Converting Sabine absorption coefficients to random incidence absorption coefficients.
Jeong, Cheol-Ho
2013-06-01
Absorption coefficients measured by the chamber method are referred to as Sabine absorption coefficients, which sometimes exceed unity due to the finite size of a sample and non-uniform intensity in the reverberation chambers under test. In this study, conversion methods from Sabine absorption coefficients to random incidence absorption coefficients are proposed. The overestimations of the Sabine absorption coefficient are investigated theoretically based on Miki's model for porous absorbers backed by a rigid wall or an air cavity, resulting in conversion factors. Additionally, three optimizations are suggested: An optimization method for the surface impedances for locally reacting absorbers, the flow resistivity for extendedly reacting absorbers, and the flow resistance for fabrics. With four porous type absorbers, the conversion methods are validated. For absorbers backed by a rigid wall, the surface impedance optimization produces the best results, while the flow resistivity optimization also yields reasonable results. The flow resistivity and flow resistance optimization for extendedly reacting absorbers are also found to be successful. However, the theoretical conversion factors based on Miki's model do not guarantee reliable estimations, particularly at frequencies below 250 Hz and beyond 2500 Hz.
Optical absorption coefficients of pure water
NASA Astrophysics Data System (ADS)
Lu, Zheng; Zhao, Xianzhen; Fry, Edward S.
2002-10-01
The integrating cavity absorption meter(ICAM), which is independent of scattering effect, is used to measure the absolute values of small optical absorption coefficients of liquid. A modified ICAM is being used to measure the absorption of water in the wavelength range 300 to 700 nm. The ultrapure water produced by a two-stages water purification system reaches Type I quality. This is equal to or better than ASTM,CAP and NCCLS water quality standards. To avoid the fact that dissolved oxygen absorbs ultraviolet light due to the photochemical effect, the water sample is delivered through a nitrogen sealed system which will prevent the sample from contacting with oxygen. A compassion of our absorption spectrum with other existing data is given.
Absorption coefficient instrument for turbid natural waters
NASA Technical Reports Server (NTRS)
Friedman, E.; Cherdak, A.; Poole, L.; Houghton, W.
1980-01-01
The paper presents an instrument that directly measures multispectral absorption coefficient of turbid natural water. Attention is given to the design, which is shown to incorporate methods for the compensation of variation in the internal light source intensity, correction of the spectrally dependent nature of the optical elements, and correction for variation in the background light level. In addition, when used in conjunction with a spectrally matched total attenuation instrument, the spectrally dependent scattering coefficient can also be derived. Finally, it is reported that systematic errors associated with multiple scattering have been estimated using Monte Carlo techniques.
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.
[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.
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
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.
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.
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.
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.
Weibel instability due to inverse bremsstrahlung absorption
Bendib, A.; Bendib, K.,; Bendib, A.; Bendib, K.; Sid, A.,; Bendib, K.,
1997-06-01
A new Weibel source due to the inverse bremsstrahlung absorption is presented. It has been shown that in homogeneous plasmas, this mechanism may drive strong collisionless Weibel modes with growth rates of order of {gamma}{approximately}10{sup 11}s{sup {minus}1} and negligible group velocities. In the laser-produced plasmas, for short laser wavelengths ({lambda}{sub L}{lt}1{mu}m) and high laser fluxes (I{gt}10{sup 14}W/cm{sup 2}), this Weibel source is most efficient as the ones due to the heat flux and the plasma expansion. The useful scaling law of the convective e-foldings, with respect to the laser and the plasma parameters, is also derived. {copyright} {ital 1997} {ital The American Physical Society}
Li, Xiaoqi; Jiang, Huabei
2013-02-21
We present a study through extensive simulation that considers the impact of inhomogeneous optical scattering coefficient distribution on recovery of optical absorption coefficient maps using tomographic photoacoustic data collected from media mimicking breast tissue. We found that while the impact of scattering heterogeneities/targets is modest on photoacoustic recovery of optical absorption coefficients, the impact of scattering contrast caused by adipose tissue, a layer of normal tissue along the boundary of the breast, is dramatic on reconstruction of optical absorption coefficients using photoacoustic data-up to 25.8% relative error in recovering the absorption coefficient is estimated in such cases. To overcome this problem, we propose a new method to enhance photoacoustic recovery of the optical absorption coefficient in heterogeneous media by considering inhomogeneous scattering coefficient distribution provided by diffuse optical tomography (DOT). Results from extensive simulations show that photoacoustic recovery of absorption coefficient maps can be improved considerably with a priori scattering information from DOT.
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.
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.
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
Size segregated light absorption coefficient of the atmospheric aerosol
NASA Astrophysics Data System (ADS)
Horvath, H.
The light absorption coefficient of atmospheric aerosols in the visible can be determined by depositing the particles on a filter and measuring its "transmission" in a special optical arrangement. With an impactor with rotating impaction plates producing a homogeneous deposit, it is possible to extend this technique to size segregated aerosol samples. A simultaneous determination of the mass size distribution is possible. Test measurements with black carbon aerosol have shown the feasibility of this method. Samples of the atmospheric aerosol have been taken in and near Vienna, in Naples and near Bologna. The light absorption of the aerosol is always highest for particle diameters between 0.1 and 0.2 μm. Only in the humid environment of the Po valley it had a slightly larger peak size, whereas the size of the nonabsorbing particles increased considerably. The light absorption of the atmospheric aerosol is always higher in an urban environment. 'The mass absorption coefficient of the aerosol at all four locations was very similar, and completely different from values which could be. expected using effective refractive indices which are frequently used in models. Using the data measured in this work two alternate models for the effective refractive index and black carbon content of the aerosol are suggested: (a) a size-dependent refractive index, where the imaginary part varies from -0.25 for particles smaller than 30 nm to - 0.003 for particles larger than 2 μm; this could especially be applied if an internal mixing of the aerosol is to be expected, or (2) a size-dependent fraction of elemental carbon in the case of external mixing with 43% of carbon particles for sizes below 30 nm decreasing to 10% for sizes up to 0.4 μm.
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.
Photon absorption potential coefficient as a tool for materials engineering
NASA Astrophysics Data System (ADS)
Akande, Raphael Oluwole; Oyewande, Emmanuel Oluwole
2016-09-01
Different atoms achieve ionizations at different energies. Therefore, atoms are characterized by different responses to photon absorption in this study. That means there exists a coefficient for their potential for photon absorption from a photon source. In this study, we consider the manner in which molecular constituents (atoms) absorb photon from a photon source. We observe that there seems to be a common pattern of variation in the absorption of photon among the electrons in all atoms on the periodic table. We assume that the electrons closest to the nucleus (En) and the electrons closest to the outside of the atom (Eo) do not have as much potential for photon absorption as the electrons at the middle of the atom (Em). The explanation we give to this effect is that the En electrons are embedded within the nuclear influence, and similarly, Eo electrons are embedded within the influence of energies outside the atom that there exists a low potential for photon absorption for them. Unlike En and Eo, Em electrons are conditioned, such that there is a quest for balance between being influenced either by the nuclear force or forces external to the atom. Therefore, there exists a higher potential for photon absorption for Em electrons than for En and Eo electrons. The results of our derivations and analysis always produce a bell-shaped curve, instead of an increasing curve as in the ionization energies, for all elements in the periodic table. We obtained a huge data of PAPC for each of the several materials considered. The point at which two or more PAPC values cross one another is termed to be a region of conflicting order of ionization, where all the atoms absorb equal portion of the photon source at the same time. At this point, a greater fraction of the photon source is pumped into the material which could lead to an explosive response from the material. In fact, an unimaginable and unreported phenomenon (in physics) could occur, when two or more PAPCs cross, and
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
Electron heating due to resonant absorption
Mizuno, K.; Spielman, R.B.; DeGroot, J.S.; Bollen, W.M.
1980-01-01
Intense, p-polarized microwaves (v/sub os//v/sub eo-/<1) are incident on an imhomogeneous plasma (10/sup 2/
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.
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.
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.
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.
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.
NASA Astrophysics Data System (ADS)
Singh, Vishwanath P.; Medhat, M. E.; Badiger, N. M.
2015-01-01
Geant4 Monte Carlo code simulations were used to solve experimental and theoretical complications for calculation of mass energy-absorption coefficients of elements, air, and compounds. The mass energy-absorption coefficients for nuclear track detectors were computed first time using Geant4 Monte Carlo code for energy 1 keV-20 MeV. Very good agreements for simulated results of mass energy-absorption coefficients for carbon, nitrogen, silicon, sodium iodide and nuclear track detectors were observed on comparison with the values reported in the literatures. Kerma relative to air for energy 1 keV-20 MeV and energy absorption buildup factors for energy 50 keV-10 MeV up to 10 mfp penetration depths of the selected nuclear track detectors were also calculated to evaluate the absorption of the gamma photons. Geant4 simulation can be utilized for estimation of mass energy-absorption coefficients in elements and composite materials.
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 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.
Bulk viscosity coefficients due to phonons in superfluid neutron stars
Manuel, Cristina; Tolos, Laura; Tarrús, Jaume E-mail: tarrus@ecm.ub.edu
2013-07-01
We calculate the three bulk viscosity coefficients as arising from the collisions among phonons in superfluid neutron stars. We use effective field theory techniques to extract the allowed phonon collisional processes, written as a function of the equation of state of the system. The solution of the dynamical evolution of the phonon number density allows us to calculate the bulk viscosity coefficients as function of the phonon collisional rate and the phonon dispersion law, which depends on the neutron pairing gap. Our method of computation is rather general, and could be used for different superfluid systems, provided they share the same underlying symmetries. We find that the behavior with temperature of the bulk viscosity coefficients is dominated by the contributions coming from the collinear regime of the 2↔3 phonon processes. For typical star radial pulsation frequencies of ω ∼ 10{sup 4}s{sup −1}, we obtain that the bulk viscosity coefficients at densities n∼>4n{sub 0} are within 10% from its static value for T∼<10{sup 9} K and for the case of strong neutron superfluidity in the core with a maximum value of the {sup 3}P{sub 2} gap above 1 MeV, while, otherwise, the static solution is not a valid approximation to the bulk viscosity coefficients. Compared to previous results from Urca and modified Urca reactions, we conclude that at T ∼ 10{sup 9}K phonon collisions give the leading contribution to the bulk viscosities in the core of the neutron stars, except for n ∼ 2n{sub 0} when the opening of the Urca processes takes place.
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.
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.
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
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.
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.
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)
Nguyen, Hieu T.; Rougieux, Fiacre E.; Mitchell, Bernhard; Macdonald, Daniel
2014-01-01
The band-band absorption coefficient in crystalline silicon has been determined using spectral photoluminescence measurements across the wavelength range of 990-1300 nm, and a parameterization of the temperature dependence has been established to allow interpolation of accurate values of the absorption coefficient for any temperature between 170 and 363 K. Band-band absorption coefficient measurements across a temperature range of 78-363 K are found to match well with previous results from MacFarlane et al. [Phys. Rev. 111, 1245 (1958)], and are extended to significantly longer wavelengths. In addition, we report the band-band absorption coefficient across the temperature range from 270-350 K with 10 K intervals, a range in which most practical silicon based devices operate, and for which there are only sparse data available at present. Moreover, the absorption coefficient is shown to vary by up to 50% for every 10 K increment around room temperature. Furthermore, the likely origins of the differences among the absorption coefficient of several commonly referenced works by Green [Sol. Energy Mater. Sol. Cells 92, 1305 (2008)], Daub and Würfel [Phys. Rev. Lett. 74, 1020 (1995)], and MacFarlane et al. [Phys. Rev. 111, 1245 (1958)] are discussed.
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
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.
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.
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…
Determination of absorption coefficients in AlInP lattice matched to GaAs
NASA Astrophysics Data System (ADS)
Cheong, J. S.; Ng, J. S.; Krysa, A. B.; Ong, J. S. L.; David, J. P. R.
2015-10-01
The absorption properties of Al0.52In0.48P have been investigated near the fundamental absorption edge by measuring the photocurrent as a function of wavelength in a series of PIN and NIP diodes. Modelling of the photocurrent in these structures enables the absorption coefficients to be determined accurately over a wide dynamic range, which allows the direct and indirect band-gap to be determined.
ERIC Educational Resources Information Center
Cordon, Gabriela B.; Lagorio, M. Gabriela
2007-01-01
A biophysical-chemistry experiment, based on the reflectance spectroscopy for calculating the absorption and scattering coefficients of leaves is described. The results show that different plants species exhibit different values for both the coefficients because of their different pigment composition.
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.
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.
Extinction and absorption coefficients and scattering phase functions of human tissues in vitro.
Marchesini, R; Bertoni, A; Andreola, S; Melloni, E; Sichirollo, A E
1989-06-15
Optical properties of different human tissues in vitro have been evaluated by measuring extinction and absorption coefficients at 635- and 515-nm wavelengths and a scattering angular dependence at 635 nm. Extinction was determined by the on-axis attenuation of light transmitted through sliced specimens of various thicknesses. The absorption coefficient was determined by placing samples into an integrating sphere. The Henyey-Greenstein function was used for fitting experimental data of the scattering pattern. The purpose of this work was to contribute to the study of light propagation in mammalian tissues. The results show that, for the investigated tissues, extinction coefficients range from ~200 to 500 cm(-1) whereas absorption coefficients, depending on wavelength, vary from 0.2 to 25 cm(-1). Scattering is forward peaked with an average cosine of ~0.7.
NASA Astrophysics Data System (ADS)
Kopelevich, Oleg V.; Filippov, Yuri V.
1994-10-01
The goal of this work is to verify different spectral models of the diffuse attenuation and absorption coefficients of sea water and to work out a recommendation for their use. It is shown that the spectral models of the diffuse attenuation coefficient Kd((lambda) ) developed by Austin, Petzold, 1984 and by Volynsky, Sud'bin, 1992 correspond with each other, as well the models of Ivanov, Shemshura, 1973 and of Kopelevich, Shemshura, 1988 for calculation of the spectral absorption coefficient a((lambda) ) on the values of Kd((lambda) ). Theoretical foundation of the relation between a((lambda) ) and Kd((lambda) ) is given. The up-to-date physical model of the sea water light absorption is considered and checked by means of comparison with measured values of the attenuation coefficient at the ultraviolet and visible spectral ranges.
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.
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.
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.
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)
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.
Measurement of the absorption coefficient of scattering liquid media by the calorimetric method
NASA Astrophysics Data System (ADS)
Butenin, A. V.; Kogan, B. Ya.
2012-02-01
Using the example of a number of hydrosols (gold nanorods and nanoshells, silver nanoshells, zinc phthalocyanine nanoparticles), we show that the absorption coefficient of a scattering liquid medium can be measured from its heating by a short-time laser irradiation. The degree of heating was determined from expansion of the liquid in an ampoule with a capillary (the principle of liquid thermometer). Irradiation was performed at a wavelength of 671 or 1069 nm. From the transmission of samples of hydrosols at these wave-lengths, the sum of the absorption and scattering coefficients has been determined. To measure the absorption spectra of scattering liquids by this method, a laser with a tunable radiation wavelength is required. In the case of monodisperse colloidal solutions, the method ensures the measurement of the absorption and scattering cross-section ratio of particles.
NASA Astrophysics Data System (ADS)
Yuan, Zhen; Jiang, Huabei
2006-06-01
We report on experimental demonstration of photoacoustic tomography for reconstructing the optical absorption coefficient images of heterogeneous media. Photoacoustic images are obtained from a series of tissuelike phantom experiments using a finite element-based reconstruction algorithm coupled with a scanning photoacoustic imaging system. The experimental results show that optical absorption images can be quantitatively reconstructed when the photon diffusion model is coupled with the Helmholtz photoacoustic wave equation.
NASA Astrophysics Data System (ADS)
Orlova, K. N.; Borovikov, I. F.; Gaidamak, M. A.
2016-08-01
The paper presents background value equivalent dose of gamma-radiation investigation in different weather: clear cloudy and overcast. The change of the dose rate of gamma radiation, depending on the weather and the ability cloudiness to shield gamma rays is shown. A new method for eliminating the consequences of accidents at nuclear power plants or plants using radioactive elements is proposed. A calculation method of cloudiness coefficient absorption and cloudiness gamma-radiation multiplicity attenuation is developed. The gamma- radiation multiplicity attenuation and the absorption coefficient of gamma radiation were calculated.
Absorptive potentials due to ionization and thermal diffuse scattering by fast electrons in crystals
Allen, L.J. ); Rossouw, C.J. )
1990-12-15
An expression for the Fourier coefficients of the absorptive potential due to electron-impact ionization in crystals is derived and the cross section is given in terms of these Fourier components. Absorptive potentials due to {ital K}-shell ionization and thermal diffuse scattering (TDS) are calculated with use of a hydrogenic model and an Einstein model, respectively. Inelastic potentials require integration over all states of the scattered electron and, for {ital K}-shell ionization, integration over all states of the ejected electron. These potentials are thus dependent on incident-beam energy, in contrast with the elastic potential. The projected spatial distribution of these potentials are plotted and compared with the elastic potential for CdTe, GaAs, Si, and diamond. The delocalization of the ionization absorptive potential is similar to that expected from classical impact-parameter arguments. The form of the TDS potential is substantially different from that due to elastic scattering, being extremely peaked on atomic positions with no absorption in the channels between atomic planes.
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.
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.
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
An analytic formula for heating due to ozone absorption
NASA Technical Reports Server (NTRS)
Lindzen, R. S.; Will, D. I.
1972-01-01
An attempt was made to devise a simple expression or formula to describe radiative heating in the atmosphere by ozone absorption. Such absorption occurs in the Hartley, Huggins, and Chappuis bands and is only slightly temperature and pressure dependent.
Leung, Hon-Wing; Paustenbach, D.J.
1994-03-01
This article reviews the scientific principles involved in determining the percutaneous absorption of chemicals. To assist industrial hygienists in assessing the risks of dermal uptake of chemicals in workplaces, lists of absorption rates and example calculations including the use of wipe sampling to estimate skin exposure are presented. Recent advances in the use of mathematical models to examine the various factors influencing the percutaneous absorption of chemicals from matrices are discussed. Results from various models suggest that the skin uptake of nonvolatile, highly lipophilic chemicals in soil will range from about 30 percent to 50 percent, while the uptake of volatile chemicals will usually be less than 5 percent. The available published information suggests the following rules of thumb: (1) the bioavailability of chemicals in media vary widely; consequently, it is important to account for matrix effects; (2) proper wipe sampling should be conducted to estimate the degree of skin contact with contaminated surfaces; (3) the hazards posed by dermal contact with certain chemicals in the workplace, particularly those with a high n-octanol:water partition coefficient, can produce an appreciable degree of the daily absorbed dose, and the dose from percutaneous absorption can often be as much as one-half that due to inhalation; and (4) the contribution to overall uptake from percutaneous absorption of chemical vapors can be significant if the atmospheric concentration of the chemicals is tenfold to one thousandfold higher than the threshold limit value, even when the worker wears protective clothing and adequate respiratory protection. 92 refs., 5 tabs.
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 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.
Carlon, H R
1980-04-01
Mass extinction coefficients of soil-derived atmospheric dusts often are determined largely by the absorption (rather than scattering) by individual particles, especially at longer IR wavelengths. Under many conditions, reasonable estimates of mass extinction coefficients of dusts can be made from absorption coefficients without the need for detailed knowledge of particle optical constants to perform, e.g., Mie calculations. This paper discusses absorption coefficients of dusts in the visible and IR wavelengths and the physical mechanisms of dust aerosol generation determining that portion of extinction attributable to absorption in a given dust cloud. Some soils, especially clays, can produce dust clouds that are almost pure. absorbers at longer IR wavelengths.
Carlon, H R
1980-03-01
Mass extinction coefficients of soil-derived atmospheric dusts often are determined largely by the absorption (rather than scattering) by individual particles, especially at longer IR wavelengths. Under many conditions, reasonable estimates of mass extinction coefficients of dusts can be made from absorption coefficients without the need for detailed knowledge of particle optical constants to perform, e.g., Mie calculations. This paper discusses absorption coefficients of dusts in the visible and IR wavelengths and the physical mechanisms of dust aerosol generation determining that portion of extinction attributable to absorption in a given dust cloud. Some soils, especially clays, can produce dust clouds that are almost pure absorbers at longer IR wavelengths.
NASA Technical Reports Server (NTRS)
Calvin, Wendy M.
1990-01-01
Reflectance spectra of carbon dioxide frosts were calculated using the optical constants provided by Warren (1986) for the wavelength region 2-6 microns. In comparing these calculated spectra to spectra of frosts observed in the laboratory and on the surface of Mars, problems in the optical constants presented by Warren (1986) became apparent. Absorption coefficients for CO2 ice have been derived using laboratory reflectance measurements and the Hapke (1981) model for calculating diffuse reflectance. This provides approximate values in regions where no data were previously available and indicates where corrections to the compilation by Warren (1986) are required. Using these coefficients to calculate the reflectance of CO2 ice at varying grain sizes indicates that a typical Mariner polar cap spectrum is dominated by absorptions due to CO2 frost or ice at grain sizes that are quite large, probably of the order of millimeters to centimeters. There are indications of contamination of water frost or dust, but confirmation will require more precise absorption coefficients for solid CO2 than can be obtained from the method used here.
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)
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.
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.
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.
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
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.
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
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 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
Khalifah, Peter
2015-01-30
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 both in computational efficiency and in gaining an intuitive understanding of the effects of absorption on the diffraction data. A matrix of absorption coefficients calculated for μ
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.
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.
Keller, M.; Bostater, C.
1997-06-01
A portable, long path length (50 cm), flow through, absorption tube system is utilized to obtain in-situ specific absorption coefficients from various water environments consisting of both clear and turbid water conditions from an underway ship or vessel. The high spectral resolution absorption signatures can be obtained and correlated with measured water quality parameters along a ship track. The long path cuvette system is capable of measuring important water quality parameters such as chlorophyll-a, seston or total suspended matter, tannins, humics, fulvic acids, or dissolved organic matter (dissolved organic carbon, DOC). The various concentrations of these substances can be determined and correlated with laboratory measurements using the double inflection ratio (DIR) of the spectra based upon derivative spectroscopy. The DIR is determined for all of the possible combinations of the bands ranging from 362-1115 nm using 252 channels, as described previously by Bostater. The information gathered from this system can be utilized in conjunction with hyperspectral imagery that allows one to relate reflectance and absorption to water quality of a particular environment. A comparison is made between absorption signatures and reflectance obtained from the Banana River, Florida.
Microwave Resonator Measurements of Atmospheric Absorption Coefficients: A Preliminary Design Study
NASA Technical Reports Server (NTRS)
Walter, Steven J.; Spilker, Thomas R.
1995-01-01
A preliminary design study examined the feasibility of using microwave resonator measurements to improve the accuracy of atmospheric absorption coefficients and refractivity between 18 and 35 GHz. Increased accuracies would improve the capability of water vapor radiometers to correct for radio signal delays caused by Earth's atmosphere. Calibration of delays incurred by radio signals traversing the atmosphere has applications to both deep space tracking and planetary radio science experiments. Currently, the Cassini gravity wave search requires 0.8-1.0% absorption coefficient accuracy. This study examined current atmospheric absorption models and estimated that current model accuracy ranges from 5% to 7%. The refractivity of water vapor is known to 1% accuracy, while the refractivity of many dry gases (oxygen, nitrogen, etc.) are known to better than 0.1%. Improvements to the current generation of models will require that both the functional form and absolute absorption of the water vapor spectrum be calibrated and validated. Several laboratory techniques for measuring atmospheric absorption and refractivity were investigated, including absorption cells, single and multimode rectangular cavity resonators, and Fabry-Perot resonators. Semi-confocal Fabry-Perot resonators were shown to provide the most cost-effective and accurate method of measuring atmospheric gas refractivity. The need for accurate environmental measurement and control was also addressed. A preliminary design for the environmental control and measurement system was developed to aid in identifying significant design issues. The analysis indicated that overall measurement accuracy will be limited by measurement errors and imprecise control of the gas sample's thermodynamic state, thermal expansion and vibration- induced deformation of the resonator structure, and electronic measurement error. The central problem is to identify systematic errors because random errors can be reduced by averaging
Parker, K; Morrison, G
2016-08-01
Occupants of former methamphetamine laboratories, often residences, may experience increased exposure through the accumulation of the methamphetamine in the organic films that coat skin and indoor surfaces. The objectives of this study were to determine equilibrium partition coefficients of vapor-phase methamphetamine with artificial sebum (AS-1), artificial sebum without fatty acids (AS-2), and real skin surface films, herein called skin oils. Sebum and skin oil-coated filters were exposed to vapor-phase methamphetamine at concentrations ranging from 8 to 159 ppb, and samples were analyzed for exposure time periods from 2 h to 60 days. For a low vapor-phase methamphetamine concentration range of ~8-22 ppb, the equilibrium partition coefficient for AS-1 was 1500 ± 195 μg/g/ppb. For a high concentration range of 98-112 ppb, the partition coefficient was lower, 459 ± 80 μg/g/ppb, suggesting saturation of the available absorption capacity. The low partition coefficient for AS-2 (33 ± 6 μg/g/ppb) suggests that the fatty acids in AS-1 and skin oil are responsible for much high partition coefficients. We predict that the methamphetamine concentration in skin lipids coating indoor surfaces can exceed recommended surface remediation standards even for air concentrations well below 1 ppb.
Spectroscopic method for determination of the absorption coefficient in brain tissue.
Johansson, Johannes D
2010-01-01
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.
Wu, Xiaojun; Zhou, Chun; Huang, Wenqian Ronny; Ahr, Frederike; Kärtner, Franz X
2015-11-16
Optical rectification with tilted pulse fronts in lithium niobate crystals is one of the most promising methods to generate terahertz (THz) radiation. In order to achieve higher optical-to-THz energy efficiency, it is necessary to cryogenically cool the crystal not only to decrease the linear phonon absorption for the generated THz wave but also to lengthen the effective interaction length between infrared pump pulses and THz waves. However, the refractive index of lithium niobate crystal at lower temperature is not the same as that at room temperature, resulting in the necessity to re-optimize or even re-build the tilted pulse front setup. Here, we performed a temperature dependent measurement of refractive index and absorption coefficient on a 6.0 mol% MgO-doped congruent lithium niobate wafer by using a THz time-domain spectrometer (THz-TDS). When the crystal temperature was decreased from 300 K to 50 K, the refractive index of the crystal in the extraordinary polarization decreased from 5.05 to 4.88 at 0.4 THz, resulting in ~1° change for the tilt angle inside the lithium niobate crystal. The angle of incidence on the grating for the tilted pulse front setup at 1030 nm with demagnification factor of -0.5 needs to be changed by 3°. The absorption coefficient decreased by 60% at 0.4 THz. These results are crucial for designing an optimum tilted pulse front setup based on lithium niobate crystals.
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.
Yuan, Zhen; Wang, Qiang; Jiang, Huabei
2007-12-24
We describe a novel reconstruction method that allows for quantitative recovery of optical absorption coefficient maps of heterogeneous media using tomographic photoacoustic measurements. Images of optical absorption coefficient are obtained from a diffusion equation based regularized Newton method where the absorbed energy density distribution from conventional photoacoustic tomography serves as the measured field data. We experimentally demonstrate this new method using tissue-mimicking phantom measurements and simulations. The reconstruction results show that the optical absorption coefficient images obtained are quantitative in terms of the shape, size, location and optical property values of the heterogeneities examined.
NASA Astrophysics Data System (ADS)
Yáñez M., J.
2011-10-01
Diabetes is a disease with no cure, but can be controlled to improve the quality of life of sufferers. Currently there are means to control, but this means they have the disadvantage that in order to measure the amount of glucose is necessary to take blood samples that are painful. This paper presents a system for measuring glucose using non-invasive optical techniques: using absorption spectroscopy and polarimetry technique. It shows the results obtained from experiments done on samples containing distilled water and different amounts of glucose to study the absorption coefficient of glucose with both techniques. Water is used because it is one of the main elements in the blood and interferes with glucose measurement. This experiment will develop a prototype to measure glucose through a non-invasive technique.
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
Pelivanov, Ivan M; Barskaya, M I; Podymova, N B; Khokhlova, Tanya D; Karabutov, Aleksander A
2009-09-30
The second part of this work describes the experimental technique of measuring the local light absorption in turbid media. The technique is based on the measurement of the amplitude of an opto-acoustic (OA) signal excited in a turbid medium under the condition of one-sided access to the object under study. An OA transducer is developed to perform the proposed measurement procedure. Experiments are conducted for the turbid media with different optical properties (light absorption and reduced scattering coefficients) and for different diameters of the incident laser beam. It is found that the laser beam diameter can be chosen so that the dependences of the measured OA signal amplitude on the light absorption coefficient coincide upon varying the reduced scattering coefficient by more than twice. The obtained numerical and experimental results demonstrate that the OA method is applicable for measuring the local light absorption coefficient in turbid media, for example, in biological tissues. (measurement of parametrs of laser radiation)
Stopping-power and mass energy-absorption coefficient ratios for Solid Water.
Ho, A K; Paliwal, B R
1986-01-01
The AAPM Task Group 21 protocol provides tables of ratios of average restricted stopping powers and ratios of mean energy-absorption coefficients for different materials. These values were based on the work of Cunningham and Schulz. We have calculated these quantities for Solid Water (manufactured by RMI), using the same x-ray spectra and method as that used by Cunningham and Schulz. These values should be useful to people who are using Solid Water for high-energy photon calibration. PMID:3724702
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)
de Santiago Duran, Oscar Cesar
Experimental identification of fluid film bearing parameters is vital to validate predictions from often restrictive computational fluid film bearing models and is also promising for condition monitoring and troubleshooting. This dissertation presents the analytical bases of two procedures for bearing supports parameter identification with potential for in-situ implementation. Bearing support coefficients are derived from measurements of rotor responses to impact loads and due to calibrated imbalances in characteristic planes. Subsequent implementation of the procedures to measurements performed in a rigid massive rotor traversing two critical speeds provides force coefficients for a novel bearing support comprising a tilting pad bearing (TPJB ) in series with an integral squeeze film damper (SFD). At a constant rotor speed, the first method requires impacts loads exerted along two lateral planes for identification of frequency-dependent force coefficients. Simulation numerical examples show the method is reliable with a reduced sensitivity to noise as the number of impacts increases (frequency averaging). In the experiments, an ad-hoc fixture delivers impacts to the rotor middle disk at speeds of 2,000 and 4,000 rpm. The experimentally identified force coefficients are in close agreement with predicted coefficients for the series support TPJB-SFD. In particular, damping coefficients are best identified around the system first natural frequency. Bearing stiffness are correctly identified in the low frequency range, but show a marked reduction at higher frequencies apparently due to inertial effects not accounted for in the model. Measurements of rotor response to calibrated imbalances allow identification of speed-dependent force coefficients. The procedure requires a minimum of two different imbalance distributions for identification of force coefficients from the two bearing supports. The rotor responses show minimal cross-coupling effects, as also predicted by
A study of the H2O absorption line shifts in the visible spectrum region due to air pressure
NASA Technical Reports Server (NTRS)
Grossmann, B. E.; Browell, E. V.; Bykov, A. D.; Kapitanov, V. A.; Korotchenko, E. A.
1990-01-01
Results of measured and calculated shift coefficients are presented for 170 absorption lines of H2O in five vibrational-rotational bands. The measurements have been carried out using highly sensitive laser spectrometers with a resolution of at least 0.01/cm; the calculations are based on the Anderson-Tsao-Curnutte-Frost method. Good agreement is obtained between the theoretical and experimental values of the shift coefficients of H2O lines due to N2, O2, and air pressure.
NASA Astrophysics Data System (ADS)
Zamani, N.; Keshavarz, A.; Nadgaran, H.
2016-06-01
In this paper, we investigate the optical absorption coefficient of hybrid structure consisting of metal nano particle (MNP) coupled to multi-layer spherical quantum dot (MSQD). Energy eigenvalues and eigenfunctions of Schrödinger equation in this structure are obtained by using numerical solution (by the fourth-order Runge-Kutta method). The effect of MNP in the vicinity of MSQD is calculated by considering local field theory. Then the variation of optical absorption coefficient hybrid structure is calculated. The results show that the presence of MNP near MSQD enhances the optical absorption coefficient. Also, by changing the distance between MNP and MSQD and radius of MNP, variation of optical absorption coefficient and refractive index changes are introduced.
NASA 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.
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.
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.
Binzoni, T; Leung, T S; Rüfenacht, D; Delpy, D T
2006-01-21
Based on quasi-elastic scattering theory (and random walk on a lattice approach), a model of laser-Doppler flowmetry (LDF) has been derived which can be applied to measurements in large tissue volumes (e.g. when the interoptode distance is >30 mm). The model holds for a semi-infinite medium and takes into account the transport-corrected scattering coefficient and the absorption coefficient of the tissue, and the scattering coefficient of the red blood cells. The model holds for anisotropic scattering and for multiple scattering of the photons by the moving scatterers of finite size. In particular, it has also been possible to take into account the simultaneous presence of both Brownian and pure translational movements. An analytical and simplified version of the model has also been derived and its validity investigated, for the case of measurements in human skeletal muscle tissue. It is shown that at large optode spacing it is possible to use the simplified model, taking into account only a 'mean' light pathlength, to predict the blood flow related parameters. It is also demonstrated that the 'classical' blood volume parameter, derived from LDF instruments, may not represent the actual blood volume variations when the investigated tissue volume is large. The simplified model does not need knowledge of the tissue optical parameters and thus should allow the development of very simple and cost-effective LDF hardware.
NASA Technical Reports Server (NTRS)
Eldridge, Jeffrey I.; Spuckler, Charles M.; Markham, James R.
2009-01-01
The temperature dependence of the scattering and absorption coefficients for a set of freestanding plasma-sprayed 8 wt% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) was determined at temperatures up to 1360 C in a wavelength range from 1.2 micrometers up to the 8YSZ absorption edge. The scattering and absorption coefficients were determined by fitting the directional-hemispherical reflectance and transmittance values calculated by a four-flux Kubelka Munk method to the experimentally measured hemispherical-directional reflectance and transmittance values obtained for five 8YSZ thicknesses. The scattering coefficient exhibited a continuous decrease with increasing wavelength and showed no significant temperature dependence. The scattering is primarily attributed to the relatively temperature-insensitive refractive index mismatch between the 8YSZ and its internal voids. The absorption coefficient was very low (less than 1 per centimeter) at wavelengths between 2 micrometers and the absorption edge and showed a definite temperature dependence that consisted of a shift of the absorption edge to shorter wavelengths and an increase in the weak absorption below the absorption edge with increasing temperature. The shift in the absorption edge with temperature is attributed to strongly temperature-dependent multiphonon absorption. While TBC hemispherical transmittance beyond the absorption edge can be predicted by a simple exponential decrease with thickness, below the absorption edge, typical TBC thicknesses are well below the thickness range where a simple exponential decrease in hemispherical transmittance with TBC thickness is expected. [Correction added after online publication August 11, 2009: "edge to a shorter wavelengths" has been updated as edge to shorter wavelengths."
NASA Astrophysics Data System (ADS)
Ajtai, T.; Schnaiter, M.; Linke, C.; Vragel, M.; Filep, Á.; Fődi, L.; Motika, G.; Bozóki, Z.; Szabó, G.
2009-04-01
Despite of its importance, the possibilities to determine the direct radiative forcing by atmospheric aerosols is very limited due to lack of the reliable on-line instruments. Therefore there is an increasing concern for novel methods promising more accurate and reliable results in this field. The accuracy and reliability of the available on-line instruments like SP2 (Single Particle Soot Photometer), MAAP (Multi Angle Absorption Photometer), are limited by the weakness of the spectral resolution or the sampling artefact of filter matrix during the light attenuation measurement on the deposited filter. These methods neither suitable for direct determination of the light absorption by aerosols nor dispose the capability of the source apportionment. In this work we present a novel photoacoustic based instrument for direct light absorption measurements in the atmosphere and demonstrate the suitability of that both in laboratory and field circumstances. We have developed a novel Multi Wavelength PhotoAcoustic System (WaSul-MuWaPas) based on the diode laser pumped, high repetition rate, Q-switched Nd:YAG laser and its frequency converted harmonics for direct determination of light absorption by aerosols. This instrument has designed to make in situ measurements at four different wavelengths simultaneously from the NIR to the UV wavelength range (1064nm, 532nm, 355nm, 266nm). The Wasul-MuWaPas measures directly the optical absorption coefficient on airborne particles, not belong to the integrated plate type technique (filter-free operation), operating at wide wavelength range (source apportionment possibilities), due to the possibilities of the wavelength independent cell constant determination the measurement method is absolute. Because of these the Wasul-MuWaPas system may become one of the best candidate for absorption measurements of various atmospheric aerosols such as black carbon, mineral dust, and secondary organic and inorganic aerosols as well as for source
NASA Astrophysics Data System (ADS)
Bondarenko, S. V.; Garanin, Sergey G.; Zhidkov, N. V.; Pinegin, A. V.; Suslov, N. A.
2012-01-01
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.
Röttgers, Rüdiger; McKee, David; Utschig, Christian
2014-10-20
The light absorption coefficient of water is dependent on temperature and concentration of ions, i.e. the salinity in seawater. Accurate knowledge of the water absorption coefficient, a, and/or its temperature and salinity correction coefficients, Ψ(T) and Ψ(S), respectively, is essential for a wide range of optical applications. Values are available from published data only at specific narrow wavelength ranges or at single wavelengths in the visible and infrared regions. Ψ(T) and Ψ(S) were therefore spectrophotometrically measured throughout the visible, near, and short wavelength infrared spectral region (400 to ~2700 nm). Additionally, they were derived from more precise measurements with a point-source integrating-cavity absorption meter (PSICAM) for 400 to 700 nm. When combined with earlier measurements from the literature in the range of 2600 - 14000 nm (wavenumber: 3800 - 700 cm(-1)), the coefficients are provided for 400 to 14000 nm (wavenumber: 25000 to 700 cm(-1)).
High resolution absorption coefficients for Freon-12. [by using tunable diode laser spectroscopy
NASA Technical Reports Server (NTRS)
Hoell, J. M.; Bair, C. H.; Williams, B.; Harward, C.
1979-01-01
The ultra high resolution absorption coefficients of the Q-branch of Freon-12 obtained with tunable diode laser spectroscopy are presented. Continuous spectra are presented from 1155/cm to 1163/cm, and absolute wavelength calibration was obtained using SO2 spectra as a standard and a 5 cm Ge etalon for relative calibration between SO2 lines. The Freon-12 data obtained at a pressure of 0.05 torr showed a rich and highly structured spectra, but with the exception of three isolated features, collisional broadening reduces the spectra to a structureless continuum for nitrogen pressures greater than 20 torr. The spectra at 1161/cm continue to exhibit structure at atmospheric pressure.
NASA Astrophysics Data System (ADS)
Kobayashi, Keiji
1997-05-01
The purpose of this study is to decrease and to remove OH ions and H2O in borosilicate glasses. Fluoride-containing borosilicate glasses followed by dry-air-bubbling showed the significant decrease of OH absorption bands around 3500 cm-1. The decrease of OH absorption bands was elucidated by the use of pyrohydrolysis reactions in these glasses where fluoride ions react with OH ions or H2O during melting. The rates of the decrease of OH absorption bands substantially depend on high valence cations of fluorides. Particularly, the decrease rates of OH absorption coefficients were in the order of ZrF4-containing glass>AlF3-containing glass>ZnF2-containing glass. ZrF4-containing glass treated by dry-air-bubbling showed a good capability to remove OH absorption band. Fluoride-containing glasses showed the low flow point in comparison with fluoride-free glasses.
Oil droplets transport due to irregular waves: Development of large-scale spreading coefficients.
Geng, Xiaolong; Boufadel, Michel C; Ozgokmen, Tamay; King, Thomas; Lee, Kenneth; Lu, Youyu; Zhao, Lin
2016-03-15
The movement of oil droplets due to waves and buoyancy was investigated by assuming an irregular sea state following a JONSWAP spectrum and four buoyancy values. A technique known as Wheeler stretching was used to model the movement of particles under the moving water surface. In each simulation, 500 particles were released and were tracked for a real time of 4.0 h. A Monte Carlo approach was used to obtain ensemble properties. It was found that small eddy diffusivities that decrease rapidly with depth generated the largest horizontal spreading of the plume. It was also found that large eddy diffusivities that decrease slowly with depth generated the smallest horizontal spreading coefficient of the plume. The increase in buoyancy resulted in a decrease in the horizontal spreading coefficient, which suggests that two-dimensional (horizontal) models that predict the transport of surface oil could be overestimating the spreading of oil. PMID:26795121
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)
Lee, H. J.; Aiona, P. K.; Nizkorodov, S.; Laskin, J.; Laskin, A.
2014-12-01
Atmospheric aerosols that absorb solar radiation have a direct effect on climate. Brown carbon (BrC) represents the type of carbonaceous aerosols characterized by large absorption coefficients in the near-UV range of the spectrum. BrC can be either directly emitted into the atmosphere from combustion sources, or be formed in the atmosphere through multi-phase reactions, such as aging of secondary organic aerosols (SOA) mediated by ammonium sulfate (AS). Under the conditions of exposure to solar radiation, both primary and secondary BrC can potentially change their molecular composition and optical properties as a result of photodegradation of chromophoric compounds. This presentation will discuss the molecular level composition, the absorption and fluorescence spectra, and the mechanism of photodegradation among several representative types of BrC. The primary BrC samples include aerosol produced by smoldering wood combustion. The secondary BrC samples include AS aged products of chamber-generated SOA, products of reaction between methylglyoxal and AS, and SOA produced by the hogh-NOx photooxdiation of aromatic compounds, such as naphthalene. This presentation will also include preliminary data on the absorption and fluorescence spectra of photo-degraded bioaerosols. In all cases, absorption spectra of extracted bulk samples are measured during irradiation by a known flux of UV or visible light. The molecular level composition of the fresh and photobleached samples are characterized by high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). Photobleaching of BrC is found to occur over a range of atmospherically relevant time scales. In many cases, the molecular level composition of photobleached BrC exhibits only subtle changes suggesting that the optical and fluorescence properties of BrC are controlled by a few compounds present in low quantities. The observed fluorescence from non-biological BrC indicates potential issues in using fluorescence
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.
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.
Absorption Coefficients of the Methane-Nitrogen Binary Ice System: Implications for Pluto
NASA Astrophysics Data System (ADS)
Protopapa, Silvia; Grundy, W.; Tegler, S.; Bergonio, J.; Boehnhardt, H.; Barrera, L.
2013-10-01
Near infrared spectroscopic measurements of Pluto display methane (CH4) ice absorption bands shifted toward shorter wavelengths compared to the central wavelengths of pure CH4 obtained in the laboratory. This shift, described by Schmitt and Quirico (1992), occurs when CH4 is dissolved at low concentrations in a matrix of solid N2, and the magnitude of the shift varies from one CH4 band to another. This is the main argument behind the modeling analysis of Pluto’s spectra available in literature, employing pure CH4 and CH4 diluted at low concentrations in N2. However, the nitrogen-methane binary phase diagram generated from X-ray diffraction studies by Prokhvatilov & Yantsevich (1983) indicates that at temperatures relevant to the surfaces of icy dwarf planets, like Pluto, two phases contribute to the absorptions: methane ice saturated with nitrogen and nitrogen ice saturated with methane. No optical constants are available so far for the latter component, limiting this way the knowledge of the methane-nitrogen mixing ratio across and into the surface of Pluto and other dwarf planets. New infrared absorption coefficient spectra of CH4-I diluted in β-N2 and β-N2 diluted in CH4-I were measured at temperatures between 40 and 90 K, in the wavelength range 0.8-2.5 μm at different mixing ratios. The spectra were derived from transmission measurements of crystals grown from the liquid phase in closed cells. In particular, a systematic study of the changes in CH4:N2 mixtures spectral behavior with mixing ratio is presented for the first time, in order to understand whether the peak frequencies of the CH4-ice bands correlate with the amount of N2-ice. We report a linear trend of the blueshifts of the CH4-ice bands vs CH4 abundance. This trend varies from band to band, while it is fairly constant with temperature. These data are applied to interpret unpublished high dispersion H and K bands spectra of Pluto acquired with the NACO instrument at the ESO VLT on 27 June 2008
Optoelectronic properties of Mg{sub 2}Si semiconducting layers with high absorption coefficients
Kato, Takashi; Sago, Yuichiro; Fujiwara, Hiroyuki
2011-09-15
In an attempt to develop a low-cost material for solar cell devices, polycrystalline magnesium silicide (poly-Mg{sub 2}Si) semiconducting layers have been prepared by applying rf magnetron sputtering using a Mg{sub 2}Si target. The optimum substrate temperature for the poly-Mg{sub 2}Si growth was found to be T{sub s} = 200 deg. C; the film deposition at higher temperatures leads to desorption of Mg atoms from the growing surface, while the amorphous phase formation occurs at room temperature. The poly-Mg{sub 2}Si layer deposited at T{sub s} = 200 deg. C shows the (111) preferential orientation with a uniform grain size of {approx}50 nm. The dielectric function of the poly-Mg{sub 2}Si layer has been determined accurately by spectroscopic ellipsometry. From the analysis, quite high absorption coefficients and an indirect gap of 0.77 eV in the poly-Mg{sub 2}Si layer have been confirmed. The above poly-Mg{sub 2}Si layer shows clear photoconductivity and can be applied as a narrow-gap bottom layer in multi-junction solar cell devices.
Noise-driven optical absorption coefficients of impurity doped quantum dots
NASA Astrophysics Data System (ADS)
Ganguly, Jayanta; Saha, Surajit; Pal, Suvajit; Ghosh, Manas
2016-01-01
We make an extensive investigation of linear, third-order nonlinear, and total optical absorption coefficients (ACs) of impurity doped quantum dots (QDs) in presence and absence of noise. The noise invoked in the present study is a Gaussian white noise. The quantum dot is doped with repulsive Gaussian impurity. Noise has been introduced to the system additively and multiplicatively. A perpendicular magnetic field acts as a source of confinement and a static external electric field has been applied. The AC profiles have been studied as a function of incident photon energy when several important parameters such as optical intensity, electric field strength, magnetic field strength, confinement energy, dopant location, relaxation time, Al concentration, dopant potential, and noise strength take on different values. In addition, the role of mode of application of noise (additive/multiplicative) on the AC profiles has also been analyzed meticulously. The AC profiles often consist of a number of interesting observations such as one photon resonance enhancement, shift of AC peak position, variation of AC peak intensity, and bleaching of AC peak. However, presence of noise alters the features of AC profiles and leads to some interesting manifestations. Multiplicative noise brings about more complexity in the AC profiles than its additive counterpart. The observations indeed illuminate several useful aspects in the study of linear and nonlinear optical properties of doped QD systems, specially in presence of noise. The findings are expected to be quite relevant from a technological perspective.
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.
NASA Astrophysics Data System (ADS)
Fairuz Budiman, Mohd; Hu, Weiguo; Igarashi, Makoto; Tsukamoto, Rikako; Isoda, Taiga; Itoh, Kohei M.; Yamashita, Ichiro; Murayama, Akihiro; Okada, Yoshitaka; Samukawa, Seiji
2012-02-01
A sub-10 nm, high-density, periodic silicon-nanodisc (Si-ND) array has been fabricated using a new top-down process, which involves a 2D array bio-template etching mask made of Listeria-Dps with a 4.5 nm diameter iron oxide core and damage-free neutral-beam etching (Si-ND diameter: 6.4 nm). An Si-ND array with an SiO2 matrix demonstrated more controllable optical bandgap energy due to the fine tunability of the Si-ND thickness and diameter. Unlike the case of shrinking Si-ND thickness, the case of shrinking Si-ND diameter simultaneously increased the optical absorption coefficient and the optical bandgap energy. The optical absorption coefficient became higher due to the decrease in the center-to-center distance of NDs to enhance wavefunction coupling. This means that our 6 nm diameter Si-ND structure can satisfy the strict requirements of optical bandgap energy control and high absorption coefficient for achieving realistic Si quantum dot solar cells.
NASA Astrophysics Data System (ADS)
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.
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.
Xia, X R; Baynes, R E; Monteiro-Riviere, N A; Riviere, J E
2007-01-01
A system coefficient approach is proposed for quantitative assessment of the solvent effects on membrane absorption from chemical mixtures. The complicated molecular interactions are dissected into basic molecular interaction forces via Abraham's linear solvation energy relationship (LSER). The molecular interaction strengths of a chemical are represented by a set of solute descriptors, while those of a membrane/chemical mixture system are represented by a set of system coefficients. The system coefficients can be determined by using a set of probe compounds with known solute descriptors. Polydimethylsiloxane (PDMS) membrane-coated fibres and 32 probe compounds were used to demonstrate the proposed approach. When a solvent was added into the chemical mixture, the system coefficients were altered and detected by the system coefficient approach. The system coefficients of the PDMS/water system were (0.09, 0.49, -1.11, -2.36, -3.78, 3.50). When 25% ethanol was added into the PDMS/water system, the system coefficients were altered significantly (0.38, 0.41, -1.18, -2.07, -3.40, 2.81); and the solvent effect was quantitatively described by the changes in the system coefficients (0.29, -0.08, -0.07, 0.29, 0.38, -0.69). The LSER model adequately described the experimental data with a correlation coefficient (r(2)) of 0.995 and F-value of 1056 with p-value less than 0.0001.
Benmakhlouf, Hamza; Bouchard, Hugo; Fransson, Annette; Andreo, Pedro
2011-11-21
Backscatter factors, B, and mass energy-absorption coefficient ratios, (μ(en)/ρ)(w, air), for the determination of the surface dose in diagnostic radiology were calculated using Monte Carlo simulations. The main purpose was to extend the range of available data to qualities used in modern x-ray techniques, particularly for interventional radiology. A comprehensive database for mono-energetic photons between 4 and 150 keV and different field sizes was created for a 15 cm thick water phantom. Backscattered spectra were calculated with the PENELOPE Monte Carlo system, scoring track-length fluence differential in energy with negligible statistical uncertainty; using the Monte Carlo computed spectra, B factors and (μ(en)/ρ)(w, air) were then calculated numerically for each energy. Weighted averaging procedures were subsequently used to convolve incident clinical spectra with mono-energetic data. The method was benchmarked against full Monte Carlo calculations of incident clinical spectra obtaining differences within 0.3-0.6%. The technique used enables the calculation of B and (μ(en)/ρ)(w, air) for any incident spectrum without further time-consuming Monte Carlo simulations. The adequacy of the extended dosimetry data to a broader range of clinical qualities than those currently available, while keeping consistency with existing data, was confirmed through detailed comparisons. Mono-energetic and spectra-averaged values were compared with published data, including those in ICRU Report 74 and IAEA TRS-457, finding average differences of 0.6%. Results are provided in comprehensive tables appropriated for clinical use. Additional qualities can easily be calculated using a designed GUI interface in conjunction with software to generate incident photon spectra.
NASA Astrophysics Data System (ADS)
Busch, T. A.; Nugent, R. E.
2003-10-01
In situ testing determined the insertion loss ( IL) and absorption coefficients of a candidate absorptive noise barrier (soundwall) to abate railway noise for residents of Anaheim, CA. A 4000 m barrier is proposed south of the tracks, but residential areas to the north have expressed concerns that barrier reflections will increase their noise exposure. To address these concerns, a 3.66 m high by 14.6 m long demonstration barrier was built in the parking lot of Edison Field, Anaheim, as part of a public open house, thereby allowing for acoustical measurements. Insertion loss ( IL) was measured in third-octave bands assuming 1/2-scale construction. The IL for three, scaled railway noise sub-sources (rail/wheel interface, locomotive, and train horn) was measured at six, scaled distances. The highest total, A-weighted IL, after corrections for finite-barrier and point-source speaker effects was 22 dB(A) for rail/wheel noise, 18 dB(A) for locomotive noise, and 20 dB(A) for train horn noise. These results can be compared favourably to IL predictions made using algorithms from the US Federal Rail Administration (FRA) noise assessment guidelines. For the actual barrier installation, shielded residential receivers located south of the project are expected to see their future noise exposures reduced from an unmitigated 78 CNEL to 65 CNEL. Absorption coefficients were measured using time delay spectrometry. At lower frequencies, measured absorption coefficients were notably less than the reverberation room results advertised in the manufacturer's literature, but generally conformed with impedance tube results. At higher frequencies the correspondence between measured absorption coefficients and reverberation room results was much improved. For the actual barrier installation, unshielded residential receivers to the north are expected to experience noise exposure increases of less than 1 dB(A). This factor of increase is consistent with a finding of no impact when assessed
Gramsch, Ernesto; Ormeño, Isabel; Palma, Guillermo; Cereceda-Balic, Francisco; Oyola, Pedro
2004-07-01
The optical absorption coefficient, particulate matter with an aerodynamic diameter <2.5 microm, and elemental carbon (EC) have been measured simultaneously during winter and spring of 2000 in the western part of Santiago, Chile (Pudahuel district). The optical measurements were carried out with a low-cost instrument recently developed at the University of Santiago. From the data, a site-specific mass absorption coefficient of 4.45+/-0.01 m2/g has been found for EC. In addition, a mass absorption coefficient of 1.02+/-0.03 m2/g has been obtained for PM2.5. These coefficients can be used during the colder months (May-August) to obtain EC concentration or PM2.5 from a measurement of the light absorption coefficient (sigmaa). The high correlation that has been found between these variables indicates that sigmaa is a good indicator of the degree of contamination of urbanized areas. The data also show an increase in PM2.5 and EC concentration during winter and an increase in the ratio of EC to PM2.5. When the EC/PM2.5 ratio is calculated during rush hour (7:00 a.m.-11:00 a.m.) and during part of the night (9:00 p.m.-2:00 a.m.), it is found that the increase is caused by higher concentration levels of EC at night. These results suggest that the rise in the EC concentration is caused by emissions from heating and air mass transport of pollution from other parts of the city, while traffic contribution remains approximately constant.
NASA Astrophysics Data System (ADS)
McKee, David; Röttgers, Rüdiger; Neukermans, Griet; Calzado, Violeta Sanjuan; Trees, Charles; Ampolo-Rella, Marina; Neil, Claire; Cunningham, Alex
2014-12-01
Understanding variability in the chlorophyll-specific absorption of marine phytoplankton, aph*Chl (λ), is essential for primary production modelling, calculation of underwater light field characteristics, and development of algorithms for remote sensing of chlorophyll concentrations. Previous field and laboratory studies have demonstrated significant apparent variability in aph*Chl (λ) for natural samples and algal cultures. However, the potential impact of measurement uncertainties on derived values of aph*Chl (λ) has received insufficient study. This study presents an analysis of measurement uncertainties for a data set collected in the Ligurian Sea in Spring and assesses the impact on estimates of aph*Chl (λ). It is found that a large proportion of apparent variability in this set of aph*Chl (λ) can be attributed to measurement errors. Application of the same analysis to the global NOMAD data set suggests that a significant fraction of variability in aph*Chl (λ) may also be due to measurement errors. The copyright line for this article was changed on 16 JAN 2015 after original online publication.
NASA Astrophysics Data System (ADS)
Riedel, D.; Castex, M. C.
First measurements of effective absorption coefficient and penetration depth are given here from the ablation of poly-methylmethacrylate (PMMA) and poly-tetrafluoroethylene (PTFE) samples at 125 nm ( 10 eV). The coherent VUV source used which provides smooth, efficient and clean etched areas, is briefly described. Experimental curves of etch depth as a function of the number of laser shots and etch rate as a function of energy density are obtained and compared with previous works performed at 157 nm (F2 laser) and 193 nm (ArF laser). Experimental results are described with a Beer-Lambert absorption law and discussed.
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.
Andreo, Pedro; Burns, David T; Salvat, Francesc
2012-04-21
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 µ(en)/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, u(c), for the µ(en)/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, u(c) is approximately 0.1%. The Type B uncertainty analysis for the ratios of µ(en)/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 (µ(en)/ρ)(graphite,air) and (µ(en)/ρ)(graphite,water) are 1.5%, and 0.5% for (µ(en)/ρ)(water,air), decreasing gradually down to u(c) = 0.1% for the three µ(en)/ρ ratios for the gamma-ray spectra. The present estimates are shown to coincide well
Velocity-Space Diffusion Coefficients Due to Full-Wave ICRF Fields in Toroidal Geometry
Harvey, R.W.; Jaeger, F.; Berry, L.A.; Batchelor, D.B.; D'Azevedo, E.; Carter, M.D.; Ershov, N.M.; Smirnov, A.P.; Bonoli, P.; Wright, J.C.; Smithe, D.N.
2005-09-26
Jaeger et al. have calculated bounce-averaged QL diffusion coefficients from AORSA full-wave fields, based on non-Maxwellian distributions from CQL3D Fokker-Planck code. A zero banana-width approximation is employed. Complementing this calculation, a fully numerical calculation of ion velocity diffusion coefficients using the full-wave fields in numerical tokamak equilibria has been implemented to determine the finite orbit width effects. The un-approximated Lorentz equation of motion is integrated to obtain the change in velocity after one complete poloidal transit of the tokamak. Averaging velocity changes over initial starting gyro-phase and toroidal angle gives bounce-averaged diffusion coefficients. The coefficients from the full-wave and Lorentz orbit methods are compared for an ITER DT second harmonic tritium ICRF heating case: the diffusion coefficients are similar in magnitude but reveal substantial finite orbit effects.
Bell, R J; Davarpanah, M; Goben, C A; Begley, D L; Bhasin, K; Alexander, R W
1975-07-01
The first measurements of the absorption coefficient of materials via surface electromagnetic wave (SEW) techniques are reported. By simply laying samples on a metal sheet on which SEW were passing, the transmittances and absorption coefficients of the sample have been determined. These measurements were made at microwave frequencies, but the general techniques are applicable over the entire frequency range from microwaves into the near ir. Solid samples were used in these measurements, but liquid or gases could also be studied by this new easy-to-use technique. Comments about the applicability of the technique to very thin samples are made. Another result reported is the existence of different propagating SEW modes as a function of the height of a sample (film thickness) measured from the metal-sample interface to the top of the sample at the sample-vacuum interface above.
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.
Absorption Coefficients of SF{6}, SF{4}, SOF{2} and SO{2}F{2} in the Vacuum Ultraviolet
NASA Astrophysics Data System (ADS)
Pradayrol, C.; Casanovas, A. M.; Deharo, I.; Guelfucci, J. P.; Casanovas, J.
1996-05-01
Absorption coefficients k0(m^{-1} 100 kPa^{-1}) of SF{6} and of its main gaseous by-products SF{4}, SOF{2} and SO{2}F{2} were measured in the VUV region. The experiments were carried out at a temperature of 298 K and a spectral resolution of 0.1 nm over the wavelength range 115 - 180 nm for SF{6}, 115 - 220 nm for SF{4}, 120 - 195 nm for SOF{2} and 120 - 210 nm for SO{2}F{2}. The highest absorption coefficient values were obtained for SF{4} and the lowest for SF{6}. Les coefficients d'absorption k0(m^{-1} 100 kPa^{-1}) du SF{6} et de ses principaux produits de décomposition gazeux, SF{4}, SOF{2} et SO{2}F{2} ont été mesurés dans le domaine de l'ultraviolet sous vide. Les expériences ont été réalisées à la température de 298 K avec une résolution de 0,1 nm dans la gamme 115 180 nm pour le SF{6}, 115 220 nm pour le SF{4}, 120 195 nm pour le SOF{2} et 120 210 nm pour le SO{2}F{2}. Les coefficients d'absorption les plus élevés ont été mesurés pour le SF{4} et les plus faibles pour le SF{6}.
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 Technical Reports Server (NTRS)
Mogro-Campero, A.; Fillius, W.
1976-01-01
The process of trapped particle absorption by the inner Jovian satellites is considered in detail taking into account both the particle and satellite motions in a magnetic dipole field which is displaced from the center of the planet and tilted with respect to the planetary rotation axis. An expression is derived for computing the sweeping time at a given satellite, defined as the time required for the satellite to sweep up a given fraction of the trapped particles within its sweeping region. By making use of the sweeping time and the radial diffusion equation of particle transport approximate expressions for the diffusion coefficient are derived. Measurements obtained by Pioneer 10 are then used to obtain estimates of the diffusion coefficient at the orbits of Io and Europa. We find that the diffusion coefficient is a function of energy and magnetic latitude for electrons in the energy range 0.7-14 MeV.
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.
Ritter, André; Anton, Gisela; Weber, Thomas
2016-01-01
A maximum-likelihood reconstruction technique for X-ray Talbot-Lau tomography is presented. This technique allows the iterative simultaneous reconstruction of discrete distributions of absorption coefficient, refractive index and a dark-field scattering coefficient. This technique avoids prior phase retrieval in the tomographic projection images and thus in principle allows reconstruction from tomographic data with less than three phase steps per projection. A numerical phantom is defined which is used to evaluate convergence of the technique with regard to photon statistics and with regard to the number of projection angles and phase steps used. It is shown that the use of a random phase sampling pattern allows the reconstruction even for the extreme case of only one single phase step per projection. The technique is successfully applied to measured tomographic data of a mouse. In future, this reconstruction technique might also be used to implement enhanced imaging models for X-ray Talbot-Lau tomography. These enhancements might be suited to correct for example beam hardening and dispersion artifacts and improve overall image quality of X-ray Talbot-Lau tomography. PMID:27695126
Bendib, A.; Tahraoui, A.; Bendib, K.; Mohammed El Hadj, K.; Hueller, S.
2005-03-01
The transport coefficients of fully ionized plasmas under the influence of a high-frequency electric field are derived solving numerically the electron Fokker-Planck equation using a perturbation method, parametrized as a function of the electron mean-free-path {lambda}{sub ei} compared to the spatial scales L. The isotropic and anisotropic contributions of the inverse bremsstrahlung heating are considered. Electron-electron collision terms are kept in the analysis, which allows us to consider with sufficient accuracy to describe plasmas with arbitrary atomic number Z. Practical numerical fits of the transport coefficients are proposed as functions of Z and the collisionality parameter {lambda}{sub ei}/L.
The Correlation Coefficient as the Ratio of Two Means: An Interpretation Due to Galton and Brogden.
ERIC Educational Resources Information Center
Price, James M.; Nicewander, W. Alan
A standard interpretation of the coefficient of correlation may be obtained from the ratio of two variances. If it is assumed that two variables, X and Y, are bivariate normal and scaled to have zero means and unit variances, it can be shown that the correlation between X and Y is the ratio of two conditional means. Galton's statistical studies of…
Reducing Bias and Error in the Correlation Coefficient Due to Nonnormality
ERIC Educational Resources Information Center
Bishara, Anthony J.; Hittner, James B.
2015-01-01
It is more common for educational and psychological data to be nonnormal than to be approximately normal. This tendency may lead to bias and error in point estimates of the Pearson correlation coefficient. In a series of Monte Carlo simulations, the Pearson correlation was examined under conditions of normal and nonnormal data, and it was compared…
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.
Kabi, Sanjib; Perera, A. G. Unil
2015-03-28
The intersublevel absorption peak energy and absorption coefficient of non-uniform quantum dot (QD) ensembles are calculated analytically. The effect of size variations and size distribution of QDs on their energy states is analyzed. The dots are considered as a quantum box with finite potential at the barriers and the size distribution described by a Gaussian function. The influence of the aspect ratio (base to height ratio) of the QDs on the optical transitions is studied. Our model predicts the dot size (height and base) accurately to determine the absorption peaks and corresponding absorption coefficient. We also compute the absorption coefficient of the QD with different size distributions to verify the results calculated using this model with the reported experimental and other theoretical results.
NASA Astrophysics Data System (ADS)
Kontani, Hiroshi; Onari, Seiichiro
2015-03-01
The origin of the structure transition and the nematic electronic states has been attracting great attention in Fe-based superconductors. Its main candidate is the orbital polarization nyz >nxz , which is microscopically reproduced by including the vertex correction on the basis of the five-orbital Hubbard model. To clarify the origin, we study the in-plane anisotropy of transport coefficients in the multiorbital Hubbard model. By introducing the orbital polarization (nyz >nxz), spin fluctuations increase at q = (π , 0) whereas they decrease at q = (0 , π) , consistently with recent neutron scattering measurements. This result leads to the strong anisotropic inelastic scattering. For this reason, the obtained thermoelectric power along y-axis (Sy) increases drastically whereas Sx decreases. The obtained sizable anisotropy Sy >>Sx is consistent with the experiment in detwinned EuFe2(As,P)2. The present study strongly supports the orbital polarization scenario.
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)
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
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.
Rasmussen, D.A.
1981-01-01
The interaction of intense microwaves with an inhomogeneous plasma is studied in two experimental devices. In the first device an investigation was made of microwave absorption and electron heating due to the parametric decay of microwaves into electron plasma waves (Two Plasmon Decay instability, TPDI), modeling a process which can occur near the quarter critical surface in laser driven pellets. P-polarized microwave (f = 1.2 GHz, P/sub 0/ less than or equal to 12 kW) are applied to an essentially collisionless, inhomogeneous plasma, in an oversized waveguide, in the U.C. Davis Prometheus III device. The initial density scale length near the quarter critical surface is quite long (L/lambda/sub De/ approx. = 3000 or k/sub 0/L approx. = 15). The observed threshold power for the TPDI is quite low (P/sub T/approx. = 0.1 kW or v/sub os//v/sub e/ approx. = 0.1). Near the threshold the decay waves only occur near the quarter critical surface. As the incident power is increased above threshold, the decay waves spread to lower densities, and for P/sub 0/ greater than or equal to lkW, (v/sub os//v/sub e/ greater than or equal to 0.3) suprathermal electron heating is strong for high powers (T/sub H/ less than or equal to 12 T/sub e/ for P/sub 0/ less than or equal to 8 kW or v/sub os//v/sub e/ less than or equal to 0.9).
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.
Cuppo, F L S; Gómez, S L; Figueiredo Neto, A M
2004-04-01
In this paper is reported a systematic experimental study of the linear-optical-absorption coefficient of ferrofluid-doped isotropic lyotropic mixtures as a function of the magnetic-grains concentration. The linear optical absorption of ferrolyomesophases increases in a nonlinear manner with the concentration of magnetic grains, deviating from the usual Beer-Lambert law. This behavior is associated to the presence of correlated micelles in the mixture which favors the formation of small-scale aggregates of magnetic grains (dimers), which have a higher absorption coefficient with respect to that of isolated grains. We propose that the indirect heating of the micelles via the ferrofluid grains (hyperthermia) could account for this nonlinear increase of the linear-optical-absorption coefficient as a function of the grains concentration.
NASA Astrophysics Data System (ADS)
El Kadadra, A.; Fellaoui, K.; Abouelaoualim, D.; Oueriagli, A.
2016-09-01
In this work, we have investigated theoretically the effects of applied electric field on the linear and nonlinear optical properties in a GaN/AlxGa1-xN double inverse parabolic quantum well for different Al concentrations at the well center. Our calculations are based on the potential morphing method in the effective mass approximation. The systematic theoretical investigation contains results with all possible combinations of the involved parameters, such as quantum well width, quantum barrier width, Al concentration at each well center and magnitude of the external electric field. Our results show that the electric fields strengths, the parameter of nanostructure and incident optical intensity have a great effect on the optical characteristics of these nanostructures. Thus, the absorption coefficients which can be suitable for great performance optical modulators and multiple infrared optical device applications can be easily obtained by tuning the external electric field value and the Al concentration at the well center.
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)
Ferreira, Amabile; Ciotti, Áurea Maria; Coló Giannini, Maria Fernanda
2014-02-01
This study characterized the variability in magnitudes and spectral shapes of the absorption coefficients of phytoplankton, detritus, and colored dissolved organic matter (CDOM) in a dynamic bay (Santos Bay) in southeastern Brazil in response to the contributions of the main estuarine channel and large tide variations, therefore in different time scales. Two strategies were adopted: (1) monthly year-round sampling in the estuarine channel and Santos Bay and (2) sampling in Santos Bay during spring/neap tides and cold/warm months. Chlorophyll-a concentration and CDOM absorption were higher during warm (wet) months, while the relative contribution of organic and inorganic particles was driven by neap/spring tide cycles. Salinity partially accounted for changes in optical variables, especially for CDOM absorption and total suspended matter (TSM) during cold months and neap tides, respectively. The spectral shapes of detritus and CDOM absorption showed relatively little variability for the entire dataset and were not considered feasible for monitoring purposes. The spectral shape of phytoplankton absorption (index of cell size) varied broadly, with no remarkable dependence on the sampling conditions. Comparison of absorption coefficients measured by the Quantitative Filter Technique (QFT) and Transmittance Reflectance (TR) method showed higher phytoplankton coefficients toward longer visible wavelengths (flatter spectra) and shallower slopes of detritus absorption yielded by the TR method. Our results also suggest that measurements at the near red spectral region result from not only scattering signals but also non-algal particle absorption.
NASA Astrophysics Data System (ADS)
Wróbel, P.; Antosiewicz, T. J.; Stefaniuk, T.; Ciesielski, A.; Iwan, A.; Wronkowska, A. A.; Wronkowski, A.; Szoplik, T.
2015-05-01
In photovoltaic devices, metal nanoparticles embedded in a semiconductor layer allow the enhancement of solar-toelectric energy conversion efficiency due to enhanced light absorption via a prolonged optical path, enhanced electric fields near the metallic inclusions, direct injection of hot electrons, or local heating. Here we pursue the first two avenues. In the first, light scattered at an angle beyond the critical angle for reflection is coupled into the semiconductor layer and confined within such planar waveguide up to possible exciton generation. In the second, light is trapped by the excitation of localized surface plasmons on metal nanoparticles leading to enhanced near-field plasmon-exciton coupling at the peak of the plasmon resonance. We report on results of a numerical experiment on light absorption in polymer- (fullerene derivative) blends, using the 3D FDTD method, where exact optical parameters of the materials involved are taken from our recent measurements. In simulations we investigate light absorption in randomly distributed metal nanoparticles dispersed in polyazomethine-(fullerene derivative) blends, which serve as active layers in bulkheterojunction polymer solar cells. In the study Ag and Al nanoparticles of different diameters and fill factors are diffused in two air-stable aromatic polyazomethines with different chemical structures (abbreviated S9POF and S15POF) mixed with phenyl-C61-butyric acid methyl ester (PCBM) or [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). The mixtures are spin coated on a 100 nm thick Al layer deposited on a fused silica substrate. Optical constants of the active layers are taken from spectroscopic ellipsometry and reflectance measurements using a rotating analyzer type ellipsometer with auto-retarder performed in the wavelength range from 225 nm to 2200 nm. The permittivities of Ag and Al particles of diameters from 20 to 60 nm are assumed to be equal to those measured on 100 to 200 nm thick metal films.
Electromagnetic power absorption and temperature changes due to brain machine interface operation.
Ibrahim, Tamer S; Abraham, Doney; Rennaker, Robert L
2007-05-01
To fully understand neural function, chronic neural recordings must be made simultaneously from 10s or 100s of neurons. To accomplish this goal, several groups are developing brain machine interfaces. For these devices to be viable for chronic human use, it is likely that they will need to be operated and powered externally via a radiofrequency (RF) source. However, RF exposure can result in tissue heating and is regulated by the FDA/FCC. This paper provides an initial estimate of the amount of tissue heating and specific absorption rate (SAR) associated with the operation of a brain-machine interface (BMI). The operation of a brain machine interface was evaluated in an 18-tissue anatomically detailed human head mesh using simulations of electromagnetics and bio-heat phenomena. The simulations were conducted with a single chip, as well as with eight chips, placed on the surface of the human brain and each powered at four frequencies (13.6 MHz, 1.0 GHz, 2.4 GHz, and 5.8 GHz). The simulated chips consist of a wire antenna on a silicon chip covered by a Teflon dura patch. SAR values were calculated using the finite-difference time-domain method and used to predict peak temperature changes caused by electromagnetic absorption in the head using two-dimensional bio-heat equation. Results due to SAR alone show increased heating at higher frequencies, with a peak temperature change at 5.8 GHz of approximately 0.018 degrees C in the single-chip configuration and 0.06 degrees C in the eight-chip configuration with 10 mW of power absorption (in the human head) per chip. In addition, temperature elevations due to power dissipation in the chip(s) were studied. Results show that for the neural tissue, maximum temperature rises of 3.34 degrees C in the single-chip configuration and 7.72 degrees C in the eight-chip configuration were observed for 10 mW dissipation in each chip. Finally, the maximum power dissipation allowable in each chip before a 1.0 degrees C temperature
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)
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)
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.
Zhang, Xi; Zheng, Shaodi; Zheng, Xiaofang; Liu, Zhengying; Yang, Wei; Yang, Mingbo
2016-03-21
In this article, the positive temperature coefficient (PTC) effect was studied for high-density polyethylene (HDPE)/carbon fiber (CF) composites. All of the samples showed a significant PTC effect during the heating processes without a negative temperature coefficient (NTC) effect, even at a temperature much higher than the melting point of the polymer matrix. An ever-increasing PTC intensity with increasing thermal cycles was observed in our study that had never been reported in previous research. The absence of a NTC effect resulted from the increased binding force between the matrix and fillers that contributed to the very special structure of CF surface. We incorporated thermal expansion theory and quantum tunneling effects to explain PTC effect. From the SEM micrographs for the HDPE/CF composites before and after the different thermal cycles, we found that the surface of CF was covered with a layer of polymer which resulted in a change in the gap length between CF and HDPE and its distribution. We believed that the gap change induced by polymer absorption on the fiber surface had a great effect on the PTC effect. PMID:26923428
piezoelectric resonance, nonlinear-optical crystals, optical absorption, heat transfer coefficient
NASA Astrophysics Data System (ADS)
Zhang, Y.; Sun, J.; Rolfe, P.
2011-06-01
Functional near-infrared spectroscopy (fNIRS) is a sensitive technique that has the potential to detect haemodynamic changes during the performance of specific activation tasks. However, in real situations, fNIRS recordings are often corrupted by physiological phenomena, especially by cardiac contraction, breathing and blood pressure fluctuations, and these forms of interference can severely limit the utility of fNIRS. We present a novel fNIRS enhancement based on the multidistance fNIRS method with short-distance and long-distance optode pairs. With this method empirical mode decomposition (EMD) is applied to decompose the superficial haemodynamic changes, derived from the short-distance fNIRS measurements, into a series of intrinsic mode functions (IMFs). By utilizing the weighting parameters for the IMFs, we perform an estimation for global interference in the desired haemodynamic changes, derived from the long-distance fNIRS measurements. We recover the evoked brain activity by minimizing least squares between the desired haemodynamic changes and the estimated global interference. To accelerate the computation, we adopt the recursive least squares (RLS) to decrease the computation complexity due to the matrix inversion. Monte Carlo simulations based on a five-layered slab model of a human adult head was implemented to evaluate our methodology. The results demonstrate that the EMD-RLS method can effectively remove contamination from the evoked brain activity.
NASA Astrophysics Data System (ADS)
Power, J. F.
2003-01-01
The problem of depth profiling optical absorption in a thermally depth variable solid is a problem of direct interest for the analysis of complex structured materials. In this work, we introduce a new algorithm to solve this problem in a planar layered sample which is impulse irradiated. The sample is comprised of "N" model layers of thickness Δx, of constant diffusivity α, where the conductivity varies depth wise with each layer. This derivation extends to the general case of a depth variable thermal reflection coefficient with depth variable optical source density. In such a sample, at finite time, t, past excitation, thermal energy can only significantly penetrate NL model layers NL≈√4αt[-ln(ɛ)] /2Δx, where ɛ is a small error (ɛ⩽10-6) and a double transit through each layer is assumed. The depth profile of optical absorption in each layer, i, is approximated by δ(x-iΔx), weighted by the optical source density Si. The temperature at x=0- just inside a front medium contacting the sample is given by T(x=0,t)= ∑ i=12NL SiṡGR(x,x0=iΔx,t)]x=0, where GR(x,x0,t) represents an effective Green's function for optical absorption at the depth x0=iΔx in the sample. The method of images1 gives GR(x,x0=iΔx,t) in the following form: [GR(x,0Δx,t)GR(x,2Δx,t)…GR(x,2NLΔx,t)]=[A10A12 A14 A16 …..A1,2NL0A32A34 A36 …..A3,2NL….0……A2NL-1,2NL][G(x-0Δx,t)G(x-2Δx,t)……G(x-2NLΔx,t)]. The G(x-nΔx,t) are shifted image fields obtained from the infinite domain Green's function for one-dimensional heat conduction. They account for thermal wave reflection/transmission over the path length nΔx from the source (at interface i) to the surface (x=0). The Ain are lumped coefficients giving the efficiency of heat transmission from the ith source to the surface for each path order n. They are determined by a mapping procedure that identifies all propagation paths of each order, n, and computes the individual and lumped reflection coefficients. Equation (2) is
NASA Astrophysics Data System (ADS)
Yahya, I.; Kusuma, J. I.; Harjana; Kristiani, R.; Hanina, R.
2016-02-01
This paper emphasizes the influence of tubular shaped microresonators phononic crystal insertion on the sound absorption coefficient of profiled sound absorber. A simple cubic and two different bodies centered cubic phononic crystal lattice model were analyzed in a laboratory test procedure. The experiment was conducted by using transfer function based two microphone impedance tube method refer to ASTM E-1050-98. The results show that sound absorption coefficient increase significantly at the mid and high-frequency band (600 - 700 Hz) and (1 - 1.6 kHz) when tubular shaped microresonator phononic crystal inserted into the tested sound absorber element. The increment phenomena related to multi-resonance effect that occurs when sound waves propagate through the phononic crystal lattice model that produce multiple reflections and scattering in mid and high-frequency band which increases the sound absorption coefficient accordingly
NASA Astrophysics Data System (ADS)
Shatsky, A. V.
2016-07-01
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.
Tonoue, Ryota; Katsura, Makoto; Hamamoto, Mai; Bessho, Hiroki; Nakashima, Satoru
2014-01-01
A method was developed to obtain the absorption coefficient spectrum of a grain of coal (as small as 10(-7)) in the region of aliphatic and aromatic C-H stretching bands (2700-3200 cm(-1)) using infrared transflection microspectroscopy. In this method, the complex refractive index n - ik was determined using an optimization algorithm with the Kramers-Kronig transform so that the calculated transflection spectrum from the Fresnel equation corresponded to the measured one. The obtained absorption coefficients were compared with the bulk values determined from the potassium bromide (KBr) pellet measurement method.
NASA Astrophysics Data System (ADS)
Green, Rebecca E.; Gould, Richard W., Jr.; Ko, Dong S.
2008-06-01
We developed statistically-based, optical models to estimate tripton (sediment/detrital) and colored dissolved organic matter (CDOM) absorption coefficients ( a sd, a g) from physical hydrographic and atmospheric properties. The models were developed for northern Gulf of Mexico shelf waters using multi-year satellite and physical data. First, empirical algorithms for satellite-derived a sd and a g were developed, based on comparison with a large data set of cruise measurements from northern Gulf shelf waters; these algorithms were then applied to a time series of ocean color (SeaWiFS) satellite imagery for 2002-2005. Unique seasonal timing was observed in satellite-derived optical properties, with a sd peaking most often in fall/winter on the shelf, in contrast to summertime peaks observed in a g. Next, the satellite-derived values were coupled with the physical data to form multiple regression models. A suite of physical forcing variables were tested for inclusion in the models: discharge from the Mississippi River and Mobile Bay, Alabama; gridded fields for winds, precipitation, solar radiation, sea surface temperature and height (SST, SSH); and modeled surface salinity and currents (Navy Coastal Ocean Model, NCOM). For satellite-derived a sd and a g time series (2002-2004), correlation and stepwise regression analyses revealed the most important physical forcing variables. Over our region of interest, the best predictors of tripton absorption were wind speed, river discharge, and SST, whereas dissolved absorption was best predicted by east-west wind speed, river discharge, and river discharge lagged by 1 month. These results suggest the importance of vertical mixing (as a function of winds and thermal stratification) in controlling a sd distribution patterns over large regions of the shelf, in comparison to advection as the most important control on a g. The multiple linear regression models for estimating a sd and a g were applied on a pixel-by-pixel basis and
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.
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.
Spatial Damping of Propagating Kink Waves Due to Resonant Absorption: Effect of Background Flow
NASA Astrophysics Data System (ADS)
Soler, R.; Terradas, J.; Goossens, M.
2011-06-01
Observations show the ubiquitous presence of propagating magnetohydrodynamic (MHD) kink waves in the solar atmosphere. Waves and flows are often observed simultaneously. Due to plasma inhomogeneity in the direction perpendicular to the magnetic field, kink waves are spatially damped by resonant absorption. The presence of flow may affect the wave spatial damping. Here, we investigate the effect of longitudinal background flow on the propagation and spatial damping of resonant kink waves in transversely nonuniform magnetic flux tubes. We combine approximate analytical theory with numerical investigation. The analytical theory uses the thin tube (TT) and thin boundary (TB) approximations to obtain expressions for the wavelength and the damping length. Numerically, we verify the previously obtained analytical expressions by means of the full solution of the resistive MHD eigenvalue problem beyond the TT and TB approximations. We find that the backward and forward propagating waves have different wavelengths and are damped on length scales that are inversely proportional to the frequency as in the static case. However, the factor of proportionality depends on the characteristics of the flow, so that the damping length differs from its static analog. For slow, sub-Alfvénic flows the backward propagating wave gets damped on a shorter length scale than in the absence of flow, while for the forward propagating wave the damping length is longer. The different properties of the waves depending on their direction of propagation with respect to the background flow may be detected by the observations and may be relevant for seismological applications.
Photoacoustic Experimental System to Confirm Infrared Absorption Due to Greenhouse Gases
ERIC Educational Resources Information Center
Kaneko, Fumitoshi; Monjushiro, Hideaki; Nishiyama, Masayoshi; Kasai, Toshio; Harris, Harold H.
2010-01-01
An experimental system for detecting infrared absorption using the photoacoustic (PA) effect is described. It is aimed for use at high-school level to illustrate the difference in infrared (IR) absorption among the gases contained in the atmosphere in connection with the greenhouse effect. The experimental system can be built with readily…
NASA Astrophysics Data System (ADS)
Müller, T.; Schladitz, A.; Kandler, K.; Wiedensohler, A.
2011-09-01
During the SAMUM-2 experiment, spectral absorption coefficients, single scattering albedos and imaginary parts of refractive indices of mineral dust particles were investigated at the Cape Verde Islands. Main absorbing constituents of airborne samples were mineral dust and soot. PM10 spectral absorption coefficients were measured using a Spectral Optical Absorption Photometer (SOAP) covering the wavelength range from 300 to 960 nm with a resolution of 25 nm. From SOAP, also information on the particle scattering coefficients could be retrieved. Spectral single scattering albedos were obtained in the wavelength range from 350 to 960 nm. Imaginary parts of the refractive index were inferred from measured particle number size distributions and absorption coefficients using Mie scattering theory. Imaginary parts for a dust case were 0.012, 0.0047 and 0.0019 at the wavelengths 450, 550 and 950 nm, respectively, and the single scattering albedos were 0.91, 0.96 and 0.98 at the same wavelengths. During a marine case, the imaginary parts of the refractive indices were 0.0045, 0.0040 and 0.0036 and single scattering albedos were 0.93, 0.95 and 0.96 at the wavelengths given above.
Shitzer, Avraham
2006-03-01
The wind-chill index (WCI), developed in Antarctica in the 1940s and recently updated by the weather services in the USA and Canada, expresses the enhancement of heat loss in cold climates from exposed body parts, e.g., face, due to wind. The index provides a simple and practical means for assessing the thermal effects of wind on humans outdoors. It is also used for indicating weather conditions that may pose adverse risks of freezing at subfreezing environmental temperatures. Values of the WCI depend on a number of parameters, i.e, temperatures, physical properties of the air, wind speed, etc., and on insolation and evaporation. This paper focuses on the effects of various empirical correlations used in the literature for calculating the convective heat transfer coefficients between humans and their environment. Insolation and evaporation are not included in the presentation. Large differences in calculated values among these correlations are demonstrated and quantified. Steady-state wind-chill-equivalent temperatures (WCETs) are estimated by a simple, one-dimensional heat-conducting hollow-cylindrical model using these empirical correlations. Partial comparison of these values with the published "new" WCETs is presented. The variability of the estimated WCETs, due to different correlations employed to calculate them, is clearly demonstrated. The results of this study clearly suggest the need for establishing a "gold standard" for estimating convective heat exchange between exposed body elements and the cold and windy environment. This should be done prior to the introduction and adoption of further modifications to WCETs and indices. Correlations to estimate the convective heat transfer coefficients between exposed body parts of humans in windy and cold environments influence the WCETs and need to be standardized. PMID:16397760
Shitzer, Avraham
2006-03-01
The wind-chill index (WCI), developed in Antarctica in the 1940s and recently updated by the weather services in the USA and Canada, expresses the enhancement of heat loss in cold climates from exposed body parts, e.g., face, due to wind. The index provides a simple and practical means for assessing the thermal effects of wind on humans outdoors. It is also used for indicating weather conditions that may pose adverse risks of freezing at subfreezing environmental temperatures. Values of the WCI depend on a number of parameters, i.e, temperatures, physical properties of the air, wind speed, etc., and on insolation and evaporation. This paper focuses on the effects of various empirical correlations used in the literature for calculating the convective heat transfer coefficients between humans and their environment. Insolation and evaporation are not included in the presentation. Large differences in calculated values among these correlations are demonstrated and quantified. Steady-state wind-chill-equivalent temperatures (WCETs) are estimated by a simple, one-dimensional heat-conducting hollow-cylindrical model using these empirical correlations. Partial comparison of these values with the published "new" WCETs is presented. The variability of the estimated WCETs, due to different correlations employed to calculate them, is clearly demonstrated. The results of this study clearly suggest the need for establishing a "gold standard" for estimating convective heat exchange between exposed body elements and the cold and windy environment. This should be done prior to the introduction and adoption of further modifications to WCETs and indices. Correlations to estimate the convective heat transfer coefficients between exposed body parts of humans in windy and cold environments influence the WCETs and need to be standardized.
NASA Astrophysics Data System (ADS)
Shitzer, Avraham
2006-03-01
The wind-chill index (WCI), developed in Antarctica in the 1940s and recently updated by the weather services in the USA and Canada, expresses the enhancement of heat loss in cold climates from exposed body parts, e.g., face, due to wind. The index provides a simple and practical means for assessing the thermal effects of wind on humans outdoors. It is also used for indicating weather conditions that may pose adverse risks of freezing at subfreezing environmental temperatures. Values of the WCI depend on a number of parameters, i.e, temperatures, physical properties of the air, wind speed, etc., and on insolation and evaporation. This paper focuses on the effects of various empirical correlations used in the literature for calculating the convective heat transfer coefficients between humans and their environment. Insolation and evaporation are not included in the presentation. Large differences in calculated values among these correlations are demonstrated and quantified. Steady-state wind-chill-equivalent temperatures (WCETs) are estimated by a simple, one-dimensional heat-conducting hollow-cylindrical model using these empirical correlations. Partial comparison of these values with the published “new” WCETs is presented. The variability of the estimated WCETs, due to different correlations employed to calculate them, is clearly demonstrated. The results of this study clearly suggest the need for establishing a “gold standard” for estimating convective heat exchange between exposed body elements and the cold and windy environment. This should be done prior to the introduction and adoption of further modifications to WCETs and indices. Correlations to estimate the convective heat transfer coefficients between exposed body parts of humans in windy and cold environments influence the WCETs and need to be standardized.
NASA Technical Reports Server (NTRS)
Bartusiak, M. F.; Becher, J.
1979-01-01
The paper describes the coloring induced by 85-MeV protons in three Schott glasses representative of glass types used as focusing elements in the International Ultraviolet Explorer Fine Error Sensor. It is shown that the absorption (i.e., coloring) induced in each glass by the radiation can be resolved into three optical absorption bands in the near UV-visible range. It is also discussed how that absorption grows with increasing dosages of protons, thus providing the means to predict degradation in any of the three glasses for a particular fluence of proton radiation.
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.
Absorption lines in the spectrum of Q0248 + 4302 due to a foreground tidal tail
Sargent, W.L.W.; Steidel, C.C. California Univ., Berkeley )
1990-08-01
The strong absorption lines in the spectrum of the quasar Q0248 + 4302 are discussed. The absorption has been shown to be produced in a sinuous tidal tail which emanates from the nearby galaxy pair G0248 + 4302A,B. There is a velocity difference of about 260 km/s between the systemic redshift of the interacting galaxies and the redshift of the tidal tail at a galactocentric distance of about 11/h kpc. The large velocity spread observed in the tail gas is probably responsible for the unusual strength of the interstellar lines. 18 refs.
NASA Technical Reports Server (NTRS)
Yoshino, K.; Stark, G.; Smith, P. L.; Parkinson, W. H.; Ito, K.
1988-01-01
Photoabsorption coefficients have been measured for the CO in interstellar clouds at a resolving power more than 20 times greater than previously obtainable. In order to facilitate comparisons, these data have been integrated over the same wavelength ranges as used in Letzelter et al. (1987). It is found that most of the results obtained for bands between 94.0 and 100.4 nm are larger than those of Letzelter; the discrepancy may be attributable to the difference between the resolving powers of the spectrometers used, because the saturation effects associated with low resolution can underestimate absorption coefficient values.
Absorption fever characteristics due to percutaneous renal biopsy-related hematoma.
Hu, Tingyang; Liu, Qingquan; Xu, Qin; Liu, Hui; Feng, Yan; Qiu, Wenhui; Huang, Fei; Lv, Yongman
2016-09-01
This study aims to describe the unique characteristics of absorption fever in patients with a hematoma after percutaneous renal biopsy (PRB) and distinguish it from secondary infection of hematoma.We retrospectively studied 2639 percutaneous renal biopsies of native kidneys. We compared the clinical characteristics between 2 groups: complication group (gross hematuria and/or perirenal hematoma) and no complication group. The axillary temperature of patients with a hematoma who presented with fever was measured at 06:00, 10:00, 14:00, and 18:00. The onset and duration of fever and the highest body temperature were recorded. Thereafter, we described the time distribution of absorption fever and obtained the curve of fever pattern.Of 2639 patients, PRB complications were observed in 154 (5.8%) patients. Perirenal hematoma was the most common complication, which occurred in 118 (4.5%) of biopsies, including 74 small hematoma cases (thickness ≤3 cm) and 44 large hematoma cases (thickness >3 cm). Major complications were observed in only 6 (0.2%) cases resulting from a large hematoma. Of 118 patients with a perirenal hematoma, absorption fever was observed in 48 cases. Furthermore, large hematomas had a 5.23-fold higher risk for absorption fever than the small ones.Blood pressure, renal insufficiency, and prothrombin time could be risk factors for complications. Fever is common in patients with hematoma because of renal biopsy and is usually noninfectious. Evaluation of patients with post-biopsy fever is necessary to identify any obvious infection sources. If no focus is identified, empiric antibiotic therapy should not be initiated nor should prophylactic antibiotics be extended for prolonged durations. Absorption fevers will resolve in time without specific therapeutic interventions.
Absorption fever characteristics due to percutaneous renal biopsy-related hematoma.
Hu, Tingyang; Liu, Qingquan; Xu, Qin; Liu, Hui; Feng, Yan; Qiu, Wenhui; Huang, Fei; Lv, Yongman
2016-09-01
This study aims to describe the unique characteristics of absorption fever in patients with a hematoma after percutaneous renal biopsy (PRB) and distinguish it from secondary infection of hematoma.We retrospectively studied 2639 percutaneous renal biopsies of native kidneys. We compared the clinical characteristics between 2 groups: complication group (gross hematuria and/or perirenal hematoma) and no complication group. The axillary temperature of patients with a hematoma who presented with fever was measured at 06:00, 10:00, 14:00, and 18:00. The onset and duration of fever and the highest body temperature were recorded. Thereafter, we described the time distribution of absorption fever and obtained the curve of fever pattern.Of 2639 patients, PRB complications were observed in 154 (5.8%) patients. Perirenal hematoma was the most common complication, which occurred in 118 (4.5%) of biopsies, including 74 small hematoma cases (thickness ≤3 cm) and 44 large hematoma cases (thickness >3 cm). Major complications were observed in only 6 (0.2%) cases resulting from a large hematoma. Of 118 patients with a perirenal hematoma, absorption fever was observed in 48 cases. Furthermore, large hematomas had a 5.23-fold higher risk for absorption fever than the small ones.Blood pressure, renal insufficiency, and prothrombin time could be risk factors for complications. Fever is common in patients with hematoma because of renal biopsy and is usually noninfectious. Evaluation of patients with post-biopsy fever is necessary to identify any obvious infection sources. If no focus is identified, empiric antibiotic therapy should not be initiated nor should prophylactic antibiotics be extended for prolonged durations. Absorption fevers will resolve in time without specific therapeutic interventions. PMID:27631225
Hayashi, Masayuki; Onodera, Kazunari; Suzuki, Kengo; Kataoka, Yuko; Tachikawa, Kazushige; Riku, Shigeo; Tanaka, Hiroshi
2011-01-01
An 82-year-old Japanese man had consciousness disturbance due to severe hypothyroidism triggered by percutaneous absorption of iodine from an iodine-containing ointment used in diabetic gangrene treatment. Laboratory data revealed extremely high urinary iodine concentrations, and chronic thyroiditis-induced hypothyroidism. Excess iodine intake can also cause hypothyroidism. It was unlikely that iodine intoxication or Hashimoto's encephalopathy had caused the consciousness disturbance. The patient regained consciousness after discontinuing the use of the ointment and commencing thyroid hormone therapy. We conclude that consciousness disturbance resulted from severe hypothyroidism caused by chronic thyroiditis and excess iodine absorption. PMID:22041370
Bulk damage and absorption in fused silica due to high-power laser applications
NASA Astrophysics Data System (ADS)
Nürnberg, F.; Kühn, B.; Langner, A.; Altwein, M.; Schötz, G.; Takke, R.; Thomas, S.; Vydra, J.
2015-11-01
Laser fusion projects are heading for IR optics with high broadband transmission, high shock and temperature resistance, long laser durability, and best purity. For this application, fused silica is an excellent choice. The energy density threshold on IR laser optics is mainly influenced by the purity and homogeneity of the fused silica. The absorption behavior regarding the hydroxyl content was studied for various synthetic fused silica grades. The main absorption influenced by OH vibrational excitation leads to different IR attenuations for OH-rich and low-OH fused silica. Industrial laser systems aim for the maximum energy extraction possible. Heraeus Quarzglas developed an Yb-doped fused silica fiber to support this growing market. But the performance of laser welding and cutting systems is fundamentally limited by beam quality and stability of focus. Since absorption in the optical components of optical systems has a detrimental effect on the laser focus shift, the beam energy loss and the resulting heating has to be minimized both in the bulk materials and at the coated surfaces. In collaboration with a laser research institute, an optical finisher and end users, photo thermal absorption measurements on coated samples of different fused silica grades were performed to investigate the influence of basic material properties on the absorption level. High purity, synthetic fused silica is as well the material of choice for optical components designed for DUV applications (wavelength range 160 nm - 260 nm). For higher light intensities, e.g. provided by Excimer lasers, UV photons may generate defect centers that effect the optical properties during usage, resulting in an aging of the optical components (UV radiation damage). Powerful Excimer lasers require optical materials that can withstand photon energy close to the band gap and the high intensity of the short pulse length. The UV transmission loss is restricted to the DUV wavelength range below 300 nm and
NASA Technical Reports Server (NTRS)
Pan, Xiaoju; Mannino, Antonio; Russ, Mary E.; Hooker, Stanford B.
2008-01-01
At present, satellite remote sensing of coastal water quality and constituent concentration is subject to large errors as compared to the capability of satellite sensors in oceanic waters. In this study, field measurements collected on a series of cruises within U.S. southern Middle Atlantic Bight (SMAB) were applied to improve retrievals of satellite ocean color products in order to examine the factors that regulate the bio-optical properties within the continental shelf waters of the SMAB. The first objective was to develop improvements in satellite retrievals of absorption coefficients of phytoplankton (a(sub ph)), colored dissolved organic matter (CDOM) (a(sub g)), non-pigmented particles (a(sub d)), and non-pigmented particles plus CDOM (a(sub dg)), and chlorophyll a concentration ([Chl_a]). Several algorithms were compared to derive constituent absorption coefficients from remote sensing reflectance (R(sub rs)) ratios. The validation match-ups showed that the mean absolute percent differences (MAPD) were typically less than 35%, although higher errors were found for a(sub d) retrievals. Seasonal and spatial variability of satellite-derived absorption coefficients and [Chl_a] was apparent and consistent with field data. CDOM is a major contributor to the bio-optical properties of the SMAB, accounting for 35-70% of total light absorption by particles plus CDOM at 443 nm, as compared to 30-45% for phytoplankton and 0-20% for non-pigmented particles. The overestimation of [Chl_a] from the operational satellite algorithms may be attributed to the strong CDOM absorption in this region. River discharge is important in controlling the bio-optical environment, but cannot explain all of the regional and seasonal variability of biogeochemical constituents in the SMAB.
NASA Technical Reports Server (NTRS)
Temma, T.; Baines, K. H.; Butler, R. A. H.; Brown, L. R.; Sagui, L.; Kleiner, I.
2006-01-01
PH3 exponential sum k coefficients were computed between 2750 and 3550/cm (2.82-3.64 (microns), in view of future application to radiative transfer analyses of Jupiter and Saturn in a phosphine absorption band near 3 microns. The temperature and pressure of this data set cover the ranges from 80 to 350 K and from 10 (exp -3)to 10(exp 1) bars, respectively. Transmission uncertainty incurred by the use of the k coefficients is smaller than a few percent as long as the radiation is confined above an altitude of a few bars in the giant planets. In spectral regions of weak absorption at high pressures close to 10 bars, contributions from far wings of strong absorption lines must be carefully taken into account. Our data set helps map the three-dimensional distribution of PH3 on the giant planets, revealing their global atmospheric dynamics extending down to the deep interior. The complete k coefficient data set of this work is available at the Web site of the NASA Planetary Data System Atmospheres Node.
Nader, Christelle Abou; Nassif, Rana; Pellen, Fabrice; Le Jeune, Bernard; Le Brun, Guy; Abboud, Marie
2015-12-10
In this paper, we present the evolution of speckle pattern polarimetric parameters in response to controlled changes in scatterer sizes, proportions, and the absorption coefficient in media. The experimental study was performed on mixtures of polystyrene microspheres with dye in order to ensure biological medium-like properties. The speckle grain sizes and degrees of polarization for linear and circular light were monitored. We observed helicity flipping in the degree of circular polarization for small scatterer proportion around 25%. Furthermore, linear depolarization decreased slightly for media containing more small particles. Good agreement was shown with numerical results computed using a Monte Carlo simulation of polarized light taking into account our experimental configuration. Speckle grain size also evolves with the increase of small scatterers as well as the media absorption coefficient. Such variations of properties are encountered during fruit maturation, in tissues in precancerous stages, and any transformation that causes a modification in particle proportions and absorption coefficient in biological media. The computed parameters proved to be sensitive to these changes.
NASA Astrophysics Data System (ADS)
Zheng, Guangming; Stramski, Dariusz; DiGiacomo, Paul M.
2015-04-01
We present a model, referred to as Generalized Stacked-Constraints Model (GSCM), for partitioning the total light absorption coefficient of natural water (with pure-water contribution subtracted), anw(λ), into phytoplankton, aph(λ), nonalgal particulate, ad(λ), and CDOM, ag(λ), components. The formulation of the model is based on the so-called stacked-constraints approach, which utilizes a number of inequality constraints that must be satisfied simultaneously by the model outputs of component absorption coefficients. A major advancement is that GSCM provides a capability to separate the ad(λ) and ag(λ) coefficients from each other using only weakly restrictive assumptions about the component absorption coefficients. In contrast to the common assumption of exponential spectral shape of ad(λ) and ag(λ) in previous models, in our model these two coefficients are parameterized in terms of several distinct spectral shapes. These shapes are determined from field data collected in the Chesapeake Bay with an ultimate goal to adequately account for the actual variability in spectral shapes of ad(λ) and ag(λ) in the study area. Another advancement of this model lies in its capability to account for potentially nonnegligible magnitude of ad(λ) in the near-infrared spectral region. Evaluation of model performance demonstrates good agreement with measurements in the Chesapeake Bay. For example, the median ratio of the model-derived to measured ad(λ), ag(λ), and aph(λ) at 443 nm is 0.913, 1.064, and 1.056, respectively. Whereas our model in its present form can be a powerful tool for regional studies in the Chesapeake Bay, the overall approach is readily adaptable to other regions or bio-optical water types.
NASA Astrophysics Data System (ADS)
Elperin, Tov; Fominykh, Andrew; Krasovitov, Boris
2016-04-01
We analyze the effects of irreversible chemical reactions of the first and higher orders and aqueous-phase dissociation reactions on the rate of trace gas scavenging by rain in the atmosphere with non-uniform concentration and temperature. We employ an one-dimensional model of precipitation scavenging of chemically active soluble gaseous pollutants that is valid for small gradients of temperature and concentration in the atmosphere. It is demonstrated that transient altitudinal distribution of concentration under the influence of rain is determined by the partial hyperbolic differential equation of the first order. Scavenging coefficients are calculated for wet removal of chlorine, nitrogen dioxide and sulfur dioxide for the exponential and linear initial altitudinal distributions of trace gases concentration in the atmosphere and linear and uniform altitudinal temperature distributions. Theoretical predictions of the dependence of the magnitude of the scavenging coefficient on rain intensity for sulfur dioxide are in a good agreement with the available atmospheric measurements.
NASA Astrophysics Data System (ADS)
Harvey, R. W.; Smirnov, A. P.; Ershov, N. M.; Bonoli, P.; Wright, J. C.; Jaeger, F.; Batchelor, D. B.; Berry, L. A.; Carter, M. D.; Smithe, D. N.
2003-10-01
Numerical calculations of bounce-averaged ion velocity-space diffusion coefficients resulting from full-wave code electromagnetic fields in tokamak geometry have been implemented by two methods: (1) appropriate averaging of velocity "kicks" during one transit of the torus cross-section calculated by direct numerical integration of the Lorentz equation of motion in tokamak and full-wave EM fields; and (2) local Fourier analysis of full-wave fields to obtain wavenumbers and polarizations, followed by analysis with a previously implemented ray-tracing/quasilinear-diffusion-coefficient calculation in the CQL3D collisional-quasilinear Fokker-Planck code. Diffusion coefficient results from the two approaches are compared. The diffusion coefficients are used in the FP code for calculation of the RF-driven nonthermal ion distributions.
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
Changes of color and water-absorption of Hungarian porous limestone due to biomineralization
NASA Astrophysics Data System (ADS)
Juhász, P.; Kopecskó, K.
2013-12-01
Bacteria induced calcium carbonate precipitation nowadays is a widely examined process being a possible alternative for traditional stone conservation methods. While research has been mostly limited to laboratory measurements, application connected, further in situ experiments should be performed in order to evaluate the applicability of the method. In our experiment, several bio-based treating compounds were compared, which have already been analyzed in different laboratories. Method for the treatment was based on the treatment of a French research group, and the compounds were applied on Hungarian porous limestone slabs, in situ. For inoculation bacteria strains Bacillus cereus and Myxococcus xanthus were used, and non-inoculated compounds were also analyzed. After the treatment, specimens were analyzed by means of discoloration effect, water absorption and migration characteristics. Almost all the treating compounds gave favorable or acceptable results for the examined properties, comparing to the properties measured in the non-cured state. Measurements on the chromatic- and on the water absorption aspects gave significant results, while further measurements are running for the more exact evaluation of the migration characteristics, i.e. effective migration depth and wetted volume.
Off-resonance energy absorption in a linear Paul trap due to mass selective resonant quenching.
Sivarajah, I; Goodman, D S; Wells, J E; Narducci, F A; Smith, W W
2013-11-01
Linear Paul traps (LPT) are used in many experimental studies such as mass spectrometry, atom-ion collisions, and ion-molecule reactions. Mass selective resonant quenching (MSRQ) is implemented in LPT either to identify a charged particle's mass or to remove unwanted ions from a controlled experimental environment. In the latter case, MSRQ can introduce undesired heating to co-trapped ions of different mass, whose secular motion is off resonance with the quenching ac field, which we call off-resonance energy absorption (OREA). We present simulations and experimental evidence that show that the OREA increases exponentially with the number of ions loaded into the trap and with the amplitude of the off-resonance external ac field. PMID:24289382
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.
NASA Astrophysics Data System (ADS)
Ivascu, I. R.; Matei, C. E.; Patachia, M.; Bratu, A. M.; Dumitras, D. C.
2016-06-01
Absorption coefficients of the ethanol vapors at atmospheric pressure and room temperature were measured by photoacoustic technique using a cw, line-tunable, frequency-stabilized CO2 laser as radiation source. The spectrum of the employed CO2 laser includes 54 lines with wavelengths in the infrared region of 9.2-10.8 μm and power levels up to 4.7 W. Measurements revealed a predominant absorption for ethanol within 9.4 μm band of the CO2 laser spectrum, where the highest values of the absorption coefficients were recorded: 3.68 cm- 1 atm- 1 at 9R(20) line and 3.65 cm- 1 atm- 1 at 9R(22) line. The estimated detection range covers six orders of magnitude, from a minimum of 30 ppbV to a maximum of 4% concentration of ethanol in nitrogen, which proves the suitability of the photoacoustic technique for accurate measurements of the ethanol concentration in various applications.
Ivascu, I R; Matei, C E; Patachia, M; Bratu, A M; Dumitras, D C
2016-06-15
Absorption coefficients of the ethanol vapors at atmospheric pressure and room temperature were measured by photoacoustic technique using a cw, line-tunable, frequency-stabilized CO2 laser as radiation source. The spectrum of the employed CO2 laser includes 54 lines with wavelengths in the infrared region of 9.2-10.8μm and power levels up to 4.7W. Measurements revealed a predominant absorption for ethanol within 9.4μm band of the CO2 laser spectrum, where the highest values of the absorption coefficients were recorded: 3.68cm(-1)atm(-1) at 9R(20) line and 3.65cm(-1)atm(-1) at 9R(22) line. The estimated detection range covers six orders of magnitude, from a minimum of 30ppbV to a maximum of 4% concentration of ethanol in nitrogen, which proves the suitability of the photoacoustic technique for accurate measurements of the ethanol concentration in various applications.
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)
Ismail, Yasser A. M.; Soga, Tetsuo; Jimbo, Takashi
2011-05-01
We surprisingly found that, organic/organic interface had a direct and pronounced impact on optical absorption and photocurrent spectra of organic solar cell at a favorable wavelength region of the visible solar spectrum. The organic/organic interface was formed as a result of connection between coumarin 6 (C6): [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) blend films and indium-tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) electrode. Optical absorption measurement was carried out for ITO/PEDOT:PSS/C6:PCBM films, while external quantum efficiency measurement was carried out for ITO/PEDOT:PSS/C6:PCBM/Al solar cells, with varying C6:PCBM blend concentration. We found that, the C6:PCBM blend in the ITO/PEDOT:PSS/C6:PCBM films had an additional feature in the absorption spectra at the wavelength range of 520-800 nm, at which the C6 dye, PCBM, PEDOT:PSS, and ITO were transparent. An additional feature, also, appeared in photocurrent spectra of the C6:PCBM films in the ITO/PEDOT:PSS/C6:PCBM/Al solar cells at the same wavelength range. The new features in the optical absorption and photocurrent spectra of the investigated solar cells originated, in all probability, due to optically induced sup-band transitions in the C6:PCBM blend films at the interface with ITO/PEDOT:PSS electrode. Thus, the C6:PCBM blend films produced a charge carrier generation interface due to connection with ITO/PEDOT:PSS electrode. As a result of this charge carrier generation interface, the power conversion efficiency of the corresponding solar cell is improved. Taking into consideration these new findings, the high-band-gap organic materials will take more importance as sensitizers in organic optoelectronic applications.
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.
Temperature waves arising due to absorption of electromagnetic radiation in laminated media
NASA Astrophysics Data System (ADS)
Khabibullin, I. L.; Konovalova, S. I.; Sadykova, L. A.
2015-05-01
Propagation of electromagnetic radiation in a moving three-layer medium is studied. It is shown that travelling temperature waves are formed due to interference of the incident wave with the wave reflected from the interface between the layers with radiation energy dissipation. The frequency, length, and velocity of these waves are found to depend on the electromagnetic radiation frequency, electrophysical and thermophysical parameters of the medium, and velocity of medium motion.
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.
Ghysels, M; Durry, G; Amarouche, N
2013-04-15
By using a tunable diode laser absorption spectrometer in conjunction with a cryogenically cooled multipath cell, we have revisited the air-induced pressure-broadening coefficients and the narrowing coefficients related to the Dicke effect, as well as the temperature dependences, for the R(18) and R(20) lines of the (10°1)I←(00°0) vibrational band at 2.68 μm of carbon dioxide. The selected transitions are used to probe in situ CO2 in the troposphere and the lower stratosphere by using balloon-borne laser sensors. The achieved measurements are thoroughly compared to existing former determinations. The impact of processing the in situ atmospheric CO2 spectra with this new set of molecular data is reported.
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)
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.
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 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
Abstract. 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
Sabau, Adrian S
2007-01-01
Lubricant spray application experiments were conducted for the die casting process. The heat flux was measured in situ using a differential thermopile sensor for three application techniques. First, the lubricant was applied under a constant flowrate while the nozzle was held in the same position. Second, the lubricant was applied in a pulsed, static manner, in which the nozzle was held over the same surface while it was turned on and off several times. Third, the lubricant was applied in a sweeping manner, in which the nozzle was moved along the die surface while it was held open. The experiments were conducted at several die temperatures and at sweep speeds of 20, 23, and 68 cm/s. The heat flux data, which were obtained with a sensor that was located in the centre of the test plate, were presented and discussed. The sensor can be used to evaluate lubricants, monitor the consistency of die lubrication process, and obtain useful process data, such as surface temperature, heat flux, and heat transfer coefficients. The heat removed from the die surface during lubricant application is necessary for (a) designing the cooling channels in the die, i.e. their size and placement, and (b) performing accurate numerical simulations of the die casting process.
NASA Technical Reports Server (NTRS)
Gao, R. S.; Hall, S. R.; Swartz, W. H.; Spackman, J. R.; Watts, L. A.; Fahey, D. W.; Aikin, K. C.; Shetter, R. E.; Bui, T. P.
2008-01-01
Results for the solar heating rates in ambient air due to absorption by black-carbon (BC) containing particles and ozone are presented as calculated from airborne observations made in the tropical tropopause layer (TTL) in January-February 2006. The method uses airborne in situ observations of BC particles, ozone and actinic flux. Total BC mass is obtained along the flight track by summing the masses of individually detected BC particles in the range 90 to 600-nm volume-equivalent diameter, which includes most of the BC mass. Ozone mixing ratios and upwelling and partial downwelling solar actinic fluxes were measured concurrently with BC mass. Two estimates used for the BC wavelength-dependent absorption cross section yielded similar heating rates. For mean altitudes of 16.5, 17.5, and 18.5 km (0.5 km) in the tropics, average BC heating rates were near 0.0002 K/d. Observed BC coatings on individual particles approximately double derived BC heating rates. Ozone heating rates exceeded BC heating rates by approximately a factor of 100 on average and at least a factor of 4, suggesting that BC heating rates in this region are negligible in comparison.
Sopori, B.L.
1995-06-20
A method and apparatus for improving the accuracy of the simulation of sunlight reaching the earth`s surface includes a relatively small heated chamber having an optical inlet and an optical outlet, the chamber having a cavity that can be filled with a heated stream of CO{sub 2} and water vapor. A simulated beam comprising infrared and near infrared light can be directed through the chamber cavity containing the CO{sub 2} and water vapor, whereby the spectral characteristics of the beam are altered so that the output beam from the chamber contains wavelength bands that accurately replicate atmospheric absorption of solar energy due to atmospheric CO{sub 2} and moisture. 8 figs.
Sopori, Bhushan L.
1995-01-01
A method and apparatus for improving the accuracy of the simulation of sunlight reaching the earth's surface includes a relatively small heated chamber having an optical inlet and an optical outlet, the chamber having a cavity that can be filled with a heated stream of CO.sub.2 and water vapor. A simulated beam comprising infrared and near infrared light can be directed through the chamber cavity containing the CO.sub.2 and water vapor, whereby the spectral characteristics of the beam are altered so that the output beam from the chamber contains wavelength bands that accurately replicate atmospheric absorption of solar energy due to atmospheric CO.sub.2 and moisture.
NASA Astrophysics Data System (ADS)
Tanifuji, T.; Sakai, D.
2015-03-01
The absorption and reduced scattering coefficients ( μa and μ's) of adult heads were determined by multidistance timeresolved reflectance measurements. The finite difference time domain analysis was used to calculate the time-resolved reflectance from adult head models. In vivo time-resolved reflectances of human heads was measured at wavelengths of 680 and 780 nm. By minimizing the objective functions that compare the theoretical and experimental time-resolved reflectances, μa and μ's of the brains were determined. The results show that the time shift tolerance of measured reflectance for reducing to less than 10% the deviations in μa and μ's due to their coupling from the values obtained by optimum time shifts is more than 20 ps at both wavelengths.
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
Tanifuji, T; Wang, L
2014-01-01
Absorption and reduced scattering coefficients (μ(a) and μ'(s)) of adult heads have been noninvasively determined by time-resolved reflectance measurements. The finite difference time domain (FDTD) analysis was used to calculate time-resolved reflectance from realistic adult head models with brain grooves containing a non-scattering layer. In vivo time-resolved reflectances of human heads were measured by a system composed of a time-correlated single photon counter and a diode laser. By minimizing the objective functions that compare theoretical and experimental time resolved reflectances, μ(a) and μ'(s) of brain were determined. It became clear that time-resolved measurements have enough sensitivity to determine both μ(a) and μ'(s) for superficial tissues, gray matter and white matter, except μ(s) for white matter.
Kocyła, Anna; Pomorski, Adam; Krężel, Artur
2015-11-01
4-(2-Pyridylazo)resorcinol (PAR) is one of the most popular chromogenic chelator used in the determination of the concentrations of various metal ions from the d, p and f blocks and their affinities for metal ion-binding biomolecules. The most important characteristics of such a sensor are the molar absorption coefficient and the metal-ligand complex dissociation constant. However, it must be remembered that these values are dependent on the specific experimental conditions (e.g. pH, solvent components, and reactant ratios). If one uses these values to process data obtained in different conditions, the final result can be under- or overestimated. We aimed to establish the spectral properties and the stability of PAR and its complexes accurately with Zn(2+), Cd(2+), Hg(2+), Co(2+), Ni(2+), Cu(2+), Mn(2+) and Pb(2+) at a multiple pH values. The obtained results account for the presence of different species of metal-PAR complexes in the physiological pH range of 5 to 8 and have been frequently neglected in previous studies. The effective molar absorption coefficient at 492 nm for the ZnHx(PAR)2 complex at pH7.4 in buffered water solution is 71,500 M(-1) cm(-1), and the dissociation constant of the complex in these conditions is 7.08×10(-13) M(2). To confirm these values and estimate the range of the dissociation constants of zinc-binding biomolecules that can be measured using PAR, we performed several titrations of zinc finger peptides and zinc chelators. Taken together, our results provide the updated parameters that are applicable to any experiment conducted using inexpensive and commercially available PAR.
Sato, Chie; Shimada, Miho; Tanikawa, Yukari; Hoshi, Yoko
2013-09-01
Expanding our previously proposed "time segment analysis" for a two-layered turbid medium, this study attempted to selectively determine the absorption coefficient (μa) of the bottom layer in a four-layered human head model with time-domain near-infrared measurements. The difference curve in the temporal profiles of the light attenuation between an object and a reference medium, which are obtained from Monte Carlo simulations, is divided into segments along the time axis, and a slope for each segment is calculated to obtain the depth-dependent μa(μaseg). The reduced scattering coefficient (μs') of the reference is determined by curve fitting with the temporal point spread function derived from the analytical solution of the diffusion equation to the time-resolved reflectance of the object. The deviation of μaseg from the actual μa is expressed by a function of the ratio of μaseg in an earlier time segment to that in a later segment for mediums with different optical properties and thicknesses of the upper layers. Using this function, it is possible to determine the μa of the bottom layer in a four-layered epoxy resin-based phantom. These results suggest that the method reported here has potential for determining the μa of the cerebral tissue in humans.
NASA Astrophysics Data System (ADS)
Cottaris, Nicolas P.
2003-09-01
The spatiochromatic receptive-field structure of neurons in the macaque visual system has been studied almost exclusively with stimuli based on the human foveal cone fundamentals of Smith and Pokorny [Vision Res. 15, 161 (1975)] and generated on cathode ray tube displays. In the current study the artifacts evoked by cone-isolating, spatially structured stimuli due to variations in the eye's preretinal absorption characteristics and axial chromatic aberration are quantified. In addition, the luminance artifacts evoked by nominally isoluminant sinusoidal grating stimuli due to the same factors are quantified. The results indicate that the spatiochromatic stimuli commonly employed to map receptive fields of neurons at eccentricities >10 deg are especially prone to artifacts and that these artifacts are maximal for the high-contrast S-cone-isolating stimuli that are often used. On the basis of these simulations, a method is introduced that improves spatiochromatic receptive-field estimates by compensating for response contributions from the incompletely silenced cone mosaics during cone-isolating stimulation.
Dhoubhadel, Mangal S.; Lakshantha, Wickramaarachchige J.; Rout, Bibhudutta; McDaniel, Floyd D.; Lightbourne, Sherard; D’Souza, Francis
2015-07-23
The quest for increased efficiency of solar cells has driven the research in synthesizing photovoltaic cells involving Si based materials. The efficiency of solar cells involving crystalline Si is stalled around 25% for the last decade. Recently Shi et al. had shown that light trapping can be enhanced by fabricating double layers of Ag nanoparticles in silicon based materials. The light trapping is critically important in a photo devices such as solar cells in order to increase light absorption and efficiency. In the present work, we report enhancement in the absorption of light in Ag ion implanted Si substrates. Multiple low energies Ag ions, ranging from ∼80 keV to ∼30 keV, with different fluences ranging from ∼1 × 10{sup 16} to ∼1 × 10{sup 17} atoms/cm{sup 2} were sequentially implanted into commercially available Si (100) substrates followed by post-thermal annealing to create different sizes of Ag nanoclusters (NC) at different depths in the top 100 nm of the Si. The absorbance of light is increased in Ag implanted Si with a significant increase in the current collection in I-V (current-voltage) photo switching measurements. The experimental photovoltaic cells fabricated with the Ag-implanted Si samples were optically characterized under AM (air mass) 1.5 solar radiation conditions (∼1.0 kW/m{sup 2}). An enhancement in the charge collection were measured in the annealed samples, where prominent Ag NCs were formed in the Si matrix compared to the as-implanted samples with amorphous layers. We believe the enhancement of the photo-current density from the samples with Ag NC is due to the improvement of efficiency of charge collection of e{sup −}-h{sup +} pairs produced by the incident light.
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
Pelivanov, Ivan M; Barskaya, M I; Podymova, N B; Khokhlova, Tanya D; Karabutov, Aleksander A
2009-09-30
A new method for measuring the local light absorption coefficient in turbid media, for example, biological tissues, is proposed. The method is based on the fact that the amplitude of the excited opto-acoustic (OA) signal is proportional to the absorbed laser power density (the product of the light absorption coefficient and the laser fluence) at the medium interface. In the first part of the paper, the influence of the laser beam diameter, the light absorption and reduced scattering coefficients on the maximal amplitude of the laser fluence at the laser beam axis in the near-surface layer of the turbid medium is studied by using the Monte-Carlo simulation. The conditions are predicted under which the amplitude of the OA signal detected in a transparent medium in contact with the scattering medium should remain proportional to the light absorption coefficient of the medium under study, when the scattering coefficient in it changes more than twice. The results of the numerical simulation are used for the theoretical substantiation of the OA method being proposed. (measurement of parametrs of laser radiation)
Gautier, C.
1995-09-01
One cloud radiation issue that has been troublesome for several decades is the absorption of solar radiation by clouds. Many hypotheses have been proposed to explain the discrepancies between observations and modeling results. A good review of these often-competing hypotheses has been provided by Stephens and Tsay. They characterize the available hypotheses as failing into three categories: (1) those linked to cloud microphysical and consequent optical properties; (2) those linked to the geometry and heterogeneity of clouds; and (3) those linked to atmospheric absorption.Current modeling practice is seriously inconsistent with new observational inferences concerning absorption of solar radiation in the atmosphere. The author and her colleagues contend that an emphasis on R may, therefore, not be the optimal way of addressing the cloud solar absorption issue. 4 refs., 1 fig.
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.
Fairchild, P.W.; Garland, N.L.; Howard, W.E. III; Lee, E.K.C.
1980-10-01
A technique for measuring ''effective'' absorption coefficients is described. It circumvents deviations from Beer's law caused when the excitation source bandwidth is larger than the absorber bandwidth. The technique employs a fluorescence cell placed after an absorption cell to selectively monitor absorption in the center region of the source line. Model calculations relating the fluorescence intensity to source and absorber line shapes indicate that this method should yield linear Beer's law plots for moderate values of k/sub 0/Nl and ..cap alpha.., where ..cap alpha.. is the ratio of the source bandwidth to the absorber bandwidth. This technique has been applied to a number of single rotational levels in the 4/sup 1//sub 0/ transition of the H/sub 2/CO A /sup 1/A/sub 2/reverse arrowX /sup 1/A/sub 1/ system using pulsed, tunable dye laser excitation. The effective absorption coefficients determined experimentally have been compared to the theoretically calculated absorption coefficients.
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.
Stramski, Dariusz; Reynolds, Rick A; Kaczmarek, Sławomir; Uitz, Julia; Zheng, Guangming
2015-08-01
Spectrophotometric measurement of particulate matter retained on filters is the most common and practical method for routine determination of the spectral light absorption coefficient of aquatic particles, a_{p}(λ), at high spectral resolution over a broad spectral range. The use of differing geometrical measurement configurations and large variations in the reported correction for pathlength amplification induced by the particle/filter matrix have hindered adoption of an established measurement protocol. We describe results of dedicated laboratory experiments with a diversity of particulate sample types to examine variation in the pathlength amplification factor for three filter measurement geometries; the filter in the transmittance configuration (T), the filter in the transmittance-reflectance configuration (T-R), and the filter placed inside an integrating sphere (IS). Relationships between optical density measured on suspensions (OD_{s}) and filters (OD_{f}) within the visible portion of the spectrum were evaluated for the formulation of pathlength amplification correction, with power functions providing the best functional representation of the relationship for all three geometries. Whereas the largest uncertainties occur in the T method, the IS method provided the least sample-to-sample variability and the smallest uncertainties in the relationship between OD_{s} and OD_{f}. For six different samples measured with 1 nm resolution within the light wavelength range from 400 to 700 nm, a median error of 7.1% is observed for predicted values of OD_{s} using the IS method. The relationships established for the three filter-pad methods are applicable to historical and ongoing measurements; for future work, the use of the IS method is recommended whenever feasible. PMID:26368092
NASA Astrophysics Data System (ADS)
Kawauchi, Satoko; Sato, Shunichi; Ooigawa, Hidetoshi; Nawashiro, Hiroshi; Ishihara, Miya; Kikuchi, Makoto
2008-02-01
We performed simultaneous measurement of light scattering and absorption due to reduction of cytochrome c oxidase as intrinsic optical signals that are related to morphological characteristics and energy metabolism, respectively, for rat brains after oxygen/glucose deprivation by saline infusion. To detect change in light scattering, we determined the wavelength that was the most insensitive to change in light absorption due to the reduction of cytochrome c oxidase on the basis of multiwavelength analysis of diffuse reflectance data set for each rat. Then the relationships between scattering signal and absorption signals related to the reductions of heme aa 3 (605 nm) and CuA (830 nm) in cytochrome c oxidase were examined. Measurements showed that after starting saline infusion, the reduction of heme aa 3 started first; thereafter triphasic, large scattering change occurred (200-300 s), during which the reduction of CuA started. Despite such complex behaviors of IOSs, almost linear correlations were seen between the scattering signal and the heme aa 3-related absorption signal, while a relatively large animal-to-animal variation was observed in the correlation between the scattering signal and CuA-related absorption signal. Transmission electron microscopic observation revealed that dendritic swelling and mitochondrial deformation occurred in the cortical surface tissue after the triphasic scattering change. These results suggest that mitochondrial energy failure accompanies morphological alteration in the brain tissue and results in change in light scattering; light scattering will become an important indicator of tissue viability in brain.
Smith, Brian M.; Barnett, J. Matthew; Ballinger, Marcel Y.
2011-01-18
This report discusses the effect of mass loading of a membrane filter on the self absorption of radioactive particles. A relationship between mass loading and percent loss of activity is presented. Sample filters were collected from Pacific Northwest National Laboratory (PNNL) facilities in order to analyze the current self absorption correction factor of 0.85 that is being used for both alpha and beta particles. Over an eighteen month period from February 2009 to July 2010, 116 samples were collected and analyzed from eight different building stacks in an effort coordinated by the Effluent Management group. Eleven unused filters were also randomly chosen to be analyzed in order to determine background radiation. All of these samples were collected and analyzed in order to evaluate the current correction factor being used.
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
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)
Aubaud, C.; Bureau, H.; Raepsaet, C.; Khodja, H.; Hirschmann, M. M.; Withers, A. C.; Bell, D. R.
2007-12-01
Fourier transform infrared (FTIR) spectroscopy is the most widely applied technique for measuring hydrogen in nominally anhydrous minerals (NAMs) and silicate glasses. FTIR is rapid, sensitive, widely available and gives information on the bonding environment of H-bearing species. H determination relies on the Beer-Lambert law and therefore requires constraints on the applicable molar absorption coefficient, ɛ. Values of ɛ may be derived only from independent absolute methods. These ɛ are now reasonably well known for glasses, but to date determinations of ɛ applicable to NAMs are extremely limited and subject to uncertainties. Most notably, the Paterson (1982) calibration gives H contents in olivine that are a factor of 2.5- 3.5 lower than those suggested by the Bell et al. JGR 2003 calibration. We performed elastic recoil detection analysis (ERDA) on a range of samples that had been previously analyzed by FTIR, including natural rhyolitic glasses (1430-1772 ppm H2O), natural and synthetic olivine (0-910 ppm), natural orthopyroxene (38-147 ppm), and natural clinopyroxene crystals (0-490 ppm). ERDA is a nuclear microprobe technique that yields matrix-independent absolute determinations of H concentration. A 3 MeV beam of 4He is employed at high spatial resolution (50 × 200 microns). The detection limit, determined from analysis of dry minerals is 150±20 ppm H2O, too great for analysis of many NAMs from the upper mantle, but applicable to H-rich natural and synthetic NAMs. For glasses, synthetic olivines, and clinopyroxenes, we found good proportionality between the measured ERDA hydrogen concentration and the linear (rhyolite) or integrated (minerals) absorbance measured by FTIR. The ɛ found for rhyolite (103±9 l/mol per cm) is close to that of 88±2 l/mol per cm given by Dobson et al. (GCA, 1989). For clinopyroxene, we obtain ɛ 47010±6070 l/mol per cm2, slightly larger than 38300±1700 l/mol per cm2 found by Bell et al. (Am. Min. 1995). Finally, for
Hasan, Mohammad; Ghatak, Ananya; Mandal, Bhabani Prasad
2014-05-15
We consider a non-Hermitian medium with a gain and loss symmetric, exponentially damped potential distribution to demonstrate different scattering features analytically. The condition for critical coupling (CC) for unidirectional wave and coherent perfect absorption (CPA) for bidirectional waves are obtained analytically for this system. The energy points at which total absorption occurs are shown to be the spectral singular points for the time reversed system. The possible energies at which CC occurs for left and right incidence are different. We further obtain periodic intervals with increasing periodicity of energy for CC and CPA to occur in this system. -- Highlights: •Energy ranges for CC and CPA are obtained explicitly for complex WS potential. •Analytical conditions for CC and CPA for PT symmetric WS potential are obtained. •Conditions for left and right CC are shown to be different. •Conditions for CC and CPA are shown to be that of SS for the time reversed system. •Our model shows the great flexibility of frequencies for CC and CPA.
de Salles, Alvaro A; Bulla, Giovani; Rodriguez, Claudio E Fernández
2006-01-01
The Specific Absorption Rate (SAR) produced by mobile phones in the head of adults and children is simulated using an algorithm based on the Finite Difference Time Domain (FDTD) method. Realistic models of the child and adult head are used. The electromagnetic parameters are fitted to these models. Comparison also are made with the SAR calculated in the children model when using adult human electromagnetic parameters values. Microstrip (or patch) antennas and quarter wavelength monopole antennas are used in the simulations. The frequencies used to feed the antennas are 1850 MHz and 850 MHz. The SAR results are compared with the available international recommendations. It is shown that under similar conditions, the 1g-SAR calculated for children is higher than that for the adults. When using the 10-year old child model, SAR values higher than 60% than those for adults are obtained.
NASA Technical Reports Server (NTRS)
Lacy, J. H.; Baas, F.; Allamandola, L. J.; Van De Bult, C. E. P.; Persson, S. E.; Mcgregor, P. J.; Lonsdale, C. J.; Geballe, T. R.
1984-01-01
Spectra obtained at a resolving power of 840, for seven protostellar sources in the region of the 4.67-micron fundamental vibrational band of CO, indicate that the deep absorption feature in W33A near 4.61 microns consists of three features which are seen in other sources, but with varying relative strength. UV-irradiation laboratory experiments with 'dirty ice' temperature cycling allow the identification of two of the features cited with solid CO and CO complexed to other molecules. Cyano group-containing molecules have a lower vapor pressure than CO, and can therefore survive in much warmer environments. The formation and location of the CO- and CN-bearing grain mantles and sources of UV irradiation in cold molecular clouds are discussed. Plausible UV light sources can produce the observed cyano group features, but only under conditions in which local heat sources do not cause evaporation of the CO molecules prior to their photoprocessing.
NASA Astrophysics Data System (ADS)
Cazorla, A.; Bahadur, R.; Suski, K. J.; Cahill, J. F.; Chand, D.; Schmid, B.; Ramanathan, V.; Prather, K. A.
2013-09-01
Estimating the aerosol contribution to the global or regional radiative forcing can take advantage of the relationship between the spectral aerosol optical properties and the size and chemical composition of aerosol. Long term global optical measurements from observational networks or satellites can be used in such studies. Using in-situ chemical mixing state measurements can help us to constrain the limitations of such estimates. In this study, the Absorption Ångström Exponent (AAE) and the Scattering Ångström Exponent (SAE) derived from 10 operational AERONET sites in California are combined for deducing chemical speciation based on wavelength dependence of the optical properties. In addition, in-situ optical properties and single particle chemical composition measured during three aircraft field campaigns in California between 2010 and 2011 are combined in order to validate the methodology used for the estimates of aerosol chemistry using spectral optical properties. Results from this study indicate a dominance of mixed types in the classification leading to an underestimation of the primary sources, however secondary sources are better classified. The distinction between carbonaceous aerosols from fossil fuel and biomass burning origins is not clear, since their optical properties are similar. On the other hand, knowledge of the aerosol sources in California from chemical studies help to identify other misclassification such as the dust contribution.
NASA Astrophysics Data System (ADS)
Pakmehr, Mehdi; Bruene, Christoph; Buhmann, Hartmut; Molenkamp, Laurens; McCombe, Bruce
2015-03-01
HgTe quantum wells (QWs) have shown a number of interesting phenomena over the past 20 years, most recently the first two-dimensional topological insulating state. We have studied thermoelectric photovoltages of 2D electrons in a 6.1 nm wide HgTe quantum well induced by cyclotron resonance absorption (B = 2 - 5 T) of a focused THz laser beam. We have estimated thermo-power coefficients by detailed analysis of the beam profile at the sample surface and the photovoltage signals developed across various contacts of a large Hall bar structure at a bath temperature of 1.6 K. We obtain reasonable values of the magneto-thermopower coefficients. Work at UB was supported by NSF DMR 1008138 and the Office of the Provost, and at the University of Wuerzburg by DARPA MESO Contract N6601-11-1-4105, by DFG Grant HA5893/4-1 within SPP 1666 and the Leibnitz Program, and the EU ERC-AG Program (Project 3-TOP.
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.
Kir'yanov, Alexander V; Barmenkov, Yuri O; Martinez, Itzel L; Kurkov, Audrey S; Dianov, Evgenii M
2006-05-01
An experimental and theoretical investigation of the nonlinear transmission coefficient in a set of Ytterbium-doped silica fibers (YFs) with various concentrations of Yb(3+) ions at continuous-wave 980-nm pumping is reported. An analysis of the obtained experimental data shows that YF transmission coefficient is notably affected by the presence of Yb(3+) - Yb(3+) ion-pairs in the fibers, especially in heavily-doped ones. The last fact is confirmed by the study of the cooperative luminescence and absorption effects in the fibers, where a detailed inspection of their dependence on Yb3+ concentration is presented. The pairs' effect is shown to seriously modify both the nonlinear character of YF transmission coefficient at lambda = 980 nm and Yb(3+) excited-state relaxation. A modeling of the experimental data is performed, which allows to find the coefficients addressing the pairs' effect in each of YFs under study and, as a result, to fit the experimentally measured dependences of YF transmission coefficient on pump power, fiber length, and Yb(3+) concentration. PMID:19516545
NASA Astrophysics Data System (ADS)
Kir'yanov, Alexander V.; Barmenkov, Yuri O.; Martinez, Itzel L.; Kurkov, Audrey S.; Dianov, Evgenii M.
2006-05-01
An experimental and theoretical investigation of the nonlinear transmission coefficient in a set of Ytterbium-doped silica fibers (YFs) with various concentrations of Yb3+ ions at continuous-wave 980-nm pumping is reported. An analysis of the obtained experimental data shows that YF transmission coefficient is notably affected by the presence of Yb3+ - Yb3+ ion-pairs in the fibers, especially in heavily-doped ones. The last fact is confirmed by the study of the cooperative luminescence and absorption effects in the fibers, where a detailed inspection of their dependence on Yb3+ concentration is presented. The pairs’ effect is shown to seriously modify both the nonlinear character of YF transmission coefficient at λ = 980 nm and Yb3+ excited-state relaxation. A modeling of the experimental data is performed, which allows to find the coefficients addressing the pairs’ effect in each of YFs under study and, as a result, to fit the experimentally measured dependences of YF transmission coefficient on pump power, fiber length, and Yb3+ concentration.
NASA Astrophysics Data System (ADS)
Hintzen, Paul; Maran, Stephen P.; Michalitsianos, Andrew G.; Foltz, Craig B.; Chaffee, Frederic H., Jr.; Kafatos, Minas
1990-01-01
The gravitational lens system 2237+0305 consists of a low-redshift barred spiral galaxy (z = 0.0394) centered on a more distant quasar (z = 1.695). Because the lensing galaxy is nearly face on, spectroscopy of the background quasar affords a unique opportunity to study the interstellar medium in the galaxy's center and . We report moderate-resolution spectroscopy of QSO2237+0305 yielding a 3σ upper limit of 72 mÅ for the rest equivalent width of Ca II K absorption due to gas in the intervening galaxy. Since gas in the Milky Way "thick disk" typically produces 220 mÅ Ca II lines along lines of sight at high galactic latitude, while our line of sight to QSO 2237+0305 is effectively the weighted mean of four lines of sight, each of which transects an entire halo diameter in the lensing galaxy rather than just a radius, our Ca II upper limit argues against the presence of such a thick disk near the center of the lensing galaxy. Also, published studies indicate that at 8200 Å, QSO 2237+0305 suffers roughly 0.5 mag of extinction due to the leasing galaxy. Assuming a normal gas-to-dust ratio and allowing for various sources of uncertainty, this absorption estimate combined with our Ca II K upper limit implies that calcium is depleted with respect to hydrogen by at least 2.7-3.7 dex, compared to solar abundances. This depletion is similar to the more extreme cases seen in our own galaxy, and higher-dispersion observations may further decrease the upper limit on Ca II absorption.
Light absorption enhancement in Ge nanomembrane and its optoelectronic application.
Kim, Munho; Liu, Shih-Chia; Kim, Tong June; Lee, Jaeseong; Seo, Jung-Hun; Zhou, Weidong; Ma, Zhenqiang
2016-07-25
In this study, the light absorption property of Ge nanomembrane (Ge NM), which incorporates hydrogen (H), in near-infrared (NIR) wavelength range was analyzed. Due to the presence of a large amount of structural defects, the light absorption coefficient of the Ge layer becomes much higher (10 times) than that of bulk Ge in the wavelength range of 1000 ~1600 nm. Increased light absorption was further measured from released Ge NM that has H incorporation in comparison to that of bulk Ge, proving the enhanced light absorption coefficient of H incorporated Ge. Finally, metal-semiconductor-metal (MSM) photodetectors were demonstrated using the H incorporated Ge on GeOI.
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.
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.
Chenoweth, Stephen F; Rundle, Howard D; Blows, Mark W
2010-06-01
Indirect genetics effects (IGEs)--when the genotype of one individual affects the phenotypic expression of a trait in another--may alter evolutionary trajectories beyond that predicted by standard quantitative genetic theory as a consequence of genotypic evolution of the social environment. For IGEs to occur, the trait of interest must respond to one or more indicator traits in interacting conspecifics. In quantitative genetic models of IGEs, these responses (reaction norms) are termed interaction effect coefficients and are represented by the parameter psi (Psi). The extent to which Psi exhibits genetic variation within a population, and may therefore itself evolve, is unknown. Using an experimental evolution approach, we provide evidence for a genetic basis to the phenotypic response caused by IGEs on sexual display traits in Drosophila serrata. We show that evolution of the response is affected by sexual but not natural selection when flies adapt to a novel environment. Our results indicate a further mechanism by which IGEs can alter evolutionary trajectories--the evolution of interaction effects themselves.
Absorption by oxygen and water vapor in the real atmosphere.
Cachorro, V E; de Frutos, A M; Casanova, J L
1987-02-01
Unexpected absorption in the real atmosphere in the window from 840 to 890 nm has been clearly observed through measurements of direct solar spectral irradiance under clear, cloud-free skies. This absorption is not predicted by the known theoretical models. The cause of this apparent absorption may be due to the presence of high thin nonvisible cirrus clouds. A quantitative evaluation of this absorption and an improvement of oxygen absorption coefficients has been carried out after a comparison of more than seventy experimental spectra. Moreover, it is necessary to take into account the different behavior of modeled and experimental data at low and high air masses.
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.
Matsuura, H.; Nakao, Y.
2007-05-15
An effect of nuclear elastic scattering on the rate coefficient of fusion reaction between field deuteron and triton in the presence of neutral beam injection heating is studied. Without assuming a Maxwellian for bulk-ion distribution function, the Boltzmann-Fokker-Planck (BFP) equations for field (bulk) deuteron, field (bulk) triton, {alpha}-particle, and beam deuteron are simultaneously solved in an ITER-like deuterium-tritium thermonuclear plasma [R. Aymar, Fusion Eng. Des. 55, 107 (2001)]. The BFP calculation shows that enhancement of the reaction rate coefficient due to knock-on tail formation in fuel-ion distribution functions becomes appreciable, especially in the case of low-density operations.
NASA Astrophysics Data System (ADS)
Pacheco, J.; Cabral, E.; Wdowinski, S.; Hernandez-Marin, M.; Ortíz, J. Á.; Solano Rojas, D. E.; Oliver-Cabrera, T.
2014-12-01
Land subsidence due to groundwater over-exploitation is a deformation process affecting many cities around the world. This type of subsidence develops gradual vertical deformations reaching only a few centimeters per year, but can affect large areas. Consequently, inhabitants of subsiding areas are not aware of the process until others effects are observed, such as ground surface faulting, damage to building, or changes in the natural superficial drain. In order to mitigate and forecast subsidence consequences, it is useful to conduct numerical modeling of the subsidence process. Modeling the subsidence includes the following three basic tasks: a) Delimitation of the shape of the deforming body; b) Determination of the forces that are causing the deformations; and c) Determination of the mechanical properties of the deforming body according with an accepted rheological model. In the case of a land subsidence process, the deforming body is the aquifer system that is being drained. Usually, stratigraphic information from pumping wells, and other geophysical data are used to define the boundaries and shape of the aquifer system. The deformation governing forces, or stresses, can be calculated using the theory of "effective stress". Mechanical properties are usually determined with laboratory testing of samples from shallow strata, because the determination of these properties in samples from the deepest strata is economically or technically unviable. Consequently, the results of the numerical modeling do not necessarily match the observed subsidence evolution and ground faulting. We present in this work numerical simulation results of the land subsiding of the Valley of Aguascalientes, Mexico. Two analyses for the same subsiding area are presented. In the first of them, we used the mechanical properties of only the shallow strata, whereas in the second analysis we used "macroscopic" mechanical properties data determined for the whole aquifer system using In
Hirtl, Rene; Schmid, Gernot
2013-09-21
A modern wireless intra-ocular pressure monitoring system, based on 13.56 MHz inductively coupled data transmission, was dosimetrically analyzed with respect to the specific absorption rate (SAR) induced inside the head and the eye due to the electromagnetic field exposure caused by the reader antenna of the transmission system. The analysis was based on numerical finite difference time domain computations using a high resolution anatomical eye model integrated in a modern commercially available anatomical model of a male head. Three different reader antenna configurations, a 7-turn elliptic (30 mm × 50 mm) antenna at 12 mm distance from the eye, a flexible circular antenna (60 mm diameter, 8 turns on 2 mm substrate) directly attached to the skin, and a circular 7-turn antenna (30 mm diameter at 12 mm distance to the eye) were analyzed, respectively. Possible influences of the eye-lid status (closed or opened) and the transponder antenna contained in a contact lens directly attached to the eye were taken into account. The results clearly demonstrated that for typical reader antenna currents required for proper data transmission, the SAR values remain far below the limits for localized exposure of the head, as defined by the International Commission for Non-Ionizing Radiation Protection. Particularly the induced SAR inside the eye was found to be substantially (orders of magnitudes for typical reader antenna currents in the order of 1 A turn) below values which have been reported to be critical with respect to thermally induced adverse health effects in eye tissues. PMID:24002053
NASA Astrophysics Data System (ADS)
Hirtl, Rene; Schmid, Gernot
2013-09-01
A modern wireless intra-ocular pressure monitoring system, based on 13.56 MHz inductively coupled data transmission, was dosimetrically analyzed with respect to the specific absorption rate (SAR) induced inside the head and the eye due to the electromagnetic field exposure caused by the reader antenna of the transmission system. The analysis was based on numerical finite difference time domain computations using a high resolution anatomical eye model integrated in a modern commercially available anatomical model of a male head. Three different reader antenna configurations, a 7-turn elliptic (30 mm × 50 mm) antenna at 12 mm distance from the eye, a flexible circular antenna (60 mm diameter, 8 turns on 2 mm substrate) directly attached to the skin, and a circular 7-turn antenna (30 mm diameter at 12 mm distance to the eye) were analyzed, respectively. Possible influences of the eye-lid status (closed or opened) and the transponder antenna contained in a contact lens directly attached to the eye were taken into account. The results clearly demonstrated that for typical reader antenna currents required for proper data transmission, the SAR values remain far below the limits for localized exposure of the head, as defined by the International Commission for Non-Ionizing Radiation Protection. Particularly the induced SAR inside the eye was found to be substantially (orders of magnitudes for typical reader antenna currents in the order of 1 A turn) below values which have been reported to be critical with respect to thermally induced adverse health effects in eye tissues.
Brassington, D.J.; Moncrieff, T.M.; Felton, R.C.; Jolliffe, B.W.; Marx, B.R.; Rowley, W.R.C.; Woods, P.T.
1984-02-01
Methods of measuring the concentration of atmospheric pollutants by laser absorption spectroscopy, such as differential absorption lidar (DIAL) and integrated long-path techniques, all rely on the validity of Beer's exponential absorption law. It is shown here that departures from this law occur if the probing laser has a bandwidth larger than the wavelength scale of structure in the absorption spectrum of the pollutant. A comprehensive experimental and theoretical treatment of the errors resulting from these departures is presented for the particular case of SO/sub 2/ monitoring at approx.300 nm. It is shown that the largest error occurs where the initial calibration measurement of absorption cross section is made at low pressure, in which case errors in excess of 5% in the cross section could occur for laser bandwidths >0.01 nm. Atmospheric measurements by DIAL or long-path methods are in most cases affected less, because pressure broadening smears the spectral structure, but when measuring high concentrations errors can exceed 5%.
Mitra, Amitava; Kesisoglou, Filippos
2013-11-01
Published reports have clearly shown that weakly basic drugs which have low solubility at high pH could have impaired absorption in patients with high gastric pH thus leading to reduced and variable bioavailability. Since such reduction in exposure can lead to significant loss of efficacy, it is imperative to (1) understand the behavior of the compound as a function of stomach pH to inform of any risk of bioavailability loss in clinical studies and (2) develop a robust formulation which can provide adequate exposure in achlorhydric patients. In this review paper, we provide an overview of the factors that can cause high gastric pH in human, discuss clinical and preclinical pharmacokinetic data for weak bases under conditions of normal and high gastric pH, and give examples of formulation strategies to minimize or mitigate the reduced absorption of weakly basic drugs under high gastric pH conditions. It should be noted that the ability to overcome pH sensitivity issues is highly compound dependent and there are no obvious and general solutions to overcome such effect. Further, we discuss, along with several examples, the use of biopharmaceutical tools such as in vitro dissolution, absorption modeling, and gastric pH modified animal models to assess absorption risk of weak bases in high gastric pH and also the use of these tools to enable development of formulations to mitigate such effects.
Subha, Radhu; Nalla, Venkatram; Ji, Wei; Feng, Xiaobo; Vijayan, C.
2014-10-15
In this work, we have investigated the multi-photon absorption induced photoluminescence in Mn{sup 2+}-doped ZnS quantum dots in the wavelength range 860 – 1050 nm (Near-Infrared Window I). The observed three-photon action cross-section has been compared with the theoretical prediction under four band approximation. An enhancement of four to five orders has been observed in the range from 970 to 1050 nm compared to the theoretical value, which is attributed to two-photon enhanced three-photon absorption. Transient lifetime measurements reveal a lifetime of 0.35 ± 0.3 ms, which is four to five orders higher than other conventional fluorescent probes.
Monitoring of MOCVD reactants by UV absorption
Baucom, K.C.; Killeen, K.P.; Moffat, H.K.
1995-07-01
In this paper, we describe how UV absorption measurements can be used to measure the flow rates of metal organic chemical vapor deposition (MOCVD) reactants. This method utilizes the calculation of UV extinction coefficients by measuring the total pressure and absorbance in the neat reactant system. The development of this quantitative reactant flow rate monitor allows for the direct measurement of the efficiency of a reactant bubbler. We demonstrate bubbler efficiency results for TMGa, and then explain some discrepancies found in the TMAl system due to the monomer to dimer equilibrium. Also, the UV absorption spectra of metal organic and hydride MOCVD reactants over the wavelength range 185 to 400 nm are reported.
Light absorption properties and absorption budget of Southeast Pacific waters
NASA Astrophysics Data System (ADS)
Bricaud, Annick; Babin, Marcel; Claustre, Hervé; Ras, JoséPhine; TièChe, Fanny
2010-08-01
Absorption coefficients of phytoplankton, nonalgal particles (NAPs), and colored dissolved organic matter (CDOM), and their relative contributions to total light absorption, are essential variables for bio-optical and biogeochemical models. However, their actual variations in the open ocean remain poorly documented, particularly for clear waters because of the difficulty in measuring very low absorption coefficients. The Biogeochemistry and Optics South Pacific Experiment (BIOSOPE) cruise investigated a large range of oceanic regimes, from mesotrophic waters around the Marquesas Islands to hyperoligotrophic waters in the subtropical gyre and eutrophic waters in the upwelling area off Chile. The spectral absorption coefficients of phytoplankton and NAPs were determined using the filter technique, while the CDOM absorption coefficients were measured using a 2 m capillary waveguide. Over the whole transect, the absorption coefficients of both dissolved and particulate components covered approximately two orders of magnitude; in the gyre, they were among the lowest ever reported for open ocean waters. In the oligotrophic and mesotrophic waters, absorption coefficients of phytoplankton and NAPs were notably lower than those measured in other oceanic areas with similar chlorophyll contents, indicating some deviation from the standard chlorophyll-absorption relationships. The contribution of absorption by NAPs to total particulate absorption showed large vertical and horizontal variations. CDOM absorption coefficients covaried with algal biomass, albeit with a high scatter. The spectral slopes of both NAP and CDOM absorption revealed structured spatial variability in relation with the trophic conditions. The relative contributions of each component to total nonwater absorption were (at a given wavelength) weakly variable over the transect, at least within the euphotic layer.
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…
Zheng, Fengang; Zhang, Peng; Wang, Xiaofeng; Huang, Wen; Zhang, Jinxing; Shen, Mingrong; Dong, Wen; Fang, Liang; Bai, Yongbin; Shen, Xiaoqing; Sun, Hua; Hao, Jianhua
2014-03-01
PZT film of 300 nm thickness was deposited on tin indium oxide (ITO) coated quartz by a sol-gel method. Four metal electrodes, such as Pt, Au, Cu and Ag, were used as top electrodes deposited on the same PZT film by sputtering at room temperature. In ITO-PZT-Ag and ITO-PZT-Au structures, the visible light (400-700 nm) can be absorbed partially by a PZT film, and the maximum efficiency of photoelectric conversion of the ITO-PZT-Ag structure was enhanced to 0.42% (100 mW cm(-2), AM 1.5G), which is about 15 times higher than that of the ITO-PZT-Pt structure. Numerical simulations show that the natural random roughness of polycrystalline-PZT-metal interface can offer a possibility of coupling between the incident photons and SPs at the metal surface. The coincidence between the calculated SP properties and the measured EQE spectra reveals the SP origin of the photovoltaic enhancement in these ITO-PZT-metal structures, and the improved photocurrent output is caused by the enhanced optical absorption in the PZT region near the metal surface, rather than by the direct charge-transfer process between two materials. PMID:24477668
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.
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.
Reinhold, J G; Faradji, B; Abadi, P; Ismail-Beigi, F
1991-07-01
During a 20 day period of high fiber consumption in the form of bread made partly from wheaten wholemeal, two men developed negative balances of calcium, magnesium, zinc and phosphorus due to increased fecal excretion of each element. The fecal losses correlated closely with fecal dry matter and phosphorus. Fecal dry matter, in turn, was directly proportional to fecal fiber excretion. Balances of nitrogen remained positive. Mineral elements were well-utilized by the same subjects during a 20 day period of white bread consumption.
Gitipour, Saeid; Firouzbakht, Saeid; Mirzaee, Ehsan; Alimohammadi, Masoumeh
2014-06-01
For years, the Dorson Abad region has been extremely polluted by Tehran Oil Refinery due to leaking from its underground pipelines, storage tanks, and evaporation ponds. To assess the concentrations of hazardous polycyclic aromatic hydrocarbon (PAH) compounds, soil samples were collected from the grounds at and adjacent to a polluted stream located in the study area. The samples were then analyzed, and the results revealed that 12 of the 16 USEPA PAHs were noticeably present in the soil, which, among them, benzo[k]fluoranthene and chrysene had the highest concentrations with averages of 357.17 and 173.38 mg/kg, respectively. A comparison of the obtained concentrations with the soil screening levels indicated that both benzo[k]fluoranthene and chrysene concentrations were substantially higher than EPA screening level values, signifying the necessity of soil remediation for these contaminants in the area. Techniques such as soil washing/flushing, high temperature thermal desorption, and solidification/stabilization were investigated for treatment of the contaminated soil; solidification/stabilization is recommended as an applicable and cost-effective remediation method for Dorson Abad due to the size of the region, relatively low cost of the binder (cement), and low volatility of benzo[k]fluoranthene and chrysene.
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).
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.
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.
Refraction and absorption of microwaves in wood
NASA Astrophysics Data System (ADS)
Ziherl, Saša; Bajc, Jurij; Čepič, Mojca
2013-03-01
A demonstration experiment for physics students showing the dependence of the refractive index and absorption coefficient of wood on the direction of microwaves is presented. Wood and microwaves enable study of anisotropic properties, which are typically found in crystals. Wood is used as the persuasive representative of uniaxial anisotropic materials due to its visible structure and its consequent anisotropic properties. Wood can be cut in a general direction and wooden plates a few centimetres thick with well-defined fibre orientation are easily prepared. Microwaves are used because wood is transparent for microwaves and their centimetre-scale wavelength is comparable to the wood structure.
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…
[Light absorption by suspended particulate matter in Chagan Lake, Jilin].
Wang, Yuan-Dong; Liu, Dian-Wei; Song, Kai-Shan; Zhang, Bai; Wang, Zong-Ming; Jiang, Guang-Ji; Tang, Xu-Guang; Lei, Xiao-Chun; Wu, Yan-Qing
2011-01-01
Spectral characteristics and the magnitudes of light absorption by suspended particulate matter were determined by spectrophotometry in this optically complex Lake Chagan waters for the purpose of surveying the natural variability of the absorption coefficients to parameterize the bio-optical models for converting satellite or in-situ water reflectance signatures into water quality information. Experiments were carried out on seasonal frozen Lake Chagan, one representative inland case-2 water body in Northeast of China. Particulate absorption properties analyzed using the field data on July 15th and October 12th 2009 were measured using the quantitative filter technique to produce absorption spectra containing several fractions that could be attributed to two main optical active constituents (OACs) phytoplankton pigments and non-algal particulates (mineral sediments, and organic detritus). Results suggested that the suspended particulate matter (SPM) concentration was higher while phytoplankton biomass (chlorophyll-a concentration) was lower in July and that in October. The spectral shape of total suspended particulate matter resembled that of non-algal particulates which contributed greater than phytoplankton in total particulate absorption during both periods. An obvious absorption peak occurring at around 440 nm exhibited an increase in phytoplankton contribution in October. Non-algal particulate absorption at 440 nm (a(NAP) (440)) had better correlation with total suspended particulate matter concentration than that with chlorophyll-a over the two periods. Light absorption by phytoplankton pigments in the Chagan lake region was generally lower than that of non-algal components. Chl. a dominating phytoplankton pigment composition functioned exponentially with its absorption coefficients at 440 and 675 nm specifically, the average values of which in July were 0.146 8 m2 x mg(-1) and 0.050 3 respectively while in October they were 0.153 3 and 0.013 2 m2 x mg(-1
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
During the month of March 2006, a number of instruments were used to determine the absorption characteristics of aerosols found in the Mexico City Megacity and nearby Valley of Mexico. These measurements were taken as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City (MAX-Mex) that was carried out in collaboration with the Megacity Interactions: Local and Global Research Observations (MILAGRO) campaign. MILAGRO was a joint effort between the DOE, NSF, NASA, and Mexican agencies aimed at understanding the impacts of a megacity on the urban and regional scale. A super-site was operated at the Instituto Mexicano de Petroleo in Mexico City (designated T-0) and at the Universidad Technologica de Tecamac (designated T-1) that was located about 35 km to the north east of the T-0 site in the State of Mexico. A third site was located at a private rancho in the State of Hidalgo approximately another 35 km to the northeast (designated T-2). Aerosol absorption measurements were taken in real time using a number of instruments at the T-0 and T-1 sites. These included a seven wavelength aethalometer, a multi-angle absorption photometer (MAAP), and a photo-acoustic spectrometer. Aerosol absorption was also derived from spectral radiometers including a multi-filter rotating band spectral radiometer (MFRSR). The results clearly indicate that there is significant aerosol absorption by the aerosols in the Mexico City megacity region. The absorption can lead to single scattering albedo reduction leading to values below 0.5 under some circumstances. The absorption is also found to deviate from that expected for a "well-behaved" soot anticipated from diesel engine emissions, i.e. from a simple 1/lambda wavelength dependence for absorption. Indeed, enhanced absorption is seen in the region of 300-450 nm in many cases, particularly in the afternoon periods indicating that secondary organic aerosols are contributing to the aerosol absorption. This is likely due
Development of Zero Coefficient of Thermal Expansion composite tubes for stable space structures
NASA Astrophysics Data System (ADS)
Strock, John D.
1992-09-01
Advanced composite materials are well suited for stable space structures due to their low Coefficient of Thermal Expansion (CTE), high stiffness and light weight. For a given design application, composite hardware can be tailored for strength, stiffness, CTE, and Coefficient of Moisture Expansion (CME). Computer modeling and laminate testing of high modulus graphite/epoxy tubes were evaluated for compressive strength, stiffness, CTE, CME and microcracking. Thermal cycling and microcracking effects on CTE were evaluated. Thin graphite/epoxy plies exhibited reduced microcracking. A zero CTE thin wall tube design resulted from the development program. Recent work on low moisture absorption resin systems is also discussed.
Prediction of sound absorption in rigid porous media with the lattice Boltzmann method
NASA Astrophysics Data System (ADS)
da Silva, Andrey Ricardo; Mareze, Paulo; Brandão, Eric
2016-02-01
In this work, sound absorption phenomena associated with the viscous shear stress within rigid porous media is investigated with a simple isothermal lattice Boltzmann BGK model. Simulations are conducted for different macroscopic material properties such as sample thickness and porosity and the results are compared with the exact analytical solution for materials with slit-like structure in terms of acoustic impedance and sound absorption coefficient. The numerical results agree very well with the exact solution, particularly for the sound absorption coefficient. The small deviations found in the low frequency limit for the real part of the acoustic impedance are attributed to the ratio between the thicknesses of the slit and the viscous boundary layer. The results suggest that the lattice Boltzmann method can be a very compelling numerical tool for simulating viscous sound absorption phenomena in the time domain, particularly due to its computational simplicity when compared to traditional continuum based techniques.
Relations among low ionosphere parameters and high frequency radio wave absorption
NASA Technical Reports Server (NTRS)
Cipriano, J. P.
1973-01-01
Charged particle conductivities measured in the very low ionosphere at White Sands Missile Range, New Mexico, and Wallops Island, Virginia, are compared with atmospheric parameters and high frequency radio wave absorption measurements. Charged particle densities are derived from the conductivity data. Between 33 and 58 km, positive conductivity correlated well with neutral atmospheric temperature, with temperature coefficients as large as 4.6%/deg K. Good correlations were also found between HF radio wave absorption and negative conductivity at altitudes as low as 53 km, indicating that the day-to-day absorption variations were principally due to variations in electron loss rate.
Measuring optical temperature coefficients of Intralipid.
McGlone, V Andrew; Martinsen, Paul; Künnemeyer, Rainer; Jordan, Bob; Cletus, Biju
2007-05-01
The temperature sensitivities of absorption and reduced scattering coefficients in the range 700-1000 nm are determined for the liquid phantom Intralipid using spatially resolved continuous wave measurements. The measurements were conducted on a 10 L heated volume of 1% Intralipid subjected to a 40-30 degrees C cooling regime. The temperature sensitivities of the absorbance coefficients are similar to that expected for pure water. However, the reduced scattering coefficients are more sensitive than can be explained by temperature related density changes, and show an unexpected relationship with wavelength. We have also found that temperature perturbations provide a useful means to evaluate instrument model performance. PMID:17440240
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.
Dahan, Arik; Amidon, Gordon L
2009-01-01
The purpose of this study was to investigate the role of P-gp efflux in the in vivo intestinal absorption process of BCS class III P-gp substrates, i.e. high-solubility low-permeability drugs. The in vivo permeability of two H (2)-antagonists, cimetidine and famotidine, was determined by the single-pass intestinal perfusion model in different regions of the rat small intestine, in the presence or absence of the P-gp inhibitor verapamil. The apical to basolateral (AP-BL) and the BL-AP transport of the compounds in the presence or absence of various efflux transporters inhibitors (verapamil, erythromycin, quinidine, MK-571 and fumitremorgin C) was investigated across Caco-2 cell monolayers. P-gp expression levels in the different intestinal segments were confirmed by immunoblotting. Cimetidine and famotidine exhibited segmental dependent permeability through the gut wall, with decreased P(eff) in the distal ileum in comparison to the proximal regions of the intestine. Coperfusion of verapamil with the drugs significantly increased the permeability in the ileum, while no significant change in the jejunal permeability was observed. Both drugs exhibited significantly greater BL-AP than AP-BL Caco-2 permeability, indicative of net mucosal secretion. Concentration dependent decrease of this secretion was obtained by the P-gp inhibitors verapamil, erythromycin and quinidine, while no effect was evident by the MRP2 inhibitor MK-571 and the BCRP inhibitor FTC, indicating that P-gp is the transporter mediates the intestinal efflux of cimetidine and famotidine. P-gp levels throughout the intestine were inversely related to the in vivo permeability of the drugs from the different segments. The data demonstrate that for these high-solubility low-permeability P-gp substrates, P-gp limits in vivo intestinal absorption in the distal segments of the small intestine; however P-gp plays a minimal role in the proximal intestinal segments due to significant lower P-gp expression levels
Model of quantum stochastic absorption in absorbing disordered media
NASA Astrophysics Data System (ADS)
Pradhan, Prabhakar
2006-08-01
Wave propagation in coherently absorbing disordered media is generally modeled by adding a complex part to the real part of the potential. In such a case, it is already understood that the complex potential plays a duel role; it acts as an absorber as well as a reflector due to the mismatch of the phase of the real and complex parts of the potential. Although this model gives expected results for weakly absorbing disordered media, it gives unphysical results for the strong-absorption regime where it causes the system to behave like a perfect reflector. To overcome this issue, we develop a model here for one-dimentional systems using stochastic absorption for the modeling of absorption by “fake,” or “side,” channels, obviating the need for a complex potential. This model of stochastic absorption eliminates the reflection that is coupled with the absorption in the complex potential model and absorption is proportional to the magnitude of the absorbing parameter. Solving the statistics of the reflection coefficient and its phase for both the models, we argue that stochastic absorption is a potentially better way of modeling absorbing disordered media.
Broadband microwave absorption spectrometer for liquid media
Mukherjee, P.; Gosnell, T.R.; Bigio, I.J.
1988-12-01
A broadband, continuous-sweep microwave spectrometer has been constructed for measurements of the absorption coefficient of aqueous solutions and other liquid media. The spectrometer makes use of the phase fluctuation optical heterodyne technique, which provides a direct measure of the microwave power deposited in the sample. Consequently, in contrast to the standard dielectrometric techniques that indirectly determine the absorption coefficient via separate measurements of the real and imaginary parts of the dielectric constant, this spectrometer directly measures the microwave absorption coefficient. Broadband spectra are obtained using a transmission line to couple microwave power into the liquid sample. The absorption spectrum for deionized water in the range 3--20 GHz is presented as an example and shows excellent agreement with calculated values of the absorption coefficient based on previously published dielectric data.
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.
NASA Astrophysics Data System (ADS)
Kim, B.; Eun, S.; Seo, W.; Park, J.; Ahn, J.; Moon, K.
2013-12-01
Aerosols in the atmosphere can scatter and absorb solar radiation and their spatial/temporal distributions are highly inhomogeneous due to short lifetimes (about a few weeks or less). Through scattering and absorption of solar radiation, aerosols directly affect visibility and climate through the modification of the Earth's energy budget (Charlson et al., 1992; Yan, 2007; Wang, 2012). This study investigates long-term trends and characteristics of aerosol light scattering coefficient at Seoul and Baengnyeongdo, 100 km upstream of Seoul, in Korea. Aerosol scattering coefficients were measured continuously with nephelometers. The analysis period is limited to one year of 2011. For the relationship analysis of extinction coefficients (σext) to visibility and aerosol optical depth, σsp observed at 3 p.m. have been used with help of aerosol absorption coefficients (σap) in order to remove its dependence upon relative humidity (RH), and also those of rainy period have been excluded. As expected, σext estimated are inversely proportional to visibility observation by eye. Aerosol extinction coefficients have been vertically integrated with an assumption of nearly well-mixed within an e-folding height to determine aerosol optical depth (τa), and compared with those retrieved from sunphotometer. The results show a reasonable agreement in spite of an inherent difference of each definition. We expect these findings would help to eventually understand aerosol radiative forcing and its effect on the regional climate change around Korea.
Theoretical Study of New Combined Absorption-Ejector Refrigeration System
NASA Astrophysics Data System (ADS)
Abed, A. M.; Sopian, K.; Alghoul, M. A.; Al-Shamani, A. N.; Ruslan, M. H.; Mat, S.
2015-09-01
An improved system of the new combined single stage absorption cycle operated with NH3/H2O as working fluid was performed. In order to enhance performance the cycle a new configuration of absorption system was utilized. The performances of two configurations of the combined absorption cycle were compared; a) with common solution heat exchanger and b) divided the streamline of solution heat exchanger to recover the internal heat. Based on the analysis, it has been shown that the second configuration a significant reduction of the required generator and absorber loads by about 20% and 17% respectively, with increased coefficient of performance (COP) about 12% compared to the first configuration. This improvement in the overall COP is found due to improve energy utilization efficiency significantly.
Infrared absorption mechanisms of black silicon
NASA Astrophysics Data System (ADS)
Cheng, Zhengxi; Chen, Yongping; Ma, Bin
2014-09-01
Black silicon has a wide spectrum of non-spectral characteristics high absorption from visible to long wave infrared band .Based on semi-empirical impurity band model, free carrier absorption, radiation transitions between the valence band and the impurity band, radiation transitions between the impurity band and the conduction band were calculated, and absorption coefficients for each process were got. The results showed that the transitions from valence band to the impurity band induced absorption in the near-infrared waveband, but it has a rapid decay with wavelength. In the shortwave mid-wave and long-wave IR bands, transitions from the impurity band to the conduction band caused a huge absorption, and the absorption coefficient was slowly decreased with increasing wavelength. The free carrier absorption dominates in long-wave band. The calculation results agreed well with the test results of plant black silicon in magnitude and trends.
Combined effects of scattering and absorption on laser speckle contrast imaging
NASA Astrophysics Data System (ADS)
Khaksari, Kosar; Kirkpatrick, Sean J.
2016-07-01
Several variables may affect the local contrast values in laser speckle contrast imaging (LSCI), irrespective of relative motion. It has been suggested that the optical properties of the moving fluid and surrounding tissues can affect LSCI values. However, a detailed study of this has yet to be presented. In this work, we examined the combined effects of the reduced scattering and absorption coefficients on LSCI. This study employs fluid phantoms with different optical properties that were developed to mimic whole blood with varying hematocrit levels. These flow phantoms were imaged with an LSCI system developed for this study. The only variable parameter was the optical properties of the flowing fluid. A negative linear relationship was seen between the changes in contrast and changes in reduced scattering coefficient, absorption coefficient, and total attenuation coefficient. The change in contrast observed due to an increase in the scattering coefficient was greater than what was observed with an increase in the absorption coefficient. The results indicate that optical properties affect contrast values and that they should be considered in the interpretation of LSCI data.
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...
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.
Terahertz absorption spectrum of triacetone triperoxide (TATP)
NASA Astrophysics Data System (ADS)
Wilkinson, John; Konek, Christopher T.; Moran, Jesse S.; Witko, Ewelina M.; Korter, Timothy M.
2009-08-01
We report here, for the first time, the terahertz absorption spectrum of triacetone triperoxide (TATP). The experimental spectra are coupled with solid-state density functional theory, and preliminary assignments are provided to gain physical insight into the experimental spectrum. The calculated absorption coefficients are in excellent agreement with experiment.
Study of Dispersion Coefficient Channel
NASA Astrophysics Data System (ADS)
Akiyama, K. R.; Bressan, C. K.; Pires, M. S. G.; Canno, L. M.; Ribeiro, L. C. L. J.
2016-08-01
The issue of water pollution has worsened in recent times due to releases, intentional or not, of pollutants in natural water bodies. This causes several studies about the distribution of pollutants are carried out. The water quality models have been developed and widely used today as a preventative tool, ie to try to predict what will be the concentration distribution of constituent along a body of water in spatial and temporal scale. To understand and use such models, it is necessary to know some concepts of hydraulic high on their application, including the longitudinal dispersion coefficient. This study aims to conduct a theoretical and experimental study of the channel dispersion coefficient, yielding more information about their direct determination in the literature.
Spatial variability of absorption properties in Lake Balaton, Hungary
NASA Astrophysics Data System (ADS)
Riddick, C. A.; Hunter, P. D.; Tyler, A. N.; Vicente, V. M.; Groom, S.; Horváth, H.; Kovacs, A.; Preston, T.; Presing, M.
2013-12-01
In order to improve robustness of current remote sensing algorithms for lake monitoring, it is vital to understand the variability of inherent optical properties (IOPs) within a lake. In this study, absorption coefficients were measured in situ at 38 stations in Lake Balaton, Hungary, using a WET Labs AC-S and AC-9 and compared to concurrent absorption measurements by dual beam spectrophotometry in the laboratory. The spatial variability of bulk and chlorophyll-specific absorption coefficients was examined across 5 basins, demonstrating a gradient in total absorption corresponding to the trophic gradient. Our data suggests that sampling conditions had an impact on particulate absorption, affecting the proportion attributed to non-algal particles (aNAP), phytoplankton (aph) or color dissolved organic matter (aCDOM). The specific absorption of phytoplankton (a*ph) spectra showed a distinct peak in the UV portion of the spectra in Basins 3 and 4 (east), which may be due to the presence of phytoplankton photoprotective pigments to compensate for lower CDOM levels in these basins. In contrast to oceans, particulate attenuation (cp) had a weaker relationship to chlorophyll-a (R2=0.15) than to total suspended matter (R2=0.84), particularly the inorganic fraction. Additionally, the relative contribution of particulate scattering (bp) to attenuation was significantly higher in Lake Balaton (up to 85-99%) than that found in previous lacustrine studies. bp also demonstrated a gradient across the lake, where values increased as the water progressed from phytoplankton-dominated to mineral-dominated. These results provide knowledge of the heterogeneity of the IOPs within Lake Balaton, which is to be considered for the future improvement of bio-optical algorithms for constituent retrieval in inland waters.
NASA Astrophysics Data System (ADS)
Jacobson, Mark Z.
2012-03-01
This study examines modeled properties of black carbon (BC), tar ball (TB), and soil dust (SD) absorption within clouds and aerosols to understand better Cloud Absorption Effects I and II, which are defined as the effects on cloud heating of absorbing inclusions in hydrometeor particles and of absorbing aerosol particles interstitially between hydrometeor particles at their actual relative humidity (RH), respectively. The globally and annually averaged modeled 550 nm aerosol mass absorption coefficient (AMAC) of externally mixed BC was 6.72 (6.3-7.3) m2/g, within the laboratory range (6.3-8.7 m2/g). The global AMAC of internally mixed (IM) BC was 16.2 (13.9-18.2) m2/g, less than the measured maximum at 100% RH (23 m2/g). The resulting AMAC amplification factor due to internal mixing was 2.41 (2-2.9), with highest values in high RH regions. The global 650 nm hydrometeor mass absorption coefficient (HMAC) due to BC inclusions was 17.7 (10.6-19) m2/g, ˜9.3% higher than that of the IM-AMAC. The 650 nm HMACs of TBs and SD were half and 1/190th, respectively, that of BC. Modeled aerosol absorption optical depths were consistent with data. In column tests, BC inclusions in low and mid clouds (CAE I) gave column-integrated BC heating rates ˜200% and 235%, respectively, those of interstitial BC at the actual cloud RH (CAE II), which itself gave heating rates ˜120% and ˜130%, respectively, those of interstitial BC at the clear-sky RH. Globally, cloud optical depth increased then decreased with increasing aerosol optical depth, consistent with boomerang curves from satellite studies. Thus, CAEs, which are largely ignored, heat clouds significantly.
NASA Astrophysics Data System (ADS)
Yoshida, Keiichiro; Nishidate, Izumi; Ishizuka, Tomohiro; Kawauchi, Satoko; Sato, Shunichi; Sato, Manabu
2015-05-01
In order to estimate multispectral images of the absorption and scattering properties in the cerebral cortex of in vivo rat brain, we investigated spectral reflectance images estimated by the Wiener estimation method using a digital RGB camera. A Monte Carlo simulation-based multiple regression analysis for the corresponding spectral absorbance images at nine wavelengths (500, 520, 540, 560, 570, 580, 600, 730, and 760 nm) was then used to specify the absorption and scattering parameters of brain tissue. In this analysis, the concentrations of oxygenated hemoglobin and that of deoxygenated hemoglobin were estimated as the absorption parameters, whereas the coefficient a and the exponent b of the reduced scattering coefficient spectrum approximated by a power law function were estimated as the scattering parameters. The spectra of absorption and reduced scattering coefficients were reconstructed from the absorption and scattering parameters, and the spectral images of absorption and reduced scattering coefficients were then estimated. In order to confirm the feasibility of this method, we performed in vivo experiments on exposed rat brain. The estimated images of the absorption coefficients were dominated by the spectral characteristics of hemoglobin. The estimated spectral images of the reduced scattering coefficients had a broad scattering spectrum, exhibiting a larger magnitude at shorter wavelengths, corresponding to the typical spectrum of brain tissue published in the literature. The changes in the estimated absorption and scattering parameters during normoxia, hyperoxia, and anoxia indicate the potential applicability of the method by which to evaluate the pathophysiological conditions of in vivo brain due to the loss of tissue viability.
Non-resonant below-bandgap two-photon absorption in quantum dot solar cells
Li, Tian; Dagenais, Mario
2015-04-27
We study the optically nonlinear sub-bandgap photocurrent generation facilitated by an extended tailing distribution of states in an InAs/GaAs quantum dots (QDs) solar cell. The tailing states function as both the energy states for low energy photon absorption and the photocarriers extraction pathway. One of the biggest advantages of our method is that it can clearly differentiate the photocurrent due to one-photon absorption (1PA) process and two-photon absorption (2PA) process. Both 1PA and 2PA photocurrent generation efficiency in an InAs/GaAs QD device operated at 1550 nm have been quantitatively evaluated. A two-photon absorption coefficient β = 5.7 cm/GW is extracted.
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.
Light absorption measurements: new techniques.
Hänel, G; Busen, R; Hillenbrand, C; Schloss, R
1982-02-01
A new radiometer is described which simplifies measurement of the radiation supply of solar wavelengths. Two methods of measuring the radiant energy absorbed by aerosol particles are described: A photometric technique is used for particles collected on filters, and a calorimetric technique is used for in situ measurements. Data collected with the radiometer and the light absorption techniques yield the heating rate of the atmosphere due to light absorption by the particles. Sample measurements show substantial atmospheric temperature increases due to absorption, especially in industrial regions.
NASA Astrophysics Data System (ADS)
Poursamad, J. B.; Phirouznia, A.; Sahrai, M.
2015-11-01
Possibility of observing third thermomechanical (TM) effect in uniform nematic liquid crystals (NLC) with proper selection of boundary conditions on the cell walls is theoretically studied. Absorption of a light wave induces the needed temperature gradient for the TM effect. The molecular director reorientation due to third TM effect and the induced phase shift on the probe beam are calculated. The forth TM coefficient can be measured directly by the method proposed in this work.
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.].
NASA Astrophysics Data System (ADS)
Nordmann, S.; Birmili, W.; Weinhold, K.; Müller, K.; Spindler, G.; Wiedensohler, A.
2013-11-01
Soot particles are a major absorber of shortwave radiation in the atmosphere. The mass absorption cross section is an essential quantity to describe this light absorption process. This work presents new experimental data on the mass absorption cross section of soot particles in the troposphere over Central Europe. Mass absorption cross sections were derived as the ratio between the light absorption coefficient determined by multiangle absorption photometry (MAAP) and the soot mass concentration determined by Raman spectroscopy. The Raman method is sensitive to graphitic structures present in the particle samples and was calibrated in the laboratory using Printex®90 model particles. Mass absorption cross sections were determined for a number of seven observation sites, ranging between 3.9 and 7.4 m2 g-1depending on measurement site and observational period. The highest values were found in a continentally aged air mass in winter, where soot particles were assumed to be mainly internally mixed. Our values are in the lower range of previously reported values, possibly due to instrumental differences to the former photometer and mass measurements. Overall, a value of 5.3m2 g-1from orthogonal regression over all samples is considered to be representative for the soot mass absorption cross section in the troposphere over Central Europe.
The effects of stage absorption on reverberation times in opera house seating areas.
Jeon, Jin Yong; Kim, Jae Ho; Ryu, Jong Kwan
2015-03-01
The effects of stage absorption on reverberation times in opera houses were investigated using computer simulations and scale model measurements. The reverberation time (RT) was measured in stalls seating with and without variable stage elements (e.g., fly curtains, side curtains, cycloramas, and stage sets). The absorption coefficients of the walls and ceiling of the stage houses were varied accordingly. It was found that variable stage elements have a significant influence on reverberation times in seating areas, particularly for a reverberant stage house, due to the low absorption of the walls and ceiling in the stage house. It was also found that the absorption coefficients of the walls and ceiling should be over 0.5 to avoid RT decreases of over 10% due to the absorption of the variable stage elements. In addition, coupled room effects were investigated both with and without variable stage elements and the results show that double slope was not found in the opera houses investigated in this study.
The effects of stage absorption on reverberation times in opera house seating areas.
Jeon, Jin Yong; Kim, Jae Ho; Ryu, Jong Kwan
2015-03-01
The effects of stage absorption on reverberation times in opera houses were investigated using computer simulations and scale model measurements. The reverberation time (RT) was measured in stalls seating with and without variable stage elements (e.g., fly curtains, side curtains, cycloramas, and stage sets). The absorption coefficients of the walls and ceiling of the stage houses were varied accordingly. It was found that variable stage elements have a significant influence on reverberation times in seating areas, particularly for a reverberant stage house, due to the low absorption of the walls and ceiling in the stage house. It was also found that the absorption coefficients of the walls and ceiling should be over 0.5 to avoid RT decreases of over 10% due to the absorption of the variable stage elements. In addition, coupled room effects were investigated both with and without variable stage elements and the results show that double slope was not found in the opera houses investigated in this study. PMID:25786925
Path length enhancement in disordered media for increased absorption.
Mupparapu, Rajeshkumar; Vynck, Kevin; Svensson, Tomas; Burresi, Matteo; Wiersma, Diederik S
2015-11-30
We theoretically and numerically investigate the capability of disordered media to enhance the optical path length in dielectric slabs and augment their light absorption efficiency due to scattering. We first perform a series of Monte Carlo simulations of random walks to determine the path length distribution in weakly to strongly (single to multiple) scattering, non-absorbing dielectric slabs under normally incident light and derive analytical expressions for the path length enhancement in these two limits. Quite interestingly, while multiple scattering is expected to produce long optical paths, we find that media containing a vanishingly small amount of scatterers can still provide high path length enhancements due to the very long trajectories sustained by total internal reflection at the slab interfaces. The path length distributions are then used to calculate the light absorption efficiency of media with varying absorption coefficients. We find that maximum absorption enhancement is obtained at an optimal scattering strength, in-between the single-scattering and the diffusive (strong multiple-scattering) regimes. This study can guide experimentalists towards more efficient and potentially low-cost solutions in photovoltaic technologies.
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.
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)
NASA Astrophysics Data System (ADS)
Miskevich, Alexander A.; Loiko, Valery A.
2015-12-01
Enhancement of the performance of photovoltaic cells through increasing light absorption due to optimization of an active layer is considered. The optimization consists in creation of particulate structure of active layer. The ordered monolayers and multilayers of submicron crystalline silicon (c-Si) spherical particles are examined. The quasicrystalline approximation (QCA) and the transfer matrix method (TMM) are used to calculate light absorption in the wavelength range from 0.28 μm to 1.12 μm. The integrated over the terrestial solar spectral irradiance "Global tilt" ASTM G173-03 absorption coefficient is calculated. In the wavelength range of small absorption index of c-Si (0.8-1.12 μm) the integral absorption coefficient of monolayer can be more than 20 times higher than the one of the plane-parallel plate of the equivalent volume of material. In the overall considered range (0.28-1.12 μm) the enhancement factor up to ~1.45 for individual monolayer is observed. Maximum value of the spectral absorption coefficient approaches unity for multilayers consisting of large amount of sparse monolayers of small particles. Multilayers with variable concentration and size of particles in the monolayer sequences are considered. Absorption increasing by such gradient multilayers as compared to the non-gradient ones is illustrated. The considered structures are promising for creation of high efficiency thin-film solar cells.
Gastrointestinal citrate absorption in nephrolithiasis
NASA Technical Reports Server (NTRS)
Fegan, J.; Khan, R.; Poindexter, J.; Pak, C. Y.
1992-01-01
Gastrointestinal absorption of citrate was measured in stone patients with idiopathic hypocitraturia to determine if citrate malabsorption could account for low urinary citrate. Citrate absorption was measured directly from recovery of orally administered potassium citrate (40 mEq.) in the intestinal lavage fluid, using an intestinal washout technique. In 7 stone patients citrate absorption, serum citrate levels, peak citrate concentration in serum and area under the curve were not significantly different from those of 7 normal subjects. Citrate absorption was rapid and efficient in both groups, with 96 to 98% absorbed within 3 hours. The absorption of citrate was less efficient from a tablet preparation of potassium citrate than from a liquid preparation, probably due to a delayed release of citrate from wax matrix. However, citrate absorption from solid potassium citrate was still high at 91%, compared to 98% for a liquid preparation. Thus, hypocitraturia is unlikely to be due to an impaired gastrointestinal absorption of citrate in stone patients without overt bowel disease.
NASA Astrophysics Data System (ADS)
Lyamani, H.; Olmo, F. J.; Alados-Arboledas, L.
Surface measurements of optical and physical aerosol properties were made at an urban site, Granada (Spain) (37.18°N, 3.58°W, 680 m a.s.l), during winter 2005-2006. Measurements included the aerosol scattering, σsca, and backscattering coefficients, σbsca, at three wavelengths (450, 550 and 700 nm) measured at low relative humidity (RH<50%) by an integrating nephelometer, the absorption coefficient at 670 nm, σabs, measured with a multi-angle absorption photometer, and aerosol size distribution in the 0.5-20 μm aerodynamic diameter range registered by an aerodynamic aerosol sizer (APS-3321, TSI). The hourly average of σsca (550 nm) ranged from 2 to 424 M m -1 with an average value of 84±62 M m -1 (±S.D.). The Angstrom exponent presented an average value of 1.8±0.3, suggesting a large fraction of fine particles at the site, an observation confirmed by aerosol size distribution measurements. The hourly average of σabs (670 nm) ranged from 1.7 to 120.5 M m -1 with an average value of 28±20 M m -1. The results indicate that the aerosol absorption coefficient in Granada was relatively large. The largest σsca value was associated with air masses that passed over heavily polluted European areas and local stagnation conditions. High absorbing aerosol level was obtained during dust transport from North Africa probably due to the presence of hematite. Based on the measured scattering and absorption coefficients, a very low average value of the single scattering albedo of 0.66±0.11 at 670 nm was calculated, suggesting that urban aerosols in this region contain a large fraction of absorbing material. A clear diurnal pattern was observed in scattering and absorption coefficients and particle concentrations with two local maxima occurring in early morning and late evening. This behavior can be explained in terms of local conditions that control the particle sources associated with traffic and upward mixing of the aerosol during the daytime development of a
NASA 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.
Two-photon absorption in gapped bilayer graphene with a tunable chemical potential.
Brinkley, M K; Abergel, D S L; Clader, B D
2016-09-14
Despite the now vast body of two-dimensional materials under study, bilayer graphene remains unique in two ways: it hosts a simultaneously tunable band gap and electron density; and stems from simple fabrication methods. These two advantages underscore why bilayer graphene is critical as a material for optoelectronic applications. In the work that follows, we calculate the one- and two-photon absorption coefficients for degenerate interband absorption in a graphene bilayer hosting an asymmetry gap and adjustable chemical potential-all at finite temperature. Our analysis is comprehensive, characterizing one- and two-photon absorptive behavior over wide ranges of photon energy, gap, chemical potential, and thermal broadening. The two-photon absorption coefficient for bilayer graphene displays a rich structure as a function of photon energy and band gap due to the existence of multiple absorption pathways and the nontrivial dispersion of the low energy bands. This systematic work will prove integral to the design of bilayer-graphene-based nonlinear optical devices.
Measurement and feature analysis of absorption spectra of four algal species
NASA Astrophysics Data System (ADS)
Zhu, Jianhua; Zhou, Hongli; Han, Bing; Li, Tongji
2016-04-01
Two methods for particulate pigments (i.e., quantitative filter technique, QFT, and in vivo measurement, InVivo, respectively) and two methods for dissolved pigments (i.e., Acetone Extracts, AceEx, and high-performance liquid chromatography, HPLC, respectively) were used to obtain the optical absorption coefficient spectra for cultures of four typical algal species. Through normalization and analysis of the spectra, it is shown that (1) the four methods are able to measure optical absorption spectra of particulate and/or dissolved pigments; (2) that the optical absorption spectra of particulate and dissolved pigments were consistent in terms of the peak position in the blue wavelength, and the difference of the peak position in the near infrared wavelength was ~10 nm between each other; and (3) that the leveling effect of the absorption spectra of particulate pigments was significant. These four methods can all effectively measure the absorption coefficients of phytoplankton pigments, while each one has its unique advantages in different applications. Therefore, appropriate method should be carefully selected for various application due to their intrinsic difference.
Two-photon absorption in gapped bilayer graphene with a tunable chemical potential
NASA Astrophysics Data System (ADS)
Brinkley, M. K.; Abergel, D. S. L.; Clader, B. D.
2016-09-01
Despite the now vast body of two-dimensional materials under study, bilayer graphene remains unique in two ways: it hosts a simultaneously tunable band gap and electron density; and stems from simple fabrication methods. These two advantages underscore why bilayer graphene is critical as a material for optoelectronic applications. In the work that follows, we calculate the one- and two-photon absorption coefficients for degenerate interband absorption in a graphene bilayer hosting an asymmetry gap and adjustable chemical potential—all at finite temperature. Our analysis is comprehensive, characterizing one- and two-photon absorptive behavior over wide ranges of photon energy, gap, chemical potential, and thermal broadening. The two-photon absorption coefficient for bilayer graphene displays a rich structure as a function of photon energy and band gap due to the existence of multiple absorption pathways and the nontrivial dispersion of the low energy bands. This systematic work will prove integral to the design of bilayer-graphene-based nonlinear optical devices.
Choi, Young-Ji; Bradley, John S; Jeong, Dae-Up
2015-01-01
This paper examines how the individual variations of chair type, row spacing, as well as the presence of occupants and carpet, combine to influence the absorption characteristics of theater chairs as a function of sample perimeter-to-area (P/A) ratios. Scale models were used to measure the interactive effects of the four test variables on the chair absorption characteristics, avoiding the practical difficulties of full scale measurements. All of the test variables led to effects that could lead to important changes to auditorium acoustics conditions. At mid and higher frequencies, the various effects can usually be explained as due to, more or less, porous absorbing material. In the 125 and 250 Hz octave bands, the major changes were attributed to resonant absorbing mechanisms. The results indicate that for accurate predictions of the effective absorption of the chairs in an auditorium, one should use the P/A method and reverberation chamber tests of the chair absorption coefficients to predict the absorption coefficients of each block of chairs and use these results as input in a room acoustics computer model of the auditorium. The application of these results to auditorium acoustics design is described, more approximate approaches are considered, and relations to existing methods are discussed.
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.
Modulation of ganciclovir intestinal absorption in presence of absorption enhancers.
Shah, Pranav; Jogani, Viral; Mishra, Pushpa; Mishra, Anil Kumar; Bagchi, Tamishraha; Misra, Ambikanandan
2007-10-01
The purpose of this investigation was to study the influences of absorption enhancers in increasing oral bioavailability of Ganciclovir (GAN) by assessing the transepithelial permeation across cell monolayers in vitro and bioavailability in rats in vivo. The permeation of GAN across Caco-2 and MDCK cell monolayers in the absence/presence of dimethyl-beta-cyclodextrin (DMbetaCD), chitosan hydrochloride (CH), sodium lauryl sulphate (SLS), and their combinations was studied for a 2-h period. GAN was administered to rats in absence/presence of absorption enhancers and drug contents in plasma were estimated. We found that the apparent permeability coefficient (Papp) of GAN in absence of absorption enhancers (control) were 0.261 +/- 0.072 x 10(-6) and 0.486 +/- 0.063 x 10(-6) cm/s in Caco-2 and MDCK cell monolayers, respectively, whereas in the presence of DMbetaCD, CH, SLS, and their combinations, Papp of GAN increased by 5- to 25-fold and 7- to 33-fold as compared to control in Caco-2 and MDCK cell monolayers, respectively. However, in rats, the maximum enhancement in bioavailability of GAN during coadministration of these absorption enhancers was only fivefold compared to GAN control. To conclude, the absorption enhancers-DMbetaCD, CH, SLS, and their combinations demonstrated significant improvement in transepithelial permeation and bioavailability of GAN.
Large persistent photochromic effect due to DX centers in AlSb doped with selenium
Becla, P.; Witt, A.G.; Lagowski, J.; Walukiewicz, W.
1995-04-01
A large photochromic effect has been observed in bulk AlSb crystals doped with Se. Illumination with light of energy higher than 1 eV leads to an increase of the absorption coefficient in the spectral range 0.1 to 1.6 eV. The enhanced absorption is persistent at temperatures below about K. The effect is a manifestation of a DX-like bistability of Se donors. The illumination transfers the from the DX center to a metastable hydrogenic level. The increased absorption with peaks around 0.2 eV and 0.5 is due to photoionization from the donor level to X{sub l} and X{sub 3} minima of the conduction band.
NASA Technical Reports Server (NTRS)
Salama, F.; Allamandola, L. J.
1991-01-01
The ultraviolet, visible, and near-infrared absorption spectra of naphthalene (C10H8) and its radical ion (C10H8/+/), formed by vacuum ultraviolet irradiation, were measured in argon and neon matrices at 4.2 K. The associated vibronic band systems and their spectroscopic assignments are discussed together with the physical and chemical conditions governing ion production in the solid phase. The absorption coefficients were calculated for the ion and found lower than previous values, presumably due to the low polarizability of the neon matrix.
Anisotropy of two-photon absorption and free-carrier effect in nonpolar GaN
Fang, Yu; Zhou, Feng; Yang, Junyi; Wu, Xingzhi; Xiao, Zhengguo; Li, Zhongguo; Song, Yinglin
2015-03-30
We reported a systematic study about the anisotropic optical nonlinearities in bulk m-plane and a-plane GaN crystals by Z-scan and pump-probe with phase object methods under picosecond at 532 nm. The two-photon absorption coefficient, which was measured as a function of polarization angle, exhibited oscillation curves with a period of π/2, indicating a highly polarized optical third-order nonlinearity in both nonpolar GaN samples. Furthermore, free-carrier absorption revealed stronger hole-related absorption for E⊥c than for E//c probe polarization. In contrast, free-carrier refraction was found almost isotropic due to electron-related refraction in the isotropic conduction bands.
Moisture Absorption of Plant Fiber under Annealed, Bleached and Mercerized Condition
NASA Astrophysics Data System (ADS)
Saikia, Dip
2010-06-01
The water absorptions behaviors of the okra fibers, which are available in north east India, were studied under ambient, annealed, bleached and mercerized conditions by using ordinary gravimetric absorption method. The gains in moisture content in the fibers due to water absorption as well as their capillarity at constant relative humidity were measured as a function of exposure time. In order to ascertain the environment factor of utility of the fibers, the moisture regain of the fibers were determined at different relative air humidity. The water yielding capacity of okra fibers was also determined in order to understand their drying properties. The diffusion coefficients of the sorption process of the fibers under ambient, annealed, bleached and mercerized conditions were estimated.
Moisture Absorption of Plant Fiber under Annealed, Bleached and Mercerized Condition
Saikia, Dip
2010-06-29
The water absorptions behaviors of the okra fibers, which are available in north east India, were studied under ambient, annealed, bleached and mercerized conditions by using ordinary gravimetric absorption method. The gains in moisture content in the fibers due to water absorption as well as their capillarity at constant relative humidity were measured as a function of exposure time. In order to ascertain the environment factor of utility of the fibers, the moisture regain of the fibers were determined at different relative air humidity. The water yielding capacity of okra fibers was also determined in order to understand their drying properties. The diffusion coefficients of the sorption process of the fibers under ambient, annealed, bleached and mercerized conditions were estimated.
Studies of Water Absorption Behavior of Plant Fibers at Different Temperatures
NASA Astrophysics Data System (ADS)
Saikia, Dip
2010-05-01
Moisture absorption of natural fiber plastic composites is one major concern in their outdoor applications. The absorbed moisture has many detrimental effects on the mechanical performance of these composites. A knowledge of the moisture diffusivity, permeability, and solubility is very much essential for the application of natural fibers as an excellent reinforcement in polymers. An effort has been made to study the water absorption behavior of some natural fibers such as bowstring hemp, okra, and betel nut at different temperatures to improve the long-term performance of composites reinforced with these fibers. The gain in moisture content in the fibers due to water absorption was measured as a function of exposure time at temperatures ranging from 300 K to 340 K. The thermodynamic parameters of the sorption process, such as diffusion coefficients and corresponding activation energies, were estimated.
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.
Sound absorption in metallic foams
NASA Astrophysics Data System (ADS)
Lu, T. J.; Hess, Audrey; Ashby, M. F.
1999-06-01
The sound absorption capacity of one type of aluminum alloy foams—trade name Alporas—is studied experimentally. The foam in its as-received cast form contains closed porosities, and hence does not absorb sound well. To make the foam more transparent to air motion, techniques based on either rolling or hole drilling are used. Under rolling, the faces of some of the cells break to form small sharp-edged cracks as observed from a scanning electronic microscope. These cracks become passage ways for the in-and-out movement of air particles, resulting in sound absorption improvement. The best performance is nevertheless achieved via hole drilling where nearly all of the sound can be absorbed at selected frequencies. Combining rolling with hole drilling does not appear to lend additional benefits for sound absorption. Image analysis is carried out to characterize the changes in cell morphologies due to rolling/compression, and the drop in elastic modulus due to the formation of cracks is recorded. The effects of varying the relative foam density and panel thickness on sound absorption are measured, and optimal relative density and thickness of the panel are identified. Analytical models are used to explain the measured increase in sound absorption due to rolling and/or drilling. Sound absorbed by viscous flow across small cracks appears to dominate over that dissipated via other mechanisms.
Influence of Brown Carbon Aerosols on Absorption Enhancement and Radiative Forcing
NASA Astrophysics Data System (ADS)
Shamjad, Puthukkadan; Nand Tripathi, Sachchida; Kant Pathak, Ravi; Hallquist, Mattias
2015-04-01
This study presents aerosol mass and optical properties measured during winter-spring months (February-March) of two consecutive years (2013-2014) from Kanpur, India located inside Gangetic Plain. Spectral absorption and scattering coefficients (405, 532 and 781 nm) of both atmospheric and denuded (at 300° C) is measured using a 3 wavelength Photo Acoustic Soot Spectrometer (PASS 3). Ratio between the atmospheric and denuded absorption is reported as enhancement in absorption (Eabs). Eabs values shows presence of large quantities of Brown Carbon (BrC) aerosols in the location. Diurnal trend of Eabs shows similar patterns at 405 and 532 nm. But at 781 nm Eabs values increased during day time (10:00 to 18:00) while that 405 and 532 nm decreased. Positive Matrix Analysis (PMF) of organic aerosols measured using HR-ToF-AMS shows factors with different trends with total absorption. Semi-volatile factor (SV-OOA) show no correlation with absorption but other factors such as Low-volatile (LV-OOA), Hydrocarbon (HOA) and Biomass burning (BBOA) organic aerosols shows a positive trend. All factors shows good correlation with scattering coefficient. Also a strong dependence of absorption is observed at 405 and 532 nm and a weak dependence at 781 nm is observed during regression analysis with factors and mass loading. We also present direct radiative forcing (DRF) calculated from measured optical properties due to total aerosol loading and only due to BrC. Total and BrC aerosol DRF shows cooling trends at top of atmosphere (TOA) and surface and warming trend in atmosphere. Days with biomass burning events shows increase in magnitude of DRF at atmosphere and surface up to 30 % corresponding to clear days. TOA forcing during biomass burning days shows increase in magnitude indicating change from negative to less negative.
Röttgers, Rüdiger; Doxaran, David; Dupouy, Cecile
2016-01-25
The accurate determination of light absorption coefficients of particles in water, especially in very oligotrophic oceanic areas, is still a challenging task. Concentrating aquatic particles on a glass fiber filter and using the Quantitative Filter Technique (QFT) is a common practice. Its routine application is limited by the necessary use of high performance spectrophotometers, distinct problems induced by the strong scattering of the filters and artifacts induced by freezing and storing samples. Measurements of the sample inside a large integrating sphere reduce scattering effects and direct field measurements avoid artifacts due to sample preservation. A small, portable, Integrating Cavity Absorption Meter setup (QFT-ICAM) is presented, that allows rapid measurements of a sample filter. The measurement technique takes into account artifacts due to chlorophyll-a fluorescence. The QFT-ICAM is shown to be highly comparable to similar measurements in laboratory spectrophotometers, in terms of accuracy, precision, and path length amplification effects. No spectral artifacts were observed when compared to measurement of samples in suspension, whereas freezing and storing of sample filters induced small losses of water-soluble pigments (probably phycoerythrins). Remaining problems in determining the particulate absorption coefficient with the QFT-ICAM are strong sample-to-sample variations of the path length amplification, as well as fluorescence by pigments that is emitted in a different spectral region than that of chlorophyll-a.
Hull, C C; Crofts, N C
1996-03-01
The Beer-Lambert law has been used to determine the total attenuation coefficient, mu t, of three hard and three soft contact lens materials. The three hard contact lens materials were PMMA, Polycon II and Boston IV whereas the 3 soft materials were chosen with differing water contents of 38, 55 and 70%, respectively. The total attenuation coefficients of all six materials were obtained from measurements of the axial transmission at 632.8 nm of a series of plano powered lenses varying in axial thickness from 0.5 to 3.5 mm. The value of the total attenuation coefficient depends on both scattering and absorption and hence PMMA and Boston IV, which both incorporated a handling tint, showed significantly higher values (P < 0.0001) of mu t (0.562 +/- 0.010 mm-1 and 0.820 +/- 0.008 mm-1, respectively) than Polycon II (mu t = 0.025 +/- 0.005 mm-1). A comparison between Polycon II and the three hydrated soft contact lens materials showed a significant increase (P < 0.02) in the total attenuation coefficients for the 38% and 55% water content materials, and a weakly significant increase for the 70% water content soft lens material (P < 0.1). On the assumption that the absorption coefficients of these four materials are approximately constant, then this change would be due to an increase in the scattering coefficient of the material and could contribute to an increase in intraocular scatter. No significant difference (P > 0.5) was found between any of the hydrated soft contact lens materials tested.
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.
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.
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).
NASA Astrophysics Data System (ADS)
Ueda, S.; Nakayama, T.; Taketani, F.; Adachi, K.; Matsuki, A.; Iwamoto, Y.; Sadanaga, Y.; Matsumi, Y.
2015-09-01
The coating of black carbon (BC) with inorganic salts and organic compounds can enhance the magnitude of light absorption by BC. To elucidate the enhancement of light absorption of aged BC particles and its relation to the mixing state and morphology of individual particles, we conducted observations of particles at an Asian outflow site in Noto Peninsula, Japan, in the spring of 2013. Absorption and scattering coefficients at 405, 532, and 781 nm and mass concentrations/mixing states of refractory-BC in PM2.5 were measured using a three-wavelength photoacoustic soot spectrometer and a single-particle soot photometer (SP2), respectively, after passage through a heater maintained at 300 or 400 °C or a bypass line maintained at room temperature (25 °C). The average enhancement of BC light absorption due to coating was estimated by comparing absorption coefficients at 781 nm for particles that with and without passing through the heater and was found to be 22-23 %. The largest enhancements (> 30 %) were observed under high absorption coefficient conditions when the air mass was long-range transported from urban areas in China. Aerosol samples were also analyzed using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray analyzer. The morphological features and mixing states of soot-containing particles of four samples collected during the high absorption coefficient events were analyzed by comparing microphotographs before and after the evaporation of beam-sensitive materials by irradiation with a high density electron beam. The majority of the soot in all samples was found as mixed particles with spherical sulfate or as clusters of sulfate spherules. For samples showing high enhancement (> 30 %) of BC light absorption, TEM showed that the internally mixed soot-containing particles tended to have a more spherical shape and to be embedded into the sulfate. The SP2 measurements also suggested that the proportion of thickly-coated soot was
NASA Astrophysics Data System (ADS)
Nima, Ciren; Frette, Øyvind; Hamre, Børge; Erga, Svein Rune; Chen, Yi-Chun; Zhao, Lu; Sørensen, Kai; Norli, Marit; Stamnes, Knut; Stamnes, Jakob J.
2016-09-01
We present data from measurements and analyses of the spectral absorption due to colored dissolved organic matter (CDOM), total suspended matter (TSM), phytoplankton, and non-algal particles (NAP) in high-latitude northern Norwegian coastal water based on samples taken in spring, summer, and autumn. The Chlorophyll-a (Chl-a) concentration was found to vary significantly with season, whereas regardless of season CDOM was found to be the dominant absorber for wavelengths shorter than 600 nm. The absorption spectral slope S350-500 for CDOM varied between 0.011 and 0.022 nm-1 with mean value and standard deviation given by (0.015 ± 0.002) nm-1. The absorption spectral slope was found to be strongly dependent on the wavelength interval used for fitting. On average, S280-500 was found to be 43% higher than S350-500. A linear relationship was found between the base 10 logarithm of the absorption coefficient at 440 nm [log(ag(440))] and S350-500. Regardless of season, phytoplankton were the dominant component of the TSM absorption indicating little influence from land drainage. The mean values of the Chl-a specific absorption coefficient of phytoplankton aph*(λ) at 440 nm and 676 nm were 0.052 m2 mg-1 and 0.023 m2 mg-1, respectively, and aph*(λ) was found to vary with season, being higher in summer and autumn than in spring. The absorption spectral slope SNAP, which is the spectral slope of absorption spectrum for non-algal particles, was lower than that for European coastal water in general. It varied between 0.0048 and 0.022 nm-1 with mean value and standard deviation given by (0.0083-1 ± 0.003) nm-1. Comparisons of absorption coefficients measured in situ using an ac-9 instrument with those measured in the laboratory from water samples show a good agreement.
Quantitative Ultrasound Imaging Using Acoustic Backscatter Coefficients.
NASA Astrophysics Data System (ADS)
Boote, Evan Jeffery
Current clinical ultrasound scanners render images which have brightness levels related to the degree of backscattered energy from the tissue being imaged. These images offer the interpreter a qualitative impression of the scattering characteristics of the tissue being examined, but due to the complex factors which affect the amplitude and character of the echoed acoustic energy, it is difficult to make quantitative assessments of scattering nature of the tissue, and thus, difficult to make precise diagnosis when subtle disease effects are present. In this dissertation, a method of data reduction for determining acoustic backscatter coefficients is adapted for use in forming quantitative ultrasound images of this parameter. In these images, the brightness level of an individual pixel corresponds to the backscatter coefficient determined for the spatial position represented by that pixel. The data reduction method utilized rigorously accounts for extraneous factors which affect the scattered echo waveform and has been demonstrated to accurately determine backscatter coefficients under a wide range of conditions. The algorithms and procedures used to form backscatter coefficient images are described. These were tested using tissue-mimicking phantoms which have regions of varying scattering levels. Another phantom has a fat-mimicking layer for testing these techniques under more clinically relevant conditions. Backscatter coefficient images were also formed of in vitro human liver tissue. A clinical ultrasound scanner has been adapted for use as a backscatter coefficient imaging platform. The digital interface between the scanner and the computer used for data reduction are described. Initial tests, using phantoms are presented. A study of backscatter coefficient imaging of in vivo liver was performed using several normal, healthy human subjects.
Two Photon Absorption And Refraction in Bulk of the Semiconducting Materials
Kumari, Vinay; Kumar, Vinod; Malik, B. P.; Mohan, Devendra; Gaur, Arun
2011-10-20
Fast electronic detection systems have opened up a number of new fields like nonlinear optics, optical communication, coherent optics, optical bistability, two/four wave mixing. The interest in this field has been stimulated by the importance of multiphoton processes in many fundamental aspects of physics. It has proved to be an invaluable tool for determining the optical and electronic properties of the solids because of the fact that one gets the information about the bulk of the material rather than the surface one. In this paper we report, the measurement of the nonlinear absorption and refraction from the band gap to half-band gap region of bulk of semiconductors in the direct and indirect band gap crystals with nanosecond laser. The measured theoretical calculated values of two-photon absorption coefficients ({beta}) and nonlinear refraction n{sub 2}({omega}) of direct band gap crystal match the earlier reported theoretical predictions. By making use of these theoretical calculated values, we have estimated {beta} and n{sub 2}({omega}) in the case of indirect band gap crystals. Low value of absorption coefficient in case of indirect band gap crystals have been attributed to phonon assisted transition while reduction in nonlinear refraction is due to the rise in saturation taking place in the absorption.
Incomplete intestinal absorption of fructose.
Kneepkens, C M; Vonk, R J; Fernandes, J
1984-08-01
Intestinal D-fructose absorption in 31 children was investigated using measurements of breath hydrogen. Twenty five children had no abdominal symptoms and six had functional bowel disorders. After ingestion of fructose (2 g/kg bodyweight), 22 children (71%) showed a breath hydrogen increase of more than 10 ppm over basal values, indicating incomplete absorption: the increase averaged 53 ppm, range 12 to 250 ppm. Four of these children experienced abdominal symptoms. Three of the six children with bowel disorders showed incomplete absorption. Seven children were tested again with an equal amount of glucose, and in three of them also of galactose, added to the fructose. The mean maximum breath hydrogen increases were 5 and 10 ppm, respectively, compared with 103 ppm after fructose alone. In one boy several tests were performed with various sugars; fructose was the only sugar incompletely absorbed, and the effect of glucose on fructose absorption was shown to be dependent on the amount added. It is concluded that children have a limited absorptive capacity for fructose. We speculate that the enhancing effect of glucose and galactose on fructose absorption may be due to activation of the fructose carrier. Apple juice in particular contains fructose in excess of glucose and could lead to abdominal symptoms in susceptible children.
Incomplete intestinal absorption of fructose.
Kneepkens, C M; Vonk, R J; Fernandes, J
1984-01-01
Intestinal D-fructose absorption in 31 children was investigated using measurements of breath hydrogen. Twenty five children had no abdominal symptoms and six had functional bowel disorders. After ingestion of fructose (2 g/kg bodyweight), 22 children (71%) showed a breath hydrogen increase of more than 10 ppm over basal values, indicating incomplete absorption: the increase averaged 53 ppm, range 12 to 250 ppm. Four of these children experienced abdominal symptoms. Three of the six children with bowel disorders showed incomplete absorption. Seven children were tested again with an equal amount of glucose, and in three of them also of galactose, added to the fructose. The mean maximum breath hydrogen increases were 5 and 10 ppm, respectively, compared with 103 ppm after fructose alone. In one boy several tests were performed with various sugars; fructose was the only sugar incompletely absorbed, and the effect of glucose on fructose absorption was shown to be dependent on the amount added. It is concluded that children have a limited absorptive capacity for fructose. We speculate that the enhancing effect of glucose and galactose on fructose absorption may be due to activation of the fructose carrier. Apple juice in particular contains fructose in excess of glucose and could lead to abdominal symptoms in susceptible children. PMID:6476870
Reference Material for Seebeck Coefficients
NASA Astrophysics Data System (ADS)
Edler, F.; Lenz, E.; Haupt, S.
2015-03-01
This paper describes a measurement method and a measuring system to determine absolute Seebeck coefficients of thermoelectric bulk materials with the aim of establishing reference materials for Seebeck coefficients. Reference materials with known thermoelectric properties are essential to allow a reliable benchmarking of different thermoelectric materials for application in thermoelectric generators to convert thermal into electrical energy or vice versa. A temperature gradient (1 to 8) K is induced across the sample, and the resulting voltage is measured by using two differential Au/Pt thermocouples. On the basis of the known absolute Seebeck coefficients of Au and Pt, the unknown Seebeck coefficient of the sample is calculated. The measurements are performed in inert atmospheres and at low pressure (30 to 60) mbar in the temperature range between 300 K and 860 K. The measurement results of the Seebeck coefficients of metallic and semiconducting samples are presented. Achievable relative measurement uncertainties of the Seebeck coefficient are on the order of a few percent.
High efficiency advanced absorption heat pump
NASA Astrophysics Data System (ADS)
Reid, E. A., Jr.
1982-03-01
A high efficiency absorption heat pump for the residential market is investigated. The performance targets established for this high efficiency absorption heat pump are a heating coefficient of performance of 1.5 and a cooling coefficient of performance of 0.8 at rating conditions, including parasitic electric power consumption. The resulting heat pump would have a space heating capacity of 68,000 BTU/hour, and a space cooling capacity of 36,000 BTU/hour at rating conditions. A very simplified schematic block diagram of the high efficiency absorption heat pump cycle is shown. High temperature, high pressure, refrigerant vapor is produced in the refrigerant generator and heat exchange system, is condensed to a liquid in the condenser, expanded to a low pressure vapor in the evaporator, and mixed with and reabsorbed into the weakened solution returned from the refrigerant generator and heat exchange system in the absorber.
Coefficient Alpha: A Reliability Coefficient for the 21st Century?
ERIC Educational Resources Information Center
Yang, Yanyun; Green, Samuel B.
2011-01-01
Coefficient alpha is almost universally applied to assess reliability of scales in psychology. We argue that researchers should consider alternatives to coefficient alpha. Our preference is for structural equation modeling (SEM) estimates of reliability because they are informative and allow for an empirical evaluation of the assumptions…
NASA Astrophysics Data System (ADS)
Huhtinen, M.; Heikkilae, M.; Andersson, R.
1987-03-01
The aim of the study was to analyze the technical and economic feasibility of absorption heat pumps in Finland. The work was done as a case study: the technical and economic analyses have been carried out for six different cases, where in each the suitable size and type of the heat pump plant and the auxiliary components and connections were specified. The study also detailed the costs concerning the procurement, installation and test runs of the machinery, as well as the savings in energy costs incurred by the introduction of the plant. Conclusions were drawn of the economic viability of the applications studied. The following cases were analyzed: heat recovery from flue gases and productin of district heat in plants using peat, natural gas, and municipal wastes as a fuel. Heat recovery in the pulp and paper industry for the upgrading of pressure of secondary steam and for the heating of white liquor and combustion and drying the air. Heat recovery in a peat-fulled heat and power plant from flue gases that have been used for the drying of peat. According to the study, the absorption heat pump suits best to the production of district heat, when the heat source is the primary energy is steam produced by the boiler. Included in the flue as condensing is the purification of flue gases. Accordingly, benefit is gained on two levels in thick applications. In heat and power plants the use of absorption heat pumps is less economical, due to the fact that the steam used by the pump reduces the production of electricity, which is rated clearly higher than heat.
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.
Contributions of dust and smoke to aerosol extinction coefficient
NASA Astrophysics Data System (ADS)
Kavouras, I. G.; Xu, J.; Etyemezian, V.; Dubois, D.; Green, M.; Pitchford, M.
2006-12-01
Estimating scattering and absorption of light by atmospheric particles is critical for evaluating effects on regional and global climate. The magnitude of the interaction between aerosol and light is strongly related to the aerosol chemical composition among other factors. Dust and smoke are major sources of atmospheric aerosol, especially in the western United States. The importance of those sources has increased in recent decades due to the extensive man-made disturbance of natural ecosystems and land management practices. The objectives of this study were to specifically estimate the impact of dust and smoke on aerosol extinction coefficient measured in the Class I areas of the western states and identify the major causes of dust and types of smoke by using: (i) positive matrix factorization (PMF) to apportion ambient aerosols by source type; (ii) air mass backward trajectory analyses; (iii) land use/soil properties and; (iv) wildlife/prescribed fire data. The study included sites from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network located in western United States. For days with the worst reconstructed light extinction when dust was the major component, contributions from transcontinental transport from Asia, windblown dust from local sources and regional transport from upwind sources were identified. Based on the analysis for days with smoke being the major component of aerosol visibility extinction, the contributions of the following types of fires were determined: (a) wildfires near the site ("hot" emissions); (b) wildfires upwind of the site (aged smoke); (c) agricultural burn emissions; (d) rangeland fires.
Convection in axially symmetric accretion discs with microscopic transport coefficients
NASA Astrophysics Data System (ADS)
Malanchev, K. L.; Postnov, K. A.; Shakura, N. I.
2016-09-01
The vertical structure of stationary thin accretion discs is calculated from the energy balance equation with heat generation due to microscopic ion viscosity η and electron heat conductivity κ, both depending on temperature. In the optically thin discs it is found that for the heat conductivity increasing with temperature, the vertical temperature gradient exceeds the adiabatic value at some height, suggesting convective instability in the upper disc layer. There is a critical Prandtl number, Pr = 4/9, above which a Keplerian disc become fully convective. The vertical density distribution of optically thin laminar accretion discs as found from the hydrostatic equilibrium equation cannot be generally described by a polytrope but in the case of constant viscosity and heat conductivity. In the optically thick discs with radiation heat transfer, the vertical disc structure is found to be convectively stable for both absorption dominated and scattering dominated opacities, unless a very steep dependence of the viscosity coefficient on temperature is assumed. A polytropic-like structure in this case is found for Thomson scattering dominated opacity.
Graph characterization via Ihara coefficients.
Ren, Peng; Wilson, Richard C; Hancock, Edwin R
2011-02-01
The novel contributions of this paper are twofold. First, we demonstrate how to characterize unweighted graphs in a permutation-invariant manner using the polynomial coefficients from the Ihara zeta function, i.e., the Ihara coefficients. Second, we generalize the definition of the Ihara coefficients to edge-weighted graphs. For an unweighted graph, the Ihara zeta function is the reciprocal of a quasi characteristic polynomial of the adjacency matrix of the associated oriented line graph. Since the Ihara zeta function has poles that give rise to infinities, the most convenient numerically stable representation is to work with the coefficients of the quasi characteristic polynomial. Moreover, the polynomial coefficients are invariant to vertex order permutations and also convey information concerning the cycle structure of the graph. To generalize the representation to edge-weighted graphs, we make use of the reduced Bartholdi zeta function. We prove that the computation of the Ihara coefficients for unweighted graphs is a special case of our proposed method for unit edge weights. We also present a spectral analysis of the Ihara coefficients and indicate their advantages over other graph spectral methods. We apply the proposed graph characterization method to capturing graph-class structure and clustering graphs. Experimental results reveal that the Ihara coefficients are more effective than methods based on Laplacian spectra.
Gromova, L V; Gruzdkov, A A
1999-06-01
In order to throw light on the mechanisms responsible for the enzyme-dependent absorption of disaccharides membrane hydrolysis of maltose and trehalose and the absorption of glucose (free and that derived from disaccharides) were studied in isolated loops (20 cm) of the rat small intestine in chronic experiments. The rates of glucose absorption were 0.26-0.81 micromol x min(-1) x cm(-1) when the loop was perfused with a 12.5 to 75.0 mmol/l free glucose solution, which is only insignificantly higher than the rates observed during perfusion with equivalent maltose solutions. The coupling coefficient (the ratio of glucose absorption rate to the rate of disaccharide hydrolysis) decreased from 0.90 to 0.60 with the increasing maltose concentrations in the infusate from 6.25 to 37.5 mmol/l, but remained unchanged (approximately 0.95) within the same range of trehalose concentrations. The permeability of the pre-epithelial barrier was equivalent to that of unstirred water layer of less than 40 microm thickness. Fluid absorption was within the range of 0.73-2.55 microl x min(-1) x cm(-1), and it showed a correlation with the rates of glucose absorption. The results agree with a model developed on the assumption that free glucose and that released from disaccharides share the same membrane transporters. It could be concluded that a close coupling of disaccharide hydrolysis with derived glucose absorption in chronic experiments is achieved mainly due to a high activity of glucose transporters, which are presumably not associated with membrane disaccharidases. The transcellular active transport is a predominant mechanism of disaccharide-derived glucose absorption under conditions close to physiological.
Interferometric measurements of thermo-optic coefficients of ZnS, CaF2, and Ge in the infrared
NASA Astrophysics Data System (ADS)
Mangin, Jacques; Strimer, Pierre; Schillinger, Marc; Meyzonnette, Jean-Louis P.; Thebault, Jacques; Aymonier, C.
1996-08-01
The thermo-optic coefficient (delta) n divided by (delta) T of CaF2, ZnS and Ge single crystals have been measured in the infrared from 20 degrees C to 100 degrees C. The laser interferometric method employed allows a determination of (delta) n divided by (delta) T with an accuracy close to 10-6K-1 in the case of nonabsorbing materials. For Ge the uncertainty is increased by a factor of 3 and is mainly due to its increasing absorption coefficient with temperature. The behavior of ZnS was examined at 1.06 micrometers and 10.6 micrometers laser radiations; CaF2 and Ge were investigated respectively at 1.06 micrometers and 10.6 micrometers.
Optical absorption and scattering properties in the East China Sea
NASA Astrophysics Data System (ADS)
Zhang, Xuan; He, Xian-qiang; Chen, Xiao-yan; Hao, Zeng-zhou; Huang, Haiqing; Zhu, Qiankun
2011-11-01
The absorption and particulate backscattering coefficients are the basic parameters of the water inherent optical properties (IOPs), which are also the basic parameters for the development and validation of the semi-analysis models of the ocean color remote sensing. In this work, the absorption and backscattering coefficients in the East China Sea (ECS) were measured in the summer and winter of 2009 using the three in-situ optical instruments, including the WET Labs acs, and the HOBI Labs HydroScat-6. Based on the in-situ measured data, the distribution of the absorption and backscattering coefficients in the ECS are analyzed. The results show that in the summer the water absorption coefficient at 440nm (a(440nm),excluding the absorption of the pure sea water) in the surface layer is ranged from 0.022 to 0.067 m-1, and the particulate backscattering coefficient at 442nm(bbp(442nm), is between 0.00064 and 0.03274 m-1. As a whole, both of the absorption and backscattering coefficients decrease with the offshore direction, and the high values located at the mouth of Changjiang River. In the winter, a(440nm) is between 0.051 and 0.887 m-1, and bbp(442nm) is ranged from 0.000639 to 0.14614 m-1 at the surface layer. The spatial distributions in winter are similar as the summer, with the high value in the coast and low value in the offshore. The absorption and backscattering coefficients in winter are significantly larger than the summer's, especially in coastal area near the mouth of Changjiang River, which maybe caused by the southward Fujian-Zhejiang coastal current occurring in winter. As the vertical profile distributions, we find that both of the absorption and backscattering coefficients present a layer structure, which caused by the stratification of the sea water in the summer; while in the winter, affected by the strong wind disturbing, both of the absorption and backscattering coefficients are thoroughly vertical mixing. To our knowledge, it is the first time
NASA Astrophysics Data System (ADS)
Rosenberg, E.; Kellner, Robert A.
1992-03-01
During the past few years, the importance of membranes in chemical and biotechnological applications, such as separation processes and biosensor construction, has dramatically increased. As a consequence, membrane properties have to be characterized very thoroughly with special respect to diffusivity and selectivity. Whereas most techniques for the determination of diffusion coefficients require sophisticated and often indirect methods for the detection of the analyte diffusing through the membrane, which generally do not allow monitoring of the diffusion process continuously, we present in this work an experimentally simple and straightforward method employing FTIR-ATR spectroscopy. The diffusion of glucose into a PVA membrane is chosen as a model example for the determination of carbohydrates in polymer matrices due to its special relevance in biosensor construction. The method is based on monitoring the time-dependent change in absorption due to the diffusion of the glucose into the polymer membrane. After reaching a steady-state, the normalized absorbance plot (A/A(infinity) ) versus time can be used for numerical evaluation. The diffusion coefficient is determined by comparing the experimental with simulated data using the membrane thickness (iota) and the diffusion coefficient D as simulation parameters. For this reason, the performance of a recursive and two non-recursive models for the description of the diffusion process is examined. Modifications in the second non-recursive algorithm finally resulted in very good agreement with the experimental data. This work marks the first application of IR-ATR spectroscopy for the determination of diffusion coefficients even as large as of the order of 10-6 cm2/sec.
Cytoplasmic hydrogen ion diffusion coefficient.
al-Baldawi, N F; Abercrombie, R F
1992-01-01
The apparent cytoplasmic proton diffusion coefficient was measured using pH electrodes and samples of cytoplasm extracted from the giant neuron of a marine invertebrate. By suddenly changing the pH at one surface of the sample and recording the relaxation of pH within the sample, an apparent diffusion coefficient of 1.4 +/- 0.5 x 10(-6) cm2/s (N = 7) was measured in the acidic or neutral range of pH (6.0-7.2). This value is approximately 5x lower than the diffusion coefficient of the mobile pH buffers (approximately 8 x 10(-6) cm2/s) and approximately 68x lower than the diffusion coefficient of the hydronium ion (93 x 10(-6) cm2/s). A mobile pH buffer (approximately 15% of the buffering power) and an immobile buffer (approximately 85% of the buffering power) could quantitatively account for the results at acidic or neutral pH. At alkaline pH (8.2-8.6), the apparent proton diffusion coefficient increased to 4.1 +/- 0.8 x 10(-6) cm2/s (N = 7). This larger diffusion coefficient at alkaline pH could be explained quantitatively by the enhanced buffering power of the mobile amino acids. Under the conditions of these experiments, it is unlikely that hydroxide movement influences the apparent hydrogen ion diffusion coefficient. PMID:1617134
Bitplane Image Coding With Parallel Coefficient Processing.
Auli-Llinas, Francesc; Enfedaque, Pablo; Moure, Juan C; Sanchez, Victor
2016-01-01
Image coding systems have been traditionally tailored for multiple instruction, multiple data (MIMD) computing. In general, they partition the (transformed) image in codeblocks that can be coded in the cores of MIMD-based processors. Each core executes a sequential flow of instructions to process the coefficients in the codeblock, independently and asynchronously from the others cores. Bitplane coding is a common strategy to code such data. Most of its mechanisms require sequential processing of the coefficients. The last years have seen the upraising of processing accelerators with enhanced computational performance and power efficiency whose architecture is mainly based on the single instruction, multiple data (SIMD) principle. SIMD computing refers to the execution of the same instruction to multiple data in a lockstep synchronous way. Unfortunately, current bitplane coding strategies cannot fully profit from such processors due to inherently sequential coding task. This paper presents bitplane image coding with parallel coefficient (BPC-PaCo) processing, a coding method that can process many coefficients within a codeblock in parallel and synchronously. To this end, the scanning order, the context formation, the probability model, and the arithmetic coder of the coding engine have been re-formulated. The experimental results suggest that the penalization in coding performance of BPC-PaCo with respect to the traditional strategies is almost negligible.
Bounds and estimates for power absorption in two-dimensional highly lossy configurations
NASA Astrophysics Data System (ADS)
Razansky, D.; Soldea, D. F.; Einziger, P. D.
2004-06-01
Electromagnetic power absorption in biological tissues has recently received due scientific and public attention, particularly, in the areas of cellular communication and hyperthermic treatments. While efficient numerical algorithms, such as the finite difference time domain technique and the method of moments, have been developed as to obtain accurate power distributions in complicated configurations, their physical interpretation and explicit dependence on problem's parameters are still difficult to achieve. In attempt to gain a clear insight into the electromagnetic power absorption mechanism as well as its estimation and relation to the Specific Absorption Rate (SAR), we have recently proposed an infinite-extent current-sheet model. Herein, the model is further extended by incorporating finite-extent sources, i.e., electric and magnetic line-sources, exciting a highly lossy semi-infinite half-space. This modification results in deeper insight and understanding of the crucially important parameters, commonly involved in realistic configurations, namely, bounds and estimates on the power absorption and radiation efficiencies, local and total SAR coupling coefficients, and effective absorption dimensions.
NASA Astrophysics Data System (ADS)
Sekhar, H.; Rakesh Kumar, Y.; Narayana Rao, D.
2015-02-01
Cuprous oxide nano clusters, micro cubes and micro particles were successfully synthesized by reducing copper (II) salt with ascorbic acid in the presence of sodium hydroxide via a co-precipitation method. The X-ray diffraction studies revealed the formation of pure single phase cubic. Raman spectrum shows the inevitable presence of CuO on the surface of the Cu2O powders which may have an impact on the stability of the phase. Transmission electron microscopy (TEM) data revealed that the morphology evolves from nanoclusters to micro cubes and micro particles by increasing the concentration of NaOH. Linear optical measurements show that the absorption peak maximum shifts towards red with changing morphology from nano clusters to micro cubes and micro particles. The nonlinear optical properties were studied using open aperture Z-scan technique with 532 nm, 6 ns laser pulses. Samples exhibited saturable as well as reverse saturable absorption. The results show that the transition from SA to RSA is ascribed to excited-state absorption (ESA) induced by two-photon absorption (TPA) process. Due to confinement effects (enhanced band gap) we observed enhanced nonlinear absorption coefficient (βeff) in the case of nano-clusters compared to their micro-cubes and micro-particles.
Multiphoton absorption in germanium using pulsed infrared free-electron laser radiation
NASA Astrophysics Data System (ADS)
Seo, D.; Gregory, J. M.; Feldman, L. C.; Tolk, N. H.; Cohen, P. I.
2011-05-01
We report wavelength- and intensity-dependent transmission measurements of intense mid-infrared radiation from the Vanderbilt free-electron laser in single-crystal Ge(100) in the wavelength range of 2.8-5.2 μm. This range accesses both the direct and indirect energy gaps in Ge, requiring in each case either two or three photons (2PA or 3PA) for absorption. Large changes in the multiphoton absorption rate are seen at the direct-to-indirect and 2PA-to-3PA transitions. Photon interactions are dominated by free-carrier absorption (FCA), primarily due to holes. The entire absorption process is modeled with the two- and three-photon absorption coefficients (β and γ) as fitting parameters. Using newly measured values of the low-intensity FCA cross sections, we find a best fit to the data at 2.8 μm that is in agreement with theory and previous measurements. We report a ratio of 175 for β across the direct-to-indirect transition, and a ratio of 5 across the same transition for γ. These ratios are independent of systematic variations in free-carrier cross sections and beam diameter.
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.
Optical-induced absorption tunability of Barium Strontium Titanate film
NASA Astrophysics Data System (ADS)
Luo, Chunya; Ji, Jie; Yue, Jin; Rao, Yunkun; Yao, Gang; Li, Dan; Zeng, Ying; Li, Renkui; Xiao, Longsheng; Liu, Xinxing; Yao, Jianquan; Ling, Furi
2016-10-01
The absorption tunability of 100 nm thickness of ferroelectric Barium Strontium Titanate (Ba0.5Sr0.5TiO3) thin films with different densities of pumped optical field is measured by terahertz time-domain spectroscopy in the range of 0.2 THz - 1.2 THz at 19 °C. Experimental results show that the absorption coefficient of BST film is approximately at 5000 cm-1-20000 cm-1 in the range of 0.2 THz - 1.2 THz and the absorption coefficient reached up to 16% when we applied the optical field up to 600 mW. The theoretical calculations reveal that increasing photoexcitation fluences is responsible for the increasing of transmission change in the conduction current density cause the absorption coefficient varied.
Absorption of microwaves in metal-ceramic powder materials
NASA Astrophysics Data System (ADS)
Egorov, S. V.; Eremeev, A. G.; Plotnikov, I. V.; Rybakov, K. I.; Kholoptsev, V. V.; Bykov, Yu. V.
2010-11-01
Sintering of metal-ceramic composites by microwave heating is a promising method for creation of functionally graded materials. In this paper, we study the absorption of microwaves in compacted mixtures of metal and dielectric powders. The coefficient of microwave absorption is calculated within the framework of the effective-medium approximation as a function of the mass fraction, dimensions, and temperature of metal particles. The experimental method for determination of the microwave absorption coefficient is proposed, which is based on measuring the temperature of the samples during their heating by microwaves in an oversized working chamber. The coefficients of microwave absorption in powder composites Al2O3-Ni, which were measured by the proposed method, are presented. An agreement between the theoretical and experimental results is demonstrated.
NASA Astrophysics Data System (ADS)
Ueda, Sayako; Nakayama, Tomoki; Taketani, Fumikazu; Adachi, Kouji; Matsuki, Atsushi; Iwamoto, Yoko; Sadanaga, Yasuhiro; Matsumi, Yutaka
2016-03-01
The coating of black carbon (BC) with inorganic salts and organic compounds can enhance the magnitude of light absorption by BC. To elucidate the enhancement of light absorption of aged BC particles and its relation to the mixing state and morphology of individual particles, we conducted observations of particles at an Asian outflow site in Noto Peninsula, Japan, in the spring of 2013. Absorption and scattering coefficients at 405, 532, and 781 nm and mass concentrations/mixing states of refractory BC in PM2.5 were measured using a three-wavelength photoacoustic soot spectrometer and a single-particle soot photometer (SP2), respectively, after passage through a thermodenuder (TD) maintained at 300 or 400 °C or a bypass line maintained at room temperature (25 °C). The average enhancement factor of BC light absorption due to coating was estimated by comparing absorption coefficients at 781 nm for particles that with and without passing through the TD at 300 °C and was found to be 1.22. The largest enhancements (> 1.30) were observed under high absorption coefficient periods when the air mass was long-range transported from urban areas in China. Aerosol samples were also analyzed using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray analyzer. The morphological features and mixing states of soot-containing particles of four samples collected during the high absorption events were analyzed by comparing microphotographs before and after the evaporation of beam-sensitive materials by irradiation with a high-density electron beam. The majority of the soot in all samples was found as mixed particles with sulfate-containing spherules or as clusters of such spherules. For samples showing high enhancement (> 1.30) of BC light absorption, the TEM showed that the internally mixed soot-containing particles tended to have a more spherical shape and to be thickly coated. The SP2 measurements also suggested that the proportion of thickly coated
Computational oral absorption simulation for low-solubility compounds.
Sugano, Kiyohiko
2009-11-01
Bile micelles play an important role in oral absorption of low-solubility compounds. Bile micelles can affect solubility, dissolution rate, and permeability. For the pH-solubility profile in bile micelles, the Henderson-Hasselbalch equation should be modified to take bile-micelle partition into account. For the dissolution rate, in the Nernst-Brunner equation, the effective diffusion coefficient in bile-micelle media should be used instead of the monomer diffusion coefficient. The diffusion coefficient of bile micelles is 8- to 18-fold smaller than that of monomer molecules. For permeability, the effective diffusion coefficient in the unstirred water layer adjacent to the epithelial membrane, and the free fraction at the epithelial membrane surface should be taken into account. The importance of these aspects is demonstrated here using several in vivo and clinical oral-absorption data of low-solubility model compounds. Using the theoretical equations, the food effect on oral absorption is further discussed.
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
Wang, Kangpeng; Ju, Yongfeng; He, Jin; Zhang, Long E-mail: lzhang@siom.ac.cn; Wang, Jun E-mail: lzhang@siom.ac.cn; Chen, Yu; Blau, Werner J.
2014-01-13
Laser propagation in a tandem structure comprising carbon nanotubes and phthalocyanines is studied by Z-scan method. Due to the different mechanisms of the two materials, the laser beam can be attenuated with different absorptivities, by changing the sequence of light passing through each material. Numerical simulations considering the effect of path length and the change of nonlinear coefficient within each material are conducted for understanding the distribution of laser intensity in the tandem system and hence, fitting of the asymmetric Z-scan curves. The results are helpful for the design of nonlinear optical devices comprising multiple nonlinear materials and mechanisms.
NASA Astrophysics Data System (ADS)
Paredes-Miranda, G.; Arnott, W. P.; Marley, N. A.; Gaffney, J. S.
2007-05-01
As part of the Megacity Impacts on Regional and Global Environments, MIRAGE-Mex deployment to Mexico City in the period of 30 days, March 2006, a suite of photoacoustic spectrometers (PAS; W. Arnott & G. Paredes), nephelometer scattering, and aetholemeter absorption instruments (N. Marley & J.Gaffney) were installed to measure at ground level the light absorption and scattering by aerosols at the urban site at Instituto Mexicano del Petroleo (Mexican Oil Institute, denoted by IMP). This IMP site gave in-situ characterization of the Mexico City plume under favorable wind conditions. The PAS used at IMP operates at 532 nm, and conveniently allowed for characterization of gaseous absorption at this wavelength as well. Light scattering measurements are accomplished within the PAS by the reciprocal nephelometery method. In the urban site the aerosol absorption coefficient typically varies between 20 and 180 Mm-1 during the course of the day and significant diurnal variation of the aerosol single scattering albedo was observed. The Las Vegas, NV site was located at East Charleston Street on January-February, 2003. In east Las Vegas typical westerly winds carry the city plume across the site. Comparisons of PAS aerosol light absorption and aetholemeter absorption measurements at 521 nm at both Las Vegas NV and Mexico City sites will be presented. We will also present a broad overview of the diurnal variation of the scattering and absorption as well as the single scattering albedo and fraction of absorption due to gases at the sites in relation to secondary aerosol formation.
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.
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.
Diffusion Coefficients in White Dwarfs
NASA Astrophysics Data System (ADS)
Saumon, D.; Starrett, C. E.; Daligault, J.
2015-06-01
Models of diffusion in white dwarfs universally rely on the coefficients calculated by Paquette et al. (1986). We present new calculations of diffusion coefficients based on an advanced microscopic theory of dense plasmas and a numerical simulation approach that intrinsically accounts for multiple collisions. Our method is validated against a state-of-the-art method and we present results for the diffusion of carbon ions in a helium plasma.
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.
Broken-cloud enhancement of solar radiation absorption
Byrne, R.N.; Somerville, R.C.; Subasilar, B.
1996-04-01
Two papers recently published in Science have shown that there is more absorption of solar radiation than estimated by current atmospheric general circulation models (GCMs) and that the discrepancy is associated with cloudy scenes. We have devised a simple model which explains this as an artifact of stochastic radiative transport. We first give a heuristic description, unencumbered by mathematical detail. Consider a simple case with clouds distributed at random within a single level whose upper and lower boundaries are fixed. The solar zenith angle is small to moderate; this is therefore an energetically important case. Fix the average areal liquid water content of the cloud layer, and take the statistics of the cloud distribution to be homogeneous within the layer. Furthermore, assume that all the clouds in the layer have the same liquid water content, constant throughout the cloud, and that apart from their droplet content they are identical to the surrounding clear sky. Let the clouds occupy on the average a fraction p{sub cld} of the volume of the cloudy layer, and let them have a prescribed distribution of sizes about some mean. This is not a fractal distribution, because it has a scale. Cloud shape is unimportant so long as cloud aspect ratios are not far from unity. Take the single-scattering albedo to be unity for the droplets in the clouds. All of the absorption is due to atmospheric gases, so the absorption coefficient at a point is the same for cloud and clear sky. Absorption by droplets is less than 10% effect in the numerical stochastic radiation calculations described below, so it is reasonable to neglect it at this level of idealization.
Comprehensive analysis of the optical Kerr coefficient of graphene
Soh, Daniel B. S.; Hamerly, Ryan; Mabuchi, Hideo
2016-08-25
We present a comprehensive analysis of the nonlinear optical Kerr effect in graphene. We directly solve the S-matrix element to calculate the absorption rate, utilizing the Volkov-Keldysh-type crystal wave functions. We then convert to the nonlinear refractive index coefficients through the Kramers-Kronig relation. In this formalism, the source of Kerr nonlinearity is the interplay of optical fields that cooperatively drive the transition from valence to conduction band. This formalism makes it possible to identify and compute the rates of distinct nonlinear processes that contribute to the Kerr nonlinear refractive index coefficient. The four identified mechanisms are two-photon absorption, Raman transition,more » self-coupling, and quadratic ac Stark effect. As a result, we present a comparison of our theory with recent experimental and theoretical results.« less
Comprehensive analysis of the optical Kerr coefficient of graphene
NASA Astrophysics Data System (ADS)
Soh, Daniel B. S.; Hamerly, Ryan; Mabuchi, Hideo
2016-08-01
We present a comprehensive analysis of the nonlinear optical Kerr effect in graphene. We directly solve the S -matrix element to calculate the absorption rate, utilizing the Volkov-Keldysh-type crystal wave functions. We then convert to the nonlinear refractive index coefficients through the Kramers-Kronig relation. In this formalism, the source of Kerr nonlinearity is the interplay of optical fields that cooperatively drive the transition from valence to conduction band. This formalism makes it possible to identify and compute the rates of distinct nonlinear processes that contribute to the Kerr nonlinear refractive index coefficient. The four identified mechanisms are two-photon absorption, Raman transition, self-coupling, and quadratic ac Stark effect. We also present a comparison of our theory with recent experimental and theoretical results.
NASA Technical Reports Server (NTRS)
Mitchell, David L.; Arnott, W. Patrick
1994-01-01
This study builds upon the microphysical modeling described in Part 1 by deriving formulations for the extinction and absorption coefficients in terms of the size distribution parameters predicted from the micro-physical model. The optical depth and single scatter albedo of a cirrus cloud can then be determined, which, along with the asymmetry parameter, are the input parameters needed by cloud radiation models. Through the use of anomalous diffraction theory, analytical expressions were developed describing the absorption and extinction coefficients and the single scatter albedo as functions of size distribution parameters, ice crystal shapes (or habits), wavelength, and refractive index. The extinction coefficient was formulated in terms of the projected area of the size distribution, while the absorption coefficient was formulated in terms of both the projected area and mass of the size distribution. These properties were formulated as explicit functions of ice crystal geometry and were not based on an 'effective radius.' Based on simulations of the second cirrus case study described in Part 1, absorption coefficients predicted in the near infrared for hexagonal columns and rosettes were up to 47% and 71% lower, respectively, than absorption coefficients predicted by using equivalent area spheres. This resulted in single scatter albedos in the near-infrared that were considerably greater than those predicted by the equivalent area sphere method. Reflectances in this region should therefore be underestimated using the equivalent area sphere approach. Cloud optical depth was found to depend on ice crystal habit. When the simulated cirrus cloud contained only bullet rosettes, the optical depth was 142% greater than when the cloud contained only hexagonal columns. This increase produced a doubling in cloud albedo. In the near-infrared (IR), the single scatter albedo also exhibited a significant dependence on ice crystal habit. More research is needed on the
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.
Maximum profit performance of an absorption refrigerator
Chen, L.; Sun, F.; Wu, C.
1996-12-01
The operation of an absorption refrigerator is viewed as a production process with exergy as its output. The relations between the optimal profit and COP (coefficient of performance), and the COP bound at the maximum profit of the refrigerator are derived based on a general heat transfer law. The results provide a theoretical basis for developing and utilizing a variety of absorption refrigerators. The focus of this paper is to search the compromise optimization between economics (profit) and the utilization factor (COP) for finite-time endoreversible thermodynamic cycles.
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.
Yb3+ doped fluorophosphate laser glasses with high gain coefficient and improved laser property
NASA Astrophysics Data System (ADS)
Wang, P. F.; Peng, B.; Li, W. N.; Hou, Ch. Q.; She, J. B.; Guo, H. T.; Lu, M.
2012-04-01
Yb3+ doped fluorophosphate glasses with high stimulated emission cross-section, large gain coefficient and low hydroxyl absorption coefficient were prepared by high temperature melting for fiber laser applications, and their spectral, general laser parameters were investigated accordingly by means of fluorescence emission spectrum, decay cure and infrared absorption spectra. Compared with previously reported fluorophosphate glasses, the investigated fluorophosphate glasses have highest grain coefficient and maintain a maximum laser systematical factor over other various types of laser glasses. The introduction of fluorides to fluorophosphate glasses results in the low level of hydroxyl absorption coefficient and concentration. All these advantages might mean that Yb3+ doped fluorophosphate glasses are a good candidate as an active laser media for short pulse, high power laser generation used for next generation nuclear fusion.
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.
NASA Astrophysics Data System (ADS)
El-Sa'Ad, Leila
1989-12-01
Available from UMI in association with The British Library. Requires signed TDF. Epoxy resins exhibit many desirable properties which make them ideal subjects for use as matrices of composite materials in many commercial, military and space applications. However, due to their high cross-link density they are often brittle. Epoxy resin networks have been modified by incorporating tough, ductile thermoplastics. Such systems are referred to as Semi-Interpenetrating Polymer Networks (Semi-IPN). Systematic modification to the thermoplastics backbone allowed the morphology of the blend to be controlled from a homogeneous one-phase structure to fully separated structures. The moisture absorption by composites in humid environments has been found to lead to a deterioration in the physical and mechanical properties of the matrix. Therefore, in order to utilize composites to their full potential, their response to hot/wet environments must be known. The aims of this investigation were two-fold. Firstly, to study the effect of varying the temperature of exposure at different stages in the absorption process on the water absorption behaviour of a TGDDM/DDS epoxy resin system. Secondly, to study water absorption characteristics, under isothermal conditions, of Semi-Interpenetrating Polymer Networks possessing different morphologies, and develop a theoretical model to evaluate the diffusion coefficients of the two-phase structures. The mathematical treatment used in this analysis was based on Fick's second law of diffusion. Tests were performed on specimens immersed in water at 10 ^circ, 40^circ and 70^circC, their absorption behaviour and swelling behaviour, as a consequence of water absorption, were investigated. The absorption results of the variable temperature absorption tests indicated a saturation dependence on the absorption behaviour. Specimens saturated at a high temperature will undergo further absorption when transferred to a lower temperature. This behaviour was
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.
Binary-YORP Coefficients for Known Asteroid Shapes
NASA Astrophysics Data System (ADS)
McMahon, Jay W.; Scheeres, D. J.
2012-10-01
The binary YORP (bYORP) effect has been hypothesized to be a significant factor in the evolution of near-Earth binary asteroid systems (Cuk and Burns, Icarus, v.176, pp.418-431, 2005; McMahon and Scheeres, CMDA, v.106, pp.261-300, 2010). However, understanding of the coefficient values for realistic asteroid shapes is lacking due to the small number of shape models available for the generally smaller secondary asteroids. Until now, we have only calculated the coefficients based on the shape of 1999 KW4 Beta, although various studies by other authors have computed coefficients for artificially generated asteroids based on Gaussian Spheres and some shape models without self-shadowing (Steinberg and Sari, The Astronomical Journal, v.141, pp.55-64, 2011). We also scaled the 1999 KW4 Beta coefficients to other binary systems with no knowledge of the other systems' secondary shapes in order to make evolutionary predictions (McMahon and Scheeres, Icarus Vol. 209, pp 494-509, 2010). In this study, we compute the bYORP coefficient for a range of asteroid shapes, using these as a stand-in for actual secondaries. This allows us to circumvent the lack of information on binary asteroid secondaries and to develop a richer database of realistic coefficients. While this approach may miss some key features of binary secondaries, at the least it provides some statistics on the expected variability of the bYORP coefficient. We analyze all available asteroid shape models on the PDS-SBN, including radar-based shape models and models estimated from past spacecraft missions. The coefficients are computed with an updated algorithm that includes the effects of self-shadowing. We also present the coefficients for perturbed versions of the available shape models, which give effective error bars to the computed coefficients due to inexact shape models. Finally, we discuss the dynamical implications of the derived bYORP coefficients on binary asteroid evolution.
Light Absorption of Stratospheric Aerosols: Long-Term Trend and Contribution by Aircraft
NASA Technical Reports Server (NTRS)
Pueschel , R. F.; Gore, Waren J. Y. (Technical Monitor)
1997-01-01
Measurements of aerosol light-absorption coefficients are useful for studies of radiative transfer and heating rates. Ogren appears to have published the first light- absorption coefficients in the stratosphere in 1981, followed by Clarke in 1983 and Pueschel in 1992. Because most stratospheric soot appears to be due to aircraft operations, application of an aircraft soot aerosol emission index to projected fuel consumption suggests a threefold increase of soot loading and light absorption by 2025. Together, those four data sets indicate an increase in mid-visible light extinction at a rate of 6 % per year. This trend is similar to the increase per year of sulfuric acid aerosol and of commercial fleet size. The proportionality between stepped-up aircraft operations above the tropopause and increases in stratospheric soot and sulfuric acid aerosol implicate aircraft as a source of stratospheric pollution. Because the strongly light-absorbing soot and the predominantly light-scattering sulfuric acid aerosol increase at similar rates, however, the mid-visible stratospheric aerosol single scatter albedo is expected to remain constant and not approach a critical value of 0.98 at which stratospheric cooling could change to warming.
In vitro percutaneous absorption enhancement of a lipophilic drug tamoxifen by terpenes.
Gao, S; Singh, J
1998-02-12
Tamoxifen is a highly lipophilic drug that is widely used in breast malignancies and also as a prophylactic therapy in women at high risk for the development of this disease. Recently, the terpenes have been reported to show an enhancement effect on percutaneous drug absorption. The effect of terpenes (e.g. carvone, 1,8-cineole, menthol, and thymol) was studied on the in vitro percutaneous absorption of tamoxifen through porcine epidermis. The above terpenes (5% w/v) in combination with 50% ethanol significantly (P < 0.01) increased the permeability coefficient of tamoxifen in comparison to the control (50% ethanol). The solubility of tamoxifen was determined in the control and enhancer solutions to correct the permeability enhancement by way of fractional solubility adjustment. Binding of tamoxifen to powdered stratum corneum from control and enhancer solutions was also determined. Binding studies reveal that the enhancement in the permeability coefficient of tamoxifen by menthol and thymol is due at least in part, to improvement in the partitioning of the drug to the stratum corneum. In conclusion, terpenes in combination with ethanol can be used to enhance the percutaneous absorption of the highly lipophilic drug tamoxifen. PMID:9685917
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
Modification of Einstein A Coefficient in Dissipative Gas Medium
NASA Technical Reports Server (NTRS)
Cao, Chang-Qi; Cao, Hui; Qin, Ke-Cheng
1996-01-01
Spontaneous radiation in dissipative gas medium such as plasmas is investigated by Langevin equations and the modified Weisskopf-Wigner approximation. Since the refractive index of gas medium is expected to be nearly unity, we shall first neglect the medium polarization effect. We show that absorption in plasmas may in certain case modify the Einstein A coefficient significantly and cause a pit in the A coefficient-density curves for relatively low temperature plasmas and also a pit in the A coefficient-temperature curves. In the next, the effect of medium polarization is taken into account in addition. To our surprise, its effect in certain case is quite significant. The dispersive curves show different behaviors in different region of parameters.
Determination of stream reaeration coefficients by use of tracers
Kilpatrick, F.A.; Rathbun, R.E.; Yotsukura, Nobuhiro; Parker, G.W.; DeLong, L.L.
1987-01-01
Stream reaeration is the physical absorption of oxygen from the atmosphere by a flowing stream. This is the primary process by which a stream replenishes the oxygen consumed in the biodegradation of organic wastes. Prior to 1965, reaeration rate coefficients could be estimated only by indirect methods. In 1965, a direct method of measuring stream reaeration coefficients was developed in which a radioactive tracer gas was injected into a stream--the tracer gas being desorbed from the stream inversely to how oxygen would be absorbed. The technique has since been modified by substituting hydrocarbon gases for the radioactive tracer gas. The slug-injection and constant-rate injection methods of performing gas tracer desorption measurements are described. Emphasis is on the use of rhodamine WT dye as a relatively conservative tracer and propane as the nonconservative gas tracer, on planning field tests, methods of injection, sampling and analysis, and computational techniques to compute desorption and reaeration coefficients. (Author 's abstract)
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.
Transport coefficients of gluonic fluid
Das, Santosh K.; Alam, Jan-e
2011-06-01
The shear ({eta}) and bulk ({zeta}) viscous coefficients have been evaluated for a gluonic fluid. The elastic, gg{yields}gg and the inelastic, number nonconserving, gg{yields}ggg processes have been considered as the dominant perturbative processes in evaluating the viscous coefficients to entropy density (s) ratios. Recently the processes: gg{yields}ggg has been revisited and a correction to the widely used Gunion-Bertsch (GB) formula has been obtained. The {eta} and {zeta} have been evaluated for gluonic fluid with the formula recently derived. At large {alpha}{sub s} the value of {eta}/s approaches its lower bound, {approx}1/4{pi}.
Surfaces with adaptive radar reflection coefficients
NASA Astrophysics Data System (ADS)
Chambers, Barry
1997-10-01
Conventional (passive) radar-absorbing materials (RAM) have been in use now for over half a century, but it is only with recent advances in conducting polymer composite materials that large-area surfaces having controllable reflection coefficients at radar frequencies have become practicable. Techniques for utilizing these new materials in re-configurable electromagnetic, or `smart', surfaces are reviewed, with due emphasis given to the problem of system integration. The discussion is complemented by modelled and measured performance data on several smart surface configurations.
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.
Shi, Zhi-Qiang; Zhang, Yun-Lin; Wang, Ming-Zhu; Liu, Xiao-Han
2013-02-01
Based on the underwater irradiance profile measurement and water samples collection in September, October 2007 in Lake Donghu, Lake Liangzi and Lake Honghu, and in April in 2010 in Lake Kuileihu, the diffuse attenuation coefficient and the dominant attenuation factors were analyzed. The ranges of diffuse attenuation coefficient and total suspended solid (TSS), organic suspended solid (OSS), inorganic suspended solid (ISS), chlorophyll a (Chla), and dissolved organic carbon (DOC) concentration varied less in Lake Donghu and Lake Kuileihu than in Lake liangzi and Lake Honghu. The regression analysis showed that ISS was the dominant affecting factor of transparency in Lake Donghu and Lake Kuileihu, but ISS and OSS jointly controlled the transparency in Lake Liangzi and Lake Honghu. The diffuse attenuation coefficient minimum occurred near 580 nm. At around 675 nm, the diffuse attenuation coefficient peak was due to phytoplankton absorption, especially at sites with high pigment concentration. The euphotic depth was less than the mean water depth in Lake Donghu, suggesting that the submerged aquatic vegetation (SAV) can not grow in the present underwater light climate. However, the euphotic depth was larger than the mean water depth in other three lakes showing that the underwater light climate can meet the light requirements for the growth of SAV. The regression analysis showed that ISS was the dominant affecting factor of PAR attenuation in Lake Donghu and Lake Kuileihu, but ISS, OSS and Chla jointly controlled PAR attenuation in lake Liangzi and lake Honghu. The significant correlation between the beam attenuatin coefficient at 750 nm and PAR difffuse attenuation coefficient showed that the particles scattering significantly contributed to underwater irradiance attenuation.
Effective Viscosity Coefficient of Nanosuspensions
NASA Astrophysics Data System (ADS)
Rudyak, V. Ya.; Belkin, A. A.; Egorov, V. V.
2008-12-01
Systematic calculations of the effective viscosity coefficient of nanosuspensions have been performed using the molecular dynamics method. It is established that the viscosity of a nanosuspension depends not only on the volume concentration of the nanoparticles but also on their mass and diameter. Differences from Einstein's relation are found even for nanosuspensions with a low particle concentration.
Aerodynamic coefficients and transformation tables
NASA Technical Reports Server (NTRS)
Ames, Joseph S
1918-01-01
The problem of the transformation of numerical values expressed in one system of units into another set or system of units frequently arises in connection with aerodynamic problems. Report contains aerodynamic coefficients and conversion tables needed to facilitate such transformation. (author)
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)
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…
NASA Technical Reports Server (NTRS)
Chandra, N.
1974-01-01
Numerical coefficients required to express the angular distribution for the rotationally elastic or inelastic scattering of electrons from a diatomic molecule were tabulated for the case of nitrogen and in the energy range from 0.20 eV to 10.0 eV. Five different rotational states are considered.
Identities for generalized hypergeometric coefficients
Biedenharn, L.C.; Louck, J.D.
1991-01-01
Generalizations of hypergeometric functions to arbitrarily many symmetric variables are discussed, along with their associated hypergeometric coefficients, and the setting within which these generalizations arose. Identities generalizing the Euler identity for {sub 2}F{sub 1}, the Saalschuetz identity, and two generalizations of the {sub 4}F{sub 3} Bailey identity, among others, are given. 16 refs.
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.
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
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
Super-Resonant Intracavity Coherent Absorption
NASA Astrophysics Data System (ADS)
Malara, P.; Campanella, C. E.; Giorgini, A.; Avino, S.; de Natale, P.; Gagliardi, G.
2016-07-01
The capability of optical resonators to extend the effective radiation-matter interaction length originates from a multipass effect, hence is intrinsically limited by the resonator’s quality factor. Here, we show that this constraint can be overcome by combining the concepts of resonant interaction and coherent perfect absorption (CPA). We demonstrate and investigate super-resonant coherent absorption in a coupled Fabry-Perot (FP)/ring cavity structure. At the FP resonant wavelengths, the described phenomenon gives rise to split modes with a nearly-transparent peak and a peak whose transmission is exceptionally sensitive to the intracavity loss. For small losses, the effective interaction pathlength of these modes is proportional respectively to the ratio and the product of the individual finesse coefficients of the two resonators. The results presented extend the conventional definition of resonant absorption and point to a way of circumventing the technological limitations of ultrahigh-quality resonators in spectroscopy and optical sensing schemes.
Enhanced absorption in silicon metamaterials waveguide structure
NASA Astrophysics Data System (ADS)
Hamouche, Houria; Shabat, Mohammed M.
2016-07-01
Metamaterial waveguide structures for silicon solar cells are a novel approach to antireflection coating structures that can be used for the achievement of high absorption in silicon solar cells. This paper investigates numerically the possibility of improving the performance of a planar waveguide silicon solar cell by incorporating a pair of silicon nitride/metamaterial layer between a semi-infinite glass cover layer and a semi-infinite silicon substrate layer. The optimized layer thicknesses of the pair are determined under the solar spectrum AM1.5 by the effective average reflectance method. The transmission and reflection coefficients are derived by the transfer matrix method for values of metamaterial's refractive index in visible and near-infrared radiation. In addition, the absorption coefficient is examined for several angles of incidence of the transverse electric polarized (TE), transverse magnetic polarized (TM) and the total (TE&TM) guided waves. Numerical results provide an extremely high absorption. The absorptivity of the structure achieves greater than 98 %.
Temperature dependence of the two photon absorption in indium arsenide
Berryman, K.W.; Rella, C.W.
1995-12-31
Nonlinear optical processes in semiconductors have long been a source of interesting physics. Two photon absorption (TPA) is one such process, in which two photons provide the energy for the creation of an electron-hole pair. Researchers at other FEL centers have studied room temperature TPA in InSb, InAs, and HgCdTe. Working at the Stanford Picosecond FEL Center, we have extended and refined this work by measuring the temperature dependence of the TPA coefficient in InAs over the range from 80 to 350 K at four wavelengths: 4.5, 5.06, 6.01, and 6.3 microns. The measurements validate the functional dependence of recent band structure calculations with enough precision to discriminate parabolic from non-parabolic models, and to begin to observe smaller effects, such as contributions due to the split-off band. These experiments therefore serve as a strong independent test of the Kane band theory, as well as providing a starting point for detailed observations of other nonlinear absorption mechanisms.
On the Ammonia Absorption on Saturn
NASA Astrophysics Data System (ADS)
Tejfel, Victor G.; Karimov, A. M.; Lyssenko, P. G.; Kharitonova, G. A.
2015-11-01
The ammonia absorption bands centered at wavelengths of 645 and 787 nm in the visible spectrum of Saturn are very weak and overlapped with more strong absorption bands of methane. Therefore, the allocation of these bands is extremely difficult. In fact, the NH3 band 787 nm is completely masked by methane. The NH3 645 nm absorption band is superimposed on a relatively weak shortwave wing of CH4 band, in which the absorption maximum lies at the wavelength of 667 nm. In 2009, during the equinox on Saturn we have obtained the series of zonal spectrograms by scanning of the planet disk from the southern to the northern polar limb. Besides studies of latitudinal variation of the methane absorption bands we have done an attempt to trace the behavior of the absorption of ammonia in the band 645 nm. Simple selection of the pure NH3 profile of the band was not very reliable. Therefore, after normalizing to the ring spectrum and to the level of the continuous spectrum for entire band ranging from 630 to 680 nm in the equivalent widths were calculated for shortwave part of this band (630-652 nm), where the ammonia absorption is present, and a portion of the band CH4 652-680 nm. In any method of eliminating the weak part of the methane uptake in the short wing show an increased ammonia absorption in the northern hemisphere compared to the south. This same feature is observed also in the behavior of weak absorption bands of methane in contrast to the more powerful, such as CH4 725 and 787 nm. This is due to the conditions of absorption bands formation in the clouds at multiple scattering. Weak absorption bands of methane and ammonia are formed on the large effective optical depths and their behavior reflects the differences in the degree of uniformity of the aerosol component of the atmosphere of Saturn.
Extraordinary Absorption of Decorated Undoped Graphene
NASA Astrophysics Data System (ADS)
Stauber, T.; Gómez-Santos, G.; de Abajo, F. Javier García
2014-02-01
We theoretically study absorption by an undoped graphene layer decorated with arrays of small particles. We discuss periodic and random arrays within a common formalism, which predicts a maximum absorption of 50% for suspended graphene in both cases. The limits of weak and strong scatterers are investigated, and an unusual dependence on particle-graphene separation is found and explained in terms of the effective number of contributing evanescent diffraction orders of the array. Our results can be important to boost absorption by single-layer graphene due to its simple setup with potential applications to light harvesting and photodetection based on energy (Förster) rather than charge transfer.
Electric modulation of optical absorption in nanowires
NASA Astrophysics Data System (ADS)
Sakr, M. R.
2016-11-01
We have calculated the effect of an external electric field on the intersubband optical absorption of a nanowire subjected to a perpendicular magnetic field and Rashba effect. The absorption peaks due to optical transitions that are forbidden in the absence of the intersubband coupling experience strong amplitude modulation. This effect is quadratic in electric fields applied along the direction of quantum confinement or perpendicularly to tune the Rashba parameter. The electric field also induces frequency modulation in the associated spectrum. On the other hand, transitions that are normally allowed show, to a large extent, a parallel band effect, and accordingly they are responsible for strong optical absorption.
Fluctuation sound absorption in quark matter
NASA Astrophysics Data System (ADS)
Kerbikov, B. O.; Lukashov, M. S.
2016-09-01
We investigate the sound absorption in quark matter due to the interaction of the sound wave with the precritical fluctuations of the diquark-pair field above Tc. The soft collective mode of the pair field is derived using the time-dependent Ginzburg-Landau functional with random Langevin forces. The strong absorption near the phase transition line may be viewed as a manifestation of Mandelshtam-Leontovich slow relaxation time theory.
Optical absorption in ion-implanted lead lanthanum zirconate titanate ceramics
NASA Astrophysics Data System (ADS)
Seager, C. H.; Land, C. E.
1984-08-01
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.
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.
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).
Carbon-Nanohorn Based Nanofluids for a Direct Absorption Solar Collector for Civil Application.
Moradi, A; Sani, E; Simonetti, M; Francini, F; Chiavazzo, E; Asinari, P
2015-05-01
Direct solar absorption has been often considered in the past as a possible solution for solar thermal collectors for residential and small commercial applications. A direct absorption could indeed improve the performance of solar collectors by skipping one step of the heat transfer mechanism in standard devices and having a more convenient temperature distribution inside the collector. Classical solar thermal collectors have a metal sheet as absorber, designed such that water has the minimum temperature in each transversal section, in order to collect as much solar thermal energy as possible. On the other hand, in a direct configuration, the hottest part of the system is the operating fluid and this allows to have a more efficient conversion. Nanofluids, i.e., fluids with a suspension of nanoparticles, such as carbon nanohorns, could be a good and innovative family of absorbing fluids owing to their higher absorption coefficient compared to the base fluid and stability under moderate temperature gradients. Moreover, carbon nanohorns offer the remarkable advantage of a reduced toxicity over other carbon nanoparticles. In this work, a three-dimensional model of the absorption phenomena in nanofluids within a cylindrical tube is coupled with a computational fluid dynamics (CFD) analysis of the flow and temperature field. Measured optical properties of nanofluids at different concentrations have been implemented in the model. Heat losses due to conduction, convection and radiation at the boundaries are considered as well.
Attribution of aerosol light absorption to black carbon and volatile aerosols.
Shrestha, Rijana; Kim, Sang-Woo; Yoon, Soon-Chang; Kim, Ji-Hyoung
2014-08-01
We investigated the contribution of volatile aerosols in light-absorption measurement by three filter-based optical instruments [aethalometer, continuous light-absorption photometer (CLAP), and continuous soot monitoring system (COSMOS)] at Gosan Climate Observatory (GCO) from February to June 2012. The aerosol absorption coefficient (σ abs) and the equivalent black carbon (BC) mass concentration (M BC) measured by the aethalometer and CLAP showed good agreement with a difference of 9 %, which is likely due to the instrumental uncertainty. However, σ abs and M BC measured by the COSMOS with a heated inlet were found to be approximately 44 and 49 % lower than those measured by the aethalometer and CLAP under ambient conditions, respectively. This difference can be attributed to the light absorption by the volatile aerosols coexisting with the BC. Even considering inherent observational uncertainty, it suggests that approximately 35-40 % difference in the σ abs and M BC can be contributed by volatile aerosols. Increase in the difference of M BC measured by the aethalometer and COSMOS with the increasing thermal organic carbon (OC) measured by Sunset OC/EC analyzer further suggests that the filter-based optical instruments without the use of a heater are likely to enhance the value of σ abs and M BC, because this sample air may contain both BC and volatile aerosols.
NASA Technical Reports Server (NTRS)
Miller, Richard L.; Belz, Mathias; DelCastillo, Carlos; Trzaska, Rick
2001-01-01
We evaluated the accuracy, sensitivity and precision of a multiple pathlength, liquid core waveguide (MPLCW) system for measuring colored dissolved organic matter (CDOM) absorption in the UV-visible spectral range (370-700 nm). The MPLCW has four optical paths (2.0, 9.8, 49.3, and 204 cm) coupled to a single Teflon AF sample cell. Water samples were obtained from inland, coastal and ocean waters ranging in salinity from 0 to 36 PSU. Reference solutions for the MPLCW were made having a refractive index of the sample. CDOM absorption coefficients, aCDOM, and the slope of the log-linearized absorption spectra, S, were compared with values obtained using a dual-beam spectrophotometer. Absorption of phenol red secondary standards measured by the MPLCW at 558 nm were highly correlated with spectrophotometer values and showed a linear response across all four pathlengths. Values of aCDOM measured using the MPLCW were virtually identical to spectrophotometer values over a wide range of concentrations. The dynamic range of aCDOM for MPLCW measurements was 0.002 - 231.5 m-1. At low CDOM concentrations spectrophotometric aCDOM were slightly greater than MPLCW values and showed larger fluctuations at longer wavelengths due to limitations in instrument precision. In contrast, MPLCW spectra followed an exponential to 600 nm for all samples.
Carbon-Nanohorn Based Nanofluids for a Direct Absorption Solar Collector for Civil Application.
Moradi, A; Sani, E; Simonetti, M; Francini, F; Chiavazzo, E; Asinari, P
2015-05-01
Direct solar absorption has been often considered in the past as a possible solution for solar thermal collectors for residential and small commercial applications. A direct absorption could indeed improve the performance of solar collectors by skipping one step of the heat transfer mechanism in standard devices and having a more convenient temperature distribution inside the collector. Classical solar thermal collectors have a metal sheet as absorber, designed such that water has the minimum temperature in each transversal section, in order to collect as much solar thermal energy as possible. On the other hand, in a direct configuration, the hottest part of the system is the operating fluid and this allows to have a more efficient conversion. Nanofluids, i.e., fluids with a suspension of nanoparticles, such as carbon nanohorns, could be a good and innovative family of absorbing fluids owing to their higher absorption coefficient compared to the base fluid and stability under moderate temperature gradients. Moreover, carbon nanohorns offer the remarkable advantage of a reduced toxicity over other carbon nanoparticles. In this work, a three-dimensional model of the absorption phenomena in nanofluids within a cylindrical tube is coupled with a computational fluid dynamics (CFD) analysis of the flow and temperature field. Measured optical properties of nanofluids at different concentrations have been implemented in the model. Heat losses due to conduction, convection and radiation at the boundaries are considered as well. PMID:26504968
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
Consistent transport coefficients in astrophysics
NASA Technical Reports Server (NTRS)
Fontenla, Juan M.; Rovira, M.; Ferrofontan, C.
1986-01-01
A consistent theory for dealing with transport phenomena in stellar atmospheres starting with the kinetic equations and introducing three cases (LTE, partial LTE, and non-LTE) was developed. The consistent hydrodynamical equations were presented for partial-LTE, the transport coefficients defined, and a method shown to calculate them. The method is based on the numerical solution of kinetic equations considering Landau, Boltzmann, and Focker-Planck collision terms. Finally a set of results for the transport coefficients derived for a partially ionized hydrogen gas with radiation was shown, considering ionization and recombination as well as elastic collisions. The results obtained imply major changes is some types of theoretical model calculations and can resolve some important current problems concerning energy and mass balance in the solar atmosphere. It is shown that energy balance in the lower solar transition region can be fully explained by means of radiation losses and conductive flux.
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.
An in silico skin absorption model for fragrance materials.
Shen, Jie; Kromidas, Lambros; Schultz, Terry; Bhatia, Sneha
2014-12-01
Fragrance materials are widely used in cosmetics and other consumer products. The Research Institute for Fragrance Materials (RIFM) evaluates the safety of these ingredients and skin absorption is an important parameter in refining systemic exposure. Currently, RIFM's safety assessment process assumes 100% skin absorption when experimental data are lacking. This 100% absorption default is not supportable and alternate default values were proposed. This study aims to develop and validate a practical skin absorption model (SAM) specific for fragrance material. It estimates skin absorption based on the methodology proposed by Kroes et al. SAM uses three default absorption values based on the maximum flux (J(max)) - namely, 10%, 40%, and 80%. J(max) may be calculated by using QSAR models that determine octanol/water partition coefficient (K(ow)), water solubility (S) and permeability coefficient (K(p)). Each of these QSAR models was refined and a semi-quantitative mechanistic model workflow is presented. SAM was validated with a large fragrance-focused data set containing 131 materials. All resulted in predicted values fitting the three-tiered absorption scenario based on Jmax ranges. This conservative SAM may be applied when fragrance material lack skin absorption data.
[Decomposing total suspended particle absorption based on the spectral correlation relationship].
Wang, Gui-Fen; Cao, Wen-Xi; Yang, Ding-Tian; Zhao, Jun
2009-01-01
A model for estimating the contributions of phytoplankton and nonalgal particles to the total particulate absorption coefficient was developed based on their separate spectral relationships, and a constrained nonlinear optimization code was used to realize the spectral decomposition. The spectral absorption of total particulate matter including phytoplankton and nonalgal particles was measured using the filter-pad method during two cruises in autumn in Northern South China Sea. Using the dataset collected in 2004, the spectral relationships of particle absorption coefficients were examined and the results showed that the phytoplankton absorption coefficients at various wavebands could be well expressed by aph (443) as the second-order quadratic equations; and the nonalgal particle absorption (aNAP(lambda)) could be successfully modeled with the simple exponential function. Based on these spectral relationships, we developed this partition model. The model was tested using the independently measured absorption by phytoplankton and nonalgal materials which were obtained in 2005 from the same area. The test results showed that the computed spectral absorption coefficients of phytoplankton and nonalgal particles were consistent with in situ measurement. Good correlations were fo und between the comput ed phytoplankton absorption coefficient and the measured value,with the determination coefficients (r2) being higher than 0.97 and slopes being around 1.0; and the RMSE values could be controlled within 17% over the main absorption wavebands such as 443, 490 and 683 nm. Compared with the other two existing models from Bricaud et al. and Oubelkheir et al., this method shows many advantages for local applications. Moreover, this model does not need any information about pigment concentrations and the selected spectral bands are consistent with the ocean color satellite sensor. This method could also be used in the total absorption coefficient decomposition which provides
The interpretation of selection coefficients.
Barton, N H; Servedio, M R
2015-05-01
Evolutionary biologists have an array of powerful theoretical techniques that can accurately predict changes in the genetic composition of populations. Changes in gene frequencies and genetic associations between loci can be tracked as they respond to a wide variety of evolutionary forces. However, it is often less clear how to decompose these various forces into components that accurately reflect the underlying biology. Here, we present several issues that arise in the definition and interpretation of selection and selection coefficients, focusing on insights gained through the examination of selection coefficients in multilocus notation. Using this notation, we discuss how its flexibility-which allows different biological units to be identified as targets of selection-is reflected in the interpretation of the coefficients that the notation generates. In many situations, it can be difficult to agree on whether loci can be considered to be under "direct" versus "indirect" selection, or to quantify this selection. We present arguments for what the terms direct and indirect selection might best encompass, considering a range of issues, from viability and sexual selection to kin selection. We show how multilocus notation can discriminate between direct and indirect selection, and describe when it can do so. PMID:25790030
Simpson, J A; Bastian, T S; Chenette, D L; Lentz, G A; McKibben, R B; Pyle, K R; Tuzzolino, A J
1980-01-25
Electrons and protons accelerated and trapped in a Saturnian magnetic field have been found by the University of Chicago experiments on Pioneer 11 within 20 Saturn radii (Rs) of the planet. In the innermost regions, strong absorption effects due to satellites and ring material were observed, and from approximately 4 Rs inwards to the outer edge of the A ring at 2.30 Rs (where the radiation is absorbed), the intensity distributions of protons (>/= 0.5 million electron volts) and electrons (2 to 20 million electron volts) were axially symmetric, consistent with a centered dipole aligned with the planetary rotation axis. The maximum fluxes observed for protons (> 35 million electron volts and for electrons < 3.4 million electron volts) were 3 x 10(4) and 3 x 10(6) per square centimeter per second, respectively. Absorption of radiation by Mimas provides a means of estimating the radial diffusion coefficient for charged particle transport. However, the rapid flux increases observed between absorption features raise new questions concerning the physics of charged particle transport and acceleration. An absorption feature near 2.5 Rs has led to the discovery of a previously unknown satellite with a diameter of approximately 200 kilometers, semimajor axis of 2.51 Rs, and eccentricity of 0.013. Radiation absorption features that suggest a nonuniform distribution of matter around Saturn have also been found from 2.34 to 2.36 Rs, near the position of the F ring discovered by the Pioneer imaging experiment. Beneath the A, B, and C rings we continued to observe a low flux of high-energy electrons. We conclude that the inner Saturn magnetosphere, because of its near-axial symmetry and the many discrete radiation absorption regions, offers a unique opportunity to study the acceleration and transport of charged particles in a planetary magnetic field.
Absorption of water and lubricating oils into porous nylon
NASA Technical Reports Server (NTRS)
Bertrand, P. A.
1995-01-01
Oil and water absorption from air into sintered porous nylon can be described by infiltration into the pores of the material. This process can be modeled by a diffusion-like mechanism. For water absorption, we find a formal diffusion coefficient of 1.5 x 10(exp -4)sq cm/min when the nylon is initially dry. The diffusion coefficient is 4 x 10(exp -6)sq cm/min when the nylon is oil-impregnated prior to air exposure. In a 52% RH atmosphere, dry nylon absorbs 3% w/w water, and oil-impregnated nylon absorbs 0.6% w/w water. For oil absorption there are three steps: (1) surface absorption and infiltration into (2) larger and (3) smaller pores. Surface absorption is too fast to be measured in these experiments. The diffusion coefficient for the second step is 6 x 10(exp -4)sq cm/min for SRG-60 oil into dry nylon and 4 x 10(exp -4)sq cm/min for air-equilibrated nylon. The diffusion coefficient for the third step is about 1 x 10(exp -6)sq cm/min for both cases. The total amount of oil absorbed is 31% w/w. The interaction between water and nylon is not as strong as that between water and cotton-phenolic: oil can replace water, and only a small amount of water can enter previously oil-impregnated nylon.
NASA Astrophysics Data System (ADS)
Ben-David, Avishai; Vanderbeek, Richard G.; Gotoff, Steven W.; D'Amico, Francis M.
1997-10-01
The effects of flight geometry, signal averaging and time- lag correlation coefficient on airborne CO2 dial lidar measurements are shown in simulations and field measurements. These factors have implications for multi- vapor measurements and also for measuring a shingle vapor with a wide absorption spectra for which one would like to make DIAL measurements at many wavelengths across the absorption spectra of the gas. Thus it is of interest to know how many wavelengths and how many groups of wavelengths can be used effectively in DIAL measurements. Our data indicate that for our lidar about 80 wavelengths can be used for DIAL measurements of a stationary vapor. The lidar signal is composed of fluctuations with three time scales: a very short time scale due to system noise which is faster than the data acquisition sampling rate of the receiver, a medium time scale due to atmospheric turbulence, and a long time scale due to slow atmospheric transmission drift from aerosol in homogeneities. The decorrelation time scale of fluctuations for airborne lidar measurements depends on the flight geometry.
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.
NASA Astrophysics Data System (ADS)
Danan, Yossef; Ilovitsh, Tali; Liu, Danping; Pinhas, Hadar; Sinvani, Moshe; Ramon, Yehonatan; Azougi, Jonathan; Douplik, Alexandre; Zalevsky, Zeev
2016-03-01
In this paper we present gold nanoparticles coated with silicon that switch the order between the scattering and the absorption magnitude at the resonance peak and tune the plasmon resonance over the spectrum. This is obtained by modifying the refractive index of the silicon coating of the nanoparticle by illuminating it with a pumping light due to the plasma dispersion effect in silicon. We also report how changing the diffraction limited point spread function through the utilization of plasma dispersion effect of the above mentioned silicon coated nanoparticles allows doing imaging with sub wavelength resolution. The plasma dispersion effect can increase the absorption coefficient of the silicon, when illuminated with a focused laser beam and as explained above it can also tune the absorption versus scattering properties of the nanoparticle. Due to the Gaussian nature of the laser illumination which has higher intensity at its peak, the plasma dispersion effect is more significant at the center of the illumination. As a consequence, the reflected light from probe beam at the near infra-red region has a sub wavelength dip that overlaps with the location of the pump illumination peak. This dip has a higher spatial frequency than an ordinary Gaussian, which enables to achieve super resolution.
Zhang, Yunlin; Yin, Yan; Wang, Mingzhu; Liu, Xiaohan
2012-05-21
We investigated phytoplankton absorption properties of Lake Taihu, in the spring and summer of 2005 and 2006, and for 17 days studied laboratory cultures of Scenedesmus obliquus (chlorophyta) and Microcystis aeruginosa (cyanophyta) to determine the effect of phytoplankton community composition and cell size on the absorption properties. There were significant seasonal differences in phytoplankton community composition and absorption coefficients. In spring, the phytoplankton community was dominated by chlorophyta with large cells, whereas in summer was dominated by cyanophyta with small cells. Phytoplankton absorption coefficients increased significantly from spring to summer, with the increase in chlorophyll a (Chla) concentration. In addition, Chla-specific absorption coefficients increased with the phytoplankton community succession from chlorophyta to cyanophyta. In culture, the cells density of S. obliquus was generally lower than that of M. aeruginosa, and Chla concentrations of S. obliquus were significantly higher than those of M. aeruginosa. Correspondingly, the Chla-specific absorption coefficients of S. obliquus were significantly lower than those of M. aeruginosa. Significant exponential correlations were found between absorption and Chla-specific absorption coefficients and Chla concentration for S. obliquus and M. aeruginosa. In addition, we developed a model to predict absorption and Chla-specific absorption coefficients using Chla concentration and cell size when data from two species was grouped together. Field and experimental results both showed that the Chla-specific absorption coefficients of cyanophyta were significantly higher than those of chlorophyta. The variability in specific absorption can attributed to phytoplankton community composition, cell size and pigment composition. As phytoplankton community composition changed significantly with season in the lake, and as variation in the cell sizes and accessory pigments of the phytoplankton
NASA Astrophysics Data System (ADS)
Wei, Ke; Xu, Zhongjie; Chen, Runze; Zheng, Xin; Cheng, Xiangai; Jiang, Tian
2016-08-01
Recently lead halide nanocrystals (quantum dots) have been reported with potential for photovoltaic and optoelectronic applications due to their excellent luminescent properties. Herein excitonic photoluminescence (PL) excited by two-photon absorption in perovskite CsPbBr3 quantum dots (QDs) have been studied across a broad temperature range from 80K to 380K. Two-photon absorption has been investigated with absorption coefficient up to 0.085 cm/GW at room temperature. Moreover, the photoluminescence excited by two-photon absorption shows a linear blue-shift (0.25meV/K) below temperature of ~220K and turned steady with fluctuation below 1nm (4.4meV) for higher temperature up to 380K. These phenomena are distinctly different from general red-shift of semiconductor and can be explained by the competition between lattice expansion and electron-phonon couplling.Our results reveal the strong nonlinear absorption and temperature-independent chromaticity in a large temperature range from 220K to 380K in the CsPbX3 QDs, which will offer new opportunities in nonlinear photonics, light-harvesting and light-emitting devices.
NASA Astrophysics Data System (ADS)
Paredes-Miranda, G.; Arnott, W. P.; Gaffney, J. S.; Marley, N. A.; Campbell, D.; Fujita, E.
2007-12-01
Aerosol light scattering and absorption measurements were deployed in and near Mexico City in March 2006 as part of the Megacity Impacts on Regional and Global Environments (MIRAGE). The primary site in Mexico City was an urban site at Instituto Mexicano del Petroleo (Mexican Oil Institute, denoted by IMP). Similar campaigns were held in Las Vegas, NV in January-February, 2003; and Los Angeles, CA at numerous sites during all seasons from 2003 through 2007. The IMP site gave in-situ characterization of the Mexico City plume under favorable wind conditions. The photoacoustic instrument (PAS) used at IMP operates at 532 nm, and conveniently allowed for characterization of gaseous absorption at this wavelength as well. Light scattering measurements are accomplished within the PAS by the reciprocal nephelometery method. In Mexico City the aerosol absorption coefficient typically varies between 20 and 180 Mm-1 during the course of the day and significant diurnal variation of the aerosol single scattering albedo was observed probably as a consequence of secondary aerosol formation. We will present the diurnal variation of the scattering and absorption as well as the single scattering albedo and fraction of absorption due to gases at the IMP site and compare with Las Vegas diurnal variation. Mexico City 'breaths' more during the course of the day than Las Vegas, Nevada in part because the latitude of Mexico City resulted in more direct solar radiation. Further insight on the meteorological connections and population dynamics will be discussed.
NASA Astrophysics Data System (ADS)
Sur, Ritobrata; Spearrin, R. Mitchell; Peng, Wen Y.; Strand, Christopher L.; Jeffries, Jay B.; Enns, Gregory M.; Hanson, Ronald K.
2016-05-01
We report measured line intensities and temperature-dependent broadening coefficients of NH3 with Ar, N2, O2, CO2, H2O, and NH3 for nine sQ(J,K) transitions in the ν2 fundamental band in the frequency range 961.5-967.5 cm-1. This spectral region was chosen due to the strong NH3 absorption strength and lack of spectral interference from H2O and CO2 for laser-based sensing applications. Spectroscopic parameters were determined by multi-line fitting using Voigt lineshapes of absorption spectra measured with two quantum cascade lasers in thermodynamically-controlled optical cells. The temperature dependence of broadening was measured over a range of temperatures between 300 and 600 K. These measurements aid the development of mid-infrared NH3 sensors for a broad range of gas mixtures and at elevated temperatures.
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.
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
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.
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.
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.
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.
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.
Electromagnetically induced absorption via incoherent collisions
Yang Xihua; Sheng Jiteng; Xiao Min
2011-10-15
We conduct theoretical studies on electromagnetically induced absorption via incoherent collisions in an inhomogeneously broadened ladder-type three-level system with the density-matrix approach. The effects of the collision-induced coherence decay rates as well as the probe laser field intensity on the probe field absorption are examined. It is shown that with the increase of the collisional decay rates in a moderate range, a narrow dip due to electromagnetically induced transparency superimposed on the Doppler-broadened absorption background can be turned into a narrow peak under the conditions that the probe field intensity is not very weak as compared to the pump field, which results from the enhancement of constructive interference and suppression of destructive interference between one-photon and multiphoton transition pathways. The physical origin of the collision-assisted electromagnetically induced absorption is analyzed with a power-series solution of the density-matrix equations.
[Microwave absorption by magnetic nanoparticles in organisms].
Bingi, V N
2011-01-01
An estimate of the rate of absorption of the electromagnetic microwaves by magnetic nanoparticles in organisms is presented. The absorption takes place due to the energy dissipation at the ferromagnetic resonance. Based on the known solution of the Landau-Lifshitz equation, the imaginary part of the complex magnetic susceptibility is evaluated that gives the absorption rate. It is shown that even in the conditions of thermal isolation of the particles, their temperature growth would be insignificant at absorption of the emission with the energy flux density of the order of 1 mW/cm2, and the given mechanism is unrelated to the observable effects of low-intensity microwaves. PMID:22279759
A New Adaptive Image Denoising Method Based on Neighboring Coefficients
NASA Astrophysics Data System (ADS)
Biswas, Mantosh; Om, Hari
2016-03-01
Many good techniques have been discussed for image denoising that include NeighShrink, improved adaptive wavelet denoising method based on neighboring coefficients (IAWDMBNC), improved wavelet shrinkage technique for image denoising (IWST), local adaptive wiener filter (LAWF), wavelet packet thresholding using median and wiener filters (WPTMWF), adaptive image denoising method based on thresholding (AIDMT). These techniques are based on local statistical description of the neighboring coefficients in a window. These methods however do not give good quality of the images since they cannot modify and remove too many small wavelet coefficients simultaneously due to the threshold. In this paper, a new image denoising method is proposed that shrinks the noisy coefficients using an adaptive threshold. Our method overcomes these drawbacks and it has better performance than the NeighShrink, IAWDMBNC, IWST, LAWF, WPTMWF, and AIDMT denoising methods.
Inclusion Analysis and Absorption Measurement in Nonlinear Crystals
Smith, L L
2005-08-26
Yttrium calcium oxyborate (YCOB) is a newly developed nonlinear optical crystal used for second harmonic generation in the Mercury laser. As with any new crystal, optical characterization of the material properties needs to be fully investigated. We are developing two new techniques to detect inclusions and measure optical absorption. With the side illuminating detection examination (SIDE) method, we hope to identify and map the size, density, and the morphology of inclusions. The multi-pass absorption technique (MPAT) will be used to help determine the absorption coefficient of various finished crystalline pieces at near-infrared wavelengths.
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.
Coefficient of thermal expansion of fluorinert as a function of volume percent absorbed air
Reilly, J.M.
1982-06-01
The relationship between the coefficient of volumetric thermal expansion of liquid Fluorinert FC-86 and the volume percent of absorbed air was examined experimentally. A special test apparatus was built for this purpose. A floating liquid seal was used to isolate the Fluorinert sample from the atmosphere. This prevented gas absorption during thermal cycling yet allowed the sample to expand and contract freely during testing. It was found that the coefficient of thermal expansion is not influenced by the percentage of absorbed air.
Change of electrical conductivity of Ar welding arc under resonant absorption of laser radiation
NASA Astrophysics Data System (ADS)
Kozakov, R.; Emde, B.; Pipa, A. V.; Huse, M.; Uhrlandt, D.; Hermsdorf, J.; Wesling, V.
2015-03-01
Experimental investigations of the impact of resonant laser absorption by a tungsten inert gas welding arc in argon are presented. The intensity increase of the arc’s radiation between the laser entrance height and the anode are observed, as well as the variation of arc voltage due to the presence of the laser beam. High-speed camera recordings from different directions combined with absolutely calibrated spectroscopic measurements allow the reconstruction of the three-dimensional emission coefficient profiles without the assumption of axial symmetry. The obtained data are evaluated within the framework of local thermodynamic equilibrium. The local increase in the temperature and conductivity due to the influence of the laser is determined. Changes in the electrical conductivity obtained from the optical measurements coincide well with the measured voltage drop, and show significant redistribution of the current density profile near the anode in particular.
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.
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.
Karino, A; Hayashi, M; Awazu, S; Hanano, M
1982-09-01
In order to study the solvent drag effect, it was shown that back flux of absorbed drug from blood to intestinal lumen can be ignored but the back flux of water cannot. Then, apparent water influx was calculated as a new measure of solvent drag based on the model in which the back flux of D2O from blood to lumen was considered during absorption. Consequently, the correlation between drug absorption clearance (CLdrug) and apparent water influx was highly significant for benzoic acid, salicylic acid, p-hydroxybenzoic acid, antipyrine, cephalexin (CEX) and cefroxadine (CXD), resulting the high solvent drag effects were detected. The mean values of the slopes in the regression lines of CLdrug versus apparent water influx, i.e., sieving coefficients, were smaller than one for benzoic acid and salicylic acid, but the values were not significantly different from one. The sieving coefficients of the other drugs were significantly smaller than one. From these results, the molecular size dependence in the reflection from the intestinal membrane during absorption was clearly shown. And the intercepts of the regression lines including diffusive permeabilities were found to be significantly different from zero in CEX and CXD. On the basis of the sieving coefficients and intercept values obtained in such ways, the appropriateness of this model was discussed.
Condensation heat transfer coefficient versus wettability
NASA Astrophysics Data System (ADS)
Roudgar, M.; De Coninck, J.
2015-05-01
In this paper we show how condensation on substrates can induce wetting behavior that is quite different from that of deposited or impinging drops. We describe surfaces with the same wettability in ambient conditions presenting different wetting behavior and growth of droplets in condensation. The experimental results show a rapid spread of droplets and formation of the film on the copper surface, while droplets on SU-8 surface remains on the regular shape while they grow within the time, without coalescence, as observed for Cu. Although the heat conductivity of SU-8 is much lower, due to a difference in wetting behavior, the heat transfer coefficient (h) is higher for dropwise condensation on Cu with a thin layer of SU-8 than filmwise on the bare copper.
Water sorption and diffusion coefficient through an experimental dental resin.
Costella, A M; Trochmann, J L; Oliveira, W S
2010-01-01
Polymeric composites have been widely used as dental restorative materials. A fundamental knowledge and understanding of the behavior of these materials in the oral cavity is essential to improve their properties and performance. In this paper we computed the data set of water absorption through an experimental dental resin blend using specimen discs of different thicknesses to estimate the diffusion coefficient. The resins were produced using Bisphenol A glycol dimethacrylate, Bisphenol A ethoxylated dimethacrylate and Triethylene glycol dimethacrylate monomers. The water sorption test method was based on International Standard ISO 4049 "Dentistry-Polymer-based filling materials". Results show a diffusion coefficient around 6.38 x 10(-8) cm(2)/s, within a variance of 0.01%, which is in good agreement with the values reported in the literature and represents a very suitable value.
Identification of a dissipation coefficient by a variational method
NASA Astrophysics Data System (ADS)
Baev, A. V.; Kutsenko, N. V.
2006-10-01
A generalized inverse problem for the identification of the absorption coefficient for a hyperbolic system is considered. The well-posedness of the problem is examined. It is proved that the regular part of the solution is an L 2 function, which reduces the inverse problem to minimizing the error functional. The gradient of the functional is determined in explicit form from the adjoint problem, and approximate formulas for its calculation are derived. A regularization algorithm for the solution of the inverse problem is considered. Numerical results obtained for various excitation sources are displayed.
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.
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.
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)
Arnold, Ian J.
Aerosols are a major contributor to the global radiation budget because they modify the planetary albedo with their optical properties. These optical properties need to be measured and understood, ideally at multiple wavelengths. This thesis describes the ongoing development of a supercontinuum based multi-wavelength photoacoustic instrument to measure the light absorption and scattering coefficients of aerosols. Collimation techniques for supercontinuum sources using lens-based and off-axis parabolic mirror-based collimators were evaluated and it was determined that the off-axis mirror had superior collimation abilities for multi-spectral beams. A proof of concept supercontinuum-based photoacoustic instrument was developed using sequential measurements at multiple wavelengths. The instrument data were in good agreement with those from a commercial 3-wavelength photoacoustic instrument and the novel instrument had minimum detectable absorption and scattering coefficients of better than 4 Mm-1 and 21 Mm-1, respectively. The instrument however suffered from poor temporal resolution due to the sequential measurement and required the development of an aerosol delivery system to deliver a slowly varying aerosol concentration. In response, a spectral modulator has been developed to frequency encode different wavelength bands for simultaneous measurement with a photoacoustic instrumen.
Size Dependence of Two-Photon Absorption in Semiconductor Quantum Dots
Dakovski, Georgi L.; Shan, Jie
2013-01-01
Quantum confinement plays an important role in the optical properties of semiconductor quantum dots (QDs). In this work, we combine experiment and modeling to systematically investigate the size dependence of the degenerate two-photon absorption (TPA) of below-band-gap radiation in CdSe QDs. The TPA coefficient β at 800 nm of CdSe QDs of varying radii was measured using femtosecond white-light transient absorption spectroscopy by probing the pump-induced bleaching at the first exciton transition energy. β was also calculated using a model based on the multiband effective-mass approximation. Satisfactory agreement between experiment and theory was obtained. Our findings show the evolution of the TPA in the QDs from that of atom-like to bulk-like with increasing the radius R. The TPA coefficient (or the volume normalized TPA cross-section) increases with radius approximately linearly in the strong confinement regime due to the rapid increase of the joint density of states for the two-photon allowed transitions, and saturates for R > 5 nm (the exciton Bohr radius), approaching that of bulk CdSe.
Percutaneous absorption of Octopirox.
Black, J G; Kamat, V B
1988-01-01
containing 1% Octopirox is 29,400, so that the possibility of systemic effects due to absorption through the skin is remote. PMID:3345970
Inferential Procedures for Correlation Coefficients Corrected for Attenuation.
ERIC Educational Resources Information Center
Hakstian, A. Ralph; And Others
1988-01-01
A model and computation procedure based on classical test score theory are presented for determination of a correlation coefficient corrected for attenuation due to unreliability. Delta and Monte Carlo method applications are discussed. A power analysis revealed no serious loss in efficiency resulting from correction for attentuation. (TJH)
Heat-transfer coefficients in agitated vessels. Sensible heat models
Kumpinsky, E.
1995-12-01
Transient models for sensible heat were developed to assess the thermal performance of agitated vessels with coils and jackets. Performance is quantified with the computation of heat-transfer coefficients by introducing vessel heating and cooling data into model equations. Of the two model categories studied, differential and macroscopic, the latter is preferred due to mathematical simplicity and lower sensitivity to experimental data variability.
n-Alcohol/Water Partition Coefficients for Decachlorobiphenyl (PCB 209)
Measurements of n-octanol/water partition coefficients (Kow) for highly hydrophobic chemicals are extremely difficult and are rarely made, in part due to the large volumes of water typically needed to quantify these compounds in the aqueous phase. An extrapolation approach using ...
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.
Bányiová, Katarína; Nečasová, Anežka; Kohoutek, Jiří; Justan, Ivan; Čupr, Pavel
2016-02-01
Due to their widespread usage, people are exposed to pesticides on a daily basis. Although these compounds may have adverse effects on their health, there is a gap in the data and the methodology needed to reliably quantify the risks of non-occupational human dermal exposure to pesticides. We used Franz cells and human skin in order to measure the dermal absorption kinetics (steady-state flux, lag time and permeability coefficient) of Carbendazim and Simazine. These parameters were then used to refine the dermal exposure model and a probabilistic simulation was used to quantify risks resulting from exposure to pesticide-polluted waters. The experimentally derived permeability coefficient was 0.0034 cm h(-1) for Carbendazim and 0.0047 cm h(-1) for Simazine. Two scenarios (varying exposure duration and concentration, i.e. environmentally relevant and maximum solubility) were used to quantify the human health risks (hazard quotients) for Carbendazim and Simazine. While no risks were determined in the case of either scenario, the permeability coefficient, which is concentration independent and donor, formulation, compound and membrane specific, may be used in other scenarios and exposure models to quantify more precisely the dermally absorbed dose during exposure to polluted water. To the best of our knowledge, the dermal absorption kinetics parameters defined here are being published for the first time. The usage of experimental permeability parameters in combination with probabilistic risk assessment thus provides a new tool for quantifying the risks of human dermal exposure to pesticides. PMID:26688251
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.
Singular topology of optical absorption in biaxial crystals.
Joly, Simon; Petit, Yannick; Boulanger, Benoît; Segonds, Patricia; Félix, Corinne; Ménaert, Bertrand; Aka, Gérard
2009-10-26
We show for the first time that biaxial crystals exhibit continua of directions of propagation where the absorption coefficient is the same for the two associated polarization modes. This statement is supported by both calculations and experimental data obtained in Nd:YCOB.
Price, Edwin R; Brun, Antonio; Gontero-Fourcade, Manuel; Fernández-Marinone, Guido; Cruz-Neto, Ariovaldo P; Karasov, William H; Caviedes-Vidal, Enrique
2015-01-01
Rapid absorption and elimination of dietary water should be particularly important to flying species and were predicted to vary with the water content of the natural diet. Additionally, high water absorption capacity was predicted to be associated with high paracellular nutrient absorption due to solvent drag. We compared the water absorption rates of sanguivorous, nectarivorous, frugivorous, and insectivorous bats in intestinal luminal perfusions. High water absorption rates were associated with high expected dietary water load but were not highly correlated with previously measured rates of (paracellular) arabinose clearance. In conjunction with these tests, we measured water absorption and the paracellular absorption of nutrients in the intestine and stomach of vampire bats using luminal perfusions to test the hypothesis that the unique elongated vampire stomach is a critical site of water absorption. Vampire bats' gastric water absorption was high compared to mice but not compared to their intestines. We therefore conclude that (1) dietary water content has influenced the evolution of intestinal water absorption capacity in bats, (2) solvent drag is not the only driver of paracellular nutrient absorption, and (3) the vampire stomach is a capable but not critical location for water absorption.
Price, Edwin R; Brun, Antonio; Gontero-Fourcade, Manuel; Fernández-Marinone, Guido; Cruz-Neto, Ariovaldo P; Karasov, William H; Caviedes-Vidal, Enrique
2015-01-01
Rapid absorption and elimination of dietary water should be particularly important to flying species and were predicted to vary with the water content of the natural diet. Additionally, high water absorption capacity was predicted to be associated with high paracellular nutrient absorption due to solvent drag. We compared the water absorption rates of sanguivorous, nectarivorous, frugivorous, and insectivorous bats in intestinal luminal perfusions. High water absorption rates were associated with high expected dietary water load but were not highly correlated with previously measured rates of (paracellular) arabinose clearance. In conjunction with these tests, we measured water absorption and the paracellular absorption of nutrients in the intestine and stomach of vampire bats using luminal perfusions to test the hypothesis that the unique elongated vampire stomach is a critical site of water absorption. Vampire bats' gastric water absorption was high compared to mice but not compared to their intestines. We therefore conclude that (1) dietary water content has influenced the evolution of intestinal water absorption capacity in bats, (2) solvent drag is not the only driver of paracellular nutrient absorption, and (3) the vampire stomach is a capable but not critical location for water absorption. PMID:26658415
Infrared differential absorption for atmospheric pollutant detection
NASA Technical Reports Server (NTRS)
Byer, R. L.
1974-01-01
Progress made in the generation of tunable infrared radiation and its application to remote pollutant detection by the differential absorption method are summarized. It is recognized that future remote pollutant measurements depended critically on the availability of high energy tunable transmitters. Futhermore, due to eye safety requirements, the transmitted frequency must lie in the 1.4 micron to 13 micron infrared spectral range.
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.
Enhanced visible and near-infrared optical absorption in silicon supersaturated with chalcogens
NASA Astrophysics Data System (ADS)
Pan, Si H.; Recht, Daniel; Charnvanichborikarn, Supakit; Williams, James S.; Aziz, Michael J.
2011-03-01
We show that single-crystal silicon supersaturated with sulfur (S), selenium (Se), or tellurium (Te) displays a substantially enhanced absorption coefficient for light with wavelengths of 400 to 1600 nm. Alloys were prepared in silicon on insulator wafers by ion implantation followed by nanosecond pulsed laser melting. Measurements of the absorption coefficient were made by direct transmission through freestanding thin films and by spectroscopic ellipsometry.
Effects of surface roughness and absorption on light propagation in graded-profile waveguides
Danilenko, S S; Osovitskii, A N
2011-06-30
This paper examines the effects of surface roughness and absorption on laser light propagation in graded-profile waveguiding structures. We derive analytical expressions for the scattering and absorption coefficients of guided waves and analyse these coefficients in relation to parameters of the waveguiding structure and the roughness of its boundary. A new approach is proposed to measuring roughness parameters of precision dielectric surfaces. Experimental evidence is presented which supports the main conclusions of the theory. (integraled-optical waweguides)
Lai, M.; Botsis, J.; Coric, D.; Cugnoni, J.
2008-08-28
The increasing needs of extending the lifetime in high-technology fields, such as space and aerospace, rail transport and naval systems, require quality enhancing of the composite materials either from a processing standing point or in the sense of resistance to service conditions. It is well accepted that the final quality of composite materials and structures is strongly influenced by processing parameters like curing and post-curing temperatures, rate of heating and cooling, applied vacuum, etc. To optimize manufacturing cycles, residual strains evolution due to chemical shrinkage and other physical parameters of the constituent materials must be characterized in situ. Such knowledge can lead to a sensible reduction in defects and to improved physical and mechanical properties of final products. In this context continuous monitoring of strains distribution developed during processing is important in understanding and retrieving components' and materials' characteristics such as local strains gradients, degree of curing, coefficient of thermal expansion, moisture absorption, etc.
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.
Moisture absorption in thin polymer films
NASA Astrophysics Data System (ADS)
Soles, Christopher; Lenhart, Joseph; Jones, Ronnie; Prabhu, Vivek; Lin, Eric; Wu, Wen-Li
2003-03-01
We explore the kinetics and dynamics of moisture transport in a series of poly(hydroxystyrene), poly(tert-butoxycarboxystyrene), and epoxy films as a function of film thickness. Specular X-ray reflectivity is used to monitor the equilibrium swelling in films exposed to water vapor while a quartz crystal microbalance is used to track the kinetics of the absorption process. For relatively thick films we find that the equilibrium swelling is nominally consistent with the bulk moisture absorption properties of the polymer. However, when the film thickness drops below 100 nm, enhanced swelling occurs and the extent of the enhancement increases with resin polarity. Below the same thickness threshold of 100 nm, we also observe a strong retardation in the uptake kinetics, i.e., a decrease in the effective diffusion coefficient of the water. The results are discussed in detail with respect to confinement of the polymer films.
Note on Two Generalizations of Coefficient Alpha.
ERIC Educational Resources Information Center
Raju, Nambury S.
1979-01-01
An important relationship is given for two generalizations of coefficient alpha: (1) Rajaratnam, Cronbach, and Gleser's generalizability formula for stratified-parallel tests, and (2) Raju's coefficient beta. (Author/CTM)
Calculation of laser absorption by metal powders in additive manufacturing.
Boley, C D; Khairallah, S A; Rubenchik, A M
2015-03-20
We have calculated the absorption of laser light by a powder of metal spheres, typical of the powder employed in laser powder-bed fusion additive manufacturing. Using ray-trace simulations, we show that the absorption is significantly larger than its value for normal incidence on a flat surface, due to multiple scattering. We investigate the dependence of absorption on powder content (material, size distribution, and geometry) and on beam size.
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.
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.
Infrared bulk and surface absorption by nearly transparent crystals.
Rosenstock, H B; Gregory, D A; Harrington, J A
1976-09-01
We present an analysis of laser calorimetric data that deduces both the bulk and the surface absorption in a single run. The method involves use of long rod geometry combined with an analytical solution of the heat equation for the temperature distribution in a sample that is heated both internally and on the surfaces. Bulk and surface absorption coefficients, heat transfer coefficient, and thermal diffusivity appear as parameters; the last is treated as known, and the thermal rise curve is fitted to the three others. The solution obtained is valid at all points and times, and measurement of the temperature during and after laser heating at different points therefore narrows the possible fit considerably. Examples illustrating the method are presented for ZnSe, CaF(2) NaF:Li, NaCl, KBr, and KC1 at 2.7 microm, 3.8 microm, and 10.6 microm. Surface absorption is found to be dominant in all cases.
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.
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…
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.
Note on Methodology: The Coefficient of Variation.
ERIC Educational Resources Information Center
Sheret, Michael
1984-01-01
Addresses applications of the coefficient of variation as a measure of educational inequality or as a means of measuring changes of inequality status. Suggests the Gini coefficient has many advantages over the coefficient of variation since it can be used with the Lorenz curve (Lorenz provides detail Gini omits). (BRR)
Is the G Index a Correlation Coefficient?
ERIC Educational Resources Information Center
Vegelius, Jan
1980-01-01
One argument against the G index is that, unlike phi, it is not a correlation coefficient; yet, G conforms to the Kendall and E-coefficient definitions. The G index is also equal to the Pearson product moment correlation coefficient obtained from double scoring. (Author/CP)
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…
Sensitivity in forward modeled hyperspectral reflectance due to phytoplankton groups
NASA Astrophysics Data System (ADS)
Manzo, Ciro; Bassani, Cristiana; Pinardi, Monica; Giardino, Claudia; Bresciani, Mariano
2016-04-01
Phytoplankton is an integral part of the ecosystem, affecting trophic dynamics, nutrient cycling, habitat condition, and fisheries resources. The types of phytoplankton and their concentrations are used to describe the status of water and the processes inside of this. This study investigates bio-optical modeling of phytoplankton functional types (PFT) in terms of pigment composition demonstrating the capability of remote sensing to recognize freshwater phytoplankton. In particular, a sensitivity analysis of simulated hyperspectral water reflectance (with band setting of HICO, APEX, EnMAP, PRISMA and Sentinel-3) of productive eutrophic waters of Mantua lakes (Italy) environment is presented. The bio-optical model adopted for simulating the hyperspectral water reflectance takes into account the reflectance dependency on geometric conditions of light field, on inherent optical properties (backscattering and absorption coefficients) and on concentrations of water quality parameters (WQPs). The model works in the 400-750nm wavelength range, while the model parametrization is based on a comprehensive dataset of WQP concentrations and specific inherent optical properties of the study area, collected in field surveys carried out from May to September of 2011 and 2014. The following phytoplankton groups, with their specific absorption coefficients, a*Φi(λ), were used during the simulation: Chlorophyta, Cyanobacteria with phycocyanin, Cyanobacteria and Cryptophytes with phycoerythrin, Diatoms with carotenoids and mixed phytoplankton. The phytoplankton absorption coefficient aΦ(λ) is modelled by multiplying the weighted sum of the PFTs, Σpia*Φi(λ), with the chlorophyll-a concentration (Chl-a). To highlight the variability of water reflectance due to variation of phytoplankton pigments, the sensitivity analysis was performed by keeping constant the WQPs (i.e., Chl-a=80mg/l, total suspended matter=12.58g/l and yellow substances=0.27m-1). The sensitivity analysis was
Backscatter coefficient estimation using tapers with gaps.
Luchies, Adam C; Oelze, Michael L
2015-04-01
When using the backscatter coefficient (BSC) to estimate quantitative ultrasound parameters such as the effective scatterer diameter (ESD) and the effective acoustic concentration (EAC), it is necessary to assume that the interrogated medium contains diffuse scatterers. Structures that invalidate this assumption can affect the estimated BSC parameters in terms of increased bias and variance and decrease performance when classifying disease. In this work, a method was developed to mitigate the effects of echoes from structures that invalidate the assumption of diffuse scattering, while preserving as much signal as possible for obtaining diffuse scatterer property estimates. Backscattered signal sections that contained nondiffuse signals were identified and a windowing technique was used to provide BSC estimates for diffuse echoes only. Experiments from physical phantoms were used to evaluate the effectiveness of the proposed BSC estimation methods. Tradeoffs associated with effective mitigation of specular scatterers and bias and variance introduced into the estimates were quantified. Analysis of the results suggested that discrete prolate spheroidal (PR) tapers with gaps provided the best performance for minimizing BSC error. Specifically, the mean square error for BSC between measured and theoretical had an average value of approximately 1.0 and 0.2 when using a Hanning taper and PR taper respectively, with six gaps. The BSC error due to amplitude bias was smallest for PR (Nω = 1) tapers. The BSC error due to shape bias was smallest for PR (Nω = 4) tapers. These results suggest using different taper types for estimating ESD versus EAC.
Calculation of combined diffusion coefficients in SF{sub 6}-Cu mixtures
Zhong, Linlin; Wang, Xiaohua Rong, Mingzhe Wu, Yi; Murphy, Anthony B.
2014-10-15
Diffusion coefficients play an important role in the description of the transport of metal vapours in gas mixtures. This paper is devoted to the calculation of four combined diffusion coefficients, namely, the combined ordinary diffusion coefficient, combined electric field diffusion coefficient, combined temperature diffusion coefficient, and combined pressure diffusion coefficient in SF{sub 6}-Cu mixtures at temperatures up to 30 000 K. These four coefficients describe diffusion due to composition gradients, applied electric fields, temperature gradients, and pressure gradients, respectively. The influence of copper fluoride and sulfide species on the diffusion coefficients is shown to be negligible. The effect of copper proportion and gas pressures on these diffusion coefficients is investigated. It is shown that increasing the proportion of copper generally increases the magnitude of the four diffusion coefficients, except for copper mole fractions of 90% or more. It is further found that increasing the pressure reduces the magnitude of the coefficients, except for the combined temperature diffusion coefficient, and shifts the maximum of all four coefficients towards higher temperatures. The results presented in this paper can be applied to the simulation of high-voltage circuit breaker arcs.
Normal incidence sound absorption measurement of individual patches in a reverberation room
NASA Astrophysics Data System (ADS)
Massarani, Paulo; Muller, Swen
2002-11-01
This work presents results of sound absorption measurement of plain patches inside a reverberation room. An in situ method has been applied (ISO 13472-1). The main purpose is to support the installation of diffusers in a reverberation room for random incidence sound absorption measurements. The in situ method is based on impulse response evaluation, in which the incident and reflected front waves can be windowed to isolate them from the room reflections. Due to the small areas of the patches (around 1 square meter) and the high reverberation time, some special steps had to be performed. In order to establish an impulse response measurement with high SNR, a long sweep sine signal with low-frequency emphasis has been used as the excitation signal. Applying the subtraction technique permitted locating the microphone very close to the sample. The sound absorption coefficient of each patch allowed selecting the most uniform set of material to compose the area required by the ISO 354. The patches not used were tested in an impedance tube, showing a good agreement between the results from the two methods. Thus, the in situ method allows quick measurement of plain samples laid on the room floor while preserving the material integrity.
Rashidian Vaziri, Mohammad Reza
2013-07-10
In this paper, the Z-scan theory for nonlocal nonlinear media has been further developed when nonlinear absorption and nonlinear refraction appear simultaneously. To this end, the nonlinear photoinduced phase shift between the impinging and outgoing Gaussian beams from a nonlocal nonlinear sample has been generalized. It is shown that this kind of phase shift will reduce correctly to its known counterpart for the case of pure refractive nonlinearity. Using this generalized form of phase shift, the basic formulas for closed- and open-aperture beam transmittances in the far field have been provided, and a simple procedure for interpreting the Z-scan results has been proposed. In this procedure, by separately performing open- and closed-aperture Z-scan experiments and using the represented relations for the far-field transmittances, one can measure the nonlinear absorption coefficient and nonlinear index of refraction as well as the order of nonlocality. Theoretically, it is shown that when the absorptive nonlinearity is present in addition to the refractive nonlinearity, the sample nonlocal response can noticeably suppress the peak and enhance the valley of the Z-scan closed-aperture transmittance curves, which is due to the nonlocal action's ability to change the beam transverse dimensions.
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.
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…
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
NASA Technical Reports Server (NTRS)
Gruszka, Marcin; Borysow, Aleksandra
1997-01-01
The collision-induced absorption (CIA)of gaseous CO2 is the primary source of far-infrared opacity of the atmosphere of Venus. At the temperatures and densities of the venusian atmosphere, the absorption is due mainly to binary collisions of CO2 molecules. Using a realistic anisotropic intermolecular potential and assuming the absorbing dipole to be due to the electrostatic induction and a quantum overlap, a series of molecular dynamics simulations were performed for the temperature range 200 to 800 K, and the roto-translational (RT) collision-induced absorption spectra at frequencies from 0 to 250 cm(exp -1) were derived. The absorption coefficient in the submillimeter region, used in constituency retrieval studies, decreases more than 10 times in the temperature range 200 to 800 K. On the other hand, the absorption coefficient at 800 K and at the frequency range above 150 cm(exp -1) was found to be almost 10 times higher than at 200 K. Earlier works relied on experimental RT CIA data at a fixed temperature of 300 K. The new, temperature-dependent absorption bands may, when included in the analysis of the atmospheric radiative transfer of the planet, help explain the observed high far-infrared opacity of the lower layers of the atmosphere. To make the results of the simulations readily available for atmospheric abundance and radiative transfer analysis, an analytic model of the roto-translational collision-induced absorption spectral profile, applicable from 200 to 800 K, is being proposed here. The FORTRAN computer code of this newly developed model is available from the authors on request.
Two-dimensional probe absorption in coupled quantum dots
NASA Astrophysics Data System (ADS)
Liu, Ningwu; Zhang, Yan; Kang, Chengxian; Wang, Zhiping; Yu, Benli
2016-07-01
We investigate the two-dimensional (2D) probe absorption in coupled quantum dots. It is found that, due to the position-dependent quantum interference effect, the 2D optical absorption spectrum can be easily controlled via adjusting the system parameters. Thus, our scheme may provide some technological applications in solid-state quantum communication.
Heat-transfer coefficients in agitated vessels. Latent heat models
Kumpinsky, E.
1996-03-01
Latent heat models were developed to calculate heat-transfer coefficients in agitated vessels for two cases: (1) heating with a condensable fluid flowing through coils and jackets; (2) vacuum reflux cooling with an overhead condenser. In either case the mathematical treatment, based on macroscopic balances, requires no iterative schemes. In addition to providing heat-transfer coefficients, the models predict flow rates of service fluid through the coils and jackets, estimate the percentage of heat transfer due to latent heat, and compute reflux rates.
Triplet absorption spectroscopy and electromagnetically induced transparency
NASA Astrophysics Data System (ADS)
Ghafoor, F.; Nazmitdinov, R. G.
2016-09-01
Coherence phenomena in a four-level atomic system, cyclically driven by three coherent fields, are investigated thoroughly at zero and weak magnetic fields. Each strongly interacting atomic state is converted to a triplet due to a dynamical Stark effect. Two dark lines with a Fano-like profile arise in the triplet absorption spectrum with anomalous dispersions. We provide conditions to control the widths of the transparency windows by means of the relative phase of the driving fields and the intensity of the microwave field, which closes the optical system loop. The effect of Doppler broadening on the results of the triplet absorption spectroscopy is analysed in detail.
Efficiency enhancement due to self-organization of nano-structures in Cd(S, Te) solar cell material
NASA Astrophysics Data System (ADS)
Sato, Kazunori; Katayama-Yoshida, Hiroshi
2014-03-01
CdTe is one of the most important solar cell materials. Its energy gap is 1.44 eV, which is ideal for solar cell application. So far, conversion efficiency of 18.3 percent has been realized, but it is lower than the Shockley-Queisser limit. In this paper, we propose computational materials design for enhancing conversion efficiency by using self-organization in Cd(Te, S) alloy semiconductor. Firstly, we performed cluster expansion of total energy of the Cd(Te, S) system and simulated self-organization of nano-structures in Cd(Te, S) by using Monte Carlo method. It is found that layered structure becomes stable by applying strain during the crystal growth. The electronic structure of the self-organized layered structure was calculated by using the hybrid method (HSE06) implemented in the VASP code to derive optical absorption coefficient. By using the calculated absorption coefficient the efficiency limit was derived based on the Shockley-Queisser theory. It is shown that the efficiency limit does not change so much due to the nano-structure formation. However, our calculation shows spatial separation between photo-generated electrons and holes. This might enhance the efficiency due to the suppression of recombination.
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
Water and tissue equivalency of some gel dosimeters for photon energy absorption.
Un, Adem
2013-12-01
The mass energy absorption coefficients,, effective atomic numbers for photon energy absorption, ZPEAeff, and effective electron numbers for photon-energy absorption, NPEAeff, is calculated for 14 polymer gel dosimeter, five gel dosimeter, soft tissue and water, in the energy range from 1 keV to 20 MeV. The ZPEAeff(Gel)/ZPEAeff(Tissue) and NPEAeff(Gel)/NPEAeff (Tissue) are used to evaluate the tissue equivalency.
Inbreeding coefficients and coalescence times.
Slatkin, M
1991-10-01
This paper describes the relationship between probabilities of identity by descent and the distribution of coalescence times. By using the relationship between coalescence times and identity probabilities, it is possible to extend existing results for inbreeding coefficients in regular systems of mating to find the distribution of coalescence times and the mean coalescence times. It is also possible to express Sewall Wright's FST as the ratio of average coalescence times of different pairs of genes. That simplifies the analysis of models of subdivided populations because the average coalescence time can be found by computing separately the time it takes for two genes to enter a single subpopulation and time it takes for two genes in the same subpopulation to coalesce. The first time depends only on the migration matrix and the second time depends only on the total number of individuals in the population. This approach is used to find FST in the finite island model and in one- and two-dimensional stepping-stone models. It is also used to find the rate of approach of FST to its equilibrium value. These results are discussed in terms of different measures of genetic distance. It is proposed that, for the purposes of describing the amount of gene flow among local populations, the effective migration rate between pairs of local populations, M, which is the migration rate that would be estimated for those two populations if they were actually in an island model, provides a simple and useful measure of genetic similarity that can be defined for either allozyme or DNA sequence data.
NASA Astrophysics Data System (ADS)
Kulikov, V. D.; Yakovlev, V. Yu.
2016-09-01
The process of light absorption by free electrons in the crystalline cadmium sulfide under irradiation by a nanosecond electron beam with the current density of 8-100 A/cm2 is studied. A superlinear increase in optical absorption is observed if the beam current density is increased from ~8 to 12 A/cm2. The nature of light absorption by thermalized electrons corresponds to the scattering on lattice defects. An increase in the exponent of the power dependence of light absorption on the wavelength with increasing beam current density is associated with the single and double ionization of donors and acceptors. It is concluded that accumulation of charge carriers occurs without capture by traps due to their impact ionization by secondary electrons, whose energy in the thermalization stage is comparable with the band gap of the crystal. According to the results of calculations, the capture cross section of electrons by holes at quadratic recombination is ~10-20 cm2, the Auger recombination coefficient is ~10-31 cm6•s-1, and the charge carrier concentration is ~1.3•1018-1.5•1019 cm-3.
Tanaka, Akiko; Furubayashi, Tomoyuki; Matsushita, Akifumi; Inoue, Daisuke; Kimura, Shunsuke; Katsumi, Hidemasa; Sakane, Toshiyasu; Yamamoto, Akira
2016-01-01
The nasal absorption of macromolecules from powder formulations and the effect of sodium carboxymethyl cellulose (CMC-Na) as a pharmaceutical excipient on their absorption were studied. Model macromolecules were fluorescein isothiocyanate-labeled dextran (average molecular weight of 4.4kDa, FD4) and insulin. The plasma concentration of FD4 after application of the powder containing 50% starch (control) was higher than that after application of the solution, and the absorption from 50% starch powder was enhanced by the substitution of starch with CMC-Na. The fractional absorption of FD4 after administration of the CMC-Na powder formulation was 30% and 40% higher than that after administration from the solution and the starch powder, respectively. The nasal absorption of insulin from the powder and the effect of CMC-Na were similar with those of FD4. The effective absorption of FD4 and insulin after application of powder with CMC-Na could be due to the increase in the nasal residence of FD4 and insulin. No damage in the nasal mucosa or dysfunction of the mucociliary clearance was observed after application of the drug powder and CMC-Na. The present findings indicate that nasal delivery of powder formulations with the addition of CMC-Na as an excipient is a promising approach for improving the nasal absorption of macromolecules. PMID:27598527
Tanaka, Akiko; Furubayashi, Tomoyuki; Matsushita, Akifumi; Inoue, Daisuke; Kimura, Shunsuke; Katsumi, Hidemasa; Sakane, Toshiyasu; Yamamoto, Akira
2016-01-01
The nasal absorption of macromolecules from powder formulations and the effect of sodium carboxymethyl cellulose (CMC-Na) as a pharmaceutical excipient on their absorption were studied. Model macromolecules were fluorescein isothiocyanate-labeled dextran (average molecular weight of 4.4kDa, FD4) and insulin. The plasma concentration of FD4 after application of the powder containing 50% starch (control) was higher than that after application of the solution, and the absorption from 50% starch powder was enhanced by the substitution of starch with CMC-Na. The fractional absorption of FD4 after administration of the CMC-Na powder formulation was 30% and 40% higher than that after administration from the solution and the starch powder, respectively. The nasal absorption of insulin from the powder and the effect of CMC-Na were similar with those of FD4. The effective absorption of FD4 and insulin after application of powder with CMC-Na could be due to the increase in the nasal residence of FD4 and insulin. No damage in the nasal mucosa or dysfunction of the mucociliary clearance was observed after application of the drug powder and CMC-Na. The present findings indicate that nasal delivery of powder formulations with the addition of CMC-Na as an excipient is a promising approach for improving the nasal absorption of macromolecules.
Tanaka, Akiko; Furubayashi, Tomoyuki; Matsushita, Akifumi; Inoue, Daisuke; Kimura, Shunsuke; Katsumi, Hidemasa; Sakane, Toshiyasu; Yamamoto, Akira
2016-01-01
The nasal absorption of macromolecules from powder formulations and the effect of sodium carboxymethyl cellulose (CMC-Na) as a pharmaceutical excipient on their absorption were studied. Model macromolecules were fluorescein isothiocyanate-labeled dextran (average molecular weight of 4.4kDa, FD4) and insulin. The plasma concentration of FD4 after application of the powder containing 50% starch (control) was higher than that after application of the solution, and the absorption from 50% starch powder was enhanced by the substitution of starch with CMC-Na. The fractional absorption of FD4 after administration of the CMC-Na powder formulation was 30% and 40% higher than that after administration from the solution and the starch powder, respectively. The nasal absorption of insulin from the powder and the effect of CMC-Na were similar with those of FD4. The effective absorption of FD4 and insulin after application of powder with CMC-Na could be due to the increase in the nasal residence of FD4 and insulin. No damage in the nasal mucosa or dysfunction of the mucociliary clearance was observed after application of the drug powder and CMC-Na. The present findings indicate that nasal delivery of powder formulations with the addition of CMC-Na as an excipient is a promising approach for improving the nasal absorption of macromolecules. PMID:27598527