Piezoelectric films for acoustoelectronic devices - Production, properties, and applications

NASA Astrophysics Data System (ADS)

Anisimkin, V. I.; Kotelianskii, I. M.

1990-06-01

Various aspects of the production of ZnO, AlN, and Ta2O5 piezoelectric films are briefly reviewed. The mininum possible absorption coefficient of surface acoustic waves in textured films is estimated theoretically with allowance for different absorption mechanisms. The results obtained are compared with those for single crystals of the same materials. Methods for calculating the absorption coefficient and temperature delay coefficient for Rayleigh and Sezawa surface acoustic waves in layered structures are proposed and verified experimentally.

High transport and excellent optical property of a two-dimensional single-layered hybrid perovskite (C4H9NH3)2PbBr4: a theoretical study.

PubMed

Lei, Jun-Hui; Zhao, Yu-Qing; Tang, Qiong; Lin, Jian-Guo; Cai, Meng-Qiu

2018-05-16

Organic-inorganic hybrid perovskites are developed to pursue high charge carrier mobility and light absorption coefficient. In this study, we present a detailed comparative research of the atomic and electronic structures of single-layered perovskites (C4H9NH3)2PbBr4 with two-dimensional/three-dimensional (2D/3D) spatial arrangement to predict the in plane charge carrier mobility along with the charge effective mass, elastic constant, and deformation potential. The calculated results reveal that the intrinsic in plane carrier mobilities of 2D single-layered hybrid perovskite (C4H9NH3)2PbBr4 along the 100 and 010 directions are superior to those of the 3D structure. Furthermore, the optical properties are calculated from the electronic structure; it is found that the light absorption spectrum of 2D single-layered perovskite (C4H9NH3)2PbBr4 with a high absorption coefficient is wider than that of the 3D phase. We speculate that the superior mobility and wider absorption spectrum of the 2D mono-layered perovskite are due to high charge density and ferroelectricity originating from structure distortion upon 3D-to-2D structure transformation. These results indicate that the 2D single-layered hybrid perovskite (C4H9NH3)2PbBr4 is a potential candidate for application in the optoelectronic and photovoltaic fields.

Absorption Coefficient of Alkaline Earth Halides.

DTIC Science & Technology

1980-04-01

not observed at low energy level , are developed at high power levels . No matter how low the absorption is. the effect is objectionable at high-energy... levels . As a natural consequence, the magnitude of the absorption coefficient is the key parameter in selecting laser window materials. Over the past...Presence of impurities can complicate the exponential tail. particularly at low absorption levels . The impurities may enter 12 the lattice singly or

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…

Investigation of radiological properties of some shielding materials on charged and uncharged radiation interaction for neutron generator

NASA Astrophysics Data System (ADS)

Büyükyıldız, Mehmet

2017-04-01

Radiation interaction parameters such as total stopping power, projected range (longitudinal and lateral) straggling, mass attenuation coefficient, effective atomic number (Zeff) and electron density (Neff) of some shielding materials were investigated for photon and heavy charged particle interactions. The ranges, stragglings and mass attenuation coefficients were calculated for the high-density polyethylene(HDPE), borated polyethylene (BPE), brick (common silica), concrete (regular), wood, water, stainless steel (304), aluminum (alloy 6061-O), lead and bismuth using SRIM Monte Carlo software and WinXCom program. In addition, effective atomic numbers (Zeff) and electron densities (Neff) of HDPE, BPE, brick (common silica), concrete (regular), wood, water, stainless steel (304) and aluminum (alloy 6061-O) were calculated in the energy region 10 keV-100 MeV using mass stopping powers and mass attenuation coefficients. Two different methods namely direct and interpolation procedures were used to calculate Zeff for comparison and significant differences were determined between the methods. Variations of the ranges, longitudinal and lateral stragglings of water, concrete and stainless steel (304) were compared with each other in the continuous kinetic energy region and discussed with respect to their Zeffs. Moreover, energy absorption buildup factors (EABF) and exposure buildup factors (EBF) of the materials were determined for gamma rays as well and were compared with each other for different photon energies and different mfps in the photon energy region 0.015-15 MeV.

Chemical compositions and reconstructed light extinction coefficients of particulate matter in a mega-city in the western Yangtze River Delta, China

NASA Astrophysics Data System (ADS)

Shen, Guofeng; Xue, Miao; Yuan, Siyu; Zhang, Jie; Zhao, Qiuyue; Li, Bing; Wu, Haisuo; Ding, Aijun

2014-02-01

Ambient particulate matter was collected in a megacity, Nanjing in western YRD during the spring and summer periods. Chemical compositions of fine PM including organic carbon, elemental carbon, elements and water soluble ions were analyzed. The light extinction coefficients were reconstructed following the IMPROVE formula. Organic matter was the most abundant composition in PM2.5 (20-25% of total mass), followed by the inorganic ions. During the spring time, geological materials contributed 25% of the total PM2.5. Estimated light extinction coefficient ranged from 133 to 560 Mm-1 with the deciview haze index value of 26-40 dv, indicating strong light extinction by PM and subsequently low visibility in the city. Reconstructed ammonium sulfate, ammonium nitrate, organic matter and light absorption carbon in fine PM contributed significantly (37 ± 10, 16 ± 6, 15 ± 4 and 10 ± 3%, respectively) to the total light extinction of PM, while soil (5-7%) and sea salt fractions (2-4%) in fine PM and coarse PM (6-11%) had relatively minor influences. The results of backward air trajectory showed that the site was strongly influenced by the air from the eastern (39%) and southeastern (29%) areas during the sampling period. Air plumes from the Southeastern had both high PM mass pollution and large light extinction, while the air mass originating from the Northwestern resulted in high PM mass loading but relatively lower light extinction.

Source apportionment of PM2.5 light extinction in an urban atmosphere in China.

PubMed

Lan, Zijuan; Zhang, Bin; Huang, Xiaofeng; Zhu, Qiao; Yuan, Jinfeng; Zeng, Liwu; Hu, Min; He, Lingyan

2018-01-01

Haze in China is primarily caused by high pollution of atmospheric fine particulates (PM 2.5 ). However, the detailed source structures of PM 2.5 light extinction have not been well established, especially for the roles of various organic aerosols, which makes haze management lack specified targets. This study obtained the mass concentrations of the chemical compositions and the light extinction coefficients of fine particles in the winter in Dongguan, Guangdong Province, using high time resolution aerosol observation instruments. We combined the positive matrix factor (PMF) analysis model of organic aerosols and the multiple linear regression method to establish a quantitative relationship model between the main chemical components, in particular the different sources of organic aerosols and the extinction coefficients of fine particles with a high goodness of fit (R 2 =0.953). The results show that the contribution rates of ammonium sulphate, ammonium nitrate, biomass burning organic aerosol (BBOA), secondary organic aerosol (SOA) and black carbon (BC) were 48.1%, 20.7%, 15.0%, 10.6%, and 5.6%, respectively. It can be seen that the contribution of the secondary aerosols is much higher than that of the primary aerosols (79.4% versus 20.6%) and are a major factor in the visibility decline. BBOA is found to have a high visibility destroying potential, with a high mass extinction coefficient, and was the largest contributor during some high pollution periods. A more detailed analysis indicates that the contribution of the enhanced absorption caused by BC mixing state was approximately 37.7% of the total particle absorption and should not be neglected. Copyright © 2017. Published by Elsevier B.V.

Deriving brown carbon from multiwavelength absorption measurements: Method and application to AERONET and Aethalometer observations

DOE PAGES

Wang, X.; Heald, C. L.; Sedlacek, A.; ...

2016-10-13

The radiative impact of organic aerosols (OA) is a large source of uncertainty in estimating the global direct radiative effect (DRE) of aerosols. This radiative impact includes not only light scattering but also light absorption from a subclass of OA referred to as brown carbon (BrC). However the absorption properties of BrC are poorly understood leading to large uncertainties in modelling studies. To obtain observational constraints from measurements, a simple Absorption Ångström Exponent (AAE) method is often used to separate the contribution of BrC absorption from that of black carbon (BC). However, this attribution method is based on assumptions regardingmore » the spectral dependence of BC that are often violated in the ambient atmosphere. Here we develop a new method that decreases the uncertainties associated with estimating BrC absorption. By applying this method to multi-wavelength absorption aerosol optical depth (AAOD) measurements at AERONET sites worldwide and surface aerosol absorption measurements at multiple ambient sites, we estimate that BrC globally contributes 6-40% of the absorption at 440nm. We find that the mass absorption coefficient of OA (OA-MAC) is positively correlated with BC/OA mass ratio. Based on the variability of BC properties and BC/OA emission ratio, we estimate a range of 0.05-1.2 m 2/g for OA-MAC at 440nm. Using the combination of AERONET and OMI UV absorption observations we estimate that the AAE 388/440nm for BrC is generally ~4 world-wide, with a smaller value in Europe (< 2). Our analyses of two surface sites (Cape Cod, to the southeast of Boston, and the GoAmazon2014/5 T3 site, to the west of Manaus, Brazil) reveal no significant relationship between BrC absorptivity and photochemical aging in typical urban influenced conditions. However, the absorption of BrC measured during the biomass burning season near Manaus is found to decrease with photochemical aging with a lifetime of ~1 day. This lifetime is comparable to previous observations within a biomass burning plume but much slower than estimated from laboratory studies.« less

[Chromophoric dissolved organic matter absorption characteristics with relation to fluorescence in typical macrophyte, algae lake zones of Lake Taihu].

PubMed

Zhang, Yun-lin; Qin, Bo-qiang; Ma, Rong-hua; Zhu, Guang-wei; Zhang, Lu; Chen, Wei-min

2005-03-01

Chromophoric dissolved organic matter (CDOM) represents one of the primary light-absorbing species in natural waters and plays a critical in determining the aquatic light field. CDOM shows a featureless absorption spectrum that increases exponentially with decreasing wavelength, which limits the penetration of biologically damaging UV-B radiation (wavelength from 280 to 320 nm) in the water column, thus shielding aquatic organisms. CDOM absorption measurements and their relationship with dissolved organic carbon (DOC), and fluorescence are presented in typical macrophyte and algae lake zone of Lake Taihu based on a field investigation in April in 2004 and lab analysis. Absorption spectral of CDOM was measured from 240 to 800 nm using a Shimadzu UV-2401PC UV-Vis recording spectrophotometer. Fluorescence with an excitation wavelength of 355 nm, an emission wavelength of 450 nm is measured using a Shimadzu 5301 spectrofluorometer. Concentrations of DOC ranged from 6.3 to 17.2 mg/L with an average of 9.08 +/- 2.66 mg/L. CDOM absorption coefficients at 280 nm and 355 nm were in the range of 11.2 - 32.6 m(-1) (average 17.46m(-1) +/- 5.75 m(-1) and 2.4 - 8.3 m(-1) (average 4.17m(-1) +/- 1.47 m(-l)), respectively. The values of the DOC-specific absorption coefficient at 355 nm ranged from 0.31 to 0.64 L x (mg x m)-1. Fluorescence emission at 450 nm, excited at 355 nm, had a mean value of 1.32nm(-1) +/- 0.84 nm(-1). A significant lake zone difference is found in DOC concentration, CDOM absorption coefficient and fluorescence, but not in DOC-specific absorption coefficient and spectral slope coefficient. This regional distribution pattern is in agreement with the location of sources of yellow substance: highest concentrations close to river mouth under the influence of river inflow, lower values in East Lake Taihu. The values of algae lake zone are obvious larger than those of macrophyte lake zone. In Meiliang Bay, CDOM absorption, DOC concentration and fluorescence tend to decreasing from inside to mouth of the Bay. The results show a good correlation between CDOM absorption and DOC coefficients during 280 - 500 nm short wavelength intervals. The R-square coefficient between CDOM absorption and DOC concentration decreases with the increase of wavelength from 280 to 500 nm. The significant linear regression correlations between fluorescence, DOC concentration and absorption coefficients were found at 355 nm. The exponential slope coefficients ranged from 13.0 to 16.4 microm(-1) with a mean value 14.37microm(-1) +/- 0.73microm(-1), 17.3microm(-1) - 20.3microm(-1) with a mean value 19.17microm(-1) +/- 0.84microm(-1) and 12.0microm(-1) - 15.8microm(-1) with a mean value 13.38microm(-1) +/- 0.82microm(-1) over the 280 - 500 nm, 280 - 360 nm and 360 - 440 nm intervals.

Measurement of the aerosol absorption coefficient with the nonequilibrium process

NASA Astrophysics Data System (ADS)

Li, Liang; Li, Jingxuan; Bai, Hailong; Li, Baosheng; Liu, Shanlin; Zhang, Yang

2018-02-01

On the basis of the conventional Jamin interferometer,the improved measuring method is proposed that using a polarization type reentrant Jamin interferometer measures atmospheric aerosol absorption coefficient under the photothermal effect.The paper studies the relationship between the absorption coefficient of atmospheric aerosol particles and the refractive index change of the atmosphere.In Matlab environment, the variation curves of the output voltage of the interferometer with different concentration aerosol samples under stimulated laser irradiation were plotted.Besides, the paper also studies the relationship between aerosol concentration and the time required for the photothermal effect to reach equilibrium.When using the photothermal interferometry the results show that the time required for the photothermal effect to reach equilibrium is also increasing with the increasing concentration of aerosol particles,the absorption coefficient and time of aerosol in the process of nonequilibrium are exponentially changing.

Controlling of the optical properties of the solutions of the PTCDI-C8 organic semiconductor

NASA Astrophysics Data System (ADS)

Erdoğan, Erman; Gündüz, Bayram

2016-09-01

N,N'-Dioctyl-3,4,9,10 perylenedicarboximide (PTCDI-C8) organic semiconductor have vast applications in solar cells, thermoelectric generators, thin film photovoltaics and many other optoelectronic devices. These applications of the materials are based on their spectral and optical properties. The solutions of the PTCDI-C8 for different molarities were prepared and the spectral and optical mesaurements were analyzed. Effects of the molarities on optical properties were investigated. Vibronic structure has been observed based on the absorption bands of PTCDI-C8 semiconductor with seven peaks at 2.292, 2.451, 2.616, 3.212, 3.851, 4.477 and 4.733 eV. The important spectral parameteres such as molar/mass extinction coefficients, absorption coefficient of the PTCDI-C8 molecule were calculated. Optical properties such as angle of incidence/refraction, optical band gap, real and imaginary parts of dielectric constant, loss factor and electrical susceptibility of the the PTCDI-C8 were obtained. Finally, we discussed these parameters for optoelectronic applications and compared with related parameters in literature.

Linear and nonlinear optical properties in an asymmetric double quantum well under intense laser field: Effects of applied electric and magnetic fields

NASA Astrophysics Data System (ADS)

Yesilgul, U.; Al, E. B.; Martínez-Orozco, J. C.; Restrepo, R. L.; Mora-Ramos, M. E.; Duque, C. A.; Ungan, F.; Kasapoglu, E.

2016-08-01

In the present study, the effects of electric and magnetic fields on the linear and third-order nonlinear optical absorption coefficients and relative change of the refractive index in asymmetric GaAs/GaAlAs double quantum wells under intense laser fields are theoretically investigated. The electric field is oriented along the growth direction of the heterostructure while the magnetic field is taken in-plane. The intense laser field is linear polarization along the growth direction. Our calculations are made using the effective-mass approximation and the compact density-matrix approach. Intense laser effects on the system are investigated with the use of the Floquet method with the consequent change in the confinement potential of heterostructures. Our results show that the increase of the electric and magnetic fields blue-shifts the peak positions of the total absorption coefficient and of the total refractive index while the increase of the intense laser field firstly blue-shifts the peak positions and later results in their red-shifting.

Hyperspectral photoacoustic spectroscopy of highly-absorbing samples for diagnostic ocular imaging applications

NASA Astrophysics Data System (ADS)

Lim, Hoong-Ta; Murukeshan, Vadakke Matham

2017-01-01

Photoacoustic spectroscopy has been used to measure optical absorption coefficient and the application of tens of wavelength bands in photoacoustic spectroscopy was reported. Using optical methods, absorption-related information is, generally, derived from reflectance or transmittance values. Hence measurement accuracy is limited for highly absorbing samples where the reflectance or transmittance is too low to give reasonable signal-to-noise ratio. In this context, this paper proposes and illustrates a hyperspectral photoacoustic spectroscopy system to measure the absorption-related properties of highly absorbing samples directly. The normalized optical absorption coefficient spectrum of the highly absorbing iris is acquired using an optical absorption coefficient standard. The proposed concepts and the feasibility of the developed diagnostic medical imaging system are demonstrated using fluorescent microsphere suspensions and porcine eyes as test samples.

Temperature and salinity correction coefficients for light absorption by water in the visible to infrared spectral region.

PubMed

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)).

Science and software support for spacecraft solar occultation experiments

NASA Technical Reports Server (NTRS)

Hessameddin, G.; Becher, J.

1982-01-01

The temperature dependence of absorption coefficients of ozone was studied between 7567 A and 3630 A. When the gas was cooled from room temperature to -108 C, an overall increase in the absorption coefficients was noticed. The maximum increase of 5% occurred at lambda = 6020 A. In general, the absorption is linearly dependent on temperature.

The contribution of malabsorption to the reduction in net energy absorption after long-limb Roux-en-Y gastric bypass.

PubMed

Odstrcil, Elizabeth A; Martinez, Juan G; Santa Ana, Carol A; Xue, Beiqi; Schneider, Reva E; Steffer, Karen J; Porter, Jack L; Asplin, John; Kuhn, Joseph A; Fordtran, John S

2010-10-01

Roux-en-Y gastric bypass (RYGB) restricts food intake, and when the Roux limb is elongated to 150 cm, the procedure is believed to induce malabsorption. Our objective was to measure total reduction in intestinal absorption of combustible energy after RYGB and the extent to which this was due to restriction of food intake or malabsorption of ingested macronutrients. Long-limb RYGB was performed in 9 severely obese patients. Dietary intake and intestinal absorption of fat, protein, carbohydrate, and combustible energy were measured before and at 2 intervals after bypass. By using coefficients of absorption to measure absorptive function, equations were developed to calculate the daily gram and kilocalorie quantities of ingested macronutrients that were not absorbed because of malabsorption or restricted food intake. Coefficients of fat absorption were 92 ± 1.3% before bypass, 72 ± 5.5% 5 mo after bypass, and 68 ± 8.7% 14 mo after bypass. There were no statistically significant effects of RYGB on protein or carbohydrate absorption coefficients, although protein coefficients decreased substantially in some patients. Five months after bypass, malabsorption reduced absorption of combustible energy by 124 ± 57 kcal/d, whereas restriction of food intake reduced energy absorption by 2062 ± 271 kcal/d. Fourteen months after bypass, malabsorption reduced energy absorption by 172 ± 60 kcal/d compared with 1418 ± 171 kcal/d caused by restricted food intake. On average, malabsorption accounted for ≈6% and 11% of the total reduction in combustible energy absorption at 5 and 14 mo, respectively, after this gastric bypass procedure.

Space-time modeling of the photon diffusion in a three-layered model: application to the study of muscular oxygenation

NASA Astrophysics Data System (ADS)

Mansouri, C.; L'Huillier, J. P.; Piron, V.

2007-07-01

This work presents results on the modeling of the photon diffusion in a three-layered model, (skin, fat and muscle). The Finite Element method was performed in order to calculate the temporal response of the above-mentioned structure. The thickness of the fat layer was varied from 1 to 15 mm to investigate the effects of increasing fat thickness on the muscle layer absorption coefficient measurements for a source-detector spacing of 30 mm. The simulated time-resolved reflectance data, at different wavelengths, were fitted to the diffusion model to yield the scattering and absorption coefficients of muscle. The errors in estimating muscle absorption coefficients μ α depend on the thickness of the fat layer and its optical properties. In addition, it was shown that it is possible to recover with a good precision (~2.6 % of error) the absorption coefficient of muscle and this up to a thickness of the fat layer not exceeding 4mm. Beyond this limit a correction is proposed in order to make measurements coherent. The muscle-corrected absorption coefficient can be then used to calculate hemoglobin oxygenation.

Solubility and diffusivity of nitrous oxide in ternary mixtures of water, monoethanolamine, and N-methyldiethanolamine and solution densities and viscosities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagewiesche, D.P.; Ashour, S.S.; Sandall, O.C.

1995-05-01

Recently, several researchers have suggested using aqueous mixtures of small amounts of monoethanolamine and much larger amounts of N-methyldiethanolamine for the absorption of CO{sub 2} and for the selective removal of H{sub 2}S from gas streams of mixtures of CO{sub 2} and H{sub 2}S. The densities and viscosities of aqueous N-methyldiethanolamine/monoethanolamine (MDEA/MEA) blends containing 30 and 40 mass % total amine with MEA concentrations of 5, 10, and 15 mass % of the total amine concentration were measured at temperatures of 303, 313, and 323 K. The diffusion coefficients and Henry`s law constants of N{sub 2}O in these solutions weremore » also measured and were used to estimate the diffusion coefficients and Henry`s law constants of CO{sub 2} in these solutions according to the N{sub 2}O/CO{sub 2} analogy technique.« less

Measuring water contents in animal organ tissues using terahertz spectroscopic imaging.

PubMed

Lee, Kyumin; Jeoung, Kiyong; Kim, Sang Hoon; Ji, Young-Bin; Son, Hyeyoung; Choi, Yuna; Huh, Young-Min; Suh, Jin-Suck; Oh, Seung Jae

2018-04-01

We investigated the water contents in several organ tissues such as the liver, spleen, kidney, and brain tissue of rats using the terahertz spectroscopic imaging technique. The water contents of the tissues were determined by using a simple equation containing the absorption coefficients of fresh and lyophilized tissues and water. We compared the measured water contents with the difference in mass of tissues before and after lyophilization. All results showed a good match except for the kidney, which has several Bowman's capsules.

Imaging of Rabbit VX-2 Hepatic Cancer by Cold and Thermal Neutron Radiography

NASA Astrophysics Data System (ADS)

Tsuchiya, Yoshinori; Matsubayashi, Masahito; Takeda, Tohoru; Lwin, Thet Thet; Wu, Jin; Yoneyama, Akio; Matsumura, Akira; Hori, Tomiei; Itai, Yuji

2003-11-01

Neutron radiography is based on differences in neutron mass attenuation coefficients among the elements and is a non-destructive imaging method. To investigate biomedical applications of neutron radiography, imaging of rabbit VX-2 liver cancer was performed using thermal and cold neutron radiography with a neutron imaging plate. Hepatic vessels and VX-2 tumor were clearly observed by neutron radiography, especially by cold neutron imaging. The image contrast of this modality was better than that of absorption-contrast X-ray radiography.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, X.; Heald, C. L.; Sedlacek, A.

The radiative impact of organic aerosols (OA) is a large source of uncertainty in estimating the global direct radiative effect (DRE) of aerosols. This radiative impact includes not only light scattering but also light absorption from a subclass of OA referred to as brown carbon (BrC). However the absorption properties of BrC are poorly understood leading to large uncertainties in modelling studies. To obtain observational constraints from measurements, a simple Absorption Ångström Exponent (AAE) method is often used to separate the contribution of BrC absorption from that of black carbon (BC). However, this attribution method is based on assumptions regardingmore » the spectral dependence of BC that are often violated in the ambient atmosphere. Here we develop a new method that decreases the uncertainties associated with estimating BrC absorption. By applying this method to multi-wavelength absorption aerosol optical depth (AAOD) measurements at AERONET sites worldwide and surface aerosol absorption measurements at multiple ambient sites, we estimate that BrC globally contributes 6-40% of the absorption at 440nm. We find that the mass absorption coefficient of OA (OA-MAC) is positively correlated with BC/OA mass ratio. Based on the variability of BC properties and BC/OA emission ratio, we estimate a range of 0.05-1.2 m 2/g for OA-MAC at 440nm. Using the combination of AERONET and OMI UV absorption observations we estimate that the AAE 388/440nm for BrC is generally ~4 world-wide, with a smaller value in Europe (< 2). Our analyses of two surface sites (Cape Cod, to the southeast of Boston, and the GoAmazon2014/5 T3 site, to the west of Manaus, Brazil) reveal no significant relationship between BrC absorptivity and photochemical aging in typical urban influenced conditions. However, the absorption of BrC measured during the biomass burning season near Manaus is found to decrease with photochemical aging with a lifetime of ~1 day. This lifetime is comparable to previous observations within a biomass burning plume but much slower than estimated from laboratory studies.« less

Bottom Extreme-Ultraviolet-Sensitive Coating for Evaluation of the Absorption Coefficient of Ultrathin Film

NASA Astrophysics Data System (ADS)

Hijikata, Hayato; Kozawa, Takahiro; Tagawa, Seiichi; Takei, Satoshi

2009-06-01

A bottom extreme-ultraviolet-sensitive coating (BESC) for evaluation of the absorption coefficients of ultrathin films such as extreme ultraviolet (EUV) resists was developed. This coating consists of a polymer, crosslinker, acid generator, and acid-responsive chromic dye and is formed by a conventional spin-coating method. By heating the film after spin-coating, a crosslinking reaction is induced and the coating becomes insoluble. A typical resist solution can be spin-coated on a substrate covered with the coating film. The evaluation of the linear absorption coefficients of polymer films was demonstrated by measuring the EUV absorption of BESC substrates on which various polymers were spin-coated.

Superlattice Intermediate Band Solar Cell on Gallium Arsenide

DTIC Science & Technology

2015-02-09

18  APPENDIX: Methodology for Calculaton of Minband Energies and Absorption Coefficient of a Superlattice...4 Figure 3. Absorption coefficient extracted from spectroscopic ellipsometry measurements of a... coefficient of a 30 period GaAs0.98N0.02 (3nm)/ Al0.20Ga0.80As (3nm) Superlattice following the methodology developed in

Multiple-scattering coefficients and absorption controlled diffusive processes

NASA Astrophysics Data System (ADS)

Godoy, Salvador; García-Colín, L. S.; Micenmacher, Victor

1999-11-01

Multiple-scattering transmission and reflection coefficients (T,R) are introduced in addition to the diffusion coefficient D for the description of ballistic diffusion in the presence of absorption. For 1D (one-dimensional) systems, the measurement of only one between T and D imposes restrictions on the possible values of the other. If D is measured, then T is bounded between the Landauer and Lambert-Beer equations. Measurements of both (T,D) imply the theoretical knowledge of the microscopic absorption Σa and scattering rΣs cross sections.

Measurement of the sound absorption coefficient for an advanced undergraduate physics laboratory

NASA Astrophysics Data System (ADS)

Macho-Stadler, E.; Elejalde-García, M. J.

2017-09-01

We present a simple experiment that allows advanced undergraduates to learn the basics of the acoustic properties of materials. The impedance tube-standing wave method is applied to study the normal absorption coefficient of acoustics insulators. The setup includes a tube, a speaker, a microphone, a digital function generator and an oscilloscope, material available in an undergraduate laboratory. Results of the change of the absorption coefficient with the frequency, the sample thickness and the sample density are analysed and compared with those obtained with a commercial system.

Bilayered Hybrid Perovskite Ferroelectric with Giant Two-Photon Absorption.

PubMed

Li, Lina; Shang, Xiaoying; Wang, Sasa; Dong, Ningning; Ji, Chengmin; Chen, Xueyuan; Zhao, Sangen; Wang, Jun; Sun, Zhihua; Hong, Maochun; Luo, Junhua

2018-06-06

Perovskite ferroelectrics with prominent nonlinear optical absorption have attracted great attention in the field of photonics. However, they are traditionally dominated by inorganic oxides and exhibit relatively small nonlinear optical absorption coefficients, which hinder their further applications. Herein, we report a new organic-inorganic hybrid bilayered perovskite ferroelectric, (C 4 H 9 NH 3 ) 2 (NH 2 CHNH 2 )Pb 2 Br 7 (1), showing an above-room-temperature Curie temperature (∼322 K) and notable spontaneous polarization (∼3.8 μC cm -2 ). Significantly, the unique quantum-well structure of 1 results in intriguing two-photon absorption properties with a giant nonlinear optical absorption coefficient as high as 5.76 × 10 3 cm GW -1 , which is almost two-orders of magnitude larger than those of mostly traditional all-inorganic perovskite ferroelectrics. To our best knowledge, 1 is the first example of hybrid ferroelectrics with giant two-photon absorption coefficient. The mechanisms for ferroelectric and two-photon absorption are revealed. This work will shed light on the design of new ferroelectrics with two-photon absorption and promote their potentials in the photonic application.

Optical absorption and scattering properties of bulk porcine muscle phantoms from interstitial radiance measurements in 650-900 nm range

NASA Astrophysics Data System (ADS)

Grabtchak, Serge; Montgomery, Logan G.; Whelan, William M.

2014-05-01

We demonstrated the application of relative radiance-based continuous wave (cw) measurements for recovering absorption and scattering properties (the effective attenuation coefficient, the diffusion coefficient, the absorption coefficient and the reduced scattering coefficient) of bulk porcine muscle phantoms in the 650-900 nm spectral range. Both the side-firing fiber (the detector) and the fiber with a spherical diffuser at the end (the source) were inserted interstitially at predetermined locations in the phantom. The porcine phantoms were prostate-shaped with ˜4 cm in diameter and ˜3 cm thickness and made from porcine loin or tenderloin muscles. The described method was previously validated using the diffusion approximation on simulated and experimental radiance data obtained for homogenous Intralipid-1% liquid phantom. The approach required performing measurements in two locations in the tissue with different distances to the source. Measurements were performed on 21 porcine phantoms. Spectral dependences of the effective attenuation and absorption coefficients for the loin phantom deviated from corresponding dependences for the tenderloin phantom for wavelengths <750 nm. The diffusion constant and the reduced scattering coefficient were very close for both phantom types. To quantify chromophore presence, the plot for the absorption coefficient was matched with a synthetic absorption spectrum constructed from deoxyhemoglobin, oxyhemoglobin and water. The closest match for the porcine loin spectrum was obtained with the following concentrations: 15.5 µM (±30% s.d.) Hb, 21 µM (±30% s.d.) HbO2 and 0.3 (±30% s.d.) fractional volume of water. The tenderloin absorption spectrum was best described by 30 µM Hb (±30% s.d), 19 µM (±30% s.d.) HbO2 and 0.3 (±30% s.d.) fractional volume of water. The higher concentration of Hb in tenderloin was consistent with a dark-red appearance of the tenderloin phantom. The method can be applied to a number of biological tissues and organs for interstitial optical interrogation.

An effective device for gas-liquid oxygen removal in enclosed microalgae culture.

PubMed

Su, Zhenfeng; Kang, Ruijuan; Shi, Shaoyuan; Cong, Wei; Cai, Zhaoling

2010-01-01

A high-performance gas-liquid transmission device (HPTD) was described in this paper. To investigate the HPTD mass transfer characteristics, the overall volumetric mass transfer coefficients, K(A)(La,CO(2)) for the absorption of gaseous CO(2) and K(A)(La,O(2)) for the desorption of dissolved O(2) were determined, respectively, by titration and dissolved oxygen electrode. The mass transfer capability of carbon dioxide was compared with that of dissolved oxygen in the device, and the operating conditions were optimized to suit for the large-scale enclosed micro-algae cultivation. Based on the effectiveness evaluation of the HPTD applied in one enclosed flat plate Spirulina culture system, it was confirmed that the HPTD can satisfy the demand of the enclosed system for carbon supplement and excessive oxygen removal.

Laboratory investigation on the role of tubular shaped micro resonators phononic crystal insertion on the absorption coefficient of profiled sound absorber

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

Light-absorbing oligomer formation in secondary organic aerosol from reactive uptake of isoprene epoxydiols.

PubMed

Lin, Ying-Hsuan; Budisulistiorini, Sri Hapsari; Chu, Kevin; Siejack, Richard A; Zhang, Haofei; Riva, Matthieu; Zhang, Zhenfa; Gold, Avram; Kautzman, Kathryn E; Surratt, Jason D

2014-10-21

Secondary organic aerosol (SOA) produced from reactive uptake and multiphase chemistry of isoprene epoxydiols (IEPOX) has been found to contribute substantially (upward of 33%) to the fine organic aerosol mass over the Southeastern U.S. Brown carbon (BrC) in rural areas of this region has been linked to secondary sources in the summer when the influence of biomass burning is low. We demonstrate the formation of light-absorbing (290 < λ < 700 nm) SOA constituents from reactive uptake of trans-β-IEPOX onto preexisting sulfate aerosols as a potential source of secondary BrC. IEPOX-derived BrC generated in controlled chamber experiments under dry, acidic conditions has an average mass absorption coefficient of ∼ 300 cm(2) g(-1). Chemical analyses of SOA constituents using UV-visible spectroscopy and high-resolution mass spectrometry indicate the presence of highly unsaturated oligomeric species with molecular weights separated by mass units of 100 (C5H8O2) and 82 (C5H6O) coincident with the observations of enhanced light absorption, suggesting such oligomers as chromophores, and potentially explaining one source of humic-like substances (HULIS) ubiquitously present in atmospheric aerosol. Similar light-absorbing oligomers were identified in fine aerosol collected in the rural Southeastern U.S., supporting their atmospheric relevance and revealing a previously unrecognized source of oligomers derived from isoprene that contributes to ambient fine aerosol mass.

Seasonal variation in chromophoric dissolved organic matter and relationships among fluorescent components, absorption coefficients and dissolved organic carbon in the Bohai Sea, the Yellow Sea and the East China Sea

NASA Astrophysics Data System (ADS)

Zhu, Wen-Zhuo; Zhang, Hong-Hai; Zhang, Jing; Yang, Gui-Peng

2018-04-01

The absorption coefficient and fluorescent components of chromophoric dissolved organic matter (CDOM) in the Bohai Sea (BS), Yellow Sea (YS), and East China Sea (ECS) in spring and autumn were analyzed in this study. Excitation-emission matrices (EEMs) combined with parallel factor analysis (PARAFAC) identified three components, namely, humic-like C1, tyrosine-like C2 and tryptophan-like C3. The seasonal variations in the vertical patterns of the CDOM absorption coefficient (aCDOM(355)) and fluorescent components were influenced by the seasonal water mass except for the terrestrial input. The relationship between aCDOM(355) and dissolved organic matter (DOC) was attributed to their own mixing behavior. The correlation of the fluorescent components with DOC was disturbed by other non-conservative processes during the export of CDOM to the open ocean. The different chemical compositions and origins of DOC and CDOM led to variability in carbon-specific CDOM absorption (a*CDOM(355)) and fluorescent component ratios (ICn/IC1). The relationship between a*CDOM(355) and aCDOM(355) demonstrated that dissolved organic matter (DOM) in the BS, but not in the ECS, highly contributed non-absorbing DOC to the total DOC concentration. The photodegradation of dominant terrestrially derived CDOM in the ECS contributed to the positive relationship between a*CDOM(355) and ICn/IC1. By contrast, the abundant autochthonous CDOM in the YS was negatively correlated with ICn/IC1 in autumn. Our established box models showed that water exchange is a potentially important source of the aromatic components in the BS, YS, and ECS. Hence, the seasonal variations in water exchange might contribute to the variability of CDOM chemical composition in the BS, YS, and ECS, and significantly influence the structure and function of their ecosystems.

Sound absorption of metallic sound absorbers fabricated via the selective laser melting process

NASA Astrophysics Data System (ADS)

Cheng, Li-Wei; Cheng, Chung-Wei; Chung, Kuo-Chun; Kam, Tai-Yan

2017-01-01

The sound absorption capability of metallic sound absorbers fabricated using the additive manufacturing (selective laser melting) method is investigated via both the experimental and theoretical approaches. The metallic sound absorption structures composed of periodic cubic cells were made of laser-melted Ti6Al4 V powder. The acoustic impedance equations with different frequency-independent and frequency-dependent end corrections factors are employed to calculate the theoretical sound absorption coefficients of the metallic sound absorption structures. The calculated sound absorption coefficients are in close agreement with the experimental results for the frequencies ranging from 2 to 13 kHz.

Modeling the reflectance of CO2 frost with new optical constants: Application to Martian south polar cap spectra

NASA Technical Reports Server (NTRS)

Hansen, Gary B.; Martin, Terry Z.

1993-01-01

New measurements of the absorption coefficients of CO2 ice, in most of the spectral range 0.2 to 3.9 microns where absorption coefficients are below 1.5 per cm, have recently been made. Although these measurements are preliminary, they contain spectral detail not seen previously in the literature. Therefore, it is useful to combine these new data with older data from spectral regions of stronger absorption and reformulate models of the albedo or reflectance of CO2 frost. These models can then be adjusted in an attempt to match measurements of Martian polar deposits, such as the set of spectra returned by the IRS instrument on Mariner 7 (1969). The new absorption coefficients of CO2 ice were measured on several samples of 41-mm thickness at 150-155 K. A portion of the spectrum from 1.9 to 3.9 microns wavelength is shown in the form of imaginary coefficient of refraction ( = linear absorption x wavelength / 4 pi). The data above 3x10(exp -5) are obtained from, except for the absorption line at 3.32 micrometers, which is extrapolated in a way that is consistent with laboratory frost measurements, but the peak level is still highly uncertain. This new imagary coefficient, combined with the real coefficient, can be immediately applied to the models for hemispherical albedo, resulting in markedly different results from those in that study. The results for an infinite optical depth layer and solar incidence of 60 degrees are plotted for a range of mean particle radii from 0.03 to 3 mm.

SU-E-T-178: Optically Stimulated Luminescence (OSL) Dosimetry: A Study of A-Al2O3:C Assessed by PENELOPE Monte Carlo Simulation.

PubMed

Nicolucci, P; Schuch, F

2012-06-01

To use the Monte Carlo code PENELOPE to study attenuation and tissue equivalence properties of a-Al2O3:C for OSL dosimetry. Mass attenuation coefficients of α-Al2O3 and α-Al2O3:C with carbon percent weight concentrations from 1% to 150% were simulated with PENELOPE Monte Carlo code and compared to mass attenuation coefficients from soft tissue for photon beams ranging from 50kV to 10MV. Also, the attenuation of primary photon beams of 6MV and 10MV and the generation of secondary electrons by α-Al2O3 :C dosimeters positioned on the entrance surface of a water phantom were studied. A difference of up to 90% was found in the mass attenuation coefficient between the pure \\agr;-A12O3 and the material with 150% weight concentration of dopant at 1.5 keV, corresponding to the K-edge photoelectric absorption of aluminum. However for energies above 80 keV the concentration of carbon does not affect the mass attenuation coefficient and the material presents tissue equivalence for the beams studied. The ratio between the mass attenuation coefficients for \\agr-A12O3:C and for soft tissue are less than unit due to the higher density of the \\agr-A12O3 (2.12 g/cm s ) and its tissue equivalence diminishes to lower concentrations of carbon and for lower energies due to the relation of the radiation interaction effects with atomic number. The larger attenuation of the primary photon beams by the dosimeter was 16% at 250 keV and the maximum increase in secondary electrons fluence to the entrance surface of the phantom was found as 91% at 2MeV. The use of the OSL dosimeters in radiation therapy can be optimized by use of PENELOPE Monte Carlo simulation to provide a study of the attenuation and response characteristics of the material. © 2012 American Association of Physicists in Medicine.

CO2 Absorption from Biogas by Glycerol: Conducted in Semi-Batch Bubble Column

NASA Astrophysics Data System (ADS)

puji lestari, Pratiwi; Mindaryani, Aswati; Wirawan, S. K.

2018-03-01

Biogas is a renewable energy source that has been developed recently. The main contents of Biogas itself are Methane and carbon dioxide (CO2) where Methane is the main component of biogas with CO2 as the highest impurities. The quality of biogas depends on the CO2 content, the lower CO2 levels, the higher biogas quality. Absorption is one of the methods to reduce CO2 level. The selections of absorbent and appropriate operating parameters are important factors in the CO2 absorption from biogas. This study aimed to find out the design parameters for CO2 absorption using glycerol that represented by the overall mass transfer coefficient (KLa) and Henry’s constant (H). This study was conducted in semi-batch bubble column. Mixed gas was contacted with glycerol in a bubble column. The concentration of CO2 in the feed gas inlet and outlet columns were analysed by Gas Chromatograph. The variables observed in this study were superficial gas velocity and temperatures. The results showed that higher superficial gas velocity and lower temperature increased the rate of absorption process and the amount of CO2 absorbed.

Effective absorption cross sections and photolysis rates of anthropogenic and biogenic secondary organic aerosols

NASA Astrophysics Data System (ADS)

Romonosky, Dian E.; Ali, Nujhat N.; Saiduddin, Mariyah N.; Wu, Michael; Lee, Hyun Ji (Julie); Aiona, Paige K.; Nizkorodov, Sergey A.

2016-04-01

Mass absorption coefficient (MAC) values were measured for secondary organic aerosol (SOA) samples produced by flow tube ozonolysis and smog chamber photooxidation of a wide range of volatile organic compounds (VOC), specifically: α-pinene, β-pinene, β-myrcene, d-limonene, farnesene, guaiacol, imidazole, isoprene, linalool, ocimene, p-xylene, 1-methylpyrrole, and 2-methylpyrrole. Both low-NOx and high-NOx conditions were employed during the chamber photooxidation experiments. MAC values were converted into effective molecular absorption cross sections assuming an average molecular weight of 300 g/mol for SOA compounds. The upper limits for the effective photolysis rates of SOA compounds were calculated by assuming unity photolysis quantum yields and convoluting the absorption cross sections with a time-dependent solar spectral flux. A more realistic estimate for the photolysis rates relying on the quantum yield of acetone was also obtained. The results show that condensed-phase photolysis of SOA compounds can potentially occur with effective lifetimes ranging from minutes to days, suggesting that photolysis is an efficient and largely overlooked mechanism of SOA aging.

PNNL Report on the Development of Bench-scale CFD Simulations for Gas Absorption across a Wetted Wall Column

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Chao; Xu, Zhijie; Lai, Canhai

This report is prepared for the demonstration of hierarchical prediction of carbon capture efficiency of a solvent-based absorption column. A computational fluid dynamics (CFD) model is first developed to simulate the core phenomena of solvent-based carbon capture, i.e., the CO2 physical absorption and chemical reaction, on a simplified geometry of wetted wall column (WWC) at bench scale. Aqueous solutions of ethanolamine (MEA) are commonly selected as a CO2 stream scrubbing liquid. CO2 is captured by both physical and chemical absorption using highly CO2 soluble and reactive solvent, MEA, during the scrubbing process. In order to provide confidence bound on themore » computational predictions of this complex engineering system, a hierarchical calibration and validation framework is proposed. The overall goal of this effort is to provide a mechanism-based predictive framework with confidence bound for overall mass transfer coefficient of the wetted wall column (WWC) with statistical analyses of the corresponding WWC experiments with increasing physical complexity.« less

Phononic glass: a robust acoustic-absorption material.

PubMed

Jiang, Heng; Wang, Yuren

2012-08-01

In order to achieve strong wide band acoustic absorption under high hydrostatic pressure, an interpenetrating network structure is introduced into the locally resonant phononic crystal to fabricate a type of phononic composite material called "phononic glass." Underwater acoustic absorption coefficient measurements show that the material owns high underwater sound absorption coefficients over 0.9 in 12-30 kHz. Moreover, the quasi-static compressive behavior shows that the phononic glass has a compressive strength over 5 MPa which is crucial for underwater applications.

Optical Properties and Aging of Light Absorbing Secondary Organic Aerosol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jiumeng; Lin, Peng; Laskin, Alexander

2016-10-14

The light-absorbing organic aerosol (OA), commonly referred to as “brown carbon (BrC)”, has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various VOC precursors, NOx concentrations, photolysis time and relative humidity (RH) on the lightmore » absorption of selected secondary organic aerosols (SOA). Light absorption of chamber generated SOA samples, especially aromatic SOA, was found to increase with NOx concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficients (MAC) value is observed from toluene SOA products formed under high NOx conditions at moderate RH, in which nitro-aromatics were previously identified as the major light absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organonitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible and UV light than SOA formed from aromatic precursors alone on a mass basis. However, the mixed-SOA absorption was underestimated when optical properties were predicted using a two-product SOA formation model, as done in many current climate models. Further investigation, including analysis on detailed mechanisms, are required to explain the discrepancy.« less

Characterization of black carbon in an urban-rural fringe area of Beijing.

PubMed

Ji, Dongsheng; Li, Liang; Pang, Bo; Xue, Peng; Wang, Lili; Wu, Yunfei; Zhang, Hongliang; Wang, Yuesi

2017-04-01

Measuring black carbon (BC) is critical to understand the impact of combustion aerosols on air quality and climate change. In this study, BC was measured in 2014 at a unique community formed with rapid economic development and urbanization in an urban-rural fringe area of Beijing. Hourly BC concentrations were 0.1-33.5 μg/m 3 with the annual average of 4.4 ± 3.7 μg/m 3 . BC concentrations had clear diurnal, weekly, and seasonal variations, and were closely related with atmospheric visibility. The absorption coefficient of aerosols increased while its contribution to extinction coefficient decreased with the enhancement of PM 2.5 concentration. The high mass absorption efficiency (MAE) of EC was attributed to a combination of coal combustion, vehicular emission and rapidly coating by water-soluble ions and organic carbon (OC). BC concentrations followed a typical lognormal pattern, with over 88% samples in 0.1-10.0 μg/m 3 . Low BC levels were mostly bounded up with winds from north and northwest. Coal combustion and biomass burning were closely associated with severe haze pollution events. Firework discharge had significant UV absorption contribution. During the Asia-Pacific Economic Cooperation (APEC) forum in November 2014, air quality obviously improved due to various control strategies. Copyright © 2017 Elsevier Ltd. All rights reserved.

[Similarities and differences in absorption characteristics and composition of CDOM between Taihu Lake and Chaohu Lake].

PubMed

Shi, Kun; Li, Yun-mei; Wang, Qiao; Yang, Yu; Jin, Xin; Wang, Yan-fei; Zhang, Hong; Yin, Bin

2010-05-01

Field experiments are conducted separately in Taihu Lake and Chaohu Lake on Apr. and Jun. 2009. The changes in absorption spectra of chromophoric dissolved organic matter (CDOM) characteristics are analyzed using spectral differential analysis technology. According the spectral differential characteristic of absorption coefficient; absorption coefficient from 240 to 450 nm is divided into different stages, and the value of spectral slope S is calculated in each stage. In Stage A, S value of CDOM in Taihu Lake and Chaohu Lake are 0.0166-0.0102 nm(-1) [average (0.0132 +/- 0.0017) nm(-1)], 0.029-0.017 nm(-1) [average (0.0214 +/- 0.0024) nm(-1)]. In Stage B, S values are 0.0187-0.0148 nm(-1) [average (0.0169 +/- 0.001) nm(-1)], 0.0179-0.0055 nm(-1) [average (0.0148 +/- 0.002) nm(-1)]. In Stage C, S values are 0.0208-0.0164 nm(-1) [average (0.0186 +/- 0.0009) nm(-1)], 0.0253-0.0161 nm(-1) [average (0.0197 +/- 0.002) nm(-1)]. The results can be concluded as: (1) Absorption coefficient of water in Taihu Lake, and its contribution to absorption of each component is less than that of water in Chaohu Lake, however the standardized absorption coefficient is larger than that in Chaohu Lake. (2) Both in Taihu Lake and Chaohu Lake, derivative spectra of CDOM absorption coefficient reached valley at 260nm, then rise to top at 290 nm, CDOM absorption coefficient can be delivered into three stages. (3) Generally speaking, content of CDOM in Taihu Lake is less than in Chaohu Lake. (4) pectrum slope (S value) of CDOM is related to composition of CDOM, when content of humic acid in CDOM gets higher, S value of Stage B is the most sensitive value, then is the S value of Stage C. Oppositely, S value of Stage B gets the most sensitive value, then is the S value of Stage A; the least sensitive value is in Stage B.

Low-temperature MIR to submillimeter mass absorption coefficient of interstellar dust analogues. II. Mg and Fe-rich amorphous silicates

NASA Astrophysics Data System (ADS)

Demyk, K.; Meny, C.; Leroux, H.; Depecker, C.; Brubach, J.-B.; Roy, P.; Nayral, C.; Ojo, W.-S.; Delpech, F.

2017-10-01

Context. To model the cold dust emission observed in the diffuse interstellar medium, in dense molecular clouds or in cold clumps that could eventually form new stars, it is mandatory to know the physical and spectroscopic properties of this dust and to understand its emission. Aims: This work is a continuation of previous studies aiming at providing astronomers with spectroscopic data of realistic cosmic dust analogues for the interpretation of observations. The aim of the present work is to extend the range of studied analogues to iron-rich silicate dust analogues. Methods: Ferromagnesium amorphous silicate dust analogues were produced by a sol-gel method with a mean composition close to Mg1-xFexSiO3 with x = 0.1, 0.2, 0.3, 0.4. Part of each sample was annealed at 500 °C for two hours in a reducing atmosphere to modify the oxidation state of iron. We have measured the mass absorption coefficient (MAC) of these eight ferromagnesium amorphous silicate dust analogues in the spectral domain 30-1000 μm for grain temperature in the range 10-300 K and at room temperature in the 5-40 μm range. Results: The MAC of ferromagnesium samples behaves in the same way as the MAC of pure Mg-rich amorphous silicate samples. In the 30-300 K range, the MAC increases with increasing grain temperature whereas in the range 10-30 K, we do not see any change of the MAC. The MAC cannot be described by a single power law in λ- β. The MAC of the samples does not show any clear trend with the iron content. However the annealing process has, on average, an effect on the MAC that we explain by the evolution of the structure of the samples induced by the processing. The MAC of all the samples is much higher than the MAC calculated by dust models. Conclusions: The complex behavior of the MAC of amorphous silicates with wavelength and temperature is observed whatever the exact silicate composition (Mg vs. Fe amount). It is a universal characteristic of amorphous materials, and therefore of amorphous cosmic silicates, that should be taken into account in astronomical modeling. The enhanced MAC of the measured samples compared to the MAC calculated for cosmic dust model implies that dust masses are overestimated by the models. The tabulated mass absorption coefficients are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/606/A50

Seven years of aerosol scattering hygroscopic growth measurements from SGP: Factors influencing water uptake: Aerosol Scattering Hygroscopic Growth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jefferson, A.; Hageman, D.; Morrow, H.

Long-term measurements of changes in the aerosol scattering coefficient hygroscopic growth at the U.S. Department of Energy Southern Great Plains site provide information on the seasonal as well as size and chemical dependence of aerosol water uptake. Annual average sub-10 μm fRH values (the ratio of aerosol scattering at 85%/40% relative humidity (RH)) were 1.78 and 1.99 for the gamma and kappa fit algorithms, respectively. Our study found higher growth rates in the winter and spring seasons that correlated with a high aerosol nitrate mass fraction. fRH exhibited strong, but differing, correlations with the scattering Ångström exponent and backscatter fraction,more » two optical size-dependent parameters. The aerosol organic mass fraction had a strong influence on fRH. Increases in the organic mass fraction and absorption Ångström exponent coincided with a decrease in fRH. Similarly, fRH declined with decreases in the aerosol single scatter albedo. The uncertainty analysis of the fit algorithms revealed high uncertainty at low scattering coefficients and increased uncertainty at high RH and fit parameters values.« less

Seven years of aerosol scattering hygroscopic growth measurements from SGP: Factors influencing water uptake: Aerosol Scattering Hygroscopic Growth

DOE PAGES

Jefferson, A.; Hageman, D.; Morrow, H.; ...

2017-09-11

Long-term measurements of changes in the aerosol scattering coefficient hygroscopic growth at the U.S. Department of Energy Southern Great Plains site provide information on the seasonal as well as size and chemical dependence of aerosol water uptake. Annual average sub-10 μm fRH values (the ratio of aerosol scattering at 85%/40% relative humidity (RH)) were 1.78 and 1.99 for the gamma and kappa fit algorithms, respectively. Our study found higher growth rates in the winter and spring seasons that correlated with a high aerosol nitrate mass fraction. fRH exhibited strong, but differing, correlations with the scattering Ångström exponent and backscatter fraction,more » two optical size-dependent parameters. The aerosol organic mass fraction had a strong influence on fRH. Increases in the organic mass fraction and absorption Ångström exponent coincided with a decrease in fRH. Similarly, fRH declined with decreases in the aerosol single scatter albedo. The uncertainty analysis of the fit algorithms revealed high uncertainty at low scattering coefficients and increased uncertainty at high RH and fit parameters values.« less

Enhancement of gravimetric forced flow through system to determine sorption, swelling, and mass transfer characteristics of liquid sorbents

NASA Astrophysics Data System (ADS)

Dresp, G.; Petermann, M.; Fieback, T. M.

2018-04-01

An existing apparatus for forced flow through of liquid sorbents has been enhanced with an optically accessible system including a transparent crucible, high pressure viewing cell, and camera. With this optical system, the active surface area between gas and liquid can be determined in situ for the first time under industrial process conditions while maintaining the accuracy of a magnetic suspension balance. Additionally, occurring swelling and the resulting buoyancy changes can now be corrected, further improving the quality of the data. Validation measurements focusing on the sorption isotherms, swelling, and bubble geometry of 1-butyl-3-methylimidazolium tetrafluoroborate with nitrogen at 303 K and up to 17 MPa, as well as with carbon dioxide at 303 K, 323 K, and 373 K at up to 3.5 MPa were completed. Absorption of nitrogen resulted in no observable volume change, whereas absorption of carbon dioxide resulted in temperature independent swelling of up to 9.8%. The gas bubble's structure and behavior during its ascend through the liquid was optically tracked in situ. Combining these two data sets with the absorption kinetics forms the basis to determine the measuring system independent mass transfer coefficients, which are applicable in other laboratory scale and industrial processes.

Long term measurements of optical properties and their hygroscopic enhancement

NASA Astrophysics Data System (ADS)

Hervo, M.; Sellegri, K.; Pichon, J. M.; Roger, J. C.; Laj, P.

2014-11-01

Optical properties of aerosols were measured from the GAW Puy de Dôme station (1465 m) over a seven year period (2006-2012). The impact of hygroscopicity on aerosol optical properties was calculated over a two year period (2010-2011). The analysis of the spatial and temporal variability of the optical properties showed that while no long term trend was found, a clear seasonal and diurnal variation was observed on the extensive parameters (scattering, absorption). Scattering and absorption coefficients were highest during the warm season and daytime, in concordance with the seasonality and diurnal variation of the PBL height reaching the site. Intensive parameters (single scattering albedo, asymmetry factor, refractive index) did not show such a strong diurnal variability, but still indicated different values depending on the season. Both extensive and intensive optical parameters were sensitive to the air mass origin. A strong impact of hygroscopicity on aerosol optical properties was calculated, mainly on aerosol scattering, with a dependence on the aerosol type. At 90% humidity, the scattering factor enhancement (fσsca) was more than 4.4 for oceanic aerosol that have mixed with a pollution plume. Consequently, the aerosol radiative forcing was estimated to be 2.8 times higher at RH = 90% and 1.75 times higher at ambient RH when hygroscopic growth of the aerosol was considered. The hygroscopicity enhancement factor of the scattering coefficient was parameterized as a function of humidity and air mass type.

Thermally induced effect on sub-band gap absorption in Ag doped CdSe thin films

NASA Astrophysics Data System (ADS)

Kaur, Jagdish; Sharma, Kriti; Bharti, Shivani; Tripathi, S. K.

2015-05-01

Thin films of Ag doped CdSe have been prepared by thermal evaporation using inert gas condensation (IGC) method taking Argon as inert gas. The prepared thin films are annealed at 363 K for one hour. The sub-band gap absorption spectra in the as deposited and annealed thin films have been studied using constant photocurrent method (CPM). The absorption coefficient in the sub-band gap region is described by an Urbach tail in both as deposited and annealed thin films. The value of Urbach energy and number density of trap states have been calculated from the absorption coefficient in the sub-band gap region which have been found to increase after annealing treatment indicating increase in disorderness in the lattice. The energy distribution of the occupied density of states below Fermi level has also been studied using derivative procedure of absorption coefficient.

Tuning the nonlinear optical absorption in Au/BaTiO3 nanocomposites with gold nanoparticle concentration

NASA Astrophysics Data System (ADS)

Bijeesh, M. M.; Shakhi, P. K.; Varier, Geetha K.; Nandakumar, P.

2018-06-01

We report on the nonlinear optical absorption coefficient of Au/BaTiO3 nanocomposite films and its dependence on gold nanoparticle concentration. Au/BaTiO3 nanocomposite films with different molar ratio of Au/Ba are prepared by sol-gel technique and characterized by X-ray diffraction, UV Visible absorption spectroscopy and high resolution transmission electron microscopy. An open aperture Z-scan technique is employed to study the third order nonlinear optical properties of Au/BaTiO3 thin films. An Nd:YAG laser operating at 532 nm wavelength having a pulse width of 5 ns is used for the measurements. The two-photon absorption coefficient of the films increases linearly with gold nanoparticle concentration and significant enhancement of nonlinear optical absorption is observed. This ability to fine tune the nonlinear optical coefficients of Au/BaTiO3 films would be handy in optical device applications.

Quantitative broadband absorption and scattering spectroscopy in turbid media by combined frequency-domain and steady state methodologies

DOEpatents

Tromberg, Bruce J [Irvine, CA; Berger, Andrew J [Rochester, NY; Cerussi, Albert E [Lake Forest, CA; Bevilacqua, Frederic [Costa Mesa, CA; Jakubowski, Dorota [Irvine, CA

2008-09-23

A technique for measuring broadband near-infrared absorption spectra of turbid media that uses a combination of frequency-domain and steady-state reflectance methods. Most of the wavelength coverage is provided by a white-light steady-state measurement, whereas the frequency-domain data are acquired at a few selected wavelengths. Coefficients of absorption and reduced scattering derived from the frequency-domain data are used to calibrate the intensity of the steady-state measurements and to determine the reduced scattering coefficient at all wavelengths in the spectral window of interest. The absorption coefficient spectrum is determined by comparing the steady-state reflectance values with the predictions of diffusion theory, wavelength by wavelength. Absorption spectra of a turbid phantom and of human breast tissue in vivo, derived with the combined frequency-domain and steady-state technique, agree well with expected reference values.

Measurements of Nascent Soot Using a Cavity Attenauted Phase Shift (CAPS)-based Single Scattering Albedo Monitor

NASA Astrophysics Data System (ADS)

Freedman, A.; Onasch, T. B.; Renbaum-Wollf, L.; Lambe, A. T.; Davidovits, P.; Kebabian, P. L.

2015-12-01

Accurate, as compared to precise, measurement of aerosol absorption has always posed a significant problem for the particle radiative properties community. Filter-based instruments do not actually measure absorption but rather light transmission through the filter; absorption must be derived from this data using multiple corrections. The potential for matrix-induced effects is also great for organic-laden aerosols. The introduction of true in situ measurement instruments using photoacoustic or photothermal interferometric techniques represents a significant advance in the state-of-the-art. However, measurement artifacts caused by changes in humidity still represent a significant hurdle as does the lack of a good calibration standard at most measurement wavelengths. And, in the absence of any particle-based absorption standard, there is no way to demonstrate any real level of accuracy. We, along with others, have proposed that under the circumstance of low single scattering albedo (SSA), absorption is best determined by difference using measurement of total extinction and scattering. We discuss a robust, compact, field deployable instrument (the CAPS PMssa) that simultaneously measures airborne particle light extinction and scattering coefficients and thus the single scattering albedo (SSA) on the same sample volume. The extinction measurement is based on cavity attenuated phase shift (CAPS) techniques as employed in the CAPS PMex particle extinction monitor; scattering is measured using integrating nephelometry by incorporating a Lambertian integrating sphere within the sample cell. The scattering measurement is calibrated using the extinction measurement of non-absorbing particles. For small particles and low SSA, absorption can be measured with an accuracy of 6-8% at absorption levels as low as a few Mm-1. We present new results of the measurement of the mass absorption coefficient (MAC) of soot generated by an inverted methane diffusion flame at 630 nm. A value of 6.60 ±0.2 m2 g-1 was determined where the uncertainty refers to the precision of the measurement. The overall accuracy of the measurement, traceable to the properties of polystyrene latex particles, is estimated to be better than ±10%.

Optical band gap and spectroscopic study of lithium alumino silicate glass containing Y3+ ions.

PubMed

Shakeri, M S; Rezvani, M

2011-09-01

The effect of different amounts of Y2O3 dopant on lithium alumino silicate (LAS) glass has been studied in this work. Glasses having 14.8Li2O-20Al2O3-65.2SiO2 (wt%) composition accompanied with Y2O3 dopant were prepared by normal melting process. In order to calculate the absorption coefficient of samples, transmittance and reflectance spectra of polished samples were measured in the room temperature. Optical properties i.e. Fermi energy level, direct and indirect optical band gaps and Urbach energy were calculated using functionality of extinction coefficient from Fermi-Dirac distribution function, Tauc's plot and the exponential part of absorption coefficient diagram, respectively. It has been clarified that variation in mentioned optical parameters is associated with the changes in physical properties of samples i.e. density or molar mass. On the other hand, increasing of Y3+ ions in the glassy microstructure of samples provides a semiconducting character to LAS glass by reducing the direct and indirect optical band gaps of glass samples from 1.97 to 1.67 and 3.46 to 2.1 (eV), respectively. These changes could be attributed to the role of Y3+ ions as the network former in the track of SiO4 tetrahedrals. Copyright © 2011 Elsevier B.V. All rights reserved.

A frequency quantum interpretation of the surface renewal model of mass transfer

PubMed Central

Mondal, Chanchal

2017-01-01

The surface of a turbulent liquid is visualized as consisting of a large number of chaotic eddies or liquid elements. Assuming that surface elements of a particular age have renewal frequencies that are integral multiples of a fundamental frequency quantum, and further assuming that the renewal frequency distribution is of the Boltzmann type, performing a population balance for these elements leads to the Danckwerts surface age distribution. The basic quantum is what has been traditionally called the rate of surface renewal. The Higbie surface age distribution follows if the renewal frequency distribution of such elements is assumed to be continuous. Four age distributions, which reflect different start-up conditions of the absorption process, are then used to analyse transient physical gas absorption into a large volume of liquid, assuming negligible gas-side mass-transfer resistance. The first two are different versions of the Danckwerts model, the third one is based on the uniform and Higbie distributions, while the fourth one is a mixed distribution. For the four cases, theoretical expressions are derived for the rates of gas absorption and dissolved-gas transfer to the bulk liquid. Under transient conditions, these two rates are not equal and have an inverse relationship. However, with the progress of absorption towards steady state, they approach one another. Assuming steady-state conditions, the conventional one-parameter Danckwerts age distribution is generalized to a two-parameter age distribution. Like the two-parameter logarithmic normal distribution, this distribution can also capture the bell-shaped nature of the distribution of the ages of surface elements observed experimentally in air–sea gas and heat exchange. Estimates of the liquid-side mass-transfer coefficient made using these two distributions for the absorption of hydrogen and oxygen in water are very close to one another and are comparable to experimental values reported in the literature. PMID:28791137

[Near ultraviolet absorption spectral properties of chromophoric dissolved organic matter in the north area of Yellow Sea].

PubMed

Wang, Lin; Zhao, Dong-Zhi; Yang, Jian-Hong; Chen, Yan-Long

2010-12-01

Chromophoric dissolved organic matter (CDOM) near ultraviolet absorption spectra contains CDOM molecular structure, composition and other important physical and chemical information. Based on the measured data of CDOM absorption coefficient in March 2009 in the north area of Yellow Sea, the present paper analyzed near ultraviolet absorption spectral properties of CDOM. The results showed that due to the impact of near-shore terrigenous input, the composition of CDOM is quite different in the north area of Yellow Sea, and this area is a typical case II water; fitted slope with specific range of spectral band and absorption coefficient at specific band can indicate the relative size of CDOM molecular weight, correlation between spectral slope of the Sg,275-300), Sg,300-350, Sg,350-400 and Sg,250-275 and the relative size of CDOM molecular weight indicative parameter M increases in turn and the highest is up to 0.95. Correlation between a(g)(lambda) and M value increases gradually with the increase in wavelength, and the highest is up to 0.92 at 400 nm; being correlated or not between spectral slope and absorption coefficient is decided by the fitting-band wavelength range for the spectra slope and the wavelength for absorption coefficient. Correlation between Sg,275-300 and a(g)(400) is the largest, up to 0.87.

During air cool process aerosol absorption detection with photothermal interferometry

NASA Astrophysics Data System (ADS)

Li, Baosheng; Xu, Limei; Huang, Junling; Ma, Fei; Wang, Yicheng; Li, Zhengqiang

2014-11-01

This paper studies the basic principle of laser photothermal interferometry method of aerosol particles absorption coefficient. The photothermal interferometry method with higher accuracy and lower uncertainty can directly measure the absorption coefficient of atmospheric aerosols and not be affected by scattered light. With Jones matrix expression, the math expression of a special polarization interferometer is described. This paper using folded Jamin interferometer, which overcomes the influence of vibration on measuring system. Interference come from light polarization beam with two orthogonal and then combine to one beam, finally aerosol absorption induced refractive index changes can be gotten with four beam of phase orthogonal light. These kinds of styles really improve the stability of system and resolution of the system. Four-channel detections interact with interference fringes, to reduce the light intensity `zero drift' effect on the system. In the laboratory, this device typical aerosol absorption index, it shows that the result completely agrees with actual value. After heated by laser, cool process of air also show the process of aerosol absorption. This kind of instrument will be used to monitor ambient aerosol absorption and suspended particulate matter chemical component. Keywords: Aerosol absorption coefficient; Photothermal interferometry; Suspended particulate matter.

[The Lambert-Beer's law characterization of formal analysis in Terahertz spectrum quantitative testing].

PubMed

Su, Hai-Xia; Zhang, Zhao-Hui; Zhao, Xiao-Yan; Li, Zhi; Yan, Fang; Zhang, Han

2013-12-01

The present paper discusses the Lambert-Beer' s law application in the terahertz spectrum, studies the single amino acid tablet sample (glutamine) and two kinds of amino acids mixture tablet (threonine and cystine) under the condition of different concentrations. Absorbance and absorption coefficient was analyzed in the description of the terahertz optical properties of matter. By comparing absorption coefficient and absorbance value of the single component in the vicinity of 1. 72 THz, we verified the material under two kinds of absorption characterization of quantity of THz wave absorption along with the change in the concentration. Using the index of goodness of fit R , it studied the stand or fall of linear relationship between the terahertz absorption quantity of material and concentration under two kinds of representation. This paper analyzes the two components mixture under two kinds of absorption characterization of quantity of terahertz absorption in 0. 3-2. 6 THz. Using the similarity co- efficient and the estimate concentration error as evaluation index, it has been clear that the absorbance of additivity instead of the absorption coefficient should be used during the terahertz spectrum quantitative test, and the Lambert-Beer's law application in the terahertz wave band was further clarified.

The absorption characteristics of the human cornea in ultraviolet-a crosslinking.

PubMed

Koppen, Carina; Gobin, Laure; Tassignon, Marie-José

2010-03-01

With respect to the safety of ultraviolet-A (UVA) crosslinking for the corneal endothelium, an absorption coefficient is used that has been calculated in riboflavin soaked porcine corneas. We aim to validate this value for clinical use by measuring the absorption coefficient for UVA 365 nm in postmortem human corneas after instilling riboflavin on the corneal surface. Corneal thickness was measured in nine pairs of human donor eyes of which one eye was subjected to manual removal of the epithelium, whereas the epithelium of the fellow eye was left intact. Both eyes were instilled with riboflavin 0.1% in dextran 20% on the intact globe. After 20 min, the corneas were rinsed, and a corneoscleral button was trephined. The transmission of the cornea for UVA 365 nm was measured by transillumination, which allows calculation of the absorption coefficient. Measurement of average corneal thickness was 658.5 +/- 51.5 microm when the epithelium was removed, and 758.3 +/- 98.8 microm without epithelial removal. The average transmittance for UVA 365 nm was 12.89 +/- 4.10% with epithelial debridement and 28.52 +/- 4.39% without (P<0.05). The resultant average absorption coefficient is 32 +/- 5 cm when the epithelium is removed and 17 +/- 2 cm when it is left intact (P<0.05). Our results show an absorption coefficient for human corneas that is much lower than the values reported in the literature. This finding may be relevant when considering endothelial safety of the clinical crosslinking treatment.

Mean absorption coefficients of He/Ar/N2/(C1-x-y , Ni x , Co y ) thermal plasmas for CNT synthesis

NASA Astrophysics Data System (ADS)

Salem, D.; Hannachi, R.; Cressault, Y.; Teulet, Ph; Béji, L.

2017-01-01

In this paper, we present the mean absorption coefficients (MACs) calculated for plasma mixtures of argon-helium-nitrogen-carbon-nickel-cobalt at 60 kPa and in a temperature range from 1 kK to 20 kK. These coefficients have been computed under the assumption of a local thermodynamic equilibrium (LTE), isothermal plasma, including atomic and molecular continuum, molecular bands and lines radiation splitted into nine spectral intervals. The results show that the continuum absorption coefficients strongly depend on photodissociation and photoionization processes of the molecular species N2, CN and C2, with a significant effect on photodetachment processes of C- in a frequency interval lower than 1  ×  1015 Hz and for low temperature (<6 kK). While at high temperature, the main contribution in continuum absorption coefficient comes from radiative recombination processes except in the infrared region (<0.5  ×  1015 Hz) where the inverse bremsstrahlung represents the most important component in continuum processes for all temperature values. On the other hand, the calculation of MAC shows that the role of molecular continuum, molecular bands and line absorption of the neutral catalysis species Ni/Co are only important in a small range of temperature and in a few spectral bands located in visible and infrared regions, while at high temperature and in UV and visible regions, the foremost contributions to MAC come from atomic continuum and line absorption.

Resonant behaviour of MHD waves on magnetic flux tubes. I - Connection formulae at the resonant surfaces. II - Absorption of sound waves by sunspots

NASA Technical Reports Server (NTRS)

Sakurai, Takashi; Goossens, Marcel; Hollweg, Joseph V.

1991-01-01

The present method of addressing the resonance problems that emerge in such MHD phenomena as the resonant absorption of waves at the Alfven resonance point avoids solving the fourth-order differential equation of dissipative MHD by recourse to connection formulae across the dissipation layer. In the second part of this investigation, the absorption of solar 5-min oscillations by sunspots is interpreted as the resonant absorption of sounds by a magnetic cylinder. The absorption coefficient is interpreted (1) analytically, under certain simplifying assumptions, and numerically, under more general conditions. The observed absorption coefficient magnitude is explained over suitable parameter ranges.

Electromagnetic absorption behaviour of ferrite loaded three phase carbon fabric composites

NASA Astrophysics Data System (ADS)

Jagatheesan, Krishnasamy; Ramasamy, Alagirusamy; Das, Apurba; Basu, Ananjan

2018-02-01

This article investigates the electromagnetic absorption behaviours of carbon helical yarn fabric reinforced composites and manganese-zinc (Mn-Zn) ferrite particles loaded 3 phase fabric composites. A carbon helical yarn having stainless steel core was prepared and made into single jersey knitted fabric. The composite was prepared by sandwiching a fabric with polypropylene films and thermal pressed. The absorption values of helical yarn fabric composite was observed to be less in the C band region (4-8 GHz). For improving the absorption coefficients of composite, Mn-Zn ferrite particles were dispersed in the polypropylene (PP) composite. The ferrite loaded PP composites exhibited better permittivity and permeability values, hence the absorption loss of the composite was improved. The helical yarn fabric reinforced with Mn-Zn ferrite/PP composite showed larger absorption coefficients than virgin PP/fabric composite. The change in thermal stability and particle size distribution in the Mn-Zn ferrite/PP composite was also analyzed. At higher ferrite concentration, bimodal particle distribution was observed which increased the conductivity and shielding effectiveness (SE) of the composite. In addition, complex permittivity value was also increased for higher incident frequency (4-8 GHz). As the ferrite content increases, the dielectric loss and magnetic permeability of PP/ferrite increases due to increased magnetic loss. Hence, ferrite loaded PP composite showed the total SE of -14.2 dB with the absorption coefficients of 0.717. The S1C7 fabric composite having ferrite dispersion showed the better absorption loss and lower reflection coefficient of 14.2 dB and 0.345 respectively compared to virgin PP/helical yarn fabric composite. The increasing ferrite content (45 wt%) improved the absorption loss and total SE. Though, ferrite based fabric composite exhibits moderate absorptive shielding, it can be used as shielding panels in the electronic industries.

Effects of Combined Surface and In-Depth Absorption on Ignition of PMMA

PubMed Central

Gong, Junhui; Chen, Yixuan; Li, Jing; Jiang, Juncheng; Wang, Zhirong; Wang, Jinghong

2016-01-01

A one-dimensional numerical model and theoretical analysis involving both surface and in-depth radiative heat flux absorption are utilized to investigate the influence of their combination on ignition of PMMA (Polymethyl Methacrylate). Ignition time, transient temperature in a solid and optimized combination of these two absorption modes of black and clear PMMA are examined to understand the ignition mechanism. Based on the comparison, it is found that the selection of constant or variable thermal parameters of PMMA barely affects the ignition time of simulation results. The linearity between tig−0.5 and heat flux does not exist anymore for high heat flux. Both analytical and numerical models underestimate the surface temperature and overestimate the temperature in a solid beneath the heat penetration layer for pure in-depth absorption. Unlike surface absorption circumstances, the peak value of temperature is in the vicinity of the surface but not on the surface for in-depth absorption. The numerical model predicts the ignition time better than the analytical model due to the more reasonable ignition criterion selected. The surface temperature increases with increasing incident heat flux. Furthermore, it also increases with the fraction of surface absorption and the radiative extinction coefficient for fixed heat flux. Finally, the combination is optimized by ignition time, temperature distribution in a solid and mass loss rate. PMID:28773940

Effects of Combined Surface and In-Depth Absorption on Ignition of PMMA.

PubMed

Gong, Junhui; Chen, Yixuan; Li, Jing; Jiang, Juncheng; Wang, Zhirong; Wang, Jinghong

2016-10-05

A one-dimensional numerical model and theoretical analysis involving both surface and in-depth radiative heat flux absorption are utilized to investigate the influence of their combination on ignition of PMMA (Polymethyl Methacrylate). Ignition time, transient temperature in a solid and optimized combination of these two absorption modes of black and clear PMMA are examined to understand the ignition mechanism. Based on the comparison, it is found that the selection of constant or variable thermal parameters of PMMA barely affects the ignition time of simulation results. The linearity between t ig -0.5 and heat flux does not exist anymore for high heat flux. Both analytical and numerical models underestimate the surface temperature and overestimate the temperature in a solid beneath the heat penetration layer for pure in-depth absorption. Unlike surface absorption circumstances, the peak value of temperature is in the vicinity of the surface but not on the surface for in-depth absorption. The numerical model predicts the ignition time better than the analytical model due to the more reasonable ignition criterion selected. The surface temperature increases with increasing incident heat flux. Furthermore, it also increases with the fraction of surface absorption and the radiative extinction coefficient for fixed heat flux. Finally, the combination is optimized by ignition time, temperature distribution in a solid and mass loss rate.

Mapping Surface Water DOC in the Northern Gulf of Mexico Using CDOM Absorption Coefficients and Remote Sensing Imagery

NASA Astrophysics Data System (ADS)

Kelly, B.; Chelsky, A.; Bulygina, E.; Roberts, B. J.

2017-12-01

Remote sensing techniques have become valuable tools to researchers, providing the capability to measure and visualize important parameters without the need for time or resource intensive sampling trips. Relationships between dissolved organic carbon (DOC), colored dissolved organic matter (CDOM) and spectral data have been used to remotely sense DOC concentrations in riverine systems, however, this approach has not been applied to the northern Gulf of Mexico (GoM) and needs to be tested to determine how accurate these relationships are in riverine-dominated shelf systems. In April, July, and October 2017 we sampled surface water from 80+ sites over an area of 100,000 km2 along the Louisiana-Texas shelf in the northern GoM. DOC concentrations were measured on filtered water samples using a Shimadzu TOC-VCSH analyzer using standard techniques. Additionally, DOC concentrations were estimated from CDOM absorption coefficients of filtered water samples on a UV-Vis spectrophotometer using a modification of the methods of Fichot and Benner (2011). These values were regressed against Landsat visible band spectral data for those same locations to establish a relationship between the spectral data, CDOM absorption coefficients. This allowed us to spatially map CDOM absorption coefficients in the Gulf of Mexico using the Landsat spectral data in GIS. We then used a multiple linear regressions model to derive DOC concentrations from the CDOM absorption coefficients and applied those to our map. This study provides an evaluation of the viability of scaling up CDOM absorption coefficient and remote-sensing derived estimates of DOC concentrations to the scale of the LA-TX shelf ecosystem.

Absorption properties of chromophoric dissolved organic matter (CDOM) in the East China Sea and the waters off eastern Taiwan

NASA Astrophysics Data System (ADS)

Zhou, Fengxia; Gao, Xuelu; Song, Jinming; Chen, Chen-Tung Arthur; Yuan, Huamao; Xing, Qianguo

2018-05-01

The absorption properties of chromophoric dissolved organic matter (CDOM) in the East China Sea (ECS) and the waters off eastern Taiwan (WET) were studied during May 2014. CDOM absorption coefficient (a280) and spectral slope (S275-295) revealed considerable spatial variations. In the ECS, the values of a280 and S275-295 presented a reverse distribution pattern. In the WET, a280 values were generally low while S275-295 values were generally high. Vertical distributions of a280 and S275-295 also varied in different regions. Terrestrial input, phytoplankton production, sediment release or photobleaching may be responsible for the dynamics of CDOM. Relationships among CDOM related parameters could partly support this conclusion. a280 were also used to trace different water masses and the result showed that the influence of Changjiang Diluted Water could reach the outer shelf of the northern ECS, and that the Kuroshio Current had a strong influence on the middle shelf of the southern ECS.

Radiation effects on beta /10.6/ of pure and europium doped KCl

NASA Technical Reports Server (NTRS)

Grimes, H. H.; Maisel, J. E.; Hartford, R. H.

1975-01-01

Changes in the optical absorption coefficient as the result of X-ray and electron bombardment of pure monocrystalline and polycrystalline KCl and of divalent europium doped polycrystalline KCl were determined. A constant heat flow calorimetric method was used to measure the optical absorption coefficients. Both 300 kV X-ray irradiation and 2 MeV electron irradiation produced increases in the optical absorption coefficient at room temperature. X-ray irradiation produced more significant changes in pure monocrystalline KCl than equivalent amounts of electron irradiation. Electron irradiation of pure and Eu-doped polycrystalline KCl produced increases in the absorption by as much as a factor of 20 over untreated material. Bleaching of the electron-irradiated doped KCl with 649 millimicron light produced a further increase.

[Optical characteristics of colored dissolved organic material (CDOM) in Yangtze Estuary].

PubMed

Zhu, Wei-Jian; Shen, Fang; Hong, Guan-Lin

2010-10-01

Absorption property of colored dissolved organic material (CDOM) is one of the most important contents to remote sensing of ocean color in estuarine and coastal areas. In this study, the optical properties and mixing behavior of CDOM in surface water of Yangtze Estuary were discussed according to the two surveys in August of 2008 and May of 2009. Based on the research, the absorption coefficient and spectral slope were discussed. It was found that in summer of 2008 CDOM absorption coefficients at 440 nm [a(g) (440)], ranged from 0.20 m(-1) to 0.73 m(-1), while the coefficients in 2009 varied between 0.20 m(-1) and 0.77 m(-1). Statistics showed that the power function model fitted the best in the regression analysis of CDOM absorption spectral. The spectral slopes (S(g2)) of CDOM calculated by the power function model ranged from 5.10 to 7.90 in Summer of 2008 and from 2.95 to 6.11 in Spring of 2009. The highest absorption coefficients of two cruises appeared both in the south passage of the Yangtze Estuary. The absorption coefficient in surfer water was observed varied tremendously in the estuary and the offshore area. And the main reason is affected by the turbidity maximum zone. It is observed that the absorption coefficients of CDOM tended to a homogeneous distribution whilst the layers of water mixed tempestuously, but otherwise it always showed a conservative mixing behavior. Because of the frequent mixture, there is not assured correlativity between S(g2) and a(g) (440). In the offshore area of Yangtze Estuary, the effecting of local production cannot be negligent, which differed from the estuary area. Yet when the hydrological environment was relatively stable, the negative relationship between them was very clear. In conclusion, the optical properties and mixing behavior of CDOM had showed tremendous different characteristics from inside the estuary to outside the estuary because of the influence of complex physical, chemical and hydrology conditions.

Estimation of water absorption coefficient using the TDR method

NASA Astrophysics Data System (ADS)

Suchorab, Zbigniew; Majerek, Dariusz; Brzyski, Przemysław; Sobczuk, Henryk; Raczkowski, Andrzej

2017-07-01

Moisture accumulation and transport in the building barriers is an important feature that influences building performance, causing serious exploitation problems as increased energy use, mold and bacteria growth, decrease of indoor air parameters that may lead to sick building syndrome (SBS). One of the parameters that is used to describe moisture characteristic of the material is water absorption coefficient being the measure of capillary behavior of the material as a function of time and the surface area of the specimen. As usual it is determined using gravimetric methods according to EN 1925:1999 standard. In this article we demonstrate the possibility of determination of water absorption coefficient of autoclaved aerated concrete (AAC) using the Time Domain Reflectometry (TDR) method. TDR is an electric technique that had been adopted from soil science and can be successfully used for real-time monitoring of moisture transport in building materials and envelopes. Data achieved using TDR readouts show high correlation with standard method of moisture absorptivity coefficient determination.

EFFECTS OF LASER RADIATION ON MATTER: Photoinduced absorption in chalcogenide glasses

NASA Astrophysics Data System (ADS)

Ponomar', V. V.

1990-08-01

A dependence of the absorption coefficient on the optical radiation intensity in the range 10 - 5 - 1 W/cm2 was observed for chalcogenide glasses at a photon energy less than the band gap of the material. The absorption coefficient depended on the irradiation time. In the case of arsenic sulfide in the range 1.6-1.7 eV an absorption peak was observed at intensities of the order of 10 - 3 W/cm2. In this part of the spectrum the absorption probably involved metastable As-As, S-Se, and Se-Se "defect" bonds and was similar to the photoinduced degradation of hydrogenated amorphous silicon.

Mixed convection and heat generation/absorption aspects in MHD flow of tangent-hyperbolic nanoliquid with Newtonian heat/mass transfer

NASA Astrophysics Data System (ADS)

Qayyum, Sajid; Hayat, Tasawar; Shehzad, Sabir Ali; Alsaedi, Ahmed

2018-03-01

This article concentrates on the magnetohydrodynamic (MHD) stagnation point flow of tangent hyperbolic nanofluid in the presence of buoyancy forces. Flow analysis caused due to stretching surface. Characteristics of heat transfer are examined under the influence of thermal radiation and heat generation/absorption. Newtonian conditions for heat and mass transfer are employed. Nanofluid model includes Brownian motion and thermophoresis. The governing nonlinear partial differential systems of the problem are transformed into a systems of nonlinear ordinary differential equations through appropriate variables. Impact of embedded parameters on the velocity, temperature and nanoparticle concentration fields are presented graphically. Numerical computations are made to obtain the values of skin friction coefficient, local Nusselt and Sherwood numbers. It is concluded that velocity field enhances in the frame of mixed convection parameter while reverse situation is observed due to power law index. Effect of Brownian motion parameter on the temperature and heat transfer rate is quite reverse. Moreover impact of solutal conjugate parameter on the concentration and local Sherwood number is quite similar.

Water equivalence of NIPAM based polymer gel dosimeters with enhanced sensitivity for x-ray CT

NASA Astrophysics Data System (ADS)

Gorjiara, Tina; Hill, Robin; Bosi, Stephen; Kuncic, Zdenka; Baldock, Clive

2013-10-01

Two new formulations of N-isopropylacrylamide (NIPAM) based three dimensional (3D) gel dosimeters have recently been developed with improved sensitivity to x-ray CT readout, one without any co-solvent and the other one with isopropanol co-solvent. The water equivalence of the NIPAM gel dosimeters was investigated using different methods to calculate their radiological properties including: density, electron density, number of electrons per grams, effective atomic number, photon interaction probabilities, mass attenuation and energy absorption coefficients, electron collisional, radiative and total mass stopping powers and electron mass scattering power. Monte Carlo modelling was also used to compare the dose response of these gel dosimeters with water for kilovoltage and megavoltage x-ray beams and for megavoltage electron beams. We found that the density and electron density of the co-solvent free gel dosimeter are more water equivalent with less than a 2.6% difference compared to a 5.7% difference for the isopropanol gel dosimeter. Both the co-solvent free and isopropanol solvent gel dosimeters have lower effective atomic numbers than water, differing by 2.2% and 6.5%, respectively. As a result, their photoelectric absorption interaction probabilities are up to 6% and 19% different from water, respectively. Compton scattering and pair production interaction probabilities of NIPAM gel with isopropanol differ by up to 10% from water while for the co-solvent free gel, the differences are 3%. Mass attenuation and energy absorption coefficients of the co-solvent free gel dosimeter and the isopropanol gel dosimeter are up to 7% and 19% lower than water, respectively. Collisional and total mass stopping powers of both gel dosimeters differ by less than 2% from those of water. The dose response of the co-solvent free gel dosimeter is water equivalent (with <1% discrepancy) for dosimetry of x-rays with energies <100 keV while the discrepancy increases (up to 5%) for the isopropanol gel dosimeter over the same energy range. For x-ray beams over the energy range 180 keV-18 MV, both gel dosimeters have less than 2% discrepancy with water. For megavoltage electron beams, the dose differences with water reach 7% and 14% for the co-solvent free gel dosimeter and the isopropanol gel dosimeter, respectively. Our results demonstrate that for x-ray beam dosimetry with photon energies higher than 100 keV and megavoltage electron beams, correction factors are needed for both NIPAM gels to be used as water equivalent dosimeters.

On the eccentricity effects on the intraband optical transitions in two dimensional quantum rings with and without donor impurity

NASA Astrophysics Data System (ADS)

Nasri, Djillali

2018-07-01

Using the plane wave expansion in the frame of the effective mass approximation, a straightforward method is presented to calculate the energy levels and the corresponding wavefunctions in a two dimensional GaAs/AlxGa1-xAs eccentric quantum rings (QRs) with and without donor impurity. The transition energy and their related optical absorption coefficients are calculated. The obtained results show that the transition energy between the ground state and the first two excited states and their related optical matrix are strongly influenced by the eccentricity and the donor position. The resonant peaks of the absorption coefficients for electron are blueshifted, while for QRs with an off center impurity the resonant peaks are red or blueshifted depending on the donor positions and eccentricity. In addition, we have found that a small eccentricity acts on the QRs qualitatively as a weak radial electric field. Moreover, an electric field is no longer able to reproduce perfectly the eccentricity effect when the eccentricity becomes relatively strong. Finally, our results are qualitatively similar to those reported in recent works dealing with concentric QRs under a radial electric field.

Synthesis and characterization of surface-modified colloidal CdTe Quantum Dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajh, T.; Micic, O.I.; Nozik, A.J.

1993-11-18

The controlled synthesis of quantized colloidal CdTe nanocrystals (in aqueous solutions) with narrow size distributions and stabilized against rapid oxidation was achieved by capping the quantum dot particles with 3-mercapto-1,2-propanediol. Nanocrystals (i.e., quantum dots) with mean diameters of 20, 25, 35, and 40 A were produced. Optical absorption spectra showed strong excitonic peaks at the smallest size; the absorption coefficient was shown to follow an inverse cube dependence on particle diameter, while the extinction coefficient per particle remained constant. The quantum yield for photoluminescence increased with decreasing particle size and reached 20% at 20 A. The valence band edges ofmore » the CdTe quantum dots were determined by pulse radiolysis experiments (hole injection from oxidizing radicals); the bandgaps were estimated from pulse radiolysis data (redox potentials of hole and electron injecting radicals) and from the optical spectra. The dependence of the CdTe bandgap on quantum dot size was found to be much weaker than predicted by the effective mass approximation; this result is consistent with recently published theoretical calculations by several groups. 36 refs., 5 figs., 1 tab.« less

Nonlinear optical response in a zincblende GaN cylindrical quantum dot with donor impurity center

NASA Astrophysics Data System (ADS)

Hoyos, Jaime H.; Correa, J. D.; Mora-Ramos, M. E.; Duque, C. A.

2016-03-01

We calculate the nonlinear optical absorption coefficient of a cylindrical zincblende GaN-based quantum dot. For this purpose, we consider Coulomb interactions between electrons and an impurity ionized donor atom. The electron-donor-impurity spectrum and the associated quantum states are calculated using the effective mass approximation with a parabolic potential energy model describing both the radial and axial electron confinement. We also include the effects of the hydrostatic pressure and external electrostatic fields. The energy spectrum is obtained through an expansion of the eigenstates as a linear combination of Gaussian-type functions which reduces the computational effort since all the matrix elements are obtained analytically. Therefore, the numerical problem is reduced to the direct diagonalization of the Hamiltonian. The obtained energies are used in the evaluation of the dielectric susceptibility and the nonlinear optical absorption coefficient within a modified two-level approach in a rotating wave approximation. This quantity is investigated as a function of the quantum dot dimensions, the impurity position, the external electric field intensity and the hydrostatic pressure. The results of this research could be important in the design and fabrication of zincblende GaN-quantum-dot-based electro-optical devices.

Improved oral bioavailability of 20(R)-25-methoxyl-dammarane-3β, 12β, 20-triol using nanoemulsion based on phospholipid complex: design, characterization, and in vivo pharmacokinetics in rats

PubMed Central

Zhang, Xiangrong; Zhang, Yi; Guo, Shuang; Bai, Feifei; Wu, Tong; Zhao, Yuqing

2016-01-01

The aim of the study was to improve the oral absorption of the compound 25-OCH3-PPD with poor hydrophilicity and lipophilicity. 25-OCH3-PPD-phospholipid complex was prepared by solvent evaporation, then characterized by differential scanning calorimetry, scanning electron microscopy, and infrared absorption spectroscopy. The aqueous solubility and oil–water partition coefficient were compared with the free compound. A nanoemulsion loaded with 25-OCH3-PPD-phospholipid complex was developed by dissolving the complex in water in the presence of hydrophilic surfactant under sonication. After oral administration of the nanoemulsion and the suspension of 25-OCH3-PPD in rats, the concentrations of 25-OCH3-PPD in plasma were determined by high-performance liquid chromatography–tandem mass spectrometry method. The results showed that the solubility of the complex in water and n-octanol was enhanced. The oil–water partition coefficient improved 1.7 times. Peak plasma concentration and area under the curve(0–24 h) of the nanoemulsion of 25-OCH3-PPD-phospholipid complex were higher than that of free compound by 3.9- and 3.5-folds. PMID:27877020

Pegylated G-CSF Inhibits Blood Cell Depletion, Increases Platelets, Blocks Splenomegaly, and Improves Survival after Whole-Body Ionizing Irradiation but Not after Irradiation Combined with Burn

DTIC Science & Technology

2014-03-05

increased granulocyte colony stim- ulating factor (G-CSF) in mouse blood for more than 7 days [7]. The increase was initially believed to be a self ...hematopoietic stem cell mobilization from the bone marrow into the bloodstream. It is involved in recovery from infection [11, 12] and wound healing [13]. Peg-G...mapping data; corrections for the 60Co decay and the small differences in the mass energy absorption coefficients for water and soft tissue were

Study of electron-related intersubband optical properties in three coupled quantum wells wires with triangular transversal section

NASA Astrophysics Data System (ADS)

Tiutiunnyk, A.; Tulupenko, V.; Akimov, V.; Demediuk, R.; Morales, A. L.; Mora-Ramos, M. E.; Radu, A.; Duque, C. A.

2015-11-01

This work concerns theoretical study of confined electrons in a low-dimensional structure consisting of three coupled triangular GaAs/AlxGa1-xAs quantum wires. Calculations have been made in the effective mass and parabolic band approximations. In the calculations a diagonalization method to find the eigenfunctions and eigenvalues of the Hamiltonian was used. A comparative analysis of linear and nonlinear optical absorption coefficients and the relative change in the refractive index was made, which is tied to the intersubband electron transitions.

Wavelength and energy dependent absorption of unconventional fuel mixtures

NASA Astrophysics Data System (ADS)

Khan, N.; Saleem, Z.; Mirza, A. A.

2005-11-01

Economic considerations of laser induced ignition over the normal electrical ignition of direct injected Compressed Natural Gas (CNG) engines has motivated automobile industry to go for extensive research on basic characteristics of leaner unconventional fuel mixtures to evaluate practical possibility of switching over to the emerging technologies. This paper briefly reviews the ongoing research activities on minimum ignition energy and power requirements of natural gas fuels and reports results of present laser air/CNG mixture absorption coefficient study. This study was arranged to determine the thermo-optical characteristics of high air/fuel ratio mixtures using laser techniques. We measured the absorption coefficient using four lasers of multiple wavelengths over a wide range of temperatures and pressures. The absorption coefficient of mixture was found to vary significantly over change of mixture temperature and probe laser wavelengths. The absorption coefficients of air/CNG mixtures were measured using 20 watts CW/pulsed CO2 laser at 10.6μm, Pulsed Nd:Yag laser at 1.06μm, 532 nm (2nd harmonic) and 4 mW CW HeNe laser at 645 nm and 580 nm for temperatures varying from 290 to 1000K using optical transmission loss technique.

Absorption and radiation of nonminimally coupled scalar field from charged BTZ black hole

NASA Astrophysics Data System (ADS)

Huang, Lu; Chen, Juhua; Wang, Yongjiu

2018-06-01

In this paper we investigate the absorption and radiation of nonminimally coupled scalar field from the charged BTZ black hole. We find the analytical expressions for the reflection coefficient, the absorption cross section and the decay rate in strong coupling case. We find that the reflection coefficient is directly governed by Hawking temperature TH, scalar wave frequency ω , Bekenstein-Hawking entropy S_{BH}, angular momentum m and coupling constant ξ.

Preparation of Oxidation-Resistant Ultra High Melting Temperature Materials and Structures Using Laser Method

DTIC Science & Technology

2009-06-06

sample within a small ceramic muffle. The microwave absorption coefficient of most ceramics is low, but increases with temperature. Thus, as the...increased using additives with higher absorption 7 coefficients . Silicon carbide has a higher loss tangent at 2.4 GHz than most ceramics, and thus...electron beam sintering. Microwave heating works well for large volumes, but ceramics normally have a low dielectric absorption constant at room

Light absorption and the photoformation of hydroxyl radical and singlet oxygen in fog waters

NASA Astrophysics Data System (ADS)

Kaur, R.; Anastasio, C.

2017-09-01

The atmospheric aqueous-phase is a rich medium for chemical transformations of organic compounds, in part via photooxidants generated within the drops. Here we measure light absorption, photoformation rates and steady-state concentrations of two photooxidants - hydroxyl radical (•OH) and singlet molecular oxygen (1O2*) - in 8 illuminated fog waters from Davis, California and Baton Rouge, Louisiana. Mass absorption coefficients for dissolved organic compounds (MACDOC) in the samples are large, with typical values of 10,000-15,000 cm2 g-C-1 at 300 nm, and absorption extends to wavelengths as long as 450-600 nm. While nitrite and nitrate together account for an average of only 1% of light absorption, they account for an average of 70% of •OH photoproduction. Mean •OH photoproduction rates in fogs at the two locations are very similar, with an overall mean of 1.2 (±0.7) μM h-1 under Davis winter sunlight. The mean (±1σ) lifetime of •OH is 1.6 (±0.6) μs, likely controlled by dissolved organic compounds. Including calculated gas-to-drop partitioning of •OH, the average aqueous concentration of •OH is approximately 2 × 10-15 M (midday during Davis winter), with aqueous reactions providing approximately one-third of the hydroxyl radical source. At this concentration, calculated lifetimes of aqueous organics are on the order of 10 h for compounds with •OH rate constants of 1 × 1010 M-1 s-1 or higher (e.g., substituted phenols such as syringol (6.4 h) and guaiacol (8.4 h)), and on the order of 100 h for compounds with rate constants near 1 × 109 M-1 s-1 (e.g., isoprene oxidation products such as glyoxal (152 h), glyoxylic acid (58 h), and pyruvic acid (239 h)). Steady-state concentrations of 1O2* are approximately 100 times higher than those of •OH, in the range of (0.1-3.0) × 10-13 M. Since 1O2* is a more selective oxidant than •OH, it will only react appreciably with electron-rich species such as dimethyl furan (lifetime of 2.0 h) and substituted polycyclic aromatic hydrocarbons (e.g., 9,10-dimethylbenz[a]anthracene with a lifetime of 0.7 h). Comparing our current Davis samples with Davis fogs collected in the late 1990s shows a decrease in dissolved organic carbon content, similar mass absorption coefficients, lower •OH concentrations, but very similar 1O2* concentrations.

Laboratory Measurements of Mass Specific Absorption Spectra for Suites of Black Carbon-like, Biomass Burning and Mineral Dust Aerosols

NASA Astrophysics Data System (ADS)

Radney, J.; Zangmeister, C.

2017-12-01

Light-absorbing atmospheric aerosols can be grouped into three categories: black carbon (BC), brown carbon (BrC) or mineral dust (MD). In many cases, the absorption of these species is best quantified using a mass-specific absorption cross section (MAC) since the particles are in the Rayleigh regime (BC) or optically thin (BrC and MD); notably, MAC values are both traceable to the SI and transferrable between photoacoustic spectroscopy and filter-based absorption measurements. Here, we present laboratory measurements of MAC for all three light-absorbing aerosol classes. Particles were size- and mass-selected using a differential mobility analyzer and aerosol particle mass analyzer, respectively, with absorption coefficients (αabs) and number concentrations (N) being measured by a broadband photoacoustic spectrometer and condensation particle counter, respectively. This suite of instrumentation allows for direct quantification of MAC from the measured parameters (MAC = αabs/Nmp). Further, the measurements contained > 8 data points spanning λ = 405 nm to 840 nm allowing for spectral curvatures (i.e. the Absorption Angstrom Exponent or AAE) to be fit from many data points versus the more common 2-point interpolations. For the carbonaceous, BC-like aerosols - five samples generated from flames, spark discharge soot (i.e. fullerene soot), graphene, reduced graphene oxide (rGO), and fullerene (C60) - we found: 1) measured MAC ranged between 2.4 m2 g-1 and 8.6 m2 g-1 at λ = 550 nm, 2) most AAEs ranged between 0.5 and 1.3; C60 AAE was 7.5 ± 0.9 and 3) MAC spectra were dependent on fuel type and formation conditions. For BrC particles generated from smoldering combustion of 3 hardwood (Oak, Hickory and Mesquite) and 3 softwood species (Western redcedar, Blue spruce and Baldcypress), we found: 1) median MAC values ranged from 1.4 x 10-2 m2 g-1 to 7.9 x 10-2 m2 g-1 at λ = 550 nm, 2) AAE values ranged between 3.5 and 6.2, and 3) Oak, Western redcedar and Blue spruce possessed statistically similar (p > 0.05) spectra while Hickory, Mesquite and Baldcypress were distinct (p < 0.01). Last, we measured seven dust and soil samples collected from across the continental U.S. and found: 1) absorption spectra can be classified as either brown/grey (AAE ≈ 3.5) or red (AAE > 4) and 2) the highest MAC at λ = 405 nm for all samples was ≈ 0.5 m2 g-1.

Improving sound absorption property of polyurethane foams doped with natural fiber

NASA Astrophysics Data System (ADS)

Azahari, M. Shafiq M.; Rus, Anika Zafiah M.; Taufiq Zaliran, M.; Kormin, Shaharuddin

2017-08-01

This study investigates the acoustics behavior of wood fibre filler of Red Meranti - filled polyurethane foam as a sound absorbing material. Three different thicknesses have been selected which is 10 mm, 20 mm and 30 mm. By choosing percentage loading of Red Meranti (RM) wood fibre of 5%, 10%, 15% and 20% added with polymer foam is namely as polymer foam (PF) composites of PF5%, PF10%, PF15% and PF20%. The sound absorption coefficient (α) and pore structure of the foam samples have been examined by using Impedance Tube test and Scanning Electron Microscopy (SEM). The results revealed that the highest thickness of highest filler loading (PF20%) gives higher sound absorption coefficient (α). The absorption frequency level is observed at 0.9922 and 0.99889 which contributed from low and high frequency absorption level respectively. The smallest pores size structure was observed with highest filler loading of PF. The higher the thickness and the higher the percentage loading of wood filler gives smaller pore structure, consequently, increased the sound absorption coefficient level.

Experimental study on the sound absorption characteristics of continuously graded phononic crystals

NASA Astrophysics Data System (ADS)

Zhang, X. H.; Qu, Z. G.; He, X. C.; Lu, D. L.

2016-10-01

Novel three-dimensional (3D) continuously graded phononic crystals (CGPCs) have been designed, and fabricated by 3D printing. Each of the CGPCs is an entity instead of a combination of several other samples, and the porosity distribution of the CGPC along the incident direction is nearly linear. The sound absorption characteristics of CGPCs were experimentally investigated and compared with those of uniform phononic crystals (UPCs) and discretely stepped phononic crystals (DSPCs). Experimental results show that CGPCs demonstrate excellent sound absorption performance because of their continuously graded structures. CGPCs have higher sound absorption coefficients in the large frequency range and more sound absorption coefficient peaks in a specific frequency range than UPCs and DSPCs. In particular, the sound absorption coefficients of the CGPC with a porosity of 0.6 and thickness of 30 mm are higher than 0.56 when the frequency is 1350-6300 Hz and are all higher than 0.2 in the studied frequency range (1000-6300 Hz). CGPCs are expected to have potential application in noise control, especially in the broad frequency and low-frequency ranges.

Visualization of hemodynamics and light scattering in exposed brain of rat using multispectral image reconstruction based on Wiener estimation method

NASA Astrophysics Data System (ADS)

Nishidate, Izumi; Ishizuka, Tomohiro; Yoshida, Keiichiro; Kawauchi, Satoko; Sato, Shunichi; Sato, Manabu

2015-07-01

We investigate a method to estimate the spectral images of reduced scattering coefficients and the absorption coefficients of in vivo exposed brain tissues in the range from visible to near-infrared wavelength (500-760 nm) based on diffuse reflectance spectroscopy using a digital RGB camera. In the proposed method, the multi-spectral reflectance images of in vivo exposed brain are reconstructed from the digital red, green, blue images using the Wiener estimation algorithm. The Monte Carlo simulation-based multiple regression analysis for the absorbance spectra is then used to specify the absorption and scattering parameters of brain tissue. In this analysis, the concentration of oxygenated hemoglobin and that of deoxygenated hemoglobin are estimated as the absorption parameters whereas the scattering amplitude a and the scattering power b in the expression of μs'=aλ-b as the scattering parameters, respectively. The spectra of absorption and reduced scattering coefficients are reconstructed from the absorption and scattering parameters, and finally, the spectral images of absorption and reduced scattering coefficients are estimated. We performed simultaneous recordings of spectral diffuse reflectance images and of the electrophysiological signals for in vivo exposed rat brain during the cortical spreading depression evoked by the topical application of KCl. Changes in the total hemoglobin concentration and the tissue oxygen saturation imply the temporary change in cerebral blood flow during CSD. Change in the reduced scattering coefficient was observed before the profound increase in the total hemoglobin concentration, and its occurrence was synchronized with the negative dc shift of the local field potential.

Optical properties of soot particles: measurement - model comparison

NASA Astrophysics Data System (ADS)

Forestieri, S.; Lambe, A. T.; Lack, D.; Massoli, P.; Cross, E. S.; Dubey, M.; Mazzoleni, C.; Olfert, J.; Freedman, A.; Davidovits, P.; Onasch, T. B.; Cappa, C. D.

2013-12-01

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 order to accurately model the direct radiative impact of black carbon (BC), the refractive index and shape dependent scattering and absorption characteristics must be known. At present, the assumed shape remains highly uncertain because BC particles are fractal-like, being agglomerates of smaller (20-40 nm) spherules, yet traditional optical models such as Mie theory typically assume a spherical particle morphology. To investigate the ability of various optical models to reproduce observed BC optical properties, we measured light absorption and extinction coefficients of methane and ethylene flame soot particles. Optical properties were measured by multiple instruments: absorption by a dual cavity ringdown photoacoustic spectrometer (CRD-PAS), absorption and scattering by a 3-wavelength photoacoustic/nephelometer spectrometer (PASS-3) and extinction and scattering by a cavity attenuated phase shift spectrometer (CAPS). Soot particle mass was quantified using a centrifugal particle mass analyzer (CPMA) and mobility size was measured with a scanning mobility particle sizer (SMPS). Measurements were made for nascent soot particles and for collapsed soot particles following coating with dioctyl sebacate or sulfuric acid and thermal denuding to remove the coating. Wavelength-dependent refractive indices for the sampled particles were derived by fitting the observed absorption and extinction cross-sections to spherical particle Mie theory and Rayleigh-Debye-Gans theory. The Rayleigh-Debye-Gans approximation assumes that the absorption properties of soot are dictated by the individual spherules and neglects interaction between them. In general, Mie theory reproduces the observed absorption and extinction cross-sections for particles with volume equivalent diameters (VED) < ~160 nm, but systematically predicts lower absorption cross-sections relative to observations for larger particles with VED > ~160 nm. The discrepancy is most pronounced for measurements made at shorter wavelengths. In contrast, Rayleigh-Debye-Gans theory, which does not assume spherical particle morphology, exhibited good agreement with the observations for all particle diameters and wavelengths. These results indicate that the use of Mie theory to describe the absorption behavior of particles >160 nm VED will underestimate the absorption by these particles. Concurrent measurements of the absorption Angstrom exponent and the single scattering albedo, and their dependence on particle size, will also be discussed.

COMPARISON OF PHOTOCHEMICAL BEHAVIOR OF VARIOUS HUMIC SUBSTANCES IN WATER: III. SPECTROSCOPIC PROPERTIES OF HUMIC SUBSTANCES

EPA Science Inventory

Spectral absorption coefficients and fluorescence quantum efficiencies were determined for humic substances from a variety of sources. Specific absorption coefficients, K(h), for humic substances at wavelengths lambda from 300 to 500 nm can be closely described by the relation Ae...

Sustainable p-type copper selenide solar material with ultra-large absorption coefficient

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Erica M.; Williams, Logan; Olvera, Alan

We report the synthesis of CTSe, a p-type titanium copper selenide semiconductor. Its band gap (1.15 eV) and its ultra-large absorption coefficient (10 5 cm −1 ) in the entire visible range make it a promising Earth-abundant solar absorber material.

Sustainable p-type copper selenide solar material with ultra-large absorption coefficient

DOE PAGES

Chen, Erica M.; Williams, Logan; Olvera, Alan; ...

2018-01-01

We report the synthesis of CTSe, a p-type titanium copper selenide semiconductor. Its band gap (1.15 eV) and its ultra-large absorption coefficient (10 5 cm −1 ) in the entire visible range make it a promising Earth-abundant solar absorber material.

ABSORBANCE, ABSORPTION COEFFICIENT, AND APPARENT QUANTUM YIELD: A COMMENT ON AMBIGUITY IN THE USE OF THESE OPTICAL CONCEPTS

EPA Science Inventory

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...

Optical properties and aging of light-absorbing secondary organic aerosol

DOE PAGES

Liu, Jiumeng; Lin, Peng; Laskin, Alexander; ...

2016-10-14

The light-absorbing organic aerosol (OA) commonly referred to as “brown carbon” (BrC) has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various volatile organic carbon (VOC) precursors, NO x concentrations, photolysis time, and relative humidity (RH) on the lightmore » absorption of selected secondary organic aerosols (SOA). Light absorption of chamber-generated SOA samples, especially aromatic SOA, was found to increase with NO x concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficient (MAC) value is observed from toluene SOA products formed under high-NO x conditions at moderate RH, in which nitro-aromatics were previously identified as the major light-absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organic nitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible (Vis) and ultraviolet (UV) light than SOA formed from aromatic precursors alone on a mass basis. However, the mixed SOA absorption was underestimated when optical properties were predicted using a two-product SOA formation model, as done in many current climate models. Further investigation, including analysis on detailed mechanisms, are required to explain the discrepancy.« less

Quantitative photoacoustic microscopy of optical absorption coefficients from acoustic spectra in the optical diffusive regime

NASA Astrophysics Data System (ADS)

Guo, Zijian; Favazza, Christopher; Garcia-Uribe, Alejandro; Wang, Lihong V.

2012-06-01

Photoacoustic (PA) microscopy (PAM) can image optical absorption contrast with ultrasonic spatial resolution in the optical diffusive regime. Conventionally, accurate quantification in PAM requires knowledge of the optical fluence attenuation, acoustic pressure attenuation, and detection bandwidth. We circumvent this requirement by quantifying the optical absorption coefficients from the acoustic spectra of PA signals acquired at multiple optical wavelengths. With the acoustic spectral method, the absorption coefficients of an oxygenated bovine blood phantom at 560, 565, 570, and 575 nm were quantified with errors of <3%. We also quantified the total hemoglobin concentration and hemoglobin oxygen saturation in a live mouse. Compared with the conventional amplitude method, the acoustic spectral method provides greater quantification accuracy in the optical diffusive regime. The limitations of the acoustic spectral method was also discussed.

Quantitative photoacoustic microscopy of optical absorption coefficients from acoustic spectra in the optical diffusive regime

PubMed Central

Guo, Zijian; Favazza, Christopher; Garcia-Uribe, Alejandro

2012-01-01

Abstract. Photoacoustic (PA) microscopy (PAM) can image optical absorption contrast with ultrasonic spatial resolution in the optical diffusive regime. Conventionally, accurate quantification in PAM requires knowledge of the optical fluence attenuation, acoustic pressure attenuation, and detection bandwidth. We circumvent this requirement by quantifying the optical absorption coefficients from the acoustic spectra of PA signals acquired at multiple optical wavelengths. With the acoustic spectral method, the absorption coefficients of an oxygenated bovine blood phantom at 560, 565, 570, and 575 nm were quantified with errors of <3%. We also quantified the total hemoglobin concentration and hemoglobin oxygen saturation in a live mouse. Compared with the conventional amplitude method, the acoustic spectral method provides greater quantification accuracy in the optical diffusive regime. The limitations of the acoustic spectral method was also discussed. PMID:22734767

Quantitative photoacoustic microscopy of optical absorption coefficients from acoustic spectra in the optical diffusive regime.

PubMed

Guo, Zijian; Favazza, Christopher; Garcia-Uribe, Alejandro; Wang, Lihong V

2012-06-01

Photoacoustic (PA) microscopy (PAM) can image optical absorption contrast with ultrasonic spatial resolution in the optical diffusive regime. Conventionally, accurate quantification in PAM requires knowledge of the optical fluence attenuation, acoustic pressure attenuation, and detection bandwidth. We circumvent this requirement by quantifying the optical absorption coefficients from the acoustic spectra of PA signals acquired at multiple optical wavelengths. With the acoustic spectral method, the absorption coefficients of an oxygenated bovine blood phantom at 560, 565, 570, and 575 nm were quantified with errors of <3%. We also quantified the total hemoglobin concentration and hemoglobin oxygen saturation in a live mouse. Compared with the conventional amplitude method, the acoustic spectral method provides greater quantification accuracy in the optical diffusive regime. The limitations of the acoustic spectral method was also discussed.

Optical properties of a multibarrier structure under intense laser fields

NASA Astrophysics Data System (ADS)

Ospina, D. A.; Akimov, V.; Mora-Ramos, M. E.; Morales, A. L.; Tulupenko, V.; Duque, C. A.

2015-11-01

Using the diagonalization method and within the effective mass and parabolic band approximations, the energy spectrum and the wave functions are investigated in biased multibarrier structure taking into account the effects of nonresonant intense laser fields. We calculated the optical properties from the susceptibility using a nonperturbative formalism recently reported. We study the changes in the intersubband optical absorption coefficients and refraction index for several values of the dressing laser parameter and for some specific values of the electric field applied along the growth direction of the heterostructure. It is concluded from our study that the peaks in the optical absorption spectrum have redshifts or blueshifts as a function of the laser parameter and the electric field. These parameters could be suitable tools for tuning the electronic and optical properties of the multibarrier structure.

Soot Particle Studies - Instrument Inter-Comparison – Project Overview

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cross, E.; Sedlacek, A.; Onasch, T. B.

2010-03-06

An inter-comparison study of instruments designed to measure the microphysical and optical properties of soot particles was completed. The following mass-based instruments were tested: Couette Centrifugal Particle Mass Analyzer (CPMA), Time-of-Flight Aerosol Mass Spectrometer - Scanning Mobility Particle Sizer (AMS-SMPS), Single Particle Soot Photometer (SP2), Soot Particle-Aerosol Mass Spectrometer (SP-AMS) and Photoelectric Aerosol Sensor (PAS2000CE). Optical instruments measured absorption (photoacoustic, interferometric, and filter-based), scattering (in situ), and extinction (light attenuation within an optical cavity). The study covered an experimental matrix consisting of 318 runs that systematically tested the performance of instruments across a range of parameters including: fuel equivalence ratiomore » (1.8 {le} {phi} {le} 5), particle shape (mass-mobility exponent (D{sub f m}), 2.0 {le} D{sub f m} {le} 3.0), particle mobility size (30 {le} d{sub m} {le} 300 nm), black carbon mass (0.07 {le} m{sub BC} {le} 4.2 fg) and particle chemical composition. In selected runs, particles were coated with sulfuric acid or dioctyl sebacate (DOS) (0.5 {le} {Delta}r{sub ve} {le} 201 nm) where {Delta}r{sub ve} is the change in the volume equivalent radius due to the coating material. The effect of non-absorbing coatings on instrument response was determined. Changes in the morphology of fractal soot particles were monitored during coating and denuding processes and the effect of particle shape on instrument response was determined. The combination of optical and mass based measurements was used to determine the mass specific absorption coefficient for denuded soot particles. The single scattering albedo of the particles was also measured. An overview of the experiments and sample results are presented.« less

Seven years of aerosol scattering hygroscopic growth measurements from SGP: Factors influencing water uptake: Aerosol Scattering Hygroscopic Growth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jefferson, A.; Hageman, D.; Morrow, H.

Long-term measurements of changes in the aerosol scattering coefficient hygroscopic growth at the U.S. Department of Energy Southern Great Plains site provide information on the seasonal as well as size and chemical dependence of aerosol hygroscopic growth. Annual average sub 10 um fRH values (the ratio of aerosol scattering at 85%/40% RH) were 1.75 and 1.87 for the gamma and kappa fit algorithms, respectively. The study found higher growth rates in the winter and spring seasons that correlated with high aerosol nitrate mass fraction. FRH, exhibited strong, but differing correlations with the scattering Ångström exponent and backscatter fraction, two opticalmore » size-dependent parameters. The aerosol organic fraction had a strong influence, with fRH decreasing with increases in the organic mass fraction and absorption Ångström exponent and increasing with the aerosol single scatter albedo. Uncertainty analysis if the fit algorithms revealed high uncertainty at low scattering coefficients and slight increases in uncertainty at high RH and fit parameters values.« less

Measurement of the mass attenuation coefficients and electron densities for BiPbSrCaCuO superconductor at different energies

NASA Astrophysics Data System (ADS)

Çevik, U.; Baltaş, H.

2007-03-01

The mass attenuation coefficients for Bi, Pb, Sr, Ca, Cu metals, Bi2O3, PbO, SrCO3, CaO, CuO compounds and solid-state forms of Bi1.7Pb0.3Sr2Ca2Cu3O10 superconductor were determined at 57.5, 65.2, 77.1, 87.3, 94.6, 122 and 136 keV energies. The samples were irradiated using a 57Co point source emitted 122 and 136 keV γ-ray energies. The X-ray energies were obtained using secondary targets such as Ta, Bi2O3 and (CH3COO)2UO22H2O. The γ- and X-rays were counted by a Si(Li) detector with a resolution of 0.16 keV at 5.9 keV. The effect of absorption edges on electron density, effective atomic numbers and their variation with photon energy in composite superconductor samples was discussed. Obtained values were compared with theoretical values.

Properties of particulate pollution in the port city of Valparaiso, Chile

NASA Astrophysics Data System (ADS)

Marín, Julio C.; Raga, Graciela B.; Arévalo, Jorge; Baumgardner, Darrel; Córdova, Ana M.; Pozo, Diana; Calvo, Ana; Castro, Amaya; Fraile, Roberto; Sorribas, Mar

2017-12-01

The city of Valparaiso is home to one of the largest commercial ports on the west coast of South America. Port activities, that continue year-round, 24 h a day and seven days a week, produce emissions of pollutants, particularly aerosol particles composed of black and brown carbon (BC and BrC) that have serious impact on human population and the local environment. A measurement program was launched to document the magnitude of selected pollutants, to identify their sources and to evaluate the meteorological processes that enhance and transport these pollutants locally and regionally. In this study, we report the measurements made during four months: 25July - 25August 2014 (referred to as August 2014 throughout the manuscript), December 2014, January 2015 and March 2015. The daily mass concentrations of equivalent black carbon (eBC), derived from measurements of the light absorption coefficient, regularly exceed 5 μg m-3, a magnitude similar to values found in megacities such as Mexico City. The daily maximum number concentration of condensation nuclei (CN) is usually larger than 30000 cm-3. The Angstrom absorption exponent (AAE), derived from the absorption coefficients at 550 nm and 870 nm, is used to identify the primary sources of BC and BrC. In colder weather, emissions from the diesel fueled buses and trucks and the consumption of kerosene and wood for residential heating are the main sources of BC. In December, local wildfires contributed to the particle mass loading, but the day-to-day variability in boundary layer height and the presence of clouds and fog in occasions inhibited high concentrations. In March, the port activities reach a yearly peak during the seasonal export of agricultural products that translates into much more ship and truck traffic leading to very high eBC concentrations, comparable to values observed during August. The variability in weather patterns underscores the complexity of meteorological processes that drive the evolution and transport of pollution in Valparaiso.

Sound absorption by clamped poroelastic plates.

PubMed

Aygun, H; Attenborough, K

2008-09-01

Measurements and predictions have been made of the absorption coefficient and the surface acoustic impedance of poroelastic plates clamped in a large impedance tube and separated from the rigid termination by an air gap. The measured and predicted absorption coefficient and surface impedance spectra exhibit low frequency peaks. The peak frequencies observed in the absorption coefficient are close to those predicted and measured in the deflection spectra of the clamped poroelastic plates. The influences of the rigidity of the clamping conditions and the width of the air gap have been investigated. Both influences are found to be important. Increasing the rigidity of clamping reduces the low frequency absorption peaks compared with those measured for simply supported plates or plates in an intermediate clamping condition. Results for a closed cell foam plate and for two open cell foam plates made from recycled materials are presented. For identical clamping conditions and width of air gap, the results for the different materials differ as a consequence mainly of their different elasticity, thickness, and cell structure.

Absorption and Scattering of Aerosol measured onboard R/V Gisang1 over the Yellow Sea

NASA Astrophysics Data System (ADS)

Inae, K.; Lee, M.; Shin, B.; Ryoo, S.; Jung, J.; Kim, S. W.

2017-12-01

Absorption and scattering coefficient were measured onboard RV Gisang 1 over the Yellow Sea (covering 124° 127°E, 31° 38°N) during May June, 2016. BC concentration was analyzed at seven wavelengths (370, 470, 520, 590, 660, 880, and 950nm) every 1 minute by Aethalometer. Scattering coefficient was measured at three wavelengths (450, 550, and 750nm) every 5 minutes with Nephelometer. The mean absorption coefficient was 1.2 Mm-1 at 880nm and the mean scattering coefficient was 116Mm-1 at 550nm. Single scattering albedo(SSA) reached the maximum value of 3.0 at 700nm. The calculated mean scattering angstrom exponent(SAE) was 1.6 and absorbing angstrom exponent(AAE) was 1.1. The AAE and SAE were higher in aged Chinese plume.

Band-edge absorption coefficients from photoluminescence in semiconductor multiple quantum wells

NASA Technical Reports Server (NTRS)

Kost, Alan; Zou, Yao; Dapkus, P. D.; Garmire, Elsa; Lee, H. C.

1989-01-01

A novel approach to determining absorption coefficients in thin films using luminescence is described. The technique avoids many of the difficulties typically encountered in measurements of thin samples, Fabry-Perot effects, for example, and can be applied to a variety of materials. The absorption edge for GaAs/AlGaAs multiple quantum well structures, with quantum well widths ranging from 54 to 193 A is examined. Urbach (1953) parameters and excitonic linewidths are tabulated.

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.

Numerical study of surface plasmon enhanced nonlinear absorption and refraction.

PubMed

Kohlgraf-Owens, Dana C; Kik, Pieter G

2008-07-07

Maxwell Garnett effective medium theory is used to study the influence of silver nanoparticle induced field enhancement on the nonlinear response of a Kerr-type nonlinear host. We show that the composite nonlinear absorption coefficient, beta(c), can be enhanced relative to the host nonlinear absorption coefficient near the surface plasmon resonance of silver nanoparticles. This enhancement is not due to a resonant enhancement of the host nonlinear absorption, but rather due to a phase shifted enhancement of the host nonlinear refractive response. The enhancement occurs at the expense of introducing linear absorption, alpha(c), which leads to an overall reduced figure of merit beta(c)/alpha(c) for nonlinear absorption. For thin (< 1 microm) composites, the use of surface plasmons is found to result in an increased nonlinear absorption response compared to that of the host material.

Listening to light scattering in turbid media: quantitative optical scattering imaging using photoacoustic measurements with one-wavelength illumination

NASA Astrophysics Data System (ADS)

Yuan, Zhen; Li, Xiaoqi; Xi, Lei

2014-06-01

Biomedical photoacoustic tomography (PAT), as a potential imaging modality, can visualize tissue structure and function with high spatial resolution and excellent optical contrast. It is widely recognized that the ability of quantitatively imaging optical absorption and scattering coefficients from photoacoustic measurements is essential before PAT can become a powerful imaging modality. Existing quantitative PAT (qPAT), while successful, has been focused on recovering absorption coefficient only by assuming scattering coefficient a constant. An effective method for photoacoustically recovering optical scattering coefficient is presently not available. Here we propose and experimentally validate such a method for quantitative scattering coefficient imaging using photoacoustic data from one-wavelength illumination. The reconstruction method developed combines conventional PAT with the photon diffusion equation in a novel way to realize the recovery of scattering coefficient. We demonstrate the method using various objects having scattering contrast only or both absorption and scattering contrasts embedded in turbid media. The listening-to-light-scattering method described will be able to provide high resolution scattering imaging for various biomedical applications ranging from breast to brain imaging.

Preliminary characterization of carbon dioxide transfer in a hollow fiber membrane module as a possible solution for gas-liquid transfer in microgravity conditions

NASA Astrophysics Data System (ADS)

Farges, Bérangère; Duchez, David; Dussap, Claude-Gilles; Cornet, Jean-François

2012-01-01

In microgravity, one of the major challenge encountered in biological life support systems (BLSS) is the gas-liquid transfer with, for instance, the necessity to provide CO2 (carbon source, pH control) and to recover the evolved O2 in photobioreactors used as atmosphere bioregenerative systems.This paper describes first the development of a system enabling the accurate characterization of the mass transfer limiting step for a PTFE membrane module used as a possible efficient solution to the microgravity gas-liquid transfer. This original technical apparatus, together with a technical assessment of membrane permeability to different gases, is associated with a balance model, determining thus completely the CO2 mass transfer problem between phases. First results are given and discussed for the CO2 mass transfer coefficient kLCO obtained in case of absorption experiments at pH 8 using the hollow fiber membrane module. The consistency of the proposed method, based on a gas and liquid phase balances verifying carbon conservation enables a very accurate determination of the kLCO value as a main limiting step of the whole process. Nevertheless, further experiments are still needed to demonstrate that the proposed method could serve in the future as reference method for mass transfer coefficient determination if using membrane modules for BLSS in reduced or microgravity conditions.

Hybrid density functional study on the mechanism for the enhanced photocatalytic properties of the ultrathin hybrid layered nanocomposite g-C3N4/BiOCl

NASA Astrophysics Data System (ADS)

Yao, Wenzhi; Zhang, Jihua; Wang, Yuanxu; Ren, Fengzhu

2018-03-01

To investigate the origin of the high photocatalytic performance of experimentally synthesized g-C3N4/ BiOCl, we studied its geometry structure, electronic structure, and photocatalytic properties by means of hybrid density-functional theory (DFT). The calculated band alignment of g-C3N4 and few-layer BiOCl sheets clearly shows that g-C3N4/ BiOCl is a standard type-II nanocomposite. The density of states, Bader charge, partial charge density, charge density difference, and the effective masses show that electron-hole pair can be effectively separated in the g-C3N4/BiOCl interface. The calculated absorption coefficients indicate an obvious redshift of the absorption edge. The band gap of g-C3N4/BiOCl can be modulated by external electric field, and a semiconductor-semimetal transition is observed. The type-II vdW heterostructure is still maintained during the changes of external electric field. Especially, when the electric field reaches to +0.7 V/Å, the impurity states have been eliminated with the band gap of 2.3 eV. An analysis of optical properties shows that the absorption coefficient in the visible-light region is enhanced considerably as the electric-field strength increases. Our calculation results suggest that the ultrathin hybrid layered g-C3N4/BiOCl nanocomposite may have significant advantages for visible-light photocatalysis.

Light absorption properties of brown carbon over the southeastern Tibetan Plateau.

PubMed

Zhu, Chong-Shu; Cao, Jun-Ji; Huang, Ru-Jin; Shen, Zhen-Xing; Wang, Qi-Yuan; Zhang, Ning-Ning

2018-06-01

We present a study of the light-absorbing properties of water-soluble brown carbon (WS-BrC) and methanol-soluble brown carbon (MeS-BrC) at a remote site (Lulang, 3326m above sea level) in the southeastern Tibetan Plateau during the period 2015-2016. The light absorption coefficients at 365nm (b abs365 ) of WS-BrC and MeS-BrC were the highest during winter and the lowest during monsoon season. MeS-BrC absorbs about 1.5 times higher at 365nm compared to WS-BrC. The absorption at 550nm appears lower compared to that of 365nm for WS-BrC and MeS-BrC, respectively. Higher average value of the absorption Ångström exponent (AAE, 365-550nm) was obtained for MeS-BrC (8.2) than that for WS-BrC (6.9). The values of the mass absorption cross section at 365nm (MAC 365 ) indicated that BrC in winter absorbs UV-visible light more efficiently than in monsoon. The results confirm the importance of BrC in contributing to light-absorbing aerosols in this region. The understanding of the light absorption properties of BrC is of great importance, especially in modeling studies for the climate effects and transport of BrC in the Tibetan Plateau. Copyright © 2017 Elsevier B.V. All rights reserved.

Molecular Chemistry of Atmospheric Brown Carbon Inferred from a Nationwide Biomass Burning Event

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Peng; Bluvshtein, Nir; Rudich, Yinon

Lag Ba'Omer, a nationwide bonfire festival in Israel, was chosen as a case study to investigate the influence of a major biomass burning event on the light absorption properties of atmospheric brown carbon (BrC). The chemical composition and optical properties of BrC chromophores were investigated using a high performance liquid chromatography (HPLC) platform coupled to photo diode array (PDA) and high resolution mass spectrometry (HRMS) detectors. Substantial increase of BrC light absorption coefficient was observed during the night-long biomass burning event. Most chromophores observed during the event were attributed to nitroaromatic compounds, comprising 28 elemental formulas of at least 63more » structural isomers. The NAC, in combination, accounted for 50-80% of the total visible light absorption (> 400 nm) by solvent extractable BrC. The results highlight that NAC, particular nitrophenols, are important light absorption contributors of biomass burning organic aerosol (BBOA), suggesting that night time chemistry of ·NO 3 and N 2O 5 with particles may play a significant role in atmospheric transformations of BrC. Nitrophenols and related compounds were especially important chromophores of BBOA. The absorption spectra of the BrC chromophores are influenced by the extraction solvent and solution pH, implying that the aerosol acidity is an important factor controlling the light absorption properties of BrC.« less

Molecular Chemistry of Atmospheric Brown Carbon Inferred from a Nationwide Biomass Burning Event

DOE PAGES

Lin, Peng; Bluvshtein, Nir; Rudich, Yinon; ...

2017-08-26

Lag Ba'Omer, a nationwide bonfire festival in Israel, was chosen as a case study to investigate the influence of a major biomass burning event on the light absorption properties of atmospheric brown carbon (BrC). The chemical composition and optical properties of BrC chromophores were investigated using a high performance liquid chromatography (HPLC) platform coupled to photo diode array (PDA) and high resolution mass spectrometry (HRMS) detectors. Substantial increase of BrC light absorption coefficient was observed during the night-long biomass burning event. Most chromophores observed during the event were attributed to nitroaromatic compounds, comprising 28 elemental formulas of at least 63more » structural isomers. The NAC, in combination, accounted for 50-80% of the total visible light absorption (> 400 nm) by solvent extractable BrC. The results highlight that NAC, particular nitrophenols, are important light absorption contributors of biomass burning organic aerosol (BBOA), suggesting that night time chemistry of ·NO 3 and N 2O 5 with particles may play a significant role in atmospheric transformations of BrC. Nitrophenols and related compounds were especially important chromophores of BBOA. The absorption spectra of the BrC chromophores are influenced by the extraction solvent and solution pH, implying that the aerosol acidity is an important factor controlling the light absorption properties of BrC.« less

Sound absorption coefficient of coal bottom ash concrete for railway application

NASA Astrophysics Data System (ADS)

Ramzi Hannan, N. I. R.; Shahidan, S.; Maarof, Z.; Ali, N.; Abdullah, S. R.; Ibrahim, M. H. Wan

2017-11-01

A porous concrete able to reduce the sound wave that pass through it. When a sound waves strike a material, a portion of the sound energy was reflected back and another portion of the sound energy was absorbed by the material while the rest was transmitted. The larger portion of the sound wave being absorbed, the lower the noise level able to be lowered. This study is to investigate the sound absorption coefficient of coal bottom ash (CBA) concrete compared to the sound absorption coefficient of normal concrete by carried out the impedance tube test. Hence, this paper presents the result of the impedance tube test of the CBA concrete and normal concrete.

Exciton diamagnetic shift and optical properties in CdSe nanocrystal quantum dots in magnetic fields

NASA Astrophysics Data System (ADS)

Wu, Shudong; Cheng, Liwen

2018-04-01

The magnetic field dependence of the optical properties of CdSe nanocrystal quantum dots (NQDs) is investigated theoretically using a perturbation method within the effective-mass approximation. The results show that the magnetic field lifts the degeneracy of the electron (hole) states. A blue-shift in the absorption spectra of m ≥ 0 exciton states is observed while the absorption peak of m < 0 exciton states is first red-shifted and then blue-shifted with increasing the magnetic field strength B. This is attributed to the interplay of the orbital Zeeman effect and the additive confinement induced by the magnetic field. The excitonic absorption coefficient is almost independent of B in the strong confinement regime. The applied magnetic field causes the splitting of degenerated exciton states, resulting in the new absorption peaks. Based on the first-order perturbation theory, we propose the analytical expressions for the exciton binding energy, exciton transition energy and exciton diamagnetic shift of 1s, 1p-1, 1p0, 1p1, 1d-2, 1d-1, 1d0, 1d1, 1d2 and 2s exciton states on the applied magnetic field in the strong confinement regime.

Determination of K shell absorption jump factors and jump ratios in the elements between Tm( Z = 69) and Os( Z = 76) by measuring K shell fluorescence parameters

NASA Astrophysics Data System (ADS)

Kaya, N.; Tıraşoğlu, E.; Apaydın, G.

2008-04-01

The K shell absorption jump factors and jump ratios have been measured in the elements between Tm ( Z = 69) and Os( Z = 76) without having any mass attenuation coefficient at the upper and lower energy branch of the K absorption edge. The jump factors and jump ratios for these elements have been determined by measuring K shell fluorescence parameters such as the total atomic absorption cross-sections, the K α X-ray production cross-sections, the intensity ratio of the K β and K α X-rays and the K shell fluorescence yields. We have performed the measurements for the calculations of these values in attenuation and direct excitation experimental geometry. The K X-ray photons are excited in the target using 123.6 keV gamma-rays from a strong 57Co source, and detected with an Ultra-LEGe solid state detector with a resolution 0.15 keV at 5.9 keV. The measured values have been compared with theoretical and others' experimental values. The results have been plotted versus atomic number.

Light-Absorbing Aerosol during NASA GRIP: Overview of Observations in the Free Troposphere and Associated with Tropical Storm Systems

NASA Astrophysics Data System (ADS)

Ziemba, L. D.; Beyersdorf, A. J.; Chen, G.; Corr, C. A.; Craig, L.; Dhaniyala, S.; Dibb, J. E.; Hudgins, C. H.; Ismail, S.; Latham, T.; Nenes, A.; Thornhill, K. L.; Winstead, E.; Anderson, B. E.

2010-12-01

Aerosols play a significant role in regulating Earth’s climate. Absorbing aerosols typically constitute a small fraction of ambient particle mass but can contribute significantly to direct and indirect climate forcing depending on size, mixing state, concentration, chemical composition, and vertical and spatial distribution. Aerosols may also significantly affect tropical storm/hurricane dynamics through direct light absorption and activation as cloud nuclei. An extensive suite of instrumentation measuring aerosol chemical, physical, and optical properties was deployed aboard the NASA DC-8 to characterize aerosol during the NASA GRIP (Genesis and Rapid Intensification Processes; August-September 2010) mission. The majority of flight time was spent at high altitude (greater than 9 km) and thus much of the sampling was done in the free troposphere, including extensive sampling in the vicinity of tropical storm systems and more diffuse cirrus clouds. With operations based in Fort Lauderdale, FL and St. Croix, U.S. Virgin Islands, a large geographic region was sampled including much of the Gulf of Mexico and tropical Atlantic Ocean. Observations are reported for light-absorbing carbon aerosol (mainly black carbon, BC) primarily using a single particle soot photometer (SP2). The SP2 employs single-particle laser-induced incandescence to provide a mass-specific measurement not subject to scattering interference that is optimal for the low concentration environments like those encountered during GRIP. BC mass concentrations, 100-500 nm size distributions, and mixing state (i.e. coating thickness of scattering material) are presented. Total and sub-micron aerosol absorption coefficients (principally from BC and dust aerosol) are reported using a particle soot absorption photometer (PSAP) along with comparisons with calculated absorption coefficients derived from SP2 observations in various conditions. In addition, dust aerosol is specifically identified using optical and aerodynamic size distributions obtained from an optical particle counter (OPC) and aerodynamic particle sizer (APS), respectively, as well as by filter-based analyses of chemical composition. BC and dust concentrations, size distribution, and optical properties are reported for clear-sky conditions and in the regions surrounding tropical storms to better understand the radial and vertical distribution of light-absorbing aerosol associated with hurricanes. Observations during GRIP are compared to an extensive characterization of the Saharan Air Layer (SAL) made during the 2006 NAMMA (NASA African Monsoon Multidisciplinary Analyses) mission to assess changes in concentration and aerosol size distribution during transport and cloud interaction.

Backscatter factors and mass energy-absorption coefficient ratios for diagnostic radiology dosimetry

NASA Astrophysics Data System (ADS)

Benmakhlouf, Hamza; Bouchard, Hugo; Fransson, Annette; Andreo, Pedro

2011-11-01

Backscatter factors, B, and mass energy-absorption coefficient ratios, (μen/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 (μen/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 (μen/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.

Neutronic reactor

DOEpatents

Wende, Charles W. J.

1976-08-17

A safety rod for a nuclear reactor has an inner end portion having a gamma absorption coefficient and neutron capture cross section approximately equal to those of the adjacent shield, a central portion containing materials of high neutron capture cross section and an outer end portion having a gamma absorption coefficient at least equal to that of the adjacent shield.

Photorefractive Nonlinear Optics

DTIC Science & Technology

1991-01-15

conjugate interferometer for the measurement of thin film thickness, refractive index and absorption coefficients. Also, we have investigated...conjugate interferometer for the measurement of thin film thickness, refractive index and absorption coefficients. Also, we have investigated...interaction by considering the refractive index grating as a linear superposition of the gratings from each of the frequency components of the

Effects of temperature-dependent molecular absorption coefficients on the thermal infrared remote sensing of the earth surface

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.

Control of optical bandgap energy and optical absorption coefficient by geometric parameters in sub-10 nm silicon-nanodisc array structure

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.

Subwavelength structure for sound absorption from graphene oxide-doped polyvinylpyrrolidone nanofibers

NASA Astrophysics Data System (ADS)

Qamoshi, Khadijeh; Rasuli, Reza

2016-09-01

We study the sound absorption of the reinforced polyvinylpyrrolidone nanofibers with graphene oxide. It is shown that reinforced nanofibers can acquire impedance-matched surface to airborne sound at special frequencies. To obtain such surface, nanofibers were spun with polyvinylpyrrolidone polymer that was doped by graphene oxide with concentrations of 0, 6 and 12 wt%. It was found that fibers without graphene oxide were spun continuously and randomly, whereas by doping with graphene oxide, the mode of fibers is changed and some nodes form on the fibers coating. The sound absorption coefficient was measured by an impedance tube based on 105341-1 ISO standard. Measurements in the frequency range from 700 to 1600 Hz show that use of graphene oxide as a reinforcing phase increases sound absorption coefficient of the samples at a frequency ~1500 Hz up to ~40 %. Angular eigenfrequency and dissipation coefficient of the samples were obtained by impedance measurement for the prepared samples. Results show that doping the polymer with graphene oxide causes an increase in the angular eigenfrequency and the dissipation coefficient.

Relationship between time-resolved and non-time-resolved Beer-Lambert law in turbid media.

PubMed

Nomura, Y; Hazeki, O; Tamura, M

1997-06-01

The time-resolved Beer-Lambert law proposed for oxygen monitoring using pulsed light was extended to the non-time-resolved case in a scattered medium such as living tissues with continuous illumination. The time-resolved Beer-Lambert law was valid for the phantom model and living tissues in the visible and near-infrared regions. The absolute concentration and oxygen saturation of haemoglobin in rat brain and thigh muscle could be determined. The temporal profile of rat brain was reproduced by Monte Carlo simulation. When the temporal profiles of rat brain under different oxygenation states were integrated with time, the absorbance difference was linearly related to changes in the absorption coefficient. When the simulated profiles were integrated, there was a linear relationship within the absorption coefficient which was predicted for fractional inspiratory oxygen concentration from 10 to 100% and, in the case beyond the range of the absorption coefficient, the deviation from linearity was slight. We concluded that an optical pathlength which is independent of changes in the absorption coefficient is a good approximation for near-infrared oxygen monitoring.

Measuring the Absorption Rate of CO 2 in Nonaqueous CO 2 -Binding Organic Liquid Solvents with a Wetted-Wall Apparatus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mathias, Paul M.; Zheng, Feng; Heldebrant, David J.

2015-09-17

The kinetics of the absorption of CO 2 into two nonaqueous CO 2-binding organic liquid (CO 2BOL) solvents were measured at T=35, 45, and 55 °C with a wetted-wall column. Selected CO 2 loadings were run with a so-called “first-generation” CO 2BOL, comprising an independent base and alcohol, and a “second-generation” CO 2BOL, in which the base and alcohol were conjoined. Liquid-film mass-transfer coefficient (k'g) values for both solvents were measured to be comparable to values for monoethanolamine and piperazine aqueous solvents under a comparable driving force, in spite of far higher solution viscosities. An inverse temperature dependence of themore » k'g value was also observed, which suggests that the physical solubility of CO 2 in organic liquids may be making CO 2 mass transfer faster than expected. Aspen Plus software was used to model the kinetic data and compare the CO 2 absorption behavior of nonaqueous solvents with that of aqueous solvent platforms. This work continues our development of the CO2BOL solvents. Previous work established the thermodynamic properties related to CO 2 capture. The present paper quantitatively studies the kinetics of CO 2 capture and develops a rate-based model.« less

Development of a High-Resolution Laser Absorption Spectroscopy Method with Application to the Determination of Absolute Concentration of Gaseous Elemental Mercury in Air.

PubMed

Srivastava, Abneesh; Hodges, Joseph T

2018-06-05

Isotope dilution-cold-vapor-inductively coupled plasma mass spectrometry (ID-CV-ICPMS) has become the primary standard for measurement of gaseous elemental mercury (GEM) mass concentration. However, quantitative mass spectrometry is challenging for several reasons including (1) the need for isotopic spiking with a standard reference material, (2) the requirement for bias-free passive sampling protocols, (3) the need for stable mass spectrometry interface design, and (4) the time and cost involved for gas sampling, sample processing, and instrument calibration. Here, we introduce a high-resolution laser absorption spectroscopy method that eliminates the need for sample-specific calibration standards or detailed analysis of sample treatment losses. This technique involves a tunable, single-frequency laser absorption spectrometer that measures isotopically resolved spectra of elemental mercury (Hg) spectra of 6 1 S 0 ← 6 3 P 1 intercombination transition near λ = 253.7 nm. Measured spectra are accurately modeled from first-principles using the Beer-Lambert law and Voigt line profiles combined with literature values for line positions, line shape parameters, and the spontaneous emission Einstein coefficient to obtain GEM mass concentration values. We present application of this method for the measurement of the equilibrium concentration of mercury vapor near room temperature. Three closed systems are considered: two-phase mixtures of liquid Hg and its vapor and binary two-phase mixtures of Hg-air and Hg-N 2 near atmospheric pressure. Within the experimental relative standard uncertainty, 0.9-1.5% congruent values of the equilibrium Hg vapor concentration are obtained for the Hg-only, Hg-air, Hg-N 2 systems, in confirmation with thermodynamic predictions. We also discuss detection limits and the potential of the present technique to serve as an absolute primary standard for measurements of gas-phase mercury concentration and isotopic composition.

A fugacity-based indoor residential pesticide fate model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bennett, Deborah H.; Furtaw, Edward J.; McKone, Thomas E.

Dermal and non-dietary pathways are potentially significant exposure pathways to pesticides used in residences. Exposure pathways include dermal contact with residues on surfaces, ingestion from hand- and object-to-mouth activities, and absorption of pesticides into food. A limited amount of data has been collected on pesticide concentrations in various residential compartments following an application. But models are needed to interpret this data and make predictions about other pesticides based on chemical properties. In this paper, we propose a mass-balance compartment model based on fugacity principles. We include air (both gas phase and aerosols), carpet, smooth flooring, and walls as model compartments.more » Pesticide concentrations on furniture and toys, and in food, are being added to the model as data becomes available. We determine the compartmental fugacity capacity and mass transfer-rate coefficient for wallboard as an example. We also present the framework and equations needed for a dynamic mass-balance model.« less

Energy-absorption spectroscopy of unitary Fermi gases in a uniform potential

NASA Astrophysics Data System (ADS)

Zhang, Pengfei; Yu, Zhenhua

2018-04-01

We propose to use the energy absorption spectroscopy to measure the kinetic coefficients of unitary Fermi gases in a uniform potential. We show that, in our scheme, the energy absorption spectrum is proportional to the dynamic structure factor of the system. The profile of the spectrum depends on the shear viscosity η , the thermal conductivity κ , and the superfluid bulk viscosity ξ3. We show that extraction of these coefficients from the spectrum is achievable in present experiments.

Effects of surface roughness and absorption on light propagation in graded-profile waveguides

DOE Office of Scientific and Technical Information (OSTI.GOV)

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)

Nonlinear Relationships Between Particulate Absorption and Chlorophyll: Detritus or Pigment Packaging

DTIC Science & Technology

1993-06-15

for another polar area. For samples from Antartic waters, the mean a*pan(4 3 5 ), normalized to chl a + pheo, was 0.0 18 m2 (mg chl a)-I (Mitchell and...specific absorption coefficients, was suggested as the cause of relatively low mean specific absorption coefficients in the Antartic . The values of c1...moored optical sensors in the Sargasso Sea. J. Geophys. Res. 97, 7399-7412. Mitchell, B.G., and 0. Holm-Hansen 1991. Bio-optical properties of Antartic

Differential Frequency Hopping (DFH) Modulation for Underwater Acoustic Communications and Networking

DTIC Science & Technology

2009-10-09

trains the coefficients c of a finite impulse response (FIR) filter by gradient descent. The coefficients at iteration k + 1 are computed with the update... absorption . Figure 9 shows the reflection loss as a function of grazing angle for this bottom model. Note that below 30◦ this bottom model predicts...less than 1 dB loss per ray bounce. 11 Figure 9: Jackson bottom reflection loss for sand at 15 kHz Absorption Loss The absorption loss in the medium was

Deep seawater inherent optical properties in the Southern Ionian Sea

NASA Astrophysics Data System (ADS)

Riccobene, G.; Capone, A.; Aiello, S.; Ambriola, M.; Ameli, F.; Amore, I.; Anghinolfi, M.; Anzalone, A.; Avanzini, C.; Barbarino, G.; Barbarito, E.; Battaglieri, M.; Bellotti, R.; Beverini, N.; Bonori, M.; Bouhadef, B.; Brescia, M.; Cacopardo, G.; Cafagna, F.; Caponetto, L.; Castorina, E.; Ceres, A.; Chiarusi, T.; Circella, M.; Cocimano, R.; Coniglione, R.; Cordelli, M.; Costa, M.; Cuneo, S.; D'Amico, A.; de Bonis, G.; de Marzo, C.; de Rosa, G.; de Vita, R.; Distefano, C.; Falchini, E.; Fiorello, C.; Flaminio, V.; Fratini, K.; Gabrielli, A.; Galeotti, S.; Gandolfi, E.; Grimaldi, A.; Habel, R.; Leonora, E.; Lonardo, A.; Longo, G.; Lo Presti, D.; Lucarelli, F.; Maccioni, E.; Margiotta, A.; Martini, A.; Masullo, R.; Megna, R.; Migneco, E.; Mongelli, M.; Montaruli, T.; Morganti, M.; Musumeci, M.; Nicolau, C. A.; Orlando, A.; Osipenko, M.; Osteria, G.; Papaleo, R.; Pappalardo, V.; Petta, C.; Piattelli, P.; Raffaelli, F.; Raia, G.; Randazzo, N.; Reito, S.; Ricco, G.; Ripani, M.; Rovelli, A.; Ruppi, M.; Russo, G. V.; Russo, S.; Russo, S.; Sapienza, P.; Sedita, M.; Schuller, J.-P.; Shirokov, E.; Simeone, F.; Sipala, V.; Spurio, M.; Taiuti, M.; Terreni, G.; Trasatti, L.; Urso, S.; Valente, V.; Vicini, P.

2007-02-01

The NEMO (NEutrino Mediterranean Observatory) Collaboration has been carrying out since 1998 an evaluation programme of deep sea sites suitable for the construction of the future Mediterranean km3 Čerenkov neutrino telescope. We investigated the seawater optical and oceanographic properties of several deep sea marine areas close to the Italian Coast. Inherent optical properties (light absorption and attenuation coefficients) have been measured as a function of depth using an experimental apparatus equipped with standard oceanographic probes and the commercial transmissometer AC9 manufactured by WETLabs. This paper reports on the visible light absorption and attenuation coefficients measured in deep seawater of a marine region located in the Southern Ionian Sea, 60 100 km SE of Capo Passero (Sicily). Data show that blue light absorption coefficient is about 0.015 m-1 (corresponding to an absorption length of 67 m) close to the one of optically pure water and it does not show seasonal variation.

Spectra of Particulate Backscattering in Natural Waters

NASA Technical Reports Server (NTRS)

Gordon, Howard, R.; Lewis, Marlon R.; McLean, Scott D.; Twardowski, Michael S.; Freeman, Scott A.; Voss, Kenneth J.; Boynton, Chris G.

2009-01-01

Hyperspectral profiles of downwelling irradiance and upwelling radiance in natural waters (oligotrophic and mesotrophic) are combined with inverse radiative transfer to obtain high resolution spectra of the absorption coefficient (a) and the backscattering coefficient (bb) of the water and its constituents. The absorption coefficient at the mesotrophic station clearly shows spectral absorption features attributable to several phytoplankton pigments (Chlorophyll a, b, c, and Carotenoids). The backscattering shows only weak spectral features and can be well represented by a power-law variation with wavelength (lambda): b(sub b) approx. Lambda(sup -n), where n is a constant between 0.4 and 1.0. However, the weak spectral features in b(sub b), suggest that it is depressed in spectral regions of strong particle absorption. The applicability of the present inverse radiative transfer algorithm, which omits the influence of Raman scattering, is limited to lambda < 490 nm in oligotrophic waters and lambda < 575 nm in mesotrophic waters.

New method to determine the refractive index and the absorption coefficient of organic nonlinear crystals in the ultra-wideband THz region.

PubMed

Ohno, Seigo; Miyamoto, Katsuhiko; Minamide, Hiroaki; Ito, Hiromasa

2010-08-02

A method for simultaneously measuring the refractive index and absorption coefficient of nonlinear optical crystals in the ultra-wideband terahertz (THz) region is described. This method is based on the analysis of a collinear difference frequency generation (DFG) process using a tunable, dual-wavelength, optical parametric oscillator. The refractive index and the absorption coefficient in the organic nonlinear crystal DAST were experimentally determined in the frequency range 2.5-26.2 THz by measuring the THz-wave output using DFG. The resultant refractive index in the x-direction was approximately 2.3, while the absorption spectrum was in good agreement with FT-IR measurements. The output of the DAST-DFG THz-wave source was optimized to the phase-matching condition using the measured refractive index spectrum in THz region, which resulted in an improvement in the output power of up to a factor of nine.

The experimental determination of atmospheric absorption from aircraft acoustic flight tests

NASA Technical Reports Server (NTRS)

Miller, R. L.; Oncley, P. B.

1971-01-01

A method for determining atmospheric absorption coefficients from acoustic flight test data is presented. Measurements from five series of acoustic flight tests were included in the study. The number of individual flights totaled 24: six Boeing 707 flights performed in May 1969 in connection with the turbofan nacelle modification program, eight flights from Boeing tests conducted during the same period, and 10 flights of the Boeing 747 airplane. The effects of errors in acoustic, meteorological, and aircraft performance and position measurements are discussed. Tabular data of the estimated sample variance of the data for each test are given for source directivity angles from 75 deg to 120 deg and each 1/3-octave frequency band. Graphic comparisons are made of absorption coefficients derived from ARP 866, using atmospheric profile data, with absorption coefficients determined by the experimental method described in the report.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Measurement of optical absorption in polycrystalline CVD diamond plates by the phase photothermal method at a wavelength of 10.6 μm

NASA Astrophysics Data System (ADS)

Luk'yanov, A. Yu; Ral'chenko, Viktor G.; Khomich, A. V.; Serdtsev, E. V.; Volkov, P. V.; Savel'ev, A. V.; Konov, Vitalii I.

2008-12-01

A highly-efficient phase photothermal method is developed for quantitative measurements of the small optical absorption coefficient in thin plates made of highly transparent materials in which bulk losses significantly exceed surface losses. The bulk absorption coefficient at 10.6 μm is estimated in polycrystalline diamond plates grown from the vapour phase (a CVD diamond). The results are compared with those for natural and synthetic diamond single crystals and with the concentrations of nitrogen and hydrogen impurities. The absorption coefficient of the best samples of the CVD diamond did not exceed 0.06 cm-1, which, taking into account the high thermal conductivity of the CVD diamond (1800-2200 W mK-1 at room temperature), makes this material attractive for fabricating output windows of high-power CO2 lasers, especially for manufacturing large-size optics.

Fixed Packed Bed Reactors in Reduced Gravity

NASA Technical Reports Server (NTRS)

Motil, Brian J.; Balakotaiah, Vemuri; Kamotani, Yasuhiro; McCready, Mark J.

2004-01-01

We present experimental data on flow pattern transitions, pressure drop and flow characteristics for cocurrent gas-liquid flow through packed columns in microgravity. The flow pattern transition data indicates that the pulse flow regime exists over a wider range of gas and liquid flow rates under microgravity conditions compared to 1-g and the widely used Talmor map in 1-g is not applicable for predicting the transition boundaries. A new transition criterion between bubble and pulse flow in microgravity is proposed and tested using the data. Since there is no static head in microgravity, the pressure drop measured is the true frictional pressure drop. The pressure drop data, which has much smaller scatter than most reported 1-g data clearly shows that capillary effects can enhance the pressure drop (especially in the bubble flow regime) as much as 200% compared to that predicted by the single phase Ergun equation. The pressure drop data are correlated in terms of a two-phase friction factor and its dependence on the gas and liquid Reynolds numbers and the Suratman number. The influence of gravity on the pulse amplitude and frequency is also discussed and compared to that under normal gravity conditions. Experimental work is planned to determine the gas-liquid and liquid-solid mass transfer coefficients. Because of enhanced interfacial effects, we expect the gas-liquid transfer coefficients kLa and kGa (where a is the gas-liquid interfacial area) to be higher in microgravity than in normal gravity at the same flow conditions. This will be verified by gas absorption experiments, with and without reaction in the liquid phase, using oxygen, carbon dioxide, water and dilute aqueous amine solutions. The liquid-solid mass transfer coefficient will also be determined in the bubble as well as the pulse flow regimes using solid benzoic acid particles in the packing and measuring their rate of dissolution. The mass transfer coefficients in microgravity will be compared to those in normal gravity cocurrent flow to determine the mass transfer enhancement and propose new mass transfer correlations for two-phase gas-liquid flows through packed beds in microgravity.

Fixed Packed Bed Reactors in Reduced Gravity

NASA Technical Reports Server (NTRS)

Motil, Brian J.; Balakotaiah, Vemuri; Kamotani, Yasuhiro; McCready, Mark J.

2004-01-01

We present experimental data on flow pattern transitions, pressure drop and flow characteristics for cocurrent gas-liquid flow through packed columns in microgravity. The flow pattern transition data indicates that the pulse flow regime exists over a wider range of gas and liquid flow rates under microgravity conditions compared to 1-g and the widely used Talmor map in 1-g is not applicable for predicting the transition boundaries. A new transition criterion between bubble and pulse flow in microgravity is proposed and tested using the data. Since there is no static head in microgravity, the pressure drop measured is the true frictional pressure drop. The pressure drop data, which has much smaller scatter than most reported 1-g data clearly shows that capillary effects can enhance the pressure drop (especially in the bubble flow regime) as much as 200% compared to that predicted by the single phase Ergun equation. The pressure drop data are correlated in terms of a two-phase friction factor and its dependence on the gas and liquid Reynolds numbers and the Suratman number. The influence of gravity on the pulse amplitude and frequency is also discussed and compared to that under normal gravity conditions. Experimental work is planned to determine the gas-liquid mass transfer coefficients. Because of enhanced interfacial effects, we expect the gas-liquid transfer coefficients k(L)a and k(G)a (where a is the gas-liquid interfacial area) to be higher in microgravity than in normal gravity at the same flow conditions. This will be verified by gas absorption experiments, with and without reaction in the liquid phase, using oxygen, carbon dioxide, water and dilute aqueous amine solutions. The liquid-solid mass transfer coefficient will also be determined in the bubble as well as the pulse flow regimes using solid benzoic acid particles in the packing and measuring their rate of dissolution. The mass transfer coefficients in microgravity will be compared to those in normal gravity cocurrent flow to determine the mass transfer enhancement and propose new mass transfer correlations for two-phase gas-liquid flows through packed beds in microgravity.

Time-resolved measurements of black carbon light absorption enhancement in urban and near-urban locations of Southern Ontario, Canada

NASA Astrophysics Data System (ADS)

Chan, T. W.; Brook, J. R.; Smallwood, G. J.; Lu, G.

2010-08-01

In this study a photoacoustic spectrometer (PA), a laser-induced incandescence instrument system (LII) and an aerosol mass spectrometer were operated in parallel for in situ measurements of black carbon (BC) light absorption enhancement. Results of a thermodenuder experiment using ambient particles in Toronto are presented first to show that LII measurements of BC are not influenced by particle coating while the PA response is enhanced and also that the nature of this enhancement is influenced by particle morphology. Comparisons of ambient PA and LII measurements at four different locations (suburban Toronto; a street canyon with heavy diesel bus traffic in Ottawa; adjacent to a commuter highway in Ottawa and; regional background air in and around Windsor, Ontario), show that the different meteorological conditions and atmospheric processes result in different particle light absorption enhancement and hence the specific attenuation coefficient (SAC). Depending upon location of measurement and the BC spherule diameter (primary particle size - PPS) measurement from the LII, the SAC varies from 2.6±0.04 to 22.5±0.7 m2 g-1. Observations from this study also show the active surface area of the BC aggregate, inferred from PPS, is an important parameter for inferring the degree of particle collapse of a BC particle. The predictability of the overall BC light absorption enhancement in the atmosphere depends not only on the coating mass but also on the source of the BC and on our ability to predict or measure the change in particle morphology as particles evolve.

A Feasibility Study for Simultaneous Measurements of Water Vapor and Precipitation Parameters using a Three-frequency Radar

NASA Technical Reports Server (NTRS)

Meneghini, R.; Liao, L.; Tian, L.

2005-01-01

The radar return powers from a three-frequency radar, with center frequency at 22.235 GHz and upper and lower frequencies chosen with equal water vapor absorption coefficients, can be used to estimate water vapor density and parameters of the precipitation. A linear combination of differential measurements between the center and lower frequencies on one hand and the upper and lower frequencies on the other provide an estimate of differential water vapor absorption. The coupling between the precipitation and water vapor estimates is generally weak but increases with bandwidth and the amount of non-Rayleigh scattering of the hydrometeors. The coupling leads to biases in the estimates of water vapor absorption that are related primarily to the phase state and the median mass diameter of the hydrometeors. For a down-looking radar, path-averaged estimates of water vapor absorption are possible under rain-free as well as raining conditions by using the surface returns at the three frequencies. Simulations of the water vapor attenuation retrieval show that the largest source of error typically arises from the variance in the measured radar return powers. Although the error can be mitigated by a combination of a high pulse repetition frequency, pulse compression, and averaging in range and time, the radar receiver must be stable over the averaging period. For fractional bandwidths of 20% or less, the potential exists for simultaneous measurements at the three frequencies with a single antenna and transceiver, thereby significantly reducing the cost and mass of the system.

Encapsulation of Ionic Liquids with an Aprotic Heterocyclic Anion (AHA-IL) for CO2 Capture: Preserving the Favorable Thermodynamics and Enhancing the Kinetics of Absorption.

PubMed

Moya, Cristian; Alonso-Morales, Noelia; de Riva, Juan; Morales-Collazo, Oscar; Brennecke, Joan F; Palomar, Jose

2018-03-08

The performance of an ionic liquid with an aprotic heterocyclic anion (AHA-IL), trihexyl(tetradecyl)phosphonium 2-cyanopyrrolide ([P 66614 ][2-CNPyr]), for CO 2 capture has been evaluated considering both the thermodynamics and the kinetics of the phenomena. Absorption gravimetric measurements of the gas-liquid equilibrium isotherms of CO 2 -AHA-IL systems were carried out from 298 to 333 K and at pressures up to 15 bar, analyzing the role of both chemical and physical absorption phenomena in the overall CO 2 solubility in the AHA-IL, as has been done previously. In addition, the kinetics of the CO 2 chemical absorption process was evaluated by in situ Fourier transform infrared spectroscopy-attenuated total reflection, following the characteristic vibrational signals of the reactants and products over the reaction time. A chemical absorption model was used to describe the time-dependent concentration of species involved in the reactive absorption, obtaining kinetic parameters (such as chemical reaction kinetic constants and diffusion coefficients) as a function of temperatures and pressures. As expected, the results demonstrate that the CO 2 absorption rate is mass-transfer-controlled because of the relatively high viscosity of AHA-IL. The AHA-IL was encapsulated in a porous carbon sphere (Encapsulated Ionic Liquid, ENIL) to improve the kinetic performance of the AHA-IL for CO 2 capture. The newly synthesized AHA-ENIL material was evaluated as a CO 2 sorbent with gravimetric absorption measurements. AHA-ENIL systems preserve the good CO 2 absorption capacity of the AHA-IL but drastically enhance the CO 2 absorption rate because of the increased gas-liquid surface contact area achieved by solvent encapsulation.

Improvement of scattering correction for in situ coastal and inland water absorption measurement using exponential fitting approach

NASA Astrophysics Data System (ADS)

Ye, Huping; Li, Junsheng; Zhu, Jianhua; Shen, Qian; Li, Tongji; Zhang, Fangfang; Yue, Huanyin; Zhang, Bing; Liao, Xiaohan

2017-10-01

The absorption coefficient of water is an important bio-optical parameter for water optics and water color remote sensing. However, scattering correction is essential to obtain accurate absorption coefficient values in situ using the nine-wavelength absorption and attenuation meter AC9. Establishing the correction always fails in Case 2 water when the correction assumes zero absorption in the near-infrared (NIR) region and underestimates the absorption coefficient in the red region, which affect processes such as semi-analytical remote sensing inversion. In this study, the scattering contribution was evaluated by an exponential fitting approach using AC9 measurements at seven wavelengths (412, 440, 488, 510, 532, 555, and 715 nm) and by applying scattering correction. The correction was applied to representative in situ data of moderately turbid coastal water, highly turbid coastal water, eutrophic inland water, and turbid inland water. The results suggest that the absorption levels in the red and NIR regions are significantly higher than those obtained using standard scattering error correction procedures. Knowledge of the deviation between this method and the commonly used scattering correction methods will facilitate the evaluation of the effect on satellite remote sensing of water constituents and general optical research using different scattering-correction methods.

Absorption coefficients and frequency shifts measurement in the spectral range of 1071.88-1084.62 cm-1 vs. pressure for chlorodifluoromethane (CHClF2) using tunable CW CO2 laser

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.

Optical band gap studies on lithium aluminum silicate glasses doped with Cr3+ ions

NASA Astrophysics Data System (ADS)

El-Diasty, Fouad; Abdel Wahab, Fathy A.; Abdel-Baki, Manal

2006-11-01

Lithium aluminum silicate glass system (LAS) implanted with chromium ions is prepared. The reflectance and transmittance measurements are used to determine the dispersion of absorption coefficient. The optical data are explained in terms of the different oxidation states adopted by the chromium ions into the glass network. It is found that the oxidation state of the chromium depends on its concentration. Across a wide spectral range, 0.2-1.6μm, analysis of the fundamental absorption edge provides values for the average energy band gaps for allowed direct and indirect transitions. The optical absorption coefficient just below the absorption edge varies exponentially with photon energy indicating the presence of Urbach's tail. Such tail is decreased with the increase of the chromium dopant. From the analysis of the optical absorption data, the absorption peak at ground state exciton energy, the absorption at band gap, and the free exciton binding energy are determined. The extinction coefficient data are used to determine the Fermi energy level of the studied glasses. The metallization criterion is obtained and discussed exploring the nature of the glasses. The measured IR spectra of the different glasses are used to throw some light on the optical properties of the present glasses correlating them with their structure and composition.

Molecular Characterization of Brown Carbon (BrC) Chromophores in Secondary Organic Aerosol Generated From Photo-Oxidation of Toluene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Peng; Liu, Jiumeng; Shilling, John E.

Atmospheric Brown carbon (BrC) is a significant contributor to light absorption and climate forcing. However, little is known about a fundamental relationship between the chemical composition of BrC and its optical properties. In this work, light-absorbing secondary organic aerosol (SOA) was generated in the PNNL chamber from toluene photo-oxidation in the presence of NOx (Tol-SOA). Molecular structures of BrC components were examined using nanospray desorption electrospray ionization (nano-DESI) and liquid chromatography (LC) combined with UV/Vis spectroscopy and electrospray ionization (ESI) high-resolution mass spectrometry (HRMS). The chemical composition of BrC chromophores and the light absorption properties of toluene SOA (Tol-SOA) dependmore » strongly on the initial NOx concentration. Specifically, Tol-SOA generated under high-NOx conditions (defined here as initial NOx/toluene of 5/1) appears yellow and mass absorption coefficient of the bulk sample (MACbulk@365nm = 0.78 m2 g-1) is nearly 80 fold higher than that measured for the Tol-SOA sample generated under low-NOx conditions (NOx/toluene < 1/300). Fifteen compounds, most of which are nitrophenols, are identified as major BrC chromophores responsible for the enhanced light absorption of Tol-SOA material produced in the presence of NOx. The integrated absorbance of these fifteen chromophores accounts for 40-60% of the total light absorbance by Tol-SOA at wavelengths between 300 nm and 500 nm. The combination of tandem LC-UV/Vis-ESI/HRMS measurements provides an analytical platform for predictive understanding of light absorption properties by BrC and their relationship to the structure of individual chromophores. General trends in the UV/vis absorption by plausible isomers of the BrC chromophores were evaluated using theoretical chemistry calculations. The molecular-level understanding of BrC chemistry is helpful for better understanding the evolution and behavior of light absorbing aerosols in the atmosphere.« less

Ultrasound in gas-liquid systems: effects on solubility and mass transfer.

PubMed

Laugier, F; Andriantsiferana, C; Wilhelm, A M; Delmas, H

2008-09-01

The effect of ultrasound on the pseudo-solubility of nitrogen in water and on gas-liquid mass transfer kinetics has been investigated in an autoclave reactor equipped with a gas induced impeller. In order to use organic liquids and to investigate the effect of pressure, gas-liquid mass transfer coefficient was calculated from the evolution of autoclave pressure during gas absorption to avoid any side-effects of ultrasound on the concentrations measurements. Ultrasound effect on the apparent solubility is very low (below 12%). Conversely ultrasound greatly improves gas-liquid mass transfer, especially below gas induction speed, this improvement being boosted by pressure. In typical conditions of organic synthesis: 323 K, 1100 rpm, 10 bar, k(L).a is multiplied by 11 with ultrasound (20 kHz/62.6 W). The impact of sonication is much higher on gassing out than on gassing in. In the same conditions, this enhancement is at least five times higher for degassing.

Comparison of different Aethalometer correction schemes and a reference multi-wavelength absorption technique for ambient aerosol data

NASA Astrophysics Data System (ADS)

Saturno, Jorge; Pöhlker, Christopher; Massabò, Dario; Brito, Joel; Carbone, Samara; Cheng, Yafang; Chi, Xuguang; Ditas, Florian; Hrabě de Angelis, Isabella; Morán-Zuloaga, Daniel; Pöhlker, Mira L.; Rizzo, Luciana V.; Walter, David; Wang, Qiaoqiao; Artaxo, Paulo; Prati, Paolo; Andreae, Meinrat O.

2017-08-01

Deriving absorption coefficients from Aethalometer attenuation data requires different corrections to compensate for artifacts related to filter-loading effects, scattering by filter fibers, and scattering by aerosol particles. In this study, two different correction schemes were applied to seven-wavelength Aethalometer data, using multi-angle absorption photometer (MAAP) data as a reference absorption measurement at 637 nm. The compensation algorithms were compared to five-wavelength offline absorption measurements obtained with a multi-wavelength absorbance analyzer (MWAA), which serves as a multiple-wavelength reference measurement. The online measurements took place in the Amazon rainforest, from the wet-to-dry transition season to the dry season (June-September 2014). The mean absorption coefficient (at 637 nm) during this period was 1.8 ± 2.1 Mm-1, with a maximum of 15.9 Mm-1. Under these conditions, the filter-loading compensation was negligible. One of the correction schemes was found to artificially increase the short-wavelength absorption coefficients. It was found that accounting for the aerosol optical properties in the scattering compensation significantly affects the absorption Ångström exponent (åABS) retrievals. Proper Aethalometer data compensation schemes are crucial to retrieve the correct åABS, which is commonly implemented in brown carbon contribution calculations. Additionally, we found that the wavelength dependence of uncompensated Aethalometer attenuation data significantly correlates with the åABS retrieved from offline MWAA measurements.

Solar cells based on particulate structure of active layer: Investigation of light absorption by an ordered system of spherical submicron silicon particles

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.

A Novel Acoustic Sensor Approach to Classify Seeds Based on Sound Absorption Spectra

PubMed Central

Gasso-Tortajada, Vicent; Ward, Alastair J.; Mansur, Hasib; Brøchner, Torben; Sørensen, Claus G.; Green, Ole

2010-01-01

A non-destructive and novel in situ acoustic sensor approach based on the sound absorption spectra was developed for identifying and classifying different seed types. The absorption coefficient spectra were determined by using the impedance tube measurement method. Subsequently, a multivariate statistical analysis, i.e., principal component analysis (PCA), was performed as a way to generate a classification of the seeds based on the soft independent modelling of class analogy (SIMCA) method. The results show that the sound absorption coefficient spectra of different seed types present characteristic patterns which are highly dependent on seed size and shape. In general, seed particle size and sphericity were inversely related with the absorption coefficient. PCA presented reliable grouping capabilities within the diverse seed types, since the 95% of the total spectral variance was described by the first two principal components. Furthermore, the SIMCA classification model based on the absorption spectra achieved optimal results as 100% of the evaluation samples were correctly classified. This study contains the initial structuring of an innovative method that will present new possibilities in agriculture and industry for classifying and determining physical properties of seeds and other materials. PMID:22163455

Observation and analysis of water inherent optical properties

NASA Astrophysics Data System (ADS)

Sun, Deyong; Li, Yunmei; Le, Chengfeng; Huang, Changchun

2008-03-01

Inherent optical property is an important part of water optical properties, and is the foundation of water color analytical model establishment. Through quantity filter technology (QFT) and backscattering meter BB9 (WETlabs Inc), absorption coefficients of CDOM, total suspended minerals and backscattering coefficients of total suspended minerals had been observed in Meiliang Bay of Taihu lake at summer and winter respectively. After analyzing the spectral characteristics of absorption and backscattering coefficients, the differences between two seasons had been illustrated adequately, and the reasons for the phenomena, which are related to the changes of water quality coefficient, had also been explained. So water environment states can be reflected by inherent optical properties. In addition, the relationship models between backscattering coefficients and suspended particle concentrations had been established, which can support coefficients for analytical models.

Photoacoustic optical properties at UV, VIS, and near IR wavelengths for laboratory generated and winter time ambient urban aerosols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gyawali, Madhu S.; Arnott, W. Patrick; Zaveri, Rahul A.

2012-03-08

We present the laboratory and ambient photoacoustic (PA) measurement of aerosol light absorption coefficients at ultraviolet wavelength (i.e., 355 nm) and compare with measurements at 405, 532, 870, and 1047 nm. Simultaneous measurements of aerosol light scattering coefficients were achieved by the integrating reciprocal nephelometer within the PA's acoustic resonator. Absorption and scattering measurements were carried out for various laboratory generated aerosols, including salt, incense, and kerosene soot to evaluate the instrument calibration and gain insight on the spectral dependence of aerosol light absorption and scattering. Ambient measurements were obtained in Reno, Nevada, between 18 December 2009 and 18 Januarymore » 2010. The measurement period included days with and without strong ground level temperature inversions, corresponding to highly polluted (freshly emitted aerosols) and relatively clean (aged aerosols) conditions. Particulate matter (PM) concentrations were measured and analyzed with other tracers of traffic emissions. The temperature inversion episodes caused very high concentration of PM{sub 2.5} and PM{sub 10} (particulate matter with aerodynamic diameters less than 2.5 {mu}m and 10 {mu}m, respectively) and gaseous pollutants: carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxide (NO{sub 2}). The diurnal change of absorption and scattering coefficients during the polluted (inversion) days increased approximately by a factor of two for all wavelengths compared to the clean days. The spectral variation in aerosol absorption coefficients indicated a significant amount of absorbing aerosol from traffic emissions and residential wood burning. The analysis of single scattering albedo (SSA), Angstrom exponent of absorption (AEA), and Angstrom exponent of scattering (AES) for clean and polluted days provides evidences that the aerosol aging and coating process is suppressed by strong temperature inversion under cloudy conditions. In general, measured UV absorption coefficients were found to be much larger for biomass burning aerosol than for typical ambient aerosols.« less

Diffuse reflectance relations based on diffusion dipole theory for large absorption and reduced scattering

NASA Astrophysics Data System (ADS)

Bremmer, Rolf H.; van Gemert, Martin J. C.; Faber, Dirk J.; van Leeuwen, Ton G.; Aalders, Maurice C. G.

2013-08-01

Diffuse reflectance spectra are used to determine the optical properties of biological samples. In medicine and forensic science, the turbid objects under study often possess large absorption and/or scattering properties. However, data analysis is frequently based on the diffusion approximation to the radiative transfer equation, implying that it is limited to tissues where the reduced scattering coefficient dominates over the absorption coefficient. Nevertheless, up to absorption coefficients of 20 m at reduced scattering coefficients of 1 and 11.5 mm-1, we observed excellent agreement (r2=0.994) between reflectance measurements of phantoms and the diffuse reflectance equation proposed by Zonios et al. [Appl. Opt. 38, 6628-6637 (1999)], derived as an approximation to one of the diffusion dipole equations of Farrell et al. [Med. Phys. 19, 879-888 (1992)]. However, two parameters were fitted to all phantom experiments, including strongly absorbing samples, implying that the reflectance equation differs from diffusion theory. Yet, the exact diffusion dipole approximation at high reduced scattering and absorption also showed agreement with the phantom measurements. The mathematical structure of the diffuse reflectance relation used, derived by Zonios et al. [Appl. Opt. 38, 6628-6637 (1999)], explains this observation. In conclusion, diffuse reflectance relations derived as an approximation to the diffusion dipole theory of Farrell et al. can analyze reflectance ratios accurately, even for much larger absorption than reduced scattering coefficients. This allows calibration of fiber-probe set-ups so that the object's diffuse reflectance can be related to its absorption even when large. These findings will greatly expand the application of diffuse reflection spectroscopy. In medicine, it may allow the use of blue/green wavelengths and measurements on whole blood, and in forensic science, it may allow inclusion of objects such as blood stains and cloth at crime scenes.

Photoacoustic Optical Properties at UV, VIS, and near IR Wavelengths for Laboratory Generated and Winter Time Ambient Urban Aerosols

NASA Technical Reports Server (NTRS)

Gyawali, M.; Arnott, W. P.; Zaveri, R. A.; Song, C.; Moosmuller, H.; Liu, L.; Mishchenko, M. I.; Chen, L.-W.A.; Green, M. C.; Watson, J. G.;

Propagation of intense laser radiation through a diffusion flame of burning oil

NASA Astrophysics Data System (ADS)

Gvozdev, S. V.; Glova, A. F.; Dubrovskii, V. Yu; Durmanov, S. T.; Krasyukov, A. G.; Lysikov, A. Yu; Smirnov, G. V.; Pleshkov, V. M.

2015-06-01

We report the results of measuring the absorption coefficient of radiation from a cw ytterbium fibre single-mode laser with the power up to 1.5 kW by a diffusion flame of oil, burning in the atmosphere air at normal pressure on a free surface. For the constant length (30 mm) and width (30 mm) of the flame and the distance 10 mm between the laser beam axis and the oil surface the dependence of the absorption coefficient, averaged over the flame length, on the mean radiation intensity (varied from 4.5 × 103 to 1.2 × 106 W cm-2) entering the flame is obtained. The qualitative explanation of nonmonotonic behaviour of the absorption coefficient versus the intensity is presented.

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.

Determination of optical band gap of powder-form nanomaterials with improved accuracy

NASA Astrophysics Data System (ADS)

Ahsan, Ragib; Khan, Md. Ziaur Rahman; Basith, Mohammed Abdul

2017-10-01

Accurate determination of a material's optical band gap lies in the precise measurement of its absorption coefficients, either from its absorbance via the Beer-Lambert law or diffuse reflectance spectrum via the Kubelka-Munk function. Absorption coefficients of powder-form nanomaterials calculated from absorbance spectrum do not match those calculated from diffuse reflectance spectrum, implying the inaccuracy of the traditional optical band gap measurement method for such samples. We have modified the Beer-Lambert law and the Kubelka-Munk function with proper approximations for powder-form nanomaterials. Applying the modified method for powder-form nanomaterial samples, both absorbance and diffuse reflectance spectra yield exactly the same absorption coefficients and therefore accurately determine the optical band gap.

Temperature and emissivity measurements at the sapphire single crystal fiber growth process

NASA Astrophysics Data System (ADS)

Bufetova, G. A.; Rusanov, S. Ya.; Seregin, V. F.; Pyrkov, Yu. N.; Tsvetkov, V. B.

2017-12-01

We present a new method for evaluation the absorption coefficient of the crystal melt around the phase transition zone for the spectral range of semitransparency. The emissivity distribution across the crystallization front of the sapphire crystal fiber was measured at the quasi-stationary laser heated pedestal growth (LHPG) process (Fejer et al., 1984; Feigelson, 1986) and the data for solid state, melt and phase transition zone (melt-solid interface) were obtained. The sapphire melt absorption coefficient was estimated to be 14 ± 2 cm-1 in the spectral range 1-1.4 μm around the melt point. It is consistent with data, obtained by different other methods. This method can be applied to determine the absorption coefficient for other materials.

Absorption Mode FT-ICR Mass Spectrometry Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Donald F.; Kilgour, David P.; Konijnenburg, Marco

2013-12-03

Fourier transform ion cyclotron resonance mass spectrometry offers the highest mass resolving power for molecular imaging experiments. This high mass resolving power ensures that closely spaced peaks at the same nominal mass are resolved for proper image generation. Typically higher magnetic fields are used to increase mass resolving power. However, a gain in mass resolving power can also be realized by phase correction of the data for absorption mode display. In addition to mass resolving power, absorption mode offers higher mass accuracy and signal-to-noise ratio over the conventional magnitude mode. Here we present the first use of absorption mode formore » Fourier transform ion cyclotron resonance mass spectrometry imaging. The Autophaser algorithm is used to phase correct each spectrum (pixel) in the image and then these parameters are used by the Chameleon work-flow based data processing software to generate absorption mode ?Datacubes? for image and spectral viewing. Absorption mode reveals new mass and spatial features that are not resolved in magnitude mode and results in improved selected ion image contrast.« less

Relative importance of black carbon, brown carbon, and absorption enhancement from clear coatings in biomass burning emissions

NASA Astrophysics Data System (ADS)

Pokhrel, Rudra P.; Beamesderfer, Eric R.; Wagner, Nick L.; Langridge, Justin M.; Lack, Daniel A.; Jayarathne, Thilina; Stone, Elizabeth A.; Stockwell, Chelsea E.; Yokelson, Robert J.; Murphy, Shane M.

2017-04-01

A wide range of globally significant biomass fuels were burned during the fourth Fire Lab at Missoula Experiment (FLAME-4). A multi-channel photoacoustic absorption spectrometer (PAS) measured dry absorption at 405, 532, and 660 nm and thermally denuded (250 °C) absorption at 405 and 660 nm. Absorption coefficients were broken into contributions from black carbon (BC), brown carbon (BrC), and lensing following three different methodologies, with one extreme being a method that assumes the thermal denuder effectively removes organics and the other extreme being a method based on the assumption that black carbon (BC) has an Ångström exponent of unity. The methodologies employed provide ranges of potential importance of BrC to absorption but, on average, there was a difference of a factor of 2 in the ratio of the fraction of absorption attributable to BrC estimated by the two methods. BrC absorption at shorter visible wavelengths is of equal or greater importance to that of BC, with maximum contributions of up to 92 % of total aerosol absorption at 405 nm and up to 58 % of total absorption at 532 nm. Lensing is estimated to contribute a maximum of 30 % of total absorption, but typically contributes much less than this. Absorption enhancements and the estimated fraction of absorption from BrC show good correlation with the elemental-carbon-to-organic-carbon ratio (EC / OC) of emitted aerosols and weaker correlation with the modified combustion efficiency (MCE). Previous studies have shown that BrC grows darker (larger imaginary refractive index) as the ratio of black to organic aerosol (OA) mass increases. This study is consistent with those findings but also demonstrates that the fraction of total absorption attributable to BrC shows the opposite trend: increasing as the organic fraction of aerosol emissions increases and the EC / OC ratio decreases.

Recording of absorption spectra by a three-beam integral technique with a tunable laser and external cavity

NASA Astrophysics Data System (ADS)

Korolenko, P. V.; Nikolaev, I. V.; Ochkin, V. N.; Tskhai, S. N.

2014-04-01

An integral method is considered for recording absorption using three laser beams transmitted through and reflected from an external cavity with the absorbing medium (R-ICOS). The method is the elaboration of a known single-beam ICOS method and allows suppression of the influence of radiation phase fluctuations in the resonator on recording weak absorption spectra. First of all, this reduces high-frequency instabilities and gives a possibility to record spectra during short time intervals. In this method, mirrors of the resonator may have moderate reflection coefficients. Capabilities of the method have been demonstrated by the examples of weak absorption spectra of atmospheric methane and natural gas in a spectral range around 1650 nm. With the mirrors having the reflection coefficients of 0.8-0.99, a spectrum can be recorded for 320 μs with the accuracy sufficient for detecting a background concentration of methane in atmosphere. For the acquisition time of 20 s, the absorption coefficients of ~2×10-8 cm-1 can be measured, which corresponds to a 40 times less molecule concentration than the background value.

Optical characteristics of Tl0.995Cu0.005InS2 single crystals

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Ali, H. A. M.; Abu-Samaha, F. S. H.

2013-04-01

Optical properties of Tl0.995Cu0.005InS2 single crystals were studied using transmittance and reflectance measurements in the spectral wavelength range of 300-2500 nm. The optical constants (n and k) were calculated at room temperature. The analysis of the spectral behavior of the absorption coefficient in the absorption region revealed indirect transition. The refractive index dispersion data were analyzed in terms of the single oscillator model. Dispersion parameters such as the single oscillator energy (Eo), the dispersion energy (Ed), the high frequency dielectric constant (ε∞), the lattice dielectric constant (εL) and the ratio of free charge carrier concentration to the effective mass (N/m*) were estimated. The third order nonlinear susceptibility (χ(3)) was calculated according to the generalized Miller's rule. Also, the real and imaginary parts of the complex dielectric constant were determined.

Real-structure effects: Band gaps of Mg_xZn_{1-x}O, Cd_xZn_{1-x}O, and n-type ZnO from ab-initio calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schleife, A; Bechstedt, F

2012-02-15

Many-body perturbation theory is applied to compute the quasiparticle electronic structures and the optical-absorption spectra (including excitonic effects) for several transparent conducting oxides. We discuss HSE+G{sub 0}W{sub 0} results for band structures, fundamental band gaps, and effective electron masses of MgO, ZnO, CdO, SnO{sub 2}, SnO, In{sub 2}O{sub 3}, and SiO{sub 2}. The Bethe-Salpeter equation is solved to account for excitonic effects in the calculation of the frequency-dependent absorption coefficients. We show that the HSE+G{sub 0}W{sub 0} approach and the solution of the Bethe-Salpeter equation are very well-suited to describe the electronic structure and the optical properties of various transparentmore » conducting oxides in good agreement with experiment.« less

A sealed titanium window proportional counter for the detection of .5-keV X rays.

NASA Technical Reports Server (NTRS)

Mcclintock, J. E.; Levine, A.; Rappaport, S.

1972-01-01

A sealed Ti window proportional counter sensitive to X radiation in the energy range 0.35-0.45 keV and above 1.5 keV is described. Measurements of the Ti mass absorption coefficients and a graphical summary of the literature values are presented. For a proportional counter with a 930 microgram/sq cm (2.1-micron) Ti window, the peak efficiency at 0.45 keV is found to lie between 4.6% and 7.1%. An application in X-ray astronomy involving a rocket observation of Sco X-1 is discussed.

Laterally coupled circular quantum dots under applied electric field

NASA Astrophysics Data System (ADS)

Duque, C. M.; Correa, J. D.; Morales, A. L.; Mora-Ramos, M. E.; Duque, C. A.

2016-03-01

The optical response of a system of two laterally coupled quantum dots with circular cross-sectional shape is investigated within the effective mass approximation, taking into account the effects of the change in the geometrical configuration, the application of an external static electric field, and the presence of a donor impurity center. The first-order dielectric susceptibility is calculated in order to derive the corresponding light absorption and relative refractive index coefficients. The possibility of tuning these optical properties by means of changes in the quantum dot symmetry and the electric field intensity is particularly discussed.

Absorption/Transmission Measurements of PSAP Particle-Laden Filters from the Biomass Burning Observation Project (BBOP) Field Campaign

PubMed Central

Presser, Cary; Nazarian, Ashot; Conny, Joseph M.; Chand, Duli; Sedlacek, Arthur; Hubbe, John M.

2017-01-01

Absorptivity measurements with a laser-heating approach, referred to as the laser-driven thermal reactor (LDTR), were carried out in the infrared and applied at ambient (laboratory) non-reacting conditions to particle-laden filters from a three-wavelength (visible) particle/soot absorption photometer (PSAP). The particles were obtained during the Biomass Burning Observation Project (BBOP) field campaign. The focus of this study was to determine the particle absorption coefficient from field-campaign filter samples using the LDTR approach, and compare results with other commercially available instrumentation (in this case with the PSAP, which has been compared with numerous other optical techniques). Advantages of the LDTR approach include 1) direct estimation of material absorption from temperature measurements (as opposed to resolving the difference between the measured reflection/scattering and transmission), 2) information on the filter optical properties, and 3) identification of the filter material effects on particle absorption (e.g., leading to particle absorption enhancement or shadowing). For measurements carried out under ambient conditions, the particle absorptivity is obtained with a thermocouple placed flush with the filter back surface and the laser probe beam impinging normal to the filter particle-laden surface. Thus, in principle one can employ a simple experimental arrangement to measure simultaneously both the transmissivity and absorptivity (at different discrete wavelengths) and ascertain the particle absorption coefficient. For this investigation, LDTR measurements were carried out with PSAP filters (pairs with both blank and exposed filters) from eight different days during the campaign, having relatively light but different particle loadings. The observed particles coating the filters were found to be carbonaceous (having broadband absorption characteristics). The LDTR absorption coefficient compared well with results from the PSAP. The analysis was also expanded to account for the filter fiber scattering on particle absorption in assessing particle absorption enhancement and shadowing effects. The results indicated that absorption enhancement effects were significant, and diminished with increased filter particle loading. PMID:28690360

Absorption/Transmission Measurements of PSAP Particle-Laden Filters from the Biomass Burning Observation Project (BBOP) Field Campaign.

PubMed

Presser, Cary; Nazarian, Ashot; Conny, Joseph M; Chand, Duli; Sedlacek, Arthur; Hubbe, John M

2017-01-01

Absorptivity measurements with a laser-heating approach, referred to as the laser-driven thermal reactor (LDTR), were carried out in the infrared and applied at ambient (laboratory) non-reacting conditions to particle-laden filters from a three-wavelength (visible) particle/soot absorption photometer (PSAP). The particles were obtained during the Biomass Burning Observation Project (BBOP) field campaign. The focus of this study was to determine the particle absorption coefficient from field-campaign filter samples using the LDTR approach, and compare results with other commercially available instrumentation (in this case with the PSAP, which has been compared with numerous other optical techniques). Advantages of the LDTR approach include 1) direct estimation of material absorption from temperature measurements (as opposed to resolving the difference between the measured reflection/scattering and transmission), 2) information on the filter optical properties, and 3) identification of the filter material effects on particle absorption (e.g., leading to particle absorption enhancement or shadowing). For measurements carried out under ambient conditions, the particle absorptivity is obtained with a thermocouple placed flush with the filter back surface and the laser probe beam impinging normal to the filter particle-laden surface. Thus, in principle one can employ a simple experimental arrangement to measure simultaneously both the transmissivity and absorptivity (at different discrete wavelengths) and ascertain the particle absorption coefficient. For this investigation, LDTR measurements were carried out with PSAP filters (pairs with both blank and exposed filters) from eight different days during the campaign, having relatively light but different particle loadings. The observed particles coating the filters were found to be carbonaceous (having broadband absorption characteristics). The LDTR absorption coefficient compared well with results from the PSAP. The analysis was also expanded to account for the filter fiber scattering on particle absorption in assessing particle absorption enhancement and shadowing effects. The results indicated that absorption enhancement effects were significant, and diminished with increased filter particle loading.

Photoacoustic optical properties at UV, VIS, and near IR wavelengths for laboratory generated and winter time ambient urban aerosols

NASA Astrophysics Data System (ADS)

Gyawali, M.; Arnott, W. P.; Zaveri, R. A.; Song, C.; Moosmüller, H.; Liu, L.; Mishchenko, M. I.; Chen, L.-W. A.; Green, M. C.; Watson, J. G.; Chow, J. C.

2011-09-01

We present the first laboratory and ambient photoacoustic (PA) measurement of aerosol light absorption coefficients at ultraviolet (UV) wavelength (i.e. 355 nm) and compare with measurements at 405, 532, 870, and 1047 nm. Simultaneous measurements of aerosol light scattering coefficients were achieved by the integrating reciprocal nephelometer within the PA';s acoustic resonator. Absorption and scattering measurements were carried out for various laboratory-generated aerosols, including salt, incense, and kerosene soot to evaluate the instrument calibration and gain insight on the spectral dependence of aerosol light absorption and scattering. Exact T-matrix method calculations were used to model the absorption and scattering characteristics of fractal-like agglomerates of different compactness and varying number of monomers. With these calculations, we attempted to estimate the number of monomers and fractal dimension of laboratory generated kerosene soot. Ambient measurements were obtained in Reno, Nevada, between 18 December 2009, and 18 January 2010. The measurement period included days with and without strong ground level temperature inversions, corresponding to highly polluted (freshly emitted aerosols) and relatively clean (aged aerosols) conditions. Particulate matter (PM) concentrations were measured and analyzed with other tracers of traffic emissions. The temperature inversion episodes caused very high concentration of PM2.5 and PM10 (particulate matter with aerodynamic diameters less than 2.5 μm and 10 μm, respectively) and gaseous pollutants: carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxide (NO2). The diurnal change of absorption and scattering coefficients during the polluted (inversion) days increased approximately by a factor of two for all wavelengths compared to the clean days. The spectral variation in aerosol absorption coefficients indicated a significant amount of absorbing aerosol from traffic emissions and residential wood burning. The analysis of single scattering albedo (SSA), Ångström exponent of absorption (AEA), and Ångström exponent of scattering (AES) for clean and polluted days provides evidences that the aerosol aging and coating process is suppressed by strong temperature inversion under cloudy conditions. In general, measured UV absorption coefficients were found to be much larger for biomass burning aerosol than for typical ambient aerosols.

Colloquium: Search for a drifting proton-electron mass ratio from H2

NASA Astrophysics Data System (ADS)

Ubachs, W.; Bagdonaite, J.; Salumbides, E. J.; Murphy, M. T.; Kaper, L.

2016-04-01

An overview is presented of the H2 quasar absorption method to search for a possible variation of the proton-electron mass ratio μ =mp/me on a cosmological time scale. The method is based on a comparison between wavelengths of absorption lines in the H2 Lyman and Werner bands as observed at high redshift with wavelengths of the same lines measured at zero redshift in the laboratory. For such comparison sensitivity coefficients to a relative variation of μ are calculated for all individual lines and included in the fitting routine deriving a value for Δ μ /μ . Details of the analysis of astronomical spectra, obtained with large 8-10 m class optical telescopes, equipped with high-resolution echelle grating based spectrographs, are explained. The methods and results of the laboratory molecular spectroscopy of H2, in particular, the laser-based metrology studies for the determination of rest wavelengths of the Lyman and Werner band absorption lines, are reviewed. Theoretical physics scenarios delivering a rationale for a varying μ are discussed briefly, as well as alternative spectroscopic approaches to probe variation of μ , other than the H2 method. Also a recent approach to detect a dependence of the proton-to-electron mass ratio on environmental conditions, such as the presence of strong gravitational fields, are highlighted. Currently some 56 H2 absorption systems are known and listed. Their usefulness to detect μ variation is discussed, in terms of column densities and brightness of background quasar sources, along with future observational strategies. The astronomical observations of ten quasar systems analyzed so far set a constraint on a varying proton-electron mass ratio of |Δ μ /μ |<5 ×1 0-6 (3 σ ), which is a null result, holding for redshifts in the range z =2.0 - 4.2 . This corresponds to look-back times of (10 - 12.4 )×109 years into cosmic history. Attempts to interpret the results from these ten H2 absorbers in terms of a spatial variation of μ are currently hampered by the small sample size and their coincidental distribution in a relatively narrow band across the sky.

Absorption of ethanol, acetone, benzene and 1,2-dichloroethane through human skin in vitro: a test of diffusion model predictions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gajjar, Rachna M.; Kasting, Gerald B., E-mail: Gerald.Kasting@uc.edu

The overall goal of this research was to further develop and improve an existing skin diffusion model by experimentally confirming the predicted absorption rates of topically-applied volatile organic compounds (VOCs) based on their physicochemical properties, the skin surface temperature, and the wind velocity. In vitro human skin permeation of two hydrophilic solvents (acetone and ethanol) and two lipophilic solvents (benzene and 1,2-dichloroethane) was studied in Franz cells placed in a fume hood. Four doses of each {sup 14}C-radiolabed compound were tested — 5, 10, 20, and 40 μL cm{sup −2}, corresponding to specific doses ranging in mass from 5.0 tomore » 63 mg cm{sup −2}. The maximum percentage of radiolabel absorbed into the receptor solutions for all test conditions was 0.3%. Although the absolute absorption of each solvent increased with dose, percentage absorption decreased. This decrease was consistent with the concept of a stratum corneum deposition region, which traps small amounts of solvent in the upper skin layers, decreasing the evaporation rate. The diffusion model satisfactorily described the cumulative absorption of ethanol; however, values for the other VOCs were underpredicted in a manner related to their ability to disrupt or solubilize skin lipids. In order to more closely describe the permeation data, significant increases in the stratum corneum/water partition coefficients, K{sub sc}, and modest changes to the diffusion coefficients, D{sub sc}, were required. The analysis provided strong evidence for both skin swelling and barrier disruption by VOCs, even by the minute amounts absorbed under these in vitro test conditions. - Highlights: • Human skin absorption of small doses of VOCs was measured in vitro in a fume hood. • The VOCs tested were ethanol, acetone, benzene and 1,2-dichloroethane. • Fraction of dose absorbed for all compounds at all doses tested was less than 0.3%. • The more aggressive VOCs absorbed at higher levels than diffusion model predictions. • We conclude that even small exposures to VOCs temporarily alter skin permeability.« less

Emission Rates and Optical Properties of Pollutants Emitted from a Traditional and an Improved Wood-Burning Cookstove

NASA Astrophysics Data System (ADS)

Kirchstetter, T.; Hadley, O. L.; Preble, C.; Gadgil, A.

2010-12-01

Traditional cooking methods in developing regions of the world generate gas and particle phase pollutants that endanger the lives of more than a billion people and contribute appreciably to the burden of climate-changing particles in the atmosphere. This presentation compares pollutant emissions from the traditional “three-stone fire” and an improved cookstove developed for refugees in Darfur: the Berkeley-Darfur Stove (BDS). The BDS was designed for increased fuel efficiency to decrease the risk of assault that women often face when gathering fuel wood. Reduced pollutant exposure and climate impact are potential co-benefits. Testing of these stoves at the Lawrence Berkeley National Laboratory facility includes 1-Hz measurements of concentrations of particulate matter, black carbon, carbon monoxide, and carbon dioxide; coefficients of particle light absorption and scattering; and absorption Angstrom exponent. Absorption and scattering coefficients were measured at 532 nm using a photoacoustic absorption instrument equipped with a reciprocal nephelometer. The BDS heated food faster and consumed less wood in cooking tests compared to the three-stone fire. The BDS emitted less carbon monoxide and particulate matter but comparable mass of black carbon compared to the three-stone fire for the same cooking task. Values of the absorption Angstrom exponent ranged from about 1 - 3, indicating the emission of both black carbon and light-absorbing organic carbon (i.e., brown carbon). Values of (dry) aerosol single scattering albedo were mostly in the range of 0.25 - 0.55, indicating that the emitted particles tend to absorb more light than they scatter. Our analysis considered the variability of pollutant emissions during different phases of the fire. Particulate matter emissions were highest during the first several minutes of cooking, which included igniting the wood, whereas carbon monoxide emissions were highest during the last several minutes of cooking when smoldering became more dominant. Comparison of photoacoustic absorption and aethalometer black carbon provided an easy means of correcting black carbon concentrations, which were low by a factor of 2 at the end of the aethalometer sampling cycle if uncorrected.

Laser ablation of PMMA doped with benzyl

NASA Astrophysics Data System (ADS)

Wang, Jun; Niino, Hiroyuki; Yabe, Akira

1998-08-01

KrF-laser ablation of poly(methylmethacrylate) (PMMA) doped with benzil was studied from the viewpoint of nonlinear absorption of the PMMA film during the laser irradiation. After measuring the relationship between the transmission and incident laser intensity, we developed a novel method to obtain absorption coefficient depending on laser intensity. Using the nonlinear absorption coefficient of PMMA doped with benzil, we succeeded in fitting the relationship of etch depth and laser intensity. The dependence of concentration of benzil in PMMA film and the difference between benzil and pyrene were also discussed.

Laser absorption spectroscopy - Method for monitoring complex trace gas mixtures

NASA Technical Reports Server (NTRS)

Green, B. D.; Steinfeld, J. I.

1976-01-01

A frequency stabilized CO2 laser was used for accurate determinations of the absorption coefficients of various gases in the wavelength region from 9 to 11 microns. The gases investigated were representative of the types of contaminants expected to build up in recycled atmospheres. These absorption coefficients were then used in determining the presence and amount of the gases in prepared mixtures. The effect of interferences on the minimum detectable concentration of the gases was measured. The accuracies of various methods of solution were also evaluated.

Re-parameterization of a quasi-analytical algorithm for colored dissolved organic matter dominant inland waters

NASA Astrophysics Data System (ADS)

Ogashawara, Igor; Mishra, Deepak R.; Nascimento, Renata F. F.; Alcântara, Enner H.; Kampel, Milton; Stech, Jose L.

2016-12-01

Quasi-Analytical Algorithms (QAAs) are based on radiative transfer equations and have been used to derive inherent optical properties (IOPs) from the above surface remote sensing reflectance (Rrs) in aquatic systems in which phytoplankton is the dominant optically active constituents (OACs). However, Colored Dissolved Organic Matter (CDOM) and Non Algal Particles (NAP) can also be dominant OACs in water bodies and till now a QAA has not been parametrized for these aquatic systems. In this study, we compared the performance of three widely used QAAs in two CDOM dominated aquatic systems which were unsuccessful in retrieving the spectral shape of IOPS and produced minimum errors of 350% for the total absorption coefficient (a), 39% for colored dissolved matter absorption coefficient (aCDM) and 7566.33% for phytoplankton absorption coefficient (aphy). We re-parameterized a QAA for CDOM dominated (hereafter QAACDOM) waters which was able to not only achieve the spectral shape of the OACs absorption coefficients but also brought the error magnitude to a reasonable level. The average errors found for the 400-750 nm range were 30.71 and 14.51 for a, 14.89 and 8.95 for aCDM and 25.90 and 29.76 for aphy in Funil and Itumbiara Reservoirs, Brazil respectively. Although QAACDOM showed significant promise for retrieving IOPs in CDOM dominated waters, results indicated further tuning is needed in the estimation of a(λ) and aphy(λ). Successful retrieval of the absorption coefficients by QAACDOM would be very useful in monitoring the spatio-temporal variability of IOPS in CDOM dominated waters.

Pressure shift coefficient measurements in an RF discharge for Ar 4s[3/2]2—5p[3/2]3 transition with the help of diodelaser absorption spectroscopy

NASA Astrophysics Data System (ADS)

Chernyshov, A. K.; Mikheyev, P. A.; Lunev, N. N.; Azyazov, V. N.

2018-04-01

Optically pumped all-rare-gas laser (OPRGL) with unique properties were recently proposed with a possibility to obtain the laser power on the order of hundreds of Watts from a cubic centimeter. To provide high laser efficiency, the pumping radiation has to match the absorption spectrum of the rare gas metastables. To meet this condition a reliable diagnostics of the key parameters of the active medium is required and knowledge of the broadening and shift coefficients for corresponding transitions of rare gases is necessary. In this paper, the diode-laser absorption spectroscopy was employed to determine the pressure shift coefficient for 811.5 nm Ar line. The value of obtained coefficient in pure argon reduced to 300 K is -(2.1 ± 0.1) × 10-10 s-1cm3. In the course of the study the pressure broadening coefficient was also evaluated and found to be (2.4 ± 0.5) × 10-10 s-1cm3.

Hydration shell parameters of aqueous alcohols: THz excess absorption and packing density.

PubMed

Matvejev, V; Zizi, M; Stiens, J

2012-12-06

Solvation in water requires minimizing the perturbations in its hydrogen bonded network. Hence solutes distort water molecular motions in a surrounding domain, forming a molecule-specific hydration shell. The properties of those hydration shells impact the structure and function of the solubilized molecules, both at the single molecule and at higher order levels. The size of the hydration shell and the picoseconds time-scale water dynamics retardation are revealed by terahertz (THz) absorption coefficient measurements. Room-temperature absorption coefficient at f = 0.28 [THz] is measured as a function of alcohol concentration in aqueous methanol, ethanol, 1,2-propanol, and 1-butanol solutions. Highly diluted alcohol measurements and enhanced overall measurement accuracy are achieved with a THz absorption measurement technique of nL-volume liquids in a capillary tube. In the absorption analysis, bulk and interfacial molecular domains of water and alcohol are considered. THz ideal and excess absorption coefficients are defined in accordance with thermodynamics mixing formulations. The parameter extraction method is developed based on a THz excess absorption model and hydrated solute molecule packing density representation. First, the hydration shell size is deduced from the hydrated solute packing densities at two specific THz excess absorption nonlinearity points: at infinite alcohol dilution (IAD) and at the THz excess absorption extremum (EAE). Consequently, interfacial water and alcohol molecular domain absorptions are deduced from the THz excess absorption model. The hydration shell sizes obtained at the THz excess absorption extremum are in excellent agreement with other reports. The hydration shells of methanol, ethanol, 1- and 2-propanol consist of 13.97, 22.94, 22.99, and 31.10 water molecules, respectively. The hydration shell water absorption is on average 0.774 ± 0.028 times the bulk water absorption. The hydration shell parameters might shed light on hydration dynamics of biomolecules.

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.

Influences of the Ratio of Polyol and MDI on the Acoustic Parameters of Polyurethane

NASA Astrophysics Data System (ADS)

Wang, Yonghua; Liu, Zheming; Wu, Haiquan; Zhang, Chengchun; Yu, Huadong; Ren, Luquan; Ichchou, Mohamed

2018-05-01

In this paper, the influence of different ratio of polyol and MDI on the absorption coefficient and acoustic parameters of polyurethane was studied. Ratio of 100:40 and 100:45 show the best sound absorption performance, and the change trend of transmission loss and sound absorption coefficient are opposite. The flow resistance increased with the increasing of the ratio of polyol and MDI, the greater the flow resistance, the worse the high frequency sound absorption property of the polyurethane. When the ratio of polyol and MDI keep 100:45, the minimum porosity of sample, the polyurethane porosity increase with the ratio of polyol and MDI increase.

A Review: Characteristics of Noise Absorption Material

NASA Astrophysics Data System (ADS)

Amares, S.; Sujatmika, E.; Hong, T. W.; Durairaj, R.; Hamid, H. S. H. B.

2017-10-01

Noise is always treated as a nuisance to human and even noise pollution appears in the environmental causing discomfort. This also concerns the engineering design that tends to cultivate this noise propagation. Solution such as using material to absorb the sound have been widely used. The fundamental of the sound absorbing propagation, sound absorbing characteristics and its factors are minimally debated. Furthermore, the method in order to pertain sound absorbing related to the sound absorption coefficient is also limited, as many studies only contributes in result basis and very little in literature aspect. This paper revolves in providing better insight on the importance of sound absorption and the materials factors in obtaining the sound absorption coefficient.

Parameterization of light absorption by components of seawater in optically complex coastal waters of the Crimea Peninsula (Black Sea).

PubMed

Dmitriev, Egor V; Khomenko, Georges; Chami, Malik; Sokolov, Anton A; Churilova, Tatyana Y; Korotaev, Gennady K

2009-03-01

The absorption of sunlight by oceanic constituents significantly contributes to the spectral distribution of the water-leaving radiance. Here it is shown that current parameterizations of absorption coefficients do not apply to the optically complex waters of the Crimea Peninsula. Based on in situ measurements, parameterizations of phytoplankton, nonalgal, and total particulate absorption coefficients are proposed. Their performance is evaluated using a log-log regression combined with a low-pass filter and the nonlinear least-square method. Statistical significance of the estimated parameters is verified using the bootstrap method. The parameterizations are relevant for chlorophyll a concentrations ranging from 0.45 up to 2 mg/m(3).

Optical properties of an anterior lamellar human cornea model based on fibrin-agarose

NASA Astrophysics Data System (ADS)

Ionescu, Ana M.; Cardona, Juan de la Cruz; Ghinea, Razvan; Garzón, Ingrid; González-Andrades, Miguel; Alaminos, Miguel; Pérez, Maria del Mar

2017-08-01

The optical evaluation carried out using the Inverse Adding-Doubling (IAD) method to determine the scattering and the absorption coefficients of the bioengineered human corneal stromas showed that this type of artificial biomaterials shared many similarities with native control cornea after four weeks of development in culture. Their absorption and reduced scattering coefficients values were higher than the ones of the control cornea, but their spectral behaviors of both coefficients were similar. Time of development in culture was an influencing factor on the results.

Two-photon absorption in arsenic sulfide glasses

NASA Astrophysics Data System (ADS)

Chunaev, D. S.; Snopatin, G. E.; Plotnichenko, V. G.; Karasik, A. Ya.

2016-10-01

The two-photon absorption coefficient of 1047-{\\text{nm}} light in {\\text{As}}35{\\text{S}}65 chalcogenide glass has been measured. CW probe radiation has been used to observe the linear absorption in glass induced by two-photon excitation. The induced absorption lifetime was found to be ∼ 2 {\\text{ms}}.

Physicochemical and Nonlinear Optical Properties of Novel Environmentally Benign Heterocyclic Azomethine Dyes: Experimental and Theoretical Studies

PubMed Central

Afzal, S. M.; Razvi, M. A. N.; Khan, Salman A.; Osman, Osman I.; Bakry, Ahmed H.; Asiri, Abdullah M.

2016-01-01

Novel heterocyclic azomethine dyes were prepared by the reaction of anthracene-9-carbaldehyde with different heterocyclic amines under microwave irradiation. Structures of the azomethine dyes were confirmed by the elemental analysis, mass spectrometry and several spectroscopic techniques. We studied absorbance and fluorescence spectra of the azomethine dyes in various solvents. They are found to be good absorbers and emitters. We also report photophysical properties like, extinction coefficient, oscillator strength, stokes shift and transition dipole moment. This reflects physicochemical behaviors of synthesized dyes. In addition, their intramolecular charge transfer and nonlinear optical properties, supported by natural bond orbital technique, were also studied computationally by density functional theory. The negative nonlinear refractive index and nonlinear absorption coefficient were measured for these dyes using the closed and open aperture Z-scan technique with a continuous wave helium-neon laser. These are found to vary linearly with solution concentration. PMID:27631371

Increasing the throughput and productivity of Caco-2 cell permeability assays using liquid chromatography-mass spectrometry: application to resveratrol absorption and metabolism.

PubMed

Li, Yongmei; Shin, Young Geun; Yu, Chongwoo; Kosmeder, Jerome W; Hirschelman, Wendy H; Pezzuto, John M; van Breemen, Richard B

2003-12-01

The Caco-2 cell monolayer permeability assay has become a standard model of human intestinal absorption and transport. This paper reviews recent progress in increasing the throughput of Caco-2 cell monolayer assays and in expanding the scope of this assay to include modeling intestinal drug metabolism. The state-of-the-art in Caco-2 cell monolayer permeability assays combines multi-well plates fitted with semi-permeable inserts on which Caco-2 cells have been cultured with liquid chromatography-mass spectrometry (LC-MS) or LC-tandem mass spectrometry (LC-MS-MS) for the quantitative analysis of test compounds and the identification of their intestinal metabolites. After reviewing the progress in increasing the throughput of Caco-2 cell monolayer assays for both modeling human intestinal permeability or transport and the metabolism of xenobiotic compounds, we demonstrate the application of LC-MS and LC-MS-MS to the measurement of resveratrol permeability and metabolism in the Caco-2 model. trans-Resveratrol (trans-3,5,4'-trihydroxystilbene) is a polyphenolic compound occurring in grapes, peanuts and other food sources, that is under investigation as a cancer chemoprevention agent. The apparent permeability coefficient for apical (AP) to basolateral (BL) movement of resveratrol was 2.0 x 10(-5)cm/sec. Resveratrol was not a substrate for P-glycoprotein or the multi-drug resistance associated proteins (MRP). No phase I metabolites were observed, but the phase II conjugates resveratrol-3-glucuronide and resveratrol-3-sulfate was identified based on LC-MS and LC-MS-MS analysis and comparison with synthetic standards. Although these data indicate that resveratrol diffuses rapidly across the intestinal epithelium, extensive phase II metabolism during absorption might reduce resveratrol bioavailability.

Nondestructive Evaluation of Advanced Materials with X-ray Phase Mapping

NASA Technical Reports Server (NTRS)

Hu, Zhengwei

2005-01-01

X-ray radiation has been widely used for imaging applications since Rontgen first discovered X-rays over a century ago. Its large penetration depth makes it ideal for the nondestructive visualization of the internal structure and/or defects of materials unobtainable otherwise. Currently used nondestructive evaluation (NDE) tools, X-ray radiography and tomography, are absorption-based, and work well in heavy-element materials where density or composition variations due to internal structure or defects are high enough to produce appreciable absorption contrast. However, in many cases where materials are light-weight and/or composites that have similar mass absorption coefficients, the conventional absorption-based X-ray methods for NDE become less useful. Indeed, the light-weight and ultra-high-strength requirements for the most advanced materials used or developed for current flight mission and future space exploration pose a great challenge to the standard NDE tools in that the absorption contrast arising from the internal structure of these materials is often too weak to be resolved. In this presentation, a solution to the problem, the use of phase information of X-rays for phase contrast X-ray imaging, will be discussed, along with a comparison between the absorption-based and phase-contrast imaging methods. Latest results on phase contrast X-ray imaging of lightweight Space Shuttle foam in 2D and 3D will be presented, demonstrating new opportunities to solve the challenging issues encountered in advanced materials development and processing.

Three Way Comparison between Two OMI/Aura and One POLDER/PARASOL Cloud Pressure Products

NASA Technical Reports Server (NTRS)

Sneep, M.; deHaan, J. F.; Stammes, P.; Vanbaunce, C.; Joiner, J.; Vasilkov, A. P.; Levelt, P. F.

2007-01-01

The cloud pressures determined by three different algorithms, operating on reflectances measured by two space-borne instruments in the "A" train, are compared with each other. The retrieval algorithms are based on absorption in the oxygen A-band near 760 nm, absorption by a collision induced absorption in oxygen near 477nm, and the filling in of Fraunhofer lines by rotational Raman scattering. The first algorithm operates on data collected by the POLDER instrument on board PARASOL, while the latter two operate on data from the OMI instrument on board Aura. The satellites sample the same air mass within about 15 minutes. Using one month of data, the cloud pressures from the three algorithms are found to show a similar behavior, with correlation coefficients larger than 0.85 between the data sets for thick clouds. The average differences in the cloud pressure are also small, between 2 and 45 hPa, for the whole data set. For optically thin to medium thick clouds, the cloud pressure the distribution found by POLDER is very similar to that found by OMI using the O2 - O2 absorption. Somewhat larger differences are found for very thick clouds, and we hypothesise that the strong absorption in the oxygen A-band causes the POLDER instrument to retrieve lower pressures for those scenes.

Spectroscopic method for determination of the absorption coefficient in brain tissue

NASA Astrophysics Data System (ADS)

Johansson, Johannes D.

2010-09-01

I use Monte Carlo simulations and phantom measurements to characterize a probe with adjacent optical fibres for diffuse reflectance spectroscopy during stereotactic surgery in the brain. Simulations and measurements have been fitted to a modified Beer-Lambert model for light transport in order to be able to quantify chromophore content based on clinically measured spectra in brain tissue. It was found that it is important to take the impact of the light absorption into account when calculating the apparent optical path length, lp, for the photons in order to get good estimates of the absorption coefficient, μa. The optical path length was found to be well fitted to the equation lp=a+b ln(Is)+c ln(μa)+d ln(Is)ln(μa), where Is is the reflected light intensity for scattering alone (i.e., zero absorption). Although coefficients a-d calculated in this study are specific to the probe used here, the general form of the equation should be applicable to similar probes.

Absorption and scattering of laser radiation by the diffusion flame of aviation kerosene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gvozdev, S V; Glova, A F; Dubrovskii, V Yu

2012-04-30

The absorption coefficient of the radiation of a repetitively pulsed Nd : YAG laser with an average output power up to 6 W and of a cw ytterbium optical fibre laser with an output power up to 3 kW was measured in the diffusion flame of aviation kerosene burning on a free surface in the atmospheric air. The absorption coefficient as a function of flame length, radiation power, and radiation intensity, which was varied in the {approx}10{sup 3} - 5 Multiplication-Sign 10{sup 4} W cm{sup -2} range, was obtained for two distances (1 and 2 cm) between the laser beammore » axis and the surface. The coefficient of radiation absorption by kerosene flame was compared with that in ethanol and kerosene - ethanol mixture flames. The radiation power scattered by a small segment of the kerosene flame irradiated by Nd : YAG laser radiation was measured as a function of longitudinal and azimuthal coordinates. An estimate was made of the total scattered radiation power.« less

Absorption and scattering of laser radiation by the diffusion flame of aviation kerosene

NASA Astrophysics Data System (ADS)

Gvozdev, S. V.; Glova, A. F.; Dubrovskii, V. Yu; Durmanov, S. T.; Krasyukov, A. G.; Lysikov, A. Yu; Smirnov, G. V.; Solomakhin, V. B.

2012-04-01

The absorption coefficient of the radiation of a repetitively pulsed Nd : YAG laser with an average output power up to 6 W and of a cw ytterbium optical fibre laser with an output power up to 3 kW was measured in the diffusion flame of aviation kerosene burning on a free surface in the atmospheric air. The absorption coefficient as a function of flame length, radiation power, and radiation intensity, which was varied in the ~103 — 5×104 W cm-2 range, was obtained for two distances (1 and 2 cm) between the laser beam axis and the surface. The coefficient of radiation absorption by kerosene flame was compared with that in ethanol and kerosene — ethanol mixture flames. The radiation power scattered by a small segment of the kerosene flame irradiated by Nd : YAG laser radiation was measured as a function of longitudinal and azimuthal coordinates. An estimate was made of the total scattered radiation power.

Remarkable optical red shift and extremely high optical absorption coefficient of V-Ga co-doped TiO2

NASA Astrophysics Data System (ADS)

Deng, Quanrong; Han, Xiaoping; Gao, Yun; Shao, Guosheng

2012-07-01

A first attempt has been made to study the effect of codoping of transition metal and sp metal on the electronic structure and associated optical properties of TiO2, through V-Ga codoped thin films. V-Ga codoped rutile TiO2 films were fabricated on fused quartz substrates using pulsed laser ablation, followed by heat treatment at high temperatures. Gigantic redshift in the optical absorption edge was observed in V-Ga co-doped TiO2 materials, from UV to infrared region with high absorption coefficient. Through combined structural characterization and theoretical modeling, this is attributed to the p-d hybridization between the two metals. This leads to additional energy bands to overlap with the minimum of the conduction band, leading to remarkably narrowed band gap free of mid-gap states. The direct-gap of the co-doped phase is key to the remarkably high optical absorption coefficient of the coped titania.

A liquid-He cryostat for structural and thermal disorder studies by X-ray absorption.

PubMed

Bouamrane, F; Ribbens, M; Fonda, E; Adjouri, C; Traverse, A

2003-07-01

A new device operating from 4.2 to 300 K is now installed on the hard X-ray station of the DCI ring in LURE in order to measure absorption coefficients. This liquid-He bath device has three optical windows. One allows the incident beam to impinge on the sample, one located at 180 degrees with respect to the sample allows transmitted beams to be detected, and another located at 90 degrees is used to detect emitted photons. Total electron yield detection mode is also possible thanks to a specific sample holder equipped with an electrode that collects the charges created by the emitted electrons in the He gas brought from the He bath around the sample. The performance of the cryostat is described by measurements of the absorption coefficients versus the temperature for Cu and Co foils. For comparison, the absorption coefficient is also measured for Cu clusters. As expected from dimension effects, the Debye temperature obtained for the clusters is lower than that of bulk Cu.

Temporal and vertical variability in optical properties of New England shelf waters during late summer and spring

NASA Astrophysics Data System (ADS)

Sosik, Heidi M.; Green, Rebecca E.; Pegau, W. Scott; Roesler, Collin S.

2001-05-01

Relationships between optical and physical properties were examined on the basis of intensive sampling at a site on the New England continental shelf during late summer 1996 and spring 1997. During both seasons, particles were found to be the primary source of temporal and vertical variability in optical properties since light absorption by dissolved material, though significant in magnitude, was relatively constant. Within the particle pool, changes in phytoplankton were responsible for much of the observed optical variability. Physical processes associated with characteristic seasonal patterns in stratification and mixing contributed to optical variability mostly through effects on phytoplankton. An exception to this generalization occurred during summer as the passage of a hurricane led to a breakdown in stratification and substantial resuspension of nonphytoplankton particulate material. Prior to the hurricane, conditions in summer were highly stratified with subsurface maxima in absorption and scattering coefficients. In spring, stratification was much weaker but increased over the sampling period, and a modest phytoplankton bloom caused surface layer maxima in absorption and scattering coefficients. These seasonal differences in the vertical distribution of inherent optical properties were evident in surface reflectance spectra, which were elevated and shifted toward blue wavelengths in the summer. Some seasonal differences in optical properties, including reflectance spectra, suggest that a significant shift toward a smaller particle size distribution occurred in summer. Shorter timescale optical variability was consistent with a variety of influences including episodic events such as the hurricane, physical processes associated with shelfbreak frontal dynamics, biological processes such as phytoplankton growth, and horizontal patchiness combined with water mass advection.

Dosimetric properties of new formulation of PRESAGE® with tin organometal catalyst: Development of sensitivity and stability to megavoltage energy.

PubMed

Khezerloo, Davood; Nedaie, Hassan Ali; Takavar, Abbas; Zirak, Alireza; Farhood, Bagher; Banaee, Nooshin; Alidokht, Eisa

2018-01-01

Tin-base catalyst is one of the widely used organometallic catalysts in polyurethane technology. The purpose of this study was to evaluate the effect of tin organometallic catalyst in the radiation response and radiological properties of a new formula of PRESAGE ® . In the study, two types of PRESAGE were fabricated. A very little amount of dibutyltindillaurate (DBTDL) (0.07% weight) was used as a catalyst in the fabrication of new PRESAGE (i.e., PRESAGE with catalyst), which components were: 93.93% weight polyurethane, 5% weight tetrachloride, and 1% weight leucomalachite green (LMG). For PRESAGE without catalyst, 94% weight polyurethane, 4% weight tetrachloride, and 2% weight LMG were used. Radiochromic response and postirradiation stability of PRESAGEs were determined. Also, radiological characteristics of PRESAGEs, such as mass density, electron density, mass attenuation coefficient, and mass stopping power in different photon energies were assessed and compared with water. The absorption peak of new PRESAGE compared to PRESAGE without catalyst was observed without change. Sensitivity of new PRESAGE was higher than PRESAGE without catalyst and its stability after the first 1 h was relatively constant. Also, Mass attenuation coefficient of new PRESAGE in energy ranges <0.1 MeV was 10% more than water, whereas the maximum difference of mass stopping power was only 3%. Tin organometallic catalyst in very low concentration can be used in fabrication of radiochromic polymer gel to achieve high sensitivity and stability as well as good radiological properties in the megavoltage photon beam.

Sound absorption study on acoustic panel from kapok fiber and egg tray

NASA Astrophysics Data System (ADS)

Kaamin, Masiri; Mahir, Nurul Syazwani Mohd; Kadir, Aslila Abd; Hamid, Nor Baizura; Mokhtar, Mardiha; Ngadiman, Norhayati

2017-12-01

Noise also known as a sound, especially one that is loud or unpleasant or that causes disruption. The level of noise can be reduced by using sound absorption panel. Currently, the market produces sound absorption panel, which use synthetic fibers that can cause harmful effects to the health of consumers. An awareness of using natural fibers from natural materials gets attention of some parties to use it as a sound absorbing material. Therefore, this study was conducted to investigate the potential of sound absorption panel using egg trays and kapok fibers. The test involved in this study was impedance tube test which aims to get sound absorption coefficient (SAC). The results showed that there was good sound absorption at low frequency from 0 Hz up to 900 Hz where the maximum absorption coefficient was 0.950 while the maximum absorption at high frequencies was 0.799. Through the noise reduction coefficient (NRC), the material produced NRC of 0.57 indicates that the materials are very absorbing. In addition, the reverberation room test was carried out to get the value of reverberation time (RT) in unit seconds. Overall this panel showed good results at low frequencies between 0 Hz up to 1500 Hz. In that range of frequency, the maximum reverberation time for the panel was 3.784 seconds compared to the maximum reverberation time for an empty room was 5.798 seconds. This study indicated that kapok fiber and egg tray as the material of absorption panel has a potential as environmental and cheap products in absorbing sound at low frequency.

Contribution of particulate brown carbon to light absorption in the rural and urban Southeast US

NASA Astrophysics Data System (ADS)

Devi, J. Jai; Bergin, Michael H.; Mckenzie, Michael; Schauer, James J.; Weber, Rodney J.

2016-07-01

Measurements of wavelength dependent aerosol light absorption coefficients were carried out as part of the Southern Oxidant and Aerosol Study (SOAS) during the summer of 2013 to determine the contribution of light absorbing organic carbon (BrC) to total aerosol light absorption in a rural location (Centreville, AL) and an urban area (Atlanta, GA). The light absorption coefficients in the near UV and visible wavelengths were measured for both ambient air, as well as ambient air heated in a thermal denuder to 200 °C to remove the semi-volatile organic compounds. Atlanta measurements show dominance of semi-volatile brown carbon with an average absorption angstrom exponent (AAE) of 1.4 before heating and about 1.0 after heating. In urban Atlanta, a decrease of about ∼35% in the light absorption coefficient at 370 nm after heating indicates that light absorbing organic compounds are a substantial fraction of the light absorption budget. Furthermore, a considerable increase in the fraction of light absorption by the semi-volatile aerosol occurs during the daytime, likely linked with photochemistry. Measurements at rural Centerville, on the other hand, do not show any major change in AAE with values before and after heating of 0.99 and 0.98, respectively. Overall the results suggest that photochemical aged urban emissions result in the presence of light absorbing BrC, while at rural locations which are dominated by aged aerosol and local biogenic emissions (based on measurements of Angstrom exponents) BrC does not significantly contribute to light absorption.

Characterization of light absorption by chromophoric dissolved organic matter (CDOM) in the upper layer of the Red Sea

NASA Astrophysics Data System (ADS)

Kheireddine, Malika; Ouhssain, Mustapha; Calleja, Maria Ll.; Morán, Xosé Anxelu G.; Sarma, Y. V. B.; Tiwari, Surya P.; Jones, Burton H.

2018-03-01

The absorption coefficient of chromophoric dissolved organic matter (CDOM) is a major variable used in developing robust bio-optical models and understanding biogeochemical processes. Over the last decade, the optical properties of CDOM in the open sea have been intensely studied. However, their variations in clear water are poorly documented, particularly in the Red Sea, owing to the absence of in situ measurements. We performed several cruises in the Red Sea to investigate the spatial distribution of the absorption coefficient of CDOM. The spectral absorption coefficients were determined from 400 nm to 740 nm using a WETLabs ac-s hyper-spectral spectrophotometer. In general, we found a latitudinal gradient in the CDOM absorption coefficient at 443 nm (aCDOM(443)) from south to north that is likely influenced by the exchange of water through the strait of Bab-el-Mandeb and the thermohaline circulation of the Red Sea. However, high aCDOM(443) values were observed in the northern Red Sea due to the existence of a sub-mesoscale feature that may induce an increase in phytoplankton production and lead to CDOM production. The aCDOM(443) covaried with the chlorophyll a concentration ([Chl a],) despite a high scatter. Furthermore, the aCDOM(443) for a given [Chl a] concentration was higher than those predicted by global ocean bio-optical models. This study advances our understanding of CDOM concentration in the Red Sea and may help improve the accuracy of the algorithms used to obtain CDOM absorption from ocean color.

Nonlinear absorption in single LaF3 and MgF2 layers at 193 nm measured by surface sensitive laser induced deflection technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muehlig, Christian; Bublitz, Simon; Kufert, Siegfried

2009-12-10

We report nonlinear absorption data of LaF3 and MgF2 single layers at 193 nm. A highly surface sensitive measurement strategy of the laser induced deflection technique is introduced and applied to measure the absorption of highly transparent thin films independently of the substrate absorption. Linear absorptions k=({alpha}x{lambda})/4{pi} of 2x10{sup -4} and 8.5x10{sup -4} (LaF3) and 1.8x10{sup -4} and 6.9x10{sup -4} (MgF2) are found. Measured two photon absorption (TPA) coefficients are {beta}=1x10{sup -4} cm/W (LaF3), 1.8x10{sup -5}, and 5.8x10{sup -5} cm/W (MgF2). The TPA coefficients are several orders of magnitude higher than typical values for fluoride single crystals, which is likelymore » to result from sequential two step absorption processes.« less

Contribution of mycosporine-like amino acids and colored dissolved and particulate matter to sea ice optical properties and ultraviolet attenuation

PubMed Central

Uusikivi, Jari; Vähätalo, Anssi V.; Granskog, Mats A.; Sommaruga, Ruben

2010-01-01

In the Baltic Sea ice, the spectral absorption coefficients for particulate matter (PM) were about two times higher at ultraviolet wavelengths than at photosynthetically available radiation (PAR) wavelengths. PM absorption spectra included significant absorption by mycosporine-like amino acids (MAAs) between 320 and 345 nm. In the surface ice layer, the concentration of MAAs (1.37 μg L−1) was similar to that of chlorophyll a, resulting in a MAAs-to-chlorophyll a ratio as high as 0.65. Ultraviolet radiation (UVR) intensity and the ratio of UVR to PAR had a strong relationship with MAAs concentration (R2 = 0.97, n = 3) in the ice. In the surface ice layer, PM and especially MAAs dominated the absorption (absorption coefficient at 325 nm: 0.73 m−1). In the columnar ice layers, colored dissolved organic matter was the most significant absorber in the UVR (< 380 nm) (absorption coefficient at 325 nm: 1.5 m−1). Our measurements and modeling of UVR and PAR in Baltic Sea ice show that organic matter, both particulate and dissolved, influences the optical properties of sea ice and strongly modifies the UVR exposure of biological communities in and under snow-free sea ice. PMID:20585592

Sound absorption characteristics of aluminum foam with spherical cells

NASA Astrophysics Data System (ADS)

Li, Yunjie; Wang, Xinfu; Wang, Xingfu; Ren, Yuelu; Han, Fusheng; Wen, Cuie

2011-12-01

Aluminum foams were fabricated by an infiltration process. The foams possess spherical cells with a fixed porosity of 65% and varied pore sizes which ranged from 1.3 to 1.9 mm. The spherical cells are interconnected by small pores or pore openings on the cell walls that cause the foams show a characteristic of open cell structures. The sound absorption coefficient of the aluminum foams was measured by a standing wave tube and calculated by a transfer function method. It is shown that the sound absorption coefficient increases with an increase in the number of pore openings in the unit area or with a decrease of the diameter of the pore openings in the range of 0.3 to 0.4 mm. If backed with an air cavity, the resonant absorption peaks in the sound absorption coefficient versus frequency curves will be shifted toward lower frequencies as the cavity depth is increased. The samples with the same pore opening size but different pore size show almost the same absorption behavior, especially in the low frequency range. The present results are in good agreement with some theoretical predictions based on the acoustic impedance measurements of metal foams with circular apertures and cylindrical cavities and the principle of electroacoustic analogy.

Emergency membrane contactor based absorption system for ammonia leaks in water treatment plants.

PubMed

Shao, Jiahui; Fang, Xuliang; He, Yiliang; Jin, Qiang

2008-01-01

Abstract Because of the suspected health risks of trihalomethanes (THMs), more and more water treatment plants have replaced traditional chlorine disinfection process with chloramines but often without the proper absorption system installed in the case of ammonia leaks in the storage room. A pilot plant membrane absorption system was developed and installed in a water treatment plant for this purpose. Experimentally determined contact angle, surface tension, and corrosion tests indicated that the sulfuric acid was the proper choice as the absorbent for leaking ammonia using polypropylene hollow fiber membrane contactor. Effects of several operating conditions on the mass transfer coefficient, ammonia absorption, and removal efficiency were examined, including the liquid concentration, liquid velocity, and feed gas concentration. Under the operation conditions investigated, the gas absorption efficiency over 99.9% was achieved. This indicated that the designed pilot plant membrane absorption system was effective to absorb the leaking ammonia in the model storage room. The removal rate of the ammonia in the model storage room was also experimentally and theoretically found to be primarily determined by the ammonia suction flow rate from the ammonia storage room to the membrane contactor. The ammonia removal rate of 99.9% was expected to be achieved within 1.3 h at the ammonia gas flow rate of 500 m3/h. The success of the pilot plant membrane absorption system developed in this study illustrated the potential of this technology for ammonia leaks in water treatment plant, also paved the way towards a larger scale application.

The application of reduced absorption cross section on the identification of the compounds with similar function-groups

NASA Astrophysics Data System (ADS)

Yu, Fei; Zuo, Jian; Mu, Kai-jun; Zhang, Zhen-wei; Zhang, Liang-liang; Zhang, Lei-wei; Zhang, Cun-lin

2013-08-01

Terahertz spectroscopy is a powerful tool for materials investigation. The low frequency vibrations were usually investigated by means of absorption coefficient regardless of the refractive index. It leads to the disregard of some inherent low-frequency vibrational information of the chemical compounds. Moreover, due to the scattering inside the sample, there are some distortions of the absorption features, so that the absorption dependent material identification is not valid enough. Here, a statistical parameter named reduced absorption cross section (RACS) is introduced. This can not only help us investigate the molecular dynamics but also distinguish one chemical compound with another which has similar function-groups. Experiments are carried out on L-Tyrosine and L-Phenylalanine and the different mass ratios of their mixtures as an example of the application of RACS. The results come out that the RACS spectrum of L-Tyrosine and L-Phenylalanine reserve the spectral fingerprint information of absorption spectrum. The log plot of RACSs of the two amino acids show power-law behavior σR(~ν) ~ (ν~α), and there is a linear relation between the wavenumber and the RACS in the double logarithmic plot. The exponents α, at the same time, are the slopes of the RACS curves in the double logarithmic plot. The big differences of the exponents α between the two amino acids and their mixtures can be seen visually from the slopes of the RACS curves. So we can use RACS analytical method to distinguish some complex compounds with similar function-groups and mixtures from another which has similar absorption peaks in THz region.

Uncertainties of optical parameters and their propagations in an analytical ocean color inversion algorithm.

PubMed

Lee, ZhongPing; Arnone, Robert; Hu, Chuanmin; Werdell, P Jeremy; Lubac, Bertrand

2010-01-20

Following the theory of error propagation, we developed analytical functions to illustrate and evaluate the uncertainties of inherent optical properties (IOPs) derived by the quasi-analytical algorithm (QAA). In particular, we evaluated the effects of uncertainties of these optical parameters on the inverted IOPs: the absorption coefficient at the reference wavelength, the extrapolation of particle backscattering coefficient, and the spectral ratios of absorption coefficients of phytoplankton and detritus/gelbstoff, respectively. With a systematically simulated data set (46,200 points), we found that the relative uncertainty of QAA-derived total absorption coefficients in the blue-green wavelengths is generally within +/-10% for oceanic waters. The results of this study not only establish theoretical bases to evaluate and understand the effects of the various variables on IOPs derived from remote-sensing reflectance, but also lay the groundwork to analytically estimate uncertainties of these IOPs for each pixel. These are required and important steps for the generation of quality maps of IOP products derived from satellite ocean color remote sensing.

Photon diffusion coefficient in scattering and absorbing media.

PubMed

Pierrat, Romain; Greffet, Jean-Jacques; Carminati, Rémi

2006-05-01

We present a unified derivation of the photon diffusion coefficient for both steady-state and time-dependent transport in disordered absorbing media. The derivation is based on a modal analysis of the time-dependent radiative transfer equation. This approach confirms that the dynamic diffusion coefficient is given by the random-walk result D = cl(*)/3, where l(*) is the transport mean free path and c is the energy velocity, independent of the level of absorption. It also shows that the diffusion coefficient for steady-state transport, often used in biomedical optics, depends on absorption, in agreement with recent theoretical and experimental works. These two results resolve a recurrent controversy in light propagation and imaging in scattering media.

Molecular Characterization of Brown Carbon in Biomass Burning Aerosol Particles.

PubMed

Lin, Peng; Aiona, Paige K; Li, Ying; Shiraiwa, Manabu; Laskin, Julia; Nizkorodov, Sergey A; Laskin, Alexander

2016-11-01

Emissions from biomass burning are a significant source of brown carbon (BrC) in the atmosphere. In this study, we investigate the molecular composition of freshly emitted biomass burning organic aerosol (BBOA) samples collected during test burns of sawgrass, peat, ponderosa pine, and black spruce. We demonstrate that both the BrC absorption and the chemical composition of light-absorbing compounds depend significantly on the type of biomass fuels. Common BrC chromophores in the selected BBOA samples include nitro-aromatics, polycyclic aromatic hydrocarbon derivatives, and polyphenols spanning a wide range of molecular weights, structures, and light absorption properties. A number of biofuel-specific BrC chromophores are observed, indicating that some of them may be used as source-specific markers of BrC. On average, ∼50% of the light absorption in the solvent-extractable fraction of BBOA can be attributed to a limited number of strong BrC chromophores. The absorption coefficients of BBOA are affected by solar photolysis. Specifically, under typical atmospheric conditions, the 300 nm absorbance decays with a half-life of ∼16 h. A "molecular corridor" analysis of the BBOA volatility distribution suggests that many BrC compounds in the fresh BBOA have low saturation mass concentration (<1 μg m -3 ) and will be retained in the particle phase under atmospherically relevant conditions.

Effects of High Hydrostatic Pressure on Water Absorption of Adzuki Beans

PubMed Central

Ueno, Shigeaki; Shigematsu, Toru; Karo, Mineko; Hayashi, Mayumi; Fujii, Tomoyuki

2015-01-01

The effect of high hydrostatic pressure (HHP) treatment on dried soybean, adzuki bean, and kintoki kidney bean, which are low-moisture-content cellular biological materials, was investigated from the viewpoint of water absorption. The samples were vacuum-packed with distilled water and pressurized at 200 MPa and 25 °C for 10 min. After the HHP treatment, time courses of the moisture contents of the samples were measured, and the dimensionless moisture contents were estimated. Water absorption in the case of soybean could be fitted well by a simple water diffusion model. High pressures were found to have negligible effects on water absorption into the cotyledon of soybean and kintoki kidney bean. A non-linear least square method based on the Weibull equation was applied for the adzuki beans, and the effective water diffusion coefficient was found to increase significantly from 8.6 × 10−13 to 6.7 × 10−10 m2/s after HHP treatment. Approximately 30% of the testa of the adzuki bean was damaged upon HHP treatment, which was comparable to the surface area of the testa in the partially peeled adzuki bean sample. Thus, HHP was confirmed to promote mass transfer to the cotyledon of legumes with a tight testa. PMID:28231195

Light absorption of organic carbon emitted from burning wood, charcoal, and kerosene in household cookstoves.

PubMed

Xie, Mingjie; Shen, Guofeng; Holder, Amara L; Hays, Michael D; Jetter, James J

2018-05-02

Household cookstove emissions are an important source of carbonaceous aerosols globally. The light-absorbing organic carbon (OC), also termed brown carbon (BrC), from cookstove emissions can impact the Earth's radiative balance, but is rarely investigated. In this work, PM 2.5 filter samples were collected during combustion experiments with red oak wood, charcoal, and kerosene in a variety of cookstoves mainly at two water boiling test phases (cold start CS, hot start HS). Samples were extracted in methanol and extracts were examined using spectrophotometry. The mass absorption coefficients (MAC λ , m 2 g -1 ) at five wavelengths (365, 400, 450, 500, and 550 nm) were mostly inter-correlated and were used as a measurement proxy for BrC. The MAC 365 for red oak combustion during the CS phase correlated strongly to the elemental carbon (EC)/OC mass ratio, indicating a dependency of BrC absorption on burn conditions. The emissions from cookstoves burning red oak have an average MAC λ 2-6 times greater than those burning charcoal and kerosene, and around 3-4 times greater than that from biomass burning measured in previous studies. These results suggest that residential cookstove emissions could contribute largely to ambient BrC, and the simulation of BrC radiative forcing in climate models for biofuel combustion in cookstoves should be treated specifically and separated from open biomass burning. Copyright © 2018 Elsevier Ltd. All rights reserved.

On iterative algorithms for quantitative photoacoustic tomography in the radiative transport regime

NASA Astrophysics Data System (ADS)

Wang, Chao; Zhou, Tie

2017-11-01

In this paper, we present a numerical reconstruction method for quantitative photoacoustic tomography (QPAT), based on the radiative transfer equation (RTE), which models light propagation more accurately than diffusion approximation (DA). We investigate the reconstruction of absorption coefficient and scattering coefficient of biological tissues. An improved fixed-point iterative method to retrieve the absorption coefficient, given the scattering coefficient, is proposed for its cheap computational cost; the convergence of this method is also proved. The Barzilai-Borwein (BB) method is applied to retrieve two coefficients simultaneously. Since the reconstruction of optical coefficients involves the solutions of original and adjoint RTEs in the framework of optimization, an efficient solver with high accuracy is developed from Gao and Zhao (2009 Transp. Theory Stat. Phys. 38 149-92). Simulation experiments illustrate that the improved fixed-point iterative method and the BB method are competitive methods for QPAT in the relevant cases.

A reduced-scale railway noise barrier's insertion loss and absorption coefficients: comparison of field measurements and predictions

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 using FRA guidelines for allowable increases of noise exposure.

Hybrid acoustic metamaterial as super absorber for broadband low-frequency sound

PubMed Central

Tang, Yufan; Ren, Shuwei; Meng, Han; Xin, Fengxian; Huang, Lixi; Chen, Tianning; Zhang, Chuanzeng; Lu, Tian Jain

2017-01-01

A hybrid acoustic metamaterial is proposed as a new class of sound absorber, which exhibits superior broadband low-frequency sound absorption as well as excellent mechanical stiffness/strength. Based on the honeycomb-corrugation hybrid core (H-C hybrid core), we introduce perforations on both top facesheet and corrugation, forming perforated honeycomb-corrugation hybrid (PHCH) to gain super broadband low-frequency sound absorption. Applying the theory of micro-perforated panel (MPP), we establish a theoretical method to calculate the sound absorption coefficient of this new kind of metamaterial. Perfect sound absorption is found at just a few hundreds hertz with two-octave 0.5 absorption bandwidth. To verify this model, a finite element model is developed to calculate the absorption coefficient and analyze the viscous-thermal energy dissipation. It is found that viscous energy dissipation at perforation regions dominates the total energy consumed. This new kind of acoustic metamaterials show promising engineering applications, which can serve as multiple functional materials with extraordinary low-frequency sound absorption, excellent stiffness/strength and impact energy absorption. PMID:28240239

Exploring the observational constraints on the simulation of brown carbon

NASA Astrophysics Data System (ADS)

Wang, X.; Heald, C. L.; Liu, J.; Weber, R. J.; Campuzano-Jost, P.; Jimenez, J. L.; Schwarz, J. P.; Perring, A. E.

2017-12-01

Brown carbon (BrC) is the component of organic aerosols (OA) which strongly absorbs solar radiation in the near-UV range of the spectrum. However the sources, evolution, and optical properties of BrC remain highly uncertain, and therefore constitute a large source of uncertainty in estimating the global direct radiative effect (DRE) of aerosols. Previous modeling studies of BrC optical properties and DRE have been unable to fully evaluate the skill of their simulations, given the lack of direct measurements of organic aerosol absorption. In this study, we develop a global model simulation (GEOS-Chem) of BrC and test it against BrC absorption measurements from two aircraft campaigns in the U.S. (SEAC4RS and DC3). To our knowledge, this is the first study to compare simulated BrC absorption with direct, continuous ambient measurements. We show that the laboratory-based BrC absorption properties from biomass burning overestimate the aircraft measurements of ambient BrC. In addition, applying a photochemical whitening scheme to simulated BrC is better able to represent the observed BrC absorption. These observations are consistent with a mass absorption coefficient (MAC) of freshly emitted biomass burning OA of 0.57m2g-1. Using the RRTMG model integrated with GEOS-Chem, we estimate that the all-sky top-of-atmosphere direct radiative effect (DRE) of OA is -0.350 Wm-2, 10% higher than that without consideration of BrC absorption. Therefore, our best estimate of the absorption DRE of BrC is +0.042 Wm-2. We suggest that the DRE of BrC has been overestimated previously due to the lack of observational constraints from direct measurements as well as neglect of the effects of photochemical whitening.

Frequency-domain optical tomographic image reconstruction algorithm with the simplified spherical harmonics (SP3) light propagation model.

PubMed

Kim, Hyun Keol; Montejo, Ludguier D; Jia, Jingfei; Hielscher, Andreas H

2017-06-01

We introduce here the finite volume formulation of the frequency-domain simplified spherical harmonics model with n -th order absorption coefficients (FD-SP N ) that approximates the frequency-domain equation of radiative transfer (FD-ERT). We then present the FD-SP N based reconstruction algorithm that recovers absorption and scattering coefficients in biological tissue. The FD-SP N model with 3 rd order absorption coefficient (i.e., FD-SP 3 ) is used as a forward model to solve the inverse problem. The FD-SP 3 is discretized with a node-centered finite volume scheme and solved with a restarted generalized minimum residual (GMRES) algorithm. The absorption and scattering coefficients are retrieved using a limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm. Finally, the forward and inverse algorithms are evaluated using numerical phantoms with optical properties and size that mimic small-volume tissue such as finger joints and small animals. The forward results show that the FD-SP 3 model approximates the FD-ERT (S 12 ) solution within relatively high accuracy; the average error in the phase (<3.7%) and the amplitude (<7.1%) of the partial current at the boundary are reported. From the inverse results we find that the absorption and scattering coefficient maps are more accurately reconstructed with the SP 3 model than those with the SP 1 model. Therefore, this work shows that the FD-SP 3 is an efficient model for optical tomographic imaging of small-volume media with non-diffuse properties both in terms of computational time and accuracy as it requires significantly lower CPU time than the FD-ERT (S 12 ) and also it is more accurate than the FD-SP 1 .

Estimation of chromophoric dissolved organic matter in the Mississippi and Atchafalaya river plume regions using above-surface hyperspectral remote sensing

NASA Astrophysics Data System (ADS)

Zhu, Weining; Yu, Qian; Tian, Yong Q.; Chen, Robert F.; Gardner, G. Bernard

2011-02-01

A method for the inversion of hyperspectral remote sensing was developed to determine the absorption coefficient for chromophoric dissolved organic matter (CDOM) in the Mississippi and Atchafalaya river plume regions and the northern Gulf of Mexico, where water types vary from Case 1 to turbid Case 2. Above-surface hyperspectral remote sensing data were measured by a ship-mounted spectroradiometer and then used to estimate CDOM. Simultaneously, water absorption and attenuation coefficients, CDOM and chlorophyll fluorescence, turbidities, and other related water properties were also measured at very high resolution (0.5-2 m) using in situ, underwater, and flow-through (shipboard, pumped) optical sensors. We separate ag, the absorption coefficient a of CDOM, from adg (a of CDOM and nonalgal particles) based on two absorption-backscattering relationships. The first is between ad (a of nonalgal particles) and bbp (total particulate backscattering coefficient), and the second is between ap (a of total particles) and bbp. These two relationships are referred as ad-based and ap-based methods, respectively. Consequently, based on Lee's quasi-analytical algorithm (QAA), we developed the so-called Extended Quasi-Analytical Algorithm (QAA-E) to decompose adg, using both ad-based and ap-based methods. The absorption-backscattering relationships and the QAA-E were tested using synthetic and in situ data from the International Ocean-Colour Coordinating Group (IOCCG) as well as our own field data. The results indicate the ad-based method is relatively better than the ap-based method. The accuracy of CDOM estimation is significantly improved by separating ag from adg (R2 = 0.81 and 0.65 for synthetic and in situ data, respectively). The sensitivities of the newly introduced coefficients were also analyzed to ensure QAA-E is robust.

Effects of the approximations of light propagation on quantitative photoacoustic tomography using two-dimensional photon diffusion equation and linearization

NASA Astrophysics Data System (ADS)

Okawa, Shinpei; Hirasawa, Takeshi; Kushibiki, Toshihiro; Ishihara, Miya

2017-12-01

Quantitative photoacoustic tomography (QPAT) employing a light propagation model will play an important role in medical diagnoses by quantifying the concentration of hemoglobin or a contrast agent. However, QPAT by the light propagation model with the three-dimensional (3D) radiative transfer equation (RTE) requires a huge computational load in the iterative forward calculations involved in the updating process to reconstruct the absorption coefficient. The approximations of the light propagation improve the efficiency of the image reconstruction for the QPAT. In this study, we compared the 3D/two-dimensional (2D) photon diffusion equation (PDE) approximating 3D RTE with the Monte Carlo simulation based on 3D RTE. Then, the errors in a 2D PDE-based linearized image reconstruction caused by the approximations were quantitatively demonstrated and discussed in the numerical simulations. It was clearly observed that the approximations affected the reconstructed absorption coefficient. The 2D PDE-based linearized algorithm succeeded in the image reconstruction of the region with a large absorption coefficient in the 3D phantom. The value reconstructed in the phantom experiment agreed with that in the numerical simulation, so that it was validated that the numerical simulation of the image reconstruction predicted the relationship between the true absorption coefficient of the target in the 3D medium and the reconstructed value with the 2D PDE-based linearized algorithm. Moreover, the the true absorption coefficient in 3D medium was estimated from the 2D reconstructed image on the basis of the prediction by the numerical simulation. The estimation was successful in the phantom experiment, although some limitations were revealed.

The NIST Quantitative Infrared Database

PubMed Central

Chu, P. M.; Guenther, F. R.; Rhoderick, G. C.; Lafferty, W. J.

1999-01-01

With the recent developments in Fourier transform infrared (FTIR) spectrometers it is becoming more feasible to place these instruments in field environments. As a result, there has been enormous increase in the use of FTIR techniques for a variety of qualitative and quantitative chemical measurements. These methods offer the possibility of fully automated real-time quantitation of many analytes; therefore FTIR has great potential as an analytical tool. Recently, the U.S. Environmental Protection Agency (U.S.EPA) has developed protocol methods for emissions monitoring using both extractive and open-path FTIR measurements. Depending upon the analyte, the experimental conditions and the analyte matrix, approximately 100 of the hazardous air pollutants (HAPs) listed in the 1990 U.S.EPA Clean Air Act amendment (CAAA) can be measured. The National Institute of Standards and Technology (NIST) has initiated a program to provide quality-assured infrared absorption coefficient data based on NIST prepared primary gas standards. Currently, absorption coefficient data has been acquired for approximately 20 of the HAPs. For each compound, the absorption coefficient spectrum was calculated using nine transmittance spectra at 0.12 cm−1 resolution and the Beer’s law relationship. The uncertainties in the absorption coefficient data were estimated from the linear regressions of the transmittance data and considerations of other error sources such as the nonlinear detector response. For absorption coefficient values greater than 1 × 10−4 μmol/mol)−1 m−1 the average relative expanded uncertainty is 2.2 %. This quantitative infrared database is currently an ongoing project at NIST. Additional spectra will be added to the database as they are acquired. Our current plans include continued data acquisition of the compounds listed in the CAAA, as well as the compounds that contribute to global warming and ozone depletion.

Seasonal And Regional Differentiation Of Bio-Optical Properties Within The North Polar Atlantic

NASA Technical Reports Server (NTRS)

Stramska, Malgorzata; Stramski, Dariusz; Kaczmarek, Slawomir; Allison, David B.; Schwarz, Jill

2005-01-01

Using data collected during spring and summer seasons in the north polar Atlantic we examined the variability of the spectral absorption, a(lambda), and backscattering, b(sub b)(lambda), coefficients of surface waters and its relation to phytoplankton pigment concentration and composition. For a given chlorophyll a concentration (TChla), the concentrations of photosynthetic carotenoids (PSC), photoprotective carotenoids (PPC), and total accessory pigments (AP) were consistently lower in spring than in summer. The chlorophyll-specific absorption coefficients of phytoplankton and total particulate matter were also lower in spring, which can be partly attributed to lower proportions of PPC, PSC, and AP in spring. The spring values of the green-to-blue band ratio of the absorption coefficient were higher than the summer ratios. The blue-to-green ratios of backscattering coefficient were also higher in spring. The higher b(sub b) values and lower blue-to-green b(sub b) ratios in summer were likely associated with higher concentrations of detrital particles in summer compared to spring. Because the product of the green-to-blue absorption ratio and the blue-to-green backscattering ratio is a proxy for the blue-to-green ratio of remote-sensing reflectance, we conclude that the performance of ocean color band-ratio algorithms for estimating pigments in the north polar Atlantic is significantly affected by seasonal shifts in the relationships between absorption and TChla as well as between backscattering and TChla. Intriguingly, however, fairly good estimate of the particulate beam attenuation coefficient at 660 nm (potential measure of total particulate matter or particulate organic carbon concentration) can be obtained by applying a single blue-to-green band-ratio algorithm for both spring and summer seasons.

Terahertz birefringence of potassium niobate crystals

NASA Astrophysics Data System (ADS)

Antsygin, V. D.; Mamrashev, A. A.; Nikolaev, N. A.

2018-03-01

We present terahertz optical properties (refractive indices and absorption coefficients) of potassium niobate crystals measured by time-domain spectroscopy in the range of 0.2-2.0 THz. We observe average refractive indices nx = 5.25, ny = 4.8, nz = 5.9 for corresponding optical axes X, Y, Z with the large birefringence of Δn = nz - ny = 1.1. We report rising absorption coefficient at higher frequencies (α ∼ 50 cm-1 at 1 THz for all three axes) while the dichroism is not pronounced. Somewhat higher absorption compared to the previous results could be attributed to some polydomain structure remaining in the crystal.

Fuel Property Determination of Biodiesel-Diesel Blends By Terahertz Spectrum

NASA Astrophysics Data System (ADS)

Zhao, Hui; Zhao, Kun; Bao, Rima

2012-05-01

The frequency-dependent absorption characteristics of biodiesel and its blends with conventional diesel fuel have been researched in the spectral range of 0.2-1.5 THz by the terahertz time-domain spectroscopy (THz-TDS). The absorption coefficient presented a regular increasing with biodiesel content. A nonlinear multivariate model that correlating cetane number and solidifying point of bio-diesel blends with absorption coefficient has been established, making the quantitative analysis of fuel properties simple. The results made the cetane number and solidifying point prediction possible by THz-TDS technology and indicated a bright future in practical application.

Large nonlinear absorption and refraction coefficients of carbon nanotubes estimated from femtosecond z-scan measurements

NASA Astrophysics Data System (ADS)

Kamaraju, N.; Kumar, Sunil; Sood, A. K.; Guha, Shekhar; Krishnamurthy, Srinivasan; Rao, C. N. R.

2007-12-01

Nonlinear transmission of 80 and 140fs pulsed light with 0.79μm wavelength through single walled carbon nanotubes suspended in water containing sodium dodecyl sulfate is studied. Pulse-width independent saturation absorption and negative cubic nonlinearity are observed, respectively, in open and closed aperture z-scan experiments. The theoretical expressions derived to analyze the z-dependent transmission in the saturable limit require two photon absorption coefficient β0˜1.4cm/MW and a nonlinear index γ ˜-5.5×10-11cm2/W to fit the data.

Borman effect in resonant diffraction of X-rays

NASA Astrophysics Data System (ADS)

Oreshko, A. P.

2013-08-01

A dynamic theory of resonant diffraction (occurring when the energy of incident radiation is close to the energy of the absorption edge of an element in the composition of a given substance) of synchronous X-rays is developed in the two-wave approximation in the coplanar Laue geometry for large grazing angles in perfect crystals. A sharp decrease in the absorption coefficient in the substance with simultaneously satisfied diffraction conditions (Borman effect) is demonstrated, and the theoretical and first experimental results are compared. The calculations reveal the possibility of applying this approach in analyzing the quadrupole-quadrupole contribution to the absorption coefficient.

Water-equivalence of gel dosimeters for radiology medical imaging.

PubMed

Valente, M; Vedelago, J; Chacón, D; Mattea, F; Velásquez, J; Pérez, P

2018-03-08

International dosimetry protocols are based on determinations of absorbed dose to water. Ideally, the phantom material should be water equivalent; that is, it should have the same absorption and scatter properties as water. This study presents theoretical, experimental and Monte Carlo modeling of water-equivalence of Fricke and polymer (NIPAM, PAGAT and itaconic acid ITABIS) gel dosimeters. Mass and electronic densities along with effective atomic number were calculated by means of theoretical approaches. Samples were scanned by standard computed tomography. Photon mass attenuation coefficients and electron stopping powers were examined. Theoretical, Monte Carlo and experimental results confirmed good water-equivalence for all gel dosimeters. Overall variations with respect to water in the low energy radiology range (up to 130 kVp) were found to be less than 3% in average. Copyright © 2018 Elsevier Ltd. All rights reserved.

A review of current knowledge concerning PM2. 5 chemical composition, aerosol optical properties and their relationships across China

NASA Astrophysics Data System (ADS)

Tao, Jun; Zhang, Leiming; Cao, Junji; Zhang, Renjian

2017-08-01

To obtain a thorough knowledge of PM2. 5 chemical composition and its impact on aerosol optical properties across China, existing field studies conducted after the year 2000 are reviewed and summarized in terms of geographical, interannual and seasonal distributions. Annual PM2. 5 was up to 6 times the National Ambient Air Quality Standards (NAAQS) in some megacities in northern China. Annual PM2. 5 was higher in northern than southern cities, and higher in inland than coastal cities. In a few cities with data longer than a decade, PM2. 5 showed a slight decrease only in the second half of the past decade, while carbonaceous aerosols decreased, sulfate (SO42-) and ammonium (NH4+) remained at high levels, and nitrate (NO3-) increased. The highest seasonal averages of PM2. 5 and its major chemical components were typically observed in the cold seasons. Annual average contributions of secondary inorganic aerosols to PM2. 5 ranged from 25 to 48 %, and those of carbonaceous aerosols ranged from 23 to 47 %, both with higher contributions in southern regions due to the frequent dust events in northern China. Source apportionment analysis identified secondary inorganic aerosols, coal combustion and traffic emission as the top three source factors contributing to PM2. 5 mass in most Chinese cities, and the sum of these three source factors explained 44 to 82 % of PM2. 5 mass on annual average across China. Biomass emission in most cities, industrial emission in industrial cities, dust emission in northern cities and ship emission in coastal cities are other major source factors, each of which contributed 7-27 % to PM2. 5 mass in applicable cities. The geographical pattern of scattering coefficient (bsp) was similar to that of PM2. 5, and that of aerosol absorption coefficient (bap) was determined by elemental carbon (EC) mass concentration and its coating. bsp in ambient condition of relative humidity (RH) = 80 % can be amplified by about 1.8 times that under dry conditions. Secondary inorganic aerosols accounted for about 60 % of aerosol extinction coefficient (bext) at RH greater than 70 %. The mass scattering efficiency (MSE) of PM2. 5 ranged from 3.0 to 5.0 m2 g-1 for aerosols produced from anthropogenic emissions and from 0.7 to 1.0 m2 g-1 for natural dust aerosols. The mass absorption efficiency (MAE) of EC ranged from 6.5 to 12.4 m2 g-1 in urban environments, but the MAE of water-soluble organic carbon was only 0.05 to 0.11 m2 g-1. Historical emission control policies in China and their effectiveness were discussed based on available chemically resolved PM2. 5 data, which provides the much needed knowledge for guiding future studies and emissions policies.

Differential-optoacoustic absorption detector

NASA Technical Reports Server (NTRS)

Shumate, M. S.

1977-01-01

Two-cell spectrophone detects trace amounts of atmospheric pollutants by measuring absorption coefficients of gases with various laser sources. Device measures pressure difference between two tapered cells with differential manometer. Background signal is reduced by balanced window heating and balanced carrier gas absorption in two cells.

Photoelectric absorption cross sections with variable abundances

NASA Technical Reports Server (NTRS)

Balucinska-Church, Monika; Mccammon, Dan

1992-01-01

Polynomial fit coefficients have been obtained for the energy dependences of the photoelectric absorption cross sections of 17 astrophysically important elements. These results allow the calculation of X-ray absorption in the energy range 0.03-10 keV in material with noncosmic abundances.

In vivo Photoacoustic Imaging of Prostate Cancer Using Targeted Contrast Agent

DTIC Science & Technology

2016-11-01

has over 15 years of experience investigating signaling in the prostate, and is well versed in both cell culture and animal models for prostate cancer...as Hb generate relatively weak photoacoustic signals (due to a small absorptivity factor or extinction coefficient) and lack cancer specificity...oxyhemoglobin (dHb) and oxyhemoglobin (HbO2) have two limitations: i) their small absorptivity factor ( extinction coefficient) leads to weak PA signals

Annual Report Number 12, 1 October 1979-30 September 1980,

DTIC Science & Technology

1980-12-01

experimental results using absorption coefficients derived from the work of Sauberer (1950), and a representative phase function derived from the results...deviations indicate that inaccuracies may be present in the absorption coefficients obtained by Sauberer . A paper describing in detail the theoretical...also needed in a number of extraterrestrial applications. The only data available between 400 and 900 nm have been those of Sauberer . He reported values

Low-resolution mapping of the effective attenuation coefficient of the human head: a multidistance approach applied to high-density optical recordings

PubMed Central

Chiarelli, Antonio M.; Maclin, Edward L.; Low, Kathy A.; Fantini, Sergio; Fabiani, Monica; Gratton, Gabriele

2017-01-01

Abstract. Near infrared (NIR) light has been widely used for measuring changes in hemoglobin concentration in the human brain (functional NIR spectroscopy, fNIRS). fNIRS is based on the differential measurement and estimation of absorption perturbations, which, in turn, are based on correctly estimating the absolute parameters of light propagation. To do so, it is essential to accurately characterize the baseline optical properties of tissue (absorption and reduced scattering coefficients). However, because of the diffusive properties of the medium, separate determination of absorption and scattering across the head is challenging. The effective attenuation coefficient (EAC), which is proportional to the geometric mean of absorption and reduced scattering coefficients, can be estimated in a simpler fashion by multidistance light decay measurements. EAC mapping could be of interest for the scientific community because of its absolute information content, and because light propagation is governed by the EAC for source–detector distances exceeding 1 cm, which sense depths extending beyond the scalp and skull layers. Here, we report an EAC mapping procedure that can be applied to standard fNIRS recordings, yielding topographic maps with 2- to 3-cm resolution. Application to human data indicates the importance of venous sinuses in determining regional EAC variations, a factor often overlooked. PMID:28466026

Low-resolution mapping of the effective attenuation coefficient of the human head: a multidistance approach applied to high-density optical recordings.

PubMed

Chiarelli, Antonio M; Maclin, Edward L; Low, Kathy A; Fantini, Sergio; Fabiani, Monica; Gratton, Gabriele

2017-04-01

Near infrared (NIR) light has been widely used for measuring changes in hemoglobin concentration in the human brain (functional NIR spectroscopy, fNIRS). fNIRS is based on the differential measurement and estimation of absorption perturbations, which, in turn, are based on correctly estimating the absolute parameters of light propagation. To do so, it is essential to accurately characterize the baseline optical properties of tissue (absorption and reduced scattering coefficients). However, because of the diffusive properties of the medium, separate determination of absorption and scattering across the head is challenging. The effective attenuation coefficient (EAC), which is proportional to the geometric mean of absorption and reduced scattering coefficients, can be estimated in a simpler fashion by multidistance light decay measurements. EAC mapping could be of interest for the scientific community because of its absolute information content, and because light propagation is governed by the EAC for source-detector distances exceeding 1 cm, which sense depths extending beyond the scalp and skull layers. Here, we report an EAC mapping procedure that can be applied to standard fNIRS recordings, yielding topographic maps with 2- to 3-cm resolution. Application to human data indicates the importance of venous sinuses in determining regional EAC variations, a factor often overlooked.

Influence of diffuse reflectance measurement accuracy on the scattering coefficient in determination of optical properties with integrating sphere optics (a secondary publication).

PubMed

Horibe, Takuro; Ishii, Katsunori; Fukutomi, Daichi; Awazu, Kunio

2015-12-30

An estimation error of the scattering coefficient of hemoglobin in the high absorption wavelength range has been observed in optical property calculations of blood-rich tissues. In this study, the relationship between the accuracy of diffuse reflectance measurement in the integrating sphere and calculated scattering coefficient was evaluated with a system to calculate optical properties combined with an integrating sphere setup and the inverse Monte Carlo simulation. Diffuse reflectance was measured with the integrating sphere using a small incident port diameter and optical properties were calculated. As a result, the estimation error of the scattering coefficient was improved by accurate measurement of diffuse reflectance. In the high absorption wavelength range, the accuracy of diffuse reflectance measurement has an effect on the calculated scattering coefficient.

Temporal Relationships Between African Dust and Chlorophyll-a in the Eastern Caribbean Basin

NASA Astrophysics Data System (ADS)

Gomez-Andujar, N. X.; Mayol-Bracero, O. L.; Torres-Delgado, E.

2017-12-01

Seasonal African Dust (AD) transports soluble iron to oligotrophic Caribbean waters, and when bioavailable, it could increase marine primary productivity (PP). Recently, the region has experienced the proliferation of unusually high quantities of Sargassum, an iron-absorbing macroalgae inhabiting the air-sea interface, which possess ecological and economic challenges and whose driving factors are still uncertain. AD events reach Puerto Rico (PR) mostly during boreal summer months. This is also the season when chlorophyll-α (CHL) concentrations are highest, when the algae starts to bloom, and when sediment plumes from the Orinoco River (ORP) also reach nutrient discharge maxima.This study seeks to better understand the temporal relationships between increases in chlorophyll-α and the presence of african dust events in the region. Aerosol data collected at the Cabezas de San Juan Atmospheric Observatory was used to identify AD events between January 2005 and December 2015. Light scattering coefficients were measured with an integrating Nephelometer, while light absorption coefficients were obtained from either the Particle Soot/Absorption Photometer (PSAP) or the Continuous Light Absorption Photometer (CLAP). Spectral properties suggesting AD events were cross-referenced with surface dust concentration image models and source-attributed air masses corresponding to dusty periods using Hybrid Single-Particle Lagrangian Integrated Trajectories (HYSPLIT). For all years with spectral data, modeled monthly wet dust deposition was correlated (r=0.64) with mean CHL concentrations from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS). Daily dust mass column densities from NASA's MERRA-2 model were also correlated (r2= 0.53) to sea surface iron concentrations from NASA's Ocean Biogeochemical Model. We present the 2010 case study, which coincides with the start of the Sargassum bloom and shows CHL peaks occurring a month before ORPs but during the AD season, suggesting the AD role in enhancing PP. Other possible influencing climatic and oceanographic variables could be associated to these observations. Further efforts include spatially linking the Floating Algae Index in satellite imagery to AD concentrations, to better predict harmful algal blooms and inform management.

Remote Sensing of the Absorption Coefficients and Chlorophyll a Concentration in the U.S. Southern Middle Atlantic Bight from SeaWiFS and MODIS-Aqua

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.

Enhancement of acoustical performance of hollow tube sound absorber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Putra, Azma, E-mail: azma.putra@utem.edu.my; Khair, Fazlin Abd, E-mail: fazlinabdkhair@student.utem.edu.my; Nor, Mohd Jailani Mohd, E-mail: jai@utem.edu.my

This paper presents acoustical performance of hollow structures utilizing the recycled lollipop sticks as acoustic absorbers. The hollow cross section of the structures is arranged facing the sound incidence. The effects of different length of the sticks and air gap on the acoustical performance are studied. The absorption coefficient was measured using impedance tube method. Here it is found that improvement on the sound absorption performance is achieved by introducing natural kapok fiber inserted into the void between the hollow structures. Results reveal that by inserting the kapok fibers, both the absorption bandwidth and the absorption coefficient increase. For testmore » sample backed by a rigid surface, best performance of sound absorption is obtained for fibers inserted at the front and back sides of the absorber. And for the case of test sample with air gap, this is achieved for fibers introduced only at the back side of the absorber.« less

Enhancement of acoustical performance of hollow tube sound absorber

NASA Astrophysics Data System (ADS)

Putra, Azma; Khair, Fazlin Abd; Nor, Mohd Jailani Mohd

2016-03-01

This paper presents acoustical performance of hollow structures utilizing the recycled lollipop sticks as acoustic absorbers. The hollow cross section of the structures is arranged facing the sound incidence. The effects of different length of the sticks and air gap on the acoustical performance are studied. The absorption coefficient was measured using impedance tube method. Here it is found that improvement on the sound absorption performance is achieved by introducing natural kapok fiber inserted into the void between the hollow structures. Results reveal that by inserting the kapok fibers, both the absorption bandwidth and the absorption coefficient increase. For test sample backed by a rigid surface, best performance of sound absorption is obtained for fibers inserted at the front and back sides of the absorber. And for the case of test sample with air gap, this is achieved for fibers introduced only at the back side of the absorber.

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.

Paper area density measurement from forward transmitted scattered light

DOEpatents

Koo, Jackson C.

2001-01-01

A method whereby the average paper fiber area density (weight per unit area) can be directly calculated from the intensity of transmitted, scattered light at two different wavelengths, one being a non-absorpted wavelength. Also, the method makes it possible to derive the water percentage per fiber area density from a two-wavelength measurement. In the optical measuring technique optical transmitted intensity, for example, at 2.1 microns cellulose absorption line is measured and compared with another scattered, optical transmitted intensity reference in the nearby spectrum region, such as 1.68 microns, where there is no absorption. From the ratio of these two intensities, one can calculate the scattering absorption coefficient at 2.1 microns. This absorption coefficient at this wavelength is, then, experimentally correlated to the paper fiber area density. The water percentage per fiber area density can be derived from this two-wavelength measurement approach.

Aliphatic Hydrocarbon Content of Interstellar Dust

NASA Astrophysics Data System (ADS)

Günay, B.; Schmidt, T. W.; Burton, M. G.; Afşar, M.; Krechkivska, O.; Nauta, K.; Kable, S. H.; Rawal, A.

2018-06-01

There is considerable uncertainty as to the amount of carbon incorporated in interstellar dust. The aliphatic component of the carbonaceous dust is of particular interest because it produces a significant 3.4 μm absorption feature when viewed against a background radiation source. The optical depth of the 3.4 μm absorption feature is related to the number of aliphatic carbon C-H bonds along the line of sight. It is possible to estimate the column density of carbon locked up in the aliphatic hydrocarbon component of interstellar dust from quantitative analysis of the 3.4 μm interstellar absorption feature providing that the absorption coefficient of aliphatic hydrocarbons incorporated in the interstellar dust is known. We report laboratory analogues of interstellar dust by experimentally mimicking interstellar/circumstellar conditions. The resultant spectra of these dust analogues closely match those from astronomical observations. Measurements of the absorption coefficient of aliphatic hydrocarbons incorporated in the analogues were carried out by a procedure combining FTIR and 13C NMR spectroscopies. The absorption coefficients obtained for both interstellar analogues were found to be in close agreement (4.76(8) × 10-18 cm group-1 and 4.69(14) × 10-18 cm group-1), less than half those obtained in studies using small aliphatic molecules. The results thus obtained permit direct calibration of the astronomical observations, providing rigorous estimates of the amount of aliphatic carbon in the interstellar medium.

Diesel vehicle and urban burning contributions to black carbon concentrations and size distributions in Tijuana, Mexico, during the Cal-Mex 2010 campaign

NASA Astrophysics Data System (ADS)

Takahama, S.; Russell, L. M.; Shores, C. A.; Marr, L. C.; Zheng, J.; Levy, M.; Zhang, R.; Castillo, E.; Rodriguez-Ventura, J. G.; Quintana, P. J. E.; Subramanian, R.; Zavala, M.; Molina, L. T.

2014-05-01

Black carbon (BC) was characterized by three complementary techniques - incandescence (single particle soot photometer, SP2, at Parque Morelos), light absorption (cavity ringdown spectrometer with integrating nephelometer, CRDS-Neph, at Parque Morelos and Aethalometers at seven locations), and volatility (volatility tandem differential mobility analyzer, V-TDMA) during the Cal-Mex 2010 campaign. SP2, CRDS-Neph, and Aethalometer measurements characterized the BC mass, and SP2 and V-TDMA measurements also quantified BC-containing particle number, from which mass-mean BC diameters were calculated. On average, the mass concentrations measured in Tijuana (1.8 ± 2.6 μg m-3 at Parque Morelos and 2.6 μg m-3 in other regions of Tijuana) were higher than in San Diego or the international border crossing (0.5 ± 0.6 μg m-3). The observed BC mass concentrations were attributable to nighttime urban burning activities and diesel vehicles, both from the local (Baja California) and transported (Southern California) diesel vehicle fleets. Comparisons of the SP2 and co-located Aethalometers indicated that the two methods measured similar variations in BC mass concentrations (correlation coefficients greater than 0.85), and the mass concentrations were similar for the BC particles identified from nighttime urban burning sources. When the BC source changed to diesel vehicle emissions, the SP2 mass concentrations were lower than the Aethalometer mass concentrations by about 50%, likely indicating a change in the mass absorption efficiency and quantification by the Aethalometers. At Parque Morelos there were up to three different-sized modes of BC mass in particles: one mode below 100 nm, one near 100 nm, and another between 200 and 300 nm. The mode between 200 and 300 nm was associated with urban burning activities that influenced the site during evening hours. When backtrajectories indicated that airmasses came from the south to the Parque Morelos site, BC mass in particles was also larger (mass median diameter of 170 nm rather than 155 nm), consistent with the higher fraction of older diesel vehicles in the Tijuana fleet compared to the vehicles found in southern California.

A synthesis of light absorption properties of the Arctic Ocean: application to semianalytical estimates of dissolved organic carbon concentrations from space

NASA Astrophysics Data System (ADS)

Matsuoka, A.; Babin, M.; Doxaran, D.; Hooker, S. B.; Mitchell, B. G.; Bélanger, S.; Bricaud, A.

2014-06-01

In addition to scattering coefficients, the light absorption coefficients of particulate and dissolved materials are the main factors determining the light propagation of the visible part of the spectrum and are, thus, important for developing ocean color algorithms. While these absorption properties have recently been documented by a few studies for the Arctic Ocean (e.g., Matsuoka et al., 2007, 2011; Ben Mustapha et al., 2012), the data sets used in the literature were sparse and individually insufficient to draw a general view of the basin-wide spatial and temporal variations in absorption. To achieve such a task, we built a large absorption database of the Arctic Ocean by pooling the majority of published data sets and merging new data sets. Our results show that the total nonwater absorption coefficients measured in the eastern Arctic Ocean (EAO; Siberian side) are significantly higher than in the western Arctic Ocean (WAO; North American side). This higher absorption is explained by higher concentration of colored dissolved organic matter (CDOM) in watersheds on the Siberian side, which contains a large amount of dissolved organic carbon (DOC) compared to waters off North America. In contrast, the relationship between the phytoplankton absorption (aϕ(λ)) and chlorophyll a (chl a) concentration in the EAO was not significantly different from that in the WAO. Because our semianalytical CDOM absorption algorithm is based on chl a-specific aϕ(λ) values (Matsuoka et al., 2013), this result indirectly suggests that CDOM absorption can be appropriately derived not only for the WAO but also for the EAO using ocean color data. Based on statistics, derived CDOM absorption values were reasonable compared to in situ measurements. By combining this algorithm with empirical DOC versus CDOM relationships, a semianalytical algorithm for estimating DOC concentrations for river-influenced coastal waters of the Arctic Ocean is presented and applied to satellite ocean color data.

Attenuation coefficients and exposure buildup factor of some rocks for gamma ray shielding applications

NASA Astrophysics Data System (ADS)

Obaid, Shamsan S.; Sayyed, M. I.; Gaikwad, D. K.; Pawar, Pravina. P.

2018-07-01

In the present work, the mass attenuation coefficient μ/ρ is investigated experimentally and theoretically for seven rocks (olivine basalt, green marble, jet black granite, telphone black granite, cuddapah limestone, white marble and pink marble). The rock samples were collected from different places of India. The mass attenuation coefficients of the samples were measured experimentally at photon energies of radioisotopes Co57 (122 keV), Ba133 (356 keV), 22Na (511 and 1275 keV), Cs137 (662 keV), Mn54 (840 keV), and Co60 (1330 keV). Theoretically, the simulation results of μ/ρ using both XCOM and MCNP5 codes were compared with experimental results and a satisfactory agreement was observed. Total atomic cross sections (σt,a) electronic cross sections (σt,e), effective atomic number (Zeff), electron density (Ne) and half value layer (HVL) were evaluated using the obtained μ/ρ values for investigated rocks. The HVL values for the selected rocks were compared with some common shielding concretes. Moreover, by Geometric Progression method (G-P) exposure buildup factor (EBF) and energy absorption buildup factor (EABF) values were calculated for incident photon energy 0.015-15 MeV up to penetration depths of 40 mean free paths. The results show that among the studied rocks pink marble possesses superior shielding properties for γ-ray. This work was carried out to explore the advantage of utilizing the selected rocks in engineering structures and building construction to shield gamma-rays.

Two-step reconstruction method using global optimization and conjugate gradient for ultrasound-guided diffuse optical tomography.

PubMed

Tavakoli, Behnoosh; Zhu, Quing

2013-01-01

Ultrasound-guided diffuse optical tomography (DOT) is a promising method for characterizing malignant and benign lesions in the female breast. We introduce a new two-step algorithm for DOT inversion in which the optical parameters are estimated with the global optimization method, genetic algorithm. The estimation result is applied as an initial guess to the conjugate gradient (CG) optimization method to obtain the absorption and scattering distributions simultaneously. Simulations and phantom experiments have shown that the maximum absorption and reduced scattering coefficients are reconstructed with less than 10% and 25% errors, respectively. This is in contrast with the CG method alone, which generates about 20% error for the absorption coefficient and does not accurately recover the scattering distribution. A new measure of scattering contrast has been introduced to characterize benign and malignant breast lesions. The results of 16 clinical cases reconstructed with the two-step method demonstrates that, on average, the absorption coefficient and scattering contrast of malignant lesions are about 1.8 and 3.32 times higher than the benign cases, respectively.

Evaluation of polymer based third order nonlinear integrated optics devices

NASA Astrophysics Data System (ADS)

Driessen, A.; Hoekstra, H. J. W. M.; Blom, F. C.; Horst, F.; Krijnen, G. J. M.; van Schoot, J. B. P.; Lambeck, P. V.; Popma, Th. J. A.; Diemeer, M. B.

1998-01-01

Nonlinear polymers are promising materials for high speed active integrated optics devices. In this paper we evaluate the perspectives polymer based nonlinear optical devices can offer. Special attention is directed to the materials aspects. In our experimental work we applied mainly Akzo Nobel DANS side-chain polymer that exhibits large second and third order coefficients. This material has been characterized by third harmonic generation, z-scan and pump-probe measurements. In addition, various waveguiding structures have been used to measure the nonlinear absorption (two photon absorption) on a ps time-scale. Finally an integrated optics Mach Zehnder interferometer has been realized and evaluated. It is shown that the DANS side-chain polymer has many of the desired properties: the material is easily processable in high-quality optical waveguiding structures, has low linear absorption and its nonlinearity has a pure electronic origin. More materials research has to be done to arrive at materials with higher nonlinear coefficients to allow switching at moderate light intensity ( < 1 W peak power) and also with lower nonlinear absorption coefficients.

Measured acoustic properties of variable and low density bulk absorbers

NASA Technical Reports Server (NTRS)

Dahl, M. D.; Rice, E. J.

1985-01-01

Experimental data were taken to determine the acoustic absorbing properties of uniform low density and layered variable density samples using a bulk absober with a perforated plate facing to hold the material in place. In the layered variable density case, the bulk absorber was packed such that the lowest density layer began at the surface of the sample and progressed to higher density layers deeper inside. The samples were placed in a rectangular duct and measurements were taken using the two microphone method. The data were used to calculate specific acoustic impedances and normal incidence absorption coefficients. Results showed that for uniform density samples the absorption coefficient at low frequencies decreased with increasing density and resonances occurred in the absorption coefficient curve at lower densities. These results were confirmed by a model for uniform density bulk absorbers. Results from layered variable density samples showed that low frequency absorption was the highest when the lowest density possible was packed in the first layer near the exposed surface. The layers of increasing density within the sample had the effect of damping the resonances.

Highlights of laser-tissue interaction mechanism

NASA Astrophysics Data System (ADS)

Gabay, Shimon

2001-10-01

The aim of this paper is to present the fundamentals of good practice when using the laser in medicine and surgery. As a 'good practice' recommendation, the laser beam wavelength and power should be determined to match the desired thermal effect. The energy losses to the surroundings of the initial absorbing volume, caused by the heat diffusion mechanism, are strongly dependent on the exposure time duration. The differences in the absorption and scattering coefficients of some tissue components are used for selectively destroying those components having the higher absorption coefficients. Selective destruction of some tissue components can be achieved even for components having the same absorption coefficient but different dimensions. The laser therapy strategy is discussed: the effective use of lasers in medicine can be achieved only if the physician has an extensive understanding of the laser-tissue interaction mechanisms; continuing education and training is a must for laser surgeons to improve their skill to get clinically optimal results.

Propagation of intense laser radiation through a diffusion flame of burning oil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gvozdev, S V; Glova, A F; Dubrovskii, V Yu

2015-06-30

We report the results of measuring the absorption coefficient of radiation from a cw ytterbium fibre single-mode laser with the power up to 1.5 kW by a diffusion flame of oil, burning in the atmosphere air at normal pressure on a free surface. For the constant length (30 mm) and width (30 mm) of the flame and the distance 10 mm between the laser beam axis and the oil surface the dependence of the absorption coefficient, averaged over the flame length, on the mean radiation intensity (varied from 4.5 × 10{sup 3} to 1.2 × 10{sup 6} W cm{sup -2})more » entering the flame is obtained. The qualitative explanation of nonmonotonic behaviour of the absorption coefficient versus the intensity is presented. (laser applications and other topics in quantum electronics)« less

Effects of Refractive Index and Diffuse or Specular Boundaries on a Radiating Isothermal Layer

NASA Technical Reports Server (NTRS)

Siegel, R.; Spuckler, C. M.

1994-01-01

Equilibrium temperatures of an absorbing-emitting layer were obtained for exposure to incident radiation and with the layer boundaries either specular or diffuse. For high refractive indices the surface condition can influence the radiative heat balance if the layer optical thickness is small. Hence for a spectrally varying absorption coefficient the layer temperature is affected if there is significant radiative energy in the spectral range with a small absorption coefficient. Similar behavior was obtained for transient radiative cooling of a layer where the results are affected by the initial temperature and hence the fraction of energy radiated in the short wavelength region where the absorption coefficient is small. The results are a layer without internal scattering. If internal scattering is significant, the radiation reaching the internal surface of a boundary is diffused and the effect of the two different surface conditions would become small.

Optical properties of the Tietz-Hua quantum well under the applied external fields

NASA Astrophysics Data System (ADS)

Kasapoglu, E.; Sakiroglu, S.; Ungan, F.; Yesilgul, U.; Duque, C. A.; Sökmen, I.

2017-12-01

In this study, the effects of the electric and magnetic fields as well as structure parameter- γ on the total absorption coefficient, including linear and third order nonlinear absorption coefficients for the optical transitions between any two subband in the Tietz-Hua quantum well have been investigated. The optical transitions were investigated by using the density matrix formalism and the perturbation expansion method. The Tietz-Hua quantum well becomes narrower (wider) when the γ - structure parameter increases (decreases) and so the energies of the bound states will be functions of this parameter. Therefore, we can provide the red or blue shift in the peak position of the absorption coefficient by changing the strength of the electric and magnetic fields as well as the structure parameters and these results can be used to adjust and control the optical properties of the Tietz-Hua quantum well.

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.

Absorption Coefficient of a Semiconductor Thin Film from Photoluminescence

NASA Astrophysics Data System (ADS)

Rey, G.; Spindler, C.; Babbe, F.; Rachad, W.; Siebentritt, S.; Nuys, M.; Carius, R.; Li, S.; Platzer-Björkman, C.

2018-06-01

The photoluminescence (PL) of semiconductors can be used to determine their absorption coefficient (α ) using Planck's generalized law. The standard method, suitable only for self-supported thick samples, like wafers, is extended to multilayer thin films by means of the transfer-matrix method to include the effect of the substrate and optional front layers. α values measured on various thin-film solar-cell absorbers by both PL and photothermal deflection spectroscopy (PDS) show good agreement. PL measurements are extremely sensitive to the semiconductor absorption and allow us to advantageously circumvent parasitic absorption from the substrate; thus, α can be accurately determined down to very low values, allowing us to investigate deep band tails with a higher dynamic range than in any other method, including spectrophotometry and PDS.

Quantification of optical absorption coefficient from acoustic spectra in the optical diffusive regime using photoacoustic microscopy

NASA Astrophysics Data System (ADS)

Guo, Zijian; Favazza, Christopher; Wang, Lihong V.

2012-02-01

Photoacoustic (PA) tomography (PAT) can image optical absorption contrast with ultrasonic spatial resolution in the optical diffusive regime. Multi-wavelength PAT can noninvasively monitor hemoglobin oxygen saturation (sO2) with high sensitivity and fine spatial resolution. However, accurate quantification in PAT requires knowledge of the optical fluence distribution, acoustic wave attenuation, and detection system bandwidth. We propose a method to circumvent this requirement using acoustic spectra of PA signals acquired at two optical wavelengths. With the acoustic spectral method, the absorption coefficients of an oxygenated bovine blood phantom at 560 and 575 nm were quantified with errors of ><5%.

Self-Normalized Photoacoustic Technique for the Quantitative Analysis of Paper Pigments

NASA Astrophysics Data System (ADS)

Balderas-López, J. A.; Gómez y Gómez, Y. M.; Bautista-Ramírez, M. E.; Pescador-Rojas, J. A.; Martínez-Pérez, L.; Lomelí-Mejía, P. A.

2018-03-01

A self-normalized photoacoustic technique was applied for quantitative analysis of pigments embedded in solids. Paper samples (filter paper, Whatman No. 1), attached with the pigment: Direct Fast Turquoise Blue GL, were used for this study. This pigment is a blue dye commonly used in industry to dye paper and other fabrics. The optical absorption coefficient, at a wavelength of 660 nm, was measured for this pigment at various concentrations in the paper substrate. It was shown that Beer-Lambert model for light absorption applies well for pigments in solid substrates and optical absorption coefficients as large as 220 cm^{-1} can be measured with this photoacoustic technique.

Measurements of photorefractive and absorptive gratings in GaAs:EL2 and their use in extracting material parameters

NASA Astrophysics Data System (ADS)

Rychnovsky, Steve; Gilbreath, G. C.; Zavriyev, A.

1996-10-01

Simultaneous measurements of the photorefractive and the absorptive grating gain components in GaAs:EL2 are made and are shown to display qualitative behavior consistent with linearized solutions of a two-carrier rate equation model. These two components, together with the linear absorption coefficient, permit determination of four independent material parameters, e.g., the ionized and the nonionized EL2 densities, the hole photoionization cross section ( sigma h), and the electro-optic coefficient (r41). Data obtained at optical wavelengths of 0.96 and 1.06 mu m indicate that sigma h and r41 are larger than published values. .

Two-photon absorption in SiO{sub 2}- and (SiO{sub 2} + GeO{sub 2})-based fibres at a wavelength of 349 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chunaev, D S; Karasik, A Ya

2014-06-30

The nonlinear two-photon light absorption coefficients have been measured in an optical fibre with a quartz glass (SiO{sub 2}) core and in a fibre with a germanosilicate glass (SiO{sub 2} + GeO{sub 2}) core. The two-photon absorption coefficient β measured at a wavelength of 349 nm in the (SiO{sub 2} + GeO{sub 2})-based fibre (13.7 cm TW{sup -1}) multiply exceeds that for the pure quartz glass optical fibre (0.54 cm TW{sup -1}). (nonlinear optical phenomena)

Determining photon energy absorption parameters for different soil samples

PubMed Central

Kucuk, Nil; Tumsavas, Zeynal; Cakir, Merve

2013-01-01

The mass attenuation coefficients (μs) for five different soil samples were measured at 661.6, 1173.2 and 1332.5 keV photon energies. The soil samples were separately irradiated with 137Cs and 60Co (370 kBq) radioactive point gamma sources. The measurements were made by performing transmission experiments with a 2″ × 2″ NaI(Tl) scintillation detector, which had an energy resolution of 7% at 0.662 MeV for the gamma-rays from the decay of 137Cs. The effective atomic numbers (Zeff) and the effective electron densities (Neff) were determined experimentally and theoretically using the obtained μs values for the soil samples. Furthermore, the Zeff and Neff values of the soil samples were computed for the total photon interaction cross-sections using theoretical data over a wide energy region ranging from 1 keV to 15 MeV. The experimental values of the soils were found to be in good agreement with the theoretical values. Sandy loam and sandy clay loam soils demonstrated poor photon energy absorption characteristics. However, clay loam and clay soils had good photon energy absorption characteristics. PMID:23179375

Fine particulate matter characteristics and its impact on visibility impairment at two urban sites in Korea: Seoul and Incheon

NASA Astrophysics Data System (ADS)

Kim, Young J.; Kim, Kyung W.; Kim, Shin D.; Lee, Bo K.; Han, Jin S.

In order to investigate the causes of visibility degradation in the metropolitan area of Seoul, extensive chemical and optical monitoring of aerosol was conducted at two urban sites; Junnong, Seoul and Yonghyun, Incheon during several seasonal intensive monitoring periods between August 2002 and August 2004. Light extinction, scattering, and absorption coefficients were measured simultaneously with a transmissometer, a nephelometer, and an aethalometer, respectively. Continuous aerosol chemical measurement was also made with Sunset elemental carbon/organic carbon (EC/OC) analyzers and on-line ion monitors. The mean light extinction budget for five major aerosol components; ammonium sulfate, ammonium nitrate, fine carbonaceous particles (EC and OC), fine soil, and coarse particle was estimated based on the measurement results. Investigation of the haze level revealed that PM 2.5 mass concentrations at Junnong and Yonghyun measured under the Worst20% condition were approximately twice those of the Best20% condition. The worst visibility condition was well correlated with increases in mass concentrations of sulfate and nitrate, and EC particles. The mass concentration of aerosol components for the Worst20% was measured to be approximately two- to four-fold higher than those for the Best20%. Degree of visibility degradation was also analyzed based on the air mass pathway information obtained using the HYSPLIT model. Average light extinction coefficients under continental air flow condition at the Junnong and Yonghyun sites were the highest values of 704±414 and 773±546 Mm -1, respectively due to increased loading of fine particles. Visibility was greatly improved at both sites when atmosphere was impacted by air mass originated from Pacific Ocean.

Secondary organic aerosol from atmospheric photooxidation of indole

NASA Astrophysics Data System (ADS)

Montoya-Aguilera, Julia; Horne, Jeremy R.; Hinks, Mallory L.; Fleming, Lauren T.; Perraud, Véronique; Lin, Peng; Laskin, Alexander; Laskin, Julia; Dabdub, Donald; Nizkorodov, Sergey A.

2017-09-01

Indole is a heterocyclic compound emitted by various plant species under stressed conditions or during flowering events. The formation, optical properties, and chemical composition of secondary organic aerosol (SOA) formed by low-NOx photooxidation of indole were investigated. The SOA yield (1. 3 ± 0. 3) was estimated from measuring the particle mass concentration with a scanning mobility particle sizer (SMPS) and correcting it for wall loss effects. The high value of the SOA mass yield suggests that most oxidized indole products eventually end up in the particle phase. The SOA particles were collected on filters and analysed offline with UV-vis spectrophotometry to measure the mass absorption coefficient (MAC) of the bulk sample. The samples were visibly brown and had MAC values of ˜ 2 m2 g-1 at λ = 300 nm and ˜ 0. 5 m2 g-1 at λ = 400 nm, comparable to strongly absorbing brown carbon emitted from biomass burning. The chemical composition of SOA was examined with several mass spectrometry methods. Direct analysis in real-time mass spectrometry (DART-MS) and nanospray desorption electrospray high-resolution mass spectrometry (nano-DESI-HRMS) were both used to provide information about the overall distribution of SOA compounds. High-performance liquid chromatography, coupled to photodiode array spectrophotometry and high-resolution mass spectrometry (HPLC-PDA-HRMS), was used to identify chromophoric compounds that are responsible for the brown colour of SOA. Indole derivatives, such as tryptanthrin, indirubin, indigo dye, and indoxyl red, were found to contribute significantly to the visible absorption spectrum of indole SOA. The potential effect of indole SOA on air quality was explored with an airshed model, which found elevated concentrations of indole SOA during the afternoon hours contributing considerably to the total organic aerosol under selected scenarios. Because of its high MAC values, indole SOA can contribute to decreased visibility and poor air quality.

Optical properties of InAs/GaAs quantum dot superlattice structures

NASA Astrophysics Data System (ADS)

Imran, Ali; Jiang, Jianliang; Eric, Deborah; Zahid, M. Noaman; Yousaf, M.; Shah, Z. H.

2018-06-01

Quantum dot (QD) structure has potential applications in modern highly efficient optoelectronic devices due to their band-tuning. The device dimensions have been miniatured with increased efficiencies by virtue of this discovery. In this research, we have presented modified analytical and simulation results of InAs/GaAs QD superlattice (QDSL). We have applied tight binding model for the investigation of ground state energies using timeindependent Schrödinger equation (SE) with effective mass approximation. It has been investigated that the electron energies are confined due to wave function delocalization in closely coupled QD structures. The minimum ground state energy can be obtained by increasing the periodicity and decreasing the barrier layer thickness. We have calculated electronics and optical properties which includes ground state energies, transition energies, density of states (DOS), absorption coefficient and refractive index, which can be tuned by structure modification. In our results, the minimum ground state energy of QDSL is achieved to be 0.25 eV with a maximum period of 10 QDs. The minimum band to band and band to continuum transition energies are 63 meV and 130 meV with 2 nm barrier layer thickness respectively. The absorption coefficient of our proposed QDSL model is found to be maximum 1.2 × 104 cm-1 and can be used for highly sensitive infrared detector and high efficiency solar cells.

Photon interaction studies using 241Am g-rays

NASA Astrophysics Data System (ADS)

Ramachandran, N.; Karunakaran Nair, K.; Abdullah, K. K.; Varier, K. M.

2006-09-01

We have carried out some photon interaction measurements using 59.54 keV γ-rays from a ^{241}Am source. These include γ attenuation studies as well as photoelectric absorption studies in various samples. The attenuation studies have been made using leaf and wood samples, samples like sand, sugar etc., which contain particles of varying sizes as well as pellets and aqueous solutions of rare earth compounds. In the case of the leaf and wood samples, we have used the γ-ray attenuation technique for the determination of the water content in fresh and dried samples. The variation of the attenuation coefficient with particle size has been investigated for sand and sugar samples. The attenuation studies as well as the photoelectric studies in the case of rare earth elements have been carried out on samples containing such elements whose K-absorption edge energies lie below and close to the γ-energy used. Suitable compounds of the rare earth elements have been chosen as mixture absorbers in these investigations. A narrow beam good geometry set-up was used for the attenuation measurements. A well-shielded scattering geometry was used for the photoelectric measurements. The mixture rule was invoked to extract the values of the mass attenuation coefficients for the elements from those of the corresponding compounds. The results are consistent with theoretical values derived from the XCOM package.

Reference-free determination of tissue absorption coefficient by modulation transfer function characterization in spatial frequency domain.

PubMed

Chen, Weiting; Zhao, Huijuan; Li, Tongxin; Yan, Panpan; Zhao, Kuanxin; Qi, Caixia; Gao, Feng

2017-08-08

Spatial frequency domain (SFD) measurement allows rapid and non-contact wide-field imaging of the tissue optical properties, thus has become a potential tool for assessing physiological parameters and therapeutic responses during photodynamic therapy of skin diseases. The conventional SFD measurement requires a reference measurement within the same experimental scenario as that for a test one to calibrate mismatch between the real measurements and the model predictions. Due to the individual physical and geometrical differences among different tissues, organs and patients, an ideal reference measurement might be unavailable in clinical trials. To address this problem, we present a reference-free SFD determination of absorption coefficient that is based on the modulation transfer function (MTF) characterization. Instead of the absolute amplitude that is used in the conventional SFD approaches, we herein employ the MTF to characterize the propagation of the modulated lights in tissues. With such a dimensionless relative quantity, the measurements can be naturally corresponded to the model predictions without calibrating the illumination intensity. By constructing a three-dimensional database that portrays the MTF as a function of the optical properties (both the absorption coefficient μ a and the reduced scattering coefficient [Formula: see text]) and the spatial frequency, a look-up table approach or a least-square curve-fitting method is readily applied to recover the absorption coefficient from a single frequency or multiple frequencies, respectively. Simulation studies have verified the feasibility of the proposed reference-free method and evaluated its accuracy in the absorption recovery. Experimental validations have been performed on homogeneous tissue-mimicking phantoms with μ a ranging from 0.01 to 0.07 mm -1 and [Formula: see text] = 1.0 or 2.0 mm -1 . The results have shown maximum errors of 4.86 and 7% for [Formula: see text] = 1.0 mm -1 and [Formula: see text] = 2.0 mm -1 , respectively. We have also presented quantitative ex vivo imaging of human lung cancer in a subcutaneous xenograft mouse model for further validation, and observed high absorption contrast in the tumor region. The proposed method can be applied to the rapid and accurate determination of the absorption coefficient, and better yet, in a reference-free way. We believe this reference-free strategy will facilitate the clinical translation of the SFD measurement to achieve enhanced intraoperative hemodynamic monitoring and personalized treatment planning in photodynamic therapy.

Two-photon interband absorption coefficients in tungstate and molybdate crystals

NASA Astrophysics Data System (ADS)

Lukanin, V. I.; Karasik, A. Ya.

2015-02-01

Two-photon absorption (TPA) coefficients were measured in tungstate and molybdate crystals - BaWO4, KGW, CaMoO4, BaMoO4, CaWO4, PbWO4 and ZnWO4 upon different orientations of excitation polarization with respect to the crystallographic axes. Trains of 25 ps pulses with variable radiation intensities of third (349 nm) harmonics of passively mode-locked 1047 nm Nd:YLF laser were used for interband two-photon excitation of the crystals. It was suggested that in the case, when 349 nm radiation pumping energy exceeds the bandgap width (hν>Eg), the nonlinear excitation process can be considered as two-step absorption. The interband two-photon absorption in all the studied crystals induces the following one-photon absorption from the exited states, which affects the nonlinear process dynamics and leads to a hysteresis in the dependence of the transmission on the excitation intensity. This fact was taken into account under analysis of the experimental dependences of the reciprocal transmission on the excitation intensity. Laser excitation in the transparency region of the crystals caused stimulated Raman scattering (SRS) not for all the crystals studied. The measured nonlinear coefficients allowed us to explain the suppression of SRS in crystals as a result of competition between the SRS and TPA.

Use of radial symmetry for the calculation of cylindrical absorption coefficients and optimal capillary loadings

DOE PAGES

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 ofmore » 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.« less

[Differences of inherent optical properties of inland lake water body in typical seasons].

PubMed

Sun, De-Yong; Li, Yun-Mei; Wang, Qiao; Le, Cheng-Fen; Huang, Chang-Chun; Wang, Li-Zhen

2008-05-01

Inherent optical property is one of the important properties of water body, which lays the foundation for the establishment of water color analytical models. By using quantity filter technology (QFT) and BB9 backscattering meter, the absorption coefficients of chromophoric dissolved organic matter (CDOM) and total suspended matters (TSM) and the backscattering coefficient of TSM in the water body at Meiliang Bay of Taihu Lake were measured in summer and winter. Based on the spectral comparison of the absorption and backscattering coefficients, their differences between the two seasons were demonstrated, and the reasons that caused these differences were also explored in the context of their relations to the changes in water quality. Consequently, water environment condition could be revealed by using the inherent optical property. The relationship between the backscattering coefficient and the TSM concentration was established, which could provide supporting coefficients to the analytical models to be developed.

A mass balance of tri-hexabrominated diphenyl ethers in lactating cows.

PubMed

Kierkegaard, Amelie; De Wit, Cynthia A; Asplund, Lillemor; McLachlan, Michael S; Thomas, Gareth O; Sweetman, Andrew J; Jones, Kevin C

2009-04-01

Beef and dairy products can be important vectors of human exposure to polybrominated diphenylethers (BDEs), and hence an understanding of BDE transfer from feed to cows' milk and tissue is important for BDE exposure assessment The fate of tri- to hexaBDEs in lactating cows exposed to a naturally contaminated diet was studied by analyzing feed, feces, and milk samples from a mass balance study. Tissue distribution was studied in one cowslaughtered afterthe experiment The carryover rates from feed to milk ranged from 0.15 to 0.35 for the major congeners. Lower values were observed for several of the tetrabrominated congeners, and this was attributed to metabolism. The dietary absorption efficiency decreased with increasing octanol-water partition coefficient of the BDE congener. The absorption behavior was consistent with a model based on chemical lipophilicity, but agreed less well with a model based on effective molecular diameter, and it violated Lipinski's "rule of 5". The lipid normalized concentrations were similar in all tissues analyzed including liver and milk, suggesting that tissue distribution is governed by partitioning into lipids. Overall, the behavior of the tri- to hexaBDEs was consistent with that observed for other classes of halogenated aromatic contaminants such as PCBs and PCDD/Fs, but it differed markedly from the behavior of the hepta- decaBDEs.

Synchrotron Photoionization Mass Spectrometry Measurements of Kinetics and Product Formation in the Allyl Radical (H2CCHCH2)Self Reaction

NASA Technical Reports Server (NTRS)

Selby, Talitha M.; Melini, giovanni; Goulay, Fabien; Leone, Stephen R.; Fahr, Askar; Taatjes, Craig A.; Osborn, David L.

2008-01-01

Product channels for the self-reaction of the resonance-stabilized allyl radical, C3H5 + C3H5, have been studied with isomeric specificity at temperatures from 300-600 K and pressures from 1-6 Torr using time-resolved multiplexed photoionization mass spectrometry. Under these conditions 1,5-hexadiene was the only C6H10 product isomer detected. The lack of isomerization of the C6H10 product is in marked contrast to the C6H6 product in the related C3H3 + C3H3 reaction, and is due to the more saturated electronic structure of the C6H10 system. The disproportionation product channel, yielding allene + propene, was also detected, with an upper limit on the branching fraction relative to recombination of 0.03. Analysis of the allyl radical decay at 298 K yielded a total rate coefficient of (2.7 +/- 0.8) x 10(exp -11) cu cm/molecule/s, in good agreement with pre.vious experimental measurements using ultraviolet kinetic absorption spectroscopy and a recent theoretical determination using variable reaction coordinate transition state theory. This result provides independent indirect support for the literature value of the allyl radical ultraviolet absorption cross-section near 223 nm.

Particle Mass in Deep-Water Benthic Nepheloid Layers: a Global Synthesis

NASA Astrophysics Data System (ADS)

Mishonov, A. V.; Gardner, W. D.; Richardson, M. J.

2016-12-01

The mass of particles in benthic nepheloid layers in the deep ocean is mapped using profiles of beam attenuation coefficient obtained with transmissometers interfaced with CTDs during WOCE, SAVE, JGOFS, CLIVAR-Repeat Hydrography, and other programs during the last four decades using data from over 8000 profiles from >70 cruises. We map the maximum concentration of particle mass near the seafloor and integrate the particle mass throughout the benthic nepheloid layer. In the Atlantic Ocean particle mass is greater in areas where eddy kinetic energy is high in overlying waters. Areas of high bottom particle concentrations and integrated benthic nepheloid layer particle loads include the western North Atlantic beneath the Gulf Stream meanders and eddies, Argentine Basin, parts of the Southern Ocean and areas around South Africa. Particle concentrations are low in most of the Pacific and tropical and subtropical Atlantic away from margins. This synthesis is useful for GEOTRACES and other global programs where knowing particle distribution is critical for understanding trace metal absorption, sediment-water exchange and near-bottom processes. Additionally, our synthesis provides baseline data to identify where mining of metal-rich nodules and metal sulfides on the seafloor may impact the benthic environment.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Metivier, H.; Bourges, J.; Fritsch, P.

Absorption and retention of neptunium were determined in baboons after intragastric administration of neptunium nitrate solutions at pH 1. The effects of mass, diet, and fasting on absorption were studied. At higher mass levels (400-800 micrograms Np/kg), absorption was about 1%; at lower mass intakes (0.0009-0.005 micrograms Np/kg), absorption was reduced by 10- to 20-fold. The addition of an oxidizing agent (Fe3+) increased gastrointestinal absorption and supported the hypothesis of a reduction of Np (V) when loss masses were ingested. Diets depleted of or enriched with hydroxy acids did not modify retention of neptunium but increased urinary excretion with increasingmore » hydroxy acid content. The diet enriched with milk components reduced absorption by a factor of 5. Potatoes increased absorption and retention by a factor 5, not necessarily due to the effect of phytate. Fasting for 12 or 24 h increased retention and absorption by factors of about 3 and 10, respectively. Data obtained in baboons when low masses of neptunium were administered suggest that the f1 factor used by ICRP should be decreased. However, fasting as encountered in certain nutritional habits is a factor to be taken into consideration.« less

Modern aspects of nonlinear convection and magnetic field in flow of thixotropic nanofluid over a nonlinear stretching sheet with variable thickness

NASA Astrophysics Data System (ADS)

Hayat, Tasawar; Qayyum, Sajid; Alsaedi, Ahmed; Ahmad, Bashir

2018-05-01

Main objective of present analysis is to study the magnetohydrodynamic (MHD) nonlinear convective flow of thixotropic nanofluid. Flow is due to nonlinear stretching surface with variable thickness. Nonlinear thermal radiation and heat generation/absorption are utilized in the energy expression. Convective conditions and zero mass flux at sheet are considered. Intention in present analysis is to develop a model for nanomaterial comprising Brownian motion and thermophoresis phenomena. Appropriate transformations are implemented for the conversion of partial differential systems into a sets of ordinary differential equations. The transformed expressions have been scrutinized through homotopic algorithm. Behavior of various sundry variables on velocity, temperature, nanoparticle concentration, skin friction coefficient and local Nusselt number are displayed through graphs. It is concluded that qualitative behaviors of temperature and thermal layer thickness are similar for radiation and temperature ratio variables. Moreover an enhancement in heat generation/absorption show rise to thermal field.

Synthesis, crystal structure, photophysical properties and theoretical studies of a novel bis(phenylisoxazolyl) benzene derivative

NASA Astrophysics Data System (ADS)

de Brito, A. C. F.; Correa, R. S.; Pinto, A. A.; Matos, M. J. S.; Tenorio, J. C.; Taylor, J. G.; Cazati, T.

2018-07-01

Isoxazoles have well established biological activities but, have been underexplored as synthetic intermediates for applications in materials science. The aims of this work are to synthesis a novel isoxazole and analyze its structural and photophysical properties for application in electronic organic materials. The novel bis (phenylisoxazolyl) benzene compound was synthesized in four steps and characterized by NMR, high resolution mass spectrometry, differential thermal analysis, infrared spectroscopy, cyclic voltammetry, ultraviolet-visible spectroscopy, fluorescence spectroscopy, DFT and TDDFT calculations. The molecule presented optical absorption in the ultraviolet region (from 290 nm to 330 nm), with maximum absorption length centered at 306 nm. The molar extinction coefficients (ε), fluorescence emission spectra and quantum efficiencies in chloroform and dimethylformamide solution were determined. Cyclic voltammetry analysis was carried out for estimating the HOMO energy level and these properties make it desirable material for photovoltaic device applications. Finally, the excited-state properties of present compound were calculated by time-dependent density functional theory (TDDFT).