10-8 cm-1 amagat-2 between 4320 and 4380 cm-1. The obtained continuum is found in good agreement with a previous measurement using much higher densities (20 amagat) and a low resolution grating spectrograph and is consistent with values currently used in the analysis of Venus spectra.
NASA Astrophysics Data System (ADS)
Qamoshi, Khadijeh; Rasuli, Reza
2016-09-01
We study the sound absorption of the reinforced polyvinylpyrrolidone nanofibers with graphene oxide. It is shown that reinforced nanofibers can acquire impedance-matched surface to airborne sound at special frequencies. To obtain such surface, nanofibers were spun with polyvinylpyrrolidone polymer that was doped by graphene oxide with concentrations of 0, 6 and 12 wt%. It was found that fibers without graphene oxide were spun continuously and randomly, whereas by doping with graphene oxide, the mode of fibers is changed and some nodes form on the fibers coating. The sound absorption coefficient was measured by an impedance tube based on 105341-1 ISO standard. Measurements in the frequency range from 700 to 1600 Hz show that use of graphene oxide as a reinforcing phase increases sound absorption coefficient of the samples at a frequency ~1500 Hz up to ~40 %. Angular eigenfrequency and dissipation coefficient of the samples were obtained by impedance measurement for the prepared samples. Results show that doping the polymer with graphene oxide causes an increase in the angular eigenfrequency and the dissipation coefficient.
Relationship between the Kubelka-Munk scattering and radiative transfer coefficients.
Thennadil, Suresh N
2008-07-01
The relationship between the Kubelka-Munk (K-M) and the transport scattering coefficient is obtained through a semi-empirical approach. This approach gives the same result as that given by Gate [Appl. Opt.13, 236 (1974)] when the incident beam is diffuse. This result and those given by Star et al. [Phys. Med. Biol.33, 437 (1988)] and Brinkworth [Appl. Opt.11, 1434 (1972)] are compared with the exact solution of the radiative transfer equation over a large range of optical properties. It is found that the latter expressions, which include an absorption component, do not give accurate results over the range considered. Using the semi-empirical approach, the relationship between the K-M and the transport scattering coefficient is derived for the case where the incident light is collimated. It is shown that although the K-M equation is derived based on diffuse incident light, it can also represent very well the reflectance from a slab of infinite thickness when the incident light is collimated. However, in this case the relationship between the coefficients has to include a function that is dependent on the anisotropy factor. Analysis indicates that the K-M transform achieves the objective of obtaining a measure that gives the ratio of absorption to scattering effects for both diffuse and collimated incident beams over a large range of optical properties.
Pu, Yang; Wang, Wubao; Al-Rubaiee, Mohammad; Gayen, Swapan Kumar; Xu, Min
2012-07-01
Optical extinction and diffuse reflection spectra of cancerous and normal prostate tissues in the 750 to 860 nm spectral range were measured. Optical extinction measurements using thin ex vivo prostate tissue samples were used to determine the scattering coefficient (μ(s)), while diffuse reflection measurements using thick prostate tissue samples were used to extract the absorption coefficient (μ(a)) and the reduced scattering coefficient (μ'(s)). The anisotropy factor (g) was obtained using the extracted values of μ(s) and μ'(s). The values of fractal dimension (D(f)) of cancerous and normal prostate tissues were obtained by fitting to the wavelength dependence of μ'(s). The number of scattering particles contributing to μ(s) as a function of particle size and the cutoff diameter d(max) as a function of g were investigated using the fractal soft tissue model and Mie theory. Results show that d(max) of the normal tissue is larger than that of the cancerous tissue. The cutoff diameter d(max) is observed to agree with the nuclear size for the normal tissues and the nucleolar size for the cancerous tissues. Transmission spectral polarization imaging measurements were performed that could distinguish the cancerous prostate tissue samples from the normal tissue samples based on the differences between their absorption and scattering parameters.
Powerful laser pulse absorption in partly homogenized foam plasma
NASA Astrophysics Data System (ADS)
Cipriani, M.; Gus'kov, S. Yu.; De Angelis, R.; Andreoli, P.; Consoli, F.; Cristofari, G.; Di Giorgio, G.; Ingenito, F.; Rupasov, A. A.
2016-03-01
The internal volume structure of a porous medium of light elements determines unique features of the absorption mechanism of laser radiation; the characteristics of relaxation and transport processes in the produced plasma are affected as well. Porous materials with an average density larger than the critical density have a central role in enhancing the pressure produced during the ablation by the laser pulse; this pressure can exceed the one produced by target direct irradiation. The problem of the absorption of powerful laser radiation in a porous material is examined both analytically and numerically. The behavior of the medium during the process of pore filling in the heated region is described by a model of viscous homogenization. An expression describing the time and space dependence of the absorption coefficient of laser radiation is therefore obtained from the model. A numerical investigation of the absorption of a nanosecond laser pulse is performed within the present model. In the context of numerical calculations, porous media with an average density larger than the critical density of the laser-produced plasma are considered. Preliminary results about the inclusion of the developed absorption model into an hydrodynamic code are presented.
NASA Astrophysics Data System (ADS)
Masoud, Mamdouh S.; Hagagg, Sawsan S.; Ali, Alaa E.; Nasr, Nessma M.
The electronic absorption spectra of gallic acid and its azo derivatives have been studied in various solvents of different polarities. Multiple regression techniques were applied to calculate the regression and correlation coefficients based on an equation that relates the wavenumbers of the absorption band maxima (υmax-) to the solvent parameters; refractive index (n), dielectric constant (D), empirical Kamlet-Taft solvent parameters, π*(dipolarity/polarizability), α (solvent hydrogen-bond donor acidity) and β (solvent hydrogen-bond acceptor basicity). The fitting coefficient obtained from this analysis allows estimating the contribution of each type of interactions relative to total spectral shifts in solution. The dependence of υmax- on the solvent parameters indicates that the obtained bands are affected by specific and non-specific solute-solvent interactions.
X-Ray Attenuation Coefficients from 10 Kev to 100 Mev,
1957-04-30
fig. 1). A well- shielded detector measures the shells account for most of the absorption by this intensity of the trinsmitted beam, and any photon...narrow-beam measurements ----------------- 2 1.4. Combination of attenuation coefficients -------------------- 2 1.5. Energy absorption...thickness is increased measures the unlikely to be absorbed. Consequently, the ab- total probability of the interaction processes. sorption coefficient
Modeling of normal incidence absorption in p-type GaAs/AlGaAs quantum well infrared detectors
NASA Astrophysics Data System (ADS)
Brown, Gail J.; Szmulowicz, Frank
1995-04-01
The absorption of infrared radiation at normal incidence in p-type GaAs/AlGaAs quantum wells, unlike in n-type, is fundamentally allowed. We have measured and theoretically modeled the bound-to-continuum absorption in these p-type materials. The infrared absorption coefficient was calculated are based on the electronic structure, wave functions and optical matrix elements obtained from an 8 X 8 envelope-function approximation (EFA) calculation. The 8 X 8 EFA Hamiltonian incorporates the coupling between the heavy, light, spin-orbit, and conduction bands. In calculating the continuum states for bound-to- continuum intersubband absorption, we do not enclose the well in an artificial box with infinite walls. A comparison of the theoretical absorption and measured photoresponse results verified the accuracy of our model and provided a basis for optimizing the design of p-type quantum wells for infrared detection.
Absorption properties of type-II InAs/InAsSb superlattices measured by spectroscopic ellipsometry
Webster, P. T.; Riordan, N. A.; Liu, S.; Zhang, Y.-H.; Johnson, S. R.; Steenbergen, E. H.
2015-02-09
Strain-balanced InAs/InAsSb superlattices offer access to the mid- to long-wavelength infrared region with what is essentially a ternary material system at the GaSb lattice constant. The absorption coefficients of InAs/InAsSb superlattices grown by molecular beam epitaxy on (100)-oriented GaSb substrates are measured at room temperature over the 30 to 800 meV photon energy range using spectroscopic ellipsometry, and the miniband structure of each superlattice is calculated using a Kronig-Penney model. The InAs/InAsSb conduction band offset is used as a fitting parameter to align the calculated superlattice ground state transition energy to the measured absorption onset at room temperature and to the photoluminescence peak energy at low temperature. It is observed that the ground state absorption coefficient and transition strength are proportional to the square of the wavefunction overlap and the ground state absorption coefficient approaches a maximum value of around 5780 cm{sup −1} as the wavefunction overlap approaches 100%. The absorption analysis of these samples indicates that the optical joint density of states is weakly dependent on the period thickness and Sb content of the superlattice, and that wavefunction overlap is the principal design parameter in terms of obtaining strong absorption in these structures.
Dai, Guang-Ming
2006-02-15
The set of Fourier series is discussed following some discussion of Zernike polynomials. Fourier transforms of Zernike polynomials are derived that allow for relating Fourier series expansion coefficients to Zernike polynomial expansion coefficients. With iterative Fourier reconstruction, Zernike representations of wavefront aberrations can easily be obtained from wavefront derivative measurements.
ERIC Educational Resources Information Center
Mohammed, Ahmed; Zeleke, Aklilu
2015-01-01
We introduce a class of second-order ordinary differential equations (ODEs) with variable coefficients whose closed-form solutions can be obtained by the same method used to solve ODEs with constant coefficients. General solutions for the homogeneous case are discussed.
Guo, Xiaowei; Wang, Dashuai; Liu, Bang; Li, Shaorong; Sheng, Xing
2016-01-25
We proposed a Fourier-series based periodic nanostructure(FSPN) for light trapping in thin film silicon solar cells. By globally optimizing the Fourier coefficients across entire silicon absorption spectrum, we obtained a FSPN structure with short circuit current density greater than 24 mA/cm(2) for a 1μm real silicon absorption layer. The spectral analysis shows at normal incidence the FSPN exhibits a collection effect of periodic gratings and performs over 84.6% better than random texture. The angular analysis shows that the FSPN outperforms grating and random textures within 70 °.
Two-photon absorption in arsenic sulfide glasses
NASA Astrophysics Data System (ADS)
Chunaev, D. S.; Snopatin, G. E.; Plotnichenko, V. G.; Karasik, A. Ya.
2016-10-01
The two-photon absorption coefficient of 1047-{\\text{nm}} light in {\\text{As}}35{\\text{S}}65 chalcogenide glass has been measured. CW probe radiation has been used to observe the linear absorption in glass induced by two-photon excitation. The induced absorption lifetime was found to be ∼ 2 {\\text{ms}}.
Soccer ball lift coefficients via trajectory analysis
NASA Astrophysics Data System (ADS)
Goff, John Eric; Carré, Matt J.
2010-07-01
We performed experiments in which a soccer ball was launched from a machine while two high-speed cameras recorded portions of the trajectory. Using the trajectory data and published drag coefficients, we extracted lift coefficients for a soccer ball. We determined lift coefficients for a wide range of spin parameters, including several spin parameters that have not been obtained by today's wind tunnels. Our trajectory analysis technique is not only a valuable tool for professional sports scientists, it is also accessible to students with a background in undergraduate-level classical mechanics.
Diffusion coefficients in leaflets of bilayer membranes.
Seki, Kazuhiko; Mogre, Saurabh; Komura, Shigeyuki
2014-02-01
We study diffusion coefficients of liquid domains by explicitly taking into account the two-layered structure called leaflets of the bilayer membrane. In general, the velocity fields associated with each leaflet are different and the layers sliding past each other cause frictional coupling. We obtain analytical results of diffusion coefficients for a circular liquid domain in a leaflet, and quantitatively study their dependence on the interleaflet friction. We also show that the diffusion coefficients diverge in the absence of coupling between the bilayer and solvents, even when the interleaflet friction is taken into account. In order to corroborate our theory, the effect of the interleaflet friction on the correlated diffusion is examined.
Kireev, S.V.; Shnyrev, S.L.; Zaspa, Yu.P.
1995-04-01
Collisional broadening coefficients are measured for iodine-127 resonance absorption lines in several rare cases of atmospheric air and CO{sub 2}. The results obtained are used to determine the optimum pressure of a gaseous mixture in a measuring cell for detecting iodine-127 by a helium-neon (633 nm) laser-induced fluorescence technique of monitoring iodine in atmospheric air.
NASA Astrophysics Data System (ADS)
Ahmadivand, Arash; Sinha, Raju; Karabiyik, Mustafa; Vabbina, Phani Kiran; Gerislioglu, Burak; Kaya, Serkan; Pala, Nezih
2017-01-01
Graphene plasmonics has been introduced as a novel platform to design various nano- and microstructures to function in a wide range of spectrum from optical to THz frequencies. Herein, we propose a tunable plasmonic metamaterial in the THz regime by using metallic (silver) concentric microscale split ring resonator arrays on a multilayer metasurface composed of silica and silicon layers. We obtained an absorption percentage of 47.9% including two strong Fano resonant dips in THz regime for the purely plasmonic metamaterial without graphene layer. Considering the data of an atomic graphene sheet (with the thickness of 0.35 nm) in both analytical and experimental regimes obtained by prior works, we employed a graphene layer under concentric split ring resonator arrays and above the multilayer metasurface to enhance the absorption ratio in THz bandwidth. Our numerical and analytical results proved that the presence of a thin graphene layer enhances the absorption coefficient of MM to 64.35%, at the highest peak in absorption profile that corresponds to the Fano dip position. We also have shown that changing the intrinsic characteristics of graphene sheet leads to shifts in the position of Fano dips and variations in the absorption efficiency. The maximum percentage of absorption ( 67%) was obtained for graphene-based MM with graphene layer with dissipative loss factor of 1477 Ω. Employing the antisymmetric feature of the split ring resonators, the proposed graphene-based metamaterial with strong polarization dependency is highly sensitive to the polarization angle of the incident THz beam.
Optical coefficients in a semiconductor quantum ring: Electric field and donor impurity effects
NASA Astrophysics Data System (ADS)
Duque, C. M.; Acosta, Ruben E.; Morales, A. L.; Mora-Ramos, M. E.; Restrepo, R. L.; Ojeda, J. H.; Kasapoglu, E.; Duque, C. A.
2016-10-01
The electron states in a two-dimensional quantum dot ring are calculated in the presence of a donor impurity atom under the effective mass and parabolic band approximations. The effect of an externally applied electric field is also taken into account. The wavefunctions are obtained via the exact diagonalization of the problem Hamiltonian using a 2D expansion within the adiabatic approximation. The impurity-related optical response is analyzed via the optical absorption, relative refractive index change and the second harmonics generation. The dependencies of the electron states and these optical coefficients with the changes in the configuration of the quantum ring system are discussed in detail.
Magneto-absorption in conical quantum dot ensemble: Possible applications for QD LED
NASA Astrophysics Data System (ADS)
Hayrapetyan, D. B.; Kazaryan, E. M.; Sarkisyan, H. A.
2016-07-01
In the framework of the adiabatic approximation, the energy states of electron, as well as the direct light absorption are investigated in conical quantum dot under the external magnetic field. Analytical expressions for the particle wave function and energy spectrum are obtained. The dependence of the absorption edge on the geometrical parameters of conical quantum dot is obtained. Selection rules are revealed for transitions between levels with different quantum numbers. Absorption coefficient dependence on the frequency of the incident light is revealed taking into account dispersion of conical quantum dot's base radius for both cases of symmetric and asymmetric distribution functions. Such structures are very promising and can be used for the element base quantum dots LEDs.
Absorptivity of water vapor for 10.6 micron radiation
NASA Technical Reports Server (NTRS)
Pugh, E. R.; Krech, R. H.
1982-01-01
Attention is called to recent measurements of the absorptivity of water vapor to 10.6-micron laser radiation made using shock-heated H2O/H2 and H2O/Ar mixtures and a probe CO2 laser. It is noted that these measurements give values about a factor of 2 lower than Ludwig's (1971) low resolution values. It is also argued that Fowler's (1981) high values are not likely to be caused by excited water molecules. It is shown that very intense laser radiation would be required to obtain any appreciable vibrational nonequilibrium. Within the narrow spectral range of 944-948/cm, no significant variation in absorption coefficient (suitably normalized) is observed as a function of laser line, water vapor concentration, total pressure, or diluent gas.
Brooksbank, W.A. Jr.; Leddicotte, G.W.; Strain, J.E.; Hendon, H.H. Jr.
1961-11-14
A means was developed for continuously computing and indicating the isotopic assay of a process solution and for automatically controlling the process output of isotope separation equipment to provide a continuous output of the desired isotopic ratio. A counter tube is surrounded with a sample to be analyzed so that the tube is exactly in the center of the sample. A source of fast neutrons is provided and is spaced from the sample. The neutrons from the source are thermalized by causing them to pass through a neutron moderator, and the neutrons are allowed to diffuse radially through the sample to actuate the counter. A reference counter in a known sample of pure solvent is also actuated by the thermal neutrons from the neutron source. The number of neutrons which actuate the detectors is a function of a concentration of the elements in solution and their neutron absorption cross sections. The pulses produced by the detectors responsive to each neu tron passing therethrough are amplified and counted. The respective times required to accumulate a selected number of counts are measured by associated timing devices. The concentration of a particular element in solution may be determined by utilizing the following relation: T2/Ti = BCR, where B is a constant proportional to the absorption cross sections, T2 is the time of count collection for the unknown solution, Ti is the time of count collection for the pure solvent, R is the isotopic ratlo, and C is the molar concentration of the element to be determined. Knowing the slope constant B for any element and when the chemical concentration is known, the isotopic concentration may be readily determined, and conversely when the isotopic ratio is known, the chemical concentrations may be determined. (AEC)
Li, Zi-qiang; He, Xin; Gao, Xiumei; Xu, Yan-yan; Wang, Yue-fei; Gu, Hui; Ji, Rui-feng; Sun, Shu-jun
2011-10-01
The objective of the present study was to develop a novel in vitro system to simulate the process of dissolution and permeation of oral solid dosage forms in vivo, and to establish a correlation between in vitro permeation and in vivo absorption that could predict the bioavailability (BA) and bioequivalence (BE) of congeneric products. The in vitro dissolution and absorption kinetics of four dosage forms of isosorbide mononitrate (ISMN) were evaluated by the USP basket/paddle system and drug dissolution/absorption simulating system (DDASS). The corresponding pharmacokinetic study was performed in beagle dogs. A comparative study was carried out between the classical and the novel method to estimate the effectiveness of the modified DDASS in simulating the course of dissolution and absorption in vivo. Indeed, the correlation coefficients of in vitro dissolution and in vivo absorption obtained from DDASS and dogs were higher. Moreover, a higher level A in vitro-in vivo correlation (IVIVC) between DDASS permeation and dog absorption was established, with correlation coefficients of 0.9968, 0.9872, 0.9921, and 0.9728. The DDASS method was more accurate at modeling the process of dissolution and absorption in vivo for both immediate-release (IR) and sustained-release (SR) dosage forms of ISMN.
NASA Astrophysics Data System (ADS)
Liu, Sheng; Wang, Yingwei; Li, Xiaohong; Lyu, Bosai; Xu, Yahui; Zhou, Jianliang; Yan, Jun; Li, Jianbo; Xiao, Si; He, Jun
2017-04-01
The extraordinary ultrafast tunable saturable absorption properties of metal complexes M(PAAL)2 (M = Co, Ni, Cu, Zn) containing redox-active 1-(2-pyridylazo)-2-acenaphthequinol ligands (PAAL) were investigated by Z-scan and pump-probe system. The obtained third-order nonlinear optical (NLO) absorption and refraction coefficient of each metal complex reach ∼10-2 cm/GW and ∼10-6 cm2/GW at 510 nm wavelength, respectively. Meanwhile, an ultrafast carrier relaxation process of approximately (200 ± 50) fs is observed for all of them. Furthermore, we found that the third-order nonlinear absorption coefficient of M(PAAL)2 is proportional to the central metal proton number. All the NLO properties indicate that those metal complexes posses potential applications for fabricating photonic devices.
Shivaramu; Amutha, R.; Ramprasath, V.
1999-05-01
Effective atomic numbers for total gamma-ray interaction with some selected thermoluminescent dosimetric compounds such as barium acetate, barium sulfate, calcium carbonate, calcium sulfate, calcium sulfate dihydrate, cadmium sulfate (anhydrous), cadmium sulfate, strontium sulfate, and lithium fluoride have been calculated in the 1-keV to 20-MeV energy region. Experimental mass attenuation coefficients and effective atomic numbers for these compounds at selected photon energies of 26.3, 33.2, 59.54, and 661.6 keV have been obtained from good geometry transmission measurements and compared with theoretical values. The effect of absorption edge on effective atomic numbers and its variation with energy, and nonvalidity of the Bragg`s mixture rule at incident photon energies closer to the absorption edges of constituent elements of compounds are discussed.
NASA Technical Reports Server (NTRS)
Hughes, William O.; McNelis, Anne M.; Chris Nottoli; Eric Wolfram
2015-01-01
The absorption coefficient for material specimens are needed to quantify the expected acoustic performance of that material in its actual usage and environment. The ASTM C423-09a standard, "Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberant Room Method" is often used to measure the absorption coefficient of material test specimens. This method has its basics in the Sabine formula. Although widely used, the interpretation of these measurements are a topic of interest. For example, in certain cases the measured Sabine absorption coefficients are greater than 1.0 for highly absorptive materials. This is often attributed to the diffraction edge effect phenomenon. An investigative test program to measure the absorption properties of highly absorbent melamine foam has been performed at the Riverbank Acoustical Laboratories. This paper will present and discuss the test results relating to the effect of the test materials' surface area, thickness and edge sealing conditions. A follow-on paper is envisioned that will present and discuss the results relating to the spacing between multiple piece specimens, and the mounting condition of the test specimen.
Heat transfer coefficient of cryotop during freezing.
Li, W J; Zhou, X L; Wang, H S; Liu, B L; Dai, J J
2013-01-01
Cryotop is an efficient vitrification method for cryopreservation of oocytes. It has been widely used owing to its simple operation and high freezing rate. Recently, the heat transfer performance of cryotop was studied by numerical simulation in several studies. However, the range of heat transfer coefficient in the simulation is uncertain. In this study, the heat transfer coefficient for cryotop during freezing process was analyzed. The cooling rates of 40 percent ethylene glycol (EG) droplet in cryotop during freezing were measured by ultra-fast measurement system and calculated by numerical simulation at different value of heat transfer coefficient. Compared with the results obtained by two methods, the range of the heat transfer coefficient necessary for the numerical simulation of cryotop was determined, which is between 9000 W/(m(2)·K) and 10000 W/(m (2)·K).
High-Absorption-Efficiency Superlattice Solar Cells by Excitons
NASA Astrophysics Data System (ADS)
Nishinaga, Jiro; Kawaharazuka, Atsushi; Onomitsu, Koji; Horikoshi, Yoshiji
2013-11-01
The effect of excitonic absorption on solar cell efficiency has been investigated using solar cells with AlGaAs/GaAs superlattice structures. Numerical calculations reveal that excitonic absorption considerably enhances the overall absorption of bulk GaAs. Excitonic absorption shows strong and sharp peaks at the absorption edge and in the energy region above the band gap. Absorption enhancement is also achieved in the AlGaAs/GaAs superlattice. The measured quantum efficiency spectra of the superlattice solar cells are quite similar to the calculated absorption spectra considering the excitonic effect. The superlattice solar cells are confirmed to have high absorption coefficient compared with the GaAs and AlGaAs bulk solar cells. These results suggest that the enhanced absorption by excitons can increase the quantum efficiency of solar cells. This effect is more prominent for the solar cells with small absorption layer thicknesses.
Quantum absorption refrigerator.
Levy, Amikam; Kosloff, Ronnie
2012-02-17
A quantum absorption refrigerator driven by noise is studied with the purpose of determining the limitations of cooling to absolute zero. The model consists of a working medium coupled simultaneously to hot, cold, and noise baths. Explicit expressions for the cooling power are obtained for Gaussian and Poisson white noise. The quantum model is consistent with the first and second laws of thermodynamics. The third law is quantified; the cooling power J(c) vanishes as J(c) ∝ T(c)(α), when T(c)→0, where α=d+1 for dissipation by emission and absorption of quanta described by a linear coupling to a thermal bosonic field, where d is the dimension of the bath.
Computing spatial information from Fourier coefficient distributions.
Heinz, William F; Werbin, Jeffrey L; Lattman, Eaton; Hoh, Jan H
2011-05-01
The spatial relationships between molecules can be quantified in terms of information. In the case of membranes, the spatial organization of molecules in a bilayer is closely related to biophysically and biologically important properties. Here, we present an approach to computing spatial information based on Fourier coefficient distributions. The Fourier transform (FT) of an image contains a complete description of the image, and the values of the FT coefficients are uniquely associated with that image. For an image where the distribution of pixels is uncorrelated, the FT coefficients are normally distributed and uncorrelated. Further, the probability distribution for the FT coefficients of such an image can readily be obtained by Parseval's theorem. We take advantage of these properties to compute the spatial information in an image by determining the probability of each coefficient (both real and imaginary parts) in the FT, then using the Shannon formalism to calculate information. By using the probability distribution obtained from Parseval's theorem, an effective distance from the uncorrelated or most uncertain case is obtained. The resulting quantity is an information computed in k-space (kSI). This approach provides a robust, facile and highly flexible framework for quantifying spatial information in images and other types of data (of arbitrary dimensions). The kSI metric is tested on a 2D Ising model, frequently used as a model for lipid bilayer; and the temperature-dependent phase transition is accurately determined from the spatial information in configurations of the system.
Measurement and feature analysis of absorption spectra of four algal species
NASA Astrophysics Data System (ADS)
Zhu, Jianhua; Zhou, Hongli; Han, Bing; Li, Tongji
2016-04-01
Two methods for particulate pigments (i.e., quantitative filter technique, QFT, and in vivo measurement, InVivo, respectively) and two methods for dissolved pigments (i.e., Acetone Extracts, AceEx, and high-performance liquid chromatography, HPLC, respectively) were used to obtain the optical absorption coefficient spectra for cultures of four typical algal species. Through normalization and analysis of the spectra, it is shown that (1) the four methods are able to measure optical absorption spectra of particulate and/or dissolved pigments; (2) that the optical absorption spectra of particulate and dissolved pigments were consistent in terms of the peak position in the blue wavelength, and the difference of the peak position in the near infrared wavelength was ~10 nm between each other; and (3) that the leveling effect of the absorption spectra of particulate pigments was significant. These four methods can all effectively measure the absorption coefficients of phytoplankton pigments, while each one has its unique advantages in different applications. Therefore, appropriate method should be carefully selected for various application due to their intrinsic difference.
Measurement and feature analysis of absorption spectra of four algal species
NASA Astrophysics Data System (ADS)
Zhu, Jianhua; Zhou, Hongli; Han, Bing; Li, Tongji
2017-03-01
Two methods for particulate pigments (i.e., quantitative filter technique, QFT, and in vivo measurement, InVivo, respectively) and two methods for dissolved pigments (i.e., Acetone Extracts, AceEx, and high-performance liquid chromatography, HPLC, respectively) were used to obtain the optical absorption coefficient spectra for cultures of four typical algal species. Through normalization and analysis of the spectra, it is shown that (1) the four methods are able to measure optical absorption spectra of particulate and/or dissolved pigments; (2) that the optical absorption spectra of particulate and dissolved pigments were consistent in terms of the peak position in the blue wavelength, and the difference of the peak position in the near infrared wavelength was 10 nm between each other; and (3) that the leveling effect of the absorption spectra of particulate pigments was significant. These four methods can all effectively measure the absorption coefficients of phytoplankton pigments, while each one has its unique advantages in different applications. Therefore, appropriate method should be carefully selected for various application due to their intrinsic difference.
Membrane-based absorption of VOCs from a gas stream
Poddar, T.K.; Majumdar, S.; Sirkar, K.K.
1996-11-01
A regenerative absorption-based process was developed for removing VOCs from N{sub 2} in an inert, nonvolatile, organic liquid flowing in compact hollow-fiber devices. The process eliminates flooding, loading, and entrainment, and can replace activated carbon adsorption. Two types of hollow-fiber membranes were studied: one with a microporous wall and the other with a highly VOC-permeable nonporous coating on the outer surface of a microporous hollow fiber. Criteria for nondispersive operation were developed for each case. Experiments were conducted for the absorption of acetone, methylene chloride, toluene, and methanol from the respective VOC-N{sub 2} gas mixture using two absorbents: silicone oil and mineral oil. The highest mass-transfer coefficient was obtained for toluene followed by methylene chloride, acetone, and methanol. Different resistances making up the overall resistance in VOC absorption were characterized comprehensively to develop a predictive capability and compare the absorption performances of two types of fibers and the two absorbents. The absorbent-filled porous membrane contributed significantly to the total mass-transfer resistance. Numerical simulations of governing equations based on a cell model agree well with experimental results.
Nonlinear absorption properties and excited state dynamics of ferrocene.
Scuppa, Stefano; Orian, Laura; Dini, Danilo; Santi, Saverio; Meneghetti, Moreno
2009-08-20
We report on the first observation of reverse saturable absorption by ferrocene (Fc) in toluene using nanosecond pulses at 532 nm. Pump and probe experiments in the visible spectral region show the existence of an excited triplet state with an intersystem crossing quantum yield S1 --> T1 of 0.085 and a molar extinction coefficient epsilon(Fc)(T) of 5650 L mol(-1) cm(-1) at 700 nm. The full understanding of the nonlinear optical behavior of Fc cannot be obtained, however, with a model that includes only the one-photon absorption from T1, but it is mandatory to consider also a simultaneous two-photon absorption from an excited singlet state of Fc (two-photon absorption cross section: 2.4 x 10(-41) cm4 s ph(-1) mol(-1)). The optical spectrum of the ground and triplet state of Fc are calculated within a TD-DFT approach considering several functionals (PBE, BLYP, LDA, OPBE) for the optimization of molecular geometry.
Water absorption of poly(methyl methacrylate) containing 4-methacryloxyethyl trimellitic anhydride.
Unemori, Masako; Matsuya, Yoko; Matsuya, Shigeki; Akashi, Akane; Akamine, Akifumi
2003-04-01
The amount of water absorption of poly(methyl methacrylate) (PMMA) containing 0, 1, 3 and 5 wt% of an adhesive monomer, 4-methacryloxyethyl trimellitic anhydride (4-META), was measured at 7 degrees C, 37 degrees C and 60 degrees C. After the water uptake reached equilibrium in specimens, they were desorbed to obtain a constant value and the absorption process was repeated. Mass changes in the second desorption were recorded for the storage temperatures of 37 degrees C and 60 degrees C. Multiple regression analyses were conducted on three independent variables, 4-META concentration, storage temperature and absorption-desorption cycle. A statistically significant relationship was found between the maximum water uptake and 4-META concentration, while there was no relationship between the maximum water uptake and diffusion coefficient obtained using the Fick's law. The negative relationship in the latter did not support the free space theory. The significant and positive relationship between the maximum water uptake and 4-META concentration demonstrates that water molecules diffuse through the formation of a hydrogen bond at polar sites. The maximum water uptake was not influenced by temperature, while the diffusion coefficient increased with the rise in temperature. The activation energy was 41-47 and 50-53 kJ/mol in the first and second absorption tests, respectively.
Concordance correlation coefficient applied to discrete data.
Carrasco, Josep L; Jover, Lluis
2005-12-30
In any field in which decisions are subject to measurements, interchangeability between the methods used to obtain these measurements is essential. To consider methods as interchangeable, a certain degree of agreement is needed between the measurements they provide. The concordance correlation coefficient is an index that assesses the strength of agreement and it has been widely applied in situations in which measurements are made on a continuous scale. Recently the concordance correlation coefficient has been defined as a specific intraclass correlation coefficient estimated by the variance components of a Normal-Normal mixed linear model. Although this coefficient was defined for the continuous scale case, it may also be used with a discrete scale. In this case the data are often transformed and normalized, and the concordance correlation is applied. This study discusses the expression of the concordance correlation coefficient for discrete Poisson data by means of the Poisson-Normal generalized linear mixed model. The behaviour of the concordance correlation coefficient estimate is assessed by means of a simulation study, in which the estimates were compared using four models: three Normal-Normal mixed models with raw data, log-transformed data and square-root transformed data, and the Poisson-Normal generalized linear mixed model. An example is provided in which two different methods are used to measure CD34+ cells.
Subpicosecond reverse saturable absorption in organic and organometallic solutions
NASA Astrophysics Data System (ADS)
Pittman, M.; Plaza, P.; Martin, M. M.; Meyer, Y. H.
1998-12-01
Solutions of several carbocyanines, phthalocyanines and naphthalocyanines were studied by time-resolved transient spectroscopy with subpicosecond white-light continuum. The excited-state absorption cross-sections of all compounds were determined from the differential spectra obtained at short delay time after excitation, by a global spectral analysis. All these molecules exhibit an excited-state absorption cross-section higher than that of the ground state at 610 nm. This spectral property gives rise to a reverse saturable absorption (RSA) effect under high laser fluences at this wavelength. Nonlinear transmission of these molecules was measured under increasing laser fluences. A three-level molecular model was used to simulate the measured nonlinear transmission and the best fits were obtained with molecular parameters in good agreement with those deduced from the analysis of the transient spectra. The use of RSA for the energy stabilization of ultrashort laser pulses was demonstrated, and a stabilization coefficient was defined as an efficient tool for characterizing nonlinear behavior of such compounds.
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
Studies of cavity enhanced absorption spectroscopy for weak absorption gas measurements
NASA Astrophysics Data System (ADS)
Li, Liucheng; Duo, Liping; Gong, Deyu; Ma, Yanhua; Zhang, Zhiguo; Wang, Yuanhu; Zhou, Dongjian; Jin, Yuqi
2017-01-01
In order to determine the concentrations of trace amount metastable species in chemical lasers, an off-axis cavity enhanced absorption spectrometer for the detection of weak absorption gases has been built with a noise equivalent absorption sensitivity of 1.6x10-8 cm-1. The absorption spectrum of trace amount gaseous ammonia and water vapor was obtained with a spectral resolution of about 78 MHz. A multiple-line absorption spectroscopic method to determine the temperature of gaseous ammonia has been developed by use of multiple lines of ammonia molecule absorption spectrum.
Arnott, W. Patrick; Moosmu''ller, Hans; Walker, John W.
2000-12-01
A nitrogen dioxide calibration method is developed to evaluate the theoretical calibration for a photoacoustic instrument used to measure light absorption by atmospheric aerosols at a laser wavelength of 532.0 nm. This method uses high concentrations of nitrogen dioxide so that both a simple extinction and the photoacoustically obtained absorption measurement may be performed simultaneously. Since Rayleigh scattering is much less than absorption for the gas, the agreement between the extinction and absorption coefficients can be used to evaluate the theoretical calibration, so that the laser gas spectra are not needed. Photoacoustic theory is developed to account for strong absorption of the laser beam power in passage through the resonator. Findings are that the photoacoustic absorption based on heat-balance theory for the instrument compares well with absorption inferred from the extinction measurement, and that both are well within values represented by published spectra of nitrogen dioxide. Photodissociation of nitrogen dioxide limits the calibration method to wavelengths longer than 398 nm. Extinction and absorption at 532 and 1047 nm were measured for kerosene-flame soot to evaluate the calibration method, and the single scattering albedo was found to be 0.31 and 0.20 at these wavelengths, respectively.
Optical absorption and radiative heat transport in olivine at high temperature
NASA Technical Reports Server (NTRS)
Shankland, T. J.; Nitsan, U.; Duba, A. G.
1979-01-01
Results are presented of measurements of the optical absorption spectra (300-8000 nm) of olivine as a function of temperature (300-1700 K) under conditions of controlled and known oxygen fugacity within the stability field of the samples. The absorption spectra are used to calculate the temperature-dependent radiative transfer coefficient of olivine and to numerically study the accuracy of the method. The present absorption measurements in olivine under oxidizing conditions known to be within the olivine stability field indicate that the effective radiative conductivity K(R) is lower than that obtained in previous studies under different experimental conditions. The lower value of K(R) makes it more likely that some of the earth's internal heat is removed by convection and less likely that thermal models involving conduction and radiation alone will satisfactorily explain thermal conditions in the earth's mantle.
Grossman, G.; Perez-Blanco, H.
1983-06-16
An improvement in an absorption heat pump cycle is obtained by adding adiabatic absorption and desorption steps to the absorber and desorber of the system. The adiabatic processes make it possible to obtain the highest temperature in the absorber before any heat is removed from it and the lowest temperature in the desorber before heat is added to it, allowing for efficient utilization of the thermodynamic availability of the heat supply stream. The improved system can operate with a larger difference between high and low working fluid concentrations, less circulation losses, and more efficient heat exchange than a conventional system.
NASA Technical Reports Server (NTRS)
Billman, K. W.; Stallcop, J. R.; Rowley, P. D.; Presley, L. L.
1972-01-01
The absorption coefficients of 1.15- and 3.39-micrometer radiation for a homogeneous H-He plasma have been measured in a temperature and electron density range where the major absorption mechanisms are electron-ion inverse bremsstrahlung and neutral-atom photoionization. Measurements were made behind both the incident and reflected shock waves in a driven tube by recording the laser intensity transmitted along the tube diameter as a function of time. The measured values compare well with those obtained from theoretical calculations for a gas in thermodynamic equilibrium.
Infrasound absorption by atmospheric clouds
NASA Astrophysics Data System (ADS)
Baudoin, Michael; Coulouvrat, Francois; Thomas, Jean-Louis
2010-05-01
A model is developed for the absorption of infrasound by atmospheric clouds made of a suspension of liquid water droplets within a gaseous mixture of water vapor and air. The model is based on the work of D.A. Gubaidullin and R.I. Nigmatulin [Int. J. Multiphase Flow, 26, 207-228, 2000], which is applied to atmospheric clouds. Three physical mechanisms are included : unsteady viscous drag associated with momentum transfers due to the translation of water droplets, unsteady thermal transfers between the liquid and gaseous phases, and mass transfers due to the evaporation or condensation of the water phase. For clouds, in the infrasonic frequency range, phase changes are the dominant mechanisms (around 1 Hz), while viscous and heat transfers become significant only around 100 Hz. Mass transfers involve two physical effects : evaporation and condensation of the water phase at the droplet surface, and diffusion of the water vapor within the gaseous phase. The first one is described through the Hertz-Knudsen-Langmuir theory based on kinetic theory. It involves a little known coefficient known as coefficient of accommodation. The second one is the classical Fick diffusion. For clouds, and unless the coefficient of accommodation is very small (far from the generally recommended value is close to one), diffusion is the main limiting effects for mass transfers. In a second stage, the sound and infrasound absorption is evaluated for various typical clouds up to about 4 km altitude. Above this altitude, the ice content of clouds is dominant compared to their water content, and the present model is not applicable. Cloud thickness, water content, and droplets size distribution are shown to be the major factors influencing the infrasound absorption. A variety of clouds have been analyzed. In most cases, it is shown that infrasound absorption within clouds is several orders larger than classical absorption (due to molecular relaxation of nitrogen and oxygen molecules in presence
Microwave radiation absorption: behavioral effects.
D'Andrea, J A
1991-07-01
The literature contains much evidence that absorption of microwave energy will lead to behavioral changes in man and laboratory animals. The changes include simple perturbations or outright stoppage of ongoing behavior. On one extreme, intense microwave absorption can result in seizures followed by death. On the other extreme, man and animals can hear microwave pulses at very low rates of absorption. Under certain conditions of exposure, animals will avoid microwaves, while under other conditions, they will actively work to obtain warmth produced by microwaves. Some research has shown behavioral effects during chronic exposure to low-level microwaves. The specific absorption rates that produce behavioral effects seem to depend on microwave frequency, but controversy exists over thresholds and mechanism of action. In all cases, however, the behavioral disruptions cease when chronic microwave exposure is terminated. Thermal changes in man and animals during microwave exposure appear to account for all reported behavioral effects.
Meyer, Wilfried; Frommhold, Lothar
2015-09-21
Coupled cluster quantum chemical calculations of the potential energy surface and the induced dipole surface are reported for the He–Ar van der Waals collisional complex. Spectroscopic parameters are derived from global analytical fits while an accurate value for the long-range dipole coefficient D{sub 7} is obtained by perturbation methods. Collision-induced absorption spectra are computed quantum mechanically and compared with existing measurements.
Absorption spectra of vanadyl ion doped in MgNH 4PO 4·6H 2O (struvite) crystal
NASA Astrophysics Data System (ADS)
Agarwal, O. P.; Chand, Prem
1984-10-01
Results of Electron Paramagnetic Resonance (EPR) and optical absorption studies of VO 2+ ion doped in struvite at room liquid nitrogen temperatures are reported. Three preferential V= O bond directions in the crystal have been identified. The optical and EPR data have shown the formation of NH 4(PO 4VO(H 2O) 5 complex in the crystal as a result of VO 2+ doping. Correlating the optical and EPR data the molecular orbital coefficients are also obtained and discussed.
Meyer, Wilfried; Frommhold, Lothar
2015-09-21
Coupled cluster quantum chemical calculations of the potential energy surface and the induced dipole surface are reported for the He-Ar van der Waals collisional complex. Spectroscopic parameters are derived from global analytical fits while an accurate value for the long-range dipole coefficient D7 is obtained by perturbation methods. Collision-induced absorption spectra are computed quantum mechanically and compared with existing measurements.
Seebeck Coefficient Measured With Differential Heat Pulses
NASA Technical Reports Server (NTRS)
Zoltan, L.; Wood, C.; Stapfer, G.
1986-01-01
Common experimental errors reduced because pulse technique suppresses drifts in thermoelectric measurements. Differential-heat-pulse apparatus measures Seebeck coefficient in semiconductors at temperatures up to 1,900 K. Sample heated to measuring temperature in furnace. Ends of sample then differentially heated a few degrees more by lamps. Differential temperature rise and consequent Seebeck voltage measured via thermocouple leads. Because pulse technique used, errors that often arise from long-term drifts in thermoelectric measurements suppressed. Apparatus works with temperature differences of only few degrees, further increasing accuracy of coefficients obtained.
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
NASA Astrophysics Data System (ADS)
Picard, Ghislain; Libois, Quentin; Arnaud, Laurent
2016-11-01
Ice is a highly transparent material in the visible. According to the most widely used database (IA2008; Warren and Brandt, 2008), the ice absorption coefficient reaches values lower than 10-3 m-1 around 400 nm. These values were obtained from a vertical profile of spectral radiance measured in a single snow layer at Dome C in Antarctica. We reproduced this experiment using an optical fiber inserted in the snow to record 56 profiles from which 70 homogeneous layers were identified. Applying the same estimation method on every layer yields 70 ice absorption spectra. They present a significant variability but absorption coefficients are overall larger than IA2008 by 1 order of magnitude at 400-450 nm. We devised another estimation method based on Bayesian inference that treats all the profiles simultaneously. It reduces the statistical variability and confirms the higher absorption, around 2 × 10-2 m-1 near the minimum at 440 nm. We explore potential instrumental artifacts by developing a 3-D radiative transfer model able to explicitly account for the presence of the fiber in the snow. The simulation shows that the radiance profile is indeed perturbed by the fiber intrusion, but the error on the ice absorption estimate is not larger than a factor of 2. This is insufficient to explain the difference between our new estimate and IA2008. The same conclusion applies regarding the plausible contamination by black carbon or dust, concentrations reported in the literature are insufficient. Considering the large number of profiles acquired for this study and other estimates from the Antarctic Muon and Neutrino Detector Array (AMANDA), we nevertheless estimate that ice absorption values around 10-2 m-1 at the minimum are more likely than under 10-3 m-1. A new estimate in the range 400-600 nm is provided for future modeling of snow, cloud, and sea-ice optical properties. Most importantly, we recommend that modeling studies take into account the large uncertainty of the ice
Loskiewicz, J; Swakoń, J; Kulczykowska, K
2000-06-01
The radiometric K, U and Th concentrations and neutron absorption cross-section sigma a of rock samples obtained from coring are analysed. The cores are from wellbores located in the Sucha-Jordanów region (Carpathian Mountains) and from gas producing Miocene formations in the Carpathian foothills. Correlation coefficients between the neutron absorption cross-section (sigma a) and K, U and Th concentrations are presented. Neural network representation of the function sigma a = f(K, U, Th) obtained for a region can later be used for sigma a estimation from spectrometric probe results in uncored wells.
NASA Astrophysics Data System (ADS)
Rama Gopal, K.; Balakrishnaiah, G.; Arafath, S. Md.; Raja Obul Reddy, K.; Siva Kumar Reddy, N.; Pavan Kumari, S.; Raghavendra Kumar, K.; Chakradhar Rao, T.; Lokeswara Reddy, T.; Reddy, R. R.; Nazeer Hussain, S.; Vasudeva Reddy, M.; Suresh Babu, S.; Mallikarjuna Reddy, P.
2017-01-01
Aerosol optical properties are continuously measured at a semi-arid station, Anantapur from June 2012 to May 2013 which describes the impact of surface aerosols on climate change over the region. Scattering coefficient (σsct) and absorption coefficient (σabs) are obtained from integrating Nephelometer and Aethalometer, respectively. Also, the single scattering albedo (ω0), Scattering/absorption Ångström exponents were examined during the period of study. Diurnal variations of σsct and σabs show a bi-peak pattern with two maxima and one minimum in a day. The largest values of σsct and σabs are obtained in winter while the lowest values are measured in monsoon. From the measurements σsct550 and σabs550 are found to be 110 ± 12.23 Mm- 1 and 33 ± 5.2 Mm- 1, respectively during the study period. An analysis of the ω0 suggests that there is a more absorbing fraction in the particle composition over the measurement site. The ω0 obtained in the surface boundary layer of Anantapur is below the critical value of 0.86 that determines the shift from cooling to warming. A relationship between scattering/absorption coefficients and scattering/absorption Ångström exponent and single scattering albedo is further examined. In order to understand the origins of the air masses in the study region, we performed seven-day back trajectory analyses based on the NOAA HYSPLIT model. These trajectories were computed at several altitudes (3000 m, 1500 m, and 500 m) for June 2012 and May 2013. These results put in evidence the need of efforts to reduce absorbing particles (black carbon) emissions to avoid the possible warming that would result from the reductions of the cooling aerosol only.
Diffusion coefficient of three-dimensional Yukawa liquids
Dzhumagulova, K. N.; Ramazanov, T. S.; Masheeva, R. U.
2013-11-15
The purpose of this work is an investigation of the diffusion coefficient of the dust component in complex plasma. The computer simulation of the Yukawa liquids was made on the basis of the Langevin equation, which takes into account the influence of buffer plasma on the dust particles dynamics. The Green–Kubo relation was used to calculate the diffusion coefficient. Calculations of the diffusion coefficient for a wide range of the system parameters were performed. Using obtained numerical data, we constructed the interpolation formula for the diffusion coefficient. We also show that the interpolation formula correctly describes experimental data obtained under microgravity conditions.
Evaluation of a compact sensor for backscattering and absorption
NASA Astrophysics Data System (ADS)
Gainusa Bogdan, Alina; Boss, Emmanuel S.
2011-07-01
Seawater inherent optical properties (IOPs) are key parameters in a wide range of applications in environmental studies and oceanographic research. In particular, the absorption coefficient (a) is the typical IOP used to obtain the concentration of chlorophyll-a in the water---a critical parameter in biological oceanography studies and the backscattering coefficient (bb) is used as a measure of turbidity. In this study, we test a novel instrument concept designed to obtain both the absorption and backscattering coefficients. The instrument would emit a collimated monochromatic light beam into the water retrieving the backscattered light intensity as a function of distance from the center of illumination. We use Monte Carlo modeling of light propagation to create an inversion algorithm that translates the signal from such an instrument into values of a and bb. Our results, based on simulations spanning the bulk of natural values of seawater IOP combinations, indicate that a 6.2cm diameter instrument with a radial resolution of 1cm would be capable of predicting bb within less than 13.4% relative difference and a within less than 57% relative difference (for 90% of the inverted a values, the relative errors fall below 29.7%). Additionally, these errors could be further reduced by constraining the inversion algorithm with information from concurrent measurements of other IOPs. Such a compact and relatively simple device could have multiple applications for in situ optical measurements, including a and bb retrievals from instrumentation mounted on autonomous underwater vehicles. Furthermore, the same methodology could possibly be used for an out-of-water sensor.
NASA Astrophysics Data System (ADS)
Asadian, M.; Saeedi, H.; Yadegari, M.; Shojaee, M.
2014-06-01
In this paper, a new mathematical model has been presented to determine the equilibrium segregation (k0) and effective segregation (keff) coefficients for neodymium (Nd) in YAG crystal grown by Czochralski (CZ) method. Determination of diffusion coefficient (DL) of Nd impurity in molten YAG is also investigated. In this model, utilizing Lambert W-function is a new idea to solve the Scheil equation for calculation of effective segregation coefficient. The Nd concentration in the crystal has been measured by optical absorption method to calculate keff. The analyses show that the keff is related to the growth parameters such as crystal growth rate (ug) and crystal rotation rate (ω), ( ug/√{ω}) but it is independent of the Nd concentration in the initial melt (C0). Based on obtained keff and experimental growth data, k0 and DL of Nd in molten YAG have been calculated. For all experiments, the average value of k0=0.216 and DL=1.4×10-6 (cm2/s) are obtained. Our results are corroborated by the theoretical and experimental data from the literature.
Intersubband absorption in Si(1-x)Ge(x/Si superlattices for long wavelength infrared detectors
NASA Technical Reports Server (NTRS)
Rajakarunanayake, Yasantha; Mcgill, Tom C.
1990-01-01
Researchers calculated the absorption strengths for intersubband transitions in n-type Si(1-x)Ge(x)/Si superlattices. These transitions can be used for the detection of long-wavelength infrared radiation. A significant advantage in Si(1-x)Ge(x)/Si supperlattice detectors is the ability to detect normally incident light; in Ga(1-x)Al(x)As/GaAs superlattices, intersubband absorption is possible only if the incident light contains a polarization component in the growth direction of the superlattice. Researchers present detailed calculation of absorption coefficients, and peak absorption wavelengths for (100), (111) and (110) Si(1-x)Ge(x)/Si superlattices. Peak absorption strengths of about 2000 to 6000 cm(exp -1) were obtained for typical sheet doping concentrations (approx. equals 10(exp 12)cm(exp -2)). Absorption comparable to that in Ga(1-x)Al(x)As/GaAs superlattice detectors, compatibility with existing Si technology, and the ability to detect normally incident light make these devices promising for future applications.
Thermophysics Characterization of Multiply Ionized Air Plasma Absorption of Laser Radiation
NASA Technical Reports Server (NTRS)
Wang, Ten-See; Rhodes, Robert; Turner, Jim (Technical Monitor)
2002-01-01
The impact of multiple ionization of air plasma on the inverse Bremsstrahlung absorption of laser radiation is investigated for air breathing laser propulsion. Thermochemical properties of multiply ionized air plasma species are computed for temperatures up to 200,000 deg K, using hydrogenic approximation of the electronic partition function; And those for neutral air molecules are also updated for temperatures up to 50,000 deg K, using available literature data. Three formulas for absorption are calculated and a general formula is recommended for multiple ionization absorption calculation. The plasma composition required for absorption calculation is obtained by increasing the degree of ionization sequentially, up to quadruple ionization, with a series of thermal equilibrium computations. The calculated second ionization absorption coefficient agrees reasonably well with that of available data. The importance of multiple ionization modeling is demonstrated with the finding that area under the quadruple ionization curve of absorption is found to be twice that of single ionization. The effort of this work is beneficial to the computational plasma aerodynamics modeling of laser lightcraft performance.
Undistorted X-ray Absorption Spectroscopy Using s-Core-Orbital Emissions.
Golnak, Ronny; Xiao, Jie; Atak, Kaan; Unger, Isaak; Seidel, Robert; Winter, Bernd; Aziz, Emad F
2016-05-12
Detection of secondary emissions, fluorescence yield (FY), or electron yield (EY), originating from the relaxation processes upon X-ray resonant absorption has been widely adopted for X-ray absorption spectroscopy (XAS) measurements when the primary absorption process cannot be probed directly in transmission mode. Various spectral distortion effects inherent in the relaxation processes and in the subsequent transportation of emitted particles (electron or photon) through the sample, however, undermine the proportionality of the emission signals to the X-ray absorption coefficient. In the present study, multiple radiative (FY) and nonradiative (EY) decay channels have been experimentally investigated on a model system, FeCl3 aqueous solution, at the excitation energy of the Fe L-edge. The systematic comparisons between the experimental spectra taken from various decay channels, as well as the comparison with the theoretically simulated Fe L-edge XA spectrum that involves only the absorption process, indicate that the detection of the Fe 3s → 2p partial fluorescence yield (PFY) gives rise to the true Fe L-edge XA spectrum. The two key characteristics generalized from this particular decay channel-zero orbital angular momentum (i.e., s orbital) and core-level emission-set a guideline for obtaining undistorted X-ray absorption spectra in the future.
Localized modes in optics of photonic liquid crystals with local anisotropy of absorption
NASA Astrophysics Data System (ADS)
Belyakov, V. A.; Semenov, S. V.
2016-05-01
The localized optical modes in spiral photonic liquid crystals are theoretically studied for the certainty at the example of chiral liquid crystals (CLCs) for the case of CLC with an anisotropic local absorption. The model adopted here (absence of dielectric interfaces in the structures under investigation) makes it possible to get rid of mixing of polarizations on the surfaces of the CLC layer and of the defect structure and to reduce the corresponding equations to only the equations for light with polarization diffracting in the CLC. The dispersion equations determining connection of the edge mode (EM) and defect mode (DM) frequencies with the CLC layer parameters (anisotropy of local absorption, CLC order parameter) and other parameters of the DMS are obtained. Analytic expressions for the transmission and reflection coefficients of CLC layer and DMS for the case of CLC with an anisotropic local absorption are presented and analyzed. It is shown that the CLC layers with locally anisotropic absorption reduce the EM and DM lifetimes (and increase the lasing threshold) in the way different from the case of CLC with an isotropic local absorption. Due to the Borrmann effect revealing of which is different at the opposite stop-band edges in the case of CLC layers with an anisotropic local absorption the EM life-times for the EM frequencies at the opposite stop-bands edges may be significantly different. The options of experimental observations of the theoretically revealed phenomena are briefly discussed.
Enhanced absorption cycle computer model
NASA Astrophysics Data System (ADS)
Grossman, G.; Wilk, M.
1993-09-01
Absorption heat pumps have received renewed and increasing attention in the past two decades. The rising cost of electricity has made the particular features of this heat-powered cycle attractive for both residential and industrial applications. Solar-powered absorption chillers, gas-fired domestic heat pumps, and waste-heat-powered industrial temperature boosters are a few of the applications recently subjected to intensive research and development. The absorption heat pump research community has begun to search for both advanced cycles in various multistage configurations and new working fluid combinations with potential for enhanced performance and reliability. The development of working absorption systems has created a need for reliable and effective system simulations. A computer code has been developed for simulation of absorption systems at steady state in a flexible and modular form, making it possible to investigate various cycle configurations with different working fluids. The code is based on unit subroutines containing the governing equations for the system's components and property subroutines containing thermodynamic properties of the working fluids. The user conveys to the computer an image of his cycle by specifying the different subunits and their interconnections. Based on this information, the program calculates the temperature, flow rate, concentration, pressure, and vapor fraction at each state point in the system, and the heat duty at each unit, from which the coefficient of performance (COP) may be determined. This report describes the code and its operation, including improvements introduced into the present version. Simulation results are described for LiBr-H2O triple-effect cycles, LiCl-H2O solar-powered open absorption cycles, and NH3-H2O single-effect and generator-absorber heat exchange cycles. An appendix contains the user's manual.
TRACK--A new method for the evaluation of low-level extinction coefficient in optical films.
Vernhes, R; Martinu, L
2015-11-02
We develop a rigorous methodology named TRACK based on the collection of multi-angle spectrophotometric transmission and reflection data in order to assess the extinction coefficient of quasi-transparent optical films. The accuracy of extinction coefficient values obtained by this method is not affected by sample non-idealities (thickness non-uniformity, refractive index inhomogeneities, anisotropy, interfaces, etc.) and therefore a simple two-layer (substrate/film) optical model can be used. The method requires the acquisition of transmission and reflection data at two angles of incidence: 10° and 65° in p polarization. Data acquired at 10° provide information about the film thickness and the refractive index, while data collected at 65° are used for absorption evaluation and extinction coefficient computation. We test this method on three types of samples: (i) a CR-39 plastic substrate coated with a thick protective coating; (ii) the same substrate coated with a thin TiO(2) film; (iii) and a thick Si(3)N(4) film deposited on Gorilla glass that presents thickness non-uniformity and refractive index gradient non-idealities. We also compare absorption and extinction coefficient values obtained at 410 and 550 nm by both TRACK and Laser Induced Deflection techniques in the case of a 1 micron thick TiO(2) coating. Both methods display consistent extinction coefficient values in the 10(-4) and 10(-5) ranges at 410 and 550 nm, respectively, which proves the validity of the methodology and provides an estimate of its accuracy limit.
NASA Astrophysics Data System (ADS)
Barseghyan, M. G.
2016-10-01
The simultaneous influence of hydrostatic pressure and intense laser field on hydrogenic donor impurity states and intraband optical absorption has been investigated in GaAs/Ga_{1-tilde{x}}Al_{tilde{x}}As quantum ring. The one-electron energy spectrum and wave functions have been found using the effective mass approximation and exact diagonalization technique. The intraband absorption coefficient is calculated for different values of the hydrostatic pressure, intense laser field parameter and different locations of hydrogenic donor impurity. The simultaneous influence of hydrostatic pressure and intense laser field shows that while the increment of the first one leads only to the blueshift of the absorption spectrum, the augmentation of the second one makes the redshift. In addition, both blueshift and redshift of the spectrum have been obtained with the changes of impurity location. The obtained theoretical results indicate good controlling means of the optical spectrum of ring-like structures by the combined influence of the considered factors.
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.
De Nicola, S; Esposito, R; Lepore, M
2003-08-01
We develop a perturbation model to predict the effect of a spatially varying absorptive inhomogeneities in a diffusing slab. The model is based on a perturbation solution of diffusion equation derived for a refractive index mismatch between the scattering slab and the surrounding medium, through the use of the extrapolated boundary conditions. We show that the model allows to compute the time-dependent relative change in the transmitted signal resulting from the presence of the inclusion. We derive simplified expressions for the perturbed time-resolved transmittance that allows to implement an efficient fitting procedure for obtaining the optical properties of the absorptive inclusion. The accuracy of the predictions of the model was investigated through comparison with the results of the Finite Element Method to solve the time-dependent diffusion equation numerically. The procedure is used to obtain the absorption perturbation parameter of an absorptive inclusion characterized by spatially dependent Gaussian distribution of its absorption coefficient located at the midplane of a scattering slab.
NASA Astrophysics Data System (ADS)
Guttmann, Anthony J.
2016-10-01
Given the first 20-100 coefficients of a typical generating function of the type that arises in many problems of statistical mechanics or enumerative combinatorics, we show that the method of differential approximants performs surprisingly well in predicting (approximately) subsequent coefficients. These can then be used by the ratio method to obtain improved estimates of critical parameters. In favourable cases, given only the first 20 coefficients, the next 100 coefficients are predicted with useful accuracy. More surprisingly, this is also the case when the method of differential approximants does not do a useful job in estimating the critical parameters, such as those cases in which one has stretched exponential asymptotic behaviour. Nevertheless, the coefficients are predicted with surprising accuracy. As one consequence, significant computer time can be saved in enumeration problems where several runs would normally be made, modulo different primes, and the coefficients constructed from their values modulo different primes. Another is in the checking of newly calculated coefficients. We believe that this concept of approximate series extension opens up a whole new chapter in the method of series analysis.
Coefficient Alpha: A Reliability Coefficient for the 21st Century?
ERIC Educational Resources Information Center
Yang, Yanyun; Green, Samuel B.
2011-01-01
Coefficient alpha is almost universally applied to assess reliability of scales in psychology. We argue that researchers should consider alternatives to coefficient alpha. Our preference is for structural equation modeling (SEM) estimates of reliability because they are informative and allow for an empirical evaluation of the assumptions…
NASA Technical Reports Server (NTRS)
Roesler, Collin S.; Pery, Mary Jane
1995-01-01
An inverse model was developed to extract the absortion and scattering (elastic and inelastic) properties of oceanic constituents from surface spectral reflectance measurements. In particular, phytoplankton spectral absorption coefficients, solar-stimulated chlorophyll a fluorescence spectra, and particle backscattering spectra were modeled. The model was tested on 35 reflectance spectra obtained from irradiance measurements in optically diverse ocean waters (0.07 to 25.35 mg/cu m range in surface chlorophyll a concentrations). The universality of the model was demonstrated by the accurate estimation of the spectral phytoplankton absorption coefficents over a range of 3 orders of magnitude (rho = 0.94 at 500 nm). Under most oceanic conditions (chlorophyll a less than 3 mg/cu m) the percent difference between measured and modeled phytoplankton absorption coefficents was less than 35%. Spectral variations in measured phytoplankton absorption spectra were well predicted by the inverse model. Modeled volume fluorescence was weakly correlated with measured chl a; fluorescence quantum yield varied from 0.008 to 0.09 as a function of environment and incident irradiance. Modeled particle backscattering coefficients were linearly related to total particle cross section over a twentyfold range in backscattering coefficents (rho = 0.996, n = 12).
NASA Astrophysics Data System (ADS)
Zuleta, J. N.; Reyes-Gómez, E.
2016-05-01
The interband optical absorption spectra of a GaAs-Ga1-xAlxAs variably spaced semiconductor superlattice under crossed in-plane magnetic and growth-direction applied electric fields are theoretically investigated. The electronic structure, transition strengths and interband absorption coefficients are analyzed within the weak and strong magnetic-field regimes. A dramatic quenching of the absorption coefficient is observed, in the weak magnetic-field regime, as the applied electric field is increased, in good agreement with previous experimental measurements performed in a similar system under growth-direction applied electric fields. A decrease of the resonant tunneling in the superlattice is also theoretically obtained in the strong magnetic-field regime. Moreover, in this case, we found an interband absorption coefficient weakly dependent on the applied electric field. Present theoretical results suggest that an in-plane magnetic field may be used to tune the optical properties of variably spaced semiconductor superlattices, with possible future applications in solar cells and magneto-optical devices.
Extinction coefficients and purity of single-walled carbon nanotubes.
Zhao, B; Itkis, M E; Niyogi, S; Hu, H; Perea, D E; Haddon, R C
2004-11-01
Single-walled carbon nanotubes (SWNTs) hold great promise for advanced applications in aerospace, electronics and medicine, yet these industries require materials with rigorous quality control. There are currently no accepted standards for quality assurance or quality control among the commercial suppliers of SWNTs. We briefly discuss the applicability of various techniques to measure SWNT purity and review, in detail, the advantages of near infrared (NIR) spectroscopy for the quantitative assessment of the bulk carbonaceous purity of SWNTs. We review the use of solution phase NIR spectroscopy for the analysis and characterization of a variety of carbon materials, emphasizing SWNTs produced by the electric arc (EA), laser oven (LO) and HiPco (HC) methods. We consider the applicability of Beer's law to carbon materials dispersed in dimethylformamide (DMF) and the effective extinction coefficients that are obtained from such dispersions. Analysis of the areal absorptivities of the second interband transition of semiconducting EA-produced SWNTs for a number of samples of differing purities has lead to an absolute molar extinction coefficient for the carbonaceous impurities in EA-produced SWNT samples. We conclude that NIR spectroscopy is the clear method of choice for the assessment of the bulk carbonaceous purity of EA-produced SWNTs, and we suggest that an absolute determination of the purity of SWNTs is within reach. Continued work in this area is expected to lead to a universal method for the assessment of the absolute bulk purity of SWNTs from all sources--such a development will be of great importance for nanotube science and for future customers for this product.
Triple effect absorption chiller utilizing two refrigeration circuits
DeVault, Robert C.
1988-01-01
A triple effect absorption method and apparatus having a high coefficient of performance. Two single effect absorption circuits are combined with heat exchange occurring between a condenser and absorber of a high temperature circuit, and a generator of a low temperature circuit. The evaporators of both the high and low temperature circuits provide cooling to an external heat load.
Asymptotic Solutions for Optical Properties of Large Particles with Strong Absorption
NASA Technical Reports Server (NTRS)
Yang, Ping; Gao, Bo-Cai; Baum, Bryan A.; Hu, Yong X.; Wiscombe, Warren J.; Mishchenko, Michael I.; Winker, Dave M.; Nasiri, Shaima L.
2001-01-01
The transverse wave condition is not applicable to the refracted electromagnetic wave within the context of geometrical optics when absorption is involved. Either the transverse magnetic (TM) or the transverse electric (TE) wave condition can be assumed for the wave to locally satisfy the electromagnetic boundary condition in a ray-tracing calculation. The assumed wave mode affects both the reflection and the refraction coefficients. As a result, nonunique solutions for these coefficients are inevitable. In this study the appropriate solutions for the Fresnel reflection-refraction coefficients are identified in light-scattering calculations based on the ray-tracing technique. In particular, a 3x2 refraction or transmission matrix is derived to account for the inhomogeneity of the refracted wave in an absorbing medium. An asymptotic solution that completely includes the effect of medium absorption on Fresnel coefficients is obtained for the scattering properties of a general polyhedral particle. Numerical results are presented for hexagonal plates and columns with both preferred and random orientations.
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
NASA Astrophysics Data System (ADS)
Chen, Lingen; Zheng, Tong; Sun, Fengrui; Wu, Chih
2004-06-01
On the basis of a four-heat-reservoir endoreversible absorption refrigeration cycle model, another linear heat transfer law [i.e., the heat-flux] is adopted, the fundamental optimal relation between the coefficient of performance (COP) and the cooling load, as well as the maximum cooling load and the corresponding COP of the cycle coupled to constant-temperature heat reservoirs are derived by using finite-time thermodynamics or thermodynamic optimization. The optimal distribution of the heat-transfer surface areas is also obtained. Moreover, the effects of the cycle parameters on the COP and the cooling load of the cycle are studied by detailed numerical examples. The results obtained herein are of importance to the optimal design and performance improvement of an absorption refrigeration cycle.
Low-Absorption Liquid Crystals for Infrared Beam Steering
2014-10-17
goals are: ri~0.2 (at-tSilri),*? (at 1 kHz), and absorption coefficient B 5/cm. 15. SUBJECT TERMS Low absorption, MWIR, chlorinated liquid crystals...spectral region of interest by deuteration, fluorination and chlorination ; 2) Employing thin cell gap by choosing a high birefringence liquid crystal...mixture. First, we synthesized several chlorinated terphenyls and made a eutectic mixture showing a low absorption window in the region of 4-5|a.m
Obtaining and maintaining funding
Beverly Hartline
1996-04-01
Obtaining and maintaining funding is important for individuals, groups, institutions, and fields. This challenge is easier during times of abundant and growing resources than it is now, when funding is tight and shrinking. Thus, to obtain and maintain funding will require: maintaining healthy funding levels for all of science; maintaining healthy funding levels for the field(s) you work in; and competing successfully for the available funds. Everyone should pay attention to the overall prospects for science funding and dedicate some effort to working with others to grow the constituency for science. Public support is likely an important prerequisite for keeping future science budgets high. In this context, researchers should share with society at large the benefits of their research, so that taxpayers can see and appreciate some return from the federal investment in science. Assuming this effort is successful, and there continue to be government and private organizations with substantial resources to invest in research, what can the individual investigator do to improve her chances? She can be clear about her goal(s) and carefully plan her effort to make maximum progress for minimum resources, especially early in her career while she is establishing a solid professional reputation. Specific useful strategies include: brainstorm funding options and select the most promising one(s); be persistent but flexible, responsive to new information and changing circumstances; provide value and assistance to prospective funding sources both before and after receiving funding; know the funding agents and what their goals are, they are the customers; promise a lot and always deliver more; build partnerships and collaboration to leverage interest and resources; and develop capabilities and ideas with a promising, irresistible future. There is no guarantee of success. For the best chances, consistently contribute positively and productively in all your efforts, and continue to
Feasibility of Obtaining Hypervelocity Acceleration Using Propellant Lined Launch Tubes
1970-10-01
ft/sec or 36,000 in/sec can not be obtained with this concept. Friction Testing - Since the coefficient of friction and the friction characteristics of...of Movie Film of Ignition 56 the cost of the motor and structural capabilities of the plexiglass disc. Therefore, the coefficient of friction of...various propellants was measured up to a velocity of 250 feet per second. The static coefficient of friction was measured first for various propellant
Biases and Standard Errors of Standardized Regression Coefficients
ERIC Educational Resources Information Center
Yuan, Ke-Hai; Chan, Wai
2011-01-01
The paper obtains consistent standard errors (SE) and biases of order O(1/n) for the sample standardized regression coefficients with both random and given predictors. Analytical results indicate that the formulas for SEs given in popular text books are consistent only when the population value of the regression coefficient is zero. The sample…
NASA Astrophysics Data System (ADS)
Sun, Y. W.; Liu, C.; Chan, K. L.; Xie, P. H.; Liu, W. Q.; Zeng, Y.; Wang, S. M.; Huang, S. H.; Chen, J.; Wang, Y. P.; Si, F. Q.
2013-08-01
In this paper, we present an optimized analysis algorithm for non-dispersive infrared (NDIR) to in situ monitor stack emissions. The proposed algorithm simultaneously compensates for nonlinear absorption and cross interference among different gases. We present a mathematical derivation for the measurement error caused by variations in interference coefficients when nonlinear absorption occurs. The proposed algorithm is derived from a classical one and uses interference functions to quantify cross interference. The interference functions vary proportionally with the nonlinear absorption. Thus, interference coefficients among different gases can be modeled by the interference functions whether gases are characterized by linear or nonlinear absorption. In this study, the simultaneous analysis of two components (CO2 and CO) serves as an example for the validation of the proposed algorithm. The interference functions in this case can be obtained by least-squares fitting with third-order polynomials. Experiments show that the results of cross interference correction are improved significantly by utilizing the fitted interference functions when nonlinear absorptions occur. The dynamic measurement ranges of CO2 and CO are improved by about a factor of 1.8 and 3.5, respectively. A commercial analyzer with high accuracy was used to validate the CO and CO2 measurements derived from the NDIR analyzer prototype in which the new algorithm was embedded. The comparison of the two analyzers show that the prototype works well both within the linear and nonlinear ranges.
NASA Astrophysics Data System (ADS)
Sun, Y.-W.; Liu, C.; Chan, K.-L.; Xie, P.-H.; Liu, W.-Q.; Zeng, Y.; Wang, S.-M.; Huang, S.-H.; Chen, J.; Wang, Y.-P.; Si, F.-Q.
2013-02-01
In this paper, we present an optimized analysis algorithm for non-dispersive infrared (NDIR) to monitor stack emissions. The newly developed analysis algorithm simultaneously compensates for nonlinear absorption and cross-interference between different gases. We present a mathematical derivation for the measurement error caused by variations in interference coefficients when nonlinear absorption occurs. The optimized algorithm is derived from a classical one and uses interference functions to quantify cross-interference. The interference functions vary proportionally with the nonlinear absorption. Thus, interference coefficients among different gases can be modeled by the interference functions whether gases are characterized by linear or nonlinear absorption. In this study, the simultaneous analysis of two components (CO2 and CO) serves as an example for the validation of the optimized algorithm. The interference functions in this case can be obtained by least-squares fitting with three-order polynomials. Experiments show that the results of cross-interference correction are improved significantly by utilizing fitted interference functions when nonlinear absorptions occur. The dynamic measurement ranges of CO2 and CO are improved by about a factor of 1.8 and 3.5, respectively. A commercial NDIR multi-gas analyzer with high accuracy was used to validate the CO and CO2 measurements derived from the NDIR analyzer prototype in which the new cross-interference correction algorithm was embedded. Both measurements well agreed.
Field verification of the wind tunnel coefficients
NASA Technical Reports Server (NTRS)
Gawronski, W. K.; Mellstrom, J. A.
1994-01-01
Accurate information about wind action on antennas is required for reliable prediction of antenna pointing errors in windy weather and for the design of an antenna controller with wind disturbance rejection properties. The wind tunnel data obtained 3 years ago using a scaled antenna model serves as an antenna industry standard, frequently used for the first purpose. The accuracy of the wind tunnel data has often been challenged, since they have not yet been tested in a field environment (full-aized antenna, real wind, actual terrain, etc.). The purpose of this investigation was to obtain selected field measurements and compare them with the available wind tunnel data. For this purpose, wind steady-state torques of the DSS-13 antenna were measured, and dimensionless wind torque coefficients were obtained for a variety of yaw and elevation angles. The results showed that the differences between the wind tunnel torque coefficients and the field torque coefficients were less than 10 percent of their values. The wind-gusting action on the antenna was characterized by the power spectra of the antenna encoder and the antenna torques. The spectra showed that wind gusting primarily affects the antenna principal modes.
NASA Astrophysics Data System (ADS)
Yao, Cheng-Bao; Wen, Xin; Li, Qiang-Hua; Yan, Xiao-Yan; Li, Jin; Zhang, Ke-Xin; Sun, Wen-Jun; Bai, Li-Na; Yang, Shou-Bin
2017-03-01
We present the structure and nonlinear absorption (NLA) properties of Cu-doped ZnO (CZO) films prepared by magnetron sputtering. The films were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that the CZO films can maintain a wurtzite structure. Furthermore, the open-aperture (OA) Z-scan measurements of the film were carried out by nanosecond laser pulse. A transition from saturable absorption (SA) to reverse saturable absorption (RSA) was observed as the excitation intensity increasing. With good excellent nonlinear optical coefficient, the samples were expected to be the potential applications in optical devices.
NASA Astrophysics Data System (ADS)
Han, Dong; Chen, Liangfu; Tao, Jinhua; Su, Lin; Li, Shenshen; Yu, Chao; Yan, Huanhuan
Inelastic Vibrational Raman Scattering (VRS) by liquid water is one significant limitation to the accuracy of the retrieval of trace gas constituents in atmosphere over waters, particularly over clear ocean waters, while using satellite data with Differential Optical Absorption Spec-troscopy technique (DOAS).The effect which is similar to the Ring effect in atmosphere results in the filling in of Fraunhofer lines, which is known as solar absorption lines. The inelastic component of the liquid water scattering causes a net increase of radiance in the line because more radiation is shifted to the wavelength of an absorption line than shifted from this wave-length to other wavelengths. The spectrum at the top of the atmosphere over land measured by OMI (Ozone Monitoring Instrument)/AURA is convolved with Vibrational Raman Scat-tering coefficients of liquid water, divided by the original measured spectrum, with a cubic polynomial subtracted off, to create differential water Ring spectrum. The OMI spectrum over land is chosen to avoid the effect of VRS by liquid water. This method has been suggested in order to obtain an effective differential water Ring coeffients for the DOAS fitting process.The differential water Ring spectrum could be used to improve the accuracy of the retrieval of the trace gases concentration. The method is not relying on RTM, which would be time-consuming and depending on lot of parameters. Therefore, it is very fast and convenient.
NASA Technical Reports Server (NTRS)
Butler, Thomas G.
1990-01-01
In modeling a complex structure the researcher was faced with a component that would have logical appeal if it were modeled as a beam. The structure was a mast of a robot controlled gantry crane. The structure up to this point already had a large number of degrees of freedom, so the idea of conserving grid points by modeling the mast as a beam was attractive. The researcher decided to make a separate problem of of the mast and model it in three dimensions with plates, then extract the equivalent beam properties by setting up the loading to simulate beam-like deformation and constraints. The results could then be used to represent the mast as a beam in the full model. A comparison was made of properties derived from models of different constraints versus manual calculations. The researcher shows that the three-dimensional model is ineffective in trying to conform to the requirements of an equivalent beam representation. If a full 3-D plate model were used in the complete representation of the crane structure, good results would be obtained. Since the attempt is to economize on the size of the model, a better way to achieve the same results is to use substructuring and condense the mast to equivalent end boundary and intermediate mass points.
Cytoplasmic hydrogen ion diffusion coefficient.
al-Baldawi, N F; Abercrombie, R F
1992-01-01
The apparent cytoplasmic proton diffusion coefficient was measured using pH electrodes and samples of cytoplasm extracted from the giant neuron of a marine invertebrate. By suddenly changing the pH at one surface of the sample and recording the relaxation of pH within the sample, an apparent diffusion coefficient of 1.4 +/- 0.5 x 10(-6) cm2/s (N = 7) was measured in the acidic or neutral range of pH (6.0-7.2). This value is approximately 5x lower than the diffusion coefficient of the mobile pH buffers (approximately 8 x 10(-6) cm2/s) and approximately 68x lower than the diffusion coefficient of the hydronium ion (93 x 10(-6) cm2/s). A mobile pH buffer (approximately 15% of the buffering power) and an immobile buffer (approximately 85% of the buffering power) could quantitatively account for the results at acidic or neutral pH. At alkaline pH (8.2-8.6), the apparent proton diffusion coefficient increased to 4.1 +/- 0.8 x 10(-6) cm2/s (N = 7). This larger diffusion coefficient at alkaline pH could be explained quantitatively by the enhanced buffering power of the mobile amino acids. Under the conditions of these experiments, it is unlikely that hydroxide movement influences the apparent hydrogen ion diffusion coefficient. PMID:1617134
Millimeter and submillimeter wave absorption by atmospheric pollutants and constituents
NASA Astrophysics Data System (ADS)
Kolbe, W. F.; Leskovar, B.
1981-10-01
Calculated absorption coefficients and rotational transition frequencies are given for a number of polar molecules of interest to pollution and energy research. The results, which are presented in graphical form for microwave frequencies up to 1400 GHz, illustrate the increased absorption line intensities occurring in the submillimeter region. For most species these absorption coefficients attain their maximum values in this region. Included in the calculations are the gases SO2, H2CO, O3, H2O, H2S, OCS, CO, NO, OH, SO, NH3, and CS. A discussion of the techniques currently available for the detection in the submillimeter region of these species is also given.
Phononic glass: a robust acoustic-absorption material.
Jiang, Heng; Wang, Yuren
2012-08-01
In order to achieve strong wide band acoustic absorption under high hydrostatic pressure, an interpenetrating network structure is introduced into the locally resonant phononic crystal to fabricate a type of phononic composite material called "phononic glass." Underwater acoustic absorption coefficient measurements show that the material owns high underwater sound absorption coefficients over 0.9 in 12-30 kHz. Moreover, the quasi-static compressive behavior shows that the phononic glass has a compressive strength over 5 MPa which is crucial for underwater applications.
Linear attenuation coefficients of tissues from 1 keV to 150 keV
NASA Astrophysics Data System (ADS)
Böke, Aysun
2014-09-01
The linear attenuation coefficients and three interaction processes have been computed for liver, kidney, muscle, fat and for a range of x-ray energies from 1 keV to 150 keV. Molecular photoelectric absorption cross sections were calculated from atomic cross section data. Total coherent (Rayleigh) and incoherent (Compton) scattering cross sections were obtained by numerical integration over combinations of F2m(x) with the Thomson formula and Sm(x) with the Klein-Nishina formula, respectively. For the coherent (Rayleigh) scattering cross section calculations, molecular form factors were obtained from recent experimental data in the literature for values of x<1 Å-1 and from the relativistic modified atomic form factors for values of x≥1 Å-1. With the inclusion of molecular interference effects in the coherent (Rayleigh) scattering, more accurate knowledge of the scatter from these tissues will be provided. The number of elements involved in tissue composition is 5 for liver, 47 for kidney, 44 for muscle and 3 for fat. The results are compared with previously published experimental and theoretical linear attenuation coefficients. In general, good agreement is obtained. The molecular form factors and scattering functions and cross sections are incorporated into a Monte Carlo program. The energy distributions of x-ray photons scattered from tissues have been simulated and the results are presented.
NASA Astrophysics Data System (ADS)
Plašil, Radek; Dohnal, Petr; Kálosi, Ábel; Roučka, Štěpán; Johnsen, Rainer; Glosík, Juraj
2017-03-01
We report measurements of the binary and ternary recombination rate coefficients of deuterated isotopologues of {{{H}}}3+. A cavity ring-down absorption spectrometer was used to monitor the fractional abundances of {{{H}}}3+, {{{H}}}2{{{D}}}+, {{HD}}2+ and {{{D}}}3+ during the decay of a plasma in He/Ar/{{{H}}}2/{{{D}}}2 mixtures. A dependence of the measured effective recombination rate coefficients on the helium buffer gas density was observed and hence both the binary and the ternary recombination rate coefficients for {{{H}}}2{{{D}}}+ and {{HD}}2+ were obtained in the temperature range 80–145 K.
Onsager coefficients for systems with periodic potentials
NASA Astrophysics Data System (ADS)
Rosas, Alexandre; Van den Broeck, Christian; Lindenberg, Katja
2016-11-01
We carry out the thermodynamic analysis of a Markovian stochastic engine, driven by a spatially and temporally periodic modulation in a d -dimensional space. We derive the analytic expressions for the Onsager coefficients characterizing the linear response regime for the isothermal transfer of one type of work (a driver) to another (a load), mediated by a stochastic time-periodic machine. As an illustration, we obtain the explicit results for a Markovian kangaroo process coupling two orthogonal directions and find extremely good agreement with numerical simulations. In addition, we obtain and discuss expressions for the entropy production, power, and efficiency for the kangaroo process.
Sedimentation of multicomponent viruses: evaluation of sedimentation coefficient ratios.
Larcom, L L; Barnett, O W
1978-01-01
Ratios of the sedimentation coefficients for alfalfa mosaic virus components are shown to be independent of the virus concentration and the density of the solvent. Different numbers of components are observed in solvents of different density. This implies that in sedimentation velocity experiments an estimate of the number of components of a multicomponent virus should involve centrifugation in solvents of different density. For some viruses, estimates of the sedimentation coefficients of individual components can be obtained from the coefficient ratios observed in unfractionated solutions and the sedimentation coefficient of the most easily purified component.
NASA Astrophysics Data System (ADS)
Eddowes, M. H.; Mills, T. N.; Delpy, D. T.
1995-05-01
A Monte Carlo model of light backscattered from turbid media has been used to simulate the effects of weak localization in biological tissues. A validation technique is used that implies that for the scattering and absorption coefficients and for refractive index mismatches found in tissues, the Monte Carlo method is likely to provide more accurate results than the methods previously used. The model also has the ability to simulate the effects of various illumination profiles and other laboratory-imposed conditions. A curve-fitting routine has been developed that might be used to extract the optical coefficients from the angular intensity profiles seen in experiments on turbid biological tissues, data that could be obtained in vivo.
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.
Chantler, C.T.; Islam, M.T.; Rae, N.A.; Tran, C.Q.; Glover, J.L.; Barnea, Z.
2012-09-25
An extension of the X-ray extended-range technique is described for measuring X-ray mass attenuation coefficients by introducing absolute measurement of a number of foils - the multiple independent foil technique. Illustrating the technique with the results of measurements for gold in the 38-50 keV energy range, it is shown that its use enables selection of the most uniform and well defined of available foils, leading to more accurate measurements; it allows one to test the consistency of independently measured absolute values of the mass attenuation coefficient with those obtained by the thickness transfer method; and it tests the linearity of the response of the counter and counting chain throughout the range of X-ray intensities encountered in a given experiment. In light of the results for gold, the strategy to be ideally employed in measuring absolute X-ray mass attenuation coefficients, X-ray absorption fine structure and related quantities is discussed.
Sound absorption by clamped poroelastic plates.
Aygun, H; Attenborough, K
2008-09-01
Measurements and predictions have been made of the absorption coefficient and the surface acoustic impedance of poroelastic plates clamped in a large impedance tube and separated from the rigid termination by an air gap. The measured and predicted absorption coefficient and surface impedance spectra exhibit low frequency peaks. The peak frequencies observed in the absorption coefficient are close to those predicted and measured in the deflection spectra of the clamped poroelastic plates. The influences of the rigidity of the clamping conditions and the width of the air gap have been investigated. Both influences are found to be important. Increasing the rigidity of clamping reduces the low frequency absorption peaks compared with those measured for simply supported plates or plates in an intermediate clamping condition. Results for a closed cell foam plate and for two open cell foam plates made from recycled materials are presented. For identical clamping conditions and width of air gap, the results for the different materials differ as a consequence mainly of their different elasticity, thickness, and cell structure.
Magnetic-doped alloys with very large Seebeck coefficients
NASA Technical Reports Server (NTRS)
Sellmeyer, D. J.; Zagarins, J.
1972-01-01
Preliminary results of this study show that, based on selection of magnetic solute and nonmagnetic solvent from periodic table, alloys having Seebeck coefficients approaching 100 micron V/K can be obtained.
Lazebnik, Mariya; Zhu, Changfang; Palmer, Gregory M.; Harter, Josephine; Sewall, Sarah; Ramanujam, Nirmala; Hagness, Susan C.
2009-01-01
Techniques utilizing electromagnetic energy at microwave and optical frequencies have been shown to be promising for breast cancer detection and diagnosis. Since different biophysical mechanisms are exploited at these frequencies to discriminate between healthy and diseased tissue, combining these two modalities may result in a more powerful approach for breast cancer detection and diagnosis. Toward this end, we performed microwave dielectric spectroscopy and optical diffuse reflectance spectroscopy measurements at the same sites on freshly-excised normal breast tissues obtained from reduction surgeries at the University of Wisconsin Hospital, using microwave and optical probes with very similar sensing volumes. We found that the microwave dielectric constant and effective conductivity are correlated with tissue composition across the entire measurement frequency range (|r|~0.5–0.6, p<0.01), and that the optical absorption coefficient at 460 nm and optical scattering coefficient are correlated with tissue composition (|r|~ 0.4–0.6, p<0.02). Finally, we found that the optical absorption coefficient at 460 nm is correlated with the microwave dielectric constant and effective conductivity (r=−0.55, p<0.01). Our results suggest that combining optical and microwave modalities for analyzing breast tissue samples may serve as a crosscheck and provide complementary information about tissue composition. PMID:18838370
Method for Calculating the Optical Diffuse Reflection Coefficient for the Ocular Fundus
NASA Astrophysics Data System (ADS)
Lisenko, S. A.; Kugeiko, M. M.
2016-07-01
We have developed a method for calculating the optical diffuse reflection coefficient for the ocular fundus, taking into account multiple scattering of light in its layers (retina, epithelium, choroid) and multiple refl ection of light between layers. The method is based on the formulas for optical "combination" of the layers of the medium, in which the optical parameters of the layers (absorption and scattering coefficients) are replaced by some effective values, different for cases of directional and diffuse illumination of the layer. Coefficients relating the effective optical parameters of the layers and the actual values were established based on the results of a Monte Carlo numerical simulation of radiation transport in the medium. We estimate the uncertainties in retrieval of the structural and morphological parameters for the fundus from its diffuse reflectance spectrum using our method. We show that the simulated spectra correspond to the experimental data and that the estimates of the fundus parameters obtained as a result of solving the inverse problem are reasonable.
Temperature-Dependent Rate Coefficients for the Reaction of CH2OO with Hydrogen Sulfide.
Smith, Mica C; Chao, Wen; Kumar, Manoj; Francisco, Joseph S; Takahashi, Kaito; Lin, Jim Jr-Min
2017-02-09
The reaction of the simplest Criegee intermediate CH2OO with hydrogen sulfide was measured with transient UV absorption spectroscopy in a temperature-controlled flow reactor, and bimolecular rate coefficients were obtained from 278 to 318 K and from 100 to 500 Torr. The average rate coefficient at 298 K and 100 Torr was (1.7 ± 0.2) × 10(-13) cm(3) s(-1). The reaction was found to be independent of pressure and exhibited a weak negative temperature dependence. Ab initio quantum chemistry calculations of the temperature-dependent reaction rate coefficient at the QCISD(T)/CBS level are in reasonable agreement with the experiment. The reaction of CH2OO with H2S is 2-3 orders of magnitude faster than the reaction with H2O monomer. Though rates of CH2OO scavenging by water vapor under atmospheric conditions are primarily controlled by the reaction with water dimer, the H2S loss pathway will be dominated by the reaction with monomer. The agreement between experiment and theory for the CH2OO + H2S reaction lends credence to theoretical descriptions of other Criegee intermediate reactions that cannot easily be probed experimentally.
Results obtained with the Tropospheric Ozone DIAL System Using a YAG Laser and Raman Cells
NASA Astrophysics Data System (ADS)
Sullivan, J. T.; McGee, T. J.; Sumnicht, G. K.
2012-12-01
This poster will detail the findings of the ground based Differential Absorption Lidar (DIAL) system built and operated at the NASA Goddard Space Flight Center (Beltsville, MD 38.99° N, 76.84° W) in 2012. Current atmospheric satellites cannot peer through the optically thick stratospheric ozone layer to remotely sense boundary layer tropospheric ozone. In order to monitor this lower ozone more effectively, NASA has funded the ground based Tropospheric Ozone Lidar Network (TOLNET) which currently consists of five stations across the US. The Goddard instrument is based on the Differential Absorption Lidar (DIAL) technique, and has initially transmitted two wavelengths, 289 and 299 nm. Ozone is absorbed more strongly at 289 nm than at 299 nm, and the DIAL technique exploits this difference between the two returned signals to obtain the ozone number density as a function of altitude. The transmitted wavelengths are generated by focusing the output of a quadrupled Nd:YAG laser beam (266 nm) into a pair of Raman Cells, filled with high pressure Hydrogen and Deuterium. Stimulated Raman Scattering within the focus shifts the pump wavelength, and the first Stokes shift in each cell produces the required wavelengths. With the knowledge of the ozone absorption coefficient at these two wavelengths, the vertical number density can then be derived. There are currently surface ozone measurements hourly and ozonesonde launches occasionally, but this system will be the first to make long term ozone profile measurements in the Washington, DC - Baltimore area.
A new method for calculating loss coefficients
Chang, Y.C.; Yang, W.T.; Liu, C.C. . Dept. of Electrical Engineering)
1994-08-01
A method is proposed which avoids many limitations associated with traditional B-coefficient loss coefficient calculation. The proposed method, unlike the traditional B-coefficient method, is very fast and can handle line outages. The method utilizes network sensitivity factors which are established from DC load flow solutions. Line outage distribution factors (ODF's) are formulated using changes in network power generations to simulate the outaged line from the network. The method avoids the use of complicated reference frame transformations based upon Kron's tensor analysis. The necessity of data normalization used in least squares and the evaluation of the slope of [theta][sub j] versus PG[sub n] is not necessary with the proposed method. Using IEEE standard 14-bus and 30-bus systems, the method's results are compared against results obtained from an AC load flow program (LFED). The method's solution speed is compared to that of the LFED method, the base case database method and the conventional B-coefficient method based on A[sub jn]-factor. The proposed method is easy to implement and, when compared to other methods, has exhibited good accuracy and rapid execution times. The method is well suited to on-line dispatch applications.
Functional constraints on phenomenological coefficients
NASA Astrophysics Data System (ADS)
Klika, Václav; Pavelka, Michal; Benziger, Jay B.
2017-02-01
Thermodynamic fluxes (diffusion fluxes, heat flux, etc.) are often proportional to thermodynamic forces (gradients of chemical potentials, temperature, etc.) via the matrix of phenomenological coefficients. Onsager's relations imply that the matrix is symmetric, which reduces the number of unknown coefficients is reduced. In this article we demonstrate that for a class of nonequilibrium thermodynamic models in addition to Onsager's relations the phenomenological coefficients must share the same functional dependence on the local thermodynamic state variables. Thermodynamic models and experimental data should be validated through consistency with the functional constraint. We present examples of coupled heat and mass transport (thermodiffusion) and coupled charge and mass transport (electro-osmotic drag). Additionally, these newly identified constraints further reduce the number of experiments needed to describe the phenomenological coefficient.
ANALYTIC FORMS OF THE PERPENDICULAR DIFFUSION COEFFICIENT IN NRMHD TURBULENCE
Shalchi, A.
2015-02-01
In the past different analytic limits for the perpendicular diffusion coefficient of energetic particles interacting with magnetic turbulence were discussed. These different limits or cases correspond to different transport modes describing how the particles are diffusing across the large-scale magnetic field. In the current paper we describe a new transport regime by considering the model of noisy reduced magnetohydrodynamic turbulence. We derive different analytic forms of the perpendicular diffusion coefficient, and while we do this, we focus on the aforementioned new transport mode. We show that for this turbulence model a small perpendicular diffusion coefficient can be obtained so that the latter diffusion coefficient is more than hundred times smaller than the parallel diffusion coefficient. This result is relevant to explain observations in the solar system where such small perpendicular diffusion coefficients have been reported.
Wang, X.; Heald, C. L.; Sedlacek, A.; de Sa, S. S.; Martin, S. T.; Alexander, M. L.; Watson, T. B.; Aiken, A. C.; Springston, S. R.; Artaxo, P.
2016-10-13
The radiative impact of organic aerosols (OA) is a large source of uncertainty in estimating the global direct radiative effect (DRE) of aerosols. This radiative impact includes not only light scattering but also light absorption from a subclass of OA referred to as brown carbon (BrC). However the absorption properties of BrC are poorly understood leading to large uncertainties in modelling studies. To obtain observational constraints from measurements, a simple Absorption Ångström Exponent (AAE) method is often used to separate the contribution of BrC absorption from that of black carbon (BC). However, this attribution method is based on assumptions regarding the spectral dependence of BC that are often violated in the ambient atmosphere. Here we develop a new method that decreases the uncertainties associated with estimating BrC absorption. By applying this method to multi-wavelength absorption aerosol optical depth (AAOD) measurements at AERONET sites worldwide and surface aerosol absorption measurements at multiple ambient sites, we estimate that BrC globally contributes 6-40% of the absorption at 440nm. We find that the mass absorption coefficient of OA (OA-MAC) is positively correlated with BC/OA mass ratio. Based on the variability of BC properties and BC/OA emission ratio, we estimate a range of 0.05-1.2 m^{2}/g for OA-MAC at 440nm. Using the combination of AERONET and OMI UV absorption observations we estimate that the AAE_{388/440nm} for BrC is generally ~4 world-wide, with a smaller value in Europe (< 2). Our analyses of two surface sites (Cape Cod, to the southeast of Boston, and the GoAmazon2014/5 T3 site, to the west of Manaus, Brazil) reveal no significant relationship between BrC absorptivity and photochemical aging in typical urban influenced conditions. However, the absorption of BrC measured during the biomass burning season near Manaus is found to decrease with photochemical aging with a lifetime of ~1 day. This lifetime is
Wang, X.; Heald, C. L.; Sedlacek, A.; ...
2016-10-13
The radiative impact of organic aerosols (OA) is a large source of uncertainty in estimating the global direct radiative effect (DRE) of aerosols. This radiative impact includes not only light scattering but also light absorption from a subclass of OA referred to as brown carbon (BrC). However the absorption properties of BrC are poorly understood leading to large uncertainties in modelling studies. To obtain observational constraints from measurements, a simple Absorption Ångström Exponent (AAE) method is often used to separate the contribution of BrC absorption from that of black carbon (BC). However, this attribution method is based on assumptions regardingmore » the spectral dependence of BC that are often violated in the ambient atmosphere. Here we develop a new method that decreases the uncertainties associated with estimating BrC absorption. By applying this method to multi-wavelength absorption aerosol optical depth (AAOD) measurements at AERONET sites worldwide and surface aerosol absorption measurements at multiple ambient sites, we estimate that BrC globally contributes 6-40% of the absorption at 440nm. We find that the mass absorption coefficient of OA (OA-MAC) is positively correlated with BC/OA mass ratio. Based on the variability of BC properties and BC/OA emission ratio, we estimate a range of 0.05-1.2 m2/g for OA-MAC at 440nm. Using the combination of AERONET and OMI UV absorption observations we estimate that the AAE388/440nm for BrC is generally ~4 world-wide, with a smaller value in Europe (< 2). Our analyses of two surface sites (Cape Cod, to the southeast of Boston, and the GoAmazon2014/5 T3 site, to the west of Manaus, Brazil) reveal no significant relationship between BrC absorptivity and photochemical aging in typical urban influenced conditions. However, the absorption of BrC measured during the biomass burning season near Manaus is found to decrease with photochemical aging with a lifetime of ~1 day. This lifetime is comparable to
A note on Hansen's coefficients in satellite theory
NASA Technical Reports Server (NTRS)
Giacaglia, G. E. O.
1976-01-01
General formulas for Hansen's coefficients in satellite theory are derived along with expressions for the eccentricity functions G and H. Recurrence relations for the eccentricity functions and their derivatives are obtained which are valid for all values of the parameter p. It is noted that the recurrence relations obtained by Challe and Laclaverie (1969) as well as by Balmino (1973) do not satisfy certain parity conditions and therefore involve coefficients outside the range of usage.
The temperature variation of hydrogen diffusion coefficients in metal alloys
NASA Technical Reports Server (NTRS)
Danford, M. D.
1990-01-01
Hydrogen diffusion coefficients were measured as a function of temperature for a few metal alloys using an electrochemical evolution technique. Results from these measurements are compared to those obtained by the time-lag method. In all cases, diffusion coefficients obtained by the electrochemical method are larger than those by the time-lag method by an order of magnitude or more. These differences are attributed mainly to hydrogen trapping.
Wrong Signs in Regression Coefficients
NASA Technical Reports Server (NTRS)
McGee, Holly
1999-01-01
When using parametric cost estimation, it is important to note the possibility of the regression coefficients having the wrong sign. A wrong sign is defined as a sign on the regression coefficient opposite to the researcher's intuition and experience. Some possible causes for the wrong sign discussed in this paper are a small range of x's, leverage points, missing variables, multicollinearity, and computational error. Additionally, techniques for determining the cause of the wrong sign are given.
Biologically-based modeling insights in inhaled vapor absorption and dosimetry.
Morris, John B
2012-12-01
The lung is a route of entry and also a target site for inhaled vapors, therefore, knowledge of the total absorbed dose and/or the dose absorbed in each airway during inhalation exposure is essential. Vapor absorption characteristics result primarily from the fact that vapors demonstrate equilibrium/saturation behavior in fluids. Thus, during inhalation exposures blood and airway tissue vapor concentrations increase to a steady state value and increase no further no matter how long the exposure. High tissue concentrations can be obtained with highly soluble vapors, thus solubility, as measured by blood:air partition coefficient, is a fundamentally important physical/chemical characteristic of vapors. While it is classically thought that vapor absorption occurs only in the alveoli it is now understood that this is not the case. Soluble vapors can be efficiently absorbed in the airways themselves and do not necessarily penetrate to the alveolar level. Such vapors are more likely to injure the proximal than distal airways because that is the site of the greatest delivered dose. There are substantial species differences in airway vapor absorption between laboratory animals and humans making interpretation of laboratory animal inhalation toxicity data difficult. Airway absorption is dependent on vapor solubility and is enhanced by local metabolism and/or direct reaction within airway tissues. Modern simulation models that incorporate terms for solubility, metabolism, and reaction rate accurately predict vapor absorption patterns in both animals and humans and have become essential tools for understanding the pharmacology and toxicology of airborne vapors.
Comprehensive analysis of the optical Kerr coefficient of graphene
Soh, Daniel B. S.; Hamerly, Ryan; Mabuchi, Hideo
2016-08-25
We present a comprehensive analysis of the nonlinear optical Kerr effect in graphene. We directly solve the S-matrix element to calculate the absorption rate, utilizing the Volkov-Keldysh-type crystal wave functions. We then convert to the nonlinear refractive index coefficients through the Kramers-Kronig relation. In this formalism, the source of Kerr nonlinearity is the interplay of optical fields that cooperatively drive the transition from valence to conduction band. This formalism makes it possible to identify and compute the rates of distinct nonlinear processes that contribute to the Kerr nonlinear refractive index coefficient. The four identified mechanisms are two-photon absorption, Raman transition, self-coupling, and quadratic ac Stark effect. As a result, we present a comparison of our theory with recent experimental and theoretical results.
Comprehensive analysis of the optical Kerr coefficient of graphene
Soh, Daniel B. S.; Hamerly, Ryan; Mabuchi, Hideo
2016-08-25
We present a comprehensive analysis of the nonlinear optical Kerr effect in graphene. We directly solve the S-matrix element to calculate the absorption rate, utilizing the Volkov-Keldysh-type crystal wave functions. We then convert to the nonlinear refractive index coefficients through the Kramers-Kronig relation. In this formalism, the source of Kerr nonlinearity is the interplay of optical fields that cooperatively drive the transition from valence to conduction band. This formalism makes it possible to identify and compute the rates of distinct nonlinear processes that contribute to the Kerr nonlinear refractive index coefficient. The four identified mechanisms are two-photon absorption, Raman transition,more » self-coupling, and quadratic ac Stark effect. As a result, we present a comparison of our theory with recent experimental and theoretical results.« less
Comprehensive analysis of the optical Kerr coefficient of graphene
NASA Astrophysics Data System (ADS)
Soh, Daniel B. S.; Hamerly, Ryan; Mabuchi, Hideo
2016-08-01
We present a comprehensive analysis of the nonlinear optical Kerr effect in graphene. We directly solve the S -matrix element to calculate the absorption rate, utilizing the Volkov-Keldysh-type crystal wave functions. We then convert to the nonlinear refractive index coefficients through the Kramers-Kronig relation. In this formalism, the source of Kerr nonlinearity is the interplay of optical fields that cooperatively drive the transition from valence to conduction band. This formalism makes it possible to identify and compute the rates of distinct nonlinear processes that contribute to the Kerr nonlinear refractive index coefficient. The four identified mechanisms are two-photon absorption, Raman transition, self-coupling, and quadratic ac Stark effect. We also present a comparison of our theory with recent experimental and theoretical results.
Water vapor-nitrogen absorption at CO2 laser frequencies
NASA Technical Reports Server (NTRS)
Peterson, J. C.; Thomas, M. E.; Nordstrom, R. J.; Damon, E. K.; Long, R. K.
1979-01-01
The paper reports the results of a series of pressure-broadened water vapor absorption measurements at 27 CO2 laser frequencies between 935 and 1082 kaysers. Both multiple traversal cell and optoacoustic (spectrophone) techniques were utilized together with an electronically stabilized CW CO2 laser. Comparison of the results obtained by these two methods shows remarkable agreement, indicating a precision which has not been previously achieved in pressure-broadened studies of water vapor. The data of 10.59 microns substantiate the existence of the large (greater than 200) self-broadening coefficients determined in an earlier study by McCoy. In this work, the case of water vapor in N2 at a total pressure of 1 atm has been treated.
The resistance coefficient of commercial round wire grids
NASA Technical Reports Server (NTRS)
Eckert, B; Pfluger, F
1942-01-01
The resistance coefficients of commercial types of round wire grids were examined for the purpose of obtaining the necessary data on supercharger test stands for throttling the inducted air to a pressure corresponding to a desired air density. The measurements of the coefficients ranged up to Reynolds numbers of 1000. In the arrangement of two grids in tandem, which was necessary in order to obtain high resistance coefficients with the solidity, that is, mesh density of grid, was found to be accompanied by a further relationship with the mutual spacing of the individual grids.
Anomalous absorption of laser light on ion acoustic fluctuations
NASA Astrophysics Data System (ADS)
Rozmus, Wojciech; Bychenkov, Valery Yu.
2016-10-01
Theory of laser light absorption due to ion acoustic turbulence (IAT) is discussed in high Z plasmas where ion acoustic waves are weakly damped. Our theory applies to the whole density range from underdense to critical density plasmas. It includes an absorption rate for the resonance anomalous absorption due to linear conversion of electromagnetic waves into electron plasma oscillations by the IAT near the critical density in addition to the absorption coefficient due to enhanced effective electron collisionality. IAT is driven by large electron heat flux through the return current instability. Stationary spectra of IAT are given by weak plasma turbulence theory and applied in description of the anomalous absorption in the inertial confinement fusion plasmas at the gold walls of a hohlraum. This absorption is anisotropic in nature due to IAT angular anisotropy and differs for p- and s-polarization of the laser radiation. Possible experiments which could identify the resonance anomalous absorption in a laser heated plasma are discussed.
Peltier Coefficient and Photon-Assisted Tunnelling in Quantum Point Contact
NASA Astrophysics Data System (ADS)
H. Aly, Arafa
2008-12-01
We present the Peltier coefficient and thermal transport in quantum point contact (QPC), under the influence of external fields and different temperatures. Also we obtain the oscillations of the Peltier coefficient in external fields. Numerical calculations of the Peltier coefficient are performed at different applied voltages, amplitudes and temperatures. The obtained results are consistent with the experimental data in the literature.
NASA Astrophysics Data System (ADS)
Kasapoglu, E.; Sakiroglu, S.; Sökmen, I.; Restrepo, R. L.; Mora-Ramos, M. E.; Duque, C. A.
2016-10-01
We have calculated the effects of electric and intense laser fields on the binding energies of the ground and some excited states of conduction electrons coupled to shallow donor impurities as well as the total optical absorption coefficient for transitions between 1s and 2p± electron-impurity states in a asymmetric parabolic GaAs/Ga1-x AlxAs quantum well. The binding energies were obtained using the effective-mass approximation within a variational scheme. Total absorption coefficient (linear and nonlinear absorption coefficient) for the transitions between any two impurity states were calculated from first- and third-order dielectric susceptibilities derived within a perturbation expansion for the density matrix formalism. Our results show that the effects of the electric field, intense laser field, and the impurity location on the binding energy of 1s-impurity state are more pronounced compared with other impurity states. If the well center is changed to be Lc<0 (Lc>0), the effective well width decreases (increases), and thus we can obtain the red or blue shift in the resonant peak position of the absorption coefficient by changing the intensities of the electric and non-resonant intense laser field as well as dimensions of the well and impurity positions.
Subbarrier absorption in a stationary superlattice
NASA Technical Reports Server (NTRS)
Arutyunyan, G. M.; Nerkararyan, K. V.
1984-01-01
The calculation of the interband absorption coefficient was carried out in the classical case, when the frequency of light was assumed to bind two miniband subbarrier states of different bands. The influence of two dimensional Mott excitons on this absorption was studied and a comparison was made with the experiment. All of these considerations were done taking into account the photon wave vector (the phase spatial heterogeneity). The basic traits of the energy spectra of superlattice semiconductors, their kinetic and optical properties, and possible means of electromagnetic wave intensification were examined. By the density matrix method, a theory of electrical and electromagnetic properties of superlattices was suggested.
Monitoring of MOCVD reactants by UV absorption
Baucom, K.C.; Killeen, K.P.; Moffat, H.K.
1995-07-01
In this paper, we describe how UV absorption measurements can be used to measure the flow rates of metal organic chemical vapor deposition (MOCVD) reactants. This method utilizes the calculation of UV extinction coefficients by measuring the total pressure and absorbance in the neat reactant system. The development of this quantitative reactant flow rate monitor allows for the direct measurement of the efficiency of a reactant bubbler. We demonstrate bubbler efficiency results for TMGa, and then explain some discrepancies found in the TMAl system due to the monomer to dimer equilibrium. Also, the UV absorption spectra of metal organic and hydride MOCVD reactants over the wavelength range 185 to 400 nm are reported.
Atmospheric absorption cell characterization
NASA Astrophysics Data System (ADS)
1982-06-01
The measurement capability of the Avionics Laboratory IR Facility was used to evaluate an absorption cell that will be used to simulate atmospheric absorption over horizontal paths of 1 - 10 km in length. Band models were used to characterize the transmittance of carbon dioxide (CO2), nitrogen (N2), and nitrous oxide (N2O) in the cell. The measured transmittance was compared to the calculated values. Nitrous oxide is important in the 4 - 4.5 micron range in shaping the weak line absorption of carbon dioxide. The absorption cell is adequate for simulating atmospheric absorption over these paths.
Collision-induced vibrational absorption in molecular hydrogens
Reddy, S.P.
1993-05-01
Collision induced absorption (CIA) spectra of the first overtone bands of H{sub 2}, D{sub 2}, and HD have been recorded for gas densities up to 500 amagat at 77-300 K. Analyses of these spectra reveal that (1) contrary to the observations in the fundamental bands, the contribution of the isotropic overlap interaction to the first overtone bands is negligible, (2) the squares of the matrix elements B{sub 32}(R)/ea{sub o} [= {lambda}{sub 32} exp(-(R-{sigma})/{rho}{sub 32}) + 3
VUV Absorption Spectroscopy of Planetary Molecules at Low Temperature
NASA Astrophysics Data System (ADS)
Jolly, A.; Benilan, Y.; Ferradaz, T.; Fray, N.; Schwell, M.
2005-08-01
A critical review of the available absorption coefficient in the vacuum ultraviolet domain (100-200 nm) has lead us to undertake new measurements at the Berlin synchrotron facility (BESSY). Many of the molecules detected in planetary atmospheres and in particular those which need to be synthesized in the laboratory, have never been measured at low temperature. The first molecules that we have studied are HCN, HC3N and C2N2. New absorption coefficients have been obtained including first spectra at low temperature (220 K). The effect of the temperature on the spectra can then be discussed in view of the application to the much colder atmosphere of Titan. The nitriles studied here play an important role in the chemistry taking place in Titan's atmosphere and are believed to be responsible for the formation of Titan's aerosols. From our measurements, we have calculated the photodissociation rates for each molecule which are essential to include in any photochemical model. This is true for Titan but also for cometary and interstellar medium models. To describe the formation of a solid phase, the models also need to include photodissociation rates for larger molecules which have not been detected yet. This will now be possible for HC5N since the first spectra of this molecule has been obtained by our team. Furthermore, the first stellar occultation measurement of Titan's atmosphere by the UV spectrometer (UVIS) on board the CASSINI spacecraft has permitted the detection of species not observed before in this wavelength domain. But it has also shown a lack of experimental data in this domain. So far, the model is not able to reproduce the observed spectral feature. C4H2 is the molecule that should explain some of the observed feature but absolute cross sections are missing. We will present our latest experimental measurements on this molecule.
Hägglund, Carl; Zeltzer, Gabriel; Ruiz, Ricardo; Thomann, Isabell; Lee, Han-Bo-Ram; Brongersma, Mark L; Bent, Stacey F
2013-07-10
Achieving complete absorption of visible light with a minimal amount of material is highly desirable for many applications, including solar energy conversion to fuel and electricity, where benefits in conversion efficiency and economy can be obtained. On a fundamental level, it is of great interest to explore whether the ultimate limits in light absorption per unit volume can be achieved by capitalizing on the advances in metamaterial science and nanosynthesis. Here, we combine block copolymer lithography and atomic layer deposition to tune the effective optical properties of a plasmonic array at the atomic scale. Critical coupling to the resulting nanocomposite layer is accomplished through guidance by a simple analytical model and measurements by spectroscopic ellipsometry. Thereby, a maximized absorption of light exceeding 99% is accomplished, of which up to about 93% occurs in a volume-equivalent thickness of gold of only 1.6 nm. This corresponds to a record effective absorption coefficient of 1.7 × 10(7) cm(-1) in the visible region, far exceeding those of solid metals, graphene, dye monolayers, and thin film solar cell materials. It is more than a factor of 2 higher than that previously obtained using a critically coupled dye J-aggregate, with a peak width exceeding the latter by 1 order of magnitude. These results thereby substantially push the limits for light harvesting in ultrathin, nanoengineered systems.
NASA Technical Reports Server (NTRS)
Miller, Richard L.; Belz, Mathias; DelCastillo, Carlos; Trzaska, Rick
2001-01-01
We evaluated the accuracy, sensitivity and precision of a multiple pathlength, liquid core waveguide (MPLCW) system for measuring colored dissolved organic matter (CDOM) absorption in the UV-visible spectral range (370-700 nm). The MPLCW has four optical paths (2.0, 9.8, 49.3, and 204 cm) coupled to a single Teflon AF sample cell. Water samples were obtained from inland, coastal and ocean waters ranging in salinity from 0 to 36 PSU. Reference solutions for the MPLCW were made having a refractive index of the sample. CDOM absorption coefficients, aCDOM, and the slope of the log-linearized absorption spectra, S, were compared with values obtained using a dual-beam spectrophotometer. Absorption of phenol red secondary standards measured by the MPLCW at 558 nm were highly correlated with spectrophotometer values and showed a linear response across all four pathlengths. Values of aCDOM measured using the MPLCW were virtually identical to spectrophotometer values over a wide range of concentrations. The dynamic range of aCDOM for MPLCW measurements was 0.002 - 231.5 m-1. At low CDOM concentrations spectrophotometric aCDOM were slightly greater than MPLCW values and showed larger fluctuations at longer wavelengths due to limitations in instrument precision. In contrast, MPLCW spectra followed an exponential to 600 nm for all samples.
Electron mobility and free-carrier absorption in GaAs - Determination of the compensation ratio
NASA Technical Reports Server (NTRS)
Walukiewicz, W.; Lagowski, L.; Jastrzebski, L.; Lichtensteiger, M.; Gatos, H. C.
1979-01-01
Theoretical calculations of electron mobility and free-carrier absorption in n-type GaAs at room temperature were carried out taking into consideration all major scattering processes. It was found that satisfactory agreement between theoretical and experimental results on free-carrier absorption is obtained only when the effect of compensation is quantitatively taken into account. In conjunction with experimental studies it is shown that the electron mobility (for n greater than 10 to the 15th per cu cm) and free-carrier absorption (for n greater than 10 to the 16th per cu cm) are sufficiently sensitive to the ionized impurity concentration to provide a reliable means for determining the compensation ratio. Convenient procedures are presented for the determination of the compensation ratio from the free-carrier absorption coefficient and from the computed values of room-temperature electron mobility. Values of the compensation ratio obtained by these two procedures are in good agreement provided the carrier-concentration variations in the material are not appreciably greater than 10%.
On the errors in measuring the particle density by the light absorption method
Ochkin, V. N.
2015-04-15
The accuracy of absorption measurements of the density of particles in a given quantum state as a function of the light absorption coefficient is analyzed. Errors caused by the finite accuracy in measuring the intensity of the light passing through a medium in the presence of different types of noise in the recorded signal are considered. Optimal values of the absorption coefficient and the factors capable of multiplying errors when deviating from these values are determined.
Kitamura, K; Goto, T; Kitade, T
1998-08-01
The absorption spectra of six phenothiazine derivatives, chlorpromazine, triflupromazine, promazine, promethazine, trifluoperazine and prochlorperazine, measured in the solutions containing various amounts of human erythrocyte ghosts (HEG) showed bathocromic shifts according to the amount of HEG. Due to the strong background signals caused by HEG, the baseline compensation was incomplete, even though the sample and the reference solutions contained the same amount of HEG, hence further spectral information could not be obtained. The second derivative spectra of these absorption spectra clearly showed the derivative isosbestic points, indicating that the residual background signal effects were entirely eliminated. The derivative intensity differences of the phenothiazines (DeltaD values) before and after the addition of HEG were measured at a specific wavelength. Using the DeltaD values, the partition coefficients (K(p)) of these drugs were calculated and obtained with R.S.D. of below 10 %. The fractions of partitioned phenothiazines calculated from the K(p) values agreed well with the experimental values. The results indicate that the derivative method can be applicable to the determination of partition coefficients of drugs to HEG without any separation procedures.
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
Sound absorption of metallic sound absorbers fabricated via the selective laser melting process
NASA Astrophysics Data System (ADS)
Cheng, Li-Wei; Cheng, Chung-Wei; Chung, Kuo-Chun; Kam, Tai-Yan
2017-01-01
The sound absorption capability of metallic sound absorbers fabricated using the additive manufacturing (selective laser melting) method is investigated via both the experimental and theoretical approaches. The metallic sound absorption structures composed of periodic cubic cells were made of laser-melted Ti6Al4 V powder. The acoustic impedance equations with different frequency-independent and frequency-dependent end corrections factors are employed to calculate the theoretical sound absorption coefficients of the metallic sound absorption structures. The calculated sound absorption coefficients are in close agreement with the experimental results for the frequencies ranging from 2 to 13 kHz.
Intracavity Dye-Laser Absorption Spectroscopy (IDLAS) for application to planetary molecules
NASA Technical Reports Server (NTRS)
Lang, Todd M.; Allen, John E., Jr.
1990-01-01
Time-resolved, quasi-continuous wave, intracavity dye-laser absorption spectroscopy is applied to the investigation of absolute absorption coefficients for vibrational-rotational overtone bands of water at visible wavelengths. Emphasis is placed on critical factors affecting detection sensitivity and data analysis. Typical generation-time dependent absorption spectra are given.
Nunes, O.A.C.
1985-09-15
The influence of a strong laser field on the optical absorption edge of a direct-gap magnetic semiconductor is considered. It is shown that as the strong laser intensity increases the absorption coefficient is modified so as to give rise to an absorption tail below the free-field forbidden gap. An application is made for the case of the EuO.
Wei, Wei; Zhu, Yong; Lin, Cheng; Tian, Li; Xu, Zu-Wen; Nong, Jin-Peng
2014-04-01
It is quite urgent to need a flexible photodetector in the ultraviolet-visible-near infrared region for building a miniaturization broadband spectrometer. In the present paper, one kind of flexible black silicon doped with sulfur and fluorine was proposed and the optical absorption spectrum was investigated in broadband region. Firstly, the electronic structure, band structure and the optical absorption properties of the flexible black silicon doped with sulfur and fluoride were calculated using the first-principles pseudo potential calculations based on density-functional theory. Then, the absorption spectrum model of the flexible black silicon was built based on both the first-principles and finite domain time difference method. The results show that the cut-off wavelength has a red shift as the band gap of doped material becomes narrower. The higher the doping concentration is, the higher the optical absorption coefficient is obtained. The absorption coefficient of flexible black silicon doped with 50% sulfur is 8.3 times higher than that of 1.5% sulfur doping sample at the wavelength of 1 500 nm while the ratio turns to be 3 times when doped with 50% and 1.5% fluoride. The black silicon with small-size surface microstructure has the highest absorptance in the near-infrared region at the same doping concentration of 50%. Finally, a sample of flexible black silicon was fabricated by the femtosecond laser auto scanning system. The test results indicate that the absorptance of the sample is higher than 95% both in the ultraviolet and visible region and is fluctuated from 70% to 80% in the near-infrared region. It shows that as a novel light-absorbing material in broadband region the flexible black silicon doped with Sulfur and Fluorine has an potential application in exploring miniaturization broadband spectroscopy.
Loch, Christian; Zakelj, Simon; Kristl, Albin; Nagel, Stefan; Guthoff, Rudolf; Weitschies, Werner; Seidlitz, Anne
2012-08-30
To treat ophthalmic diseases like glaucoma or inflammatory disorders topically applied ophthalmic formulations such as eye drops are usually used. In addition, novel ophthalmic implants releasing drug substances locally into different parts of the eye are available today. In the work presented here, the permeability coefficients of selected drugs (ciprofloxacin hydrochloride, lidocaine hydrochloride, timolol maleate) for ophthalmic tissues were determined using side-by-side diffusion chambers (so-called Ussing chambers). Sclera, conjunctiva, cornea, choroidea-retina-complex and a complex of conjunctiva-sclera-choroidea-retina were excised from fresh porcine, rabbit and bovine eyes. In the porcine eye tissues the highest P(app) values were obtained for conjunctiva with the exception of lidocaine. Therefore, it can be estimated that a certain amount of drug diffuses or is transported through conjunctiva after application. The P(app) values for sclera were also higher than those for cornea and even more, the surface area of sclera which is available for drug absorption is much larger than that of cornea when applying an implant. The obtained permeability coefficients for sclera and conjunctiva indicate that the administration of periocular implants can be an alternative to topically applied formulations. The complexes of the tissues were a significantly (p<0.01) stronger barrier to the investigated substances than the separated tissues. Distinct differences in permeability coefficients between the investigated animal tissues were observed. Overall the highest P(app) values for all mounted tissues were obtained with the rabbit, followed by porcine and bovine eyes. Because of these distinct interspecies differences one must be very careful when selecting the proper animal model for the permeability experiments.
Modification of Einstein A Coefficient in Dissipative Gas Medium
NASA Technical Reports Server (NTRS)
Cao, Chang-Qi; Cao, Hui; Qin, Ke-Cheng
1996-01-01
Spontaneous radiation in dissipative gas medium such as plasmas is investigated by Langevin equations and the modified Weisskopf-Wigner approximation. Since the refractive index of gas medium is expected to be nearly unity, we shall first neglect the medium polarization effect. We show that absorption in plasmas may in certain case modify the Einstein A coefficient significantly and cause a pit in the A coefficient-density curves for relatively low temperature plasmas and also a pit in the A coefficient-temperature curves. In the next, the effect of medium polarization is taken into account in addition. To our surprise, its effect in certain case is quite significant. The dispersive curves show different behaviors in different region of parameters.
Determination of stream reaeration coefficients by use of tracers
Kilpatrick, F.A.; Rathbun, R.E.; Yotsukura, Nobuhiro; Parker, G.W.; DeLong, L.L.
1987-01-01
Stream reaeration is the physical absorption of oxygen from the atmosphere by a flowing stream. This is the primary process by which a stream replenishes the oxygen consumed in the biodegradation of organic wastes. Prior to 1965, reaeration rate coefficients could be estimated only by indirect methods. In 1965, a direct method of measuring stream reaeration coefficients was developed in which a radioactive tracer gas was injected into a stream--the tracer gas being desorbed from the stream inversely to how oxygen would be absorbed. The technique has since been modified by substituting hydrocarbon gases for the radioactive tracer gas. The slug-injection and constant-rate injection methods of performing gas tracer desorption measurements are described. Emphasis is on the use of rhodamine WT dye as a relatively conservative tracer and propane as the nonconservative gas tracer, on planning field tests, methods of injection, sampling and analysis, and computational techniques to compute desorption and reaeration coefficients. (Author 's abstract)
The use of trivalent chromium bath to obtain a solar selective black chromium coating
NASA Astrophysics Data System (ADS)
Survilienė, S.; Češūnienė, A.; Juškėnas, R.; Selskienė, A.; Bučinskienė, D.; Kalinauskas, P.; Juškevičius, K.; Jurevičiūtė, I.
2014-06-01
Black chromium coatings were electrodeposited from a trivalent chromium bath using a ZnO additive as a second main component. Black chromium was electrodeposited on steel and copper plates and substrates plated with bright nickel prior to black chromium electrodeposition. The black chromium coatings were characterized by XRD and SEM. The XRD data suggest that the phase structure of black chromium may be defined as a zinc solid solution in chromium or a chromium solid solution in zinc depending on the chromium/zinc ratio in the deposit. The role of substrate finish was evaluated through the corrosion resistance and reflectance of black chromium. According to corrosion tests the samples plated with bright nickel prior to black chromium deposition have shown the highest corrosion resistance. The electrodeposited black chromium possesses good optical properties for the absorption of solar energy. The absorption coefficient of black chromium was found to be over 0.99 for the samples obtained without the Ni undercoat and below 0.99 for those obtained with the use of Ni undercoat. However, the use of nickel undercoat before black chromium plating is recommended because it remarkably improves the corrosion resistance of samples.
Seebeck coefficient of one electron
Durrani, Zahid A. K.
2014-03-07
The Seebeck coefficient of one electron, driven thermally into a semiconductor single-electron box, is investigated theoretically. With a finite temperature difference ΔT between the source and charging island, a single electron can charge the island in equilibrium, directly generating a Seebeck effect. Seebeck coefficients for small and finite ΔT are calculated and a thermally driven Coulomb staircase is predicted. Single-electron Seebeck oscillations occur with increasing ΔT, as one electron at a time charges the box. A method is proposed for experimental verification of these effects.
Enhancing rigid frame porous layer absorption with three-dimensional periodic irregularities.
Groby, J-P; Brouard, B; Dazel, O; Nennig, B; Kelders, L
2013-02-01
This papers reports a three-dimensional (3D) extension of the model proposed by Groby et al. [J. Acoust. Soc. Am. 127, 2865-2874 (2010)]. The acoustic properties of a porous layer backed by a rigid plate with periodic rectangular irregularities are investigated. The Johnson-Champoux-Allard model is used to predict the complex bulk modulus and density of the equivalent fluid in the porous material. The method of variable separation is used together with the radiation conditions and Floquet theorem to derive the analytical expression for the acoustic reflection coefficient from the porous layer with 3D inhomogeneities. Finite element method is also used to validate the proposed analytical solution. The theoretical and numerical predictions agree well with the experimental data obtained from an impedance tube experiment. It is shown that the measured acoustic absorption coefficient spectrum exhibits a quasi-total absorption peak at the predicted frequency of the mode trapped in the porous layer. When more than one irregularity per spatial period is considered, additional absorption peaks are observed.
Synopsis of Mid-latitude Radio Wave Absorption in Europe
NASA Technical Reports Server (NTRS)
Torkar, K. M.; Friedrich, M.
1984-01-01
Radio wave absorption data covering almost two years from Europe to Central Asia are presented. They are normalized by relating them to a reference absorption. Every day these normalized data are fitted to a mathematical function of geographical location in order to obtain a daily synopsis of radio wave absorption. A film of these absorption charts was made which is intended to reveal movements of absorption or absorption anomaly. In addition, radiance (temperature) data from the lower D-region are also plotted onto these charts.
NASA Astrophysics Data System (ADS)
Mathan Kumar, K.; John Peter, A.; Lee, C. W.
2011-12-01
Electronic energies of an exciton confined in a strained Zn1- x Cd x Se/ZnSe quantum dot have been computed as a function of dot radius with various Cd content. Calculations have been performed using Bessel function as an orthonormal basis for different confinement potentials of barrier height considering the internal electric field induced by the spontaneous and piezoelectric polarizations. The optical absorption coefficients and the refractive index changes between the ground state ( L = 0) and the first excited state ( L = 1) are investigated. It is found that the optical properties in the strained ZnCdSe/ZnSe quantum dot are strongly affected by the confinement potentials and the dot radii. The intensity of the total absorption spectra increases for the transition between higher levels. The obtained optical nonlinearity brings out the fact that it should be considered in calculating the optical properties in low dimensional semiconductors especially in quantum dots.
High temperature measurement of water vapor absorption
NASA Technical Reports Server (NTRS)
Keefer, Dennis; Lewis, J. W. L.; Eskridge, Richard
1985-01-01
An investigation was undertaken to measure the absorption coefficient, at a wavelength of 10.6 microns, for mixtures of water vapor and a diluent gas at high temperature and pressure. The experimental concept was to create the desired conditions of temperature and pressure in a laser absorption wave, similar to that which would be created in a laser propulsion system. A simplified numerical model was developed to predict the characteristics of the absorption wave and to estimate the laser intensity threshold for initiation. A non-intrusive method for temperature measurement utilizing optical laser-beam deflection (OLD) and optical spark breakdown produced by an excimer laser, was thoroughly investigated and found suitable for the non-equilibrium conditions expected in the wave. Experiments were performed to verify the temperature measurement technique, to screen possible materials for surface initiation of the laser absorption wave and to attempt to initiate an absorption wave using the 1.5 kW carbon dioxide laser. The OLD technique was proven for air and for argon, but spark breakdown could not be produced in helium. It was not possible to initiate a laser absorption wave in mixtures of water and helium or water and argon using the 1.5 kW laser, a result which was consistent with the model prediction.
Theory of graphene saturable absorption
NASA Astrophysics Data System (ADS)
Marini, A.; Cox, J. D.; García de Abajo, F. J.
2017-03-01
Saturable absorption is a nonperturbative nonlinear optical phenomenon that plays a pivotal role in the generation of ultrafast light pulses. Here we show that this effect emerges in graphene at unprecedentedly low light intensities, thus opening avenues to new nonlinear physics and applications in optical technology. Specifically, we theoretically investigate saturable absorption in extended graphene by developing a semianalytical nonperturbative single-particle approach, describing electron dynamics in the atomically-thin material using the two-dimensional Dirac equation for massless Dirac fermions, which is recast in the form of generalized Bloch equations. By solving the electron dynamics nonperturbatively, we account for both interband and intraband contributions to the intensity-dependent saturated conductivity and conclude that the former dominates regardless of the intrinsic doping state of the material. We obtain results in qualitative agreement with atomistic quantum-mechanical simulations of graphene nanoribbons including electron-electron interactions, finite-size, and higher-band effects. Remarkably, such effects are found to affect mainly the linear absorption, while the predicted saturation intensities are in good quantitative agreement in the limit of extended graphene. Additionally, we find that the modulation depth of saturable absorption in graphene can be electrically manipulated through an externally applied gate voltage. Our results are relevant for the development of graphene-based optoelectronic devices, as well as for applications in mode-locking and random lasers.
Slow light and saturable absorption
NASA Astrophysics Data System (ADS)
Selden, A. C.
2009-06-01
Quantitative analysis of slow light experiments utilising coherent population oscillation (CPO) in a range of saturably absorbing media, including ruby and alexandrite, Er3+:Y2SiO5, bacteriorhodopsin, semiconductor quantum devices and erbium-doped optical fibres, shows that the observations may be more simply interpreted as saturable absorption phenomena. A basic two-level model of a saturable absorber displays all the effects normally associated with slow light, namely phase shift and modulation gain of the transmitted signal, hole burning in the modulation frequency spectrum and power broadening of the spectral hole, each arising from the finite response time of the non-linear absorption. Only where hole-burning in the optical spectrum is observed (using independent pump and probe beams), or pulse delays exceeding the limits set by saturable absorption are obtained, can reasonable confidence be placed in the observation of slow light in such experiments. Superluminal (“fast light”) phenomena in media with reverse saturable absorption (RSA) may be similarly explained.
NASA Technical Reports Server (NTRS)
Chandra, N.
1974-01-01
Numerical coefficients required to express the angular distribution for the rotationally elastic or inelastic scattering of electrons from a diatomic molecule were tabulated for the case of nitrogen and in the energy range from 0.20 eV to 10.0 eV. Five different rotational states are considered.
Identities for generalized hypergeometric coefficients
Biedenharn, L.C.; Louck, J.D.
1991-01-01
Generalizations of hypergeometric functions to arbitrarily many symmetric variables are discussed, along with their associated hypergeometric coefficients, and the setting within which these generalizations arose. Identities generalizing the Euler identity for {sub 2}F{sub 1}, the Saalschuetz identity, and two generalizations of the {sub 4}F{sub 3} Bailey identity, among others, are given. 16 refs.
Effective Viscosity Coefficient of Nanosuspensions
NASA Astrophysics Data System (ADS)
Rudyak, V. Ya.; Belkin, A. A.; Egorov, V. V.
2008-12-01
Systematic calculations of the effective viscosity coefficient of nanosuspensions have been performed using the molecular dynamics method. It is established that the viscosity of a nanosuspension depends not only on the volume concentration of the nanoparticles but also on their mass and diameter. Differences from Einstein's relation are found even for nanosuspensions with a low particle concentration.
Integer Solutions of Binomial Coefficients
ERIC Educational Resources Information Center
Gilbertson, Nicholas J.
2016-01-01
A good formula is like a good story, rich in description, powerful in communication, and eye-opening to readers. The formula presented in this article for determining the coefficients of the binomial expansion of (x + y)n is one such "good read." The beauty of this formula is in its simplicity--both describing a quantitative situation…
Wood-Polymer composites obtained by gamma irradiation
Gago, J.; Lopez, A.; Rodriguez, J.; Santiago, J.; Acevedo, M.
2007-10-26
In this work we impregnate three Peruvian woods (Calycophy spruceanum Be, Aniba amazonica Meiz and Hura crepitans L) with styrene-polyester resin and methyl methacrylate. The polymerization of the system was promoted by gamma radiation and the experimental optimal condition was obtained with styrene-polyester 1:1 and 15 kGy. The obtained composites show reduced water absorption and better mechanical properties compared to the original wood. The structure of the wood-polymer composites was studied by light microscopy. Water absorption and hardness were also obtained.
Anomalous atmospheric absorption spectra due to water dimer
NASA Astrophysics Data System (ADS)
Cai, Peipei; Zhang, Hansheng; Shen, Shanxiong; Cheng, I.-Shan
1986-11-01
The anomalous atmospheric absorption spectra in the window wavelength region of 8-14 microns have been suggested due to the water dimer. Based on laboratory measurements, water continuum CO2 laser absorption spectra and a resonance absorption line due to the weak local wave vapor pure rotational transition have been reported. The equilibrium concentration of water dimers in the atmosphere, the electronic binding energy and the theoretical calculations for absorption attenuation have been obtained in agreement with published data.
Zero Pearson coefficient for strongly correlated growing trees
NASA Astrophysics Data System (ADS)
Dorogovtsev, S. N.; Ferreira, A. L.; Goltsev, A. V.; Mendes, J. F. F.
2010-03-01
We obtained Pearson’s coefficient of strongly correlated recursive networks growing by preferential attachment of every new vertex by m edges. We found that the Pearson coefficient is exactly zero in the infinite network limit for the recursive trees (m=1) . If the number of connections of new vertices exceeds one (m>1) , then the Pearson coefficient in the infinite networks equals zero only when the degree distribution exponent γ does not exceed 4. We calculated the Pearson coefficient for finite networks and observed a slow power-law-like approach to an infinite network limit. Our findings indicate that Pearson’s coefficient strongly depends on size and details of networks, which makes this characteristic virtually useless for quantitative comparison of different networks.
Zero Pearson coefficient for strongly correlated growing trees.
Dorogovtsev, S N; Ferreira, A L; Goltsev, A V; Mendes, J F F
2010-03-01
We obtained Pearson's coefficient of strongly correlated recursive networks growing by preferential attachment of every new vertex by m edges. We found that the Pearson coefficient is exactly zero in the infinite network limit for the recursive trees (m=1). If the number of connections of new vertices exceeds one (m>1), then the Pearson coefficient in the infinite networks equals zero only when the degree distribution exponent gamma does not exceed 4. We calculated the Pearson coefficient for finite networks and observed a slow power-law-like approach to an infinite network limit. Our findings indicate that Pearson's coefficient strongly depends on size and details of networks, which makes this characteristic virtually useless for quantitative comparison of different networks.
Direct Extraction of One-loop Integral Coefficients
Forde, Darren
2007-04-16
We present a general procedure for obtaining the coefficients of the scalar bubble and triangle integral functions of one-loop amplitudes. Coefficients are extracted by considering two-particle and triple unitarity cuts of the corresponding bubble and triangle integral functions. After choosing a specific parameterization of the cut loop momentum we can uniquely identify the coefficients of the desired integral functions simply by examining the behavior of the cut integrand as the unconstrained parameters of the cut loop momentum approach infinity. In this way we can produce compact forms for scalar integral coefficients. Applications of this method are presented for both QCD and electroweak processes, including an alternative form for the recently computed three-mass triangle coefficient in the six-photon amplitude A{sub 6}(1{sup -}, 2{sup +}, 3{sup -}, 4{sup +}, 5{sup -}, 6{sup +}). The direct nature of this extraction procedure allows for a very straightforward automation of the procedure.
Determination of absolute internal conversion coefficients using the SAGE spectrometer
NASA Astrophysics Data System (ADS)
Sorri, J.; Greenlees, P. T.; Papadakis, P.; Konki, J.; Cox, D. M.; Auranen, K.; Partanen, J.; Sandzelius, M.; Pakarinen, J.; Rahkila, P.; Uusitalo, J.; Herzberg, R.-D.; Smallcombe, J.; Davies, P. J.; Barton, C. J.; Jenkins, D. G.
2016-03-01
A non-reference based method to determine internal conversion coefficients using the SAGE spectrometer is carried out for transitions in the nuclei of 154Sm, 152Sm and 166Yb. The Normalised-Peak-to-Gamma method is in general an efficient tool to extract internal conversion coefficients. However, in many cases the required well-known reference transitions are not available. The data analysis steps required to determine absolute internal conversion coefficients with the SAGE spectrometer are presented. In addition, several background suppression methods are introduced and an example of how ancillary detectors can be used to select specific reaction products is given. The results obtained for ground-state band E2 transitions show that the absolute internal conversion coefficients can be extracted using the methods described with a reasonable accuracy. In some cases of less intense transitions only an upper limit for the internal conversion coefficient could be given.
Super-Resonant Intracavity Coherent Absorption
NASA Astrophysics Data System (ADS)
Malara, P.; Campanella, C. E.; Giorgini, A.; Avino, S.; de Natale, P.; Gagliardi, G.
2016-07-01
The capability of optical resonators to extend the effective radiation-matter interaction length originates from a multipass effect, hence is intrinsically limited by the resonator’s quality factor. Here, we show that this constraint can be overcome by combining the concepts of resonant interaction and coherent perfect absorption (CPA). We demonstrate and investigate super-resonant coherent absorption in a coupled Fabry-Perot (FP)/ring cavity structure. At the FP resonant wavelengths, the described phenomenon gives rise to split modes with a nearly-transparent peak and a peak whose transmission is exceptionally sensitive to the intracavity loss. For small losses, the effective interaction pathlength of these modes is proportional respectively to the ratio and the product of the individual finesse coefficients of the two resonators. The results presented extend the conventional definition of resonant absorption and point to a way of circumventing the technological limitations of ultrahigh-quality resonators in spectroscopy and optical sensing schemes.
Enhanced absorption in silicon metamaterials waveguide structure
NASA Astrophysics Data System (ADS)
Hamouche, Houria; Shabat, Mohammed M.
2016-07-01
Metamaterial waveguide structures for silicon solar cells are a novel approach to antireflection coating structures that can be used for the achievement of high absorption in silicon solar cells. This paper investigates numerically the possibility of improving the performance of a planar waveguide silicon solar cell by incorporating a pair of silicon nitride/metamaterial layer between a semi-infinite glass cover layer and a semi-infinite silicon substrate layer. The optimized layer thicknesses of the pair are determined under the solar spectrum AM1.5 by the effective average reflectance method. The transmission and reflection coefficients are derived by the transfer matrix method for values of metamaterial's refractive index in visible and near-infrared radiation. In addition, the absorption coefficient is examined for several angles of incidence of the transverse electric polarized (TE), transverse magnetic polarized (TM) and the total (TE&TM) guided waves. Numerical results provide an extremely high absorption. The absorptivity of the structure achieves greater than 98 %.
Numerical Integral of Resistance Coefficients in Diffusion
NASA Astrophysics Data System (ADS)
Zhang, Q. S.
2017-01-01
The resistance coefficients in the screened Coulomb potential of stellar plasma are evaluated to high accuracy. I have analyzed the possible singularities in the integral of scattering angle. There are possible singularities in the case of an attractive potential. This may result in a problem for the numerical integral. In order to avoid the problem, I have used a proper scheme, e.g., splitting into many subintervals where the width of each subinterval is determined by the variation of the integrand, to calculate the scattering angle. The collision integrals are calculated by using Romberg’s method, therefore the accuracy is high (i.e., ∼10‑12). The results of collision integrals and their derivatives for ‑7 ≤ ψ ≤ 5 are listed. By using Hermite polynomial interpolation from those data, the collision integrals can be obtained with an accuracy of 10‑10. For very weakly coupled plasma (ψ ≥ 4.5), analytical fittings for collision integrals are available with an accuracy of 10‑11. I have compared the final results of resistance coefficients with other works and found that, for a repulsive potential, the results are basically the same as others’ for an attractive potential, the results in cases of intermediate and strong coupling show significant differences. The resulting resistance coefficients are tested in the solar model. Comparing with the widely used models of Cox et al. and Thoul et al., the resistance coefficients in the screened Coulomb potential lead to a slightly weaker effect in the solar model, which is contrary to the expectation of attempts to solve the solar abundance problem.
Solving Second-Order Differential Equations with Variable Coefficients
ERIC Educational Resources Information Center
Wilmer, A., III; Costa, G. B.
2008-01-01
A method is developed in which an analytical solution is obtained for certain classes of second-order differential equations with variable coefficients. By the use of transformations and by repeated iterated integration, a desired solution is obtained. This alternative method represents a different way to acquire a solution from classic power…
Performance Analysis of Solution Transportation Absorption Chiller
NASA Astrophysics Data System (ADS)
Kiani, Behdad; Hamamoto, Yoshinori; Akisawa, Atsushi; Kashiwagi, Takao
Thermally activated advanced absorption cycles are considered promising candidates to replace CFCs, HCFCs and HFCs for residential and commercial applications. In such absorption systems, it is desirable to utilize the waste heat from industries for heating and cooling applications in commercial and residential sectors. For this purpose, it is necessary to transport energy over some distance because the waste heat source and demand are generally located apart from each other. Transportation of steam, hot water or chilled water requires high construction costs for insulation. There is an efficient method of energy transportation using absorption system called “ Solution Transportation Absorption System (STA)”. The solution is transported at an ambient temperature so that tube-insulations not required. This paper shows the simulation of the abovementioned system and the optimal result, using mathematical optimization. The optimum system with industry‧s waste heat utilization is obtained. At the end, the effect on the pollution emission and energy conservation is obtained.
Effect of morphology and solvent on two-photon absorption of nano zinc oxide
Kavitha, M.K.; Haripadmam, P.C.; Gopinath, Pramod; Krishnan, Bindu; John, Honey
2013-05-15
Highlights: ► ZnO nanospheres and triangular structures synthesis by novel precipitation technique. ► The effect of precursor concentration on the size and shape of nano ZnO. ► Open aperture Z-scan measurements of the ZnO nanoparticle dispersions. ► Nanospheres exhibit higher two photon absorption coefficient than triangular nanostructures. ► Nanospheres dispersed in water exhibit higher two photon absorption coefficient than its dispersion in 2-propanol. - Abstract: In this paper, we report the effect of morphology and solvent on the two-photon absorption of nano zinc oxide. Zinc oxide nanoparticles in two different morphologies like nanospheres and triangular nanostructures are synthesized by novel precipitation technique and their two-photon absorption coefficient is measured using open aperture Z-scan technique. Experimental results show that the zinc oxide nanospheres exhibit higher two-photon absorption coefficient than the zinc oxide triangular nanostructures. The zinc oxide nanospheres dispersed in water exhibit higher two-photon absorption coefficient than that of its dispersion in 2-propanol. The zinc oxide nanospheres dispersed in water shows a decrease in two-photon absorption coefficient with an increase in on-axis irradiance. The result confirms the dependence of shape and solvent on the two-photon absorption of nano zinc oxide.
Transport coefficients of He(+) ions in helium.
Viehland, Larry A; Johnsen, Rainer; Gray, Benjamin R; Wright, Timothy G
2016-02-21
This paper demonstrates that the transport coefficients of (4)He(+) in (4)He can be calculated over wide ranges of E/N, the ratio of the electrostatic field strength to the gas number density, with the same level of precision as can be obtained experimentally if sufficiently accurate potential energy curves are available for the X(2)Σu (+) and A(2)Σg (+) states and one takes into account resonant charge transfer. We start by computing new potential energy curves for these states and testing their accuracy by calculating spectroscopic values for the separate states. It is established that the potentials obtained by extrapolation of results from d-aug-cc-pVXZ (X = 6, 7) basis sets using the CASSCF+MRCISD approach are each in exceptionally close agreement with the best potentials available and with experiment. The potentials are then used in a new computer program to determine the semi-classical phase shifts and the transport cross sections, and from these the gaseous ion transport coefficients are determined. In addition, new experimental values are reported for the mobilities of (4)He(+) in (4)He at 298.7 K, as a function of E/N, where careful consideration is given to minimizing various sources of uncertainty. Comparison with previously measured values establishes that only one set of previous data is reliable. Finally, the experimental and theoretical ion transport coefficients are shown to be in very good to excellent agreement, once corrections are applied to account for quantum-mechanical effects.
A generating function for certain coefficients involving several complex variables.
Srivastava, H M
1970-10-01
In an attempt to unify a number of generating functions for certain classes of generalized hypergeometric polynomials, Lagrange's expansion formula is applied to prove a generating relation for an n-dimensional polynomial with arbitrary coefficients. It is also shown how these coefficients can be specialized to obtain the generalized Lauricella function as a generating function for a class of generalized hypergeometric polynomials of several complex variables.
A general relationship for the second virial refraction coefficient
Seminogov, V.N.; Sinel'nikov, S.P.; Timoshenko, N.I.; Yamnov, A.L.
1986-05-01
Experimental data have been used to obtain a general formula for the second virial refraction coefficient as a function of temperature. A qualitative analysis of the formula is given. Laser techinques have substantially extended the scope for optical methods in thermophysical research, including high-temperature processes. The general formula for the second virial refraction coefficient presented enables one to calculate polarizabilities at low densities.
Advanced regenerative absorption refrigeration cycles
Dao, Kim
1990-01-01
Multi-effect regenerative absorption cycles which provide a high coefficient of performance (COP) at relatively high input temperatures. An absorber-coupled double-effect regenerative cycle (ADR cycle) (10) is provided having a single-effect absorption cycle (SEA cycle) (11) as a topping subcycle and a single-effect regenerative absorption cycle (1R cycle) (12) as a bottoming subcycle. The SEA cycle (11) includes a boiler (13), a condenser (21), an expansion device (28), an evaporator (31), and an absorber (40), all operatively connected together. The 1R cycle (12) includes a multistage boiler (48), a multi-stage resorber (51), a multisection regenerator (49) and also uses the condenser (21), expansion device (28) and evaporator (31) of the SEA topping subcycle (11), all operatively connected together. External heat is applied to the SEA boiler (13) for operation up to about 500 degrees F., with most of the high pressure vapor going to the condenser (21) and evaporator (31) being generated by the regenerator (49). The substantially adiabatic and isothermal functioning of the SER subcycle (12) provides a high COP. For higher input temperatures of up to 700 degrees F., another SEA cycle (111) is used as a topping subcycle, with the absorber (140) of the topping subcycle being heat coupled to the boiler (13) of an ADR cycle (10). The 1R cycle (12) itself is an improvement in that all resorber stages (50b-f) have a portion of their output pumped to boiling conduits (71a-f) through the regenerator (49), which conduits are connected to and at the same pressure as the highest pressure stage (48a) of the 1R multistage boiler (48).
Solar absorption surface panel
Santala, Teuvo J.
1978-01-01
A composite metal of aluminum and nickel is used to form an economical solar absorption surface for a collector plate wherein an intermetallic compound of the aluminum and nickel provides a surface morphology with high absorptance and relatively low infrared emittance along with good durability.
Rectal absorption of propylthiouracil.
Bartle, W R; Walker, S E; Silverberg, J D
1988-06-01
The rectal absorption of propylthiouracil (PTU) was studied and compared to oral absorption in normal volunteers. Plasma levels of PTU after administration of suppositories of PTU base and PTU diethanolamine were significantly lower compared to the oral route. Elevated plasma reverse T3 levels were demonstrated after each treatment, however, suggesting a desirable therapeutic effect at this dosage level for all preparations.
The dyadic diffraction coefficient for a curved edge
NASA Technical Reports Server (NTRS)
Kouyoumjian, R. G.; Pathak, P. H.
1974-01-01
A compact dyadic diffraction coefficient for electromagnetic waves obliquely incident on a curved edge formed by perfectly conducting curved or plane surfaces is obtained. This diffraction coefficent remains valid in the transition regions adjacent to shadow and reflection boundaries, where the diffraction coefficients of Keller's original theory fail. The method is on Keller's method of the canonical problem, which in this case is the perfectly conducting wedge illuminated by plane, cylindrical, conical, and spherical waves. When the proper ray fixed coordinate system is introduced, the dyadic diffraction coefficient for the wedge is found to be the sum of only two dyads, and it is shown that this is also true for the dyadic diffraction coefficients of higher order edges. One dyad contains the acoustic soft diffraction coefficient; the other dyad contains the acoustic hard diffraction coefficient. The expressions for the acoustic wedge diffraction coefficients contain Fresnel integrals, which ensure that the total field is continuous at shadow and reflection boundaries. The diffraction coefficients have the same form for the different types of edge illumination; only the arguments of the Fresnel integrals are different. Since diffraction is a local phenomenon, and locally the curved edge structure is wedge shaped, this result is readily extended to the curved edge.
Hou, Jipeng; He, Xin; Xu, Xuefang; Shi, Xiaoyan; Xu, Yanyan; Liu, Changxiao
2012-11-01
The aim of this study was to evaluate the oral absorption of two chemicals simultaneously using a drug dissolution/absorption simulating system (DDASS), and to establish a correlation between DDASS and in vivo absorption to clarify the prediction of this in vitro model. Ferulic acid (FA) and tetrahydropalmatine (THP), the components of Angelicae Sinensis Radix and Corydalis Yanhusuo Rhizoma, respectively, were chosen as model compounds. Three groups including FA, THP, and FA and THP together (FA + THP) were studied in DDASS. The corresponding in vivo pharmacokinetics study was performed in rats. Then the correlation was analysed between DDASS permeation in vitro and rat absorption data in vivo. A strong level A correlation (r > 0.84) was obtained after a correlation coefficient test (p < 0.05 or 0.01). Moreover, when FA and THP were used together in DDASS, the cumulative permeation of FA increased by 38.5%, while THP permeation decreased by 25.8%. In rats, the area under the concentration-time curve from time to infinity for FA increased 2.6-fold, while THP decreased 19.6%. The changes in rat intestinal permeation modeled by the DDASS were consistent with the absorption changes in rats. We conclude that DDASS is a valid in vitro model to evaluate oral absorption of two drug components simultaneously and reflect the in vivo characteristics of drug absorption accurately.
Fast, low-noise, mode-by-mode, cavity-enhanced absorption spectroscopy by diode-laser self-locking
NASA Astrophysics Data System (ADS)
Morville, J.; Kassi, S.; Chenevier, M.; Romanini, D.
2005-06-01
A new technique of cavity enhanced absorption spectroscopy is described. Molecular absorption spectra are obtained by recording the transmission maxima of the successive TEMoo resonances of a high-finesse optical cavity when a Distributed Feedback Diode Laser is tuned across them. A noisy cavity output is usually observed in such a measurement since the resonances are spectrally narrower than the laser. We show that a folded (V-shaped) cavity can be used to obtain selective optical feedback from the intracavity field which builds up at resonance. This induces laser linewidth reduction and frequency locking. The linewidth narrowing eliminates the noisy cavity output, and allows measuring the maximum mode transmissions accurately. The frequency locking permits the laser to scan stepwise through the successive cavity modes. Frequency tuning is thus tightly optimized for cavity mode injection. Our setup for this technique of Optical-Feedback Cavity-Enhanced Absorption Spectroscopy (OF-CEAS) includes a 50 cm folded cavity with finesse ˜20 000 (ringdown time ˜20 μs) and allows recording spectra of up to 200 cavity modes (2 cm-1) using 100 ms laser scans. We obtain a noise equivalent absorption coefficient of ˜5×10-10 cm-1 for 1 s averaging over scans, with a dynamic range of four orders of magnitude.
Transport coefficients of quantum plasmas
Bennaceur, D.; Khalfaoui, A.H. )
1993-09-01
Transport coefficients of fully ionized plasmas with a weakly coupled, completely degenerate electron gas and classical ions with a wide range of coupling strength are expressed within the Bloch transport equation. Using the Kohler variational principle the collision integral of the quantum Boltzmann equation is derived, which accounts for quantum effects through collective plasma oscillations. The physical implications of the results are investigated through comparisons with other theories. For practical applications, electrical and thermal conductivities are derived in simple analytical formulas. The relation between these two transport coefficients is expressed in an explicit form, giving a generalized Wiedemann-Franz law, where the Lorentz ratio is a dependent function of the coupling parameter and the degree of degeneracy of the plasma.
High temperature Seebeck coefficient metrology
Martin, J.; Tritt, T.; Uher, C.
2010-12-15
We present an overview of the challenges and practices of thermoelectric metrology on bulk materials at high temperature (300 to 1300 K). The Seebeck coefficient, when combined with thermal and electrical conductivity, is an essential property measurement for evaluating the potential performance of novel thermoelectric materials. However, there is some question as to which measurement technique(s) provides the most accurate determination of the Seebeck coefficient at high temperature. This has led to the implementation of nonideal practices that have further complicated the confirmation of reported high ZT materials. To ensure meaningful interlaboratory comparison of data, thermoelectric measurements must be reliable, accurate, and consistent. This article will summarize and compare the relevant measurement techniques and apparatus designs required to effectively manage uncertainty, while also providing a reference resource of previous advances in high temperature thermoelectric metrology.
Study of Dispersion Coefficient Channel
NASA Astrophysics Data System (ADS)
Akiyama, K. R.; Bressan, C. K.; Pires, M. S. G.; Canno, L. M.; Ribeiro, L. C. L. J.
2016-08-01
The issue of water pollution has worsened in recent times due to releases, intentional or not, of pollutants in natural water bodies. This causes several studies about the distribution of pollutants are carried out. The water quality models have been developed and widely used today as a preventative tool, ie to try to predict what will be the concentration distribution of constituent along a body of water in spatial and temporal scale. To understand and use such models, it is necessary to know some concepts of hydraulic high on their application, including the longitudinal dispersion coefficient. This study aims to conduct a theoretical and experimental study of the channel dispersion coefficient, yielding more information about their direct determination in the literature.
Portable vapor diffusion coefficient meter
Ho, Clifford K.
2007-06-12
An apparatus for measuring the effective vapor diffusion coefficient of a test vapor diffusing through a sample of porous media contained within a test chamber. A chemical sensor measures the time-varying concentration of vapor that has diffused a known distance through the porous media. A data processor contained within the apparatus compares the measured sensor data with analytical predictions of the response curve based on the transient diffusion equation using Fick's Law, iterating on the choice of an effective vapor diffusion coefficient until the difference between the predicted and measured curves is minimized. Optionally, a purge fluid can forced through the porous media, permitting the apparatus to also measure a gas-phase permeability. The apparatus can be made lightweight, self-powered, and portable for use in the field.
Full wave-field reflection coefficient inversion.
Dettmer, Jan; Dosso, Stan E; Holland, Charles W
2007-12-01
This paper develops a Bayesian inversion for recovering multilayer geoacoustic (velocity, density, attenuation) profiles from a full wave-field (spherical-wave) seabed reflection response. The reflection data originate from acoustic time series windowed for a single bottom interaction, which are processed to yield reflection coefficient data as a function of frequency and angle. Replica data for inversion are computed using a wave number-integration model to calculate the full complex acoustic pressure field, which is processed to produce a commensurate seabed response function. To address the high computational cost of calculating short range acoustic fields, the inversion algorithms are parallelized and frequency averaging is replaced by range averaging in the forward model. The posterior probability density is interpreted in terms of optimal parameter estimates, marginal distributions, and credibility intervals. Inversion results for the full wave-field seabed response are compared to those obtained using plane-wave reflection coefficients. A realistic synthetic study indicates that the plane-wave assumption can fail, producing erroneous results with misleading uncertainty bounds, whereas excellent results are obtained with the full-wave reflection inversion.
Characteristic Simulation of the Waste-Heat Utilization Absorption Cycles
NASA Astrophysics Data System (ADS)
Yoon, Jung-In; Oh, Hoo-Kyu; Kashiwagi, Takao
In the recent years double effect cycles have gathered a lot of attention because of their good efficiency particularly fitting with preoccupation of energy saving and with recent environmental problems. Simulation studies on double effect absorption cycles for refrigeration purposes have been performed for H2O/LiBr fair. The purpose of this study is the objective for evaluating the possibilities of effectively utilizing waste-heat as a secondary heat source for the low temperature generator. The efficiency of the different cycles have been studied and the simulation results show that higher coefficient of performance could be obtained for standard parallel cycle (TYPE PA). The optimum designs and operating conditions were determined based on the operating conditions and the coefficient of performance. The effectiveness of introducing a waste-heat source of about the same temperature level as the low temperature generator is demonstrated. If the cycles are assisted by fuel cell waste-heat, the input of waste-heat to low temperature generation parallel cycle (TYPE PB) yields highest COP.
Human intestinal absorption--neutral molecules and ionic species.
Abraham, Michael H
2014-07-01
Analysis of percentage human intestinal absorption (%HIA) for 280 drugs shows that an excellent fit can be obtained using only three descriptors for neutral molecules with a SD of 13.9%. Use of descriptors for individual cations and anions does not lead to any better goodness-of-fit. It is noted that diffusion coefficients in water for ionized molecules are almost identical to those for the corresponding neutral molecules. Comparison of equation coefficients for HIA with those for other processes shows that HIA resembles diffusion in water but does not resemble permeation through biological bilayers. It is shown that compound substituent effects on HIA are near those for diffusion but are far away from substituent effects on permeation through a typical bilayer. Calculations indicate that rates of permeation through an unstirred mucosal layer are of the same order as experimental rates of permeation in HIA. It is concluded that for the 280 compound set, diffusion through the unstirred mucosal layer is the rate determining step. The effect on pK(a) in transfer of acids and bases from water to another solvent, and of diffusion past a negative charge in a phase/bilayer is also considered.
Equilibrium absorptive partitioning theory between multiple aerosol particle modes
NASA Astrophysics Data System (ADS)
Crooks, Matthew; Connolly, Paul; Topping, David; McFiggans, Gordon
2016-10-01
An existing equilibrium absorptive partitioning model for calculating the equilibrium gas and particle concentrations of multiple semi-volatile organics within a bulk aerosol is extended to allow for multiple involatile aerosol modes of different sizes and chemical compositions. In the bulk aerosol problem, the partitioning coefficient determines the fraction of the total concentration of semi-volatile material that is in the condensed phase of the aerosol. This work modifies this definition for multiple polydisperse aerosol modes to account for multiple condensed concentrations, one for each semi-volatile on each involatile aerosol mode. The pivotal assumption in this work is that each aerosol mode contains an involatile constituent, thus overcoming the potential problem of smaller particles evaporating completely and then condensing on the larger particles to create a monodisperse aerosol at equilibrium. A parameterisation is proposed in which the coupled non-linear system of equations is approximated by a simpler set of equations obtained by setting the organic mole fraction in the partitioning coefficient to be the same across all modes. By perturbing the condensed masses about this approximate solution a correction term is derived that accounts for many of the removed complexities. This method offers a greatly increased efficiency in calculating the solution without significant loss in accuracy, thus making it suitable for inclusion in large-scale models.
Udoh, A P
1995-12-01
Varying concentrations of lanthanum and strontium were added to solutions of ashed unused lubricating oils for the determination of calcium, magnesium and zinc content using flame atomic absorption spectrophotometry. At least 3000 mug g(-1) of lanthanum or strontium was required to completely overcome the interference of the phosphate ion, PO(3-)(4), and give peak values for calcium. The presence of lanthanum or strontium did not cause an appreciable increase in the amount of magnesium and zinc obtained from the analyses. The method is fast and reproducible, and the coefficients of variation calculated for the elements using one of the samples were 1.6% for calcium, 3.5% for magnesium and 0.2% for zinc. Results obtained by this method were better than those obtained by other methods for the same samples.
Petawatt laser absorption bounded
Levy, Matthew C.; Wilks, Scott C.; Tabak, Max; Libby, Stephen B.; Baring, Matthew G.
2014-01-01
The interaction of petawatt (1015 W) lasers with solid matter forms the basis for advanced scientific applications such as table-top particle accelerators, ultrafast imaging systems and laser fusion. Key metrics for these applications relate to absorption, yet conditions in this regime are so nonlinear that it is often impossible to know the fraction of absorbed light f, and even the range of f is unknown. Here using a relativistic Rankine-Hugoniot-like analysis, we show for the first time that f exhibits a theoretical maximum and minimum. These bounds constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. For applications needing to circumvent the absorption bounds, these results will accelerate a shift from solid targets, towards structured and multilayer targets, and lead the development of new materials. PMID:24938656
Convection coefficients at building surfaces
NASA Astrophysics Data System (ADS)
Kammerud, R. C.; Altmayer, E.; Bauman, F. S.; Gadgil, A.; Bohn, M.
1982-09-01
Correlations relating the rate of heat transfer from the surfaces of rooms to the enclosed air are being developed, based on empirical and analytic examinations of convection in enclosures. The correlations express the heat transfer rate in terms of boundary conditions relating to room geometry and surface temperatures. Work to date indicates that simple convection coefficient calculation techniques can be developed, which significantly improve accuracy of heat transfer predictions in comparison with the standard calculations recommended by ASHRAE.
Polarization dependence of absorption by bound electrons in self-assembled quantum dots
NASA Astrophysics Data System (ADS)
Ameen, Tarek A.; El-Batawy, Yasser M.
2013-05-01
In this paper, the effects of the incident light polarization on the bound to continuum linear absorption coefficient of quantum dot devices have been investigated. The study is based on the effective mass theory and the Non Equilibrium Green's Function formalism. For the bound to continuum component of the absorption coefficient, both of in-plane and perpendicular polarization effects are studied for different sizes of conical quantum dots. Generally, decreasing the dot's dimensions results in an increase of the in-plane polarized light absorption and in moving the absorption peak towards longer wavelengths. On the other hand, decreasing the dot's dimensions results in a decrease of the perpendicularly polarized light absorption coefficient and in moving the absorption peak towards longer wavelengths.
An in silico skin absorption model for fragrance materials.
Shen, Jie; Kromidas, Lambros; Schultz, Terry; Bhatia, Sneha
2014-12-01
Fragrance materials are widely used in cosmetics and other consumer products. The Research Institute for Fragrance Materials (RIFM) evaluates the safety of these ingredients and skin absorption is an important parameter in refining systemic exposure. Currently, RIFM's safety assessment process assumes 100% skin absorption when experimental data are lacking. This 100% absorption default is not supportable and alternate default values were proposed. This study aims to develop and validate a practical skin absorption model (SAM) specific for fragrance material. It estimates skin absorption based on the methodology proposed by Kroes et al. SAM uses three default absorption values based on the maximum flux (J(max)) - namely, 10%, 40%, and 80%. J(max) may be calculated by using QSAR models that determine octanol/water partition coefficient (K(ow)), water solubility (S) and permeability coefficient (K(p)). Each of these QSAR models was refined and a semi-quantitative mechanistic model workflow is presented. SAM was validated with a large fragrance-focused data set containing 131 materials. All resulted in predicted values fitting the three-tiered absorption scenario based on Jmax ranges. This conservative SAM may be applied when fragrance material lack skin absorption data.
Ozone absorption into excised porcine and sheep tracheae by a bolus-response method
Ben-Jebria, A.; Hu, S.C.; Kitzmiller, E.L.; Ultman, J.S. )
1991-12-01
The absorption of ozone (O3) into excised porcine and sheep tracheae was characterized by a bolus-response experiment in which a bolus with a peak O3 concentration of 1 ppm was rapidly injected into a steadily flowing airstream entering the trachea. Using a fast-responding chemiluminescent analyzer of the authors design, the O3 concentration curves at the proximal end (i.e., the bolus input) and at the distal end (i.e., the response) of the trachea were monitored. Each concentration curve was numerically integrated, and the fraction of O3 absorbed in the trachea was obtained by subtracting from unity the ratio of the response integral to the bolus input integral. Average values of ozone-absorbed fraction decreased from about 0.50 to 0.15 at increasing airflows from 50 to 200 ml/sec. A diffusion theory that includes the effects of bulk convection, axial dispersion, and first-order absorption was developed to relate the fractional absorption to an overall mass transfer coefficient (K). The results indicate that K is independent of airflow, suggesting that the diffusion resistance in mucus is much greater than that in the gas phase. The time-weighted integrals of the concentration curves were also computed, allowing the mean residence time of O3 in the trachea (delta tau) to be determined. As predicted by the diffusion theory, delta tau was inversely related to the rate of O3 absorption.
NASA Technical Reports Server (NTRS)
Hood, L. L.
1983-01-01
A modeling analysis is carried out of six experimental phase space density profiles for nearly equatorially mirroring protons using methods based on the approach of Thomsen et al. (1977). The form of the time-averaged radial diffusion coefficient D(L) that gives an optimal fit to the experimental profiles is determined under the assumption that simple satellite plus Ring E absorption of inwardly diffusing particles and steady-state radial diffusion are the dominant physical processes affecting the proton data in the L range that is modeled. An extension of the single-satellite model employed by Thomsen et al. to a model that includes multisatellite and ring absorption is described, and the procedures adopted for estimating characteristic satellite and ring absorption times are defined. The results obtained in applying three representative solid-body absorption models to evaluate D(L) in the range where L is between 4 and 16 are reported, and a study is made of the sensitivity of the preferred amplitude and L dependence for D(L) to the assumed model parameters. The inferred form of D(L) is then compared with that which would be predicted if various proposed physical mechanisms for driving magnetospheric radial diffusion are operative at Saturn.
Absorption by H2O and H2O-N2 mixtures at 153 GHz
NASA Technical Reports Server (NTRS)
Bauer, A.; Godon, M.; Carlier, J.; Ma, Q.; Tippings, R. H.
1993-01-01
New experimental data on and a theoretical analysis of the absorption coefficient at 153 GHz are presented for pure water vapor and water vapor-nitrogen mixtures. This frequency is 30 GHz lower than the resonant frequency of the nearest strong water line (183 GHz) and complements our previous measurements at 213 GHz. The pressure dependence is observed to be quadratic in the case of pure water vapor, while in the case of mixtures there are both linear and quadratic density components. By fitting our experimental data taken at several temperatures we have obtained the temperature dependence of the absorption. Our experimental data are compared to several theoretical models with and without a continuum contribution, and we find that none of the models is in very good agreement with the data; in the case of pure water vapor, the continuum contribution calculated using the recent theoretical absorption gives the best results. In general, the agreement between the data and the various models is less satisfactory than found previously in the high-frequency wing. The anisotropy in the observed absorption differs from that currently used in atmospheric models.
NASA Astrophysics Data System (ADS)
Chehrghani, A.; Torkamany, M. J.
2014-01-01
In this paper, the spectral and nonlinear optical properties of a colloidal solution of platinum nanoparticles (Pt NPs) in water are presented. The Pt NPs were prepared by laser ablation of a Pt metallic target in distilled water using a 1064 nm high frequency Nd:YAG laser. The intensity-dependent nonlinear optical absorption and nonlinear refraction behaviors of the sample exposed to the 532 nm nanosecond laser pulses were investigated by applying the Z-scan technique. The saturated nonlinear absorption coefficient 5.4 × 10-7 cm W-1 was obtained in a saturation intensity of 1.8 × 107 W cm-2. The saturable absorption response of the Pt NPs was switched to the reverse saturable absorption in the higher laser intensities. The nonlinear refractive index that has a negative value was increased from -3.5 × 10-13 cm2 W-1 up to -15 × 10-13 cm2 W-1 by increasing the laser intensity.
Visibility Estimation for Neutron Resonance Absorption Radiography using a Pulsed Neutron Source
NASA Astrophysics Data System (ADS)
Kai, Tetsuya; Maekawa, Fujio; Oshita, Hidetoshi; Sato, Hirotaka; Shinohara, Takenao; Ooi, Motoki; Harada, Masahide; Uno, Shoji; Otomo, Toshiya; Kamiyama, Takashi; Kiyanagi, Yoshiaki
Neutron resonance absorption radiography is a technique to enhance neutron transmission images of specific nucleus at neutron resonance energies. Demonstration measurements by using a lithium-glass pixel type scintillator and a gas electron multiplication (GEM) neutron detector were carried out at NOBORU beam line in MLF/J-PARC for sodium, manganese, cobalt, copper, zinc, molybdenum, cadmium, indium, tantalum and gold. To discuss advantages of the resonance absorption radiography the mass attenuation coefficient at resonance energy of each element was compared to that at 25 meV. In addition a visibility index derived by a resonance peak cross section and a relative width (full width at half maximum divided by its resonance energy) was proposed to summarize visibility of the neutron resonance absorption radiography for natural elements. The values of visibility index and the resonance energy indicated that large advantages of the resonance absorption radiography were obtainable for the following elements: sodium (Na), manganese (Mn), cobalt (Co), rhodium (Rh), silver (Ag), cadmium (Cd), indium (In), xenon (Xe), cesium (Cs), samarium (Sm), europium (Eu), dysprosium (Dy), erbium (Er), thulium (Tm), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), iridium (Ir) and gold (Au).
Enhancement of intensity-dependent absorption in InP and GaAs at 1.9 microns by doping
NASA Technical Reports Server (NTRS)
Li, N.-L.; Bass, M.; Swimm, R.
1985-01-01
It is pointed out that the study of intensity-dependent absorption (IDA) in general, and two-photon absorption (TPA), in particular, has suffered from experimental difficulties and inadequate theoretical models. Bass et al. (1979) could improve the experimental situation by making use of laser calorimetry to obtain directly the TPA coefficient of a medium with a high degree of sensitivity. In the present investigation, the employed technique has been used to study the effect of deep level dopants on IDA in InP and GaAs. It is found that the coefficient for IDA is strongly dependent on the presence of Fe in InP and Cr in GaAs. The conducted investigation had the objective to examine the effect of deep level impurities on IDA processes in InP and GaAs. Fe-doped InP and Cr-doped GaAs were compared with undoped crystals.
An inequality for longitudinal and transverse wave attenuation coefficients.
Norris, Andrew N
2017-01-01
Total absorption, defined as the net flux of energy out of a bounded region averaged over one cycle for time harmonic motion, must be non-negative when there are no sources of energy within the region. This passivity condition places constraints on the non-dimensional absorption coefficients of longitudinal and transverse waves, γL and γT, in isotropic linearly viscoelastic materials. Typically, γL, γT are small, in which case the constraints imply that coefficients of attenuation per unit length, αL, αT, must satisfy the inequality αL/αT≥4cT(3)/3cL(3) where cL, cT are the wave speeds. This inequality, which as far as the author is aware, has not been presented before, provides a relative bound on wave speed in terms of attenuation, or vice versa. It also serves as a check on the consistency of ultrasonic measurements from the literature, with most but not all of the data considered passing the positive absorption test.
Absorption of ultrasound waves during dynamic processes in disperse systems
NASA Astrophysics Data System (ADS)
Kol'tsova, I. S.; Khomutova, A. S.
2016-11-01
Measurements of ultrasound wave absorption are conducted at a frequency of 3 MHz in 3% suspensions of starch, gelatin, and lactose. It is shown that the dynamics of the additional ultrasound wave absorption coefficient in the suspensions carries information on the processes of swelling, dissolution, and the phase and structural periods occurring in the interaction of the disperse and dispersoid phases; it also reflects the influence of the temperature field on these processes.
Ultraviolet absorption spectra of metalorganic molecules diluted in hydrogen gas
NASA Astrophysics Data System (ADS)
Itoh, Hideo; Watanabe, Masanobu; Mukai, Seiji; Yajima, Hiroyoshi
1988-12-01
Ultraviolet absorption spectra of trimethyl gallium, triethyl gallium, and trimethyl aluminum diluted in hydrogen gas were measured as a function of the wavelength (185-350 nm) and the concentration of the molecules (4.8×10 -6 -1.6×10 -4 mol/liter). Their absorbances changed linearly with the concentration of the molecules, which allowed us to calculate the molar absorption coefficients of the molecules on the basis of the Beer-Lambert law.
Absorption of water and lubricating oils into porous nylon
NASA Technical Reports Server (NTRS)
Bertrand, P. A.
1995-01-01
Oil and water absorption from air into sintered porous nylon can be described by infiltration into the pores of the material. This process can be modeled by a diffusion-like mechanism. For water absorption, we find a formal diffusion coefficient of 1.5 x 10(exp -4)sq cm/min when the nylon is initially dry. The diffusion coefficient is 4 x 10(exp -6)sq cm/min when the nylon is oil-impregnated prior to air exposure. In a 52% RH atmosphere, dry nylon absorbs 3% w/w water, and oil-impregnated nylon absorbs 0.6% w/w water. For oil absorption there are three steps: (1) surface absorption and infiltration into (2) larger and (3) smaller pores. Surface absorption is too fast to be measured in these experiments. The diffusion coefficient for the second step is 6 x 10(exp -4)sq cm/min for SRG-60 oil into dry nylon and 4 x 10(exp -4)sq cm/min for air-equilibrated nylon. The diffusion coefficient for the third step is about 1 x 10(exp -6)sq cm/min for both cases. The total amount of oil absorbed is 31% w/w. The interaction between water and nylon is not as strong as that between water and cotton-phenolic: oil can replace water, and only a small amount of water can enter previously oil-impregnated nylon.
NASA Technical Reports Server (NTRS)
Mushotzky, Richard (Technical Monitor); Elvis, Martin
2004-01-01
The aim of the proposal is to investigate the absorption properties of a sample of inter-mediate redshift quasars. The main goals of the project are: Measure the redshift and the column density of the X-ray absorbers; test the correlation between absorption and redshift suggested by ROSAT and ASCA data; constrain the absorber ionization status and metallicity; constrain the absorber dust content and composition through the comparison between the amount of X-ray absorption and optical dust extinction. Unanticipated low energy cut-offs where discovered in ROSAT spectra of quasars and confirmed by ASCA, BeppoSAX and Chandra. In most cases it was not possible to constrain adequately the redshift of the absorber from the X-ray data alone. Two possibilities remain open: a) absorption at the quasar redshift; and b) intervening absorption. The evidences in favour of intrinsic absorption are all indirect. Sensitive XMM observations can discriminate between these different scenarios. If the absorption is at the quasar redshift we can study whether the quasar environment evolves with the Cosmic time.
Optoelectronic properties and Seebeck coefficient in SnSe thin films
NASA Astrophysics Data System (ADS)
Urmila, K. S.; Namitha, T. A.; Rajani, J.; Philip, R. R.; Pradeep, B.
2016-09-01
SnSe thin films of thickness 180 nm have been deposited on glass substrates by reactive evaporation at an optimized substrate temperature of 523 ± 5 K and pressure of 10-5 mbar. The as-prepared SnSe thin films are characterized for their structural, optical and electrical properties by various experimental techniques. The p-type conductivity, near-optimum direct band gap, high absorption coefficient and good photosensitivity of the SnSe thin film indicate its suitability for photovoltaic applications. The optical constants, loss factor, quality factor and optical conductivity of the films are evaluated. The results of Hall and thermoelectric power measurements are correlated to determine the density of states, Fermi energy and effective mass of carriers and are obtained as 2.8 × 1017 cm-3, 0.03 eV and 0.05m 0 respectively. The high Seebeck coefficient ≈ 7863 μV/K, reasonably good power factor ≈ 7.2 × 10-4 W/(m·K2) and thermoelectric figure of merit ≈ 1.2 observed at 42 K suggests that, on further work, the prepared SnSe thin films can also be considered as a possible candidate for cryogenic thermoelectric applications.
Experimental determination of partition coefficient for β-pinene ozonolysis products in SOA
NASA Astrophysics Data System (ADS)
Gensch, Iulia; Hohaus, Thorsten; Kimmel, Joel; Jayne, John T.; Worsnop, Douglas R.; Kiendler-Scharr, Astrid
2013-04-01
In the present study, simultaneous measurement of β-pinene ozonolysis products in the gas phase by Proton Transfer Reaction - Time of Flight Mass Spectrometry (PTR-ToFMS) and particle phase by using an Aerosol Collection Module coupled to a Gas Chromatograph - Mass Spectrometer (ACM-GC-MS) were employed to determine the equilibrium partitioning coefficient (Kp) of several semi-volatile organic species. Mean Kp values of 6.7 10-5 ± 2.5 10-5 for nopinone, 4.8 10-4 ± 1.7 10-4 for apoverbenone, 7.0 10-4 ± 1.7 10-4 for oxonopinone and 1.9 10-3 ± 1.1 10-3 for hydroxynopinone were obtained. The results were compared with calculations arising from studies on the gas-particle partitioning, based on the Pankow absorption model. The experimental partition coefficients are two to three orders of magnitudes higher than the calculated values, leading to the conclusion that the amount of semi-volatile organic compounds in secondary organic aerosol (SOA) is currently underestimated by the theory, thus impacting on the modeling of the organic matter in the atmosphere.
Zhang, Yunlin; Yin, Yan; Wang, Mingzhu; Liu, Xiaohan
2012-05-21
We investigated phytoplankton absorption properties of Lake Taihu, in the spring and summer of 2005 and 2006, and for 17 days studied laboratory cultures of Scenedesmus obliquus (chlorophyta) and Microcystis aeruginosa (cyanophyta) to determine the effect of phytoplankton community composition and cell size on the absorption properties. There were significant seasonal differences in phytoplankton community composition and absorption coefficients. In spring, the phytoplankton community was dominated by chlorophyta with large cells, whereas in summer was dominated by cyanophyta with small cells. Phytoplankton absorption coefficients increased significantly from spring to summer, with the increase in chlorophyll a (Chla) concentration. In addition, Chla-specific absorption coefficients increased with the phytoplankton community succession from chlorophyta to cyanophyta. In culture, the cells density of S. obliquus was generally lower than that of M. aeruginosa, and Chla concentrations of S. obliquus were significantly higher than those of M. aeruginosa. Correspondingly, the Chla-specific absorption coefficients of S. obliquus were significantly lower than those of M. aeruginosa. Significant exponential correlations were found between absorption and Chla-specific absorption coefficients and Chla concentration for S. obliquus and M. aeruginosa. In addition, we developed a model to predict absorption and Chla-specific absorption coefficients using Chla concentration and cell size when data from two species was grouped together. Field and experimental results both showed that the Chla-specific absorption coefficients of cyanophyta were significantly higher than those of chlorophyta. The variability in specific absorption can attributed to phytoplankton community composition, cell size and pigment composition. As phytoplankton community composition changed significantly with season in the lake, and as variation in the cell sizes and accessory pigments of the phytoplankton
Multiple element airfoils optimized for maximum lift coefficient.
NASA Technical Reports Server (NTRS)
Ormsbee, A. I.; Chen, A. W.
1972-01-01
Optimum airfoils in the sense of maximum lift coefficient are obtained for incompressible fluid flow at large Reynolds number. The maximum lift coefficient is achieved by requiring that the turbulent skin friction be zero in the pressure rise region on the airfoil upper surface. Under this constraint, the pressure distribution is optimized. The optimum pressure distribution is a function of Reynolds number and the trailing edge velocity. Geometries of those airfoils which will generate these optimum pressure distributions are obtained using a direct-iterative method which is developed in this study. This method can be used to design airfoils consisting of any number of elements. Numerical examples of one- and two-element airfoils are given. The maximum lift coefficients obtained range from 2 to 2.5.
Atmospheric particulate absorption and black carbon measurement.
Lindberg, J D; Douglass, R E; Garvey, D M
1999-04-20
It is convenient to measure the optical attenuation A of the combination of a layer of atmospheric particulate matter and the quartz fiber filter on which it has been collected. The problem of relating A to the absorption and scattering coefficients k and s of the particulate matter itself is treated as a problem in diffuse reflectance spectroscopy using the KubelkaMunk theory. The results show that although, in general, A is a nonlinear function strongly dependent on both s and k, for a limited range of s and sample thickness d, A can be a practically linear function of k. Fortunately, this range includes that common to atmospheric particulate samples. Furthermore, it is shown that if the filter's reflectance is sufficiently high, A can be nearly independent of s. This is in agreement with experimental and, for the limiting case when the substrate filter reflectance is unity, theoretical results obtained by other researchers. Use of such measurements of A as a means of determining the black carbon mass loading C on a filter is also investigated. It is shown that when the black carbon mass fraction f(c) is high, as it is for samples collected in large urban areas, A is a predictable and practically linear function of C. However, when f(c) is low, as it is for many rural locations, then the slope of the function A(C) is strongly dependent on f(c), leading to possible overestimates of C. This problem can be alleviated by making the measurement of A at near-infrared wavelengths rather than in the visible spectrum.