NASA Astrophysics Data System (ADS)
Li, Xiaoqi; Jiang, Huabei
2013-02-01
We present a study through extensive simulation that considers the impact of inhomogeneous optical scattering coefficient distribution on recovery of optical absorption coefficient maps using tomographic photoacoustic data collected from media mimicking breast tissue. We found that while the impact of scattering heterogeneities/targets is modest on photoacoustic recovery of optical absorption coefficients, the impact of scattering contrast caused by adipose tissue, a layer of normal tissue along the boundary of the breast, is dramatic on reconstruction of optical absorption coefficients using photoacoustic data—up to 25.8% relative error in recovering the absorption coefficient is estimated in such cases. To overcome this problem, we propose a new method to enhance photoacoustic recovery of the optical absorption coefficient in heterogeneous media by considering inhomogeneous scattering coefficient distribution provided by diffuse optical tomography (DOT). Results from extensive simulations show that photoacoustic recovery of absorption coefficient maps can be improved considerably with a priori scattering information from DOT.
Radiometer gives true absorption and emission coefficients
NASA Technical Reports Server (NTRS)
Fymat, A. L.
1977-01-01
Novel radiometer, unaffected by scattering and polarization, measures true absorption and emmission coefficients for arbitrary mixture of gases and polluting particles. It has potential astronomical, meteorological, and environmental applications, such as determination of radiative heat budget, aerosol relative concentration, and morphology of cloud, haze, and fog formations. Data and temperature can be coupled directly to small computer for online calculation of radiation coefficients.
Determination of absorption coefficients of thin films
Lodenquai, J.F. )
1994-08-01
The equations that are usually presented as those used to determine the absorption coefficients of materials in film form based on measurements of transmission and reflection coefficients are fundamentally incorrect. These equations omit a multiplicative factor arising from the complex nature of the refractive indices of the materials. This factor enters explicitly into the relationship between the transmission and reflection coefficients for such materials and is not necessarily close to unity, although in practice this factor can be approximated by unity at least in the infrared through the optical range of wavelengths.
Inversion of instantaneous equivalent absorption coefficient and its application
Weihua, W. )
1992-01-01
Absorption coefficient is an important parameter for reservoir description. The major troubles in extracting absorption coefficient from seismic data are amplitude and waveform distortions; they greatly restrict the inversion which is based on reflection amplitude variation or reflection frequency variation. This paper presents a new method which avoids amplitude and uses waveform variation gradient in wave propagation to make the inversion of absorption coefficient. Apparent absorption coefficient and pseudo absorption coefficient are adopted so as to remove the influence which the waveform distortion due to thin bed tuning brings to absorption coefficient extraction. The final instantaneous equivalent absorption coefficient, a true absorption coefficient which reflects real absorptive character of a seismic medium, can be obtained by subtracting the pseudo absorption coefficient (inversely calculated using maximum entropy) from the apparent absorption coefficient the authors have calculated.
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.
Linear and nonlinear optical absorption coefficients of spherical dome shells
NASA Astrophysics Data System (ADS)
Guo, Kangxian; Liu, Guanghui; Huang, Lu; Zheng, Xianyi
2015-08-01
Linear and nonlinear optical absorption coefficients of spherical dome shells are theoretically investigated within analytical wave functions and numerical quantized energy levels. Our results show that the inner radius, the outer radius and the cut-off angle of spherical dome shells have great influences on linear and nonlinear optical absorption coefficients as well as the total optical absorption coefficients. It is found that with the increase of the inner radius and the outer radius, linear and nonlinear optical absorption coefficients exhibit a blueshift and a redshift, respectively. However, with the increase of the cut-off angle, linear and nonlinear optical absorption coefficients do not shift. Besides, the resonant peaks of linear and nonlinear optical absorption coefficients climb up and then decrease with increasing the cut-off angle. The influences of the incident optical intensity on the total optical absorption coefficients are studied. It is found that the bleaching effect occurs at higher incident optical intensity.
Effect of applied mechanical stress on absorption coefficient of compounds
Gupta, Manoj Kumar; Singh, Gurinderjeet; Dhaliwal, A. S.; Kahlon, K. S.
2015-08-28
The absorption coefficient of given materials is the parameter required for the basic information. The measurement of absorption coefficient of compounds Al{sub 2}O{sub 3}, CaCO{sub 3}, ZnO{sub 2}, SmO{sub 2} and PbO has been taken at different incident photon energies 26, 59.54, 112, 1173, 1332keV. The studies involve the measurements of absorption coefficient of the self supporting samples prepared under different mechanical stress. This mechanical stress is render in terms of pressure up to 0-6 ton by using hydraulic press. Measurements shows that absorption coefficient of a material is directly proportional to applied mechanical stress on it up to some extent then become independent. Experimentally measured results are in fairly good agreement with in theoretical values obtained from WinXCOM.
Effect of applied mechanical stress on absorption coefficient of compounds
NASA Astrophysics Data System (ADS)
Gupta, Manoj Kumar; Singh, Gurinderjeet; Dhaliwal, A. S.; Kahlon, K. S.
2015-08-01
The absorption coefficient of given materials is the parameter required for the basic information. The measurement of absorption coefficient of compounds Al2O3, CaCO3, ZnO2, SmO2 and PbO has been taken at different incident photon energies 26, 59.54, 112, 1173, 1332keV. The studies involve the measurements of absorption coefficient of the self supporting samples prepared under different mechanical stress. This mechanical stress is render in terms of pressure up to 0-6 ton by using hydraulic press. Measurements shows that absorption coefficient of a material is directly proportional to applied mechanical stress on it up to some extent then become independent. Experimentally measured results are in fairly good agreement with in theoretical values obtained from WinXCOM.
Photosensitizer absorption coefficient modeling and necrosis prediction during Photodynamic Therapy.
Salas-García, Irene; Fanjul-Vélez, Félix; Arce-Diego, José Luis
2012-09-01
The development of accurate predictive models for Photodynamic Therapy (PDT) has emerged as a valuable tool to adjust the current therapy dosimetry to get an optimal treatment response, and definitely to establish new personal protocols. Several attempts have been made in this way, although the influence of the photosensitizer depletion on the optical parameters has not been taken into account so far. We present a first approach to predict the spatio-temporal variation of the photosensitizer absorption coefficient during PDT applied to dermatological diseases, taking into account the photobleaching of a topical photosensitizer. This permits us to obtain the photons density absorbed by the photosensitizer molecules as the treatment progresses and to determine necrosis maps to estimate the short term therapeutic effects in the target tissue. The model presented also takes into account an inhomogeneous initial photosensitizer distribution, light propagation in biological media and the evolution of the molecular concentrations of different components involved in the photochemical reactions. The obtained results allow to investigate how the photosensitizer depletion during the photochemical reactions affects light absorption by the photosensitizer molecules as the optical radiation propagates through the target tissue, and estimate the necrotic tumor area progression under different treatment conditions. PMID:22704663
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.
[Influencing factors in measuring absorption coefficient of suspended particulate matters].
Yu, Xiao-long; Shen, Fang; Zhang, Jin-fang
2013-05-01
Absorption coefficient of suspended particulate matters in natural water is one of the key parameters in ocean color remote sensing. In order to study the influencing factors that affect the measurement, a series of experiments were designed to measure samples using transmittance method (T method), transmittance-reflectance method (T-R method) and absorptance method (A method). The results shows that absorption coefficient measured by the A method has a much lower error compared to the T method and T-R method due to influencing factors,such as filter-to-filter variations, water content of the filter, and homogeneity of filter load and so on. Another factor influence absorption coefficient is path-length amplification induced by multiple scattering inside the filter. To determine the path-length amplification, the true absorption was measured by AC-s (WetLabs). The linear fitting result shows that the mean path-length amplification is much higher for the A method than that of the T-R method and the T method (4.01 versus 2.20 and 2.32), and the corresponding correlation coefficient are 0.90, 0.87 and 0.80. For the A method and the T-R method, higher correlation coefficients are calculated when using polynomial fitting, and the value are 0.95 and 0.94. Analysis of the mean relative error caused by different influencing factors indicates that path-length amplification is the largest error source in measuring the absorption coefficient. PMID:23914523
Absorption coefficients of a hydrogen plasma for laser radiation
NASA Technical Reports Server (NTRS)
Stallcop, J. R.
1974-01-01
The formalism for the calculation of the absorption of radiation by a hydrogen plasma at common laboratory conditions is summarized. The hydrogen plasma absorption coefficient for laser radiation has been computed for a wide range of electron densities and temperatures (10,000-40,000 K). The results of this computation are presented in a graphical form that permits a determination of the absorption coefficient for the following laser wavelengths: 0.176, 0.325, 0.337, 0.442, 0.488, 0.515, 0.633, 0.694, 1.06, 1.15, 2.36, 3.39, 5.40 and 10.6 microns. The application of these results and laser radiation absorption measurements to plasma diagnostics is discussed briefly.
Scattering and absorption coefficients of silica-doped alumina aerogels.
Fu, Tairan; Tang, Jiaqi; Chen, Kai; Zhang, Fan
2016-02-01
Alumina-based aerogels are especially useful in many applications due to their excellent stability at high temperatures. This study experimentally analyzed the radiative properties of silica-doped alumina aerogels through spectral directional-hemispherical measurements for wavelengths of 0.38-25 μm. The silica-doped alumina aerogel samples were prepared with a 1.4∶1 molar ratio of silica to alumina. A two-flux model was used to describe the radiation propagation in a 1D scattering absorbing sample to derive expressions for the normal-hemispherical transmittances and reflectances based on the transport approximation. The normal-hemispherical transmittances and reflectances were measured at various spectral wavelengths and sample thicknesses using the integrating sphere method. The spectral absorption and transport scattering coefficients of silica-doped alumina aerogels were then determined from the measured normal-hemispherical data. The absorption and transport scattering coefficients of silica-doped alumina aerogels are (0.1 cm-1, 36 cm-1) and (0.1 cm-1, 112 cm-1) for wavelengths of 0.38-8.0 μm. The spectral transport scattering coefficient varies in the opposite direction from the spectral absorption coefficient for various wavelengths. The radiative properties for silica and alumina aerogels were quite different for the absorption coefficient for wavelengths of 2.5-8.0 μm and for the transport scattering coefficient for wavelengths of 0.38-2.5 and 3.5-6.0 μm. The measured radiative properties were used to predict the spectral normal-hemispherical reflectance and transmittance of the silica-doped alumina aerogels for various sample thicknesses and wavelengths. The predicted values do not change for the sample thicknesses greater than a critical value. The analysis provides valuable reference data for alumina aerogels for high-temperature applications. PMID:26836071
Absorption-coefficient-determination method for particulate materials.
Lindberg, J D; Douglass, R E; Garvey, D M
1994-07-01
A method is presented for determining the optical absorption coefficient, or the imaginary refractive index, of particulate material that has been collected from aerosols or hydrosols by means of filtration. The method, based on the Kubelka-Munk theory of diffuse reflectance, is nondestructive and requires no other knowledge of the sample than the amount present, the specific gravity, and an estimate of the real index of refraction. The theoretical development of the method is discussed along with an analysis of photometric and gravimetric errors. We test the method by comparing results obtained for powdered didymium glass with measurements made before the glass was crushed. An example of the method's application to the determination of the absorption coefficient of atmospheric dust at UV, visible, and near-IR wavelengths is also presented. PMID:20935789
A high absorption coefficient DL-MPP imitating owl skin
NASA Astrophysics Data System (ADS)
Guo, Lijun; Zhao, Zhan; Kong, Deyi; Wu, Shaohua; Du, Lidong; Fang, Zhen
2012-11-01
This paper proposes a high absorption coefficient micro-perforated panel (MPP) imitating owl skin structure for acoustic noise reduction. Compared to the traditional micro-perforated panel, this device has two unique characteristics-simulating the owl skin structure, its radius of perforated apertures even can be as small as 55μ, and its material is silicon and fabricated by micro-electrical mechanical system (MEMS) technology; So that its absorption coefficients of acoustic noise for normal incidence sound wave whose frequencies arrange from 1.5 kHz to 6.0 kHz are all above 0.8 which is the owl's hunts sensitivity frequency band. Double leaf MPP fabricated by MEMS technology is an absolutely bionic success in functional-imitation.
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.
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.
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.
Highlighting material structure with transmission electron diffraction correlation coefficient maps.
Kiss, Ákos K; Rauch, Edgar F; Lábár, János L
2016-04-01
Correlation coefficient maps are constructed by computing the differences between neighboring diffraction patterns collected in a transmission electron microscope in scanning mode. The maps are shown to highlight material structural features like grain boundaries, second phase particles or dislocations. The inclination of the inner crystal interfaces are directly deduced from the resulting contrast. PMID:26866276
Oceanic tide maps and spherical harmonic coefficients from Geosat altimetry
NASA Technical Reports Server (NTRS)
Cartwright, D. E.; Ray, R. D.; Sanchez, B. V.
1991-01-01
Maps and tables for the global ocean tides, 69 degree N to 68 degree S, derived from two years of Geosat altimetry are presented. Global maps of local and Greenwich admittance of the (altimetric) ocean tide, and maps of amplitude and Greenwich phase lag of the ocean tide are shown for M(sub 2), S(sub 2), N(sub 2), O(sub 1), and K(sub 1). Larger scale maps of amplitude and phases are also shown for regional areas of special interest. Spherical harmonic coefficients of the ocean tide through degree and order 8 are tabulated for the six major constituents.
Absorption coefficient at 10.6 microm in CdTe modulator crystals.
Tucker, A W; Birnbaum, M; Montes, H; Fincher, C L
1982-08-15
The bulk and surface absorption coefficients of CdTe modulator crystals at 10.6 microm were compared with those of single-crystal KC1 and NaCl which served to calibrate the laser calorimeter. High-resistivity (>10(7) ohm/cm) CdTe crystals exhibited a bulk absorption coefficient of 0.0014 cm(-1). PMID:20396150
NASA Technical Reports Server (NTRS)
Molina, L. T.; Grant, W. B.
1984-01-01
The absorption spectra of three hydrazines and four of their air-oxidation products were measured in the 9-12-micron spectral region with a Fourier transform infrared (FTIR) spectrometer with a 0.05-kayser resolution to determine absorption coefficients at CO2 and tunable diode laser wavelengths. The measurements agreed well with published CO2 laser determinations for many of the absorption coefficients, except where the published values are thought to be in error. The coefficients were then used to estimate the sensitivity for remote detection of these gases using CO2 and tunable diode lasers in long-path differential absorption measurements.
Measurement of the absorption coefficient of acoustical materials using the sound intensity method
NASA Technical Reports Server (NTRS)
Atwal, Mahabir S.; Crocker, Malcolm J.
1987-01-01
In this study the possibility of using the two-microphone sound intensity technique to measure the normal incidence and the random incidence sound absorption coefficient was investigated. The normal incidence absorption coefficient was determined by measuring the intensity incidence on the sample and the intensity reflected by the sample placed in an anechoic chamber. The random incidence absorption coefficient was determined by measuring the intensity incident on the sample and the intensity reflected by the sample placed in a reverberation chamber. Absorption coefficient results obtained by the sound intensity technique were compared with standard techniques, namely the reverberation chamber and the standing wave tube. The major advantages of using the sound intensity technique are that it permits 'in situ' measurements and the absorption coefficient for a large range of frequencies can be obtained from a single measurement.
Dynamic absorption coefficients of CAR and non-CAR resists at EUV
NASA Astrophysics Data System (ADS)
Fallica, Roberto; Stowers, Jason K.; Grenville, Andrew; Frommhold, Andreas; Robinson, Alex P. G.; Ekinci, Yasin
2016-03-01
The dynamic absorption coefficients of several CAR and non-CAR EUV photoresists are measured experimentally using a specifically developed setup in transmission mode at the XIL beamline of the Swiss Light Source. The absorption coefficient α and the Dill parameters ABC were measured with unprecedented accuracy. In general the α of resists match very closely with the theoretical value calculated from elemental densities and absorption coefficients, whereas exceptions are observed. In addition, through the direct measurements of the absorption coefficients and dose-to-clear values, we introduce a new figure of merit called Chemical Sensitivity to account for all the post-absorption chemical reaction ongoing in the resist, which is also predicts a quantitative clearing volume, and respectively clearing radius, due to the photon absorption in the resist. These parameters may help in deeper insight into the underlying mechanisms of EUV concept of clearing volume and clearing radius are then defined and quantitatively calculated.
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.
NASA Astrophysics Data System (ADS)
Müller, T.; Schladitz, A.; Massling, A.; Kaaden, N.; Kandler, K.; Wiedensohler, A.
2009-02-01
ABSTRACT During the SAMUM-1 experiment, absorption coefficients and imaginary parts of refractive indices of mineral dust particles were investigated in southern Morocco. Main absorbing constituents of airborne samples were identified to be iron oxide and soot. Spectral absorption coefficients were measured using a spectral optical absorption photometer (SOAP) in the wavelength range from 300 to 800 nm with a resolution of 50 nm. A new method that accounts for a loading-dependent correction of fibre filter based absorption photometers, was developed. The imaginary part of the refractive index was determined using Mie calculations from 350 to 800 nm. The spectral absorption coefficient allowed a separation between dust and soot absorption. A correlation analysis showed that the dust absorption coefficient is correlated (R2 up to 0.55) with the particle number concentration for particle diameters larger than 0.5 μm, whereas the coefficient of determination R2 for smaller particles is below 0.1. Refractive indices were derived for both the total aerosol and a dust aerosol that was corrected for soot absorption. Average imaginary parts of refractive indices of the entire aerosol are 7.4 × 10-3, 3.4 × 10-3 and 2.0 × 10-3 at wavelengths of 450, 550 and 650 nm. After a correction for the soot absorption, imaginary parts of refractive indices are 5.1 × 10-3, 1.6 × 10-3 and 4.5 × 10-4.
NASA Technical Reports Server (NTRS)
Stallcop, J. R.
1974-01-01
The theory for calculating the absorption of laser radiation by hydrogen is outlined for the temperatures and pressures of common laboratory plasmas. Nonhydrogenic corrections for determining the absorption by helium are also included. The coefficients for the absorption of He-Ne laser radiation at the wavelengths of 0.633, 1.15, and 3.39 microns in a H plasma is presented for temperatures in the range from 10,000 to 40,000 K and electron number densities in the range from 10 to the 15th power to 10 to the 18th power per cu cm. The total absorption of a H-He plasma calculated from this theory is compared with the measured absorption. The theoretical composition of the H-He absorption is analyzed with respect to the significant absorption processes, inverse bremsstrahlung, photoionization, resonance excitation, and photodetachment.
Absorption Coefficient Imaging by Near-Field Scanning Optical Microscopy in Bacteria
NASA Astrophysics Data System (ADS)
de Paula, Ana M.; Chaves, Claudilene R.; Silva, Haroldo B.; Weber, Gerald
2003-06-01
We present a method for obtaining a position-dependent absorption coefficient from near-field scanning optical transmission microscopy. We show that the optical transmission intensity can be combined with the topography, resulting into an absorption coefficient that simplifies the analysis of different materials within a sample. The method is tested with the dye rhodamine 6G, and we show some analysis in biological samples such as bacteria Klebsiella pneumoniae and Pseudomonas aeruginosa . The calculated absorption coefficient images show important details of the bacteria, in particular for P. aeruginosa , in which membrane vesicles are clearly seen.
Binary TLBO algorithm assisted for designing plasmonic nano bi-pyramids-based absorption coefficient
NASA Astrophysics Data System (ADS)
Akhlaghi, Majid; Emami, Farzin; Nozhat, Najmeh
2014-07-01
A new efficient binary optimization method based on Teaching-Learning-Based Optimization (TLBO) algorithm is proposed to design an array of plasmonic nano bi-pyramids in order to achieve maximum absorption coefficient spectrum. In binary TLBO, a group of learners consisting of a matrix with binary entries controls the presence ('1') or the absence ('0') of nanoparticles in the array. Simulation results show that absorption coefficient strongly depends on the localized position of plasmonic nanoparticles. Non-periodic structures have more appropriate response in term of absorption coefficient. This approach is useful in optical applications such as solar cells and plasmonic nano antenna.
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.
NASA Astrophysics Data System (ADS)
Wex, Heike; Neusüß, Christian; Wendisch, Manfred; Stratmann, Frank; Koziar, Christian; Keil, Andreas; Wiedensohler, Alfred; Ebert, Martin
2002-11-01
Comparisons between measured and calculated aerosol scattering, backscattering, and absorption coefficients were made based on in situ, ground-based measurements during the Melpitz INTensive (MINT) and Lindenberg Aerosol Characterization Experiment 1998 (LACE 98) field studies. Furthermore, airborne measurements made with the same type of instruments are reviewed and compared with the ground-based measurements. Agreement between measured and calculated values is on the order of ±20% for scattering and backscattering coefficients. A sensitivity analysis showed a large influence on the calculated particle scattering and backscattering coefficients resulting from sizing uncertainties in the measured number size distributions. Measured absorption coefficients were significantly smaller than the corresponding calculated values. The largest uncertainty for the calculated absorption coefficients resulted from the size-dependent fraction of elemental carbon (EC) of the aerosol. A correction for the measured fractions of EC could significantly improve the agreement between measured and calculated absorption coefficients. The overall uncertainty of the calculated values was investigated with a Monte Carlo method by simultaneously and randomly varying the input parameters of the calculations, where the variation of each parameter was bounded by its uncertainty. The measurements were mostly found to be within the range of uncertainties of the calculations, with uncertainties for the calculated scattering and backscattering coefficients of about ±20% and for the absorption coefficients of about ±30%. Thus, to increase the accuracy of calculated scattering, backscattering, and absorption coefficients, it is crucial to further reduce the error in particle number size distribution measurement techniques. In addition, further improvement of the techniques for measuring absorption coefficients and further investigation of the measurement of the fraction of EC of the aerosol is
Moore, Travis J; Jones, Matthew R
2015-02-20
Knowledge of the spectral absorption coefficient of fused silica optical fibers is important in modeling heat transfer in the processes and applications in which these fibers are used. An experimental method used to measure the spectral absorption coefficient of optical fibers is presented. Radiative energy from a blackbody radiator set at different temperatures is directed through the optical fibers and into an FTIR spectrometer. Spectral instrument response functions are calculated for different fiber lengths. The ratios of the slopes of the instrument response functions for the different lengths of fibers are used to solve for the spectral absorption coefficient of the fibers. The spectral absorption coefficient of low OH pure fused silica optical fibers is measured between the wavelengths 1.5 and 2.5 μm. PMID:25968202
A method for determination mass absorption coefficient of gamma rays by Compton scattering.
El Abd, A
2014-12-01
A method was proposed for determination mass absorption coefficient of gamma rays for compounds, alloys and mixtures. It is based on simulating interaction processes of gamma rays with target elements having atomic numbers from Z=1 to Z=92 using the MCSHAPE software. Intensities of Compton scattered gamma rays at saturation thicknesses and at a scattering angle of 90° were calculated for incident gamma rays of different energies. The obtained results showed that the intensity of Compton scattered gamma rays at saturations and mass absorption coefficients can be described by mathematical formulas. These were used to determine mass absorption coefficients for compound, alloys and mixtures with the knowledge of their Compton scattered intensities. The method was tested by calculating mass absorption coefficients for some compounds, alloys and mixtures. There is a good agreement between obtained results and calculated ones using WinXom software. The advantages and limitations of the method were discussed. PMID:25241360
NASA Technical Reports Server (NTRS)
Billman, K. W.; Rowley, P. D.; Stallcop, J. R.; Presley, L.
1974-01-01
The absorption coefficients of 0.633-, 1.15-, and 3.39-micron laser radiation for a homogeneous H-He plasma have been measured in the temperature range from 12.2 to 21.7 (x 1000 K) and in the electron number density range 0.45 to 6.5 (x 10 to the 17th power per cu cm). Good agreement is found between the experimentally determined total absorption for each of the wavelengths and that calculated from theory. Furthermore, because the 3.39-micron absorption is dominated by inverse bremsstrahlung, while the 0.633-micron absorption is dominated by photoionization and resonance absorption, the experiment indicates a correct assessment by the theory of these individual absorption mechanisms.
Hoge, F E; Wright, C W; Lyon, P E; Swift, R N; Yungel, J K
1999-12-20
Oceanic radiance model inversion methods are used to develop a comprehensive algorithm for retrieval of the absorption coefficients of phycourobilin (PUB) pigment, type I phycoerythrobilin (PEB) pigment rich in PUB, and type II PEB deficient in PUB pigment (together with the usual "big three" inherent optical properties: the total backscattering coefficient and the absorption coefficients of chromophoric dissolved organic matter (CDOM)-detritus and phytoplankton). This fully modeled inversion algorithm is then simplified to yield a hybrid modeled-unmodeled inversion algorithm in which the phycoerythrin (PE) absorption coefficient is retrieved as unmodeled 488-nm absorption (which exceeds the modeled phytoplankton and the CDOM-detritus absorption coefficients). Each algorithm was applied to water-leaving radiances, but only hybrid modeled-unmodeled inversions yielded viable retrievals of the PE absorption coefficient. Validation of the PE absorption coefficient retrieval was achieved by relative comparison with airborne laser-induced PEB fluorescence. The modeled-unmodeled retrieval of four inherent optical properties by direct matrix inversion is rapid and well conditioned, but the accuracy is strongly limited by the accuracy of the three principal inherent optical property models across all four spectral bands. Several research areas are identified to enhance the radiance-model-based retrievals: (a) improved PEB and PUB absorption coefficient models, (b) PE spectral shifts induced by PUB chromophore substitution at chromophore binding sites, (c) specific absorption-sensitive phytoplankton absorption modeling, (d) total constituent backscattering modeling, (e) unmodeled carotinoid and phycocyanin absorption that are not now accounted for in the chlorophyll-dominated phytoplankton absorption coefficient model, and (f) iterative inversion techniques to solve for six constituents with only five radiances. Although considerable progress has been made toward the
NASA Astrophysics Data System (ADS)
Hoge, Frank E.; Wright, C. Wayne; Lyon, Paul E.; Swift, Robert N.; Yungel, James K.
1999-12-01
Oceanic radiance model inversion methods are used to develop a comprehensive algorithm for retrieval of the absorption coefficients of phycourobilin (PUB) pigment, type I phycoerythrobilin (PEB) pigment rich in PUB, and type II PEB deficient in PUB pigment (together with the usual big three inherent optical properties: the total backscattering coefficient and the absorption coefficients of chromophoric dissolved organic matter (CDOM) detritus and phytoplankton). This fully modeled inversion algorithm is then simplified to yield a hybrid modeled unmodeled inversion algorithm in which the phycoerythrin (PE) absorption coefficient is retrieved as unmodeled 488-nm absorption (which exceeds the modeled phytoplankton and the CDOM detritus absorption coefficients). Each algorithm was applied to water-leaving radiances, but only hybrid modeled unmodeled inversions yielded viable retrievals of the PE absorption coefficient. Validation of the PE absorption coefficient retrieval was achieved by relative comparison with airborne laser-induced PEB fluorescence. The modeled unmodeled retrieval of four inherent optical properties by direct matrix inversion is rapid and well conditioned, but the accuracy is strongly limited by the accuracy of the three principal inherent optical property models across all four spectral bands. Several research areas are identified to enhance the radiance-model-based retrievals: (a) improved PEB and PUB absorption coefficient models, (b) PE spectral shifts induced by PUB chromophore substitution at chromophore binding sites, (c) specific absorption-sensitive phytoplankton absorption modeling, (d) total constituent backscattering modeling, (e) unmodeled carotinoid and phycocyanin absorption that are not now accounted for in the chlorophyll-dominated phytoplankton absorption coefficient model, and (f) iterative inversion techniques to solve for six constituents with only five radiances. Although considerable progress has been made toward the satellite
Apparent diffusion coefficient map of a case of extramedullary plasmacytoma
Ramachandran, Amrutha; Inyang, Alero F; Subhawong, Ty K
2016-01-01
Plasmacytomas are rare tumors, which arise from the monoclonal proliferation of malignant plasma cells. They may affect either the bony skeleton or rarely the soft tissues, the latter being referred to as extramedullary or extraosseous. We report a case of an extramedullary plasmacytoma that presented as a soft tissue mass involving the muscles of the left leg, in a patient who was previously treated for multiple myeloma. We describe the MR Imaging characteristics of the tumor and highlight the usefulness of diffusion-weighted imaging with apparent diffusion coefficient mapping. PMID:27200157
NASA Astrophysics Data System (ADS)
Hirasawa, T.; Ishihara, M.; Tsujita, K.; Hirota, K.; Irisawa, K.; Kitagaki, M.; Fujita, M.; Kikuchi, M.
2012-02-01
In photo-acoustic (PA) imaging, valuable medical applications based on optical absorption spectrum such as contrast agent imaging and blood oxygen saturation measurement have been investigated. In these applications, there is an essential requirement to determine optical absorption coefficients accurately. In present, PA signal intensities have been commonly used to determine optical absorption coefficients. This method achieves practical accuracy by combining with radiative transfer analysis. However, time consumption of radiative transfer analysis and effects of signal generation efficiencies were problems of this method. In this research, we propose a new method to determine optical absorption coefficients using continuous wavelet transform (CWT). We used CWT to estimate instantaneous frequencies of PA signals which reflects optical absorption distribution. We validated the effectiveness of CWT in determination of optical absorption coefficients through an experiment. In the experiment, planar shaped samples were illuminated to generate PA signal. The PA signal was measured by our fabricated PA probe in which an optical fiber and a ring shaped P(VDFTrFE) ultrasound sensor were coaxially aligned. Optical properties of samples were adjusted by changing the concentration of dye solution. Tunable Ti:Sapphire laser (690 - 1000 nm) was used as illumination source. As a result, we confirmed strong correlation between optical absorption coefficients of samples and the instantaneous frequency of PA signal obtained by CWT. Advantages of this method were less interference of light transfer and signal generation efficiency.
Experiment to Determine the Absorption Coefficient of Gamma Rays as a Function of Energy.
ERIC Educational Resources Information Center
Ouseph, P. J.; And Others
1982-01-01
Simpler than x-ray diffractometer experiments, the experiment described illustrates certain concepts regarding the interaction of electromagnetic rays with matter such as the exponential decrease in the intensity with absorber thickness, variation of the coefficient of absorption with energy, and the effect of the K-absorption edge on the…
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.
High speed friction microscopy and nanoscale friction coefficient mapping
NASA Astrophysics Data System (ADS)
Bosse, James L.; Lee, Sungjun; Andersen, Andreas Sø; Sutherland, Duncan S.; Huey, Bryan D.
2014-11-01
As mechanical devices in the nano/micro length scale are increasingly employed, it is crucial to understand nanoscale friction and wear especially at technically relevant sliding velocities. Accordingly, a novel technique has been developed for friction coefficient mapping (FCM), leveraging recent advances in high speed AFM. The technique efficiently acquires friction versus force curves based on a sequence of images at a single location, each with incrementally lower loads. As a result, true maps of the coefficient of friction can be uniquely calculated for heterogeneous surfaces. These parameters are determined at a scan velocity as fast as 2 mm s-1 for microfabricated SiO2 mesas and Au coated pits, yielding results that are identical to traditional speed measurements despite being ~1000 times faster. To demonstrate the upper limit of sliding velocity for the custom setup, the friction properties of mica are reported from 200 µm s-1 up to 2 cm s-1. While FCM is applicable to any AFM and scanning speed, quantitative nanotribology investigations of heterogeneous sliding or rolling components are therefore uniquely possible, even at realistic velocities for devices such as MEMS, biological implants, or data storage systems.
Tunable diode laser measurements of HO2NO2 absorption coefficients near 12.5 microns
NASA Technical Reports Server (NTRS)
May, R. D.; Molina, L. T.; Webster, C. R.
1988-01-01
A tunable diode laser spectrometer has been used to measure absorption coefficients of peroxynitric acid (HO2NO2) near the 803/cm Q branch. HO2NO2 concentrations in a low-pressure flowing gas mixture were determined from chemical titration procedures and UV absorption spectroscopy. The diode laser measured absorption coefficients, at a spectral resolution of better than 0.001/cm, are about 10 percent larger than previous Fourier transform infrared measurements made at a spectral resolution of 0.06/cm.
Hessler, J.P.; Ogren, P.J.
1992-08-31
A technique was developed for determining relative importance and correlation between reactions making up a complex kinetic system. This technique was used to investigate measurements of optical absorption cross sections and the correlation between cross sections and measured rate coefficients. It is concluded that (1) species, initial conditions, and temporal regions may be identified where cross sections may be measured without interference from the kinetic behavior of the observed species and (2) experiments designed to measure rate coefficients will always be correlated with the absorption cross section of the observed species. This correlation may reduce the accuracy of rate coefficient measurements.
A reverberation room round robin on the determination of absorption coefficients
NASA Astrophysics Data System (ADS)
Kath, U.
In ten reverberation rooms with very different volumes and different room shapes, the absorption coefficients for mineral fiber mat were measured. The particular feature of this round robin was that the absorption material was much thicker than in other similar experiments and that it was measured not only with an area of 12 sq m on the floor, but also as a complete surface covering of a small wall in order to avoid the edge effect. The decay curves were evaluated in at least two institutions and the absorption coefficients were calculated using the Eyring equation. The absorption coefficients were quite dispersed from one room to another and also from one-third octave band to the adjacent ones. Errors due to change are small, thus one is dealing with systematic errors.
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.
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.
Ottink, Marco; Brunskog, Jonas; Jeong, Cheol-Ho; Fernandez-Grande, Efren; Trojgaard, Per; Tiana-Roig, Elisabet
2016-01-01
Absorption coefficients are mostly measured in reverberation rooms or with impedance tubes. Since these methods are only suitable for measuring the random incidence and the normal incidence absorption coefficient, there exists an increasing need for absorption coefficient measurement of finite absorbers at oblique incidence in situ. Due to the edge diffraction effect, oblique incidence methods considering an infinite sample fail to measure the absorption coefficient at large incidence angles of finite samples. This paper aims for the development of a measurement method that accounts for the finiteness of the absorber. A sound field model, which accounts for scattering from the finite absorber edges, assuming plane wave incidence is derived. A significant influence of the finiteness on the radiation impedance and the corresponding absorption coefficient is found. A finite surface method, which combines microphone array measurements over a finite sample with the sound field model in an inverse manner, is proposed. Besides, a temporal subtraction method, a microphone array method, impedance tube measurements, and an equivalent fluid model are used for validation. The finite surface method gives promising agreement with theory, especially at near grazing incidence. Thus, the finite surface method is proposed for further measurements at large incidence angles. PMID:26827003
NASA Astrophysics Data System (ADS)
Liu, Qiang; Huang, Hong-Hua; Wang, Yao; Wang, Gui-Shi; Cao, Zhen-Song; Liu, Kun; Chen, Wei-Dong; Gao, Xiao-Ming
2014-06-01
The atmospheric aerosol absorption capacity is a critical parameter determining its direct and indirect effects on climate. Accurate measurement is highly desired for the study of the radiative budget of the Earth. A multi-wavelength (405 nm, 532 nm, 780 nm) aerosol absorption meter based on photoacoustic spectroscopy (PAS) invovling a single cylindrical acoustic resonator is developed for measuring the aerosol optical absorption coefficients (OACs). A sensitivity of 1.3 Mm-1 (at 532 nm) is demonstrated. The aerosol absorption meter is successfully tested through measuring the OACs of atmospheric nigrosin and ambient aerosols in the suburbs of Hefei city. The absorption cross section and absorption Ångström exponent (AAE) for ambient aerosol are determined for characterizing the component of the ambient aerosol.
Minority carrier diffusion lengths and absorption coefficients in silicon sheet material
NASA Technical Reports Server (NTRS)
Dumas, K. A.; Swimm, R. T.
1980-01-01
Most of the methods which have been developed for the measurement of the minority carrier diffusion length of silicon wafers require that the material have either a Schottky or an ohmic contact. The surface photovoltage (SPV) technique is an exception. The SPV technique could, therefore, become a valuable diagnostic tool in connection with current efforts to develop low-cost processes for the production of solar cells. The technique depends on a knowledge of the optical absorption coefficient. The considered investigation is concerned with a reevaluation of the absorption coefficient as a function of silicon processing. A comparison of absorption coefficient values showed these values to be relatively consistent from sample to sample, and independent of the sample growth method.
NASA Astrophysics Data System (ADS)
O'Brien, J. J.
2002-09-01
The absorption spectrum of methane has been recorded in the visible to near-IR region using the intracavity laser spectroscopy technique. Spectra are recorded at high spectral resolution for narrow overlapping intervals in the region for room and 77 K temperature methane samples. After spectra are deconvolved for the instrument function, absorption coefficients are derived. These will be presented (750-940 nm for room temperature methane; 850-920 nm for 77 K methane) and compared with results reported by other workers. Future work in this area also will be indicated. Support from NASA's Planetary Atmospheres Program (NAG5-6091 and a Major Equipment Grant) is gratefully acknowledged.
Measurement of nanofluids absorption coefficient by Moiré deflectometry technique
NASA Astrophysics Data System (ADS)
Madanipour, Khosro; Koohian, Ataollah; Shahrabi Farahani, Shahrzad
2015-05-01
Nanoparticles exhibit many unique and interesting optical properties which make them very useful in biomedical applications. In order to employ NPs for disease treatment, comprehensive knowledge of their important properties is crucial. One of these parameters is absorption coefficient. In this work, absorption coefficient of a nanofluid (Au nanoparticles in water) is measured by using Moiré deflectometry technique. Two laser beams are used: a comparatively high intensity laser beam as interacting beam and a low intensity as a probe beam. This method is fast, easy and nonscanning, also insensitive to vibrations.
NASA Astrophysics Data System (ADS)
Ladhaf, Bibifatima M.; Pawar, Pravina P.
2015-04-01
We measured here the mass attenuation coefficients (μ/ρ) of carbohydrates, Esculine (C15H16O9), Sucrose (C12H22O11), Sorbitol (C6H14O6), D-Galactose (C6H12O6), Inositol (C6H12O6), D-Xylose (C5H10O5) covering the energy range from 122 keV up to 1330 keV photon energies by using gamma ray transmission method in a narrow beam good geometry set-up. The gamma-rays were detected using NaI(Tl) scintillation detection system with a resolution of 8.2% at 662 keV. The attenuation coefficient data were then used to obtain the total attenuation cross-section (σtot), molar extinction coefficients (ε), mass-energy absorption coefficients (μen/ρ) and effective (average) atomic energy-absorption cross section (σa,en) of the compounds. These values are found to be in good agreement with the theoretical values calculated based on XCOM data.
Photoacoustic measurements of black carbon light absorption coefficients in Irbid city, Jordan.
Hamasha, Khadeejeh M; Arnott, W Patrick
2010-07-01
There is a need to recognize air pollution levels by particles, especially in developing countries such as Jordan where data are scarce due to the absence of routine monitoring of ambient air quality. This study aims at studying the air quality in different locations at Irbid, Jordan through the measurement and analysis of the time series of black carbon light absorption coefficients (B (abs)). Black carbon light absorption coefficients were measured with a photoacoustic instrument at a wavelength of 870 nm. The measurements were conducted during July 2007 at six sites in Irbid city, Jordan. Comparisons of black carbon concentrations at various locations were conducted to understand where values tend to be largest. The average value of B (abs) of all sites was 40.4 Mm(-1). The largest value of B (abs) was 61.2 Mm(-1) at Palestine Street which is located at a very crowded street in a highly populated region in the city center. The lowest value was 14.1 Mm(-1) at Thirtieth Street which is located at a main street in an open plain region in the east of the city. The black carbon light absorption coefficients fluctuate above a background level (transported black carbon from the neighboring states), which are almost identical at all sampling sites. The light absorption coefficients will be used as a benchmark in later years as combustion efficiencies and population patterns change. PMID:19479334
The average ion model. Computation of the absorption and emission coefficients in hot plasmas
NASA Astrophysics Data System (ADS)
Gauthier, Jean-Claude; Geindre, Jean-Paul
1988-06-01
A program was developed to evaluate the emission and absorption plasma coefficient variations as a function of the density, temperature and the atomic number of the specimen. The treatment is simplified because of the reduced number of characteristic frequencies which are necessary for the hydrodynamic code. The approach is less efficient when applied to high Z atoms.
Liu, Qiang; Niu, Ming-Sheng; Wang, Gui-Shi; Cao, Zhen-Song; Liu, Kun; Chen, Wei-Dong; Gao, Xiao-Ming
2013-07-01
In the present paper, the authors focus on the effect of the resonance frequency shift due to the changes in temperature and humidity on the PA signal, present several methods to control the noise derived form gas flow and vibration from the sampling pump. Based on the efforts mentioned above, a detection limit of 1.4 x 10(-8) W x cm(-1) x Hz(-1/2) was achieved for the measurement of atmospheric aerosols absorption coefficient. During the experiments, the PA cell was calibrated with the absorption of standard NO2 gas at 532 nm and the atmospheric aerosols were measured continuously. The measurement results show that the PAS is suitable for the real-time measurement of the absorption coefficient of atmospheric aerosols in their natural suspended state. PMID:24059163
NASA Astrophysics Data System (ADS)
Utry, N.; Ajtai, T.; Pintér, M.; Tombácz, E.; Illés, E.; Bozóki, Z.; Szabó, G.
2014-09-01
Mass specific optical absorption coefficients of various mineral dust components including silicate clays (illite, kaolin and bentonite), oxides (quartz, hematite and rutile), and carbonate (limestone) were determined at wavelengths of 1064, 532, 355 and 266 nm. These values were calculated from aerosol optical absorption coefficients measured by a multi-wavelength photoacoustic (PA) instrument, the mass concentration and the number size distribution of the generated aerosol samples as well as the size transfer functions of the measuring instruments. These results are expected to have considerable importance in global radiative forcing calculations. They can also serve as reference for validating calculated wavelength dependent imaginary parts (κ) of complex refractive indices which up to now have been typically deduced from bulk phase measurements by using indirect measurement methods. Accordingly, the presented comparison of the measured and calculated aerosol optical absorption spectra revealed the strong need for standardized sample preparation and measurement methodology in case of bulk phase measurements.
Temperature- and pressure-dependent absorption coefficients for CO2 and O2 at 193 nm
NASA Astrophysics Data System (ADS)
Hartinger, K. T.; Nord, S.; Monkhouse, P. B.
Absorption of laser radiation at 193 nm by CO2 and O2 was studied at a series of different temperatures up to 1273 K and pressures up to 1 bar. The spectrum for CO2 was found to be broadband, so that absorption could be fitted to a Beer-Lambert law. On the other hand, the corresponding O2 spectrum is strongly structured and parameterisation requires a more complex relation, depending on both temperature and the product (pressure × absorption path length). In this context, the influence of spectral structure on the resulting spectrally integrated absorption coefficients is discussed. Using the fitting parameters obtained, effective transmissions at 193 nm can be calculated for a wide range of experimental conditions. As an illustration of the practical application of these data, the calculation of effective transmission for a typical industrial flue gas is described.
NASA Astrophysics Data System (ADS)
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.
NASA Astrophysics Data System (ADS)
Goela, P.; Icely, J.; Cristina, S.; Newton, A.
2010-12-01
Variability of particulate absorption coefficients was studied off the south-west coast of Portugal, as part of a validation exercise for the Medium Resolution Image Spectrometer Sensor. Regular sampling campaigns occurred at three stations on a transect from inshore to offshore to compare fluctuations in these coefficients at the local scale. Transmittance-reflectance method with sodium hypochlorite bleaching was used to determine absorption coefficients for phytoplankton and non-algal particles. Photosynthetic pigment concentrations were determined by High Performance Liquid Chromatography. Results show that the absorption of light by particulate matter is almost totally dependent on the phytoplankton, with no significant contribution from non-algal particles, both in coastal and oceanic waters. Specific phytoplankton coefficients show significant fluctuations between seasons and stations, ranging from 0.012 to 0.038 at 678 nm. Particulate absorption is dominant over dissolved absorption. The variations in the coefficients of absorption are analysed as a function of species assemblages.
NASA Astrophysics Data System (ADS)
Wichmann, Janine; Janssen, Nicole A. H.; van der Zee, Saskia; Brunekreef, Bert
Population studies indicate that study participants living near major roads are more prone to chronic respiratory symptoms, lung function decrements and hospital admissions for asthma. The majority of the studies used proxy measures, such as distance to major roads or traffic intensity in the surroundings of the home. Few studies have communicated findings of concurrently performed measurements of outdoor, indoor and personal air pollution in urban streets with high- and low-traffic density. Measuring light absorption or reflectance of particulate matter (PM) collected on filters is an alternative method to determine elemental carbon, a marker for particles produced by incomplete combustion, compared to expensive and destructive analytical methods. This study sets out to test the null hypothesis that there is no difference in personal and indoor filter absorption coefficients for participants living along busy and quiet roads in Amsterdam. In one study we measured personal and indoor absorption coefficients in a sample of adults (50-70 years) and, in another study, the indoor levels in a population of adults (50-70 years) and school children (10-12 years). In the first study, the ratios of personal and indoor absorption coefficients in homes along busy roads compared with homes on quiet streets were significantly higher by 29% for personal measurements ( n=16 days, p<0.001), and by 19% for indoor measurements ( n=20, p<0.001), while in the second study, the ratio for the indoor measurements was higher by 26% ( n=25 days, p<0.05). Exposure differences between homes along busy compared to homes along quiet streets remained and significant after adjustment for potential indoor sources (such as cooking and use of unvented heating appliances). This study therefore provides tentative support for the use of the type of road as proxy measure for indoor and personal absorption coefficient measurements in epidemiological studies due to the limitations of the study.
NASA Astrophysics Data System (ADS)
Yoshida, Kenichiro
2016-08-01
We derived the absorption coefficient ( μ a) and the reduced scattering coefficient ( μ s') using the edge-loss method (ELM) and the video reflectometry method (VRM), and compared the results. In a previous study, we developed the ELM to easily evaluate the lateral spread in the skin; the VRM is a conventional method. The ELM measures the translucency index, which is correlated with μ a and μ s'. To obtain a precise estimation of these parameters, we improved the treatment of a white standard and the surface reflection. For both skin phantoms and actual skin, the values for μ a and μ s' that we obtained using the ELM were similar to those obtained using the VRM, when μ a/ μ s' was less than or equal to 0.05 and the diffusion approximation was applicable. Under this condition, the spectral reflectivity is greater than 0.4. In this study, we considered wavelengths longer than 600 nm for Types III and IV of the Fitzpatrick scale. For skin, the repeatability errors of the parameters obtained with the ELM were smaller than those obtained with the VRM; this can be an advantage in field tests.
NASA Astrophysics Data System (ADS)
Yoshida, Kenichiro
2016-07-01
We derived the absorption coefficient (μ a) and the reduced scattering coefficient (μ s') using the edge-loss method (ELM) and the video reflectometry method (VRM), and compared the results. In a previous study, we developed the ELM to easily evaluate the lateral spread in the skin; the VRM is a conventional method. The ELM measures the translucency index, which is correlated with μ a and μ s'. To obtain a precise estimation of these parameters, we improved the treatment of a white standard and the surface reflection. For both skin phantoms and actual skin, the values for μ a and μ s' that we obtained using the ELM were similar to those obtained using the VRM, when μ a/μ s' was less than or equal to 0.05 and the diffusion approximation was applicable. Under this condition, the spectral reflectivity is greater than 0.4. In this study, we considered wavelengths longer than 600 nm for Types III and IV of the Fitzpatrick scale. For skin, the repeatability errors of the parameters obtained with the ELM were smaller than those obtained with the VRM; this can be an advantage in field tests.
A new photoacoustic method based on the modulation of the light induced absorption coefficient
NASA Astrophysics Data System (ADS)
Engel, S.; Wenisch, C.; Müller, F. A.; Gräf, S.
2016-04-01
The present study reports on a new photoacoustic (PA) measurement method that is suitable for the investigation of light induced absorption effects including e.g. excited state absorption. Contrary to the modulation of the radiation intensity used in conventional PA-methods, the key principle of this novel setup is based on the modulation of the induced absorption coefficient by light. For this purpose, a pump-probe setup with a pulsed pump laser beam and a continuous probe laser beam is utilized. In this regime, the potential influence of heat on the PA-signal is much smaller when compared to arrangements with pulsed probe beam and continuous pump beam. Beyond that, the negative effect of thermal lenses can be neglected. Thus, the measurement technique is well-suited for materials exhibiting a strong absorption at the pump wavelength. The quantitative analysis of the induced absorption coefficient was achieved by the calibration of the additional PA-signal caused by the continuous probe laser to the PA-signal resulting from the pulsed pump laser using thallium bromoiodide (KRS-5) as sample material.
NASA Astrophysics Data System (ADS)
Chrobak, Ł.; Maliński, M.; Pawlak, M.
2014-11-01
This paper presents a method of the measurement of the optical absorption coefficient of the Ar8+ ions implanted layers in the p-type silicon substrate. The absorption coefficient is calculated using a value of the attenuation of amplitudes of a photothermal radiometry (PTR) and/or a modulation free carrier absorption (MFCA) signals and the implanted layer thickness calculated by means of the TRIM program. The proposed method can be used to indicate the amorphization of the ions implanted layers.
Absorption coefficients of GeSn extracted from PIN photodetector response
NASA Astrophysics Data System (ADS)
Ye, Kaiheng; Zhang, Wogong; Oehme, Michael; Schmid, Marc; Gollhofer, Martin; Kostecki, Konrad; Widmann, Daniel; Körner, Roman; Kasper, Erich; Schulze, Jörg
2015-08-01
In this paper the optical absorption of the GeSn PIN photodetector was investigated. The vertical GeSn PIN photodetectors were fabricated by molecular beam epitaxy (MBE) and dry etching. By means of current density-voltage (J-V) and capacity-voltage (C-V) measurements the photodetector device was characterized. The absorption coefficients of GeSn material were finally extracted from the optical response of PIN structure. With further direct bandgap analysis the influences of device structure was proved negligible.
Heat/Mass Transfer Coefficients of an Absorber in Absorption Refrigeration System
NASA Astrophysics Data System (ADS)
Fujita, Isamu; Hihara, Eiji
This paper presents a new method to calculate heat and mass transfer coefficients applicable to the vertical tube or plate type absorber of absorption refrigeration system. Conventional method for calculating the coefficients using logarithmic mean temperature/ concentration differences is criticized for its lacking in the theoretical rationality and usually giving untrue values except some limited situations such that temperature of the solution can be assumed to change linearly along the heat transfer surface. The newly introduced method, which is intended to overcome this difficulty, is verified by numerical simulation and is accompanied by an example applied to the experimental results.
Index of Refraction and Absorption Coefficient Spectra of Paratellurite in the Terahertz Region
NASA Astrophysics Data System (ADS)
Unferdorben, Márta; Buzády, Andrea; Hebling, János; Kiss, Krisztián; Hajdara, Ivett; Kovács, László; Péter, Ágnes; Pálfalvi, László
2016-07-01
Index of refraction and absorption coefficient spectra of pure paratellurite (α-TeO2) crystal as a potential material for terahertz (THz) applications were determined in the 0.25-2 THz frequency range at room temperature by THz time domain spectroscopy (THz-TDS). The investigation was performed with beam polarization both parallel (extraordinary polarization) and perpendicular (ordinary polarization) to the optical axis [001] of the crystal. Similarly to the visible spectral range, positive birefringence was observed in the THz range as well. It was shown that the values of the refractive index for extraordinary polarization are higher and show significantly larger dispersion than for the ordinary one. The absorption coefficient values are also larger for extraordinary polarization. The measured values were fitted by theoretical curves derived from the complex dielectric function containing independent terms of Lorentz oscillators due to phonon-polariton resonances. The results are compared with earlier publications, and the observed significant discrepancies are discussed.
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
Majaron, Boris; Milanic, Matija
2008-01-01
Although photothermal radiometric (PTR) measurements commonly employ broad-band signal acquisition to increase the signal-to-noise ratio, all reported studies apply a fixed infrared (IR) absorption coefficient to simplify the involved signal analysis. In samples with large spectral variation of micro(lambda) in mid-IR, which includes most biological tissues, the selection of the effective IR absorption coefficient value (micro(eff)) can strongly affect the accuracy of the result. We present a novel analytical approach for the determination of optimal micro(eff) from spectral properties of the sample and radiation detector. In extensive numerical simulations of pulsed PTR temperature profiling in human skin using three common IR radiation detectors and several acquisition spectral bands, we demonstrate that our approach produces viable values micro(eff). Two previously used analytical estimations perform much worse in the same comparison. PMID:18182701
Determination of RW3-to-water mass-energy absorption coefficient ratio for absolute dosimetry.
Seet, Katrina Y T; Hanlon, Peta M; Charles, Paul H
2011-12-01
The measurement of absorbed dose to water in a solid-phantom may require a conversion factor because it may not be radiologically equivalent to water. One phantom developed for the use of dosimetry is a solid water, RW3 white-polystyrene material by IBA. This has a lower mass-energy absorption coefficient than water due to high bremsstrahlung yield, which affects the accuracy of absolute dosimetry measurements. In this paper, we demonstrate the calculation of mass-energy absorption coefficient ratios, relative to water, from measurements in plastic water and RW3 with an Elekta Synergy linear accelerator (6 and 10 MV photon beams) as well as Monte Carlo modeling in BEAMnrc and DOSXYZnrc. From this, the solid-phantom-to-water correction factor was determined for plastic water and RW3. PMID:21960410
NASA Astrophysics Data System (ADS)
Ren, Yatao; Qi, Hong; Zhao, Fangzhou; Ruan, Liming; Tan, Heping
2016-02-01
A secondary optimization technique was proposed to estimate the temperature-dependent thermal conductivity and absorption coefficient. In the proposed method, the stochastic particle swarm optimization was applied to solve the inverse problem. The coupled radiation and conduction problem was solved in a 1D absorbing, emitting, but non-scattering slab exposed to a pulse laser. It is found that in the coupled radiation and conduction problem, the temperature response is highly sensitive to conductivity but slightly sensitive to the optical properties. On the contrary, the radiative intensity is highly sensitive to optical properties but slightly sensitive to thermal conductivity. Therefore, the optical and thermal signals should both be considered in the inverse problem to estimate the temperature-dependent properties of the transparent media. On this basis, the temperature-dependent thermal conductivity and absorption coefficient were both estimated accurately by measuring the time-dependent temperature, and radiative response at the boundary of the slab.
Ren, Yatao; Qi, Hong; Zhao, Fangzhou; Ruan, Liming; Tan, Heping
2016-01-01
A secondary optimization technique was proposed to estimate the temperature-dependent thermal conductivity and absorption coefficient. In the proposed method, the stochastic particle swarm optimization was applied to solve the inverse problem. The coupled radiation and conduction problem was solved in a 1D absorbing, emitting, but non-scattering slab exposed to a pulse laser. It is found that in the coupled radiation and conduction problem, the temperature response is highly sensitive to conductivity but slightly sensitive to the optical properties. On the contrary, the radiative intensity is highly sensitive to optical properties but slightly sensitive to thermal conductivity. Therefore, the optical and thermal signals should both be considered in the inverse problem to estimate the temperature-dependent properties of the transparent media. On this basis, the temperature-dependent thermal conductivity and absorption coefficient were both estimated accurately by measuring the time-dependent temperature, and radiative response at the boundary of the slab. PMID:26912418
NASA Astrophysics Data System (ADS)
Salazar, Agustín; Fuente, Raquel; Apiñaniz, Estibaliz; Mendioroz, Arantza; Celorrio, R.
2011-08-01
The aim of this work is to analyze the ability of modulated photothermal radiometry to retrieve the thermal diffusivity and the optical absorption coefficient of layered materials simultaneously. First, we extend the thermal quadrupole method to calculate the surface temperature of semitransparent multilayered materials. Then, this matrix method is used to evaluate the influence of heat losses by convection and radiation, the influence of the use of thin paint layers on the accuracy of thermal diffusivity measurements, and the effect of lateral heat diffusion due to the use of Gaussian laser beams. Finally, we apply the quadrupole method to retrieve (a) the thermal contact resistance in glass stacks and (b) the thermal diffusivity and optical absorption coefficient depth profiles in heterogeneous materials with continuously varying physical properties, as is the case of functionally graded materials and partially cured dental resins.
Measurement and calculation of the sound absorption coefficient of pine wood charcoal
NASA Astrophysics Data System (ADS)
Suh, Jae Gap; Baik, Kyung min; Kim, Yong Tae; Jung, Sung Soo
2013-10-01
Although charcoal has been widely utilized for physical therapy and as a deodorant, water purifier, etc. due to its porous features, research on its role as a sound-absorbing material is rarely found. Thus, the sound absorption coefficients of pine wood charcoal were measured using an impedance tube and were compared with the theoretical predictions in the frequency range of 500˜ 5000 Hz. The theory developed in the current study only considers the lowest possible mode propagating along the air channels of the charcoal and shows good agreements with the measurements. As the frequency is increased, the sound absorption coefficients of pine wood charcoals also increase, but are lower than those of other commonly-used sound-absorbing materials.
Sadler, M.; Charlson, R.J.; Rosen, H.; Novakov, T.
1980-07-01
The absorption coefficients determined by the integrating plate method and the laser transmission method are found to be comparable and highly correlated. Furthermore, a high correlation is found between these absorption coefficients and the carbon content of the aerosol in urbanized regions.
Infrared absorption-coefficient data on SF6 applicable to atmospheric remote sensing
NASA Technical Reports Server (NTRS)
Varanasi, P.; Gopalan, A.; Brannon, J. F., Jr.
1992-01-01
Spectral absorption coefficients, k(nu)/cm per atm, of SF6 have been measured in the central Q-branches of the nu(3)-fundamental at 947/cm at various temperature-pressure combinations representing tangent heights in solar-occultation experiments or layers in the atmosphere. The data obtained with the Doppler-limited spectral resolution (about 0.0001/cm) of a tunable-diode laser spectrometer are useful in the atmospheric remote sensing of this trace gas.
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.
Khalifah, Peter
2015-02-01
The problem of numerically evaluating absorption correction factors for cylindrical samples has been revisited using a treatment that fully takes advantage of the sample symmetry. It is shown that the path lengths for all points within the sample at all possible diffraction angles can be trivially determined once the angle-dependent distance distribution for a single line of points is calculated. This provides advantages in both computational efficiency and in gaining an intuitive understanding of the effects of absorption on diffraction data. A matrix of absorption coefficients calculated for µR products between 0 and 20 for diffraction angles θ_{D} of 0° to 90° were used to examine the influence of (1) capillary diameter and of (2) sample density on the overall scattered intensity as a function of diffraction angle, where µ is the linear absorption coefficient for the sample and R is the capillary radius. Based on this analysis, the optimal sample loading for a capillary experiment to maximize diffraction at angles of 0 – 50° is in general expected to be achieved when the maximum radius capillary compatible with the beam is used, and when the sample density is adjusted to be 3/(4µR) of its original density.
Khalifah, Peter
2015-02-01
The problem of numerically evaluating absorption correction factors for cylindrical samples has been revisited using a treatment that fully takes advantage of the sample symmetry. It is shown that the path lengths for all points within the sample at all possible diffraction angles can be trivially determined once the angle-dependent distance distribution for a single line of points is calculated. This provides advantages in both computational efficiency and in gaining an intuitive understanding of the effects of absorption on diffraction data. A matrix of absorption coefficients calculated for µR products between 0 and 20 for diffraction angles θD of 0°more » to 90° were used to examine the influence of (1) capillary diameter and of (2) sample density on the overall scattered intensity as a function of diffraction angle, where µ is the linear absorption coefficient for the sample and R is the capillary radius. Based on this analysis, the optimal sample loading for a capillary experiment to maximize diffraction at angles of 0 – 50° is in general expected to be achieved when the maximum radius capillary compatible with the beam is used, and when the sample density is adjusted to be 3/(4µR) of its original density.« less
Two-photon interband absorption coefficients in tungstate and molybdate crystals
NASA Astrophysics Data System (ADS)
Lukanin, V. I.; Karasik, A. Ya.
2015-02-01
Two-photon absorption (TPA) coefficients were measured in tungstate and molybdate crystals - BaWO4, KGW, CaMoO4, BaMoO4, CaWO4, PbWO4 and ZnWO4 upon different orientations of excitation polarization with respect to the crystallographic axes. Trains of 25 ps pulses with variable radiation intensities of third (349 nm) harmonics of passively mode-locked 1047 nm Nd:YLF laser were used for interband two-photon excitation of the crystals. It was suggested that in the case, when 349 nm radiation pumping energy exceeds the bandgap width (hν>Eg), the nonlinear excitation process can be considered as two-step absorption. The interband two-photon absorption in all the studied crystals induces the following one-photon absorption from the exited states, which affects the nonlinear process dynamics and leads to a hysteresis in the dependence of the transmission on the excitation intensity. This fact was taken into account under analysis of the experimental dependences of the reciprocal transmission on the excitation intensity. Laser excitation in the transparency region of the crystals caused stimulated Raman scattering (SRS) not for all the crystals studied. The measured nonlinear coefficients allowed us to explain the suppression of SRS in crystals as a result of competition between the SRS and TPA.
Parthasarathy, Ranganathan; Misra, Anil; Park, Jonggu; Ye, Qiang; Spencer, Paulette
2012-01-01
The diffusion of water into dentin adhesive polymers and leaching of unpolymerized monomer from the adhesive are linked to their mechanical softening and hydrolytic degradation. Therefore, diffusion coefficient data are critical for the mechanical design of these polymeric adhesives. In this study, diffusion coefficients of water and leachables were obtained for sixteen methacrylate-based crosslinked polymers using absorption experiments. The experimental mass change data was interpreted using numerical solution of the two-dimensional diffusion equations. The calculated diffusion coefficients varied from 1.05 × 10−8 cm2/sec (co-monomer TMTMA) to 3.15 × 10−8 cm2/sec (co-monomer T4EGDMA). Correlation of the diffusion coefficients with crosslink density and hydrophilicity showed an inverse trend (R2 = 0.41). The correlation of diffusion coefficient with crosslink density and hydrophilicity are closer for molecules differing by simple repeat units (R2 = 0.95). These differences in the trends reveal mechanisms of interaction of the diffusing water with the polymer structure. PMID:22430592
Microwave Resonator Measurements of Atmospheric Absorption Coefficients: A Preliminary Design Study
NASA Technical Reports Server (NTRS)
Walter, Steven J.; Spilker, Thomas R.
1995-01-01
A preliminary design study examined the feasibility of using microwave resonator measurements to improve the accuracy of atmospheric absorption coefficients and refractivity between 18 and 35 GHz. Increased accuracies would improve the capability of water vapor radiometers to correct for radio signal delays caused by Earth's atmosphere. Calibration of delays incurred by radio signals traversing the atmosphere has applications to both deep space tracking and planetary radio science experiments. Currently, the Cassini gravity wave search requires 0.8-1.0% absorption coefficient accuracy. This study examined current atmospheric absorption models and estimated that current model accuracy ranges from 5% to 7%. The refractivity of water vapor is known to 1% accuracy, while the refractivity of many dry gases (oxygen, nitrogen, etc.) are known to better than 0.1%. Improvements to the current generation of models will require that both the functional form and absolute absorption of the water vapor spectrum be calibrated and validated. Several laboratory techniques for measuring atmospheric absorption and refractivity were investigated, including absorption cells, single and multimode rectangular cavity resonators, and Fabry-Perot resonators. Semi-confocal Fabry-Perot resonators were shown to provide the most cost-effective and accurate method of measuring atmospheric gas refractivity. The need for accurate environmental measurement and control was also addressed. A preliminary design for the environmental control and measurement system was developed to aid in identifying significant design issues. The analysis indicated that overall measurement accuracy will be limited by measurement errors and imprecise control of the gas sample's thermodynamic state, thermal expansion and vibration- induced deformation of the resonator structure, and electronic measurement error. The central problem is to identify systematic errors because random errors can be reduced by averaging
Spectroscopic method for determination of the absorption coefficient in brain tissue
NASA Astrophysics Data System (ADS)
Johansson, Johannes D.
2010-09-01
I use Monte Carlo simulations and phantom measurements to characterize a probe with adjacent optical fibres for diffuse reflectance spectroscopy during stereotactic surgery in the brain. Simulations and measurements have been fitted to a modified Beer-Lambert model for light transport in order to be able to quantify chromophore content based on clinically measured spectra in brain tissue. It was found that it is important to take the impact of the light absorption into account when calculating the apparent optical path length, lp, for the photons in order to get good estimates of the absorption coefficient, μa. The optical path length was found to be well fitted to the equation lp=a+b ln(Is)+c ln(μa)+d ln(Is)ln(μa), where Is is the reflected light intensity for scattering alone (i.e., zero absorption). Although coefficients a-d calculated in this study are specific to the probe used here, the general form of the equation should be applicable to similar probes.
Sound absorption coefficient in situ: an alternative for estimating soil loss factors.
Freire, Rosane; Meletti de Abreu, Marco Henrique; Okada, Rafael Yuri; Soares, Paulo Fernando; GranhenTavares, Célia Regina
2015-01-01
The relationship between the sound absorption coefficient and factors of the Universal Soil Loss Equation (USLE) was determined in a section of the Maringá Stream basin, Paraná State, by using erosion plots. In the field, four erosion plots were built on a reduced scale, with dimensions of 2.0×12.5m. With respect to plot coverage, one was kept with bare soil and the others contained forage grass (Brachiaria), corn and wheat crops, respectively. Planting was performed without any type of conservation practice in an area with a 9% slope. A sedimentation tank was placed at the end of each plot to collect the material transported. For the acoustic system, pink noise was used in the measurement of the proposed monitoring, for collecting information on incident and reflected sound pressure levels. In general, obtained values of soil loss confirmed that 94.3% of material exported to the basin water came from the bare soil plot, 2.8% from the corn plot, 1.8% from the wheat plot, and 1.1% from the forage grass plot. With respect to the acoustic monitoring, results indicated that at 16kHz erosion plot coverage type had a significant influence on the sound absorption coefficient. High correlation coefficients were found in estimations of the A and C factors of the USLE, confirming that the acoustic technique is feasible for the determination of soil loss directly in the field. PMID:24972796
Pressure-induced absorption coefficients for radiative transfer calculations in Titan's atmosphere
NASA Technical Reports Server (NTRS)
Courtin, Regis
1988-01-01
The semiempirical theory of Birnbaum and Cohen (1976) is used to calculate the FIR pressure-induced absorption (PIA) spectra of N2, CH4, N2 + Ar, N2 + CH4, and N2 + H2 under conditions like those in the Titan troposphere. The results are presented graphically and compared with published data from laboratory measurements of PIA in the same gases and mixtures (Dagg et al., 1986; Dore et al., 1986). Good agreement is obtained, with only a slight underestimation of PIA at 300-400/cm in the case of CH4. The absorption coefficients are presented in tables, and it is suggested that the present findings are of value for evaluating the effects of tropospheric clouds on the Titan FIR spectrum and studying the greenhouse effect near the Titan surface.
Uzhegov, V.N.; Kozlov, V.S.; Panchenko, M.V.; Pkhalagov, Yu.A.; Pol'kin, V.V.; Terpugova, S.A.; Shmargunov, V.P.; Yausheva, E.P.
2005-03-18
The problem of the choice of the aerosol optical constants and, in particular, imaginary part of the refractive index of particles in visible and infrared (IR) wavelength ranges is very important for calculation of the global albedo of the atmosphere in climatic models. The available models of the aerosol optical constants obtained for the prescribed chemical composition of particles (see, for example, Ivlev et al. 1973; Ivlev 1982; Volz 1972), often are far from real aerosol. It is shown in (Krekov et al. 1982) that model estimates of the optical characteristics of the atmosphere depending on the correctness of real and imaginary parts of the aerosol complex refractive index can differ by some hundreds percent. It is known that the aerosol extinction coefficient {alpha}({lambda}) obtained from measurements on a long horizontal path can be represented as {alpha}({lambda})={sigma}({lambda})+{beta}({lambda}), where {sigma} is the directed light scattering coefficient, and {beta} is the aerosol absorption coefficient. The coefficient {sigma}({lambda}) is measured by means of a nephelometer. Seemingly, if measure the values {alpha}({lambda}) and {sigma}({lambda}), it is easy to determine the value {beta}({lambda}). However, in practice it is almost impossible for a number of reasons. Firstly, the real values {alpha}({lambda}) and {sigma}({lambda}) are very close to each other, and the estimate of the parameter {beta}({lambda}) is concealed by the errors of measurements. Secondly, the aerosol optical characteristics on the long path and in the local volume of nephelometer can be different, that also leads to the errors in estimating {beta}({lambda}). Besides, there are serious difficulties in performing spectral measurements of {sigma}({lambda}) in infrared wavelength range. Taking into account these circumstances, in this paper we consider the statistical technique, which makes it possible to estimate the absorption coefficient of real aerosol on the basis of analysis
A comparison of methods for the measurement of the absorption coefficient in natural waters
NASA Technical Reports Server (NTRS)
Pegau, W. Scott; Cleveland, Joan S.; Doss, W.; Kennedy, C. Dan; Maffione, Robert A.; Mueller, James L.; Stone, R.; Trees, Charles C.; Weidemann, Alan D.; Wells, Willard H.
1995-01-01
In the spring of 1992 an optical closure experiment was conducted at Lake Pend Orielle, Idaho. A primary objective of the experiment was to compare techniques for the measurement of the spectral absorption coefficent and other inherent optical properties of natural waters. Daily averages of absorption coefficents measured using six methods are compared at wavelengths of 456, 488, and 532 nm. Overall agreement was within 40% at 456 nm and improved with increasing wavelength to 25% at 532 nm. These absorption measurements were distributed over the final 9 days of the experiement, when bio-optical conditions in Lake Pend Oreille (as indexed by the beam attenuation coefficent c(sub p)(660) and chlorophyll a fluorescence profiles) were representative of those observed throughout the experiment. However, profiles of stimulated chlorophyll a fluorescence and beam transmission showed that bio-optical properties in the lake varied strongly on all time and space scales. Therefore environmental variabilty contributed significantly to deviations between daily mean absorption coefficients measured using the different techniques.
Mesure de coefficients d'absorption de plasmas créés par laser nanoseconde
NASA Astrophysics Data System (ADS)
Thais, F.; Chenais-Popovics, C.; Eidmann, K.; Bastiani, S.; Blenski, T.; Gilleron, F.
2005-06-01
La mesure des coefficients d'absorption dans les plasmas chauds est particulièrement utile dans le domaine de la fusion par confinement inertiel ainsi que dans divers contextes en astrophysique. Le développement des calculs de physique atomique qui y sont associés repose sur des hypothèses qu'il est nécessaire de vérifier dans la plus large gamme possible de conditions physiques. Nous présentons ici la méthode de mesure et d'analyse employée en nous appuyant sur l'exemple des cibles multicouches nickel/aluminium.
Determination of Absorption Coefficient of a Solution by a Simple Experimental Setup
NASA Astrophysics Data System (ADS)
Gopalakrishnan, Deepak; Akhildev, C.; Sreenivasan, P. V.; Leelamma, K. K.; Joseph, Lyjo K.; Anila, E. I.
2011-10-01
The absorption coefficients of aqueous potassium permanganate (KMnO4) solution at 638.8 nm for various concentrations are determined using a simple experimental set up. The setup consists of He-Ne laser source (Red, 638.8 nm, 10 mW), a glass jar in which the KMnO4 sample is taken, a mirror strip inclined at 45° to direct the laser beam towards the bottom of the glass jar, a traveling microscope to adjust the position of light dependent resistor (LDR) and a digital multimeter to measure the resistance.
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
Theoretical calculations of nonlinear refraction and absorption coefficients of doped graphene
NASA Astrophysics Data System (ADS)
Margulis, Vl A.; Muryumin, E. E.; Gaiduk, E. A.
2014-12-01
In this study, we present the first theoretical predictions concerning the nonlinear refractive and absorptive properties of the doped graphene in which the Fermi energy {{E}F} of charge carriers (noninteracting massless Dirac fermions) is controlled by an external gate voltage. We base our study on the original perturbation theory technique developed by Genkin and Mednis (1968 Sov. Phys. JETP 27 609) for calculating the nonlinear-optical (NLO) response coefficients of bulk crystalline semiconductors with partially filled bands. Using a simple tight-binding model for the π-electron energy bands of graphene, we obtain analytic expressions for the nonlinear refractive index {{n}2}(ω ) and the nonlinear absorption coefficient {{α }2}(ω ) of the doped graphene at photon energies above twice the value of the Fermi energy (\\hbar ω \\gt 2{{E}F}). We show that in this spectral region, both the nonlinear refraction ant the nonlinear absorption are determined predominantly by the combined processes which simultaneously involve intraband and interband motion of π-electrons. Our calculations indicate that extremely large negative values of n2 (of the order of -{{10}-6} cm2 W-1) can be achieved in the graphene at a relatively low doping level (of about 1012 cm-2) provided that the excitation frequency slightly exceeds the threshold frequency corresponding to the onset of interband transitions. With a further increase of the radiation frequency, the {{n}2}(ω ) becomes positive and begins to decrease in its absolute magnitude. The peculiar frequency dispersion of n2 and a negative sign of the {{α }2} (absorption bleaching), as predicted by our theory, suggest that the doped graphene is a prospective NLO material to be used in practical optical switching applications.
From discrete Painlevé equations to mappings with periodic coefficients and back
NASA Astrophysics Data System (ADS)
Ramani, A.; Grammaticos, B.; Tamizhmani, K. M.
2010-12-01
We investigate relations between two families of discrete Painlevé equations obtained respectively from degenerate forms of q-PIII and q-PVI. Our approach is based on the recently derived extensions of QRT mappings to ones with periodic coefficients. We establish the relationships that exist between the two families by deautonomizing the corresponding mappings with periodic coefficients. In the process we obtain mappings that cannot be extended to q-Painlevé forms and show that these mappings are not of infinite order.
NASA Technical Reports Server (NTRS)
Harward, C. N.
1977-01-01
Measurements were performed to determine the pressure and temperature dependence of CFM-12 absorption coefficients for CO2 waveguide laser radiation. The absorption coefficients of CFM-12 for CO2 waveguide laser radiation were found to have no spectral structure within small spectral bandwidths around the CO2 waveguide laser lines in the CO2 spectral band for pressures above 20 torr. All of the absorption coefficients for the CO2 laser lines studied are independent of pressure above 100 torr, except for the P(36) laser CO2 spectral band. The absorption coefficients associated with the P(42) line in the same band showed the greatest change with temperature, and it also has the largest value of all the lines studied.
NASA Astrophysics Data System (ADS)
Zamani, N.; Keshavarz, A.; Nadgaran, H.
2016-06-01
In this paper, we investigate the optical absorption coefficient of hybrid structure consisting of metal nano particle (MNP) coupled to multi-layer spherical quantum dot (MSQD). Energy eigenvalues and eigenfunctions of Schrödinger equation in this structure are obtained by using numerical solution (by the fourth-order Runge-Kutta method). The effect of MNP in the vicinity of MSQD is calculated by considering local field theory. Then the variation of optical absorption coefficient hybrid structure is calculated. The results show that the presence of MNP near MSQD enhances the optical absorption coefficient. Also, by changing the distance between MNP and MSQD and radius of MNP, variation of optical absorption coefficient and refractive index changes are introduced.
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.
Majaron, Boris; Verkruysse, Wim; Tanenbaum, B Samuel; Milner, Thomas E; Nelson, J Stuart
2002-06-01
Pulsed photothermal radiometry can be used for non-invasive depth profiling of optically scattering samples, including biological tissues such as human skin. Computational reconstruction of the laser-induced temperature profile from recorded radiometric signals is sensitive to the value of the tissue absorption coefficient in the infrared detection band (muIR). While assumed constant in reported reconstruction algorithms, muIR of human skin varies by two orders of magnitude in the commonly used 3-5 microm detection band. We analyse the problem of selecting the effective absorption coefficient value to be used with such algorithms. In a numerical simulation of photothermal profiling we demonstrate that results can be markedly impaired, unless the reconstruction algorithm is augmented by accounting for spectral variation muIR(lambda). Alternatively, narrowing the detection band to 4.5-5 microm reduces the spectral variation muIR(lambda) to a level that permits the use of the simpler, unaugmented algorithm. Implementation of the latter approach for depth profiling of port wine stain birthmarks in vivo is presented and discussed. PMID:12108776
NASA Astrophysics Data System (ADS)
Markushev, D. D.; Ordonez-Miranda, J.; Rabasović, M. D.; Galović, S.; Todorović, D. M.; Bialkowski, S. E.
2015-06-01
The open-cell photoacoustic signal measured in the transmission configuration for aluminum thin plates with thicknesses of 280 μm, 197 μm, and 112 μm is experimentally and theoretically analyzed, in the 20 Hz-7 kHz modulation frequency range. It is shown that the observed differences between the predictions of the standard thermoelastic model and the experiment data of both the amplitude and phase of the photoacoustic signal can be overcome by considering the aluminum samples coated with a thin layer of black paint as volume-absorber materials. This new approach provides a quite good agreement with the obtained experimental data, in the whole frequency range, and yields an effective absorption coefficient of (16 ± 2) mm-1, for a 280 μm-thick sample. The introduction of the finite absorption coefficient led to the correct ratio between the thermal diffusion and thermoelastic components of the photoacoustic signal. Furthermore, it is found that the "volume-absorber" approach accurately describes the behavior of the amplitude, but not that of the phase recorded for a 112 μm-thick sample, due to its relatively strong thermoelastic bending, which is not considered by this theory. Within the approximation of the small bending, the proposed "volume-absorber" model provides a reliable description of the photoacoustic signal for Al samples thicker than 112 μm, and extends the applicability of the classical "opaque" approach.
NASA Astrophysics Data System (ADS)
Guo, Kangxian; Zhang, Zhongmin; Mou, Sen; Xiao, Bo
2015-05-01
The analytical expressions of linear and nonlinear optical absorption coefficients and refractive index changes in a quantum dot with a hydrogenic impurity are obtained by using the compact-density-matrix approach and iterative method. The wave functions and the energy levels are obtained by using the variational method. Numerical results show that the optical absorption coefficients and refractive index changes are strongly affected by the hydrogenic impurity.
Translation of Bernstein Coefficients Under an Affine Mapping of the Unit Interval
NASA Technical Reports Server (NTRS)
Alford, John A., II
2012-01-01
We derive an expression connecting the coefficients of a polynomial expanded in the Bernstein basis to the coefficients of an equivalent expansion of the polynomial under an affine mapping of the domain. The expression may be useful in the calculation of bounds for multi-variate polynomials.
NASA Astrophysics Data System (ADS)
O'Brien, J. J.; Cao, H.
2000-10-01
Methane spectral features are prominent in the reflected sunlight spectra from the outer planets and some of their major satellites and can provide useful information on the atmospheres of those bodies. Methane bands occurring in the visible to near-IR region are particularly important because for many of these planetary bodies, methane bands occurring in the IR are saturated. Spectral observations of these bodies also are being made at increasingly higher resolution. In order to interpret the planetary spectra, laboratory data for methane obtained at appropriate sample conditions and spectral resolution are required. Since the visible to near-IR spectrum of methane is intrinsically weak, sensitive techniques are required to perform the laboratory measurements. We have employed the intracavity laser spectroscopy (ILS) technique to record methane spectrum in the visible to near-IR region. New results for room temperature methane in the 10,635 - 13,300 cm-1 region and for liquid nitrogen temperature (77 K) methane in the 10,860 - 11,605 cm-1 region will be presented. Spectra throughout the more strongly absorbing sections will be shown. These spectra are acquired at a resolution of 400,000 - 500,000 and are calibrated using iodine reference spectra acquired from an extra-cavity cell at nearly the same time as when the methane data are recorded. From the spectra, absorption coefficients are determined and these are presented as averages over 1 Å and 1 cm-1 intervals. In order to obtain the results, spectra are deconvolved for the instrument function using a Fourier transform technique. The validity of the approach is verified from studies of isolated oxygen lines in the A band occurring around 760 nm. Good agreement is observed between the intensity values determined from the FT deconvolution and integration method and those derived by fitting the observed line profiles to Voigt line-shapes convoluted with the instrument function. The methane results are compared
Hoche, S; Hussein, M A; Becker, T
2015-03-01
The accuracy of density, reflection coefficient, and acoustic impedance determination via multiple reflection method was validated experimentally. The ternary system water-maltose-ethanol was used to execute a systematic, temperature dependent study over a wide range of densities and viscosities aiming an application as inline sensor in beverage industries. The validation results of the presented method and setup show root mean square errors of: 1.201E-3 g cm(-3) (±0.12%) density, 0.515E-3 (0.15%) reflection coefficient and 1.851E+3 kg s(-1) m(-2) (0.12%) specific acoustic impedance. The results of the diffraction corrected absorption showed an average standard deviation of only 0.12%. It was found that the absorption change shows a good correlation to concentration variations and may be useful for laboratory analysis of sufficiently pure liquids. The main part of the observed errors can be explained by the observed noise, temperature variation and the low signal resolution of 50 MHz. In particular, the poor signal-to-noise ratio of the second reflector echo was found to be a main accuracy limitation. Concerning the investigation of liquids the unstable properties of the reference material PMMA, due to hygroscopicity, were identified to be an additional, unpredictable source of uncertainty. While dimensional changes can be considered by adequate methodology, the impact of the time and temperature dependent water absorption on relevant reference properties like the buffer's sound velocity and density could not be considered and may explain part of the observed deviations. PMID:25465962
Measuring absorption coefficient of scattering liquids using a tube inside an integrating sphere.
Villanueva, Yolanda; Veenstra, Colin; Steenbergen, Wiendelt
2016-04-10
A method for measuring the absorption coefficient μ_{a} of absorbing and scattering liquid samples is presented. The sample is injected into a small transparent tube mounted through an integrating sphere. Two models for determining the absorption coefficient using the relative optical output signal are described and validated using aqueous ink absorbers of 0.5 vol.% (0.3 mm^{-1}<μ_{a}<1.55 mm^{-1}) and 1.0 vol.% (1.0 mm^{-1}<μ_{a}<4.0 mm^{-1}) concentrations with 1 vol.% (μs'≈1.4 mm^{-1}) and 10 vol.% (μs'≈14 mm^{-1}) Intralipid dilutions. The low concentrations give μ_{a} and μ_{s} values, which are comparable with those of biological tissues. One model assumes a uniform light distribution within the sample, which is valid for low absorption. Another model considers light attenuation that obeys Lambert-Beer's law, which may be used for relatively high absorption. Measurements with low and high scattering samples are done for the wavelength range of 400-900 nm. Measured spectra of purely absorbing samples are within 15% agreement with measurements using standard transmission spectrophotometry. For 0.5 vol.% ink absorbers and at wavelengths below 700 nm, measured μ_{a} values are higher for samples with low scattering and lower for those with high scattering. At wavelengths above 700 nm, measured μ_{a} values do not vary significantly with amount of scattering. For 1.0 vol.% ink absorbers, measured spectra do not change with low scattering. These results indicate that the method can be used for measuring absorption spectra of scattering liquid samples with optical properties similar to biological absorbers, particularly at wavelengths above 700 nm, which is difficult to accomplish with standard transmission spectrophotometry. PMID:27139871
Determination of absorption coefficient based on laser beam thermal blooming in gas-filled tube.
Hafizi, B; Peñano, J; Fischer, R; DiComo, G; Ting, A
2014-08-01
Thermal blooming of a laser beam propagating in a gas-filled tube is investigated both analytically and experimentally. A self-consistent formulation taking into account heating of the gas and the resultant laser beam spreading (including diffraction) is presented. The heat equation is used to determine the temperature variation while the paraxial wave equation is solved in the eikonal approximation to determine the temporal and spatial variation of the Gaussian laser spot radius, Gouy phase (longitudinal phase delay), and wavefront curvature. The analysis is benchmarked against a thermal blooming experiment in the literature using a CO₂ laser beam propagating in a tube filled with air and propane. New experimental results are presented in which a CW fiber laser (1 μm) propagates in a tube filled with nitrogen and water vapor. By matching laboratory and theoretical results, the absorption coefficient of water vapor is found to agree with calculations using MODTRAN (the MODerate-resolution atmospheric TRANsmission molecular absorption database) and HITRAN (the HIgh-resolution atmospheric TRANsmission molecular absorption database). PMID:25090334
The Optical Absorption Coefficient of Bean Seeds Investigated Using Photoacoustic Spectroscopy
NASA Astrophysics Data System (ADS)
Sanchez-Hernandez, G.; Hernandez-Aguilar, C.; Dominguez-Pacheco, A.; Cruz-Orea, A.; Perez-Reyes, M. C. J.; Martinez, E. Moreno
2015-06-01
A knowledge about seed optical parameters is of great relevance in seed technology practice. Such parameters provide information about its absorption and reflectance, which could be useful for biostimulation processes, by light sources, in early stages of seed germination. In the present research photoacoustic spectroscopy (PAS) and the Rosencwaig and Gersho model were used to determine the optical absorption coefficient () of five varieties of bean seeds ( Phaseolus vulgaris L.), of different productive cycles; the seeds were biostimulated by laser treatment to evaluate the effects of biostimulation pre-sowing. It was found that the bean varieties V1, V2, V4, and V5 were optically opaque in the visible spectrum; in the case of the V3 variety, this sample was optically transparent from 680 nm. The varieties of the studied bean seeds showed significant statistical differences in sizes and also in their optical absorption spectra. The biostimulation effects showed that the seed samples with a higher optical penetration length had a positive biostimulation, in the percentage of germination, obtaining an enhancement of 47 % compared to the control sample. The utility of PAS for the optical characterization of seeds has been demonstrated in this study of the laser biostimulation process of this kind of samples.
Jacques, S L; McAuliffe, D J
1991-06-01
The explosive vaporization of melanosomes in situ in skin during pulsed laser irradiation (pulse duration less than 1 microsecond) is observed as a visible whitening of the superficial epidermal layer due to stratum corneum disruption. In this study, the ruby laser (694 nm) was used to determine the threshold radiant exposure, H0 (J/cm2), required to elicit whitening for in vitro black (Negroid) human skin samples which were pre-equilibrated at an initial temperature, Ti, of 0, 20, or 50 degrees C. A plot of H0 vs Ti yields a straight line whose x-intercept indicates the threshold temperature of explosive vaporization to be 112 +/- 7 degrees C (SD, N = 3). The slope, delta H0/delta Ti, specifies the internal absorption coefficient, mua, within the melanosome: mua = -rho C/(slope(1 + 7.1 Rd)), where rho C is the product of density and specific heat, and Rd is the total diffuse reflectance from the skin. A summary of the absorption spectrum (mua) for the melanosome interior (351-1064 nm) is presented based on H0 data from this study and the literature. The in vivo absorption spectrum (380-820 nm) for human epidermal melanin was measured by an optical fiber spectrophotometer and is compared with the melanosome spectrum. PMID:1886936
De Roo, Jonathan; Ibáñez, Maria; Geiregat, Pieter; Nedelcu, Georgian; Walravens, Willem; Maes, Jorick; Martins, Jose C; Van Driessche, Isabel; Kovalenko, Maksym V; Hens, Zeger
2016-02-23
Lead halide perovskite materials have attracted significant attention in the context of photovoltaics and other optoelectronic applications, and recently, research efforts have been directed to nanostructured lead halide perovskites. Collodial nanocrystals (NCs) of cesium lead halides (CsPbX3, X = Cl, Br, I) exhibit bright photoluminescence, with emission tunable over the entire visible spectral region. However, previous studies on CsPbX3 NCs did not address key aspects of their chemistry and photophysics such as surface chemistry and quantitative light absorption. Here, we elaborate on the synthesis of CsPbBr3 NCs and their surface chemistry. In addition, the intrinsic absorption coefficient was determined experimentally by combining elemental analysis with accurate optical absorption measurements. (1)H solution nuclear magnetic resonance spectroscopy was used to characterize sample purity, elucidate the surface chemistry, and evaluate the influence of purification methods on the surface composition. We find that ligand binding to the NC surface is highly dynamic, and therefore, ligands are easily lost during the isolation and purification procedures. However, when a small amount of both oleic acid and oleylamine is added, the NCs can be purified, maintaining optical, colloidal, and material integrity. In addition, we find that a high amine content in the ligand shell increases the quantum yield due to the improved binding of the carboxylic acid. PMID:26786064
Absorption coefficients of selected explosives and related compounds in the range of 0.1-2.8 THz.
Chen, Jian; Chen, Yunqing; Zhao, Hongwei; Bastiaans, Glenn J; Zhang, X-C
2007-09-17
We have investigated the absorption spectra of seventeen explosives and related compounds (ERCs) by using terahertz time-domain spectroscopy in the 0.1-2.8 THz region. Most of these substances show characteristic absorption features in this frequency range. The measured absorption coefficients of these ERCs form a database, which is of great importance for biochemical, defense and security related applications. PMID:19547570
NASA Technical Reports Server (NTRS)
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."
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.
Spectral absorption-coefficient data on HCFC-22 and SF6 for remote-sensing applications
NASA Technical Reports Server (NTRS)
Varanasi, P.; Li, Z.; Nemtchinov, V.; Cherukuri, A.
1994-01-01
Spectral absorption-coefficients (cross-sections) kappa(sub nu) (/cm/atm) have been measured in the 7.62, 8.97, and 12.3 micrometer bands of HCFC-22 (CHClF2) and the 10.6 micrometer bands of SF6 employing a high-resolution Fourier-transform spectrometer. Temperature and total pressure have been varied to simulate conditions corresponding to tropospheric and stratospheric layers in the atmosphere. The kappa(sub nu) are compared with values measured by us previously using a tunable diode laser spectrometer and with the appropriate entries in HITRAN and GEISA, two of the databases known to the atmospheric scientist. The measured absolute intensities of the bands are compared with previously published values.
Madelin, Guillaume; Grucker, Daniel; Franconi, Jean-Michel; Thiaudiere, Eric
2006-07-01
In this study, magnetic resonance imaging (MRI) is used to visualize acoustic streaming in liquids. A single-shot spin echo sequence (HASTE) with a saturation band perpendicular to the acoustic beam permits the acquisition of an instantaneous image of the flow due to the application of ultrasound. An average acoustic streaming velocity can be estimated from the MR images, from which the ultrasonic absorption coefficient and the bulk viscosity of different glycerol-water mixtures can be deduced. In the same way, this MRI method could be used to assess the acoustic field and time-average power of ultrasonic transducers in water (or other liquids with known physical properties), after calibration of a geometrical parameter that is dependent on the experimental setup. PMID:16650447
Huang, Chuan; Graff, Christian G.; Clarkson, Eric W.; Bilgin, Ali; Altbach, Maria I.
2011-01-01
Recently, there has been an increased interest in quantitative MR parameters to improve diagnosis and treatment. Parameter mapping requires multiple images acquired with different timings usually resulting in long acquisition times. While acquisition time can be reduced by acquiring undersampled data, obtaining accurate estimates of parameters from undersampled data is a challenging problem, in particular for structures with high spatial frequency content. In this work, Principal Component Analysis (PCA) is combined with a model-based algorithm to reconstruct maps of selected principal component coefficients from highly undersampled radial MRI data. This novel approach linearizes the cost function of the optimization problem yielding a more accurate and reliable estimation of MR parameter maps. The proposed algorithm - REconstruction of Principal COmponent coefficient Maps (REPCOM) using Compressed Sensing - is demonstrated in phantoms and in vivo and compared to two other algorithms previously developed for undersampled data. PMID:22190358
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.
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)
Wang, Gufeng; Karnes, John; Bunker, Christopher E.; Lei Geng, M.
2006-11-01
We demonstrate the feasibility of using two-dimensional correlation coefficient mapping to classify gas chromatograms of environmental hazards. Correct identification and classification of the contaminants is the prerequisite for their appropriate treatment and containments. A data set consisting of 76 gas chromatograms of eight types of jet fuels, which are common sources of hydrocarbon contamination in ground water, is examined with two-dimensional statistical sample-sample correlation coefficients. Analysis demonstrates that jet fuel samples of the same type correlate strongly with each other but less significantly with other jet fuel classes. According to the magnitude of the correlation coefficients between each pair of the samples, jet fuel types of each sample in the data set can be assigned with an accuracy of 100% through a leave-one-out cross validation (LOOCV) procedure. Correlation coefficient mapping is thus a promising method to classify samples of environmental importance.
Wei, Jianwei; Lee, Zhongping
2015-02-01
The light absorption of phytoplankton and colored detrital matter (CDM), which includes contribution of gelbstoff and detrital matters, has distinctive yet overlapping features in the ultraviolet (UV) and visible domain. The CDM absorption (a(dg)) increases exponentially with decreasing wavelength while the absorption coefficient of phytoplankton (a(ph)) generally decreases toward the shorter bands for the range of 350-450 nm. It has long been envisioned that including ocean color measurements in the UV range may help the separation of these two components from the remotely sensed ocean color spectrum. An attempt is made in this study to provide an analytical assessment of this expectation. We started with the development of an absorption decomposition model [quasi-analytical algorithm (QAA)-UV], analogous to the QAA, that partitions the total absorption coefficient using information at bands 380 and 440 nm. Compared to the retrieval results relying on the absorption information at 410 and 440 nm of the original QAA, our analyses indicate that QAA-UV can improve the retrieval of a(ph) and a(dg), although the improvement in accuracy is not significant for values at 440 nm. The performance of the UV-based algorithm is further evaluated with in situ measurements. The limited improvement observed with the field measurements highlights that the separation of a(dg) and a(ph) is highly dependent on the accuracy of the ocean color measurements and the estimated total absorption coefficient. PMID:25967770
NASA Astrophysics Data System (ADS)
Wu, J.; Hong, H.; Shang, S.; Dai, M.; Lee, Z.
2007-05-01
We examined the temporal and spatial variabilities of phytoplankton absorption coefficients (αphλ)) and their relationships with physical processes in the northern South China Sea from two cruise surveys during spring (May 2001) and late autumn (November 2002). A large river plume induced by heavy precipitation in May stimulated a phytoplankton bloom on the inner shelf, causing significant changes in the surface water in αph values and B/R ratios (αph(440)/αph(675)). This was consistent with the observed one order of magnitude elevation of chlorophyll α and a shift from a pico/nano dominated phytoplankton community to one dominated by micro-algae. At the seasonal level, enhanced vertical mixing due to strengthened northeast monsoon in November has been observed to result in higher surface αph(675) (0.002-0.006 m-1 higher) and less pronounced subsurface maximum on the outer shelf/slope in November as compared that in May. Measurements of αph and B/R ratios from three transects in November revealed a highest surface αph(675) immediately outside the mouth of the Pearl River Estuary, whereas lower αph(675) and higher B/R ratios were featured in the outer shelf/slope waters, demonstrating the respective influence of the Pearl River plume and the oligotrophic nature of South China Sea water. The difference in spectral shapes of phytoplankton absorption (measured by B/R ratios and bathochromic shifts) on these three transects infers that picoprocaryotes are the major component of the phytoplankton community on the outer shelf/slope rather than on the inner shelf. In addition, a regional tuning of the phytoplankton absorption spectral model (Carder et al., 1999) demonstrated a greater spatial variation than seasonal variation in the lead parameter a0(λ). These results suggest that phytoplankton absorption properties in a coastal region such as the northern South China Sea are complex and region-based parameterization is mandatory in order for remote sensing
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)
Vivacqua, Marco; Espinosa, Daniel; Martins Figueiredo Neto, Antônio
2012-06-01
We investigate the occurrence of the optical Kerr effect and two-photon absorption when an oil-based magnetic Fe3O4 nanoparticles colloidal suspension is illuminated with high intensity femtosecond laser pulses. The frequency of the pulses is controlled and the Z-scan technique is employed in our measurements of the nonlinear optical Kerr coefficient (n2) and two-photon absorption coefficient (β). From these values it was possible to calculate the real and imaginary parts of the third-order susceptibility. We observed that increasing the pulse frequency, additional physical processes take place, increasing artificially the absolute values of n2 and β. The experimental conditions are discussed to assure the obtention of reliable values of these nonlinear optical parameters, which may be useful in all-optical switching and optical power limiting applications.
NASA Astrophysics Data System (ADS)
Cacciani, Marco; Disarra, Alcide; Fiocco, Giorgio
1987-06-01
Instrumentation for the absolute measurement of the ozone absorption coefficient in the Huggins bands at different temperatures was set up. Ozone is produced with an electrical discharge and stored cryogenically; differential absorption measurements are carried out in a slowly evolving mixture of ozone and molecular oxygen. Results in the region 339 to 362 nm at temperatures between minus 30 and plus 40 C are reported. Results support Katayama's (1979) model of the transitions giving rise to the Huggins absorption bands of ozone. For measurements of atmospheric ozone profiles by DIAL techniques, the results on the temperature dependence of the absorption coefficient at the wavelength corresponding to the third harmonic of an NdYAG laser are stressed.
Mass-energy absorption coefficient and backscatter factor ratios for kilovoltage x-ray beams
NASA Astrophysics Data System (ADS)
Ma, C.-M.; Seuntjens, J. P.
1999-01-01
For low-energy (up to 150 kV) x-rays, the ratio of mass-energy absorption coefficients for water to air, , and the backscatter factor B are used in the conversion of air kerma, measured free-in-air, to water kerma on the surface of a water phantom. For clinical radiotherapy, similar conversion factors are needed for the determination of the absorbed dose to biological tissues on (or near) the surface of a human body. We have computed the ratios and B factor ratios for different biological tissues including muscle, soft tissue, lung, skin and bone relative to water. The ratios were obtained by integrating the respective mass-energy absorption coefficients over the in-air primary photon spectra. We have also calculated the ratios at different depths in a water phantom in order to convert the measured in-phantom water kerma to the absorbed dose to various biological tissues. The EGS4/DOSIMETER Monte Carlo code system has been used for the simulation of the energy fluence at different depths in a water phantom irradiated by a kilovoltage x-ray beam of variable beam quality (HVL: 0.1 mm Al-5 mm Cu), field size and source-surface distance (SSD). The same code was also used in the calculation of the B factor ratios, soft tissue to water and bone to water. The results show that the B factor for bone differs from the B factor for water by up to 20% for a 100 kV beam (HVL: 2.65 mm Al) with a 100 field. On the other hand, the difference in the B factor between water and soft tissue is insignificant (well within 1% generally). This means that the B factors for water may be directly used to
NASA Technical Reports Server (NTRS)
Smith, Wm. Hayden; Conner, Charles P.; Baines, Kevin H.
1990-01-01
A novel laser intracavity photoacoustic spectroscopy method allowing high sample control accuracy due to the small sample volume required has been used to obtain absorption coefficients for the CH4 6190 A band as a function of temperature, from 290 to 100 K. The peak absorption coefficient is found to increase from 0.6 to 1.0/cm, and to be accompanied by significant band shape changes. When used to further constrain the Baines and Bergstrahl (1986) standard model of the Uranus atmosphere, the low-temperature data yield an excellent fit to the bandshape near the 6190 A band's minimum.
Smith, WM.H.; Conner, C.P.; Baines, K.H. JPL, Pasadena, CA )
1990-05-01
A novel laser intracavity photoacoustic spectroscopy method allowing high sample control accuracy due to the small sample volume required has been used to obtain absorption coefficients for the CH{sub 4} 6190 A band as a function of temperature, from 290 to 100 K. The peak absorption coefficient is found to increase from 0.6 to 1.0/cm, and to be accompanied by significant band shape changes. When used to further constrain the Baines and Bergstrahl (1986) standard model of the Uranus atmosphere, the low-temperature data yield an excellent fit to the bandshape near the 6190 A band's minimum. 18 refs.
Rowley, R.L.; Adams, M.E.; Marshall, T.L.; Oscarson, J.L.; Wilding, W.V.; Anderson, D.J.
1997-03-01
Natural gas processors use amine treating processes to remove the acid gases H{sub 2}S and CO{sub 2} from gas streams. Absorption rates of gaseous CO{sub 2} into aqueous N-methyldiethanolamine (MDEA) solutions were measured in a quiescent, inverted-tube diffusiometer by monitoring the rate of pressure drop. The absorption rate was found to be insensitive to the diffusion coefficient of CO{sub 2} in solution but very sensitive to the diffusion rate of bicarbonate and protonated MDEA ions. Evidence also suggested that chemical reaction equilibrium is rapid relative to diffusion. A numerical model was developed on the basis of these observations. The model was used to regress diffusion coefficients of bicarbonate and protonated amine, which must be equivalent by electroneutrality arguments, from measured absorption rates. Complete modeling of the absorption process also required data for the diffusion coefficient of MDEA in water. These were measured using a Taylor dispersion apparatus. CO{sub 2} absorption rates and diffusion coefficients of bicarbonate and protonated MDEA were obtained at 298.2 K and 318.2 K in solutions containing 20, 35, and 50 mass % MDEA in water.
Majaron, Boris; Milanic, Matija
2007-02-21
Spectral variation of the sample absorption coefficient in mid-infrared (muIR) demands caution in photothermal radiometric measurements, because a constant muIR is regularly assumed in inverse analysis of the acquired signals. Adverse effects of such approximation were recently demonstrated in numerical simulations of pulsed photothermal radiometric (PPTR) temperature profiling in soft biological tissues, utilizing a general-purpose optimization code in the reconstruction process. We present here an original reconstruction code, which combines a conjugate gradient minimization algorithm with non-negativity constraint to the sought temperature vector. For the same test examples as in the former report (hyper-Gaussian temperature profiles, InSb detector with 3-5 microm acquisition band, signal-to-noise ratio SNR=300) we obtain markedly improved reconstruction results, both when using a constant value mueff and when the spectral variation muIR(lambda) is accounted for in the analysis. By comparing the results, we find that the former approach introduces observable artefacts, especially in the superficial part of the profile (z<100 microm). However, the artefacts are much less severe than previously reported and are almost absent in the case of a deeper, single-lobed test profile. We demonstrate that the observed artefacts do not result from sub-optimal selection of mueff, and that they vary with specific realizations of white noise added to the simulated signals. The same holds also for a two-lobed test profile. PMID:17264372
NASA Astrophysics Data System (ADS)
Fuente, Raquel; Apiñaniz, Estibaliz; Mendioroz, Arantza; Salazar, Agustín
2011-08-01
Modulated photothermal radiometry (PTR) has been widely used to measure the thermal diffusivity of bulk materials. The method is based on illuminating the sample with a plane light beam and measuring the infrared emission with an infrared detector. The amplitude and phase of the PTR voltage is recorded as a function of the modulation frequency and then fitted to the theoretical model. In this work, we test the ability of modulated PTR to retrieve simultaneously the thermal diffusivity and the optical absorption coefficient of homogeneous slabs. In order to eliminate the instrumental factor, self-normalization is used, i.e., the ratio of the PTR signal recorded at the rear and front surfaces. The influence of the multiple reflections of the light beam, the heat losses, and the transparency to infrared wavelengths are analyzed. Measurements performed on a wide variety of homogeneous materials, covering the whole range from transparent to opaque, confirm the validity of the method. In Part II of this work, the method is extended to multilayered materials.
Noise-driven optical absorption coefficients of impurity doped quantum dots
NASA Astrophysics Data System (ADS)
Ganguly, Jayanta; Saha, Surajit; Pal, Suvajit; Ghosh, Manas
2016-01-01
We make an extensive investigation of linear, third-order nonlinear, and total optical absorption coefficients (ACs) of impurity doped quantum dots (QDs) in presence and absence of noise. The noise invoked in the present study is a Gaussian white noise. The quantum dot is doped with repulsive Gaussian impurity. Noise has been introduced to the system additively and multiplicatively. A perpendicular magnetic field acts as a source of confinement and a static external electric field has been applied. The AC profiles have been studied as a function of incident photon energy when several important parameters such as optical intensity, electric field strength, magnetic field strength, confinement energy, dopant location, relaxation time, Al concentration, dopant potential, and noise strength take on different values. In addition, the role of mode of application of noise (additive/multiplicative) on the AC profiles has also been analyzed meticulously. The AC profiles often consist of a number of interesting observations such as one photon resonance enhancement, shift of AC peak position, variation of AC peak intensity, and bleaching of AC peak. However, presence of noise alters the features of AC profiles and leads to some interesting manifestations. Multiplicative noise brings about more complexity in the AC profiles than its additive counterpart. The observations indeed illuminate several useful aspects in the study of linear and nonlinear optical properties of doped QD systems, specially in presence of noise. The findings are expected to be quite relevant from a technological perspective.
NASA Astrophysics Data System (ADS)
Clark, Christopher J. R.; Schofield, Simon P.; Gomez, Haley L.; Davies, Jonathan I.
2016-06-01
We use the published photometry and spectroscopy of 22 galaxies in the Herschel Reference Survey to determine that the value of the dust mass absorption coefficient κd at a wavelength of 500 μm is kappa _{500} = 0.051^{+0.070}_{-0.026} m^{2 kg^{-1}}. We do so by taking advantage of the fact that the dust-to-metals ratio in the interstellar medium of galaxies appears to be constant. We argue that our value for κd supersedes that of James et al. - who pioneered this approach for determining κd - because we take advantage of superior data, and account for a number of significant systematic effects that they did not consider. We comprehensively incorporate all methodological and observational contributions to establish the uncertainty on our value, which represents a marked improvement on the oft-quoted `order-of-magnitude' uncertainty on κd. We find no evidence that the value of κd differs significantly between galaxies, or that it correlates with any other measured or derived galaxy properties. We note, however, that the availability of data limits our sample to relatively massive (109.7 < M⋆ < 1011.0 M⊙), high metallicity (8.61 < [ 12 + log_{10} fracOH ] < 8.86) galaxies; future work will allow us to investigate a wider range of systems.
NASA Astrophysics Data System (ADS)
Vuye, Cedric; Vanlanduit, Steve; Guillaume, Patrick
2009-06-01
When using optical measurements of the sound fields inside a glass tube, near the material under test, to estimate the reflection and absorption coefficients, not only these acoustical parameters but also confidence intervals can be determined. The sound fields are visualized using a scanning laser Doppler vibrometer (SLDV). In this paper the influence of different test signals on the quality of the results, obtained with this technique, is examined. The amount of data gathered during one measurement scan makes a thorough statistical analysis possible leading to the knowledge of confidence intervals. The use of a multi-sine, constructed on the resonance frequencies of the test tube, shows to be a very good alternative for the traditional periodic chirp. This signal offers the ability to obtain data for multiple frequencies in one measurement, without the danger of a low signal-to-noise ratio. The variability analysis in this paper clearly shows the advantages of the proposed multi-sine compared to the periodic chirp. The measurement procedure and the statistical analysis are validated by measuring the reflection ratio at a closed end and comparing the results with the theoretical value. Results of the testing of two building materials (an acoustic ceiling tile and linoleum) are presented and compared to supplier data.
Effects of nanosilver on sound absorption coefficients in solid wood species.
Taghiyari, Hamid Reza; Esmailpour, Ayoub; Zolfaghari, Habib
2016-06-01
Sound absorption coefficients (ACs) were determined in five solid woods (poplar, beech, walnut, mulberry, and fir) in the longitudinal and tangential directions at four different frequencies of 800, 1000, 2000, and 4000 Hz. The length of the longitudinal and tangential specimens was 50-mm and 10-mm, respectively. Separate sets of specimens were impregnated with either nanosilver suspension or water. The size range of nanoparticles was 30-80 nm. Results showed that sound ACs were lower in longitudinal specimens because sound waves could penetrate the open ends of vessels more easily, being trapped and damped there. Impregnation with both nanosilver suspension and water resulted in a significant decrease in the sound ACs. The decrease in the ACs was due to the collapsing and accumulation of perforation plates and cell parts, blocking the way through which waves could pass through the vessels. This caused higher damping due to a phenomenon called vibration decay. Correlation between gas permeability versus sound AC is significantly dependant on the porous structure of individual specimens. PMID:27256895
Determination of the diffusion length and the optical self absorption coefficient using EBIC model
NASA Astrophysics Data System (ADS)
Guermazi, S.; Guermazi, H.; Mlik, Y.; El Jani, B.; Grill, C.; Toureille, A.
2001-10-01
We have developed a model of calculation of the induced current due to an electron beam. The expression for the electron beam induced current (EBIC) with an extended generation profile is obtained via the resolution of a steady state continuity equation by the Green function method, satisfying appropriated boundary conditions to the physical model. The generation profile takes into account the lateral diffusion, the effect of defects, dislocations and recombination surfaces besides the number of absorbed electrons and that of diffuse electrons as a function of the depth. In the case of a Schottky diode Au/GaAs obtained by metalorganic vapour phase epitaxy (MOVPE) method, the theoretical induced current profile is compared to the experimental one and to theoretical profiles whose analytical expressions are given by van Roosbroeck and Bresse. The minority carriers diffusion length L_n = 2 μm and the optical self-absorption coefficient a=0.034 μm^{-1} can be deduced from the experimental current profile, measured by scanning electron microscopy. The theoretical curve, obtained from the proposed model is in a good agreement with the experimental one for surface recombination velocity 10^6 cm s^{-1} except for distances far from the depletion layer (x_0 > 2.3 μm) where the photocurrent produced by the multiple process of the reabsorbed recombination radiation is preponderant. Our results are in agreement with those obtained by other experimental techniques on the same samples.
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.
Chazel, V; Houpert, P; Paquet, F; Ansoborlo, E
2001-01-01
In the Human Respiratory Tract Model (HRTM) described in ICRP Publication 66, time-dependent dissolution is described by three parameters: the fraction dissolved rapidly, fr, and the rapid and slow dissolution rates sr and ss. The effect of these parameters on the dose coefficient has been studied. A theoretical analysis was carried out to determine the sensitivity of the dose coefficient to variations in the values of these absorption parameters. Experimental values of the absorption parameters and the doses per unit intake (DPUI) were obtained from in vitro dissolution tests, or from in vivo experiments with rats, for five industrial uranium compounds UO2, U3O8, UO4, UF4 and a mixture of uranium oxides. These compounds were classified in terms of absorption types (F, M or S) according to ICRP. The overall result was that the factor which has the greatest influence on the dose coefficient was the slow dissolution rate ss. This was verified experimentally, with a variation of 20% to 55% for the DPUI according to the absorption type of the compound. In contrast, the rapid dissolution rate sr had little effect on the dose coefficient, excepted for Type F compounds. PMID:11487809
Several important optical terms such as "absorbance" and "absorption coefficient" are frequently used ambiguously in the current peer-reviewed literature. Since they are important terms that are required to derive other quantities such as the "apparent quantum yield" of photoprod...
NASA Technical Reports Server (NTRS)
Barstow, M. A.; Lewis, M.; Petre, R.
1983-01-01
Transmittances of thin-film filters fabricated for an extreme-UV astronomy sounding-rocket experiment yield values for the linear absorption coefficient of beryllium in the 50-300-A wavelength range, in which previous measurements are sparse. The inferred values are consistent with the lowest data previously published and may have important consequences for extreme-UV astronomers.
NASA Astrophysics Data System (ADS)
Ebrahimipour, Bahareh Alsadat; Askari, Hassan Ranjbar; Ramezani, Ali Behjat
2016-09-01
The interlevel absorption coefficient of CdSe/ZnS and ZnS/CdSe core-shell Quantum Dot (QD) in luminescent solar concentrators (LSCs) is reported. By considering the quantum confinement effects, the wave functions and eigenenergies of electrons in the nonperturebative system consists of a core-shell QD have been numerically calculated under the frame work of effective-mass approximation by solving a three-dimensional Schrӧdinger equation. And then the absorption coefficient is obtained under density matrix approximation considering in the polymer sheets of the concentrator including the core-shell QDs. The effect of the hetero-structure geometry upon the energy spectrum and absorption coefficient associated to interlevel transitions was also considered. The results show that the core-shell QDs can absorb the photons with higher energy in solar spectrum as compared to the inverted core-shell. And with a small shell layer diameter, the core-shell QDs produce larger linear absorption coefficients and consequently higher efficiency values, however it is inversed for inverted core-shell QDs. The work described here gives a detailed insight into the promise of QD-based LSCs and the optoelectronic devices applications.
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.
Absorption coefficient of urban aerosol in Nanjing, west Yangtze River Delta, China
NASA Astrophysics Data System (ADS)
Zhuang, B. L.; Wang, T. J.; Liu, J.; Ma, Y.; Yin, C. Q.; Li, S.; Xie, M.; Han, Y.; Zhu, J. L.; Yang, X. Q.; Fu, C. B.
2015-12-01
Absorbing aerosols can significantly modulate short-wave solar radiation in the atmosphere, affecting regional and global climate. The aerosol absorption coefficient (AAC) is an indicator that assesses the impact of absorbing aerosols on radiative forcing. In this study, the near-surface AAC and absorption Ångström exponent (AAE) in the urban area of Nanjing, China, are characterized on the basis of measurements in 2012 and 2013 using the seven-channel Aethalometer (model AE-31, Magee Scientific, USA). The AAC is estimated with direct and indirect corrections, which result in consistent temporal variations and magnitudes of AAC at 532 nm. The mean AAC at 532 nm is about 43.23 ± 28.13 M m-1 in the urban area of Nanjing, which is much lower than that in Pearl River Delta and the same as in rural areas (Lin'an) in Yangtze River Delta. The AAC in the urban area of Nanjing shows strong seasonality (diurnal variations); it is high in cold seasons (at rush hour) and low in summer (in the afternoon). It also shows synoptic and quasi-2-week cycles in response to weather systems. Its frequency distribution follows a typical log-normal pattern. The 532 nm AAC ranging from 15 to 65 M m-1 dominates, accounting for more than 72 % of the total data samples in the entire study period. Frequent high pollution episodes, such as those observed in June 2012 and in winter 2013, greatly enhanced AAC and altered its temporal variations and frequency distributions. These episodes are mostly due to local emissions and regional pollution. Air masses flowing from northern China to Nanjing can sometimes be highly polluted and lead to high AAC at the site. AAE at 660/470 nm from the Schmid correction (Schmid et al., 2006) is about 1.56, which might be more reasonable than from the Weingartner correction (Weingartner et al., 2003). Low AAEs mainly occur in summer, likely due to high relative humidity (RH) in the season. AAC increases with increasing AAE at a fixed aerosol loading. The RH
Absorption coefficient of urban aerosol in Nanjing, west Yangtze River Delta of China
NASA Astrophysics Data System (ADS)
Zhuang, B. L.; Wang, T. J.; Liu, J.; Ma, Y.; Yin, C. Q.; Li, S.; Xie, M.; Han, Y.; Zhu, J. L.; Yang, X. Q.; Fu, C. B.
2015-06-01
Absorbing aerosols can significantly modulate shortwave solar radiation in the atmosphere, affecting regional and global climate. Aerosol absorption coefficient (AAC) is an indicator to assess the impact of absorbing aerosols on radiative forcing. In this study, the near-surface AAC and absorption angstrom exponent (AAE) in urban Nanjing, China, are characterized on the basis of measurements in 2012 and 2013 using the 7-channel Aethalometer (model AE-31, Magee Scientific, USA). The AAC is estimated with direct and indirect corrections, which show consistent temporal variations and magnitudes of AAC at 532 nm. The mean AAC at 532 nm is about 43.23 ± 28.13 M m-1 in urban Nanjing, which is much lower than that in Pearl River Delta and as the same as that in rural areas (Lin'an) in Yangtze River Delta. The AAC in urban Nanjing shows strong seasonality (diurnal variations), high in cold seasons (at rush hours) and low in summer (in afternoon). It also show synoptic and quasi-two-week cycles in response to weather systems. Its frequency distribution follows a typical lognormal pattern. The 532 nm-AAC ranging from 15 to 65 M m-1 dominates, accounting for more than 72% of the total data samples in the entire study period. Frequent high pollution episodes, such as those observed in June 2012 and in winter 2013, greatly enhanced AAC and altered its temporal variations and frequency distributions. These episodes are mostly due to local emissions and regional pollutions. Air masses from northern China to Nanjing can sometimes be highly polluted and lead to high AAC at the site. AAE at 660/470 nm from the Schmid correction (Schmid et al., 2006) is about 1.56, which might be more reasonable compared to that from the Weingartner correction (Weingartner et al., 2003). Low AAEs mainly appear in summer in response to the relative humidity (RH). AAC increases with increasing AAE at a fixed aerosol loading. The RH-AAC relationship is more complex. Overall, AAC peaks around RH values
NASA Technical Reports Server (NTRS)
Mcpeters, R. D.; Bass, A. M.
1982-01-01
Real structure is revealed, by an analysis of continuous scan data from the solar backscattered UV instrument on Nimbus 7, in the backscattered atmospheric albedo region between 300 and 310 nm where spectral anomalies have been reported in ground-based observation. The spectral anomalies are explainable as structure at the 1-5% level in the ozone absorption coefficient, as measured by Bass and Paur (1981). The new absorption coefficient measurements are judged to approach the 1%-level of accuracy in atmospheric radiation calculation, which should resolve discrepancies between different Dobson wavelength pairs and between different instruments and permit the more accurate analysis of such second-order effects as NO emission, SO2 absorption in polluted atmospheres, and Raman scattering effects.
How to measure and predict the molar absorption coefficient of a protein.
Pace, C. N.; Vajdos, F.; Fee, L.; Grimsley, G.; Gray, T.
1995-01-01
The molar absorption coefficient, epsilon, of a protein is usually based on concentrations measured by dry weight, nitrogen, or amino acid analysis. The studies reported here suggest that the Edelhoch method is the best method for measuring epsilon for a protein. (This method is described by Gill and von Hippel [1989, Anal Biochem 182:319-326] and is based on data from Edelhoch [1967, Biochemistry 6:1948-1954]). The absorbance of a protein at 280 nm depends on the content of Trp, Tyr, and cystine (disulfide bonds). The average epsilon values for these chromophores in a sample of 18 well-characterized proteins have been estimated, and the epsilon values in water, propanol, 6 M guanidine hydrochloride (GdnHCl), and 8 M urea have been measured. For Trp, the average epsilon values for the proteins are less than the epsilon values measured in any of the solvents. For Tyr, the average epsilon values for the proteins are intermediate between those measured in 6 M GdnHCl and those measured in propanol. Based on a sample of 116 measured epsilon values for 80 proteins, the epsilon at 280 nm of a folded protein in water, epsilon (280), can best be predicted with this equation: epsilon (280) (M-1 cm-1) = (#Trp)(5,500) + (#Tyr)(1,490) + (#cystine)(125) These epsilon (280) values are quite reliable for proteins containing Trp residues, and less reliable for proteins that do not. However, the Edelhoch method is convenient and accurate, and the best approach is to measure rather than predict epsilon. PMID:8563639
A spatially varying coefficient model for mapping PM10 air quality at the European scale
NASA Astrophysics Data System (ADS)
Hamm, N. A. S.; Finley, A. O.; Schaap, M.; Stein, A.
2015-02-01
Particulate matter (PM) air quality in Europe has improved substantially over the past decades, but it still poses a significant threat to human health. Accurate regional scale maps of PM10 concentrations are needed for monitoring progress in mitigation strategies and monitoring compliance with statutory limit values. Chemistry transport models (CTM) use emission databases and simulate the transport and deposition of pollutants. They deliver such maps but are known to be inaccurate. A promising approach is to use geostatistics to model the relationship between the in situ observations and the CTM. This has been shown to be more accurate than using either observations or CTM's alone. This paper presents a spatially varying coefficients (SVC) geostatistical model as an extension of the standard spatially varying intercept (SVI) geostatistical model. SVC allowed the regression coefficient to vary spatially according to a covariance function, the parameters of which were estimated from the data. It was built as a Bayesian hierarchical model and implemented using Markov chain Monte Carlo. The procedure was applied to Airbase PM10 observations and LOTOS-EUROS simulated PM10 for central, southern and eastern Europe. Model-fit diagnostics showed that SVC delivered a better fit to the data than SVI. Mapping the spatially varying coefficients allowed identification of the locations where the CTM performed well or poorly. This could be used for objective CTM evaluation purposes. The posterior predictive simulations were also used to map median PM10 concentrations as well as the probability of exceeding the 50 μg m-3 EU daily PM10 concentration threshold. Although posterior median prediction accuracy was similar for SVI and SVC, SVC better modelled the process and yielded narrower credible intervals. As such, SVC was more appropriate for quantifying uncertainty and for mapping threshold exceedances. The resulting maps may be used to guide air quality assessment and mitigation
The absorption coefficient of the liquid N2 2.15-micron band and application to Triton
NASA Technical Reports Server (NTRS)
Grundy, William M.; Fink, Uwe
1991-01-01
The present measurements of the temperature dependence exhibited by the liquid N2 2.15-micron 2-0 collision-induced band's absorption coefficient and integrated absorption show the latter to be smaller than that of the N2 gas, and to decrease with decreasing temperature. Extrapolating this behavior to Triton's nominal surface temperature yields a new estimate of the N2-ice grain size on the Triton south polar cap; a mean N2 grain size of 0.7-3.0 cm is consistent with grain growth rate calculation results.
NASA Astrophysics Data System (ADS)
Andreo, Pedro; Burns, David T.; Salvat, Francesc
2012-04-01
A systematic analysis of the available data has been carried out for mass energy-absorption coefficients and their ratios for air, graphite and water for photon energies between 1 keV and 2 MeV, using representative kilovoltage x-ray spectra for mammography and diagnostic radiology below 100 kV, and for 192Ir and 60Co gamma-ray spectra. The aim of this work was to establish ‘an envelope of uncertainty’ based on the spread of the available data. Type A uncertainties were determined from the results of Monte Carlo (MC) calculations with the PENELOPE and EGSnrc systems, yielding mean values for µen/ρ with a given statistical standard uncertainty. Type B estimates were based on two groupings. The first grouping consisted of MC calculations based on a similar implementation but using different data and/or approximations. The second grouping was formed by various datasets, obtained by different authors or methods using the same or different basic data, and with different implementations (analytical, MC-based, or a combination of the two); these datasets were the compilations of NIST, Hubbell, Johns-Cunningham, Attix and Higgins, plus MC calculations with PENELOPE and EGSnrc. The combined standard uncertainty, uc, for the µen/ρ values for the mammography x-ray spectra is 2.5%, decreasing gradually to 1.6% for kilovoltage x-ray spectra up to 100 kV. For 60Co and 192Ir, uc is approximately 0.1%. The Type B uncertainty analysis for the ratios of µen/ρ values includes four methods of analysis and concludes that for the present data the assumption that the data interval represents 95% confidence limits is a good compromise. For the mammography x-ray spectra, the combined standard uncertainties of (µen/ρ)graphite,air and (µen/ρ)graphite,water are 1.5%, and 0.5% for (µen/ρ)water,air, decreasing gradually down to uc = 0.1% for the three µen/ρ ratios for the gamma-ray spectra. The present estimates are shown to coincide well with those of Hubbell (1977 Rad. Res
I-scan thermal lens experiment in the pulse regime for measuring two-photon absorption coefficient
NASA Astrophysics Data System (ADS)
Rodríguez, L.; Echevarria, L.; Fernandez, A.
2007-09-01
We present a new pump-probe mode-mismatched thermal lens method for pulse excitation aimed to the measurement of nonlinear absorption coefficient in optical materials. We develop a theoretical model based on the Fresnel diffraction approximation and their predictions are verified experimentally with samples of Rhodamine 6G and Rhodamine B in ethanol solution. The principal advantage of this technique is that it does not require any mechanical movement during measurement. Below we perform the new type of thermal lens experiment in the pulse regime for the measurement of nonlinear absorption coefficient in transparent samples and we demonstrate the validity of theoretical predictions using an alternative method to the classical thermal lens technique.
Lawniczak, Michał; Hul, Oleh; Bauch, Szymon; Seba, Petr; Sirko, Leszek
2008-05-01
We present the results of an experimental and numerical study of the distribution of the reflection coefficient P(R) and the distributions of the imaginary P(v) and the real P(u) parts of the Wigner reaction K matrix for irregular fully connected hexagon networks (graphs) in the presence of strong absorption. In the experiment we used microwave networks, which were built of coaxial cables and attenuators connected by joints. In the numerical calculations experimental networks were described by quantum fully connected hexagon graphs. The presence of absorption introduced by attenuators was modeled by optical potentials. The distribution of the reflection coefficient P(R) and the distributions of the reaction K matrix were obtained from measurements and numerical calculations of the scattering matrix S of the networks and graphs, respectively. We show that the experimental and numerical results are in good agreement with the exact analytic ones obtained within the framework of random matrix theory. PMID:18643145
Quantitative mapping of the per‐axon diffusion coefficients in brain white matter
Kruggel, Frithjof; Alexander, Daniel C.
2015-01-01
Purpose This article presents a simple method for estimating the effective diffusion coefficients parallel and perpendicular to the axons unconfounded by the intravoxel fiber orientation distribution. We also call these parameters the per‐axon or microscopic diffusion coefficients. Theory and Methods Diffusion MR imaging is used to probe the underlying tissue material. The key observation is that for a fixed b‐value the spherical mean of the diffusion signal over the gradient directions does not depend on the axon orientation distribution. By exploiting this invariance property, we propose a simple, fast, and robust estimator of the per‐axon diffusion coefficients, which we refer to as the spherical mean technique. Results We demonstrate quantitative maps of the axon‐scale diffusion process, which has factored out the effects due to fiber dispersion and crossing, in human brain white matter. These microscopic diffusion coefficients are estimated in vivo using a widely available off‐the‐shelf pulse sequence featuring multiple b‐shells and high‐angular gradient resolution. Conclusion The estimation of the per‐axon diffusion coefficients is essential for the accurate recovery of the fiber orientation distribution. In addition, the spherical mean technique enables us to discriminate microscopic tissue features from fiber dispersion, which potentially improves the sensitivity and/or specificity to various neurological conditions. Magn Reson Med, 2015. Magn Reson Med 75:1752–1763, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. PMID:25974332
NASA Technical Reports Server (NTRS)
Varanasi, Prasad
1992-01-01
Spectral absorption coefficients k(v) in the atmospheric window are reported for CFC-11 and CFC-12. Data obtained with a grating spectrometer are compared with NCAR cross sections and measurements of k(v) made with a tunable diode laser spectrometer at various temperature-pressure combinations representing tangent heights or layers in the atmosphere are presented. The results are suitable for atmospheric remote sensing and global warming studies.
NASA Technical Reports Server (NTRS)
Wan, Zhengming; Dozier, Jeff
1992-01-01
The effect of temperature-dependent molecular absorption coefficients on thermal infrared spectral signatures measured from satellite sensors is investigated by comparing results from the atmospheric transmission and radiance codes LOWTRAN and MODTRAN and the accurate multiple scattering radiative transfer model ATRAD for different atmospheric profiles. The sensors considered include the operational NOAA AVHRR and two research instruments planned for NASA's Earth Observing System (EOS): MODIS-N (Moderate Resolution Imaging Spectrometer-Nadir-Mode) and ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer). The difference in band transmittance is as large as 6 percent for some thermal bands within atmospheric windows and more than 30 percent near the edges of these atmospheric windows. The effect of temperature-dependent molecular absorption coefficients on satellite measurements of sea-surface temperature can exceed 0.6 K. Quantitative comparison and factor analysis indicate that more accurate measurements of molecular absorption coefficients and better radiative transfer simulation methods are needed to achieve SST accuracy of 0.3 K, as required for global numerical models of climate, and to develop land-surface temperature algorithms at the 1-K accuracy level.
NASA Astrophysics Data System (ADS)
Zhevstovskikh, I. V.; Okulov, V. I.; Gudkov, V. V.; Mayakin, V. Yu.; Sarychev, M. N.; Andriichuk, M. D.; Paranchich, L. D.
2015-05-01
The effects of the interaction of ultrasound with donor d electrons of cobalt impurity atoms at low concentrations in mercury selenide crystals have been investigated. The temperature dependences of the electronic contribution to the absorption coefficient at a frequency of 53 MHz in crystals with cobalt concentrations from 1018 to 1020 cm-3 and in the undoped crystal have been observed experimentally. It has been found that crystals with impurities are characterized by an anomalous nonmonotonic temperature dependence of the absorption coefficient of the slow transverse wave in a narrow temperature range near 10 K. A smooth monotonic temperature dependence has been observed for longitudinal and fast transverse waves. Based on the developed theoretical interpretation, it has been established that the anomaly in the temperature dependence of the absorption coefficient of a slow transverse wave is associated with the hybridization of impurity d states in the conduction band of the crystal. A comparison of the theoretical and experimental dependences has made it possible to determine the parameters characterizing the hybridized electronic states.
Levine, Zachary H.; Grantham, Steven; Tarrio, Charles; Paterson, David J.; McNulty, Ian; Levin, T. M.; Ankudinov, Alexei L.; Rehr, John J.
2003-01-01
The mass absorption coefficients of tungsten and tantalum were measured with soft x-ray photons from 1450 eV to 2350 eV using an undulator source. This region includes the M3, M4, and M5 absorption edges. X-ray absorption fine structure was calculated within a real-space multiple scattering formalism; the predicted structure was observed for tungsten and to a lesser degree tantalum as well. Separately, the effects of dynamic screening were observed as shown by an atomic calculation within the relativistic time-dependent local-density approximation. Dynamic screening effects influence the spectra at the 25 % level and are observed for both tungsten and tantalum. We applied these results to characterize spatially-resolved spectra of a tungsten integrated circuit interconnect obtained using a scanning transmission x-ray microscope. The results indicate tungsten fiducial markers were deposited into silica trenches with a depths of 50 % and 60 % of the markers’ heights.
Performance back-deduction from a loading to flow coefficient map: Application to radial turbine
NASA Astrophysics Data System (ADS)
Carbonneau, Xavier; Binder, Nicolas
2012-12-01
Radial turbine stages are often used for applications requiring off-design operation, as turbocharging for instance. The off-design ability of such stages is commonly analyzed through the traditional turbine map, plotting the reduced mass-flow against the pressure-ratio, for reduced-speed lines. However, some alternatives are possible, such as the flow-coefficient ( Ψ) to loading-coefficient ( φ) diagram where the pressure-ratio lines are actually straight lines, very convenient property to perform prediction. A robust method re-creating this map from a predicted Ψ-φ diagram is needed. Recent work has shown that this back-deduction quality, without the use of any loss models, depends on the knowledge of an intermediate pressure-ratio. A modelization of this parameter is then proposed. The comparison with both experimental and CFD results is presented, with quite good agreement for mass flow rate and rotational speed, and for the intermediate pressure ratio. The last part of the paper is dedicated to the application of the intermediate pressure-ratio knowledge to the improvement of the deduction of the pressure ratio lines in the Ψ-φ diagram. Beside this improvement, the back-deduction method of the classical map is structured, applied and evaluated.
NASA Astrophysics Data System (ADS)
Bernhard, G.; Evans, R. D.; Labow, G. J.; Oltmans, S. J.
2005-05-01
The Dobson spectrophotometer is the primary standard instrument for ground-based measurements of total column ozone. The accuracy of its data depends on the knowledge of ozone absorption coefficients used for data reduction. We document an error in the calculations that led to the set of absorption coefficients currently recommended by the World Meteorological Organisation (WMO). This error has little effect because an empirical adjustment was applied to the original calculations before the coefficients were adopted by WMO. We provide evidence that this adjustment was physically sound. The coefficients recommended by WMO are applied in the Dobson network without correction for the temperature dependence of the ozone absorption cross sections. On the basis of data measured by Dobson numbers 80 and 82, which were operated by the National Oceanic and Atmospheric Administration (NOAA) Climate Monitoring and Diagnostics Laboratory at the South Pole, we find that omission of temperature corrections may lead to systematic errors in Dobson ozone data of up to 4%. The standard Dobson ozone retrieval method further assumes that the ozone layer is located at a fixed height. This approximation leads to errors in air mass calculations, which are particularly relevant at high latitudes where ozone measurements are performed at large solar zenith angles (SZA). At the South Pole, systematic errors caused by this approximation may exceed 2% for SZAs larger than 80°. The bias is largest when the vertical ozone distribution is distorted by the "ozone hole" and may lead to underestimation of total ozone by 4% at SZA = 85° (air mass 9). Dobson measurements at the South Pole were compared with ozone data from a collocated SUV-100 UV spectroradiometer and Version 8 overpass data from NASA's Total Ozone Mapping Spectrometer (TOMS). Uncorrected Dobson ozone values tend to be lower than data from the two other instruments when total ozone is below 170 Dobson units or SZAs are larger than
Figueroa, C.; Brizuela, H.; Heluani, S. P.
2014-05-21
The backscattering coefficient is a magnitude whose measurement is fundamental for the characterization of materials with techniques that make use of particle beams and particularly when performing microanalysis. In this work, we report the results of an analytic method to calculate the backscattering and absorption coefficients of electrons in similar conditions to those of electron probe microanalysis. Starting on a five level states ladder model in 3D, we deduced a set of integro-differential coupled equations of the coefficients with a method know as invariant embedding. By means of a procedure proposed by authors, called method of convergence, two types of approximate solutions for the set of equations, namely complete and simple solutions, can be obtained. Although the simple solutions were initially proposed as auxiliary forms to solve higher rank equations, they turned out to be also useful for the estimation of the aforementioned coefficients. In previous reports, we have presented results obtained with the complete solutions. In this paper, we present results obtained with the simple solutions of the coefficients, which exhibit a good degree of fit with the experimental data. Both the model and the calculation method presented here can be generalized to other techniques that make use of different sorts of particle beams.
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.
The changes and causes of reduced visibility in the Eastern U.S. during the past three decades were examined. Contour maps of local midday extinction coefficients (inversely related to visibility) are presented for the years 1958-1962.
Real-time HF Radio Absorption Maps Incorporating Riometer and Satellite Measurements
NASA Astrophysics Data System (ADS)
Rogers, Neil; Honary, Farideh; Warrington, Mike; Stocker, Alan; Danskin, Donald
2016-04-01
A real-time model of HF radio propagation conditions is being developed as a service for aircraft communications at high latitudes. An essential component of this is a real-time map of the absorption of HF (3-30 MHz) radio signals in the D-region ionosphere. Empirical, climatological Polar Cap Absorption (PCA) models in common usage cannot account for day-to-day variations in ionospheric composition and are inaccurate during the large changes in recombination rate at twilight. However, parameters of such models may be optimised using an age-weighted regression to absorption measurements from riometers in Canada and Scandinavia. Such parameters include the day- and night-time sensitivity to proton flux as measured on a geostationary satellite (GOES). Modelling the twilight transition as a linear or Gauss error function over a range of solar-zenith angles (χl < χ < χu) is found to provide greater accuracy than 'Earth shadow' methods (as applied in the Sodankylä Ionospheric Chemistry (SIC) model, for example) due to a more gradual ionospheric response for χ < 90° . The fitted χl parameter is found to be most variable, with smaller values (as low as 60°) post-sunrise compared with pre-sunset. Correlation coefficients of model parameters between riometers are presented and these provide a means of appropriately weighting individual riometer contributions in an assimilative PCA model. At times outside of PCA events, the probability of absorption in the auroral zones is related to the energetic electron flux inside the precipitation loss cone, as measured on the polar-orbiting POES satellites. This varies with magnetic local time, magnetic latitude and geomagnetic activity, and its relation to the real-time solar wind - magnetospheric coupling function [Newell et al., 2007] will be presented. Reference: Newell, P. T., T. Sotirelis, K. Liou, C.-I. Meng, and F. J. Rich (2007), A nearly universal solar wind-magnetosphere coupling function inferred from 10
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.
NASA Astrophysics Data System (ADS)
Smagin, N. V.; Krutyansky, L. M.; Zelenova, Z. V.; Brysev, A. P.
2014-03-01
Acoustic absorption has been measured in a series of biological tissue specimens—porcine muscle, renal and fat tissues—by the standard insert-substitution method, as well as by ultrasonic phase conjugation. Comparison of the experimental results and revealed differences confirm the promise of using phase conjugate waves to measure acoustic losses in biological objects. It is demonstrated that in inhomogeneous tissues, the phase conjugation method makes it possible to obtain a more reliable estimate of dissipative losses.
NASA Astrophysics Data System (ADS)
Pérez Reyes, Ma. C.; Hernandez-Aguilar, C.; Dominguez-Pacheco, A.; Cruz-Orea, A.; Moreno Martínez, E.
2015-09-01
Laser light as a biostimulator has been applied in agriculture, and some scientific reports evidence its usefulness. A knowledge about seed optical parameters is of great relevance in the biostimulation process, because information can be provided about the light absorption of seeds. Thus, the objective of the present study was to determine the optical absorption coefficient (β ) of barley ( Hordeum vulgare L.) seeds by means of photoacoustic spectroscopy; these seeds were studied in two conditions: seeds in their natural color and seeds dyed with methylene blue. The seeds were biostimulated by a laser beam (650 nm wavelength) to evaluate the effects of pre-sowing biostimulation in natural mycobiota associated with different laser irradiation times (0 s, 60 s, 120 s, 240 s, and 480 s). The results of this research demonstrated changes in the optical parameters (absorption and penetration) that occur in the seeds by changing the natural condition to a dyed condition. The dyed seeds, by the methylene blue photosensitizer, become optically opaque, producing greater optical absorption at 650 nm which causes an increase in the effect of laser stimulation. The experimental results showed that the biggest mycobiota reduction (52 %) corresponded to dyed seeds irradiated with a laser for 120 s.
Absorption coefficients and band strengths for the 703 nm and 727 bands of methane at 77 K
O`Brien, J.J.; Singh, K.
1996-12-31
The technique of intracavity laser spectroscopy has been used to obtain methane absorption spectra for the vibrational overtone bands that occur around 703 nm and 727 nm. Absorption coefficients for the 690-742 nm range have been obtained for a sample temperature of 77 K at a spectral resolution of <0.02 cm{sup -1}. A new method of data analysis is utilized in obtaining the results. It involves deconvolving the many ILS spectral profiles that comprise the absorption bands and summing the results. Values averaged over 1 cm{sup -1} and 1 {Angstrom} intervals are provided. Band strengths also are obtained. The total intensities of the 703 and 727 nm bands are in reasonable agreement with previous laboratory determinations which were obtained for relatively high pressures of methane at room temperature using lower spectral resolution. The methane bands appear in the reflected sunlight spectra from the outer planets. Results averaged over 1 nm intervals are compared with other laboratory studies and with those derived from observations of the outer planets. The band profiles differ considerably from other laboratory results but are in good accord with the planetary observations. Laboratory spectra of methane at appropriate conditions are required for the proper interpretation of the observational data. Absorption spectra can provide some of the most sensitive diagnostic data on the atmospheres of those bodies.
NASA Astrophysics Data System (ADS)
Leid, Terrence Vincent
The emission of electron cyclotron radiation parallel to the magnetic field direction near the fundamental frequency from a fully ionized, multi-component plasma, is investigated for finite (omega)(,p)/(omega)(,c) within the Klimontovich formalism. Each species may have T(,(PARLL)) different from T(,(PERP)) and may possess a loss cone. We use a bi- maxwellian with an analytic loss cone for each component. In addition, the source function for a multi-component plasma is calculated. We find that for a Maxwellian distribution function the emission coefficient is that of a system of shielded charges. It is shown that only in the case of a tenuous Maxwellian plasma is the source function the Rayleigh-Jeans blackbody intensity. For the case of the Maxwellian we present experimental evidence for finite density emission, (omega)('2)(,p)/(omega)('2) >> (beta). We have constructed a computer code that solves the radiative transfer equation. The resulting power spectra are used as an aid in extracting from experimental data the temperature and density of the various components of the TMX-Upgrade end cell plasma. The code compares both the Ellis-Tsakiris scheme for computing the emission coefficient for a multi-component plasma and the finite density multi -component emission coefficient. The Ellis- Tsakiris scheme estimates the emission coefficient by assuming. that each species radiates independently of each other.('1) Results are presented for the case of the TMX -Upgrade tandem mirror device. ('1)R. F. Ellis and G. D. Tsakiris, Nucl. Fusion 23, 1115 (1984).
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.
MAPPING DUST THROUGH EMISSION AND ABSORPTION IN NEARBY GALAXIES
Kreckel, Kathryn; Groves, Brent; Schinnerer, Eva; Meidt, Sharon E.; Tabatabaei, Fatemeh S.; Johnson, Benjamin D.; Aniano, Gonzalo; Calzetti, Daniela; Croxall, Kevin V.; Draine, Bruce T.; Gordon, Karl D.; Crocker, Alison F.; Smith, J. D. T.; Dale, Daniel A.; Hunt, Leslie K.; Kennicutt, Robert C.
2013-07-01
Dust has long been identified as a barrier to measuring inherent galaxy properties. However, the link between dust and attenuation is not straightforward and depends on both the amount of dust and its distribution. Herschel imaging of nearby galaxies undertaken as part of the KINGFISH project allows us to map the dust as seen in emission with unprecedented sensitivity and {approx}1 kpc resolution. We present here new optical integral field unit spectroscopy for eight of these galaxies that provides complementary 100-200 pc scale maps of the dust attenuation through observation of the reddening in both the Balmer decrement and the stellar continuum. The stellar continuum reddening, which is systematically less than that observed in the Balmer decrement, shows no clear correlation with the dust, suggesting that the distribution of stellar reddening acts as a poor tracer of the overall dust content. The brightest H II regions are observed to be preferentially located in dusty regions, and we do find a correlation between the Balmer line reddening and the dust mass surface density for which we provide an empirical relation. Some of the high-inclination systems in our sample exhibit high extinction, but we also find evidence that unresolved variations in the dust distribution on scales smaller than 500 pc may contribute to the scatter in this relation. We caution against the use of integrated A{sub V} measures to infer global dust properties.
NASA Astrophysics Data System (ADS)
Kim, J. H.; Kim, S. W.; Yoon, S. C.; Park, R.; Ogren, J. A.
2014-12-01
Filter-based instrument, such as aethalometer, is being widely used to measure equivalent black carbon(EBC) mass concentration and aerosol absorption coefficient(AAC). However, many other previous studies have poited that AAC and its aerosol absorption angstrom exponent(AAE) are strongly affected by the multi-scattering correction factor(C) when we retrieve AAC from aethalometer EBC mass concentration measurement(Weingartner et al., 2003; Arnott et al., 2005; Schmid et al., 2006; Coen et al., 2010). We determined the C value using the method given in Weingartner et al. (2003) by comparing 7-wavelngth aethalometer (AE-31, Magee sci.) to 3-wavelength Photo-Acoustic Soot Spectrometer (PASS-3, DMT) at Gosan climate observatory, Korea(GCO) during Cheju ABC plume-asian monsoon experiment(CAPMEX) campaign(August and September, 2008). In this study, C was estimated to be 4.04 ± 1.68 at 532 nm and AAC retrieved with this value was decreased as approximately 100% as than that retrieved with soot case value from Weingartner et al (2003). We compared the AAC determined from aethalomter measurements to that from collocated Continuous Light Absorption Photometer (CLAP) measurements from January 2012 to December 2013 at GCO and found good agreement in both AAC and AAE. This result suggests the determination of site-specific C is crucially needed when we calculate AAC from aethalometer measurements.
NASA Astrophysics Data System (ADS)
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.
Inverse Bremsstrahlung in Astrophysical Plasmas: The Absorption Coefficients and Gaunt Factors
NASA Astrophysics Data System (ADS)
Mihajlov, A. A.; Srećković, V. A.; Sakan, N. M.
2015-12-01
The electron-ion inverse Bremsstrahlung is considered here as a factor of the influence on the opacity of the different stellar atmospheres and other astrophysical plasmas. It is shown that this process can be successfully described in the frames of cut-off Coulomb potential model within the regions of the electron densities and temperatures. The relevant quantum mechanical method of the calculation of the corresponding spectral coefficient processes is described and discussed. The results obtained for the plasmas with the electron densities from 1014 c m -3 to 2ṡ1019 c m -3 and temperatures from 5ṡ103 K to 3ṡ104 K in the wavelength region 100 nm< λ<3000 nm are presented. Also, these results can be of interest for different laboratory plasmas.
Absorption coefficients of the methane-nitrogen binary ice system: Implications for Pluto
NASA Astrophysics Data System (ADS)
Protopapa, S.; Grundy, W. M.; Tegler, S. C.; Bergonio, J. M.
2015-06-01
The methane-nitrogen phase diagram of Prokhvatilov and Yantsevich (1983. Sov. J. Low Temp. Phys. 9, 94-98) indicates that at temperatures relevant to the surfaces of icy dwarf planets like Pluto, two phases contribute to the methane absorptions: nitrogen saturated with methane N2 ‾ :CH4 and methane saturated with nitrogen CH4 ‾ :N2 . No optical constants are available so far for the latter component limiting construction of a proper model, in compliance with thermodynamic equilibrium considerations. New optical constants for solid solutions of methane diluted in nitrogen (N2 :CH4) and nitrogen diluted in methane (CH4 :N2) are presented at temperatures between 40 and 90 K, in the wavelength range 1.1-2.7 μm at different mixing ratios. These optical constants are derived from transmission measurements of crystals grown from the liquid phase in closed cells. A systematic study of the changes of methane and nitrogen solid mixtures spectral behavior with mixing ratio and temperature is presented.
NASA Astrophysics Data System (ADS)
Yu, Shao-De; Wu, Shi-Bin; Wang, Hao-Yu; Wei, Xin-Hua; Chen, Xin; Pan, Wan-Long; Hu, Jiani; Xie, Yao-Qin
2015-12-01
Similarity coefficient mapping (SCM) aims to improve the morphological evaluation of weighted magnetic resonance imaging However, how to interpret the generated SCM map is still pending. Moreover, is it probable to extract tissue dissimilarity messages based on the theory behind SCM? The primary purpose of this paper is to address these two questions. First, the theory of SCM was interpreted from the perspective of linear fitting. Then, a term was embedded for tissue dissimilarity information. Finally, our method was validated with sixteen human brain image series from multi-echo . Generated maps were investigated from signal-to-noise ratio (SNR) and perceived visual quality, and then interpreted from intra- and inter-tissue intensity. Experimental results show that both perceptibility of anatomical structures and tissue contrast are improved. More importantly, tissue similarity or dissimilarity can be quantified and cross-validated from pixel intensity analysis. This method benefits image enhancement, tissue classification, malformation detection and morphological evaluation. Project supported in part by the National High Technology Research and Development Program of China (Grant Nos. 2015AA043203 and 2012AA02A604), the National Natural Science Foundation of China (Grant Nos. 81171402, 61471349, and 81501463), the Innovative Research Team Program of Guangdong Province, China (Grant No. 2011S013), the Science and Technological Program for Higher Education, Science and Research, and Health Care Institutions of Guangdong Province, China (Grant No. 2011108101001), the Natural Science Foundation of Guangdong Province, China (Grant No. 2014A030310360), the Fundamental Research Program of Shenzhen City, China (Grant No. JCYJ20140417113430639), and Beijing Center for Mathematics and Information Interdisciplinary Sciences, China.
NASA Astrophysics Data System (ADS)
Tran, Huong; Du, Wei; Ghetmiri, Seyed A.; Mosleh, Aboozar; Sun, Greg; Soref, Richard A.; Margetis, Joe; Tolle, John; Li, Baohua; Naseem, Hameed A.; Yu, Shui-Qing
2016-03-01
The absorption coefficient and refractive index of Ge1-xSnx alloys (x from 0% to 10%) were characterized for the wavelength range from 1500 to 2500 nm via spectroscopic ellipsometry at room temperature. By applying physical models to fit the obtained data, two empirical formulae with extracted constants and coefficients were developed: (1) Absorption coefficient. The absorption regarding Urbach tail, indirect and direct bandgap transitions were comprehensively taken into account; (2) refractive index. The Sellmeier coefficients associated with dispersion relationship were extracted. In these formulae, the Sn composition and strain percentage were the input parameters, by inputting which the spectral absorption coefficient and spectral refractive index can be obtained. Since the absorption coefficient is key information to determine the performance of the photodetectors including operation wavelength range, responsivity, and specific detectivity, and the refractive index is very useful for the design of the anti-reflection coating for photodetectors and the layer structure for waveguides, the developed formulae could simplify the optoelectronic device design process due to their parameter-based expressions.
Falcao-Filho, E.L.; Araujo, Cid B. de; Bosco, C.A.C.; Maciel, G.S.; Acioli, L.H.; Nalin, M.; Messaddeq, Y.
2005-01-01
Antimony glasses based on the composition Sb{sub 2}O{sub 3}-SbPO{sub 4} were prepared and characterized. The samples present high refractive index, good transmission from 380 to 2000 nm, and high thermal stability. The nonlinear refractive index, n{sub 2}, of the samples was studied using the optical Kerr shutter technique at 800 nm. The third-order correlation signals between pump and probe pulses indicate ultrafast response (<100 fs) for all compositions. Enhancement of n{sub 2} was observed by adding lead oxide to the Sb{sub 2}O{sub 3}-SbPO{sub 4} composition. Large values of n{sub 2}{approx_equal}10{sup -14} cm{sup 2}/W and negligible two-photon absorption coefficients (smaller than 0.01 cm/GW) were determined for all samples. The glass compositions studied present appropriate figure-of-merit for all-optical switching applications.
NASA Astrophysics Data System (ADS)
McGillen, Max R.; Bernard, François; Fleming, Eric L.; Burkholder, James B.
2015-07-01
HCFC-133a (CF3CH2Cl), an ozone-depleting substance, is primarily removed from the atmosphere by gas-phase reaction with OH radicals and by UV photolysis. The rate coefficient, k, for the OH + HCFC-133a reaction was measured between 233 and 379 K and is given by k(T) = (9.32 ± 0.8) × 10-13 exp(-(1296 ± 28)/T), where k(296 K) was measured to be (1.10 ± 0.02) × 10-14 (cm3 molecule-1 s-1) (2σ precision uncertainty). The HCFC-133a UV absorption spectrum was measured between 184.95 and 240 nm at 213-323 K, and a spectrum parameterization is presented. The HCFC-133a atmospheric loss processes, lifetime, ozone depletion potential, and uncertainties were evaluated using a 2-D atmospheric model. The global annually averaged steady state lifetime and ozone depletion potential (ODP) were determined to be 4.45 (4.04-4.90) years and 0.017 (±0.001), respectively, where the ranges are based solely on the 2σ uncertainty in the kinetic and photochemical parameters. The infrared absorption spectrum of HCFC-133a was measured, and its global warming potential was determined to be 380 on the 100 year time horizon.
NASA Astrophysics Data System (ADS)
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.
NASA Astrophysics Data System (ADS)
Villanueva, Yolanda; Hondebrink, Erwin; Petersen, Wilma; Steenbergen, Wiendelt
2015-03-01
A method for simultaneously measuring the absorption coefficient μa and Grüneisen parameter Γ of biological absorbers in photoacoustics is designed and implemented using a coupled-integrating sphere system. A soft transparent tube with inner diameter of 0.58mm is used to mount the liquid absorbing sample horizontally through the cavity of two similar and adjacent integrating spheres. One sphere is used for measuring the sample's μa using a continuous halogen light source and a spectrometer fiber coupled to the input and output ports, respectively. The other sphere is used for simultaneous photoacoustic measurement of the sample's Γ using an incident pulsed light with wavelength of 750nm and a flat transducer with central frequency of 5MHz. Absolute optical energy and pressure measurements are not necessary. However, the derived equations for determining the sample's μa and Γ require calibration of the setup using aqueous ink dilutions. Initial measurements are done with biological samples relevant to biomedical imaging such as human whole blood, joint and cyst fluids. Absorption of joint and cyst fluids is enhanced using a contrast agent like aqueous indocyanine green dye solution. For blood sample, measured values of μa = 0.580 +/- 0.016 mm-1 and Γ = 0.166 +/- 0.006 are within the range of values reported in literature. Measurements with the absorbing joint and cyst fluid samples give Γ values close to 0.12, which is similar to that of water and plasma.
NASA Astrophysics Data System (ADS)
Wei, Jianwei; Lee, Zhongping; Ondrusek, Michael; Mannino, Antonio; Tzortziou, Maria; Armstrong, Roy
2016-03-01
The spectral slope of the absorption coefficient of colored dissolved and detrital material (CDM), Scdm (units: nm-1), is an important optical parameter for characterizing the absorption spectral shape of CDM. Although highly variable in natural waters, in most remote sensing algorithms, this slope is either kept as a constant or empirically modeled with multiband ocean color in the visible domain. In this study, we explore the potential of semianalytically retrieving Scdm with added ocean color information in the ultraviolet (UV) range between 360 and 400 nm. Unique features of hyperspectral remote sensing reflectance in the UV-visible wavelengths (360-500 nm) have been observed in various waters across a range of coastal and open ocean environments. Our data and analyses indicate that ocean color in the UV domain is particularly sensitive to the variation of the CDM spectral slope. Here, we used a synthesized dataset to show that adding UV wavelengths to the ocean color measurements will improve the retrieval of Scdm from remote sensing reflectance considerably, while the spectral band settings of past and current satellite ocean color sensors cannot fully account for the spectral variation of remote sensing reflectance. Results of this effort support the concept to include UV wavelengths in the next generation of satellite ocean color sensors.
NASA Astrophysics Data System (ADS)
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.
NASA Astrophysics Data System (ADS)
Osicka, Teresa; Freedman, Matthew T.; Ahmed, Farid
2006-03-01
Using CT images from the National Lung Screening Trial (NLST) of the National Cancer Institute (NCI), interpreted by radiologists at the Georgetown University, our goal was to investigate the feature extraction method using discrete wavelet transform (DWT) and to demonstrate their potential in distinguishing between benign and malignant nodule status. We analyzed multiple 2 mm thick slices of 40 subjects with benign nodules and 7 subjects with malignant nodules for a total of 112 and 78 slices, respectively. Data was analyzed in the region-of-interest (ROI) that included nodule and surrounding areas in three different-sized windows. A linear discriminant analysis (LDA) of wavelets coefficients was used for data analysis. In particular we examined discriminative power of the wavelet based features using Fisher LDA, and evaluated the classification results using decision matrix (DM) for matched sample (MS). For visualization we used 3-D Heat Maps, originally developed in MATLAB(R) (MathWorks, Natick, MA) for gene expression array analysis, modified to display the magnitude of similarities between cases under analysis. The use of DWT in the image pre-processing modules resulted in a significant improvement in discrimination between benign and malignant nodules. The results show better classification accuracy with the DWT based features, as compared to previously proposed classification features (p-values: 0.008, 0.022, and 0.039, depending on window size). The Heat Maps provide useful data visualization for further investigation as they have the ability to identify cases that should be further explored to understand why some of the benign nodules look similar to malignant in the wavelet domain.
Jacobs, Michael A; Ouwerkerk, Ronald; Petrowski, Kyle; Macura, Katarzyna J
2008-12-01
Prostate cancer is a major health problem, and the exploration of noninvasive imaging methods that have the potential to improve specificity while maintaining high sensitivity is still critically needed. Tissue changes induced by tumor growth can be visualized by magnetic resonance imaging (MRI) methods. Current MRI methods include conventional T2-weighted imaging, diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) mapping and magnetic resonance spectroscopy (MRS). Techniques such as DWI/ADC provide functional information about the behavior of water molecules in tissue; MRS can provide biochemical information about the presence or absence of certain metabolites, such as choline, creatine, and citrate. Finally, vascular parameters can be investigated using dynamic contrast-enhanced MRI. Moreover, with whole-body MRI and DWI, metastatic disease can be evaluated in 1 session and may provide a way to monitor treatment. Therefore, when combining these various methods, a multiparametric data set can be built to assist in the detection, localization, assessment of prostate cancer aggressiveness, and tumor staging. Such a comprehensive approach offers more power to evaluate prostate disease than any single measure alone. In this article, we focus on the role of DWI/ADC and MRS in the detection and characterization using both in vivo and ex vivo imaging of prostate pathology. PMID:19512848
NASA Astrophysics Data System (ADS)
Yahya, I.; Kusuma, J. I.; Harjana; Kristiani, R.; Hanina, R.
2016-02-01
This paper emphasizes the influence of tubular shaped microresonators phononic crystal insertion on the sound absorption coefficient of profiled sound absorber. A simple cubic and two different bodies centered cubic phononic crystal lattice model were analyzed in a laboratory test procedure. The experiment was conducted by using transfer function based two microphone impedance tube method refer to ASTM E-1050-98. The results show that sound absorption coefficient increase significantly at the mid and high-frequency band (600 - 700 Hz) and (1 - 1.6 kHz) when tubular shaped microresonator phononic crystal inserted into the tested sound absorber element. The increment phenomena related to multi-resonance effect that occurs when sound waves propagate through the phononic crystal lattice model that produce multiple reflections and scattering in mid and high-frequency band which increases the sound absorption coefficient accordingly
NASA Technical Reports Server (NTRS)
Clark, Roger N.; Swayze, Gregg A.; Koch, Christopher; Ager, Cathy
1992-01-01
Vegetation covers a large portion of the Earth's land surface. Remotely sensing quantitative information from vegetation has proven difficult because in a broad sense, all vegetation is similar from a chemical viewpoint, and most healthy plants are green. Plant species are generally characterized by the leaf and flower or fruit morphology, not by remote sensing spectral signatures. But to the human eye, many plants show varying shades of green, so there is direct evidence for spectral differences between plant types. Quantifying these changes in a predictable manner has not been easy. The Clark spectral features mapping algorithm was applied to mapping spectral features in vegetation species.
NASA Astrophysics Data System (ADS)
Shatsky, A. V.
2016-08-01
We consider the problem of the influence of diffraction effects on the result of measuring the absorption coefficient of ultrasound in weakly absorbing liquids by the pulse method. Diffraction attenuation of an ultrasonic signal in a measuring cell using solid-state delay lines is calculated. It is shown that the use of delay lines of the ultrasonic signal leads to a considerable distortion of the measured absorption coefficient in the low-frequency range from the true value and can either overestimate or underestimate the results.
Prisutova, Jevgenija; Horoshenkov, Kirill; Groby, Jean-Philippe; Brouard, Bruno
2014-12-01
The measurement of acoustic material characteristics using a standard impedance tube method is generally limited to the plane wave regime below the tube cut-on frequency. This implies that the size of the tube and, consequently, the size of the material specimen must remain smaller than a half of the wavelength. This paper presents a method that enables the extension of the frequency range beyond the plane wave regime by at least a factor of 3, so that the size of the material specimen can be much larger than the wavelength. The proposed method is based on measuring of the sound pressure at different axial locations and applying the spatial Fourier transform. A normal mode decomposition approach is used together with an optimization algorithm to minimize the discrepancy between the measured and predicted sound pressure spectra. This allows the frequency and angle dependent reflection and absorption coefficients of the material specimen to be calculated in an extended frequency range. The method has been tested successfully on samples of melamine foam and wood fiber. The measured data are in close agreement with the predictions by the equivalent fluid model for the acoustical properties of porous media. PMID:25480044
NASA Astrophysics Data System (ADS)
Okawa, Shinpei; Hirasawa, Takeshi; Kushibiki, Toshihiro; Ishihara, Miya
2015-03-01
Quantification of the optical properties of the tissues and blood by noninvasive photoacoustic (PA) imaging may provide useful information for screening and early diagnosis of diseases. Linearized 2D image reconstruction algorithm based on PA wave equation and the photon diffusion equation (PDE) can reconstruct the image with computational cost smaller than a method based on 3D radiative transfer equation. However, the reconstructed image is affected by the differences between the actual and assumed light propagations. A quantitative capability of a linearized 2D image reconstruction was investigated and discussed by the numerical simulations and the phantom experiment in this study. The numerical simulations with the 3D Monte Carlo (MC) simulation and the 2D finite element calculation of the PDE were carried out. The phantom experiment was also conducted. In the phantom experiment, the PA pressures were acquired by a probe which had an optical fiber for illumination and the ring shaped P(VDF-TrFE) ultrasound transducer. The measured object was made of Intralipid and Indocyanine green. In the numerical simulations, it was shown that the linearized image reconstruction method recovered the absorption coefficients with alleviating the dependency of the PA amplitude on the depth of the photon absorber. The linearized image reconstruction method worked effectively under the light propagation calculated by 3D MC simulation, although some errors occurred. The phantom experiments validated the result of the numerical simulations.
NASA Astrophysics Data System (ADS)
Fuente, R.; Mendioroz, A.; Apiñaniz, E.; Salazar, A.
2012-11-01
Modulated photothermal radiometry (PTR) and a modulated photopyroelectric (PPE) technique have been widely used to measure the thermal diffusivity of bulk materials. The method is based on illuminating the sample with a plane light beam and measuring the infrared emission with an infrared detector (PTR) or the electric voltage produced by a pyroelectric sensor in contact with the sample (PPE). The amplitude and phase of both photothermal signals are recorded as a function of the modulation frequency and then fitted to the theoretical model. In this work, we compare the ability of modulated PTR and PPE to retrieve simultaneously the thermal diffusivity and the optical absorption coefficient of homogeneous slabs. In order to eliminate the instrumental factor, self-normalization is used, i.e., the ratio of the photothermal signal recorded at the rear and front surfaces. The influence of the multiple reflections of the light beam and the transparency to infrared wavelengths are analyzed. Measurements performed on a wide variety of homogeneous materials, transparent and opaque, good and bad thermal conductors, confirm the validity of the method. The advantages and disadvantages of both techniques are discussed.
Bénilan, Y; Bruston, P; Raulin, F; Courtin, R; Guillemin, J C
1995-01-01
The interpretation of mid-UV albedo spectra of planetary atmospheres, especially that of Titan, is the main goal of the SIPAT (Spectroscopie uv d'Interet Prebiologique dans l'Atmosphere de Titan) research program. This laboratory experiment has been developed in order to systematically determine the absorption coefficients of molecular compounds which are potential absorbers of scattered sunlight in planetary atmospheres, with high spectral resolution, and at various temperatures below room temperature. From photochemical modelling and experimental simulations, we may expect triacetylene (C6H2) to be present in the atmosphere of Titan, even though it has not yet been detected. We present here the first determination of the absolute absorption coefficient of that compound in the 200-300 nm range and at two temperatures (296 K and 233 K). The temperature dependence of the C6H2 absorption coefficient in that wavelength range is compared to that previously observed in the case of cyanoacetylene (HC3N). We then discuss the implications of the present results for the interpretation of Titan UV spectra, where it appears that large uncertainities can be introduced either by the presence of trace impurities in laboratory samples or by the variations of absorption coefficients with temperature. PMID:11538441
NASA Astrophysics Data System (ADS)
sharma, N.; Arnold, I. J.; Moosmuller, H.; Arnott, P.; Mazzoleni, C.
2012-12-01
the Desert Research Institute, measuring absorption and scattering coefficients of kerosene soot and sodium chloride aerosols. As a reference system we used a commercial three-wavelength photoacoustic-nephelometer instrument (DMT Inc.). Here, we present the results of this laboratory intercomparison.
NASA Technical Reports Server (NTRS)
Wilkerson, T. D.; Schwemmer, G.; Gentry, B.; Giver, L. P.
1979-01-01
Intensities and N2 collision-broadening coefficients are measured for 62 water vapor absorption lines between 715 and 732 nm potentially applicable to laser remote sensing of atmospheric water vapor. Absolute line strengths and widths were determined from spectra corrected for instrument resolution, air-path absorption and Lorentz and Doppler broadening for pure water vapor and water vapor-nitrogen mixtures in a multipass absorption cell with a base path length of 25 m (White cell). Line strengths are observed to range from 4 x 10 to the -25th to 4 x 10 to the -23rd kayser/molecule per sq cm, and collision broadening coefficients are found to be approximately equal to 0.1 kayser/atm.
NASA Astrophysics Data System (ADS)
More, Chaitali V.; Lokhande, Rajkumar M.; Pawar, Pravina. P.
2016-05-01
Mass attenuation coefficients of amino acids such as n-acetyl-l-tryptophan, n-acetyl-l-tyrosine and d-tryptophan were measured in the energy range 0.122-1.330 MeV. NaI (Tl) scintillation detection system was used to detect gamma rays with a resolution of 8.2% at 0.662 MeV. The measured attenuation coefficient values were then used to determine the mass energy-absorption coefficients (σa,en) and average atomic energy-absorption cross sections (μen/ρ) of the amino acids. Theoretical values were calculated based on XCOM data. Theoretical and experimental values are found to be in good agreement.
Free carrier absorption and lifetime mapping in 4H SiC epilayers
Galeckas, A.; Grivickas, V.; Linnros, J.; Bleichner, H.
1997-04-01
Results of carrier lifetime studies in low-doped epitaxial 4H SiC layers are reported. The free carrier absorption (FCA) technique was applied to extract carrier lifetime parameters and their spatial distribution in a wide photoexcitation range. The FCA magnitude is shown to scale linearly with the photoinjected carrier concentration, while the absorption cross section increases according to a {lambda}{sup 4.4} law for near infrared wavelengths. High spatial resolution carrier lifetime mapping of large 4H SiC areas revealed features related to structural imperfections of epilayers. Finally, a density dependent fast lifetime component was observed at high injection levels and attributed to band-to-band Auger recombination. {copyright} {ital 1997 American Institute of Physics.}
NASA Astrophysics Data System (ADS)
Chen, Jun; Cui, Tingwei; Quan, Wenting
2015-01-01
this study, a neural network-based four-band model (NNFM) for the global oceanic and coastal waters has been developed in order to retrieve the total absorption coefficients a(λ). The applicability of the quasi-analytical algorithm (QAA) and NNFM models is evaluated by five independent data sets. Based on the comparison of a(λ) predicted by these two models with the field measurements taken from the global oceanic and coastal waters, it was found that both the QAA and NNFM models had good performances in deriving a(λ), but that the NNFM model works better than the QAA model. The results of the QAA model-derived a(λ), especially in highly turbid waters with strong backscattering properties of optical activity, was found to be lower than the field measurements. The QAA and NNFM models-derived a(λ) could be obtained from the MODIS data after atmospheric corrections. When compared with the field measurements, the NNFM model decreased by a 0.86-24.15% uncertainty (root-mean-square relative error) of the estimation from the QAA model in deriving a(λ) from the Bohai, Yellow, and East China seas. Finally, the NNFM model was applied to map the global climatological seasonal mean a(443) for the time range of July 2002 to May 2014. As expected, the a(443) value around the coastal regions was always larger than the open ocean around the equator. Viewed on a global scale, the oceans at a high latitude exhibited higher a(443) values than those at a low latitude.
Nelson, G.J.; Chu, Y.; Harris, W.M.; Izzo, J.R.; Grew, K.N., Chiu, W.K.S.; Yi, J.; Andrews, J.C.; Liu, Y., Pierro, P.
2011-04-28
The reduction-oxidation cycling of the nickel-based oxides in composite solid oxide fuel cells and battery electrodes is directly related to cell performance. A greater understanding of nickel redox mechanisms at the microstructural level can be achieved in part using transmission x-ray microscopy (TXM) to explore material oxidation states. X-ray nanotomography combined with x-ray absorption near edge structure (XANES) spectroscopy has been applied to study samples containing distinct regions of nickel and nickel oxide (NiO) compositions. Digitally processed images obtained using TXM demonstrate the three-dimensional chemical mapping and microstructural distribution capabilities of full-field XANES nanotomography.
Mikhaylova, A.; Davidson, M.; Toastmann, H.; Channell, J.E.T.; Guyodo, Y.; Batich, C.; Dobson, J.
2008-06-16
This work describes a novel method for the detection, identification and mapping of anomalous iron compounds in mammalian brain tissue using X-ray absorption spectroscopy. We have located and identified individual iron anomalies in an avian tissue model associated with ferritin, biogenic magnetite and haemoglobin with a pixel resolution of less than 5 {micro}m. This technique represents a breakthrough in the study of both intra- and extra-cellular iron compounds in brain tissue. The potential for high-resolution iron mapping using microfocused X-ray beams has direct application to investigations of the location and structural form of iron compounds associated with human neurodegenerative disorders - a problem which has vexed researchers for 50 years.
Mikhaylova, A; Davidson, M; Toastmann, H; Channell, J.E.T; Guyodo, Y; Batich, C; Dobson, J
2005-01-01
This work describes a novel method for the detection, identification and mapping of anomalous iron compounds in mammalian brain tissue using X-ray absorption spectroscopy. We have located and identified individual iron anomalies in an avian tissue model associated with ferritin, biogenic magnetite and haemoglobin with a pixel resolution of less than 5 μm. This technique represents a breakthrough in the study of both intra- and extra-cellular iron compounds in brain tissue. The potential for high-resolution iron mapping using microfocused X-ray beams has direct application to investigations of the location and structural form of iron compounds associated with human neurodegenerative disorders—a problem which has vexed researchers for 50 years. PMID:16849161
NASA Technical Reports Server (NTRS)
Giver, L. P.; Gentry, B.; Schwemmer, G.; Wilkerson, T. D.
1982-01-01
Intensities were measured for 97 lines of H2O vapor between 932 and 961 nm. The lines were selected for their potential usefulness for remote laser measurements of H2O vapor in the earth's atmosphere. The spectra were obtained with several different H2O vapor abundances and N2 broadening gas pressures; the spectral resolution was 0.046/cm FWHM. Measured H2O line intensities range from 7 x 10 to the -25th to 7 x 10 to the -22nd/cm per (molecules/sq cm). H2O self-broadening coefficients were measured for 13 of these strongest lines; the mean value was 0.5/cm per atm. N2-collision-broadening coefficients were measured for 73 lines, and the average was 0.11 cm per atm HWHM. Pressure shifts in air were determined for a sample of six lines between 948 and 950 nm; these lines shift to lower frequency by an amount comparable to 0.1 of the collision-broadened widths measured in air or N2. The measured intensities of many lines of 300-000 band are much larger than expected from prior computations, in some cases by over an order of magnitude. Coriolis interactions with the stronger 201-000 band appear to be the primary cause of the enhancement of these line intensities.
NASA Astrophysics Data System (ADS)
Pawlak, M.
2015-01-01
In this paper, a non-contact method that allows to determine the carrier concentration in CdSe crystals is presented. The method relies on the measurement of the effective infrared absorption coefficient by means of the photothermal infrared radiometry (PTR). In order to obtain the effective infrared absorption coefficient and thermal diffusivity, the frequency characteristics of the PTR signal were analyzed in the frame of a one-dimensional heat transport model for infrared semitransparent crystals. The carrier concentrations were estimated using a theory introduced by Ruda and a recently proposed normalization procedure for the PTR signal. The deduced carrier concentrations of the investigated CdSe crystals are in reasonable agreement with those obtained using Hall measurements and infrared spectroscopy. The method presented in this paper can also be applied to other semiconductors with the carrier concentration in the range of 1014-1017 cm-3.
Yuan, Liu; Lu, Kun; Xia, Benzheng; Zhang, Jianqi; Wang, Zhen; Wang, Zaiyu; Deng, Dan; Fang, Jin; Zhu, Lingyun; Wei, Zhixiang
2016-07-01
Acceptor end-capping of oligomeric conjugated molecules is found to be an effective strategy for simultaneous spectral broadening, extinction coefficient enhancement, and energy level optimization, resulting in profoundly enhanced power conversion efficiencies (of 9.25% and 8.91%) compared to the original oligomers. This strategy is effective in overcoming the absorption disadvantage of oligomers and small molecules due to conjugation limitation. PMID:27172541
NASA Astrophysics Data System (ADS)
Grier, C. J.; Hall, P. B.; Brandt, W. N.; Trump, J. R.; Shen, Yue; Vivek, M.; Filiz Ak, N.; Chen, Yuguang; Dawson, K. S.; Denney, K. D.; Green, Paul J.; Jiang, Linhua; Kochanek, C. S.; McGreer, Ian D.; Pâris, I.; Peterson, B. M.; Schneider, D. P.; Tao, Charling; Wood-Vasey, W. M.; Bizyaev, Dmitry; Ge, Jian; Kinemuchi, Karen; Oravetz, Daniel; Pan, Kaike; Simmons, Audrey
2015-06-01
We report the discovery of rapid variations of a high-velocity C iv broad absorption line trough in the quasar SDSS J141007.74+541203.3. This object was intensively observed in 2014 as a part of the Sloan Digital Sky Survey Reverberation Mapping Project, during which 32 epochs of spectroscopy were obtained with the Baryon Oscillation Spectroscopic Survey spectrograph. We observe significant (>4σ) variability in the equivalent width (EW) of the broad (˜4000 km s-1 wide) C iv trough on rest-frame timescales as short as 1.20 days (˜29 hr), the shortest broad absorption line variability timescale yet reported. The EW varied by ˜10% on these short timescales, and by about a factor of two over the duration of the campaign. We evaluate several potential causes of the variability, concluding that the most likely cause is a rapid response to changes in the incident ionizing continuum. If the outflow is at a radius where the recombination rate is higher than the ionization rate, the timescale of variability places a lower limit on the density of the absorbing gas of ne ≳ 3.9 × 105 cm-3. The broad absorption line variability characteristics of this quasar are consistent with those observed in previous studies of quasars, indicating that such short-term variability may in fact be common and thus can be used to learn about outflow characteristics and contributions to quasar/host-galaxy feedback scenarios.
Abbas Ghaleb, Khalil; Georges, Joseph
2006-01-01
Two-photon absorption of the solvent under pulsed-laser excitation at 266 nm produces a high background thermal lens signal interfering with the analyte signal. Discrimination of both solvent and analyte signals along with calibration of the photothermal response has allowed the determination of the two-photon absorption coefficient of ethanol. The obtained value, 3.0x10(-10) cm W-1, is close to the literature values obtained from transmittance measurements using picosecond or femtosecond laser pulses. PMID:16454917
NASA Technical Reports Server (NTRS)
Pan, Xiaoju; Mannino, Antonio; Russ, Mary E.; Hooker, Stanford B.
2008-01-01
At present, satellite remote sensing of coastal water quality and constituent concentration is subject to large errors as compared to the capability of satellite sensors in oceanic waters. In this study, field measurements collected on a series of cruises within U.S. southern Middle Atlantic Bight (SMAB) were applied to improve retrievals of satellite ocean color products in order to examine the factors that regulate the bio-optical properties within the continental shelf waters of the SMAB. The first objective was to develop improvements in satellite retrievals of absorption coefficients of phytoplankton (a(sub ph)), colored dissolved organic matter (CDOM) (a(sub g)), non-pigmented particles (a(sub d)), and non-pigmented particles plus CDOM (a(sub dg)), and chlorophyll a concentration ([Chl_a]). Several algorithms were compared to derive constituent absorption coefficients from remote sensing reflectance (R(sub rs)) ratios. The validation match-ups showed that the mean absolute percent differences (MAPD) were typically less than 35%, although higher errors were found for a(sub d) retrievals. Seasonal and spatial variability of satellite-derived absorption coefficients and [Chl_a] was apparent and consistent with field data. CDOM is a major contributor to the bio-optical properties of the SMAB, accounting for 35-70% of total light absorption by particles plus CDOM at 443 nm, as compared to 30-45% for phytoplankton and 0-20% for non-pigmented particles. The overestimation of [Chl_a] from the operational satellite algorithms may be attributed to the strong CDOM absorption in this region. River discharge is important in controlling the bio-optical environment, but cannot explain all of the regional and seasonal variability of biogeochemical constituents in the SMAB.
Kulp, T.J.; Shinn, J.
1995-04-01
The accurate characterization of the latent infrared (IR) absorption in the atmospheric window regions continues to be an area of research interest for the global climate modeling community. In the window between 8 and 14 {mu}m, this absorption can be attributed primarily to water vapor. It consists of (1) weak lines originating from the edge of the water vapor pure rotational band (at low wavenumbers) and the trailing P-branch of the v{sub 2} rovibrational band (at the high-wavenumber boundary of the window); and (2) the water vapor continuum absorption. The goal of our project has been to improve our quantitative and physical understanding of both of these absorption processes. Specifically, our immediate aims are to fill gaps in the experimental radiative transfer databases pertaining to the line parameters (i.e., line intensities and broadening coefficients) and to the self- and foreign-broadened water vapor continuum. To accomplish our goals, we have made long-pathlength absorption measurements using a Fourier transform infrared spectrometer (FTIR) (for the continuum and line measurements, at low resolution) and a tunable diode laser absorption spectrometer (TDLAS) (for the line measurements, at high resolution). These measurements were made on gas samples contained in a 400-m maximum pathlength Horn Pimentel multipass cell designed and constructed for this project.
NASA Astrophysics Data System (ADS)
Fairuz Budiman, Mohd; Hu, Weiguo; Igarashi, Makoto; Tsukamoto, Rikako; Isoda, Taiga; Itoh, Kohei M.; Yamashita, Ichiro; Murayama, Akihiro; Okada, Yoshitaka; Samukawa, Seiji
2012-02-01
A sub-10 nm, high-density, periodic silicon-nanodisc (Si-ND) array has been fabricated using a new top-down process, which involves a 2D array bio-template etching mask made of Listeria-Dps with a 4.5 nm diameter iron oxide core and damage-free neutral-beam etching (Si-ND diameter: 6.4 nm). An Si-ND array with an SiO2 matrix demonstrated more controllable optical bandgap energy due to the fine tunability of the Si-ND thickness and diameter. Unlike the case of shrinking Si-ND thickness, the case of shrinking Si-ND diameter simultaneously increased the optical absorption coefficient and the optical bandgap energy. The optical absorption coefficient became higher due to the decrease in the center-to-center distance of NDs to enhance wavefunction coupling. This means that our 6 nm diameter Si-ND structure can satisfy the strict requirements of optical bandgap energy control and high absorption coefficient for achieving realistic Si quantum dot solar cells.
NASA Technical Reports Server (NTRS)
Surinov, Y. A.; Sosnovyy, N. V.
1975-01-01
Local and average radiation functions, which represent purely geometric characteristics of the radiating system, are used to determine the absorptivity in a system of bodies separated by an attenuating medium.
NASA Technical Reports Server (NTRS)
Baines, Kevin H.; West, Robert A.; Giver, Lawrence P.; Moreno, Fernando
1993-01-01
Near-infrared 10/cm resolution spectra of methane obtained at various temperatures, pressures, and abundances are fit to a quasi-random narrow-band model. Exponential-sum absorption coefficients for three temperatures (112, 188, and 295 K), and 20 pressures from 0.0001 to 5.6 bars, applicable to the cold environments of the major planets, are then derived from the band model for the 230 wavelengths measured from 1.6 to 2.5 microns. RMS deviations between the laboratory and the exponential-sum synthetic transmissions are reported for the best fitting 50 wavelengths. Deviations relevant to broadband, 1-percent spectral resolution observations are also presented. The validity of exponential-sum coefficients derived from broadband (10/cm) transmission data is demonstrated via direct comparison with line-by-line calculations. The complete atlas of coefficients is available from the Planetary Data System-Planetary Atmospheres Discipline Node.
NASA Astrophysics Data System (ADS)
Thomas, S.; Koch-Mueller, M.; Reichart, P.; Rhede, D.; Thomas, R.
2007-12-01
Conventionally applied Infrared (IR) calibrations [1, 2] for quantitative water analyses in solids are established on hydrous minerals and glasses with several wt% water. These calibrations are based on a negative correlation between the IR molar absorption coefficient (ɛ) for water and the mean wavenumber of the corresponding OH pattern. The correlation reflects the dependence of the OH band position on the appropriate O- H...O distances and thereby the magnitude of the dipole momentum which is proportional to the band intensity. However, it has been observed that these calibrations can not be adopted to nominally anhydrous minerals (NAMs) [3].To study the potential dependence of ɛ on structure and chemistry in NAMs we synthesized olivine and SiO2 polymorphs with specific isolated hydroxyl point defects, e.g. quartz, coesite and stishovite with B3++H+=Si4+ and/or Al3++H+=Si4+ substitutions. Experiments were performed with water in excess in piston cylinder and multi-anvil presses. Single crystal IR spectra demonstrate that we successfully managed to seperate generally complex OH patterns as e.g. observed in natural quartz and synthetic coesite. We quantified sample water contents of both natural samples and our run products by applying proton-proton-scattering [4], confocal microRaman spectroscopy [5] and Secondary Ion mass spectrometry. Resulting water concentrations were used to calculate new mineral specific ɛs. For olivine with the mean wavenumber of 3517 cm-1 we determined an ɛ value of 41,000±5,000 lmol-1H2Ocm-2. Quantification of olivine with the mean wavenumber of 3550 cm-1 in contrast resulted in an ɛ value of 47,000±1,000 lmol-1H2Ocm-2. Taking into account previous studies [6, 7] there is evidence to suggest a linear wavenumber dependent correlation for olivine, where ɛ increases with decreasing wavenumber. In case of the SiO2 system it turns out that the magnitude of ɛ within one structure type is independent of the liable OH point defect and
NASA Astrophysics Data System (ADS)
Narayan, Raghuram
1997-12-01
The main topics in this dissertation are (a) Investigation of Electro-Optic (EO) coefficient variation in lithium niobate and (b) the design, fabrication and analysis of coplanar waveguide resonant electrodes for EO modulators. An optical sampling technique is used to determine the EO coefficient variations in lithium niobate processed using the titanium in-diffusion technique and the Annealed Proton Exchange (APE) technique. A spatial mapping of the EO coefficients in lithium niobate is presented. The measurements enable us to quantitatively estimate the reduction in the EO coefficient as a function of the processing conditions. The results clearly indicate that samples processed using titanium in-diffusion show no degradation of the EO coefficient. Samples processed using the APE technique display a dramatic drop in the processed region immediately after the proton exchange step. Thermal annealing is shown to restore the EO coefficient in the proton exchanged regions. But the efficacy of thermal annealing is dependent on the initial proton exchange process. Prolonged thermal annealing is effective in restoring the EO coefficients provided the initial proton exchange depth is less than 1.5/mu m. Coplanar Waveguide (CPW) is a popular planar transmission line because of its tight confinement and non-dispersive nature at high frequencies (>60 GHz). In this dissertation, several CPW resonant electrodes have been fabricated, tested and analyzed. The advantage of CPW resonant electrode structure is that there is an enhancement in the field strength by a factor proportional to /sqrt[Q], where Q is the quality factor of the resonator. The dis-advantage is that the device is narrow-band in its frequency response. The focus of this dissertation is to investigate the design and fabrication issues related to CPW resonators. The results indicate the need for better design tools to properly predict the performance of the resonator and in general CPW structures. The measurements
NASA Astrophysics Data System (ADS)
Baldassarre, L.; Giliberti, V.; Rosa, A.; Ortolani, M.; Bonamore, A.; Baiocco, P.; Kjoller, K.; Calvani, P.; Nucara, A.
2016-02-01
Infrared (IR) nanospectroscopy performed in conjunction with atomic force microscopy (AFM) is a novel, label-free spectroscopic technique that meets the increasing request for nano-imaging tools with chemical specificity in the field of life sciences. In the novel resonant version of AFM-IR, a mid-IR wavelength-tunable quantum cascade laser illuminates the sample below an AFM tip working in contact mode, and the repetition rate of the mid-IR pulses matches the cantilever mechanical resonance frequency. The AFM-IR signal is the amplitude of the cantilever oscillations driven by the thermal expansion of the sample after absorption of mid-IR radiation. Using purposely nanofabricated polymer samples, here we demonstrate that the AFM-IR signal increases linearly with the sample thickness t for t \\gt 50 nm, as expected from the thermal expansion model of the sample volume below the AFM tip. We then show the capability of the apparatus to derive information on the protein distribution in single cells through mapping of the AFM-IR signal related to the amide-I mid-IR absorption band at 1660 cm-1. In Escherichia Coli bacteria we see how the topography changes, observed when the cell hosts a protein over-expression plasmid, are correlated with the amide I signal intensity. In human HeLa cells we obtain evidence that the protein distribution in the cytoplasm and in the nucleus is uneven, with a lateral resolution better than 100 nm.
NASA Astrophysics Data System (ADS)
Vogel, L.; Sihler, H.; Lampel, J.; Wagner, T.; Platt, U.
2012-04-01
Optical remote sensing via Differential Optical Absorption Spectroscopy (DOAS) has become a standard technique to assess various trace gases in the atmosphere. Measurement instruments are usually classified into active instruments applying an artificial light source and passive instruments using natural light sources, e.g., scattered or direct sunlight. Platforms range from ground based to satellites and trace gases are studied in all kinds of different environments. Naturally, the evaluation of gathered spectra needs to be tuned to each specific case and trace gas of interest due to the wide range of measurement conditions, atmospheric compositions and instruments used. A well chosen evaluation wavelength range is crucial to the DOAS technique. It should be as large as possible and include the largest differential absorption features of the trace gas of interest in order to maximize sensitivity. However, the differential optical densities of other absorbers should be minimized in order to prevent interferences between different absorption cross sections. Furthermore, instrumental specific features and wavelength dependent radiative transfer effects may have malicious effects and lead to erroneous values. Usually a compromise needs to be found depending on the conditions at hand. Evaluation wavelength range mapping is an easily applied tool to visualize wavelength depending evaluation features of DOAS and to find the optimal retrieval wavelength range. As an example, synthetic spectra are studied which simulate passive DOAS measurements of stratospheric bromine monoxide (BrO) by Zenith-DOAS and Multi-Axis DOAS (MAX-DOAS) measurements of BrO in volcanic plumes. The influence of the I0-effect and the Ring-effect on the respective retrievals are demonstrated. However, due to the general nature of the tool it is applicable to any DOAS measurement and the technique also allows to study any other wavelength dependent influences on retrieved trace gas columns.
NASA Astrophysics Data System (ADS)
Utry, N.; Ajtai, T.; Pintér, M.; Tombácz, E.; Illés, E.; Bozóki, Z.; Szabó, G.
2015-01-01
Mass-specific optical absorption coefficients (MACs) and the imaginary part (κ) of the refractive indices of various mineral dust components including silicate clays (illite, kaolin and bentonite), oxides (quartz, hematite and rutile), and carbonate (limestone) were determined at the wavelengths of 1064, 532, 355 and 266 nm. The MAC values were calculated from aerosol optical absorption coefficients measured by a multi-wavelength photoacoustic (PA) instrument, the mass concentration and the number size distribution of the generated aerosol samples as well as the size transfer functions of the measuring instruments. Values of κ were calculated from the measured and particle-loss-corrected data by using a Mie-theory-based retrieval algorithm. The determined values could be used for comparisons with calculated wavelength-dependent κ values typically deduced from bulk-phase measurements by using indirect measurement methods. Accordingly, the presented comparison of the measured and calculated aerosol optical absorption spectra revealed the strong need for standardized sample preparation and measurement methodology in case of bulk-phase measurements.
Ivascu, I R; Matei, C E; Patachia, M; Bratu, A M; Dumitras, D C
2016-06-15
Absorption coefficients of the ethanol vapors at atmospheric pressure and room temperature were measured by photoacoustic technique using a cw, line-tunable, frequency-stabilized CO2 laser as radiation source. The spectrum of the employed CO2 laser includes 54 lines with wavelengths in the infrared region of 9.2-10.8μm and power levels up to 4.7W. Measurements revealed a predominant absorption for ethanol within 9.4μm band of the CO2 laser spectrum, where the highest values of the absorption coefficients were recorded: 3.68cm(-1)atm(-1) at 9R(20) line and 3.65cm(-1)atm(-1) at 9R(22) line. The estimated detection range covers six orders of magnitude, from a minimum of 30ppbV to a maximum of 4% concentration of ethanol in nitrogen, which proves the suitability of the photoacoustic technique for accurate measurements of the ethanol concentration in various applications. PMID:27045783
NASA Astrophysics Data System (ADS)
Ivascu, I. R.; Matei, C. E.; Patachia, M.; Bratu, A. M.; Dumitras, D. C.
2016-06-01
Absorption coefficients of the ethanol vapors at atmospheric pressure and room temperature were measured by photoacoustic technique using a cw, line-tunable, frequency-stabilized CO2 laser as radiation source. The spectrum of the employed CO2 laser includes 54 lines with wavelengths in the infrared region of 9.2-10.8 μm and power levels up to 4.7 W. Measurements revealed a predominant absorption for ethanol within 9.4 μm band of the CO2 laser spectrum, where the highest values of the absorption coefficients were recorded: 3.68 cm- 1 atm- 1 at 9R(20) line and 3.65 cm- 1 atm- 1 at 9R(22) line. The estimated detection range covers six orders of magnitude, from a minimum of 30 ppbV to a maximum of 4% concentration of ethanol in nitrogen, which proves the suitability of the photoacoustic technique for accurate measurements of the ethanol concentration in various applications.
SHETTY, ANIL N.; CHIANG, SHARON; MALETIC-SAVATIC, MIRJANA; KASPRIAN, GREGOR; VANNUCCI, MARINA; LEE, WESLEY
2016-01-01
In this article, we discuss the theoretical background for diffusion weighted imaging and diffusion tensor imaging. Molecular diffusion is a random process involving thermal Brownian motion. In biological tissues, the underlying microstructures restrict the diffusion of water molecules, making diffusion directionally dependent. Water diffusion in tissue is mathematically characterized by the diffusion tensor, the elements of which contain information about the magnitude and direction of diffusion and is a function of the coordinate system. Thus, it is possible to generate contrast in tissue based primarily on diffusion effects. Expressing diffusion in terms of the measured diffusion coefficient (eigenvalue) in any one direction can lead to errors. Nowhere is this more evident than in white matter, due to the preferential orientation of myelin fibers. The directional dependency is removed by diagonalization of the diffusion tensor, which then yields a set of three eigenvalues and eigenvectors, representing the magnitude and direction of the three orthogonal axes of the diffusion ellipsoid, respectively. For example, the eigenvalue corresponding to the eigenvector along the long axis of the fiber corresponds qualitatively to diffusion with least restriction. Determination of the principal values of the diffusion tensor and various anisotropic indices provides structural information. We review the use of diffusion measurements using the modified Stejskal–Tanner diffusion equation. The anisotropy is analyzed by decomposing the diffusion tensor based on symmetrical properties describing the geometry of diffusion tensor. We further describe diffusion tensor properties in visualizing fiber tract organization of the human brain.
Lumia, Richard; Baevsky, Yvonne H.
2000-01-01
Flood-frequency relations that are developed by fitting the logarithms of annual peak discharges to a Pearson Type-III distribution are sensitive to skew coefficients. Estimates of population skew for a site are improved when computed from the weighted average of (1) the sample (station) skew, and (2) an unbiased, generalized skew estimate. A weighting technique based on the number of years of record at each of 226 sites was used to develop a contour map of unbiased, generalized skew coefficients for New York. An attempt was made to group (regionalize) the station skew coefficients into five hydrologically similar areas of New York, but the statewide version proved to be as accurate as the regionalized version and therefore was adopted as the final generalized skew-coefficient map for New York. An error analysis showed the statewide contour map to have lower MSE?s (mean square errors) than those computed from (1) the five regional skewcoefficient contour maps, (2) a previously used (1982) nationwide skew coefficient map, and (3) the weighted mean of skew coefficients for sites within each of five hydrologically uniform, but distinct areas of New York.
NASA Astrophysics Data System (ADS)
Vogel, L.; Sihler, H.; Lampel, J.; Wagner, T.; Platt, U.
2012-06-01
Remote sensing via differential optical absorption spectroscopy (DOAS) has become a standard technique to identify and quantify trace gases in the atmosphere. The technique is applied in a variety of configurations, commonly classified into active and passive instruments using artificial and natural light sources, respectively. Platforms range from ground based to satellite instruments and trace-gases are studied in all kinds of different environments. Due to the wide range of measurement conditions, atmospheric compositions and instruments used, a specific challenge of a DOAS retrieval is to optimize the parameters for each specific case and particular trace gas of interest. This becomes especially important when measuring close to the detection limit. A well chosen evaluation wavelength range is crucial to the DOAS technique. It should encompass strong absorption bands of the trace gas of interest in order to maximize the sensitivity of the retrieval, while at the same time minimizing absorption structures of other trace gases and thus potential interferences. Also, instrumental limitations and wavelength depending sources of errors (e.g. insufficient corrections for the Ring effect and cross correlations between trace gas cross sections) need to be taken into account. Most often, not all of these requirements can be fulfilled simultaneously and a compromise needs to be found depending on the conditions at hand. Although for many trace gases the overall dependence of common DOAS retrieval on the evaluation wavelength interval is known, a systematic approach to find the optimal retrieval wavelength range and qualitative assessment is missing. Here we present a novel tool to determine the optimal evaluation wavelength range. It is based on mapping retrieved values in the retrieval wavelength space and thus visualize the consequence of different choices of retrieval spectral ranges, e.g. caused by slightly erroneous absorption cross sections, cross correlations and
NASA Astrophysics Data System (ADS)
DeMilo, Charles; Brukilacchio, Thomas; Soller, Babs R.; Soyemi, Olusola
2004-06-01
A visible-near IR (500-1,000nm) fiber optic sensor is under development that is intended to non-invasively assess muscle metabolism through the measurement of tissue pH and oxygen partial pressure. These parameters are calculated from the spectra of hemoglobin and myoglobin in muscle. The sensor consists of transmit (illumination) fibers and receive (detection) fibers that are coupled to a spectrometer. Light from the probe must penetrate below the surface of the skin and into a 5-10mm thick layer of muscle. A study was conducted to quantify the relationship between transmit and receive fiber separation and sensor penetration depth below the surface of the skin. A liquid phantom was created to replicate the absorption (μa) and reduced scatter coefficient (μs') profiles typically found in human blood and tissue. The phantom consisted of a solution of Intralipid and India ink in the appropriate concentrations to achieve desired reduced scatter coefficient and absorption profiles. The reduced scatter coefficient of the liquid phantom was achieved to an accuracy of +/-10% compared to previously published data. A fixed illumination fiber and translatable detector fiber were placed in the liquid phantom, and the fiber separation was varied from 3-40mm. Values of μa and μs' varied from 0.03-0.40 cm-1 and 5.0-15.0 cm-1 respectively. Results from the experiment demonstrate a strong correlation between penetration depth and fiber separation. Additionally, it was found that penetration depth was not substantially influenced by absorption and scatter concentration. As signal-to-noise is an important parameter in many non-invasive biomedical applications, the relative signal as a function of fiber separation was determined to follow an exponential relationship.
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.
NASA Astrophysics Data System (ADS)
Degrelle, D.; Mavon, C.; Groetz, J.-E.
2016-04-01
This study presents a numerical method in order to determine the mass attenuation coefficient of a sample with an unknown chemical composition at low energy. It is compared with two experimental methods: a graphic method and a transmission method. The method proposes to realise a numerical absorption calibration curve to process experimental results. Demineralised water with known mass attenuation coefficient (0.2066cm2g-1 at 59.54 keV) is chosen to confirm the method. 0.1964 ± 0.0350cm2g-1 is the average value determined by the numerical method, that is to say less than 5% relative deviation compared to more than 47% for the experimental methods.
NASA Astrophysics Data System (ADS)
Deckers, Elke; Claeys, Claus; Atak, Onur; Groby, Jean-Philippe; Dazel, Olivier; Desmet, Wim
2016-05-01
This paper presents an extension to the Wave Based Method to predict the absorption, reflection and transmission coefficients of a porous material with an embedded periodic set of inclusions. The porous unit cell is described using the Multi-Level methodology and by embedding Bloch-Floquet periodicity conditions in the weighted residual scheme. The dynamic pressure field in the semi-infinite acoustic domains is approximated using a novel wave function set that fulfils the Helmholtz equation, the Bloch-Floquet periodicity conditions and the Sommerfeld radiation condition. The method is meshless and computationally efficient, which makes it well suited for optimisation studies.
NASA Astrophysics Data System (ADS)
Pei, Yaling; Graber, Harry L.; Barbour, Randall L.
2001-06-01
In this report, we present a method to reduce the cross-talk problem in optical tomography. The method described is an extension of a previously reported perturbation formulation related to relative detector values, and employs a weight matrix scaling technique together with a constrained CGD method for imaging reconstruction. Results from numerical and experimental studies using DC measurement data demonstrate that the approach can effectively isolate absorption and scattering heterogeneities, even for complex combinations of perturbations in optical properties. The derive method is remarkably stable to errors originating from an insufficiently accurate estimate of properties of the reference medium.
2012-01-01
The linear and nonlinear intraband optical absorption coefficients in GaAs three-dimensional single quantum rings are investigated. Taking into account the combined effects of hydrostatic pressure and electric field, applied along the growth direction of the heterostructure, the energies of the ground and first excited states of a donor impurity have been found using the effective mass approximation and a variational method. The energies of these states are examined as functions of the dimensions of the structure, electric field, and hydrostatic pressure. We have also investigated the dependencies of the linear, nonlinear, and total optical absorption coefficients as a function of incident photon energy for several configurations of the system. It is found that the variation of distinct sizes of the structure leads to either a redshift and/or a blueshift of the resonant peaks of the intraband optical spectrum. In addition, we have found that the application of an electric field leads to a redshift, whereas the influence of hydrostatic pressure leads to a blueshift (in the case of on-ring-center donor impurity position) of the resonant peaks of the intraband optical spectrum. PMID:23021497
NASA Astrophysics Data System (ADS)
Martínez-Orozco, J. C.; Rodríguez-Magdaleno, K. A.; Suárez-López, J. R.; Duque, C. A.; Restrepo, R. L.
2016-04-01
In this work we present theoretical results for the electronic structure as well as for the absorption coefficient and relative refractive index change for an asymmetric double δ-doped like confining potential in the active region of a Multiple Independent Gate Field Effect Transistor (MIGFET) system. We model the potential profile as a double δ-doped like potential profile between two Schottky (parabolic) potential barriers that are just the main characteristics of the MIGFET configuration. We investigate the effect of external electromagnetic fields in this kind of quantum structures, in particular we applied a homogeneous constant electric field in the growth direction z as well as a homogeneous constant magnetic field in the x-direction. In general we conclude that by applying electromagnetic fields we can modulate the resonant peaks of the absorption coefficient as well as their energy position. Also with such probes it is possible to control the nodes and amplitude of the relative refractive index changes related to resonant intersubband optical transitions.
Barseghyan, Manuk G; Restrepo, Ricardo L; Mora-Ramos, Miguel E; Kirakosyan, Albert A; Duque, Carlos A
2012-01-01
: The linear and nonlinear intraband optical absorption coefficients in GaAs three-dimensional single quantum rings are investigated. Taking into account the combined effects of hydrostatic pressure and electric field, applied along the growth direction of the heterostructure, the energies of the ground and first excited states of a donor impurity have been found using the effective mass approximation and a variational method. The energies of these states are examined as functions of the dimensions of the structure, electric field, and hydrostatic pressure. We have also investigated the dependencies of the linear, nonlinear, and total optical absorption coefficients as a function of incident photon energy for several configurations of the system. It is found that the variation of distinct sizes of the structure leads to either a redshift and/or a blueshift of the resonant peaks of the intraband optical spectrum. In addition, we have found that the application of an electric field leads to a redshift, whereas the influence of hydrostatic pressure leads to a blueshift (in the case of on-ring-center donor impurity position) of the resonant peaks of the intraband optical spectrum. PMID:23021497
NASA Astrophysics Data System (ADS)
Consalvi, J. L.; Nmira, F.
2016-03-01
The main objective of this article is to quantify the influence of the soot absorption coefficient-Planck function correlation on radiative loss and flame structure in an oxygen-enhanced propane turbulent diffusion flame. Calculations were run with and without accounting for this correlation by using a standard k-ε model and the steady laminar flamelet model (SLF) coupled to a joint Probability Density Function (PDF) of mixture fraction, enthalpy defect, scalar dissipation rate, and soot quantities. The PDF transport equation is solved by using a Stochastic Eulerian Field (SEF) method. The modeling of soot production is carried out by using a flamelet-based semi-empirical acetylene/benzene soot model. Radiative heat transfer is modeled by using a wide band correlated-k model and turbulent radiation interactions (TRI) are accounted for by using the Optically-Thin Fluctuation Approximation (OTFA). Predicted soot volume fraction, radiant wall heat flux distribution and radiant fraction are in good agreement with the available experimental data. Model results show that soot absorption coefficient and Planck function are negatively correlated in the region of intense soot emission. Neglecting this correlation is found to increase significantly the radiative loss leading to a substantial impact on flame structure in terms of mean and rms values of temperature. In addition mean and rms values of soot volume fraction are found to be less sensitive to the correlation than temperature since soot formation occurs mainly in a region where its influence is low.
NASA Astrophysics Data System (ADS)
Tan, K. C.; Lim, H. S.; MatJafri, M. Z.
2012-11-01
Among all the greenhouse gases, methane is the most dynamic and abundant greenhouse gas in the atmosphere. The global concentrations of atmospheric methane has increased more than doubled since pre-industrial times, with a current globally-averaged mixing ratio of ~ 1750 ppbv. Due to its high growth rate, methane brings significant effects on climate and atmospheric chemistry. There has a significant gap for variables between anthropogenic and natural sources and sinks of methane. Satellite observation of methane has been identified that it can provide the precise and accurate data globally, which sensitive to the small regional biases. We present measurements from Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) included on the European environmental satellite ENVISAT, launched on 1st of March 2002. Main objective of this study is to examine the methane distribution over Peninsular Malaysia using SCIAMACHY level-3 data. They are derived from the near-infrared nadir observations of the SCIAMACHY at the University of Bremen through scientific WFM-DOAS retrieval algorithm version 2.0.2.Maps of time averaged (yearly, tri-monthly) methane was generated and analyzed over Peninsular Malaysia for the year 2003 using PCI Geomatica 10.3 image processing software. The maps show dry-air column averaged mixing ratios of methane (denoted XCH4). It was retrieved using the interpolation technique. The concentration changes within boundary layer at all altitude levels are equally sensitive through the SCIAMACHY near-infrared nadir observations. Hence, we can make observation of methane at surface source region. The results successfully identify the area with highest and lowest concentration of methane at Peninsular Malaysia using SCIAMACHY data. Therefore, the study is suitable to examine the distribution of methane at tropical region.
Papernov, S.; Tait, A.; Bittle, W.; Schmid, A.W.; Oliver, J.B.; Kupinski, P.
2011-02-01
Nanosecond-pulse UV-laser-damage initiation in multilayer coatings comprised from metal oxide as a high-index component, and silica oxide as a low-index material, is strongly linked to metal oxide. The nature of the absorbing species and their physical properties remain unknown because of extremely small sizes. Previous experimental evidence provided by high-resolution mapping of damage morphology points to a few-nanometer scale of these absorbers. This work demonstrates submicrometer mapping of 355-nm absorption in HfO2 monolayers using a recently developed photothermal heterodyne imaging technique. Comparison of absorption maps with spatial distribution of UV pulsed-laser–induced damage morphology allows one to better estimate the size and densities of nanoscale absorbing defects in hafnia thin films. Possible defect-formation mechanisms are discussed.
NASA Astrophysics Data System (ADS)
Rosati, B.; Weingartner, E.; Gysel, M.; Tillmann, R.; Mentel, T. F.; Decesari, S.; Marinoni, A.; Gobbi, G. P.; Fierli, F.; Cairo, F.; Bucci, S.; Zanatta, M.; Größ, J.; Baltensperger, U.
2014-12-01
Aerosol particles influence the Earth's radiation budget by interacting with the incoming sunlight. The chemical composition and size of aerosol particles determine their potential to scatter and absorb radiation as well as their capability to take up water (Zieger et al., 2011). If particles are hygroscopic their optical properties will be altered at enhanced relative humidities (RH) due to the increase in size and change in index of refraction. It is known that RH but also the chemical composition of aerosols change with altitude (Morgan et al., 2010) which makes it very important to investigate optical properties at different heights. Within the Pan-European Gas-Aerosols-climate interaction Study (PEGASOS) a set of instruments was installed on a Zeppelin to investigate changes of light scattering and absorption in the planetary boundary layer. In order to obtain the scattering properties, Mie calculations were performed for size distributions recorded with SMPS (scanning mobility particle sizer) and WELAS (optical size spectrometer). The index of refraction and the hygroscopicity of the aerosol particles were measured with the white-light humidified optical particle spectrometer (WHOPS). These measurements further allowed studying the RH-dependence of the optical properties. Moreover, a seven wavelength portable aethalometer was employed to determine the light absorption properties of the aerosol. In this work we will present vertical profiles of scattering and absorption coefficients measured during Zeppelin flights of the PEGASOS campaigns in Italy in 2012. Additionally comparisons with ground based measurements from nephelometers and aethalometers, as well as remote sensing results will be shown. W.T. Morgan et al., Enhancement of the aerosol direct radiative effect by semi-volatile aerosol components: Airborne measurements in North-Western Europe, Atmospheric Chemistry and Physics 10(2010), pp. 8151-8171.P. Zieger et al., Comparison of ambient aerosol
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.
Greening, Gage J; Istfan, Raeef; Higgins, Laura M; Balachandran, Kartik; Roblyer, Darren; Pierce, Mark C; Muldoon, Timothy J
2014-01-01
Optical phantoms are used in the development of various imaging systems. For certain applications, the development of thin phantoms that simulate the physical size and optical properties of tissue is important. Here, we demonstrate a method for producing thin phantom layers with tunable optical properties using poly(dimethylsiloxane) (PDMS) as a substrate material. The thickness of each layer (between 115 and 880 μm) was controlled using a spin coater. The reduced scattering and absorption coefficients were controlled using titanium dioxide and alcohol-soluble nigrosin, respectively. These optical coefficients were quantified at six discrete wavelengths (591, 631, 659, 691, 731, and 851 nm) at varying concentrations of titanium dioxide and nigrosin using spatial frequency domain imaging. From the presented data, we provide lookup tables to determine the appropriate concentrations of scattering and absorbing agents to be used in the design of PDMS-based phantoms with specific optical coefficients. In addition, heterogeneous phantoms mimicking the layered features of certain tissue types may be fabricated from multiple stacked layers, each with custom optical properties. These thin, tunable PDMS optical phantoms can simulate many tissue types and have broad imaging calibration applications in endoscopy, diffuse optical spectroscopic imaging, and optical coherence tomography, etc. PMID:25387084
Chou, D.-Y.; Yang, M.-H.; Zhao Hui; Liang Zhichao; Sun, M.-T.
2009-11-20
Observed acoustic power in magnetic regions is lower than the quiet Sun because of absorption, emissivity reduction, and local suppression of solar acoustic waves in magnetic regions. In the previous studies, we have developed a method to measure the coefficients of absorption, emissivity reduction, and local suppression of sunspots. In this study, we go one step further to measure the spatial distributions of three coefficients in two active regions, NOAA 9055 and 9057. The maps of absorption, emissivity reduction, and local suppression coefficients correlate with the magnetic map, including plage regions, except the emissivity reduction coefficient of NOAA 9055 where the emissivity reduction coefficient is too weak and lost among the noise.
Global absorption center map of the mafic minerals on the Moon as viewed by CE-1 IIM data
NASA Astrophysics Data System (ADS)
Wu, Yunzhao; Zhang, Xia; Yan, Bokun; Gan, Fuping; Tang, Zesheng; Xu, Aoao; Zheng, Yongchun; Zou, Yongliao
2010-12-01
Determining the global distribution of minerals on the Moon has been an important goal of lunar science. Hyperspectral remote sensing is an important approach to acquiring minerals on the Moon on the global scale. The wavelength of the absorption band center is the key parameter for identifying minerals with reflectance spectra as well as remote sensing data. The global absorption center map of the mafic minerals of the Moon was produced for the first time with the Chang'E-1 IIM data. This map shows the global distribution of mafic minerals such as orthopyroxenes, clinopyroxenes, and olivine and even plagioclase feldspar of the Moon. The validation for some representative areas indicates that the global map is reliable and even more detailed than the results derived from Clementine-data. Moreover, our method is insensitive to the topography and viewing and illumination geometries. The global absorption band center map not only contributes to the lunar science research, but also has other implications to be further studied. Moreover, the preprocessing methods such as calibration and correction introduced in this study can be useful in other research with IIM data.
Fasano, William J; Baer, Kevin N
2006-01-01
Vinyl toluene is one of several methylstyrene monomers that provide improved performance in resins for specialty paints, hydrocarbon resins for adhesives, specialty polymers, and unsaturated polyester resins. The purpose of this study was to determine a permeability coefficient (Kp) and short-term absorption rate for vinyl toluene using human cadaver skin mounted in an in vitro static diffusion cell model with an exposure area of 0.64 cm2. For the Kp determination, vinyl toluene was applied at a rate of 100 microL/cm2 to 6 skin replicates representing 4 human subjects. Serial receptor fluid samples were collected at 1, 2, 4, 8, 12, 24, 36, and 48 h postapplication and analyzed for vinyl toluene by HPLC-UV. Based on the slope at steady-state (203.3 microg cm(-2) h(-1) +/- 120.0 microg cm(-2) h(-1)) and the concentration of the applied dose of vinyl toluene, taken as its density (894,600 microg/cm3), the Kp was calculated to be 2.27 x 10(-4) cm/h (+/-1.34 x 10(-4) cm/h). For the short-term absorption experiments, 12 skin replicates representing 3 human subjects were employed. Following 10- and 60-min exposures to a finite dose of vinyl toluene (10 microL/cm2), the respective short-term absorption rates were calculated to be 66.0 (+/-29.9) and 104.2 (+/-63.0) microg cm(-2) h(-1). These data provide industrial hygienists and safety personnel values to estimate the amount of vinyl toluene that may be absorbed via the dermal exposure route, given a variety of exposure scenarios, and the time it takes (skin absorption time) to reach a body burden equal to the Occupational Safety and Health Administrative permissible exposure level (OSHA PEL) or ACGIH TLV. PMID:16455589
Mean absorption coefficient of H2O-air-MgCl2/CaCl2/NaCl thermal plasmas
NASA Astrophysics Data System (ADS)
Hannachi, R.; Cressault, Y.; Salem, D.; Teulet, Ph; Béji, L.; Ben Lakhdar, Z.
2012-12-01
Under the local thermodynamic equilibrium hypothesis, the mean absorption coefficients (MACs) were calculated for H2O-air-MgCl2/CaCl2/NaCl thermal plasmas in a temperature range from 300 to 30 000 K and at atmospheric pressure. The MACs were computed under the hypothesis of isothermal plasmas which allows a good description of the radiation absorbed in cold regions. In this study, we took into account the absorption radiation resulting from the atomic continuum, molecular continuum, atomic lines and some molecular bands. Free-free transitions (bremsstrahlung) and free-bound (electron-ion recombination and electron attachment) or bound-free transitions in terms of absorption were considered for the calculation of atomic continuum. For bound-bound transitions, natural, resonance, van der Waals, Stark and Doppler effects were taken into account for the line broadenings while the escape factors were used to treat the self-absorption of the resonance lines. Molecular continuum was considered for the main molecules (H2, O2, N2, OH, NO, H2O, N2O, NO2, O3, NO3 and N2O5) whereas we studied only diatomic systems O2, N2, NO and N_2^+ for the absorption of molecular bands. The influence of the proportion of MgCl2, CaCl2 or NaCl in a water-air mixture was analysed as the effect of the strong self-absorbed resonance lines of the alkaline salts (Ca, Ca+, Na, Na+, Mg, Mg+, Cl and Cl+). Our results show that a low concentration of alkaline salts (less than 1% in molar proportions) in the plasma increased the MACs at low temperatures (T < 10 000 K) due to the resonance lines mainly localized in the near-UV and visible spectral regions in opposition to hydrogen, oxygen or nitrogen species for which 90% of them exist in ultraviolet. In addition to the atomic and molecular continuum, the absorption radiation of molecular bands is important at low temperatures.
NASA Astrophysics Data System (ADS)
Bailey, Mandy; van Loon, Jacco Th.; Sarre, Peter J.; Beckman, John E.
2015-12-01
Diffuse interstellar bands (DIBs) trace warm neutral and weakly ionized diffuse interstellar medium (ISM). Here we present a dedicated, high signal-to-noise spectroscopic survey of two of the strongest DIBs, at 5780 and 5797 Å, in optical spectra of 666 early-type stars in the Small and Large Magellanic Clouds, along with measurements of the atomic Na I D and Ca II K lines. The resulting maps show for the first time the distribution of DIB carriers across large swathes of galaxies, as well as the foreground Milky Way ISM. We confirm the association of the 5797 Å DIB with neutral gas, and the 5780 Å DIB with more translucent gas, generally tracing the star-forming regions within the Magellanic Clouds. Likewise, the Na I D line traces the denser ISM whereas the Ca II K line traces the more diffuse, warmer gas. The Ca II K line has an additional component at ˜200-220 km s-1 seen towards both Magellanic Clouds; this may be associated with a pan-Magellanic halo. Both the atomic lines and DIBs show sub-pc-scale structure in the Galactic foreground absorption; the 5780 and 5797 Å DIBs show very little correlation on these small scales, as do the Ca II K and Na I D lines. This suggests that good correlations between the 5780 and 5797 Å DIBs, or between Ca II K and Na I D, arise from the superposition of multiple interstellar structures. Similarity in behaviour between DIBs and Na I in the Small Magellanic Cloud (SMC), Large Magellanic Cloud (LMC) and Milky Way suggests the abundance of DIB carriers scales in proportion to metallicity.
NASA Astrophysics Data System (ADS)
Hoge, Frank E.; Vodacek, Anthony; Swift, Robert N.; Yungel, James K.; Blough, Neil V.
1995-10-01
The absorption coefficient of chromophoric dissolved organic matter (CDOM) at 355 nm has been retrieved from airborne laser-induced and water Raman-normalized CDOM fluorescence. Four combined airborne and ship field experiments have demonstrated that (1) the airborne CDOM fluorescence-to--water Raman ratio is linearly related to concurrent quinine-sulfate-standardized CDOM shipboard fluorescence measurements over a wide range of water masses (coastal to blue water); (2) the vicarious calibration of the airborne fluorosensor in units traceable to a fluorescence standard can be established and then maintained over an extended time period by tungsten lamp calibration; (3) the vicariously calibrated airborne CDOM fluorescence-to-water Raman ratio can be directly applied to previously developed
NASA Astrophysics Data System (ADS)
Mandal, Arkajit; Sarkar, Sucharita; Ghosh, Arghya Pratim; Ghosh, Manas
2015-12-01
We make an extensive investigation of total optical absorption coefficient (TOAC) of impurity doped quantum dots (QDs) in presence and absence of Gaussian white noise. The TOAC profiles have been monitored against incident photon energy with special emphasis on the roles played by the electric field, magnetic field, and the dot confinement potential. Presence of impurity also influences the TOAC profile. In general, presence of noise causes enhancement of TOAC over that of noise-free condition. However, the interplay between the noise and the quantities like electric field, magnetic field, confinement potential and impurity potential bring about rich subtleties in the TOAC profiles. The said subtleties are often manifested by the alterations in TOAC peak intensity, extent of TOAC peak bleaching, and value of saturation intensity. The findings reveal some technologically relevant aspects of TOAC for the doped QD systems, specially in presence of noise.
NASA Astrophysics Data System (ADS)
Huffman, H. Dale
Using the IMPROVE network aerosol data from rural or remote sites across the United States, the ratio of the optically measured light absorption coefficient ( σa) to the elemental carbon measured by Thermal/Optical Reflectance (TOR) analysis consistently indicates an absorption efficiency that is twice the accepted value of 10m 2g -1. Correlations between σa and the TOR carbon strongly suggest that the discrepancy is due to an underevaluation of light-absorbing carbon rather than to an overestimation of σa or a real, higher value of the absorption efficiency. In particular, past doubts about the accuracy and precision of the IMPROVE σa measurement are here shown to be unsupported by the IMPROVE data. The large empirical correction that is applied to this σa measurement, for multiple scattering effects due to filter mass loading, is given a new explanation as the effect of an increasing forward scattering fraction as sample thickness increases. The old explanation of shadowing by overlying particles in the sample is rejected as having just the opposite effect to that needed to explain the correction. The use of a diffuse source rather than a laser beam is indicated as a way to avoid the large empirical correction of σa. Modelling of the light absorption by TOR carbon measurements, at twelve remote sites over a wide portion of the western United States, suggests the following errors in the current interpretation of TOR analysis for these sites: (1) The pyrolysis correction, based upon optical reflectance monitoring, appears to be largely wrong; and (2) The carbon evolving between 450 and 550°C in a pure helium atmosphere, currently interpreted as organic and therefore non-light-absorbing, appears to be as strongly light-absorbing as elemental carbon. However, the present analysis indicates that for a large majority (˜90%) of samples the light-absorbing carbons, as reinterpreted herein, are not only measured accurately by TOR, they are also reasonably well
NASA Astrophysics Data System (ADS)
Montes-Hugo, Martin; Xie, Huxiang
2015-10-01
The inversion of individual inherent optical properties (IOPs) is very challenging in optically complex waters and within the violet spectral range (i.e., 380-450 nm) due to the strong light attenuation caused by chromophoric dissolved organic matter, nonalgal particulates, and phytoplankton. Here we present a technique to better discriminate light absorption contributions due to phytoplankton based on a hybrid model (QAA-hybrid) that combines regional Saint Lawrence System estimates of IOPs derived from a quasi-analytical algorithm (hereafter QAA-SLE) and empirical relationships between salinity and IOPs. Preliminary results in the Saint Lawrence System during May 2000 and April 2001 showed that QAA-hybrid estimates of phytoplankton absorption coefficient at 443 nm have a smaller bias with respect to in situ measurements (root-mean-square deviation, RMSD = 0.156) than those derived from QAA-SLE (RMSD = 0.341). These results were valid for surface waters (i.e., 0-5 m depth) of the lower estuary with a salinity and chlorophyll-a concentration range of 22-28 psu and 2.1-13.8 mg m-3, respectively.
NASA Astrophysics Data System (ADS)
Turgut, U.; Simsek, O.; Büyükkasap, E.
2007-08-01
The total mass attenuation coefficients for elements Cr, Co and Fe and compounds CrCl_{2}, CrCl_{3}, Cr_{2}(SO_{4})_{3}K_{2}SO_{4}\\cdot24H_{2}O, CoO, CoCl_{2}, Co(CH_{3}COO)_{2}, FePO_{4}, FeCl_{3}\\cdot6H_{2}O, Fe(SO_{4})_{2}NH_{4}\\cdot12H_{2}O were measured at different energies between 4.508 and 14.142 keV using secondary excitation method. Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr were chosen as secondary exciters. 59.5 keV γ-rays emitted from a ^{241}Am annular source were used to excite a secondary exciter and K_{α}(K-L_{3}, L_{2}) lines emitted by the secondary exciter were counted by a Si(Li) detector with a resolution of 160 eV at 5.9 keV. It was observed that mixture rule method is not a suitable method for determination of the mass attenuation coefficients of compounds, especially at an energy that is near the absorption edge. The obtained values were compared with theoretical values.
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)
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
Ashoor, Mansour; Asgari, Afrouz; Khorshidi, Abdollah; Rezaei, Ali
2015-01-01
Purpose: Estimation of Compton attenuation and the photoelectric absorption coefficients were explored at various depths. Methods: A new method was proposed for estimating the depth based on the convolution of two exponential functions, namely convolution of scattering and primary functions (CSPF), which the convolved result will conform to the photopeak region of energy spectrum with the variable energy-window widths (EWWs) and a theory on the scattering cross-section. The triple energy-windows (TEW) and extended triple energy-windows scatter correction (ETEW) methods were used to estimate the scattered and primary photons according to the energy spectra at various depths due to a better performance than the other methods in nuclear medicine. For this purpose, the energy spectra were employed, and a distinct phantom along with a technetium-99 m source was simulated by Monte Carlo method. Results: The simulated results indicate that the EWW, used to calculate the scattered and primary counts in terms of the integral operators on the functions, was proportional to the depth as an exponential function. The depth will be calculated by the combination of either TEW or ETEW and proposed method resulting in the distinct energy-window. The EWWs for primary photons were in good agreement with those of scattered photons at the same as depths. The average errors between these windows for both methods TEW, and ETEW were 7.25% and 6.03% at different depths, respectively. The EWW value for functions of scattered and primary photons was reduced by increasing the depth in the CSPF method. Conclusions: This coefficient may be an index for the scattering cross-section. PMID:26170567
Protasenko, Vladimir; Bacinello, Daniel; Kuno, Masaru
2006-12-21
Absorption cross-sections and corresponding molar extinction coefficients of solution-based CdSe and CdTe nanowires (NWs) are determined. Chemically grown semiconductor NWs are made via a recently developed solution-liquid-solid (SLS) synthesis, employing low melting Au/Bi bimetallic nanoparticle "catalysts" to induce one-dimensional (1D) growth. Resulting wires are highly crystalline and have diameters between 5 and 12 nm as well as lengths exceeding 10 microm. Narrow diameters, below twice the corresponding bulk exciton Bohr radius of each material, place CdSe and CdTe NWs within their respective intermediate to weak confinement regimes. Supporting this are solution linear absorption spectra of NW ensembles showing blue shifts relative to the bulk band gap as well as structure at higher energies. In the case of CdSe, the wires exhibit band edge emission as well as strong absorption/emission polarization anisotropies at the ensemble and single-wire levels. Analogous photocurrent polarization anisotropies have been measured in recently developed CdSe NW photodetectors. To further support fundamental NW optical/electrical studies as well as to promote their use in device applications, experimental absorption cross-sections are determined using correlated transmission electron microscopy, UV/visible extinction spectroscopy, and inductively coupled plasma atomic emission spectroscopy. Measured CdSe NW cross-sections for 1 microm long wires (diameters, 6-42 nm) range from 6.93 x 10(-13) to 3.91 x 10(-11) cm2 at the band edge (692-715 nm, 1.73-1.79 eV) and between 3.38 x 10(-12) and 5.50 x 10(-11) cm2 at 488 nm (2.54 eV). Similar values are obtained for 1 microm long CdTe NWs (diameters, 7.5-11.5 nm) ranging from 4.32 x 10(-13) to 5.10 x 10(-12) cm2 at the band edge (689-752 nm, 1.65-1.80 eV) and between 1.80 x 10(-12) and 1.99 x 10(-11) cm2 at 2.54 eV. These numbers compare well with previous theoretical estimates of CdSe/CdTe NW cross-sections far to the blue of the
NASA Astrophysics Data System (ADS)
Kaya, Necati; Tıraşoğlu, Engin; Apaydın, Gökhan; Aylıkcı, Volkan; Cengiz, Erhan
2007-08-01
The K-shell absorption jump factors and jump ratios were derived from new mass attenuation coefficients measured using an energy dispersive X-ray fluorescence (EDXRF) spectrometer for Tm, Yb elements being Tm 2O 3, Yb 2O 3 compounds and pure Lu, Hf, Ta, W, Re and Os. The measurements, in the region 56-77 keV, were done in a transmission geometry utilizing the K α1 , K α2 , K β1 and K β2 X- rays from different secondary source targets (Yb, Ta, Os, W, Re and Ir, etc.) excited by the 123.6 keV γ-photons from an 57Co annular source and detected by an Ultra-LEGe solid state detector with a resolution of 150 eV at 5.9 keV. Experimental results have been compared with theoretically calculated values. The measured values of Tm, Yb, Lu, Hf, Ta, W, Re and Os are reported here for the first time.
Nelson, George J.; Harris, William M.; Izzo, John R. Jr.; Grew, Kyle N.; Chiu, Wilson K. S.; Chu, Yong S.; Yi, Jaemock; Andrews, Joy C.; Liu Yijin; Pianetta, Piero
2011-04-25
The reduction-oxidation cycling of the nickel-based oxides in composite solid oxide fuel cells and battery electrodes is directly related to cell performance. A greater understanding of nickel redox mechanisms at the microstructural level can be achieved in part using transmission x-ray microscopy (TXM) to explore material oxidation states. X-ray nanotomography combined with x-ray absorption near edge structure (XANES) spectroscopy has been applied to study samples containing distinct regions of nickel and nickel oxide (NiO) compositions. Digitally processed images obtained using TXM demonstrate the three-dimensional chemical mapping and microstructural distribution capabilities of full-field XANES nanotomography.
NASA Astrophysics Data System (ADS)
Nelson, George J.; Harris, William M.; Izzo, John R.; Grew, Kyle N.; Chiu, Wilson K. S.; Chu, Yong S.; Yi, Jaemock; Andrews, Joy C.; Liu, Yijin; Pianetta, Piero
2011-04-01
The reduction-oxidation cycling of the nickel-based oxides in composite solid oxide fuel cells and battery electrodes is directly related to cell performance. A greater understanding of nickel redox mechanisms at the microstructural level can be achieved in part using transmission x-ray microscopy (TXM) to explore material oxidation states. X-ray nanotomography combined with x-ray absorption near edge structure (XANES) spectroscopy has been applied to study samples containing distinct regions of nickel and nickel oxide (NiO) compositions. Digitally processed images obtained using TXM demonstrate the three-dimensional chemical mapping and microstructural distribution capabilities of full-field XANES nanotomography.
NASA Astrophysics Data System (ADS)
De Siena, Luca; Calvet, Marie; Watson, Keira J.; Jonkers, Art R. D.; Thomas, Christine
2016-04-01
Frequency-dependent peak-delay times and coda quality factors have been used jointly to separate seismic absorption from scattering quantitatively in Earth media at regional and lithospheric scale; to this end, we measure and map these two quantities at Mount St. Helens volcano. The results show that we can locate and characterise volcanic and geological structures using their unique contribution to seismic attenuation. At 3 Hz a single high-scattering and high-absorption anomaly outlines the debris flows that followed the 1980 explosive eruption, as deduced by comparison with remote sensing imagery. The flows overlay a NNW-SSE interface, separating rocks of significant varying properties down to 2-4 km, and coinciding with the Saint Helens Seismic Zone. High-scattering and high-absorption anomalies corresponding to known locations of magma emplacement follow this signature under the volcano, showing the important interconnections between its feeding systems and the regional tectonic boundaries. With frequency increasing from 6 to 18 Hz the NNW-SSE tectonic/feeding trends rotate around an axis centered on the volcano in the direction of the regional-scale magmatic arc (SW-NE). While the aseismic high-scattering region WSW of the volcano shows no evidence of high absorption, the regions of highest-scattering and absorption are consistently located at all frequencies under either the eastern or the south-eastern flank of the volcanic edifice. From the comparison with the available geological and geophysical information we infer that these anomalies mark both the location and the trend of the main feeding systems at depths greater than 4 km.
NASA Astrophysics Data System (ADS)
De Siena, L.; Calvet, M.; Watson, K. J.; Jonkers, A. R. T.; Thomas, C.
2016-05-01
Frequency-dependent peak-delay times and coda quality factors have been used jointly to separate seismic absorption from scattering quantitatively in Earth media at regional and continental scale; to this end, we measure and map these two quantities at Mount St. Helens volcano. The results show that we can locate and characterize volcanic and geological structures using their unique contribution to seismic attenuation. At 3 Hz a single high-scattering and high-absorption anomaly outlines the debris flows that followed the 1980 explosive eruption, as deduced by comparison with remote sensing imagery. The flows overlay a NNW-SSE interface, separating rocks of significant varying properties down to 2-4 km, and coinciding with the St. Helens Seismic Zone. High-scattering and high-absorption anomalies corresponding to known locations of magma emplacement follow this signature under the volcano, showing the important interconnections between its feeding systems and the regional tectonic boundaries. With frequency increasing from 6 to 18 Hz the NNW-SSE tectonic/feeding trends rotate around an axis centered on the volcano in the direction of the regional-scale magmatic arc (SW-NE). While the aseismic high-scattering region WSW of the volcano shows no evidence of high absorption, the regions of highest-scattering and absorption are consistently located at all frequencies under either the eastern or the south-eastern flank of the volcanic edifice. From the comparison with the available geological and geophysical information we infer that these anomalies mark both the location and the trend of the main feeding systems at depths greater than 4 km.
Time-resolved refractive index and absorption mapping of light-plasma filaments in water.
Minardi, Stefano; Gopal, Amrutha; Tatarakis, Michael; Couairon, Arnaud; Tamosauskas, Gintaras; Piskarskas, Rimtautas; Dubietis, Audrius; Di Trapani, Paolo
2008-01-01
By means of a quantitative shadowgraphic method, we performed a space-time characterization of the refractive index variation and transient absorption induced by a light-plasma filament generated by a 120 fs laser pulse in water. The formation and evolution of the plasma channel in the proximity of the nonlinear focus were observed with a 23 fs time resolution. PMID:18157267
Mapping the Local Interstellar Medium Using High-Resolution UV Absorption Spectroscopy
NASA Astrophysics Data System (ADS)
Malamut, Craig; Redfield, S.; Linsky, J.
2013-01-01
Observations using the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope have provided high-resolution near ultraviolet spectra showing MgII, FeII and MnII absorption in the local interstellar medium (LISM). The sample includes sight lines towards over 30 stars within 100 parsecs and across a wide range of spectral types. Observations span the entire sky, probing previously unobserved regions of the LISM. The heavy ions studied in this survey produce narrow absorption features that make possible the identification of multiple interstellar components. Our simultaneous fits of the MgII, FeII, and MnII doublets reveal anywhere from one to six individual absorption components in a particular sight line, where the number of absorbers roughly correlates with the length of the sight line. The simultaneous fitting procedure reduces the systematic errors involved in continuum placement and number of absorbers. Already, sight lines show evidence of previously unidentified clouds within the Local Bubble. These measurements will be added to a growing data set of 81 near UV sight lines. The increase in the number of sight lines will test and improve a three dimensional kinematic model of the local interstellar medium. With an improved understanding of the LISM's kinematical structure, it will be possible to distinguish blended components within the absorption features of lighter ions. Specifically, the MAST Archive contains FUV observations of interstellar absorption by low mass ions (DI, CII, NI, OI) along the the same sight lines. The combination of these data will constrain properties of the LISM such as temperature, turbulence, ionization, abundances and depletions. We acknowledge support for this project through NASA HST Grant GO-11568 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555, and a student research fellowship from the
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)
De Siena, Luca; Calvet, Marie; Thomas, Christine
2015-04-01
Knowing how seismic waves lose their energy in space and frequency is both critical for understating volcanic structures and important to detect eventual changes in their seismic and volcanic activity. We measure both the peak-delay time and the coda quality factor on seismic envelopes recorded at Mount St. Helens volcano between 2000 and 2003, just before its 2004 explosive eruption. By the 2D mapping of these two frequency-dependent quantities we obtain S-wave scattering and absorption maps in the pre-eruptive phase of the volcano. We use a 2D K-means cluster analysis to highlight correlations in the frequency-dependent spatial patterns and interpret the results in terms of tectonic and feeding structures. The transition between the high-velocity and high-scattering Siletz terrane and the low-velocity and high-absorption Cascade arc crust is a persistent signature in the entire frequency range. At high frequencies, we observe strong correlation between high-scattering, high-absorption, and high P-wave heterogeneity (this last tomographically derived between depths of 0 and 10 km). In our interpretation, this correlation is a direct consequence of resonance effects, induced by the presence of melt and fluid inclusions as well as residuals of previous eruptions. The area of maximum heterogeneity is located south-south-west of the central crater: the region shows selective high absorption characteristics at 6 Hz only. If this supports the presence of a previously-inferred aseismic magma chamber intersecting the south-south-western flank of the volcano, the selectivity suggests a depth extension of the magma chamber lower than 1 km. The most important high-scattering and high-absorption signature at high frequencies remains a NNW-SSE suture crossing the volcanic cone and parallel to the St. Helens Seismic Zone. The trend confirms the persistent major role of the main direction of regional structural stress in the uprise of magma/fluid filled materials in the first
NASA Astrophysics Data System (ADS)
Al-Hawat, Sharif
2013-02-01
Infrared (IR) absorption in the spectral range of (1071.88-1084.62 cm-1) vs. pressure in chlorodifluoromethane (CFC-22, F-22, and CHClF2) was studied using a tunable continuous wave (CW) CO2 laser radiation on 9R branch lines with a maximum output power of about 2.12 W, provided with an absorber cell located outside the laser cavity. The absorption coefficients were determined vs. the gas pressure between 0.2 mbar and 170 mbar at lines from 9R branch for CFC-22. The frequency shifts of the absorption lines of CFC-22 in relative to the central frequencies of laser lines were calculated vs. the pressure on the basis of these absorption coefficients. The chosen lines were selected according to IR spectrum of the studied gas given by HITRAN cross section database. So the absorption was achieved for CFC-22 at the spectral lines of 9R branch situated from 9R (10) to 9R (30) emitted by a tunable CW CO2 laser. The absorption cross sections of CFC-22 determined in this work were compared with the relevant data given by HITRAN cross section database and a reasonable agreement was observed.
Stadler, H; Klock, E; Skritek, P; Mach, R L; Zerobin, W; Farnleitner, A H
2010-01-01
Because spring water quality from alpine karst aquifers can change very rapidly during event situations, water abstraction management has to be performed in near real-time. Four summer events (2005-2008) at alpine karst springs were investigated in detail in order to evaluate the spectral absorption coefficient at 254 nm (SAC254) as a real-time early warning proxy for faecal pollution. For the investigation Low-Earth-Orbit (LEO) Satellite-based data communication between portable hydrometeorological measuring stations and an automated microbiological sampling device was used. The method for event triggered microbial sampling and analyzing was already established and described in a previous paper. Data analysis including on-line event characterisation (i.e. precipitation, discharge, turbidity, SAC254) and comprehensive E. coli determination (n>800) indicated that SAC254 is a useful early warning proxy. Irrespective of the studied event situations SAC254 always increased 3 to 6 hours earlier than the onset of faecal pollution, featuring different correlation phases. Furthermore, it seems also possible to use SAC254 as a real-time proxy parameter for estimating the extent of faecal pollution after establishing specific spring and event-type calibrations that take into consideration the variability of the occurrence and the transferability of faecal material It should be highlighted that diffuse faecal pollution from wildlife and live stock sources was responsible for spring water contamination at the investigated catchments. In this respect, the SAC254 can also provide useful information to support microbial source tracking efforts where different situations of infiltration have to be investigated. PMID:20962406
Spatial mapping of greenhouse gases using laser absorption spectrometers at local scales of interest
Dobler, Jeremy
2015-09-22
This presentation provides and overview of the development off the GreenLITE system for spatial mapping of atmospheric CO2. The original system was developed for supporting MRV activities for ground carbon storage facilities and has since been expanded to cover larger areas and other applications.
NASA Astrophysics Data System (ADS)
Oh, Jaehong; Lee, Changno
2015-02-01
As the need for efficient methods to accurately update and refine geospatial satellite image databases is increasing, we have proposed the use of 3-dimensional digital maps for the fully-automated RPCs bias compensation of high resolution satellite imagery. The basic idea is that the map features are scaled and aligned to the image features, except for the local shift, through the RPCs-based image projection, and then the shifts are automatically determined over the entire image space by template-based edge matching of the heterogeneous data set. This enables modeling of RPCs bias compensation parameters for accurate georeferencing. The map features are selected based on four suggested rules. Experiments were carried out for three Kompsat-2 images and stereo IKONOS images with 1:5000 scale Korean national topographic maps. Image matching performance is discussed with justification of the parameter selection, and the georeferencing accuracy is analyzed. The experimental results showed the automated approach can achieve one-pixel level of georeferencing accuracy, enabling economical hybrid map creation as well as large scale map updates.
NASA Astrophysics Data System (ADS)
Zhang, Shirui; Wang, Jihua; Dong, Daming; Zheng, Wengang; Zhao, Xiande
2013-02-01
An open-path tunable diode laser absorption spectroscopy (OP-TDLAS) detector was applied to detect the methane emission from a biogas plant in a dairy farm. Two OP-TDLAS scanning systems were built according to maximum likelihood with expectation minimization (MLEM) and smooth basis function minimization (SBFM) algorithms to reconstruct the two-dimensional (2-D) distribution maps. Six reconstruction maps with the resolution of 30×80 were obtained by the MLEM algorithm with "grid translation method" and three reconstruction maps were obtained by the SBFM algorithm with 2-D Gaussian model. The maximum mixing ratio in the first result was between 0.85 and 1.30 ppm, while it was between 1.14 and 1.30 ppm in the second result. The average mixing ratio in the first result was between 0.54 and 0.49 ppm, and between 0.56 and 0.65 ppm in the second result. The reconstruction results validated that the two algorithms could effectively reflect the methane mixing ratio distribution within the target area. However, with the more simple optical rays and less equipment requirements, the OP-TDLAS scanning system based on SBFM algorithm provides a useful monitoring tool of methane emissions in agricultural production.
Rea, A.H.; Tortorelli, R.L.
1997-01-01
This digital report contains two digital-map grids of data that were used to develop peak-flow regression equations in Tortorelli, 1997, 'Techniques for estimating peak-streamflow frequency for unregulated streams and streams regulated by small floodwater retarding structures in Oklahoma,' U.S. Geological Survey Water-Resources Investigations Report 97-4202. One data set is a grid of mean annual precipitation, in inches, based on the period 1961-90, for Oklahoma. The data set was derived from the PRISM (Parameter-elevation Regressions on Independent Slopes Model) mean annual precipitation grid for the United States, developed by Daly, Neilson, and Phillips (1994, 'A statistical-topographic model for mapping climatological precipitation over mountainous terrain:' Journal of Applied Meteorology, v. 33, no. 2, p. 140-158). The second data set is a grid of generalized skew coefficients of logarithms of annual maximum streamflow for Oklahoma streams less than or equal to 2,510 square miles in drainage area. This grid of skew coefficients is taken from figure 11 of Tortorelli and Bergman, 1985, 'Techniques for estimating flood peak discharges for unregulated streams and streams regulated by small floodwater retarding structures in Oklahoma,' U.S. Geological Survey Water-Resources Investigations Report 84-4358. To save disk space, the skew coefficient values have been multiplied by 100 and rounded to integers with two significant digits. The data sets are provided in an ASCII grid format.
NASA Astrophysics Data System (ADS)
Le Roy, Robert J.; Meshkov, Vladimir V.; Stolyarov, Andrej V.
2009-06-01
We have shown that one and two-parameter analytical mapping functions such as r(y;bar{r}, α)=bar{r}[1 + {1}/{α} tan(π y/2)] and r(y;bar{r})=bar{r} [ {1+ y}/{1-y} ] transform the conventional radial Schrödinger equation into equivalent alternate forms {d^2φ(y)}/{dy^2} = [{π^2}/{4}+({2μ}/ {hbar^2} ) g^2(y) [E - U(r(y))
Near infrared iron absorption bands: Applications to geologic mapping and mineral exploration
NASA Technical Reports Server (NTRS)
Rowan, L. C.
1972-01-01
A spectroscopic analysis of the difference in reflectance of iron-rich and iron-poor minerals was made. Attempts were made to use these minima contrast in geological mapping and metallic mineral exploration of large areas from near infrared and visible satellite images. Data cover pertinent laboratory spectroscopic investigations, applications of spectral differences to the discrimination of two important metamorphic rock types, and mineral exploration by aircraft in Beartooth Mountains, Montana.
NASA Astrophysics Data System (ADS)
Shibata, Kenji; Suenaga, Kazufumi; Watanabe, Kazutoshi; Horikiri, Fumimasa; Mishima, Tomoyoshi; Shiratani, Masaharu
2012-07-01
We have found an effective method for the evaluation of the crystal orientation of (K,Na)NbO3 (KNN) films in the (K,Na)NbO3/Pt/Ti/SiO2/Si structure using X-ray diffraction (XRD) reciprocal space maps. Previously, the crystal structure and orientation of such (K,Na)NbO3 films were evaluated using 2θ/θ XRD, and were considered to be the pseudocubic perovskite structure with preferential (001) orientation and no (111) orientation. Here, we applied the new method using XRD reciprocal space maps, and discovered that the (K,Na)NbO3 films had some degree of KNN(111) orientation. We calculated the KNN(001)- and KNN(111)-orientation volume fractions for the (K,Na)NbO3 films from the (101) diffraction peaks originating from the KNN(001)- and KNN(111)-orientation elements in the XRD reciprocal space maps, considering the calibration factors obtained from pole-figure simulations, and examined the relationship between the crystal orientation and d31 piezoelectric coefficient in the (K,Na)NbO3 films. The results indicated that the d31 piezoelectric coefficient increases with increasing (001)-orientation volume fraction.
NASA Technical Reports Server (NTRS)
Siegman, A. E.; Wang, S. C.
1970-01-01
Absorptivity, transition probability and collision broadening frequency of dimethylether at 3.51 micron He-Xe laser wavelength, noting pressure dependence, transition lifetime and saturation intensity
Spatial mapping of greenhouse gases using laser absorption spectrometers at local scales of interest
NASA Astrophysics Data System (ADS)
Dobler, Jeremy; Zaccheo, T. S.; Blume, Nathan; Braun, Michael; Botos, Chris; Pernini, Timothy G.
2015-10-01
Over the past two years a new system capable of measuring the 2-D spatial distribution of atmospheric CO2 over areas on the order of 1 km2 and time scales of a few minutes, has been developed and demonstrated. The Greenhouse gas Laser Imaging Tomography Experiment (GreenLITE) - developed under a cooperative agreement with the National Energy Technology Laboratory (NETL) of the U.S. Department of Energy (DOE) - attempts to improve monitoring capabilities of Ground Carbon Storage (GCS) sites. GreenLITE sensors are based on an intensity modulated continuous wave (IM-CW) approach developed at ITT (now part of Harris Corp.) in 2004. The GreenLITE system recently completed a remote deployment of nearly 4,000 hours at a GCS site in Illinois. It provided continuous, real-time spatial distribution maps of CO2 via an open web-based interface from February to August 2015. In early 2015 we began work on a new implementation of GreenLITE capable of providing similar measurements over a 25 km2 area and are planning to test the system over a 5 km range late summer 2015. If successful the system will be deployed in an urban environment late 2015, demonstrating the utility of real-time 2-D spatial mapping of CO2 concentrations at this scale. This paper will review the concept for this new measurement capability, including results from the 1 km system. Ultimately, the measurement concept can be adapted to other greenhouse gases such as CH4 and NO2.
Mapping absorption processes onto a Markov chain, conserving the mean first passage time
NASA Astrophysics Data System (ADS)
Biswas, Katja
2013-04-01
The dynamics of a multidimensional system is projected onto a discrete state master equation using the transition rates W(k → k‧ t, t + dt) between a set of states {k} represented by the regions {ζk} in phase or discrete state space. Depending on the dynamics Γi(t) of the original process and the choice of ζk, the discretized process can be Markovian or non-Markovian. For absorption processes, it is shown that irrespective of these properties of the projection, a master equation with time-independent transition rates \\bar{W}(k\\rightarrow k^{\\prime }) can be obtained, which conserves the total occupation time of the partitions of the phase or discrete state space of the original process. An expression for the transition probabilities \\bar{p}(k^{\\prime }|k) is derived based on either time-discrete measurements {ti} with variable time stepping Δ(i + 1)i = ti + 1 - ti or the theoretical knowledge at continuous times t. This allows computational methods of absorbing Markov chains to be used to obtain the mean first passage time (MFPT) of the system. To illustrate this approach, the procedure is applied to obtain the MFPT for the overdamped Brownian motion of particles subject to a system with dichotomous noise and the escape from an entropic barrier. The high accuracy of the simulation results confirms with the theory.
Werts, Martinus H V; Raimbault, Vincent; Texier-Picard, Rozenn; Poizat, Rémi; Français, Olivier; Griscom, Laurent; Navarro, Julien R G
2012-02-21
A simple and versatile methodology has been developed for the simultaneous measurement of multiple concentration profiles of colourants in transparent microfluidic systems, using a conventional transmitted light microscope, a digital colour (RGB) camera and numerical image processing combined with multicomponent analysis. Rigorous application of the Beer-Lambert law would require monochromatic probe conditions, but in spite of the broad spectral bandwidths of the three colour channels of the camera, a linear relation between the measured optical density and dye concentration is established under certain conditions. An optimised collection of dye solutions for the quantitative optical microscopic characterisation of microfluidic devices is proposed. Using the methodology for optical concentration measurement we then implement and validate a simplified and robust method for the microfluidic measurement of diffusion coefficients using an H-filter architecture. It consists of measuring the ratio of the concentrations of the two output channels of the H-filter. It enables facile determination of the diffusion coefficient, even for non-fluorescent molecules and nanoparticles, and is compatible with non-optical detection of the analyte. PMID:22228225
Morgan, M.A.
1989-07-01
Potential energy surfaces for photorotamerization of two intramolecularly hydrogen-bonded molecules, o-hydroxybenzaldehyde (OHBA) and methyl salicylate (MS), isolated in cryogenic matrices have been spectroscopically mapped. In addition, the external heavy atom effect of krypton and xenon matrices on the coupling between the S{sub 1} and T{sub 1} surfaces of 4-(dimethylamino)benzonitrile has been examined. Heavy atom matrices are known to increase rates of spin-forbidden processes. The phosphorescence intensity of DMABN increases in krypton and xenon matrices, while the fluorescence intensity, and phosphorescence and fluorescence lifetimes, decrease. These effects are interpreted in terms of a model in which the phosphorescence rate constant increases 300-fold in xenon compared to argon, while the rate constants for intersystem crossing and nonradiative relaxation from the triplet state increase by factors of less than 5. Lifetime measurements in argon matrices doped with heavy atoms indicate that even one heavy atom neighbor has a significant effect on both singlet and triplet lifetimes. 78 refs., 35 figs., 15 tabs.
NASA Astrophysics Data System (ADS)
Hippensteele, Steven A.; Poinsatte, Philip E.
1993-08-01
In this transient technique the preheated isothermal model wall simulates the classic one-dimensional, semi-infinite wall heat transfer conduction problem. By knowing the temperature of the air flowing through the model, the initial temperature of the model wall, and the surface cooling rate measured at any location with time (using the fast-response liquid-crystal patterns recorded on video tape), the heat transfer coefficient can be calculated for the color isothermal pattern produced. Although the test was run transiently, the heat transfer coefficients are for the steady-state case. The upstream thermal boundary condition was considered to be isothermal. This transient liquid-crystal heat-transfer technique was used in a transient air tunnel in which a square-inlet, 3-to-1 exit transition duct was placed. The duct was preheated prior to allowing room temperature air to be suddenly drawn through it. The resulting isothermal contours on the duct surfaces were revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record was made of the temperature and time data for all points on the duct surfaces during each test. The duct surfaces were uniformly heated using two heating systems: the first was an automatic temperature-controlled heater blanket completely surrounding the test duct like an oven, and the second was an internal hot-air loop through the inside of the test duct. The hot-air loop path was confined inside the test duct by insulated heat dams located at the inlet and exit ends of the test duct. A recirculating fan moved hot air into the duct inlet, through the duct, out of the duct exit, through the oven, and back to the duct inlet. The temperature nonuniformity of the test duct model wall was held very small. Test results are reported for two inlet Reynolds numbers of 200,000 and 1,150,000 (based on the square-inlet hydraulic diameter) and two free-stream turbulence
NASA Technical Reports Server (NTRS)
Hippensteele, Steven A.; Poinsatte, Philip E.
1993-01-01
In this transient technique the preheated isothermal model wall simulates the classic one-dimensional, semi-infinite wall heat transfer conduction problem. By knowing the temperature of the air flowing through the model, the initial temperature of the model wall, and the surface cooling rate measured at any location with time (using the fast-response liquid-crystal patterns recorded on video tape), the heat transfer coefficient can be calculated for the color isothermal pattern produced. Although the test was run transiently, the heat transfer coefficients are for the steady-state case. The upstream thermal boundary condition was considered to be isothermal. This transient liquid-crystal heat-transfer technique was used in a transient air tunnel in which a square-inlet, 3-to-1 exit transition duct was placed. The duct was preheated prior to allowing room temperature air to be suddenly drawn through it. The resulting isothermal contours on the duct surfaces were revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record was made of the temperature and time data for all points on the duct surfaces during each test. The duct surfaces were uniformly heated using two heating systems: the first was an automatic temperature-controlled heater blanket completely surrounding the test duct like an oven, and the second was an internal hot-air loop through the inside of the test duct. The hot-air loop path was confined inside the test duct by insulated heat dams located at the inlet and exit ends of the test duct. A recirculating fan moved hot air into the duct inlet, through the duct, out of the duct exit, through the oven, and back to the duct inlet. The temperature nonuniformity of the test duct model wall was held very small. Test results are reported for two inlet Reynolds numbers of 200,000 and 1,150,000 (based on the square-inlet hydraulic diameter) and two free-stream turbulence
NASA Astrophysics Data System (ADS)
Pedone, Maria; Aiuppa, Alessandro; Giudice, Gaetano; Grassa, Fausto; Chiodini, Giovanni; Valenza, Mariano
2014-05-01
Near-infrared room-temperature Tunable Diode Lasers (TDL) have recently found increased usage in atmospheric chemistry and air monitoring research, but applications in Volcanology are still limited to a few examples. Here, we explored the potentiality of a commercial infrared laser unit (GasFinder 2.0 from Boreal Laser Ltd) to measurement of volcanic CO2 flux emissions. Our field tests were conducted at Campi Flegrei (near Pozzuoli, Southern Italy), where the GasFinder was used (during three campaigns in October 2012, January 2013 and May 2013) to repeatedly measure the path-integrated concentrations of CO2 along cross-sections of the atmospheric plumes of the two main fumarolic fields in the area (Solfatara and Pisciarelli). By using ad-hoc designed field-set-up and a tomographic post-processing routine, we resolved, for each of the 2 manifestations, the contour maps of CO2 concentrations in their atmospheric plumes, from the integration of which (and after multiplication by the plumes' transport speeds) the CO2 fluxes were finally obtained [1]. The so-calculated fluxes average of 490 tons/day, which agrees well with independent evaluations of Aiuppa et al. (2013) [2] (460 tons/day on average), and support a significant contribution of fumaroles to the total CO2 budget. The cumulative (fumarole [this study] +soil [2]) CO2 output from Campi Flegrei is finally evaluated at 1600 tons/day. The application of lasers to volcanic gas studies is still an emerging (though intriguing) research field, and requires more testing and validation experiments. We conclude that TDL technique may valuably assist CO2 flux quantification at a number of volcanic targets worldwide. [1] Pedone M. et al. (2013) Gold2013:abs:5563, Goldschmidt Conference, session 11a. [2] Aiuppa A. et al. (2013) Geochemistry Geophysics Geosystems. doi: 10.1002/ggge.20261. [3] Chiodini G. et al. (2010) Journal of Geophysical Research, Volume 115, B03205. doi:10.1029/2008JB006258.
Metin, Melike R.; Aydın, Hasan; Çetin, Hüseyin; Özmen, Evrim; Kayaçetin, Serra
2016-01-01
Objectives: To establish retrospectively the relation between the histopathologic grade of colorectal liver metastasis and apparent diffusion coefficient (ADC) values of hepatic metastases of colorectal adenocarcinomas. Methods: The diagnoses of liver metastases were confirmed with biopsy, surgery, and follow-up imaging findings. Twenty-six patients with 94 liver metastasis were included in the study. Of 94 masses, 59 were poorly-differentiated adenocarcinoma, 18 were moderately-differentiated adenocarcinoma, and 17 were well-differentiated regarding the diameters, ADC values, and ratio index (RI) values. Kolmogorov-smirnov normality test, Kruskal-wallis analysis of variance, Mann-Whitney U test with Bonferroni correction, Spearman correlation analysis, and receiver operating characteristics curve methods were applied to evaluate the statistical relations. Results: There was a statistically significant difference in terms of ADC values and RI between poorly-differentiated adenocarcinoma and moderately-differentiated adenocarcinoma plus well-differentiated adenocarcinomas. Poorly-differentiated adenocarcinomas have the lowest ADC values and highest RI values among other groups. Conclusion: Use of ADC values alone can be executed for the diagnosis of focal hepatic masses and also can aid in the differentiation of benign and malignant hepatic lesions. PMID:27052280
NASA Astrophysics Data System (ADS)
Pawlak, M.; Maliński, M.; Firszt, F.; Pelzl, J.; Ludwig, A.; Marasek, A.
2014-03-01
In this work we demonstrate the ability to measure the effective infrared absorption coefficient in semiconductors by a photothermal infrared radiometry (PTR) experiment, and its correlation with the Hall carrier concentration. The amplitude and phase of the PTR signal were measured for Cd1-xMgxSe mixed crystals, with the magnesium content varying from x = 0 to x = 0.15. The PTR experiments were performed at room temperature in thermal reflection and transmission configurations using a mercury cadmium telluride infrared detector. The PTR data were analyzed in the frame of the one-dimensional heat transport model for infrared semi-transparent crystals. Based on the variation of the normalized PTR phase and amplitude on the modulation frequency, the thermal diffusivity and the effective infrared absorption coefficient were obtained by fitting the theoretical expression to experimental data and compared with the Hall carrier concentration determined by supplementary Hall experiments. A linear relationship between the effective infrared absorption coefficient and the Hall carrier concentration was found which is explained in the frame of the Drude theory. The uncertainty of the measured slope was 6%. The value of the slope depends on (1) the sample IR absorption spectrum and (2) the spectral range of the infrared detector. It has to be pointed out that this method is suitable for use in an industrial environment for a fast and contactless carrier concentration measurement. This method can be used for the characterization of other semiconductors after a calibration procedure is carried out. In addition, the PTR technique yields information on the thermal properties in the same experiment.
NASA Astrophysics Data System (ADS)
Künecke, U.; Wellmann, P. J.
2006-06-01
In an earlier paper [P.J. Wellmann, A. Albrecht, U. Künecke, B. Birkmann, G. Mueller, M. Jurisch, Eur. Phys. J. Appl. Phys. 27, 357 (2004)] an optical method based on whole wafer absorption measurements was presented to determine the charge carrier concentration and its lateral distribution in n-type (Si/Te) doped GaAs. The submitted results for Si-doped GaAs gave rise to questions concerning the interpretation of absorption mappings in wafers with high dislocation densities. GaAs substrates for optoelectronic devices are strongly affected by dislocations.{ }Therefore further studies were conducted: absorption and Hall measurements were performed on GaAs:Si wafers with high and low dislocation densities. Absorption in Si-doped GaAs is far more complex than in Te-doped GaAs. It shows a co-dependency on charge carrier concentration and dislocation content which causes complications in the quantitative optical determination of the charge carrier concentration. Qualitatively, absorption mappings depict dislocations and variations of charge carrier concentration very well.
NASA Astrophysics Data System (ADS)
Nikulin, A. Yu.; Davis, J. R.; Jones, N. T.; Zaumseil, P.
1998-11-01
An experimental-analytical method for the nondestructive structural and chemical composition mapping of single-crystal alloys is proposed, implemented, and successfully tested. The technique is based on analytical measurements of phase and amplitude changes in a narrow polychromatic region near the absorption edge of the alloy impurity. Synchrotron radiation energies of 11.096-11.105 keV were used to measure the Bragg diffraction profiles near the absorption edge of germanium at 11.103 keV in SiGe/Si crystal alloy superstructures. Physical dimensions and chemical composition of SiGe alloys were determined with a spatial resolution 8.6 Å.
ERIC Educational Resources Information Center
Kinney, Douglas M.; McIntosh, Willard L.
1979-01-01
The area of geological mapping in the United States in 1978 increased greatly over that reported in 1977; state geological maps were added for California, Idaho, Nevada, and Alaska last year. (Author/BB)
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)
Ptashnik, Igor V.; McPheat, Robert; Polyansky, Oleg L.; Shine, Keith P.; Smith, Kevin M.
2016-07-01
Intensities and self-broadening coefficients are presented for about 460 of the strongest water vapour lines in the spectral regions 1400-1840 cm-1 and 3440-3970 cm-1 at room temperature, obtained from rather unique measurements using a 5-mm-path-length cell. The retrieved spectral line parameters are compared with those in the HITRAN database ver. 2008 and 2012 and with recent ab-initio calculations. Both the retrieved intensities and half-widths are on average in reasonable agreement with those in HITRAN-2012. Maximum systematic differences do not exceed 4% for intensities (1600 cm-1 band) and 7% for self-broadening coefficients (3600 cm-1 band). For many lines however significant disagreements were detected with the HITRAN-2012 data, exceeding the average uncertainty of the retrieval. In addition, water vapour line parameters for 5300 cm-1 (1.9 μm) band reported by us in 2005 were also compared with HITRAN-2012, and show average differences of 4-5% for both intensities and half-widths.
Midgley, Stewart; Schleich, Nanette
2015-05-01
A novel method for dual-energy X-ray analysis (DEXA) is tested using measurements of the X-ray linear attenuation coefficient μ. The key is a mathematical model that describes elemental cross sections using a polynomial in atomic number. The model is combined with the mixture rule to describe μ for materials, using the same polynomial coefficients. Materials are characterized by their electron density Ne and statistical moments Rk describing their distribution of elements, analogous to the concept of effective atomic number. In an experiment with materials of known density and composition, measurements of μ are written as a system of linear simultaneous equations, which is solved for the polynomial coefficients. DEXA itself involves computed tomography (CT) scans at two energies to provide a system of non-linear simultaneous equations that are solved for Ne and the fourth statistical moment R4. Results are presented for phantoms containing dilute salt solutions and for a biological specimen. The experiment identifies 1% systematic errors in the CT measurements, arising from third-harmonic radiation, and 20-30% noise, which is reduced to 3-5% by pre-processing with the median filter and careful choice of reconstruction parameters. DEXA accuracy is quantified for the phantom as the mean absolute differences for Ne and R4: 0.8% and 1.0% for soft tissue and 1.2% and 0.8% for bone-like samples, respectively. The DEXA results for the biological specimen are combined with model coefficients obtained from the tabulations to predict μ and the mass energy absorption coefficient at energies of 10 keV to 20 MeV. PMID:25931101
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.
Doughty, Benjamin; Simpson, Mary Jane; Yang, Bin; Xiao, Kai; Ma, Ying -Zhong
2016-02-16
This work aims to simplify multi-dimensional femtosecond transient absorption microscopy (TAM) data into decay associated amplitude maps that describe the spatial distributions of dynamical processes occurring on various characteristic timescales. Application of this method to TAM data obtained from a model methyl-ammonium lead iodide (CH3NH3PbI3) perovskite thin film allows us to simplify the dataset consisting of a 68 time-resolved images into 4 decay associated amplitude maps. These maps provide a simple means to visualize the complex electronic excited-state dynamics in this system by separating distinct dynamical processes evolving on characteristic timescales into individual spatial images. This approach provides new insightmore » into subtle aspects of ultrafast relaxation dynamics associated with excitons and charge carriers in the perovskite thin film, which have recently been found to coexist at spatially distinct locations.« less
40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.
Code of Federal Regulations, 2011 CFR
2011-07-01
... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The...
40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.
Code of Federal Regulations, 2012 CFR
2012-07-01
... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The...
40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.
Code of Federal Regulations, 2013 CFR
2013-07-01
... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The...
40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.
Code of Federal Regulations, 2010 CFR
2010-07-01
... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The...
40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.
Code of Federal Regulations, 2014 CFR
2014-07-01
... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The...
Stock, S. R.; Barss, J.; Dahl, T.; Veis, A.; Almer, J. D.; De Carlo, F.
2003-05-01
In sea urchin teeth, the keel plays an important structural role, and this paper reports results of microstructural characterization of the keel of Lytechinus variegatus using two noninvasive synchrotron x-ray techniques: x-ray absorption microtomography (microCT) and x-ray diffraction mapping. MicroCT with 14 keV x-rays mapped the spatial distribution of mineral at the 1.3 microm level in a millimeter-sized fragment of a mature portion of the keel. Two rows of low absorption channels (i.e., primary channels) slightly less than 10 microm in diameter were found running linearly from the flange to the base of the keel and parallel to its sides. The primary channels paralleled the oral edge of the keel, and the microCT slices revealed a planar secondary channel leading from each primary channel to the side of the keel. The primary and secondary channels were more or less coplanar and may correspond to the soft tissue between plates of the carinar process. Transmission x-ray diffraction with 80.8 keV x-rays and a 0.1 mm beam mapped the distribution of calcite crystal orientations and the composition Ca(1-x)Mg(x)CO(3) of the calcite. Unlike the variable Mg concentration and highly curved prisms found in the keel of Paracentrotus lividus, a constant Mg content (x = 0.13) and relatively little prism curvature was found in the keel of Lytechinus variegatus.
NASA Astrophysics Data System (ADS)
Tanifuji, T.
2016-03-01
Time-resolved multi-distance measurements are studied to retrieve absorption and reduced scattering coefficients of adult heads, which have enough depth sensitivity to determine the optical parameters in superficial tissues and brain separately. Measurements were performed by putting the injection and collection fibers on the left semi-sphere of the forehead, with the injection fiber placed toward the temporal region, and by moving the collection fiber between 10 and 60 mm from the central sulcus. It became clear that optical parameters of the forehead at all collection fibers were reasonably determined by selecting the appropriate visibility length of the geometrical head models, which is related to head surface curvature at each position.
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.
Doughty, Benjamin; Simpson, Mary Jane; Yang, Bin; Xiao, Kai; Ma, Ying-Zhong
2016-03-18
This work aims to simplify multi-dimensional femtosecond transient absorption microscopy (TAM) data into decay associated amplitude maps (DAAMs) that describe the spatial distributions of dynamical processes occurring on various characteristic timescales. Application of this method to TAM data obtained from a model methyl-ammonium lead iodide (CH3NH3PbI3) perovskite thin film allows us to simplify the data set comprising 68 time-resolved images into four DAAMs. These maps offer a simple means to visualize the complex electronic excited-state dynamics in this system by separating distinct dynamical processes evolving on characteristic timescales into individual spatial images. This approach provides new insight into subtle aspects of ultrafast relaxation dynamics associated with excitons and charge carriers in the perovskite thin film, which have recently been found to coexist at spatially distinct locations. PMID:27308671
NASA Astrophysics Data System (ADS)
Doughty, Benjamin; Simpson, Mary Jane; Yang, Bin; Xiao, Kai; Ma, Ying-Zhong
2016-03-01
This work aims to simplify multi-dimensional femtosecond transient absorption microscopy (TAM) data into decay associated amplitude maps (DAAMs) that describe the spatial distributions of dynamical processes occurring on various characteristic timescales. Application of this method to TAM data obtained from a model methyl-ammonium lead iodide (CH3NH3PbI3) perovskite thin film allows us to simplify the data set comprising 68 time-resolved images into four DAAMs. These maps offer a simple means to visualize the complex electronic excited-state dynamics in this system by separating distinct dynamical processes evolving on characteristic timescales into individual spatial images. This approach provides new insight into subtle aspects of ultrafast relaxation dynamics associated with excitons and charge carriers in the perovskite thin film, which have recently been found to coexist at spatially distinct locations.
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
NASA Astrophysics Data System (ADS)
Dutta, R.; Gupta, N.; Srianand, R.; O'Meara, J. M.
2016-03-01
We study the properties of H I gas in the outer regions (˜2r25) of a spiral galaxy, UGC 00439 (z = 0.017 69), using H I 21-cm absorption towards different components of an extended background radio source, J0041-0043 (z = 1.679). The radio source exhibits a compact core coincident with the optical quasar and two lobes separated by ˜7 kpc, all at an impact parameter ˜25 kpc. The H I 21-cm absorption detected towards the southern lobe is found to extend over ˜2 kpc2. The absorbing gas shows sub-kpc-scale structures with the line-of-sight velocities dominated by turbulent motions. Much larger optical depth variations over 4-7 kpc scale are revealed by the non-detection of H I 21-cm absorption towards the radio core and the northern lobe, and the detection of Na I and Ca II absorption towards the quasar. This could reflect a patchy distribution of cold gas in the extended H I disc. We also detect H I 21-cm emission from UGC 00439 and two other galaxies within ˜150 kpc to it, that probably form an interacting group. However, no H I 21-cm emission from the absorbing gas is detected. Assuming a linear extent of ˜4 kpc, as required to cover both the core and the southern lobe, we constrain the spin temperature ≲ 300 K for the absorbing gas. The kinematics of the gas and the lack of signatures of any ongoing in situ star formation are consistent with the absorbing gas being at the kinematical minor axis and corotating with the galaxy. Deeper H I 21-cm observations would help to map in greater detail both the large- and small-scale structures in the H I gas associated with UGC 00439.
NASA Astrophysics Data System (ADS)
Nowack, Lea; Grolimund, Daniel; Samson, Vallerie; Marone, Federica; Wood, Vanessa
2016-02-01
Since the commercialization of lithium ion batteries (LIBs), layered transition metal oxides (LiMO2, where M = Co, Mn, Ni, or mixtures thereof) have been materials of choice for LIB cathodes. During cycling, the transition metals change their oxidation states, an effect that can be tracked by detecting energy shifts in the X-ray absorption near edge structure (XANES) spectrum. X-ray absorption spectroscopy (XAS) can therefore be used to visualize and quantify lithiation kinetics in transition metal oxide cathodes; however, in-situ measurements are often constrained by temporal resolution and X-ray dose, necessitating compromises in the electrochemistry cycling conditions used or the materials examined. We report a combined approach to reduce measurement time and X-ray exposure for operando XAS studies of lithium ion batteries. A highly discretized energy resolution coupled with advanced post-processing enables rapid yet reliable identification of the oxidation state. A full-field microscopy setup provides sub-particle resolution over a large area of battery electrode, enabling the oxidation state within many transition metal oxide particles to be tracked simultaneously. Here, we apply this approach to gain insights into the lithiation kinetics of a commercial, mixed-metal oxide cathode material, nickel cobalt aluminium oxide (NCA), during (dis)charge and its degradation during overcharge.
Nowack, Lea; Grolimund, Daniel; Samson, Vallerie; Marone, Federica; Wood, Vanessa
2016-01-01
Since the commercialization of lithium ion batteries (LIBs), layered transition metal oxides (LiMO2, where M = Co, Mn, Ni, or mixtures thereof) have been materials of choice for LIB cathodes. During cycling, the transition metals change their oxidation states, an effect that can be tracked by detecting energy shifts in the X-ray absorption near edge structure (XANES) spectrum. X-ray absorption spectroscopy (XAS) can therefore be used to visualize and quantify lithiation kinetics in transition metal oxide cathodes; however, in-situ measurements are often constrained by temporal resolution and X-ray dose, necessitating compromises in the electrochemistry cycling conditions used or the materials examined. We report a combined approach to reduce measurement time and X-ray exposure for operando XAS studies of lithium ion batteries. A highly discretized energy resolution coupled with advanced post-processing enables rapid yet reliable identification of the oxidation state. A full-field microscopy setup provides sub-particle resolution over a large area of battery electrode, enabling the oxidation state within many transition metal oxide particles to be tracked simultaneously. Here, we apply this approach to gain insights into the lithiation kinetics of a commercial, mixed-metal oxide cathode material, nickel cobalt aluminium oxide (NCA), during (dis)charge and its degradation during overcharge. PMID:26908198
NASA Astrophysics Data System (ADS)
Kriss, Gerard A.; Agn Storm Team
2015-01-01
The AGN STORM collaboration monitored the Seyfert 1 galaxy NGC 5548 over a six-month period, with observations spanning the hard X-ray to mid-infrared wavebands. The core of this campaign was an intensive HST COS program, which obtained 170 far-ultraviolet spectra at approximately daily intervals, with twice-per-day monitoring of the X-ray, near-UV, and optical bands during much of the same period using Swift. The broad UV absorption lines discovered by Kaastra et al. (2014) and associated with the new soft X-ray obscurer are continuously present in the STORM campaign COS spectra. Their strength varies with the degree of soft X-ray obscuration as revealed by the Swift X-ray spectra. The narrow associated absorption lines in the UV spectrum of NGC 5548 remain strong. The lower-ionization transitions that appeared concurrently with the soft X-ray obscuration vary in response to the changing UV flux on a daily basis. Their depths over the longer term, however, also respond to the strength of the soft X-ray obscuration, indicating that the soft X-ray obscurer has a significant influence on the ionizing UV continuum that is not directly tracked by the observable UV continuum itself.
Nowack, Lea; Grolimund, Daniel; Samson, Vallerie; Marone, Federica; Wood, Vanessa
2016-01-01
Since the commercialization of lithium ion batteries (LIBs), layered transition metal oxides (LiMO2, where M = Co, Mn, Ni, or mixtures thereof) have been materials of choice for LIB cathodes. During cycling, the transition metals change their oxidation states, an effect that can be tracked by detecting energy shifts in the X-ray absorption near edge structure (XANES) spectrum. X-ray absorption spectroscopy (XAS) can therefore be used to visualize and quantify lithiation kinetics in transition metal oxide cathodes; however, in-situ measurements are often constrained by temporal resolution and X-ray dose, necessitating compromises in the electrochemistry cycling conditions used or the materials examined. We report a combined approach to reduce measurement time and X-ray exposure for operando XAS studies of lithium ion batteries. A highly discretized energy resolution coupled with advanced post-processing enables rapid yet reliable identification of the oxidation state. A full-field microscopy setup provides sub-particle resolution over a large area of battery electrode, enabling the oxidation state within many transition metal oxide particles to be tracked simultaneously. Here, we apply this approach to gain insights into the lithiation kinetics of a commercial, mixed-metal oxide cathode material, nickel cobalt aluminium oxide (NCA), during (dis)charge and its degradation during overcharge. PMID:26908198
NASA Astrophysics Data System (ADS)
Li, Wenshan; Hennrich, Frank; Flavel, Benjamin S.; Kappes, Manfred M.; Krupke, Ralph
2016-09-01
The length of single-walled carbon nanotubes (SWCNTs) is an important metric for the integration of SWCNTs into devices and for the performance of SWCNT-based electronic or optoelectronic applications. In this work we propose a rather simple method based on electric-field induced differential absorption spectroscopy to measure the chiral-index-resolved average length of SWCNTs in dispersions. The method takes advantage of the electric-field induced length-dependent dipole moment of nanotubes and has been verified and calibrated by atomic force microscopy. This method not only provides a low cost, in situ approach for length measurements of SWCNTs in dispersion, but due to the sensitivity of the method to the SWCNT chiral index, the chiral index dependent average length of fractions obtained by chromatographic sorting can also be derived. Also, the determination of the chiral-index resolved length distribution seems to be possible using this method.
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…
O'Day, P; Carroll, S A; Bajt, S
2003-01-16
Synchrotron X-ray absorption spectroscopy (XAS) is one of the few techniques that can supply molecular-scale information for a variety of elements at concentrations relevant to natural systems in non-vacuum conditions. Bulk XAS analysis supplies the dominant chemical bonding mode(s) for a specific element. In complex materials such as natural soils and sediments, however, the dominant mode may not necessarily be the most reactive because changes in speciation at surfaces may results in changes in reactivity. Our previous work at Naval Air Station (NAS) Alameda (CA) focused on in situ metal chemistry in surface and deep sediments, and the impact of metal mobility by sediment oxidation. Estuary sediments at the Alameda Naval Station Air in California have elevated metal concentrations that increase with increasing depth. The metal concentrations in these sediments are: Cd (10-350 ppm), Cr (200-1000 ppm), Cu (100-230 ppm), Pb (200-1200 ppm) and Zn (250-600 ppm). We have extensively characterized these sediments using bulk XAS and other non-synchrotron supporting methods [ 1]. In this experiment, we collected fluorescence element maps using synchrotron X-ray microprobe of unreacted and seawater-oxidized sediment samples from Alameda NAS to determine the spatial distribution and correlation of lead, zinc, and iron. We then compared micro-XANES spectra for lead and zinc collected with the X-ray microprobe to previously collected bulk XANES spectra. The results from our bulk XAS characterization of the sediments showed both oxide and sulfide components for the trace metals. However, the bulk XAS data were not able to identify the composition of the oxide component (i.e. carbonate or hydroxide), nor could absorbed species or solid solutions be definitively identified. Our objective in using micro-XANES and fluorescence element maps was to attempt a more precise identification of metal speciation in or on individual particles.
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.
Hillyard, Patrick B.; Kuchibhatla, Satyanarayana V N T; Glover, T. E.; Hertlein, M. P.; Huse, N.; Nachimuthu, Ponnusamy; Saraf, Laxmikant V.; Thevuthasan, Suntharampillai; Gaffney, Kelly J.
2009-09-29
We have used time-resolved soft x-ray spectroscopy to investigate the electronic structure of optically excited cuprous oxide at the O K-edge and the Cu L3-edge. The 400 nm optical excitation shifts the Cu and O absorptions to lower energy, but does not change the integrated x-ray absorption significantly for either edge. The constant integrated x-ray absorption cross-section indicates that that the conduction band and valence band edges have very similar Cu 3d and O 2p orbital contributions. The 2.1 eV optical band gap of Cu2O significantly exceeds the one eV shift in the Cu L3- and O K-edges absorption edges induced by optical excitation, demonstrating the importance of core-hole excitonic effects and valence electron screening in the x-ray absorption process.
Hillyard, P. W.; Kuchibhatla, S. V. N. T.; Glover, T. E.; Hertlein, M. P.; Huse, Nils; Nachimuthu, P.; Saraf, L. V.; Thevuthasan, S.; Gaffney, K. J.
2010-05-02
We have used time-resolved soft x-ray spectroscopy to investigate the electronic structure of optically excited cuprous oxide at the O K-edge and the Cu L3-edge. The 400 nm optical excitation shifts the Cu and O absorptions to lower energy, but does not change the integrated x-ray absorption significantly for either edge. The constant integrated x-ray absorption cross-section indicates that the conduction-band and valence-band edges have very similar Cu 3d and O 2p orbital contributions. The 2.1 eV optical band gap of Cu2O significantly exceeds the one eV shift in the Cu L3- and O K-edges absorption edges induced by optical excitation, demonstrating the importance of core-hole excitonic effects and valence electron screening in the x-ray absorption process.
Mapping Pesticide Partition Coefficients By Electromagnetic Induction
Technology Transfer Automated Retrieval System (TEKTRAN)
A potential method for reducing pesticide leaching is to base application rates on the leaching potential of a specific chemical and soil combination. However, leaching is determined in part by the partitioning of the chemical between the soil and soil solution, which varies across a field. Standard...
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…
Visible absorption spectrum of liquid ethylene
Nelson, Edward T.; Patel, C. Kumar N.
1981-01-01
The visible absorption spectrum of liquid ethylene at ≈ 108 K from 5500 Å to 7200 Å was measured by using a pulsed tunable dye laser, immersed-transducer, gated-detection opto-acoustic spectroscopy technique. The absorption features show the strongest band with an absorption coefficient of ≈2 × 10-2 cm-1 and the weakest band with an absorption coefficient of ≈1 × 10-4 cm-1. Proposed assignments of the observed absorption peaks involve combinations of overtones of local and normal modes of vibration of ethylene. PMID:16592978
Shawahna, R.; Rahman, NU.
2011-01-01
Background and the purpose of the study Partition coefficients (log D and log P) and molecular surface area (PSA) are potential predictors of the intestinal permeability of drugs. The aim of this investigation was to evaluate and compare these intestinal permeability indicators. Methods Aqueous solubility data were obtained from literature or calculated using ACD/Labs and ALOGPS. Permeability data were predicted based on log P, log D at pH 6.0 (log D6.0), and PSA. Results Metoprolol's log P, log D6.0, and a PSA of <65 Å correctly predicted 55.9%, 50.8% and 54.2% of permeability classes, respectively. Labetalol's log P, log D6.0 and PSA correctly predicted 54.2%, 64.4% and 61% of permeability classes, respectively. Log D6.0 correlated well (81%) with Caco-2 permeability (Papp). Of the list of national essential medicines, 135 orally administered drugs were classified into biopharmaceutical classification system (BCS). Of these, 57 (42.2%), 28 (20.7%), 44 (32.6%), and 6 (4.4%) were class I, II, III and IV respectively. Conclusion Log D6.0 showed better prediction capability than log P. Metoprolol as permeability internal standard was more conservative than labetalol. PMID:22615645
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.
Diffuse reflection coefficient of a stratified sea.
Haltrin, V I
1999-02-20
A differential equation of a Riccati type for the diffuse reflection coefficient of a stratified sea is proposed. For a homogeneous sea with arbitrary inherent optical properties this equation is solved analytically. For an inhomogeneous sea it is solved approximately for any arbitrary stratification. The resulting equation expresses the diffuse reflection coefficient of the sea through vertical profiles of absorption and backscattering coefficients, bottom albedo, and sea depth. The results of calculations with this equation are compared with Monte Carlo computations. It was found that the precision of this approach is in the range of 15%. PMID:18305694
Coefficients for Interrater Agreement.
ERIC Educational Resources Information Center
Zegers, Frits E.
1991-01-01
The degree of agreement between two raters rating several objects for a single characteristic can be expressed through an association coefficient, such as the Pearson product-moment correlation. How to select an appropriate association coefficient, and the desirable properties and uses of a class of such coefficients--the Euclidean…
Optical absorption components of light-modulated absorption spectrum of CdS
NASA Technical Reports Server (NTRS)
Conway, E. J.; Long, E. R.
1975-01-01
The amplitude and decay coefficient of light-induced modulation of absorption (LIMA) was measured as a function of wavelength from 535 to 850 nm for single-crystal CdS. The decay coefficient exhibited a discontinuous resonance at 710 nm which was due to the overlap and cancellation of two opposing absorption changes. A method was developed to separate these opposing absorption changes using the measured decay coefficients. The discrete-level-to-band energy for one absorption change was found to be 1.64 eV. An improved model was developed which contains two associated levels in the band gap separated by 0.32 eV.
Implications of NGA for NEHRP site coefficients
Borcherdt, Roger D.
2012-01-01
Three proposals are provided to update tables 11.4-1 and 11.4-2 of Minimum Design Loads for Buildings and Other Structures (7-10), by the American Society of Civil Engineers (2010) (ASCE/SEI 7-10), with site coefficients implied directly by NGA (Next Generation Attenuation) ground motion prediction equations (GMPEs). Proposals include a recommendation to use straight-line interpolation to infer site coefficients at intermediate values of ̅vs (average shear velocity). Site coefficients are recommended to ensure consistency with ASCE/SEI 7-10 MCER (Maximum Considered Earthquake) seismic-design maps and simplified site-specific design spectra procedures requiring site classes with associated tabulated site coefficients and a reference site class with unity site coefficients. Recommended site coefficients are confirmed by independent observations of average site amplification coefficients inferred with respect to an average ground condition consistent with that used for the MCER maps. The NGA coefficients recommended for consideration are implied directly by the NGA GMPEs and do not require introduction of additional models.
Ostlund, Richard E
2002-03-01
Cholesterol absorption is a key regulatory point in human lipid metabolism because it determines the amount of endogenous biliary as well as dietary cholesterol that is retained, thereby influencing whole body cholesterol balance. Plant sterols (phytosterols) and the drug ezetimibe reduce cholesterol absorption and low-density lipoprotein cholesterol in clinical trials, complementing the statin drugs, which inhibit cholesterol biosynthesis. The mechanism of cholesterol absorption is not completely known but involves the genes ABC1, ABCG5, and ABCG8, which are members of the ATP-binding cassette protein family and appear to remove unwanted cholesterol and phytosterols from the enterocyte. ABC1 is upregulated by the liver X (LXR) and retinoid X (RXR) nuclear receptors. Acylcholesterol acytransferase-2 is an intestinal enzyme that esterifies absorbed cholesterol and increases cholesterol absorption when dietary intake is high. New clinical treatments based on better understanding of absorption physiology are likely to substantially improve clinical cholesterol management in the future. PMID:17033296
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.
Nondestructive Method For Measuring The Scattering Coefficient Of Bulk Material
NASA Astrophysics Data System (ADS)
Groenhuis, R. A. J.; ten Bosch, J. J.
1981-05-01
During demineralization and remineralization of dental enamel its structure changes resulting in a change of the absorption and scattering coefficients of the enamel. By measuring these coefficients during demineralization and remineralization these processes can be monitored in a non-destructive way. For this purpose an experimental arrangement was made: a fibre illuminates a spot on the sample with monochromatic light with a wave-length between 400 nm and 700 nm; a photomultiplier measures the luminance of the light back-scattered by the sample as a function of the distance from the measuring snot to the spot of illumination. In a Monte Carlo-model this luminance is simulated using the same geometry given the scattering and absorption coefficients in a sample. Then the scattering and absorption coefficients in the sample are determined by selecting the theoretical curve fitting the experimental one. Scattering coefficients below 10 mm-1 and absorption coefficients obtained with this method on calibration samples correspond well with those obtained with another method. Scattering coefficients above 10 mm-1 (paper samples) were measured ton low. This perhaps is caused by the anisotropic structure of paper sheets. The method is very suitable to measure the scattering and absorption coefficients of bulk materials.
De Brier, Niels; Gomand, Sara V; Donner, Erica; Paterson, David; Smolders, Erik; Delcour, Jan A; Lombi, Enzo
2016-08-01
Several studies have suggested that the majority of iron (Fe) and zinc (Zn) in wheat grains are associated with phytate, but a nuanced approach to unravel important tissue-level variation in element speciation within the grain is lacking. Here, we present spatially resolved Fe-speciation data obtained directly from different grain tissues using the newly developed synchrotron-based technique of X-ray absorption near-edge spectroscopy imaging, coupling this with high-definition μ-X-ray fluorescence microscopy to map the co-localization of essential elements. In the aleurone, phosphorus (P) is co-localized with Fe and Zn, and X-ray absorption near-edge structure imaging confirmed that Fe is chelated by phytate in this tissue layer. In the crease tissues, Zn is also positively related to P distribution, albeit less so than in the aleurone. Speciation analysis suggests that Fe is bound to nicotianamine rather than phytate in the nucellar projection, and that more complex Fe structures may also be present. In the embryo, high Zn concentrations are present in the root and shoot primordium, co-occurring with sulfur and presumably bound to thiol groups. Overall, Fe is mainly concentrated in the scutellum and co-localized with P. This high resolution imaging and speciation analysis reveals the complexity of the physiological processes responsible for element accumulation and bioaccessibility. PMID:27038325
Diffusion coefficients of several aqueous alkanolamine solutions
Snijder, E.D.; Riele, M.J.M. te; Versteeg, G.F.; Swaaij, W.P.M. van . Dept. of Chemical Engineering)
1993-07-01
In absorption processes of acid gases (H[sub 2]S, CO[sub 2], COS) in alkanolamine solutions, diffusion coefficients are used for the calculation of the mass transfer rate. The Taylor dispersion technique was applied for the determination of diffusion coefficients of various systems. Experiments with the system KCl in water showed that the experimental setup provides accurate data. For the alkanolamines monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA), and di-2-propanolamine (DIPA), correlations for the diffusion coefficient as a function of temperature at different concentrations are given. A single relation for every amine has been derived which correlates the diffusion coefficients as a function of temperature and concentration. The temperature was varied between 298 and 348 K, and the concentration between 0 and 4000-5000 mol/m[sup 3]. Furthermore, a modified Stokes-Einstein relation is presented for the prediction of the diffusion coefficients in the alkanolamines in relation to the viscosity of the solvent and the diffusion coefficient at infinite dilution. The diffusion coefficients at low concentrations are compared with some available relations for the estimation of diffusion coefficients at infinite dilution, and it appears that the agreement is fairly good.
NASA Astrophysics Data System (ADS)
Wuhrer, R.; Moran, K.
2014-03-01
Quantitative X-ray mapping with silicon drift detectors and multi-EDS detector systems have become an invaluable analysis technique and one of the most useful methods of X-ray microanalysis today. The time to perform an X-ray map has reduced considerably with the ability to map minor and trace elements very accurately due to the larger detector area and higher count rate detectors. Live X-ray imaging can now be performed with a significant amount of data collected in a matter of minutes. A great deal of information can be obtained from X-ray maps. This includes; elemental relationship or scatter diagram creation, elemental ratio mapping, chemical phase mapping (CPM) and quantitative X-ray maps. In obtaining quantitative x-ray maps, we are able to easily generate atomic number (Z), absorption (A), fluorescence (F), theoretical back scatter coefficient (η), and quantitative total maps from each pixel in the image. This allows us to generate an image corresponding to each factor (for each element present). These images allow the user to predict and verify where they are likely to have problems in our images, and are especially helpful to look at possible interface artefacts. The post-processing techniques to improve the quantitation of X-ray map data and the development of post processing techniques for improved characterisation are covered in this paper.
NASA Astrophysics Data System (ADS)
Dobler, J. T.; Braun, M.; Blume, N.; McGregor, D.; Zaccheo, T. S.; Pernini, T.; Botos, C.
2014-12-01
We will present the development of the Greenhouse gas Laser Imaging Tomography Experiment (GreenLITE). GreenLITE consists of two laser based transceivers and a number of retro-reflectors to measure differential transmission (DT) of a number of overlapping chords in a plane over the site being monitored. The transceivers use the Intensity Modulated Continuous Wave (IM-CW) approach, which is a technique that allows simultaneous transmission/reception of multiple fixed wavelength lasers and a lock-in, or matched filter, to measure amplitude and phase of the different wavelengths in the digital domain. The technique was developed by Exelis and has been evaluated using an airborne demonstrator for the past 10 years by NASA Langley Research Center. The method has demonstrated high accuracy and high precision measurements as compared to an in situ monitor tracable to WMO standards, agreeing to 0.65 ppm +/-1.7 ppm. The GreenLITE system is coupled to a cloud-based data storage and processing system that takes the measured chord data, along with auxiliary data to retrieve an average CO2 concentration per chord and which combines the chords to provide an estimate of the spatial distribution of CO2 concentration in the plane. A web-based interface allows users to view real-time CO2 concentrations and 2D concentration maps of the area being monitored. The 2D maps can be differenced as a function of time for an estimate of the flux across the plane measured by the system. The system is designed to operate autonomously from semi-remote locations with a very low maintenance cycle. Initial instrument tests, conducted in June, showed signal to noise in the measured ratio of >3000 for 10 s averages. Additional local field testing and a quantifiable field testing at the Zero Emissions Research and Technology (ZERT) site in Bozeman, MT are planned for this fall. We will present details on the instrument and software tools that have been developed, along with results from the local
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.
NASA Astrophysics Data System (ADS)
Lehmann, Johannes; Liang, Biqing; Solomon, Dawit; Lerotic, Mirna; LuizãO, Flavio; Kinyangi, James; SchäFer, Thorsten; Wirick, Sue; Jacobsen, Chris
2005-03-01
Small-scale heterogeneity of organic carbon (C) forms in soils is poorly quantified since appropriate analytical techniques were not available up to now. Specifically, tools for the identification of functional groups on the surface of micrometer-sized black C particles were not available up to now. Scanning Transmission X-ray Microscopy (STXM) using synchrotron radiation was used in conjunction with Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy to investigate nano-scale distribution (50-nm resolution) of C forms in black C particles and compared to synchrotron-based FTIR spectroscopy. A new embedding technique was developed that did not build on a C-based embedding medium and did not pose the risk of heat damage to the sample. Elemental sulfur (S) was melted to 220°C until it polymerized and quenched with liquid N2 to obtain a very viscous plastic S in which the black C could be embedded until it hardened to a noncrystalline state and was ultrasectioned. Principal component and cluster analysis followed by singular value decomposition was able to resolve distinct areas in a black carbon particle. The core of the studied biomass-derived black C particles was highly aromatic even after thousands of years of exposure in soil and resembled the spectral characteristics of fresh charcoal. Surrounding this core and on the surface of the black C particle, however, much larger proportions of carboxylic and phenolic C forms were identified that were spatially and structurally distinct from the core of the particle. Cluster analysis provided evidence for both oxidation of the black C particle itself as well as adsorption of non-black C. NEXAFS spectroscopy has great potential to allow new insight into black C properties with important implications for biogeochemical cycles such as mineralization of black C in soils and sediments, and adsorption of C, nutrients, and pollutants as well as transport in the geosphere, hydrosphere, and atmosphere.
Research on absorption test methods of Yb-doped double cladding fiber
NASA Astrophysics Data System (ADS)
Wang, Pupu; Li, Rundong; Rong, Liang; Ji, Wei; Gao, Yankun; Jiang, Cong; Gu, Shaoyi
2016-01-01
Absorption coefficient is a very useful feature for active fiber. In fiber laser system, the length of active fiber is chosen according to absorption coefficient. And the length of fiber can directly influence the feature of fiber laser. Therefore, how to obtain an accurate absorption coefficient is very important. Because fiber exists re-emission in typical absorption band pumped by power. It is difficult to accurately measure absorption coefficient. The absorption coefficients of Yb-doped double cladding fiber at 975 nm measured by several methods were compared. In conclusion, for the fibers with same length pumped by white light, the absorption coefficient is the highest when cutback only once. Meanwhile, when fibers with different length were measured by the same method, the absorption coefficient is inversely proportional to optical fiber length.
Barsony, Mary; Wolf-Chase, Grace A.; Ciardi, David R.
2010-09-01
The outflow driven by the Class 0 protostar, IRAS 16253-2429, is associated with bipolar cavities visible in scattered mid-infrared light, which we refer to as the Wasp-Waist Nebula. InfraRed Spectometer (IRS) scan mapping with the Spitzer Space Telescope of a {approx}1' x 2' area centered on the protostar was carried out. The outflow is imaged in six pure rotational (0-0 S(2) through 0-0 S(7)) H{sub 2} lines, revealing a distinct, S-shaped morphology in all maps. A source map in the 11.3 {mu}m polycyclic aromatic hydrocarbon (PAH) feature is presented in which the protostellar envelope appears in absorption. This is the first detection of absorption in the 11.3 {mu}m PAH feature. Spatially resolved excitation analysis of positions in the blue- and redshifted outflow lobes, with extinction-corrections determined from archival Spitzer 8 {mu}m imaging, shows remarkably constant temperatures of {approx}1000 K in the shocked gas. The radiated luminosity in the observed H{sub 2} transitions is found to be 1.94 {+-} 0.05 x 10{sup -5} L{sub sun} in the redshifted lobe and 1.86 {+-} 0.04 x 10{sup -5} L{sub sun} in the blueshifted lobe. These values are comparable to the mechanical luminosity of the flow. By contrast, the mass of hot (T {approx} 1000 K) H{sub 2} gas is 7.95 {+-} 0.19 x 10{sup -7} M{sub sun} in the redshifted lobe and 5.78 {+-} 0.17 x 10{sup -7} M{sub sun} in the blueshifted lobe. This is just a tiny fraction, of order 10{sup -3}, of the gas in the cold (30 K), swept-up gas mass derived from millimeter CO observations. The H{sub 2} ortho/para ratio of 3:1 found at all mapped points in this flow suggests previous passages of shocks through the gas. Comparison of the H{sub 2} data with detailed shock models of Wilgenbus et al. shows the emitting gas is passing through Jump (J-type) shocks. Pre-shock densities of 10{sup 4} cm{sup -3{<=}} n {sub H{<=}} 10{sup 5} cm{sup -3} are inferred for the redshifted lobe and n {sub H{<=}} 10{sup 3} cm{sup -3} for the
NASA Astrophysics Data System (ADS)
Barsony, Mary; Wolf-Chase, Grace A.; Ciardi, David R.; O'Linger, JoAnn
2010-09-01
The outflow driven by the Class 0 protostar, IRAS 16253-2429, is associated with bipolar cavities visible in scattered mid-infrared light, which we refer to as the Wasp-Waist Nebula. InfraRed Spectometer (IRS) scan mapping with the Spitzer Space Telescope of a ~1' × 2' area centered on the protostar was carried out. The outflow is imaged in six pure rotational (0-0 S(2) through 0-0 S(7)) H2 lines, revealing a distinct, S-shaped morphology in all maps. A source map in the 11.3 μm polycyclic aromatic hydrocarbon (PAH) feature is presented in which the protostellar envelope appears in absorption. This is the first detection of absorption in the 11.3 μm PAH feature. Spatially resolved excitation analysis of positions in the blue- and redshifted outflow lobes, with extinction-corrections determined from archival Spitzer 8 μm imaging, shows remarkably constant temperatures of ~1000 K in the shocked gas. The radiated luminosity in the observed H2 transitions is found to be 1.94 ± 0.05 × 10-5 L sun in the redshifted lobe and 1.86 ± 0.04 × 10-5 L sun in the blueshifted lobe. These values are comparable to the mechanical luminosity of the flow. By contrast, the mass of hot (T ~ 1000 K) H2 gas is 7.95 ± 0.19 × 10-7 M sun in the redshifted lobe and 5.78 ± 0.17 × 10-7 M sun in the blueshifted lobe. This is just a tiny fraction, of order 10-3, of the gas in the cold (30 K), swept-up gas mass derived from millimeter CO observations. The H2 ortho/para ratio of 3:1 found at all mapped points in this flow suggests previous passages of shocks through the gas. Comparison of the H2 data with detailed shock models of Wilgenbus et al. shows the emitting gas is passing through Jump (J-type) shocks. Pre-shock densities of 104 cm-3<= n H <= 105 cm-3 are inferred for the redshifted lobe and n H <= 103 cm-3 for the blueshifted lobe. Shock velocities are 5 km s-1 <= vs <= 10 km s-1 for the redshifted gas and vs = 10 km s-1 for the blueshifted gas. Initial transverse (to the shock
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)
NASA Astrophysics Data System (ADS)
Chantler, C. T.
2000-07-01
Reliable knowledge of the complex x-ray form factor [Re(f ) and f″] and the photoelectric attenuation coefficient (σPE) is required for crystallography, medical diagnosis, radiation safety, and XAFS studies. Discrepancies between currently used theoretical approaches of 200% exist for numerous elements from 1 to 3 keV x-ray energies. The key discrepancies are due to the smoothing of edge structure, the use of nonrelativistic wave functions, and the lack of appropriate convergence of wave functions. This paper addresses these key discrepancies and derives new theoretical results of substantially higher accuracy in near-edge soft x-ray regions. The high-energy limitations of the current approach are also illustrated. The energy range covered is 0.1 to 10 keV. The associated figures and tabulation demonstrate the current comparison with alternate theory and with available experimental data. In general, experimental data are not sufficiently accurate to establish the errors and inadequacies of theory at this level. However, the best experimental data and the observed experimental structure as a function of energy are strong indicators of the validity of the current approach. New developments in experimental measurement hold great promise in making critical comparisons with theory in the near future.
Photoelectric absorption cross sections with variable abundances
NASA Technical Reports Server (NTRS)
Balucinska-Church, Monika; Mccammon, Dan
1992-01-01
Polynomial fit coefficients have been obtained for the energy dependences of the photoelectric absorption cross sections of 17 astrophysically important elements. These results allow the calculation of X-ray absorption in the energy range 0.03-10 keV in material with noncosmic abundances.
Dynamic performance testing of prototype 3 ton air-cooled carrier absorption chiller
Borst, R.R.; Wood, B.D.
1985-05-01
The performance of a prototype 3 ton cooling capacity air-cooled lithium bromide/water absorption chiller was tested using an absorption chiller test facility which was modified to expand its testing capabilities to include air-cooled chillers in addition to water-cooled chillers. Temperatures of the three externally supplied fluid loops: hot water, chilled water, and cooling air, were varied in order to determine the effects this would have on the two principal measures of chiller performance: cooling capacity and thermal coefficient of performance (COP). A number of interrelated factors were identified as contributing to less than expected performance. For comparison, experimental correlations of other investigators for this and other similar absorption chillers are presented. These have been plotted as both contour and three-dimensional performance maps in order to more clearly show the functional dependence of the chiller performance on the fluid loop temperatures.
Dynamic performance testing of prototype 3 ton air-cooled carrier absorption chiller
NASA Astrophysics Data System (ADS)
Borst, R. R.; Wood, B. D.
1985-05-01
The performance of a prototype three ton cooling capacity air-cooled lithium bromide/water absorption chiller was tested using an absorption chiller test facility which was modified to expand its testing capabilities to include air-cooled chillers in addition to water-cooled chillers. Temperatures of the three externally supplied fluid loops: hot water, chilled water, and cooling air, were varied in order to determine the effects this would have on the two principal measures of chiller performance: cooling capacity and thermal coefficient of performance (COP). A number of interrelated factors were identified as contributing to less than expected performance. For comparison, experimental correlations of other investigators for this and other similar absorption chillers are presented. These have been plotted as both contour and three-dimensional performance maps in order to more clearly show the functional dependence of the chiller performance on the fluid loop temperatures.
Ceschin, Rafael; Kurland, Brenda F.; Abberbock, Shira R.; Ellingson, Benjamin M.; Okada, Hideho; Jakacki, Regina I.; Pollack, Ian F.; Panigrahy, Ashok
2015-01-01
Background and Purpose Immune response to cancer therapy may result in pseudoprogression, which can only be identified retrospectively and which may disrupt an effective therapy. This study assesses whether serial parametric response mapping (PRM, a voxel-by-voxel method of image analysis also known as functional diffusion mapping) analysis of ADC measurements following peptide-based vaccination may help prospectively distinguish progression from pseudoprogression in pediatric patients with diffuse intrinsic pontine gliomas. Materials and Methods From 2009–2012, 21 children age 4–18 with diffuse intrinsic pontine gliomas were enrolled in a serial peptide-based vaccination protocol following radiotherapy. DWI was acquired before immunotherapy and at six week intervals during vaccine treatment. Pseudoprogression was identified retrospectively based on clinical and radiographic findings, excluding DWI. Parametric response mapping was used to analyze 96 scans, comparing ADC measures at multiple time points (from first vaccine to up to 12 weeks after the vaccine was halted) to pre-vaccine baseline values. Log-transformed fractional increased ADC (fiADC), fractional decreased ADC (fdADC), and parametric response mapping ratio (fiADC/fdADC) were compared between patients with and without pseudoprogression, using generalized estimating equations with inverse weighting by cluster size. Results Median survival was 13.1 months from diagnosis (range 6.4–24.9 months). Four of 21 children (19%) were assessed as experiencing pseudoprogression. Patients with pseudoprogression had higher fitted average log-transformed parametric response mapping ratios (p=0.01) and fiADCs (p=0.0004), compared to patients without pseudoprogression. Conclusion Serial parametric response mapping of ADC, performed at multiple time points of therapy, may distinguish pseudoprogression from true progression in patients with diffuse intrinsic pontine gliomas treated with peptide-based vaccination
NASA Astrophysics Data System (ADS)
Samatham, Ravikant; Jacques, Steven L.
2013-02-01
Different techniques have been developed to determine the optical properties of turbid media, which include collimated transmission, diffuse reflectance, adding-doubling and goniometry. While goniometry can be used to determine the anisotropy of scattering (g), other techniques are used to measure the absorption coefficient and reduced scattering coefficient (μs(1-g)). But separating scattering coefficient (μs) and anisotropy of scattering from reduced scattering coefficient has been tricky. We developed an algorithm to determine anisotropy of scattering from the depth dependent decay of reflectance-mode confocal scanning laser microscopy (rCSLM) data. This report presents the testing of the algorithm on tissue phantoms with different anisotropies (g = 0.127 to 0.868, at 488 nm wavelength). Tissue phantoms were made from polystyrene microspheres (6 sizes 0.1-0.5 μm dia.) dispersed in both aqueous solutions and agarose gels. Three dimensional images were captured. The rCSLM-signal followed an exponential decay as a function of depth of the focal volume, R(z)ρexp(-μz) where ρ (dimensionless, ρ = 1 for a mirror) is the local reflectivity and μ [cm-1] is the exponential decay constant. The theory was developed to uniquely map the experimentally determined μ and ρ into the optical scattering properties μs and g. The values of μs and g depend on the composition and microstructure of tissues, and allow characterization of a tissue.
Generalized skew coefficients for flood-frequency analysis in Minnesota
Lorenz, D.L.
1997-01-01
This report presents an evaluation of generalized skew coefficients used in flood-frequency analysis. Station skew coefficients were computed for 267 long-term stream-gaging stations in Minnesota and the surrounding states of Iowa, North and South Dakota, Wisconsin, and the provinces of Manitoba and Ontario, Canada. Generalized skew coefficients were computed from station skew coefficients using a locally weighted regression technique. The resulting regression trend surface was the generalized skew coefficient map, except for the North Shore area, and has a mean square error of 0.182.
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.
Bounding the Bogoliubov coefficients
Boonserm, Petarpa; Visser, Matt
2008-11-15
While over the last century or more considerable effort has been put into the problem of finding approximate solutions for wave equations in general, and quantum mechanical problems in particular, it appears that as yet relatively little work seems to have been put into the complementary problem of establishing rigourous bounds on the exact solutions. We have in mind either bounds on parametric amplification and the related quantum phenomenon of particle production (as encoded in the Bogoliubov coefficients), or bounds on transmission and reflection coefficients. Modifying and streamlining an approach developed by one of the present authors [M. Visser, Phys. Rev. A 59 (1999) 427-438, (arXiv:quant-ph/9901030)], we investigate this question by developing a formal but exact solution for the appropriate second-order linear ODE in terms of a time-ordered exponential of 2x2 matrices, then relating the Bogoliubov coefficients to certain invariants of this matrix. By bounding the matrix in an appropriate manner, we can thereby bound the Bogoliubov coefficients.
Scanning measurement of Seebeck coefficient of a heated sample
Snyder, G. Jeffrey; Iwanaga, Shiho
2016-04-19
A novel scanning Seebeck coefficient measurement technique is disclosed utilizing a cold scanning thermocouple probe tip on heated bulk and thin film samples. The system measures variations in the Seebeck coefficient within the samples. The apparatus may be used for two dimensional mapping of the Seebeck coefficient on the bulk and thin film samples. This technique can be utilized for detection of defective regions, as well as phase separations in the sub-mm range of various thermoelectric materials.
Sensitivity of room acoustic parameters to changes in scattering coefficients
NASA Astrophysics Data System (ADS)
Rathsam, Jonathan; Wang, Lily M.
2001-05-01
This project uses the room acoustics computer modeling program, ODEON, to investigate the sensitivity of room acoustic parameters to changes in scattering coefficients. Particularly, the study is interested in determining if the results from certain room models are more sensitive to scattering coefficients than from other models, due to their geometry or absorption characteristics. If so, how can one quantify a model's susceptibility to being sensitive to scattering? Various models of three real spaces in Omaha, Nebraska are tested. The predicted reverberation, clarity, and spaciousness parameters are compared at various receiver locations, while the scattering coefficient of all surfaces is varied from 0 to 0.1, 0.3, 0.5, and 0.8. The resulting data are analyzed by frequency according to the (1) average absorption of the room; (2) magnitude variation of absorption within the room; (3) spatial distribution of absorption within the room; and (4) level of model detail. Initial results indicate that parameters studied may show more sensitivity to scattering coefficients in models that have a wider range of absorption values, more disparate distribution of absorption, and lower detail level. Various schemes that include these aspects are proposed for computing a model's sensitivity to changes in scattering.
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.
Geometric absorption of electromagnetic angular momentum
NASA Astrophysics Data System (ADS)
Konz, C.; Benford, Gregory
2003-10-01
Circularly polarized electromagnetic fields carry both energy and angular momentum. We investigate the conditions under which a circularly polarized wave field transfers angular momentum to a perfectly conducting macroscopic object, using exact electromagnetic wave theory in a steady-state calculation. We find that axisymmetric perfect conductors cannot absorb or radiate angular momentum when illuminated. However, any asymmetry allows absorption. A rigorous, steady-state solution of the boundary value problem for the reflection from a perfectly conducting infinite wedge shows that waves convey angular momentum at the edges of asymmetries. Conductors can also radiate angular momentum, so their geometric absorption coefficient for angular momentum can be negative. Such absorption or radiation depends solely on the specific geometry of the conductor. The geometric absorption coefficient can be as high as 0.8, and the coefficient for radiation can be -0.4, larger than typical material absorption coefficients. We apply the results to recent experiments which spun roof-shaped aluminum sheets with polarized microwave beams. Applications of geometric, instead of material, absorption can be quite varied. Though experiments testing these ideas will be simpler at microwavelengths, the ideas work for optical ones as well.
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)
Ruell, Jeffrey A; Tsinman, Konstantin L; Avdeef, Alex
2003-12-01
Iso-pH mapping unstirred parallel artificial membrane permeability assay (PAMPA) was used to measure the effective permeability, P(e), as a function of pH from 3 to 10, of five weak monoprotic acids (ibuprofen, naproxen, ketoprofen, salicylic acid, benzoic acid), an ampholyte (piroxicam), five monoprotic weak bases (imipramine, verapamil, propranolol, phenazopyridine, metoprolol), and a diprotic weak base (quinine). The intrinsic permeability, P(o), the unstirred water layer (UWL) permeability, P(u), and the apparent pK(a) (pK(a)(flux)) were determined from the pH dependence of logP(e). The underlying permeability-pH equations were derived for multiprotic weak acids, weak bases and ampholytes. The average thickness of the unstirred water layer on each side of the membrane was estimated to be nearly 2000 microm, somewhat larger than that found in Caco-2 permeability assays (unstirred). Since the UWL thickness in the human intestine is believed to be about forty times smaller, it is critical to correct the in vitro permeability data for the effect of the UWL. Without such correction, the in vitro permeability coefficient of lipophilic molecules would be indicative only of the property of water. In single-pH PAMPA (e.g. pH 7.4), the uncertainty of the UWL contribution can be minimized if a specially-selected pH (possibly different from 7.4) were used in the assay. From the analysis of the shapes of the log P(e)-pH plots, a method to improve the selection of the assay pH, called pK(a)(flux)-optimized design (pOD-PAMPA), was described and tested. From an optimally-selected assay pH, it is possible to estimate P(o), as well as the entire membrane permeability-pH profile. PMID:14659483
Distribution of reflection coefficients in absorbing chaotic microwave cavities.
Méndez-Sánchez, R A; Kuhl, U; Barth, M; Lewenkopf, C H; Stöckmann, H-J
2003-10-24
The distribution of reflection coefficients P(R) for chaotic microwave cavities with time-reversal symmetry is investigated in different absorption and antenna coupling regimes. For all regimes the agreement between experimental distributions and random-matrix theory predictions is very good, provided both the antenna coupling T(a) and the wall absorption strength T(w) are taken into account in an appropriate way. These parameters are determined by independent experimental quantities. PMID:14611349
Infrared absorption modeling of VOx microbolometer
NASA Astrophysics Data System (ADS)
Aggoun, Mehdi; Jiang, Jianliang; Khan, M. K.
2015-08-01
The absorption model plays an important role in the design of the microbolometer structure regarding the determination of the optimum thickness of the structure layers. Moreover, the infrared absorption depends on the wavelength of the radiation and the material properties. In this paper, we presented an Infrared absorption model with absorption coefficient of 96% at maximum absorption wavelength of 9.89μm which is very close to the expected value 10μm. This model was established by using MATLAB so that the simulation of the infrared absorption of the VOx microbolometer could be accomplished. In order to confirm the role of this modeling in the design of the device structure, comparison with other structures is also studied in this paper.
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.
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.
In-vivo absorption properties of algal pigments
NASA Astrophysics Data System (ADS)
Bidigare, Robert R.; Ondrusek, Michael E.; Morrow, John H.; Kiefer, Dale A.
1990-09-01
Estimates of the in vivo specific absorption coefficients (m2 mg'; 400-750 nm, 2 nm intervals) for the major algal pigment groups (chlorophylls, carotenoids and phycobilins) are presented. "Unpackaged" absorption coefficients were initially obtained by measuring the absorption properties of pure pigment standards spectrophotometrically and "shifting" their absorption maxima to match in vivo positions. Two approaches for estimating the phytoplankton absorption coefficient (spectral reconstruction and spectral decomposition) are compared by linear regression analysis, incorporating concurrent measurements of particulate absorption and pigmentation performed in the Sargasso Sea. Results suggest that "pigment package" effects are minimal for natural assemblages of open-oceanic phytoplankton and that accessory pigments do not always co-vary with chlorophyll a over depth and time.
Imaging of highly turbid media by the absorption method
NASA Astrophysics Data System (ADS)
Contini, Daniele; Liszka, Heather; Sassaroli, Angelo; Zaccanti, Giovanni
1996-05-01
The results of a study on imaging that is based on the absorption method are presented. This method is based on attenuation measurements carried out in the presence of a sufficiently high absorption coefficient by the use of a continuous-wave source. The benefit of absorption on image quality comes from the strong attenuation of photons traveling along long trajectories. When the absorption coefficient is increased, the received energy decreases, but the mean path length of received photons decreases. The effect of increasing the absorption coefficient is similar to that of decreasing the gating time when the time-gating technique is used. Experimental results showed that the spatial resolution obtained with the absorption technique is similar to that obtained with the time-gating technique. method, spatial resolution, turbid media.
Geometrical interpretation of optical absorption
Monzon, J. J.; Barriuso, A. G.; Sanchez-Soto, L. L.; Montesinos-Amilibia, J. M.
2011-08-15
We reinterpret the transfer matrix for an absorbing system in very simple geometrical terms. In appropriate variables, the system appears as performing a Lorentz transformation in a (1 + 3)-dimensional space. Using homogeneous coordinates, we map that action on the unit sphere, which is at the realm of the Klein model of hyperbolic geometry. The effects of absorption appear then as a loxodromic transformation, that is, a rhumb line crossing all the meridians at the same angle.
Formaldehyde absorption toward W51
NASA Technical Reports Server (NTRS)
Kogut, A.; Smoot, G. F.; Bennett, C. L.; Petuchowski, S. J.
1989-01-01
Formaldehyde (H2CO) absorption toward the H II region complex W51A (G49.5 - 0.4) in the 6 cm and 2 cm wavelength rotational transitions has been measured with angular resolution of about 0.15 pc. The continuum H II region shows a large, previously undetected shell structure 5.5 pc along the major axis. The absorption, converted to optical depth, shows a higher degree of clumping throughout the map than previous maps at lower resolution; in particular, two narrow regions of enhanced opacity are observed. The absorption in the velocity range 64-67 km/s LSR extends over most of the region, with an observed velocity gradient of 5.2 km/s pc. The opacity structure largely parallels the velocity structure, with a ridge of enhanced opacity to the north of the highest velocity feature. The S/N of the maps allows accurate modeling of the spectral profiles. Nine distinct clumps in the foreground clouds have been identified and parametrized, and column densities for the 1(11) and 2(12) rotational levels of orthoformaldehyde have been derived.
Averaging Internal Consistency Reliability Coefficients
ERIC Educational Resources Information Center
Feldt, Leonard S.; Charter, Richard A.
2006-01-01
Seven approaches to averaging reliability coefficients are presented. Each approach starts with a unique definition of the concept of "average," and no approach is more correct than the others. Six of the approaches are applicable to internal consistency coefficients. The seventh approach is specific to alternate-forms coefficients. Although the…
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.
Drag Coefficient of Hexadecane Particles
NASA Astrophysics Data System (ADS)
Nakao, Yoshinobu; Hishida, Makoto; Kajimoto, Sadaaki; Tanaka, Gaku
This paper deals with the drag coefficient of solidified hexadecane particles and their free rising velocity in liquid. The drag coefficient was experimentally investigated in Reynolds number range of about 40-300. The present experimental results are summarized in the following; (1) the drag coefficient of solidified hexadecane particles formed in liquid coolant by direct contact cooling is higher than that of a smooth surface sphere, this high drag coefficient seems to be attributed to the non-smooth surface of the solidified hexadecane particles, (2) experimental correlation for the drag coefficient of the solidified hexadecane particles was proposed, (3 ) the measured rising velocity of the solidified hexadecane particle agrees well with the calculated one, (4) the drag coefficients of hexadecane particles that were made by pouring hexadecane liquid into a solid hollow sphere agreed well with the drag coefficient of smooth surface sphere.
The electron diffusion coefficient in Jupiter's magnetosphere
NASA Technical Reports Server (NTRS)
Birmingham, T.; Northrop, T.; Baxter, R.; Hess, W.; Lojko, M.
1974-01-01
A steady-state model of Jupiter's electron radiation belt is developed. The model includes injection from the solar wind, radial diffusion, energy degradation by synchrotron radiation, and absorption at Jupiter's surface. A diffusion coefficient of the form D sub RR/R sub J squared = k times R to the m-th power is assumed, and then observed data on synchrotron radiation are used to fit the model. The free parameters determined from this fit are m = 1.95 plus or minus 0.5, k = 1.7 plus or minus 0.5 x 10 to the 9th power per sec, and the magnetic moment of injected particles equals 770 plus or minus 300 MeV/G. The value of m shows quite clearly that the diffusion is not caused by magnetic pumping by a variable solar wind or by a fluctuating convection electric field. The process might be field line exchange driven by atmospheric-ionospheric winds; our diffusion coefficient has roughly the same radial dependence but is considerably smaller in magnitude than the upper bound diffusion coefficients recently suggested for this process by Brice and McDonough (1973) and Jacques and Davis (1972).
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.
Quadrature formulas for Fourier coefficients
NASA Astrophysics Data System (ADS)
Bojanov, Borislav; Petrova, Guergana
2009-09-01
We consider quadrature formulas of high degree of precision for the computation of the Fourier coefficients in expansions of functions with respect to a system of orthogonal polynomials. In particular, we show the uniqueness of a multiple node formula for the Fourier-Tchebycheff coefficients given by Micchelli and Sharma and construct new Gaussian formulas for the Fourier coefficients of a function, based on the values of the function and its derivatives.
Gold analysis by the gamma absorption technique.
Kurtoglu, Arzu; Tugrul, A Beril
2003-01-01
Gold (Au) analyses are generally performed using destructive techniques. In this study, the Gamma Absorption Technique has been employed for gold analysis. A series of different gold alloys of known gold content were analysed and a calibration curve was obtained. This curve was then used for the analysis of unknown samples. Gold analyses can be made non-destructively, easily and quickly by the gamma absorption technique. The mass attenuation coefficients of the alloys were measured around the K-shell absorption edge of Au. Theoretical mass attenuation coefficient values were obtained using the WinXCom program and comparison of the experimental results with the theoretical values showed generally good and acceptable agreement. PMID:12485656
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…
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.
The relativistic Doppler broadening of the line absorption profile
NASA Astrophysics Data System (ADS)
Kichenassamy, S.; Krikorian, R.; Nikogosian, A.
1982-06-01
The classical results of Doppler broadening of the line absorption profile are generalized to a relativistic gas in thermal equilibrium by taking into account the relativistic variance of the volume absorption coefficients of the gas, as derived by L. H. Thomas. This variance produces a small correction, even in the non-relativistic approximation.
Coefficient adaptive triangulation for strongly anisotropic problems
D`Azevedo, E.F.; Romine, C.H.; Donato, J.M.
1996-01-01
Second order elliptic partial differential equations arise in many important applications, including flow through porous media, heat conduction, the distribution of electrical or magnetic potential. The prototype is the Laplace problem, which in discrete form produces a coefficient matrix that is relatively easy to solve in a regular domain. However, the presence of anisotropy produces a matrix whose condition number is increased, making the resulting linear system more difficult to solve. In this work, we take the anisotropy into account in the discretization by mapping each anisotropic region into a ``stretched`` coordinate space in which the anisotropy is removed. The region is then uniformly triangulated, and the resulting triangulation mapped back to the original space. The effect is to generate long slender triangles that are oriented in the direction of ``preferred flow.`` Slender triangles are generally regarded as numerically undesirable since they tend to cause poor conditioning; however, our triangulation has the effect of producing effective isotropy, thus improving the condition number of the resulting coefficient matrix.
RADIONUCLIDE RISK COEFFICIENT UNCERTAINTY REPORT
EPA has published excess cancer risk coefficients for the US population in Federal Guidance Report 13 (FGR 13). FGR 13 gives separate risk coefficients for food ingestion, water ingestion, inhalation, and external exposure for each of over 800 radionuclides. Some information on...
Standardized Discriminant Coefficients: A Rejoinder.
ERIC Educational Resources Information Center
Mueller, Ralph O.; Cozad, James B.
1993-01-01
Although comments of D.J. Nordlund and R. Nagel are welcomed, their arguments are not sufficient to accept the recommendation of using total variance estimates to standardize canonical discriminant function coefficients. If standardized coefficients are used to help interpret a discriminant analysis, pooled within-group variance estimates should…
Gamma ray attenuation coefficient measurement for neutron-absorbent materials
NASA Astrophysics Data System (ADS)
Jalali, Majid; Mohammadi, Ali
2008-05-01
The compounds Na 2B 4O 7, H 3BO 3, CdCl 2 and NaCl and their solutions attenuate gamma rays in addition to neutron absorption. These compounds are widely used in the shielding of neutron sources, reactor control and neutron converters. Mass attenuation coefficients of gamma related to the four compounds aforementioned, in energies 662, 778.9, 867.38, 964.1, 1085.9, 1173, 1212.9, 1299.1,1332 and 1408 keV, have been determined by the γ rays transmission method in a good geometry setup; also, these coefficients were calculated by MCNP code. A comparison between experiments, simulations and Xcom code has shown that the study has potential application for determining the attenuation coefficient of various compound materials. Experiment and computation show that H 3BO 3 with the lowest average Z has the highest gamma ray attenuation coefficient among the aforementioned compounds.
Enhanced squeezing by absorption
NASA Astrophysics Data System (ADS)
Grünwald, P.; Vogel, W.
2016-04-01
Absorption is usually expected to be detrimental to quantum coherence effects. However, there have been few studies into the situation for complex absorption spectra. We consider the resonance fluorescence of excitons in a semiconductor quantum well. The creation of excitons requires absorption of the incoming pump-laser light. Thus, the absorption spectrum of the medium acts as a spectral filter for the emitted light. Surprisingly, absorption can even improve quantum effects, as is demonstrated for the squeezing of the resonance fluorescence of the quantum-well system. This effect can be explained by an improved phase matching due to absorption.
Absorption refrigeration machine driven by solar heat
NASA Astrophysics Data System (ADS)
Keizer, C.; Liem, S. H.
1980-04-01
A mathematical model of a single and a two stage solar absorption refrigeration system is developed in which data of collectors and weather data can be implicated. The influence of the generator, the absorber efficiencies, and the cooling temperature on the coefficient of performance (COP) of a single and two stage absorption refrigeration process are investigated. For low generator temperatures the absorber efficiency has more influence on COP than the generator efficiency. Only spectral selective double window and high performance collectors can be used for air cooled solar absorption refrigeration systems at an evaporator temperature of -5 C. It is concluded that a water cooled solar absorption refrigeration system in combination with a solar tapwater installation for household use can be achieved with 6 to 8 square meters high performance collector area.
Radiative properties of the background aerosol: absorption component of extinction.
Clarke, A D; Charlson, R J
1985-07-19
The light-scattering and light-absorption coefficients of the global background aerosol define its single-scatter albedo. Continuous, simultaneous measurements of these optical coefficients were made on a daily basis for the remote marine mid-troposphere; such measurements are essential for assessment of the effects of aerosol on atmospheric radiative transfer. Measurements of light-absorption coefficients made at the Mauna Loa Observatory in Hawaii were higher than expected, and the single-scatter albedo was lower than the value often used in radiative transfer models. Soot appears to be the most likely primary absorber, and hemispheric dispersal of this combustion-derived material is suggested. PMID:17759145
Conversion coefficients of the isomeric state in {sup 72}Br
Briz, J. A.; Borge, M. J. G.; Maira, A.; Perea, A.; Tengblad, O.; Agramunt, J.; Algora, A.; Estevez, E.; Nacher, E.; Rubio, B.; Fraile, L. M.; Deo, A.; Farrelly, G.; Gelletly, W.; Podolyak, Z.
2010-04-26
In order to determine the Gamow-Teller strength distribution for the N Z nucleus {sup 72}Kr an experiment was performed with a Total Absorption Gamma Spectrometer. To fully accomplish this task it is crucial to determine the multipolarity of the low energy transitions as the spin-parity of the daughter ground state has been debated. This is done by experimental determination of the conversion coefficients. Preliminary results for the multipolarity and conversion coefficients of the transition connecting the isomeric state at 101 keV with the {sup 72}Br ground state are presented.
... this page: //medlineplus.gov/ency/article/003606.htm D-xylose absorption To use the sharing features on this page, please enable JavaScript. D-xylose absorption is a laboratory test to determine ...
Ultraviolet (250-550 nm) absorption spectrum of pure water.
Mason, John D; Cone, Michael T; Fry, Edward S
2016-09-01
Data for the spectral light absorption of pure water from 250 to 550 nm have been obtained using an integrating cavity made from a newly developed diffuse reflector with a very high UV reflectivity. The data provide the first scattering-independent measurements of absorption coefficients in the spectral gap between well-established literature values for the absorption coefficients in the visible (>400 nm) and UV (<200 nm). A minimum in the absorption coefficient has been observed in the UV at 344 nm; the value is 0.000811±0.000227 m^{-1}. PMID:27607297
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.
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.
Fuel Temperature Coefficient of Reactivity
Loewe, W.E.
2001-07-31
A method for measuring the fuel temperature coefficient of reactivity in a heterogeneous nuclear reactor is presented. The method, which is used during normal operation, requires that calibrated control rods be oscillated in a special way at a high reactor power level. The value of the fuel temperature coefficient of reactivity is found from the measured flux responses to these oscillations. Application of the method in a Savannah River reactor charged with natural uranium is discussed.
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.
NASA Astrophysics Data System (ADS)
Li, H.; Chang, C.; Cheng, H. H.; Sun, G.; Soref, R. A.
2016-05-01
We report an investigation on the absorption mechanism of a GeSn photodetector with 2.4% Sn composition in the active region. Responsivity is measured and absorption coefficient is calculated. Square root of absorption coefficient linearly depends on photon energy indicating an indirect transition. However, the absorption coefficient is found to be at least one order of magnitude higher than that of most other indirect materials, suggesting that the indirect optical absorption transition cannot be assisted only by phonon. Our analysis of absorption measurements by other groups on the same material system showed the values of absorption coefficient on the same order of magnitude. Our study reveals that the strong enhancement of absorption for the indirect optical transition is the result of alloy disorder from the incorporation of the much larger Sn atoms into the Ge lattice that are randomly distributed.
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.
Metrics for comparison of crystallographic maps
Urzhumtsev, Alexandre; Afonine, Pavel V.; Lunin, Vladimir Y.; Terwilliger, Thomas C.; Adams, Paul D.
2014-10-01
Numerical comparison of crystallographic contour maps is used extensively in structure solution and model refinement, analysis and validation. However, traditional metrics such as the map correlation coefficient (map CC, real-space CC or RSCC) sometimes contradict the results of visual assessment of the corresponding maps. This article explains such apparent contradictions and suggests new metrics and tools to compare crystallographic contour maps. The key to the new methods is rank scaling of the Fourier syntheses. The new metrics are complementary to the usual map CC and can be more helpful in map comparison, in particular when only some of their aspects, such as regions of high density, are of interest.
Definition and analysis of the lineshape matching coefficient in diode-pumped alkali vapor lasers
NASA Astrophysics Data System (ADS)
Shen, Binglin; Pan, Bailiang; Yang, Jing; Qian, Aiqing; Jiao, Jian
2014-12-01
For diode-pumped alkali lasers (DPALs), the matching of lineshape between D2 absorption line and pump light greatly affects the properties of laser output; however, there is rare theoretical study on the quantitative description of the lineshape matching coefficient. In this paper, we put forward a formula to describe the lineshape matching coefficient that represents the matching degree between D2 absorption line and pump light. Dependences of the matching coefficient and optical-optical efficiency on the linewidth ratio between D2 absorption line and pump light, and the center frequency shift of pump light caused by mode hopping are calculated and compared with experimental results in literatures. Results show the definition of lineshape matching coefficient can provide an effective way to improve the pump efficiency of DPALs.
Formaldehyde Absorption toward W51
Kogut, A.; Smoot, G.F.; Bennett, C.L.; Petuchowski, S.J.
1988-04-01
We have measured formaldehyde (H{sub 2}CO) absorption toward the HII region complex W51A (G49.5-0.4) in the 6 cm and 2 cm wavelength rotational transitions with angular resolution of approximately 4 inch. The continuum HII region shows a large, previously undetected shell structure 5.5 pc along the major axis. We observe no H{sub 2}CO emission in regions of low continuum intensity. The absorption, converted to optical depth, shows a higher degree of clumping than previous maps at lower resolution. The good S/N of the maps allows accurate estimation of the complicated line profiles, showing some of the absorbing clouds to be quite patchy. We list the properties of the opacity spectra for a number of positions both in the clumps and in the more diffuse regions of the absorbing clouds, and derive column densities for the 1{sub 11} and 2{sub 12} rotational levels of ortho-formaldehyde.
Experimental study of the light absorption in sea water by thermal lens spectroscopy
NASA Astrophysics Data System (ADS)
Velásquez, A.; Sira, E.; Silva, S.; Cabrera, H.
2016-01-01
Thermal lens spectroscopy is well known as highly sensitive technique enabling measurements of low absorption and concentration determination of various compounds. The optical absorption coefficients of doubly distilled water and samples of water from different places of the open Ocean and different coastal regions have been measured at 532.8 nm wavelength using this technique. The method enables sensitive, rapid and reproducible determination of small variations of the absorption coefficient which are related with small trace contaminations in sea water.
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.
NASA Technical Reports Server (NTRS)
Van Der Meer, Freek D.
1994-01-01
High-spectral resolution images (AVIRIS) of the cuprite mining area were used to evaluate atmospheric calibration algorithms and test several mineral mapping techniques. Four scene normalization techniques were used: (1) the flat-field method, (2) the internal average reflectance method, (3) the empirical line method, and (4) the atmospheric absorption removal method (ATREM). The algorithms were evaluated in terms of their spectral interpret- ability and their ability to remove both solar irradiance and atmospheric absorption features, noise, and artifacts. Noise was quantified by calculating the coefficient of variation of the spectra, and spectral interpretability was quantified by calcu- lating a difference spectrum (eg, laboratory spectrum minus pixel spectrum) for areas with known occurrences of clay minerals. These difference spectra were useful in evaluating the degree of removal of atmospheric features. The empirical line method produced the best calibration results. Mineral mapping as done using (1) color-composites of bands on the shoulders and centers of expected absorption features, (2) color-coded spectra, and (3) spectral angle mapping.
NASA Astrophysics Data System (ADS)
Tripathi, Suvagata
The infrared region of electromagnetic radiation is attractive for communication applications as the scattering is lower compared to that in the visible spectrum. Infrared lasers are widely used in bar-code scanners, laser rangefinders and topology mapping applications. Typically, the direction of a laser beam is altered by mechanically moving a mirror or a lens. But this process can impose severe limitations on critical performance parameters (longevity, precision, response time etc.) of the device. Thus, electro-optic control of the direction of the beam is highly desired. Commercial liquid crystals (LCs) are less than ideal for this purpose because they almost invariably have several absorption bands in the infrared region. For example, several absorption bands exist in the mid-infrared region (3-5 mum) due to common structure features found in LCs such as CH, CH 2, CH3 and CN. In the off-resonance regions, the baseline absorption coefficient can take very high value (up to alpha ~10/cm). This absorption loss becomes especially significant if the optical path is long. As the molecular vibration frequency (o) depends upon the spring constant (kappa) and the effective mass (m) of a diatomic group by the equation = √(kappa/m), replacement of hydrogen atoms in a molecule with heavier atoms can shift the absorptions to the far infrared region, thus making the midwave infrared region more transparent. Another strategy has been to develop high birefringence LCs so that lower liquid crystal cell gap can be used, thus minimizing the absorption loss due to the LC layer. But most of these materials have problems with UV stability. In the scope of this thesis, several strategies are investigated to mitigate the absorption loss in the midwave infrared region. The ultimate goal of this thesis is to develop LCs that will have both high birefringence and low absorption properties in the midwave-infrared region. Another goal of the thesis is to develop materials for
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.
Third Order Elastic Coefficients of Rocks
NASA Astrophysics Data System (ADS)
Bandyopadhyay, K.
2006-12-01
We present a methodology to determine third order elastic (TOE) coefficients of rock from velocity measurements at different hydrostatic stress level. TOE coefficients help us to obtain a quantitative measure of the variation of velocity with stress. It is one of the most general ways to parameterize the stress sensitivity of rocks. We usually determine the isotropic TOE coefficients from measurements of all the independent stiffness elements under non-hydrostatic stress. However, for initially isotropic or weakly anisotropic rocks, most of the laboratory experiments are carried out under hydrostatic stress. In that case, the measurements of P- and S-wave velocities at different hydrostatic pressure alone are not enough to invert for the isotropic TOE parameters. In this underdetermined situation, more information about the rock microstructure causing the non-linearity is required to predict seismic velocities at any arbitrary stress state. Our workflow is based on the model of Mavko et al. (1995) to compute stress-induced anisotropy. This model assumes that the cause of elastic nonlinearity is the presence of compliant crack-like pore. The pressure dependence of generalized compliances is mainly governed by normal tractions resolved across cracks. This assumption allows one to map the pressure dependence from hydrostatic stress to any state of stress. Applying the model of Mavko et al. (1995), we obtain the full stiffness tensor at different non-hydrostatic stress levels from the usual Vp and Vs measurements. Changes in elastic stiffness elements from a reference state of stress are then used to invert for the TOE coefficients, C111, C112 and C123 using the third order stress- strain relations. This method allows us to compute the TOE elements using hydrostatic measurements of an initially isotropic rock. We show an application of the workflow with laboratory measurements of P- and S-wave velocities under varying hydrostatic stress. This enables us to express
Transport coefficients of heavy baryons
NASA Astrophysics Data System (ADS)
Tolos, Laura; Torres-Rincon, Juan M.; Das, Santosh K.
2016-08-01
We compute the transport coefficients (drag and momentum diffusion) of the low-lying heavy baryons Λc and Λb in a medium of light mesons formed at the later stages of high-energy heavy-ion collisions. We employ the Fokker-Planck approach to obtain the transport coefficients from unitarized baryon-meson interactions based on effective field theories that respect chiral and heavy-quark symmetries. We provide the transport coefficients as a function of temperature and heavy-baryon momentum, and analyze the applicability of certain nonrelativistic estimates. Moreover we compare our outcome for the spatial diffusion coefficient to the one coming from the solution of the Boltzmann-Uehling-Uhlenbeck transport equation, and we find a very good agreement between both calculations. The transport coefficients for Λc and Λb in a thermal bath will be used in a subsequent publication as input in a Langevin evolution code for the generation and propagation of heavy particles in heavy-ion collisions at LHC and RHIC energies.
NASA Astrophysics Data System (ADS)
Bek, R.; Steeb, S.
1981-02-01
Using the pulse-echo method the ultrasonic velocity and absorption was measured with Bi-In-melts in the temperature range from liquidus up to more than 600 °C. The frequencies used reached from 10 MHz up to 130 MHz. Within the experimental accuracy no frequency dependence of the absorption coefficient α/f2 could be detected. An excess absorption can be observed, which for the molten elements can be explained by fluctuations of the packing density. For the molten alloys additionally concentration fluctuations play an important role. Thus an understanding of the temperature dependency of the ultrasonic velocity and absorption can be achieved.
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.
Analysis of internal conversion coefficients
Coursol; Gorozhankin; Yakushev; Briancon; Vylov
2000-03-01
An extensive database has been assembled that contains the three most widely used sets of calculated internal conversion coefficients (ICC): [Hager R.S., Seltzer E.C., 1968. Internal conversion tables. K-, L-, M-shell Conversion coefficients for Z = 30 to Z = 103, Nucl. Data Tables A4, 1-237; Band I.M., Trzhaskovskaya M.B., 1978. Tables of gamma-ray internal conversion coefficients for the K-, L- and M-shells, 10 < or = Z < or = 104, Special Report of Leningrad Nuclear Physics Institute; Rosel F., Fries H.M., Alder K., Pauli H.C., 1978. Internal conversion coefficients for all atomic shells, At. Data Nucl. Data Tables 21, 91-289] and also includes new Dirac Fock calculations [Band I.M. and Trzhaskovskaya M.B., 1993. Internal conversion coefficients for low-energy nuclear transitions, At. Data Nucl. Data Tables 55, 43-61]. This database is linked to a computer program to plot ICCs and their combinations (sums and ratios) as a function of Z and energy, as well as relative deviations of ICC or their combinations for any pair of tabulated data. Examples of these analyses are presented for the K-shell and total ICCs of the gamma-ray standards [Hansen H.H., 1985. Evaluation of K-shell and total internal conversion coefficients for some selected nuclear transitions, Eur. Appl. Res. Rept. Nucl. Sci. Tech. 11.6 (4) 777-816] and for the K-shell and total ICCs of high multipolarity transitions (total, K-, L-, M-shells of E3 and M3 and K-shell of M4). Experimental data sets are also compared with the theoretical values of these specific calculations. PMID:10724406
Repasky, Kevin
2014-03-31
A scanning differential absorption lidar (DIAL) instrument for monitoring carbon dioxide has been developed. The laser transmitter uses two tunable discrete mode laser diodes (DMLD) operating in the continuous wave (cw) mode with one locked to the online absorption wavelength and the other operating at the offline wavelength. Two in-line fiber optic switches are used to switch between online and offline operation. After the fiber optic switch, an acousto- optic modulator (AOM) is used to generate a pulse train used to injection seed an erbium doped fiber amplifier (EDFA) to produce eye-safe laser pulses with maximum pulse energies of 66 {micro}J, a pulse repetition frequency of 15 kHz, and an operating wavelength of 1.571 {micro}m. The DIAL receiver uses a 28 cm diameter Schmidt-Cassegrain telescope to collect that backscattered light, which is then monitored using a photo-multiplier tube (PMT) module operating in the photon counting mode. The DIAL instrument has been operated from a laboratory environment on the campus of Montana State University, at the Zero Emission Research Technology (ZERT) field site located in the agricultural research area on the western end of the Montana State University campus, and at the Big Sky Carbon Sequestration Partnership site located in north-central Montana. DIAL data has been collected and profiles have been validated using a co-located Licor LI-820 Gas Analyzer point sensor.
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.
ABSORPTION OF p MODES BY THIN MAGNETIC FLUX TUBES
Jain, Rekha; Hindman, Bradley W.; Braun, Doug C.; Birch, Aaron C.
2009-04-10
We study the interaction between p modes and the many magnetic fibrils that lace the solar convection zone. In particular, we investigate the resulting absorption of p-mode energy by the fibril magnetic field. Through mechanical buffeting, the p modes excite tube waves on the magnetic fibrils-in the form of longitudinal sausage waves and transverse kink waves. The tube waves propagate up and down the magnetic fibrils and out of the p-mode cavity, thereby removing energy from the incident acoustic waves. We compute the absorption coefficient associated with this damping mechanism and model the absorption that would be observed for magnetic plage. We compare our results to the absorption coefficient that is measured using the local-helioseismic technique of ridge-filtered holography. We find that, depending on the mode order and the photospheric boundary conditions, we can achieve absorption coefficients for simulated plage that exceed 50%. The observed increase of the absorption coefficient as a function of frequency is reproduced for all model parameters.
NASA Astrophysics Data System (ADS)
Wu, Di; Chen, Maosi; Wang, Qiao; Gao, Wei
2013-12-01
Blue algae and green algae are the dominant phytoplankton groups that contribute to the eutrophication and the water bloom in inland water of China. The absorption coefficients (spectra) of the algae, which do not change with its intrinsic optical characteristics and the observation geometry, are strictly additive quantities. The characteristics of the absorption spectra of the two algae are presented. The pure blue algae and the pure green algae cultured in the laboratory environment are diluted and mixed at ten volume ratios. The Quantitative Filter Technique was applied to measure their absorption spectra. The "hot-ethanol extraction" method was chosen to calculate their concentration of Chlorophyll a. The retrieval algorithm developed in this study extracts the mapping information between each individual alga and their Chlorophyll a concentration via Continuous Wavelet Transform, and retrieves the Chlorophyll a concentration of each alga in their mixture using a trust region optimizer. The results show that the retrieved and the measured Chlorophyll a concentrations of the blue algae and the green algae components in the ten mixture match well with the average relative error of 5.55%.
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.
ERIC Educational Resources Information Center
Day, Dennis
1994-01-01
Explains a social studies lesson for third graders that uses KidPix, a computer software graphics program to help students make maps and map keys. Advantages to using the computer versus hand drawing maps are discussed, and an example of map requirements for the lesson is included. (LRW)
ERIC Educational Resources Information Center
Callison, Daniel
2001-01-01
Explains concept mapping as a heuristic device that is helpful in visualizing the relationships between and among ideas. Highlights include how to begin a map; brainstorming; map applications, including document or information summaries and writing composition; and mind mapping to strengthen note-taking. (LRW)
NASA Astrophysics Data System (ADS)
Chang, Cheng; Xu, Wei; Chen-Wiegart, Yu-chen Karen; Wang, Jun; Yu, Dantong
2013-12-01
X-ray Absorption Near Edge Structure (XANES) imaging, an advanced absorption spectroscopy technique, at the Transmission X-ray Microscopy (TXM) Beamline X8C of NSLS enables high-resolution chemical mapping (a.k.a. chemical composition identification or chemical spectra fitting). Two-Dimensional (2D) chemical mapping has been successfully applied to study many functional materials to decide the percentages of chemical components at each pixel position of the material images. In chemical mapping, the attenuation coefficient spectrum of the material (sample) can be fitted with the weighted sum of standard spectra of individual chemical compositions, where the weights are the percentages to be calculated. In this paper, we first implemented and compared two fitting approaches: (i) a brute force enumeration method, and (ii) a constrained least square minimization algorithm proposed by us. Next, as 2D spectra fitting can be conducted pixel by pixel, so theoretically, both methods can be implemented in parallel. In order to demonstrate the feasibility of parallel computing in the chemical mapping problem and investigate how much efficiency improvement can be achieved, we used the second approach as an example and implemented a parallel version for a multi-core computer cluster. Finally we used a novel way to visualize the calculated chemical compositions, by which domain scientists could grasp the percentage difference easily without looking into the real data.
NASA Technical Reports Server (NTRS)
1995-01-01
In the early 1990s, the Ohio State University Center for Mapping, a NASA Center for the Commercial Development of Space (CCDS), developed a system for mobile mapping called the GPSVan. While driving, the users can map an area from the sophisticated mapping van equipped with satellite signal receivers, video cameras and computer systems for collecting and storing mapping data. George J. Igel and Company and the Ohio State University Center for Mapping advanced the technology for use in determining the contours of a construction site. The new system reduces the time required for mapping and staking, and can monitor the amount of soil moved.
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…
Prediction of stream volatilization coefficients
Rathbun, Ronald E.
1990-01-01
Equations are developed for predicting the liquid-film and gas-film reference-substance parameters for quantifying volatilization of organic solutes from streams. Molecular weight and molecular-diffusion coefficients of the solute are used as correlating parameters. Equations for predicting molecular-diffusion coefficients of organic solutes in water and air are developed, with molecular weight and molal volume as parameters. Mean absolute errors of prediction for diffusion coefficients in water are 9.97% for the molecular-weight equation, 6.45% for the molal-volume equation. The mean absolute error for the diffusion coefficient in air is 5.79% for the molal-volume equation. Molecular weight is not a satisfactory correlating parameter for diffusion in air because two equations are necessary to describe the values in the data set. The best predictive equation for the liquid-film reference-substance parameter has a mean absolute error of 5.74%, with molal volume as the correlating parameter. The best equation for the gas-film parameter has a mean absolute error of 7.80%, with molecular weight as the correlating parameter.
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.
Estimating the Polyserial Correlation Coefficient.
ERIC Educational Resources Information Center
Bedrick, Edward J.; Breslin, Frederick C.
1996-01-01
Simple noniterative estimators of the polyserial correlation coefficient are developed by exploiting a general relationship between the polyserial correlation and the point polyserial correlation to give extensions of the biserial estimators of K. Pearson (1909), H. E. Brogden (1949), and F. M. Lord (1963) to the multicategory setting. (SLD)
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.
Super-Resonant Intracavity Coherent Absorption
Malara, P.; Campanella, C. E.; Giorgini, A.; Avino, S.; De Natale, P.; Gagliardi, G.
2016-01-01
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. PMID:27364475
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 %.
Heat exchange model in absorption chamber of water-direct-absorption-typed laser energy meter
NASA Astrophysics Data System (ADS)
Feng Wei, Ji; Qun Sun, Li; Zhang, Kai; Hu, XiaoYang; Zhou, Shan
2015-04-01
The interaction between laser and water flow is very complicated in the absorption chamber of a high energy laser (HEL) energy meter which directly uses water as an absorbing medium. Therefore, the heat exchange model cannot be studied through traditional methods, but it is the most important factor to improve heat exchange efficiency in the absorption chamber. After the exchanges of heat and mass were deeply analyzed, experimental study and numerical fitting were brought out. The original testing data of laser power and water flow temperature at one moment were utilized to calculate those at the next moment, and then the calculated temperature curve was compared with the measured one. If the two curves matched well, the corresponding coefficient was obtained. Meanwhile, numerous experiments were performed to study the effects of laser power, duration, focal spot scale, and water flow rate on heat exchange coefficient. In addition, the relationship between water phase change and heat exchange was analyzed. The heat exchange coefficient was increased by optimizing the construction of the absorption chamber or increasing water flow rate. The results provide the reference for design of water-direct-absorption-typed HEL energy meters, as well as for analysis of the interaction between other similar lasers and water flow.
Multi-parameter optical image interpretations based on self-organizing mapping
NASA Astrophysics Data System (ADS)
Klose, Christian D.; Klose, A. K.; Netz, U.; Scheel, A.; Beuthan, J.; Hielscher, Andreas H.
2008-02-01
We found that using more than one parameter derived from optical tomographic images can lead to better image classification results compared to cases when only one parameter is used.. In particular we present a multi-parameter classification approach, called self-organizing mapping (SOM), for detecting synovitis in arthritic finger joints based on sagittal laser optical tomography (SLOT). This imaging modality can be used to determine various physical parameters such as minimal absorption and scattering coefficients in an image of the proximal interphalengeal joint. Results were compared to different gold standards: magnet resonance imaging, ultra-sonography and clinical evaluation. When compared to classifications based on single-parameters, e.g., absorption minimum only, the study reveals that multi-parameter classifications lead to higher classification sensitivities and specificities and statistical significances with p-values <5 per cent. Finally, the data suggest that image analyses are more reliable and avoid ambiguous interpretations when using more than one parameter.
Aerosol optical absorption measurements with photoacoustic spectroscopy
NASA Astrophysics Data System (ADS)
Liu, Kun; Wang, Lei; Liu, Qiang; Wang, Guishi; Tan, Tu; Zhang, Weijun; Chen, Weidong; Gao, Xiaoming
2015-04-01
Many parameters related to radiative forcing in climate research are known only with large uncertainties. And one of the largest uncertainties in global radiative forcing is the contribution from aerosols. Aerosols can scatter or absorb the electromagnetic radiation, thus may have negative or positive effects on the radiative forcing of the atmosphere, respectively [1]. And the magnitude of the effect is directly related to the quantity of light absorbed by aerosols [2,3]. Thus, sensitivity and precision measurement of aerosol optical absorption is crucial for climate research. Photoacoustic spectroscopy (PAS) is commonly recognized as one of the best candidates to measure the light absorption of aerosols [4]. A PAS based sensor for aerosol optical absorption measurement was developed. A 532 nm semiconductor laser with an effective power of 160 mW was used as a light source of the PAS sensor. The PAS sensor was calibrated by using known concentration NO2. The minimum detectable optical absorption coefficient (OAC) of aerosol was determined to be 1 Mm-1. 24 hours continues measurement of OAC of aerosol in the ambient air was carried out. And a novel three wavelength PAS aerosol OAC sensor is in development for analysis of aerosol wavelength-dependent absorption Angstrom coefficient. Reference [1] U. Lohmann and J. Feichter, Global indirect aerosol effects: a review, Atmos. Chem. Phys. 5, 715-737 (2005) [2] M. Z. Jacobson, Strong radiative heating due to the mixing state of black carbon in atmospheric aerosols, Nature 409, 695-697 (2001) [3] V. Ramanathan and G. Carmichae, Global and regional climate changes due to black carbon, nature geoscience 1, 221-227 (2008) [4] W.P Arnott, H. Moosmuller, C. F. Rogers, T. Jin, and R. Bruch, Photoacoustic spectrometer for measuring light absorption by aerosol: instrument description. Atmos. Environ. 33, 2845-2852 (1999).
Optical absorption in ion-implanted lead lanthanum zirconate titanate ceramics
Seager, C.H.; Land, C.E.
1984-08-15
Optical absorption measurements have been performed on unmodified and on ion-implanted lead lanthanum zirconate titanate ceramics using the photothermal deflection spectroscopy technique. Bulk absorption coefficients depend on the average grain size of the material while the absorption associated with the ion-damaged layers does not. The damage-induced surface absorptance correlates well with the photosensitivity observed in implanted PLZT devices, supporting earlier models for the enhanced imaging efficiency of the materials.
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.
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.
NASA Astrophysics Data System (ADS)
Gu, S. Q.; Taylor, P. C.; Nitta, S.
1991-08-01
We have used the photoluminescence (PL) generated in a thin-film sample of a-Si:H to probe low absorption levels by measuring the absorption of the PL as it travels down the length of the film in a waveguide mode. This technique, which we have called PL absorption spectroscopy of PLAS, allows the measurement of values of the absorption coefficient α down to about 0.1 cm-1. Because this technique probes the top and bottom surfaces of the a-Si:H sample, it is important to separate surface from bulk absorption mechanisms. An improved sample geometry has been employed to facilitate this separation. One sample consisted of an a-Si1-xNix:H/a-Si:H/ a-Si1-xNx:H/NiCr layered structure where the silicon nitride layers served as the cladding layers for the waveguide. In a second sample the a-Si:H layer was interrupted near the middle for two separate, thin (100 Å) layers of a-Si1-xNx:H in order to check for the importance of the absorption at the silicon/silicon nitride interfaces in these PLAS measurements. Changes in the below-gap absorption on light soaking were examined using irradiation from an Ar+ laser (5145 Å, ˜200 mW/cm2 for 5.5 hours at 300 K). The silicon/silicon nitride interface is responsible for an absorption which has a shoulder near 1.2 eV while the bulk a-Si:H absorption exhibits no such shoulder. The metastable, optically-induced increase in the below gap absorption appears to come entirely from the bulk of the a-Si:H. These low temperature PLAS measurements are compared with those obtained at 300 K by photothermal deflection spectroscopy.
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
Petawatt laser absorption bounded
NASA Astrophysics Data System (ADS)
Levy, Matthew C.; Wilks, Scott C.; Tabak, Max; Libby, Stephen B.; Baring, Matthew G.
2014-06-01
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.
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
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.
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.
Percutaneous absorption of drugs.
Wester, R C; Maibach, H I
1992-10-01
The skin is an evolutionary masterpiece of living tissue which is the final control unit for determining the local and systemic availability of any drug which must pass into and through it. In vivo in humans, many factors will affect the absorption of drugs. These include individual biological variation and may be influenced by race. The skin site of the body will also influence percutaneous absorption. Generally, those body parts exposed to the open environment (and to cosmetics, drugs and hazardous toxic substances) are most affected. Treating patients may involve single daily drug treatment or multiple daily administration. Finally, the body will be washed (normal daily process or when there is concern about skin decontamination) and this will influence percutaneous absorption. The vehicle of a drug will affect release of drug to skin. On skin, the interrelationships of this form of administration involve drug concentration, surface area exposed, frequency and time of exposure. These interrelationships determine percutaneous absorption. Accounting for all the drug administered is desirable in controlled studies. The bioavailability of the drug then is assessed in relationship to its efficacy and toxicity in drug development. There are methods, both quantitative and qualitative, in vitro and in vivo, for studying percutaneous absorption of drugs. Animal models are substituted for humans to determine percutaneous absorption. Each of these methods thus becomes a factor in determining percutaneous absorption because they predict absorption in humans. The relevance of these predictions to humans in vivo is of intense research interest. The most relevant determination of percutaneous absorption of a drug in humans is when the drug in its approved formulation is applied in vivo to humans in the intended clinical situation. Deviation from this scenario involves the introduction of variables which may alter percutaneous absorption. PMID:1296607
Ionization coefficients in gas mixtures
NASA Astrophysics Data System (ADS)
Marić, D.; Šašić, O.; Jovanović, J.; Radmilović-Rađenović, M.; Petrović, Z. Lj.
2007-03-01
We have tested the application of the common E/N ( E—electric field, N—gas number density) or Wieland approximation [Van Brunt, R.J., 1987. Common parametrizations of electron transport, collision cross section, and dielectric strength data for binary gas mixtures. J. Appl. Phys. 61 (5), 1773-1787.] and the common mean energy (CME) combination of the data for pure gases to obtain ionization coefficients for mixtures. Test calculations were made for Ar-CH4, Ar-N2, He-Xe and CH4-N2 mixtures. Standard combination procedure gives poor results in general, due to the fact that the electron energy distribution is considerably different in mixtures and in individual gases at the same values of E/N. The CME method may be used for mixtures of gases with ionization coefficients that do not differ by more than two orders of magnitude which is better than any other technique that was proposed [Marić, D., Radmilović-Rađenović, M., Petrović, Z.Lj., 2005. On parametrization and mixture laws for electron ionization coefficients. Eur. Phys. J. D 35, 313-321.].
Geoghegan, Patrick J; Shen, Bo; Keinath, Christopher M.; Garrabrant, Michael A.
2016-01-01
Commercial hot water heating accounts for approximately 0.78 Quads of primary energy use with 0.44 Quads of this amount from natural gas fired heaters. An ammonia-water based commercial absorption system, if fully deployed, could achieve a high level of savings, much higher than would be possible by conversion to the high efficiency nonheat-pump gas fired alternatives. In comparison with air source electric heat pumps, the absorption system is able to maintain higher coefficients of performance in colder climates. The ammonia-water system also has the advantage of zero Ozone Depletion Potential and low Global Warming Potential. A thermodynamic model of a single effect ammonia-water absorption system for commercial space and water heating was developed, and its performance was investigated for a range of ambient and return water temperatures. This allowed for the development of a performance map which was then used in a building energy modeling software. Modeling of two commercial water heating systems was performed; one using an absorption heat pump and another using a condensing gas storage system. The energy and financial savings were investigated for a range of locations and climate zones in the southern and south central United States. A follow up paper will analyze northern and north/central regions. Results showed that the system using an absorption heat pump offers significant savings.
Effect of noise on the standard mapping
Karney, C.F.F.; Rechester, A.B.; White, R.B.
1981-03-01
The effect of a small amount of noise on the standard mapping is considered. Whenever the standard mapping possesses accelerator models (where the action increases approximately linearly with time), the diffusion coefficient contains a term proportional to the reciprocal of the variance of the noise term. At large values of the stochasticity parameter, the accelerator modes exhibit a universal behavior. As a result the dependence of the diffusion coefficient on stochasticity parameter also shows some universal behavior.
Analytic expressions for ULF wave radiation belt radial diffusion coefficients
Ozeke, Louis G; Mann, Ian R; Murphy, Kyle R; Jonathan Rae, I; Milling, David K
2014-01-01
We present analytic expressions for ULF wave-derived radiation belt radial diffusion coefficients, as a function of L and Kp, which can easily be incorporated into global radiation belt transport models. The diffusion coefficients are derived from statistical representations of ULF wave power, electric field power mapped from ground magnetometer data, and compressional magnetic field power from in situ measurements. We show that the overall electric and magnetic diffusion coefficients are to a good approximation both independent of energy. We present example 1-D radial diffusion results from simulations driven by CRRES-observed time-dependent energy spectra at the outer boundary, under the action of radial diffusion driven by the new ULF wave radial diffusion coefficients and with empirical chorus wave loss terms (as a function of energy, Kp and L). There is excellent agreement between the differential flux produced by the 1-D, Kp-driven, radial diffusion model and CRRES observations of differential electron flux at 0.976 MeV—even though the model does not include the effects of local internal acceleration sources. Our results highlight not only the importance of correct specification of radial diffusion coefficients for developing accurate models but also show significant promise for belt specification based on relatively simple models driven by solar wind parameters such as solar wind speed or geomagnetic indices such as Kp. Key Points Analytic expressions for the radial diffusion coefficients are presented The coefficients do not dependent on energy or wave m value The electric field diffusion coefficient dominates over the magnetic PMID:26167440
The Impact of Eddy and Roughness Coefficients in Tsunami Modeling
NASA Astrophysics Data System (ADS)
Gayer, Gerhard; Leschka, Stefan
2010-05-01
Within the German-Indonesian Tsunami Early Warning System (GITEWS) project the German Research Centre Geesthacht (GKSS) and DHI-WASY investigated the impact of tsunamis in densely populated coastal areas of Indonesia. By performing hundreds of numerical simulations in three highly resolved (~10 m) priority areas, namely Kuta (Bali), Padang (West-Sumatra), and Cilacap (southern coast of Java), we established a scenario data base for the preparation of hazard and risk maps. In preparation for this work we examined the dependency of tsunami modeling results on eddy coefficients and Manning's roughness coefficients. The hydrodynamical models MIKE 21 HD and MIKE 21 BW were applied in 11 artificial set-ups with linearized bathymetries. By varying the coefficients over a large range of physically relevant values we found the impact on tsunami wave heights and run-up heights. For the scenario simulations we used MIKE 21 FM. We shortly present a method of preparing very detailed roughness maps (Manning coefficients assigned to 43 land-use classes) and show comparisons of simulations using this differentiated roughness information with simulations using constant values, the later a widely used approach.
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.
Comparison of absorption after inhalation and instillation of uranium octoxide.
Pellow, P G D; Hodgson, S A; Hodgson, A; Rance, E; Ellender, M; Guilmette, R A; Stradling, G N
2003-01-01
Values for the absorption parameters were compared after inhalation or intratracheal instillation of 1.5 microm mass median aerodynamic diameter (MMAD) 233U3O8 particles into the lungs of HMT strain rats. The two sets of parameter values were similar, as were the calculated dose coefficients and predicted biokinetics for workers. Hence the inhalation and instillation techniques can probably both be used to generate values of the absorption parameters for U3O8. PMID:14526937
A reflectance model for non-contact mapping of venous oxygen saturation using a CCD camera
NASA Astrophysics Data System (ADS)
Li, Jun; Dunmire, Barbrina; Beach, Kirk W.; Leotta, Daniel F.
2013-11-01
A method of non-contact mapping of venous oxygen saturation (SvO2) is presented. A CCD camera is used to image skin tissue illuminated alternately by a red (660 nm) and an infrared (800 nm) LED light source. Low cuff pressures of 30-40 mmHg are applied to induce a venous blood volume change with negligible change in the arterial blood volume. A hybrid model combining the Beer-Lambert law and the light diffusion model is developed and used to convert the change in the light intensity to the change in skin tissue absorption coefficient. A simulation study incorporating the full light diffusion model is used to verify the hybrid model and to correct a calculation bias. SvO2 in the fingers, palm, and forearm for five volunteers are presented and compared with results in the published literature. Two-dimensional maps of venous oxygen saturation are given for the three anatomical regions.
Michael Goodchild recently gave eight reasons why traditional maps are limited as communication devices, and how interactive internet mapping can overcome these limitations. In the past, many authorities in cartography, from Jenks to Bertin, have emphasized the importance of sim...
NASA Astrophysics Data System (ADS)
A wall-sized geological map of Kentucky, the product of 18 years of work, has just been released. Produced by the U.S. Geological Survey (USGS) in cooperation with the Kentucky Geological Survey (KGS) at the University of Kentucky, the map is unique, according to state geologist Donald Haney, because it is the first and only state map ever produced in detailed form from geologic quadrangle maps already available from the KGS.At a scale of 1:250,000, the map shows the surface distribution of various types of rock throughout the state, as well as geologic structure, faults, and surface coal beds. Numerous geologic sections, stratigraphic diagrams, correlation charts, and structure sections accompany the map. Compiled by R. C. McDowell and S. L. Moore of the USGS and by G. J . Grabowski of the KGS, the map was made by photoreducing and generalizing the detailed geologic quadrangle maps.
1994-01-01
Map Adventures, with seven accompanying lessons, is appropriate for grades K-3. Students will learn basic concepts for visualizing objects from different perspectives and how to understand /and use maps.
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.
The temperature dependence of collision-induced absorption by oxygen near 6 microns
NASA Technical Reports Server (NTRS)
Orlando, John J.; Tyndall, Geoffrey S.; Nickerson, Karen E.; Calvert, Jack G.
1991-01-01
Coefficients for oxygen absorption in the infrared induced by collisions with O2 and N2 are reported over the range 1400-1800/cm and 225-356 K. These coefficients are used to calculate the absorption for O2 in air as a function of temperature and wavenumber, and comparisons are made with previous determinations. In addition, structured absorption features superimposed on the broad collision-induced absorption band, which were observed at all temperatures studied, are interpreted in terms of the presence of (O2)2 and O2-N2 van der Waals molecules.
Absorption of infrared radiation by electrons in the field of a neutral hydrogen atom
NASA Technical Reports Server (NTRS)
Stallcop, J. R.
1974-01-01
An analytical expression for the absorption coefficient is developed from a relationship between the cross-section for inverse bremsstrahlung absorption and the cross-section for electron-atom momentum transfer; it is accurate for those photon frequencies v and temperatures such that hv/kT is small. The determination of the absorption of infrared radiation by free-free transitions of the negative hydrogen ion has been extended to higher temperatures. A simple analytical expression for the absorption coefficient has been derived.
Weber, Jessie R.; Cuccia, David J.; Johnson, William R.; Bearman, Gregory H.; Durkin, Anthony J.; Hsu, Mike; Lin, Alexander; Binder, Devin K.; Wilson, Dan; Tromberg, Bruce J.
2011-01-01
We present an approach for rapidly and quantitatively mapping tissue absorption and scattering spectra in a wide-field, noncontact imaging geometry by combining multifrequency spatial frequency domain imaging (SFDI) with a computed-tomography imaging spectrometer (CTIS). SFDI overcomes the need to spatially scan a source, and is based on the projection and analysis of periodic structured illumination patterns. CTIS provides a throughput advantage by simultaneously diffracting multiple spectral images onto a single CCD chip to gather spectra at every pixel of the image, thus providing spatial and spectral information in a single snapshot. The spatial-spectral data set was acquired 30 times faster than with our wavelength-scanning liquid crystal tunable filter camera, even though it is not yet optimized for speed. Here we demonstrate that the combined SFDI-CTIS is capable of rapid, multispectral imaging of tissue absorption and scattering in a noncontact, nonscanning platform. The combined system was validated for 36 wavelengths between 650–1000 nm in tissue simulating phantoms over a range of tissue-like absorption and scattering properties. The average percent error for the range of absorption coefficients (μa) was less than 10% from 650–800 nm, and less than 20% from 800–1000 nm. The average percent error in reduced scattering coefficients (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}\\mu_{\\rm s}^{\\prime}\\end{equation*} \\end{document}μs′) was less than 5% from 650–700 nm and less than 3% from 700–1000 nm. The SFDI-CTIS platform was applied to a mouse model of brain injury in order to demonstrate the utility of this approach in characterizing spatially and spectrally varying tissue optical properties. PMID:21280902
Epidermal melanin absorption in human skin
NASA Astrophysics Data System (ADS)
Norvang Nilsen, Lill T.; Fiskerstrand, Elisanne J.; Nelson, J. Stuart; Berns, Michael W.; Svaasand, Lars O.
1996-01-01
The principle of laser induced selective photothermolysis is to induced thermal damage to specific targets in such a manner that the temperature of the surrounding tissue is maintained below the threshold for thermal damage. The selectivity is obtained by selection of a proper wavelength and pulse duration. The technique is presently being used in the clinic for removal of port-wine stains. The presence of melanin in the epidermal layer can represent a limitation to the selectivity. Melanin absorption drops off significantly with increasing wavelength, but is significant in the entire wavelength region where the blood absorption is high. Treatment of port-wine stain in patients with high skin pigmentation may therefore give overheating of the epidermis, resulting in epidermal necrosis. Melanosomal heating is dependent on the energy and duration of the laser pulse. The heating mechanism for time scales less than typically 1 microsecond(s) corresponds to a transient local heating of the individual melanosomes. For larger time scales, heat diffusion out of the melanosomes become of increased importance, and the temperature distribution will reach a local steady state condition after typically 10 microsecond(s) . For even longer pulse duration, heat diffusing from neighboring melanosomes becomes important, and the temperature rise in a time scale from 100 - 500 microsecond(s) is dominated by this mechanism. The epidermal heating during the typical 450 microsecond(s) pulse used for therapy is thus dependent on the average epidermal melanin content rather than on the absorption coefficient of the individual melanosomes. This study will present in vivo measurements of the epidermal melanin absorption of human skin when exposed to short laser pulses (< 0.1 microsecond(s) ) from a Q-switched ruby laser and with long laser pulses (approximately 500 microsecond(s) ) from a free-running ruby laser or a long pulse length flashlamp pumped dye laser. The epidermal melanin
Asteroid 951 Gaspra Near Infrared Mapping Spectrometer Radiance Data
NASA Astrophysics Data System (ADS)
Granahan, J. C., Jr.
2015-12-01
Five radiance spectra of asteroid 951 Gaspra have been archived in the Small Bodies Node of the NASA Planetary Data System [Granahan, 2014]. The radiance spectra were created from uncalibrated Galileo spacecraft Near Infrared Mapping Spectrometer files archived in the Imaging Node of the NASA Planetary Data System. The NASA Galileo spacecraft observed asteroid 951 Gaspra on October 29, 1991 with the Near Infrared Mapping Spectrometer (NIMS) at wavelengths ranging from 0.7 - 5.2 micrometers [Carlson et al., 1992]. The five radiance spectra consist of two 17, two 100, and one 329 spectral channel data sets. They record data that was acquired by NIMS at ranges between 27232.6 to 14723.8 kilometers from asteroid 951 Gaspra. The uncalibrated NIMS data were converted into radiance spectra using calibration coefficients obtained during the Galileo mission's first Earth encounter on December 8, 1990. The archived radiance spectral data is located at the URL (Universal Record Locator): http://sbn.psi.edu/pds/resource/gaspraspec.html and contains radiance, solar, incidence over flux, and data documentation. This archived data set contains a variety of spectral signatures. These signatures include absorptions near 1.0, 2.0, 2.8, 3.4, and 4.5 micrometers. The 1.0 and 2.0 micrometer features are indicators of olivine and pyroxene on the asteroid surface. The 2.8 micrometer feature has a shape similar to the combined spectra of multiple iron bearing phyllosilicates. The 3.4 micrometer feature is in the same location as absorptions created by a carbon-hydrogen bond. The 4.5 micrometer feature, present only in the 329 channel data set, corresponds in position to absorptions detected in sulfate minerals. Carlson, R. W., et al. (1992) Bull. of the A.A.S., 24, 932. Granahan, J. C. (2014), GO-A-NIMS-3-GASPRASPEC-V1.0, NASA Planetary Data System.
Air broadening coefficients for the ν3 band of hydroperoxyl radicals
NASA Astrophysics Data System (ADS)
Minamida, Maya; Tonokura, Kenichi
2014-11-01
Using mid-infrared laser absorption spectroscopy, we investigated the room-temperature pressure broadening coefficients for hydroperoxyl radicals (HO2) in nitrogen and oxygen over the 1060.0-1065.5 cm-1 range of the ν3 band. The HO2 radicals were produced by flash photolysis of a chlorine/1,4-cyclohexadiene/oxygen mixture. The 20 measured absorption profiles were analyzed with Voigt functions. Air broadening coefficients were estimated from the nitrogen- and oxygen-broadening results and compared with previous results. We discuss the dependence of air broadening on rotational states.
Compounds affecting cholesterol absorption
NASA Technical Reports Server (NTRS)
Hua, Duy H. (Inventor); Koo, Sung I. (Inventor); Noh, Sang K. (Inventor)
2004-01-01
A class of novel compounds is described for use in affecting lymphatic absorption of cholesterol. Compounds of particular interest are defined by Formula I: ##STR1## or a pharmaceutically acceptable salt thereof.
Grossman, Gershon
1984-01-01
The efficiency of an absorption heat pump system is improved by conducting liquid from a second stage evaporator thereof to an auxiliary heat exchanger positioned downstream of a primary heat exchanger in the desorber of the system.
Grossman, G.
1982-06-16
The efficiency of an absorption heat pump system is improved by conducting liquid from a second stage evaporator thereof to an auxiliary heat exchanger positioned downstream of a primary heat exchanger in the desorber of the system.
Hellier, M. D.; Holdsworth, C. D.; McColl, I.; Perrett, D.
1972-01-01
A quantitative perfusion method has been used to study intestinal absorption of two dipeptides—glycyl-glycine and glycyl-l-alanine—in normal subjects. In each case, the constituent amino acids were absorbed faster when presented as dipeptides than as free amino acids, suggesting intact dipeptide transport. During absorption constituent amino acids were measured within the lumen and it is suggested that these represent amino acids which have diffused back to the lumen after absorption as dipeptide. Portal blood analyses during absorption of a third dipeptide, glycyl-l-lysine, have shown that this dipeptide, known to be transported intact from the intestinal lumen, is hydrolysed to its constitutent amino acids before it reaches portal venous blood. PMID:4652039
Solar selective absorption coatings
Mahoney, Alan R.; Reed, Scott T.; Ashley, Carol S.; Martinez, F. Edward
2004-08-31
A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.
Solar selective absorption coatings
Mahoney, Alan R.; Reed, Scott T.; Ashley, Carol S.; Martinez, F. Edward
2003-10-14
A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.
Development of solar driven absorption air conditioners and heat pumps
NASA Astrophysics Data System (ADS)
Dao, K.; Wahlig, M.; Wali, E.; Rasson, J.; Molishever, E.
1980-03-01
The development of absorption refrigeration systems for solar active heating and cooling applications is discussed. The approaches investigated are those using air-cooled condenser-absorber and those leading to coefficient of performances (COP) that increase continuously with heat source temperature. This is primarily an experimental project, with the emphasis on designing, fabricating and testing absorption chillers in operating regimes that are particularly suited for solar energy applications. Its demonstrated that the conventional single-effect ammonia-water absorption cycle can be used (with minor modifications) for solar cooling.
Measurements of thermal accommodation coefficients.
Rader, Daniel John; Castaneda, Jaime N.; Torczynski, John Robert; Grasser, Thomas W.; Trott, Wayne Merle
2005-10-01
A previously-developed experimental facility has been used to determine gas-surface thermal accommodation coefficients from the pressure dependence of the heat flux between parallel plates of similar material but different surface finish. Heat flux between the plates is inferred from measurements of temperature drop between the plate surface and an adjacent temperature-controlled water bath. Thermal accommodation measurements were determined from the pressure dependence of the heat flux for a fixed plate separation. Measurements of argon and nitrogen in contact with standard machined (lathed) or polished 304 stainless steel plates are indistinguishable within experimental uncertainty. Thus, the accommodation coefficient of 304 stainless steel with nitrogen and argon is estimated to be 0.80 {+-} 0.02 and 0.87 {+-} 0.02, respectively, independent of the surface roughness within the range likely to be encountered in engineering practice. Measurements of the accommodation of helium showed a slight variation with 304 stainless steel surface roughness: 0.36 {+-} 0.02 for a standard machine finish and 0.40 {+-} 0.02 for a polished finish. Planned tests with carbon-nanotube-coated plates will be performed when 304 stainless-steel blanks have been successfully coated.
Optical absorption of nanoporous silicon: quasiparticle band gaps and absorption spectra
NASA Astrophysics Data System (ADS)
Shi, Guangsha; Kioupakis, Emmanouil
2013-03-01
Silicon is an earth-abundant material of great importance in semiconductors electronics, but its photovoltaic applications are limited by the low absorption coefficient in the visible due to its indirect band gap. One strategy to improve the absorbance is to perforate silicon with nanoscale pores, which introduce carrier scattering that enables optical transitions across the indirect gap. We used density functional and many-body perturbation theory in the GW approximation to investigate the electronic and optical properties of porous silicon for various pore sizes, spacings, and orientations. Our calculations include up to 400 atoms in the unit cell. We will discuss the connection of the band-gap value and absorption coefficient to the underlying nanopore geometry. The absorption coefficient in the visible range is found to be optimal for appropriately chosen nanopore size, spacing, and orientation. Our work allows us to predict porous-silicon structures that may have optimal performance in photovoltaic applications. This research was supported as part of CSTEC, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science. Computational resources were provided by the DOE NERSC facility.
Measurements of spectral attenuation coefficients in the lower Chesapeake Bay
NASA Technical Reports Server (NTRS)
Houghton, W. M.
1983-01-01
The spectral transmission was measured for water samples taken in the lower Chesapeake Bay to allow characterization of several optical properties. The coefficients of total attenuation, particle attenuation, and absorption by dissolved organic matter were determined over a wavelength range from 3500 A to 8000 A. The data were taken over a 3 year period and at a number of sites so that an indication of spatial and temporal variations could be obtained. The attenuations determined in this work are, on the average, 10 times greater than those obtained by Hulburt in 1944, which are commonly accepted in the literature for Chesapeake Bay attenuation.
Seven-effect absorption refrigeration
DeVault, Robert C.; Biermann, Wendell J.
1989-01-01
A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit.
Seven-effect absorption refrigeration
DeVault, R.C.; Biermann, W.J.
1989-05-09
A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit. 1 fig.
Free-Carrier Absorption in Silicon from First Principles
NASA Astrophysics Data System (ADS)
Shi, Guangsha; Kioupakis, Emmanouil
The absorption of light by free carriers in semiconductors such as silicon results in intraband electron or hole excitations, and competes with optical transitions across the band gap. Free-carrier absorption therefore reduces the efficiency of optoelectronic devices such as solar cells because it competes with the generation of electron-hole pairs. In this work, we use first-principles calculations based on density functional theory to investigate direct and phonon-assisted free-carrier absorption in silicon. We determine the free-carrier absorption coefficient as a function of carrier concentration and temperature and compare to experiment. We also identify the dominant phonon modes that contributing to phonon-assisted free-carrier absorption processes, and analyze the results to evaluate the impact of this loss mechanism on the efficiency of silicon solar cells. This research was supported by the National Science Foundation CAREER award through Grant No. DMR-1254314. Computational resources were provided by the DOE NERSC facility.
NASA Technical Reports Server (NTRS)
Hoepffner, Nicolas; Sathyendranath, Shubha
1993-01-01
The contributions of detrital particles and phytoplankton to total light absorption are retrieved by nonlinear regression on the absorption spectra of total particles from various oceanic regions. The model used explains more than 96% of the variance in the observed particle absorption spectra. The resulting absorption spectra of phytoplankton are then decomposed into several Gaussian bands reflecting absorption by phytoplankton pigments. Such a decomposition, combined with high-performance liquid chromatography data on phytoplankton pigment concentrations, allows the computation of specific absorption coefficients for chlorophylls a, b, and c and carotenoids. The spectral values of these in vivo absorption coefficients are then discussed, considering the effects of secondary pigments which were not measured quantitatively. We show that these coefficients can be used to reconstruct the absorption spectra of phytoplankton at various locations and depths. Discrepancies that do occur at some stations are explained in terms of particle size effect. These coefficients can be used to determine the concentrations of phytoplankton pigments in the water, given the absorption spectrum of total particles.
Liu, Houquan; She, Weilong
2015-03-14
The pockels effect could be utilized to measure spin current in semiconductors for linear electro-optic coefficient can be induced by spin current. When dc electric field is applied, the carriers will shift in k space, which could lead to the change of refraction and absorption coefficients. In this paper, we investigate the influence of the induced change of the refraction and absorption coefficients on the measurement of spin current by pockels effect in GaAs.
Higher Order Macro Coefficients in Periodic Homogenization
NASA Astrophysics Data System (ADS)
Conca, Carlos; San Martin, Jorge; Smaranda, Loredana; Vanninathan, Muthusamy
2011-09-01
A first set of macro coefficients known as the homogenized coefficients appear in the homogenization of PDE on periodic structures. If energy is increased or scale is decreased, these coefficients do not provide adequate approximation. Using Bloch decomposition, it is first realized that the above coefficients correspond to the lowest energy and the largest scale. This naturally paves the way to introduce other sets of macro coefficients corresponding to higher energies and lower scales which yield better approximation. The next task is to compare their properties with those of the homogenized coefficients. This article reviews these developments along with some new results yet to be published.
Ratios of internal conversion coefficients
Raman, S.; Ertugrul, M.; Nestor, C.W. . E-mail: CNestorjr@aol.com; Trzhaskovskaya, M.B.
2006-03-15
We present here a database of available experimental ratios of internal conversion coefficients for different atomic subshells measured with an accuracy of 10% or better for a number of elements in the range 26 {<=} Z {<=} 100. The experimental set involves 414 ratios for pure and 1096 ratios for mixed-multipolarity nuclear transitions in the transition energy range from 2 to 2300 keV. We give relevant theoretical ratios calculated in the framework of the Dirac-Fock method with and without regard for the hole in the atomic subshell after conversion. For comparison, the ratios obtained within the relativistic Hartree-Fock-Slater approximation are also presented. In cases where several ratios were measured for the same transition in a given isotope in which two multipolarities were involved, we present the mixing ratio {delta} {sup 2} obtained by a least squares fit.
NASA Astrophysics Data System (ADS)
Sun, Yang; Li, Zhaohui; Huang, Aigen; Li, Qihu
2015-10-01
Piezoelectric shunt damping technology has been applied in the field of underwater sound absorption in recent years. In order to achieve broadband echo reduction, semi-active control of sound absorption of multi-layered piezoelectric coating by shunt damping is significant. In this paper, a practical method is proposed to control the underwater sound absorption coefficients of piezoelectric coating layers by combining design of the shunt impedance that allows certain sound absorption coefficients at setting frequencies. A one-dimensional electro-acoustic model of the piezoelectric coating and the backing is established based on the Mason equivalent circuit theory. First, the shunt impedance of the coating is derived under the constraint of sound absorption coefficient at one frequency. Then, taking the 1-3 piezoelectric composite coating as an example, the sound absorption properties of the coating shunted to the designed shunt impedance are investigated. Next, on the basis of that, an iterative method for two constrained frequencies and an optimizing algorithm for multiple constrained frequencies are provided for combining design of the shunt impedances. At last, an experimental sample with four piezoelectric material layers is manufactured, of which the sound absorption coefficients are measured in an impedance tube. The experimental results show good agreement with the finite element simulation results. It is proved that a serial R-L circuit can control the peak frequency, maximum and bandwidth of the sound absorption coefficient and the combining R-L circuits shunted to multiple layers can control the sound absorption coefficients at multiple frequencies.
NASA Astrophysics Data System (ADS)
Harikrishnan, L.; Maiya, M. P.; Tiwari, S.; Wohlfeil, A.; Ziegler, F.
2009-10-01
In this paper the heat and mass transfer characteristics of a horizontal tube absorber for the mixture R134a/DMAC in terms of experimentally gained heat and mass transfer coefficients are presented. The heat transfer coefficient is mainly dependent on the solution’s mass flow rate. The mass transfer coefficient is strongly related to the subcooling of the solution. The data are compared to experimental absorption characteristics of water into aqueous lithium bromide in an absorption chiller. The mass transfer coefficients are of similar size whereas the heat transfer coefficients are about one order of magnitude smaller for R134a-DMAC.
Petawatt laser absorption bounded
NASA Astrophysics Data System (ADS)
Levy, Matthew; Wilks, Scott; Tabak, Max; Libby, Stephen; Baring, Matthew
2014-10-01
The interaction of petawatt (1015 W) lasers with solid matter forms the basis for advanced scientific applications such as table-top relativistic particle accelerators, ultrafast charged particle imaging systems and fast ignition inertial confinement 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. In this presentation, using a relativistic Rankine-Hugoniot-like analysis, we show how to derive the theoretical maximum and minimum of f. These boundaries constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. Close agreement is shown with several dozens of published experimental data points and simulation results, helping to confirm the theory. 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.
Potassium emission absorption system. Topical report 12
Bauman, L.E.
1995-04-01
The Potassium Emission Absorption System is one of the advanced optical diagnostics developed at Mississippi State University to provide support for the demonstration of prototype-scale coal-fired combustion magnetohydrodynamic (MHD) electrical power generation. Intended for application in the upstream of an MHD flow, the system directly measures gas temperature and neutral potassium atom number density through spectroscopic emission absorption techniques. From these measurements the electron density can be inferred from a statistical equilibrium calculation and the electron conductivity in the MHD channel found by use of an electron mobility model. The instrument has been utilized for field test measurements on MHD facilities for almost a decade and has been proven to provide useful measurements as designed for MHD nozzle, channel, and diffuser test sections. The theory of the measurements, a system description, its capabilities, and field test measurement results are reported here. During the development and application of the instrument several technical issues arose which when addressed advanced the state of the art in emission absorption measurement. Studies of these issues are also reported here and include: two-wavelength measurements for particle-laden flows, potassium D-line far wing absorption coefficient, bias in emission absorption measurements arising from dirty windows and misalignments, non-coincident multiwavelength emission absorption sampling errors, and lineshape fitting for boundary layer flow profile information. Although developed for NLHD application, the instrument could be applied to any high temperature flow with a resonance line in the 300 to 800 nm range, for instance other types of flames, rocket plumes or low temperature plasmas.
Enhanced absorption cycle computer model. Final report
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 temperatures 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 absorptions 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-H{sub 2}O triple-effect cycles, LiCl-H{sub 2}O solar-powered open absorption cycles, and NH{sub 3}-H{sub 2}O single-effect and generator-absorber heat exchange cycles. An appendix contains the User`s Manual.
Wavelength and energy dependent absorption of unconventional fuel mixtures
NASA Astrophysics Data System (ADS)
Khan, N.; Saleem, Z.; Mirza, A. A.
2005-11-01
Economic considerations of laser induced ignition over the normal electrical ignition of direct injected Compressed Natural Gas (CNG) engines has motivated automobile industry to go for extensive research on basic characteristics of leaner unconventional fuel mixtures to evaluate practical possibility of switching over to the emerging technologies. This paper briefly reviews the ongoing research activities on minimum ignition energy and power requirements of natural gas fuels and reports results of present laser air/CNG mixture absorption coefficient study. This study was arranged to determine the thermo-optical characteristics of high air/fuel ratio mixtures using laser techniques. We measured the absorption coefficient using four lasers of multiple wavelengths over a wide range of temperatures and pressures. The absorption coefficient of mixture was found to vary significantly over change of mixture temperature and probe laser wavelengths. The absorption coefficients of air/CNG mixtures were measured using 20 watts CW/pulsed CO2 laser at 10.6μm, Pulsed Nd:Yag laser at 1.06μm, 532 nm (2nd harmonic) and 4 mW CW HeNe laser at 645 nm and 580 nm for temperatures varying from 290 to 1000K using optical transmission loss technique.
Tone-burst technique measures high-intensity sound absorption
NASA Technical Reports Server (NTRS)
Powell, J. G.; Van Houten, J. J.
1971-01-01
Tone-burst technique, in which narrow-bandwidth, short-duration sonic pulse is propagated down a standing-wave tube, measures sound absorbing capacity of materials used in jet engine noise abatement. Technique eliminates effects of tube losses and yields normal-incidence absorption coefficient of specimen.
NASA Technical Reports Server (NTRS)
1994-01-01
A NASA Center for the Commercial Development of Space (CCDS) - developed system for satellite mapping has been commercialized for the first time. Global Visions, Inc. maps an area while driving along a road in a sophisticated mapping van equipped with satellite signal receivers, video cameras and computer systems for collecting and storing mapping data. Data is fed into a computerized geographic information system (GIS). The resulting amps can be used for tax assessment purposes, emergency dispatch vehicles and fleet delivery companies as well as other applications.
Absorption of visible radiation by aerosols in the volcanic plume of mount st. Helens.
Ogren, J A; Charlson, R J; Radke, L F; Domonkos, S K
1981-02-20
Samples of particles from Mount St. Helens were collected in both the stratosphere and troposphere for measurement of the light absorption coefficient. Results indicate that the stratospheric dust had a small but finite absorption coefficient ranging up to 2 x 10(-7) per meter at a wavelength of 0.55 micrometer, which is estimated to yield an albedo for single scatter of 0.98 or greater. Tropospheric results showed similar high values of an albedo for single scatter. PMID:17740397
X-Ray Attenuation and Absorption for Materials of Dosimetric Interest
National Institute of Standards and Technology Data Gateway
SRD 126 X-Ray Attenuation and Absorption for Materials of Dosimetric Interest (Web, free access) Tables and graphs of the photon mass attenuation coefficient and the mass energy-absorption coefficient are presented for all of the elements Z = 1 to 92, and for 48 compounds and mixtures of radiological interest. The tables cover energies of the photon (x-ray, gamma ray, bremsstrahlung) from 1 keV to 20 MeV.
Absorption of visible radiation by aerosols in the volcanic plume of Mount St. Helens
NASA Technical Reports Server (NTRS)
Ogren, J. A.; Charlson, R. J.; Radke, L. F.; Domonkos, S. K.
1981-01-01
Samples of particles from Mount St. Helens were collected in both the stratosphere and troposphere for measurement of the light absorption coefficient. Results indicate that the stratospheric dust had a small but finite absorption coefficient ranging up to 2 x 10 to the minus 7 per meter at a wavelength of 0.55 micron, which is estimated to yield an albedo for single scatter of 0.98 or greater. Tropospheric results showed similar high values of an albedo for single scatter
Absorption of visible radiation by aerosols in the volcanic plume of Mount St. Helens
Ogren, J.A.; Charlson, R.J.; Radke, L.F.; Domonkos, S.K.
1981-01-01
Samples of particles from Mount St. Helens were collected in both the stratosphere and troposhere for measurement of the light absorption coefficient. Results indicate that the stratospheric dust had a small but finite absorption coefficient ranging up to 2 x 10-7 per meter at a wavelength of 0.55 micrometer, which is estimated to yield an albedo for single scatter of 0.98 or greater. Tropospheric results showed similar high values of an albedo for single scatter.
Ultraviolet Absorption by Secondary Organic Aerosols
NASA Astrophysics Data System (ADS)
Madronich, S.; Lee-Taylor, J. M.; Hodzic, A.; Aumont, B.
2014-12-01
Secondary organic aerosols (SOA) are typically formed in the atmosphere by the condensation of a myriad of intermediates from the photo-oxidation of volatile organic compounds (VOCs). Many of these partly oxidized molecules have functional groups (chromophores) that absorb at the ultraviolet (UV) wavelengths available in the troposphere (λ ≳ 290 nm). We used the explicit chemical model GECKO-A (Generator of Explicit Chemistry and Kinetics for Organics in the Atmosphere) to estimate UV absorption cross sections for the gaseous and particulate components of SOA from different precursors (biogenic and anthropogenic) and formed in different environments (low and high NOx, day and night). Model predictions are evaluated with laboratory and field measurements of SOA UV optical properties (esp. mass absorption coefficients and single scattering albedo), and implications are presented for surface UV radiation trends, urban actinic flux modification, and SOA lifetimes.
Direct determination of absorption anisotropy in colloidal quantum rods
NASA Astrophysics Data System (ADS)
Kamal, John Sundar; Gomes, Raquel; Hens, Zeger; Karvar, Masoumeh; Neyts, Kristiaan; Compernolle, Sien; Vanhaecke, Frank
2012-01-01
We propose a direct method to determine absorption anisotropy of colloidal quantum rods. In this method, the rods are aligned in solution by using an alternating electric field and we measure simultaneously the resulting average change in absorption. We show that a frequency window for the electric field exists in which the change in absorbance as a function of field strength can be analyzed in terms of the quantum-rod dipole moment and the absorption coefficient for light that is polarized parallel or perpendicular to the long axis of the rod. The approach is verified by measuring the absorbance change of CdSe rods at 400 nm as a function of field strength, where we demonstrate excellent agreement between experiment and theory. This enables us to propose improved values for the CdSe quantum-rod extinction coefficient. Next, we analyze CdSe/CdS dot-in-rods and find that the absorption of the first exciton transition is fully anisotropic, with a vanishing absorption coefficient for light that is polarized perpendicularly to the long axis of the rods.
Microwave peak absorption frequency of liquid
NASA Astrophysics Data System (ADS)
Han, Guangze; Chen, Mingdong
2008-09-01
Microwave-assisted extraction is a new effective method which has practical applications in many fields. Microwave heating is one of its physical mechanisms, and it also has the characteristic of selectivity. When the applied microwave frequency equals a certain absorption frequency of the material (or specific component), the material will intensively absorb microwave energy. This is also known as resonant absorption, and the frequency is called the peak absorption frequency which depends on the physical structure of the material. In this work, dynamic hydrogen bond energy was included in molecular activation energy; with the liquid cell model, the expression of interaction energy between dipolar molecules was derived. The rotational relaxation time was gotten from the Eyring viscosity formula. Then based on the relationship between dielectric dissipation coefficient and relaxation time, the expression of microwave peak absorption frequency as a function of the material physical structure, rotational inertia and electrical dipole moment of molecules was established. These theoretical formulas were applied to water and benzene, and the calculated results agree fairly well with the experimental data. This work can not only deepen the study of the interaction between microwave and material, but also provide a possible guide for the experiment of microwave-assisted extraction.
Percutaneous absorption from soil.
Andersen, Rosa Marie; Coman, Garrett; Blickenstaff, Nicholas R; Maibach, Howard I
2014-01-01
Abstract Some natural sites, as a result of contaminants emitted into the air and subsequently deposited in soil or accidental industrial release, have high levels of organic and non-organic chemicals in soil. In occupational and recreation settings, these could be potential sources of percutaneous exposure to humans. When investigating percutaneous absorption from soil - in vitro or vivo - soil load, particle size, layering, soil "age" time, along with the methods of performing the experiment and analyzing the results must be taken into consideration. Skin absorption from soil is generally reduced compared with uptake from water/acetone. However, the absorption of some compounds, e.g., pentachlorophenol, chlorodane and PCB 1254, are similar. Lipophilic compounds like dichlorodiphenyltrichloroethane, benzo[A]pyrene, and metals have the tendency to form reservoirs in skin. Thus, one should take caution in interpreting results directly from in vitro studies for risk assessment; in vivo validations are often required for the most relevant risk assessment. PMID:25205703
Judd, Linda J.; Asquith, William H.; Slade, Raymond M., Jr.
1996-01-01
This report presents two techniques to estimate generalized skew coefficients used for log-Pearson Type III peak-streamflow frequency analysis of natural basins in Texas. A natural basin has less than 10 percent impervious cover, and less than 10 percent of its drainage area is controlled by reservoirs. The estimation of generalized skew coefficients is based on annual peak and historical peak streamflow for all U.S. Geological Survey streamflow-gaging stations having at least 20 years of annual peak-streamflow record from natural basins in Texas. Station skew coefficients calculated for each of 255 Texas stations were used to estimate generalized skew coefficients for Texas. One technique to estimate generalized skew coefficients involved the use of regression equations developed for each of eight regions in Texas, and the other involved development of a statewide map of generalized skew coefficients. The weighted mean of the weighted mean standard errors of the regression equations for the eight regions is 0.36 log10 skew units, and the weighted mean standard error of the map is 0.35 log10 skew units. The technique based on the map is preferred for estimating generalized skew coefficients because of its smooth transition from one region of the State to another.
Multiplasmon Absorption in Graphene
NASA Astrophysics Data System (ADS)
Jablan, Marinko; Chang, Darrick E.
2015-06-01
We show that graphene possesses a strong nonlinear optical response in the form of multiplasmon absorption, with exciting implications in classical and quantum nonlinear optics. Specifically, we predict that graphene nanoribbons can be used as saturable absorbers with low saturation intensity in the far-infrared and terahertz spectrum. Moreover, we predict that two-plasmon absorption and extreme localization of plasmon fields in graphene nanodisks can lead to a plasmon blockade effect, in which a single quantized plasmon strongly suppresses the possibility of exciting a second plasmon.
Chaotic Systems with Absorption
NASA Astrophysics Data System (ADS)
Altmann, Eduardo G.; Portela, Jefferson S. E.; Tél, Tamás
2013-10-01
Motivated by applications in optics and acoustics we develop a dynamical-system approach to describe absorption in chaotic systems. We introduce an operator formalism from which we obtain (i) a general formula for the escape rate κ in terms of the natural conditionally invariant measure of the system, (ii) an increased multifractality when compared to the spectrum of dimensions Dq obtained without taking absorption and return times into account, and (iii) a generalization of the Kantz-Grassberger formula that expresses D1 in terms of κ, the positive Lyapunov exponent, the average return time, and a new quantity, the reflection rate. Simulations in the cardioid billiard confirm these results.
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.
M-Bonomial Coefficients and Their Identities
ERIC Educational Resources Information Center
Asiru, Muniru A.
2010-01-01
In this note, we introduce M-bonomial coefficients or (M-bonacci binomial coefficients). These are similar to the binomial and the Fibonomial (or Fibonacci-binomial) coefficients and can be displayed in a triangle similar to Pascal's triangle from which some identities become obvious.
Soccer Ball Lift Coefficients via Trajectory Analysis
ERIC Educational Resources Information Center
Goff, John Eric; Carre, Matt J.
2010-01-01
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…
Standards for Standardized Logistic Regression Coefficients
ERIC Educational Resources Information Center
Menard, Scott
2011-01-01
Standardized coefficients in logistic regression analysis have the same utility as standardized coefficients in linear regression analysis. Although there has been no consensus on the best way to construct standardized logistic regression coefficients, there is now sufficient evidence to suggest a single best approach to the construction of a…
Monochromatic calculations of atmospheric radiative transfer due to molecular line absorption
NASA Technical Reports Server (NTRS)
Chou, M.-D.; Kouvaris, L.
1986-01-01
Sensitivity studies related to the effects of line cutoff, spectral resolution, and temperature and pressure interpolations in radiative transfer have been performed so that a data set of absorption coefficients for water vapor, CO2, and O3 may be created efficiently. Results show that computations of absorption coefficients are affected only slightly by cutting a line off at a wave number 190 times the Lorentz half width from the center, or equivalently, cutting off 0.33 percent of the line intensity from the wings. To achieve a relative cooling rate error smaller than 2 percent, it is sufficient to precompute the absorption coefficient at three temperatures (210, 250, and 290 K) and 19 pressures with Delta (log 10 p) = 0.2. The absorption coefficient at other conditions can be interpolated linearly with pressure and exponentially with a quadratic in temperature. For the spectral resolution the absorption coefficients can be adequately computed at 0.01, 0.002, 0.005, and 0.025/cm intervals in the thermal water vapor, the CO2 and O3 bands, and the solar water vapor bands, respectively, which limits the error to only a few percent in the cooling and heating rates. Using the precomputed absorption coefficients, repeated monochromatic calculations of atmospheric heating/cooling rates for radiation model developments and for comparison with less detailed calculations are no longer difficult.
Beranek, Leo L
2006-09-01
Historically, two equations have been used for predicting reverberation times, Sabine and Eyring. A precise means is presented for determining Eyring absorption coefficients alpha(eyring) when the Sabine coefficients alpha(sabine) are known, and vice versa. Thus, either formula can be used provided the absorption coefficients for the Sabine formula are allowed to exceed 1.0. The Sabine formula is not an approximation to the Eyring equation and is not a shortcoming. Given low reverberation times, the ratio of alpha(sabine) to alpha(eyring) may become greater than 2.0. It is vital that, for correct prediction of reverberation times, the absorption coefficients used in either formula must have been determined in spaces similar in size and shape, with similar locations of high absorption (audience) areas, and with similar reverberation times. For concert halls, it is found that, when the audience area (fully occupied) and midfrequency reverberation time are postulated, the hall volume is directly proportional to the audience absorption coefficient. Approximately 6% greater room volumes are needed when choosing nonrectangular versus classical-rectangular shaped halls and approximately 10% greater volumes when choosing heavily upholstered versus medium upholstered chairs. Determinations of audience sound absorption coefficients are presented, based on published acoustical and architectural data for 20 halls. PMID:17004464
Unusually high sound absorption in topological interlocking materials
NASA Astrophysics Data System (ADS)
Estrin, Yuri; Molotnikov, Andrey; Carlesso, Mateus
2015-04-01
Topological interlocking materials are a new class of architectured materials, which have a range of unusual mechanical and acoustic properties. We present a novel approach for combating noise pollution based on the concept of topological interlocking. Specifically, we propose to segment monolithic plates into an assembly of topologically interlocked building blocks and show experimentally that this leads to a spectacular increase of the sound absorption coefficient over that in the original material, as exemplified by ceramics. Measurements of the airflow resistance confirmed the primary role of segmentation in enhancing sound absorption capability of the material in the audible frequency range. The absorption coefficient was further boosted by design of the material itself. The new material design proposed poses some interesting challenges to theory of sound wave propagation in heterogeneous media.
[Spectral absorption properties of the water constituents in the estuary of Zhujiang River].
Wang, Shan-shan; Wang, Yong-bo; Fu, Qing-hua; Yin, Bin; Li, Yun-mei
2014-12-01
Spectral absorption properties of the water constituents is the main factor affecting the light field under the surface of the water and the spectrum above the surface of the water. Thus, the study is useful for understanding of the water spectral property and the remote reversing of water quality parameters. Absorption properties of total suspended particles, non-algal particles, phytoplankton and CDOM were analyzed using the 30 samples collected in July 2013 in the estuary of Zhujiang River. The results indicated that: (1) the non-algal particles absorption dominated the absorption of the total suspended particles; (2) the absorption coefficient of the non-algal particles, which mainly came from the terrigenous deposits, decreased exponentially from short to long wavelength. In addition, the average value and spatial variation of the slope S(d) were higher than those in inland case- II waters; (3) the absorption coefficient of phytoplankton in 440 nm showed a better polynomial relationship with chlorophyll a concentration, while the absorption coefficient of phytoplankton in 675 nm linearly related with the chlorophyll a concentration. Moreover, the influence of accessory pigments on phytoplankton absorption coefficient mainly existed in the range of short wavelength, and Chlorophyll a was the main influencing factor for phytoplankton absorption in long wavelength. The specific absorption coefficient of phytoplankton decreased the power exponentially with the increase of the chlorophyll a concentration; (4) CDOM mainly came from the terrigenous sources and its spectral curve had an absorption shoulder between 250-290 nm. Thus, a piecewise S(g) fitting function could effectively express CDOM absorption properties, i.e., M value and S(g) value in period A (240-260 nm) showed a strong positive correlation. The M value was low, and the humic acid had a high proportion in CDOM; (5) the non-algal particles absorption dominated the total absorption in the estuary of
NASA Astrophysics Data System (ADS)
Linnros, Jan
1998-07-01
A contactless, all-optical technique for semiconductor charge carrier lifetime characterization is reviewed. The technique is based upon measurements of free carrier absorption transients by an infrared probe beam following electron-hole pair excitation by a pulsed laser beam. Main features are a direct probing of the excess carrier density coupled with a homogeneous carrier distribution within the sample, enabling precision studies of different recombination mechanisms. We show that the method is capable of measuring the lifetime over a broad range of injections (1013-1018 cm-3) probing both the minority carrier lifetime, the high injection lifetime and Auger recombination, as well as the transition between these ranges. Performance and limitations of the technique, such as lateral resolution, are addressed while application of the technique for lifetime mapping and effects of surface recombination is outlined in a companion article [J. Appl. Phys. 84, 284 (1998), part II]. Results from detailed studies of the injection dependence yield good agreement with the Shockley-Read-Hall theory, whereas the coefficient for Auger recombination shows an apparent shift to a higher value, with respect to the traditionally accepted value, at carrier densities below ˜2-5×1017 cm-3. Data also indicate an increased value of the coefficient for bimolecular recombination (radiative or trap-assisted Auger) from the generally accepted value. Measurements on an electron irradiated wafer and wafers of exceptionally high carrier lifetimes are also discussed within the framework of different recombination mechanisms.
Ballistic Coefficient Prediction for Resident Space Objects
NASA Astrophysics Data System (ADS)
Russell, R.; Arora, N.; Vittaldev, V.; Gaylor, D.
2012-09-01
Recent improvements in atmospheric density modeling now provide more confidence in spacecraft ballistic coefficient (BC) estimations, which were previously corrupted by large errors in density. Without attitude knowledge, forecasting the true BC for accurate future state and uncertainty predictions remains elusive. In this paper, our objective is to improve this predictive capability for ballistic coefficients for Resident Space Objects (RSOs), thus improving the existing drag models and associated accuracy of the U.S. Space Object Catalog. To work towards this goal we implement a two-pronged strategy that includes elements of time series analysis and physics based simulations. State-of-the-art empirical time series prediction methods are applied and tested on BC time series in the context of both simulation data and actual data provided by the Air Force. An archive of simulated BC data is generated using custom 6DOF high fidelity simulations for RSOs using plate models for shapes. The simulator includes force and torque perturbations due to the nonspherical Earth, third-body perturbations, SRP, and atmospheric drag. The simulated BC profiles demonstrate significant variation over short time spans (due primarily to varying frontal areas), providing motivation to improve future BC estimation strategies. The 6DOF modeling is intended to provide a physics-based BC data set to complement the BC data set provided by the AF. For the ‘black-box' time series algorithms, a variety of approaches are considered, whereas two prediction models showed the most promising performance: a multi-tone harmonic model and an autoregressive (AR) model. Both the multi-tone harmonic model and the AR model are subjected to multiple levels of optimizations resulting in highly optimized final models that are tuned specifically with the 205 BC time series provided by the AF. Two versions of the AR model are developed based on the model prediction methodology. The second version of the AR
Coefficients of Productivity for Yellowstone's Grizzly Bear Habitat
Mattson, David John; Barber, Kim; Maw, Ralene; Renkin, Roy
2004-01-01
This report describes methods for calculating coefficients used to depict habitat productivity for grizzly bears in the Yellowstone ecosystem. Calculations based on these coefficients are used in the Yellowstone Grizzly Bear Cumulative Effects Model to map the distribution of habitat productivity and account for the impacts of human facilities. The coefficients of habitat productivity incorporate detailed information that was collected over a 20-year period (1977-96) on the foraging behavior of Yellowstone's bears and include records of what bears were feeding on, when and where they fed, the extent of that feeding activity, and relative measures of the quantity consumed. The coefficients also incorporate information, collected primarily from 1986 to 1992, on the nutrient content of foods that were consumed, their digestibility, characteristic bite sizes, and the energy required to extract and handle each food. Coefficients were calculated for different time periods and different habitat types, specific to different parts of the Yellowstone ecosystem. Stratifications included four seasons of bear activity (spring, estrus, early hyperphagia, late hyperphagia), years when ungulate carrion and whitebark pine seed crops were abundant versus not, areas adjacent to (<100 m) or far away from forest/nonforest edges, and areas inside or outside of ungulate winter ranges. Densities of bear activity in each region, habitat type, and time period were incorporated into calculations, controlling for the effects of proximity to human facilities. The coefficients described in this report and associated estimates of grizzly bear habitat productivity are unique among many efforts to model the conditions of bear habitat because calculations include information on energetics derived from the observed behavior of radio-marked bears.
ERIC Educational Resources Information Center
DiSpezio, Michael A.
1991-01-01
Presented is a cooperative learning activity in which students assume different roles in an effort to produce a relief map of the ocean floor. Materials, procedures, definitions, student roles, and questions are discussed. A reproducible map for the activity is provided. (CW)
ERIC Educational Resources Information Center
Martin, Josh
2012-01-01
After accepting the principal position at Farmersville (TX) Junior High, the author decided to increase instructional rigor through question mapping because of the success he saw using this instructional practice at his prior campus. Teachers are the number one influence on student achievement (Marzano, 2003), so question mapping provides a…
ERIC Educational Resources Information Center
Geological Survey (Dept. of Interior), Reston, VA.
This curriculum packet about maps, with seven accompanying lessons, is appropriate for students in grades K-3. Students learn basic concepts for visualizing objects from different perspectives and how to understand and use maps. Lessons in the packet center on a story about a little girl, Nikki, who rides in a hot-air balloon that gives her, and…
NASA Astrophysics Data System (ADS)
Hohmann, Martin; Lengenfelder, B.; Kanawade, R.; Klämpfl, F.; Schmidt, Michael
2015-12-01
Coherent light propagating through turbid media is attenuated due to scattering and absorption. The decrease of the intensity of the coherent light is described by the attenuation coefficient. The measured decay of the coherent light through turbid media with optical coherence tomography (OCT) can be used to reconstruct the attenuation coefficient. Since most of the OCT systems work in the near-infrared region, they are the optical window from 800-1400 nm in tissue. Hence, the most part of the attenuation coefficient is caused due to the scattering. Therefore, deriving the attenuation coefficient is one way to get an approximation of the scattering coefficient which is difficult to access even up to day. Moreover, OCT measurements are one of the few possibilities to derive physical properties with micrometre resolution of the media under investigation.
Multi-mode interference revealed by two photon absorption in silicon rich SiO{sub 2} waveguides
Manna, S. E-mail: mattia.mancinelli@unitn.it; Ramiro-Manzano, F.; Mancinelli, M. E-mail: mattia.mancinelli@unitn.it; Turri, F.; Pavesi, L.; Ghulinyan, M.; Pucker, G.
2015-02-16
Photoluminescence (PL) from Si nanocrystals (NCs) excited by two-photon absorption (TPA) has been observed in Si nanocrystal-based waveguides fabricated by plasma enhanced chemical vapor deposition. The TPA excited photoluminescence emission resembles the one-photon excited photoluminescence arising from inter-band transitions in the quantum confined Si nanocrystals. By measuring the non-linear transmission of waveguides, a large TPA coefficient of β up to 10{sup −8 }cm/W has been measured at 1550 nm. These values of β depend on the Si NCs size and are two orders of magnitude larger than the bulk silicon value. Here, we propose to use the TPA excited visible PL emission as a tool to map the spatial intensity profile of the 1550 nm propagating optical modes in multimode waveguides. In this way, multimode interference has been revealed experimentally and confirmed through a finite element simulation.
For a bimodal size distribution of ambient aerosol, an upper limit in particle size can be chosen for the fine aerosol fraction so that the extinction coefficient for light scattering and absorption is directly proportional to the fine mass concentration, with no dependence on th...
Characteristic of Absorption Heat Transfer using LiBr+LiI Solution
NASA Astrophysics Data System (ADS)
Tsujimori, Atsushi; Ozaki, Eiichi; Nakao, Kazushige
LiBr-H20 absorption chiller is widely used in Japan, and many research have been made for absorption characteristic in terms of enhancing heat transfer. Another study have been performed for widening working range with higher crystallization limits, and it was reported that adding LiI salt to LiBr-H20 working fluid provide about 5 [mass%] higher crystallization limit under the condition of absorption pressure range. It is necessary to reveal absorption heat transfer performance to utilize this working fluid pair for absorption chiller. In this study absorption heat transfer characteristic was investigated for horizontal and vertical tube. As a result, it was found that heat transfer coefficient increased as mass flow rate of solution increased and mass concentration of solution decrease and that these characteristic were almost the same as LiBr solution, though this solution gave slightly less heat transfer coefficient than LiBr solution.
Rae, Nicholas A.; Chantler, Christopher T.; Barnea, Zwi; Jonge, Martin D. de; Tran, Chanh Q.; Hester, James R.
2010-02-15
The x-ray mass attenuation coefficients of zinc are measured in a high-accuracy experiment between 7.2 and 15.2 keV with an absolute accuracy of 0.044% and 0.197%. This is the most accurate determination of any attenuation coefficient on a bending-magnet beamline and reduces the absolute uncertainty by a factor of 3 compared to earlier work by advances in integrated column density determination and the full-foil mapping technique described herein. We define a relative accuracy of 0.006%, which is not the same as either the precision or the absolute accuracy. Relative accuracy is the appropriate parameter for standard implementation of analysis of near-edge spectra. Values of the imaginary components f'' of the x-ray form factor of zinc are derived. Observed differences between the measured mass attenuation coefficients and various theoretical calculations reach a maximum of about 5% at the absorption edge and up to 2% further than 1 keV away from the edge. The measurements invite improvements in the theoretical calculations of mass attenuation coefficients of zinc.
ERIC Educational Resources Information Center
Hamilton, M. W.
2007-01-01
A nonlinear aspect of the acousto-optic interaction that is analogous to multi-photon absorption is discussed. An experiment is described in which the second-order acousto-optically scattered intensity is measured and found to scale with the square of the acoustic intensity. This experiment using a commercially available acousto-optic modulator is…
Total absorption Cherenkov spectrometers
NASA Astrophysics Data System (ADS)
Malinovski, E. I.
2015-05-01
A short review of 50 years of work done with Cherenkov detectors in laboratories at the Lebedev Physical Institute is presented. The report considers some issues concerning the use of Cherenkov total absorption counters based on lead glass and heavy crystals in accelerator experiments.
Cholesterol Absorption and Metabolism.
Howles, Philip N
2016-01-01
Inhibitors of cholesterol absorption have been sought for decades as a means to treat and prevent cardiovascular diseases (CVDs) associated with hypercholesterolemia. Ezetimibe is the one clear success story in this regard, and other compounds with similar efficacy continue to be sought. In the last decade, the laboratory mouse, with all its genetic power, has become the premier experimental model for discovering the mechanisms underlying cholesterol absorption and has become a critical tool for preclinical testing of potential pharmaceutical entities. This chapter briefly reviews the history of cholesterol absorption research and the various gene candidates that have come under consideration as drug targets. The most common and versatile method of measuring cholesterol absorption is described in detail along with important considerations when interpreting results, and an alternative method is also presented. In recent years, reverse cholesterol transport (RCT) has become an area of intense new interest for drug discovery since this process is now considered another key to reducing CVD risk. The ultimate measure of RCT is sterol excretion and a detailed description is given for measuring neutral and acidic fecal sterols and interpreting the results. PMID:27150091
Lipids: Absorption and transport
Technology Transfer Automated Retrieval System (TEKTRAN)
Due to the hydrophobic nature of lipids, dietary fat is handled differently than protein or carbohydrate with respect with digestion and absorption. Dietary fats are broken down throughout the gastrointestinal system. A unique group of enzymes and cofactors allows this process to proceed in an eff...
Technology Transfer Automated Retrieval System (TEKTRAN)
Zinc is a vital mineral in human nutrition, and rare cases of overt zinc deficiency are well described in term and preterm infants. A variety of methods have been developed to assess zinc absorption, retention, and balance in humans, either using mass (metabolic) balance or stable isotope-based METH...
NASA Astrophysics Data System (ADS)
Harrop, N.; Wolf, S.; Maerten, O.; Dudek, K.; Ballach, S.; Kramer, R.
2016-03-01
Modern high brilliance near infrared lasers have seen a tremendous growth in applications throughout the world. Increased productivity has been achieved by higher laser power and increased brilliance of lasers. Positive impacts on the performance and costs of parts are opposed to threats on process stability and quality, namely shift of focus position over time. A high initial process quality will be reduced by contamination of optics, eventually leading to a focus shift or even destruction of the optics. Focus analysis at full power of multi-kilowatt high brilliance lasers is a very demanding task because of high power densities in the spot and the high power load on optical elements. With the newly developed high power projection optics, the High-Power Micro-Spot Monitor High Brilliance (HP-MSM-HB) is able to measure focus diameter as low as 20 μm at power levels up to 10 kW at very low internal focus shift. A main driving factor behind thermally induced focus shift is the absorption level of the optical element. A newly developed measuring system is designed to determine the relative absorption level in reference to a gold standard. Test results presented show a direct correlation between absorption levels and focus shift. The ability to determine the absorption level of optical elements as well as their performance at full processing power before they are put to use, enables a high level of quality assurance for optics manufacturers and processing head manufacturers alike.
Technology Transfer Automated Retrieval System (TEKTRAN)
Optical absorption and scattering properties are useful for quantifying light interaction with plant tissue, as well as for quality assessment of horticultural products. The aim of this research was to measure the absorption and reduced scattering coefficient spectra of two cultivars of apple (Malus...
Stratospheric infrared continuum absorptions observed by the ATMOS instrument
NASA Technical Reports Server (NTRS)
Rinsland, C. P.; Zander, R.; Namkung, J. S.; Farmer, C. B.; Norton, R. H.
1989-01-01
A quantitative analysis of infrared continuum absorption features observed in ATMOS/Spacelab 3 (1985) spectra of the lower stratosphere is reported. Continuous absorption produced primarily by the collision-induced fundamental vibration-rotation band of O2 and to a lesser extent by the superposition of H2O far line wings has been observed in the 1400 to 1800/cm interval below tangent heights of about 25 km. Continuum optical depths measured in microwindows nearly free of atmospheric line absorption are 0.78 + or - 0.06 times those calculated with the O2 absorption coefficients of Timofeyev and Tonkov (1978). Transmittance measurements in microwindows between 2395 and 2535/cm have been used to study continuous absorption from the collision induced fundamental vibration-rotation band of N2 and the far wings of strong CO2 lines. The measured transmittances have been analyzed to derive best fit absorption coefficients for the N2 pressure-induced band at lower stratospheric temperatures (about 210 K).
Comparison of vertical aerosol extinction coefficients from in-situ and LIDAR measurements
NASA Astrophysics Data System (ADS)
Rosati, B.; Herrmann, E.; Bucci, S.; Fierli, F.; Cairo, F.; Gysel, M.; Tillmann, R.; Größ, J.; Gobbi, G. P.; Di Liberto, L.; Di Donfrancesco, G.; Wiedensohler, A.; Weingartner, E.; Virtanen, A.; Mentel, T. F.; Baltensperger, U.
2015-07-01
Vertical profiles of aerosol optical properties were explored in a case study near the San Pietro Capofiume (SPC) ground station during the PEGASOS Po Valley campaign in the summer of 2012. A Zeppelin NT airship was employed to investigate the effect of the dynamics of the planetary boundary layer at altitudes between ~ 50-800 m above ground. Determined properties included the aerosol size distribution, the hygroscopic growth factor, the effective index of refraction and the light absorption coefficient. The first three parameters were used to retrieve the light scattering coefficient. Simultaneously, direct measurements of both the scattering and absorption coefficient were carried out at the SPC ground station. Additionally, a LIDAR system provided aerosol extinction coefficients for a vertically resolved comparison between in-situ and remote sensing results. First, the airborne results at low altitudes were validated with the ground measurements. Agreement within approximately ±25 and ±20% was found for the dry scattering and absorption coefficient, respectively. The single scattering albedo, ranged between 0.83 to 0.95, indicating the importance of the absorbing particles in the Po Valley region. A clear layering of the atmosphere was observed during the beginning of the flight (until ~ 10 local time) before the mixed layer (ML) was fully developed. Highest extinction coefficients were found at low altitudes, in the new ML, while values in the residual layer, which could be probed at the beginning of the flight at elevated altitudes, were lower. At the end of the flight (after ~ 12 local time) the ML was fully developed, resulting in constant extinction coefficients at all altitudes measured on the Zeppelin NT. LIDAR results captured these dynamic features well and good agreement was found for the extinction coefficients compared to the in-situ results, using fixed LIDAR ratios (LR) between 30 and 70 sr for the altitudes probed with the Zeppelin. These LR are
NASA Astrophysics Data System (ADS)
Hosseinpour, Parinaz; Soltani-Vala, Ali; Barvestani, Jamal
2016-06-01
In this paper, the influence of impurity parameters on the electron energy spectrum and absorption coefficients in a parabolic quantum dot and in the presence of Rashba spin-orbit interaction subjected to a perpendicular magnetic field is studied. The impurity potential is approximated by a Gaussian form. We have shown that in the both cases of a repulsive and attractive Gaussian impurity, the absorption coefficients are strongly affected by the decay length. These coefficients show blue (red) shift as the decay length of repulsive (attractive) impurity is increased. The dependence of the absorption coefficients on the impurity position is also examined for different polarizations. Our results show that the absorption coefficient has local maximum (minimum) for a given value of impurity position for Y-polarized (X-polarized) light.