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Sample records for absorption studies revealed

  1. Galactic Soft X-ray Emission Revealed with Spectroscopic Study of Absorption and Emission Spectra

    NASA Astrophysics Data System (ADS)

    Yamasaki, Noriko Y.; Mitsuda, K.; Takei, Y.; Hagihara, T.; Yoshino, T.; Wang, Q. D.; Yao, Y.; McCammon, D.

    2010-03-01

    Spectroscopic study of Oxygen emission/absorption lines is a new tool to investigate the nature of the soft X-ray background. We investigated the emission spectra of 14 fields obtained by Suzaku, and detected OVII and OVIII lines separately. There is an almost isotropic OVII line emission with 2 LU intensity. As the attenuation length in the Galactic plane for that energy is short, that OVII emission should arise within 300 pc of our neighborhood. In comparison with the estimated emission measure for the local bubble, the most plausible origin of this component is the solar wind charge exchange with local interstellar materials. Another component presented from the correlation between the OVII and OVIII line intensity is a thermal emission with an apparent temperature of 0.2 keV with a field-to-field fluctuation of 10% in temperature, while the intensity varies about a factor of 4. By the combination analysis of the emission and the absorption spectra, we can investigate the density and the scale length of intervening plasma separately. We analyzed the Chanrdra grating spectra of LMC X-3 and PKS 2155-304, and emission spectra toward the line of sight by Suzaku. In both cases, the combined analysis showed that the hot plasma is not iso-thermal nor uniform. Assuming an exponential disk distribution, the thickness of the disk is as large as a few kpc. It suggests that there is a thick hot disk or hot halo surrounding our Galaxy, which is similar to X-ray hot haloes around several spiral galaxies.

  2. Revealing spectral features in two-photon absorption spectrum of Hoechst 33342: a combined experimental and quantum-chemical study.

    PubMed

    Olesiak-Banska, Joanna; Matczyszyn, Katarzyna; Zaleśny, Robert; Murugan, N Arul; Kongsted, Jacob; Ågren, Hans; Bartkowiak, Wojciech; Samoc, Marek

    2013-10-10

    We present the results of wide spectral range Z-scan measurements of the two-photon absorption (2PA) spectrum of the Hoechst 33342 dye. The strongest 2PA of the dye in aqueous solution is found at 575 nm, and the associated two-photon absorption cross section is 245 GM. A weak but clearly visible 2PA band at ∼850 nm is also observed, a feature that could not be anticipated from the one-photon absorption spectrum. On the basis of the results of hybrid quantum mechanics/molecular mechanics calculations, we put forward a notion that the long-wavelength feature observed in the two-photon absorption spectrum of Hoechst 33342 is due to the formation of dye aggregates.

  3. Different speciation for bromine in brown and red algae, revealed by in vivo X-ray absorption spectroscopic studies.

    PubMed

    Küpper, Frithjof C; Leblanc, Catherine; Meyer-Klaucke, Wolfram; Potin, Philippe; Feiters, Martin C

    2014-08-01

    Members of various algal lineages are known to be strong producers of atmospherically relevant halogen emissions, that is a consequence of their capability to store and metabolize halogens. This study uses a noninvasive, synchrotron-based technique, X-ray absorption spectroscopy, for addressing in vivo bromine speciation in the brown algae Ectocarpus siliculosus, Ascophyllum nodosum, and Fucus serratus, the red algae Gracilaria dura, G. gracilis, Chondrus crispus, Osmundea pinnatifida, Asparagopsis armata, Polysiphonia elongata, and Corallina officinalis, the diatom Thalassiosira rotula, the dinoflagellate Lingulodinium polyedrum and a natural phytoplankton sample. The results highlight a diversity of fundamentally different bromine storage modes: while most of the stramenopile representatives and the dinoflagellate store mostly bromide, there is evidence for Br incorporated in nonaromatic hydrocarbons in Thalassiosira. Red algae operate various organic bromine stores - including a possible precursor (by the haloform reaction) for bromoform in Asparagopsis and aromatically bound Br in Polysiphonia and Corallina. Large fractions of the bromine in the red algae G. dura and C. crispus and the brown alga F. serratus are present as Br(-) defects in solid KCl, similar to what was reported earlier for Laminaria parts. These results are discussed according to different defensive strategies that are used within algal taxa to cope with biotic or abiotic stresses.

  4. 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.

  5. Combined Spectroscopic and Calorimetric Studies to Reveal Absorption Mechanisms and Conformational Changes of Protein on Nanoporous Biomaterials

    PubMed Central

    Ahmadi, Saharnaz; Farokhi, Maryam; Padidar, Parisa; Falahati, Mojtaba

    2015-01-01

    In this study the effect of surface modification of mesoporous silica nanoparticles (MSNs) on its adsorption capacities and protein stability after immobilization of beta-lactoglobulin B (BLG-B) was investigated. For this purpose, non-functionalized (KIT-6) and aminopropyl-functionalized cubic Ia3d mesoporous silica ([n-PrNH2-KIT-6]) nanoparticles were used as nanoporous supports. Aminopropyl-functionalized mesoporous nanoparticles exhibited more potential candidates for BLG-B adsorption and minimum BLG leaching than non-functionalized nanoparticles. It was observed that the amount of adsorbed BLG is dependent on the initial BLG concentration for both KIT-6 and [n-PrNH2-KIT-6] mesoporous nanoparticles. Also larger amounts of BLG-B on KIT-6 was immobilized upon raising the temperature of the medium from 4 to 55 °C while such increase was undetectable in the case of immobilization of BLG-B on the [n-PrNH2-KIT-6]. At temperatures above 55 °C the amounts of adsorbed BLG on both studied nanomaterials decreased significantly. By Differential scanning calorimetry or DSC analysis the heterogeneity of the protein solution and increase in Tm may indicate that immobilization of BLG-B onto the modified KIT-6 results in higher thermal stability compared to unmodified one. The obtained results provide several crucial factors in determining the mechanism(s) of protein adsorption and stability on the nanostructured solid supports and the development of engineered nano-biomaterials for controlled drug-delivery systems and biomimetic interfaces for the immobilization of living cells. PMID:26230687

  6. Combined Spectroscopic and Calorimetric Studies to Reveal Absorption Mechanisms and Conformational Changes of Protein on Nanoporous Biomaterials.

    PubMed

    Ahmadi, Saharnaz; Farokhi, Maryam; Padidar, Parisa; Falahati, Mojtaba

    2015-07-29

    In this study the effect of surface modification of mesoporous silica nanoparticles (MSNs) on its adsorption capacities and protein stability after immobilization of beta-lactoglobulin B (BLG-B) was investigated. For this purpose, non-functionalized (KIT-6) and aminopropyl-functionalized cubic Ia3d mesoporous silica ([n-PrNH2-KIT-6]) nanoparticles were used as nanoporous supports. Aminopropyl-functionalized mesoporous nanoparticles exhibited more potential candidates for BLG-B adsorption and minimum BLG leaching than non-functionalized nanoparticles. It was observed that the amount of adsorbed BLG is dependent on the initial BLG concentration for both KIT-6 and [n-PrNH2-KIT-6] mesoporous nanoparticles. Also larger amounts of BLG-B on KIT-6 was immobilized upon raising the temperature of the medium from 4 to 55 °C while such increase was undetectable in the case of immobilization of BLG-B on the [n-PrNH2-KIT-6]. At temperatures above 55 °C the amounts of adsorbed BLG on both studied nanomaterials decreased significantly. By Differential scanning calorimetry or DSC analysis the heterogeneity of the protein solution and increase in Tm may indicate that immobilization of BLG-B onto the modified KIT-6 results in higher thermal stability compared to unmodified one. The obtained results provide several crucial factors in determining the mechanism(s) of protein adsorption and stability on the nanostructured solid supports and the development of engineered nano-biomaterials for controlled drug-delivery systems and biomimetic interfaces for the immobilization of living cells.

  7. Microwave-assisted synthesis of water-soluble, fluorescent gold nanoclusters capped with small organic molecules and a revealing fluorescence and X-ray absorption study

    NASA Astrophysics Data System (ADS)

    Helmbrecht, C.; Lützenkirchen-Hecht, D.; Frank, W.

    2015-03-01

    Colourless solutions of blue light-emitting, water-soluble gold nanoclusters (AuNC) were synthesized from gold colloids under microwave irradiation using small organic molecules as ligands. Stabilized by 1,3,5-triaza-7-phosphaadamantane (TPA) or l-glutamine (GLU), fluorescence quantum yields up to 5% were obtained. AuNC are considered to be very promising for biological labelling, optoelectronic devices and light-emitting materials but the structure-property relationships have still not been fully clarified. To expand the knowledge about the AuNC apart from their fluorescent properties they were studied by X-ray absorption spectroscopy elucidating the oxidation state of the nanoclusters' gold atoms. Based on curve fitting of the XANES spectra in comparison to several gold references, optically transparent fluorescent AuNC are predicted to be ligand-stabilized Au5+ species. Additionally, their near edge structure compared with analogous results of polynuclear clusters known from the literature discloses an increasing intensity of the feature close to the absorption edge with decreasing cluster size. As a result, a linear relationship between the cluster size and the X-ray absorption coefficient can be established for the first time.Colourless solutions of blue light-emitting, water-soluble gold nanoclusters (AuNC) were synthesized from gold colloids under microwave irradiation using small organic molecules as ligands. Stabilized by 1,3,5-triaza-7-phosphaadamantane (TPA) or l-glutamine (GLU), fluorescence quantum yields up to 5% were obtained. AuNC are considered to be very promising for biological labelling, optoelectronic devices and light-emitting materials but the structure-property relationships have still not been fully clarified. To expand the knowledge about the AuNC apart from their fluorescent properties they were studied by X-ray absorption spectroscopy elucidating the oxidation state of the nanoclusters' gold atoms. Based on curve fitting of the XANES

  8. A (14)C-leucine absorption, distribution, metabolism and excretion (ADME) study in adult Sprague-Dawley rat reveals β-hydroxy-β-methylbutyrate as a metabolite.

    PubMed

    Lee, Anthony J; Beno, David W A; Zhang, Xiaolin; Shapiro, Robin; Mason, Mark; Mason-Bright, Tanita; Surber, Bruce; Edens, Neilé K

    2015-05-01

    Leucine is an essential branched-chain amino acid that acts as a substrate for protein synthesis and as a signaling molecule. Leucine not incorporated into muscle protein is ultimately oxidized through intermediates such as β-hydroxy-β-methylbutyrate (HMB) which itself is reported to enhance muscle mass and function in rats and humans. HMB has been reported in the plasma following oral leucine administration in sheep and pigs but not in Sprague-Dawley rats, the standard preclinical model. Therefore, we conducted radiolabeled absorption, distribution, metabolism and excretion (ADME) studies in rats using a low (3 mg/kg) or high dose (1,000 mg/kg) of (14)C-leucine. Blood, tissue, and urine samples were analyzed for (14)C-leucine and its metabolites by HPLC-MS. Our results show for the first time that (14)C-HMB appears in plasma and urine of rats following an oral dose of (14)C-leucine. (14)C-leucine appears in plasma as (14)C-α-ketoisocaproic acid (KIC) with a slower time course than (14)C-HMB, a putative product of KIC. Further, two novel metabolites of leucine were detected in urine, N-acetyl leucine and glycyl leucine. Mass balance studies demonstrate that excretory routes accounted for no more than 0.9 % of the radiolabel and approximately 61 % of the dose was recovered in the carcass. Approximately 65 % of the dose was recovered in total, suggesting that approximately one-third of the leucine dose is oxidized to CO2. In conclusion, this study demonstrates endogenous production of HMB from leucine in adult rats, a standard preclinical model used to guide design of clinical trials in nutrition.

  9. 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

  10. 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.

  11. 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.

  12. Case Studies Reveal Camper Growth.

    ERIC Educational Resources Information Center

    Brannan, Steve; Fullerton, Ann

    1999-01-01

    Case studies in the National Camp Evaluation Project and National Inclusive Camp Practices project used interviews with counselors and parents about camper's growth to yield qualitative data for camp program evaluation. The importance, methods, and benefits of case studies are described. Sidebars give examples of comments on perceived camper…

  13. Quantum dot photodegradation due to CdSe-ZnO charge transfer: Transient absorption study

    NASA Astrophysics Data System (ADS)

    Žídek, K.; Zheng, K.; Chábera, P.; Abdellah, M.; Pullerits, T.

    2012-06-01

    We study changes in ultrafast transient absorption due to photodegradation of quantum dots attached to ZnO nanowire. The time-resolved measurements reveal impact of photodegradation on three distinct kinetic components present in transient absorption τ ˜ 7 ps, 80 ps, and 7.5 ns). In addition, we observe superlinear dependence of photodegradation rate on concentration of excited electrons. The data are used to evaluate the mean electron back-recombination time of ˜1 μs.

  14. A ghostly damped Ly α system revealed by metal absorption lines

    NASA Astrophysics Data System (ADS)

    Fathivavsari, H.; Petitjean, P.; Zou, S.; Noterdaeme, P.; Ledoux, C.; Krühler, T.; Srianand, R.

    2017-03-01

    We report the discovery of the first 'ghostly' damped Ly α absorption system (DLA), which is identified by the presence of absorption from strong low-ion species at zabs = 1.704 65 along the line of sight to the quasar SDSS J113341.29-005740.0 with zem = 1.704 41. No Ly α absorption trough is seen associated with these absorptions because the DLA trough is filled with the leaked emission from the broad emission-line region of the quasar. By modelling the quasar spectrum and analysing the metal lines, we derive log N(H I)(cm-2) ∼21.0 ± 0.3. The DLA cloud is small (≤0.32 pc), thus not covering entirely the broad-line region and is located at ≥39 pc from the central active galactic nucleus (AGN). Although the DLA is slightly redshifted relative to the quasar, its metallicity ([S/H] = -0.41 ± 0.30) is intermediate between what is expected from infalling and outflowing gas. It could be possible that the DLA is part of some infalling material accreting on to the quasar host galaxy through filaments, and that its metallicity is raised by mixing with the enriched outflowing gas emanating from the central AGN. Current DLA surveys miss these 'ghostly' DLAs, and it would be important to quantify the statistics of this population by searching the Sloan Digital Sky Survey (SDSS) data base using metal absorption templates.

  15. Radiant energy absorption studies for laser propulsion. [gas dynamics

    NASA Technical Reports Server (NTRS)

    Caledonia, G. E.; Wu, P. K. S.; Pirri, A. N.

    1975-01-01

    A study of the energy absorption mechanisms and fluid dynamic considerations for efficient conversion of high power laser radiation into a high velocity flow is presented. The objectives of the study are: (1) to determine the most effective absorption mechanisms for converting laser radiation into translational energy, and (2) to examine the requirements for transfer of the absorbed energy into a steady flow which is stable to disturbances in the absorption zone. A review of inverse Bremsstrahlung, molecular and particulate absorption mechanisms is considered and the steady flow and stability considerations for conversion of the laser power to a high velocity flow in a nozzle configuration is calculated. A quasi-one-dimensional flow through a nozzle was formulated under the assumptions of perfect gas.

  16. Energy absorption studied to reduce aircraft crash forces

    NASA Technical Reports Server (NTRS)

    1981-01-01

    The NASA/FAA aircraft safety reseach programs for general aviation aircraft are discussed. Energy absorption of aircraft subflooring and redesign of interior flooring are being studied. The testing of energy absorbing configurations is described. The three NASA advanced concepts performed at neary the maximum possible amount of energy absorption, and one of two minimum modifications concepts performed well. Planned full scale tests are described. Airplane seat concepts are being considered.

  17. Revealing the underlying absorption and emission mechanism of nitrogen doped graphene quantum dots.

    PubMed

    Niu, Xianghong; Li, Yunhai; Shu, Huabing; Wang, Jinlan

    2016-11-24

    Nitrogen-doped graphene quantum dots (N-GQDs) hold promising application in electronics and optoelectronics because of their excellent photo-stability, tunable photoluminescence and high quantum yield. However, the absorption and emission mechanisms have been debated for years. Here, by employing time-dependent density functional theory, we demonstrate that the different N-doping types and positions give rise to different absorption and emission behaviors, which successfully addresses the inconsistency observed in different experiments. Specifically, center doping creates mid-states, rendering non-fluorescence, while edge N-doping modulates the energy levels of excited states and increases the radiation transition probability, thus enhancing fluorescence strength. More importantly, the even hybridization of frontier orbitals between edge N atoms and GQDs leads to a blue-shift of both absorption and emission spectra, while the uneven hybridization of frontier orbitals induces a red-shift. Solvent effects on N-GQDs are further explored by the conductor-like screening model and it is found that strong polarity of the solvent can cause a red-shift and enhance the intensity of both absorption and emission spectra.

  18. Further studies of human whole-body radiofrequency absorption rates.

    PubMed

    Hill, D A

    1985-01-01

    Further studies of human whole-body radiofrequency (RF) absorption rates were carried out using a TEM-cell exposure system. Experiments were done at one frequency near the grounded resonance frequency (approximately 40 MHz), and at several below-resonance frequencies. Absorption rates are small for the K and H orientations of the body, even when grounded. For the body trunk in an E orientation, the absorption rate of a sitting person is about half of the rate for the same person standing with arms at the sides; the latter in turn is about half the rate for the same subject standing with arms over the head. Two-body interactions cause no increase in absorption rates for grounded people. They do, however, increase the absorption rates for subjects in an E orientation in free space; the largest interaction occurs when one subject is lambda/2 behind the other (as seen by the incident wave). When these results are applied to practical occupational exposure situations, the whole-body specific absorption rate does not exceed the ANSI limit of 0.4 W/kg for exposures permitted by the ANSI standard (C95.1-1982) at frequencies from 7 to 40 MHz.

  19. Study report on a double isotope method of calcium absorption

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Some of the pros and cons of three methods to study gastrointestinal calcium absorption are briefly discussed. The methods are: (1) a balance study; (2) a single isotope method; and (3) a double isotope method. A procedure for the double isotope method is also included.

  20. 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.

  1. Theoretical study on absorption and emission spectra of adenine analogues.

    PubMed

    Liu, Hongxia; Song, Qixia; Yang, Yan; Li, Yan; Wang, Haijun

    2014-04-01

    Fluorescent nucleoside analogues have attracted much attention in studying the structure and dynamics of nucleic acids in recent years. In the present work, we use theoretical calculations to investigate the structural and optical properties of four adenine analogues (termed as A1, A2, A3, and A4), and also consider the effects of aqueous solution and base pairing. The results show that the fluorescent adenine analogues can pair with thymine to form stable H-bonded WC base pairs. The excited geometries of both adenine analogues and WC base pairs are similar to the ground geometries. The absorption and emission maxima of adenine analogues are greatly red shifted compared with nature adenine, the oscillator strengths of A1 and A2 are stronger than A3 and A4 in both absorption and emission spectra. The calculated low-energy peaks in the absorption spectra are in good agreement with the experimental data. In general, the aqueous solution and base pairing can slightly red-shift both the absorption and emission maxima, and can increase the oscillator strengths of absorption spectra, but significantly decrease the oscillator strengths of A3 in emission spectra.

  2. In vivo studies of biotin absorption in distal rat intestine

    SciTech Connect

    Bowman, B.B.; Rosenberg, I.H.

    1986-03-01

    The authors have extended their previous studies of biotin absorption in rat proximal jejunum (PJ) to examine biotin absorptive capacity of rat ileum (I) and proximal colon (PC) using in vivo intestinal loop technique. Intestinal loops (2.5 cm) were filled with 0.3 ml of solution containing (/sup 3/H)-biotin and (/sup 14/C)-inulin in phosphate buffer, pH 6.5. Biotin absorption was determined on the basis of luminal biotin disappearance after correction for inulin recovery and averaged (pmol/loop-10 min; X +/- SEM). In related experiments, 5-cm loops of PJ, distal I (DI), or PC were filled with 0.5 ml of solution of similar composition (1.0 ..mu..M biotin). The abdominal cavity was closed and the rats were allowed to recover from anesthesia, then sacrificed 3 hr after injection. Biotin absorption averaged 96.2% (PJ), 93.2% (DI), and 25.8% (PC) of the dose administered. These differences were reflected in the radioactive biotin content of plasma and intestinal loop, kidney, and liver. These data demonstrate significant biotin absorption in rat DI and PC, as required if the intestinal microflora are to be considered as a source of biotin for the host.

  3. Mid-infrared Laser Absorption Diagnostics for Detonation Studies

    NASA Astrophysics Data System (ADS)

    Spearrin, R. M.; Goldenstein, C. S.; Jeffries, J. B.; Hanson, R. K.

    Detonation-based engines represent a challenging application for diagnostics due to the wide range of thermodynamic conditions involved (T~500-3000 K, P~2-60 atm) and the short time scales of change (~10- 6 to 10- 4 sec) associated with such systems. Non-intrusive laser absorption diagnostics can provide high time-resolution and have been employed extensively in shock tube kinetics experiments (P~1-20 atm), offering high potential for application in detonation environments with modest utilization to date [1-4]. Limiting factors in designing effective tunable laser absorption sensors for detonation engines can be divided into two sets of challenges: high-pressure, high-temperature absorption spectroscopy and harsh thermo-mechanical environments. The present work, conducted in a high-pressure shock tube and operating detonation combustor, addresses both sets of difficulties, with the objective of developing time-resolved, in-situ temperature and concentration sensors for detonation studies.

  4. Auto-oligomerization and hydration of pyrrole revealed by x-ray absorption spectroscopy

    SciTech Connect

    Advanced Light Source; Schwartz, Craig P.; Uejio, Janel S.; Duffin, Andrew M.; England, Alice H.; Prendergast, David; Saykally, Richard J

    2009-05-29

    Near edge x-ray absorption fine structure (NEXAFS) spectra have been measured at the carbon and nitrogen K-edges of the prototypical aromatic molecule, pyrrole, both in the gas phase and when solvated in water, and compared with spectra simulated using a combination of classical molecular dynamics and first principles density functional theory in the excited state core hole approximation. The excellent agreement enabled detailed assignments. Pyrrole is highly reactive, particularly in water, and reaction products formed by the auto-oligomerization of pyrrole are identified. The solvated spectra have been measured at two different temperatures, indicating that the final states remain largely unaffected by both hydration and temperature. This is somewhat unexpected, since the nitrogen in pyrrole can donate a hydrogen bond to water.

  5. The Nature of the Vela Supernova Remnant as Revealed by O VI and C IV Absorption

    NASA Technical Reports Server (NTRS)

    Lines, Nichols J.; Slavin, J.; Anderson, C.

    2001-01-01

    Highly ionized gas, in particular C IV and O VI, is produced in the interstellar medium in regions with hot (T approx. 10(exp 6) K) X-ray emitting gas and at the boundaries where hot gas and cooler (T approx. 10(exp 4) K) gas interact. Supernova remnant shocks produce most of the hot gas in the ISM and, if they are in the correct range of speeds, should produce observable quantities of C IV and O VI absorption. In turn, the column densities of these ions are potentially powerful diagnostics of the shock speed and interstellar environment in which the SNR is evolving. With the advent of FUSE, the power of this diagnostic technique is now available. We have FUSE data toward 8 stars behind the Vela SNR, and have developed a data reduction and analysis method that produces reasonably reliable O VI column densities, in spite of the complexities of the FUSE spectra in this region. In order to gain insight into the observational results, the Vela SNR evolution was modelled using Piecewise Parabolic Method numerical hydrodynamics code. The code is 1-D and incorporates non-equilibrium ionization, radiative cooling, thermal conduction and magnetic pressure.

  6. Absorption Reveals and Hydrogen Addition Explains New Interstellar Aldehydes: Propenal and Propanal

    NASA Technical Reports Server (NTRS)

    Hollis, J. M.; Jewell, P. R.; Lovas, F. J.; Remijan, A.; Mollendal, H.

    2004-01-01

    New interstellar molecules propenal (CH2CHCHO) and propanal (CH3CH2CHO) have been detected largely in absorption toward the star-forming region Sagittarius B2(N) by means of rotational transitions observed with the 100-m Green Bank Telescope (GBT) operating in the range of 18 GHz (lambda approximately 1.7 cm) to 26 GHz (lambda approximately 1.2 cm). The GBT was also used to observe the previously reported interstellar aldehyde propynal (HC2CHO) in Sagittarius B2(N) which is known for large molecules believed to form on interstellar grains. The presence of these three interstellar aldehydes toward Sagittarius B2(N) strongly suggests that simple hydrogen addition on interstellar grains accounts for successively larger molecular species: from propynal to propenal and from propenal to propanal. Energy sources within Sagittarius B2(N) likely permit the hydrogen addition reactions on grain surfaces to proceed. This work demonstrates that successive hydrogen addition is probably an important chemistry route in the formation of a number of complex interstellar molecules. We also searched for but did not detect the three-carbon sugar glyceraldehyde (CH2OHCHOHCHO).

  7. A study of sound absorption by street canyon boundaries and asphalt rubber concrete pavement

    NASA Astrophysics Data System (ADS)

    Drysdale, Graeme Robert

    A sound field model, based on a classical diffusion equation, is extended to account for sound absorption in a diffusion parameter used to model sound energy in a narrow street canyon. The model accounts for a single sound absorption coefficient, separate accommodation coefficients and a combination of separate absorption and accommodation coefficients from parallel canyon walls. The new expressions are compared to the original formula through numerical simulations to reveal the effect of absorption on sound diffusion. The newly established analytical formulae demonstrate satisfactory agreement with their predecessor under perfect reflection. As well, the influence of the extended diffusion parameter on normalized sound pressure levels in a narrow street canyon is in agreement with experimental data. The diffusion parameters are used to model sound energy density in a street canyon as a function of the sound absorption coefficient of the street canyon walls. The acoustic and material properties of conventional and asphalt rubber concrete (ARC) pavement are also studied to assess how the crumb rubber content influences sound absorption in street canyons. The porosity and absolute permeability of compacted specimens of asphalt rubber concrete are measured and compared to their normal and random incidence sound absorption coefficients as a function of crumb rubber content in the modified binder. Nonlinear trends are found between the sound absorption coefficients, porosity and absolute permeability of the compacted specimens and the percentage of crumb rubber in the modified binders. The cross-sectional areas of the air voids on the surfaces of the compacted specimens are measured using digital image processing techniques and a linear relationship is obtained between the average void area and crumb rubber content. The measured material properties are used to construct an empirical formula relating the average porosity, normal incidence noise reduction coefficients and

  8. Experimental studies of a zeeman-tuned xenon laser differential absorption apparatus.

    PubMed

    Linford, G J

    1973-06-01

    A Zeeman-tuned cw xenon laser differential absorption device is described. The xenon laser was tuned by axial magnetic fields up to 5500 G generated by an unusually large water-cooled dc solenoid. Xenon laser lines at 3.37 micro, 3.51 micro, and 3.99 micro were tuned over ranges of 6 A, 6 A, and 11 A, respectively. To date, this apparatus has been used principally to study the details of formaldehyde absorption lines lying near the 3 .508-micro xenon laser transition. These experiments revealed that the observed absorption spectrum of formaldehyde exhibits a sufficiently unique spectral structure that the present technique may readily be used to measure relative concentrations of formaldehyde in samples of polluted air.

  9. Spectroscopic study of low-temperature hydrogen absorption in palladium

    SciTech Connect

    Ienaga, K. Takata, H.; Onishi, Y.; Inagaki, Y.; Kawae, T.; Tsujii, H.; Kimura, T.

    2015-01-12

    We report real-time detection of hydrogen (H) absorption in metallic palladium (Pd) nano-contacts immersed in liquid H{sub 2} using inelastic electron spectroscopy (IES). After introduction of liquid H{sub 2}, the spectra exhibit the time evolution from the pure Pd to the Pd hydride, indicating that H atoms are absorbed in Pd nano-contacts even at the temperature where the thermal process is not expected. The IES time and bias voltage dependences show that H absorption develops by applying bias voltage 30 ∼ 50 mV, which can be explained by quantum tunneling. The results represent that IES is a powerful method to study the kinetics of high density H on solid surface.

  10. Physical, Optical absorption and EPR studies on fluoro- bismuthate glasses

    NASA Astrophysics Data System (ADS)

    Srinivasu, Ch; Samee, M. A.; Edukondalu, A.; Laxmi Kanth, C.; Rahman, Syed

    2015-02-01

    Glasses of the xLiF-(50-x)Li2O-20SrO-30Bi2O3 system, with 0 <= x <= 20 mole % were studied by EPR and Optical measurements. The changes in both density and molar volume indicate structural modifications occur due to addition of LiF. The glass transition temperatures are observed to decrease with an increase in LiF content in the compositions. The local structure around Cu2+ ions has been examined by means of electron paramagnetic resonance and optical absorption measurements. It is observed that the spin-Hamiltonian parameters calculated from the EPR spectra are influenced by the glass composition. The Cu2+ ions are in well-defined axial sites but subjected to small distortion leading to the broadening of the spectra. The spin-Hamiltonian parameter values indicate that the ground state of Cu2+ is and the site symmetry around Cu2+ ions is tetragonally distorted octahedral. The optical absorption spectra exhibited a broad band corresponding to the d-d transition bands of Cu2+ ion. By correlating EPR and optical absorption data, the bond parameters are evaluated.

  11. Multi-mode interference revealed by two photon absorption in silicon rich SiO{sub 2} waveguides

    SciTech Connect

    Manna, S. E-mail: mattia.mancinelli@unitn.it; Ramiro-Manzano, F.; Mancinelli, M. E-mail: mattia.mancinelli@unitn.it; Turri, F.; Pavesi, L.; Ghulinyan, M.; Pucker, G.

    2015-02-16

    Photoluminescence (PL) from Si nanocrystals (NCs) excited by two-photon absorption (TPA) has been observed in Si nanocrystal-based waveguides fabricated by plasma enhanced chemical vapor deposition. The TPA excited photoluminescence emission resembles the one-photon excited photoluminescence arising from inter-band transitions in the quantum confined Si nanocrystals. By measuring the non-linear transmission of waveguides, a large TPA coefficient of β up to 10{sup −8 }cm/W has been measured at 1550 nm. These values of β depend on the Si NCs size and are two orders of magnitude larger than the bulk silicon value. Here, we propose to use the TPA excited visible PL emission as a tool to map the spatial intensity profile of the 1550 nm propagating optical modes in multimode waveguides. In this way, multimode interference has been revealed experimentally and confirmed through a finite element simulation.

  12. Sound absorption study of raw and expanded particulate vermiculites

    NASA Astrophysics Data System (ADS)

    Vašina, Martin; Plachá, Daniela; Mikeska, Marcel; Hružík, Lumír; Martynková, Gražyna Simha

    2016-12-01

    Expanded and raw vermiculite minerals were studied for their ability to absorb sound. Phase and structural characterization of the investigated vermiculites was found similar for both types, while morphology and surface properties vary. Sound waves reflect in wedge-like structure and get minimized, and later are absorbed totally. We found that thanks to porous character of expanded vermiculite the principle of absorption of sound into layered vermiculite morphology is analogous to principle of sound minimization in "anechoic chambers." It was found in this study that the best sound damping properties of the investigated vermiculites were in general obtained at higher powder bed heights and higher excitation frequencies.

  13. Infrared absorption study of neutron-transmutation-doped germanium

    NASA Technical Reports Server (NTRS)

    Park, I. S.; Haller, E. E.

    1988-01-01

    Using high-resolution far-infrared Fourier transform absorption spectroscopy and Hall effect measurements, the evolution of the shallow acceptor and donor impurity levels in germanium during and after the neutron transmutation doping process was studied. The results show unambiguously that the gallium acceptor level concentration equals the concentration of transmutated Ge-70 atoms during the whole process indicating that neither recoil during transmutation nor gallium-defect complex formation play significant roles. The arsenic donor levels appear at full concentration only after annealing for 1 h at 450 C. It is shown that this is due to donor-radiation-defect complex formation. Again, recoil does not play a significant role.

  14. Extended x-ray absorption fine structure studies of hemoglobin

    SciTech Connect

    Shulman, R.G.

    1987-02-01

    Results of extended x-ray absorption fine structure (EXAFS) studies of the iron atom in deoxygenated hemoglobin are reviewed. It is shown that the iron-porphinato nitrogen distance has been determined to be 2.06 +/- 0.01 A by two independent investigations. Difficulties experienced in using this distance to calculate the iron's distance above the plane by triangulation are shown to be due to ignoring differences between ferrous and ferric hemes. It is concluded that the iron is 0.2 +/- 0.1/0.2 A above the plane of the nitrogens as originally shown.

  15. Optical absorption near infrared and EPR studies of mottramite

    NASA Astrophysics Data System (ADS)

    Lakshmi Reddy, S.; Reddy, K. N. M.; Siva Reddy, G.; Endo, Tamio; Frost, R. L.

    2010-06-01

    Mottramite mineral from Tsumeb Corporation Mine, Tsumeb, Otavi, Namibia, is investigated in this present work. The mineral contains vanadium and copper contents of 22.73% and 16.84% by weight, respectively, as V2O5 and CuO. An electron paramagnetic resonance (EPR) study confirmed the presence of Cu(II) with g = 2.2. The optical absorption spectrum of mottramite indicates that Cu(II) is present in a rhombic environment. Near infrared results are due to water fundamentals.

  16. Systematic trend of water vapour absorption in red giant atmospheres revealed by high resolution TEXES 12 μm spectra

    NASA Astrophysics Data System (ADS)

    Ryde, N.; Lambert, J.; Farzone, M.; Richter, M. J.; Josselin, E.; Harper, G. M.; Eriksson, K.; Greathouse, T. K.

    2015-01-01

    Context. The structures of the outer atmospheres of red giants are very complex. Recent interpretations of a range of different observations have led to contradictory views of these regions. It is clear, however, that classical model photospheres are inadequate to describe the nature of the outer atmospheres. The notion of large optically thick molecular spheres around the stars (MOLspheres) has been invoked in order to explain spectro-interferometric observations and low- and high-resolution spectra. On the other hand high-resolution spectra in the mid-IR do not easily fit into this picture because they rule out any large sphere of water vapour in LTE surrounding red giants. Aims: In order to approach a unified scenario for these outer regions of red giants, more empirical evidence from different diagnostics are needed. Our aim here is to investigate high-resolution, mid-IR spectra for a range of red giants, spanning spectral types from early K to mid M. We want to study how the pure rotational lines of water vapour change with effective temperature, and whether we can find common properties that can put new constraints on the modelling of these regions, so that we can gain new insights. Methods: We have recorded mid-IR spectra at 12.2 - 12.4 μm at high spectral resolution of ten well-studied bright red giants, with TEXES mounted on the IRTF on Mauna Kea. These stars span effective temperatures from 3450 K to 4850 K. Results: We find that all red giants in our study cooler than 4300 K, spanning a wide range of effective temperatures (down to 3450 K), show water absorption lines stronger than expected and none are detected in emission, in line with what has been previously observed for a few stars. The strengths of the lines vary smoothly with spectral type. We identify several spectral features in the wavelength region that are undoubtedly formed in the photosphere. From a study of water-line ratios of the stars, we find that the excitation temperatures, in the

  17. Transient absorption studies of vibrational relaxation and photophysics of Prussian blue and ruthenium purple nanoparticles

    NASA Astrophysics Data System (ADS)

    Weidinger, D.; Brown, D. J.; Owrutsky, J. C.

    2011-03-01

    excitation indicated from 800 pump-IR probe results. However, IR pump-800 nm probe studies reveal that excitation of the CN band directly results in a decreased visible absorption that decays in 18 ps rather than an induced absorption at 800 nm. Characteristics of the IR pump-800 nm probe, especially that it induces a bleach instead of an absorption, unambiguously indicate that the transient absorption from the 800 nm pump-800 nm probe is dominated by states other than the CN bands and is attributed to population in other, probably lower frequency, vibrational modes excited following visible excitation and rapid BET.

  18. Absorption and fluorescent spectral studies of imidazophenazine derivatives

    NASA Astrophysics Data System (ADS)

    Ryazanova, O. A.; Zozulya, V. N.; Voloshin, I. M.; Karachevtsev, V. A.; Makitruk, V. L.; Stepanian, S. G.

    2004-07-01

    Absorption and fluorescent spectra as well as fluorescence polarization degree of imidazo-[4,5-d]-phenazine (F1) and its two modified derivatives, 2-trifluoridemethylimidazo-[4,5-d]-phenazine (F2) and 1,2,3-triazole-[4,5-d]-phenazine (F3), were investigated in organic solvents of various polarities and hydrogen bonding abilities. Extinction coefficients of F2 and F3 are increased, their fluorescence Stokes shifts are reduced in comparison with those for unmodified imidazophenazine. For F3 a red shift of the longwave absorption band is observed by 15-20 nm. Modifications of imidazophenazine have led to a sufficient increase of fluorescence polarization degrees that enables to use F2 and F3 as promising fluorescent probes with polarization method application. The configuration, atomic charge distribution and dipole moments of the isolated dye molecules in the ground state were calculated by the DFT method. The computation has revealed that ground state dipole moments of F1, F2, and F3 differ slightly and are equal to 3.5, 3.2, and 3.7 D, respectively. The changes in dipole moments upon the optical excitation for all derivatives estimated using Lippert equation were found to be Δ μ=9 D. The energies of the electronic S 1←S 0 transition in solvents of different proton donor abilities were determined, and energetic diagram illustrating the substituent effect was plotted. For nucleoside analogs of these compounds, covalently incorporated into a nucleotide chain, we have considered a possibility to use them as fluorescent reporters of hybridization of antisense oligonucleotides, as well as molecular anchors for its stabilization.

  19. Emission and Absorption Study of the Vela Supernova Remnant

    NASA Astrophysics Data System (ADS)

    Raymond, John C.

    The combination of emission and absorption studies of the shocked gas in a supernova remnant can provide information not available from either study by itself, especially relating to the liberation of refractory elements from interstellar grains in the cooling zone behind the shock and the effects of departures from steady flow. No such combined studies have been attempted due to the need for a hot, bright background star behind supernova remnant nebulosity bright enough for emission line observations. Wallerstein and Balick have discovered a suitable patch of nebulosity in the Vela Supernova Remnant adjacent to the B3 III star HD 72088. IUE spectra of the star show a 94 km/s component in C IV and Si IV in absorption, and the optical spectra of Wallerstein and Balick show strong high excitation emission lines close to the star. We wish to obtain IUE spectra of the nebulosity as close to the star as possible and further high dispersion spectra of the star to improve the signal-tonoise.

  20. X-ray absorption studies of battery materials

    SciTech Connect

    McBreen, J.

    1996-10-01

    X-ray absorption spectroscopy (XAS) is ideal for {ital in}{ital situ} studies of battery materials because both the probe and signal are penetrating x rays. The advantage of XAS being element specific permits investigation of the environment of a constituent element in a composite material. This makes it very powerful for studying electrode additives and corrosion of individual components of complex metal hydride alloys. The near edge part of the spectrum (XANES) provides information on oxidation state and site symmetry of the excited atom. This is particularly useful in study of corrosion and oxidation changes in cathode materials during charge/discharge cycle. Extended fine structure (EXAFS) gives structural information. Thus the technique provides both chemical and structural information. Since XAS probes only short range order, it can be applied to study of amorphous electrode materials and electrolytes. This paper discusses advantages and limitations of the method, as well as some experimental aspects.

  1. Studies on the Inhibition of Intestinal Absorption of Radioactive Strontium

    PubMed Central

    Waldron-Edward, Deirdre; Paul, T. M.; Skoryna, Stanley C.

    1964-01-01

    A method is reported which permits selective suppression of absorption of radioactive strontium from ingested food material, permitting calcium to be available to the body. Studies were carried out by measuring bone uptake of Sr89 and Ca45 when various amounts of sodium alginate were fed with the diet. Long-term studies were made in which two different levels of radioactivity were used, to determine the pattern of Sr89 deposition with continuous intake of binding agent. It was found that administration of sodium alginate as a jelly overcomes the problem of constipation and effectively reduces Sr89 uptake, up to 83%. This fact represents a significant finding with respect to the use of the compound in human subjects. Addition of sodium alginate to drinking water is effective with low levels of Sr89 intake. This naturally occurring water-soluble macromolecular substance possesses several advantages in use for the suppression of absorption of radioactive strontium when compared with synthetic ion exchange resins: there is no disturbance of electrolyte balance; efficiency is not reduced by treatment over a prolonged period of time; and finally, the product is palatable. PMID:14222668

  2. Ultrafast transient absorption studies of single metal and semiconductor nanowires

    NASA Astrophysics Data System (ADS)

    Hartland, Gregory V.; Carey, Christopher R.; Staleva, Hristina

    2010-02-01

    Single particle transient absorption experiments have been used to study metallic and semiconducting nanowires. For the metal wires the major result is the observation of modulations in the transient absorption traces due to coherently excited breathing modes. The vibrational periods depend on the dimensions of the nanowire, and the decay times are sensitive to the environment. The nanowires in our experiments are spin coated from a polymer solution onto a glass substrate, and experience a range of different environments. This causes large variations in the quality factor of the breathing mode for different wires. Semiconducting nanowires of CdTe and CdSe were also examined. The CdTe wires show fast picosecond time scale dynamics, which are assigned to charge carrier trapping at surface states of the wires. In contrast, CdSe nanowires show no dynamics on the time scale of our measurements. For the CdTe nanowires the charge carrier trapping times vary from wire-to-wire, and also vary with position in a single wire. This is attributed to differences in surface chemistry. Overall these experiments illustrate the important of single particle techniques for studying nanomaterials, especially for elucidating how differences in local environment and structure affect dynamics.

  3. Multiple pre-edge structures in Cu K -edge x-ray absorption spectra of high- Tc cuprates revealed by high-resolution x-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Gougoussis, C.; Rueff, J.-P.; Calandra, M.; D'Astuto, M.; Jarrige, I.; Ishii, H.; Shukla, A.; Yamada, I.; Azuma, M.; Takano, M.

    2010-06-01

    Using high-resolution x-ray absorption spectroscopy and state-of-the-art electronic structure calculations we demonstrate that the pre-edge region at the Cu K edge of high- Tc cuprates is composed of several excitations invisible in standard x-ray absorption spectra. We consider in detail the case of Ca2-xCuO2Cl2 and show that the many pre-edge excitations (two for c -axis polarization, four for in-plane polarization and out-of-plane incident x-ray momentum) are dominated by off-site transitions and intersite hybridization. This demonstrates the relevance of approaches beyond the single-site model for the description of the pre edges of correlated materials. Finally, we show the occurrence of a doubling of the main edge peak that is most visible when the polarization is along the c axis. This doubling, that has not been seen in any previous absorption data in cuprates, is not reproduced by first-principles calculations. We suggest that this peak is due to many-body charge-transfer excitations while all the other visible far-edge structures are single particle in origin. Our work indicates that previous interpretations of the Cu K -edge x-ray absorption spectra in high- Tc cuprates can be profitably reconsidered.

  4. Picosecond transient absorption study of photodissociated carboxy hemoglobin and myoglobin

    SciTech Connect

    Janes, S.M.; Dalickas, G.A.; Eaton, W.A.; Hochstrasser, R.M.

    1988-09-01

    The optical transient absorption spectra at 30 ps and 6.5 ns after photolysis are compared for both carboxy hemoglobin (HbCO) and carboxy myoglobin (MbCO). Both 355- and 532-nm excitation pulses were used. In all cases the shapes of the optical difference spectra thus generated are stationary over the complete time-scale studied. The photolysis spectra for MbCO are not significantly different from the equilibrium difference spectra generated on the same picosecond spectrometer when measured to an accuracy of +/- 0.5 nm. In addition, spectral parameters for delegated HbCO generated on the same spectrometer but detected by two different techniques, either by a Vidicon detector or point by point with photomultiplier tubes, are reported; the results are different from some of the previously reported picosecond experiments.

  5. Study of the absorption coefficient in layers of a semiconductor laser heterostructure

    SciTech Connect

    Veselov, D A; Pikhtin, N A; Lyutetskiy, A V; Nikolaev, D N; Slipchenko, S O; Sokolova, Z N; Shamakhov, V V; Shashkin, I S; Voronkova, N V; Tarasov, I S

    2015-07-31

    A method of studying the absorption coefficient in layers of semiconductor lasers is proposed. Using lasers based on MOVPE-grown separate-confinement heterostructures with a broadened waveguide, the absorption coefficient is investigated under pulsed current pumping. It is found that when the pump current flows through the laser in question, an additional internal optical absorption arises in the heterostructure layers. It is shown that an increase in the pump current density up to 20 kA cm{sup -2} leads to an increase in absorption up to 2.5 cm{sup -1}. The feasibility of studying free-carrier absorption in the active region is demonstrated. (lasers)

  6. [Study on near-infrared absorption mechanism of alkali lignin].

    PubMed

    Wu, Xin-sheng; Xie, Yi-min; Liu, Huan-bin; Wu, Hong

    2006-06-01

    The results showed that o-quinone and q-quinone had strong absorption while vanillin had nearly no absorption in the 800-900 nm range of near-infrared spectroscopy through the comparison of their near-infrared absorption spectra. It was proved that quinone structure of alkali lignin had strong absorption in the 800-900 nm range of near-infrared spectroscopy. The change in the absorbency of oleander milled wood lignin treated with NaOH and Na2 S before and after is greater than that in the absorbency of ginkgo milled wood lignin treated with NaOH and Na2 S before and after because more quinone structure was formed in the process of oleander milled wood lignin treated with NaOH and Na2 S. The finding well explained that cooking liquor of hardwood was much stronger than that of softwood while their pulp kappa number was very near.

  7. Fundamental Study of Absorption Cycle without Electric Solution Pump

    NASA Astrophysics Data System (ADS)

    Tsujimori, Atsushi; Sato, Kazuo; Nakao, Kazushige; Ohgushi, Tetsuro; Katsuta, Masafumi

    The absorption refrigerant cycle has been used in Japan, as energy shortage problem is more and more serious and environmental protection is of increasing importance. This type of air conditioner and chiller consume less electric power input than the electric one. However, the absorption refrigerator of large cooling capacity consumes some electric power with the required facility. Then in this research, the absorption cycle without the electric solution pump is proposed using a capillary pump and the possibility of making this cycle running using LiBr solution as a working fluid is investigated. As a result, it was found that the absorption cycle could be reached using a capillary wick in the generator to circulate the refrigerant and kept the strong and weak solution low pressure.

  8. [The study of absorption spectrum for cell substrate].

    PubMed

    Zhao, Yuan-Li; Zhang, Feng-Qiu; Ge, Xiang-Hong; Yao, Shu-Xia; Liang, Er-jun

    2004-08-01

    The authors collected the absorption spectrum of RPMI 1640 and DMEM substrates that cultivated Hela and CNE by UV-3101 spectrophotometer and analysed the absorbability of proteins in the substrate. The absorption peaks of the RPMI 1 640 culture medium that cultivated cells for different times shifted from 227 to 222 or 218 nm and from 278 to 280 nm respectively; while during growing course of cultivated cells, one of the absorption peaks of DMEM culture medium shifted from 224 nm to one near 221 nm, and the absorption peak 278 nm almost had no shift. All of these shifts show that the content of each amino acid such as tryptophan and casein has already changed. That is, during the growing course of cultivating cancer cells, the tryptophan and casein were not depleted equivalently. In the growth period of Hela and CNE, they consumed different amino acid. So they need different component proportion for amino acid.

  9. Povidone iodine skin absorption: an ex-vivo study.

    PubMed

    Nesvadbova, Martina; Crosera, Matteo; Maina, Giovanni; Larese Filon, Francesca

    2015-06-15

    Povidone iodine is a water-soluble complex used to disinfect the skin surface and it exerts prolonged germicidal action against a broad spectrum of germs. Indeed, it is often applied on burned skin, large wounds, deep tissues or mucosa. Notably some surgical hand-scrub solutions, which are considered safe antiseptics, contain large amounts of iodine that can be absorbed by skin. The aim of present study was to study the skin absorption of iodine after the application on the skin of povidone-iodine solution, used by health care workers during surgical procedure. We use Franz diffusion static cells with human skin. After 24h from the beginning of our measurement the iodine concentration in the receiving compartment was 11.59±6.3μg/cm(2). The medium flux calculated was 0.73±0.33μg/cm(2)/h with a lag time of 8.9±1.5h. These in vitro results confirmed that povidone iodine could pass through the skin in a relevant amount that can explain the clinical findings in burned or surgically treated patients. In professional use the repetitive contact with povidone iodine, also as soap, can cause iodine skin permeation that must be considered when the washing procedures are repeated more than 20 times a day.

  10. Millisecond Photoinduced Absorption Studies of Pyridine-Based Copolymer Films

    NASA Astrophysics Data System (ADS)

    Coplin, K. A.; Clark, D. T.; Jessen, S. W.; Epstein, A. J.; Fu, D.-K.; Swager, T. M.

    1997-03-01

    We present a study of the photoexcited states in copolymers of poly(p-pyridyl vinylene) and poly(p-phenylene vinylene) (PPyVPR_iV) with sidegroups R_1=C_12H_25 or R_2=COOC_12H_25 attached at the 2 and 5 positions of the phenyl ring. Previous studies discussed the millisecond photoinduced absorption (ms PA) characteristics of PPyVPR_iV powders(S.W. Jessen et al.), Synth. Met., in press.. In particular, triplet-triplet (T-T) transitions were observed at 1.6 eV for both materials. Additional polaron signatures were also observed in both the electronic ( ~ 0.85 eV) and infrared (1100 - 1600 cm-1) regions of the photoinduced spectrum. We compare these powder results with ms PA features for film morphologies of both the copolymers. We observe a weaker ( ~ 10X) T-T^* transition for copolymer films cast from xylene solution indicating a reduction in triplet exciton production as compared to powder samples. These results are contrasted with the behavior we reported(S.W. Jessen et al.), to be published. earlier for film and powder samples of the parent polymer poly(p-pyridyl vinylene).

  11. Millimeter-wave Absorption Studies of Molecules in Diffuse Clouds

    NASA Astrophysics Data System (ADS)

    Lucas, Robert; Liszt, Harvey S.

    1999-10-01

    With IRAM instruments in the last few years, we have been using compact extragalactic millimeter wave radio sources as background objects to study the absorption spectrum of diffuse interstellar gas at millimeter wavelengths. The molecular content of interstellar gas has turned out to be unexpectedly rich. Simple polyatomic molecules such as HCO+, C2H are quite ubiquitous near the Galactic plane (beta < 15o), and many species are detected in some directions (CO, HCO+, H2CO, HCN, HNC, CN, C2H, C3H2, H2S, CS, HCS+, SO, SiO). Remarkable proportionality relations are found between related species such as HCO+ and OH, or CN, HCN and HNC. The high abundance of some species is still a challenge for current models of diffuse cloud chemistry. A factor of 10 increase in the sensitivity will make such studies achievable in denser clouds, where the chemistry is still more active and where abundances are nowadays only available by emission measurements, and thus subject to uncertainties due to sometimes poorly understood line formation and excitation conditions.

  12. Satellite and Ground-based Radiometers Reveal Much Lower Dust Absorption of Sunlight than Used in Climate Models

    NASA Technical Reports Server (NTRS)

    Kaufman, Y. J.; Tanre, D.; Dubovik, O.; Karnieli, A.; Remer, L. A.; Einaudi, Franco (Technical Monitor)

    2000-01-01

    The ability of dust to absorb solar radiation and heat the atmosphere is one of the main uncertainties in climate modeling and the prediction of climate change. Dust absorption is not well known due to limitations of in situ measurements. New techniques to measure dust absorption are needed in order to assess the impact of dust on climate. Here we report two new independent remote sensing techniques that provide sensitive measurements of dust absorption. Both are based on remote sensing. One uses satellite spectral measurements, the second uses ground based sky measurements from the AERONET network. Both techniques demonstrate that Saharan dust absorption of solar radiation is several times smaller than the current international standards. Dust cooling of the earth system in the solar spectrum is therefore significantly stronger than recent calculations indicate. We shall also address the issue of the effects of dust non-sphericity on the aerosol optical properties.

  13. Intestinal absorption of aloin, aloe-emodin, and aloesin; A comparative study using two in vitro absorption models.

    PubMed

    Park, Mi-Young; Kwon, Hoon-Jeong; Sung, Mi-Kyung

    2009-01-01

    Aloe products are one of the top selling health-functional foods in Korea, however the adequate level of intake to achieve desirable effects are not well understood. The objective of this study was to determine the intestinal uptake and metabolism of physiologically active aloe components using in vitro intestinal absorption model. The Caco-2 cell monolayer and the everted gut sac were incubated with 5-50 microM of aloin, aloe-emodin, and aloesin. The basolateral appearance of test compounds and their glucuronosyl or sulfated forms were quantified using HPLC. The % absorption of aloin, aloe-emodin, and aloesin was ranged from 5.51% to 6.60%, 6.60% to 11.32%, and 7.61% to 13.64%, respectively. Up to 18.15%, 18.18%, and 38.86% of aloin, aloe-emodin, and aloesin, respectively, was absorbed as glucuronidated or sulfated form. These results suggest that a significant amount is transformed during absorption. The absorption rate of test compounds except aloesin was similar in two models; more aloesin was absorbed in the everted gut sac than in the Caco-2 monolayer. These results provide information to establish adequate intake level of aloe supplements to maintain effective plasma level.

  14. Shock absorption in lumbar disc prosthesis: a preliminary mechanical study.

    PubMed

    LeHuec, J C; Kiaer, T; Friesem, T; Mathews, H; Liu, M; Eisermann, L

    2003-08-01

    Lumbar disc prostheses have been used in treating symptomatic degenerative disc diseases. A few prostheses of the ball-socket design are currently available for clinical use, the joint mechanism being materialized either with a hard polymer core or a metal-to-metal couple. Other prostheses of "shock absorber" design were not available at the time of the study. The objective of this work was to establish whether there was a difference in the shock absorption capacity between a device having an ultra-high-molecular-weight polyethylene center core and a device having a metal-on-metal bearing. Vibration and shock loading were applied to two lumbar total disc prostheses: PRODISC, manufactured by Spine Solutions, and MAVERICK Total Disc Replacement, manufactured by Medtronic Sofamor Danek. The shock absorption capacity of the device was evaluated by comparing the input and the output force measurements. The disc prosthesis was mounted onto a test apparatus. Each side of the device was equipped with a force sensor. The input shock load and the output resulting forces were simultaneously measured and recorded. The loading force pattern included 1). a static preload of 350 N plus an oscillating vibration of 100 N with frequency sweeping from 0 to 100 Hz and 2). a sudden shock load of 250 N applied over a 0.1-second interval. Both input and output signal data were processed and were transformed into their frequency spectrums. The vibration and shock transmissibility of the device, defined as the ratio of the output spectrum over the input spectrum, were calculated in sweeping the frequency from 0 to 100 Hz. The phase deviation was calculated to characterize the shock absorber effects. For both tested devices under vibration and shock loading, the phase angle displacement between the input and the output signals was 10 degrees. Under oscillating vibration loading, both tested devices had a transmission ratio higher than 99.8%. Over the frequency interval 1-100 Hz, the

  15. Light Scattering and Absorption Studies of Sickle Cell Hemoglobin

    NASA Astrophysics Data System (ADS)

    Kim-Shapiro, Daniel

    1997-11-01

    The use of physical techniques has been very important in understanding the pathophysiology of sickle cell disease. In particular, light scattering and absorption studies have been used to measure the kinetics of sickle cell hemoglobin polymerization and depolymerization (melting). The theory of sickle cell polymerization that has been derived and tested by these methods has not only led to an increased understanding of the pathophysiology of the disease but has also led to improved treatment strategies. Sickle cell disease effects about 1 out of 600 people of African descent born in the United States. The disease is caused by a mutant form of hemoglobin (the oxygen transporting molecule in the blood), hemoglobin S (HbS), which differs from normal adult hemoglobin by the substitution of a single amino acid for another. The polymerization of HbS, which occurs under conditions of low oxygen pressure, causes distortion and increased rigidity of the sickle red blood cell that leads to blockage of the capillaries and a host of resulting complications. The disease is associated with tissue damage, severe painful crises and a high degree of mortality. Light scattering studies of purified HbS and whole cells (conducted by F.A. Ferrone, J. Hofrichter, W.A. Eaton, and their associates) have been used to determine the mechanism of HbS polymerization. Polymerization will generally not occur when the hemoglobin is in an oxygen-rich environment. The question is, when HbS is rapidly deoxygenated (as it is when going from the lungs to the tissues) what is the kinetics of polymerization? Photolysis methods were used to rapidly deoxygenate HbS and light scattering was used as a function of time to measure the kinetics of polymerization. Polarized light scattering may be a more effective way to measure polymer content than total intensity light scattering. It was found that no polymerization occurs during a period of time called the delay time and subsequent polymerization occurs

  16. Mechanism of Formation of Copper(II) Chloro Complexes Revealed by Transient Absorption Spectroscopy and DFT/TDDFT Calculations.

    PubMed

    Mereshchenko, Andrey S; Olshin, Pavel K; Karabaeva, Kanykey E; Panov, Maxim S; Wilson, R Marshall; Kochemirovsky, Vladimir A; Skripkin, Mikhail Yu; Tveryanovich, Yury S; Tarnovsky, Alexander N

    2015-07-16

    Copper(II) complexes are extremely labile with typical ligand exchange rate constants on the order of 10(6)-10(9) M(-1) s(-1). As a result, it is often difficult to identify the actual formation mechanism of these complexes. In this work, using UV-vis transient absorption when probing in a broad time range (20 ps to 8 μs) in conjunction with DFT/TDDFT calculations, we studied the dynamics and underlying reaction mechanisms of the formation of extremely labile copper(II) CuCl4(2-) chloro complexes from copper(II) CuCl3(-) trichloro complexes and chloride ions. These two species, produced via photochemical dissociation of CuCl4(2-) upon 420 nm excitation into the ligand-to-metal-charge-transfer electronic state, are found to recombine into parent complexes with bimolecular rate constants of (9.0 ± 0.1) × 10(7) and (5.3 ± 0.4) × 10(8) M(-1) s(-1) in acetonitrile and dichloromethane, respectively. In dichloromethane, recombination occurs via a simple one-step addition. In acetonitrile, where [CuCl3](-) reacts with the solvent to form a [CuCl3CH3CN](-) complex in less than 20 ps, recombination takes place via ligand exchange described by the associative interchange mechanism that involves a [CuCl4CH3CN](2-) intermediate. In both solvents, the recombination reaction is potential energy controlled.

  17. Theoretical and experimental study on the electronic structure and optical absorption properties of P-doped TiO 2

    NASA Astrophysics Data System (ADS)

    Xu, Ling; Tang, Chao-Qun; Qian, Jun; Huang, Zong-Bin

    2010-02-01

    Phosphorus-doped nanosized TiO 2 powders were prepared by a sol-gel technology. The optical absorption studies revealed that the spectral responses of phosphorus-doped (P-doped) TiO 2 powders shift to the visible light region. The optimum phosphorus (P) content in our experiments is 16.7% (mol), and the corresponding absorption edge shifts to 450 nm. Furthermore, our ab initio calculations support the conclusion that the doping of phosphorus can reduce the band gap by mixing the P 3p states with O 2p states. The theoretical lattice parameters and optimum phosphorus content are in agreement with the experimental results.

  18. Theoretical Study of New Combined Absorption-Ejector Refrigeration System

    NASA Astrophysics Data System (ADS)

    Abed, A. M.; Sopian, K.; Alghoul, M. A.; Al-Shamani, A. N.; Ruslan, M. H.; Mat, S.

    2015-09-01

    An improved system of the new combined single stage absorption cycle operated with NH3/H2O as working fluid was performed. In order to enhance performance the cycle a new configuration of absorption system was utilized. The performances of two configurations of the combined absorption cycle were compared; a) with common solution heat exchanger and b) divided the streamline of solution heat exchanger to recover the internal heat. Based on the analysis, it has been shown that the second configuration a significant reduction of the required generator and absorber loads by about 20% and 17% respectively, with increased coefficient of performance (COP) about 12% compared to the first configuration. This improvement in the overall COP is found due to improve energy utilization efficiency significantly.

  19. Study on moisture absorption and sweat discharge of honeycomb polyester fiber

    NASA Astrophysics Data System (ADS)

    Feng, Aifen; Zhang, Yongjiu

    2015-07-01

    The moisture absorption and liberation properties of honeycomb polyester fiber were studied in order to understand its moisture absorption and sweat discharge. Through testing moisture absorption and liberation regains of honeycomb polyester fiber and normal polyester fiber in standard atmospheric conditions, their moisture absorption and liberation curves were depicted, and the regression equations of moisture regains to time during their reaching the balance of moisture absorption and moisture liberation were obtained according to the curves. Their moisture absorption and liberation rate curves were analyzed and the regression equations of the rates to time were obtained. The results shows that the moisture regain of honeycomb polyester fiber is much bigger than the normal polyester fiber's, and the initial moisture absorption and moisture liberation rates of the former are much higher than the latter's, so that the moisture absorbance and sweat discharge of honeycomb polyester fiber are excellent.

  20. Protonation effects on the UV/Vis absorption spectra of imatinib: a theoretical and experimental study.

    PubMed

    Grante, Ilze; Actins, Andris; Orola, Liana

    2014-08-14

    An experimental and theoretical investigation of protonation effects on the UV/Vis absorption spectra of imatinib showed systematic changes of absorption depending on the pH, and a new absorption band appeared below pH 2. These changes in the UV/Vis absorption spectra were interpreted using quantum chemical calculations. The geometry of various imatinib cations in the gas phase and in ethanol solution was optimized with the DFT/B3LYP method. The resultant geometries were compared to the experimentally determined crystal structures of imatinib salts. The semi-empirical ZINDO-CI method was employed to calculate the absorption lines and electronic transitions. Our study suggests that the formation of the extra near-UV absorption band resulted from an increase of imatinib trication concentration in the solution, while the rapid increase of the first absorption maximum could be attributed to both the formation of imatinib trication and tetracation.

  1. 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.

  2. A study of the absorption features of Makemake

    NASA Astrophysics Data System (ADS)

    Alvarez-Candal, A.; Pinilla-Alonso, N.; Ortiz, J.; Duffard, R.; Carvano, J.; de Pra, M.

    2014-07-01

    Most transneptunian objects do not show prominent absorption features due to the size and location [1]. Nevertheless, absorption due to water ice and volatile ices do appear on a few large objects, particularly those that have good signal-to-noise-ratio spectra. In particular, methane appears in three dwarf planets (Pluto, Eris, and Makemake), as well as in some smaller objects, such as Quaoar and probably Sedna, and in Neptune's satellite Triton. Methane has such intense absorption features that even small amounts of methane on the surface dominate the reflectance spectra in the visible and near-infrared range, making it a great tool to probe surfaces, especially, considering that the depth of the bands could be used as a proxy for physical depths and that shifts in the bands with respect to laboratory measurements could point to possible dilutions (as seen in Pluto and Eris; for instance [3] and references therein). Aiming at gaining a deeper insight into Makemake's surface through its methane absorption bands, we have observed it with X-Shooter at the VLT with a medium spectral resolution in the range of 0.4--1.8 microns. In this work, we present the results of comparing these features with those of methane in the laboratory and the same features in Eris and Pluto, within the context of methane-dominated spectra of dwarf planets.

  3. [Study of Terahertz Amplitude Imaging Based on the Mean Absorption].

    PubMed

    Zhang, Zeng-yan; Ji, Te; Xiao, Ti-qiao; Zhao, Hong-wei; Chen, Min; Yu, Xiao-han; Tong, Ya-jun; Zhu, Hua-chun; Peng, Wei-wei

    2015-12-01

    A new method of terahertz (THz) imaging based on the mean absorption is proposed. Terahertz radiation is an electromagnetic radiation in the range between millimeter waves and far infrared. THz pulse imaging emerges as a novel tool in many fields because of its low energy and non-ionizing character, such as material, chemical, biological medicine and food safety. A character of THz imaging technique is it can get large amount of information. How to extract the useful parameter from the large amount of information and reconstruct sample's image is a key technology in THz imaging. Some efforts have been done for advanced visualization methods to extract the information of interest from the raw data. Both time domain and frequency domain visualization methods can be applied to extract information on the physical properties of samples from THz imaging raw data. The process of extracting useful parameter from raw data of the new method based on the mean absorption was given in this article. This method relates to the sample absorption and thickness, it delivers good signal to noise ratio in the images, and the dispersion effects are cancelled. A paper with a "THz" shape hole was taken as the sample to do the experiment. Traditional THz amplitude imaging methods in time domain and frequency domain are used to achieve the sample's image, such as relative reduction of pulse maximum imaging method, relative power loss imaging method, and relative power loss at specific frequency imaging method. The sample's information that reflected by these methods and the characteristics of these methods are discussed. The method base on the mean absorption within a certain frequency is also used to reconstruct sample's image. The experimental results show that this new method can well reflect the true information of the sample. And it can achieve a clearer image than the other traditional THz amplitude imaging methods. All the experimental results and theoretical analyses indicate that

  4. Revealing electronic structure changes in Chevrel phase cathodes upon Mg insertion using X-ray absorption spectroscopy

    SciTech Connect

    Wan, Liwen F.; Wright, Joshua; Perdue, Brian R.; Fister, Timothy T.; Kim, Soojeong; Apblett, Christopher A.; Prendergast, David

    2016-06-10

    Following previous work predicting the electronic response of the Chevrel phase Mo6S8 upon Mg insertion (Thole et al., Phys. Chem. Chem. Phys., 2015, 17, 22548), we provide the experimental proof, evident in X-ray absorption spectroscopy, to illustrate the charge compensation mechanism of the Chevrel phase compound during Mg insertion and de-insertion processes.

  5. Non-destructive studies of fuel pellets by neutron resonance absorption radiography and thermal neutron radiography

    NASA Astrophysics Data System (ADS)

    Tremsin, A. S.; Vogel, S. C.; Mocko, M.; Bourke, M. A. M.; Yuan, V.; Nelson, R. O.; Brown, D. W.; Feller, W. B.

    2013-09-01

    Many isotopes in nuclear materials exhibit strong peaks in neutron absorption cross sections in the epithermal energy range (1-1000 eV). These peaks (often referred to as resonances) occur at energies specific to particular isotopes, providing a means of isotope identification and concentration measurements. The high penetration of epithermal neutrons through most materials is very useful for studies where samples consist of heavy-Z elements opaque to X-rays and sometimes to thermal neutrons as well. The characterization of nuclear fuel elements in their cladding can benefit from the development of high resolution neutron resonance absorption imaging (NRAI), enabled by recently developed spatially-resolved neutron time-of-flight detectors. In this technique the neutron transmission of the sample is measured as a function of spatial location and of neutron energy. In the region of the spectra that borders the resonance energy for a particular isotope, the reduction in transmission can be used to acquire an image revealing the 2-dimensional distribution of that isotope within the sample. Provided that the energy of each transmitted neutron is measured by the neutron detector used and the irradiated sample possesses neutron absorption resonances, then isotope-specific location maps can be acquired simultaneously for several isotopes. This can be done even in the case where samples are opaque or have very similar transmission for thermal neutrons and X-rays or where only low concentrations of particular isotopes are present (<0.1 atom% in some cases). Ultimately, such radiographs of isotope location can be utilized to measure isotope concentration, and can even be combined to produce three-dimensional distributions using tomographic methods. In this paper we present the proof-of-principle of NRAI and transmission Bragg edge imaging performed at Flight Path 5 (FP5) at the LANSCE pulsed, moderated neutron source of Los Alamos National Laboratory. A set of urania mockup

  6. Study on Absorption Heat Pump Using Untapped Energy Resource

    NASA Astrophysics Data System (ADS)

    Okamoto, Hiroaki; Hihara, Eiji; Bando, Shigeru; Oka, Masahiro; Ichikawa, Toru; Kojima, Hiroshi

    The spread of absorption heat pump is considered an effective strategy to reduce the emission of greenhouse gases andthe heat island impact. However, its large volume and low efficiency as compare to vapor-compression system haverestricted its application area. In order to develop a compact and high-efficiency absorption heat pump, we propose a newtype of system which adopting triple effect cycle at cooling, while double effect at heating. In addition, unused energy,such as sewage water, is used in this system to improve the COP furthermore. System performances were evaluated by discussing the COP, highest pressure, highest temperature, strongest solutionconcentration, and energy consumption at part-load operation. By using sewage water as heat source, COP increaseswhile the highest pressure, highest temperature and strongest solution concentration decrease. From a standpointofperformance at heating and energy consumption, it is found that the proposed system works well and more effective thanthe existing system.

  7. Infrared band absorptance correlations and applications to nongray radiation. [mathematical models of absorption spectra for nongray atmospheres in order to study air pollution

    NASA Technical Reports Server (NTRS)

    Tiwari, S. N.; Manian, S. V. S.

    1976-01-01

    Various mathematical models for infrared radiation absorption spectra for atmospheric gases are reviewed, and continuous correlations for the total absorptance of a wide band are presented. Different band absorptance correlations were employed in two physically realistic problems (radiative transfer in gases with internal heat source, and heat transfer in laminar flow of absorbing-emitting gases between parallel plates) to study their influence on final radiative transfer results. This information will be applied to the study of atmospheric pollutants by infrared radiation measurement.

  8. Atomic absorption determination of tin in foods: collaborative study.

    PubMed

    Elkins, E R; Sulek, A

    1979-09-01

    Samples of green beans, applesauce, and a fruit juice were fortified with tin at 3 levels. Collaborators were asked to digest the samples, using HNO3-H2SO4, add methanol to enhance the absorption signal, and aspirate directly, using a nitrous oxide-acetylene flame. Results were received from 8 laboratories including 4 from Europe. However, only 6 laboratories used the prescribed methodology. All results were considered acceptable. The method has been adopted as interim official first action.

  9. Study of Water Absorption Lines in the Near Infrared

    DTIC Science & Technology

    1975-02-17

    the absorption coefficient is better approximated by the sum of Matcha -N«. oec short range contribution and W-BB dispersion contribution. The...and W. Byers Brown, Molecular Physics 2S, 1105 (1973). 5. R. L. Matcha and R. K. Nesbet, Phys. Rev. 1_6_0, 72 (1967). I H. B. Levine, Phys. Rev...reasurcrents of Ouren, ^eltqen Gaide, Helbing and Pauly. The dipole moment function is taken from ab initio 9 calculations of Matcha and Nesbet. With

  10. Total Absorption Study of Beta Decays Relevant for Nuclear Applications and Nuclear Structure

    SciTech Connect

    Algora, A.; Valencia, E.; Taín, J.L.; Jordan, M.D.; Agramunt, J.; Rubio, B.; Estevez, E.; Molina, F.; Montaner, A.; Guadilla, V.; Fallot, M.; Porta, A.; Zakari-Issoufou, A.-A.; Bui, V.M.; and others

    2014-06-15

    An overview is given of our activities related to the study of the beta decay of neutron rich nuclei relevant for nuclear applications. Recent results of the study of the beta decay of {sup 87,88}Br using a new segmented total absorption spectrometer are presented. The measurements were performed at the IGISOL facility using trap-assisted total absorption spectroscopy.

  11. Total Absorption Study of Beta Decays Relevant for Nuclear Applications and Nuclear Structure

    SciTech Connect

    Algora, A.; Valencia, E.; Tain, J. L.; Jordan, M. D.; Agramunt, J.; Rubio, B.; Estevez, E.; Molina, F.; Montaner, A.; Guadilla, V.; Fallot, M.; Podolyak, Zs.; Regan, P. H.; Gelletly, W.; Bowry, M.; Mason, P.; Farrelly, G. F.; Rissanen, J.; Eronen, T.; Moore, I.; Penttila, H.; Aysto, J.; Eloma, V.; Hakala, J.; Jokinen, A.; Kolkinen, V.; Reponen, M.; Sonnenschein, V.; Cano-Ott, D.; Martinez, T.; Mendoza, E.; Garcia, A. R.; Gomez-Hornillos, M. B.; Gorlychev, V.; Caballero-Folch, R.; Kondev, F. G.; Sonzogni, A. A.

    2014-06-01

    We present an overview of our activities related to the study of the beta decay of neutron rich nuclei relevant for nuclear applications. Recent results of the study of the beta decay of Br using a new segmented total absorption spectrometer are presented. Our measurements were performed at the IGISOL facility using trap-assisted total absorption spectroscopy.

  12. Calorimetry study of microwave absorption of some solid materials.

    PubMed

    He, Chun Lin; Ma, Shao Jian; Su, Xiu Juan; Chen, Yan Qing; Liang, Yu Shi

    2013-01-01

    In practice, the dielectric constant of a material varies the applied frequency the material composition, particle size, purity, temperature, physical state (solid or liquid), and moisture content. All of these parameters might change during processing, therefore, it is difficult to predict how well a material will absorb microwave energy in a given process. When the temperature is measured by a digital thermometer, it could not accurately reflect the true temperature of the bulk materials, especially for mixed materials. Thus, in this paper we measured the microwave absorption characteristics of different materials by calorimetry. The microwave power levels, irradiation times, and masses of the materials were varied. It was difficult to predict the microwave energy absorption characteristics of reagent-grade inorganic compounds based on their color, metallic cation, or water stoichiometry. CuO, MnO2, Fe3O4, and MnSO4 x H2O (Taishan) strongly absorbed microwave energy. Most of the remaining inorganic compounds were poor absorbers, with silica hardly absorbing any microwave energy. Carbon-based materials had significantly different microwave absorption characteristics. Activated carbon and coke were especially sensitive to microwaves, but different types of coal were poor absorbers. The jamesonite concentrate absorbed microwave energy strongly, while the zinc concentrate was a poor absorber.

  13. Study of nonlinear optical absorption properties of V2O5 nanoparticles in the femtosecond excitation regime

    NASA Astrophysics Data System (ADS)

    Molli, Muralikrishna; Bhat Kademane, Abhijit; Pradhan, Prabin; Sai Muthukumar, V.

    2016-08-01

    In this work, we report for the first time, the nonlinear optical absorption properties of vanadium pentoxide (V2O5) nanoparticles in the femtosecond excitation regime. V2O5 nanoparticles were synthesized through solution combustion technique. The as-synthesized samples were further characterized using XRD, FESEM, EDAX, TEM and UV-visible spectroscopy. X-ray diffraction results revealed the crystalline nature of the nanoparticles. Electron microscopy studies showed the size of the nanoparticles to be ~200 nm. Open-aperture z-scan technique was employed to study the nonlinear optical absorption behavior of the synthesized samples using a 100-fs laser pulses at 800 nm from a regeneratively amplified Ti: sapphire laser. The mechanism of nonlinear absorption was found to be a three-photon absorption process which was explained using the density of states of V2O5 obtained using density functional theory. These nanoparticles exhibit strong intensity-dependent nonlinear optical absorption and hence could be considered for optical-power-limiting applications.

  14. High-pressure Evolution of Fe2O3 Electronic Structure Revealed by X-ray Absorption

    SciTech Connect

    S Wang; W Mao; A Sorini; C Chen; T Devereaux; Y Ding; Y Xiao; P Chow; N Hiraoka; et al.

    2011-12-31

    We report the high-pressure measurement of the Fe K edge in hematite (Fe{sub 2}O{sub 3}) by x-ray absorption spectroscopy in partial fluorescence yield geometry. The pressure-induced evolution of the electronic structure as Fe{sub 2}O{sub 3} transforms from a high-spin insulator to a low-spin metal is reflected in the x-ray absorption pre-edge. The crystal-field splitting energy was found to increase monotonically with pressure up to 48 GPa, above which a series of phase transitions occur. Atomic multiplet, cluster diagonalization, and density-functional calculations were performed to simulate the pre-edge absorption spectra, showing good qualitative agreement with the measurements. The mechanism for the pressure-induced electronic phase transitions of Fe{sub 2}O{sub 3} is discussed and it is shown that ligand hybridization significantly reduces the critical high-spin/low-spin transition pressure.

  15. High-Pressure Evolution of Fe2O3 Electronic Structure Revealed by X-ray Absorption

    SciTech Connect

    Kao, Chi-Chang

    2011-08-12

    We report the first high pressure measurement of the Fe K-edge in hematite (Fe{sub 2}O{sub 3}) by X-ray absorption spectroscopy in partial fluorescence yield geometry. The pressure-induced evolution of the electronic structure as Fe{sub 2}O{sub 3} transforms from a high-spin insulator to a low-spin metal is reflected in the x-ray absorption pre-edge. The crystal field splitting energy was found to increase monotonically with pressure up to 48 GPa, above which a series of phase transitions occur. Atomic multiplet, cluster diagonalization, and density-functional calculations were performed to simulate the pre-edge absorption spectra, showing good qualitative agreement with the measurements. The mechanism for the pressure-induced phase transitions of Fe{sub 2}O{sub 3} is discussed and it is shown that ligand hybridization significantly reduces the critical high-spin/low-spin gap pressure.

  16. Laser engines operating by resonance absorption. [thermodynamic feasibility study

    NASA Technical Reports Server (NTRS)

    Garbuny, M.; Pechersky, M. J.

    1976-01-01

    Basic tutorial article on the thermodynamic feasibility of laser engines at the present state of the art. Three main options are considered: (1) laser power applied externally to a heat reservoir (boiler approach); (2) internal heating of working fluid by resonance absorption; and (3) direct conversion of selective excitation into work. Only (2) is considered practically feasible at present. Basic concepts and variants, efficiency relations, upper temperature limits of laser engines, selection of absorbing gases, engine walls, bleaching, thermodynamic cycles of optimized laser engines, laser-powered turbines, laser heat pumps are discussed. Photon engines and laser dissociation engines are also considered.

  17. Adsorption of mercury on lignin: combined surface complexation modeling and X-ray absorption spectroscopy studies.

    PubMed

    Lv, Jitao; Luo, Lei; Zhang, Jing; Christie, Peter; Zhang, Shuzhen

    2012-03-01

    Adsorption of mercury (Hg) on lignin was studied at a range of pH values using a combination of batch adsorption experiments, a surface complexation model (SCM) and synchrotron X-ray absorption spectroscopy (XAS). Surface complexation modeling indicates that three types of acid sites on lignin surfaces, namely aliphatic carboxylic-, aromatic carboxylic- and phenolic-type surface groups, contributed to Hg(II) adsorption. The bond distance and coordination number of Hg(II) adsorption samples at pH 3.0, 4.0 and 5.5 were obtained from extended X-ray absorption fine structure (EXAFS) spectroscopy analysis. The results of SCM and XAS combined reveal that the predominant adsorption species of Hg(II) on lignin changes from HgCl(2)(0) to monodentate complex -C-O-HgCl and then bidentate complex -C-O-Hg-O-C- with increasing pH value from 2.0 to 6.0. The good agreement between SCM and XAS results provides new insight into understanding the mechanisms of Hg(II) adsorption on lignin.

  18. Solvent effects on the absorption and fluorescence spectra of rhaponticin: Experimental and theoretical studies

    NASA Astrophysics Data System (ADS)

    Sun, Yang; Liang, Xuhua; Zhao, Yingyong; Fan, Jun

    2013-02-01

    Rhaponticin (RH) possesses a variety of pharmacological activities including potent antitumor, antitumor-promoting, antithrombotic, antioxidant and vasorelaxant effects. The fundamental photophysics of RH is not well understood. In this work, solvent effect on the photoluminescence behavior of RH was studied by fluorescence and absorption spectra. The bathchromic shift was observed in absorption and fluorescence spectra with the increase of solvents polarity, which implied that transition involved was π → π*. A quantitative estimation of the contribution from different solvatochromic parameters, like normalized transition energy value (ETN), was made using the linear stokes shift (Δν) relationship based on the Lippert-Suppan equation. The ground state and excited state dipole moments were calculated by quantum-mechanical second-order perturbation method as a function of the dielectric constant (ɛ) and refractive index (n). The result was found to be 2.23 and 3.67 D in ground state and excited state respectively. The density functional theory (DFT) was used to obtain the most stable structure, electronic excitation energy, dipole moments and charge distribution. The analysis revealed that the RH exhibited strong photoinduced intramolecular charge transfer (ICT), and the intermolecular hydrogen bonding ability of the solvent was the most important parameter to characterize the photophysics behavior of RH. The hydrogen bonding effect occurred at the localized electron-acceptor oxygen at the glycoside bond. The experimental and theoretical results would help us better understand the photophysical properties of RH.

  19. Study of nonlinear optical absorption properties of Sb2Se3 nanoparticles in the nanosecond and femtosecond excitation regime

    NASA Astrophysics Data System (ADS)

    Molli, Muralikrishna; Pradhan, Prabin; Dutta, Devarun; Jayaraman, Aditya; Bhat Kademane, Abhijit; Muthukumar, V. Sai; Kamisetti, Venkataramaniah; Philip, Reji

    2016-05-01

    In this work, we report for the first time, the nonlinear optical absorption properties of antimony selenide (Sb2Se3) nanoparticles synthesized through solvothermal route. X-ray diffraction results revealed the crystalline nature of the nanoparticles. Electron microscopy studies revealed that the nanoparticles are in the range of 10-40 nm. Elemental analysis was performed using EDAX. The nanosecond optical limiting effect was characterized by using fluence-dependent transmittance measurements with 15-ns laser pulses at 532 and 1064 nm excitation wavelengths. Mechanistically, effective two-photon (2PA) absorption and nonlinear scattering processes were the dominant nonlinear processes at both the wavelengths. At 800 nm excitation in the femtosecond regime (100 fs), the nonlinear optical absorption was found to be a three-photon (3PA) process. Both 2PA and 3PA processes were explained using the band structure and density of states of Sb2Se3 obtained using density functional theory. These nanoparticles exhibit strong intensity-dependent nonlinear optical absorption and hence could be considered to have optical power-limiting applications in the visible range.

  20. Iron absorption in raw and cooked bananas: A field study using stable isotopes in women

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Banana is a staple food in many regions with high iron deficiency and may be a potential vehicle for iron fortification. However, iron absorption from bananas is not known. The objective of this study was to evaluate total iron absorption from raw and cooked bananas. Thirty women (34.9 +/- 6.6 years...

  1. Studies of selected transuranium and lanthanide triiodides under pressure using absorption spectrophotometry

    SciTech Connect

    Haire, R.G.; Young, J.P.; Peterson, J.R.; Benedict, U.

    1986-01-01

    The anhydrous triiodides of plutonium, americium, and curium under pressure have been investigated using absorption spectrophotometry. These initial studies on plutonium and curium triiodides together with the published data for americium triiodide show that the rhombohedral (BiI/sub 3/-type structure) form of these compounds can be converted to the same orthorhombic (PuBr/sub 3/-type structure) form by applying pressure at room temperature. Absorption spectrophotometry can often differentiate between two crystallographic forms of materials and has been used in the present high pressure studies to monitor the effects of pressure on the triiodides. A complication in these studies of the triiodides is a significant shift of their absorption edges from the near uv to the visible spectral region with pressure. With curium triiodide this shift causes interference with the major f-f absorption peaks and precludes identification by absorption spectrophotometry of the high pressure phase of CmI/sub 3/. 21 refs., 2 figs.

  2. Case study for a high temperature ultraviolet absorption hygrometer

    SciTech Connect

    Gersh, M.E.; Bangert, M. ); Matthew, M.W. ); Lowe, R. )

    1989-10-01

    The motivation for this program is the observation that the use of reliable and accurate hygrometers to monitor or control the processes in industrial drying chambers could result in a significant reduction in the energy usage of the United States. At the present time, there are no commercially available hygrometers which have the required characteristics of a measurement capability at simultaneously high temperature and humidity, along with the ability to operate for long periods in a severely contaminating and/or particle-laden environment. The goal of this program was the development of an industrial hygrometer which can be employed to monitor the humidity during industrial drying operations. This requires a device which can operate at temperatures up to 500{degree}C, at high humidity (50--100%), and in environments containing particulates and/or fouling or corrosive vapors. The approach taken by Spectral Sciences, Inc. (SSI) for the development of a practical hygrometer for these operational conditions is the use of the differential absorption of light by water vapor. Light absorbed at two ultraviolet (UV) wavelengths determines the absolute humidity (measurement of temperature by conventional means also permits the determination of relative humidity). Due to the use of this principle to measure the humidity, we have termed this instrument an Ultraviolet Absorption Hygrometer (UVAH). 11 figs.

  3. Electronic structure of an [FeFe] hydrogenase model complex in solution revealed by X-ray absorption spectroscopy using narrow-band emission detection.

    PubMed

    Leidel, Nils; Chernev, Petko; Havelius, Kajsa G V; Schwartz, Lennart; Ott, Sascha; Haumann, Michael

    2012-08-29

    High-resolution X-ray absorption spectroscopy with narrow-band X-ray emission detection, supported by density functional theory calculations (XAES-DFT), was used to study a model complex, ([Fe(2)(μ-adt)(CO)(4)(PMe(3))(2)] (1, adt = S-CH(2)-(NCH(2)Ph)-CH(2)-S), of the [FeFe] hydrogenase active site. For 1 in powder material (1(powder)), in MeCN solution (1'), and in its three protonated states (1H, 1Hy, 1HHy; H denotes protonation at the adt-N and Hy protonation of the Fe-Fe bond to form a bridging metal hydride), relations between the molecular structures and the electronic configurations were determined. EXAFS analysis and DFT geometry optimization suggested prevailing rotational isomers in MeCN, which were similar to the crystal structure or exhibited rotation of the (CO) ligands at Fe1 (1(CO), 1Hy(CO)) and in addition of the phenyl ring (1H(CO,Ph), 1HHy(CO,Ph)), leading to an elongated solvent-exposed Fe-Fe bond. Isomer formation, adt-N protonation, and hydride binding caused spectral changes of core-to-valence (pre-edge of the Fe K-shell absorption) and of valence-to-core (Kß(2,5) emission) electronic transitions, and of Kα RIXS data, which were quantitatively reproduced by DFT. The study reveals (1) the composition of molecular orbitals, for example, with dominant Fe-d character, showing variations in symmetry and apparent oxidation state at the two Fe ions and a drop in MO energies by ~1 eV upon each protonation step, (2) the HOMO-LUMO energy gaps, of ~2.3 eV for 1(powder) and ~2.0 eV for 1', and (3) the splitting between iron d(z(2)) and d(x(2)-y(2)) levels of ~0.5 eV for the nonhydride and ~0.9 eV for the hydride states. Good correlations of reduction potentials to LUMO energies and oxidation potentials to HOMO energies were obtained. Two routes of facilitated bridging hydride binding thereby are suggested, involving ligand rotation at Fe1 for 1Hy(CO) or adt-N protonation for 1HHy(CO,Ph). XAES-DFT thus enables verification of the effects of ligand

  4. Anomalous evolution of broadband optical absorption reveals dynamic solid state reorganization during eumelanin build-up in thin films.

    PubMed

    Bonavolontà, Carmela; Lisio, Corrado de; d'Ischia, Marco; Maddalena, Pasqualino; Manini, Paola; Pezzella, Alessandro; Valentino, Massimo

    2017-03-31

    The origin of eumelanin optical properties remains a formidable conundrum preventing a detailed understanding of the complex photo-protective role of these widespread natural pigments and the rational design of innovative bioinspired materials for optoelectronic applications. Here we report the unusual kinetic and thickness-dependent evolution of the optical properties of black eumelanin polymers generated by spontaneous aerial polymerization of 5,6-dihydroxyindole (DHI) thin films (0.1-1 μm), consistent with peculiar solid state reorganization mechanisms governing broadband absorption. The complete reversal of eumelanin UV-visible transmittance spectrum curvature on passing from 0.2 to 0.5 μm thick films, the marked increase in visible extinction coefficients with increasing film thickness and the higher UV extinction coefficients in slowly vs. rapidly generated polymers concur to support distinct dynamic regimes of solid-state molecular reorganization at the nanoscale level and to do affect the development of broadband visible absorption. Solid state control of molecular reorganization disclosed herein may delineate new rational strategies for tuning optical properties in eumelanin thin films for optoelectronic applications.

  5. Studies of Arctic Middle Atmosphere Chemistry using Infrared Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Lindenmaier, Rodica

    The objective of this Ph.D. project is to investigate Arctic middle atmosphere chemistry using solar infrared absorption spectroscopy. These measurements were made at the Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka, Nunavut, which is operated by the Canadian Network for the Detection of Atmospheric Change (CANDAC). This research is part of the CANDAC/PEARL Arctic Middle Atmosphere Chemistry theme and aims to improve our understanding of the processes controlling the stratospheric ozone budget using measurements of the concentrations of stratospheric constituents. The instrument, a Bruker IFS 125HR Fourier transform infrared (FTIR) spectrometer, has been specifically designed for high-resolution measurements over a broad spectral range and has been used to measure reactive species, source gases, reservoirs, and dynamical tracers at PEARL since August 2006. The first part of this research focuses on the optimization of ozone retrievals, for which 22 microwindows were studied and compared. The spectral region from 1000 to 1005 cm-1 was found to be the most sensitive in both the stratosphere and troposphere, giving the highest number of independent pieces of information and the smallest total error for retrievals at Eureka. Similar studies were performed in coordination with the Network for the Detection of Atmospheric Composition Change for nine other species, with the goal of improving and harmonizing the retrieval parameters among all Infrared Working Group sites. Previous satellite validation exercises have identified the highly variable polar conditions of the spring period to be a challenge. In this work, comparisons between the 125HR and ACE-FTS (Atmospheric Chemistry Experiment-Fourier transform spectrometer) from 2007 to 2010 have been used to develop strict criteria that allow the ground and satellite-based instruments to be confidently compared. After applying these criteria, the differences between the two instruments were generally

  6. Photoisomerization of ethyl ferulate: A solution phase transient absorption study

    NASA Astrophysics Data System (ADS)

    Horbury, Michael D.; Baker, Lewis A.; Rodrigues, Natércia D. N.; Quan, Wen-Dong; Stavros, Vasilios G.

    2017-04-01

    Ethyl ferulate (ethyl 4-hydroxy-3-methoxycinnamate) is currently used as a sunscreening agent in commercial sunscreen blends. Recent time-resolved gas-phase measurements have demonstrated that it possesses long-lived (>ns) electronic excited states, counterintuitive to what one might anticipate for an effective sunscreening agent. In the present work, the photodynamics of ethyl ferulate in cyclohexane, are explored using time-resolved transient electronic absorption spectroscopy, upon photoexcitation to the 11ππ∗ and 21ππ∗ states. We demonstrate that ethyl ferulate undergoes efficient non-radiative decay to repopulate the electronic ground state, mediated by trans-cis isomerization. These results strongly suggest that even mild perturbations induced by a non-polar solvent, as may be found in a closer-to-market sunscreen blend, may contribute to our understanding of ethyl ferulate's role as a sunscreening agent.

  7. [Study on temperature dependence of ultraviolet absorption cross sections of nitric oxide at high temperatures].

    PubMed

    Zhou, Jie; Zhang, Shi-Liang; Chen, Xiao-Hu

    2007-07-01

    To study the temperature dependence of ultraviolet absorption characteristics of NO species in flue gas, the absorption cross sections of NO in the spectral region 200-230 nm at temperatures ranging from 285 to 410 K were measured using a grating monochromator with 0.2 nm resolution, a deuterium lamp and a specially-fabricated closed sample cell. The absorption spectrum of NO consists of discrete bands superimposed on a continuous base. Results indicated that discrete absorption bands were present with a fixed wavelength interval of roughly 10.5 nm. The peaks of discrete bands decreased first and started to increase later as the temperature rose from 285 to 410 K, with a maximum relative variation of 19.3%. Peak position and half width of the absorption peaks did not exhibit apparent change with the variation of temperature. Continuous absorption cross section increased monotonously with the temperature, and the variation gradient gradually decrease with wavelength red shift. The absorption cross section of NO should not be considered as constant when applied in online monitoring of NO concentration in flue gas. A compensation calculation of absorption cross section with respect to temperature effect is indispensable for the purpose of improving online measurement precision of NO concentration.

  8. Studies of OH - absorption and optical absorption spectra in LiNbO 3 : Mg, Ti crystals

    NASA Astrophysics Data System (ADS)

    Liu, Jianjun; Zhang, Wanlin; Zhang, Guangyin

    1996-02-01

    The OH - absorption spectra and the UV absorption edges of LiNbO 3 : Mg, Ti crystals have been measured. It is shown that Ti doping raises the Mg doping threshold level, and shifts the absorption edge towards longer wavelengths. The results can be explained by the formation of Mg Li2+Ti Nb4+ pairs after all antisite defects Nb Li have been replaced.

  9. Preparation, characterization and nonlinear absorption studies of cuprous oxide nanoclusters, micro-cubes and micro-particles

    NASA Astrophysics Data System (ADS)

    Sekhar, H.; Narayana Rao, D.

    2012-07-01

    Cuprous oxide nanoclusters, micro-cubes and micro-particles were successfully synthesized by reducing copper(II) salt with ascorbic acid in the presence of sodium hydroxide via a co-precipitation method. The X-ray diffraction and FTIR studies revealed that the formation of pure single-phase cubic. Raman and EPR spectral studies show the presence of CuO in as-synthesized powders of Cu2O. Transmission electron microscopy and field emission scanning electron microscopy data revealed that the morphology evolves from nanoclusters to micro-cubes and micro-particles by increasing the concentration of NaOH. Linear optical measurements show absorption peak maximum shifts towards red with changing morphology from nanoclusters to micro-cubes and micro-particles. The nonlinear optical properties were studied using open aperture Z-scan technique with 532 nm 6 ns laser pulses. Samples-exhibited both saturable as well as reverse saturable absorption. Due to confinement effects (enhanced band gap), we observed enhanced nonlinear absorption coefficient (β) in the case of nanoclusters compared to their micro-cubes and micro-particles.

  10. High resolution UV absorption studies of N2, SO2

    NASA Astrophysics Data System (ADS)

    Smith, Peter L.; Stark, G.; Rufus, J.; Yoshino, K.; Huber, K. P.; Ito, K.; Thorne, A. P.

    The most prominent EUV emission features in the airglows of Titan and Triton, where N2 is the major atmospheric constituent, originate from the N2c'4 1Σu+(v=0) level. We report new photoabsorption measurements of 43 rotational line oscillator strengths in the c'4(0)-X(0) band of N2. These are the first measurements of individual line f-values for this band. Such values, which are important for models of atmospheres at various temperatures, cannot be reliably calculated from band f-values and Hönl-London factors because of perturbations. A summation over the integrated cross sections of the measured lines yields a room temperature band f-value of 0.132±0.020. SO2 is an important constituent of the atmospheres of Io and Venus. Accurate photoabsorption cross section data at the temperatures of these planetary atmospheres are required for the interpretation of SO2 observations and for reliable photochemical models. Our high-resolution (λ/Δλ ≈ 450,000), room-temperature measurements of SO2 absorption cross sections in the wavelength region 198 to 220 nm [Stark et al., JGR Planets, 104, 16,585 (1999)] are being extended to lower temperatures. This work was supported in part by NASA Grant NAG5-6222 to Wellesley College.

  11. Transcriptional analysis of porcine intestinal mucosa infected with Salmonella Typhimurium revealed a massive inflammatory response and disruption of bile acid absorption in ileum.

    PubMed

    Uribe, Juber Herrera; Collado-Romero, Melania; Zaldívar-López, Sara; Arce, Cristina; Bautista, Rocío; Carvajal, Ana; Cirera, Susanna; Claros, M Gonzalo; Garrido, Juan J

    2016-01-07

    Infected pork meat is an important source of non-typhoidal human salmonellosis. Understanding of molecular mechanisms involved in disease pathogenesis is important for the development of therapeutic and preventive strategies. Thus, hereby we study the transcriptional profiles along the porcine intestine during infection with Salmonella Typhimurium, as well as post-transcriptional gene modulation by microRNAs (miRNA). Sixteen piglets were orally challenged with S. Typhimurium. Samples from jejunum, ileum and colon, collected 1, 2 and 6 days post infection (dpi) were hybridized to mRNA and miRNA expression microarrays and analyzed. Jejunum showed a reduced transcriptional response indicating mild inflammation only at 2 dpi. In ileum inflammatory genes were overexpressed (e.g., IL-1B, IL-6, IL-8, IL1RAP, TNFα), indicating a strong immune response at all times of infection. Infection also down-regulated genes of the FXR pathway (e.g., NR1H4, FABP6, APOA1, SLC10A2), indicating disruption of the bile acid absorption in ileum. This result was confirmed by decreased high-density lipoprotein cholesterol in serum of infected pigs. Ileal inflammatory gene expression changes peaked at 2 dpi and tended to resolve at 6 dpi. Furthermore, miRNA analysis of ileum at 2 dpi revealed 62 miRNAs potentially regulating target genes involved in this inflammatory process (e.g., miR-374 and miR-451). In colon, genes involved in epithelial adherence, proliferation and cellular reorganization were down-regulated at 2 and 6 dpi. In summary, here we show the transcriptional changes occurring at the intestine at different time points of the infection, which are mainly related to inflammation and disruption of the bile acid metabolism.

  12. Studies of solvent effects on reaction dynamics using ultrafast transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Harris, Don Ahmasi

    Ultrafast transient absorption spectroscopy was used to investigate the solvent dependent reaction dynamics of two prototypical chemical systems: (1) The ring-opening reaction of 1,3-cyclohexadiene, the isolated chromophore in Provitamin D, and (2) The photolysis of various Vitamin B12 cofactors. We investigated the influence of solvent polarity on the ground state conformational relaxation of 1,3,5-cis hexatriene subsequent to the ring opening of 1,3-cyclohexadiene in methanol and 1-propanol solvents. Comparisons to the conformational relaxation in alkane solvents studied earlier demonstrated a surprising influence of solvent polarity on single bond isomerization. Temperature dependent transient absorption measurements were performed on 1,3,5-cis hexatriene in cyclohexane and 1-propanol to determine the effect of solvent polarity on the activation energy barrier for ground state single bond isomerization. These measurements conclude that the polar solvent lowers the energy barrier for single bond isomerization allowing conformational relaxation to proceed faster in alcohol solvents compared to alkane solvents. With no perceived polar transition state for single bond isomerization, this result disagrees with the conventional view of solvation and differentiates the single bond isomerization dynamics of polyenes from alkanes. Transient absorption spectroscopy was also utilized to study the solvent effects in the photolysis of various B12 cofactors in different environments. We investigated the solvent dependent photolysis of adenosylcobalamin, methylcobalamin, and cyanocobalamin in water and ethylene glycol as a function of solvent temperature. In comparing the radical cage escape of adenosylcobalamin and cyanocobalamin, we determined a larger than expected hydrodynamic radii for the diffusing radicals in water compared to ethylene glycol, thus making necessary a revised perspective of solvent interaction with the diffusing radical. In addition, we investigated the

  13. Studies on absorption and metabolism of palatinose (isomaltulose) in rats.

    PubMed

    Tonouchi, Hidekazu; Yamaji, Taketo; Uchida, Masayuki; Koganei, Megumi; Sasayama, Akina; Kaneko, Tetsuo; Urita, Yoshihisa; Okuno, Masahiro; Suzuki, Kouji; Kashimura, Jun; Sasaki, Hajime

    2011-01-01

    We evaluated the absorption and metabolism of palatinose in rats by the carbohydrate load test and the 13C- and H2-breath tests. We compared the results of these tests with those of sucrose, since sucrose is an isomer of palatinose and generally known to be degraded and absorbed from the small intestine. In the carbohydrate load test, blood glucose and plasma insulin levels after oral administration of palatinose rose more gradually and reached a maximum that was lower than that after sucrose administration. In the 13C-breath test, rats were orally administrated [1-13C]sucrose or [1-13C]palatinose and housed in a chamber. The expired air in the chamber was collected, and the level of 13CO2 in the expired air was measured at appropriate intervals for 360 min. The value of time taken to reach the maximum concentration for expired 13CO2 from [1-13Cglucose] ([1-13Cglc]) and [1-13Cfructose] ([1-13Cfru]) palatinose was significantly longer than that from [1-13Cglc] and [1-13Cfru]sucrose, respectively. The value of area under the curve (AUC) for [1-13Cglc]palatinose was larger than that for [1-13Cglc]sucrose, but AUC for [1-13Cfru] showed no difference between palatinose and sucrose. In the H2-breath test, the concentration of H2 in the expired air was measured for 420 min. H2 was hardly detected with both palatinose and sucrose and no significant difference was observed between the two groups. These results suggest that palatinose is utilised in vivo at a rate equal to that of sucrose.

  14. A comparative study of the PIFA and printed monopole antenna EM absorption.

    PubMed

    Hossain, Md Ikbal; Iqbal Faruque, Mohammad Rashed; Islam, Mohammad Tariqul

    2017-02-01

    This paper represents a comparative study on electromagnetic (EM) absorption in the human head between a printed monopole antenna and a planar inverted-F antenna (PIFA). The specific absorption rate (SAR) values and total absorbed power in the human head phantom are used to evaluate EM absorption for both antennae. Moreover, antenna performances in terms of return loss, radiation efficiency, and gain are also investigated in this study. The finite integration technique (FIT) based on CST Microwave studio and SAM head phantom are used in this study. The antenna performances are measured in an anechoic chamber and the SAR is tested using COMOSAR measurement system. The obtained results indicate that the printed monopole antenna lead to higher EM absorption in the human head as compared to PIFA for both GSM frequencies.

  15. Picosecond absorption studies on the photodissociation of alpha- and beta-nitrosyl hemoglobin monomers

    SciTech Connect

    Guest, C.R.; Noe, L.J.

    1988-10-01

    Transient absorption studies of the pump-probe type were performed on the NO forms of the alpha- and beta-monomers of hemoglobin using a Nd3+ phosphate-glass laser. A second harmonic 531-nm, 8-ps fwhm pulse pumped the Q-band while a delayed continuum generated pulse was used to monitor pi pi* Soret absorption changes in the 410-453-nm region. Photodissociation of nitrosyl alpha- and beta-monomers was found to differ markedly from the tetramer in what we believe to be the formation of a five-coordinate HbNO (with proximal imidazole detached) photoproduct within the first 50 ps after photon absorption.

  16. Study on NO(2) absorption by ascorbic acid and various chemicals.

    PubMed

    Li, Wei; Wu, Cheng-Zhi; Fang, He-Liang; Shi, Yao; Lei, Le-Cheng

    2006-01-01

    Study on NO(2) absorption aimed at seeking a better NO(2) absorption chemical at pH 4.5 approximately 7.0 for application to existing wet flue gas desulfurization (FGD). The results from the double-stirred reactor indicated that ascorbic acid has very high absorption rate at this pH range. The rate constant of ascorbic acid reaction with NO(2) (0 approximately 1,000 x 10(-6) mol/mol) is about 3.54 x 10(6) mol/(Ls) at pH 5.4 approximately 6.5 at 55 degrees C.

  17. Study on NO2 absorption by ascorbic acid and various chemicals*

    PubMed Central

    Li, Wei; Wu, Cheng-zhi; Fang, He-liang; Shi, Yao; Lei, Le-cheng

    2006-01-01

    Study on NO2 absorption aimed at seeking a better NO2 absorption chemical at pH 4.5~7.0 for application to existing wet flue gas desulfurization (FGD). The results from the double-stirred reactor indicated that ascorbic acid has very high absorption rate at this pH range. The rate constant of ascorbic acid reaction with NO2 (0~1000×10−6 mol/mol) is about 3.54×106 mol/(L·s) at pH 5.4~6.5 at 55 °C. PMID:16365924

  18. Trends in reactivity of electrodeposited 3d transition metals on gold revealed by operando soft x-ray absorption spectroscopy during water splitting

    NASA Astrophysics Data System (ADS)

    Velasco-Vélez, J. J.; Jones, Travis E.; Pfeifer, Verena; Dong, Chung-Li; Chen, Yu-Xun; Chen, Chieh-Ming; Chen, Hsin-Yu; Lu, Ying-Rui; Chen, Jin-Ming; Schlögl, R.; Knop-Gericke, A.; Chuang, C.-H.

    2017-01-01

    We activated gold electrodes for their use as electrocatalyst for water splitting by electrodepositing Cu, Ni and Co. A combination of operando x-ray absorption spectroscopy and potentiometric control under aqueous conditions revealed the trends in reactivity yielded by these electrodes, which are directly associated with the cross- and overpotentials as well as the occupancy of the 3d orbitals. It was found that under anodic polarization the materials electrodeposited on gold suffer from a lack of stability, while under cathodic polarization they exhibit stable behavior. The observed activity is strongly related to the lack of stability shown by these composites under anodic polarization revealing a dynamic process ruled by corrosion. By operando x-ray absorption, we established that the overall enhancement of the activity for the oxygen evolution reaction is directly attributable to the cross-potential and corrosion process of the electrodeposited materials. It is associated with the high potential deposition, which is the origin of the incipient oxidation-corrosion resistance of the lattice. We conclude that the observed trends in the total current are directly associated with the loss of oxygen in the metal-oxide lattice and the subsequent dissolution of metallic ions in the electrolyte under anodic polarization.

  19. Nustar Reveals an Intrinsically X-ray Weak Broad Absorption Line Quasar in the Ultraluminous Infrared Galaxy Markarian 231

    NASA Technical Reports Server (NTRS)

    Teng, Stacy H.; Brandt. W. N.; Harrison, F. A.; Luo, B.; Alexander, D. M.; Bauer, F. E.; Boggs, S. E.; Christensen, F. E.; Comastri, A.; Craig, W. W.; Fabian, A. C.; Farrah, D.; Fiore, F.; Gandhi, P.; Grefenstette, B. W.; Hailey, C. J.; Hickox, R. C.; Madsen, K. K.; Ptak, A. F.; Rigby, Jane Rebecca; Risaliti, G.; Saz, C.; Stern, D.; Veilleux, S.; Walton, D. J.; Wik, D. R.; Zhang, W. W.

    2014-01-01

    We present high-energy (3-30 keV) NuSTAR observations of the nearest quasar, the ultraluminous infrared galaxy (ULIRG) Markarian 231 (Mrk 231), supplemented with new and simultaneous low-energy (0.5-8 keV) data from Chandra. The source was detected, though at much fainter levels than previously reported, likely due to contamination in the large apertures of previous non-focusing hard X-ray telescopes. The full band (0.5-30 keV) X-ray spectrum suggests the active galactic nucleus (AGN) in Mrk 231 is absorbed by a patchy and Compton-thin N(sub H) approx. 1.2(sup +0.3) sub-0.3) x 10(exp 23) / sq cm) column. The intrinsic X-ray luminosity L(sub 0.5-30 Kev) approx. 1.0 x 10(exp 43) erg /s) is extremely weak relative to the bolometric luminosity where the 2-10 keV to bolometric luminosity ratio is approx. 0.03% compared to the typical values of 2-15%. Additionally, Mrk 231 has a low X-ray-to-optical power law slope alpha(sub 0X) approx. -1.7. It is a local example of a low-ionization broad absorption line (LoBAL) quasar that is intrinsically X-ray weak. The weak ionizing continuum may explain the lack of mid-infrared [O IV], [Ne V], and [Ne VI] fine-structure emission lines which are present in sources with otherwise similar AGN properties. We argue that the intrinsic X-ray weakness may be a result of the super-Eddington accretion occurring in the nucleus of this ULIRG, and may also be naturally related to the powerful wind event seen in Mrk 231, a merger remnant escaping from its dusty cocoon.

  20. Transient absorption studies of the primary charge separation in photosystem II

    SciTech Connect

    Donovan, B.; Walker, L.A. II; Yocum, C.F.; Sension, R.J.

    1996-02-01

    Femtosecond transient absorption studies of the primary charge separation in photosystem II (PSII) are presented. A careful study of the dependence of the observed signal on laser intensity demonstrates that the multiple excitation of reaction centers produces additional fast components not observed at low excitation energy. In the regime where the observed signals are linear with excitation energy, a 20 {+-} 2 ps rise of the pheophytin anion absorption, bleach of the pheophytin Q{sub {chi}} absorption, and appearance of the chlorophyll cation absorption are observed. Three different protocols, involving varying exposure of the PSII complex to the detergent Triton X-100, are used to prepare D1-D2-cyt b{sub 559} complexes from spinach. The kinetic signals are independent of the method of sample preparation. 35 refs., 5 figs.

  1. [Dithiobis-succinimidyl propionate on gold island films: surface-enhanced infrared absorption spectroscopy study].

    PubMed

    Guo, Hao; Ding, Li; Zhang, Tian-Jie; Mao, Yan-Li

    2013-05-01

    Dithiobis-succinimidyl propionate (DTSP), an important homobifunctional crosslinker, has been widely used for the covalent immobilization of proteins onto solid supports by amine coupling. In the present study, adsorption of DTSP on vacuum-deposited gold island films was analyzed by means of surface-enhanced infrared absorption spectroscopy (SEIRAS). For the sake of a reliable assignment of the vibrational spectra, IR intensity of the adsorption model of TSP on one gold surface was calculated using density functional theory (DFT) at the Beck' s three-parameter Lee-Yang-Parr (B3LYP) level with the LANL2DZ basis set. SEIRAS and multiple-angle-of-incidence polarization infrared reflection-absorption spectroscopy indicated that TSP is arranged orderly in a tilted fashion with a dihedral angle of 65 degrees between the plane of succinimidyl ring and the gold surface. The binding kinetics revealed that that the time constant of self-assembly of the TSP layer is 220 sec. Furthermore, the coupling process of amino-nitrilotriacetic acid (ANTA) with surface-bound TSP monolayer was monitored in situ by SEIRAS. Three negative bands observed at 1 807, 1 776, and 1 728 cm(-1) respectively provided direct evidence for the reaction of the succinimidyl ester. The appearance of one intense band at 1 566 cm(-1) gave a clear support for the presence of the cross-link between ANTA and TSP. We hope that the results in current investigation will contribute to the better understanding of properties of DTSP and related reactions at the molecular level.

  2. The molecular pathway to ZIF-7 microrods revealed by in situ time-resolved small- and wide-angle X-ray scattering, quick-scanning extended X-ray absorption spectroscopy, and DFT calculations.

    PubMed

    Goesten, Maarten; Stavitski, Eli; Pidko, Evgeny A; Gücüyener, Canan; Boshuizen, Bart; Ehrlich, Steven N; Hensen, Emiel J M; Kapteijn, Freek; Gascon, Jorge

    2013-06-10

    We present an in situ small- and wide-angle X-ray scattering (SAXS/WAXS) and quick-scanning extended X-ray absorption fine-structure (QEXAFS) spectroscopy study on the crystallization of the metal-organic framework ZIF-7. In combination with DFT calculations, the self-assembly and growth of ZIF-7 microrods together with the chemical function of the crystal growth modulator (diethylamine) are revealed at all relevant length scales, from the atomic to the full crystal size.

  3. Theoretical study of negative thermal expansion in Y2Mo3O12: effect of water absorption

    NASA Astrophysics Data System (ADS)

    Sun, Qiang; Wu, Mingyi; Wang, Lei; Jia, Yu

    2013-03-01

    Y2Mo3O12 exhibits negative thermal expansion (NTE) in a large temperature range (473 ~ 1173 K). However, the material strongly absorb water and form a stable trihydrate structure, where the NTE disappears. Raman spectra revealed that some vibrational modes were missing in the hydrated structure. By DFT calculations, absorption of water in Y2Mo3O12 has been studied. Our results showed that water can strongly absorb in Y2Mo3O12 with O end of the water binding to Y cation, while one hydrogen approaches to the bridge O, which shared by polyhedrons YO6 and MoO4, and forms hydrogen bond. The absorption of water leads the angle of Y-O-Mo reduced, decreasing Y-Mo distance and consequently the volume of the material contracted. Calculated phonon spectra showed that the transverse vibration of Y-O-Mo is restricted due to water absorption. As a result, the NTE, originated from the vibrational mode, is hindered. Our MD simulations also revealed that water can easily diffuse and cross different channels in the material with the aid of Y cations.

  4. The origin of the unusual Qy red shift in LH1-RC complexes from purple bacteria Thermochromatium tepidum as revealed by Stark absorption spectroscopy.

    PubMed

    Ma, Fei; Yu, Long-Jiang; Wang-Otomo, Zheng-Yu; van Grondelle, Rienk

    2015-12-01

    Native LH1-RC of photosynthetic purple bacteria Thermochromatium (Tch.) tepidum, B915, has an ultra-red BChl a Qy absorption. Two blue-shifted complexes obtained by chemical modification, B893 and B882, have increasing full widths at half maximum (FWHM) and decreasing transition dipole oscillator strength. 77K Stark absorption spectroscopy studies were employed for the three complexes, trying to understand the origin of the 915 nm absorption. We found that Tr(∆α) and |∆μ| of both Qy and carotenoid (Car) bands are larger than for other purple bacterial LH complexes reported previously. Moreover, the red shifts of the Qy bands are associated with (1) increasing Tr(∆α) and |∆μ| of the Qy band, (2) the red shift of the Car Stark signal and (3) the increasing |∆μ| of the Car band. Based on the results and the crystal structure, a combined effect of exciton-charge transfer (CT) states mixing, and inhomogeneous narrowing of the BChl a site energy is proposed to be the origin of the 915 nm absorption. CT-exciton state mixing has long been found to be the origin of strong Stark signal in LH1 and special pair, and the more extent of the mixing in Tch. tepidum LH1 is mainly the consequence of the shorter BChl-BChl distances. The less flexible protein structure results in a smaller site energy disorder (inhomogeneous narrowing), which was demonstrated to be able to influence |∆μ| and absorption.

  5. Topical absorption and toxicity studies of jet fuel hydrocarbons in skin

    NASA Astrophysics Data System (ADS)

    Muhammad, Faqir

    Kerosene-based fuels have been used for many decades. Over 2 million military and civilian personnel each year are occupationally exposed to various jet fuel mixtures. Dermatitis is one of the major health concerns associated with these exposures. In the past, separate absorption and toxicity studies have been conducted to find the etiology of such skin disorders. There was a need for integrated absorption and toxicity studies to define the causative constituents of jet fuel responsible for skin irritation. The focus of this thesis was to study the percutaneous absorption and to identify the hydrocarbons (HC) causing irritation in jet fuels so that preventive measures could be taken in the future. The initial study was conducted to understand the possible mechanism for additive interactions on hydrocarbon absorption/disposition in silastic, porcine skin and isolated perfused porcine skin flap (IPPSF) models. The influence of JP-8 (100) additives (MDA, BHT, 8Q405) on the dermal kinetics of 14C-naphthalene and 14C/3H-dodecane as markers of HC absorption was evaluated. This study indicated that individual and combination of additives influenced marker disposition in different membranes. MDA was a significant suppressor while BHT was a significant enhancer of naphthalene absorption in IPPSF. The 8Q405 significantly reduced naphthalene content in dosed silastic and skin indicating a direct interaction between additive and marker HC. Similarly, the individual MDA and BHT significantly retained naphthalene in the stratum corneum of porcine skin, but the combination of both of these additives statistically decreased the marker retention in the stratum corneum suggesting a potential biological interaction. This study concluded that all components of a chemical mixture should be assessed since the effects of single components administered alone or as pairs may be confounded when all are present in the complete mixture. However, this study indicated that the marker HC

  6. Effects of long chain fatty acids on solute absorption: perfusion studies in the human jejunum.

    PubMed Central

    Ammon, H V; Thomas, P J; Phillips, S F

    1977-01-01

    Perfusion studies were performed in healthy volunteers to test the hypothesis that net fluid secretion induced by fatty acids is accompanied by parallel reduction in solute transport. Ricinoleic acid provoked a marked net secretion of fluid and concomitantly inhibited the absorption of all solutes tested; these included glucose, xylose, L-leucine, L-lysine, Folic acid, and 2-mono-olein. Oleic acid also reduced net fluid and solute transport, but was less potent in reducing solute absorption than was ricinoleic acid. When fluid secretion was induced osmotically with mannitol, glucose and xylose absorption was not affected. The mechanism for this generalised effect of fatty acids on solute absorption is uncertain, possibly nonspecific, and might be related to mucosal damage and altered mucosal permeability induced by these agents. PMID:590838

  7. The Ablation Properties of CO2 Laser Irradiating to Absorption Media: An In Vitro Study

    PubMed Central

    Sattayut, Sajee; Hortong, Kittiwut; Kitichaiwan, Chorpaka

    2012-01-01

    This study aimed to compare histological affected zone of tissue samples irradiated by defocused CO2 laser at 1, 2, and 3W continuous wave with and without absorption media. The in vitro experiment was conducted in 70 tissue blocks. The samples were randomly allocated into 7 groups: 10 samples each group, namely, the groups irradiated with 1, 2, and 3W, defocused CO2 laser for 5 seconds, the groups irradiated with 1, 2, and 3W, defocused CO2 laser to the absorption media, and the media alone group as a control. Then the samples were stained with Masson's trichrome and measured the affected borders under light microscope at 10 × 10 magnification. There was no histological alteration in the groups irradiated with the defocused CO2 laser to the absorption media while the groups without using the absorption media showed the tissue alteration by photoablation. PMID:23227050

  8. Using high spectral resolution spectrophotometry to study broad mineral absorption features on Mars

    NASA Technical Reports Server (NTRS)

    Blaney, D. L.; Crisp, D.

    1993-01-01

    Traditionally telescopic measurements of mineralogic absorption features have been made using relatively low to moderate (R=30-300) spectral resolution. Mineralogic absorption features tend to be broad so high resolution spectroscopy (R greater than 10,000) does not provide significant additional compositional information. Low to moderate resolution spectroscopy allows an observer to obtain data over a wide wavelength range (hundreds to thousands of wavenumbers) compared to the several wavenumber intervals that are collected using high resolution spectrometers. However, spectrophotometry at high resolution has major advantages over lower resolution spectroscopy in situations that are applicable to studies of the Martian surface, i.e., at wavelengths where relatively weak surface absorption features and atmospheric gas absorption features both occur.

  9. A study of energy absorption rate in a quantum dot and metallic nanosphere hybrid system

    NASA Astrophysics Data System (ADS)

    Schindel, Daniel; Singh, Mahi R.

    2015-09-01

    We have studied energy absorption rate in a quantum dot-metallic nanosphere system embedded on a dielectric substrate. We applied a control field to induce dipole moments in the quantum dot and the metal nanosphere, and monitored the energy absorption using a probe field. These external fields induce dipole moments in the metal nanosphere and the quantum dot, and these two structures interact with one another via the dipole-dipole interaction. The density matrix method was used to evaluate the absorption, indicating that it can be shifted by moving the metal nanosphere close to the quantum dot. Also, absorption efficiency can either be quenched or enhanced by the addition of a metal nanosphere. This hybrid system can be used to create ultrafast switching and sensing nanodevices.

  10. Two-photon absorption in oxazole derivatives: An experimental and quantum chemical study

    NASA Astrophysics Data System (ADS)

    Silva, D. L.; De Boni, L.; Correa, D. S.; Costa, S. C. S.; Hidalgo, A. A.; Zilio, S. C.; Canuto, S.; Mendonca, C. R.

    2012-05-01

    Experimental and theoretical studies on the two-photon absorption properties of two oxazole derivatives: 2,5-diphenyloxazole (PPO) and 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) are presented. The two-photon absorption cross-section spectra were determined by means of the Z-scan technique, from 460 up to 650 nm, and reached peak values of 84 GM for PBD and 27 GM for PPO. Density Functional Theory and response function formalism are used to determine the molecular structures and the one- and two-photon absorption properties and to assist in the interpretation of the experimental results. The Polarizable Continuum Model in one-photon absorption calculations is used to estimate solvent effects.

  11. Study of absorption and re-emission processes in a ternary liquid scintillation system

    NASA Astrophysics Data System (ADS)

    Xiao, Hua-Lin; Li, Xiao-Bo; Zheng, Dong; Cao, Jun; Wen, Liang-Jian; Wang, Nai-Yan

    2010-11-01

    Liquid scintillators are widely used as the neutrino target in neutrino experiments. The absorption and emission of different components of a ternary liquid scintillator (Linear Alkyl Benzene (LAB) as the solvent, 2,5-diphenyloxazole (PPO) as the fluor and p-bis-(o-methylstyryl)-benzene (bis-MSB) as wavelength shifter) are studied. It is shown that the absorption of this liquid scintillator is dominant by LAB and PPO at wavelengths less than 349 nm, and the absorption by bis-MSB becomes prevalent at the wavelength larger than 349 nm. The fluorescence quantum yields, which are the key parameters to model the absorption and re-emission processes in large liquid scintillation detectors, are measured.

  12. Literature study of microwave-assisted digestion using electrothermal atomic absorption spectrometry.

    PubMed

    Chakraborty, R; Das, A K; Cervera, M L; De La Guardia, M

    1996-05-01

    The literature on the use of microwave-assisted digestion procedures for subsequent sample analysis by means of electrothermal atomic absorption spectrometry (ETAAS) is reviewed. The literature survey reveals that this digestion technique has been applied mainly for biological materials. The elements most extensively determined by this method are cadmium and lead followed by copper, chromium, nickel and iron. The microwave digestion conditions, ETAAS furnace programmes and analytical details of the developed methodologies have been carefully revised.

  13. Comparative QSAR studies on PAMPA/modified PAMPA for high throughput profiling of drug absorption potential with respect to Caco-2 cells and human intestinal absorption

    NASA Astrophysics Data System (ADS)

    Verma, Rajeshwar P.; Hansch, Corwin; Selassie, Cynthia D.

    2007-01-01

    Despite the dramatic increase in speed of synthesis and biological evaluation of new chemical entities, the number of compounds that survive the rigorous processes associated with drug development is low. Thus, an increased emphasis on thorough ADMET (absorption, distribution, metabolism, excretion and toxicity) studies based on in vitro and in silico approaches allows for early evaluation of new drugs in the development phase. Artificial membrane permeability measurements afford a high throughput, relatively low cost but labor intensive alternative for in vitro determination of drug absorption potential; parallel artificial membrane permeability assays have been extensively utilized to determine drug absorption potentials. The present study provides comparative QSAR analysis on PAMPA/modified PAMPA for high throughput profiling of drugs with respect to Caco-2 cells and human intestinal absorption.

  14. Inhibition by Natural Dietary Substances of Gastrointestinal Absorption of Starch and Sucrose in Rats 2. Subchronic Studies

    PubMed Central

    Preuss, Harry G.; Echard, Bobby; Bagchi, Debasis; Stohs, Sidney

    2007-01-01

    Acute oral consumption of various natural inhibitors of amylase (bean and hibiscus extracts) and sucrase (L-arabinose) reduce absorption of starch and sucrose respectively in rats and pigs measured by lessened appearance of circulating glucose levels. The present subchronic study was designed to determine whether these selected inhibitors of gastrointestinal starch and sucrose absorption (so-called “carb blockers”) remain effective with continued use and to assess their metabolic influences after prolonged intake. Sprague-Dawley rats were gavaged twice daily over nine weeks with either water or an equal volume of water containing a formula that included bean and hibiscus extracts and L-arabinose. To estimate CHO absorption, control and treated Sprague-Dawley rats were gavaged with either water alone or an equal volume of water containing glucose, rice starch, sucrose, or combined rice starch and sucrose. Circulating glucose was measured at timed intervals over four hours. The ability to decrease starch and sucrose absorption use. No toxic effects (hepatic, renal, hematologic) were evident. Blood chemistries revealed significantly lower circulating glucose levels and a trend toward decreased HbA1C in the nondiabetic rats receiving the natural formulation compared to control. Subchronic administration of enzyme inhibitors was also associated with many metabolic changes including lowered systolic blood pressure and altered fluid-electrolyte balance. We postulate that proper intake of natural amylase and sucrase inhibitors may be useful in the prevention and treatment of many chronic disorders associated with perturbations in glucose-insulin homeostasis secondary to the rapid absorption of refined CHO. PMID:17713601

  15. [Near infrared Cavity enhanced absorption spectroscopy study of NO2O].

    PubMed

    Wu, Zhi-wei; Dong, Yan-ting; Zhou, Wei-dong

    2014-08-01

    Using a tunable near infrared external cavity diode laser and a 650 mm long high finesse optical cavity consisting of two highly reflective (R=99.97% at 6561.39 cm(-1)) plan-concave mirrors of curvature radius approximately 1000 mm, a cavity enhanced absorption spectroscopy (CEAS) system was made. The absorption spectra centered at 6561.39 cm(-1) of pure N2O gas and gas mixtures of N2O and N2 were recorded. According to the absorption of N2O at 6561.39 cm(-1) in the cavity, the measured effective absorption path was about 1460 km. The spectra line intensity and line-width of N2O centered at 6561.39 cm(-1) were carefully studied. The relationship between the line-width of absorption spectra and the gas pressure was derived. The pressure broadening parameter of N2 gas for NO2O line centered at 6 561. 39 cm(-1) was deduced and given a value of approximately (0.114 +/- 0.004) cm(-1) x atm(-1). The possibility to detect trace N2O gas in mixture using this CEAS system was investigated. By recording the ab- sorption spectra of N2O gas mixtures at different concentration, the relationship between the line intensity and gas concentration was derived. The minimum detectable absorption was found to be 2.34 x 10(-7) cm(-1) using this cavity enhanced absorption spectroscopy system. And te measurement precision in terms of relative standard deviation (RSD) for N2O is approximately 1.73%, indicating the possibility of using the cavity enhanced absorption spectroscopy system for micro gas N2O analysis in the future.

  16. Mg-induced increase of bandgap in Zn1-xMgxO nanorods revealed by x-ray absorption and emission spectroscopy

    SciTech Connect

    Pong, Way-Faung; Chiou, J. W.; Tsai, H. M.; Pao, C. W.; Chien, F. Z.; Pong, W. F.; Chen, C. W.; Tsai, M.-H.; Wu, J. J.; Ko, C. H.; Chiang, H. H.; Lin, H.-J.; Lee, J. F.; Guo, J.-H.

    2008-07-10

    X-ray absorption near-edge structure (XANES) and x-ray emission spectroscopy (XES) measurements were used to investigate the effect of Mg doping in ZnO nanorods. The intensities of the features in the O K-edge XANES spectra of Zn{sub 1-x}Mg{sub x}O nanorods are lower than those of pure ZnO nanorods, suggesting that Mg doping increases the negative effective charge of O ions. XES and XANES spectra of O 2p states indicate that Mg doping raises (lowers) the conduction-band-minimum (valence-band-maximum) and increases the bandgap. The bandgap is found to increase linearly with the Mg content, as revealed by photoluminescence and combined XANES and XES measurements.

  17. X-Ray Absorption Spectroscopy and Computer Modelling Study of Nanocrystalline Binary Alkaline Earth Fluorides

    NASA Astrophysics Data System (ADS)

    Chadwick, A. V.; Düvel, A.; Heitjans, P.; Pickup, D. M.; Ramos, S.; Sayle, D. C.; Sayle, T. X. T.

    2015-04-01

    Nanocrystalline samples of Ba1-xCaxF2 prepared by high-energy milling show an unusually high F- ion conductivity, which exhibit a maximum in the magnitude and a minimum in the activation energy at x = 0.5. Here, we report an X-ray absorption spectroscopy (XAS) at the Ca and Sr K edges and the Ba L3 edge and a molecular dynamics (MD) simulation study of the pure and mixed fluorides. The XAS measurements on the pure binary fluorides, CaF2, SrF2 and BaF2 show that high-energy ball-milling produces very little amorphous material, in contrast to the results for ball milled oxides. XAS measurements of Ba1-xCaxF2 reveal that for 0 < x <1 there is considerable disorder in the local environments of the cations which is highest for x = 0.5. Hence the maximum in the conductivity corresponds to the composition with the maximum level of local disorder. The MD calculations also show a highly disordered structure consistent with the XAS results and similarly showing maximum disorder at x = 0.5.

  18. Ultrafast transient absorption studies of ruthenium and rhenium dipyridophenazine complexes bound to DNA and polynucleotides

    NASA Astrophysics Data System (ADS)

    Creely, Caitriona M.; Kelly, John M.; Feeney, M. M.; Hudson, S.; Penedo, J. C.; Blau, Werner J.; Elias, B.; Kirsch-De Mesmaeker, Andree; Matousek, P.; Towrie, M.; Parker, A. W.; Dyer, J. S.; George, Mikhael W.; Coates, C. G.; McGarvey, John J.

    2003-03-01

    We report on ultrafast pump and probe studies of biological systems, in the form of polynucleotide and calf thymus DNA complexes. Molecules for study are bound to the polynucleotides and probed in the visible region to observe changes in the absorption over time. Various dipyridophenazine metal complexes are studied alone and complexed with DNA or synthetic polynucleotides to investigate changes occurring in their excited states upon interacting with nucleobases. Transient absorption measurements are performed pumping at 400nm and probing from 450-700nm with pulse duration of 400fs.

  19. A follow-up study of lead absorption in cows as an indicator of environmental lead pollution

    SciTech Connect

    Prpic-Majic, D.; Karacic, V.; Skender, Lj. )

    1990-07-01

    In a previous study, lead absorption in cows grazing in the vicinity of a lead smeltery and in a control area was presented for two periods. The first period was in 1976, two years before the installation of an effective gas cleaning system in the lead smeltery, and the second period was in 1982, four years after the sanitation. The results obtained in the lead smeltery area revealed a highly significant improvement of all biochemical indicators of lead absorption intensity in cows during 1982 in comparison with the same findings during 1976. However, in spite of the lower lead absorption in 1982, blood lead concentration and {sigma}-aminolevulinic acid dehydratase activity in 1982 were still highly significantly different from the same findings in cows from the control area. Consequently the study was continued in 1984 and 1988 under identical conditions. The main object of the paper is a critical evaluation of the results obtained in relation to environmental monitoring in the same lead smeltery area.

  20. Vitamin D-mediated calcium absorption in patients with clinically stable Crohn's disease: a pilot study.

    PubMed

    Kumari, Meena; Khazai, Natasha B; Ziegler, Thomas R; Nanes, Mark S; Abrams, Steven A; Tangpricha, Vin

    2010-08-01

    Vitamin D is the critical hormone for intestinal absorption of calcium. Optimal calcium absorption is important for proper mineralization of bone in the prevention of osteoporosis and osteoporotic fractures, among other important functions. Diseases associated with gut inflammation, such as Crohn's disease (CD), may impair calcium absorption. This pilot study evaluated vitamin D- dependent calcium absorption in subjects with CD. Male subjects with CD (n=4) and healthy age-matched controls (n=5) were studied. All subjects had fractional calcium absorption (FCA; by the dual calcium isotope method), serum 25-hydroxyvitamin D, serum calcium and 24 h urinary calcium excretion measurements at baseline. The FCA in response to vitamin D therapy was re-assessed following administration of oral calcitriol 0.25 mcg twice daily for 1 wk, followed by oral calcitriol 0.50 mcg twice daily for 1 wk. Serum calcium and 24 h urinary calcium determinations were re-assessed after each increasing dose of calcitriol as safety measures. There was no significant difference in calcium FCA at baseline or after increasing doses of calcitriol between the CD and controls. FCA in the control and CD group was approximately 35% at baseline, which increased to 60% after calcitriol therapy. No subject developed hypercalcemia or hypercalciuria. Our results suggest that CD patients have a normal response to vitamin D in enhancing the efficacy of calcium absorption. This suggests that stable CD patients can follow calcium and vitamin D guidelines of non-CD adults. Other factors independent of vitamin D status may impair intestinal calcium absorption in CD, including the degree and location of inflammation, presence of surgical resection and/or use of glucocorticoids.

  1. Study of the absorption spectra of Fricke Xylenol Orange gel dosimeters

    SciTech Connect

    Gambarini, Grazia; Artuso, Emanuele; Liosi, Giulia Maria; Giacobbo, Francesca; Mariani, Mari; Brambilla, Luigi; Castiglioni, Chiara; Carrara, Mauro; Pignoli, Emanuele

    2015-07-01

    A systematic study of the absorption spectra of Fricke Xylenol Orange gel dosimeters has been performed, in the wavelength range from 300 nm to 700 nm. The spectrum of Xylenol Orange (without ferrous sulphate solution) has been achieved, in order to subtract its contribution from the absorption spectra of the irradiated Fricke Xylenol Orange gel dosimeters. The absorbance due to ferric ions chelated by Xylenol Orange has been studied for various irradiation doses. Two absorbance peaks are visible, mainly at low doses: the first peak increases with the dose more slowly than the second one. This effect can explain the apparent threshold dose that was frequently evidenced. (authors)

  2. Resolution Effects on Quasar Absorption Line Studies of ΛCDM Simulations

    NASA Astrophysics Data System (ADS)

    Kacprzak, Glenn; Ceverino, D.; Churchill, C. W.; Murphy, M. T.; Evans, J. L.

    2009-01-01

    The technique of using background quasars to study absorption lines produced by gaseous halos of foreground galaxies provides a uniquely powerful tool to probe the gas-galaxy and IGM interface. With absorption lines, we are capable of studying the kinematic, chemical, and ionization conditions of galactic halos over all redshifts out to projected galactocentric radii of several 100 kpc. However, interpreting these data can be difficult. We have recently begun to produce similar absorption line observations of galaxies and their gaseous halos in LCDM cosmological simulations in order to constrain the dynamic interaction of the galaxy/halo/cosmic web environment and the distribution of gas within halos. The simulations are performed using the Eulerian Gasdynamics plus N-body Adaptive Refinement Tree (ART) code, were the highest resolution gas cells are 20-100 pc. However, absorption lines are primarily produced/observed in the halos of galaxies where the resolution is lower. Here, we quantify how varying the resolution affects the measured absorption velocity spreads, number of clouds, and covering fractions of halo gas within the simulated galaxies. This is an important step toward understanding the interplay between halo gas kinematics and small scale structure. It is crucial that we understand these effects in order to correctly interpret our observations.

  3. Myo-inositol inhibits intestinal glucose absorption and promotes muscle glucose uptake: a dual approach study.

    PubMed

    Chukwuma, Chika Ifeanyi; Ibrahim, Mohammed Auwal; Islam, Md Shahidul

    2016-12-01

    The present study investigated the effects of myo-inositol on muscle glucose uptake and intestinal glucose absorption ex vivo as well as in normal and type 2 diabetes model of rats. In ex vivo study, both intestinal glucose absorption and muscle glucose uptake were studied in isolated rat jejunum and psoas muscle respectively in the presence of increasing concentrations (2.5 % to 20 %) of myo-inositol. In the in vivo study, the effect of a single bolus dose (1 g/kg bw) of oral myo-inositol on intestinal glucose absorption, blood glucose, gastric emptying and digesta transit was investigated in normal and type 2 diabetic rats after 1 h of co-administration with 2 g/kg bw glucose, when phenol red was used as a recovery marker. Myo-inositol inhibited intestinal glucose absorption (IC50 = 28.23 ± 6.01 %) and increased muscle glucose uptake, with (GU50 = 2.68 ± 0.75 %) or without (GU50 = 8.61 ± 0.55 %) insulin. Additionally, oral myo-inositol not only inhibited duodenal glucose absorption and reduced blood glucose increase, but also delayed gastric emptying and accelerated digesta transit in both normal and diabetic animals. Results of this study suggest that dietary myo-inositol inhibits intestinal glucose absorption both in ex vivo and in normal or diabetic rats and also promotes muscle glucose uptake in ex vivo condition. Hence, myo-inositol may be further investigated as a possible anti-hyperglycaemic dietary supplement for diabetic foods and food products.

  4. Sensitive and rapid laser diagnostic for shock tube kinetics studies using cavity-enhanced absorption spectroscopy.

    PubMed

    Sun, Kai; Wang, Shengkai; Sur, Ritobrata; Chao, Xing; Jeffries, Jay B; Hanson, Ronald K

    2014-04-21

    We report the first application of cavity-enhanced absorption spectroscopy (CEAS) using a coherent light source for sensitive and rapid gaseous species time-history measurements in a shock tube. Off-axis alignment and fast scanning of the laser wavelength were used to minimize coupling noise in a low-finesse cavity. An absorption gain factor of 83 with a measurement time resolution of 20 µs was demonstrated for C2H2 detection using a near-infrared transition near 1537 nm, corresponding to a noise-equivalent detection limit of 20 ppm at 296 K and 76 ppm at 906 K at 50 kHz. This substantial gain in signal, relative to conventional single-pass absorption, will enable ultra-sensitive species detection in shock tube kinetics studies, particularly useful for measurements of minor species and for studies of dilute reactive systems.

  5. Feasibility of a 3D human airway epithelial model to study respiratory absorption.

    PubMed

    Reus, Astrid A; Maas, Wilfred J M; Jansen, Harm T; Constant, Samuel; Staal, Yvonne C M; van Triel, Jos J; Kuper, C Frieke

    2014-03-01

    The respiratory route is an important portal for human exposure to a large variety of substances. Consequently, there is an urgent need for realistic in vitro strategies for evaluation of the absorption of airborne substances with regard to safety and efficacy assessment. The present study investigated feasibility of a 3D human airway epithelial model to study respiratory absorption, in particular to differentiate between low and high absorption of substances. Bronchial epithelial models (MucilAir™), cultured at the air-liquid interface, were exposed to eight radiolabeled model substances via the apical epithelial surface. Absorption was evaluated by measuring radioactivity in the apical compartment, the epithelial cells and the basolateral culture medium. Antipyrine, caffeine, naproxen and propranolol were highly transported across the epithelial cell layer (>5%), whereas atenolol, mannitol, PEG-400 and insulin were limitedly transported (<5%). Results indicate that the 3D human airway epithelial model used in this study is able to differentiate between substances with low and high absorption. The intra-experimental reproducibility of the results was considered adequate based on an average coefficient of variation (CV) of 15%. The inter-experimental reproducibility of highly absorbed compounds was in a similar range (CV of 15%), but this value was considerably higher for those compounds that were limitedly absorbed. No statistical significant differences between different donors and experiments were observed. The present study provides a simple method transposable in any lab, which can be used to rank the absorption of chemicals and pharmaceuticals, and is ready for further validation with respect to reproducibility and capacity of the method to predict respiratory transport in humans.

  6. Gamma-irradiation and UV-C light-induced lipid peroxidation: a Fourier transform-infrared absorption spectroscopic study.

    PubMed

    Kinder, R; Ziegler, C; Wessels, J M

    1997-05-01

    Fourier transform-infrared spectroscopy of dry, multibilayer films has been used to study gamma-radiation and UV-C light induced lipid peroxidation in 1,2-dilinoleoyl-sn-glycero-3-phosphocholine liposomes. The observed spectral changes were compared with the results obtained from measurement of hydroperoxides, conjugated dienes and to the formation of thiobarbituric acid reactive substances, such as malondialdehyde (MDA) or MDA-like substances. Upon irradiation a decrease in intensity of the asymmetric C - H stretching vibration (va(CH2)) of the isolated cis C = C - H groups (3010 cm-1) was observed. Directly correlated with the decrease of the va(CH2) absorption was a shift of the asymmetric phosphate ester stretching vibration (va(P = O)) towards smaller wavenumbers (1260-->1244 cm-1), indicating that the lipid peroxidation induced molecular alterations in the fatty acid chains influence the packing of the phospholipids in dry multibilayer films. In addition, the formation of a new absorption band at 1693 cm-1 could be detected, the intensity of which was comparable with the formation of thiobarbituric acid reactive substances and, therefore, attributed to the (C = O) stretching of alpha, beta unsaturated aldehydes. Dose-dependent studies using ionizing radiation showed that the decrease of va(CH2) was directly correlated with an increase in absorption of the conjugated dienes at 234 nm and with the formation of hydroperoxides suggesting that the absorption at 3010 cm-1 is solely due to isolated cis C = C - H groups and hence subject to the early stages of the radical chain reaction. UV-C light induced lipid peroxidation revealed a non-linear decrease of I3010, which was directly correlated with the formation of hydroperoxides. The observed early saturation of the conjugated dienes was attributed to an early photodecomposition of the conjugated double bonds.

  7. A Study on the Excitation and Resonant Absorption of Coronal Loop Kink Oscillations

    NASA Astrophysics Data System (ADS)

    Yu, Dae Jung; Van Doorsselaere, Tom

    2016-11-01

    We study theoretically the issue of externally driven excitations of standing kink waves and their resonant absorption into torsionally polarized m = 1 waves in the coronal loops in pressureless plasmas. We use the ideal MHD equations, for which we develop an invariant imbedding method available in cylindrical geometry. We assume a sinusoidal density profile at the loop boundary where the density inside the loop is lower than the outside and vice versa. We present field distributions for these two cases and find that they have similar behaviors. We compare the results for the overdense loops, which describe the usual coronal loops, with the analytical solutions of Soler et al. obtained using the Frobenius method. Our results show some similarity for thin nonuniform layers but deviate a lot for thick nonuniform layers. For the first case, which describes the wave train propagation in funnels, we find that resonant absorption depends crucially on the thickness of the nonuniform boundary, loop length, and density contrast. The resonant absorption of the kink mode is dominant when the loop length is sufficiently larger compared with its radius (thin loop). The behavior of the far-field pattern of the scattered wave by the coronal loop is closely related to that of the resonant absorption. For the mode conversion phenomena in inhomogeneous plasmas, a certain universal behavior of the resonant absorption is found for the first time. We expect that the main feature may also apply to the overdense loops and discuss its relation to the damping rate.

  8. Iron absorption in raw and cooked bananas: a field study using stable isotopes in women

    PubMed Central

    García, Olga P.; Martínez, Mara; Romano, Diana; Camacho, Mariela; de Moura, Fabiana F.; Abrams, Steve A.; Khanna, Harjeet K.; Dale, James L.; Rosado, Jorge L.

    2015-01-01

    Background Banana is a staple food in many regions with high iron deficiency and may be a potential vehicle for iron fortification. However, iron absorption from bananas is not known. Objective The objective of this study was to evaluate total iron absorption from raw and cooked bananas. Design Thirty women (34.9±6.6 years) from rural Mexico were randomly assigned to one of two groups each consuming: 1) 480 g/day of raw banana for 6 days, or 2) 500 g/day of cooked banana for 4 days. Iron absorption was measured after extrinsically labeling with 2 mg of 58Fe and a reference dose of 6 mg 57Fe; analysis was done using ICP-MS. Results Iron content in cooked bananas was significantly higher than raw bananas (0.53 mg/100 g bananas vs. 0.33 mg/100 mg bananas, respectively) (p<0.001). Percent iron absorption was significantly higher in raw bananas (49.3±21.3%) compared with cooked banana (33.9±16.2%) (p=0.035). Total amount of iron absorbed from raw and cooked bananas was similar (0.77±0.33 mg vs. 0.86±0.41 mg, respectively). Conclusion Total amount of absorbed iron is similar between cooked and raw bananas. The banana matrix does not affect iron absorption and is therefore a potential effective target for genetic modification for iron biofortification. PMID:25660254

  9. Soft X-Ray Irradiation Effects of Li2O2, Li2CO3 and Li2O Revealed by Absorption Spectroscopy

    PubMed Central

    Qiao, Ruimin; Chuang, Yi-De; Yan, Shishen; Yang, Wanli

    2012-01-01

    Li2O2, Li2CO3, and Li2O are three critical compounds in lithium-air and lithium-ion energy storage systems. Extensive measurements have been carried out to study the chemical species and their evolutions at difference stages of the device operation. While x-ray spectroscopy has been demonstrated to be one of the most powerful tools for such purpose, no systematic study on the irradiation effects have been reported. Here we carry out extensive time, position, and irradiation dependent Li K-edge soft x-ray absorption spectroscopy on these compounds with so far the best energy resolution. The ultra-high resolution in the current study allows the features in the absorption spectra to be well-resolved. The spectral lineshape thus serves as the fingerprints of these compounds, enabling the tracking of their evolution under x-ray irradiation. We found that both Li2O2 and Li2CO3 evidently evolve towards Li2O under the soft x-ray irradiation with Li2CO3 exhibiting a surprisingly higher sensitivity to x-rays than Li2O2. On the other hand, Li2O remains the most stable compound despite experiencing substantial irradiation dose. We thus conclude that high resolution soft x-ray spectroscopy could unambiguously fingerprint different chemical species, but special cautions on irradiation effects would be needed in performing the experiments and interpreting the data properly. PMID:23145116

  10. Studies of Water Absorption Behavior of Plant Fibers at Different Temperatures

    NASA Astrophysics Data System (ADS)

    Saikia, Dip

    2010-05-01

    Moisture absorption of natural fiber plastic composites is one major concern in their outdoor applications. The absorbed moisture has many detrimental effects on the mechanical performance of these composites. A knowledge of the moisture diffusivity, permeability, and solubility is very much essential for the application of natural fibers as an excellent reinforcement in polymers. An effort has been made to study the water absorption behavior of some natural fibers such as bowstring hemp, okra, and betel nut at different temperatures to improve the long-term performance of composites reinforced with these fibers. The gain in moisture content in the fibers due to water absorption was measured as a function of exposure time at temperatures ranging from 300 K to 340 K. The thermodynamic parameters of the sorption process, such as diffusion coefficients and corresponding activation energies, were estimated.

  11. Numerical study of plasmonic absorption enhancement in semiconductor absorbers by metallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Hornich, Julian; Pflaum, Christoph; Brabec, Christoph; Forberich, Karen

    2016-09-01

    We are studying the influence of spherical silver nanoparticles (AgNP) in absorbing media by numerically solving the Maxwell's equations. Our simulations show that the near-field absorption enhancement introduced by a single AgNP in the surrounding medium is increasing with the growing particle diameter. However, we observe that the relative absorption per particle volume is on a similar level for different particle sizes; hence, different numbers of particles with the same total volume yield the same near-field absorption enhancement. We also investigate the effect of non-absorbing shells around the AgNP with the conclusion that even very thin shells suppress the beneficial effects of the particles noticeably. Additionally, we include AgNP in an organic solar cell at different vertical positions with different particle spacings and observe the beneficial effects for small AgNP and the scattering dependent performance for larger particles.

  12. Study of the analytical methods for iron determination in complex organic liquids by atomic absorption spectrometry

    SciTech Connect

    Torre, M.; Gonzalez, M.C.; Jimenez, O.; Rodriquez, A.R. )

    1990-01-01

    In the determination of iron in complex organic liquids by atomic absorption spectrometry (A.A.S.), methods of sample preparation, such as dilution with an organic solvent and sample pretreatment to destroy organic material, are investigated. Moreover, methods of analysis using calibration curve and standard additions are presented. The possible cause of error associated with iron determination in organic samples by flame (F-A.A.S.) and graphite furnace (GF-A.A.S.) atomic absorption spectrometry are discussed. From all of these studies, the use of graphite furnace atomic absorption spectrometry after sample dilution with methyl isobutyl ketone, and the use of the method of standard additions are advised for iron determination.

  13. [Study on transient absorption spectrum of tungsten nanoparticle with HepG2 tumor cell].

    PubMed

    Cao, Lin; Shu, Xiao-Ning; Liang, Dong; Wang, Cong

    2014-07-01

    Significance of this study lies in tungsten nano materials can be used as a preliminary innovative medicines applied basic research. This paper investigated the inhibition of tungsten nanoparticles which effected on human hepatoma HepG2 cells by MTT. The authors use transient absorption spectroscopy (TAS) technology absorption and emission spectra characterization of charge transfer between nanoparticles and tumor cell. The authors discussed the role of the tungsten nanoparticles in the tumor early detection of the disease and its anti-tumor properties. In the HepG2 experiments system, 100-150 microg x mL(-1) is the best drug concentration of anti-tumor activity which recact violently within 6 hours and basically completed in 24 hours. The results showed that transient absorption spectroscopy can be used as tumor detection methods and characterization of charge transfer between nano-biosensors and tumor cells. Tungsten nanoparticles have potential applications as anticancer drugs.

  14. 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.

  15. In vivo absorption studies of insulin from an oral delivery system.

    PubMed

    Jerry, N; Anitha, Y; Sharma, C P; Sony, P

    2001-01-01

    Alginate microspheres prepared by an emulsion-based process were loaded with insulin by a remote loading process. We observed that the time of exposure, pH of the remote loading medium, and beta-cyclodextrin complexation of insulin influenced drug loading. In vivo absorption studies of insulin from optimized microspheres were carried out in diabetic albino rats. Serum sugar levels on administration of multiple oral doses of the microspheres and a radioimmunoassay for serum insulin indicated absorption of insulin from the gastrointestinal region. This process could be utilized for the development of an oral insulin delivery system.

  16. Subpicosecond UV spectroscopy of carbonmonoxy-myoglobin: absorption and circular dichroism studies.

    PubMed

    Dartigalongue, Thibault; Niezborala, Claire; Hache, François

    2007-04-07

    A thorough absorption and circular dichroism study is performed in carbonmonoxy-myoglobin with a sub-picosecond visible pump, ultraviolet probe experiment. Differential absorption in the 220-360 nm range shows that the time-resolved response mainly comes from the heme and that aromatic amino acids do not contribute significantly. Time-resolved CD at 260 nm shows no dynamics and confirms this result. On the contrary, a strong CD dynamics is observed at 230 nm. This signal could originate from transient deformation of the alpha-helices in the protein.

  17. Atomic absorption spectrophotometric method for determination of polydimethylsiloxane residues in pineapple juice: collaborative study.

    PubMed

    Parker, R D

    1990-01-01

    An atomic absorption spectrophotometric method for determination of polydimethylsiloxane (PDMS) residues in pineapple juice was collaboratively studied by 9 laboratories. PDMS residues are extracted from pineapple juice with 4-methyl-2-pentanone and the extracted silicone is measured by atomic absorption spectrophotometry using a nitrous oxide/acetylene flame. Collaborators analyzed 5 samples including 1 blind duplicate. Reproducibility relative standard deviations (RSDR) were 13.1% at 31 ppm, 6.9% at 18 ppm, 14.8% at 7.9 ppm, and 16.1% at 4.9 ppm PDMS. The method has been approved interim official first action by AOAC.

  18. Measurements of trace constituents from atmospheric infrared emission and absorption spectra, a feasibility study

    NASA Technical Reports Server (NTRS)

    Goldman, A.; Williams, W. J.; Murcray, D. G.

    1974-01-01

    The feasibility of detecting eight trace constituents (CH4, HCl, HF, HNO3, NH3, NO, NO2 and SO2) against the rest of the atmospheric background at various altitudes from infrared emission and absorption atmospheric spectra was studied. Line-by-line calculations and observational data were used to establish features that can be observed in the atmospheric spectrum due to each trace constituent. Model calculations were made for experimental conditions which approximately represent state of the art emission and absorption spectrometers.

  19. Parametric Study of the Absorption Cross-Section for a Moderately Conducting Thin Cylinder.

    NASA Astrophysics Data System (ADS)

    Gurton, Kristan Peter

    A system has been developed to measure the absorption cross section of a single carbon fiber at 35 GHz as a function of length, orientation, and diameter. Typical lengths considered ranged from 1 to 20 mm, and diameters ranged from 3 to 8 um. The results were compared with the modified integral equation calculations of Waterman and Pedersen that describe the scattering and absorption behavior for a wire of finite length and conductivity. Good agreement was found for all lengths, orientations, and diameters studied.

  20. Parametric study of the absorption cross section for a moderately conducting thin cylinder

    NASA Astrophysics Data System (ADS)

    Gurton, Kristan P.; Bruce, Charles W.

    1995-05-01

    A system has been developed to measure the absorption cross section for a single carbon fiber at 35 GHz as a function of length, orientation, and diameter. Typical lengths of the fibers considered ranged from 1 to 20 mm, and diameters ranged from 3 to 8 mu m. The results were compared with the modified integral equation calculations of Waterman and Pedersen that describe the scattering and absorption behavior for a wire of finite length and conductivity. Good agreement was found for all lengths, orientations, and diameters studied.

  1. Non-degenerate two-photon absorption in silicon waveguides. Analytical and experimental study

    DOE PAGES

    Zhang, Yanbing; Husko, Chad; Lefrancois, Simon; ...

    2015-06-22

    We theoretically and experimentally investigate the nonlinear evolution of two optical pulses in a silicon waveguide. We provide an analytic solution for the weak probe wave undergoing non-degenerate two-photon absorption (TPA) from the strong pump. At larger pump intensities, we employ a numerical solution to study the interplay between TPA and photo-generated free carriers. We develop a simple and powerful approach to extract and separate out the distinct loss contributions of TPA and free-carrier absorption from readily available experimental data. Our analysis accounts accurately for experimental results in silicon photonic crystal waveguides.

  2. Ultrafast Time-Resolved Emission and Absorption Spectra of meso-Pyridyl Porphyrins upon Soret Band Excitation Studied by Fluorescence Up-Conversion and Transient Absorption Spectroscopy.

    PubMed

    Venkatesh, Yeduru; Venkatesan, M; Ramakrishna, B; Bangal, Prakriti Ranjan

    2016-09-08

    A comprehensive study of ultrafast molecular relaxation processes of isomeric meso-(pyridyl) porphyrins (TpyPs) has been carried out by using femtosecond time-resolved emission and absorption spectroscopic techniques upon pumping at 400 nm, Soret band (B band or S2), in 4:1 dichloromethane (DCM) and tetrahydrofuran (THF) solvent mixture. By combined studies of fluorescence up-conversion, time-correlated single photon counting, and transient absorption spectroscopic techniques, a complete model with different microscopic rate constants associated with elementary processes involved in electronic manifolds has been reported. Besides, a distinct coherent nuclear wave packet motion in Qy state is observed at low-frequency mode, ca. 26 cm(-1) region. Fluorescence up-conversion studies constitute ultrafast time-resolved emission spectra (TRES) over the whole emission range (430-710 nm) starting from S2 state to Qx state via Qy state. Careful analysis of time profiles of up-converted signals at different emission wavelengths helps to reveal detail molecular dynamics. The observed lifetimes are as indicated: A very fast decay component with 80 ± 20 fs observed at ∼435 nm is assigned to the lifetime of S2 (B) state, whereas being a rise component in the region of between 550 and 710 nm emission wavelength pertaining to Qy and Qx states, it is attributed to very fast internal conversion (IC) occurring from B → Qy and B → Qx as well. Two distinct components of Qy emission decay with ∼200-300 fs and ∼1-1.5 ps time constants are due to intramolecular vibrational redistribution (IVR) induced by solute-solvent inelastic collisions and vibrational redistribution induced by solute-solvent elastic collision, respectively. The weighted average of these two decay components is assigned as the characteristic lifetime of Qy, and it ranges between 0.3 and 0.5 ps. An additional ∼20 ± 2 ps rise component is observed in Qx emission, and it is assigned to the formation time of

  3. Characterization of gastrointestinal absorption of digoxin involving influx and efflux transporter in rats: application of mdr1a knockout (-/-) rats into absorption study of multiple transporter substrate.

    PubMed

    Suzuki, Motoya; Komura, Hiroshi; Yoshikawa, Tomonori; Enya, Seiji; Nagao, Akemi; Takubo, Hiroaki; Kogayu, Motohiro

    2014-11-01

    1.  This study was aimed to characterize gastrointestinal absorption of digoxin using wild-type (WT) and multidrug resistance protein 1a [mdr1a; P-glycoprotein (P-gp)] knockout (-/-) rats. 2.  In WT rats, the area under the plasma concentration-time curve (AUC) of oral digoxin increased after oral pretreatment with quinidine at 30 mg/kg compared with non-treatment, but the increasing ratio tended to decrease at a high dose of 100 mg/kg. In mdr1a (-/-) rats, however, quinidine pretreatment caused a dose-dependent decrease in the AUC. 3.  Quinidine pretreatment did not alter the hepatic availability of digoxin, indicating that the changes in the digoxin AUC were attributable to inhibition of the absorption process by quinidine; i.e. inhibition of influx by quinidine in mdr1a (-/-) rats and inhibition of efflux and influx by quinidine in WT rats. 4.  An in situ rat intestinal closed loop study using naringin implied that organic anion transporting peptide (Oatp) 1a5 may be a responsible transporter in the absorption of digoxin. 5.  These findings imply that the rat absorption behavior of digoxin is possibly governed by Oatp1a5-mediated influx and P-gp-mediated efflux. The mdr1a (-/-) rat is therefore a useful in vivo tool to investigate drug absorption associated with multiple transporters including P-gp.

  4. FDTD/TDSE study of surface-enhanced infrared absorption by metal nanoparticles.

    SciTech Connect

    Chang, S.-H.; Schatz, G. C.; Gray, S. K.; Chemistry; Northwestern Univ.; National Cheng-Kung Univ.

    2006-01-01

    We study surface-enhanced infrared absorption, including multiphoton processes, due to the excitation of surface plasmons on metal nanoparticles. The time-dependent Schroedinger equation and finite-difference time-domain method are self-consistently coupled to treat the problem.

  5. High Pressure X-ray Absorption Studies on Correlated-Electron Systems

    SciTech Connect

    Cornelius, Andrew L.

    2016-08-26

    This project used high pressure to alter the electron-electron and electron-lattice interactions in rare earth and actinide compounds. Knowledge of these properties is the starting points for a first-principles understanding of electronic and electronically related macroscopic properties. The research focused on a systematic study of x-ray absorption measurements on rare earth and actinide compounds.

  6. Microwave Resonator Measurements of Atmospheric Absorption Coefficients: A Preliminary Design Study

    NASA Technical Reports Server (NTRS)

    Walter, Steven J.; Spilker, Thomas R.

    1995-01-01

    A preliminary design study examined the feasibility of using microwave resonator measurements to improve the accuracy of atmospheric absorption coefficients and refractivity between 18 and 35 GHz. Increased accuracies would improve the capability of water vapor radiometers to correct for radio signal delays caused by Earth's atmosphere. Calibration of delays incurred by radio signals traversing the atmosphere has applications to both deep space tracking and planetary radio science experiments. Currently, the Cassini gravity wave search requires 0.8-1.0% absorption coefficient accuracy. This study examined current atmospheric absorption models and estimated that current model accuracy ranges from 5% to 7%. The refractivity of water vapor is known to 1% accuracy, while the refractivity of many dry gases (oxygen, nitrogen, etc.) are known to better than 0.1%. Improvements to the current generation of models will require that both the functional form and absolute absorption of the water vapor spectrum be calibrated and validated. Several laboratory techniques for measuring atmospheric absorption and refractivity were investigated, including absorption cells, single and multimode rectangular cavity resonators, and Fabry-Perot resonators. Semi-confocal Fabry-Perot resonators were shown to provide the most cost-effective and accurate method of measuring atmospheric gas refractivity. The need for accurate environmental measurement and control was also addressed. A preliminary design for the environmental control and measurement system was developed to aid in identifying significant design issues. The analysis indicated that overall measurement accuracy will be limited by measurement errors and imprecise control of the gas sample's thermodynamic state, thermal expansion and vibration- induced deformation of the resonator structure, and electronic measurement error. The central problem is to identify systematic errors because random errors can be reduced by averaging

  7. Results of Self-Absorption Study on the Versapor 3000 Filters for Radioactive Particulate Air Sampling

    SciTech Connect

    Barnett, J. Matthew

    2008-08-22

    Since the mid-1980s the Pacific Northwest National Laboratory (PNNL) has used a value of 0.85 as a correction factor for the self absorption of activity of particulate radioactive air samples. More recently, an effort was made to evaluate the current particulate radioactive air sample filters (Versapor® 3000) used at PNNL for self absorption effects. There were two methods used in the study, 1) to compare the radioactivity concentration by direct gas-flow proportional counting of the filter to the results obtained after acid digestion of the filter and counting again by gas-flow proportional detection and 2) to evaluate sample filters by high resolution visual/infrared microscopy to determine the depth of material loading on or in the filter fiber material. Sixty samples were selected from the archive for acid digestion in the first method and about 30 samples were selected for high resolution visual/infrared microscopy. Mass loading effects were also considered. From the sample filter analysis, large error is associated with the average self absorption factor, however, when the data is compared directly one-to-one, statistically, there appears to be good correlation between the two analytical methods. The mass loading of filters evaluated was <0.2 mg cm-2 and was also compared against other published results. The microscopy analysis shows the sample material remains on the top of the filter paper and does not imbed into the filter media. Results of the microscopy evaluation lead to the conclusion that there is not a mechanism for significant self absorption. The overall conclusion is that self-absorption is not a significant factor in the analysis of filters used at PNNL for radioactive air stack sampling of radionuclide particulates and that an applied correction factor is conservative in determining overall sample activity. A new self absorption factor of 1.0 is recommended.

  8. Side chain variations on a series of dicyanovinyl-terthiophenes: a photoinduced absorption study.

    PubMed

    Ziehlke, Hannah; Fitzner, Roland; Koerner, Christian; Gresser, Roland; Reinold, Egon; Bäuerle, Peter; Leo, Karl; Riede, Moritz K

    2011-08-04

    We characterize a series of dicyanovinyl-terthiophenes with different alkyl side chains. Variations of side chain substitution patterns and length mainly affect the morphology of the evaporated thin films, which in turn sensitively influences properties like absorption, energy levels, and thin film roughness. To investigate changes in transfer processes between electron donor (D) and acceptor (A) molecules due to side chain variations, we use photoinduced absorption spectroscopy (PIA). PIA probes the long-living photoexcited species at the D-A interface: triplet excitons, cations, and anions. For a blend layer of dicyanovinyl-terthiophene and the electron acceptor fullerene C(60), an energy transfer via the singlet and triplet manifold of C(60) occurs. The recombination dynamics of the triplet excitons reveal two components that differ in their lifetime and generation rate by 1 order of magnitude. By comparing the dynamics of triplet excitons in neat and blend layers, we estimate the energy transfer efficiency in dependence of the type of side chain. The compound with methyl side chains shows remarkable properties regarding thin film absorption, surface roughness, and energy transfer efficiency, which we attribute to the specific nanomorphology of the thin film.

  9. Shock induced chemistry in liquids studied with ultrafast dynamic ellipsometry and visible transient absorption spectroscopy.

    PubMed

    Dang, N C; Bolme, C A; Moore, D S; McGrane, S D

    2012-10-25

    The response to ultrafast laser shock loading of nine liquids was monitored in an effort to reveal evidence of chemical changes occurring during the first 350 ps following the shock front. In an effort to compare molecular structures possessing a variety of common bonding patterns, data were acquired for the liquids: cyclohexane, cyclohexene, 1,3-cyclohexadiene, benzene, water, acetonitrile, acrylonitrile, tert-butylacetylene, and phenylacetylene. Transient absorption spectra were measured in the spectral region from 440 to 780 nm over shock stress states from 7 to 20 GPa. Ultrafast dynamic ellipsometry was used to measure the shock and particle velocity as well as the shocked refractive index. Significant transient absorption attributed to chemical reaction was observed for shocked phenylacetylene and acrylonitrile. Evidence of volume decreasing chemical reactions was also observed in the ultrafast dynamic ellipsometry data for phenylacetylene and acrylonitrile. The liquid 1,3-cyclohexadiene exhibited volume decreasing reaction in the ultrafast dynamic ellipsometry data but did not exhibit an increase in the transient absorption spectra. There was no evidence of chemical reaction in cyclohexane, cyclohexene, benzene, water, acetonitrile, or tert-butylacetylene in the first 350 ps, despite the application of shock stress that was in many cases well above the reaction threshold observed at microsecond time scales.

  10. Sub-bandgap absorption in polymer-fullerene solar cells studied by temperature-dependent external quantum efficiency and absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Presselt, Martin; Herrmann, Felix; Shokhovets, Sviatoslav; Hoppe, Harald; Runge, Erich; Gobsch, Gerhard

    2012-07-01

    We study the sub-bandgap (SBG) absorption in solar cells made of poly(3-hexylthiophene-2,5-diyl) and [6,6]-phenylC61-butyric-acid-methyl-ester by photothermal deflection absorption spectroscopy and measurement of temperature-dependent external-quantum-efficiency (EQE) spectra. Several models for SBG absorption are critically reviewed in view of the EQE results. The latter suggest polaron-related transitions as origin of the Gaussian SBG peak near 1.6 eV. Intermolecular charge transfer (CT) excitations as an explanation cannot completely be ruled out. However, the assumption of CT excitons with large binding energies is difficult to reconcile with the rapid loss of weight of the Gaussian SBG-peak seen in EQE above room temperature.

  11. Simulation of carbon dioxide absorption by sodium hydroxide solution in a packed bed and studying the effect of operating parameters on absorption

    SciTech Connect

    Yazdanbakhsh, Farzad; Soltani Goharrizi, Ata'ollah; Hashemipour Rafsanjani, Hassan

    2007-07-01

    Available in abstract form only. Full text of publication follows: In this study. simulation of carbon dioxide absorption by Sodium Hydroxide solution in a packed bed has been investigated. At first, mass and energy balances were applied around a differential height of the bed. So, the governing equations were obtained. Surface renewal theory by Danckwerts was used to represent the mass transfer operation Finally, by changing the operating parameters like solvent temperature, inlet gas composition pressure and height of the bed, the effect of these parameters on the absorption and the composition of carbon dioxide in exit stream have been investigated. (authors)

  12. Ultrafast Excited-State Dynamics of 6-Azauracil Studied by Femtosecond Transient Absorption Spectroscopy.

    PubMed

    Hua, XinZhong; Hua, LinQiang; Liu, XiaoJun

    2015-12-31

    The excited-state dynamics of 6-azauracil in different solvents have been studied using femtosecond transient absorption spectroscopy. The molecule is populated to the S2 state with a pump pulse at 264 nm. Broad-band white light continuum which covers from 320 to 600 nm is used as the probe. With a global fitting analysis of the measured transient spectra, three decay time constants, i.e., <0.3, 5.2 ± 0.1, and >1000 ps, are directly obtained in the solvent of acetonitrile. These newly observed lifetime constants are important in clarifying its decay dynamics as well as in providing a criterion for the ultrafast dynamics simulations in 6-azauracil using quantum chemical theories. In combination with previous theoretical works, the main decay channel is proposed: the initially populated S2 decays to S1 through internal conversion in <0.3 ps, followed by an intersystem crossing from S1 to T1 in 5.2 ± 0.1 ps. The >1000 ps component is due to the decay of the T1 state. A comparison of the excited-state dynamics in different solvents reveals that the decay from S1 to T1 shows a clear dependence on the polarity of the solvents. With higher polarity, the S1 excited state decays faster. This observation is in line with the prediction by Etinski et al. [ Phys. Chem. Chem. Phys. 2010 , 12 , 15665 - 15671 ], where a blue-shift of the T1 state potential energy surface leading to an increase of the intersystem crossing rate was proposed. With the new information obtained in the present measurement, a clearer picture of the decay dynamics of 6-azauracil on the S2 excited state is provided.

  13. A theoretical and experimental study of calcium, iron, zinc, cadmium, and sodium ions absorption by aspartame.

    PubMed

    Mahnam, Karim; Raisi, Fatame

    2017-03-01

    Aspartame (L-Aspartyl-L-phenylalanine methyl ester) is a sweet dipeptide used in some foods and beverages. Experimental studies show that aspartame causes osteoporosis and some illnesses, which are similar to those of copper and calcium deficiency. This raises the issue that aspartame in food may interact with cations and excrete them from the body. This study aimed to study aspartame interaction with calcium, zinc, iron, sodium, and cadmium ions via molecular dynamics simulation (MD) and spectroscopy. Following a 480-ns molecular dynamics simulation, it became clear that the aspartame is able to sequester Fe(2+), Ca(2+), Cd(2+), and Zn(2+) ions for a long time. Complexation led to increasing UV-Vis absorption spectra and emission spectra of the complexes. This study suggests a potential risk of cationic absorption of aspartame. This study suggests that purification of cadmium-polluted water by aspartame needs a more general risk assessment.

  14. Assessment of in vitro human dermal absorption studies on pesticides to determine default values, opportunities for read-across and influence of dilution on absorption.

    PubMed

    Aggarwal, M; Battalora, M; Fisher, P; Hüser, A; Parr-Dobrzanski, R; Soufi, M; Mostert, V; Strupp, C; Whalley, P; Wiemann, C; Billington, R

    2014-04-01

    Dermal absorption is an integral part of non-dietary human safety risk assessments for agrochemicals. Typically, dermal absorption data for agrochemical active substances are generated from the undiluted formulation concentrate and its spray dilutions. European Food Safety Authority (EFSA) guidance, which combines highly conservative default values, very limited opportunities for read-across from existing data and other overly conservative conclusions, was the driver for this assessment. To investigate the reliability of the EFSA guidance, a homogeneous data-set of 190 GLP and OECD guideline compliant in vitro human skin studies, chosen to match the test method preferred by EU data requirements, was evaluated. These studies represented a wide range of active substances, formulation types, and concentrations. In alignment with EFSA guidance on human exposure assessment, a conservative estimate of absorption (95th percentile) was chosen to define defaults, which were also based on the EFSA worst-case assumption that all material in skin, excluding the first two tape strips, is absorbed. The analysis supports dermal absorption defaults of 6% for liquid concentrates, 2% for solid concentrates, and 30% for all spray dilutions, irrespective of the active substance concentration. Relatively high dermal absorption values for organic solvent-based formulations, compared to water-based or solid concentrates, support their use as worst-case surrogate data for read-across to other formulation types. The current review also shows that dermal absorption of sprays does not increase linearly with increasing dilution, and provides a novel, science-based option for extrapolation from existing data.

  15. Kinetic study of carbon dioxide absorption into glycine promoted diethanolamine (DEA)

    NASA Astrophysics Data System (ADS)

    Pudjiastuti, Lily; Susianto, Altway, Ali; IC, Maria Hestia; Arsi, Kartika

    2015-12-01

    In industry, especially petrochemical, oil and natural gas industry, required separation process of CO2 gas which is a corrosive gas (acid gas). This characteristic can damage the plant utility and piping systems as well as reducing the caloric value of natural gas. Corrosive characteristic of CO2 will appear in areas where there is a decrease in temperature and pressure, such as at the elbow pipe, tubing, cooler and injector turbine. From disadvantages as described above, then it is important to do separation process in the CO2 gas stream, one of the method for remove CO2 from the gas stream is reactive absorption using alkanolamine based solution with promotor. Therefore, this study is done to determine the kinetics constant of CO2 absorption in diethanolamine (DEA) solution using a glycine promoter. Glycine is chosen as a promoter because glycine is a primary amine compound which is reactive, moreover, glycine has resistance to high temperatures so it will not easy to degradable and suitable for application in industry. The method used in this study is absorption using laboratory scale wetted wall column equipment at atmospheric of pressure. This study will to provide the reaction kinetics data information in order to optimize the separation process of CO2 in the industrialized world. The experimental results show that rising temperatures from 303,15 - 328,15 K and the increase of concentration of glycine from 1% - 3% weight will increase the absorption rate of carbon dioxide in DEA promoted with glycine by 24,2% and 59,764% respectively, also the reaction kinetic constant is 1.419 × 1012 exp (-3634/T) (m3/kmol.s). This result show that the addition of glycine as a promoter can increase absorption rate of carbon dioxide in diethanolamine solution and cover the weaknesses of diethanolamine solution.

  16. Replication Study: Melanoma genome sequencing reveals frequent PREX2 mutations

    PubMed Central

    Horrigan, Stephen K; Courville, Pascal; Sampey, Darryl; Zhou, Faren; Cai, Steve

    2017-01-01

    In 2015, as part of the Reproducibility Project: Cancer Biology, we published a Registered Report (Chroscinski et al., 2014) that described how we intended to replicate selected experiments from the paper "Melanoma genome sequencing reveals frequent PREX2 mutations" (Berger et al., 2012). Here we report the results of those experiments. We regenerated cells stably expressing ectopic wild-type and mutant phosphatidylinositol-3,4,5-trisphosphate-dependent Rac exchange factor 2 (PREX2) using the same immortalized human NRASG12D melanocytes as the original study. Evaluation of PREX2 expression in these newly generated stable cells revealed varying levels of expression among the PREX2 isoforms, which was also observed in the stable cells made in the original study (Figure S6A; Berger et al., 2012). Additionally, ectopically expressed PREX2 was found to be at least 5 times above endogenous PREX2 expression. The monitoring of tumor formation of these stable cells in vivo resulted in no statistically significant difference in tumor-free survival driven by PREX2 variants, whereas the original study reported that these PREX2 mutations increased the rate of tumor incidence compared to controls (Figure 3B and S6B; Berger et al., 2012). Surprisingly, the median tumor-free survival was 1 week in this replication attempt, while 70% of the control mice were reported to be tumor-free after 9 weeks in the original study. The rapid tumor onset observed in this replication attempt, compared to the original study, makes the detection of accelerated tumor growth in PREX2 expressing NRASG12D melanocytes extremely difficult. Finally, we report meta-analyses for each result. DOI: http://dx.doi.org/10.7554/eLife.21634.001 PMID:28100394

  17. Local electronic states of Fe4N films revealed by x-ray absorption spectroscopy and x-ray magnetic circular dichroism

    NASA Astrophysics Data System (ADS)

    Ito, Keita; Toko, Kaoru; Takeda, Yukiharu; Saitoh, Yuji; Oguchi, Tamio; Suemasu, Takashi; Kimura, Akio

    2015-05-01

    We performed x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements at Fe L2,3 and N K-edges for Fe4N epitaxial films grown by molecular beam epitaxy. In order to clarify the element specific local electronic structure of Fe4N, we compared experimentally obtained XAS and XMCD spectra with those simulated by a combination of a first-principles calculation and Fermi's golden rule. We revealed that the shoulders observed at Fe L2,3-edges in the XAS and XMCD spectra were due to the electric dipole transition from the Fe 2p core-level to the hybridization state generated by σ* anti-bonding between the orbitals of N 2p at the body-centered site and Fe 3d on the face-centered (II) sites. Thus, the observed shoulders were attributed to the local electronic structure of Fe atoms at II sites. As to the N K-edge, the line shape of the obtained spectra was explained by the dipole transition from the N 1s core-level to the hybridization state formed by π* and σ* anti-bondings between the Fe 3d and N 2p orbitals. This hybridization plays an important role in featuring the electronic structures and physical properties of Fe4N.

  18. Local electronic states of Fe{sub 4}N films revealed by x-ray absorption spectroscopy and x-ray magnetic circular dichroism

    SciTech Connect

    Ito, Keita; Toko, Kaoru; Suemasu, Takashi; Takeda, Yukiharu; Saitoh, Yuji; Oguchi, Tamio; Kimura, Akio

    2015-05-21

    We performed x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements at Fe L{sub 2,3} and N K-edges for Fe{sub 4}N epitaxial films grown by molecular beam epitaxy. In order to clarify the element specific local electronic structure of Fe{sub 4}N, we compared experimentally obtained XAS and XMCD spectra with those simulated by a combination of a first-principles calculation and Fermi's golden rule. We revealed that the shoulders observed at Fe L{sub 2,3}-edges in the XAS and XMCD spectra were due to the electric dipole transition from the Fe 2p core-level to the hybridization state generated by σ* anti-bonding between the orbitals of N 2p at the body-centered site and Fe 3d on the face-centered (II) sites. Thus, the observed shoulders were attributed to the local electronic structure of Fe atoms at II sites. As to the N K-edge, the line shape of the obtained spectra was explained by the dipole transition from the N 1s core-level to the hybridization state formed by π* and σ* anti-bondings between the Fe 3d and N 2p orbitals. This hybridization plays an important role in featuring the electronic structures and physical properties of Fe{sub 4}N.

  19. Studies on mass energy-absorption coefficients and effective atomic energy-absorption cross sections for carbohydrates

    NASA Astrophysics Data System (ADS)

    Ladhaf, Bibifatima M.; Pawar, Pravina P.

    2015-04-01

    We measured here the mass attenuation coefficients (μ/ρ) of carbohydrates, Esculine (C15H16O9), Sucrose (C12H22O11), Sorbitol (C6H14O6), D-Galactose (C6H12O6), Inositol (C6H12O6), D-Xylose (C5H10O5) covering the energy range from 122 keV up to 1330 keV photon energies by using gamma ray transmission method in a narrow beam good geometry set-up. The gamma-rays were detected using NaI(Tl) scintillation detection system with a resolution of 8.2% at 662 keV. The attenuation coefficient data were then used to obtain the total attenuation cross-section (σtot), molar extinction coefficients (ε), mass-energy absorption coefficients (μen/ρ) and effective (average) atomic energy-absorption cross section (σa,en) of the compounds. These values are found to be in good agreement with the theoretical values calculated based on XCOM data.

  20. Ethiopian population dermatoglyphic study reveals linguistic stratification of diversity.

    PubMed

    Yohannes, Seile; Bekele, Endashaw

    2015-01-01

    The manifestation of ethnic, blood type, & gender-wise population variations regarding Dermatoglyphic manifestations are of interest to assess intra-group diversity and differentiation. The present study reports on the analysis of qualitaive and quantitative finger Dermatoglyphic traits of 382 individuals cross-sectionally sampled from an administrative region of Ethiopia, consisting of five ethnic cohorts from the Afro-Asiatic & Nilo-Saharan affiliations. These Dermatoglyphic parameters were then applied in the assessment of diversity & differentiation, including Heterozygosity, Fixation, Panmixia, Wahlund's variance, Nei's measure of genetic diversity, and thumb & finger pattern genotypes, which were inturn used in homology inferences as summarized by a Neighbour-Joining tree constructed from Nei's standard genetic distance. Results revealed significant correlation between Dermatoglyphics & population parameters that were further found to be in concordance with the historical accounts of the ethnic groups. Such inductions as the ancient north-eastern presence and subsequent admixure events of the Oromos (PII= 15.01), the high diversity of the Amharas (H= 0.1978, F= 0.6453, and P= 0.4144), and the Nilo-Saharan origin of the Berta group (PII= 10.66) are evidences to this. The study has further tested the possibility of applying Dermatoglyphics in population genetic & anthropologic research, highlighting on the prospect of developing a method to trace back population origins & ancient movement patterns. Additionally, linguistic clustering was deemed significant for the Ethiopian population, coinciding with recent genome wide studies that have ascertained that linguistic clustering as to being more crucial than the geographical patterning in the Ethiopian context. Finally, Dermatoglyphic markers have been proven to be endowed with a strong potential as non-invasive preliminary tools applicable prior to genetic studies to analyze ethnically sub-divided populations and

  1. X-ray absorption spectral studies of copper (II) mixed ligand complexes

    NASA Astrophysics Data System (ADS)

    Soni, B.; Dar, Davood Ah; Shrivastava, B. D.; Prasad, J.; Srivastava, K.

    2014-09-01

    X-ray absorption spectra at the K-edge of copper have been studied in two copper mixed ligand complexes, one having tetramethyethylenediamine (tmen) and the other having tetraethyethylenediamine (teen) as one of the ligands. The spectra have been recorded at BL-8 dispersive extended X-ray absorption fine structure (EXAFS) beamline at the 2.5 GeV INDUS- 2 synchrotron, RRCAT, Indore, India. The data obtained has been processed using the data analysis program Athena. The energy of the K-absorption edge, chemical shift, edge-width and shift of the principal absorption maximum in the complexes have been determined and discussed. The values of these parameters have been found to be approximately the same in both the complexes indicating that the two complexes possess similar chemical environment around the copper metal atom. The chemical shift has been utilized to estimate effective nuclear charge on the absorbing atom. The normalized EXAFS spectra have been Fourier transformed. The position of the first peak in the Fourier transform gives the value of first shell bond length, which is shorter than the actual bond length because of energy dependence of the phase factors in the sine function of the EXAFS equation. This distance is thus the phase- uncorrected bond length. Bond length has also been determined by Levy's, Lytle's and Lytle, Sayers and Stern's (LSS) methods. The results obtained from LSS and the Fourier transformation methods are comparable with each other, since both are phase uncorrected bond lengths.

  2. The Intervening Galaxies Hypothesis of the Absorption Spectra of Quasi-Stellar Objects: Some Statistical Studies

    NASA Astrophysics Data System (ADS)

    Duari, Debiprosad; Narlikar, Jayant V.

    This paper examines, in the light of the available data, the hypothesis that the heavy element absorption line systems in the spectra of QSOs originate through en-route absorption by intervening galaxies, halos etc. Several statistical tests are applied in two different ways to compare the predictions of the intervening galaxies hypothesis (IGH) with actual observations. The database is taken from a recent 1991 compilation of absorption line systems by Junkkarinen, Hewitt and Burbidge. Although, prima facie, a considerable gap is found between the predictions of the intervening galaxies hypothesis and the actual observations despite inclusion of any effects of clustering and some likely selection effects, the gap narrows after invoking evolution in the number density of absorbers and allowing for the incompleteness and inhomogeneity of samples examined. On the latter count the gap might be bridgeable by stretching the parameters of the theory. It is concluded that although the intervening galaxies hypothesis is a possible natural explanation to account for the absorption line systems and may in fact do so in several cases, it seems too simplistic to be able to account for all the available data. It is further stressed that the statistical techniques described here will be useful for future studies of complete and homogenous samples with a view to deciding the extent of applicability of the IGH.

  3. Substituted benzoxadiazoles as fluorogenic probes: a computational study of absorption and fluorescence.

    PubMed

    Brown, Alex; Ngai, Tsz Yan; Barnes, Marie A; Key, Jessie A; Cairo, Christopher W

    2012-01-12

    General chemical strategies which provide controlled changes in the emission or absorption properties of biologically compatible fluorophores remain elusive. One strategy employed is the conversion of a fluorophore-attached alkyne (or azide) to a triazole through a copper-catalyzed azide-alkyne coupling (CuAAC) reaction. In this study, we have computationally examined a series of structurally related 2,1,3-benzoxadiazole (benzofurazan) fluorophores and evaluated changes in their photophysical properties upon conversion from alkyne (or azide) to triazole forms. We have also determined the photophysical properties for a known set of benzoxadiazole compounds. The absorption and emission energies have been determined computationally using time-dependent density functional theory (TD-DFT) with the Perdew, Burke, and Ernzerhof exchange-correlation density functional (PBE0) and the 6-31+G(d) basis set. The TD-DFT results consistently agreed with the experimentally determined absorption and emission wavelengths except for certain compounds where charge-transfer excited states occurred. In addition to determining the absorption and emission wavelengths, simple methods for predicting relative quantum yields previously derived from semiempirical calculations were reevaluated on the basis of the new TD-DFT results and shown to be deficient. These results provide a necessary framework for the design of new substituted benzoxadiazole fluorophores.

  4. An x-ray absorption spectroscopy study of Mo oxidation in Pb at elevated temperatures

    SciTech Connect

    Liu, Shanshan; Olive, Daniel; Terry, Jeff; Segre, Carlo U.

    2009-06-30

    The corrosion of fuel cladding and structural materials by lead and lead-bismuth eutectic in the liquid state at elevated temperatures is an issue that must be considered when designing advanced nuclear systems and high-power spallation neutron targets. In this work, lead corrosion studies of molybdenum were performed to investigate the interaction layer as a function of temperature by X-ray absorption spectroscopy. In situ X-ray absorption measurements on a Mo substrate with a 3-6 {micro}m layer of Pb deposited by thermal evaporation were performed at temperatures up to 900 C and at a 15{sup o} angle to the incident X-rays. The changes in the local atomic structure of the corrosion layer are visible in the difference extended X-ray absorption fine structure and the linear combination fitting of the X-ray absorption near-edge structure to as-deposited molybdenum sample and molybdenum oxide (MoO{sub 2} and MoO{sub 3}) standards. The data are consistent with the appearance of MoO{sub 3} in an intermediate temperature range (650-800 C) and the more stable MoO{sub 2} phase dominating at high and low temperatures.

  5. Study on the Partial Load Characteristics of Double-Effect Absorption Systems

    NASA Astrophysics Data System (ADS)

    Kawakami, Ryuichiro; Fukuchi, Toru; Kaita, Yoshio

    Simulation analysis was carried out to study the partial load characteristics of three different types of double-effect LiBr-water absorption cycle, namely series flow, parallel flow and reverse flow. A computer program was developed for this study to simulate the behavior of the absorption cycles equipped with flow rate control of absorbent, cooling water and chilling water on partial load. The effects of the flow rate control on the coefficient of performance (COP), the maximum temperature and maximum pressure were studied. The results show that not only flow rate control of absorbent is essential for high COP on the partial load, but also flow rate control of cooling water and chilling water is recommendable to save the power of pumping.

  6. On the enzymatic activity of catalase: an iron L-edge X-ray absorption study of the active centre.

    PubMed

    Bergmann, Nora; Bonhommeau, Sébastien; Lange, Kathrin M; Greil, Stefanie M; Eisebitt, Stefan; de Groot, Frank; Chergui, Majed; Aziz, Emad F

    2010-05-14

    Catalase and methaemoglobin have very similar haem groups, which are both ferric, yet catalase decomposes hydrogen peroxide to water and oxygen very efficiently, while methaemoglobin does not. Structural studies have attributed this behaviour to their different distal environments. Here we present Fe L(2,3)-edge X-ray absorption spectra of these proteins in physiological solutions, which reveal clear differences in their electronic structures, in that pi back-donation of the Fe atom occurs in catalase, which confers on it a partial ferryl (Fe(4+)) character, while this is not the case in methaemoglobin. The origin of the Fe(4+) character stems from the proximal tyrosine residue. We also find that both systems are in a high spin state. Temperature effects influence the spectra of catalase only weakly, in agreement with previous studies of its chemical activity. We conclude that the high activity of catalase is not only determined by its distal environment but also by its partial ferryl character.

  7. Spectral Apparatus with a Cryogenic, High-Throughput, Multipass Gas Cell for Studies of Absorption of Radiation by Gaseous Media

    NASA Astrophysics Data System (ADS)

    Moskalenko, N. I.; Mirumyants, S. O.; Parzhin, S. N.; Dodov, I. R.

    2016-11-01

    Spectral systems with an MKhK-6 cryogenic, high-throughput, multipass gas cell for studying the absorption spectra of gaseous media with high spectral resolution in the 0.1-6 μm range at pressures of 100 to 5·106 Pa and temperatures of 180-300 K are discussed. Their use in measurements of spectral absorption coefficients, temperature dependences of the spectral transmission function, and parameters of spectral absorption lines is examined.

  8. Comparative study on three highly sensitive absorption measurement techniques characterizing lithium niobate over its entire transparent spectral range.

    PubMed

    Leidinger, M; Fieberg, S; Waasem, N; Kühnemann, F; Buse, K; Breunig, I

    2015-08-24

    We employ three highly sensitive spectrometers: a photoacoustic spectrometer, a photothermal common-path interferometer and a whispering-gallery-resonator-based absorption spectrometer, for a comparative study of measuring the absorption coefficient of nominally transparent undoped, congruently grown lithium niobate for ordinarily and extraordinarily polarized light in the wavelength range from 390 to 3800 nm. The absorption coefficient ranges from below 10(-4) cm(-1) up to 2 cm(-1). Furthermore, we measure the absorption at the Urbach tail as well as the multiphonon edge of the material by a standard grating spectrometer and a Fourier-transform infrared spectrometer, providing for the first time an absorption spectrum of the whole transparency window of lithium niobate. The absorption coefficients obtained by the three highly sensitive and independent methods show good agreement.

  9. Atomic structure of machined semiconducting chips: An x-ray absorption spectroscopy study

    SciTech Connect

    Paesler, M.; Sayers, D.

    1988-12-01

    X-ray absorption spectroscopy (XAS) has been used to examine the atomic structure of chips of germanium that were produced by single point diamond machining. It is demonstrated that although the local (nearest neighbor) atomic structure is experimentally quite similar to that of single crystal specimens information from more distant atoms indicates the presence of considerable stress. An outline of the technique is given and the strength of XAS in studying the machining process is demonstrated.

  10. Optical and ultraviolet absorption studies of cool gas in the Milky Way halo

    NASA Technical Reports Server (NTRS)

    Danly, L.

    1990-01-01

    This paper focuses on the contributions from absorption techniques to the knowledge of halo gas with temperatures below 10 to the 5th K. The results from observations of the neutral and singly ionized species on the nature of cool gas in the halo, its structure and its kinematics are presented. An overview of past and optical and ultraviolet observational studies of halo gas is included.

  11. X-ray absorption study of ceria nanorods promoting the disproportionation of hydrogen peroxide.

    PubMed

    Wu, Tai-Sing; Zhou, Yunyun; Sabirianov, Renat F; Mei, Wai-Ning; Soo, Yun-Liang; Cheung, Chin Li

    2016-04-11

    A quasi in situ X-ray absorption study demonstrated that the disproportionation of hydrogen peroxide (H2O2) promoted by ceria nanorods was associated with a reversible Ce(3+)/Ce(4+) reaction and structural transformations in ceria. The direction of this reversible reaction was postulated to depend on the H2O2 concentration and the fraction of Ce(3+) species in ceria nanorods.

  12. The study of absorption kinetics of berberine based on portal vein in rat, and the influence of verapamil and borneol to its absorption ability by UHPLC method.

    PubMed

    Zou, Liang; Li, Rui; Wang, Ping; Xiao, Yan; Xu, Li-Jia; He, Yu-Xin; Zhao, Gang; Peng, Lian-Xin

    2014-09-01

    This paper aims to investigate the portal-vein absorption kinetics of berberine in rat, and the influence of P-gp inhibitors such as verapamil and borneol, to its absorption ability. In the paper, a validated UHPLC method was established to determine the berberine in plasma, and the portal-vein absorption model was applied to conduct the pharmacokinetic study. Animals were divided into four groups as follow: group berberine group (BG); group verapamil + berberine group (VBG); group borneol + berberine group (BBG) and group long-term use of borneol + berberine group (LBBG). Plasma samples were obtained at regular time intervals after administration and separated on Agilent 1290 Infinity UHPLC instrument. The method showed good linearity (r = 0.9988) over wide dynamic ranges (4.08-163.20 ng/mL). Variations within- and between-batch never exceeded 7.58 and 2.21 %, respectively. The extraction recovery rates ranged from 85.34 to 111.62 %. We discovered that the AUC of four group exhibited no significant differences (P > 0.05), and co-administration of berberine with borneol of group BBG and group LBBG in advance could both reduce the T max and C max as compared to group BG (P < 0.05), while co-administration of verapamil seems to have had little influence to berberine's absorption ability.

  13. Resonant absorption induced fast melting studied with mid-IR QCLs

    NASA Astrophysics Data System (ADS)

    Lu, Jie; Lv, Yankun; Ji, Youxin; Tang, Xiaoliang; Qi, Zeming; Li, Liangbin

    2017-02-01

    We demonstrate the use of a pump-probe setup based on two mid-infrared quantum cascade lasers (QCLs) to investigate the melting and crystallization of materials through resonant absorption. A combination of pump and probe beams fulfills the two-color synchronous detection. Furthermore, narrow linewidth advances the accuracy of measurements and the character of broad tuning range of QCLs enables wide applications in various sample and multiple structures. 1-Eicosene was selected as a simple model system to verify the feasibility of this method. A pulsed QCL was tuned to the absorption peak of CH2 bending vibration at 1467 cm-1 to resonantly heat the sample. The other QCL in continuous mode was tuned to 1643 cm-1 corresponding the C=C stretching vibration to follow the fast melting dynamics. By monitoring the transmission intensity variation of pump and probe beams during pump-probe experiments, the resonant absorption induced fast melting and re-crystallization of 1-Eicosene can be studied. Results show that the thermal effect and melting behaviors strongly depend on the pump wavelength (resonant or non-resonant) and energy, as well as the pump time. The realization and detection of melting and recrystallization can be performed in tens of milliseconds, which improves the time resolution of melting process study based on general mid-infrared spectrum by orders of magnitude. The availability of resonant heating and detections based on mid-infrared QCLs is expected to enable new applications in melting study.

  14. The electronic absorption study of imide anion radicals in terms of time dependent density functional theory.

    PubMed

    Andrzejak, Marcin; Sterzel, Mariusz; Pawlikowski, Marek T

    2005-07-01

    The absorption spectra of the N-(2,5-di-tert-butylphenyl) phthalimide (1-), N-(2,5-di-tert-butylphenyl)-1,8-naphthalimide (2-) and N-(2,5-di-tert-butylphenyl)-perylene-3,4-dicarboximide (3-) anion radicals are studied in terms of time dependent density functional theory (TDDFT). For these anion radicals a large number electronic states (from 30 to 60) was found in the visible and near-IR regions (5000-45,000 cm(-1)). In these regions the TD/B3LYP treatment at the 6-1+G* level is shown to reproduce satisfactorily the empirical absorption spectra of all three anion radicals studied. The most apparent discrepancies between purely electronic theory and the experiment could be found in the excitation region corresponding to D0-->D1 transitions in the 2- and 3- molecules. For these species we argue that the structures seen in the lowest energy part of the absorptions of the 2- and 3- species are very likely due to Franck-Condon (FC) activity of the totally symmetric vibrations not studied in this Letter.

  15. The electronic absorption study of imide anion radicals in terms of time dependent density functional theory

    NASA Astrophysics Data System (ADS)

    Andrzejak, Marcin; Sterzel, Mariusz; Pawlikowski, Marek T.

    2005-07-01

    The absorption spectra of the N-(2,5-di- tert-butylphenyl) phthalimide ( 1-), N-(2,5-di- tert-butylphenyl)-1,8-naphthalimide ( 2-) and N-(2,5-di- tert-butylphenyl)-perylene-3,4-dicarboximide ( 3-) anion radicals are studied in terms of time dependent density functional theory (TDDFT). For these anion radicals a large number electronic states (from 30 to 60) was found in the visible and near-IR regions (5000-45000 cm -1). In these regions the TD/B3LYP treatment at the 6-1+G* level is shown to reproduce satisfactorily the empirical absorption spectra of all three anion radicals studied. The most apparent discrepancies between purely electronic theory and the experiment could be found in the excitation region corresponding to D0→ D1 transitions in the 2- and 3- molecules. For these species we argue that the structures seen in the lowest energy part of the absorptions of the 2- and 3- species are very likely due to Franck-Condon (FC) activity of the totally symmetric vibrations not studied in this Letter.

  16. An X-ray absorption study of selenium confined in channels of cancrinite: Evidence for dimerisation in highly oriented chains

    NASA Astrophysics Data System (ADS)

    Kolobov, Alexander V.; Oyanagi, Hiroyuki; Poborchii, Vladimir V.; Tanaka, Kazunobu

    1997-09-01

    Local structure of one-dimensional selenium chains in cancrinite channels have been studied by polarised X-ray absorption. Polarised EXAFS reveals that selenium atoms are one-fold coordinated and well-aligned along the c-axis of cancrinite. The obtained SeSe bond length is 2.40 ± 0.01 Å. The results provide direct evidence for dimerisation of selenium chains and suggest incommensurate intercalation of dimers which do not form a triplet (π-bond) state or a dangling bond state. Highly anisotropic polarisation dependence of XANES demonstrate that antibonding 4p(σ ∗) states are partially filled suggesting a charge transfer from Na cations located in the channels.

  17. Nonlinear absorption kinetics of self-emulsifying drug delivery systems (SEDDS) containing tocotrienols as lipophilic molecules: in vivo and in vitro studies.

    PubMed

    Alqahtani, Saeed; Alayoubi, Alaadin; Nazzal, Sami; Sylvester, Paul W; Kaddoumi, Amal

    2013-07-01

    Self-emulsifying drug delivery systems (SEDDS) have been broadly used to promote the oral absorption of poorly water-soluble drugs. The purpose of the current study was to evaluate the in vivo oral bioavailability of vitamin E isoforms, δ-tocotrienol (δ-T3) and γ-tocotrienol (γ-T3) administered as SEDDS, as compared to commercially available UNIQUE E® Tocotrienols capsules. Results from studies in rats showed that low dose treatment with δ-T3 (90%) and γ-T3 (10%) formulated SEDDS showed bioavailability of 31.5% and 332%, respectively. However, bioavailability showed a progressive decrease with increased treatment dose that displayed nonlinear absorption kinetics. Additional in vitro studies examining cellular uptake studies in Caco 2 cells revealed that the SEDDS formulation increased passive permeability of δ-T3 and γ-T3 by threefold as compared to the commercial capsule formulation. These studies also showed that free surfactants decreased δ-T3 and γ-T3 absorption. Specifically, combined treatment cremophor EL or labrasol with tocotrienols caused a 60-85% reduction in the cellular uptake of δ-T3 and γ-T3 and these effects appear to result from surfactant-induced inhibition of the δ-T3 and γ-T3 transport protein Niemann-Pick C1-like 1 (NPC1L1). In summary, results showed that SEDDS formulation significantly increases the absorption and bioavailability δ-T3 and γ-T3. However, this effect is self-limiting because treatment with increasing doses of SEDDS appears to be associated with a corresponding increase in free surfactants levels that directly and negatively impact tocotrienol transport protein function and results in nonlinear absorption kinetics and a progressive decrease in δ-T3 and γ-T3 absorption and bioavailability.

  18. Time-resolved absorption studies of the ZnSe/ZnSTe superlattice

    NASA Astrophysics Data System (ADS)

    Wang, H.; Sou, I. K.; Wong, G. K. L.; Wong, K. S.

    2001-04-01

    The time-resolved differential absorption of the ZnSe/ZnSTe superlattice is studied using femtosecond pump-probe measurements. Transient spectral hole burning due to the initial nonthermal carrier distribution is observed at zero time delay and the carriers are thermalized within 0.5 ps. The high-energy tail of the differential absorption spectra was used to deduce the effective temperature of the thermalized carriers. Rapid hot-carrier cooling from a temperature of 763 to 450 K within the first 4 ps is observed, with carrier cooling slowing down hence. This initial fast hot-carrier cooling is consistent with the strong carrier-phonon interaction in large gap II-VI semiconductors.

  19. Parametric study of power absorption from electromagnetic waves by small ferrite spheres

    NASA Technical Reports Server (NTRS)

    Englert, Gerald W.

    1989-01-01

    Algebraic expressions in terms of elementary mathematical functions are derived for power absorption and dissipation by eddy currents and magnetic hysteresis in ferrite spheres. Skin depth is determined by using a variable inner radius in descriptive integral equations. Numerical results are presented for sphere diameters less than one wavelength. A generalized power absorption parameter for both eddy currents and hysteresis is expressed in terms of the independent parameters involving wave frequency, sphere radius, resistivity, and complex permeability. In general, the hysteresis phenomenon has a greater sensitivity to these independent parameters than do eddy currents over the ranges of independent parameters studied herein. Working curves are presented for obtaining power losses from input to the independent parameters.

  20. The study on the light absorption and transmission laws of the blood components

    NASA Astrophysics Data System (ADS)

    Chen, Zulin; Lai, Yan; Ge, Haiyan; Xu, Zhangrui

    2003-12-01

    Aim: This experiment studied the light absorption laws of the blood components between 240-800nm. Methods: The absorbance and transmittance of the blood components were measured by applying a model UV-365 double beam scanning spectrophotometer with an integral sphere, between 240-800nm. Results: The results show: 1) The absorbance and transmittance laws resemble each other in blood of the Groups A,B,AB and O. 2) Between 600-800nm, the absorbances of the whole blood, erythrocyte, leukocyte, plasma and serum are less than 5%, while the transmittances of them are more than 95%. 3) To erythrocyte and lymphocyte, typical absorption peaks appear at 416.57+/-1.90, 542.71+/-1.80, 578.57+/-1.81nm. Conclusion: These results provide some useful parameters for the optical properties of blood and the clinical applications.

  1. X-ray absorption spectroscopic studies of mononuclear non-heme iron enzymes

    SciTech Connect

    Westre, Tami E.

    1996-01-01

    Fe-K-edge X-ray absorption spectroscopy (XAS) has been used to investigate the electronic and geometric structure of the iron active site in non-heme iron enzymes. A new theoretical extended X-ray absorption fine structure (EXAFS) analysis approach, called GNXAS, has been tested on data for iron model complexes to evaluate the utility and reliability of this new technique, especially with respect to the effects of multiple-scattering. In addition, a detailed analysis of the 1s→3d pre-edge feature has been developed as a tool for investigating the oxidation state, spin state, and geometry of iron sites. Edge and EXAFS analyses have then been applied to the study of non-heme iron enzyme active sites.

  2. High-resolution optical and ultraviolet absorption-line studies of interstellar gas

    NASA Technical Reports Server (NTRS)

    Cowie, Lennox L.; Songaila, Antoinette

    1986-01-01

    Recent progress in the characterization of the interstellar medium (ISM) by means of optical and UV spectral data is summarized. The gas is studied by focusing on background stars whose spectra can be accurately modeled to provide the light source for the absorption-line scans. The capabilities of earth- and space-based instruments which have been and are used for the surveys are delineated. The distributions of diffuse gas densities and characteristics of the cold, warm and hot gas in the Galaxy are described in terms of the elemental abundances, kinetics and distributions of the gas. Particular note is taken of gas in the solar neighborhood and around SNR, and of absorption-line data of cosmological significance.

  3. The physicochemical parameters of marker compounds and vehicles for use in in vitro percutaneous absorption studies.

    PubMed

    Kaca, Monika; Bock, Udo; Tawfik Jalal, Mohamed; Harms, Meike; Hoffmann, Christine; Müller-Goymann, Christel; Netzlaff, Frank; Schäfer, Ulrich; Lehr, Claus-Michael; Haltner-Ukomadu, Eleonore

    2008-05-01

    In order to prepare for a validation study to compare percutaneous absorption through reconstructed human epidermis with ex vivo skin absorption through human and animal skin, nine test compounds, covering a wide range of physicochemical properties were selected, namely: benzoic acid; caffeine; clotrimazole; digoxin; flufenamic acid; ivermectin; mannitol; nicotine; and testosterone. The donor and receptor media for the test substances, the addition of a solubiliser for the lipophilic compounds, as well as the stability and solubility of the test substances in the vehicles, were systematically analysed. Hydrophilic molecules, being freely soluble in water, were applied in buffered saline solutions. In order to overcome solubility restrictions for lipophilic compounds, the non-ionic surfactant, Igepal CA-630, was added to the donor vehicle, and, in the case of clotrimazole and ivermectin, also to the receptor fluid. The model molecules showed a suitable solubility and stability in the selected donor and receptor media throughout the whole duration of the test.

  4. Review of Russian language studies on radionuclide behaviour in agricultural animals: part 1. Gut absorption.

    PubMed

    Fesenko, S; Isamov, N; Howard, B J; Voigt, G; Beresford, N A; Sanzharova, N

    2007-01-01

    An extensive programme of experiments was conducted in the former USSR on transfer of radionuclides to a wide range of different agricultural animals. Only a few of these studies were made available in the English language literature or taken into account in international reviews of gastrointestinal uptake. The paper gives extended information on Russian research on radionuclide absorption in the gut of farm animals performed in controlled field and laboratory experiments from the 1960s to the current time. The data presented in the paper, together with English language values, will be used to provide recommended values of absorption specifically for farm animals within the revision of the IAEA Handbook of Parameter Values IAEA [International Atomic Energy Agency, 1994. Handbook of Parameter Values for the Prediction of Radionuclide Transfer in Temperate Environments, IAEA technical reports series No. 364. International Atomic Energy Agency, Vienna].

  5. Electron Spin Resonance and optical absorption spectroscopic studies of manganese centers in aluminium lead borate glasses.

    PubMed

    SivaRamaiah, G; LakshmanaRao, J

    2012-12-01

    Electron Spin Resonance (ESR) and optical absorption studies of 5Al(2)O(3)+75H(3)BO(3)+(20-x)PbO+xMnSO(4) (where x=0.5, 1,1.5 and 2 mol% of MnSO(4)) glasses at room temperature have been studied. The ESR spectrum of all the glasses exhibits resonance signals with effective isotropic g values at ≈2.0, 3.3 and 4.3. The ESR resonance signal at isotropic g≈2.0 has been attributed to Mn(2+) centers in an octahedral symmetry. The ESR resonance signals at isotropic g≈3.3 and 4.3 have been attributed to the rhombic symmetry of the Mn(2+) ions. The zero-field splitting parameter (zfs) has been calculated from the intensities of the allowed hyperfine lines. The optical absorption spectrum exhibits an intense band in the visible region and it has been attributed to (5)E(g)→(5)T(2g) transition of Mn(3+)centers in an octahedral environment. The optical band gap and the Urbach energies have been calculated from the ultraviolet absorption edges.

  6. Studies on different iron source absorption by in situ ligated intestinal loops of broilers.

    PubMed

    Jia, Y F; Jiang, M M; Sun, J; Shi, R B; Liu, D S

    2015-02-01

    The objective of this study was to investigate the iron source absorption in the small intestine of broiler. In situ ligated intestinal loops of 70 birds were poured into one of seven solutions, including inorganic iron (FeSO4, Fe2(SO4)3), organic Fe glycine chelate (Fe-Gly(II), Fe-Gly(III)), the mixtures (FeSO4 with glycine (Fe+Gly(II)), Fe2(SO4)3 with glycine (Fe+Gly(III)), and no Fe source (control). The total volume of 3-mL solution (containing 1 mg of elemental Fe) was injected into intestinal loops, and then 120-min incubation was performed. Compared with inorganic iron groups, in which higher FeSO4 absorption than Fe2(SO4)3 was observed, supplementation with organic Fe glycine chelate significantly increased the Fe concentration in the duodenum and jejunum (P < 0.05), however, decreased DMT1 and DcytB messenger RNA (mRNA) levels (P < 0.05). Organic Fe glycine chelate (Fe-Gly(II), Fe-Gly(III)) increased serum iron concentration (SI), compared with inorganic 3 valence iron groups (Fe2(SO4)3 and Fe+Gly(III)) (P < 0.05); moreover, lower TIBC value was observed for the chelate (P < 0.05); however, mixture of inorganic iron and glycine did not have a positive role at DMT1 and DcytB mRNA levels, SI and Fe concentrations in the small intestine. Those results indicated that the absorption of organic Fe glycine chelate was more effective than that of inorganic Fe, and the orders of iron absorption in the small intestine were: Fe-Gly(II), Fe-Gly(III) > FeSO4, Fe+Gly(II) > Fe2(SO4)3, Fe+Gly(III). Additionally, the simple mixture of inorganic iron and glycine could not increase Fe absorption, and the duodenum was the main site of Fe absorption in the intestines of broilers and the ileum absorbed iron rarely.

  7. Numerical and experimental study of the effect of microslits on the normal absorption of structural metamaterials

    NASA Astrophysics Data System (ADS)

    Ruiz, H.; Claeys, C. C.; Deckers, E.; Desmet, W.

    2016-03-01

    Resonant metamaterials are emerging as novel concepts to reduce noise levels in targeted frequency zones, so-called stop bands. The metamaterial concept improves acoustic behaviour through an increase of the insertion loss. This paper concerns a first investigation on the absorption capabilities of a resonant metamaterial when thermo-viscous effects are incorporated via the addition of microslits. In a previous work, a resonant metamaterial was obtained through the inclusion of resonating structures into cavities of an open honeycomb assembly. In this study, the air gap of the honeycomb structure is reduced so as to provide viscous losses for the travelling waves. Considering that the created resonant structures with open cavities are rigid, an equivalent fluid model is used to calculate the acoustical properties of a so called microslit metamaterial. It is demonstrated that the unit cell structure can be divided into parallel elements for which the acoustic impedance can be computed via the transfer matrix approach TMM in parallel and series. Likewise, it is shown that the structural response can be predicted by FEM models allowing studying the structural effects separately from the viscous-thermal effects predicted by the equivalent fluid model. Moreover, the combined effect of both approaches is shown experimentally where it is observed that: (i) The absorption of the resonant metamaterial is increased by the addition of microslits, (ii) the modes of the test sample appear as small peaks on the absorption curve of the microslit metamaterial, (iii) the structural modes are grouped below and above the stop band and, (iv) the resonant structures do not lead to additional absorption in the stop band region. Analytical models are compared to experimental measurements to validate the models and to show the potential of this material assembly.

  8. Incorporation of Trace Elements in Ancient and Modern Human Bone: An X-Ray Absorption Spectroscopy Study

    NASA Astrophysics Data System (ADS)

    Pingitore, N. E.; Cruz-Jimenez, G.; Price, T. D.

    2001-12-01

    X-ray absorption spectroscopy (XAS) affords the opportunity to probe the atomic environment of trace elements in human bone. We are using XAS to investigate the mode(s) of incorporation of Sr, Zn, Pb, and Ba in both modern and ancient (and thus possibly altered) human and animal bone. Because burial and diagenesis may add trace elements to bone, we performed XAS analysis on samples of pristine contemporary and ancient, buried human and animal bone. We assume that deposition of these elements during burial occurs by processes distinct from those in vivo, and this will be reflected in their atomic environments. Archaeologists measure strontium in human and animal bone as a guide to diet. Carnivores show lower Sr/Ca ratios than their herbivore prey due to discrimination against Sr relative to Ca up the food chain. In an initial sample suite no difference was observed between modern and buried bone. Analysis of additional buried samples, using a more sensitive detector, revealed significant differences in the distance to the second and third neighbors of the Sr in some of the buried samples. Distances to the first neighbor, oxygen, were similar in all samples. Zinc is also used in paleo-diet studies. Initial x-ray absorption spectroscopy of a limited suite of bones did not reveal any differences between modern and buried samples. This may reflect the limited number of samples examined or the low levels of Zn in typical aqueous solutions in soils. Signals from barium and lead were too low to record useful XAS spectra. Additional samples will be studied for Zn, Ba, and Pb. We conducted our XAS experiments on beam lines 4-1 and 4-3 at the Stanford Synchrotron Radiation Laboratory. Data were collected in the fluorescence mode, using a Lytle detector and appropriate filter, and a solid state, 13-element Ge-detector.

  9. Single molecule studies reveal new mechanisms for microtubule severing

    NASA Astrophysics Data System (ADS)

    Ross, Jennifer; Diaz-Valencia, Juan Daniel; Morelli, Margaret; Zhang, Dong; Sharp, David

    2011-03-01

    Microtubule-severing enzymes are hexameric complexes made from monomeric enzyme subunits that remove tubulin dimers from the microtubule lattice. Severing proteins are known to remodel the cytoskeleton during interphase and mitosis, and are required in proper axon morphology and mammalian bone and cartilage development. We have performed the first single molecule imaging to determine where and how severing enzymes act to cut microtubules. We have focused on the original member of the group, katanin, and the newest member, fidgetin to compare their biophysical activities in vitro. We find that, as expected, severing proteins localize to areas of activity. Interestingly, the association is very brief: they do not stay bound nor do they bind cooperatively at active sites. The association duration changes with the nucleotide content, implying that the state in the catalytic cycle dictates binding affinity with the microtubule. We also discovered that, at lower concentrations, both katanin and fidgetin can depolymerize taxol-stabilized microtubules by removing terminal dimers. These studies reveal the physical regulation schemes to control severing activity in cells, and ultimately regulate cytoskeletal architecture. This work is supported by the March of Dimes Grant #5-FY09-46.

  10. VO2+ ions in zinc lead borate glasses studied by EPR and optical absorption techniques.

    PubMed

    Prakash, P Giri; Rao, J Lakshmana

    2005-09-01

    Electron paramagnetic resonance (EPR) and optical absorption spectra of vanadyl ions in zinc lead borate (ZnO-PbO-B2O3) glass system have been studied. EPR spectra of all the glass samples exhibit resonance signals characteristic of VO2+ ions. The values of spin-Hamiltonian parameters indicate that the VO2+ ions in zinc lead borate glasses were present in octahedral sites with tetragonal compression and belong to C4V symmetry. The spin-Hamiltonian parameters g and A are found to be independent of V2O5 content and temperature but changing with ZnO content. The decrease in Deltag( parallel)/Deltag( perpendicular) value with increase in ZnO content indicates that the symmetry around VO2+ ions is more octahedral. The decrease in intensity of EPR signal above 10 mol% of V2O5 is attributed to a fall in the ratio of the number of V4+ ions (N4) to the number of V5+ ions (N5). The number of spins (N) participating in resonance was calculated as a function of temperature for VO2+ doped zinc lead borate glass sample and the activation energy was calculated. From the EPR data, the paramagnetic susceptibility was calculated at various temperatures and the Curie constant was evaluated from the 1/chi-T graph. The optical absorption spectra show single absorption band due to VO2+ ions in tetragonally distorted octahedral sites.

  11. Dimerization of single selenium chains confined in nanochannels of cancrinite: An x-ray absorption study

    NASA Astrophysics Data System (ADS)

    Kolobov, A. V.; Oyanagi, H.; Poborchii, V. V.; Tanaka, K.

    1999-04-01

    Local structure of selenium confined in nanochannels of cancrinite (Can-Se) single crystal and powder samples have been studied by polarized x-ray absorption. The spectra for a single crystal are strongly anisotropic implying linear arrangement of Se species. Polarization dependence of extended x-ray absorption fine structure (EXAFS) data provides direct evidence that dimers with the bond length of 2.40+/-0.01 Å are formed. Polarized x-ray absorption near-edge structure (XANES) spectra demonstrate that they are aligned along the channel of cancrinite. Deconvolution of XANES spectra into Lorentzians (localized states) and the remaining steplike function (continuous states) shows that two localized state peaks are present. While the one polarized parallel to the cancrinite axis is strongly polarized, the other one is essentially isotropic. Comparison of XANES peak positions for Can-Se with that for bulk selenium provides evidence for negative charge on dimers. Despite strong temperature dependence of Raman-scattering spectra found earlier, EXAFS data do not exhibit any noticeable temperature dependence. Possible mechanisms for dimer stabilization are discussed.

  12. Study of acyl group migration by femtosecond transient absorption spectroscopy and computational chemistry.

    PubMed

    Pritchina, Elena A; Gritsan, Nina P; Burdzinski, Gotard T; Platz, Matthew S

    2007-10-25

    The primary photophysical and photochemical processes in the photochemistry of 1-acetoxy-2-methoxyanthraquinone (1a) were studied using femtosecond transient absorption spectroscopy. Excitation of 1a at 270 nm results in the population of a set of highly excited singlet states. Internal conversion to the lowest singlet npi* excited state, followed by an intramolecular vibrational energy redistribution (IVR) process, proceeds with a time constant of 150 +/- 90 fs. The 1npi* excited state undergoes very fast intersystem crossing (ISC, 11 +/- 1 ps) to form the lowest triplet pipi* excited state which contains excess vibrational energy. The vibrational cooling occurs somewhat faster (4 +/- 1 ps) than ISC. The primary photochemical process, migration of acetoxy group, proceeds on the triplet potential energy surface with a time constant of 220 +/- 30 ps. The transient absorption spectra of the lowest singlet and triplet excited states of 1a, as well as the triplet excited state of the product, 9-acetoxy-2-methoxy-1,10-anthraquinone (2a), were detected. The assignments of the transient absorption spectra were supported by time-dependent DFT calculations of the UV-vis spectra of the proposed intermediates. All of the stationary points for acyl group migration on the triplet and ground state singlet potential energy surfaces were localized, and the influence of the acyl group substitution on the rate constants of the photochemical and thermal processes was analyzed.

  13. A study on optical absorption and constants of doped poly(ethylene oxide)

    NASA Astrophysics Data System (ADS)

    Al-Faleh, R. S.; Zihlif, A. M.

    2011-05-01

    Thin films of polymer electrolyte based on poly(ethylene oxide) doped with sodium iodide (NaI) were prepared using the solution cast method. The films obtained have average thickness of 70 μm and different NaI concentrations. Absorption and reflectance spectra of UV-radiation were studied in the wavelength range 300-800 nm. The optical results were analyzed in terms of absorption formula for non-crystalline materials. The optical energy gap and the basic optical constants, refractive index, and dielectric constants of the prepared films have been investigated and showed a clear dependence on the NaI concentration. The interpreted absorption mechanism is a direct electron transition. The observed optical energy gap for neat poly(ethylene oxide) is about 2.6 eV, and decreases to a value 2.36 eV for the film of 15 wt% NaI content. It was found that the calculated refractive index and the dielectric constants of the polymer electrolyte thin films increase with NaI content. Models were used to describe the dependences of the dielectric constant on the NaI concentration, and the refractive index on the incident photon energy.

  14. Study of optical properties and effective three-photon absorption in Bi-doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Karthikeyan, B.; Sandeep, C. S. Suchand; Philip, Reji; Baesso, M. L.

    2009-12-01

    In this paper we report the linear and nonlinear optical properties of Bi-doped ZnO nanoparticles. Bi-doped ZnO nanoparticles were prepared through the wet chemical method at room temperature. Optical absorption measurements show that the exciton peaks are situated at 272 and 368 nm, which are attributed to the n=2 and n=1 exciton states, respectively. Transmission electron microscopy measurements reveal the size and shape of the particles and energy dispersive X-ray measurements confirm the doping of Bi in ZnO. Steady state photoluminescence measurements show that the emission is composed of five peaks. Open aperture z-scan measurements done at 532 nm using 5 ns, 300 μJ laser pulses reveal nonlinear absorption which arises from an effective three-photon absorption process.

  15. 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.

  16. Energy absorption ability of buckyball C720 at low impact speed: a numerical study based on molecular dynamics

    PubMed Central

    2013-01-01

    The dynamic impact response of giant buckyball C720 is investigated by using molecular dynamics simulations. The non-recoverable deformation of C720 makes it an ideal candidate for high-performance energy absorption. Firstly, mechanical behaviors under dynamic impact and low-speed crushing are simulated and modeled, which clarifies the buckling-related energy absorption mechanism. One-dimensional C720 arrays (both vertical and horizontal alignments) are studied at various impact speeds, which show that the energy absorption ability is dominated by the impact energy per buckyball and less sensitive to the number and arrangement direction of buckyballs. Three-dimensional stacking of buckyballs in simple cubic, body-centered cubic, hexagonal, and face-centered cubic forms are investigated. Stacking form with higher occupation density yields higher energy absorption. The present study may shed lights on employing C720 assembly as an advanced energy absorption system against low-speed impacts. PMID:23360618

  17. In-situ x-ray absorption study of copper films in ground watersolutions

    SciTech Connect

    Kvashnina, K.O.; Butorin, S.M.; Modin, A.; Soroka, I.; Marcellini, M.; Nordgren, J.; Guo, J.-H.; Werme, L.

    2007-10-29

    This study illustrates how the damage from copper corrosion can be reduced by modifying the chemistry of the copper surface environment. The surface modification of oxidized copper films induced by chemical reaction with Cl{sup -} and HCO{sub 3}{sup -} in aqueous solutions was monitored by in situ X-ray absorption spectroscopy. The results show that corrosion of copper can be significantly reduced by adding even a small amount of sodium bicarbonate. The studied copper films corroded quickly in chloride solutions, whereas the same solution containing 1.1 mM HCO{sub 3}{sup -} prevented or slowed down the corrosion processes.

  18. Dynamics of Charged Excitons and Biexcitons in CsPbBr3 Perovskite Nanocrystals Revealed by Femtosecond Transient-Absorption and Single-Dot Luminescence Spectroscopy.

    PubMed

    Yarita, Naoki; Tahara, Hirokazu; Ihara, Toshiyuki; Kawawaki, Tokuhisa; Sato, Ryota; Saruyama, Masaki; Teranishi, Toshiharu; Kanemitsu, Yoshihiko

    2017-03-16

    Metal-halide perovskite nanocrystals (NCs) are promising photonic materials for use in solar cells, light-emitting diodes, and lasers. The optoelectronic properties of these devices are determined by the excitons and exciton complexes confined in their NCs. In this study, we determined the relaxation dynamics of charged excitons and biexcitons in CsPbBr3 NCs using femtosecond transient-absorption (TA), time-resolved photoluminescence (PL), and single-dot second-order photon correlation spectroscopy. Decay times of ∼40 and ∼200 ps were obtained from the TA and PL decay curves for biexcitons and charged excitons, respectively, in NCs with an average edge length of 7.7 nm. The existence of charged excitons even under weak photoexcitation was confirmed by the second-order photon correlation measurements. We found that charged excitons play a dominant role in luminescence processes of CsPbBr3 NCs. Combining different spectroscopic techniques enabled us to clarify the dynamical behaviors of excitons, charged excitons, and biexcitons.

  19. Electronic structure of self-doped layered Eu3F4Bi2S4 material revealed by x-ray absorption spectroscopy and photoelectron spectromicroscopy

    NASA Astrophysics Data System (ADS)

    Paris, E.; Sugimoto, T.; Wakita, T.; Barinov, A.; Terashima, K.; Kandyba, V.; Proux, O.; Kajitani, J.; Higashinaka, R.; Matsuda, T. D.; Aoki, Y.; Yokoya, T.; Mizokawa, T.; Saini, N. L.

    2017-01-01

    We have studied the electronic structure of Eu3F4Bi2S4 using a combination of Eu L3-edge x-ray absorption spectroscopy (XAS) and space-resolved angle-resolved photoemission spectroscopy (ARPES). From the Eu L3-edge XAS, we have found that the Eu in this system is in mixed valence state with coexistence of Eu2 +/Eu3 + . The bulk charge doping was estimated to be ˜0.3 per Bi site in Eu3F4Bi2S4 , which corresponds to the nominal x in a typical REO1 -xFxBiS2 system (RE: rare-earth elements). From the space-resolved ARPES, we have ruled out the possibility of any microscale phase separation of Eu valence in the system. Using a microfocused beam we have observed the band structure as well as the Fermi surface that appeared similar to other compounds of this family with disconnected rectangular electronlike pockets around the X point. The Luttinger volume analysis gives the effective carrier to be 0.23 electrons per Bi site in Eu3F4Bi2S4 , indicating that the system is likely to be in the underdoped region of its superconducting phase diagram.

  20. X-ray absorption spectroscopy and EPR studies of oriented spinach thylakoid preparations

    SciTech Connect

    Andrews, J.C. |

    1995-08-01

    In this study, oriented Photosystem II (PS II) particles from spinach chloroplasts are studied with electron paramagnetic resonance (EPR) and x-ray absorption spectroscopy (XAS) to determine more details of the structure of the oxygen evolving complex (OEC). The nature of halide binding to Mn is also studied with Cl K-edge and Mn EXAFS (extended x-ray absorption fine structure) of Mn-Cl model compounds, and with Mn EXAFS of oriented PS II in which Br has replaced Cl. Attention is focused on the following: photosynthesis and the oxygen evolving complex; determination of mosaic spread in oriented photosystem II particles from signal II EPR measurement; oriented EXAFS--studies of PS II in the S{sub 2} state; structural changes in PS II as a result of treatment with ammonia: EPR and XAS studies; studies of halide binding to Mn: Cl K-edge and Mn EXAFS of Mn-Cl model compounds and Mn EXAFS of oriented Br-treated photosystem II.

  1. X-ray absorption fine structure and X-ray excited optical luminescence studies of II-VI semiconducting nanostructures

    NASA Astrophysics Data System (ADS)

    Murphy, Michael Wayne

    2010-06-01

    Various II-VI semiconducting nanomaterials such as ZnO-ZnS nanoribbons (NRs), CdSxSe1-x nanostructures, ZnS:Mn NRs, ZnS:Mn,Eu nanoprsims (NPs), ZnO:Mn nanopowders, and ZnO:Co nanopowders were synthesized for study. These materials were characterized by techniques such as scanning electron microscopy, transmission electron microscopy, element dispersive X-ray spectroscopy, selected area electron diffraction, and X-ray diffraction. The electronic and optical properties of these nanomaterials were studied by X-ray absorption fine structure (XAFS) spectroscopy and X-ray excited optical luminescence (XEOL) techniques, using tuneable soft X-rays from a synchrotron light source. The complementary nature ofthe XAFS and XEOL techniques give site, element and chemical specific measurements which allow a better understanding of the interplay and role of each element in the system. Chemical vapour deposition (CVD) of ZnS powder in a limited oxygen environment resulted in side-by-side biaxial ZnO-ZnS NR heterostructures. The resulting NRs contained distinct wurtzite ZnS and wurtzite ZnO components with widths of 10--100 nm and 20 --500 nm, respectively and a uniform interface region of 5-15 nm. XAFS and XEOL measurements revealed the luminescence of ZnO-ZnS NRs is from the ZnO component. The luminescence of CdSxSe1-x nanostructures is shown to be dependent on the S to Se ratio, with the band-gap emission being tunable between that of pure CdS and CdSe. Excitation of the CdSxSe 1-x nanostructures by X-ray in XEOL has revealed new de-excitation channels which show a defect emission band not seen by laser excitation. CVD of Mn2+ doped ZnS results in nanostructures with luminescence dominated by the yellow Mn2+ emission due to energy transfer from the ZnS host to the Mn dopant sites. The addition of EuCl3 to the reactants in the CVD process results in a change in morphology from NR to NP. Zn1-xMnxO and Zn1-xCOxO nanopowders were prepared by sol-gel methods at dopant concentrations

  2. Ultrafast transient absorption studies of hematite nanoparticles: the effect of particle shape on exciton dynamics.

    PubMed

    Fitzmorris, Bob C; Patete, Jonathan M; Smith, Jacqueline; Mascorro, Xiomara; Adams, Staci; Wong, Stanislaus S; Zhang, Jin Z

    2013-10-01

    Much progress has been made in using hematite (α-Fe2 O3 ) as a potentially practical and sustainable material for applications such as solar-energy conversion and photoelectrochemical (PEC) water splitting; however, recent studies have shown that the performance can be limited by a very short charge-carrier diffusion length or exciton lifetime. In this study, we performed ultrafast studies on hematite nanoparticles of different shapes to determine the possible influence of particle shape on the exciton dynamics. Nanorice, multifaceted spheroidal nanoparticles, faceted nanocubes, and faceted nanorhombohedra were synthesized and characterized by using SEM and XRD techniques. Their exciton dynamics were investigated by using femtosecond transient absorption (TA) spectroscopy. Although the TA spectral features differ for the four samples studied, their decay profiles are similar, which can be fitted with time constants of 1-3 ps, approximately 25 ps, and a slow nanosecond component extending beyond the experimental time window that was measured (2 ns). The results indicate that the overall exciton lifetime is weakly dependent on the shape of the hematite nanoparticles, even though the overall optical absorption and scattering are influenced by the particle shape. This study suggests that other strategies need to be developed to increase the exciton lifetime or to lengthen the exciton diffusion length in hematite nanostructures.

  3. In vitro predictions of skin absorption of caffeine, testosterone, and benzoic acid: a multi-centre comparison study.

    PubMed

    van de Sandt, J J M; van Burgsteden, J A; Cage, S; Carmichael, P L; Dick, I; Kenyon, S; Korinth, G; Larese, F; Limasset, J C; Maas, W J M; Montomoli, L; Nielsen, J B; Payan, J-P; Robinson, E; Sartorelli, P; Schaller, K H; Wilkinson, S C; Williams, F M

    2004-06-01

    To obtain better insight into the robustness of in vitro percutaneous absorption methodology, the intra- and inter-laboratory variation in this type of study was investigated in 10 European laboratories. To this purpose, the in vitro absorption of three compounds through human skin (9 laboratories) and rat skin (1 laboratory) was determined. The test materials were benzoic acid, caffeine, and testosterone, representing a range of different physico-chemical properties. All laboratories performed their studies according to a detailed protocol in which all experimental details were described and each laboratory performed at least three independent experiments for each test chemical. All laboratories assigned the absorption of benzoic acid through human skin, the highest ranking of the three compounds (overall mean flux of 16.54+/-11.87 microg/cm(2)/h). The absorption of caffeine and testosterone through human skin was similar, having overall mean maximum absorption rates of 2.24+/-1.43 microg/cm(2)/h and 1.63+/-1.94 microg/cm(2)/h, respectively. In 7 out of 9 laboratories, the maximum absorption rates of caffeine were ranked higher than testosterone. No differences were observed between the mean absorption through human skin and the one rat study for benzoic acid and testosterone. For caffeine the maximum absorption rate and the total penetration through rat skin were clearly higher than the mean value for human skin. When evaluating all data, it appeared that no consistent relation existed between the diffusion cell type and the absorption of the test compounds. Skin thickness only slightly influenced the absorption of benzoic acid and caffeine. In contrast, the maximum absorption rate of testosterone was clearly higher in the laboratories using thin, dermatomed skin membranes. Testosterone is the most lipophilic compound and showed also a higher presence in the skin membrane after 24 h than the two other compounds. The results of this study indicate that the in

  4. Carbon dioxide postcombustion capture: a novel screening study of the carbon dioxide absorption performance of 76 amines

    SciTech Connect

    Graeme Puxty; Robert Rowland; Andrew Allport; Qi Yang; Mark Bown; Robert Burns; Marcel Maeder; Moetaz Attalla

    2009-08-15

    The significant and rapid reduction of greenhouse gas emissions is recognized as necessary to mitigate the potential climate effects from global warming. The postcombustion capture (PCC) and storage of carbon dioxide (CO{sub 2}) produced from the use of fossil fuels for electricity generation is a key technology needed to achieve these reductions. The most mature technology for CO{sub 2} capture is reversible chemical absorption into an aqueous amine solution. In this study the results from measurements of the CO{sub 2} absorption capacity of aqueous amine solutions for 76 different amines are presented. Measurements were made using both a novel isothermal gravimetric analysis (IGA) method and a traditional absorption apparatus. Seven amines, consisting of one primary, three secondary, and three tertiary amines, were identified as exhibiting outstanding absorption capacities. Most have a number of structural features in common including steric hindrance and hydroxyl functionality 2 or 3 carbons from the nitrogen. Initial CO{sub 2} absorption rate data from the IGA measurements was also used to indicate relative absorption rates. Most of the outstanding performers in terms of capacity also showed initial absorption rates comparable to the industry standard monoethanolamine (MEA). This indicates, in terms of both absorption capacity and kinetics, that they are promising candidates for further investigation. 30 refs., 8 figs.

  5. Carbon dioxide postcombustion capture: a novel screening study of the carbon dioxide absorption performance of 76 amines.

    PubMed

    Puxty, Graeme; Rowland, Robert; Allport, Andrew; Yang, Qi; Bown, Mark; Burns, Robert; Maeder, Marcel; Attalla, Moetaz

    2009-08-15

    The significant and rapid reduction of greenhouse gas emissions is recognized as necessary to mitigate the potential climate effects from global warming. The postcombustion capture (PCC) and storage of carbon dioxide (CO2) produced from the use of fossil fuels for electricity generation is a key technology needed to achieve these reductions. The most mature technology for CO2 capture is reversible chemical absorption into an aqueous amine solution. In this study the results from measurements of the CO2 absorption capacity of aqueous amine solutions for 76 different amines are presented. Measurements were made using both a novel isothermal gravimetric analysis (IGA) method and a traditional absorption apparatus. Seven amines, consisting of one primary, three secondary, and three tertiary amines, were identified as exhibiting outstanding absorption capacities. Most have a number of structural features in common including steric hindrance and hydroxyl functionality 2 or 3 carbons from the nitrogen. Initial CO2 absorption rate data from the IGA measurements was also used to indicate relative absorption rates. Most of the outstanding performers in terms of capacity also showed initial absorption rates comparable to the industry standard monoethanolamine (MEA). This indicates, in terms of both absorption capacity and kinetics, that they are promising candidates for further investigation.

  6. Chemical Modification of Graphene Oxide by Nitrogenation: An X-ray Absorption and Emission Spectroscopy Study

    PubMed Central

    Chuang, Cheng-Hao; Ray, Sekhar C.; Mazumder, Debarati; Sharma, Surbhi; Ganguly, Abhijit; Papakonstantinou, Pagona; Chiou, Jau-Wern; Tsai, Huang-Ming; Shiu, Hung-Wei; Chen, Chia-Hao; Lin, Hong-Ji; Guo, Jinghua; Pong, Way-Faung

    2017-01-01

    Nitrogen-doped graphene oxides (GO:Nx) were synthesized by a partial reduction of graphene oxide (GO) using urea [CO(NH2)2]. Their electronic/bonding structures were investigated using X-ray absorption near-edge structure (XANES), valence-band photoemission spectroscopy (VB-PES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). During GO:Nx synthesis, different nitrogen-bonding species, such as pyrrolic/graphitic-nitrogen, were formed by replacing of oxygen-containing functional groups. At lower N-content (2.7 at%), pyrrolic-N, owing to surface and subsurface diffusion of C, N and NH is deduced from various X-ray spectroscopies. In contrast, at higher N-content (5.0 at%) graphitic nitrogen was formed in which each N-atom trigonally bonds to three distinct sp2-hybridized carbons with substitution of the N-atoms for C atoms in the graphite layer. Upon nitrogen substitution, the total density of state close to Fermi level is increased to raise the valence-band maximum, as revealed by VB-PES spectra, indicating an electron donation from nitrogen, molecular bonding C/N/O coordination or/and lattice structure reorganization in GO:Nx. The well-ordered chemical environments induced by nitrogen dopant are revealed by XANES and RIXS measurements. PMID:28186190

  7. Chemical Modification of Graphene Oxide by Nitrogenation: An X-ray Absorption and Emission Spectroscopy Study.

    PubMed

    Chuang, Cheng-Hao; Ray, Sekhar C; Mazumder, Debarati; Sharma, Surbhi; Ganguly, Abhijit; Papakonstantinou, Pagona; Chiou, Jau-Wern; Tsai, Huang-Ming; Shiu, Hung-Wei; Chen, Chia-Hao; Lin, Hong-Ji; Guo, Jinghua; Pong, Way-Faung

    2017-02-10

    Nitrogen-doped graphene oxides (GO:Nx) were synthesized by a partial reduction of graphene oxide (GO) using urea [CO(NH2)2]. Their electronic/bonding structures were investigated using X-ray absorption near-edge structure (XANES), valence-band photoemission spectroscopy (VB-PES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). During GO:Nx synthesis, different nitrogen-bonding species, such as pyrrolic/graphitic-nitrogen, were formed by replacing of oxygen-containing functional groups. At lower N-content (2.7 at%), pyrrolic-N, owing to surface and subsurface diffusion of C, N and NH is deduced from various X-ray spectroscopies. In contrast, at higher N-content (5.0 at%) graphitic nitrogen was formed in which each N-atom trigonally bonds to three distinct sp(2)-hybridized carbons with substitution of the N-atoms for C atoms in the graphite layer. Upon nitrogen substitution, the total density of state close to Fermi level is increased to raise the valence-band maximum, as revealed by VB-PES spectra, indicating an electron donation from nitrogen, molecular bonding C/N/O coordination or/and lattice structure reorganization in GO:Nx. The well-ordered chemical environments induced by nitrogen dopant are revealed by XANES and RIXS measurements.

  8. Chemical Modification of Graphene Oxide by Nitrogenation: An X-ray Absorption and Emission Spectroscopy Study

    NASA Astrophysics Data System (ADS)

    Chuang, Cheng-Hao; Ray, Sekhar C.; Mazumder, Debarati; Sharma, Surbhi; Ganguly, Abhijit; Papakonstantinou, Pagona; Chiou, Jau-Wern; Tsai, Huang-Ming; Shiu, Hung-Wei; Chen, Chia-Hao; Lin, Hong-Ji; Guo, Jinghua; Pong, Way-Faung

    2017-02-01

    Nitrogen-doped graphene oxides (GO:Nx) were synthesized by a partial reduction of graphene oxide (GO) using urea [CO(NH2)2]. Their electronic/bonding structures were investigated using X-ray absorption near-edge structure (XANES), valence-band photoemission spectroscopy (VB-PES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). During GO:Nx synthesis, different nitrogen-bonding species, such as pyrrolic/graphitic-nitrogen, were formed by replacing of oxygen-containing functional groups. At lower N-content (2.7 at%), pyrrolic-N, owing to surface and subsurface diffusion of C, N and NH is deduced from various X-ray spectroscopies. In contrast, at higher N-content (5.0 at%) graphitic nitrogen was formed in which each N-atom trigonally bonds to three distinct sp2-hybridized carbons with substitution of the N-atoms for C atoms in the graphite layer. Upon nitrogen substitution, the total density of state close to Fermi level is increased to raise the valence-band maximum, as revealed by VB-PES spectra, indicating an electron donation from nitrogen, molecular bonding C/N/O coordination or/and lattice structure reorganization in GO:Nx. The well-ordered chemical environments induced by nitrogen dopant are revealed by XANES and RIXS measurements.

  9. Cu K-edge X-ray Absorption Spectroscopy Reveals Differential Copper Coordimation Within Amyloid-beta Oligomers Compared to Amyloid-beta Monomers

    SciTech Connect

    J Shearer; P Callan; T Tran; V Szalai

    2011-12-31

    The fatal neurodegenerative disorder Alzheimer's disease (AD) has been linked to the formation of soluble neurotoxic oligomers of amyloid-{beta} (A{beta}) peptides. These peptides have high affinities for copper cations. Despite their potential importance in AD neurodegeneration few studies have focused on probing the Cu{sup 2+/1+} coordination environment within A{beta} oligomers. Herein we present a Cu K-edge X-ray absorption spectroscopic study probing the copper-coordination environment within oligomers of A{beta}(42) (sequence: DAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVVIA). We find that the Cu{sup 2+} cation is contained within a square planar mixed N/O ligand environment within A{beta}(42) oligomers, which is similar to the copper coordination environment of the monomeric forms of {l_brace}Cu{sup II}A{beta}(40){r_brace} and {l_brace}Cu{sup II}A{beta}(16){r_brace}. Reduction of the Cu{sup 2+} cation within the A{beta}(42) oligomers to Cu{sup 1+} yields a highly dioxygen sensitive copper-species that contains Cu{sup 1+} in a tetrahedral coordination geometry. This can be contrasted with monomers of {l_brace}Cu{sup I}A{beta}(40){r_brace} and {l_brace}Cu{sup I}A{beta}(16){r_brace}, which contain copper in a dioxygen inert linear bis-histidine ligand environment [Shearer and Szalai, J. Am. Chem. Soc., 2008, 130, 17826]. The biological implications of these findings are discussed.

  10. High-energy resolution X-ray absorption and emission spectroscopy reveals insight into unique selectivity of La-based nanoparticles for CO2

    PubMed Central

    Hirsch, Ofer; Kvashnina, Kristina O.; Luo, Li; Süess, Martin J.; Glatzel, Pieter; Koziej, Dorota

    2015-01-01

    The lanthanum-based materials, due to their layered structure and f-electron configuration, are relevant for electrochemical application. Particularly, La2O2CO3 shows a prominent chemoresistive response to CO2. However, surprisingly less is known about its atomic and electronic structure and electrochemically significant sites and therefore, its structure–functions relationships have yet to be established. Here we determine the position of the different constituents within the unit cell of monoclinic La2O2CO3 and use this information to interpret in situ high-energy resolution fluorescence-detected (HERFD) X-ray absorption near-edge structure (XANES) and valence-to-core X-ray emission spectroscopy (vtc XES). Compared with La(OH)3 or previously known hexagonal La2O2CO3 structures, La in the monoclinic unit cell has a much lower number of neighboring oxygen atoms, which is manifested in the whiteline broadening in XANES spectra. Such a superior sensitivity to subtle changes is given by HERFD method, which is essential for in situ studying of the interaction with CO2. Here, we study La2O2CO3-based sensors in real operando conditions at 250 °C in the presence of oxygen and water vapors. We identify that the distribution of unoccupied La d-states and occupied O p- and La d-states changes during CO2 chemoresistive sensing of La2O2CO3. The correlation between these spectroscopic findings with electrical resistance measurements leads to a more comprehensive understanding of the selective adsorption at La site and may enable the design of new materials for CO2 electrochemical applications. PMID:26668362

  11. Small copper clusters studied by x-ray absorption near-edge structure

    NASA Astrophysics Data System (ADS)

    Oyanagi, H.; Sun, Z. H.; Jiang, Y.; Uehara, M.; Nakamura, H.; Yamashita, K.; Orimoto, Y.; Zhang, L.; Lee, C.; Fukano, A.; Maeda, H.

    2012-04-01

    The local structure of copper nanoparticles grown in organic solution by reducing Cu(II) hexafluoroacetylacetonate [Cu(hfac)2] was studied as-grown by the Cu K-edge x-ray absorption near-edge structure (XANES). Comparison of the experimental XANES spectra with reference materials indicated small copper clusters are formed by ligand-exchange with oleylamine and subsequent reducing by diphenylsilane. The multiple-scattering (MS) calculation for various model clusters consisting of 13-135 atoms suggests that small (13-19 atom) Cu clusters are stabilized without a large deformation.

  12. Metal release in metallothioneins induced by nitric oxide: X-ray absorption spectroscopy study.

    PubMed

    Casero, Elena; Martín-Gago, José A; Pariente, Félix; Lorenzo, Encarnación

    2004-12-01

    Metallothioneins (MTs) are low molecular weight proteins that include metal ions in thiolate clusters. The capability of metallothioneins to bind different metals has suggested their use as biosensors for different elements. We study here the interaction of nitric oxide with rat liver MTs by using in situ X-ray absorption spectroscopy techniques. We univocally show that the presence of NO induces the release of Zn atoms from the MT structure to the solution. Zn ions transform in the presence of NO from a tetrahedral four-fold coordinated environment in the MT into a regular octahedral six-fold coordinated state, with interatomic distances compatible with those of Zn solvated in water.

  13. Model studies of laser absorption computed tomography for remote air pollution measurement

    NASA Technical Reports Server (NTRS)

    Wolfe, D. C., Jr.; Byer, R. L.

    1982-01-01

    Model studies of the potential of laser absorption-computed tomography are presented which demonstrate the possibility of sensitive remote atmospheric pollutant measurements, over kilometer-sized areas, with two-dimensional resolution, at modest laser source powers. An analysis of this tomographic reconstruction process as a function of measurement SNR, laser power, range, and system geometry, shows that the system is able to yield two-dimensional maps of pollutant concentrations at ranges and resolutions superior to those attainable with existing, direct-detection laser radars.

  14. EPR and optical absorption study of Cu2+ doped lithium sulphate monohydrate (LSMH) single crystals

    NASA Astrophysics Data System (ADS)

    Sheela, K. Juliet; Krishnan, S. Radha; Shanmugam, V. M.; Subramanian, P.

    2016-05-01

    EPR study of Cu2+ doped NLO active Lithium Sulphate monohydrate (Li2SO4.H2O) single crystals were grown successfully by slow evaporation method at room temperature. The principal values of g and A tensors indicate existence of orthorhombic symmetry around the Cu2+ ion. From the direction cosines of g and A tensors, the locations of Cu2+ in the lattice have been identified as interstitial site. Optical absorption confirms the rhombic symmetry and ground state wave function of the Cu2+ ion in a lattice as dx2-y2.

  15. Total Absorption Spectroscopy Study of (92)Rb Decay: A Major Contributor to Reactor Antineutrino Spectrum Shape.

    PubMed

    Zakari-Issoufou, A-A; Fallot, M; Porta, A; Algora, A; Tain, J L; Valencia, E; Rice, S; Bui, V M; Cormon, S; Estienne, M; Agramunt, J; Äystö, J; Bowry, M; Briz, J A; Caballero-Folch, R; Cano-Ott, D; Cucoanes, A; Elomaa, V-V; Eronen, T; Estévez, E; Farrelly, G F; Garcia, A R; Gelletly, W; Gomez-Hornillos, M B; Gorlychev, V; Hakala, J; Jokinen, A; Jordan, M D; Kankainen, A; Karvonen, P; Kolhinen, V S; Kondev, F G; Martinez, T; Mendoza, E; Molina, F; Moore, I; Perez-Cerdán, A B; Podolyák, Zs; Penttilä, H; Regan, P H; Reponen, M; Rissanen, J; Rubio, B; Shiba, T; Sonzogni, A A; Weber, C

    2015-09-04

    The antineutrino spectra measured in recent experiments at reactors are inconsistent with calculations based on the conversion of integral beta spectra recorded at the ILL reactor. (92)Rb makes the dominant contribution to the reactor antineutrino spectrum in the 5-8 MeV range but its decay properties are in question. We have studied (92)Rb decay with total absorption spectroscopy. Previously unobserved beta feeding was seen in the 4.5-5.5 region and the GS to GS feeding was found to be 87.5(25)%. The impact on the reactor antineutrino spectra calculated with the summation method is shown and discussed.

  16. L-edge X-ray absorption studies of neptunium compounds

    NASA Astrophysics Data System (ADS)

    Bertram, S.; Kaindl, G.; Jové, J.; Pagès, M.

    1989-06-01

    The x-ray absorption near-edge structure (XANES) at the Np-L thresholds was investigated for Np compounds with formal valencies III to VII. At LIII, single and double-peaked white lines are observed corresponding to different final states that are populated through core excitation and 5f/ligand hybridization. For the non-metallic Np compounds studied, the weighted mean values of the LIII-XANES shifts relative to NpO2 exhibit a clear correlation with the isomer shifts of the 59-keV Mössbauer resonance of 237Np.

  17. Excited-state symmetry breaking of linear quadrupolar chromophores: A transient absorption study

    NASA Astrophysics Data System (ADS)

    Dozova, Nadia; Ventelon, Lionel; Clermont, Guillaume; Blanchard-Desce, Mireille; Plaza, Pascal

    2016-11-01

    The photophysical properties of two highly symmetrical quadrupolar chromophores were studied by both steady-state and transient absorption spectroscopy. Their excited-state behavior is dominated by the solvent-induced Stokes shift of the stimulated-emission band. The origin of this shift is attributed to symmetry breaking that confers a non-vanishing dipole moment to the excited state of both compounds. This dipole moment is large and constant in DMSO, whereas symmetry breaking appears significantly slower and leading to smaller excited-state dipole in toluene. Time-dependant increase of the excited-state dipole moment induced by weak solvation is proposed to explain the results in toluene.

  18. Extended X-ray absorption fine structure (EXAFS) study of CaSO 4:Dy phosphors

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, D.; Bakshi, A. K.; Ciatto, G.; Aquilanti, G.; Pradhan, A. S.; Pascarelli, S.

    2006-03-01

    Extended X-ray absorption fine structure (EXAFS) measurements have been carried out on CaSO 4:Dy phosphors at the Dy L 3 edge with synchrotron radiation. The data have been analysed to find out the Dy-S and Dy-O bond lengths in the neighborhood of the Dy atoms. Measurements have been carried out over several samples thermally annealed for different cycles at 400 °C in air for 1 h and the change in bond lengths in samples with increasing number of annealing cycles have been studied by analyzing the EXAFS data.

  19. X-ray absorption in GaGdN: A study of local structure

    NASA Astrophysics Data System (ADS)

    Martínez-Criado, G.; Sancho-Juan, O.; Garro, N.; Sans, J. A.; Cantarero, A.; Susini, J.; Roever, M.; Mai, D.-D.; Bedoya-Pinto, A.; Malindretos, J.; Rizzi, A.

    2008-07-01

    In this study, we report on the incorporation of dilute Gd amounts into GaN films grown by molecular beam epitaxy. A combination of x-ray fluorescence with x-ray absorption spectroscopic techniques enabled us to examine not only the distribution of rare earth atoms in the GaN matrix but also the short-range structural order. Our results show Gd atoms in a trivalent state with tetrahedral coordination, thus substituting Ga in the wurtzite GaN structure.

  20. Human in vivo and in vitro studies on gastrointestinal absorption of titanium dioxide nanoparticles.

    PubMed

    Jones, Kate; Morton, Jackie; Smith, Ian; Jurkschat, Kerstin; Harding, Anne-Helen; Evans, Gareth

    2015-03-04

    The study was designed to conduct human in vivo and in vitro studies on the gastrointestinal absorption of nanoparticles, using titanium dioxide as a model compound, and to compare nanoparticle behaviour with that of larger particles. A supplier's characterisation data may not fully describe a particle formulation. Most particles tested agreed with their supplied characterisation when assessed by particle number but significant proportions of 'nanoparticle formulations' were particles >100nm when assessed by particle weight. Oral doses are measured by weight and it is therefore important that the weight characterisation is taken into consideration. The human volunteer studies demonstrated that very little titanium dioxide is absorbed gastrointestinally after an oral challenge. There was no demonstrable difference in absorption for any of the three particle sizes tested. All tested formulations were shown to agglomerate in simulated gastric fluid, particularly in the smaller particle formulations. Further agglomeration was observed when dispersing formulations in polymeric or elemental foods. Virtually no translocation of titanium dioxide particles across the cell layer was demonstrated. This study found no evidence that nanoparticulate titanium dioxide is more likely to be absorbed in the gut than micron-sized particles.

  1. X-ray absorption and diffraction study of II VI dilute oxide semiconductor alloy epilayers

    NASA Astrophysics Data System (ADS)

    Boscherini, F.; Malvestuto, M.; Ciatto, G.; D'Acapito, F.; Bisognin, G.; DeSalvador, D.; Berti, M.; Felici, M.; Polimeni, A.; Nabetani, Y.

    2007-11-01

    Dilute oxide semiconductor alloys obtained by adding oxygen to a II-VI binary compound are of potential applicative interest for blue-light emitters in which the oxygen content could be used to tune the band gap. Moreover, their properties can be usefully compared to the more thoroughly studied dilute nitrides in order to gain insight into the common mechanisms which give rise to their highly non-linear physical properties. Recently, it has been possible to deposit ZnSeO and ZnSeOS epilayers on GaAs(001), which exhibit a red-shift of the band gap and giant optical bowing. In order to provide a structural basis for an understanding of their physical properties, we have performed a study of a set of ZnSeO and ZnSeOS epilayers on GaAs by high resolution x-ray diffraction and x-ray absorption fine structure. We have found that the strain goes from compressive to tensile with increasing O and S concentration and that, while all epilayers are never found to be pseudomorphic, the ternary ones exhibit a low relaxed fraction if compared to the ZnSe/GaAs sample. O K-edge x-ray absorption near edge spectra and corresponding simulations within the full multiple-scattering regime show that O is substitutionally incorporated in the host lattice. Zn and Se K-edge extended x-ray absorption fine structure detect the formation of Zn-O and Zn-S bonds; the analysis of these spectra within multiple-scattering theory has allowed us to measure the local structural parameters. The value of Zn-Se bond length is found to be in agreement with estimates based on models of local distortions in strained and relaxed epilayers; an increase of the mean-square relative displacement is detected at high O and S concentration and is related to both intrinsic and extrinsic factors.

  2. Evaluation of indomethacin percutaneous absorption from nanostructured lipid carriers (NLC): in vitro and in vivo studies.

    PubMed

    Ricci, Maurizio; Puglia, Carmelo; Bonina, Francesco; Di Giovanni, Caterina; Giovagnoli, Stefano; Rossi, Carlo

    2005-05-01

    The aim of this study was the evaluation, in vitro and in vivo, of indomethacin (IND) release through the skin from nanostructured lipid carriers (NLC). NLC were prepared by ultrasonication, and were characterized in order to determine drug content, and particle size; finally the NLC were processed to hydrogels (A and B). The IND release pattern from NLC hydrogels was evaluated in vitro, to determine its percutaneous absorption through excised human skin (stratum corneum and epidermis, SCE), and in vivo. To evaluate the in vivo IND release, two methods were employed: (1) the IND topical anti-inflammatory activity was determined at different time-points after its cutaneous application; in this case, the UVB-induced erythema on healthy human volunteers, chosen as inflammatory model, was monitored by reflectance visible spectrophotometry; (2) the extent of IND absorption into human skin was performed by the tape-stripping technique. The in vitro percutaneous absorption studies showed lower fluxes of IND through SCE membranes from NLC hydrogels (A and B) in comparison to an aqueous dispersion (C) and a hydro-alcoholic gel (D) both containing free IND. The findings from the former in vivo method showed that the anti-inflammatory effect, following IND topical application, was more prolonged with IND-loaded NLC gel formulation (A) if compared to formulation C and D. The results from tape stripping technique confirmed the trend obtained by the former in vivo method and indicated that IND topical bioavailability in the stratum corneum varied substantially depending upon the formulations (A-D).

  3. Study on dissolution and absorption of four dosage forms of isosorbide mononitrate: level A in vitro-in vivo correlation.

    PubMed

    Li, Zi-qiang; He, Xin; Gao, Xiumei; Xu, Yan-yan; Wang, Yue-fei; Gu, Hui; Ji, Rui-feng; Sun, Shu-jun

    2011-10-01

    The objective of the present study was to develop a novel in vitro system to simulate the process of dissolution and permeation of oral solid dosage forms in vivo, and to establish a correlation between in vitro permeation and in vivo absorption that could predict the bioavailability (BA) and bioequivalence (BE) of congeneric products. The in vitro dissolution and absorption kinetics of four dosage forms of isosorbide mononitrate (ISMN) were evaluated by the USP basket/paddle system and drug dissolution/absorption simulating system (DDASS). The corresponding pharmacokinetic study was performed in beagle dogs. A comparative study was carried out between the classical and the novel method to estimate the effectiveness of the modified DDASS in simulating the course of dissolution and absorption in vivo. Indeed, the correlation coefficients of in vitro dissolution and in vivo absorption obtained from DDASS and dogs were higher. Moreover, a higher level A in vitro-in vivo correlation (IVIVC) between DDASS permeation and dog absorption was established, with correlation coefficients of 0.9968, 0.9872, 0.9921, and 0.9728. The DDASS method was more accurate at modeling the process of dissolution and absorption in vivo for both immediate-release (IR) and sustained-release (SR) dosage forms of ISMN.

  4. Application of quantum cascade laser absorption spectroscopy to studies of fluorocarbon molecules

    NASA Astrophysics Data System (ADS)

    Welzel, S.; Stepanov, S.; Meichsner, J.; Röpcke, J.

    2009-03-01

    The recent advent of quantum cascade lasers (QCLs) enables room-temperature mid-infrared spectrometer operation which is particularly favourable for industrial process monitoring and control, i.e. the detection of transient and stable molecular species. Conversely, fluorocarbon containing radio-frequency discharges are of special interest for plasma etching and deposition as well as for fundamental studies on gas phase and plasma surface reactions. The application of QCL absorption spectroscopy to such low pressure plasmas is typically hampered by non-linear effects connected with the pulsed mode of the lasers. Nevertheless, adequate calibration can eliminate such effects, especially in the case of complex spectra where single line parameters are not available. In order to facilitate measurements in fluorocarbon plasmas, studies on complex spectra of CF4 and C3F8 at 7.86 μm (1269 - 1275 cm-1) under low pressure conditions have been performed. The intra-pulse mode, i.e. pulses of up to 300 ns, was applied yielding highly resolved spectral scans of ~ 1 cm-1 coverage. Effective absorption cross sections were determined and their temperature dependence was studied in the relevant range up to 400 K and found to be non-negligible.

  5. Single-molecule spectroscopy and femtosecond transient absorption studies on the excitation energy transfer process in ApcE(1-240) dimers.

    PubMed

    Long, Saran; Zhou, Meng; Tang, Kun; Zeng, Xiao-Li; Niu, Yingli; Guo, Qianjin; Zhao, Kai-Hong; Xia, Andong

    2015-05-28

    ApcE(1-240) dimers with one intrinsic phycocyanobilin (PCB) chromophore in each monomer that is truncated from the core-membrane linker (ApcE) of phycobilisomes (PBS) in Nostoc sp. PCC 7120 show a sharp and significantly red-shifted absorption. Two explanations either conformation-dependent Förster resonance energy transfer (FRET) or the strong exciton coupling limit have been proposed for red-shifted absorption. This is a classic example of the special pair in the photosynthetic light harvesting proteins, but the mechanism of this interaction is still a matter of intense debate. We report the studies using single-molecule and transient absorption spectra on the interaction in the special pair of ApcE dimers. Our results demonstrate the presence of conformation-dependent FRET between the two PCB chromophores in ApcE dimers. The broad distributions of fluorescence intensities, lifetimes and polarization difference from single-molecule measurements reveal the heterogeneity of local protein-pigment environments in ApcE dimers, where the same molecular structures but different protein environments are the main reason for the two PCB chromophores with different spectral properties. The excitation energy transfer rate between the donor and the acceptor about (110 ps)(-1) is determined from transient absorption measurements. The red-shifted absorption in ApcE dimers could result from more extending conformation, which shows another type of absorption redshift that does not depend on strong exciton coupling. The results here stress the importance of conformation-controlled spectral properties of the chemically identical chromophores, which could be a general feature to control energy/electron transfer, widely existing in the light harvesting complexes.

  6. IN SITU STUDIES OF CORROSION USING X-RAY ABSORPTION NEAR SPECTROSCOPY (XANES)

    SciTech Connect

    ISAACS, H.S.; SCHMUKI, P.; VIRTANEN, S.

    2001-03-25

    Applications of x-ray absorption near-edge spectroscopy (XANES) and the design of cells for in situ corrosion studies are reviewed. Passive films studies require very thin metal or alloy layers be used having a thickness of the order of the films formed because of penetration of the x-ray beam into the metal substrate. The depth of penetration in water also limits the thickness of solutions that can be used because of water reduces the x-ray intensity. Solution thickness must also be limited in studies of conversion layer formation studies because the masking of the Cr in solution. Illustrative examples are taken from the anodic behavior of Al-Cr alloys, the growth of passive films on Fe and stainless steels, and the formation of chromate conversion layers on Al.

  7. Feasibility study of a novel pressure recovery system for CO2-COIL based on chemical absorption

    NASA Astrophysics Data System (ADS)

    Li, Qingwei; Jin, Yuqi; Geng, Zicai; Li, Yongzhao; Zhang, Yuelong; Sang, Fengting

    2015-02-01

    A chemical oxygen-iodine laser (COIL) is an electronic transition, low pressure, high throughput system. The use of this laser demands a suitable pressure recovery system. This paper proposed a novel pressure recovery system based on chemical absorption and the feasibility for COIL with CO2 as buffer gas (CO2-COIL) was investigated. The novel pressure recovery system works by chemisorbing the CO2-COIL effluents into two fixed-beds maintained at initial temperature of around 293-323K. Compared with the cryosorption system for N2-COIL based on physical absorption, the novel chemisorptions based pressure recovery system has a simpler logistics and a shorter run-to-run preparation time. Two kinds of solid chemo-sorbents were designed and synthesized. One was used for chemisorbing the oxidizing gases such as O2 ,Cl2 and I2, another was used for chemisorbing the acidic gas such as CO2. The capacities of the two sorbents were measured to be 3.12 mmol(O2)/g and 3.84 mmol (CO2) /g, respectively. It indicated that the synthesized sorbents could effectively chemosorb the CO2-COIL effluents. Secondly, analog test equipment was set up and used to study the feasibility of the novel pressure recovery system used for CO2-COIL. The test results showed that the novel pressure recovery system could maintain the pressure under 6 Torr for tens seconds under the continuous gas flow. It showed that the novel pressure recovery system for CO2-COIL based on chemical absorption is feasible.

  8. In vitro study of transporters involved in intestinal absorption of inorganic arsenic.

    PubMed

    Calatayud, Marta; Barrios, Julio A; Vélez, Dinoraz; Devesa, Vicenta

    2012-02-20

    Inorganic arsenic (iAs) [As(III)+As(V)] is a drinking water contaminant, and human exposure to these arsenic species has been linked with a wide range of health effects. The main path of exposure is the oral route, and the intestinal epithelium is the first physiological barrier that iAs must cross in order to be absorbed. However, there is a lack of information about intestinal iAs absorption. The aim of this study was to evaluate the participation of certain transporters [glucose transporters (GLUT and SGLT), organic anion transporting polypeptides (OATPs), aquaporins (AQPs), and phosphate transporters (NaPi and PiT)] in intestinal absorption of As(V) and As(III), using the Caco-2 cell line as a model of the intestinal epithelium. For this purpose, the effects of chemical inhibition and gene silencing of the transporters of interest on iAs uptake were evaluated, and also the differential expression of these transporters after treatment with iAs. The results show that chemical inhibition using rifamycin SV (OATP inhibitor), phloridzin (SGLT inhibitor), phloretin (GLUT and AQP inhibitor), and copper sulfate (AQP inhibitor) leads to a significant reduction in the apparent permeability and cellular retention of As(III). RT-qPCR indicates up-regulation of GLUT2, GLUT5, OATPB, AQP3, and AQP10 after exposure to As(III), while exposure to As(V) increases the expression of sodium-dependent phosphate transporters, especially NaPiIIb. Gene silencing of OATPB, AQP10, and GLUT5 for As(III) and NaPiIIb for As(V) significantly reduces uptake of the inorganic forms. These results indicate that these transporters may be involved in intestinal absorption of iAs.

  9. An x-ray absorption spectroscopy study of Ni-Mn-Ga shape memory alloys.

    PubMed

    Sathe, V G; Dubey, Aditi; Banik, Soma; Barman, S R; Olivi, L

    2013-01-30

    The austenite to martensite phase transition in Ni-Mn-Ga ferromagnetic shape memory alloys was studied by extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) spectroscopy. The spectra at all the three elements', namely, Mn, Ga and Ni, K-edges in several Ni-Mn-Ga samples (with both Ni and Mn excess) were analyzed at room temperature and low temperatures. The EXAFS analysis suggested a displacement of Mn and Ga atoms in opposite direction with respect to the Ni atoms when the compound transforms from the austenite phase to the martensite phase. The first coordination distances around the Mn and Ga atoms remained undisturbed on transition, while the second and subsequent shells showed dramatic changes indicating the presence of a modulated structure. The Mn rich compounds showed the presence of antisite disorder of Mn and Ga. The XANES results showed remarkable changes in the unoccupied partial density of states corresponding to Mn and Ni, while the electronic structure of Ga remained unperturbed across the martensite transition. The post-edge features in the Mn K-edge XANES spectra changed from a double peak like structure to a flat peak like structure upon phase transition. The study establishes strong correlation between the crystal structure and the unoccupied electronic structure in these shape memory alloys.

  10. VUV Fourier-transform absorption study of the Lyman and Werner bands in D2.

    PubMed

    de Lange, Arno; Dickenson, Gareth D; Salumbides, Edcel J; Ubachs, Wim; de Oliveira, Nelson; Joyeux, Denis; Nahon, Laurent

    2012-06-21

    An extensive survey of the D(2) absorption spectrum has been performed with the high-resolution VUV Fourier-transform spectrometer employing synchrotron radiation. The frequency range of 90,000-119,000 cm(-1) covers the full depth of the potential wells of the B (1)Σ(u)(+), B' (1)Σ(u)(+), and C (1)Π(u) electronic states up to the D(1s) + D(2l) dissociation limit. Improved level energies of rovibrational levels have been determined up to respectively v = 51, v = 13, and v = 20. Highest resolution is achieved by probing absorption in a molecular gas jet with slit geometry, as well as in a liquid helium cooled static gas cell, resulting in line widths of ≈0.35 cm(-1). Extended calibration methods are employed to extract line positions of D(2) lines at absolute accuracies of 0.03 cm(-1). The D (1)Π(u) and B'' (1)Σ(u)(+) electronic states correlate with the D(1s) + D(3l]) dissociation limit, but support a few vibrational levels below the second dissociation limit, respectively, v = 0-3 and v = 0-1, and are also included in the presented study. The complete set of resulting level energies is the most comprehensive and accurate data set for D(2). The observations are compared with previous studies, both experimental and theoretical.

  11. Studying metal ion-protein interactions: electronic absorption, circular dichroism, and electron paramagnetic resonance.

    PubMed

    Quintanar, Liliana; Rivillas-Acevedo, Lina

    2013-01-01

    Metal ions play a wide range of important functional roles in biology, and they often serve as cofactors in enzymes. Some of the metal ions that are essential for life are strongly associated with proteins, forming obligate metalloproteins, while others may bind to proteins with relatively low affinity. The spectroscopic tools presented in this chapter are suitable to study metal ion-protein interactions. Metal sites in proteins are usually low symmetry centers that differentially absorb left and right circularly polarized light. The combination of electronic absorption and circular dichroism (CD) in the UV-visible region allows the characterization of electronic transitions associated with the metal-protein complex, yielding information on the geometry and nature of the metal-ligand interactions. For paramagnetic metal centers in proteins, electron paramagnetic resonance (EPR) is a powerful tool that provides information on the chemical environment around the unpaired electron(s), as it relates to the electronic structure and geometry of the metal-protein complex. EPR can also probe interactions between the electron spin and nuclear spins in the vicinity, yielding valuable information on some metal-ligand interactions. This chapter describes each spectroscopic technique and it provides the necessary information to design and implement the study of metal ion-protein interactions by electronic absorption, CD, and EPR.

  12. Results of Self-Absorption Study on the Versapor 3000 Filters for Radioactive Particulate Air Sampling

    SciTech Connect

    Barnett, J. Matthew; Cullinan, Valerie I.; Barnett, Debra S.; Trang-Le, Truc LT; Bliss, Mary; Greenwood, Lawrence R.; Ballinger, Marcel Y.

    2009-02-17

    effects. The microscopy analysis compares different filter loadings and shows that smaller particle sizes (under 10 micron) can readily be seen on the more lightly loaded filters. At higher loadings, however, the particle size is harder to differentiate. This study provides data on actual stack emission samples showing a range of mass loading conditions and visual evidence of particle size and distribution and also presents the difficulties in quantifying self-absorption effects using actual samples.

  13. Molecular dynamics simulation and TDDFT study of the structures and UV-vis absorption spectra of MCT-β-CD and its inclusion complexes.

    PubMed

    Lu, Huijuan; Wang, Yujiao; Xie, Xiaomei; Chen, Feifei; Li, Wei

    2015-01-01

    In this research, the inclusion ratios and inclusion constants of MCT-β-CD/PERM and MCT-β-CD/CYPERM inclusion complexes were measured by UV-vis and fluorescence spectroscopy. The inclusion ratios are both 1:1, and the inclusion constants are 60 and 342.5 for MCT-β-CD/PERM and MCT-β-CD/CYPERM, respectively. The stabilities of inclusion complexes were investigated by MD simulation. MD shows that VDW energy plays a vital role in the stability of inclusion complex, and the destruction of inclusion complex is due to the increasing temperature. The UV-vis absorption spectra of MCT-β-CD and its inclusion complexes were studied by time-dependent density functional theory (TDDFT) method employing BLYP-D3, B3LYP-D3 and M06-2X-D3 functionals. BLYP-D3 well reproduces the UV-vis absorption spectrum and reveals that the absorption bands of MCT-β-CD mainly arise from n→π(∗) and n→σ(∗) transition, and those of inclusion complexes mainly arise from intramolecular charge transfer (ICT). ICT results in the shift of main absorption bands of MCT-β-CD.

  14. Chloride ligation in inorganic manganese model compounds relevant to Photosystem II studied using X-ray absorption spectroscopy

    PubMed Central

    Pizarro, Shelly A.; Visser, Hendrik; Cinco, Roehl M.; Robblee, John H.; Pal, Samudranil; Mukhopadhyay, Sumitra; Mok, Henry J.; Sauer, Kenneth; Wieghardt, Karl; Armstrong, William H.

    2014-01-01

    Chloride ions are essential for proper function of the photosynthetic oxygen-evolving complex (OEC) of Photosystem II (PS II). Although proposed to be directly ligated to the Mn cluster of the OEC, the specific structural and mechanistic roles of chloride remain unresolved. This study utilizes X-ray absorption spectroscopy (XAS) to characterize the Mn–Cl interaction in inorganic compounds that contain structural motifs similar to those proposed for the OEC. Three sets of model compounds are examined; they possess core structures MnIV3O4X (X = Cl, F, or OH) that contain a di-μ-oxo and two mono-μ-oxo bridges or MnIV2O2X (X = Cl, F, OH, OAc) that contain a di-μ-oxo bridge. Each set of compounds is examined for changes in the XAS spectra that are attributable to the replacement of a terminal OH or F ligand, or bridging OAc ligand, by a terminal Cl ligand. The X-ray absorption near edge structure (XANES) shows changes in the spectra on replacement of OH, OAc, or F by Cl ligands that are indicative of the overall charge of the metal atom and are consistent with the electronegativity of the ligand atom. Fourier transforms (FTs) of the extended X-ray absorption fine structure (EXAFS) spectra reveal a feature that is present only in compounds where chloride is directly ligated to Mn. These FT features were simulated using various calculated Mn–X interactions (X = O, N, Cl, F), and the best fits were found when a Mn–Cl interaction at a 2.2–2.3 Å bond distance was included. There are very few high-valent Mn halide complexes that have been synthesized, and it is important to make such a comparative study of the XANES and EXAFS spectra because they have the potential for providing information about the possible presence or absence of halide ligation to the Mn cluster in PS II. PMID:14758524

  15. Experimental studies on WDM to TDM signal conversions using gigahertz electro-absorption modulators

    NASA Astrophysics Data System (ADS)

    Yang, Tianxin; Gao, Peirui; Ge, Chunfeng; Wang, Zhaoying

    2016-02-01

    A method of optical signal conversions at high data rates from wavelength division multiplexing (WDM) signals to time division multiplexing (TDM) signals is demonstrated and studied experimentally using the cross-absorption effect of electro-absorption modulator (EAM). A multi-wavelength light source is designed and built up as a set of WDM carriers which are gated as the WDM pulse signals to be converted. The spectrum of the WDM signals covers more than 40 nm so that is proved that the wavelengths in the whole C+L band can be converted to a single wavelength at which the TDM signal is formed at the output of the system. The pulse width of the WDM signals which is input into the EAM device is about 2.586 ns. And the signal to noise ratio after conversion is about 7dB. It shows that EAM has strong noise immunity in the all-optical wavelength conversion experiment. And it is observed that the conversion of signals at the short wavelength shows higher conversion efficiency than the long-wavelength signals in the EAM device to a probe wavelength at the center of C band.

  16. Extended x-ray absorption fine structure studies of IBS Fe--Tb alloy films

    SciTech Connect

    Harris, V.G.; Aylesworth, K.D.; Kim, K.H.; Elam, W.T.; Koon, N.C. )

    1991-11-15

    We have employed extended x-ray absorption fine structure (EXAFS) analysis to study the compositional dependence of the atomic structure in Fe--Tb alloy films. Fourier transforms of EXAFS data, relative to both the Fe {ital K} and the Tb {ital L}{sub III} absorption edges, provide information about the local atomic environments relative to each atom. Results indicate the Fe EXAFS data to be dominated by Fe--Fe correlations, and consists of contributions from two Fe atomic shells at radial distances near 2.47 and 2.66 A and a Tb shell near 2.91 A. The coordination number of the Fe shells are measured to increase, while radial distances decrease, with increased Fe content. The Tb EXAFS data was found to have an atomic shells of Fe and Tb at 2.91 and 3.47 A, respectively. Analysis suggests that the Fe shell is very disordered and is comprised of approximately 9.5 atoms while the Tb shell has {approx}3 atoms.

  17. Z-scan study of nonlinear absorption in reduced LiNbO{sub 3} crystals

    SciTech Connect

    Kostritskii, S. M.; Aillerie, M.

    2012-05-15

    The nonlinear absorption (NLA) was studied by open-aperture Z-scan experiments in the chemically reduced nominally pure LiNbO{sub 3} crystals at cw-illumination with the red (644 nm) and green (514.5 nm) laser beams. The magnitude of the measured NLA is considerably different from the reported Z-scan results obtained in as-grown LiNbO{sub 3}. The positive sign of NLA obtained with the red light has been related to the generation of the small bound polarons absorbing in red and near-IR ranges. Application of green light results in the light-induced transparency, i.e., the Z-scan traces show negative sign of NLA. Intensity dependence of Z-scan traces allows for conclusion that the photo-induced dissociation of small Nb{sub Li}{sup 4+}:Nb{sub Nb}{sup 4+} bipolarons and sequent generation of small polarons gives the dominating contribution to the nonlinear optical absorption in reduced crystals with a large bipolarons concentration.

  18. Time-resolved X-ray Absorption Spectroscopy for Electron Transport Study in Warm Dense Gold

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Won; Bae, Leejin; Engelhorn, Kyle; Heimann, Philip; Ping, Yuan; Barbrel, Ben; Fernandez, Amalia; Beckwith, Martha Anne; Cho, Byoung-Ick; GIST Team; IBS Team; LBNL Collaboration; SLAC Collaboration; LLNL Collaboration

    2015-11-01

    The warm dense Matter represents states of which the temperature is comparable to Fermi energy and ions are strongly coupled. One of the experimental techniques to create such state in the laboratory condition is the isochoric heating of thin metal foil with femtosecond laser pulses. This concept largely relies on the ballistic transport of electrons near the Fermi-level, which were mainly studied for the metals in ambient conditions. However, they were barely investigated in warm dense conditions. We present a time-resolved x-ray absorption spectroscopy measured for the Au/Cu dual layered sample. The front Au layer was isochorically heated with a femtosecond laser pulse, and the x-ray absorption changes around L-edge of Cu, which was attached on the backside of Au, was measured with a picosecond resolution. Time delays between the heating of the `front surface' of Au layer and the alternation of x-ray spectrum of Cu attached on the `rear surface' of Au indicate the energetic electron transport mechanism through Au in the warm dense conditions. IBS (IBS-R012-D1) and the NRF (No. 2013R1A1A1007084) of Korea.

  19. [Experimental study on CO2 absorption by aqueous ammonia-based blended absorbent].

    PubMed

    Xia, Zhi-Xiang; Xiang, Qun-Yang; Zhou, Xu-Ping; Fang, Meng-Xiang

    2014-07-01

    A crucial problem for the promising absorbent aqueous ammonia (NH3) is the low CO2 absorption rate. The mass transfer coefficient (K(G)) of CO2 in aqueous NH3-based absorbents on a wetted wall column facility was investigated. Monoethanolamine (MEA), piperazine (PZ), 1-methyl piperazine (1-MPZ) and 2-methyl piperazine (2-MPZ) were introduced into NH3 solutions as additives, all of which significantly increased the mass transfer coefficient of CO2 in the solutions. With CO2 loading of 0, 0.1, 0.3, 0.5 mol x mol(-1), K(G) of 3 mol x L(-1) NH3 + 0.3 mol x L(-1) PZ blended solution increased by 2, 2.2, 2.2, and 1.9 fold as compared to that of 3 mol x L(-1) NH3. Typically, PZ, the additive with best performance, was chosen for further study. The effects of temperature and PZ concentration on CO2 absorption in PZ solution and the blended NH3/PZ solution. The calculated pseudo first order rate constant [42.7 m3 x (mol x s)(-1)] was analyzed to further elucidate the reaction mechanism in the blended NH3/PZ solution.

  20. [Study on Differential Optical Absorption Spectroscopy Data Processing Based on Chirp-Z Transformation].

    PubMed

    Zheng, Hai-ming; Li, Guang-jie; Wu, Hao

    2015-06-01

    Differential optical absorption spectroscopy (DOAS) is a commonly used atmospheric pollution monitoring method. Denoising of monitoring spectral data will improve the inversion accuracy. Fourier transform filtering method is effectively capable of filtering out the noise in the spectral data. But the algorithm itself can introduce errors. In this paper, a chirp-z transform method is put forward. By means of the local thinning of Fourier transform spectrum, it can retain the denoising effect of Fourier transform and compensate the error of the algorithm, which will further improve the inversion accuracy. The paper study on the concentration retrieving of SO2 and NO2. The results show that simple division causes bigger error and is not very stable. Chirp-z transform is proved to be more accurate than Fourier transform. Results of the frequency spectrum analysis show that Fourier transform cannot solve the distortion and weakening problems of characteristic absorption spectrum. Chirp-z transform shows ability in fine refactoring of specific frequency spectrum.

  1. Regional variations in percutaneous absorption of methimazole: an in vitro study on cat skin.

    PubMed

    Hill, K E; Chambers, J P; Jones, B R; Bolwell, C F; Aberdein, D; Mills, P C

    2015-12-01

    The use of transdermal gel medications in cats has become popular in veterinary medicine due to the ease of administration compared to oral medication. The research to support systemic absorption of drugs after transdermal gel administration and the preferred skin region to apply these drugs in cats is limited. The aim of this study was to characterize the effect of different skin regions on the percutaneous absorption pharmacokinetics of a commercially available transdermal methimazole after a finite dose was applied to feline skin in vitro. A commercial formulation of methimazole (10 mg) was applied to four skin regions (the inner stratum corneum of the ear, groin, neck, and thorax regions) from six cats. The receptor medium was sampled up to 36 h postapplication, and methimazole concentrations were measured using high-performance liquid chromatography. Methimazole was absorbed more completely across the pinnal skin, compared to the groin, neck, and thorax (P < 0.001), which justifies application to the pinna to maximize efficacy and also to minimize the effects of grooming.

  2. Reconstructed epidermis versus human and animal skin in skin absorption studies.

    PubMed

    Schreiber, S; Mahmoud, A; Vuia, A; Rübbelke, M K; Schmidt, E; Schaller, M; Kandárová, H; Haberland, A; Schäfer, U F; Bock, U; Korting, H C; Liebsch, M; Schäfer-Korting, M

    2005-09-01

    European chemical policy in general and the REACH initiative in particular will increase the number of chemical substances submitted to toxicological evaluation by several orders of magnitude compared to the current status. To limit animal exposure the resulting enormous increase in testing, however, asks for validated in vitro test systems. While the OECD favours in vitro testing for cutaneous absorption using viable human and animal skin (Guideline 428) the availability of viable human skin is already limited today. We present a comparison of various in vitro techniques suitable for routine skin absorption studies including commercially available reconstructed human epidermis which may be a reliable alternative to excised human and animal skin. In order to develop a protocol for the subsequent transfer to partner laboratories the experimental set-up was analysed stepwise using the OECD reference compounds caffeine and testosterone. Franz cell type, the donor and receptor media for hydrophilic/lipophilic substances, albumin and tensid addition, and storage conditions of the excised skins were systematically varied. A protocol has been developed which now allows to proceed to the pre-validation process.

  3. Reconstructed human epidermis for skin absorption testing: results of the German prevalidation study.

    PubMed

    Schäfer-Korting, Monika; Bock, Udo; Gamer, Armin; Haberland, Annekathrin; Haltner-Ukomadu, Eleonore; Kaca, Monika; Kamp, Hennicke; Kietzmann, Manfred; Korting, Hans Christian; Krächter, Hans-Udo; Lehr, Claus-Michael; Liebsch, Manfred; Mehling, Annette; Netzlaff, Frank; Niedorf, Frank; Rübbelke, Maria K; Schäfer, Ulrich; Schmidt, Elisabeth; Schreiber, Sylvia; Schröder, Klaus-Rudolf; Spielmann, Horst; Vuia, Alexander

    2006-06-01

    Exposure to chemicals absorbed by the skin can threaten human health. In order to standardise the predictive testing of percutaneous absorption for regulatory purposes, the OECD adopted guideline 428, which describes methods for assessing absorption by using human and animal skin. In this study, a protocol based on the OECD principles was developed and prevalidated by using reconstructed human epidermis (RHE). The permeation of the OECD standard compounds, caffeine and testosterone, through commercially available RHE models was compared to that of human epidermis and animal skin. In comparison to human epidermis, the permeation of the chemicals was overestimated when using RHE. The following ranking of the permeation coefficients for testosterone was obtained: SkinEthic > EpiDerm, EPISKIN > human epidermis, bovine udder skin, pig skin. The ranking for caffeine was: SkinEthic, EPISKIN > bovine udder skin, EpiDerm, pig skin, human epidermis. The inter-laboratory and intra-laboratory reproducibility was good. Long and variable lag times, which are a matter of concern when using human and pig skin, did not occur with RHE. Due to the successful transfer of the protocol, it is now in the validation process.

  4. Study of lithium absorption by users of spas treated with lithium ion.

    PubMed

    McCarty, J D; Carter, S P; Fletcher, M J; Reape, M J

    1994-05-01

    This study examines the possible dermal absorption of lithium ion into the blood serum of spa/hot tub bathers. Fifty-three participants (28 males and 25 females) spent 20 minutes per day, 4 days per week for 2 consecutive weeks in one of two assigned spas. The participants were randomly assigned to one of the two spas after matching based on sex, age, and use of oral contraceptives. The test spa contained 40 +/- 5 ppm lithium ion, while the control spa contained no additional lithium ion above the background levels of approximately 0.02 ppm. The exposure in the spa treated with lithium ion (from lithium chloride) simulated the maximum exposure that would be expected in a spa sanitized with lithium hypochlorite. The two spas were maintained at 101 +/- 2 degrees F. Serum lithium ion levels before and after spa use were determined using graphite-furnace atomic absorption spectroscopy with a minimum detectable level of lithium ion in serum of 2 micrograms l-1 (ppb). There was no statistically significant difference in serum lithium levels between the control and treatment group at any stage. We conclude that dermal exposure to lithium ion (as would be present after treatment of a spa with lithium hypochlorite) did not result in a detectable increase in the serum lithium ion level.

  5. Multitargeting by curcumin as revealed by molecular interaction studies.

    PubMed

    Gupta, Subash C; Prasad, Sahdeo; Kim, Ji Hye; Patchva, Sridevi; Webb, Lauren J; Priyadarsini, Indira K; Aggarwal, Bharat B

    2011-11-01

    Curcumin (diferuloylmethane), the active ingredient in turmeric (Curcuma longa), is a highly pleiotropic molecule with anti-inflammatory, anti-oxidant, chemopreventive, chemosensitization, and radiosensitization activities. The pleiotropic activities attributed to curcumin come from its complex molecular structure and chemistry, as well as its ability to influence multiple signaling molecules. Curcumin has been shown to bind by multiple forces directly to numerous signaling molecules, such as inflammatory molecules, cell survival proteins, protein kinases, protein reductases, histone acetyltransferase, histone deacetylase, glyoxalase I, xanthine oxidase, proteasome, HIV1 integrase, HIV1 protease, sarco (endo) plasmic reticulum Ca(2+) ATPase, DNA methyltransferases 1, FtsZ protofilaments, carrier proteins, and metal ions. Curcumin can also bind directly to DNA and RNA. Owing to its β-diketone moiety, curcumin undergoes keto-enol tautomerism that has been reported as a favorable state for direct binding. The functional groups on curcumin found suitable for interaction with other macromolecules include the α, β-unsaturated β-diketone moiety, carbonyl and enolic groups of the β-diketone moiety, methoxy and phenolic hydroxyl groups, and the phenyl rings. Various biophysical tools have been used to monitor direct interaction of curcumin with other proteins, including absorption, fluorescence, Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopy, surface plasmon resonance, competitive ligand binding, Forster type fluorescence resonance energy transfer (FRET), radiolabeling, site-directed mutagenesis, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), immunoprecipitation, phage display biopanning, electron microscopy, 1-anilino-8-naphthalene-sulfonate (ANS) displacement, and co-localization. Molecular docking, the most commonly employed computational tool for calculating binding affinities and predicting

  6. The irradiation of ammonia ice studied by near edge x-ray absorption spectroscopy

    SciTech Connect

    Parent, Ph.; Bournel, F.; Lasne, J.; Laffon, C.; Carniato, S.; Lacombe, S.; Strazzulla, G.; Gardonio, S.; Lizzit, S.; Kappler, J.-P.; Joly, L.

    2009-10-21

    A vapor-deposited NH{sub 3} ice film irradiated at 20 K with 150 eV photons has been studied with near-edge x-ray absorption fine structure (NEXAFS) spectroscopy at the nitrogen K-edge. Irradiation leads to the formation of high amounts (12%) of molecular nitrogen N{sub 2}, whose concentration as a function of the absorbed energy has been quantified to 0.13 molecule/eV. The stability of N{sub 2} in solid NH{sub 3} has been also studied, showing that N{sub 2} continuously desorbs between 20 and 95 K from the irradiated ammonia ice film. Weak concentrations (<1%) of other photoproducts are also detected. Our NEXAFS simulations show that these features own to NH{sub 2}, N{sub 2}H{sub 2}, and N{sub 3}{sup -}.

  7. Study of sub band gap absorption of Sn doped CdSe thin films

    NASA Astrophysics Data System (ADS)

    Kaur, Jagdish; Rani, Mamta; Tripathi, S. K.

    2014-04-01

    The nanocrystalline thin films of Sn doped CdSe at different dopants concentration are prepared by thermal evaporation technique on glass substrate at room temperature. The effect of Sn doping on the optical properties of CdSe has been studied. A decrease in band gap value is observed with increase in Sn concentration. Constant photocurrent method (CPM) is used to study the absorption coefficient in the sub band gap region. Urbach energy has been obtained from CPM spectra which are found to increase with amount of Sn dopants. The refractive index data calculated from transmittance is used for the identification of oscillator strength and oscillator energy using single oscillator model which is found to be 7.7 and 2.12 eV, 6.7 and 2.5 eV for CdSe:Sn 1% and CdSe:Sn 5% respectively.

  8. An EPR and optical absorption study of Cu(2+) doped in disodium malonate trihydrate single crystal.

    PubMed

    Yarbaşi, Zeynep; Karabulut, Bünyamin; Karabulut, Abdulhalik

    2009-03-01

    Single crystals and powder electron paramagnetic resonance (EPR) studies of Cu(2+)-doped disodium malonate trihydrate [C(3)H(2)O(4)Na(2).3H(2)O] have been carried out at room temperature. The angular variation of the disodium malonate trihydrate single crystal have shown that two different Cu(2+) complexes are located in different chemical environments, and each environment contains one magnetically inequivalent Cu(2+) sites in distinct orientations occupying substitutional positions in the lattice and show very high angular dependence. The principal values of the g and the hyperfine tensors were determined and were found to be in agreement with the literature values. Crystal field around the Cu(2+) ion is nearly rhombic. The optical absorption studies show two bands at 603nm (16584cm(-1)) and 890nm (11236cm(-1)) which confirm the rhombic symmetry. The crystals field parameters and than the wave function are determined.

  9. An EPR and optical absorption study of Cu 2+ doped in disodium malonate trihydrate single crystal

    NASA Astrophysics Data System (ADS)

    Yarbaşı, Zeynep; Karabulut, Bünyamin; Karabulut, Abdulhalik

    2009-03-01

    Single crystals and powder electron paramagnetic resonance (EPR) studies of Cu 2+-doped disodium malonate trihydrate [C 3H 2O 4Na 2·3H 2O] have been carried out at room temperature. The angular variation of the disodium malonate trihydrate single crystal have shown that two different Cu 2+ complexes are located in different chemical environments, and each environment contains one magnetically inequivalent Cu 2+ sites in distinct orientations occupying substitutional positions in the lattice and show very high angular dependence. The principal values of the g and the hyperfine tensors were determined and were found to be in agreement with the literature values. Crystal field around the Cu 2+ ion is nearly rhombic. The optical absorption studies show two bands at 603 nm (16584 cm -1) and 890 nm (11236 cm -1) which confirm the rhombic symmetry. The crystals field parameters and than the wave function are determined.

  10. Ray trace algorithm description for the study of pump power absorption in double clad fibers

    NASA Astrophysics Data System (ADS)

    Narro, R.; Rodriguez, E.; Ponce, L.; de Posada, E.; Flores, T.; Arronte, M.

    2011-09-01

    An algorithm for the analysis of the double clad fiber design is presented. The algorithm developed in the MATLAB computing language, is based on ray tracing method applied to three-dimensional graphics figures which are composed of a set of plans. The algorithm can evaluate thousands of ray paths in sequence and its corresponding pump absorption in each of the elements of the fiber according to the Lambert-Beer law. The beam path is evaluated in 3 dimensions considering the losses by reflexion and refraction in the faces and within the fiber. Due to its flexibility, the algorithm can be used to study the ray propagation in single mode or multimode fibers, bending effects in fibers, variable geometries of the inner clad and the core, and could also be used to study tappers.

  11. Graphite furnace and hydride generation atomic absorption spectrometric determination of cadmium, lead, and tin traces in natural surface waters: study of preconcentration technique performance.

    PubMed

    Tsogas, George Z; Giokas, Dimosthenis L; Vlessidis, Athanasios G

    2009-04-30

    In this study three major types of preconcentration methods based upon different principles (cation exchange, physical absorption and hydrophobic extraction) were evaluated and optimized for the extraction and determination of three highly toxic heavy metals namely Cd, Pb and Sn by graphite furnace and hybrid generation atomic absorption spectrometry in real samples. The optimum analytical conditions were examined and the analytical features of each method were revealed and compared. Detection limits as low as 0.003-0.025 microg L(-1) for Cd(2+), 0.05-0.10 microg L(-1) for Pb(2+) and 0.1-0.25 microg L(-1) for Sn(4+) depending on the extraction method were obtained with RSD values between 3.08% and 6.11%. A preliminary assessment of the pollution status of three important natural ecosystems in Epirus region (NW Greece) was performed and some early conclusions were drawn and discussed.

  12. The electronic states of 2-furanmethanol (furfuryl alcohol) studied by photon absorption and electron impact spectroscopies

    NASA Astrophysics Data System (ADS)

    Giuliani, A.; Walker, I. C.; Delwiche, J.; Hoffmann, S. V.; Limão-Vieira, P.; Mason, N. J.; Heyne, B.; Hoebeke, M.; Hubin-Franskin, M.-J.

    2003-10-01

    The photoelectron spectrum of 2-furanmethanol (furfuryl alcohol) has been measured for ionization energies between 8 and 11.2 eV and the first three ionization bands assigned to π3, π2, and no ionizations in order of increasing binding energy. The photoabsorption spectrum has been recorded in the gas phase using both a synchrotron radiation source (5-9.91 eV, 248-125 nm) and electron energy-loss spectroscopy under electric-dipole conditions (5-10.9 eV, 248-90 nm). The (UV) absorption spectrum has also been recorded in solution (4.2-6.36 eV, 292-195 nm). The electronic excitation spectrum appears to be dominated by transitions between π and π* orbitals in the aromatic ring, leading to the conclusion that the frontier molecular orbitals of furan are affected only slightly on replacement of a H atom by the -CH2OH group. Additional experiments investigating electron impact at near-threshold energies have revealed two low-lying triplet states and at least one electron/molecule shape resonance. Dissociative electron attachment also shows to be widespread in furfuryl alcohol.

  13. Role of chronic toxicology studies in revealing new toxicities.

    PubMed

    Galijatovic-Idrizbegovic, Alema; Miller, Judith E; Cornell, Wendy D; Butler, James A; Wollenberg, Gordon K; Sistare, Frank D; DeGeorge, Joseph J

    2016-12-01

    Chronic (>3 months) preclinical toxicology studies are conducted to support the safe conduct of clinical trials exceeding 3 months in duration. We have conducted a review of 32 chronic toxicology studies in non-rodents (22 studies in dogs and 10 in non-human primates) and 27 chronic toxicology studies in rats dosed with Merck compounds to determine the frequency at which additional target organ toxicities are observed in chronic toxicology studies as compared to subchronic studies of 3 months in duration. Our review shows that majority of the findings are observed in the subchronic studies since additional target organs were not observed in 24 chronic non rodent studies and in 21 chronic rodent studies. However, 6 studies in non rodents and 6 studies in rodents yielded new findings that were not seen in studies of 3-month or shorter duration. For 3 compounds the new safety findings did contribute to termination of clinical development plans. Although the incidence of compound termination associated with chronic toxicology study observations is low (∼10%), the observations made in these studies can be important for evaluating human safety risk.

  14. A QM/MM study of absorption spectra of uracil derivatives in aqueous solution

    NASA Astrophysics Data System (ADS)

    Nakayama, Akira

    2016-12-01

    The absorption spectra of three representative uracil derivatives (uracil, thymine, and 5-fluorouracil) in aqueous solution are investigated by the QM/MM approach, where the CASPT2 method is employed to evaluate the excitation energies. The computed absorption spectra are in good agreement with the experimental results, and in particular, the relative values of the absorption maximum between these derivatives are well reproduced in the simulations.

  15. Measurements of the Absorption by Auditorium SEATING—A Model Study

    NASA Astrophysics Data System (ADS)

    BARRON, M.; COLEMAN, S.

    2001-01-01

    One of several problems with seat absorption is that only small numbers of seats can be tested in standard reverberation chambers. One method proposed for reverberation chamber measurements involves extrapolation when the absorption coefficient results are applied to actual auditoria. Model seat measurements in an effectively large model reverberation chamber have allowed the validity of this extrapolation to be checked. The alternative barrier method for reverberation chamber measurements was also tested and the two methods were compared. The effect on the absorption of row-row spacing as well as absorption by small numbers of seating rows was also investigated with model seats.

  16. Shock tube study on the thermal decomposition of fluoroethane using infrared laser absorption detection of hydrogen fluoride.

    PubMed

    Matsugi, Akira; Shiina, Hiroumi

    2014-08-28

    Motivated by recent shock tube studies on the thermal unimolecular decomposition of fluoroethanes, in which unusual trends have been reported for collisional energy-transfer parameters, the rate constants for the thermal decomposition of fluoroethane were investigated using a shock tube/laser absorption spectroscopy technique. The rate constants were measured behind reflected shock waves by monitoring the formation of HF by IR absorption at the R(1) transition in the fundamental vibrational band near 2476 nm using a distributed-feedback diode laser. The peak absorption cross sections of this absorption line have also been determined and parametrized using the Rautian-Sobel'man line shape function. The rate constant measurements covered a wide temperature range of 1018-1710 K at pressures from 100 to 290 kPa, and the derived rate constants were successfully reproduced by the master equation calculation with an average downward energy transfer, ⟨ΔEdown⟩, of 400 cm(-1).

  17. Influence of the extent of hemoglobin hydrolysis on the digestive absorption of heme iron. An in vitro study.

    PubMed

    Vaghefi, Nikta; Nedjaoum, Fouzia; Guillochon, Didier; Bureau, François; Arhan, Pierre; Bouglé, Dominique

    2002-08-14

    This study was designed to assess the interactions of heme with peptides produced by enzyme hydrolysis of hemoglobin, and their relationship with heme iron absorption. Bovine hemoglobin was hydrolyzed by pepsin or by subtilisin, which differ in their hydrolysis processes. The hydrolysis rate ranged from 0 (native hemoglobin) to 15%. Heme solubility and heme-peptides interactions were compared to iron absorption by the Ussing chamber model, at intestinal pH (7.5). Increasing hemoglobin hydrolysis enhanced iron absorption; the highest value was reached between 8 and 11% hydrolysis, whatever the enzyme used. Comparing the products of hydrolysis of the two enzymes showed that heme iron absorption depends not only on its solubility, but relies mainly on the balance between the strength of heme-peptides and the polymerization rate of heme.

  18. Application of X-ray Absorption Spectroscopy to the study of nuclear structural materials

    NASA Astrophysics Data System (ADS)

    Liu, Shanshan

    One of key technologies for the next generation nuclear systems are advanced materials, including high temperature structural materials, fast neutron resistance core materials and so on. Local structure determination in these systems, which often are crystallographically intractable, is critical to gaining an understanding of their properties. In this thesis, X-ray Absorption Spectroscopy (XAS), including Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES), is used to examine the geometric and electronic structure of nuclear structural materials under varying conditions. The thesis is divided into two main sections. The first examines the structural analysis of nanostructured ferritic alloys (NFA) which are dispersion strengthened by an ultra high density of Y-Ti-O enriched nano-features, resulting in remarkable high temperature creep strength and radiation damage resistance. Titanium and Yttrium K-edge XAS shows commercial alloys MA957 and J12YWT more closely resemble the as received Fe-14Cr-3W-0.4Ti (wt. %) powders, and mechanically alloyed (MA) powders with 0.25Y2O3 (wt. %). It shows that a significant fraction of substitutional Ti remains dissolved in the (BCC) ferrite matrix. In contrast, annealed powders and hot isostatic press (HIP) consolidated alloys show high temperature heat treatments shift the Y and Ti to more oxidized states that are consistent with combinations of Y2Ti2O7 and, especially, TiO. The second section describes corrosion studies of Pb with 316L stainless steel, molybdenum and spinet (MgAl2O4) at high temperature by XAS. The corrosion of fuel cladding and structural materials by liquid lead at elevated temperatures is an issue that must be considered when designing advanced nuclear systems and high-power spallation neutron targets. The results of ex-situ studies show that a Mo substrate retained a smooth and less corroded surface than 316L stainless steel sample at elevated temperature. In

  19. Solvent effect on the absorption spectra of coumarin 120 in water: A combined quantum mechanical and molecular mechanical study.

    PubMed

    Sakata, Tetsuya; Kawashima, Yukio; Nakano, Haruyuki

    2011-01-07

    The solvent effect on the absorption spectra of coumarin 120 (C120) in water was studied utilizing the combined quantum mechanical∕molecular mechanical (QM∕MM) method. In molecular dynamics (MD) simulation, a new sampling scheme was introduced to provide enough samples for both solute and solvent molecules to obtain the average physical properties of the molecules in solution. We sampled the structure of the solute and solvent molecules separately. First, we executed a QM∕MM MD simulation, where we sampled the solute molecule in solution. Next, we chose random solute structures from this simulation and performed classical MD simulation for each chosen solute structure with its geometry fixed. This new scheme allowed us to sample the solute molecule quantum mechanically and sample many solvent structures classically. Excitation energy calculations using the selected samples were carried out by the generalized multiconfigurational perturbation theory. We succeeded in constructing the absorption spectra and realizing the red shift of the absorption spectra found in polar solvents. To understand the motion of C120 in water, we carried out principal component analysis and found that the motion of the methyl group made the largest contribution and the motion of the amino group the second largest. The solvent effect on the absorption spectrum was studied by decomposing it in two components: the effect from the distortion of the solute molecule and the field effect from the solvent molecules. The solvent effect from the solvent molecules shows large contribution to the solvent shift of the peak of the absorption spectrum, while the solvent effect from the solute molecule shows no contribution. The solvent effect from the solute molecule mainly contributes to the broadening of the absorption spectrum. In the solvent effect, the variation in C-C bond length has the largest contribution on the absorption spectrum from the solute molecule. For the solvent effect on the

  20. Electronic topological transition in zinc under pressure: An x-ray absorption spectroscopy study

    SciTech Connect

    Aquilanti, G.; Trapananti, A.; Pascarelli, S.; Minicucci, M.; Principi, E.; Liscio, F.; Twarog, A.

    2007-10-01

    Zinc metal has been studied at high pressure using x-ray absorption spectroscopy. In order to investigate the role of the different degrees of hydrostaticity on the occurrence of structural anomalies following the electronic topological transition, two pressure transmitting media have been used. Results show that the electronic topological transition, if it exists, does not induce an anomaly in the local environment of compressed Zn as a function of hydrostatic pressure and any anomaly must be related to a loss of hydrostaticity of the pressure transmitting medium. The near-edge structures of the spectra, sensitive to variations in the electronic density of states above the Fermi level, do not show any evidence of electronic transition whatever pressure transmitting medium is used.

  1. X-ray absorption studies of Ti/polymer and Cr/polymer interfaces

    SciTech Connect

    Opila, R.L.; Konstadinidis, K.; Ibidunni, A.O; Davenport, A.J.; Isaacs, H.S.

    1993-11-01

    The interface formed between metals, Ti and Cr, and polymers, epoxy, and triazine, have been studied, non-destructively, using x-ray absorption spectroscopy. The metals were sputtered onto the polymer surfaces. Titanium reacts extensively, up to Ti thickness of 100 {Angstrom} while Cr remains primarily metallic. In situ heating at 200{degree}C increases the extent of reaction for both metals. Heating has a greater effect on metal/epoxy interfaces than metal/triazine. Titanium and Cr were ion implanted into the polymer in order to determine the interactions of isolated metal atoms with the polymer. Titanium and Cr appear to form oxides as the final reaction product, and the Ti is tetrahedrally coordinated.

  2. Biomimetic environment to study E. coli complex I through surface-enhanced IR absorption spectroscopy.

    PubMed

    Kriegel, Sébastien; Uchida, Taro; Osawa, Masatoshi; Friedrich, Thorsten; Hellwig, Petra

    2014-10-14

    In this study complex I was immobilized in a biomimetic environment on a gold layer deposited on an ATR-crystal in order to functionally probe the enzyme against substrates and inhibitors via surface-enhanced IR absorption spectroscopy (SEIRAS) and cyclic voltammetry (CV). To achieve this immobilization, two methods based on the generation of a high affinity self-assembled monolayer (SAM) were probed. The first made use of the affinity of Ni-NTA toward a hexahistidine tag that was genetically engineered onto complex I and the second exploited the affinity of the enzyme toward its natural substrate NADH. Experiments were also performed with complex I reconstituted in lipids. Both approaches have been found to be successful, and electrochemically induced IR difference spectra of complex I were obtained.

  3. X-ray absorption studies of gamma irradiated Nd doped phosphate glass

    SciTech Connect

    Rai, V. N.; Rajput, Parasmani; Jha, S. N.; Bhattacharyya, D.

    2015-06-24

    This paper presents the X-ray absorption near edge structure (XANES) studies of Nd doped phosphate glasses before and after gamma irradiation. The intensity and location of L{sub III} edge white line peak of Nd changes depending on its concentration as well as on the ratio of O/Nd in the glass matrix. The decrease in the peak intensity of white line after gamma irradiation indicates towards reduction of Nd{sup 3+} to Nd{sup 2+} in the glass matrix, which increases with an increase in the doses of gamma irradiation. Similarity in the XANES spectra of Nd doped phosphate glasses and Nd{sub 2}O{sub 3} suggests that coordination geometry around Nd{sup 3+} in glass samples may be identical to that of Nd{sub 2}O{sub 3}.

  4. Electronic absorption spectra and energy gap studies of Er3+ ions in different chlorophosphate glasses.

    PubMed

    Ratnakaram, Y C; Reddy, A Viswanadha; Chakradhar, R P Sreekanth

    2002-06-01

    Spectroscopic properties of Er3+ ions in different chlorophosphate glasses 50P2O5-30Na2HPO4-19.8RCl (R = Li, Na, K, Ca and Pb) are studied. The direct and indirect optical band gaps (Eopt) and the various spectroscopic parameters (E1, E2, E3, and zeta4f and alpha) are reported. The oscillator strengths of the transitions in the absorption spectrum are parameterized in terms of three Judd-Ofelt intensity parameters (omega2, omega4 and omega6). These intensity parameters are used to predict the transition probabilities (A), radiative lifetimes (tauR), branching ratios (beta) and integrated cross sections (sigma) for stimulated emission. Attention has been paid to the trend of the intensity parameters over hypersensitive transitions and optical band gaps. The lifetimes and branching ratios of certain transitions are compared with other glass matrices.

  5. Ultrafast optical nonlinearity, electronic absorption, vibrational spectra and solvent effect studies of ninhydrin.

    PubMed

    Sajan, D; Devi, T Uma; Safakath, K; Philip, Reji; Němec, Ivan; Karabacak, M

    2013-05-15

    FT-IR, FT-Raman and UV-Vis spectra of the nonlinear optical molecule ninhydrin have been recorded and analyzed. The equilibrium geometry, bonding features, and harmonic vibrational wavenumbers have been investigated with the help of B3LYP density functional theory method. A detailed interpretation of the vibrational spectra is carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. Solvent effects have been calculated using time-dependent density functional theory in combination with the polarized continuum model. Natural bond orbital analysis confirms the occurrence of strong intermolecular hydrogen bonding in the molecule. Employing the open-aperture z-scan technique, nonlinear optical absorption of the sample has been studied in the ultrafast and short-pulse excitation regimes, using 100 fs and 5 ns laser pulses respectively. It is found that ninhydrin exhibits optical limiting for both excitations, indicating potential photonic applications.

  6. Studies on Nonoxynol-9. II. Intravaginal absorption, distribution, metabolism and excretion in rats and rabbits.

    PubMed

    Chvapil, M; Eskelson, C D; Stiffel, V; Owen, J A; Droegemueller, W

    1980-09-01

    Some pharmacological aspects of Igepal CO-630, used by some pharmaceutical companies as the source of nonylphenoxypoly (ethyleneoxy) ethanol (Nonoxynol-9, N-9) in various spermicidal formulations, were studied. It was found that Igepal CO-630 contains at least 13 components, 70% having molecular weights near that of N-9. After intravaginal administration, the detergent is rapidly and quantitatively absorbed through the vaginal wall into the systemic circulation. The rate of vaginal absorption of N-9 depends on the vehicle in which the detergent is carried. Once in the blood, N-9 is excreted by liver-bile-feces and the kidney-urine routes, the first being more effective in rats, the latter in rabbits. Following intravaginal or intraperitoneal injection of radioactive N-9, the highest content of radioactivity was found in the liver and kidney. The detergent was detected in the milk of lactating rats and the serum of their pups within two hours after the intravaginal dose.

  7. EPR and optical absorption studies on Gd 3+ ions in ammonium hydrogen malonate single crystals

    NASA Astrophysics Data System (ADS)

    Kripal, Ram; Mishra, Indrajeet

    2010-01-01

    X-Band electron paramagnetic resonance (EPR) studies of Gd 3+ ions in ammonium hydrogen malonate single crystals have been done at room temperature. Detailed EPR analysis indicates the presence of four physically equivalent but magnetically inequivalent sites. The zero-field splitting parameters and g factor are determined. The Gd 3+ ion is in 8S state; its levels are split by the action of the crystalline electric field of monoclinic symmetry. The optical absorption spectra of Gd 3+ ions in single crystals of ammonium hydrogen malonate are also recorded at room temperature. The energy levels of the 4f 7 configuration are calculated and compared with those observed experimentally. The values of E1=5854±11, E2=31±0.36, E3=592±3.3 and ζ 4f=1595±25 cm -1 are found to give the best over-all agreement between experimentally observed and calculated levels.

  8. Uranium and thorium sorption on minerals studied by x-ray absorption spectroscopy

    SciTech Connect

    Hudson, E.A.; Terminello, L.J.; Viani, B.E.

    1995-12-01

    Several actinide-mineral sorption systems were studied by uranium and thorium L{sub 3}-edge x-ray absorption spectroscopy. A series of layer silicate minerals, including micas, were selected for their systematic variations in surface structure, e.g. degree of permanent negative charge on the basal planes. An expansible layer silicate, vermiculite, was treated to provide several different interlayer spacings, allowing variations in the accessibility of interior cation exchange sites. The finely powdered minerals were exposed to aqueous solutions of uranyl chloride or thorium chloride. Analysis of the EXAFS and XANES spectra indicates the influence of the mineral substrate upon the local structure of the bound actinide species. Trends in the data are interpreted based upon the known variations in mineral structure.

  9. Mechanism of Pb Adsorption to Fatty Acid Langmuir Monolayers Studied by X-ray Absorption Fine Structure Spectroscopy

    SciTech Connect

    Boyanov, M.I.; Kmetko, J.; Shibata, T.; Datta, A.; Dutta, P.; Bunker, B.A.

    2010-09-30

    The local atomic environment of lead (Pb) adsorbed to a CH{sub 3}(CH{sub 2}){sub 19}COOH Langmuir monolayer was investigated in situ using grazing-incidence X-ray absorption fine structure (GI-XAFS) spectroscopy at the Pb L{sub III} edge. Measurements were performed at pH 6.5 of the 10{sup -5} M PbCl{sub 2} solution subphase, a condition under which grazing incidence diffraction (GID) revealed a large-area commensurate superstructure underneath the close-packed organic monolayer. The XAFS results indicate covalent binding of the Pb cations to the carboxyl headgroups, and the observed Pb-Pb coordination suggests that the metal is adsorbed as a hydrolysis polymer, rather than as individual Pb{sup 2+} ions. The data are consistent with a bidentate chelating mechanism and a one Pb atom to one carboxyl headgroup binding stoichiometry. We discuss how this adsorption model can explain the peculiarities observed with Pb in previous metal-Langmuir monolayer studies. A systematic study of lead perchlorate and lead acetate aqueous solutions is presented and used in the analysis. XAFS multiple scattering effects from alignment of the Pb-C-C atoms in the lead acetate solutions are reported.

  10. Implementing Japanese Lesson Study in Foreign Countries: Misconceptions Revealed

    ERIC Educational Resources Information Center

    Fujii, Toshiakira

    2014-01-01

    This paper is based on data gathered during visits to Uganda and Malawi, conducted by the International Math-teacher Professionalization Using Lesson Study (IMPULS) project and the Japanese International Cooperation Agency (JICA). The author's observations and experiences highlighted misconceptions about lesson study. The paper concludes that some…

  11. Study Reveals Brain Biology behind Self-Control

    ERIC Educational Resources Information Center

    Sparks, Sarah D.

    2011-01-01

    A new neuroscience twist on a classic psychology study offers some clues to what makes one student able to buckle down for hours of homework before a test while his classmates party. The study published in the September 2011 edition of "Proceedings of the National Academy of Science," suggests environmental cues may "hijack" the brain's mechanisms…

  12. Optimizing organic photovoltaics using tailored heterojunctions: A photoinduced absorption study of oligothiophenes with low band gaps

    NASA Astrophysics Data System (ADS)

    Schueppel, R.; Schmidt, K.; Uhrich, C.; Schulze, K.; Wynands, D.; Brédas, J. L.; Brier, E.; Reinold, E.; Bu, H.-B.; Baeuerle, P.; Maennig, B.; Pfeiffer, M.; Leo, K.

    2008-02-01

    A power conversion efficiency of 3.4% with an open-circuit voltage of 1V was recently demonstrated in a thin film solar cell utilizing fullerene C60 as acceptor and a new acceptor-substituted oligothiophene with an optical gap of 1.77eV as donor [K. Schulze , Adv. Mater. (Weinheim, Ger.) 18, 2872 (2006)]. This prompted us to systematically study the energy- and electron transfer processes at the oligothiophene:fullerene heterojunction for a homologous series of these oligothiophenes. Cyclic voltammetry and ultraviolet photoelectron spectroscopy data show that the heterojunction is modified due to tuning of the highest occupied molecular orbital energy for different oligothiophene chain lengths, while the lowest unoccupied molecular orbital energy remains essentially fixed due to the presence of electron-withdrawing end groups (dicyanovinyl) attached to the oligothiophene. Use of photoinduced absorption (PA) allows the study of the electron transfer process at the heterojunction to C60 . Quantum-chemical calculations performed at the density functional theory and/or time-dependent density functional theory level and cation absorption spectra of diluted DCVnT provide an unambiguous identification of the transitions observed in the PA spectra. Upon increasing the effective energy gap of the donor-acceptor pair by increasing the ionization energy of the donor, photoinduced electron transfer is eventually replaced with energy transfer, which alters the photovoltaic operation conditions. The optimum open-circuit voltage of a solar cell is thus a trade-off between efficient charge separation at the interface and maximized effective gap. It appears that the open-circuit voltages of 1.0-1.1V in our solar cell devices have reached an optimum since higher voltages result in a loss in charge separation efficiency.

  13. Absorption Spectroscopy Study of Acid-Base and Metal-Binding Properties of Flavanones

    NASA Astrophysics Data System (ADS)

    Shubina, V. S.; Shatalina, Yu. V.

    2013-11-01

    We have used absorption spectroscopy to study the acid-base and metal-binding properties of two structurally similar flavanones: taxifolin and naringenin. We have determined the acid dissociation constants for taxifolin (pKa1 = 7.10 ± 0.05, pKa2 = 8.60 ± 0.09, pKa3 = 8.59 ± 0.19, pKa4 = 11.82 ± 0.36) and naringenin (pKa1 = 7.05 ± 0.05, pKa2 = 8.85 ± 0.09, pKa3 = 12.01 ± 0.38). The appearance of new absorption bands in the visible wavelength region let us determine the stoichiometric composition of the iron (II) complexes of the flavanones. We show that at pH 5, in solution there is a mixture of complexes between taxifolin and iron (II) ions in stoichiometric ratio 2:1 and 1:2, while at pH 7.4 and pH 9, we detect a 1:1 taxifolin:Fe(II) complex. We established that at these pH values, naringenin forms a 2:1 complex with iron (II) ions. We propose structures for the complexes formed. Comprehensive study of the acid-base properties and the metal-binding capability of the two structurally similar flavanones let us determine the structure-properties relation and the conditions under which antioxidant activity of the polyphenols appears, via chelation of variable-valence metal ions.

  14. Studies of fullerene absorption and production using an infrared free-electron laser

    SciTech Connect

    Affatigato, M.; Haglund, R.F.; Ying, Z.C.; Compton, R.N.

    1995-12-31

    Tunable photon sources such as free-electron lasers are potentially valuable tools in spectroscopic studies of fullerenes, a new class of carbon materials with unique cage structures. We have used the infrared free-electron-laser facility at Vanderbilt University to study the infrared absorption of gas-phase fullerene molecules and also to investigate the effects of an infrared laser in the synthesis and crystallization of fullerene materials. In one experiment, fullerene vapor was created in a heat pipe through which the FEL beam was passed; the transmission of the FEL beam relative to a reference detector was measured as a function of wavelength. A large (>10%) absorption of the IR laser was observed when it passed through C{sub 60} vapor at {approximately}800{degrees}C. Due to the broad spectral width of the FEL as well as spectral congestion, no spectral peaks were seen when the laser wavelength was tuned across a T{sub 1u}C{sub 60} IR mode near 7.0 {mu}. However, it is expected that the vibrational features can be resolved experimentally by passing the transmitted beam through a monochromator. In a separate experiment, the FEL beam was focused onto a surface of graphite or graphite/metal mixture target. Various fullerene molecules, including endohedral types, were produced when the soot was recovered from the ablation chamber. The yield of the products was measured to be {approximately}0.4 g/J of the incident laser energy. However, both the yield and the product distribution are virtually, the same as those in experiments using a nanosecond Nd:YAG laser. This suggests that the laser wavelength is not a crucial parameter in making fullerenes by laser ablation. Even when the laser is at resonance with one of the vibrational modes of C{sub 60}, the fullerene production is neither substantially enhanced nor suppressed.

  15. [Study on the thermodynamical molar absorptivity of the interaction of cobalt(II) and the histidine].

    PubMed

    Chen, L; Zhang, D; Yang, D; He, Z; Wang, Y

    1999-02-01

    In this paper UV-Vis absorption spectrum of Cobalt(II) with the histidine and the thermodynamical molar absorptivity of the complex reaction were determined and the complexes of Cobalt(II) with the histidine were compared in terms of stability.

  16. Study on Nonlinear Absorption Effect of Nanosecond Pulse Laser Irradiation for GaAs.

    PubMed

    Sun, Wenjun; Liu, Zhongyang; Zhou, Haijiao

    2016-04-01

    In order to research nonlinear absorption effect of pulse laser irradiation for GaAs, a physical model of Gaussian distribution pulse laser irradiation for semiconductor material was established by software COMSOL Multiphysics. The thermal effects of semiconductor material GaAs was analyzed under irradiation of nanosecond pulse laser with wavelength of 1064 nm. The radial and transverse temperature distribution of semiconductor material GaAs was calculated under irradiation of nanosecond pulse laser with different power density by solving the thermal conduction equations. The contribution of one-photon absorption, two-photon absorption and free carrier absorption to temperature of GaAs material were discussed. The results show that when the pulse laser power density rises to 10(10) W/cm2, free carrier absorption played a leading role and it was more than that of one-photon absorption of material. The temperature contribution of two-photon absorption and free carrier absorption could be ignored at laser power density lower than 10(8) W/cm2. The result is basically consistent with relevant experiments, which shows that physical model constructed is valid.

  17. Suitability of skin integrity tests for dermal absorption studies in vitro.

    PubMed

    Guth, Katharina; Schäfer-Korting, Monika; Fabian, Eric; Landsiedel, Robert; van Ravenzwaay, Ben

    2015-02-01

    Skin absorption testing in vitro is a regulatory accepted alternative method (OECD Guideline 428). Different tests can be applied to evaluate the integrity of the skin samples. Here, we compared the pre- or post-run integrity tests (transepidermal electrical resistance, TEER; transepidermal water loss, TEWL; absorption of the reference compounds water, TWF, or methylene blue, BLUE) and additionally focused on co-absorption of a (3)H-labeled internal reference standard (ISTD) as integrity parameter. The results were correlated to absorption profiles of various test compounds. Limit values of 2kΩ, 10 gm(-2)h(-1) and 4.5∗10(-3)cmh(-1) for the standard methods TEER, TEWL and TWF, respectively, allowed distinguishing between impaired and intact human skin samples in general. Single skin samples did, however, not, poorly and even inversely correlate with the test-compound absorption. In contrast, results with ISTD (e.g. (3)H-testosterone) were highly correlated to the absorption of (14)C-labeled test compounds. Importantly, ISTD did not influence analytics or absorption of test compounds. Therefore, ISTD, especially when adjusted to the physico-chemical properties of test compounds, is a promising concept to assess the integrity of skin samples during the whole course of absorption experiments. However, a historical control dataset is yet necessary for a potential routine application.

  18. Vitamin D-mediated calcium absorption in patients with clinically stable Crohn's disease: a pilot study

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vitamin D is the critical hormone for intestinal absorption of calcium. Optimal calcium absorption is important for proper mineralization of bone in the prevention of osteoporosis and osteoporotic fractures, among other important functions. Diseases associated with gut inflammation, such as Crohn's ...

  19. Operando soft X-ray absorption spectroscopic study on a solid oxide fuel cell cathode during electrochemical oxygen reduction.

    PubMed

    Nakamura, Takashi; Oike, Ryo; Kimura, Yuta; Tamenori, Yusuke; Kawada, Tatsuya; Amezawa, Koji

    2017-03-16

    Operando soft X-ray absorption spectroscopic technique, which could analyze electronic structures of the electrode materials at elevated temperature and controlled atmosphere under electrochemical polarization, was established and its availability was demonstrated by investigating electronic structural changes of an La2NiO4+d dense film electrode during electrochemical oxygen reduction reaction. Clear O K-edge and Ni L-edge X-ray absorption spectra could be obtained below 773 K in fully atmospheric pressure of 100 ppm O2-He, 0.1% O2-He and 1% O2-He gas mixtures. By the PO2 change and the application of electrical potential, considerable spectral changes were observed in O K-edge X-ray absorption spectra while only small spectral changes were observed in Ni L-edge X-ray absorption spectra. Pre-edge peak of the O K-edge X-ray absorption spectra, which reflects the unoccupied pDOS of Ni3d-O2p hybridization, increased/deceased with cathodic/anodic polarization, respectively. The electronic structural changes of the outermost orbital of the electrode material due to electrochemical polarization were successfully confirmed by the operando X-ray absorption spectroscopy developed in this study.

  20. Factors affecting the absorption maxima of acidic forms of bacteriorhodopsin. A study with artificial pigments.

    PubMed Central

    Albeck, A.; Friedman, N.; Sheves, M.; Ottolenghi, M.

    1989-01-01

    The absorption maximum (568 nm) of light-adapted bacteriorhodopsin bR568 undergoes reversible changes after acidification. At pH 2.9, the absorption shifts to 605 nm (forming bR605) and it blue shifts to 565 nm, after further acidification to pH approximately 0.5 (forming bR565). Molecular models accounting for such acid-induced changes are relevant to the structure and function of bacteriorhodopsin. In the present study we approached the problem by applying artificial bR pigments based on selectively modified synthetic retinals. This may allow direct identification of the specific regions in the retinal binding site where the above changes in the protein-retinal interactions take place. We investigated the spectroscopic effects of acid in a variety of artificial pigments, including cyaninelike retinals, retinals bearing bulky groups at C4, short polyenes, and retinals in which the beta-ionone ring was substituted by aromatic rings. The results provide direct evidence for the hypothesis that the generation of bR605 is due to changes in polyene-opsin interactions in the vicinity of the Schiff base linkage. The second transition (to bR565) was not observed in artificial pigments bearing major changes in the ring structure of the retinal. Two approaches accounting for this observation are presented. One argues that the generation of bR565 is associated with acid-induced changes in retinal-protein interactions in the vicinity of the retinal ring. The second involves changes in polyene-opsin interactions in the vicinity of the Schiff base linkage. For both bRw and bRN5, our results do not discriminate between the direct titration of negative or dipolar protein groups in the binding site and changes in the retinal-protein interactions induced by changes in the protein structure outside of the binding site. PMID:2611336

  1. Study on synchronous detection method of methane and ethane with laser absorption spectroscopy technology

    NASA Astrophysics Data System (ADS)

    He, Ying; Zhang, Yu-jun; You, Kun; Gao, Yan-wei; Chen, Chen; Liu, Jian-guo; Liu, Wen-qing

    2016-10-01

    The main ingredient of mash gas is alkenes, and methane is the most parts of mash gas and ethane is a small portion of it. Fast, accurate, real-time measurement of methane and ethane concentration is an important task for preventing coal mining disaster. In this research, a monitoring system with tunable diode laser absorption spectroscopy (TDLAS) technology has been set up for simultaneous measurement of methane and ethane, and a DFB laser at wavelength of 1.653μm was used as the laser source. The absorption spectroscopy information of methane and ethane, especially the characteristic of the spectrum peak positions and relative intensity were determined by available spectral structures from previous study and available database. Then, the concentration inversion algorithm method based on the spectral resolution and feature extraction was designed for methane and ethane synchronous detection. At last, the continuously experimental results obtained by different concentration of methane and ethane sample gases with the multiple reflection cell and the standard distribution system. In this experiment, the standard distribution system made with the standard gas and two high precision mass flow meters of D07 Sevenstar series whose flow velocity is 1l/min and 5l/min respectively. When the multiple reflection cell work stably, the biggest detection error of methane concentration inversion was 3.7%, and the biggest detection error of ethane was 4.8%. So it is verified that this concentration inversion algorithm works stably and reliably. Thus, this technology could realize the real-time, fast and continuous measurement requirement of mash gas and it will provide the effective technical support to coal mining production in safety for our country.

  2. Energy transfer in LHCII monomers at 77K studied by sub-picosecond transient absorption spectroscopy.

    PubMed

    Kleima, F J; Gradinaru, C C; Calkoen, F; van Stokkum, I H; van Grondelle, R; van Amerongen, H

    1997-12-09

    Energy transfer from chlorophyll b (Chl b) to chlorophyll a (Chl a) in monomeric preparations of light-harvesting complex II (LHCII) from spinach was studied at 77 K using pump-probe experiments. Sub-picosecond excitation pulses centered at 650 nm were used to excite preferentially Chl b and difference absorption spectra were detected from 630 to 700 nm. Two distinct Chl b to Chl a transfer times, approximately 200 fs and 3 ps, were found. A clearly distinguishable energy transfer process between Chl a molecules occurred with a time constant of 18 ps. The LHCII monomer data are compared to previously obtained LHCII trimer data, and both data sets are fitted simultaneously using a global analysis fitting routine. Both sets could be described with the following time constants: 140 fs, 600 fs, 8 ps, 20 ps, and 2.9 ns. In both monomers and trimers 50% of the Chl b to Chl a transfer is ultrafast (<200 fs). However, for monomers this transfer occurs to Chl a molecules that absorb significantly more toward shorter wavelengths than for trimers. Part of the transfer from Chl b to Chl a that occurs with a time constant of 600 fs in trimers is slowed down to several picoseconds in monomers. However, it is argued that observed differences between monomers and trimers should be ascribed to the loss of some Chl a upon monomerization or a shift of the absorption maximum of one or several Chl a molecules. It is concluded that Chl b to Chl a transfer occurs only within monomeric subunits of the trimers and not between different subunits.

  3. Developmental palaeontology of Reptilia as revealed by histological studies.

    PubMed

    Scheyer, Torsten M; Klein, Nicole; Sander, P Martin

    2010-06-01

    Among the fossilized ontogenetic series known for tetrapods, only more basal groups like temnospondyl amphibians have been used extensively in developmental studies, whereas reptilian and synapsid data have been largely neglected so far. However, before such ontogenetic series can be subject to study, the relative age and affiliation of putative specimens within a series has to be verified. Bone histology has a long-standing tradition as being a source of palaeobiological and growth history data in fossil amniotes and indeed, the analysis of bone microstructures still remains the most important and most reliable tool for determining the absolute ontogenetic age of fossil vertebrates. It is also the only direct way to reconstruct life histories and growth strategies for extinct animals. Herein the record of bone histology among Reptilia and its application to elucidate and expand fossilized ontogenies as a source of developmental data are reviewed.

  4. Future volcanic lake research: revealing secrets from poorly studied lakes

    NASA Astrophysics Data System (ADS)

    Rouwet, D.; Tassi, F.; Mora-Amador, R. A.

    2012-04-01

    Volcanic lake research boosted after the 1986 Lake Nyos lethal gas burst, a limnic rather than volcanic event. This led to the formation of the IAVCEI-Commission on Volcanic Lakes, which grew out into a multi-disciplinary scientific community since the 1990's. At Lake Nyos, a degassing pipe is functional since 2001, and two additional pipes were added in 2011, aimed to prevent further limnic eruption events. There are between 150 and 200 volcanic lakes on Earth. Some acidic crater lakes topping active magmatic-hydrothermal systems are monitored continuously or discontinuously. Such detailed studies have shown their usefulness in volcanic surveillance (e.g. Ruapehu, Yugama-Kusatsu-Shiran, Poás). Others are "Nyos-type" lakes, with possible gas accumulation in bottom waters and thus potentially hazardous. "Nyos-type" lakes tend to remain stably stratified in tropical and sub-tropical climates (meromictic), leading to long-term gas build-up and thus higher potential risk. In temperate climates, such lakes tend to turn over in winter (monomictic), and thus liberating its gas charge yearly. We line out research strategies for the different types of lakes. We believe a complementary, multi-disciplinary approach (geochemistry, geophysics, limnology, biology, statistics, etc.) will lead to new insights and ideas, which can be the base for future following-up and monitoring. After 25 years of pioneering studies on rather few lakes, the scientific community should be challenged to study the many poorly studied volcanic lakes, in order to better constrain the related hazard, based on probabilistic approaches.

  5. Yeast studies reveal moonlighting functions of the ancient actin cytoskeleton

    PubMed Central

    Sattlegger, Evelyn; Chernova, Tatiana A.; Gogoi, Neeku M.; Pillai, Indu V.; Chernoff, Yury O.; Munn, Alan L.

    2014-01-01

    Classic functions of the actin cytoskeleton include control of cell size and shape and the internal organisation of cells. These functions are manifest in cellular processes of fundamental importance throughout biology such as the generation of cell polarity, cell migration, cell adhesion and cell division. However, studies in the unicellular model eukaryote Saccharomyces cerevisiae (Baker's yeast) are giving insights into other functions in which the actin cytoskeleton plays a critical role. These include endocytosis, control of protein translation and determination of protein 3-dimensional shape (especially conversion of normal cellular proteins into prions). Here we present a concise overview of these new "moonlighting" roles for the actin cytoskeleton and how some of these roles might lie at the heart of important molecular switches. This is an exciting time for researchers interested in the actin cytoskeleton. We show here how studies of actin are leading us into many new and exciting realms at the interface of genetics, biochemistry and cell biology. While many of the pioneering studies have been conducted using yeast, the conservation of the actin cytoskeleton and its component proteins throughout eukaryotes suggests that these new roles for the actin cytoskeleton may not be restricted to yeast cells but rather may reflect new roles for the actin cytoskeleton of all eukaryotes. PMID:25138357

  6. Orientation and electronic structure of ion exchanged dye molecules on mica: An X-ray absorption study

    SciTech Connect

    Fischer, D.; Caseri, W.R.; Haehner, G.

    1998-02-15

    Dye molecules are frequently used to determine the specific surface area and the ion exchange capacity of high-surface-area materials such as mica. The organic molecules are often considered to be planar and to adsorb in a flat orientation. In the present study the authors have investigated the orientation and electronic structure of crystal violet (CV) and malachite green (MG) on muscovite mica, prepared by immersing the substrates for extended periods into aqueous solutions of the dyes of various concentrations. The K{sup +} ions of the mica surface are replaced by the organic cations via ion exchange. X-ray photoelectron spectroscopy reveals that only one amino group is involved in the interaction of CV and MG with the muscovite surface, i.e., certain resonance structures are abolished upon adsorption. With near edge X-ray absorption fine structure spectroscopy a significant tilt angle with respect to the surface was found for all investigated species. A flat orientation, as has often been proposed before, can effectively be ruled out. Hence, results are in marked contrast to the often quoted orientation and suggest that the specific surface areas determined with dyes may, in general, be overestimated.

  7. Time-dependent X-ray absorption spectroscopic (XAS) study on the transformation of zinc basic salt into bis(N-oxopyridine-2-thionato) zinc (II).

    PubMed

    Paek, Seung-Min; Jo, Won-Young; Park, Man; Choy, Jin-Ho

    2007-11-01

    Solid transchelation reaction was established for the synthesis of bis(N-oxopyridine-2-thionato) zinc (II), commonly known as zinc pyrithione (ZPT), to control particle size using zinc basic salt (ZBS) and aqueous sodium pyrithione solution. Distinguished from ZPT particles prepared by usual precipitation reaction, the obtained ZPT nanoparticles exhibited very narrow size distribution. X-ray absorption spectroscopy (XAS) at Zn K-edge was systematically examined to elucidate time-dependent local structural evolution during solid transchelation reaction. X-ray absorption near edge structure (XANES) analysis clearly revealed that local environment around zinc atoms transformed into pentahedron as reaction proceeded. Based on quantitative X-ray diffraction and XANES analysis, we made structural models. Theoretical XAS spectrum calculated with FEFF code could reproduce experimental one, suggesting that XAS analysis could be very powerful tool to probe phase transformation. Furthermore, according to extended X-ray absorption fine structure (EXAFS) fitting results, Zn-O distance in reaction products gradually increased from 1.96 to 2.07 angstroms, suggesting that zinc atoms bounded with oxygen ones in ZBS were transchelated with pyrithione ligands. This study could be a strong evidence for the usefulness of XAS to study time-dependent structural transformation of nanocrystalline materials.

  8. Study on the highly transmitted Ag-In2O3/glass nanocomposite material: fabrication, microstructure and nonlinear absorption effects

    NASA Astrophysics Data System (ADS)

    Han, Liyuan; Yin, Dewu; Xu, Qin; Yang, Xinyu; Gao, Xiaoli; Lu, Xue; Liu, Haitao

    2016-11-01

    We fabricated a highly transmitted Ag-In2O3/glass nanocomposite material through a sol-gel method plus a controlled gas. Microstructural analysis revealed that the Ag and In elements in the Ag-In2O3 nanostructure exist in two forms: crystalline Ag nanoparticles and non-crystalline In2O3. And the crystalline Ag nanoparticles show the small size, uniform distribution and good dispersion in the glass host, thus triggering the surface plasmon resonance (SPR) effect and the quantum confinement effect. Remarkably, the Ag-In2O3/glass nanocomposite material exhibits the high transmittance greater than 70% in almost the whole visible spectral range. Open-aperture Z-scan technique further showed a typical two-photon absorption effect in the Ag-In2O3/glass nanocomposite material, where the nonlinear absorption coefficient was determined to be ~1.1  ×  10-9 cm W-1, and interestingly, the normalized transmittance decreased with increasing input fluence. The present results blaze a new path to develop the metal/glass nanocomposite materials with high transmittance, significant nonlinear absorption effects and potential optical limiting behavior. In addition, the mechanism on the nonlinear absorption effects were also discussed in this paper, such as the SPR effect, the quantum confinement effect, the thermal effects, the nonlinear scattering effect and the resonant nonlinear effect.

  9. Studies of Ancient Lice Reveal Unsuspected Past Migrations of Vectors

    PubMed Central

    Drali, Rezak; Mumcuoglu, Kosta Y.; Yesilyurt, Gonca; Raoult, Didier

    2015-01-01

    Lice are among the oldest parasites of humans representing an excellent marker of the evolution and migration of our species over time. Here, we analyzed by real-time polymerase chain reaction (RT-PCR) developed in this study the mitochondrial DNA of seven ancient head louse eggs found on hair remains recovered from two sites in Israel: 1) five nits dating from Chalcolithic period (4,000 bc) were found in the Cave of the Treasure located at Nahal Mishmar, in the Judean Desert and 2) two nits dating from Early Islamic Period (ad 650–810) were found in Nahal Omer in the Arava Valley (between Dead Sea and Red Sea). Our results suggest that these eggs belonged to people originating from west Africa based on identification of the louse mitochondrial sub-clade specific to that region. PMID:26078317

  10. Epistatic study reveals two genetic interactions in blood pressure regulation

    PubMed Central

    2013-01-01

    Background Although numerous candidate gene and genome-wide association studies have been performed on blood pressure, a small number of regulating genetic variants having a limited effect have been identified. This phenomenon can partially be explained by possible gene-gene/epistasis interactions that were little investigated so far. Methods We performed a pre-planned two-phase investigation: in phase 1, one hundred single nucleotide polymorphisms (SNPs) in 65 candidate genes were genotyped in 1,912 French unrelated adults in order to study their two-locus combined effects on blood pressure (BP) levels. In phase 2, the significant epistatic interactions observed in phase 1 were tested in an independent population gathering 1,755 unrelated European adults. Results Among the 9 genetic variants significantly associated with systolic and diastolic BP in phase 1, some may act through altering the corresponding protein levels: SNPs rs5742910 (Padjusted≤0.03) and rs6046 (Padjusted =0.044) in F7 and rs1800469 (Padjusted ≤0.036) in TGFB1; whereas some may be functional through altering the corresponding protein structure: rs1800590 (Padjusted =0.028, SE=0.088) in LPL and rs2228570 (Padjusted ≤9.48×10-4) in VDR. The two epistatic interactions found for systolic and diastolic BP in the discovery phase: VCAM1 (rs1041163) * APOB (rs1367117), and SCGB1A1 (rs3741240) * LPL (rs1800590), were tested in the replication population and we observed significant interactions on DBP. In silico analyses yielded putative functional properties of the SNPs involved in these epistatic interactions trough the alteration of corresponding protein structures. Conclusions These findings support the hypothesis that different pathways and then different genes may act synergistically in order to modify BP. This could highlight novel pathophysiologic mechanisms underlying hypertension. PMID:23298194

  11. Toward picosecond time-resolved X-ray absorption studies of interfacial photochemistry

    NASA Astrophysics Data System (ADS)

    Gessner, Oliver; Mahl, Johannes; Neppl, Stefan

    2016-05-01

    We report on the progress toward developing a novel picosecond time-resolved transient X-ray absorption spectroscopy (TRXAS) capability for time-domain studies of interfacial photochemistry. The technique is based on the combination of a high repetition rate picosecond laser system with a time-resolved X-ray fluorescent yield setup that may be used for the study of radiation sensitive materials and X-ray spectroscopy compatible photoelectrochemical (PEC) cells. The mobile system is currently deployed at the Advanced Light Source (ALS) and may be used in all operating modes (two-bunch and multi-bunch) of the synchrotron. The use of a time-stamping technique enables the simultaneous recording of TRXAS spectra with delays between the exciting laser pulses and the probing X-ray pulses spanning picosecond to nanosecond temporal scales. First results are discussed that demonstrate the viability of the method to study photoinduced dynamics in transition metal-oxide semiconductor (SC) samples under high vacuum conditions and at SC-liquid electrolyte interfaces during photoelectrochemical water splitting. Opportunities and challenges are outlined to capture crucial short-lived intermediates of photochemical processes with the technique. This work was supported by the Department of Energy Office of Science Early Career Research Program.

  12. Non-invasive gas monitoring in newborn infants using diode laser absorption spectroscopy: a case study

    NASA Astrophysics Data System (ADS)

    Lundin, Patrik; Svanberg, Emilie K.; Cocola, Lorenzo; Lewander, Märta; Andersson-Engels, Stefan; Jahr, John; Fellman, Vineta; Svanberg, Katarina; Svanberg, Sune

    2012-03-01

    Non-invasive diode laser spectroscopy was, for the first time, used to assess gas content in the intestines and the lungs of a new-born, 4 kg, baby. Two gases, water vapor and oxygen, were studied with two low-power tunable diode lasers, illuminating the surface skin tissue and detecting the diffusely emerging light a few centimeters away. The light, having penetrated into the tissue, had experienced absorption by gas located in the lungs and in the intestines. Very distinct water vapor signals were obtained from the intestines while imprint from oxygen was lacking, as expected. Detectable, but minor, signals of water vapor were also obtained from the lungs, illuminating the armpit area and detecting below the collar bone. Water vapor signals were seen but again oxygen signals were lacking, now due to the difficulties of penetration of the oxygen probing light into the lungs of this full-term baby. Ultra-sound images were obtained both from the lungs and from the stomach of the baby. Based on dimensions and our experimental findings, we conclude, that for early pre-term babies, also oxygen should be detectable in the lungs, in addition to intestine and lung detection of water vapor. The present paper focuses on the studies of the intestines while the lung studies will be covered in a forthcoming paper.

  13. A Trade-Off Study Revealing Nested Timescales of Constraint

    PubMed Central

    Wijnants, M. L.; Cox, R. F. A.; Hasselman, F.; Bosman, A. M. T.; Van Orden, G.

    2012-01-01

    This study investigates human performance in a cyclic Fitts task at three different scales of observation, either in the presence (difficult condition) or in the absence (easy condition) of a speed–accuracy trade-off. At the fastest scale, the harmonicity of the back and forth movements, which reflects the dissipation of mechanical energy, was measured within the timeframe of single trials. At an intermediate scale, speed and accuracy measures were determined over a trial. The slowest scale pertains to the temporal structure of movement variability, which evolves over multiple trials. In the difficult condition, reliable correlations across each of the measures corroborated a coupling of nested scales of performance. Participants who predominantly emphasized the speed-side of the trade-off (despite the instruction to be both fast and accurate) produced more harmonic movements and clearer 1/f scaling in the produced movement time series, but were less accurate and produced more random variability in the produced movement amplitudes (vice versa for more accurate participants). This implied that speed–accuracy trade-off was accompanied by a trade-off between temporal and spatial streams of 1/f scaling, as confirmed by entropy measures. In the easy condition, however, no trade-offs nor couplings among scales of performance were observed. Together, these results suggest that 1/f scaling is more than just a byproduct of cognition. These findings rather support the claim that interaction-dominant dynamics constitute a coordinative basis for goal-directed behavior. PMID:22654760

  14. Toxin Diversity Revealed by a Transcriptomic Study of Ornithoctonus huwena

    PubMed Central

    He, Quanze; Liu, Jinyan; Luo, Ji; Zhu, Li; Lu, Shanshan; Huang, Pengfei; Chen, Xinyi; Zeng, Xiongzhi; Liang, Songping

    2014-01-01

    Spider venom comprises a mixture of compounds with diverse biological activities, which are used to capture prey and defend against predators. The peptide components bind a broad range of cellular targets with high affinity and selectivity, and appear to have remarkable structural diversity. Although spider venoms have been intensively investigated over the past few decades, venomic strategies to date have generally focused on high-abundance peptides. In addition, the lack of complete spider genomes or representative cDNA libraries has presented significant limitations for researchers interested in molecular diversity and understanding the genetic mechanisms of toxin evolution. In the present study, second-generation sequencing technologies, combined with proteomic analysis, were applied to determine the diverse peptide toxins in venom of the Chinese bird spider Ornithoctonus huwena. In total, 626 toxin precursor sequences were retrieved from transcriptomic data. All toxin precursors clustered into 16 gene superfamilies, which included six novel superfamilies and six novel cysteine patterns. A surprisingly high number of hypermutations and fragment insertions/deletions were detected, which accounted for the majority of toxin gene sequences with low-level expression. These mutations contribute to the formation of diverse cysteine patterns and highly variable isoforms. Furthermore, intraspecific venom variability, in combination with variable transcripts and peptide processing, contributes to the hypervariability of toxins in venoms, and associated rapid and adaptive evolution of toxins for prey capture and defense. PMID:24949878

  15. Studies of recombinant TWA1 reveal constitutive dimerization

    PubMed Central

    Francis, Ore; Baker, Genevieve E.; Race, Paul R.

    2016-01-01

    The mammalian muskelin/RanBP9/C-terminal to LisH (CTLH) complex and the Saccharomyces cerevisiae glucose-induced degradation (GID) complex are large, multi-protein complexes that each contain a RING E3 ubiquitin ligase. The yeast GID complex acts to degrade a key enzyme of gluconeogenesis, fructose 1,6-bisphosphatase, under conditions of abundant fermentable carbon sources. However, the assembly and functions of the mammalian complex remain poorly understood. A striking feature of these complexes is the presence of multiple proteins that contain contiguous lissencephaly-1 homology (LisH), CTLH and C-terminal CT11-RanBP9 (CRA) domains. TWA1/Gid8, the smallest constituent protein of these complexes, consists only of LisH, CTLH and CRA domains and is highly conserved in eukaryotes. Towards better knowledge of the role of TWA1 in these multi-protein complexes, we established a method for bacterial expression and purification of mouse TWA1 that yields tag-free, recombinant TWA1 in quantities suitable for biophysical and biochemical studies. CD spectroscopy of recombinant TWA1 indicated a predominantly α-helical protein. Gel filtration chromatography, size-exclusion chromatography (SEC) with multi-angle light scattering (SEC-MALS) and native PAGE demonstrated a propensity of untagged TWA1 to form stable dimers and, to a lesser extent, higher order oligomers. TWA1 has a single cysteine residue, Cys139, yet the dimeric form was preserved when TWA1 was purified in the presence of the reducing agent tris(2-carboxyethyl)phosphine (TCEP). These findings have implications for understanding the molecular role of TWA1 in the yeast GID complex and related multi-protein E3 ubiquitin ligases identified in other eukaryotes. PMID:27920276

  16. Spectrum of excess partial molar absorptivity. I. Near infrared spectroscopic study of aqueous acetonitrile and acetone.

    PubMed

    Koga, Yoshikata; Sebe, Fumie; Minami, Takamasa; Otake, Keiko; Saitow, Ken-ichi; Nishikawa, Keiko

    2009-09-03

    We study the mixing schemes or the molecular processes occurring in aqueous acetonitrile (ACN) and acetone (ACT) by near-infrared spectroscopy (NIR). Both solutions (any other aqueous solutions) are not free from strong and complex intermolecular interactions. To tackle such a many-body problem, we first use the concept of the excess molar absorptivity, epsilonE, which is a function of solute mole fraction in addition to that of wavenumber, nu. The plots of epsilonE calculated from NIR spectra for both aqueous solutions against nu showed two clearly separated bands at 5020 and 5230 cm(-1); the former showed negative and the latter positive peaks. At zero and unity mole fractions of solute, epsilonE is identically zero independent of nu. Similar to the thermodynamic excess functions, both negative and positive bands grow in size from zero to the minimum (or the maximum) and back to zero, as the mole fraction varies from 0 to 1. Since the negative band's nu-locus coincides with the NIR spectrum of ice, and the positive with that of liquid H(2)O, we suggest that on addition of solute the "ice-likeness" decreases and the "liquid-likeness" increases, reminiscent of the two-mixture model for liquid H(2)O. The modes of these variations, however, are qualitatively different between ACN-H(2)O and ACT-H(2)O. The former ACN is known to act as a hydrophobe and ACT as a hydrophile from our previous thermodynamic studies. To see the difference more clearly, we introduced and calculated the excess partial molar absorptivity of ACN and ACT, epsilon(E)(N) and epsilon(E)(T), respectively. The mole fraction dependences of epsilon(E)(N) and epsilon(E)(T) show qualitatively different behavior and are consistent with the detailed mixing schemes elucidated by our earlier differential thermodynamic studies. Furthermore, we found in the H(2)O-rich region that the effect of hydrophobic ACN is acted on the negative band at 5020 cm(-1), while that of hydrophilic ACT is on the positive high

  17. Characteristics of Organobentonite and Study of Iodide Adsorption on Organobentonite using X-ray Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Yoon, J.; Ha, J.; Hwang, B.; Hwang, J.; Brown, G. E.

    2008-12-01

    The adsorption of iodide on untreated bentonite and bentonites modified with organic cation (i.e., hexadecylpyridinium chloride monohydrate (HDP+)) was investigated, and the organobentonites were characterized using uptake measurements, micro X-ray diffraction (micro-XRD), and electrophoretic mobility measurements prior to reaction with KI solutions. Uptake measurements indicate that bentonite has a high affinity for HDP+. Increasing [HDP+](aq) results in an increase in HDP+ uptake on bentonite by up to 280% of the CEC equivalents of bentonite, and causes a concomitant increase in Na released as a result of the replacement of exchangeable inorganic cations in bentonite interlayers. Based micro-XRD, the d001 spacing of untreated bentonite was 1.22 nm whereas organobentonites modified with HDP+ at different equivalent amounts, corresponding to 100%, 200%, and 400% of the cation exchange capacity (CEC) of bentonite, showed d001 spacings of 1.96 nm, 3.77 nm, and 3.77 nm, respectively. Our micro-XRD study indicates that organobentonites significantly expanded in basal spacing and organic cations were substantially intercalated into the interlayer spaces of montmorillonite. The electrophoretic mobility indicates that the untreated bentonite had a negative surface charge over the entire pH range examined (pH 2-12) whereas the organobentonite at an equivalent amount corresponding to 200% of the CEC had a positive surface charge over this pH range. We found significant differences in adsorption capacities of iodide depending on the bentonite properties as follows: iodide adsorption capacities were 439 mmol/kg for the bentonite modified with HDP+ at an equivalent amount corresponding to 200% of the CEC of bentonite whereas no adsorption of iodide was observed for the untreated bentonite. The molecular environments of iodine adsorbed on organobentonites were further studied using I K-edge and LIII-edge x-ray absorption spectroscopy (XAS). The X-ray absorption near

  18. Optical absorption, Mössbauer, and FTIR spectroscopic studies of two blue bazzites

    NASA Astrophysics Data System (ADS)

    Taran, Michail N.; Dyar, M. Darby; Khomenko, Vladimir M.; Boesenberg, Joseph S.

    2017-02-01

    Two samples of bazzite, a very rare Sc analog of beryl, from Tørdal, Telemark, Norway and Kent, Central Kazakhstan were studied by electron microprobe, optical absorption, and Mössbauer spectroscopies; the latter sample was also studied by FTIR. Electron microprobe results show that the Norway bazzite is composed of two bazzites with slightly different FeO contents, viz. 5.66 and 5.43 wt%. The Kazakhstan sample consists of several varieties of bazzite displaying strong differences in iron, manganese, magnesium, and aluminum contents (in wt%): FeO from 2.02 to 6.73, MnO from 0.89 to 2.98, MgO from 0.37 to 1.86, and Al2O3 from 0.30 to 1.30. Mössbauer spectroscopy shows different degrees of iron oxidation. The Norway bazzite is completely Fe2+, while the Kazakhstan sample contains roughly equivalent Fe3+ and Fe2+ accommodated in the octahedral site. The difference in iron oxidation causes strong variations in the intensity of the broad optical absorption band around 13,850 cm-1, which is assigned to Fe2+ → Fe3+ IVCT; as a result, there are strong differences in the intensity of blue color. Dichroism (E||c ≫ E⊥c) is much stronger in the Kazakhstan sample than in the Norway one. Intensities of the electronic spin-allowed bands of [6]Fe2+ at 8900 and 10,400 cm-1 are somewhat higher in the latter than in the former. FTIR spectra of the sample from Kent show the presence of only water type II molecules with the H-H vector perpendicular to the c-axis, in contrast to more typical beryls that always show at least weak minor bands of H2O I. This result shows that trapped water molecules in structural channels of studied bazzite occupy only sites next to or between six-membered rings centered by Na atoms. Definite structure can be observed in the vicinities of ν2 and ν3 peaks. Peaks at 1621 and 3663 cm-1 are assigned to "doubly coordinated" H2O (IId), whereas maximums at 1633 and 3643 cm-1 likely represent "singly coordinated" H2O (IIs). Interpretation of the third

  19. Interaction of Isophorone with Pd(111): A Combination of Infrared Reflection–Absorption Spectroscopy, Near-Edge X-ray Absorption Fine Structure, and Density Functional Theory Studies

    PubMed Central

    2014-01-01

    Atomistic level understanding of interaction of α,β-unsaturated carbonyls with late transition metals is a key prerequisite for rational design of new catalytic materials with the desired selectivity toward C=C or C=O bond hydrogenation. The interaction of this class of compounds with transition metals was investigated on α,β-unsaturated ketone isophorone on Pd(111) as a prototypical system. In this study, infrared reflection–absorption spectroscopy (IRAS), near-edge X-ray absorption fine structure (NEXAFS) experiments, and density functional theory calculations including van der Waals interactions (DFT+vdW) were combined to obtain detailed information on the binding of isophorone to palladium at different coverages and on the effect of preadsorbed hydrogen on the binding and adsorption geometry. According to these experimental observations and the results of theoretical calculations, isophorone adsorbs on Pd(111) in a flat-lying geometry at low coverages. With increasing coverage, both C=C and C=O bonds of isophorone tilt with respect to the surface plane. The tilting is considerably more pronounced for the C=C bond on the pristine Pd(111) surface, indicating a prominent perturbation and structural distortion of the conjugated π system upon interaction with Pd. Preadsorbed hydrogen leads to higher tilting angles of both π bonds, which points to much weaker interaction of isophorone with hydrogen-precovered Pd and suggests the conservation of the in-plane geometry of the conjugated π system. The results of the DFT+vdW calculations provide further insights into the perturbation of the molecular structure of isophorone on Pd(111). PMID:26089998

  20. Interaction of Isophorone with Pd(111): A Combination of Infrared Reflection-Absorption Spectroscopy, Near-Edge X-ray Absorption Fine Structure, and Density Functional Theory Studies.

    PubMed

    Dostert, Karl-Heinz; O'Brien, Casey P; Riedel, Wiebke; Savara, Aditya; Liu, Wei; Oehzelt, Martin; Tkatchenko, Alexandre; Schauermann, Swetlana

    2014-12-04

    Atomistic level understanding of interaction of α,β-unsaturated carbonyls with late transition metals is a key prerequisite for rational design of new catalytic materials with the desired selectivity toward C=C or C=O bond hydrogenation. The interaction of this class of compounds with transition metals was investigated on α,β-unsaturated ketone isophorone on Pd(111) as a prototypical system. In this study, infrared reflection-absorption spectroscopy (IRAS), near-edge X-ray absorption fine structure (NEXAFS) experiments, and density functional theory calculations including van der Waals interactions (DFT+vdW) were combined to obtain detailed information on the binding of isophorone to palladium at different coverages and on the effect of preadsorbed hydrogen on the binding and adsorption geometry. According to these experimental observations and the results of theoretical calculations, isophorone adsorbs on Pd(111) in a flat-lying geometry at low coverages. With increasing coverage, both C=C and C=O bonds of isophorone tilt with respect to the surface plane. The tilting is considerably more pronounced for the C=C bond on the pristine Pd(111) surface, indicating a prominent perturbation and structural distortion of the conjugated π system upon interaction with Pd. Preadsorbed hydrogen leads to higher tilting angles of both π bonds, which points to much weaker interaction of isophorone with hydrogen-precovered Pd and suggests the conservation of the in-plane geometry of the conjugated π system. The results of the DFT+vdW calculations provide further insights into the perturbation of the molecular structure of isophorone on Pd(111).

  1. The kinetics of intestinal calcium absorption in the rat: an analytical and model building study.

    PubMed

    de Labriolle-Vaylet, C; Bouvet, D; Brezillon, P; Milhaud, G; Staub, J F

    1986-04-01

    The experimental data obtained from in vivo single pass perfusion of duodenal, jejunal, and ileal intestinal segments of 33- and 50-day-old rats have been used to test a series of models for calcium absorption. Each model was checked for the statistical validity and goodness-of-fit with the experimental data. The model adopted for the duodenum and jejunum had two major components, one saturable and the other nonsaturable, and a minor secretory component. This model was not applicable to ileal calcium absorption. Here the secretory component appeared to be much more important, and the absorption parameters varied in such a manner as to suggest that this intestinal segment was capable of short term autoregulation of dietary calcium absorption.

  2. A study of pump power absorption efficiency of a diode side-pumped thin disk laser

    NASA Astrophysics Data System (ADS)

    Guo, Wei-rong; Feng, Chi; Li, Qiang; Yan, Le-lun; Jiang, Meng-hua

    2011-06-01

    A method computing the absorption efficiency with the difference between pump power entering the thin disk and pump power transmitted through the disk is introduced. Compared with directly computing the absorbed power, the method presented here needs much less computation to achieve the same accuracy, making it possible to compare much more absorption efficiency values at higher accuracy with a few parameters varied within certain ranges. Nonabsorption loss values were calculated with absorption coefficient, array distance and round disk radius varied within certain ranges. Results of calculation showed that the nonabsorption loss generally increases with increasing array distance, decreases with increasing round disk radius and decreases with increasing absorption coefficient. The method introduced by this paper presents a theoretical reference for the optimal design of thin disk lasers.

  3. The mechanism of lowering cholesterol absorption by calcium studied by using an in vitro digestion model.

    PubMed

    Vinarova, Liliya; Vinarov, Zahari; Tcholakova, Slavka; Denkov, Nikolai D; Stoyanov, Simeon; Lips, Alex

    2016-01-01

    Studies in humans show that a calcium-enriched diet leads to lower cholesterol in blood serum. This phenomenon is usually explained in the literature with a reduced cholesterol absorption in the small intestine. Our study aims to clarify the effect of calcium on the solubilisation of cholesterol and fatty acid in the dietary mixed micelles (DMM), viz. on the bioaccessibility of these lipophilic substances in the gut. We use an in vitro digestion model which mimics very closely the intestinal pH-profile and the composition of the intestinal fluids. We quantified the effects of Ca(2+) concentration on the lipid solubilization for fats and oils with different saturated/unsaturated fatty acid (FA) contents. We found that the increase of calcium significantly decreases the solubilization of cholesterol, FA and MG. Most importantly, we observe a clear positive correlation between the amounts of solubilized cholesterol, on one side, and solubilized free fatty acids and monoglycerides, on the other side. The main conclusion is that Ca(2+) ions strongly affect the bioaccessibility of both cholesterol and saturated FA. Therefore, calcium may decrease the serum cholesterol via two complementary mechanisms: (1) fatty acid precipitation by calcium ions reduces the solubilisation capacity of the DMM, thus decreasing the levels of solubilised (bioaccessible) cholesterol; (2) the observed strong decrease of the bioaccessible saturated FA, in its own turn, may suppress the cholesterol synthesis in the liver.

  4. Tailored heterojunctions for efficient thin-film organic solar cells: a photoinduced absorption study

    NASA Astrophysics Data System (ADS)

    Schueppel, R.; Schmidt, K.; Uhrich, C.; Schulze, K.; Wynands, D.; Brédas, J. L.; Maennig, B.; Pfeiffer, M.; Leo, K.; Brier, E.; Reinold, E.; Bu, H.-B.; Baeuerle, P.

    2007-09-01

    Recently, we have demonstrated an open circuit voltage of 1.0V and a power conversion efficiency of 3.4% in thin film solar cells, utilizing a new acceptor-substituted oligothiophene with an optical gap of 1.77 eV as donor and C 60 as acceptor. Stimulated by this result, we systematically study the energy and electron transfer processes taking place at the oligothiophene:fullerene heterojunction along a homologous series of these oligothiophenes. The heterojunction is modified by tuning the HOMO level using different oligothiophene chain lengths, while the LUMO level is essentially fixed by the choice of the acceptor-type end-groups (dicyanovinyl) attached to the oligothiophene. We study electron transfer at the heterojunction to C 60 using photoinduced absorption. The observed transitions are unambiguously identified by TD-DFT calculations. With increasing the effective energy gap of the donor-acceptor pair, charge carrier dissociation following the photoinduced electron transfer is eventually replaced by recombination into the triplet state, which alters the photovoltaic operation conditions. Therefore, the optimum open-circuit voltage of a solar cell is a trade-off between an efficient charge separation at the interface and a maximized effective gap. We conclude that values between 1.0 and 1.1 V for the open-circuit voltage in our solar cell devices present an optimum, as higher voltages were only achieved with concomitant losses in charge separation efficiency.

  5. High-resolution x-ray absorption spectroscopy studies of metal compounds in neurodegenerative brain tissue

    NASA Astrophysics Data System (ADS)

    Collingwood, J. F.; Mikhaylova, A.; Davidson, M. R.; Batich, C.; Streit, W. J.; Eskin, T.; Terry, J.; Barrea, R.; Underhill, R. S.; Dobson, J.

    2005-01-01

    Fluorescence mapping and microfocus X-ray absorption spectroscopy are used to detect, locate and identify iron biominerals and other inorganic metal accumulations in neurodegenerative brain tissue at sub-cellular resolution (<5 microns). Recent progress in developing the technique is reviewed. Synchrotron X-rays are used to map tissue sections for metals of interest, and XANES and XAFS are used to characterise anomalous concentrations of the metals in-situ so that they can be correlated with tissue structures and disease pathology. Iron anomalies associated with biogenic magnetite, ferritin and haemoglobin are located and identified in an avian tissue model with a pixel resolution ~5 microns. Subsequent studies include brain tissue sections from transgenic Huntington's mice, and the first high-resolution mapping and identification of iron biominerals in human Alzheimer's and control autopsy brain tissue. Technical developments include use of microfocus diffraction to obtain structural information about biominerals in-situ, and depositing sample location grids by lithography for the location of anomalies by conventional microscopy. The combined techniques provide a breakthrough in the study of both intra- and extra-cellular iron compounds and related metals in tissue. The information to be gained from this approach has implications for future diagnosis and treatment of neurodegeneration, and for our understanding of the mechanisms involved.

  6. High-resolution x-ray absorption spectroscopy studies of metal compounds in neurodegenerative brain tissue

    SciTech Connect

    Collingwood, J.F.; Mikhaylova, A.; Davidson, M.R.; Batich, C.; Streit, W.J.; Eskin, T.; Terry, J.; Barrea, R.; Underhill, R.S.; Dobson, J.

    2008-06-16

    Fluorescence mapping and microfocus X-ray absorption spectroscopy are used to detect, locate and identify iron biominerals and other inorganic metal accumulations in neurodegenerative brain tissue at sub-cellular resolution (< 5 microns). Recent progress in developing the technique is reviewed. Synchrotron X-rays are used to map tissue sections for metals of interest, and XANES and XAFS are used to characterize anomalous concentrations of the metals in-situ so that they can be correlated with tissue structures and disease pathology. Iron anomalies associated with biogenic magnetite, ferritin and haemoglobin are located and identified in an avian tissue model with a pixel resolution {approx} 5 microns. Subsequent studies include brain tissue sections from transgenic Huntington's mice, and the first high-resolution mapping and identification of iron biominerals in human Alzheimer's and control autopsy brain tissue. Technical developments include use of microfocus diffraction to obtain structural information about biominerals in-situ, and depositing sample location grids by lithography for the location of anomalies by conventional microscopy. The combined techniques provide a breakthrough in the study of both intra- and extra-cellular iron compounds and related metals in tissue. The information to be gained from this approach has implications for future diagnosis and treatment of neurodegeneration, and for our understanding of the mechanisms involved.

  7. Heavy Metals Effect on Cyanobacteria Synechocystis aquatilis Study Using Absorption, Fluorescence, Flow Cytometry, and Photothermal Measurements

    NASA Astrophysics Data System (ADS)

    Dudkowiak, A.; Olejarz, B.; Łukasiewicz, J.; Banaszek, J.; Sikora, J.; Wiktorowicz, K.

    2011-04-01

    The toxic effect of six heavy metals on cyanobacteria Synechocystis aquatilis was studied by absorption, fluorescence, flow cytometry, and photothermal measurements. This study indicates that at the concentration used, the cyanobacteria are more sensitive to silver, copper, and mercury than to cadmium, lead, and zinc metals. Disregarding the decrease in the yields of the related radiative processes caused by photochemical processes and/or damage to phycobilisomes, no changes were detected in the efficiency of thermal deactivation processes within a few microseconds, which can indicate the lack of disturbances in the photosynthetic light reaction and the lack of damage to the photosystem caused by the heavy metal ions in the concentrations used. The results demonstrate that the relative values of fluorescence yield as well as promptly generated heat calculated for the metal-affected and unaffected (reference) bacteria are sensitive indicators of environmental pollution with heavy metal ions, whereas the complementary methods proposed could be used as a noninvasive and fast procedure for in vivo assessment of their toxicity.

  8. Radiation absorption in different kinds of tissue analysis: ex vivo study with supercontinuum laser source

    NASA Astrophysics Data System (ADS)

    Fornaini, Carlo; Merigo, Elisabetta; Selleri, Stefano; Cucinotta, Annamaria

    2016-03-01

    With the introduction of more and more new wavelengths, one of the main problems of medical laser users was centered on the study of laser-tissue interactions with the aim of determining the ideal wavelength for their treatments. The aim of this ex vivo study was to determine, by means of the utilization of a supercontinuum source, the amount of transmitted energy of different wavelengths in different organ samples obtained by Sprague Dawley rats. Supercontinuum light is generated by exploiting high optical non-linearity in a material and it combines the broadband attributes of a lamp with the spatial coherence and high brightness of laser. Even if the single transmission measurement does not allow us to separate out the respective contribution of scattering and absorption, it gives us an evaluation of the wavelengths not interacting with the tissue. In this way, being possible to determine what of the laser wavelengths are not useful or active in the different kinds of tissue, physicians may choose the proper device for his clinical treatments.

  9. Laboratory studies of infrared absorption by NO2 and HNO3

    NASA Technical Reports Server (NTRS)

    Murcray, D. G.; Goldman, A.; Bonomo, F.

    1975-01-01

    Data concerning the quantitative absorption in the 11 and 22 micron region by HNO3 were obtained. Results are presented indicating the temperature dependence of these bands of HNO3 vapor. The 21.8 micron absorption bands of HNO3 vapor at 40 C are discussed along with the integrated intensity and line parameters for the 6.2 micron band of NO2.

  10. [Study of cholesterol concentration based on serum UV-visible absorption spectrum].

    PubMed

    Zhu, Wei-Hua; Zhao, Zhi-Min; Guo, Xin; Chen, Hui

    2009-04-01

    In the present paper, UV-visible absorption spectrum and neural network theory were used for the analysis of cholesterol concentration. Experimental investigation shows that the absorption spectrum has the following characteristics in the wave band of 350-600 nm: (1) There is a stronger absorption peak at 416 nm for the test sample with different cholesterol concentration; (2) There is a shoulder peak between 450 and 500 nm, whose central wavelength is 460 nm; (3) There is a weaker peak at 578 nm; (4) Absorption spectrums shape of different cholesterol concentration is different obviously. The absorption spectrum of serum is the synthesis result of cholesterol and other components (such as sugar), and the information is contained at each wavelength. There is no significant correlation between absorbance and cholesterol content at 416 nm, showing a random relation, so whether cholesterol content is abnormal is not determined by the absorbance peak at 416 nm. Based on the evident correlation between serum absorption spectrum and cholesterol concentration in the wave band of 455-475 nm, a neural network model was built to predict the cholesterol concentration. The correlation coefficient between predicted cholesterol content output A and objectives T reaches 0.968, which can be regarded as better prediction, and it provides a spectra test method of cholesterol concentration.

  11. A study on the inhibitory mechanism for cholesterol absorption by α-cyclodextrin administration

    PubMed Central

    Furune, Takahiro; Ikuta, Naoko; Ishida, Yoshiyuki; Okamoto, Hinako; Nakata, Daisuke; Terao, Keiji

    2014-01-01

    Summary Background: Micelle formation of cholesterol with lecithin and bile salts is a key process for intestinal absorption of lipids. Some dietary fibers commonly used to reduce the lipid content in the body are thought to inhibit lipid absorption by binding to bile salts and decreasing the lipid solubility. Amongst these, α-cyclodextrin (α-CD) is reportedly one of the most powerful dietary fibers for decreasing blood cholesterol. However, it is difficult to believe that α-CD directly removes cholesterol because it has a very low affinity for cholesterol and its mechanism of action is less well understood than those of other dietary fibers. To identify this mechanism, we investigated the interaction of α-CD with lecithin and bile salts, which are essential components for the dissolution of cholesterol in the small intestine, and the effect of α-CD on micellar solubility of cholesterol. Results: α-CD was added to Fed-State Simulated Intestinal Fluid (FeSSIF), and precipitation of a white solid was observed. Analytical data showed that the precipitate was a lecithin and α-CD complex with a molar ratio of 1:4 or 1:5. The micellar solubility of cholesterol in the mixture of FeSSIF and α-CD was investigated, and found to decrease through lecithin precipitation caused by the addition of α-CD, in a dose-dependent manner. Furthermore, each of several other water-soluble dietary fibers was added to the FeSSIF, and no precipitate was generated. Conclusion: This study suggests that α-CD decreases the micellar solubility of cholesterol in the lumen of the small intestine via the precipitation of lecithin from bile salt micelles by complex formation with α-CD. It further indicates that the lecithin precipitation effect on the bile salt micelles by α-CD addition clearly differs from addition of other water-soluble dietary fibers. The decrease in micellar cholesterol solubility in the FeSSIF was the strongest with α-CD addition. PMID:25550749

  12. X-ray diffraction and absorption spectroscopic studies of copper mixed ligand complexes with aminophenol as one of the ligands

    NASA Astrophysics Data System (ADS)

    Mishra, A.; Jain, Garima; Patil, H.

    2012-05-01

    X-ray diffraction (XRD) and X-ray absorption spectroscopic (XAS) studies have been conducted on two copper complexes, i.e., copper macrocyclic complex of succinic acid and ortho aminophenol (complex-1) and copper macrocyclic complex of pthalic acid and ortho aminophenol (complex-2). The diffraction pattern of the complexes have been recorded using Rigaku RINT-2000 X-ray diffractometer equipped with rotating anode X-ray tube operated at 40 kV and 100 mA. The X-ray absorption spectra of the complexes have been recorded at the K-edge of copper on Cauchois type bent crystal spectrograph having radius 0.4 m employing a mica crystal, oriented to reflect from (100) planes, for dispersion. The X-ray absorption near edge structure (XANES) parameters, viz., chemical shift, energy position of the principal absorption maximum and edge-width have been determined and discussed. From the extended X-ray absorption fine structure (EXAFS) data, the bond lengths have been calculated using three methods, namely, Levy's method, Lytle, Sayers and Stern's (LSS) method and Fourier transformation method. The results obtained have been compared with each other and discussed.

  13. Activable enriched stable isotope iron-58 for monitoring absorption rate of juvenile athletes for iron: a case study.

    PubMed

    Qian, Qinfang; Chai, Zhifang; Feng, Weiyu; Chen, Jidi; Zhang, Peiqun; Pan, Jianxiang

    2002-09-01

    Activable enriched stable isotopes can play a unique role in studies of nutritional status, metabolism, absorption rates, and bioavailability of minerals. As a practical example, eight juvenile athletes were selected to test the absorption rates of iron during training and non-training periods by enriched stable isotope of Fe-58 (enriched degree: 51.1%) via activation analysis Fe-58 (n, gamma) Fe-59 of the collected feces samples. The results indicated that the average iron absorption rates of the juvenile athletes with and without training are 9.1 +/- 2.8 and 11.9 +/- 4.7%, respectively, which implies that the long-term endurance training with high intensity makes the iron absorption rate of athletes lower. In the meantime, the comparison of the activable enriched isotope technique with atomic absorption spectrometry was performed, which showed that the former was better than the latter in reliability and sensitivity. It is because this nuclear method can distinguish the exogenous and endogenous iron in the samples, but not for non-nuclear methods.

  14. Effect of low zinc intake on absorption and excretion of zinc by infants studied with 70Zn as extrinsic tag.

    PubMed

    Ziegler, E E; Serfass, R E; Nelson, S E; Figueroa-Colón, R; Edwards, B B; Houk, R S; Thompson, J J

    1989-11-01

    The effect of low dietary intake of zinc was studied in six normal infants with the use of 70Zn as an extrinsic tag. Of the two study formulas, one provided a zinc intake similar to that of customary infant formulas ("high" intake), whereas the other provided a "low" zinc intake. Two zinc absorption studies were performed with each formula (sequence: high-low-low-high). Extrinsically labeled formula was fed for 24 h and excreta were collected for 72 h. Zinc isotope ratios were determined by inductively coupled plasma mass spectrometry (ICP/MS). When zinc intake was high, net zinc absorption was 9.1 +/- 8.7% (mean +/- SD) of intake and net zinc retention was 74 +/- 91 micrograms/(kg.d). True zinc (70Zn) absorption was 16.8 +/- 5.8% of intake and fecal excretion of endogenous zinc was 78 +/- 56 micrograms/(kg.d). When zinc intake was low, net absorption of zinc increased significantly (P less than 0.001) to 26.0 +/- 13.0% of intake, but net retention was not significantly different at 42 +/- 33 micrograms/(kg.d). True absorption of zinc also increased significantly (P less than 0.001) to 41.1 +/- 7.8% of intake, whereas fecal endogenous zinc decreased (P less than 0.05) to 34 +/- 16 micrograms/(kg.d) during low zinc intake. Thus, infants maintain zinc balance in the face of low zinc intake through increased efficiency of absorption and decreased excretion of endogenous zinc.

  15. First in-flight synchrotron X-ray absorption and photoemission study of carbon soot nanoparticles

    NASA Astrophysics Data System (ADS)

    Ouf, F.-X.; Parent, P.; Laffon, C.; Marhaba, I.; Ferry, D.; Marcillaud, B.; Antonsson, E.; Benkoula, S.; Liu, X.-J.; Nicolas, C.; Robert, E.; Patanen, M.; Barreda, F.-A.; Sublemontier, O.; Coppalle, A.; Yon, J.; Miserque, F.; Mostefaoui, T.; Regier, T. Z.; Mitchell, J.-B. A.; Miron, C.

    2016-11-01

    Many studies have been conducted on the environmental impacts of combustion generated aerosols. Due to their complex composition and morphology, their chemical reactivity is not well understood and new developments of analysis methods are needed. We report the first demonstration of in-flight X-ray based characterizations of freshly emitted soot particles, which is of paramount importance for understanding the role of one of the main anthropogenic particulate contributors to global climate change. Soot particles, produced by a burner for several air-to-fuel ratios, were injected through an aerodynamic lens, focusing them to a region where they interacted with synchrotron radiation. X-ray photoelectron spectroscopy and carbon K-edge near-edge X-ray absorption spectroscopy were performed and compared to those obtained for supported samples. A good agreement is found between these samples, although slight oxidation is observed for supported samples. Our experiments demonstrate that NEXAFS characterization of supported samples provides relevant information on soot composition, with limited effects of contamination or ageing under ambient storage conditions. The highly surface sensitive XPS experiments of airborne soot indicate that the oxidation is different at the surface as compared to the bulk probed by NEXAFS. We also report changes in soot’s work function obtained at different combustion conditions.

  16. X-ray absorption structural study of a reversible, photoexcited charge-transfer state

    SciTech Connect

    Chen, L.X.; Bowman, M.K.; Norris, J.R. Univ. of Chicago, IL ); Montano, P.A. )

    1993-05-19

    Electron-transfer reactions can be accompanied by significant nuclear movements. Nuclear motion appears to be especially vital to the reversible, photoinduced charge-transfer chemistry of cyclopentadienylnickel nitrosyl (C[sub 5]H[sub 5]NiNO). Although extended X-ray absorption fine structure (EXAFS) spectroscopy has recorded photoinduced changes in the ligation of myoglobins, similar X-ray studies of electron-transfer chemistry have not been reported. Here we examine reversible, photoinduced structural changes in C[sub 5]H[sub 5]NiNO by EXAFS and propose a mechanism for the electron-transfer chemistry. This work demonstrates that EXAFS can measure distance changes accompanying photoinduced electron transfer to provide new details of the geometry of photoexcited state and suggests that electron transfer occurs in the transient, optically excited states of C[sub 5]H[sub 5]NiNO and C[sub 5]H[sub 5]NiNO[sup CT] as dictated by NO movement that produces either C[sub 5]H[sub 5]NiNO[sup CT] or C[sub 5]H[sub 5]NiNO[sup GS]. 14 refs., 2 figs.

  17. ab initio study of hot carriers in the first picosecond after sunlight absorption in silicon.

    PubMed

    Bernardi, Marco; Vigil-Fowler, Derek; Lischner, Johannes; Neaton, Jeffrey B; Louie, Steven G

    2014-06-27

    Hot carrier thermalization is a major source of efficiency loss in solar cells. Because of the subpicosecond time scale and complex physics involved, a microscopic characterization of hot carriers is challenging even for the simplest materials. We develop and apply an ab initio approach based on density functional theory and many-body perturbation theory to investigate hot carriers in semiconductors. Our calculations include electron-electron and electron-phonon interactions, and require no experimental input other than the structure of the material. We apply our approach to study the relaxation time and mean free path of hot carriers in Si, and map the band and k dependence of these quantities. We demonstrate that a hot carrier distribution characteristic of Si under solar illumination thermalizes within 350 fs, in excellent agreement with pump-probe experiments. Our work sheds light on the subpicosecond time scale after sunlight absorption in Si, and constitutes a first step towards ab initio quantification of hot carrier dynamics in materials.

  18. Study of Water Absorption in Raffia vinifera Fibres from Bandjoun, Cameroon

    PubMed Central

    Sikame Tagne, N. R.; Njeugna, E.; Fogue, M.; Drean, J.-Y.; Nzeukou, A.; Fokwa, D.

    2014-01-01

    The study is focused on the water diffusion phenomenon through the Raffia vinifera fibre from the stem. The knowledge on the behavior of those fibres in presence of liquid during the realization of biocomposite, is necessary. The parameters like percentage of water gain at the point of saturation, modelling of the kinetic of water absorption, and the effective diffusion coefficient were the main objectives. Along a stem of raffia, twelve zones of sampling were defined. From Fick's 2nd law of diffusion, a new model was proposed and evaluated compared to four other models at a constant temperature of 23°C. From the proposed model, the effective diffusion coefficient was deduced. The percentage of water gain was in the range of 303–662%. The proposed model fitted better to the experimental data. The estimated diffusion coefficient was evaluated during the initial phase and at the final phase. In any cross section located along the stem of Raffia vinifera, it was found that the effective diffusion coefficient increases from the periphery to the centre during the initial and final phases. PMID:24592199

  19. Electronic transitions and fermi edge singularity in polar heterostructures studied by absorption and emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Pandey, S.; Cavalcoli, D.; Minj, A.; Fraboni, B.; Cavallini, A.; Gamarra, P.; Poisson, M. A.

    2012-12-01

    Optically induced electronic transitions in nitride based polar heterostructures have been investigated by absorption and emission spectroscopy. Surface photovoltage (SPV), photocurrent (PC), and photo luminescence spectroscopy have been applied to high quality InAlN/AlN/GaN structures to study the optical properties of two dimensional electron gas. Energy levels within the two dimensional electron gas (2DEG) well at the interface between the GaN and AlN have been directly observed by SPV and PC. Moreover, a strong enhancement of the photoluminescence intensity due to holes recombining with electrons at the Fermi Energy, known as fermi energy singularity, has been observed. These analyses have been carried out on InAlN/AlN/GaN heterojunctions with the InAlN barrier layer having different In content, a parameter which affects the energy levels within the 2DEG well as well as the optical signal intensity. The measured energy values are in a very good agreement with the ones obtained by Schrödinger-Poisson simulations.

  20. Photoacoustic study of percutaneous absorption of Carbopol and transdermic gels for topic use in skin

    NASA Astrophysics Data System (ADS)

    Rossi, R. C. P.; de Paiva, R. F.; da Silva, M. D.; Barja, P. R.

    2008-01-01

    Topical medicine application has been used to treat a good number of pathological processes. Its efficacy is associated to an efficient penetration of the drug in the internal skin layers, promoting systemic effects and excluding the possibility of drug degradation by the digestive tract and hepatic elimination. This work analyzes the penetration kinetics of two soluble bases employed as vehicles for topic application: superficial gel (Carbopol 940) and transdermic (transdermal) gel. Analysis was performed with the photoacoustic technique, based upon the absorption of modulated light by a sample with subsequent conversion of the absorbed energy in heat, generating acoustic waves in the air layer adjacent to the sample. Each of the two vehicles was evaluated through in vivo (human skin) and in vitro application. Measurements in vitro employed samples of VitroSkin (synthetic material with properties similar to those of real skin, employed in the pharmaceutical industry research). Results show that the permeation was faster for the transdermal gel, both for in vivo and in vitro measurements, indicating that in vitro measurements may be utilized in qualitative, comparative permeation studies.

  1. [Advances in studies of absorption and utilization of amino acids by plants: A review].

    PubMed

    Cao, Xiao-chuang; Wu, Liang-huan; Ma, Qing-xu; Jin, Qian-yu

    2015-03-01

    Plant can directly take up the intact amino acids, thus bypass the microbial mineralization of organic nitrogen. As an excellent carbon and nitrogen source, there exists competition for amino acid absorption between plant roots.and soil microorganisms. And the total flux of amino acids in soil may be enormous due to the extensive sources and short half-life. Studies on amino acid nitrogen nutritional contribution for plant by the technique of nitrogen isotopic tracer, has become a research topic in recent years ,which will help us better understand the principle of soil fertility. This paper summarized the recent researches on amino acid morphological characteristics in soil and its metabolic mechanism and nitrogen nutritional contribution for plant in different ecosystems, and discussed the present status and development trend of the amino acid circulation mechanism in the plant-soil-microorganism ecosystem and its bioavailability for plant. Finally, the topics of environmental regulating mechanism of amino acid bioavailability, amino acid carbon-nitrogen metabolism, and how to improve the field organic nitrogen management were all the core issues to be resolved.

  2. First in-flight synchrotron X-ray absorption and photoemission study of carbon soot nanoparticles

    PubMed Central

    Ouf, F.-X.; Parent, P.; Laffon, C.; Marhaba, I.; Ferry, D.; Marcillaud, B.; Antonsson, E.; Benkoula, S.; Liu, X.-J.; Nicolas, C.; Robert, E.; Patanen, M.; Barreda, F.-A.; Sublemontier, O.; Coppalle, A.; Yon, J.; Miserque, F.; Mostefaoui, T.; Regier, T. Z.; Mitchell, J.-B. A.; Miron, C.

    2016-01-01

    Many studies have been conducted on the environmental impacts of combustion generated aerosols. Due to their complex composition and morphology, their chemical reactivity is not well understood and new developments of analysis methods are needed. We report the first demonstration of in-flight X-ray based characterizations of freshly emitted soot particles, which is of paramount importance for understanding the role of one of the main anthropogenic particulate contributors to global climate change. Soot particles, produced by a burner for several air-to-fuel ratios, were injected through an aerodynamic lens, focusing them to a region where they interacted with synchrotron radiation. X-ray photoelectron spectroscopy and carbon K-edge near-edge X-ray absorption spectroscopy were performed and compared to those obtained for supported samples. A good agreement is found between these samples, although slight oxidation is observed for supported samples. Our experiments demonstrate that NEXAFS characterization of supported samples provides relevant information on soot composition, with limited effects of contamination or ageing under ambient storage conditions. The highly surface sensitive XPS experiments of airborne soot indicate that the oxidation is different at the surface as compared to the bulk probed by NEXAFS. We also report changes in soot’s work function obtained at different combustion conditions. PMID:27883014

  3. Extended X-ray absorption studies of copper (II) dibenzoyal methane diquinoline complexes

    NASA Astrophysics Data System (ADS)

    Mishra, A.; Sharma, P.; Malviya, P. K.

    2013-06-01

    X-ray K-absorption spectroscopic studies have been carried out on copper (II) mixed-ligand complexes. Copper is a transition metal, which in the zero oxidation state has an electron configuration of [Ar] 4s24p63d9. Copper is found in three different oxidation states: Cu(I), Cu(II), and Cu(III). In the copper (II) oxidation state, the metal has 9 d electrons. Jahn-Teller distortion causes a splitting of eg and t2g orbitals. Most Cu(II) complexes are square planar for this reason. In a series of those compounds, we have prepared copper (II) complexes containing two nitrato ligands and a 2,2'-dipyridylamine(dpa) derivative ligand. The 2,2' - dipyridylamine and its derivatives have been widely used for metal complexes because of their good chelating property, structural flexibility. we have estimated the average metalligand bond distances from the fine structure data. We have determined the bond lengths for the copper (II) complexes with the help of Levy's, LSS, Fourier transform, Lytle's Methods.

  4. Percutaneous absorption of benzophenone-3 loaded lipid nanoparticles and polymeric nanocapsules: A comparative study.

    PubMed

    Gilbert, E; Roussel, L; Serre, C; Sandouk, R; Salmon, D; Kirilov, P; Haftek, M; Falson, F; Pirot, F

    2016-05-17

    For the last years, the increase of the number of skin cancer cases led to a growing awareness of the need of skin protection against ultraviolet (UV) radiations. Chemical UV filters are widely used into sunscreen formulations as benzophenone-3 (BP-3), a usually used broad spectrum chemical UV filter that has been shown to exercise undesirable effects after topical application. Innovative sunscreen formulations are thus necessary to provide more safety to users. Lipid carriers seem to be a good alternative to formulate chemical UV filters reducing their skin penetration while maintaining good photo-protective abilities. The aim of this work was to compare percutaneous absorption and cutaneous bioavailability of BP-3 loaded into solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC), nanostructured polymeric lipid carriers (NPLC) and nanocapsules (NC). Particle size, zeta potential and in vitro sun protection factor (SPF) of nanoparticle suspensions were also investigated. Results showed that polymeric lipid carriers, comprising NPLC and NC, significantly reduced BP-3 skin permeation while exhibiting the highest SPF. This study confirms the interesting potential of NPLC and NC to formulate chemical UV filters.

  5. Photooxidation and photoaquation of iron hexacyanide in aqueous solution: A picosecond X-ray absorption study.

    PubMed

    Reinhard, M; Penfold, T J; Lima, F A; Rittmann, J; Rittmann-Frank, M H; Abela, R; Tavernelli, I; Rothlisberger, U; Milne, C J; Chergui, M

    2014-03-01

    We present a picosecond Fe K-edge absorption study of photoexcited ferrous and ferric hexacyanide in water under 355 and 266 nm excitation. Following 355 nm excitation, the transient spectra for the ferrous and ferric complexes exhibit a red shift of the edge reflecting an increased electron density at the Fe atom. For the former, an enhanced pre-edge transition is also observed. These observations are attributed to the aquated [Fe(CN)5OH2](3-) species, based on quantum chemical calculations which also provide structural parameters. Upon 266 nm excitation of the ferric complex, a transient reminiscent of the aquated species is observed (appearance of a pre-edge feature and red shift of the edge) but it is different from that obtained under 355 nm excitation. This points to a new reaction channel occurring through an intermediate state lying between these two excitation energies. Finally, 266 nm excitation of the ferrous species is dominated by the photooxidation channel with formation of the ferric complex as main photoproduct. However, we observe an additional minor photoproduct, which is identical to the 266 nm generated photoproduct of the ferric species, suggesting that under our experimental conditions, the pump pulse photooxidises the ferrous complex and re-excites the primary ferric photoproduct.

  6. Photooxidation and photoaquation of iron hexacyanide in aqueous solution: A picosecond X-ray absorption study

    PubMed Central

    Reinhard, M.; Penfold, T. J.; Lima, F. A.; Rittmann, J.; Rittmann-Frank, M. H.; Abela, R.; Tavernelli, I.; Rothlisberger, U.; Milne, C. J.; Chergui, M.

    2014-01-01

    We present a picosecond Fe K-edge absorption study of photoexcited ferrous and ferric hexacyanide in water under 355 and 266 nm excitation. Following 355 nm excitation, the transient spectra for the ferrous and ferric complexes exhibit a red shift of the edge reflecting an increased electron density at the Fe atom. For the former, an enhanced pre-edge transition is also observed. These observations are attributed to the aquated [Fe(CN)5OH2]3− species, based on quantum chemical calculations which also provide structural parameters. Upon 266 nm excitation of the ferric complex, a transient reminiscent of the aquated species is observed (appearance of a pre-edge feature and red shift of the edge) but it is different from that obtained under 355 nm excitation. This points to a new reaction channel occurring through an intermediate state lying between these two excitation energies. Finally, 266 nm excitation of the ferrous species is dominated by the photooxidation channel with formation of the ferric complex as main photoproduct. However, we observe an additional minor photoproduct, which is identical to the 266 nm generated photoproduct of the ferric species, suggesting that under our experimental conditions, the pump pulse photooxidises the ferrous complex and re-excites the primary ferric photoproduct. PMID:26798775

  7. Semiempirical MNDO and UV Absorption Studies on Tautomerism of 2-Quinolones

    NASA Astrophysics Data System (ADS)

    Mirek, Julian; Syguła, Andrzej

    1982-11-01

    Semiempirical MNDO calculations with geometry optimization were carried out for seven 4-X-2-quinolone tautomers (X = H, CH3, Cl, OCH3, N(CH3)2, COOH, COOCH3). The results show that 2-hydroxyquinolines are less stabilized compared to 2-quinoIones than 2-hydroxypyridines vs. 2-pyridones. The earlier estimated correction applied to these MNDO results suggests that 4-X-2-quinolones have lower chemical binding energies than the corresponding 4-X-2- hydroxyquinolines by ca. 2.1-3.3 kcal/mol. It is additionally shown that the substituent in position 4 does not influence significantly the relative stabilities of the tautomers. The results of the calculations are verified by UV absorption studies of diluted decane solutions of 2-quinolones at ca. 120°. CNDO/S-Cl-1 calculations based on the optimal MNDO geometries were carried out for 4-X-2- quinolone tautomers. The results generally agree well with the experimental data. A disagreement of the data for 4-COOR-2-quinolones is rationalized.

  8. First in-flight synchrotron X-ray absorption and photoemission study of carbon soot nanoparticles.

    PubMed

    Ouf, F-X; Parent, P; Laffon, C; Marhaba, I; Ferry, D; Marcillaud, B; Antonsson, E; Benkoula, S; Liu, X-J; Nicolas, C; Robert, E; Patanen, M; Barreda, F-A; Sublemontier, O; Coppalle, A; Yon, J; Miserque, F; Mostefaoui, T; Regier, T Z; Mitchell, J-B A; Miron, C

    2016-11-24

    Many studies have been conducted on the environmental impacts of combustion generated aerosols. Due to their complex composition and morphology, their chemical reactivity is not well understood and new developments of analysis methods are needed. We report the first demonstration of in-flight X-ray based characterizations of freshly emitted soot particles, which is of paramount importance for understanding the role of one of the main anthropogenic particulate contributors to global climate change. Soot particles, produced by a burner for several air-to-fuel ratios, were injected through an aerodynamic lens, focusing them to a region where they interacted with synchrotron radiation. X-ray photoelectron spectroscopy and carbon K-edge near-edge X-ray absorption spectroscopy were performed and compared to those obtained for supported samples. A good agreement is found between these samples, although slight oxidation is observed for supported samples. Our experiments demonstrate that NEXAFS characterization of supported samples provides relevant information on soot composition, with limited effects of contamination or ageing under ambient storage conditions. The highly surface sensitive XPS experiments of airborne soot indicate that the oxidation is different at the surface as compared to the bulk probed by NEXAFS. We also report changes in soot's work function obtained at different combustion conditions.

  9. Incontinence pad absorption and skin barrier creams: a non-patient study.

    PubMed

    Dykes, Peter; Bradbury, Sarah

    2016-12-08

    Exposure of the skin to excessive moisture, such as in cases of incontinence, can damage its natural barrier function and lead to tissue damage and breakdown. Common methods for managing incontinence and preventing related skin damage include the use of incontinence pads and the application of skin barrier creams to reduce exposure to moisture and irritants. Previous reports have indicated that barrier creams can transfer onto incontinence pads from the skin and reduce their absorbency, and thus the efficacy of both products. This study, using non-patient volunteers, investigated the effect on incontinence pad absorbency of Medi Derma-S and Medi Derma-Pro; two products from the Medi Skin Protection range, in comparison with other market-leading products. Results indicated that, while there was a small degree of product transfer onto the incontinence pads, this did not have a major impact on the absorption of synthetic urine. Medi Derma-S and Medi Derma-Pro performed consistently with other similar market-leading products.

  10. Theoretical modeling of the spectroscopic absorption properties of luciferin and oxyluciferin: A critical comparison with recent experimental studies

    NASA Astrophysics Data System (ADS)

    Anselmi, Massimiliano; Marocchi, Simone; Aschi, Massimiliano; Amadei, Andrea

    2012-01-01

    Firefly luciferin and its oxidated form, oxyluciferin, are two heterocyclic compounds involved in the enzymatic reaction, catalyzed by redox proteins called luciferases, which provides the bioluminescence in a wide group of arthropods. Whereas the electronic absorption spectra of D-luciferin in water at different pHs are known since 1960s, only recently reliable experimental electronic spectra of oxyluciferin have become available. In addition oxyluciferin is involved in a triple chemical equilibria (deprotonation of the two hydroxyl groups and keto-enol tautomerism of the 4-hydroxythiazole ring), that obligates to select during an experiment a predominant species, tuning pH or solvent polarity besides introducing chemical modifications. In this study we report the absorption spectra of luciferin and oxyluciferin in each principal chemical form, calculated by means of perturbed matrix method (PMM), which allowed us to successfully introduce the effect of the solvent on the spectroscopic absorption properties, and compare the result with available experimental data.

  11. A doubly curved elliptical crystal spectrometer for the study of localized x-ray absorption in hot plasmas

    SciTech Connect

    Cahill, Adam D. Hoyt, Cad L.; Pikuz, Sergei A.; Shelkovenko, Tania; Hammer, David A.

    2014-10-15

    X-ray absorption spectroscopy is a powerful tool for the diagnosis of plasmas over a wide range of both temperature and density. However, such a measurement is often limited to probing plasmas with temperatures well below that of the x-ray source in order to avoid object plasma emission lines from obscuring important features of the absorption spectrum. This has excluded many plasmas from being investigated by this technique. We have developed an x-ray spectrometer that provides the ability to record absorption spectra from higher temperature plasmas than the usual approach allows without the risk of data contamination by line radiation emitted by the plasma under study. This is accomplished using a doubly curved mica crystal which is bent both elliptically and cylindrically. We present here the foundational work in the design and development of this spectrometer along with initial results obtained with an aluminum x-pinch as the object plasma.

  12. Laboratory studies at high resolution of the infrared absorption spectra of a number of gases found in planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Hunt, R. H.

    1983-01-01

    The infrared absorption spectra of a number of gases found in planetary atmospheres were studied at high resolution. Absorption line measurements which can be of value for the interpretation of planetary spectra in terms of molecular abundances and conditions in the planetary atmospheres were provided. The high resolution spectra have yielded measurements of individual vibration rotation line parameters including positions, strengths, pressure broadened widths and, where assignments were unknown, the temperature sensitivity of the strengths. Such information allows the determinations of the absorption of a given molecular gas under planetary conditions of temperature and pressure and at the same time it provides the data necessary if the spectra are to be understood in terms of basic molecular theory. Thus this work has included spectral analysis in the form of line assignments as well as fitting of the data to Hamiltonian models. Such fitting is very useful in that it helps to confirm and extend the assignments.

  13. Pressure influence on the structural characteristics of modified absorptive glass mat separators: A standard contact porosimetry study

    NASA Astrophysics Data System (ADS)

    Burashnikova, M. M.; Khramkova, T. S.; Kazarinov, I. A.; Shmakov, S. L.

    2015-09-01

    The article presents a comparative analysis of the structural characteristics of absorptive glass mats manufactured by "Hollingsworth & Vose" (a 2.8 mm thickness) and "Bernard Dumas" (a 3.0 mm thickness) modified by impregnation with polymeric emulsions based on polyvinylidene fluoride, a polyvinylpyrrolidone styrene copolymer, and polytetrafluoroethylene, by means of standard contact porosimetry. The key study is influence of features of the porous structure on the compression properties, the rate of wicking, and the oxygen cycle efficiency in lead-acid battery mock-ups under several plate-group compression pressures. It is found that the treatment of the absorptive glass mat separators with polymeric emulsions leads to redistribution of their pores by size. An increased pressure in the electrode unit insignificantly changes the pore structure of the modified absorptive glass mat separators, and the oxygen cycle efficiency rises in comparison with unmodified separators.

  14. A study on flexural and water absorption of surface modified rice husk flour/E-glass/polypropylene hybrid composite

    NASA Astrophysics Data System (ADS)

    Rassiah, K.; Sin, T. W.; Ismail, M. Z.

    2016-10-01

    This work is to study the effects of rice husk (RH)/E-Glass (EG)/polypropylene (PP) hybrid composites in terms of flexural and water absorption properties. The tests conducted are the flexural test and also the water absorption test using two types of water: distilled and sea water. The hybrid composites are prepared with various ratios of fibre weight fractions and the rice husk is treated using 2% Sodium Hydroxide (NaOH) to improve interaction and adhesion between the non-polar matrix and the polar lignocellulosic fibres. It was found that the content of rice husk/E-Glass fillers affected the structural integrity and flexural properties of hybrid composites. In addition, a higher ratio of rice husk contributes to higher water absorption in the hybrid composites.

  15. High-speed laser-induced fluorescence and spark plug absorption sensor diagnostics for mixing and combustion studies in engines.

    PubMed

    Cundy, Michael; Schucht, Torsten; Thiele, Olaf; Sick, Volker

    2009-02-01

    Simultaneous high-speed in-cylinder measurements of laser-induced fluorescence of biacetyl as a fuel tracer and mid-infrared broadband absorption of fuel and combustion products (water and carbon dioxide) using a spark plug probe are compared in an optical engine. The study addresses uncertainties and the applicability of absorption measurements at a location slightly offset to the spark plug when information about mixing at the spark plug is desired. Absorbance profiles reflect important engine operation events, such as valve opening and closing, mixing, combustion, and outgassing from crevices.

  16. Z-scanning under monochromatic laser pumping: a study of saturatable absorption in a suspension of multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Mikheev, G. M.; Krivenkov, R. Yu; Mikheev, K. G.; Okotrub, A. V.; Mogileva, T. N.

    2016-08-01

    A system has been developed and designed based on a single-mode single-frequency passive Q-switched pulsed YAG : Nd3+ laser to investigate with high accuracy the nonlinear optical properties of a liquid placed in an optical cell with uncoated input windows. The efficiency of this system is demonstrated by examples of studying the saturable absorption of an aqueous suspension of multiwalled carbon nanotubes and the nonlinear absorption of a colour glass filter ZhS18 at a wavelength of 532 nm.

  17. Microwave absorption studies of magnetic sublattices in microwave sintered Cr3+ doped SrFe12O19

    NASA Astrophysics Data System (ADS)

    Praveena, K.; Sadhana, K.; Liu, Hsiang-Lin; Bououdina, M.

    2017-03-01

    The partial substitution of Fe3+ by Cr3+ in strontium hexaferrite has shown to be an effective method to tailor anisotropy for many novel microwave applications. Some basic studies have revealed that this substitution leads to unusual interactions among the magnetic sublattices of the hexaferrite. In order to investigate these interactions, Cr3+ doped SrCrxFe12-xO19 (x=0.0, 0.1, 0.3, 0.5, 0.7 and 0.9) (m-type) hexaferrites were prepared by microwave-hydrothermal (m-H) method and subsequently sintered at 950 °C/90 min using microwave furnace. The magnetic hysteresis (m-H) loops revealed the ferromagnetic nature of nanoparticles (NPs). The coercive field was increasing from 3291 Oe to 7335 Oe with increasing chromium content. This resulting compacts exhibited high squareness ratio (Mr/Ms-80%). The intrinsic coercivity (Hci) above 1,20,000 Oe and high values of magnetocrystalline anisotropy revealed that all samples are magnetically hard materials. A material with high loss as well as high dielectric constant may be desired in applications such as electromagnetic (EM) wave absorbing coatings. The room temperature complex dielectric and magnetic properties (ε‧, ε‧‧, μ‧ and μ‧‧) of Cr3+ doped SrFe12O19 were measured in X-band region. The frequency dependent dielectric and magnetic losses were increasing to large extent. The reflection coefficient varied from -16 to -33 dB at 10.1 GHz as Cr3+ concentration increased from x=0.0 to x=0.9. Ferromagnetic resonance spectra (FMR) were measured in the X-band (9.4 GHz), linewidth decreases with chromium concentration from 1368 to 752 Oe from x=0.0 to x=0.9, which is quite low compared to commercial samples. We also have detailed origins of the FMR linewidth broadenings in terms of some important theoretical models. These results show that chromium doped strontium hexaferrites are useful for microwave absorption in the X-band frequency and also have potential for use in low frequency self-biased microwave

  18. The use of reconstructed human epidermis for skin absorption testing: Results of the validation study.

    PubMed

    Schäfer-Korting, Monika; Bock, Udo; Diembeck, Walter; Düsing, Hans-Jürgen; Gamer, Armin; Haltner-Ukomadu, Eleonore; Hoffmann, Christine; Kaca, Monika; Kamp, Hennicke; Kersen, Silke; Kietzmann, Manfred; Korting, Hans Christian; Krächter, Hans-Udo; Lehr, Claus-Michael; Liebsch, Manfred; Mehling, Annette; Müller-Goymann, Christel; Netzlaff, Frank; Niedorf, Frank; Rübbelke, Maria K; Schäfer, Ulrich; Schmidt, Elisabeth; Schreiber, Sylvia; Spielmann, Horst; Vuia, Alexander; Weimer, Michaela

    2008-05-01

    A formal validation study was performed, in order to investigate whether the commercially-available reconstructed human epidermis (RHE) models, EPISKIN, EpiDerm and SkinEthic, are suitable for in vitro skin absorption testing. The skin types currently recommended in the OECD Test Guideline 428, namely, ex vivo human epidermis and pig skin, were used as references. Based on the promising outcome of the prevalidation study, the panel of test substances was enlarged to nine substances, covering a wider spectrum of physicochemical properties. The substances were tested under both infinite-dose and finite-dose conditions, in ten laboratories, under strictly controlled conditions. The data were subjected to independent statistical analyses. Intra-laboratory and inter-laboratory variability contributed almost equally to the total variability, which was in the same range as that in preceding studies. In general, permeation of the RHE models exceeded that of human epidermis and pig skin (the SkinEthic RHE was found to be the most permeable), yet the ranking of substance permeation through the three tested RHE models and the pig skin reflected the permeation through human epidermis. In addition, both infinite-dose and finite-dose experiments are feasible with RHE models. The RHE models did not show the expected significantly better reproducibility, as compared to excised skin, despite a tendency toward lower variability of the data. Importantly, however, the permeation data showed a sufficient correlation between all the preparations examined. Thus, the RHE models, EPISKIN, EpiDerm and SkinEthic, are appropriate alternatives to human and pig skin, for the in vitro assessment of the permeation and penetration of substances when applied as aqueous solutions.

  19. Effects of xylitol on carbohydrate digesting enzymes activity, intestinal glucose absorption and muscle glucose uptake: a multi-mode study.

    PubMed

    Chukwuma, Chika Ifeanyi; Islam, Md Shahidul

    2015-03-01

    The present study investigated the possible mechanism(s) behind the effects of xylitol on carbohydrate digesting enzymes activity, muscle glucose uptake and intestinal glucose absorption using in vitro, ex vivo and in vivo experimental models. The effects of increasing concentrations of xylitol (2.5%-40% or 164.31 mM-2628.99 mM) on alpha amylase and alpha glucosidase activity in vitro and intestinal glucose absorption and muscle glucose uptake were investigated under ex vivo conditions. Additionally, the effects of an oral bolus dose of xylitol (1 g per kg BW) on gastric emptying and intestinal glucose absorption and digesta transit in the different segments of the intestinal tract were investigated in normal and type 2 diabetic rats at 1 hour after dose administration, when phenol red was used as a recovery marker. Xylitol exhibited concentration-dependent inhibition of alpha amylase (IC₅₀ = 1364.04 mM) and alpha glucosidase (IC₅₀ = 1127.52 mM) activity in vitro and small intestinal glucose absorption under ex vivo condition. Xylitol also increased dose dependent muscle glucose uptake with and without insulin, although the uptake was not significantly affected by the addition of insulin. Oral single bolus dose of xylitol significantly delayed gastric emptying, inhibited intestinal glucose absorption but increased the intestinal digesta transit rate in both normal and diabetic rats compared to their respective controls. The data of this study suggest that xylitol reduces intestinal glucose absorption via inhibiting major carbohydrate digesting enzymes, slowing gastric emptying and fastening the intestinal transit rate, but increases muscle glucose uptake in normal and type 2 diabetic rats.

  20. [Study on removing the lamp spectrum structure in differential optical absorption spectroscopy].

    PubMed

    Qu, Xiao-ying; Li, Yu-jin

    2010-11-01

    Differential optical absorption spectroscopy (DOAS) technique has been used to measure trace gases in the atmosphere by their strongly structured absorption of radiation in the UV and visible spectral range, and nowadays this technique has been widely utilized to measure trace polluted gases in the atmosphere e.g. SO2, NO2, O3, HCHO, etc. However, there exists lamp (xenon lamp or deuteriumlamp) spectrum structure in the measured band (300-700 nm) of the absorption spectra of atmosphere, which badly impacts on precision of retrieving the concentration of trace gases in the atmosphere. People home and abroad generally employ two ways to handle this problem, one is segmenting band retrieving method, another is remedial retrieving method. In the present paper, a new retrieving method to deal with this trouble is introduced. The authors used moving-window average smoothing method to obtain the slow part of the absorption spectra of atmosphere, then achieved the lamp (xenon lamp in the paper) spectrum structure in the measured band of the absorption spectra of atmosphere. The authors analyzed and retrieved the measured spectrum of the atmosphere, and the result is better than the forenamed ways. Chi-square of residuum is 2.995 x 10(-4), and this method was proved to be able to avoid shortcoming of choosing narrowband and disadvantage of discovering the new component of atmosphere in retrieving the concentration of air pollutants and measuring the air pollutants.

  1. Studying the complex absorption profiles of Si IV in 21 HiBALQSO spectra

    NASA Astrophysics Data System (ADS)

    Stathopoulos, D.; Danezis, E.; Lyratzi, E.; Antoniou, A.; Popović, L. Č.; Tzimeas, D.; Dimitrijević, M. S.

    2014-12-01

    We investigate the physical conditions and kinematics of broad absorption line region clouds of Si IV in 21 HiBAL Quasars. We use the Danezis et al. method [1], [2], [3] in order to fit and analyze the broad absorption troughs of Si IV resonance lines in the UV region of the electromagnetic spectrum. We find that the BAL flow is not smooth but instead plasma clouds are formed in it. BAL troughs present multicomponent structure which indicates the existence of more than one absorbing cloud in the line of sight, where every absorbing cloud produces a Si IV doublet. We show that the blending of these doublets produces the apparent broad absorption troughs we observe. One of our main achievements is that we managed to decompose and deblend each complex absorption trough to the individual doublets that it consists of. Apart from that, we succeeded in deblending the resonance lines of every doublet. By achieving accurate fits to the BAL troughs we calculated some physical and kinematical parameters that describe the plasma clouds in the line of sight. These parameters are: the radial outflow velocities of the clouds, the random velocities of ions inside each plasma cloud, the apparent optical depth in the center of every absorption component, the FWHM and the equivalent width. As a final step we correlate these physical parameters in order to draw useful conclusions.

  2. Kondo screening and beyond: An x-ray absorption and dichroism study of CePt5/Pt(111 )

    NASA Astrophysics Data System (ADS)

    Praetorius, C.; Fauth, K.

    2017-03-01

    We use x-ray absorption spectroscopy as well as its linear and circular magnetic dichroisms to characterize relevant interactions and energy scales in the surface intermetallic CePt5/Pt(111 ). The experiments provide insight into crystal field splitting, effective paramagnetic moments, their Kondo screening and mutual interactions, and thus into many aspects which typically determine the low-temperature behavior of correlated rare-earth compounds. Exploiting the tunability of Ce valence through the thickness-dependent epitaxial strain at the CePt5/Pt(111 ) interface, we are able to systematically investigate the impact of hybridization strength on these interactions. Considerable Kondo screening is indeed observed at all CePt5 thicknesses, and found to be strongest in case of strongest hybridization. While the magnetic response is commensurate with an impurity Kondo scale of TK≳102 K for specimen temperatures T ≳30 K, this is no longer the case at lower temperature. Its detailed study by x-ray circular magnetic dichroism (XMCD) at one specific thickness of CePt5 reveals an anomaly of the susceptibility at T*≈25 K instead, which we tentatively associate with the onset of lattice coherence. At lowest temperature we observe paramagnetic saturation with a small Ce 4 f saturation magnetization. Within the framework of itinerant 4 f electrons, saturation is due to a field-induced Lifshitz transition involving a very heavy band with correspondingly small degeneracy temperature of TF≈7 K. This small energy scale results in the persistence of Curie-Weiss behavior across the entire range of experimentally accessible temperatures (T ≳2 K). Our work highlights the potential of magnetic circular dichroism studies in particular for Kondo and heavy-fermion materials, which so far has remained largely unexplored.

  3. NuSTAR reveals an intrinsically X-ray weak broad absorption line quasar in the ultraluminous infrared galaxy Markarian 231

    SciTech Connect

    Teng, Stacy H.; Rigby, J. R.; Brandt, W. N.; Luo, B.; Harrison, F. A.; Grefenstette, B. W.; Madsen, K. K.; Alexander, D. M.; Gandhi, P.; Bauer, F. E.; Boggs, S. E.; Craig, W. W.; Christensen, F. E.; Comastri, A.; Fabian, A. C.; Farrah, D.; Fiore, F.; Hailey, C. J.; Hickox, R. C.; Ptak, A. F.; and others

    2014-04-10

    We present high-energy (3-30 keV) NuSTAR observations of the nearest quasar, the ultraluminous infrared galaxy (ULIRG) Markarian 231 (Mrk 231), supplemented with new and simultaneous low-energy (0.5-8 keV) data from Chandra. The source was detected, though at much fainter levels than previously reported, likely due to contamination in the large apertures of previous non-focusing hard X-ray telescopes. The full band (0.5-30 keV) X-ray spectrum suggests the active galactic nucleus (AGN) in Mrk 231 is absorbed by a patchy and Compton-thin (N{sub H}∼1.2{sub −0.3}{sup +0.3}×10{sup 23} cm{sup –2}) column. The intrinsic X-ray luminosity (L {sub 0.5–30} {sub keV} ∼ 1.0 × 10{sup 43} erg s{sup –1}) is extremely weak relative to the bolometric luminosity where the 2-10 keV to bolometric luminosity ratio is ∼0.03% compared to the typical values of 2%-15%. Additionally, Mrk 231 has a low X-ray-to-optical power law slope (α{sub OX} ∼ –1.7). It is a local example of a low-ionization broad absorption line quasar that is intrinsically X-ray weak. The weak ionizing continuum may explain the lack of mid-infrared [O IV], [Ne V], and [Ne VI] fine-structure emission lines which are present in sources with otherwise similar AGN properties. We argue that the intrinsic X-ray weakness may be a result of the super-Eddington accretion occurring in the nucleus of this ULIRG, and may also be naturally related to the powerful wind event seen in Mrk 231, a merger remnant escaping from its dusty cocoon.

  4. Study on Coloration Mechanism of Chinese Ancient Ceramics by X-ray Absorption Near-edge Structure

    NASA Astrophysics Data System (ADS)

    Peng, Y. H.; Xie, Z.; He, J. F.; Liu, Q. H.; Pan, Z. Y.; Cheng, W. R.; Wei, S. Q.

    2013-04-01

    The Fe K-edge X-ray absorption near-edge structure (XANES) spectra of a series of ceramic shards were measured by fluorescence mode to reveal the color-generating techniques of Chinese porcelain. The analysis disclosed relationships among the chemical form of the iron, the firing conditions and the colors of the ceramics. The results indicate that the coloration for different ceramics depend on the valence states of iron as the main color element in glaze and the proportion of Fe2+ and Fe3+ was attributed to the baking technology. The findings provide important information for archaeologist on the coloration researches.

  5. Absorption spectroscopic study of synergistic extraction of praseodymium with benzoyl acetone in presence of crown ether.

    PubMed

    Banerjee, Shrabanti; Bhattacharya, Sumanta; Basu, Sukalyan

    2005-04-01

    The extraction behaviour of Pr(III) from aqueous nitric acid medium employing benzoylacetone has been studied in presence of two crown ethers, viz., 15-crown-5 and benzo-15-crown-5 in chloroform medium using UV-vis absorption spectroscopy. The binary equilibrium constant (logk(ex)) for the complex [Pr(benzoylacetonate)(NO3(-))2(H(2)O)] in organic phase was found to be 1.170. The overall equilibrium constants (logK) for the ternary species [Pr(benzoylacetonate)(crown ether)(NO3(-))(2)] were estimated to be 4.01 and 4.41 for 15-crown-5 and benzo-15-crown-5, respectively. The trend in the equilibrium constant values were very much in accordance with the nature of substitution of the donor moiety. The extraction of Pr(III) by the benzoylacetone-crown ether combination was maximum at pH 3.0 and extraction decreases with increase in pH. It has been found that the extent of extraction of Pr(III) in organic phase as the binary as well as ternary complex [Pr(benzoylacetonate)(NO3(-))(2)(H(2)O)] and [Pr(benzoylacetonate)(crown ether)(NO3(-))(2)] increases with increase in concentration of the ligand. Similar trend is observed in the extraction by only donors. Enthalpies and entropies of formation for the ternary extraction process have been estimated. In addition, the effect of NaNO(3) as foreign salt was also studied and it was observed that with increase in ionic strength, percentage extraction increases.

  6. A simulation study on the abatement of CO2 emissions by de-absorption with monoethanolamine.

    PubMed

    Greer, T; Bedelbayev, A; Igreja, J M; Gomes, J F; Lie, B

    2010-01-01

    Because of the adverse effect of CO2 from fossil fuel combustion on the earth's ecosystems, the most cost-effective method for CO2 capture is an important area of research. The predominant process for CO2 capture currently employed by industry is chemical absorption in amine solutions. A dynamic model for the de-absorption process was developed with monoethanolamine (MEA) solution. Henry's law was used for modelling the vapour phase equilibrium of the CO2, and fugacity ratios calculated by the Peng-Robinson equation of state (EOS) were used for H2O, MEA, N2 and O2. Chemical reactions between CO2 and MEA were included in the model along with the enhancement factor for chemical absorption. Liquid and vapour energy balances were developed to calculate the liquid and vapour temperature, respectively.

  7. Electronic structure of warm dense copper studied by ultrafast x-ray absorption spectroscopy.

    PubMed

    Cho, B I; Engelhorn, K; Correa, A A; Ogitsu, T; Weber, C P; Lee, H J; Feng, J; Ni, P A; Ping, Y; Nelson, A J; Prendergast, D; Lee, R W; Falcone, R W; Heimann, P A

    2011-04-22

    We use time-resolved x-ray absorption spectroscopy to investigate the unoccupied electronic density of states of warm dense copper that is produced isochorically through the absorption of an ultrafast optical pulse. The temperature of the superheated electron-hole plasma, which ranges from 4000 to 10 000 K, was determined by comparing the measured x-ray absorption spectrum with a simulation. The electronic structure of warm dense copper is adequately described with the high temperature electronic density of state calculated by the density functional theory. The dynamics of the electron temperature is consistent with a two-temperature model, while a temperature-dependent electron-phonon coupling parameter is necessary.

  8. Supramolecular complex coupled to a metal nanoparticle: computational studies on the optical absorption.

    PubMed

    Zelinskyy, Yaroslav; Zhang, Yuan; May, Volkhard

    2012-11-26

    Absorption spectra of a supramolecular complex (SC) placed in the proximity of a spherical metal nanoparticle (MNP) are computed. A description of the absorption is used that is based on a density matrix propagation. The applied density matrix theory starts from a microscopic model including the Coulomb interaction between the SC and the MNP. This interaction is dominated by an energy exchange coupling between the excitations of the SC and the multipolar excitations of the MNP. Its nonperturbative consideration results in a shift and a broadening of all Frenkel-exciton levels as well as an oscillator strength change. If a J-aggregate type SC near a MNP is considered, all exciton levels strongly contribute to the absorption what is in contrast to the isolated SC.

  9. A feasibility study on oxidation state of arsenic in cut tobacco, mainstream cigarette smoke and cigarette ash by X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, C.; Hu, J.; McAdam, K. G.

    2009-11-01

    This work describes the application of synchrotron-based X-ray Absorption Near-Edge Structure spectroscopy to study the oxidation state of arsenic in cigarette mainstream smoke, cut tobacco and cigarette ash. The level of arsenic in the total particulate matter of the smoke is approximately 1 ppm for the standard research reference cigarette 2R4F and its replacement 3R4F. Smoke particulate samples collected by a conventional glass-fiber membrane (commercially known as Cambridge filter pad) and a jet-impaction method were analyzed and compared. In addition smoke particulate samples were aged either at ambient temperature or at 195 K. X-ray Absorption Near-Edge Structure spectroscopy results revealed that the cut tobacco powder and cigarette ash contained almost exclusively As V. The smoke particulate samples however contained a mixture of As III and As V. The As V in the smoke particulate was reduced to As III upon aging. Stabilizing the smoke particulate matter at 195 K by solid CO 2 slowed down this aging reaction and revealed a higher percentage of As V. This behavior is consistent with the redox properties of the arsenic species and the smoke particulate matrix.

  10. Analysis of Intra- and Intersubject Variability in Oral Drug Absorption in Human Bioequivalence Studies of 113 Generic Products.

    PubMed

    Sugihara, Masahisa; Takeuchi, Susumu; Sugita, Masaru; Higaki, Kazutaka; Kataoka, Makoto; Yamashita, Shinji

    2015-12-07

    In this study, the data of 113 human bioequivalence (BE) studies of immediate release (IR) formulations of 74 active pharmaceutical ingredients (APIs) conducted at Sawai Pharmaceutical Co., Ltd., was analyzed to understand the factors affecting intra- and intersubject variabilities in oral drug absorption. The ANOVA CV (%) calculated from area under the time-concentration curve (AUC) in each BE study was used as an index of intrasubject variability (Vintra), and the relative standard deviation (%) in AUC was used as that of intersubject variability (Vinter). Although no significant correlation was observed between Vintra and Vinter of all drugs, Vintra of class 3 drugs was found to increase in association with a decrease in drug permeability (P(eff)). Since the absorption of class 3 drugs was rate-limited by the permeability, it was suggested that, for such drugs, the low P(eff) might be a risk factor to cause a large intrasubject variability. To consider the impact of poor water solubility on the variability in BE study, a parameter of P(eff)/Do (Do; dose number) was defined to discriminate the solubility-limited and dissolution-rate-limited absorption of class 2 drugs. It was found that the class 2 drugs with a solubility-limited absorption (P(eff)/Do < 0.149 × 10(-4) cm/s) showed high intrasubject variability. Furthermore, as a reason for high intra- or intersubject variability in AUC for class 1 drugs, effects of drug metabolizing enzymes were investigated. It was demonstrated that intrasubject variability was high for drugs metabolized by CYP3A4 while intersubject variability was high for drugs metabolized by CYP2D6. For CYP3A4 substrate drugs, the Km value showed the significant relation with Vintra, indicating that the affinity to the enzyme can be a parameter to predict the risk of high intrasubject variability. In conclusion, by analyzing the in house data of human BE study, low permeability, solubility-limited absorption, and high affinity to CYP3A4 are

  11. 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.

  12. The Study of the Effect of Solvents Absorption in PET Packaging Films

    NASA Astrophysics Data System (ADS)

    Denktaş, Cenk; Yildirim, Hüseyin

    2007-04-01

    The effects of absorption solvents into poly(ethylene terephtalete) (PET) films, which are used as food packaging materials, was investigated by DSC, SEM and mechanical methods at various temperatures (5, 25 and 40 °C) and for different periods (1-8 weeks), respectively. Due to the interaction of PET films with solvents, there had been serious deformation on the surface morphology of PET films. Plasticizer effects occurrence, because of absorption of solvents, caused weakening of mechanical properties of PET films. As a result, there had been a 42.88 % and 39.20 % decrease in stress at break at 5 °C for 8 weeks, respectively.

  13. Effect of dietary fiber on absorption of B-6 vitamers in a rat jejunal perfusion study.

    PubMed

    Nguyen, L B; Gregory, J F; Cerda, J J

    1983-09-01

    Previous research has indicated that dietary fiber may affect the absorption and utilization of certain nutrients. To determine the effect of certain fiber materials on the absorption of B-6 vitamers, jejunal segments from young male adult rats were perfused in situ with a control solution containing 0.02 mM pyridoxine (PN), 0.02 mM pyridoxal (PL), and 0.02 mM pyridoxamine (PM), followed by a test solution containing the same vitamin B-6 mixture and one of five fiber-rich test materials (cellulose, pectin, lignin, homogenized fresh carrot, or carrot homogenized after 10 min boiling) added at a concentration of 1-3%. The mean absorption rates of PL, PN, and PM from the control solution were, respectively, 3.66 +/- 0.23, 2.06 +/- 0.23, and 1.74 +/- 0.37 nmole/min/20 cm jejunal segment. There were no significant differences between the absorption rates of B-6 vitamers from control and test solutions containing cellulose, pectin, and lignin. The absorption rates of PM and PL were significantly depressed (P less than 0.05 and P less than 0.01, respectively) by the presence of fresh or cooked carrot. The absorption rate of PN in presence of cooked carrot was also decreased relative to the control value but the difference was only marginally significant (P less than 0.10). When the concentration of fresh carrot in the test solution was increased to 10% by weight and the perfusion rate was decreased from 1.91 to 0.49 ml/min in a second perfusion experiment, there was a significant increase in variability and the differences between absorption rates of the B-6 vitamers in control and test solutions were not statistically significant. The limited evidence of adverse effect of carrot on absorption of vitamin B-6 suggested the need for further clarification of the influence of dietary fiber in an unrefined state on the bioavailability of vitamin B-6.

  14. [Studies on the absorption, excretion and distribution of aclacinomycin A: absorption, excretion and distribution of aclacinomycin A in mice, rabbits and dogs by photometric assay (author's transl)].

    PubMed

    Iguchi, H; Matsushita, Y; Ohmori, K; Hirano, S; Kiyosaki, T; Hori, S; Tone, H; Oki, T

    1980-02-01

    An anthracycline antitumor antibiotic, aclacinomycin A, was given to mice, rabbits or dogs intravenously to study the pharmacokinetics by photometric assay based on the absorption of anthracycline ring. The drug was rapidly eliminated from the blood in these animals. Drug levels were much higher in the blood cells than in the plasma. Tissue levels in dogs were 50 approximately 100 times higher than the blood levels, which showed the drug was rapidly transferred from the blood to tissues after administration. Higher levels were observed in the lungs, spleen and lymph nodes, where the drug was present as aclacinomycin A itself and the glycoside-type metabolites that were biologically active. The active form was also detected in the pancreas, heart, thymus, bone marrow and gastrointestinal tract. In the liver and kidneys, biologically inactive aglycone-type metabolites were observed. About 2 approximately 4% of the drug given to rabbits or dogs was recovered in the urine by 72 hours after administration, in which only 10% of the excreted drug was active form in rabbits but about 65% in dogs. The rest was inactive aglycone-type metabolites that were excreted almost in the conjugated form. Biliary excretion also contributed to the total clearance of the drug. Aclacinomycin A was absorbed even by oral administration in rabbits and dogs. Tissue distribution of the drug orally given to dogs was similar to that in intravenous administration, except that higher levels of active form were detected in the gastrointestinal tract and of inactive form in the liver.

  15. A X-Ray Absorption Study on Melting, Double Electron Excitation and Hemerythrin.

    NASA Astrophysics Data System (ADS)

    Zhang, Ke.

    In this study, X-ray absorption spectroscopy is applied to three systems: xenon atoms; an oxygen transport protein--hemerythrin; and mercury impurities in lead metal. An X-ray absorption experiment on xenon gas shows a clear evidence of the electron shaking up (off) from the valence shells when an L-shell electron is excited. A (DELTA)SCF (self consistent field) calculation in the dipole approximation was performed, which used a local exchange potential and the sudden approximation. The calculation shows that the (DELTA)SCF model is qualitatively and semi -quantitatively correct. The lowest lying shake up channel was found to be more than 70 percent of the total double excitation strength. The model was also used to investigate the many-body effect in the EXAFS. Various forms of hemerythrin (Hr) and their model compounds have been measured by EXAFS. The data analysis shows that the oxy-form of Hr is similar to the met-forms. On release of O(,2) in oxy-Hr, the (mu)-oxo bridge with Fe -O distance of 1.8 (ANGSTROM) is converted to a (mu)-OH bridge of 2.0 (ANGSTROM) and the iron-iron distance is changed from 3.24 (ANGSTROM) to 3.50 (ANGSTROM). Accompanying this change is a large increase in vibrational amplitude around the active site. The entropy increase associated with this vibrational change contributes most of the entropy change driving the transition. A new error analysis procedure is introduced to estimate the fitting errors introduced by modeling the unknown with the standards. It is found that the dominant part of the errors was introduced by the modeling itself, namely, the standards used are not quite transferable with the unknowns. The EXAFS on the samples of Hg impurities in Pb and pure Pb have been measured in the temperature range from 10 K to right below the melting temperatures. The measurement focuses on the local structure of both lead and mercury atoms, which is an advantage provided by the technique. The Debye-Waller factor (DWF) change exhibits

  16. Feasibility study of mid-infrared absorption spectroscopy using electrospray ionization

    NASA Astrophysics Data System (ADS)

    Ahmed, Tahsin; Foster, Erick; Bohn, Paul; Howard, Scott

    2016-09-01

    Precise detection of trace amount of molecules, such as the disease biomarkers present in biofluids or explosive residues, requires high sensitivity detection. electrospray ionization-mass spectrometry (ESI-MS) is a common and effective technique for sensitive trace molecular detection in small-volume liquid samples. In ESI-MS, nano-liter volume samples are ionized and aerosolized by ESI, and fed into MS for mass analysis. ESI-MS has proven to be a reliable ionization technique for coupling liquid phase separations like liquid chromatography (LC) and capillary zone electrophoresis (CE) with the highly specific resolving power of MS. While CE and ESI can be performed on a microfluidic chip having a footprint of a few cm2, MS is typically at least 100 times bigger in size than a micro-chip. A reduced size, weight, and power profile would enable semi-portable applications in forensics, environmental monitoring, defense, and biological/pharmaceutical applications. To achieve this goal, we present an initial study evaluating the use of mid-infrared absorption spectroscopy (MIRAS) in place of MS to create a ESI-MIRAS system. To establish feasibility, we perform ESI-MIRAS on phospholipid samples, which have been previously demonstrated to be separable by CE. Phospholipids are biomarkers of degenerative neurological, kidney, and bone diseases and can be found in biofluids such as blood, urine and cerebrospinal fluid. To establish sensitivity limits, calibration samples of 100 μM concentration are electrospray deposited on to a grounded Si wafer for different times (1 minutes to 4 minutes with a 1 minute step). The minimum detectable concentration-time product, where a FTIR globar is used as the MIR source, is found 200 μM·s.

  17. X-ray absorption and electrochemical studies of direct methanol fuel cell catalysts

    SciTech Connect

    Zurawski, D.J.; Aldykiewicz, A.J. Jr.; Baxter, S.F.; Krumpelt, M.

    1996-12-31

    In order for polymer electrolyte fuel cells to operate directly on methanol instead of hydrogen, a distinct advantage for portable applications, methanol oxidation must be catalyzed effectively in the acidic environment of the cell. Platinum-ruthenium and platinum-ruthenium oxide are generally considered to be the most active catalysts for this purpose. The presence of ruthenium significantly enhances the activity of platinum in these catalysts, for reasons not yet fully understood. We are using X-ray absorption spectroscopy (XAS) and electrochemical techniques to evaluate the mechanisms proposed to account for this enhancement in order to further improve the catalyst`s activity. We are considering three enhancement mechanisms. An intermediate in the oxidation of methanol on platinum is carbon monoxide and its oxidation is the rate-determining step in the overall oxidation mechanism. It has been proposed that ruthenium facilitates the removal of carbon monoxide from the platinum surface. First, it has been proposed that ruthenium decreases the strength of the platinum-carbon monoxide bond. Carbon monoxide bonds to the catalyst by interacting with the d-band of platinum, therefore a change in the d-band occupancy of platinum as a result of alloying may influence the bond strength of carbon monoxide. Another proposed enhancement mechanism involves lowering of the potential for the formation of the CO-oxidizing species. Finally, the binary catalysts may have a structure which is more conducive to the methanol dehydrogenation and carbon monoxide reactions. Based on these three proposed enhancement mechanisms, a goal of this study is to correlate catalyst electronic properties, structure, and oxidation state with the performance of proton-exchange membrane (Nafion) direct methanol fuel cells.

  18. Single crystal EPR, optical absorption and superposition model study of Cr 3+ doped ammonium dihydrogen phosphate

    NASA Astrophysics Data System (ADS)

    Kripal, Ram; Pandey, Sangita

    2010-06-01

    The electron paramagnetic resonance (EPR) studies are carried out on Cr 3+ ion doped ammonium dihydrogen phosphate (ADP) single crystals at room temperature. Four magnetically inequivalent sites for chromium are observed. No hyperfine structure is obtained. The crystal-field and spin Hamiltonian parameters are calculated from the resonance lines obtained at different angular rotations. The zero field and spin Hamiltonian parameters of Cr 3+ ion in ADP are calculated as: | D| = (257 ± 2) × 10 -4 cm -1, | E| = (79 ± 2) × 10 -4 cm -1, g = 1.9724 ± 0.0002 for site I; | D| = (257 ± 2) × 10 -4 cm -1, | E| = (77 ± 2) × 10 -4 cm -1, g = 1.9727 ± 0.0002 for site II; | D| = (259 ± 2) × 10 -4 cm -1, | E| = (78 ± 2) × 10 -4 cm -1, g = 1.9733 ± 0.0002 for site III; | D| = (259 ± 2) × 10 -4 cm -1, | E| = (77 ± 2) × 10 -4 cm -1, g = 1.973 ± 0.0002 for site IV, respectively. The site symmetry of Cr 3+ doped single crystal is discussed on the basis of EPR data. The Cr 3+ ion enters the lattice substitutionally replacing the NH 4+ sites. The optical absorption spectra are recorded in 195-925 nm wavelength range at room temperature. The energy values of different orbital levels are determined. On the basis of EPR and optical data, the nature of bonding in the crystal is discussed. The calculated values of Racah interelectronic repulsion parameters ( B and C), cubic crystal-field splitting parameter ( Dq) and nephelauxetic parameters ( h and k) are: B = 640, C = 3070, Dq = 2067 cm -1, h = 1.44 and k = 0.21, respectively. ZFS parameters are also determined using Bkq parameters from superposition model.

  19. Determination and interference studies of bismuth by tungsten trap hydride generation atomic absorption spectrometry.

    PubMed

    Kula, Ibrahim; Arslan, Yasin; Bakirdere, Sezgin; Titretir, Serap; Kendüzler, Erdal; Ataman, O Yavuz

    2009-11-15

    The determination of bismuth requires sufficiently sensitive procedures for detection at the microg L(-1) level or lower. W-coil was used for on-line trapping of volatile bismuth species using HGAAS (hydride generation atomic absorption spectrometry); atom trapping using a W-coil consists of three steps. Initially BiH(3) gas is formed by hydride generation procedure. The analyte species in vapor form are transported through the W-coil trap held at 289 degrees C where trapping takes place. Following the preconcentration step, the W-coil is heated to 1348 degrees C; analyte species are released and transported to flame-heated quartz atom cell where the atomic signal is formed. In our study, interferences have been investigated in detail during Bi determination by hydride generation, both with and without trap in the same HGAAS system. Interferent/analyte (mass/mass) ratio was kept at 1, 10 and 100. Experiments were designed for carrier solutions having 1.0M HNO(3). Interferents such as Fe, Mn, Zn, Ni, Cu, As, Se, Cd, Pb, Au, Na, Mg, Ca, chloride, sulfate and phosphate were examined. The calibration plot for an 8.0 mL sampling volume was linear between 0.10 microg L(-1) and 10.0 microg L(-1) of Bi. The detection limit (3s/m) was 25 ng L(-1). The enhancement factor for the characteristic concentration (C(o)) was found to be 21 when compared with the regular system without trap, by using peak height values. The validation of the procedure was performed by the analysis of the certified water reference material and the result was found to be in good agreement with the certified values at the 95% confidence level.

  20. Comparative Characterization Study of a LaBr3(Ce) Scintillation Crystal in Two Surface Wrapping Scenarios: Absorptive and Reflective

    PubMed Central

    Aldawood, Saad; Castelhano, Ines; Gernhäuser, Roman; Van Der Kolff, Hugh; Lang, Christian; Liprandi, Silvia; Lutter, Rudolf; Maier, Ludwig; Marinšek, Tim; Schaart, Dennis R.; Parodi, Katia; Thirolf, Peter G.

    2015-01-01

    The properties of a 50 mm × 50 mm × 30 mm monolithic LaBr3:Ce scintillator crystal coupled to a position-sensitive multi-anode photomultiplier (PMT, Hamamatsu H9500), representing the absorbing detector of a Compton camera under study for online ion (proton) beam range verification in hadron therapy, was evaluated in combination with either absorptive or reflective crystal surface coating. This study covered an assessment of the energy and position-dependent energy resolution, exhibiting a factor of 2.5–3.5 improvement for the reflectively wrapped crystal at 662 keV. The spatial dependency was investigated using a collimated 137Cs source, showing a steep degradation of the energy resolution at the edges and corners of the absorptively wrapped crystal. Furthermore, the time resolution was determined to be 273 ps (FWHM) and 536 ps (FWHM) with reflective and absorptive coating, respectively, using a 60Co source. In contrast, the light spread function (LSF) of the light amplitude distribution on the PMT segments improved for the absorptively wrapped detector. Both wrapping modalities showed almost no differences in the energy-dependent photopeak detection efficiency. PMID:26697405

  1. Assessment of an extended dataset of in vitro human dermal absorption studies on pesticides to determine default values, opportunities for read-across and influence of dilution on absorption.

    PubMed

    Aggarwal, M; Fisher, P; Hüser, A; Kluxen, F M; Parr-Dobrzanski, R; Soufi, M; Strupp, C; Wiemann, C; Billington, R

    2015-06-01

    Dermal absorption is a key parameter in non-dietary human safety assessments for agrochemicals. Conservative default values and other criteria in the EFSA guidance have substantially increased generation of product-specific in vitro data and in some cases, in vivo data. Therefore, data from 190 GLP- and OECD guideline-compliant human in vitro dermal absorption studies were published, suggesting EFSA defaults and criteria should be revised (Aggarwal et al., 2014). This follow-up article presents data from an additional 171 studies and also the combined dataset. Collectively, the data provide consistent and compelling evidence for revision of EFSA's guidance. This assessment covers 152 agrochemicals, 19 formulation types and representative ranges of spray concentrations. The analysis used EFSA's worst-case dermal absorption definition (i.e., an entire skin residue, except for surface layers of stratum corneum, is absorbed). It confirmed previously proposed default values of 6% for liquid and 2% for solid concentrates, irrespective of active substance loading, and 30% for all spray dilutions, irrespective of formulation type. For concentrates, absorption from solvent-based formulations provided reliable read-across for other formulation types, as did water-based products for solid concentrates. The combined dataset confirmed that absorption does not increase linearly beyond a 5-fold increase in dilution. Finally, despite using EFSA's worst-case definition for absorption, a rationale for routinely excluding the entire stratum corneum residue, and ideally the entire epidermal residue in in vitro studies, is presented.

  2. Low-potential iron-sulfur centers in photosystem I: an X-ray absorption spectroscopy study.

    PubMed

    McDermott, A E; Yachandra, V K; Guiles, R D; Britt, R D; Dexheimer, S L; Sauer, K; Klein, M P

    1988-05-31

    We have measured the X-ray absorption spectra of Fe in photosystem I (PS I) preparations from spinach and a thermophilic cyanobacterium, Synechococcus sp., to characterize structures of the Fe complexes that function as electron acceptors in PS I. These acceptors include centers A and B, which are probably typical [4Fe-4S] ferredoxins, and X. The structure of X is not known, but its electron paramagnetic resonance (EPR) spectrum has generated the suggestions that it is either a [2Fe-2S] or [4Fe-4S] ferredoxin or an Fe-quinone species. The iron X-ray absorption K-edge and iron extended X-ray absorption fine structure (EXAFS) spectra reveal that essentially all of the 11-14 Fe atoms present in the reaction center are present in the form of Fe-S centers and that not more than 1 atom out of 12 could be octahedral or oxygen-coordinated Fe. This suggests that, besides A and B, additional Fe-S clusters are present which are likely to be X. Our EXAFS spectra cannot be simulated adequately by a mixture of [4Fe-4S] ferredoxins with typical bond lengths and disorder parameters because the amplitude of Fe backscattering is small; however, excellent simulations of the data are consistent with a mixture of [2Fe-2S] ferredoxins and [4Fe-4S] ferredoxins, or with unusually distorted [4Fe-4S] clusters. We presume that the [2Fe-2S] or distorted [4Fe-4S] centers are X. The X-ray absorption spectra of PS I preparations from Synechococcus and spinach are essentially indistinguishable.

  3. Experimental study of negative temperatures in lithium-bromide absorption refrigerating machines

    NASA Astrophysics Data System (ADS)

    Stepanov, K. I.; Mukhin, D. G.; Alekseenko, S. V.; Volkova, O. V.

    2015-07-01

    The authors have developed a method and presented experimental data for obtaining negative temperatures of evaporation in lithium-bromide absorption chillers driven by heat recovery. It has been found that the attainable temperature of the refrigerated medium is the value of -5 °C.

  4. 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.

  5. [CPFA (coupled plasma filtration absorption) treatment of septic shock. A retrospective study of nine patients].

    PubMed

    Maruccio, Gianfranco; Montanaro, Alessio; Schiavone, Palmira; Fumarola, Martino; Flores, Antonio; Strippoli, Paolo; Caretto, Vincenzo; Paladini, Daniele; Ramunni, Alfonso

    2012-01-01

    Coupled plasma filtration absorption (CPFA) can increase blood pressure in septic shock and reduce fever during and after treatment. It is not able to stop the activation of intravascular coagulation and does not reduce the need for dialysis or the overall mortality.

  6. Predisposition for Nightmares: A Study of Hypnotic Ability, Vividness of Imagery, and Absorption.

    ERIC Educational Resources Information Center

    Belicki, Kathryn; Belicki, Denis

    1986-01-01

    Examined relationships of nightmare frequency to hypnotic ability, vividness of visual imagery, and the tendency to become absorbed in fantasy-like experiences. Use of Mark's Vividness of Visual Imagery Questionnaire, and Rotenberg and Bowers' Absorption scale showed individuals with frequent nightmares to score higher on hypnotizability,…

  7. A multivariant study of the absorption properties of poly(glutaric-acid-glycerol) films

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The solvent absorption into the matrix of poly(glutaric acid-glycerol) films made with or without either iminodiacetic acid, sugarcane bagasse, pectin, corn fiber gum or microcrystalline cellulose have been evaluated. The films were incubated in various solvent systems for 24h. The amounts of solve...

  8. Bilirubin calculi crushing by laser irradiation at a molecular oscillating region wavelength based on infrared absorption spectrum analysis using a free-electron laser: an experimental study.

    PubMed

    Watanabe, M; Kajiwara, H; Awazu, K; Aizawa, K

    2001-01-01

    We investigated a new laser technique of crushing bilirubin calculi, our aim being to crush calculi in isolation using a minimally invasive procedure. Infrared absorption spectrum analysis of the bilirubin calculi was conducted, revealing maximum absorption spectrum at a wavelength of the C=O stretching vibration of ester binding that exists within the molecular structure of bilirubin calcium. As an experiment to crush calculi using the free-electron laser, we set the laser at the effective irradiation wavelength of ester binding, and conducted noncontact irradiation of the bilirubin calculi. The calculi began to slowly ablate until the irradiated site had been completely obliterated after 20s of irradiation. Moreover, absorption spectrum analysis of the irradiated site, from a comparison of absorption peak ratios, revealed that absorption peak intensities decreased over time at the absorption wavelength of ester binding. These findings suggest that irradiation of molecular oscillating region wavelengths peculiar to calculi based on infrared absorption spectrum analysis results in the gradual crushing of calculi in isolation by breaking down their molecular structure.

  9. [Rat intestine absorption kinetics study on cucurbitacin B-sodium deoxycholate/phospholipid mixed nanomicelles with in vitro everted gut sacs model].

    PubMed

    Cheng, Ling; Shen, Bao-de; Li, Juan-juan; Qiu, Ling; Shen, Gang; Zhang, Li-hong; Han, Jin; Yuan, Hai-long

    2015-07-01

    To investigate the absorption kinetics of Cu B-SDC/PLC-MMs in rat different intestinal segments and compared with the absorption of Cu B suspension. The in vitro everted gut sacs model was established to study the absorption characteristics of Cu B-SDC/ PLC-MMs in rat duodenum, jejunum, ileum and colon, and the content of cucurbitacin B was detected by HPLC method, and the effects of concentrations on intestinal absorption were evaluated as well. The results showed that the absorption of Cu B-SDC/PLC-MMs was linearity at different intestine segment and different concentrations (R2 > 0.9), which was consistent with zero order rate process. The Ka of different intestine segments showed a concentration-dependent increasing along with the raised concentration of Cu B-SDC/ PLC-MMs, indicating that it was likely to be a mechanism of passive absorption. The best absorption site of Cu B-SDC/PLC-MMs was ileum, and its absorptions in different intestinal segments were superior to cucurbitacin B suspension. SDC/PLC-MMs could significantly enhance the intestinal absorption of cucurbitacin B, and the study of intestinal absorption kinetics of Cu B-SDC/PLC-MMs had gave a support to its further reasonable solidfication.

  10. Fast exhaust channel optical absorption method and apparatus to study the gas exchange in large diesel engines

    NASA Astrophysics Data System (ADS)

    Vattulainen, J.; Hernberg, R.; Hattar, C.; Gros, S.

    1998-01-01

    An optical absorption spectroscopic method and apparatus with shorter than 1 ms response time have been used to study the gas exchange processes in realistic conditions for a single cylinder of a large diesel engine. The method is based on measuring the differential line-of-sight optical uv absorption of the exhaust-gas-contained SO2 as a function of time in the exhaust port area just after the exhaust valves. The optical absorption by SO2 is determined from light transmission measurements at 280 and 340 nm performed through optical probes installed into the exhaust channel wall. The method has been applied to a continuously fired, large, medium speed production-line-type diesel engine with 990 kW rated power. The test engine was operated with standard light fuel oil (MDO Termoshell) and with light fuel oil treated with a sulfur additive {Di-Tert-Butyldisulfid [(CH3)3C]2S2}. The latter was to improve the optical absorption signals without increasing the fouling of the exhaust channel optical probes as in the case of heavier fuel oil qualities. In the reported case of a four-stroke diesel engine measurement results show that the method can provide time-resolved information of the SO2 density in the exhaust channel and thus give information on the single-cylinder gas exchange. During the inlet and exhaust valve overlap period the moment of fresh air entering into the measurement volume can be detected. If independent exhaust gas temperature and pressure data are available, the absorption measurements can readily be used for determining the burnt gas fraction in the exhaust channel. In this work the possibility of using the optical absorption measurement to determine the instaneous exhaust gas temperature was studied. Based on known fuel properties and conventional averaged SO2 measurements from the exhaust channel a known concentration of SO2 was assumed in the exhaust gas after the exhaust valves opening and before the inlet and exhaust valves overlap period

  11. Small-scale studies of roasted ore waste reveal extreme ranges of stable mercury isotope signatures

    NASA Astrophysics Data System (ADS)

    Smith, Robin S.; Wiederhold, Jan G.; Jew, Adam D.; Brown, Gordon E.; Bourdon, Bernard; Kretzschmar, Ruben

    2014-07-01

    Active and closed Hg mines are significant sources of Hg contamination to the environment, mainly due to large volumes of mine waste material disposed of on-site. The application of Hg isotopes as source tracer from such contaminated sites requires knowledge of the Hg isotope signatures of different materials potentially released to the environment. Previous work has shown that calcine, the waste residue of the on-site ore roasting process, can exhibit distinct Hg isotope signatures compared with the primary ore. Here, we report results from a detailed small-scale study of Hg isotope variations in calcine collected from the closed New Idria Hg mine, San Benito County, CA, USA. The calcine samples exhibited different internal layering features which were investigated using optical microscopy, micro X-ray fluorescence, micro X-ray absorption spectroscopy (μ-XAS), and stable Hg isotope analysis. Significant Fe, S, and Hg concentration gradients were found across the different internal layers. Isotopic analyses revealed an extreme variation with pronounced isotopic gradients across the internal layered features. Overall, δ202Hg (±0.10‰, 2 SD) describing mass-dependent fractionation (MDF) ranged from -5.96 to 14.49‰, which is by far the largest range of δ202Hg values reported for any environmental sample. In addition, Δ199Hg (±0.06‰, 2 SD) describing mass-independent fractionation (MIF) ranged from -0.17 to 0.21‰. The μ-XAS analyses suggested that cinnabar and metacinnabar are the dominant Hg-bearing phases in the calcine. Our results demonstrate that the incomplete roasting of HgS ores in Hg mines can cause extreme mass-dependent Hg isotope fractionations at the scale of individual calcine pieces with enrichments in both light and heavy Hg isotopes relative to the primary ore signatures. This finding has important implications for the application of Hg isotopes as potential source tracers for Hg released to the environment from closed Hg mines and

  12. Absorption-improving effects of chitosan oligomers based on their mucoadhesive properties: a comparative study on the oral and pulmonary delivery of calcitonin.

    PubMed

    Zhang, Hailong; Huang, Xiaoyan; Sun, Ya; Xing, Jianfeng; Yamamoto, Akira; Gao, Yang

    2016-09-01

    Effects of chitosan oligomers with different types and varying concentrations on the intestinal and pulmonary absorptions of calcitonin were investigated in rats by an in situ closed loop method and an in vivo pulmonary absorption experiment, respectively. Various chitosan oligomers demonstrated different efficiencies in improving the intestinal and pulmonary absorptions of calcitonin, and chitosan hexamer with the optimal concentration of 0.5% (w/v) showed the greatest absorption enhancing effect. Moreover, pharmacodynamic parameters of calcitonin after its coadministration intrapulmonarily with various chitosan oligomers were consistently larger than that in the intestinal delivery, indicating the superior potential of pulmonary administration for systemic delivery of calcitonin. Furthermore, various chitosan oligomers neither obviously increased release amounts of protein nor activities of lactate dehydrogenase (LDH) in bronchoalveolar lavage fluid (BALF), revealing the safety of these chitosan oligomers to lung tissue. In addition, bioadhesions of various chitosan oligomers were well consistent with their absorption enhancing effects in the absorption experiment, suggesting the contribution of mucoadhesive properties of chitosan oligomers to their absorption improving effects. Taken together, chitosan oligomers, especially chitosan hexamer, can effectively improve the intestinal and pulmonary absorptions of calcitonin partly due to the mucoadhesion between positive chitosan oligomers and negative mucus in the membrane.

  13. Zinc Absorption Is Not Related to Dietary Phytate Intake in Infants and Young Children Based on Modeling Combined Data from Multiple Studies123

    PubMed Central

    Miller, Leland V; Hambidge, K Michael; Krebs, Nancy F

    2015-01-01

    Background: It is widely understood that the 2 primary factors affecting dietary zinc absorption in adults are the quantities of zinc and phytate in the diet. Although a similar association of absorption to dietary zinc and phytate is presumed to exist in children, to our knowledge, no large-scale examination of the relation of zinc absorption to dietary and growth factors has been conducted. Objective: The goal was to apply an adult absorption model and related models to data from zinc absorption studies of infants and children in order to determine the nature of the relation of zinc absorption to dietary zinc and phytate, age, body size, and zinc homeostatic variables. Methods: Data from 236 children between 8 and 50 mo of age were obtained from stable-isotope studies of zinc absorption. Statistical and mechanistic models were fit to the data using linear and nonlinear regression analysis. Results: The effect of dietary phytate on zinc absorption when controlling for dietary zinc was very small and not statistically discernable (P = 0.29). A 500-mg/d increase in dietary phytate reduced absorbed zinc by <0.04 mg/d. Absorption was observed to vary with age, weight, and height (P < 0.0001) when controlling for dietary zinc. For example, absorption from 6 mg/d of dietary zinc increased by as much as 0.2 mg/d with a 12-mo increase in age. Absorption varied with weight and exchangeable zinc pool size (0.01 < P < 0.05) when controlling for dietary zinc and age. Conclusions: The absence of a detectable phytate effect on zinc absorption raises caution about use of dietary phytate:zinc molar ratios to predict zinc bioavailability and does not support phytate reduction as a strategy to improve zinc status of young children. The effect of age on zinc absorption and the absence of a phytate effect should facilitate estimations of dietary zinc needs in young children. PMID:26108545

  14. A kinetic approach to the study of absorption of solutes by isolated perfused small intestine

    PubMed Central

    Fisher, R. B.; Gardner, M. L. G.

    1974-01-01

    1. A new technique has been developed for making serial measurements of water and solute absorption from the lumen of isolated small intestine. 2. The isolated intestine is perfused in a single pass with a segmented flow of slugs of liquid separated by bubbles of oxygen-carbon dioxide mixture. Simultaneous collections are made of effluent from the lumen and of the fluid which is transported across the mucosa. This latter fluid appears to be a fair sample of the tissue fluid. 3. Conditions in the lumen can be changed within less than 5 min. The effects of two or more treatments applied to the same segment of intestine can be determined and the time course of a change in luminal conditions. 4. The rate of appearance of solutes on the serosal side depends on the rate of water absorption, and changes exponentially towards a steady state. The rate constant is a function of tissue fluid volume. 5. In the steady state the concentration of glucose in the tissue fluid is 71 mM when the luminal concentration is 28 mM, and is 45 mM when the luminal concentration is 8·3 mM. 6. For solutes such as glucose for which reflux from tissue fluid to lumen is small relative to flux from lumen to tissue fluid, the time of attainment of a steady state in secretion is usually 50-60 min. 7. For solutes such as sodium for which the reflux is relatively high, the steady state may be reached in 15-20 min. 8. The Km for glucose absorption (14-19 mM) is much lower than is found with unsegmented flow perfusion. 9. These findings emphasize problems in interpreting results from other types of intestinal preparation. 10. The rate of glucose absorption from the lumen falls only gradually when the luminal sodium concentration is reduced abruptly. In contrast the rate of glucose absorption falls suddenly when the luminal glucose concentration is reduced abruptly. This suggests that glucose absorption is not directly dependent on luminal sodium ions. ImagesPlate 1 PMID:4422346

  15. Charge transport and absorption study of metal nanoparticle plasmonics for organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Xue, Mei; Zhu, Jinfeng; Shen, Huajun; Kim, Seongku; Ho, Jack J.; Qasem, Hussam Aldeen S.; Otaibi, Zaid S. Al; Wang, Kang L.; Device Research Laboratory, Ucla Team; Kacst/California Institute Of Excellence On Green Nanotechnology Team

    2011-03-01

    A hybrid plasmonic nanostructure of an optically sensitive heterojunction organic film incorporating metal nanoparticles is fabricated. From the Charge Extraction in Linearly Increasing Voltage (CELIV) measurements, the mobility of this hybrid plasmonic nanostructure has been experimentally extracted to be at least one order of the magnitude higher than that of the organic film without metal nanoparticles. The measured absorption spectrum also shows the increasing of the intensity by around 28% as well as the broadening of the spectrum. The theoretical calculation confirms this broadband optical absorption enhancement results from localized surface plasmon resonance. The optimization of the density of the metal nanoparticles has been done to achieve the best performance for the photovoltaic devices. This work is supported in part by KACST/California Institute of Excellence on Green Nanotechnology.

  16. X-ray absorption fine structure study of heavily P doped (111) and (001) diamond

    NASA Astrophysics Data System (ADS)

    Shikata, Shinichi; Yamaguchi, Koji; Fujiwara, Akihiko; Tamenori, Yusuke; Yahiro, Jumpei; Kunisu, Masahiro; Yamada, Takatoshi

    2017-02-01

    X-ray absorption fine structure (XANES) measurements were carried out for P doped (111) and (001) diamond films, and the results were compared with those from simulations. For the (111) spectrum, the main strong peak observed at 2147.0 eV and three broad peaks centered at 2150 eV, 2157 eV, and 2165 eV were observed. The assignment with the estimation by the simulation of the XANES peaks showed the interstitial sites additional to the substitutional site. The Extended X-ray Absorption Fine Structure (EXAFS) result of the P doped (111) diamond showed that the first and second neighboring peaks are observed at 1.21 A and 2.0 A, respectively. The assignment with the estimation by the simulation of the EXAFS peaks also showed the interstitial sites additional to the substitutional site. Overall, P in diamonds presumably has dopant sites in both the substitutional and interstitial sites.

  17. Absorption of lithium in montmorillonite: a density functional theory (DFT) study.

    PubMed

    Wungu, Triati Dewi Kencana; Aspera, Susan Menez; David, Melanie Yadao; Dipojono, Hermawan Kresno; Nakanishi, Hiroshi; Kasai, Hideaki

    2011-04-01

    The absorption of lithium in montmorillonite [LiSi8(Al3Mg)O20(OH)4] was investigated using Density Functional Theory (DFT). The final position of lithium after absorption was found to be in good agreement with an experimental observation where lithium atom migrated from the interlayer into the vacant octahedral site of montmorillonite. The lithium absorbed on montmorillonite was held together by a very strong attraction between ions and exhibited an insulating behavior as depicted from the density of states curve. Due to the presence of lithium in the octahedral site of montmorillonite, the OH group reoriented itself perpendicular to the ab plane and an electron of lithium was transferred in order to compensate the existing net charge of montmorillonite caused by isomorphous substitutions. Relative small charge transfer was observed between lithium and montmorillonite.

  18. Preliminary study of neutron absorption by concrete with boron carbide addition

    SciTech Connect

    Abdullah, Yusof Yusof, Mohd Reusmaazran; Zali, Nurazila Mat; Ahmad, Megat Harun Al Rashid Megat; Yazid, Hafizal; Ariffin, Fatin Nabilah Tajul; Ahmad, Sahrim; Hamid, Roszilah; Mohamed, Abdul Aziz

    2014-02-12

    Concrete has become a conventional material in construction of nuclear reactor due to its properties like safety and low cost. Boron carbide was added as additives in the concrete construction as it has a good neutron absorption property. The sample preparation for concrete was produced with different weight percent of boron carbide powder content. The neutron absorption rate of these samples was determined by using a fast neutron source of Americium-241/Be (Am-Be 241) and detection with a portable backscattering neutron detector. Concrete with 20 wt % of boron carbide shows the lowest count of neutron transmitted and this indicates the most neutrons have been absorbed by the concrete. Higher boron carbide content may affect the concrete strength and other properties.

  19. Surface-enhanced infrared absorption studies towards a new optical biosensor

    PubMed Central

    Stäb, Julia; Adam, Jennifer T; Gauglitz, Günter

    2016-01-01

    Reflectometric interference spectroscopy (RIfS), which is well-established in the visual regime, measures the optical thickness change of a sensitive layer caused, e.g., by binding an analyte. When operated in the mid-infrared range the sensor provides additional information via weak absorption spectra (fingerprints). The originally poor spectra are magnified by surface-enhanced infrared absorption (SEIRA). This is demonstrated using the broad complex fluid water band at 3300 cm−1, which is caused by superposition of symmetric, antisymmetric stretching vibration, and the first overtone of the bending vibration under the influence of H-bonds and Fermi resonance effect. The results are compared with a similar experiment performed with an ATR (attenuated total reflectance) set-up. PMID:28144523

  20. Preliminary study of neutron absorption by concrete with boron carbide addition

    NASA Astrophysics Data System (ADS)

    Abdullah, Yusof; Ariffin, Fatin Nabilah Tajul; Hamid, Roszilah; Yusof, Mohd Reusmaazran; Zali, Nurazila Mat; Ahmad, Megat Harun Al Rashid Megat; Yazid, Hafizal; Ahmad, Sahrim; Mohamed, Abdul Aziz

    2014-02-01

    Concrete has become a conventional material in construction of nuclear reactor due to its properties like safety and low cost. Boron carbide was added as additives in the concrete construction as it has a good neutron absorption property. The sample preparation for concrete was produced with different weight percent of boron carbide powder content. The neutron absorption rate of these samples was determined by using a fast neutron source of Americium-241/Be (Am-Be 241) and detection with a portable backscattering neutron detector. Concrete with 20 wt % of boron carbide shows the lowest count of neutron transmitted and this indicates the most neutrons have been absorbed by the concrete. Higher boron carbide content may affect the concrete strength and other properties.

  1. EPR and optical absorption studies of Cu{sup 2+} ions in alkaline earth alumino borate glasses

    SciTech Connect

    Ramesh Kumar, V.; Rao, J.L. . E-mail: jlrao46@yahoo.co.in; Gopal, N.O.

    2005-08-11

    Electron paramagnetic resonance (EPR) and optical absorption spectra of Cu{sup 2+} ions in alkaline earth alumino borate glasses doped with different concentrations of CuO have been studied. The EPR spectra of all the glasses exhibit the resonance signals, characteristic of Cu{sup 2+} ions present in axially elongated octahedral sites. The number of spins participating in the resonance has been calculated as a function of temperature for calcium alumino borate (CaAB) glass doped with 0.1 mol% of CuO. From the EPR data, the paramagnetic susceptibility ({chi}) was calculated at different temperatures (T) and from the 1/{chi}-T graph, the Curie temperature of the glass has been evaluated. The optical absorption spectra of all the glasses show a single broad band, which has been assigned to the {sup 2}B{sub 1g} {yields} {sup 2}B{sub 2g} transition of the Cu{sup 2+} ions. The variation in the intensity of optical absorption with the ionic radius of the alkaline earth ion has been explained based on the Coulombic forces. By correlating the EPR and optical absorption spectral data, the nature of the in-plane {sigma} bonding between Cu{sup 2+} ion and the ligands is estimated. From the fundamental ultraviolet absorption edges of the glasses, the optical energy gap (E {sub opt}) and the Urbach energy ({delta}E) are evaluated. The variation in E {sub opt} and {delta}E is explained based on the number of defect centers in the glass.

  2. Quantitative imaging of airway liquid absorption in cystic fibrosis.

    PubMed

    Locke, Landon W; Myerburg, Michael M; Markovetz, Matthew R; Parker, Robert S; Weber, Lawrence; Czachowski, Michael R; Harding, Thomas J; Brown, Stefanie L; Nero, Joseph A; Pilewski, Joseph M; Corcoran, Timothy E

    2014-09-01

    New measures are needed to rapidly assess emerging treatments for cystic fibrosis (CF) lung disease. Using an imaging approach, we evaluated the absorptive clearance of the radiolabeled small molecule probe diethylene triamine penta-acetic acid (DTPA) as an in vivo indicator of changes in airway liquid absorption. DTPA absorption and mucociliary clearance rates were measured in 21 patients with CF (12 adults and nine children) and nine adult controls using nuclear imaging. The effect of hypertonic saline on DTPA absorption was also studied. In addition, in vitro studies were conducted to identify the determinants of transepithelial DTPA absorption. CF patients had significantly increased rates of DTPA absorption compared with control subjects but had similar mucociliary clearance rates. Treatment with hypertonic saline resulted in a decrease in DTPA absorption and an increase in mucociliary clearance in 11 out of 11 adult CF patients compared with treatment with isotonic saline. In vitro studies revealed that ∼ 50% of DTPA absorption can be attributed to transepithelial fluid transport. Apically applied mucus impedes liquid and DTPA absorption. However, mucus effects become negligible in the presence of an osmotic stimulus. Functional imaging of DTPA absorption provides a quantifiable marker of immediate response to treatments that promote airway surface liquid hydration.

  3. A spectroscopic study on the absorption of carbonic anhydrase onto the nanoporous silica nanoparticle.

    PubMed

    Khameneh, Hannaneh Pourjabbari; Bolouri, Termeh Ghorbanian; Nemati, Fahimeh; Rezvani, Fatemeh; Attar, Farnoosh; Saboury, Ali Akbar; Falahati, Mojtaba

    2017-06-01

    Herein, KIT-6 nanoporous silica nanoparticles were used as a solid support for immobilization of bovine carbonic anhydrase, isoform II (BCA II). The zeta potential study revealed that KIT-6 and BCA II provided negative (-13.58±1.95mV) and positive (4.23±0.72mV) charge distribution, respectively. Dynamic light scattering (DLS) analysis also showed that the hydrodynamic radius of KIT-6 is less than 100nm. In addition, the structural studies of free and immobilized BCA II against urea-induced denaturation were investigated by circular dichroism (CD) and fluorescence spectroscopy. CD studies showed that the absorbed BCA II, in comparison with the free enzyme, demonstrated higher stability against rising urea concentration. Fluorescence spectroscopy showed lower values of Stern- Volmer constant (KSV) for immobilized BCA II relative to free enzyme, reflecting the relative enzyme stability of BCA II after immobilization. Melting temperature (Tm) measurement of free and immobilized BCA II showed that immobilized enzyme had a more stable structure (Tm=71.9°C) relative to the free counterpart (Tm=64.7°C). In addition, the immobilized BCA II showed pronounced stability against pH and thermal deactivation. This study may provide new and complementary details regarding the design and development of enzymes in industrial applications.

  4. Conformational study of the chromophore of C-phycocyanin by resonance raman and electronic absorption spectroscopy.

    NASA Astrophysics Data System (ADS)

    Margulies, L.; Toporowicz, M.

    1988-05-01

    The conformation of the chromophore of C-phycocyanin (PC) was investigated by using electronic absorption and resonance Raman spectroscopy, and theoretical calculations. Using an A-dihydrobilindione as model compound, the syn, syn, syn conformation was established for the isolated chromophore in solution. For the native PC, the best results were obtained by considering the syn, syn, anti conformation, although the possibility of having a syn, anti, anti conformation could not be excluded.

  5. Development of In Vitro Isolated Perfused Porcine Skin Flaps for Study of Percutaneous Absorption of Xenobiotics

    DTIC Science & Technology

    1987-06-30

    radiolabeled benzoic acid (B), caffeine’ (C), diisopro- pylfluorophosphidate (D), parathion (P), malathion (M), progesterone (R), testosterone (T), and...Curves of Benzoic Acid (B) and caffeine (C) in the IPPSF .................. 53 16. Absorption Rate-Time Curves of the Organo- phosphates DFP (D), Malathion ...Boston, MA). (2,3- C] Malathion (specific activity = 37 mCi/mmol), (ring 2,6-1 4 C]parathion (sp. act. = 21 mCi/mmol), (ring 4- 1 4 C)progesterone

  6. Studies of the differential absorption rocket experiment. [to measure atmospheric electron density

    NASA Technical Reports Server (NTRS)

    Ginther, J. C.; Smith, L. G.

    1975-01-01

    Investigations of the ionosphere, in the rocket program of the Aeronomy Laboratory, include a propagation experiment, the data from which may be analyzed in several modes. This report considers in detail the differential absorption experiment. The sources of error and limitations of sensitivity are discussed. Methods of enhancing the performance of the experiment are described. Some changes have been made in the system and the improvement demonstrated. Suggestions are made for further development of the experiment.

  7. Ab initio study of optical absorption spectra of semiconductors and conjugated polymers

    SciTech Connect

    Tiago, M.L.; Chang, Eric K.; Rohlfing, Michael; Louie, Steven G.

    2000-04-30

    The effects of electron-hole interaction on the optical properties of a variety of materials have been calculated using an ab initio method based on solving the Bethe-Salpeter equation. Results on selected semiconductors, insulators, and semiconducting polymers are presented. In the cases of alpha-quartz (SiO2) and poly-phenylene-vinylene, resonant excitonic states qualitatively alter the absorption spectra.

  8. Secondary Structure and Pd(II) Coordination in S-Layer Proteins from Bacillus sphaericus Studied by Infrared and X-Ray Absorption Spectroscopy

    PubMed Central

    Fahmy, Karim; Merroun, Mohamed; Pollmann, Katrin; Raff, Johannes; Savchuk, Olesya; Hennig, Christoph; Selenska-Pobell, Sonja

    2006-01-01

    The S-layer of Bacillus sphaericus strain JG-A12, isolated from a uranium-mining site, exhibits a high metal-binding capacity, indicating that it may provide a protective function by preventing the cellular uptake of heavy metals and radionuclides. This property has allowed the use of this and other S-layers as self-assembling organic templates for the synthesis of nanosized heavy metal cluster arrays. However, little is known about the molecular basis of the metal-protein interactions and their impact on secondary structure. We have studied the secondary structure, protein stability, and Pd(II) coordination in S-layers from the B. sphaericus strains JG-A12 and NCTC 9602 to elucidate the molecular basis of their biological function and of the metal nanocluster growth. Fourier transform infrared spectroscopy reveals similar secondary structures, containing ∼35% β-sheets and little helical structure. pH-induced infrared absorption changes of the side-chain carboxylates evidence a remarkably low pK < 3 in both strains and a structural stabilization when Pd(II) is bound. The COO−-stretching absorptions reveal a predominant Pd(II) coordination by chelation/bridging by Asp and Glu residues. This agrees with XANES and EXAFS data revealing oxygens as coordinating atoms to Pd(II). The additional participation of nitrogen is assigned to side chains rather than to the peptide backbone. The topology of nitrogen- and carboxyl-bearing side chains appears to mediate heavy metal binding to the large number of Asp and Glu in both S-layers at particularly low pH as an adaptation to the environment from which the strain JG-A12 has been isolated. These side chains are thus prime targets for the design of engineered S-layer-based nanoclusters. PMID:16698775

  9. Large-scale correlated study of excited state absorptions in naphthalene and anthracene.

    PubMed

    Sony, Priya; Shukla, Alok

    2009-07-07

    In this paper, we report theoretical calculations of the photoinduced absorption (PA) spectrum of naphthalene and anthracene, with the aim of understanding those excited states, which are invisible in the linear optical absorption. The excited state absorption spectra are computed from the 1B(2u)(+) and the 1B(3u)(+) states and a detailed analysis of the many-body character of the states contributing to various peaks in the spectra is presented. The calculations are performed using the Pariser-Parr-Pople (PPP) Hamiltonian, along with the full configuration interaction technique. The role of Coulomb parameters used in the PPP Hamiltonian is examined by considering standard Ohno parameters, as well as a screened set of parameters. The results of our calculations are extensively compared with the experimental data where available and very good agreement has been obtained. Moreover, our calculations predict the presence of high intensity features which, to the best of our knowledge, have not been explored earlier. We also present concrete predictions on the polarization properties of the PA spectrum, which can be verified in experiments performed on oriented samples.

  10. Protonation State of MnFe and FeFe Cofactors in a Ligand-Binding Oxidase Revealed by X-ray Absorption, Emission, and Vibrational Spectroscopy and QM/MM Calculations.

    PubMed

    Kositzki, Ramona; Mebs, Stefan; Marx, Jennifer; Griese, Julia J; Schuth, Nils; Högbom, Martin; Schünemann, Volker; Haumann, Michael

    2016-10-03

    Enzymes with a dimetal-carboxylate cofactor catalyze reactions among the top challenges in chemistry such as methane and dioxygen (O2) activation. Recently described proteins bind a manganese-iron cofactor (MnFe) instead of the classical diiron cofactor (FeFe). Determination of atomic-level differences of homo- versus hetero-bimetallic cofactors is crucial to understand their diverse redox reactions. We studied a ligand-binding oxidase from the bacterium Geobacillus kaustophilus (R2lox) loaded with a FeFe or MnFe cofactor, which catalyzes O2 reduction and an unusual tyrosine-valine ether cross-link formation, as revealed by X-ray crystallography. Advanced X-ray absorption, emission, and vibrational spectroscopy methods and quantum chemical and molecular mechanics calculations provided relative Mn/Fe contents, X-ray photoreduction kinetics, metal-ligand bond lengths, metal-metal distances, metal oxidation states, spin configurations, valence-level degeneracy, molecular orbital composition, nuclear quadrupole splitting energies, and vibrational normal modes for both cofactors. A protonation state with an axial water (H2O) ligand at Mn or Fe in binding site 1 and a metal-bridging hydroxo group (μOH) in a hydrogen-bonded network is assigned. Our comprehensive picture of the molecular, electronic, and dynamic properties of the cofactors highlights reorientation of the unique axis along the Mn-OH2 bond for the Mn1(III) Jahn-Teller ion but along the Fe-μOH bond for the octahedral Fe1(III). This likely corresponds to a more positive redox potential of the Mn(III)Fe(III) cofactor and higher proton affinity of its μOH group. Refined model structures for the Mn(III)Fe(III) and Fe(III)Fe(III) cofactors are presented. Implications of our findings for the site-specific metalation of R2lox and performance of the O2 reduction and cross-link formation reactions are discussed.

  11. 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.

  12. Cooperative enhancement of TPA in cruciform double-chain DSB derivation: a femtosecond transient absorption spectra study

    NASA Astrophysics Data System (ADS)

    He, X.; Wang, Y.; Yang, Z.; Ma, Y.; Yang, Y.

    2010-09-01

    Femtosecond time-resolved transient absorption (TA) spectra study was adopted to study the mechanism of the cooperative enhancement of two-photon absorption (TPA) cross section from the linear structure 1,4-di(4'-N,N-diphenylaminostyryl)benzene (DPA-DSB) to its cruciform double-chain dimer DPA-TSB. The results suggested that a non-emissive intramolecular charge-transfer (ICT) state, ICT’, was present upon excitation in the dimer, which was absent in the monomer. The existence of this non-emissive state, indicating the enhancement of the intramolecular charge-transfer of the dimer, should be the reason for the cooperative enhancement of the TPA cross section of the dimer compared to the monomer.

  13. X-Ray Absorption Studies of Vanadium-Containing Metal Oxide Nanocrystals

    SciTech Connect

    Hohn, Keith, L.

    2006-01-09

    Metal oxide nanocrystals offer significant potential for use as catalysts or catalyst supports due to their high surface areas and unique chemical properties that result from the high number of exposed corners and edges. However, little is known about the catalytic activity of these materials, especially as oxidation catalysts. This research focused on the preparation, characterization and use of vanadium-containing nanocrystals as selective oxidation catalysts. Three vanadium-containing nanocrystals were prepared using a modified sol-gel procedure: V/MgO, V/SiO2, and vanadium phosphate (VPO). These represent active oxidation catalysts for a number of industrially relevant reactions. The catalysts were characterized by x-ray diffraction and Raman, UV-VIS, infrared and x-ray absorption spectroscopies with the goal of determining the primary structural and chemical differences between nanocrystals and microcrystals. The catalytic activity of these catalysts was also studied in oxidative dehydrogenation of butane and methanol oxidation to formaldehyde. V/MgO nanocrystals were investigated for activity in oxidative dehydrogenation of butane and compared to conventional V/MgO catalysts. Characterization of V/MgO catalysts using Raman spectroscopy and x-ray absorption spectroscopy showed that both types of catalysts contained magnesium orthovanadate at vanadium loadings below 15 weight%, but above that loading, magnesium pyrovanadate may have been present. In general, MgO nanocrystals had roughly half the crystal size and double the surface area of the conventional MgO. In oxidative dehydrogenation of butane, nanocrystalline V/MgO gave higher selectivity to butene than conventional V/MgO at the same conversion. This difference was attributed to differences in vanadium domain size resulting from the higher surface areas of the nanocrystalline support, since characterization suggested that similar vanadium phases were present on both types of catalysts. Experiments in

  14. State of Ni in catalysts for glycerol hydrogenation and methane steam reforming as studied by X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Tkachenko, O. P.; Kustov, L. M.

    2013-06-01

    X-ray absorption spectroscopy is used to study 1% Ni/Al2O3, 5% Ni/Al2O3, and 5% Ni/TiO2 catalysts for glycerol and methane conversion. The effect of treatment in H2 under microwave irradiation on the reduction of part of the nickel to the metallic state in the titanium oxide-supported catalyst is demonstrated.

  15. Absorption coefficients of CFC-11 and CFC-12 needed for atmospheric remote sensing and global warming studies

    NASA Technical Reports Server (NTRS)

    Varanasi, Prasad

    1992-01-01

    Spectral absorption coefficients k(v) in the atmospheric window are reported for CFC-11 and CFC-12. Data obtained with a grating spectrometer are compared with NCAR cross sections and measurements of k(v) made with a tunable diode laser spectrometer at various temperature-pressure combinations representing tangent heights or layers in the atmosphere are presented. The results are suitable for atmospheric remote sensing and global warming studies.

  16. Gas cell based on optical contacting for fundamental spectroscopy studies with initial reference absorption spectrum of H2O vapor at 1723 K and 0.0235 bar

    NASA Astrophysics Data System (ADS)

    Melin, Scott T.; Sanders, Scott T.

    2016-09-01

    A gas cell, using optically contacted sapphire windows to form a hot vapor seal, has been created for high temperature fundamental spectroscopy studies. It is designed to operate at temperatures from 280-2273 K and pressures from vacuum to 1.3 bar. Using the cell in conjunction with an external cavity diode laser spectrometer, a reference H2O vapor absorption spectrum at P=0.0235±0.0036 bar and T=1723±6 K was measured with 0.0001 cm-1 resolution over the 7326-7598 cm-1 range. Comparison of the measured spectrum to simulations reveals errors in both the HITEMP and BT2 databases. This work establishes heated static cell capabilities at temperatures well above the typical limit of approximately 1300 K set by quartz material properties. This paper addresses the design of the cell as well as the cell's limitations.

  17. X-ray absorption spectroscopic studies of the dinuclear iron center in methane monooxygenase and the sulfure and chlorine centers in photographic materials

    SciTech Connect

    DeWitt, J.G.

    1992-12-01

    The dinuclear iron center of the hydroxylase component of soluble methane monooxygenase (MMO) from Methylococcus capsulatus and Methylosinus trichosporiwn has been studied by X-ray absorption spectroscopy. Analysis of the Fe K-edge EXAFS revealed that the first shell coordination of the Fe(HI)Fe(IH) oxidized state of the hydroxylase from M. capsulatus consists of approximately 6 N and 0 atoms at an average distance of 2.04 [Angstrom]. The Fe-Fe distance was determined to be 3.4 [Angstrom]. No evidence for the presence of a short oxo bridge in the iron center of the oxidized hydroxylase was found, suggesting that the active site of MMO is significantly different from the active sites of the dinuclear iron proteins hemery and ribonucleotide reductase. In addition, the results of the first shell fits suggest that there are more oxygen than nitrogen donor ligands.

  18. X-ray absorption spectroscopic studies of the dinuclear iron center in methane monooxygenase and the sulfure and chlorine centers in photographic materials

    SciTech Connect

    DeWitt, Jane G.

    1992-12-01

    The dinuclear iron center of the hydroxylase component of soluble methane monooxygenase (MMO) from Methylococcus capsulatus and Methylosinus trichosporiwn has been studied by X-ray absorption spectroscopy. Analysis of the Fe K-edge EXAFS revealed that the first shell coordination of the Fe(HI)Fe(IH) oxidized state of the hydroxylase from M. capsulatus consists of approximately 6 N and 0 atoms at an average distance of 2.04 Å. The Fe-Fe distance was determined to be 3.4 Å. No evidence for the presence of a short oxo bridge in the iron center of the oxidized hydroxylase was found, suggesting that the active site of MMO is significantly different from the active sites of the dinuclear iron proteins hemery and ribonucleotide reductase. In addition, the results of the first shell fits suggest that there are more oxygen than nitrogen donor ligands.

  19. Rapid conversion of the ester prodrug abiraterone acetate results in intestinal supersaturation and enhanced absorption of abiraterone: in vitro, rat in situ and human in vivo studies.

    PubMed

    Stappaerts, Jef; Geboers, Sophie; Snoeys, Jan; Brouwers, Joachim; Tack, Jan; Annaert, Pieter; Augustijns, Patrick

    2015-02-01

    The aim of this study was to evaluate the intestinal disposition of abiraterone acetate, an ester prodrug of the anticancer agent abiraterone. Stability of the prodrug and solubility and dissolution characteristics of both abiraterone and abiraterone acetate were monitored in vitro. Moreover, the in vivo intraluminal concentrations of abiraterone and abiraterone acetate upon intake of one tablet of 250 mg abiraterone acetate were assessed in healthy volunteers. The intestinal absorption resulting from the intraluminal behavior of the ester prodrug was determined using the rat in situ intestinal perfusion technique with mesenteric blood sampling. Simulated and aspirated human intestinal fluids of the fasted state were used as solvent systems. Upon incubation of abiraterone acetate in human intestinal fluids in vitro, rapid hydrolysis of the prodrug was observed, generating abiraterone concentrations largely exceeding the apparent solubility of abiraterone, suggesting the existence of intestinal supersaturation. These findings were confirmed in vivo, by intraluminal sampling of duodenal fluids upon oral intake of an abiraterone acetate tablet by healthy volunteers. Rat in situ intestinal perfusion experiments performed with suspensions of abiraterone and abiraterone acetate in human intestinal fluids of the fasted state revealed significantly higher flux values upon perfusion with the prodrug than with abiraterone. Moreover, rat in situ intestinal perfusion with abiraterone acetate suspensions in simulated fluids of the fasted state in presence or absence of esterases demonstrated that increased hydrolytic activity of the perfusion medium was beneficial to the intestinal absorption of abiraterone. In conclusion, the rapid hydrolysis of abiraterone acetate in the intraluminal environment appears to result in fast and extensive generation of abiraterone supersaturation, creating a strong driving force for abiraterone absorption.

  20. Theoretical study of electronic absorption spectroscopy of propadienylidene molecule vis-â-vis the observed diffuse interstellar bands

    NASA Astrophysics Data System (ADS)

    Reddy, Samala Nagaprasad; Mahapatra, S.

    2012-07-01

    Observation of broad and diffuse interstellar bands (DIBs) at 4881 Å and 5440 Å assigned to the optical absorption spectrum of Y-shaped propadienylidene (H2Cdbnd Cdbnd C:) molecule is theoretically examined in this paper. This molecule apparently absorbs in the same wavelength region as the observed DIBs and was suggested to be a potential carrier of these DIBs. This assignment mostly relied on the experimental data from radioastronomy and laboratory measurements. Motivated by these available experimental data we attempt here a theoretical study and investigate the detailed electronic structure and nuclear dynamics underlying the electronic absorption bands of propadienylidene molecule. Our results show that this molecule indeed absorbs in the wavelength region of the recorded DIBs. Strong nonadiabatic coupling between its energetically low-lying electronic states plays major role, initiates ultrafast internal conversion and contributes to the spectral broadening. Theoretical findings are finally compared with the available experimental and theoretical data and discussed in connection with the recorded DIBs.

  1. Absorption and fluorescence of PRODAN in phospholipid bilayers: a combined quantum mechanics and classical molecular dynamics study.

    PubMed

    Cwiklik, Lukasz; Aquino, Adelia J A; Vazdar, Mario; Jurkiewicz, Piotr; Pittner, Jiří; Hof, Martin; Lischka, Hans

    2011-10-20

    Absorption and fluorescence spectra of PRODAN (6-propionyl-2-dimethylaminonaphthalene) were studied by means of the time-dependent density functional theory and the algebraic diagrammatic construction method. The influence of environment, a phosphatidylcholine lipid bilayer and water, was taken into account employing a combination of quantum chemical calculations with empirical force-field molecular dynamics simulations. Additionally, experimental absorption and emission spectra of PRODAN were measured in cyclohexane, water, and lipid vesicles. Both planar and twisted configurations of the first excited state of PRODAN were taken into account. The twisted structure is stabilized in both water and a lipid bilayer, and should be considered as an emitting state in polar environments. Orientation of the excited dye in the lipid bilayer significantly depends on configuration. In the bilayer, the fluorescence spectrum can be regarded as a combination of emission from both planar and twisted structures.

  2. A comparative study on the ionic liquid [bmim][BF 4] and its solution with transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhu, Guanglai; Wu, Guozhong; Xu, Xinsheng; Ji, Xuehan

    2011-11-01

    A detailed study was explored to compare the transient absorption spectra of the neat 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF 4]) with its solution in water or acetonitrile. It was concluded that the excited triplet state 3[bmim] +* was produced after 266 nm laser irradiation, and then the neutral radical [bmim] rad and the cation radical [bmim] 2+rad were formed through two possible paths. The transient absorption spectra of the neat [bmim][BF 4] and its solution were similar but the reaction kinetics were different due to their different local structures such as dimeric or cluster. The energy transfer between excited [bmim][BF 4] and β-carotene further affirmed the existence of 3[bmim] +*. And the reaction that the hydrated electron captured by [bmim] + to produce [bmim] rad in solution was observed.

  3. Voltage-controlled magnetic anisotropy in Fe|MgO tunnel junctions studied by x-ray absorption spectroscopy

    SciTech Connect

    Miwa, Shinji Matsuda, Kensho; Tanaka, Kazuhito; Goto, Minori; Suzuki, Yoshishige; Kotani, Yoshinori; Nakamura, Tetsuya

    2015-10-19

    In this study, voltage-controlled magnetic anisotropy (VCMA) in Fe|MgO tunnel junctions was investigated via the magneto-optical Kerr effect, soft x-ray absorption spectroscopy, and magnetic circular dichroism spectroscopy. The Fe|MgO tunnel junctions showed enhanced perpendicular magnetic anisotropy under external negative voltage, which induced charge depletion at the Fe|MgO interface. Despite the application of voltages of opposite polarity, no trace of chemical reaction such as a redox reaction attributed to O{sup 2−} migration was detected in the x-ray absorption spectra of the Fe. The VCMA reported in the Fe|MgO-based magnetic tunnel junctions must therefore originate from phenomena associated with the purely electric effect, that is, surface electron doping and/or redistribution induced by an external electric field.

  4. ON ABSORPTION BY CIRCUMSTELLAR DUST, WITH THE PROGENITOR OF SN 2012aw AS A CASE STUDY

    SciTech Connect

    Kochanek, C. S.; Khan, R.; Dai, X.

    2012-11-01

    We use the progenitor of SN 2012aw to illustrate the consequences of modeling circumstellar dust using Galactic (interstellar) extinction laws that (1) ignore dust emission in the near-IR and beyond, (2) average over dust compositions, and (3) mischaracterize the optical/UV absorption by assuming that scattered photons are lost to the observer. The primary consequences for the progenitor of SN 2012aw are that both the luminosity and the absorption are significantly overestimated. In particular, the stellar luminosity is most likely in the range 10{sup 4.8} < L {sub *}/L {sub Sun} < 10{sup 5.0} and the star was not extremely massive for a Type IIP progenitor, with M {sub *} < 15 M {sub Sun }. Given the properties of the circumstellar dust and the early X-ray/radio detections of SN 2012aw, the star was probably obscured by an ongoing wind with M-dot {approx}10{sup -5.5} to 10{sup -5.0} M {sub Sun} yr{sup -1} at the time of the explosion, roughly consistent with the expected mass-loss rates for a star of its temperature (T{sub *} {approx_equal} 3600{sup +300} {sub -200} K) and luminosity. In the spirit of Galactic extinction laws, we supply simple interpolation formulae for circumstellar extinction by dusty graphitic and silicate shells as a function of wavelength ({lambda} {>=} 0.3 {mu}m) and total (absorption plus scattering) V-band optical depth ({tau}{sub V} {<=} 20). These do not include the contributions of dust emission, but provide a simple, physical alternative to incorrectly using interstellar extinction laws.

  5. A comparative study of intervening and associated H I 21-cm absorption profiles in redshifted galaxies

    NASA Astrophysics Data System (ADS)

    Curran, S. J.; Duchesne, S. W.; Divoli, A.; Allison, J. R.

    2016-11-01

    The star-forming reservoir in the distant Universe can be detected through H I 21-cm absorption arising from either cool gas associated with a radio source or from within a galaxy intervening the sightline to the continuum source. In order to test whether the nature of the absorber can be predicted from the profile shape, we have compiled and analysed all of the known redshifted (z ≥ 0.1) H I 21-cm absorption profiles. Although between individual spectra there is too much variation to assign a typical spectral profile, we confirm that associated absorption profiles are, on average, wider than their intervening counterparts. It is widely hypothesized that this is due to high-velocity nuclear gas feeding the central engine, absent in the more quiescent intervening absorbers. Modelling the column density distribution of the mean associated and intervening spectra, we confirm that the additional low optical depth, wide dispersion component, typical of associated absorbers, arises from gas within the inner parsec. With regard to the potential of predicting the absorber type in the absence of optical spectroscopy, we have implemented machine learning techniques to the 55 associated and 43 intervening spectra, with each of the tested models giving a ≳ 80 per cent accuracy in the prediction of the absorber type. Given the impracticability of follow-up optical spectroscopy of the large number of 21-cm detections expected from the next generation of large radio telescopes, this could provide a powerful new technique with which to determine the nature of the absorbing galaxy.

  6. Interaction between Bisphosphonates and Mineral Water: Study of Oral Risedronate Absorption in Rats.

    PubMed

    Itoh, Akihisa; Akagi, Yuuki; Shimomura, Hitoshi; Aoyama, Takao

    2016-01-01

    Bisphosphonates are antiosteoporotic agents prescribed for patients with osteoporosis. Drug package inserts for bisphosphonate supplements indicate that their bioavailability is reduced by high levels of metal cations (Ca(2+), Mg(2+), etc.). However, standards for these cations in water used for taking risedronate have not been defined. Here, we examined the effect of calcium and magnesium in mineral waters on the bioavailability of the third-generation bisphosphonate, risedronate, following oral administration in rats. As risedronate is unchanged and eliminated renally, risedronate absorption was estimated from the amount excreted in the urine. Risedronate was dissolved in mineral water samples and administered orally at 0.35 mg/kg. Urine samples were collected for 24 h after dosing. Risedronate was extracted from urine using ion-pair solid-phase cartridges and quantified by HPLC with UV detection (262 nm). Cumulative recovery of risedronate was calculated from the amount excreted in the urine. The 24-h recovery of risedronate from evian® (0.32±0.02% [mean±standard deviation (S.D.)], n=4) and Contrex(®) (0.22±0.05%) mineral waters was significantly lower than that from tap water (0.47±0.04%, p<0.01). Absorption of risedronate in calcium chloride and magnesium chloride aqueous solutions of the same hardness (822 mg/L) was 54% (0.27±0.04%) and 12% (0.51±0.08%) lower, respectively, compared with ultrapure water; suggesting that absorption of risedronate declines as the calcium concentration of mineral waters increases. Consumption of mineral waters containing high levels of calcium (80 mg/L or above), such as evian® and Contrex(®), is therefore not recommended when taking risedronate.

  7. X-ray absorption spectroscopic studies of the active sites of nickel- and copper-containing metalloproteins

    SciTech Connect

    Tan, G.O.

    1993-06-01

    X-ray absorption spectroscopy (XAS) is a useful tool for obtaining structural and chemical information about the active sites of metalloproteins and metalloenzymes. Information may be obtained from both the edge region and the extended X-ray absorption fine structure (EXAFS) or post-edge region of the K-edge X-ray absorption spectrum of a metal center in a compound. The edge contains information about the valence electronic structure of the atom that absorbs the X-rays. It is possible in some systems to infer the redox state of the metal atom in question, as well as the geometry and nature of ligands connected to it, from the features in the edge in a straightforward manner. The EXAFS modulations, being produced by the backscattering of the ejected photoelectron from the atoms surrounding the metal atom, provide, when analyzed, information about the number and type of neighbouring atoms, and the distances at which they occur. In this thesis, analysis of both the edge and EXAFS regions has been used to gain information about the active sites of various metalloproteins. The metalloproteins studied were plastocyanin (Pc), laccase and nickel carbon monoxide dehydrogenase (Ni CODH). Studies of Cu(I)-imidazole compounds, related to the protein hemocyanin, are also reported here.

  8. [Absorption spectrum study of HeLa cells treated with vacuum and low-energy ions implantation].

    PubMed

    Zhang, Feng-Qiu; Zhao, Yuan-Li; Ge, Xiang-Hong; Liu, Wei; Zhang, Guang-Shui; Qin, Guang-Yong

    2009-08-01

    Mineral oil was selected to protect HeLa cells from water evaporation during low-energy ions implantation in the present paper. Then, HeLa cells having been treated with vacuum and low-energy N+ ions implantation were used to collect ultraviolet absorption spectrum by spectrophotometer. Analytical results indicated that HeLa cells had some characteristic absorption peaks near 202 and 260 nm, respectively. And then the study also found: (1) The spectral intensity increased with the vacuum treatment time. In addition, the effect of vacuum on cellular spectrum was greater than that of mineral oil. (2) The influence of low energy N+ ions on absorption spectrum was far more than that of vacuum. (3) The spectral intensity increased with the implantation dose. According to these results, the effect of low-energy N+ ions implantation and vacuum on tumorous cells (HeLa cells), especially on the molecular configuration and component of tumorous cells (HeLa cells) was discussed. In a word, this study provides a basis for further research on the functionary mechanism of low-energy ions implantation on biomaterial.

  9. Infrared study of the absorption edge of {beta}-InN films grown on GaN/MgO structures

    SciTech Connect

    Perez-Caro, M.; Rodriguez, A. G.; Vidal, M. A.; Navarro-Contreras, H.

    2010-07-15

    Infrared optical studies were carried out in a group of cubic InN samples grown by gas source molecular beam epitaxy on MgO (001) substrates. Room temperature (RT) reflectance and low-temperature (LT) transmittance measurements were performed by using fast Fourier transform infrared spectrometry. Reflectance fittings allowed to establish that {beta}-InN films have large free-carrier concentrations present (>10{sup 19} cm{sup -3}), a result that is corroborated by Hall effect measurements. Each sample explored exhibited a different optical absorption edge. The Varshni parameters that describe adequately the optical absorption edge responses with temperature are obtained for the set of samples studied. The observed temperatures changes, from LT to RT, are the lowest reported for III-V semiconductor binary compounds. The temperature coefficient of the conduction band depends on the strength of the electron-phonon interaction (e-ph-i), as well as on the thermal expansion. It has been predicted that cubic InN has one of the smallest e-ph-i of all III-V compounds, which is corroborated by these results. The variation in values of absorption edges is clearly consistent with the Burstein-Moss and band renormalization effects, produced by high free electron concentrations. It is shown that the conduction band in {beta}-InN, analogous to wurtzite InN, follows a nonparabolic behavior.

  10. Study on the Coordination Structure of Pt Sorbed on Bacterial Cells Using X-Ray Absorption Fine Structure Spectroscopy

    PubMed Central

    Tanaka, Kazuya; Watanabe, Naoko

    2015-01-01

    Biosorption has been intensively investigated as a promising technology for the recovery of precious metals from solution. However, the detailed mechanism responsible for the biosorption of Pt on a biomass is not fully understood because of a lack of spectroscopic studies. We applied X-ray absorption fine structure spectroscopy to elucidate the coordination structure of Pt sorbed on bacterial cells. We examined the sorption of Pt(II) and Pt(IV) species on bacterial cells of Bacillus subtilis and Shewanella putrefaciens in NaCl solutions. X-ray absorption near-edge structure and extended X-ray absorption fine structure (EXAFS) of Pt-sorbed bacteria suggested that Pt(IV) was reduced to Pt(II) on the cell’s surface, even in the absence of an organic material as an exogenous electron donor. EXAFS spectra demonstrated that Pt sorbed on bacterial cells has a fourfold coordination of chlorine ions, similar to PtCl42-, which indicated that sorption on the protonated amine groups of the bacterial cells. This work clearly demonstrated the coordination structure of Pt sorbed on bacterial cells. The findings of this study will contribute to the understanding of Pt biosorption on biomass, and facilitate the development of recovery methods for rare metals using biosorbent materials. PMID:25996945

  11. Electronic Absorption Spectra of Tetrapyrrole-Based Pigments via TD-DFT: A Reduced Orbital Space Study.

    PubMed

    Shrestha, Kushal; Virgil, Kyle A; Jakubikova, Elena

    2016-07-28

    Tetrapyrrole-based pigments play a crucial role in photosynthesis as principal light absorbers in light-harvesting chemical systems. As such, accurate theoretical descriptions of the electronic absorption spectra of these pigments will aid in the proper description and understanding of the overall photophysics of photosynthesis. In this work, time-dependent density functional theory (TD-DFT) at the CAM-B3LYP/6-31G* level of theory is employed to produce the theoretical absorption spectra of several tetrapyrrole-based pigments. However, the application of TD-DFT to large systems with several hundreds of atoms can become computationally prohibitive. Therefore, in this study, TD-DFT calculations with reduced orbital spaces (ROSs) that exclude portions of occupied and virtual orbitals are pursued as a viable, computationally cost-effective alternative to conventional TD-DFT calculations. The effects of reducing orbital space size on theoretical spectra are qualitatively and quantitatively described, and both conventional and ROS results are benchmarked against experimental absorption spectra of various tetrapyrrole-based pigments. The orbital reduction approach is also applied to a large natural pigment assembly that comprises the principal light-absorbing component of the reaction center in purple bacteria. Overall, we find that TD-DFT calculations with proper and judicious orbital space reductions can adequately reproduce conventional, full orbital space, TD-DFT results of all pigments studied in this work.

  12. X-Ray Absorption Fine Structure Study for Fe60Ni40 Alloy

    SciTech Connect

    Yang, Dong-Seok; Oh, Kyuseung; Na, Wonkyung; Kim, Nayoung; Yoo, Yong-Goo; Min, Seung-Gi; Yu, Seong-Cho

    2007-02-02

    Fe60Ni40 alloys were fabricated by the mechanical alloying process with process periods of 1, 2, 4, 6, 12 and 24 hours, respectively. The formation of alloy and the structural evolution of the alloy were examined by X-ray diffraction and extended X-ray absorption fine structure methods. With increase of alloying time the BCC phase of iron was changed significantly during the mechanical alloying process. The alloying was activated in about 6 hours and completed in about 24 hours.

  13. X-ray absorption studies of uranium sorption on mineral substrates

    SciTech Connect

    Hudson, E.A.; Terminello, L.J.; Viani, B.E.

    1994-11-01

    Uranium L{sub 3}-edge x-ray absorption spectra have been measured for uranium-mineral sorption systems. An expansible layer silicate, vermiculite, was treated to obtain a collapsed and non-expanding phase, thereby limiting access to the interior cation exchange sites. Samples were prepared by exposing the finely powdered mineral, in the natural and modified form, to aqueous solutions of uranyl chloride. EXAFS spectra of the encapsulated samples were measured at the Stanford Synchrotron Radiation Laboratory. Results indicate that the uranyl ion possesses a more symmetric local structure within the interlayer regions of vermiculite than on the external surfaces.

  14. An x-ray absorption spectroscopy study of Cd binding onto a halophilic archaeon

    NASA Astrophysics Data System (ADS)

    Showalter, Allison R.; Szymanowski, Jennifer E. S.; Fein, Jeremy B.; Bunker, Bruce A.

    2016-05-01

    X-ray absorption spectroscopy (XAS) and cadmium (Cd) isotherm experiments determine how Cd adsorbs to the surface of halophilic archaeon Halobacterium noricense. This archaeon, isolated from the Waste Isolation Pilot Plant (WIPP) near Carlsbad, New Mexico could be involved with the transport of toxic metals stored in the transuranic waste in the salt mine. The isotherm experiments show that adsorption is relatively constant across the tolerable pH range for H. noricense. The XAS results indicate that Cd adsorption occurs predominately via a sulfur site, most likely sulfhydryl, with the same site dominating all measured pH values.

  15. A Comprehensive Study of Broad Absorption Line Quasars. I. Prevalence of HeI* Absorption Line Multiplets in Low-ionization Objects

    NASA Astrophysics Data System (ADS)

    Liu, Wen-Juan; Zhou, Hongyan; Ji, Tuo; Yuan, Weimin; Wang, Ting-Gui; Jian, Ge; Shi, Xiheng; Zhang, Shaohua; Jiang, Peng; Shu, Xinwen; Wang, Huiyuan; Wang, Shu-Fen; Sun, Luming; Yang, Chenwei; Liu, Bo; Zhao, Wen

    2015-03-01

    Neutral helium multiplets, He i* λ λ 3189,3889,10830, are very useful diagnostics for the geometry and physical conditions of the absorbing gas in quasars. So far only a handful of He i* detections have been reported. Using a newly developed method, we detected the He i*λ 3889 absorption line in 101 sources of a well-defined sample of 285 Mg ii broad absorption line (BAL) quasars selected from SDSS DR5. This has increased the number of He i* BAL quasars by more than one order of magnitude. We further detected He i*λ 3189 in 50% (52/101) of the quasars in the sample. The detection fraction of He i* BALs in Mg ii BAL quasars is ∼35% as a whole, and it increases dramatically with increasing spectral signal-to-noise ratio (S/N), from ∼18% at S/N ≤slant 10 to ∼93% at S/N ≥slant 35. This suggests that He i* BALs could be detected in most Mg ii LoBAL quasars, provided the spectra S/N is high enough. Such a surprisingly high He i* BAL fraction is actually predicted from photoionization calculations based on a simple BAL model. The result indicates that He i* absorption lines can be used to search for BAL quasars at low z, which cannot be identified by ground-based optical spectroscopic surveys with commonly seen UV absorption lines. Using He i* λ3889, we discovered 19 BAL quasars at z\\lt 0.3 from the available SDSS spectral database. The fraction of He i* BAL quasars is similar to that of LoBAL objects.

  16. Study on the Relationship between the Depth of Spectral Absorption and the Content of the Mineral Composition of Biotite.

    PubMed

    Yang, Chang-bao; Zhang, Chen-xi; Liu, Fang; Jiang, Qi-gang

    2015-09-01

    The mineral composition of rock is one of the main factors affecting the spectral reflectance characteristics, and it's an important reason for generating various rock characteristic spectra. This study choose the rock samples provided by Jet Propulsion Laboratory (JPL) (including all kinds of mineral percentage of rocks, and spectral reflectances range from 0.35 to 2.50 μm wavelength measured by ASD spectrometer), and the various types of mineral spectral reflectances contained within the rocks are the essential data. Using the spectral linear mixture model of rocks and their minerals, firstly, a simulation study on the mixture of rock and mineral composition is achieved, the experimental results indicate that rock spectral curves using the model which based on the theory of the linear mixture are able to simulate better and preserve the absorption characteristics of various mineral components well. Then, 8 samples which contain biotite mineral are picked from the rock spectra of igneous, biotite contents and the absorption depth characteristics of spectral reflection at 2.332 μm, furthermore, a variety of linear and nonlinear normal statistical models are used to fit the relationship between the depth of absorption spectra and the content of the mineral composition of biotite, finally, a new simulation model is build up with the Growth and the Exponential curve model, and a statistical response relationship between the spectral absorption depth and the rock mineral contents is simulated by using the new model, the fitting results show that the correlation coefficient reaches 0.9984 and the standard deviation is 0.572, although the standard deviation using Growth and Exponential model is less than the two model combined with the new model fitting the standard deviation, the correlation coefficient of the new model had significantly increased, which suggesting that the, new model fitting effect is closer to the measured values of samples, it proves that the

  17. Interaction of Angeli's salt with cytochrome P450 1A2 distal mutants: an optical absorption spectral study.

    PubMed

    Shibata, Y; Sato, H; Sagami, I; Shimizu, T

    1997-11-14

    Angeli's salt, Na2N2O3 or O-N=N+-(OH)(O-) in aqueous solution, is known to release NO- or NO., which relaxes vascular tissue and lowers blood pressure. In the liver, the most abundant heme enzyme is cytochrome P450. In the present study, we studied the effect of rat liver cytochrome P450 1A2 (P450 1A2) in regard to its catalysis of the N=N bond scission of Angeli's salt with optical absorption spectra. Also, we examined the contribution of putative distal amino acids of P450 1A2 to the reaction with the salt. We found that wild-type Fe3+ P450 1A2 markedly enhances the N=N scission of the salt up to 100 fold in terms of absorption spectroscopy. A Fe3+ P450 1A2-NO complex with an absorption peak at 435 nm was formed when the salt was added and the complex was then changed to a 6-coordinated Fe2+-NO complex having a 440-nm peak. Glu318Asp, Glu318Ala and Thr319Ala mutants at the putative distal site of P450 1A2 formed a 5-coordinated Fe2+-NO complex having a 400-nm absorption, that was not formed with the wild type. The Glu318Ala mutant, in particular, did not form the Fe3+-NO complex with the addition of Angeli's salt. The presence of L-Cys, reduced glutathione, catalase or superoxide dismutase markedly stabilized the Fe3+ wild type-NO complex. Thus, our data suggests that the N=N bond of Angeli's salt is cleaved with the P450 1A2 active site and NO- or NO. is released. We discuss mechanisms of redox and ligand changes of the P450 heme.

  18. A comparison study of linear reconstruction techniques for diffuse optical tomographic imaging of absorption coefficient

    NASA Astrophysics Data System (ADS)

    Gaudette, Richard J.; Brooks, Dana H.; Di Marzio, Charles A.; Kilmer, Misha E.; Miller, Eric L.; Gaudette, Thomas; Boas, David A.

    2000-04-01

    We compare, through simulations, the performance of four linear algorithms for diffuse optical tomographic reconstruction of the three-dimensional distribution of absorption coefficient within a highly scattering medium using the diffuse photon density wave approximation. The simulation geometry consisted of a coplanar array of sources and detectors at the boundary of a half-space medium. The forward solution matrix is both underdetermined, because we estimate many more absorption coefficient voxels than we have measurements, and ill-conditioned, due to the ill-posedness of the inverse problem. We compare two algebraic techniques, ART and SIRT, and two subspace techniques, the truncated SVD and CG algorithms. We compare three-dimensional reconstructions with two-dimensional reconstructions which assume all inhomogeneities are confined to a known horizontal slab, and we consider two `object-based' error metrics in addition to mean square reconstruction error. We include a comparison using simulated data generated using a different FDFD method with the same inversion algorithms to indicate how our conclusions are affected in a somewhat more realistic scenario. Our results show that the subspace techniques are superior to the algebraic techniques in localization of inhomogeneities and estimation of their amplitude, that two-dimensional reconstructions are sensitive to underestimation of the object depth, and that an error measure based on a location parameter can be a useful complement to mean squared error.

  19. Computational Studies of Drug Release, Transport and Absorption in the Human Intestines

    NASA Astrophysics Data System (ADS)

    Behafarid, Farhad; Brasseur, J. G.; Vijayakumar, G.; Jayaraman, B.; Wang, Y.

    2016-11-01

    Following disintegration of a drug tablet, a cloud of particles 10-200 μm in diameter enters the small intestine where drug molecules are absorbed into the blood. Drug release rate depends on particle size, solubility and hydrodynamic enhancements driven by gut motility. To quantify the interrelationships among dissolution, transport and wall permeability, we apply lattice Boltzmann method to simulate the drug concentration field in the 3D gut released from polydisperse distributions of drug particles in the "fasting" vs. "fed" motility states. Generalized boundary conditions allow for both solubility and gut wall permeability to be systematically varied. We apply a local 'quasi-steady state' approximation for drug dissolution using a mathematical model generalized for hydrodynamic enhancements and heterogeneity in drug release rate. We observe fundamental differences resulting from the interplay among release, transport and absorption in relationship to particle size distribution, luminal volume, motility, solubility and permeability. For example, whereas smaller volume encourages higher bulk concentrations and reduced release rate, it also encourages higher absorption rate, making it difficult to generalize predictions. Supported by FDA.

  20. Femtosecond X-ray absorption study of electron localization in photoexcited anatase TiO2

    PubMed Central

    Santomauro, F. G.; Lübcke, A.; Rittmann, J.; Baldini, E.; Ferrer, A.; Silatani, M.; Zimmermann, P.; Grübel, S.; Johnson, J. A.; Mariager, S. O.; Beaud, P.; Grolimund, D.; Borca, C.; Ingold, G.; Johnson, S.L.; Chergui, M.

    2015-01-01

    Transition metal oxides are among the most promising solar materials, whose properties rely on the generation, transport and trapping of charge carriers (electrons and holes). Identifying the latter’s dynamics at room temperature requires tools that combine elemental and structural sensitivity, with the atomic scale resolution of time (femtoseconds, fs). Here, we use fs Ti K-edge X-ray absorption spectroscopy (XAS) upon 3.49 eV (355 nm) excitation of aqueous colloidal anatase titanium dioxide nanoparticles to probe the trapping dynamics of photogenerated electrons. We find that their localization at Titanium atoms occurs in <300 fs, forming Ti3+ centres, in or near the unit cell where the electron is created. We conclude that electron localization is due to its trapping at pentacoordinated sites, mostly present in the surface shell region. The present demonstration of fs hard X-ray absorption capabilities opens the way to a detailed description of the charge carrier dynamics in transition metal oxides. PMID:26437873

  1. Femtosecond X-ray absorption study of electron localization in photoexcited anatase TiO2.

    PubMed

    Santomauro, F G; Lübcke, A; Rittmann, J; Baldini, E; Ferrer, A; Silatani, M; Zimmermann, P; Grübel, S; Johnson, J A; Mariager, S O; Beaud, P; Grolimund, D; Borca, C; Ingold, G; Johnson, S L; Chergui, M

    2015-10-06

    Transition metal oxides are among the most promising solar materials, whose properties rely on the generation, transport and trapping of charge carriers (electrons and holes). Identifying the latter's dynamics at room temperature requires tools that combine elemental and structural sensitivity, with the atomic scale resolution of time (femtoseconds, fs). Here, we use fs Ti K-edge X-ray absorption spectroscopy (XAS) upon 3.49 eV (355 nm) excitation of aqueous colloidal anatase titanium dioxide nanoparticles to probe the trapping dynamics of photogenerated electrons. We find that their localization at Titanium atoms occurs in <300 fs, forming Ti(3+) centres, in or near the unit cell where the electron is created. We conclude that electron localization is due to its trapping at pentacoordinated sites, mostly present in the surface shell region. The present demonstration of fs hard X-ray absorption capabilities opens the way to a detailed description of the charge carrier dynamics in transition metal oxides.

  2. Anharmonic resonance absorption of short laser pulses in clusters: A molecular dynamics simulation study

    NASA Astrophysics Data System (ADS)

    Mahalik, S. S.; Kundu, M.

    2016-12-01

    Linear resonance (LR) absorption of an intense 800 nm laser light in a nano-cluster requires a long laser pulse >100 fs when Mie-plasma frequency ( ω M ) of electrons in the expanding cluster matches the laser frequency (ω). For a short duration of the pulse, the condition for LR is not satisfied. In this case, it was shown by a model and particle-in-cell (PIC) simulations [Phys. Rev. Lett. 96, 123401 (2006)] that electrons absorb laser energy by anharmonic resonance (AHR) when the position-dependent frequency Ω [ r ( t ) ] of an electron in the self-consistent anharmonic potential of the cluster satisfies Ω [ r ( t ) ] = ω . However, AHR remains to be a debate and still obscure in multi-particle plasma simulations. Here, we identify AHR mechanism in a laser driven cluster using molecular dynamics (MD) simulations. By analyzing the trajectory of each MD electron and extracting its Ω [ r ( t ) ] in the self-generated anharmonic plasma potential, it is found that electron is outer ionized only when AHR is met. An anharmonic oscillator model, introduced here, brings out most of the features of MD electrons while passing the AHR. Thus, we not only bridge the gap between PIC simulations, analytical models, and MD calculations for the first time but also unequivocally prove that AHR process is a universal dominant collisionless mechanism of absorption in the short pulse regime or in the early time of longer pulses in clusters.

  3. Comparative study of absorption in tilted silicon nanowire arrays for photovoltaics

    PubMed Central

    2014-01-01

    Silicon nanowire arrays have been shown to demonstrate light trapping properties and promising potential for next-generation photovoltaics. In this paper, we show that the absorption enhancement in vertical nanowire arrays on a perfectly electric conductor can be further improved through tilting. Vertical nanowire arrays have a 66.2% improvement in ultimate efficiency over an ideal double-pass thin film of the equivalent amount of material. Tilted nanowire arrays, with the same amount of material, exhibit improved performance over vertical nanowire arrays across a broad range of tilt angles (from 38° to 72°). The optimum tilt of 53° has an improvement of 8.6% over that of vertical nanowire arrays and 80.4% over that of the ideal double-pass thin film. Tilted nanowire arrays exhibit improved absorption over the solar spectrum compared with vertical nanowires since the tilt allows for the excitation of additional modes besides the HE 1m modes that are excited at normal incidence. We also observed that tilted nanowire arrays have improved performance over vertical nanowire arrays for a large range of incidence angles (under about 60°). PMID:25435833

  4. Strontium localization in bone tissue studied by X-ray absorption spectroscopy.

    PubMed

    Frankær, Christian Grundahl; Raffalt, Anders Christer; Stahl, Kenny

    2014-02-01

    Strontium has recently been introduced as a pharmacological agent for the treatment and prevention of osteoporosis. We determined the localization of strontium incorporated into bone matrix from dogs treated with Sr malonate by X-ray absorption spectroscopy. A new approach for analyzing the X-ray absorption spectra resulted in a compositional model and allowed the relative distribution of strontium in the different bone components to be estimated. Approximately 35-45% of the strontium present is incorporated into calcium hydroxyapatite (CaHA) by substitution of some of the calcium ions occupying highly ordered sites, and at least 30% is located at less ordered sites where only the first solvation shell is resolved, suggesting that strontium is surrounded by only oxygen atoms similar to Sr(2+) in solution. Strontium was furthermore shown to be absorbed in collagen in which it obtains a higher structural order than when present in serum but less order than when it is incorporated into CaHA. The total amount of strontium in the samples was determined by inductively coupled plasma mass spectrometry, and the amount of Sr was found to increase with increasing dose levels and treatment periods, whereas the relative distribution of strontium among the different components appears to be independent of treatment period and dose level.

  5. Mid-Latitude D-Region Absorption Studies in the Space Weather Context: Modeling Results

    NASA Astrophysics Data System (ADS)

    Eccles, V.; Sojka, J.; Rice, D.; Hunsucker, R. D.

    2003-12-01

    A Data-Driven D-region (DDDR) model has been created to ingest real-time geophysical data streams into a D-region electron density model for improved determinations of D-region specification with respect to HF propagation and absorption characteristics. The model is based on the disturbed D-region model of Swider and Foley ["Steady-State Multi-Ion Disturbed D-Region Model", AFGL-TR-78-0155, June 1978] for quick calculation of the global electron density profile from 60 to 100 km altitude. The model is driven by geophysical indices and ingests x-ray observations and solar wind particle observations (NOAA/GOES 12 satellite) into ionization drivers to the weather-sensitive D region model. The DDDR model and the Ionospheric Forecast Model (IFM) are run for the time period of May 25 to June 25 of 2003 and used to calculate HF signal propagation and strength from WWV, WWVH, and CHU standard time-frequency stations to the HF monitoring stations of the HF Investigation and D region Ionosphere Variation Experiment (HIDAVE). The monitoring sites are at Klamath Falls, OR and Bear Lake Observatory, UT. Day-to-day trends in HF absorption are examined in the data-model comparison as well as the D region response to solar flares from Class C to Class X.

  6. Comparative study of absorption in tilted silicon nanowire arrays for photovoltaics.

    PubMed

    Kayes, Md Imrul; Leu, Paul W

    2014-01-01

    Silicon nanowire arrays have been shown to demonstrate light trapping properties and promising potential for next-generation photovoltaics. In this paper, we show that the absorption enhancement in vertical nanowire arrays on a perfectly electric conductor can be further improved through tilting. Vertical nanowire arrays have a 66.2% improvement in ultimate efficiency over an ideal double-pass thin film of the equivalent amount of material. Tilted nanowire arrays, with the same amount of material, exhibit improved performance over vertical nanowire arrays across a broad range of tilt angles (from 38° to 72°). The optimum tilt of 53° has an improvement of 8.6% over that of vertical nanowire arrays and 80.4% over that of the ideal double-pass thin film. Tilted nanowire arrays exhibit improved absorption over the solar spectrum compared with vertical nanowires since the tilt allows for the excitation of additional modes besides the HE 1m modes that are excited at normal incidence. We also observed that tilted nanowire arrays have improved performance over vertical nanowire arrays for a large range of incidence angles (under about 60°).

  7. Study of the absorption coefficient of alpha particles to lower hybrid waves in tokamak

    SciTech Connect

    Wang, Jianbing Zhang, Xianmei Yu, Limin Zhao, Xiang

    2014-02-12

    Part of the energy of the Lower Hybrid (LH) waves may be absorbed by the α particles via the so-called perpendicular landau damping mechanism, which depends on various parameters of fusion reactors and the LH waves. In this article, we calculate the absorption coefficient γ{sub α} of LH waves due to α particles. Results show that, the γ{sub α} increases with the parallel refraction index n{sub ∥} while deceases with increasing the frequency of LH waves ω{sub LH} over a wide range. Higher background plasma temperature and toroidal magnetic field will increase the absorption, and there is a peak value of γ{sub α} when n{sub e}≈8×10{sup 19}m{sup −3} for ITER-like scenario. The thermal corrections to the cold plasma dispersion relation will change the damping rate to a certain extent under some specific conditions. We have also evaluated the fraction of LH power absorbed by the alpha particles, η ≈ 0.47% and 4.1% for an LH frequency of 5 GHz and 3.7 GHz respectively for ITER-like scenario. This work gives the effective reference for the choice of parameters of future fusion reactors.

  8. Anisotropy of chemical bonds in collagen molecules studied by X-ray absorption near-edge structure (XANES) spectroscopy.

    PubMed

    Lam, Raymond S K; Metzler, Rebecca A; Gilbert, Pupa U P A; Beniash, Elia

    2012-03-16

    Collagen type I fibrils are the major building blocks of connective tissues. Collagen fibrils are anisotropic supramolecular structures, and their orientation can be revealed by polarized light microscopy and vibrational microspectroscopy. We hypothesized that the anisotropy of chemical bonds in the collagen molecules, and hence their orientation, might also be detected by X-ray photoemission electron spectromicroscopy (X-PEEM) and X-ray absorption near-edge structure (XANES) spectroscopy, which use linearly polarized synchrotron light. To test this hypothesis, we analyzed sections of rat-tail tendon, composed of parallel arrays of collagen fibrils. The results clearly indicate that XANES-PEEM is sensitive to collagen fibril orientation and, more specifically, to the orientations of carbonyl and amide bonds in collagen molecules. These data suggest that XANES-PEEM is a promising technique for characterizing the chemical composition and structural organization at the nanoscale of collagen-based connective tissues, including tendons, cartilage, and bone.

  9. Ab Initio Study of the Effects of Surface Chemistry and Size on Xray Absorption Spectra of CdSe Nanoparticles

    NASA Astrophysics Data System (ADS)

    Whitley, Heather; Prendergast, David; Ogitsu, Tadashi; Schwegler, Eric

    2009-03-01

    The specificity of their opto-electronic properties with respect to size, shape, and surface chemistry, as well as cost-effective solution based methods of synthesis, make CdSe nanoparticles a material of choice for use in novel opto-electronic devices, such as photovoltaics and field effect transistors. Developing methods by which these nanomaterials can be systematically engineered to meet specific device goals is largely dependent on understanding how surface passivation and reconstruction affect the properties of a given nanomaterial. Xray absorption spectroscopy (XAS) is an ideal method for structural analysis, but its application to studying nanomaterial surfaces is nontrivial due to the convolution of the absorption of surface atoms with those within the nanomaterial. We utilize ab initio methods to investigate the dependence of the Cd L-edge xray absorption cross-section on the size and passivation for Cd atoms both at the surface and within the core of CdSe nanomaterials. We aim to enable routine surface characterization of CdSe nanomaterials via XAS. Prepared by LLNL under Contract DE-AC52 07NA27344.

  10. The effects of a static magnetic field on the microwave absorption of hydrogen plasma in carbon nanotubes: a numerical study

    NASA Astrophysics Data System (ADS)

    Peng, Zhi-Hua; Gong, Xue-Yu; Peng, Yan-Feng; Guo, Yan-Chun; Ning, Yan-Tao

    2012-07-01

    We theoretically investigate the microwave absorption properties of hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes under an external static magnetic field in the frequency range 0.3 GHz to 30 GHz, using the Maxwell equations in conjunction with a general expression for the effective complex permittivity of magnetized plasma known as the Appleton—Hartree formula. The effects of the external static magnetic field intensity and the incident microwave propagation direction on the microwave absorption of hydrogen plasma in CNTs are studied in detail. The numerical results indicate that the microwave absorption properties of hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes can be obviously improved when the external static magnetic field is applied to the material. It is found that the specified frequency microwave can be strongly absorbed by the hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes over a wide range of incidence angles by adjusting the external magnetic field intensity and the parameters of the hydrogen plasma.

  11. A comparative study of one- and two-photon absorption properties of pyrene and perylene diimide derivatives.

    PubMed

    Liu, Xiao-Ting; Zhao, Yang; Ren, Ai-Min; Feng, Ji-Kang

    2011-06-01

    Two important classes of organic molecules, perylene diimide (PDI) and pyrene derivatives have been found to possess relatively excellent photophysical and photochemical properties and especially high two-photon absorption cross sections (δ(T)(max)). Herein, one-photon absorption (OPA) and two-photon absorption (TPA) properties of some novel PDI and pyrene derivatives were comparatively investigated by the density functional theory (DFT) and Zerner's intermediate neglect of differential overlap (ZINDO) methods. The calculated results indicate that with respect to PDI derivatives, the maximum TPA cross-sections for pyrene compounds increase obviously, the maximum peaks of OPA and TPA spectra are blue-shifted, the ΔE(H-L) (energy gaps between the highest occupied orbital and the lowest unoccupied orbital) increase. The different π-conjugated bridges (fluorene and pyrene) and terminal groups have slight effect on the OPA properties. Nevertheless, the molecules bearing 1,6-disubstituted pyrene as the π-conjugated bridge display the largest δ(T)(max) in both series of compounds 3 and 4. Moreover, the δ(T)(max) values of molecules with benzothiazole-substituted terminal groups are larger than those of the molecules with diphenylamine, which is attributed to benzothiazole groups stabilizing the planarity of the branch parts, extending the conjugated length and increasing the π-electron delocalized extent. Furthermore, the molecular size has marked effect on OPA and TPA properties. It is worthy to mention that cruciform 8 displays the largest δ(T)(max) among all the studied molecules in the range of 600-1100 nm. This research could provide a better understanding for the origin of the linear and nonlinear optical properties, and it would be helpful to gain more information about designing two-photon absorption materials with large δ(T)(max).

  12. [Ebstein's anomaly revealed by fetal-placental anasarca. Original case study].

    PubMed

    Hadraoui, Hanaa El; Barkat, Amina

    2016-01-01

    Ebstein's anomaly is a congenital heart defect rarely revealed by fetal-placental anasarca. Our study reports an original case of Ebstein's anomaly diagnosed during fetal-placental anasarca assessment, revealed by antenatal ultrasound, objectifying hydramnios, ascites and pericardial effusion. Echocardiography allowed the identification of Ebstein's disease with significant tricuspid insufficiency, mitral regurgitation (grade 3) and patent ductus arteriosus. The closure of the ductus arteriosus associated with the decrease of pulmonary resistance using optimal ventilation allowed hemodynamic improvement and patient survival.

  13. X-ray absorption studies of metalloprotein structure: cytochrome P-450, horseradish peroxidase, plastocyanin and laccase

    SciTech Connect

    Penner-Hahn, J.E.

    1984-03-01

    Extended x-ray absorption fine structure (EXAFS) has been developed to determine the structure of metalloproteins. EXAFS data have been collected and analysed for four states in the catalytic cycle of bacterial cytochrome P-450/sub CAM/. This data demonstrates that sulfur is retained as an axial ligand in the reduced forms of the enzyme. EXAFS and edge data have been analysed for the high-valent states of horseradish peroxidase (HRP), and for high-valent iron-porphyrin model compounds. These data provide the first direct confirmation of the presence of a ferryl Fe=O coordination in HRP and in some of the model compounds. The polarized single-crystal EXAFS spectra of plastocyanin have been measured as a function of both orientation and temperature. These data demonstrate that at room temperature the relative motions of the Cu and the S(Met) are essentially uncorrelated.

  14. Studies of Y-Ba-Cu-O single crystals by x-ray absorption spectroscopy

    SciTech Connect

    Krol, A.; Ming, Z.H.; Kao, Y.H.; Nuecker, N.; Roth, G.; Fink, J.; Smith, G.C.; Erband, A.; Mueller-Vogt, G.; Karpinski, J.; Kaldis, E.; Schoenmann, K.

    1992-02-01

    The symmetry and density of unoccupied states of YBa{sub 2}Cu{sub 3}O{sub 7} YBa{sub 2}Cu{sub 4}O{sub 8} have been investigated by orientation dependent x-ray absorption spectroscopy on the O 1s edge using a bulk-sensitive fluorescence-yield-detection method. It has been found that the O 2p holes are distributed equally between the CuO{sub 2} planes and CuO chains and that the partial density of unoccupied O 2p states in the CuO{sub 2} planes are identical in both systems investigated. The upper Hubbard band has been observed in the planes but not in the chains in both systems. 18 refs.

  15. Extended X-ray absorption fine structural studies of copper and nickel ferrites

    NASA Astrophysics Data System (ADS)

    Malviya, P. K.; Sharma, P.; Mishra, Ashutosh; Bhalse, D.

    2014-09-01

    The Cu-Ni ferrites with general formula Cu1-xNix Fe2O4 (where x=0.0, 0.05, 0.10, 0. 15, 0.20) were prepared by solid state root method. X-ray, K- absorption fine structural measurements were carried out. EXAFS spectra have been recorded at the K-edge of Fe using the dispersive EXAFS (DEXAFS) beam line at 2.5GeV Indus-2 synchrotron radiation source RRCAT, Indore, India. The EXAFS data have been analysed using the computer software Athena. These have been used to determine the bond lengths in these ferrites with the help of four different methods, namely, Levy's, Lytle's and Lytle, Sayers and Stern's (LSS) methods.

  16. Absorption of NH3 on pristine and defected boron nitride nanosheets: A first principle study

    NASA Astrophysics Data System (ADS)

    Li, Hui; Chen, Zheng; Fang, Xiaoliang; Tie, Deyou

    2015-12-01

    Versatile functional groups can be connected to Boron Nitride nanosheet (BNNS) through Lewis acid/base interaction for targeted applications. However, there have been few experimental reports about Lewis acid attack at the N atoms on BNNS, so far as we see. VdW-DFT is employed in this paper to investigate the interaction between NH3 representing Lewis base and pristine or defected BNNS. Comparing the binding energy, separation and charge distribution of NH3 and pristine or defected BNNS systems, the distinctive defect in BNNS is found to be the key role in the absorption progress. Thus, it is supposed that the missing of Lewis acid and BNNS complex can be attributed to the absence of N vacancies and B-edges in BNNS.

  17. Theoretical study on the sound absorption of electrolytic solutions. I. Theoretical formulation.

    PubMed

    Yamaguchi, T; Matsuoka, T; Koda, S

    2007-04-14

    A theory is formulated that describes the sound absorption of electrolytic solutions due to the relative motion of ions, including the formation of ion pairs. The theory is based on the Kubo-Green formula for the bulk viscosity. The time correlation function of the pressure is projected onto the bilinear product of the density modes of ions. The time development of the product of density modes is described by the diffusive limit of the generalized Langevin equation, and approximate expressions for the three- and four-body correlation functions required are given with the hypernetted-chain integral equation theory. Calculations on the aqueous solutions of model electrolytes are performed. It is demonstrated that the theory describes both the activated barrier crossing between contact and solvent-separated ion pairs and the Coulombic correlation between ions.

  18. Absorption and resonance Raman study of the pyromellitic diahydride anion via density functional theory

    NASA Astrophysics Data System (ADS)

    Andruniow, T.; Pawlikowski, M.

    2000-05-01

    The electronic structure of the low-energy states of the pyromellitic diahydride (PMDA) anion is investigated in terms of the VWN (Vosco-Wilk-Nusair) the BP (Becke-Perdew) and the B3LYP density functional (DF) methods employed with 6-31G * basis sets. All the methods are shown to reproduce correctly the absorption and resonance Raman spectra in the region corresponding to the low-energy 1 2Au→1 2B3g transition. The discrepancies between the theory and experiment are attributed to a (weak) Dushinsky effect predominately due to a mixing of the ν3=1593 cm -1 and ν4=1342 cm -1 vibrations in the 1 2B3 g state of the PMDA radical.

  19. Correcting for telluric absorption: Methods, case studies, and release of the TelFit code

    SciTech Connect

    Gullikson, Kevin; Kraus, Adam; Dodson-Robinson, Sarah

    2014-09-01

    Ground-based astronomical spectra are contaminated by the Earth's atmosphere to varying degrees in all spectral regions. We present a Python code that can accurately fit a model to the telluric absorption spectrum present in astronomical data, with residuals of ∼3%-5% of the continuum for moderately strong lines. We demonstrate the quality of the correction by fitting the telluric spectrum in a nearly featureless A0V star, HIP 20264, as well as to a series of dwarf M star spectra near the 819 nm sodium doublet. We directly compare the results to an empirical telluric correction of HIP 20264 and find that our model-fitting procedure is at least as good and sometimes more accurate. The telluric correction code, which we make freely available to the astronomical community, can be used as a replacement for telluric standard star observations for many purposes.

  20. Local structure studies of some cobalt (II) complexes using extended X-ray absorption fine structure

    NASA Astrophysics Data System (ADS)

    Mishra, Ashutosh; Ninama, Samrath; Trivedi, Apurva

    2014-09-01

    Extended X-ray Absorption Fine Structure (EXAFS) analysis of Cobalt (II) complex as a ligand of 2 -methyl-3-[(bis-aniline(R) phenyl]-3H-l,5 benzodiazepine for finding local structure using conventional method .The Co(II) complexes were prepared by chemical root method. The EXAFS spectra were recorded at Cobalt K-edge i.e.; 7709 eV using Dispersive EXFAS beam line at 2.5GeV Indus-2 Synchrotron Radiation Source(SRS) at RRCAT, Indore, India. The recorded EXAFS data were analysed using the computer software Athena for determine the nearest neighbouring distances (bond lengths) of these complexes with conventional methods and it compared with Fourier transform(FT) analysis. The Fourier Transform convert EXAFS data signal into r-space or k-space. This is useful for visualizing the major contributions to the EXAFS spectrum.

  1. [Studies on the remote measurement of the emission of formaldehyde by mobile differential optical absorption spectroscopy].

    PubMed

    Wu, Feng-Cheng; Xie, Pin-Hua; Li, Ang; Si, Fu-Qi; Dou, Ke; Liu, Yu; Xu, Jin; Wang, Jie

    2011-11-01

    Formaldehyde (HCHO) is the most abundant carbonyl compounds that play an important role in atmospheric chemistry and photochemical reactions. Formaldehyde is an important indicator of atmospheric reactivity and urban atmospheric aerosol precursors. In the present paper, the emission of formaldehyde from chemical area was measured using the mobile differential optical absorption spectroscopy (DOAS). This instrument uses the zenith scattered sunlight as the light source with successful sampling in the area loop. Vertical column density was retrieved by this system, combined with the meteorological wind field and car speed information, the emission of formaldehyde in the area was estimated. The authors carried out the measuring experiment in one chemical plant in Beijing using this technology. The result showed that the average value of the flux of formaldehyde in this area was 605 kg x h(-1) during the measuring period.

  2. An induction heater device for studies of magnetic hyperthermia and specific absorption ratio measurements.

    PubMed

    Cano, M E; Barrera, A; Estrada, J C; Hernandez, A; Cordova, T

    2011-11-01

    The development of a device for generating ac magnetic fields based on a resonant inverter is presented, which has been specially designed to carry out experiments of magnetic hyperthermia. By determining the electric current in the LC resonant circuit, a maximum intensity of magnetic field around of 15 mT is calculated, with a frequency around of 206 kHz. This ac magnetic field is able to heat powdered magnetic materials embedded in biological systems to be used in biomedical applications. Indeed, in order to evaluate the sensitivity of the device we also present the measurements of the specific absorption rate in phantoms performed with commercially prepared Fe(3)O(4) and distilled water at different concentrations.

  3. Pyrolysis of Organo-As Precursors Studied by Surface Photo-Absorption

    NASA Astrophysics Data System (ADS)

    Yamauchi, Yoshiharu; Kobayashi, Naoki

    1991-12-01

    Surface Photo-Absorption (SPA) is an in situ optical technique for monitoring growth processes. It can measure the dynamics of surface reaction on a growth surface. We use SPA to investigate the pyrolysis of As precursors such as organo-arsenic and arsine (AsH3), and estimate the decomposition activation energies of these As precursors. The results indicate that tertiary butylarsine (tBAs), diethylarsine (DEAsH) and AsH3 which all contain a hydrogen-As bond, have lower activation energies than might be expected from the average bond strength, indicating that their pyrolysis processes are well catalyzed by the GaAs surface. On ther other hand, trialkylarsine such as trimethylarsine (TMAs) and triethylarsine (TEAs) have high activation energies. As expected from the low activation energy, high-quality GaAs can be grown using tBAs.

  4. Note: Sample chamber for in situ x-ray absorption spectroscopy studies of battery materials

    SciTech Connect

    Pelliccione, CJ; Timofeeva, EV; Katsoudas, JP; Segre, CU

    2014-12-01

    In situ x-ray absorption spectroscopy (XAS) provides element-specific characterization of both crystalline and amorphous phases and enables direct correlations between electrochemical performance and structural characteristics of cathode and anode materials. In situ XAS measurements are very demanding to the design of the experimental setup. We have developed a sample chamber that provides electrical connectivity and inert atmosphere for operating electrochemical cells and also accounts for x-ray interactions with the chamber and cell materials. The design of the sample chamber for in situ measurements is presented along with example XAS spectra from anode materials in operating pouch cells at the Zn and Sn K-edges measured in fluorescence and transmission modes, respectively. (C) 2014 AIP Publishing LLC.

  5. Electronic structure of fluorinated multiwalled carbon nanotubes studied using x-ray absorption and photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Brzhezinskaya, M. M.; Muradyan, V. E.; Vinogradov, N. A.; Preobrajenski, A. B.; Gudat, W.; Vinogradov, A. S.

    2009-04-01

    This paper presents the results of combined investigation of the chemical bond formation in fluorinated multiwalled carbon nanotubes (MWCNTs) with different fluorine contents (10-55wt%) and reference compounds (highly oriented pyrolytic graphite crystals and “white” graphite fluoride) using x-ray absorption and photoelectron spectroscopy at C1s and F1s thresholds. Measurements were performed at BESSY II (Berlin, Germany) and MAX-laboratory (Lund, Sweden). The analysis of the soft x-ray absorption and photoelectron spectra points to the formation of covalent chemical bonding between fluorine and carbon atoms in the fluorinated nanotubes. It was established that within the probing depth (˜15nm) of carbon nanotubes, the process of fluorination runs uniformly and does not depend on the fluorine concentration. In this case, fluorine atoms interact with MWCNTs through the covalent attachment of fluorine atoms to graphene layers of the graphite skeleton (phase 1) and this bonding is accompanied by a change in the hybridization of the 2s and 2p valence electron states of the carbon atom from the trigonal (sp2) to tetrahedral (sp3) hybridization and by a large electron transfer between carbon an fluorine atoms. In the MWCNT near-surface region the second fluorine-carbon phase with weak electron transfer is formed; it is located mainly within two or three upper graphene monolayers, and its contribution becomes much poorer as the probing depth of fluorinated multiwalled carbon nanotubes (F-MWCNTs) increases. The defluorination process of F-MWCNTs on thermal annealing has been investigated. The conclusion has been made that F-MWCNT defluorination without destruction of graphene layers is possible.

  6. Kolliphor surfactants affect solubilization and bioavailability of fenofibrate. Studies of in vitro digestion and absorption in rats.

    PubMed

    Berthelsen, Ragna; Holm, René; Jacobsen, Jette; Kristensen, Jakob; Abrahamsson, Bertil; Müllertz, Anette

    2015-04-06

    Selection of excipients for drug formulations requires both intellectual and experimental considerations as many of the used excipients are affected by physiological factors, e.g., they may be digested by pancreatic enzymes in the gastrointestinal tract. In the present paper we have looked systematically into the differences between Kolliphor ELP, EL, and RH40 and how they affect the bioavailability of fenofibrate, through pharmacokinetic studies in rats and in vitro lipolysis studies. The study design was made as simple as possible to avoid confounding factors, for which reason the tested formulations only comprised an aqueous micellar solution of the model drug (fenofibrate) in varying concentrations (2-25% (w/v)) of the three tested surfactants. Increased concentrations of Kolliphor ELP and EL led to increased fenofibrate AUC0-24h values. For the Kolliphor RH40 formulations, an apparent fenofibrate absorption optimum was seen at 15% (w/v) surfactant, displaying both the highest AUC0-24h and Cmax. The reduced absorption of fenofibrate from the formulation containing the highest level of surfactant (25% w/v) was thought to be caused by some degree of trapping within Kolliphor RH40 micelles. In vitro, Kolliphor ELP and EL were found to be more prone to digestion than Kolliphor RH40, though not affecting the in vivo results. The highest fenofibrate bioavailability was attained from formulations with high Kolliphor ELP/EL levels (25% (w/v)), indicating that these surfactants are the better choice for solubilizing fenofibrate in order to increase the absorption upon oral administration. Due to drug dependent effects of the different types of Kolliphor, more studies are recommended in order to understand which type of Kolliphor is best suited for a given drug.

  7. Study of the Photodegradation Process of Vitamin E Acetate by Optical Absorption, Fluorescence, and Thermal Lens Spectroscopy

    NASA Astrophysics Data System (ADS)

    Tiburcio-Moreno, J. A.; Marcelín-Jiménez, G.; Leanos-Castaneda, O. L.; Yanez-Limon, J. M.; Alvarado-Gil, J. J.

    2012-11-01

    The stability of vitamin E acetate exposed to ultraviolet (UV) light was studied using three spectroscopic methods. An ethanol solution of vitamin E acetate was treated with either UVC light (254 nm) or UVA light (366 nm) during a period of 10 min followed by a study of UV-Vis optical absorption, then by fluorescence spectroscopy excitation by UV radiation at either 290 nm or 368 nm and, finally the solution was studied by thermal lens spectroscopy. Immediately, the same solution of vitamin E acetate was subjected to the UV irradiation process until completion of six periods of irradiation and measurements. UVC light treatment induced the appearance of a broad absorption band in the range of 310 nm to 440 nm with maximum absorbance at 368 nm, which progressively grew as the time of the exposure to UVC light increases. In contrast, UVA light treatment did not affect the absorption spectra of vitamin E acetate. Fluorescence spectra of the vitamin E acetate (without UV light treatment) showed no fluorescence when excited with 368 nm while exciting with 290 nm, an intense and broad emission band (300 nm to 440 nm) with a maximum at 340 nm appeared. When vitamin E acetate was treated with UVC light, this emission band progressively decreased as the time of the UVC light irradiation grew. No signal from UV-untreated vitamin E acetate could be detected by the thermal lens method. Interestingly, as the time of the UVC light treatment increased, the thermal lens signal progressively grew. Additional experiments performed to monitor the time evolution of the process during continuous UVC treatment of the vitamin E acetate using thermal lens spectroscopy exhibited a progressive increase of the thermal lens signal reaching a plateau at about 8000 s. This study shows that the vitamin E acetate is stable when it is irradiated with UVA light, while the irradiation with UVC light induces the formation of photodegradation products. Interestingly, this photodegradation process using

  8. Structural Studies of the Alzheimer's Amyloid Precursor Protein Copper-Binding Domain Reveal How It Binds Copper Ions

    SciTech Connect

    Kong, G.K.-W.; Adams, J.J.; Harris, H.H.; Boas, J.F.; Curtain, C.C.; Galatis, D.; Master, C.L.; Barnham, K.J.; McKinstry, W.J.; Cappai, R.; Parker, M.W.; /Sydney U. /Monash U. /Melbourne U.

    2007-07-09

    Alzheimer's disease (AD) is the major cause of dementia. Amyloid {beta} peptide (A {beta}), generated by proteolytic cleavage of the amyloid precursor protein (APP), is central to AD pathogenesis. APP can function as a metalloprotein and modulate copper (Cu) transport, presumably via its extracellular Cu-binding domain (CuBD). Cu binding to the CuBD reduces A{beta} levels, suggesting that a Cu mimetic may have therapeutic potential. We describe here the atomic structures of apo CuBD from three crystal forms and found they have identical Cu-binding sites despite the different crystal lattices. The structure of Cu[2+]-bound CuBD reveals that the metal ligands are His147, His151, Tyrl68 and two water molecules, which are arranged in a square pyramidal geometry. The site resembles a Type 2 non-blue Cu center and is supported by electron paramagnetic resonance and extended X-ray absorption fine structure studies. A previous study suggested that Met170 might be a ligand but we suggest that this residue plays a critical role as an electron donor in CuBDs ability to reduce Cu ions. The structure of Cu[+]-bound CuBD is almost identical to the Cu[2+]-bound structure except for the loss of one of the water ligands. The geometry of the site is unfavorable for Cu[+], thus providing a mechanism by which CuBD could readily transfer Cu ions to other proteins.

  9. Inhibition by Natural Dietary Substances of Gastrointestinal Absorption of Starch and Sucrose in Rats and Pigs: 1. Acute Studies

    PubMed Central

    Preuss, Harry G.; Echard, Bobby; Bagchi, Debasis; Stohs, Sidney

    2007-01-01

    Rapid gastrointestinal absorption of refined carbohydrates (CHO) is linked to perturbed glucose-insulin metabolism that is, in turn, associated with many chronic health disorders. We assessed the ability of various natural substances, commonly referred to as “CHO blockers,” to influence starch and sucrose absorption in vivo in ninety-six rats and two pigs. These natural enzyme inhibitors of amylase/sucrase reportedly lessen breakdown of starches and sucrose in the gastrointestinal tract, limiting their absorption. To estimate absorption, groups of nine SD rats were gavaged with water or water plus rice starch and/or sucrose; and circulating glucose was measured at timed intervals thereafter. For each variation in the protocol a total of at least nine different rats were studied with an equal number of internal controls on three different occasions. The pigs rapidly drank CHO and inhibitors in their drinking water. In rats, glucose elevations above baseline over four hours following rice starch challenge as estimated by area-under-curve (AUC) were 40%, 27%, and 85% of their internal control after ingesting bean extract, hibiscus extract, and l-arabinose respectively in addition to the rice starch. The former two were significantly different from control. L-Arabinose virtually eliminated the rising circulating glucose levels after sucrose challenge, whereas hibiscus and bean extracts were associated with lesser decreases than l-arabinose that were still significantly lower than control. The glucose elevations above baseline over four hours in rats receiving sucrose (AUC) were 51%, 43% and 2% of control for bean extract, hibiscus extract, and L-arabinose, respectively. Evidence for dose-response of bean and hibiscus extracts is reported. Giving the natural substances minus CHO challenge caused no significant changes in circulating glucose concentrations, indicating no major effects on overall metabolism. A formula combining these natural products significantly

  10. Geometric Structure Determination of N694C Lipoxygenase: a Comparative Near-Edge X-Ray Absorption Spectroscopy And Extended X-Ray Absorption Fine Structure Study

    SciTech Connect

    Sarangi, R.; Hocking, R.K.; Neidig, M.L.; Benfatto, M.; Holman, T.R.; Solomon, E.I.; Hodgson, K.O.; Hedman, B.

    2009-05-27

    The mononuclear nonheme iron active site of N694C soybean lipoxygenase (sLO1) has been investigated in the resting ferrous form using a combination of Fe-K-pre-edge, near-edge (using the minuit X-ray absorption near-edge full multiple-scattering approach), and extended X-ray absorption fine structure (EXAFS) methods. The results indicate that the active site is six-coordinate (6C) with a large perturbation in the first-shell bond distances in comparison to the more ordered octahedral site in wild-type sLO1. Upon mutation of the asparigine to cystiene, the short Fe-O interaction with asparigine is replaced by a weak Fe-(H{sub 2}O), which leads to a distorted 6C site with an effective 5C ligand field. In addition, it is shown that near-edge multiple scattering analysis can give important three-dimensional structural information, which usually cannot be accessed using EXAFS analysis. It is further shown that, relative to EXAFS, near-edge analysis is more sensitive to partial coordination numbers and can be potentially used as a tool for structure determination in a mixture of chemical species.

  11. 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

  12. Energy Absorption in a Shear-Thickening Fluid

    NASA Astrophysics Data System (ADS)

    Afeshejani, Seyed Hossein Amiri; Sabet, Seyed Ali Reza; Zeynali, Mohammad Ebrahim; Atai, Mohammad

    2014-12-01

    This study investigates energy absorption in a shear-thickening fluid (STF) containing nano-size fumed silica as a suspending material. Fumed silica particles in 20, 30, and 40 wt.% were used in polyethylene glycol and ethylene glycol. Three areas were studied, namely: energy absorption of STF pre-impregnated aramid fabric, neat STF under high-velocity impact, and flexible foam soaked in STF under low-velocity drop weight impact. Results showed moderate energy absorption in STF pre-impregnated aramid fabric compared to dry fabric. High-velocity impact tests also revealed higher fabric weave density, and multi-layered target plays vital role in optimum performance of SFT impregnated targets. High-velocity impact tests on the neat STF showed good energy absorption at velocities near STF critical shear rate. Low-velocity drop weight impact test on flexible foam soaked in STF also indicated significant energy absorption.

  13. Extended x-ray absorption fine structure spectroscopy and first-principles study of SnWO4

    NASA Astrophysics Data System (ADS)

    Kuzmin, A.; Anspoks, A.; Kalinko, A.; Timoshenko, J.; Kalendarev, R.

    2014-04-01

    The local atomic structure in α- and β-SnWO4 was studied by synchrotron radiation W L3-edge x-ray absorption spectroscopy at 10 and 300 K. Strongly distorted WO6 octahedra were found in α-SnWO4, whereas nearly regular WO4 tetrahedra were observed in β-SnWO4, confirming previous results. The structural results obtained were supported by the first-principles calculations, suggesting that the second-order Jahn-Teller effect is responsible for octahedral distortion.

  14. Effect of Pressure on Magnetoelastic Coupling in 3d Metal Alloys Studied with X-Ray Absorption Spectroscopy

    SciTech Connect

    Pascarelli, S.; Trapananti, A.; Mathon, O.; Aquilanti, G.; Ruffoni, M. P.; Ostanin, S.; Staunton, J. B.; Pettifer, R. F.

    2007-12-07

    Using x-ray absorption spectroscopy, we have studied the effect of pressure on femtometer-scale bond strain due to anisotropic magnetostriction in a thin FeCo film. At 7 GPa local magnetostrictive strain is found to be larger than at ambient, in agreement with spin-polarized ab initio electronic structure calculations, but contrary to the expected effect of compression on bond stiffness. The availability of high pressure data on local magnetostrictive strain opens new capabilities for validating theoretical predictions and can lead to the development of materials with the desired properties.

  15. A reaction cell with sample laser heating for in situ soft X-ray absorption spectroscopy studies under environmental conditions.

    PubMed

    Escudero, Carlos; Jiang, Peng; Pach, Elzbieta; Borondics, Ferenc; West, Mark W; Tuxen, Anders; Chintapalli, Mahati; Carenco, Sophie; Guo, Jinghua; Salmeron, Miquel

    2013-05-01

    A miniature (1 ml volume) reaction cell with transparent X-ray windows and laser heating of the sample has been designed to conduct X-ray absorption spectroscopy studies of materials in the presence of gases at atmospheric pressures. Heating by laser solves the problems associated with the presence of reactive gases interacting with hot filaments used in resistive heating methods. It also facilitates collection of a small total electron yield signal by eliminating interference with heating current leakage and ground loops. The excellent operation of the cell is demonstrated with examples of CO and H2 Fischer-Tropsch reactions on Co nanoparticles.

  16. A study on transmission characteristics and specific absorption rate using impedance-matched electrodes for various human body communication.

    PubMed

    Machida, Yuta; Yamamoto, Takahiko; Koshiji, Kohji

    2013-01-01

    Human body communication (HBC) is a new communication technology that has presented potential applications in health care and elderly support systems in recent years. In this study, which is focused on a wearable transmitter and receiver for HBC in a body area network (BAN), we performed electromagnetic field analysis and simulation using the finite difference time domain (FDTD) method with various models of the human body. Further we redesigned a number of impedance-matched electrodes to allow transmission without stubs or transformers. The specific absorption rate (SAR) and transmission characteristics S21 of these electrode structures were compared for several models.

  17. Interaction of chlorpromazine and trifluoperazine with ionic micelles: electronic absorption spectroscopy studies

    NASA Astrophysics Data System (ADS)

    Caetano, Wilker; Tabak, Marcel

    1999-10-01

    The characteristics of binding of two phenothiazine antipsychotic drugs, namely, chlorpromazine (CPZ) and trifluoperazine (TFP), to cationic cetyltrimethylammonium chloride (CTAC), zwitterionic N-hexadecyl- N, N-dimethyl-3-ammonio-1-propanesulfonate (HPS), neutral t-octylphenoxypolyethoxyethanol (TRITON X-100) and polyoxyethylene dodecyl ether (Brij-35) micelles were investigated using electronic absorption spectroscopy. Binding constants Kb and p Ka values of drugs in micelles were estimated using the red shifts of the maximum absorption upon alkalization or in the presence of detergents. The p Ka of TFP seems to be shifted by 2.5-4.1 units to lower values in the presence of different surfactants as compared to the experimental value of p Ka obtained in buffer which is around 7.0. Consideration of the second p Ka around 4.0 reported in the literature for TFP leads to a better rationalization of p Ka changes for this compound. The changes in p Ka contributed by electrostatic effects are all positive, small for CTAC (+0.2), and greater for HPS (+0.9). For CPZ the p Ka shift due to its interaction with micelles is in the 0.7-2.3 range, the direction of the shift depending on the charge of the polar head. The electrostatic contribution for the shift is great for CTAC (-0.8) and smaller for HPS (+0.2). This result suggests a more polar localization in the micelle of CPZ as compared to TFP. The values of binding constants Kb for TFP and CPZ in different protonation states show that electrostatic interactions are essential in the affinity of the drugs to micelles bearing different charges on their headgroups (CTAC, HPS). Data for Brij-35 demonstrate that the additional charge on the TFP ring at pH 2.0 leads to a decrease of binding constant probably due to the repulsion of the phenothiazine ring from the protons accumulated at the polar head of the micelle at acidic pH values. For this micelle at pH 5.0 TFP has a Kb 3-fold greater than that for CPZ while at pH 2.0 Kb for

  18. Microarray analysis of high-glucose diet-induced changes in mRNA expression in jejunums of C57BL/6J mice reveals impairment in digestion, absorption.

    PubMed

    Du, Dan; Shi, Yong-Hui; Le, Guo-Wei

    2010-04-01

    Long term intake of high-glucose diet (HGD) may induce many diseases such as dyslipidemia, fatty liver and diabetes disease. Most of the research for molecular mechanisms of the association between HGD and the above diseases focus on the metabolism of glucose and lipid. However, there are few studies on molecular mechanism of the effect of HGD on digestion and absorption. We used HGD (containing 20% glucose) to feed C57BL/6J mice for 4 weeks, detected the expressions of 13,098 genes in jejunums of C57BL/6J mice with DNA microarray. Microarray analysis showed the expression of genes related to digestive enzyme, gastrointestinal peptide and nutrient transporters were significantly changed, which indicated that HGD induced the suppression of digestive enzyme gene expression, attenuation of alimentary tract movement and nutrient transportation. In one word, the microarray analysis suggested that HGD impaired the function of digestion and absorption in jejunum of C57BL/6J mice. We validated our microarray findings by conducting real-time RT-PCR assays on selected genes and detecting the activities of disaccharidases such as lactase, maltase and sucrase in jejunum of C57BL/6J mice.

  19. X-ray absorption spectroscopy studies of reactions of technetium, uranium and neptunium with mackinawite.

    PubMed

    Livens, Francis R; Jones, Mark J; Hynes, Amanda J; Charnock, John M; Mosselmans, J Fred W; Hennig, Christoph; Steele, Helen; Collison, David; Vaughan, David J; Pattrick, Richard A D; Reed, Wendy A; Moyes, Lesley N

    2004-01-01

    Technetium, uranium and neptunium may all occur in the environment in more than one oxidation state (IV or VII, IV or VI and IV or V respectively). The surface of mackinawite, the first-formed iron sulfide phase in anoxic conditions, can promote redox changes so a series of laboratory experiments were carried out to explore the interactions of Tc, U and Np with this mineral. The products of reaction were characterised using X-ray absorption spectroscopy. Technetium, added as TcO4(-), is reduced to oxidation state IV and forms a TcS(2)-like species. On oxidation of the mackinawite in air to form goethite, Tc remains in oxidation state IV but in an oxide, rather than a sulfide environment. At low concentrations, uranium forms uranyl surface complexes on oxidised regions of the mackinawite surface but at higher concentrations, the uranium promotes surface oxidation and forms a mixed oxidation state oxide phase. Neptunium is reduced to oxidation IV and forms a surface complex with surface sulfide ions. The remainder of the Np coordination sphere is filled with water molecules or hydroxide ions.

  20. An X-ray diffraction and X-ray absorption spectroscopy joint study of neuroglobin.

    PubMed

    Arcovito, Alessandro; Moschetti, Tommaso; D'Angelo, Paola; Mancini, Giordano; Vallone, Beatrice; Brunori, Maurizio; Della Longa, Stefano

    2008-07-01

    Neuroglobin (Ngb) is a member of the globin family expressed in the vertebrate brain, involved in neuroprotection. A combined approach of X-ray diffraction (XRD) on single crystal and X-ray absorption spectroscopy (XAS) in solution, allows to determine the oxidation state and the structure of the Fe-heme both in the bis-histidine and the CO-bound (NgbCO) states. The overall data demonstrate that under X-ray the iron is photoreduced fairly rapidly, and that the previously reported X-ray structure of ferric Ngb [B. Vallone, K. Nienhaus, M. Brunori, G.U. Nienhaus, Proteins 56 (2004) 85-92] very likely refers to a photoreduced species indistinguishable from the dithionite reduced protein. Results from the XAS analysis of NgbCO in solution are in good agreement with XRD data on the crystal. However prolonged X-ray exposure at 15K determines CO release. This preliminary result paves the way to experiments aimed at the characterization of pentacoordinate ferrous Ngb, the only species competent in binding external ligands such as O2, CO or NO.

  1. Soft x-ray absorption spectroscopy studies of doped Pr-containing cuprates

    NASA Astrophysics Data System (ADS)

    Chen, J. M.; Liu, S. J.; Chang, C. F.; Lin, J.-Y.; Gou, Y. S.; Yang, H. D.

    2003-01-01

    Using high-resolution O K-edge x-ray absorption near-edge-structure (XANES) spectroscopy, unoccupied states of the YxPr1-xBa2Cu3O7 (x=0 1) thin films and polycrystalline Pr1-xCaxBa2Cu3O7 (x=0 0.3) as well as R0.8Pr0.2Ba2Cu3O7 samples (R=Tm, Dy, Gd, and Sm) are investigated. In YxPr1-xBa2Cu3O7, hole numbers in the CuO2 planes decrease significantly with increasing Pr doping level. Hole carriers generated via Ca doping in Pr1-xCaxBa2Cu3O7 are directed predominantly into both the Zhang-Rice and Fehrenbacher-Rice (FR) states, while those in the CuO3 ribbons remain almost unchanged with Ca substitution. In R0.8Pr0.2Ba2Cu3O7, the hole content in the CuO2 planes decreases monotonically with increasing ionic size of the R3+ ions, confirming the hole depletion effect based on the Pr 4f O 2p hybridization. We demonstrate the spectroscopic evidence of the existence of the FR states. The present XANES results provide a deeper understanding of the nature of hybridization and the origin of the ionic size effect.

  2. X-ray absorption spectroscopy study of a copper-containing material after thermal treatment.

    PubMed

    Wei, Y-L; Huang, M-Y; Wang, H-C; Huang, H-C; Lee, J-F

    2006-04-17

    Thermal immobilization of copper contaminant in a copper-containing solid material collected from local copper smelting and foundry area is investigated in the present work. X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) are employed for copper speciation. XAS results indicate that cupric hydroxide is the major copper species in the solid material dried at 105 degrees C. After being subjected to a 500 degrees C thermal process, cupric hydroxide still remains as the main copper species, but some Cu(II) is chemically reduced to Cu(I). More cupric hydroxide is progressively converted to Cu(I) as the sample was heated at 1100 degrees C than that heated at 500 degrees C. The sample heated at 500 degrees C is in its original powder form. However, thermal treatment at 1100 degrees C transforms the powder into a hardened granule-like form that is much bigger in size and difficult to be ground into powders. The sample is sintered with the sparingly soluble cuprous oxide and elemental copper being encapsulated inside. Toxicity characteristic leaching procedure (TCLP) results depict that amount of copper leached from the sample (containing 133,000 mg copper kg-1) heated at 1100 degrees C for 2 h is considerably minor, being 367 mg copper kg-1.

  3. Plasmon resonances of Ag(001) and Ag(111) studied by power density absorption and photoyield

    NASA Astrophysics Data System (ADS)

    Raseev, Georges

    2013-09-01

    This paper models the surface and bulk plasmon resonances in photoabsorption and photoelectron spectra (PES) of the Ag(001) and the Ag(111) surfaces in the region of 2.8-10 eV excited with a p or transverse magnetic linearly polarized laser incident at 45°. Using the recently developed vector potential from electron density-coupled integro-differential equations (VPED-CIDE, [1,2]) model, we calculate the electron escaping probability from the power density absorption, Feibelman's parameter d⊥, the reflectance and the Fermi PE cross section. In the PES experiment the work function is lowered from 4.5 to 2.8 eV by adsorption of sodium. In our model, this lowering is introduced by adding a phenomenological term to the DFT-LDA model potential of Chulkov et al. [3]. For both Ag(001) and Ag(111), the calculated observables display two plasmon resonances, the multipole surface at 3.70 eV and the bulk at 3.90 eV, in fair agreement with the experimental PES of Barman et al. [4,5] and the reflectance. Except for the Fermi PE cross section of Ag(001) which does not display the multipole surface plasmon resonance at 3.70 eV. This poor result is probably due to a poor calculation of the conduction band wave functions obtained from the Schrödinger equation using the modified DFT-LDA model potential of Chulkov et al.

  4. The Nissl substance of living and fixed spinal ganglion cells. II. An ultraviolet absorption study.

    PubMed

    DEITCH, A D; MOSES, M J

    1957-05-25

    Living chick spinal ganglion neurons grown for 19 to 25 days in vitro were photographed with a color-translating ultraviolet microscope (UV-91) at 265, 287, and 310 mmicro. This instrument was unique in permitting rapid accumulation of ultraviolet information with minimal damage to the cell. In the photographs taken at 265 mmicro of the living neurons, discrete ultraviolet-absorbing cytoplasmic masses were observed which were found to be virtually unchanged in appearance after formalin fixation. These were identical with the Nissl bodies of the same cells seen after staining with basic dyes. The correlation of ultraviolet absorption, ribonuclease extraction, and staining experiments with acid and basic dyes confirmed the ribonucleoprotein nature of these Nissl bodies in the living and fixed cells. No change in distribution or concentration of ultraviolet-absorbing substance was observed in the first 12 ultraviolet photographs of a neuron, and it is concluded that the cells had not been subjected to significant ultraviolet damage during the period of photography. On the basis of these observations, as well as previous findings with phase contrast microscopy, it is concluded that Nissl bodies preexist in the living neuron as discrete aggregates containing high concentrations of nucleoprotein.

  5. [Study on in vitro release and percutaneous absorption of Huoxue Zhitong gel].

    PubMed

    Yu, Juan; Du, Mao-bo; Liu, Shu-zhi; Song, Li-hua; Shen, Shuo; Liu, Dao-fang

    2014-12-01

    To evaluate in vitro release and transdermal behaviors of Huoxue Zhitong gel, modified Franz diffusion cell methods was applied to investigate in vitro transdermal absorption of Huoxue Zhitong gel and the content of paeonolan in receptor fluid composed of PEG400%-95% ethanol-water (l:3:6)were determined by HPLC. The results were processed and different equations were fitted. The release law were in accordance with Weibull equation and the fitting equation was In[-1/(1 - Q)] = -0.790 51nt - 1.7012 (r = 0.9809). In 8 hours, cumulative release of paeonol was 85. 18% and the release rate was 2.827 µg . cm-2 h-1. Transdermal actions were consistent with zero-level model fit and the fitting equation was Q(t) = 1.7579t + 0. 7213 (r = 0.9991). In 8 hours, cumulative transdermal rate and transmission rate of paeonol was 54. 85%, 1. 820 µg . cm-2 h-1. So the Huoxue Zhitong gel had a good release and transdermal properties.

  6. X-ray absorption studies of uranium sorption on mineral substrates

    SciTech Connect

    Hudson, E.A.; Terminello, L.J.; Viani, B.E.; Reich, T.; Bucher, J.J.; Shuh, D.K.; Edelstein, N.M.

    1995-09-01

    Aqueous transport of actinides in the geosphere can be significantly retarded by sorption and/or precipitation upon mineral surfaces. Despite the importance of this effect to environmental remediation efforts and nuclear waste repository design, there is only limited direct knowledge about the microscopic nature of the actinide-mineral interaction. Here, uranium L{sub 3}-edge x-ray absorption spectra have been measured for uranium-mineral sorption systems. An expansible layer silicate, vermiculite, was treated to obtain a collapsed phase, thereby limiting access to the interior cation exchange sites. Samples were prepared by exposing the finely powdered mineral, in the natural and modified form, to aqueous solutions of uranyl chloride. EXAFS spectra of the encapsulated samples were measured at the Stanford Synchrotron Radiation Laboratory. Results indicate that the uranyl ion possesses a more symmetric local structure for the natural vermiculite than for the collapsed form, suggesting structural differences between uranyl species within the interlayer regions of vermiculite and on the external surfaces.

  7. Optimization studies on TFC membrane for Membrane Gas Absorption (MGA) application

    NASA Astrophysics Data System (ADS)

    Sunarti, A. R.; Ahmad, A. L.

    2013-06-01

    A thin film composite (TFC) membrane has been developed by coating polydimethylsiloxane (PDMS) and glutaraldehyde (GH) on a surface porous polyvinylideneflouride (PVDF) membrane for membrane gas absorption (MGA) application. The optimum conditions for dip coating method were determined using response surface methodology (RSM). A central composite design (CCD) was used to investigate the effects of two independent factors, which PDMS concentrations (wt%) and dipping time (s) of GH on the four specific responses which are CO2 and N2 permeances, selectivity and contact angle (CA) value. The optimum conditions for PDMS concentration and GH dipping time are 10 wt% and 19 s, respectively where 354 GPU for CO2 permeance, 66 GPU for N2 permeance, 5.4 of selectivity and 132° of CA value were obtained. Through atomic force microscopy (AFM) analysis, the result shown the root mean square roughness (Rms) of the TFC membrane was 381 nm and it was double from untreated membrane Rms value. Therefore, the roughness of the surface membrane contributed to the performance of the separation in the process flow such as in MGA application. By coating PDMS, hydrophobicity of the surface membrane was improved as well

  8. Optical absorption and emission spectroscopy studies of ammonia-containing plasmas

    NASA Astrophysics Data System (ADS)

    Kang, S. J.; Donnelly, V. M.

    2007-05-01

    The chemistry of NH3/Ar/He plasmas was investigated, using a combination of ultraviolet (UV) optical absorption spectroscopy (OAS) and optical emission spectroscopy (OES). Absolute NH3 number densities in 1 Torr plasmas were measured by OAS as a function of inductively coupled plasma power and substrate heater temperature (Th). OES and actinometry were used to determine semi-quantitative H-atom density. A 'self-actinometry' method was introduced to measure the absolute number density of N2 that formed following the dissociation of NH3 and secondary reactions. In this approach, small amounts of N2 are added to the NH3-containing plasma, leading to an increase in the N2(C 3 Πu → B 3 Πg) emission intensity. This provides an accurate calibration factor for converting relative N2 emission intensities into absolute number densities. The number densities of NH3 were found to decrease with increasing power and Th, reaching >90% dissociation at 400 W and 900 K. N2 densities increased with power and Th. The majority of dissociated NH3 was converted to N2 (i.e. the total nitrogen content was conserved in the sum of these two species). The major hydrogen-containing species appeared to be H2; however, a substantial amount of H-atoms (comparable to H2) was present at the highest powers.

  9. ESR, optical absorption, and luminescence studies of the peroxy-radical defect in topaz

    SciTech Connect

    Priest, V.; Cowan, D.L. ); Yasar, H.; Ross, F.K. , University of Missouri-Columbia, Columbia, Missouri )

    1991-11-01

    Fast-neutron irradiation of natural topaz crystals produces a single paramagnetic radiation damage center in high concentration. ESR of this center shows a holelike spectrum with {ital S}=1/2 and a strongly anisotropic {ital g} tensor: {ital g}{sub {ital x}{ital x}}=2.0027, {ital g}{sub {ital y}{ital y}}=2.0055, and {ital g}{sub {ital z}{ital z}}=2.0407. We identify this defect as an intrinsic O{sub 2}{sup {minus}} center in the form of a peroxy radical. The orientation of the {ital g} tensor helps confirm this assignment, as does the extraordinary thermal stability; annealing temperatures near 800 {degree}C are required for complete removal. Two uv absorption bands are associated with the peroxy radical, each with oscillator strength near 0.09. Pumping in the higher energy band leads to a polarization-sensitive 2.5-eV luminescence; the other uv band apparently relaxes nonradiatively.

  10. Coupling MD Simulations and X-ray Absorption Spectroscopy to Study Ions in Solution

    SciTech Connect

    Marcos, E. Sanchez; Beret, E. C.; Martinez, J. M.; Pappalardo, R. R.; Ayala, R.; Munoz-Paez, A.

    2007-11-29

    The structure of ionic solutions is a key-point in understanding physicochemical properties of electrolyte solutions. Among the reduced number of experimental techniques which can supply direct information on the ion environment, X-ray Absorption techniques (XAS) have gained importance during the last decades although they are not free of difficulties associated to the data analysis leading to provide reliable structures. Computer simulations of ions in solution is a theoretical alternative to provide information on the solvation structure. Thus, the use of computational chemistry can increase the understanding of these systems although an accurate description of ionic solvation phenomena represents nowadays a significant challenge to theoretical chemistry. We present: (a) the assignment of features in the XANES spectrum to well defined structural motif in the ion environment, (b) MD-based evaluation of EXAFS parameters used in the fitting procedure to make easier the structural resolution, and (c) the use of the agreement between experimental and simulated XANES spectra to help in the choice of a given intermolecular potential for Computer Simulations. Chemical problems examined are: (a) the identification of the second hydration shell in dilute aqueous solutions of highly-charged cations, such as Cr{sup 3+}, Rh{sup 3+}, Ir{sup 3+}, (b) the invisibility by XAS of certain structures characterized by Computer Simulations but exhibiting high dynamical behavior and (c) the solvation of Br{sup -} in acetonitrile.

  11. Study of gain and photoresponse characteristics for back-illuminated separate absorption and multiplication GaN avalanche photodiodes

    SciTech Connect

    Wang, Xiaodong; Pan, Ming; Hou, Liwei; Xie, Wei; Hu, Weida Xu, Jintong; Li, Xiangyang; Chen, Xiaoshuang Lu, Wei

    2014-01-07

    The gain and photoresponse characteristics have been numerically studied for back-illuminated separate absorption and multiplication (SAM) GaN avalanche photodiodes (APDs). The parameters of fundamental models are calibrated by simultaneously comparing the simulated dark and light current characteristics with the experimental results. Effects of environmental temperatures and device dimensions on gain characteristics have been investigated, and a method to achieve the optimum thickness of charge layer is obtained. The dependence of gain characteristics and breakdown voltage on the doping concentration of the charge layer is also studied in detail to get the optimal charge layer. The bias-dependent spectral responsivity and quantum efficiency are then presented to study the photoresponse mechanisms inside SAM GaN APDs. It is found the responsivity peak red-shifts at first due to the Franz-Keldysh effect and then blue-shifts due to the reach-through effect of the absorption layer. Finally, a new SAM GaN/AlGaN heterojunction APD structure is proposed for optimizing SAM GaN APDs.

  12. Study on the release of fenofibrate nanosuspension in vitro and its correlation with in situ intestinal and in vivo absorption kinetics in rats.

    PubMed

    Xu, Yuanlong; Wang, Yonglu; Li, Xue Ming; Huang, Qinqin; Chen, Wei; Liu, Ran; Chen, BaoAn; Wei, Ping

    2014-07-01

    As an oral delivery carrier for poorly water soluble drugs, the nanosuspension was prepared by melt emulsification method combined with high-pressure homogenization. The objective of this study was to clarify the absorption mechanism in rats of fenofibrate nanosuspension using the model of in situ gut perfusion. The release rate of drug from nanosuspension was fast which about 70% of the drug would be released within 5 minutes. The absorption of fenofibrate nanosuspension in the gastrointestinal (GI) tract was studied by the in situ closed loop method in rats. It was found that the absorption process in intestine was first-process with passive diffusion mechanism, and the whole intestine was the major segment for the drug absorption. Additionally, GI absorption in situ studies indicated that the fenofibrate nanosuspension had great success in regard to enhancement of intestinal absorption compared to the fenofibrate suspension of coarse powder. The pharmacokinetic characteristics were studied in rats after oral administration of fenofibrate nanosuspension or suspension at the dosage of 27 mg/kg. The plasma concentration-time curve was fitted to the one-compartment model. The correlation between in vitro dissolution (P), in situ intestinal absorption (F) and in vivo absorption (Fa) in rats was investigated with the results as follows: Fa = 6.2061P-456.38(r = 0.9559), F = 3.6911P-2.2169(r = 0.970), F = 0.5095P + 44.189(r = 0.9609). The highest level A could be obtained from the in vitro--in vivo correlation (IVIVC) between dissolution percentage and intestinal absorption of the fenofibrate nanosuspension in rats. Consequently, the in situ intestinal perfusion model could be used to predict the in vivo pharmacokinetic characteristics in rats.

  13. Feasibility study of SWIR light absorption enhancement in PbS and PbSe nano-structure layers using surface plasmon polariton

    NASA Astrophysics Data System (ADS)

    Nissim, Nimrod; Rosenblit, Michael; Sarusi, Gabby

    2017-03-01

    We present a theoretical feasibility study of the use of reflection grating couplers in order to harness the Surface Plasmon Polariton (SPP) to increase the absorption efficiency in the short wavelength infrared (SWIR) spectral range of a novel SWIR to visible (VIS) direct up-conversion imaging device. This device detects the SWIR spectral band photons using high absorption PbSe/CdSe core-shell, PbS nano-spheres or PbSe nano-columns. In order to further enhance the absorption of the SWIR light within the nano-structure layer we propose to add another light absorption enhancement, known as SPP enhanced absorption. The idea is to cover the absorber layer surface with a structured metal layer that will ignite SPPs on the metal - dielectric interface, by coupling between the incident TM polarized photons and the SPP modes; this results in better field confinement at the interface that will further increase the SWIR absorption of this thin layer. Calculation of the field profile of the surface plasmon (SP) in the SWIR range shows perpendicular dominance of the SP's electrical field direction on the dielectric layer side (the PbS or PbSe/CdSe absorption layer side). Based on this result, it was found that, due to the use of quantum confined and, thus, high oscillator strength nanostructures, there is only a marginal increase in the absorption and, hence, in the quantum efficiency when using the SPP enhancement technique. Nevertheless, we show that one of the proposed configurations of the metal grating coupler, having a lamellar structure with a pitch of 1.38μm, a duty cycle (DC) of 0.12μm and a height of 60nm, is predicted to increase the total layer's absorption by 9.5%, mainly due to efficient light scattering rather than to SPP enhanced absorption.

  14. Copper doped TiO2 nanoparticles characterized by X-ray absorption spectroscopy, total scattering, and powder diffraction – a benchmark structure–property study

    SciTech Connect

    Lock, Nina; Jensen, Ellen M. L.; Mi, Jianli; Mamakhel, Aref; Norén, Katarina; Qingbo, Meng; Iversen, Bo B.

    2013-01-01

    Metal functionalized nanoparticles potentially have improved properties e.g. in catalytic applications, but their precise structures are often very challenging to determine. Here we report a structural benchmark study based on tetragonal anatase TiO2 nanoparticles containing 0–2 wt% copper. The particles were synthesized by continuous flow synthesis under supercritical water–isopropanol conditions. Size determination using synchrotron PXRD, TEM, and X-ray total scattering reveals 5–7 nm monodisperse particles. The precise dopant structure and thermal stability of the highly crystalline powders were characterized by X-ray absorption spectroscopy and multi-temperature synchrotron PXRD (300–1000 K). The combined evidence reveals that copper is present as a dopant on the particle surfaces, most likely in an amorphous oxide or hydroxide shell. UV-VIS spectroscopy shows that copper presence at concentrations higher than 0.3 wt% lowers the band gap energy. The particles are unaffected by heating to 600 K, while growth and partial transformation to rutile TiO2 occur at higher temperatures. Anisotropic unit cell behavior of anatase is observed as a consequence of the particle growth (a decreases and c increases).

  15. Radiation effects in water ice: a near-edge x-ray absorption fine structure study.

    PubMed

    Laffon, C; Lacombe, S; Bournel, F; Parent, Ph

    2006-11-28

    The changes in the structure and composition of vapor-deposited ice films irradiated at 20 K with soft x-ray photons (3-900 eV) and their subsequent evolution with temperatures between 20 and 150 K have been investigated by near-edge x-ray absorption fine structure spectroscopy (NEXAFS) at the oxygen K edge. We observe the hydroxyl OH, the atomic oxygen O, and the hydroperoxyl HO(2) radicals, as well as the oxygen O(2) and hydrogen peroxide H(2)O(2) molecules in irradiated porous amorphous solid water (p-ASW) and crystalline (I(cryst)) ice films. The evolution of their concentrations with the temperature indicates that HO(2), O(2), and H(2)O(2) result from a simple step reaction fuelled by OH, where O(2) is a product of HO(2) and HO(2) a product of H(2)O(2). The local order of ice is also modified, whatever the initial structure is. The crystalline ice I(cryst) becomes amorphous. The high-density amorphous phase (I(a)h) of ice is observed after irradiation of the p-ASW film, whose initial structure is the normal low-density form of the amorphous ice (I(a)l). The phase I(a)h is thus peculiar to irradiated ice and does not exist in the as-deposited ice films. A new "very high density" amorphous phase-we call I(a)vh-is obtained after warming at 50 K the irradiated p-ASW ice. This phase is stable up to 90 K and partially transforms into crystalline ice at 150 K.

  16. Flash-induced absorption spectroscopy studies of copper interaction with photosystem II in higher plants.

    PubMed

    Schröder, W P; Arellano, J B; Bittner, T; Barón, M; Eckert, H J; Renger, G

    1994-12-30

    Measurements of flash-induced absorption changes at 325, 436, and 830 nm and of oxygen evolution were performed in order to analyze in detail the inhibition of photosystem II (PS II) by Cu(II) in PS II membrane fragments from spinach. (a) The kinetics of P680+ reduction become markedly slower in the presence of 100 microM CuSO4. (b) The CuSO4-induced kinetics of P680+ reduction are dominated by a 140-160-microsecond decay. (c) The extent of these 140-160-microsecond kinetics, normalized to the overall decay, remains virtually unaffected by addition of the exogenous PS II donor, NH2OH. (d) In thoroughly dark-adapted samples the CuSO4-induced 140-160-microsecond kinetics are already observed after the first flash and remain unchanged by a train of excitation flashes. (e) The extent of P680+ and QA- formation under repetitive flash excitation is not diminished by addition of 100 microM CuSO4. (f) The induction of microsecond kinetics of P680+ reduction at the expense of ns kinetics and the inhibition of the saturation rate of oxygen evolution exhibit the same dependence on CuSO4 concentration. (g) CuSO4 also transforms the 10-20-microsecond reduction of P680+ by TyrZ in Tris-washed PS II membrane fragments into 140-160-microsecond kinetics without any effect on the extent of flash-induced P680+ formation. These results unambiguously show that Cu(II) does not affect the charge separation (P680+QA-), but instead specifically modifies TyrZ and/or its micro environment so that the electron transfer to P680+ becomes blocked.

  17. Using resonance light scattering and UV/vis absorption spectroscopy to study the interaction between gliclazide and bovine serum albumin.

    PubMed

    Zhang, Qiu-Ju; Liu, Bao-Sheng; Li, Gai-Xia; Han, Rong

    2016-08-01

    At different temperatures (298, 310 and 318 K), the interaction between gliclazide and bovine serum albumin (BSA) was investigated using fluorescence quenching spectroscopy, resonance light scattering spectroscopy and UV/vis absorption spectroscopy. The first method studied changes in the fluorescence of BSA on addition of gliclazide, and the latter two methods studied the spectral change in gliclazide while BSA was being added. The results indicated that the quenching mechanism between BSA and gliclazide was static. The binding constant (Ka ), number of binding sites (n), thermodynamic parameters, binding forces and Hill's coefficient were calculated at three temperatures. Values for the binding constant obtained using resonance light scattering and UV/vis absorption spectroscopy were much greater than those obtained from fluorescence quenching spectroscopy, indicating that methods monitoring gliclazide were more accurate and reasonable. In addition, the results suggest that other residues are involved in the reaction and the mode 'point to surface' existed in the interaction between BSA and gliclazide. Copyright © 2015 John Wiley & Sons, Ltd.

  18. Human volunteer study on the inhalational and dermal absorption of N-methyl-2-pyrrolidone (NMP) from the vapour phase.

    PubMed

    Bader, Michael; Wrbitzky, Renate; Blaszkewicz, Meinolf; Schäper, Michael; van Thriel, Christoph

    2008-01-01

    N-Methyl-2-pyrrolidone (NMP) is a versatile organic solvent frequently used for surface cleaning such as paint stripping or graffiti removal. Liquid NMP is rapidly absorbed through the skin but dermal vapour phase absorption might also play an important role for the uptake of the solvent. This particular aspect was investigated in an experimental study with 16 volunteers exposed to 80 mg/m(3) NMP for 8 h under either whole-body, i.e. inhalational plus dermal, or dermal-only conditions. Additionally, the influence of moderate physical workload on the uptake of NMP was studied. The urinary concentrations of NMP and its metabolites 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI) were followed for 48 h and analysed by gas chromatography-mass spectrometry (GC-MS). Percutaneous uptake delayed the elimination peak times and the apparent biological half-lives of NMP and 5-HNMP. Under resting conditions, dermal-only exposure resulted in the elimination of 71 +/- 8 mg NMP equivalents as compared to 169 +/- 15 mg for whole-body exposure. Moderate workload yielded 79 +/- 8 mg NMP (dermal-only) and 238 +/- 18 mg (whole-body). Thus, dermal absorption from the vapour phase may contribute significantly to the total uptake of NMP, e.g. from workplace atmospheres. As the concentration of airborne NMP does not reflect the body dose, biomonitoring should be carried out for surveillance purposes.

  19. Excitonic absorption intensity of semiconducting and metallic carbon nanotubes.

    PubMed

    Verdenhalven, Eike; Malić, Ermin

    2013-06-19

    The knowledge of the intrinsic absorption intensity of each carbon nanotube is of crucial importance for the optical assignment of nanotube species and the estimation of their abundance in a sample. Based on a microscopic approach, we calculate excitonic absorption spectra for a variety of semiconducting and metallic nanotubes, revealing a clear diameter, chirality, and family dependence of the absorption intensity. In particular, we also study the appearance of excited excitonic transitions, which are shown to be well pronounced for semiconducting nanotubes, reaching intensities of up to 10% of the main transition. We find that nanotubes with large diameters show the most pronounced absorption intensities, confirming well the experimentally observed trend. Depending on the CNT family and transition, the absorption is enhanced or reduced with the chiral angle. This behavior reflects well the qualitative chirality dependence of the analytically derived optical matrix element.

  20. Iron distances in hemoglobin: comparison of x-ray crystallographic and extended x-ray absorption fine structure studies

    SciTech Connect

    Fermi, G.; Perutz, M.F.; Shulman, R.G.

    1987-09-01

    A comparison is presented of the structures obtained around the iron atom in deoxyhemoglobin (Hb). The data come from extended x-ray absorption fine structure (EXAFS) studies of the iron, which gave Fe-porphyrin nitrogen distances of 2.06 +- 0.01 A, and from the most recent high-resolution x-ray crystallographic study, which gave exactly the same distance-2.06 +- 0.02 A. The distance of Fe above the plane of the porphyrin nitrogens was 0.38 +- 0.04 A from the crystallographic study; this value is not far from the upper limit of the distances 0.20 +- /sub 0.20//sup 0.10/ A calculated from the EXAFS experiment by triangulation. These distances above the nitrogen plane are shorter than those estimated in the earliest x-ray structures

  1. TD-DFT Study of Absorption and Emission Spectra of 2-(2'-Aminophenyl)benzothiazole Derivatives in Water.

    PubMed

    Manojai, Natthaporn; Daengngern, Rathawat; Kerdpol, Khanittha; Kungwan, Nawee; Ngaojampa, Chanisorn

    2017-03-01

    Reduction of aromatic azides to amines is an important property of hydrogen sulphide (H2S) which is useful in fluorescence microscopy and H2S probing in cells. The aim of this work is to study the substituent effect on the absorption and emission spectra of 2-(2'-aminophenyl)benzothiazole (APBT) in order to design APBT derivatives for the use of H2S detection. Absorption and emission spectra of APBT derivatives in aqueous environment were calculated using density functional theory (DFT) and time-dependent DFT (TD-DFT) at B3LYP/6-311+G(d,p) level. The computed results favoured the substitution of strong electron-donating group on the phenyl ring opposite to the amino group for their large Stokes' shifts and emission wavelengths of over 600 nm. Also, three designed compounds were suggested as potential candidates for the fluorescent probes. Such generalised guideline learnt from this work can also be useful in further designs of other fluorescent probes of H2S in water.

  2. A Comparative Study of Molecular Structure, pKa, Lipophilicity, Solubility, Absorption and Polar Surface Area of Some Antiplatelet Drugs

    PubMed Central

    Remko, Milan; Remková, Anna; Broer, Ria

    2016-01-01

    Theoretical chemistry methods have been used to study the molecular properties of antiplatelet agents (ticlopidine, clopidogrel, prasugrel, elinogrel, ticagrelor and cangrelor) and several thiol-containing active metabolites. The geometries and energies of most stable conformers of these drugs have been computed at the Becke3LYP/6-311++G(d,p) level of density functional theory. Computed dissociation constants show that the active metabolites of prodrugs (ticlopidine, clopidogrel and prasugrel) and drugs elinogrel and cangrelor are completely ionized at pH 7.4. Both ticagrelor and its active metabolite are present at pH = 7.4 in neutral undissociated form. The thienopyridine prodrugs ticlopidine, clopidogrel and prasugrel are lipophilic and insoluble in water. Their lipophilicity is very high (about 2.5–3.5 logP values). The polar surface area, with regard to the structurally-heterogeneous character of these antiplatelet drugs, is from very large interval of values of 3–255 Å2. Thienopyridine prodrugs, like ticlopidine, clopidogrel and prasugrel, with the lowest polar surface area (PSA) values, exhibit the largest absorption. A high value of polar surface area (PSA) of cangrelor (255 Å2) results in substantial worsening of the absorption in comparison with thienopyridine drugs. PMID:27007371

  3. Ultrasonic velocity and absorption study of binary mixtures of cyclohexane with acrylonitrile by interferometric method at different frequencies

    NASA Astrophysics Data System (ADS)

    Pawar, N. R.; Chimankar, O. P.; Bhandakkar, V. D.; Padole, N. N.

    2012-12-01

    The ultrasonic velocity (u), absorption (α), density (ρ), and viscosity (η) has been measured at different frequencies (1MHz to 10MHz) in the binary mixtures of cyclohexane with acrylonitriile over the entire range of composition at temperature 303K. Vander Waal's constant (b), adiabatic compressibility (βa), acoustic impedance (Z), molar volume (V), free length (Lf), free volume, internal pressure, intermolecular radius and relative association have been also calculated. A special application for acrylonitrile is in the manufacture of carbon fibers. These are produced by paralysis of oriented poly acrylonitrile fibers and are used to reinforce composites for high-performance applications in the aircraft, defense and aerospace industries. Other applications of acrylonitrile are in the production of fatty amines, ion exchange resins and fatty amine amides used in cosmetics, adhesives, corrosion inhibitors and water-treatment resins. Cyclohexane derivatives can be used for the synthesis of pharmaceuticals, dyes, herbicides, plant growth regulator, plasticizers, rubber chemicals, nylon, cyclamens and other organic compounds. In the view of these extensive applications of acrylonitrile and cyclohexane in the engineering process, textile and pharmaceutical industries present study provides qualitative information regarding the nature and strength of interaction in the liquid mixtures through derive parameters from ultrasonic velocity and absorption measurement.

  4. Absorption spectrophotometric and X-ray diffraction studies of the trichlorides of berkelium-249 and californium-249

    SciTech Connect

    Peterson, J.R.; Young, J.P.; Ensor, D.D.; Haire, R.G.

    1986-10-08

    Absorption spectrophotometric and X-ray powder diffraction methods have been applied to a study of the trichlorides of /sup 249/Bk and /sup 248/Cf and their relationship through the ..beta.. decay of /sup 249/Bk. BkCl/sub 3/ has been prepared for the first time in the PuBr/sub 3/-type orthorhombic modification by quenching from the melt. Each of the crystal forms (UCl/sub 3/-type hexagonal and PuBr/sub 3/-type orthorhombic) of BkCl/sub 3/ and CfCl/sub 3/ has been characterized on the basis of its solid-state absorption spectrum. The orthorhombic forms of BkCl/sub 3/ and CfCl/sub 3/ are the high-temperature modifications with respect to the hexagonal phases, with the apparent transition temperatures near the melting points of BkCl/sub 3/ (876 K) and CfClnumber (818 K). Orthorhombic BkCl/sub 3/ transmutes to orthorhombic CfCl/sub 3/ and hexagonal BkCl/sub 3/ transmutes to hexagonal CfCl/sub 3/. Thus, it was found that both the oxidation state and the crystal structure of the parent /sup 249/Bk compound were retained by the daughter /sup 249/Cf compound through ..beta.. decay in the bulk phase solid state. 11 references, 5 figures.

  5. [Study on the effect of solar spectra on the retrieval of atmospheric CO2 concentration using high resolution absorption spectra].

    PubMed

    Hu, Zhen-Hua; Huang, Teng; Wang, Ying-Ping; Ding, Lei; Zheng, Hai-Yang; Fang, Li

    2011-06-01

    Taking solar source as radiation in the near-infrared high-resolution absorption spectrum is widely used in remote sensing of atmospheric parameters. The present paper will take retrieval of the concentration of CO2 for example, and study the effect of solar spectra resolution. Retrieving concentrations of CO2 by using high resolution absorption spectra, a method which uses the program provided by AER to calculate the solar spectra at the top of atmosphere as radiation and combine with the HRATS (high resolution atmospheric transmission simulation) to simulate retrieving concentration of CO2. Numerical simulation shows that the accuracy of solar spectrum is important to retrieval, especially in the hyper-resolution spectral retrieavl, and the error of retrieval concentration has poor linear relation with the resolution of observation, but there is a tendency that the decrease in the resolution requires low resolution of solar spectrum. In order to retrieve the concentration of CO2 of atmosphere, the authors' should take full advantage of high-resolution solar spectrum at the top of atmosphere.

  6. Ab initio x-ray absorption near-edge structure study of Ti K-edge in rutile.

    PubMed

    Chaboy, J; Nakajima, N; Tezuka, Y

    2007-07-04

    This work reports a theoretical x-ray absorption near-edge structure (XANES) spectroscopy study at the Ti K-edge in TiO(2) rutile. We present detailed ab initio computations of the Ti K-edge XANES spectrum performed within the multiple-scattering framework. An extensive discussion is presented concerning the size of the cluster needed to reproduce the experimental spectrum, especially regarding the split main absorption line. In addition, the role of the exchange and correlation potential (ECP) in reproducing all the experimental XANES features is discussed. The best agreement between experimental data and computations is obtained by using real ECP potentials, i.e. the energy-dependent Dirac-Hara exchange potential, or by using only the real part of the energy-dependent Hedin-Lundqvist complex potential, together with an additional imaginary constant to account for the core-hole lifetime and the experimental resolution. The addition of the imaginary part of the HL potential worsens the agreement between the experimental and calculated spectra, indicating the failure of the complex part of the Hedin-Lundqvist ECP in accounting for the electron damping in these systems.

  7. Laser Absorption Measurements of Equivalence Ratios Studied Along With Their Coupling to Pressure Fluctuations in Lean Premixed Prevaporized (LPP) Combustion

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet

    2001-01-01

    Concerns about damaging the Earth's ozone layer as a result of high levels of nitrogen oxides (known collectively as NOx) from high-altitude, high-speed aircraft have prompted the study of lean premixed prevaporized (LPP) combustion in aircraft engines. LPP combustion reduces NOx emissions principally by reducing the peak flame temperatures inside an engine. Recent advances in LPP technologies have realized exceptional reductions in pollutant emissions (single-digit ppm NOx for example). However, LPP combustion also presents major challenges: combustion instability and dynamic coupling effects between fluctuations in heat-release rate, dynamic pressure, and fuel pressure. These challenges are formidable and can literally shake an engine apart if uncontrolled. To better understand this phenomenon so that it can be controlled, we obtained real-time laser absorption measurements of the fuel vapor concentration (and equivalence ratio) simultaneously with the dynamic pressure, flame luminosity, and time-averaged gaseous emissions measurements in a research-type jet-A-fueled LPP combustor. The measurements were obtained in NASA Glenn Research Center's CE-5B optically accessible flame tube facility. The CE-5B facility provides inlet air temperatures and pressures similar to the actual operating conditions of real aircraft engines. The laser absorption measurements were performed using an infrared 3.39 micron HeNe laser in conjunction with a visible HeNe laser for liquid droplet scattering compensation.

  8. Experimental study on energy absorption of foam filled kraft paper honeycomb subjected to quasi-static uniform compression loading

    NASA Astrophysics Data System (ADS)

    Abd Kadir, N.; Aminanda, Y.; Ibrahim, M. S.; Mokhtar, H.

    2016-10-01

    A statistical analysis was performed to evaluate the effect of factor and to obtain the optimum configuration of Kraft paper honeycomb. The factors considered in this study include density of paper, thickness of paper and cell size of honeycomb. Based on three level factorial design, two-factor interaction model (2FI) was developed to correlate the factors with specific energy absorption and specific compression strength. From the analysis of variance (ANOVA), the most influential factor on responses and the optimum configuration was identified. After that, Kraft paper honeycomb with optimum configuration is used to fabricate foam-filled paper honeycomb with five different densities of polyurethane foam as filler (31.8, 32.7, 44.5, 45.7, 52 kg/m3). The foam-filled paper honeycomb is subjected to quasi-static compression loading. Failure mechanism of the foam-filled honeycomb was identified, analyzed and compared with the unfilled paper honeycomb. The peak force and energy absorption capability of foam-filled paper honeycomb are increased up to 32% and 30%, respectively, compared to the summation of individual components.

  9. Development of the isolated perfused porcine skin flap for in vitro studies of percutaneous absorption pharmacokinetics and cutaneous biotransformation

    SciTech Connect

    Carver, M.P.

    1988-01-01

    The isolated perfused porcine skin flap (IPPSF) has proven to be a valuable in vitro tool for studying the physiology and biochemistry of skin and for identifying biochemical and histological markers of direct cutaneous toxicity. The present experiments were undertaken for two purposes: (1) to develop a pharmacokinetic model, based on dermal penetration in the IPPSF, which is predictive of percutaneous absorption in vivo, and (2) to examine cutaneous biotransformation of the important agricultural poison parathion (P). Dosing solutions of {sup 14}C-radiolabelled compounds representing 3 chemical classes-organic acid/base (benzoic acid (B), caffeine (C)), organophosphate (OP) pesticides, and steroid hormones, were applied topically in ethanol at 40 {mu}m cm{sup {minus}2}, both in vivo and on the IPPSF. A 3-compartment pharmacokinetic model describing mass transfer from the surface (C{sub 1}), diffusion through epidermis and dermis (C{sub 2}), and transfer into the perfusate (C{sub 3}), was developed based on flux through the IPPSF from 0-8 hr. Model simulations were predictive of percutaneous absorption in vivo for the OP's and steroids. Modification of the basic 3-compartment model to account for fast and slow tissue-release processes (B) and for flux-dependent perfusage flow increases (C), provided excellent in vivo-in vitro correlation over all 7 compounds.

  10. A spatiotemporal study of the relativistic nonlinear effects on laser absorption by a finite-size magneto plasma

    NASA Astrophysics Data System (ADS)

    Mehdian, Hasan; Kargarian, Ameneh; Hajisharifi, Kamal; Hasanbeigi, Ali

    2014-12-01

    In this paper, the relativistic electromagnetic 1.5 dimensional particle-in-cell code has been employed to investigate the temporal behavior of nonlinear absorption of a short intense laser pulse in finite-size magnetized sub-critical (i.e. under the critical density) plasma. This work has been done by relying on a detailed temporal study of the phase-mixing and scattering processes occurring in the finite-size system of laser-plasma interaction. Part of the results obtained in this manuscript confirm recent important theoretical findings, including the wave-breaking or phase-mixing phenomena of relativistic upper-hybrid (UH) oscillations in magnetized plasma [C. Maity, A. Sarka, P.K. Shukla, N. Chakrabarti, Phys. Rev. Lett. 110, 215002 (2013)]. Moreover, we found the explicit reasons for the anomalous behavior of the absorption rate in magnetized plasma by scrutinising the phase-mixing time and scattering process in finite-size magnetized plasma for different values of laser and plasma parameters.

  11. Optical and structural properties of plasma-treated Cordyceps bassiana spores as studied by circular dichroism, absorption, and fluorescence spectroscopy

    SciTech Connect

    Lee, Geon Joon Sim, Geon Bo; Choi, Eun Ha; Kim, Jun Young; Jang, Siun; Kim, Seong Hwan

    2015-01-14

    To understand the killing mechanism of fungal spores by plasma treatment, the optical, structural, and biological properties of the insect pathogenic fungus Cordyceps bassiana spores were studied. A nonthermal atmospheric-pressure plasma jet (APPJ) was used to treat the spores in aqueous solution. Optical emission spectra of the APPJ acquired in air indicated emission peaks corresponding to hydroxyl radicals and atomic oxygen. When the APPJ entered the aqueous solution, additional reactive species were derived from the interaction of plasma radicals with the aqueous solution. Fluorescence and absorption spectroscopy confirmed the generation of hydroxyl radicals and hydrogen peroxide in the plasma-activated water (PAW). Spore counting showed that plasma treatment significantly reduced spore viability. Absorption spectroscopy, circular dichroism (CD) spectroscopy, and agarose gel electrophoresis of the DNA extracted from plasma-treated spores showed a reduction in spore DNA content. The magnitude of the dip in the CD spectrum was lower in the plasma-treated spores than in the control, indicating that plasma treatment causes structural modifications and/or damage to cellular components. Tryptophan fluorescence intensity was lower in the plasma-treated spores than in the control, suggesting that plasma treatment modified cell wall proteins. Changes in spore viability and DNA content were attributed to structural modification of the cell wall by reactive species coming from the APPJ and the PAW. Our results provided evidence that the plasma radicals and the derived reactive species play critical roles in fungal spore inactivation.

  12. Optical and structural properties of plasma-treated Cordyceps bassiana spores as studied by circular dichroism, absorption, and fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Geon Joon; Sim, Geon Bo; Choi, Eun Ha; Kwon, Young-Wan; Kim, Jun Young; Jang, Siun; Kim, Seong Hwan

    2015-01-01

    To understand the killing mechanism of fungal spores by plasma treatment, the optical, structural, and biological properties of the insect pathogenic fungus Cordyceps bassiana spores were studied. A nonthermal atmospheric-pressure plasma jet (APPJ) was used to treat the spores in aqueous solution. Optical emission spectra of the APPJ acquired in air indicated emission peaks corresponding to hydroxyl radicals and atomic oxygen. When the APPJ entered the aqueous solution, additional reactive species were derived from the interaction of plasma radicals with the aqueous solution. Fluorescence and absorption spectroscopy confirmed the generation of hydroxyl radicals and hydrogen peroxide in the plasma-activated water (PAW). Spore counting showed that plasma treatment significantly reduced spore viability. Absorption spectroscopy, circular dichroism (CD) spectroscopy, and agarose gel electrophoresis of the DNA extracted from plasma-treated spores showed a reduction in spore DNA content. The magnitude of the dip in the CD spectrum was lower in the plasma-treated spores than in the control, indicating that plasma treatment causes structural modifications and/or damage to cellular components. Tryptophan fluorescence intensity was lower in the plasma-treated spores than in the control, suggesting that plasma treatment modified cell wall proteins. Changes in spore viability and DNA content were attributed to structural modification of the cell wall by reactive species coming from the APPJ and the PAW. Our results provided evidence that the plasma radicals and the derived reactive species play critical roles in fungal spore inactivation.

  13. Occupied and unoccupied electronic structures of an L-cysteine film studied by core-absorption and resonant photoelectron spectroscopies

    NASA Astrophysics Data System (ADS)

    Kamada, M.; Hideshima, T.; Azuma, J.; Yamamoto, I.; Imamura, M.; Takahashi, K.

    2016-04-01

    Unoccupied and occupied electronic structures of an L-cysteine film have been studied by absorption and resonant photoelectron spectroscopies. Core absorptions at S-L, C-K, N-K, and O-K levels indicate that the lower unoccupied states are predominantly composed of oxygen-2p, carbon-2p, and sulfur-4s+3d orbitals, while higher unoccupied states may be attributed dominantly to nitrogen-np (n ≥ 3), oxygen-np (n ≥ 3), and sulfur-ns+md (n ≥ 4, m ≥ 3) orbitals. Resonant photoelectron spectra at S-L23 and O-K levels indicate that the highest occupied state is originated from sulfur-3sp orbitals, while oxygen-2sp orbitals contribute to the deeper valence states. The delocalization lifetimes of the oxygen-1s and sulfur-2p excited states are estimated from a core-hole clock method to be about 9 ± 1 and 125 ± 25 fs, respectively.

  14. Genome-wide association study reveals sex-specific selection signals against autosomal nucleotide variants.

    PubMed

    Ryu, Dongchan; Ryu, Jihye; Lee, Chaeyoung

    2016-05-01

    A genome-wide association study (GWAS) was conducted to examine genetic associations of common autosomal nucleotide variants with sex in a Korean population with 4183 males and 4659 females. Nine genetic association signals were identified in four intragenic and five intergenic regions (P<5 × 10(-8)). Further analysis with an independent data set confirmed two intragenic association signals in the genes encoding protein phosphatase 1, regulatory subunit 12B (PPP1R12B, intron 12, rs1819043) and dynein, axonemal, heavy chain 11 (DNAH11, intron 61, rs10255013), which are directly involved in the reproductive system. This study revealed autosomal genetic variants associated with sex ratio by GWAS for the first time. This implies that genetic variants in proximity to the association signals may influence sex-specific selection and contribute to sex ratio variation. Further studies are required to reveal the mechanisms underlying sex-specific selection.

  15. Studies on optically induced nonlinear absorption and refractive index of Br1 crystal for near IR optical switching application

    NASA Astrophysics Data System (ADS)

    Bharath, D.; Kalainathan, S.

    2014-07-01

    A newly synthesized 2-{3-[2-(4-bromophenyl) vinyl]-5, 5-dimethylcyclo-hex-2-en-1-ylidene} malononitrile (Br1) organic compound has been studied. Br1 crystals were grown by employing the solution growth method. The single crystal XRD analysis shows that Br1 crystallizes in the monoclinic space group P21/c, with cell parameters a=10.064(5), b=11.218, c=14.862 and V=1667.2. TG and DTA studies show Br1 melts at 195.1 °C and decomposes at 352 °C. UV absorption spectrum of Br1 crystal shows the cutoff wavelength at 614 nm, and the wide transparency of crystal is in the region of 615-1550 nm. The optical constants are theoretically calculated in the optical communication range 1300-1550 nm. The refractive index of Br1 crystal (1.655) has been measured using Abbe's refractometer. Z-scan technique with He-Ne laser has measured the optical nonlinearity of Br1 crystal along the a, b and c axes. The mechanism of the nonlinear variation of crystal can be regarded as the thermal nonlinear effects. The largest third order nonlinear refractive index is along the c-axis, possessing a value of 11.6194×10-6 esu which is larger than that of the a and b axes. Photoinduced absorption is responsible for the optical absorption of the organic molecular crystal. The two figures of merit, W=47>1 and T=0.12<1 are suitable for optical switching application. Photoluminescence spectrum of crystal has been studied using xenon lamp in the wavelength range of 450-700 nm. The sharp emission of photoluminescence spectrum is excited at 642.74 nm (137711 a.u). Laser damage threshold of Br1 crystal has been studied using Nd-YAG laser. The laser energy is initiating the crack at 89.4 mJ after 10 s on the surface (100) of Br1 crystal.

  16. Reactivity of the laccase trinuclear copper active site with dioxygen: An x-ray absorption edge study

    SciTech Connect

    Cole, J.L.; Tan, G.O.; Yang, E.K.; Hodgson, K.O.; Solomon, E.I. )

    1990-03-14

    The multicopper oxidases (laccase, ascorbate oxidase, ceruloplasmin) catalyze the four-electron reduction of dioxygen to water. Laccase contains four Cu atoms: a type 1, a type 2, and a coupled binuclear type 3 center. Low-temperature MCD studies of laccase have demonstrated that the type 2 and type 3 centers comprise a trinuclear Cu cluster site and this model has been supported in a recent x-ray crystal structure of ascorbate oxidase. In the present study, x-ray absorption edge spectroscopy has been used to determine Cu oxidation states following reaction of reduced laccase derivatives with dioxygen, leading to a description of which of the Cu centers is required for reactivity.

  17. Absorption and Luminescence Studies of Some Highly Fluorescent Derivatives of Vitamin B1; Solvent and pH Effects

    NASA Astrophysics Data System (ADS)

    Marciniak, B.; Koput, J.; Kozubek, H.

    1990-08-01

    The influence of solvent on the UV-visible absorption and luminescence spectra of some highly fluorescent vitamin B1 derivatives, the products of the reaction of N-methylated vitamin B1 with cytidine (I), adenosine (II) and 2-amino-4-methylpyridine (III) is studied. Spectroscopic manifestations of protonation of I and II are also investigated using a semiempirical INDO/S CI method. Singlet and triplet energy levels of the free ion and several protonated species are calculated, and transition energies and oscillator strengths are compared with the experimental spectra. Calculated charge densities on heteroatoms in the ground and excited singlet and triplet states are correlated with changes of the experimental pKa values with excitation. The results for I and II are compared with those for the trimethylated pyrichrominium ion (III) previously studied

  18. Retrieval and molecule sensitivity studies for the global ozone monitoring experiment and the scanning imaging absorption spectrometer for atmospheric chartography

    NASA Technical Reports Server (NTRS)

    Chance, Kelly V.; Burrows, John P.; Schneider, Wolfgang

    1991-01-01

    The Global Ozone Monitoring Experiment (GOME) and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) are diode based spectrometers that will make atmospheric constituent and aerosol measurements from European satellite platforms beginning in the mid 1990's. GOME measures the atmosphere in the UV and visible in nadir scanning, while SCIAMACHY performs a combination of nadir, limb, and occultation measurements in the UV, visible, and infrared. A summary is presented of the sensitivity studies that were performed for SCIAMACHY measurements. As the GOME measurement capability is a subset of the SCIAMACHY measurement capability, the nadir, UV, and visible portion of the studies is shown to apply to GOME as well.

  19. Applications of extended X-ray absorption fine-structure spectroscopy to studies of bimetallic nanoparticle catalysts.

    PubMed

    Frenkel, Anatoly I

    2012-12-21

    Extended X-ray absorption fine structure (EXAFS) spectroscopy has been used to study short range order in heterometallic alloys for almost four decades. In this critical review, experimental, theoretical and data analytical approaches are revisited to examine their power, and limitations, in studies of bimetallic nanocatalysts. This article covers the basics of EXAFS experiments, data analysis, and modelling of nanoscale clusters. It demonstrates that, in the best case scenario, quantitative information about the nanocatalyst's size, shape, details of core-shell architecture, as well as static and dynamic disorder in metal-metal bond lengths can be obtained. The article also emphasizes the main challenge accompanying such insights: the need to account for the statistical nature of the EXAFS technique, and discusses corrective strategies.

  20. A diamond anvil cell with resistive heating for high pressure and high temperature x-ray diffraction and absorption studies.

    PubMed

    Pasternak, Sebastien; Aquilanti, Giuliana; Pascarelli, Sakura; Poloni, Roberta; Canny, Bernard; Coulet, Marie-Vanessa; Zhang, Lin

    2008-08-01

    In this paper we describe a prototype of a diamond anvil cell (DAC) for high pressure/high temperature studies. This DAC combines the use of a resistive oven of 250 W power in a very small volume, associated with special conical seats for Boehler-type diamond anvils in order to have a large angular acceptance. To protect the diamond anvils from burning and to avoid the oven oxidation, the heated DAC is enclosed in a vacuum chamber. The assemblage was used to study the melting curve of germanium at high pressure (up to 20 GPa) and high temperature (up to 1200 K) using x-ray diffraction and x-ray absorption spectroscopy.