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Sample records for al 1s-2p absorption

  1. Al 1s-2p Absorption Spectroscopy of Shock-Wave Heating and Compression in Laser-Driven Planar Foil

    SciTech Connect

    Sawada, H.; Regan, S.P.; Radha, P.B.; Epstein, R.; Li, D.; Goncharov, V.N.; Hu, S.X.; Meyerhofer, D.D.; Delettrez, J.A.; Jaanimagi, P.A.; Smalyuk, V.A.; Boehly, T.R.; Sangster, T.C.; Yaakobi, B.; Mancini, R.C.

    2009-05-19

    Time-resolved Al 1s-2p absorption spectroscopy is used to diagnose direct-drive, shock-wave heating and compression of planar targets having nearly Fermi-degenerate plasma conditions (Te ~ 10–40 eV, rho ~ 3–11 g/cm^3) on the OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. A planar plastic foil with a buried Al tracer layer was irradiated with peak intensities of 10^14–10^15 W/cm^2 and probed with the pseudocontinuum M-band emission from a point-source Sm backlighter in the range of 1.4–1.7 keV. The laser ablation process launches 10–70 Mbar shock waves into the CH/Al/CH target. The Al 1s-2p absorption spectra were analyzed using the atomic physic code PRISMSPECT to infer Te and rho in the Al layer, assuming uniform plasma conditions during shock-wave heating, and to determine when the heat front penetrated the Al layer. The drive foils were simulated with the one-dimensional hydrodynamics code LILAC using a flux-limited (f =0.06 and f =0.1) and nonlocal thermal-transport model [V. N. Goncharov et al., Phys. Plasmas 13, 012702 (2006)]. The predictions of simulated shock-wave heating and the timing of heat-front penetration are compared to the observations. The experimental results for a wide variety of laser-drive conditions and buried depths have shown that the LILAC predictions using f = 0.06 and the nonlocal model accurately model the shock-wave heating and timing of the heat-front penetration while the shock is transiting the target. The observed discrepancy between the measured and simulated shock-wave heating at late times of the drive can be explained by the reduced radiative heating due to lateral heat flow in the corona.

  2. Al 1s-2p absorption spectroscopy of shock-wave heating and compression in laser-driven planar foil

    SciTech Connect

    Sawada, H.; Regan, S. P.; Radha, P. B.; Epstein, R.; Li, D.; Goncharov, V. N.; Hu, S. X.; Meyerhofer, D. D.; Delettrez, J. A.; Jaanimagi, P. A.; Smalyuk, V. A.; Boehly, T. R.; Sangster, T. C.; Yaakobi, B.; Mancini, R. C.

    2009-05-15

    Time-resolved Al 1s-2p absorption spectroscopy is used to diagnose direct-drive, shock-wave heating and compression of planar targets having nearly Fermi-degenerate plasma conditions (T{sub e}{approx}10-40 eV, {rho}{approx}3-11 g/cm{sup 3}) on the OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. A planar plastic foil with a buried Al tracer layer was irradiated with peak intensities of 10{sup 14}-10{sup 15} W/cm{sup 2} and probed with the pseudocontinuum M-band emission from a point-source Sm backlighter in the range of 1.4-1.7 keV. The laser ablation process launches 10-70 Mbar shock waves into the CH/Al/CH target. The Al 1s-2p absorption spectra were analyzed using the atomic physic code PRISMSPECT to infer T{sub e} and {rho} in the Al layer, assuming uniform plasma conditions during shock-wave heating, and to determine when the heat front penetrated the Al layer. The drive foils were simulated with the one-dimensional hydrodynamics code LILAC using a flux-limited (f=0.06 and f=0.1) and nonlocal thermal-transport model [V. N. Goncharov et al., Phys. Plasmas 13, 012702 (2006)]. The predictions of simulated shock-wave heating and the timing of heat-front penetration are compared to the observations. The experimental results for a wide variety of laser-drive conditions and buried depths have shown that the LILAC predictions using f=0.06 and the nonlocal model accurately model the shock-wave heating and timing of the heat-front penetration while the shock is transiting the target. The observed discrepancy between the measured and simulated shock-wave heating at late times of the drive can be explained by the reduced radiative heating due to lateral heat flow in the corona.

  3. 1s2p resonant inelastic x-ray scattering in {alpha}-Fe{sub 2}O{sub 3}

    SciTech Connect

    Caliebe, W.A.; Kao, C.; Hastings, J.B.; Taguchi, M.; Kotani, A.; Uozumi, T.; de Groot, F.M.

    1998-11-01

    We report experimental and theoretical results on the Fe {ital K} edge x-ray absorption spectrum and 1s2p resonant inelastic x-ray scattering (RIXS) spectra in {alpha}-Fe{sub 2}O{sub 3}. The results are interpreted using an FeO{sub 6}{sup 9}{minus} cluster model with intra-atomic multiplet coupling and interatomic covalency hybridization. The 1s2p RIXS is treated as a coherent second-order optical process. It is shown that the double-peak structure in the pre-edge region of Fe {ital K} absorption spectrum is due to the cubic crystal-field splitting, and that the intensity of the e{sub g} (t{sub 2g}) component in the 1s2p resonant inelastic spectrum is enhanced by tuning the incident photon energy to the e{sub g} (t{sub 2g}) component in the absorption spectrum. {copyright} {ital 1998} {ital The American Physical Society}

  4. Numerical Method for Inverting 1s2p Resonant Inelastic X-ray Scattering Spectra: Interpretation of Hidden Electronic Excitations in CuO

    SciTech Connect

    Dräger, G.; Machek, P

    2009-01-01

    Direct inversion of resonant inelastic x-ray scattering spectra (RIXSS) has been carried out using a numerical method for solving first-kind Fredholm integral equations. Hereby, the oscillator strength distribution (OSD), which is proportional to the empty density of states at the absorption edge, has been obtained from the experimental Cu 1s2p RIXSS of CuO. In particular, the inversion of RIXSS measured at incident energies below the K level threshold provides OSD having a better resolution than it can be achieved with one of the customary x-ray absorption near-edge structure spectroscopies. This can be explained by the virtual character of the intermediate states at low energy excitation. By means of the presented method a so-called 'hidden electronic excitation' of CuO has been identified as a very weak core excitation. Furthermore, numerical interpretation of polarized spectra has revealed the py-like character of the excited states in a suitable local reference frame. The obtained results are promising for further applications of the method, preferred in the field of strongly correlated materials.

  5. Experimental investigation of X-ray spectral absorption coefficients in heated Al and Ge on the Iskra-5 laser facility

    SciTech Connect

    Bondarenko, S V; Garanin, Sergey G; Zhidkov, N V; Pinegin, A V; Suslov, N A

    2012-01-31

    We set forth the data of experimental investigation of X-ray spectral absorption coefficients in the 1.1 - 1.6 keV photon energy range for Al and Ge specimens bulk heated by soft X-ray radiation. Two experimental techniques are described: with the use of one facility channel and the heating of specimens by the X-ray radiation from a plane burnthrough target, as well as with the use of four channels and the heating by the radiation from two cylindrical targets with internal input of laser radiation. The X-ray radiation absorption coefficients were studied by way of transmission absorption spectroscopy using backlighting X-ray radiation from a point source. The results of investigation of X-ray spectral absorption coefficients on the 1s - 2p transitions in Al atoms and the 2p - 3d transitions in Ge atoms are presented.

  6. Temporally resolved characterization of shock-heated foam target with Al absorption spectroscopy for fast electron transport study

    NASA Astrophysics Data System (ADS)

    Yabuuchi, T.; Sawada, H.; Regan, S. P.; Anderson, K.; Wei, M. S.; Betti, R.; Hund, J.; Key, M. H.; Mackinnon, A. J.; McLean, H. S.; Paguio, R. R.; Patel, P. K.; Saito, K. M.; Stephens, R. B.; Wilks, S. C.; Beg, F. N.

    2012-09-01

    The CH foam plasma produced by a laser-driven shock wave has been characterized by a temporally resolved Al 1s-2p absorption spectroscopy technique. A 200 mg/cm3 foam target with Al dopant was developed for this experiment, which used an OMEGA EP [D. D. Meyerhofer et al., J. Phys.: Conf. Ser. 244, 032010 (2010)] long pulse beam with an energy of 1.2 kJ and 3.5 ns pulselength. The plasma temperatures were inferred with the accuracy of 5 eV from the fits to the measurements using an atomic physics code. The results show that the inferred temperature is sustained at 40-45 eV between 6 and 7 ns and decreases to 25 eV at 8 ns. 2-D radiation hydrodynamic simulations show a good agreement with the measurements. Application of the shock-heated foam plasma platform toward fast electron transport experiments is discussed.

  7. Measurement of the 1s2s 1S0-1s2p 3P1 intercombination interval in helium-like silicon.

    PubMed

    Redshaw, M; Myers, E G

    2002-01-14

    Using Doppler-tuned fast-beam laser spectroscopy the 1s2s 1S0-1s2p 3P1 intercombination interval in 28Si12+ has been measured to be 7230.5(2) cm(-1). The experiment made use of a single-frequency Nd:YAG (1.319 microm) laser and a high-finesse optical buildup cavity. The result provides a precision test of modern relativistic and QED atomic theory.

  8. Atomic, Molecular, and Optical Physics: Optical Excitation Function of H(1s-2p) Produced by electron Impact from Threshold to 1.8 keV

    NASA Technical Reports Server (NTRS)

    James, G. K.; Slevin, J. A.; Shemansky, D. E.; McConkey, J. W.; Bray, I.; Dziczek, D.; Kanik, I.; Ajello, J. M.

    1997-01-01

    The optical excitation function of prompt Lyman-Alpha radiation, produced by electron impact on atomic hydrogen, has been measured over the extended energy range from threshold to 1.8 keV. Measurements were obtained in a crossed-beams experiment using both magnetically confined and electrostatically focused electrons in collision with atomic hydrogen produced by an intense discharge source. A vacuum-ultraviolet mono- chromator system was used to measure the emitted Lyman-Alpha radiation. The absolute H(1s-2p) electron impact excitation cross section was obtained from the experimental optical excitation function by normalizing to the accepted optical oscillator strength, with corrections for polarization and cascade. Statistical and known systematic uncertainties in our data range from +/- 4% near threshold to +/- 2% at 1.8 keV. Multistate coupling affecting the shape of the excitation function up to 1 keV impact energy is apparent in both the present experimental data and present theoretical results obtained with convergent close- coupling (CCC) theory. This shape function effect leads to an uncertainty in absolute cross sections at the 10% level in the analysis of the experimental data. The derived optimized absolute cross sections are within 7% of the CCC calculations over the 14 eV-1.8 keV range. The present CCC calculations converge on the Bethe- Fano profile for H(1s-2p) excitation at high energy. For this reason agreement with the CCC values to within 3% is achieved in a nonoptimal normalization of the experimental data to the Bethe-Fano profile. The fundamental H(1s-2p) electron impact cross section is thereby determined to an unprecedented accuracy over the 14 eV - 1.8 keV energy range.

  9. Measurement of 1s2s 3S1-1s2p 3P2,0 wavelengths in heliumlike silicon

    NASA Astrophysics Data System (ADS)

    Howie, David J. H.; Hallett, William A.; Myers, Edmund G.; Dietrich, Daniel D.; Silver, Joshua D.

    1994-06-01

    We have measured the vacuum-ultraviolet 1s2s 3S1-1s2p 3P2,0 transition wavelengths in heliumlike silicon by photographic spectroscopy of a beam-foil source. The results are 814.71+/-0.02 Å and 878.68+/-0.03 Å, respectively, and represent a sensitive test of present relativistic and quantum electrodynamic calculations. Comparisons are made between our results, previous measurements of these transitions, and the current theories. Good agreement is obtained, particularly with recent relativistic many-body perturbation calculations. A discussion of future measurements of this interval is also presented.

  10. Hydrogen absorption and desorption in rapidly solidified Mg- Al alloys

    NASA Astrophysics Data System (ADS)

    Urgnani, J.; Di Chio, M.; Palumbo, M.; Feuerbacher, M.; Fernandez, J. F.; Leardini, F.; Baricco, M.

    2009-01-01

    The addition of Al to Mg has been indicated as a suitable way to destabilise the hydride phase, in order to bring the absorption and desorption reactions close to reasonable temperatures and pressure values for hydrogen storage. Rapid solidification is known to refine the microstructure of Mg-Al alloys and it might improve the H2 absorption/desorption kinetics. In this paper, the interaction of H2 with rapidly solidified Mg-Al alloys have been studied for three different composition: Mg38.5Al61.5, Mg69Al31 and Mg72Al28. For Mg72Al28, no significant changes in the microstructure have been obtained by rapid solidification. In Mg69Al31, a significant grain refinement has been observed, whereas, for Mg38.5Al61.5, the formation of a metastable hexagonal phase has been found. In all cases, a disproportionation reaction has been observed after H2 absorption, leading to MgH2. After heating up to 430 °C the hydrogenated samples, a main desorption reaction from MgH2 has been observed, which brings again to the starting phases. Experimental results have been discussed on the basis of a thermodynamic assessment of the Mg-Al-H system.

  11. Reexamination of the He- 1s2p2 4Pe shape resonance: Details of its properties and a precise electron affinity for He 2 3S

    NASA Astrophysics Data System (ADS)

    Walter, C. W.; Seifert, J. A.; Peterson, J. R.

    1994-09-01

    The huge He- 4Pe shape resonance was reexamined in photodetachment using a titanium:sapphire laser tuned over the energy range 9740-10 300 cm-1. This range covered well below the He (2 3P) threshold and included the entire resonance region. The uncertainties in the earlier data [Peterson et al., Phys. Rev. Lett. 55, 692 (1985)] were greatly reduced. The new (old) experimental value for the electron affinity of He (2 3S) is 77.67+/-0.12 meV (77.6+/-1.0 meV), in fair agreement with the most accurate theoretical value, 77.51+/-0.04 meV, of Bunge and Bunge [Phys. Rev. A 30, 2179 (1984)]. This resonance lies 10.80+/-0.07 meV above the He 2 3P threshold, and has a decay width of Γ=7.16+/-0.07 meV. The ratio of the cross section at resonance to the continuum at the threshold is σR/σ0=89+/-5. This study provides by far the most detailed experimental view of an electronic shape resonance.

  12. Measurement and analysis of x-ray absorption in Al and MgF2 plasmas heated by Z-pinch radiation.

    PubMed

    Rochau, Gregory A; Bailey, J E; Macfarlane, J J

    2005-12-01

    High-power Z pinches on Sandia National Laboratories' Z facility can be used in a variety of experiments to radiatively heat samples placed some distance away from the Z-pinch plasma. In such experiments, the heating radiation spectrum is influenced by both the Z-pinch emission and the re-emission of radiation from the high-Z surfaces that make up the Z-pinch diode. To test the understanding of the amplitude and spectral distribution of the heating radiation, thin foils containing both Al and MgF2 were heated by a 100-130 TW Z pinch. The heating of these samples was studied through the ionization distribution in each material as measured by x-ray absorption spectra. The resulting plasma conditions are inferred from a least-squares comparison between the measured spectra and calculations of the Al and Mg 1s-->2p absorption over a large range of temperatures and densities. These plasma conditions are then compared to radiation-hydrodynamics simulations of the sample dynamics and are found to agree within 1sigma to the best-fit conditions. This agreement indicates that both the driving radiation spectrum and the heating of the Al and MgF2 samples is understood within the accuracy of the spectroscopic method.

  13. Pressure dependence of Se absorption lines in AlSb

    SciTech Connect

    Hsu, L. |; Haller, E.E.; Ramdas, A.K.

    1996-09-01

    Using far infrared absorption spectroscopy, the authors have investigated electronic transition spectra of Se donors in AlSb as a function of hydrostatic pressure. At least two distinct ground to bound excited state transition lines, which depend quadratically on the pressure, can be seen. At pressures between 30 and 50 kbar, evidence of an anti-crossing between one of the electronic transitions and a peak which they attribute to the 2 zone center LO phonon mode can be seen.

  14. Oscillator strengths for 1s2 1S0-1s2p 3P1,2 transitions in helium-like carbon, nitrogen and oxygen including the effects of a finite nuclear mass

    NASA Astrophysics Data System (ADS)

    Morton, Donald C.; Drake, G. W. F.

    2016-12-01

    We have calculated the electric dipole (E1) and magnetic quadrupole (M2) oscillator strengths and spontaneous decay rates for the 1{{{s}}}2{}1{{{S}}}0{--}1{{s}}2{{p}}{}3{{{P}}}{1,2} spin-changing transitions of helium-like C v, N vi and O vii. We added the effects of the finite nuclear mass and the anomalous magnetic moment of the electron including an extra term derived by Pachucki. For the E1 calculations we used the Breit approximation and pseudostate expansions to perform the perturbation sums over intermediate states in both the length and velocity gauge as a check on numerical accuracy and the validity of the transition operators. There is some cancellation in the corrections for the nuclear mass and the electron anomaly so that if one is included the other should not be ignored

  15. High absorption efficiency of AlGaAs/GaAs superlattice solar cells

    NASA Astrophysics Data System (ADS)

    Nishinaga, Jiro; Kawaharazuka, Atsushi; Horikoshi, Yoshiji

    2015-05-01

    The effects of excitonic absorption on the solar cell efficiency have been investigated in solar cells with AlGaAs/GaAs superlattice absorption layers. Numerical calculations reveal that excitonic absorption considerably enhances the overall absorption coefficient. The excitonic absorption shows strong peaks at the absorption edge and in the energy region above the band gap. Absorption enhancement is also achieved in the AlGaAs/GaAs superlattice. The measured quantum efficiency spectra of superlattice solar cells at room temperature are reasonably well reproduced by simulations taking excitonic effects into account. The superlattice solar cells are confirmed to have a high absorbance and good temperature stability. The theoretical analysis of the experimental results confirms that the enhanced excitonic absorption in the superlattice absorption layers survives even at 100 °C, which is considered as the actual device temperature under realistic device operations.

  16. Determination of absorption coefficients in AlInP lattice matched to GaAs

    NASA Astrophysics Data System (ADS)

    Cheong, J. S.; Ng, J. S.; Krysa, A. B.; Ong, J. S. L.; David, J. P. R.

    2015-10-01

    The absorption properties of Al0.52In0.48P have been investigated near the fundamental absorption edge by measuring the photocurrent as a function of wavelength in a series of PIN and NIP diodes. Modelling of the photocurrent in these structures enables the absorption coefficients to be determined accurately over a wide dynamic range, which allows the direct and indirect band-gap to be determined.

  17. Core-excitonic lines at the Al 2p surface optical-absorption threshold of AlAs and AlP

    NASA Astrophysics Data System (ADS)

    Kelly, M. K.; Niles, D. W.; Perfetti, P.; Colavita, E.; Savoia, A.; Margaritondo, G.; Henzler, M.

    1985-10-01

    The optical-absorption spectra of AlAs and AlP exhibit unusual features-strong Al 2p core-excitonic lines. The data were obtained with synchrotron-radiation photoemission in the partial-yield mode. The analysis was based on the approach proposed by Johnson, Fock, Ley, and Cardona for AlSb and on Onodera and Toyozawa's exciton theory.

  18. Absorption cross sections and kinetics of formation of AlO at 298 K

    NASA Astrophysics Data System (ADS)

    Gómez Martín, Juan Carlos; Daly, Shane M.; Brooke, James S. A.; Plane, John M. C.

    2017-05-01

    The rate coefficient of the Al + O2 reaction has been measured in a laser ablation-fast flow tube apparatus by monitoring atomic Al resonance absorption and AlO laser induced fluorescence (LIF). The rate constant has been found to be k(298 K) = (1.68 ± 0.24) × 10-10 cm3 molecule-1 s-1. Under conditions of near-stoichiometric conversion of Al into AlO, the absorption cross section of AlO at the bandhead of the B2Σ+(v' = 0) ← X2Σ+(v'' = 0) transition has been determined to be σ(298 K, 1 hPa) = (6.7 ± 1.6) × 10-15 cm2 molecule-1 (0.003 nm resolution), in very good agreement with theoretical predictions.

  19. Wet etching and infrared absorption of AlN bulk single crystals

    NASA Astrophysics Data System (ADS)

    Weiwei, Li; Youwen, Zhao; Zhiyuan, Dong; Jun, Yang; Weijie, Hu; Jianhong, Ke

    2009-07-01

    The defects and the lattice perfection of an AlN (0001) single crystal grown by the physical vapor transport (PVT) method were investigated by wet etching, X-ray diffraction (XRD), and infrared absorption, respectively. A regular hexagonal etch pit density (EPD) of about 4000 cm-2 is observed on the (0001) Al surface of an AlN single crystal. The EPD exhibits a line array along the slip direction of the wurtzite structure, indicating a quite large thermal stress born by the crystal in the growth process. The XRD full width at half maximum (FWHM) of the single crystal is 35 arcsec, suggesting a good lattice perfection. Pronounced infrared absorption peaks are observed at wave numbers of 1790, 1850, 2000, and 3000 cm-1, respectively. These absorptions might relate to impurities O, C, Si and their complexes in AlN single crystals.

  20. Origins of optical absorption and emission lines in AlN

    SciTech Connect

    Yan, Qimin; Janotti, Anderson; Van de Walle, Chris G.; Scheffler, Matthias

    2014-09-15

    To aid the development of AlN-based optoelectronics, it is essential to identify the defects that cause unwanted light absorption and to minimize their impact. Using hybrid functional calculations, we investigate the role of native defects and their complexes with oxygen, a common impurity in AlN. We find that Al vacancies are the source of the absorption peak at 3.4 eV observed in irradiated samples and of the luminescence signals at 2.78 eV. The absorption peak at ∼4.0 eV and higher, and luminescence signals around 3.2 and 3.6 eV observed in AlN samples with high oxygen concentrations are attributed to complexes of Al vacancies and oxygen impurities. We also propose a transition involving Al and N vacancies and oxygen impurities that may be a cause of the absorption band peaked at 2.9 eV.

  1. Effects of hydrogen absorption in TbNiAl and UNiAl

    SciTech Connect

    Bordallo, H.N.; Nakotte, H.; Schultz, A.; Kolomiets, A.V.; Havela, L.; Andreev, A.V.

    1998-12-31

    Although hydrides of intermetallic compounds are used extensively as hydrogen-storage media, little is known about the exact nature of metal-hydrogen interactions. However, this knowledge is of essential importance for the understanding of thermodynamics and other properties. Hydrides (deuterides) of TbNiAl and UNiAl have been widely studied because of drastic increase of magnetic ordering temperature under hydrogenation. Here the authors report neutron-diffraction results of the three deuterides, TbNiAlD{sub 1.28}, TbNiAlD{sub 0.8}a nd UNiAlD{sub 2.23}.

  2. Linear intersubband optical absorption in the semiparabolic quantum wells based on AlN/AlGaN/AlN under a uniform electric field

    NASA Astrophysics Data System (ADS)

    Tien, Nguyen Thanh; Hung, Nguyen Nhut Tuan; Nguyen, Tieu Tin; Thao, Pham Thi Bich

    2017-08-01

    The linear intersubband optical absorption in the polarization semiparabolic quantum wells (SPQWs) are investigated for typical AlN/AlxGa 1-x N/AlN. First, the one-dimensional Poisson and Schrödinger equations have been solved by the variational method within a finite potential barrier model and a bent band figured by all confinement sources (realistic model). Then, the intersubband optical absorption between the lowest two subbands has been theoretically studied under an uniform external electric field. Computed results including the effective confining potential profile, the wave function and the distribution of electron gas in quantum wells, intersubband optical absorption coefficient have been discussed. Our calculation shows that the positive interface polarization charges affect on the distribution of the two-dimensional electron gas (2DEG) in SPQWs so it has great influences on the total optical absorption coefficients significantly.

  3. High pressure Raman and visible absorption study of AlH3

    NASA Astrophysics Data System (ADS)

    Shimura, N.; Takeichi, T.; Kume, T.; Sasaki, S.; Shimizu, H.; Ohmura, A.; Ikeda, K.; Nakamori, Y.; Orimo, S.

    2010-03-01

    Raman and visible absorption spectra of AlH3 were measured at high pressures in order to clarify the structural and electronic phase transitions. For the Raman results, abrupt decrease in Raman intensity was found at 30 GPa, implying that there exists a structural transition from the α phase to higher pressure phase. Correspondingly, the spectral change in the optical absorption was observed at almost the same pressure of 30 GPa. From the absorption measurements, the band gap is expected to close at the pressure higher than 50 GPa.

  4. Terahertz intersubband absorption in GaN/AlGaN step quantum wells

    NASA Astrophysics Data System (ADS)

    Machhadani, H.; Kotsar, Y.; Sakr, S.; Tchernycheva, M.; Colombelli, R.; Mangeney, J.; Bellet-Amalric, E.; Sarigiannidou, E.; Monroy, E.; Julien, F. H.

    2010-11-01

    We demonstrate terahertz intersubband absorptions at frequencies of 2.1 THz (λ ≈143 μm) and 4.2 THz (λ ≈70 μm) in nitride-based semiconductor quantum wells. The structures consist of a 3 nm thick GaN well, an Al0.05Ga0.95N step barrier, and a 3 nm thick Al0.1Ga0.9N barrier. The absorption is detected at 4.7 K. The structure design has been optimized to approach a flat-band potential in the wells to allow for an intersubband absorption in the terahertz frequency range and to maximize the optical dipole moments.

  5. Defect assisted saturable absorption characteristics in Al and Li doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    K. M., Sandeep; Bhat, Shreesha; S. M., Dharmaprakash; P. S., Patil; Byrappa, K.

    2016-09-01

    The influence of different doping ratios of Al and Li on the nonlinear optical properties, namely, a two-photon absorption and a nonlinear refraction using single beam Z-scan technique, of nano-crystalline ZnO thin films has been investigated in the present study. A sol-gel spin-coated pure ZnO, Al-doped ZnO (AZO), and Li-doped ZnO (LZO) thin films have been prepared. The stoichiometric deviations induced by the occupancy of Al3+ and Li+ ions at the interstitial sites injects the compressive stress in the AZO and LZO thin films, respectively, while the extended defect states below the conduction band leads to a redshift of energy band gap in the corresponding films as compared to pure ZnO thin film. Switching from an induced absorption in ZnO and 1 at. wt. % doped AZO and LZO films to a saturable absorption (SA) in 2 at. wt. % doped AZO and LZO films has been observed, and it is attributed to the saturation of a linear absorption of the defect states. The closed aperture Z-scan technique revealed the self-focusing (a positive nonlinear refractive index) in all the films, which emerge out of the thermo-optical effects due to the continuous illumination of laser pulses. A higher third-order nonlinear optical susceptibility χ(3) of the order 10-3 esu has been observed in all the films.

  6. Anormalous Optical Absorption in Porous Al_2O3 Host Matrix---Nano-Oxide Particle Nanocomposites

    NASA Astrophysics Data System (ADS)

    Zhang, Lide; Zhang, Biao; Mo, Chimei

    1996-03-01

    Porous Al_2O3 host matrix---nano-γ-Fe_2O3 particle composites (porous nanocomposite) were prepared by pyrolysis of Fe(NO_3)_39H_2O in porous nano- Al_2O3 matrix at 250^0C. Comparing with simple nanocomposites formed by mixing nano-γ-Fe_2O3 and compacting at room temperature, followed by annealing at 250^0C, the following anomalous optical behaviors were observed: for porous nanocomposite containing 5% Fe_2O_3, the aborption edge shifts obviously from 827nm to 543nm, and with increasing dopping amount of Fe_2O3 from 5% to 70%, blue shift phenomina decreases. Namely, the absorption edge moves from 543nm to 710nm. The mechanism of shift of the absorption edge is discussed.

  7. K-shell transition absorption measurement of radiatively heated Al plasma

    NASA Astrophysics Data System (ADS)

    Yang, Jiamin; Zhang, Jiyang; Ding, Yaonan; Peng, Yonglun; Li, Jiaming; Zheng, Zhijian; Yang, Guohong; Zhang, Wenhai; Li, Jun

    2003-12-01

    High temperature aluminum plasmas have been produced by irradiating the layered Au-Al foils with the smoothed high power laser at the Xingguang II laser facility. High-resolution transmission spectrum of the Al plasma has been measured by using penta-erythritol tetrakis (hydroxymethy) methane C(CH2OH)4 crystal spectrometer. Absorption lines of the aluminum ion transition 1s-np(n=3,4,5) in the region of 0.61-0.70 nm, have been observed and identified. The unresolved transition array model has been introduced to calculate the transmission spectra of aluminum plasma. The measured transmission spectrum has been compared with those calculated.

  8. Pseudo-square AlGaN/GaN quantum wells for terahertz absorption

    NASA Astrophysics Data System (ADS)

    Beeler, M.; Bougerol, C.; Bellet-Amalric, E.; Monroy, E.

    2014-09-01

    THz intersubband transitions are reported down to 160 μm within AlGaN/GaN heterostructures following a 4-layer quantum well design. In such a geometry, the compensation of the polarization-induced internal electric field is obtained through creating a gradual increase in polarization field throughout the quantum "trough" generated by three low-Al-content layers. The intersubband transitions show tunable absorption with respect to doping level as well as geometrical variations which can be regulated from 53 to 160 μm. They also exhibit tunnel-friendly designs which can be easily integrated into existing intersubband device architectures.

  9. Neutron absorption of Al-Si-Mg-B{sub 4}C composite

    SciTech Connect

    Abdullah, Yusof Yusof, Mohd Reusmaazran; Ibrahim, Anis Syukriah; Daud, Abdul Razak

    2016-01-22

    Al-Si-Mg-B{sub 4}C composites containing 2-8 wt% of B{sub 4}C were prepared by stir casting technique. Homogenization treatment was carried out at temperatures of 540°C for 4 houra and followed by ageing at 180°C for 2 houra. Microstructure and phase identification were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively. Neutron absorption study was investigated using neutron source Am/Be{sup 241}. The result indicated that higher B{sub 4}C content improved the neutron absorption property. Meanwhile homogeneity of the composite was increased by ageing processes. This composite is potential to be used as neutron shielding material especially for nuclear reactor application.

  10. Neutron absorption of Al-Si-Mg-B4C composite

    NASA Astrophysics Data System (ADS)

    Abdullah, Yusof; Ibrahim, Anis Syukriah; Daud, Abdul Razak; Yusof, Mohd Reusmaazran

    2016-01-01

    Al-Si-Mg-B4C composites containing 2-8 wt% of B4C were prepared by stir casting technique. Homogenization treatment was carried out at temperatures of 540°C for 4 houra and followed by ageing at 180°C for 2 houra. Microstructure and phase identification were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively. Neutron absorption study was investigated using neutron source Am/Be241. The result indicated that higher B4C content improved the neutron absorption property. Meanwhile homogeneity of the composite was increased by ageing processes. This composite is potential to be used as neutron shielding material especially for nuclear reactor application.

  11. Enhanced Dielectric Properties and High-Temperature Microwave Absorption Performance of Zn-Doped Al2O3 Ceramic

    NASA Astrophysics Data System (ADS)

    Wang, Yuan; Luo, Fa; Wei, Ping; Zhou, Wancheng; Zhu, Dongmei

    2015-07-01

    To improve the dielectric and microwave absorption properties of Al2O3 ceramic, Zn-doped Al2O3 ceramic was prepared by conventional ceramic processing. X-ray diffraction analysis confirmed that Zn atoms successfully entered the Al2O3 ceramic lattice and occupied Al sites. The complex permittivity increased with increasing Zn concentration, which is mainly attributed to the increase in charged vacancy defects and densification of the Al2O3 ceramic. In addition, the temperature-dependent complex permittivity of 3% Zn-doped Al2O3 ceramic was determined in the temperature range from 298 K to 873 K. Both the real and imaginary parts of the complex permittivity increased monotonically with increasing temperature, which can be ascribed to the shortened relaxation time and increasing electrical conductivity. The increased complex permittivity leads to a great improvement in microwave absorption. In particular, when the temperature is up to 873 K, the 3% Zn-doped Al2O3 ceramic exhibited the best absorption performance with a maximum peak (-12.1 dB) and broad effective absorption bandwidth (reflection loss less than -10 dB from 9.3 GHz to 12.3 GHz). These results reveal that Zn-doped Al2O3 ceramic is a promising candidate for use as a kind of high-temperature microwave absorption material.

  12. Absorption and diffusion of oxygen in the Ti3Al alloy

    NASA Astrophysics Data System (ADS)

    Bakulin, A. V.; Latyshev, A. M.; Kulkova, S. E.

    2017-07-01

    The absorption and diffusion of oxygen in the Ti3Al alloy are studied by the projector augmented wave within the density functional theory. The highest absorption energies are shown to correspond to the sites in the octahedra formed by six titanium atoms, and the presence of aluminum in the nearest neighbors leads to a substantial decrease in the binding energy of oxygen in the alloy by approximately 1.5 eV. The energy barriers of oxygen diffusion between various interstices in the crystal lattice of the alloy are estimated, and the preferred migration paths in the (0001) plane and the [0001] direction are determined. It is found that the migration barrier from the most preferred octahedral O1 site to distorted tetrahedral Ti-site (2.42 eV) is a key barrier and limits the oxygen diffusion in the alloy. The calculated temperature diffusion coefficient of oxygen in the Ti3Al alloy and the activation energies determined in two directions agree with the experimental data.

  13. Dramatic enhancement of near-infrared intersubband absorption in c-plane AlInN/GaN superlattices

    SciTech Connect

    Shirazi-HD, M.; Turkmeneli, K.; Dai, S.; Edmunds, C.; Malis, O.; Liu, S.; Shao, J.; Gardner, G.; Zakharov, D. N.; Manfra, M. J.

    2016-03-21

    We report substantial improvement of near-infrared (2–2.6 μm) intersubband absorption in c-plane AlInN/GaN superlattices grown by molecular beam epitaxy. Progress was obtained through optimization of AlInN growth conditions using an AlInN growth rate of 0.9-nm/min at substrate temperature of 550 °C, as well as by judiciously placing the charge into two delta-doping sheets. Structural characterization suggests that AlInN crystal quality is enhanced and interface roughness is reduced. Importantly, near-infrared absorption data indicate that the optical quality of the AlInN/GaN superlattices is now comparable with that of AlN/GaN superlattices designed to exploit near-infrared intersubband transitions.

  14. Flaky FeSiAl alloy-carbon nanotube composite with tunable electromagnetic properties for microwave absorption

    PubMed Central

    Huang, Lina; Liu, Xiaofang; Chuai, Dan; Chen, Yaxin; Yu, Ronghai

    2016-01-01

    Flaky FeSiAl alloy/multi-wall carbon nanotube (FeSiAl/MWCNT) composite was fabricated by facile and scalable ball milling method. The morphology and electromagnetic properties of the FeSiAl alloy can be well tuned by controlling the milling time. It is found that the magnetic loss of the FeSiAl alloy is improved by optimizing the milling time due to the increased anisotropy field. Meanwhile the addition of MWCNTs enhances the dielectric loss of the composite by increasing the interfacial polarizations, dipolar polarizations and conductive paths. Relative to conventional FeSiAl absorbers, the FeSiAl/MWCNT composite exhibits greatly improved microwave absorption performance with advantages of strong absorption and small thickness. The minimum reflection loss of the composite reaches −42.8 dB at 12.3 GHz at a very thin thickness of 1.9 mm. PMID:27762327

  15. Flaky FeSiAl alloy-carbon nanotube composite with tunable electromagnetic properties for microwave absorption.

    PubMed

    Huang, Lina; Liu, Xiaofang; Chuai, Dan; Chen, Yaxin; Yu, Ronghai

    2016-10-20

    Flaky FeSiAl alloy/multi-wall carbon nanotube (FeSiAl/MWCNT) composite was fabricated by facile and scalable ball milling method. The morphology and electromagnetic properties of the FeSiAl alloy can be well tuned by controlling the milling time. It is found that the magnetic loss of the FeSiAl alloy is improved by optimizing the milling time due to the increased anisotropy field. Meanwhile the addition of MWCNTs enhances the dielectric loss of the composite by increasing the interfacial polarizations, dipolar polarizations and conductive paths. Relative to conventional FeSiAl absorbers, the FeSiAl/MWCNT composite exhibits greatly improved microwave absorption performance with advantages of strong absorption and small thickness. The minimum reflection loss of the composite reaches -42.8 dB at 12.3 GHz at a very thin thickness of 1.9 mm.

  16. Flaky FeSiAl alloy-carbon nanotube composite with tunable electromagnetic properties for microwave absorption

    NASA Astrophysics Data System (ADS)

    Huang, Lina; Liu, Xiaofang; Chuai, Dan; Chen, Yaxin; Yu, Ronghai

    2016-10-01

    Flaky FeSiAl alloy/multi-wall carbon nanotube (FeSiAl/MWCNT) composite was fabricated by facile and scalable ball milling method. The morphology and electromagnetic properties of the FeSiAl alloy can be well tuned by controlling the milling time. It is found that the magnetic loss of the FeSiAl alloy is improved by optimizing the milling time due to the increased anisotropy field. Meanwhile the addition of MWCNTs enhances the dielectric loss of the composite by increasing the interfacial polarizations, dipolar polarizations and conductive paths. Relative to conventional FeSiAl absorbers, the FeSiAl/MWCNT composite exhibits greatly improved microwave absorption performance with advantages of strong absorption and small thickness. The minimum reflection loss of the composite reaches ‑42.8 dB at 12.3 GHz at a very thin thickness of 1.9 mm.

  17. Can plasmonic Al nanoparticles improve absorption in triple junction solar cells?

    PubMed Central

    Yang, L.; Pillai, S.; Green, M. A.

    2015-01-01

    Plasmonic nanoparticles located on the illuminated surface of a solar cell can perform the function of an antireflection layer, as well as a scattering layer, facilitating light-trapping. Al nanoparticles have recently been proposed to aid photocurrent enhancements in GaAs photodiodes in the wavelength region of 400–900 nm by mitigating any parasitic absorption losses. Because this spectral region corresponds to the top and middle sub-cell of a typical GaInP/GaInAs/Ge triple junction solar cell, in this work, we investigated the potential of similar periodic Al nanoparticles placed on top of a thin SiO2 spacer layer that can also serve as an antireflection coating at larger thicknesses. The particle period, diameter and the thickness of the oxide layers were optimised for the sub-cells using simulations to achieve the lowest reflection and maximum external quantum efficiencies. Our results highlight the importance of proper reference comparison, and unlike previously published results, raise doubts regarding the effectiveness of Al plasmonic nanoparticles as a suitable front-side scattering medium for broadband efficiency enhancements when compared to standard single-layer antireflection coatings. However, by embedding the nanoparticles within the dielectric layer, they have the potential to perform better than an antireflection layer and provide enhanced response from both the sub-cells. PMID:26138405

  18. Can plasmonic Al nanoparticles improve absorption in triple junction solar cells?

    PubMed

    Yang, L; Pillai, S; Green, M A

    2015-07-03

    Plasmonic nanoparticles located on the illuminated surface of a solar cell can perform the function of an antireflection layer, as well as a scattering layer, facilitating light-trapping. Al nanoparticles have recently been proposed to aid photocurrent enhancements in GaAs photodiodes in the wavelength region of 400-900 nm by mitigating any parasitic absorption losses. Because this spectral region corresponds to the top and middle sub-cell of a typical GaInP/GaInAs/Ge triple junction solar cell, in this work, we investigated the potential of similar periodic Al nanoparticles placed on top of a thin SiO2 spacer layer that can also serve as an antireflection coating at larger thicknesses. The particle period, diameter and the thickness of the oxide layers were optimised for the sub-cells using simulations to achieve the lowest reflection and maximum external quantum efficiencies. Our results highlight the importance of proper reference comparison, and unlike previously published results, raise doubts regarding the effectiveness of Al plasmonic nanoparticles as a suitable front-side scattering medium for broadband efficiency enhancements when compared to standard single-layer antireflection coatings. However, by embedding the nanoparticles within the dielectric layer, they have the potential to perform better than an antireflection layer and provide enhanced response from both the sub-cells.

  19. Intersubband transition in lattice-matched BGaN/AlN quantum well structures with high absorption coefficients.

    PubMed

    Park, Seoung-Hwan; Ahn, Doyeol; Park, Chan-Yong

    2017-02-20

    Intersubband absorption properties of lattice-matched BGaN/AlN quantum well (QW) structures grown on AlN substrate are theoretically investigated using an effective mass theory considering the nonparabolicity of the conduction band. These results are compared with those of GaN/AlN QW structures. The intersubband absorption coefficient of the BGaN/AlN QW structure is shown to be enhanced significantly, compared to that of the conventional GaN/AlN QW structure. This can be explained by the fact that the BGaN/AlN QW structure exhibits larger intersuband dipole moment and quasi-Fermi-level separation than the GaN/AlN QW structure, due to the increase in the carrier confinement by a larger internal field. We expect that the BGaN/AlN QW structure with a high absorption coefficient can be used for telecommunication applications at 1.55 µm under the lattice-matched condition, instead of the conventional GaN/AlN QW structure with the large strain.

  20. Theory and X-ray Absorption Spectroscopy for Aluminum Coordination Complexes – Al K-Edge Studies of Charge and Bonding in (BDI)Al, (BDI)AlR2, and (BDI)AlX2 Complexes.

    PubMed

    Altman, Alison B; Pemmaraju, C D; Camp, Clément; Arnold, John; Minasian, Stefan G; Prendergast, David; Shuh, David K; Tyliszczak, Tolek

    2015-08-19

    Polarized aluminum K-edge X-ray absorption near edge structure (XANES) spectroscopy and first-principles calculations were used to probe electronic structure in a series of (BDI)Al, (BDI)AlX2, and (BDI)AlR2 coordination compounds (X = F, Cl, I; R = H, Me; BDI = 2,6-diisopropylphenyl-β-diketiminate). Spectral interpretations were guided by examination of the calculated transition energies and polarization-dependent oscillator strengths, which agreed well with the XANES spectroscopy measurements. Pre-edge features were assigned to transitions associated with the Al 3p orbitals involved in metal-ligand bonding. Qualitative trends in Al 1s core energy and valence orbital occupation were established through a systematic comparison of excited states derived from Al 3p orbitals with similar symmetries in a molecular orbital framework. These trends suggested that the higher transition energies observed for (BDI)AlX2 systems with more electronegative X(1-) ligands could be ascribed to a decrease in electron density around the aluminum atom, which causes an increase in the attractive potential of the Al nucleus and concomitant increase in the binding energy of the Al 1s core orbitals. For (BDI)Al and (BDI)AlH2 the experimental Al K-edge XANES spectra and spectra calculated using the eXcited electron and Core-Hole (XCH) approach had nearly identical energies for transitions to final state orbitals of similar composition and symmetry. These results implied that the charge distributions about the aluminum atoms in (BDI)Al and (BDI)AlH2 are similar relative to the (BDI)AlX2 and (BDI)AlMe2 compounds, despite having different formal oxidation states of +1 and +3, respectively. However, (BDI)Al was unique in that it exhibited a low-energy feature that was attributed to transitions into a low-lying p-orbital of b1 symmetry that is localized on Al and orthogonal to the (BDI)Al plane. The presence of this low-energy unoccupied molecular orbital on electron-rich (BDI)Al distinguishes

  1. Compensation in Al-doped ZnO by Al-related acceptor complexes: synchrotron x-ray absorption spectroscopy and theory.

    PubMed

    T-Thienprasert, J; Rujirawat, S; Klysubun, W; Duenow, J N; Coutts, T J; Zhang, S B; Look, D C; Limpijumnong, S

    2013-02-01

    The synchrotron x-ray absorption near edge structures (XANES) technique was used in conjunction with first-principles calculations to characterize Al-doped ZnO films. Standard characterizations revealed that the amount of carrier concentration and mobility depend on the growth conditions, i.e. H(2) (or O(2))/Ar gas ratio and Al concentration. First-principles calculations showed that Al energetically prefers to substitute on the Zn site, forming a donor Al(Zn), over being an interstitial (Al(i)). The measured Al K-edge XANES spectra are in good agreement with the simulated spectra of Al(Zn), indicating that the majority of Al atoms are substituting for Zn. The reduction in carrier concentration or mobility in some samples can be attributed to the Al(Zn)-V(Zn) and 2Al(Zn)-V(Zn) complex formations that have similar XANES features. In addition, XANES of some samples showed additional features that are the indication of some α-Al(2)O(3) or nAl(Zn)-O(i) formation, explaining their poorer conductivity.

  2. Modeling of normal incidence absorption in p-type GaAs/AlGaAs quantum well infrared detectors

    NASA Astrophysics Data System (ADS)

    Brown, Gail J.; Szmulowicz, Frank

    1995-04-01

    The absorption of infrared radiation at normal incidence in p-type GaAs/AlGaAs quantum wells, unlike in n-type, is fundamentally allowed. We have measured and theoretically modeled the bound-to-continuum absorption in these p-type materials. The infrared absorption coefficient was calculated are based on the electronic structure, wave functions and optical matrix elements obtained from an 8 X 8 envelope-function approximation (EFA) calculation. The 8 X 8 EFA Hamiltonian incorporates the coupling between the heavy, light, spin-orbit, and conduction bands. In calculating the continuum states for bound-to- continuum intersubband absorption, we do not enclose the well in an artificial box with infinite walls. A comparison of the theoretical absorption and measured photoresponse results verified the accuracy of our model and provided a basis for optimizing the design of p-type quantum wells for infrared detection.

  3. Microporous Ni@NiO nanoparticles prepared by chemically dealloying Al3Ni2@Al nanoparticles as a high microwave absorption material

    NASA Astrophysics Data System (ADS)

    Pang, Yu; Xie, Xiubo; Li, Da; Chou, Wusheng; Liu, Tong

    2017-03-01

    The Al3Ni2@Al nanoparticles (NPs) were prepared from Ni45Al55 master alloy by hydrogen plasma-metal reaction method, and were subsequently dealloyed to produce porous Ni@NiO NPs of 36 nm. The pore size ranges from 0.7 to 1.6 nm, leading to large specific surface area of 69.5 m2/g and big pore volume of 0.507 cc/g. The saturation magnetization (MS) and coercivity (HC) of the microporous Ni@NiO NPs are 11.5 emu/g and 5.2 Oe. They exhibit high microwave absorption performance with a minimum reflection coefficient (RC) of -86.9 dB and an absorption bandwidth of 2.6 GHz (RC≤-10 dB) at thickness of 4.5 mm. The enhanced microwave absorption properties are attributed to the synergistic effect of the magnetic Ni core and dielectric NiO shell, and the micropore architecture. The NPs with micropore morphology and core/shell structure open a new way to modify the microwave absorption performance.

  4. Differential absorption lidar measurements of atmospheric water vapor using a pseudonoise code modulated AlGaAs laser. Thesis

    NASA Technical Reports Server (NTRS)

    Rall, Jonathan A. R.

    1994-01-01

    Lidar measurements using pseudonoise code modulated AlGaAs lasers are reported. Horizontal path lidar measurements were made at night to terrestrial targets at ranges of 5 and 13 km with 35 mW of average power and integration times of one second. Cloud and aerosol lidar measurements were made to thin cirrus clouds at 13 km altitude with Rayleigh (molecular) backscatter evident up to 9 km. Average transmitter power was 35 mW and measurement integration time was 20 minutes. An AlGaAs laser was used to characterize spectral properties of water vapor absorption lines at 811.617, 816.024, and 815.769 nm in a multipass absorption cell using derivative spectroscopy techniques. Frequency locking of an AlGaAs laser to a water vapor absorption line was achieved with a laser center frequency stability measured to better than one-fifth of the water vapor Doppler linewidth over several minutes. Differential absorption lidar measurements of atmospheric water vapor were made in both integrated path and range-resolved modes using an externally modulated AlGaAs laser. Mean water vapor number density was estimated from both integrated path and range-resolved DIAL measurements and agreed with measured humidity values to within 6.5 percent and 20 percent, respectively. Error sources were identified and their effects on estimates of water vapor number density calculated.

  5. [Determination of Pb and Al in blood and hair of child using transverse heated graphite furnace atomic absorption spectroscopy].

    PubMed

    Niu, Feng-lan; Xie, Wen-bing; Li, Chen-xu; Dong, Wei-yan

    2005-04-01

    Pb and Al in blood and hair of child were determined by transverse heated graphite furnace atomic absorption spectrometry with NH4H2PO4 and Mg(NO3)2 as a modifier, which enhanced the temperature of ashing, eliminated the matrix interference and memorial effect. The method is rapid, simple and accurate. The characteristic mass of the method was 2.3 x 10(-11) g and 2.2 x 10(-11) g for Pb and Al respectively. The relative standard deviation of Pb and Al was 3.0% and 11.4%, respectively, and the recovery was 96%-102%.

  6. Filled tetrahedral semiconductor Li3 Al N2 studied with optical absorption: Application of the interstitial insertion rule

    NASA Astrophysics Data System (ADS)

    Kushida, K.; Kaneko, Y.; Kuriyama, K.

    2004-12-01

    The band gap nature of a filled tetrahedral semiconductor Li3AlN2 [viewed as the assemblage of eight hypothetical zinc-blende AlN sublattices (Li0.5Al0.5N)- filled with He-like Li+ interstitials at the empty tetrahedral sites next to the anions] is studied by an optical absorption method. The optical absorption studies show a tendency that Li3AlN2 is direct with a band gap of 4.40eV , whereas zinc-blende AlN has been estimated to be indirect from a first-principles calculation. The band gap value was confirmed by photoacoustic spectroscopy. According to the interstitial insertion rule of Wood , these results suggest that the insertion of Li+ ions into the interstitial sites in hypothetical zinc-blende AlN sublattices (Li0.5Al0.5N)- causes an upward shift of the X conduction band due to a Pauli repulsion of conduction electrons, exposing the Γ point as the conduction band minimum and resulting in a direct band gap.

  7. Investigation of the mica x-ray absorption near-edge structure spectral features at the Al K-edge

    NASA Astrophysics Data System (ADS)

    Wu, Ziyu; Marcelli, A.; Cibin, G.; Mottana, A.; Della Ventura, G.

    2003-10-01

    Near-edge features of Al x-ray absorption near-edge structure (XANES) spectra in aluminosilicate compounds with mixed coordination number are usually assigned to a fourfold coordinated site contribution followed by a sixfold coordinated site contribution that is displaced towards higher energy because of the increasing ligand nucleus potentials, neglecting possible contributions due to bond distance variations and local geometrical distortion. Here we present and discuss the Al K-edge XANES spectra of synthetic micas with either fourfold coordinated Al (phlogopite), or with sixfold coordinated Al (polylithionite), as well as with mixed coordination (preiswerkite). Multiple scattering simulations of XANES spectra demonstrate that octahedral contributions may overlap the tetrahedral ones so that the lower energy structures in mixed coordination compounds may be associated with the octahedral sites. This unexpected behaviour can be described as due to the effect of a significant reduction of the ligand field strength (i.e. large local distortion and Al-O bond distances).

  8. [Characteristics of the absorption spectra of the mixtures of C42(Al), C32 (Si) and so on].

    PubMed

    Chen, W

    1998-12-01

    The mixtures containing C42 (A1), C32 (Si), C30 (Ca) and C28 (Fe) are produced by means of arc discharge and He gas convection. The spectra are measured and compared with the absorption spectra of all carbon molecules. The result shows that after imbeded in all carbon molecules, the Al, Si, Ca and Fe atoms do not change the positions of the absorption peak of original molecules, but only change the probability of pi --> pi* transition and n --> pi* transition of these molecules.

  9. Discrepancies between photocurrent and absorption spectroscopies in intersubband photoionization from GaAs/AlGaAs multiquantum wells

    NASA Astrophysics Data System (ADS)

    Rosencher, E.; Martinet, E.; Luc, F.; Bois, Ph.; Böckenhoff, E.

    1991-12-01

    Intersubband transitions between a bound state and extended states in GaAs/AlGaAs multiquantum wells are studied by simultaneous absorption and photocurrent spectroscopy under different electric field conditions. It is found that both types of spectra exhibit different line shapes, with the photocurrent maximum occurring at lower photon energy than in absorption spectra. Moreover, there is a blue shift of absorption peak and a red shift of photocurrent peak with increasing electric fields. These results suggest that a sequential mechanism is involved in the photocurrent collection from the quantum well. The blue shift is then well fitted by a quadratic Stark effect and the red shift by a barrier lowering mechanism.

  10. Amplified spontaneous emission measurement of a line-narrowed, tunable, Ti:Al2O3 amplifier using rubidium absorption

    NASA Technical Reports Server (NTRS)

    Barnes, James C.; Barnes, Norman P.; Lockard, George E.; Cross, Patricia L.

    1989-01-01

    Amplified spontaneous emission, ASE, generated by a Ti:Al2O3 laser amplifier has been measured as a function of pump energy, and thus gain, using the atomic absorption of rubidium, Rb, gas at 0.780 micron. By tuning the Ti:Al2O3 laser, the Rb cell could selectively absorb the narrow spectral bandwidth laser radiation while transmitting the wide spectral bandwidth ASE. Transmission of laser amplifier pulses through a Rb absorption cell, measured at various temperatures, thus allows the measurement of the weak ASE in the vicinity of the strong laser pulse. A model for the transmission of Rb as a function of temperature and wavelength has been developed. The measured transmissions are in good agreement with the transmission model predictions.

  11. Al III, Si IV, and C IV absorption toward zeta Ophiuchi: Evidence for photionized and collisionally ionized gas

    NASA Technical Reports Server (NTRS)

    Sembach, Kenneth R.; Savage, Blair D.; Jenkins, Edward B.

    1994-01-01

    We present Goddard High-Resolution Spectrograph observations at 3.5 km/s resolution and signal-to-noise ratios of 30 to 60 for the Al III, Si IV, and N V absorption lines in the far-ultraviolet spectrum of the O9.5 V star zeat Ophiuchi. The measurement reveal three types of highly ionized gas along the 140 pc line of sight. (1) Narrow components of Al III (b = 4.3 km/s, the mean value of (v(helio)) = -7.8 km/s; b = 3.2 km/s, the mean value of (v(sub helio)) = -14.4 km/s) and Si IV (b = 5.3 km/s, the mean value of (v(sub helio)) = -15.0 km/s) trace photionized gas in the expanding H II region surrounding zeta Oph. The observed magnitude and direction of the velocity offset between the Al III and Si IV profiles can be explained by models of H II regions that incorporate expansion. Narrow C IV absorption associated with the H II region is not detected. Predictions of the expected amounts of Si IV and C IV overestimate the column densities of these ions by factors of 30 and more than 10, respectively. The discrepancy may be due to the effects of elemental depletions in the gas and/or to the interaction of the stellar wind with surrounding matter. (2) Broad (b = 15 to 18 km/s) and weak Si IV and C IV absorption components are detected near the mean value of (v(sub helio)) = -26 km/s. The high-ionization species associated with these absorption components are probably produced by electron collisional ionization in a heated gas. This absorption may be physically related to the zeta Oph bow shock ot to a cloud complex situated within the local interstellar medium at d less than 60 pc. The C IV to Si IV column density ratio in this gas is 8, a factor of 6 less than conductive interface models predict, but this discrepancy may be removed by considering the effects of self-photoionization within the cooling gas in the model calculations. (3) A broad (b = 13 km/s) and weak C IV absorption feature detected at the mean value of (v(sub helio)) = -61 km/s is not seen in other

  12. The dependence of C IV broad absorption line properties on accompanying Si IV and Al III absorption: relating quasar-wind ionization levels, kinematics, and column densities

    SciTech Connect

    Filiz Ak, N.; Brandt, W. N.; Schneider, D. P.; Trump, J. R.; Hall, P. B.; Anderson, S. F.; Hamann, F.; Myers, Adam D.; Pâris, I.; Petitjean, P.; Ross, Nicholas P.; Shen, Yue; York, Don

    2014-08-20

    We consider how the profile and multi-year variability properties of a large sample of C IV Broad Absorption Line (BAL) troughs change when BALs from Si IV and/or Al III are present at corresponding velocities, indicating that the line of sight intercepts at least some lower ionization gas. We derive a number of observational results for C IV BALs separated according to the presence or absence of accompanying lower ionization transitions, including measurements of composite profile shapes, equivalent width (EW), characteristic velocities, composite variation profiles, and EW variability. We also measure the correlations between EW and fractional-EW variability for C IV, Si IV, and Al III. Our measurements reveal the basic correlated changes between ionization level, kinematics, and column density expected in accretion-disk wind models; e.g., lines of sight including lower ionization material generally show deeper and broader C IV troughs that have smaller minimum velocities and that are less variable. Many C IV BALs with no accompanying Si IV or Al III BALs may have only mild or no saturation.

  13. Temperature dependence of mid-infrared intersubband absorption in AlGaN/GaN multiple quantum wells

    SciTech Connect

    Kotani, Teruhisa; Arita, Munetaka; Hoshino, Katsuyuki; Arakawa, Yasuhiko

    2016-02-01

    The temperature dependence of the mid-infrared intersubband (ISB) absorption in non-polar (m-plane) and polar (c-plane) AlGaN/GaN quantum wells (QWs) is studied. The ISB absorption shifts to higher energy as the temperature is reduced from 300 K to below 10 K. Both m-plane and c-plane QWs show a small energy shift (1.6–2.6 meV) compared to AlGaAs/GaAs (3.5–5.2 meV) and AlSb/InAs (6.2 and 12 meV) QWs. Theoretical calculations considering the temperature induced material constant changes show good agreement with the experimental results. These results suggest that ISB transition energies in AlGaN/GaN QWs are more stable against temperature change mainly because of the heavy effective masses and small nonparabolicities.

  14. Multiscale modelling of Interaction of Alane Clusters on Al(111) surface: A Reactive Force Field and Infrared Absorption Spectroscopy Approach

    NASA Astrophysics Data System (ADS)

    Ojwang, Julius; van Duin, Adri; Goddard, William, III; van Santen, Rutger

    2010-10-01

    Alanes are believed to be the ubiquitous facilitators of mass transport of aluminum atoms during the thermal decomposition of NaAlH4. Alanes also take part on decomposition of AlH3, another important material for hydrogen storage. We have used interplay of theoretical simulations (reactive force field and density functional theory) and experiments (IR reflection absorption spectroscopy) to address the issue of the role of alanes as facilitators of mass transport of aluminum atoms. We have obtained valuable details on the mechanism of formation and agglomeration of alanes on Al(111) surface. Our simulations show that, on the Al(111) surface, alanes oligomerize into larger alanes. The identification of these string like intermediates as a precursor to the bulk hydride phase allows us to explain the loss of resolution in surface IR experiments with increasing hydrogen coverage on single crystal Al(111) surface. This is in excellent agreement with the experimental works of Go et al. (E. Go, K. Thuermer, J.E. Reutt-Robey, Surf. Sci.,437:377(1999)).

  15. Effect of doping on the intersubband absorption in Si- and Ge-doped GaN/AlN heterostructures.

    PubMed

    Ajay, A; Lim, C B; Browne, D A; Polaczyński, J; Bellet-Amalric, E; Bleuse, J; den Hertog, M I; Monroy, E

    2017-10-06

    In this paper, we study band-to-band and intersubband (ISB) characteristics of Si- and Ge-doped GaN/AlN heterostructures (planar and nanowires) structurally designed to absorb in the short-wavelength infrared region, particularly at 1.55 μm. Regarding the band-to-band properties, we discuss the variation of the screening of the internal electric field by free carriers, as a function of the doping density and well/nanodisk size. We observe that nanowire heterostructures consistently present longer photoluminescence decay times than their planar counterparts, which supports the existence of an in-plane piezoelectric field associated to the shear component of the strain tensor in the nanowire geometry. Regarding the ISB characteristics, we report absorption covering 1.45-1.75 μm using Ge-doped quantum wells, with comparable performance to Si-doped planar heterostructures. We also report similar ISB absorption in Si- and Ge-doped nanowire heterostructures indicating that the choice of dopant is not an intrinsic barrier for observing ISB phenomena. The spectral shift of the ISB absorption as a function of the doping concentration due to many body effects confirms that Si and Ge efficiently dope GaN/AlN nanowire heterostructures.

  16. Effect of doping on the intersubband absorption in Si- and Ge-doped GaN/AlN heterostructures

    NASA Astrophysics Data System (ADS)

    Ajay, A.; Lim, C. B.; Browne, D. A.; Polaczyński, J.; Bellet-Amalric, E.; Bleuse, J.; den Hertog, M. I.; Monroy, E.

    2017-10-01

    In this paper, we study band-to-band and intersubband (ISB) characteristics of Si- and Ge-doped GaN/AlN heterostructures (planar and nanowires) structurally designed to absorb in the short-wavelength infrared region, particularly at 1.55 μm. Regarding the band-to-band properties, we discuss the variation of the screening of the internal electric field by free carriers, as a function of the doping density and well/nanodisk size. We observe that nanowire heterostructures consistently present longer photoluminescence decay times than their planar counterparts, which supports the existence of an in-plane piezoelectric field associated to the shear component of the strain tensor in the nanowire geometry. Regarding the ISB characteristics, we report absorption covering 1.45–1.75 μm using Ge-doped quantum wells, with comparable performance to Si-doped planar heterostructures. We also report similar ISB absorption in Si- and Ge-doped nanowire heterostructures indicating that the choice of dopant is not an intrinsic barrier for observing ISB phenomena. The spectral shift of the ISB absorption as a function of the doping concentration due to many body effects confirms that Si and Ge efficiently dope GaN/AlN nanowire heterostructures.

  17. Dielectric and Microwave Absorption Properties of TiC-Al2O3/Silica Coatings at High Temperature

    NASA Astrophysics Data System (ADS)

    Wang, Yuan; Luo, Fa; Zhou, Wancheng; Zhu, Dongmei

    2017-08-01

    The dielectric property and microwave attenuation performance of a TiC micropowder-filled Al2O3/silica coating were studied. The permittivity of the coating increases gradually with increasing TiC content, which can be attributed to the enhancement of polarization ability and the increase of coating conductivity. Meanwhile, the high-temperature microwave attenuation property of the 30 wt.% TiC-loaded coating was investigated in the temperature range of 25-250°C. Both the real and imaginary parts of complex permittivity exhibit obvious temperature-dependent behavior and increase with the rise of temperature. In the studied temperature range, this coating exhibits an excellent microwave absorption property. A strong absorption peak with minimum RL of -55.2 dB is obtained at 11.8 GHz when the temperature reaches 150°C. Furthermore, the absorption bandwidth (RL ≤ -10 dB) exhibits a widening tendency with the increase of temperature. As the temperature rises from 25°C to 250°C, the effective bandwidth (RL ≤ -10 dB) expands from 2.2 GHz to 3.2 GHz. These results suggest that the TiC-Al2O3/silica coating could be a desirable candidate for microwave absorbtion in the measured frequency and temperature ranges.

  18. Synthesis and UV absorption properties of 5-sulfosalicylate-intercalated Zn-Al layered double hydroxides

    SciTech Connect

    Zhang Linyan; Lin Yanjun; Tuo Zhenjun; Evans, David G.; Li Dianqing

    2007-04-15

    5-sulfosalicylic acid (SSA) anions have been intercalated into layered double hydroxides (LDHs) by an anion-exchange reaction using ZnAl-NO{sub 3}-LDHs as a precursor. The samples were characterized by XRD, FT-IR, TG-DTA/MS and UV-visible spectroscopy. The results show that the NO{sub 3} {sup -} anions in the precursor have been completely replaced by SSA anions to give ZnAl-SSA-LDHs having a high degree of crystallinity. Detailed studies reveal the existence of a supramolecular structure in ZnAl-SSA-LDHs involving electrostatic attraction between opposite charges, hydrogen bonding and other weak chemical bonding interactions between host layers and SSA anions. The thermal stability of ZnAl-SSA-LDHs is considerably enhanced compared with that of a mixture of ZnAl-NO{sub 3}-LDHs and SSA. After addition of 2.0 wt% ZnAl-SSA-LDHs to polypropylene (PP), the resistance of the polymer to UV degradation is significantly improved. - Graphical abstract: UV-visible absorbance curves of SSA (a), ZnAl-NO{sub 3}-LDHs precursor (b) and ZnAl-SSA-LDHs (c)

  19. Luminescence and optical absorption properties of Nd(3+) ions in K-Mg-Al phosphate and fluorophosphate glasses.

    PubMed

    Surendra Babu, S; Babu, P; Jayasankar, C K; Joshi, A S; Speghini, A; Bettinelli, M

    2006-04-26

    Absorption and emission properties and fluorescence lifetimes for the [Formula: see text] transition of Nd(3+) ions embedded in P(2)O(5)-K(2)O-MgO-Al(2)O(3) (PKMA)-based glasses modified with AlF(3) and BaF(2) are reported at room temperature. The observed energy levels of Nd(3+) ions in these glasses have been analysed through a semi-empirical free-ion Hamiltonian model. The spin-orbit interaction and net electrostatic interaction experienced by the Nd(3+) ions follow the trend as PKMA>PKMA+AlF(3)> PKMA+BaF(2) glasses. Judd-Ofelt analysis has been carried out on the absorption spectra of 1.0 mol% Nd(3+)-doped glasses to predict the radiative properties for the fluorescent levels of the Nd(3+) ion. Branching ratios and stimulated emission cross-sections show that the [Formula: see text] transition of the glasses under investigation has the potential for laser applications. The Inokuti-Hirayama model has been applied to investigate the non-radiative relaxation of the Nd(3+) ion emitting state, (4)F(3/2). Based on the decay curve analysis, concentration quenching of the (4)F(3/2) emission has been attributed to a cross-relaxation process between the Nd(3+) ions.

  20. COMMENT ON TRITIUM ABSORPTION-DESORPTION CHARACTERISTICS OF LANI4.25AL0.75

    SciTech Connect

    Walters, T

    2007-04-10

    The thermodynamic data for LaNi{sub 4.25}Al{sub 0.75} tritide, reported by Wang et al. (W.-d. Wang et al., J. Alloys Compd. (2006) doi:10.1016/j.jallcom.206.09.122), are in variance with our published data. The plateau pressures for the P-C-T isotherms at all temperatures are significantly lower than published data. As a result, the derived thermodynamic parameters, {Delta}H{sup o} and {Delta}S{sup o}, are questionable. Using the thermodynamic parameters derived from the data reported by Wang et al. will result in under estimating the expected pressures, and therefore not provide the desired performance for storing and processing tritium.

  1. Electromagnetic and Microwave Absorption Properties of Hybrid FeCrAl/Ti3SiC2 Composite in X-Band

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Si, Jiajia; Li, Yunyu; Luo, Fa; Su, Xiaolei; Xu, Jie; Wang, Junbo; He, Xinhai; Shi, Yimin

    2017-08-01

    Hybrid magnetic-dielectric absorbers for electromagnetic applications consisting of FeCrAl and Ti3SiC2 powders have been fabricated by a ball-milling process and their electromagnetic characteristics and microwave absorption performance investigated in the frequency range from 8.2 GHz to 12.4 GHz. The dielectric loss increased with increasing Ti3SiC2 content, while the magnetic loss decreased. The electromagnetic parameters of the hybrid FeCrAl/Ti3SiC2 powders could be adjusted by adding various contents of Ti3SiC2. The hybrid powder with 20 wt.% Ti3SiC2 and 80 wt.% FeCrAl presented the most favorable microwave absorption performance. For the sample with thickness of 2.6 mm, effective absorption (<-10 dB) was obtained in the frequency range from 8.4 GHz to 12.1 GHz with a minimum value of -43.6 dB at 9.7 GHz. These results indicate that hybrid FeCrAl/Ti3SiC2 powders with appropriate weight ratio present better absorption performance than FeCrAl powder alone. This study makes a significant contribution to exploration of microwave absorption materials with low density, thin thickness, broad absorption bandwidth, and strong absorptivity.

  2. X-ray absorption and magnetic circular dichroism studies of Co2FeAl in magnetic tunnel junctions

    SciTech Connect

    Ebke, D.; Kugler, Z.; Thomas, P.; Schebaum, O.; Schafers, M.; Nissen, D.; Schmalhorst, J.; Hutten, A.; Arenholz, E.; Thomas, A.

    2010-01-11

    The bulk magnetic moment and the element specific magnetic moment of Co{sub 2}FeAl thin films were examined as a function of annealing temperature by alternating gradient magnetometer (AGM) and X-ray absorption spectroscopy (XAS)/X-ray magnetic circular dichroism (XMCD), respectively. A high magnetic moment can be achieved for all annealing temperatures and the predicted bulk and interface magnetic moment of about 5 {tilde A}{sub B} are reached via heating. We will also present tunnel magnetoresistance (TMR) values of up to 153% at room temperature and 260% at 13 K for MgO based magnetic tunnel junctions (MTJs) with Co{sub 2}FeAl and Co-Fe electrodes.

  3. Terahertz intersubband absorption in non-polar m-plane AlGaN/GaN quantum wells

    NASA Astrophysics Data System (ADS)

    Edmunds, C.; Shao, J.; Shirazi-HD, M.; Manfra, M. J.; Malis, O.

    2014-07-01

    We demonstrate THz intersubband absorption (15.6-26.1 meV) in m-plane AlGaN/GaN quantum wells. We find a trend of decreasing peak energy with increasing quantum well width, in agreement with theoretical expectations. However, a blue-shift of the transition energy of up to 14 meV was observed relative to the calculated values. This blue-shift is shown to decrease with decreasing charge density and is, therefore, attributed to many-body effects. Furthermore, a ˜40% reduction in the linewidth (from roughly 8 to 5 meV) was obtained by reducing the total sheet density and inserting undoped AlGaN layers that separate the wavefunctions from the ionized impurities in the barriers.

  4. Photogalvanic effects for interband absorption in AlGaN /GaN superlattices

    NASA Astrophysics Data System (ADS)

    Cho, K. S.; Chen, Y. F.; Tang, Y. Q.; Shen, B.

    2007-01-01

    The linear and circular photogalvanic effects (CPGEs), induced by ultraviolet (325nm) radiation, have been observed in the (0001)-oriented Al0.15Ga0.85N/GaN superlattices. The CPGE current changes sign upon reversing the radiation helicity, and it is up to two orders of magnitude larger than that obtained by far-infrared radiation. This result suggests the existence of a sizeable Rashba spin splitting in AlGaN /GaN superlattices. It also provides a possibility for the generation of spin orientation-induced current at room temperature.

  5. Double frequency absorption induced by Al-Si Schottky barrier potential and mechanism of two-photon response

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoting; Gao, Yanjun; Chen, Zhanguo; Jia, Gang; Liu, Yunlong; Liu, Xiuhuan; Zh, Yuhong

    2006-01-01

    By observing two-photon response and anisotropy of the light-induced voltage in Si-Al Schottky barrier potential of the Si MSM (Metal-Semiconductor-Metal) planar structure two-photon response optical detector. It is certified from the experimental and theoretical analysis that the built-in electric field generated by the Schottky barrier potential will induce the phenomena of optical rectification in Si photodiode. Thus, it is deduced that there must be double-frequency absorption (DFA) caused by phase-mismatch in the mechanism of two-photon response of Si photodiode. If the intensity of the built-in electric field is strong enough, the DFA will be the main feature of the two-photon response.

  6. Understanding H isotope adsorption and absorption of Al-alloys using modeling and experiments (LDRD: #165724)

    SciTech Connect

    Ward, Donald K.; Zhou, Xiaowang; Karnesky, Richard A.; Kolasinski, Robert; Foster, Michael E.; Thurmer, Konrad; Chao, Paul; Epperly, Ethan Nicholas; Zimmerman, Jonathan A.; Wong, Bryan M.; Sills, Ryan B.

    2015-09-01

    Current austenitic stainless steel storage reservoirs for hydrogen isotopes (e.g. deuterium and tritium) have performance and operational life-limiting interactions (e.g. embrittlement) with H-isotopes. Aluminum alloys (e.g.AA2219), alternatively, have very low H-isotope solubilities, suggesting high resistance towards aging vulnerabilities. This report summarizes the work performed during the life of the Lab Directed Research and Development in the Nuclear Weapons investment area (165724), and provides invaluable modeling and experimental insights into the interactions of H isotopes with surfaces and bulk AlCu-alloys. The modeling work establishes and builds a multi-scale framework which includes: a density functional theory informed bond-order potential for classical molecular dynamics (MD), and subsequent use of MD simulations to inform defect level dislocation dynamics models. Furthermore, low energy ion scattering and thermal desorption spectroscopy experiments are performed to validate these models and add greater physical understanding to them.

  7. Nonlinear absorption properties of AlGaAs/GaAs multiple quantum wells grown by metalorganic chemical vapor deposition

    NASA Technical Reports Server (NTRS)

    Lee, Hsing-Chung; Kost, A.; Kawase, M.; Hariz, A.; Dapkus, P. Daniel

    1988-01-01

    The nonlinear absorption properties of the excitonic resonances associated with multiple quantum wells (MQWs) in AlGaAs/GaAs grown by metalorganic chemical vapor deposition are reported. The dependence of the saturation properties on growth parameters, especially growth temperature, and the well width are described. The minimum measured saturation intensity for these materials is 250 W/sq cm, the lowest reported value to date. The low saturation intensities are the result of excellent minority carrier properties. A systematic study of minority carrier lifetimes in quantum wells are reported. Lifetimes range from 50-350 ns depending on growth temperature and well width. When corrected for lateral diffusion effects and the measured minority carrier lifetime, the saturation data suggest that saturation intensities as low as 2.3 W/sq cm can be achieved in this system. The first measurements of the dependence of the exciton area and the magnitude of the excitonic absorption on well width are prsented. The growth of MQW structures on transparent GaP substrates is demonstrated and the electroabsorption properties of these structures are reviewed.

  8. Nonlinear absorption properties of AlGaAs/GaAs multiple quantum wells grown by metalorganic chemical vapor deposition

    NASA Technical Reports Server (NTRS)

    Lee, Hsing-Chung; Kost, A.; Kawase, M.; Hariz, A.; Dapkus, P. Daniel

    1988-01-01

    The nonlinear absorption properties of the excitonic resonances associated with multiple quantum wells (MQWs) in AlGaAs/GaAs grown by metalorganic chemical vapor deposition are reported. The dependence of the saturation properties on growth parameters, especially growth temperature, and the well width are described. The minimum measured saturation intensity for these materials is 250 W/sq cm, the lowest reported value to date. The low saturation intensities are the result of excellent minority carrier properties. A systematic study of minority carrier lifetimes in quantum wells are reported. Lifetimes range from 50-350 ns depending on growth temperature and well width. When corrected for lateral diffusion effects and the measured minority carrier lifetime, the saturation data suggest that saturation intensities as low as 2.3 W/sq cm can be achieved in this system. The first measurements of the dependence of the exciton area and the magnitude of the excitonic absorption on well width are prsented. The growth of MQW structures on transparent GaP substrates is demonstrated and the electroabsorption properties of these structures are reviewed.

  9. Effects of magnetic field and the built-in internal fields on the absorption coefficients in a strained wurtzite GaN/AlGaN quantum dot

    NASA Astrophysics Data System (ADS)

    Minimala, N. S.; Peter, A. John

    2013-02-01

    Effects of magnetic field strength and the built-in electric fields on the exciton binding energy and the non-linear optical property such as absorption coefficients in a GaN/AlGaN wide band gap heterostructure are investigated. The internal fields due to spontaneous and piezo-electric polarizations are included in the Hamiltonian. Our results show that the optical absorption coefficients strongly depend on the internal fields and the applied magnetic field.

  10. Measurement of the femtosecond optical absorption of LaAlO3/SrTiO3 heterostructures: evidence for an extremely slow electron relaxation at the interface.

    PubMed

    Yamada, Yasuhiro; Sato, Hiroki K; Hikita, Yasuyuki; Hwang, Harold Y; Kanemitsu, Yoshihiko

    2013-07-26

    The photocarrier relaxation dynamics of an n-type LaAlO3/SrTiO3 heterointerface is investigated using femtosecond transient absorption (TA) spectroscopy at low temperatures. In both LaAlO3/SrTiO3 heterostructures and electron-doped SrTiO3 bulk crystals, the TA spectrum shows a Drude-like free carrier absorption immediately after excitation. In addition, a broad absorption band gradually appears within 40 ps, which corresponds to the energy relaxation of photoexcited free electrons into self-trapped polaron states. We reveal that the polaron formation time is enhanced considerably at the LaAlO3/SrTiO3 heterointerface as compared to bulk crystals. Further, we discuss the interface effects on the electron relaxation dynamics in conjunction with the splitting of the t2g subbands due to the interface potential.

  11. Physical, Mechanical and Water Absorption Behaviour of Coir Fiber Reinforced Epoxy Composites Filled With Al2O3 Particulates

    NASA Astrophysics Data System (ADS)

    Das, Geetanjali; Biswas, Sandhayarani

    2016-02-01

    The objective of the present work is to study the physical, mechanical and water absorption behaviour of coir fiber reinforced epoxy composites filled with Al2O3 particulates. Composites with different compositions were prepared by varying the length of the fiber and content of fiber using hand lay-up technique. The experimental investigation reveals that the properties of composite increases with the incorporation of Al2O3 particulates. It is observed that the density of composites increases with increase in fiber content, while a decrease in density is observed with increase in fiber length. The strength properties of the composites increases with the increase in fiber content up to 15 wt.% and 12mm fiber length, however further increase in fiber length and fiber content the value decreases. The maximum tensile strength of 25.71MPa, flexural strength of 29.75MPa and impact strength of 14.76kJ/m2 is obtained for composites with 12 mm fiber length and 15 wt.% of fiber content. The hardness and tensile modulus, on the other hand, increases with increase in fiber length and fiber content. The maximum hardness value of 19.52Hv and tensile modulus of 3.412GPa is obtained for composites with 15mm fiber length and 20 wt.% of fiber content. Finally, morphological analysis is also carried out using scanning electron microscope (SEM) to study the fracture behaviour of the composite samples.

  12. Effect of transverse electric field and temperature on light absorption in GaAs/AlGaAs tunnel-coupled quantum wells

    SciTech Connect

    Firsov, D. A.; Vorobjev, L. E.; Vinnichenko, M. Ya. Balagula, R. M.; Kulagina, M. M.; Vasil’iev, A. P.

    2015-11-15

    The photoluminescence and intersubband absorption spectra are studied in GaAs/AlGaAs tunnel- coupled quantum well structures. The peak positions in the photoluminescence and absorption spectra are consistent with the theoretically calculated energies of optical carrier transitions. The effect of a transverse electric field and temperature on intersubband light absorption is studied. It is caused by electron redistribution between the size-quantization levels and a variation in the energy spectrum of quantum wells. The variation in the refractive index in the energy region of observed intersubband transitions is estimated using Kramers–Kronig relations.

  13. Thermochemical Capture of Carbon Dioxide on Lithium Aluminates (LiAlO{sub 2} and Li{sub 5}AlO{sub 4}): A New Option for the CO{sub 2} Absorption

    SciTech Connect

    Avalos-Rendon, T.; Casa-Madrid, J.; Pfeiffer, H.

    2009-06-15

    Lithium aluminates (LiAlO{sub 2} and Li{sub 5}AlO{sub 4}) were synthesized, characterized, and tested as possible CO{sub 2} captors. LiAlO{sub 2} did not seem to have good qualities for the CO{sub 2} absorption. On the contrary, Li{sub 5}AlO{sub 4} showed excellent behavior as a possible CO{sub 2} captor. Li{sub 5}AlO{sub 4} was thermally analyzed under a CO{sub 2} flux dynamically and isothermically at different temperatures. These results clearly showed that Li5AlO{sub 4} is able to absorb CO{sub 2} in a wide temperature range (200-700{sup o}C). Nevertheless, an important sintering effect was observed during the thermal treatment of the samples, which produced an atypical behavior during the CO{sub 2} absorption at low temperatures. However, at high temperatures, once the lithium diffusion is activated, the sintering effect did not interfere with the CO{sub 2} absorption. Eyring's model was used to determine the activation enthalpies of the CO{sub 2} absorption (15.6 kJ/mol) and lithium diffusion (52.1 kJ/mol); the last one is the limiting process.

  14. InGaAlAs RW-based electro-absorption-modulated DFB-lasers for high-speed applications

    NASA Astrophysics Data System (ADS)

    Moehrle, Martin; Klein, Holger; Bornholdt, Carsten; Przyrembel, Georges; Sigmund, Ariane; Molzow, Wolf-Dietrich; Troppenz, Ute; Bach, Heinz-Gunter

    2014-05-01

    Electro-absorption modulated 10G and 25G DFB lasers (EML) are key components in transmission systems for long reach (up to 10 km) and extended reach (up to 80 km) applications. The next generation Ethernet will most likely be 400 Gb/s which will require components with even higher bandwidth. Commercially available EMLs are regarded as high-cost components due to their separate epitaxial butt-coupling growth process to separately optimize the DFB laser and the electro-absorption modulator (EAM). Alternatively the selective area growth (SAG) technique is used to achieve different MQW bandgaps in the DFB and EAM section of an EML. However for a lot of applications an emission wavelength within a narrow wavelength window is required enforcing a temperature controlled operation. All these applications can be covered with the developed EML devices that use a single InGaAlAs MQW waveguide for both the DFB and the EAM enabling a low-cost fabrication process similar to a conventional DFB laser diode. It will be shown that such devices can be used for 25Gb/s and 40Gb/s applications with excellent performance. By an additional monolithic integration of an impedance matching circuit the module fabrication costs can be reduced but also the modulation bandwidth of the devices can be further enhanced. Up to 70Gb/s modulation with excellent eye openings can be achieved. This novel approach opens the possibility for 100Gb/s NRZ EMLs and thus 4x100Gb/s NRZ EML-based transmitters in future. Also even higher bitrates seem feasible using more complex modulation formats such as e.g. DMT and PAM.

  15. Probing the local environment of substitutional Al^{3+} in goethite using X-ray absorption spectroscopy and first-principles calculations

    NASA Astrophysics Data System (ADS)

    Ducher, Manoj; Blanchard, Marc; Vantelon, Delphine; Nemausat, Ruidy; Cabaret, Delphine

    2016-03-01

    We present experimental and calculated Al K-edge X-ray absorption near-edge structure (XANES) spectra of aluminous goethite with 10-33 mol% of AlOOH and diaspore. Significant changes are observed experimentally in the near- and pre-edge regions with increasing Al concentration in goethite. First-principles calculations based on density functional theory (DFT) reproduce successfully the experimental trends. This permits to identify the electronic and structural parameters controlling the spectral features and to improve our knowledge of the local environment of {Al}^{3+} in the goethite-diaspore partial solid solution. In the near-edge region, the larger peak spacing in diaspore compared to Al-bearing goethite is related to the nature (Fe or Al) of the first cation neighbours around the absorbing Al atom (Al*). The intensity ratio of the two near-edge peaks, which decreases with Al concentration, is correlated with the average distance of the first cations around Al* and the distortion of the {AlO}_6 octahedron. Finally, the decrease in intensity of the pre-edge features with increasing Al concentration is due to the smaller number of Fe atoms in the local environment of Al since Al atoms tend to cluster. In addition, it is found that the pre-edge features of the Al K-edge XANES spectra enable to probe indirectly empty 3 d states of Fe. Energetic, structural and spectroscopic results suggest that for Al concentrations around 10 mol%, Al atoms can be considered as isolated, whereas above 25 mol%, Al clusters are more likely to occur.

  16. Aluminum incorporation in Ti{sub 1-x}Al{sub x}N films studied by x-ray absorption near-edge structure

    SciTech Connect

    Gago, R.; Redondo-Cubero, A.; Endrino, J. L.; Jimenez, I.; Shevchenko, N.

    2009-06-01

    The local bonding structure of titanium aluminum nitride (Ti{sub 1-x}Al{sub x}N) films grown by dc magnetron cosputtering with different AlN molar fractions (x) has been studied by x-ray absorption near-edge structure (XANES) recorded in total electron yield mode. Grazing incidence x-ray diffraction (GIXRD) shows the formation of a ternary solid solution with cubic structure (c-Ti{sub 1-x}Al{sub x}N) that shrinks with the incorporation of Al and that, above a solubility limit of xapprox0.7, segregation of w-AlN and c-Ti{sub 1-x}Al{sub x}N phases occurs. The Al incorporation in the cubic structure and lattice shrinkage can also be observed using XANES spectral features. However, contrary to GIXRD, direct evidence of w-AlN formation is not observed, suggesting a dominance and surface enrichment of cubic environments. For x>0.7, XANES shows the formation of Ti-Al bonds, which could be related to the segregation of w-AlN. This study shows the relevance of local-order information to assess the atomic structure of Ti{sub 1-x}Al{sub x}N solutions.

  17. Changes in the optical absorption induced by sequential exposition to short- and long-wavelength radiation in the BTO:Al crystal

    NASA Astrophysics Data System (ADS)

    Shandarov, S. M.; Dyu, V. G.; Kisteneva, M. G.; Khudyakova, E. S.; Smirnov, S. V.; Akrestina, A. S.; Kargin, Yu F.

    2017-02-01

    Modifications of the spectral dependences of the optical absorption induced in the Bi12TiO20:Al crystal as a result of sequential exposition to cw laser radiation first with the wavelength λ g = 532 nm and then with the longer wavelength λ l,n = 588, 633, 655, 658, 663, 700, 780, 871, or 1064 nm are investigated. We revealed that after the short-wavelength exposition to radiation with λg = 532 nm, the optical absorption in the crystal increases, and in the range 470-1000 nm, yields the spectrum whose form is independent of a prehistory. The subsequent exposition to longer-wavelength radiation leads to bleaching of the crystal in the examined spectral range. A maximum diminishing of the optical absorption in the crystal is observed upon exposure to radiation with the wavelength λ l,5 = 663 nm. To describe the experimentally observed reversible changes in the optical absorption spectrum in the Bi12TiO20:Al we use the impurity absorption model that takes into account the photoinduced transitions between two metastable states of a deep defect center leading to the change of its position in the crystal lattice under conditions of strong lattice relaxation.

  18. Bolometric detection of magnetoplasma resonances in microwave absorption by two-dimensional electron systems based on doping layer conductivity measurements in GaAs/AlGaAs heterostructures

    SciTech Connect

    Dorozhkin, S. I. Sychev, D. V.; Kapustin, A. A.

    2014-11-28

    We have implemented a new bolometric method to detect resonances in magneto-absorption of microwave radiation by two-dimensional electron systems (2DES) in selectively doped GaAs/AlGaAs heterostructures. Radiation is absorbed by the 2DES and the thermally activated conductivity of the doping layer supplying electrons to the 2DES serves as a thermometer. The resonant absorption brought about by excitation of the confined magnetoplasma modes appears as peaks in the magnetic field dependence of the low-frequency impedance measured between the Schottky gate and 2DES.

  19. High dose neutron irradiation of MgAl2O4 spinel: effects of post-irradiation thermal annealing on EPR and optical absorption

    SciTech Connect

    Ibarra, A.; Bravo, D.; Lopez, F J.; Garner, Francis A.

    2005-01-01

    Electron paramagnetic resonance (EPR) and optical absorption spectra were measured during thermal annealing for stoichiometric MgAl2O4 spinel that was previously irradiated in FFTF-MOTA at {approx}405 C to {approx}50 dpa. Both F and F+ centres are to persist up to very high temperatures (over 700C), suggesting the operation of an annealing mechanism based on evaporation from extended defects Using x-ray irradiation following the different annealing steps it was shown that the optical absorption band is related to a sharp EPR band at g=2.0005 and that the defect causing these effects is the F+ centre.

  20. An X-ray absorption spectroscopic study of the metal site preference in Al{sub 1-x}Ga{sub x}FeO{sub 3}

    SciTech Connect

    Walker, James D.S.; Grosvenor, Andrew P.

    2013-01-15

    Magnetoelectric materials have potential for being introduced into next generation technologies, especially memory devices. The AFeO{sub 3} (Pna2{sub 1}; A=Al, Ga) system has received attention to better understand the origins of magnetoelectric coupling. The magnetoelectric properties this system exhibits depend on the amount of anti-site disorder present, which is affected by the composition and the method of synthesis. In this study, Al{sub 1-x}Ga{sub x}FeO{sub 3} was synthesized by the ceramic method and studied by X-ray absorption spectroscopy. Al L{sub 2,3}-, Ga K-, and Fe K-edge spectra were collected to examine how the average metal coordination number changes with composition. Examination of XANES spectra from Al{sub 1-x}Ga{sub x}FeO{sub 3} indicate that with increasing Ga content, Al increasingly occupies octahedral sites while Ga displays a preference for occupying the tetrahedral site. The Fe K-edge spectra indicate that more Fe is present in the tetrahedral site in AlFeO{sub 3} than in GaFeO{sub 3}, implying more anti-site disorder is present in AlFeO{sub 3}. - Graphical abstract: Al{sub 1-x}Ga{sub x}FeO{sub 3} has been investigated by XANES. Through examination of Al L{sub 2,3}-, Ga K-, and Fe K-edge XANES spectra, it was found that more anti-site disorder of the Fe atoms is present in AlFeO{sub 3} compared to in GaFeO{sub 3}. Highlights: Black-Right-Pointing-Pointer Al{sub 1-x}Ga{sub x}FeO{sub 3} was investigated by X-ray absorption spectroscopy. Black-Right-Pointing-Pointer Ga prefers to occupy the tetrahedral site in Al{sub 1-x}Ga{sub x}FeO{sub 3}. Black-Right-Pointing-Pointer Fe prefers to occupy the octahedral sites in Al{sub 1-x}Ga{sub x}FeO{sub 3} as x increases. Black-Right-Pointing-Pointer More anti-site disorder is present in AlFeO{sub 3} compared to in GaFeO{sub 3.}.

  1. Intersubband absorption of cubic GaN/Al(Ga)N quantum wells in the near-infrared to terahertz spectral range

    NASA Astrophysics Data System (ADS)

    Machhadani, H.; Tchernycheva, M.; Sakr, S.; Rigutti, L.; Colombelli, R.; Warde, E.; Mietze, C.; As, D. J.; Julien, F. H.

    2011-02-01

    The intersubband absorption of cubic GaN/Al(Ga)N quantum wells is studied experimentally and theoretically over a wide spectral range. By changing the quantum well thickness it is possible to tune the intersubband absorption peak wavelength from 1.4 μm (214 THz) to 63 μm (4.76 THz). Comparing the experimental results with simulations based on the effective-mass model we demonstrate that the GaN/AlN conduction-band offset is higher than 1.2 eV. The best fit with the experimental data is achieved for a conduction-band offset of 1.4 eV and for a GaN effective mass of 0.11m0.

  2. Evolution of dielectric function of Al-doped ZnO thin films with thermal annealing: effect of band gap expansion and free-electron absorption.

    PubMed

    Li, X D; Chen, T P; Liu, Y; Leong, K C

    2014-09-22

    Evolution of dielectric function of Al-doped ZnO (AZO) thin films with annealing temperature is observed. It is shown that the evolution is due to the changes in both the band gap and the free-electron absorption as a result of the change of free-electron concentration of the AZO thin films. The change of the electron concentration could be attributed to the activation of Al dopant and the creation/annihilation of the donor-like defects like oxygen vacancy in the thin films caused by annealing.

  3. Quasi-bound states and continuum absorption background of polar Al{sub 0.5}Ga{sub 0.5}N/GaN quantum dots

    SciTech Connect

    Elmaghraoui, D. Triki, M.; Jaziri, S.; Leroux, M.; Brault, J.

    2014-07-07

    A theoretical interpretation of the photoluminescence excitation spectra of self-organized polar GaN/(Al,Ga)N quantum dots is presented. A numerical method assuming a realistic shape of the dots and including the built-in electric field effects is developed to calculate their energy structure and hence their optical absorption. The electron and hole spectra show the existence of a set of quasi-bound states that does not originate from the wetting layer and plays a crucial role in the observed absorption spectrum of the GaN/(Al,Ga)N dots. Transitions involving these quasi-bound states and wetting layer states give a sufficient explanation for the observed continuum absorption background. The properties of this absorption band, especially its extension, depend strongly on the dot's size. Our simulation provides a natural explanation of the experimental luminescence excitation spectra of ensembles of dots of different heights. Our theoretical model can be convenient for future optical studies including systems with more complicated potentials.

  4. [Al

    PubMed

    Purath; Köppe; Schnöckel

    1999-10-04

    A "naked" aluminum atom links two aluminum tetrahedra in the [Al(7){N(SiMe(3))(2)}(6)](-) ion (see picture), which results from the reaction of a metastable AlCl solution with LiN(SiMe(3))(2) and crystallizes with [Li(OEt(2))(3)](+) as cation. This unique structure among molecular metal atom clusters represents a small but characteristic section of cubic close-packed aluminum.

  5. Microvoid, Si, H, and Al dynamics in a-Si:H/Al2O3/Al structures: A small-angle x-ray-scattering and infrared-absorption study

    NASA Astrophysics Data System (ADS)

    Shinar, J.; Jia, H.; Shinar, R.; Chen, Y.; Williamson, D. L.

    1994-09-01

    A small-angle x-ray-scattering (SAXS) and infrared-absorption study of microvoid dynamics and hydrogen evolution in a-Si:H is described. In films deposited on Al foil by rf sputtering, annealing at 350 °C and above sharply increased the integrated SAXS intensity Q, although the overall film density remained nearly constant. Incipient formation of microcrystalline Si domains by Si diffusing into the Al substrate is insufficient to account for the increased SAXS intensity. Rather, the close correlation between Q and the Si-bonded H content CH suggests that it more likely results from migration of Si-bonded H to deep traps at the microvoid surfaces and its accumulation as H2 in the isolated voids. The density of the Si network then increases as its H content decreases, and the void sizes increase as hydrogen accumulates in them. These processes are discussed in relation to well-known characteristics of hydrogen diffusion in a-Si:H. In contrast to the noncolumnar samples, the values of Q and CH of the columnarlike film did not change during prolonged annealing (beyond 6 h) at 430 °C. This behavior is believed to result from migration of most of the Si-bonded H to the internal surfaces of that film, recombination to molecular H2, and its escape through the largely interconnected voids. Most of the remaining hydrogen was then probably bonded to the void surfaces in isolated sites which are not adjacent to a neighboring H atom. Annealing for 6 h at 430 °C also resulted in some crystallization sufficient to be detected by x-ray diffraction (XRD) and Raman scattering. Annealing for 18 h at that temperature sharply reduced the SAXS tilt-angle dependence of the columnarlike film. Finally, following 36 h at that temperature, the Raman and XRD spectra indicated that ~50 vol. % of the film was still amorphous. Auger profiles yielded an Al concentration which increased from ~2.2 at. % near the surface to ~3.1 at. % near the substrate of that film. However, the sharp reduction

  6. Effects of an Al(3+)- and Mg(2+)-containing antacid, ferrous sulfate, and calcium carbonate on the absorption of nemonoxacin (TG-873870) in healthy Chinese volunteers.

    PubMed

    Zhang, Yi-fan; Dai, Xiao-jian; Wang, Ting; Chen, Xiao-yan; Liang, Li; Qiao, Hua; Tsai, Cheng-yuan; Chang, Li-wen; Huang, Ping-ting; Hsu, Chiung-yuan; Chang, Yu-ting; Tsai, Chen-en; Zhong, Da-fang

    2014-12-01

    To evaluate the effects of an Al(3+)- and Mg(2+)-containing antacid, ferrous sulfate, and calcium carbonate on the absorption of nemonoxacin in healthy humans. Two single-dose, open-label, randomized, crossover studies were conducted in 24 healthy male Chinese volunteers (12 per study). In Study 1, the subjects orally received nemonoxacin (500 mg) alone, or an antacid (containing 318 mg of Al(3+) and 496 mg of Mg(2+)) plus nemonoxacin administered 2 h before, concomitantly or 4 h after the antacid. In Study 2, the subjects orally received nemonoxacin (500 mg) alone, or nemonoxacin concomitantly with ferrous sulfate (containing 60 mg of Fe(2+)) or calcium carbonate (containing 600 mg of Ca(2+)). Concomitant administration of nemonoxacin with the antacid significantly decreased the area under the concentration-time curve from time 0 to infinity (AUC0-∞) for nemonoxacin by 80.5%, the maximum concentration (Cmax) by 77.8%, and urine recovery (Ae) by 76.3%. Administration of nemonoxacin 4 h after the antacid decreased the AUC0-∞ for nemonoxacin by 58.0%, Cmax by 52.7%, and Ae by 57.7%. Administration of nemonoxacin 2 h before the antacid did not affect the absorption of nemonoxacin. Administration of nemonoxacin concomitantly with ferrous sulfate markedly decreased AUC0-∞ by 63.7%, Cmax by 57.0%, and Ae by 59.7%, while concomitant administration of nemonoxacin with calcium carbonate mildly decreased AUC0-∞ by 17.8%, Cmax by 14.3%, and Ae by 18.4%. Metal ions, Al(3+), Mg(2+), and Fe(2+) markedly decreased the absorption of nemonoxacin in healthy Chinese males, whereas Ca(2+) had much weaker effects. To avoid the effects of Al(3+) and Mg(2+)-containing drugs, nemonoxacin should be administered ≥2 h before them.

  7. Effects of an Al3+- and Mg2+-containing antacid, ferrous sulfate, and calcium carbonate on the absorption of nemonoxacin (TG-873870) in healthy Chinese volunteers

    PubMed Central

    Zhang, Yi-fan; Dai, Xiao-jian; Wang, Ting; Chen, Xiao-yan; Liang, Li; Qiao, Hua; Tsai, Cheng-yuan; Chang, Li-wen; Huang, Ping-ting; Hsu, Chiung-yuan; Chang, Yu-ting; Tsai, Chen-en; Zhong, Da-fang

    2014-01-01

    Aim: To evaluate the effects of an Al3+- and Mg2+-containing antacid, ferrous sulfate, and calcium carbonate on the absorption of nemonoxacin in healthy humans. Methods: Two single-dose, open-label, randomized, crossover studies were conducted in 24 healthy male Chinese volunteers (12 per study). In Study 1, the subjects orally received nemonoxacin (500 mg) alone, or an antacid (containing 318 mg of Al3+ and 496 mg of Mg2+) plus nemonoxacin administered 2 h before, concomitantly or 4 h after the antacid. In Study 2, the subjects orally received nemonoxacin (500 mg) alone, or nemonoxacin concomitantly with ferrous sulfate (containing 60 mg of Fe2+) or calcium carbonate (containing 600 mg of Ca2+). Results: Concomitant administration of nemonoxacin with the antacid significantly decreased the area under the concentration-time curve from time 0 to infinity (AUC0–∞) for nemonoxacin by 80.5%, the maximum concentration (Cmax) by 77.8%, and urine recovery (Ae) by 76.3%. Administration of nemonoxacin 4 h after the antacid decreased the AUC0–∞ for nemonoxacin by 58.0%, Cmax by 52.7%, and Ae by 57.7%. Administration of nemonoxacin 2 h before the antacid did not affect the absorption of nemonoxacin. Administration of nemonoxacin concomitantly with ferrous sulfate markedly decreased AUC0–∞ by 63.7%, Cmax by 57.0%, and Ae by 59.7%, while concomitant administration of nemonoxacin with calcium carbonate mildly decreased AUC0–∞ by 17.8%, Cmax by 14.3%, and Ae by 18.4%. Conclusion: Metal ions, Al3+, Mg2+, and Fe2+ markedly decreased the absorption of nemonoxacin in healthy Chinese males, whereas Ca2+ had much weaker effects. To avoid the effects of Al3+ and Mg2+-containing drugs, nemonoxacin should be administered ≥2 h before them. PMID:25327812

  8. Nonlinear absorption coefficient and optically detected electrophonon resonance in cylindrical GaAs/AlAs quantum wires with different confined phonon models

    NASA Astrophysics Data System (ADS)

    Khoa, Doan Quoc; Phuong, Le Thi Thu; Hoi, Bui Dinh

    2017-03-01

    A quantum kinetic equation for electrons interacting with confined phonons is used to investigate the nonlinear absorption of an intense electromagnetic wave by electrons in cylindrical GaAs/AlAs quantum wires. The analytic expression for absorption coefficient is calculated for three models of confined optical phonons: the dielectric continuum (DC), hydrodynamic continuum (HC), and Huang-Zhu (HZ) models. The absorption coefficient depends on the square of the electromagnetic wave amplitude. The electrophonon resonance and optically detected electrophonon resonance (ODEPR) are observed through the absorption spectrum. The full width at half maximum (the line-width) of the ODEPR peaks is obtained by a computational method. The line-width is found to increase with increasing temperature and decrease with increasing the quantum wire radius. In particular, numerical results show that the DC and HZ models lead to a similar behaviour of electron - confined phonon interaction whereas the HC model results in a quite different one, especially at small quantum wire radius. For large quantum wire radii, above mentioned phonon models have equivalent contributions to the ODEPR line-width.

  9. Enhanced Rates of Hydrogen Absorption Resulting from Oxidation of Pd and Internal Oxidation of Pd-Al Alloys

    SciTech Connect

    Shanahan, K.L.

    1999-08-20

    The goal of this research was the determination of the relative rates before and after internal oxidation of Pd--Al alloys and oxidation (Pd) and this is independent of whether heat transfer is the rate-limiting step for the internally oxidized Pd--Al alloys rather than a more fundamental step.

  10. X-ray absorption of a warm dense aluminum plasma created by an ultra-short laser pulse

    NASA Astrophysics Data System (ADS)

    Lecherbourg, L.; Renaudin, P.; Bastiani-Ceccotti, S.; Geindre, J.-P.; Blancard, C.; Cossé, P.; Faussurier, G.; Shepherd, R.; Audebert, P.

    2007-05-01

    Point-projection K-shell absorption spectroscopy has been used to measure absorption spectra of transient aluminum plasma created by an ultra-short laser pulse. The 1s-2p and 1s-3p absorption lines of weakly ionized aluminum were measured for an extended range of densities in a low-temperature regime. Independent plasma characterization was obtained using frequency domain interferometry diagnostic (FDI) that allows the interpretation of the absorption spectra in terms of spectral opacities. A detailed opacity code using the density and temperature inferred from the FDI reproduce the measured absorption spectra except in the last stage of the recombination phase.

  11. Mid-infrared electro-luminescence and absorption from AlGaN/GaN-based multi-quantum well inter-subband structures

    SciTech Connect

    Hofstetter, Daniel; Bour, David P.; Kirste, Lutz

    2014-06-16

    We present electro-modulated absorption and electro-luminescence measurements on chirped AlGaN/GaN-based multi-quantum well inter-subband structures grown by metal-organic vapour phase epitaxy. The absorption signal is a TM-polarized, 70 meV wide feature centred at 230 meV. At medium injection current, a 58 meV wide luminescence peak corresponding to an inter-subband transition at 1450 cm{sup −1} (180 meV) is observed. Under high injection current, we measured a 4 meV wide structure peaking at 92.5 meV in the luminescence spectrum. The energy location of this peak is exactly at the longitudinal optical phonon of GaN.

  12. Local atomic structure investigation of AlFeCuCrMgx (0.5, 1, 1.7) high entropy alloys: X-ray absorption spectroscopy study

    NASA Astrophysics Data System (ADS)

    Maulik, Ornov; Patra, N.; Bhattacharyya, D.; Jha, S. N.; Kumar, Vinod

    2017-02-01

    The present paper reports local atomic structure investigation of novel AlFeCuCrMgx (x=0.5, 1, 1.7) high entropy alloys (HEAs) produced by mechanical alloying using Fe, Cr and Cu K-edge X-ray absorption near edge spectroscopy (XANES) and extended x-ray absorption fine structure (EXAFS) spectroscopy. XANES spectra measured at Fe and Cr K-edges resemble that of the respective pure metal foils, while the spectrum measured at Cu K-edge manifests the presence of some other phases in the as-milled alloys. The radial distribution functions (RDFs) obtained from Fourier transformation of EXAFS spectra support the formation of disordered BCC structure.

  13. Investigation of quadratic electro-optic effects and electro-absorption process in GaN/AlGaN spherical quantum dot

    PubMed Central

    2014-01-01

    Quadratic electro-optic effects (QEOEs) and electro-absorption (EA) process in a GaN/AlGaN spherical quantum dot are theoretically investigated. It is found that the magnitude and resonant position of third-order nonlinear optical susceptibility depend on the nanostructure size and aluminum mole fraction. With increase of the well width and barrier potential, quadratic electro-optic effect and electro-absorption process nonlinear susceptibilities are decreased and blueshifted. The results show that the DC Kerr effect in this case is much larger than that in the bulk case. Finally, it is observed that QEOEs and EA susceptibilities decrease and broaden with the decrease of relaxation time. PMID:24646318

  14. Site partitioning of Cr3+ in the trichroic alexandrite BeAl2O4:Cr3+ crystal: contribution from x-ray absorption spectroscopy.

    PubMed

    Bordage, Amélie; Rossano, Stéphanie; Horn, Adolf Heinrich; Fuchs, Yves

    2012-06-06

    X-ray absorption spectroscopy measurements at the Cr K-edge of a trichroic crystal of alexandrite BeAl(2)O(4):Cr(3+) for different orientations of the crystal with respect to the polarization and direction of the x-ray incident beam have been performed. Analysis of the experimental spectra with the help of first-principles calculations of x-ray absorption spectra allowed us to estimate the proportion of chromium Cr(3+) cations among the two different octahedral sites of the alexandrite structure (70% in the C(s) site-30% in the C(i) site). The methodology presented in this work opens up new possibilities in the field of mineralogy for the study of complex minerals containing several sites potentially occupied by several transition elements or for solid solutions.

  15. Site partitioning of Cr3+ in the trichroic alexandrite BeAl2O4:Cr3+ crystal: contribution from x-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Bordage, Amélie; Rossano, Stéphanie; Horn, Adolf Heinrich; Fuchs, Yves

    2012-06-01

    X-ray absorption spectroscopy measurements at the Cr K-edge of a trichroic crystal of alexandrite BeAl2O4:Cr3+ for different orientations of the crystal with respect to the polarization and direction of the x-ray incident beam have been performed. Analysis of the experimental spectra with the help of first-principles calculations of x-ray absorption spectra allowed us to estimate the proportion of chromium Cr3+ cations among the two different octahedral sites of the alexandrite structure (70% in the Cs site-30% in the Ci site). The methodology presented in this work opens up new possibilities in the field of mineralogy for the study of complex minerals containing several sites potentially occupied by several transition elements or for solid solutions.

  16. Ultra-violet absorption induced modifications in bulk and nanoscale electrical transport properties of Al-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata

    2015-08-01

    Using conductive atomic force microscopy and Kelvin probe force microscopy, we study local electrical transport properties in aluminum-doped zinc oxide (ZnO:Al or AZO) thin films. Current mapping shows a spatial variation in conductivity which corroborates well with the local mapping of donor concentration (˜1020 cm-3). In addition, a strong enhancement in the local current at grains is observed after exposing the film to ultra-violet (UV) light which is attributed to persistent photocurrent. Further, it is shown that UV absorption gives a smooth conduction in AZO film which in turn gives rise to an improvement in the bulk photoresponsivity of an n-AZO/p-Si heterojunction diode. This finding is in contrast to the belief that UV absorption in an AZO layer leads to an optical loss for the underneath absorbing layer of a heterojunction solar cell.

  17. Ultra-violet absorption induced modifications in bulk and nanoscale electrical transport properties of Al-doped ZnO thin films

    SciTech Connect

    Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata

    2015-08-07

    Using conductive atomic force microscopy and Kelvin probe force microscopy, we study local electrical transport properties in aluminum-doped zinc oxide (ZnO:Al or AZO) thin films. Current mapping shows a spatial variation in conductivity which corroborates well with the local mapping of donor concentration (∼10{sup 20 }cm{sup −3}). In addition, a strong enhancement in the local current at grains is observed after exposing the film to ultra-violet (UV) light which is attributed to persistent photocurrent. Further, it is shown that UV absorption gives a smooth conduction in AZO film which in turn gives rise to an improvement in the bulk photoresponsivity of an n-AZO/p-Si heterojunction diode. This finding is in contrast to the belief that UV absorption in an AZO layer leads to an optical loss for the underneath absorbing layer of a heterojunction solar cell.

  18. Multiscale modeling of interaction of alane clusters on Al(111) surfaces: A reactive force field and infrared absorption spectroscopy approach

    NASA Astrophysics Data System (ADS)

    Ojwang, J. G. O.; Chaudhuri, Santanu; van Duin, Adri C. T.; Chabal, Yves J.; Veyan, Jean-Francois; van Santen, Rutger; Kramer, Gert Jan; Goddard, William A.

    2010-02-01

    We have used reactive force field (ReaxFF) to investigate the mechanism of interaction of alanes on Al(111) surface. Our simulations show that, on the Al(111) surface, alanes oligomerize into larger alanes. In addition, from our simulations, adsorption of atomic hydrogen on Al(111) surface leads to the formation of alanes via H-induced etching of aluminum atoms from the surface. The alanes then agglomerate at the step edges forming stringlike conformations. The identification of these stringlike intermediates as a precursor to the bulk hydride phase allows us to explain the loss of resolution in surface IR experiments with increasing hydrogen coverage on single crystal Al(111) surface. This is in excellent agreement with the experimental works of Go et al. [E. Go, K. Thuermer, and J. E. Reutt-Robey, Surf. Sci. 437, 377 (1999)]. The mobility of alanes molecules has been studied using molecular dynamics and it is found that the migration energy barrier of Al2H6 is 2.99 kcal/mol while the prefactor is D0=2.82×10-3 cm2/s. We further investigated the interaction between an alane and an aluminum vacancy using classical molecular dynamics simulations. We found that a vacancy acts as a trap for alane, and eventually fractionates/annihilates it. These results show that ReaxFF can be used, in conjunction with ab initio methods, to study complex reactions on surfaces at both ambient and elevated temperature conditions.

  19. Multiscale modeling of interaction of alane clusters on Al(111) surfaces: a reactive force field and infrared absorption spectroscopy approach.

    PubMed

    Ojwang, J G O; Chaudhuri, Santanu; van Duin, Adri C T; Chabal, Yves J; Veyan, Jean-Francois; van Santen, Rutger; Kramer, Gert Jan; Goddard, William A

    2010-02-28

    We have used reactive force field (ReaxFF) to investigate the mechanism of interaction of alanes on Al(111) surface. Our simulations show that, on the Al(111) surface, alanes oligomerize into larger alanes. In addition, from our simulations, adsorption of atomic hydrogen on Al(111) surface leads to the formation of alanes via H-induced etching of aluminum atoms from the surface. The alanes then agglomerate at the step edges forming stringlike conformations. The identification of these stringlike intermediates as a precursor to the bulk hydride phase allows us to explain the loss of resolution in surface IR experiments with increasing hydrogen coverage on single crystal Al(111) surface. This is in excellent agreement with the experimental works of Go et al. [E. Go, K. Thuermer, and J. E. Reutt-Robey, Surf. Sci. 437, 377 (1999)]. The mobility of alanes molecules has been studied using molecular dynamics and it is found that the migration energy barrier of Al(2)H(6) is 2.99 kcal/mol while the prefactor is D(0)=2.82 x 10(-3) cm(2)/s. We further investigated the interaction between an alane and an aluminum vacancy using classical molecular dynamics simulations. We found that a vacancy acts as a trap for alane, and eventually fractionates/annihilates it. These results show that ReaxFF can be used, in conjunction with ab initio methods, to study complex reactions on surfaces at both ambient and elevated temperature conditions.

  20. Formation and bonding of alane clusters on Al(111) surfaces studied by infrared absorption spectroscopy and theoretical modeling.

    PubMed

    Chaudhuri, Santanu; Rangan, Sylvie; Veyan, Jean-Francois; Muckerman, James T; Chabal, Yves J

    2008-08-13

    Alanes are believed to be the mass transport intermediate in many hydrogen storage reactions and thus important for understanding rehydrogenation kinetics for alanates and AlH3. Combining density functional theory (DFT) and surface infrared (IR) spectroscopy, we provide atomistic details about the formation of alanes on the Al(111) surface, a model environment for the rehydrogenation reactions. At low coverage, DFT predicts a 2-fold bridge site adsorption for atomic hydrogen at 1150 cm(-1), which is too weak to be detected by IR but was previously observed in electron energy loss spectroscopy. At higher coverage, steps are the most favorable adsorption sites for atomic H adsorption, and it is likely that the AlH3 molecules form (initially strongly bound to steps) at saturation. With increasing exposures AlH3 is extracted from the step edge and becomes highly mobile on the terraces in a weakly bound state, accounting for step etching observed in previous STM studies. The mobility of these weakly bound AlH3 molecules is the key factor leading to the growth of larger alanes through AlH3 oligomerization. The subsequent decomposition and desorption of alanes is also investigated and compared to previous temperature programmed desorption studies.

  1. Picosecond excitonic absorption recovery of 100 nm GaAs/AlGaAs narrow multiple quantum-well wires

    NASA Astrophysics Data System (ADS)

    Tackeuchi, Atsushi; Kitada, Hideki; Arimoto, Hiroshi; Sugiyama, Yoshihiro; Endoh, Akira; Nakata, Yoshiaki; Inata, Tsuguo; Muto, Shunichi

    1991-08-01

    We report the time-resolved absorption measurement of narrow multiple quantum-well (MQW) wires to investigate their fast recoveries from excitonic absorption bleaching. Wires down to 130 nm were fabricated from MQWs using focused ion beam lithography and electron cyclotron-resonance chlorine-plasma etching. In this structure, the photoexcited carriers diffuse toward the sidewalls and recombine on the surface of the sidewalls. We show that the strong optical nonlinearity of excitons is preserved, even in wires of 130 nm width, and having a fast recovery time in the picosecond region. We also briefly discuss the possibility of making quantum wires which have a faster recovery time and larger optical nonlinearity.

  2. Experimental analysis of energy absorption behaviour of Al-tube filled with pumice lightweight concrete under axial loading condition

    NASA Astrophysics Data System (ADS)

    Rajak, D. K.; Deshpande, P. G.; Kumaraswamidhas, L. A.

    2017-08-01

    This Paper aimed at experimental investigation of compressive behaviour of square tube filled with pumice lightweight concrete (PLC). Square section of 20×20×30 mm is investigated, which is the backbone structure. The compression deformation result shows the better folding mechanism, displacement value, and energy absorption. PLC concrete filled with aluminium thin-wall tubes has been revealed superior energy absorption capacity (EAC) under low strain rate at room temperature. Superior EAC resulted as a result of mutual deformation benefit between aluminium section and PLC is also analysed. PLC was characterised by Fourier Transform Infrared (FTIR) and Field Emission Scanning Electron Microscopy (FESEM), and Energy Dispersive X-ray Spectrometry (EDX) analysis for better understanding of material behaviour. Individual and comparative load bearing graphs is logged for better prospective of analysing. Novel approach aimed at validation of porous lightweight concrete for better lightweight EA filler material.

  3. Nonlinear absorption and optical strength of BaF{sub 2} and Al{sub 2}O{sub 3} at the wavelength of 248 nm

    SciTech Connect

    Morozov, Nikolai V; Sergeev, P B; Reiterov, V M

    1999-11-30

    An experimental investigation was made of the dependence of the transmission of BaF{sub 2} and Al{sub 2}O{sub 3} samples on the intensity of KrF-laser radiation ({lambda} = 248 nm) pulses of 85 ns duration. The two-photon absorption coefficients were found at {lambda} = 248 nm and their values for these two crystals were 0.5 {+-} 0.2 and 2 {+-} 1 cm Gw{sup -1}. The surface and bulk laser breakdown thresholds were determined for these samples. (nonlinear optical phenomena)

  4. XANES (X-ray Absorption Near Edge Structure) investigation of cerium as an inhibitor for Al alloys

    SciTech Connect

    Davenport, A.J.; Isaacs, H.S. ); Kendig, M.W. . Science Center)

    1991-01-01

    Cerium ions are under investigation as possible replacements for toxic chromates. The use of cerium ions as corrosion inhibitors for aluminum alloys is investigated using XANES (x-ray absorption near edge structure). On immersion in a dilute solution of cerium ions, cerium is incorporated into the oxide films on aluminum alloys in either the 3- or 4-valent state depending upon the alloy and on the surface preparation. 7 refs., 2 figs.

  5. Electronic structure of Al-doped ZnO transparent conductive thin films studied by x-ray absorption and emission spectroscopies

    SciTech Connect

    Huang, W. H.; Sun, S. J.; Chiou, J. W.; Chou, H.; Chan, T. S.; Lin, H.-J.; Kumar, Krishna; Guo, J.-H.

    2011-11-15

    This study used O K-, Zn L{sub 3}-, Zn K-, and Al K-edges x-ray absorption near-edge structure (XANES) and O K-edge x-ray emission spectroscopy (XES) measurements to investigate the electronic structure of transparent Al-doped ZnO (AZO) thin film conductors. The samples were prepared on glass substrates at a low temperature near 77 K by using a standard RF sputtering method. High-purity Ne (5N) was used as the sputtering gas. The crystallography of AZO thin films gradually transformed from the ZnO wurtize structure to an amorphous structure during sample deposition, which suggests the suitability to grow on flexible substrates, eliminating the severe degradation due to fragmentation by repeated bending. The O K- and Zn L{sub 3}-edges XANES spectra of AZO thin films revealed a decrease in the number of both O 2p and Zn 3d unoccupied states when the pressure of Ne was increased from 5 to 100 mTorr. In contrast, Al K-edges XANES spectra showed that the number of unoccupied states of Al 3p increased in conjunction with the pressure of Ne, indicating an electron transfer from Al to O atoms, and suggesting that Al doping increases the negative effective charge of oxygen ions. XES and XANES spectra of O 2p states at the O K-edge also revealed that Al doping not only raised the conduction-band-minimum, but also increased the valence-band-maximum and the band-gap. The results indicate that the reduction in conductivity of AZO thin films is due to the generation of ionic characters, the increase in band-gap, and the decrease in density of unoccupied states of oxygen.

  6. Low absorption loss p-AlGaN superlattice cladding layer for current-injection deep ultraviolet laser diodes

    SciTech Connect

    Martens, M.; Kuhn, C.; Ziffer, E.; Simoneit, T.; Rass, J.; Wernicke, T.; Kueller, V.; Knauer, A.; Einfeldt, S.; Weyers, M.; Kneissl, M.

    2016-04-11

    Current injection into AlGaN-based laser diode structures with high aluminum mole fractions for deep ultraviolet emission is investigated. The electrical characteristics of laser diode structures with different p-AlGaN short period superlattice (SPSL) cladding layers with various aluminum mole fractions are compared. The heterostructures contain all elements that are needed for a current-injection laser diode including cladding and waveguide layers as well as an AlGaN quantum well active region emitting near 270 nm. We found that with increasing aluminum content in the p-AlGaN cladding, the diode turn-on voltage increases, while the series resistance slightly decreases. By introducing an SPSL instead of bulk layers, the operating voltage is significantly reduced. A gain guided broad area laser diode structure with transparent p-Al{sub 0.70}Ga{sub 0.30}N waveguide layers and a transparent p-cladding with an average aluminum content of 81% was designed for strong confinement of the transverse optical mode and low optical losses. Using an optimized SPSL, this diode could sustain current densities of more than 4.5 kA/cm{sup 2}.

  7. Low absorption loss p-AlGaN superlattice cladding layer for current-injection deep ultraviolet laser diodes

    NASA Astrophysics Data System (ADS)

    Martens, M.; Kuhn, C.; Ziffer, E.; Simoneit, T.; Kueller, V.; Knauer, A.; Rass, J.; Wernicke, T.; Einfeldt, S.; Weyers, M.; Kneissl, M.

    2016-04-01

    Current injection into AlGaN-based laser diode structures with high aluminum mole fractions for deep ultraviolet emission is investigated. The electrical characteristics of laser diode structures with different p-AlGaN short period superlattice (SPSL) cladding layers with various aluminum mole fractions are compared. The heterostructures contain all elements that are needed for a current-injection laser diode including cladding and waveguide layers as well as an AlGaN quantum well active region emitting near 270 nm. We found that with increasing aluminum content in the p-AlGaN cladding, the diode turn-on voltage increases, while the series resistance slightly decreases. By introducing an SPSL instead of bulk layers, the operating voltage is significantly reduced. A gain guided broad area laser diode structure with transparent p-Al0.70Ga0.30N waveguide layers and a transparent p-cladding with an average aluminum content of 81% was designed for strong confinement of the transverse optical mode and low optical losses. Using an optimized SPSL, this diode could sustain current densities of more than 4.5 kA/cm2.

  8. The role of scattering and absorption on the optical properties of birefringent polycrystalline ceramics: Modeling and experiments on ruby (Cr:Al2O3)

    NASA Astrophysics Data System (ADS)

    Penilla, E. H.; Hardin, C. L.; Kodera, Y.; Basun, S. A.; Evans, D. R.; Garay, J. E.

    2016-01-01

    Light scattering due to birefringence has prevented the use of polycrystalline ceramics with anisotropic optical properties in applications such as laser gain media. However, continued development of processing technology has allowed for very low porosity and fine grains, significantly improving transparency and is paving the way for polycrystalline ceramics to be used in demanding optical applications. We present a method for producing highly transparent Cr3+ doped Al2O3 (ruby) using current activated pressure assisted densification. The one-step doping/densification process produces fine grained ceramics with well integrated (doped) Cr, resulting in good absorption and emission. In order to explain the light transmission properties, we extend the analytical model based on the Rayleigh-Gans-Debye approximation that has been previously used for undoped alumina to include absorption. The model presented captures reflection, scattering, and absorption phenomena in the ceramics. Comparison with measured transmission confirms that the model adequately describes the properties of polycrystalline ruby. In addition the measured emission spectra and emission lifetime are found to be similar to single crystals, confirming the high optical quality of the ceramics.

  9. Influence of delta doping on intersubband transition and absorption in AlGaN/GaN step quantum wells for terahertz applications

    NASA Astrophysics Data System (ADS)

    Tang, Chenjie; Shi, Junxia

    2015-05-01

    Effects of delta doping location and density on intersubband transitions in AlGaN/GaN step quantum wells for terahertz (THz) applications have been investigated by solving Schrödinger and Poisson equations self-consistently. It shows that delta doping near the GaN well/AlGaN step well interface causes a blue-shift, while delta doping in the barrier or near barrier/GaN well and barrier/step well interfaces cause a red-shift first and then a blue-shift with increasing doping density. The shifts are attributed to the combination of many body effect and internal field modulation effect, and can be more than 200% or 70% of the e1-e2 transition energy, as for blue-shift or red-shift, respectively. In addition, the influences of delta-doping location and density on the absorption coefficient are also investigated in detail. Delta doping at the middle of a layer is found much more desirable over uniform-doping in order to improve the absorption coefficient, especially in the step well.

  10. Simultaneous generation of intersubband absorption and quantum well intermixing through silicon ion implantation in undoped InGaAs/AlAsSb coupled double quantum wells

    NASA Astrophysics Data System (ADS)

    Cong, G. W.; Akimoto, R.; Gozu, S.; Mozume, T.; Hasama, T.; Ishikawa, H.

    2010-03-01

    We demonstrated the intersubband absorption in undoped InGaAs/AlAsSb coupled double quantum wells through silicon ion implantation and rapid thermal annealing. For an implantation dose of 1×1014 cm-2, the actual carrier density of a sample annealed at 600 °C for 1 min was ˜7.5×1013 cm-2 (˜75% activation efficiency); the activation energy was ˜1.41 eV. The simultaneously generated quantum well intermixing (QWI) was nonuniform due to the silicon ion distribution. The effects of QWI nonuniformity on both intersubband and interband transitions were explained by eight-band k ṡp calculation. This study will open a route for monolithic integration of intersubband-transition-based high-speed all-optical switches.

  11. Origin of improved scintillation efficiency in (Lu,Gd)3(Ga,Al)5O12:Ce multicomponent garnets: An X-ray absorption near edge spectroscopy study

    NASA Astrophysics Data System (ADS)

    Wu, Yuntao; Luo, Jialiang; Nikl, Martin; Ren, Guohao

    2014-01-01

    In the recent successful improvement of scintillation efficiency in Lu3Al5O12:Ce driven by Ga3+ and Gd3+ admixture, the "band-gap engineering" and energy level positioning have been considered the valid strategies so far. This study revealed that this improvement was also associated with the cerium valence instability along with the changes of chemical composition. By utilizing X-ray absorption near edge spectroscopy technique, tuning the Ce3+/Ce4+ ratio by Ga3+ admixture was evidenced, while it was kept nearly stable with the Gd3+ admixture. Ce valence instability and Ce3+/Ce4+ ratio in multicomponent garnets can be driven by the energy separation between 4f ground state of Ce3+ and Fermi level.

  12. [Determination of Al, Be, Cd, Co, Cr, Mn, Ni, Pb, Se and Tl in whole blood by atomic absorption spectrometry without preliminary sample digestion].

    PubMed

    Ivanenko, N B; Ivanenko, A A; Solov'ev, N D; Navolotskiĭ, D V; Pavlova, O V; Ganeev, A A

    2014-01-01

    Methods of whole blood trace element determination by Graphite furnace atomic absorption spectrometry (in the variant of Zeeman's modulation polarization spectrometry) have been proposed. They do not require preliminary sample digestion. Furnace programs, modifiers and blood dilution factors were optimized. Seronorm™ human whole blood reference materials were used for validation. Dynamic ranges (for undiluted blood samples) were: Al 8 ¸ 210 мg/L; Be 0.3 ¸ 50 мg/L; Cd 0.2 ¸ 75 мg/L; Сo 5 ¸ 350 мg/L; Cr 10 ¸ 100 мg/L; Mn 6 ¸ 250 мg/L; Ni 10 ¸ 350 мg/L; Pb 3 ¸ 240 мg/L; Se 10 ¸ 500 мg/L; Tl 2 ¸ 600 мg/L. Precision (RSD) for the middle of dynamic range ranged from 5% for Mn to 11 for Se.

  13. The temperature dependence of intersubband absorption in a barrier-doped GaAs/Al 0.3Ga 0.7As quantum well structure

    NASA Astrophysics Data System (ADS)

    Szmulowicz, F.; Manasreh, M. O.; Fischer, D. W.; Madarasz, F.; Evans, K. R.; Stutz, E.; Vaughan, T.

    We compare the results of an envelope function (EFA) calculation of absorption spectra as a function of temperature of a barrier-doped GaAs/Al 0.3Ga 0.7As multiple quantum well (MQW) with experimental results. The linewidth, total integrated area, and peak positions of the intersubband transition (IT) in the MQW were measured as a function of temperature with the infrared absorption technique. We infer the density of electrons σ in the well from the total integrated intensity of the IT. Using the temperature dependence of σ we find that the Fermi energy in our MQW is also temperature dependent. The peak position of the IT is found to exhibit a nonlinear blue shift as the temperature is lowered. We calculate a one-electron energy band structure of the MQW versus the in-plane wave vector as a function of temperature using Ekenberg's nonparabolic-anisotropic EFA formalism. In our calculation we employ temperature dependent effective masses in both the well and barrier materials and temperature dependent conduction band offset and nonparabolicity parameter. Using the calculated bands and Fermi distribution functions to reflect the occupancies of both the ground and excited states with temperature dependent Fermi levels, we also obtain the optical absorption spectra as a function of temperature. These "raw" calculated spectra are then convoluted with a Lorentzian broadening function using the broadening parameters obtained from the measured lineshapes. The peak of the broadened spectra shows hardly any shift as a function of temperature. We conclude that the exchange interaction for the ground state electrons, which is temperature dependent owing to the temperature dependence of σ, is responsible for the observed peak positions as well as for their blue shift.

  14. Probing the effect of dopants (donors) within InAs/InGaAs/InAlAs Asymmetric Heterostructure wafer by magneto-THz spectroscopy

    NASA Astrophysics Data System (ADS)

    Pakmehr, Mehdi; Heyn, Christian; Hansen, Wolfgang

    Probing the effect of impurities within semiconductor structures have been the topic of interest both from applied and scientific point of views. We studied the effect of dopants (donors) within InAs/InGaAs/InAlAs asymmetric heterostructure wafer by means of THz magneto-transmission (TR) spectroscopy, in conjunction with THz magneto-photoresponse (PR) spectroscopy. The sample wafer has been immersed in pumped liquid Helium at 1.6 K, while being exposed to sweeping magnetic field up to 10 Tesla, with THz laser beam (1.4 THz) being focused on sample by off-axis parabolic mirror. The transmitted beam was detected by silicon composite bolometer. Two broad absorption features other than sharp Cyclotron resonance (CR) absorption dip within magneto-TR signal attributed to 1s -->2P transition within donors of doped layer (InAlAs) in heterostructure. We plan to discuss the analysis of magneto-TR signal, in conjunction with Magneto-PR signals from Hall bar samples made from same type of wafer at same frequency to clarify how dopants could possibly alter these signals.

  15. Characterization by X-Ray Absorption, X-Ray Powder Diffraction, and Magnetic Susceptibility of Cu Zn Co Al Containing Hydroxycarbonates, Oxycarbonates, Oxides, and Their Products of Reduction

    NASA Astrophysics Data System (ADS)

    Porta, Piero; Morpurgo, Simone; Pettiti, Ida

    1996-02-01

    Copper-zinc-cobalt-aluminium-containing crystalline hydroxycarbonates having hydrotalcite structure have been prepared by coprecipitation. X-ray powder diffraction (XRPD), magnetic susceptibility, and extended X-ray absorption fine structure (EXAFS) indicate that Cu2+, Zn2+, and Co2+are present in an octahedral environment. Calcination of the hydroxycarbonates at 723 K produces quasi-amorphous oxycarbonates where Cu2+and Co2+still retain octahedral coordination and cobalt is almost completely oxidized to Co3+. The coordination of Zn2+, at this stage, is intermediate between the octahedral one of the precursors and the tetrahedral one of ZnO and Zn-based spinels. Further calcination at 973 K produces a mixture of crystalline oxides such as CuO, ZnO, CuAl2O4, ZnAl2O4, and ZnCo2O4. EXAFS analysis of these samples indicates that copper is mainly in a fourfold coordination (although two longer Cu-O distances are also detected), zinc is tetrahedral, and cobalt (as Co3+) is essentially octahedral. EXAFS and XANES investigations performed afterin situreduction (10% H2/N2, at 523 and 623 K) on the oxycarbonates and oxides reveal that the total Cu2+→ Cu0reduction occurs only at 623 K in both series of samples, Co3+is reduced to Co2+only at 623 K in the oxycarbonates, and Zn2+is never reduced.

  16. Synthesis temperature effect on the structural features and optical absorption of Zn(1-x)Co(x)Al2O4 oxides.

    PubMed

    Gaudon, M; Apheceixborde, A; Ménétrier, M; Le Nestour, A; Demourgues, A

    2009-10-05

    Zinc/cobalt aluminates with spinel-type structure were prepared by a polymeric route, leading to a pure phase with controlled grain size. The prepared pigments were characterized by powder X-ray diffraction Rietveld analyses in order to determine structural features, scanning electron microscopy for morphological investigation, helium pycnometry and (27)Al MAS NMR in order to highlight the occurrence of defects inside the structure, and UV-visible-near-IR spectroscopy to identify electronic transitions responsible for the compounds' color. The green-blue coloration of these pigments is known to be dependent on the sample thermal history. Here, for the first time, the Zn(1-x)Co(x)Al(2)O(4) color is newly interpreted. The pigment is green once synthesized at low temperature (i.e., with diminution of the pigment grain size); this variation was attributed to the appearance of a new absorption band located at about 500 nm, linked to a complex network feature involving Co ions in octahedral sites as well as oxygen and cationic vacancies. Hence, this work shows the possibility of easily getting a nonstoichiometric network with an abnormal cationic distribution from "chimie douce" processes with moderate synthesis temperature, and so various colorations for the same composition.

  17. X-Ray Absorption Spectroscopy Of Thin Foils Irradiated By An Ultra-short Laser Pulse

    SciTech Connect

    Renaudin, P.; Blancard, C.; Cosse, P.; Faussurier, G.; Lecherbourg, L.; Audebert, P.; Bastiani-Ceccotti, S.; Geindre, J.-P.; Shepherd, R.

    2007-08-02

    Point-projection K-shell absorption spectroscopy has been used to measure absorption spectra of transient plasma created by an ultra-short laser pulse. The 1s-2p and 1s-3p absorption lines of weakly ionized aluminum and the 2p-3d absorption lines of bromine were measured over an extended range of densities in a low-temperature regime. Independent plasma characterization was obtained using frequency domain interferometry diagnostic (FDI) that allows the interpretation of the absorption spectra in terms of spectral opacities. Assuming local thermodynamic equilibrium, spectral opacity calculations have been performed using the density and temperature inferred from the FDI diagnostic to compare to the measured absorption spectra. A good agreement is obtained when non-equilibrium effects due to non-stationary atomic physics are negligible at the x-ray probe time.

  18. X-Ray Absorption Spectroscopy Of Thin Foils Irradiated By An Ultra-short Laser Pulse

    NASA Astrophysics Data System (ADS)

    Renaudin, P.; Lecherbourg, L.; Blancard, C.; Cossé, P.; Faussurier, G.; Audebert, P.; Bastiani-Ceccotti, S.; Geindre, J.-P.; Shepherd, R.

    2007-08-01

    Point-projection K-shell absorption spectroscopy has been used to measure absorption spectra of transient plasma created by an ultra-short laser pulse. The 1s-2p and 1s-3p absorption lines of weakly ionized aluminum and the 2p-3d absorption lines of bromine were measured over an extended range of densities in a low-temperature regime. Independent plasma characterization was obtained using frequency domain interferometry diagnostic (FDI) that allows the interpretation of the absorption spectra in terms of spectral opacities. Assuming local thermodynamic equilibrium, spectral opacity calculations have been performed using the density and temperature inferred from the FDI diagnostic to compare to the measured absorption spectra. A good agreement is obtained when non-equilibrium effects due to non-stationary atomic physics are negligible at the x-ray probe time.

  19. An analysis of temperature-dependent absorption and photocurrent spectra in BaAl{sub 2}Se{sub 4} layers

    SciTech Connect

    Hong, K. J.; Jeong, T. S.; Youn, C. J.; Moon, J. D.

    2015-04-28

    The temperature-dependent photoresponse behavior of BaAl{sub 2}Se{sub 4} layers has been investigated through the analysis of optical absorption and photocurrent (PC) spectra. Based on these results, the optical band gap was well expressed by E{sub g}(T) = E{sub g}(0) − 4.39 × 10{sup −4}T{sup 2}/(T + 250), where E{sub g}(0) is estimated to be 3.4205, 3.6234, and 3.8388 eV for the transitions corresponding to the valence band states Γ{sub 3}(A), Γ{sub 4}(B), and Γ{sub 5}(C), respectively. From the PC measurement, three peaks A, B, and C corresponded with the intrinsic transitions from the valence band states of Γ{sub 3}(A), Γ{sub 4}(B), and Γ{sub 5}(C) to the conduction band state of Γ{sub 1}, respectively. According to the selection rule, the crystal field and spin orbit splitting were found to be 0.2029 and 0.2154 eV, respectively, through the direct use of PC spectroscopy. However, the PC intensities decreased with lowering temperature. In the log J{sub ph} versus 1/T plot, the dominant trap level at the high-temperature region was observed and its value was 12.7 meV. This level corresponds to the activation energy for the electronic transition from the shallow donor levels to the edge of the conduction band. It is estimated that the decrease in the PC intensity is caused by trapping centers related to native defects in the BaAl{sub 2}Se{sub 4} layers. Consequently, this trap level limited the PC intensity with decreasing temperature.

  20. 69. INTERIOR VIEW OF THE ABSORPTION TOWER BUILDING, ABSORPTION TOWER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    69. INTERIOR VIEW OF THE ABSORPTION TOWER BUILDING, ABSORPTION TOWER UNDER CONSTRUCTION. (DATE UNKNOWN). - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  1. Ultratrace determination of arsenic in water samples by electrothermal atomic absorption spectrometry after pre-concentration with Mg-Al-Fe ternary layered double hydroxide nano-sorbent.

    PubMed

    Abdolmohammad-Zadeh, Hossein; Jouyban, Abolghasem; Amini, Roghayeh

    2013-11-15

    A selective solid phase extraction method, based on nano-structured Mg-Al-Fe(NO3(-)) ternary layered double hydroxide as a sorbent, is developed for the pre-concentration of ultra-trace levels of arsenic (As) prior to determination by electrothermal atomic absorption spectrometry. It is found that both As(III) and As(V) could be quantitatively retained on the sorbent within a wide pH range of 4-12. Accordingly, the presented method is applied to determination of total inorganic As in aqueous solutions. Maximum analytical signal of As is achieved when the pyrolysis and atomization temperatures are close to 900 °C and 2300 °C, respectively. Several variables affecting the extraction efficiency including pH, sample flow rate, amount of nano-sorbent, elution conditions and sample volume are optimized. Under the optimized conditions, the limit of detection (3Sb/m) and the relative standard deviation are 4.6 pg mL(-1) and 3.9%, respectively. The calibration graph is linear in the range of 15.0-650 pg mL(-1) with a correlation coefficient of 0.9979, sorption capacity and pre-concentration factor are 8.68 mg g(-1) and 300, respectively. The developed method is validated by the analysis of a standard reference material (SRM 1643e) and is successfully applied to the determination of ultra-trace amounts of As in different water samples.

  2. Size control of Au nanoparticles on TiO2 and Al2O3 by DP Urea: optical absorption and electron microscopy as control probes.

    PubMed

    Reyes-Esqueda, Jorge Alejandro; Salvador, Amado Bautista; Zanella, Rodolfo

    2008-08-01

    Gold nanoparticles supported on TiO2 and Al2O3 were prepared by using the deposition-precipitation with urea (DP Urea) method. The control of the particle size was achieved by varying both, the stirring time during the deposition-precipitation (DP) procedure and the conditions of thermal treatment. We focused mainly on the stirring time and the treatment temperature, although gas flow and type of atmosphere also influence importantly the particle's size and shape, as we shall show. The optical response of metallic nanoparticles is given by its surface plasmon resonance and its position and shape depends strongly on the size and the shape of the nanoparticle, as well as on its surrounding. Then, we followed the control of the nanoparticles size by using mainly optical absorption measurements, which gave us account of the size and the shape of the nanoparticles and the effect of the support on their optical response. These optical results were compared to, and supported with, TEM micrographs of our samples.

  3. Discovery of Galactic O iv and O v X-ray absorption due to transition temperature gas in the PKS 2155-304 spectrum

    NASA Astrophysics Data System (ADS)

    Nevalainen, J.; Wakker, B.; Kaastra, J.; Bonamente, M.; Snowden, S.; Paerels, F.; de Vries, C.

    2017-09-01

    Far-ultraviolet (FUV) observations have revealed transition temperature gas (TTG; log T(K) 5), located in the lower Galactic halo and in high-velocity clouds. However, the corresponding X-ray absorption has so far remained mostly undetected. In order to make an improvement in this respect in Galactic X-ray absorption studies, we accumulated very deep ( 3 Ms) spectra of the blazar PKS 2155-304 obtained with the spectrometers RGS1, RGS2, LETG/HRC, and LETG/ACIS-S and studied the absorption lines due to the intervening Galactic components. The very high quality of the data and coverage of important wavelengths with at least two independent instruments allowed us to reliably detect 10 Galactic lines with better than 99.75% confidence. We discovered significant absorption from blended O iv transitions 1s-2p 2S (22.571 Å), 1s-2p 2P (22.741 Å), and 1s-2p 2D (22.777 Å), and from the O v transition 1s-2p (22.370 Å) from TTG at log T(K)=5.2 ± 0.1. A joint X-ray and FUV analysis indicated that photoionisation is negligible for this component and that the gas is in a cooling transition phase. However, the temperature is high enough that the column density ratio N(O iv)/N(O v) is not significantly different from that in collisional ionisation equilibrium (CIE). Under CIE we obtained NOIV = 3.6 ± 2.0 ×1015 cm-2, corresponding to NH = 1.0 ± 0.5 ×1019(Z⊙/ZTTG) cm-2.

  4. Suppression of near-edge optical absorption band in sputter deposited HfO{sub 2}-Al{sub 2}O{sub 3} nanolaminates containing nonmonoclinic HfO{sub 2}

    SciTech Connect

    Hoppe, E. E.; Aita, C. R.

    2008-04-07

    Nanolaminates of polycrystalline (tetragonal+orthorhombic) HfO{sub 2} and amorphous Al{sub 2}O{sub 3} are sputter deposited on unheated fused SiO{sub 2}, air annealed at 573-1273 K, and analyzed by x-ray diffraction and spectrophometry. Significant O 2p{yields}Hf 5d interband absorption occurs in all films at energy E{>=}6.2 eV. For E<6.2 eV, films annealed below 1273 K retain a featureless optical absorption edge despite further crystallization. A band with a 5.65 eV onset concurrently develops with m-HfO{sub 2} crystallization after a 1273 K anneal, indicating this phase and not nanocrystallinity per se is responsible for increased absorption.

  5. Electronic and Chemical State of Aluminum from the Single- (K) and Double-Electron Excitation (KLII&III, KLI) X-ray Absorption Near-Edge Spectra of α-Alumina, Sodium Aluminate, Aqueous Al(3+)·(H2O)6, and Aqueous Al(OH)4(-).

    PubMed

    Fulton, John L; Govind, Niranjan; Huthwelker, Thomas; Bylaska, Eric J; Vjunov, Aleksei; Pin, Sonia; Smurthwaite, Tricia D

    2015-07-02

    We probe, at high energy resolution, the double electron excitation (KLII&II) X-ray absorption region that lies approximately 115 eV above the main Al K-edge (1566 eV) of α-alumina and sodium aluminate. The two solid standards, α-alumina (octahedral) and sodium aluminate (tetrahedral), are compared to aqueous species that have the same Al coordination symmetries, Al(3+)·6H2O (octahedral) and Al(OH)4(-) (tetrahedral). For the octahedral species, the edge height of the KLII&III-edge is approximately 10% of the main K-edge; however, the edge height is much weaker (3% of K-edge height) for Al species with tetrahedral symmetry. For the α-alumina and aqueous Al(3+)·6H2O the KLII&III spectra contain white line features and extended absorption fine structure (EXAFS) that mimics the K-edge spectra. The KLII&III-edge feature interferes with an important region in the EXAFS spectra of the crystalline and aqueous standards. The K-edge spectra and K-edge energy positions are predicted using time-dependent density functional theory (TDDFT). The TDDFT calculations for the K-edge X-ray absorption near-edge spectra (XANES) reproduce the observed transitions in the experimental spectra of the four Al species. The KLII&II and KLI onsets and their corresponding chemical shifts for the four standards are estimated using the delta self-consistent field (ΔSCF) method.

  6. Linear and nonlinear optical absorption coefficients and refractive index changes in GaN/Al{sub x}Ga{sub (1−x)}N double quantum wells operating at 1.55 μm

    SciTech Connect

    Dakhlaoui, Hassen

    2015-04-07

    In the present paper, the linear and nonlinear optical absorption coefficients and refractive index changes between the ground and the first excited states in double GaN/Al{sub x}Ga{sub (1−x)}N quantum wells are studied theoretically. The electronic energy levels and their corresponding wave functions are obtained by solving Schrödinger-Poisson equations self-consistently within the effective mass approximation. The obtained results show that the optical absorption coefficients and refractive index changes can be red- and blue-shifted through varying the left quantum well width and the aluminum concentration x{sub b2} of the central barrier, respectively. These structural parameters are found to present optimum values for carrying out the transition of 0.8 eV (1.55 μm). Furthermore, we show that the desired transition can also be achieved by replacing the GaN in the left quantum well with Al{sub y}Ga{sub (1−y)}N and by varying the aluminum concentration y{sub Al}. The obtained results give a new degree of freedom in optoelectronic device applications such as optical fiber telecommunications operating at (1.55 μm)

  7. Soft X-ray absorption spectroscopy of La{sub 0.7}Ca{sub 0.3}Mn{sub 1−X}Al{sub X}O{sub 3} thin films

    SciTech Connect

    Kumar, Manish Choudhary, R. J. Phase, D. M.

    2014-04-24

    Epitaxial thin films of rare earth manganites have generated much attention recently due to their rich phase diagram. The electronic structure of these films is playing a very crucial role and demands a fundamental understanding prior to device fabrication. We have investigated the electronic structure of La{sub 0.7}Ca{sub 0.3}Mn{sub 1−X}Al{sub X}O{sub 3} (X=0, 0.15) epitaxial thin films by soft X-ray absorption spectroscopy technique using the surface sensitive total electron yield (TEY) mode.

  8. Free carrier absorption in self-activated PbWO4 and Ce-doped Y3(Al0.25Ga0.75)3O12 and Gd3Al2Ga3O12 garnet scintillators

    NASA Astrophysics Data System (ADS)

    Auffray, E.; Korjik, M.; Lucchini, M. T.; Nargelas, S.; Sidletskiy, O.; Tamulaitis, G.; Tratsiak, Y.; Vaitkevičius, A.

    2016-08-01

    Nonequilibrium carrier dynamics in the scintillators prospective for fast timing in high energy physics and medical imaging applications was studied. The time-resolved free carrier absorption investigation was carried out to study the dynamics of nonequilibrium carriers in wide-band-gap scintillation materials: self-activated led tungstate (PbWO4, PWO) ant two garnet crystals, GAGG:Ce and YAGG:Ce. It was shown that free electrons appear in the conduction band of PWO and YAGG:Ce crystals within a sub-picosecond time scale, while the free holes in GAGG:Ce appear due to delocalization from Gd3+ ground states to the valence band within a few picoseconds after short-pulse excitation. The influence of Gd ions on the nonequilibrium carrier dynamics is discussed on the base of comparison the results of the free carrier absorption in GAGG:Ce containing gadolinium and in YAGG without Gd in the host lattice.

  9. Properties of impurity-bearing ferrihydrite II: Insights into the surface structure and composition of pure, Al- and Si-bearing ferrihydrite from Zn(II) sorption experiments and Zn K-edge X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Cismasu, A. Cristina; Levard, Clément; Michel, F. Marc; Brown, Gordon E.

    2013-10-01

    Naturally occurring ferrihydrite often contains impurities such as Al and Si, which can impact its chemical reactivity with respect to metal(loid) adsorption and (in)organic or microbially induced reductive dissolution. However, the surface composition of impure ferrihydrites is not well constrained, and this hinders our understanding of the factors controlling the surface reactivity of these nanophases. In this study, we conducted Zn(II) adsorption experiments combined with Zn K-edge X-ray absorption spectroscopy measurements on pure ferrihydrite (Fh) and Al- or Si-bearing ferrihydrites containing 10 and 20 mol% Al or Si (referred to as 10AlFh, 20AlFh and 10SiFh, 20SiFh) to evaluate Zn(II) uptake in relation to Zn(II) speciation at their surfaces. Overall, Zn(II) uptake at the surface of AlFh is similar to that of pure Fh, and based on Zn K-edge EXAFS data, Zn(II) speciation at the surface of Fh and AlFh also appears similar. Binuclear bidentate IVZn-VIFe complexes (at ∼3.46 Å (2C[1]) and ∼3.25 Å (2C[2])) were identified at low Zn(II) surface coverages from Zn K-edge EXAFS fits. With increasing Zn(II) surface coverage, the number of second-neighbor Fe ions decreased, which was interpreted as indicating the formation of IVZn polymers at the ferrihydrite surface, and a deviation from Langmuir uptake behavior. Zn(II) uptake at the surface of SiFh samples was more significant than at Fh and AlFh surfaces, and was attributed to the formation of outer-sphere complexes (on average 24% of sorbed Zn). Although similar Zn-Fe/Zn distances were obtained for the Zn-sorbed SiFh samples, the number of Fe second neighbors was lower in comparison with Fh. The decrease in second-neighbor Fe is most pronounced for sample 20SiFh, suggesting that the amount of reactive surface Fe sites diminishes with increasing Si content. Although our EXAFS results shown here do not provide evidence for the existence of Zn-Al or Zn-Si complexes, their presence is not excluded for Zn-sorbed Al

  10. Ab-initio computation of electronic, and transport properties of wurtzite aluminum nitride (W-AlN) and microwave absorption properties of multi-walled carbon nanotubes (outer diameter 20-30 nanometers)-epoxy composites

    NASA Astrophysics Data System (ADS)

    Nwigboji, Ifeanyi Humphrey

    In Section I, We report findings from several ab-initio, self-consistent calculations of electronic and transport properties of wurtzite aluminum nitride (w-AlN). Our calculations utilized a local density approximation (LDA) potential and the linear combination of Gaussian orbitals (LCGO). Unlike some other density functional theory (DFT) calculations, we employed the Bagayoko, Zhao, and Williams' method, enhanced by Ekuma and Franklin (BZW-EF). The BZW-EF method verifiably leads to the minima of the occupied energies; these minima, the low laying unoccupied energies, and related wave functions provide the most variationally and physically valid density functional theory (DFT) description of the ground states of materials under study. With multiple oxidation states of Al (Al3+ to Al) and the availability of N3- to N, the BZW-EF method required several sets of self-consistent calculations with different ionic species as input. The binding energy for (Al3+ & N3-) as input was 1.5 eV larger in magnitude than those for other input choices; the results discussed here are those from the calculation that led to the absolute minima of the occupied energies with this input. Our calculated, direct band gap for w-AlN, at the Gamma point, is 6.28 eV, in excellent agreement with the 6.28 eV experimental value at 5K. We discuss the bands, total and partial densities of states, and calculated, effective masses. In section II, multi-walled carbon nanotubes (MWCNTs)-epoxy composites with MWCNTs of outer diameters (OD) of 20-30nm was fabricated. The MWCNT loadings in the composites were controlled from 1-10 wt. %. An Agilent PNA Network analyzer was utilized in the measurements of microwave absorption (MA) properties of these MWCNTs-epoxy composites over a wide frequency range of 1-26.5GHz.The measurement results showed that MA strongly depends on MWCNTs loadings in the composites. In addition, the microwave reflection, transmission, and dielectric permittivity of the MWCNTs

  11. Ultraviolet absorption spectrum of HOCl

    NASA Technical Reports Server (NTRS)

    Burkholder, James B.

    1993-01-01

    The room temperature UV absorption spectrum of HOCl was measured over the wavelength range 200 to 380 nm with a diode array spectrometer. The absorption spectrum was identified from UV absorption spectra recorded following UV photolysis of equilibrium mixtures of Cl2O/H2O/HOCl. The HOCl spectrum is continuous with a maximum at 242 nm and a secondary peak at 304 nm. The measured absorption cross section at 242 nm was (2.1 +/- 0.3) x 10 exp -19/sq cm (2 sigma error limits). These results are in excellent agreement with the work of Knauth et al. (1979) but in poor agreement with the more recent measurements of Mishalanie et al. (1986) and Permien et al. (1988). An HOCl nu2 infrared band intensity of 230 +/- 35/sq cm atm was determined based on this UV absorption cross section. The present results are compared with these previous measurements and the discrepancies are discussed.

  12. Synthesis, crystal growth, structural determination, and optical absorption spectroscopy of the magnetoplumbite type compound LaNiAl 11O 19

    NASA Astrophysics Data System (ADS)

    Laville, F.; Perrin, M.; Lejus, A. M.; Gasperin, M.; Moncorge, R.; Vivien, D.

    1986-12-01

    Single crystals of LaNiAl 11O 19 have been grown from the melt using either the Verneuil flame fusion process or floating zone method. The resolution of the crystal structure indicates that this compound is of the distorted magnetoplumbite type (hexagonal {P6 3}/{mmc}) and that Ni is sheared between tetrahedral and octahedral sites of the spinel blocks. This compound has also been prepared in powdered form by annealing coprecipitates of amorphous oxides at medium temperature. The thermal evolution of the coprecipitates leading to the magnetoplumbite phase has been studied simultaneously by X-ray diffraction and diffuse reflectance spectroscopy. All the main transitions of electronic spectra of the LaNiAl 11 O 19 have been assigned. The existence of a certain amount of octahedral Ni in this material makes it a possible candidate as infrared tunable laser. This potential application will be discussed in a forthcoming paper.

  13. The absorption tunability and enhanced electromagnetic coupling of terahertz-plasmons in grating-gate AlN/GaN plasmonic device.

    PubMed

    Wang, Lin; Chen, Xiaoshuang; Hu, Weida; Yu, Anqi; Wang, Shaowei; Lu, Wei

    2013-05-06

    This paper describes the dynamic interaction between plasmons in a two dimensional electron gas system under electrical tuning to the high density regime in AlN/GaN high electron mobility transistor. The results demonstrate an enhanced resonance when the two plasmons are commonly excited, during which the potentially splitting phenomenon of such resonance is explored in detail. An asymmetrical plasmon possess wide frequency tunability has also been demonstrated in the AlN/GaN system, on the contrary, the results also indicate a finite tunable regime of symmetrical-plasmons as limited by the coupling strength between such plasmons. For the devices with narrow gate-fingers, significant near-field enhancement can be obtained due to the strong cavity pumping of electromagnetic energy. These properties may have important applications including high-responsivity quantum-dot detection systems, THz modulator etc.

  14. Atmospheric absorption of sound - Update

    NASA Technical Reports Server (NTRS)

    Bass, H. E.; Sutherland, L. C.; Zuckerwar, A. J.

    1990-01-01

    Best current expressions for the vibrational relaxation times of oxygen and nitrogen in the atmosphere are used to compute total absorption. The resulting graphs of total absorption as a function of frequency for different humidities should be used in lieu of the graph published earlier by Evans et al (1972).

  15. Electronic and chemical state of aluminum from the single- (K) and double-electron excitation (KLII&III, KLI) x-ray absorption near-edge spectra of α-alumina, sodium aluminate, aqueous Al³⁺•(H₂O)₆, and aqueous Al(OH)₄⁻

    SciTech Connect

    Fulton, John L.; Govind, Niranjan; Huthwelker, Thomas; Bylaska, Eric J.; Vjunov, Aleksei; Pin, Sonia; Smurthwaite, Tricia D.

    2015-07-02

    We probe, at high energy resolution, the double electron excitation (KLII&II) x-ray absorption region that lies approximately 115 eV above the main Al K-edge (1566 eV) of α-alumina and sodium aluminate. The two solid standards, α-alumina (octahedral) and sodium aluminate (tetrahedral) are compared to aqueous species that have the same Al coordination symmetries, Al³⁺•6H₂O (octahedral) and Al(OH)₄⁻ (tetrahedral). For the octahedral species, the edge height of the KLII&III-edge is approximately 10% of the main K-edge however the edge height is much weaker (3% of K-edge height) for Al species with tetrahedral symmetry. For the α-alumina and aqueous Al³⁺•6H₂O the KLII&III spectra contain white line features and extended absorption fine structure (EXAFS) that mimics the K-edge spectra. The KLII&III-edge feature interferes with an important region of the extended-XAFS region of the spectra for the K-edge of the crystalline and aqueous standards. The K-edge spectra and K-edge positions are predicted using time-dependent density functional theory (TDDFT). The TDDFT calculations for the K-edge XANES spectra reproduce the observed transitions in the experimental spectra of the four Al species. The KLII&III and KLI onsets and their corresponding chemical shifts for the four standards are estimated using the delta self-consistent field (ΔSCF) method. Research by JLF, NG, EJB, AV, TDS was supported by U.S. Department of Energy’s (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. NG thanks Amity Andersen for help with the α-Al₂O₃ and tetrahedral sodium aluminate (NaAlO₂) clusters. All the calculations were performed using the Molecular Science Computing Capability at EMSL, a national scientific user facility sponsored by the U.S. Department of Energy’s Office of Biological and Environmental Research and located at

  16. Origin of improved scintillation efficiency in (Lu,Gd){sub 3}(Ga,Al){sub 5}O{sub 12}:Ce multicomponent garnets: An X-ray absorption near edge spectroscopy study

    SciTech Connect

    Wu, Yuntao Luo, Jialiang; Ren, Guohao; Nikl, Martin

    2014-01-01

    In the recent successful improvement of scintillation efficiency in Lu{sub 3}Al{sub 5}O{sub 12}:Ce driven by Ga{sup 3+} and Gd{sup 3+} admixture, the “band-gap engineering” and energy level positioning have been considered the valid strategies so far. This study revealed that this improvement was also associated with the cerium valence instability along with the changes of chemical composition. By utilizing X-ray absorption near edge spectroscopy technique, tuning the Ce{sup 3+}/Ce{sup 4+} ratio by Ga{sup 3+} admixture was evidenced, while it was kept nearly stable with the Gd{sup 3+} admixture. Ce valence instability and Ce{sup 3+}/Ce{sup 4+} ratio in multicomponent garnets can be driven by the energy separation between 4f ground state of Ce{sup 3+} and Fermi level.

  17. The atomic structural dynamics of γ-Al2O3 supported Ir-Pt nanocluster catalysts prepared from a bimetallic molecular precursor: a study using aberration-corrected electron microscopy and X-ray absorption spectroscopy.

    PubMed

    Small, Matthew W; Sanchez, Sergio I; Menard, Laurent D; Kang, Joo H; Frenkel, Anatoly I; Nuzzo, Ralph G

    2011-03-16

    This study describes a prototypical, bimetallic heterogeneous catalyst: compositionally well-defined Ir-Pt nanoclusters with sizes in the range of 1-2 nm supported on γ-Al(2)O(3). Deposition of the molecular bimetallic cluster [Ir(3)Pt(3)(μ-CO)(3)(CO)(3)(η-C(5)Me(5))(3)] on γ-Al(2)O(3), and its subsequent reduction with hydrogen, provides highly dispersed supported bimetallic Ir-Pt nanoparticles. Using spherical aberration-corrected scanning transmission electron microscopy (C(s)-STEM) and theoretical modeling of synchrotron-based X-ray absorption spectroscopy (XAS) measurements, our studies provide unambiguous structural assignments for this model catalytic system. The atomic resolution C(s)-STEM images reveal strong and specific lattice-directed strains in the clusters that follow local bonding configurations of the γ-Al(2)O(3) support. Combined nanobeam diffraction (NBD) and high-resolution transmission electron microscopy (HRTEM) data suggest the polycrystalline γ-Al(2)O(3) support material predominantly exposes (001) and (011) surface planes (ones commensurate with the zone axis orientations frequently exhibited by the bimetallic clusters). The data reveal that the supported bimetallic clusters exhibit complex patterns of structural dynamics, ones evidencing perturbations of an underlying oblate/hemispherical cuboctahedral cluster-core geometry with cores that are enriched in Ir (a result consistent with models based on surface energetics, which favor an ambient cluster termination by Pt) due to the dynamical responses of the M-M bonding to the specifics of the adsorbate and metal-support interactions. Taken together, the data demonstrate that strong temperature-dependent charge-transfer effects occur that are likely mediated variably by the cluster-support, cluster-adsorbate, and intermetallic bonding interactions.

  18. A comprehensive investigation of structural, morphological, hydrogen absorption and magnetic properties of MmNi4.22Co0.48Mn0.15Al0.15 alloy

    NASA Astrophysics Data System (ADS)

    Zareii, Seyyed Mojtaba; Arabi, Hadi; Pourarian, Faiz

    2014-05-01

    A comprehensive study of structural, morphological, hydrogen absorption and magnetic properties of MmNi4.22 Co0.48Mn0.15Al0.15 alloy as a promising hydrogen storage media was investigated. The X-ray diffraction (XRD) profiles show that the alloy maintains its crystal structure (hexagonal LaNi5-type) even after 30 hydrogenation/dehydrogenation (H/D) cycles. However, the XRD peaks are found to be slightly broadened after cycling. SEM images reveal that particles size of the cycled sample decreases, with more uniform particle size distribution compared to noncycled ones. The pressure-composition (PC) isotherms and kinetics curves of hydrogen absorption reaction were obtained at different working temperatures by using a homemade Sievert apparatus. The enthalpy and entropy of hydride formation of the alloy were evaluated. Furthermore, the Jander diffusion and Johnson-Mehl-Avrami models as the fitting models were employed to study the kinetic mechanism of hydriding reaction and its activation energy. The room temperature magnetic measurements indicate that the milling and H/D cycling change the magnetic properties of the as-annealed alloy.

  19. Structure-processing correlations and mechanical properties in freeze-cast Ti-6Al-4V with highly aligned porosity and a lightweight Ti-6Al-4V-PMMA composite with excellent energy absorption capability

    DOE PAGES

    Weaver, Jordan S.; Kalidindi, Surya R.; Wegst, Ulrike G. K.

    2017-02-12

    In contrast to freeze-cast ceramics and polymers, few freeze-cast metals have been described, to date. This systematic study on structure-processing correlations in freeze-cast Ti-6Al-4V scaffolds reports how processing parameters determine the architecture formed during the directional solidification of water-based metal slurries and after sintering. Additionally, sedimentation in the slurry during freezing and volume shrinkage during burnout and sintering were found to significantly affect both structure and properties of the scaffolds. In using two freezing rates, 1 and 10 °C min-1, two water-based polymer solutions as binders (chitosan and carboxymethyl cellulose) and two different metal volume fractions in the slurry, 20more » and 30 vol%, Ti-6Al-4V scaffolds could be prepared with pore length, width, and porosity ranging from 41 to 523 μm, 14.5–76.5 μm, and 65 to 34%, respectively. Their compressive strength, stiffness, and toughness (work to 20% strain) fall in the range of 83–412 MPa, 7–29 GPa, and 14–122 MJ m-3, respectively. In order to improve the properties a select composition was infiltrated with poly(methyl methacrylate). This increased the average yield strength by a factor of 2.3 from 83 to 193 MPa and the average toughness (work to 50% strain) by a factor of 2.7 from 28.1 to 76.8 MJ m-3.« less

  20. Lifetime-Broadening-Suppressed X-ray Absorption Spectrum of β-YbAlB4 Deduced from Yb 3d → 2p Resonant X-ray Emission Spectroscopy

    NASA Astrophysics Data System (ADS)

    Kawamura, Naomi; Kanai, Noriko; Hayashi, Hisashi; Matsuda, Yasuhiro H.; Mizumaki, Masaichiro; Kuga, Kentaro; Nakatsuji, Satoru; Watanabe, Shinji

    2017-01-01

    In this work, the Yb 3d → 2p (Yb Lα1,2) resonant X-ray emission spectrum of β-YbAlB4 was acquired using excitation energies around the Yb L3-edge, at 2 K. Subsequently, the lifetime-broadening-suppressed (LBS) X-ray absorption structure (XAS) spectrum was obtained using the SIM-RIXS program. This spectrum was found to exhibit clearly resolved pre-edge and shoulder structures. Resonant Lα1 emission spectra were well reproduced from LBS-XAS profiles over wide ranges of excitation and emission energies. In contrast, noticeable discrepancies appeared between the experimental and simulated Lα2 emission spectra, suggesting an effect resulting from M4M5O1 Coster-Kronig transitions. LBS-XAS, in conjunction with partial fluorescence yield (PFY) XAS and transmission XAS, determined a value for the Yb valence (v) in β-YbAlB4 of 2.76 ± 0.08 at 2 K. Despite this relatively large uncertainty in v, each method provided a consistent variation in valence (δv) as the temperature was raised from 2 to 280 K: 0.060 ± 0.004 (LBS-XAS), 0.061 ± 0.005 (PFY-XAS) and 0.058 ± 0.007 (transmission XAS). The smaller δv associated with LBS-XAS demonstrates the greater precision of this method.

  1. Adsorption state and morphology of anthraquinone-2-carboxylic acid deposited from solution onto the atomically-smooth native oxide surface of Al(111) films studied by infrared reflection absorption spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy.

    PubMed

    Higo, Morihide; Miake, Takeshi; Mitsushio, Masaru; Yoshidome, Toshifumi; Ozono, Yoshihisa

    2008-03-01

    The adsorption state and morphology of anthraquinone-2-carboxylic acid (AQ-2-COOH) deposited from acetone solutions (0.02 - 1.00 mg ml(-1)) onto atomically-smooth native oxide surfaces of Al(111) films were investigated by infrared reflection absorption spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The atomically-smooth oxide surfaces were prepared by vacuum evaporation of Al on mica substrates at 350 degrees C, followed by oxidation in an oxygen-dc glow discharge at room temperature. It was found that AQ-2-COOH is adsorbed on the film surfaces in both the neutral and ionized state, where the amount of the neutral molecules increases with increasing concentration. This molecule is adsorbed as both a uniform nanometer-scale film, and as micrometer-sized particles with heights ranging from 10 to 200 nm above the film surface. The volumes of the particles of deposited AQ-2-COOH increased with increasing concentration. It is concluded that the particles are microcrystallites of neutral AQ-2-COOH and that the thin uniform film results from AQ-2-COOH anion formation on the film surfaces. A comparison of the results obtained by use of these surface analytical techniques clearly shows the features and advantages of these tools.

  2. Nutrient absorption.

    PubMed

    Rubin, Deborah C

    2004-03-01

    Our understanding of nutrient absorption continues to grow, from the development of unique animal models and from studies in which cutting-edge molecular and cellular biologic approaches have been used to analyze the structure and function of relevant molecules. Studies of the molecular genetics of inherited disorders have also provided many new insights into these processes. A major advance in lipid absorption has been the cloning and characterization of several intestinal acyl CoA:monoacylglycerol acyltransferases; these may provide new targets for antiobesity drug therapy. Studies of intestinal cholesterol absorption and reverse cholesterol transport have encouraged the development of novel potential treatments for hyperlipidemia. Observations in genetically modified mice and in humans with mutations in glucose transporter 2 suggest the importance of a separate microsomal membrane transport pathway for glucose transport. The study of iron metabolism has advanced greatly with the identification of the hemochromatosis gene and the continued examination of the genetic regulation of iron absorptive pathways. Several human thiamine transporters have been identified, and their specific roles in different tissues are being explored.

  3. PERITONEAL ABSORPTION

    PubMed Central

    Hahn, P. F.; Miller, L. L.; Robscheit-Robbins, F. S.; Bale, W. F.; Whipple, G. H.

    1944-01-01

    The absorption of red cells from the normal peritoneum of the dog can be demonstrated by means of red cells labeled with radio-iron incorporated in the hemoglobin of these red cells. Absorption in normal dogs runs from 20 to 100 per cent of the amount given within 24 hours. Dogs rendered anemic by bleeding absorb red cells a little less rapidly—ranging from 5 to 80 per cent of the injected red cells. Doubly depleted dogs (anemic and hypoproteinemic) absorb even less in the three experiments recorded. This peritoneal absorption varies widely in different dogs and even in the same dog at different times. We do not know the factors responsible for these variations but there is no question about active peritoneal absorption. The intact red cells pass readily from the peritoneal cavity into lymph spaces in diaphragm and other areas of the peritoneum. The red cells move along the lymphatics and through the lymph glands with little or no phagocytosis and eventually into the large veins through the thoracic ducts. PMID:19871404

  4. X-ray absorption spectroscopy, EELS, and full-potential augmented plane wave study of the electronic structure of Ti{sub 2}AlC, Ti{sub 2}AlN, Nb{sub 2}AlC, and (Ti{sub 0.5}Nb{sub 0.5}){sub 2}AlC

    SciTech Connect

    Hug, G.; Jaouen, M.; Barsoum, M.W.

    2005-01-01

    The structural parameters of various Haegg phases (H or M{sub n+1}AX{sub n} phases) are studied experimentally by x-ray and electron spectroscopies, x-ray diffraction, and ab initio full potential as well as full mutiple scattering theoretical calculations. Experimentally it was found that the structure of all ternary compounds analyzed herein are relaxed. The values of the lattice parameters and relaxations obtained from ab initio calculations are in excellent agreement with those deduced from the analysis of the experimental data. The bonding scheme has been analyzed and the charge transfer between constituting atoms determined. It is demonstrated that the strength and electrical transport properties in these materials are principally governed by the metallic planes. For the solid solution (Ti{sub 0.5}Nb{sub 0.5}){sub 2}AlC, the most salient result is that the basal planes are corrugated, which could explain the solid solution scattering observed in this H phase.

  5. High-Absorption-Efficiency Superlattice Solar Cells by Excitons

    NASA Astrophysics Data System (ADS)

    Nishinaga, Jiro; Kawaharazuka, Atsushi; Onomitsu, Koji; Horikoshi, Yoshiji

    2013-11-01

    The effect of excitonic absorption on solar cell efficiency has been investigated using solar cells with AlGaAs/GaAs superlattice structures. Numerical calculations reveal that excitonic absorption considerably enhances the overall absorption of bulk GaAs. Excitonic absorption shows strong and sharp peaks at the absorption edge and in the energy region above the band gap. Absorption enhancement is also achieved in the AlGaAs/GaAs superlattice. The measured quantum efficiency spectra of the superlattice solar cells are quite similar to the calculated absorption spectra considering the excitonic effect. The superlattice solar cells are confirmed to have high absorption coefficient compared with the GaAs and AlGaAs bulk solar cells. These results suggest that the enhanced absorption by excitons can increase the quantum efficiency of solar cells. This effect is more prominent for the solar cells with small absorption layer thicknesses.

  6. Anomalous absorption in H2CO molecule

    NASA Astrophysics Data System (ADS)

    Chandra, Suresh; Musrif, P. G.; Shinde, S. V.

    2006-03-01

    Snyder et al. (1969) detected H2 CO through its transition 110 - 111 at 4.829 GHz in absorption in the interstellar medium in a number of galactic and extragalactic sources (M17, W3, W3(OH position), W49, NGC 2024, DR 21, W43, W44, W51, Sgr A, Sgr B2, W33, NGC 6334, Cas A, and 3C 123). This transition of H2 CO was found in anomalous absorption by Palmer et al. (1969) in the direction of four dark nebulae. In some objects, this transition has however been detected in emission and even as a maser line (Forster et al. 1980; Whiteoak et al. 1983). Evans et al. (1970) reported detection of H2 CO molecule through its transition 211 - 212 at 14.488 GHz in absorption in some cosmic objects. This transition was also found in anomalous absorption by Evans et al. (1975). Since the transition 110 - 111 is considered as a unique probe of high density gas at low temperature, the study of H2 CO in cosmic objects is of great importance. Garrison et al. (1975) investigated the problem of anomalous absorption of 110 - 111 and 211 -212 transitions of H2 CO where they accounted for 8 energy levels connected by 10 radiative transitions and considered a kinetic temperature of 5 - 20 K. They found weak anomalous absorption of 110 - 111 and 211 - 212 transitions of H2 CO.

  7. ABSORPTION ANALYZER

    DOEpatents

    Brooksbank, W.A. Jr.; Leddicotte, G.W.; Strain, J.E.; Hendon, H.H. Jr.

    1961-11-14

    A means was developed for continuously computing and indicating the isotopic assay of a process solution and for automatically controlling the process output of isotope separation equipment to provide a continuous output of the desired isotopic ratio. A counter tube is surrounded with a sample to be analyzed so that the tube is exactly in the center of the sample. A source of fast neutrons is provided and is spaced from the sample. The neutrons from the source are thermalized by causing them to pass through a neutron moderator, and the neutrons are allowed to diffuse radially through the sample to actuate the counter. A reference counter in a known sample of pure solvent is also actuated by the thermal neutrons from the neutron source. The number of neutrons which actuate the detectors is a function of a concentration of the elements in solution and their neutron absorption cross sections. The pulses produced by the detectors responsive to each neu tron passing therethrough are amplified and counted. The respective times required to accumulate a selected number of counts are measured by associated timing devices. The concentration of a particular element in solution may be determined by utilizing the following relation: T2/Ti = BCR, where B is a constant proportional to the absorption cross sections, T2 is the time of count collection for the unknown solution, Ti is the time of count collection for the pure solvent, R is the isotopic ratlo, and C is the molar concentration of the element to be determined. Knowing the slope constant B for any element and when the chemical concentration is known, the isotopic concentration may be readily determined, and conversely when the isotopic ratio is known, the chemical concentrations may be determined. (AEC)

  8. Investigation of short-range structural order in Zr69.5Cu12Ni11Al7.5 and Zr41.5Ti41.5Ni17 glasses, using X-ray absorption spectroscopy and ab initio molecular dynamics simulations.

    PubMed

    Lahiri, Debdutta; Sharma, Surinder M; Verma, Ashok K; Vishwanadh, B; Dey, G K; Schumacher, Gerhard; Scherb, Tobias; Riesemeier, Heinrich; Reinholz, Uwe; Radtke, Martin; Banerjee, S

    2014-11-01

    Short-range order has been investigated in Zr69.5Cu12Ni11Al7.5 and Zr41.5Ti41.5Ni17 metallic glasses using X-ray absorption spectroscopy and ab initio molecular dynamics simulations. While both of these alloys are good glass formers, there is a difference in their glass-forming abilities (Zr41.5Ti41.5Ni17 > Zr69.5Cu12Ni11Al7.5). This difference is explained by inciting the relative importance of strong chemical order, icosahedral content, cluster symmetry and configuration diversity.

  9. Energy Absorption of Composite Materials.

    DTIC Science & Technology

    1983-03-01

    34 tion in a helicopter crash is accomplished Foye , et al. [4 an 5] examlnei th, primarily through three mechanisms; strok- energy absorption chara"tr...irar [3] and Foye , et al. [4]. No significant o. ’, energy release was obse:’viV-cirur, i m: rcg . . the Gr/FE tubes s .. 0T Fu!.A 4r /-e 45rK r5 1...K/E, GI/E, hybrid com- posite tubes and aluminum tubes. The 5. R. L. Foye , and W. T. H,.dg, " r following statements are based on results Results from

  10. Studies on the Structural Transformation of Pt Clusters with Adsorbed Hydrogen on α-Al2O3(0001) Using Multiple Scattering Approach to Pt L3-edge Polarized X-Ray Absorption Near Edge Structure Spectra for the Pt Cluster

    NASA Astrophysics Data System (ADS)

    Ohtani, Kunihiro

    1998-03-01

    The X-ray absorption near edge structure (XANES) or the Extended X-ray absorption fine structure (EXAFS) study with polarization dependence is useful for determining the structures of the metal clusters. We have calculated Pt L3-edge XANES spectra for various structures of Pt clusters with adsorbed hydrogen, such as the one-layer-thick raft, and the hemispherical and spherical structures on α-Al2O3(0001), using the full multiple scattering approach. Comparison of the calculated results with the experimental results have yielded important information. With an increase in the spherically symmetric character of Pt clusters, the influence of Pt-support interaction on the XANES spectra decreases, that is, the hydrogen-Pt interaction plays a dominant role in such cases. We expect that Pt clusters with the one-layer-thick raft, or hemispherical structures are on the top site of surface oxygen atoms.

  11. Diagnosing ALS

    MedlinePlus

    ... that a person diagnosed with ALS seek a second opinion from an ALS "expert" - someone who diagnoses and treats many ALS patients and has training in this medical specialty. The ALS Association maintains a list of recognized experts in the field of ALS. See ALS Association Certified Centers of ...

  12. Sb surfactant mediated growth of InAs/AlAs{sub 0.56}Sb{sub 0.44} strained quantum well for intersubband absorption at 1.55 μm

    SciTech Connect

    Zhao, Yu; Bertru, Nicolas; Folliot, Hervé; Perrin, Mathieu; Nicolaï, Julien; Gatel, Christophe; Warot-Fonrose, B.; Ponchet, Anne

    2015-02-23

    Surfactant mediated growth of strained InAs/AlAs{sub 0.56}Sb{sub 0.44} quantum wells on InP (001) substrate is investigated. X ray diffraction and transmission electron microscopy analysis reveal that the supply of antimony on InAs surface delays the 2D to 3D growth transition and allows the growth of thick InAs/AlAsSb quantum wells. Quantum well as thick as 7 ML, without defect was achieved by Sb surfactant mediated growth. Further high resolution transmission electron microscopy measurement and geometric phase analysis show that InAs/AlAsSb interfaces are not abrupt. At InAs on AlAsSb interface, the formation of a layer presenting lattice parameter lower than InP leads to a tensile stress. From energetic consideration, the formation of As rich AlAsSb layer at interface is deduced. At AlAsSb on InAs interface, a compressive layer is formed. The impact on optical properties and the chemical composition of this layer are discussed from microscopic analysis and photoluminescence experiments.

  13. Light Absorption By Coated Soot

    NASA Astrophysics Data System (ADS)

    Sedlacek, A. J.; Lee, J.; Onasch, T. B.; Davidovits, P.; Cross, E. S.

    2009-12-01

    The contribution of aerosol absorption on direct radiative forcing is still an active area of research, in part, because aerosol extinction is dominated by light scattering and, in part, because the primary absorbing aerosol of interest, soot, exhibits complex aging behavior that alters its optical properties. The consequences of this can be evidenced by the work of Ramanathan and Carmichael (2008) who suggest that incorporating the atmospheric heating due to brown clouds will increase black carbon (BC) radiative forcing from the IPCC best estimate of 0.34 Wm-2 (±0.25 Wm-2) (IPCC 2007) to 0.9 Wm-2. This noteworthy degree of the uncertainty is due largely to the interdependence of BC optical properties on particle mixing state and aggregate morphology, each of which changes as the particle ages in the atmosphere and becomes encapsulated within a coating of inorganic and/or organic substances. With the advent of techniques that can directly measure aerosol light absorption without influences due to collection substrate or light scattering (e.g., photoacoustic spectroscopy (Arnott et al., 2005; Lack et al., 2006) and photothermal interferometry (Sedlacek and Lee 2007)) the potential exists for quantifying this interdependence. In July 2008, a laboratory-based measurement campaign, led by Boston College and Aerodyne, was initiated to begin addressing this interdependence. To achieve this objective measurements of both the optical and physical properties of flame-generated soot under nascent, coated and denuded conditions were conducted. In this paper, light absorption by dioctyl sebacate (DOS) encapsulated soot and sulfuric acid coated soot using the technique of photothermal interferometry will be presented. In the case of DOS-coated soot, a monotonic increase in light absorption as a function DOS coating thickness to nearly 100% is observed. This observation is consistent with a coating-induced amplification in particle light absorption. (Bond et al. 2006) However

  14. Theory of absorption-induced transparency

    NASA Astrophysics Data System (ADS)

    Rodrigo, Sergio G.; Martín-Moreno, L.

    2014-09-01

    Absorption induced transparency consists in a transmission peak observed in holey metal films when a molecular dye is deposited on top of it [Hutchison et al., Angew. Chem. Int. Ed. 50, 2085 (2011)]. This transmission feature appears unexpectedly close to one of the absorption energies of the molecules, hence its name. Tentative explanations pointed to strong-coupling interactions between plasmons and molecules. However, we recently demonstrated the actual mechanism behind, which takes place through a strong modification of the propagation constant of holes. We also found that absorption induced transparency occurs in single holes and it is not restricted to the optical range.

  15. ALS Association

    MedlinePlus

    ... toward a world without ALS! Walk to Defeat ALS® Walk to Defeat ALS® draws people of all ... We need your help. I Will Advocate National ALS Registry The National ALS Registry is a congressionally ...

  16. Absorption-Line Studies of Seyfert Galaxies

    NASA Astrophysics Data System (ADS)

    Shull, J. Michael

    We propose to undertake a "reverberation analysis" of the variable absorption lines ill two Seyfert Galaxies (NGC 4051 and Mrk 279) to help understand the origin of intrinsic absorption lines in AGNs. Stich an analysis is a powerful tool for elucidating the radial distribution of absorbing gas in the broad-line region (BLR) and narrow-line region (NLR). Only two Seyferts have previously been studied with this technique: NGC 4151 (Bromage el al. 1985; Clavel et al. 1987) and NGC 3516 (Voit, Shull, and Begelman 1987). The absorption features have been interpreted as an outflow of ionized clouds from the nuclear region or from an accretion disk affected by UV/X-ray heating. Neither the source of the absorbing gas in these Seyferts nor the "gene" which distingishes them from other Seyferts is known. Until the 1984 onset of absorption in Mrk 279, broad self-absorbed. lines had been observed only in Seyferts of low intrinsic luminosity, such as NGC 4051. Mrk 279 is intrinsically much brighter, and therefore more quasar-like, than the other three absorptionline Seyfert I's in the CfA sample. Thus, it may show how the absorption phenomenon changes at higher luminosity and could bridge the gap between the low luminosity absorption-line Seyferts and the well-studied broad absorption-line (BAL) QSO's. In addition, Mrk 279's significant redshift will allow us to study, for the first time, the Ly-alpha line in an absorption-line Seyfert. With 3 US-1 shifts for each of these two underobserved Seyferts, we can double the number of objects in which absorption-line variability has been studied and investigate why the absorption-line strengths correlate or anti-correlate with the UV continuum.

  17. The difficulty of measuring the absorption of scattered sunlight by H2O and CO2 in volcanic plumes: A comment on Pering et al. “A novel and inexpensive method for measuring volcanic plume water fluxes at high temporal resolution,” Remote Sens. 2017, 9, 146

    USGS Publications Warehouse

    Kern, Christoph

    2017-01-01

    In their recent study, Pering et al. (2017) presented a novel method for measuring volcanic water vapor fluxes. Their method is based on imaging volcanic gas and aerosol plumes using a camera sensitive to the near-infrared (NIR) absorption of water vapor. The imaging data are empirically calibrated by comparison with in situ water measurements made within the plumes. Though the presented method may give reasonable results over short time scales, the authors fail to recognize the sensitivity of the technique to light scattering on aerosols within the plume. In fact, the signals measured by Pering et al. are not related to the absorption of NIR radiation by water vapor within the plume. Instead, the measured signals are most likely caused by a change in the effective light path of the detected radiation through the atmospheric background water vapor column. Therefore, their method is actually based on establishing an empirical relationship between in-plume scattering efficiency and plume water content. Since this relationship is sensitive to plume aerosol abundance and numerous environmental factors, the method will only yield accurate results if it is calibrated very frequently using other measurement techniques.

  18. Platinum Inhibits Low-Temperature Dry Lean Methane Combustion through Palladium Reduction in Pd-Pt/Al2 O3 : An In Situ X-ray Absorption Study.

    PubMed

    Nassiri, Hanieh; Lee, Kee-Eun; Hu, Yongfeng; Hayes, Robert E; Scott, Robert W J; Semagina, Natalia

    2017-01-18

    Palladium-platinum bimetallic catalysts supported on alumina with palladium/platinum molar ratios ranging from 0.25 to 4 are studied in dry lean methane combustion in the temperature range of 200 to 500 °C. Platinum addition decreases the catalyst activity, which cannot be explained by the decrease in dispersion or the structure sensitivity of the reaction. In situ X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopy measurements have been conducted for monometallic Pd, Pt, and 2:1 Pd-Pt catalysts. Monometallic palladium is fully oxidized in the full temperature range, whereas platinum addition promotes palladium reduction, even in a reactive oxidizing environment. The Pd/PdO weight ratio in bimetallic Pd-Pt 2:1 catalysts decreases from 98/2 to 10/90 in the 200-500 °C temperature range under the reaction conditions. Thus, platinum promotes the formation of the reduced palladium phase with a significantly lower activity than that of oxidized palladium. The study sheds light on the effect of platinum on the state of the active palladium surface under low-temperature dry lean methane combustion conditions, which is important for methane-emission control devices. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. A search for intervening HI absorption

    NASA Astrophysics Data System (ADS)

    Reeves, Sarah N.; Sadler, Elaine M.; Allison, James R.; Koribalski, Baerbel S.; Curran, Stephen J.

    2013-03-01

    HI absorption-line studies provide a unique probe of the gas distribution and kinematics in galaxies well beyond the local universe (z ≳ 0.3). HI absorption-line surveys with next-generation radio telescopes will provide the first large-scale studies of HI in a redshift regime which is poorly understood. However, we currently lack the understanding to infer galaxy properties from absorption-line observations alone. To address this issue, we are conducting a search for intervening HI absorption in a sample of 20 nearby galaxies. Our aim is to investigate how the detection rate varies with distance from the galaxy. We target sight-lines to bright continuum sources, which intercept known gas-rich galaxies, selected from the HIPASS Bright Galaxy Catalogue (Koribalski et al. 2004). In our pilot sample, six galaxies with impact parameters < 20 kpc, we do not detect any absorption lines - although all are detected in 21cm emission. This indicates that an absorption non-detection cannot simply be interpreted as an absence of neutral gas - see Fig. 1. Our detection rate is low compared to previous surveys e.g. Gupta et al. (2010). This is, at least partially, due to the high resolution of the observations reducing the flux of the background source, which will also be an issue in future surveys, such as ASKAP-FLASH.

  20. [Study on lead absorption in pumpkin by atomic absorption spectrophotometry].

    PubMed

    Li, Zhen-Xia; Sun, Yong-Dong; Chen, Bi-Hua; Li, Xin-Zheng

    2008-07-01

    A study was carried out on the characteristic of lead absorption in pumpkin via atomic absorption spectrophotometer. The results showed that lead absorption amount in pumpkin increased with time, but the absorption rate decreased with time; And the lead absorption amount reached the peak in pH 7. Lead and cadmium have similar characteristic of absorption in pumpkin.

  1. Picosecond excite-and-probe absorption measurement of the intra-2E(g)E(3/2)-state vibrational relaxation time in Ti(3+):Al2O3

    NASA Technical Reports Server (NTRS)

    Gayen, S. K.; Wang, W. B.; Petricevic, V.; Yoo, K. M.; Alfano, R. R.

    1987-01-01

    The Ti(3+)-doped Al2O3 has been recently demonstrated to be a tunable solid-state laser system with Ti(3+) as the laser-active ion. In this paper, the kinetics of vibrational transitions in the 2E(g)E(3/2) electronic state of Ti(3+):Al2O3a (crucial for characterizing new host materials for the Ti ion) was investigated. A 527-nm 5-ps pulse was used to excite a band of higher vibrational levels of the 2E(g)E(3/2) state, and the subsequent growth of population in the zero vibrational level and lower vibrational levels was monitored by a 3.9-micron picosecond probe pulse. The time evolution curve in the excited 2E(g)E(3/2) state at room temperature was found to be characterized by a sharp rise followed by a long decay, the long lifetime decay reflecting the depopulation of the zero and the lower vibrational levels of the 2E(g)E(3/2) state via radiative transitions. An upper limit of 3.5 ps was estimated for intra-2E(g)E(3/2)-state vibrational relaxation time.

  2. Picosecond excite-and-probe absorption measurement of the intra-2E(g)E(3/2)-state vibrational relaxation time in Ti(3+):Al2O3

    NASA Technical Reports Server (NTRS)

    Gayen, S. K.; Wang, W. B.; Petricevic, V.; Yoo, K. M.; Alfano, R. R.

    1987-01-01

    The Ti(3+)-doped Al2O3 has been recently demonstrated to be a tunable solid-state laser system with Ti(3+) as the laser-active ion. In this paper, the kinetics of vibrational transitions in the 2E(g)E(3/2) electronic state of Ti(3+):Al2O3a (crucial for characterizing new host materials for the Ti ion) was investigated. A 527-nm 5-ps pulse was used to excite a band of higher vibrational levels of the 2E(g)E(3/2) state, and the subsequent growth of population in the zero vibrational level and lower vibrational levels was monitored by a 3.9-micron picosecond probe pulse. The time evolution curve in the excited 2E(g)E(3/2) state at room temperature was found to be characterized by a sharp rise followed by a long decay, the long lifetime decay reflecting the depopulation of the zero and the lower vibrational levels of the 2E(g)E(3/2) state via radiative transitions. An upper limit of 3.5 ps was estimated for intra-2E(g)E(3/2)-state vibrational relaxation time.

  3. ALS - resources

    MedlinePlus

    Resources - ALS ... The following organizations are good resources for information on amyotrophic lateral sclerosis : Muscular Dystrophy Association -- www.mda.org/disease/amyotrophic-lateral-sclerosis National Amyotrophic Lateral Sclerosis (ALS) ...

  4. The oscillator strength in atomic absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Hannaford, P.

    1994-12-01

    The role of the oscillator strength, f, in the theory of atomic absorption is investigated. For a pure natural broadened absorption line, the peak absorption coefficient α o is independent of the oscillator strength. The peak absorption coefficient becomes dependent on f only through additional broadening processes such as Doppler or collisional broadening. The peak cross section for resonance absorption, α 0/ N1, for a closed transition with equal statistical weights is given by σ 0 = 2πXXX 2 = ( 2/π)/[c n(ω 0)] (where XXX = λ/2π and n(ω 0) is the spectral mode density of the radiation field at the resonance frequency ω 0) and physically represents the cross-sectional area per allowed mode of the radiation field per unit time per unit frequency interval, multiplied by a lineshape factor 2/π. A summary is presented of some recent determinations of oscillator strengths of atomic absorption lines, based on lifetime measurements made in this laboratory. The results are used to revise values of the theoretical characteristic mass for Ag, Al, Au, Ca, Cu, Mo, Na, Ti and V used in absolute analysis by graphite furnace atomic absorption spectroscopy.

  5. Ultraviolet interstellar absorption lines from low-z galaxies

    NASA Astrophysics Data System (ADS)

    Sahu, M. S.

    1997-05-01

    The importance of studying absorption lines from z<<0.1 galaxies are discussed. The Mg II λλ2796 and 2803 Å doublet absorption is sensitive to low column density gas and has been used to search for absorption lines from low-z galaxies. Recent studies of abundances and depletion patterns toward the Small Magellanic Cloud (Welty et al. 1997) and the NGC 1705 sightline (Sahu & Blades, 1997) are reviewed.

  6. A Lithium Bromide Absorption Chiller with Cold Storage

    DTIC Science & Technology

    2011-01-15

    TO R A G E A LITHIUM BROMIDE ABSORPTION CHILLER WITH COLD STORAGE William Gerstler, et al, General Electric Global Research UNCLASSIFIED UNLIMITED...Research ABSTRACT A LiBr-based absorption chiller can use waste heat or solar energy to produce useful space cooling for small buildings...However, operating this absorption chiller at high ambient tem- peratures may result in performance degradation, crystallization in the absorber, and

  7. Adsorption studies of Cd(II) onto Al 2O 3/Nb 2O 5 mixed oxide dispersed on silica matrix and its on-line preconcentration and determination by flame atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Mendonça Costa, Lucimara; Ribeiro, Emerson Schwingel; Segatelli, Mariana Gava; do Nascimento, Danielle Raphael; de Oliveira, Fernanda Midori; Tarley, César Ricardo Teixeira

    2011-05-01

    The present study describes the adsorption characteristic of Cd(II) onto Nb 2O 5/Al 2O 3 mixed oxide dispersed on silica matrix. The characterization of the adsorbent has been carried out by infrared spectroscopy (IR), scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), energy dispersive X-ray fluorescence analysis (EDXRF) and specific surface area ( SBET). From batch experiments, adsorption kinetic of Cd(II) was described by a pseudo-second-order kinetic model. The Langmuir linear isotherm fitted to the experimental adsorption isotherm very well, and the maximum adsorption capacity was found to be 17.88 mg g -1. Using the effective material, a method for Cd(II) preconcentration at trace level was developed. The method was based on on-line adsorption of Cd(II) onto SiO 2/Al 2O 3/Nb 2O 5 at pH 8.64, in which the quantitative desorption occurs with 1.0 mol L -1 hydrochloric acid towards FAAS detector. The experimental parameters related to the system were studied by means of multivariate analysis, using 2 4 full factorial design and Doehlert matrix. The effect of SO 42-, Cu 2+, Zn 2+ and Ni 2+ foreign ions showed no interference at 1:100 analyte:interferent proportion. Under the most favorable experimental conditions, the preconcentration system provided a preconcentration factor of 18.4 times, consumption index of 1.08 mL, sample throughput of 14 h -1, concentration efficiency of 4.35 min -1, linear range from 5.0 up to 35.0 μg L -1 and limits of detection and quantification of 0.19 and 0.65 μg L -1 respectively. The feasibility of the proposed method for Cd(II) determination was assessed by analysis of water samples, cigarette sample and certified reference materials TORT-2 (Lobster hepatopancreas) and DOLT-4 (Dogfish liver).

  8. Solar absorption surface panel

    DOEpatents

    Santala, Teuvo J.

    1978-01-01

    A composite metal of aluminum and nickel is used to form an economical solar absorption surface for a collector plate wherein an intermetallic compound of the aluminum and nickel provides a surface morphology with high absorptance and relatively low infrared emittance along with good durability.

  9. Rectal absorption of propylthiouracil.

    PubMed

    Bartle, W R; Walker, S E; Silverberg, J D

    1988-06-01

    The rectal absorption of propylthiouracil (PTU) was studied and compared to oral absorption in normal volunteers. Plasma levels of PTU after administration of suppositories of PTU base and PTU diethanolamine were significantly lower compared to the oral route. Elevated plasma reverse T3 levels were demonstrated after each treatment, however, suggesting a desirable therapeutic effect at this dosage level for all preparations.

  10. Petawatt laser absorption bounded

    PubMed Central

    Levy, Matthew C.; Wilks, Scott C.; Tabak, Max; Libby, Stephen B.; Baring, Matthew G.

    2014-01-01

    The interaction of petawatt (1015 W) lasers with solid matter forms the basis for advanced scientific applications such as table-top particle accelerators, ultrafast imaging systems and laser fusion. Key metrics for these applications relate to absorption, yet conditions in this regime are so nonlinear that it is often impossible to know the fraction of absorbed light f, and even the range of f is unknown. Here using a relativistic Rankine-Hugoniot-like analysis, we show for the first time that f exhibits a theoretical maximum and minimum. These bounds constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. For applications needing to circumvent the absorption bounds, these results will accelerate a shift from solid targets, towards structured and multilayer targets, and lead the development of new materials. PMID:24938656

  11. [Study on cadmium absorption in pumpkin by atomic absorption spectrophotometry].

    PubMed

    Li, Zhen-Xia; Jing, Rui-Jun; Dong, Wei-Hua; Li, Xin-Zheng; Liu, Hong

    2006-08-01

    A study was carried out on the characteristic of cadmium absorption in pumpkin by atomic absorption spectrophotometer. The results show that the cadmium absorption amount in pumpkin increased with the increase in cadmium concentration. Meanwhile the cadmium absorption amount in pumpkin increased with time. Eight hours after being cultured in the liquid, the cadmium absorption amount became saturated. The cadmium absorption rate reached the peak after 2 hours, then the absorption rate gradually reduced. The cadmium absorption amount in pumpkin is less in acid or alkali compared with neutral condition. And the absorption amount became minimum in pH 3, while maximum in pH 7.

  12. Solvent effects on the absorption and emission spectra of novel (E)-4-((4-(heptyloxy)phenyl)diazenyl)benzyl (((9H-fluoren-9-yl)methoxy)carbonyl)-D-alaninate (Fmoc-al-az): Determination of dipole moment by experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Y, Tej Varma; Agarwal, Devesh S.; Sarmah, Amrit; Joshi, Lata; Sakhuja, Rajeev; Pant, Debi D.

    2017-02-01

    Amino acid appended azobenzene hybrid has been synthesized (Fmoc-al-az) and its electronic absorbance and fluorescence spectra were recorded at room temperature in a series of polar and non-polar solvents. The ground state and excited state dipole moments were calculated using solvatochromic shift method. A DFT based study was also performed using- Gaussian09 program package. We have observed that the absorption spectra don't show sensitive behavior to the change in the polarity of the solvent, whereas a bathochromic shift was observed in the fluorescence spectra as we moved from non-polar to polar solvents indicating a π→π* transition. It was observed that the dipole moment in the excited state is much higher than the ground state, due to the amino acid containing hydrogen bond acceptor (Osbnd Cdbnd O) and hydrogen bond donor (sbnd NH) in Fmoc-al-az increasing the reorientation tendency of the solvent molecule around the dye therefore enhancing the stabilization of the excited state which is attributed to the high polarity of the excited states. DFT level electronic structure calculations are also performed for a better molecular level understanding of the experimental observations. We obtained a good correlation between the theoretical studies and experimental results.

  13. Resonant enhancement of second order sideband generation for intraexcitonic transitions in GaAs/AlGaAs multiple quantum wells

    NASA Astrophysics Data System (ADS)

    Wagner, M.; Schneider, H.; Winnerl, S.; Helm, M.; Roch, T.; Andrews, A. M.; Schartner, S.; Strasser, G.

    2009-06-01

    We present an experimental study on efficient second order sideband generation in symmetric undoped GaAs/AlGaAs multiple quantum wells. A near-infrared laser tuned to excitonic interband transitions is mixed with an in-plane polarized terahertz beam from a free-electron laser. The terahertz beam is tuned either to the intraexcitonic heavy-hole 1s-2p transition or to the interexcitonic heavy-hole light-hole transition. We find strong evidence that the intraexcitonic transition is of paramount influence on n =±2 sideband generation, leading to an order-of-magnitude resonant enhancement of the conversion efficiency up to 0.1% at low temperature. At room temperature, the efficiency drops only by a factor of 7 for low terahertz powers.

  14. Local relaxation around [6]Cr3+ in synthetic pyrope knorringite garnets, [8]Mg3[6](Al1-X CrX3+)2[4]Si3O12, from electronic absorption spectra

    NASA Astrophysics Data System (ADS)

    Taran, M. N.; Langer, K.; Abs-Wurmbach, I.; Frost, D. J.; Platonov, A. N.

    2004-12-01

    Pyrope-knorringite garnets, Mg3(Al1-X Cr3+X)2Si3O12 with X=0.25, 0.50, and 1.00, were synthesized between 9 and 16 GPa and 1300 and 1600 °C, using multianvil high-pressure techniques. The garnets with X=0.25 and 0.50 are fine-grained, pink and violet in color. The end-member knorringites with X=1.00 are black when compact and gray when coarse-grained. The fine powder is greenish gray in natural light and pale pink under a tungsten lamp. Powder remission spectra in the wavenumber range 30 000 10 000 cm-1 on finely powdered crystals were measured by two different methods: (I.) by the use of a small integrating sphere for small samples or (II.) microscope-spectrometric measurement using diffusely reflected radiation from a 45° illuminated microsample. Both methods yielded similar diffuse reflectance spectra. The following crystal-field parameters of [6]Cr3+ were determined for garnets with X=0.25, 0.50, 1.00: 10 Dq=17 856, 17 596, 17 286 cm-1; and B=654, 677, 706 cm-1; nephelauxetic ratio β=(Bfield/Bfree)= 0.71, 0.74, 0.77. The β-values indicate decreasing covalency of the Cr O bond with increasing Cr content. The 10 Dq value for together with the mean Cr O distance in end-member knorringite, 1.96 Å (Novak and Gibbs 1971), were used to calculate from the spectral data, local mean Cr O distances (Langer 2001a) as a function of composition. The results indicate relatively strong local site relaxation with a value of ɛ=0.77.

  15. XUV Absorption by Solid Density Aluminum

    SciTech Connect

    Iglesias, C A

    2009-09-21

    An inverse bremsstrahlung model for plasmas and simple metals that approximates the cold, solid Al experimental data below the L-edge is applied to matter conditions relevant to XUV laser applications. The model involves an all-order calculation using a semi-analytical effective electron-ion interaction. The predicted increases in XUV absorption with rising temperature occur via two effects: increased availability of final states from reduced electron degeneracy and a stronger electron-ion interaction from reduced screening. Discrepancies in the temperature dependence as well as other details between the present approach and a recently proposed absorption model are discussed.

  16. Quasar Absorption Studies

    NASA Technical Reports Server (NTRS)

    Mushotzky, Richard (Technical Monitor); Elvis, Martin

    2004-01-01

    The aim of the proposal is to investigate the absorption properties of a sample of inter-mediate redshift quasars. The main goals of the project are: Measure the redshift and the column density of the X-ray absorbers; test the correlation between absorption and redshift suggested by ROSAT and ASCA data; constrain the absorber ionization status and metallicity; constrain the absorber dust content and composition through the comparison between the amount of X-ray absorption and optical dust extinction. Unanticipated low energy cut-offs where discovered in ROSAT spectra of quasars and confirmed by ASCA, BeppoSAX and Chandra. In most cases it was not possible to constrain adequately the redshift of the absorber from the X-ray data alone. Two possibilities remain open: a) absorption at the quasar redshift; and b) intervening absorption. The evidences in favour of intrinsic absorption are all indirect. Sensitive XMM observations can discriminate between these different scenarios. If the absorption is at the quasar redshift we can study whether the quasar environment evolves with the Cosmic time.

  17. Percutaneous absorption of arsenic from environmental media.

    PubMed

    Lowney, Yvette W; Ruby, Michael V; Wester, Ronald C; Schoof, Rosalind A; Holm, Stewart E; Hui, Xiao-Ying; Barbadillo, Sherry; Maibach, Howard I

    2005-03-01

    Current knowledge of percutaneous absorption of arsenic is based on studies of rhesus monkeys using soluble arsenic in aqueous solution, and soluble arsenic mixed with soil (Wester et al., 1993). These studies produced mean dermal absorption rates in the range of 2.0-6.4% of the applied dose. Subsequently, questions arose as to whether these results represent arsenic absorption from environmental media. Factors such as chemical interactions, the presence of other metals, and the effects of weathering on environmental media all can affect the nature of arsenic and its potential for percutaneous absorption. Therefore, research specific to more relevant matrices is important. The focus of this effort is to outline study design considerations, including particle size, application rates, means of ensuring skin contact and appropriate statistical evaluation of the data. Appropriate reference groups are also important. The potential for background exposure to arsenic in the diet possibly obscuring a signal from a dermally applied dose of arsenic will also be addressed. We conclude that there are likely to be many site- or sample-specific factors that will control the absorption of arsenic, and matrix-specific analyses may be required to understand the degree of percutaneous absorption.

  18. Water-related absorption in fibrous diamonds

    NASA Astrophysics Data System (ADS)

    Zedgenizov, D. A.; Shiryaev, A. A.; Kagi, H.; Navon, O.

    2003-04-01

    Cubic and coated diamonds from several localities (Brasil, Canada, Yakutia) were investigated using spectroscopic techniques. Special emphasis was put on investigation of water-related features of transmission Infra-red and Raman spectra. Presence of molecular water is inferred from broad absorption bands in IR at 3420 and 1640 cm-1. These bands were observed in many of the investigated samples. It is likely that molecular water is present in microinclusions in liquid state, since no clear indications of solid H_2O (ice VI-VII, Kagi et al., 2000) were found. Comparison of absorption by HOH and OH vibrations shows that diamonds can be separated into two principal groups: those containing liquid water (direct proportionality of OH and HOH absorption) and those with stronger absorption by OH group. Fraction of diamonds in every group depends on their provenance. There might be positive correlation between internal pressure in microinclusions (determined using quartz barometer, Navon et al., 1988) and affiliation with diamonds containing liquid water. In many cases absorption by HOH vibration is considerably lower than absorption by hydroxyl (OH) group. This may be explained if OH groups are partially present in mineral and/or melt inclusions. This hypothesis is supported by following fact: in diamonds with strong absorption by silicates and other minerals shape and position of the OH band differs from that in diamonds with low absorption by minerals. Moreover, in Raman spectra of individual inclusions sometimes the broad band at 3100 cm-1 is observed. This band is OH-related. In some samples water distribution is not homogeneous. Central part of the diamond usually contains more water than outer parts, but this is not a general rule for all the samples. Water absorption usually correlated with absorption of other components (carbonates, silicates and others). At that fibrous diamonds with relatively high content of silicates are characterized by molecular water. OH

  19. Absorption heat pump system

    DOEpatents

    Grossman, Gershon

    1984-01-01

    The efficiency of an absorption heat pump system is improved by conducting liquid from a second stage evaporator thereof to an auxiliary heat exchanger positioned downstream of a primary heat exchanger in the desorber of the system.

  20. Absorption heat pump system

    DOEpatents

    Grossman, G.

    1982-06-16

    The efficiency of an absorption heat pump system is improved by conducting liquid from a second stage evaporator thereof to an auxiliary heat exchanger positioned downstream of a primary heat exchanger in the desorber of the system.

  1. Compounds affecting cholesterol absorption

    NASA Technical Reports Server (NTRS)

    Hua, Duy H. (Inventor); Koo, Sung I. (Inventor); Noh, Sang K. (Inventor)

    2004-01-01

    A class of novel compounds is described for use in affecting lymphatic absorption of cholesterol. Compounds of particular interest are defined by Formula I: ##STR1## or a pharmaceutically acceptable salt thereof.

  2. Soliton absorption spectroscopy

    PubMed Central

    Kalashnikov, V. L.; Sorokin, E.

    2010-01-01

    We analyze optical soliton propagation in the presence of weak absorption lines with much narrower linewidths as compared to the soliton spectrum width using the novel perturbation analysis technique based on an integral representation in the spectral domain. The stable soliton acquires spectral modulation that follows the associated index of refraction of the absorber. The model can be applied to ordinary soliton propagation and to an absorber inside a passively modelocked laser. In the latter case, a comparison with water vapor absorption in a femtosecond Cr:ZnSe laser yields a very good agreement with experiment. Compared to the conventional absorption measurement in a cell of the same length, the signal is increased by an order of magnitude. The obtained analytical expressions allow further improving of the sensitivity and spectroscopic accuracy making the soliton absorption spectroscopy a promising novel measurement technique. PMID:21151755

  3. Optical absorption measurement system

    DOEpatents

    Draggoo, Vaughn G.; Morton, Richard G.; Sawicki, Richard H.; Bissinger, Horst D.

    1989-01-01

    The system of the present invention contemplates a non-intrusive method for measuring the temperature rise of optical elements under high laser power optical loading to determine the absorption coefficient. The method comprises irradiating the optical element with a high average power laser beam, viewing the optical element with an infrared camera to determine the temperature across the optical element and calculating the absorption of the optical element from the temperature.

  4. Solar selective absorption coatings

    DOEpatents

    Mahoney, Alan R.; Reed, Scott T.; Ashley, Carol S.; Martinez, F. Edward

    2003-10-14

    A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.

  5. Solar selective absorption coatings

    DOEpatents

    Mahoney, Alan R.; Reed, Scott T.; Ashley, Carol S.; Martinez, F. Edward

    2004-08-31

    A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.

  6. Intranasal absorption of oxymorphone.

    PubMed

    Hussain, M A; Aungst, B J

    1997-08-01

    The nasal bioavailability of oxymorphone HCI was determined. Rats were surgically prepared to isolate the nasal cavity, into which a solution of oxymorphone was administered. A reference group of rats was administered oxymorphone HCl intravenously. Plasma oxymorphone concentrations were determined by HPLC. Nasal absorption was rapid, nasal bioavailability was 43%, and the iv and nasal elimination profiles were similar. Oxymorphone HCI appears to have the solubility, potency, and absorption properties required for efficient nasal delivery, which is an alternative to injections.

  7. High Temperature in Absorption Measurements.

    DTIC Science & Technology

    1981-09-01

    drives a laser-supported detonation (LSD) wave into the A1 w I-r cow 0. U) z ~Ll N wi N Cl, 0 z 2- Z LU-4 00 0.0 w IL >- z U I -4 CLL0 0 44 CCOw . z C/z...of liquid water at 5 1 1 7 -5 H !4 E0;’.- ’VTY OF vi7ER VADCR" TC-_ 1011~W 1 [ Il .. * ... , ICm .AYg DI - . . ,0 0 : ~L ’ --- ,oo., ,"I~ i 1:, ,. 2a...T-OK Fig. 31 UTRC4 calculated NH3 absorption coefficient. 51 S -AL. 8.8 x 10" 20R2 I a Th where a is in cm2 , R is in cm and Th is in dynes, while t

  8. Seven-effect absorption refrigeration

    DOEpatents

    DeVault, R.C.; Biermann, W.J.

    1989-05-09

    A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit. 1 fig.

  9. Seven-effect absorption refrigeration

    DOEpatents

    DeVault, Robert C.; Biermann, Wendell J.

    1989-01-01

    A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit.

  10. WAVELENGTH MEASUREMENTS OF K TRANSITIONS OF OXYGEN, NEON, AND MAGNESIUM WITH X-RAY ABSORPTION LINES

    SciTech Connect

    Liao Jinyuan; Zhang Shuangnan; Yao Yangsen

    2013-09-10

    Accurate atomic transition data are important in many astronomical research areas, especially for studies of line spectroscopy. Whereas transition data of He-like and H-like ions (i.e., ions in high-charge states) have been accurately calculated, the corresponding data of K transitions of neutral or low-ionized metal elements are still very uncertain. Spectroscopy of absorption lines produced in the interstellar medium (ISM) has been proven to be an effective way to measure the central wavelengths of these atomic transitions. In this work, we analyze 36 Chandra High Energy Transmission Grating observations to search for and measure the ISM absorption lines along sight lines to 11 low-mass X-ray binaries. We correct the Galactic rotation velocity to the rest frame for every observation and then use two different methods to merge all the corrected spectra to a co-added spectrum. However, the co-added spectra obtained by this method exhibit biases, toward to either observations with high counts or lines with high signal-to-noise ratios. We do a Bayesian analysis of several significantly detected lines to obtain the systematic uncertainty and the bias correction for other lines. Compared to previous studies, our results improve the wavelength accuracy by a factor of two to five and significantly reduce the systematic uncertainties and biases. Several weak transitions (e.g., 1s-2p of Mg IV and Mg V; 1s-3p of Mg III and Mg V) are also detected for the first time, albeit with low significance; future observations with improved accuracy are required to confirm these detections.

  11. Intestinal absorption of aluminium in renal failure.

    PubMed

    Drüeke, Tilman B

    2002-01-01

    The proportion of the daily ingested aluminium that is absorbed in the intestinal tract has remained a matter of debate for many years because no reliable method of measurement was available. Studies with earlier analytic techniques reported fractional absorption of aluminium from as little as 0.001% to as much as 27% of an oral dose. Measurement of (26)Al by high-energy accelerator mass spectrometry has permitted more accurate analyses. In normal young rats, 0.05-0.1% of ingested aluminium is absorbed in the intestine, of which roughly half goes to the skeleton within 2 h, whereas the remaining half is excreted in the urine, most of it within 48 h. Deposition in organs other than the skeleton appears to be negligible. In healthy human volunteers, the most recent estimates of fractional intestinal (26)Al absorption were also in the range of 0.06-0.1%. In both rats and humans, intestinal absorption of aluminium is subject to many systemic and local factors. The latter include various compounds with which aluminium is complexed in the gut lumen, and gastric acidity. The influence of food is controversial; however, absorption appears higher in the fasted than the post-prandial state. Luminal phosphate concentration decreases aluminium absorption, whereas citrate increases it. For theoretical reasons, silicates should prevent aluminium absorption, but experimental evidence has not supported this theory. Whether water hardness affects aluminium bioavailability remains a matter of debate. General conditions may also modify aluminium absorption and deposition in bone. Examples of these general factors include the uraemic syndrome, diabetes mellitus, secondary hyperparathyroidism, vitamin D status, Alzheimer's disease and Down's syndrome. Awareness of intestinal absorption of aluminium is particularly important, given that aluminium-based binders continue to be used in uraemic patients, despite the hazards of aluminium accumulation. The lessons we have learned about

  12. Effects of silicon on gastrointestinal absorption of aluminium

    SciTech Connect

    Edwardson, J.A.; Moore, P.B.; Ferrier, I.N.; Lilley, J.S.; Newton, G.W.A.; Barker, J.; Templar, J.; Day, J.P.

    1993-07-24

    The reported geographical association between Alzheimer's disease and levels of aluminium (Al) in water supplies may reflect the inverse relation between Al and silicon (Si) concentrations in water, and the potential for Si to reduce the bioavailability of the metal. The authors tested this hypothesis using isotopic [sup 26]Al tracer administered orally to five healthy volunteers in the presence and absence of Si. Dissolved Si, at a concentration found in some water supplies reduced the peak plasma [sup 26]Al concentration to 15% of the value obtained in the absence of Si. The results indicate that dissolved Si is an important factor in limiting the absorption of dietary Al.

  13. OH measurement by laser light absorption

    NASA Technical Reports Server (NTRS)

    Perner, D.

    1986-01-01

    Since the first attempt to measure atmospheric hydroxyl radicals by optical absorption in 1975 (Perner et al., 1976) this method has been continuously developed further and its major obstacles and limitations are known today. The laser beam needs to be expanded in order to reduce the beam divergence. At the same time the energy density of the laser beam which produces OH via ozone photolysis is reduced to such an extent that the self-produced OH concentration ranges well below the atmospheric value. Atmospheric absorptions should be observed over a wide spectral range so that not only the OH radicals are properly identified by several rotational lines but their absorption can be corrected for interfering absorptions from other air constituents as SO2, CH2O, CS2, etc., which can be identified in a wide spectral range with more confidence. Air turbulence demands fast spectral scanning or probing on and off the absorption line. Energy requirements should be kept small in field operations. In the experiment frequency doubled dye laser pulses at 308 nm are produced. The picosecond light pulses are expected to show a smooth profile (light intensity against wavelength) which will be broadened to the required spectral width according to the uncertainty principle. The pump laser will be an optoacoustically modulated Nd:YAG laser.

  14. Structurally tunable resonant absorption bands in ultrathin broadband plasmonic absorbers.

    PubMed

    Butun, Serkan; Aydin, Koray

    2014-08-11

    Light absorption is a fundamental optical process playing significantly important role in wide variety of applications ranging from photovoltaics to photothermal therapy. Semiconductors have well-defined absorption bands with low-energy edge dictated by the band gap energy, therefore it is rather challenging to tune the absorption bandwidth of semiconductors. However, resonant absorbers based on plasmonic nanostructures and optical metamaterials emerged as alternative light absorbers due to spectrally selective absorption bands resulting from optical resonances. Recently, a broadband plasmonic absorber design was introduced by Aydin et al. with a reasonably high broadband absorption. Based on that design, here, structurally tunable, broadband absorbers with improved performance are demonstrated. This broadband absorber has a total thickness of 190 nm with 80% average measured absorption (90% simulated absorption) over the entire visible spectrum (400 - 700 nm). Moreover, the effect of the metal and the oxide thicknesses on the absorption spectra are investigated and results indicate that the shorter and the longer band-edge of broadband absorption can be structurally tuned with the metal and the oxide thicknesses, as well as with the resonator size. Detailed numerical simulations shed light on the type of optical resonances that contribute to the broadband absorption response and provide a design guideline for realizing plasmonic absorbers with structurally tunable bandwidths.

  15. Absorption heat pump system

    DOEpatents

    Grossman, Gershon; Perez-Blanco, Horacio

    1984-01-01

    An improvement in an absorption heat pump cycle is obtained by adding adiabatic absorption and desorption steps to the absorber and desorber of the system. The adiabatic processes make it possible to obtain the highest temperature in the absorber before any heat is removed from it and the lowest temperature in the desorber before heat is added to it, allowing for efficient utilization of the thermodynamic availability of the heat supply stream. The improved system can operate with a larger difference between high and low working fluid concentrations, less circulation losses, and more efficient heat exchange than a conventional system.

  16. Two-Phonon Absorption

    ERIC Educational Resources Information Center

    Hamilton, M. W.

    2007-01-01

    A nonlinear aspect of the acousto-optic interaction that is analogous to multi-photon absorption is discussed. An experiment is described in which the second-order acousto-optically scattered intensity is measured and found to scale with the square of the acoustic intensity. This experiment using a commercially available acousto-optic modulator is…

  17. Visual Absorption Capability

    Treesearch

    Lee Anderson; Jerry Mosier; Geoffrey Chandler

    1979-01-01

    Visual absorption capability (VAC) is a tool to assess a landscape's susceptibility to visual change caused by man's activities. This paper explores different descriptive approaches to VAC and addresses in depth the development of the VAC process used on the Klamath National Forest. Four biophysical factors were selected to assess VAC for the lands within the...

  18. Bioacoustic Absorption Spectroscopy

    DTIC Science & Technology

    2016-06-07

    simulation of the effects of absorptivity due to fish on transmission loss in shallow water, Proceedings of the Oceans 96 Conference, IEEE Press. PATENTS ...The Naval Research Laboratory has decided to apply for an international patent on my design of low cost, ultra-wide bandwidth, light weight, autonomous

  19. Two-Phonon Absorption

    ERIC Educational Resources Information Center

    Hamilton, M. W.

    2007-01-01

    A nonlinear aspect of the acousto-optic interaction that is analogous to multi-photon absorption is discussed. An experiment is described in which the second-order acousto-optically scattered intensity is measured and found to scale with the square of the acoustic intensity. This experiment using a commercially available acousto-optic modulator is…

  20. Observations of interstellar helium with a gas absorption cell - Limits on the bulk velocity of the interstellar medium

    NASA Technical Reports Server (NTRS)

    Freeman, J.; Paresce, F.; Bowyer, S.; Lampton, M.

    1976-01-01

    Results are reported for observations of solar 584-A flux resonantly scattered by the 1s(2)-1s2p transition of neutral interstellar helium. A photometer equipped with a helium gas-absorption cell and flown aboard a sounding rocket to a peak altitude of 185 km was employed to observe the sky in Perseus. The data reduction procedure is described, including subtraction of the terrestrial atmospheric background, calculation of the solar flux, and reduction of the number density of scatters to a function of phase-space parameters of the local interstellar medium. The ratio of 584-A fluxes observed with the gas cell full and empty is computed and compared with numerical models of the interstellar-helium flow through the solar system. The results show that the bulk speed of the distant interstellar medium with respect to the sun is unlikely to be less than 10 to 15 km/s, at the 2-sigma level. Since this value is inconsistent with results obtained from Lyman-alpha observations, it is suggested that either the total ionization rate for helium is variable or present models of the behavior of the local interstellar medium need further refinement.

  1. X-ray absorption and emission spectroscopy of Cr(III) (hydr)oxides: analysis of the K-pre-edge region.

    PubMed

    Frommer, Jakob; Nachtegaal, Maarten; Czekaj, Izabela; Weng, Tsu-Chien; Kretzschmar, Ruben

    2009-11-05

    Pre-edge spectral features below the main X-ray absorption K-edge of transition metals show a pronounced chemical sensitivity and are promising sources of structural information. Nevertheless, the use of pre-edge analysis in applied research is limited because of the lack of definite theoretical peak-assignments. The aim of this study was to determine the factors affecting the chromium K-pre-edge features in trivalent chromium-bearing oxides and oxyhydroxides. The selected phases varied in the degree of octahedral polymerization and the degree of iron-for-chromium substitution in the crystal structure. We investigated the pre-edge fine structure by means of high-energy-resolution fluorescence detected X-ray absorption spectroscopy and by 1s2p resonant X-ray emission spectroscopy. Multiplet theory and full multiple-scattering calculations were used to analyze the experimental data. We show that the chromium K-pre-edge contains localized and nonlocalized transitions. Contributions arising from nonlocalized metal-metal transitions are sensitive to the nearest metal type and to the linkage mode between neighboring metal octahedra. Analyzing these transitions opens up new opportunities for investigating the local coordination environment of chromium in poorly ordered solids of environmental relevance.

  2. Energy absorption of refractory absorber with periodic nanostructures

    NASA Astrophysics Data System (ADS)

    Kang, Yuchen; Yang, Shuhan; Wang, Yanhong; Wu, Jingzhi

    2016-10-01

    Refractory material with surface plasmonic structures have the function of spectrum selective absorption and radiation spectrum regulation. In this paper, we design an absorber with periodic cylindrical nanostructures and a dielectric layer of Al2O3 based on the substrate of metal Tantalum (Ta). The energy absorption characteristics of the absorber have been simulated and analyzed by changing various constructional parameters. The simulation results indicate that structural parameters have great influence on the spectrum absorption in the range of wavelength 400-4000nm. The period and radius of nanostructure have a important effect on the absorption peaks in the infrared region. Infrared absorption peak can reach more than 99% and produce a red shift due to parameters changing. At the whole visible field, the absorption enhancement effect is significant. The refractive index and thickness of dielectric layer also have an obviously effect on the absorption spectrum. Furthermore, it is also obviously that thickness of dielectric layer has enhancement effect on absorption of infrared spectrum. The research found that the absorption and radiation spectrum of surface plasmonic materials can be effectively controlled by combining the high temperature radiation characteristics of high temperature metal. Thermophotovoltaic system can provide a kind of new methods and ideas for improving conversion efficiency, energy saving and consumption reducing.

  3. Perspectives on iron absorption.

    PubMed

    Hallberg, Leif; Hulthén, Lena

    2002-01-01

    Newly established relationships between dietary iron absorption and serum ferritin and between serum ferritin and iron stores permit calculation of amounts of stored iron under different conditions at steady states when absorption equals losses. The rate of growth of stores can also be calculated. All calculations are based on observations and require no model assumptions. Present analyses demonstrated an effective control of iron absorption preventing development of iron overload in otherwise healthy subjects even if the diet is fortified with iron and even if meat intake is high. There are strong relationships between iron requirements, bioavailability of dietary iron, and amounts of stored iron. Our observations that a reduction in iron stores and a calculated decrease of hemoglobin iron had the same increasing effect on iron absorption suggest that the control of iron absorption is mediated from a common cell, which may register both size of iron stores and hemoglobin iron deficit. We suggest that the hepatocyte is that cell. Nutritional iron deficiency is especially critical in menstruating women, in the latter third of pregnancy, during adolescence for both girls and boys, and in the weaning period from 4 to 6 months to 2 years of age. The body possesses remarkable, potential control systems of probable very ancient origin capable of preventing both iron deficiency and iron overload. Present problems with iron deficiency being the most frequent deficiency disorder are related to nonbiological changes in our societies over the most recent 10,000 years. This perspective on iron homeostasis or iron balance is mainly based on studies in humans of clinical and epidemiological observations, trying to understand why iron deficiency is the most frequent deficiency disorder in the world in spite of the ingenious mechanisms in the body that should prevent it. Withdrawal of iron fortification of flour in Sweden in 1994 led to a significant increase in iron deficiency

  4. Determination of iridium in mafic rocks by atomic absorption

    USGS Publications Warehouse

    Grimaldi, F.S.; Schnepfe, M.M.

    1970-01-01

    Iridium is determined in mineralized mafic rocks by atomic absorption after fire-assay concentration into a gold bead. Interelement interferences in the atomic-absorption determination are removed and Ir sensitivity is increased by buffering the solutions with a mixture of copper and sodium sulphates. Substantial amounts of Ag, Al, Au, Bi, Ca, Cd, Co, Cr, Fe, Ho, Hg, K, La, Mg, Mn, Mo, Ni, Pb, Te, Ti, V, Y, Zn and platinum metals can be tolerated in the atomic-absorption determination. The sensitivity and detection limits are 3.2 and 0.25 ppm of Ir, respectively. ?? 1970.

  5. Quantum absorption refrigerator.

    PubMed

    Levy, Amikam; Kosloff, Ronnie

    2012-02-17

    A quantum absorption refrigerator driven by noise is studied with the purpose of determining the limitations of cooling to absolute zero. The model consists of a working medium coupled simultaneously to hot, cold, and noise baths. Explicit expressions for the cooling power are obtained for Gaussian and Poisson white noise. The quantum model is consistent with the first and second laws of thermodynamics. The third law is quantified; the cooling power J(c) vanishes as J(c) ∝ T(c)(α), when T(c)→0, where α=d+1 for dissipation by emission and absorption of quanta described by a linear coupling to a thermal bosonic field, where d is the dimension of the bath.

  6. Acoustic absorption by sunspots

    NASA Technical Reports Server (NTRS)

    Braun, D. C.; Labonte, B. J.; Duvall, T. L., Jr.

    1987-01-01

    The paper presents the initial results of a series of observations designed to probe the nature of sunspots by detecting their influence on high-degree p-mode oscillations in the surrounding photosphere. The analysis decomposes the observed oscillations into radially propagating waves described by Hankel functions in a cylindrical coordinate system centered on the sunspot. From measurements of the differences in power between waves traveling outward and inward, it is demonstrated that sunspots appear to absorb as much as 50 percent of the incoming acoustic waves. It is found that for all three sunspots observed, the amount of absorption increases linearly with horizontal wavenumber. The effect is present in p-mode oscillations with wavelengths both significantly larger and smaller than the diameter of the sunspot umbrae. Actual absorption of acoustic energy of the magnitude observed may produce measurable decreases in the power and lifetimes of high-degree p-mode oscillations during periods of high solar activity.

  7. Vehicular impact absorption system

    NASA Technical Reports Server (NTRS)

    Knoell, A. C.; Wilson, A. H. (Inventor)

    1978-01-01

    An improved vehicular impact absorption system characterized by a plurality of aligned crash cushions of substantially cubic configuration is described. Each consists of a plurality of voided aluminum beverage cans arranged in substantial parallelism within a plurality of superimposed tiers and a covering envelope formed of metal hardware cloth. A plurality of cables is extended through the cushions in substantial parallelism with an axis of alignment for the cushions adapted to be anchored at each of the opposite end thereof.

  8. Hydrogen Absorption by Niobium.

    DTIC Science & Technology

    1982-04-13

    incorporate an independent means for ascertaining surface cleanliness (e.g. AES). The form of the absorption curve in Fig. 7 appears to agree with that...very interesting study and is well within the capabilities of the systen designed, if the surface cleanliness can be assured. Wire specimens have a...assessing surface cleanliness would be an important supporting technique for understanding the results of these measurements. The simple kinetic

  9. Improved 20- to 32-GHz atmospheric absorption model

    NASA Astrophysics Data System (ADS)

    Cruz Pol, Sandra L.; Ruf, Christopher S.; Keihm, Stephen J.

    1998-09-01

    An improved model for the absorption of the atmosphere near the 22-GHz water vapor line is presented. The Van Vleck-Weisskopf line shape is used with a simple parameterized version of the model from Liebe et al. [1993] for the water vapor absorption spectra and a scaling of the model from Rosenkranz [1993] for the 20- to 32-GHz oxygen absorption. Radiometric brightness temperature measurements from two sites of contrasting climatological properties, San Diego, California, and West Palm Beach, Florida, were used as ground truth for comparison with in situ radiosonde-derived brightness temperatures under clear-sky conditions. Estimation of the new model's four parameters, related to water vapor line strength, line width and continuum absorption, and far-wing oxygen absorption, was performed using the Newton-Raphson inversion method. Improvements to the water vapor line strength and line width parameters are found to be statistically significant. The accuracy of the new absorption model is estimated to be 3% between 20 and 24 GHz, degrading to 8% near 32 GHz. In addition, the Hill line shape asymmetry ratio was evaluated in several currently used models to show the agreement of the data with Van Vleck-Weisskopf based models and to rule out water vapor absorption models near 22 GHz given by Waters [1976] and Ulaby et al. [1981], which are based on the Gross line shape.

  10. Relic Neutrino Absorption Spectroscopy

    SciTech Connect

    Eberle, b

    2004-01-28

    Resonant annihilation of extremely high-energy cosmic neutrinos on big-bang relic anti-neutrinos (and vice versa) into Z-bosons leads to sizable absorption dips in the neutrino flux to be observed at Earth. The high-energy edges of these dips are fixed, via the resonance energies, by the neutrino masses alone. Their depths are determined by the cosmic neutrino background density, by the cosmological parameters determining the expansion rate of the universe, and by the large redshift history of the cosmic neutrino sources. We investigate the possibility of determining the existence of the cosmic neutrino background within the next decade from a measurement of these absorption dips in the neutrino flux. As a by-product, we study the prospects to infer the absolute neutrino mass scale. We find that, with the presently planned neutrino detectors (ANITA, Auger, EUSO, OWL, RICE, and SalSA) operating in the relevant energy regime above 10{sup 21} eV, relic neutrino absorption spectroscopy becomes a realistic possibility. It requires, however, the existence of extremely powerful neutrino sources, which should be opaque to nucleons and high-energy photons to evade present constraints. Furthermore, the neutrino mass spectrum must be quasi-degenerate to optimize the dip, which implies m{sub {nu}} 0.1 eV for the lightest neutrino. With a second generation of neutrino detectors, these demanding requirements can be relaxed considerably.

  11. Corrosion Problems in Absorption Chillers

    ERIC Educational Resources Information Center

    Stetson, Bruce

    1978-01-01

    Absorption chillers use a lithium bromide solution as the medium of absorption and water as the refrigerant. Discussed are corrosion and related problems, tests and remedies, and cleaning procedures. (Author/MLF)

  12. Corrosion Problems in Absorption Chillers

    ERIC Educational Resources Information Center

    Stetson, Bruce

    1978-01-01

    Absorption chillers use a lithium bromide solution as the medium of absorption and water as the refrigerant. Discussed are corrosion and related problems, tests and remedies, and cleaning procedures. (Author/MLF)

  13. BASIC STUDIES IN PERCUTANEOUS ABSORPTION.

    DTIC Science & Technology

    SKIN(ANATOMY), *BIOLOGICAL ABSORPTION, BIOLOGICAL ABSORPTION, SKIN(ANATOMY), BIOCHEMISTRY, MEMBRANES(BIOLOGY), PERMEABILITY, LIPIDS, PROTEINS, AMINO ... ACIDS , WATER, PH FACTOR, CHROMATOGRAPHIC ANALYSIS, THERMAL PROPERTIES, TEMPERATURE, HUMIDITY, HISTOLOGY, ADULTS, INFANTS, HUMANS, MONKEYS.

  14. AL Amyloidosis

    PubMed Central

    2012-01-01

    Definition of the disease AL amyloidosis results from extra-cellular deposition of fibril-forming monoclonal immunoglobulin (Ig) light chains (LC) (most commonly of lambda isotype) usually secreted by a small plasma cell clone. Most patients have evidence of isolated monoclonal gammopathy or smoldering myeloma, and the occurrence of AL amyloidosis in patients with symptomatic multiple myeloma or other B-cell lymphoproliferative disorders is unusual. The key event in the development of AL amyloidosis is the change in the secondary or tertiary structure of an abnormal monoclonal LC, which results in instable conformation. This conformational change is responsible for abnormal folding of the LC, rich in β leaves, which assemble into monomers that stack together to form amyloid fibrils. Epidemiology AL amyloidosis is the most common type of systemic amyloidois in developed countries with an estimated incidence of 9 cases/million inhabitant/year. The average age of diagnosed patients is 65 years and less than 10% of patients are under 50. Clinical description The clinical presentation is protean, because of the wide number of tissues or organs that may be affected. The most common presenting symptoms are asthenia and dyspnoea, which are poorly specific and may account for delayed diagnosis. Renal manifestations are the most frequent, affecting two thirds of patients at presentation. They are characterized by heavy proteinuria, with nephrotic syndrome and impaired renal function in half of the patients. Heart involvement, which is present at diagnosis in more than 50% of patients, leading to restrictive cardiopathy, is the most serious complication and engages prognosis. Diagnostic methods The diagnosis relies on pathological examination of an involved site showing Congo red-positive amyloid deposits, with typical apple-green birefringence under polarized light, that stain positive with an anti-LC antibody by immunohistochemistry and/or immunofluorescence. Due to the

  15. Atmospheric absorption near 2400 kayser

    NASA Technical Reports Server (NTRS)

    Susskind, J.; Searl, J. E.

    1977-01-01

    Theoretical atmospheric absorption spectra between 2385 and 2425 kayser are shown to give excellent agreement with high resolution observations. Most of the atmospheric absorption in this region arises from continuum features due to absorption of N2 and the wings of distant CO2 lines. The treatment of each of these factors is discussed.

  16. Acoustic Absorption Characteristics of People.

    ERIC Educational Resources Information Center

    Kingsbury, H. F.; Wallace, W. J.

    1968-01-01

    The acoustic absorption characteristics of informally dressed college students in typical classroom seating are shown to differ substantially from data for formally dressed audiences in upholstered seating. Absorption data, expressed as sabins per person or absorption coefficient per square foot, shows that there is considerable variation between…

  17. Optical absorption in amorphous silicon

    SciTech Connect

    O`Leary, S.K.; Zukotynski, S.; Perz, J.M.; Sidhu, L.S.

    1996-12-31

    The role that disorder plays in shaping the form of the optical absorption spectrum of hydrogenated amorphous silicon is investigated. Disorder leads to a redistribution of states, which both reduces the Tauc gap and broadens the absorption tail. The observed relationship between the Tauc gap and the breadth of the absorption tail is thus explained.

  18. Acoustic Absorption Characteristics of People.

    ERIC Educational Resources Information Center

    Kingsbury, H. F.; Wallace, W. J.

    1968-01-01

    The acoustic absorption characteristics of informally dressed college students in typical classroom seating are shown to differ substantially from data for formally dressed audiences in upholstered seating. Absorption data, expressed as sabins per person or absorption coefficient per square foot, shows that there is considerable variation between…

  19. Absorption heat pumps

    NASA Astrophysics Data System (ADS)

    Huhtinen, M.; Heikkilae, M.; Andersson, R.

    1987-03-01

    The aim of the study was to analyze the technical and economic feasibility of absorption heat pumps in Finland. The work was done as a case study: the technical and economic analyses have been carried out for six different cases, where in each the suitable size and type of the heat pump plant and the auxiliary components and connections were specified. The study also detailed the costs concerning the procurement, installation and test runs of the machinery, as well as the savings in energy costs incurred by the introduction of the plant. Conclusions were drawn of the economic viability of the applications studied. The following cases were analyzed: heat recovery from flue gases and productin of district heat in plants using peat, natural gas, and municipal wastes as a fuel. Heat recovery in the pulp and paper industry for the upgrading of pressure of secondary steam and for the heating of white liquor and combustion and drying the air. Heat recovery in a peat-fulled heat and power plant from flue gases that have been used for the drying of peat. According to the study, the absorption heat pump suits best to the production of district heat, when the heat source is the primary energy is steam produced by the boiler. Included in the flue as condensing is the purification of flue gases. Accordingly, benefit is gained on two levels in thick applications. In heat and power plants the use of absorption heat pumps is less economical, due to the fact that the steam used by the pump reduces the production of electricity, which is rated clearly higher than heat.

  20. An in silico skin absorption model for fragrance materials.

    PubMed

    Shen, Jie; Kromidas, Lambros; Schultz, Terry; Bhatia, Sneha

    2014-12-01

    Fragrance materials are widely used in cosmetics and other consumer products. The Research Institute for Fragrance Materials (RIFM) evaluates the safety of these ingredients and skin absorption is an important parameter in refining systemic exposure. Currently, RIFM's safety assessment process assumes 100% skin absorption when experimental data are lacking. This 100% absorption default is not supportable and alternate default values were proposed. This study aims to develop and validate a practical skin absorption model (SAM) specific for fragrance material. It estimates skin absorption based on the methodology proposed by Kroes et al. SAM uses three default absorption values based on the maximum flux (J(max)) - namely, 10%, 40%, and 80%. J(max) may be calculated by using QSAR models that determine octanol/water partition coefficient (K(ow)), water solubility (S) and permeability coefficient (K(p)). Each of these QSAR models was refined and a semi-quantitative mechanistic model workflow is presented. SAM was validated with a large fragrance-focused data set containing 131 materials. All resulted in predicted values fitting the three-tiered absorption scenario based on Jmax ranges. This conservative SAM may be applied when fragrance material lack skin absorption data.

  1. Ultraviolet absorption hygrometer

    DOEpatents

    Gersh, Michael E.; Bien, Fritz; Bernstein, Lawrence S.

    1986-01-01

    An ultraviolet absorption hygrometer is provided including a source of pulsed ultraviolet radiation for providing radiation in a first wavelength region where water absorbs significantly and in a second proximate wavelength region where water absorbs weakly. Ultraviolet radiation in the first and second regions which has been transmitted through a sample path of atmosphere is detected. The intensity of the radiation transmitted in each of the first and second regions is compared and from this comparison the amount of water in the sample path is determined.

  2. Ultraviolet absorption hygrometer

    DOEpatents

    Gersh, M.E.; Bien, F.; Bernstein, L.S.

    1986-12-09

    An ultraviolet absorption hygrometer is provided including a source of pulsed ultraviolet radiation for providing radiation in a first wavelength region where water absorbs significantly and in a second proximate wavelength region where water absorbs weakly. Ultraviolet radiation in the first and second regions which has been transmitted through a sample path of atmosphere is detected. The intensity of the radiation transmitted in each of the first and second regions is compared and from this comparison the amount of water in the sample path is determined. 5 figs.

  3. Modular total absorption spectrometer

    NASA Astrophysics Data System (ADS)

    Karny, M.; Rykaczewski, K. P.; Fijałkowska, A.; Rasco, B. C.; Wolińska-Cichocka, M.; Grzywacz, R. K.; Goetz, K. C.; Miller, D.; Zganjar, E. F.

    2016-11-01

    The design and performance of the Modular Total Absorption Spectrometer built and commissioned at the Oak Ridge National Laboratory is presented. The active volume of the detector is approximately one ton of NaI(Tl), which results in very high full γ energy peak efficiency of 71% at 6 MeV and nearly flat efficiency of around 81.5% for low energy γ-rays between 300 keV and 1 MeV. In addition to the high peak efficiency, the modular construction of the detector permits the use of a γ-coincidence technique in data analysis as well as β-delayed neutron observation.

  4. 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.

  5. The HI absorption "Zoo"

    NASA Astrophysics Data System (ADS)

    Geréb, K.; Maccagni, F. M.; Morganti, R.; Oosterloo, T. A.

    2015-03-01

    We present an analysis of the H I 21 cm absorption in a sample of 101 flux-selected radio AGN (S1.4 GHz> 50 mJy) observed with the Westerbork Synthesis Radio Telescope (WSRT). We detect H I absorption in 32 objects (30% of the sample). In a previous paper, we performed a spectral stacking analysis on the radio sources, while here we characterize the absorption spectra of the individual detections using the recently presented busy function. The H I absorption spectra show a broad variety of widths, shapes, and kinematical properties. The full width half maximum (FWHM) of the busy function fits of the detected H I lines lies in the range 32 km s-1absorption (FW20) lies in the range 63 km s-1 200 km s-1). We study the kinematical and radio source properties of each group, with the goal of identifying different morphological structures of H I. Narrow lines mostly lie at the systemic velocity and are likely produced by regularly rotating H I disks or gas clouds. More H I disks can be present among galaxies with lines of intermediate widths; however, the H I in these sources is more unsettled. We study the asymmetry parameter and blueshift/redshift distribution of the lines as a function of their width. We find a trend for which narrow profiles are also symmetric, while broad lines are the most asymmetric. Among the broadest lines, more lines appear blueshifted than redshifted, similarly to what was found by previous studies. Interestingly, symmetric broad lines are absent from the sample. We argue that if a profile is broad, it is also asymmetric and shifted relative to the systemic velocity because it is tracing unsettled H I gas. In particular, besides three of the broadest (up to FW20 = 825 km s-1

  6. An aerosol absorption remote sensing algorithm

    NASA Astrophysics Data System (ADS)

    Zhai, P.; Winker, D. M.; Hu, Y.; Trepte, C. R.; Lucker, P. L.

    2013-12-01

    Aerosol absorption plays an important role in the climate by modulating atmospheric radiative forcing processes. Unfortunately aerosol absorption is very difficult to obtain via satellite remote sensing techniques. In this work we have built an algorithm to obtain aerosol absorption optical depth using both measurements from a passive O2 A-band spectrometer and an active lidar. The instrument protocols for these two satellite instruments are the O2 A-band spectrometer onboard the Orbiting Carbon Observatory (OCO-2) and the CALIOP onboard CALIPSO. The aerosol height and typing information is obtained from the CALIOP measurement. The aerosol extinction and absorption optical depths are then retrieved by fitting the forward model simulations to the O2 A-band spectrometer measurements. The forward model simulates the scattering and absorption of solar light at high spectral resolution in the O2 A-band region. The O2 and other gas absorption coefficients near 0.76 micron are calculated by either the line-by-line code (for instance, the Atmospheric Radiative Transfer Simulator) or the OCO2 ABSCO Look-Up-Table. The line parameters used are from the HITRAN 2008 database (http://www.cfa.harvard.edu/hitran/). The multiple light scattering by molecules, aerosols, and clouds is handled by the radiative transfer model based on the successive order of scattering method (Zhai et al, JQSRT, Vol. 111, pp. 1025-1040, 2010). The code is parallelized with Message Passing Interface (MPI) for better efficiency. The aerosol model is based on Shettle and Fenn (AFGL-TR 790214, 1979) with variant relative humidity. The vertical distribution of the aerosols and clouds will be read in from the CALIPSO product (http://www-calipso.larc.nasa.gov). The surface albedo is estimated by the continuum of the three bands of OCO2 payloads. Sensitivity study shows that the Gaussian quadrature (stream) number should be at least 12 to ensure the reflectance error is within 0.5% at the top of the atmosphere

  7. Enigmatic photon absorption in plasmas near solar interior conditions

    NASA Astrophysics Data System (ADS)

    Iglesias, Carlos A.

    2015-06-01

    Large systematic discrepancies between theoretical and experimental photon absorption of Fe plasmas applicable to the solar interior were reported [Bailey et al., Nature 517, 56 (2015)]. The disagreement is examined in the context of the Thomas-Reiche-Kuhn f-sum rule. The analysis identifies several anomalies in the experimental results.

  8. Analyzing Water's Optical Absorption

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A cooperative agreement between World Precision Instruments (WPI), Inc., and Stennis Space Center has led the UltraPath(TM) device, which provides a more efficient method for analyzing the optical absorption of water samples at sea. UltraPath is a unique, high-performance absorbance spectrophotometer with user-selectable light path lengths. It is an ideal tool for any study requiring precise and highly sensitive spectroscopic determination of analytes, either in the laboratory or the field. As a low-cost, rugged, and portable system capable of high- sensitivity measurements in widely divergent waters, UltraPath will help scientists examine the role that coastal ocean environments play in the global carbon cycle. UltraPath(TM) is a trademark of World Precision Instruments, Inc. LWCC(TM) is a trademark of World Precision Instruments, Inc.

  9. Differential optoacoustic absorption detector

    NASA Technical Reports Server (NTRS)

    Shumate, M. S. (Inventor)

    1978-01-01

    A differential optoacoustic absorption detector employed two tapered cells in tandem or in parallel. When operated in tandem, two mirrors were used at one end remote from the source of the beam of light directed into one cell back through the other, and a lens to focus the light beam into the one cell at a principal focus half way between the reflecting mirror. Each cell was tapered to conform to the shape of the beam so that the volume of one was the same as for the other, and the volume of each received maximum illumination. The axes of the cells were placed as close to each other as possible in order to connect a differential pressure detector to the cells with connecting passages of minimum length. An alternative arrangement employed a beam splitter and two lenses to operate the cells in parallel.

  10. Two absorption furosemide prodrugs.

    PubMed

    Mombrú, A W; Mariezcurrena, R A; Suescun, L; Pardo, H; Manta, E; Prandi, C

    1999-03-15

    The structures of two absorption furosemide prodrugs, hexanoyloxymethyl 4-chloro-N-furfuryl-5-sulfamoyl-anthranilate (C19H23CIN2O7S), (I), and benzoyloxymethyl 4-chloro-N-furfuryl-5-sulfamoylanthranilate (C20H17CIN2O7S), (II), are described in this paper and compared with furosemide and four other prodrugs. The molecular conformations of both compounds are similar to those of the other prodrugs; the packing and the crystal system are the primary differences. Compound (I) crystallizes in the trigonal space group R3 and compound (II) in the monoclinic space group P2(1)/n. The packing of both structures is stabilized by a three-dimensional hydrogen-bond network.

  11. Quantitatively probing the Al distribution in zeolites.

    PubMed

    Vjunov, Aleksei; Fulton, John L; Huthwelker, Thomas; Pin, Sonia; Mei, Donghai; Schenter, Gregory K; Govind, Niranjan; Camaioni, Donald M; Hu, Jian Zhi; Lercher, Johannes A

    2014-06-11

    The degree of substitution of Si(4+) by Al(3+) in the oxygen-terminated tetrahedra (Al T-sites) of zeolites determines the concentration of ion-exchange and Brønsted acid sites. Because the location of the tetrahedra and the associated subtle variations in bond angles influence the acid strength, quantitative information about Al T-sites in the framework is critical to rationalize catalytic properties and to design new catalysts. A quantitative analysis is reported that uses a combination of extended X-ray absorption fine structure (EXAFS) analysis and (27)Al MAS NMR spectroscopy supported by DFT-based molecular dynamics simulations. To discriminate individual Al atoms, sets of ab initio EXAFS spectra for various T-sites are generated from DFT-based molecular dynamics simulations, allowing quantitative treatment of the EXAFS single- and multiple-photoelectron scattering processes out to 3-4 atom shells surrounding the Al absorption center. It is observed that identical zeolite types show dramatically different Al distributions. A preference of Al for T-sites that are part of one or more 4-member rings in the framework over those T-sites that are part of only 5- and 6-member rings in an HBEA150 zeolite has been determined using this analysis.

  12. Quantitatively Probing the Al Distribution in Zeolites

    SciTech Connect

    Vjunov, Aleksei; Fulton, John L.; Huthwelker, Thomas; Pin, Sonia; Mei, Donghai; Schenter, Gregory K.; Govind, Niranjan; Camaioni, Donald M.; Hu, Jian Z.; Lercher, Johannes A.

    2014-06-11

    The degree of substitution of Si4+ by Al3+ in the oxygen-terminated tetrahedra (Al T-sites) of zeolites determines the concentration of ion-exchange and Brønsted acid sites. As the location of the tetrahedra and the associated subtle variations in bond angles influence the acid strength, quantitative information about Al T-sites in the framework is critical to rationalize catalytic properties and to design new catalysts. A quantitative analysis is reported that uses a combination of extended X-ray absorption fine structure (EXAFS) analysis and 27Al MAS NMR spectroscopy supported by DFT-based molecular dynamics simulations. To discriminate individual Al atoms, sets of ab initio EXAFS spectra for various T-sites are generated from DFT-based molecular dynamics simulations allowing quantitative treatment of the EXAFS single- and multiple-photoelectron scattering processes out to 3-4 atom shells surrounding the Al absorption center. It is observed that identical zeolite types show dramatically different Al-distributions. A preference of Al for T-sites that are part of one or more 4-member rings in the framework over those T-sites that are part of only 5- and 6-member rings in the HBEA150 sample has been determined from a combination of these methods. This work was supported by the U. S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences.

  13. Effect of applied mechanical stress on absorption coefficient of compounds

    SciTech Connect

    Gupta, Manoj Kumar; Singh, Gurinderjeet; Dhaliwal, A. S.; Kahlon, K. S.

    2015-08-28

    The absorption coefficient of given materials is the parameter required for the basic information. The measurement of absorption coefficient of compounds Al{sub 2}O{sub 3}, CaCO{sub 3}, ZnO{sub 2}, SmO{sub 2} and PbO has been taken at different incident photon energies 26, 59.54, 112, 1173, 1332keV. The studies involve the measurements of absorption coefficient of the self supporting samples prepared under different mechanical stress. This mechanical stress is render in terms of pressure up to 0-6 ton by using hydraulic press. Measurements shows that absorption coefficient of a material is directly proportional to applied mechanical stress on it up to some extent then become independent. Experimentally measured results are in fairly good agreement with in theoretical values obtained from WinXCOM.

  14. Methane Absorption Coefficients for the Jovian Planets and Titan

    NASA Astrophysics Data System (ADS)

    Karkoschka, Erich; Tomasko, M. G.

    2009-09-01

    We combined 11 data sets of methane transmission measurements within 0.4-5.5 micrometer wavelength in order to better understand the variation of methane absorption with temperature and pressure for conditions in the atmospheres of the Jovian planets and Titan. Eight data sets are based on published laboratory measurements. Another two data sets come from two spectrometers onboard the Huygens probe that measured methane absorption inside Titan's atmosphere (Tomasko et al. 2008, PSS 56, 624). We present the data with a refined analysis. The last data set consists of Hubble Space Telescope images of Jupiter taken in 2005 and 2007 as Ganymede started to be occulted by Jupiter. Using Ganymede as a light source, we probed Jupiter's stratosphere with large methane pathlengths. Below 1000 nm wavelength, we find methane absorption coefficients generally similar to those by Karkoschka (1998, Icarus 133, 134). We added descriptions of temperature and pressure dependence, which are typically small in this wavelength range. Data in this wavelength range are consistent with each other, except between 882 and 902 nm wavelength where laboratory data predict larger absorptions in the Jovian atmospheres than observed. We present possible explanations. Above 1000 nm, our analysis of the Huygens data confirms methane absorption coefficients by Irwin et al. (2006, Icarus 181, 309) at their laboratory temperatures. Huygens data are consistent with Irwin's model of the pressure dependence of methane absorption. However, when large extrapolations were needed, such as from laboratory data above 200 K to Titan's temperatures near 80 K, Irwin's model of temperature dependence predicts absorption coefficients up to 100 times lower than measured by Huygens. We combined Irwin's and Huygens' data to obtain more reliable methane absorption coefficients for the temperatures in the atmospheres of the Jovian planets and Titan. This research was supported by NASA grants NAG5-12014 and NNX08AE74G.

  15. Nonlinear optical absorption in the core shell nanowire

    NASA Astrophysics Data System (ADS)

    Kouhi, Mohammad

    2017-09-01

    In this paper, the effect of incident light intensity, relaxation time, core radius and shell thickness on linear, nonlinear, total optical absorption coefficients and refractive index changes in GaN/Al0.1Ga0.9N core-shell nanowire are theoretically investigated. The presented nanostructure is a cylindrical quantum wire including a shell around the cylinder core. By numerical solution of Schrödinger equation in the cylindrical coordinates with effective mass approximation, the optical absorption coefficients are calculated. The results show that the magnitude of optical absorption coefficients can be adjusted by varying the relaxation time. The positions of resonant peaks of optical absorption coefficients are redshifted by increase of core radius due to decrease of the energy difference between two energy levels. With increase of shell thickness initially, the resonance wavelength of absorption coefficient increases (redshift) and magnitude of absorption coefficient decreases. Then with more increases of the shell thickness, redshifting of resonance wavelength is stopped and magnitude of absorption coefficient is increased. There is a significant increase in the refractive index change with increase of relaxation time.

  16. A parameterization for the absorption of solar radiation by water vapor in the earth's atmosphere

    NASA Technical Reports Server (NTRS)

    Wang, W.-C.

    1976-01-01

    A parameterization for the absorption of solar radiation as a function of the amount of water vapor in the earth's atmosphere is obtained. Absorption computations are based on the Goody band model and the near-infrared absorption band data of Ludwig et al. A two-parameter Curtis-Godson approximation is used to treat the inhomogeneous atmosphere. Heating rates based on a frequently used one-parameter pressure-scaling approximation are also discussed and compared with the present parameterization.

  17. X-ray Absorption Spectroscopy

    SciTech Connect

    Yano, Junko; Yachandra, Vittal K.

    2009-07-09

    This review gives a brief description of the theory and application of X-ray absorption spectroscopy, both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), especially, pertaining to photosynthesis. The advantages and limitations of the methods are discussed. Recent advances in extended EXAFS and polarized EXAFS using oriented membranes and single crystals are explained. Developments in theory in understanding the XANES spectra are described. The application of X-ray absorption spectroscopy to the study of the Mn4Ca cluster in Photosystem II is presented.

  18. BASIC STUDIES IN PERCUTANEOUS ABSORPTION.

    DTIC Science & Technology

    FATTY ACIDS, *SKIN(ANATOMY), ABSORPTION, ALKYL RADICALS, AMIDES, DIFFUSION, ELECTRON MICROSCOPY, HUMIDITY, LABORATORY ANIMALS, LIPIDS, ORGANIC SOLVENTS, PENETRATION, PRIVATION, PROTEINS, RATS, TEMPERATURE, WATER

  19. Optical absorption and luminescence studies of fast neutron-irradiated complex oxides for jewellery applications

    NASA Astrophysics Data System (ADS)

    Mironova-Ulmane, N.; Skvortsova, V.; Popov, A. I.

    2016-07-01

    We studied the optical absorption and luminescence of agate (SiO2), topaz (Al2[SiO4](F,OH)2), beryl (Be3Al2Si6O18), and prehnite (Ca2Al(AlSi3O10)(OH)2) doped with different concentrations of transition metal ions and exposed to fast neutron irradiation. The exchange interaction between the impurity ions and the defects arising under neutron irradiation causes additional absorption as well as bands' broadening in the crystals. These experimental results allow us to suggest the method for obtaining new radiation-defect induced jewellery colors of minerals due to neutron irradiation.

  20. Detection of water vapour absorption around 363nm in measured atmospheric absorption spectra and its effect on DOAS evaluations

    NASA Astrophysics Data System (ADS)

    Lampel, Johannes; Polyansky, Oleg. L.; Kyuberis, Alexandra A.; Zobov, Nikolai F.; Tennyson, Jonathan; Lodi, Lorenzo; Pöhler, Denis; Frieß, Udo; Platt, Ulrich; Beirle, Steffen; Wagner, Thomas

    2016-04-01

    Water vapour is known to absorb light from the microwave region to the blue part of the visible spectrum at a decreasing magnitude. Ab-initio approaches to model individual absorption lines of the gaseous water molecule predict absorption lines until its dissociation limit at 243 nm. We present first evidence of water vapour absorption at 363 nm from field measurements based on the POKAZATEL absorption line list by Polyansky et al. (2016) using data from Multi-Axis differential optical absorption spectroscopy (MAX-DOAS) and Longpath (LP)-DOAS measurements. The predicted absorptions contribute significantly to the observed optical depths with up to 2 × 10-3. Their magnitude correlates well (R2 = 0.89) to simultaneously measured well-established water vapour absorptions in the blue spectral range from 452-499 nm, but is underestimated by a factor of 2.6 ± 0.6 in the ab-initio model. At a spectral resolution of 0.5nm this leads to a maximum absorption cross-section value of 5.4 × 10-27 cm2/molec at 362.3nm. The results are independent of the employed cross-section data to compensate for the overlayed absorption of the oxygen dimer O4. The newly found absorption can have a significant impact on the spectral retrieval of absorbing trace-gas species in the spectral range around 363 nm. Its effect on the spectral analysis of O4, HONO and OClO are discussed.

  1. Dataset used to improve liquid water absorption models in the microwave

    SciTech Connect

    Turner, David

    2015-12-14

    Two datasets, one a compilation of laboratory data and one a compilation from three field sites, are provided here. These datasets provide measurements of the real and imaginary refractive indices and absorption as a function of cloud temperature. These datasets were used in the development of the new liquid water absorption model that was published in Turner et al. 2015.

  2. Infrared absorption spectra of metal carbides, nitrides and sulfides

    NASA Technical Reports Server (NTRS)

    Kammori, O.; Sato, K.; Kurosawa, F.

    1981-01-01

    The infrared absorption spectra of 12 kinds of metal carbides, 11 kinds of nitrides, and 7 kinds of sulfides, a total of 30 materials, were measured and the application of the infrared spectra of these materials to analytical chemistry was discussed. The measurements were done in the frequency (wave length) range of (1400 to 400/cm (7 to 25 mu). The carbides Al4C3, B4C, the nitrides AlN, BN, Si3N4, WB, and the sulfides Al2S3, FeS2, MnS, NiS and PbS were noted to have specific absorptions in the measured region. The sensitivity of Boron nitride was especially good and could be detected at 2 to 3 micrograms in 300 mg of potassium bromide.

  3. Optical properties of TiAlC/TiAlCN/TiAlSiCN/TiAlSiCO/TiAlSiO tandem absorber coatings by phase-modulated spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Jyothi, J.; Biswas, A.; Sarkar, P.; Soum-Glaude, A.; Nagaraja, H. S.; Barshilia, Harish C.

    2017-07-01

    TiAlC, TiAlCN, TiAlSiCN, TiAlSiCO, and TiAlSiO layers of thicknesses 2.2 μm, 755, 491, 393, and 431 nm, respectively, were deposited on stainless steel, silicon, and glass substrates to study their refractive indices and extinction coefficients using the phase-modulated spectroscopic ellipsometry in the wavelength range of 300-1200 nm. Absorption coefficient of each layer was calculated from the extinction coefficient of the layer. The results indicate that the first three layers (i.e., TiAlC, TiAlCN, and TiAlSiCN) are absorbing in nature, while TiAlSiCO and TiAlSiO act as intermediate and antireflection layers. Subsequently, a tandem absorber of TiAlC/TiAlCN/TiAlSiCN/TiAlSiCO/TiAlSiO with layer thicknesses of 62, 20, 18, 16, and 27 nm, respectively, was deposited on stainless steel substrates to fabricate a spectrally selective coating with absorptance of 0.961 and emittance of 0.15 at 82 °C. The obtained refractive indices and extinction coefficients of the tandem absorber were used to simulate the reflectance of the deposited tandem absorber using SCOUT software. Simulated reflectance data of the tandem absorber showed a good agreement with the experimental data measured by UV-Vis-NIR and FTIR spectrophotometry. The angular dependence of the selective properties of the tandem absorber was studied by measuring the reflectance spectra of the tandem absorber at different incident angles.

  4. Percutaneous absorption of urea.

    PubMed

    Ackermann, C; Flynn, G L; Wyk, C J

    1985-12-01

    Synopsis The effect of several variables on the in vitro permeation of urea through hairless mouse skin has been studied in order to determine the causes of an increasing permeability phenomenon found in studies with a range of hydrophilic compounds. The permeation of urea increased for a period of approximately 100 h after which a steady state permeation pattern was observed for approximately 25 h. Urea did not effect its own permeation in concentrations between 0.01 M and 1.67 M, and the same pattern of increasing permeation was followed in the presence of (N-morpholine)propanesulphonic acid and tris(hydroxyme)amino-methane buffers, as in the presence of normal saline. Urea did not affect the permeation of tritiated water. Methanol and water exhibited the same pattern of increasing permeation as urea. The continuously increasing permeation rate of urea up to 100 h is believed to be due to penetration and extensive association of water with the components of the stratum corneum, altering the ultra-structure of the stratum corneum and leading to the formation of large and extensive hydrophilic diffusion channels which do not exist in fresh, untreated skin. These presumed channels open the stratum corneum to facile permeation of highly polar substances such as urea. The physical events leading up to the ultra structural changes within the tissue at the microscopic level remain obscure and are the subject of ongoing research. L'absorption percutanée de l'urée.

  5. 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.

  6. Solar Absorption in Cloudy Atmospheres

    NASA Technical Reports Server (NTRS)

    Harshvardhan; Ridgway, William; Ramaswamy, V.; Freidenreich, S. M.; Batey, Michael

    1996-01-01

    The theoretical computations used to compute spectral absorption of solar radiation are discussed. Radiative properties relevant to the cloud absorption problem are presented and placed in the context of radiative forcing. Implications for future measuring programs and the effect of horizontal inhomogeneities are discussed.

  7. HYDROGEN ADSORPTION ON β-TiAl (001) AND Ni/TiAl (001) SURFACES

    NASA Astrophysics Data System (ADS)

    Mubarak, A. A. Karim; Alelaimi, Mahmoud

    2014-04-01

    In this paper, we present first principles calculations of the energetic, electronic and magnetic properties of the variant termination of TiAl (001) and Ni/TiAl (001) surfaces with and without hydrogen atoms. The calculations have been performed within the density functional theory using full-potential linearized augmented plane wave method. The generalized gradient approximation (GGA) is utilized as the exchange-correlation energy. The octahedral site is the stable absorption site of H atom in the β-TiAl system. This absorption reduces the cohesive energy of β-TiAl system due to increase in the lattice constant. The surface energy for both TiAl (001) terminations is calculated. The stable adsorption site of H atoms on the variant termination of TiAl (001) surface is performed. The adsorption energy of hydrogen on Ti is more energetic than that on Al. The adsorption of H atom on both terminations of H/Ni/TiAl (001) is more preferable at the bridge site. The adsorption energies are enhanced on Ni atom due to the contraction between d-Ni bands and TiAl substrate band.

  8. Optical absorption of silicon nanowires

    SciTech Connect

    Xu, T.; Lambert, Y.; Krzeminski, C.; Grandidier, B.; Stievenard, D.; Leveque, G.; Akjouj, A.; Pennec, Y.; Djafari-Rouhani, B.

    2012-08-01

    We report on simulations and measurements of the optical absorption of silicon nanowires (NWs) versus their diameter. We first address the simulation of the optical absorption based on two different theoretical methods: the first one, based on the Green function formalism, is useful to calculate the scattering and absorption properties of a single or a finite set of NWs. The second one, based on the finite difference time domain (FDTD) method, is well-adapted to deal with a periodic set of NWs. In both cases, an increase of the onset energy for the absorption is found with increasing diameter. Such effect is experimentally illustrated, when photoconductivity measurements are performed on single tapered Si nanowires connected between a set of several electrodes. An increase of the nanowire diameter reveals a spectral shift of the photocurrent intensity peak towards lower photon energies that allow to tune the absorption onset from the ultraviolet radiations to the visible light spectrum.

  9. Bile salts and calcium absorption.

    PubMed

    Webling, D D; Holdsworth, E S

    1966-09-01

    1. The study of the effect of bile salts on enhancing calcium absorption in the rachitic chick has been extended to bile salts not present in chick bile, e.g. glycine conjugates and bile alcohol sulphates. 2. Bile and bile salts cause an increase in calcium absorption from sparingly soluble calcium hydrogen phosphate when compared with a suspension of calcium hydrogen phosphate in saline. 3. If the bile ducts of normal rats are tied the absorption of calcium from calcium hydrogen phosphate decreases but can be restored by giving bile salts with the calcium salt. 4. Bile salts increase solubility in water of the sparingly soluble calcium salts, phytate and phosphate at pH values between 6 and 8. 5. Bile salts increase the solubility in lipid solvents of calcium in approximately the same proportion as they increase the absorption of calcium from the gut. 6. The physiological role of bile in calcium absorption and its mode of action are discussed.

  10. Gas-absorption process

    DOEpatents

    Stephenson, Michael J.; Eby, Robert S.

    1978-01-01

    This invention is an improved gas-absorption process for the recovery of a desired component from a feed-gas mixture containing the same. In the preferred form of the invention, the process operations are conducted in a closed-loop system including a gas-liquid contacting column having upper, intermediate, and lower contacting zones. A liquid absorbent for the desired component is circulated through the loop, being passed downwardly through the column, regenerated, withdrawn from a reboiler, and then recycled to the column. A novel technique is employed to concentrate the desired component in a narrow section of the intermediate zone. This technique comprises maintaining the temperature of the liquid-phase input to the intermediate zone at a sufficiently lower value than that of the gas-phase input to the zone to effect condensation of a major part of the absorbent-vapor upflow to the section. This establishes a steep temperature gradient in the section. The stripping factors below this section are selected to ensure that virtually all of the gases in the downflowing absorbent from the section are desorbed. The stripping factors above the section are selected to ensure re-dissolution of the desired component but not the less-soluble diluent gases. As a result, a peak concentration of the desired component is established in the section, and gas rich in that component can be withdrawn therefrom. The new process provides important advantages. The chief advantage is that the process operations can be conducted in a single column in which the contacting zones operate at essentially the same pressure.

  11. Determination of palladium and platinum by atomic absorption

    USGS Publications Warehouse

    Schnepfe, M.M.; Grimaldi, F.S.

    1969-01-01

    Palladium and platinum are determined by atomic absorption after fire-assay concentration into a gold bead. The limit of determination is ~0??06 ppm in a 20-g sample. Serious depressive interelement interferences are removed by buffering the solutions with a mixture of cadmium and copper sulphates with cadmium and copper concentrations each at 0??5%. Substantial amounts of Ag, Al, Au, Bi, Ca, Co, Cr, Fe, Hg, K, La, Mg, Mn, Mo, Na, Ni, Pb, Te, Ti, V, Y, Zn, and the platinum metals do not interfere in the atomic-absorption determination. ?? 1969.

  12. Atomic-absorption determination of rhodium in chromite concentrates

    USGS Publications Warehouse

    Schnepfe, M.M.; Grimaldi, F.S.

    1969-01-01

    Rhodium is determined in chromite concentrates by atomic absorption after concentration either by co-precipitation with tellurium formed by the reduction of tellurite with tin(II) chloride or by fire assay into a gold bead. Interelement interferences in the atomic-absorption determination are removed by buffering the solutions with lanthanum sulphate (lanthanum concentration 1%). Substantial amounts of Ag, Al, Au, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ho, Hg, K, La, Mg, Mn, Mo, Na, Ni, Pb, Te, Ti, V, Y, Zn and platinum metals can be tolerated. A lower limit of approximately 0.07 ppm Rh can be determined in a 3-g sample. ?? 1969.

  13. Gastrointestinal citrate absorption in nephrolithiasis

    NASA Technical Reports Server (NTRS)

    Fegan, J.; Khan, R.; Poindexter, J.; Pak, C. Y.

    1992-01-01

    Gastrointestinal absorption of citrate was measured in stone patients with idiopathic hypocitraturia to determine if citrate malabsorption could account for low urinary citrate. Citrate absorption was measured directly from recovery of orally administered potassium citrate (40 mEq.) in the intestinal lavage fluid, using an intestinal washout technique. In 7 stone patients citrate absorption, serum citrate levels, peak citrate concentration in serum and area under the curve were not significantly different from those of 7 normal subjects. Citrate absorption was rapid and efficient in both groups, with 96 to 98% absorbed within 3 hours. The absorption of citrate was less efficient from a tablet preparation of potassium citrate than from a liquid preparation, probably due to a delayed release of citrate from wax matrix. However, citrate absorption from solid potassium citrate was still high at 91%, compared to 98% for a liquid preparation. Thus, hypocitraturia is unlikely to be due to an impaired gastrointestinal absorption of citrate in stone patients without overt bowel disease.

  14. Gastrointestinal citrate absorption in nephrolithiasis

    NASA Technical Reports Server (NTRS)

    Fegan, J.; Khan, R.; Poindexter, J.; Pak, C. Y.

    1992-01-01

    Gastrointestinal absorption of citrate was measured in stone patients with idiopathic hypocitraturia to determine if citrate malabsorption could account for low urinary citrate. Citrate absorption was measured directly from recovery of orally administered potassium citrate (40 mEq.) in the intestinal lavage fluid, using an intestinal washout technique. In 7 stone patients citrate absorption, serum citrate levels, peak citrate concentration in serum and area under the curve were not significantly different from those of 7 normal subjects. Citrate absorption was rapid and efficient in both groups, with 96 to 98% absorbed within 3 hours. The absorption of citrate was less efficient from a tablet preparation of potassium citrate than from a liquid preparation, probably due to a delayed release of citrate from wax matrix. However, citrate absorption from solid potassium citrate was still high at 91%, compared to 98% for a liquid preparation. Thus, hypocitraturia is unlikely to be due to an impaired gastrointestinal absorption of citrate in stone patients without overt bowel disease.

  15. Differential-absorption photoacoustic imaging.

    PubMed

    Huang, Sheng-Wen; Eary, Janet F; Jia, Congxian; Huang, Lingyun; Ashkenazi, Shai; O'Donnell, Matthew

    2009-08-15

    We present differential-absorption photoacoustic imaging, which detects the difference between transient and ground-state absorption, for contrast enhancement based on suppressing undesired objects. Two tubes were imaged. One contains a Pt(II) octaethylporphine (PtOEP) dye solution and serves as an object of interest, while the other contains an IR-783 (from Sigma-Aldrich) dye solution and serves as an object to suppress. Although the IR-783 tube dominates the conventional photoacoustic image, it is suppressed by 43 dB and consequently significantly overwhelmed by the PtOEP tube in the differential-absorption photoacoustic image. Imaging depth in this mode is also discussed.

  16. AlGaAs diode pumped tunable chromium lasers

    DOEpatents

    Krupke, William F.; Payne, Stephen A.

    1992-01-01

    An all-solid-state laser system is disclosed wherein the laser is pumped in the longwave wing of the pump absorption band. By utilizing a laser material that will accept unusually high dopant concentrations without deleterious effects on the crystal lattice one is able to compensate for the decreased cross section in the wing of the absorption band, and the number of pump sources which can be used with such a material increases correspondingly. In a particular embodiment a chromium doped colquiriite-structure crystal such as Cr:LiSrAlF.sub.6 is the laser material. The invention avoids the problems associated with using AlGaInP diodes by doping the Cr:LiSrAlF.sub.6 heavily to enable efficient pumping in the longwave wing of the absorption band with more practical AlGaAs diodes.

  17. The source of 3-μm absorption in Jupiter’s clouds: Reanalysis of ISO observations using new NH3 absorption models

    NASA Astrophysics Data System (ADS)

    Sromovsky, L. A.; Fry, P. M.

    2010-11-01

    A prominent characteristic of jovian near-IR spectra is the widely distributed presence of a strong absorption at wavelengths from about 2.9 μm to 3.1 μm, first noticed in a 3-μm spectrum obtained by the Infrared Space Observatory (ISO) in 1996. While Brooke et al. (Brooke, T.Y., Knacke, R.F., Encrenaz, T., Drossart, P., Crisp, D., Feuchtgruber, H. [1998]. Icarus 136, 1-13) were able to fit the ISO spectrum very well using ammonia ice as the sole source of particulate absorption, Irwin et al. (Irwin, P.G.J., Weir, A.L., Taylor, F.W., Calcutt, S.B., Carlson, R.W. [2001]. Icarus 149, 397-415) noted that their best-fit cloud model implied a strong absorption at 2 μm that was not observed in Galileo NIMS spectra, raising questions about the source of the absorption. Subsequent significant revisions in ammonia gas absorption models (Bowles, N., Calcutt, S., Irwin, P., Temple, J. [2008]. Icarus 196, 612-614) also raised questions about these conclusions because ammonia gas absorption overlaps regions of ammonia ice absorption. Our reanalysis, based on improved ammonia absorption models, finds that the ISO spectrum can be well fit by models that include both NH 3 ice and solid NH 4SH, with the latter substance providing most of the absorption. The component due to NH 3 is very possibly due to NH 3 present as a coating on either large ( r ˜ 15 μm) NH 4SH particles in a deeper layer at ˜550 mb or on small ( r ˜ 0.3 μm) photochemical haze particles in a lower pressure layer at ˜370 mb. Neither option creates conflict with the lack of significant NH 3 absorption features at thermal wavelengths.

  18. Two Photon Absorption Characterization

    DTIC Science & Technology

    1989-05-15

    0 . cc, > 4) ( AL ) 01N3NIISVI Sample #10 2 1T =9K X =9.20 t 0 9.4 4 01 z 0 (L Cl) 102 z 0 0 0 0 0 2 4 6 ...1.6x10 5 122.0 0.237 9.8 - 4 n, 2.8x101 4 1.2x] 0 5 125.0 0.239 10.0 60.0 5 n, 2.3x,014 1.3x, 0 5 136.0 0.245 10.4 - - 6 n, - 5x1014 cc 1x105...222.0 0.294 - 116.0 111.5 10 p, 1.5xlO1 5 500.0 225.0 0.298 - 108.0 113.0 Sample #2 T=7K k=9.22 .m ci, z 0 C,)w > 9.77 0 20

  19. Encapsulation effects on carbonaceous aerosol light absorption

    SciTech Connect

    Sedlacek, A.J.; Onasch, T.; Davidovits, P.; Cross, E.; Mazzoleni, C.

    2010-03-15

    monotonic increase in light absorption to nearly 100% is observed as a function of DOS coating thickness. This observation is consistent with a coating-induced amplification in particle light absorption (Bond et al. 2006). In contrast, light absorption by sulfuric acid-coated soot displays unexpectedly complex behavior where the degree of amplification appears to be dependent upon the underlying soot core diameter.

  20. Microwave radiation absorption: behavioral effects.

    PubMed

    D'Andrea, J A

    1991-07-01

    The literature contains much evidence that absorption of microwave energy will lead to behavioral changes in man and laboratory animals. The changes include simple perturbations or outright stoppage of ongoing behavior. On one extreme, intense microwave absorption can result in seizures followed by death. On the other extreme, man and animals can hear microwave pulses at very low rates of absorption. Under certain conditions of exposure, animals will avoid microwaves, while under other conditions, they will actively work to obtain warmth produced by microwaves. Some research has shown behavioral effects during chronic exposure to low-level microwaves. The specific absorption rates that produce behavioral effects seem to depend on microwave frequency, but controversy exists over thresholds and mechanism of action. In all cases, however, the behavioral disruptions cease when chronic microwave exposure is terminated. Thermal changes in man and animals during microwave exposure appear to account for all reported behavioral effects.

  1. Neutron absorption constraints on the composition of 4 Vesta

    USGS Publications Warehouse

    Prettyman, Thomas H.; Mittlefehldt, David W.; Yamashita, Naoyuki; Beck, Andrew W.; Feldman, William C.; Hendricks, John S.; Lawrence, David J.; McCoy, Timothy J.; McSween, Harry Y.; Paplowski, Patrick N.; Reedy, Robert C.; Toplis, Michael J.; Le Corre, Lucille; Mizzon, Hugau; Reddy, Vishnu; Titus, Timothy N.; Raymond, Carol A.; Russell, Christopher T.

    2013-01-01

    Global maps of the macroscopic thermal neutron absorption cross section of Vesta's regolith by the Gamma Ray and Neutron Detector (GRaND) on board the NASA Dawn spacecraft provide constraints on the abundance and distribution of Fe, Ca, Al, Mg, and other rock-forming elements. From a circular, polar low-altitude mapping orbit, GRaND sampled the regolith to decimeter depths with a spatial resolution of about 300 km. At this spatial scale, the variation in neutron absorption is about seven times lower than that of the Moon. The observed variation is consistent with the range of absorption for howardite whole-rock compositions, which further supports the connection between Vesta and the howardite, eucrite, and diogenite meteorites. We find a strong correlation between neutron absorption and the percentage of eucritic materials in howardites and polymict breccias, which enables petrologic mapping of Vesta's surface. The distribution of basaltic eucrite and diogenite determined from neutron absorption measurements is qualitatively similar to that indicated by visible and near infrared spectroscopy. The Rheasilvia basin and ejecta blanket has relatively low absorption, consistent with Mg-rich orthopyroxene. Based on a combination of Fe and neutron absorption measurements, olivine-rich lithologies are not detected on the spatial scales sampled by GRaND. The sensitivity of GRaND to the presence of mantle material is described and implications for the absence of an olivine signature are discussed. High absorption values found in Vesta's “dark” hemisphere, where exogenic hydrogen has accumulated, indicate that this region is richer in basaltic eucrite, representative of Vesta's ancient upper crust.

  2. Neutron absorption constraints on the composition of 4 Vesta

    NASA Astrophysics Data System (ADS)

    Prettyman, Thomas H.; Mittlefehldt, David W.; Yamashita, Naoyuki; Beck, Andrew W.; Feldman, William C.; Hendricks, John S.; Lawrence, David J.; McCoy, Timothy J.; McSween, Harry Y.; Peplowski, Patrick N.; Reedy, Robert C.; Toplis, Michael J.; Corre, Lucille; Mizzon, Hugau; Reddy, Vishnu; Titus, Timothy N.; Raymond, Carol A.; Russell, Christopher T.

    2013-11-01

    Global maps of the macroscopic thermal neutron absorption cross section of Vesta's regolith by the Gamma Ray and Neutron Detector (GRaND) on board the NASA Dawn spacecraft provide constraints on the abundance and distribution of Fe, Ca, Al, Mg, and other rock-forming elements. From a circular, polar low-altitude mapping orbit, GRaND sampled the regolith to decimeter depths with a spatial resolution of about 300 km. At this spatial scale, the variation in neutron absorption is about seven times lower than that of the Moon. The observed variation is consistent with the range of absorption for howardite whole-rock compositions, which further supports the connection between Vesta and the howardite, eucrite, and diogenite meteorites. We find a strong correlation between neutron absorption and the percentage of eucritic materials in howardites and polymict breccias, which enables petrologic mapping of Vesta's surface. The distribution of basaltic eucrite and diogenite determined from neutron absorption measurements is qualitatively similar to that indicated by visible and near infrared spectroscopy. The Rheasilvia basin and ejecta blanket has relatively low absorption, consistent with Mg-rich orthopyroxene. Based on a combination of Fe and neutron absorption measurements, olivine-rich lithologies are not detected on the spatial scales sampled by GRaND. The sensitivity of GRaND to the presence of mantle material is described and implications for the absence of an olivine signature are discussed. High absorption values found in Vesta's "dark" hemisphere, where exogenic hydrogen has accumulated, indicate that this region is richer in basaltic eucrite, representative of Vesta's ancient upper crust.

  3. Absorptive thermodynamic apparatus and method

    SciTech Connect

    Kantor, F.W.

    1988-02-02

    This patent describes an absorptive thermodynamic device including an absorber chamber in which a gas is absorbed in an absorbant liquid, a separator chamber having means for conducting heat into a liquid in the chamber to drive the gas out of the liquid, means for pumping the liquid through a closed circuit path including the absorber and separator chambers, and means for conducting from the absorber chamber to the separator chamber heat developed by the absorption of the gas in the liquid.

  4. Arsenate uptake by Al nanoclusters and other Al-based sorbents during water treatment.

    PubMed

    Mertens, Jasmin; Rose, Jérôme; Wehrli, Bernhard; Furrer, Gerhard

    2016-01-01

    In many parts of the world, arsenic from geogenic and anthropogenic sources deteriorates the quality of drinking water resources. Effective methods of arsenic removal include adsorption and coagulation with iron- and aluminum-based materials, of which polyaluminum chloride is widely employed as coagulant in water treatment due to its low cost and high efficiency. We compared the arsenic uptake capacity and the arsenic bonding sites of different Al-based sorbents, including Al nanoclusters, polyaluminum chloride, polyaluminum granulate, and gibbsite. Extended X-ray absorption fine structure (EXAFS) spectroscopy revealed that As(V) forms bidentate-binuclear complexes in interaction with all Al-based removal agents. The octahedral configuration of nanoclusters and the distribution of sorption sites remain the same in all types of removal agents consisting of nano-scale Al oxyhydroxide particles. The obtained distances for As(V)-O and As(V)-Al agreed with previously published data and were found to be 1.69 ± 0.02 Å and 3.17-3.21 Å, respectively. Our study suggests that As(V) binds to Al nanoclusters as strongly as to Al oxide surfaces. The As sorption capacity of Al nanoclusters was found to be very similar to that of Al clusters in a polyaluminum chloride. The most efficient Al-based sorbents for arsenic removal were Al nanoclusters, followed by polyaluminum granulate.

  5. Reflective-tube absorption meter

    NASA Astrophysics Data System (ADS)

    Zaneveld, J. Ronald V.; Bartz, Robert; Kitchen, James C.

    1990-09-01

    The design and calibration of a proposed in situ spectral absorption meter is evaluated using a laboratory prototype. The design includes a silver coated (second-surface) glass tube, a tungsten light source (stabilized by means of optical feedback), a monochromator, and a solid state detector. The device measures the absorption coefficient plus a portion of the volume scattering function. Theoretical analyses and laboratory experiments which explore the magnitude and variation of the errors due to scattering and internal reflections are described. Similar analyses are performed on the Cary 1 18 Spectrophotometer to allow cross calibration. Algorithms to yield the abscrption coefficient and the zenith-sun diffuse attenuation coefficient are presented and evaluated. Simultaneous measurement of the beam attenuation or backscattering coefficient allows use of algoriThms with much narrower error bands. The various methods of obtaining absorption and diffuse attenuation values are compared. Procedures for using reverse osmosis filtration to produce a clean water calibration standard are described. An absorption spectrum for pure water is obtained. Development of the absorption meter is proceeding along two lines: 1) a two-wavelength side-by-side LED is being fabricated to allow an in situ chlorophyll a absorption meter to be constructed, and 2) scientific projects using a shipboard or laboratory flow.-through pumping system are being planned.

  6. Incomplete intestinal absorption of fructose.

    PubMed Central

    Kneepkens, C M; Vonk, R J; Fernandes, J

    1984-01-01

    Intestinal D-fructose absorption in 31 children was investigated using measurements of breath hydrogen. Twenty five children had no abdominal symptoms and six had functional bowel disorders. After ingestion of fructose (2 g/kg bodyweight), 22 children (71%) showed a breath hydrogen increase of more than 10 ppm over basal values, indicating incomplete absorption: the increase averaged 53 ppm, range 12 to 250 ppm. Four of these children experienced abdominal symptoms. Three of the six children with bowel disorders showed incomplete absorption. Seven children were tested again with an equal amount of glucose, and in three of them also of galactose, added to the fructose. The mean maximum breath hydrogen increases were 5 and 10 ppm, respectively, compared with 103 ppm after fructose alone. In one boy several tests were performed with various sugars; fructose was the only sugar incompletely absorbed, and the effect of glucose on fructose absorption was shown to be dependent on the amount added. It is concluded that children have a limited absorptive capacity for fructose. We speculate that the enhancing effect of glucose and galactose on fructose absorption may be due to activation of the fructose carrier. Apple juice in particular contains fructose in excess of glucose and could lead to abdominal symptoms in susceptible children. PMID:6476870

  7. Abu al-Layth al-Libi

    DTIC Science & Technology

    2015-02-01

    jihadi doctrine, al-Libi enrolled himself in the recently erected and highly popular al-Faruq 2 “Al-Sahab Releases ‘Winds of Paradise , Part III...February 2008, http://news.bbc.co.uk/2/hi/south_asia/7220823.stm. 3 “Al-Sahab Releases ‘Winds of Paradise , Part III,’” Global Terrorism Research Project...5 “Al-Sahab Releases ‘Winds of Paradise , Part III,’” Global Terrorism Research Project. 6 Ibid. The date provided in the video is 1410

  8. Absorption of solar radiation in broken clouds

    SciTech Connect

    Zuev, V.E.; Titov, G.A.; Zhuravleva, T.B.

    1996-04-01

    It is recognized now that the plane-parallel model unsatisfactorily describes the transfer of radiation through broken clouds and that, consequently, the radiation codes of general circulation models (GCMs) must be refined. However, before any refinement in a GCM code is made, it is necessary to investigate the dependence of radiative characteristics on the effects caused by the random geometry of cloud fields. Such studies for mean fluxes of downwelling and upwelling solar radiation in the visible and near-infrared (IR) spectral range were performed by Zuev et al. In this work, we investigate the mean spectral and integrated absorption of solar radiation by broken clouds (in what follows, the term {open_quotes}mean{close_quotes} will be implied but not used, for convenience). To evaluate the potential effect of stochastic geometry, we will compare the absorption by cumulus (0.5 {le} {gamma} {le} 2) to that by equivalent stratus ({gamma} <<1) clouds; here {gamma} = H/D, H is the cloud layer thickness and D the characteristic horizontal cloud size. The equivalent stratus clouds differ from cumulus only in the aspect ratio {gamma}, all the other parameters coinciding.

  9. What Is ALS?

    MedlinePlus

    ... Javits, actor David Niven, “Sesame Street” creator Jon Stone, boxing champion Ezzard Charles, NBA Hall of Fame ... Help for People with ALS and Caregivers Read stories from families living with ALS Forms of ALS ...

  10. Fat-soluble vitamin intestinal absorption: absorption sites in the intestine and interactions for absorption.

    PubMed

    Goncalves, Aurélie; Roi, Stéphanie; Nowicki, Marion; Dhaussy, Amélie; Huertas, Alain; Amiot, Marie-Josèphe; Reboul, Emmanuelle

    2015-04-01

    The interactions occurring at the intestinal level between the fat-soluble vitamins A, D, E and K (FSVs) are poorly documented. We first determined each FSV absorption profile along the duodenal-colonic axis of mouse intestine to clarify their respective absorption sites. We then investigated the interactions between FSVs during their uptake by Caco-2 cells. Our data show that vitamin A was mostly absorbed in the mouse proximal intestine, while vitamin D was absorbed in the median intestine, and vitamin E and K in the distal intestine. Significant competitive interactions for uptake were then elucidated among vitamin D, E and K, supporting the hypothesis of common absorption pathways. Vitamin A also significantly decreased the uptake of the other FSVs but, conversely, its uptake was not impaired by vitamins D and K and even promoted by vitamin E. These results should be taken into account, especially for supplement formulation, to optimise FSV absorption.

  11. Substitutional alloy of Ce and Al

    PubMed Central

    Zeng, Qiao-Shi; Ding, Yang; Mao, Wendy L.; Luo, Wei; Blomqvist, Andreas; Ahuja, Rajeev; Yang, Wenge; Shu, Jinfu; Sinogeikin, Stas V.; Meng, Yue; Brewe, Dale L.; Jiang, Jian-Zhong; Mao, Ho-kwang

    2009-01-01

    The formation of substitutional alloys has been restricted to elements with similar atomic radii and electronegativity. Using high-pressure at 298 K, we synthesized a face-centered cubic disordered alloy of highly dissimilar elements (large Ce and small Al atoms) by compressing the Ce3Al intermetallic compound >15 GPa or the Ce3Al metallic glass >25 GPa. Synchrotron X-ray diffraction, Ce L3-edge absorption spectroscopy, and ab initio calculations revealed that the pressure-induced Kondo volume collapse and 4f electron delocalization of Ce reduced the differences between Ce and Al and brought them within the Hume-Rothery (HR) limit for substitutional alloying. The alloy remained after complete release of pressure, which was also accompanied by the transformation of Ce back to its ambient 4f electron localized state and reversal of the Kondo volume collapse, resulting in a non-HR alloy at ambient conditions. PMID:19188608

  12. Bile salts and calcium absorption

    PubMed Central

    Webling, D. D'A.; Holdsworth, E. S.

    1966-01-01

    1. The study of the effect of bile salts on enhancing calcium absorption in the rachitic chick has been extended to bile salts not present in chick bile, e.g. glycine conjugates and bile alcohol sulphates. 2. Bile and bile salts cause an increase in calcium absorption from sparingly soluble calcium hydrogen phosphate when compared with a suspension of calcium hydrogen phosphate in saline. 3. If the bile ducts of normal rats are tied the absorption of calcium from calcium hydrogen phosphate decreases but can be restored by giving bile salts with the calcium salt. 4. Bile salts increase solubility in water of the sparingly soluble calcium salts, phytate and phosphate at pH values between 6 and 8. 5. Bile salts increase the solubility in lipid solvents of calcium in approximately the same proportion as they increase the absorption of calcium from the gut. 6. The physiological role of bile in calcium absorption and its mode of action are discussed. PMID:4291037

  13. Absorption and Metabolism of Xanthophylls

    PubMed Central

    Kotake-Nara, Eiichi; Nagao, Akihiko

    2011-01-01

    Dietary carotenoids, especially xanthophylls, have attracted significant attention because of their characteristic biological activities, including anti-allergic, anti-cancer, and anti-obese actions. Although no less than forty carotenoids are ingested under usual dietary habits, only six carotenoids and their metabolites have been found in human tissues, suggesting selectivity in the intestinal absorption of carotenoids. Recently, facilitated diffusion in addition to simple diffusion has been reported to mediate the intestinal absorption of carotenoids in mammals. The selective absorption of carotenoids may be caused by uptake to the intestinal epithelia by the facilitated diffusion and an unknown excretion to intestinal lumen. It is well known that β-carotene can be metabolized to vitamin A after intestinal absorption of carotenoids, but little is known about the metabolic transformation of non provitamin A xanthophylls. The enzymatic oxidation of the secondary hydroxyl group leading to keto-carotenoids would occur as a common pathway of xanthophyll metabolism in mammals. This paper reviews the absorption and metabolism of xanthophylls by introducing recent advances in this field. PMID:21747746

  14. Multiple Absorption Components in the Post-Periastron He I P Cygni Absorption Troughs of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Richardson, Noel D.; Damineli, Augusto; Gull, Ted; Moffat, Anthony; Groh, Jose; St.-Jean, Lucas; Walter, Frederick M.; Teodoro, Mairan; Madura, Tom; Corcoran, Michael; Hamaguchi, Kenji; Russell, Christopher

    2015-01-01

    We have obtained more than 100 high spectral resolution (R approx. 90,000) spectra of the massive binary star eta Carinae since 2012 in an effort to continue our orbital and long-term echelle monitoring of this extreme binary (Richardson et al. 2010, AJ, 139, 1534) with the CHIRON spectrograph on the CTIO 1.5 m telescope (Tokovinin et al. 2013, PASP, 125, 1336) in the 4550-7500A region. We increased our monitoring efforts and observation frequency as the periastron event of 2014 has approached, and resumed observations in October. We note that since mid-October, we have observed unusual multiple absorption components in the P Cygni troughs of the He I lines (4714, 5876, 6678, and 7065; 4921 and 5015 are blended with Fe II). In particular, we note that these components extend to -700 km/s, well beyond the terminal wind speed of the primary. These absorptions are likely related to clumps and turbulence in the wind-wind collision region and bow shock, as suggested by the high-velocity absorption observed by Groh et al. (2010, A&A, 519, 9) in the He I 10830A transition and our pre-periastron observations (Richardson et al. 2014, ATel #6336). In these cases, we suspect that we look along an arm of the shock cone and that we see a fast absorption change from the other collision region shortly after periastron. Further, high spectral resolution data are highly encouraged, especially for resolving powers greater than 50,000. These observations were obtained with the CTIO 1.5 m telescope, operated by the SMARTS Consortium, and were obtained through both SMARTS and NOAO programs 2012A-0216, 2012B-0194, and 2013b-0328. We thank Emily MacPherson (Yale) for her efforts in scheduling the observations that we have and will obtain in the coming weeks and months.

  15. Electronic Spectroscopy of AlArn Clusters: Evidence for Surface Binding of Al Atoms

    NASA Astrophysics Data System (ADS)

    Okumura, Mitchio; Spotts, James M.; Wong, Chi-Kin

    1997-04-01

    Solvent-induced-frequency shifts and splittings of the 3p arrow 3d transition of Al atoms in Al(Ar)n clusters were studied to investigate the site occupied by the Al atom in these clusters. The electronic spectra were recorded near 300 nm for several sizes in the range n = 1 to 60 by resonant two-photon photoionization spectroscopy. The observed bands differ significantly from UV absorption spectra of Al atoms in Ar matrices, and the variations in splittings and shifts as a function of cluster size do not converge on the matrix limit. These results are interpreted with a model in which the Al atom is bound to the surface of an Arn cluster rather than solvated within the cluster interior.

  16. APM Z >=4 QSO Survey: Spectra and Intervening Absorption Systems

    NASA Astrophysics Data System (ADS)

    Storrie-Lombardi, L. J.; McMahon, R. G.; Irwin, M. J.; Hazard, C.

    1996-09-01

    The APM multicolor survey for bright z > 4 objects, covering 2500 deg^2^ of sky to m_r_ ~ 19, resulted in the discovery of 31 quasars with z ~> 4. High signal-to-noise optical spectrophotometry at 5 A resolution has been obtained for the 28 quasars easily accessible from the northern hemisphere. These spectra have been surveyed to create new samples of high-redshift Lyman-limit systems, damped Lyα absorbers, and metal absorption systems (e.g., C IV and Mg II). In this paper we present the spectra, together with line lists of the detected absorption systems. The QSOs display a wide variety of emission- and absorption-line characteristics, with five exhibiting broad absorption lines and one with extremely strong emission lines (BR 2248 - 1242). Eleven candidate damped Lyα absorption systems have been identified covering the redshift range 2.8 <= z <= 4.4 (eight with z > 3.5). An analysis of the measured redshifts of the high-ionization emission lines with the low-ionization lines shows them to be blueshifted by 430 +/- 60 km s^-1^. In a previous paper (by Storrie-Lombardi et al.) we discussed the redshift evolution of the Lyman limit systems cataloged here. In subsequent papers we will discuss the properties of the Lyα forest absorbers and the redshift and column density evolution of the damped Lyα absorbers.

  17. The distribution of absorptive power dissipation in irradiated nanoparticulate system

    NASA Astrophysics Data System (ADS)

    Li, Jiayu; Yang, Jian; Gu, Xiaobing

    2016-10-01

    The knowledge of local radiant absorption is important to the nanostructure optimization, it is beneficial to the applications in energy harvesting, optical heating, photocatalysis, etc. In this paper, FDTD model is constructed for the distribution of absorptive power dissipation in irradiated nanoparticulate system. The theoretical model extended from Mie theory is used to examine the FDTD model, the parameters and conditions set for FDTD simulation are confirmed based on the comparison. Then, the influence of Ag nanoparticle on the absorptive properties of nearby TiO2 nanoparticle is investigated by FDTD simulation at the wavelength of 0.25 μm. It is indicated that suitable distance between TiO2 and Ag particles is beneficial to the spectral radiant absorption of TiO2 particle. Considering the agglomeration of nanoparticles and the oxidation at the TiO2-Ag interface, the Ag core coated with Al2O3 shell is suggested, and the simulated results indicated that the shell thickness and the Ag core size need to be optimized for enhancing the radiant absorption of TiO2 particle.

  18. Enhanced absorption cycle computer model

    NASA Astrophysics Data System (ADS)

    Grossman, G.; Wilk, M.

    1993-09-01

    Absorption heat pumps have received renewed and increasing attention in the past two decades. The rising cost of electricity has made the particular features of this heat-powered cycle attractive for both residential and industrial applications. Solar-powered absorption chillers, gas-fired domestic heat pumps, and waste-heat-powered industrial temperature boosters are a few of the applications recently subjected to intensive research and development. The absorption heat pump research community has begun to search for both advanced cycles in various multistage configurations and new working fluid combinations with potential for enhanced performance and reliability. The development of working absorption systems has created a need for reliable and effective system simulations. A computer code has been developed for simulation of absorption systems at steady state in a flexible and modular form, making it possible to investigate various cycle configurations with different working fluids. The code is based on unit subroutines containing the governing equations for the system's components and property subroutines containing thermodynamic properties of the working fluids. The user conveys to the computer an image of his cycle by specifying the different subunits and their interconnections. Based on this information, the program calculates the temperature, flow rate, concentration, pressure, and vapor fraction at each state point in the system, and the heat duty at each unit, from which the coefficient of performance (COP) may be determined. This report describes the code and its operation, including improvements introduced into the present version. Simulation results are described for LiBr-H2O triple-effect cycles, LiCl-H2O solar-powered open absorption cycles, and NH3-H2O single-effect and generator-absorber heat exchange cycles. An appendix contains the user's manual.

  19. Absorption-heat-pump system

    DOEpatents

    Grossman, G.; Perez-Blanco, H.

    1983-06-16

    An improvement in an absorption heat pump cycle is obtained by adding adiabatic absorption and desorption steps to the absorber and desorber of the system. The adiabatic processes make it possible to obtain the highest temperature in the absorber before any heat is removed from it and the lowest temperature in the desorber before heat is added to it, allowing for efficient utilization of the thermodynamic availability of the heat supply stream. The improved system can operate with a larger difference between high and low working fluid concentrations, less circulation losses, and more efficient heat exchange than a conventional system.

  20. Advanced absorption heat pump cycles

    NASA Astrophysics Data System (ADS)

    Reimann, R. C.

    The main goal is the development of significantly improved absorption machinery. This was to be directed specifically towards the development of a direct natural gas-fired absorption heat pump with both heating and cooling efficiencies advanced beyond current commercial offerings. These were to be accomplished through the use of novel and superior cycles, or by improved component performance. To keep the focus on machinery, the stipulation was agreed that candidate absorbent-refrigerant combinations were to be selected from among those whose properties were adequately known to permit cycle calculations and preliminary machine layouts.

  1. Transient absorption spectroscopy of laser shocked explosives

    SciTech Connect

    Mcgrane, Shawn D; Dang, Nhan C; Whitley, Von H; Bolome, Cindy A; Moore, D S

    2010-01-01

    Transient absorption spectra from 390-890 nm of laser shocked RDX, PETN, sapphire, and polyvinylnitrate (PVN) at sub-nanosecond time scales are reported. RDX shows a nearly linear increase in absorption with time after shock at {approx}23 GPa. PETN is similar, but with smaller total absorption. A broad visible absorption in sapphire begins nearly immediately upon shock loading but does not build over time. PVN exhibits thin film interference in the absorption spectra along with increased absorption with time. The absorptions in RDX and PETN are suggested to originate in chemical reactions happening on picosecond time scales at these shock stresses, although further diagnostics are required to prove this interpretation.

  2. Toward a better understanding of pesticide dermal absorption: diffusion model analysis of parathion absorption in vitro and in vivo.

    PubMed

    Miller, Matthew A; Kasting, Gerald B

    2010-01-01

    Human skin absorption of radiolabeled parathion was studied in vitro at specific doses (mass loadings) of 0.4, 4.0, 41, or 117 microg/cm(2), with and without occlusion. The compound was applied in small volumes of acetone solution to split-thickness skin. Permeation of radiolabel into the receptor solutions was monitored for 76 h, after which the tissue was dissected and analyzed for residual radioactivity. For the 3 lower doses, cumulative permeation after 76 h was approximately dose-proportional, ranging from 28.5-30.5% of applied dose (unoccluded) to 45.5-55.7% (occluded). Total absorption, calculated as receptor fluid plus dermis content, followed a similar pattern. Both permeation rate and total absorption continued to increase up to the highest dose tested, consistent with results from other laboratories. These results are compared with predictions from a previously developed skin diffusion model (Kasting et al., 2008a). The model predicted total absorption to within a factor of 1.4 at 0.4 microg/cm(2) and 1.6 at 4 microg/cm(2), but substantially underpredicted absorption at the 2 higher doses. The analysis showed that parathion partitioned more favorably into the stratum corneum than the diffusion model prediction. Nevertheless, comparison of the model predictions to a previously reported human study showed that the skin absorption model, when corrected for surface losses occurring in vivo, satisfactorily described in vivo dermal absorption of parathion applied at 4 microg/cm(2) to various body sites.

  3. Aerosol Absorption Measurements in MILAGRO.

    NASA Astrophysics Data System (ADS)

    Gaffney, J. S.; Marley, N. A.; Arnott, W. P.; Paredes-Miranda, L.; Barnard, J. C.

    2007-12-01

    During the month of March 2006, a number of instruments were used to determine the absorption characteristics of aerosols found in the Mexico City Megacity and nearby Valley of Mexico. These measurements were taken as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City (MAX-Mex) that was carried out in collaboration with the Megacity Interactions: Local and Global Research Observations (MILAGRO) campaign. MILAGRO was a joint effort between the DOE, NSF, NASA, and Mexican agencies aimed at understanding the impacts of a megacity on the urban and regional scale. A super-site was operated at the Instituto Mexicano de Petroleo in Mexico City (designated T-0) and at the Universidad Technologica de Tecamac (designated T-1) that was located about 35 km to the north east of the T-0 site in the State of Mexico. A third site was located at a private rancho in the State of Hidalgo approximately another 35 km to the northeast (designated T-2). Aerosol absorption measurements were taken in real time using a number of instruments at the T-0 and T-1 sites. These included a seven wavelength aethalometer, a multi-angle absorption photometer (MAAP), and a photo-acoustic spectrometer. Aerosol absorption was also derived from spectral radiometers including a multi-filter rotating band spectral radiometer (MFRSR). The results clearly indicate that there is significant aerosol absorption by the aerosols in the Mexico City megacity region. The absorption can lead to single scattering albedo reduction leading to values below 0.5 under some circumstances. The absorption is also found to deviate from that expected for a "well-behaved" soot anticipated from diesel engine emissions, i.e. from a simple 1/lambda wavelength dependence for absorption. Indeed, enhanced absorption is seen in the region of 300-450 nm in many cases, particularly in the afternoon periods indicating that secondary organic aerosols are contributing to the aerosol absorption. This is likely due

  4. Metal powder absorptivity: Modeling and experiment

    SciTech Connect

    Boley, C. D.; Mitchell, S. C.; Rubenchik, A. M.; Wu, S. S. Q.

    2016-08-10

    Here, we present results of numerical modeling and direct calorimetric measurements of the powder absorptivity for a number of metals. The modeling results generally correlate well with experiment. We show that the powder absorptivity is determined, to a great extent, by the absorptivity of a flat surface at normal incidence. Our results allow the prediction of the powder absorptivity from normal flat-surface absorptivity measurements.

  5. Metal powder absorptivity: Modeling and experiment

    SciTech Connect

    Boley, C. D.; Mitchell, S. C.; Rubenchik, A. M.; Wu, S. S. Q.

    2016-08-10

    Here, we present results of numerical modeling and direct calorimetric measurements of the powder absorptivity for a number of metals. The modeling results generally correlate well with experiment. We show that the powder absorptivity is determined, to a great extent, by the absorptivity of a flat surface at normal incidence. Our results allow the prediction of the powder absorptivity from normal flat-surface absorptivity measurements.

  6. Alanes formation on the Al(111) surface

    NASA Astrophysics Data System (ADS)

    Rangan, Sylvie; Veyan, Jean-Francois; Chabal, Yves J.; Chaudhuri, Santanu; Muckerman, James T.

    2008-03-01

    Alane clusters (AlxHy) are believed to be the ubiquitous intermediates in hydrogen storage reactions for a wide variety of alanates (LiAlH4, NaAlH4) currently considered for hydrogen storage. The formation and behavior of alanes at surfaces appear to control and limit the efficiency of hydrogen storage. In particular, hydrogen adsorption on the Al(111) surface leads to the coexistence of several adsorbed species, the concentration of which is affected by the step density, the surface coverage and the temperature. We combine density functional theory (DFT) and surface infra-red (IR) absorption spectroscopy to uncover the mechanisms for alane formation on Al(111) surfaces. At low coverage, DFT predicts a two-fold bridge site adsorption for atomic hydrogen, consistent with previous Electron Energy Loss Spectroscopy measurements. At higher coverage, the formation of small chemisorbed AlH3 occurs at the step edges. With increasing coverage AlH3 is extracted from the step edge and becomes highly mobile on the terraces in a weakly bound state. This mobility is the key factor leading to the growth of larger alanes through AlH3 oligomerization. For these large alanes, previous Thermal Programmed Desorption studies are discussed and compared to the thermal stability observed in IR.

  7. Oxygen Absorption in Cooling Flows.

    PubMed

    Buote

    2000-04-01

    The inhomogeneous cooling flow scenario predicts the existence of large quantities of gas in massive elliptical galaxies, groups, and clusters that have cooled and dropped out of the flow. Using spatially resolved, deprojected X-ray spectra from the ROSAT PSPC, we have detected strong absorption over energies approximately 0.4-0.8 keV intrinsic to the central approximately 1&arcmin; of the galaxy NGC 1399, the group NGC 5044, and the cluster A1795. These systems have among the largest nearby cooling flows in their respective classes and low Galactic columns. Since no excess absorption is indicated for energies below approximately 0.4 keV, the most reasonable model for the absorber is warm, collisionally ionized gas with T=105-106 K in which ionized states of oxygen provide most of the absorption. Attributing the absorption only to ionized gas reconciles the large columns of cold H and He inferred from Einstein and ASCA with the lack of such columns inferred from ROSAT and also is consistent with the negligible atomic and molecular H inferred from H i and CO observations of cooling flows. The prediction of warm ionized gas as the product of mass dropout in these and other cooling flows can be verified by Chandra and X-Ray Multimirror Mission.

  8. Quasistellar Objects: Intervening Absorption Lines

    NASA Astrophysics Data System (ADS)

    Charlton, J.; Churchill, C.; Murdin, P.

    2000-11-01

    Every parcel of gas along the line of sight to a distant QUASAR will selectively absorb certain wavelengths of continuum light of the quasar due to the presence of the various chemical elements in the gas. Through the analysis of these quasar absorption lines we can study the spatial distributions, motions, chemical enrichment and ionization histories of gaseous structures from REDSHIFT five unti...

  9. Ultraviolet and Light Absorption Spectrometry.

    ERIC Educational Resources Information Center

    Hargis, L. G.; Howell, J. A.

    1984-01-01

    Reviews developments in ultraviolet and light absorption spectrometry from December 1981 through November 1983, focusing on the chemistry involved in developing suitable reagents, absorbing systems, and methods of determination, and on physical aspects of the procedures. Includes lists of spectrophotometric methods for metals, non-metals, and…

  10. High temperature in absorption measurements

    NASA Astrophysics Data System (ADS)

    Krech, R. H.; Pugh, E. R.

    1981-09-01

    The temperature dependence of the absorption coefficient of water vapor was measured to determine the feasibility of using water vapor as a molecular seed to couple 10.6 micrometer CO2 laser radiation into a propellant for use in a high performance laser heated rocket thruster. A series of shock tube experiments were performed to determine the temperature dependence of the absorption coefficient of water vapor at high temperatures on the P(16), P(18) and P(20) 10.6 micrometer CO2 laser transitions. Measurements were made behind both incident and reflected shock waves encompassing a temperature range from 600 K to 3700 K at pressures from 1 to 40 atmospheres in 2, 5, and 10 mole percent water vapor in argon gas mixtures. Within the spectral range (944 to 948 cm) covered, no significant variation in the absorption coefficient was observed as a function of laser wavelength, water concentration, total pressure, or collision partner. Observations suggest that the water lines are sufficiently broadened to act as a continuum absorber under conditions to be found in a laser-heated rocket thruster. The measured laser high temperature absorption coefficients are 50 percent lower than the values obtained from the Ludwig empirical curve fit to low resolution data.

  11. Slow light and saturable absorption

    NASA Astrophysics Data System (ADS)

    Selden, A. C.

    2009-06-01

    Quantitative analysis of slow light experiments utilising coherent population oscillation (CPO) in a range of saturably absorbing media, including ruby and alexandrite, Er3+:Y2SiO5, bacteriorhodopsin, semiconductor quantum devices and erbium-doped optical fibres, shows that the observations may be more simply interpreted as saturable absorption phenomena. A basic two-level model of a saturable absorber displays all the effects normally associated with slow light, namely phase shift and modulation gain of the transmitted signal, hole burning in the modulation frequency spectrum and power broadening of the spectral hole, each arising from the finite response time of the non-linear absorption. Only where hole-burning in the optical spectrum is observed (using independent pump and probe beams), or pulse delays exceeding the limits set by saturable absorption are obtained, can reasonable confidence be placed in the observation of slow light in such experiments. Superluminal (“fast light”) phenomena in media with reverse saturable absorption (RSA) may be similarly explained.

  12. Neutron Absorption in Geological Material

    NASA Astrophysics Data System (ADS)

    Løvhøiden, G.; Andersen, E.

    1990-01-01

    Thermal neutron absorption cross section of geological samples is determined with the steady state neutron source method. Cross section measurements of North Sea sediments demonstrate that also materials with high contents of clay minerals may be investigated with the steady state method.

  13. Ultraviolet and Light Absorption Spectrometry.

    ERIC Educational Resources Information Center

    Hargis, L. G.; Howell, J. A.

    1984-01-01

    Reviews developments in ultraviolet and light absorption spectrometry from December 1981 through November 1983, focusing on the chemistry involved in developing suitable reagents, absorbing systems, and methods of determination, and on physical aspects of the procedures. Includes lists of spectrophotometric methods for metals, non-metals, and…

  14. Comparative absorption of curcumin formulations.

    PubMed

    Jäger, Ralf; Lowery, Ryan P; Calvanese, Allison V; Joy, Jordan M; Purpura, Martin; Wilson, Jacob M

    2014-01-24

    The potential health benefits of curcumin are limited by its poor solubility, low absorption from the gut, rapid metabolism and rapid systemic elimination. The purpose of this study was the comparative measurement of the increases in levels of curcuminoids (curcumin, demethoxycurcumin, bisdemethoxycurcumin) and the metabolite tetrahydrocurcumin after oral administration of three different curcumin formulations in comparison to unformulated standard. The relative absorption of a curcumin phytosome formulation (CP), a formulation with volatile oils of turmeric rhizome (CTR) and a formulation of curcumin with a combination of hydrophilic carrier, cellulosic derivatives and natural antioxidants (CHC) in comparison to a standardized curcumin mixture (CS) was investigated in a randomized, double-blind, crossover human study in healthy volunteers. Samples were analyzed by HPLC-MS/MS. Total curcuminoids appearance in the blood was 1.3-fold higher for CTR and 7.9-fold higher for CP in comparison to unformulated CS. CHC showed a 45.9-fold higher absorption over CS and significantly improved absorption over CP (5.8-fold) and CTR (34.9-fold, all p < 0.001). A formulation of curcumin with a combination of hydrophilic carrier, cellulosic derivatives and natural antioxidants significantly increases curcuminoid appearance in the blood in comparison to unformulated standard curcumin CS, CTR and CP.

  15. Comparative absorption of curcumin formulations

    PubMed Central

    2014-01-01

    Background The potential health benefits of curcumin are limited by its poor solubility, low absorption from the gut, rapid metabolism and rapid systemic elimination. The purpose of this study was the comparative measurement of the increases in levels of curcuminoids (curcumin, demethoxycurcumin, bisdemethoxycurcumin) and the metabolite tetrahydrocurcumin after oral administration of three different curcumin formulations in comparison to unformulated standard. Methods The relative absorption of a curcumin phytosome formulation (CP), a formulation with volatile oils of turmeric rhizome (CTR) and a formulation of curcumin with a combination of hydrophilic carrier, cellulosic derivatives and natural antioxidants (CHC) in comparison to a standardized curcumin mixture (CS) was investigated in a randomized, double-blind, crossover human study in healthy volunteers. Samples were analyzed by HPLC-MS/MS. Results Total curcuminoids appearance in the blood was 1.3-fold higher for CTR and 7.9-fold higher for CP in comparison to unformulated CS. CHC showed a 45.9-fold higher absorption over CS and significantly improved absorption over CP (5.8-fold) and CTR (34.9-fold, all p < 0.001). Conclusion A formulation of curcumin with a combination of hydrophilic carrier, cellulosic derivatives and natural antioxidants significantly increases curcuminoid appearance in the blood in comparison to unformulated standard curcumin CS, CTR and CP. PMID:24461029

  16. Migrant labor absorption in Malaysia.

    PubMed

    Nayagam, J

    1992-01-01

    The use of migrant workers to ease labor shortages caused by rapid industrialization in Malaysia during the twentieth century is examined. "This paper will focus on: (1) the extent, composition and distribution of migrant workers; (2) the labor shortage and absorption of migrant workers; and (3) the role of migrant workers in the government's economic restructuring process."

  17. Theory of graphene saturable absorption

    NASA Astrophysics Data System (ADS)

    Marini, A.; Cox, J. D.; García de Abajo, F. J.

    2017-03-01

    Saturable absorption is a nonperturbative nonlinear optical phenomenon that plays a pivotal role in the generation of ultrafast light pulses. Here we show that this effect emerges in graphene at unprecedentedly low light intensities, thus opening avenues to new nonlinear physics and applications in optical technology. Specifically, we theoretically investigate saturable absorption in extended graphene by developing a semianalytical nonperturbative single-particle approach, describing electron dynamics in the atomically-thin material using the two-dimensional Dirac equation for massless Dirac fermions, which is recast in the form of generalized Bloch equations. By solving the electron dynamics nonperturbatively, we account for both interband and intraband contributions to the intensity-dependent saturated conductivity and conclude that the former dominates regardless of the intrinsic doping state of the material. We obtain results in qualitative agreement with atomistic quantum-mechanical simulations of graphene nanoribbons including electron-electron interactions, finite-size, and higher-band effects. Remarkably, such effects are found to affect mainly the linear absorption, while the predicted saturation intensities are in good quantitative agreement in the limit of extended graphene. Additionally, we find that the modulation depth of saturable absorption in graphene can be electrically manipulated through an externally applied gate voltage. Our results are relevant for the development of graphene-based optoelectronic devices, as well as for applications in mode-locking and random lasers.

  18. H{alpha} ABSORPTION IN TRANSITING EXOPLANET ATMOSPHERES

    SciTech Connect

    Christie, Duncan; Arras, Phil; Li Zhiyun E-mail: pla7y@virginia.edu

    2013-08-01

    Absorption of stellar H{alpha} by the upper atmosphere of the planet HD 189733b has recently been detected by Jensen et al. Motivated by this observation, we have developed a model for atomic hydrogen in the n = 2 state and compared the resulting H{alpha} line profile to the observations. The model atmosphere is in hydrostatic balance, as well as thermal and photoionization equilibrium. Collisional and radiative transitions are included in the determination of the n = 2 state level population. We find that H{alpha} absorption is dominated by an optical depth {tau} {approx} 1 shell, composed of hydrogen in the metastable 2s state that is located below the hydrogen ionization layer. The number density of the 2s state within the shell is found to vary slowly with radius, while that of the 1s state falls rapidly. Thus while the Ly{alpha} absorption, for a certain wavelength, occurs inside a relatively well defined impact parameter, the contribution to H{alpha} absorption is roughly uniform over the entire atomic hydrogen layer. The model can approximately reproduce the observed Ly{alpha} and H{alpha} integrated transit depths for HD 189733b by using an ionization rate enhanced over that expected for the star by an order of magnitude. For HD 209458b, we are unable to explain the asymmetric H{alpha} line profile observed by Jensen et al., as the model produces a symmetric line profile with transit depth comparable to that of HD 189733b. In an appendix, we study the effect of the stellar Ly{alpha} absorption on the net cooling rate.

  19. Luminescence and photoinduced absorption in ytterbium-doped optical fibres

    SciTech Connect

    Rybaltovsky, A A; Aleshkina, S S; Likhachev, M E; Bubnov, M M; Umnikov, A A; Yashkov, M V; Gur'yanov, Aleksei N; Dianov, Evgenii M

    2011-12-31

    Photochemical reactions induced in the glass network of an ytterbium-doped fibre core by IR laser pumping and UV irradiation have been investigated by analysing absorption and luminescence spectra. We have performed comparative studies of the photoinduced absorption and luminescence spectra of fibre preforms differing in core glass composition: Al{sub 2}O{sub 3} : SiO{sub 2}, Al{sub 2}O{sub 3} : Yb{sub 2}O{sub 3} : SiO{sub 2}, and P{sub 2}O{sub 5} : Yb{sub 2}O{sub 3} : SiO{sub 2}. The UV absorption spectra of unirradiated preform core samples show strong bands peaking at 5.1 and 6.5 eV, whose excitation plays a key role in photoinduced colour centre generation in the glass network. 'Direct' UV excitation of the 5.1- and 6.5-eV absorption bands at 244 and 193 nm leads to the reduction of some of the Yb{sup 3+} ions to Yb{sup 2+}. The photodarkening of ytterbium-doped fibres by IR pumping is shown to result from oxygen hole centre generation. A phenomenological model is proposed for the IR-pumping-induced photodarkening of ytterbium-doped fibres. The model predicts that colour centre generation in the core glass network and the associated absorption in the visible range result from a cooperative effect involving simultaneous excitation of a cluster composed of several closely spaced Yb{sup 3+} ions.

  20. Optical absorptions of polyfluorene transistors

    NASA Astrophysics Data System (ADS)

    Deng, Yvonne Y.; Sirringhaus, Henning

    2005-07-01

    Conjugated polymers are a promising class of materials for organic electronics. While the progress in device performance is impressive, the basics of charge transport still pose many open questions. Specifically, conduction at the comparatively rough polymer-polymer interface in an all-polymer field-effect transistor is expected to be different from a sharp interface with an inorganic dielectric, such as silicon dioxide. In this work, charge modulation spectroscopy (CMS) is used to study the optical absorptions in the presence of charges in situ in the transistor structure. This allows direct observation of the charge carriers in the operational device via their spectroscopic signature; the technique is by design very sensitive to the properties of the semiconductor-dielectric interface. The semiconducting copolymer poly( 9,9' -dioctyl-fluorene-co-bithiophene) (F8T2) is incorporated into a top-gate thin-film transistor structure with a polymer dielectric layer deposited by spin coating and inkjet-printed polymer electrodes. A prominent charge-induced absorption at 1.65eV is observed as well as a shoulder at 1.3eV and a tail extending toward the absorption edge. The bias dependence of the CMS signature confirms that intermixing of the polymer layers is minimal, as expected from the excellent transistor characteristics. Polarization-dependent CMS measurements on aligned transistors show that the main feature at 1.65eV is strongly polarized whereas the shoulder is unpolarized. This observation, as well as further experimental evidence, lead to the conclusion that while the main absorption is attributable to the intrinsic, polaronic absorption in F8T2, the shoulder is likely to originate from a defect state.

  1. 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.

  2. Atmospheric Measurements by Cavity Enhanced Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Yi, Hongming; Wu, Tao; Coeur-Tourneur, Cécile; Fertein, Eric; Gao, Xiaoming; Zhao, Weixiong; Zhang, Weijun; Chen, Weidong

    2015-04-01

    Since the last decade, atmospheric environmental monitoring has benefited from the development of novel spectroscopic measurement techniques owing to the significant breakthroughs in photonic technology from the UV to the infrared spectral domain [1]. In this presentation, we will overview our recent development and applications of cavity enhanced absorption spectroscopy techniques for in situ optical monitoring of chemically reactive atmospheric species (such as HONO, NO3, NO2, N2O5) in intensive campaigns [2] and/or in smog chamber studies [3]. These field deployments demonstrated that modern photonic technologies (newly emergent light sources combined with high sensitivity spectroscopic techniques) can provide a useful tool to improve our understanding of tropospheric chemical processes which affect climate, air quality, and the spread of pollution. Experimental detail and preliminary results will be presented. Acknowledgements. The financial support from the French Agence Nationale de la Recherche (ANR) under the NexCILAS (ANR-11-NS09-0002) and the CaPPA (ANR-10-LABX-005) contracts is acknowledged. References [1] X. Cui, C. Lengignon, T. Wu, W. Zhao, G. Wysocki, E. Fertein, C. Coeur, A. Cassez,L. Croisé, W. Chen, et al., "Photonic Sensing of the Atmosphere by absorption spectroscopy", J. Quant. Spectrosc. Rad. Transfer 113 (2012) 1300-1316 [2] T. Wu, Q. Zha, W. Chen, Z. XU, T. Wang, X. He, "Development and deployment of a cavity enhanced UV-LED spectrometer for measurements of atmospheric HONO and NO2 in Hong Kong", Atmos. Environ. 95 (2014) 544-551 [3] T. Wu, C. Coeur-Tourneur, G. Dhont,A. Cassez, E. Fertein, X. He, W. Chen,"Application of IBBCEAS to kinetic study of NO3 radical formation from O3 + NO2 reaction in an atmospheric simulation chamber", J. Quant. Spectrosc. Rad. Transfer 133 (2014)199-205

  3. Strong light absorption of self-organized 3-D nanospike arrays for photovoltaic applications.

    PubMed

    Yu, Rui; Ching, Kwong-Lung; Lin, Qingfeng; Leung, Siu-Fung; Arcrossito, Diaz; Fan, Zhiyong

    2011-11-22

    Three-dimensional (3-D) nanostructures have been widely explored for efficient light trapping; however, many of the nanostructure fabrication processes reported have high cost and/or limited scalability. In this work, self-organized 3-D Al nanospike arrays were successfully fabricated on thin Al foils with controlled nanospike geometry such as height and pitch. Thereafter, photovoltaic materials of a-Si and CdTe thin films were conformally deposited on the nanospikes structures thus forming 3-D nanostructures with strong light absorption over a broad wavelength range and photon incident angle. Specifically, 100 nm-thick CdTe film on nanospikes showed 97% peak absorption, and up to 95% day-integrated sunlight absorption. These results indicate that self-organized 3-D Al nanospike arrays can serve as lightweight and low cost substrates for cost-effective thin film photovoltaics. © 2011 American Chemical Society

  4. /Cu-Al System

    NASA Astrophysics Data System (ADS)

    Kish, Orel; Froumin, Natalya; Aizenshtein, Michael; Frage, Nachum

    2014-05-01

    Wettability and interfacial interaction of the Ta2O5/Cu-Al system were studied. Pure Cu does not wet the Ta2O5 substrate, and improved spreading is achieved when relatively a high fraction of the active element (~40 at.% Al) was added. The Al2O3 and AlTaO4 phases were observed at the Ta2O5/Cu-Al interface. A thermodynamic evaluation allowed us to suggest that the lack of wetting bellow 40 at.% Al is due to the presence of a native oxide, which covers the drop. The conditions of the native oxide decomposition and the formation of the volatile Al2O suboxide strongly depend on the vacuum level during sessile drop experiments and the composition of the Cu-Al alloy. In our case, Al contents greater than 40% provides thermodynamic conditions for the formation of Al2O (as a result of Al reaction with Al2O3) and the drop spreading. It was suggested that the final contact angle in the Ta2O5/Cu-Al system (50°) is determined by Ta adsorption on the newly formed alumina interlayer.

  5. Infrasound absorption by atmospheric clouds

    NASA Astrophysics Data System (ADS)

    Baudoin, Michael; Coulouvrat, Francois; Thomas, Jean-Louis

    2010-05-01

    A model is developed for the absorption of infrasound by atmospheric clouds made of a suspension of liquid water droplets within a gaseous mixture of water vapor and air. The model is based on the work of D.A. Gubaidullin and R.I. Nigmatulin [Int. J. Multiphase Flow, 26, 207-228, 2000], which is applied to atmospheric clouds. Three physical mechanisms are included : unsteady viscous drag associated with momentum transfers due to the translation of water droplets, unsteady thermal transfers between the liquid and gaseous phases, and mass transfers due to the evaporation or condensation of the water phase. For clouds, in the infrasonic frequency range, phase changes are the dominant mechanisms (around 1 Hz), while viscous and heat transfers become significant only around 100 Hz. Mass transfers involve two physical effects : evaporation and condensation of the water phase at the droplet surface, and diffusion of the water vapor within the gaseous phase. The first one is described through the Hertz-Knudsen-Langmuir theory based on kinetic theory. It involves a little known coefficient known as coefficient of accommodation. The second one is the classical Fick diffusion. For clouds, and unless the coefficient of accommodation is very small (far from the generally recommended value is close to one), diffusion is the main limiting effects for mass transfers. In a second stage, the sound and infrasound absorption is evaluated for various typical clouds up to about 4 km altitude. Above this altitude, the ice content of clouds is dominant compared to their water content, and the present model is not applicable. Cloud thickness, water content, and droplets size distribution are shown to be the major factors influencing the infrasound absorption. A variety of clouds have been analyzed. In most cases, it is shown that infrasound absorption within clouds is several orders larger than classical absorption (due to molecular relaxation of nitrogen and oxygen molecules in presence

  6. The molecular basis of ultrasonic absorption by proteins

    SciTech Connect

    Edmonds, P.D.

    1982-01-01

    This article reviews significant advances in understanding the basis for the magnitude of ultrasonic absorption in proteins and related biological materials. Carstensen and Schwan's accurate and extensive measurements on blood and hemoglobin solutions provided the initial experimental data; these were augmented by data from measurements on aqueous solutions of gelatin, bovine serum albumin, lysozyme, various polypeptides, and amino acids. The initial frequency range of 1-10 MHz was expanded to 0.035-1000 MHz; temperature and pH dependences of absorption were studied. Theoretical approaches included consideration of the relative motion of blood cells in plasma, perturbation of water structure around macromolecules, solvation of charged entities, proton-transfer reactions, and helix-coil transitions. Proton-transfer reactions between amino and carboxylic groups and water proved to be largely responsible for the observed peaks in pH dependence of absorption coefficient; the peaks occurred in the basic and acidic regions corresponding to the pKs for titration of these groups. Such reactions could not account for the magnitude of absorption at physiological pH because only histidine titrated in this range. Extensive analysis, using relaxation theory, and measurements have shown that the proton transfer reaction between the imidazole group of histidine and hydrogen phosphate ion (in solution) provides sufficient volume change for significant ultrasonic absorption at physiological pH. Excellent agreement between theory and experiment was found with the peptide bacitracin in phosphate buffer solutions. By generalizing these results to the case of a protein, Slutsky wt al estimated maximum values of frequency-dependent absorption coefficients for typical tissue and found them to be correct to order of magnitude.

  7. ALS (Amyotrophic Lateral Sclerosis)

    MedlinePlus

    ... risk factors for veterans include exposure to lead, pesticides, and other environmental toxins. ALS is recognized as ... from scientific studies suggests that both genetics and environment play a role in the development of ALS. ...

  8. Lou Gehrig's Disease (ALS)

    MedlinePlus

    ... 1930s. People in England and Australia call ALS motor neurone disease (MND). The French refer to it ... about ALS in 1869. Lou Gehrig's disease damages motor neurons in the brain and spinal cord. Motor ...

  9. Optical absorption properties of dielectric composite films doped with metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Lu, Huiwen; Wang, Weitian

    2017-06-01

    Composite thin films formed by using nanometer-sized metal particles embedded in dielectric matrices were fabricated by using a pulsed laser deposition technique to co-deposit the metal and the ceramic targets. The optical absorption properties were measured at wavelength from 350 to 800 nm, and the absorption peak due to the surface plasmon resonance of the metal particles was found. The effects of different metal particles (Au, Ag, Fe, Co) and different embedding matrices (SrTiO3, Al2O3, and TiO2) on the optical absorption properties of dielectric composite films are discussed. Strong absorption peaks can be found in composite films doped with noble-metal particles while the composites doped with most transition-metal particles show ordinary absorption patterns. The dielectric properties of the metal particles and the refractive indices of the embedding matrices were responsible for the observed results.

  10. Surface plasmon resonance absorption of composite films doped with metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Lu, Huiwen; Wang, Weitian

    2017-06-01

    Composite thin films formed by nanometer-sized metal particles embedded in dielectric matrices were fabricated by codepositing the metal and ceramic targets using a pulsed laser deposition technique. The optical absorption properties were measured from 350 to 800 nm, and the absorption peak due to the surface plasmon resonance of metal particles was found. The effects of different metal particles (Au, Ag, Fe, and Co) and embedding matrices (SrTiO3, Al2O3, and TiO2) on the optical absorption properties of the composite films were discussed. Strong absorption peaks can be found in composite films doped with noble metal particles, while most transition metal particles show ordinary absorption patterns. Dielectric properties of metal particles and the refractive index of embedding matrices were responsible for the observed results.

  11. Comparison on the interaction of Al3+/nano-Al13 with calf thymus DNA /salmon sperm DNA

    NASA Astrophysics Data System (ADS)

    Ma, Fei; Ma, Yue; Du, Changwen; Yang, Xiaodi; Shen, Renfang

    2015-11-01

    The conformation change, binding mode and binding site between Al3+/nano-Al13 and calf thymus DNA/salmon sperm DNA were investigated by UV-vis absorption, FTIR spectra, Raman spectroscopy and CD spectra, as well as melting curves measurement. The UV-vis spectra and circular dichroism spectra results suggested that the phosphate group structure was changed when Al3+ interacted with DNA, while the double-helix was distorted when nano-Al13 interacted with DNA. The FTIR and Raman spectroscopy revealed that the binding sites were Al3+ … PO2, Al3+ … N7/guanine PO2 … Al13 … N7-C8/guanine with calf thymus DNA, and Al3+ … N3-O2/cytosine, Al3+ … N7-C8/guanine, PO2 … Al13 … N7-C8/guanine, PO2 … Al13 … N1/adenine with salmon sperm DNA, respectively. The electrostatic binding was existed between Al3+ and DNA, and the electrostatic binding and complexing were found between nano-Al13 and DNA.

  12. Effect of Al Doping on Optical Band Gap Energy of Al-TiO2 Thin Films.

    PubMed

    Song, Yo-Seung; Kim, Bae-Yeon; Cho, Nam-Ihn; Lee, Deuk Yong

    2015-07-01

    Al-TiO2 thin films were prepared using a sol-gel derived spin coating by varying the Al/Ti molar ratio from 0 to 0.73 to investigate the effect of Al doping on the optical band gap energy (Eg) of the films. GAXRD results indicated that Al-TiO2 is composed of anatase and FTO phases when the Al/Ti molar ratio was less than 0.18. Above 0.38, no other peaks except FTO were found and transparency of the films was severely deteriorated. Eg of Al-TiO2 decreased from 3.20 eV to 2.07 eV when the Al/Ti ratio was raised from 0 to 0.38. Eg of 2.59 eV was found for the anatase Al-TiO2 films having the Al/Ti ratio of 0.18. The absorption band of Al-TiO2 coatings shifted dramatically from the UV region to the visible region with increasing the amount of Al dopant. The Al doping was mainly attributed to the optical band gap energy of Al-TiO2.

  13. Temperature shift of intraband absorption peak in tunnel-coupled QW structure

    NASA Astrophysics Data System (ADS)

    Akimov, V.; Firsov, D. A.; Duque, C. A.; Tulupenko, V.; Balagula, R. M.; Vinnichenko, M. Ya.; Vorobjev, L. E.

    2017-04-01

    An experimental study of the intersubband light absorption by the 100-period GaAs/Al0.25Ga0.75As double quantum well heterostructure doped with silicon is reported and interpreted. Small temperature redshift of the 1-3 intersubband absorption peak is detected. Numerical calculations of the absorption coefficient including self-consistent Hartree calculations of the bottom of the conduction band show good agreement with the observed phenomena. The temperature dependence of energy gap of the material and the depolarization shift should be accounted for to explain the shift.

  14. Tunable diode laser absorption sensor for temperature and velocity measurements of O2 in air flows

    NASA Technical Reports Server (NTRS)

    Philippe, L. C.; Hanson, R. K.

    1991-01-01

    A fast and nonintrusive velocity and temperature diagnostic based on oxygen absorption is presented. The system uses a GaAlAs tunable diode laser, ramped and modulated in wavelength at high frequency. Detection is performed at twice the modulating frequency, leading to second harmonic absorption lineshapes. Velocity is inferred from the wavelength shift of the absorption line center due to the Doppler effect. Temperature is determined by comparing experimental and calculated lineshapes. Capabilities of the technique for studies of transient high-speed flows are demonstrated in shock tube experiments. Good agreement is obtained with predicted temperatures and velocities when pressure-induced shifts are accounted for.

  15. Enhancement of optical absorption in silicon thin-film solar cells with metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Shi, Bo; Wang, Wei; Yu, Xueqing; Yang, Lili; Xu, Yuanpei

    2017-05-01

    Light trapping structures are a promising method of improving the efficiency of solar cells. We focused on the plasmonic thin-film solar cell. A structure is proposed consisting of an indium tin oxide layer with embedded metal nanoparticles, a hydrogenated amorphous silicon (a-Si:H) layer, and an aluminum (Al) layer. The finite-difference-time-domain (FDTD) method was used to calculate the absorption characteristics of the a-Si:H thin-film solar cells containing nanoparticles. By arranging the material, size, and locations of metal nanoparticles to maximize the scattering and minimize absorption of nanoparticles themselves, the optical absorption in the solar cell is significantly enhanced.

  16. Optical absorption in trilayer graphene

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Zhang, Fan; Niu, Qian

    2013-03-01

    We use a low energy effective model to analyze the optical responses of trilayer graphene samples. We first show that optical absorption of the ABA-stacked trilayer has strong dependence on both the Fermi energy and optical frequency, which is in sharp contrast to that of ABC-stacked trilayer graphene. Secondly, we are able to determine the possible existence of trigonal warping effects in the bandstructure of ABC-stacked trilayer graphene by a divergence in the absorption spectra at around 10 meV. In addition, we can partially distinguish the vairious broken symmetry states driven by electron-electron interactions in ABC-stacked trilayer graphene. In particular, the quantum anomalous Hall (QAH) state is sensitive to the polarization of the incident light, giving a way to detect its possible existence.

  17. Iodine Absorption Cells Purity Testing.

    PubMed

    Hrabina, Jan; Zucco, Massimo; Philippe, Charles; Pham, Tuan Minh; Holá, Miroslava; Acef, Ouali; Lazar, Josef; Číp, Ondřej

    2017-01-06

    This article deals with the evaluation of the chemical purity of iodine-filled absorption cells and the optical frequency references used for the frequency locking of laser standards. We summarize the recent trends and progress in absorption cell technology and we focus on methods for iodine cell purity testing. We compare two independent experimental systems based on the laser-induced fluorescence method, showing an improvement of measurement uncertainty by introducing a compensation system reducing unwanted influences. We show the advantages of this technique, which is relatively simple and does not require extensive hardware equipment. As an alternative to the traditionally used methods we propose an approach of hyperfine transitions' spectral linewidth measurement. The key characteristic of this method is demonstrated on a set of testing iodine cells. The relationship between laser-induced fluorescence and transition linewidth methods will be presented as well as a summary of the advantages and disadvantages of the proposed technique (in comparison with traditional measurement approaches).

  18. The Intestinal Absorption of Folates

    PubMed Central

    Visentin, Michele; Diop-Bove, Ndeye; Zhao, Rongbao; Goldman, I. David

    2014-01-01

    The properties of intestinal folate absorption were documented decades ago. However, it was only recently that the proton-coupled folate transporter (PCFT) was identified and its critical role in folate transport across the apical brush-border membrane of the proximal small intestine established by the loss-of-function mutations identified in the PCFT gene in subjects with hereditary folate malabsorption and, more recently, by the Pcft-null mouse. This article reviews the current understanding of the properties of PCFT-mediated transport and how they differ from those of the reduced folate carrier. Other processes that contribute to the transport of folates across the enterocyte, along with the contribution of the enterohepatic circulation, are considered. Important unresolved issues are addressed, including the mechanism of intestinal folate absorption in the absence of PCFT and regulation of PCFT gene expression. The impact of a variety of ions, organic molecules, and drugs on PCFT-mediated folate transport is described. PMID:24512081

  19. Landing gear energy absorption system

    NASA Technical Reports Server (NTRS)

    Hansen, Christopher P. (Inventor)

    1994-01-01

    A landing pad system is described for absorbing horizontal and vertical impact forces upon engagement with a landing surface where circumferentially arranged landing struts respectively have a clevis which receives a slidable rod member and where the upper portion of a slidable rod member is coupled to the clevis by friction washers which are force fit onto the rod member to provide for controlled constant force energy absorption when the rod member moves relative to the clevis. The lower end of the friction rod is pivotally attached by a ball and socket to a support plate where the support plate is arranged to slide in a transverse direction relative to a housing which contains an energy absorption material for absorbing energy in a transverse direction.

  20. Photodetector with enhanced light absorption

    DOEpatents

    Kane, James

    1985-01-01

    A photodetector including a light transmissive electrically conducting layer having a textured surface with a semiconductor body thereon. This layer traps incident light thereby enhancing the absorption of light by the semiconductor body. A photodetector comprising a textured light transmissive electrically conducting layer of SnO.sub.2 and a body of hydrogenated amorphous silicon has a conversion efficiency about fifty percent greater than that of comparative cells. The invention also includes a method of fabricating the photodetector of the invention.

  1. Molecfit: Telluric absorption correction tool

    NASA Astrophysics Data System (ADS)

    Smette, A.; Kausch, W.; Sana, H.; Noll, S.; Horst, H.; Kimeswenger, S.; Barden, M.; Szyszka, C.; Jones, A. M.; Gallene, A.; Vinther, J.; Ballester, P.; Kerber, F.

    2015-01-01

    Molecfit corrects astronomical observations for atmospheric absorption features based on fitting synthetic transmission spectra to the astronomical data, which saves a significant amount of valuable telescope time and increases the instrumental efficiency. Molecfit can also estimate molecular abundances, especially the water vapor content of the Earth’s atmosphere. The tool can be run from a command-line or more conveniently through a GUI.

  2. Optical Absorption Characteristics of Aerosols.

    DTIC Science & Technology

    1985-09-11

    properties of the powder as well as the thickness of the layer. For a layer that is thick enough so that no light is transmitted, the Kubelka -- Munk theory...which is a two stream radiative transfer model, relates the reflectance to the ratio of the absorption to the scattering. The Kubelka - Munk theory has...of the aerosol material is known. Under the assumptions of the Kubelka - Munk . theory, the imaginary component of the refractive index is deter- mined

  3. Geometrical interpretation of optical absorption

    SciTech Connect

    Monzon, J. J.; Barriuso, A. G.; Sanchez-Soto, L. L.; Montesinos-Amilibia, J. M.

    2011-08-15

    We reinterpret the transfer matrix for an absorbing system in very simple geometrical terms. In appropriate variables, the system appears as performing a Lorentz transformation in a (1 + 3)-dimensional space. Using homogeneous coordinates, we map that action on the unit sphere, which is at the realm of the Klein model of hyperbolic geometry. The effects of absorption appear then as a loxodromic transformation, that is, a rhumb line crossing all the meridians at the same angle.

  4. Comparative study on the influence of Al component at GaAlAs layer for GaAs/AlGaAs photocathode

    NASA Astrophysics Data System (ADS)

    Xu, Yuan; Chang, Benkang; Chen, Xinlong; Qian, Yunsheng

    2017-08-01

    We designed two transmission-mode GaAs/AlGaAs photocathodes with different Al x Ga1-x As layers, one has an Al x Ga1-x As layer with the Al component ranging from 0.9 to 0, and the other has a fixed Al component 0.7. Using the first-principle method, we calculated the electronic structure and absorption spectrum of Al x Ga1-x As at x = 0, 0.25, 0.5, 0.75 and 1, calculation results suggest that with the increase of the Al component, the band gap of Al x Ga1-x As increases. Then we activated the two samples, and obtained the spectral response curves and quantum efficiency curves; it is found that sample 1 has a better shortwave response and higher quantum efficiency at short wavelengths. Combined with the band structure diagram of the transmission-mode GaAs/AlGaAs photocathode and the fitted performance parameters, we analyze the phenomenon. It is found that the transmission-mode GaAs/AlGaAs photocathode with variable Al component and various doping structure can form a two-stage built-in electric field, which improves the probability of shortwave response photoelectrons escaping to the vacuum. In conclusion, such a structure reduces the influence of back-interface recombination, improves the shortwave response of the transmission-mode photocathode. Project supported by the National Natural Science Foundation of China (Nos. 91433108, 61301023).

  5. Diffusion-absorption heat pump

    NASA Astrophysics Data System (ADS)

    Wang, Lie; Herold, Keith E.

    1992-06-01

    The diffusion-absorption heat pump offers advantages including no moving parts, noise and vibration free operation and operation without electric power. An example of such a cycle is the gas-fired domestic refrigerator. The cycle is similar to an absorption cycle but differs in that an auxiliary gas is used to equalize the pressures throughout the system and to allow a heat driven bubble pump. A modeling study of several cycle variations of diffusion-absorption heat pump technology was conducted to calculate the potential for improving cycle performance. A computer simulation model was developed for each of the cycle variations. Thermodynamic and transport property models were developed for the ammonia/water working fluid with both hydrogen and helium as the pressure equalizing gas. The modeling results are presented for helium. The major conclusions of the study are also valid for hydrogen. The inert gas charge pressure as well as the effectiveness of the auxiliary gas heat exchanger (AGHX) were found to have a significant influence on coefficient of performance (COP). Detailed modeling of the influence of the AGHX on the COP of the cycle was performed. In addition to the thermodynamic model, fluid and heat transfer models for the AGHX have been developed. The integration of cycle fluid and heat transfer models was performed in order to examine the coupling of the components.

  6. Formaldehyde absorption toward W51

    NASA Technical Reports Server (NTRS)

    Kogut, A.; Smoot, G. F.; Bennett, C. L.; Petuchowski, S. J.

    1989-01-01

    Formaldehyde (H2CO) absorption toward the H II region complex W51A (G49.5 - 0.4) in the 6 cm and 2 cm wavelength rotational transitions has been measured with angular resolution of about 0.15 pc. The continuum H II region shows a large, previously undetected shell structure 5.5 pc along the major axis. The absorption, converted to optical depth, shows a higher degree of clumping throughout the map than previous maps at lower resolution; in particular, two narrow regions of enhanced opacity are observed. The absorption in the velocity range 64-67 km/s LSR extends over most of the region, with an observed velocity gradient of 5.2 km/s pc. The opacity structure largely parallels the velocity structure, with a ridge of enhanced opacity to the north of the highest velocity feature. The S/N of the maps allows accurate modeling of the spectral profiles. Nine distinct clumps in the foreground clouds have been identified and parametrized, and column densities for the 1(11) and 2(12) rotational levels of orthoformaldehyde have been derived.

  7. Ray tracing and ECRH absorption modeling in the HSX stellarator

    NASA Astrophysics Data System (ADS)

    Weir, G. M.; Likin, K. M.; Marushchenko, N. B.; Turkin, Y.

    2015-09-01

    To increase flexibility in ECRH experiments on the helically symmetric experiment (HSX), a second gyrotron and transmission line have been installed. The second antenna includes a steerable mirror for off-axis heating, and the launched power may be modulated for use in heat pulse propagation experiments. The extraordinary wave at the second harmonic of the electron gyrofrequency or the ordinary wave at the fundamental resonance are used for plasma start-up and heating on HSX. The tracing visualized ray tracing code (Marushchenko et al 2007 Plasma Fusion Res. 2 S1129) is used to estimate single-pass absorption and to model multi-pass wave damping in the three-dimensional HSX geometry. The single-pass absorption of the ordinary wave at the fundamental resonance is calculated to be as high as 30%, while measurements of the total absorption indicate that 45% of the launched power is absorbed. A multi-pass ray tracing model correctly predicts the experimental absorption and indicates that the launched power is absorbed within the plasma core (r/a≤slant 0.2 ).

  8. Absorption Spectroscopy in Homogeneous and Micellar Solutions.

    ERIC Educational Resources Information Center

    Shah, S. Sadiq; Henscheid, Leonard G.

    1983-01-01

    Describes an experiment which has helped physical chemistry students learn principles of absorption spectroscopy, the effect of solvent polarity on absorption spectra, and some micellar chemistry. Background information and experimental procedures are provided. (JN)

  9. Absorption Amelioration of Amorphous Si Film by Introducing Metal Silicide Nanoparticles.

    PubMed

    Sun, Hui; Wu, Hsuan-Chung; Chen, Sheng-Chi; Ma Lee, Che-Wei; Wang, Xin

    2017-12-01

    Amorphous Si (a-Si) films with metal silicide are expected to enhance the absorption ability of pure a-Si films. In this present study, NiSi (20 nm)/Si (40 nm) and AlSi (20 nm)/Si (40 nm) bilayer thin films are deposited through radio frequency (RF) sputtering at room temperature. The influence of the film's composition and the annealing temperature on the film's optical absorption is investigated. The results show that all the NiSi/Si films and AlSi/Si films possess higher absorption ability compared to a pure a-Si film (60 nm). After annealing from 400 to 600 °C under vacuum for 1 h, the Si layer remains amorphous in both NiSi/Si films and AlSi/Si films, while the NiSi layer crystallizes into NiSi2 phase, whereas Al atoms diffuse through the whole film during the annealing process. Consequently, with increasing the annealing temperature, the optical absorption of NiSi/Si films increases, while that of AlSi/Si films obviously degrades.

  10. [Application of atomic absorption spectrometry in the engine knock detection].

    PubMed

    Chen, Li-Dan

    2013-02-01

    Because existing human experience diagnosis method and apparatus for auxiliary diagnosis method are difficult to diagnose quickly engine knock. Atomic absorption spectrometry was used to detect the automobile engine knock in in innovative way. After having determined Fe, Al, Cu, Cr and Pb content in the 35 groups of Audi A6 engine oil whose travel course is 2 000 -70 000 kilometers and whose sampling interval is 2 000 kilometers by atomic absorption spectrometry, the database of primary metal content in the same automobile engine at different mileage was established. The research shows that the main metal content fluctuates within a certain range. In practical engineering applications, after the determination of engine oil main metal content and comparison with its database value, it can not only help to diagnose the type and location of engine knock without the disintegration and reduce vehicle maintenance costs and improve the accuracy of engine knock fault diagnosis.

  11. Terminal Velocity Infall in QSO Absorption Line Halos

    NASA Astrophysics Data System (ADS)

    Benjamin, Robert A.

    We explore the hypothesis that clouds detected in quasar absorption line systems are falling at a terminal velocity toward the center of high redshift gaseous galactic halos. Since both the ionization level and terminal velocity of halo clouds increase with increasing distance from the central galaxy, velocity resolved profiles of highly ionized gas are predicted to have a greater width than low ionization gas. A line of sight passing through the center of gaseous halo (an idealized damped Ly alpha system), yields low ionization absorption at the velocity of the galaxy, flanked by high ionization on either side. Reasonable halo parameters yield total velocity extents for C IV of Delta v_{C IV}=100-200 km s^{-1}, in agreement with many systems observed by Lu et al (1997). The remaining systems may better described by the rotating disk model of Prochaska & Wolfe (1998). Finally, observational tests are suggested for verifying or falsifying the terminal velocity hypothesis for these systems.

  12. Different Mechanisms of Four Aluminum (Al)-Resistant Transgenes for Al Toxicity in Arabidopsis1

    PubMed Central

    Ezaki, Bunichi; Katsuhara, Maki; Kawamura, Masako; Matsumoto, Hideaki

    2001-01-01

    We have characterized the mechanism of action of four transgenes (AtBCB [Arabidopsis blue copper-binding protein], parB [tobacco {Nicotiana tabacum} glutathione S-transferase], NtPox [tobacco peroxidase], and NtGDI1 [tobacco GDP dissociation inhibitor]) that independently Al resistance on transgenic Arabidopsis. All four transgenic lines showed lower deposition of callose after Al treatment than the Landsberg erecta ecotype of Arabidopsis, confirming that the four genes function to ameliorate Al toxicity. Influx and efflux experiments of Al ions suggested that the AtBCB gene may suppress Al absorption, whereas expression of the NtGDI1 gene promotes a release of Al in the root tip region of Arabidopsis. The total enzyme activities of glutathione S-transferases or peroxidases in transgenic lines carrying either the parB or NtPox genes were significantly higher than in the Landsberg erecta ecotype of Arabidopsis, and these enzyme activities were maintained at higher levels during Al stress. Furthermore, lipid peroxidation caused by Al stress was repressed in these two transgenic lines, suggesting that overexpression of these two genes diminishes oxidative damage caused by Al stress. Al-treated roots of transgenic plants were also stained by 4′,6-diamino-2-phenylindole to monitor cell death caused by Al toxicity. The result suggested that cell death is repressed in the NtPox line. Analysis of F1 hybrids between the four transgenic lines suggests that more resistant transgenic plants can be constructed by combinations of these four genes. PMID:11706174

  13. Absorption characteristics of forest fire particulate matter

    Treesearch

    E.M. Patterson; Charles K. McMahon

    1984-01-01

    Abstract. Absorption properties of smokes from laboratory fires that represent prescription hums in the Southern states have been quantified to relate variations in measured absorption parameters to variation in fire conditions and to estimate emission factors for elemental carbon. Results showed significant differences in absorption of the smoke...

  14. Magnetotunneling absorption in double quantum wells

    SciTech Connect

    Lyo, S.K.

    1996-06-01

    Tunneling absorption is calculated in weakly coupled n-type asymmetric double quantum wells in an in-plane magnetic field using a linear response theory. Photon-assisted tunneling occurs between the ground sublevels of the quantum wells. We show that the absorption threshold, the resonance energy of absorption, and the linewidth depend sensitively on the magnetic field and the temperature.

  15. Absorption, Creativity, Peak Experiences, Empathy, and Psychoticism.

    ERIC Educational Resources Information Center

    Mathes, Eugene W.; And Others

    Tellegen and Atkinson suggested that the trait of absorption may play a part in meditative skill, creativity, capacity for peak experiences, and empathy. Although the absorption-meditative skill relationship has been confirmed, other predictions have not been tested. Tellegen and Atkinson's Absorption Scale was completed by undergraduates in four…

  16. Absorption, Creativity, Peak Experiences, Empathy, and Psychoticism.

    ERIC Educational Resources Information Center

    Mathes, Eugene W.; And Others

    Tellegen and Atkinson suggested that the trait of absorption may play a part in meditative skill, creativity, capacity for peak experiences, and empathy. Although the absorption-meditative skill relationship has been confirmed, other predictions have not been tested. Tellegen and Atkinson's Absorption Scale was completed by undergraduates in four…

  17. Relationship between the magnetic moment of Lu and the magnetic behavior of (Y{sub y}Lu{sub 1-y})(Co{sub 1-x}Al{sub x}){sub 2} from x-ray absorption spectroscopy and x-ray magnetic circular dichroism

    SciTech Connect

    Chaboy, J.; Piquer, C.; Laguna-Marco, M. A.; Kawamura, N.; Suzuki, M.; Takagaki, M.

    2007-02-01

    We present an x-ray magnetic circular dichroism (XMCD) study performed at both the Co K edge and the Lu L{sub 2,3} edges on (Y{sub y}Lu{sub 1-y})(Co{sub 1-x}Al{sub x}){sub 2} systems. The XMCD spectra reflect the different magnetic character of these systems, allowing us to monitor the transition from weak to strong ferromagnetism. The XMCD at the Lu L{sub 2,3} edges indicates the existence of an ordered 5d moment at the lutetium sites that is coupled antiparallel to the Co moment. Estimates of the magnetic moment of Lu have been obtained by applying the XMCD sum rules. Our results show that there is a correlation between the Lu 5d-induced magnetic moment and the magnetic character of the (Y{sub y}Lu{sub 1-y})(Co{sub 1-x}Al{sub x}){sub 2} compounds. These results suggest that the developing of the Lu moment plays an important role in reinforcing the magnetic interactions and favoring the ferromagnetic character of the Lu-rich compounds.

  18. The Absorption Spectrum of PKS 1756+237

    NASA Astrophysics Data System (ADS)

    Bauer, J. M.; Roth, K. C.; Jim, K. T. C.

    1998-05-01

    We are involved in a program to investigate the relationship between damped Lyalpha absorption systems and the interstellar medium of our own galaxy and nearby galaxies. This ultimately requires the proper identification of the systems responsible for the absorption so that a connection may be drawn between the absorption characteristics and the physical characteristics of the absorber, such as galaxy morphology, size, brightness, and separation from the QSO line of sight (see Jim & Roth, Kolhatkar et al., and Roth et al. also presenting here). PKS 1756+237 is a relatively bright QSO (m_V~18.0) with an emission redshift of z=1.721. There are two strong intervening absorption line systems at redshifts of 1.426 and 1.673. Both systems exhibit strong low-ionization lines, and so are believed to originate in the inner regions of galactic systems at some stage of formation. We obtained two hours of high quality HIRES spectra on the Keck 10m telescope for this QSO in May, 1997. The 6.5 km/s (0.09 Angstroms FWHM) resolution of this data is a ten-fold improvement over existing data, providing kinematic information as well as significantly improved column density measurements. Preliminary analysis of the data suggests the existence of significant Ni II abundance at z=1.67, possibly indicating a damped absorber system. The spectra cover the C II and Si II lines, enabling us to search for associated fine-structure excitation. These spectra also cover several additional low and high-ionization species from which we derive abundance and kinematic information. Images of this QSO, acquired at the UH 2.2m telescope using the QUIRC infrared and Tek2048 optical cameras with UH's tip-tilt system, show possible candidates for absorber systems.

  19. An alternative model for photodynamic therapy of cancers: Hot-band absorption

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Chen, Jiyao

    2013-12-01

    The sulfonated aluminum phthalocyanine (AlPcS), a photosensitizer for photodynamic cancer therapy (PDT), has an absorption tail in the near-infrared region (700-900 nm) which is so-called hot band absorption (HBA). With the HBA of 800 nm, the up-conversion excitation of AlPcS was achieved followed by the anti-Stocks emission (688 nm band) and singlet oxygen production. The HBA PDT of AlPcS seriously damaged the KB and HeLa cancer cells, with a typical light dose dependent mode. Particularly, the in vitro experiments with the AlPcS shielding solutions further showed that the HBA PDT can overcome a self-shielding effect benefiting the PDT applications.

  20. Glucagon receptor antagonism induces increased cholesterol absorption[S

    PubMed Central

    Guan, Hong-Ping; Yang, Xiaodong; Lu, Ku; Wang, Sheng-Ping; Castro-Perez, Jose M.; Previs, Stephen; Wright, Michael; Shah, Vinit; Herath, Kithsiri; Xie, Dan; Szeto, Daphne; Forrest, Gail; Xiao, Jing Chen; Palyha, Oksana; Sun, Li-Ping; Andryuk, Paula J.; Engel, Samuel S.; Xiong, Yusheng; Lin, Songnian; Kelley, David E.; Erion, Mark D.; Davis, Harry R.; Wang, Liangsu

    2015-01-01

    Glucagon and insulin have opposing action in governing glucose homeostasis. In type 2 diabetes mellitus (T2DM), plasma glucagon is characteristically elevated, contributing to increased gluconeogenesis and hyperglycemia. Therefore, glucagon receptor (GCGR) antagonism has been proposed as a pharmacologic approach to treat T2DM. In support of this concept, a potent small-molecule GCGR antagonist (GRA), MK-0893, demonstrated dose-dependent efficacy to reduce hyperglycemia, with an HbA1c reduction of 1.5% at the 80 mg dose for 12 weeks in T2DM. However, GRA treatment was associated with dose-dependent elevation of plasma LDL-cholesterol (LDL-c). The current studies investigated the cause for increased LDL-c. We report findings that link MK-0893 with increased glucagon-like peptide 2 and cholesterol absorption. There was not, however, a GRA-related modulation of cholesterol synthesis. These findings were replicated using structurally diverse GRAs. To examine potential pharmacologic mitigation, coadministration of ezetimibe (a potent inhibitor of cholesterol absorption) in mice abrogated the GRA-associated increase of LDL-c. Although the molecular mechanism is unknown, our results provide a novel finding by which glucagon and, hence, GCGR antagonism govern cholesterol metabolism. PMID:26373568

  1. [The percutaneous absorption of diclofenac].

    PubMed

    Riess, W; Schmid, K; Botta, L; Kobayashi, K; Moppert, J; Schneider, W; Sioufi, A; Strusberg, A; Tomasi, M

    1986-07-01

    The percutaneous absorption of diclofenac diethylammonium 1.16% (w/w) in a combination of emulsion cream and gel (Voltaren Emulgel) and of diclofenac sodium 1% (w/w) in a cream formulation (Voltaren cream) was investigated in guinea-pig, rabbit and man. The percutaneous absorption of diclofenac sodium in guinea-pig was 3 to 6% of the dose when the cream formulation in doses of 320, 100 or 40 mg was applied on 10 cm2 of occluded skin and left in place for 6 h. The transdermal delivery of 14C-labelled diclofenac yielded plateau plasma concentrations of radiotracer from 1.5 h after application until removal of the residual cream. Subsequently the steady state drug depots in the skin and muscle tissue were depleted promptly. During daily administration the steady state levels in the muscle tissue in proximity to the application site were about 3 times higher than in distant muscle tissue. By topical application on knee joints of rabbits diclofenac penetrated into the patellar ligament, the adipose corpus and the synovial fluid. In man the percutaneous absorption was 6% of the dose when the Emulgel formulation was spread by 5 mg/cm2 and left for 12 h on non-occluded skin. The pattern of metabolites of diclofenac in human urine was the same after topical and oral administration. In man, upon daily topical administration of 3 times 2.5 g cream formulation (10 mg/cm2) the diclofenac steady state plasma levels were 20 to 40 nmol/l.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. Advanced regenerative absorption refrigeration cycles

    DOEpatents

    Dao, Kim

    1990-01-01

    Multi-effect regenerative absorption cycles which provide a high coefficient of performance (COP) at relatively high input temperatures. An absorber-coupled double-effect regenerative cycle (ADR cycle) (10) is provided having a single-effect absorption cycle (SEA cycle) (11) as a topping subcycle and a single-effect regenerative absorption cycle (1R cycle) (12) as a bottoming subcycle. The SEA cycle (11) includes a boiler (13), a condenser (21), an expansion device (28), an evaporator (31), and an absorber (40), all operatively connected together. The 1R cycle (12) includes a multistage boiler (48), a multi-stage resorber (51), a multisection regenerator (49) and also uses the condenser (21), expansion device (28) and evaporator (31) of the SEA topping subcycle (11), all operatively connected together. External heat is applied to the SEA boiler (13) for operation up to about 500 degrees F., with most of the high pressure vapor going to the condenser (21) and evaporator (31) being generated by the regenerator (49). The substantially adiabatic and isothermal functioning of the SER subcycle (12) provides a high COP. For higher input temperatures of up to 700 degrees F., another SEA cycle (111) is used as a topping subcycle, with the absorber (140) of the topping subcycle being heat coupled to the boiler (13) of an ADR cycle (10). The 1R cycle (12) itself is an improvement in that all resorber stages (50b-f) have a portion of their output pumped to boiling conduits (71a-f) through the regenerator (49), which conduits are connected to and at the same pressure as the highest pressure stage (48a) of the 1R multistage boiler (48).

  3. Analysis of the excited-state absorption spectral bandshape of oligofluorenes

    NASA Astrophysics Data System (ADS)

    Hayes, Sophia C.; Silva, Carlos

    2010-06-01

    We present ultrafast transient absorption spectra of two oligofluorene derivatives in dilute solution. These spectra display a photoinduced absorption band with clear vibronic structure, which we analyze rigorously using a time-dependent formalism of absorption to extract the principal excited-state vibrational normal-mode frequencies that couple to the electronic transition, the configurational displacement of the higher-lying excited state, and the reorganization energies. We can model the excited-state absorption spectrum using two totally symmetric vibrational modes with frequencies 450 (dimer) or 400 cm-1 (trimer), and 1666 cm-1. The reorganization energy of the ground-state absorption is rather insensitive to the oligomer length at 230 meV. However, that of the excited-state absorption evolves from 58 to 166 meV between the oligofluorene dimer and trimer. Based on previous theoretical work [A. Shukla et al., Phys. Rev. B 67, 245203 (2003)], we assign the absorption spectra to a transition from the 1Bu excited state to a higher-lying mAg state, and find that the energy of the excited-state transition with respect to the ground-state transition energy is in excellent agreement with the theoretical predictions for both oligomers studied here. These results and analysis permit profound understanding of the nature of excited-state absorption in π-conjugated polymers, which are the subject of general interest as organic semiconductors in the solid state.

  4. Pseudopotential calculations and photothermal lensing measurements of two-photon absorption in solids

    SciTech Connect

    White, W.T. III

    1985-11-04

    We have studied two-photon absorption in solids theoretically and experimentally. We have shown that it is possible to use accurate band structure techniques to compute two-photon absorption spectra within 15% of measured values in a wide band-gap material, ZnS. The empirical pseudopotential technique that we used is significantly more accurate than previous models of two-photon absorption in zinc blende materials, including present tunneling theories (which are essentially parabolic-band results in disguise) and the nonparabolic-band formalism of Pidgeon et al. and Weiler. The agreement between our predictions and previous measurements allowed us to use ZnS as a reference material in order to validate a technique for measuring two-photon absorption that was previously untried in solids, pulsed dual-beam thermal lensing. With the validated technique, we examined nonlinear absorption in one other crystal (rutile) and in several glasses, including silicates, borosilicates, and one phosphate glass. Initially, we believed that the absorption edges of all the materials were comparable; however, subsequent evidence suggested that the effective band-gap energies of the glasses were above the energy of two photons in our measurement. Therefore, we attribute the nonlinear absorption that we observed in glasses to impurities or defects. The measured nonlinear absorption coefficients were of the order of a few cm/TW in the glasses and of the order of 10 cm/GW in the crystals, four orders of magnitude higher than in glasses. 292 refs.

  5. Frequency of Oxygen VI in Intervening QSO Absorption Systems

    NASA Astrophysics Data System (ADS)

    Burles, Scott; Tytler, David

    1994-12-01

    We have conducted the first survey for QSO with O VI lambda lambda 1032,1038 absorption lines. We obtained medium resolution (R ~ 1300), high signal-to-noise (~ 20) spectra of 11 QSOs (0.53<= zem <=2.08) taken with the Faint Object Spectrograph from the Hubble Space Telescope Archive. The O VI doublet is found exclusively in the Lyman-alpha forest. All previous surveys of metal lines in QSO absorption systems were done redward of Lyalpha emission, avoiding blending due to Lyman-alpha forest clouds. The higher density of lines in the Lyman-alpha forest demands new stringent criteria to ensure the identification of the O VI doublet. We used simulated spectra to determine the statistical significance of lines indentified in the Lyman-alpha forest. We found 12 O VI doublets and 9 are expected to be real. Six constitute a uniform sample with both lines exceeding a rest equivalent width of W_r =0.21 Angstroms. The number of O VI doublets per unit redshift is = 1.0 +/-0.6 at a mean absorption redshift of zave = 0.9. For comparable W_r the density of O VI absorbers is similar to Mg II (Tytler et al 1986; Steidel & Sargent 1992) and C IV absorbers (Sargent et al 1988; Bahcall et al 1993). We searched for other common ions in the O VI absorption systems. Out of 8 O VI absorption systems in which C IV is also found, C IV is stronger in all except zabs=1.0828 towards PG1206+459 which we believe is collisionally ionized. A rough estimate of the cosmological mass density of O VI is carried out. If we assume that O VI lines are linear, we get a lower limit of Omega (OVI) >= 3 times 10(-9) h(-1}_{100) . Since O > O VI, if the mean metal abundance were below 0.002 solar, then the accompanying Hydrogen and Helium would account for all baryons in the universe. We conclude that mean abundances are above 0.002 solar, and much greater if the gas is not highly ionized (O >> O VI).

  6. NEUTRON ABSORPTION AND SHIELDING DEVICE

    DOEpatents

    Axelrad, I.R.

    1960-06-21

    A neutron absorption and shielding device is described which is adapted for mounting in a radiation shielding wall surrounding a radioactive area through which instrumentation leads and the like may safely pass without permitting gamma or neutron radiation to pass to the exterior. The shielding device comprises a container having at least one nonrectilinear tube or passageway means extending therethrough, which is adapted to contain instrumentation leads or the like, a layer of a substance capable of absorbing gamma rays, and a solid resinous composition adapted to attenuate fast-moving neutrons and capture slow- moving or thermal neutrons.

  7. Microwave Absorption Characteristics of Tire

    NASA Astrophysics Data System (ADS)

    Zhang, Yuzhe; Hwang, Jiann-Yang; Peng, Zhiwei; Andriese, Matthew; Li, Bowen; Huang, Xiaodi; Wang, Xinli

    The recycling of waste tires has been a big environmental problem. About 280 million waste tires are produced annually in the United States and more than 2 billion tires are stockpiled, which cause fire hazards and health issues. Tire rubbers are insoluble elastic high polymer materials. They are not biodegradable and may take hundreds of years to decompose in the natural environment. Microwave irradiation can be a thermal processing method for the decomposition of tire rubbers. In this study, the microwave absorption properties of waste tire at various temperatures are characterized to determine the conditions favorable for the microwave heating of waste tires.

  8. Carbon Dioxide Absorption Heat Pump

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor)

    2002-01-01

    A carbon dioxide absorption heat pump cycle is disclosed using a high pressure stage and a super-critical cooling stage to provide a non-toxic system. Using carbon dioxide gas as the working fluid in the system, the present invention desorbs the CO2 from an absorbent and cools the gas in the super-critical state to deliver heat thereby. The cooled CO2 gas is then expanded thereby providing cooling and is returned to an absorber for further cycling. Strategic use of heat exchangers can increase the efficiency and performance of the system.

  9. Absorption of CO laser radiation by NO

    NASA Technical Reports Server (NTRS)

    Hanson, R. K.; Monat, J. P.; Kruger, C. H.

    1976-01-01

    The paper describes absorption calculations and measurements at selected infrared CO laser wavelengths which are nearly coincident with absorption lines in the fundamental vibration-rotation band of NO near 5.3 microns. Initial work was directed towards establishing the optimal CO laser-NO absorption line coincidence for high temperature applications. Measurements of the absorption coefficient at this optimal laser wavelength were carried out, first using a room-temperature absorption cell for high-temperature calculations and then using a shock tube, for the temperature range 630-4000 K, to validate the high temperature calculations.

  10. Tunneling induced absorption with competing Nonlinearities

    PubMed Central

    Peng, Yandong; Yang, Aihong; Xu, Yan; Wang, Peng; Yu, Yang; Guo, Hongju; Ren, Tingqi

    2016-01-01

    We investigate tunneling induced nonlinear absorption phenomena in a coupled quantum-dot system. Resonant tunneling causes constructive interference in the nonlinear absorption that leads to an increase of more than an order of magnitude over the maximum absorption in a coupled quantum dot system without tunneling. Resonant tunneling also leads to a narrowing of the linewidth of the absorption peak to a sublinewidth level. Analytical expressions show that the enhanced nonlinear absorption is largely due to the fifth-order nonlinear term. Competition between third- and fifth-order nonlinearities leads to an anomalous dispersion of the total susceptibility. PMID:27958303

  11. Absorption and fluorescence of single molecules.

    PubMed

    Butter, J Y P; Hecht, B; Crenshaw, B R; Weder, C

    2006-10-21

    Simultaneous detection of single molecules by absorption and fluorescence is demonstrated using confocal microscopy at cryogenic temperature. Dynamical processes such as blinking and spectral jumping of single emitters are observed in both detection channels. The relative magnitude of fluorescence and absorption varies between molecules. In particular, we observe molecules that do not emit detectable Stokes-shifted fluorescence but show a strong absorption signal. The fact that coherent resonant scattering underlies the absorption process is demonstrated by a correlation between small linewidth and large absorption amplitude.

  12. Impact of nonintentional Al impurity to carrier lifetime and diffusion in sublimation grown 3C heterostructures

    NASA Astrophysics Data System (ADS)

    Ščajev, P.; Jarašiunas, K.; Kadys, A.; Storasta, J.; Abramov, P. L.; Lebedev, S. P.; Lebedev, A. A.

    2010-11-01

    Using optical techniques, we analyzed an impact of non-intentional Al mpurity and twin boundaries to photoelectrical properties of sublimation-grown 3C heterostructures. Differential transmission techniques revealed Al related contribution to probe beam absorption with cross-section σAl = (1.8±0.5)×10-17 cm2 at 1064 nm, being four times stronger that the free-carrier absorption cross-section at given wavelength. Temperature dependent carrier recombination rates provided trap activation energy of 170 and 210 meV in two samples with different Al concentration. Saturation of probe beam absorption with excitation allowed determination of electrically active Al concentration, not gettered at grain boundaries. Increase of room-temperature mobility with injection in the highly defective layer and the corresponding lifetime decrease pointed out contribution of point and structural defects to carrier scattering.

  13. Fabrication of Spherical AlSi10Mg Powders by Radio Frequency Plasma Spheroidization

    NASA Astrophysics Data System (ADS)

    Wang, Linzhi; Liu, Ying; Chang, Sen

    2016-05-01

    Spherical AlSi10Mg powders were prepared by radio frequency plasma spheroidization from commercial AlSi10Mg powders. The fabrication process parameters and powder characteristics were investigated. Field emission scanning electron microscope, X-ray diffraction, laser particle size analyzer, powder rheometer, and UV/visible/infrared spectrophotometer were used for analyses and measurements of micrographs, phases, granulometric parameters, flowability, and laser absorption properties of the powders, respectively. The results show that the obtained spherical powders exhibit good sphericity, smooth surfaces, favorable dispersity, and excellent fluidity under appropriate feeding rate and flow rate of carrier gas. Further, acicular microstructures of the spherical AlSi10Mg powders are composed of α-Al, Si, and a small amount of Mg2Si phase. In addition, laser absorption values of the spherical AlSi10Mg powders increase obviously compared with raw material, and different spectra have obvious absorption peaks at a wavelength of about 826 nm.

  14. Five-Photon Absorption and Selective Enhancement of Multiphoton Absorption Processes.

    PubMed

    Friese, Daniel H; Bast, Radovan; Ruud, Kenneth

    2015-05-20

    We study one-, two-, three-, four-, and five-photon absorption of three centrosymmetric molecules using density functional theory. These calculations are the first ab initio calculations of five-photon absorption. Even- and odd-order absorption processes show different trends in the absorption cross sections. The behavior of all even- and odd-photon absorption properties shows a semiquantitative similarity, which can be explained using few-state models. This analysis shows that odd-photon absorption processes are largely determined by the one-photon absorption strength, whereas all even-photon absorption strengths are largely dominated by the two-photon absorption strength, in both cases modulated by powers of the polarizability of the final excited state. We demonstrate how to selectively enhance a specific multiphoton absorption process.

  15. Five-Photon Absorption and Selective Enhancement of Multiphoton Absorption Processes

    PubMed Central

    2015-01-01

    We study one-, two-, three-, four-, and five-photon absorption of three centrosymmetric molecules using density functional theory. These calculations are the first ab initio calculations of five-photon absorption. Even- and odd-order absorption processes show different trends in the absorption cross sections. The behavior of all even- and odd-photon absorption properties shows a semiquantitative similarity, which can be explained using few-state models. This analysis shows that odd-photon absorption processes are largely determined by the one-photon absorption strength, whereas all even-photon absorption strengths are largely dominated by the two-photon absorption strength, in both cases modulated by powers of the polarizability of the final excited state. We demonstrate how to selectively enhance a specific multiphoton absorption process. PMID:26120588

  16. Analysis of cement by atomic absorption spectrophotometry and volumetric method.

    PubMed

    Choi, K K; Lam, L; Luk, S F

    1994-01-01

    A new method to determine the composition of cement raw mix and cement is devised. The sample was fused with a mixture of sodium carbonate and lithium tetraborate (3:1) at 925 degrees C for 10 min. The fusion cake was dissolved in hydrochloric acid. The concentration of analyte in solution was either determined by atomic absorption spectrophotometry or titrimetry. The proposed method is quick and the analysis for interested oxides (SiO(2), Al(2)O(3), Fe(2)O(3), and CaO) can be completed within 1 hr. The accuracy and precision are comparable to that of X-ray fluorescence spectrometry.

  17. Electronic structure of aluminium trihydride studied using soft x-ray emission and absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Takeda, Y.; Saitoh, Y.; Saitoh, H.; Machida, A.; Aoki, K.; Yamagami, H.; Muro, T.; Kato, Y.; Kinoshita, T.

    2011-10-01

    We have performed soft x-ray emission spectroscopy (SXES) and soft x-ray absorption spectroscopy (SXAS) experiments on aluminum hydride α-AlH3. The occupied and unoccupied electronic states of the Al 3p partial density of states are obtained experimentally. By comparing the data from Al metal and α-AlH3, a band gap with a few eV is found for α-AlH3. In addition, the occupied states of α-AlH3 have a larger spectral intensity than that of Al metal, indicating an increase in the number of electrons with the Al 3p character through Al-H bond formations. The results of a band-structure calculation account for the formation of the energy gap and the increase of the Al 3p electrons qualitatively. This suggests that a covalent-like nature is important to the Al-H bond in α-AlH3.

  18. Energy absorption of composite materials

    NASA Technical Reports Server (NTRS)

    Farley, G. L.

    1983-01-01

    Results of a study on the energy absorption characteristics of selected composite material systems are presented and the results compared with aluminum. Composite compression tube specimens were fabricated with both tape and woven fabric prepreg using graphite/epoxy (Gr/E), Kevlar (TM)/epoxy (K/E) and glass/epoxy (Gl/E). Chamfering and notching one end of the composite tube specimen reduced the peak load at initial failure without altering the sustained crushing load, and prevented catastrophic failure. Static compression and vertical impact tests were performed on 128 tubes. The results varied significantly as a function of material type and ply orientation. In general, the Gr/E tubes absorbed more energy than the Gl/E or K/E tubes for the same ply orientation. The 0/ + or - 15 Gr/E tubes absorbed more energy than the aluminum tubes. Gr/E and Gl/E tubes failed in a brittle mode and had negligible post crushing integrity, whereas the K/E tubes failed in an accordian buckling mode similar to the aluminum tubes. The energy absorption and post crushing integrity of hybrid composite tubes were not significantly better than that of the single material tubes.

  19. Iron Absorption in Drosophila melanogaster

    PubMed Central

    Mandilaras, Konstantinos; Pathmanathan, Tharse; Missirlis, Fanis

    2013-01-01

    The way in which Drosophila melanogaster acquires iron from the diet remains poorly understood despite iron absorption being of vital significance for larval growth. To describe the process of organismal iron absorption, consideration needs to be given to cellular iron import, storage, export and how intestinal epithelial cells sense and respond to iron availability. Here we review studies on the Divalent Metal Transporter-1 homolog Malvolio (iron import), the recent discovery that Multicopper Oxidase-1 has ferroxidase activity (iron export) and the role of ferritin in the process of iron acquisition (iron storage). We also describe what is known about iron regulation in insect cells. We then draw upon knowledge from mammalian iron homeostasis to identify candidate genes in flies. Questions arise from the lack of conservation in Drosophila for key mammalian players, such as ferroportin, hepcidin and all the components of the hemochromatosis-related pathway. Drosophila and other insects also lack erythropoiesis. Thus, systemic iron regulation is likely to be conveyed by different signaling pathways and tissue requirements. The significance of regulating intestinal iron uptake is inferred from reports linking Drosophila developmental, immune, heat-shock and behavioral responses to iron sequestration. PMID:23686013

  20. QED-driven laser absorption

    NASA Astrophysics Data System (ADS)

    Levy, Matthew; Blackburn, T.; Ratan, N.; Sadler, J.; Ridgers, C.; Kasim, M.; Ceurvorst, L.; Holloway, J.; Baring, M.; Bell, A.; Glenzer, S.; Gregori, G.; Ilderton, A.; Marklund, M.; Tabak, M.; Wilks, S.; Norreys, P.

    2016-10-01

    Absorption covers the physical processes which convert intense photon flux into energetic particles when a high-power laser (I >1018 W cm-2 where I is intensity at 1 μm wavelength) illuminates optically-thick matter. It underpins important applications of petawatt laser systems today, e.g., in isochoric heating of materials. Next-generation lasers such as ELI are anticipated to produce quantum electrodynamical (QED) bursts of γ-rays and anti-matter via the multiphoton Breit-Wheeler process which could enable scaled laboratory probes, e.g., of black hole winds. Here, applying strong-field QED to advances in plasma kinematic theory, we present a model elucidating absorption limited only by an avalanche of self-created electron-positron pairs at ultra-high-field. The model, confirmed by multidimensional QED-PIC simulations, works over six orders of magnitude in optical intensity and reveals this cascade is initiated at 1.8 x 1025 W cm-2 using a realistic linearly-polarized laser pulse. Here the laser couples its energy into highly-collimated electrons, ions, γ-rays, and positrons at 12%, 6%, 58% and 13% efficiency, respectively. We remark on attributes of the QED plasma state and possible applications.

  1. Circumgalactic Oxygen Absorption and Feedback

    NASA Astrophysics Data System (ADS)

    Mathews, William G.; Prochaska, J. Xavier

    2017-09-01

    O vi absorption in quasar spectra caused by intervening circumgalactic atmospheres suggests a downturn in the atmospheric column density in sightlines passing beyond about 100 kpc from central star-forming galaxies. This turnover supports the hypothesis that the oxygen originates in the central galaxies. When converted into oxygen space density using an Abel integral inversion, the O vi columns require ≳ {10}9 M ⊙ of oxygen concentrated near 100 kpc. Circumgalactic gas within this radius cools in less than 1 Gyr and radiates ∼ {10}42.2 erg s‑1 overall. The feedback power necessary to maintain such oxygen-rich atmospheres for many Gyr cannot be easily supplied by galactic supernovae. However, massive central black holes in star-forming galaxies may generate sufficient accretion power and intermittent shock waves at r∼ 100 {kpc} to balance circumgalactic radiation losses in late-type {L}\\star galaxies. The relative absence of O vi absorption observed in early-type, passive {L}\\star galaxies may arise from enhanced AGN feedback from their more massive central black holes.

  2. Absorption in Extended Inhomogeneous Clouds

    NASA Technical Reports Server (NTRS)

    Joiner, Joanna; Vasilkov, Alexander; Spurr, Robert; Bhartia, P. K.; Krotkov, Nick

    2008-01-01

    The launch of several different sensors, including CloudSat, into the A-train constellation of satellites allows us for the first time to compute absorption that can occur in realistic vertically inhomogeneous clouds including multiple cloud decks. CloudSat data show that these situations are common. Therefore, understanding vertically inhomogeneous clouds is important from both climate and satellite atmospheric composition remote sensing perspectives. Satellite passive sensors that operate from the near IR to the UV often rely on radiative cloud pressures derived from absorption in oxygen bands (A, B, gamma, or O2-O2 bands) or from rotational-Raman scattering in order to retrieve information about atmospheric trace gases. The radiative cloud pressure is distinct from the physical cloud top derived from thermal infrared measurements. Therefore, the combination of information from different passive sensors yields some information about the cloud vertical profile. When either or both the clouds or atmospheric absorbers (trace gases and aerosols) are vertically inhomogeneous, the use of an effective cloud pressure derived from these approaches may lead to errors. Here, we focus on several scenarios (deep convective clouds and distinct two layer clouds) based on realistic cloud optical depth vertical profiles derived from the CloudSatfMODIS combination. We focus on implications for trace-gas column amount retrievals (specifically ozone and NO2) and derived surface UV irradiance from the Ozone Monitoring Instrument (OMI) on the Atrain Aura platform.

  3. Iron absorption in Drosophila melanogaster.

    PubMed

    Mandilaras, Konstantinos; Pathmanathan, Tharse; Missirlis, Fanis

    2013-05-17

    The way in which Drosophila melanogaster acquires iron from the diet remains poorly understood despite iron absorption being of vital significance for larval growth. To describe the process of organismal iron absorption, consideration needs to be given to cellular iron import, storage, export and how intestinal epithelial cells sense and respond to iron availability. Here we review studies on the Divalent Metal Transporter-1 homolog Malvolio (iron import), the recent discovery that Multicopper Oxidase-1 has ferroxidase activity (iron export) and the role of ferritin in the process of iron acquisition (iron storage). We also describe what is known about iron regulation in insect cells. We then draw upon knowledge from mammalian iron homeostasis to identify candidate genes in flies. Questions arise from the lack of conservation in Drosophila for key mammalian players, such as ferroportin, hepcidin and all the components of the hemochromatosis-related pathway. Drosophila and other insects also lack erythropoiesis. Thus, systemic iron regulation is likely to be conveyed by different signaling pathways and tissue requirements. The significance of regulating intestinal iron uptake is inferred from reports linking Drosophila developmental, immune, heat-shock and behavioral responses to iron sequestration.

  4. Iodine Absorption Cells Purity Testing

    PubMed Central

    Hrabina, Jan; Zucco, Massimo; Philippe, Charles; Pham, Tuan Minh; Holá, Miroslava; Acef, Ouali; Lazar, Josef; Číp, Ondřej

    2017-01-01

    This article deals with the evaluation of the chemical purity of iodine-filled absorption cells and the optical frequency references used for the frequency locking of laser standards. We summarize the recent trends and progress in absorption cell technology and we focus on methods for iodine cell purity testing. We compare two independent experimental systems based on the laser-induced fluorescence method, showing an improvement of measurement uncertainty by introducing a compensation system reducing unwanted influences. We show the advantages of this technique, which is relatively simple and does not require extensive hardware equipment. As an alternative to the traditionally used methods we propose an approach of hyperfine transitions’ spectral linewidth measurement. The key characteristic of this method is demonstrated on a set of testing iodine cells. The relationship between laser-induced fluorescence and transition linewidth methods will be presented as well as a summary of the advantages and disadvantages of the proposed technique (in comparison with traditional measurement approaches). PMID:28067834

  5. Formaldehyde Absorption toward W51

    SciTech Connect

    Kogut, A.; Smoot, G.F.; Bennett, C.L.; Petuchowski, S.J.

    1988-04-01

    We have measured formaldehyde (H{sub 2}CO) absorption toward the HII region complex W51A (G49.5-0.4) in the 6 cm and 2 cm wavelength rotational transitions with angular resolution of approximately 4 inch. The continuum HII region shows a large, previously undetected shell structure 5.5 pc along the major axis. We observe no H{sub 2}CO emission in regions of low continuum intensity. The absorption, converted to optical depth, shows a higher degree of clumping than previous maps at lower resolution. The good S/N of the maps allows accurate estimation of the complicated line profiles, showing some of the absorbing clouds to be quite patchy. We list the properties of the opacity spectra for a number of positions both in the clumps and in the more diffuse regions of the absorbing clouds, and derive column densities for the 1{sub 11} and 2{sub 12} rotational levels of ortho-formaldehyde.

  6. Sulphate absorption across biological membranes.

    PubMed

    Mitchell, Stephen C; Waring, Rosemary H

    2016-01-01

    1. Sulphonation is unusual amongst the common Phase II (condensation; synthetic) reactions experienced by xenobiotics, in that the availability of the conjugating agent, sulphate, may become a rate-limiting factor. This sulphate is derived within the body via the oxygenation of sulphur moieties liberated from numerous ingested compounds including the sulphur-containing amino acids. Preformed inorganic sulphate also makes a considerable contribution to this pool. 2. There has been a divergence of opinion as to whether or not inorganic sulphate may be readily absorbed from the gastrointestinal tract and this controversy still continues in some quarters. Even more so, is the vexing question of potential absorption of inorganic sulphate via the lungs and through the skin. 3. This review examines the relevant diverse literature and concludes that sulphate ions may move across biological membranes by means of specific transporters and, although the gastrointestinal tract is by far the major portal of entry, some absorption across the lungs and the skin may take place under appropriate circumstances.

  7. The photoionization spectrum of neutral aluminium, Al I

    NASA Technical Reports Server (NTRS)

    Roig, R. A.

    1975-01-01

    The absorption spectrum of Al I has been studied for the wavelength range 1160 to 2000 A by the flash pyrolysis technique. Wavelengths and derived energy levels are reported for 70 new lines converging on the 3s3p(3)P(0) limits of Al II. The autoionization parameters of the 3p(2)P(0)-3p(2)(2)S doublet have been measured. Good agreement is obtained with the experiment of Kohl and Parkinson and the recent calculation of Le Dourneuf et al. The relative photoionization cross section has been measured in the wavelength region 1200 A to 2000 A.

  8. Intersubband absorption in Si(1-x)Ge(x/Si superlattices for long wavelength infrared detectors

    NASA Technical Reports Server (NTRS)

    Rajakarunanayake, Yasantha; Mcgill, Tom C.

    1990-01-01

    Researchers calculated the absorption strengths for intersubband transitions in n-type Si(1-x)Ge(x)/Si superlattices. These transitions can be used for the detection of long-wavelength infrared radiation. A significant advantage in Si(1-x)Ge(x)/Si supperlattice detectors is the ability to detect normally incident light; in Ga(1-x)Al(x)As/GaAs superlattices, intersubband absorption is possible only if the incident light contains a polarization component in the growth direction of the superlattice. Researchers present detailed calculation of absorption coefficients, and peak absorption wavelengths for (100), (111) and (110) Si(1-x)Ge(x)/Si superlattices. Peak absorption strengths of about 2000 to 6000 cm(exp -1) were obtained for typical sheet doping concentrations (approx. equals 10(exp 12)cm(exp -2)). Absorption comparable to that in Ga(1-x)Al(x)As/GaAs superlattice detectors, compatibility with existing Si technology, and the ability to detect normally incident light make these devices promising for future applications.

  9. Thermally induced nonlinear optical absorption in metamaterial perfect absorbers

    SciTech Connect

    Guddala, Sriram Kumar, Raghwendra; Ramakrishna, S. Anantha

    2015-03-16

    A metamaterial perfect absorber consisting of a tri-layer (Al/ZnS/Al) metal-dielectric-metal system with top aluminium nano-disks was fabricated by laser-interference lithography and lift-off processing. The metamaterial absorber had peak resonant absorbance at 1090 nm and showed nonlinear absorption for 600ps laser pulses at 1064 nm wavelength. A nonlinear saturation of reflectance was measured to be dependent on the average laser power incident and not the peak laser intensity. The nonlinear behaviour is shown to arise from the heating due to the absorbed radiation and photo-thermal changes in the dielectric properties of aluminium. The metamaterial absorber is seen to be damage resistant at large laser intensities of 25 MW/cm{sup 2}.

  10. Direct Absorption Spectroscopy with Electro-Optic Frequency Combs

    NASA Astrophysics Data System (ADS)

    Fleisher, Adam J.; Long, David A.; Plusquellic, David F.; Hodges, Joseph T.

    2017-06-01

    The application of electro-optic frequency combs to direct absorption spectroscopy has increased research interest in high-agility, modulator-based comb generation. This talk will review common architectures for electro-optic frequency comb generators as well as describe common self-heterodyne and multi-heterodyne (i.e., dual-comb) detection approaches. In order to achieve a sufficient signal-to-noise ratio on the recorded interferogram while allowing for manageable data volumes, broadband electro-optic frequency combs require deep coherent averaging, preferably in real-time. Applications such as cavity-enhanced spectroscopy, precision atomic and molecular spectroscopy, as well as time-resolved spectroscopy will be introduced. D.A. Long et al., Opt. Lett. 39, 2688 (2014) A.J. Fleisher et al., Opt. Express 24, 10424 (2016)

  11. Thermally induced nonlinear optical absorption in metamaterial perfect absorbers

    NASA Astrophysics Data System (ADS)

    Guddala, Sriram; Kumar, Raghwendra; Ramakrishna, S. Anantha

    2015-03-01

    A metamaterial perfect absorber consisting of a tri-layer (Al/ZnS/Al) metal-dielectric-metal system with top aluminium nano-disks was fabricated by laser-interference lithography and lift-off processing. The metamaterial absorber had peak resonant absorbance at 1090 nm and showed nonlinear absorption for 600ps laser pulses at 1064 nm wavelength. A nonlinear saturation of reflectance was measured to be dependent on the average laser power incident and not the peak laser intensity. The nonlinear behaviour is shown to arise from the heating due to the absorbed radiation and photo-thermal changes in the dielectric properties of aluminium. The metamaterial absorber is seen to be damage resistant at large laser intensities of 25 MW/cm2.

  12. The absorption spectra of carbonates and their precursors.

    NASA Astrophysics Data System (ADS)

    Koike, C.; Chihara, H.; Suto, H.

    The carbonates calcite and dolomite have been discovered in the dust shells of evolved stars (Kemper et al. 2002) and young proto stars (Ceccarelli et al. 2002). The mechanism for carbonate formation with a aqueous or non-aqueous process were discussed in their papers. These processes have not yet been reproduced in a laboratory experiment. First of all, we measured the mass absorption spectra of varous carbonates were measured in the mid- and far-infrared region. These spectra show very strong and broad peaks in the far-infrared region. The calcite and dolomite have peaks at about 92 microns and 63 microns, respectively. The alternative process of carbonates has not yet been clear. We investigate the alternative process measuring the spectra of the precursors of carbonates. We will report the preliminary results and discuss about the alternative process comparing the measured spectra of the precursors with the observation.

  13. Optical Absorption Spectra of Hydrous Wadsleyite to 32 GPa

    NASA Astrophysics Data System (ADS)

    Thomas, S.; Goncharov, A. F.; Jacobsen, S. D.; Bina, C. R.; Frost, D. J.

    2009-05-01

    Optical absorption spectra of high-pressure minerals can be used as indirect tools to calculate radiative conductivity of the Earth's interior [e.g., 1]. Recent high-pressure studies show that e.g. ringwoodite, γ-(Mg,Fe)2SiO4, does not become opaque in the near infrared and visible region, as previously assumed, but remains transparent to 21.5 GPa [2]. Therefore, it has been concluded that radiative heat transfer does not necessarily become blocked at high pressures of the mantle and ferromagnesian minerals actually could contribute to the heat flow in the Earth's interior [2]. In this study we use gem-quality single-crystals of hydrous Fe-bearing wadsleyite, β-(Mg,Fe)2SiO4, that were synthesized at 18 GPa and 1400 °C in a multianvil apparatus. Crystals were analyzed by Mössbauer and Raman spectroscopy, electron microprobe analysis and single-crystal X-ray diffraction. For absorption measurements a double-polished 50 μm sized single-crystal of wadsleyite was loaded in a diamond-anvil cell with neon as pressure medium. Optical absorption spectra were recorded at ambient conditions as well as up to 32 GPa from 400 to 50000 cm-1. At ambient pressure the absorption spectrum reveals two broad bands at - 10000 cm-1 and -15000 cm-1, and an absorption edge in the visible-ultraviolet range. With increasing pressure the absorption spectrum changes, both bands continuously shift to higher frequencies as has been observed for ringwoodite [2], but is contrary to earlier presumptions for wadsleyite [3]. Here, we will discuss band assignment along with the influence of iron, compare our results to previous absorption studies of mantle materials [2], and analyze possible implications for radiative conductivity of the transition zone. References: [1] Goncharov et al. (2008), McGraw Yearbook Sci. Tech., 242-245. [2] Keppler & Smyth (2005), Am. Mineral., 90 1209-1212. [3] Ross (1997), Phys. Chem. Earth, 22 113-118.

  14. Genetic testing in ALS

    PubMed Central

    McLaughlin, Russell L.; Heverin, Mark; Thorpe, Owen; Abrahams, Sharon; Al-Chalabi, Ammar; Hardiman, Orla

    2017-01-01

    Objective: To determine the degree of consensus among clinicians on the clinical use of genetic testing in amyotrophic lateral sclerosis (ALS) and the factors that determine decision-making. Methods: ALS researchers worldwide were invited to participate in a detailed online survey to determine their attitudes and practices relating to genetic testing. Results: Responses from 167 clinicians from 21 different countries were analyzed. The majority of respondents (73.3%) do not consider that there is a consensus definition of familial ALS (FALS). Fifty-seven percent consider a family history of frontotemporal dementia and 48.5% the presence of a known ALS genetic mutation as sufficient for a diagnosis of FALS. Most respondents (90.2%) offer genetic testing to patients they define as having FALS and 49.4% to patients with sporadic ALS. Four main genes (SOD1, C9orf72, TARDBP, and FUS) are commonly tested. A total of 55.2% of respondents would seek genetic testing if they had personally received a diagnosis of ALS. Forty-two percent never offer presymptomatic testing to family members of patients with FALS. Responses varied between ALS specialists and nonspecialists and based on the number of new patients seen per year. Conclusions: There is a lack of consensus among clinicians as to the definition of FALS. Substantial variation exists in attitude and practices related to genetic testing of patients and presymptomatic testing of their relatives across geographic regions and between experienced specialists in ALS and nonspecialists. PMID:28159885

  15. Ligand effects on the X-ray absorption of a nickel porphyrin complex: a simulation study

    NASA Astrophysics Data System (ADS)

    Campbell, Luke; Tanaka, Satoshi; Mukamel, Shaul

    2004-04-01

    We present a simulation of the X-ray absorption near-edge spectrum (XANES) of the metal porphyrin NiTPP (nickel tetraphenylporphyrin) and investigate the changes to the spectrum caused by adding piperidine ligands to the metal atom. The main features in the experimental spectrum (Chen et al., Science 292 (2001) 262) are interpreted in terms of changes in the electronic structure.

  16. Interstellar formaldehyde. I - The collisional pumping mechanism for anomalous 6-centimeter absorption.

    NASA Technical Reports Server (NTRS)

    Thaddeus, P.

    1972-01-01

    Investigation of the quantum mechanics of the collisional pumping process which Townes and Cheung (1969) propose as the cause of 'anomalous' formaldehyde absorption in diffuse dark nebulae discussed by Palmer et al. (1969). Quantum effects are taken into account in an attempt to determine whether such nebulae are likely to provide the physical conditions required for the collisional pumping process.

  17. Preparation of broadband absorption ceramic coatings by using plasma electrolytic deposition

    NASA Astrophysics Data System (ADS)

    Yao, Caizhen; Li, Yuan; Li, Qin; Lu, Songtao; Wu, Xiaohong; Jiang, Yong; Gao, Wei; Yan, Hongwei; Wang, Haijun; Ye, Yayun

    2017-07-01

    Two types of black ceramic coatings with high spectrum absorptivity were prepared on Al alloy substrate by using plasma electrolytic deposition method. The spectrum absorption properties of coatings were tested by using 355 nm ultraviolet laser pulses. Particle counter device was employed to collect and analyze the particles formed during the irradiation process. Experimental results showed that the coatings have porous structures. The sample coatings 1 and 2 have thickness of 120 μm and 60 μm with holes’ diameter of about 70 μm and 15 μm, respectively. The coating 1 is mainly composed of Al2O3 and SiO2 while coating 2 consists of Al2O3. The reflectivity of both coatings is much lower than that of Al alloy substrate. The absorptivity of samples 1 and 2 is about 99.88% and 99.92% for wavelength from 300 nm to 800 nm. The mechanisms of spectrum absorption were also explored.

  18. Interstellar formaldehyde. I - The collisional pumping mechanism for anomalous 6-centimeter absorption.

    NASA Technical Reports Server (NTRS)

    Thaddeus, P.

    1972-01-01

    Investigation of the quantum mechanics of the collisional pumping process which Townes and Cheung (1969) propose as the cause of 'anomalous' formaldehyde absorption in diffuse dark nebulae discussed by Palmer et al. (1969). Quantum effects are taken into account in an attempt to determine whether such nebulae are likely to provide the physical conditions required for the collisional pumping process.

  19. Direct Electrothermal Atomic Absorption Determination of Trace Elements in Body Fluids (Review)

    NASA Astrophysics Data System (ADS)

    Zacharia, A. N.; Arabadji, M. V.; Chebotarev, A. N.

    2017-03-01

    This review is focused on the state and development of tendencies of electrothermal atomic absorption spectroscopy over the last 25 years (from 1990 to 2016) in the direct determination of Cu, Zn, Pb, Cd, Mn, Se, As, Cr, Co, Ni, Al, and Hg in body fluids such as blood, urine, saliva, and breast milk.

  20. Assessing the absorption of new pharmaceuticals.

    PubMed

    Hidalgo, I J

    2001-11-01

    The advent of more efficient methods to synthesize and screen new chemical compounds is increasing the number of chemical leads identified in the drug discovery phase. Compounds with good biological activity may fail to become drugs due to insufficient oral absorption. Selection of drug development candidates with adequate absorption characteristics should increase the probability of success in the development phase. To assess the absorption potential of new chemical entities numerous in vitro and in vivo model systems have been used. Many laboratories rely on cell culture models of intestinal permeability such as, Caco-2, HT-29 and MDCK. To attempt to increase the throughput of permeability measurements, several physicochemical methods such as, immobilized artificial membrane (IAM) columns and parallel artificial membrane permeation assay (PAMPA) have been used. More recently, much attention has been given to the development of computational methods to predict drug absorption. However, it is clear that no single method will sufficient for studying drug absorption, but most likely a combination of systems will be needed. Higher throughput, less reliable methods could be used to discover 'loser' compounds, whereas lower throughput, more accurate methods could be used to optimize the absorption properties of lead compounds. Finally, accurate methods are needed to understand absorption mechanisms (efflux-limited absorption, carrier-mediated, intestinal metabolism) that may limit intestinal drug absorption. This information could be extremely valuable to medicinal chemists in the selection of favorable chemo-types. This review describes different techniques used for evaluating drug absorption and indicates their advantages and disadvantages.

  1. X-ray absorption spectroscopy on the basis of hybrid X-pinch radiation

    SciTech Connect

    Tilikin, I. N. Shelkovenko, T. A.; Pikuz, S. A.; Knapp, P. F.; Hammer, D. A.

    2015-07-15

    Results of experiments on X-ray absorption spectroscopy carried out at the BIN (270 kA, 100 ns) and XP (450 kA, 45 ns) facilities are presented. Continuum radiation of a Mo hybrid X-pinch was used as probing radiation, against which absorption lines of the plasma of exploded Al wires placed in the return current circuit of a hybrid X-pinch, as well as in a two- and four-wire array, were observed. The experiments have demonstrated that the radiation of a hybrid X-pinch hot spot can be used as probing radiation for X-ray absorption spectroscopy and that, in many parameters, such a source surpasses those on the basis of laser-produced plasma. The plasma parameters in arrays made of two and four Al wires were studied experimentally.

  2. X-ray absorption spectroscopy on the basis of hybrid X-pinch radiation

    NASA Astrophysics Data System (ADS)

    Tilikin, I. N.; Shelkovenko, T. A.; Pikuz, S. A.; Knapp, P. F.; Hammer, D. A.

    2015-07-01

    Results of experiments on X-ray absorption spectroscopy carried out at the BIN (270 kA, 100 ns) and XP (450 kA, 45 ns) facilities are presented. Continuum radiation of a Mo hybrid X-pinch was used as probing radiation, against which absorption lines of the plasma of exploded Al wires placed in the return current circuit of a hybrid X-pinch, as well as in a two- and four-wire array, were observed. The experiments have demonstrated that the radiation of a hybrid X-pinch hot spot can be used as probing radiation for X-ray absorption spectroscopy and that, in many parameters, such a source surpasses those on the basis of laser-produced plasma. The plasma parameters in arrays made of two and four Al wires were studied experimentally.

  3. FUV Reflectance of Recently Prepared Al Protected with AlF3: COR Program Technology Development

    NASA Technical Reports Server (NTRS)

    Quijada, Manuel

    2016-01-01

    Astronomical observations in the Far Ultraviolet (FUV) spectral region are some of the more challenging due to the very distant and faint objects that are typically searched for in cosmic origin studies such as origin of large scale structure, the formation, evolution, and age of galaxies and the origin of stellar and planetary systems. These challenges are driving the need to improve the performance of optical coatings over a wide spectral range that would increase reflectance in mirrors and reduced absorption in dielectric filters used in optical telescope for FUV observations. This paper will present recent advances in reflectance performance for Al+AlF3 mirrors optimized for Lyman-alpha wavelength by performing the deposition of the AlF3 overcoat at elevated substrate temperatures.

  4. Ventilatory Control in ALS

    PubMed Central

    Nichols, Nicole L.; Van Dyke, J.; Nashold, L.; Satriotomo, I.; Suzuki, M.; Mitchell, G.S.

    2015-01-01

    Amyotrophic lateral sclerosis (ALS) is a fatal, progressive neurodegenerative disease. ALS selectively causes degeneration in upper and lower (spinal) motor neurons, leading to muscle weakness, paralysis and death by ventilatory failure. Although ventilatory failure is generally the cause of death in ALS, little is known concerning the impact of this disorder on respiratory motor neurons, the consequences of respiratory motor neuron cell death, or the ability of the respiratory control system to “fight back” via mechanisms of compensatory respiratory plasticity. Here we review known effects of ALS on breathing, including possible effects on rhythm generation, respiratory motor neurons, and their target organs: the respiratory muscles. We consider evidence for spontaneous compensatory plasticity, preserving breathing well into disease progression despite dramatic loss of spinal respiratory motor neurons. Finally, we review current and potential therapeutic approaches directed toward preserving the capacity to breathe in ALS patients. PMID:23692930

  5. X-ray absorption spectroscopy of bacterial sulfur globules

    SciTech Connect

    George, Graham N.

    2002-08-01

    Sulfur K-edge X-ray absorption spectroscopy is a powerful in situ probe of sulfur biochemistry in intact cells and tissues. Under favorable circumstances the technique can provide quantitative information on the chemical identify of the sulfur species that are present in a sample. Prange et al. have recently reported an X-ray absorption spectroscopic study of bacterial sulfur storage globules. Unfortunately there are substantial problems with the experimental technique employed that, they contend, lead to completely erroneous conclusions. In the more recent of their two papers Prange et al. employed a curve-fitting method similar to that used by us (for more than 10 years). In essence, the method employs simply fitting a linear combination of the spectra of standard compounds to that of the unknown, in this case cultures of bacterial cells. This type of analysis can provide quantitative estimates of the individual sulfur types in the sample, but is critically dependent upon the choice of reference spectra. Prange et al. deduce substantial differences between the chemical forms of sulfur stored in the globules of different organisms; they conclude that the globules of Beggiatoa alba and Thiomargarita namibiensis contain cyclo-octasulfur (S{sub 8}), while those of other organisms contain polythionates (Acidithiobacillus ferrooxidans) and polymeric sulfur (e.g. Allochromatium vinosum). This is in contradiction with an earlier study, in which they found that sulfur in all globule species examined resembled that expected for various sized spherical particles of S{sub 8}. The discrepancy is due to an experimental artefact in the work of Prange et al. arising from their choice of transmittance detection, which is also discussed.

  6. X-ray absorption of Azotobacter vinelandii vanadium nitrogenase

    SciTech Connect

    George, G.N.; Coyle, C.L.; Hales, B.J.; Cramer, S.P.

    1988-06-08

    Evidence for the existence of a vanadium-containing nitrogenase has existed for more than half a century, but progress in understanding this enzyme has only come recently. In 1980, Bishop and co-workers proposed that an alternative nitrogen-fixing enzyme exists in Azotobacter vinelandii and subsequently proposed that vanadium was involved. In 1986, Robson et al. demonstrated clearly that the alternate nitrogenase from Azotobacter chroococcum, Acl*, contained vanadium instead of molybdenum. Hales et al. have shown the vanadium is also found in the Azotobacter vinelandii alternative component I, Avl'. The molybdenum and vanadium nitrogenase proteins are similar in many respects. Like the molybdenum enzyme, both Acl* and Avl' exhibit an EPR spectrum characteristic of a species with an S = 3/2 ground state; Avl' also contains the so-called P-clusters. Additionally Acl* has recently been shown to possess an N-methylformamide soluble cofactor, FeVco, analogous to the well-known iron-molybdenum cofactor FeMoco. Arber et al. have reported X-ray absorption spectra for the Acl* enzyme and interpreted the EXAFS as evidence for a V-Fe-S cluster. The local vanadium structure is proposed to resemble a recently synthesized cubane-like VFe/sub 3/S/sub 4/ cluster, and analogies are drawn with the EXAFS-derived structure reported for the molybdenum nitrogenases. The authors report herein an X-ray absorption spectroscopic study of A. vinelandii vanadium nitrogenase, Avl', which supports and extends the work of Arber et al.

  7. A contribution of black and brown carbon to the aerosol light absorption

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Woo; Cho, Chaeyoon; Jo, Duseong; Park, Rokjin

    2017-04-01

    Black carbon (BC) is functionally defined as the absorbing component of atmospheric total carbonaceous aerosols and is typically dominated by soot-like elemental carbon (EC). Organic carbon (OC) has also been shown to absorb strongly at visible to UV wavelengths and the absorbing organics are referred to as brown carbon (BrC; Alexander et al., 2008). These two aerosols contribute to solar radiative forcing through absorption of solar radiation and heating of the absorbing aerosol layer, but most optical instruments that quantify light absorption are unable to distinguish one type of absorbing aerosol from another (Moosmüller et al. 2009). In this study, we separate total aerosol absorption from these two different light absorbers from co-located simultaneous in-situ measurements, such as Continuous Soot Monitoring System (COSMOS), Continuous Light Absorption Photometer (CLAP) and Sunset EC/OC analyzer, at Gosan climate observatory, Korea. We determine the mass absorption cross-section (MAC) of BC, and then estimate the contribution of BC and BrC on aerosol light absorption, together with a global 3-D chemical transport model (GEOS-Chem) simulation. At 565 nm wavelength, BC MAC is found to be about 5.4±2.8 m2 g-1 from COSMOS and Sunset EC/OC analyzer measurements during January-May 2012. This value is similar to those from Alexander et al. (2008; 4.3 ˜ 4.8 m2 g-1 at 550 nm) and Chung et al. (2012; 5.1 m2 g-1 at 520 nm), but slightly lower than Bond and Bergstrom (2006; 7.5±1.2 m2 g-1 at 550 nm). The COMOS BC mass concentration calculated with 5.4 m2 g-1 of BC MAC shows a good agreement with thermal EC concentration, with a good slope (1.1). Aerosol absorption coefficient and BC mass concentration from COSMOS, meanwhile, are approximately 25 ˜ 30 % lower than those of CLAP. This difference can be attributable to the contribution of volatile light-absorbing aerosols (i.e., BrC). The absorption coefficient of BrC, which is determined by the difference of

  8. Backscatter absorption gas imaging system

    DOEpatents

    McRae, T.G. Jr.

    A video imaging system for detecting hazardous gas leaks. Visual displays of invisible gas clouds are produced by radiation augmentation of the field of view of an imaging device by radiation corresponding to an absorption line of the gas to be detected. The field of view of an imager is irradiated by a laser. The imager receives both backscattered laser light and background radiation. When a detectable gas is present, the backscattered laser light is highly attenuated, producing a region of contrast or shadow on the image. A flying spot imaging system is utilized to synchronously irradiate and scan the area to lower laser power requirements. The imager signal is processed to produce a video display.

  9. Acoustic Absorption in Porous Materials

    NASA Technical Reports Server (NTRS)

    Kuczmarski, Maria A.; Johnston, James C.

    2011-01-01

    An understanding of both the areas of materials science and acoustics is necessary to successfully develop materials for acoustic absorption applications. This paper presents the basic knowledge and approaches for determining the acoustic performance of porous materials in a manner that will help materials researchers new to this area gain the understanding and skills necessary to make meaningful contributions to this field of study. Beginning with the basics and making as few assumptions as possible, this paper reviews relevant topics in the acoustic performance of porous materials, which are often used to make acoustic bulk absorbers, moving from the physics of sound wave interactions with porous materials to measurement techniques for flow resistivity, characteristic impedance, and wavenumber.

  10. HI Absorption in Merger Remnants

    NASA Technical Reports Server (NTRS)

    Teng, Stacy H.; Veileux, Sylvain; Baker, Andrew J.

    2012-01-01

    It has been proposed that ultraluminous infrared galaxies (ULIRGs) pass through a luminous starburst phase, followed by a dust-enshrouded AGN phase, and finally evolve into optically bright "naked" quasars once they shed their gas/dust reservoirs through powerful wind events. We present the results of our recent 21- cm HI survey of 21 merger remnants with the Green Bank Telescope. These remnants were selected from the QUEST (Quasar/ULIRG Evolution Study) sample of ULIRGs and PG quasars; our targets are all bolometrically dominated by AGN and sample all phases of the proposed ULIRG -> IR-excess quasar -> optical quasar sequence. We explore whether there is an evolutionary connection between ULIRGs and quasars by looking for the occurrence of HI absorption tracing neutral gas outflows; our results will allow us to identify where along the sequence the majority of a merger's gas reservoir is expelled.

  11. Backscatter absorption gas imaging system

    DOEpatents

    McRae, Jr., Thomas G.

    1985-01-01

    A video imaging system for detecting hazardous gas leaks. Visual displays of invisible gas clouds are produced by radiation augmentation of the field of view of an imaging device by radiation corresponding to an absorption line of the gas to be detected. The field of view of an imager is irradiated by a laser. The imager receives both backscattered laser light and background radiation. When a detectable gas is present, the backscattered laser light is highly attenuated, producing a region of contrast or shadow on the image. A flying spot imaging system is utilized to synchronously irradiate and scan the area to lower laser power requirements. The imager signal is processed to produce a video display.

  12. Quantum-enhanced absorption refrigerators

    NASA Astrophysics Data System (ADS)

    Correa, Luis A.; Palao, José P.; Alonso, Daniel; Adesso, Gerardo

    2014-02-01

    Thermodynamics is a branch of science blessed by an unparalleled combination of generality of scope and formal simplicity. Based on few natural assumptions together with the four laws, it sets the boundaries between possible and impossible in macroscopic aggregates of matter. This triggered groundbreaking achievements in physics, chemistry and engineering over the last two centuries. Close analogues of those fundamental laws are now being established at the level of individual quantum systems, thus placing limits on the operation of quantum-mechanical devices. Here we study quantum absorption refrigerators, which are driven by heat rather than external work. We establish thermodynamic performance bounds for these machines and investigate their quantum origin. We also show how those bounds may be pushed beyond what is classically achievable, by suitably tailoring the environmental fluctuations via quantum reservoir engineering techniques. Such superefficient quantum-enhanced cooling realises a promising step towards the technological exploitation of autonomous quantum refrigerators.

  13. Energy absorption by polymer crazing

    NASA Technical Reports Server (NTRS)

    Pang, S. S.; Zhang, Z. D.; Chern, S. S.; Hsiao, C. C.

    1983-01-01

    During the past thirty years, a tremendous amount of research was done on the development of crazing in polymers. The phenomenon of crazing was recognized as an unusual deformation behavior associated with a process of molecular orientation in a solid to resist failure. The craze absorbs a fairly large amount of energy during the crazing process. When a craze does occur the surrounding bulk material is usually stretched to several hundred percent of its original dimension and creates a new phase. The total energy absorbed by a craze during the crazing process in creep was calculated analytically with the help of some experimental measurements. A comparison of the energy absorption by the new phase and that by the original bulk uncrazed medium is made.

  14. Multistage quantum absorption heat pumps

    NASA Astrophysics Data System (ADS)

    Correa, Luis A.

    2014-04-01

    It is well known that heat pumps, while being all limited by the same basic thermodynamic laws, may find realization on systems as "small" and "quantum" as a three-level maser. In order to quantitatively assess how the performance of these devices scales with their size, we design generalized N-dimensional ideal heat pumps by merging N -2 elementary three-level stages. We set them to operate in the absorption chiller mode between given hot and cold baths and study their maximum achievable cooling power and the corresponding efficiency as a function of N. While the efficiency at maximum power is roughly size-independent, the power itself slightly increases with the dimension, quickly saturating to a constant. Thus, interestingly, scaling up autonomous quantum heat pumps does not render a significant enhancement beyond the optimal double-stage configuration.

  15. Multistage quantum absorption heat pumps.

    PubMed

    Correa, Luis A

    2014-04-01

    It is well known that heat pumps, while being all limited by the same basic thermodynamic laws, may find realization on systems as "small" and "quantum" as a three-level maser. In order to quantitatively assess how the performance of these devices scales with their size, we design generalized N-dimensional ideal heat pumps by merging N-2 elementary three-level stages. We set them to operate in the absorption chiller mode between given hot and cold baths and study their maximum achievable cooling power and the corresponding efficiency as a function of N. While the efficiency at maximum power is roughly size-independent, the power itself slightly increases with the dimension, quickly saturating to a constant. Thus, interestingly, scaling up autonomous quantum heat pumps does not render a significant enhancement beyond the optimal double-stage configuration.

  16. Quantum-enhanced absorption refrigerators

    PubMed Central

    Correa, Luis A.; Palao, José P.; Alonso, Daniel; Adesso, Gerardo

    2014-01-01

    Thermodynamics is a branch of science blessed by an unparalleled combination of generality of scope and formal simplicity. Based on few natural assumptions together with the four laws, it sets the boundaries between possible and impossible in macroscopic aggregates of matter. This triggered groundbreaking achievements in physics, chemistry and engineering over the last two centuries. Close analogues of those fundamental laws are now being established at the level of individual quantum systems, thus placing limits on the operation of quantum-mechanical devices. Here we study quantum absorption refrigerators, which are driven by heat rather than external work. We establish thermodynamic performance bounds for these machines and investigate their quantum origin. We also show how those bounds may be pushed beyond what is classically achievable, by suitably tailoring the environmental fluctuations via quantum reservoir engineering techniques. Such superefficient quantum-enhanced cooling realises a promising step towards the technological exploitation of autonomous quantum refrigerators. PMID:24492860

  17. Olefin recovery via chemical absorption

    SciTech Connect

    Barchas, R.

    1998-06-01

    The recovery of fight olefins in petrochemical plants has generally been accomplished through cryogenic distillation, a process which is very capital and energy intensive. In an effort to simplify the recovery process and reduce its cost, BP Chemicals has developed a chemical absorption technology based on an aqueous silver nitrate solution. Stone & Webster is now marketing, licensing, and engineering the technology. The process is commercially ready for recovering olefins from olefin derivative plant vent gases, such as vents from polyethylene, polypropylene, ethylene oxide, and synthetic ethanol units. The process can also be used to debottleneck C{sub 2} or C{sub 3} splinters, or to improve olefin product purity. This paper presents the olefin recovery imp technology, discusses its applications, and presents economics for the recovery of ethylene and propylene.

  18. Sound absorption with green materials

    NASA Astrophysics Data System (ADS)

    Trematerra, Amelia; Lombardi, Ilaria

    2017-07-01

    Green materials are a valid alternative to traditional materials that are by-products of processing oil. At the end of their useful life, green materials can be disposed of without polluting the environment. They are now being used in the construction and automotive industries. While, studies are currently being carried out in the aviation sector on the use of green materials for non-structural components of airplanes. Green materials can be used to improve the acoustic comfort inside buildings as well as mitigate reverberation, echoes effects and reduce the transmission of noise between rooms. In this paper, the acoustic measurements of the properties of green materials are reported. The absorption coefficient of samples of the materials were measured in the frequency range from 200 Hz to 2,000 Hz with an impedance tube, with the flow resistance being measured.

  19. Computer programs for absorption spectrophotometry.

    PubMed

    Jones, R N

    1969-03-01

    Brief descriptions are given of twenty-two modular computer programs for performing the basic numerical computations of absorption spectrophotometry. The programs, written in Fortran IV for card input and output, are available from the National Research Council of Canada. The input and output formats are standardized to permit easy interfacing to yield more complex data processing systems. Though these programs were developed for ir spectrophotometry, they are readily modified for use with digitized visual and uv spectrophotometers. The operations covered include ordinate and abscissal unit and scale interconversions, ordinate addition and subtraction, location of band maxima and minima, smoothing and differentiation, slit function convolution and deconvolution, band profile analysis and asymmetry quantification, Fourier transformation to time correlation curves, multiple overlapping band separation in terms of Cauchy (Lorentz), Gauss, Cauchy-Gauss product, and Cauchy-Gauss sum functions and cell path length determination from fringe spacing analysis.

  20. Direct Absorption Receiver flow experiments

    NASA Astrophysics Data System (ADS)

    Chavez, J. M.; Tyner, C. E.; Couch, W. A.

    1987-09-01

    In a solar central receiver system Direct Absorption Receiver (DAR), the heat absorbing fluid (a blackened molten nitrate salt) flows in a thin film down a vertical panel (rather than through tubes as in conventional receiver designs) and absorbs the concentrated solar flux directly. To better understand flow phenomena in this type of receiver, we are conducting flow tests using water (because its flow properties are similar to molten salt) and a 3 MWt solar-heated DAR panel research experiment using salt. In this paper we discuss the results of the water flow testing, including manifold development, film stability, wave phenomena, and wind and natural convection effects on flow. In addition, we describe the design of the panel research experiment and planned testing.

  1. 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

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

    PubMed

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

    2013-08-01

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

  3. Implications of New Methane Absorption Coefficients on Uranus Vertical Structure Derived from Near-IR Spectra

    NASA Astrophysics Data System (ADS)

    Fry, Patrick M.; Sromovsky, L. A.

    2009-09-01

    Using new methane absorption coefficients from Karkoschka and Tomasko (2009, submitted to Icarus, "Methane Absorption Coefficients for the Jovian Planets from Laboratory, Huygens, and HST Data"), we fit Uranus near-IR spectra previously analyzed in Sromovsky et al. (2006, Icarus 182, 577-593, Fink and Larson, 1979 J- and H-band), Sromovsky and Fry (2008, Icarus 193, 252-266, 2006 NIRC2 J- and H-band, 2006 SpeX) using Irwin et al. (2006, Icarus 181, 309-319) methane absorption coefficients. Because the new absorption coefficients usually result in higher opacities at the low temperatures seen in Uranus' upper troposphere, our previously derived cloud altitudes are expected to generally rise to higher altitudes. For example, using Lindal et al. (1987, JGR 92, 14987-15001) model D temperature and methane abundance profiles, we are better able to fit the J-band 43-deg. south bright band with the new coefficients (chi-square=205, vs. 315 for Irwin), with the pressure of the upper tropospheric cloud decreasing to 1.6 bars (from 2.4 bars using Irwin coefficients). Improvements in fitting H-band spectra from the same latitude are not as readily obtained. Derived upper tropospheric cloud pressures are very similar using the two absorption datasets (1.6-1.7 bars), but the character of the fits differs. New Karkoschka and Tomasko coefficients better fit some details in the 1.5-1.58 micron region, but Irwin fits the broad absorption band wing at 1.61-1.62 microns better, and the fit chi-square values are similar (K&T: 243, Irwin: 220). Results for a higher methane concentration (Lindal et al. model F) were similar. Whether the new coefficients will simply raise derived altitudes across the planet or will result in fundamental changes in structure is as yet unclear. This work was suported by NASA planetary astronomy and planetary atmospheres programs.

  4. Superfluid inhomogeneity and microwave absorption in a model for thin high- Tc superconducting films

    NASA Astrophysics Data System (ADS)

    Barabash, Sergey V.; Stroud, David

    2003-10-01

    We investigate the microwave absorption arising from inhomogeneity in the superfluid density of thin high- Tc superconducting films. Such inhomogeneities may arise from a wide variety of sources, including quenched random disorder and static charge density waves such as stripes. We show that both mechanisms will inevitably produce additional absorption at finite frequencies. We present simple model calculations for this extra absorption, and discuss applications to other transport properties in high- Tc materials. Finally, we discuss the connection of these predictions to recent measurements by Corson et al. (Nature (London) 398 (1999) 221) of absorption by the high-temperature superconductor Bi 2Sr 2CaCu 2O 8+δ in the THz frequency regime.

  5. Narrow absorption lines with two observations from the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Chen, Zhi-Fu; Gu, Qiu-Sheng; Chen, Yan-Mei; Cao, Yue

    2015-07-01

    We assemble 3524 quasars from the Sloan Digital Sky Survey (SDSS) with repeated observations to search for variations of the narrow C IV λ λ 1548,1551 and Mg II λ λ 2796,2803 absorption doublets in spectral regions shortward of 7000 Å in the observed frame, which corresponds to time-scales of about 150-2643 d in the quasar rest frame. In these quasar spectra, we detect 3580 C IV absorption systems with zabs = 1.5188-3.5212 and 1809 Mg II absorption systems with zabs = 0.3948-1.7167. In term of the absorber velocity (β) distribution in the quasar rest frame, we find a substantial number of C IV absorbers with β < 0.06, which might be connected to absorption of quasar outflows. The outflow absorption peaks at υ ≈ 2000 km s^{-1} and drops rapidly below this peak value. Among 3580 C IV absorption systems, 52 systems (˜1.5 per cent) show obvious variations in equivalent widths in the absorber rest frame (Wr): 16 enhanced, 16 emerged, 12 weakened and 8 disappeared systems, respectively. We find that changes in Wrλ1548 are related neither to the time-scales of the two SDSS observations nor to absorber velocities in the quasar rest frame. Variable absorption in low-ionization species is important to constrain the physical conditions of the absorbing gas. There are two variable Mg II absorption systems measured from SDSS spectra detected by Hacker et al. However, in our Mg II absorption sample, we find that neither shows variable absorption with confident levels of >4σ for λ2796 lines and >3σ for λ2803 lines.

  6. Analysis of frequency dependent pump light absorption

    NASA Astrophysics Data System (ADS)

    Wohlmuth, Matthias; Pflaum, Christoph

    2011-03-01

    Simulations have to accurately model thermal lensing in order to help improving resonator design of diode pumped solid state lasers. To this end, a precise description of the pump light absorption is an important prerequisite. In this paper, we discuss the frequency dependency of the pump light absorption in the laser crystal and its influence on the simulated laser performance. The results show that the pump light absorption has to include the spectral overlap of the emitting pump source and the absorbing laser material. This information can either be used for a fully frequency dependent absorption model or, at least in the shown examples, to compute an effective value for an exponential Beer-Lambert law of absorption. This is particularly significant at pump wavelengths coinciding with a peak of absorption. Consequences for laser stability and performance are analyzed for different pump wavelengths in a Nd:YAG laser.

  7. Infrared absorption modeling of VOx microbolometer

    NASA Astrophysics Data System (ADS)

    Aggoun, Mehdi; Jiang, Jianliang; Khan, M. K.

    2015-08-01

    The absorption model plays an important role in the design of the microbolometer structure regarding the determination of the optimum thickness of the structure layers. Moreover, the infrared absorption depends on the wavelength of the radiation and the material properties. In this paper, we presented an Infrared absorption model with absorption coefficient of 96% at maximum absorption wavelength of 9.89μm which is very close to the expected value 10μm. This model was established by using MATLAB so that the simulation of the infrared absorption of the VOx microbolometer could be accomplished. In order to confirm the role of this modeling in the design of the device structure, comparison with other structures is also studied in this paper.

  8. Optical absorption and transmission in a molybdenum disulfide monolayer

    NASA Astrophysics Data System (ADS)

    Rukelj, Zoran; Štrkalj, Antonio; Despoja, Vito

    2016-09-01

    Our recently proposed theoretical formulation [presented in D. Novko et al., Phys. Rev. B 93, 125413 (2016), 10.1103/PhysRevB.93.125413] is used to study optical absorption and transmission in molybdenum disulfide (MoS2) monolayer as a function of incident photon energy and angle. The investigation is not focused on exploration of well-documented spin-orbit split excitons around optical absorption onset, but rather on the most intensive features in absorption spectrum in the visible and near-ultraviolet photon energy range (1.7 -4 eV ). It is shown that three most intensive peaks, at 2.7, 3.1, and 3.7 eV, result from transitions between Mo(d ) and S(p ) valence and conduction bands and that the character of their charge/current density fluctuations is intrinsically in plane, located in the molybdenum plane. This also implies that MoS2 monolayer is completely transparent when illuminated by grazing incidence p -polarized light. The validity of the presented results is supported by our effective two-band tight-binding model and finally by good agreement with some recent experimental results.

  9. Studies of cavity enhanced absorption spectroscopy for weak absorption gas measurements

    NASA Astrophysics Data System (ADS)

    Li, Liucheng; Duo, Liping; Gong, Deyu; Ma, Yanhua; Zhang, Zhiguo; Wang, Yuanhu; Zhou, Dongjian; Jin, Yuqi

    2017-01-01

    In order to determine the concentrations of trace amount metastable species in chemical lasers, an off-axis cavity enhanced absorption spectrometer for the detection of weak absorption gases has been built with a noise equivalent absorption sensitivity of 1.6x10-8 cm-1. The absorption spectrum of trace amount gaseous ammonia and water vapor was obtained with a spectral resolution of about 78 MHz. A multiple-line absorption spectroscopic method to determine the temperature of gaseous ammonia has been developed by use of multiple lines of ammonia molecule absorption spectrum.

  10. Atomic absorption spectroscopy in ion channel screening.

    PubMed

    Stankovich, Larisa; Wicks, David; Despotovski, Sasko; Liang, Dong

    2004-10-01

    This article examines the utility of atomic absorption spectroscopy, in conjunction with cold flux assays, to ion channel screening. The multiplicity of ion channels that can be interrogated using cold flux assays and atomic absorption spectroscopy is summarized. The importance of atomic absorption spectroscopy as a screening tool is further elaborated upon by providing examples of the relevance of ion channels to various physiological processes and targeted diseases.

  11. Absorption Coefficient of Alkaline Earth Halides.

    DTIC Science & Technology

    1980-04-01

    levels . As a natural consequence, the magnitude of the absorption coefficient is the key parameter in selecting laser window materials. Over the past...of as can be achieved through improved crystal growing techniques and surface polishing. 2.5. Urbach’s Rule A central question for the development of...high absorption levels , inaccuracies progressively increasing with decreasing absorption level , a natural consequence of decreasing in instrumental

  12. Theory of Two-Photon Absorptions in Graphene Fragments

    NASA Astrophysics Data System (ADS)

    Aryanpour, K.; Shukla, A.; Mazumdar, S.; Sandhu, A.; Roberts, A.

    2012-02-01

    Electron-electron correlations in graphene is currently an active field of research [1-3]. The carbon atoms in graphene have the same sp^2 hybridization as in strongly correlated π-conjugated polymer systems. The low energy behavior in graphene however appears to be reasonably described within the one-electron Dirac massless fermions model. Historically, the occurrence of the lowest two-photon state below the optical one-photon state provided the strongest proof for strong electron correlations in linear polyenes [4]. We systematically study the Coulomb interaction effects on the ground state and nonlinear absorptions in graphene fragments as a function of system size, beginning from the smallest stable fragment coronene. We report high order calculations of one- vs two-photon spin singlet and triplet states, in coronene, hexabenzocoronene and other molecular fragments that clearly indicate the strong role of electron-electron interactions. We will discuss the implications of our work on molecular systems for the thermodynamic limit of graphene. [4pt] [1] Siegel David A.; et al., PNAS, v108, 28, 11365-11369 (2011)[0pt] [2] Gr"onqvist J. H.; et al., arXiv: 1107.5653v1[0pt] [3] Uchoa B.; et al., arXiv: 1109.1577v1[0pt] [4] Ramasesha S.; et al., J. Chem. Phys. 80, 3278 (1984)

  13. ALS2 mutations

    PubMed Central

    Schneider, Susanne A.; Carr, Lucinda; Deuschl, Guenther; Hopfner, Franziska; Stamelou, Maria; Wood, Nicholas W.; Bhatia, Kailash P.

    2014-01-01

    Objective: To determine the genetic etiology in 2 consanguineous families who presented a novel phenotype of autosomal recessive juvenile amyotrophic lateral sclerosis associated with generalized dystonia. Methods: A combination of homozygosity mapping and whole-exome sequencing in the first family and Sanger sequencing of candidate genes in the second family were used. Results: Both families were found to have homozygous loss-of-function mutations in the amyotrophic lateral sclerosis 2 (juvenile) (ALS2) gene. Conclusions: We report generalized dystonia and cerebellar signs in association with ALS2-related disease. We suggest that the ALS2 gene should be screened for mutations in patients who present with a similar phenotype. PMID:24562058

  14. Sulphur trioxide absorption apparatus and process

    SciTech Connect

    Cameron, G.M.

    1987-03-31

    This patent describes a contact process for producing a concentrated sulphuric acid from dry sulphur dioxide and oxygen containing mixtures which employs the absorption of sulphur trioxide from a hot, dry gas stream containing sulphur trioxide into at least one sulphuric acid stream. The improvement described here comprises: (a) feeding the gas stream to a lower packed absorption zone contained within an absorption tower; (b) feeding a first sulphuric acid stream to the lower absorption zone to effect absorption of a major portion of the sulphur trioxide from the gas stream into the first sulphuric acid stream to produce a first enriched sulphuric acid stream and a depleted sulphur trioxide gas stream; (c) feeding the depleted sulphur trioxide gas stream to an upper packed absorption zone above the lower absorption zone within the tower; and (d) feeding a second sulphuric acid stream to the upper absorption zone to effect absorption of substantially all of the sulphur trioxide remaining in the depleted sulphur trioxide gas stream to produce a second enriched sulphuric acid stream and a substantially sulphur trioxide-free gas stream.

  15. Study of Evanescence Wave Absorption in Lindane

    NASA Astrophysics Data System (ADS)

    Marzuki, A.; Prasetyo, E.; Gitrin, M. P.; Suryanti, V.

    2017-02-01

    Evanescent wave field has been studied for the purpose of tailoring fiber sensor capable of detecting lindane concentration in a solution. The mounted fiber was optically polished such that part of the fiber clad is stripped off. To study the evanescent wave field absorption in lindane solution, the unclad fiber was immersed in the solution. Light coming out of the fiber was studied at different wavelength each for different lindane concentration. It was shown that evanescent wave field absorption is stronger at wavelength corresponding to lindane absorption band as has been shown from absorption studies lindane in UV-VIS-NIR spectrophotometer.

  16. Neural regulation of intestinal nutrient absorption.

    PubMed

    Mourad, Fadi H; Saadé, Nayef E

    2011-10-01

    The nervous system and the gastrointestinal (GI) tract share several common features including reciprocal interconnections and several neurotransmitters and peptides known as gut peptides, neuropeptides or hormones. The processes of digestion, secretion of digestive enzymes and then absorption are regulated by the neuro-endocrine system. Luminal glucose enhances its own absorption through a neuronal reflex that involves capsaicin sensitive primary afferent (CSPA) fibres. Absorbed glucose stimulates insulin release that activates hepatoenteric neural pathways leading to an increase in the expression of glucose transporters. Adrenergic innervation increases glucose absorption through α1 and β receptors and decreases absorption through activation of α2 receptors. The vagus nerve plays an important role in the regulation of diurnal variation in transporter expression and in anticipation to food intake. Vagal CSPAs exert tonic inhibitory effects on amino acid absorption. It also plays an important role in the mediation of the inhibitory effect of intestinal amino acids on their own absorption at the level of proximal or distal segment. However, chronic extrinsic denervation leads to a decrease in intestinal amino acid absorption. Conversely, adrenergic agonists as well as activation of CSPA fibres enhance peptides uptake through the peptide transporter PEPT1. Finally, intestinal innervation plays a minimal role in the absorption of fat digestion products. Intestinal absorption of nutrients is a basic vital mechanism that depends essentially on the function of intestinal mucosa. However, intrinsic and extrinsic neural mechanisms that rely on several redundant loops are involved in immediate and long-term control of the outcome of intestinal function.

  17. Terahertz wave absorption via preformed air plasma

    NASA Astrophysics Data System (ADS)

    Zhao, Ji; Zhang, LiangLiang; Wu, Tong; Zhang, CunLin; Zhao, YueJin

    2016-12-01

    Terahertz wave generation from laser-induced air plasma has continued to be an exciting field of research over the course of the past decade. In this paper, we report on an investigation concerning terahertz wave absorption with preformed plasma created by another laser pulse. We examine terahertz absorption behavior by varying the pump power and then analyze the polarization effect of the preplasma beam on terahertz wave absorption. The results of experiments conducted in which a type-I beta barium borate (BBO) crystal is placed before the preformed air plasma indicate that the fundamental (ω) and second harmonic (2ω) pulses can also influence terahertz absorption.

  18. Low cost and high performance Al nanoparticles for broadband light trapping in Si wafer solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Yinan; Ouyang, Zi; Stokes, Nicholas; Jia, Baohua; Shi, Zhengrong; Gu, Min

    2012-04-01

    In this paper low cost and earth abundant Al nanoparticles are simulated and compared with noble metal nanoparticles Ag and Au for plasmonic light trapping in Si wafer solar cells. It has been found tailored Al nanoparticles enable broadband light trapping leading to a 28.7% photon absorption enhancement in Si wafers, which is much larger than that induced by Ag or Au. Once combined with the SiNx anti-reflection coating, Al nanoparticles can produce a 42.5% enhancement, which is 4.3% higher than the standard SiNx due to the increased absorption in both the blue and near-infrared regions.

  19. Fractional Zinc Absorption for Men, Women, and Adolescents Is Overestimated in the Current Dietary Reference Intakes.

    PubMed

    Armah, Seth M

    2016-06-01

    The fractional zinc absorption values used in the current Dietary Reference Intakes (DRIs) for zinc were based on data from published studies. However, the inhibitory effect of phytate was underestimated because of the low phytate content of the diets in the studies used. The objective of this study was to estimate the fractional absorption of dietary zinc from the US diet by using 2 published algorithms. Nutrient intake data were obtained from the NHANES 2009-2010 and the corresponding Food Patterns Equivalents Database. Data were analyzed with the use of R software by taking into account the complex survey design. The International Zinc Nutrition Consultative Group (IZiNCG; Brown et al. Food Nutr Bull 2004;25:S99-203) and Miller et al. (Br J Nutr 2013;109:695-700) models were used to estimate zinc absorption. Geometric means (95% CIs) of zinc absorption for all subjects were 30.1% (29.9%, 30.2%) or 31.3% (30.9%, 31.6%) with the use of the IZiNCG model and Miller et al. model, respectively. For men, women, and adolescents, absorption values obtained in this study with the use of the 2 models were 27.2%, 31.4%, and 30.1%, respectively, for the IZiNCG model and 28.0%, 33.0%, and 31.6%, respectively, for the Miller et al. model, compared with the 41%, 48%, and 40%, respectively, used in the current DRIs. For preadolescents, estimated absorption values (31.1% and 32.8% for the IZiNCG model and Miller et al. model, respectively) compare well with the conservative estimate of 30% used in the DRIs. When the new estimates of zinc absorption were applied to the current DRI values for men and women, the results suggest that the Estimated Average Requirement (EAR) and RDA for these groups need to be increased by nearly one-half of the current values in order to meet their requirements for absorbed zinc. These data suggest that zinc absorption is overestimated for men, women, and adolescents in the current DRI. Upward adjustments of the DRI for these groups are recommended.

  20. Role of the ionization potential in nonequilibrium metals driven to absorption saturation.

    PubMed

    Mincigrucci, R; Bencivenga, F; Capotondi, F; Principi, E; Giangrisostomi, E; Battistoni, A; Caputo, M; Casolari, F; Gessini, A; Manfredda, M; Pedersoli, E; Masciovecchio, C

    2015-07-01

    A composite metallic foil (Al/Mg/Al) has been exposed to intense sub-100 fs free electron laser (FEL) pulses and driven to ultrafast massive photoionization. The resulting nonequilibrium state of matter has been monitored through absorption spectroscopy across the L(2,3) edge of Mg as a function of the FEL fluence. The raw spectroscopic data indicate that at about 100J/cm(2) the main absorption channels of the sample, i.e., Mg (2p→free) and oxidized Al (valence→free), are almost saturated. The spectral behavior of the induced transparency has been interpreted with an analytical approach based on an effective ionization potential of the generated solid-density plasma.

  1. Initial Symptoms of ALS

    MedlinePlus

    ... Combine your passion and commitment to finding a cure for ALS while achieving physical challenges through athletic events Register ... - 1275 K Street NW - Suite 250 - Washington, DC 20005 All content and works posted on this website are owned ...

  2. Genetic Testing for ALS

    MedlinePlus

    ... Some medical centers may require a neurological exam, psychological assessment and counseling before predictive testing. If a person in the family with ALS has a negative genetic test result (no identified genetic mutation), testing family members ...

  3. Lou Gehrig's Disease (ALS)

    MedlinePlus

    ... when it becomes necessary. For instance, a power wheelchair can enable a paralyzed person with ALS to ... done these things despite being confined to a wheelchair for many years, being able to move only ...

  4. Rub al Khali, Arabia

    NASA Image and Video Library

    2008-08-08

    NASA Terra spacecraft shows the Rub al Khali, one of the largest sand deserts in the world, encompassing most of the southern third of the Arabian Peninsula; it includes parts of Oman, United Arab Emirates, and Yemen.

  5. Ag-Al-Ca

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 1 http://dx.doi.org/10.1007/97.etType="URL"/> 'Systems from Ag-Al-Ca to Au-Pd-Si' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'Ag-Al-Ca' with the content:

  6. Time Variable Associated Absorption in the QSO UM 675

    NASA Astrophysics Data System (ADS)

    Hamann, F. W.; Barlow, T. A.; Beaver, E. A.; Burbidge, E. M.; Cohen, R. D.; Junkkarinen, V. T.; Lyons, R. W.

    1994-05-01

    We discuss dramatic changes in the z_a ~ z_e absorption system of the z_e = 2.15 QSO UM 675 (Q0150-203). The C IV lambda 1550 and N V lambda 1240 doublets at z_a = 2.1344 strengthened by a factor of ~ 3 between the observations of Sargent, Boksenberg and Steidel (1988, ApJS, 68, 539; measured November 1981) and our earliest measurements (November and December 1990). During this time, C IV in the z_a = 2.0083 system may also have strengthened. The variability of other lines in these systems is unknown. Continued monitoring is in progress. We consider several models of the z_a ~ z_e absorption environment, and conclude that the absorbing clouds are close to the QSO and photoionized by the QSO continuum. The variability timescale (<~2.9 yrs rest) requires gas densities gap 4000 cm(-3) to allow changes in the ionization balance. This minimum density, and the high ionization needed to produce the Ne VIII lambda 774 and O VI lambda 1035 absorptions reported previously (E. M. Burbidge et al., 1993, BAAS, 24, 1135), requires clouds <~200 pc from the QSO. The full range of absorption line ionizations (including C III lambda 977 and N III lambda 989) implies that the clouds are segregated, spanning a factor of gap 10 in distance or gap 100 in density. Across these regions the H I fraction varies from ~ 10(-3) to ~ 10(-6) . The total hydrogen column ranges from a few times 10(18) cm(-2) in the low ionization gas to ~ 10(20) cm(-2) where the Ne VIII lines form. The Lyman continuum is expected to be optically thin throughout, consistent with the measured absence of a Lyman edge. The metal abundances are roughly solar or above. Implications of these results are discussed. This work is supported by NASA grant NAG 5-1630.

  7. First-principles calculation of ground and excited-state absorption spectra of ruby and alexandrite considering lattice relaxation

    NASA Astrophysics Data System (ADS)

    Watanabe, Shinta; Sasaki, Tomomi; Taniguchi, Rie; Ishii, Takugo; Ogasawara, Kazuyoshi

    2009-02-01

    We performed first-principles calculations of multiplet structures and the corresponding ground-state absorption and excited-state absorption spectra for ruby (Cr3+:α-Al2O3) and alexandrite (Cr3+:BeAl2O4) which included lattice relaxation. The lattice relaxation was estimated using the first-principles total energy and molecular-dynamics method of the CASTEP code. The multiplet structure and absorption spectra were calculated using the configuration-interaction method based on density-functional calculations. For both ruby and alexandrite, the theoretical absorption spectra, which were already in reasonable agreement with experimental spectra, were further improved by consideration of lattice relaxation. In the case of ruby, the peak positions and peak intensities were improved through the use of models with relaxations of 11 or more atoms. For alexandrite, the polarization dependence of the U band was significantly improved, even by a model with a relaxation of only seven atoms.

  8. DDA Modeling for the Mid-IR Absorption of Irregularly Shaped Crystalline Forsterite Grains

    NASA Astrophysics Data System (ADS)

    Lindsay, Sean; Wooden, D. H.; Kelley, M. S.; Harker, D. E.; Woodward, C. E.; Murphy, J.

    2010-10-01

    An analysis of the Spitzer IRS spectra of the Deep Impact ejecta of comet 9P/Tempel 1 (Wooden et al. 2010, 42nd DPS Meeting) in conjunction with the dynamics of the ejecta grains (Kelley et al. 2010, 42nd DPS Meeting) strongly suggests that ecliptic comets have comae dominated by large (> 10 - 20 micron in radii) porous grains with Mg-rich crystal inclusions. In fact, Kelley et al. (2010) conclude that many ecliptic comets may be dominated by such grains with a high crystalline fraction, approximately 40% by mass, despite their generally weak silicate emission feature. To date, no model for the optical properties in the mid-IR of multi-mineralic large porous grains with silicate crystal inclusions, has been performed. We have initiated a program to compute the absorption and scattering efficiencies for these grains. Presented here are the 3 - 40 micron absorption efficiencies for models of sub-micron sized crystalline forsterite grains of irregular shape. We use the Discrete Dipole Approximation (DDA) to create discrete targets of forsterite that can be included in large porous aggregates. Computations are performed on the NAS Pleiades supercomputer. Our calculated absorption efficiencies for individual grains of forsterite are in agreement with laboratory measurements (Tamanai et al. 2006; Koike et al. 2003) and the continuous distribution of ellipsoids (CDE) method by Harker et al. (2007). We find for discrete grains that grain shape has a strong effect on the peak location of a crystalline resonance and that mimicking the physical properties of forsterite is important. Also presented are the absorption efficiencies for simple multi-component aggregates and for collections of forsterite crystals of different size and shape to replicate laboratory samples. This research is supported by the NASA GSRP Program.

  9. The absorption of polymeric composites

    NASA Astrophysics Data System (ADS)

    Řídký, R.; Popovič, M.; Rolc, S.; Drdlová, M.; Krátký, J.

    2016-06-01

    An absorption capacity of soft, viscoelastic materials at high strain rates is important for wide range of practical applications. Nowadays there are many variants of numerical models suitable for this kind of analysis. The main difficulty is in selection of the most realistic numerical model and a correct setup of many unknown material constants. Cooperation between theoretical simulations and real testing is next crucial point in the investigation process. Standard open source material database offer material properties valid for strain rates less than 250 s-1. There are experiments suitable for analysis of material properties with strain rates close to 2000 s-1. The high strain-rate characteristics of a specific porous blast energy absorbing material measured by modified Split Hopkinson Pressure Bar apparatus is presented in this study. Testing these low impedance materials using a metallic split Hopkinson pressure bar setup results in poor signal to noise ratios due to impedance mismatching. These difficulties are overcome by using polymeric Hopkinson bars. Conventional Hopkinson bar analysis cannot be used on the polymeric bars due to the viscoelastic nature of the bar material. One of the possible solution leads to complex and frequency depended Young modulus of testing bars material. This testing technique was applied to materials composed of porous glass/ceramic filler and polymeric binder, with density of 125 - 300 kg/m3 and particle size in range of 50 µm - 2 mm. The achieved material model was verified in practical application of sandwich structure includes polymeric composites under a blast test.

  10. Fluid absorption solar energy receiver

    NASA Technical Reports Server (NTRS)

    Bair, Edward J.

    1993-01-01

    A conventional solar dynamic system transmits solar energy to the flowing fluid of a thermodynamic cycle through structures which contain the gas and thermal energy storage material. Such a heat transfer mechanism dictates that the structure operate at a higher temperature than the fluid. This investigation reports on a fluid absorption receiver where only a part of the solar energy is transmitted to the structure. The other part is absorbed directly by the fluid. By proportioning these two heat transfer paths the energy to the structure can preheat the fluid, while the energy absorbed directly by the fluid raises the fluid to its final working temperature. The surface temperatures need not exceed the output temperature of the fluid. This makes the output temperature of the gas the maximum temperature in the system. The gas can have local maximum temperatures higher than the output working temperature. However local high temperatures are quickly equilibrated, and since the gas does not emit radiation, local high temperatures do not result in a radiative heat loss. Thermal radiation, thermal conductivity, and heat exchange with the gas all help equilibrate the surface temperature.

  11. Three-Dimensional FIB/EBSD Characterization of Irradiated HfAl3-Al Composite

    SciTech Connect

    Hua, Zilong; Guillen, Donna Post; Harris, William; Ban, Heng

    2016-09-01

    A thermal neutron absorbing material, comprised of 28.4 vol% HfAl3 in an Al matrix, was developed to serve as a conductively cooled thermal neutron filter to enable fast flux materials and fuels testing in a pressurized water reactor. In order to observe the microstructural change of the HfAl3-Al composite due to neutron irradiation, an EBSD-FIB characterization approach is developed and presented in this paper. Using the focused ion beam (FIB), the sample was fabricated to 25µm × 25µm × 20 µm and mounted on the grid. A series of operations were carried out repetitively on the sample top surface to prepare it for scanning electron microscopy (SEM). First, a ~100-nm layer was removed by high voltage FIB milling. Then, several cleaning passes were performed on the newly exposed surface using low voltage FIB milling to improve the SEM image quality. Last, the surface was scanned by Electron Backscattering Diffraction (EBSD) to obtain the two-dimensional image. After 50 to 100 two-dimensional images were collected, the images were stacked to reconstruct a three-dimensional model using DREAM.3D software. Two such reconstructed three-dimensional models were obtained from samples of the original and post-irradiation HfAl3-Al composite respectively, from which the most significant microstructural change caused by neutron irradiation apparently is the size reduction of both HfAl3 and Al grains. The possible reason is the thermal expansion and related thermal strain from the thermal neutron absorption. This technique can be applied to three-dimensional microstructure characterization of irradiated materials.

  12. Iron absorption from intrinsically-labeled lentils

    USDA-ARS?s Scientific Manuscript database

    Low iron (Fe) absorption from important staple foods may contribute to Fe deficiency in developing countries. To date, there are few studies examining the Fe bioavailability of pulse crops as commonly prepared and consumed by humans. The objectives of this study were to characterize the Fe absorpt...

  13. Energy Absorption Behaviors of Nanoporous Systems

    DTIC Science & Technology

    2005-01-01

    energy absorption isotherms : (a) the first loading-unloading cycle; (b) the second, the third, and the fourth loading-unloading cycles without thermal...change, AV (cm- /g) Fig.7 The energy absorption isotherms under a cyclic loading in a 23. lwt% aqueous solution of NaC1. 80

  14. Do Atoms Really "Emit" Absorption Lines?

    ERIC Educational Resources Information Center

    Brecher, Kenneth

    1991-01-01

    Presents three absorption line sources that enhance student understanding of the phenomena associated with the interaction of light with matter and help dispel the misconception that atoms "emit" absorption lines. Sources include neodymium, food coloring and other common household liquids, and fluorescent materials. (MDH)

  15. Fixed energy X-ray absorption voltammetry.

    PubMed

    Minguzzi, Alessandro; Lugaresi, Ottavio; Locatelli, Cristina; Rondinini, Sandra; D'Acapito, Francesco; Achilli, Elisabetta; Ghigna, Paolo

    2013-08-06

    In this paper, the fixed energy X-ray absorption voltammetry (FEXRAV) is introduced. FEXRAV represents a novel in situ X-ray absorption technique for fast and easy preliminary characterization of electrode materials and consists of recording the absorption coefficient at a fixed energy while varying at will the electrode potential. The energy is chosen close to an X-ray absorption edge, in order to give the maximum contrast between different oxidation states of an element. It follows that any shift from the original oxidation state determines a variation of the absorption coefficient. Although the information given by FEXRAV obviously does not supply the detailed information of X-ray absorption near edge structure (XANES) or extended X-ray absorption fine structure (EXAFS), it allows to quickly map the oxidation states of the element under consideration within the selected potential windows. This leads to the rapid screening of several systems under different experimental conditions (e.g., nature of the electrolyte, potential window) and is preliminary to more deep X-ray absorption spectroscopy (XAS) characterizations, like XANES or EXAFS. In addition, the time-length of the experiment is much shorter than a series of XAS spectra and opens the door to kinetic analysis.

  16. A Low-Cost Quantitative Absorption Spectrophotometer

    ERIC Educational Resources Information Center

    Albert, Daniel R.; Todt, Michael A.; Davis, H. Floyd

    2012-01-01

    In an effort to make absorption spectrophotometry available to high school chemistry and physics classes, we have designed an inexpensive visible light absorption spectrophotometer. The spectrophotometer was constructed using LEGO blocks, a light emitting diode, optical elements (including a lens), a slide-mounted diffraction grating, and a…

  17. Low absorptance porcelain-on-aluminum coating

    NASA Technical Reports Server (NTRS)

    Leggett, H.

    1979-01-01

    Porcelain thermal-control coating for aluminum sheet and foil has solar absorptance of 0.22. Specially formulated coating absorptance is highly stable, changing only 0.03 after 1,000 hours of exposure to simulated sunlight and can be applied by standard commercial methods.

  18. High-Absorptance Radiative Heat Sink

    NASA Technical Reports Server (NTRS)

    Cafferty, T.

    1983-01-01

    Absorptance of black-painted open-cell aluminum honeycomb improved by cutting honeycomb at angle or bias rather than straight across. This ensures honeycomb cavities escapes. At each reflection radiation attenuated by absorption. Applications include space-background simulators, space radiators, solar absorbers, and passive coolers for terrestrial use.

  19. Atmospheric Solar Heating in Minor Absorption Bands

    NASA Technical Reports Server (NTRS)

    Chou, Ming-Dah

    1998-01-01

    Solar radiation is the primary source of energy driving atmospheric and oceanic circulations. Concerned with the huge computing time required for computing radiative transfer in weather and climate models, solar heating in minor absorption bands has often been neglected. The individual contributions of these minor bands to the atmospheric heating is small, but collectively they are not negligible. The solar heating in minor bands includes the absorption due to water vapor in the photosynthetically active radiation (PAR) spectral region from 14284/cm to 25000/cm, the ozone absorption and Rayleigh scattering in the near infrared, as well as the O2 and CO2 absorption in a number of weak bands. Detailed high spectral- and angular-resolution calculations show that the total effect of these minor absorption is to enhance the atmospheric solar heating by approximately 10%. Depending upon the strength of the absorption and the overlapping among gaseous absorption, different approaches are applied to parameterize these minor absorption. The parameterizations are accurate and require little extra time for computing radiative fluxes. They have been efficiently implemented in the various atmospheric models at NASA/Goddard Space Flight Center, including cloud ensemble, mesoscale, and climate models.

  20. A Low-Cost Quantitative Absorption Spectrophotometer

    ERIC Educational Resources Information Center

    Albert, Daniel R.; Todt, Michael A.; Davis, H. Floyd

    2012-01-01

    In an effort to make absorption spectrophotometry available to high school chemistry and physics classes, we have designed an inexpensive visible light absorption spectrophotometer. The spectrophotometer was constructed using LEGO blocks, a light emitting diode, optical elements (including a lens), a slide-mounted diffraction grating, and a…

  1. 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.

  2. Absorption of sound by tree bark

    Treesearch

    G. Reethof; L. D. Frank; O. H. McDaniel

    1976-01-01

    Laboratory tests were conducted with a standing wave tube to measure the acoustic absorption of normally incident sound by the bark of six species of trees. Twelve bark samples, 10 cm in diameter, were tested. Sound of seven frequencies between 400 and 1600 Hz was used in the measurements. Absorption was generally about 5 percent; it exceeded 10 percent for only three...

  3. Low absorptance porcelain-on-aluminum coating

    NASA Technical Reports Server (NTRS)

    Leggett, H.

    1979-01-01

    Porcelain thermal-control coating for aluminum sheet and foil has solar absorptance of 0.22. Specially formulated coating absorptance is highly stable, changing only 0.03 after 1,000 hours of exposure to simulated sunlight and can be applied by standard commercial methods.

  4. Do Atoms Really "Emit" Absorption Lines?

    ERIC Educational Resources Information Center

    Brecher, Kenneth

    1991-01-01

    Presents three absorption line sources that enhance student understanding of the phenomena associated with the interaction of light with matter and help dispel the misconception that atoms "emit" absorption lines. Sources include neodymium, food coloring and other common household liquids, and fluorescent materials. (MDH)

  5. Frequently Asked Questions about ALS and the ALS Registry

    MedlinePlus

    ... long do people with familial ALS live? Do clusters of ALS possibly exist? (I have been told ... related?) What are the problems with studying possible clusters of ALS? What are motor neuron (nerve cell) ...

  6. The infrared spectrum of Al2H6 in solid hydrogen.

    PubMed

    Andrews, Lester; Wang, Xuefeng

    2003-03-28

    Although many volatile binary boron hydride compounds are known, binary aluminum hydride chemistry is limited to the polymeric (AlH3)(n) solid. The reaction of laser-ablated aluminum atoms and pure H2 during codeposition at 3.5 kelvin, followed by ultraviolet irradiation and annealing to 6.5 kelvin, allows dimerization of the intermediate AlH3 photolysis product to form Al2H6. The Al2H6 molecule is identified by seven new infrared absorptions that are accurately predicted by quantum chemical calculations for dibridged Al2H6, a molecule that is isostructural with diborane.

  7. Radiative Properties of Ceramic Al2O3, AlN and Si3N4—II: Modeling

    NASA Astrophysics Data System (ADS)

    Yang, Peiyan; Cheng, Qiang; Zhang, Zhuomin

    2017-08-01

    In Part I of this study (Cheng et al. in Int J Thermophys 37: 62, 2016), the reflectance and transmittance of dense ceramic plates were measured at wavelengths from 0.4 μm to about 20 μm. The samples of Al2O3 and AlN are semitransparent in the wavelength region from 0.4 μm to about 7 μm, where volume scattering dominates the absorption and scattering behaviors. On the other hand, the Si3N4 plate is opaque in the whole wavelength region. In the mid-infrared region, all samples show phonon vibration bands and surface reflection appears to be strong. The present study focuses on modeling the radiative properties and uses an inverse method to obtain the scattering and absorption coefficients of Al2O3 and AlN in the semitransparent region from the measured directional-hemispherical reflectance and transmittance. The scattering coefficient is also predicted using Mie theory for comparison. The Lorentz oscillator model is applied to fit the reflectance spectra of AlN and Si3N4 from 1.6 μm to 20 μm in order to obtain their optical constants. It is found that the phonon modes for Si3N4 are much stronger in the polycrystalline sample studied here than in amorphous films reported previously.

  8. Novel absorption detection techniques for capillary electrophoresis

    SciTech Connect

    Xue, Yongjun

    1994-07-27

    Capillary electrophoresis (CE) has emerged as one of the most versatile separation methods. However, efficient separation is not sufficient unless coupled to adequate detection. The narrow inner diameter (I.D.) of the capillary column raises a big challenge to detection methods. For UV-vis absorption detection, the concentration sensitivity is only at the μM level. Most commercial CE instruments are equipped with incoherent UV-vis lamps. Low-brightness, instability and inefficient coupling of the light source with the capillary limit the further improvement of UV-vis absorption detection in CE. The goals of this research have been to show the utility of laser-based absorption detection. The approaches involve: on-column double-beam laser absorption detection and its application to the detection of small ions and proteins, and absorption detection with the bubble-shaped flow cell.

  9. Near-infrared absorptions of monomethylhydrazine

    NASA Technical Reports Server (NTRS)

    Murray, Mark; Kurtz, Joe

    1993-01-01

    The peak absorption coefficients for two near-infrared absorptions of monomethylhydrazine, CH3-N2H3, (MMH) were measured. Absorption bands located at 1.524 micrometers (6560/cm), 1.557 micrometers (6423/cm), and 1.583 micrometers (6316/cm) are assigned to the Delta upsilon = 2 overtones of the infared N-H stretching fundamentals at 3317, 3245 and 3177/cm. An absorption band located at 1.04 micrometers (9620 +/- 100/cm) is assigned to the Delta upsilon = 3 overtone of one of these fundamentals. The peak absorption coefficients (alpha(sub 10)) at 1.524 micrometers (6560 +/- 20/cm) and 1.04 micrometers (9620 +/- 100/cm) are 31 x 10(exp -3) and 0.97 x 10(exp -3)/(cm atm), respectively. Uncertainties in these coefficients were estimated to be less than +/- 20% due primarily to uncertainties in the partial vapor pressure of MMH.

  10. Absorption imaging of a single atom

    NASA Astrophysics Data System (ADS)

    Streed, Erik W.; Jechow, Andreas; Norton, Benjamin G.; Kielpinski, David

    2012-07-01

    Absorption imaging has played a key role in the advancement of science from van Leeuwenhoek's discovery of red blood cells to modern observations of dust clouds in stellar nebulas and Bose-Einstein condensates. Here we show the first absorption imaging of a single atom isolated in a vacuum. The optical properties of atoms are thoroughly understood, so a single atom is an ideal system for testing the limits of absorption imaging. A single atomic ion was confined in an RF Paul trap and the absorption imaged at near wavelength resolution with a phase Fresnel lens. The observed image contrast of 3.1 (3)% is the maximum theoretically allowed for the imaging resolution of our set-up. The absorption of photons by single atoms is of immediate interest for quantum information processing. Our results also point out new opportunities in imaging of light-sensitive samples both in the optical and X-ray regimes.

  11. [Effect of altitude on iron absorption].

    PubMed

    Pizarro, F; Zavaleta, N; Hertrampf, E; Berlanga, R; Camborda, L; Olivares, M

    1998-03-01

    Iron bioavailability was evaluated in people living in high altitudes. Absorption was estimated from a reference dose of ferrous ascorbate and from a standard diet of wheat flour, using extrinsic tag radioisotope technique of 55Fe and 59Fe. Twenty four volunteers, healthy women, with ages ranging from 28 to 45 years, participated. Of those, eleven lived at 3450 meters above sea level (m.a.s.l.) in Huancayo city-Peru (study group), and 13 lived in Santiago de Chile at 630 m.a.s.l. (control group). Iron absorption from reference dose of ferrous ascorbate was 32.0% and 31.1% in the study and control groups respectively. The geometric mean of iron absorption from the standard diet, corrected to 40% of absorption of reference dose, was 9.0% and 6.9% in the study and control groups respectively (NS). The results suggest that altitude does not produce a high iron absorption in highlander residents.

  12. Absorption imaging of a single atom.

    PubMed

    Streed, Erik W; Jechow, Andreas; Norton, Benjamin G; Kielpinski, David

    2012-07-03

    Absorption imaging has played a key role in the advancement of science from van Leeuwenhoek's discovery of red blood cells to modern observations of dust clouds in stellar nebulas and Bose-Einstein condensates. Here we show the first absorption imaging of a single atom isolated in a vacuum. The optical properties of atoms are thoroughly understood, so a single atom is an ideal system for testing the limits of absorption imaging. A single atomic ion was confined in an RF Paul trap and the absorption imaged at near wavelength resolution with a phase Fresnel lens. The observed image contrast of 3.1 (3)% is the maximum theoretically allowed for the imaging resolution of our set-up. The absorption of photons by single atoms is of immediate interest for quantum information processing. Our results also point out new opportunities in imaging of light-sensitive samples both in the optical and X-ray regimes.

  13. Creating semiconductor metafilms with designer absorption spectra

    PubMed Central

    Kim, Soo Jin; Fan, Pengyu; Kang, Ju-Hyung; Brongersma, Mark L.

    2015-01-01

    The optical properties of semiconductors are typically considered intrinsic and fixed. Here we leverage the rapid developments in the field of optical metamaterials to create ultrathin semiconductor metafilms with designer absorption spectra. We show how such metafilms can be constructed by placing one or more types of high-index semiconductor antennas into a dense array with subwavelength spacings. It is argued that the large absorption cross-section of semiconductor antennas and their weak near-field coupling open a unique opportunity to create strongly absorbing metafilms whose spectral absorption properties directly reflect those of the individual antennas. Using experiments and simulations, we demonstrate that near-unity absorption at one or more target wavelengths of interest can be achieved in a sub-50-nm-thick metafilm using judiciously sized and spaced Ge nanobeams. The ability to create semiconductor metafilms with custom absorption spectra opens up new design strategies for planar optoelectronic devices and solar cells. PMID:26184335

  14. Polarization in a mineral absorption band

    NASA Technical Reports Server (NTRS)

    Pieters, C. E.

    1974-01-01

    A theoretical and experimental study was undertaken to examine the polarimetric properties of light reflected from a particulate surface in the spectral region (0.7 to 1.1 micrometer) of a mineral electronic-transition absorption band. The purpose of the investigation was to show that spectral polarimetry is an alternative diagnostic tool to absolute reflectivity measurements for some applications, notably the determination of absorption-band positions for the lunar surface. The major results are: (1) polarization increases significantly in an absorption band at large phase angles; (2) the wavelength of the maximum of the polarization variation corresponds directly with the center of the absorption band; (3) the amount of increase of polarization for minerals with an absorption band is dependent on particle size; and (4) the fractional change of polarization with wavelength is greater for mixtures with transparent minerals than with absorbing minerals. The magnitude of change, however, is greater for mixtures with absorbing minerals.

  15. The UV/Vis absorption spectrum of matrix-isolated dichlorine peroxide, ClOOCl.

    PubMed

    von Hobe, Marc; Stroh, Fred; Beckers, Helmut; Benter, Thorsten; Willner, Helge

    2009-03-14

    UV/Vis absorption spectra of ClOOCl isolated in neon matrices were measured in the wavelength range 220-400 nm. The purity of the trapped samples was checked by infrared and UV/Vis matrix spectroscopy as well as low-temperature Raman spectroscopy. At wavelengths below 290 nm, the results agree with the UV spectrum recently published by Pope et al. [J. Phys. Chem. A, 2007, 111, 4322-4332]. However, the observed absorption in the long wavelength tail of the spectrum-relevant for polar stratospheric ozone loss-is substantially higher than reported by Pope et al. Our results suggest the existence of a ClOOCl electronic state manifold leading to an absorption band similar to those of the near UV spectrum of Cl(2). The differences to previous studies can be accounted for quantitatively by contributions to the reported absorption spectra caused by impurities. The observed band in the long wavelength tail is supported by several high-level ab initio calculations. However, questions arise concerning absolute values of the ClOOCl cross sections, an issue that needs to be revisited in future studies. With calculated photolysis rates based on our spectrum scaled to previous cross sections at the peak absorption, the known polar catalytic ozone-destruction cycles to a large extent account for the observed ozone depletion in the spring polar stratosphere.

  16. Low-reflective wire-grid polarizers with absorptive interference overlayers.

    PubMed

    Suzuki, Motofumi; Takada, Akio; Yamada, Takatoshi; Hayasaka, Takashi; Sasaki, Kouji; Takahashi, Eiji; Kumagai, Seiji

    2010-04-30

    Wire-grid (WG) polarizers with low reflectivity for visible light have been successfully developed. We theoretically consider the optical properties of simple sandwich structures of absorptive layer/transparent layer (gap layer)/high-reflective mirrors and found that it is possible to develop an antireflection (AR) coating owing to the interference along with the absorption in the absorptive layer. A wide variety of materials can be used for AR coatings by tuning the thicknesses of both the absorptive and the gap layers. This AR concept has been applied to reduce the reflectance of WG polarizers of Al. FeSi(2) as an absorptive layer has been deposited by the glancing angle deposition technique immediately on the top of Al wires covered with a thin SiO(2) layer as a gap layer. For the optimum combination of the thicknesses of FeSi(2) and SiO(2), the reflectance becomes lower than a few per cent, independent of the polarization, whereas the transmission polarization properties remain good. Because low-reflective (LR) WG polarizers are completely composed of inorganic materials, they are useful for applications requiring high-temperature durability such as liquid crystal projection displays.

  17. Multiple Velocity Components in the CIV Absorption Line of NGC5548

    NASA Astrophysics Data System (ADS)

    Mathur, S.; Elvis, M.; Wilkes, B. J.

    1998-12-01

    The bright, variable, Seyfert 1 galaxy NGC 5548 has been extensively studied at many wavelengths. It has been a target of reverberation mapping experiments in the optical and UV (Peterson et al. 1992, Clavel et al. 1991, Korista et al. 1995). These have led to the accurate determination of the physical size of the BELR. The UV spectrum also shows absorption lines (Shull & Sachs 1993, Mathur, Elvis & Wilkes 1995 (MEW95)). Recently, based on ASCA and HST FOS data, MEW95 showed that the ionizaed X-ray and UV absorption in NGC5548 is likely to originate in the same material. We have now obtained high resolution GHRS spectrum around the CIV line. We find that the absorption line splits into multiple velocity components. The X-ray absorber would be associated with one of these components. We also have a tentative evidence for inflow based on the redshifted absorption component. This is in accord with the radial infall in NGC 5548 found by Done & Krolik (1996) based on the kinematic model of the BELR.

  18. Time-dependent oral absorption models

    NASA Technical Reports Server (NTRS)

    Higaki, K.; Yamashita, S.; Amidon, G. L.

    2001-01-01

    The plasma concentration-time profiles following oral administration of drugs are often irregular and cannot be interpreted easily with conventional models based on first- or zero-order absorption kinetics and lag time. Six new models were developed using a time-dependent absorption rate coefficient, ka(t), wherein the time dependency was varied to account for the dynamic processes such as changes in fluid absorption or secretion, in absorption surface area, and in motility with time, in the gastrointestinal tract. In the present study, the plasma concentration profiles of propranolol obtained in human subjects following oral dosing were analyzed using the newly derived models based on mass balance and compared with the conventional models. Nonlinear regression analysis indicated that the conventional compartment model including lag time (CLAG model) could not predict the rapid initial increase in plasma concentration after dosing and the predicted Cmax values were much lower than that observed. On the other hand, all models with the time-dependent absorption rate coefficient, ka(t), were superior to the CLAG model in predicting plasma concentration profiles. Based on Akaike's Information Criterion (AIC), the fluid absorption model without lag time (FA model) exhibited the best overall fit to the data. The two-phase model including lag time, TPLAG model was also found to be a good model judging from the values of sum of squares. This model also described the irregular profiles of plasma concentration with time and frequently predicted Cmax values satisfactorily. A comparison of the absorption rate profiles also suggested that the TPLAG model is better at prediction of irregular absorption kinetics than the FA model. In conclusion, the incorporation of a time-dependent absorption rate coefficient ka(t) allows the prediction of nonlinear absorption characteristics in a more reliable manner.

  19. Light Absorption and Utilization by Phytoplankton.

    NASA Astrophysics Data System (ADS)

    Nelson, Norman Bradford

    1994-01-01

    The impact of biological and optical factors on light absorption by phytoplankton ceIls was assessed for cultures of dinoflagellates and for natural communities in the Southern California Bight. Pigment-specific light absorption in cultures of dinoflagellates was an inverse function of cellular pigment concentration, which varied 3-fold with photoadaptation. In the low-biomass (< 1 mg m^{-3} chlorophyll a), summertime conditions in the Southern California Bight, the phytoplankton communities were usually dominated by small (<5 μm) cells, so absorption was primarily a function of the water column pigment concentrations. Algorithms for estimating phytoplankton light absorption based on pigmentation and cell size parameters provided accurate estimates of photosynthetic light absorption despite the presence of the 'package effect,' which is a reduction in specific absorption of phytoplankton due to incorporating pigments into discrete cells. The package effect was found by theoretical calculations to increase depth-integrated primary productivity rates for large phytoplankton cells in dense phytoplankton blooms. No similar increases were found for similar cells in low-biomass (< 1 mg m^{-3} chlorophyll a), oceanic conditions. A close relationship was found between photosynthetic light absorption, chlorophyll a fluorescence excitation spectra, and photosynthetic carbon fixation action spectra of samples collected in the Southern California Bight. Photosynthetically active light absorption was found by this relationship to be on average 52% of total light absorption by phytoplankton in surface waters, and 85% at the subsurface chlorophyll a maximum depth. To support these investigations, I developed a new technique for accurately measuring phytoplankton light absorption by using an integrating sphere.

  20. Time-dependent oral absorption models

    NASA Technical Reports Server (NTRS)

    Higaki, K.; Yamashita, S.; Amidon, G. L.

    2001-01-01

    The plasma concentration-time profiles following oral administration of drugs are often irregular and cannot be interpreted easily with conventional models based on first- or zero-order absorption kinetics and lag time. Six new models were developed using a time-dependent absorption rate coefficient, ka(t), wherein the time dependency was varied to account for the dynamic processes such as changes in fluid absorption or secretion, in absorption surface area, and in motility with time, in the gastrointestinal tract. In the present study, the plasma concentration profiles of propranolol obtained in human subjects following oral dosing were analyzed using the newly derived models based on mass balance and compared with the conventional models. Nonlinear regression analysis indicated that the conventional compartment model including lag time (CLAG model) could not predict the rapid initial increase in plasma concentration after dosing and the predicted Cmax values were much lower than that observed. On the other hand, all models with the time-dependent absorption rate coefficient, ka(t), were superior to the CLAG model in predicting plasma concentration profiles. Based on Akaike's Information Criterion (AIC), the fluid absorption model without lag time (FA model) exhibited the best overall fit to the data. The two-phase model including lag time, TPLAG model was also found to be a good model judging from the values of sum of squares. This model also described the irregular profiles of plasma concentration with time and frequently predicted Cmax values satisfactorily. A comparison of the absorption rate profiles also suggested that the TPLAG model is better at prediction of irregular absorption kinetics than the FA model. In conclusion, the incorporation of a time-dependent absorption rate coefficient ka(t) allows the prediction of nonlinear absorption characteristics in a more reliable manner.

  1. Two-photon absorption cross section of excited phthalocyanines by a femtosecond Ti-sapphire laser.

    PubMed

    Mir, Youssef; van Lier, Johan E; Allard, Jean-François; Morris, Denis; Houde, Daniel

    2009-03-01

    In the past few years, photodynamic therapy (PDT) has become a major treatment for neovascular age-related macular degeneration (AMD) in which there is abnormal growth of choroidal neovasculature (CNV) that eventually obscures central vision, leading to blindness. However, one of the main limitations of current PDT is the relatively low specificity of the photosensitizer (PS) and light for pathological tissue which may induce damage to adjacent healthy tissue. An alternative approach to circumvent the specificity limitation is to improve the irradiation process. In particular two photon (2-gamma) excitation promises a more precise illumination of the target tissue. PS are activated by the simultaneous absorption of 2-gamma delivered by ultra-fast pulses of near infrared light. In order to evaluate the efficiency of phthalocyanine (Pc) dyes for 2-gamma absorption we measured 2-gamma absorption cross sections (sigma(2)) of a number of metalated Pc (MPc) dyes at lambda(ex) = 800 nm using a femtosecond laser. The studied Pc molecules vary by the type of the central metal ion (Al or Zn) and the number of peripheral sulfo substituents (MPcS). Each MPc dye of our series shows an improved 2-gamma absorption sigma(2) as compared to that obtained for Photofrin (3.1 +/- 0.1 GM, with 1 GM = 10(-50) cm(4) s photon(-1) mol(-1)), the PS currently approved for 1-gamma PDT. Our data show an 2.5-fold enhancement for AlPcCl, AlPcS(2adj) and ZnPcS(3)C(9), up to 10-fold (28.6 +/- 0.72 GM) for the ZnPcS(4) dye relative to Photofrin. These findings confirm the efficiency of Pc for 2-gamma absorption processes and represent the first detailed comparison study of 2-gamma absorption sigma(2) between Photofrin and Pc dyes.

  2. Band edge modulation and interband optical transition in AlN:Mg_{{\\rm{Al}}}-O_{{\\rm{N}}} nanotubes

    NASA Astrophysics Data System (ADS)

    Huang, Pu; Shi, Jun-jie; Zhang, Min; Jiang, Xin-he; Zhong, Hong-xia; Ding, Yi-min; Lu, Jing; Wang, Xihua

    2014-04-01

    AlN nanotubes (NTs) have many novel characteristics and great potential applications in electronic and optoelectronic nanodevices. However, little is known about the influence of Mg_{{\\rm{Al}}}-O_{{\\rm{N}}} co-doping effects on their optical properties. Here, we focus on investigating the electronic structures, clarify the interband optical transition mechanism and give a clear atomic picture for the important electron/hole localization centre in AlN:Mg_{{\\rm{Al}}}-O_{{\\rm{N}}} NTs using the GGA-1/2 method. We find that the Mg_{{\\rm{Al}}} doping efficiency can be improved effectively due to O_{{\\rm{N}}} doping in AlN NTs. The Mg_{{\\rm{Al}}} and O_{{\\rm{N}}} form Mg_{{\\rm{Al}}}-O_{{\\rm{N}}} defect complex easily along the AlN NT axis (C-axis). The Mg_{{\\rm{Al}}}-O_{{\\rm{N}}} defect complex can result in a remarkable charge transfer around it and modify the valence band maximum and conduction band minimum significantly. Meanwhile, the Mg_{{\\rm{Al}}}-O_{{\\rm{N}}} defect complex also forms the important exciton localization centre and effectively enhances the interband radiative recombination rate. Moreover, the light emission/absorption sensitively depends on its polarization. The parallel polarized light ({\\mathbf{E}}\\shortparallel {\\rm{C}}) is much stronger than the perpendicular one ({\\mathbf{E}}\\bot {\\rm{C}}). The Mg_{{\\rm{Al}}}-O_{{\\rm{N}}} co-doping thus paves a new way for improving the performance of electronic and optoelectronic nanodevices based on AlN NTs.

  3. Epidemiology of ALS.

    PubMed

    Nelson, L M

    Amyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disorder of unknown etiology. ALS onset is rare before age 40 and increases with age thereafter. Men are at higher risk than women (ratio 1.3:1). Other than age and gender, the only indisputable risk factor for ALS is genetic susceptibility, with familial cases occurring in about 10% of most case series. Genetic linkage studies have provided evidence that a mutant form of the gene that codes for Cu/Zn superoxide dismutase, an endogenous free radical scavenger, is important in 15-20% of familial cases. Epidemiologic studies have identified associations of sporadic ALS with work in occupations that involve toxicant exposure. Environmental toxicants may act against a background of increased genetic susceptibility; however, genetically acquired biochemical defects have not been identified in sporadic ALS patients. Other epidemiologic theories of disease etiology have emphasized the potential role of physical trauma, electrical shock, and vigorous physical exertion, but evidence regarding these factors is inconsistent.

  4. Monitoring Telluric Absorption with CAMAL

    NASA Astrophysics Data System (ADS)

    Baker, Ashley D.; Blake, Cullen H.; Sliski, David H.

    2017-08-01

    Ground-based astronomical observations may be limited by telluric water vapor absorption, which is highly variable in time and significantly complicates both spectroscopy and photometry in the near-infrared (NIR). To achieve the sensitivity required to detect Earth-sized exoplanets in the NIR, simultaneous monitoring of precipitable water vapor (PWV) becomes necessary to mitigate the impact of variable telluric lines on radial velocity measurements and transit light curves. To address this issue, we present the Camera for the Automatic Monitoring of Atmospheric Lines (CAMAL), a stand-alone, inexpensive six-inch aperture telescope dedicated to measuring PWV at the Fred Lawrence Whipple Observatory on Mount Hopkins. CAMAL utilizes three narrowband NIR filters to trace the amount of atmospheric water vapor affecting simultaneous observations with the MINiature Exoplanet Radial Velocity Array (MINERVA) and MINERVA-Red telescopes. Here, we present the current design of CAMAL, discuss our data analysis methods, and show results from 11 nights of PWV measurements taken with CAMAL. For seven nights of data we have independent PWV measurements extracted from high-resolution stellar spectra taken with the Tillinghast Reflector Echelle Spectrometer (TRES) also located on Mount Hopkins. We use the TRES spectra to calibrate the CAMAL absolute PWV scale. Comparisons between CAMAL and TRES PWV estimates show excellent agreement, matching to within 1 mm over a 10 mm range in PWV. Analysis of CAMAL’s photometric precision propagates to PWV measurements precise to better than 0.5 mm in dry (PWV < 4 mm) conditions. We also find that CAMAL-derived PWVs are highly correlated with those from a GPS-based water vapor monitor located approximately 90 km away at Kitt Peak National Observatory, with a root mean square PWV difference of 0.8 mm.

  5. Metal-organic frameworks as potential shock absorbers: the case of the highly flexible MIL-53(Al).

    PubMed

    Yot, Pascal G; Boudene, Zoubeyr; Macia, Jasmine; Granier, Dominique; Vanduyfhuys, Louis; Verstraelen, Toon; Van Speybroeck, Veronique; Devic, Thomas; Serre, Christian; Férey, Gérard; Stock, Norbert; Maurin, Guillaume

    2014-08-28

    The mechanical energy absorption ability of the highly flexible MIL-53(Al) MOF material was explored using a combination of experiments and molecular simulations. A pressure-induced transition between the large pore and the closed pore forms of this solid was revealed to be irreversible and associated with a relatively large energy absorption capacity. Both features make MIL-53(Al) the first potential MOF candidate for further use as a shock absorber.

  6. Poster 7: Could PAH or HAC explain the Titan's stratosphere absorption around 3.4 µm revealed by solar occultations?

    NASA Astrophysics Data System (ADS)

    Cordier, Daniel; Cours, Thibaud; Rey, Michael; Maltagliati, Luca; Seignovert, Benoit; Biennier, Ludovic

    2016-06-01

    In 2006, during Cassini's 10th flyby of Titan (T10), Bellucci et al. (2009) observed a solar occultation by Titan's atmosphere through the solar port of the Cassini/VIMS instrument. These authors noticed the existence of an unexplained additional absorption superimposed to the CH4 3.3 µm band. Because they were unable to model this absorption with gases, they attributed this intriguing feature to the signature of solid state organic components. Kim et al. (2011) revisited the data collected by Bellucci et al. (2009) and they considered the possible contribution of aerosols formed by hydrocarbon ices. They specifically took into account C2H6, CH4, CH3CN, C5H12 and C6H12 ices. More recently, Maltagliati et al. (2015) analyzed a set of four VIMS solar occultations, corresponding to flybys performed between January 2006 and September 2011 at different latitudes. They confirmed the presence of the 3.3 µm absorption in all occultations and underlined the possible importance of gaseous ethane, which has a strong plateau of absorption lines in that wavelength range.In this work, we show that neither hydrocarbon ices nor molecular C2H6 cannot satisfactorily explain the observed absorption. Our simulations speak in favor of an absorption due to the presence of PAH molecules or HAC in the stratosphere of Titan. PAH have been already considered by Lopes-Puertas et al. (2013) at altitudes larger than ˜900 km and tentatively identified in the stratosphere by Maltagliati et al. (2015); PAH and HAC are good candidates for Titan's aerosols precursors.

  7. Statins: Do They Cause ALS?

    MedlinePlus

    Statins: Do they cause ALS? Do statins cause amyotrophic lateral sclerosis (ALS)? Answers from Francisco Lopez-Jimenez, M.D. ... D. References Sorensen HT, et al. Statins and amyotrophic lateral sclerosis: The level of evidence for an association. Journal ...

  8. Photoelectron spectroscopy of the aluminum hydride anions: AlH2-, AlH3-, Al2H6-, Al3H9-, and Al4H12-

    NASA Astrophysics Data System (ADS)

    Zhang, Xinxing; Wang, Haopeng; Collins, Evan; Lim, Alane; Ganteför, Gerd; Kiran, Boggavarapu; Schnöckel, Hansgeorg; Eichhorn, Bryan; Bowen, Kit

    2013-03-01

    We report measurements of the negative ion photoelectron spectra of the simple aluminum hydride anions: AlH2-, AlH3-, Al2H6-, Al3H9-, and Al4H12-. From these spectra, we measured the vertical detachment energies of the anions, and we estimated the electron affinities of their neutral counterparts. Our results for AlH2-, AlH3-, and Al2H6- were also compared with previous predictions by theory.

  9. Photoelectron spectroscopy of the aluminum hydride anions: AlH2(-), AlH3(-), Al2H6(-), Al3H9(-), and Al4H12(-).

    PubMed

    Zhang, Xinxing; Wang, Haopeng; Collins, Evan; Lim, Alane; Ganteför, Gerd; Kiran, Boggavarapu; Schnöckel, Hansgeorg; Eichhorn, Bryan; Bowen, Kit

    2013-03-28

    We report measurements of the negative ion photoelectron spectra of the simple aluminum hydride anions: AlH2(-), AlH3(-), Al2H6(-), Al3H9(-), and Al4H12(-). From these spectra, we measured the vertical detachment energies of the anions, and we estimated the electron affinities of their neutral counterparts. Our results for AlH2(-), AlH3(-), and Al2H6(-) were also compared with previous predictions by theory.

  10. Numerical simulation of infrared radiation absorption for diagnostics of gas-aerosol medium by remote sensing data

    NASA Astrophysics Data System (ADS)

    Voitsekhovskaya, O. K.; Egorov, O. V.; Kashirskii, D. E.; Shefer, O. V.

    2015-11-01

    Calculated absorption spectra of the mixture of gases (H2O, CO, CO2, NO, NO2, and SO2) and aerosol (soot and Al2O3), contained in the exhausts of aircraft and rocket engines are demonstrated. Based on the model of gas-aerosol medium, a numerical study of the spectral dependence of the absorptance for different ratios of gas and aerosol components was carried out. The influence of microphysical and optical properties of the components of the mixture on the spectral features of absorption of gas-aerosol medium was established.

  11. Recent Observations of Intrinsic UV Absorption Lines in Seyfert Galaxies with STIS

    NASA Astrophysics Data System (ADS)

    Crenshaw, D. M.; Kraemer, S. B.; Ruiz, J. R.

    2000-05-01

    We present recent observations of the intrinsic UV absorption lines in several Seyfert 1 galaxies with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST). Echelle observations of NGC 4151 on 1999 June 19 indicate that the continuum and broad emission lines were at a low state at this time. Consequently, strong low-ionization absorption lines appear in the spectra, including numerous metastable Fe II lines. A feature in the blue wing of the C IV emission line, identified as a transient C IV absorption line at high outflow velocity by Weymann et al., turns out to be a fine-structure Si II line. Our current work focuses on determining the physical conditions in different kinematic components of the absorption using detailed photoionization models. Our STIS echelle observations of NGC 3783 on 2000 February 27 reveal that a new component of C IV and N V absorption has appeared since the last GHRS observation 5 years earlier, at a radial velocity of -800 km/sec relative to the systemic velocity. In addition, the component at -1400 km/sec has become much stronger and is present in Si IV, indicating a lower ionization state compared to the other components. We have also obtained low-resolution UV spectra of the Seyfert 1 galaxy NGC 3227, which is characterized by significant reddening of the continuum and emission lines. In addition to saturated absorption from high-ionization lines, we detect strong absorption in the Si IV and Mg II lines. This confirms our prediction that a lukewarm absorber that occults much of the narrow-line region is responsible for the reddening (Kraemer et al. 2000), rather than a large neutral column or a dusty X-ray absorber.

  12. On the NH3 absorption depression observable at Northern low latitudes of Jupiter

    NASA Astrophysics Data System (ADS)

    Tejfel, Victor G.; Vdovichenko, Vladimir D.; Lysenko, Peter G.; Karimov, Alibek M.; Kirienko, Galina A.; Bondarenko, Natalya N.; Kharitonova, Galina

    2016-10-01

    From February to April of 2016, we carried out a special series of spectrophotometric observations of Jupiter to study the current behavior of the ammonia absorption at the low latitudes of the Northern hemisphere, where in 2004 we have found a well-defined depression of the 787 nm NH3 absorption band intensity (V.Tejfel et al., Bull.AAS, 2005, Vol. 37, p.682). In subsequent years, an existence of this depression was annually confirmed by spectral observations, although we were noticing its variable character. During observations of 2016 we obtained more than 2,500 CCD-spectrograms, including the spectra of the central meridian, the GRS, and 12 scans of Jovian disk on different dates (70 zonal spectra in each scan). The 787 nm NH3 absorption band was extracted with using of ratios of the Jovian spectra to the Saturn's disk spectrum that was taken as a reference. The depression of absorption in this band begins almost from the equator, and its maximum occurs at the planetographic latitude of 100N then the absorption increases again approaching to the latitude of 200N. The equivalent bandwidths corresponding to these latitudes are equal to 18.7 ± 1.4 A, 14.4 ± 1.0 A and 17.8 ± 0.8A. The 645 nm NH3 absorption band also shows depletion at the low latitudes of the Northern hemisphere, but it is less pronounced. At the temperate latitudes of the Northern hemisphere this band's absorption is systematically lower than the Southern Hemisphere's ones. We will continue research in this direction, especially because recently a significant depletion of gaseous NH3 has also been found with using of the VLA with high resolution (I. de Pater et al., Science, 2016, Vol. 352, Issue 6290, p.1290-1294) at the low latitudes of the Northern hemisphere in the region of the NEB.

  13. Novel xenon calibration scheme for two-photon absorption laser induced fluorescence of hydrogen

    SciTech Connect

    Elliott, Drew; Scime, Earl; Short, Zachary

    2016-11-15

    Two photon absorption laser induced fluorescence (TALIF) measurements of neutral hydrogen and its isotopes are typically calibrated by performing TALIF measurements on krypton with the same diagnostic system and using the known ratio of the absorption cross sections [K. Niemi et al., J. Phys. D 34, 2330 (2001)]. Here we present the measurements of a new calibration method based on a ground state xenon scheme for which the fluorescent emission wavelength is nearly identical to that of hydrogen, thereby eliminating chromatic effects in the collection optics and simplifying detector calibration. We determine that the ratio of the TALIF cross sections of xenon and hydrogen is 0.024 ± 0.001.

  14. Novel xenon calibration scheme for two-photon absorption laser induced fluorescence of hydrogen

    NASA Astrophysics Data System (ADS)

    Elliott, Drew; Scime, Earl; Short, Zachary

    2016-11-01

    Two photon absorption laser induced fluorescence (TALIF) measurements of neutral hydrogen and its isotopes are typically calibrated by performing TALIF measurements on krypton with the same diagnostic system and using the known ratio of the absorption cross sections [K. Niemi et al., J. Phys. D 34, 2330 (2001)]. Here we present the measurements of a new calibration method based on a ground state xenon scheme for which the fluorescent emission wavelength is nearly identical to that of hydrogen, thereby eliminating chromatic effects in the collection optics and simplifying detector calibration. We determine that the ratio of the TALIF cross sections of xenon and hydrogen is 0.024 ± 0.001.

  15. VizieR Online Data Catalog: QSOs narrow absorption line variability (Hacker+, 2013)

    NASA Astrophysics Data System (ADS)

    Hacker, T. L.; Brunner, R. J.; Lundgren, B. F.; York, D. G.

    2013-06-01

    Catalogues of 2,522 QAL systems and 33 variable NAL systems detected in SDSS DR7 quasars with repeat observations. The object identifiers, position coordinates, and plate-MJD-fibre designations are taken from the SpecObjAll table in the SDSS Catalogue Archive Server (CAS) while the quasar redshifts (zqso) are from Hewett & Wild (2010, Cat. J/MNRAS/405/2302). The absorption system redshift (zabs), system grade, and detected lines are outputs of the York et al. (2013, in. prep.) QAL detection pipeline. Some absorption lines are flagged based on alternate identifications (a), proximity of masked pixels (b), or questionable continuum fits (c). (3 data files).

  16. A numerical study of a method for measuring the effective in situ sound absorption coefficient.

    PubMed

    Kuipers, Erwin R; Wijnant, Ysbrand H; de Boer, André

    2012-09-01

    The accuracy of a method [Wijnant et al., Proc. of ISMA 31, Leuven, Belgium (2010), Vol. 31] for measurement of the effective area-averaged in situ sound absorption coefficient is investigated. Based on a local plane wave assumption, this method can be applied to sound fields for which a model is not available. Investigations were carried out by means of finite element simulations for a typical case. The results show that the method is a promising method for determining the effective area-averaged in situ sound absorption coefficient in complex sound fields.

  17. Doublet structure of bands of low-frequency IR absorption spectra of some aromatic compounds

    NASA Astrophysics Data System (ADS)

    Demchuk, Yu. S.; Vandyukov, A. E.; Vandyukov, E. A.

    2000-12-01

    To increase the efficiency of identifying the complex aromatic compounds, the present paper gives the results of investigating the low-frequency region of the IR absorption and recorded doublet structure of absorption bands of the deformation(al) vibrations of naphtalene-, anthracene-, phenantrene-, pyrene- and coronene molecules in a fine- disperse state in matrices of KBr, polyethylene and in a vaseline oil. Parameters of changing the position of the centers of doublet components and the relationship of their intensities in changing the temperature are determined. Parameters of doublet components in dependence on the concentration of aromatic molecules in KBr tablets are investigated.

  18. Sub- and Superluminal Propagation of Intense Pulses in Media with Saturated and Reverse Absorption

    NASA Astrophysics Data System (ADS)

    Agarwal, G. S.; Dey, Tarak Nath

    2004-05-01

    We develop models for the propagation of intense pulses in solid state media which can have either saturated absorption or reverse absorption. We model subluminal propagation in ruby and superluminal propagation in alexandrite as three and four level systems, respectively, coupled to Maxwell's equations. We present results well beyond the traditional pump-probe approach and explain the experiments of Bigelow et al. [

    Phys. Rev. Lett.PRLTAO0031-9007 90, 113903 (2003); 10.1103/PhysRevLett.90.113903
    ScienceSCIEAS0036-8075 301, 200 (2003)
    ] on solid state materials.

  19. ALS superbend magnet system

    SciTech Connect

    Zbasnik, J.; Wang, S.T.; Chen, J.Y.; DeVries, G.J.; DeMarco, R.; Fahmie, M.; Geyer, A.; Green, M.A.; Harkins, J.; Henderson, T.; Hinkson, J.; Hoyer, E.H.; Krupnick, J.; Marks, S.; Ottens, F.; Paterson, J.A.; Pipersky, P.; Portmann, G.; Robin, D.A.; Schlueter, R.D.; Steier, C.; Taylor, C.E.; Wahrer, R.

    2000-09-15

    The Lawrence Berkeley National Laboratory is preparing to upgrade the Advanced Light Source (ALS) with three superconducting dipoles (Superbends). In this paper we present the final magnet system design which incorporates R&D test results and addresses the ALS operational concerns of alignment, availability, and economy. The design incorporates conduction-cooled Nb-Ti windings and HTS current leads, epoxy-glass suspension straps, and a Gifford-McMahon cryocooler to supply steady state refrigeration. We also present the current status of fabrication and testing.

  20. Lactose enhances mineral absorption in infancy.

    PubMed

    Ziegler, E E; Fomon, S J

    1983-05-01

    To determine if lactose promotes the intestinal absorption of calcium and other minerals by infants, metabolic balance studies were performed with infants fed two formulas nearly identical in composition except for carbohydrate. One contained only lactose and the other contained sucrose and corn starch hydrolysate. Each of six normal infants had two balance studies performed with each formula in alternating sequence. When lactose was the carbohydrate, net absorption and net retention of calcium were significantly greater than when lactose was not present in the formula. Absorptions of magnesium and manganese were also significantly enhanced by lactose. Absorptions of copper and zinc were somewhat greater (not statistically significant) when lactose was present, whereas absorption of iron was not affected. Absorption of phosphorus was not different, but urinary excretion was less when the lactose containing formula was fed and, hence, net retention of phosphorus was significantly enhanced. These results confirm findings from animal studies and previous human studies and show that, in infants, lactose has a significant and sustained promoting effect on absorption of calcium and other minerals.

  1. The effect of volatility on percutaneous absorption.

    PubMed

    Rouse, Nicole C; Maibach, Howard I

    2016-01-01

    Topically applied chemicals may volatilize, or evaporate, from skin leaving behind a chemical residue with new percutaneous absorptive capabilities. Understanding volatilization of topical medications, such as sunscreens, fragrances, insect repellants, cosmetics and other commonly applied topicals may have implications for their safety and efficacy. A systematic review of English language articles from 1979 to 2014 was performed using key search terms. Articles were evaluated to assess the relationship between volatility and percutaneous absorption. A total of 12 articles were selected and reviewed. Key findings were that absorption is enhanced when coupled with a volatile substance, occlusion prevents evaporation and increases absorption, high ventilation increases volatilization and reduces absorption, and pH of skin has an affect on a chemical's volatility. The articles also brought to light that different methods may have an affect on volatility: different body regions; in vivo vs. in vitro; human vs. Data suggest that volatility is crucial for determining safety and efficacy of cutaneous exposures and therapies. Few articles have been documented reporting evaporation in the context of percutaneous absorption, and of those published, great variability exists in methods. Further investigation of volatility is needed to properly evaluate its role in percutaneous absorption.

  2. Gastrointestinal absorption of Np in rats

    SciTech Connect

    Wirth, R.; Volf, V.

    1985-11-01

    The effect of Np mass and the acidity of the administered Np solutions as well as the age, sex and nutritional status of the animals injected or gavaged with 239Np or 237Np were determined. The latter factor proved to be dominant for absorption of Np from the gut. Thus in fasting weanling and young adult male rats, the absorption of 239Np was sixfold higher (0.18% and 0.12%, respectively) than in fed ones (0.03% and 0.02%, respectively). Absorption by fasted adult females was 0.05% of the administered 239Np, about half of that of adult males. Raising the Np-mass gavaged to fasted female rats to 1 and 10 mg 237Np/kg resulted in an absorption of 0.23% and 0.26%, respectively. Thus, an increased absorption of Np in adult rats seems to be expected only if a large mass is ingested. No dependence of the absorption of Np on nitric acid concentration was found. The data obtained after oral administration of 238Pu and 239Np to adult rats suggest that the f1 factor recommended by the ICRP for fractional absorption of soluble Np compounds from the gut should be decreased, whereas the f1 factor for soluble Pu compounds should be raised.

  3. Interstellar absorption lines in the spectrum of Gamma Velorum

    NASA Technical Reports Server (NTRS)

    Morton, D. C.; Bhavsar, S. P.

    1979-01-01

    Copernicus scans of selected interstellar absorption lines in the UV spectrum of Gamma Vel are analyzed, together with ground-based data, to obtain column densities for various ion states of C, N, O, Na, Mg, Al, Si, P, S, Cl, Ar, Ca, Mn, Fe, and CO. N I and O I are fitted to a single empirical curve of growth with a velocity parameter (b) of 8 km/s; Mg II, Si II, P II, S II, Mn II, and Fe II are fitted to another curve with b between 3 and 9 km/s. Abundance determinations relative to H I show that: (1) C, N, P, S, and Ar are probably close to their solar values; (2) O may be depleted by about a factor of 2; (3) Mg, Al, Si, Cl, Mn, and Fe are depleted by a factor of 4 or more: (4) Al is depleted by at least a factor of 10 in the H II region; and (5) both N V and O VI are present, but not C IV. The N V/O VI ratio implies that the electron temperature in the H II region is about 275,000 K.

  4. Effects of two cations on gastrointestinal absorption of ofloxacin.

    PubMed Central

    Martínez Cabarga, M; Sánchez Navarro, A; Colino Gandarillas, C I; Domínguez-Gil, A

    1991-01-01

    A study was performed to establish the effect of Al3+ and Fe2+ cations on the absorption of ofloxacin when it is administered orally at a dose of 200 mg. The study was carried out with nine volunteers, who each received three treatments (A [200 mg of ofloxacin], B [200 mg of ofloxacin plus 11 g of colloidal aluminum phosphate], and C [200 mg of ofloxacin plus 1,050 mg of FeSO4]) according to a Latin square design; the washout period was 1 week. The analytical technique was a microbiological diffusion method. The pharmacokinetic parameters were calculated from the cumulative urinary excretion data and from a sigma-minus plot. The total amount of ofloxacin excreted in urine had a mean value of 163.59 +/- 22.13 mg when ofloxacin was administered alone, 152.41 +/- 18.76 mg when it was administered with Al3+, and 146.49 +/- 14.85 mg when it was administered with Fe2+. No statistically significant differences were found in the F values (fractions of dose absorbed) obtained with ofloxacin alone and ofloxacin plus Al3+ (P = 0.341). When ofloxacin alone was compared with joint administration with Fe2+ the value of F decreased 10.85%; this difference is statistically significant (P = 2.623 x 10(-2)). PMID:1759833

  5. Intercalation of IR absorber into layered double hydroxides: Preparation, thermal stability and selective IR absorption

    SciTech Connect

    Zhu, Haifeng; Tang, Pinggui; Feng, Yongjun; Wang, Lijing; Li, Dianqing

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer PMIDA anions were intercalated into Mg{sub 2}Al-NO{sub 3} LDH by anion-exchange method. Black-Right-Pointing-Pointer The prepared material has highly selective IR absorption property in 9-11 {mu}m. Black-Right-Pointing-Pointer The obtained material has practical applications as heat-retaining additive. -- Abstract: N-phosphonomethyl aminodiacetic acid (PMIDA) was intercalated into the interlayer spacing of layered double hydroxides (LDH) by an anion-exchange method. The intercalated LDHs were characterized by various techniques such as powder X-ray diffraction (XRD), FT-IR spectroscopy, elemental analysis and simultaneous thermogravimetric and mass spectrometry (TG-MS) in details. The results show the formation of Mg{sub 2}Al-PMIDA LDH based on the expansion of d-spacing from 0.89 nm to 1.22 nm and the disappearance of the characteristic IR absorption band at 1384 cm{sup -1} for NO{sub 3}{sup -} anions. The incorporation of Mg{sub 2}Al-PMIDA LDH into the low density polyethylene (LDPE) as an additive enhances the selectivity of IR absorption in the main wavelength region 9-11 {mu}m for radiant heat loss at night. Mg{sub 2}Al-PMIDA LDH as a heat-retaining additive has practical application in agricultural plastic films.

  6. Evanescent wave absorption measurements of corroded materials using ATR and optical fibers

    NASA Astrophysics Data System (ADS)

    Namkung, Juock; Hoke, Mike; Schwartz, Andy

    2011-06-01

    The purpose of this research effort is to develop an in-situ corrosion sensing capability. The technique will permit detection of corrosion on and within aircraft structures. This includes component junctions that are susceptible to corrosion but which are not accessible for visual inspection. The prototype experimental configuration we are developing includes long wave infrared transmitting optical fiber probes interfaced with a Fourier Transform Infrared (FTIR) interferometer for evanescent wave absorption spectroscopic measurements. The mature and fielded technique will allow periodic remote sensing for detection of corrosion and for general onboard aircraft structural health monitoring. An experimental setup using an Attenuated Total Reflection (ATR) crystal integrated with an FTIR spectrometer has been assembled. Naturally occurring corrosion including Aluminum Hydroxide [Al(OH)3] is one of the main corrosion products of aluminum the principle structural metal of aircraft. Absorption spectra of our model corrosion product, pure Al(OH)3, have been collected with this ATR/FTIR experimental setup. The Al(OH)3spectra serve as reference spectral signatures. The spectra of corrosion samples from a simulated corrosion process have been collected and compared with the reference Al(OH)3 spectra. Also absorption spectra of naturally occurring corrosion collected from a fielded corroded aircraft part have been obtained and compared with the spectra from the simulated corrosion.

  7. Observation of reflectionless absorption due to spatial Kramers-Kronig profile.

    PubMed

    Ye, Dexin; Cao, Cheng; Zhou, Tianyi; Huangfu, Jiangtao; Zheng, Guoan; Ran, Lixin

    2017-07-03

    As a fundamental phenomenon in electromagnetics and optics, material absorption has been extensively investigated for centuries. However, omnidirectional, reflectionless absorption in inhomogeneous media has yet to be observed. Previous research on transformation optics indicated that such absorption cannot easily be implemented without involving gain media. A recent theory on wave propagation, however, implies the feasibility to implement such absorption requiring no gain, provided that the permittivity profile of this medium can satisfy the spatial Kramers-Kronig relations. In this work, we implement such a profile over a broad frequency band based on a novel idea of space-frequency Lorentz dispersion. A wideband, omnidirectionally reflectionless absorption is then experimentally observed in the gigahertz range, and is in good agreement with theoretical analysis and full-wave simulations. The proposed method based on the space-frequency dispersion implies the practicability to construct gain-free omnidirectionally non-reflecting absorbers.Reflectionless absorption independent of the angle of incidence usually requires the introduction of gain media into the system. Here, Ye et al. implement a recent theoretical proposal to achieve this with a spatially varying permittivity, showing that this approach is experimentally feasible.

  8. Propagation-invariant classification of sounds in channels with dispersion and absorption.

    PubMed

    Okopal, Greg; Loughlin, Patrick J

    2010-11-01

    In a previous paper [G. Okopal et al., J. Acoust. Soc. Am. 123, 832-841 (2008)], a method to obtain features of a wave that are unaffected by dispersion, per mode, was developed for improving classification of underwater sounds (e.g., sonar backscatter). The current paper builds on this work and presents additional contributions. First, it is shown that the dispersion-invariant moments developed previously are not invariant to frequency-dependent attenuation (absorption); consequently, their classification performance degrades in such channels. Second, a feature extraction method is developed to obtain features that are invariant to dispersion, and to two forms of absorption (known a priori): namely, absorption that yields spectral magnitude attenuation (in dB) that is linear with frequency, and linear with log-frequency. Third, the relationship of these absorption- and dispersion-invariant moment (ADIM) features to the cepstrum of the wave is examined, and it is shown that cepstral moments are also invariant to dispersion, and to the first form of absorption for odd-order moments. Finally, simulations are conducted to illustrate the performance of the ADIMs and cepstral moments on classifying the backscatter from steel shells in a dispersive channel with absorption. Receiver operator characteristic curves quantify the superior discriminability of the ADIMs and cepstral moments compared to ordinary moments.

  9. Mechanistic study of inhibition of levofloxacin absorption by aluminum hydroxide.

    PubMed

    Tanaka, M; Kurata, T; Fujisawa, C; Ohshima, Y; Aoki, H; Okazaki, O; Hakusui, H

    1993-10-01

    The mechanisms of reduction in absorption of levofloxacin (LVFX) by coadministration of aluminum hydroxide were studied. The partition coefficient of LVFX (0.1 mM) between chloroform and phosphate buffer (pH 5.0) was reduced by 60 to 70% with the addition of metal ions such as Cu2+, Al3+, and Fe2+ (0.8 mM), which indicated the formation of LVFX-metal ion chelates. However, there was no significant difference in absorption from rat intestine between the synthetic LVFX-Al3+ (1:1) chelate (6.75 mM) and LVFX (6.75 mM) in an in situ recirculation experiment. On the other hand, Al(NO3)3 (1.5 mM) significantly inhibited the absorption of LVFX (1.5 mM) by 20% of the control in the in situ ligated loop experiment, in which partial precipitation of aluminum hydroxide was observed in the dosing solution. Data for adsorption of LVFX and ofloxacin (OFLX) from aqueous solution by aluminum hydroxide were shown to fit Langmuir plots, and the adsorptive capacities (rmax) and the K values were 7.0 mg/g and 1.77 x 10(4) M-1 for LVFX and 7.4 mg/g and 1.42 x 10(4) M-1 for OFLX, respectively. The rate of adsorption of several quinolones (50 microM) onto aluminum hydroxide (2.5 mg/ml) followed the order norfloxacin (NFLX) (72.0%) > enoxacin (ENX) (61.0%) > OFLX (47.2%) approximately LVFX (48.1%). The elution rate of adsorbed quinolones with water followed the rank order LVFX (17.9%) approximately OFLX (20.9%) approximately ENX (18.3%) > NFLX (11.9%). These results strongly suggest that adsorption of quinolones by aluminum hydroxide reprecipitated in the small intestine would play an important role in the reduced bioavailability of quinolones after coadministration with aluminum-containing antacids.

  10. Mechanistic study of inhibition of levofloxacin absorption by aluminum hydroxide.

    PubMed Central

    Tanaka, M; Kurata, T; Fujisawa, C; Ohshima, Y; Aoki, H; Okazaki, O; Hakusui, H

    1993-01-01

    The mechanisms of reduction in absorption of levofloxacin (LVFX) by coadministration of aluminum hydroxide were studied. The partition coefficient of LVFX (0.1 mM) between chloroform and phosphate buffer (pH 5.0) was reduced by 60 to 70% with the addition of metal ions such as Cu2+, Al3+, and Fe2+ (0.8 mM), which indicated the formation of LVFX-metal ion chelates. However, there was no significant difference in absorption from rat intestine between the synthetic LVFX-Al3+ (1:1) chelate (6.75 mM) and LVFX (6.75 mM) in an in situ recirculation experiment. On the other hand, Al(NO3)3 (1.5 mM) significantly inhibited the absorption of LVFX (1.5 mM) by 20% of the control in the in situ ligated loop experiment, in which partial precipitation of aluminum hydroxide was observed in the dosing solution. Data for adsorption of LVFX and ofloxacin (OFLX) from aqueous solution by aluminum hydroxide were shown to fit Langmuir plots, and the adsorptive capacities (rmax) and the K values were 7.0 mg/g and 1.77 x 10(4) M-1 for LVFX and 7.4 mg/g and 1.42 x 10(4) M-1 for OFLX, respectively. The rate of adsorption of several quinolones (50 microM) onto aluminum hydroxide (2.5 mg/ml) followed the order norfloxacin (NFLX) (72.0%) > enoxacin (ENX) (61.0%) > OFLX (47.2%) approximately LVFX (48.1%). The elution rate of adsorbed quinolones with water followed the rank order LVFX (17.9%) approximately OFLX (20.9%) approximately ENX (18.3%) > NFLX (11.9%). These results strongly suggest that adsorption of quinolones by aluminum hydroxide reprecipitated in the small intestine would play an important role in the reduced bioavailability of quinolones after coadministration with aluminum-containing antacids. Images PMID:8257141

  11. Selective coherent perfect absorption in metamaterials

    SciTech Connect

    Nie, Guangyu; Shi, Quanchao; Zhu, Zheng; Shi, Jinhui

    2014-11-17

    We show multi-band coherent perfect absorption (CPA) in simple bilayered asymmetrically split ring metamaterials. The selectivity of absorption can be accomplished by separately excited electric and magnetic modes in a standing wave formed by two coherent counterpropagating beams. In particular, each CPA can be completely switched on/off by the phase of a second coherent wave. We propose a practical scheme for realizing multi-band coherent perfect absorption of 100% that is allowed to work from microwave to optical frequency.

  12. The effect of tea on iron absorption.

    PubMed Central

    Disler, P B; Lynch, S R; Charlton, R W; Torrance, J D; Bothwell, T H; Walker, R B; Mayet, F

    1975-01-01

    The effect of tea on iron absorption was studied in human volunteers. Absorption from solutions of FeCl3 and FeSO4, bread, a meal of rice with potato and onion soup, and uncooked haemoglobin was inhibited whether ascorbic acid was present or not. No inhibition was noted if the haemoglobin was cooked. The effect on the absorption of non-haem iron was ascribed to the formation of insoluble iron tannate complexes. Drinking tannin-containing beverages such as tea with meals may contribute to the pathogenesis of iron deficiency if the diet consists largely of vegetable foodstuffs. PMID:1168162

  13. Absorption of surface acoustic waves by graphene

    NASA Astrophysics Data System (ADS)

    Zhang, S. H.; Xu, W.

    2011-06-01

    We present a theoretical study on interactions of electrons in graphene with surface acoustic waves (SAWs). We find that owing to momentum and energy conservation laws, the electronic transition accompanied by the SAW absorption cannot be achieved via inter-band transition channels in graphene. For graphene, strong absorption of SAWs can be observed in a wide frequency range up to terahertz at room temperature. The intensity of SAW absorption by graphene depends strongly on temperature and can be adjusted by changing the carrier density. This study is relevant to the exploration of the acoustic properties of graphene and to the application of graphene as frequency-tunable SAW devices.

  14. The gastrointestinal absorption of the actinide elements.

    PubMed

    Harrison, J D

    1991-03-01

    The greatest uncertainty in dose estimates for the ingestion of long-lived, alpha-emitting isotopes of the actinide elements is in the values used for their fractional absorption from the gastrointestinal tract (f1 values). Recent years have seen a large increase in the available data on actinide absorption. Human data are reviewed here, together with animal data, to illustrate the effect on absorption of chemical form, incorporation into food materials, fasting and other dietary factors, and age at ingestion. The f1 values recommended by the International Commission on Radiological Protection, by an Expert Group of the Nuclear Energy Agency and by the National Radiological Protection Board are discussed.

  15. Not-so-resonant, resonant absorption

    NASA Astrophysics Data System (ADS)

    Brunel, F.

    1987-07-01

    When an intense electromagnetic wave is incident obliquely on a sharply bounded overdense plasma, strong energy absorption can be accounted for by the electrons that are dragged into the vacuum and sent back into the plasma with velocities v~=vosc. This mechanism is more efficient than usual resonant absorption for vosc/ω>L, with L being the density gradient length. In the very high-intensity CO2-laser-target interaction, this mechanism may account for most of the energy absorption.

  16. Total absorption by degenerate critical coupling

    SciTech Connect

    Piper, Jessica R. Liu, Victor; Fan, Shanhui

    2014-06-23

    We consider a mirror-symmetric resonator with two ports. We show that, when excited from a single port, complete absorption can be achieved through critical coupling to degenerate resonances with opposite symmetry. Moreover, any time two resonances with opposite symmetry are degenerate in frequency and absorption is always significantly enhanced. In contrast, when two resonances with the same symmetry are nearly degenerate, there is no absorption enhancement. We numerically demonstrate these effects using a graphene monolayer on top of a photonic crystal slab, illuminated from a single side in the near-infrared.

  17. Cloud Microphysics and Absorption Validation

    NASA Technical Reports Server (NTRS)

    Ackerman, Steven

    2002-01-01

    Vertical distributions of particle size and habit were developed from in-situ data collected from three midlatitude cirrus field campaigns (FIRE-1, FIRE-2, and ARM IOP). These new midlatitude microphysical models were used to develop new cirrus scattering models at a number of wavelengths appropriate for use with the MODIS imager (Nasiri et al. 2002). This was the first successful collaborative effort between all the investigators on this proposal. Recent efforts have extended the midlatitude cirrus cloud analyses to tropical cirrus, using in-situ data collected during the Tropical Rainfall Measurement Mission (TRMM) Kwajalein field campaign in 1999. We note that there are critical aspects to the work: a) Improvement in computing the scattering and radiative properties of ice crystals; b) Requirement for copious amounts of cirrus in-situ data, presented in terms of both particle size and habit distributions; c) Development of cirrus microphysical and optical models for various satellite, aircraft, and ground-based instruments based on the theoretical calculations and in-situ measurements; d) Application to satellite data.

  18. Absorption and emission spectroscopy in natural and synthetic corundum

    NASA Astrophysics Data System (ADS)

    Spinolo, G.; Palanza, V.; Ledonne, A.; Paleari, A.

    2009-04-01

    In the frame of an extensive project on the optical characterization of the many varieties of corundum (see:www.gemdata.mater.unimib.it ) we reconsidered the current interpretation of the absorption spectra with particular attention to the bands attributed to the IVCT mechanism Fe2+→ Fe3+ and Fe2+→Ti4+. A detailed study was devoted to natural metamorphic and Verneuil synthetic pale blue sapphires . In that paper (I.Fontana et al 2008) we gave experimental evidence that the band at 17500 cm-1 often attributed to Fe2+→Ti4+ IVCT transitions is in reality due to the 4T2 crystal field transition of Cr3+ partially overlapped by the 2E of Ti3+. The results of radio and photoluminescence excitation experiments obtained there, led us to propose that the color of these sapphires is mainly due to Cr in its two valence states ; Ti 3+ and Fe3+ have a minor role. After those encouraging results, we decided to apply the same approach to the study of deep blue and yellow sapphires of magmatic origin. Evaluation of impurity ion concentration by EDXRF revealed that in all these samples the concentration of Fe is quite high (around 1%) while Cr and Ti are barely detectable. Characteristic of the absorption spectra of deep blue samples is the dominant presence of the 5E spin allowed transition of Fe2+; Fe3+ has a minor role due to the fact that all d5 transitions are spin forbidden and ,consequently, very weak. In yellow sapphires Fe is totally in its 3+ valence state. In these cases, the color from yellow to blue, sometimes even within the same sample, depends. on oxidizing or reducing growth conditions. Even if the concentrations of Cr and Ti are very low, their characteristic emissions are the only ones observable down to 10000 cm-1 in radio and photoluminescence spectra. This piece of evidence suggested us to propose for the absorption bands present in the 14000 to 21000 cm-1 range, often attributed to IVCT, the same attribution given to the analogous bands in metamorphic

  19. Al Shanker Remembers.

    ERIC Educational Resources Information Center

    American Educator, 2000

    2000-01-01

    In a 1996 interview shortly before his death, Al Shanker, longtime president of the American Federation of Teachers, discussed such topics as: his own educational experiences; how he learned about political fighting in the Boy Scouts; the appeal of socialism; multinational corporations and the nation state; teaching tough students; and John Dewey…

  20. Fosetyl-al

    Integrated Risk Information System (IRIS)

    Integrated Risk Information System ( IRIS ) Chemical Assessment Summary U.S . Environmental Protection Agency National Center for Environmental Assessment This IRIS Summary has been removed from the IRIS database and is available for historical reference purposes . ( July 2016 ) Fosetyl - al ; CASRN