Science.gov

Sample records for hydrogen deuterium carbon

  1. Water, hydrogen, deuterium, carbon, carbon-13, and oxygen-18 content of selected lunar material

    USGS Publications Warehouse

    Friedman, I.; O'Neil, J.R.; Adami, L.H.; Gleason, J.D.; Hardcastle, K.

    1970-01-01

    The water content of the breccia is 150 to 455 ppm, with a ??D from -580 to -870 per mil. Hydrogen gas content is 40 to 53 ppm with a ??D of -830 to -970 per mil. The CO2 is 290 to 418 ppm with S 13C = + 2.3 to + 5.1 per mil and ??18O = 14.2 to 19.1 per mil. Non-CO2 carbon is 22 to 100 ppm, ??18C = -6.4 to -23.2 per mil. Lunar dust is 810 ppm H2O (D = 80 ppm) and 188 ppm total carbon (??13C = -17.6 per mil). The 18O analyses of whole rocks range from 5.8 to 6.2 per mil. The temperature of crystallization of type B rocks is 1100?? to 1300??C, based on the oxygen isotope fractionation between coexisting plagioclase and ilmenite.

  2. Cryogenic tritium-hydrogen-deuterium and deuterium-tritium layer implosions with high density carbon ablators in near-vacuum hohlraums

    NASA Astrophysics Data System (ADS)

    Meezan, N. B.; Berzak Hopkins, L. F.; Le Pape, S.; Divol, L.; MacKinnon, A. J.; Döppner, T.; Ho, D. D.; Jones, O. S.; Khan, S. F.; Ma, T.; Milovich, J. L.; Pak, A. E.; Ross, J. S.; Thomas, C. A.; Benedetti, L. R.; Bradley, D. K.; Celliers, P. M.; Clark, D. S.; Field, J. E.; Haan, S. W.; Izumi, N.; Kyrala, G. A.; Moody, J. D.; Patel, P. K.; Ralph, J. E.; Rygg, J. R.; Sepke, S. M.; Spears, B. K.; Tommasini, R.; Town, R. P. J.; Biener, J.; Bionta, R. M.; Bond, E. J.; Caggiano, J. A.; Eckart, M. J.; Gatu Johnson, M.; Grim, G. P.; Hamza, A. V.; Hartouni, E. P.; Hatarik, R.; Hoover, D. E.; Kilkenny, J. D.; Kozioziemski, B. J.; Kroll, J. J.; McNaney, J. M.; Nikroo, A.; Sayre, D. B.; Stadermann, M.; Wild, C.; Yoxall, B. E.; Landen, O. L.; Hsing, W. W.; Edwards, M. J.

    2015-06-01

    High Density Carbon (or diamond) is a promising ablator material for use in near-vacuum hohlraums, as its high density allows for ignition designs with laser pulse durations of <10 ns. A series of Inertial Confinement Fusion (ICF) experiments in 2013 on the National Ignition Facility [Moses et al., Phys. Plasmas 16, 041006 (2009)] culminated in a deuterium-tritium (DT) layered implosion driven by a 6.8 ns, 2-shock laser pulse. This paper describes these experiments and comparisons with ICF design code simulations. Backlit radiography of a tritium-hydrogen-deuterium (THD) layered capsule demonstrated an ablator implosion velocity of 385 km/s with a slightly oblate hot spot shape. Other diagnostics suggested an asymmetric compressed fuel layer. A streak camera-based hot spot self-emission diagnostic (SPIDER) showed a double-peaked history of the capsule self-emission. Simulations suggest that this is a signature of low quality hot spot formation. Changes to the laser pulse and pointing for a subsequent DT implosion resulted in a higher temperature, prolate hot spot and a thermonuclear yield of 1.8 × 1015 neutrons, 40% of the 1D simulated yield.

  3. Cryogenic tritium-hydrogen-deuterium and deuterium-tritium layer implosions with high density carbon ablators in near-vacuum hohlraums

    SciTech Connect

    Meezan, N. B. Hopkins, L. F. Berzak; Pape, S. Le; Divol, L.; MacKinnon, A. J.; Döppner, T.; Ho, D. D.; Jones, O. S.; Khan, S. F.; Ma, T.; Milovich, J. L.; Pak, A. E.; Ross, J. S.; Thomas, C. A.; Benedetti, L. R.; Bradley, D. K.; Celliers, P. M.; Clark, D. S.; Field, J. E.; Haan, S. W.; and others

    2015-06-15

    High Density Carbon (or diamond) is a promising ablator material for use in near-vacuum hohlraums, as its high density allows for ignition designs with laser pulse durations of <10 ns. A series of Inertial Confinement Fusion (ICF) experiments in 2013 on the National Ignition Facility [Moses et al., Phys. Plasmas 16, 041006 (2009)] culminated in a deuterium-tritium (DT) layered implosion driven by a 6.8 ns, 2-shock laser pulse. This paper describes these experiments and comparisons with ICF design code simulations. Backlit radiography of a tritium-hydrogen-deuterium (THD) layered capsule demonstrated an ablator implosion velocity of 385 km/s with a slightly oblate hot spot shape. Other diagnostics suggested an asymmetric compressed fuel layer. A streak camera-based hot spot self-emission diagnostic (SPIDER) showed a double-peaked history of the capsule self-emission. Simulations suggest that this is a signature of low quality hot spot formation. Changes to the laser pulse and pointing for a subsequent DT implosion resulted in a higher temperature, prolate hot spot and a thermonuclear yield of 1.8 × 10{sup 15} neutrons, 40% of the 1D simulated yield.

  4. Energy Levels of Hydrogen and Deuterium

    National Institute of Standards and Technology Data Gateway

    SRD 142 Energy Levels of Hydrogen and Deuterium (Web, free access)   This database provides theoretical values of energy levels of hydrogen and deuterium for principle quantum numbers n = 1 to 200 and all allowed orbital angular momenta l and total angular momenta j. The values are based on current knowledge of the revelant theoretical contributions including relativistic, quantum electrodynamic, recoil, and nuclear size effects.

  5. The hydrogen-deuterium exchange at α-carbon atom in N,N,N-trialkylglycine residue: ESI-MS studies.

    PubMed

    Rudowska, Magdalena; Wojewska, Dominika; Kluczyk, Alicja; Bąchor, Remigiusz; Stefanowicz, Piotr; Szewczuk, Zbigniew

    2012-06-01

    Derivatization of peptides as quaternary ammonium salts (QAS) is a known method for sensitive detection by electrospray ionization tandem mass spectrometry. Hydrogens at α-carbon atom in N,N,N-trialkylglycine residue can be easily exchanged by deuterons. The exchange reaction is base-catalyzed and is dramatically slow at lower pH. Introduced deuterons are stable in acidic aqueous solution and are not back-exchanged during LC-MS analysis. Increased ionization efficiency, provided by the fixed positive charge on QAS group, as well as the deuterium labeling, enables the analysis of trace amounts of peptides. PMID:22403022

  6. The Hydrogen-Deuterium Exchange at α-Carbon Atom in N,N,N-Trialkylglycine Residue: ESI-MS Studies

    NASA Astrophysics Data System (ADS)

    Rudowska, Magdalena; Wojewska, Dominika; Kluczyk, Alicja; Bąchor, Remigiusz; Stefanowicz, Piotr; Szewczuk, Zbigniew

    2012-06-01

    Derivatization of peptides as quaternary ammonium salts (QAS) is a known method for sensitive detection by electrospray ionization tandem mass spectrometry. Hydrogens at α-carbon atom in N, N, N-trialkylglycine residue can be easily exchanged by deuterons. The exchange reaction is base-catalyzed and is dramatically slow at lower pH. Introduced deuterons are stable in acidic aqueous solution and are not back-exchanged during LC-MS analysis. Increased ionization efficiency, provided by the fixed positive charge on QAS group, as well as the deuterium labeling, enables the analysis of trace amounts of peptides.

  7. Hydrogen-deuterium exchange in structural biology

    NASA Astrophysics Data System (ADS)

    Schoenborn, B. P.; Ramakrishnan, V.; Schneider, D.

    1986-03-01

    The large difference in neutron scattering length of hydrogen and deuterium atoms provides a unique tool to study biological macromolecules. These molecules exist in an aqueous environment and have an atomic composition of about 50% hydrogen atoms with the rest being mainly carbon, oxygen and nitrogen. By simply changing the ratio of hydrogen to deuterium the contrast of a sample constituent can be changed without altering the chemical composition. The scattering difference between the hydrogen isotopes has now been used to study structural details of proteins, viruses, nucleic acid protein complexes and membranes. The use of small-angle scattering analysis from proteins in solution is a particularly good example of the power of this new technique. From the first experiments with myoglobin, hemoglobin and TMV solutions in 1968 at the HFBR in Brookhaven it became, however, soon evident that the flux was low and the detection system of a conventional spectrometer was inadequate to measure precisely small differences in the scattering pattern. Since these solution scattering patterns are circularly symmetrical, a development of multidetector systems was the first step to alleviate the need for better data. From an early five detector system [1] the development of linear and two-dimensional position sensitive detectors continues to this day [2-6]. Today, position sensitive area-detectors with an efficiency of 80% and 1.3 mm resolution with an active area of 50 cm × 50 cms are available. These detectors have a counting rate capability of 2 × 10 5 neutrons/s. Other instrumentation developments to facilitate the study of biomolecules include (1) cold moderators, (2) thin film multilayer monochromators [7-9], (3) neutron guides made either of multilayer supermirrors or coated with 58Ni [10,11], (4) various crystal and mirror focusing devices [12,13]. Some of these features have been incorporated in a small-angle neutron spectrometer at the High Flux Beam Reactor at the Brookhaven National Laboratory. This spectrometer has a unique combination of features such as a high resolution area-detector, adjustable wavelength bandwidth and automated sample changer.

  8. Deuterium retention in tungsten coating layers irradiated with deuterium and carbon ions

    NASA Astrophysics Data System (ADS)

    Fukumoto, M.; Nakano, T.; Ueda, Y.; Itami, K.; Kubo, H.

    2015-07-01

    The effects of carbon ion fraction on deuterium retention in tungsten coating layers were investigated by irradiating the layers with mixed deuterium and carbon ion beams. The mixed ion beams had atomic carbon fractions of up to 3.2% and the sample temperature was either 500 or 700 K. Graphite was formed in the tungsten coating layer at the both temperatures; however, tungsten carbide and ditungsten carbide were not formed at the both temperatures. At 500 K, deuterium was trapped at intrinsic defects and carbon was accumulated in the tungsten coating layer. At 700 K, although trapping deuterium at intrinsic defects was difficult, deuterium was trapped predominantly at carbon accumulated in the tungsten coating layer. Analysis of deuterium desorption spectrum by multipeak fitting suggests that deuterium was retained by C-D bonds in the tungsten coating layer at 700 K.

  9. Carbon Nanotube Based Deuterium Ion Source for Improved Neutron Generators

    SciTech Connect

    Fink, R. L.; Jiang, N.; Thuesen, L.; Leung, K. N.; Antolak, A. J.

    2009-03-10

    Field ionization uses high electric fields to cause the ionization and emission of ions from the surface of a sharp electrode. We are developing a novel field ionization neutron generator using carbon nanotubes (CNT) to produce the deuterium ion current. The generator consists of three major components: a deuterium ion source made of carbon nanotubes, a smooth negatively-biased target electrode, and a secondary electron suppression system. When a negative high voltage is applied on the target electrode, a high gradient electric field is formed at the tips of the carbon nanotubes. This field is sufficiently strong to create deuterium (D) ions at or near the nanotubes which are accelerated to the target causing D-D reactions to occur and the production of neutrons. A cross magnetic field is used to suppress secondary emission electrons generated on the target surface. We have demonstrated field ionization currents of 70 nA (1 {mu}A/cm{sup 2}) at hydrogen gas pressure of 10 mTorr. We have found that the current scales proportionally with CNT area and also with the gas pressure in the range of 1 mTorr to 10 mTorr. We have demonstrated pulse cut-off times as short as 2 {mu}sec. Finally, we have shown the feasibility of generating neutrons using deuterium gas.

  10. The deuterium content of atmospheric molecular hydrogen

    NASA Astrophysics Data System (ADS)

    Gerst, Steven Gregory

    2000-09-01

    A new technique for the separation of molecular hydrogen (H2) from air and the determination of its deuterium (D) content is presented. A high-pressure air sample in an aluminum cylinder is condensed at -196C, whereby H2 contained in the air sample is enriched in the gaseous headspace above the liquefied air. The H2-enriched headspace is bled into a vacuum extraction line where the H2 is oxidized to H2O for cryogenic isolation from the air stream. The captured water is reduced back to H2 for determination of its D/H ratio via isotope-ratio mass spectrometry (?D is reported in permil () vs. Vienna Standard Mean Ocean Water, where ?D = ((D/H)sample/(D/H) VSMOW - 1)*1000). Air samples for ?D analyses were collected in November-December 1998 on a transect from Seattle, WA, 48N, to McMurdo, Antarctica, 71S (n = 19), and over a two-year interval on the Washington Coast, 48N (n = 11), and Point Barrow, AK, 71N (n = 6). Results indicate that the average ?D of global atmospheric H2 is +130 +/- 4, with average ?D values of +123 +/- 3 and +138 +/- 8 in the northern and southern hemispheres, respectively. Comparison of background and polluted samples in the Seattle area indicate the ?D of H2 produced by anthropogenic activities (e.g. automobiles) is -1961 +/- 10. Laboratory combustion studies of pine needles and pine branches indicate that the ?D of H2 emitted during biomass burning is -293 +/- 60. The results of field experiments (n = 6) using a large chamber to isolate a volume of air in contact with soil imply that the H2 removed during soil uptake has a ?D value 57 +/- 24 lower than that of atmospheric H2. The constraints that these preliminary isotopic measurements place on the global H2 budget are limited by the unmeasured isotopic composition of photochemically produced H2, ?Dh?. However, the global H2 isotope balance implies that the average global value of ?Dh? must be +130, and this value is demonstrated to be plausible. Therefore, it is concluded that the available isotopic measurements are not in disagreement with the global H2 budget, as had been previously suggested.

  11. Heterogeneous Catalysis: Deuterium Exchange Reactions of Hydrogen and Methane

    ERIC Educational Resources Information Center

    Mirich, Anne; Miller, Trisha Hoette; Klotz, Elsbeth; Mattson, Bruce

    2015-01-01

    Two gas phase deuterium/hydrogen exchange reactions are described utilizing a simple inexpensive glass catalyst tube containing 0.5% Pd on alumina through which gas mixtures can be passed and products collected for analysis. The first of these exchange reactions involves H[subscript 2] + D[subscript 2], which proceeds at temperatures as low as 77

  12. Ordered ground states of metallic hydrogen and deuterium

    NASA Technical Reports Server (NTRS)

    Ashcroft, N. W.

    1981-01-01

    The physical attributes of some of the more physically distinct ordered states of metallic hydrogen and metallic deuterium at T = 0 and nearby are discussed. The likelihood of superconductivity in both is considered with respect to the usual coupling via the density fluctuations of the ions.

  13. Heterogeneous Catalysis: Deuterium Exchange Reactions of Hydrogen and Methane

    ERIC Educational Resources Information Center

    Mirich, Anne; Miller, Trisha Hoette; Klotz, Elsbeth; Mattson, Bruce

    2015-01-01

    Two gas phase deuterium/hydrogen exchange reactions are described utilizing a simple inexpensive glass catalyst tube containing 0.5% Pd on alumina through which gas mixtures can be passed and products collected for analysis. The first of these exchange reactions involves H[subscript 2] + D[subscript 2], which proceeds at temperatures as low as 77…

  14. Equations of state for hydrogen and deuterium.

    SciTech Connect

    Kerley, Gerald Irwin

    2003-12-01

    This report describes the complete revision of a deuterium equation of state (EOS) model published in 1972. It uses the same general approach as the 1972 EOS, i.e., the so-called 'chemical model,' but incorporates a number of theoretical advances that have taken place during the past thirty years. Three phases are included: a molecular solid, an atomic solid, and a fluid phase consisting of both molecular and atomic species. Ionization and the insulator-metal transition are also included. The most important improvements are in the liquid perturbation theory, the treatment of molecular vibrations and rotations, and the ionization equilibrium and mixture models. In addition, new experimental data and theoretical calculations are used to calibrate certain model parameters, notably the zero-Kelvin isotherms for the molecular and atomic solids, and the quantum corrections to the liquid phase. The report gives a general overview of the model, followed by detailed discussions of the most important theoretical issues and extensive comparisons with the many experimental data that have been obtained during the last thirty years. Questions about the validity of the chemical model are also considered. Implications for modeling the 'giant planets' are also discussed.

  15. Lifetimes of Hydrogen and Deuterium Related Vibrational Modes in Silicon

    SciTech Connect

    Budde, M.; Luepke, G.; Chen, E; Zhang, X.; Tolk, N. H.; Feldman, L. C.; Tarhan, E.; Ramdas, A. K.; Stavola, M.

    2001-10-01

    Lifetimes of hydrogen and deuterium related stretch modes in Si are measured by high-resolution infrared absorption spectroscopy and transient bleaching spectroscopy. The lifetimes are found to be extremely dependent on the defect structure, ranging from 2 to 295 ps. Against conventional wisdom, we find that lifetimes of Si-D modes typically are longer than for the corresponding Si-H modes. The potential implications of the results on the physics of electronic device degradation are discussed.

  16. Reactivity of TiO 2 with hydrogen and deuterium

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Sushchikh, M.; Mills, G.; Metiu, H.; McFarland, E.

    2004-05-01

    The reactivity of rutile phase TiO 2 (1 1 0) and polycrystalline anatase surfaces with molecular and ionized deuterium and hydrogen was investigated. Thermal Desorption Spectroscopy (TDS), following exposure to more than 100 kL of molecular deuterium, showed a D 2 desorption peak at ˜440 K on both single crystal rutile and polycrystalline anatase surfaces. The desorption peak was observed following exposure only at surface temperatures between 140-270 K. Ionized D 2 is significantly more reactive with the titania surface and two desorption peaks at 380 K and ˜550 K were observed together with a small D 2O peak observed at ˜440 K. Dosing the surfaces with hydrogen and deuterium either in succession or as a mixture showed HD desorption with no change in the desorption peaks, consistent with dissociative adsorption of both ionized and molecular species. The experimental data was compared to Density Functional Theory calculations and modeled as a two-step process of hydrogen dissociation at oxygen vacancy sites on TiO 2.

  17. HYDROGEN AND DEUTERIUM NMR OF SOLIDS BY MAGIC ANGLE SPINNING

    SciTech Connect

    Eckman, R.R.

    1982-10-01

    The nuclear magnetic resonance of solids has long been characterized by very large spectral broadening which arises from internuclear dipole-dipole coupling or the nuclear electric quadrupole interaction. These couplings can obscure the smaller chemical shift interaction and make that information unavailable. Two important and difficult cases are that of hydrogen and deuterium. For example, the homonuclear dipolar broadening, HD, for hydrogen is usually several tens of kilohertz. For deuterium, HD is relatively small; however, the quadrupole interaction causes a broadening which can be hundreds of kilohertz in polycrystalline or amorphous solids. The development of cross polarization, heteronuclear radiofrequency decoupling, and coherent averaging of nuclear spin interactions has provided measurement of chemical shift tensors in solids. Recently, double quantum NMR and double quantum decoupling have led to measurement of deuterium and proton chemical shift tensors, respectively. A general problem of these experiments is the overlapping of the tensor powder pattern spectra of magnetically distinct sites which cannot be resolved. In this work, high resolution NMR of hydrogen and deuterium in solids is demonstrated. For both nuclei, the resonances are narrowed to obtain liquid-like isotropic spectra by high frequency rotation of the sample about an axis inclined at the magic angle, {beta}{sub m} = Arccos(3{sup -1/2}), with respect to the direction of the external magnetic field. Two approaches have been developed for each nucleus. For deuterium, the powder spectra were narrowed by over three orders of magnitude by magic angle rotation with precise control of {beta}. A second approach was the observation of deuterium double quantum transitions under magic angle rotation. For hydrogen, magic angle rotation alone could be applied to obtain the isotropic spectrum when H{sub D} was small. This often occurs naturally when the nuclei are semi-dilute or involved in internal motion. In the general case of large H{sub D}, isotropic spectra were obtained by dilution of {sup 1}H with {sup 2}H combined with magic angle rotation. The resolution obtained represents the practical limit for proton NMR of solids. Theoretical and technical aspects are described in the text with comments on the application of the principles to other nuclei of interest.

  18. Measurement of the ratio of hydrogen to deuterium at the KSTAR 2009 experimental campaign

    SciTech Connect

    Kwak, Jong-Gu; Wang, Son Jong; Kim, Sun Ho; Park, Jae Min; Na, Hoon Kyun

    2010-10-15

    The control of the ratio of hydrogen to the deuterium is one of the very important issues for ion cyclotron range of frequency (ICRF) minority heating as well as the plasma wall interaction in the tokamak. The ratio of hydrogen to deuterium during the tokamak shot was deduced from the emission spectroscopy measurements during the KSTAR 2009 experimental campaign. Graphite tiles were used for the plasma facing components (PFCs) at KSTAR and its surface area exposed to the plasma was about 11 m{sup 2}. The data showed that it remained as high as around 50% during the campaign period because graphite tiles were exposed to the air for about two months and the hydrogen contents at the tiles are not fully pumped out due to the lack of baking on the PFC in the 2009 campaign. The validation of the spectroscopy method was checked by using the Zeeman effects and the ratio of hydrogen to the deuterium is compared with results from the residual gas analysis. During the tokamak shot, the ratio is low below 10% initially and saturated after around 1 s. When there is a hydrogen injection to the vessel via ion cyclotron wall conditioning and the boronization process where the carbone is used, the ratio of the hydrogen to the deuterium is increased by up to 100% and it recovers to around 50% after one day of operation. However it does not decrease below 50% at the end of the experimental campaign. It was found that the full baking on the PFC (with a high temperature and sufficient vacuum pumping) is required for the ratio control which guarantees the efficient ICRF heating at the KSTAR 2010 experimental campaign.

  19. The pion nucleon scattering lengths from pionic hydrogen and deuterium

    NASA Astrophysics Data System (ADS)

    Schröder, H.-Ch.; Badertscher, A.; Goudsmit, P. F. A.; Janousch, M.; Leisi, H. J.; Matsinos, E.; Sigg, D.; Zhao, Z. G.; Chatellard, D.; Egger, J.-P.; Gabathuler, K.; Hauser, P.; Simons, L. M.; Rusi El Hassani, A. J.

    2001-07-01

    This is the final publication of the ETH Zurich Neuchâtel PSI collaboration on the pionic hydrogen and deuterium precision X-ray experiments. We describe the recent hydrogen 3 p 1 s measurement, report on the determination of the Doppler effect correction to the transition line width, analyze the deuterium shift measurement and discuss implications of the combined hydrogen and deuterium results. From the pionic hydrogen 3 p 1 s transition experiments we obtain the strong-interaction energy level shift \\varepsilon_{1s} = -7.108±0.013 (stat.)±0.034 (syst.) eV and the total decay width Γ_{1s} = 0.868±0.040 (stat.)±0.038 (syst.) eV of the 1s state. Taking into account the electromagnetic corrections we find the hadronic π N s-wave scattering amplitude a_{π-prightarrowπ-p} = 0.0883±0.0008 m_{π}^{-1} for elastic scattering and a_{π-prightarrowπ0n} = -0.128±0.006 m_{π} ^{-1} for single charge exchange, respectively. We then combine the pionic hydrogen results with the 1 s level shift measurement on pionic deuterium and test isospin symmetry of the strong interaction: our data are still compatible with isospin symmetry. The isoscalar and isovector π N scattering lengths (within the framework of isospin symmetry) are found to be b_0 = -0.0001^{+0.0009}_{-0.0021} m_{π}^{-1} and b1 = -0.0885^{+0.0010}_{-0.0021} m_{π} ^{-1}, respectively. Using the GMO sum rule, we obtain from b_1 a new value of the π N coupling constant (g_{π N} = 13.21_{-0.05}^{+0.11}) from which follows the Goldberger Treiman discrepancy Δ_{{GT}} =0.027_{-0.008}^{+0.012}. The new values of b_0 and g_{π N} imply an increase of the nucleon sigma term by at least 9 MeV.

  20. Diffusion of hydrogen and deuterium in Zr-Al

    SciTech Connect

    Knize, R.J.; Cecchi, J.L.

    1982-10-01

    Optimization of getter performance necessitates a detailed understanding of the getter operation for a variety of experimental parameters, including pressure, temperature, getter mass, and getter thickness. For pumping at low pressures or during slow desorption, the getter operation will be dependent primarily on surface kinetics, which have been described previously. During pumping at higher pressures or during rapid desorption, bulk diffusion may play an important role. In this paper we present the first measurements of the diffusivities of hydrogen (D/sub H/) and deuterium (D/sub D/) in Zr-Al as determined from detailed analysis of desorption.

  1. Infrared spectroscopy of solid hydrogen sulfide and deuterium sulfide.

    PubMed

    Fathe, Kristin; Holt, Jennifer S; Oxley, Susan P; Pursell, Christopher J

    2006-09-21

    The infrared spectra of solid hydrogen sulfide (H2S) and deuterium sulfide (D2S) were collected at very low temperatures. Vapor deposition of thin films at the lowest temperature of 10 K produced amorphous solids while deposition at 70 K yielded the crystalline phase III. Infrared interference fringe patterns produced by the films during deposition were used to determine the film thickness. Careful measurement of the integrated absorbance peaks, along with the film thickness, allowed determination of the integrated band intensities. This report represents the first complete presentation of the infrared spectra of the amorphous solids. Observations of peaks near 3.915 and 1.982 microm (ca. 2554 and 5045 cm(-1), respectively) may be helpful in the conclusive identification of solid hydrogen sulfide on the surface of Io, a moon of Jupiter. PMID:16970373

  2. Diffusion of hydrogen, deuterium, and tritium in niobium

    SciTech Connect

    Matusiewicz, Gerald Robert

    1981-01-01

    The diffusion of hydrogen in niobium was investigated over the temperature range 148 to 500 degrees Kelvin, using measurements of the elastic after effect caused by long range diffusion (the Gorsky Effect). Relaxation curves for pure annealed niobium were generally not of the single exponential form expected from the Gorsky Effect theory, but were described well by a sum of two exponential curves with different amplitudes and relaxation times. The effects of oxygen and nitrogen interstitials on the diffusion were studied and were not in agreement with conventional trapping models. Deuterium and tritium diffusion in niobium were also studied, and a non-classical isotope effect was observed. Hydrogen diffusion coefficients in several Nb-Ta alloys were measured, and the diffusivity in all these alloys exhibited a non-Arrhenius temperature dependence. Experimental results were compared to several models for diffusion and trapping. A model is presented which can account for the form of the relaxation curves observed in pure, annealed niobium.

  3. Experimental results of hydrogen distillation at the low power cryogenic column for the production of deuterium depleted hydrogen

    SciTech Connect

    Alekseev, I.; Fedorchenko, O.; Kravtsov, P.; Vasilyev, A.; Vznuzdaev, M.

    2008-07-15

    The Deuterium Removal Unit (DRU) has been designed and built at the Petersburg Nuclear Physics Inst. (PNPI) to produce isotopically pure hydrogen with deuterium content less than 1 ppm. The cryogenic distillation column of 2.2 cm inner diameter and 155 cm packing height is the main element of the DRU. Column performances at different hydrogen distillation operating modes have been measured. The height equivalent to theoretical plate (HETP) for the column is 2.2 cm and almost constant over a wide range of vapour flow rates. Deuterium depleted hydrogen with a deuterium content of less than 0.1 ppm was produced in required quantity. (authors)

  4. Pion Electroproduction form Helium 3, Deuterium, and Hydrogen

    SciTech Connect

    S. Avery

    2002-05-01

    A series of measurements for pion electroproduction from helium-3, deuterium, and hydrogen were completed at the Thomas Jefferson National Accelerator Facility by the NucPi Collaboration. E91003 began taking data in February 1998 and was completed in April 1998. The longitudinal and transverse parts of the differential cross section were extracted, by means of a Rosenbluth type separation, in the direction parallel to the virtual photon, at Q 2 = 0.4 GeV 2 , for W = 1.15 and W = 1.6 GeV. The mass dependence of the longitudinal cross section should provide insight into the surprising apparent absence of any significant cross section enhancement due to excess pions in the nuclear medium.

  5. Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 3. Estimating Surface Area Exposure by Deuterium Uptake

    NASA Astrophysics Data System (ADS)

    Khakinejad, Mahdiar; Ghassabi Kondalaji, Samaneh; Donohoe, Gregory C.; Valentine, Stephen J.

    2016-03-01

    Gas-phase hydrogen deuterium exchange (HDX), collision cross section (CCS) measurement, and molecular dynamics simulation (MDS) techniques were utilized to develop and compare three methods for estimating the relative surface area exposure of separate peptide chains within bovine insulin ions. Electrosprayed [M - 3H]3- and [M - 5H]5- insulin ions produced a single conformer type with respective collision cross sections of 528 ± 5 Å2 and 808 ± 2 Å2. [M - 4H]4- ions were comprised of more compact (Ω = 676 ± 3 Å2) and diffuse (i.e., more elongated, Ω = 779 ± 3 Å2) ion conformer types. Ions were subjected to HDX in the drift tube using D2O as the reagent gas. Collision-induced dissociation was used to fragment mobility-selected, isotopically labeled [M - 4H]4- and [M - 5H]5- ions into the protein subchains. Deuterium uptake levels of each chain can be explained by limited inter-chain isotopic scrambling upon collisional activation. Using nominal ion structures from MDS and a hydrogen accessibility model, the deuterium uptake for each chain was correlated to its exposed surface area. In separate experiments, the per-residue deuterium content for the protonated and deprotonated ions of the synthetic peptide KKDDDDDIIKIIK were compared. The differences in deuterium content indicated the regional HDX accessibility for cations versus anions. Using ions of similar conformational type, this comparison highlights the complementary nature of HDX data obtained from positive- and negative-ion analysis.

  6. Thermotransport of hydrogen and deuterium in vanadium, niobium and tantalum alloys

    SciTech Connect

    Smith, M.F.

    1981-10-01

    Heats of transport have been determined for thermotransport of hydrogen and deuterium in pure vanadium, niobium and tantalum; in vanadium alloyed with either niobium, titanium or chromium; and in niobium-tantalum alloys. In all cases, thermotransport was toward colder regions and was significantly greater for deuterium than for hydrogen. A mass spectrometric technique was used to simultaneously measure heats of transport for hydrogen and deuterium in a single specimen containing both isotopes. This technique greatly increased the precision with which isotope effects in the heat of transport could be measured. The predominant effect of alloying was to dramatically increase thermotransport; however, thermotransport decreased as niobium was added to tantalum.

  7. Counter-Permeation of Deuterium and Hydrogen Through INCONEL 600[reg

    SciTech Connect

    Takeda, Tetsuaki; Iwatsuki, Jin

    2004-04-15

    Permeation of hydrogen isotopes through a high-temperature alloy used for heat exchanger and catalyst pipes is an important problem in the hydrogen production system connected to the High-Temperature Engineering Test Reactor (HTTR). The objective of this study is to investigate the effect of the existence of hydrogen in an outside pipe on the amount of permeated deuterium through the pipe. It was found that the amount of permeated deuterium decreases by increasing the partial pressure of hydrogen in the outside pipe when the partial pressure of deuterium in the pipe is lower than 100 Pa and that of hydrogen in the outside pipe is larger than 10 kPa. The amount of permeated deuterium on counter permeation was predicted quantitatively by using an effectiveness factor for diffusivity of deuterium in metals and by taking into account the equilibrium state for hydrogen, deuterium, and HD molecules on the metal surface. From the results obtained in this study, it is supposed that the amount of tritium transferred from the primary circuit of the HTTR to the hydrogen production system will be reduced by the existence of high-pressure hydrogen in the catalyst pipe of the steam reformer.

  8. Probing protein ensemble rigidity and hydrogen-deuterium exchange

    NASA Astrophysics Data System (ADS)

    Sljoka, Adnan; Wilson, Derek

    2013-10-01

    Protein rigidity and flexibility can be analyzed accurately and efficiently using the program floppy inclusion and rigid substructure topography (FIRST). Previous studies using FIRST were designed to analyze the rigidity and flexibility of proteins using a single static (snapshot) structure. It is however well known that proteins can undergo spontaneous sub-molecular unfolding and refolding, or conformational dynamics, even under conditions that strongly favor a well-defined native structure. These (local) unfolding events result in a large number of conformers that differ from each other very slightly. In this context, proteins are better represented as a thermodynamic ensemble of ‘native-like’ structures, and not just as a single static low-energy structure. Working with this notion, we introduce a novel FIRST-based approach for predicting rigidity/flexibility of the protein ensemble by (i) averaging the hydrogen bonding strengths from the entire ensemble and (ii) by refining the mathematical model of hydrogen bonds. Furthermore, we combine our FIRST-ensemble rigidity predictions with the ensemble solvent accessibility data of the backbone amides and propose a novel computational method which uses both rigidity and solvent accessibility for predicting hydrogen-deuterium exchange (HDX). To validate our predictions, we report a novel site specific HDX experiment which characterizes the native structural ensemble of Acylphosphatase from hyperthermophile Sulfolobus solfataricus (Sso AcP). The sub-structural conformational dynamics that is observed by HDX data, is closely matched with the FIRST-ensemble rigidity predictions, which could not be attained using the traditional single ‘snapshot’ rigidity analysis. Moreover, the computational predictions of regions that are protected from HDX and those that undergo exchange are in very good agreement with the experimental HDX profile of Sso AcP.

  9. Recombinant Nepenthesin II for Hydrogen/Deuterium Exchange Mass Spectrometry.

    PubMed

    Yang, Menglin; Hoeppner, Morgan; Rey, Martial; Kadek, Alan; Man, Petr; Schriemer, David C

    2015-07-01

    The pitcher secretions of the Nepenthes genus of carnivorous plants contain a proteolytic activity that is very useful for hydrogen/deuterium exchange mass spectrometry (HX-MS). Our efforts to reconstitute pitcher fluid activity using recombinant nepenthesin I (one of two known aspartic proteases in the fluid) revealed a partial cleavage profile and reduced enzymatic stability in certain HX-MS applications. We produced and characterized recombinant nepenthesin II to determine if it complemented nepenthesin I in HX-MS applications. Nepenthesin II shares many properties with nepenthesin I, such as fast digestion at reduced temperature and pH, and broad cleavage specificity, but in addition, it cleaves C-terminal to tryptophan. Neither enzyme reproduces the C-terminal proline cleavage we observed in the natural extract. Nepenthesin II is considerably more resistant to chemical denaturants and reducing agents than nepenthesin I, and it possesses a stability profile that is similar to that of pepsin. Higher stability combined with the slightly broader cleavage specificity makes nepenthesin II a useful alternative to pepsin and a more complete replacement for pitcher fluid in HX-MS applications. PMID:25993527

  10. Hydrogen, Deuterium and Tritium in Palladium: An Elastic Constants Study

    SciTech Connect

    Bach, H.T.; Schwarz, R.B.; Tuggle, D.G.

    2005-07-15

    We have used resonant ultrasound spectroscopy to measure the three independent elastic constants of Pd-H, Pd-D, and Pd-T single crystal at 300K as a function of hydrogen, deuterium, and tritium concentration, respectively. The addition of interstitial H (D, or T) atoms, located at (0,1/2,0) in the fcc Pd lattice, affects all three elastic constants C', C{sub 44}, and B. In the mixed ({alpha}+{beta}) phase, and with increasing H isotope, the shear modulus C' shows an abnormal softening whereas C{sub 44} and B do not. This is explained in terms of Zener-type an elastic relaxations affecting the shape of the hydride phases in the coherent({alpha}+{beta}) two-phase mixture In the single {beta}-phase, C' shows a strong isotope dependence whereas C{sub 44} and B show none. This behavior is explained in terms of differences in the excitation of optical phonons. In Pd-T, {sup 3}He is produced by the radioactive decay of tritium. We have measured in situ the swelling and the change in the elastic constants in Pd-T as a function of aging time. Aging ({sup 3}He formation) affects all three elastic constants. These measurements are being used to understand the early stages of {sup 3}H-{sup 3}He cluster formation in aged Pd-T crystal.

  11. Hydrogen, deuterium and tritium in palladium: An eleastic constants study

    SciTech Connect

    Bach, H. T.; Schwarz, R. B.; Tuggle, D. G.

    2004-01-01

    We have used resonant ultrasound spectroscopy to measure the three independent elastic constants of Pd-H, Pd-D, and Pd-T single crystal at 300K as a junction of hydrogen, deuterium, and tritium concentration, respectively. The addition of interstitial H (D, or T) atoms, located at (0, 1/2, 0) in the fcc Pd lattice, affects all three elastic constants C, C{sub 44}, and B. In the mixed (a+{beta}) phase, and with increasing H isotope, the shear modulus C' shows an abnormal softening whereas C{sub 44} and B do not. This is explained in terms of Zener-type anelastic relaxations affecting the shape of the hydride phases in the coherent ({alpha}+{beta}) two-phase mixture In the single {beta}-phase, C' shows a strong isotope dependence whereas C{sub 44} and B show none. This behavior is explained in terms of differences in the excitation of optical phonons. In Pd-T, {sup 3}He is produced by the radioactive decay of tritium. We have measured in situ the swelling and the change in the elastic constants in Pd-T as a function of aging time. Aging ({sup 3}He formation) affects all three elastic constants. These measurements are being used to understand the early stages of {sup 3}H-{sup 3}He clusterformation in aged Pd-T crystal.

  12. Retention property of deuterium for fuel recovery in divertor by using hydrogen storage material

    NASA Astrophysics Data System (ADS)

    Mera, Saori; Tonegawa, Akira; Matsumura, Yoshihito; Sato, Kohnosuke; Kawamura, Kazutaka

    2014-10-01

    Magnetic confinement fusion reactor by using Deuterium and Tritium of hydrogen isotope as fuels is suggested as one of the future energy source. Most fuels don't react and are exhausted out of fusion reactor. Especially, Tritium is radioisotope and rarely exists in nature, so fuels recovery is necessary. This poster presentation will explain about research new fuel recovery method by using hydrogen storage materials in divertor simulator TPD-Sheet IV. Samples are tungsten coated with titanium; tungsten of various thickness, and titanium films deposited by ion plating on tungsten substrates. The sample surface temperature is measured by radiation thermometer. Retention property of deuterium after deuterium plasma irradiation was examined with thermal desorption spectroscopy (TDS). As a result, the TDS measurement shows that deuterium is retained in titanium. Therefore, Titanium as a hydrogen storage material expects to be possible to use separating and recovering fuel particles in divertor.

  13. Charged Pion Photoproduction from Hydrogen and Deuterium at Jefferson Lab

    SciTech Connect

    Haiyan Gao

    2003-02-01

    The {gamma}n {yields} {pi}{sup -}p and {gamma}p {yields} {pi}{sup +}n reactions are essential probes of the transition from meson-nucleon degrees of freedom to quark-gluon degrees of freedom in exclusive processes. The cross sections of these processes are also, advantageous, for the investigation of oscillatory behavior around the quark counting prediction, since they decrease relatively slower with energy compared with other photon-induced processes. Moreover, these photoreactions in nuclei can probe the QCD nuclear filtering and color transparency effects. In this talk, I discuss the preliminary results on the {gamma}p {yields} {pi}{sup +}n and {gamma}n {yields} {pi}{sup -}p processes at a center-of-mass angle of 90{sup o} from Jefferson Lab experiment E94-104. I also discuss a new experiment in which singles {gamma}p {yields} {pi}{sup +}n measurement from hydrogen, and coincidence {gamma}n {yields} {pi}{sup -}p measurements at the quasifree kinematics from deuterium and {sup 12}C for photon energies between 2.25 GeV to 5.8 GeV in fine steps at a center-of-mass angle of 90{sup o} are planned. The proposed measurement will allow a detailed investigation of the oscillatory scaling behavior in photopion production processes and the study of the nuclear dependence of rather mysterious oscillations with energy that previous experiments have indicated. The various nuclear and perturbative QCD approaches, ranging from Glauber theory, to quark-counting, to Sudakov-corrected independent scattering, make dramatically different predictions for the experimental outcomes.

  14. Dynamic deuterium recycling on tungsten under carbon-deuterium implantation circumstance

    NASA Astrophysics Data System (ADS)

    Taguchi, Tomohisa; Kobayashi, Makoto; Kawasaki, Kiyotaka; Miyahara, Yuto; Ashikawa, Naoko; Sagara, Akio; Yoshida, Naoaki; Miyamoto, Mitsutaka; Ono, Kotaro; Hatano, Yuji; Oya, Yasuhisa; Okuno, Kenji

    2013-07-01

    Dynamics of deuterium recycling, including retention and sputtering behaviors was studied for C+ implanted tungsten. The amount of deuterium trapped by irradiation damages was clearly increased in the C+ implantation sample because the irradiation damages in the C+ implanted sample were formed more than those in the only D2+ implanted one. In addition, the deuterium diffusion toward the bulk would be refrained by the formation of W-C mixed layer, which would work as the deuterium diffusion barrier. The in situ sputtered particle measurement system has been established and revealed that the formation of hydrocarbons such as CD4 was directly observed during D2+ implantation into the C+ implanted tungsten. In the lower deuterium fluence, the CD4 sputtering rate was enhanced with increasing the deuterium fluence. It was considered that the sputtering rate of CD4 would be controlled by the concentration of deuterium on the top surface of the W-C mixed layer.

  15. Laser separation of hydrogen isotopes: Tritium-from-deuterium recovery

    SciTech Connect

    Magnotta, F.; Herman, I.P.; Aldridge, F.T.; Maienschein, J.L.

    1984-02-01

    Single-step enrichment factors exceeding 15,000 have been observed in the removal of tritium-from-deuterium by 12 ..mu..m laser multiple-photon dissociation of chloroform. The photochemistry and photophysics of this process is discussed along with prospects for implementation of this method in practical heavy water reactor detritiation. 7 refs., 7 figs., 1 tab.

  16. Measurement of the nuclear polarization of hydrogen and deuterium molecules using a Lamb-shift polarimeter

    SciTech Connect

    Engels, Ralf Gorski, Robert; Grigoryev, Kiril; Mikirtychyants, Maxim; Rathmann, Frank; Seyfarth, Hellmut; Ströher, Hans; Weiss, Philipp; Kochenda, Leonid; Kravtsov, Peter; Trofimov, Viktor; Tschernov, Nikolay; Vasilyev, Alexander; Vznuzdaev, Marat; Schieck, Hans Paetz gen.

    2014-10-15

    Lamb-shift polarimeters are used to measure the nuclear polarization of protons and deuterons at energies of a few keV. In combination with an ionizer, the polarization of hydrogen and deuterium atoms was determined after taking into account the loss of polarization during the ionization process. The present work shows that the nuclear polarization of hydrogen or deuterium molecules can be measured as well, by ionizing the molecules and injecting the H{sub 2}{sup +} (or D{sub 2}{sup +}) ions into the Lamb-shift polarimeter.

  17. Computation of hyperfine energies of hydrogen, deuterium and tritium quantum dots

    NASA Astrophysics Data System (ADS)

    Çakır, Bekir; Özmen, Ayhan; Yakar, Yusuf

    2016-01-01

    The hyperfine energies and hyperfine constants of the ground and excited states of hydrogen, deuterium and tritium quantum dots(QDs) are calculated. Quantum genetic algorithm (QGA) and Hartree-Fock-Roothaan (HFR) methods are employed to calculate the unperturbed wave functions and energy eigenvalues. The results show that in the medium and strong confinement regions the hyperfine energy and hyperfine constant are strongly affected by dot radius, impurity charge, electron spin orientation, impurity spin and impurity magnetic moment. Besides, in all dot radii, the hyperfine splitting and hyperfine constant of the confined hydrogen and tritium atoms are approximately equivalent to each other and they are greater than the confined deuterium atom.

  18. Longitudinal Lelectroproduction of Charged Pions on Hydrogen, Deuterium, and Helium 3

    SciTech Connect

    David Gaskell

    2001-05-01

    Conventional pictures of nuclear interactions, in which the pion mediates the long/medium range part of the nuclear force, predict an enhancement of the virtual pion cloud in nuclei relative to that in the free nucleon. Jefferson Lab Experiment E91003 measured charged pion electroproduction from Hydrogen, Deuterium, and Helium-3. The longitudinal cross section, which in the limit of pole dominance can be viewed as the quasifree knockout of a virtual pion, was extracted via a Rosenbluth separation. The longitudinal cross sections from Deuterium and Helium-3 were compared to Hydrogen to look for signatures of the nuclear pions.

  19. Hydrogen/deuterium exchange on aromatic rings during atmospheric pressure chemical ionization mass spectrometry.

    PubMed

    Davies, Noel W; Smith, Jason A; Molesworth, Peter P; Ross, John J

    2010-04-15

    It has been demonstrated that substituted indoles fully labelled with deuterium on the aromatic ring can undergo substantial exchange back to partial and even fully protonated forms during atmospheric pressure chemical ionisation (APCI) liquid chromatography/mass spectrometry (LC/MS). The degree of this exchange was strongly dependent on the absolute quantity of analyte, the APCI desolvation temperature, the nature of the mobile phase, the mobile phase flow rate and the instrument used. Hydrogen/deuterium (H/D) exchange on several other aromatic ring systems during APCI LC/MS was either undetectable (nitrobenzene, aniline) or extremely small (acetanilide) compared to the effect observed for substituted indoles. This observation has major implications for quantitative assays using deuterium-labelled internal standards and for the detection of deuterium-labelled products from isotopically labelled feeding experiments where there is a risk of back exchange to the protonated form during the analysis. PMID:20213724

  20. The ground state properties of spin-aligned atomic hydrogen, deuterium, and tritium

    NASA Technical Reports Server (NTRS)

    Etters, R. D.; Dugan, J. V., Jr.; Palmer, R. W.

    1975-01-01

    The internal energy, pressure, and compressibility of ground-state, spin-aligned atomic hydrogen, deuterium, and tritium are calculated assuming that all pair interactions occur via the atomic triplet (spin-aligned) potential. The conditions required to obtain atomic hydrogen and its isotopes in bulk are discussed; such a development would be of value in propulsion systems because of the light mass and energetic recombination of atomic hydrogen. Results show that atomic triplet hydrogen and deuterium remain gaseous at 0 K, and that tritium forms a liquid with a binding energy of approximately -0.75 K per atom at a molar volume of 130 cu cm per mole. The pair distribution function for these systems is calculated, and the predicted superfluid behavior of atomic triplet hydrogen and tritium is briefly discussed.

  1. Deuterium inventory in Tore Supra: Contribution of carbon deposits outgassing

    NASA Astrophysics Data System (ADS)

    Panayotis, S.; Pégourié, B.; Caprin, E.; Douai, D.; Hatchressian, J.-C.; Negrier, V.; Pascal, J.-Y.; Vartanian, S.; Bucalossi, J.; Monier-Garbet, P.

    2013-07-01

    In carbon dominated devices, the in vessel D inventory obtained from post-mortem analyses of plasma facing component samples is generally smaller by a factor of ˜4 than that estimated from gas balance measurements. However, for an accurate evaluation of the wall inventory, gas balance measurements must be done not only during discharges and conditioning procedures, but also in between discharges and during vents. From the analysis of the whole Tore Supra database for the 2002-2007 period, we show that long term outgassing during nights, weekends and vents is essential for evaluating the deuterium release. Taking these contributions into account reconciles the gas balance and post-mortem estimations of fuel retention.

  2. Dual Studies on a Hydrogen-Deuterium Exchange of Resorcinol and the Subsequent Kinetic Isotope Effect

    ERIC Educational Resources Information Center

    Giles, Richard; Kim, Iris; Chao, Weyjuin Eric; Moore, Jennifer; Jung, Kyung Woon

    2014-01-01

    An efficient laboratory experiment has been developed for undergraduate students to conduct hydrogen-deuterium (H-D) exchange of resorcinol by electrophilic aromatic substitution using D[subscript 2]O and a catalytic amount of H[subscript 2]SO[subscript 4]. The resulting labeled product is characterized by [superscript 1]H NMR. Students also

  3. Dual Studies on a Hydrogen-Deuterium Exchange of Resorcinol and the Subsequent Kinetic Isotope Effect

    ERIC Educational Resources Information Center

    Giles, Richard; Kim, Iris; Chao, Weyjuin Eric; Moore, Jennifer; Jung, Kyung Woon

    2014-01-01

    An efficient laboratory experiment has been developed for undergraduate students to conduct hydrogen-deuterium (H-D) exchange of resorcinol by electrophilic aromatic substitution using D[subscript 2]O and a catalytic amount of H[subscript 2]SO[subscript 4]. The resulting labeled product is characterized by [superscript 1]H NMR. Students also…

  4. Hydrogen fluoride and deuterium fluoride lasers. Citations from the International Aerospace Abstracts data base

    NASA Technical Reports Server (NTRS)

    Mauk, S. C.

    1980-01-01

    Research cited from the international literature adresses various aspects of hydrogen fluoride and deuterium fluoride lasers. Topics covered include flows, laser outputs, molecular relaxation, molecular rotation, energy conversion efficiency, reaction kinetics, and laser materials. Continous wave and pulsed laser are considered. This updated bibliography contains 283 citations, 53 of which are new additions to the previous edition.

  5. Isotope effects in dense solid hydrogen - Phase transition in deuterium at 190 + or - 20 GPa

    NASA Technical Reports Server (NTRS)

    Hemley, R. J.; Mao, H. K.

    1989-01-01

    Raman measurements of solid normal deuterium compressed in a diamond-anvil cell indicate that the material undergoes a structural phase transformation at 190 + or - 20 GPa and 77 K. Spectroscopically, the transition appears analogous to that observed in hydrogen at 145 + or - 5 GPa. The large isotope effect on the transition pressure suggests there is a significant vibrational contribution to the relative stability of the solid phases of hydrogen at very high densities.

  6. Definitive proof of graphene hydrogenation by Clemmensen reduction: use of deuterium labeling

    NASA Astrophysics Data System (ADS)

    Sofer, Zdeněk; Jankovský, Ondřej; Libánská, Alena; Šimek, Petr; Nováček, Michal; Sedmidubský, David; Macková, Anna; Mikšová, Romana; Pumera, Martin

    2015-06-01

    Graphane is one of the most intensively studied derivatives of graphene. Here we demonstrate the evaluation of exact degree of graphene hydrogenation using the Clemmensen reduction reaction and deuterium labeling. The Clemmensen reduction reaction is based on application of zinc in an acid environment. It effectively reduces various functional groups (like ketones) present in graphite oxide. However, the mechanism of reduction is still unknown and elusive. Here we bring a major insight into the mechanisms of the Clemmensen reduction via deuterium labeling and the topochemical approach applied on graphite oxide. The use of deuterated reactants and the exact measurement of deuterium concentration in reduced/hydrogenated graphene by nuclear methods can be used for accurate estimation of C-H bond abundance in graphene. Various topochemical configurations of experiments showed that the reduction of a ketonic group proceeds in contact with the zinc metal by a carbenoid mechanism. Our results showed that the application of nuclear methods of isotope analysis in combination with deuterium labeling represents a very effective tool for investigation of graphene based materials. Our results demonstrate that graphene based materials can also be effectively used for the investigation of organic reaction mechanisms, because the robust structure of graphene allows the use of various spectroscopic techniques which could not be applied on small organic molecules.Graphane is one of the most intensively studied derivatives of graphene. Here we demonstrate the evaluation of exact degree of graphene hydrogenation using the Clemmensen reduction reaction and deuterium labeling. The Clemmensen reduction reaction is based on application of zinc in an acid environment. It effectively reduces various functional groups (like ketones) present in graphite oxide. However, the mechanism of reduction is still unknown and elusive. Here we bring a major insight into the mechanisms of the Clemmensen reduction via deuterium labeling and the topochemical approach applied on graphite oxide. The use of deuterated reactants and the exact measurement of deuterium concentration in reduced/hydrogenated graphene by nuclear methods can be used for accurate estimation of C-H bond abundance in graphene. Various topochemical configurations of experiments showed that the reduction of a ketonic group proceeds in contact with the zinc metal by a carbenoid mechanism. Our results showed that the application of nuclear methods of isotope analysis in combination with deuterium labeling represents a very effective tool for investigation of graphene based materials. Our results demonstrate that graphene based materials can also be effectively used for the investigation of organic reaction mechanisms, because the robust structure of graphene allows the use of various spectroscopic techniques which could not be applied on small organic molecules. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01356a

  7. Spontaneous versus induced hydrogen and deuterium helical shaped plasmas with electron internal transport barriers

    NASA Astrophysics Data System (ADS)

    Gobbin, M.; Franz, P.; Auriemma, F.; Lorenzini, R.; Marrelli, L.

    2015-09-01

    Electron internal transport barriers (eITBs) in high current plasmas with helical equilibria of the reversed field pinch experiment RFX-mod are analyzed and characterized in detail thanks to a high time resolution double filter diagnostic for the electron temperature spatial profile determination. The large amount of data provided by this diagnostic has required the development of dedicated algorithms and the identification of suitable parameters, reported and described in this paper, in order to perform automatic statistical studies. These numerical tools have been used to examine the effect of three dimensional (3D) magnetic fields applied by the RFX-mod 192 active coils in deuterium and hydrogen discharges with the aim to improve the sustainment and control of helical equilibria with eITBs. It is shown that 3D fields partially increase the occurring of helical states but with only a moderate effect on the eITBs duration; moreover, they have a different impact on the confinement properties in hydrogen and deuterium discharges. Numerical simulations, by the Hamiltonian guiding center code ORBIT, investigate the effect of magnetic topology in plasmas with and without the application of 3D fields on deuterium and hydrogen test ions transport. Results from numerical studies are in agreement with estimates of the particle confinement times showing that particle transport is reduced in deuterium plasmas but not significantly affected by the application of helical boundary conditions.

  8. Hydrogen and deuterium NMR of solids by magic-angle spinning

    SciTech Connect

    Eckman, R.R.

    1982-10-01

    The nuclear magnetic resonance of solids has long been characterized by very large specral broadening which arises from internuclear dipole-dipole coupling or the nuclear electric quadrupole interaction. These couplings can obscure the smaller chemical shift interaction and make that information unavailable. Two important and difficult cases are that of hydrogen and deuterium. The development of cross polarization, heteronuclear radiofrequency decoupling, and coherent averaging of nuclear spin interactions has provided measurement of chemical shift tensors in solids. Recently, double quantum NMR and double quantum decoupling have led to measurement of deuterium and proton chemical shift tensors, respectively. A general problem of these experiments is the overlapping of the tensor powder pattern spectra of magnetically distinct sites which cannot be resolved. In this work, high resolution NMR of hydrogen and deuterium in solids is demonstrated. For both nuclei, the resonances are narrowed to obtain liquid-like isotropic spectra by high frequency rotation of the sample about an axis inclined at the magic angle, ..beta../sub m/ = Arccos (3/sup -1/2/), with respect to the direction of the external magnetic field. For deuterium, the powder spectra were narrowed by over three orders of magnitude by magic angle rotation with precise control of ..beta... A second approach was the observation of deuterium double quantum transitions under magic angle rotation. For hydrogen, magic angle rotation alone could be applied to obtain the isotropic spectrum when H/sub D/ was small. This often occurs naturally when the nuclei are semi-dilute or involved in internal motion. In the general case of large H/sub D/, isotropic spectra were obtained by dilution of /sup 1/H with /sup 2/H combined with magic angle rotation. The resolution obtained represents the practical limit for proton NMR of solids.

  9. Definitive proof of graphene hydrogenation by Clemmensen reduction: use of deuterium labeling.

    PubMed

    Sofer, Zdeněk; Jankovský, Ondřej; Libánská, Alena; Šimek, Petr; Nováček, Michal; Sedmidubský, David; Macková, Anna; Mikšová, Romana; Pumera, Martin

    2015-06-21

    Graphane is one of the most intensively studied derivatives of graphene. Here we demonstrate the evaluation of exact degree of graphene hydrogenation using the Clemmensen reduction reaction and deuterium labeling. The Clemmensen reduction reaction is based on application of zinc in an acid environment. It effectively reduces various functional groups (like ketones) present in graphite oxide. However, the mechanism of reduction is still unknown and elusive. Here we bring a major insight into the mechanisms of the Clemmensen reduction via deuterium labeling and the topochemical approach applied on graphite oxide. The use of deuterated reactants and the exact measurement of deuterium concentration in reduced/hydrogenated graphene by nuclear methods can be used for accurate estimation of C-H bond abundance in graphene. Various topochemical configurations of experiments showed that the reduction of a ketonic group proceeds in contact with the zinc metal by a carbenoid mechanism. Our results showed that the application of nuclear methods of isotope analysis in combination with deuterium labeling represents a very effective tool for investigation of graphene based materials. Our results demonstrate that graphene based materials can also be effectively used for the investigation of organic reaction mechanisms, because the robust structure of graphene allows the use of various spectroscopic techniques which could not be applied on small organic molecules. PMID:26015058

  10. Synthesis, structural investigations, hydrogen-deuterium exchange studies, and molecular modeling of conformationally stablilized aromatic oligoamides.

    PubMed

    Yan, Yan; Qin, Bo; Ren, Changliang; Chen, Xiuying; Yip, Yeow Kwan; Ye, Ruijuan; Zhang, Dawei; Su, Haibin; Zeng, Huaqiang

    2010-04-28

    Biasing the conformational preferences of aromatic oligoamides by internally placing intramolecular hydrogen bonds has led to a series of stably folded molecular strands. This article presents the results from extensive solid-state, solution, and computational studies on these folding oligomers. Depending on its backbone length, an oligoamide adopts a crescent or helical conformation. Surprisingly, despite the highly repetitive nature of the backbone, the internally placed, otherwise very similar intramolecular hydrogen bonds showed significantly different stabilities as demonstrated by hydrogen-deuterium exchange data. It was also observed that the hydrogen-bonding strength can be tuned by adjusting the substituents attached to the exterior of the aromatic backbones. Examining the amide hydrogen-deuterium exchange rates of trimers revealed that a six-membered hydrogen bond nearing the ester end is the weakest among all the four intramolecular hydrogen bonds of a molecule. This observation was verified by ab initio quantum mechanical calculations at the level of B3LYP/6-31G*. Such a "weak point" creates the "battle of the bulge" where backbone twisting is centered, which is consistently observed in the solid-state structures of the four trimer molecules studied. In the solid state, the oligomers assemble into interesting one-dimensional structures. A pronounced columnar packing of short oligomers (i.e., dimers, trimers, and tetramer) and channel-like, potentially ion-conducting stacks of longer oligomers (i.e., tetramer, pentamer, and hexamer) were observed. PMID:20364840

  11. Measuring the hydrogen/deuterium exchange of proteins at high spatial resolution by mass spectrometry: overcoming gas-phase hydrogen/deuterium scrambling.

    PubMed

    Rand, Kasper D; Zehl, Martin; Jørgensen, Thomas J D

    2014-10-21

    Proteins are dynamic molecules that exhibit conformational flexibility to function properly. Well-known examples of this are allosteric regulation of protein activity and ligand-induced conformational changes in protein receptors. Detailed knowledge of the conformational properties of proteins is therefore pertinent to both basic and applied research, including drug development, since the majority of drugs target protein receptors and a growing number of drugs introduced to the market are therapeutic peptides or proteins. X-ray crystallography provides a static picture at atomic resolution of the lowest-energy structure of the native ensemble. There is a growing need for sensitive analytical tools to explore all of the significant molecular structures in the conformational landscape of proteins. Hydrogen/deuterium exchange monitored by mass spectrometry (HDX-MS) has recently emerged as a powerful method for characterizing protein conformational dynamics. The basis of this method is the fact that backbone amides in stable hydrogen-bonded structures (e.g., α-helices and β-sheets) are protected against exchange with the aqueous solvent. All protein structures are dynamic, however, and eventually all of the protecting hydrogen bonds will transiently break as the protein--according to thermodynamic principles--cycles through partially unfolded states that correspond to excited free energy levels. As a result, all of the backbone amides will eventually become temporarily solvent-exposed and exchange-competent over time. Consequently, a folded protein in D2O will gradually incorporate deuterium into its backbone amides, and the kinetics of the process can be readily monitored by mass spectrometry. The deuterium uptake kinetics for the intact protein (global exchange kinetics) represents the sum of the exchange kinetics for the individual backbone amides. Local exchange kinetics is typically achieved by using pepsin digestion under quench conditions (i.e., under cold acidic conditions where the amide hydrogen exchange rate is slowed by many orders of magnitude). The ability to localize the individual deuterated residues (the spatial resolution) is determined by the size (typically ∼7-15 residues) and the number of peptic peptides. These peptides provide a relatively coarse-grained picture of the protein dynamics. A fundamental understanding of the relationship between protein function/dysfunction and conformational dynamics requires in many cases higher resolution and ultimately single-residue resolution. In this Account, we summarize our efforts to achieve single-residue deuterium levels in proteins by electron-based or laser-induced gas-phase fragmentation methods. A crucial analytical requirement for this approach is that the pattern of deuterium labeling from solution is retained in the gas-phase fragment ions. It is therefore essential to control and minimize any occurrence of gas-phase randomization of the solution deuterium label (H/D scrambling) during the MS experiment. For this purpose, we have developed model peptide probes to accurately measure the onset and extent of H/D scrambling. Our analytical procedures to control the occurrence of H/D scrambling are detailed along with the physical parameters that induce it during MS analysis. In light of the growing use of gas-phase dissociation experiments to measure the HDX of proteins in order to obtain a detailed characterization and understanding of the dynamic conformations and interactions of proteins at the molecular level, we discuss the perspectives and challenges of future high-resolution HDX-MS methodology. PMID:25171396

  12. Hydrogen-deuterium exchange on plasma-exposed W and SS surface

    NASA Astrophysics Data System (ADS)

    Takagi, Ikuji; Nomura, Shinji; Minamimoto, Toshihiro; Akiyoshi, Masafumi; Kobayashi, Taishi; Sasaki, Takayuki

    2015-08-01

    The desorption cross section for hydrogen isotopes adsorbed on stainless steel (SS) and tungsten (W) has been evaluated experimentally to provide basic information on tritium exchange. One side of a sample sheet was alternately exposed to H and D plasma, and deuterium density on the surface was repeatedly observed using nuclear reaction analysis (NRA) under continuous plasma exposure. From the time dependent change in the deuterium density, the desorption cross sections for SS and W were estimated to be 6.9 ± 2.3 × 10-23 m2 and 4.6 ± 1.0 × 10-23 m2, respectively. No significant differences in the cross section between H and D plasma were observed. Recombinative desorption was found to dominate the desorption process owing to the low incident energy of hydrogen atoms.

  13. Improved Sequence Resolution by Global Analysis of Overlapped Peptides in Hydrogen/Deuterium Exchange Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Fajer, Piotr G.; Bou-Assaf, George M.; Marshall, Alan G.

    2012-07-01

    Management of the enormous amount of data produced during solution-phase hydrogen/deuterium exchange monitored by mass spectrometry has stimulated software analysis development. The proteolysis step of the experiment generates multiple peptide fragments, most of which overlap. Prior automated data reduction algorithms extract the deuteration level for individual peptides, but do not exploit the additional information arising from fragment overlap. Here, we describe an algorithm that determines discrete rate constant values to each of the amide hydrogens in overlapped fragments. By considering all of the overlapped peptide segments simultaneously, sequence resolution can be improved significantly, sometimes to the individual amino acid level. We have validated the method with simulated deuterium uptake data for seven overlapped fragments of a poly-Ala nonapeptide, and then applied it to extract rate constant values for the first 29 N-terminal amino acids of C22A FK506-binding protein.

  14. High-temperature study of superconducting hydrogen and deuterium sulfide

    NASA Astrophysics Data System (ADS)

    Durajski, A. P.; Szczȩśniak, R.; Pietronero, L.

    2016-05-01

    Hydrogen-rich compounds are extensively explored as candidates for a high-temperature superconductors. Currently, the measured critical temperature of $203$ K in hydrogen sulfide (H$_3$S) is among the highest over all-known superconductors. In present paper, using the strong-coupling Eliashberg theory of superconductivity, we compared in detail the thermodynamic properties of two samples containing different hydrogen isotopes H$_3$S and D$_3$S at $150$ GPa. Our research indicates that it is possible to reproduce the measured values of critical temperature $203$ K and $147$ K for H$_3$S and D$_3$S by using a Coulomb pseudopotential of $0.123$ and $0.131$, respectively. However, we also discuss a scenario in which the isotope effect is independent of pressure and the Coulomb pseudopotential for D$_3$S is smaller than for H$_3$S. For both scenarios, the energy gap, specific heat, thermodynamic critical field and related dimensionless ratios are calculated and compared with other conventional superconductors. We shown that the existence of the strong-coupling and retardation effects in the systems analysed result in significant differences between values obtained within the framework of the Eliashberg formalism and the prediction of the Bardeen-Cooper-Schrieffer theory.

  15. Effects of atomic hydrogen and deuterium exposure on high polarization GaAs photocathodes

    SciTech Connect

    M. Baylac; P. Adderley; J. Brittian; J. Clark; T. Day; J. Grames; J. Hansknecht; M. Poelker; M. Stutzman; A. T. Wu; A. S. Terekhov

    2005-12-01

    Strained-layer GaAs and strained-superlattice GaAs photocathodes are used at Jefferson Laboratory to create high average current beams of highly spin-polarized electrons. High electron yield, or quantum efficiency (QE), is obtained only when the photocathode surface is atomically clean. For years, exposure to atomic hydrogen or deuterium has been the photocathode cleaning technique employed at Jefferson Laboratory. This work demonstrates that atomic hydrogen cleaning is not necessary when precautions are taken to ensure that clean photocathode material from the vendor is not inadvertently dirtied while samples are prepared for installation inside photoemission guns. Moreover, this work demonstrates that QE and beam polarization can be significantly reduced when clean high-polarization photocathode material is exposed to atomic hydrogen from an rf dissociator-style atomic hydrogen source. Surface analysis provides some insight into the mechanisms that degrade QE and polarization due to atomic hydrogen cleaning.

  16. Strong intramolecular hydrogen bonding involving nitro- and acetyl groups. Deuterium isotope effects on chemical shifts

    NASA Astrophysics Data System (ADS)

    West-Nielsen, Mikkel; Dominiak, Paulina M.; Wozniak, Krzystzof; Hansen, Poul Erik

    2006-05-01

    A number of o-hydroxyacetylnitrobenzenes have been synthesized and their structures (X-ray and/or ab initio DFT calculations) have been determined. The intramolecular hydrogen bonds show correlations between the distances: O⋯O, O-H, C dbnd6 O and O⋯H for both hydrogen bonds to acetyl and nitro groups. Rather short O⋯O distances and strong hydrogen bonds are obtained in a number of compounds, e.g. 1,3-diacetyl-5-nitro-2,4,6-trihydroxybenzene. Deuterium isotope effects on 1H and 13C chemical shifts have been determined. 2ΔC(OD) isotope effects correlate well with O⋯O distances, whereas 4ΔC dbnd6 O(OD) isotope effects do not. The latter become unusually large in 3,5-dinitro substituted derivatives. Deuterium isotope effects on 13C chemical shifts especially 2ΔC(OD), 5ΔCH 3(OD) and 4ΔC dbnd6 O(OD) are used to evaluate steric and electronic contributions to resonance assisted hydrogen bonds. The effects are analysed using principal component analysis (PCA) techniques. Direct transmission of isotope effects via hydrogen bonds is demonstrated. DFT calculated NMR chemical shifts are shown to be useful in choosing between possible rotameric structures. X-ray analysis is used to determine structures in the solid. 'Bond localization' is shown to be important in understanding the effects of substituents. Intra molecular hydrogen bonds with acetyl or nitro groups as acceptors and OH groups as donors are compared. They are structurally similar but hydrogen bonds involving nitro groups are weaker for similar compounds. An unusual hydrogen bond pattern is observed in 1-acetyl-3,5-dinitro-2,4,6-trihydroxybenzene (two OH groups forms hydrogen bonds to the same nitro group). OH chemical shifts correlate with calculated Mulliken charges of OH for both hydrogen bonds to acetyl and nitro groups.

  17. Functionalization of Carbon Nanotubes using Atomic Hydrogen

    NASA Technical Reports Server (NTRS)

    Khare, Bishun N.; Cassell, Alan M.; Nguyen, Cattien V.; Meyyappan, M.; Han, Jie; Arnold, Jim (Technical Monitor)

    2001-01-01

    We have investigated the irradiation of multi walled and single walled carbon nanotubes (SWNTs) with atomic hydrogen. After irradiating the SWNT sample, a band at 2940/cm (3.4 microns) that is characteristic of the C-H stretching mode is observed using Fourier transform infrared (FTIR) spectroscopy. Additional confirmation of SWNT functionalization is tested by irradiating with atomic deuterium. A weak band in the region 1940/cm (5.2 micron) to 2450/cm (4.1 micron) corresponding to C-D stretching mode is also observed in the FTIR spectrum. This technique provides a clean gas phase process for the functionalization of SWNTs, which could lead to further chemical manipulation and/or the tuning of the electronic properties of SWNTs for nanodevice applications.

  18. Two-chamber hydrogen generation and application: access to pressurized deuterium gas.

    PubMed

    Modvig, Amalie; Andersen, Thomas L; Taaning, Rolf H; Lindhardt, Anders T; Skrydstrup, Troels

    2014-06-20

    Hydrogen and deuterium gas were produced and directly applied in a two-chamber system. These gaseous reagents were generated by the simple reaction of metallic zinc with HCl in water for H2 and DCl in deuterated water for D2. The setup proved efficient in classical Pd-catalyzed reductions of ketones, alkynes, alkenes, etc. in near-quantitative yields. The method was extended to the synthesis and isotope labeling of quinoline and 1,2,3,4-tetrahydroquinoline derivatives. Finally, CX-546 and Olaparib underwent efficient Ir-catalyzed hydrogen isotope exchange reactions. PMID:24870212

  19. Production of negative hydrogen and deuterium ions in microwave-driven ion sources.

    SciTech Connect

    Spence, D.

    1998-09-11

    The authors report progress they have made in the production of negative hydrogen and deuterium atomic ions in magnetically-confined microwave-driven (2.45 GHz) ion sources. The influence of source surface material, microwave power, source gas pressure and magnetic field configuration on the resulting ion current is discussed. Results strongly suggest that, at least in the source, vibrationally excited molecular hydrogen, the precursor to atomic negative ion production, is produced via a surface mechanism suggested by Hall et al. rather than via a gas phase reaction as is generally believed to be the case in most ion sources.

  20. Kinetic Method for Hydrogen-Deuterium-Tritium Mixture Distillation Simulation

    SciTech Connect

    Sazonov, A.B.; Kagramanov, Z.G.; Magomedbekov, E.P.

    2005-07-15

    Simulation of hydrogen distillation plants requires mathematical procedures suitable for multicomponent systems. In most of the present-day simulation methods a distillation column is assumed to be composed of theoretical stages, or plates. However, in the case of a multicomponent mixture theoretical plate does not exist.An alternative kinetic method of simulation is depicted in the work. According to this method a system of mass-transfer differential equations is solved numerically. Mass-transfer coefficients are estimated with using experimental results and empirical equations.Developed method allows calculating the steady state of a distillation column as well as its any non-steady state when initial conditions are given. The results for steady states are compared with ones obtained via Thiele-Geddes theoretical stage technique and the necessity of using kinetic method is demonstrated. Examples of a column startup period and periodic distillation simulations are shown as well.

  1. Hydrogen Storage in Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Gilbert, Joseph; Gilbert, Matthew; Naab, Fabian; Savage, Lauren; Holland, Wayne; Duggan, Jerome; McDaniel, Floyd

    2004-10-01

    Hydrogen as a fuel source is an attractive, relatively clean alternative to fossil fuels. However, a major limitation in its use for the application of automobiles has been the requirement for an efficient hydrogen storage medium. Current hydrogen storage systems are: physical storage in high pressure tanks, metal hydride, and gas-on-solid absorption. However, these methods do not fulfill the Department of Energy's targeted requirements for a usable hydrogen storage capacity of 6.5 wt.%, operation near ambient temperature and pressure, quick extraction and refueling, reliability and reusability.Reports showing high capacity hydrogen storage in single-walled carbon nanotubes originally prompted great excitement in the field, but further research has shown conflicting results. Results for carbon nanostructures have ranged from less than 1 wt.% to 70 wt.%. The wide range of adsorption found in previous experiments results from the difficulty in measuring hydrogen in objects just nanometers in size. Most previous experiments relied on weight analysis and residual gas analysis to determine the amount of hydrogen being adsorbed by the CNTs. These differing results encouraged us to perform our own analysis on single-walled (SWNTs), double-walled (DWNTs), and multi-walled carbon nanotubes (MWNTs), as well as carbon fiber. We chose to utilize direct measurement of hydrogen in the materials using elastic recoil detection analysis (ERDA). This work was supported by the National Science Foundation's Research Experience for Undergraduates and the University of North Texas.

  2. The solubility of hydrogen and deuterium in alloyed, unalloyed and impure plutonium metal

    SciTech Connect

    Richmond, Scott; Bridgewater, Jon S; Ward, John W; Allen, Thomas A

    2009-01-01

    Pressure-Composition-Temperature (PCT) data are presented for the plutonium-hydrogen (Pu-H) and plutonium-deuterium (Pu-D) systems in the solubility region up to terminal solubility (precipitation of PuH{sub 2}). The heats of solution for PuH{sub s} and PuD{sub s} are determined from PCT data in the ranges 350-625 C for gallium alloyed Pu and 400-575 C for unalloyed Pu. The solubility of high purity plutonium alloyed with 2 at.% gallium is compared to high purity unalloyed plutonium. Significant differences are found in hydrogen solubility for unalloyed Pu versus gallium alloyed Pu. Differences in hydrogen solubility due to an apparent phase change are observable in the alloyed and unalloyed solubilities. The effect of iron impurities on Pu-Ga alloyed Pu is shown via hydrogen solubility data as preventing complete homogenization.

  3. Kinetics of hydrogen/deuterium exchanges in cometary ices

    NASA Astrophysics Data System (ADS)

    Faure, Mathilde; Quirico, Eric; Faure, Alexandre; Schmitt, Bernard; Theulé, Patrice; Marboeuf, Ulysse

    2015-11-01

    The D/H composition of volatile molecules composing cometary ices brings key constraints on the origin of comets, on the extent of their presolar heritage, as well as on the origin of atmospheres and hydrospheres of terrestrial planets. Nevertheless, the D/H composition may have been modified to various extents in the nucleus when a comet approaches the Sun and experiences deep physical and chemical modifications in its subsurface. We question here the evolution of the D/H ratio of organic species by proton exchanges with water ice. We experimentally studied the kinetics of D/H exchanges on the ice mixtures H2O:CD3OD, H2O:CD3ND2 and D2O:HCN. Our results show that fast exchanges occur on the -OH and -NH2 chemical groups, which are processed through hydrogen bonds exchanges with water and by the molecular mobility triggered by structural changes, such as glass transition or crystallization. D/H exchanges kinetic is best described by a second-order kinetic law with activation energies of 4300 ± 900 K and 3300 ± 100 K for H2O:CD3OD and H2O:CD3ND2 ice mixtures, respectively. The corresponding pre-exponential factors ln(A(s-1)) are 25 ± 7 and 20 ± 1, respectively. No exchange was observed in the case of HCN trapped in D2O ice. These results strongly suggest that upon thermal heating (1) -OH and -NH2 chemical groups of any organic molecules loose their primordial D/H composition and equilibrate with water ice, (2) HCN does not experience proton transfer and keeps a primordial D/H composition and (3) C-H chemical groups are not isotopically modified.

  4. Localizing Carbohydrate Binding Sites in Proteins Using Hydrogen/Deuterium Exchange Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Zhang, Jingjing; Kitova, Elena N.; Li, Jun; Eugenio, Luiz; Ng, Kenneth; Klassen, John S.

    2016-01-01

    The application of hydrogen/deuterium exchange mass spectrometry (HDX-MS) to localize ligand binding sites in carbohydrate-binding proteins is described. Proteins from three bacterial toxins, the B subunit homopentamers of Cholera toxin and Shiga toxin type 1 and a fragment of Clostridium difficile toxin A, and their interactions with native carbohydrate receptors, GM1 pentasaccharides (β-Gal-(1→3)-β-GalNAc-(1→4)[α-Neu5Ac-(2→3)]-β-Gal-(1→4)-Glc), Pk trisaccharide (α-Gal-(1→4)-β-Gal-(1→4)-Glc) and CD-grease (α-Gal-(1→3)-β-Gal-(1→4)-β-GlcNAcO(CH2)8CO2CH3), respectively, served as model systems for this study. Comparison of the differences in deuterium uptake for peptic peptides produced in the absence and presence of ligand revealed regions of the proteins that are protected against deuterium exchange upon ligand binding. Notably, protected regions generally coincide with the carbohydrate binding sites identified by X-ray crystallography. However, ligand binding can also result in increased deuterium exchange in other parts of the protein, presumably through allosteric effects. Overall, the results of this study suggest that HDX-MS can serve as a useful tool for localizing the ligand binding sites in carbohydrate-binding proteins. However, a detailed interpretation of the changes in deuterium exchange upon ligand binding can be challenging because of the presence of ligand-induced changes in protein structure and dynamics.

  5. Deuterium to carbon cross-polarization in liquid crystals

    NASA Astrophysics Data System (ADS)

    Hodgkinson, Paul; Auger, Cline; Emsley, Lyndon

    1998-08-01

    The theory describing nuclear cross-polarization from a spin-1 to spin-1/2 is generalized to sweeps of the radio-frequency field amplitude. This allows efficient cross-polarization over the entire width of the deuterium NMR spectrum of partially oriented systems, such as liquid crystals. Such experiments permit the assignment and measurement of the deuterium quadrupolar couplings, and hence the quantification of the order parameters which characterize the dynamics of such systems. The evolution of the spin system can be understood in terms of individual quasiadiabatic population exchanges, allowing the prediction of the effects of the various experimental parameters on the efficiency of cross-polarization.

  6. Raman measurements of phase transitions in dense solid hydrogen and deuterium to 325 GPa

    PubMed Central

    Zha, Chang-sheng; Cohen, R. E.; Mao, Ho-kwang; Hemley, Russell J.

    2014-01-01

    Raman spectroscopy of dense hydrogen and deuterium performed to 325 GPa at 300 K reveals previously unidentified transitions. Detailed analysis of the spectra from multiple experimental runs, together with comparison with previous infrared and Raman measurements, provides information on structural modifications of hydrogen as a function of density through the I–III–IV transition sequence, beginning near 200 GPa at 300 K. The data suggest that the transition sequence at these temperatures proceeds by formation of disordered stacking of molecular and distorted layers. Weaker spectral changes are observed at 250, 285, and 300 GPa, that are characterized by discontinuities in pressure shifts of Raman frequencies, and changes in intensities and linewidths. The results indicate changes in structure and bonding, molecular orientational order, and electronic structure of dense hydrogen at these conditions. The data suggest the existence of new phases, either variations of phase IV, or altogether new structures. PMID:24639543

  7. Online deuterium hydrogen exchange and protein digestion coupled with ion mobility spectrometry and tandem mass spectrometry.

    PubMed

    Donohoe, Gregory C; Arndt, James R; Valentine, Stephen J

    2015-05-19

    Online deuterium hydrogen exchange (DHX) and pepsin digestion (PD) is demonstrated using drift tube ion mobility spectrometry (DTIMS) coupled with linear ion trap (LTQ) mass spectrometry (MS) with electron transfer dissociation (ETD) capabilities. DHX of deuterated ubiquitin, followed by subsequent quenching and digestion, is performed within ∼60 s, yielding 100% peptide sequence coverage. The high reproducibility of the IMS separation allows spectral feature matching between two-dimensional IMS-MS datasets (undeuterated and deuterated) without the need for dataset alignment. Extracted ion drift time distributions (XIDTDs) of deuterated peptic peptides are mobility-matched to corresponding XIDTDs of undeuterated peptic peptides that were identified using collision-induced dissociation (CID). Matching XIDTDs allows a straightforward identification and deuterium retention evaluation for labeled peptides. Aside from the mobility separation, the ion trapping capabilities of the LTQ, combined with ETD, are demonstrated to provide single-residue resolution. Deuterium retention for the c- series ions across residues M(1)-L(15) and N(25)-R(42) are in good agreement with the known secondary structural elements within ubiquitin. PMID:25893550

  8. Origin of Terrestrial Water: Hydrogen/Deuterium Fractionation into Earth's Core

    NASA Astrophysics Data System (ADS)

    Wu, J.; Buseck, P. R.

    2014-12-01

    Hydrogen isotopic compositions are among the most important constraints on the origin of Earth's water. Earth's bulk water content, which is small but not negligible, is significantly greater than what the thermal gradient of the solar nebula disk would suggest for planetesimal materials condensed at one astronomical unit. The proto-solar nebula is a likely source of early Earth's water, with probable contributions from one or more of the following: water-rich planetesimals, ordinary and carbonaceous meteorites, comets, asteroids, and interplanetary dust particles. However, all of these sources have been questioned, and the proposed proto-solar nebular origin has been disputed in light of the large difference in hydrogen isotopic composition between it and terrestrial water. Current opposition to the solar nebular hypothesis is based on the critical assumption that no processes in the interior of the early Earth changed the isotopic composition of hydrogen. Nevertheless, a hypothesized hydrogenation reaction of liquid iron (2Fe + xH2 ? 2FeHx) during core formation likely provided a fractionation mechanism between hydrogen and deuterium (D). We propose that modern D/H ratios at Earth's surface resulted from this isotopic fractionation and that terrestrial water originated from oxidation of proto-solar hydrogen dissolved in the magma ocean in the early Earth by coexisting oxides (such as FeO). Thus, the isotopic composition of water on Earth can be mainly explained by internal terrestrial processes.

  9. Influence of Murchison Minerals on Hydrogen-Deuterium Exchange of Amino Acids

    NASA Astrophysics Data System (ADS)

    Lerner, N. R.

    1993-07-01

    The amino acids found on the Murchison meteorite are deuterium enriched. For the glycine-alanine fraction, delta D = +2448 per mil, and for the alpha-amino isobutyric acid fraction, delta D = +149 per mil [1]. In order to retain such levels of deuterium enrichment, the amino acids found in Murchison must have not only retained the deuterium enrichment of their interstellar precursors (delta D > +1500 per mil [2]) during synthesis, as has been recently shown [3], but they must have also retained their deuterium label during the aqueous alteration phase [4]. By measuring the rates of deuterium exchange of amino acids with D(sub)2O, limits can be set on the length of time and the conditions under which the Murchison parent body experienced an aqueous environment. The rates of hydrogen-deuterium exchange of nondeuterated glycine, alanine, alpha-amino isobutyric acid, and amino diacetic acid have been measured in D(sub)2O as a function of temperature, pH, and the presence of Murchison minerals. In addition to the amino and carboxylic hydrogens, only the alpha- hydrogens of glycine, alanine, and amino diacetic acid are found to exchange. Even for solutions maintained for weeks at temperatures as high as 120 degrees C, no exchange was observed with the hydrogens of the methyl groups of alanine or alpha-amino isobutyric acid. The rate of exchange for alpha-hydrogens of amino acids is first-order with respect to the amino acid concentration. Increasing the pH of the solution markedly increases the rate of exchange. For example, at 115 degrees C and pH 4.0, 7.0, and 10 the rates are 14, 30, and 125 yr^-1 respectively for glycine and 2.0, 3.5, and 14 yr^-1 respectively for alanine. In a pH-6.0 D(sub)2O solution of amino acids containing Murchison dust the rates are 135 yr^-1 for glycine and 32 yr^-1 for alanine, rates close to those for the pH 10 solution. Activation energies for exchange were obtained from Arrhenius plots constructed from measurements made between 70 degrees C and 155 degrees C in solutions containing Murchison dust. For both glycine and alanine the activation energy is -25 kcal/mole. Using this value, we have calculated the half-lives for complete exchange of the alpha-hydrogens of glycine and alanine for the temperature range thought to have existed on the parent body during aqueous alteration [5]. The half-lives at 0 degrees C and 20 degrees C are 7500 yr and 300 yr respectively for glycine and 55,000 yr and 2100 yr respectively for alanine. Murchison amino acid fraction IV [1] was known to contain impurities and hence the measured delta D value represents a lower limit for alpha-amino isobutyric acid. Assuming that all the deuterium recovered from fraction IV came from alpha-amino isobutryric acid, and that one atom of nitrogen is recovered for each molecule of alpha-amino isobutyric acid, a maximum delta D value of +2600 per mil can be calculated for this amino acid. This is comparable to delta D for the glycine-alanine fraction, which is mainly glycine [6]. In an aqueous environment glycine loses deuterium relatively rapidly while alpha-amino isobutyric acid does not undergo exchange. Hence the similarity in the delta D values of both fractions indicates that the period of aqueous alteration is less than the half-life for hydrogen-deuterium exchange of glycine. References: [1] Pizzarello S. et al. (1991) GCA, 55, 905-910. [2] Zinner E. (1988) In Meteorites and the Early Solar System (J. R. Kerridge and M. S. Matthews, eds.), 956-983, Univ. of Arizona. [3] Lerner N. R. et al. (1993) GCA, in press. [4] Bunch T. E. and Chang S. (1980) GCA, 44, 1543-1577. [5] Clayton R. N. and Mayeda T. K. (1984) EPSL, 67, 151-161. [6] Shock E. L. and Shulte M. D. (1990) GCA, 54, 3159-3173.

  10. The deuterium/hydrogen distribution in chondritic organic matter attests to early ionizing irradiation

    NASA Astrophysics Data System (ADS)

    Laurent, Boris; Roskosz, Mathieu; Remusat, Laurent; Robert, Franois; Leroux, Hugues; Vezin, Herv; Depecker, Christophe; Nuns, Nicolas; Lefebvre, Jean-Marc

    2015-10-01

    Primitive carbonaceous chondrites contain a large array of organic compounds dominated by insoluble organic matter (IOM). A striking feature of this IOM is the systematic enrichment in deuterium compared with the solar hydrogen reservoir. This enrichment has been taken as a sign of low-temperature ion-molecule or gas-grain reactions. However, the extent to which Solar System processes, especially ionizing radiation, can affect D/H ratios is largely unknown. Here, we report the effects of electron irradiation on the hydrogen isotopic composition of organic precursors containing different functional groups. From an initial terrestrial composition, overall D-enrichments and differential intramolecular fractionations comparable with those measured in the Orgueil meteorite were induced. Therefore, ionizing radiation can quantitatively explain the deuteration of organics in some carbonaceous chondrites. For these meteorites, the precursors of the IOM may have had the same isotopic composition as the main water reservoirs of the inner Solar System.

  11. The deuterium/hydrogen distribution in chondritic organic matter attests to early ionizing irradiation

    PubMed Central

    Laurent, Boris; Roskosz, Mathieu; Remusat, Laurent; Robert, François; Leroux, Hugues; Vezin, Hervé; Depecker, Christophe; Nuns, Nicolas; Lefebvre, Jean-Marc

    2015-01-01

    Primitive carbonaceous chondrites contain a large array of organic compounds dominated by insoluble organic matter (IOM). A striking feature of this IOM is the systematic enrichment in deuterium compared with the solar hydrogen reservoir. This enrichment has been taken as a sign of low-temperature ion-molecule or gas-grain reactions. However, the extent to which Solar System processes, especially ionizing radiation, can affect D/H ratios is largely unknown. Here, we report the effects of electron irradiation on the hydrogen isotopic composition of organic precursors containing different functional groups. From an initial terrestrial composition, overall D-enrichments and differential intramolecular fractionations comparable with those measured in the Orgueil meteorite were induced. Therefore, ionizing radiation can quantitatively explain the deuteration of organics in some carbonaceous chondrites. For these meteorites, the precursors of the IOM may have had the same isotopic composition as the main water reservoirs of the inner Solar System. PMID:26461170

  12. The deuterium/hydrogen distribution in chondritic organic matter attests to early ionizing irradiation.

    PubMed

    Laurent, Boris; Roskosz, Mathieu; Remusat, Laurent; Robert, François; Leroux, Hugues; Vezin, Hervé; Depecker, Christophe; Nuns, Nicolas; Lefebvre, Jean-Marc

    2015-01-01

    Primitive carbonaceous chondrites contain a large array of organic compounds dominated by insoluble organic matter (IOM). A striking feature of this IOM is the systematic enrichment in deuterium compared with the solar hydrogen reservoir. This enrichment has been taken as a sign of low-temperature ion-molecule or gas-grain reactions. However, the extent to which Solar System processes, especially ionizing radiation, can affect D/H ratios is largely unknown. Here, we report the effects of electron irradiation on the hydrogen isotopic composition of organic precursors containing different functional groups. From an initial terrestrial composition, overall D-enrichments and differential intramolecular fractionations comparable with those measured in the Orgueil meteorite were induced. Therefore, ionizing radiation can quantitatively explain the deuteration of organics in some carbonaceous chondrites. For these meteorites, the precursors of the IOM may have had the same isotopic composition as the main water reservoirs of the inner Solar System. PMID:26461170

  13. Permeation of several gases through elastomers, with emphasis on the deuterium/hydrogen pair

    SciTech Connect

    Fitch, M.W.; Koros, W.J. ); Nolen, R.L.; Carnes, J.R. )

    1993-02-10

    The diffusion and permeation coefficients for He, H[sub 2], D[sub 2], O[sub 2], and N[sub 2] in a variety of elastomers were measured by simple manometric methods. The elastomers studied were butyl rubber; Hypalon[reg sign] 40 and 45; Viton[reg sign] E60 and GF; Hydrin[reg sign] 100 and filled Hydrin[reg sign] 100; Kraton[reg sign] G, FG, and KG VTEOS; EPDM; epoxidized natural rubber; and neoprene. Consistent with earlier studies, elastomers with higher glass transition temperatures exhibited lower diffusion coefficients. The ratio of diffusion coefficients of the hydrogen isotope pair differed from the purely molecular-weight-based prediction. Deuterium's slightly smaller size relative to hydrogen is consistent with observed deviations from the molecular-weight-based diffusion coefficient ratio.

  14. A technique for determining the deuterium/hydrogen contrast map in neutron macromolecular crystallography.

    PubMed

    Chatake, Toshiyuki; Fujiwara, Satoru

    2016-01-01

    A difference in the neutron scattering length between hydrogen and deuterium leads to a high density contrast in neutron Fourier maps. In this study, a technique for determining the deuterium/hydrogen (D/H) contrast map in neutron macromolecular crystallography is developed and evaluated using ribonuclease A. The contrast map between the D2O-solvent and H2O-solvent crystals is calculated in real space, rather than in reciprocal space as performed in previous neutron D/H contrast crystallography. The present technique can thus utilize all of the amplitudes of the neutron structure factors for both D2O-solvent and H2O-solvent crystals. The neutron D/H contrast maps clearly demonstrate the powerful detectability of H/D exchange in proteins. In fact, alternative protonation states and alternative conformations of hydroxyl groups are observed at medium resolution (1.8 Å). Moreover, water molecules can be categorized into three types according to their tendency towards rotational disorder. These results directly indicate improvement in the neutron crystal structure analysis. This technique is suitable for incorporation into the standard structure-determination process used in neutron protein crystallography; consequently, more precise and efficient determination of the D-atom positions is possible using a combination of this D/H contrast technique and standard neutron structure-determination protocols. PMID:26894536

  15. Hydrogen-deuterium exchange in imidazole as a tool for studying histidine phosphorylation.

    PubMed

    Cebo, Małgorzata; Kielmas, Martyna; Adamczyk, Justyna; Cebrat, Marek; Szewczuk, Zbigniew; Stefanowicz, Piotr

    2014-12-01

    Isotope exchange at the histidine C2 atom of imidazole in D2O solution is well known to occur at a significantly slower rate than the exchange of amide protons. Analysis of the kinetics of this isotope-exchange reaction is proposed herein as a method of detecting histidine phosphorylation. This modification of His-containing peptides is challenging to pinpoint because of its instability under acidic conditions as well as during CID-MS analysis. In this work, we investigated the effect of phosphorylation of the histidine side chain in peptides on deuterium-hydrogen exchange (DHX) in the imidazole. The results demonstrate that phosphorylation dramatically slows the rate of the DHX reaction. This phenomenon can be applied to detect phosphorylation of peptides at the histidine residue (e.g., in enzymatic digests). We also found that the influence of the peptide sequence on the exchange kinetics is relatively small. A CID fragmentation experiment revealed that there was no detectable hydrogen scrambling in peptides deuterated at C2 of the imidazole ring. Therefore, MS/MS can be used to directly identify the locations of deuterium ions incorporated into peptides containing multiple histidine moieties. PMID:25354888

  16. Isotopic effect study in the LHCD and LHH experiments in hydrogen/deuterium plasmas of the FT-2 tokamak

    SciTech Connect

    Lashkul, S. I.; Altukhov, A. B.; Gusakov, E. Z.; Dyachenko, V. V.; Esipov, L. A.; Irzak, M. A.; Kantor, M. Yu.; Kouprienko, D. V.; Saveliev, A. N.; Shatalin, S. V.; Stepanov, A. Yu.

    2014-02-12

    Results of comparative experimental studies of the efficiency of lower hybrid current drive (LHCD) and lower hybrid heating (LHH) in the FT-2 tokamak in hydrogen and deuterium plasmas are presented. In the new comparative experimental runs in deuterium/hydrogen plasmas suppression of the LHCD and beginning of the interaction of LH waves with ions is controlled by the plasma density rise. Role of parametric instabilities in CD switch-off is considered. In order to analyze the experimentally observed effect of LHCD the GRILL3D and FRTC codes has been used.

  17. Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 2. Assessing Charge Site Location and Isotope Scrambling

    NASA Astrophysics Data System (ADS)

    Khakinejad, Mahdiar; Ghassabi Kondalaji, Samaneh; Donohoe, Gregory C.; Valentine, Stephen J.

    2016-03-01

    Ion mobility spectrometry (IMS) coupled with gas-phase hydrogen deuterium exchange (HDX)-mass spectrometry (MS) and molecular dynamic simulations (MDS) has been used for structural investigation of anions produced by electrospraying a sample containing a synthetic peptide having the sequence KKDDDDDIIKIIK. In these experiments the potential of the analytical method for locating charge sites on ions as well as for utilizing collision-induced dissociation (CID) to reveal the degree of deuterium uptake within specific amino acid residues has been assessed. For diffuse (i.e., more elongated) [M - 2H]2- ions, decreased deuterium content along with MDS data suggest that the D4 and D6 residues are charge sites, whereas for the more diffuse [M - 3H]3- ions, the data suggest that the D4, D7, and the C-terminus are deprotonated. Fragmentation of mobility-selected, diffuse [M - 2H]2- ions to determine deuterium uptake at individual amino acid residues reveals a degree of deuterium retention at incorporation sites. Although the diffuse [M - 3H]3- ions may show more HD scrambling, it is not possible to clearly distinguish HD scrambling from the expected deuterium uptake based on a hydrogen accessibility model. The capability of the IMS-HDX-MS/MS approach to provide relevant details about ion structure is discussed. Additionally, the ability to extend the approach for locating protonation sites on positively-charged ions is presented.

  18. Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 2. Assessing Charge Site Location and Isotope Scrambling

    NASA Astrophysics Data System (ADS)

    Khakinejad, Mahdiar; Ghassabi Kondalaji, Samaneh; Donohoe, Gregory C.; Valentine, Stephen J.

    2016-01-01

    Ion mobility spectrometry (IMS) coupled with gas-phase hydrogen deuterium exchange (HDX)-mass spectrometry (MS) and molecular dynamic simulations (MDS) has been used for structural investigation of anions produced by electrospraying a sample containing a synthetic peptide having the sequence KKDDDDDIIKIIK. In these experiments the potential of the analytical method for locating charge sites on ions as well as for utilizing collision-induced dissociation (CID) to reveal the degree of deuterium uptake within specific amino acid residues has been assessed. For diffuse (i.e., more elongated) [M - 2H]2- ions, decreased deuterium content along with MDS data suggest that the D4 and D6 residues are charge sites, whereas for the more diffuse [M - 3H]3- ions, the data suggest that the D4, D7, and the C-terminus are deprotonated. Fragmentation of mobility-selected, diffuse [M - 2H]2- ions to determine deuterium uptake at individual amino acid residues reveals a degree of deuterium retention at incorporation sites. Although the diffuse [M - 3H]3- ions may show more HD scrambling, it is not possible to clearly distinguish HD scrambling from the expected deuterium uptake based on a hydrogen accessibility model. The capability of the IMS-HDX-MS/MS approach to provide relevant details about ion structure is discussed. Additionally, the ability to extend the approach for locating protonation sites on positively-charged ions is presented.

  19. Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 2. Assessing Charge Site Location and Isotope Scrambling.

    PubMed

    Khakinejad, Mahdiar; Ghassabi Kondalaji, Samaneh; Donohoe, Gregory C; Valentine, Stephen J

    2016-03-01

    Ion mobility spectrometry (IMS) coupled with gas-phase hydrogen deuterium exchange (HDX)-mass spectrometry (MS) and molecular dynamic simulations (MDS) has been used for structural investigation of anions produced by electrospraying a sample containing a synthetic peptide having the sequence KKDDDDDIIKIIK. In these experiments the potential of the analytical method for locating charge sites on ions as well as for utilizing collision-induced dissociation (CID) to reveal the degree of deuterium uptake within specific amino acid residues has been assessed. For diffuse (i.e., more elongated) [M - 2H](2-) ions, decreased deuterium content along with MDS data suggest that the D4 and D6 residues are charge sites, whereas for the more diffuse [M - 3H](3-) ions, the data suggest that the D4, D7, and the C-terminus are deprotonated. Fragmentation of mobility-selected, diffuse [M - 2H](2-) ions to determine deuterium uptake at individual amino acid residues reveals a degree of deuterium retention at incorporation sites. Although the diffuse [M - 3H](3-) ions may show more HD scrambling, it is not possible to clearly distinguish HD scrambling from the expected deuterium uptake based on a hydrogen accessibility model. The capability of the IMS-HDX-MS/MS approach to provide relevant details about ion structure is discussed. Additionally, the ability to extend the approach for locating protonation sites on positively-charged ions is presented. Graphical Abstract ᅟ. PMID:26802030

  20. NMR studies of metal-hydrogen systems lutetium trideuteride and zirconium beryllium (hydrogen/deuterium)

    NASA Astrophysics Data System (ADS)

    Kodibagkar, Vikram Divakar

    2002-11-01

    LuD3 is a complicated hcp rare-earth trihydride, with disorder evident in NMR and neutron diffraction. Deuterium NMR spectra were obtained and relaxation times T1 and T2 were measured at different values of temperature. Three-pulse spin alignment echo experiments were also conducted for detecting slower motions. Deuterium spectra below room-T show substantial disorder (with small distortions), in agreement with neutron diffraction. Above room-T, NMR spectral features sharpen, showing that the disorder/distortions are motionally averaged away. The overall NMR linewidth is independent of temperature and the high-T spectra fit reasonably to the sum of three quadrupolar doublets corresponding to three distinct deuterium sites. Long-range diffusion remains too slow (even at 364 K) to average the components into a single feature. 3-pulse spin-alignment echo data show diffusive motion down to 219 K. The motion of H/D atoms in ZrBe2(H/D)x (x ≈ 1.5) was also studied using deuterium and beryllium NMR. A temperature-induced structural transition was observed near 240 K in the deuteride and near 200 K in the hydride. In the deuteride, on decreasing the temperature below 240 K, T2 decreases rapidly and T1 increases rapidly, indicating that the D atom mobility is dramatically reduced. From the 9Be spectra of ZrBe2(H/D)x we see the presence of the transition in both the hydride and deuteride at 200 K and 235 K respectively. Above the transition temperature a single pair of quadrupolar satellites is seen. Each quadrupolar satellite splits into two resonances (with splittings nu Q1 and nuQ2) below the transition temperature in the hydride and deuteride. We propose that the transition involves ordering of the H/D vacancies (25% at x = 1.5). 9Be NMR also demonstrates a strong preferential alignment of the powder particles of ZrBe2Hx and ZrBe2Dx in the high magnetic fields used for NMR. This alignment, which indicates a high anisotropy in the magnetic susceptibility, is not seen in the bare compound ZrBe2.

  1. Carbon-14 and deuterium isotope effects in the borderline solvolysis of isopropyl. beta. -naphthalenesulfonate

    SciTech Connect

    Ando, T.; Yamataka, H.; Tamura, S.; Hanafusa, T.

    1982-10-06

    The present investigation verifies that ..cap alpha..- and ..beta..-carbon-14 kinetic isotope effects are sensitive to mechanistic changes in the borderline solvolysis. Model calculations of kinetic isotope effects using the observed data for all the carbons and deuteriums enables one to describe the variable transition-state structures of the solvolysis of simple secondary substrates, which is still a subject of much debate in recent years. A study along this line is now in progress.

  2. The effect of hydrogen/deuterium introduction on photoluminescence of 3C-SiC crystals

    SciTech Connect

    Lee, B.K.; Steckl, A.J.; Zavada, J.M.; Wilson, R.G.

    1998-12-31

    The effect of the incorporation and annealing of deuterium in 3C-SiC on its photoluminescence is reported. A 3C-SiC crystal has been implanted with 100 kev deuterium and subsequently annealed at temperatures between 1015 C and 1220 C for 1 to 5 minutes. SIMS depth profiles indicate hydrogen is strongly trapped by defects generated through ion bombardment, but a gradual damage repairing occurs during annealing. Photoluminescence was measured with 488 nm Ar laser excitation for sample temperatures from 89 K to 400 K. The PL peak wavelength of 540 nm at room temperature has shifted to 538 nm at 89 K. The peak PL intensity decreases with measurement temperature while its full width at half maximum (FWHM) exhibits an increasing trend. PL data were taken at five annealing stages. The post-implantation peak PL intensity and its integrated area increase initially with annealing temperature and time. After the final annealing at 1218 C for 2 minute, PL intensity and its integrated area exhibit a decrease in level.

  3. Structural changes of ultrasonicated bovine serum albumin revealed by hydrogen-deuterium exchange and mass spectrometry.

    PubMed

    Zhang, Qiuting; Tu, Zongcai; Wang, Hui; Huang, Xiaoqin; Sha, Xiaomei; Xiao, Hui

    2014-11-01

    The structural changes of bovine serum albumin (BSA) under high-intensity ultrasonication were investigated by fluorescence spectroscopy and mass spectrometry. Evidence for the ultrasonication-induced conformational changes of BSA was provided by the intensity changes and maximum-wavelength shift in fluorescence spectrometry. Matrix-assisted laser desorption-ionization time-of-flight mass spectroscopy (MALDI-TOF MS) revealed the increased intensity of the peak at the charge state +5 and a newly emerged peak at charge state +6, indicating that the protein became unfolded after ultrasonication. Prevalent unfolding of BSA after ultrasonication was revealed by hydrogen-deuterium exchange coupled with mass spectrometry (HDX-MS). Increased intensity and duration of ultrasonication further promoted the unfolding of the protein. The unfolding induced by ultrasonication goes through an intermediate state similar to that induced by a low concentration of denaturant. PMID:25224638

  4. Aspartic protease nepenthesin-1 as a tool for digestion in hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Kadek, Alan; Mrazek, Hynek; Halada, Petr; Rey, Martial; Schriemer, David C; Man, Petr

    2014-05-01

    Hydrogen/deuterium exchange coupled to mass spectrometry (HXMS) utilizes enzymatic digestion of proteins to localize the information about altered exchange patterns in protein structure. The ability of the protease to produce small peptides and overlapping fragments and provide sufficient coverage of the protein sequence is essential for localizing regions of interest. Recently, it was shown that there is an interesting group of proteolytic enzymes from carnivorous pitcher plants of the genus Nepenthes. In this report, we describe successful immobilization and the use of one of these enzymes, nepenthesin-1, in HXMS workflow. In contrast to pepsin, it has different cleavage specificities, and despite its high inherent susceptibility to reducing and denaturing agents, it is very stable upon immobilization and withstands even high concentration of guanidine hydrochloride and reducing agents. We show that denaturing agents can alter digestion by reducing protease activity and/or substrate solubility, and additionally, they influence the trapping of proteolytic peptides onto the reversed phase resin. PMID:24661217

  5. Dual Studies on a HydrogenDeuterium Exchange of Resorcinol and the Subsequent Kinetic Isotope Effect

    PubMed Central

    2015-01-01

    An efficient laboratory experiment has been developed for undergraduate students to conduct hydrogendeuterium (HD) exchange of resorcinol by electrophilic aromatic substitution using D2O and a catalytic amount of H2SO4. The resulting labeled product is characterized by 1H NMR. Students also visualize a significant kinetic isotope effect (kH/kD ? 3 to 4) by adding iodine tincture to solutions of unlabeled resorcinol and the HD exchange product. This method is highly adaptable to fit a target audience and has been successfully implemented in a pedagogical capacity with second-year introductory organic chemistry students as part of their laboratory curriculum. It was also adapted for students at the advanced high school level. PMID:25132687

  6. Time-Resolved Pulsed Hydrogen/Deuterium Exchange Mass Spectrometry Probes Gaseous Proteins Structural Kinetics

    NASA Astrophysics Data System (ADS)

    Rajabi, Khadijeh

    2015-01-01

    A pulsed hydrogen/deuterium exchange (HDX) method has been developed for rapid monitoring of the exchange kinetics of protein ions with D2O a few milliseconds after electrospray ionization (ESI). The stepwise gradual evolution of HDX of multiply charged protein ions was monitored using the pulsed HDX mass spectrometry technique. Upon introducing a very short pulse of D2O (in the μs to ms time scale) into the linear ion trap (LIT) of a time-of-flight (TOF) mass spectrometer, bimodal distributions were detected for the ions of cytochrome c and ubiquitin. Mechanistic details of HDX reactions for ubiquitin and cytochrome c in the gas phase were uncovered and the structural transitions were followed by analyzing the kinetics of HDX.

  7. HDXFinder: Automated Analysis and Data Reporting of Deuterium/Hydrogen Exchange Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Miller, Danny E.; Prasannan, Charulata B.; Villar, Maria T.; Fenton, Aron W.; Artigues, Antonio

    2012-02-01

    Hydrogen/deuterium exchange in combination with mass spectrometry (H/D MS) is a sensitive technique for detection of changes in protein conformation and dynamics. However, wide application of H/D MS has been hindered, in part, by the lack of computational tools necessary for efficient analysis of the large data sets associated with this technique. We report a novel web-based application for automatic analysis of H/D MS experimental data. This application relies on the high resolution of mass spectrometers to extract all isotopic envelopes before correlating these envelopes with individual peptides. Although a fully automatic analysis is possible, a variety of graphical tools are included to aid in the verification of correlations and rankings of the isotopic peptide envelopes. As a demonstration, the rate constants for H/D exchange of peptides from rabbit muscle pyruvate kinase are mapped onto the structure of this protein.

  8. Method and source for producing a high concentration of positively charged molecular hydrogen or deuterium ions

    DOEpatents

    Ehlers, Kenneth W.; Leung, Ka-Ngo

    1988-01-01

    A high concentration of positive molecular ions of hydrogen or deuterium gas is extracted from a positive ion source having a short path length of extracted ions, relative to the mean free path of the gas molecules, to minimize the production of other ion species by collision between the positive ions and gas molecules. The ion source has arrays of permanent magnets to produce a multi-cusp magnetic field in regions remote from the plasma grid and the electron emitters, for largely confining the plasma to the space therebetween. The ion source has a chamber which is short in length, relative to its transverse dimensions, and the electron emitters are at an even shorter distance from the plasma grid, which contains one or more extraction apertures.

  9. Conformational analysis of g protein-coupled receptor signaling by hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Li, Sheng; Lee, Su Youn; Chung, Ka Young

    2015-01-01

    Conformational change and protein-protein interactions are two major mechanisms of membrane protein signal transduction, including G protein-coupled receptors (GPCRs). Upon agonist binding, GPCRs change conformation, resulting in interaction with downstream signaling molecules such as G proteins. To understand the precise signaling mechanism, studies have investigated the structural mechanism of GPCR signaling using X-ray crystallography, nuclear magnetic resonance (NMR), or electron paramagnetic resonance. In addition to these techniques, hydrogen/deuterium exchange mass spectrometry (HDX-MS) has recently been used in GPCR studies. HDX-MS measures the rate at which peptide amide hydrogens exchange with deuterium in the solvent. Exposed or flexible regions have higher exchange rates and excluded or ordered regions have lower exchange rates. Therefore, HDX-MS is a useful tool for studying protein-protein interfaces and conformational changes after protein activation or protein-protein interactions. Although HDX-MS does not give high-resolution structures, it analyzes protein conformations that are difficult to study with X-ray crystallography or NMR. Furthermore, conformational information from HDX-MS can help in the crystallization of X-ray crystallography by suggesting highly flexible regions. Interactions between GPCRs and downstream signaling molecules are not easily analyzed by X-ray crystallography or NMR because of the large size of the GPCR-signaling molecule complexes, hydrophobicity, and flexibility of GPCRs. HDX-MS could be useful for analyzing the conformational mechanism of GPCR signaling. In this chapter, we discuss details of HDX-MS for analyzing GPCRs using the β2AR-G protein complex as a model system. PMID:25950969

  10. Solution and gas phase hydrogen/deuterium exchange of oligoamide complexes by nanoelectrospray mass spectrometry

    NASA Astrophysics Data System (ADS)

    Jiang, Honghai; Dolan, Anthony R.; Li, Minfeng; Moy, Marie A.; Gong, Bing; Wood, Troy D.

    2007-03-01

    Hydrogen bonding is crucial to biological systems and is intrinsic to non-covalent interactions. They are important in the formation of higher order structures of proteins as well as in the interactions of proteins with other biological molecules. Electrospray ionization (ESI) is an important tool in the study and characterization of molecular complexes and has proven to be extremely powerful and invaluable in the studying of biomolecular structures and non-covalent interactions. We have utilized solution and gas phase hydrogen/deuterium exchange (HDX) as a method to determine the specificity of supramolecular complex formation using monomers possessing sites containing hydrogen-bond donor and acceptor groups. By comparing the average number of exchanges for the monomer subunits to the average number of exchanges for the complex, we can distinguish if a specific complex is formed in solution, or whether it is the artifact of a gas phase process during ESI. In this paper we have investigated several non-covalent supramolecular complexes by nanoelectrospray (nanoESI) mass spectrometry (MS). By using the solution and gas phase HDX, we were able to identify several specific supramolecular complexes. Thus, solution and gas phase HDX combined with nanoESI-MS provides for a convenient method in ascertaining the origin and stability of non-covalent complexes.

  11. ARTICLES: Numerical investigation of a purely chemical generator of atomic gaseous hydrogen (deuterium) and of a cw H(D)-O3-CO2 laser utilizing this generator

    NASA Astrophysics Data System (ADS)

    Bashkin, A. S.; Gamzatov, N. M.; Oraevskiĭ, A. N.

    1987-02-01

    A numerical investigation is reported of a generator of atomic gaseous hydrogen (or deuterium) and of a cw low-toxicity H(D)-O3-CO2 laser utilizing this generator. A high nonequilibrium concentration of H (D) atoms is achieved in a supersonic oxygen-hydrogen (or oxygen-deuterium) flame in this generator. Hydrogen (deuterium) combustion regimes convenient for experimental realization and characterized by a molar concentration of atomic hydrogen (deuterium) in the flame by up to ~15%, are identified. Numerical optimization of all the components of a cw laser system in respect of the principal parameters is used to show that a cw D-O3-CO2 laser utilizing this chemical generator of deuterium atoms can have high output characteristics: a specific output power of ~140 W·sec·g-1, a chemical efficiency of ~10%, and an inversion zone of over 30 cm length in the downstream direction.

  12. In situ study of erosion and deposition of amorphous hydrogenated carbon films by exposure to a hydrogen atom beam

    SciTech Connect

    Markelj, Sabina; Pelicon, Primoz; Cadez, Iztok; Schwarz-Selinger, Thomas; Jacob, Wolfgang

    2012-07-15

    This paper reports on the first dual-beam experiment employing a hydrogen atom beam for sample exposure and an ion beam for analysis, enabling in situ and real-time studies of hydrogen atom interaction with materials. The erosion of an amorphous hydrogenated carbon (a-C:H) layer by deuterium atoms at 580 K sample temperature was studied and the uptake of deuterium during the erosion process was measured in real time. The deuterium areal density increased at the beginning to 7.3 Multiplication-Sign 10{sup 15} D cm{sup -2}, but then stabilized at a constant value of 5.5 Multiplication-Sign 10{sup 15} D cm{sup -2}. Formation of a polymer-like deposit on an a-C:H layer held at room temperature and subjected to the deuterium atom beam was observed and also studied in situ. For both erosion and deposition studies an a-{sup 13}C:H layer on top of an Si substrate was used as a sample, making the experiments isotopically fully specified and thereby differentiating the deposited from the original layer and the interacting D atoms from H atoms present in the layer and in the residual vacuum. From the deposition study it was shown that carbon in the deposited layer originates from carbon-carrying species in the background vacuum that interact with hydrogen atoms. The areal density of the carbon at the surface was determined from the energy shift of the Si edge in the Rutherford backscattering spectrum. The cross section for {sup 7}Li on D at 4.3 MeV Li ion energy and at a recoil angle of 30 Degree-Sign was also determined to be (236 {+-} 16) Multiplication-Sign 10{sup -27} cm{sup 2}/sr. This is a factor of 3 {+-} 0.2 times higher than the Rutherford elastic cross section.

  13. Dissociative adsorption of molecular deuterium and thermal stability onto hydrogenated, bare and ion beam damaged poly- and single crystalline diamond surfaces

    NASA Astrophysics Data System (ADS)

    Michaelson, Sh.; Chandran, M.; Zalkind, S.; Shamir, N.; Akhvlediani, R.; Hoffman, A.

    2015-12-01

    In this work we report on dissociative adsorption of deuterium (D2) on bare, hydrogenated and ion beam bombarded polycrystalline and single crystalline diamond surfaces. Polycrystalline diamond films with an average grain size of ~ 300 nm were deposited on silicon substrates by hot filament chemical vapor deposition technique from methane/hydrogen gas mixture. Deposited films were characterized using Raman spectroscopy, atomic force microscopy and scanning electron microscopy to estimate the phase composition and microstructure. High resolution electron energy loss spectroscopy and direct recoil spectrometry were used to study hydrogen (deuterium) bonding configuration of the upper surface region. Near surface amorphization was achieved by 1 keV Ar+ implantation at ~ 1 × 1015 ions/cm2 at room temperature (RT). As deposited and Ar+ bombarded films are annealed to 500-1000 °C in ultra-high vacuum conditions and also under D2 partial pressure of 5 × 10- 6 Torr. For comparison, key experiments were repeated on the single crystal (100) diamond. Our results clearly show the preferential dissociative adsorption of D2 on low hybridized carbon (sp/sp2) states with activation temperature as low as RT, but with a lower thermal stability compared to pure diamond Csbnd D bonds.

  14. Precision measurements on kaonic hydrogen and kaonic deuterium: DEAR and SIDDHARTA

    NASA Astrophysics Data System (ADS)

    Iliescu, M.

    2005-06-01

    The SIDDHARTA ( SIlicon Drift Detector for Hadronic Atom Research by Timing Application) experiment [J. Zmeskal, SIDDHARTA Technical Note IR-2 (2003); C. Curceanu (Petrascu), SID-DHARTA Technical Note IR-3 (2003)] represents the scientific and technical development of DEAR ( DAΦNE Exotic Atom Research) [S. Bianco et al., Rivista del Nuovo Cimento 22 (11) (1999) 1], as part of the program dedicated to exotic atoms at DAΦNE [G. Vignola, Proc. of the "5th European Particle Accelerator Conference", Sitges, Eds. S. Myres et al., Institute of Physics Publishing, Bristol and Philadelphia (1996) 22]. The objective consists in an eV precision measurement of the kaonic hydrogen K line shift and width induced by the strong interaction, and the first measurement of kaonic deuterium. These values will allow a precise determination of antikaon-nucleon scattering lengths and a better understanding of the chiral symmetry breaking scenario in the strangeness sector. DEAR performed the most precise measurement up to now on kaonic hydrogen, at the end of 2002. The SIDDHARTA collaboration is developing a new set of large area, triggerable X-ray Silicon Drift Detectors (SDD), which will improve by 2 orders of magnitude the background rejection, allowing to reach the proposed objectives. The results of DEAR, as well as the state of the art of the new setup are presented.

  15. ORFEUS II echelle spectra: deuterium and molecular hydrogen in the ISM towards BD +39 3226

    NASA Astrophysics Data System (ADS)

    Bluhm, H.; Marggraf, O.; de Boer, K. S.; Richter, P.; Heber, U.

    1999-12-01

    In ORFEUS II spectra of the sdO star BD +39 3226 interstellar hydrogen and deuterium is detected. >From Ly alpha profile fitting and a curve of growth analysis of the Lyman series of H I and D I we derive the column densities N_H = 1.20+0.28}-0.22}{*10{20 cm-2 and N_D = 1.45+0.50}-0.38}{*10{15 cm-2. >From the analysis of metal absorption lines in ORFEUS and IUE spectra we obtain column densities for 11 elements. In addition, we examine absorption lines of H_2 for rotational excitation states up to J=7. We find an H_2 ortho-to-para ratio of 2.5, the fractional abundance of molecular hydrogen has a low value of log f=-4.08 for a total amount of N(H_2)=4.8+2.0}-1.6}{*10{15cm- 2. The column densities of the excitation states reveal a moderate Boltzmann excitation temperature of 130 K and an equivalent excitation temperature for the excited upper states due to UV pumping of <1800 K. Based on data obtained under the DARA ORFEUS guest observer programme

  16. Structural analysis of the interleukin-8/glycosaminoglycan interactions by amide hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Hofmann, Tommy; Samsonov, Sergey A; Pichert, Annelie; Lemmnitzer, Katharina; Schiller, Jürgen; Huster, Daniel; Pisabarro, M Teresa; von Bergen, Martin; Kalkhof, Stefan

    2015-11-01

    The recruitment of different chemokines and growth factors by glycosaminoglycans (GAGs) such as chondroitin sulfate or hyaluronan plays a critical role in wound healing processes. Thus, there is a special interest in the design of artificial extracellular matrices with improved properties concerning GAG interaction with common regulating proteins. In this study, amide hydrogen/deuterium (H/D) exchange mass spectrometry (HDX MS) combined with molecular modeling and docking experiments was used to obtain structural models of proinflammatory chemokine interleukin-8 (IL-8) in complex with hexameric chondroitin sulfate. Experiments on the intact protein showed a difference in deuterium labeling of IL-8 due to chondroitin sulfate binding. The extent of deuteration was reduced from 24% to 13% after 2 min exchange time, which corresponds to a reduced exchange of approximately 10 backbone amides. By local HDX MS experiments, H/D exchange information on the complete sequence of IL-8 could be obtained. A significantly reduced H/D exchange, especially of the C-terminal α-helical region comprising amino acids 70-77 and to the loop comprising amino acids 27-29 was observed in the presence of chondroitin sulfate. HDX MS data were used to model the IL-8/chondroitin sulfate complex. The binding interface of IL-8 and chondroitin sulfate determined this way correlated excellently with the corresponding NMR based atomistic model previously published. Our results demonstrate that HDX-MS in combination with molecular modeling is a valuable approach for the analysis of protein/GAG complexes at physiological pH, temperature, and salt concentration. The fact that HDX-MS requires only micrograms of protein and GAGs makes it a very promising technique to address protein-GAG interactions. PMID:25726910

  17. Nepenthesin from monkey cups for hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Rey, Martial; Yang, Menglin; Burns, Kyle M; Yu, Yaping; Lees-Miller, Susan P; Schriemer, David C

    2013-02-01

    Studies of protein dynamics, structure and interactions using hydrogen/deuterium exchange mass spectrometry (HDX-MS) have sharply increased over the past 5-10 years. The predominant technology requires fast digestion at pH 2-3 to retain deuterium label. Pepsin is used almost exclusively, but it provides relatively low efficiency under the constraints of the experiment, and a selectivity profile that renders poor coverage of intrinsically disordered regions. In this study we present nepenthesin-containing secretions of the pitcher plant Nepenthes, commonly called monkey cups, for use in HDX-MS. We show that nepenthesin is at least 1400-fold more efficient than pepsin under HDX-competent conditions, with a selectivity profile that mimics pepsin in part, but also includes efficient cleavage C-terminal to "forbidden" residues K, R, H, and P. High efficiency permits a solution-based analysis with no detectable autolysis, avoiding the complication of immobilized enzyme reactors. Relaxed selectivity promotes high coverage of disordered regions and the ability to "tune" the mass map for regions of interest. Nepenthesin-enriched secretions were applied to an analysis of protein complexes in the nonhomologous end-joining DNA repair pathway. The analysis of XRCC4 binding to the BRCT domains of Ligase IV points to secondary interactions between the disordered C-terminal tail of XRCC4 and remote regions of the BRCT domains, which could only be identified with a nepenthesin-based workflow. HDX data suggest that stalk-binding to XRCC4 primes a BRCT conformation in these remote regions to support tail interaction, an event which may be phosphoregulated. We conclude that nepenthesin is an effective alternative to pepsin for all HDX-MS applications, and especially for the analysis of structural transitions among intrinsically disordered proteins and their binding partners. PMID:23197791

  18. Catalytic hydrogenation of carbon monoxide

    SciTech Connect

    Wayland, B.B.

    1992-12-01

    This project is focused on developing strategies to accomplish the reduction and hydrogenation of carbon monoxide to produce organic oxygenates at mild conditions. Our approaches to this issue are based on the recognition that rhodium macrocycles have unusually favorable thermodynamic values for producing a series of intermediate implicated in the catalytic hydrogenation of CO. Observations of metalloformyl complexes produced by reactions of H{sub 2} and CO, and reductive coupling of CO to form metallo {alpha}-diketone species have suggested a multiplicity of routes to organic oxygenates that utilize these species as intermediates. Thermodynamic and kinetic-mechanistic studies are used in constructing energy profiles for a variety of potential pathways, and these schemes are used in guiding the design of new metallospecies to improve the thermodynamic and kinetic factors for individual steps in the overall process. Variation of the electronic and steric effects associated with the ligand arrays along with the influences of the reaction medium provide the chemical tools for tuning these factors. Emerging knowledge of the factors that contribute to M-H, M-C and M-O bond enthalpies is directing the search for ligand arrays that will expand the range of metal species that have favorable thermodynamic parameters to produce the primary intermediates for CO hydrogenation. Studies of rhodium complexes are being extended to non-macrocyclic ligand complexes that emulate the favorable thermodynamic features associated with rhodium macrocycles, but that also manifest improved reaction kinetics. Multifunctional catalyst systems designed to couple the ability of rhodium complexes to produce formyl and diketone intermediates with a second catalyst that hydrogenates these imtermediates are promising approaches to accomplish CO hydrogenation at mild conditions.

  19. Carbon and hydrogen isotope fractionation by moderately thermophilic methanogens

    NASA Astrophysics Data System (ADS)

    Valentine, David L.; Chidthaisong, Amnat; Rice, Andrew; Reeburgh, William S.; Tyler, Stanley C.

    2004-04-01

    A series of laboratory studies were conducted to increase understanding of stable carbon ( 13C/ 12C) and hydrogen (D/H) isotope fractionation arising from methanogenesis by moderately thermophilic acetate- and hydrogen-consuming methanogens. Studies of the aceticlastic reaction were conducted with two closely related strains of Methanosaeta thermophila. Results demonstrate a carbon isotope fractionation of only 7 (? = 1.007) between the methyl position of acetate and the resulting methane. Methane formed by this process is enriched in 13C when compared with other natural sources of methane; the magnitude of this isotope effect raises the possibility that methane produced at elevated temperature by the aceticlastic reaction could be mistaken for thermogenic methane based on carbon isotopic content. Studies of H 2/CO 2 methanogenesis were conducted with Methanothermobacter marburgensis. The fractionation of carbon isotopes between CO 2 and CH 4 was found to range from 22 to 58 (1.023 ? ? ? 1.064). Greater fractionation was associated with low levels of molecular hydrogen and steady-state metabolism. The fractionation of hydrogen isotopes between source H 2O and CH 4 was found to range from 127 to 275 (1.16 ? ? ? 1.43). Fractionation was dependent on growth phase with greater fractionation associated with later growth stages. The maximum observed fractionation factor was 1.43, independent of the ?D-H 2 supplied to the culture. Fractionation was positively correlated with temperature and/or metabolic rate. Results demonstrate significant variability in both hydrogen and carbon isotope fractionation during methanogenesis from H 2/CO 2. The relatively small fractionation associated with deuterium during H 2/CO 2 methanogenesis provides an explanation for the relatively enriched deuterium content of biogenic natural gas originating from a variety of thermal environments. Results from these experiments are used to develop a hypothesis that differential reversibility in the enzymatic steps of the H 2/CO 2 pathway gives rise to variability in the observed carbon isotope fractionation. Results are further used to constrain the overall efficiency of electron consumption by way of the hydrogenase system in M. marburgensis, which is calculated to be less than 55%.

  20. The ratio of deuterium to hydrogen in interstellar space. III - The lines of sight to Zeta Puppis and Gamma Cassiopeiae

    NASA Technical Reports Server (NTRS)

    Vidal-Madjar, A.; Laurent, C.; Bonnet, R. M.; York, D. G.

    1977-01-01

    An extensive set of measurements of the ratio of deuterium to hydrogen in the interstellar medium has been undertaken. The general observing program is described along with the data reduction techniques used to separate the complex deuterium and hydrogen profiles, and the results of the measurements for two stars, Zeta Pup and Gamma Cas. For Gamma Cas, log N(D)/N(H) is found to be approximately -4.8, in agreement with previous measurements. For Zeta Pup, a complicated structure of absorbing clouds in the interstellar medium is inferred. The best value of log N(D)/N(H) is about -4.6 for each of two components. One component is probably more complex than can be demonstrated directly at the resolution employed, and log N(D)N(H) could be -4.0 or larger in this component.

  1. HDX Match Software for the Data Analysis of Top-Down ECD-FTMS Hydrogen/Deuterium Exchange Experiments

    NASA Astrophysics Data System (ADS)

    Petrotchenko, Evgeniy V.; Borchers, Christoph H.

    2015-11-01

    Hydrogen/deuterium exchange (HDX) combined with mass spectrometry is a powerful technique for studying protein structure. The recently developed top-down ECD-FTMS HDX approach (Pan J. et al., JACS, 2008) allows determination of the hydrogen/deuterium exchange of a protein's amide bonds, down to the single residue resolution. One of the existing limitations of this technology has been the laborious manual analysis of the MS/MS spectra. Here we present a software program for processing the data from these experiments. This program assigns the c- and z-fragment ion series of the protein, and calculates the number of the exchanged amide protons for each fragment by fitting the theoretically predicted isotopic envelopes of the deuterated fragments to the experimental data.

  2. Continuous and pulsed hydrogen-deuterium exchange and mass spectrometry characterize CsgE oligomerization.

    PubMed

    Wang, Hanliu; Shu, Qin; Rempel, Don L; Frieden, Carl; Gross, Michael L

    2015-10-27

    We report the use of hydrogen-deuterium amide exchange coupled to mass spectrometry (HDX-MS) to study the interfaces of and conformational changes accompanying CsgE oligomerization. This protein plays an important role in enteric bacteria biofilm formation. Biofilms provide protection for enteric bacteria from environmental extremes and raise concerns about controlling bacteria and infectious disease. Their proteinaceous components, called curli, are extracellular functional amyloids that initiate surface contact and biofilm formation. The highly regulated curli biogenesis involves a major subunit, CsgA, a minor subunit CsgB, and a series of other accessory proteins. CsgE, possibly functioning as oligomer, is a chaperonin-like protein that delivers CsgA to an outer-membrane bound oligomeric CsgG complex. No higher-order structure, or interfaces and dynamics of its oligomerization, however, are known. In this work, we determined regions involved in CsgE self-association by continuous HDX, and, on the basis of that, prepared a double mutant W48A/F79A, derived from interface alanine scan, and verified that it exists as monomer. Using pulsed HDX and MS, we suggest there is a structural rearrangement occurring during the oligomerization of CsgE. PMID:26418947

  3. Differential hydrogen/deuterium exchange mass spectrometry analysis of protein–ligand interactions

    PubMed Central

    Chalmers, Michael J; Busby, Scott A; Pascal, Bruce D; West, Graham M; Griffin, Patrick R

    2011-01-01

    Functional regulation of ligand-activated receptors is driven by alterations in the conformational dynamics of the protein upon ligand binding. Differential hydrogen/deuterium exchange (HDX) coupled with mass spectrometry has emerged as a rapid and sensitive approach for characterization of perturbations in conformational dynamics of proteins following ligand binding. While this technique is sensitive to detecting ligand interactions and alterations in receptor dynamics, it also can provide important mechanistic insights into ligand regulation. For example, HDX has been used to determine a novel mechanism of ligand activation of the nuclear receptor peroxisome proliferator activated receptor-γ, perform detailed analyses of binding modes of ligands within the ligand-binding pocket of two estrogen receptor isoforms, providing insight into selectivity, and helped classify different types of estrogen receptor-α ligands by correlating their pharmacology with the way they interact with the receptor based solely on hierarchical clustering of receptor HDX signatures. Beyond small-molecule–receptor interactions, this technique has also been applied to study protein–protein complexes, such as mapping antibody–antigen interactions. In this article, we summarize the current state of the differential HDX approaches and the future outlook. We summarize how HDX analysis of protein–ligand interactions has had an impact on biology and drug discovery. PMID:21329427

  4. Microscopic self-dynamics in liquid hydrogen and in its mixtures with deuterium

    SciTech Connect

    Colognesi, D.; Celli, M.; Zoppi, M.; Neumann, M.

    2004-12-01

    We have measured the dynamic structure factor of liquid parahydrogen, pure and mixed with deuterium, in various thermodynamic conditions using incoherent inelastic neutron scattering. The experiments were carried out on TOSCA-II, a new time-of-flight, inverse-geometry, crystal-analyzer spectrometer. After an accurate data reduction, the high-energy parts of the neutron spectra recorded in backward scattering were studied through the modified Young and Koppel model, from which the mean kinetic energy values for a hydrogen molecule were estimated. In addition the low-energy parts of the neutron spectra recorded in forward scattering were analyzed in the framework of the Gaussian approximation and fitted through a Levesque-Verlet model for the velocity autocorrelation function. Thus various physical quantities are determined and compared with accurate path integral Monte Carlo simulations. Despite the excellent quality of these fits, the velocity autocorrelation functions derived from the forward-scattering data appear totally unable to properly describe the backward-scattering ones. These findings prove an unquestionable breakdown of the Gaussian approximation in semiquantum liquids. The present results appear of great interest and suggest further investigation on the limits of the widely used Gaussian approximation.

  5. Elastic properties of Pd-hydrogen, Pd-deuterium, and Pd-tritium single crystals

    SciTech Connect

    Schwarz, R.B. . E-mail: rxzs@lanl.gov; Bach, H.T.; Harms, U.; Tuggle, D.

    2005-02-01

    We used a resonant-ultrasound-spectroscopy technique to measure the three independent elastic constants of PdH{sub x}, PdD{sub x}, and PdT{sub x} single crystals at 300 K. For 0.1x0.62 our PdH{sub x} crystals are two-phase mixtures of coherent {alpha} and {beta} hydride phases. For increasing x in this range, C{sub 44} decreases monotonically whereas C'=12(C11-C12) has a concave parabolic dependence. This difference is because C' is softened by an anelastic relaxation resulting from acoustic-stress-induced changes in the shape of the coherent lenticular-shape precipitates ({beta}-hydride precipitates in {alpha}-hydride matrix and {alpha}-hydride precipitates in {beta}-hydride matrix). In the {beta}-phase C' and C{sub 44} decrease with increasing hydrogen (or deuterium or tritium) content. Furthermore, C' exhibits a strong isotope effect whereas C{sub 44} does not. This effect is attributed to differences in the excitation of optical phonons in Pd-H, Pd-D and Pd-T.

  6. The effect of the cw hydrogen/deuterium fluoride chemical laser with different diluents

    SciTech Connect

    Jiang, Z.; Hua, W.; Chen, J.; Zhao, Y.

    1996-12-31

    The He is usually used as diluent in combustion cw hydrogen/deuterium fluoride (HF/DF) chemical lasers. Sometimes the N{sub 2} is also used as diluent in cw HF/DF chemical laser because N{sub 2} is cheaper than the He. It was thought that the efficiency of cw HF/DF laser with N{sub 2} diluent was lower than that of HF/DF laser with He diluent since the molecular weight of N{sub 2} is heavier than that of He. In this paper, the performance of cw DF chemical lasers with He and N{sub 2} diluent was investigated. The small signal gain, power spectral distributions, cavity pressure, power and the efficiency of DF lasers with these two diluents have been calculated using a finite-difference technique for the numerical integration of the steady and unsteady Navier-Stokes equation with reactive flow (compressibility scaling method -- CSM), which was developed in the chemical gas dynamic laboratory of the state institute of applied chemistry in Russia. The numerical results show that the efficiency of DF lasers with Na{sub 2} diluent is not lower than that of the lasers with He diluent.

  7. Localized Hydration in Lyophilized Myoglobin by Hydrogen-Deuterium Exchange Mass Spectrometry. 1. Exchange Mapping

    PubMed Central

    Sophocleous, Andreas M.; Zhang, Jun; Topp, Elizabeth M.

    2012-01-01

    The local effects of hydration on myoglobin (Mb) in solid matrices containing mannitol or sucrose (1:1 w/w, protein:additive) were mapped using hydrogen-deuterium exchange with mass spectrometric analysis (HDX-MS) at 5°C and compared to solution controls. Solid powders were exposed to D2O(g) at controlled activity (aw) followed by reconstitution and analysis of the intact protein and peptides produced by pepsin digestion. HDX varied with matrix type, aw, and position along the protein backbone. HDX was less in sucrose matrices than in mannitol matrices at all aw while the difference in solution was negligible. Differences in HDX in the two matrices were detectable despite similarities in their bulk water content. The extent of exchange in solids is proposed as a measure of the hydration of exchangeable amide groups, as well as protein conformation and dynamics; pepsin digestion allows these effects to be mapped with peptide-level resolution. PMID:22352965

  8. Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 1. Peptides to Proteins

    NASA Astrophysics Data System (ADS)

    Donohoe, Gregory C.; Khakinejad, Mahdiar; Valentine, Stephen J.

    2015-04-01

    Ion mobility spectrometry (IMS) coupled with hydrogen deuterium exchange (HDX)-mass spectrometry (MS) has been used to study the conformations of negatively-charged peptide and protein ions. Results are presented for ion conformers of angiotensin 1, a synthetic peptide (SP), bovine insulin, ubiquitin, and equine cytochrome c. In general, the SP ion conformers demonstrate a greater level of HDX efficiency as a greater proportion of the sites undergo HDX. Additionally, these ions exhibit the fastest rates of exchange. Comparatively, the angiotensin 1 ions exhibit a lower rate of exchange and HDX level presumably because of decreased accessibility of exchange sites by charge sites. The latter are likely confined to the peptide termini. Insulin ions show dramatically reduced HDX levels and exchange rates, which can be attributed to decreased conformational flexibility resulting from the disulfide bonds. For the larger ubiquitin and protein ions, increased HDX is observed for larger ions of higher charge state. For ubiquitin, a conformational transition from compact to more elongated species (from lower to higher charge states) is reflected by an increase in HDX levels. These results can be explained by a combination of interior site protection by compact conformers as well as decreased access by charge sites. The elongated cytochrome c ions provide the largest HDX levels where higher values correlate with charge state. These results are consistent with increased exchange site accessibility by additional charge sites. The data from these enhanced IMS-HDX experiments are described in terms of charge site location, conformer rigidity, and interior site protection.

  9. Start2Fold: a database of hydrogen/deuterium exchange data on protein folding and stability

    PubMed Central

    Pancsa, Rita; Varadi, Mihaly; Tompa, Peter; Vranken, Wim F.

    2016-01-01

    Proteins fulfil a wide range of tasks in cells; understanding how they fold into complex three-dimensional (3D) structures and how these structures remain stable while retaining sufficient dynamics for functionality is essential for the interpretation of overall protein behaviour. Since the 1950's, solvent exchange-based methods have been the most powerful experimental means to obtain information on the folding and stability of proteins. Considerable expertise and care were required to obtain the resulting datasets, which, despite their importance and intrinsic value, have never been collected, curated and classified. Start2Fold is an openly accessible database (http://start2fold.eu) of carefully curated hydrogen/deuterium exchange (HDX) data extracted from the literature that is open for new submissions from the community. The database entries contain (i) information on the proteins investigated and the underlying experimental procedures and (ii) the classification of the residues based on their exchange protection levels, also allowing for the instant visualization of the relevant residue groups on the 3D structures of the corresponding proteins. By providing a clear hierarchical framework for the easy sharing, comparison and (re-)interpretation of HDX data, Start2Fold intends to promote a better understanding of how the protein sequence encodes folding and structure as well as the development of new computational methods predicting protein folding and stability. PMID:26582925

  10. Automated Hydrogen/Deuterium Exchange Electron Transfer Dissociation High Resolution Mass Spectrometry Measured at Single-Amide Resolution

    NASA Astrophysics Data System (ADS)

    Landgraf, Rachelle R.; Chalmers, Michael J.; Griffin, Patrick R.

    2012-02-01

    Hydrogen deuterium exchange mass spectrometry (HDX-MS) is a well established method for the measurement of solution-phase deuterium incorporation into proteins, which can provide insight into protein conformational mobility. However, most HDX measurements are constrained to regions of the protein where pepsin proteolysis allows detection at peptide resolution. Recently, single-amide resolution deuterium incorporation has been achieved by limiting gas-phase scrambling in the mass spectrometer. This was accomplished by employing a combination of soft ionization and desolvation conditions coupled with the radical-driven fragmentation technique electron transfer dissociation (ETD). Here, a hybrid LTQ-Orbitrap XL is systematically evaluated for its utility in providing single-amide deuterium incorporation for differential HDX analysis of a nuclear receptor upon binding small molecule ligands. We are able to show that instrumental parameters can be optimized to minimize scrambling and can be incorporated into an established and fully automated HDX platform making differential single-amide HDX possible for bottom-up analysis of complex systems. We have applied this system to determine differential single amide resolution HDX data for the peroxizome proliferator activated receptor bound with two ligands of interest.

  11. Disiloxane Synthesis Based on Silicon-Hydrogen Bond Activation using Gold and Platinum on Carbon in Water or Heavy Water.

    PubMed

    Sawama, Yoshinari; Masuda, Masahiro; Yasukawa, Naoki; Nakatani, Ryosuke; Nishimura, Shumma; Shibata, Kyoshiro; Yamada, Tsuyoshi; Monguchi, Yasunari; Suzuka, Hiroyasu; Takagi, Yukio; Sajiki, Hironao

    2016-05-20

    Disiloxanes possessing a silicon-oxygen linkage are important as frameworks for functional materials and coupling partners for Hiyama-type cross coupling. We found that disiloxanes were effectively constructed of hydrosilanes catalyzed by gold on carbon in water as the solvent and oxidant in association with the emission of hydrogen gas at room temperature. The present oxidation could proceed via various reaction pathways, such as the hydration of hydrosilane into silanol, dehydrogenative coupling of hydrosilane into disilane, and the subsequent corresponding reactions to disiloxane. Additionally, the platinum on carbon catalyzed hydrogen-deuterium exchange reaction of arylhydrosilanes as substrates in heavy water proceeded on the aromatic nuclei at 80 °C with high deuterium efficiency and high regioselectivity at the only meta and para positions of the aromatic-silicon bond to give the deuterium-labeled disiloxanes. PMID:27129497

  12. Nanostructural activated carbons for hydrogen storage

    NASA Astrophysics Data System (ADS)

    Li, Suoding

    A series of nanostructured activated carbons have been synthesized from poly(ether ether ketone) (PEEK), and its derivatives. These carbons, with surface area exceeding 3000 m2/g and with average pore diameters of ≤ 20 A, are proven to be superior hydrogen storage materials, with hydrogen storage capacities up to 5.5 wt% at 77 K and 45 atm. The porous texture of these carbons was controlled via optimizing three synthetic steps: thermo-oxidation of PEEK in air, pyrolysis or carbonization of the oxidized PEEK in an inert atmosphere, and activation of the pre-carbonized PEEK with metal hydroxide. Thermo-oxidation of PEEK and carbonization process were thoroughly studied. These processes have been investigated by MDSC, FTIR, TGA and Py-MS. The pyrolysis or carbonization of PEEK involves the degradation of PEEK chains in three stages. Carbon morphology, including crystallinity and porous texture, is readily controlled by adjusting carbonization temperature. Activation of PEEK carbons, using inorganic bases and other activation agents, produces microporous carbons having a very narrow pore size distribution and an average pore diameter of ≤ 20 A. The activation control parameters including activation agent, activation temperature, time and carbon morphology have been investigated extensively. High surface area activated carbon is obtained by activating a highly amorphous carbon with a high activation agent/carbon ratio at 800°C. Theoretical calculations show that the pores with smaller diameter, especially smaller than 7 A, favor hydrogen adsorption. The experimental results confirm this fact and show that: (1) the hydrogen adsorption capacity per unit surface area at 77 K and 1 bar is larger in the smaller pores, (2) gravimetric hydrogen storage capacity (W(H2)) is directly proportional to the ultramicropore (< 7 A) volume; and (3) the volumetric hydrogen storage capacity is directly proportional to the volume fraction of ultramicropores in carbon. Hydrogen adsorption in activated carbons synthesized from PEEK and poly(ether imide) blends, poly(phenylene oxide), polybenzimidazole and lignin show similar trends. In addition, W( H2) progressively increases as surface area increases for the carbons with similar average pore diameters. Keywords. carbon, activated carbon, poly(ether ether ketone), poly(ether imide), poly(phenylene oxide), polybenzimidazole, lignin, gas adsorption, hydrogen storage

  13. Theoretical modeling of infrared spectra of the hydrogen and deuterium bond in aspirin crystal

    NASA Astrophysics Data System (ADS)

    Ghalla, Houcine; Rekik, Najeh; Michta, Anna; Oujia, Brahim; Flakus, Henryk T.

    2010-01-01

    An extended quantum theoretical approach of the ? IR lineshape of cyclic dimers of weakly H-bonded species is proposed. We have extended a previous approach [M.E.-A. Benmalti, P. Blaise, H.T. Flakus, O. Henri-Rousseau, Chem. Phys. 320 (2006) 267] by accounting for the anharmonicity of the slow mode which is described by a "Morse" potential in order to reproduce the polarized infrared spectra of the hydrogen and deuterium bond in acetylsalicylic acid (aspirin) crystals. From comparison of polarized IR spectra of isotopically neat and isotopically diluted aspirin crystals it resulted that centrosymmetric aspirin dimer was the bearer of the crystal main spectral properties. In this approach, the adiabatic approximation is performed for each separate H-bond bridge of the dimer and a strong non-adiabatic correction is introduced into the model via the resonant exchange between the fast mode excited states of the two moieties. Within the strong anharmonic coupling theory, according to which the X-H?⋯Y high-frequency mode is anharmonically coupled to the H-bond bridge, this model incorporated the Davydov coupling between the excited states of the two moieties, the quantum direct and indirect dampings and the anharmonicity for the H-bond bridge. The spectral density is obtained within the linear response theory by Fourier transform of the damped autocorrelation functions. The evaluated spectra are in fairly good agreement with the experimental ones by using a minimum number of independent parameters. The effect of deuteration has been well reproduced by reducing simply the angular frequency of the fast mode and the anharmonic coupling parameter.

  14. Nondissociative electron and photon ionization cross sections of molecular hydrogen and deuterium

    NASA Astrophysics Data System (ADS)

    Liu, Xianming; Shemansky, Donald E.

    2012-05-01

    State-to-state [X 1Σ+g(vi) → X 2Σ+g(vj)] and quasi state-specific [X 1Σ+g(vi, Ji) → X 2Σ+g(vj)] photon and electron-impact ionization cross sections of hydrogen and deuterium molecules have been obtained with a combined analysis of experimental measurement and theoretical calculations. Rotation state ionization transitions are considered using the p-partial wave approximation. Previously calculated photoionization transition moments are refined and extended to ˜300 eV using accurate experimental photoionization cross sections. The transition moments are used to obtain the photoionization cross sections and oscillator strengths for the H2 and D2 X 1Σ+g(vi, Ji) → H+2 and D+2 X 2Σ+g(vj, Jj) transitions. The calculated ionization oscillator strengths, together with excitation functions derived from electron-impact ionization measurements of H2, enable accurate determination of electron-impact ionization cross sections for both H2 and D2 transitions to (vj, Jj) levels of the X 2Σ+g state at energies ranging from threshold to the non-relativistic limit. The autoionizing singlet-ungerade states contribute at least 0.6-1% of the total e+H2 →H+2 cross section. The e+D2 →D+2 and e+H2 →H+2 cross sections are very similar above the threshold energy region. The D2 cross section is ˜1.6% larger than the H2 cross section. Thermally averaged nondissociative ionization cross sections of H2 and D2 at temperatures appropriate for plasma and planetary applications have been tabulated.

  15. Guanine nucleotide induced conformational change of Cdc42 revealed by hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Yang, Sheng-Wei; Ting, Hsiu-Chi; Lo, Yi-Ting; Wu, Ting-Yuan; Huang, Hung-Wei; Yang, Chia-Jung; Chan, Jui-Fen Riva; Chuang, Min-Chieh; Hsu, Yuan-Hao Howard

    2016-01-01

    Cdc42 regulates pathways related to cell division. Dysregulation of Cdc42 can lead to cancer, cardiovascular diseases and neurodegenerative diseases. GTP induced activation mechanism plays an important role in the activity and biological functions of Cdc42. P-loop, Switch I and Switch II are critical regions modulating the enzymatic activity of Cdc42. We applied amide hydrogen/deuterium exchange coupled with liquid chromatography mass spectrometry (HDXMS) to investigate the dynamic changes of apo-Cdc42 after GDP, GTP and GMP-PCP binding. The natural substrate GTP induced significant decreases of deuteration in P-loop and Switch II, moderate changes of deuteration in Switch I and significant changes of deuteration in the ?7 helix, a region far away from the active site. GTP binding induced similar effects on H/D exchange to its non-hydrolysable analog, GMP-PCP. HDXMS results indicate that GTP binding blocked the solvent accessibility in the active site leading to the decrease of H/D exchange rate surrounding the active site, and further triggered a conformational change resulting in the drastic decrease of H/D exchange rate at the remote ?7 helix. Comparing the deuteration levels in three activation states of apo-Cdc42, Cdc42-GDP and Cdc42-GMP-PCP, the apo-Cdc42 has the most flexible structure, which can be stabilized by guanine nucleotide binding. The rates of H/D exchange of Cdc42-GDP are between the GMP-PCP-bound and the apo form, but more closely to the GMP-PCP-bound form. Our results show that the activation of Cdc42 is a process of conformational changes involved with P-loop, Switch II and ?7 helix for structural stabilization. PMID:26542736

  16. Gas phase recombination of hydrogen and deuterium atoms. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Trainor, D. W.; Ham, D. O.; Kaufman, F.

    1973-01-01

    Rate constants for the reaction H + H + M - H2 + M, with M = H2, He, and Ar were measured over the temperature range 77 to 298 K. Hydrogen atoms were produced by thermal dissociation and absolute atom concentrations were measured through use of self-balancing, isothermal catalytic probe detector. The specific rate constants were 8.1 + or - 0.4 x 10 to the minus 33rd power, 7.0 + or - 0.4 x 10 to the minus 33rd power, and 9.2 + or - 0.6 x at 298 K for M = H2, He, and Ar respectively; these values rising to 18.5 + or - 2.2 x 10 to the minus 33rd power, 12.0 + or - 1.5 x 10 to the minus 33rd power, and 27.4 + or - 4.6 x 10 to the minus 33rd power cm to the 6th power/molecules sq/sec at 77 K. for the equivalent deuterium atom process with D2 as the third body, the rate constants are 6.1 + or - 0.3 x 10 to the minus 33rd power cm to the 6th power/molecules sq/sec at 298 K and 15.1 + or - 1.0 x 10 to the minus 33rd power cm to the 6th power/molecules sq/sec at 77 K. These values are compared with previous experimental measurements and with recent theoretical calculations.

  17. Structural Insights of Glucan Phosphatase Dynamics using Amide Hydrogen/Deuterium Exchange Mass Spectrometry

    PubMed Central

    Hsu, Simon; Kim, Youngjun; Li, Sheng; Durrant, Eric S.; Pace, Rachel M.; Woods, Virgil L.; Gentry, Matthew S.

    2009-01-01

    Laforin and Starch Excess 4 (SEX4) are founding members of a class of phosphatases that dephosphorylate phosphoglucans. Each protein contains a carbohydrate binding module (CBM) and a dual specificity phosphatase (DSP) domain. The gene encoding laforin is mutated in a fatal neurodegenerative disease called Lafora disease (LD). In the absence of laforin function, insoluble glucans accumulate that are hyperphosphorylated and exhibit sparse branching. It is hypothesized that these accumulations trigger the neurodegeneration and premature death of LD patients. We recently demonstrated that laforin removes phosphate from phosphoglucans and hypothesized that this function inhibits insoluble glucan accumulation. Loss of SEX4 function in plants yields a similar cellular phenotype; cells accumulate an excess amount of insoluble, hyperphosphorylated glucans. While multiple groups have shown that these phosphatases dephosphorylate phosphoglucans, there is no structure of a glucan phosphatase and little is known about the mechanism whereby they perform this action. We utilized hydrogen-deuterium exchange mass spectrometry (DXMS) and structural modeling to probe the conformational and structural dynamics of the glucan phosphatase SEX4. We found that the enzyme does not undergo a global conformational change upon glucan binding, but instead undergoes minimal rearrangement upon binding. The CBM undergoes increased protection from deuteration when bound to glucans, confirming its role in glucan binding. More interestingly, we identified structural components of the DSP that also undergo increased protection from deuteration upon glucan addition. To determine the position of these regions, we generated a homology model of the SEX4 DSP. The homology model shows that all of these regions are adjacent the DSP active site. Therefore, our results suggest that these regions of the DSP participate in presenting the phosphoglucan to the active site and provide the first structural analysis and mode of action of this unique class of phosphatases. PMID:19754155

  18. Operation of a cw rf driven ion source with hydrogen and deuterium gas{sup a}

    SciTech Connect

    Melnychuk, S.T.; Debiak, T.W.; Sredniawski, J.J.

    1996-04-01

    We will describe the operation of a cw rf driven multicusp ion source designed for extraction of high current hydrogen and deuterium beams. The source is driven at 2 MHz by a 2.5 turn induction antenna immersed in the plasma. Bare stainless-steel and porcelain-coated Cu antennas have been used. The plasma load is matched to the rf generator by a variable tap {ital N}:1 transformer isolated to 46 kV, and an LC network on the secondary. With H{sub 2} gas the source can be operated at pressures between 5 and 60 mT with power reflection coefficients {lt}0.01. The extracted ion current density with a porcelain-coated antenna is approximately given by 35 mA/cm{sup 2}/kW with an 80 G dipole filter field for input powers from 3.5 to 6.6 kW. The current density remained constant for operation with a 6 and an 8 mm aperture. The source has been operated for 260 h at 3.6 kW with a single-porcelain-coated antenna. Mass spectrometer measurements of the extracted beam at this power show a species mix for H{sup +}:H{sup +}{sub 2}:H{sup +}{sub 3}:OH{sup +} of 0.49: 0.04: 0.42: 0.04. The calculated beam divergence using the IGUN code is compared with the measured divergence from an electrostatic sweep emittance scanner designed for high-power cw beam diagnostics. Phase space measurements at 40 kV and 23 mA beam current result in a normalized rms emittance of 0.09 {pi}mmmrad. {copyright} {ital 1996 American Institute of Physics.}

  19. Impact of temperature during He+ implantation on deuterium retention in tungsten, tungsten with carbon deposit and tungsten carbide

    NASA Astrophysics Data System (ADS)

    Oya, Yasuhisa; Sato, Misaki; Li, Xiaochun; Yuyama, Kenta; Fujita, Hiroe; Sakurada, Shodai; Uemura, Yuki; Hatano, Yuji; Yoshida, Naoaki; Ashikawa, Naoko; Sagara, Akio; Chikada, Takumi

    2016-02-01

    Temperature dependence on deuterium (D) retention for He+ implanted tungsten (W) was studied by thermal desorption spectroscopy (TDS) to evaluate the tritium retention behavior in W. The activation energies were evaluated using Hydrogen Isotope Diffusion and Trapping (HIDT) simulation code and found to be 0.55 eV, 0.65 eV, 0.80 eV and 1.00 eV. The heating scenarios clearly control the D retention behavior and, dense and large He bubbles could work as a D diffusion barrier toward the bulk, leading to D retention enhancement at lower temperature of less than 430 K, even if the damage was introduced by He+ implantation. By comparing the D retention for W, W with carbon deposit and tungsten carbide (WC), the dense carbon layer on the surface enhances the dynamic re-emission of D as hydrocarbons, and induces the reduction of D retention. However, by He+ implantation, the D retention was increased for all the samples.

  20. Atmospheric Pressure Photo Ionization Hydrogen/Deuterium Exchange Mass Spectrometry—a Method to Differentiate Isomers by Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Ahmed, Arif; Kim, Sunghwan

    2013-12-01

    In this report, a method for in-source hydrogen/deuterium (H/D) exchange at atmospheric pressure is reported. The method was named atmospheric pressure photo ionization hydrogen/deuterium exchange mass spectrometry (APPI HDX MS). H/D exchange was performed by mixing samples dissolved in toluene with CH3OD solvent and analyzing the mixture using atmospheric pressure photo ionization mass spectrometry (APPI-MS). The APPI HDX spectra obtained with contact times between the analyte solution and methanol-OD (CH3OD) of < 0.5 s or 1 h showed the same pattern of H/D exchange. Therefore, it was concluded that APPI HDX occurred in the source but not in the solution. The proposed method does not require a specific type of mass spectrometer and can be performed at atmospheric pressure. H/D exchange can be performed in any laboratory with a mass spectrometer and a commercial APPI source. Using this method, multiple H/D exchanges of aromatic hydrogen and/or H/D exchange of active hydrogen were observed. These results demonstrated that H/D exchange can be used to distinguish between isomers containing primary, secondary, and tertiary amines, as well as pyridine and pyrrole functional groups.

  1. Differential Mobility Spectrometry-Hydrogen Deuterium Exchange (DMS-HDX) as a Probe of Protein Conformation in Solution.

    PubMed

    Zhu, Shaolong; Campbell, J Larry; Chernushevich, Igor; Le Blanc, J C Yves; Wilson, Derek J

    2016-06-01

    Differential mobility spectrometry (DMS) is an ion mobility technique that has been adopted chiefly as a pre-filter for small- to medium-sized analytes (<1 000 Da). With the exception of a handful of studies that employ an analogue of DMS-field asymmetric waveform ion mobility spectroscopy (FAIMS)-the application of DMS to intact biomacromolecules remains largely unexplored. In this work, we employ DMS combined with gas-phase hydrogen deuterium exchange (DMS-HDX) to probe the gas-phase conformations generated from proteins that were initially folded, partially-folded, and unfolded in solution. Our findings indicate that proteins with distinct structural features in solution exhibit unique deuterium uptake profiles as function of their optimal transmission through the DMS. Ultimately we propose that DMS-HDX can, if properly implemented, provide rapid measurements of liquid-phase protein structural stability that could be of use in biopharmaceuticals development. Graphical Abstract ᅟ. PMID:26965162

  2. Differential Mobility Spectrometry-Hydrogen Deuterium Exchange (DMS-HDX) as a Probe of Protein Conformation in Solution

    NASA Astrophysics Data System (ADS)

    Zhu, Shaolong; Campbell, J. Larry; Chernushevich, Igor; Le Blanc, J. C. Yves; Wilson, Derek J.

    2016-03-01

    Differential mobility spectrometry (DMS) is an ion mobility technique that has been adopted chiefly as a pre-filter for small- to medium-sized analytes (<1 000 Da). With the exception of a handful of studies that employ an analogue of DMS—field asymmetric waveform ion mobility spectroscopy (FAIMS)—the application of DMS to intact biomacromolecules remains largely unexplored. In this work, we employ DMS combined with gas-phase hydrogen deuterium exchange (DMS-HDX) to probe the gas-phase conformations generated from proteins that were initially folded, partially-folded, and unfolded in solution. Our findings indicate that proteins with distinct structural features in solution exhibit unique deuterium uptake profiles as function of their optimal transmission through the DMS. Ultimately we propose that DMS-HDX can, if properly implemented, provide rapid measurements of liquid-phase protein structural stability that could be of use in biopharmaceuticals development.

  3. Screen-printed digital microfluidics combined with surface acoustic wave nebulization for hydrogen-deuterium exchange measurements.

    PubMed

    Monkkonen, Lucas; Edgar, J Scott; Winters, Daniel; Heron, Scott R; Mackay, C Logan; Masselon, Christophe D; Stokes, Adam A; Langridge-Smith, Patrick R R; Goodlett, David R

    2016-03-25

    An inexpensive digital microfluidic (DMF) chip was fabricated by screen-printing electrodes on a sheet of polyimide. This device was manually integrated with surface acoustic wave nebulization (SAWN) MS to conduct hydrogen/deuterium exchange (HDX) of peptides. The HDX experiment was performed by DMF mixing of one aqueous droplet of angiotensin II with a second containing various concentrations of D2O. Subsequently, the degree of HDX was measured immediately by SAWN-MS. As expected for a small peptide, the isotopically resolved mass spectrum for angiotensin revealed that maximum deuterium exchange was achieved using 50% D2O. Additionally, using SAWN-MS alone, the global HDX kinetics of ubiquitin were found to be similar to published NMR data and back exchange rates for the uncooled apparatus using high inlet capillary temperatures was less than 6%. PMID:26826755

  4. Carbon-hydrogen bonding in near-frictionless carbon

    NASA Astrophysics Data System (ADS)

    Johnson, J. A.; Woodford, J. B.; Rajput, D.; Kolesnikov, A. I.; Schleuter, J. A.; Eryilmaz, O. L.; Erdemir, A.

    2008-09-01

    The uniquely low friction behavior of near-frictionless carbon (NFC) as compared to conventional diamondlike carbon (DLC) is determined by the bonding within the film. Inelastic neutron scattering (INS) and Fourier transform infrared (FTIR) spectroscopy were used to probe the bonding environment of carbon and hydrogen; both INS and FTIR can probe the whole sample. Previous work has focused on surface studies; the present results show that in the film as a whole the majority of the hydrogen is adjacent to sp3-bonded carbon. In addition this work has determined the absence of any molecular hydrogen in NFC.

  5. Carbon and hydrogen isotopic composition of bacterial methane in a shallow freshwater lake

    SciTech Connect

    Woltemate, I.; Whiticar, M.J.; Schoell, M.

    1984-09-01

    Anoxic sediments from freshwater environments such as bogs, swamps, and lakes undergoing early diagenesis are frequently characterized by the formation of biogenic methane. Freshwater biogenic methanes exhibit carbon and hydrogen isotopic values strongly depleted in C-13 and deuterium relative to the respective values for carbon dioxide and formation water. The percentages of methane generated by fermentation and carbon dioxide reduction can be estimated by comparison of hydrogen isotopes in the formation water and methane. On the basis of these hydrogen isotope data, about 75% of the methane formation in Wurmsee comes from acetate reduction. Fermentation is thus the dominant although not exclusive process. Carbon dioxide reduction contributed the balance of the bacterial methane generated. 35 references, 5 figures, 1 table.

  6. Hydrogen-deuterium exchange of aromatic amines and amides using deuterated trifluoroacetic acid

    PubMed Central

    Giles, Richard; Lee, Amy; Jung, Erica; Kang, Aaron; Jung, Kyung Woon

    2014-01-01

    The H-D exchange of aromatic amines and amides, including pharmaceutically relevant compounds such as acetaminophen and diclofenac, was investigated using CF3COOD as both the sole reaction solvent and source of deuterium label. The described method is amenable to efficient deuterium incorporation for a wide variety of substrates possessing both electron-donating and electron-withdrawing substituents. Best results were seen with less basic anilines and highly activated acetanilides, reflecting the likelihood of different mechanistic pathways. PMID:25641994

  7. Deuterium dynamics in the icosahedral and amorphous phases of the Ti40Zr40Ni20 hydrogen-absorbing alloy studied by 2H NMR

    NASA Astrophysics Data System (ADS)

    Gradišek, A.; Kocjan, A.; McGuiness, P. J.; Apih, T.; Kim, Hae Jin; Dolinšek, J.

    2008-11-01

    The Ti40Zr40Ni20 hydrogen-absorbing alloy was prepared in the icosahedral and amorphous phases by controlling the rotation speed of the melt-spinning method of sample preparation, and the deuterium dynamics was investigated by 2H NMR dynamic lineshape and spin-lattice relaxation. The results were analysed by the lineshape and relaxation models that assume deuterium thermally activated hopping within a manifold of different chemical environments. The observed 8% larger activation energy for the deuterium hopping over the interstitial sites and the 10% larger static spectrum width of the amorphous phase, as compared to the icosahedral phase, can be accounted for by the larger deuterium content of the investigated amorphous sample. From the deuterium dynamics point of view, the icosahedral phase is not special with respect to the amorphous modification of the same material.

  8. Designing Microporus Carbons for Hydrogen Storage Systems

    SciTech Connect

    Alan C. Cooper

    2012-05-02

    An efficient, cost-effective hydrogen storage system is a key enabling technology for the widespread introduction of hydrogen fuel cells to the domestic marketplace. Air Products, an industry leader in hydrogen energy products and systems, recognized this need and responded to the DOE 'Grand Challenge' solicitation (DOE Solicitation DE-PS36-03GO93013) under Category 1 as an industry partner and steering committee member with the National Renewable Energy Laboratory (NREL) in their proposal for a center-of-excellence on Carbon-Based Hydrogen Storage Materials. This center was later renamed the Hydrogen Sorption Center of Excellence (HSCoE). Our proposal, entitled 'Designing Microporous Carbons for Hydrogen Storage Systems,' envisioned a highly synergistic 5-year program with NREL and other national laboratory and university partners.

  9. Desorption of hydrogen trapped in carbon and graphite

    NASA Astrophysics Data System (ADS)

    Atsumi, H.; Takemura, Y.; Miyabe, T.; Konishi, T.; Tanabe, T.; Shikama, T.

    2013-11-01

    Thermal desorption behavior of deuterium (D2) from isotropic graphites and a carbon fiber carbon composite (CFC) charged with D2 gas has been investigated to obtain information concerning hydrogen recycling and tritium inventory in fusion experimental devices as well as a futuristic fusion reactor. After thermal desorption experiments were conducted at temperatures up to 1740 K, a desorption peak at approximately 1600 K (peak 4) was discovered. This is in addition to the previously known peak at approximately 1300 K (peak 3). Peak 3 can be attributed to the release of deuterium controlled by the diffusion process in a graphite filler grain and peak 4 can be attributed to the detrapping of deuterium released from an interstitial cluster loop edge site. Activation energies of peaks 3 and 4 are estimated to be 3.48 and 6.93 eV, respectively. TDS spectra of D2 from graphite and CFCs had previously not been thoroughly investigated. A desorption peak at approximately 1600 K was discovered in the TDS spectra for all samples heated with a linear ramp rate of 0.1 K/s. For an isotropic graphite, ISO-880U, four desorption peaks were recognized in the TDS spectra at approximately 660 K, 900 K, 1300 K, and 1600 K. These peaks were named as peaks 1, 2, 3, and 4 in order of increasing temperature. Major desorption peaks (i.e., peaks 3 and 4) were analyzed and discussed in detail. The temperature of peak 3 was dependent on the size of a graphite filler grain. The desorption process is suggested to be controlled by deuterium diffusion within the filler grain with a strong influence of trapping sites, where the migration takes place as a sequence of detrapping and retrapping. The desorption for peak 4 can be ascribed to the detrapping reaction from an interstitial cluster loop edge site. Activation energies were estimated from the peak shift by varying the heating rate of TDS to be 3.48 and 6.93 eV for peaks 3 and 4, respectively. Theoretical desorption curves for peaks 3 and 4 with the above mentioned activation energies were narrower than those for the experimental desorption curve. The observed peak broadening can be attributed to the effects of grain size and activation energy distributions.

  10. Using Hydrogen/Deuterium Exchange Mass Spectrometry to Study Conformational Changes in Granulocyte Colony Stimulating Factor upon PEGylation

    NASA Astrophysics Data System (ADS)

    Wei, Hui; Ahn, Joomi; Yu, Ying Qing; Tymiak, Adrienne; Engen, John R.; Chen, Guodong

    2012-03-01

    PEGylation is the covalent attachment of polyethylene glycol to proteins, and it can be used to alter immunogenicity, circulating half life and other properties of therapeutic proteins. To determine the impact of PEGylation on protein conformation, we applied hydrogen/deuterium exchange mass spectrometry (HDX MS) to analyze granulocyte colony stimulating factor (G-CSF) upon PEGylation as a model system. The combined use of HDX automation technology and data analysis software allowed reproducible and robust measurements of the deuterium incorporation levels for peptic peptides of both PEGylated and non-PEGylated G-CSF. The results indicated that significant differences in deuterium incorporation were induced by PEGylation of G-CSF, although the overall changes observed were quite small. PEGylation did not result in gross conformational rearrangement of G-CSF. The data complexity often encountered in HDX MS measurements was greatly reduced through a data processing and presentation format designed to facilitate the comparison process. This study demonstrates the practical utility of HDX MS for comparability studies, process monitoring, and protein therapeutic characterization in the biopharmaceutical industry.

  11. Exclusive Photoproduction of Charged Pions in Hydrogen and Deuterium from 1 to 6 GeV

    SciTech Connect

    Lingyan Zhu

    2004-02-28

    The study of the transition region in the description of exclusive processes and hadron structure, from the nucleon-meson degrees of freedom in meson-exchange models at low energy to the quark-gluon degrees of freedom in pQCD at high energy, is essential for us to understand the strong interaction. The differential cross section measurements for exclusive reactions at fixed center-of-mass angles enable us to investigate the constituent counting rule, which explicitly connects the quark-gluon degrees of freedom to the energy dependence of differential cross sections. JLab Experiment E94-104 was carried out in Hall A with two high resolution spectrometers. It included the coincidence cross section measurement for the [gamma]n --> pi{sup -}[p] process with a deuterium target and the singles measurement for the [gamma]p --> pi{sup +}[n] process with a hydrogen target. The untagged real photons were generated by the electron beam impinging on a copper radiator. The photon energies ranged from 1.1 to 5.5 GeV, corresponding to the center-of-mass energies from 1.7 to 3.4 GeV. The pion center-of-mass angles were fixed at 50 deg, 70 deg, 90 deg, and also 100 deg, 110 deg at a few energies. The JLab E94-104 data presented in this thesis contain four interesting features. The data exhibit a global scaling behavior for both [pi]{sup -} and [pi]{sup +} photoproduction at high energies and high transverse momenta, consistent with the constituent counting rule and the existing [pi]{sup +} photoproduction data. This implies that the quark-gluon degrees of freedom start to play a role at this energy scale. The data suggests possible substructure of the scaling behavior, which might be oscillations around the scaling value. There are several possible mechanisms that can cause oscillations, for example the one associated with the generalized constituent counting rule involving quark orbital angular momentum. The data show an enhancement in the scaled cross section at center-of-mass energy near 2.2 GeV, where baryon resonances are not as well known as those at low energies. The differential cross section ratios for exclusive [gamma]n --> pi{sup -}[p] to [gamma]p --> pi{sup +}[n] process at [theta]{sub cm} = 90 deg start to show consistency with the prediction based on one-hard-gluon-exchange diagrams at high energies.

  12. Interaction of hydrogen with novel carbon materials

    NASA Astrophysics Data System (ADS)

    Ye, Yun

    The hydrogen storage properties of some carbon materials were studied. Graphite nanofibers (GNF) were synthesized by catalytic decomposition of ethylene and hydrogen. Catalyst supported carbon materials were prepared by impregnation process. Hydrogen desorption and adsorption properties of graphite nanofibers, single-walled carbon nanotubes (SWNT), fullerene materials and catalysts supported carbon materials were measured volumetrically using a Sievert's apparatus. The hydrogen desorption capacity of GNF was typically less than 0.2 wt%. A phase transition between crystal SWNT and a new hydride phase was found at high pressures at 80K. The phase transition was of first order, and involved the separation of the individual tubes within a rope, exposing a high surface area for hydrogen adsorption. From the change in chemical potential of the hydrogen gas upon adsorption, we were able to calculate the cohesive van der Waals energy between the tubes as 5 meV/C atom. This is much smaller than expected from previous theoretical work, and shows that defects in the crystal structure cause large suppressions of the cohesive energy. We were able to alter this cohesive energy by changing the state of the material. Over several cycles of isotherm measurements at 77 K, the hydrogen storage capacities of one of the fullerite samples increased from an initial value of 0.4 wt% for the first cycle to a capacity of 4.2 wt% for the fourth cycle. Correspondingly, the surface area increased from 0.9 m2/gm to 11 m2/gm, and showed a phase transformation, characterized by X-ray powder diffraction. By adding Ni particles onto the sample, the hydrogen storage capacity of fullerite and activated carbon sample was increased. The adsorption of hydrogen on Ni particle can not account for the total increased capacity even by assuming complete coverage of hydrogen molecules on the Ni particle surface.

  13. A deuterium and carbon nuclear magnetic resonance spectroscopic investigation of blood flow and carbohydrate metabolism

    SciTech Connect

    Bosch, C.S.E.

    1988-01-01

    The purpose of this study is the development and application of nuclear magnetic resonance (NMR) spectroscopic techniques for this study of whole tissue metabolism, tissue perfusion and blood flow. The feasibility of spin imaging deuterium-enriched tissue water is demonstrated in cat brain in vivo and in situ. The potential application of D{sub 2}O administration to deuterium-flow-imaging is considered. NMR investigations of hepatic carbohydrate metabolism were performed in rat liver in vivo and in situ. A coaxial, double-surface-coil, double-resonance probe was developed for carbon detection while decoupling neighboring proton scalar interactions ({sup 13}C-({sup 1}H)) in hepatic tissue within the living animal. Hormonal and substrate regulation of hepatic glucose and glycogen metabolism was investigated by monitoring the metabolic fate of an administered c-dose of (1-{sup 13}C)glucose. Label flux was directed primarily into newly-synthesized {sup 13}C-labeled glycogen. A multiple resonance ({sup 1}H, {sup 13}C, {sup 31}P) liver perfusion probe was designed for complimentary carbohydrate metabolic studies in rat liver in vitro. A description of the {sup 13}C-({sup 1}H)/{sup 31}P NMR perfusion probe is given. The surgical technique used for liver excision and peripheral life-support apparatus required to maintain hepatic function are also detailed.

  14. Investigation of the gas-phase hydrogen/deuterium exchange behavior of aromatic dicarboxylic acids in a quadrupole ion trap

    NASA Astrophysics Data System (ADS)

    Chipuk, Joseph E.; Brodbelt, Jennifer S.

    2007-11-01

    Gas-phase hydrogen/deuterium (H/D) exchange reactions of four deprotonated aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid and 2,6-naphthalic acid) with D2O were performed in a quadrupole ion trap mass spectrometer. Experimental results showed significant differences in the rate and extent of exchange when the relative position of the carboxylic acid groups varied. Spontaneous and near complete exchange of one aromatic hydrogen atom occurred when the carboxylic acid groups were in the meta-position, whereas no additional exchange was observed for either the ortho- or para-isomers or for the structurally similar naphthalic acid. Computational investigations support the participation of several possible exchange mechanisms with the contribution of each relying heavily on the relative orientation of the acid moieties. A relay mechanism that bridges the deprotonation site and the labile hydrogen site appears to be responsible for the H/D exchange of not only the labile hydrogen atom of isophthalic acid, but also for the formation of a stable carbanion and corresponding subsequent exchange of one aromatic hydrogen atom. The impact of hydrogen bonding on the relay mechanism is demonstrated by the reaction of phthalic acid as the extent and rate of reaction are greatly retarded by the favorable interaction of the two carboxylic acid groups. Finally, a flip-flop mechanism is likely responsible for the exchange of both terephthalic acid and 2,6-naphthalic acid where the reactive sites are too remote for exchange via relay.

  15. Some implications of a new value for the primordial solar deuterium-hydrogen ratio.

    NASA Technical Reports Server (NTRS)

    Black, D. C.

    1971-01-01

    Some astrophysical implications of a primordial solar D/H ratio of 0.000015 are investigated. Perhaps the most interesting aspects of the D/H ratio concern galactic evolution and cosmology. It is shown that the initial galactic abundance of deuterium exceeds by at least a factor of 30 the abundance expected from known galactic production mechanisms. If a Friedmann cosmology is a correct description of the universe, it must be an open one unless some as yet unknown mechanism is invo ked to produce deuterium and He-3.

  16. Hydrogen storage on activated carbon. Final report

    SciTech Connect

    Schwarz, J.A.

    1994-11-01

    The project studied factors that influence the ability of carbon to store hydrogen and developed techniques to enhance that ability in naturally occurring and factory-produced commercial carbon materials. During testing of enhanced materials, levels of hydrogen storage were achieved that compare well with conventional forms of energy storage, including lead-acid batteries, gasoline, and diesel fuel. Using the best materials, an electric car with a modern fuel cell to convert the hydrogen directly to electricity would have a range of over 1,000 miles. This assumes that the total allowable weight of the fuel cell and carbon/hydrogen storage system is no greater than the present weight of batteries in an existing electric vehicle. By comparison, gasoline cars generally are limited to about a 450-mile range, and battery-electric cars to 40 to 60 miles. The project also developed a new class of carbon materials, based on polymers and other organic compounds, in which the best hydrogen-storing factors discovered earlier were {open_quotes}molecularly engineered{close_quotes} into the new materials. It is believed that these new molecularly engineered materials are likely to exceed the performance of the naturally occurring and manufactured carbons seen earlier with respect to hydrogen storage.

  17. Synthesis of carbon-14 and deuterium labeled N-nitroso-2 (3',7'-dimethyl-2',6'-octadienyl) aminoethanols

    USGS Publications Warehouse

    Abidi, S.L.; Idelson, A.L.

    1981-01-01

    Methods of preparation of carbon-14 and deuterium labeled N-nitroso-2(3,7-dimethyl-2,6-octadienyl) aminoethanols are described. The primary synthetic method involved alkylation of ethanolamine or ethylglycine with suitable chlorides and subsequent mild nitrosation. Isomeric 14C-nitrosamines were also prepared by selective -cleavage of the di-substituted ethanolamine with nitrous acid.

  18. Investigating the Interaction between the Neonatal Fc Receptor and Monoclonal Antibody Variants by Hydrogen/Deuterium Exchange Mass Spectrometry*

    PubMed Central

    Jensen, Pernille Foged; Larraillet, Vincent; Schlothauer, Tilman; Kettenberger, Hubert; Hilger, Maximiliane; Rand, Kasper D.

    2015-01-01

    The recycling of immunoglobulins by the neonatal Fc receptor (FcRn) is of crucial importance in the maintenance of antibody levels in plasma and is responsible for the long half-lives of endogenous and recombinant monoclonal antibodies. From a therapeutic point of view there is great interest in understanding and modulating the IgG–FcRn interaction to optimize antibody pharmacokinetics and ultimately improve efficacy and safety. Here we studied the interaction between a full-length human IgG1 and human FcRn via hydrogen/deuterium exchange mass spectrometry and targeted electron transfer dissociation to map sites perturbed by binding on both partners of the IgG–FcRn complex. Several regions in the antibody Fc region and the FcRn were protected from exchange upon complex formation, in good agreement with previous crystallographic studies of FcRn in complex with the Fc fragment. Interestingly, we found that several regions in the IgG Fab region also showed reduced deuterium uptake. Our findings indicate the presence of hitherto unknown FcRn interaction sites in the Fab region or a possible conformational link between the IgG Fc and Fab regions upon FcRn binding. Further, we investigated the role of IgG glycosylation in the conformational response of the IgG–FcRn interaction. Removal of antibody glycans increased the flexibility of the FcRn binding site in the Fc region. Consequently, FcRn binding did not induce a similar conformational stabilization of deglycosylated IgG as observed for the wild-type glycosylated IgG. Our results provide new molecular insight into the IgG–FcRn interaction and illustrate the capability of hydrogen/deuterium exchange mass spectrometry to advance structural proteomics by providing detailed information on the conformation and dynamics of large protein complexes in solution. PMID:25378534

  19. Qualitative and quantitative analysis of mixtures of compounds containing both hydrogen and deuterium

    NASA Technical Reports Server (NTRS)

    Crespi, H. L.; Harkness, L.; Katz, J. J.; Norman, G.; Saur, W.

    1969-01-01

    Method allows qualitative and quantitative analysis of mixtures of partially deuterated compounds. Nuclear magnetic resonance spectroscopy determines location and amount of deuterium in organic compounds but not fully deuterated compounds. Mass spectroscopy can detect fully deuterated species but not the location.

  20. ALKYL AND HYDRIDE BIS (TRIMETHYLSILYL)AMIDO DERIVATIVES OF THE ACTINIDE ELEMENTS: PREPARATION AND HYDROGEN-DEUTERIUM EXCHANGE

    SciTech Connect

    Simpson, Stephen J.; Turner, Howard W.; Andersen, Richard A.

    1980-09-01

    The monomeric, hydrocarbon-soluble monohydrides and monodeuterides of the actinide metals (thorium or uranium) of the type HM[N(SiMe{sub 3}){sub 2}]{sub 3} have been prepared. Their reaction chemistry, n-BuLi followed by MeBr yields MeM[N(SiMe{sub 3}){sub 2}]{sub 3} and borane in tetrahydrofuran yields BH{sub 4}M[N(SiMe{sub 3}){sub 2}]{sub 3}, suggests that the hydrogen atom is hydridic. Pyrolysis of the hydrides yields the novel, four-membered ring metallocycle, [(Me{sub 3}Si){sub 2}N]{sub 2} - MCH{sub 2}Si(Me){sub 2}NSiMe{sub 3} where M is Th or U. These metallocycles are the key intermediates in the hydrogen-deuterium exchange reaction that yields {[(CD{sub 3}){sub 3}Si]{sub 2}N}{sub 3}MD.

  1. Structure-resonance theory and the kinetics of the electrophilic deuterium-hydrogen exchange in benzenoid hydrocarbons

    SciTech Connect

    Shawali, A.S.; Parkanyi, C.; Herndon, W.C.

    1982-01-01

    Structure-resonance theory has recently been shown to correlate and to predict various physical and chemical properties of ..pi..-electron hydrocarbons. The major advantage of this theory is its simplicity. Its application requires only an enumeration of Kekule' structures, since it has been shown that an algorithm, logarithm of the Kekule' corrected structure count, gives an excellent approximation of the gound-state eigenvalues of the structure-function Hamiltonian matrix. The purpose of this contribution is to show that the structure-resonance theory can be used to correlate the rates of both the deuterium-hydrogen and hydrogen-deuterium exchange reactions of benzenoid hydrocarbons. Logarithms of the rates of deuterodeprotonation of nine alternant hydrocarbons and protodedeuteration of five hydrocarbons containing 17 and 12 different reaction sites, respectively, are correlated with the logarithms of the structure counts of the intermediate, ln SC/sub I/, and the reactant, ln SC/sub R/, and with their ratio, ln (SC/sub I//SC/sub R/). The quality of the correlations is very good. The results indicate that the differences in reactivities of benzenoid hydrocarbons in aromatic substitution reactions are due to differences in their resonance energies and that hyperconjugation does not play a significant role in the stabilization of the intermediates in the reaction studied.

  2. A matrix-isolation study of the water- d1 iodine atom complex and the equilibrium between its hydrogen-bonded and deuterium-bonded forms

    NASA Astrophysics Data System (ADS)

    Engdahl, Anders; Nelander, Bengt

    1985-12-01

    The interaction between water (H 2O, HDO, D 2O) or hydrogen chloride and iodine or bromine, (I -, I 2, Br -, Br 2) in argon matrices has been studied with IR spectroscopy. The spectra show that water forms a hydrogen bond to atomic iodine. Molecular iodine, atomic and molecular bromine are bound to the water oxygen. Hydrogen chloride forms hydrogen-bonded complexes with I -, I 2, Br - and Br 2. HDO forms preferentially deuterium bonds with atomic iodine but hydrogen-bonded HDO is present in equilibrium with the deuterium-bonded form. Temperature-dependency studies make it possible to estimate that the H-bonded form is 26 cm -1 less stable than the D-bonded form.

  3. Inhomogeneous carbon bonding in hydrogenated amorphous carbon films

    NASA Astrophysics Data System (ADS)

    Grill, A.; Meyerson, B. S.; Patel, V. V.; Reimer, J. A.; Petrich, M. A.

    1987-04-01

    Hard-carbon films prepared by the rf-plasma decomposition of acetylene have been investigated by high-resolution 13C nuclear magnetic resonance spectroscopy, x-ray photoelectron spectroscopy (XPS), and the H(15Nα,γ)C nuclear resonant reaction. It was found that the ratio of sp2:sp3 bound carbon was 1.6, and that virtually all sp3 carbon atoms are, in fact, bound to one or more hydrogen atoms. Bulk layers contain about 40% hydrogen; however, results of the measurements of the hydrogen concentration, as well as those of XPS, confirm that the composition and properties of these carbon films are a strong function of their distance from the initial growth interface, and are spatially varying over the first 40 nm.

  4. The solubility of hydrogen and deuterium in alloyed, unalloyed and impure plutonium metal

    SciTech Connect

    Richmond, Scott; Bridgewater, Jon S; Ward, John W; Allen, Thomas H

    2010-01-01

    Hydrogen is exothermically absorbed in many transition metals, all rare earths and the actinides. The hydrogen gas adsorbs, dissociates and diffuses into these metals as atomic hydrogen. Absorbed hydrogen is generally detrimental to Pu, altering its properties and greatly enhancing corrosion. Measuring the heat of solution of hydrogen in Pu and its alloys provides significant insight into the thermodynamics driving these changes. Hydrogen is present in all Pu metal unless great care is taken to avoid it. Heats of solution and formation are provided along with evidence for spinodal decomposition.

  5. Rapid Annealing Of Amorphous Hydrogenated Carbon

    NASA Technical Reports Server (NTRS)

    Alterovitz, Samuel A.; Pouch, John J.; Warner, Joseph D.

    1989-01-01

    Report describes experiments to determine effects of rapid annealing on films of amorphous hydrogenated carbon. Study represents first efforts to provide information for applications of a-C:H films where rapid thermal processing required. Major finding, annealing causes abrupt increase in absorption and concomitant decrease in optical band gap. Most of change occurs during first 20 s, continues during longer annealing times. Extend of change increases with annealing temperature. Researchers hypothesize abrupt initial change caused by loss of hydrogen, while gradual subsequent change due to polymerization of remaining carbon into crystallites or sheets of graphite. Optical band gaps of unannealed specimens on silicon substrates lower than those of specimens on quartz substrates.

  6. Peptide-Column Interactions and Their Influence on Back Exchange Rates in Hydrogen/Deuterium Exchange-MS

    NASA Astrophysics Data System (ADS)

    Sheff, Joey G.; Rey, Martial; Schriemer, David C.

    2013-07-01

    Hydrogen/deuterium exchange (HDX) methods generate useful information on protein structure and dynamics, ideally at the individual residue level. Most MS-based HDX methods involve a rapid proteolytic digestion followed by LC/MS analysis, with exchange kinetics monitored at the peptide level. Localizing specific sites of HDX is usually restricted to a resolution the size of the host peptide because gas-phase processes can scramble deuterium throughout the peptide. Subtractive methods may improve resolution, where deuterium levels of overlapping and nested peptides are used in a subtractive manner to localize exchange to smaller segments. In this study, we explore the underlying assumption of the subtractive method, namely, that the measured back exchange kinetics of a given residue is independent of its host peptide. Using a series of deuterated peptides, we show that secondary structure can be partially retained under quenched conditions, and that interactions between peptides and reversed-phase LC columns may both accelerate and decelerate residue HDX, depending upon peptide sequence and length. Secondary structure is induced through column interactions in peptides with a solution-phase propensity for structure, which has the effect of slowing HDX rates relative to predicted random coil values. Conversely, column interactions can orient random-coil peptide conformers to accelerate HDX, the degree to which correlates with peptide charge in solution, and which can be reversed by using stronger ion pairing reagents. The dependency of these effects on sequence and length suggest that subtractive methods for improving structural resolution in HDX-MS will not offer a straightforward solution for increasing exchange site resolution.

  7. Equilibrium carbon and hydrogen isotope fractionation in iron

    NASA Astrophysics Data System (ADS)

    Schauble, E. A.

    2009-12-01

    Recent theoretical and experimental studies (e.g., [1-3]) have suggested that Si- and Fe-isotopic signatures can be used to characterize the compositions and conditions of segregation of metallic cores in planetary interiors. This study expands the theoretical framework to include carbon and hydrogen, which may also be alloying elements. Hydrogen (D/H) and carbon (13C/12C) fractionations in iron-rich metallic melts are estimated by modeling analogous iron-rich crystals, i.e., dhcp-FeH and η-Fe2C. C- and H-atoms in these crystals are completely coordinated by iron. The driving energy for equilibrium fractionation is assumed to come from the reduction of vibrational frequencies when heavy isotopes are substituted for light ones; vibrations are assumed to be harmonic. This treatment is crude at high temperature, and for the relatively anharmonic vibrations typical of hydrogen-bearing substances, but may provide a reasonably accurate, semi-quantitative approximation of real fractionation behavior. Vibrational frequencies of all crystals are modeled with density functional theory, using gradient-corrected functionals and ultrasoft pseudopotentials. For both carbon and hydrogen, the models suggest that the metal phase will be strongly depleted in heavy isotopes. At 2000 K, 1 atm, η-Fe2C will have 3‰ lower 13C/12C than coexisting diamond. Combining this result with previous high-temperature theoretical and experimental studies (e.g., [4]), metal-graphite fractionation is expected to be very similar, while metal-CO2 fractionation will be almost twice as large, ca. -5‰. Deuterium/hydrogen fractionations are expected to be an order of magnitude larger, with 50-70‰ lower D/H in dhcp-FeH than in coexisting H2 gas at 2000 K, and approximately 100‰ lower D/H than water vapor. These fractionations are much larger than those inferred for silicon and iron, as expected given the differences in atomic mass. References: 1. Georg et al. (2007) Nature 447:1102; 2. Rustad & Yin (2009) Nature Geoscience doi:10.1038/ngeo546; 3. Polyakov (2009) Science 323:912; 4. Polyakov & Kharlashina (1995) GCA 59:2561.

  8. Supercritical fluid chromatography coupled with in-source atmospheric pressure ionization hydrogen/deuterium exchange mass spectrometry for compound speciation.

    PubMed

    Cho, Yunju; Choi, Man-Ho; Kim, Byungjoo; Kim, Sunghwan

    2016-04-29

    An experimental setup for the speciation of compounds by hydrogen/deuterium exchange (HDX) with atmospheric pressure ionization while performing chromatographic separation is presented. The proposed experimental setup combines the high performance supercritical fluid chromatography (SFC) system that can be readily used as an inlet for mass spectrometry (MS) and atmospheric pressure photo ionization (APPI) or atmospheric pressure chemical ionization (APCI) HDX. This combination overcomes the limitation of an approach using conventional liquid chromatography (LC) by minimizing the amount of deuterium solvents used for separation. In the SFC separation, supercritical CO2 was used as a major component of the mobile phase, and methanol was used as a minor co-solvent. By using deuterated methanol (CH3OD), AP HDX was achieved during SFC separation. To prove the concept, thirty one nitrogen- and/or oxygen-containing standard compounds were analyzed by SFC-AP HDX MS. The compounds were successfully speciated from the obtained SFC-MS spectra. The exchange ions were observed with as low as 1% of CH3OD in the mobile phase, and separation could be performed within approximately 20min using approximately 0.24mL of CH3OD. The results showed that SFC separation and APPI/APCI HDX could be successfully performed using the suggested method. PMID:27020885

  9. Gas-phase hydrogen/deuterium exchange in a travelling wave ion guide for the examination of protein conformations

    PubMed Central

    Rand, Kasper D.; Pringle, Steven D.; Murphy, James P.; Fadgen, Keith E.; Brown, Jeff; Engen, John R.

    2009-01-01

    Accumulating evidence suggests that solution-phase conformations of small globular proteins and large molecular protein assemblies can be preserved for milliseconds after electrospray ionization. Thus, the study of proteins in the gas-phase on this time-scale is highly desirable. Here we demonstrate that a travelling wave ion guide (TWIG) of a Synapt mass spectrometer offers a highly suitable environment for rapid and efficient gas-phase hydrogen/deuterium exchange (HDX). Gaseous ND3 was introduced into either the source TWIG or the TWIG located just after the ion mobility cell, such that ions underwent HDX as they passed through the ND3 on the way to the time-of-flight analyzer. The extent of deuterium labeling could be controlled by varying the quantity of ND3 or the speed of the travelling wave. The gas-phase HDX of model peptides corresponded to labeling of primarily fast exchanging sites due to the short labeling times (ranging from 0.1 to 10 ms). In addition to peptides, gas-phase HDX of ubiquitin, cytochrome c, lysozyme and apomyoglobin were examined. We conclude that HDX of protein ions in a TWIG is highly sensitive to protein conformation, enables the detection of conformers present on sub-milliseconds timescales and can readily be combined with ion mobility spectrometry. PMID:19921790

  10. Combining Ion Mobility Spectrometry with Hydrogen-Deuterium Exchange and Top-Down MS for Peptide Ion Structure Analysis

    NASA Astrophysics Data System (ADS)

    Khakinejad, Mahdiar; Kondalaji, Samaneh Ghassabi; Maleki, Hossein; Arndt, James R.; Donohoe, Gregory C.; Valentine, Stephen J.

    2014-12-01

    The gas-phase conformations of electrosprayed ions of the model peptide KKDDDDIIKIIK have been examined by ion mobility spectrometry (IMS) and hydrogen deuterium exchange (HDX)-tandem mass spectrometry (MS/MS) techniques. [M+4H]4+ ions exhibit two conformers with collision cross sections of 418 Å2 and 471 Å2. [M+3H]3+ ions exhibit a predominant conformer with a collision cross section of 340 Å2 as well as an unresolved conformer (shoulder) with a collision cross section of ~367 Å2. Maximum HDX levels for the more compact [M+4H]4+ ions and the compact and partially-folded [M+3H]3+ ions are ~12.9, ~15.5, and ~14.9, respectively. Ion structures obtained from molecular dynamics simulations (MDS) suggest that this ordering of HDX level results from increased charge-site/exchange-site density for the more compact ions of lower charge. Additionally, a new model that includes two distance calculations (charge site to carbonyl group and carbonyl group to exchange site) for the computer-generated structures is shown to better correlate to the experimentally determined per-residue deuterium uptake. Future comparisons of IMS-HDX-MS data with structures obtained from MDS are discussed with respect to novel experiments that will reveal the HDX rates of individual residues.

  11. Testing the performance of a cryogenic visualization system on thermal counterflow by using hydrogen and deuterium solid tracers

    NASA Astrophysics Data System (ADS)

    La Mantia, M.; Chagovets, T. V.; Rotter, M.; Skrbek, L.

    2012-05-01

    An experimental apparatus has been designed to analyze by visualization cryogenic flows of liquid 4He and consequently address unresolved problems of quantum turbulence. The newly implemented flow visualization setup is described and its specific features discussed. Thermal counterflow experiments have been performed and the motion of solid hydrogen and deuterium tracers studied by using the particle tracking velocimetry technique in order to probe the system capabilities. It is shown that the obtained results are consistent with the two-fluid model describing the behavior of superfluid 4He. A number of technical and fundamental issues, such as particles' aggregation, role of rotating particles in counterflow and evidence of non-Gaussian distribution of tracers' velocities, are also discussed. The apparatus appears to be well-suited to the task of analyzing cryogenic flows and potentially capable of obtaining new results stimulating further understanding of the underlying physics.

  12. Water on Mars: Clues from Deuterium/Hydrogen and Water Contents of Hydrous Phases in SNC Meteorites.

    PubMed

    Watson, L L; Hutcheon, I D; Epstein, S; Stolper, E M

    1994-07-01

    Ion microprobe studies of hydrous amphibole, biotite, and apatite in shergottite-nakhlite-chassignite (SNC) meteorites, probable igneous rocks from Mars, indicate high deuterium/hydrogen (D/H) ratios relative to terrestrial values. The amphiboles contain roughly one-tentn as much water as expected, suggesting that SNC magmas were less hydrous than previously proposed. The high but variable D/H values of these minerals are best explained by postcrystallization D enrichment of initially D-poor phases by martian crustal fluids with near atmospheric D/H (about five times the terrestrial value). These igneous phases do not directly reflect the D/H ratios of martian "magmatic" water but provide evidence for a D-enriched martian crustal water reservoir. PMID:17774694

  13. Influence of domain interactions on conformational mobility of the progesterone receptor detected by hydrogen/deuterium exchange mass spectrometry

    PubMed Central

    Goswami, Devrishi; Callaway, Celetta; Pascal, Bruce D.; Kumar, Raj; Edwards, Dean P.; Griffin, Patrick R.

    2015-01-01

    Structural and functional details of the N-terminal activation function 1 (AF1) of most nuclear receptors are poorly understood due to the highly dynamic intrinsically disordered nature of this domain. A hydrogen/deuterium exchange (HDX) mass spectrometry based investigation of TATA box binding protein (TBP) interaction with various domains of progesterone receptor (PR) demonstrate that agonist bound PR interaction with TBP via AF1 impacts the mobility of the C-terminal AF2. Results from HDX and other biophysical studies involving agonist and antagonist bound full length PR and isolated PR domains reveals the molecular mechanism underlying synergistic transcriptional activation mediated by AF1 and AF2, dominance of PR-B isoform over PR-A, and the necessity of AF2 for full AF1-mediated transcriptional activity. These results provide a comprehensive picture elaborating the underlying mechanism of PR-TBP interactions as a model for studying NR-transcription factor functional interactions. PMID:24909783

  14. Characterizing rapid, activity-linked conformational transitions in proteins via sub-second hydrogen deuterium exchange mass spectrometry.

    PubMed

    Resetca, Diana; Wilson, Derek J

    2013-11-01

    This review outlines the application of time-resolved electrospray ionization mass spectrometry (TRESI-MS) and hydrogen-deuterium exchange (HDX) to study rapid, activity-linked conformational transitions in proteins. The method is implemented on a microfluidic chip which incorporates all sample-handling steps required for a 'bottom-up' HDX workflow: a capillary mixer for sub-second HDX labeling, a static mixer for HDX quenching, a microreactor for rapid protein digestion, and on-chip electrospray. By combining short HDX labeling pulses with rapid digestion, this approach provides a detailed characterization of the structural transitions that occur during protein folding, ligand binding, post-translational modification and catalytic turnover in enzymes. This broad spectrum of applications in areas largely inaccessible to conventional techniques means that microfluidics-enabled TRESI-MS/HDX is a unique and powerful approach for investigating the dynamic basis of protein function. PMID:23663649

  15. Erosion and redeposition behavior of selected NET-candidate materials under high-flux hydrogen, deuterium plasma bombardment in pisces

    NASA Astrophysics Data System (ADS)

    Franconi, E.; Hirooka, Y.; Conn, R. W.; Leung, W. K.; Labombard, B.; Nygren, R. E.

    1989-04-01

    Plasma erosion and redeposition behavior of selected candidate materials for plasma-facing components in the NET-machine have been investigated using the PISCES-A facility. Materials studied include SiC-impregnated graphite, 2D graphite weaves with and without CVD-SiC coatings, and isotropic graphite. These specimens were exposed to continuous hydrogen or deuterium plasmas under the following conditions: electron temperature range from 5 to 35 eV; plasma density range from 5 10 11 to 1 10 12 cm -3; flux range from 5 10 17 to 2 10 18 ions cm -2 s -1; fluence of the order from 10 21 to 10 22 ions/cm 2; bombarding energies of 50 and 100 eV; target temperature range from 300 to 1000C. The erosion yield of SiC-impregnated graphite due to deuterium plasma bombardment is found to be a factor of 2 to 3 less than that of isotropic graphite materials. A further factor of 2-3 reduction in the erosion yield is observed in when redeposition associated with reionization of sputtered particle becomes significant. From post-bombardment surface analysis with AES, the surface composition in terms of the Si/C of SiC-impregnated graphite ratio is found to increase from 0.15 to 0.7 after hydrogen plasma bombardment to a fluence around 4 10 21 ions/cm 2 at 350 C. However, the final surface composition appears to remain unchanged up to 4 10 22 ions/cm 2, the highest fluence in the present study. Significant surface morphological modifications of SiC-impregnated graphite are observed after the high-fluence plasma exposure. Several structural problems such as coating-substrate adhesion have been pointed out for SiC-coated 2D graphite weave.

  16. Gas-Phase Hydrogen-Deuterium Exchange Labeling of Select Peptide Ion Conformer Types: a Per-Residue Kinetics Analysis

    NASA Astrophysics Data System (ADS)

    Khakinejad, Mahdiar; Kondalaji, Samaneh Ghassabi; Tafreshian, Amirmahdi; Valentine, Stephen J.

    2015-07-01

    The per-residue, gas-phase hydrogen deuterium exchange (HDX) kinetics for individual amino acid residues on selected ion conformer types of the model peptide KKDDDDDIIKIIK have been examined using ion mobility spectrometry (IMS) and HDX-tandem mass spectrometry (MS/MS) techniques. The [M + 4H]4+ ions exhibit two major conformer types with collision cross sections of 418 Å2 and 446 Å2; the [M + 3H]3+ ions also yield two different conformer types having collision cross sections of 340 Å2 and 367 Å2. Kinetics plots of HDX for individual amino acid residues reveal fast- and slow-exchanging hydrogens. The contributions of each amino acid residue to the overall conformer type rate constant have been estimated. For this peptide, N- and C-terminal K residues exhibit the greatest contributions for all ion conformer types. Interior D and I residues show decreased contributions. Several charge state trends are observed. On average, the D residues of the [M + 3H]3+ ions show faster HDX rate contributions compared with [M + 4H]4+ ions. In contrast the interior I8 and I9 residues show increased accessibility to exchange for the more elongated [M + 4H]4+ ion conformer type. The contribution of each residue to the overall uptake rate showed a good correlation with a residue hydrogen accessibility score model calculated using a distance from charge site and initial incorporation site for nominal structures obtained from molecular dynamic simulations (MDS).

  17. Analysis of palladium coatings to remove hydrogen isotopes from zirconium fuel rods in Canada deuterium uranium-pressurized heavy water reactors; Thermal and neutron diffusion effects

    SciTech Connect

    Stokes, C.L.; Buxbaum, R.E. )

    1992-05-01

    This paper reports that, in pressurized heavy water nuclear reactors of the type standardly used in Canada (Canada deuterium uranium-pressurized heavy water reactors), the zirconium alloy pressure tubes of the core absorb deuterium produced by corrosion reactions. This deuterium weakens the tubes through hydrogen embrittlement. Thin palladium coatings on the outside of the zirconium are analyzed as a method for deuterium removal. This coating is expected to catalyze the reaction D{sub 2} + 1/2O{sub 2} {r reversible} D{sub 2}O when O{sub 2} is added to the annular (insulating) gas in the tubes. Major reductions in the deuterium concentration and, hence, hydrogen embrittlement are predicted. Potential problems such as plating the tube geometry, neutron absorption, catalyst deactivation, radioactive waste production, and oxygen corrosion are shown to be manageable. Also, a simple set of equations are derived to calculate the effect on diffusion caused by neutron interactions. Based on calculations of ordinary and neutron flux induced diffusion, a palladium coating of 1 {times} 10{sup {minus}6} m is recommended. This would cost approximately $60,000 per reactor unit and should more than double reactor lifetime. Similar coatings and similar interdiffusion calculations might have broad applications.

  18. Synthesis of hydrogen-carbon clathrate material and hydrogen evolution therefrom at moderate temperatures and pressures

    DOEpatents

    Lueking, Angela; Narayanan, Deepa

    2011-03-08

    A process for making a hydrogenated carbon material is provided which includes forming a mixture of a carbon source, particularly a carbonaceous material, and a hydrogen source. The mixture is reacted under reaction conditions such that hydrogen is generated and/or released from the hydrogen source, an amorphous diamond-like carbon is formed, and at least a portion of the generated and/or released hydrogen associates with the amorphous diamond-like carbon, thereby forming a hydrogenated carbon material. A hydrogenated carbon material including a hydrogen carbon clathrate is characterized by evolution of molecular hydrogen at room temperature at atmospheric pressure in particular embodiments of methods and compositions according to the present invention.

  19. Simultaneous profiling of hydrogen and deuterium by 2.6 MeV He4e ERDA using a ΔE - E telescope detector

    NASA Astrophysics Data System (ADS)

    Wielunski, M.; Mayer, M.; Behrisch, R.; Roth, J.; Scherzer, B. M. U.

    1997-01-01

    For depth profiling of hydrogen isotopes by elastic recoil detection analysis (ERDA) with 2.6 MeV He4e ions a special ΔE - E telescope type detector system was tested. It allows the separation of hydrogen and deuterium recoils as well as backscattered helium particles. For particle identification from the energy loss Δ E a thin 3.7 μm silicon transmission detector was used while the residual energy was measured with a standard 100 μm PIPS silicon surface barrier detector. The depth profiles of deuterium and hydrogen were measured at plasma deposited a-C:H:D layers as well as at samples exposed to plasma discharges in the tokamak experiment ASDEX-Upgrade.

  20. Hydrogen and deuterium in myoglobin as seen by a neutron structure determination at 1.5 A resolution.

    PubMed

    Ostermann, Andreas; Tanaka, Ichiro; Engler, Niklas; Niimura, Nobuo; Parak, Fritz G

    2002-03-28

    From the first days of protein neutron structure determination sperm whale myoglobin was an object under investigation [Nature 224 (1969) 143, J. Mol. Biol. 220 (1991) 381]. Nevertheless myoglobin is still of interest [Proc. Natl. Acad. Sci. USA 97 (2000) 3872]. The feasibility of the monochromatic neutron diffractometer BIX-3 at the JRR-3M reactor at the JAERI [J. Phys. Chem. Solids 60 (1999) 1623], to collect high-resolution diffraction data in a relatively short time stimulated us to repeat the structural determination of myoglobin. The structure of metmyoglobin has been determined up to a resolution of 1.5 A. The hydrogen atoms were replaced in part, by deuterium soaking the crystals for more than 10 years in D(2)O. A refinement of all atoms has been performed including the refinement of individual mean square displacements and occupancies of the exchangeable protons in backbone hydrogen bonds. A method is described to show clear negative scattering densities of the H atoms. Water molecules within the protein and on the molecule surface are shown. The exchangeability of H atoms is correlated with structural distribution and flexibility. PMID:12062378

  1. Hexicon 2: Automated Processing of Hydrogen-Deuterium Exchange Mass Spectrometry Data with Improved Deuteration Distribution Estimation

    NASA Astrophysics Data System (ADS)

    Lindner, Robert; Lou, Xinghua; Reinstein, Jochen; Shoeman, Robert L.; Hamprecht, Fred A.; Winkler, Andreas

    2014-06-01

    Hydrogen-deuterium exchange (HDX) experiments analyzed by mass spectrometry (MS) provide information about the dynamics and the solvent accessibility of protein backbone amide hydrogen atoms. Continuous improvement of MS instrumentation has contributed to the increasing popularity of this method; however, comprehensive automated data analysis is only beginning to mature. We present Hexicon 2, an automated pipeline for data analysis and visualization based on the previously published program Hexicon (Lou et al. 2010). Hexicon 2 employs the sensitive NITPICK peak detection algorithm of its predecessor in a divide-and-conquer strategy and adds new features, such as chromatogram alignment and improved peptide sequence assignment. The unique feature of deuteration distribution estimation was retained in Hexicon 2 and improved using an iterative deconvolution algorithm that is robust even to noisy data. In addition, Hexicon 2 provides a data browser that facilitates quality control and provides convenient access to common data visualization tasks. Analysis of a benchmark dataset demonstrates superior performance of Hexicon 2 compared with its predecessor in terms of deuteration centroid recovery and deuteration distribution estimation. Hexicon 2 greatly reduces data analysis time compared with manual analysis, whereas the increased number of peptides provides redundant coverage of the entire protein sequence. Hexicon 2 is a standalone application available free of charge under http://hx2.mpimf-heidelberg.mpg.de.

  2. Optimization and Application of APCI Hydrogen-Deuterium Exchange Mass Spectrometry (HDX MS) for the Speciation of Nitrogen Compounds

    NASA Astrophysics Data System (ADS)

    Acter, Thamina; Cho, Yunju; Kim, Sungji; Ahmed, Arif; Kim, Byungjoo; Kim, Sunghwan

    2015-09-01

    A systematic study was performed to investigate the utility of atmospheric pressure chemical ionization hydrogen-deuterium exchange mass spectrometry (APCI HDX MS) to identify the structures of nitrogen-containing aromatic compounds. First, experiments were performed to determine the optimized experimental conditions, with dichloromethane and CH3OD found to be good cosolvents for APCI HDX. In addition, a positive correlation between the heated capillary temperature and the observed HDX signal was observed, and it was suggested that the HDX reaction occurred when molecules were contained in the solvent cluster. Second, 20 standard nitrogen-containing compounds were analyzed to investigate whether speciation could be determined based on the different types of ions produced from nitrogen-containing compounds with various functional groups. The number of exchanges occurring within the compounds correlated well with the number of active hydrogen atoms attached to nitrogen, and it was confirmed that APCI HDX MS could be used to determine speciation. The results obtained by APCI HDX MS were combined with the subsequent investigation of the double bond equivalence distribution and indicated that resins of shale oil extract contained mostly pyridine type nitrogen compounds. This study confirmed that APCI HDX MS can be added to previously reported chemical ionization, electrospray ionization, and atmospheric pressure photo ionization-based HDX methods, which can be used for structural elucidation by mass spectrometry.

  3. Optimization and Application of APCI Hydrogen-Deuterium Exchange Mass Spectrometry (HDX MS) for the Speciation of Nitrogen Compounds.

    PubMed

    Acter, Thamina; Cho, Yunju; Kim, Sungji; Ahmed, Arif; Kim, Byungjoo; Kim, Sunghwan

    2015-09-01

    A systematic study was performed to investigate the utility of atmospheric pressure chemical ionization hydrogen-deuterium exchange mass spectrometry (APCI HDX MS) to identify the structures of nitrogen-containing aromatic compounds. First, experiments were performed to determine the optimized experimental conditions, with dichloromethane and CH(3)OD found to be good cosolvents for APCI HDX. In addition, a positive correlation between the heated capillary temperature and the observed HDX signal was observed, and it was suggested that the HDX reaction occurred when molecules were contained in the solvent cluster. Second, 20 standard nitrogen-containing compounds were analyzed to investigate whether speciation could be determined based on the different types of ions produced from nitrogen-containing compounds with various functional groups. The number of exchanges occurring within the compounds correlated well with the number of active hydrogen atoms attached to nitrogen, and it was confirmed that APCI HDX MS could be used to determine speciation. The results obtained by APCI HDX MS were combined with the subsequent investigation of the double bond equivalence distribution and indicated that resins of shale oil extract contained mostly pyridine type nitrogen compounds. This study confirmed that APCI HDX MS can be added to previously reported chemical ionization, electrospray ionization, and atmospheric pressure photo ionization-based HDX methods, which can be used for structural elucidation by mass spectrometry. PMID:26115964

  4. Characterization of IgG1 Conformation and Conformational Dynamics by Hydrogen/Deuterium Exchange Mass Spectrometry

    SciTech Connect

    Houde, Damian; Arndt, Joseph; Domeier, Wayne; Berkowitz, Steven; Engen, John R.

    2009-04-22

    Protein function is dictated by protein conformation. For the protein biopharmaceutical industry, therefore, it is important to have analytical tools that can detect changes in protein conformation rapidly, accurately, and with high sensitivity. In this paper we show that hydrogen/deuterium exchange mass spectrometry (H/DX-MS) can play an important role in fulfilling this need within the industry. H/DX-MS was used to assess both global and local conformational behavior of a recombinant monoclonal IgG1 antibody, a major class of biopharmaceuticals. Analysis of exchange into the intact, glycosylated IgG1 (and the Fab and Fc regions thereof) showed that the molecule was folded, highly stable, and highly amenable to analysis by this method using less than a nanomole of material. With improved chromatographic methods, peptide identification algorithms and data-processing steps, the analysis of deuterium levels in peptic peptides produced after labeling was accomplished in 1--2 days. On the basis of peptic peptide data, exchange was localized to specific regions of the antibody. Changes to IgG1 conformation as a result of deglycosylation were determined by comparing exchange into the glycosylated and deglycosylated forms of the antibody. Two regions of the IgG1 (residues 236-253 and 292-308) were found to have altered exchange properties upon deglycosylation. These results are consistent with previous findings concerning the role of glycosylation in the interaction of IgG1 with Fc receptors. Moreover, the data clearly illustrate how H/DX-MS can provide important characterization information on the higher order structure of antibodies and conformational changes that these molecules may experience upon modification.

  5. Effective Application of Bicelles for Conformational Analysis of G Protein-Coupled Receptors by Hydrogen/Deuterium Exchange Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Duc, Nguyen Minh; Du, Yang; Thorsen, Thor S.; Lee, Su Youn; Zhang, Cheng; Kato, Hideaki; Kobilka, Brian K.; Chung, Ka Young

    2015-05-01

    G protein-coupled receptors (GPCRs) have important roles in physiology and pathology, and 40% of drugs currently on the market target GPCRs for the treatment of various diseases. Because of their therapeutic importance, the structural mechanism of GPCR signaling is of great interest in the field of drug discovery. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) is a useful tool for analyzing ligand binding sites, the protein-protein interaction interface, and conformational changes of proteins. However, its application to GPCRs has been limited for various reasons, including the hydrophobic nature of GPCRs and the use of detergents in their preparation. In the present study, we tested the application of bicelles as a means of solubilizing GPCRs for HDX-MS studies. GPCRs (e.g., β2-adrenergic receptor [β2AR], μ-opioid receptor, and protease-activated receptor 1) solubilized in bicelles produced better sequence coverage (greater than 90%) than GPCRs solubilized in n-dodecyl-β-D-maltopyranoside (DDM), suggesting that bicelles are a more effective method of solubilization for HDX-MS studies. The HDX-MS profile of β2AR in bicelles showed that transmembrane domains (TMs) undergo lower deuterium uptake than intracellular or extracellular regions, which is consistent with the fact that the TMs are highly ordered and embedded in bicelles. The overall HDX-MS profiles of β2AR solubilized in bicelles and in DDM were similar except for intracellular loop 3. Interestingly, we detected EX1 kinetics, an important phenomenon in protein dynamics, at the C-terminus of TM6 in β2AR. In conclusion, we suggest the application of bicelles as a useful method for solubilizing GPCRs for conformational analysis by HDX-MS.

  6. Effective application of bicelles for conformational analysis of G protein-coupled receptors by hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Duc, Nguyen Minh; Du, Yang; Thorsen, Thor S; Lee, Su Youn; Zhang, Cheng; Kato, Hideaki; Kobilka, Brian K; Chung, Ka Young

    2015-05-01

    G protein-coupled receptors (GPCRs) have important roles in physiology and pathology, and 40% of drugs currently on the market target GPCRs for the treatment of various diseases. Because of their therapeutic importance, the structural mechanism of GPCR signaling is of great interest in the field of drug discovery. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) is a useful tool for analyzing ligand binding sites, the protein-protein interaction interface, and conformational changes of proteins. However, its application to GPCRs has been limited for various reasons, including the hydrophobic nature of GPCRs and the use of detergents in their preparation. In the present study, we tested the application of bicelles as a means of solubilizing GPCRs for HDX-MS studies. GPCRs (e.g., β2-adrenergic receptor [β2AR], μ-opioid receptor, and protease-activated receptor 1) solubilized in bicelles produced better sequence coverage (greater than 90%) than GPCRs solubilized in n-dodecyl-β-D-maltopyranoside (DDM), suggesting that bicelles are a more effective method of solubilization for HDX-MS studies. The HDX-MS profile of β2AR in bicelles showed that transmembrane domains (TMs) undergo lower deuterium uptake than intracellular or extracellular regions, which is consistent with the fact that the TMs are highly ordered and embedded in bicelles. The overall HDX-MS profiles of β2AR solubilized in bicelles and in DDM were similar except for intracellular loop 3. Interestingly, we detected EX1 kinetics, an important phenomenon in protein dynamics, at the C-terminus of TM6 in β2AR. In conclusion, we suggest the application of bicelles as a useful method for solubilizing GPCRs for conformational analysis by HDX-MS. PMID:25740347

  7. Hydrogen/Deuterium Exchange and Electron-Transfer Dissociation Mass Spectrometry Determine the Interface and Dynamics of Apolipoprotein E Oligomerization

    PubMed Central

    Huang, Richard Y-C.; Garai, Kanchan; Frieden, Carl; Gross, Michael L.

    2011-01-01

    Apolipoprotein E, a 34 kDa protein, plays a key role in triglyceride and cholesterol metabolism. Of the three common isoforms (ApoE2, 3 and 4), only ApoE4 is a risk factor for Alzheimer’s Disease. All three isoforms of wild-type ApoE self-associate to form oligomers, a process that may have functional consequences. Although the C-terminal domain, residues 216–299, of ApoE is believed to mediate self-association, the specific residues involved in this process are not known. Here we report the use of hydrogen/deuterium exchange (H/DX) coupled with enzymatic digestion to identify those regions in the sequence of full-length apoE involved in oligomerization. For this determination, we compared the results of H/DX of the wild-type proteins and those of monomeric forms obtained by modifying four residues in the C-terminal domain. The three wild type and mutant isoforms show similar structures based on their similar H/DX kinetics and extents of exchange. Regions of the C-terminus (residues 230–270) of the ApoE isoforms show significant differences of deuterium uptake between oligomeric and monomeric forms, confirming that oligomerization occurs at these regions. To achieve single amino acid resolution, we examined the extents of H/DX by using electron transfer dissociation (ETD) fragmentation of peptides representing selected regions of both the monomeric and the oligomeric forms of ApoE4. From these experiments, we could identify the specific residues involved in ApoE oligomerization. In addition, our results verify that ApoE4 is composed of a compact structure at its N-terminal domain. Regions of C-terminal domain, however, appear to lack defined structure. PMID:21899263

  8. NRA of hydrogen in glassy polymeric carbon

    NASA Astrophysics Data System (ADS)

    Zimmerman, R. L.; Ila, D.; Jenkins, G. M.; Hirvonen, J. K.; Maleki, H.

    1997-02-01

    Glassy Polymeric Carbon (GPC) is prepared from a precursor resin by careful heat treatment. Heat Treatment Temperatures (HTT) above 1500 °C are believed to expel all hydrogen and oxygen from the grafene structure of GPC. However, we have shown that significant amounts of oxygen remain sequestered in the pores of GPC even at HTT's above 1500 °C. In the present study we report the detection of similar amounts of hydrogen for various heat treatment temperatures up to 2500 °C. A Nuclear Reaction Analysis (NRA) method with the 1H(15N,αγ)12C reaction and a specifically designed coincidence array is used to detect the 4.43 MeV gamma ray whose yield is proportional to the hydrogen content in the GPC. The H:C atomic ratio decreases with increasing HTT and we show that it exceeds 1:100 even for a HTT of 2500 °C.

  9. Catalytic carbon membranes for hydrogen production

    SciTech Connect

    Damle, A.S.; Gangwal, S.K.

    1992-01-01

    Commercial carbon composite microfiltration membranes may be modified for gas separation applications by providing a gas separation layer with pores in the 1- to 10-nm range. Several organic polymeric precursors and techniques for depositing a suitable layer were investigated in this project. The in situ polymerization technique was found to be the most promising, and pure component permeation tests with membrane samples prepared with this technique indicated Knudsen diffusion behavior. The gas separation factors obtained by mixed-gas permeation tests were found to depend strongly on gas temperature and pressure indicating significant viscous flow at high-pressure conditions. The modified membranes were used to carry out simultaneous water gas shift reaction and product hydrogen separation. These tests indicated increasing CO conversions with increasing hydrogen separation. A simple process model was developed to simulate a catalytic membrane reactor. A number of simulations were carried out to identify operating conditions leading to product hydrogen concentrations over 90 percent. (VC)

  10. SISGR - Hydrogen Caged in Carbon-Exploration of Novel Carbon-Hydrogen Interactions

    SciTech Connect

    Lueking, Angela; Badding, John; Crespi, Vinent

    2015-12-01

    Hydrogen trapped in a carbon cage, captured through repulsive interactions, is a novel concept in hydrogen storage. Trapping hydrogen via repulsive interactions borrows an idea from macroscale hydrogen storage (i.e. compressed gas storage tanks) and reapplies these concepts on the nanoscale in specially designed molecular containers. Under extreme conditions of pressure, hydrogen solubility in carbon materials is expected to increase and carbon is expected to restructure to minimize volume via a mixed sp2/sp3 hydrogenated state. Thermodynamics dictate that pre-formed C-H structures will rearrange with increased pressure, yet the final carbon-hydrogen interactions may be dependent upon the mechanism by which hydrogen is introduced. Gas “trapping” is meant to denote gas present in a solid in a high density, adsorbed-like state, when the external pressure is much less than that necessary to provide a comparable fluid density. Trapping thus denotes a kinetically metastable state rather than thermodynamic equilibrium. This project probed mechanochemical means to polymerize select hydrocarbons in the presence of gases, in an attempt to form localized carbon cages that trap gases via repulsive interactions. Aromatic, polyaromatic, and hydroaromatic molecules expected to undergo cyclo-addition reactions were polymerized at high (~GPa) pressures to form extended hydrogenated amorphous carbon networks. Notably, aromatics with a pre-existing internal free volume (such as Triptycene) appeared to retain an internal porosity upon application of pressure. However, a high photoluminescence background after polymerization precluded in situ identification of trapped gases. No spectroscopic evidence was found after depressurization that would be indicative of pockets of trapped gases in a localized high-pressure environment. Control studies suggested this measurement may be insensitive to gases at low pressure. Similarly, no spectral fingerprint was found for gas-imbued spherical carbon nanoshells, even after chemical “capping” of the gas-imbued nanoshells to limit gas diffusivity. Subsequently, spectral probes of gas vibrational modes adsorbed in various carbon nanostructures (including activated carbons, single-wall carbon nanotubes, polymers of intrinsic microporosity (PIMs), and UV-irradiated PIMs with decreased pore size) were found only at high pressure. The vibrational mode of the adsorbed film became perturbed in high density films, and the perturbation was sensitive to surface functional groups, pore size, and pore dimension. Experimental results were corroborated with first-principle modeling using density functional theory. Development of semi-empirical correlations that relate the spectral features to pore dimension, geometry, and chemical potential of the adsorbed film are on-going.

  11. Production of highly spin-polarized atomic hydrogen and deuterium by spin-exchange optical pumping

    SciTech Connect

    Redsun, S.G.; Knize, R.J.; Cates, G.D.; Happer, W. )

    1990-08-01

    We have produced highly spin-polarized atomic hydrogen by spin-exchange optical pumping. A tunable ring dye laser is used to polarize rubidium atoms by optical pumping. The cell containing the rubidium vapor is coated with paraffin in order to reduce spin relaxation due to wall collisions. Hydrogen gas is dissociated in an inductive discharge and flows continuously through the cell, in which the hydrogen atoms are polarized by spin-exchange collisions with the polarized rubidium atoms. Atomic-hydrogen polarization as high as 2{l angle}{ital J}{sub {ital z}}{r angle}{sub H}=0.72(6) has been observed, which is the highest polarization yet produced by this method. However, the rubidium polarization may be limited to this value due to radiation trapping at higher rubidium densities. The spin-relaxation rate of atomic hydrogen on a paraffin-coated cell is also measured and corresponds to about 7600 wall bounces between wall relaxation.

  12. Determination of diffusion coefficients of hydrogen and deuterium in Zr-2.5%Nb pressure tube material using hot vacuum extraction-quadrupole mass spectrometry

    NASA Astrophysics Data System (ADS)

    Shrivastava, Komal Chandra; Kulkarni, A. S.; Ramanjaneyulu, P. S.; Sunil, Saurav; Saxena, M. K.; Singh, R. N.; Tomar, B. S.; Ramakumar, K. L.

    2015-06-01

    The diffusion coefficients of hydrogen and deuterium in Zr-2.5%Nb alloy were measured in the temperature range 523 to 673 K, employing hot vacuum extraction-quadrupole mass spectrometry (HVE-QMS). One end of the Zr-2.5%Nb alloy specimens was charged electrolytically with the desired hydrogen isotope. After annealing at different temperatures for a predetermined time, the specimens were cut into thin slices, which were analyzed for their H2/D2 content using the HVE-QMS technique. The depth profile data were fitted into the equation representing the solution of Fick's second law of diffusion. The activation energy of hydrogen/deuterium diffusion was obtained from the Arrhenius relation between the diffusion coefficient and temperature. The temperature dependent diffusion coefficient can be represented as DH = 1.41 × 10-7 exp(-36,000/RT) and DD = 6.16 × 10-8 exp(-35,262/RT) for hydrogen and deuterium, respectively.

  13. Thermochemical generation of hydrogen and carbon dioxide

    NASA Technical Reports Server (NTRS)

    Lawson, Daniel D. (Inventor); England, Christopher (Inventor)

    1984-01-01

    Mixing of carbon in the form of high sulfur coal with sulfuric acid reduces the temperature of sulfuric acid decomposition from 830.degree. C. to between 300.degree. C. and 400.degree. C. The low temperature sulfuric acid decomposition is particularly useful in thermal chemical cycles for splitting water to produce hydrogen. Carbon dioxide is produced as a commercially desirable byproduct. Lowering of the temperature for the sulfuric acid decomposition or oxygen release step simplifies equipment requirements, lowers thermal energy input and reduces corrosion problems presented by sulfuric acid at conventional cracking temperatures. Use of high sulfur coal as the source of carbon for the sulfuric acid decomposition provides an environmentally safe and energy efficient utilization of this normally polluting fuel.

  14. Hydrogenated amorphous carbon grains in Comet Halley

    SciTech Connect

    Colangeli, L.; Schwehm, G.; Bussoletti, E.; Fonti, S.; Blanco, A. ESA, Space Science Dept., Noordwijk Osservatorio Astronomico di Capodimonte, Naples Lecce Universita )

    1990-01-01

    Recent IR observations of Comets Halley, Wilson, and Bradfield have shown the existence of an emission feature falling at around 3.4 microns. In this paper, it is shown that a good fit of both the IR continuum and the band can be obtained by assuming a simple thermal emission model based upon the optical properties of hydrogenated amorphous carbon (HAC) grains, measured in laboratory. The best fits of P/Halley's spectra are obtained for HAC dust amounts which appear consistent with the constraints imposed by the observed production rates. The presence of amorphous carbon solid particles is also supported on the basis of in situ mass spectrometry measurements performed by the Vega 1/2 and Giotto spacecraft in the environment of P/Halley. At present, it appears reasonable to suggest that amorphous carbon grains are able to match the observations and can be considered among likely candidates for cometary materials. 51 refs.

  15. Spherical cauliflower-like carbon dust formed by interaction between deuterium plasma and graphite target and its internal structure

    NASA Astrophysics Data System (ADS)

    Ohno, N.; Yoshimi, M.; Tokitani, M.; Takamura, S.; Tokunaga, K.; Yoshida, N.

    2009-06-01

    Simulated experiments to produce carbon dust particles with cauliflower structure have been performed in a liner plasma device, NAGDIS-II by exposing high density deuterium plasma to a graphite sample (IG-430U). Formation of carbon dust depends on the surface temperature and the incident ion energy. At a surface temperature 600-700 K, a lot of isolated spherical dust particles are observed on the graphite target. The internal structure of an isolated dust particle was observed with Focused Ion Beam (FIB) system and Transmission Electron Microscope (TEM) in detail. FIB analysis clearly shows there exist honey-combed cell structure with thin carbon walls in the dust particle and the dust particle grows from the graphite surface. TEM image also shows that the dust particle is made of amorphous carbon with crystallized grains with diameters of 10-50 nm.

  16. Functionalized carbon nanostructures for hydrogen catalysis

    NASA Astrophysics Data System (ADS)

    Hu, Lung-Hao

    Sodium borohydride, NaBH4, is widely used as a source of pure hydrogen. Hydrogen is of interest because it is a source of clean energy. It can be converted directly into electrical energy by means of fuel cells. One of the objectives of this thesis was to develop a new catalytic process to (i) enhance the rate of hydrogen generation, and (ii) to achieve hydrogen generation equal to 100% of the theoretically expected value. The catalyst investigated in this research is constructed by starting from single wall carbon nanotubes (SWNT). This material has a very high specific surface area and good conductivity. The SWNT were formed into a paper by a special filtration process. Polysilazane, a polymeric precursor (Ceraset(TM)-SN from KiON Corp., Wiesbaden, Germany) was diluted by acetone and then layered onto SWNT paper. The Ceraset coated SWNT was then pyrolyzed at 1100°C for three hours to form a silicon carbonitride (SiCN), polymer derived ceramic (PDC), layer on the surface of SWNT filtered paper. This functionalized SiCN carbon nanotube paper (SiCN/CNT) was used as the substrate for catalyst dispersions. The catalyst consisted of transition metals, Pt/Pd/Ru. Suspension solutions of Pt, Pd and Ru were impregnated onto the SiCN/CNT paper with the expectation of creating a monolayer of these transition metals on surface of the SiCN/CNT substrate. It is likely that an interaction could occur between the transition metals and the silicon atoms present in the SiCN layer on the surface of the carbon nanotubes. It is known that transition metals and silicon react to form silicides, suggesting the formation of a strong Si-transition metal bond. Therefore, it is possible that this bond could provide good wetting of metal atoms on SiCN functionalized carbon nanotube substrate. In the limit a monolayer of the transition metals may be achieved, which would correspond to a near zero dihedral angle between the substrate and the cluster of transition metals. In such a scenario a very high activity of the catalyst can be achieved raising the figure of merit for hydrogen generation nearly to its highest possible value. The catalytic performance is also related to the intrinsic activity of chemical composition of the catalyst. In the present work, the use of catalysts of a ternary composition has been discovered to enhance the activity of the catalyst. The experiments presented in this work use Pt/Pd/Ru catalyzed SiCN/CNT as the catalyst to react with sodium borohydride for the hydrogen generation. The thickness of SiCN/CNT paper is one of the factors, which influences the hydrogen generation rate: thinner papers produce higher rates of hydrogen generation. The likely reason for this phenomenon is that hydrogen bubbles can become trapped within the mesh of carbon nanotubes that constitute the paper-like structure of the catalyst. It is hypothesized that hydrogen bubbles can escape more easily from the interior of the paper if the paper is thinner. The effect of the paper thickness on the hydrogen generation rate forms the first part of the thesis. In the next phase of the thesis, thin film structures of carbon nanotubes, about 300 nm high, were created to serve as the catalyst substrates. Transition metals were deposited on to these substrates by an electrophoretic process. In these catalysts huge increases in hydrogen generation rates, relative to the CNT-paper architecture, were achieved. Indeed the Figure of Merit (FOM), expressed as liters per minute of hydrogen generated per gram of the precious metals, per unit molar concentration of NaBH4, (Lmin-1g met-1[NaBH4]-1), of these "thin film CNT" catalysts was up to three orders of magnitude greater than could be achieved with the thick CNT paper, as described in the first part of the thesis. These values for the FOM are more than two orders of magnitude greater than the highest values for hydrogen generation from NaBH4 reported in the literature. The reaction mechanism and the catalytic efficiency in the present work is described in terms of an electric charge transfer, as has been proposed in the literature. In this mechanism the negative charge on the BH4 - ion is transferred with one hydrogen atom via SiCN/CNT structure, which increases the catalytic activity. (Abstract shortened by UMI.)

  17. Hydrogen and deuterium transport and inventory parameters in a Cu?0.65Cr?0.08Zr alloy for fusion reactor applications

    NASA Astrophysics Data System (ADS)

    Serra, E.; Perujo, A.

    1998-10-01

    A time dependent permeation method has been used to measure the transport and inventory parameters of hydrogen and deuterium in the precipitation hardened (PH) Cu-0.65 wt% Cr-0.08 wt% Zr alloy (ELBRODUR HF). The measurements cover the temperature range from 553 to 773 K using a hydrogen or deuterium pressure in the range 1-100 kPa. The permeabilities, diffusivities and Sieverts' constant values for ELBRODUR obtained in this work were about 2 time higher, 2 times lower and between 3 and 10 time higher respectively to that of Cu (F. Reiter et al., A compilation of Tritium Material Interaction Parameters in Fusion Reactor Materials, EUR 15217 EN (1993)) in the temperature range studied. Using the measured diffusivities and Sieverts' constant values for H 2 and D 2 and a quantum-mechanical model, an extrapolation for tritium is also presented.

  18. Photobiological hydrogen production and carbon dioxide sequestration

    NASA Astrophysics Data System (ADS)

    Berberoglu, Halil

    Photobiological hydrogen production is an alternative to thermochemical and electrolytic technologies with the advantage of carbon dioxide sequestration. However, it suffers from low solar to hydrogen energy conversion efficiency due to limited light transfer, mass transfer, and nutrient medium composition. The present study aims at addressing these limitations and can be divided in three parts: (1) experimental measurements of the radiation characteristics of hydrogen producing and carbon dioxide consuming microorganisms, (2) solar radiation transfer modeling and simulation in photobioreactors, and (3) parametric experiments of photobiological hydrogen production and carbon dioxide sequestration. First, solar radiation transfer in photobioreactors containing microorganisms and bubbles was modeled using the radiative transport equation (RTE) and solved using the modified method of characteristics. The study concluded that Beer-Lambert's law gives inaccurate results and anisotropic scattering must be accounted for to predict the local irradiance inside a photobioreactor. The need for accurate measurement of the complete set of radiation characteristics of microorganisms was established. Then, experimental setup and analysis methods for measuring the complete set of radiation characteristics of microorganisms have been developed and successfully validated experimentally. A database of the radiation characteristics of representative microorganisms have been created including the cyanobacteria Anabaena variabilis, the purple non-sulfur bacteria Rhodobacter sphaeroides and the green algae Chlamydomonas reinhardtii along with its three genetically engineered strains. This enabled, for the first time, quantitative assessment of the effect of genetic engineering on the radiation characteristics of microorganisms. In addition, a parametric experimental study has been performed to model the growth, CO2 consumption, and H 2 production of Anabaena variabilis as functions of irradiance and CO2 concentration. Kinetic models were successfully developed based on the Monod model and on a novel scaling analysis employing the CO2 consumption half-time as the time scale. Finally, the growth and hydrogen production of Anabaena variabilis have been compared in a flat panel photobioreactor using three different nutrient media under otherwise similar conditions. Light to hydrogen energy conversion efficiency for Allen-Arnon medium was superior by a factor of 5.5 to both BG-11 and BG-11o media. This was attributed to the presence of vanadium and larger heterocyst frequency observed in the Allen-Arnon medium.

  19. Liquid-solid phase transition of hydrogen and deuterium in silica aerogel

    NASA Astrophysics Data System (ADS)

    Van Cleve, E.; Worsley, M. A.; Kucheyev, S. O.

    2014-10-01

    Behavior of hydrogen isotopes confined in disordered low-density nanoporous solids remains essentially unknown. Here, we use relaxation calorimetry to study freezing and melting of H2 and D2 in an ˜85%-porous base-catalyzed silica aerogel. We find that liquid-solid transition temperatures of both isotopes inside the aerogel are depressed. The phase transition takes place over a wide temperature range of ˜4 K and non-trivially depends on the liquid filling fraction, reflecting the broad pore size distribution in the aerogel. Undercooling is observed for both H2 and D2 confined inside the aerogel monolith. Results for H2 and D2 are extrapolated to tritium-containing hydrogens with the quantum law of corresponding states.

  20. Liquid–solid phase transition of hydrogen and deuterium in silica aerogel

    SciTech Connect

    Van Cleve, E.; Worsley, M. A.; Kucheyev, S. O.

    2014-10-28

    Behavior of hydrogen isotopes confined in disordered low-density nanoporous solids remains essentially unknown. Here, we use relaxation calorimetry to study freezing and melting of H{sub 2} and D{sub 2} in an ∼85%-porous base-catalyzed silica aerogel. We find that liquid–solid transition temperatures of both isotopes inside the aerogel are depressed. The phase transition takes place over a wide temperature range of ∼4 K and non-trivially depends on the liquid filling fraction, reflecting the broad pore size distribution in the aerogel. Undercooling is observed for both H{sub 2} and D{sub 2} confined inside the aerogel monolith. Results for H{sub 2} and D{sub 2} are extrapolated to tritium-containing hydrogens with the quantum law of corresponding states.

  1. Applications of nuclear reaction analysis for determining hydrogen and deuterium distribution in metals

    SciTech Connect

    Altstetter, C.J.

    1981-01-01

    The use of ion beams for materials analysis has made a successful transition from the domain of the particle physicist to that of the materials scientist. The subcategory of this field, nuclear reaction analysis, is just now undergoing the transition, particularly in applications to hydrogen in materials. The materials scientist must locate the nearest accelerator, because now he will find that using it can solve mysteries that do not yield to other techniques. 9 figures

  2. Analysis of Protein Conformation and Dynamics by Hydrogen/Deuterium Exchange MS

    PubMed Central

    Engen, John R.

    2009-01-01

    synopsis Recent technological advances hydrogen exchange MS have led to improvements in the techniques ability to analyze the shape and movements of proteins. John Engen of Northeastern University gives a much needed update on the field. The cover, created by Engen, shows proteins swimming in an H2O/D2O solution with a sample mass spectrum in the background. PMID:19788312

  3. Hydrogen-bond-dynamics-based switching of conductivity and magnetism: a phase transition caused by deuterium and electron transfer in a hydrogen-bonded purely organic conductor crystal.

    PubMed

    Ueda, Akira; Yamada, Shota; Isono, Takayuki; Kamo, Hiromichi; Nakao, Akiko; Kumai, Reiji; Nakao, Hironori; Murakami, Youichi; Yamamoto, Kaoru; Nishio, Yutaka; Mori, Hatsumi

    2014-08-27

    A hydrogen bond (H-bond) is one of the most fundamental and important noncovalent interactions in chemistry, biology, physics, and all other molecular sciences. Especially, the dynamics of a proton or a hydrogen atom in the H-bond has attracted increasing attention, because it plays a crucial role in (bio)chemical reactions and some physical properties, such as dielectricity and proton conductivity. Here we report unprecedented H-bond-dynamics-based switching of electrical conductivity and magnetism in a H-bonded purely organic conductor crystal, κ-D3(Cat-EDT-TTF)2 (abbreviated as κ-D). This novel crystal κ-D, a deuterated analogue of κ-H3(Cat-EDT-TTF)2 (abbreviated as κ-H), is composed only of a H-bonded molecular unit, in which two crystallographically equivalent catechol-fused ethylenedithiotetrathiafulvalene (Cat-EDT-TTF) skeletons with a +0.5 charge are linked by a symmetric anionic [O···D···O](-1)-type strong H-bond. Although the deuterated and parent hydrogen systems, κ-D and κ-H, are isostructural paramagnetic semiconductors with a dimer-Mott-type electronic structure at room temperature (space group: C2/c), only κ-D undergoes a phase transition at 185 K, to change to a nonmagnetic insulator with a charge-ordered electronic structure (space group: P1). The X-ray crystal structure analysis demonstrates that this dramatic switching of the electronic structure and physical properties originates from deuterium transfer or displacement within the H-bond accompanied by electron transfer between the Cat-EDT-TTF π-systems, proving that the H-bonded deuterium dynamics and the conducting TTF π-electron are cooperatively coupled. Furthermore, the reason why this unique phase transition occurs only in κ-D is qualitatively discussed in terms of the H/D isotope effect on the H-bond geometry and potential energy curve. PMID:25127315

  4. Effect of deuterium substitution for hydrogen in surface functionalisation of hydrophilic nanosilicon particles on their spectral and dynamic properties

    SciTech Connect

    Kompanets, V O; Chekalin, S V; Dorofeev, S G; Kononov, N N; Barzilovich, P Yu; Ishchenko, A A

    2014-06-30

    Broadband femtosecond spectroscopy has been used to study two types of hydrophilic silicon nanoparticles: (1) photoluminescent, passivated with deuterium and oxidised in fully deuterated dimethyl sulphoxide, and (2) nonluminescent (control samples having a similar crystalline core), passivated with hydrogen and oxidised in dimethyl sulphoxide. We have found significant differences in ultrafast spectral – temporal induced absorption dynamics between the two types of nanoparticles in the energy range corresponding to their calculated band gap. The observed distinction is due to the considerably higher oxidation rate of silicon on the surface of the deuterated samples in comparison with the undeuterated ones and with the associated increase in the number of photoluminescence centres on the surface of the nanoparticles. In the samples containing self-trapped exciton (STE) energy states responsible for the photoluminescence in the red spectral region, carrier capture at these levels and carrier relaxation to the ground state have characteristic times in the femtosecond range. In the samples free of STE states, excited carriers relax to the conduction band bottom in a characteristic time of several picoseconds. (extreme light fields and their applications)

  5. Application of a New Ensemble Conserving Quantum Dynamics Simulation Algorithm to Liquid para-Hydrogen and ortho-Deuterium

    SciTech Connect

    Smith, Kyle K.G.; Poulsen, Jens Aage; Nyman, Gunnar; Cunsolo, Alessandro; Rossky, Peter J.

    2015-06-30

    Here, we apply the Feynman-Kleinert Quasi-Classical Wigner (FK-QCW) method developed in our previous work [Smith et al., J. Chem. Phys. 142, 244112 (2015)] for the determination of the dynamic structure factor of liquid para-hydrogen and ortho-deuterium at state points of (T = 20.0 K, n = 21.24 nm-3) and (T = 23.0 K, n = 24.61 nm-3), respectively. When applied to this challenging system, it is shown that this new FK-QCW method consistently reproduces the experimental dynamic structure factor reported by Smith et al. [J. Chem. Phys. 140, 034501 (2014)] for all momentum transfers considered. Moreover, this shows that FK-QCW provides a substantial improvement over the Feynman-Kleinert linearized path-integral method, in which purely classical dynamics are used. Furthermore, for small momentum transfers, it is shown that FK-QCW provides nearly the same results as ring-polymer molecular dynamics (RPMD), thus suggesting that FK-QCW provides a potentially more appealing algorithm than RPMD since it is not formally limited to correlation functions involving linear operators.

  6. Characterization of Stress-Exposed Granulocyte Colony Stimulating Factor Using ELISA and Hydrogen/Deuterium Exchange Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Tsuchida, Daisuke; Yamazaki, Katsuyoshi; Akashi, Satoko

    2014-10-01

    Information on the higher-order structure is important in the development of biopharmaceutical drugs. Recently, hydrogen/deuterium exchange coupled with mass spectrometry (HDX-MS) has been widely used as a tool to evaluate protein conformation, and unique automated systems for HDX-MS are now commercially available. To investigate the potential of this technique for the prediction of the activity of biopharmaceuticals, granulocyte colony stimulating factor (G-CSF), which had been subjected to three different stress types, was analyzed using HDX-MS and through comparison with receptor-binding activity. It was found that HDX-MS, in combination with ion mobility separation, was able to identify conformational changes in G-CSF induced by stress, and a good correlation with the receptor-binding activity was demonstrated, which cannot be completely determined by conventional peptide mapping alone. The direct evaluation of biological activity using bioassay is absolutely imperative in biopharmaceutical development, but HDX-MS can provide the alternative information in a short time on the extent and location of the structural damage caused by stresses. Furthermore, the present study suggests the possibility of this system being a versatile evaluation method for the preservation stability of biopharmaceuticals.

  7. Study of the conformational change of adsorbed proteins on biomaterial surfaces using hydrogen-deuterium exchange with mass spectroscopy.

    PubMed

    Kim, Jinku

    2016-05-01

    There is no doubt that protein adsorption plays a crucial role in determining biocompatibility of biomaterials. Despite the information of the identity and composition of blood plasma/serum proteins adsorbed on surfaces of biomaterials to understand which proteins are involved in blood/biomaterial interactions, it still does not provide information about the conformations and orientations of adsorbed protein, which are very important in determining biological responses to biomaterials. Therefore, our laboratory has developed an experimental technology to probe protein conformations on materials that is applicable to mixtures of proteins. Herein, the new application of hydrogen/deuterium (H/D) exchange combined with mass spectrometry was applied to determine conformational changes of adsorbed proteins at biomaterial surfaces. The results suggest that there may be a significant conformational change in adsorbed proteins at 'low' bulk concentrations that leads to a large change in the kinetics of H/D exchange as compared to 'high' bulk concentrations. This technique may eventually be useful for the study of the kinetics of protein conformational changes. PMID:26896658

  8. Conformational Analysis of Proteins in Highly Concentrated Solutions by Dialysis-Coupled Hydrogen/Deuterium Exchange Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Houde, Damian; Nazari, Zeinab E.; Bou-Assaf, George M.; Weiskopf, Andrew S.; Rand, Kasper D.

    2016-02-01

    When highly concentrated, an antibody solution can exhibit unusual behaviors, which can lead to unwanted properties, such as increased levels of protein aggregation and unusually high viscosity. Molecular modeling, along with many indirect biophysical measurements, has suggested that the cause for these phenomena can be due to short range electrostatic and/or hydrophobic protein-protein interactions. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) is a useful tool for investigating protein conformation, dynamics, and interactions. However, "traditional" continuous dilution labeling HDX-MS experiments have limited utility for the direct analysis of solutions with high concentrations of protein. Here, we present a dialysis-based HDX-MS (di-HDX-MS) method as an alternative HDX-MS labeling format, which takes advantage of passive dialysis rather than the classic dilution workflow. We applied this approach to a highly concentrated antibody solution without dilution or significant sample manipulation, prior to analysis. Such a method could pave the way for a deeper understanding of the unusual behavior of proteins at high concentrations, which is highly relevant for development of biopharmaceuticals in industry.

  9. Application of a New Ensemble Conserving Quantum Dynamics Simulation Algorithm to Liquid para-Hydrogen and ortho-Deuterium

    DOE PAGESBeta

    Smith, Kyle K.G.; Poulsen, Jens Aage; Nyman, Gunnar; Cunsolo, Alessandro; Rossky, Peter J.

    2015-06-30

    Here, we apply the Feynman-Kleinert Quasi-Classical Wigner (FK-QCW) method developed in our previous work [Smith et al., J. Chem. Phys. 142, 244112 (2015)] for the determination of the dynamic structure factor of liquid para-hydrogen and ortho-deuterium at state points of (T = 20.0 K, n = 21.24 nm-3) and (T = 23.0 K, n = 24.61 nm-3), respectively. When applied to this challenging system, it is shown that this new FK-QCW method consistently reproduces the experimental dynamic structure factor reported by Smith et al. [J. Chem. Phys. 140, 034501 (2014)] for all momentum transfers considered. Moreover, this shows that FK-QCWmore » provides a substantial improvement over the Feynman-Kleinert linearized path-integral method, in which purely classical dynamics are used. Furthermore, for small momentum transfers, it is shown that FK-QCW provides nearly the same results as ring-polymer molecular dynamics (RPMD), thus suggesting that FK-QCW provides a potentially more appealing algorithm than RPMD since it is not formally limited to correlation functions involving linear operators.« less

  10. Conformational Analysis of Proteins in Highly Concentrated Solutions by Dialysis-Coupled Hydrogen/Deuterium Exchange Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Houde, Damian; Nazari, Zeinab E.; Bou-Assaf, George M.; Weiskopf, Andrew S.; Rand, Kasper D.

    2016-04-01

    When highly concentrated, an antibody solution can exhibit unusual behaviors, which can lead to unwanted properties, such as increased levels of protein aggregation and unusually high viscosity. Molecular modeling, along with many indirect biophysical measurements, has suggested that the cause for these phenomena can be due to short range electrostatic and/or hydrophobic protein-protein interactions. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) is a useful tool for investigating protein conformation, dynamics, and interactions. However, "traditional" continuous dilution labeling HDX-MS experiments have limited utility for the direct analysis of solutions with high concentrations of protein. Here, we present a dialysis-based HDX-MS (di-HDX-MS) method as an alternative HDX-MS labeling format, which takes advantage of passive dialysis rather than the classic dilution workflow. We applied this approach to a highly concentrated antibody solution without dilution or significant sample manipulation, prior to analysis. Such a method could pave the way for a deeper understanding of the unusual behavior of proteins at high concentrations, which is highly relevant for development of biopharmaceuticals in industry.

  11. Proton nuclear magnetic resonance spectroscopy of human transferrin N-terminal half-molecule: titration and hydrogen-deuterium exchange

    SciTech Connect

    Valcour, A.A.; Woodworth, R.C.

    1987-06-02

    The binding of Ga(III) to the proteolytically derived N-terminal half-molecule of human transferrin (HTF/2N) was studied by proton nuclear magnetic resonance spectroscopy. The pH-dependent titration curves of the histidinyl C(2) proton chemical shifts were altered upon formation of the GaIIIHTF/2N(C/sub 2/O/sub 4/) ternary complex. Two high-pK'a histidines failed to titrate when the metal and synergistic anion formed a complex with the protein. These results implicated two histidinyl residues as direct ligands to the metal. The rates of hydrogen-deuterium exchange for the C(2) protons of certain histidinyl residues were substantially decreased by metal ion binding. The two ligand histidines were protected from exchange, and a third, low-pK'a, histidinyl residue was protected. We propose that this third histidinyl residue is involved in anion binding and may serve as the base in the putative proton-relay scheme proposed for complex formation.

  12. Applications of hydrogen deuterium exchange (HDX) for the characterization of conformational dynamics in light-activated photoreceptors

    PubMed Central

    Lindner, Robert; Heintz, Udo; Winkler, Andreas

    2015-01-01

    Rational design of optogenetic tools is inherently linked to the understanding of photoreceptor function. Structural analysis of elements involved in signal integration in individual sensor domains provides an initial idea of their mode of operation, but understanding how local structural rearrangements eventually affect signal transmission to output domains requires inclusion of the effector regions in the characterization. However, the dynamic nature of these assemblies renders their structural analysis challenging and therefore a combination of high- and low-resolution techniques is required to appreciate functional aspects of photoreceptors. This review focuses on the potential of hydrogen-deuterium exchange coupled to mass spectrometry (HDX-MS) for complementing the structural characterization of photoreceptors. In this respect, the ability of HDX-MS to provide information on conformational dynamics and the possibility to address multiple functionally relevant states in solution render this methodology ideally suitable. We highlight recent examples demonstrating the potential of HDX-MS and discuss how these results can help to improve existing optogenetic systems or guide the design of novel optogenetic tools. PMID:26157802

  13. Conformational Analysis of Proteins in Highly Concentrated Solutions by Dialysis-Coupled Hydrogen/Deuterium Exchange Mass Spectrometry.

    PubMed

    Houde, Damian; Nazari, Zeinab E; Bou-Assaf, George M; Weiskopf, Andrew S; Rand, Kasper D

    2016-04-01

    When highly concentrated, an antibody solution can exhibit unusual behaviors, which can lead to unwanted properties, such as increased levels of protein aggregation and unusually high viscosity. Molecular modeling, along with many indirect biophysical measurements, has suggested that the cause for these phenomena can be due to short range electrostatic and/or hydrophobic protein-protein interactions. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) is a useful tool for investigating protein conformation, dynamics, and interactions. However, "traditional" continuous dilution labeling HDX-MS experiments have limited utility for the direct analysis of solutions with high concentrations of protein. Here, we present a dialysis-based HDX-MS (di-HDX-MS) method as an alternative HDX-MS labeling format, which takes advantage of passive dialysis rather than the classic dilution workflow. We applied this approach to a highly concentrated antibody solution without dilution or significant sample manipulation, prior to analysis. Such a method could pave the way for a deeper understanding of the unusual behavior of proteins at high concentrations, which is highly relevant for development of biopharmaceuticals in industry. Graphical Abstract ᅟ. PMID:26860088

  14. Application of a new ensemble conserving quantum dynamics simulation algorithm to liquid para-hydrogen and ortho-deuterium

    NASA Astrophysics Data System (ADS)

    Smith, Kyle K. G.; Poulsen, Jens Aage; Nyman, Gunnar; Cunsolo, Alessandro; Rossky, Peter J.

    2015-06-01

    We apply the Feynman-Kleinert Quasi-Classical Wigner (FK-QCW) method developed in our previous work [Smith et al., J. Chem. Phys. 142, 244112 (2015)] for the determination of the dynamic structure factor of liquid para-hydrogen and ortho-deuterium at state points of (T = 20.0 K, n = 21.24 nm-3) and (T = 23.0 K, n = 24.61 nm-3), respectively. When applied to this challenging system, it is shown that this new FK-QCW method consistently reproduces the experimental dynamic structure factor reported by Smith et al. [J. Chem. Phys. 140, 034501 (2014)] for all momentum transfers considered. This shows that FK-QCW provides a substantial improvement over the Feynman-Kleinert linearized path-integral method, in which purely classical dynamics are used. Furthermore, for small momentum transfers, it is shown that FK-QCW provides nearly the same results as ring-polymer molecular dynamics (RPMD), thus suggesting that FK-QCW provides a potentially more appealing algorithm than RPMD since it is not formally limited to correlation functions involving linear operators.

  15. Activity-regulating structural changes and autoantibody epitopes in transglutaminase 2 assessed by hydrogen/deuterium exchange.

    PubMed

    Iversen, Rasmus; Mysling, Simon; Hnida, Kathrin; Jrgensen, Thomas J D; Sollid, Ludvig M

    2014-12-01

    The multifunctional enzyme transglutaminase 2 (TG2) is the target of autoantibodies in the gluten-sensitive enteropathy celiac disease. In addition, the enzyme is responsible for deamidation of gluten peptides, which are subsequently targeted by T cells. To understand the regulation of TG2 activity and the enzyme's role as an autoantigen in celiac disease, we have addressed structural properties of TG2 in solution by using hydrogen/deuterium exchange monitored by mass spectrometry. We demonstrate that Ca(2+) binding, which is necessary for TG2 activity, induces structural changes in the catalytic core domain of the enzyme. Cysteine oxidation was found to abolish these changes, suggesting a mechanism whereby disulfide bond formation inactivates the enzyme. Further, by using TG2-specific human monoclonal antibodies generated from intestinal plasma cells of celiac disease patients, we observed that binding of TG2 by autoantibodies can induce structural changes that could be relevant for the pathogenesis. Detailed mapping of two of the main epitopes targeted by celiac disease autoantibodies revealed that they are located adjacent to each other in the N-terminal part of the TG2 molecule. PMID:25404341

  16. Effect of deuterium substitution for hydrogen in surface functionalisation of hydrophilic nanosilicon particles on their spectral and dynamic properties

    NASA Astrophysics Data System (ADS)

    Kompanets, V. O.; Chekalin, S. V.; Dorofeev, S. G.; Kononov, N. N.; Barzilovich, P. Yu; Ishchenko, A. A.

    2014-06-01

    Broadband femtosecond spectroscopy has been used to study two types of hydrophilic silicon nanoparticles: (1) photoluminescent, passivated with deuterium and oxidised in fully deuterated dimethyl sulphoxide, and (2) nonluminescent (control samples having a similar crystalline core), passivated with hydrogen and oxidised in dimethyl sulphoxide. We have found significant differences in ultrafast spectral - temporal induced absorption dynamics between the two types of nanoparticles in the energy range corresponding to their calculated band gap. The observed distinction is due to the considerably higher oxidation rate of silicon on the surface of the deuterated samples in comparison with the undeuterated ones and with the associated increase in the number of photoluminescence centres on the surface of the nanoparticles. In the samples containing self-trapped exciton (STE) energy states responsible for the photoluminescence in the red spectral region, carrier capture at these levels and carrier relaxation to the ground state have characteristic times in the femtosecond range. In the samples free of STE states, excited carriers relax to the conduction band bottom in a characteristic time of several picoseconds.

  17. Analysis of distinct molecular assembly complexes of keratin K8 and K18 by hydrogen-deuterium exchange.

    PubMed

    Premchandar, Aiswarya; Kupniewska, Anna; Tarnowski, Krzysztof; Mücke, Norbert; Mauermann, Monika; Kaus-Drobek, Magdalena; Edelman, Aleksander; Herrmann, Harald; Dadlez, Michał

    2015-12-01

    Keratins are intermediate filament (IF) proteins that form complex filament systems in epithelial cells, thus serving as scaffolding elements and mechanical stress absorbers. The building blocks of keratin IFs are parallel coiled-coil dimers of two distinct sequence-related proteins distinguished as type I and type II keratins. To gain more insight into their structural dynamics, we resorted to hydrogen-deuterium exchange mass spectrometry of keratins K8 and K18, which are characteristic for simple epithelial cells. Using this powerful technique not employed with IFs before, we mapped patterns of protected versus unprotected regions in keratin complexes at various assembly levels. In particular, we localized protein segments exhibiting different hydrogen exchange patterns in tetramers versus filaments. We observed a general pattern of precisely positioned regions of stability intertwining with flexible regions, mostly represented by the non-α-helical segments. Notably, some regions within the coiled-coil domains are significantly more dynamic than others, while the IF-consensus motifs at the end domains of the central α-helical "rod" segment, which mediate the "head-to-tail" dimer-dimer interaction in the filament elongation process, become distinctly more protected upon formation of filaments. Moreover, to gain more insight into the dynamics of the individual keratins, we investigated the properties of homomeric preparations of K8 and K18. The physiological importance of keratins without a partner is encountered in both pathological and experimental situations when one of the two species is present in robust excess or completely absent, such as in gene-targeted mice. PMID:26434626

  18. Antibody structural integrity of site-specific antibody-drug conjugates investigated by hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Pan, Lucy Yan; Salas-Solano, Oscar; Valliere-Douglass, John F

    2015-06-01

    We present the results of a hydrogen/deuterium exchange mass spectrometric (HDX-MS) investigation of an antibody-drug conjugate (ADC) comprised of drug-linkers conjugated to cysteine residues that have been engineered into heavy chain (HC) fragment crystallizable (Fc) domain at position 239. A side-by-side comparison of the HC Ser239 wild type (wt) monoclonal antibody (mAb) and the engineered Cys239 mAb indicates that site directed mutagenesis of Ser239 to cysteine has no impact on the HDX kinetics of the mAb. According to the crystal structure of a homologous immunoglobulin G1 (IgG1) antibody (PDB: 1HZH ), the backbone amide of Ser239 is hydrogen-bonded to Val264 backbone amide in the wt-mAb studied here. Replacing Ser239 with a Cys residue does not alter the exchange kinetics of the backbone amide of Val264 suggesting that either Ser or Cys at position 239 has similar amide-hydrogen bonding with Val264. However, a small segment in CH2 domain of the ADC ((264)VDVS) was found to have a slightly increased HDX rate compared to the wt- and C239-mAb constructs. The slightly increased HDX rate of the segment (264)VDVS in ADCs indicates that the further modification of Cys239 with drug-linkers only attenuates the local backbone amide hydrogen-bonding network between Cys239 and Val264. All other regions which are proximal to the site of drug conjugation are unaffected. The results demonstrate that the site-specific drug conjugation at the engineered Cys residue at the position 239 of HC does not impact the structural integrity of antibodies. The results also highlight the utility of applying HDX-MS to ADCs to gain a molecular level insight into the impact of site-specific conjugation technologies on the higher-order structure (HOS) of mAbs. The methodology can be applied generally to site-specific ADC modalities to understand the individual contributions of site-mutagenesis and drug-linker conjugation on the HOS of therapeutic candidate ADCs. PMID:25938577

  19. Neutron structure of subtilisin BPN prime : Effects of chemical environment on hydrogen-bonding geometrics and the pattern of hydrogen-deuterium exchange in secondary structure elements

    SciTech Connect

    Kossiakoff, A.A.; Ultsch, M. ); White, S. ); Eigenbrot, C. )

    1991-02-05

    The neutron structure of subtilisin BPN{prime} has been refined and analyzed at 2.0-{angstrom} resolution. The structure studied was a mutant variant of subtilisin, Met222 {yields} Gln, and was used because large, uninhibited crystals could be grown, which was not the case for the native molecule. Comparison of the structure with that of the native molecule indicated that the two structures are essentially the same. Using the capability of the neutron method to locate hydrogen and deuterium atoms, the protonation states of the six histidine residues were assigned. The active site histidine, His64, was found to be neutral at the pH of the analysis (pH 6.1). This group has an unexpectedly low pK{sub a} compared to assignments made by other techniques. The altered pK{sub a} of the group could result from electrostatic effects of other molecules in the crystal lattice. The dihedral conformations of a majority of the hydroxyl rotors were assigned. The hydrogen exchange pattern of subtilisin identified the {beta}-sheet and {alpha}-helix secondary structure elements to be the most resistant to exchange. Fifty-five percent of the peptide amide hydrogens were fully exchanged, 15% unexchanged, and 30% partially exchanged. The largest concentration of unexchanged sites was in the seven-stranded parallel {beta}-sheet, in which there were 11 fully protected groups. Little correlation was found between H-bound length and angle and a peptide group's susceptibility toward exchange. Of the five {alpha}-helices the most protected from exchange is the one defined by residues 224-236. The pattern of exchange identifies regions in this helix where the H-bonding regularity is disrupted.

  20. Tunneling effects in the kinetics of helium and hydrogen isotopes desorption from single-walled carbon nanotube bundles

    SciTech Connect

    Danilchenko, B. A. Yaskovets, I. I.; Uvarova, I. Y.; Dolbin, A. V.; Esel'son, V. B.; Basnukaeva, R. M.; Vinnikov, N. A.

    2014-04-28

    The kinetics of desorption both helium isotopes and molecules of hydrogen and deuterium from open-ended or γ-irradiated single-walled carbon nanotube bundles was investigated in temperature range of 10–300 K. The gases desorption rates obey the Arrhenius law at high temperatures, deviate from it with temperature reduction and become constant at low temperatures. These results indicate the quantum nature of gas outflow from carbon nanotube bundles. We had deduced the crossover temperature below which the quantum corrections to the effective activation energy of desorption become significant. This temperature follows linear dependence against the inverse mass of gas molecule and is consistent with theoretical prediction.

  1. Nonthermal escape of hydrogen and deuterium from Venus and implications for loss of water

    NASA Technical Reports Server (NTRS)

    Kumar, S.; Hunten, D. M.; Pollack, J. B.

    1983-01-01

    As the dominant nonthermal mechanism for the escape of hydrogen in past Venus atmospheres, the charge exchange of H(+) with H would have provided an escape flux close to the diffusion-limiting value for H-mixing ratios up to 0.002 at the homopause, which also marks the onset of hydrodynamic flow. Charge exchange therefore represents a viable mechanism through which Venus could have lost up to an earth-equivalent ocean of water from its atmosphere over geologic time. Present Venus atmosphere estimates are based on in situ Pioneer Venus mission measurements, and assumptions in the course of extrapolation to past atmospheres have been with respect to the nature of the bulge, circulation pattern, and ion temperature.

  2. High-resolution NMR of hydrogen in organic solids by DNP enhanced natural abundance deuterium spectroscopy

    NASA Astrophysics Data System (ADS)

    Rossini, Aaron J.; Schlagnitweit, Judith; Lesage, Anne; Emsley, Lyndon

    2015-10-01

    We demonstrate that high field (9.4 T) dynamic nuclear polarization (DNP) at cryogenic (∼100 K) sample temperatures enables the rapid acquisition of natural abundance 1H-2H cross-polarization magic angle spinning (CPMAS) solid-state NMR spectra of organic solids. Spectra were obtained by impregnating substrates with a solution of the stable DNP polarizing agent TEKPol in tetrachloroethane. Tetrachloroethane is a non-solvent for the solids, and the unmodified substrates are then polarized through spin diffusion. High quality natural abundance 2H CPMAS spectra of histidine hydrochloride monohydrate, glycylglycine and theophylline were acquired in less than 2 h, providing direct access to hydrogen chemical shifts and quadrupolar couplings. The spectral resolution of the 2H solid-state NMR spectra is comparable to that of 1H spectra obtained with state of the art homonuclear decoupling techniques.

  3. Confinement of hydrogen at high pressure in carbon nanotubes

    DOEpatents

    Lassila, David H.; Bonner, Brian P.

    2011-12-13

    A high pressure hydrogen confinement apparatus according to one embodiment includes carbon nanotubes capped at one or both ends thereof with a hydrogen-permeable membrane to enable the high pressure confinement of hydrogen and release of the hydrogen therethrough. A hydrogen confinement apparatus according to another embodiment includes an array of multi-walled carbon nanotubes each having first and second ends, the second ends being capped with palladium (Pd) to enable the high pressure confinement of hydrogen and release of the hydrogen therethrough as a function of palladium temperature, wherein the array of carbon nanotubes is capable of storing hydrogen gas at a pressure of at least 1 GPa for greater than 24 hours. Additional apparatuses and methods are also presented.

  4. Hydrogen-deuterium exchange and mass spectrometry reveal the pH-dependent conformational changes of diphtheria toxin T domain.

    PubMed

    Li, Jing; Rodnin, Mykola V; Ladokhin, Alexey S; Gross, Michael L

    2014-11-01

    The translocation (T) domain of diphtheria toxin plays a critical role in moving the catalytic domain across the endosomal membrane. Translocation/insertion is triggered by a decrease in pH in the endosome where conformational changes of T domain occur through several kinetic intermediates to yield a final trans-membrane form. High-resolution structural studies are only applicable to the static T-domain structure at physiological pH, and studies of the T-domain translocation pathway are hindered by the simultaneous presence of multiple conformations. Here, we report the application of hydrogen-deuterium exchange mass spectrometry (HDX-MS) for the study of the pH-dependent conformational changes of the T domain in solution. Effects of pH on intrinsic HDX rates were deconvolved by converting the on-exchange times at low pH into times under our "standard condition" (pH 7.5). pH-Dependent HDX kinetic analysis of T domain clearly reveals the conformational transition from the native state (W-state) to a membrane-competent state (W(+)-state). The initial transition occurs at pH 6 and includes the destabilization of N-terminal helices accompanied by the separation between N- and C-terminal segments. The structural rearrangements accompanying the formation of the membrane-competent state expose a hydrophobic hairpin (TH8-9) to solvent, prepare it to insert into the membrane. At pH 5.5, the transition is complete, and the protein further unfolds, resulting in the exposure of its C-terminal hydrophobic TH8-9, leading to subsequent aggregation in the absence of membranes. This solution-based study complements high resolution crystal structures and provides a detailed understanding of the pH-dependent structural rearrangement and acid-induced oligomerization of T domain. PMID:25290210

  5. Differential isotopic enrichment to facilitate characterization of asymmetric multimeric proteins using hydrogen/deuterium exchange mass spectrometry

    PubMed Central

    Pascal, Bruce D.; Bauman, Joseph D.; Patel, Disha; Arnold, Eddy; Griffin, Patrick R.

    2015-01-01

    Hydrogen/deuterium exchange (HDX) coupled to mass spectrometry has emerged as a powerful tool for analyzing the conformational dynamics of protein-ligand and protein-protein interactions. Recent advances in instrumentation and methodology have expanded the utility of HDX for the analysis of large and complex proteins; however, asymmetric dimers with shared amino acid sequence present a unique challenge for HDX because assignment of peptides with identical sequence to their subunit of origin remains ambiguous. Here we report the use of differential isotopic labeling to facilitate HDX analysis of multimers using HIV-1 reverse transcriptase (RT) as a model. RT is an asymmetric heterodimer of 51 kDa (p51) and 66 kDa (p66) subunits. The first 440 residues of p51 and p66 are identical. In this study differentially labeled RT was reconstituted from isotopically enriched (15N-labeled) p51 and unlabeled p66. In order to enable detection of 15N-deuterated RT peptides, the software HDX Workbench was modified to follow a 100% 15N model. Our results demonstrated that 15N enrichment of p51 did not affect its conformational dynamics compared to unlabeled p51, but 15N-labeled p51 did show different conformational dynamics than p66 in the RT heterodimer. Differential HDX-MS of isotopically labeled RT in the presence of the nonnucleoside reverse transcriptase inhibitor (NNRTI) efavirenz (EFV) showed subunit-specific perturbation in the rate of HDX consistent with previously published results and the RT-EFV co-crystal structure. PMID:25763479

  6. Comparative Analysis of Oxy-Hemoglobin and Aquomet-Hemoglobin by Hydrogen/Deuterium Exchange Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Sowole, Modupeola A.; Konermann, Lars

    2013-07-01

    The function of hemoglobin (Hb) as oxygen transporter is mediated by reversible O2 binding to Fe(2+) heme in each of the α and β subunits. X-ray crystallography revealed different subunit arrangements in oxy-Hb and deoxy-Hb. The deoxy state is stabilized by additional contacts, causing a rigidification that results in strong protection against hydrogen/deuterium exchange (HDX). Aquomet-Hb is a dysfunctional degradation product with four water-bound Fe(3+) centers. Heme release from aquomet-Hb is relatively facile, triggering oxidative damage of membrane lipids. Aquomet-Hb crystallizes in virtually the same conformation as oxy-Hb. Hence, it is commonly implied that the solution-phase properties of aquomet-Hb should resemble those of the oxy state. This work compares the structural dynamics of oxy-Hb and aquomet-Hb by HDX mass spectrometry (MS). It is found that the aquomet state exhibits a solution-phase structure that is significantly more dynamic, as manifested by elevated HDX levels. These enhanced dynamics affect the aquomet α and β subunits in a different fashion. The latter undergoes global destabilization, whereas the former shows elevated HDX levels only in the heme binding region. It is proposed that these enhanced dynamics play a role in facilitating heme release from aquomet-Hb. Our findings should be of particular interest to the MS community because oxy-Hb and aquomet-Hb serve as widely used test analytes for probing the relationship between biomolecular structure in solution and in the gas phase. We are not aware of any prior comparative HDX/MS experiments on oxy-Hb and aquomet-Hb.

  7. Operation of a cw rf driven ion source with hydrogen and deuterium gas (abstract){sup a}

    SciTech Connect

    Melnychuk, S.T.; Debiak, T.W.; Sredniawski, J.J.

    1996-03-01

    We will describe the operation of a cw rf driven multicusp ion source designed for extraction of high current hydrogen and deuterium beams. The source is driven at 2 MHz by a 2.5 turn induction antenna immersed in the plasma. Bare stainless-steel and porcelain-coated Cu antennas have been used. The plasma load is matched to the rf generator by a variable tap {ital N}:1 transformer isolated to 46 kV, and an LC network on the secondary. With H{sub 2} gas the source can be operated at pressures between 5 and 60 mT with power reflection coefficients {lt}0.01. The extracted ion current density with a porcelain-coated antenna is approximately given by 35 mA/cm{sup 2}/kW with an 80 G dipole filter field for input powers from 3.5 to 6.6 kW. The current density remained constant for operation with a 6 and an 8 mm aperture. The source has been operated for 260 h at 3.6 kW with a single-porcelain-coated antenna. Mass spectrometer measurements of the extracted beam at this power show a species mix for H{sup +}:H{sup +}{sub 2}:H{sup +}{sub 3}:OH{sup +} of 0.49: 0.04: 0.42: 0.04. The calculated beam divergence using the IGUN code is compared with the measured divergence from an electrostatic sweep emittance scanner designed for high-power cw beam diagnostics. Phase space measurements at 40 kV and 23 mA beam current result in a normalized rms emittance of 0.09 {pi}mmmrad. {copyright} {ital 1996 American Institute of Physics.}

  8. Carbonate thermochemical cycle for the production of hydrogen

    DOEpatents

    Collins, Jack L [Knoxville, TN; Dole, Leslie R [Knoxville, TN; Ferrada, Juan J [Knoxville, TN; Forsberg, Charles W [Oak Ridge, TN; Haire, Marvin J [Oak Ridge, TN; Hunt, Rodney D [Oak Ridge, TN; Lewis Jr., Benjamin E [Knoxville, TN; Wymer, Raymond G [Oak Ridge, TN

    2010-02-23

    The present invention is directed to a thermochemical method for the production of hydrogen from water. The method includes reacting a multi-valent metal oxide, water and a carbonate to produce an alkali metal-multi-valent metal oxide compound, carbon dioxide, and hydrogen.

  9. Formation of Cosmic Carbon Dust Analogs in Partially Hydrogenated Atmospheres

    NASA Technical Reports Server (NTRS)

    Blanco, A.; Fonti, S.; Muci, A. M.; Orofino, V.

    1996-01-01

    We present here UV-visible spectra of carbon grains produced by direct condensation of the carbon vapors in partially hydrogenated atmospheres. The freshly formed grains exhibit an extinction peak in the wavelength range 200-240 nm whose exact position depends on the hydrogen abundance. The results are discussed in terms of formation and evolution of circumstellar and interstellar cosmic dust.

  10. Synthesis, characterization and hydrogen storage studies on porous carbon

    NASA Astrophysics Data System (ADS)

    Ruz, Priyanka; Banerjee, Seemita; Pandey, M.; Sudarsan, V.

    2015-06-01

    Porous carbon sample has been prepared, using zeolite-Y as template followed by annealing at 800°C, with view to estimate the extent of hydrogen storage by the sample. Based on XRD, 13C MAS NMR and Raman spectroscopic studies it is confirmed that the porous Carbon sample contains only sp2 hybridized carbon. The hydrogen sorption isotherms have been recorded for the sample at 273, 223K and 123K and the maximum hydrogen absorption capacity is found to be 1.47wt% at 123K. The interaction energy of hydrogen with the carbon framework was determined to be ˜ 10 kJ mol-1at lower hydrogen uptake and gradually decreases with increase in hydrogen loading.

  11. Vacuum ultraviolet photolysis of hydrogenated amorphous carbons . I. Interstellar H2 and CH4 formation rates

    NASA Astrophysics Data System (ADS)

    Alata, I.; Cruz-Diaz, G. A.; Muñoz Caro, G. M.; Dartois, E.

    2014-09-01

    Context. The interstellar hydrogenated amorphous carbons (HAC or a-C:H) observed in the diffuse medium are expected to disappear in a few million years, according to the destruction time scale from laboratory measurements. The existence of a-C:H results from the equilibrium between photodesorption, radiolysis, hydrogenation and resilience of the carbonaceous network. During this processing, many species are therefore injected into the gas phase, in particular H2, but also small organic molecules, radicals or fragments. Aims: We perform experiments on interstellar a-C:H analogs to quantify the release of these species in the interstellar medium. Methods: The vacuum ultraviolet (VUV) photolysis of interstellar hydrogenated amorphous carbon analogs was performed at low (10 K) to ambient temperature, coupled to mass-spectrometry detection and temperature-programed desorption. Using deuterium isotopic substitution, the species produced were unambiguously separated from background contributions. Results: The VUV photolysis of hydrogenated amorphous carbons leads to the efficient production of H2 molecules, but also to small hydrocarbons. Conclusions: These species are formed predominantly in the bulk of the a-C:H analog carbonaceous network, in addition to the surface formation. Compared with species made by the recombination of H atoms and physisorbed on surfaces, they diffuse out at higher temperatures. In addition to the efficient production rate, it provides a significant formation route in environments where the short residence time scale for H atoms inhibits H2 formation on the surface, such as PDRs. The photolytic bulk production of H2 with carbonaceous hydrogenated amorphous carbon dust grains can provide a very large portion of the contribution to the H2 molecule formation. These dust grains also release small hydrocarbons (such as CH4) into the diffuse interstellar medium, which contribute to the formation of small carbonaceous radicals after being dissociated by the UV photons in the considered environment. This extends the interstellar media environments where H2 and small hydrocarbons can be produced.

  12. Carbon and hydrogen isotopic compositions of products of open-system catalytic hydrogenation of CO2: Implications for abiogenic hydrocarbons in Earth’s crust

    NASA Astrophysics Data System (ADS)

    Taran, Y. A.; Kliger, G. A.; Cienfuegos, E.; Shuykin, A. N.

    2010-11-01

    This paper reports the isotope effects in an open-system Fischer-Tropsch type (FTT) synthesis, with implications for the origin of natural abiogenic hydrocarbons. The starting form of carbon was CO 2, with carbon and hydrogen isotopic compositions measured for products of catalytic hydrogenation of CO 2 on iron and cobalt catalysts (FTCO 2-Fe and FTCO 2-Co) at 350 and 245 °C, respectively, and 10 MPa. The carbon isotopic composition of the resulting saturated hydrocarbons (alkanes) as a function of carbon number shows a positive trend for both FTCO 2-Fe and FTCO 2-Co, with a fractionation of 2-4‰ and 3-6‰ between CH 4 and C 2H 6 over the Fe and Co catalysts, respectively. The unsaturated hydrocarbons (alkenes) do not show any trend. A strong kinetic isotope fractionation (>40‰) occurred between CO 2 and CH 4 in both experiments. The hydrogen isotope fractionation between alkanes appeared to be similar to that found in natural (thermogenic and biogenic) gases, with enrichment in deuterium of longer hydrocarbon chains; the dominant H/D fractionation occurred between CH 4 and C 2H 6. Alkenes in the products of the FTCO 2-Fe reaction are enriched in deuterium (˜50‰) and do not show any trend versus carbon number. We suggest that other than FTT reactions or a simple mixing are responsible for the occurrence of the inverse isotopic trends in both δ 13C and δD found in light hydrocarbons in some terrestrial environments and meteorites.

  13. DEVELOPMENT OF DOPED NANOPOROUS CARBONS FOR HYDROGEN STORAGE

    SciTech Connect

    Angela D. Lueking; Qixiu Li; John V. Badding; Dania Fonseca; Humerto Gutierrez; Apurba Sakti; Kofi Adu; Michael Schimmel

    2010-03-31

    Hydrogen storage materials based on the hydrogen spillover mechanism onto metal-doped nanoporous carbons are studied, in an effort to develop materials that store appreciable hydrogen at ambient temperatures and moderate pressures. We demonstrate that oxidation of the carbon surface can significantly increase the hydrogen uptake of these materials, primarily at low pressure. Trace water present in the system plays a role in the development of active sites, and may further be used as a strategy to increase uptake. Increased surface density of oxygen groups led to a significant enhancement of hydrogen spillover at pressures less than 100 milibar. At 300K, the hydrogen uptake was up to 1.1 wt. % at 100 mbar and increased to 1.4 wt. % at 20 bar. However, only 0.4 wt% of this was desorbable via a pressure reduction at room temperature, and the high lowpressure hydrogen uptake was found only when trace water was present during pretreatment. Although far from DOE hydrogen storage targets, storage at ambient temperature has significant practical advantages oner cryogenic physical adsorbents. The role of trace water in surface modification has significant implications for reproducibility in the field. High-pressure in situ characterization of ideal carbon surfaces in hydrogen suggests re-hybridization is not likely under conditions of practical interest. Advanced characterization is used to probe carbon-hydrogen-metal interactions in a number of systems and new carbon materials have been developed.

  14. ETD in a Traveling Wave Ion Guide at Tuned Z-Spray Ion Source Conditions Allows for Site-Specific Hydrogen/Deuterium Exchange Measurements

    PubMed Central

    Rand, Kasper D.; Pringle, Steven D.; Morris, Michael; Engen, John R.; Brown, Jeffery M.

    2012-01-01

    The recent application of electron transfer dissociation (ETD) to measure the hydrogen exchange of proteins in solution at single-residue resolution (HX-ETD) paves the way for mass spectrometry-based analyses of biomolecular structure at an unprecedented level of detail. The approach requires that activation of polypeptide ions prior to ETD is minimal so as to prevent undesirable gas-phase randomization of the deuterium label from solution (i.e., hydrogen scrambling). Here we explore the use of ETD in a traveling wave ion guide of a quadrupole-time-of-flight (Q-TOF) mass spectrometer with a “Z-spray” type ion source, to measure the deuterium content of individual residues in peptides. We systematically identify key parameters of the Z-spray ion source that contribute to collisional activation and define conditions that allow ETD experiments to be performed in the traveling wave ion guide without gas-phase hydrogen scrambling. We show that ETD and supplemental collisional activation in a subsequent traveling wave ion guide allows for improved extraction of residue-specific deuterium contents in peptides with low charge. Our results demonstrate the feasibility, and illustrate the advantages of performing HX-ETD experiments on a high-resolution Q-TOF instrument equipped with traveling wave ion guides. Determination of parameters of the Z-spray ion source that contribute to ion heating are similarly pertinent to a growing number of MS applications that also rely on an energetically gentle transfer of ions into the gas-phase, such as the analysis of biomolecular structure by native mass spectrometry in combination with gas-phase ion-ion/ion-neutral reactions or ion mobility spectrometry. PMID:21952892

  15. CO/sub 2/DBr precursor geometry limited reaction of deuterium with carbon dioxide

    SciTech Connect

    Buelow, S.; Radhakrishnan, G.; Wittig, C.

    1987-10-08

    The authors report nascent OD(X/sup 2/II) rotational, vibrational, spin-orbit, and ..lambda..-doublet excitations from reactions of deuterium atoms with CO/sub 2/. D atoms are produced by the 193-nm photolysis of DBr (h nu - D/sub 0/ = 244 kJ mol/sup -1/) (i) within a weakly bonded CO/sub 2/DBr complex, and (ii) under 300 K single-collision bulk conditions. The differences between the resulting OD distributions are modest, and the present results are similar to those of the analogous H + CO/sub 2/ system.

  16. Detection of Hydrogen Spillover in Palladium-Modified Activated Carbon Fibers During Hydrogen Adsorption

    SciTech Connect

    Contescu, Cristian I; Brown, Craig; Liu, Yun; Bhat, Vinay V; Gallego, Nidia C

    2009-01-01

    Palladium-modified activated carbon fibers (Pd-ACF) are being evaluated for adsorptive hydrogen storage at near-ambient conditions because of their enhanced hydrogen uptake in comparison to Pd-free activated carbon fibers (ACF). The net uptake enhancement (at room temperature and 20 bar) is in excess of the amount corresponding to formation of Pd hydride, and is usually attributed to hydrogen spillover. In this paper, inelastic neutron scattering was used to demonstrate the formation of new C-H bonds in Pd-containing activated carbon fibers after exposure to hydrogen at 20 oC and 1.6 MPa, at the expense of physisorbed H2. This finding is a post-factum proof of the atomic nature of H species formed in presence of a Pd catalyst, and of their subsequent spillover and binding to the carbon support. Chemisorption of hydrogen may explain the reduction in hydrogen uptake from first to second adsorption cycle.

  17. Carbon nanotubes in hydrogen fuel cells

    NASA Astrophysics Data System (ADS)

    Tang, Jason Ming-Young

    2007-12-01

    Carbon nanotubes possess exceptional mechanical and electrical properties such as high tensile strength, great resilience, high thermal and electrical conductivity, high specific surface area, and high temperature stability. The coexistence of these desirable properties in one material makes carbon nanotubes a fascinating candidate for incorporation into a fuel cell to improve its performance and decrease the thickness of the fuel cell structure. SWNTs were formed into a free-standing film as a gas diffusion layer in a fuel cell, taking the place of the more traditional carbon fiber based paper and potentially offer a thinner gas diffusion layer. Fuel cell membrane electrode assemblies with ultralow Pt cathode loadings of 6 mug Pt/cm2 and 12 pmug Pt/cm2 at the cathode have been fabricated using thin films of Pt supported on MWNTs (Pt/MWNTs). These loadings are lower than conventional Pt cathode loadings by a factor of 16 to 33. Surprisingly high fuel cell performance is obtained for such a low Pt loading. This simple and promising new fuel cell architecture uses no Nafion in the catalyst layer as is of conventional fuel cells. A free-standing thin film of Pt/SWNTs also was successfully demonstrated without the use of Nafion in the catalyst layer. Both the Pt/SWNT free-standing thin film and Pt/MWNT thin film catalyst layers exhibit higher performance when compared with a catalyst layer (without Nafion) made from commercially available E-TEK electrocatalyst made of Pt supported on XC-72 carbon black. Additionally, Pt/MWNTs were also found to allow for the consolidation of the microporous layer and catalyst layer into one layer. This is just another simplification of the fuel cell architecture that was provided by the introduction of carbon nanotubes into the different components of the hydrogen fuel cell. The sum of these improvements could potentially revolutionize the fuel cell architecture and provide thinner fuel cells with higher volumetric power densities for use in automotive applications and space exploration where system size is crucial.

  18. EPR and FTIR Spectroscopy of CARBON(4), CARBON(3) Hydrogen and Oxygen CARBON(3) Hydrogen in Solid Neon and Argon

    NASA Astrophysics Data System (ADS)

    Jiang, Qian

    The electron-paramagnetic-resonance spectrum of C_4 in a neon matrix at {~}4 K formed by the vacuum-ultraviolet photolysis of 1,3-butadiene has been investigated to seek evidence for the bending of the molecule, which had previously been indicated by the results of EPR and FTIR measurements made on C_4 trapped in argon at 10 K. The observed spectra, which include ^ {13}C hyperfine splitting and zero-field splitting data, confirm the splitting of the perpendicular xy_1 and xy_2 lines of triplet C_4 into separate x and y components, which is indicative of the unequivalent axes of a bent molecule. A Fourier transform infrared isotopic study has been made of the deuterium and carbon-13 substituted C _3H radical produced by trapping in solid Ar the products of the vacuum ultraviolet photolysis of CH_3CHCH_2 (propylene) or a mixture of methane and acetylene. The 1824.7 and 1159.8 cm^{-1} absorptions, which in earlier work using only deuterium isotosopic data could be assigned to either the cyclic or linear isomer, can now be definitely identified on the basis of extensive ^{13}C isotopic measurements as the nu_2(sigma^+) and nu_3(sigma^+) fundamentals of linear C_3H. The frequencies of the fundamentals and D and ^ {13}C isotopic shifts are in good agreement with the predictions of preliminary ab initio calculations for the linear isomer. The identification of a fundamental vibration of the HCCCO radical has been made, for the first time, in a FTIR study involving extensive isotopic measurements. An absorption at 2308.6 cm^{-1} has been assigned to the nu_2, antisymmetric CCCO stretching mode of HCCCO which was produced by trapping in Ar the products of the vacuum ultraviolet (VUV) photolysis of a mixture of acetylene and carbon monoxide. The assignment is confirmed by measurements for a variety of D, ^{18}O, and ^{13}C substituted isotopomers.

  19. In situ deuterium observation in deuterium-implanted tungsten

    NASA Astrophysics Data System (ADS)

    Furuta, Yoshinori; Takagi, Ikuji; Kawamura, Shotaro; Yamamichi, Kazuyoshi; Akiyoshi, Masafumi; Sasaki, Takayuki; Kobayashi, Taishi

    2013-11-01

    In order to evaluate the tritium inventory in plasma-facing tungsten components of a fusion reactor, deuterium depth profiles in tungsten were observed in situ using nuclear reaction analysis (NRA) under continuous implantation of 3 keV D ions. Measurements were conducted at temperatures of 384, 473, 573 and 673 K. Recombination coefficients and rate constants for the surface recombination process were estimated from the observed deuterium concentration. It is indicated that the measured surface recombination rate constant is applied in a case wherein tungsten is exposed to hydrogen particles of various energies from a fusion plasma. The measured recombination coefficient was identical to that found by a different technique in a previous work. Deuterium in trap sites was found to contribute to deuterium retention in the samples as well as to deuterium in solution sites. The deuterium retention was low in the 384 K sample, in which trap sites had not appeared. Deuterium retention was very low in the 673 K sample, where most deuterium atoms were detrapped and desorbed. At an intermediate temperature of 473 K, the retention showed a maximum value due to a large occupancy of deuterium over many trap sites. The dependence of the retention on deuterium fluence was explained assuming that trap sites were produced by implantation.

  20. Determining interstellar hydrogen and deuterium column densities by means of the Lyman channel of the SPECTRUM UV Rowland spectrograph: a pre-launch feasibility study

    NASA Astrophysics Data System (ADS)

    Franchini, Mariagrazia; Morossi, Carlo; Vladilo, G.

    1996-10-01

    Our current knowledge of production and destruction of light elements in astrophysical processes suggests that deuterium is produced during Big Bang nucleosynthesis and destroyed when cycled through stars. Primordial deuterium abundance can be determined by measuring the D/H ratio in a variety of astrophysical environments with different degrees of chemical evolution: the D/H ratio of unprocessed material directly gives the primordial value, while the ratio in processed material is expected to be lower and consistent with the predictions of galactic chemical evolution models. Here we focus our attention on deuterium abundance determinations of chemically processed material such as the interstellar gas in our Galaxy. Up to now, most of the determinations of deuterium abundance have been performed in the solar system or in local interstellar clouds. However, the overall accuracy of the measurements in local clouds is still insufficient to probe evolutionary trends. New D/H measurements in clouds at different locations in our Galaxy would be necessary to establish this issue, while interstellar measurements in nearby galaxies would give further constraints on the deuterium evolution in different galactic environments. With this goal in mind we have evaluated the capability of the Lyman channel of the SPECTRUM UV Rowland spectrography in determining deuterium column density in distant interstellar clouds. Three packages have been used to obtain realistic predicted spectra and to derive `observed' column densities: (1) the MIDAS package `CLOUD', to generate theoretical interstellar absorption profiles; (2) the `Synth' package developed in the IRAF environment by two of the authors to simulate spectroscopic observations of point sources obtainable with an astronomical spectrograph, (3) the FITLYMAN package inside the Lyman context of MIDAS to derive `observed' column densities from predicted spectra. The minimum exposure times, t(subscript min), required to obtain a approximately 0.1 dex accuracy in the `observed' column densities, were derived by varying the input interstellar hydrogen column density. As a result, we show that the Lyman channel of the SPECTRUM UV Rowland spectrograph is up to the task of deriving accurate H and D column densities of low and medium column density interstellar clouds while it fails for N(HI) >= 10(superscript 21) atoms cm(superscript -2).

  1. Effect of hydrogenation on interaction force among carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Fallah, Ahmadreza; Nakayama, Yoshikazu

    2013-04-01

    Hydrogenation of carbon nanotubes (CNTs) was achieved with flowing hydrogen gas and heating CNTs up to 800 °C. Electron microcopy images show the etching effect of the hydrogen as well as the appearance of defects after hydrogenation. Infrared spectroscopy confirmed the presence of CHx groups on the sidewalls of the functionalized CNTs. Raman spectra of the pristine and hydrogenated samples revealed a transition from graphitic to a disordered and defected structure by increasing the hydrogenation time. We measured the interaction force among CNTs in the pristine and hydrogenated samples. Results showed that the interaction force is reduced sharply upon hydrogenation. After examination of the relation between different experimentally obtained results and the interaction force trend, we discuss how hydrogenation affects the interaction force among CNTs by increasing roughness and formation of repulsive dipoles on the CNT surface.

  2. Carbon and hydrogen isotope effects in the open-system Fischer-Tropsch type reactions. Implications for abiogenic hydrocarbons in the Earth Crust

    NASA Astrophysics Data System (ADS)

    Taran, Y.

    2009-05-01

    This study aims to clarify the isotope effects in the open-system Fischer-Tropsh type (FTT) synthesis with application to the problem of 'abiogenic' hydrocarbons. Carbon and hydrogen isotopic compositions were measured for products of catalytic hydrogenation of CO2 on cobalt and iron catalysts at 245° C and 350° C and 10 MPa in a flow-through reactor. No carbon isotope fractionation between methane and longer hydrocarbons was observed, independently on the CO2 conversion. The hydrogen isotope fractionation appeared to be similar to that found in natural ('thermogenic' and 'biogenic') gases with the enrichment in deuterium of longer hydrocarbon chains and the higher effects for the Co-catalyst. It can be suggested that other than FTT reactions or a simple mixing are responsible for the occurrence of 'inverse' isotopic trends in both carbon and hydrogen isotopic composition found in light hydrocarbons in some specific terrestrial environments and meteorites.

  3. Microwave characteristics of nonuniform hydrogen gas in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Babaei, S.; Babaei, Sh

    2009-04-01

    Absorption, reflection and transmission of microwaves (MWs) from nonuniform hydrogen gas in carbon nanotubes immersed by an ambient uniform magnetic field of various strengths are studied in this paper. The effects of the hydrogen parameters and the magnetic field strength on the absorbed, reflected and transmitted powers are discussed. The hydrogen slab is modelled by a series of uniform hydrogen subslabs. The calculation results show that the effects of the magnetic field strength and the density gradient on the absorbed power, as well as the frequency band of resonant absorption, are significant. Broadband absorption of MWs can be achieved by changing the magnetic field strength and hydrogen density.

  4. Deuterium-tritium pulse propulsion with hydrogen as propellant and the entire space-craft as a gigavolt capacitor for ignition

    NASA Astrophysics Data System (ADS)

    Winterberg, F.

    2013-08-01

    A deuterium-tritium (DT) nuclear pulse propulsion concept for fast interplanetary transport is proposed utilizing almost all the energy for thrust and without the need for a large radiator: By letting the thermonuclear micro-explosion take place in the center of a liquid hydrogen sphere with the radius of the sphere large enough to slow down and absorb the neutrons of the DT fusion reaction, heating the hydrogen to a fully ionized plasma at a temperature of ∼105 K. By using the entire spacecraft as a magnetically insulated gigavolt capacitor, igniting the DT micro-explosion with an intense GeV ion beam discharging the gigavolt capacitor, possible if the space craft has the topology of a torus.

  5. Intramolecular hydrogen bonding of the enol forms of β-ketoamides and β-ketothioamides. Deuterium isotope effects on 13C chemical shifts

    NASA Astrophysics Data System (ADS)

    Hansen, Poul Erik; Duus, Fritz; Bolvig, Simon; Jagodzinski, Tadeusz S.

    1996-04-01

    Deuterium isotope effects of 13C chemical shifts are studied in a series of enol and keto forms of β-ketoamides and the corresponding thioamides. In addition, the 2,6-cyclohexanediketo-1-amides and thioamides are studied. The effects of ring size (five- and six-membered rings) on the isotope effects and the tautomeric nature of the systems are also looked into. Rather unusual isotope effects are found for the amides, indicating a tautomeric system of the CONHRCOHNHR type. This is supported by the 17O chemical shift studies. The isotope effects of the simple amides are compared with those of the tetracyclines and piroxicams. The study of N-phenyl-3-phenyl-3-oxo-propiothioamide at low temperature reveals that this thioamide exists as a mixture of s-cis and s-trans species. The isotope effects and the influence of intramolecular hydrogen bonding in the two species can thus be studied. Thioamides of indan-1,3-diones show tautomeric behaviour, as revealed by very large deuterium isotope effects of both signs. Deuteriation shifts the equilibrium in the direction of the thioamide. Finally, the tendency of a series of β-hydroxy esters, thioesters, anhydrides, amides, thioamides, aldehydes and ketones to become tautomeric is discussed in terms of hydrogen bonding, isotope effects, 2ΔC(OD), and the nature of the acceptor.

  6. On the role of atomic metastability in the production of Balmer line radiation from ‘cold’ atomic hydrogen, deuterium and hydrogenic ion impurities in fusion edge plasmas

    NASA Astrophysics Data System (ADS)

    Hey, J. D.

    2012-03-01

    Published arguments, which assign an important role to atomic metastability in the production of ‘narrow’ Zeeman component radiation from the boundary region of fusion plasmas, are examined critically in relation to l-redistribution by proton and electron collisions, and mixing of unperturbed atomic states by the ion microfield and microfield gradient. It is concluded that these important processes indeed severely constrain the contribution from ‘metastable’ states to the generation of the hydrogen Balmer spectra, for electron concentrations above 1012 cm-3, as pointed out before by the present author (Hey et al 1999 J. Phys. B: At. Mol. Opt. Phys. 32 3555). The analysis of collision-induced l-redistribution represents an extension of that used previously (Hey et al 1996 Contrib. Plasma Phys. 36 583), applicable up to higher electron densities. For comparison purposes, we also consider the question of metastability of ionized helium in a low-temperature plasma, and that of some common hydrogenic impurities (C5+ and Ne9+) in a hydrogen (deuterium) fusion plasma. While for low nuclear charge Z the metastability of 2s1/2 levels is quenched by the plasma environment, it is much reduced in high-Z ions owing to the rapid increase with Z of the two-photon electric dipole (2E1) and magnetic dipole (M1) spontaneous transition rates to the ground state, whereas the role of the plasma in these cases is less important. The main new principle elaborated in this work is the sensitivity of atomic line strengths, and hence collision strengths, to perturbation by the plasma environment for transitions between fine-structure sublevels of the same principal quantum number. As the plasma microfield strength grows, ‘allowed’ transitions diminish in strength, while ‘forbidden’ transitions grow. However, owing to violation of the parity selection rule, there is an overall loss of collision strength available to transitions, resulting from the appearance of significant ‘self-strength’ contributions, in accord with the sum rules for the line strengths, which remain valid over the range of fields considered. Thus, the relative effectiveness per perturber of both electron and ion collisions, for inducing population transfer between fine-structure sublevels, diminishes as the sublevels evolve from a fine-structure dominated to a Stark-effect-dominated regime. In the concluding discussion, we mention that this finding may have a bearing on discrepancies claimed between Stark broadening theory developed by Griem (1967 Astrophys. J. 148 547) and by Watson (2006 J. Phys.B: At. Mol. Opt. Phys. 39 1889), and the measurements of Bell and co-workers (2000 Publ. Astron. Soc. Pac. 112 1236; 2011 Astrophys. Space Sci. 335 451) for high-n radio recombination lines from galactic H II regions. In the absence of detailed modelling to test this suggestion, however, it would be premature to attempt to draw any firm conclusions along these lines. This manuscript is dedicated to the memory of my esteemed colleague Dr. rer. nat. Manfred Korten (1940-2010).

  7. Physisorption of molecular hydrogen on carbon nanotube with vacant defects

    SciTech Connect

    Sun, Gang; Shen, Huaze; Wang, Enge; Xu, Limei; Tangpanitanon, Jirawat; Wen, Bo; Xue, Jianming

    2014-05-28

    Physisorption of molecular hydrogen on single-walled carbon nanotubes (SWCNTs) is important for its engineering applications and hydrogen energy storage. Using molecular dynamics simulation, we study the physisorption of molecular hydrogen on a SWCNT with a vacant defect, focusing on the effect of the vacant defect size and external parameters such as temperature and pressure. We find that hydrogen can be physisorbed inside a SWCNT through a vacant defect when the defect size is above a threshold. By controlling the size of the defects, we are able to extract hydrogen molecules from a gas mixture and store them inside the SWCNT. We also find that external parameters, such as low temperature and high pressure, enhance the physisorption of hydrogen molecules inside the SWCNT. In addition, the storage efficiency can be improved by introducing more defects, i.e., reducing the number of carbon atoms on the SWCNT.

  8. Hydrogen storage in carbon materialspreliminary results

    NASA Astrophysics Data System (ADS)

    Jrissen, Ludwig; Klos, Holger; Lamp, Peter; Reichenauer, Gudrun; Trapp, Victor

    1998-08-01

    Recent developments aiming at the accelerated commercialization of fuel cells for automotive applications have triggered an intensive research on fuel storage concepts for fuel cell cars. The fuel cell technology currently lacks technically and economically viable hydrogen storage technologies. On-board reforming of gasoline or methanol into hydrogen can only be regarded as an intermediate solution due to the inherently poor energy efficiency of such processes. Hydrogen storage in carbon nanofibers may lead to an efficient solution to the above described problems.

  9. Hydrogen adsorption on carbon-doped boron nitride nanotube.

    PubMed

    Baierle, Rogério J; Piquini, Paulo; Schmidt, Tomé M; Fazzio, Adalberto

    2006-10-26

    The adsorption of atomic and molecular hydrogen on carbon-doped boron nitride nanotubes is investigated within the ab initio density functional theory. The binding energy of adsorbed hydrogen on carbon-doped boron nitride nanotube is substantially increased when compared with hydrogen on nondoped nanotube. These results are in agreement with experimental results for boron nitride nanotubes (BNNT) where dangling bonds are present. The atomic hydrogen makes a chemical covalent bond with carbon substitution, while a physisorption occurs for the molecular hydrogen. For the H(2) molecule adsorbed on the top of a carbon atom in a boron site (BNNT + C(B)-H(2)), a donor defect level is present, while for the H(2) molecule adsorbed on the top of a carbon atom in a nitrogen site (BNNT + C(N)-H(2)), an acceptor defect level is present. The binding energies of H(2) molecules absorbed on carbon-doped boron nitride nanotubes are in the optimal range to work as a hydrogen storage medium. PMID:17048943

  10. {sup 13}C NMR spectroscopy of amorphous hydrogenated carbon and amorphous hydrogenated boron carbide

    SciTech Connect

    Braddock-Wilking, J.; Lin, S.; Feldman, B.J.

    1999-04-01

    We report the {sup 13}C NMR spectrum of amorphous hydrogenated carbon and boron carbide. The amorphous hydrogenated carbon spectra consist primarily of an sp{sup 3} line at 40 ppm and an sp{sup 2} line at 140 ppm and are in reasonable agreement with the recent theoretical calculations of Mauri, Pfrommer, and Louie, but there are some notable discrepancies. The amorphous hydrogenated boron carbide spectra are very different from those of amorphous hydrogenated carbon, being dominated by one line at 15 ppm. We interpret this line as due to carbon bound in boron carbide icosahedra, because polycrystalline boron carbide with boron carbide icosahedra as the unit cell gives very similar NMR spectra. {copyright} {ital 1999} {ital The American Physical Society}

  11. Microwave interaction with nonuniform hydrogen gas in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Babaei, S.; Babaei, Sh.

    2009-03-01

    In this paper we study the reflection, absorption, and transmission of microwave from nonuniform hydrogen gas in carbon nanotubes, grown by iron-catalyzed high-pressure carbon monoxide disproportionate (HiPco) process. A discussion on the effect of various hydrogen gas parameters on the reflected power, absorbed power, and transmitted power is presented. The nonuniform hydrogen gas slab is modeled by a series of subslabs. The overall number density profile across the whole slab follows a parabolic function. The total reflected, absorbed, and transmitted powers are then deduced and their functional dependence on the number density, collision frequency, and angle of propagation is studied.

  12. Extraordinary hydrogen evolution and oxidation reaction activity from carbon nanotubes and graphitic carbons.

    PubMed

    Das, Rajib Kumar; Wang, Yan; Vasilyeva, Svetlana V; Donoghue, Evan; Pucher, Ilaria; Kamenov, George; Cheng, Hai-Ping; Rinzler, Andrew G

    2014-08-26

    The hydrogen evolution reaction, 2H(+) + 2e(–) → H2, and its converse, the hydrogen oxidation reaction, H2 → 2H(+) + 2e(–), are central to any realization of a hydrogen economy. Various forms of carbon have been used for decades as the precious metal catalyst support in these reactions. Here we report the unexpected result that single-wall carbon nanotubes and some graphitic carbons, activated by brief exposure to electrochemical potentials that induce hydrogen evolution in intercalating acids combined with extended soak times in such acids, acquire an activity for these reactions that exceeds that of known nonprecious metal catalysts. PMID:25017805

  13. Polar Aprotic Modifiers for Chromatographic Separation and Back-Exchange Reduction for Protein Hydrogen/Deuterium Exchange Monitored by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Valeja, Santosh G.; Emmett, Mark R.; Marshall, Alan G.

    2012-04-01

    Hydrogen/deuterium exchange monitored by mass spectrometry is an important non-perturbing tool to study protein structure and protein-protein interactions. However, water in the reversed-phase liquid chromatography mobile phase leads to back-exchange of D for H during chromatographic separation of proteolytic peptides following H/D exchange, resulting in incorrect identification of fast-exchanging hydrogens as unexchanged hydrogens. Previously, fast high-performance liquid chromatography (HPLC) and supercritical fluid chromatography have been shown to decrease back-exchange. Here, we show that replacement of up to 40% of the water in the LC mobile phase by the modifiers, dimethylformamide (DMF) and N-methylpyrrolidone (NMP) (i.e., polar organic modifiers that lack rapid exchanging hydrogens), significantly reduces back-exchange. On-line LC micro-ESI FT-ICR MS resolves overlapped proteolytic peptide isotopic distributions, allowing for quantitative determination of the extent of back-exchange. The DMF modified solvent composition also improves chromatographic separation while reducing back-exchange relative to conventional solvent.

  14. Polar Aprotic Modifiers for Chromatographic Separation and Back-Exchange Reduction for Protein Hydrogen/Deuterium Exchange Monitored by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

    PubMed Central

    Valeja, Santosh G.; Emmett, Mark R.; Marshall, Alan G.

    2013-01-01

    Hydrogen/deuterium exchange monitored by mass spectrometry is an important non-perturbing tool to study protein structure and protein–protein interactions. However, water in the reversed-phase liquid chromatography mobile phase leads to back-exchange of D for H during chromatographic separation of proteolytic peptides following H/D exchange, resulting in incorrect identification of fast-exchanging hydrogens as unexchanged hydrogens. Previously, fast high-performance liquid chromatography (HPLC) and supercritical fluid chromatography have been shown to decrease back-exchange. Here, we show that replacement of up to 40% of the water in the LC mobile phase by the modifiers, dimethylformamide (DMF) and N-methylpyrrolidone (NMP) (i.e., polar organic modifiers that lack rapid exchanging hydrogens), significantly reduces back-exchange. On-line LC micro-ESI FT-ICR MS resolves overlapped proteolytic peptide isotopic distributions, allowing for quantitative determination of the extent of back-exchange. The DMF modified solvent composition also improves chromatographic separation while reducing back-exchange relative to conventional solvent. PMID:22298288

  15. Predicting Protein Aggregation during Storage in Lyophilized Solids Using Solid State Amide Hydrogen/Deuterium Exchange with Mass Spectrometric Analysis (ssHDX-MS)

    PubMed Central

    2015-01-01

    Solid state amide hydrogen/deuterium exchange with mass spectrometric analysis (ssHDX-MS) was used to assess the conformation of myoglobin (Mb) in lyophilized formulations, and the results correlated with the extent of aggregation during storage. Mb was colyophilized with sucrose (1:1 or 1:8 w/w), mannitol (1:1 w/w), or NaCl (1:1 w/w) or in the absence of excipients. Immediately after lyophilization, samples of each formulation were analyzed by ssHDX-MS and Fourier transform infrared spectroscopy (FTIR) to assess Mb conformation, and by dynamic light scattering (DLS) and size exclusion chromatography (SEC) to determine the extent of aggregation. The remaining samples were then placed on stability at 25 °C and 60% RH or 40 °C and 75% RH for up to 1 year, withdrawn at intervals, and analyzed for aggregate content by SEC and DLS. In ssHDX-MS of samples immediately after lyophilization (t = 0), Mb was less deuterated in solids containing sucrose (1:1 and 1:8 w/w) than in those containing mannitol (1:1 w/w), NaCl (1:1 w/w), or Mb alone. Deuterium uptake kinetics and peptide mass envelopes also indicated greater Mb structural perturbation in mannitol, NaCl, or Mb-alone samples at t = 0. The extent of deuterium incorporation and kinetic parameters related to rapidly and slowly exchanging amide pools (Nfast, Nslow), measured at t = 0, were highly correlated with the extent of aggregation on storage as measured by SEC. In contrast, the extent of aggregation was weakly correlated with FTIR band intensity and peak position measured at t = 0. The results support the use of ssHDX-MS as a formulation screening tool in developing lyophilized protein drug products. PMID:24816133

  16. Hydrogen-deficient atmospheres for cool carbon stars

    NASA Technical Reports Server (NTRS)

    Johnson, H. R.; Bower, C. D.; Lemke, D. A.; Luttermoser, D. G.; Petrakis, J. P.; Reinhart, M. D.; Welch, K. A.; Alexander, D. R.; Goebel, J. H.

    1985-01-01

    Motivated by recent work which hints at a possible deficiency of hydrogen in non-Mira N-type carbon stars and to further explore the parameter space of chemical composition, computations have been made of a series of hydrogen-deficient models for carbon stars. For these models Teff = 3000 K, and log g = 0.0. Solar abundances are used for all elements except for carbon (which is enhanced to give C/O = 1.05), hydrogen, and helium. As the fractional abundance of hydrogen is decreased, being replaced by helium, the temperature-optical depth relation is affected only slightly, but the temperature-pressure relation is changed. The most striking change in the emergent flux is the decrease of the H(-) peak at 1.65 micron compared with the blackbody peak at 1.00 micron.

  17. Deuterium-free water (1H2O) in complex life-support systems of long-term space missions.

    PubMed

    Sinyak, Y; Grigoriev, A; Gaydadimov, V; Gurieva, T; Levinskih, M; Pokrovskii, B

    2003-04-01

    Heavy water containing deuterium displays toxic property. It is stated that any quantity of a heavy isotope of hydrogen--deuterium--is undesirable to animals and plants. It was earlier shown by us that physical-chemical life support systems on board the "MIR" station fractionate (change) isotopes of hydrogen, oxygen and carbon. Therefore, the problem of regenerative systems in habitable space objects should include removal, from water, of a heavy stable isotope of hydrogen--deuterium. In this article we consider one method of obtaining deuterium-free water--decomposition of distillate water in an electrolyser to hydrogen and oxygen with subsequent synthesis in a catalytic or high-temperature reactor. The influence of deuterium-free water on the growth and development of Arabidopsis thaliana and Japanese quail is investigated. It is shown that with the help of the electrolysis method it is possible to fabricate water containing 80% less deuterium in comparison with SMOW. Experimentally, it is proved on a culture of Arabidopsis thaliana and Japanese quail that water with reduced contents of deuterium (80%) displays positive biological activity. PMID:12575722

  18. TENSILE TESTING OF CARBON STEEL IN HIGH PRESSURE HYDROGEN

    SciTech Connect

    Duncan, A; Thad Adams, T; Ps Lam, P

    2007-05-02

    An infrastructure of new and existing pipelines and systems will be required to carry and to deliver hydrogen as an alternative energy source under the hydrogen economy. Carbon and low alloy steels of moderate strength are currently used in hydrogen delivery systems as well as in the existing natural gas systems. It is critical to understand the material response of these standard pipeline materials when they are subjected to pressurized hydrogen environments. The methods and results from a testing program to quantify hydrogen effects on mechanical properties of carbon steel pipeline and pipeline weld materials are provided. Tensile properties of one type of steel (A106 Grade B) in base metal, welded and heat affected zone conditions were tested at room temperature in air and high pressure (10.34 MPa or 1500 psig) hydrogen. A general reduction in the materials ability to plastically deform was noted in this material when specimens were tested in hydrogen. Furthermore, the primary mode of fracture was changed from ductile rupture in air to cleavage with secondary tearing in hydrogen. The mechanical test results will be applied in future analyses to evaluate service life of the pipelines. The results are also envisioned to be part of the bases for construction codes and structural integrity demonstrations for hydrogen service pipeline and vessels.

  19. Conformational dynamics of human FXR-LBD ligand interactions studied by hydrogen/deuterium exchange mass spectrometry: Insights into the antagonism of the hypolipidemic agent Z-guggulsterone

    PubMed Central

    Yang, Liping; Broderick, David; Jiang, Yuan; Hsu, Victor; Maier, Claudia S.

    2014-01-01

    Farnesoid X Receptor (FXR) is a member of the nuclear receptor superfamily of transcription factors that plays a key role in the regulation of bile acids, lipid and glucose metabolisms. The regulative function of FXR is governed by conformational changes of the ligand binding domain (LBD) upon ligand binding. Although FXR is a highly researched potential therapeutic target, only a limited number of FXR-agonist complexes have been successfully crystallized and subsequently yielded high resolution structures. There is currently no structural information of any FXR-antagonist complexes publically available. We therefore explored the use of amide hydrogen/deuterium exchange (HDX) coupled with mass spectrometry for characterizing conformational changes in the FXR-LBD upon ligand binding. Ligand-specific deuterium incorporation profiles were obtained for three FXR ligand chemotypes: GW4064, a synthetic non-steroidal high affinity agonist; the bile acid chenodeoxycholic acid (CDCA), the endogenous low affinity agonist of FXR; and Z-guggulsterone (GG), an in vitro antagonist of the steroid chemotype. Comparison of the HDX profiles of their ligand-bound FXR-LBD complexes revealed a unique mode of interaction for GG. The conformational features of the FXR-LBD-antagonist interaction are discussed. PMID:24953769

  20. Investigation of Morphology and Hydrogen Adsorption Capacity of Disordered Carbons

    NASA Astrophysics Data System (ADS)

    He, Lilin; Melnichenko, Yuri; Gallego, Nidia; Contescu, Cristian

    2014-03-01

    We have applied small angle neutron scattering (SANS) technique to study the morphologies and hydrogen adsorption capabilities of wood-based ultramicroporous carbon and poly(furfuryl alcohol) derived carbon. The Polydispersed Spherical model and chord length analysis of the scattering profiles were performed to obtain morphological parameters such as average pore size and pore size distribution of the dry carbons, which agreed reasonably well with the independent gas sorption measurements. The hydrogen physisorbed in these two carbons at room temperature and moderate pressures was investigated by In-situ SANS measurements. The experimental data analyzed using a modified Kalliat model for decoupling scattering contributions from pores with different sizes indicates that the molecular hydrogen condenses preferentially in narrow micropores at all measured pressures, which supports the theoretical prediction by quantum mechanical and thermodynamical models.

  1. Hydrogen sensing characteristics from carbon nanotube field emissions

    NASA Astrophysics Data System (ADS)

    Dong, Changkun; Luo, Haijun; Cai, Jianqiu; Wang, Fuquan; Zhao, Yangyang; Li, Detian

    2016-03-01

    An innovative hydrogen sensing concept is demonstrated based on the field emission from multi-walled carbon nanotubes, where the low emission currents rise in proportion to hydrogen partial pressures above 10-9 Torr. Experimental and first principles studies reveal that the sensing mechanism is attributed to the effective work function reduction from dissociative hydrogen chemisorption. The embedded Ni catalyst would assist both the hydrogen dissociation and work function reduction. This technique is promising to build miniature low cost hydrogen sensors for multiple applications. This work is valuable for studies of nanocarbon-gas reaction mechanisms and the work function properties in adsorption related applications, including field emission, hydrogen storage, energy cells, and gas sensing.

  2. Hydrogen sensing characteristics from carbon nanotube field emissions.

    PubMed

    Dong, Changkun; Luo, Haijun; Cai, Jianqiu; Wang, Fuquan; Zhao, Yangyang; Li, Detian

    2016-03-01

    An innovative hydrogen sensing concept is demonstrated based on the field emission from multi-walled carbon nanotubes, where the low emission currents rise in proportion to hydrogen partial pressures above 10(-9) Torr. Experimental and first principles studies reveal that the sensing mechanism is attributed to the effective work function reduction from dissociative hydrogen chemisorption. The embedded Ni catalyst would assist both the hydrogen dissociation and work function reduction. This technique is promising to build miniature low cost hydrogen sensors for multiple applications. This work is valuable for studies of nanocarbon-gas reaction mechanisms and the work function properties in adsorption related applications, including field emission, hydrogen storage, energy cells, and gas sensing. PMID:26890686

  3. A comparative neutronic feasibility study for a hydrogen, deuterium and helium cold neutron sources situated in the center of a nuclear reactor core

    NASA Astrophysics Data System (ADS)

    Chatila, Malek

    A tool was developed to calculate the average cold neutron flux that could be generated for a spherically shaped cold neutron source situated in the center of a nuclear reactor core. The tool also estimates the subsequent nuclear heating of the cold source. The results were compared for three different cold source mediums; hydrogen, deuterium and helium. The tool utilizes the consistent energy dependent P1 equations to generate the fast neutron energy spectrum, the Grueling-Goertzel equations to generate the slow spectrum and the Proton Gas Model to generate the cold energy spectrum. These spectrums are then used to collapse the group constants into three energy groups. The cold flux that can be generated in different mediums is then calculated by utilizing the three energy group constants in SN-6, 2 regions calculations.

  4. Amide-resolved hydrogen-deuterium exchange measurements from membrane-reconstituted polypeptides using exchange trapping and semiselective two-dimensional NMR.

    PubMed

    Dempsey, C E

    1994-11-01

    Amide-resolved, hydrogen-deuterium exchange from bee venom melittin reconstituted in fully hydrated vesicles suspended in D(2)O buffer was measured using a technique involving (1) trapping samples throughout an exchange time course by rapid freezing and lyophilization; and (2) dissolving the dried peptide/lipid mixtures in deuteromethanol to record high-resolution spectra using semiselective excitation pulses to select peptide amide signals in the presence of large excess lipid signals. Two-dimensional, amide-selective GaussNOESY and fingerprint-selective off-diagonal PingCOSY spectra are shown to be suitable for rapid acquisition of amide-selective spectra, obtained throughout a time course of amide exchange in the membrane-bound state. Membrane-reconstituted melittin is shown to contain two sequences of exchange-stable amides, corresponding to helical regions on either side of the single proline residue. PMID:22911389

  5. Approach to characterization of the higher order structure of disulfide-containing proteins using hydrogen/deuterium exchange and top-down mass spectrometry.

    PubMed

    Wang, Guanbo; Kaltashov, Igor A

    2014-08-01

    Top-down hydrogen/deuterium exchange (HDX) with mass spectrometric (MS) detection has recently matured to become a potent biophysical tool capable of providing valuable information on higher order structure and conformational dynamics of proteins at an unprecedented level of structural detail. However, the scope of the proteins amenable to the analysis by top-down HDX MS still remains limited, with the protein size and the presence of disulfide bonds being the two most important limiting factors. While the limitations imposed by the physical size of the proteins gradually become more relaxed as the sensitivity, resolution and dynamic range of modern MS instrumentation continue to improve at an ever accelerating pace, the presence of the disulfide linkages remains a much less forgiving limitation even for the proteins of relatively modest size. To circumvent this problem, we introduce an online chemical reduction step following completion and quenching of the HDX reactions and prior to the top-down MS measurements of deuterium occupancy of individual backbone amides. Application of the new methodology to the top-down HDX MS characterization of a small (99 residue long) disulfide-containing protein β2-microglobulin allowed the backbone amide protection to be probed with nearly a single-residue resolution across the entire sequence. The high-resolution backbone protection pattern deduced from the top-down HDX MS measurements carried out under native conditions is in excellent agreement with the crystal structure of the protein and high-resolution NMR data, suggesting that introduction of the chemical reduction step to the top-down routine does not trigger hydrogen scrambling either during the electrospray ionization process or in the gas phase prior to the protein ion dissociation. PMID:24988145

  6. Application of atmospheric pressure photo ionization hydrogen/deuterium exchange high-resolution mass spectrometry for the molecular level speciation of nitrogen compounds in heavy crude oils.

    PubMed

    Cho, Yunju; Ahmed, Arif; Kim, Sunghwan

    2013-10-15

    We report here for the first time the application of atmospheric pressure photo ionization hydrogen/deuterium exchange (APPI HDX) coupled to high-resolution mass spectrometry for molecular level speciation of nitrogen containing compounds in crude oils. The speciation was done based on different combinations of ions produced from nitrogen containing compounds with various functional groups. To prove the concept, 20 nitrogen containing standard compounds were analyzed. As a result, it was shown that the nitrogen containing compound (M) with a primary amine functional group mainly produced a combination of [M - 2H + 2D](•+) and ([M - 2H + 2D] + D)(+) ions, one with a secondary amine including alkylated or phenylated pyrrole a combination of [M - H + D](•+) and ([M - H + D] + D)(+), one with a tertiary amine including N-alkylated or phenylated pyrrole a combination of [M](•+) and [M + D](+), and one with a pyridine functional group mostly [M + D](+) ions. The concept was successfully applied to do nitrogen speciation of resins fractions of two oil samples. Combined with the subsequent investigation of double bond equivalence distribution, it was shown that resins of Qinhuangdao crude oil sample contained mostly alkylated pyrrole and N-alkylated pyrrole type compounds but resins of shale oil extract contained mostly pyridine type nitrogen compounds. It was also shown that the speciation of individual elemental composition was also possible by use of this method. Overall, this study clearly shows that atmospheric pressure photo ionization hydrogen/deuterium exchange (APPI HDX) coupled to high-resolution mass spectrometry is a powerful analytical method to do nitrogen speciation of crude oil compounds at the molecular level. PMID:24033284

  7. Shock compression of precompressed deuterium

    SciTech Connect

    Armstrong, M R; Crowhurst, J C; Zaug, J M; Bastea, S; Goncharov, A F; Militzer, B

    2011-07-31

    Here we report quasi-isentropic dynamic compression and thermodynamic characterization of solid, precompressed deuterium over an ultrafast time scale (< 100 ps) and a microscopic length scale (< 1 {micro}m). We further report a fast transition in shock wave compressed solid deuterium that is consistent with the ramp to shock transition, with a time scale of less than 10 ps. These results suggest that high-density dynamic compression of hydrogen may be possible on microscopic length scales.

  8. Kaon Electroproduction on Deuterium

    SciTech Connect

    David Abbott; Abdellah Ahmidouch, Pawel Ambrozewicz; Chris Armstrong; John Arrington; K. Assamagan; Kevin Bailey; Oliver K. Baker; Shelton Beedoe; Elizabeth Beise; Herbert Breuer; Roger Carlini; Jinseok Cha; G. Collins; C. Cothran; W.J. Cummings; Samuel Danagoulian; Fraser Duncan; Jim Dunne; Dipangkar Dutta; Tom Eden; Rolf Ent; Lars Ewell; H.T. Fortune; Haiyan Gao; Donald Geesaman; Kenneth Gustafsson; Paul Gueye; Jens-Ole Hansen; Wendy Hinton; Hal Jackson; Cynthia Keppel; Andi Klein; D. Koltenok; David Mack; Richard Madey; Pete Markowitz; C.J. Martoff; David Meekins; Joseph Mitchell; R. Mohring; Hamlet Mkrtchyan; S.K. Mtingwa; Tom O'Neill; Gabriel Niculescu; Ioana Niculescu; Dave Potterveld; John Price; Philip Roos; Brian Raue; J.J. Reidy; Juerg Reinhold; G. Savage; Reyad Sawafta; J.P. Schiffer; Ralph Segel; Stepan Stepanyan; V. Tadevosian; Liguang Tang; B. Terburg; Stephen Wood; Chen Yan; Ben Zeidman; Beni Zihlmann

    1998-08-01

    Kaon electroproduction on deuterium and hydrogen targets has been measured at beam energies of 3.245 and 2.445GeV and momentum transfer Q{sup 2}=0.38 and O.5(GeV/c ){sup 2} Associated production off a proton in the deuteron exhibits a quasifree production mechanism. The electroproduction of a Sigma - off the neutron could be extracted for the first time with reasonable errors.

  9. MECHANICAL TESTING OF CARBON STEEL IN HIGH PRESSURE HYDROGEN

    SciTech Connect

    Duncan, A

    2006-05-11

    The methods and interim results from a testing program to quantify hydrogen effects on mechanical properties of carbon steel pipeline and pipeline weld materials are provided. The scope is carbon steels commonly used for natural gas pipelines in the United States that are candidates for hydrogen service in the hydrogen economy. The mechanical test results will be applied in future analyses to evaluate service life of the pipelines. The results are also envisioned to be part of the bases for construction codes and structural integrity demonstrations for hydrogen service pipeline and vessels. Tensile properties of one type of steel (A106 Grade B) in base metal, welded and heat affected zone conditions were tested at room temperature in air and high pressure (1500 psig) hydrogen. A general reduction in the materials ability to plastically deform was noted in this material when specimens were tested in 1500 psig hydrogen. Furthermore, the primary mode of fracture was changed from ductile rupture in air to cleavage with secondary tearing in hydrogen. The mechanical test program will continue with tests to quantify the fracture behavior in terms of J-R curves for these materials at air and hydrogen pressure conditions.

  10. The ratio of deuterium to hydrogen in interstellar space. IV - The lines of sight to Delta, Epsilon, and Iota Orionis

    NASA Technical Reports Server (NTRS)

    Laurent, C.; Vidal-Madjar, A.; York, D. G.

    1979-01-01

    Deuterium absorption features in spectra of Delta, Epsilon, and Iota Ori obtained with Copernicus are analyzed. The Iota Ori line-of-sight analysis, which is quite detailed because of the high-velocity H I components superposed on the deuterium features, gives a D/H ratio (which is uncertain because of a complex profile) of 0.000014. A D/H ratio of the order of 7 millionths is determined for Delta and Epsilon Ori. For the complex line profiles involved, one may regard this as a formal lower limit. Several attempts were made to increase the ratio N(D I)/N(H I) in the context of reasonable models for the line of sight, but with no success; the derived values are therefore regarded as actual values, not lower limits. Since the derived value is an average on the line of sight, the possibility cannot be ruled out that the true ratios N(D I)/N(H I) in individual nearby components differ from the mean values. The mean value for these two directions is lower by a factor of 4 than the best value for the Zeta Pup line of sight (the highest yet derived for path lengths greater than 50 pc).

  11. THE REMOVAL OF CARBON/BEUTERIUM FROM STAINLESS STEEL AND TUNGSTEN BY TRANSFERRED-ARC CLEANING

    SciTech Connect

    K. J. HOLLIS; R. G. CASTRO; ET AL

    2001-04-01

    Tungsten and stainless steel samples have been contaminated with deuterium and carbon to simulate deposited layers in magnetic-confinement fusion devices. Deuterium and carbon were co-deposited onto the sample surfaces using a deuterium plasma seeded with varying amounts of deuterated methane. Deuterium was also implanted into the samples in an accelerator to simulate hydrogen isotope ion implantation conditions in magnetic confinement fusion devices. Cathodic arc, or transferred-arc (TA) cleaning was employed to remove the deposits from the samples. The samples were characterized by ion beam analysis both before and after cleaning to determine deuterium and carbon concentrations present. The deuterium content was greatly reduced by the cleaning thus demonstrating the possibility of using the TA cleaning technique for removing deuterium and/or tritium from components exposed to D-T fuels. Removal of surface layers and significant reduction of subsurface carbon concentrations was also observed.

  12. Hydrogen Storage in the Carbon Dioxide - Formic Acid Cycle.

    PubMed

    Fink, Cornel; Montandon-Clerc, Mickael; Laurenczy, Gabor

    2015-01-01

    This year Mankind will release about 39 Gt carbon dioxide into the earth's atmosphere, where it acts as a greenhouse gas. The chemical transformation of carbon dioxide into useful products becomes increasingly important, as the CO(2) concentration in the atmosphere has reached 400 ppm. One approach to contribute to the decrease of this hazardous emission is to recycle CO(2), for example reducing it to formic acid. The hydrogenation of CO(2) can be achieved with a series of catalysts under basic and acidic conditions, in wide variety of solvents. To realize a hydrogen-based charge-discharge device ('hydrogen battery'), one also needs efficient catalysts for the reverse reaction, the dehydrogenation of formic acid. Despite of the fact that the overwhelming majority of these reactions are carried out using precious metals-based catalysts (mainly Ru), we review here developments for catalytic hydrogen evolution from formic acid with iron-based complexes. PMID:26842324

  13. Hydrogen Confinement in Carbon Nanopores: Extreme Densification at Ambient Temperature

    SciTech Connect

    Gallego, Nidia C; He, Lilin; Saha, Dipendu; Contescu, Cristian I; Melnichenko, Yuri B

    2011-01-01

    In-situ small angle neutron scattering (SANS) studies of hydrogen confined in small pores of polyfurfuryl alcohol-derived activated carbon (PFAC) at room-temperature provided for the first time its phase behavior in equilibrium with external H2 at pressures up to 200 bar. The data was used to evaluate the density of the adsorbed fluid, which appears to be a function of both pore size and pressure, and approaches the liquid hydrogen density in narrow nanopores at 200 bar. The surface-molecule interactions responsible for densification of hydrogen within the pores create internal pressures which exceed by a factor of up to ~ 60 the external gas pressures, confirming the benefits of adsorptive over compressive storage. These results can be utilized to guide the development of new carbon adsorbents tailored for maximum hydrogen storage capacities at near ambient temperatures.

  14. Methanation of gas streams containing carbon monoxide and hydrogen

    DOEpatents

    Frost, Albert C.

    1983-01-01

    Carbon monoxide-containing gas streams having a relatively high concentration of hydrogen are pretreated so as to remove the hydrogen in a recoverable form for use in the second step of a cyclic, essentially two-step process for the production of methane. The thus-treated streams are then passed over a catalyst to deposit a surface layer of active surface carbon thereon essentially without the formation of inactive coke. This active carbon is reacted with said hydrogen removed from the feed gas stream to form methane. The utilization of the CO in the feed gas stream is appreciably increased, enhancing the overall process for the production of relatively pure, low-cost methane from CO-containing waste gas streams.

  15. Theoretical analysis of hydrogen spillover mechanism on carbon nanotubes.

    PubMed

    Juarez-Mosqueda, Rosalba; Mavrandonakis, Andreas; Kuc, Agnieszka B; Pettersson, Lars G M; Heine, Thomas

    2015-01-01

    The spillover mechanism of molecular hydrogen on carbon nanotubes in the presence of catalytically active platinum clusters was critically and systematically investigated by using density-functional theory. Our simulation model includes a Pt4 cluster for the catalyst nanoparticle and curved and planar circumcoronene for two exemplary single-walled carbon nanotubes (CNT), the (10,10) CNT and one of large diameter, respectively. Our results show that the H2 molecule dissociates spontaneously on the Pt4 cluster. However, the dissociated H atoms have to overcome a barrier of more than 2 eV to migrate from the catalyst to the CNT, even if the Pt4 cluster is at full saturation with six adsorbed and dissociated hydrogen molecules. Previous investigations have shown that the mobility of hydrogen atoms on the CNT surface is hindered by a barrier. We find that instead the Pt4 catalyst may move along the outer surface of the CNT with activation energy of only 0.16 eV, and that this effect offers the possibility of full hydrogenation of the CNT. Thus, although we have not found a low-energy pathway to spillover onto the CNT, we suggest, based on our calculations and calculated data reported in the literature, that in the hydrogen-spillover process the observed saturation of the CNT at hydrogen background pressure occurs through mobile Pt nanoclusters, which move on the substrate more easily than the substrate-chemisorbed hydrogens, and deposit or reattach hydrogens in the process. Initial hydrogenation of the carbon substrate, however, is thermodynamically unfavoured, suggesting that defects should play a significant role. PMID:25699250

  16. Theoretical analysis of hydrogen spillover mechanism on carbon nanotubes

    PubMed Central

    Juarez-Mosqueda, Rosalba; Mavrandonakis, Andreas; Kuc, Agnieszka B.; Pettersson, Lars G. M.; Heine, Thomas

    2015-01-01

    The spillover mechanism of molecular hydrogen on carbon nanotubes in the presence of catalytically active platinum clusters was critically and systematically investigated by using density-functional theory. Our simulation model includes a Pt4 cluster for the catalyst nanoparticle and curved and planar circumcoronene for two exemplary single-walled carbon nanotubes (CNT), the (10,10) CNT and one of large diameter, respectively. Our results show that the H2 molecule dissociates spontaneously on the Pt4 cluster. However, the dissociated H atoms have to overcome a barrier of more than 2 eV to migrate from the catalyst to the CNT, even if the Pt4 cluster is at full saturation with six adsorbed and dissociated hydrogen molecules. Previous investigations have shown that the mobility of hydrogen atoms on the CNT surface is hindered by a barrier. We find that instead the Pt4 catalyst may move along the outer surface of the CNT with activation energy of only 0.16 eV, and that this effect offers the possibility of full hydrogenation of the CNT. Thus, although we have not found a low-energy pathway to spillover onto the CNT, we suggest, based on our calculations and calculated data reported in the literature, that in the hydrogen-spillover process the observed saturation of the CNT at hydrogen background pressure occurs through mobile Pt nanoclusters, which move on the substrate more easily than the substrate-chemisorbed hydrogens, and deposit or reattach hydrogens in the process. Initial hydrogenation of the carbon substrate, however, is thermodynamically unfavoured, suggesting that defects should play a significant role. PMID:25699250

  17. Material processing with hydrogen and carbon monoxide on Mars

    NASA Technical Reports Server (NTRS)

    Hepp, Aloysius F.; Landis, Geoffrey A.; Linne, Diane L.

    1991-01-01

    Several novel proposals are examined for propellant production from carbon dioxide and monoxide and hydrogen. Potential uses were also examined of CO as a fuel or as a reducing agent in metal oxide processing as obtained or further reduced to carbon. Hydrogen can be reacted with CO to produce a wide variety of hydrocarbons, alcohols, and other organic compounds. Methanol, produced by Fischer-Tropsch chemistry may be useful as a fuel; it is easy to store and handle because it is a liquid at Mars temperatures. The reduction of CO2 to hydrocarbons such as methane or acetylene can be accomplished with hydrogen. Carbon monoxide and hydrogen require cryogenic temperatures for storage as liquids. Noncryogenic storage of hydrogen may be accomplished using hydrocarbons, inorganic hydrides, or metal hydrides. Noncryogenic storage of CO may be accomplished in the form of iron carbonyl (FE(CO)5) or other metal carbonyls. Low hydrogen content fuels such as acetylene (C2H2) may be effective propellants with low requirements for earth derived resources. The impact on manned Mars missions of alternative propellant production and utilization is discussed.

  18. Isotopic inferences of ancient biochemistries - Carbon, sulfur, hydrogen, and nitrogen

    NASA Technical Reports Server (NTRS)

    Schidlowski, M.; Hayes, J. M.; Kaplan, I. R.

    1983-01-01

    In processes of biological incorporation and subsequent biochemical processing sizable isotope effects occur as a result of both thermodynamic and kinetic fractionations which take place during metabolic and biosynthetic reactions. In this chapter a review is provided of earlier work and recent studies on isotope fractionations in the biogeochemical cycles of carbon, sulfur, hydrogen, and nitrogen. Attention is given to the biochemistry of carbon isotope fractionation, carbon isotope fractionation in extant plants and microorganisms, isotope fractionation in the terrestrial carbon cycle, the effects of diagenesis and metamorphism on the isotopic composition of sedimentary carbon, the isotopic composition of sedimentary carbon through time, implications of the sedimentary carbon isotope record, the biochemistry of sulfur isotope fractionation, pathways of the biogeochemical cycle of nitrogen, and the D/H ratio in naturally occurring materials.

  19. Inelastic Neutron Scattering from Hydrogen Adsorbed in Carbon

    NASA Astrophysics Data System (ADS)

    Olsen, Raina; Beckner, Matthew; Taub, Haskell; Pfeifer, Peter; Wexler, Carlos

    2011-03-01

    Inelastic neutron scattering (INS) from adsorbed hydrogen offers a powerful tool to probe the local adsorption environment of storage material. We will show recently measured INS spectra of hydrogen adsorbed on four different carbon samples and discuss the interpretation of their spectral features, using previous theoretical calculations. Both rotational and vibrational transitions can be observed, along with free recoil scattering parallel to the adsorption plane. The spectra from carbon nanotubes and activated carbon are well explained by theory. However, the spectra from PVDC carbon is quite unusual. This material is based upon work supported in part by the Department of Energy under Award Nos. DE-FG02-07ER46411, DE-FG36-08GO18142, and DE-AC02-06CH11357.

  20. Electrochemical hydrogen storage in single-walled carbon nanotube paper.

    PubMed

    Guo, Z P; Ng, S H; Wang, J Z; Huang, Z G; Liu, H K; Too, C O; Wallace, G G

    2006-03-01

    Single-walled carbon nanotube (SWNT) papers were successfully prepared by dispersing SWNTs in Triton X-100 solution, then filtered by PVDF membrane (0.22 microm pore size). The electrochemical behavior and the reversible hydrogen storage capacity of single-walled carbon nanotube (SWNT) papers have been investigated in alkaline electrolytic solutions (6 N KOH) by cyclic voltammetry, linear micropolarization, and constant current charge/discharge measurements. The effect of thickness and the addition of carbon black on hydrogen adsorption/desorption were also investigated. It was found that the electrochemical charge-discharge mechanism occurring in SWNT paper electrodes is somewhere between that of carbon nanotubes (physical process) and that of metal hydride electrodes (chemical process), and consists of a charge-transfer reaction (Reduction/Oxidation) and a diffusion step (Diffusion). PMID:16573126

  1. Molecular simulation of hydrogen adsorption in single-walled carbon nanotubes and idealized carbon slit pores

    NASA Astrophysics Data System (ADS)

    Wang, Qinyu; Johnson, J. Karl

    1999-01-01

    The adsorption of hydrogen gas into single-walled carbon nanotubes (SWNTs) and idealized carbon slit pores is studied by computer simulation. Hydrogen-hydrogen interactions are modeled with the Silvera-Goldman potential. The Crowell-Brown potential is used to model the hydrogen-carbon interactions. Calculations include adsorption inside the tubes, in the interstitial regions of tube arrays, and on the outside surface of isolated tubes. Quantum effects are included through implementation of the path integral formalism. Comparison with classical simulations gives an indication of the importance of quantum effects for hydrogen adsorption. Quantum effects are important even at 298 K for adsorption in tube interstices. We compare our simulations with experimental data for SWNTs, graphitic nanofibers, and activated carbon. Adsorption isotherms from simulations are in reasonable agreement with experimental data for activated carbon, but do not confirm the large uptake reported for SWNTs and nanofibers. Although the adsorption potential for hydrogen in SWNTs is enhanced relative to slit pores of the same size, our calculations show that the storage capacity of an array of tubes is less than that for idealized slit pore geometries, except at very low pressures. Ambient temperature isotherms indicate that an array of nanotubes is not a suitable sorbent material for achieving DOE targets for vehicular hydrogen storage.

  2. Material processing with hydrogen and carbon monoxide on Mars

    NASA Technical Reports Server (NTRS)

    Hepp, Aloysius F.; Linne, Diane L.; Landis, Geoffrey A.

    1991-01-01

    Several novel proposals are examined for propellant production from carbon dioxide and monoxide and hydrogen. Potential uses were also examined of CO as a fuel or as a reducing agent in metal oxide processing as obtained or further reduced to carbon. Hydrogen can be reacted with CO to produce a wide variety of hydrocarbons, alcohols, and other organic compounds. Methanol, produced by Fischer-Tropsch chemistry may be useful as a fuel; it is easy to store and handle because it is a liquid at Mars temperatures. The reduction of CO2 to hydrocarbons such as methane or acetylene can be accomplished with hydrocarbons. Carbon monoxide and hydrogen require cryogenic temperatures for storage as liquid. Noncryogenic storage of hydrogen may be accomplished using hydrocarbons, inorganic hydrides, or metal hydrides. Noncryogenic storage of CO may be accomplished in the form of iron carbonyl (FE(CO)5) or other metal carbonyls. Low hydrogen content fuels such as acetylene (C2H2) may be effective propellants with low requirements for earth derived resources. The impact on manned Mars missions of alternative propellant production and utilization is discussed.

  3. A Hydrogen-Deuterium Exchange Study on Nickel-based Binary-Ternary Amorphous and Crystalline Membranes

    NASA Astrophysics Data System (ADS)

    Adibhatla, Anasuya

    Hydrogen is a major role player in current global sustainable energy scenario. Research around the world is carried out to harness hydrogen from all possible sources. One of these sources is water gas shift reaction after the coal gasification process. Sustainable infrastructure can be viable in countries like USA and Australia, making this process viable. Various methods are used to harness this hydrogen from the water gas. One of these methods is the use of inorganic membranes based on Pd, Ag, Ni, Zr and other transition metals. Pd addition to the membranes makes the membranes more expensive for commercial use. Various bulk properties like hydrogen permeation and absorption are studied on Pd and Pd-based alloys. Alternate alloys based on Ni, V, Ta etc are being studied to substitute the use of Pd making this technology more cost efficient. A current balance in research in this area is fund to exist by coating the non-precious metal membranes with Pd to improve the surface interaction with hydrogen. The nature of membranes used for hydrogen separation is important aspect for the overall performance. Crystalline materials provide better bulk properties, however, are not durable under high temperature and hydrogen pressure. In this research, non-Pd coated Ni-based amorphous membranes were made by melt spin technique, which have been studied for their surface properties. Gas phase H2-D2 exchange reaction has been carried out on the membrane surface. This provides a measure of catalytic activity of the above mentioned membranes. More studies included the crystallographic phase change determination, bulk hydrogen solubility measurements, surface conduction measurements and surface morphological studies. During this research, it has been observed that crystalline materials provide more surface activity for hydrogen than their amorphous counterparts. Ni64Zr36 alloy has been shown to exhibit similar kinetic rates as metallic Ni. Also, microkinetic analysis was performed to determine the heat of hydrogen absorption and desorption on the alloy surface. Electrochemical Impedance Spectroscopy was conducted on the membranes to determine the surface resistance and it was found that Ni64Zr36 as-spun ribbon displayed highest resistance while Ni60Ta20Zr20 showed lowest resistance. Absorption studies on Ni60V 40 binary alloy and Ni60V20Zr20 ternary alloy indicated that the addition of Zr to these non-coated alloys increased the hydrogen solubility in the bulk. SEM and TEM analyses showed the presence of possible nano crystalline phases in Ni64Zr36 membrane. XRD and SEM studies conducted on post treated samples showed the possible phase segregation of Ni and ZrO2. Ni60Nb40 did not show any phase transformations after hydrogen heat treated unlike its ternary composition, Ni60Nb20Zr20. It is noteworthy to mention that bubbles were observed during SEM on Ni 64Zr36 post-treated sample on the surface due to possible hydrogen trapping and subsequent release of hydrogen gas.

  4. Isotopic fractionation of carbon, deuterium, and nitrogen: a full chemical study

    NASA Astrophysics Data System (ADS)

    Roueff, E.; Loison, J. C.; Hickson, K. M.

    2015-04-01

    Context. The increased sensitivity and high spectral resolution of millimeter telescopes allow the detection of an increasing number of isotopically substituted molecules in the interstellar medium. The 14N/15N ratio is difficult to measure directly for molecules containing carbon. Aims: Using a time-dependent gas-phase chemical model, we check the underlying hypothesis that the 13C/12C ratio of nitriles and isonitriles is equal to the elemental value. Methods: We built a chemical network that contains D, 13C, and 15N molecular species after a careful check of the possible fractionation reactions at work in the gas phase. Results: Model results obtained for two different physical conditions that correspond to a moderately dense cloud in an early evolutionary stage and a dense, depleted prestellar core tend to show that ammonia and its singly deuterated form are somewhat enriched in 15N, which agrees with observations. The 14N/15N ratio in N2H+ is found to be close to the elemental value, in contrast to previous models that obtain a significant enrichment, because we found that the fractionation reaction between 15N and N2H+ has a barrier in the entrance channel. The high values of the N2H+/15NNH+ and N2H+/N15NH+ ratios derived in L1544 cannot be reproduced in our model. Finally, we find that nitriles and isonitriles are in fact significantly depleted in 13C, thereby challenging previous interpretations of observed C15N, HC15N, and H15NC abundances from 13C containing isotopologues. Appendices are available in electronic form at http://www.aanda.org

  5. Hydrogen pumping in amorphous deutered carbon films irradiated by swift heavy ions

    NASA Astrophysics Data System (ADS)

    Pawlak, F.; Balanzat, E.; Dufour, Ch.; Laurent, A.; Paumier, E.; Perriere, J.; Stoquert, J. P.; Toulemonde, M.

    1997-02-01

    Deutered amorphous carbon films have been irradiated at GANIL using 5 to 10 MeV/u sulfur beam with an electronic stopping power from 1 to 1.4 keV/nm. Such films have been deposited on silicon substrates by decomposition of CD 4 gas containing 10% of CH 4 in a dc multipolar plasma. After irradiation, they were analyzed firstly using absorption infrared spectroscopy to determine the number of CD and CH bonds. Secondly, deuterium, hydroge and carbon areal density were determined by ERDA and RBS. The results analysis shows a decrease of the atomic ratio ( {D}/{C}) as well as CD bonds down to a minimum value versus the fluence without a threshold fluence and in the same time an increase of the atomic ratio ( {H}/{C}) as well as CH bonds to a maximum value. So we may conclude that the hydrogen pumped after the irradiation is stabilized on broken (or unpaired) bonds.

  6. Properties Of Plasma-Deposited Amorphous Hydrogenated Carbon

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Pouch, John J.; Alterovitz, Samuel A.

    1992-01-01

    Report reviews experimental research on plasma-deposited films of hydrogenated amorphous carbon. Such films exhibit electrical resistivity, semi-transparency, mechanical hardness, and chemical inertness. Useful as gate dielectrics and passivating layers in semiconductor devices, insulators for metal/insulator/metal devices, and masks in nanometer lithography. Show promise as wear-resistant, hard solid lubricating coats for bearings and optical components.

  7. Mean excitation energy for molecules of hydrogen and carbon

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Kamaratos, E.

    1981-01-01

    The Gordon-Kim electron gas model of molecular bonding is used to calculate correction factors for the Bragg rule for molecules of hydrogen and carbon. General rules for molecular mean excitation energies are obtained that agree to about 4% with experimental values.

  8. Storage of Hydrogen in Single-Walled Carbon Nanotubes

    SciTech Connect

    Dillon, A. C.; Jones, K. M.; Bekkedahl, T. A.; Kiang, C. H.; Bethune, D. S.; Heben, M. J.

    1997-03-27

    Pores of molecular dimensions can adsorb large quantities of gases owing to the enhanced density of the adsorbed material inside the pores, a consequence of the attractive potential of the pore walls. Pederson and Broughton have suggested that carbon nanotubes, which have diameters of typically a few nanometres, should be able to draw up liquids by capillarity, and this effect has been seen for low-surface-tension liquids in large-diameter, multi-walled nanotubes. Here we show that a gas can condense to high density inside narrow, single-walled nanotubes (SWNTs). Temperature-programmed desorption spectroscopy shows that hydrogen will condense inside SWNTs under conditions that do not induce adsorption within a standard mesoporous activated carbon. The very high hydrogen uptake in these materials suggests that they might be effective as a hydrogen-storage material for fuel-cell electric vehicles.

  9. Estimating groundwater mixing and origin in an overexploited aquifer in Guanajuato, Mexico, using stable isotopes (strontium-87, carbon-13, deuterium and oxygen-18).

    PubMed

    Horst, Axel; Mahlknecht, Jürgen; Merkel, Broder J

    2007-12-01

    Stable Isotopes (strontium-87, deuterium and oxygen-18, carbon-13) have been used to reveal different sources of groundwater and mixing processes in the aquifer of the Silao-Romita Valley in the state of Guanajuato, Mexico. Calcite dissolution appeared to be the main process of strontium release leading to relatively equal (87)Sr/(86)Sr ratios of 0.7042-0.7062 throughout the study area which could be confirmed by samples of carbonate rocks having similar Sr ratios (0.7041-0.7073). delta(13)C values (-11.91- -6.87 per thousand VPDB) of groundwaters confirmed the solution of carbonates but indicated furthermore influences of soil-CO(2). Deuterium and (18)O contents showed a relatively narrow range of-80.1- -70.0 per thousand VSMOW and -10.2- -8.8 per thousand, VSMOW, respectively but are affected by evaporation and mixing processes. The use of delta(13)C together with (87)Sr/(86)Sr revealed three possible sources: (i) carbonate-controlled waters showing generally higher Sr-concentrations, (ii) fissure waters with low-strontium contents and (iii) infiltrating water which is characterized by low delta(13)C and (87)Sr/(86)Sr ratios. The third component is affected by evaporation processes taking place before and during infiltration which might be increased by extraction and reinfiltration (irrigation return flow). PMID:18041622

  10. Retention and enrichment of tungsten-containing carbon films under deuterium beam impact

    NASA Astrophysics Data System (ADS)

    Sauter, P. A.; Balden, M.

    2013-09-01

    Retention and enrichment of a model system for mixed layers, tungsten-containing carbon films (a-C:W), were investigated with respect to the interaction with D ions. a-C:W was exposed to a mass-separated, mono-energetic D beam (200 eV/D, 1.2 × 1015 D cm-2 s-1). The W concentration in the films (0-7.5 at.%), the specimen temperature during D beam exposure (300-1300 K) and the fluence (Φ) of incident D (1015-1020 D cm-2) were varied. Analysis of retention and enrichment were performed by nuclear reaction analysis and Rutherford backscattering spectrometry, respectively. At 300 K and fluences up to 1019 D cm-2, the increase of the D inventory with fluence in a-C:W cannot be distinguished from a-C and pyrolytic graphite, e.g., above ˜1017 D cm-2 the D inventory increases with fluence according to Φx (x = 0.1). Above a fluence of 1019 D cm-2, however, the D inventory depends strongly on the W concentration. At a fluence of 1020 D cm-2 the D inventory is increased to the 1.5-fold of the D inventory of pyrolytic graphite for 1% and 2.5% a-C:W and it is decreased to the half value of the D inventory of pyrolytic graphite for 7.5% a-C:W. At temperatures above 300 K, following trends are observed: With increasing temperature, the D inventory increases more strongly with fluence and D reaches depths far beyond the width of the ion range. However, the D inventory does not increase with fluence according to Φx, especially at fluences above 1019 D cm-2. The peak near the surface (<70 nm) in Fig. 2a, which was increasing with decreasing temperature, is caused by an accumulation of D at surface near zones, which can be reached by energetic D. This is interpreted in the following way: Bonding states with a lower binding energy than the thermal energy at 900 K, which were unoccupied before decreasing the temperature, were becoming occupied during the decrease of the temperature; the saturation level of the implantation zone is lowered at 900 K compared to 300 K. Before the decrease of the temperature, D was able to reach depths (⩽600 nm; Fig. 2a), which are beyond the peak near the surface and thus cannot be reached by energetic D. Consequently, it can be concluded that the tail to lower energies in the NRA spectrum is caused by a diffusive process of D into depth (˜90% of the total inventory), i.e., a-C:W allows a kind of diffusive transport of D into depths beyond the implantation zone. (Note that these depths will be denoted as the diffusion depth in the following.) Bonding states occupied at 900 K during beam exposure are not depleted after the exposure is stopped (Fig. 2b). This interpretation is confirmed by the release of D towards the surface after the heat treatment at 1300 K (Fig. 2c). Additional bonding states, which were occupied at 1100 K, were depleted raising the temperature above 1100 K. Heat treatment at 1100 K and at 1300 K (Fig. 2c) showed a diffusive transport of D, which is directed towards the surface without the presence of an impacting D beam. In other words, the presence of a D beam is a necessary condition for the diffusive transport of D into depth.

  11. Atypical Hydrogen Uptake on Chemically Activated, Ultramicroporous Carbon

    SciTech Connect

    Bhat, Vinay V; Contescu, Cristian I; Gallego, Nidia C; Baker, Frederick S

    2010-01-01

    Hydrogen adsorption at near-ambient temperatures on ultramicroporous carbon (UMC), derived through secondary chemical activation from a wood-based activated carbon was studied using volumetric and gravimetric methods. The results showed that physisorption is accompanied by a process of different nature that causes slow uptake at high pressures and hysteresis on desorption. In combination, this results in unusually high levels of hydrogen uptake at near-ambient temperatures and pressures (e.g. up to 0.8 wt % at 25 oC and 2 MPa). The heat of adsorption corresponding to the slow process leading to high uptake (17 20 kJ/mol) is higher than usually reported for carbon materials, but the adsorption kinetics is slow, and the isotherms exhibit pronounced hysteresis. These unusual properties were attributed to contributions from polarization-enhanced physisorption caused by traces of alkali metals residual from chemical activation. The results support the hypothesis that polarization-induced physisorption in high surface area carbons modified with traces of alkali metal ions is an alternate route for increasing the hydrogen storage capacity of carbon adsorbents.

  12. The calcium-modulated structures of calmodulin and S100b proteins are useful to monitor hydrogen/deuterium exchange efficiency using matrix-assisted laser desorption ionization time-of-flight mass spectrometry.

    PubMed

    Pingerelli, Peter L; Ozols, Victor V; Saleem, Haroon; Anderson, Carly R; Burns, Richard S

    2009-01-01

    Hydrogen/deuterium exchange (HDX) using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF) is a sensitive, salt-tolerant and high-throughput method useful to probe protein conformation and molecular interactions. However, a drawback of the MALDI HDX technique is that sample preparation methods can typically result in higher levels of artificial deuterium in-exchange and/or hydrogen back- exchange just prior to or during mass analysis; this may impair data reproducibility and impede structural and kinetic data interpretation. While methods to minimize effects of back-exchange during protein analyte deposition on MALDI plates have been reported, this study presents a readily available, highly sensitive protein control set to facilitate rapid MALDI HDX protocol workup. The Ca(2+)-induced solvent accessible surface area (ASA) changes of calmodulin (CaM) and S100 proteins were employed to monitor and optimize HDX protocol efficiency. Under non- stringent room temperature conditions, the Ca(2+)-induced deuterium exchange of CaM, DeltaD(ca2+ -apo), MH(+) shifts -17 to -24 Da, while S100 DeltaD(ca2+ -apo) MH(+) shifts +8 to +12 Da. By comparing the divergent CaM and S100 Ca(2+)-induced deuterium mass shift differences, HDX sample workup and MALDI plate spotting conditions can easily be monitored. PMID:19940340

  13. Formaldehyde metabolism by Escherichia coli. Carbon and solvent deuterium incorporation into glycerol, 1,2-propanediol, and 1,3-propanediol

    SciTech Connect

    Hunter, B.K.; Nicholls, K.M.; Sanders, J.K.

    1985-07-16

    Escherichia coli were grown on 14.3% uniformly TC-labeled glucose as the sole carbon source and challenged anaerobically with 90% TC-labeled formaldehyde. The major multiply labeled metabolites were identified by TC NMR spectroscopy to be glycerol and 1,2-propanediol, and a minor metabolite was shown to be 1,3-propanediol. In each case, formaldehyde is incorporated only into the C1 position. A novel form of TC NMR isotope dilution analysis of the major products reveals that all the 1,2-diol C1 is formaldehyde derived but that about 40% of the glycerol C1 is derived from bacterial sources. Glycerokinase converted the metabolite (1- TC)glycerol to equal amounts of (3- TC)glycerol 3-phosphate and (1- TC)glycerol 3-phosphate, demonstrating that the metabolite is racemic. When ( TC)formaldehyde incubation was carried out in H2O/D2O mixtures, deuterium incorporation was detected by beta- and gamma-isotope shifts. The 1,3-diol is deuterium labeled only at C2 and only once, while the 1,2-diol and glycerol are each labeled independently at both C2 and C3; C3 is multiply labeled. Deuterium incorporation levels are different for each metabolite, indicating that the biosynthetic pathways probably diverge early.

  14. Stable Hydrogen and Carbon Isotope Fractionation during Microbial Toluene Degradation: Mechanistic and Environmental Aspects†

    PubMed Central

    Morasch, Barbara; Richnow, Hans H.; Schink, Bernhard; Meckenstock, Rainer U.

    2001-01-01

    Primary features of hydrogen and carbon isotope fractionation during toluene degradation were studied to evaluate if analysis of isotope signatures can be used as a tool to monitor biodegradation in contaminated aquifers. D/H hydrogen isotope fractionation during microbial degradation of toluene was measured by gas chromatography. Per-deuterated toluene-d8 and nonlabeled toluene were supplied in equal amounts as growth substrates, and kinetic isotope fractionation was calculated from the shift of the molar ratios of toluene-d8 and nondeuterated toluene. The D/H isotope fractionation varied slightly for sulfate-reducing strain TRM1 (slope of curve [b] = −1.219), Desulfobacterium cetonicum (b = −1.196), Thauera aromatica (b = −0.816), and Geobacter metallireducens (b = −1.004) and was greater for the aerobic bacterium Pseudomonas putida mt-2 (b = −2.667). The D/H isotope fractionation was 3 orders of magnitude greater than the 13C/12C carbon isotope fractionation reported previously. Hydrogen isotope fractionation with nonlabeled toluene was 1.7 and 6 times less than isotope fractionation with per-deuterated toluene-d8 and nonlabeled toluene for sulfate-reducing strain TRM1 (b = −0.728) and D. cetonicum (b = −0.198), respectively. Carbon and hydrogen isotope fractionation during toluene degradation by D. cetonicum remained constant over a growth temperature range of 15 to 37°C but varied slightly during degradation by P. putida mt-2, which showed maximum hydrogen isotope fractionation at 20°C (b = −4.086) and minimum fractionation at 35°C (b = −2.138). D/H isotope fractionation was observed only if the deuterium label was located at the methyl group of the toluene molecule which is the site of the initial enzymatic attack on the substrate by the bacterial strains investigated in this study. Use of ring-labeled toluene-d5 in combination with nondeuterated toluene did not lead to significant D/H isotope fractionation. The activity of the first enzyme in the anaerobic toluene degradation pathway, benzylsuccinate synthase, was measured in cell extracts of D. cetonicum with an initial activity of 3.63 mU (mg of protein)−1. The D/H isotope fractionation (b = −1.580) was 30% greater than that in growth experiments with D. cetonicum. Mass spectroscopic analysis of the product benzylsuccinate showed that H atoms abstracted from the toluene molecules by the enzyme were retained in the same molecules after the product was released. Our findings revealed that the use of deuterium-labeled toluene was appropriate for studying basic features of D/H isotope fractionation. Similar D/H fractionation factors for toluene degradation by anaerobic bacteria, the lack of significant temperature dependence, and the strong fractionation suggest that analysis of D/H fractionation can be used as a sensitive tool to assess degradation activities. Identification of the first enzyme reaction in the pathway as the major fractionating step provides a basis for linking observed isotope fractionation to biochemical reactions. PMID:11571192

  15. Restricted dynamics of molecular hydrogen confined in activated carbon nanopores

    SciTech Connect

    Contescu, Cristian I; Saha, Dipendu; Gallego, Nidia C; Mamontov, Eugene; Kolesnikov, Alexander I; Bhat, Vinay V

    2012-01-01

    Quasi-elastic neutron scattering was used for characterization of dynamics of molecular hydrogen confined in narrow nanopores of two activated carbon materials: PFAC (derived from polyfurfuryl alcohol) and UMC (ultramicroporous carbon). Fast, but incomplete ortho-para conversion was observed at 10 K, suggesting that scattering originates from the fraction of unconverted ortho isomer which is rotation-hindered because of confinement in nanopores. Hydrogen molecules entrapped in narrow nanopores (<7 ) were immobile below 22-25 K. Mobility increased rapidly with temperature above this threshold, which is 8 K higher than the melting point of bulk hydrogen. Diffusion obeyed fixed-jump length mechanism, indistinguishable between 2D and 3D processes. Thermal activation of diffusion was characterized between ~22 and 37 K, and structure-dependent differences were found between the two carbons. Activation energy of diffusion was higher than that of bulk solid hydrogen. Classical notions of liquid and solid do not longer apply for H2 confined in narrow nanopores.

  16. Carbon-palladium films as gas sensors (hydrogen, ammonia, methane)

    NASA Astrophysics Data System (ADS)

    Rymarczyk, Joanna; Kamińska, Anna; Krawczyk, Sławomir

    2014-11-01

    In this paper we present the results of the resistances changes of carbon-palladium films under the influences of gas like hydrogen, ammonia and methane. Our research has shown that carbon-palladium films (C-Pd films) according to the form and the structure in which they appear, they can respond to a variety of gases. The C-Pd film obtained by Physical Vapor Deposition (PVD) method is sensitive to hydrogen and do not respond to the ammonia. Thermal modification of the C-Pd film in Chemical Vapor Deposition (CVD) process affects the morphology of the film, increases its resistance and it causes that this film begins to react to the ammonia. This change causes that this film stops responding on hydrogen. Film sensitive to methane was obtained by changing the technology conditions of the PVD process. The reaction of C-Pd film on the hydrogen and the ammonia is increase resistance, while film sensitive to methane reacts by decrease of initial resistance value. In both cases, the changes are reversible after cleaning by air atmosphere. Different varieties of C-Pd films can be used to build selective sensors for hydrogen, ammonia and methane.

  17. Carbon Nanotube/Magnesium Composite as a Hydrogen Source.

    PubMed

    Yu, Min Kyu; Se, Kwon Oh; Kim, Min Joong; Hwang, Jae Won; Yoon, Byoung Young; Kwon, Hyuk Sang

    2015-11-01

    Hydrogen produced using the steam reforming process contains sulfur and carbon monoxide that are harmful to the Pt catalyst in proton-exchange-membrane fuel cells (PEMFCs). However, CO-free hydrogen can be generated from the hydrolysis of either Al in strongly alkaline water or Mg in neutral water with chlorides such as sea water. The hydrogen generation rate from the hydrolysis of Mg is extremely slow and linearly proportional to the corrosion rate of Mg in chloride water. In this work, we fabricated a carbon nanotube (CNT)--reinforced Mg--matrix composite by Spark Plasma Sintering as a fast hydrogen generation source for a PEMFC. The CNTs distributed in the Mg matrix act as numerous local cathodes, and hence cause severe galvanic corrosion between the Mg-matrix anode and CNT-cathode in NaCl solution. It was found that the hydrogen generation rate from the hydrolysis of the 5 vol.% CNT/Mg composite is 3300 times faster than that of the Mg without CNTs due primarily to the galvanic corrosion effect. PMID:26726603

  18. Closed system Fischer-Tropsch synthesis over meteoritic iron, iron ore and nickel-iron alloy. [deuterium-carbon monoxide reaction catalysis

    NASA Technical Reports Server (NTRS)

    Nooner, D. W.; Gibert, J. M.; Gelpi, E.; Oro, J.

    1976-01-01

    Experiments were performed in which meteoritic iron, iron ore and nickel-iron alloy were used to catalyze (in Fischer-Tropsch synthesis) the reaction of deuterium and carbon monoxide in a closed vessel. Normal alkanes and alkenes and their monomethyl substituted isomers and aromatic hydrocarbons were synthesized. Iron oxide and oxidized-reduced Canyon Diablo used as Fischer-Tropsch catalysts were found to produce aromatic hydrocarbons in distributions having many of the features of those observed in carbonaceous chondrites, but only at temperatures and reaction times well above 300 C and 6-8 h.

  19. Measurements of the Neutron Cross Sections of Hydrogen and Deuterium in H{sub 2}O-D{sub 2}O Mixtures Using the Deep Inelastic Neutron-Scattering Technique

    SciTech Connect

    Blostein, J. J.; Palomino, L. A. Rodriguez; Dawidowski, J.

    2009-03-06

    We investigated the neutron cross sections of hydrogen and deuterium by means of the deep inelastic neutron-scattering technique in H{sub 2}O-D{sub 2}O mixtures. The interest in this work was to examine the anomalous behavior in the hydrogen neutron cross section reported in the past in similar experiments that raised a yet unsettled controversy. The measurements were made at the Bariloche pulsed neutron source (Argentina) in pure H{sub 2}O and D{sub 2}O, with mixtures of molar concentrations of deuterium of x{sub D}=0.3 and 0.4, at room temperature, under the same experimental conditions as the former experiments. The results are in good agreement with the standard cross sections and are incompatible with the anomalies pointed out.

  20. Differentiating the role of lithium and oxygen in retaining deuterium on lithiated plasma-facing components

    NASA Astrophysics Data System (ADS)

    Taylor, Chase

    2013-10-01

    Lithium wall conditioning has been implemented in nearly a dozen fusion devices, resulting in significantly improved plasma performance. Improvements are manifest as a reduction and eventual elimination of edge localized modes, reduced edge neutral density, reduced deuterium recycling, and some reduction in impurities. Initially, researchers assumed that lithium, via a direct lithium-deuterium bond, was directly responsible for these improvements. Our experiments and atomistic simulations have revealed that lithium coatings play a much more indirect role in improving plasma performance. The presence of oxygen in tokamaks is ubiquitously viewed as unfavorable. However, recent results show that lithium reduces oxygen impurities and surprisingly uses the oxygen to retain deuterium. Experiments using X-ray photoelectron spectroscopy identify that oxygen immediately begins to accumulate on lithium conditioned surfaces. Tight-binding density functional theory simulations tested various carbon matrices with and without lithium, oxygen, and hydrogen, and identified that oxygen plays the key role in retaining deuterium. In fact, a simulated PFC with 20% oxygen in carbon retains more deuterium than does 20% lithium in carbon. Recent experiments implanted oxygen in graphite to match simulations; however, we were unable to achieve the simulated results because all implanted oxygen was released upon deuterium bombardment. We therefore conclude that while oxygen retains deuterium, lithium plays an indispensible role in this process. Lithium attracts and retains oxygen, and then oxygen binds and retains deuterium. Work supported by USDOE Contracts DE-FG02-08ER54990 and DOE ID Field Office contract DE-AC07-05ID14517.

  1. Using hydrogen deuterium exchange mass spectrometry to engineer optimized constructs for crystallization of protein complexes: Case study of PI4KIIIβ with Rab11.

    PubMed

    Fowler, Melissa L; McPhail, Jacob A; Jenkins, Meredith L; Masson, Glenn R; Rutaganira, Florentine U; Shokat, Kevan M; Williams, Roger L; Burke, John E

    2016-04-01

    The ability of proteins to bind and interact with protein partners plays fundamental roles in many cellular contexts. X-ray crystallography has been a powerful approach to understand protein-protein interactions; however, a challenge in the crystallization of proteins and their complexes is the presence of intrinsically disordered regions. In this article, we describe an application of hydrogen deuterium exchange mass spectrometry (HDX-MS) to identify dynamic regions within type III phosphatidylinositol 4 kinase beta (PI4KIIIβ) in complex with the GTPase Rab11. This information was then used to design deletions that allowed for the production of diffraction quality crystals. Importantly, we also used HDX-MS to verify that the new construct was properly folded, consistent with it being catalytically and functionally active. Structures of PI4KIIIβ in an Apo state and bound to the potent inhibitor BQR695 in complex with both GTPγS and GDP loaded Rab11 were determined. This hybrid HDX-MS/crystallographic strategy revealed novel aspects of the PI4KIIIβ-Rab11 complex, as well as the molecular mechanism of potency of a PI4K specific inhibitor (BQR695). This approach is widely applicable to protein-protein complexes, and is an excellent strategy to optimize constructs for high-resolution structural approaches. PMID:26756197

  2. Using hydrogen deuterium exchange mass spectrometry to engineer optimized constructs for crystallization of protein complexes: Case study of PI4KIIIβ with Rab11

    PubMed Central

    Fowler, Melissa L.; McPhail, Jacob A.; Jenkins, Meredith L.; Masson, Glenn R.; Rutaganira, Florentine U.; Shokat, Kevan M.; Williams, Roger L.

    2016-01-01

    Abstract The ability of proteins to bind and interact with protein partners plays fundamental roles in many cellular contexts. X‐ray crystallography has been a powerful approach to understand protein‐protein interactions; however, a challenge in the crystallization of proteins and their complexes is the presence of intrinsically disordered regions. In this article, we describe an application of hydrogen deuterium exchange mass spectrometry (HDX‐MS) to identify dynamic regions within type III phosphatidylinositol 4 kinase beta (PI4KIIIβ) in complex with the GTPase Rab11. This information was then used to design deletions that allowed for the production of diffraction quality crystals. Importantly, we also used HDX‐MS to verify that the new construct was properly folded, consistent with it being catalytically and functionally active. Structures of PI4KIIIβ in an Apo state and bound to the potent inhibitor BQR695 in complex with both GTPγS and GDP loaded Rab11 were determined. This hybrid HDX‐MS/crystallographic strategy revealed novel aspects of the PI4KIIIβ‐Rab11 complex, as well as the molecular mechanism of potency of a PI4K specific inhibitor (BQR695). This approach is widely applicable to protein‐protein complexes, and is an excellent strategy to optimize constructs for high‐resolution structural approaches. PMID:26756197

  3. Structure-dependent degradation of polar compounds in weathered oils observed by atmospheric pressure photo-ionization hydrogen/deuterium exchange ultrahigh resolution mass spectrometry.

    PubMed

    Islam, Ananna; Kim, Donghwi; Yim, Un Hyuk; Shim, Won Joon; Kim, Sunghwan

    2015-10-15

    The resin fractions of fresh mixtures of three oils spilled during the M/V Hebei Spirit oil spill, as well as weathered oils collected at weathering stages II and IV from the oil spill site were analyzed and compared by atmospheric pressure photo-ionization hydrogen/deuterium exchange mass spectrometry (HDX MS). The significantly decreased abundance of N(+) and [N-H+D](+) ions suggested that secondary and tertiary amine-containing compounds were preferentially degraded during the early stage of weathering. [N+H](+) and [N+D](+) ions previously attributed to pyridine-type compounds degraded more slowly than secondary and tertiary amine-containing compounds. The preferential degradation of nitrogen-containing compounds was confirmed by photo-degradation experiments using 15 standard compounds. In addition, significant increases of [S1O1+H](+) and [S1O1+D](+) ions with higher DBE values were observed from fresh oil mixtures as compared to stages II and IV samples, and that could be linked with the decrease of higher DBE compounds of the S1 class. This study presented convincing arguments and evidence demonstrating that secondary and tertiary amines were more vulnerable to photo-degradation than compounds containing pyridine, and hence, preferential degradation depending on chemical structures must be considered in the production of hazardous or toxic components. PMID:25913675

  4. Fluoroketone Inhibition of Ca2+-Independent Phospholipase A2 through Binding Pocket Association Defined by Hydrogen/Deuterium Exchange and Molecular Dynamics

    PubMed Central

    2012-01-01

    The mechanism of inhibition of group VIA Ca2+-independent phospholipase A2 (iPLA2) by fluoroketone (FK) ligands is examined by a combination of deuterium exchange mass spectrometry (DXMS) and molecular dynamics (MD). Models for iPLA2 were built by homology with the known structure of patatin and equilibrated by extensive MD simulations. Empty pockets were identified during the simulations and studied for their ability to accommodate FK inhibitors. Ligand docking techniques showed that the potent inhibitor 1,1,1,3-tetrafluoro-7-phenylheptan-2-one (PHFK) forms favorable interactions inside an active-site pocket, where it blocks the entrance of phospholipid substrates. The polar fluoroketone headgroup is stabilized by hydrogen bonds with residues Gly486, Gly487, and Ser519. The nonpolar aliphatic chain and aromatic group are stabilized by hydrophobic contacts with Met544, Val548, Phe549, Leu560, and Ala640. The binding mode is supported by DXMS experiments showing an important decrease of deuteration in the contact regions in the presence of the inhibitor. The discovery of the precise binding mode of FK ligands to the iPLA2 should greatly improve our ability to design new inhibitors with higher potency and selectivity. PMID:23256506

  5. Correlating excipient effects on conformational and storage stability of an IgG1 monoclonal antibody with local dynamics as measured by hydrogen/deuterium-exchange mass spectrometry.

    PubMed

    Manikwar, Prakash; Majumdar, Ranajoy; Hickey, John M; Thakkar, Santosh V; Samra, Hardeep S; Sathish, Hasige A; Bishop, Steven M; Middaugh, C Russell; Weis, David D; Volkin, David B

    2013-07-01

    The effects of sucrose and arginine on the conformational and storage stability of an IgG1 monoclonal antibody (mAb) were monitored by differential scanning calorimetry (DSC) and size-exclusion chromatography (SEC), respectively. Excipient effects on protein physical stability were then compared with their effects on the local flexibility of the mAb in solution at pH 6, 25°C using hydrogen/deuterium-exchange mass spectrometry (H/D-MS). Compared with a 0.1 M NaCl control, sucrose (0.5 M) increased conformational stability (T(m) values), slowed the rate of monomer loss, reduced the formation of insoluble aggregates, and resulted in a global trend of small decreases in local flexibility across most regions of the mAb. In contrast, the addition of arginine (0.5 M) decreased the mAb's conformational stability, increased the rate of loss of monomer with elevated levels of soluble and insoluble aggregates, and led to significant increases in the local flexibility in specific regions of the mAb, most notably within the constant domain 2 of the heavy chain (C(H)2). These results provide new insights into the effect of sucrose and arginine on the local dynamics of IgG1 domains as well as preliminary correlations between local flexibility within specific segments of the C(H)2 domain (notably heavy chain 241-251) and the mAb's overall physical stability. PMID:23620222

  6. Load-dependent destabilization of the γ-rotor shaft in FOF1 ATP synthase revealed by hydrogen/deuterium-exchange mass spectrometry.

    PubMed

    Vahidi, Siavash; Bi, Yumin; Dunn, Stanley D; Konermann, Lars

    2016-03-01

    FoF1 is a membrane-bound molecular motor that uses proton-motive force (PMF) to drive the synthesis of ATP from ADP and Pi. Reverse operation generates PMF via ATP hydrolysis. Catalysis in either direction involves rotation of the γε shaft that connects the α3β3 head and the membrane-anchored cn ring. X-ray crystallography and other techniques have provided insights into the structure and function of FoF1 subcomplexes. However, interrogating the conformational dynamics of intact membrane-bound FoF1 during rotational catalysis has proven to be difficult. Here, we use hydrogen/deuterium exchange mass spectrometry to probe the inner workings of FoF1 in its natural membrane-bound state. A pronounced destabilization of the γ C-terminal helix during hydrolysis-driven rotation was observed. This behavior is attributed to torsional stress in γ, arising from γ⋅⋅⋅α3β3 interactions that cause resistance during γ rotation within the apical bearing. Intriguingly, we find that destabilization of γ occurs only when FoF1 operates against a PMF-induced torque; the effect disappears when PMF is eliminated by an uncoupler. This behavior resembles the properties of automotive engines, where bearings inflict greater forces on the crankshaft when operated under load than during idling. PMID:26884184

  7. The hydrogen and carbon isotopic composition of methane from natural gases of various origins

    NASA Astrophysics Data System (ADS)

    Schoell, Martin

    1980-05-01

    The deuterium concentrations (δD vs SMOW) of biogenic methanes from world-wide occurrences range from -180 to -280%. and were found to be depleted in deuterium by approx. 160%. compared to the deuterium concentration of their associated waters. Theoretical considerations support this relationship to be the result of bacterial transformation of CO 2 to methane and is therefore indicative of the biogenic origin of methane. Thermogenic gases with high C 2+ concentrations (wet gases associated with crude oil) have D/H ratios from -260 to -150%. with deuterium contents tending to increase with decreasing wetness. Dry gases which are not associated with petroleum are more enriched in deuterium (-180 to -130%.) and show an increase in deuterium with increasing rank of the source beds as it is similarly known for carbon-13. Many dry gases in young sedimentary basins were found to contain significant amounts of C 2+ hydrocarbons. These gases cannot be grouped with either the biogenic or thermogenic gases and their methane is concluded to be of mixed biogenic and thermochemical origin. Using a δ 13C /δD diagrammatic display of the isotope data of methanes the various genetic groups of natural gases can be defined more clearly.

  8. Electronic and Mechanical Properties of Hydrogen Functionalized Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Yang, Liu; Han, Jie; Jaffe, Richard L.; Arnold, Jim (Technical Monitor)

    2001-01-01

    We examined the electronic and mechanical properties of hydrogen functionalized carbon nanotubes. The functionalization pattern covers two extreme groups. One group has randomly selected functionalization sites including one to twenty percent of the carbon atoms. The other group has regularly patterned functional sites parallel to the tube axis. Metallic, small-gap semiconducting and large-gap semiconducting carbon nanotubes are studied. The results reveal that the electronic properties of the tubes are very sensitive to the degree of functionalization, with even one percent functionalization being enough to render metallic tubes semiconducting. On the other hand, the mechanical properties, like tensile modulus, are much less sensitive to functionalization. For carbon nanotubes functionalized with specific patterns, the electric properties depends strongly on the nature of the functionalization pattern.

  9. Catalytic carbon membranes for hydrogen production. Final report

    SciTech Connect

    Damle, A.S.; Gangwal, S.K.

    1992-01-01

    Commercial carbon composite microfiltration membranes may be modified for gas separation applications by providing a gas separation layer with pores in the 1- to 10-nm range. Several organic polymeric precursors and techniques for depositing a suitable layer were investigated in this project. The in situ polymerization technique was found to be the most promising, and pure component permeation tests with membrane samples prepared with this technique indicated Knudsen diffusion behavior. The gas separation factors obtained by mixed-gas permeation tests were found to depend strongly on gas temperature and pressure indicating significant viscous flow at high-pressure conditions. The modified membranes were used to carry out simultaneous water gas shift reaction and product hydrogen separation. These tests indicated increasing CO conversions with increasing hydrogen separation. A simple process model was developed to simulate a catalytic membrane reactor. A number of simulations were carried out to identify operating conditions leading to product hydrogen concentrations over 90 percent. (VC)

  10. Hydrogenated 5-carbon compound and method of making

    DOEpatents

    Elliott, Douglas C.; Frye, John G.

    1999-01-01

    The present invention is based upon the surprising discovery that a 5-carbon compound selected from the group of 4-oxopentanoic acid, at least one lactone of 4-oxopentanoic acid, and combinations thereof, may be hydrogenated with a bimetallic catalyst of a noble metal in combination with a second metal and preserve the pendant methyl group. It was further unexpectedly discovered that the same conditions of bimetallic catalyst in the presence of hydrogen are useful for catalyzing the different intermediate reactions for example angelicalactone to gamma-valerolactone and gamma-valerolactone to 1,4-pentanediol. Finally, it was surprising that levulinic acid could be converted to 2-methyltetrahydrofuran with heating in the presence of the bimetallic catalyst and hydrogen in a single process vessel. The method of the present invention unexpectedly produced a fuel or fuel component having 2-methyltetrahydrofuran either in a yield greater than 4.5 mol % or in combination with alcohols.

  11. Hydrogenated 5-carbon compound and method of making

    DOEpatents

    Elliott, D.C.; Frye, J.G.

    1999-03-16

    The present invention is based upon the surprising discovery that a 5-carbon compound selected from the group of 4-oxopentanoic acid, at least one lactone of 4-oxopentanoic acid, and combinations thereof, may be hydrogenated with a bimetallic catalyst of a noble metal in combination with a second metal and preserve the pendant methyl group. It was further unexpectedly discovered that the same conditions of bimetallic catalyst in the presence of hydrogen are useful for catalyzing the different intermediate reactions, for example, angelicalactone to gamma-valerolactone and gamma-valerolactone to 1,4-pentanediol. Finally, it was surprising that levulinic acid could be converted to 2-methyltetrahydrofuran with heating in the presence of the bimetallic catalyst and hydrogen in a single process vessel. The method of the present invention unexpectedly produced a fuel or fuel component having 2-methyltetrahydrofuran either in a yield greater than 4.5 mol % or in combination with alcohols. 8 figs.

  12. Nanotube-derived carbon foam for hydrogen sorption.

    PubMed

    Ding, Feng; Lin, Yu; Krasnov, Pavel O; Yakobson, Boris I

    2007-10-28

    A new kind of carbon foam, which is based on the welding of single-walled carbon nanotubes, is built in a computer simulation. Its precisely defined architecture and all atomic positions allow one to perform detailed theoretical analysis of the properties. Such foam is as light as 19 of steel, while its stiffness is similar and nearly isotropic, and it represents a strong three-dimensional material with various possible applications. Furthermore, its nanoporous structure is accessible to molecular hydrogen and the potential surface analysis indicates that it should be an excellent hydrogen storage medium. Importantly, such foam is a feasible structure that can be produced based on the known tube/fullerene welding techniques. PMID:17979367

  13. Renewable hydrogen and carbon nanotubes from biodiesel waste glycerol

    PubMed Central

    Wu, Chunfei; Wang, Zichun; Williams, Paul T.; Huang, Jun

    2013-01-01

    In this report, we introduce a novel and commercially viable method to recover renewable hydrogen and carbon nanotubes from waste glycerol produced in the biodiesel process. Gas-phase catalytic reforming converts glycerol to clean hydrogen fuel and by replacing the problematical coke formed on the catalyst with high value carbon nanotubes, added value can be realised. Additional benefits of around 2.8 kg CNTs from the reforming of 1 tonne of glycerol and the production of 500 Nm3 H2 could have a considerable impact on the economics of glycerol utilization. Thereby, the contribution of this research will be a significant step forward in solving a current major technical and economic challenge faced by the biofuels industry. PMID:24067754

  14. Renewable hydrogen and carbon nanotubes from biodiesel waste glycerol.

    PubMed

    Wu, Chunfei; Wang, Zichun; Williams, Paul T; Huang, Jun

    2013-01-01

    In this report, we introduce a novel and commercially viable method to recover renewable hydrogen and carbon nanotubes from waste glycerol produced in the biodiesel process. Gas-phase catalytic reforming converts glycerol to clean hydrogen fuel and by replacing the problematical coke formed on the catalyst with high value carbon nanotubes, added value can be realised. Additional benefits of around 2.8 kg CNTs from the reforming of 1 tonne of glycerol and the production of 500 Nm(3) H2 could have a considerable impact on the economics of glycerol utilization. Thereby, the contribution of this research will be a significant step forward in solving a current major technical and economic challenge faced by the biofuels industry. PMID:24067754

  15. Optimization of Nano-Carbon Materials for Hydrogen Sorption

    SciTech Connect

    Yakobson, Boris I

    2013-08-02

    Research undertaken has added to the understanding of several critical areas, by providing both negative answers (and therefore eliminating expensive further studies of unfeasible paths) and positive feasible options for storage. Theoretical evaluation of the early hypothesis of storage on pure carbon single wall nanotubes (SWNT) has been scrutinized with the use of comprehensive computational methods (and experimental tests by the Center partners), and demonstrated that the fundamentally weak binding energy of hydrogen is not sufficiently enhanced by the SWNT curvature or even defects, which renders carbon nanotubes not practical media. More promising direction taken was towards 3-dimensional architectures of high porosity where concurrent attraction of H2 molecule to surrounding walls of nano-scale cavities can double or even triple the binding energy and therefore make hydrogen storage feasible even at ambient or somewhat lower temperatures. An efficient computational tool has been developed for the rapid capacity assessment combining (i) carbon-foam structure generation, (ii) accurate empirical force fields, with quantum corrections for the lightweight H2, and (iii) grand canonical Monte Carlo simulation. This made it possible to suggest optimal designs for carbon nanofoams, obtainable via welding techniques from SWNT or by growth on template-zeolites. As a precursor for 3D-foams, we have investigated experimentally the synthesis of VANTA (Vertically Aligned NanoTube Arrays). This can be used for producing nano-foams. On the other hand, fluorination of VANTA did not show promising increase of hydrogen sorption in several tests and may require further investigation and improvements. Another significant result of this project was in developing a fundamental understanding of the elements of hydrogen spillover mechanisms. The benefit of developed models is the ability to foresee possible directions for further improvement of the spillover mechanism.

  16. Electrochemical studies of hydrogen evolution, storage and oxidation on carbon nanotube electrodes

    NASA Astrophysics Data System (ADS)

    Prosini, Pier Paolo; Pozio, Alfonso; Botti, Sabina; Ciardi, Roberto

    Carbon nanotube films produced on a Si(1 0 0) substrate without any metal catalyst were used as electrodes in galvanic cells. The electrochemical mechanism of hydrogen evolution, storage and oxidation was studied using cyclic voltammetry and galvanostatic polarisation. Cyclic voltammetry showed that hydrogen is easily produced on the carbon nanotube surface, but a significant overvoltage was observed for hydrogen oxidation. The kinetics of hydrogen evolution influenced the quantity of hydrogen stored in the nanotube, which increased with increasing discharge currents.

  17. Deuterium separation by infrared-induced addition reaction

    DOEpatents

    Marling, John B.

    1977-01-01

    A method for deuterium enrichment by the infrared-induced addition reaction of a deuterium halide with an unsaturated aliphatic compound. A gaseous mixture of a hydrogen halide feedstock and an unsaturated aliphatic compound, particularly an olefin, is irradiated to selectively vibrationally excite the deuterium halide contained therein. The excited deuterium halide preferentially reacts with the unsaturated aliphatic compound to produce a deuterated addition product which is removed from the reaction mixture.

  18. Sulfur and Hydrogen Isotope Anomalies in Meteorite Sulfonic Acids

    NASA Technical Reports Server (NTRS)

    Cooper, George W.; Thiemens, Mark H.; Jackson, Teresa L.; Chang, Sherwood

    1997-01-01

    Intramolecular carbon, hydrogen, and sulfur isotope ratios were measured on a homologous series of organic sulfonic acids discovered in the Murchison meteorite. Mass-independent sulfur isotope fractionations were observed along with high deuterium/hydrogen ratios. The deuterium enrichments indicate formation of the hydrocarbon portion of these compounds in a low-temperature environment that is consistent with that of interstellar clouds. Sulfur-33 enrichments observed in methanesulfonic acid could have resulted from gas-phase ultraviolet irradiation of a precursor, carbon disulfide. The source of the sulfonic acid precursors may have been the reactive interstellar molecule carbon monosulfide.

  19. Infrared emission from hydrogenated amorphous carbon and amorphous carbon grains in the interstellar medium

    NASA Technical Reports Server (NTRS)

    Duley, W. W.; Jones, A. P.; Taylor, S. D.; Williams, D. A.

    1993-01-01

    The correlations deduced by Boulanger et al. (1990) from IRAS maps of the Chamaeleon, Taurus and Ursa Major molecular cloud complexes are interpreted in terms of the evolutionary hydrogenated amorphous carbon model of interstellar dust. In particular, regions of relatively strong 12-micron emission may be regions where recently accreted carbon is being converted by ambient UV to small PAHs in situ. Regions of weak 12-micron emission are probably quiescent regions where carbon has been annealed to amorphous carbon. Observational consequences of these inferences are briefly described.

  20. Hydrogen storage reactions on titanium decorated carbon nanocones theoretical study

    NASA Astrophysics Data System (ADS)

    Shalabi, A. S.; Taha, H. O.; Soliman, K. A.; Abeld Aal, S.

    2014-12-01

    Hydrogen storage reactions on Ti decorated carbon nanocones (CNC) are investigated by using the state of the art density functional theory calculations. The single Ti atom prefers to bind at the bridge site between two hexagonal rings, and can bind up to 6 hydrogen molecules with average adsorption energies of -1.73, -0.74, -0.57, -0.45, -0.42, and -0.35 eV per hydrogen molecule. No evidence for metal clustering in the ideal circumstances, and the hydrogen storage capacity is expected to be as large as 14.34 wt%. Two types of interactions are recognized. While the interaction of 2H2 with Ti-CNC is irreversible at 532 K, the interaction of 3H2 with Ti-CNC is reversible at 392 K. Further characterizations of the former two reactions are considered in terms of projected densities of states, simulated infrared and proton magnetic resonance spectra, electrophilicity, and statistical thermodynamic stability. The free energy of the highest hydrogen storage capacity reaction between 6H2 and Ti-CNC meets the ultimate targets of department of energy at (233.15 K) and (11.843 atm) with surface coverage (0.941) and (direct/inverse) rate constants ratio (1.35).

  1. A ground state morphed intermolecular potential for the hydrogen bonded and van der Waals isomers in OC:HI and a prediction of an anomalous deuterium isotope effect.

    PubMed

    Rivera-Rivera, Luis A; Wang, Zhongcheng; McElmurry, Blake A; Willaert, Fabrice F; Lucchese, Robert R; Bevan, John W; Suenram, Richard D; Lovas, Frank J

    2010-11-14

    An extended analysis of the noncovalent interaction OC:HI is reported using microwave and infrared supersonic jet spectroscopic techniques. All available spectroscopic data then provide the basis for generating an accurately determined vibrationally complete semiempirical intermolecular potential function using a four-dimensional potential coordinate morphing methodology. These results are consistent with the existence of four bound isomers: OC-HI, OC-IH, CO-HI, and CO-IH. Analysis also leads to unequivocal characterization of the common isotopic ground state as having the OC-HI structure and with the first excited state having the OC-IH structure with an energy of 3.4683(80) cm(-1) above the ground state. The potential is consistent with the following barriers between the pairs of isomers: 382(4) cm(-1) (OC-IH/OC-HI), 294(5) cm(-1) (CO-IH/CO-HI), 324(3) cm(-1) (OC-IH/CO-IH), and 301(2) cm(-1) (OC-HI/CO-HI) defined with respect to each lower minimum. The potential is also determined to have a linear OC-IH van der Waals global equilibrium minimum structure having R(e)=4.180(11) Å, θ(1)=0.00(1)°, and θ(2)=0.00(1)°. This is differentiated from its OC-HI ground state hydrogen bound structure having R(0)=4.895(1) Å, θ(1)=20.48(1)°, and θ(2)=155.213(1)° where the distances are defined between the centers of mass of the monomers and θ(1) and θ(2) as cos(-1)[(1/2)] for i=1 and 2. A fundamentally new molecular phenomenon - ground state isotopic isomerization is proposed based on the generated semiempirical potential. The protonated ground state hydrogen-bonded OC-HI structure is predicted to be converted on deuteration to the corresponding ground state van der Waals OC-ID isomeric structure. This results in a large anomalous isotope effect in which the R(0) center of mass distance between monomeric components changes from 4.895(1) to 4.286(1) Å. Such a proposed isotopic effect is demonstrated to be a consequence of differential zero point energy factors resulting from the shallower nature of hydrogen bonding at a local potential minimum (greater quartic character of the potential) relative to the corresponding van der Waals global minimum. Further consequences of this anomalous deuterium isotope effect are also discussed. PMID:21073221

  2. Ab-initio modeling of carbon and carbon-hydrogen defects in InAs

    NASA Astrophysics Data System (ADS)

    Torres, V. J. B.; Coutinho, J.; Briddon, P. R.

    2007-12-01

    Carbon is a common acceptor in several III-V semicondutors. In InAs, carbon replaces arsenic atoms, and when exposed to hydrogen, Raman and infra-red (IR) spectra reveal carbon-hydrogen centers. We perform density functional-pseudopotential studies to identify the observed Raman and IR lines. We replace an arsenic atom by carbon in a 64 atom InAs supercell, and investigated the energetics of a variety of possible hydrogen positions. In the lowest total energy configuration, hydrogen sits on a bond center position (BC), between the carbon and its indium first nearest neighbor. When hydrogen sits on the anti-bonding position to the carbon site the total energy is 0.4 eV higher than the BC structure. Other configurations showed higher energies. The local vibrational modes (LVM) of substitutional carbon were calculated at 502 cm -1, with a downward 13C-isotope shift of 19 cm -1. This is in excellent agreement with experimental data, were the frequency and shift were measured at 530 and 19 cm -1, respectively. C-H related LVMs for the BC configuration were obtained at 2744.9 cm -1 (A 1-), 502.2 cm -1 (E +) and 394.5 cm -1 (A 1+), which agree well with the experimental data at 2686.6, 518.2 and 393.2 cm -1, respectively. When 13C replaces 12C, the calculated downward shifts are 7.5 (A 1-), 15.7 (E +) and 13.7 cm -1 (A 1+), matching well the experimental data 7.7, 15.4 and 13.5 cm -1, respectively. An additional unreported H-wag mode is predicted at 689 cm -1.

  3. Characterization of the International Humic Substances Society standard and reference fulvic and humic acids by solution state carbon-13 (13C) and hydrogen-1 (1H) nuclear magnetic resonance spectrometry

    USGS Publications Warehouse

    Thorn, Kevin A.; Folan, Daniel W.; MacCarthy, Patrick

    1989-01-01

    Standard and reference samples of the International Humic Substances Society have been characterized by solution state carbon-13 and hydrogen-1 nuclear magnetic resonance (NMR) spectrometry. Samples included the Suwannee River, soil, and peat standard fulvic and humic acids, the Leonardite standard humic acid, the Nordic aquatic reference fulvic and humic acids, and the Summit Hill soil reference humic acid. Aqueous-solution carbon-13 NMR analyses included the measurement of spin-lattice relaxation times, measurement of nuclear Overhauser enhancement factors, measurement of quantitative carbon distributions, recording of attached proton test spectra, and recording of spectra under nonquantitative conditions. Distortionless enhancement by polarization transfer carbon-13 NMR spectra also were recorded on the Suwannee River fulvic acid in deuterated dimethyl sulfoxide. Hydrogen-1 NMR spectra were recorded on sodium salts of the samples in deuterium oxide. The carbon aromaticities of the samples ranged from 0.24 for the Suwannee River fulvic acid to 0.58 for the Leonardite humic acid.

  4. Biochemical hydrogen isotope fractionation during biosynthesis in higher plants reflects carbon metabolism of the plant

    NASA Astrophysics Data System (ADS)

    Cormier, Marc-André; Kahmen, Ansgar

    2015-04-01

    Compound-specific isotope analyses of plant material are frequently applied to understand the response of plants to the environmental changes. As it is generally assume that the main factors controlling δ2H values in plants are the plant's source water and evaporative deuterium enrichment of leaf water, hydrogen isotope analyses of plant material are mainly applied regarding hydrological conditions at different time scales. However, only few studies have directly addressed the variability of the biochemical hydrogen isotope fractionation occurring during biosynthesis of organic compounds (ɛbio), accounting also for a large part in the δ2H values of plants but generally assumed to be constant. Here we present the results from a climate-controlled growth chambers experiment where tested the sensitivity of ɛbio to different light treatments. The different light treatments were applied to induce different metabolic status (autotrophic vs. heterotrophic) in 9 different plant species that we grew from large storage organs (e.g. tubers or roots). The results show a systematic ɛbio shift (up to 80 ) between the different light treatments for different compounds (i.e. long chain n-alkanes and cellulose). We suggest that this shift is due to the different NADPH pools used by the plants to build up the compounds from stored carbohydrates in heterotrophic or autotrophic conditions. Our results have important implications for the calibration and interpretation of sedimentary and tree rings records in geological studies. In addition, as the δ2H values reflect also strongly the carbon metabolism of the plant, our findings support the idea of δ2H values as an interesting proxy for plant physiological studies.

  5. Water electrolysis with a conducting carbon cloth: subthreshold hydrogen generation and superthreshold carbon quantum dot formation.

    PubMed

    Biswal, Mandakini; Deshpande, Aparna; Kelkar, Sarika; Ogale, Satishchandra

    2014-03-01

    A conducting carbon cloth, which has an interesting turbostratic microstructure and functional groups that are distinctly different from other ordered forms of carbon, such as graphite, graphene, and carbon nanotubes, was synthesized by a simple one-step pyrolysis of cellulose fabric. This turbostratic disorder and surface chemical functionalities had interesting consequences for water splitting and hydrogen generation when such a cloth was used as an electrode in the alkaline electrolysis process. Importantly, this work also gives a new twist to carbon-assisted electrolysis. During electrolysis, the active sites in the carbon cloth allow slow oxidation of its surface to transform the surface groups from COH to COOH and so forth at a voltage as low as 0.2 V in a two-electrode system, along with platinum as the cathode, instead of 1.23 V (plus overpotential), which is required for platinum, steel, or even graphite anodes. The quantity of subthreshold hydrogen evolved was 24 mL cm(-2)  h(-1) at 1 V. Interestingly, at a superthreshold potential (>1.23 V+overpotential), another remarkable phenomenon was found. At such voltages, along with the high rate and quantity of hydrogen evolution, rapid exfoliation of the tiny nanoscale (5-7 nm) units of carbon quantum dots (CQDs) are found in copious amounts due to an enhanced oxidation rate. These CQDs show bright-blue fluorescence under UV light. PMID:24492961

  6. Hydrogen storage and delivery: the carbon dioxide - formic acid couple.

    PubMed

    Laurenczy, Gábor

    2011-01-01

    Carbon dioxide and the carbonates, the available natural C1 sources, can be easily hydrogenated into formic acid and formates in water; the rate of this reduction strongly depends on the pH of the solution. This reaction is catalysed by ruthenium(II) pre-catalyst complexes with a large variety of water-soluble phosphine ligands; high conversions and turnover numbers have been realised. Although ruthenium(II) is predominant in these reactions, the iron(II) - tris[(2-diphenylphosphino)-ethyl]phosphine (PP3) complex is also active, showing a new perspective to use abundant and inexpensive iron-based compounds in the CO2 reduction. In the catalytic hydrogenation cycles the in situ formed metal hydride complexes play a key role, their structures with several other intermediates have been proven by multinuclear NMR spectroscopy. In the other hand safe and convenient hydrogen storage and supply is the fundamental question for the further development of the hydrogen economy; and carbon dioxide has been recognised to be a viable H2 vector. Formic acid--containing 4.4 weight % of H2, that is 53 g hydrogen per litre--is suitable for H2 storage; we have shown that in aqueous solutions it can be selectively decomposed into CO-free (CO < 10 ppm) CO2 and H2. The reaction takes place under mild experimental conditions and it is able to generate high pressure H2 (up to 600 bar). The cleavage of HCOOH is catalysed by several hydrophilic Ru(II) phosphine complexes (meta-trisulfonated triphenylphosphine, mTPPTS, being the most efficient one), either in homogeneous systems or as immobilised catalysts. We have also shown that the iron(II)--hydrido tris[(2-diphenylphosphino)ethyl]phosphine complex catalyses with an exceptionally high rate and efficiency (turnover frequency, TOF = 9425 h(-1)mol(-1); turnover number, TON = 92400) the formic acid cleavage, in environmentally friendly propylene carbonate solution, opening the way to use cheap, non-noble metal based catalysts for this reaction, too. PMID:22026175

  7. Structural basis of specific interactions of Lp-PLA2 with HDL revealed by hydrogen deuterium exchange mass spectrometry[S

    PubMed Central

    Cao, Jian; Hsu, Yuan-Hao; Li, Sheng; Woods, Virgil L.; Dennis, Edward A.

    2013-01-01

    Lipoprotein-associated phospholipase A2 (Lp-PLA2), specifically Group VIIA PLA2, is a member of the phospholipase A2 superfamily and is found mainly associated with LDL and HDL in human plasma. Lp-PLA2 is considered as a risk factor, a potential biomarker, a target for therapy in the treatment of cardiovascular disease, and evidence suggests that the level of Lp-PLA2 in plasma is associated with the risk of future cardiovascular and stroke events. The differential location of the enzyme in LDL/HDL lipoproteins has been suggested to affect Lp-PLA2 function and/or its physiological role and an abnormal distribution of the enzyme may correlate with diseases. Although a mutagenesis study suggested that a surface helix (residues 362–369) mediates the association between Lp-PLA2 and HDL, the molecular details and mechanism of association has remained unknown. We have now employed hydrogen deuterium exchange mass spectrometry to characterize the interaction between recombinant human Lp-PLA2 and human HDL. We have found that specific residues 113–120, 192–204, and 360–368 likely mediate HDL binding. In a previous study, we showed that residues 113–120 are important for Lp-PLA2-liposome interactions. We now find that residues 192–204 show a decreased deuteration level when Lp-PLA2 is exposed to apoA-I, but not apoA-II, the most abundant apoproteins in HDL, and additionally, residues 360–368 are only affected by HDL.The results suggest that apoA-I and phospholipid membranes play crucial roles in Lp-PLA2 localization to HDL. PMID:23089916

  8. Effect of Fc-Glycan Structure on the Conformational Stability of IgG Revealed by Hydrogen/Deuterium Exchange and Limited Proteolysis.

    PubMed

    Fang, Jing; Richardson, Jason; Du, Zhimei; Zhang, Zhongqi

    2016-02-16

    Human therapeutic immunoglobulin gamma (IgG) molecules contain an N-glycan on each of their Fc CH2 domains. These glycans include high-mannose, hybrid, and complex types. Recombinant IgG molecules containing high-mannose glycans have been shown to clear faster in human blood, and exhibit decreased thermal stability. The molecular mechanism behind these observations, however, is not well understood. In this work, we used hydrogen/deuterium exchange combined with mass spectrometry (HDX MS), as well as proteolytic degradation under a native-like condition, to assess the impact of different glycoforms on the molecular structure and stability of recombinant IgG1 and IgG2 molecules expressed from Chinese hamster ovary cells. Our HDX MS data indicate that the conformation of these IgG molecules was indeed influenced by the glycan structure. IgG molecules containing high-mannose and hybrid glycans showed more conformational flexibility in the CH2 domain. This conclusion was further supported by the analysis of glycopeptides released from these molecules by trypsin digestion under a native-like condition. The higher CH2 conformational flexibility of IgG molecules with high-mannose and hybrid glycans contributes to their decreased thermal stability. IgG molecules containing sialylated glycans in the CH2 domain exhibited similar enzymatic degradation behavior as high-mannose glycans, suggesting decreased CH2-domain stability compared to shorter complex glycans, likely resulting from steric effect that decreased the glycan-CH2 domain interaction. PMID:26812426

  9. Optimization and application of atmospheric pressure chemical and photoionization hydrogen-deuterium exchange mass spectrometry for speciation of oxygen-containing compounds.

    PubMed

    Acter, Thamina; Kim, Donghwi; Ahmed, Arif; Jin, Jang Mi; Yim, Un Hyuk; Shim, Won Joon; Kim, Young Hwan; Kim, Sunghwan

    2016-05-01

    This paper presents a detailed investigation of the feasibility of optimized positive and negative atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) and atmospheric pressure photoionization (APPI) MS coupled to hydrogen-deuterium exchange (HDX) for structural assignment of diverse oxygen-containing compounds. The important parameters for optimization of HDX MS were characterized. The optimized techniques employed in the positive and negative modes showed satisfactory HDX product ions for the model compounds when dichloromethane and toluene were employed as a co-solvent in APCI- and APPI-HDX, respectively. The evaluation of the mass spectra obtained from 38 oxygen-containing compounds demonstrated that the extent of the HDX of the ions was structure-dependent. The combination of information provided by different ionization techniques could be used for better speciation of oxygen-containing compounds. For example, (+) APPI-HDX is sensitive to compounds with alcohol, ketone, or aldehyde substituents, while (-) APPI-HDX is sensitive to compounds with carboxylic functional groups. In addition, the compounds with alcohol can be distinguished from other compounds by the presence of exchanged peaks. The combined information was applied to study chemical compositions of degraded oils. The HDX pattern, double bond equivalent (DBE) distribution, and previously reported oxidation products were combined to predict structures of the compounds produced from oxidation of oil. Overall, this study shows that APCI- and APPI-HDX MS are useful experimental techniques that can be applied for the structural analysis of oxygen-containing compounds. Graphical Abstract Structural assignment of oxygen-containing compounds by (+/-) APCI/APPI HDX-MS and their speciation in degraded oil. PMID:26898203

  10. Understanding the conformational impact of chemical modifications on monoclonal antibodies with diverse sequence variation using hydrogen/deuterium exchange mass spectrometry and structural modeling.

    PubMed

    Zhang, Aming; Hu, Ping; MacGregor, Paul; Xue, Yu; Fan, Haihong; Suchecki, Peter; Olszewski, Leonard; Liu, Aston

    2014-04-01

    Chemical modifications can potentially induce conformational changes near the modification site and thereby impact the safety and efficacy of protein therapeutics. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) has emerged as a powerful analytical technique with high spatial resolution and sensitivity in detecting such local conformational changes. In this study, we utilized HDX-MS combined with structural modeling to examine the conformational impact on monoclonal antibodies (mAbs) caused by common chemical modifications including methionine (Met) oxidation, aspartic acid (Asp) isomerization, and asparagine (Asn) deamidation. Four mAbs with diverse sequences and glycosylation states were selected. The data suggested that the impact of Met oxidation was highly dependent on its location and glycosylation state. For mAbs with normal glycosylation in the Fc region, oxidation of the two conserved Met252 and Met428 (Kabat numbering) disrupted the interface interactions between the CH2 and CH3 domains, thus leading to a significant decrease in CH2 domain thermal stability as well as a slight increase in aggregation propensity. In contrast, Met oxidation in the variable region and CH3 domain had no detectable impact on mAb conformation. For aglycosylated mAb, Met oxidation could cause a more global conformational change to the whole CH2 domain, coincident with the larger decrease in thermal stability and significant increase in aggregation rate. Unlike Met oxidation, Asn deamidation and Asp isomerization mostly had very limited effects on mAb conformation, with the exception of succiminide intermediate formation which induced a measurable local conformational change to be more solvent protected. Structural modeling suggested that the succinimide intermediate was stabilized by adjacent aromatic amino acids through ring-ring stacking interactions. PMID:24597564

  11. Interdependence of coenzyme-induced conformational work and binding potential in yeast alcohol and porcine heart lactate dehydrogenases: a hydrogen-deuterium exchange study

    SciTech Connect

    De Weck, Z.; Pande, J.; Kaegi, J.H.R.

    1987-07-28

    Binding of NAD coenzymes to yeast alcohol dehydrogenase (YADH) and porcine heart lactate dehydrogenase (PHLDH) was studied by hydrogen-deuterium exchange with the infrared technique. Conformational changes in the enzymes specific to the coenzymes and their fragments were observed, and the pH dependence of the exchange reaction shows that it conforms to the EX-2 scheme. In both YADH and PHLDH the magnitude of the conformational change as measured by exchange retardation is considerably larger for the NAD/sup +/ than for NADH. Studies with coenzyme fragments like ADP-ribose, ADP, and AMP also highlight the lack of rigorous correlation between structural features such as charge and size and their influence on exchange behavior. Ternary complexes such as YADH-NAD/sup +/-pyrazole, PHLDH-NAD/sup +/-oxalate, and PHLDH-NADH-oxamate, which mimic the transition state, have a significantly more pronounced effect on exchange rates than the corresponding binary complexes. The outstanding feature of this study is the demonstration that in the binary enzyme-coenzyme complexes the more loosely bound NAD/sup +/ is more effective in retarding exchange than the more firmly bound NADH. These differences are attributed to the unequal structural constraints exerted by the two coenzymes upon the enzymes, which translate to unequal expenditure of transconformational work in the formation of the two complexes. The opposing variation in the free energy of binding and the transconformational work expended can be viewed as an unequal partitioning of the net free energy gain resulting from the protein-ligand interaction into a binding term and that required for conformational change.

  12. Dimerization of the type IV pilin from Pseudomonas aeruginosa strain K122-4 results in increased helix stability as measured by time-resolved hydrogen-deuterium exchange

    PubMed Central

    Lento, Cristina; Wilson, Derek J.; Audette, Gerald F.

    2015-01-01

    Truncated pilin monomers from Pseudomonas aeruginosa strain K122-4 (ΔK122) have been shown to enter a monomer-dimer equilibrium in solution prior to oligomerization into protein nanotubes. Here, we examine the structural changes occurring between the monomeric and dimeric states of ΔK122 using time-resolved hydrogen-deuterium exchange mass spectrometry. Based on levels of deuterium uptake, the N-terminal α-helix and the loop connecting the second and third strands of the anti-parallel β-sheet contribute significantly to pilin dimerization. Conversely, the antiparallel β-sheet and αβ loop region exhibit increased flexibility, while the receptor binding domain retains a rigid conformation in the equilibrium state. PMID:26798830

  13. Gas phase hydrogen permeation in alpha titanium and carbon steels

    NASA Technical Reports Server (NTRS)

    Johnson, D. L.; Shah, K. K.; Reeves, B. H.; Gadgeel, V. L.

    1980-01-01

    Commercially pure titanium and heats of Armco ingot iron and steels containing from 0.008-1.23 w/oC were annealed or normalized and machined into hollow cylinders. Coefficients of diffusion for alpha-Ti and alpha-Fe were determined by the lag-time technique. Steady state permeation experiments yield first power pressure dependence for alpha-Ti and Sievert's law square root dependence for Armco iron and carbon steels. As in the case of diffusion, permeation data confirm that alpha-titanium is subject to at least partial phase boundary reaction control while the steels are purely diffusion controlled. The permeation rate in steels also decreases as the carbon content increases. As a consequence of Sievert's law, the computed hydrogen solubility decreases as the carbon content increases. This decreases in explained in terms of hydrogen trapping at carbide interfaces. Oxidizing and nitriding the surfaces of alpha-titanium membranes result in a decrease in the permeation rate for such treatment on the gas inlet surfaces but resulted in a slight increase in the rate for such treatment on the gas outlet surfaces. This is explained in terms of a discontinuous TiH2 layer.

  14. Synthesis, characterization, and modeling of hydrogen storage in carbon aerogels

    SciTech Connect

    Pekala, R.W.; Coronado, P.R.; Calef, D.F.

    1995-04-01

    Carbon aerogels are a special class of open-cell foams with an ultrafine cell/pore size (<50 nm), high surface area (600-800 m{sup 2}/g), and a solid matrix composed of interconnected colloidal-like particles or fibers with characteristic diameters of 10 nm. These materials are usually synthesized from the sol-gel polymerization of resorcinol-formaldehyde or phenolic-furfural, followed by supercritical extraction of the solvent and pyrolysis in an inert atmosphere. The resultant aerogel has a nanocrystalline structure with micropores (<2 nm diameter) located within the solid matrix. Carbon aerogel monoliths can be prepared at densities ranging from 0.05-1.0 g/cm{sup 3}, leading to volumetric surface areas (> 500 m{sup 2}/cm{sup 3}) that are much larger than commercially available materials. This research program is directed at optimization of the aerogel structure for maximum hydrogen adsorption over a wide range of temperatures and pressures. Computer modeling of hydrogen adsorption at carbon surfaces was also examined.

  15. Voltammetric detection of hydrogen peroxide at carbon fiber microelectrodes.

    PubMed

    Sanford, Audrey L; Morton, Stephen W; Whitehouse, Kelsey L; Oara, Hannah M; Lugo-Morales, Leyda Z; Roberts, James G; Sombers, Leslie A

    2010-06-15

    Hydrogen peroxide is a reactive oxygen species that is implicated in a number of neurological disease states and that serves a critical role in normal cell function. It is commonly exploited as a reporter molecule enabling the electrochemical detection of nonelectroactive molecules at electrodes modified with substrate-specific oxidative enzymes. We present the first voltammetric characterization of rapid hydrogen peroxide fluctuations at an uncoated carbon fiber microelectrode, demonstrating unprecedented chemical and spatial resolution. The carbon surface was electrochemically conditioned on the anodic scan and the irreversible oxidation of peroxide was detected on the cathodic scan. The oxidation potential was dependent on scan rate, occurring at +1.2 V versus Ag/AgCl at a scan rate of 400 V.s(-1). The relationship between peak oxidation current and concentration was linear across the physiological range tested, with deviation from linearity above 2 mM and a detection limit of 2 muM. Peroxide was distinguished from multiple interferents, both in vitro and in brain slices. The enzymatic degradation of peroxide was monitored, as was peroxide evolution in response to glucose at a glucose oxidase modified carbon fiber electrode. This novel approach provides the requisite sensitivity, selectivity, spatial and temporal resolution to study dynamic peroxide fluctuations in discrete biological locations. PMID:20503997

  16. Hydrogen-Stimulated Gene Expression by Salmonella enterica serovar Typhimurium in a Carbon Limited Environment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Background: Salmonella enterica serovar Typhimurium can utilize molecular hydrogen for growth and amino acid transport during anaerobic growth in a carbon limited environment. In this study we identified hydrogen-stimulated gene expression changes contributing to Salmonella survival. Methods: Micr...

  17. Performance of CVD and CVR coated carbon-carbon in high temperature hydrogen

    NASA Astrophysics Data System (ADS)

    Adams, J. W.; Barletta, R. E.; Svandrlik, J.; Vanier, P. E.

    As a part of the component development process for the particle bed reactor (PBR), it is necessary to develop coatings which will be time and temperature stable at extremely high temperatures in flowing hydrogen. These coatings must protect the underlying carbon structure from attack by the hydrogen coolant. Degradation which causes small changes in the reactor component, e.g. hole diameter in the hot frit, can have a profound effect on operation. The ability of a component to withstand repeated temperature cycles is also a coating development issue. Coatings which crack or spall under these conditions would be unacceptable. While refractory carbides appear to be the coating material of choice for carbon substrates being used in PBR components, the method of applying these coatings can have a large effect on their performance. Two deposition processes for these refractory carbides, chemical vapor deposition (CVD) and chemical vapor reaction (CVR), have been evaluated. Screening tests for these coatings consisted of testing of coated 2-D and 3-D weave carbon-carbon in flowing hot hydrogen at one atmosphere. Carbon loss from these samples was measured as a function of time. Exposure temperatures up to 3,000 K were used, and samples were exposed in a cyclical fashion cooling to room temperature between exposures. The results of these measurements are presented along with an evaluation of the relative merits of CVR and CVD coatings for this application.

  18. Polarizability calculations on water, hydrogen, oxygen, and carbon dioxide

    NASA Technical Reports Server (NTRS)

    Nir, S.; Adams, S.; Rein, R.

    1973-01-01

    A semiclassical model of damped oscillators is used as a basis for the calculation of the dispersion of the refractive index, polarizability, and dielectric permeability in water, hydrogen, and oxygen in liquid and gaseous states, and in gaseous carbon dioxide. The absorption coefficient and the imaginary part of the refractive index are also calculated at corresponding wavelengths. A good agreement is obtained between the observed and calculated values of refractive indices, and between those of absorption coefficients in the region of absorption bands. The calculated values of oscillator strengths and damping factors are also discussed. The value of the polarizability of liquid water was about 2.8 times that of previous calculations.

  19. Iron-catalyzed hydrogenation of bicarbonates and carbon dioxide to formates.

    PubMed

    Zhu, Fengxiang; Zhu-Ge, Ling; Yang, Guangfu; Zhou, Shaolin

    2015-02-01

    The catalytic hydrogenation of carbon dioxide and bicarbonate to formate has been explored extensively. The vast majority of the known active catalyst systems are based on precious metals. Herein, we describe an effective, phosphine-free, air- and moisture-tolerant catalyst system based on Knölker's iron complex for the hydrogenation of bicarbonate and carbon dioxide to formate. The catalyst system can hydrogenate bicarbonate at remarkably low hydrogen pressures (1-5 bar). PMID:25603778

  20. Single Membrane Reactor Configuration for Separation of Hydrogen, Carbon Dioxide and Hydrogen Sulfide

    SciTech Connect

    Micheal Roberts; Robert Zabransky; Shain Doong; Jerry Lin

    2008-05-31

    The objective of the project was to develop a novel complementary membrane reactor process that can consolidate two or more downstream unit operations of a coal gasification system into a single module for production of a pure stream of hydrogen and a pure stream of carbon dioxide. The overall goals were to achieve higher hydrogen production efficiencies, lower capital costs and a smaller overall footprint than what could be achieved by utilizing separate components for each required unit process/operation in conventional coal-to-hydrogen systems. Specifically, this project was to develop a novel membrane reactor process that combines hydrogen sulfide removal, hydrogen separation, carbon dioxide separation and water-gas shift reaction into a single membrane configuration. The carbon monoxide conversion of the water-gas-shift reaction from the coal-derived syngas stream is enhanced by the complementary use of two membranes within a single reactor to separate hydrogen and carbon dioxide. Consequently, hydrogen production efficiency is increased. The single membrane reactor configuration produces a pure H{sub 2} product and a pure CO{sub 2} permeate stream that is ready for sequestration. This project focused on developing a new class of CO{sub 2}-selective membranes for this new process concept. Several approaches to make CO{sub 2}-selective membranes for high-temperature applications have been tested. Membrane disks using the technique of powder pressing and high temperature sintering were successfully fabricated. The powders were either metal oxide or metal carbonate materials. Experiments on CO{sub 2} permeation testing were also performed in the temperature range of 790 to 940 C for the metal carbonate membrane disks. However, no CO{sub 2} permeation rate could be measured, probably due to very slow CO{sub 2} diffusion in the solid state carbonates. To improve the permeation of CO{sub 2}, one approach is to make membranes containing liquid or molten carbonates. Several different types of dual-phase membranes were fabricated and tested for their CO{sub 2} permeation in reducing conditions without the presence of oxygen. Although the flux was quite low, on the order of 0.01-0.001 cc STP/cm{sup 2}/min, the selectivity of CO{sub 2}/He was almost infinite at temperatures of about 800 C. A different type of dual-phase membrane prepared by Arizona State University (ASU) was also tested at GTI for CO{sub 2} permeation. The measured CO{sub 2} fluxes were 0.015 and 0.02 cc STP/cm{sup 2}/min at 750 and 830 C, respectively. These fluxes were higher than the previous flux obtained ({approx}0.01 cc STP/cm{sup 2}/min) using the dual-phase membranes prepared by GTI. Further development in membrane development should be conducted to improve the CO{sub 2} flux. ASU has also focused on high temperature permeation/separation experiments to confirm the carbon dioxide separation capabilities of the dual-phase membranes with La{sup 0.6}Sr{sub 0.4}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} (LSCF6482) supports infiltrated with a Li/Na/K molten carbonate mixture (42.5/32.5/25.0 mole %). The permeation experiments indicated that the addition of O{sub 2} does improve the permeance of CO{sub 2} through the membrane. A simplified membrane reactor model was developed to evaluate the performance of the process. However, the simplified model did not allow the estimation of membrane transport area, an important parameter for evaluating the feasibility of the proposed membrane reactor technology. As a result, an improved model was developed. Results of the improved membrane reactor model show that the membrane shift reaction has promise as a means to simplify the production of a clean stream of hydrogen and a clean stream of carbon dioxide. The focus of additional development work should address the large area required for the CO{sub 2} membrane as identified in the modeling calculations. Also, a more detailed process flow diagram should be developed that includes integration of cooling and preheating feed streams as well as particulate removal so that steam and power generation could be optimized. For the tubular membranes that were fabricated by solution impregnation with metal carbonates, difficulties were encountered in removing the impurity salts that were trapped inside the porous support tube. The membrane tube would continue losing weight even after being heated up to 500 C in air and could not maintain its nonporous characteristics. This approach was therefore abandoned. Dual-phase membranes with molten carbonates were subsequently shown to have CO{sub 2} permeability in reducing conditions without the presence of oxygen; they were also tested for H{sub 2}S permeation. Permeation tests were conducted with a gas feed composition consisting of 33.6% CO{sub 2}, 8.4% He, 57.6% H{sub 2} and 0.4% H{sub 2}S at temperatures between 820 and 850 C and a pressure of 1 bar.

  1. Microwave attenuation of hydrogen plasma in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Babaei, S.; Solari, M. Sh.

    2008-12-01

    The attenuation (ATT) of hydrogen plasma in carbon nanotubes, grown by iron-catalyzed high-pressure carbon monoxide disproportionate process, is investigated. The effects of the incident wave, the electron density, the collision frequency, the thermal frequency, and the cyclotron frequency on the ATT of the microwave are discussed. Moreover, the impacts of thermal frequency and cyclotron frequency on the ATT are investigated separately. Numerical results indicate that position of the ATT peak and the ATT level depend on the incident frequency, the electron density, the collision frequency, the thermal frequency, and the cyclotron frequency. The results show that the cyclotron frequency highly influences the ATT level. In contrast, the shift frequency is more affected by the thermal frequency. The ATT is more sensitive at the middle band of incident frequency.

  2. Membrane-based systems for carbon capture and hydrogen purification

    SciTech Connect

    Berchtold, Kathryn A

    2010-11-24

    This presentation describes the activities being conducted at Los Alamos National Laboratory to develop carbon capture technologies for power systems. This work is aimed at continued development and demonstration of a membrane based pre- and post-combustion carbon capture technology and separation schemes. Our primary work entails the development and demonstration of an innovative membrane technology for pre-combustion capture of carbon dioxide that operates over a broad range of conditions relevant to the power industry while meeting the US DOE's Carbon Sequestration Program goals of 90% CO{sub 2} capture at less than a 10% increase in the cost of energy services. Separating and capturing carbon dioxide from mixed gas streams is a first and critical step in carbon sequestration. To be technically and economically viable, a successful separation method must be applicable to industrially relevant gas streams at realistic temperatures and pressures as well as be compatible with large gas volumes. Our project team is developing polymer membranes based on polybenzimidazole (PBI) chemistries that can purify hydrogen and capture CO{sub 2} at industrially relevant temperatures. Our primary objectives are to develop and demonstrate polymer-based membrane chemistries, structures, deployment platforms, and sealing technologies that achieve the critical combination of high selectivity, high permeability, chemical stability, and mechanical stability all at elevated temperatures (> 150 C) and packaged in a scalable, economically viable, high area density system amenable to incorporation into an advanced Integrated Gasification Combined-Cycle (IGCC) plant for pre-combustion CO{sub 2} capture. Stability requirements are focused on tolerance to the primary synthesis gas components and impurities at various locations in the IGCC process. Since the process stream compositions and conditions (temperature and pressure) vary throughout the IGCC process, the project is focused on the optimization of a technology that could be positioned upstream or downstream of one or more of the water-gas-shift reactors (WGSRs) or integrated with a WGSR.

  3. Combustion characteristics of hydrogen. Carbon monoxide based gaseous fuels

    NASA Technical Reports Server (NTRS)

    Notardonato, J. J.; White, D. J.; Kubasco, A. J.; Lecren, R. T.

    1981-01-01

    An experimental rig program was conducted with the objective of evaluating the combuston performance of a family of fuel gases based on a mixture of hydrogen and carbon monoxide. These gases, in addition to being members of a family, were also representative of those secondary fuels that could be produced from coal by various gasification schemes. In particular, simulated Winkler, Lurgi, and Blue-water low and medium energy content gases were used as fuels in the experimental combustor rig. The combustor used was originally designed as a low NOx rich-lean system for burning liquid fuels with high bound nitrogen levels. When used with the above gaseous fuels this combustor was operated in a lean-lean mode with ultra long residence times. The Blue-water gas was also operated in a rich-lean mode. The results of these tests indicate the possibility of the existence of an 'optimum' gas turbine hydrogen - carbon monoxide based secondary fuel. Such a fuel would exhibit NOx and high efficiency over the entire engine operating range. It would also have sufficient stability range to allow normal light-off and engine acceleration. Solar Turbines Incorporated would like to emphasize that the results presented here have been obtained with experimental rig combustors. The technologies generated could, however, be utilized in future commercial gas turbines.

  4. Isotopic exchange of carbon-bound hydrogen over geologic timescales

    NASA Astrophysics Data System (ADS)

    Sessions, Alex L.; Sylva, Sean P.; Summons, Roger E.; Hayes, John M.

    2004-04-01

    The increasing popularity of compound-specific hydrogen isotope (D/H) analyses for investigating sedimentary organic matter raises numerous questions about the exchange of carbon-bound hydrogen over geologic timescales. Important questions include the rates of isotopic exchange, methods for diagnosing exchange in ancient samples, and the isotopic consequences of that exchange. This article provides a review of relevant literature data along with new data from several pilot studies to investigate such issues. Published experimental estimates of exchange rates between organic hydrogen and water indicate that at warm temperatures (50-100°C) exchange likely occurs on timescales of 10 4 to 10 8 yr. Incubation experiments using organic compounds and D-enriched water, combined with compound-specific D/H analyses, provide a new and highly sensitive method for measuring exchange at low temperatures. Comparison of δD values for isoprenoid and n-alkyl carbon skeletons in sedimentary organic matter provides no evidence for exchange in young (<1 Ma), cool sediments, but strong evidence for exchange in ancient (>350 Ma) rocks. Specific rates of exchange are probably influenced by the nature and abundance of organic matter, pore-water chemistry, the presence of catalytic mineral surfaces, and perhaps even enzymatic activity. Estimates of equilibrium fractionation factors between organic H and water indicate that typical lipids will be depleted in D relative to water by ˜75 to 140‰ at equilibrium (30°C). Thus large differences in δD between organic molecules and water cannot be unambiguously interpreted as evidence against hydrogen exchange. A better approach may be to use changes in stereochemistry as a proxy for hydrogen exchange. For example, estimated rates of H exchange in pristane are similar to predicted rates for stereochemical inversion in steranes and hopanes. The isotopic consequences of this exchange remain in question. Incubations of cholestene with D 2O indicate that the number of D atoms incorporated during structural rearrangements can be far less than the number of C-H bonds that are broken. Sample calculations indicate that, for steranes in immature sediments, the D/H ratio imparted by biosynthesis may be largely preserved in spite of significant structural changes.

  5. Deuterium enrichment by selective photo-induced dissociation of an organic carbonyl compound

    DOEpatents

    Marling, John B.

    1981-01-01

    A method for producing a deuterium enriched material by photoinduced dissociation which uses as the working material a gas phase photolytically dissociable organic carbonyl compound containing at least one hydrogen atom bonded to an atom which is adjacent to a carbonyl group and consisting of molecules wherein said hydrogen atom is present as deuterium and molecules wherein said hydrogen atom is present as another isotope of hydrogen. The organic carbonyl compound is subjected to intense infrared radiation at a preselected wavelength to selectively excite and thereby induce dissociation of the deuterium containing species to yield a deuterium enriched stable molecular product. Undissociated carbonyl compound, depleted in deuterium, is preferably redeuterated for reuse.

  6. Magnetic Carbon Supported Palladium Nanoparticles: An Efficient and Sustainable Catalyst for Hydrogenation Reactions

    EPA Science Inventory

    Magnetic carbon supported Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; the catalyst can be used for the hydrogenation of alkenes and reduction of aryl nitro compounds.

  7. Performance of carbon-based hot frit substrates: I, Low pressure helium and hydrogen testing

    SciTech Connect

    Barletta, R.; Adams, J.; Svandrlik, J.; Powell, J.R.

    1993-07-01

    The performance of various carbon-based materials in flowing, high-temperature helium and hydrogen is described. These materials which are candidate hot frit substrates for possible application in a PBR include various grades of graphite, carbon-carbon and vitreous carbon. Vitreous carbon showed extremely good performance in helium, while that of the various graphite grades was quite variable and, in some cases, poor. Purified grades performed better than unpurified grades, but in all cases large sample-to-sample variations in weight loss were observed. For carbon-carbon samples, the performance was intermediate. Since the weight loss in these samples was in large measure due to the loss of the densification media, improvements in the performance of carbon-carbon may be possible. With respect to the performance in hydrogen, high weight losses were observed, re-enforcing the need for coating carbon-based materials for service in a flowing hydrogen environment.

  8. Different conformational dynamics of β-arrestin1 and β-arrestin2 analyzed by hydrogen/deuterium exchange mass spectrometry

    SciTech Connect

    Yun, Youngjoo; Kim, Dong Kyun; Seo, Min-Duk; Kim, Kyeong-Man; Chung, Ka Young

    2015-01-30

    Highlights: • The conformational dynamics of β-arrestin1 or β-arrestin2 were analyzed by HDX-MS. • β-Strands II through IV were more dynamic in β-arrestin2 than in β-arrestin1. • The middle loop was less dynamic in β-arrestin2 than in β-arrestin1. • Upon pre-activation by the R169E mutation, β-arrestins became more dynamic. • Pre-activation affected a wider region of β-arrestin1 compared to β-arrestin2. - Abstract: Arrestins have important roles in G protein-coupled receptor (GPCR) signaling including desensitization of GPCRs and G protein-independent signaling. There have been four arrestins identified: arrestin1, arrestin2 (e.g. β-arrestin1), arrestin3 (e.g. β-arrestin2), and arrestin4. β-Arrestin1 and β-arrestin2 are ubiquitously expressed and regulate a broad range of GPCRs, while arrestin1 and arrestin4 are expressed in the visual system. Although the functions of β-arrestin1 and β-arrestin2 widely overlap, β-arrestin2 has broader receptor selectivity, and a few studies have suggested that β-arrestin1 and β-arrestin2 have distinct cellular functions. Here, we compared the conformational dynamics of β-arrestin1 and β-arrestin2 by hydrogen/deuterium exchange mass spectrometry (HDX-MS). We also used the R169E mutant as a pre-activation model system. HDX-MS data revealed that β-strands II through IV were more dynamic in β-arrestin2 in the basal state, while the middle loop was more dynamic in β-arrestin1. With pre-activation, both β-arrestin1 and β-arrestin2 became more flexible, but broader regions of β-arrestin1 became flexible compared to β-arrestin2. The conformational differences between β-arrestin1 and β-arrestin2 in both the basal and pre-activated states might determine their different receptor selectivities and different cellular functions.

  9. Trapping state of hydrogen isotopes in carbon and graphite investigated by thermal desorption spectrometry

    SciTech Connect

    Atsumi, H.; Tanabe, T.; Shikama, T.

    2015-03-15

    Thermal desorption spectrometry (TDS) has been investigated to obtain fundamental information of tritium behavior in graphite and carbon materials especially at high temperatures. 29 brands of graphite, HOPG, glassy carbon and CFC materials charged with deuterium gas are tested up to the temperature of 1735 K with a heating rate of 0.1 K/s. TDS spectra have five peaks at 600-700 K, around 900 K, 1200 K, 1300-1450 K and 1600-1650 K. The amounts of released deuterium have been compared with crystallographic parameters derived from XRD analysis. The results can be summarized as follows. First, TDS spectra of deuterium were quite varied among the samples tested, such as existence of peaks, peak temperatures and release amounts of deuterium. Secondly, TDS spectra may consist of five peaks, which are peak 1 (600-700 K), peak 2 (around 900 K), peak 3 (around 1200 K), peak 4 (1300-1450 K) and peak 5 (1600-1650 K). Thirdly, the correlations between the estimated surface area of edge surface and the total amount of released deuterium could be observed for peaks 4 and 5. Fourthly, high energy trapping site (peak 5) may exist even at edge surface or a near surface region, not only for intercalary. And fifth, in order to obtain the lower tritium retention for graphite and CFC materials, the material should be composed of a filler grain with a smaller crystallite size or having the smaller net edge surface in its structure. It is shown that heat treatment does not reduce originally existing trapping sites but trapping sites generated by neutron irradiation for instance can be reduced in some degree.

  10. Thermocatalytic process for CO.sub.2-free production of hydrogen and carbon from hydrocarbons

    DOEpatents

    Muradov, Nazim Z.

    2011-08-23

    A novel process and apparatus are disclosed for sustainable CO.sub.2-free production of hydrogen and carbon by thermocatalytic decomposition (dissociation, pyrolysis, cracking) of hydrocarbon fuels over carbon-based catalysts in the absence of air and/or water. The apparatus and thermocatalytic process improve the activity and stability of carbon catalysts during the thermocatalytic process and produce both high purity hydrogen (at least, 99.0 volume %) and carbon, from any hydrocarbon fuel, including sulfurous fuels. In a preferred embodiment, production of hydrogen and carbon is achieved by both internal and external activation of carbon catalysts. Internal activation of carbon catalyst is accomplished by recycling of hydrogen-depleted gas containing unsaturated and aromatic hydrocarbons back to the reactor. External activation of the catalyst can be achieved via surface gasification with hot combustion gases during catalyst heating. The process and apparatus can be conveniently integrated with any type of fuel cell to generate electricity.

  11. Development of Affordable, Low-Carbon Hydrogen Supplies at an Industrial Scale

    ERIC Educational Resources Information Center

    Roddy, Dermot J.

    2008-01-01

    An existing industrial hydrogen generation and distribution infrastructure is described, and a number of large-scale investment projects are outlined. All of these projects have the potential to generate significant volumes of low-cost, low-carbon hydrogen. The technologies concerned range from gasification of coal with carbon capture and storage

  12. Development of Affordable, Low-Carbon Hydrogen Supplies at an Industrial Scale

    ERIC Educational Resources Information Center

    Roddy, Dermot J.

    2008-01-01

    An existing industrial hydrogen generation and distribution infrastructure is described, and a number of large-scale investment projects are outlined. All of these projects have the potential to generate significant volumes of low-cost, low-carbon hydrogen. The technologies concerned range from gasification of coal with carbon capture and storage…

  13. Deep inelastic structure functions from electron scattering on hydrogen, deuterium, and iron at 0. 6 GeV sup 2 le Q sup 2 le 30. 0 GeV sup 2

    SciTech Connect

    Whitlow, L.W.

    1990-03-01

    We report the final results from experiment E140, a recent deep inelastic electron-deuterium and electron-iron scattering experiment at SLAC. In addition, we present the results of a combined global analysis of all SLAC deep inelastic electron-hydrogen and electron-deuterium cross section measurements between 1970 and 1983. Data from seven earlier experiments are re-radiatively corrected and normalized to experiment E140. We report extractions of R(x,Q{sup 2}) and F{sub 2}(x,Q{sup 2}) for hydrogen and deuterium over the entire SLAC kinematic range: .06{le} x {le}.90 and 0.6{le} Q{sup 2} {le}30.0 (GeV{sup 2}). We fine that R{sup p} = R{sup d}, as expected by QCD. Extracted values of R(x,Q{sup 2}) are significantly larger than predictions based on QCD and on QCD with the inclusion of kinematic target mass terms. This difference indicates that dynamical higher twist effects may be important in the SLAC kinematic range. A best fit empirical model of R(x,Q{sup 2}) is used to extract F{sub 2} from each cross section measurement. These F{sub 2} extractions are compared with F{sub 2} data from EMC and BCDMS. Agreement is observed with EMC when the EMC data are multiplied by 1.07. Agreement is observed with BCDMS over a limited range in x. The ratios of F{sub 2}{sup d}/F{sub 2}{sup p} are examined for Q{sup 2} dependence. We observe a significant negative slope for x {le} .6, and a significant positive slope above x > .7, in excellent agreement with predictions based on QCD with the inclusion of kinematic target mass terms. 111 refs., 40 figs., 34 tabs.

  14. Production of carbon monoxide-free hydrogen and helium from a high-purity source

    DOEpatents

    Golden, Timothy Christopher; Farris, Thomas Stephen

    2008-11-18

    The invention provides vacuum swing adsorption processes that produce an essentially carbon monoxide-free hydrogen or helium gas stream from, respectively, a high-purity (e.g., pipeline grade) hydrogen or helium gas stream using one or two adsorber beds. By using physical adsorbents with high heats of nitrogen adsorption, intermediate heats of carbon monoxide adsorption, and low heats of hydrogen and helium adsorption, and by using vacuum purging and high feed stream pressures (e.g., pressures of as high as around 1,000 bar), pipeline grade hydrogen or helium can purified to produce essentially carbon monoxide -free hydrogen and helium, or carbon monoxide, nitrogen, and methane-free hydrogen and helium.

  15. Direct measurement of hydrogen adsorption in carbon nanotubes/nanofibers by elastic recoil detection

    NASA Astrophysics Data System (ADS)

    Naab, F. U.; Dhoubhadel, M.; Gilbert, J. R.; Gilbert, M. C.; Savage, L. K.; Holland, O. W.; Duggan, J. L.; McDaniel, F. D.

    2006-07-01

    Physi- or chemi-sorption of hydrogen in solid materials offers a viable medium for hydrogen storage since the concentration of hydrogen can exceed that in its gaseous form at high compression. Due to their unique architecture, carbon nanotubes are potentially an excellent carbon-based adsorbent for hydrogen. In this work, we report direct measurements of hydrogen adsorption using elastic recoil detection analysis in single-walled, double-walled, and multi-walled nanotubes, as well as carbon nanofibers. Results are presented for hydrogen adsorption treatment at ambient temperature and above, where chemical rather than physical adsorption is anticipated. The results show that the concentration of hydrogen in all samples over the range of conditions investigated is below 1 wt.%, which is well below that required for a viable storage media.

  16. A comparative theoretical study of metal functionalized carbon nanocones and carbon nanocone sheets as potential hydrogen storage materials.

    PubMed

    Shalabi, A S; Soliman, K A; Taha, H O

    2014-09-28

    The hydrogen storage of Ti functionalized carbon nanocones and carbon nanocone sheets is investigated by using the state-of-the-art density functional theory calculations. The Ti atom prefers to bind at the hollow site of the hexagonal ring. The average adsorption energies corrected for dispersion forces are -0.54 and -0.39 eV per hydrogen molecule. With no metal clustering, the system gravimetric capacities are expected to be as large as 9.31 and 11.01 wt%. The hydrogen storage reactions are characterized in terms of simulated infrared spectra, projected densities of states, kinetics, and statistical thermodynamics. The free energies and enthalpies of the Ti functionalized carbon nanocone meet the ultimate targets of the Department of Energy for all temperatures and pressures. The closest reactions to zero free energy occur at 378.15 K/2.961 atm for carbon nanocones and 233.15 K/2.961 atm for carbon nanocone sheets. The translational component is found to exert a dominant effect on the total entropy change with temperature. More promising thermodynamics are assigned to the hydrogenation of Ti functionalized carbon nanocone sheets at 233.15 K. As the temperature is increased, the lifetimes of the hydrogen molecules adsorbed at the surface drop and the rate constants increase. At fixed pressure, the rate constants of hydrogenation of Ti functionalized carbon nanocones are smaller than those of Ti functionalized carbon nanocone sheets, while the lifetimes are greater. PMID:25099825

  17. Alignment of nematic LCs on surface of amorphous hydrogenated carbon

    NASA Astrophysics Data System (ADS)

    Konshina, Elena A.

    1996-01-01

    Observations of the nematic LCs alignment on the surface of amorphous hydrogenated carbon (a-C:H) layers are reported. These layers were prepared from toluene by plasma-activated chemical vapors deposition process. It was found that the surface of as prepared films had produced parallel alignment of alkylcyanobiphenyls LC mixture with positive dielectric anisotropy. Thea-C:H layers surface treated by means of the oxygen plasma could orientate the same LCs homeotropically. It was established the dependencies of the pretilt angle of LCs on the glow discharge power during deposition of a-C:H layers and the oxygen plasma treatment dose of their surface after the preparation. A simple model to explain these observations is presented.

  18. Sustainable production of green feed from carbon dioxide and hydrogen.

    PubMed

    Landau, Miron V; Vidruk, Roxana; Herskowitz, Moti

    2014-03-01

    Carbon dioxide hydrogenation to form hydrocarbons was conducted on two iron-based catalysts, prepared according to procedures described in the literature, and on a new iron spinel catalyst. The CO2 conversion measured in a packed-bed reactor was limited to about 60% because of excessive amounts of water produced in this process. Switching to a system of three packed-bed reactors in series with interim removal of water and condensed hydrocarbons increased CO2 conversion to as much as 89%. The pure spinel catalyst displayed a significantly higher activity and selectivity than those of the other iron catalysts. This process produces a product called green feed, which is similar in composition to the product of a high-temperature, iron-based Fischer–Tropsch process from syngas. The green feed can be readily converted into renewable fuels by well-established technologies. PMID:24678062

  19. Thermodynamics of the hydrogenation of oxides of carbon

    SciTech Connect

    Anderson, R.B.

    1986-09-25

    Thermodynamics is appropriate to a symposium honoring Paul Emmett. Paul used thermo sagaciously in his research, and when reliable values were not available, he determined the required data. The energetics for producing a vast array of organic molecules by hydrogenating oxides of carbon are favorable. However, if the possible products are assumed to be in equilibrium, the predominant and nearly only product is methane. Thus, to make higher paraffins, olefins, alcohols, etc. the catalyst must be selective. Part of this selectivity arises from selective poisoning of the catalyst by CO. Similarly, equilibrium is usually not attained in the water gas shift, except for some conditions with catalysts containing Fe, Mo, and W. Hence, the distribution of product should be of great diagnostic value for interpreting the mechanisms of the Fischer-Tropsch and higher alcohol syntheses.

  20. Calculation of deuterium isotope effects in proton transfer reactions

    NASA Astrophysics Data System (ADS)

    Scheiner, Steve

    1994-05-01

    Various levels of theory are tested for the purpose of computing the rate constant for proton transfer reactions. Standard transition state theory is applied to a series of molecules with a progressively more bent intramolecular hydrogen bond. The systems all display similar deuterium isotope effects (DIEs); the larger DIE at low temperature is attributed to zero-point vibrational effects. However, when tunneling is incorporated via a microcanonical approach, a dramatically enhanced effect is observed for the most distorted H-bond. The energy barrier for proton transfer between carbon atoms involved in triple bonds is smaller than for carbons with lesser multiplicity. The DIE displays a sensitivity to temperature that is least for the carbon atoms with the greatest multiplicity of bonding. The tunneling obtained by following the minimum energy reaction path along the potential energy surface is similar to that when the potential is approximated by an Eckart barrier. However, significant discrepancies are observed at temperatures below about 250 K.

  1. Kinetic modelling of molecular hydrogen transport in microporous carbon materials.

    SciTech Connect

    Hankel, M.; Zhang, H.; Nguyen, T. X.; Bhatia, S. K.; Gray, S. K.; Smith, S. C.

    2011-01-01

    The proposal of kinetic molecular sieving of hydrogen isotopes is explored by employing statistical rate theory methods to describe the kinetics of molecular hydrogen transport in model microporous carbon structures. A Lennard-Jones atom-atom interaction potential is utilized for the description of the interactions between H{sub 2}/D{sub 2} and the carbon framework, while the requisite partition functions describing the thermal flux of molecules through the transition state are calculated quantum mechanically in view of the low temperatures involved in the proposed kinetic molecular sieving application. Predicted kinetic isotope effects for initial passage from the gas phase into the first pore mouth are consistent with expectations from previous modeling studies, namely, that at sufficiently low temperatures and for sufficiently narrow pore mouths D{sub 2} transport is dramatically favored over H{sub 2}. However, in contrast to expectations from previous modeling, the absence of any potential barrier along the minimum energy pathway from the gas phase into the first pore mouth yields a negative temperature dependence in the predicted absolute rate coefficients - implying a negative activation energy. In pursuit of the effective activation barrier, we find that the minimum potential in the cavity is significantly higher than in the pore mouth for nanotube-shaped models, throwing into question the common assumption that passage through the pore mouths should be the rate-determining step. Our results suggest a new mechanism that, depending on the size and shape of the cavity, the thermal activation barrier may lie in the cavity rather than at the pore mouth. As a consequence, design strategies for achieving quantum-mediated kinetic molecular sieving of H{sub 2}/D{sub 2} in a microporous membrane will need, at the very least, to take careful account of cavity shape and size in addition to pore-mouth size in order to ensure that the selective step, namely passage through the pore mouth, is also the rate determining step.

  2. Hydrogen Adsorption in Carbon-Based Materials Studied by NMR

    NASA Astrophysics Data System (ADS)

    Wu, Yue

    2006-11-01

    Hydrogen storage is a key component for hydrogen economy. So far, storage materials with large storage capacity and suitable adsorption energy remain elusive. The identification of future storage materials depends crucially on the understanding of adsorption mechanisms. Here we show that nuclear magnetic resonance (NMR) is a sensitive and quantitative probe for detecting adsorbed gas molecules (such as H2, methane, and ethane) in carbon-based materials [1]. Adsorbed gas molecules can be identified through characteristic NMR signatures such as spectral lineshape and spin dynamics, which is determined by the distinct dynamic properties of the adsorbed molecules. NMR is shown to be valuable for the understanding of adsorption mechanisms. In our studies, NMR measurements were carried out in-situ under given H2 pressure up to a pressure of over 100 atm. From such ^1H NMR measurement, the amount of adsorbed H2 molecules can be determined versus pressure. This gives an alternative method for measuring the adsorption isotherms where the H2 signature is identified based on spin properties rather than weight or volume as in gravimetric and volumetric measurements. In addition, properties of molecular dynamics can be obtained at the same time providing information on the adsorption mechanisms. [1] A. Kleinhammes, S.-H. Mao, X.-J. Yang, X.-P. Tang, H. Shimoda, J. P. Lu, O. Zhou, and Y. Wu, Phys. Rev. B. 68, 075418 (2003).

  3. Hydrogen induced redox mechanism in amorphous carbon resistive random access memory

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Jiun; Chen, Hsin-Lu; Young, Tai-Fa; Chang, Ting-Chang; Tsai, Tsung-Ming; Chang, Kuan-Chang; Zhang, Rui; Chen, Kai-Huang; Lou, Jen-Chung; Chu, Tian-Jian; Chen, Jung-Hui; Bao, Ding-Hua; Sze, Simon M.

    2014-01-01

    We investigated the bipolar resistive switching characteristics of the resistive random access memory (RRAM) device with amorphous carbon layer. Applying a forming voltage, the amorphous carbon layer was carbonized to form a conjugation double bond conductive filament. We proposed a hydrogen redox model to clarify the resistive switch mechanism of high/low resistance states (HRS/LRS) in carbon RRAM. The electrical conduction mechanism of LRS is attributed to conductive sp2 carbon filament with conjugation double bonds by dehydrogenation, while the electrical conduction of HRS resulted from the formation of insulating sp3-type carbon filament through hydrogenation process.

  4. Hydrogen induced redox mechanism in amorphous carbon resistive random access memory

    PubMed Central

    2014-01-01

    We investigated the bipolar resistive switching characteristics of the resistive random access memory (RRAM) device with amorphous carbon layer. Applying a forming voltage, the amorphous carbon layer was carbonized to form a conjugation double bond conductive filament. We proposed a hydrogen redox model to clarify the resistive switch mechanism of high/low resistance states (HRS/LRS) in carbon RRAM. The electrical conduction mechanism of LRS is attributed to conductive sp2 carbon filament with conjugation double bonds by dehydrogenation, while the electrical conduction of HRS resulted from the formation of insulating sp3-type carbon filament through hydrogenation process. PMID:24475979

  5. Cometary deuterium.

    PubMed

    Meier, R; Owen, T C

    1999-01-01

    Deuterium fractionations in cometary ices provide important clues to the origin and evolution of comets. Mass spectrometers aboard spaceprobe Giotto revealed the first accurate D/H ratios in the water of Comet 1P/Halley. Ground-based observations of HDO in Comets C/1996 B2 (Hyakutake) and C/1995 O1 (Hale-Bopp), the detection of DCN in Comet Hale-Bopp, and upper limits for several other D-bearing molecules complement our limited sample of D/H measurements. On the basis of this data set all Oort cloud comets seem to exhibit a similar (D/H)H2O ratio in H2O, enriched by about a factor of two relative to terrestrial water and approximately one order of magnitude relative to the protosolar value. Oort cloud comets, and by inference also classical short-period comets derived from the Kuiper Belt cannot be the only source for the Earth's oceans. The cometary O/C ratio and dynamical reasons make it difficult to defend an early influx of icy planetesimals from the Jupiter zone to the early Earth. D/H measurements of OH groups in phyllosilicate rich meteorites suggest a mixture of cometary water and water adsorbed from the nebula by the rocky grains that formed the bulk of the Earth may be responsible for the terrestrial D/H. The D/H ratio in cometary HCN is 7 times higher than the value in cometary H2O. Species-dependent D-fractionations occur at low temperatures and low gas densities via ion-molecule or grain-surface reactions and cannot be explained by a pure solar nebula chemistry. It is plausible that cometary volatiles preserved the interstellar D fractionation. The observed D abundances set a lower limit to the formation temperature of (30 +/- 10) K. Similar numbers can he derived from the ortho-to-para ratio in cometary water, from the absence of neon in cometary ices and the presence of S2. Noble gases on Earth and Mars, and the relative abundance of cometary hydrocarbons place the comet formation temperature near 50 K. So far all cometary D/H measurements refer to bulk compositions, and it is conceivable that significant departures from the mean value could occur at the grain-size level. Strong isotope effects as a result of coma chemistry can be excluded for molecules H2O and HCN. A comparison of the cometary (D/H)H2O ratio with values found in the atmospheres of the outer planets is consistent with the long-held idea that the gas planets formed around icy cores with a high cometary D/H ratio and subsequently accumulated significant amounts of H2 from the solar nebula with a low protosolar D/H. PMID:11543290

  6. Catalytic Metal Free Production of Large Cage Structure Carbon Particles: A Candidate for Hydrogen Storage

    NASA Technical Reports Server (NTRS)

    Kimura, Yuki; Nuth, Joseph A., III; Ferguson, Frank T.

    2005-01-01

    We will demonstrate that carbon particles consisting of large cages can be produced without catalytic metal. The carbon particles were produced in CO gas as well as by introduction of 5% methane gas into the CO gas. The gas-produced carbon particles were able to absorb approximately 16.2 wt% of hydrogen. This value is 2.5 times higher than the 6.5 wt% goal for the vehicular hydrogen storage proposed by the Department of Energy in the USA. Therefore, we believe that this carbon particle is an excellent candidate for hydrogen storage for fuel cells.

  7. Apparatus for hydrogen and carbon production via carbon aerosol-catalyzed dissociation of hydrocarbons

    NASA Technical Reports Server (NTRS)

    Muradov, Nazim Z. (Inventor); Smith, Franklyn (Inventor); Tabatabaie-Raissi, Ali (Inventor)

    2012-01-01

    A novel process and apparatus is disclosed for sustainable, continuous production of hydrogen and carbon by catalytic dissociation or decomposition of hydrocarbons at elevated temperatures using in-situ generated carbon particles. Carbon particles are produced by decomposition of carbonaceous materials in response to an energy input. The energy input can be provided by at least one of a non-oxidative and oxidative means. The non-oxidative means of the energy input includes a high temperature source, or different types of plasma, such as, thermal, non-thermal, microwave, corona discharge, glow discharge, dielectric barrier discharge, or radiation sources, such as, electron beam, gamma, ultraviolet (UV). The oxidative means of the energy input includes oxygen, air, ozone, nitrous oxide (NO.sub.2) and other oxidizing agents. The method, apparatus and process of the present invention is applicable to any gaseous or liquid hydrocarbon fuel and it produces no or significantly less CO.sub.2 emissions compared to conventional processes.

  8. Thermodynamic analysis of Glycerol Steam Reforming for hydrogen production with in situ hydrogen and carbon dioxide separation

    NASA Astrophysics Data System (ADS)

    Silva, Joel M.; Soria, M. A.; Madeira, Luis M.

    2015-01-01

    A thermodynamic study of Glycerol Steam Reforming (GSR) for hydrogen production with in situ carbon dioxide and hydrogen (reaction products) simultaneous removal was performed. The sorption-enhanced membrane reactor (SEMR) was divided into multiple sub-Gibbs reactors and the Gibbs free energy minimization method was employed. The effects of temperature (600-800 K), molar water-to-glycerol feed ratio (WGFR) (3-9), pressure (1-5 atm) and fraction of hydrogen and carbon dioxide removal (f, 0-0.99) on the GSR process were target of investigation. A hydrogen yield (total moles of hydrogen produced/mole of reacted glycerol) very close to the stoichiometric value of 7 was obtained at 700 K, WGFR of 9, 1 atm and for fCO2 = 0.99 and fH2 = 0.80. This corresponds to an enhancement of 217%, 47% and 22% in terms of hydrogen yield comparatively to the traditional reactor (TR), sorption-enhanced reactor (SER) with carbon dioxide capture (fCO2 = 0.99) and membrane reactor (MR) with hydrogen separation (fH2 = 0.80) , respectively. In terms of coke, its formation was only observed under WGFRs below the stoichiometric value of 3.

  9. Role of Nonmetallic Inclusions in Hydrogen Embrittlement of High-Strength Carbon Steels with Different Microalloying

    NASA Astrophysics Data System (ADS)

    Todoshchenko, Olga Madelen Ingrid; Yagodzinskyy, Yuriy; Saukkonen, Tapio; Hänninen, Hannu

    2014-10-01

    High-strength carbon steels of 1200 MPa strength level with different microalloying were tensile tested at constant extension rate and constant load under continuous electrochemical hydrogen charging. The results show that hydrogen markedly reduces elongation and time to fracture of all the studied steels. Fractography of the steels shows that nonmetallic inclusions (NMIs) play the major role in crack initiation in hydrogen-charged specimens. The role of NMIs in the hydrogen-induced fracture of steels is discussed.

  10. Sublattice segregation of hydrogen adsorbates in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Lawlor, James; Ferreira, Mauro S.

    2015-09-01

    Recent experimental observations have reported that, rather than randomly distributed, nitrogen atoms may prefer to be located on one of the two sublattices of graphene. It has been suggested that such a preference may present a possible avenue to tailor the band gap of graphene while maintaining its excellent electronic transport properties. Among the proposed mechanisms to explain this effect is the suggestion that long-range interimpurity interactions mediated by the conduction electrons of graphene may give rise to the asymmetry between sublattice occupations. Electron-mediated interactions are known to be prevalent not only between N atoms but also between impurities that are adsorbed to a specific location within the hexagonal structure, namely to the top of the carbon atom. Furthermore, this interaction is known to become more long ranged as the dimensionality of the system is lowered. For that reason, in this paper we investigate whether a similar sublattice asymmetry appears in the case of metallic carbon nanotubes doped with hydrogen adatoms. Our results indicate that similar sublattice asymmetries are observable and even more pronounced in small-diameter CNTs with a dilute concentration of adsorbates, diminishing with increasing diameter or impurity concentrations.

  11. Synthesis of deuterium-labeled fluphenazine.

    PubMed

    Shetty, H U; Hawes, E M; Midha, K K

    1984-01-01

    The propylpiperazine side chain of fluphenazine has been labeled with two, four, and six deuterium atoms by lithium aluminum deuteride reduction of the appropriate ester or imide. The gamma-carbon of the propyl group was labeled with two deuterium atoms by reduction of 10- (2-methoxycarbonylethyl) -2-trifluoromethyl-10H-phenothiazine, while four deuterium atoms were incorporated into the piperazine ring by reduction of 10-[3-(3,5-dioxo-1-piperazinyl)propyl]-2-trifluoromethyl-10H-pheno thiazine. The latter reduction gave the d4-labeled N-deshydroxyethyl metabolite of fluphenazine. PMID:6694091

  12. Synthesis of deuterium-labeled fluphenazine

    SciTech Connect

    Shetty, H.U.; Hawes, E.M.; Midha, K.K.

    1984-01-01

    The propylpiperazine side chain of fluphenazine has been labeled with two, four, and six deuterium atoms by lithium aluminum deuteride reduction of the appropriate ester or imide. The gamma-carbon of the propyl group was labeled with two deuterium atoms by reduction of 10- (2-methoxycarbonylethyl) -2-trifluoromethyl-10H-phenothiazine, while four deuterium atoms were incorporated into the piperazine ring by reduction of 10-(3-(3,5-dioxo-1-piperazinyl)propyl)-2-trifluoromethyl-10H-pheno thiazine. The latter reduction gave the d4-labeled N-deshydroxyethyl metabolite of fluphenazine.

  13. Hydrogen Adsorption on Activated Carbon an Carbon Nanotubes Using Volumetric Differential Pressure Technique

    NASA Astrophysics Data System (ADS)

    Sanip, S. M.; Saidin, M. A. R.; Aziz, M.; Ismail, A. F.

    2010-03-01

    A simple hydrogen adsorption measurement system utilizing the volumetri differential pressure technique has been designed, fabricated and calibrated. Hydroge adsorption measurements have been carried out at temperatures 298 K and 77 K on activate carbon and carbon nanotubes with different surface areas. The adsorption data obtained will b helpful in understanding the adsorption property of the studied carbon materials using th fundamentals of adsorption theory. The principle of the system follows the Sievert-type metho The system measures a change in pressure between the reference cell, R1 and the sample cell S1, S2, S3 over a certain temperature range. R1, S1, S2, and S3 having known fixed volume The sample temperatures will be monitored by thermocouple TC while the pressures in R1 an S1, S2, S3 will be measured using a digital pressure transducer. The maximum operatin pressure of the pressure transducer is 20 bar and calibrated with an accuracy of ±0.01 bar. Hig purity hydrogen is being used in the system and the amount of samples for the study is betwee 1.0-2.0 grams. The system was calibrated using helium gas without any samples in S1, S2 an S3. This will provide a correction factor during the adsorption process providing an adsorption free reference point when using hydrogen gas resulting in a more accurate reading of th adsorption process by eliminating the errors caused by temperature expansion effects and oth non-adsorption related phenomena. The ideal gas equation of state is applied to calculate th hydrogen adsorption capacity based on the differential pressure measurements. Activated carbo with a surface area of 644.87 m2/g showed a larger amount of adsorption as compared to multiwalled nanotubes (commercial) with a surface area of 119.68 m2/g. This study als indicated that there is a direct correlation between the amounts of hydrogen adsorbed an surface area of the carbon materials under the conditions studied and that the adsorption significant at 77 K.

  14. Exploring the Origins of Deuterium Enrichments in Solar Nebular Organics

    NASA Astrophysics Data System (ADS)

    Cleeves, L. Ilsedore; Bergin, Edwin A.; O'D. Alexander, Conel M.; Du, Fujun; Graninger, Dawn; Öberg, Karin I.; Harries, Tim J.

    2016-03-01

    Deuterium-to-hydrogen (D/H) enrichments in molecular species provide clues about their original formation environment. The organic materials in primitive solar system bodies generally have higher D/H ratios and show greater D/H variation when compared to D/H in solar system water. We propose this difference arises at least in part due to (1) the availability of additional chemical fractionation pathways for organics beyond that for water, and (2) the higher volatility of key carbon reservoirs compared to oxygen. We test this hypothesis using detailed disk models, including a sophisticated, new disk ionization treatment with a low cosmic-ray ionization rate, and find that disk chemistry leads to higher deuterium enrichment in organics compared to water, helped especially by fractionation via the precursors CH2D+/CH3+. We also find that the D/H ratio in individual species varies significantly depending on their particular formation pathways. For example, from ˜20-40 au, CH4 can reach {{D}}/{{H}}˜ 2× {10}-3, while D/H in CH3OH remains locally unaltered. Finally, while the global organic D/H in our models can reproduce intermediately elevated D/H in the bulk hydrocarbon reservoir, our models are unable to reproduce the most deuterium-enriched organic materials in the solar system, and thus our model requires some inheritance from the cold interstellar medium from which the Sun formed.

  15. 40 CFR 415.330 - Applicability; description of the carbon monoxide and by-product hydrogen production subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... carbon monoxide and by-product hydrogen production subcategory. 415.330 Section 415.330 Protection of... MANUFACTURING POINT SOURCE CATEGORY Carbon Monoxide and By-Product Hydrogen Production Subcategory § 415.330 Applicability; description of the carbon monoxide and by-product hydrogen production subcategory. The...

  16. 40 CFR 415.330 - Applicability; description of the carbon monoxide and by-product hydrogen production subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... carbon monoxide and by-product hydrogen production subcategory. 415.330 Section 415.330 Protection of... MANUFACTURING POINT SOURCE CATEGORY Carbon Monoxide and By-Product Hydrogen Production Subcategory § 415.330 Applicability; description of the carbon monoxide and by-product hydrogen production subcategory. The...

  17. 40 CFR 415.330 - Applicability; description of the carbon monoxide and by-product hydrogen production subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... carbon monoxide and by-product hydrogen production subcategory. 415.330 Section 415.330 Protection of... MANUFACTURING POINT SOURCE CATEGORY Carbon Monoxide and By-Product Hydrogen Production Subcategory § 415.330 Applicability; description of the carbon monoxide and by-product hydrogen production subcategory. The...

  18. 40 CFR 415.330 - Applicability; description of the carbon monoxide and by-product hydrogen production subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... carbon monoxide and by-product hydrogen production subcategory. 415.330 Section 415.330 Protection of... MANUFACTURING POINT SOURCE CATEGORY Carbon Monoxide and By-Product Hydrogen Production Subcategory § 415.330 Applicability; description of the carbon monoxide and by-product hydrogen production subcategory. The...

  19. 40 CFR 415.330 - Applicability; description of the carbon monoxide and by-product hydrogen production subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... carbon monoxide and by-product hydrogen production subcategory. 415.330 Section 415.330 Protection of... MANUFACTURING POINT SOURCE CATEGORY Carbon Monoxide and By-Product Hydrogen Production Subcategory § 415.330 Applicability; description of the carbon monoxide and by-product hydrogen production subcategory. The...

  20. Atomically isolated nickel species anchored on graphitized carbon for efficient hydrogen evolution electrocatalysis

    PubMed Central

    Fan, Lili; Liu, Peng Fei; Yan, Xuecheng; Gu, Lin; Yang, Zhen Zhong; Yang, Hua Gui; Qiu, Shilun; Yao, Xiangdong

    2016-01-01

    Hydrogen production through electrochemical process is at the heart of key renewable energy technologies including water splitting and hydrogen fuel cells. Despite tremendous efforts, exploring cheap, efficient and durable electrocatalysts for hydrogen evolution still remains as a great challenge. Here we synthesize a nickel–carbon-based catalyst, from carbonization of metal-organic frameworks, to replace currently best-known platinum-based materials for electrocatalytic hydrogen evolution. This nickel-carbon-based catalyst can be activated to obtain isolated nickel atoms on the graphitic carbon support when applying electrochemical potential, exhibiting highly efficient hydrogen evolution performance with high exchange current density of 1.2 mA cm−2 and impressive durability. This work may enable new opportunities for designing and tuning properties of electrocatalysts at atomic scale for large-scale water electrolysis. PMID:26861684

  1. Two different carbon-hydrogen complexes in silicon with closely spaced energy levels

    NASA Astrophysics Data System (ADS)

    Stübner, R.; Kolkovsky, Vl.; Weber, J.

    2015-08-01

    An acceptor and a single donor state of carbon-hydrogen defects (CHA and CHB) are observed by Laplace deep level transient spectroscopy at 90 K. CHA appears directly after hydrogenation by wet chemical etching or hydrogen plasma treatment, whereas CHB can be observed only after a successive annealing under reverse bias at about 320 K. The activation enthalpies of these states are 0.16 eV for CHA and 0.14 eV for CHB. Our results reconcile previous controversial experimental results. We attribute CHA to the configuration where substitutional carbon binds a hydrogen atom on a bond centered position between carbon and the neighboring silicon and CHB to another carbon-hydrogen defect.

  2. Atomically isolated nickel species anchored on graphitized carbon for efficient hydrogen evolution electrocatalysis

    NASA Astrophysics Data System (ADS)

    Fan, Lili; Liu, Peng Fei; Yan, Xuecheng; Gu, Lin; Yang, Zhen Zhong; Yang, Hua Gui; Qiu, Shilun; Yao, Xiangdong

    2016-02-01

    Hydrogen production through electrochemical process is at the heart of key renewable energy technologies including water splitting and hydrogen fuel cells. Despite tremendous efforts, exploring cheap, efficient and durable electrocatalysts for hydrogen evolution still remains as a great challenge. Here we synthesize a nickel-carbon-based catalyst, from carbonization of metal-organic frameworks, to replace currently best-known platinum-based materials for electrocatalytic hydrogen evolution. This nickel-carbon-based catalyst can be activated to obtain isolated nickel atoms on the graphitic carbon support when applying electrochemical potential, exhibiting highly efficient hydrogen evolution performance with high exchange current density of 1.2 mA cm-2 and impressive durability. This work may enable new opportunities for designing and tuning properties of electrocatalysts at atomic scale for large-scale water electrolysis.

  3. Atomically isolated nickel species anchored on graphitized carbon for efficient hydrogen evolution electrocatalysis.

    PubMed

    Fan, Lili; Liu, Peng Fei; Yan, Xuecheng; Gu, Lin; Yang, Zhen Zhong; Yang, Hua Gui; Qiu, Shilun; Yao, Xiangdong

    2016-01-01

    Hydrogen production through electrochemical process is at the heart of key renewable energy technologies including water splitting and hydrogen fuel cells. Despite tremendous efforts, exploring cheap, efficient and durable electrocatalysts for hydrogen evolution still remains as a great challenge. Here we synthesize a nickel-carbon-based catalyst, from carbonization of metal-organic frameworks, to replace currently best-known platinum-based materials for electrocatalytic hydrogen evolution. This nickel-carbon-based catalyst can be activated to obtain isolated nickel atoms on the graphitic carbon support when applying electrochemical potential, exhibiting highly efficient hydrogen evolution performance with high exchange current density of 1.2 mA cm(-2) and impressive durability. This work may enable new opportunities for designing and tuning properties of electrocatalysts at atomic scale for large-scale water electrolysis. PMID:26861684

  4. Effect of γ-ray irradiation on the sorption of hydrogen by nanoporous carbon materials

    NASA Astrophysics Data System (ADS)

    Dolbin, A. V.; Manzhelii, V. G.; Esel'son, V. B.; Gavrilko, V. G.; Vinnikov, N. A.; Basnukaeva, R. M.; Khlistyuck, M. V.; Maletskii, V. P.; Nikolaev, V. G.; Kudriachenko, E. V.; Uvarova, I. Yu.; Tripachko, N. A.; Koda, V. Yu.

    2015-04-01

    The effects of radiation exposure in a hydrogen atmosphere on hydrogen sorption by a synthetic porous carbon nanosorbent, SCN (spherical carbonite saturated). The exposure was created by γ-rays from cobalt-60 (photon energy 1.2 MeV, irradiation dose 4.8 × 107 rad) in a normal hydrogen atmosphere at a pressure of 1 atm and a temperature of 300 K. The processes of hydrogen sorption-desorption by SCN samples before and after irradiation were studied in a temperature interval of 15-1173 K. It was found that the irradiation of SCN in a hydrogen atmosphere significantly increased the amount hydrogen sorbed in the sample. We conducted a comparison with the results of earlier studies investigating the influence of irradiation on the sorption of hydrogen by single-walled carbon nanotubes. The amount of physically sorbed hydrogen in the synthetic SCN sorbent that was irradiated in the hydrogen atmosphere, is four times greater than the amount of hydrogen that was physically sorbed by the single-walled carbon nanotubes that were irradiated under similar conditions. At a temperature below 25 K, the hydrogen diffusion in the SCN was almost temperature independent for the porous subsystem with the highest diffusion coefficients, which is typical for cases when the tunnel diffusion mechanism dominates the thermodynamic mechanism.

  5. Muon catalyzed fusion experiments on muonic deuterium atom deceleration in thin solid deuterium films

    NASA Astrophysics Data System (ADS)

    Strasser, P.; Ishida, K.; Sakamoto, S.; Shimomura, K.; Kawamura, N.; Torikai, E.; Iwasaki, M.; Nagamine, K.

    1996-02-01

    Muon catalyzed fusion was investigated in a series of thin solid deuterium films by detecting protons from dd fusion. Two different contributions to the total fusion yield resulting from dμ atoms emitted from a primary hydrogen layer and from incident muons directly stopped in the deuterium film itself were observed. The thickness dependence of the fusion yield suggested the importance of molecular effects in dμ elastic scattering in D 2.

  6. Ab initio molecular dynamics simulation study of successive hydrogenation reactions of carbon monoxide producing methanol.

    PubMed

    Pham, Thi Nu; Ono, Shota; Ohno, Kaoru

    2016-04-14

    Doing ab initio molecular dynamics simulations, we demonstrate a possibility of hydrogenation of carbon monoxide producing methanol step by step. At first, the hydrogen atom reacts with the carbon monoxide molecule at the excited state forming the formyl radical. Formaldehyde was formed after adding one more hydrogen atom to the system. Finally, absorption of two hydrogen atoms to formaldehyde produces methanol molecule. This study is performed by using the all-electron mixed basis approach based on the time dependent density functional theory within the adiabatic local density approximation for an electronic ground-state configuration and the one-shot GW approximation for an electronic excited state configuration. PMID:27083723

  7. Ab initio molecular dynamics simulation study of successive hydrogenation reactions of carbon monoxide producing methanol

    NASA Astrophysics Data System (ADS)

    Pham, Thi Nu; Ono, Shota; Ohno, Kaoru

    2016-04-01

    Doing ab initio molecular dynamics simulations, we demonstrate a possibility of hydrogenation of carbon monoxide producing methanol step by step. At first, the hydrogen atom reacts with the carbon monoxide molecule at the excited state forming the formyl radical. Formaldehyde was formed after adding one more hydrogen atom to the system. Finally, absorption of two hydrogen atoms to formaldehyde produces methanol molecule. This study is performed by using the all-electron mixed basis approach based on the time dependent density functional theory within the adiabatic local density approximation for an electronic ground-state configuration and the one-shot GW approximation for an electronic excited state configuration.

  8. Structure and hydrogen adsorption properties in low density nanoporous carbons from simulations

    SciTech Connect

    Peng, L.; Morris, James R

    2012-01-01

    We systematically model the hydrogen adsorption in nanoporous carbons over a wide range of carbon bulk densities (0.6 - 2.4 g/cm3) by using tight binding molecular dynamics simulations for the carbon structures and thermodynamics calculations of the hydrogen adsorption. The resulting structures are in good agreement with the experimental data of ultra-microporous carbon (UMC), a wood-based activated carbon, as indicated by comparisons of the microstructure at atomic level, pair distribution function, and pore size distribution. The hydrogen adsorption calculations in carbon structures demonstrate both a promising hydrogen storage capacity (excess uptake of 1.33 wt% at 298K and 5 MPa, for carbon structures at the lower range of densities) and a reasonable heat of adsorption (12-22 kJ/mol). This work demonstrates that increasing the heat of adsorption does not necessarily increase the hydrogen uptake. In fact, the available adsorption volume is as important as the isosteric heat of adsorption for hydrogen storage in nanoporous carbons.

  9. Populations of np terms (n=2-4) for 10-500-keV/amu deuterium ions exiting from carbon foils

    NASA Astrophysics Data System (ADS)

    Baudinet-Robinet, Y.; Dumont, P. D.

    1984-11-01

    Relative beam-foil populations of np terms (n=2-4) in deuterium have been measured as a function of the the projectile energy in the energy range 10~200 keV/amu, the excitation functions of the np terms studied decrease as E-3 and follow closely the equilibrium neutral fraction (φ0) variation of deuterons (or protons) emerging from a carbon foil. This result is discussed in the frame of the kinetic model proposed recently by Kreussler and Sizmann for calculating φ0 and some information concerning the ratio of atomic cross sections for the production and destruction of np states will be tentatively deduced. At energies E<200 keV/amu, the behavior of the excitation functions of np terms (n=2-4) is compatible with a decrease of the ratio of the np population to the ground-state population with respect to that ratio at higher energies. The relation N2p(v)=Cv12φ0(v) (C being a normalization constant) fits very well the 2p population results in the energy range 10-200 keV/amu.

  10. Fast-quench reactor for hydrogen and elemental carbon production from natural gas and other hydrocarbons

    DOEpatents

    Detering, Brent A.; Kong, Peter C.

    2006-08-29

    A fast-quench reactor for production of diatomic hydrogen and unsaturated carbons is provided. During the fast quench in the downstream diverging section of the nozzle, such as in a free expansion chamber, the unsaturated hydrocarbons are further decomposed by reheating the reactor gases. More diatomic hydrogen is produced, along with elemental carbon. Other gas may be added at different stages in the process to form a desired end product and prevent back reactions. The product is a substantially clean-burning hydrogen fuel that leaves no greenhouse gas emissions, and elemental carbon that may be used in powder form as a commodity for several processes.

  11. Palladium on Nitrogen-Doped Mesoporous Carbon: A Bifunctional Catalyst for Formate-Based, Carbon-Neutral Hydrogen Storage.

    PubMed

    Wang, Fanan; Xu, Jinming; Shao, Xianzhao; Su, Xiong; Huang, Yanqiang; Zhang, Tao

    2016-02-01

    The lack of safe, efficient, and economical hydrogen storage technologies is a hindrance to the realization of the hydrogen economy. Reported herein is a reversible formate-based carbon-neutral hydrogen storage system that is established over a novel catalyst comprising palladium nanoparticles supported on nitrogen-doped mesoporous carbon. The support was fabricated by a hard template method and nitridated under a flow of ammonia. Detailed analyses demonstrate that this bicarbonate/formate redox equilibrium is promoted by the cooperative role of the doped nitrogen functionalities and the well-dispersed, electron-enriched palladium nanoparticles. PMID:26763714

  12. Hydrogen-deuterium exchange between TpRu(PMe3)(L)X (L = PMe3 and X = OH, OPh, Me, Ph, or NHPh; L = NCMe and X = Ph) and deuterated arene solvents: evidence for metal-mediated processes.

    PubMed

    Feng, Yuee; Lail, Marty; Foley, Nicholas A; Gunnoe, T Brent; Barakat, Khaldoon A; Cundari, Thomas R; Petersen, Jeffrey L

    2006-06-21

    At elevated temperatures (90-130 degrees C), complexes of the type TpRu(PMe3)2X (X = OH, OPh, Me, Ph, or NHPh; Tp = hydridotris(pyrazolyl)borate) undergo regioselective hydrogen-deuterium (H/D) exchange with deuterated arenes. For X = OH or NHPh, H/D exchange occurs at hydroxide and anilido ligands, respectively. For X = OH, OPh, Me, Ph, or NHPh, isotopic exchange occurs at the Tp 4-positions with only minimal deuterium incorporation at the Tp 3- or 5-positions or PMe3 ligands. For TpRu(PMe3)(NCMe)Ph, the H/D exchange occurs at 60 degrees C at all three Tp positions and the phenyl ring. TpRu(PMe3)2Cl, TpRu(PMe3)2OTf (OTf = trifluoromethanesulfonate), and TpRu(PMe3)2SH do not initiate H/D exchange in C6D6 after extended periods of time at elevated temperatures. Mechanistic studies indicate that the likely pathway for the H/D exchange involves ligand dissociation (PMe3 or NCMe), Ru-mediated activation of an aromatic C-D bond, and deuteration of basic nondative ligand (hydroxide or anilido) or Tp positions via net D+ transfer. PMID:16771513

  13. Quantum fluctuations increase the self-diffusive motion of para-hydrogen in narrow carbon nanotubes.

    PubMed

    Kowalczyk, Piotr; Gauden, Piotr A; Terzyk, Artur P; Furmaniak, Sylwester

    2011-05-28

    Quantum fluctuations significantly increase the self-diffusive motion of para-hydrogen adsorbed in narrow carbon nanotubes at 30 K comparing to its classical counterpart. Rigorous Feynman's path integral calculations reveal that self-diffusive motion of para-hydrogen in a narrow (6,6) carbon nanotube at 30 K and pore densities below ∼29 mmol cm(-3) is one order of magnitude faster than the classical counterpart. We find that the zero-point energy and tunneling significantly smoothed out the free energy landscape of para-hydrogen molecules adsorbed in a narrow (6,6) carbon nanotube. This promotes a delocalization of the confined para-hydrogen at 30 K (i.e., population of unclassical paths due to quantum effects). Contrary the self-diffusive motion of classical para-hydrogen molecules in a narrow (6,6) carbon nanotube at 30 K is very slow. This is because classical para-hydrogen molecules undergo highly correlated movement when their collision diameter approached the carbon nanotube size (i.e., anomalous diffusion in quasi-one dimensional pores). On the basis of current results we predict that narrow single-walled carbon nanotubes are promising nanoporous molecular sieves being able to separate para-hydrogen molecules from mixtures of classical particles at cryogenic temperatures. PMID:21503294

  14. Ellipsometric and optical study of amorphous hydrogenated carbon films

    NASA Technical Reports Server (NTRS)

    Alterovitz, S. A.; Warner, J. D.; Liu, D. C.; Pouch, J. J.

    1986-01-01

    A low-frequency plasma deposition system was used to prepare amorphous hydrogenated carbon (a-C:H) films. The growth energy was varied by changing the power and/or pressure of the plasma. Ellipsometry and optical absorption were used to obtain the optical energy gap, the density of states, and the refractive index. Ion sputtering was used in conjunction with ellipsometry and Auger electron spectroscopy to get absolute sputtering rates. The plasma deposited a-C:H is amorphous with an optical energy gap of approximately 2.0-2.4 eV. These a-C:H films have higher density and/or hardness, higher refractive index, and lower optical energy gaps with increasing energy of the particles in the plasma, while the density of states remains unchanged. These results are in agreement with, and give a fine-tuned positive confirmation to, an existing conjecture on the nature of the a-C:H films (Kaplan et al., 1985).

  15. Comparison of carbon incorporation on the clean and hydrogenated Si( 0 0 1 ) reconstructed surfaces

    NASA Astrophysics Data System (ADS)

    Sonnet, Ph.; Stauffer, L.

    2002-06-01

    The size difference between carbon and silicon makes carbon incorporation in a silicon matrix difficult. We present here, in the framework of first-principle calculations, a systematic comparison of the initial stages of carbon penetration in the hydrogenated and non-hydrogenated Si(0 0 1) surfaces. The effect of the carbon position with respect to the surface predominates in the dihydrure phase, while the nature of the carbon adsorption site (α or β) plays the main role in the case of the non-hydrogenated surface. In both cases, C-C interactions can modify these schemes and third neighbour positions are favoured in the fourth and fifth layers, as observed in the silicon bulk. An energetic study as a function of the carbon chemical potential in the 0 to -7.4 eV range shows no transition points at which the preferred structures could change.

  16. The Effect of Carbon Monoxide on the Hydrogen Permeability of a Palladium Membrane

    NASA Astrophysics Data System (ADS)

    Katoh, Masahiro; Nishihara, Katsunori; Kinouchi, Koji; Chohama, Koichi; Horikawa, Toshihide; Tomida, Tahei; Sotowa, Ken-Ichiro

    Plating thin Palladium (Pd) film on the outer surface of a porous stainless steel tube enables very rapid hydrogen permeation with an absolute selectivity. Methane steam reforming for hydrogen production is performed in a Pd membrane reactor. In this reaction, carbon monoxide (CO) synthesized is known to affect hydrogen permeability. The effect on hydrogen permeability and the membrane stability were investigated. After hydrogen was flowed through Pd membrane for 1 hour, CO (1%, 10%, 100% diluted by helium) was flowed on the membrane for 1 hour, and hydrogen was re-permeated through the membrane. Under the all experiment, the temperature, the differential pressure and the flow rate of non-permeation side were 823K, 0.1 MPa and 10 ml·min-1, respectively. After the re-permeating hydrogen, the hydrogen permeation rate increased gradually. Finally the rate arrived at the constant value before CO was flowed. But the necessary time was depend on the concentration of CO. The necessary time for three concentration of CO 1%, 10%, and 100% were 30min, 60min, and 180min, respectively. The reason was that depositing carbon from CO affected to hydrogen permeability. The carbon was changed to methane by hydrogen flow and the membrane was recycled.

  17. Electronic structures of hydrogen functionalized carbon nanotube: Density functional theory (DFT) study

    NASA Astrophysics Data System (ADS)

    Tachikawa, Hiroto; Iyama, Tetsuji; Kawabata, Hiroshi

    2016-05-01

    Electronic structures and formation mechanism of hydrogen functionalized carbon nanotube (CNT) have been investigated by means of density functional theory (DFT) method. The mechanism of hydrogen addition reaction to the CNT surface was also investigated. Pure and boron-nitrogen (BN) substituted CNT (denoted by CNT and BN-CNT, respectively) were examined as the carbon nanotubes. It was found that the additions of hydrogen atom to B (boron atom) and C (carbon atom) sites of BN-CNT proceed without activation barrier, whereas the hydrogenation of N (nitrogen atom) site needs the activation energy. The electronic states of hydrogen functionalized CNT and BN-CNT were discussed on the basis of theoretical results.

  18. Insight into the mechanism of the thermal reduction of graphite oxide: deuterium-labeled graphite oxide is the key.

    PubMed

    Sofer, Zden?k; Jankovsk, Ond?ej; imek, Petr; Sedmidubsk, David; turala, Ji?; Kosina, Ji?; Mikov, Romana; Mackov, Anna; Mikulics, Martin; Pumera, Martin

    2015-05-26

    For the past decade, researchers have been trying to understand the mechanism of the thermal reduction of graphite oxide. Because deuterium is widely used as a marker in various organic reactions, we wondered if deuterium-labeled graphite oxide could be the key to fully understand this mechanism. Graphite oxides were prepared by the Hofmann, Hummers, Staudenmaier, and Brodie methods, and a deuterium-labeled analogue was synthesized by the Hofmann method. All graphite oxides were analyzed not only using the traditional techniques but also by gas chromatography-mass spectrometry (GC-MS) during exfoliation in hydrogen and nitrogen atmospheres. GC-MS enabled us to compare differences between the chemical compositions of the organic exfoliation products formed during the thermal reduction of these graphite oxides. Nuclear analytical methods (Rutherford backscattering spectroscopy, elastic recoil detection analysis) were used to calculate the concentrations of light elements, including the ratio of hydrogen to deuterium. Combining all of these results we were able to determine graphite oxide's thermal reduction mechanism. Carbon dioxide, carbon monoxide, and water are formed from the thermal reduction of graphite oxide. This process is also accompanied by various radical reactions that lead to the formation of a large amount of carcinogenic volatile organic compounds, and this will have major safety implications for the mass production of graphene. PMID:25894311

  19. Conformational changes of the glucocorticoid receptor ligand binding domain induced by ligand and cofactor binding, and the location of cofactor binding sites determined by hydrogen/deuterium exchange mass spectrometry

    PubMed Central

    Frego, Lee; Davidson, Walter

    2006-01-01

    HXMS (hydrogen/deuterium exchange mass spectrometry) of the glucocorticoid receptor ligand-binding domain (GR LBD) complexed with the agonist dexamethasone and the antagonist RU-486 is described. Variations in the rates of exchange were observed in regions consistent with the published crystal structures of GR LBD complexed with RU-486 when compared with the GR dexamethasone complex. We also report the HXMS results for agonist-bound GR LBD with the coactivator transcriptional intermediary factor 2 (TIF2) and anatagonist-bound GR LBD with nuclear receptor corepressor (NCoR). Alterations in exchange rates observed for agonist-bound GR LBD with TIF2 present were consistent with the published crystal structural contacts for the complex. Alterations in exchange rates observed for antagonist-bound GR LBD with NCoR were a subset of those observed with TIF2 binding, suggesting a common or overlapping binding site for coactivator and corepressor. PMID:16600964

  20. The effect of post-exposure heat treatment on the hydrogen embrittlement of high carbon steel

    SciTech Connect

    Robinson, M.J.; Sharp, R.M.

    1985-10-01

    High carbon steel wires were loaded in tension to 79% ultimate tensile strength (UTS) and cathodically charged with hydrogen. The times to failure by hydrogen embrittlement (HE) were statistically analyzed to obtain the minimum incubation time and the mean time to failure. Electrochemical measurements of the mobile hydrogen content showed that baking the wires for 2 h at 200 C was effective in reducing the lattice hydrogen concentration to the same level as in uncharged material. Baking dramatically increased the embrittlement susceptibility of the high carbon wire, however, reducing both the minimum incubation time and the mean time to failure. These unexpected findings are explained by the effect of temperature on reversible and irreversible hydrogen trapping. Baking this material is believed to release hydrogen from relatively low energy innocuous traps and allow it to concentrate in traps with higher interaction energies. Upon reloading, these sites act as significant stress concentrators, leading to more rapid failure.

  1. Molten metal reactor and method of forming hydrogen, carbon monoxide and carbon dioxide using the molten alkaline metal reactor

    DOEpatents

    Bingham, Dennis N.; Klingler, Kerry M.; Turner, Terry D.; Wilding, Bruce M.

    2012-11-13

    A molten metal reactor for converting a carbon material and steam into a gas comprising hydrogen, carbon monoxide, and carbon dioxide is disclosed. The reactor includes an interior crucible having a portion contained within an exterior crucible. The interior crucible includes an inlet and an outlet; the outlet leads to the exterior crucible and may comprise a diffuser. The exterior crucible may contain a molten alkaline metal compound. Contained between the exterior crucible and the interior crucible is at least one baffle.

  2. Deuterium in Iceland waters

    USGS Publications Warehouse

    Friedman, I.; Sigurgeirsson, T.; Gardarsson, O.

    1963-01-01

    From the deuterium analysis of 159 samples of water collected in Iceland from hot-water boreholes, cold and hot springs, rivers and rain, the geographical distribution of deuterium in surface waters is plotted. On the basis of the deuterium analysis, the water from boreholes near Reykjavik does not originate from local precipitation. The variation of deuterium content of these water wells with time suggests that these data can be used to determine the time of travel of recharge water to the various boreholes, as well as the surface recharge area. ?? 1963.

  3. Temperature dependence of deuterium retention in tungsten deposits by deuterium ion irradiation

    NASA Astrophysics Data System (ADS)

    Katayama, K.; Uehara, K.; Date, H.; Fukada, S.; Watanabe, H.

    2015-08-01

    Tungsten (W) deposits were formed by hydrogen plasma sputtering and blisters were observed on the surface. The W deposits and W foils were exposed to deuterium ions with 2 keV-D2+ to doses of 1.0 × 1021 D2+/m2 at 294 and 773 K in addition to 573 K in the present authors' previous work. Hydrogen isotopes release behaviors from the W deposits and W foils were observed by the thermal desorption spectroscopy method. The amount of deuterium released from the W deposit was considerably larger than that from W foil. The obtained deuterium retention in D/m2 was in the range of deuterium retention in polycrystalline tungsten. Not only implanted deuterium but also hydrogen, which was incorporated during the sputtering-deposition process, were released from the W deposits. A hydrogen release peak at around 1100 K was observed for the W deposits. This is considered to be due to the rupture of the blisters.

  4. Tribological studies of amorphous hydrogenated carbon films in a vacuum, spacelike environment

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    1991-01-01

    Recent work on the adhesion and friction properties of plasma-deposited amorphous hydrogenated carbon films and their dependence on preparation conditions are reviewed. The results of the study indicate that plasma deposition enables one to deposit a variety of amorphous hydrogenated carbon (a-C:H) exhibiting diamondlike friction behavior. The plasma-deposited a-C:H films can be effectively used as hard lubricating films on ceramic materials such as silicon nitride in vacuum.

  5. Carbon-13 in black sea waters and implications for the origin of hydrogen sulfide.

    PubMed

    Deuser, W G

    1970-06-26

    A combination of measurements of carbon-13 and the hydrogen sulfide content in Black Sea waters with available data on the total carbon dioxide in these waters indicates that the contribution of organic sulfur to the hydrogen sulfide lies between 3 and 5 percent and increases with depth. Likely causes for the increase are increasing productivity or upward movement of the anoxic zone during the facts last 2000 year. PMID:17759339

  6. Deuterium labeled studies of coal liquefaction mechanism

    SciTech Connect

    Morris, T.H.; Kline, E.A. )

    1989-04-01

    The mechanism of the formation of perylene in the presence of H-donor solvents and d{sub 10}-pyrine was studied. Pyrene has been shown to shuttle hydrogen atoms in coal liquefaction studies. Two H-donors, fluorene and 9,10-dihydrophenanthrene were reacted with d{sub 10}-pyrine and 1,1{prime}-binaphthyl in benzene at 470{degree}C for two hours. d{sub 10}-pyrine was synthesized by heating pyrene in a Parr bottle at 270{degree}C for 24 hours in the presence of deuterium choloide in deuterium oxide with a chromium metal catalyst. Mass spectral data showed deuterium incorporated mainly in the reactant binaphthyl and the product perylene probably at the 1, 4, 5 and 8-positions. No deuterium incorporation in the H-donors suggested no shuttling by these compounds while decreased deuterium in the d{sub 10}-pyrine denoted some kind of activity. Significant amounts of deuterium only on perylene and binaphthyl supported the bimolecular reaction between organic molecules.

  7. Hydrogen production using thermocatalytic decomposition of methane on Ni30/activated carbon and Ni30/carbon black.

    PubMed

    Srilatha, K; Viditha, V; Srinivasulu, D; Ramakrishna, S U B; Himabindu, V

    2016-05-01

    Hydrogen is an energy carrier of the future need. It could be produced from different sources and used for power generation or as a transport fuel which mainly in association with fuel cells. The primary challenge for hydrogen production is reducing the cost of production technologies to make the resulting hydrogen cost competitive with conventional fuels. Thermocatalytic decomposition (TCD) of methane is one of the most advantageous processes, which will meet the future demand, hence an attractive route for COx free environment. The present study deals with the production of hydrogen with 30 wt% of Ni impregnated in commercially available activated carbon and carbon black catalysts (samples coded as Ni30/AC and Ni30/CB, respectively). These combined catalysts were not attempted by previous studies. Pure form of hydrogen is produced at 850 °C and volume hourly space velocity (VHSV) of 1.62 L/h g on the activity of both the catalysts. The analysis (X-ray diffraction (XRD)) of the catalysts reveals moderately crystalline peaks of Ni, which might be responsible for the increase in catalytic life along with formation of carbon fibers. The activity of carbon black is sustainable for a longer time compared to that of activated carbon which has been confirmed by life time studies (850 °C and 54 sccm of methane). PMID:26233751

  8. Structure, hydrogen bonding and thermal expansion of ammonium carbonate monohydrate

    PubMed Central

    Fortes, A. Dominic; Wood, Ian G.; Alfè, Dario; Hernández, Eduardo R.; Gutmann, Matthias J.; Sparkes, Hazel A.

    2014-01-01

    We have determined the crystal structure of ammonium carbonate monohydrate, (NH4)2CO3·H2O, using Laue single-crystal diffraction methods with pulsed neutron radiation. The crystal is orthorhombic, space group Pnma (Z = 4), with unit-cell dimensions a = 12.047 (3), b = 4.453 (1), c = 11.023 (3) Å and V = 591.3 (3) Å3 [ρcalc = 1281.8 (7) kg m−3] at 10 K. The single-crystal data collected at 10 and 100 K are complemented by X-ray powder diffraction data measured from 245 to 273 K, Raman spectra measured from 80 to 263 K and an athermal zero-pressure calculation of the electronic structure and phonon spectrum carried out using density functional theory (DFT). We find no evidence of a phase transition between 10 and 273 K; above 273 K, however, the title compound transforms first to ammonium sesquicarbonate monohydrate and subsequently to ammonium bicarbonate. The crystallographic and spectroscopic data and the calculations reveal a quite strongly hydrogen-bonded structure (E HB ≃ 30–40 kJ mol−1), on the basis of H⋯O bond lengths and the topology of the electron density at the bond critical points, in which there is no free rotation of the ammonium cation at any temperature. The barrier to free rotation of the ammonium ions is estimated from the observed librational frequency to be ∼ 36 kJ mol−1. The c-axis exhibits negative thermal expansion, but the thermal expansion behaviour of the a and b axes is ormal. PMID:25449618

  9. Structure, hydrogen bonding and thermal expansion of ammonium carbonate monohydrate.

    PubMed

    Fortes, A Dominic; Wood, Ian G; Alfè, Dario; Hernández, Eduardo R; Gutmann, Matthias J; Sparkes, Hazel A

    2014-12-01

    We have determined the crystal structure of ammonium carbonate monohydrate, (NH4)2CO3·H2O, using Laue single-crystal diffraction methods with pulsed neutron radiation. The crystal is orthorhombic, space group Pnma (Z = 4), with unit-cell dimensions a = 12.047 (3), b = 4.453 (1), c = 11.023 (3) Å and V = 591.3 (3) Å(3) [ρcalc = 1281.8 (7) kg m(-3)] at 10 K. The single-crystal data collected at 10 and 100 K are complemented by X-ray powder diffraction data measured from 245 to 273 K, Raman spectra measured from 80 to 263 K and an athermal zero-pressure calculation of the electronic structure and phonon spectrum carried out using density functional theory (DFT). We find no evidence of a phase transition between 10 and 273 K; above 273 K, however, the title compound transforms first to ammonium sesquicarbonate monohydrate and subsequently to ammonium bicarbonate. The crystallographic and spectroscopic data and the calculations reveal a quite strongly hydrogen-bonded structure (EHB ≃ 30-40 kJ mol(-1)), on the basis of H...O bond lengths and the topology of the electron density at the bond critical points, in which there is no free rotation of the ammonium cation at any temperature. The barrier to free rotation of the ammonium ions is estimated from the observed librational frequency to be ∼ 36 kJ mol(-1). The c-axis exhibits negative thermal expansion, but the thermal expansion behaviour of the a and b axes is ormal. PMID:25449618

  10. Detection of New Infrared Spectral Features in Hydrogenated Amorphous Carbon

    NASA Astrophysics Data System (ADS)

    Grishko, V. I.; Duley, W. W.

    2000-11-01

    We have obtained high-resolution (1 cm-1) spectra of hydrogenated amorphous carbon (HAC) in both emission and absorption. Deconvolution of these spectra into Gaussian-Lorentzian components reveal two new features at 3098 cm-1 (3.23 μm) and 2890 cm-1 (3.46 μm) attributable to nonaromatic CCH2 and tertiary CH groups, respectively. In addition, relatively sharp lines (Δν~25 cm-1), which we assign to CH2 groups in cyclohydrocarbon molecules such as hexahydropyrene, appear on heating HAC to 800 K. We propose that these molecules are the precursors of Hn polycyclic aromatic hydrocarbons seen in low-excitation protoplanetary nebulae. The profile of the 2890 cm-1 (3.46 μm) tertiary CH feature detected as a component of HAC is very similar to that observed in dark clouds where it has been attributed to interstellar diamond-like material. An absorption/emission feature at 3098 cm-1 (3.23 μm) should also be present in ``transition'' sources, i.e., regions where the composition of the carbonaceous gas/dust component is evolving from a saturated, CH2, CH3-rich material to less saturated aromatic material. The role of H atom reaction and UV irradiation in determining spectra in the 2.8-3.7 μm region is briefly discussed. On the basis of our laboratory data we find that the absence of CH2, CH3 absorption in dark clouds can be understood if H atom reactions with HAC are inhibited as a result of an increased rate of gas-phase reactions.

  11. Transition metal activation and functionalization of carbon-hydrogen bonds

    SciTech Connect

    Jones, W.D.

    1990-07-01

    This project is directed toward the continued investigation of the fundamental thermodynamic and kinetic factors that influence carbon-hydrogen bond activation at homogeneous transition metal centers. The project is also directed toward the conversion of hydrocarbons into functionalized products of potential use to chemical industry. In the past year, advances have been made in both understanding the interactions of hydrocarbons with metals and in the functionalized of hydrocarbons. Major advanced that have been made include: (1) We have found that RhCl(PR{sub 3}){sub 2}(CNR) complexes can catalyze the insertion of isonitriles into the C-H bonds of arenes upon photolysis. (2) We have also examined reactions of a series of arenes with (C{sub 5}Me{sub 5})Rh(PMe{sub 3})PhH and begun to map out the kinetic and thermodynamic preferences for arene coordination. (3) We have begun to examine the reactions of rhodium pyrazolylborates for isonitrile functionalization of C-H bonds. (4) We have completed studies of the reactions of (C{sub 5}Me{sub 5})Rh(PMe{sub 3})H{sub 2} with D{sub 2} and PMe{sub 3} that indicate that both {eta}{sup 5} {yields} {eta}{sup 3} ring slippage and metal to ring hydride migration occur more faciley than reductive elimination of H{sub 12}. (5) We have examined the reactions of heterocycles with (C{sub 5}Me{sub 5})Rh(PMe{sub 3})PhH and found that pyrrole and furan undergo C-H or N-H activation.

  12. Transition metal activation and functionalization of carbon-hydrogen bonds

    SciTech Connect

    Jones, W.D.

    1991-06-01

    This project is directed towards the continued investigation of the fundamental thermodynamic and kinetic factors that influence carbon-hydrogen bond activation at homogeneous transition metal centers. The project is also directed towards the conversion of hydrocarbons into functionalized products of potential use to the chemical industry. In the past two years, advances have been made in both understanding the interactions of hydrocarbons with metals and in the functionalization of hydrocarbons. Major advances that have been made include: (1) We have found that RhCl(PR{sub 3}){sub 2}(CNR) complexes can catalyze the insertion of isonitriles into the C-H bonds of arenes upon photolysis. (2) We have also examined reactions of a series of arenes with (C{sub 5}Me{sub 5})Rh(PMe{sub 3})PhH and begun to map out the kinetic and thermodynamic preferences for arene coordination. (3) We have begun to examine the reactions of rhodium isonitrile pyrazolylborates for alkane and arene C-H bond activation. A new, labile, carbodiimide precursor has been developed for these studies. (4) We have completed studies of the reactions of (C{sub 5}Me{sub 5)}Rh(PMe{sub 3})H{sub 2} with D{sub 2} and PMe{sub 3} that indicate that both {eta}{sup 5} {yields} {eta}{sup 3} ring slippage and metal to ring hydride migration occur more facilely than thermal reductive elimination of H{sub 2}. (5) We have examined the reactions of heterocycles with (C{sub 5}Me{sub 5})Rh(PMe{sub 3})PhH and found that pyrrole and furan undergo C-H or N-H activation. Thiophene, however, undergoes C-S bond oxidative addition, and the mechanism of activation has been shown to proceed through sulfur coordination prior to C-S insertion. 43 refs., 9 figs., 4 tabs.

  13. Design and Development of New Carbon-Based Sorbent Systems for an Effective Containment of Hydrogen

    SciTech Connect

    Alan C. Cooper

    2012-05-03

    This is a summary for work performed under cooperative agreement DE FC36 04GO14006 (Design and Development of New Carbon-based Sorbent Systems for an Effective Containment of Hydrogen). The project was directed to discover new solid and liquid materials that use reversible catalytic hydrogenation as the mechanism for hydrogen capture and storage. After a short period of investigation of solid materials, the inherent advantages of storing and transporting hydrogen using liquid-phase materials focused our attention exclusively on organic liquid hydrogen carriers (liquid carriers). While liquid carriers such as decalin and methylcyclohexane were known in the literature, these carriers suffer from practical disadvantages such as the need for very high temperatures to release hydrogen from the carriers and difficult separation of the carriers from the hydrogen. In this project, we were successful in using the prediction of reaction thermodynamics to discover liquid carriers that operate at temperatures up to 150 C lower than the previously known carriers. The means for modifying the thermodynamics of liquid carriers involved the use of certain molecular structures and incorporation of elements other than carbon into the carrier structure. The temperature decrease due to the more favorable reaction thermodynamics results in less energy input to release hydrogen from the carriers. For the first time, the catalytic reaction required to release hydrogen from the carriers could be conducted with the carrier remaining in the liquid phase. This has the beneficial effect of providing a simple means to separate the hydrogen from the carrier.

  14. Hydrogen and elemental carbon production from natural gas and other hydrocarbons

    DOEpatents

    Detering, Brent A.; Kong, Peter C.

    2002-01-01

    Diatomic hydrogen and unsaturated hydrocarbons are produced as reactor gases in a fast quench reactor. During the fast quench, the unsaturated hydrocarbons are further decomposed by reheating the reactor gases. More diatomic hydrogen is produced, along with elemental carbon. Other gas may be added at different stages in the process to form a desired end product and prevent back reactions. The product is a substantially clean-burning hydrogen fuel that leaves no greenhouse gas emissions, and elemental carbon that may be used in powder form as a commodity for several processes.

  15. Performance of allotropic forms of carbon in hydrogen at high temperatures

    SciTech Connect

    Schweitzer, D.G.; Sastre, C.

    1991-01-02

    There is considerable evidence that at temperatures near 3000{degree}K the mass loss of many graphites in at least pressure (1 atm) hydrogen cannot be accounted for by the formation of methane, acetylene, or other hydrocarbons. Although some data indicate that some graphitic carbons exhibit particulate mass loss in vacuum and inert gas, there is sufficient data comparing mass loss in hydrogen and inert environments to determine if hydrogen catalyzes particulate mass loss through evaporation in some materials, or if heavy inert gases reduce evaporation rates. Data pertinent to these effects are particularly important for the high temperature heat treated glassy carbons that appear resistant to both chemical oxidation and abnormally high mass loss due to particulate emission. At the present time, it is our belief that some factors of carbon may have the potential to retain integrity for short times in hydrogen at temperatures near 3000{degree}K. 29 refs., 5 figs., 2 tabs.

  16. Nature of the Bound States of Molecular Hydrogen in Carbon Nanohorns

    SciTech Connect

    Fernandez-Alonso, F.; Bermejo, F. J.; Cabrillo, C.; Leon, V.; Saboungi, M. L.

    2007-05-25

    The effects of confining molecular hydrogen within carbon nanohorns are studied via high-resolution quasielastic and inelastic neutron spectroscopies. Both sets of data are remarkably different from those obtained in bulk samples in the liquid and crystalline states. At temperatures where bulk hydrogen is liquid, the spectra of the confined sample show an elastic component indicating a significant proportion of immobile molecules as well as distinctly narrower quasielastic line widths and a strong distortion of the line shape of the para{yields}ortho rotational transition. The results show that hydrogen interacts far more strongly with such carbonous structures than it does to carbon nanotubes, suggesting that nanohorns and related nanostructures may offer significantly better prospects as lightweight media for hydrogen storage applications.

  17. Effects of hydrogen on carbon steels at the Multi-Function Waste Tank Facility

    SciTech Connect

    Carlos, W.C.

    1995-02-08

    Concern has been expressed that hydrogen produced by corrosion, radiolysis, and decomposition of the waste could cause embrittlement of the carbon steel waste tanks at Hanford. The concern centers on the supposition that the hydrogen evolved in many of the existing tanks might penetrate the steel wall of the tank and cause embrittlement that might lead to catastrophic failure. This document reviews literature on the effects of hydrogen on the carbon steel proposed for use in the Multi-Function Waste Tank Facility for the time periods before and during construction as well as for the operational life of the tanks. The document draws several conclusions about these effects. Molecular hydrogen is not a concern because it is not capable of entering the steel tank wall. Nascent hydrogen produced by corrosion reactions will not embrittle the steel because the mild steel used in tank construction is not hard enough to be susceptible to hydrogen stress cracking and the corrosion product hydrogen is not produced at a rate sufficient to cause either loss in tensile ductility or blistering. If the steel intended for use in the tanks is produced to current technology, fabricated in accordance with good construction practice, postweld heat treated, and operated within the operating limits defined, hydrogen will not adversely affect the carbon steel tanks during their 50-year design life. 26 refs.

  18. Analysis of diffential absorption lidar technique for measurements of anhydrous hydrogen chloride from solid rocket motors using a deuterium fluoride laser

    NASA Technical Reports Server (NTRS)

    Bair, C. H.; Allario, F.

    1977-01-01

    An active optical technique (differential absorption lidar (DIAL)) for detecting, ranging, and quantifying the concentration of anhydrous HCl contained in the ground cloud emitted by solid rocket motors (SRM) is evaluated. Results are presented of an experiment in which absorption coefficients of HCl were measured for several deuterium fluoride (DF) laser transitions demonstrating for the first time that a close overlap exists between the 2-1 P(3) vibrational transition of the DF laser and the 1-0 P(6) absorption line of HCl, with an absorption coefficient of 5.64 (atm-cm) to the -1 power. These measurements show that the DF laser can be an appropriate radiation source for detecting HCl in a DIAL technique. Development of a mathematical computer model to predict the sensitivity of DIAL for detecting anhydrous HCl in the ground cloud is outlined, and results that assume a commercially available DF laser as the radiation source are presented.

  19. Direct and reversible hydrogenation of CO2 to formate by a bacterial carbon dioxide reductase.

    PubMed

    Schuchmann, K; Müller, V

    2013-12-13

    Storage and transportation of hydrogen is a major obstacle for its use as a fuel. An increasingly considered alternative for the direct handling of hydrogen is to use carbon dioxide (CO2) as an intermediate storage material. However, CO2 is thermodynamically stable, and developed chemical catalysts often require high temperatures, pressures, and/or additives for high catalytic rates. Here, we present the discovery of a bacterial hydrogen-dependent carbon dioxide reductase from Acetobacterium woodii directly catalyzing the hydrogenation of CO2. We also demonstrate a whole-cell system able to produce formate as the sole end product from dihydrogen (H2) and CO2 as well as syngas. This discovery opens biotechnological alternatives for efficient CO2 hydrogenation either by using the isolated enzyme or by employing whole-cell catalysis. PMID:24337298

  20. Nanostructured Pt decorated graphene and multi walled carbon nanotube based room temperature hydrogen gas sensor.

    PubMed

    Kaniyoor, Adarsh; Imran Jafri, R; Arockiadoss, T; Ramaprabhu, S

    2009-12-01

    Herein, we report the fabrication of hydrogen gas sensors based on noble nanometal decorated one dimensional multi walled carbon nanotubes and two dimensional graphene by a simple drop casting technique, with practical applications in view. Pt decorated functionalized graphene sheets (Pt/f-G) and Pt decorated functionalized multi walled carbon nanotubes (Pt/f-MWNT) were synthesized and employed as hydrogen sensors. Systematic investigation of hydrogen sensing, at a low detection level of 4 vol% hydrogen in air, of (Pt/f-G) reveals a response time comparable to that of (Pt/f-MWNT) but with a two fold increase in the sensitivity at room temperature. These sensors were also found to be stable over repeated cycles of hydrogenation and dehydrogenation. PMID:20648277

  1. NMR Stratagems for the Study of Multiple Kinetic Hydrogen/Deuterium Isotope Effectsof Proton Exchange. Example: Di-p-fluorophenylformamidine/THF

    NASA Astrophysics Data System (ADS)

    Limbach, Hans-Heinrich; Meschede, Ludger; Scherer, Gerd

    1989-05-01

    Stratagems are presented for the determination of kinetic isotope effects of proton exchange reactions by dynamic NMR spectroscopy. In such experiments, lineshape analyses and/or polarization transfer experiments are performed on the exchanging protons or deuterons as well as on remote spins, as a function of the deuterium fraction in the mobile proton sites. These methods are NMR analogs of previous proton inventory techniques involving classical kinetic methods. A theory is developed in order to derive the kinetic isotope effects as well as the number of transferred protons from the experimental NMR spectra. The technique is then applied to the problem of proton exchange in the system 15N,15N'-di-p-fluorophenylibrmamidine, a nitrogen analog of formic acid, dissolved in tetrahydrofuran-d8 (THF). DFFA forms two conformers in THF to which s-trans and s-cis structures have been assigned. Only the s-trans conformer is able to dimerize and exchange protons. Lineshape simulations and magnetization transfer experiments were carried out at 189,2 K, at a concentration of 0.02 mol l-1, as a function of the deuterium fraction D in the 1H-15N sites. Using 1H NMR spectroscopy, a linear dependence of the inverse proton lifetimes on D was observed. From this it was concluded that two protons are transported in the rate limiting step of the proton exchange. This result is expected for a double proton transfer in an s-trans dimer with a cyclic structure. The full kinetic HH/HD/DD isotope effects of 233:11:1 at 189 K were determined through 19F NMR experiments on the same samples. The deviation from the rule of geometric mean, although substantial, is much smaller than found in previous studies of intramolecular HH transfer reactions. Possible causes of this effect are discussed.

  2. The Path of Carbon in Photosynthesis IX. Photosynthesis, Photoreduction, and the Hydrogen-Oxygen-Carbon Dioxide Dark Reaction

    DOE R&D Accomplishments Database

    Badin, E. J.; Calvin, M.

    1950-02-01

    A comparison of the rates of fixation of Carbon 14 dioxide in algae for the processes of photosynthesis, photoreduction and the hydrogen-oxygen-carbon dioxide dark reaction has been made. For the same series of experiments, rates of incorporation of tracer carbon into the separate soluble components using the radiogram method have been determined. The mechanism of carbon dioxide uptake has been shown to occur via two distinct paths. In all cases studied, essentially the same compounds appear radioactive. The distribution with time, however, differs markedly.

  3. Towards the mechanism of electrochemical hydrogen storage in nanostructured carbon materials

    NASA Astrophysics Data System (ADS)

    Jurewicz, K.; Frackowiak, E.; Béguin, F.

    The mechanism of electrochemical hydrogen storage in a nanostructured carbon electrode using the electrodecomposition of KOH and H2SO4 aqueous solutions has been investigated by means of galvanostatic and voltammetry techniques. The role of charging the electrical double layer is carefully considered during the process of hydrogen insertion and deinsertion into carbon, i.e. electroreduction and electrooxidation, respectively. Once the electrode potential becomes lower than the equilibrium potential, hydrogen in the zero oxidation state is formed by the reduction of water in alkaline solution or the reduction of hydronium ions H3O+ in acidic medium. In the next step, hydrogen is physically adsorbed (Had) onto the carbon surface and diffuses into the bulk of the carbon material with an efficiency which depends on the type of electrolyte. A higher amount of hydrogen is stored using the KOH medium, and the galvanostatic oxidation shows a well-defined plateau around -0.5 V vs. Normal Hydrogen Electrode (NHE). Due to the high overvoltage value in KOH (η=0.55 V), the recombination steps of Had leading to molecular hydrogen evolution through the chemical (Tafel) or electrochemical (Heyrovsky) reactions are less favoured than in an H2SO4 medium (η=0.32 V). Hence, a meaningful sorption of hydrogen is observed only in the basic electrolyte which shows a reversible capacity of 350 mAh/g (i.e. 1.3 wt.%) with a good electrical efficiency. Such performance demonstrates that nanostructured activated carbons might be a promising alternative to metallic alloys for electrochemical hydrogen storage.

  4. Measuring the primordial deuterium abundance during the cosmic dark ages.

    PubMed

    Sigurdson, Kris; Furlanetto, Steven R

    2006-09-01

    We discuss how measurements of fluctuations in the absorption of cosmic microwave background photons by neutral gas at redshifts z approximately 7-200 could reveal the primordial deuterium abundance of the Universe. The strength of the cross-correlation of brightness-temperature fluctuations in the redshifted 21-cm line of hydrogen with those in the redshifted 92-cm line of deuterium is proportional to the value of the deuterium-to-hydrogen ratio [D/H] fixed during big bang nucleosynthesis. Although challenging, this measurement would provide the cleanest possible determination of [D/H], free from contamination by structure formation processes at lower redshifts. We additionally report our result for the thermal spin-change cross section in deuterium-hydrogen scattering. PMID:17026353

  5. Carbide-Derived Carbons with Tunable Porosity Optimized for Hydrogen Storage

    SciTech Connect

    Fisher, John E.; Gogotsi, Yury; Yildirim, Taner

    2010-01-07

    On-board hydrogen storage is a key requirement for fuel cell-powered cars and trucks. Porous carbon-based materials can in principle adsorb more hydrogen per unit weight at room temperature than liquid hydrogen at -176 oC. Achieving this goal requires interconnected pores with very high internal surface area, and binding energies between hydrogen and carbon significantly enhanced relative to H2 on graphite. In this project a systematic study of carbide-derived carbons, a novel form of porous carbon, was carried out to discover a high-performance hydrogen sorption material to meet the goal. In the event we were unable to improve on the state of the art in terms of stored hydrogen per unit weight, having encountered the same fundamental limit of all porous carbons: the very weak interaction between H2 and the carbon surface. On the other hand we did discover several strategies to improve storage capacity on a volume basis, which should be applicable to other forms of porous carbon. Further discoveries with potentially broader impacts include • Proof that storage performance is not directly related to pore surface area, as had been previously claimed. Small pores (< 1.5 nm) are much more effective in storing hydrogen than larger ones, such that many materials with large total surface areas are sub-par performers. • Established that the distribution of pore sizes can be controlled during CDC synthesis, which opens the possibility of developing high performance materials within a common family while targeting widely disparate applications. Examples being actively pursued with other funding sources include methane storage, electrode materials for batteries and supercapacitors with record high specific capacitance, and perm-selective membranes which bind cytokines for control of infections and possibly hemodialysis filters.

  6. Carbon, Hydrogen, and Oxygen Isotope Ratios of Cellulose from Plants Having Intermediary Photosynthetic Modes 1

    PubMed Central

    Sternberg, Leonel O'Reilly; Deniro, Michael J.; Ting, Irwin P.

    1984-01-01

    Carbon and hydrogen isotope ratios of cellulose nitrate and oxygen isotope ratios of cellulose from species of greenhouse plants having different photosynthetic modes were determined. When hydrogen isotope ratios are plotted against carbon isotope ratios, four clusters of points are discernible, each representing different photosynthetic modes: C3 plants, C4 plants, CAM plants, and C3 plants that can shift to CAM or show the phenomenon referred to as CAM-cycling. The combination of oxygen and carbon isotope ratios does not distinguish among the different photosynthetic modes. Analysis of the carbon and hydrogen isotope ratios of cellulose nitrate should prove useful for screening different photosynthetic modes in field specimens that grew near one another. This method will be particularly useful for detection of plants which show CAM-cycling. PMID:16663360

  7. Suppressed thermal conductivity of ultrathin carbon nanotube(2, 1) upon hydrogenation

    SciTech Connect

    Zhang, Tingting; Zhu, Liyan Chen, Guibin

    2015-09-21

    Non-equilibrium molecular dynamic simulations reveal that the thermal conductivity of ultrathin carbon nanotube (CNT)(2, 1) is significantly suppressed upon hydrogenation. The addition of hydrogen atoms to two-coordinated carbon atoms lowers the participation ratios of phonon modes, thus indicating that the spatial distribution of phonons becomes localized. Furthermore, the phonon lifetimes are remarkably shortened in hydrogenated CNT(2, 1) (HCNT(2, 1)) compared with those of bare CNT(2, 1). The lowered participation ratios and lifetimes of phonon modes are responsible for the significant reduction of thermal conductivity in HCNT(2, 1). Our study is also helpful for understanding the weakened thermal transport abilities in carbon polymers, namely, the cross links formed between individual polymer chains will hinder the thermal conduction along polymers, even though the single straight carbon polymer has a high and divergent thermal conductivity.

  8. Continuous monitoring of hydrogen and carbon dioxide at Stromboli volcano

    NASA Astrophysics Data System (ADS)

    Di Martino, Roberto M. R.; Camarda, Marco; Gurrieri, Sergio; Valenza, Mariano

    2015-04-01

    Geochemical monitoring of fumarole and soil gases is a powerful tool for volcano surveillance, for investigating the subsurface magma dynamics, and for hazard assessment in volcanic areas. The monitoring of both carbon dioxide (CO2) flux, and hydrogen (H2) concentration in active volcanic areas helps to improve the understanding of the processes linking the surface gas emissions, the chemistry of the magmatic gases, and the volcanic activity. The CO2 flux measurement is a routine technique for volcano monitoring purposes, because of CO2 is the second-abundant component of the gas phase in silicate magmas, attaining saturation at the mantle to deep crustal level. The H2 concentration has provided indications concerning the oxygen fugacity of magmatic gases, a parameter that changes over a wide range of low values (10-16 - 10-8 bar), and affects the redox state of multivalent elements. This study reports on the use a tailor-made automatic system developed for continuous monitoring purposes of H2 concentration and CO2 flux in the summit area of Stromboli volcano (Aeolian islands). The automatic device consists of an H2-selective electrochemical sensor, and two IR-spectrophotometers for measuring the CO2 flux in agreement with the dynamic concentration method. The data collected by the automatic system deployed at Stromboli from 19 May 2009 to 15 December 2010 are presented herein. The data processing provides a better understanding of the relationships between the evolution of the low temperature fumarolic emissions, and the volcanic activity. The results of the data analysis indicates that the high frequency variations exhibited by CO2 flux and H2 concentration are positively correlated with the eruptive activity of Stromboli, typically changing on time scale of hours or days. Furthermore, the investigation of the relationships between CO2 flux and H2 concentration provides an evaluation of the depth of the degassing source, by which the gas mixture containing H2 and CO2 starts to move through the rock fractures. Our data indicates that the depth of the degassing source ranges between 2 and 4 km in the volcano plumbing system, in agreement with the magma storage zone that has been proposed by other geochemical, volcanological, petrological and geophysical investigations.

  9. Transition metal activation and functionalization of carbon-hydrogen bonds

    SciTech Connect

    Jones, W.D.

    1992-06-01

    We are investigating the fundamental thermodynamic and kinetic factors that influence carbon-hydrogen bond activation at homogeneous transition metal centers and the conversion of hydrocarbons into functionalized products of potential use to the chemical industry. Advances have been made in both understanding the interactions of hydrocarbons with metals and in the functionalization of hydrocarbons. We have found that RhCl(PR{sub 3}){sub 2}(CNR) complexes can catalyze the insertion of isonitriles into the C-H bonds or arenes upon photolysis. The mechanism of these reactions was found to proceed by way of initial phosphine dissociation, followed by C-H activation and isonitrile insertion. We have also examined reactions of a series of arenes with (C{sub 5}Me{sub 5})Rh(PMe{sub 3})PhH and begun to map out the kinetic and thermodynamic preferences for arene coordination. The effects of resonance, specifically the differences in the Hueckel energies of the bound vs free ligand, are now believed to fully control the C-H activation/{eta}{sup 2}-coordination equilibria. We have begun to examine the reactions of rhodium isonitrile pyrazolylborates for alkane and arene C-H bond activation. A new, labile, carbodiimide precursor has been developed for these studies. We have completed studies of the reactions of (C{sub 5}Me{sub 5})Rh(PMe{sub 3})H{sub 2} with D{sub 2} and PMe{sub 3} that indicate that both {eta}{sup 5} {yields} {eta}{sup 3} ring slippage and metal to ring hydride migration occur more facilely than thermal reductive elimination of H{sub 2}. We have examined the reactions of heterocycles with (C{sub 5}Me{sub 5})Rh(PMe{sub 3})PhH and found that pyrrole and furan undergo C-H or N-H activation. Thiophene, however, undergoes C-S bond oxidative addition, and the mechanism of activation has been shown to proceed through sulfur coordination prior to C-S insertion.

  10. Rhodium-catalyzed hydrogenation of carbon dioxide to formic acid

    SciTech Connect

    Tsai, Jing-Cherng; Nicholas, K.M.

    1992-06-17

    The complex [Rh(NBD)(PMe{sub 2}Ph){sub 3}]BF{sub 4} (2; NBD = norbornadiene) has been found to serve as a precatalyst for the hydrogenation of carbon dioxide to formic acid at moderate temperatures in THF solution, with turnover numbers of 10-60/day. Water accelerates formic acid production, whereas PMe{sub 2}Ph is an inhibitor. Kinetic studies show that the rate of formic acid appearance in first order each in [2], pH{sub 2}, and p{sub CO2} in the range 50-300 psi (following prehydrogenation). In situ high-pressure IR and NMR experiments reveal that the addition of H{sub 2} to [Rh(NBD)(PMe{sub 2}Ph){sub 3}]BF{sub 4} (2) produces rhodium dihydride complexes [H{sub 2}Rh(PMe{sub 2}Ph){sub 3}(S)]BF{sub 4}(4, 5; S = H{sub 2}O, THF) and [H{sub 2}Rh(PMe{sub 2}Ph){sub 4}]BF{sub 4} (3). IR and NMR studies of the reaction of 3-5 with CO{sub 2} indicate that 3 is unreactive toward CO{sub 2} but that 4 and 5 insert CO{sub 2} to give species 6 and 7, formulated as formato complexes [HRh(S)(PMe{sub 2}Ph){sub 2}({eta}{sup 2}-OCHO)]BF{sub 4}, respectively; complexes 6 and 7 are also detected under catalytic conditions by IR spectroscopy. Aquo dihydride complex 4 has been found to insert CO{sub 2} more rapidly than the THF complex 5. [H{sub 2}Rh(PMe{sub 2}Ph){sub 3}(S)]BF{sub 4} (4, 5) also catalyze the decomposition of formic acid to CO{sub 2} and H{sub 2}. Combined kinetic and spectroscopic results suggest that reductive elimination of formic acid from the intermediate formato complexes is the rate-limiting step in the catalytic cycle. 30 refs., 11 figs., 1 tab.

  11. SPITZER OBSERVATIONS OF SHOCK-EXCITED HYDROGEN DEUTERIDE IN IC 443C, HH 7, AND HH 54: PROBING THE GAS-PHASE DEUTERIUM ABUNDANCE IN THE DENSE INTERSTELLAR MEDIUM

    SciTech Connect

    Yuan Yuan; Neufeld, David A.; Sonnentrucker, Paule; Melnick, Gary J.; Watson, Dan M.

    2012-07-10

    We present and analyze observations-carried out using the Infrared Spectrograph (IRS) on the Spitzer Space Telescope-of the R(3) and R(4) pure rotational lines of hydrogen deuteride (HD) detected from shock-heated material associated with the supernova remnant IC 443C and with the Herbig-Haro objects HH 7 and HH 54. Assuming a continuous temperature distribution for gas observed along the sight lines, we have constrained the gas density to be in the {approx}10{sup 3}-10{sup 4} cm{sup -3} range, using both spectroscopic data for H{sub 2}, HD, and CO from IRS and from the Infrared Space Observatory (ISO), as well as photometric data from Spitzer's Infrared Array Camera. The derived HD abundance relative to H{sub 2} is quite sensitive to the assumed excitation conditions in the emitting gas. Assuming that HD accounts for all gas-phase deuterium in the emitting material, and using all the available spectroscopic data to constrain the excitation conditions, we obtained gas-phase deuterium abundances [D/H]{sub gas} of 0.95{sup +0.54}{sub -0.27} Multiplication-Sign 10{sup -5} and 0.87{sup +0.31}{sub -0.27} Multiplication-Sign 10{sup -5} (statistical errors only) for IC 443C and HH 54, respectively. The uncertainties in the HD abundance are dominated by systematic effects related to the poorly known excitation conditions, and more accurate estimates of the HD abundance in shocked molecular clouds will require measurements of the emission in additional HD rotational transitions.

  12. An international multi-laboratory investigation of carbon-based hydrogen sorbent materials

    NASA Astrophysics Data System (ADS)

    Hurst, Katherine E.; Parilla, Philip A.; O'Neill, Kevin J.; Gennett, Thomas

    2016-01-01

    New materials are needed to achieve the hydrogen storage targets set out by the US Department of Energy for fuel cell vehicular applications. In order to enable the pathway toward this discovery, precise and accurate characterization of the hydrogen storage performance of these materials is needed. Determining the precise and accurate hydrogen storage capacity of materials requires rigorous attention to detailed experimental parameters and methodology. Slight errors in even small experimental details can result in a large deviation in the determination of the material's true characteristics. Here, we compare measurements of the gravimetric excess hydrogen uptake capacities for two different carbon sorbent materials measured by different laboratories at ambient and liquid N2 temperatures. The participants for this study consist of research laboratories led by experienced scientists in the hydrogen storage field. This collaborative evaluation of standard sorbents illustrated considerable reproducibility over a broad range of materials' hydrogen sorption gravimetric capacities.

  13. Preparation and characterization of ordered porous carbons for increasing hydrogen storage behaviors

    SciTech Connect

    Lee, Seul-Yi; Park, Soo-Jin

    2011-10-15

    We prepared ordered porous carbons (PCs) by using a replication method that had well-organized mesoporous silica as a template with various carbonization temperatures in order to investigate the possibility of energy storage materials. The microstructure and morphologies of the samples are characterized by XRD, TEM, and FT-Raman spectroscopy. N{sub 2} adsorption isotherms are analyzed by the t-plot method, as well as the BET and the H-K method in order to characterize the specific surface area, pore volume, and pore size distribution of the samples, respectively. The capacity of the hydrogen adsorption of the samples is evaluated by BEL-HP at 77 K and 1 bar. From the results, we are able to confirm that the synthesis of the samples can be accurately governed by the carbonization temperature, which is one of the effective parameters for developing the textural properties of the carbon materials, which affects the behaviors of the hydrogen storage. - Graphical abstract: It is described that the considerable long-range ordering and the presence of mono-dimensional aligned channels between the two aligned nanorods of the porous framework from the SBA-15 was retained in the T-950 sample during the carbonization process. Highlights: > Ordered porous carbons (PCs) are synthesized with various carbonization temperatures by using a replication method. > Carbonization temperature plays an important role in shrinking the micropores during the carbonization process of PCs. > The textural and structural properties of the PCs are good parameters for enhancing the hydrogen storage capacity.

  14. Carbon Dioxide in Exoplanetary Atmospheres: Rarely Dominant Compared to Carbon Monoxide and Water in Hot, Hydrogen-dominated Atmospheres

    NASA Astrophysics Data System (ADS)

    Heng, Kevin; Lyons, James R.

    2016-02-01

    We present a comprehensive study of the abundance of carbon dioxide in exoplanetary atmospheres in hot, hydrogen-dominated atmospheres. We construct novel analytical models of systems in chemical equilibrium that include carbon monoxide, carbon dioxide, water, methane and acetylene and relate the equilibrium constants of the chemical reactions to temperature and pressure via the tabulated Gibbs free energies. We prove that such chemical systems may be described by a quintic equation for the mixing ratio of methane. By examining the abundances of these molecules across a broad range of temperatures (spanning equilibrium temperatures from 600 to 2500 K), pressures (via temperature-pressure profiles that explore albedo and opacity variations) and carbon-to-oxygen ratios, we conclude that carbon dioxide is subdominant compared to carbon monoxide and water. Atmospheric mixing does not alter this conclusion if carbon dioxide is subdominant everywhere in the atmosphere. Carbon dioxide and carbon monoxide may attain comparable abundances if the metallicity is greatly enhanced, but this property is negated by temperatures above 1000 K. For hydrogen-dominated atmospheres, our generic result has the implication that retrieval studies may wish to set the subdominance of carbon dioxide as a prior of the calculation and not let its abundance completely roam free as a fitting parameter, because it directly affects the inferred value of the carbon-to-oxygen ratio and may produce unphysical conclusions. We discuss the relevance of these implications for the hot Jupiter WASP-12b and suggest that some of the previous results are chemically impossible. The relative abundance of carbon dioxide to acetylene is potentially a sensitive diagnostic of the carbon-to-oxygen ratio.

  15. Hydrogen venting characteristics of commercial carbon-composite filters and applications to TRU waste

    SciTech Connect

    Callis, E.L.; Marshall, R.S.; Cappis, J.H.

    1997-04-01

    The generation of hydrogen (by radiolysis) and of other potentially flammable gases in radioactive wastes which are in contact with hydrogenous materials is a source of concern, both from transportation and on-site storage considerations. Because very little experimental data on the generation and accumulation of hydrogen was available in actual waste materials, work was initiated to experimentally determine factors affecting the concentration of hydrogen in the waste containers, such as the hydrogen generation rate, (G-values) and the rate of loss of hydrogen through packaging and commercial filter-vents, including a new design suitable for plastic bags. This report deals only with the venting aspect of the problem. Hydrogen venting characteristics of two types of commercial carbon-composite filter-vents, and two types of PVC bag closures (heat-sealed and twist-and-tape) were measured. Techniques and equipment were developed to permit measurement of the hydrogen concentration in various layers of actual transuranic (TRU) waste packages, both with and without filter-vents. A test barrel was assembled containing known configuration and amounts of TRU wastes. Measurements of the hydrogen in the headspace verified a hydrogen release model developed by Benchmark Environmental Corporation. These data were used to calculate revised wattage Emits for TRU waste packages incorporating the new bag filter-vent.

  16. Compound-specific carbon, nitrogen, and hydrogen isotopic ratios for amino acids in CM and CR chondrites and their use in evaluating potential formation pathways

    NASA Astrophysics Data System (ADS)

    Elsila, Jamie E.; Charnley, Steven B.; Burton, Aaron S.; Glavin, Daniel P.; Dworkin, Jason P.

    2012-09-01

    Stable hydrogen, carbon, and nitrogen isotopic ratios (δD, δ13C, and δ15N) of organic compounds can reveal information about their origin and formation pathways. Several formation mechanisms and environments have been postulated for the amino acids detected in carbonaceous chondrites. As each proposed mechanism utilizes different precursor molecules, the isotopic signatures of the resulting amino acids may indicate the most likely of these pathways. We have applied gas chromatography with mass spectrometry and combustion isotope ratio mass spectrometry to measure the compound-specific C, N, and H stable isotopic ratios of amino acids from seven CM and CR carbonaceous chondrites: CM1/2 Allan Hills (ALH) 83100, CM2 Murchison, CM2 Lewis Cliff (LEW) 90500, CM2 Lonewolf Nunataks (LON) 94101, CR2 Graves Nunataks (GRA) 95229, CR2 Elephant Moraine (EET) 92042, and CR3 Queen Alexandra Range (QUE) 99177. We compare the isotopic compositions of amino acids in these meteorites with predictions of expected isotopic enrichments from potential formation pathways. We observe trends of decreasing δ13C and increasing δD with increasing carbon number in the α-H, α-NH2 amino acids that correspond to predictions made for formation via Strecker-cyanohydrin synthesis. We also observe light δ13C signatures for β-alanine, which may indicate either formation via Michael addition or via a pathway that forms primarily small, straight-chain, amine-terminal amino acids (n-ω-amino acids). Higher deuterium enrichments are observed in α-methyl amino acids, indicating formation of these amino acids or their precursors in cold interstellar or nebular environments. Finally, individual amino acids are more enriched in deuterium in CR chondrites than in CM chondrites, reflecting different parent-body chemistry.

  17. Compound-Specific Carbon, Nitrogen, and Hydrogen Isotopic Ratios for Amino Acids in CM and CR Chondrites and their use in Evaluating Potential Formation Pathways

    NASA Technical Reports Server (NTRS)

    Elsila, Jamie E.; Charnley, Steven B.; Burton, Aaron S.; Glavin, Daniel P.; Dworkin, Jason P.

    2012-01-01

    Stable hydrogen, carbon, and nitrogen isotopic ratios (oD, 013C, and olSN) of organic compounds can revcal information about their origin and formation pathways. Several formation mechanisms and environments have been postulated for the amino acids detected in carbonaceous chondrites. As each proposed mechanism utilizes different precursor molecules, the isotopic signatures of the resulting amino acids may indicate the most likely of these pathways. We have applied gas chromatography with mass spectrometry and combustion isotope ratio mass spectrometry to measure the compound-specific C, N, and H stable isotopic ratios of amino acids from seven CM and CR carbonaceous chondrites: CM1I2 Allan Hills (ALH) 83100, CM2 Murchison, CM2 Lewis Cliff (LEW) 90500, CM2 Lonewolf Nunataks (LON) 94101, CRZ Graves Nunataks (GRA) 95229, CRZ Elephant Moraine (EET) 92042, and CR3 Queen Alexandra Range (QUE) 99177. We compare the isotopic compositions of amino acids in these meteorites with predictions of expected isotopic enrichments from potential formation pathways. We observe trends of decreasing ODC and increasing oD with increasing carbon number in the aH, (l-NH2 amino acids that correspond to predictions made for formation via Streckercyanohydrin synthesis. We also observe light ODC signatures for -alanine, which may indicate either formation via Michael addition or via a pathway that forms primarily small, straight-chain, amine-terminal amino acids (n-ro-amino acids). Higher deuterium enrichments are observed in amethyl amino acids, indicating formation of these amino acids or their precursors in cold interstellar or nebular environments. Finally, individual amino acids are more enriched in deuterium in CR chondrites than CM chondrites, reflecting different parent-body chemistry.

  18. Selective Catalytic Oxidation of Hydrogen Sulfide on Activated Carbons Impregnated with Sodium Hydroxide

    SciTech Connect

    Schwartz, Viviane; Baskova, Svetlana; Armstrong, Timothy R.

    2009-01-01

    Two activated carbons of different origin were impregnated with the solution of sodium hydroxide (NaOH) of various concentrations up to 10 wt %, and the effect of impregnation on the catalytic performance of the carbons was evaluated. The catalytic activity was analyzed in terms of the capacity of carbons for hydrogen sulfide (H2S) conversion and removal from hydrogen-rich fuel streams and the emission times of H2S and the products of its oxidation [e.g., sulfur dioxide (SO2) and carbonyl sulfide (COS)]. The results of impregnation showed a significant improvement in the catalytic activity of both carbons proportional to the amount of NaOH introduced. NaOH introduces hydroxyl groups (OH-) on the surface of the activated carbon that increase its surface reactivity and its interaction with sulfur-containing compounds.

  19. Suppression of hydrogenated carbon film deposition and hydrogen isotope retention by nitrogen addition into cold remote H/D and CH4 mixture plasmas

    NASA Astrophysics Data System (ADS)

    Iida, K.; Notani, M.; Uesugi, Y.; Tanaka, Y.; Ishijima, T.

    2015-08-01

    Control of tritium retention and its removal from the first wall of future fusion devices are one of the most crucial issues for safety and effective use for fuel. Nitrogen addition into remote edge plasmas has been considered and tested as an effective method for suppression of carbon film deposition and reduction of hydrogen isotope absorption in the deposited films. In this paper we have investigated the scavenger effects of nitrogen injected into low temperature D2/CH4 plasmas on hydrogenated carbon film growth using a small helical device. The result of the deposition shows that the key reactive particles with CN and ND(H) bonds to suppression of hydrogenated carbon film growth and hydrogen isotope absorption are much slowly generated compared with hydrocarbon particles such as CD(H)x and C2D(H)x. This may be due to the slow atomic nitrogen diffusion into hydrogenated carbon layer and the chemical equilibrium between nitrogen absorption.

  20. Contrasting H-mode behaviour with deuterium fuelling and nitrogen seeding in the all-carbon and metallic versions of JET

    NASA Astrophysics Data System (ADS)

    Maddison, G. P.; Giroud, C.; Alper, B.; Arnoux, G.; Balboa, I.; Beurskens, M. N. A.; Boboc, A.; Brezinsek, S.; Brix, M.; Clever, M.; Coelho, R.; Coenen, J. W.; Coffey, I.; da Silva Aresta Belo, P. C.; Devaux, S.; Devynck, P.; Eich, T.; Felton, R. C.; Flanagan, J.; Frassinetti, L.; Garzotti, L.; Groth, M.; Jachmich, S.; Järvinen, A.; Joffrin, E.; Kempenaars, M. A. H.; Kruezi, U.; Lawson, K. D.; Lehnen, M.; Leyland, M. J.; Liu, Y.; Lomas, P. J.; Lowry, C. G.; Marsen, S.; Matthews, G. F.; McCormick, G. K.; Meigs, A. G.; Morris, A. W.; Neu, R.; Nunes, I. M.; Oberkofler, M.; Rimini, F. G.; Saarelma, S.; Sieglin, B.; Sips, A. C. C.; Sirinelli, A.; Stamp, M. F.; van Rooij, G. J.; Ward, D. J.; Wischmeier, M.; EFDA Contributors, JET

    2014-07-01

    The former all-carbon wall on JET has been replaced with beryllium in the main torus and tungsten in the divertor to mimic the surface materials envisaged for ITER. Comparisons are presented between type I H-mode characteristics in each design by examining respective scans over deuterium fuelling and impurity seeding, required to ameliorate exhaust loads both in JET at full capability and in ITER. Attention is focused upon a common high-triangularity, single-null divertor configuration at 2.5 MA, q95 ≈ 3.5 yielding the most robust all-C performance. Contrasting results between the alternative linings are found firstly in unseeded plasmas, for which purity is improved and intrinsic radiation reduced in the ITER-like wall (ILW) but normalized energy confinement is ≈30% lower than in all-C counterparts, owing to a commensurately lower (electron) pedestal temperature. Divertor recycling is also radically altered, with slower, inboard-outboard asymmetric transients at ELMs and spontaneous oscillations in between them. Secondly, nitrogen seeding elicits opposite responses in the ILW to all-C experience, tending to raise plasma density, reduce ELM frequency, and above all to recover (electron) pedestal pressure, hence global confinement, almost back to previous levels. A hitherto unrecognized role of light impurities in pedestal stability and dynamics is consequently suggested. Thirdly, while heat loads on the divertor outboard target between ELMs are successfully reduced in proportion to the radiative cooling and ELM frequency effects of N in both wall environments, more surprisingly, average power ejected by ELMs also declines in the same proportion for the ILW. Detachment between transients is simultaneously promoted. Finally, inter-ELM W sources in the ILW divertor tend to fall with N input, although core accumulation possibly due to increased particle confinement still leads to significantly less steady conditions than in all-C plasmas. This limitation of ILW H-modes so far will be readdressed in future campaigns to continue progress towards a fully integrated scenario suitable for D-T experiments on JET and for ‘baseline’ operation on ITER. The diverse changes in behaviour between all-C and ILW contexts demonstrate essentially the strong impact which boundary conditions and intrinsic impurities can have on tokamak-plasma states.

  1. Process for producing methane from gas streams containing carbon monoxide and hydrogen

    DOEpatents

    Frost, Albert C.

    1980-01-01

    Carbon monoxide-containing gas streams are passed over a catalyst capable of catalyzing the disproportionation of carbon monoxide so as to deposit a surface layer of active surface carbon on the catalyst essentially without formation of inactive coke thereon. The surface layer is contacted with steam and is thus converted to methane and CO.sub.2, from which a relatively pure methane product may be obtained. While carbon monoxide-containing gas streams having hydrogen or water present therein can be used only the carbon monoxide available after reaction with said hydrogen or water is decomposed to form said active surface carbon. Although hydrogen or water will be converted, partially or completely, to methane that can be utilized in a combustion zone to generate heat for steam production or other energy recovery purposes, said hydrogen is selectively removed from a CO--H.sub.2 -containing feed stream by partial oxidation thereof prior to disproportionation of the CO content of said stream.

  2. Tailoring of nanoscale porosity in carbide-derived carbons for hydrogen storage.

    PubMed

    Gogotsi, Yury; Dash, Ranjan K; Yushin, Gleb; Yildirim, Taner; Laudisio, Giovanna; Fischer, John E

    2005-11-23

    The poor performance of hydrogen storage materials continues to hinder development of fuel cell-powered automobiles. Nanoscale carbons, in particular (activated carbon, exfoliated graphite, fullerenes, nanotubes, nanofibers, and nanohorns), have not fulfilled their initial promise. Here we show that carbon materials can be rationally designed for H2 storage. Carbide-derived carbons (CDC), a largely unknown class of porous carbons, are produced by high-temperature chlorination of carbides. Metals and metalloids are removed as chlorides, leaving behind a collapsed noncrystalline carbon with up to 80% open pore volume. The detailed nature of the porosity-average size and size distribution, shape, and total specific surface area (SSA)-can be tuned with high sensitivity by selection of precursor carbide (composition, lattice type) and chlorination temperature. The optimum temperature is bounded from below by thermodynamics and kinetics of chlorination reactions and from above by graphitization, which decreases SSA and introduces H2-sorbing surfaces with binding energies too low to be useful. Intuitively, pores of different size and shape should not contribute equally to hydrogen storage. By correlating pore properties with 77 K H2 isotherms from a wide variety of CDCs, we experimentally confirm that gravimetric hydrogen storage capacity normalized to total pore volume is optimized in materials with primarily micropores ( approximately 1 nm) rather than mesopores. Thus, in agreement with theoretical predictions, a narrow size distribution of small pores is desirable for storing hydrogen, while large pores merely degrade the volumetric storage capacity. PMID:16287270

  3. Single Pd atoms in activated carbon fibers and their contribution to hydrogen storage

    SciTech Connect

    Contescu, Cristian I; van Benthem, Klaus; Li, Sa; Bonifacio, Cecile S; Pennycook, Stephen J; Jena, Puru; Gallego, Nidia C

    2011-01-01

    Palladium-modified activated carbon fibers (Pd-ACF) were synthesized by meltspinning, carbonization and activation of an isotropic pitch carbon precursor premixed with an organometallic Pd compound. The hydrogen uptake at 25 oC and 20 bar on Pd- ACF exceeded the expected capacity based solely on Pd hydride formation and hydrogen physisorption on the microporous carbon support. Aberration-corrected scanning transmission electron microscopy (STEM) with sub- ngstrom spatial resolution provided unambiguous identification of isolated Pd atoms occurring in the carbon matrix that coexist with larger Pd particles. First principles calculations revealed that each single Pd atom can form Kubas-type complexes by binding up to three H2 molecules in the pressure range of adsorption measurements. Based on Pd atom concentration determined from STEM images, the contribution of various mechanisms to the excess hydrogen uptake measured experimentally was evaluated. With consideration of Kubas binding as a viable mechanism (along with hydride formation and physisorption to carbon support) the role of hydrogen spillover in this system may be smaller than previously thought.

  4. Spot-free catalysis using gold carbon nanotube & gold graphene composites for hydrogen evolution reaction

    NASA Astrophysics Data System (ADS)

    Sai Siddhardha, R. S.; Lakshminarayanan, V.; Ramamurthy, Sai Sathish

    2015-08-01

    Hydrogen has been proposed as the green fuel of the future in the wake of depleting fossil fuels. Recently, carbon paste electrodes (CPE) modified with nanomaterials as electrocatalysts have drawn wide attention for hydrogen evolution reaction (HER) in acid medium. The CPEs are advantageous owing to their chemical stability and ease of fabrication. Their applications for HER without any modification, however, are hampered on account of large hydrogen overpotential associated with carbon surface. In the present study, CPE has been modified with novel gold composites as electro-catalysts for HER in acid medium. The nanocomposites have shown ∼100 fold increased current density than unmodified CPE at -0.3 V. Most strikingly for the first time, this study has quantitatively brought out the difference in catalysis between surfactant capped and pristine gold nanoparticles in terms of their application as spot-free catalysts towards hydrogen gas production by electrochemical route.

  5. Hydrogen-bond acidic functionalized carbon nanotubes (CNTs) with covalently-bound hexafluoroisopropanol groups

    SciTech Connect

    Fifield, Leonard S.; Grate, Jay W.

    2010-06-01

    Fluorinated hydrogen-bond acidic groups are directly attached to the backbone of single walled carbon nanotubes (SWCNTs) without the introduction of intermediate electron donating surface groups. Hexafluoroalcohol functional groups are exceptionally strong hydrogen bond acids, and are added to the nanotube surface using the aryl diazonium approach to create hydrogen-bond acidic carbon nanotube (CNT) surfaces. These groups can promote strong hydrogen-bonding interactions with matrix materials in composites or with molecular species to be concentrated and sensed. In the latter case, this newly developed material is expected to find useful application in chemical sensors and in CNT-based preconcentrator devices for the detection of pesticides, chemical warfare agents and explosives.

  6. "TOF2H": A precision toolbox for rapid, high density/high coverage hydrogen-deuterium exchange mass spectrometry via an LC-MALDI approach, covering the data pipeline from spectral acquisition to HDX rate analysis

    PubMed Central

    Nikamanon, Pornpat; Pun, Elroy; Chou, Wayne; Koter, Marek D; Gershon, Paul D

    2008-01-01

    Background Protein-amide proton hydrogen-deuterium exchange (HDX) is used to investigate protein conformation, conformational changes and surface binding sites for other molecules. To our knowledge, software tools to automate data processing and analysis from sample fractionating (LC-MALDI) mass-spectrometry-based HDX workflows are not publicly available. Results An integrated data pipeline (Solvent Explorer/TOF2H) has been developed for the processing of LC-MALDI-derived HDX data. Based on an experiment-wide template, and taking an ab initio approach to chromatographic and spectral peak finding, initial data processing is based on accurate mass-matching to fully deisotoped peaklists accommodating, in MS/MS-confirmed peptide library searches, ambiguous mass-hits to non-target proteins. Isotope-shift re-interrogation of library search results allows quick assessment of the extent of deuteration from peaklist data alone. During raw spectrum editing, each spectral segment is validated in real time, consistent with the manageable spectral numbers resulting from LC-MALDI experiments. A semi-automated spectral-segment editor includes a semi-automated or automated assessment of the quality of all spectral segments as they are pooled across an XIC peak for summing, centroid mass determination, building of rates plots on-the-fly, and automated back exchange correction. The resulting deuterium uptake rates plots from various experiments can be averaged, subtracted, re-scaled, error-barred, and/or scatter-plotted from individual spectral segment centroids, compared to solvent exposure and hydrogen bonding predictions and receive a color suggestion for 3D visualization. This software lends itself to a "divorced" HDX approach in which MS/MS-confirmed peptide libraries are built via nano or standard ESI without source modification, and HDX is performed via LC-MALDI using a standard MALDI-TOF. The complete TOF2H package includes additional (eg LC analysis) modules. Conclusion "TOF2H" provides a comprehensive HDX data analysis package that has accelerated the processing of LC-MALDI-based HDX data in the authors' lab from weeks to hours. It runs in a standard MS Windows (XP or Vista) environment, and can be downloaded or obtained from the authors at no cost. PMID:18803853

  7. Dissociation of CH4 by electron impact: Production of metastable hydrogen and carbon fragments

    NASA Technical Reports Server (NTRS)

    Finn, T. G.; Carnahan, B. L.; Zipf, E. C.

    1974-01-01

    Metastable fragments produced by electron impact excitation of CH4 have been investigated for incident electron energies from threshold to 300 eV. Only metastable hydrogen and carbon atoms were observed. Onset energies for the production of metastable hydrogen atoms were observed at electron impact energies of 22.0 + or - .5 eV, 25.5 + or - .6 eV, 36.7 + or - .6 eV and 66 + or - 3 eV, and at 26.6 + or - .6 eV for the production of metastable carbon atoms. Most of the fragments appear to have been formed in high-lying Rydberg states. The total metastable hydrogen cross section reaches a maximum value of approximately 1 X 10 to the minus 18th power sq cm at 100 eV. At the same energy, the metastable carbon cross section is 2 x 10 to the minus 19th power sq cm.

  8. Simulation of hydrogen adsorption on carbon nanotubes with different chirality parameters

    NASA Astrophysics Data System (ADS)

    Gromov, S. V.; Burmistrov, I. N.; Ilinykh, I. A.; Kuznetsov, D. V.

    2016-01-01

    The hydrogen adsorption properties and surface charge distribution of single-walled carbon nanotubes (SWCNTs) with chirality parameters of (5, 5), (9, 5), (9, 9) were investigated using molecular dynamics methods. Relation between maximum hydrogen uptake and SWCNT structural properties was investigated. It was shown that surface charge distribution of chiral nanotubes could not be compensated for the same amount of steps that leads to fully neutral CNT with armchair structure.

  9. Relation of Hydrogen and Methane to Carbon Monoxide in Exhaust Gases from Internal-Combustion Engines

    NASA Technical Reports Server (NTRS)

    Gerrish, Harold C; Tessmann, Arthur M

    1935-01-01

    The relation of hydrogen and methane to carbon monoxide in the exhaust gases from internal-combustion engines operating on standard-grade aviation gasoline, fighting-grade aviation gasoline, hydrogenated safety fuel, laboratory diesel fuel, and auto diesel fuel was determined by analysis of the exhaust gases. Two liquid-cooled single-cylinder spark-ignition, one 9-cylinder radial air-cooled spark-ignition, and two liquid-cooled single-cylinder compression-ignition engines were used.

  10. Evaluation of the isosteric heat of adsorption at zero coverage for hydrogen on activated carbons

    NASA Astrophysics Data System (ADS)

    Dohnke, E.; Beckner, M.; Romanos, J.; Olsen, R.; Wexler, C.; Pfeifer, P.

    2011-03-01

    Activated carbons made from corn cob show promise as materials for high-capacity hydrogen storage. As part of our characterization of these materials, we are interested in learning how different production methods affect the adsorption energies. In this talk, we will show how hydrogen adsorption isotherms may be used to calculate these adsorption energies at zero coverage using Henry's law. We will additionally discuss differences between the binding energy and the isosteric heat of adsorption by applying this analysis at different temperatures.

  11. Very broad-band structure and emission by hydrogenated amorphous carbon

    NASA Astrophysics Data System (ADS)

    Duley, W. W.; Whittet, D. C. B.

    1990-01-01

    New laboratory data show that an efficient broad-band luminescence is emitted by hydrogenated amorphous carbon (HAC) solids with large hydrogen content. The peak wavelength and spectral extent of this emission closely coincides with the wavelength dependence of the very broad structure (VBS). It is suggested that a polymeric form of HAC may be present in diffuse clouds. Emission from this material should be observable in the spectrum of the diffuse galactic light.

  12. Hydrogenolysis Of 5-Carbon Sugars, Sugar Alcohols And Compositions For Reactions Involving Hydrogen

    DOEpatents

    Werpy, Todd A.; Frye, Jr., John G.; Zacher, Alan H.; Miller, Dennis J.

    2004-01-13

    Methods and compositions for reactions of hydrogen over a Re-containing catalyst with compositions containing a 5-carbon sugar, sugar alcohol, or lactic acid are described. It has been surprisingly discovered that reaction with hydrogen over a Re-containing multimetallic catalyst resulted in superior conversion and selectivity to desired products such as propylene glycol. A process for the synthesis of PG from lactate or lactic acid is also described.

  13. Hydrogenolysis of 5-carbon sugars, sugar alcohols, and other methods and compositions for reactions involving hydrogen

    DOEpatents

    Werpy, Todd A [West Richland, WA; Zacher, Alan H [Kennewick, WA

    2002-11-12

    Methods and compositions for reactions of hydrogen over a Re-containing catalyst with compositions containing a 5-carbon sugar, sugar alcohol, or lactic acid are described. It has been surprisingly discovered that reaction with hydrogen over a Re-containing multimetallic catalyst resulted in superior conversion and selectivity to desired products such as propylene glycol. A process for the synthesis of PG from lactate or lactic acid is also described.

  14. Dynamic response of a carbon nanotube-based rotary nano device with different carbon-hydrogen bonding layout

    NASA Astrophysics Data System (ADS)

    Yin, Hang; Cai, Kun; Wan, Jing; Gao, Zhaoliang; Chen, Zhen

    2016-03-01

    In a nano rotational transmission system (RTS) which consists of a single walled carbon nanotube (SWCNT) as the motor and a coaxially arranged double walled carbon nanotube (DWCNT) as a bearing, the interaction between the motor and the rotor in bearing, which has great effects on the response of the RTS, is determined by their adjacent edges. Using molecular dynamics (MD) simulation, the interaction is analyzed when the adjacent edges have different carbon-hydrogen (Csbnd H) bonding layouts. In the computational models, the rotor in bearing and the motor with a specific input rotational speed are made from the same armchair SWCNT. Simulation results demonstrate that a perfect rotational transmission could happen when the motor and rotor have the same Csbnd H bonding layout on their adjacent ends. If only half or less of the carbon atoms on the adjacent ends are bonded with hydrogen atoms, the strong attraction between the lower speed (100 GHz) motor and rotor leads to a synchronous rotational transmission. If only the motor or the rotor has Csbnd H bonds on their adjacent ends, no rotational transmission happens due to weak interaction between the bonded hydrogen atoms on one end with the sp1 bonded carbon atoms on the other end.

  15. Carbon hybridized halloysite nanotubes for high-performance hydrogen storage capacities

    NASA Astrophysics Data System (ADS)

    Jin, Jiao; Fu, Liangjie; Yang, Huaming; Ouyang, Jing

    2015-07-01

    Hybrid nanotubes of carbon and halloysite nanotubes (HNTs) with different carbon:HNTs ratio were hydrothermally synthesized from natural halloysite and sucrose. The samples display uniformly cylindrical hollow tubular structure with different morphologies. These hybrid nanotubes were concluded to be promising medium for physisorption-based hydrogen storage. The hydrogen adsorption capacity of pristine HNTs was 0.35% at 2.65 MPa and 298 K, while that of carbon coated HNTs with the pre-set carbon:HNTs ratio of 3:1 (3C-HNTs) was 0.48% under the same condition. This carbon coated method could offer a new pattern for increasing the hydrogen adsorption capacity. It was also possible to enhance the hydrogen adsorption capacity through the spillover mechanism by incorporating palladium (Pd) in the samples of HNTs (Pd-HNTs) and 3C-HNTs (Pd-3C-HNTs and 3C-Pd-HNTs are the samples with different location of Pd nanoparticles). The hydrogen adsorption capacity of the Pd-HNTs was 0.50% at 2.65 MPa and 298 K, while those of Pd-3C-HNTs and 3C-Pd-HNTs were 0.58% and 0.63%, respectively. In particular, for this spillover mechanism of Pd-carbon-HNTs ternary system, the bidirectional transmission of atomic and molecular hydrogen (3C-Pd-HNTs) was concluded to be more effective than the unidirectional transmission (Pd-3C-HNTs) in this work for the first time.

  16. Synthesis of superlow friction carbon films from highly hydrogenated methane plasmas.

    SciTech Connect

    Erdemir, A.; Eryilmaz, O. L.; Nilufer, I. B.; Fenske, G. R.

    2000-10-13

    In this study, we investigated the friction and wear performance of diamondlike carbon films (DLC) derived from increasingly hydrogenated methane plasmas. The films were deposited on steel substrates by a plasma-enhanced chemical vapor deposition process at room temperature and the tribological tests were performed in dry nitrogen. Tests results revealed a close correlation between the hydrogen in source gas plasma and the friction and wear coefficients of the DLC films. Specifically, films grown in plasmas with higher hydrogen-to-carbon ratios had much lower friction coefficients and wear rates than did films derived from source gases with lower hydrogen-to-carbon ratios. The lowest friction coefficient (0.003) was achieved with a film derived from 25% methane--75% hydrogen, while a coefficient of 0.015 was found for films derived from pure methane. Similar correlations were observed for wear rates. Films derived from hydrogen-rich plasmas had the least wear, while films derived from pure methane suffered the highest wear. We used a combination of surface analytical methods to characterize the structure and chemistry of the DLC films and worn surfaces.

  17. Optimizing the Binding Energy of Hydrogen on Nanostructured Carbon Materials through Structure Control and Chemical Doping

    SciTech Connect

    Jie Liu

    2011-02-01

    The DOE Hydrogen Sorption Center of Excellence (HSCoE) was formed in 2005 to develop materials for hydrogen storage systems to be used in light-duty vehicles. The HSCoE and two related centers of excellence were created as follow-on activities to the DOE Office of Energy Efficiency and Renewable Energy’s (EERE’s) Hydrogen Storage Grand Challenge Solicitation issued in FY 2003. The Hydrogen Sorption Center of Excellence (HSCoE) focuses on developing high-capacity sorbents with the goal to operate at temperatures and pressures approaching ambient and be efficiently and quickly charged in the tank with minimal energy requirements and penalties to the hydrogen fuel infrastructure. The work was directed at overcoming barriers to achieving DOE system goals and identifying pathways to meet the hydrogen storage system targets. To ensure that the development activities were performed as efficiently as possible, the HSCoE formed complementary, focused development clusters based on the following four sorption-based hydrogen storage mechanisms: 1. Physisorption on high specific surface area and nominally single element materials 2. Enhanced H2 binding in Substituted/heterogeneous materials 3. Strong and/or multiple H2 binding from coordinated but electronically unsatruated metal centers 4. Weak Chemisorption/Spillover. As a member of the team, our group at Duke studied the synthesis of various carbon-based materials, including carbon nanotubes and microporous carbon materials with controlled porosity. We worked closely with other team members to study the effect of pore size on the binding energy of hydrogen to the carbon –based materials. Our initial project focus was on the synthesis and purification of small diameter, single-walled carbon nanotubes (SWNTs) with well-controlled diameters for the study of their hydrogen storage properties as a function of diameters. We developed a chemical vapor deposition method that synthesized gram quantities of carbon nanotubes with average diameter size at less than 1 nm. However, initial tests performed at our collaborator’s lab at the National Renewable Energy Laboratory (NREL) did not indicate improved hydrogen sorption properties for the smaller-diameter nanotubes (compared with other types of nanotubes). As work continued, the difficulties in purification, large-scale synthesis, and stability of small diameter SWNTs became a major concern. In 2008, the Department of Energy (DOE) made a no-go decision on future applied R&D investment in pure, undoped, single-walled carbon nanotubes for vehicular hydrogen storage.2 The second phase of the project involved developing a low-cost and scalable approach for the synthesis of microporous carbon materials with well-controlled pore sizes that would be suitable for hydrogen storage. The team studied several approaches, including the use of different zeolites as a template, the use of organic micelle structures as a template, and the slow oxidation of polymer precursors. Among them, the slow activation of Polyether ether ketone (PEEK) under either CO2 environment or H2O vapor produced microporous carbon with an average pore size of less than 2 nm. Initial testing at 77K at both NREL and the California Institute of Technology (CalTech) showed that these materials can store ~5.1 wt% hydrogen (excess) at 40 bar and 77K. The main feature to note with this material is that while the excess gravimetric capacities (>5 wt% at 77K) and specific surface areas (>3100 m2/g) are similar to AX-21 and other “super activated” commercial carbon sorbents at the same temperatures and pressures, due to the smaller pore sizes, bulk densities greater than 0.7 g/ml can be achieved, enabling excess volumetric capacities greater than 35 g/L; more than double that of AX-21.

  18. Hydrogenation of PAH molecules through interaction with hydrogenated carbonaceous grains.

    PubMed

    Thrower, John D; Friis, Emil E; Skov, Anders L; Jørgensen, Bjarke; Hornekær, Liv

    2014-02-28

    Carbonaceous materials contribute to a significant proportion of the interstellar dust inventory. Reactions on such grain surfaces are thought to play important roles in interstellar chemical networks. Of particular importance are reactions involving hydrogen atoms, and pathways to the formation of the most abundant molecular species, H2. Polycyclic aromatic hydrocarbons (PAHs) are an additional carbon reservoir, accounting for around 10% of the galactic carbon budget. Using thermal desorption and mass spectrometric techniques, we have investigated the interaction between PAH molecules and carbonaceous grain surfaces. We demonstrate that deuterium atoms adsorbed on graphite can react with adsorbed PAH molecules, forming superhydrogenated PAH species. Furthermore, by considering the number of D-atoms remaining bound to the graphite surface and the additional D-atoms in the observed superhydrogenated species, we see evidence for a significant release of deuterium from the graphite surface. We suggest that further reactive processes may be responsible for part of this deuterium loss, indicating that PAHs adsorbed on hydrogenated carbonaceous grains in warm interstellar environments may serve as a route to release H2 as well as forming superhydrogenated PAH species. PMID:24270708

  19. Efficient and durable hydrogen evolution electrocatalyst based on nonmetallic nitrogen doped hexagonal carbon

    PubMed Central

    Liu, Yanming; Yu, Hongtao; Quan, Xie; Chen, Shuo; Zhao, Huimin; Zhang, Yaobin

    2014-01-01

    The feasibility of renewable energy technology, hydrogen production by water electrolysis, depends on the design of efficient and durable electrocatalyst composed of earth-abundant elements. Herein, a highly active and stable nonmetallic electrocatalyst, nitrogen doped hexagonal carbon (NHC), was developed for hydrogen production. It exhibited high activity for hydrogen evolution with a low overpotential of only 65 mV, an apparent exchange current density of 5.7 × 10−2 mA cm−2 and a high hydrogen production rate of 20.8 mL cm−2 h−1 at −0.35 V. The superior hydrogen evolution activity of NHC stemmed from the intrinsic electrocatalytic property of hexagonal nanodiamond, the rapid charge transfer and abundance of electrocatalytic sites after nitrogen doping. Moreover, NHC was stable in a corrosive acidic solution during electrolysis under high current density. PMID:25354806

  20. LITERATURE SURVEY OF GASEOUS HYDROGEN EFFECTS ON THE MECHANICAL PROPERTIES OF CARBON AND LOW ALLOY STEELS

    SciTech Connect

    Lam, P; Robert Sindelar, R; Thad Adams, T

    2007-04-18

    Literature survey has been performed for a compendium of mechanical properties of carbon and low alloy steels following hydrogen exposure. The property sets include yield strength, ultimate tensile strength, uniform elongation, reduction of area, threshold stress intensity factor, fracture toughness, and fatigue crack growth. These properties are drawn from literature sources under a variety of test methods and conditions. However, the collection of literature data is by no means complete, but the diversity of data and dependency of results in test method is sufficient to warrant a design and implementation of a thorough test program. The program would be needed to enable a defensible demonstration of structural integrity of a pressurized hydrogen system. It is essential that the environmental variables be well-defined (e.g., the applicable hydrogen gas pressure range and the test strain rate) and the specimen preparation be realistically consistent (such as the techniques to charge hydrogen and to maintain the hydrogen concentration in the specimens).

  1. LITERATURE SURVEY OF GASEOUS HYDROGEN EFFECTS ON THE MECHANICAL PROPERTIES OF CARBON AND LOW ALLOY STEELS

    SciTech Connect

    Lam, P; Andrew Duncan, A; Robert Sindelar, R; Thad Adams, T

    2009-04-27

    Literature survey has been performed for a compendium of mechanical properties of carbon and low alloy steels following hydrogen exposure. The property sets include yield strength, ultimate tensile strength, uniform elongation, reduction of area, threshold stress intensity factor, fracture toughness, and fatigue crack growth. These properties are drawn from literature sources under a variety of test methods and conditions. However, the collection of literature data is by no means complete, but the diversity of data and dependency of results in test method is sufficient to warrant a design and implementation of a thorough test program. The program would be needed to enable a defensible demonstration of structural integrity of a pressurized hydrogen system. It is essential that the environmental variables be well-defined (e.g., the applicable hydrogen gas pressure range and the test strain rate) and the specimen preparation be realistically consistent (such as the techniques to charge hydrogen and to maintain the hydrogen concentration in the specimens).

  2. Blending materials composed of boron, nitrogen and carbon to transform approaches to liquid hydrogen stores.

    PubMed

    Whittemore, Sean M; Bowden, Mark; Karkamkar, Abhijeet; Parab, Kshitij; Neiner, Doinita; Autrey, Tom; Ishibashi, Jacob S A; Chen, Gang; Liu, Shih-Yuan; Dixon, David A

    2016-04-14

    Mixtures of hydrogen storage materials containing the elements of boron, nitrogen, carbon, i.e., isomers of BN cyclopentanes are examined to find a 'fuel blend' that remains a liquid phase throughout hydrogen release, maximizes hydrogen storage density, minimizes impurities and remains thermally stable at ambient temperatures. We find that the mixture of ammonia borane dissolved in 3-methyl-1,2-dihydro-1,2-azaborolidine (compound B) provide a balance of these properties and provides ca. 5.6 wt% hydrogen. The two hydrogen storage materials decompose at a faster rate than either individually and products formed are a mixture of molecular trimers. Digestion of the product mixture formed from the decomposition of the AB + B fuel blend with methanol leads to the two corresponding methanol adducts of the starting material and not a complex mixture of adducts. The work shows the utility of using blends of materials to reduce volatile impurities and preserve liquid phase. PMID:26629961

  3. Microwave absorption by hydrogen plasma in carbon nanotubes films with layered dielectric structure

    NASA Astrophysics Data System (ADS)

    Peng, Zhihua; Liu, Baoxing; Peng, Yanfeng; Jia, Peng; Zhan, Xiaogui; Xie, Ningyu

    2015-05-01

    A layered structure model is proposed for microwave dielectric properties of nonhomogeneous hydrogen plasma in carbon nanotubes (CNTs) film. Using the transfer matrix method for solving electromagnetic wave propagation equation, the microwave attenuation of the film is calculated in the range of 0-30 GHz under different conditions. It is found theoretically that with the increase of hydrogen plasma nonhomogeneity, the frequency bandwidth of strong microwave absorption by the film increases markedly. The application of a moderate static magnetic field can effectively improve microwave attenuation properties of hydrogen plasma in CNTs. The numerical results are in good agreement with the available experimental data.

  4. The effect of hydrogen on the parameters of plastic deformation localization in low carbon steel

    SciTech Connect

    Lunev, Aleksey G. E-mail: nadjozhkin@ispms.tsc.ru; Nadezhkin, Mikhail V. E-mail: nadjozhkin@ispms.tsc.ru; Shlyakhova, Galina V.; Barannikova, Svetlana A.; Zuev, Lev B.

    2014-11-14

    In the present study, the effect of interstitial hydrogen atoms on the mechanical properties and plastic strain localization patterns in tensile tested polycrystals of low-carbon steel Fe-0.07%C has been studied using double exposure speckle photography technique. The main parameters of plastic flow localization at various stages of deformation hardening have been determined in polycrystals of steel electrolytically saturated with hydrogen in a three-electrode electrochemical cell at a controlled constant cathode potential. Also, the effect of hydrogen on changing of microstructure by using optical microscopy has been demonstrated.

  5. Microwave response of magnetized hydrogen plasma in carbon nanotubes: multiple reflection effects.

    PubMed

    Moradi, Afshin

    2010-04-01

    We derived simple sets of equations to describe the microwave response of the magnetized hydrogen plasma slab embedded inside carbon nanotubes, which were grown by iron-catalyzed high-pressure disproportionation. These equations, which are useful when interference effects due to multiple reflections between plasma film interfaces are small, were used to analyze the reflection, absorption, and transmission coefficients of the magnetized hydrogen plasma slab. A discussion on the effects of the continuously changing external magnetic field and hydrogen plasma parameters on the reflected power, absorbed power, and transmitted power in the system is presented. PMID:20357852

  6. Hydrogenated carbon nanotubes: x-ray absorption spectroscopy and ab initio simulation analysis

    NASA Astrophysics Data System (ADS)

    Brzhezinskaya, M.; Yalovega, G.; Shmatko, V.; Klyushin, A.; Bogoslavskaya, E.; Krestinin, A.; Bashkin, I.

    2013-04-01

    The paper presents the results of investigation of the chemical bond formation in hydrogenated single-walled carbon nanotubes using X-ray absorption spectroscopy. All measurements were performed with the use of synchrotron radiation at BESSY II. The C1s absorption spectra point to formation of covalent chemical bonding between the hydrogen and carbon atoms in H-SWNTs. The investigation of the H-SWNT local structure has been carried out on the basis of the semi-empirical PM6 method (MOPAC 2009) and Finite Difference method. The possibility of H-SWNTs dehydrogenation was also investigated.

  7. Carbon Sources for Yeast Growth as a Precondition of Hydrogen Peroxide Induced Hormetic Phenotype

    PubMed Central

    Vasylkovska, Ruslana; Petriv, Natalia; Semchyshyn, Halyna

    2015-01-01

    Hormesis is a phenomenon of particular interest in biology, medicine, pharmacology, and toxicology. In this study, we investigated the relationship between H2O2-induced hormetic response in S. cerevisiae and carbon sources in yeast growth medium. In general, our data indicate that (i) hydrogen peroxide induces hormesis in a concentration-dependent manner; (ii) the effect of hydrogen peroxide on yeast reproductive ability depends on the type of carbon substrate in growth medium; and (iii) metabolic and growth rates as well as catalase activity play an important role in H2O2-induced hormetic response in yeast. PMID:26843865

  8. Stable hydrogen and carbon isotope ratios of extractable hydrocarbons in the Murchison meteorite

    NASA Technical Reports Server (NTRS)

    Krishnamurthy, R. V.; Epstein, S.; Pizzarello, S.; Cronin, J. R.; Yuen, G. U.

    1991-01-01

    A fairly fool-proof method to ensure that the compounds isolated from meteorites are truly part of the meteorites and not an artifact introduced by exposure to the terrestrial environment, storage, or handling is presented. The stable carbon and hydrogen isotope ratios in several of the chemical compounds extracted from the Murchison meteorite were measured. The results obtained by studying the amino acids in this meteorite gave very unusual hydrogen and carbon isotope ratios. The technique was extended to the different classes of hydrocarbons and the hydrocarbons were isolated using a variety of separation techniques. The results and methods used in this investigation are described in this two page paper.

  9. Improvement of Electron Field Emission in Patterned Carbon Nanotubes by High Temperature Hydrogen Plasma Treatment.

    PubMed

    Wang, Sigen; Sellin, Paul J; Lian, Jun; Ozsan, Ersin; Chang, Sha

    2009-02-01

    In this paper, we report a significant improvement of electron field emission property in patterned carbon nanotubes films by using a high temperature (650 °C) hydrogen plasma treatment. This treatment was found to greatly increase the emission current, emission uniformity and stability. The mechanism study showed that these enhanced properties are attributed to the lowering of the potential barrier and the creation of geometrical features through the removal of amorphous carbon, catalyst particles and the saturation of dangling bonds after such a hydrogen plasma treatment. PMID:19946566

  10. Improvement of Electron Field Emission in Patterned Carbon Nanotubes by High Temperature Hydrogen Plasma Treatment

    PubMed Central

    Wang, Sigen; Sellin, Paul. J.; Lian, Jun; Özsan, Ersin; Chang, Sha

    2009-01-01

    In this paper, we report a significant improvement of electron field emission property in patterned carbon nanotubes films by using a high temperature (650 °C) hydrogen plasma treatment. This treatment was found to greatly increase the emission current, emission uniformity and stability. The mechanism study showed that these enhanced properties are attributed to the lowering of the potential barrier and the creation of geometrical features through the removal of amorphous carbon, catalyst particles and the saturation of dangling bonds after such a hydrogen plasma treatment. PMID:19946566

  11. Migration Mechanism for Atomic Hydrogen in Porous Carbon Materials

    SciTech Connect

    Narayanan, B.; Zhao, Y. F.; Ciobanu, C. V.

    2012-05-14

    To explain the fast kinetics of H in porous carbon, we propose that the migration relies on H hopping from a carbon nanotube (CNT) to another. Using density functional theory, we have found that the barrier for H hopping becomes smaller than that for diffusion along a tube for certain CNT separations, decreasting to less than 0.5 eV for separations of -3.1 {angstrom}. Such significant reduction occurs irrespective of radius, chirality, registry, and orientation of the two CNTs: the diffusion is thus facilitated by the porous nature of the material itself. The mechanism proposed is applicable for any porous carbon-based nanomaterials.

  12. Supercritical carbon dioxide: an inert solvent for catalytic hydrogenation?

    PubMed

    Burgener, Marco; Ferri, Davide; Grunwaldt, Jan-Dierk; Mallat, Tamas; Baiker, Alfons

    2005-09-01

    Various surface species originating from the reaction between CO2 and H2 over Al2O3-supported Pt, Pd, Rh, and Ru model catalysts were investigated by attenuated total reflection infrared (ATR-IR) spectroscopy under high-pressure conditions. Two different spectroscopic cells were used: a variable-volume view cell equipped with ATR-crystal and transmission IR windows (batch reactor) and a continuous-flow cell also equipped with a reflection element for ATR-IR spectroscopy. The study corroborated that CO formation from dense CO2 in the presence of hydrogen occurs over all Pt-group metals commonly used in heterogeneous catalytic hydrogenations in supercritical CO2 (scCO2). In the batch reactor cell, formation of CO was detected on all metals at 50 and 90 degrees C, with the highest rate on Pt. Additional surface species were observed on Pt/Al2O3 at 150 bar under static conditions. It seems that further reaction of CO with hydrogen is facilitated by the higher surface concentration at higher pressure. In the continuous-flow cell, CO coverage on Pt/Al2O3 was less prominent than that in the batch reactor cell. A transient experiment in the continuous-flow cell additionally revealed CO formation on Pt/Al2O3 at 120 bar after switching the feed from a H2-ethane to a H2-CO2 mixture. The in situ ATR-IR measurements indicate that CO formation in CO2-H2 mixtures is normally a minor side reaction during hydrogenation reactions on Pt-group metal catalysts, and dense ("supercritical") CO2 may be considered as a relatively "inert" solvent in many practical applications. However, blocking of specific sites on the metal surface by CO and consecutive products can affect structure sensitive hydrogenation reactions and may be at the origin of unexpected shifts in the product distribution. PMID:16853138

  13. Hydrogen Generation During the Corrosion of Carbon Steel in Oxalic Acid

    SciTech Connect

    WIERSMA, BRUCEJ.

    2004-08-01

    A literature review of the corrosion mechanism for carbon steel in oxalic acid was performed to determine the ratio of moles of iron corroded to moles of hydrogen evolved during the corrosion of iron in oxalic acid. The theory of corrosion of carbon steel in oxalic acid and experimental work were reviewed. It was concluded that the maximum ratio of moles of hydrogen evolved to moles of iron corroded is 1:1. This ratio would be observed in a de-aerated environment. If oxygen or other oxidizing species are present, the ratio could be much less than 1:1. Testing would be necessary to determine how much less than 1:1 the ratio might be. Although the ratio of hydrogen evolution to iron corroded will not exceed 1:1, the total amount of hydrogen evolved can be influenced by such things as a decrease in the exposed surface area, suppression of hydrogen generation by gamma radiation, the presence of corrosion products on steel surface, etc. These and other variables present during chemical cleaning operations of the waste tank have not been examined by the tests reported in the literature i.e., the tests have focused on clean corrosion coupons in oxalic acid solutions. It is expected that most of these variables would reduce the total amount of hydrogen evolved. Further testing would need to be performed to quantify the reduction in hydrogen generation rate associated with these variables.

  14. Renewable Hydrogen Carrier Carbohydrate: Constructing the Carbon-Neutral Carbohydrate Economy

    SciTech Connect

    Zhang, Y.-H. Percival; Mielenz, Jonathan R

    2011-01-01

    Abstract The hydrogen economy presents an appealing energy future but its implementation must solve numerous problems ranging from low-cost sustainable production, high-density storage, costly infrastructure, to eliminating safety concern. The use of renewable carbohydrate as a high-density hydrogen carrier and energy source for hydrogen production is possible due to emerging cell-free synthetic biology technology called cell-free synthetic pathway biotransformation (SyPaB). Assembly of numerous enzymes and co-enzymes in vitro can create complicated set of biological reactions or pathways that microorganisms cannot complete, for example, C6H10O5 (aq) + 7 H2O (l) 12 H2 (g) + 6 CO2 (g) (PLoS One 2007, 2:e456). Thanks to 100% selectivity of enzymes, modest reaction conditions, and high-purity of generated hydrogen, carbohydrate is a promising hydrogen carrier for end users. Gravimetric density of carbohydrate is 14.8 H2 mass% if water can be recycled from PEM fuel cells or 8.33% H2 mass% without water recycling. Renewable carbohydrate can be isolated from plant biomass or would be produced from a combination of solar electricity/hydrogen and carbon dioxide fixation mediated by high-efficiency artificial photosynthesis mediated by SyPaB. The construction of this carbon-neutral carbohydrate economy would address numerous sustainability challenges, such as electricity and hydrogen storage, CO2 fixation and long-term storage, water conservation, transportation fuel production, plus feed and food production.

  15. New Pathways and Metrics for Enhanced, Reversible Hydrogen Storage in Boron-Doped Carbon Nanospaces

    SciTech Connect

    Pfeifer, Peter; Wexler, Carlos; Hawthorne, M. Frederick; Lee, Mark W.; Jalistegi, Satish S.

    2014-08-14

    This project, since its start in 2007—entitled “Networks of boron-doped carbon nanopores for low-pressure reversible hydrogen storage” (2007-10) and “New pathways and metrics for enhanced, reversible hydrogen storage in boron-doped carbon nanospaces” (2010-13)—is in support of the DOE's National Hydrogen Storage Project, as part of the DOE Hydrogen and Fuel Cells Program’s comprehensive efforts to enable the widespread commercialization of hydrogen and fuel cell technologies in diverse sectors of the economy. Hydrogen storage is widely recognized as a critical enabling technology for the successful commercialization and market acceptance of hydrogen powered vehicles. Storing sufficient hydrogen on board a wide range of vehicle platforms, at energy densities comparable to gasoline, without compromising passenger or cargo space, remains an outstanding technical challenge. Of the main three thrust areas in 2007—metal hydrides, chemical hydrogen storage, and sorption-based hydrogen storage—sorption-based storage, i.e., storage of molecular hydrogen by adsorption on high-surface-area materials (carbons, metal-organic frameworks, and other porous organic networks), has emerged as the most promising path toward achieving the 2017 DOE storage targets of 0.055 kg H2/kg system (“5.5 wt%”) and 0.040 kg H2/liter system. The objective of the project is to develop high-surface-area carbon materials that are boron-doped by incorporation of boron into the carbon lattice at the outset, i.e., during the synthesis of the material. The rationale for boron-doping is the prediction that boron atoms in carbon will raise the binding energy of hydro- gen from 4-5 kJ/mol on the undoped surface to 10-14 kJ/mol on a doped surface, and accordingly the hydro- gen storage capacity of the material. The mechanism for the increase in binding energy is electron donation from H2 to electron-deficient B atoms, in the form of sp2 boron-carbon bonds. Our team is proud to have demonstrated the predicted increase in binding energy experimentally, currently at ~10 kJ/mol. The synthetic route for incorporation of boron at the outset is to create appropriately designed copoly- mers, with a boron-free and a boron-carrying monomer, followed by pyrolysis of the polymer, yielding a bo- ron-substituted carbon scaffold in which boron atoms are bonded to carbon atoms by synthesis. This is in contrast to a second route (funded by DE-FG36-08GO18142) in which first high-surface area carbon is cre- ated and doped by surface vapor deposition of boron, with incorporation of the boron into the lattice the final step of the fabrication. The challenge in the first route is to create high surface areas without compromising sp2 boron-carbon bonds. The challenge in the second route is to create sp2 boron-carbon bonds without com- promising high surface areas.

  16. Preparation, microstructure and hydrogen sorption properties of nanoporous carbon aerogels under ambient drying

    NASA Astrophysics Data System (ADS)

    Tian, H. Y.; Buckley, C. E.; Mulè, S.; Paskevicius, M.; Dhal, B. B.

    2008-11-01

    Organic aerogels are prepared by the sol-gel method from polymerization of resorcinol with furfural. These aerogels are further carbonized in nitrogen in order to obtain their corresponding carbon aerogels (CA); a sample which was carbonized at 900 °C was also activated in a carbon dioxide atmosphere at 900 °C. The chemical reaction mechanism and optimum synthesis conditions are investigated by means of Fourier transform infrared spectroscopy and thermoanalyses (thermogravimetric/differential thermal analyses) with a focus on the sol-gel process. The carbon aerogels were investigated with respect to their microstructures, using small angle x-ray scattering (SAXS), transmission electron microscopy (TEM) and nitrogen adsorption measurements at 77 K. SAXS studies showed that micropores with a radius of gyration of <0.35 ± 0.07 to 0.55 ± 0.05 nm were present, and TEM measurements and nitrogen adsorption showed that larger mesopores were also present. Hydrogen storage properties of the CA were also investigated. An activated sample with a Brunauer-Emmett-Teller surface area of 1539 ± 20 m2 g-1 displayed a reasonably high hydrogen uptake at 77 K with a maximum hydrogen sorption of 3.6 wt% at 2.5 MPa. These results suggest that CA are promising candidate hydrogen storage materials.

  17. Measurements of the nucleon structure function in the range 0.002 < x < 0.17 and 00.2 < Q2 < 8 GeV2 in deuterium, carbon and calcium

    NASA Astrophysics Data System (ADS)

    European Muon Collaboration; Arneodo, M.; Arvidson, A.; Aubert, J. J.; Badelek, B.; Beaufays, J.; Bee, C. P.; Benchouk, C.; Berghoff, G.; Bird, I. G.; Blum, D.; Böhm, E.; de Bouard, X.; Brasse, F. W.; Braun, H.; Broll, C.; Brown, S. C.; Brück, H.; Calén, H.; Chima, J. S.; Ciborowski, J.; Clifft, R.; Coignet, G.; Combley, F.; Coughlan, J.; d'Agostini, G.; Dahlgren, S.; Derado, I.; Dreyer, T.; Drees, J.; Düren, M.; Eckardt, V.; Edwards, A.; Edwards, M.; Ernst, T.; Eszes, G.; Favier, J.; Ferrero, M. I.; Figiel, J.; Flauger, W.; Foster, J.; Gabathuler, E.; Gajewski, J.; Gamet, R.; Geddes, N.; Grafström, P.; Gustafsson, L.; Haas, J.; Hagberg, E.; Hasert, F. J.; Hayman, P.; Heusse, P.; Jaffre, M.; Jacholkowska, A.; Janata, F.; Jancso, G.; Johnson, A. S.; Kabuss, E. M.; Kellner, G.; Krüger, A.; Krüger, J.; Kullander, S.; Landgraf, U.; Lanske, D.; Loken, J.; Long, K.; Maire, M.; Malecki, P.; Manz, A.; Maselli, S.; Mohr, W.; Montanet, F.; Montgomery, H. E.; Nagy, E.; Nassalski, J.; Norton, P. R.; Oakham, F. G.; Osborne, A. M.; Pascaud, C.; Pawlik, B.; Payre, P.; Peroni, C.; Peschel, H.; Pessard, H.; Pettingale, J.; Pietrzyk, B.; Poensgen, B.; Pötsch, M.; Renton, P.; Ribarics, P.; Rith, K.; Rondio, E.; Sandacz, A.; Scheer, M.; Schlagböhmer, A.; Schiemann, H.; Schmitz, N.; Schneegans, M.; Scholz, M.; Schouten, M.; Schröder, T.; Schultze, K.; Sloan, T.; Stier, H. E.; Studt, M.; Taylor, G. N.; Thenard, J. M.; Thompson, J. C.; de la Torre, A.; Toth, J.; Urban, L.; Urban, L.; Wallucks, W.; Whalley, M.; Wheeler, S.; Williams, W. S. C.; Wimpenny, S. J.; Windmolders, R.; Wolf, G.

    1990-03-01

    Small angle scattering of 280 GeV positive muons by deuterium, carbon and calcium has been measured at scattering angles down to 2 mrad. The nucleon structure function F2 extracted from deuterium does not show a significant x dependence in the measured range of Q2 and its Q2 dependence is linear in logQ2. For calcium, a depletion of F2 is observed at low x by 30% as compared with the values at x = 0.1 where F2(Ca) and F2 (D) are not significantly different. This depletion is attributed to shadowing. The carbon structure function exhibits a similar, but less pronounced, x dependence. Such behaviour is observed to be independent of Q2. The data are consistent with those obtained from other charged lepton experiments both at similar and higher values of x and Q2 and considerably extend the range of the measurements down to the low values of x to be measured in forthcoming experiments at HERA.

  18. Preparation and characterization of ordered porous carbons for increasing hydrogen storage behaviors

    NASA Astrophysics Data System (ADS)

    Lee, Seul-Yi; Park, Soo-Jin

    2011-10-01

    We prepared ordered porous carbons (PCs) by using a replication method that had well-organized mesoporous silica as a template with various carbonization temperatures in order to investigate the possibility of energy storage materials. The microstructure and morphologies of the samples are characterized by XRD, TEM, and FT-Raman spectroscopy. N 2 adsorption isotherms are analyzed by the t-plot method, as well as the BET and the H-K method in order to characterize the specific surface area, pore volume, and pore size distribution of the samples, respectively. The capacity of the hydrogen adsorption of the samples is evaluated by BEL-HP at 77 K and 1 bar. From the results, we are able to confirm that the synthesis of the samples can be accurately governed by the carbonization temperature, which is one of the effective parameters for developing the textural properties of the carbon materials, which affects the behaviors of the hydrogen storage.

  19. Carbon nanofiber mesoporous films: efficient platforms for bio-hydrogen oxidation in biofuel cells.

    PubMed

    de Poulpiquet, Anne; Marques-Knopf, Helena; Wernert, Véronique; Giudici-Orticoni, Marie Thérèse; Gadiou, Roger; Lojou, Elisabeth

    2014-01-28

    The discovery of oxygen and carbon monoxide tolerant [NiFe] hydrogenases was the first necessary step toward the definition of a novel generation of hydrogen fed biofuel cells. The next important milestone is now to identify and overcome bottlenecks limiting the current densities, hence the power densities. In the present work we report for the first time a comprehensive study of herringbone carbon nanofiber mesoporous films as platforms for enhanced biooxidation of hydrogen. The 3D network allows mediatorless hydrogen oxidation by the membrane-bound hydrogenase from the hyperthermophilic bacterium Aquifex aeolicus. We investigate the key physico-chemical parameters that enhance the catalytic efficiency, including surface chemistry and hierarchical porosity of the biohybrid film. We also emphasize that the catalytic current is limited by mass transport inside the mesoporous carbon nanofiber film. Provided hydrogen is supplied inside the carbon film, the combination of the hierarchical porosity of the carbon nanofiber film with the hydrophobicity of the treated carbon material results in very high efficiency of the bioelectrode. By optimization of the whole procedure, current densities as high as 4.5 mA cm(-2) are reached with a turnover frequency of 48 s(-1). This current density is almost 100 times higher than when hydrogenase is simply adsorbed at a bare graphite electrode, and more than 5 times higher than the average of the previous reported current densities at carbon nanotube modified electrodes, suggesting that carbon nanofibers can be efficiently used in future sustainable H2/O2 biofuel cells. PMID:24296569

  20. System and method for controlling hydrogen elimination during carbon nanotube synthesis from hydrocarbons

    DOEpatents

    Reilly, Peter T. A.

    2010-03-23

    A system and method for producing carbon nanotubes by chemical vapor deposition includes a catalyst support having first and second surfaces. The catalyst support is capable of hydrogen transport from the first to the second surface. A catalyst is provided on the first surface of the catalyst support. The catalyst is selected to catalyze the chemical vapor deposition formation of carbon nanotubes. A fuel source is provided for supplying fuel to the catalyst.

  1. Hydrogen Storage in Novel Carbon-Based Nanostructured Materials

    SciTech Connect

    Whitney, E. S.; Curtis, C. J.; Engtrakul, C.; Davis, M. F.; Su, T.; Parilla, P. A.; Simpson, L. J.; Blackburn, J. L.; Zhao, Y.; Kim, Y.-H.; Zhang, S. B.; Heben, M. J.; Dillon, A. C.

    2006-01-01

    Experimental wet chemical approaches to complex an iron atom with two C60 fullerenes, representing a new molecule, dubbed a 'bucky dumbbell', have been demonstrated. The structure of this molecule has been determined by 13C solid-state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR). Furthermore, this structure has been shown to have unique binding sites for dihydrogen molecules with the technique of temperature programmed desorption (TPD). The new adsorption sites have binding energies that are stronger than that observed for hydrogen physisorbed on planar graphite, but significantly weaker than a chemical C-H bond. Further development of these molecules could make them ideal candidates for onboard vehicular hydrogen storage.

  2. Mechanistic deductions from multiple kinetic and solvent deuterium isotope effects and pH studies of pyridoxal phosphate dependent carbon-carbon lyases: escherichia coli tryptophan indole-lyase

    SciTech Connect

    Kiick, D.M.; Phillips, R.S.

    1988-09-20

    Analysis of the pH dependence of the kinetic parameters and competitive inhibitor Ki values for tryptophan indole-lyase suggests two enzymic groups must be unprotonated in order to facilitate binding and catalysis of tryptophan. The V/K for tryptophan and the pKi for oxindolyl-L-alanine, a putative transition state analogue and competitive inhibitor, decrease below two pK values of 7.6 and 6.0, while the Ki for L-alanine, also a competitive inhibitor, is 3300-fold larger (20 mM) than that for oxindolyl-L-alanine and increases below a single pK of 7.6. A single pK of 7.6 is also observed in the V/K profile for the alternate substrate, S-methyl-L-cysteine. Therefore, the enzymic group with a pK of 7.6 is responsible for proton abstraction at the 2-position of tryptophan, while the enzymic group with a pK of 6.0 interacts with the indole portion of tryptophan and probably catalyzes formation of the indolenine tautomer of tryptophan (in concert with proton transfer to C-3 of indole from the group with pK 7.6) to facilitate carbon-carbon bond cleavage and elimination of indole. The pH variation of the primary deuterium isotope effects for proton abstraction at the 2-position of tryptophan (DV = 2.5 and D(V/Ktrp) = 2.8) are pH independent, while the Vmax for tryptophan or S-methyl-L-cysteine is the same and also pH independent. Thus, substrates bind only to the correctly protonated form of the enzyme. Further, tryptophan is not sticky, and the pK values observed in both V/K profiles are the correct ones.

  3. HYDROGENATION OF POLYCYCLIC AROMATIC COMPOUNDS USING NI SUPPORT ON H-BETA ZEOLITE IN SUPERCRITICAL CARBON DIOXIDE

    EPA Science Inventory

    The primary rationale for use of supercritical carbon dioxide as a solvent in hydrogenation is the elimination of mass transfer limitations, through enhancement of the solubility of hydrogen at the reaction locus. Hydrogenation of anthracene was performed using NiHB-zeolite catal...

  4. Comparative analysis of deuterium ions implanted and deuterium atoms saturated at high pressure in pure pd and Pd diluted alloys

    NASA Astrophysics Data System (ADS)

    Didyk, A. Yu.; Kulikauskas, V. S.; Wiśniewski, R.; Wilczynska, T.; Kitowski, K.

    2012-01-01

    Pd and its diluted alloys (Pd-Ag, Pd-Pt, Pd-Ru, Pd-Rh) were implanted by 25 keV deuterium ions at a fluence interval of (1.2-2.3) × 1022 m-2. The same property alloys were saturated by deuterium atoms using high pressure chamber during long period with temperature stabilization and electrical resistance measurement of standard Pd wire. The post-treatment depth distributions of deuterium and accompanied hydrogen atoms were measured immediately after implantation (ten days) and after definite time period (three months) after saturation with the usage of elastic recoil detection analysis (ERDA). After two months, the measurements were repeated. The comparison of obtained results in both series of studies allowed one to make an important observation of a relative stability of deuterium and hydrogen atoms in pure Pd and its diluted alloys.

  5. Transition of single-walled carbon nanotubes from metallic to semiconducting in field-effect transistors by hydrogen plasma treatment.

    PubMed

    Zheng, Gang; Li, Qunqing; Jiang, Kaili; Zhang, Xiaobo; Chen, Jia; Ren, Zheng; Fan, Shoushan

    2007-06-01

    We report hydrogen plasma treatment results on converting the metallic single-walled carbon nanotubes to semiconducting single-walled carbon nanotubes. We found that the as-grown single-walled carbon nanotubes (SWNTs) can be sorted as three groups which behave as metallic, as-metallic, and semiconducting SWNTs. These three groups have different changes under hydrogen plasma treatment and successive annealing process. The SWNTs can be easily hydrogenated in the hydrogen plasma environment and the as-metallic SWNTs can be transformed to semiconducting SWNTs. The successive annealing process can break the C-H bond, so the conversion is reversible. PMID:17508771

  6. Mechanism for high hydrogen storage capacity on metal-coated carbon nanotubes: A first principle analysis

    SciTech Connect

    Lu, Jinlian; Xiao, Hong; Cao, Juexian

    2012-12-15

    The hydrogen adsorption and binding mechanism on metals (Ca, Sc, Ti and V) decorated single walled carbon nanotubes (SWCNTs) are investigated using first principle calculations. Our results show that those metals coated on SWCNTs can uptake over 8 wt% hydrogen molecules with binding energy range -0.2--0.6 eV, promising potential high density hydrogen storage material. The binding mechanism is originated from the electrostatic Coulomb attraction, which is induced by the electric field due to the charge transfer from metal 4s to 3d. Moreover, we found that the interaction between the H{sub 2}-H{sub 2} further lowers the binding energy. - Graphical abstract: Five hydrogen molecules bound to individual Ca decorated (8, 0) SWCNT : a potential hydrogen-storage material. Highlights: Black-Right-Pointing-Pointer Each transition metal atom can adsorb more than four hydrogen molecules. Black-Right-Pointing-Pointer The interation between metal and hydrogen molecule is electrostatic coulomb attraction. Black-Right-Pointing-Pointer The electric field is induced by the charge transfer from metal 4s to metal 3d. Black-Right-Pointing-Pointer The adsorbed hydrogen molecules which form supermolecule can further lower the binding energy.

  7. Effect of changes in the deuterium content of drinking water on the hydrogen isotope ratio of urinary steroids in the context of sports drug testing.

    PubMed

    Piper, Thomas; Degenhardt, Karoline; Federherr, Eugen; Thomas, Andreas; Thevis, Mario; Saugy, Martial

    2013-03-01

    The hydrogen isotope ratio (HIR) of body water and, therefore, of all endogenously synthesized compounds in humans, is mainly affected by the HIR of ingested drinking water. As a consequence, the entire organism and all of its synthesized substrates will reflect alterations in the isotope ratio of drinking water, which depends on the duration of exposure. To investigate the effect of this change on endogenous urinary steroids relevant to doping-control analysis the hydrogen isotope composition of potable water was suddenly enriched from -50 to 200 ‰ and maintained at this level for two weeks for two individuals. The steroids under investigation were 5β-pregnane-3α,20α-diol, 5α-androst-16-en-3α-ol, 3α-hydroxy-5α-androstan-17-one (ANDRO), 3α-hydroxy-5β-androstan-17-one (ETIO), 5α-androstane-3α,17β-diol, and 5β-androstane-3α,17β-diol (excreted as glucuronides) and ETIO, ANDRO and 3β-hydroxyandrost-5-en-17-one (excreted as sulfates). The HIR of body water was estimated by determination of the HIR of total native urine, to trace the induced changes. The hydrogen in steroids is partly derived from the total amount of body water and cholesterol-enrichment could be calculated by use of these data. Although the sum of changes in the isotopic composition of body water was 150 ‰, shifts of approximately 30 ‰ were observed for urinary steroids. Parallel enrichment in their HIR was observed for most of the steroids, and none of the differences between the HIR of individual steroids was elevated beyond recently established thresholds. This finding is important to sports drug testing because it supports the intended use of this novel and complementary methodology even in cases where athletes have drunk water of different HIR, a plausible and, presumably, inevitable scenario while traveling. PMID:23128907

  8. Catalysts based on activated aluminum alloys. I. A study of copper-alumina catalysts by XPS and deuterium-hydrogen exchange

    SciTech Connect

    Yakerson, V.I.; Subbotin, A.N.; Gudkov, B.S.; Tkachenko, O.P.; Sarmurzina, R.G.

    1994-09-01

    Surface compositions and electron states of elements in copper-containing catalysts prepared by water treatment of copper-aluminum alloys activated by indium and gallium are studied by XPS. The copper contents in the surface layers of the catalysts is found to be less than that in the bulk. Fast isotopic H{sub 2}-D{sub 2} exchange at 70-200{degrees}C on reduced copper-containing samples and the absence of the exchange on copper-free samples indicate dissociative hydrogen adsorption on copper-containing active sites. The activation energy for the isotopic exchange is essentially dependent on the procedure of catalyst preparation.

  9. Hydrogen in Gallium Nitride Grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Ambacher, O.; Angerer, H.; Dimitrov, R.; Rieger, W.; Stutzmann, M.; Dollinger, G.; Bergmaier, A.

    1997-01-01

    The role of hydrogen in gallium nitride was studied on thin films of GaN on sapphire prepared at substrate temperatures in the range of 600 to 1100 °C. By using triethylgallium and ammonia as precursor and hydrogen and/or nitrogen as transport gases, we have observed a strong influence of molecular hydrogen on the deposition rate and the structural properties of epitaxial GaN. By elastic recoil detection analysis and thermal desorption measurements we were able to determine the total concentration of nitrogen, hydrogen and carbon in the bulk material. Isotope substitution of hydrogen by deuterium in the H2 carrier gas did not give rise to a noticeable deuterium incorporation, showing that the sources for hydrogen are the metalorganic precursor, ammonia or reaction products of both. Once incorporated, thermally activated hydrogen effusion from n-type GaN occurs with an activation energy of more than 3.9 eV. With the help of mass spectrometry we established hydrogen effusion from heavily magnesium-doped (2 at%) GaN at temperatures between 600 and 700 °C, which is the temperature range used for acceptor activation.

  10. Structural characterization of sputtered hydrogenated amorphous carbon films by solid state nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Cho, Gyunggoo; Yen, Bing K.; Klug, Christopher A.

    2008-07-01

    Solid state nuclear magnetic resonance (NMR) methods have been used to investigate the effect of H content on the structure of sputtered hydrogenated amorphous carbon a-C:H films. Carbon-13 NMR spectra of a-C:H consist of two broad peaks at 135 and 40 ppm, which correspond to the sp2 and sp3 carbons, respectively. Surprisingly, the sp2/sp3 carbon ratio (2.0±0.3) is relatively independent of the H content in the range of 13%-35%. Hence, all a-C:H films contain approximately 66% graphitelike sp2 carbon. Cross polarization and spectral editing experiments reveal that the nonprotonated (quaternary) sp3 carbon fraction reaches as high as 30% at low H concentrations of 13%-23%. As the H content exceeds 23%, however, quaternary carbon bonds are terminated by H atoms to form protonated sp3 carbons, such as methylene (CH2) and methine (CH). Our results show that the hardness of a-C:H correlates with the quaternary carbon fraction rather than the sp2/sp3 ratio, as commonly believed. We also report the first extensive studies of both H1 and C13 spin-lattice relaxation for sputtered a-C:H. Relaxation data for hydrogen and carbon indicate that the unpaired electrons are probably equally distributed among sp2 and sp3 carbons. Moreover, the number of unpaired electrons in the a-C:H samples is relatively independent of H content, as revealed by spin counting experiments. C13 and H1 magnetization recovery curves for samples with H content up to 28% can be fitted with a single exponential, which is in contrast to the biexponential behavior reported for plasma-enhanced chemical vapor deposition (PECVD) a-C:H films. Hence, our results for sputtered a-C:H films do not support the model of proton-rich and proton-deficient regions proposed for PECVD carbon.

  11. Predicting hydrogen and methane adsorption in carbon nanopores for energy storage

    NASA Astrophysics Data System (ADS)

    Ihm, Yungok; Morris, James; Cooper, Valentino; Morris Lab, U. tennessee Collaboration; Advanced material Group, ORNL Collaboration

    2013-03-01

    There are increasing demands for alternate fuels for transportation, which requires safe, high energy density, lightweight storage materials. Experimental measurements and theoretical predictions show relatively low hydrogen storage capacities in various porous materials, limiting hydrogen as a viable alternative for automobiles. In this work, we use a continuum model based on van der Waals density functional (vdW-DF) calculations to elucidate the role that long-range interactions play in the hydrogen adsorption properties of model slit nanopores in carbon. The proper treatment of long-range interactions gives an optimal pore size for hydrogen storage of 8-9 Å (larger than previously predicted). Remarkably, we find a peak hydrogen density close to that of liquid H2 at ambient temperatures, in agreement with recent experimental results on pore-size dependent adsorption in nanoporous carbon. We then show that such nanopores would be better suited to storing methane, possibly providing an alternative to fill the gap between the capacity required by DOE goals and that attainable with current hydrogen storage technology. Research supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division.

  12. The Role of Hydrogen in Small Amorphous Carbon Grains: The IR Spectrum

    NASA Technical Reports Server (NTRS)

    Mennella, V.; Colangeli, L.; Pestellini, C. Cecchi; Palomba, E.; Palumbo, P.; Rotundi, A.; Bussoletti, E.

    1996-01-01

    Preliminary results on the evolution of the IR spectrum of hydrogenated carbon grains as a function of heat treatment are presented. The transformation of C-H and C-C bonding configurations is considered and the correlation with other properties of grains, such as their microstructure, is analyzed.

  13. SELECTIVE HYDROGENATION OF ANHYDRIDES TO LACTONES UNDER SUPERCRITICAL CARBON DIOXIDE MEDIUM

    EPA Science Inventory

    Selective Hydrogenation of Anhydrides to Lactones Under Supercritical Carbon Dioxide Medium

    Endalkachew Sahle-Demessie Unnikrishnan R Pillai
    U.S. EPA , 26 W. Martin Luther King Dr. Cincinnati, OH 45268 Phone: 513-569-7739
    Fax: 513-569-7677
    Abstract:
    Hydrogenat...

  14. Mass transport at the cathode of a hydrogen fuel cell in the presence of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Nechitailov, A. A.; Glebova, N. V.; Krasnova, A. O.; Tomasov, A. A.; Zelenina, N. K.

    2015-11-01

    The influence of carbon nanotubes (CNTs) in the composition of a porous cathode on the increase in the current density of the corresponding standard cathode is studied during the operation of an oxygen-hydrogen fuel cell. The influence of CNTs caused by structure and mass exchange is investigated.

  15. Direct synthesis of formic acid from carbon dioxide by hydrogenation in acidic media

    PubMed Central

    Moret, Séverine; Dyson, Paul J.; Laurenczy, Gábor

    2014-01-01

    The chemical transformation of carbon dioxide into useful products becomes increasingly important as CO2 levels in the atmosphere continue to rise as a consequence of human activities. In this article we describe the direct hydrogenation of CO2 into formic acid using a homogeneous ruthenium catalyst, in aqueous solution and in dimethyl sulphoxide (DMSO), without any additives. In water, at 40 °C, 0.2 M formic acid can be obtained under 200 bar, however, in DMSO the same catalyst affords 1.9 M formic acid. In both solvents the catalysts can be reused multiple times without a decrease in activity. Worldwide demand for formic acid continues to grow, especially in the context of a renewable energy hydrogen carrier, and its production from CO2 without base, via the direct catalytic carbon dioxide hydrogenation, is considerably more sustainable than the existing routes. PMID:24886955

  16. Direct synthesis of formic acid from carbon dioxide by hydrogenation in acidic media.

    PubMed

    Moret, Séverine; Dyson, Paul J; Laurenczy, Gábor

    2014-01-01

    The chemical transformation of carbon dioxide into useful products becomes increasingly important as CO2 levels in the atmosphere continue to rise as a consequence of human activities. In this article we describe the direct hydrogenation of CO2 into formic acid using a homogeneous ruthenium catalyst, in aqueous solution and in dimethyl sulphoxide (DMSO), without any additives. In water, at 40 °C, 0.2 M formic acid can be obtained under 200 bar, however, in DMSO the same catalyst affords 1.9 M formic acid. In both solvents the catalysts can be reused multiple times without a decrease in activity. Worldwide demand for formic acid continues to grow, especially in the context of a renewable energy hydrogen carrier, and its production from CO2 without base, via the direct catalytic carbon dioxide hydrogenation, is considerably more sustainable than the existing routes. PMID:24886955

  17. Research Progress on the Indirect Hydrogenation of Carbon Dioxide to Methanol.

    PubMed

    Du, Xian-Long; Jiang, Zheng; Su, Dang Sheng; Wang, Jian-Qiang

    2016-02-01

    Methanol is a sustainable source of liquid fuels and one of the most useful organic chemicals. To date, most of the work in this area has focused on the direct hydrogenation of CO2 to methanol. However, this process requires high operating temperatures (200-250 °C), which limits the theoretical yield of methanol. Thus, it is desirable to find a new strategy for the efficient conversion of CO2 to methanol at relatively low reaction temperatures. This Minireview seeks to outline the recent advances on the indirect hydrogenation of CO2 to methanol. Much emphasis is placed on discussing specific systems, including hydrogenation of CO2 derivatives (organic carbonates, carbamates, formates, cyclic carbonates, etc.) and cascade reactions, with the aim of critically highlighting both the achievements and remaining challenges associated with this field. PMID:26692565

  18. Probing the Room Temperature Spatial Distribution of Hydrogen in Nanoporous Carbon by Use of Small-Angle Neutron Scattering

    SciTech Connect

    Tsao, Cheng-Si; Li, Mingda; Zhang, Yang; Leao, Juscelino B; Chiang, Wei-Shan; Chung, Tsui-Yun; Tzeng, Yi-Ren; Chen, Sow-hsin H

    2010-01-01

    The spatial distribution of hydrogen physically adsorbed in a nanoporous carbon at room temperature (RT) as a function of H2 gas pressure is investigated for the first time using small-angle neutron scattering (SANS). A hierarchical pore structure consisting of micropores and a fractal mesopore network of the used activated carbon is also studied to correlate the relationship between the spatial distribution of hydrogen and the pore confinement. The cylinder-like cluster of aggregated hydrogen is formed and is confined in the disklike micropore. The evolution of spatial structures of adsorbed hydrogen with hydrogen pressure is elucidated. A direct experimental observation of the spatial distribution and the behavior of hydrogen adsorbed in the porous materials at RT is still scarce to date. The analysis results obtained by SANS provide new information for the future investigations of the RT storage mechanism of hydrogen in the nanoporous materials developed for the purpose of on-board hydrogen storage.

  19. Tritium catalyzed deuterium tokamaks

    SciTech Connect

    Greenspan, E.; Miley, G.H.; Jung, J.; Gilligan, J.

    1984-04-01

    A preliminary assessment of the promise of the Tritium Catalyzed Deuterium (TCD) tokamak power reactors relative to that of deuterium-tritium (D-T) and catalyzed deuterium (Cat-D) tokamaks is undertaken. The TCD mode of operation is arrived at by converting the /sup 3/He from the D(D,n)/sup 3/He reaction into tritium, by neutron capture in the blanket; the tritium thus produced is fed into the plasma. There are three main parts to the assessment: blanket study, reactor design and economic analysis and an assessment of the prospects for improvements in the performance of TCD reactors (and in the promise of the TCD mode of operation, in general).

  20. Plasma deposition of amorphous hydrogenated carbon films on III-V semiconductors

    NASA Technical Reports Server (NTRS)

    Pouch, John J.; Warner, Joseph D.; Liu, David C.; Alterovitz, Samuel A.

    1988-01-01

    Amorphous hydrogenated carbon films were grown on GaAs, InP and fused silica substrates using plasmas generated from hydrocarbon gases. Methane and n-butane sources were utilized. The effects of flow rate and power density on film growth were investigated. Carbon was the major constituent in the films. The degree of asymmetry at the carbon-semiconductor interface was approximately independent of the power density. Different H-C bonding configurations were detected by the technique of secondary-ion mass spectrometry. Band gaps up to 3 eV were obtained from optical absorption studies. Breakdown strengths as high as 600 MV/m were measured.

  1. Vacuum ultraviolet of hydrogenated amorphous carbons. II. Small hydrocarbons production in Photon Dominated Regions

    NASA Astrophysics Data System (ADS)

    Alata, I.; Jallat, A.; Gavilan, L.; Chabot, M.; Cruz-Diaz, G. A.; Munoz Caro, G. M.; Béroff, K.; Dartois, E.

    2015-12-01

    Context. Hydrogenated amorphous carbons (a-C:H) are a major component of the carbonaceous solids present in the interstellar medium. The production and existence of these grains is connected in particular with the balance between their photolysis, radiolysis, and hydrogenation. During grain processing, H2 and other small organic molecules, radicals, and fragments are released into the gas phase. Aims: We perform photolytic experiments on laboratory produced interstellar a-C:H analogues to monitor and quantify the release of species and compare to relevant observations in the interstellar medium. Methods: Hydrogenated amorphous carbon analogues at low temperature are exposed to ultraviolet (UV) photons, under ultra-high vacuum conditions. The species produced are monitored using mass spectrometry and post irradiation temperature-programmed desorption. Additional experiments are performed using deuterated analogues and the species produced are unambiguously separated from background contributions. We implement the laboratory measured yields for the released species in a time dependent model to investigate the effect of the UV photon irradiation of hydrogenated amorphous carbons in a photon dominated region, and estimate the associated time scale. Results: The UV photolysis of hydrogenated amorphous carbons leads to the production of H2 molecules and small hydrocarbons. The model shows that the photolytic evolution of a-C:Hs in photon dominated regions, such as the Horsehead Nebula, can raise the abundance of carbonaceous molecules by several orders of magnitude at intermediate visual extinctions, i.e., after the C+ maximum and before the dense cloud conditions prevail where models generally show a minimum abundance for such carbonaceous species. The injection time peak ranges from a thousand to ten thousand years in the models, considering only the destruction of such grains and no re-hydrogenation. This time scale is consistent with the estimated advection front of a photon dominated region, which replenishes it with freshly exposed material. Appendices are available in electronic form at http://www.aanda.org

  2. ENHANCED HYDROGEN ECONOMICS VIA COPRODUCTION OF FUELS AND CARBON PRODUCTS

    SciTech Connect

    Kennel, Elliot B; Bhagavatula, Abhijit; Dadyburjor, Dady; Dixit, Santhoshi; Garlapalli, Ravinder; Magean, Liviu; Mukkha, Mayuri; Olajide, Olufemi A; Stiller, Alfred H; Yurchick, Christopher L

    2011-03-31

    This Department of Energy National Energy Technology Laboratory sponsored research effort to develop environmentally cleaner projects as a spin-off of the FutureGen project, which seeks to reduce or eliminate emissions from plants that utilize coal for power or hydrogen production. New clean coal conversion processes were designed and tested for coproducing clean pitches and cokes used in the metals industry as well as a heavy crude oil. These new processes were based on direct liquefaction and pyrolysis techniques that liberate volatile liquids from coal without the need for high pressure or on-site gaseous hydrogen. As a result of the research, a commercial scale plant for the production of synthetic foundry coke has broken ground near Wise, Virginia under the auspices of Carbonite Inc. This plant will produce foundry coke by pyrolyzing a blend of steam coal feedstocks. A second plant is planned by Quantex Energy Inc (in Texas) which will use solvent extraction to coproduce a coke residue as well as crude oil. A third plant is being actively considered for Kingsport, Tennessee, pending a favorable resolution of regulatory issues.

  3. Hydrogen storage capacity characterization of carbon nanotubes by a microgravimetrical approach.

    PubMed

    Lan, Aidong; Mukasyan, Alexander

    2005-08-25

    An accurate gravimetric apparatus based on a contactless magnetic suspension microbalance was developed. This unit was used to measure the hydrogen storage capacity for a variety of carbon nanotubes (CNTs) at room temperature and hydrogen pressures up to 11.5 MPa. The results show that regardless of their synthesis methods, purities, and nanostructures all investigated CNT products possess relatively low hydrogen storage capacities (<0.2 wt %). For comparison, the adsorption characteristics of theses samples were also measured at a pressure of 0.1 MPa and liquid nitrogen temperature (approximately 77 K) by a conventional volumetric approach. The methodological aspects related to the accuracy of the hydrogen uptake measurements are also discussed. PMID:16853032

  4. The influence of microstructure on the hydrogen embrittlement in a low carbon steel

    SciTech Connect

    Liou, H.Y.; Wang, S.C.; Hsieh, R.I.

    1994-12-31

    A low carbon steel was heat-treated by various processes, so that different microstructures including ferrite + pearlite, bainite, bainite + martensite, martensite, and temper martensite were obtained. These heat-treated specimens were used to evaluate the hydrogen embrittlement characteristics by HIC immersion test and Charpy impact test. The results indicated that hydrogen cracking in the as-received specimen is the worst and the air cooling, oil cooling and high temperature tempered specimens have the better HIC resistance. These results demonstrated that the pearlite band structure is the most important HIC propagation path. The Charpy impact testing results for specimens without and with hydrogen charging showed that the absorbed energies of H-charged specimens did not change or even increase. The dislocation density seems to play an important role on the variation of impact absorbed energy. The detail effects of microstructure on the hydrogen embrittlement was discussed in this paper.

  5. Confident methods for the evaluation of the hydrogen content in nanoporous carbon microfibers

    PubMed Central

    2012-01-01

    Nanoporous carbon microfibers were grown by chemical vapor deposition in the vapor-liquid solid mode using different fluid hydrocarbons as precursors in different proportions. The as-grown samples were further treated in argon and hydrogen atmospheres at different pressure conditions and annealed at several temperatures in order to deduce the best conditions for the incorporation and re-incorporation of hydrogen into the microfibers through the nanopores. Since there are some discrepancies in the results on the hydrogen content obtained under vacuum conditions, in this work, we have measured the hydrogen content in the microfibers using several analytical methods in ambient conditions: surface tension, mass density, and Raman measurements. A discussion on the validity of the results obtained through the correlation between them is the purpose of the present work. PMID:23095321

  6. Fractionation of carbon and hydrogen isotopes by methane-oxidizing bacteria

    USGS Publications Warehouse

    Coleman, D.D.; Risatti, J.B.; Schoell, M.

    1981-01-01

    Carbon isotopic analysis of methane has become a popular technique in the exploration for oil and gas because it can be used to differentiate between thermogenic and microbial gas and can sometimes be used for gas-source rock correlations. Methane-oxidizing bacteria, however, can significantly change the carbon isotopic composition of methane; the origin of gas that has been partially oxidized by these bacteria could therefore be misinterpreted. We cultured methane-oxidizing bacteria at two different temperatures and monitored the carbon and hydrogen isotopic compositions of the residual methane. The residual methane was enriched in both 13C and D. For both isotopic species, the enrichment at equivalent levels of conversion was greater at 26??C than at 11.5??C. The change in ??D relative to the change in ??13C was independent of temperature within the range studied. One culture exhibited a change in the fractionation pattern for carbon (but not for hydrogen) midway through the experiment, suggesting that bacterial oxidation of methane may occur via more than one pathway. The change in the ??D value for the residual methane was from 8 to 14 times greater than the change in the ??13C value, indicating that combined carbon and hydrogen isotopic analysis may be an effective way of identifying methane which has been subjected to partial oxidation by bacteria. ?? 1981.

  7. Nanoporous carbons derived from binary carbides and their optimization for hydrogen storage

    NASA Astrophysics Data System (ADS)

    Dash, Ranjan Kumar

    On-board hydrogen storage is one of the major hurdles for success of hydrogen economy. Hydrogen storage using physisorption technique demands highly porous materials. Carbide derived carbons (CDC), a new class of porous carbons produced by thermo chemical etching of metal atoms from carbides were selected as a method for producing highly porous material for hydrogen storage. In order to synthesize tunable nanoporous carbon and to establish a structure-property relation between initial metal carbide and resultant nanoporous carbon, CDCs were synthesized from four metal carbides, two that have uniform carbon to carbon distance in the lattice structure (ZrC, TiC and SiC) and one that has a non-uniform carbon distribution in the lattice (B4C). It was shown that a uniform distribution of carbon atoms in the carbide is important for obtaining a narrow pore size distribution (PSD). CDC derived from B 4C had a relatively broad PSD and contained mesopores even at the lowest synthesis temperature, while the CDC produced from SiC maintained a narrow PSD even at the synthesis temperature of 1200°C. CDC produced from ZrC and TiC has a narrow PSD at low synthesis temperature and pores gets wider at higher temperatures. Comparison of CDCs produced from ZrC, TiC and B 4C shows that CDCs produced from ZrC and TiC show a lower degree of ordering than that from B4C at high temperatures. Unlike CDCs produced from ZrC and TiC, the PSD of CDCs from B4C does not change appreciably in the 600-1200°C range. CDCs produced from ZrC and TiC can have both narrowly distributed micropores (pores smaller than 2 nm) and mesopores (pores larger than 2 nm), depending on synthesis temperature. In this work, it is demonstrated that porosity of CDC can be fine tuned with a high accuracy by using different starting carbides and varying the synthesis temperatures. This is very important in many applications of porous carbon, especially for gas storage. CDC from ZrC, TiC, B4C and SiC resulted in a family of high surface area nanoporous carbons (300 to 2300 m2/g) of average pore size ranging from 0.5 to 1.4 nm, A systematic study on hydrogen storage capacity of CDCs and comparison with other materials including metal organic framework (MOF-5), single (SWCNT) and multi-walled carbon nanotubes (MWCNT) dispelled the popular myth that hydrogen physisorption is directly proportional to SSA, and provided guidance for optimal design by showing that a large volume of small open pores is the key to high hydrogen uptake at cryogenic temperatures and ambient pressure. Values up to 3 wt.% and 30 kg/m3 have been demonstrated in CDCs; these are twice what can be stored in MOF-5 and several times higher than has been achieved in SWCNT or MWCNT at 77 K and atmospheric pressure. The isosteric heat of hydrogen adsorption up to 11 kJ/mole of CDCs is higher than that reported for activated carbon, CNT and MOF.

  8. Alcohol additive effect in hydrogen generation from water with carbon by photochemical reaction

    NASA Astrophysics Data System (ADS)

    Maeda, Kosuke; Ozaki, Nobuhiko; Akimoto, Ikuko

    2014-01-01

    We have found a novel photochemical activity of carbon powder to generate hydrogen-included gas by irradiating nanosecond laser pulse on carbon aqueous suspension at room temperature. In this study, we investigate alcohol additive effect to improve the gas generation efficiency in Bincho-tan charcoal aqueous suspension. We find that the generated gas volume with 50 wt % ethanol addition increases twice as much as that without ethanol. Components of the generated gas are analyzed to be 50% of hydrogen, 20% of carbon monoxide, and others, being similar to that generated with pure water suspension. Possible roles of ethanol are discussed as an agent in photochemical reactions and/or as a hole scavenger reagent in a photocatalytic reaction.

  9. Stereoselective hydrogenation of olefins using rhodium-substituted carbonic anhydrase--a new reductase.

    PubMed

    Jing, Qing; Okrasa, Krzysztof; Kazlauskas, Romas J

    2009-01-01

    One useful synthetic reaction missing from nature's toolbox is the direct hydrogenation of substrates using hydrogen. Instead nature uses cofactors like NADH to reduce organic substrates, which adds complexity and cost to these reductions. To create an enzyme that can directly reduce organic substrates with hydrogen, researchers have combined metal hydrogenation catalysts with proteins. One approach is an indirect link where a ligand is linked to a protein and the metal binds to the ligand. Another approach is direct linking of the metal to protein, but nonspecific binding of the metal limits this approach. Herein, we report a direct hydrogenation of olefins catalyzed by rhodium(I) bound to carbonic anhydrase (CA-[Rh]). We minimized nonspecific binding of rhodium by replacing histidine residues on the protein surface using site-directed mutagenesis or by chemically modifying the histidine residues. Hydrogenation catalyzed by CA-[Rh] is slightly slower than for uncomplexed rhodium(I), but the protein environment induces stereoselectivity favoring cis- over trans-stilbene by about 20:1. This enzyme is the first cofactor-independent reductase that reduces organic molecules using hydrogen. This catalyst is a good starting point to create variants with tailored reactivity and selectivity. This strategy to insert transition metals in the active site of metalloenzymes opens opportunities to a wider range of enzyme-catalyzed reactions. PMID:19115310

  10. The primordial abundance of deuterium: ionization correction

    NASA Astrophysics Data System (ADS)

    Cooke, Ryan; Pettini, Max

    2016-01-01

    We determine the relative ionization of deuterium and hydrogen in low metallicity damped Lyman α (DLA) and sub-DLA systems using a detailed suite of photoionization simulations. We model metal-poor DLAs as clouds of gas in pressure equilibrium with a host dark matter halo, exposed to the Haardt & Madau background radiation of galaxies and quasars at redshift z ≃ 3. Our results indicate that the deuterium ionization correction correlates with the H I column density and the ratio of successive ion stages of the most commonly observed metals. The N(N II)/N(N I) column density ratio provides the most reliable correction factor, being essentially independent of the gas geometry, H I column density, and the radiation field. We provide a series of convenient fitting formulae to calculate the deuterium ionization correction based on observable quantities. The ionization correction typically does not exceed 0.1 per cent for metal-poor DLAs, which is comfortably below the current measurement precision (2 per cent). However, the deuterium ionization correction may need to be applied when a larger sample of D/H measurements becomes available.

  11. Electron transport properties of a single-walled carbon nanotube in the presence of hydrogen cyanide: first-principles analysis.

    PubMed

    Srivastava, Anurag; Sharma, Vikash; Kaur, Kamalpreet; Khan, Md Shahzad; Ahuja, Rajeev; Rao, V K

    2015-07-01

    First-principles analysis based on density functional theory was performed to compute the electronic and transport properties of a single-walled carbon nanotube in the presence of hydrogen cyanide. A chiral (4,1) carbon nanotube was found to become less metallic as the number of hydrogen cyanide molecules nearby increased. When there were a sufficient number of hydrogen cyanide molecules close to the nanotube, it became semiconducting. This metallic to semiconducting transformation of the nanotube was verified by analyzing its conductance and current as a function of the number of molecules of hydrogen cyanide present. The conductivity of the carbon nanotube was very high when no hydrogen cyanide molecules were present, but decreased considerably when even just a single hydrogen cyanide molecule approached the surface of the nanotube. PMID:26072123

  12. Surface morphology, cohesive and adhesive properties of amorphous hydrogenated carbon nanocomposite films

    NASA Astrophysics Data System (ADS)

    Lazauskas, A.; Grigaliūnas, V.; Meškinis, Š.; Ecarla, F.; Baltrusaitis, J.

    2013-07-01

    In this work, amorphous hydrogenated carbon (a-C:H), SiOx containing a-C:H (a-C:H/SiOx) and nitrogen-doped a-C:H/SiOx (a-C:H:N/SiOx) thin films were deposited on chromium thin film coated glass using a closed drift ion beam source. Acetylene gas, hexamethyldisiloxane and hydrogen or 20% nitrogen/hydrogen mixture were used as precursors. Resulting hydrogenated carbon thin film surface morphology as well as their cohesive and adhesive properties were studied using progressive loading scratch tests followed by optical microscopy analysis. Surface analysis was also performed using atomic force microscopy via topography, surface morphology parameter, height distribution histogram and bearing ratio curve based hybrid parameter measurements. The a-C:H/SiOx and a-C:H:N/SiOx thin films showed better mechanical strength as compared to the conventional a-C:H films. X-ray photoelectron spectroscopy was used to determine the chemical composition of these films. It showed increased amounts of silicon and absence of terminal oxygenated carbon bonds in a-C:H:N/SiOx thin film which was attributed to its improved mechanical properties.

  13. Creation of active sites by impregnation of carbon fibers: application to the fixation of hydrogen sulfide.

    PubMed

    Meljac, Laure; Perier-Camby, Laurent; Thomas, Gérard

    2004-06-01

    Activated carbon fibers, which exhibit high specific area and numerous active surface sites, constitute very powerful adsorbents and are widely used in filtration to eliminate pollutants from liquid or gaseous effluents. The fibers studied in this work are devoted to the filtration of gaseous effluent containing very small amounts (few vpm) of hydrogen sulfide. Preliminary experiments evidenced that these fibers weakly adsorb hydrogen sulfide. To improve their fixation capacity toward H(2)S the activated fibers are impregnated in an aqueous solution of potassium hydroxide. The impregnation treatment usually takes place before activation but in this work it occurs at room temperature after activation of the fibers. A further thermal treatment is performed to increase the efficiency of the system. The overall treatment leads to the creation of basic sites showing a great activity for H(2)S gas in the presence of water vapor. The mechanism has been established by a series of characterizations before, during, and after the different operation units. The KOH deposited after impregnation is carbonated into KHCO(3) at room temperature and then decomposed into K(2)CO(3) during the thermal treatment. K(2)CO(3) and H(2)S dissolve in a liquid aqueous solution formed on the fiber surface. Then carbonate ions and H(2)S molecules react together almost completely to yield HS(-) species. As a consequence the sorption capacities of hydrogen sulfide on the impregnated fibers are much higher, even for small hydrogen sulfide volume fractions. PMID:15120288

  14. (Carbon and hydrogen metabolism of green algae in light and dark)

    SciTech Connect

    Not Available

    1990-01-01

    The focus of this project was the elucidation of anaerobic metabolism in ecuaryotic green algae, chlamydomonas reinhardii. Chlamydomonas is a versatile organism that can grow under disparate conditions such as fresh water lakes and sewage ponds. The cell an photoassimilate CO{sub 2} aerobically and anaerobically, the latter after adaptation'' to a hydrogen metabolism. It can recall the knallgas or oxyhydrogen reaction and utilize hydrogen the simplest of all reducing agents for the dark assimilation of CO{sub 2} by the photosynthetic carbon reduction cycle. The dark reduction with hydrogen lies on the border line between autotrophic and heterotrophic carbon assimilation. Both autotrophic and heterotrophic bacteria are known in which molecular hydrogen can replace either inorganic or organic hydrogen donors. Here the dark reduction of CO{sub 2} acquires a particular importance since it occurs in the same cell that carries on photoreduction and photosynthesis. We will demonstrate here that the alga chloroplast possesses a respiratory capacity. It seems likely that Chlamydomonas may have retained the chloroplastic respiratory pathway because of the selective advantage provided to the algae under a wide range of environmental conditions that the cells experience in nature. The ability to cycle electrons and poise the reduction level of the photosynthetic apparatus under aerobic and microaerobic conditions could allow more efficient CO{sub 2} fixation and enhanced growth under unfavorable conditions or survival under more severe conditions.

  15. Near-surface hydrogen depletion of diamond-like carbon films produced by direct ion deposition

    NASA Astrophysics Data System (ADS)

    Markwitz, Andreas; Gupta, Prasanth; Mohr, Berit; Hübner, René; Leveneur, Jerome; Zondervan, Albert; Becker, Hans-Werner

    2016-03-01

    Amorphous atomically flat diamond-like carbon (DLC) coatings were produced by direct ion deposition using a system based on a Penning ion source, butane precursor gas and post acceleration. Hydrogen depth profiles of the DLC coatings were measured with the 15N R-NRA method using the resonant nuclear reaction 1H(15N, αγ)12C (Eres = 6.385 MeV). The films produced at 3.0-10.5 kV acceleration voltage show two main effects. First, compared to average elemental composition of the film, the near-surface region is hydrogen depleted. The increase of the hydrogen concentration by 3% from the near-surface region towards the bulk is attributed to a growth model which favours the formation of sp2 hybridised carbon rich films in the film formation zone. Secondly, the depth at which the maximum hydrogen concentration is measured increases with acceleration voltage and is proportional to the penetration depth of protons produced by the ion source from the precursor gas. The observed effects are explained by a deposition process that takes into account the contributions of ion species, hydrogen effusion and preferential displacement of atoms during direct ion deposition.

  16. Polygeneration of SNG, hydrogen, power, and carbon dioxide from Texas lignite

    SciTech Connect

    Gray, D.; Salerno, S.; Tomlinson, G.; Marano, J.J.

    2004-12-15

    This feasibility study has shown that siting a mine mouth lignite fed gasification plant in Texas to produce hydrogen, SNG, electric power, and carbon dioxide could be economically feasible in an era of high natural gas prices. Because of the high moisture content of the lignite the choice of gasification system becomes an important issue. Hydrogen produced from Texas lignite in a coproduction plant could be produced in the range $5.20-$6.20/MMBTU (HHV basis) equivalent to between $0.70 and $0.84 per kilogram. This range of hydrogen costs is equivalent to hydrogen produced by steam methane reforming of natural gas if the natural gas feed price was between $3.00 and $4.00/MMBTU. With natural gas prices continuing to remain above $5.00/MMBTU this concept of using Texas lignite for hydrogen production would be economically viable. For the production of SNG from Texas lignite, the costs range from $6.90-$5.00/MMBTU (HHV basis). If natural gas prices remain above $5.00/MMBTU then the configuration using the advanced dry feed gasification system would be economically viable for production of SNG. This option may be even more attractive with other low rank coals such as Wyoming subbituminous and North Dakota lignite coals that are priced lower than Texas lignite. Production of electric power from these conceptual coproduction plants provides a valuable revenue stream. The opportunity to sell carbon dioxide for EOR in Texas provided another valuable revenue stream for the plants. The break even cost of recovering the carbon dioxide ranged from about $5.50 to $7.75 per ton depending on whether SNG or hydrogen was the product.

  17. Toward New Candidates for Hydrogen Storage: High Surface Area Carbon Aerogels

    SciTech Connect

    Kabbour, H; Baumann, T F; Satcher, J H; Saulnier, A; Ahn, C C

    2007-02-05

    We report the hydrogen surface excess sorption saturation value of 5.3 wt% at 30 bar pressure at 77 K, from an activated carbon aerogel with a surface area of 3200 m{sup 2}/g as measured by Brunauer-Emmett-Teller (BET) analysis. This sorption value is one of the highest we have measured in a material of this type, comparable to values obtained in high surface area activated carbons. We also report, for the first time, the surface area dependence of hydrogen surface excess sorption isotherms of carbon aerogels at 77 K. Activated carbon aerogels with surface areas ranging from 1460 to 3200 m{sup 2}/g are evaluated and we find a linear dependence of the saturation of the gravimetric density with BET surface area for carbon aerogels up to 2550 m{sup 2}/g, in agreement with data from other types of carbons reported in the literature. Our measurements show these materials to have a differential enthalpy of adsorption at zero coverage of {approx}5 to 7 kJ/mole. We also show that the introduction of metal nanoparticles of nickel improves the sorption capacity while cobalt additions have no effect.

  18. Hydrogen and oxygen trapping and retention in stainless steel and graphite materials irradiated in plasma

    NASA Astrophysics Data System (ADS)

    Begrambekov, L.; Ayrapetov, A.; Ermakov, V.; Kaplevsky, A.; Sadovsky, Ya.; Shigin, P.

    2013-11-01

    The paper presents the results of experimental investigation of energy and flux dependences of hydrogen isotopes and oxygen trapping in carbon materials (carbon fiber composite and pyrolitic graphite), and metals (stainless steel and nickel) under irradiation in the deuterium gas discharge plasma with and without oxygen addition. The dependence of hydrogen trapping on ion energy, ion current density, oxygen addition in deuterium plasma are presented and analyzed. The sorbed molecules, containing hydrogen atoms from the residual gas and deuterium atoms of the working gas are shown to be the important source of hydrogen trapping in both carbon based materials and stainless steel. Irradiation of the SS vacuum vessel with the neutrals or/and ions of (D2 + O2) plasma initiate the hydrogen diffusion from the vessel wall and H2, HD, D2O, HDO, H2O molecule formation on the wall surface. Trapping of the low energy plasma particles and the particles from the sorbed molecules as well as modification of working gas composition are considered as the processes provided at the expense of the potential energy of plasma particles with respect to the surface and occurred through their inelastic collisions with the surface. The hydrogen trapping occurred due to “potential” processes was named as “potential”, and in contrast the trapping of fast particles due to their kinetic energy was labeled as “kinetic”.

  19. The role of destabilization of palladium hydride on the hydrogen uptake of Pd-containing activated carbons

    SciTech Connect

    Bhat, Vinay V; Contescu, Cristian I; Gallego, Nidia C

    2009-01-01

    This paper reports on differences in stability of Pd hydride phases in palladium particles with various degrees of contact with microporous carbon supports. A sample containing Pd embedded in activated carbon fiber (Pd-ACF; 2 wt% Pd) was compared with commercial Pd nanoparticles deposited on microporous activated carbon (Pd-catalyst, 3 wt% Pd) and with support-free nanocrystalline palladium (Pd-black). The morphology of materials was characterized by electron microscopy, and the phase transformations were analyzed over a large range of hydrogen partial pressures (0.003 - 10 bar) and at several temperatures using in-situ X-ray diffraction. The results were verified with volumetric hydrogen uptake measurements. Results indicate that higher degree of Pd-carbon contacts for Pd particles embedded in a microporous carbon matrix induce efficient pumping of hydrogen out of -PdHx. It was also found that thermal cleaning of carbon surface groups prior to exposure to hydrogen further enhances the hydrogen pumping power of the microporous carbon support. In brief, this study highlights that the stability of -PdHx phase supported on carbon depends on the degree of contact between Pd-carbon and the nature of the carbon surface.

  20. Hydrogenation of Carbon Dioxide to Methane by Ruthenium Nanoparticles in Ionic Liquid.

    PubMed

    Melo, Catarina I; Szczepańska, Anna; Bogel-Łukasik, Ewa; Nunes da Ponte, Manuel; Branco, Luís C

    2016-05-23

    The efficient transformation of carbon dioxide into fuels can be an excellent alternative to sequestration. In this work, we describe CO2 hydrogenation to methane in imidazolium-based ionic liquid media, using ruthenium nanoparticles prepared in situ as catalyst. The best yield of methane (69 %) was achieved using 0.24 mol % ruthenium catalyst (in [omim][NTf2 ], 1-octyl-3-methylimidazolium bistrifluoromethanesulfonylimide, at 40 bar of hydrogen pressure plus 40 bar of CO2 pressure, and at 150 °C. PMID:27114238