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1

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

NASA Astrophysics Data System (ADS)

Derivatization of peptides as quaternary ammonium salts (QAS) is a known method for sensitive detection by electrospray ionization tandem mass spectrometry. Hydrogens at ?-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.

Rudowska, Magdalena; Wojewska, Dominika; Kluczyk, Alicja; B?chor, Remigiusz; Stefanowicz, Piotr; Szewczuk, Zbigniew

2012-06-01

2

Collision-induced absorption spectra of hydrogen in the first overtone region and the fundamental band of deuterium in binary mixtures: Deuterium-nitrogen, deuterium-carbon monoxide, deuterium-helium, deuterium-argon and deuterium-krypton  

NASA Astrophysics Data System (ADS)

The present research project consisted of three distinct spectral regions of study. First there was a refinement to the spectral analysis of the collision-induced absorption (CIA) spectra of the first overtone band of hydrogen. This consisted primarily of an investigation of the density dependence of the so-called "fudge factor" by use of various semi-empirical line shapes. The second part was an analysis of the CIA of the fundamental band of D2 in D2-N2 and D2-CO mixtures. The absorption coefficients were determined using appropriate statistical methods applied to a density expansion of the integrated absorption of the spectra, as well as calculation of the characteristic parameters of various semi-empirical line shapes applied to the experimental data. The third part of the thesis consisted of a systematic study of the CIA spectra of the fundamental band of D2 enhanced by He, Ar, and Kr at room temperature. The absorption coefficients were determined using appropriate statistical methods applied to a density expansion of the integrated absorption of the spectra, and the characteristic parameters of various semi-empirical line shapes were deduced from a nonlinear fitting procedure applied to the experimental data. During the course of the above work, the FORTRAN programs used to transform the raw data into the desired numerical quantities and complete the necessary analysis were updated and as necessary completely rewritten to advance the data analysis. This work was commenced in earnest during the author's M.Sc. thesis with the goal being to maximize the robust nature of the analysis and propagation of errors throughout all calculations to obtain maximum reliability in the results.

Stamp, Clifford Francis Joseph

3

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.

4

Hydrogen and deuterium diffusion in lithium hydride  

NASA Astrophysics Data System (ADS)

Hydrogen is considered a promising candidate to achieve an alternative source to overcome future energy supply problems. Very recently, an ab initio molecular dynamics study of the hydrogen diffusion in sodium and lithium hydrides appeared by Ramzan and Ahuja [J. Appl. Phys. 106, 016104 (2009)]. Here, we alternatively report the calculation of the temperature dependence of the diffusion coefficients of hydrogen and deuterium in LiH in terms of a thermodynamical model. The resulting values agree fairly well with experimental data.

Dologlou, Elisabeth

2010-04-01

5

Hydrogen-deuterium exchange in structural biology  

NASA Astrophysics Data System (ADS)

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.

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

1986-03-01

6

Hydrogen and deuterium retention in wall samples of JET  

NASA Astrophysics Data System (ADS)

The amounts of H and D trapped in the surface layers of samples made out of C, Ni, Inconel and Si, installed at the vessel walls of JET and removed after the 1984 and 1985 periods of operation were measured. After the 1984 operation period the D concentration in carbon probes was of the order of 5 × 10 19/m 2. while the hydrogen was about a factor of 40 higher. This can be attributed to a final glow discharge cleaning in hydrogen at the end of the operation period. After the 1984 period of operation the amounts of deuterium and hydrogen were nearly equal at about 5 × 10 21/m 2. A comparison of the amounts of deuterium and hydrogen with the amount of carbon deposition on the Inconel wall samples shows a ratio of about 0.3 to 0.4 (H + D) per C-atom. The hydrogen concentrations trapped in the vessel wall correspond to more than 100 times the amount of hydrogen isotopes in the plasma during a discharge.

Behrisch, R.; Ehrenberg, J.; Wielunski, M.; Martinelli, A. P.; Bergsåker, H.; Emmoth, B.; de Kock, L.; Coad, J. P.

1987-02-01

7

Temperature dependent deuterium quadrupole coupling constants of short hydrogen bonds  

E-print Network

Temperature dependent deuterium quadrupole coupling constants of short hydrogen bonds Xingang Zhao January 2006 Abstract Very short hydrogen bonds universally show large positive dependences and intermode couplings. q 2006 Published by Elsevier B.V. Keywords: Hydrogen bonds; NMR; Deuterium quadrupole 1

Barsegov, Valeri

8

Deuterium Uptake in Magnetic-Fusion Devices with Lithium-Conditioned Carbon Walls  

NASA Astrophysics Data System (ADS)

Lithium wall conditioning has lowered hydrogenic recycling and dramatically improved plasma performance in many magnetic-fusion devices. In this Letter, we report quantum-classical atomistic simulations and laboratory experiments that elucidate the roles of lithium and oxygen in the uptake of hydrogen in amorphous carbon. Surprisingly, we show that lithium creates a high oxygen concentration on a carbon surface when bombarded by deuterium. Furthermore, surface oxygen, rather than lithium, plays the key role in trapping hydrogen.

Krstic, P. S.; Allain, J. P.; Taylor, C. N.; Dadras, J.; Maeda, S.; Morokuma, K.; Jakowski, J.; Allouche, A.; Skinner, C. H.

2013-03-01

9

Quadrupolar Ordering in Solid Hydrogen and Deuterium.  

NASA Astrophysics Data System (ADS)

A study is presented of NMR absorption spectra and relaxation in solid hydrogen and solid deuterium at temperatures accessible via dilution refrigeration, with emphasis on the local ordering phenomena which occur for temperatures T(, )<(, )300mK and concentrations X of J = 1 molecules which apparently preclude Pa(,3) ordering (0.2 < X < 0.5). An important aspect of these experiments was the use of large thermal contact areas in conjunction with nuclear magnetic thermometry. This permitted an accurate assessment of the thermal gradients produced by spin-species conversion within the samples. In H(,2), the line broadening associated with lowering temperature for X < 0.5 was found to be very gradual, showing no evidence for a phase transition or for a well -defined spin-glass-like transition. Absorption line shapes were identical on warming and cooling, aside from small changes attributable to ortho-para conversion, provided that confusion with the irreversible crystal-structure change which occurs near X = 0.5 was avoided. The line -shape data for X = 0.43 were fitted to a model incorporating a broad distribution of energy splittings for the J = 1 molecules. The relaxation time for holes burned in the line for ortho concentrations X < 0.5 was also measured. In D(,2), the spin-lattice relaxation time t(,1) for J = 0 molecules was measured at a Larmor frequency of 46MHz for temperatures 40mK < T < 700mK and para-concentrations 0.24 < X < 0.31. The discontinuity in the derivative of t(,1) with respect to temperature for T (DBLTURN) 170mK which had been reported in the literature was not confirmed. Rather, our data showed an extremely broad minimum in t(,1)(T) for T (DBLTURN) 300mK. Taken together with higher-temperature measurements that have been reported by others, our data suggest an gradual slowing-down of orientational fluctuations as the temperature is lowered. A model of cross-relaxation was developed which allows the relaxation time of J = 1 molecules in D(,2) to be inferred from the observed relaxation time for J = 0 molecules. The inferred J = 1 relaxation time was fitted to a model of thermally-activated orientational fluctuations. This procedure suggested that the thermal barriers to molecular reorientation are randomly distributed between 0.2K and 1.0K.

Candela, Donald

10

Appendix A SIMS profiles of hydrogen and deuterium in diamond  

E-print Network

127 Appendix A SIMS profiles of hydrogen and deuterium in diamond A.1 Introduction A diamond sample ion­beam doping. Impurity levels were profiled as a function of depth from the diamond surface using­type reactor, consisting of a quartz tube with diamond­coated quartz substrate holder. The substrate

Goddard III, William A.

11

Hydrogen/deuterium fractionation factors of the aqueous ligand of cobalt in Co(H sub 2 O) sub 6 sup 2+ and Co(II)-substituted carbonic anhydrase  

SciTech Connect

The author has measured the hydrogen/deuterium fractionation factor for the rapidly exchanging aqueous ligands of cobalt in Co(H{sub 2}O){sub 6}{sup 2+} and in three Co(II)-substituted isozymes of carbonic anhydrase. The fractionation factor was determined from NMR relaxation rates at 300 MHz of the protons of water in mixed solutions of H{sub 2}O and D{sub 2}O containing these complexes. In each case, the paramagnetic contribution to 1/T{sub 2} was greater than to 1/T{sub 1}, consistent with a chemical shift mechanism affecting 1/T{sub 2}. The fractionation factors obtained from T{sub 2} were 0.73 {plus minus} 0.02 for Co(H{sub 2}O){sub 6}{sup 2+}, 0.72 {plus minus} 0.02 for Co(II)-substituted carbonic anhydrase I, 0.77 {plus minus} 0.01 for Co(II)-substituted carbonic anhydrase II, and 1.00 {plus minus} 0.07 for Co(Il)-substituted carbonic anhydrase III. He concluded that fractionation factors in these cases determined from T{sub 1} and T{sub 2} measured isotope preferences for different populations of ligand sites. Since T{sub 2} has a large contribution from a chemical shift mechanism, the fractionation factor determined from T{sub 2} has a large contribution of the fractionation of inner shell ligands. The fractionation factor of Co(H{sub 2}O){sub 6}{sup 2+} was used to interpret the solvent hydrogen isotope effects on the formation of complexes of cobalt with the bidentate ligands glycine, N,N-dimethylglycine, and acetylacetone. The contribution of the fractionation factor of the inner water shell in Co(H{sub 2}O){sub 6}{sup 2+} did not account completely for the measured isotope effect, and that the hydrogen/deuterium fractionation of outer shell water makes a large contribution to the isotope effect on the formation of these complexes.

Kassebaum, J.W.

1988-01-01

12

Hydrogen and deuterium trapping in iron  

SciTech Connect

The research described is directed at present almost exclusively to hydrogen transport, including both chemical and physical trapping, in iron and iron-base alloys. Some attention is directed to isotope effects. Efforts are made to clarify and understand hydrogen-related phenomena which are believed to be of direct importance to practical performance.

Johnson, H.H.; Lin, R.W.

1981-02-01

13

The pion nucleon scattering lengths from pionic hydrogen and deuterium  

NASA Astrophysics Data System (ADS)

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 ?_{1s} = 0.868±0.040 (stat.)±0.038 (syst.) eV of the 1s state. Taking into account the electromagnetic corrections we find the hadronic ? N s-wave scattering amplitude a_{?-prightarrow?-p} = 0.0883±0.0008 m_{?}^{-1} for elastic scattering and a_{?-prightarrow?0n} = -0.128±0.006 m_{?} ^{-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 ? N scattering lengths (within the framework of isospin symmetry) are found to be b_0 = -0.0001^{+0.0009}_{-0.0021} m_{?}^{-1} and b1 = -0.0885^{+0.0010}_{-0.0021} m_{?} ^{-1}, respectively. Using the GMO sum rule, we obtain from b_1 a new value of the ? N coupling constant (g_{? N} = 13.21_{-0.05}^{+0.11}) from which follows the Goldberger Treiman discrepancy ?_{{GT}} =0.027_{-0.008}^{+0.012}. The new values of b_0 and g_{? N} imply an increase of the nucleon sigma term by at least 9 MeV.

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

14

Equations of state for hydrogen and deuterium.  

SciTech Connect

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.

Kerley, Gerald Irwin (Kerley Technical Services, Appomattox, VA)

2003-12-01

15

HYDROGEN AND DEUTERIUM NMR OF SOLIDS BY MAGIC ANGLE SPINNING  

SciTech Connect

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.

Eckman, R.R.

1982-10-01

16

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

SciTech Connect

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.

Kwak, Jong-Gu; Wang, Son Jong; Kim, Sun Ho [Korea Atomic Energy Research Institute, 1045 Daedeok-daero, Yuseong, Daejeon, South Korea, 305-353 (Korea, Republic of); Park, Jae Min; Na, Hoon Kyun [National Fusion Research Institute, Yuseong, Daejeon, South Korea, 305-333 (Korea, Republic of)

2010-10-15

17

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

PubMed

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(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. PMID:21034038

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

2010-10-01

18

Measurement of the ratio of hydrogen to deuterium at the KSTAR 2009 experimental campaigna)  

NASA Astrophysics Data System (ADS)

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 m2. 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.

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

2010-10-01

19

Simulation of the CLAS12 dual hydrogen-deuterium target  

NASA Astrophysics Data System (ADS)

The primary mission of Jefferson Lab (Jlab) is to reveal the quark and gluon structure of nucleons and nuclei and to deepen our understanding of matter and quark confinement. This mission will be done using a 12-GeV electron beam incident on nuclear targets. One approved experiment E12-07-104 will measure the elastic scattering of electrons from deuterium to extract the neutron magnetic form factor (GM^n) using the CLAS12 detector. Calibrations will be done with a dual, co-linear target consisting of liquid hydrogen(LH2) and liquid deuterium (LD2) cells. The hydrogen target is used for calibration, and the deuterium one provides the data for the physics analysis. A CLAS12 simulation has been developed called gemc, where Geant4 is used to simulate the components of CLAS12. We have added the dual LH2-LD2 target to the gemc simulation. The targets parameters are stored in a mysql database and then read into the simulation at run time. Simulated particles start at a random point in the target volume and are propagated through the CLAS12 detector. We will present initial results showing the effect of target size and position on the distribution of hits in CLAS12.

Musalo, Christopher; Gilfoyle, Gerard

2011-10-01

20

Hydrogen/deuterium fractionation factors of the aqueous ligand of cobalt in Co(H sub 2 O) sub 6 sup 2+ and Co(II)-substituted carbonic anhydrase  

SciTech Connect

The authors have measured the hydrogen/deuterium fractionation factor for the rapidly exchanging, water ligands of cobalt in Co(H{sub 2}O){sub 6}{sup 2+} and in two Co(II)-substituted isozymes of carbonic anhydrase. The fractionation factor was determined from NMR relaxation rates at 300 MHz of the protons of water in mixed solutions of H{sub 2}O and D{sub 2}O containing these complexes. In each case, the paramagnetic contribution to 1/T{sub 2} was greater than to 1/T{sub 1}, consistent with a chemical shift mechanism affecting 1/T{sub 2}. The fractionation factors obtained from T{sub 1} for Co(H{sub 2}O){sub 6}{sup 2+} and for the isozymes of Co(II)-substituted carbonic anhydrase were close to the fractionation factor for bulk water which is unity. The fractionation factors obtained from T{sub 2} were 0.73 {plus minus}0.02 for Co(H{sub 2}O){sub 6}{sup 2+} and 0.72 {plus minus} 0./02 for Co(II)-substituted carbonic anhydrase I, with a value of 0.77 {plus minus} 0.01 for isozyme II. They concluded that fractionation factors in these cases determined from T{sub 1} and T{sub 2} measured isotope preferences for different populations of ligand sites. They suggest that since T{sub 2} has a large contribution from a chemical shift mechanism, the fractionation factor determined from T{sub 2} has a large contribution of the fractionation of inner-shell ligands. The fractionation factors determined from T{sub 1} are close to unity, the value of the fractionation factor of bulk water, and contain a large contribution of the fractionation of outer-shell water.

Kassebaum, J.W.; Silverman, D.N. (Univ. of Florida, Gainesville (USA))

1989-03-29

21

Diffusion of hydrogen and deuterium in Zr-Al  

SciTech Connect

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.

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

1982-10-01

22

Theory of the hydrogen-deuterium isotope shift  

SciTech Connect

We present an overview of the contributions to the isotope shift of the 1[ital S]-2[ital S] transition between hydrogen and deuterium. We have calculated an additional contribution to the energy, due to the exchange of a virtual transverse photon between the electron and the deuteron. We also correct the previously evaluated finite-size and recoil contributions [F. Schmidt-Kaler [ital et] [ital al]., Phys. Rev. Lett. 70, 2261 (1993)]. Our result is 670 994 445(33) kHz, which is in disagreement with the experimental value of 670 994 337(22) KHz. This discrepancy is probably caused by an incorrect value for the deuteron radius.

Pachucki, K.; Weitz, M.; Haensch, T.W. (Max-Planck-Institut fuer Quantenoptik, Ludwig-Prandtl-Strasse 10, 85748 Garching (Germany))

1994-04-01

23

Diffusion of hydrogen, deuterium, and tritium in niobium  

SciTech Connect

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.

Matusiewicz, Gerald Robert

1981-01-01

24

Thermodesorption of deuterium from a porous graphitic carbon  

NASA Astrophysics Data System (ADS)

Thermodesorption of hydrogen isotopes from graphite is of interest for current thermonuclear fusion experiments since the plasma properties are strongly affected by the recycling of gases between the plasma and the graphite tiles used to protect the limiters and the wall of the tokamak. Graphitic Matrix A3-3 specimens were exposed at 900° C to deuterium partial pressures of 7.6 or 74 Pa until the adsorption equilibrium was established. Subsequently, the thermodesorption of deuterium was measured at temperatures up to 1700°C. D 2 desorption commenced at - 900°C. The release spectrum consists of a broad peak with a weak shoulder near 1180°C for an initial surface concentration of n1( t=0) = 2.2 × 10 14D/ cm2 and a shoulder near 1120°C for n1( t=0) = 6.6 × 10 14D/ cm2. The maximum of the release rate is observed at Tp = 1500° C. The results are explained by assuming associative desorption of deuterium with an activation energy of desorption Ed = 3.8 eV/ D2 around 1150°C and release of a large fraction of the adsorbed deuterium from pores by a short range diffusion process at higher temperatures.

Hoinkis, E.

1991-07-01

25

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

SciTech Connect

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.

Smith, M.F.

1981-10-01

26

HYDROGEN DISTILLATION AT THE DEUTERIUM REMOVAL UNIT OF MuCap EXPERIMENT  

E-print Network

321 HYDROGEN DISTILLATION AT THE DEUTERIUM REMOVAL UNIT OF MuCap EXPERIMENT I.A. Alekseev, E hydrogen gas (so- called protium) must be used. It is necessary to avoid transfers of - to impurities imposes strict and critical requirements on the hydrogen gas system supporting the detector. Desirable

Titov, Anatoly

27

Deuterium and hydrogen tunneling in the hydrogenation of 4-oxocyclohexa-2,5-dienylidene.  

PubMed

4-Oxocyclohexa-2,5-dienylidene is a highly reactive triplet ground state carbene that is hydrogenated in solid H2, HD, and D2 at temperatures as low as 3?K. The mechanism of the insertion of the carbene into dihydrogen was investigated by IR and EPR spectroscopy and by kinetic studies. H or D atoms were observed as products of the reaction with H2 and D2, respectively, whereas HD produces exclusively D atoms. The hydrogenation shows a very large kinetic isotope effect and remarkable isotope selectivity, as was expected for a tunneling reaction. The experiments, therefore, provide clear evidence for both hydrogen tunneling and the rare deuterium tunneling in an intermolecular reaction. PMID:24796726

Henkel, Stefan; Ertelt, Melanie; Sander, Wolfram

2014-06-16

28

Venus was wet - A measurement of the ratio of deuterium to hydrogen  

NASA Technical Reports Server (NTRS)

The deuterium-hydrogen abundance ratio in the Venus atmosphere was measured while the inlets to the Pioneer Venus large probe mass spectrometer were coated with sulfuric acid from Venus' clouds. The ratio is 0.016 + or - 0.002. The hundredfold enrichment of deuterium means that at least 0.3 percent of a terrestrial ocean was outgassed on Venus, but is consistent with a much greater production.

Donahue, T. M.; Hoffman, J. H.; Hodges, R. R., Jr.; Watson, A. J.

1982-01-01

29

Ab initio molecular dynamics study of the hydrogen-deuterium exchange in bulk lithiumborohydride (LiBH4)  

NASA Astrophysics Data System (ADS)

The hydrogen storage is still a challenge for mobile applications. The diffusion of hydrogen in solids is considered as a general model system but there is limited knowledge available for the dynamics of hydrogen in complex hydrides. In this letter, we present a systematic approach to study the hydrogen-deuterium exchange in bulk LiBH4 based on ab initio molecular dynamics. Our results predict the single hydrogen (deuterium) exchange in LiBH4, which supports the experimental results. The self-diffusion constant ?D? of deuterium in LiBH4 is around 1.42×10-8 m2 s-1.

Ramzan, M.; Ahuja, R.

2009-04-01

30

Calculated fractionation factors for carbon and hydrogen isotope exchange in the system calcite-carbon dioxide-graphite-methane-hydrogen-water vapor  

Microsoft Academic Search

Isotopic fractionation factors have been calculated for deuterium exchange between hydrogen, water vapor and methane, and for carbon-13 exchange between graphite, calcite, carbon dioxide and methane. These fractionation factors have been tabulated at various intervals between 0 and 700°C. Some geochemical applications of the calculated data are discussed

Y. Bottinga

1969-01-01

31

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

SciTech Connect

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.

Engels, Ralf, E-mail: r.w.engels@fz-juelich.de; Gorski, Robert; Grigoryev, Kiril; Mikirtychyants, Maxim; Rathmann, Frank; Seyfarth, Hellmut; Ströher, Hans; Weiss, Philipp [Institut für Kernphysik, Forschungszentrum Jülich, Wilhelm-Johnen-Str. 1, 52428 Jülich (Germany); Kochenda, Leonid; Kravtsov, Peter; Trofimov, Viktor; Tschernov, Nikolay; Vasilyev, Alexander; Vznuzdaev, Marat [Laboratory of Cryogenic and Superconductive Technique, Petersburg Nuclear Physics Institute, Orlova Roscha 1, 188300 Gatchina (Russian Federation); Schieck, Hans Paetz gen. [Institut für Kernphysik, Universität zu Köln, Zülpicher Str. 77, 50937 Köln (Germany)

2014-10-15

32

Longitudinal-Transverse Separations of Structure Functions at Low $Q^2$ for Hydrogen and Deuterium  

SciTech Connect

We report on a study of the longitudinal to transverse cross section ratio, R={sigma}{sub L} {sigma}{sub T}, at low values of x and Q{sup 2}, as determined from inclusive inelastic electron-hydrogen and electron-deuterium scattering data from Jefferson Lab Hall C spanning the four-momentum transfer range 0.06 < Q{sup 2} < 2.8 GeV{sup 2}. Even at the lowest values of Q{sup 2}, R remains nearly constant and does not disappear with decreasing Q{sup 2}, as expected. We find a nearly identical behavior for hydrogen and deuterium.

V. Tvaskis; M. E. Christy; J. Arrington; R. Asaturyan; O. K. Baker; H. P. Blok; P. Bosted; M. Boswell; A. Bruell; A. Cochran; L. Cole; J. Crowder; J. Dunne; R. Ent; H. C. Fenker; B. W. Filippone; K. Garrow; A. Gasparian; J. Gomez; H.E. Jackson; C. E. Keppel; E. Kinney; Y. Liang; W. Lorenzon; A. Lung; D. J. Mack; J. W. Martin; K. McIlhany; D. Meekins; R. G. Milner; J. H. Mitchell; H. Mkrtchyan; B. Moreland; V. Nazaryan; I. Niculescu; A. Opper; R. B. Piercey; D.H. Potterveld; B. Rose; Y. Sato; W. Seo; G. Smith; K. Spurlock; G. van der Steenhoven; S. Stepanyan; V. Tadevosian; A. Uzzle; W. F. Vulcan; S. A. Wood; B. Zihlmann; V. Ziskin

2006-11-20

33

Hydrogen storage in carbon nanostructures  

Microsoft Academic Search

Carbon nanotubes have been known for more than 10 years. It is a challenge to fill their unique tubular structure with metals and gases. Especially, the absorption of hydrogen in single wall nanotubes has attracted many research groups worldwide. The values published for the quantity of hydrogen absorbed in nanostructured carbon materials varies between 0.4 and 67 mass%. With the

A. Züttel; P. Sudan; Ph. Mauron; T. Kiyobayashi; Ch. Emmenegger; L. Schlapbach

2002-01-01

34

Online hydrogen/deuterium exchange performed in the ion mobility cell of a hybrid mass spectrometer.  

PubMed

The present paper describes the performance of online, gas-phase hydrogen/deuterium exchange implemented in the ion mobility cell of a quadrupole time-of-flight mass spectrometer. Deuterium oxide and deuterated methanol were utilized to create deuterated vapor that is introduced into the ion mobility region of the mass spectrometer. Hydrogen/deuterium exchange occurs spontaneously in the milliseconds time frame without the need of switching the instrument into ion mobility mode. The exchange was studied in case of low molecular weight molecules and proteins. The observed number of exchanged hydrogens was equal to the number of theoretically exchangeable hydrogens for all low molecular weight compounds. This method needs only minimal instrumental modifications, is simple, cheap, environment friendly, compatible with ultraperformance liquid chromatography, and can be implemented on commercially available instruments. It does not compromise choice of liquid chromatographic solvents and accurate mass or parallel-fragmentation (MS(E)) methods. The performance of this method was compared to that of conventional alternatives where the deuterated solvent is introduced into the cone gas of the instrument. Although the degree of exchange was similar between the two methods, the "cone gas method" requires 10 times higher deuterated solvent volumes (50 muL/min) and offers reduced sensitivity in the tandem mass spectrometry (MS/MS) mode. The presented method is suggested as a standard future element of mass spectrometers to aid online structural characterization of unknowns and to study conformational changes of proteins with hydrogen/deuterium exchange. PMID:19848411

Nagy, Kornél; Redeuil, Karine; Rezzi, Serge

2009-11-15

35

Functional visualization of viral molecular motor by hydrogen-deuterium exchange reveals transient states.  

PubMed

Molecular motors undergo cyclical conformational changes and convert chemical energy into mechanical work. The conformational dynamics of a viral packaging motor, the hexameric helicase P4 of dsRNA bacteriophage phi8, was visualized by hydrogen-deuterium exchange and high-resolution mass spectrometry. Concerted changes of exchange kinetics revealed a cooperative unit that dynamically links ATP-binding sites and the central RNA-binding channel. The cooperative unit is compatible with a structure-based model in which translocation is mediated by a swiveling helix. Deuterium labeling also revealed the transition state associated with RNA loading, which proceeds via opening of the hexameric ring. The loading mechanism is similar to that of other hexameric helicases. Hydrogen-deuterium exchange provides an important link between time-resolved spectroscopic observations and high-resolution structural snapshots of molecular machines. PMID:15834422

Lísal, Jirí; Lam, Tukiet T; Kainov, Denis E; Emmett, Mark R; Marshall, Alan G; Tuma, Roman

2005-05-01

36

The HERMES polarized hydrogen and deuterium gas target in the HERA electron storage ring  

Microsoft Academic Search

The HERMES hydrogen and deuterium nuclear-polarized gas targets have been in use since 1996 with the polarized electron beam of HERA at DESY to study the spin structure of the nucleon. Polarized atoms from a Stern–Gerlach Atomic Beam Source are injected into a storage cell internal to the HERA electron ring. Atoms diffusing from the center of the storage cell

A. Airapetian; N. Akopov; Z. Akopov; M. Amarian; A. Andrus; E. C. Aschenauer; W. Augustyniak; R. Avakian; A. Avetissian; E. Avetissian; P. Bailey; D. Balin; C. Baumgarten; M. Beckmann; S. Belostotski; N. Bianchi; H. P. Blok; H. Böttcher; A. Borissov; A. Borysenko; M. Bouwhuis; B. Braun; A. Brüll; V. Bryzgalov; G. P. Capitani; M. Capiluppi; T. Chen; G. Ciullo; M. Contalbrigo; G. Court; P. F. Dalpiaz; R. De Leo; M. Demey; L. De Nardo; E. De Sanctis; E. Devitsin; P. Di Nezza; M. Düren; M. Ehrenfried; A. Elalaoui-Moulay; G. Elbakian; F. Ellinghaus; U. Elschenbroich; R. Fabbri; A. Fantoni; A. Fechtchenko; L. Felawka; S. Frullani; G. Gapienko; V. Gapienko; F. Garibaldi; K. Garrow; G. Gavrilov; V. Gharibyan; G. Graw; O. Grebeniouk; I. M. Gregor; C. Hadjidakis; W. Haeberli; K. Hafidi; M. Hartig; D. Hasch; D. Heesbeen; M. Henoch; R. Hertenberger; W. H. A. Hesselink; A. Hillenbrand; M. Hoek; Y. Holler; B. Hommez; I. Hristova; G. Iarygin; A. Ivanilov; A. Izotov; H. E. Jackson; A. Jgoun; R. Kaiser; E. Kinney; A. Kisselev; T. Kobayashi; N. Koch; H. Kolster; M. Kopytin; V. Korotkov; V. Kozlov; B. Krauss; V. G. Krivokhijine; L. Lagamba; L. Lapikás; A. Laziev; P. Lenisa; P. Liebing; L. A. Linden-Levy; W. Lorenzon; H. Lu; J. Lu; S. Lu; B.-Q. Ma; B. Maiheu; N. C. R. Makins; Y. Mao; B. Marianski; H. Marukyan; V. Mexner; N. Meyners; R. Mussa; O. Mikloukho; C. A. Miller; Y. Miyachi; V. Muccifora; A. Nagaitsev; E. Nappi; Y. Naryshkin; A. Nass; M. Negodaev; W.-D. Nowak; K. Oganessyan; H. Ohsuga; A. Osborne; N. Pickert; D. H. Potterveld; M. Raithel; D. Reggiani; P. E. Reimer; A. Reischl; A. R. Reolon; C. Riedl; K. Rith; G. Rosner; A. Rostomyan; L. Rubacek; J. Rubin; D. Ryckbosch; Y. Salomatin; I. Sanjiev; I. Savin; C. Schill; G. Schnell; K. P. Schüler; J. Seele; R. Seidl; B. Seitz; R. Shanidze; C. Shearer; T.-A. Shibata; V. Shutov; K. Sinram; W. Sommer; M. Stancari; M. Statera; E. Steffens; J. J. M. Steijger; H. Stenzel; J. Stewart; F. Stinzing; P. Tait; H. Tanaka; S. Taroian; B. Tchuiko; A. Terkulov; A. Trzcinski; M. Tytgat; A. Vandenbroucke; P. van der Nat; G. van der Steenhoven; Y. van Haarlem; M. C. Vetterli; V. Vikhrov; M. G. Vincter; C. Vogel; J. Volmer; S. Wang; J. Wendland; J. Wilbert; T. Wise; G. Ybeles Smit; Y. Ye; Z. Ye; S. Yen; B. Zihlmann; P. Zupranski

2005-01-01

37

Hydrogen storage in carbon nanostructures  

Microsoft Academic Search

The paper gives a critical review of the literature on hydrogen storage in carbon nanostructures. Furthermore, the hydrogen storage of graphite, graphite nanofibers (GNFs), and single-walled carbon nanotubes (SWNTs) was measured by thermal desorption spectroscopy (TDS). The samples were ball milled under Ar or D2 atmosphere in order to modify the microstructure which was characterized by X-ray diffraction, scanning electron

M Hirscher; M Becher; M Haluska; A Quintel; V Skakalova; Y.-M Choi; U Dettlaff-Weglikowska; S Roth; I Stepanek; P Bernier; A Leonhardt; J Fink

2002-01-01

38

Ultraviolet observations of cool stars. VII - Local interstellar hydrogen and deuterium Lyman-alpha  

NASA Technical Reports Server (NTRS)

High-resolution Copernicus spectra of Epsilon Eri and Epsilon Ind containing interstellar hydrogen and deuterium L-alpha absorption lines are presented, reduced, and analyzed. Parameters of the interstellar hydrogen and deuterium toward these two stars are derived independently, without any assumptions concerning the D/H ratio. Copernicus spectra of Alpha Aur and Alpha Cen A are reanalyzed, and limits on the D/H number-density ratio consistent with the data for all four stars are considered. A comparison of the present estimates for the parameters of the local interstellar medium with those obtained by other techniques shows that there is no compelling evidence for significant variations in the hydrogen density and D/H ratio in the local interstellar medium. On this basis the hypothesis of an approaching local interstellar cloud proposed by Vidal-Madjar et al. (1978) is rejected

Mcclintock, W.; Henry, R. C.; Linsky, J. L.; Moos, H. W.

1978-01-01

39

Carbon and hydrogen isotopic compositions of New Zealand geothermal gases  

NASA Astrophysics Data System (ADS)

Carbon and hydrogen isotopic compositions are reported for methane, hydrogen and carbon dioxide from four New Zealand geothermal areas: Ngawha, Wairakei, Broadlands and Tikitere. Carbon-13 contents are between -24.4 and -29.5%. (PDB) for methane, and between -3.2 and -9.1%. for carbon dioxide. Deuterium contents are between -142 and -197%. (SMOW) for methane and between -310 and -600%. for hydrogen. The different areas have different isotopic compositions with some general relationships to reservoir temperature. The isotopic exchange of hydrogen with water indicates acceptable reservoir temperatures of 180-260°C from most spring samples but often higher than measured temperatures in well samples. Indicated temperatures assuming 13C equilibria between CH 4 and CO 2 are 100-200°C higher than measured maxima. This difference may be due to partial isotopic equilibration or may reflect the origin of the methane. Present evidence cannot identify whether the methane is primordial, or from decomposing sediments or from reduction of magmatic CO 2. The isotopic equilibria between CH 4, CO 2, H 2 and H 2O are reviewed and a new semi-empirical temperature scale proposed for deuterium exchange between methane and water.

Lyon, G. L.; Hulston, J. R.

1984-06-01

40

Hydrogen and deuterium NMR of solids by magic-angle spinning  

SciTech Connect

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.

Eckman, R.R.

1982-10-01

41

Lifetime and population of the 2S state in muonic hydrogen and deuterium  

NASA Astrophysics Data System (ADS)

Radiative deexcitation (RD) of the metastable 2S state of muonic hydrogen and deuterium atoms has been observed. In muonic hydrogen, we improve the precision on lifetime and population (formation probability) values for the short-lived ?p(2S) component, and give an upper limit for RD of long-lived ?p(2S) atoms. In muonic deuterium at 1 hPa, 3.1±0.3% of all stopped muons form ?d(2S) atoms. The short-lived 2S component has a population of 1.35-0.33+0.57% and a lifetime of ?2Sshort(?d)=138-34+32 ns. We see evidence for RD of long-lived ?d(2S) with a lifetime of ?2Slong(?d)=1.15-0.53+0.75?s. This is interpreted as formation and decay of excited muonic molecules.

Diepold, Marc; Amaro, Fernando D.; Antognini, Aldo; Biraben, François; Cardoso, João M. R.; Covita, Daniel S.; Dax, Andreas; Dhawan, Satish; Fernandes, Luis M. P.; Giesen, Adolf; Gouvea, Andrea L.; Graf, Thomas; Hänsch, Theodor W.; Indelicato, Paul; Julien, Lucile; Kao, Cheng-Yang; Knowles, Paul; Kottmann, Franz; Le Bigot, Eric-Olivier; Liu, Yi-Wei; Lopes, José A. M.; Ludhova, Livia; Monteiro, Cristina M. B.; Mulhauser, Françoise; Nebel, Tobias; Nez, François; Rabinowitz, Paul; dos Santos, Joaquim M. F.; Schaller, Lukas A.; Schuhmann, Karsten; Schwob, Catherine; Taqqu, David; Veloso, João F. C. A.; Vogelsang, Jan; Pohl, Randolf

2013-10-01

42

Ionization of molecular hydrogen and deuterium by a frequency-doubled Ti:sapphire laser pulses  

E-print Network

A theoretical study of the intense-field single ionization of molecular hydrogen or deuterium oriented either parallel or perpendicular to a linear polarized laser pulse (400 nm) is performed for different internuclear separations and pulse lengths in an intensity range of $(2-13)\\times10^{13} $W cm$^{-2}$. The investigation is based on a non-perturbative treatment that solves the full time-dependent Schr\\"odinger equation of both correlated electrons within the fixed-nuclei and the dipole approximation. The results for various internuclear separations are used to obtain the ionization yields of molecular hydrogen and deuterium in their ground vibrational states. An atomic model is used to identify the influence of the intrinsic diatomic two-center character of the problem.

Vanne, Yulian V

2009-01-01

43

Precision measurement of the hydrogen and deuterium 1 S ground state Lamb shift  

SciTech Connect

We report on new precision measurements of the 1[ital S] ground state Lamb shift in hydrogen and deuterium, based on a direct frequency comparison of the 1[ital S]-2[ital S] and 2[ital S]-4[ital S] two-photon resonances. By observing the 2[ital S]-4[ital S] transition via blue Balmer-[beta] fluorescence we are now surpassing the accuracy of the 2[ital S] Lamb shift. Our results of 8172.86(6) MHz for hydrogen and 8184.00(8) MHz for deuterium are not in perfect agreement with the theoretical predictions of 8173.12(6) and 8184.13(6) MHz, respectively. We also derive values for the Rydberg constant and the electron-proton mass ratio.

Weitz, M.; Huber, A.; Schmidt-Kaler, F.; Leibfried, D.; Haensch, T.W. (Max-Planck-Institut fuer Quantenoptik, 85748 Garching (Germany))

1994-01-17

44

Ionization of molecular hydrogen and deuterium by a frequency-doubled Ti:sapphire laser pulses  

E-print Network

A theoretical study of the intense-field single ionization of molecular hydrogen or deuterium oriented either parallel or perpendicular to a linear polarized laser pulse (400 nm) is performed for different internuclear separations and pulse lengths in an intensity range of $(2-13)\\times10^{13} $W cm$^{-2}$. The investigation is based on a non-perturbative treatment that solves the full time-dependent Schr\\"odinger equation of both correlated electrons within the fixed-nuclei and the dipole approximation. The results for various internuclear separations are used to obtain the ionization yields of molecular hydrogen and deuterium in their ground vibrational states. An atomic model is used to identify the influence of the intrinsic diatomic two-center character of the problem.

Yulian V. Vanne; Alejandro Saenz

2009-09-18

45

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

SciTech Connect

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.

Richmond, Scott [Los Alamos National Laboratory; Bridgewater, Jon S [Los Alamos National Laboratory; Ward, John W [Los Alamos National Laboratory; Allen, Thomas A [Los Alamos National Laboratory

2009-01-01

46

Hydrogenation of single-walled carbon nanotubes  

E-print Network

Towards the development of a useful mechanism for hydrogen storage, we have studied the hydrogenation of single-walled carbon nanotubes with atomic hydrogen using core-level photoelectron spectroscopy and x-ray absorption spectroscopy. We find that atomic hydrogen creates C-H bonds with the carbon atoms in the nanotube walls and such C-H bonds can be com-pletely broken by heating to 600 oC. We demonstrate approximately 65+/-15 at % hydrogenation of carbon atoms in the single-walled carbon nanotubes which is equivalent to 5.1+/-1.2 weight % hydrogen capacity. We also show that the hydrogenation is a reversible process.

Anton Nikitin; Hirohito Ogasawara; David Mann; Reinhard Denecke; Zhiyong Zhang; Hongjie Dai; KJ Cho; Anders Nilsson

2005-10-14

47

Deuterium diffusion and retention in a tungsten-carbon multilayer system  

NASA Astrophysics Data System (ADS)

A tungsten-carbon multilayer system deposited by magnetron sputtering was used as a model system to study deuterium diffusion in tungsten, carbon and related carbides. After deposition the as-deposited multilayer films were annealed at different temperatures to achieve different structures. The structural changes due to annealing were investigated by Rutherford backscattering spectrometry and X-ray diffraction. The results show that diffusion and interaction between tungsten and carbon sets in at 1150 K. Different types of tungsten carbides including WC and W2C were formed during different heat treatments. Deuterium implantation experiments proved that deuterium diffusion in this multilayer system can be reduced substantially by formation of the tungsten carbide WC and can be almost completely suppressed by formation of the tungsten subcarbide W2C.

Wang, P.; Jacob, W.

2014-06-01

48

Nuclear micro-beam analysis of deuterium distribution in carbon fibre composites for controlled fusion devices  

NASA Astrophysics Data System (ADS)

Probes made of carbon fibre composite NB41 were exposed to deuterium plasmas in the TEXTOR tokamak and in a simulator of plasma-wall interactions, PISCES. The aim was to assess the deuterium retention and its lateral and depth distribution. The analysis was performed by means of D( 3He, p) 4He and 12C( 3He, p) 14N nuclear reactions analysis using a standard (1 mm spot) and micro-beam (20 ?m resolution). The measurements have revealed non uniform distribution of deuterium atoms in micro-regions: differences by a factor of 3 between the maximum and minimum deuterium concentrations. The differences were associated with the orientation and type of fibres for samples exposed in PICSES. For surface structure in the erosion zone of samples exposed to a tokamak plasma the micro-regions were more complex. Depth profiling has indicated migration of fuel into the bulk of materials.

Petersson, P.; Kreter, A.; Possnert, G.; Rubel, M.

2010-06-01

49

state. However, the rates of hydrogen/deuterium exchange demonstrate that the conformation of human PrPC is not  

E-print Network

state. However, the rates of hydrogen/deuterium exchange demonstrate that the conformation of human, and can be Structural mobility of the human prion protein probed by backbone hydrogen exchange Laszlo L. P8 1TD, UK.4Krebs Institute for Biomolecular Research, Dept. of Molecular Biology and Biotechnology

Hosszu, Laszlo

50

Difference in Fibril Core Stability between Two Tau Four-Repeat Domain Proteins: A Hydrogen-Deuterium Exchange Coupled to  

E-print Network

Difference in Fibril Core Stability between Two Tau Four-Repeat Domain Proteins: A Hydrogen for Biological Sciences, Tata Institute of Fundamental Research, Bangalore 560 065, India *S Supporting hydrogen-deuterium exchange coupled to mass spectrometry as a tool. While the two fibrils are found

51

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

PubMed Central

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

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

2014-01-01

52

Hydrogen adsorption in different carbon nanostructures  

Microsoft Academic Search

Hydrogen adsorption in different carbonaceous materials with optimized structure was investigated at room temperature and 77K. Activated carbon, amorphous carbon nanotubes, SWCNTs and porous carbon samples all show the same adsorption properties. The fast kinetics and complete reversibility of the process indicate that the interaction between hydrogen molecules and the carbon nanostructure is due to physisorption. At 77K the adsorption

Barbara Panella; Michael Hirscher; Siegmar Roth

2005-01-01

53

NMR-Based Detection of Hydrogen/Deuterium Exchange in Liposome-Embedded Membrane Proteins  

PubMed Central

Membrane proteins play key roles in biology. Determination of their structure in a membrane environment, however, is highly challenging. To address this challenge, we developed an approach that couples hydrogen/deuterium exchange of membrane proteins to rapid unfolding and detection by solution-state NMR spectroscopy. We show that the method allows analysis of the solvent protection of single residues in liposome-embedded proteins such as the 349-residue Tom40, the major protein translocation pore in the outer mitochondrial membrane, which has resisted structural analysis for many years. PMID:25375235

Yao, Xuejun; Dürr, Ulrich H. N.; Gattin, Zrinka; Laukat, Yvonne; Narayanan, Rhagavendran L.; Brückner, Ann-Kathrin; Meisinger, Chris; Lange, Adam; Becker, Stefan; Zweckstetter, Markus

2014-01-01

54

Analysis of Overlapped and Noisy Hydrogen/Deuterium Exchange Mass Spectra  

NASA Astrophysics Data System (ADS)

Noisy and overlapped mass spectrometry data hinder the sequence coverage that can be obtained from hydrogen deuterium exchange analysis, and places a limit on the complexity of the samples that can be studied by this technique. Advances in instrumentation have addressed these limits, but as the complexity of the biological samples under investigation increases, these problems are re-encountered. Here we describe the use of binomial distribution fitting with asymmetric linear squares regression for calculating the accurate deuterium content for mass envelopes of low signal or that contain significant overlap. The approach is demonstrated with a test data set of HIV Env gp140 wherein inclusion of the new analysis regime resulted in obtaining exchange data for 42 additional peptides, improving the sequence coverage by 11 %. At the same time, the precision of deuterium uptake measurements was improved for nearly every peptide examined. The improved processing algorithms also provide an efficient method for deconvolution of bimodal mass envelopes and EX1 kinetic signatures. All these functions and visualization tools have been implemented in the new version of the freely available software, HX-Express v2.

Guttman, Miklos; Weis, David D.; Engen, John R.; Lee, Kelly K.

2013-12-01

55

The torque dependence of the H-mode power threshold in hydrogen, deuterium and helium plasmas in DIII-D  

SciTech Connect

On DIII-D, the H-mode power threshold has been determined for hydrogen, deuterium and helium plasmas heated by neutral beam injection and/or by electron cyclotron heating and as a function of the applied torque plasmas for plasma configurations in the favourable ion grad-B drift direction. The H-mode threshold power has been determined to increase with input torque for all the main ion species (hydrogen, deuterium and helium). The H-mode threshold power for similar plasma parameters and configurations is the least for deuterium, followed by helium and hydrogen in that order. The plasma geometry also affects the power threshold, which is dependent on the X-point height.

Gohil, P. [General Atomics; Jernigan, T. C. [Oak Ridge National Laboratory (ORNL); Osborne, T.H. [General Atomics, San Diego; Scoville, J. T. [General Atomics, San Diego; Strait, E. J. [General Atomics

2010-01-01

56

Hydrogen and deuterium incorporation and transport in hafnium-based dielectric films on silicon  

SciTech Connect

Hydrogen and deuterium incorporation into nitrided and non-nitrided hafnium silicate films on Si during thermal annealing in {sup 1}H- and {sup 2}H-containing atmospheres was investigated. {sup 1}H profiling was accessed by means of nuclear resonant reaction profiling, whereas {sup 2}H incorporation was quantified by nuclear reaction analysis. The effects of preannealing in different atmospheres and temperatures were determined, as well as the losses of {sup 1}H and {sup 2}H from these structures during postannealing in vacuum. The results reveal a rather uniform depth distribution of incorporated {sup 1}H, in striking contrast with previous studies on hydrogen in silicon oxide and oxynitrides and hafnium oxide films on Si. These results are discussed in terms of the defects present in each one of the structures studied here.

Pezzi, R.P.; Miotti, L.; Bastos, K.P.; Soares, G.V.; Driemeier, C.; Baumvol, I.J.R.; Punchaipetch, P.; Pant, G.; Gnade, B.E.; Wallace, R.M.; Rotondaro, A.; Visokay, J.M.; Chambers, J.J.; Colombo, L. [Instituto de Fisica, UFRGS, Av. Bento Goncalves, 9500, Porto Alegre, RS, Brazil 91509-900 (Brazil); Centro de Ciencias Exatas e Tecnologicas, UCS, Caxias do Sul, RS, Brazil 95070-560 (Brazil); Department of Electrical Engineering, University of Texas at Dallas, Richardson, Texas 75083 (United States); Silicon Technology Development, Texas Instruments Incorporated, Dallas, Texas (United States)

2004-10-18

57

Pulsed hydrogen–deuterium exchange mass spectrometry probes conformational changes in amyloid beta (A?) peptide aggregation  

PubMed Central

Probing the conformational changes of amyloid beta (A?) peptide aggregation is challenging owing to the vast heterogeneity of the resulting soluble aggregates. To investigate the formation of these aggregates in solution, we designed an MS-based biophysical approach and applied it to the formation of soluble aggregates of the A?42 peptide, the proposed causative agent in Alzheimer’s disease. The approach incorporates pulsed hydrogen–deuterium exchange coupled with MS analysis. The combined approach provides evidence for a self-catalyzed aggregation with a lag phase, as observed previously by fluorescence methods. Unlike those approaches, pulsed hydrogen–deuterium exchange does not require modified A?42 (e.g., labeling with a fluorophore). Furthermore, the approach reveals that the center region of A?42 is first to aggregate, followed by the C and N termini. We also found that the lag phase in the aggregation of soluble species is affected by temperature and Cu2+ ions. This MS approach has sufficient structural resolution to allow interrogation of A? aggregation in physiologically relevant environments. This platform should be generally useful for investigating the aggregation of other amyloid-forming proteins and neurotoxic soluble peptide aggregates. PMID:23959898

Zhang, Ying; Rempel, Don L.; Zhang, Jun; Sharma, Anuj K.; Mirica, Liviu M.; Gross, Michael L.

2013-01-01

58

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

SciTech Connect

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.

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. [A. F. Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021, St. Petersburg (Russian Federation); Shatalin, S. V. [St. Petersburg State Polytekhnical University, St. Petersburg (Russian Federation); Stepanov, A. Yu. [A.F. Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021, St. Petersburg (Russian Federation)

2014-02-12

59

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

SciTech Connect

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.

Markelj, Sabina; Pelicon, Primoz; Cadez, Iztok; Schwarz-Selinger, Thomas; Jacob, Wolfgang [Jozef Stefan Institute and Association EURATOM-MHEST, Jamova cesta 39, SI-1000 Ljubljana (Slovenia); Max-Planck-Institut fuer Plasmaphysik (IPP), EURATOM Association, Boltzmannstr. 2, D-85748 Garching (Germany)

2012-07-15

60

Catalytic hydrogenation of carbon monoxide  

SciTech Connect

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.

Wayland, B.B.

1992-12-01

61

The hydrogen/deuterium isotope effect of the host material on the lifetime of organic light-emitting diodes.  

PubMed

The hydrogen/deuterium primary kinetic isotope effect provides useful information about the degradation mechanism of OLED host materials. Thus, replacement of labile C-H bonds in the host with C-D bonds increases the device lifetime by a factor of five without loss of efficiency, and replacement with C-C bonds by a factor of 22.5. PMID:25325237

Tsuji, Hayato; Mitsui, Chikahiko; Nakamura, Eiichi

2014-12-01

62

Hydrogen on Cobalt: The Effects of Carbon Monoxide and Sulphur Additives on the D2/Co(0001) System  

NASA Astrophysics Data System (ADS)

Hydrogen reaction on catalytic surfaces is an important field of research in fuel cell science. The adsorption of hydrogen (deuterium) on Co(0001) and the influence of carbon monoxide and sulphur on the adsorption were studied by XPS, TDS, WF measurements and LEED. The WF increased due to D2 adsorption, revealing the electronegative character of deuterium. It was found that the deuterium saturation coverage is âe 1/4 0.17 ML at 320 K and âe 1/4 0.27 ML at 180 K. The activation energy for desorption was estimated to be 33 kJ/mol. The coadsorption measurements with CO indicated a decrease in the deuterium yield by 50%. A downward shift of 50 K in the deuterium desorption temperature was observed as a consequence of coadsorbed CO, but changes in the CO desorption were minimal. At small CO exposures the (2 A~— 2) LEED structure of deuterium was seen, while at exposures of above 5 L the (2 âeš 3 A~— 2 âeš 3)R30… structure was detected by LEED as with pure CO adsorption. Coadsorption with sulphur led also to a decrease in the D2 yield leading to a complete inhibition of hydrogen adsorption at sulphur saturation. The sulphur (2 A~— 2) LEED structure did not underwent changes due to deuterium adsorption. As assumed, sulphur worked as a strong poison to the adsorption on Co(0001).

Habermehl-Cwirzen, K. M. E.; Kauraala, K.; Lahtinen, J.

63

Observation of crystallization slowdown in supercooled para-hydrogen and ortho-deuterium quantum liquid mixtures  

E-print Network

We report a quantitative experimental study of the crystallization kinetics of supercooled quantum liquid mixtures of para-hydrogen (pH$_2$) and ortho-deuterium (oD$_2$) by high spatial resolution Raman spectroscopy of liquid microjets. We show that in a wide range of compositions the crystallization rate of the isotopic mixtures is significantly reduced with respect to that of the pure substances. To clarify this behavior we have performed path-integral simulations of the non-equilibrium pH$_2$-oD$_2$ liquid mixtures, revealing that differences in quantum delocalization between the two isotopic species translate into different effective particle sizes. Our results provide first experimental evidence for crystallization slowdown of quantum origin, offering a benchmark for theoretical studies of quantum behavior in supercooled liquids.

Matthias Kühnel; José M. Fernández; Filippo Tramonto; Guzmán Tejeda; Elena Moreno; Anton Kalinin; Marco Nava; Davide E. Galli; Salvador Montero; Robert E. Grisenti

2014-10-10

64

Activation of AMP-activated protein kinase revealed by hydrogen/deuterium exchange Mass Spectrometry  

PubMed Central

Summary AMP-Activated protein kinase (AMPK) monitors cellular energy, regulates genes involved in ATP synthesis and consumption, and is allosterically activated by nucleotides and synthetic ligands. Analysis of the intact enzyme by hydrogen/deuterium exchange mass spectrometry reveals conformational perturbations of AMPK in response to binding of nucleotides, cyclodextrin and a synthetic small molecule activator, A769662. Results from this analysis clearly show that binding of AMP leads to conformational changes primarily in the ? subunit of AMPK and subtle changes in the ? and ? subunits. In contrast, A769662 causes profound conformational changes in the glycogen binding module of the ? subunit and in the kinase domain of the ? subunit suggesting that the molecular binding site of latter resides between the ? and ? subunits. The distinct short and long-range perturbations induced upon binding of AMP and A769662 suggest fundamentally different molecular mechanisms for activation of AMPK by these two ligands. PMID:24076403

Landgraf, Rachelle R.; Goswami, Devrishi; Rajamohan, Francis; Harris, Melissa S.; Calabrese, Matthew; Hoth, Lise R.; Magyar, Rachelle; Pascal, Bruce D.; Chalmers, Michael J.; Busby, Scott A.; Kurumbail, Ravi; Griffin, Patrick R.

2013-01-01

65

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

DOEpatents

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.

Ehlers, Kenneth W. (Alamo, CA); Leung, Ka-Ngo (Hercules, CA)

1988-01-01

66

Cross section models for cold neutron scattering from liquid hydrogen and liquid deuterium  

NASA Astrophysics Data System (ADS)

For the evaluation of cold and ultracold neutron production, cross section models for neutron scattering from liquid hydrogen and liquid deuterium are developed. They are based on the proper treatment of molecular motions in the liquids in terms of individual translations and intermolecular correlations. Intramolecular motions such as nuclear spin correlations, free rotations and harmonic vibrations are also included. The calculated results agree very well with the experimental results, both double-differential and total, at different temperatures between the melting and boiling points in different ortho-para contents for a wide range of incident neutron energies. It is expected that the present models serve as cross-section data for the optimum design of advanced neutron sources.

Morishima, N.; Mizobuchi, D.

1994-10-01

67

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

NASA Astrophysics Data System (ADS)

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 ?s 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.

Rajabi, Khadijeh

2015-01-01

68

Dynamics of the ?2-adrenergic G-protein coupled receptor revealed by hydrogen-deuterium exchange  

PubMed Central

To examine the molecular details of ligand activation of G-protein coupled receptor (GPCRs), emphasis has been placed on structure determination of these receptors with stabilizing ligands. Here we present the methodology for receptor dynamics characterization of the GPCR human ?2 adrenergic receptor bound to the inverse agonist carazolol using the technique of amide hydrogen/deuterium exchange coupled with mass spectrometry (HDX MS). The HDX MS profile of receptor bound to carazolol is consistent with thermal parameter observations in the crystal structure and provides additional information in highly dynamic regions of the receptor and chemical modifications demonstrating the highly complementary nature of the techniques. Following optimization of HDX experimental conditions for this membrane protein, better than 89% sequence coverage was obtained for the receptor. The methodology presented paves the way for future analysis of ?2AR bound to pharmacologically distinct ligands as well as analysis of other GPCR family members. PMID:20058880

Zhang, Xi; Chien, Ellen Y.T.; Chalmers, Michael J.; Pascal, Bruce D.; Gatchalian, Jovylyn; Stevens, Raymond C.; Griffin, Patrick R.

2010-01-01

69

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

NASA Astrophysics Data System (ADS)

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.

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

2012-02-01

70

Decreases in deuterium pumping by St707 getter alloy caused by carbon dioxide preexposure  

SciTech Connect

Intentional passivation of the deuterium pumping of the solid getter alloy St707 has been attempted by exposing samples of St707 to carbon dioxide at different pressures, temperatures and exposure times relevant for application to the getter modules in the ALT-I pump limiter. It was found that one of the most effective treatments examined was a 30 min, 1 Torr exposure at approximately 100 /sup 0/C. This preexposure kept the getter pumping speed less than 0.001 of its rated value for about 3 min when exposed to deuterium at 1 Torr and 30 /sup 0/C. After this ''incubation'' period, the getter speed increases to values greater than approx.1% of fully activated values. If left under high deuterium pressure, the getter eventually flakes off the substrate. Video observations of the flaking process indicate that individual particles leave the constantan getter substrate at velocities of 1 m/s. Attempts at passivating the getter using oxygen and carbon monoxide were found to be no more effective than using carbon dioxide, suggesting that there is no way to completely passivate the getter with these gases at pressures low enough for application to in situ getter arrays used in tokamaks.

Malinowski, M.E.

1985-05-01

71

High-resolution spectroscopy of the 1[ital S]-2[ital S] transition of atomic hydrogen and deuterium  

SciTech Connect

Two-photon spectroscopy of the hydrogen 1[ital S]-2[ital S] transition in a cold atomic beam has reached a resolution [Delta][nu]/[nu] of 1 part in 10[sup 11] in hydrogen and 7 parts in 10[sup 12] in deuterium. The hydrogen and deuterium 1[ital S]-2[ital S] transition frequencies have been determined with a precision of 1 part in 10[sup 11]. This leads to an accurate value for the Rydberg constant, while the 1[ital S] Lamb shift and the isotope shift are determined with order of magnitude improvements over previous measurements. We describe in detail the 1[ital S]-2[ital S] spectrometer, calculate the line shape of the resonance, and compare it to the experimental data.

Schmidt-Kaler, F.; Leibfried, D.; Seel, S.; Zimmermann, C.; Koenig, W.; Weitz, M.; Haensch, T.W. (Max-Planck-Institut fuer Quantenoptik, D-85748 Garching (Germany))

1995-04-01

72

Microsecond pulsed hydrogen/deuterium exchange of electrosprayed ubiquitin ions stored in a linear ion trap.  

PubMed

A pulse of D2O vapour on the order of microseconds is allowed to react with the +6 to +9 charge states of ubiquitin confined in a linear ion trap (LIT). Two envelopes of peaks are detected for the ions of ubiquitin, corresponding to the ions that exchange more quickly and more slowly. The deuterium uptake of the protonated sites on ubiquitin ions accounts for the ion population with the fast exchange. The hydrogen/deuterium exchange (HDX) kinetics of ubiquitin ions trapped in the LIT for 200 ms showed comparable structural transitions to those trapped for 300 ms. When ions are trapped for longer, i.e. up to 2000 ms, mainly the slow exchanging ion population is detected. In all experiments the +7 ions exchange the most, suggesting a short distance between the surface protonated sites and nearby charged sites, and concomitantly high accessibility of surface protonated sites towards D2O. The +6 ions are more compact than the +7 ions but have one fewer protonated site, therefore fewer surface availabilities for D2O attack. The data suggest that the +6 ions keep most of their solution-phase contacts intact while the hydrophobic core is slightly interrupted in the +7 ions, possibly due to the exposure of charged His68 that is normally buried in the hydrophobic pocket. The +8 and +9 ions have more protonated sites but are less compact than the +7 ions because of Coulombic repulsion, resulting in a larger distance between the protonated sites and the basic sites. The data indicate that the HDX mechanism of ions with the slower exchange corresponding to the second envelope of peaks is primarily governed via a relay mechanism. The results suggest that the pulsed HDX MS method is sampling a population of ubiquitin ions with a similar backbone fold to the solution. PMID:25553956

Rajabi, Khadijeh

2015-02-01

73

Nepenthesin from Monkey Cups for Hydrogen/Deuterium Exchange Mass Spectrometry*  

PubMed Central

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

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

2013-01-01

74

Principal processes occurring at simultaneous bombardment of tungsten by carbon and deuterium ions  

SciTech Connect

Simultaneous bombardment of tungsten with deuterium and carbon leads to both tungsten erosion and implantation of carbon and deuterium in the W surface. These processes have been studied experimentally by simultaneous bombardment of magnetron deposited W layers with D and C ions at energies in the keV range. The experimental results were compared to numerical simulations using the TRIDYN code. The key parameter separating steady-state W erosion from continuous growth of a C layer on the surface is the C fraction in the incident flux. The dynamical change of the surface composition with increasing fluence was monitored in situ by ion beam analysis. The experimental results are well reproduced by the TRIDYN simulations, which are based on a kinematic model of ion scattering in the target. Significant contributions by chemical effects outside the scope of the TRIDYN model can therefore be excluded. A negligible contribution of chemical effects is also supported by the measured concentrations of retained D, which are not sufficient to create a significant contribution of chemical reactions with carbon to implantation and sputtering. Surface roughness of the specimens was found to be the key parameter for the observed shift of the transition point from continuous C layer growth to steady-state tungsten erosion with increasing D fraction in the incident ions.

Bizyukov, Ivan; Krieger, Karl [Kharkiv National University, Faculty of Physics and Technologies, 31 Kurchatov Ave., Kharkiv 61108 (Ukraine); Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstr. 2, 85748 Garching (Germany)

2007-10-01

75

VIBRIO CHOLERAE TOXIN-COREGULATED PILUS STRUCTURE ANALYZED BY HYDROGEN/DEUTERIUM EXCHANGE MASS SPECTROMETRY  

PubMed Central

SUMMARY The bacterial pathogen Vibrio cholerae uses toxin-coregulated pili (TCP) to colonize the human intestine, causing the severe diarrheal disease cholera. TCP are long, thin, flexible homopolymers of the TcpA subunit that self-associate to hold cells together in microcolonies and serve as the receptor for the cholera toxin phage. To better understand TCP’s roles in pathogenesis, we characterized its structure using hydrogen/deuterium exchange mass spectrometry and computational modeling. We show that the pilin subunits are held together by tight-packing of the N-terminal ?-helices, but loose packing of the C-terminal globular domains leaves substantial gaps on the filament surface. These gaps expose a glycine-rich, amphipathic segment of the N-terminal ?-helix, contradicting the consensus view that this region is buried in the filament core. Our results explain extreme filament flexibility, suggest a molecular basis for pilus:pilus interactions, and reveal a previously unrecognized therapeutic target for V. cholerae and other enteric pathogens. PMID:18184591

Li, Juliana; Lim, Mindy S.; Li, Sheng; Brock, Melissa; Pique, Michael E.; Woods, Virgil L.; Craig, Lisa

2008-01-01

76

A new method to produce cold atomic hydrogen and deuterium beams  

SciTech Connect

A new method to produce cold atomic hydrogen and deuterium beams is described. This technique can be applied to development of internal polarized targets. The proposed scheme is to combine the low density beam of atoms from a dissociator of a conventional atomic-beam source with a supersonic carrier gas jet formed by a circular converging-diverging Laval nozzle surrounding the central one. A computer code for a realistic description of the formation of the atomic beam inside the supersonic carrier gas jet has been developed and applied for computer simulations of different nozzle geometries, various combinations of gas and carrier gas, and different mixtures of partly dissociated gas, like H-H{sub 2} and D-D{sub 2}. The calculations indicate that with a carrier gas flow of about six times higher than the inner atomic beam, the central beam is confined, which should result in a better forward intensity and much lower beam temperature. An experimental study of this new method is in progress.

Varentsov, Victor L.; Ignatiev, Alexei A. [St. Petersburg Institute for Informatics and Automation, 39, 14th Line, St. Petersburg, 199178 (Russian Federation); Steffens, Erhard; Koch, Norbert [Physikalisches Institut, Universitaet Erlangen-Nuernberg, Erwin-Rommel Str. 1, D-91058 Erlangen (Germany)

1998-01-20

77

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

PubMed Central

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-?, 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-? 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

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

2011-01-01

78

Using hydrogen-deuterium exchange to monitor protein structure in the presence of gold nanoparticles.  

PubMed

The potential applications of protein-functionalized gold nanoparticles (AuNPs) have motivated many studies characterizing protein-AuNP interactions. However, the lack of detailed structural information has hindered our ability to understand the mechanism of protein adsorption on AuNPs. In order to determine the structural perturbations that occur during adsorption, hydrogen/deuterium exchange (HDX) of amide protons was measured for two proteins by NMR. Specifically, we measured both slow (5-300 min) and fast (10-500 ms) H/D exchange rates for GB3 and ubiquitin, two well-characterized proteins. Overall, amide exchange rates are very similar in the presence and absence of AuNPs, supporting a model where the adsorbed protein remains largely folded on the AuNP surface. Small differences in exchange rates are observed for several loop residues, suggesting that the secondary structure remains relatively rigid while loops and surface residues can experience perturbations upon binding. Strikingly, several of these residues are close to lysines, which supports a model where positive surface residues may interact favorably with AuNP-bound citrate. Because these proteins appear to remain folded on AuNP surfaces, these studies suggest that it may be possible to engineer functional AuNP-based nanoconjugates without the use of chemical linkers. PMID:25265213

Wang, Ailin; Vo, Tam; Le, Vu; Fitzkee, Nicholas C

2014-12-11

79

Desorption of hydrogen trapped in carbon and graphite  

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

80

Hydrogen storage on activated carbon. Final report  

SciTech Connect

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.

Schwarz, J.A. [Syracuse Univ., NY (United States). Dept. of Chemical Engineering and Materials Science

1994-11-01

81

Enumeration of labile hydrogens in natural organic matter by use of hydrogen/deuterium exchange Fourier transform ion cyclotron resonance mass spectrometry.  

PubMed

A method to enumerate labile hydrogens in all constituents of molecular ensemble of natural organic matter (NOM) based on our previously developed simple hydrogen/deuterium (H/D) exchange (electrospray ionization (ESI) ion source (Kostyukevich et al. Anal. Chem. 2013, 85, 5330) and ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry is presented. The method was applied for analysis of Suwannee River fulvic acid (SRFA), which is an International Humic Substances Society standard, as well as Siberian crude oil; and lignosulfonate. We found that SRFA and lignosulfonate molecules contain 2-5 labile hydrogens, and their number increases with the number of oxygens in the molecule. Also, we observed that compounds of Siberian crude oil ionizing in positive-ESI mode do not have labile hydrogens, while compounds ionizing in negative-ESI mode have one labile hydrogen that detaches during ESI ionization. PMID:24098913

Kostyukevich, Yury; Kononikhin, Alexey; Popov, Igor; Kharybin, Oleg; Perminova, Irina; Konstantinov, Andrey; Nikolaev, Eugene

2013-11-19

82

Dynamic Structural Changes During Complement C3 Activation Analyzed by Hydrogen/Deuterium Exchange Mass Spectrometry  

PubMed Central

Proteolytic cleavage of component C3 to C3b is a central step in the activation of complement. Whereas C3 is largely biologically inactive, C3b is directly involved in various complement activities. While the recently described crystal structures of C3 and C3b provide a molecular basis of complement activation, they do not reflect the dynamic changes that occur in solution. In addition, the available C3b structures diverge in some important aspects. Here we have utilized hydrogen/deuterium exchange coupled with mass spectrometry (HDX-MS) to investigate relative changes in the solution-phase structures of C3 and C3b. By combining two forms of mass spectrometry we could maximize the primary sequence coverage of C3b and demonstrate the feasibility of this method for large plasma proteins. While the majority of the 82 peptides that could be followed over time showed only minor alterations in HDX, we observed clear changes in solvent accessibility for 16 peptides, primarily in the ?-chain (?’NT, MG6-8, CUB, TED, C345C domains). Most of these peptides could be directly linked to the structural transitions visible in the crystal structures and revealed additional information about the probability of the structural variants of C3b. In addition, a discontinuous cluster of seven peptides in the MG3, MG6, LNK and ?’NT domains showed a decreased accessibility after activation to C3b. Although no gross conformational changes are detected in the crystal structure, this area may reflect a structurally flexible region in solution that contributes to C3 activation and function. PMID:18456336

Schuster, Michael C.; Ricklin, Daniel; Papp, Krisztián; Molnar, Kathleen S.; Coales, Stephen J.; Hamuro, Yoshitomo; Sfyroera, Georgia; Chen, Hui; Winters, Michael S.; Lambris, John D.

2008-01-01

83

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

PubMed

An extended quantum theoretical approach of the nu(X-H) 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. PMID:19884041

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

2010-01-01

84

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

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

85

Amide hydrogen/deuterium exchange & MALDI-TOF mass spectrometry analysis of Pak2 activation.  

PubMed

Amide hydrogen/deuterium exchange (H/D exchange) coupled with mass spectrometry has been widely used to analyze the interface of protein-protein interactions, protein conformational changes, protein dynamics and protein-ligand interactions. H/D exchange on the backbone amide positions has been utilized to measure the deuteration rates of the micro-regions in a protein by mass spectrometry(1,2,3). The resolution of this method depends on pepsin digestion of the deuterated protein of interest into peptides that normally range from 3-20 residues. Although the resolution of H/D exchange measured by mass spectrometry is lower than the single residue resolution measured by the Heteronuclear Single Quantum Coherence (HSQC) method of NMR, the mass spectrometry measurement in H/D exchange is not restricted by the size of the protein(4). H/D exchange is carried out in an aqueous solution which maintains protein conformation. We provide a method that utilizes the MALDI-TOF for detection(2), instead of a HPLC/ESI (electrospray ionization)-MS system(5,6). The MALDI-TOF provides accurate mass intensity data for the peptides of the digested protein, in this case protein kinase Pak2 (also called ?-Pak). Proteolysis of Pak 2 is carried out in an offline pepsin digestion. This alternative method, when the user does not have access to a HPLC and pepsin column connected to mass spectrometry, or when the pepsin column on HPLC does not result in an optimal digestion map, for example, the heavily disulfide-bonded secreted Phospholipase A(2;) (sPLA(2;)). Utilizing this method, we successfully monitored changes in the deuteration level during activation of Pak2 by caspase 3 cleavage and autophosphorylation(7,8,9). PMID:22143461

Hsu, Yuan-Hao; Traugh, Jolinda A

2011-01-01

86

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

NASA Astrophysics Data System (ADS)

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.

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

2010-01-01

87

Structural insights into glucan phosphatase dynamics using amide hydrogen-deuterium exchange mass spectrometry.  

PubMed

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 that are hyperphosphorylated and exhibit sparse branching accumulate. 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; an excess amount of insoluble, hyperphosphorylated glucans accumulates in cells. 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 has improved protection from deuteration when bound to glucans, confirming its role in glucan binding. More interestingly, we identified structural components of the DSP that also have improved 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 to the DSP active site. Therefore, our results suggest that these regions of the DSP participate in the presentation of the phosphoglucan to the active site and provide the first structural analysis and mode of action of this unique class of phosphatases. PMID:19754155

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

2009-10-20

88

Rapid Annealing Of Amorphous Hydrogenated Carbon  

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

89

Comparison of deuterium and hydrogen dissociation with a surface-wave discharge dissociator and a SiO 2 sputtered nozzle  

NASA Astrophysics Data System (ADS)

The deuterium dissociation degree has been measured using a new type of dissociator based on a Surface-Wave Discharge (SWD) at 2.45 GHz, equipped with a SiO 2 sputtered conical-shaped aluminum nozzle. Deuterium dissociation measurements are reported as function of oxygen fraction, microwave power and gas throughput, and compared with hydrogen dissociation values obtained with the same dissociator.

Dalpiaz, P. F.; Kubischta, W.; Masoli, F.; Reali, A.; Slavich, P.

1998-02-01

90

Precision measurement of the 1{ital S} ground-state Lamb shift in atomic hydrogen and deuterium by frequency comparison  

SciTech Connect

We have measured the hydrogen and deuterium 1{ital S} Lamb shift by direct optical frequency comparison of the 1{ital S}-2{ital S} and 2{ital S}-4{ital S}/4{ital D} two-photon transitions. Our result of 8172.874(60) MHz for the 1{ital S} Lamb shift in hydrogen is in agreement with the theoretical value of 8172.802(40) MHz. For the 1{ital S} Lamb shift in deuterium, we obtain a value of 8183.807(78) MHz, from which we derive a deuteron matter radium of 1.945(28) fm. The precision of our value for the 1{ital S} Lamb shift has surpassed that of radio frequency measurements of the 2{ital S}-2{ital P} Lamb shift. By comparison with a recent absolute measurement of the hydrogen 1{ital S}-2{ital S} transition frequency, we deduce a value for the Rydberg constant {ital R}{sub {infinity}}=109 737.315 684 9(30) cm{sup {minus}1}.

Weitz, M.; Huber, A.; Schmidt-Kaler, F.; Leibfried, D.; Vassen, W.; Zimmermann, C.; Pachucki, K.; Haensch, T.W. [Max-Planck-Institut fuer Quantenoptik, 85748 Garching (Germany)] [Max-Planck-Institut fuer Quantenoptik, 85748 Garching (Germany); Julien, L.; Biraben, F. [Laboratoire Kastler Brossel, Universite Pierre et Marie Curie, 75230 Paris Cedex 05 (France)] [Laboratoire Kastler Brossel, Universite Pierre et Marie Curie, 75230 Paris Cedex 05 (France)

1995-10-01

91

Surface Diffusion of Hydrogen and Deuterium on NICKEL(100) and NICKEL(111) Investigated by Linear Optical Diffraction  

NASA Astrophysics Data System (ADS)

A novel linear optical diffraction technique was developed and used to study the diffusion of hydrogen and deuterium atoms on Ni(100) and (111) surfaces. The technique is shown to be sensitive to <2% of a monolayer. Quantum tunneling diffusion was observed on both surfaces. On Ni(100), an activated tunneling behavior is observed which can be explained by the theory of small polarons. On Ni(111), a non-activated tunneling behavior is observed, which confirms previous observations made by Gomer and coworkers using a field emission microscope.

Lee, Anthony Story

92

Mitigation of carbon erosion in beryllium seeded deuterium plasma under bombardment by argon and helium ions in PISCES-B  

NASA Astrophysics Data System (ADS)

The influence of argon and helium impurities on chemical erosion of carbon by deuterium and on the mitigation of erosion by the beryllium seeding has been studied in the PISCES-B linear plasma device. Optical spectroscopy has been used to quantify the amounts of Be, Ar and He in the deuterium plasma and to monitor the reduction of the CD band as a measure of carbon chemical erosion of the fine-grain graphite target. The addition of Ar and He has not resulted in an increase of the carbon erosion rate. Moreover, the characteristic time for the Be layer formation was in agreement with the reference exposures. It can be concluded, that for the covered range of experimental parameters the addition of Ar and He to plasma does not affect the formation of the protective Be carbide layer and the associated mitigation of carbon erosion.

Kreter, A.; Nishijima, D.; Baldwin, M. J.; Doerner, R. P.; Pospieszczyk, A.

2011-10-01

93

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

NASA Astrophysics Data System (ADS)

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.

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

2012-03-01

94

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

PubMed Central

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 though 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. PMID:22227798

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

2012-01-01

95

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

SciTech Connect

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.

Lingyan Zhu

2004-02-28

96

Resolving Isotopic Fine Structure to Detect and Quantify Natural Abundance- and Hydrogen/Deuterium Exchange-Derived Isotopomers  

PubMed Central

Hydrogen/deuterium exchange (HDX) mass spectrometry (MS) is used for analyzing protein dynamics, protein folding/unfolding, and molecular interactions. Until this study, HDX MS experiments employed mass spectral resolving powers that afforded only one peak per nominal mass in a given peptide’s isotope distribution, and HDX MS data analysis methods were developed accordingly. A level of complexity that is inherent to HDX MS remained unaddressed, namely, various combinations of natural abundance heavy isotopes and exchanged deuterium shared the same nominal mass and overlapped at previous resolving powers. For example, an A + 2 peak is comprised of (among other isotopomers) a two-2H-exchanged/zero-13C isotopomer, a one-2H-exchanged/one-13C isotopomer, and a zero-2H-exchanged/two-13C isotopomer. Notably, such isotopomers differ slightly in mass as a result of the ~3 mDa mass defect between 2H and 13C atoms. Previous HDX MS methods did not resolve these isotopomers, requiring a natural-abundance-only (before HDX or “time zero”) spectrum and data processing to remove its contribution. It is demonstrated here that high-resolution mass spectrometry can be used to detect isotopic fine structure, such as in the A + 2 profile example above, deconvolving the isotopomer species resulting from deuterium incorporation. Resolving isotopic fine structure during HDX MS therefore permits direct monitoring of HDX, which can be calculated as the sum of the fractional peak magnitudes of the deuterium-exchanged isotopomers. This obviates both the need for a time zero spectrum as well as data processing to account for natural abundance heavy isotopes, saving instrument and analysis time. PMID:24328359

Liu, Qian; Easterling, Michael L.; Agar, Jeffrey N.

2014-01-01

97

Influence of beryllium carbide formation on deuterium retention and release  

NASA Astrophysics Data System (ADS)

The inconel cladding tiles of the ITER-like-wall to be tested at JET will be coated by a beryllium layer. Carbon containing tiles will be also present. These materials are sputtered in the high flux (1022 m-2 s-1 or higher) of the deuterium-tritium plasma. Ionized by the energetic electrons and with hydrogen isotope ions they will be implanted or re-deposited, creating composite layers.In order to study the deuterium retention and release, mixed layers were prepared using the thermionic arc method.Deuterium implantation was performed using a high current ion source at room temperature using a deuterium ion beam with energy of 200 eV/D. Thermal Desorption Spectroscopy (TDS) analyses were correlated with the beryllium/carbon relative concentrations of the prepared films. At higher carbon concentrations the peak value from TDS spectra corresponding to beryllium was lower and an increased peak corresponding to the carbon was observed.

Porosnicu, C.; Anghel, A.; Sugiyama, K.; Krieger, K.; Roth, J.; Lungu, C. P.

2011-08-01

98

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

PubMed

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

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

2015-01-01

99

Deuterium-Tritium Pulse Propulsion with Hydrogen as Propellant and the Entire Spacecraft as a Gigavolt Capacitor for Ignition  

E-print Network

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: 1. 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. 2. 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.

Friedwardt Winterberg

2012-07-31

100

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

DOEpatents

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.

Lueking, Angela (State College, PA); Narayanan, Deepa (Redmond, WA)

2011-03-08

101

Relativistic reduced-mass and recoil corrections to vacuum polarization in muonic hydrogen, muonic deuterium, and muonic helium ions  

SciTech Connect

The reduced-mass dependence of relativistic and radiative effects in simple muonic bound systems is investigated. The spin-dependent nuclear recoil correction of order (Z{alpha}){sup 4} {mu}{sup 3}/m{sub N}{sup 2} is evaluated for muonic hydrogen and deuterium and muonic helium ions ({mu} is the reduced mass and m{sub N} is the nuclear mass). Relativistic corrections to vacuum polarization of order {alpha}(Z{alpha}){sup 4}{mu} are calculated, with a full account of the reduced-mass dependence. The results shift theoretical predictions. The radiative-recoil correction to vacuum polarization of order {alpha}(Z{alpha}){sup 5} ln{sup 2}(Z{alpha}){mu}{sup 2}/m{sub N} is obtained in leading logarithmic approximation. The results emphasize the need for a unified treatment of relativistic corrections to vacuum polarization in muonic hydrogen, muonic deuterium, and muonic helium ions, where the mass ratio of the orbiting particle to the nuclear mass is larger than the fine-structure constant.

Jentschura, U. D. [Department of Physics, Missouri University of Science and Technology, Rolla, Missouri 65409 (United States)

2011-07-15

102

Search for narrow states in the inclusive ?-ray spectra resulting from antiproton annihilations at rest in liquid hydrogen and deuterium  

NASA Astrophysics Data System (ADS)

The energy spectrum of ? rays produced in proton-antiproton annihilation at rest in hydrogen and deuterium has been measured with good energy resolution and high statistics. The data were taken using the PS183 magnetic pair spectrometer at CERN's Low Energy Antiproton Ring. A detailed search of the ? spectrum yielded no evidence of ? transitions to narrow states with widths consistent with the spectrometer resolution. In hydrogen, upper limits (95% C.L.) are obtained for the yield of narrow states of (2-5)×10-4 for states below 1700 MeV/c2, and (5-10)×10-4 for states between 1700 and 1800 MeV/c2. In deuterium, the corresponding upper limits are (1-7)×10-3 for masses between 700 and 1730 MeV/c2, and (1-2)×10-3 for masses between 1750 and 1835 MeV/c2. These results contradict reports of the observation of narrow lines made by previous experiments.

Graf, N. A.; Fero, M.; Gee, M.; Mandelkern, M.; Ray, R.; Schultz, D.; Schultz, J.; Usher, T.; Armstrong, T. A.; Biard, J.; Lewis, R. A.; Playfer, S. M.; Smith, G. A.; Soulliere, M. J.; Bassalleck, B.; Wolfe, D. M.; Denes, P.; Büche, G.; Bürcker, L.; Koch, H.; Schwertel, J.; Angelopoulos, A.; Apostolakis, A.; Rozaki, H.; Sakelliou, L.

1991-10-01

103

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

SciTech Connect

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.

Shawali, A.S. (Univ. of Cairo, Giza, Egypt); Parkanyi, C.; Herndon, W.C.

1982-01-01

104

Gas-phase hydrogen/deuterium exchange of dinucleotides and 5'-monophosphate dinucleotides in a quadrupole ion trap  

NASA Astrophysics Data System (ADS)

Gas-phase hydrogen/deuterium (H/D) exchange reactions of four deprotonated dinucleotides (dAA, dAG, dGA, dGG) and their 5'-monophosphate analogs (5'-dAA, 5'-dAG, 5'-dGA, 5'-dGG) with D2O were performed in a quadrupole ion trap mass spectrometer. Significant differences in the rates and extents of exchange were found when the 5'-hydroxyl group of the dinucleotides was replaced by a phosphate functionality. Extensive and nucleobase-dependent exchange occurred for the deprotonated 5'-monophosphate dinucleotides, whereas the dinucleotides all exhibited essentially the same limited exchange. Results for the isomeric 5'-monophosphates, 5'-dAG and 5'-dGA, were remarkably different, indicating that the H/D exchange reaction was sequence dependent. An elaborate array of computations was performed to investigate the gas-phase structures of the ions individually and also as participants in ion-molecule complexes with D2O. Integration of the experimental and theoretical results supports a relay exchange mechanism and suggests that the exchange behavior depends highly on the identity and sequence of the nucleobases as well as their ability to interact with the deprotonation site. Finally, a shuttling mechanism is proposed to possibly account for the bimodal H/D exchange behavior observed for deprotonated 5'P-dGA. In this case, hydrogen bonding between the nucleobases in concert with interaction from the deuterating agent creates an ion-molecule complex in which hydrogen and deuterium atoms may be shuttled amongst the hydrogen-bonded participants.

Chipuk, Joseph E.; Brodbelt, Jennifer S.

2009-10-01

105

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)

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 ? 13C and ?D found in light hydrocarbons in some terrestrial environments and meteorites.

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

2010-11-01

106

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

NASA Technical Reports Server (NTRS)

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.

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

1969-01-01

107

Hydrogen storage in sonicated carbon materials  

NASA Astrophysics Data System (ADS)

The hydrogen storage in purified single-wall carbon nanotubes (SWNTs), graphite and diamond powder was investigated at room temperature and ambient pressure. The samples were sonicated in 5 M HNO3 for various periods of time using an ultrasonic probe of the alloy Ti-6Al-4V. The goal of this treatment was to open the carbon nanotubes. The maximum value of overall hydrogen storage was found to be 1.5 wt%, as determined by thermal desorption spectroscopy. The storage capacity increases with sonication time. The sonication treatment introduces particles of the Ti alloy into the samples, as shown by X-ray diffraction, transmission electron microscopy, and chemical analysis. All of the hydrogen uptake can be explained by the assumption that the hydrogen is only stored in the Ti-alloy particles. The presence of Ti-alloy particles does not allow the determination of whether a small amount of hydrogen possibly is stored in the SWNTs themselves, and the fraction of nanotubes opened by the sonication treatment is unknown.

Hirscher, M.; Becher, M.; Haluska, M.; Dettlaff-Weglikowska, U.; Quintel, A.; Duesberg, G. S.; Choi, Y.-M.; Downes, P.; Hulman, M.; Roth, S.; Stepanek, I.; Bernier, P.

2001-03-01

108

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

SciTech Connect

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.

Richmond, Scott [Los Alamos National Laboratory; Bridgewater, Jon S [Los Alamos National Laboratory; Ward, John W [Los Alamos National Laboratory; Allen, Thomas H [Los Alamos National Laboratory

2010-01-01

109

Deuterium-carbon multiple-quantum NMR in liquid crystals: polarization transfer and off-magic-angle spinning  

Microsoft Academic Search

The polarization transfer dynamics in a recently introduced deuterium-carbon NMR correlation method is studied, both theoretically and experimentally. The technique, which exploits heteronuclear multiple-quantum coherences, is useful for measuring and assigning 2 H quadrupolar couplings in ordered media. It is also shown that the experiment is suitable for implementation under off-magic-angle spinning conditions. The approach is demonstrated on a perdeuterated

Dick Sandström; Herbert Zimmermann

2002-01-01

110

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

Microsoft Academic Search

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

Malek Chatila

2003-01-01

111

Combining ion mobility spectrometry with hydrogen-deuterium exchange and top-down MS for peptide ion structure analysis.  

PubMed

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 Å(2) and 471 Å(2). [M+3H](3+) ions exhibit a predominant conformer with a collision cross section of 340 Å(2) as well as an unresolved conformer (shoulder) with a collision cross section of ~367 Å(2). 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. PMID:25267084

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

2014-12-01

112

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

PubMed Central

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

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

2009-01-01

113

Functional Unfolding of ?1-Antitrypsin Probed by Hydrogen-Deuterium Exchange Coupled with Mass Spectrometry*S?  

PubMed Central

The native state of ?1-antitrypsin (?1AT), a member of the serine protease inhibitor (serpin) family, is considered a kinetically trapped folding intermediate that converts to a more stable form upon complex formation with a target protease. Although previous structural and mutational studies of ?1AT revealed the structural basis of the native strain and the kinetic trap, the mechanism of how the native molecule overcomes the kinetic barrier to reach the final stable conformation during complex formation remains unknown. We hypothesized that during complex formation, a substantial portion of the molecule undergoes unfolding, which we dubbed functional unfolding. Hydrogen-deuterium exchange coupled with ESI-MS was used to analyze this serpin in three forms: native, complexing, and complexed with bovine ?-trypsin. Comparing the deuterium content at the corresponding regions of these three samples, we probed the unfolding of ?1AT during complex formation. A substantial portion of the ?1AT molecule unfolded transiently during complex formation, including not only the regions expected from previous structural studies, such as the reactive site loop, helix F, and the following loop, but also regions not predicted previously, such as helix A, strand 6 of ?-sheet B, and the N terminus. Such unfolding of the native interactions may elevate the free energy level of the kinetically trapped native serpin sufficiently to cross the transition state during complex formation. In the current study, we provide evidence that protein unfolding has to accompany functional execution of the protein molecule. PMID:19136720

Baek, Je-Hyun; Yang, Won Suk; Lee, Cheolju; Yu, Myeong-Hee

2009-01-01

114

Simulataneous profiling of hydrogen and deuterium by 2.6 MeV 4He ERDA using a ?E - E telescope detector  

Microsoft Academic Search

For depth profiling of hydrogen isotopes by elastic recoil detection analysis (ERDA) with 2.6 MeV 4He ions a special ?E - 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 ?E a thin 3.7 ?m silicon transmission detector was used

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

1997-01-01

115

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

Microsoft Academic Search

For depth profiling of hydrogen isotopes by elastic recoil detection analysis (ERDA) with 2.6 MeV He4e ions a special DeltaE - 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 Delta E a thin 3.7 mum silicon transmission detector was

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

1997-01-01

116

Hydrogen Raman shifts in carbon nanotubes from molecular dynamics simulation  

E-print Network

Hydrogen Raman shifts in carbon nanotubes from molecular dynamics simulation S.J.V. Frankland *, D hydrogen in individual single-shell carbon nanotubes and nanotube ropes using a semiclassical model. The calculations predict that isolated hydrogen molecules inside of nanotubes have a Raman frequency that increases

Brenner, Donald W.

117

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

PubMed

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

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

1994-07-01

118

Latitudinal distribution of the deuterium to hydrogen ratio in the atmospheric water vapor retrieved from IMG/ADEOS data  

NASA Astrophysics Data System (ADS)

Latitudinal distribution of the columnar deuterium/hydrogen ratio of atmospheric water vapor, ?Dvap, was retrieved from high-resolution infrared spectra. Interferometric Monitor for Greenhouse gases (IMG) sensor aboard the ADvanced Earth Observing Satellite (ADEOS) observed the spectra over the ocean during the operational period from December 1996 through June 1997. The latitudinal mean ?Dvap was relatively large with values around -100‰ in the tropical region decreasing down to minimal values of -800‰ at high latitudes. For retrieving ?Dvap, a type of spectral fitting method was adopted using a forward/retrieval calculation code developed by Gribanov et al. [2001]. This method is expected to be applicable for data analyses of future satellite sensors such as IASI and TES.

Zakharov, Vyacheslav I.; Imasu, Ryoichi; Gribanov, Konstantin G.; Hoffmann, Georg; Jouzel, Jean

2004-06-01

119

LETTER TO THE EDITOR: Suppression of hydrogenated carbon film deposition by scavenger techniques and their application to the tritium inventory control of fusion devices  

NASA Astrophysics Data System (ADS)

The well-known radical and ion scavenger techniques of application in amorphous hydrogenated carbon film deposition studies are investigated in relation to the mechanism of tritium and deuterium co-deposition in carbon-dominated fusion devices. A particularly successful scheme results from the injection of nitrogen into methane/hydrogen plasmas for conditions close to those prevailing in the divertor region of present fusion devices. A complete suppression of the a-C : H film deposition has been achieved for N2/CH4 ratios close to one in methane (5%)/hydrogen DC plasma. The implications of these findings in the tritium retention control in future fusion reactors are addressed.

Tabarés, F. L.; Tafalla, D.; Tanarro, I.; Herrero, V. J.; Islyaikin, A.; Maffiotte, C.

2002-08-01

120

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

NASA Astrophysics Data System (ADS)

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 1000°C. 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.

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

1989-04-01

121

Enhanced gas-phase hydrogen-deuterium exchange of oligonucleotide and protein ions stored in an external multipole ion reservoir.  

PubMed

Rapid gas-phase hydrogen-deuterium (H-D) exchange from D(2)O and ND(3) into oligonucleotide and protein ions was achieved during storage in a hexapole ion reservoir. Deuterated gas is introduced through a capillary line that discharges directly into the low-pressure region of the reservoir. Following exchange, the degree of H-D exchange is determined using Fourier transform ion cyclotron resonance mass spectrometry. Gas-phase H-D exchange experiments can be conducted more than 100 times faster than observed using conventional in-cell exchange protocols that require lower gas pressures and additional pump-down periods. The short experimental times facilitate the quantitation of the number of labile hydrogens for less reactive proteins and structured oligonucleotides. For ubiquitin, we observe approximately 65 H-D exchanges after 20 s. Exchange rates of > 250 hydrogens s(-1) are observed for oligonucleotide ions when D(2)O or ND(3) is admitted directly into the external ion reservoir owing to the high local pressure in the hexapole. Partially deuterated oligonucleotide ions have been fragmented in the reservoir using infrared multiphoton dissociation (IRMPD). The resulting fragment ions show that exchange predominates at charged sites on the 5'- and 3'-ends of the oligonucleotide, whereas exchange is slower in the core. This hardware configuration is independent of the mass detector and should be compatible with other mass spectrometric platforms including quadrupole ion trap and time-of-flight mass spectrometers. PMID:10633235

Hofstadler, S A; Sannes-Lowery, K A; Griffey, R H

2000-01-01

122

ORIGINAL RESEARCH Hydrogen and carbon isotope fractionation during  

E-print Network

ORIGINAL RESEARCH Hydrogen and carbon isotope fractionation during degradation of chloromethane, hydrogen isotope fractionation, methylotrophic bacteria. Correspondence Thierry Nadalig, Universite de-FID equipment by REALISE (http://realise. unistra.fr), the Alsace network for research and engineering

Paris-Sud XI, Université de

123

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

NASA Astrophysics Data System (ADS)

For depth profiling of hydrogen isotopes by elastic recoil detection analysis (ERDA) with 2.6 MeV He4e ions a special ?E - 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 ? E a thin 3.7 ?m silicon transmission detector was used while the residual energy was measured with a standard 100 ?m 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.

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

1997-01-01

124

The Speed of Oil and Mercury Diffusion Pumps for Hydrogen, Helium and Deuterium  

Microsoft Academic Search

Data on several standard diffusion pumps indicate that the speed for hydrogen may be considerably less than 3.8 times the rated speed for air depending on the jet design, pump fluid, heater input, and speed of the fore pump. Evidence is presented that this reduction in speed is partly the result of diffusion of hydrogen back through the vapor jet

B. B. Dayton

1948-01-01

125

Structure and function of circadian clock proteins and deuterium isotope effects in nucleic acid hydrogen bonds  

E-print Network

-terminal domain. Hydrogen bonds are of paramount importance in nucleic acid structure and function. Here we show that changes in the width and anharmonicity of vibrational potential energy wells of hydrogen bonded groups can be measured in nucleic acids and can...

Vakonakis, Ioannis

2005-08-29

126

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

SciTech Connect

The kinetics of desorption both helium isotopes and molecules of hydrogen and deuterium from open-ended or ?-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.

Danilchenko, B. A., E-mail: danil@iop.kiev.ua; Yaskovets, I. I.; Uvarova, I. Y. [Institute of Physics NASU, Pr. Nauki 46, 03680 Kiev (Ukraine); Dolbin, A. V.; Esel'son, V. B.; Basnukaeva, R. M.; Vinnikov, N. A. [B. Verkin Institute for Low Temperature Physics and Engineering NASU, 47 Lenin Ave., Kharkov 61103 (Ukraine)

2014-04-28

127

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

NASA Astrophysics Data System (ADS)

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.

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

2009-06-01

128

Carbon assisted water electrolysis for hydrogen generation  

NASA Astrophysics Data System (ADS)

Carbon Assisted Water Electrolysis (CAWE) is an energy efficient process in that H2 can be produced at lower applied voltage (˜1.0 V) compared to nearly 2.0 V needed for ordinary water electrolysis for the same H2 evolution rate. In this process, carbon is oxidized to oxides of carbon at the anode of an electrochemical cell and hydrogen is produced at the cathode. These gases are produced in relatively pure state and would be collected in a separate chamber. In this paper, we present the results of influence of various operating parameters on efficiency of CAWE process. The results showed that H2 can be produced at applied voltages Eo as low as 1.0V (vs. SHE) and its production rate is strongly dependent on the type of the carbon used and its concentration in the electrolyte. It has also been found that the performance of CAWE process is higher in acidic electrolyte than in alkaline electrolyte.

Sabareeswaran, S.; Balaji, R.; Ramya, K.; Rajalakshmi, N.; Dhathathereyan, K. S.

2013-06-01

129

Hexicon 2: automated processing of hydrogen-deuterium exchange mass spectrometry data with improved deuteration distribution estimation.  

PubMed

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. PMID:24676893

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

2014-06-01

130

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

131

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

SciTech Connect

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.

Houde, Damian; Arndt, Joseph; Domeier, Wayne; Berkowitz, Steven; Engen, John R.; (NEU); (Biogen)

2009-04-22

132

Confinement of hydrogen at high pressure in carbon nanotubes  

DOEpatents

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.

Lassila, David H. (Aptos, CA); Bonner, Brian P. (Livermore, CA)

2011-12-13

133

Refinement of the experimental dynamic structure factor for liquid para-hydrogen and ortho-deuterium using semi-classical quantum simulation  

SciTech Connect

The dynamic structure factor of liquid para-hydrogen and ortho-deuterium in corresponding thermodynamic states (T = 20.0?K, n = 21.24?nm{sup ?3}) and (T = 23.0?K, n = 24.61?nm{sup ?3}), respectively, has been computed by both the Feynman-Kleinert linearized path-integral (FK-LPI) and Ring-Polymer Molecular Dynamics (RPMD) methods and compared with Inelastic X Ray Scattering spectra. The combined use of computational and experimental methods enabled us to reduce experimental uncertainties in the determination of the true sample spectrum. Furthermore, the refined experimental spectrum of para-hydrogen and ortho-deuterium is consistently reproduced by both FK-LPI and RPMD results at momentum transfers lower than 12.8?nm{sup ?1}. At larger momentum transfers the FK-LPI results agree with experiment much better for ortho-deuterium than for para-hydrogen. More specifically we found that for k ? 20.0 nm{sup ?1} para-hydrogen provides a test case for improved approximations to quantum dynamics.

Smith, Kyle K. G., E-mail: kylesmith@utexas.edu; Rossky, Peter J., E-mail: peter.rossky@austin.utexas.edu [Institute for Computational Engineering and Sciences and Department of Chemistry, University of Texas at Austin, Austin, Texas 78712 (United States); Poulsen, Jens Aage, E-mail: jens72@chem.gu.se [Department of Physical Chemistry, Goteborg University, S-412-96 Goteborg (Sweden); Cunsolo, A., E-mail: acunsolo@bnl.gov [Photon Sciences Directorate, Brookhaven National Laboratory, P.O. Box 5000, Upton, New York 11973 (United States)

2014-01-21

134

Sub-Zero Temperature Chromatography for Reduced Back-Exchange and Improved Dynamic Range in Amide Hydrogen Deuterium Exchange Mass Spectrometry  

PubMed Central

Amide hydrogen/deuterium exchange is a commonly used technique for studying the dynamics of proteins and their interactions with other proteins or ligands. When coupled with liquid chromatography and mass spectrometry, hydrogen/deuterium exchange provides several unique advantages over other structural characterization techniques including very high sensitivity, the ability to analyze proteins in complex environments, and a large mass range. A fundamental limitation of the technique arises from the loss of deuterium label (back-exchange) during the course of the analysis. A method to limit loss of label during the separation stage of the analysis using sub-zero temperature reversed-phase chromatography is presented. The approach is facilitated by the use of buffer modifiers that prevent freezing. We evaluated ethylene glycol, dimethyl formamide, formamide, and methanol for their freezing point suppression capabilities, effects on peptide retention, and their compatibilities with electrospray ionization. Ethylene glycol was used extensively because of its good electrospray ionization compatibility; however formamide has potential to be a superior modifier if detrimental effects on ionization can be overcome. It is demonstrated using suitable buffer modifiers that separations can be performed at temperatures as low as ?30°C with negligible loss of deuterium label, even during long chromatographic separations. The reduction in back-exchange is shown to increase the dynamic range of HDX MS in terms of mixture complexity, and the magnitude with which changes in deuteration level can be quantified. PMID:23025328

Venable, John D.; Okach, Linda; Agarwalla, Sanjay; Brock, Ansgar

2012-01-01

135

The effect of a nitrogen-rich surface layer on the sub-surface deuterium (hydrogen) concentration distribution in titanium  

NASA Astrophysics Data System (ADS)

Deuterium and nitrogen depth profiles in Ti with modified surfaces have been measured with Auger electron spectroscopy, secondary ion mass spectroscopy, and D( 3He,p) 4He nuclear reaction analysis. Nitrogen-rich surfaces layers of varying thicknesses were created on Ti by exposure to N 2 gas at 650°C. Deuterium loading was performed by exposure to 1 Torr of D 2 gas at 500°C. The deuterium distribution was influenced by nitrogen in the near-surface regions of all samples. Specifically, deuterium solubility was suppressed in surface regions of high (greater than 1%) nitrogen concentration. The deuterium solubility also remained low within the first few microns, well beyond the region of high nitrogen concentration. This effect is attributed to internal elastic stresses imposed by the non-deuterium absorbing nitrogen-rich layer on the Ti. These stresses prohibit the volume expansion associated with deuterium absorption. We estimate stresses on the order of 3-4 GPa are required to suppress the deuterium solubility to the values observed. The deuterium absorption kinetics were observed to depend systematically on the thickness of the nitrogen-rich layer. This is consistent with limited solubility near the surface or a surface poisoning effect influencing the overall deuterium diffusion from the gas phase into the Ti bulk.

Costescu, Corneliu I.; Heuser, Brent J.

2000-04-01

136

Novel role of boron on carbon-based hydrogen storage  

Microsoft Academic Search

Carbon materials such as fullerenes and nanotubes are one of the promising materials for hydrogen storage. To increase H intake, however, a lot remains to be done. First principles calculations show that in such materials, substitutional boron can greatly increase the binding between hydrogen molecules and the carbon hosts, via a non-classical chemical binding mechanism in which the two un-dissociated

Yong-Hyun Kim; Yufeng Zhao; S. B. Zhang

2004-01-01

137

Carbonate thermochemical cycle for the production of hydrogen  

DOEpatents

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.

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

2010-02-23

138

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

139

On the control of carbon nanostructures for hydrogen storage applications  

Microsoft Academic Search

The storage of hydrogen in different carbon nanostructures has been investigated using classical Monte–Carlo simulations techniques. Very low hydrogen uptakes (?1% wt) have been calculated for single-walled and double-walled carbon nanotubes, as well as for graphite nanofibers at 293 K and 10 MPa. The amount of hydrogen uptake strongly depends on the porosity within the nanostructure network where optimal arrangements

Patrice Guay; Barry L. Stansfield; Alain Rochefort

2004-01-01

140

The effect of a nitrogen-rich surface layer on the sub-surface deuterium (hydrogen) concentration distribution in titanium  

Microsoft Academic Search

Deuterium and nitrogen depth profiles in Ti with modified surfaces have been measured with Auger electron spectroscopy, secondary ion mass spectroscopy, and D(3He,p)4He nuclear reaction analysis. Nitrogen-rich surfaces layers of varying thicknesses were created on Ti by exposure to N2 gas at 650°C. Deuterium loading was performed by exposure to 1Torr of D2 gas at 500°C. The deuterium distribution was

Corneliu I. Costescu; Brent J. Heuser

2000-01-01

141

Gas-phase hydrogen/deuterium exchange of 5'- and 3'-mononucleotides in a quadrupole ion trap: exploring the role of conformation and system energy.  

PubMed

Gas-phase hydrogen/deuterium (H/D) exchange reactions for deprotonated 2'-deoxy-5'-monophosphate and 2'-deoxy-3'-monophosphate nucleotides with D(2)O were performed in a quadrupole ion trap mass spectrometer. To augment these experiments, molecular modeling was also conducted to identify likely deprotonation sites and potential gas-phase conformations of the anions. A majority of the 5'-monophosphates exchanged extensively with several of the compounds completely incorporating deuterium in place of their labile hydrogen atoms. In contrast, most of the 3'-monophosphate isomers exchanged relatively few hydrogen atoms, even though the rate of the first two exchanges was greater than observed for the 5'-monophosphates. Mononucleotides that failed to incorporate more than two deuterium atoms under default reaction conditions were often found to exchange more extensively when reactions were performed under higher energy conditions. Integration of the experimental and theoretical results supports the use of a relay exchange mechanism and suggests that the exchange behavior depends highly on the identity and orientation of the nucleobase and the position and flexibility of the deprotonated phosphate moiety. These observations also highlight the importance of the distance between the various participating groups in addition to their gas-phase acidity and basicity. PMID:17289398

Chipuk, Joseph E; Brodbelt, Jennifer S

2007-04-01

142

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

SciTech Connect

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

Altstetter, C.J.

1981-01-01

143

Parameter dependence of the radial electric field in the edge pedestal of hydrogen, deuterium and helium plasmas  

NASA Astrophysics Data System (ADS)

The characteristics of the edge radial electric field (Er) are studied in deuterium, hydrogen and helium plasmas at ASDEX Upgrade. The minimum of the Er well is analyzed as a function of pedestal parameters and the best correlation is found between the depth of the Er well and the ion pressure at the pedestal top. This result is consistent with Er being balanced by the main ion pressure gradient term. Studying the radial position of the Er minimum reveals that the Er well moves closer to the last closed flux surface the deeper the Er well is. This suggests that for deeper Er wells the distance between the steepest gradients in the ion temperature and ion density profile is reduced. The width of the Er well shows no significant variations despite changing the ion temperature, magnetic field and plasma particle species. At AUG, the Er well is on average 1.2 cm wide. A multi-machine comparison supports a machine size scaling of Er and indicates that the Er shear layer covers the outer 2% of the plasma minor radius independent of the size of the machine. Based on this scaling, the width of the Er well in ITER is estimated to ?4 cm.

Viezzer, E.; Pütterich, T.; McDermott, R. M.; Conway, G. D.; Cavedon, M.; Dunne, M. G.; Dux, R.; Wolfrum, E.; the ASDEX Upgrade Team

2014-07-01

144

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

PubMed Central

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 Ca2+ 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

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

2014-01-01

145

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

PubMed

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 reveal 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 nuclear receptor (NR)-transcription factor functional interactions. PMID:24909783

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

2014-07-01

146

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

NASA Astrophysics Data System (ADS)

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.

Tsuchida, Daisuke; Yamazaki, Katsuyoshi; Akashi, Satoko

2014-10-01

147

Mapping Residual Structure in Intrinsically Disordered Proteins at Residue Resolution Using Millisecond Hydrogen/Deuterium Exchange and Residue Averaging.  

PubMed

Measurement of residual structure in intrinsically disordered proteins can provide insights into the mechanisms by which such proteins undergo coupled binding and folding. The present work describes an approach to measure residual structure in disordered proteins using millisecond hydrogen/deuterium (H/D) exchange in a conventional bottom-up peptide-based workflow. We used the exchange mid-point, relative to a totally deuterated control, to quantify the rate of H/D exchange in each peptide. A weighted residue-by-residue average of these midpoints was used to map the extent of residual structure at near single-residue resolution. We validated this approach both by simulating a disordered protein and experimentally using the p300 binding domain of ACTR, a model disordered protein already well-characterized by other approaches. Secondary structure elements mapped in the present work are in good agreement with prior nuclear magnetic resonance measurements. The new approach was somewhat limited by a loss of spatial resolution and subject to artifacts because of heterogeneities in intrinsic exchange. Approaches to correct these limitations are discussed. PMID:25481641

Keppel, Theodore R; Weis, David D

2014-12-01

148

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)

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.

Jiang, Qian

149

Stable carbon and hydrogen isotope fractionation of dissolved organic groundwater pollutants by equilibrium sorption  

NASA Astrophysics Data System (ADS)

Linear free energy relationships (LFERs) were established which relate equilibrium vapor-liquid isotope effects to stable carbon and hydrogen isotope enrichment factors for equilibrium sorption to geosorbents. The LFERs were established for normal, cyclic or branched alkanes, monoaromatic hydrocarbons, and chloroethenes. These LFERs predict that isotopic light compounds sorb more strongly than their heavy counterparts. Defining fractionation as in classical literature by "heavy divided by light", carbon enrichment factors for equilibrium sorption were derived which ranged from - 0.13 ± 0.04‰ (benzene) to - 0.52 ± 0.19‰ (trichloroethene at 5-15 °C). Hydrogen enrichment factors for sorption of 14 different compounds were between - 2.4 and - 9.2‰. For perdeuterated hydrocarbons the predicted enrichment factors ranged from - 19 ± 5.4‰ (benzene) to - 64 ± 30‰ (cyclohexane). Equilibrium sorption experiments with a soil and activated carbon as sorbents were performed in the laboratory for perdeuterocyclohexane and perdeuterotoluene. The measured D/H enrichments agreed with the LFER prediction for both compounds and both sorbents within the uncertainty estimate of the prediction. The results of this work suggest that equilibrium sorption does create only very small isotope shifts for 13C in groundwater pollutants in aquifers. It is also suggested that deuterium shifts are expected to be higher, especially for strongly sorbing pollutants.

Höhener, Patrick; Yu, Xianjing

2012-03-01

150

Enzymatic functionalization of carbon-hydrogen bonds.  

PubMed

The development of new catalytic methods to functionalize carbon-hydrogen (C-H) bonds continues to progress at a rapid pace due to the significant economic and environmental benefits of these transformations over traditional synthetic methods. In nature, enzymes catalyze regio- and stereoselective C-H bond functionalization using transformations ranging from hydroxylation to hydroalkylation under ambient reaction conditions. The efficiency of these enzymes relative to analogous chemical processes has led to their increased use as biocatalysts in preparative and industrial applications. Furthermore, unlike small molecule catalysts, enzymes can be systematically optimized via directed evolution for a particular application and can be expressed in vivo to augment the biosynthetic capability of living organisms. While a variety of technical challenges must still be overcome for practical application of many enzymes for C-H bond functionalization, continued research on natural enzymes and on novel artificial metalloenzymes will lead to improved synthetic processes for efficient synthesis of complex molecules. In this critical review, we discuss the most prevalent mechanistic strategies used by enzymes to functionalize non-acidic C-H bonds, the application and evolution of these enzymes for chemical synthesis, and a number of potential biosynthetic capabilities uniquely enabled by these powerful catalysts (110 references). PMID:21079862

Lewis, Jared C; Coelho, Pedro S; Arnold, Frances H

2011-04-01

151

Sticking coefficient of hydrogen and deuterium on silicates under interstellar conditions  

E-print Network

Sticking of H and D atoms on interstellar dust grains is the first step in molecular hydrogen formation, which is a key reaction in the InterStellar Medium (ISM). After studying the sticking coefficients of H2 and D2 molecules on amorphous silicate surfaces experimentally and theoretically, we extrapolate the results to the sticking coefficient of atoms and propose a formulae that gives the sticking coefficients of H and D on both silicates and icy dust grains. In our experiments, we used the King and Wells method for measuring the sticking coefficients of H2 and D2 molecules on a silicate surface held at 10 K. It consists of measuring with a QMS (quadrupole mass spectrometer) the signals of H2 and D2 molecules reflected by the surface during the exposure of the sample to the molecular beam at a temperature ranging from 20 K to 340 K. We tested the efficiency of a physical model, developed previously for sticking on water-ice surfaces. We applied this model to our experimental results for the sticking coeffic...

Chaabouni, H; Baouche, S; Dulieu, F; Matar, E; Congiu, E; Gavilan, L; Lemaire, J L

2012-01-01

152

Extreme deuterium enrichment in stratospheric hydrogen and the global atmospheric budget of H2.  

PubMed

Molecular hydrogen (H2) is the second most abundant trace gas in the atmosphere after methane (CH4). In the troposphere, the D/H ratio of H2 is enriched by 120 per thousand relative to the world's oceans. This cannot be explained by the sources of H2 for which the D/H ratio has been measured to date (for example, fossil fuels and biomass burning). But the isotopic composition of H2 from its single largest source--the photochemical oxidation of methane--has yet to be determined. Here we show that the D/H ratio of stratospheric H2 develops enrichments greater than 440 per thousand, the most extreme D/H enrichment observed in a terrestrial material. We estimate the D/H ratio of H2 produced from CH4 in the stratosphere, where production is isolated from the influences of non-photochemical sources and sinks, showing that the chain of reactions producing H2 from CH4 concentrates D in the product H2. This enrichment, which we estimate is similar on a global average in the troposphere, contributes substantially to the D/H ratio of tropospheric H2. PMID:12931182

Rahn, Thom; Eiler, John M; Boering, Kristie A; Wennberg, Paul O; McCarthy, Michael C; Tyler, Stanley; Schauffler, Sue; Donnelly, Stephen; Atlas, Elliot

2003-08-21

153

Hydrogen-deuterium exchange mass spectrometry as an emerging analytical tool for stabilization and formulation development of therapeutic monoclonal antibodies.  

PubMed

The dynamic nature of the structure of monoclonal antibodies (mAbs) can be probed at a resolution of 5-20 residues using hydrogen-deuterium exchange mass spectrometry (H/D-MS). Recent studies using H/D-MS have shown that distinct regions of IgG1 mAbs experience significant changes in backbone dynamics in response to specific physicochemical alterations, varying solution conditions, or exposure to different environmental stresses. Tracking such changes in local dynamics may therefore serve as a key analytical tool, not only to monitor stability changes, but also to design improved, and more stable formulations of therapeutic mAbs in pharmaceutical dosage forms. This review article describes the H/D-MS method as applied to the analysis of formulations containing mAbs and summarizes recent studies monitoring changes in mAb local dynamics in response to chemical modifications, physical degradation, and presence of stabilizing and destabilizing excipients. Furthermore, the nature of the local dynamics of a highly conserved peptide segment in the CH 2 domain of IgG1 mAbs is reviewed, and the results are correlated with decreased pharmaceutical stability, supporting the identification of a common aggregation hotspot sequence in the Fc region of human IgG1 mAbs. In addition, unresolved challenges (and opportunities) in applying H/D-MS technology for stabilization and formulation development of mAbs are discussed. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 104:327-345, 2015. PMID:25354868

Majumdar, Ranajoy; Middaugh, C Russell; Weis, David D; Volkin, David B

2015-02-01

154

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

NASA Astrophysics Data System (ADS)

The function of hemoglobin (Hb) as oxygen transporter is mediated by reversible O2 binding to Fe(2+) heme in each of the ? and ? 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 ? and ? 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.

Sowole, Modupeola A.; Konermann, Lars

2013-07-01

155

Modified carbon nanostructures as materials for hydrogen storage  

NASA Astrophysics Data System (ADS)

Within the framework of ab initio simulation, a number of modifications of well-known carbon nanostructures are proposed, which could form the basis for designing materials with high adsorptivity for molecular hydrogen.

Avdeenkov, A. V.; Bibikov, A. V.; Bodrenko, I. V.; Nikolaev, A. V.; Taran, M. D.; Tkalya, E. V.

2009-11-01

156

Physisorption of molecular hydrogen on carbon nanotube with vacant defects  

SciTech Connect

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.

Sun, Gang; Shen, Huaze; Wang, Enge; Xu, Limei, E-mail: limei.xu@pku.edu.cn [International Center for Quantum Materials and School of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China); Tangpanitanon, Jirawat [University of Cambridge, Cambridge, Cambridgeshire CB2 1TP (United Kingdom); Wen, Bo [International Center for Quantum Materials and School of Physics, Peking University, Beijing 100871 (China); Beijing Computational Science Research Center, Heqing Street, Haidian District, Beijing 100084 (China); Xue, Jianming [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Center for Applied Physics and Technology, Peking University, Beijing 100871 (China)

2014-05-28

157

Hydrogen evolution on hydrophobic aligned carbon nanotube arrays.  

PubMed

We investigate for the first time hydrophobic carbon nanotube-based electrochemical cells as an alternative solution to hydrogen sorting. We show that the electrically conducting surface of the nanotube arrays can be used as a cathode for hydrogen generation and absorption by electrolyzing water. We support our findings with Raman and gas chromatography measurements. These results suggest that carbon nanotube forests, presenting a unique combination of hydrophobicity and conductivity, are suitable for application in fuel cells and microelectromechanical devices. PMID:19928998

Misra, Abha; Giri, Jyotsnendu; Daraio, Chiara

2009-12-22

158

Quantum rotation of hydrogen in single-wall carbon nanotubes  

E-print Network

, hydrogen storage sys- tems have been the focus of much recent research and development activity. A safeQuantum rotation of hydrogen in single-wall carbon nanotubes C.M. Brown a,b , T. Yildirim b , D of Standards and Technology, NIST Center for Neutron Research, Gaithersburg, MD 208991, USA c Center for Basic

Yildirim, Taner

159

Adsorption of hydrogen and deuterium atoms on the (0001) graphite surface  

NASA Astrophysics Data System (ADS)

Adsorption of H and D on HOPG surfaces was studied with thermal desorption (TDS), electronic (ELS), and high-resolution electron-energy-loss (HREELS) spectroscopies. After admission of H (D) from thermal (2000 K) atom sources to clean graphite surfaces TD spectra revealed recombinative molecular H2 (D2) desorption in a main peak around 445 K (490 K) and a minor peak at 560 K (580 K). After admission of higher fluences the main peak shifts to 460 K (500 K) and develops a shoulder at 500 K (540 K). The saturation coverages were calculated as 0.4plus-or-minus0.2 for H and D and initial sticking coefficients of 0.4plus-or-minus0.2 were obtained. Through leading edge analysis of the TD spectra desorption activation energies for H and D were determined as 0.6 and 0.95 eV, respectively. EL spectra suggest a 16% loss of the sp2 character of the surface carbon 2sp electrons upon D adsorption. HREEL spectra of H (D) graphite covered surfaces reveal in addition to two graphite-intrinsic optical phonon losses vibrational features at 1210 and 2650 cm-1 (and 640 and 1950 cm-1). These frequencies are in excellent agreement with those obtained from a recently published H (D)/graphite potential energy surface. A theoretical description of the desorption process through calculated H+H/graphite potential surfaces reveals the desorption mechanism and desorption activation energies which are in good agreement with the measured data.

Zecho, Thomas; Guttler, Andreas; Sha, Xianwei; Jackson, Bret; Kuppers, Jurgen

2002-11-01

160

Characterization of Carbon Aerogels as Scaffolds for Hydrogen Storage Materials.  

NASA Astrophysics Data System (ADS)

Alkali borohydrides are strong candidates for on-board hydrogen storage. Nanoconfinement of these materials in carbon aerogels improves the kinetics for the dehydrogenation reaction. Efforts have been made to understand the mechanisms behind this improvement. Prompt gamma activation analysis shows that the amount of hydrogen bound to the bare aerogel from the synthesis is dependent on pyrolysis temperature. Neutron vibrational spectra show that these hydrogen atoms are primarily sp^2 bound to the carbon scaffold. Small angle neutron scattering (SANS) data have been collected for the bare aerogel and the aerogel partly and entirely filled with LiBH4 providing information about the pore filling and morphology.

Verdal, Nina; Udovic, Terrence; Hartman, Michael; Bacon, Margaret; Vajo, John; Gross, Adam; Baumann, Theodore; Rush, John

2010-03-01

161

Microwave interaction with nonuniform hydrogen gas in carbon nanotubes  

SciTech Connect

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.

Babaei, S. [Department of Physics, Amirkabir University of Technology, Tehran 15875-4413 (Iran, Islamic Republic of); Amirkabir Nanotechnology Research Institute (NTRI), Tehran 15914 (Iran, Islamic Republic of); Babaei, Sh. [Department of Electronic Engineering, Isfahan University, Isfahan 81746-73441 (Iran, Islamic Republic of); Amirkabir Nanotechnology Research Institute (NTRI), Tehran 15914 (Iran, Islamic Republic of)

2009-03-15

162

Deuterium isotope effects on the carbon-13 chemical shifts in 2-substituted 2-nonbornyl cations  

SciTech Connect

Deuterium isotope effects on /sup 13/C chemical shifts have been examined as a function of location of deuterium in the C/sub 3/-exo or C/sub 3/-endo positions and as a function of increasing electron demand in the series 2-norbornanone, 2-aryl-2-nonbornyl cations, and 2-methyl-2-norbornyl cation. Comparison with isotope shifts in 2-aryl-2-propyl cations demonstrates a change in the type of response to isotopic perturbation in 2-aryl-2-norbornyl cations as electron demand increases. The results are consistent with the onset of sigma-bridging as electron demand increases. The observed isotope shift at a cation center is suggested to be a sum of contributions from a small upfield shift due to perturbation of the sigma-framework (inductive-type perturbation), a downfield shift due to perturbation of hyperconjugation, and a potentially large upfield shift from perturbation of three-center, two-electron bonding. NMR isotope shifts may be a particularly sensitive probe of sigma-bridging because of the vibrational origin of the isotope effect.

Servis, K.L.; Domenick, R.L.; Forsyth, D.A.; Pan, Y.

1987-11-25

163

Hydrogen Storage on Metal-Doped Ordered Mesoporous Carbons  

E-print Network

Materials Advanced Materials #12;Group Members Ph.D.: P. Patil, D. Saha; P. Teli; K. Pingali; V. UpadhyayulaHydrogen Storage on Metal-Doped Ordered Mesoporous Carbons Shuguang Deng New Mexico State in Ordered Mesoporous Carbon Synthesized by Soft-Template Approach" J. Porous Media, 13, 39-50 (2010). 9

Johnson, Eric E.

164

Methane Decomposition: Production of Hydrogen and Carbon Filaments  

E-print Network

Methane Decomposition: Production of Hydrogen and Carbon Filaments BY T.V. CHOUDHARYa AND D. Fuel cells can be broadly classified into two types; high temperature fuel cells such as molten carbonate fuel cells (MCFCs) and solid oxide polymer fuel cells (SOFCs), which operate at temperatures above

Goodman, Wayne

165

Ion cyclotron resonance frequency heating of deuterium plasmas in the Joint European Torus: Interpretation of measurements of minority hydrogen isotope ion distribution functions  

NASA Astrophysics Data System (ADS)

An iterative method for solving the hot-plasma dispersion relation and computing power deposition during multispecies minority ion cyclotron resonance frequency (ICRF) heating experiments has been presented in a companion paper [D. Testa, W.G.F.Core, and A.Gondhalekar, Phys. Plasmas (this issue)]. Here this method is further developed to model and validate the measurements of minority hydrogen isotope ion distribution functions during multispecies second harmonic ICRF heating of deuterium plasmas in the Joint European Torus [J.Wesson, Tokamaks (Clarendon, Oxford, 1997), pp. 581-603].

Testa, D.; Core, W. G. F.; Gondhalekar, A.

1999-09-01

166

Caesium Free Negative Ion Sources for Neutral Beam Injectors: a Study of Negative Ion Production on Graphite Surface in Hydrogen and Deuterium Plasma  

SciTech Connect

Negative ion generation on HOPG graphite surface has been studied in hydrogen and deuterium plasma. We measure Ion Distribution Function (IDF) of negative ions coming from graphite surface bombarded by positive ions in H{sub 2}/D{sub 2} plasmas. We showed that negative ions flux was proportional to positive ion flux and was strongly dependant on impinging energy. IDF study shows two generation mechanisms are involved: sputtering of adsorbed H/D as negative ions and, in a less important way, double electron capture. We compare H{sub 2}/D{sub 2} plasmas, and point out isotopic effect between H{sup -} and D{sup -} production.

Schiesko, L.; Carrere, M.; Cartry, G.; Layet, J.-M. [Plasma Surface, PIIM, UMR 6633, Universite de Provence-CNRS, Centre Scientifique de Saint Jerome, case 241, 13397 Marseille Cedex 20 (France)

2009-03-12

167

Characterization of hydrogen absorption/desorption states on lithium-carbon-hydrogen system by neutron diffraction  

NASA Astrophysics Data System (ADS)

The nanostructural hydrogenated graphite (CnanoHx) was synthesized from graphite by ball milling under hydrogen (H2) atmosphere. In this product, characteristic hydrogenated states in the form of polarized hydrocarbon groups (?CH, ?CH2, and ?CH3) are realized in the nanoscale. By synthesizing the composite of CnanoHx and lithium hydride (LiH), known as the Li ?C?H system, hydrogen was desorbed at 350°C, which is a lower temperature compared to the decomposition temperature of each component. It is considered that this hydrogen desorption would be induced by destabilization of each hydrogen absorbed state due to an interaction between the polarized C ?H groups in CnanoHx and LiH. Therefore, in order to understand the hydrogen absorption/desorption mechanism of the Li ?C?H system, it is an important issue to investigate the change in the C ?H groups during hydrogen absorption/desorption reactions in the composite. The correlations among atoms contained in this composite are examined by neutron diffraction measurements, where the protium/deuterium (H/D) isotopic substitution was used to clarify the location of hydrogen atoms in this composite. Some C ?D and Li ?D correlations are found from the radial distribution function [RDF(r)] obtained by the neutron diffraction for the CnanoDx and LiD composite. After dehydrogenation, C ?C triple bond and Li ?C bond, ascribed to lithium carbide (Li2C2), are observed. Furthermore, the RDF(r ) corresponding to rehydrogenated composite indicates the presence of not only the Li ?D correlation but also the C ?D one.

Miyaoka, Hiroki; Itoh, Keiji; Fukunaga, Toshiharu; Ichikawa, Takayuki; Kojima, Yoshitsugu; Fuji, Hironobu

2008-09-01

168

In-Situ Cavity Ringdown Spectroscopy of Methane Produced by Chemical Erosion of Carbon Surfaces by Deuterium Ions  

NASA Astrophysics Data System (ADS)

Carbon plasma-facing surfaces in tokamaks are subject to chemical erosion due to hydrocarbon (e.g.CD4,C2D6) formation when deuterium ions and atoms are present. Understanding the formation, transport, breakup, and redeposition of these hydrocarbons is important for predicting the amount of tritium, which will become stored in the walls of ITER during operation. Traditionally, CD4 release from carbon surfaces is estimated by using passive spectroscopy of CD-band emission. Calibration of these measurements requires either complex modeling of the CD4 to CD breakup chain in the plasma or injection of a calibrated flow of CD4 from the material surface. Ideally, one would like a direct, non-perturbing measurement of the methane production at the plasma-facing surface under a variety of plasma conditions. We are developing a technique that accomplishes this by using near-IR cavity ringdown spectroscopy: a high-Q cavity whose optical path includes the near-surface region of the carbon tile allows for in-situ monitoring of CD4 production in the PISCES-A plasma device. By simultaneously measuring the absorption of IR radiation by CD4 molecules and emission of CD-band photons, we can determine the range of plasma conditions where CD emission provides an accurate measure of CD4 release. This work supported by grant DE-FG03-95ER-54301 from the US DoE.

Umstadter, K. R.; Hollmann, E.; Gharavi, M.; Doerner, R.; Tynan, G.

2006-10-01

169

Hydrogen and helium recycling in tokamaks with carbon walls  

NASA Astrophysics Data System (ADS)

This paper presents a review of hydrogen and helium recycling phenomena in tokamaks with limiters and walls largely made out of carbon (graphite, a-C:H layers). The key points of interest are the plasma fuelling efficiency, the wall pumping phenomena as observed in JET, TFTR, TEXTOR and other machines under various fuelling schemes (gas, neutral beams, pellets), the release of hydrogen/helium from material surfaces during and after plasma discharges and the long term retention (total particle inventory) of hydrogen in graphite or carbonised structures in tokamaks. The effect of a combined hydrogen/helium plasma on recycling is also discussed. It is shown that only part of the above phenomena can be understood in terms of processes between hydrogen/helium and carbon as known from simulation experiments (ion beams, gas discharge facilities) and that others (in particular the JET wall pumping phenomenon) have still to be explained. Possible mechanisms are outlined and discussed by means of global models.

Ehrenberg, J.; Coad, P.; De Kock, L.; Erents, S. K.; Gondhalekar, A.; Goodall, D.; Hancock, J.; Harbour, P.; Jones, T. T. C.; McCracken, G.; Morgan, P.; Nicholson, C.; Neill, G.; O'Rourke, J.; Partridge, J.; Pick, M.; Simpson, J.; Sonnenberg, K.; Stevens, A.; Stamp, M.; Stott, P.; Summers, D.; Tagle, T.; Vince, J.

1989-04-01

170

Controlled carbon nitride growth on surfaces for hydrogen evolution electrodes.  

PubMed

Efficient and low-cost electrocatalysts for the hydrogen evolution reaction are highly desired for future renewable energy systems. Described herein is the reduction of water to hydrogen using a metal-free carbon nitride electrocatalyst which operates in neutral and alkaline environments. An efficient, easy, and general method for growing ordered carbon nitride on different electrodes was developed. The metal-free catalyst demonstrates low overpotential values, which are comparable to those of non-noble metals, with reasonable current densities. The facile deposition method enables the fabrication of many electronic and photoelectronic devices based on carbon nitride for renewable energy applications. PMID:24574144

Shalom, Menny; Gimenez, Sixto; Schipper, Florian; Herraiz-Cardona, Isaac; Bisquert, Juan; Antonietti, Markus

2014-04-01

171

TENSILE TESTING OF CARBON STEEL IN HIGH PRESSURE HYDROGEN  

SciTech Connect

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.

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

2007-05-02

172

Mass spectral characterization of ergot alkaloids by electrospray ionization, hydrogen/deuterium exchange, and multiple stage mass spectrometry: Usefulness of precursor ion scan experiments.  

PubMed

Six ergot alkaloids belonging to the lysergic acid derivatives (ergonovine (EGN) and methysergide hydrogen maleinate (MHM)) and peptide-type derivatives (ergocristine (EGR), ergotamine (EGT), ergocornine (EGC) and alpha-ergokryptine (EGK)) were studied by positive electrospray tandem mass spectrometry. The fragmentation mechanisms of these compounds were studied by collision-induced dissociation (CID) using triple quadrupole and ion trap mass spectrometers, and the nature of the major product ions further confirmed by hydrogen/deuterium (H/D) exchange experiments. A common abundant product ion at m/z 223 was characteristic of the two classes of ergot alkaloids. Therefore, a precursor ion scan of m/z 223 that triggers information data acquisition (IDA) in combination with CID experiments was used to identify other potential ergot alkaloids. Using this approach, it was possible to confirm the presence of ergosine, another peptide-type ergot alkaloid, in a rye flour extract at trace levels. PMID:16941545

Mohamed, Rayane; Gremaud, Eric; Tabet, Jean-Claude; Guy, Philippe A

2006-01-01

173

Assessing Carbon and Hydrogen Isotopic Fractionation of Diesel Fuel n-alkanes During Progressive Evaporation.  

PubMed

Compound-specific isotope analysis offers potential for fingerprinting of diesel fuels, however, possible confounding effects of isotopic fractionation due to evaporation need to be assessed. This study measured the fractionation of the stable carbon and hydrogen isotopes in n-alkane compounds in neat diesel fuel during evaporation. Isotope ratios were measured using a continuous flow gas chromatograph/isotope ratio mass spectrometer. Diesel samples were progressively evaporated at 24 ± 2°C for 21 days. Increasing depletion of deuterium in nC12 -nC17 alkanes in the remaining liquid with increasing carbon chain length was observed. Negligible carbon isotope fractionation was observed. Preferential vaporization was measured for the shorter chain n-alkanes and the trend decreased with increasing chain length. The decrease in ?(2) H values indicates the preferential vaporization of the isotopically heavier species consistent with available quantitative data for hydrocarbons. These results are most important in the application of stable isotope technology to forensic analysis of diesel. PMID:25131396

Muhammad, Syahidah A; Hayman, Alan R; Van Hale, Robert; Frew, Russell D

2015-01-01

174

Accessibility changes within diphtheria toxin T domain when in the functional molten globule state, as determined using hydrogen/deuterium exchange measurements.  

PubMed

The translocation domain (T domain) of diphtheria toxin adopts a partially folded state, the so-called molten globule state, to become functional at acidic pH. We compared, using hydrogen/deuterium exchange experiments associated with MS, the structures of the T domain in its soluble folded state at neutral pH and in its functional molten globule state at acidic pH. In the native state, the alpha-helices TH5 and TH8 are identified as the core of the domain. Based on the high-resolution structure of the T domain, we propose that TH8 is highly protected because it is buried within the native structure. According to the same structure, TH5 is partly accessible at the surface of the T domain. We propose that its high protection is caused by the formation of dimers. Within the molten globule state, high protection is still observed within the helical hairpin TH8-TH9, which is responsible for the insertion of the T domain into the membrane. In the absence of the lipid bilayer, this hydrophobic part of the domain self-assembles, leading to the formation of oligomers. Overall, hydrogen/deuterium-exchange measurements allow the analysis of interaction contacts within small oligomers made of partially folded proteins. Such information, together with crystal structure data, are particularly valuable for using to analyze the self-assembly of proteins. PMID:20050921

Man, Petr; Montagner, Caroline; Vitrac, Heidi; Kavan, Daniel; Pichard, Sylvain; Gillet, Daniel; Forest, Eric; Forge, Vincent

2010-02-01

175

Computational Investigation and Hydrogen/Deuterium Exchange of the Fixed Charge Derivative Tris(2,4,6-Trimethoxyphenyl)Phosphonium: Implications for the Aspartic Acid Cleavage Mechanism  

SciTech Connect

Aspartic acid (Asp)-containing peptides with the fixed charge derivative tris(2,4,6-trimethoxyphenyl) phosphonium (tTMP-P+) were explored computationally and experimentally by H/D exchange and fragmentation studies in order to probe the phenomenon of selective cleavage C-terminal to Asp in the absence of a ''mobile'' proton. Ab initio modeling of the tTMP-P+ electrostatic potential demonstrates the positive charge is distributed on the phosphonium group and therefore is not initiating or directing fragmentation as would a ''mobile'' proton. Geometry optimizations and vibrational analyses of different aspartic acid conformations show the aspartic acid structure with a hydrogen bond between the side chain hydroxy and backbone carbonyl lies 2.8 kcal/mol above the lowest energy conformer. In reactions with D2O, the phosphonium-derived doubly charged peptide (H+)P+LDIFSDF rapidly exchanges all 12 of its exchangeable hydrogens for deuterium and also displays a non-exchanging population. With no added proton, P+LDIFSDF exchanges a maximum of four of eleven exchangeable hydrogens for deuterium. No exchange is observed when all acidic groups are converted to the corresponding methyl esters. Together, these H/D exchange results indicate that the acidic hydrogens are ''mobile locally'' because they are able to participate in exchange even in the absence of an added proton. Fragmentation of two distinct (H+)P+LDIFSDF ion populations shows the non-exchanging population displays selective cleavage, while the exchanging population fragments more evenly across the peptide backbone. This result demonstrates that H/D exchange can sometimes distinguish between and provide a means of separation of different protonation motifs, and that these protonation motifs can have an effect on the fragmentation.

Herrmann, Kristin A.; Wysocki, Vicki H.; Vorpagel, Erich R.

2005-05-25

176

Methanation of gas streams containing carbon monoxide and hydrogen  

DOEpatents

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.

Frost, Albert C. (Congers, NY)

1983-01-01

177

Theoretical analysis of hydrogen spillover mechanism on carbon nanotubes  

PubMed Central

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.

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

2015-01-01

178

Effects of hydrogen adsorption on single-wall carbon nanotubes: Metallic hydrogen decoration O. Gulseren,1,2  

E-print Network

Effects of hydrogen adsorption on single-wall carbon nanotubes: Metallic hydrogen decoration O. Gu¨lseren,1,2 T. Yildirim,1 and S. Ciraci3 1 NIST Center for Neutron Research, National Institute of Standards of carbon nanotubes undergo dramatic changes with hydrogen chemisorption from first principle calculations

Yildirim, Taner

179

Molecular dynamics simulations of amorphous hydrogenated carbon under high hydrogen fluxes.  

PubMed

We study the flux dependence of the carbon erosion yield and the hydrogen enrichment of the surface in the high flux regime at 10(28) ions per m(2) s and higher by using molecular dynamics (MD). We simulate an amorphous hydrogenated carbon sample exposed to high flux hydrogen bombardment with a hydrogen energy of 10 eV at surface temperatures of 700 and 1000 K. As interaction potential the reactive empirical bond order potential of Brenner-Beardmore is taken and energy dissipation is simulated with the Berendsen thermostat. The simulation results show that the carbon erosion yield is higher for higher sample temperatures but does not show a strong dependence on the hydrogen flux. Hence, the hydrogen enrichment in the upper surface layer observed in the simulations most likely does not contribute to the erosion yield reduction in the experiments. Furthermore, the composition of the eroded material shows a slight increase in CH, C(2)H and C(2)H(2) for higher fluxes, whereas species with more hydrogen, C atoms and C(2) are decreased. However, the H : C ratio in the eroded material shows no flux dependence. PMID:19851562

de Rooij, E D; von Toussaint, U; Kleyn, A W; Goedheer, W J

2009-11-14

180

Deuterium and carbon-13 tagging studies of the plasma pyrolysis of coal  

Microsoft Academic Search

When coal is pyrolyzed in a high temperature plasma, acetylene is the principal hydrocarbon product formed; it was found, furthermore, that yields of acetylene in a hydrogen plasma are greater than in an argon plasma. In order to separate the process of hydrocarbon formation during coal pyrolysis from the subsequent quenching step, acetylene decomposition studies were carried out. Acetylene was

V. J. Krukonis; R. E. Gannon; M. Modell

1976-01-01

181

Nanopores of carbon nanotubes as practical hydrogen storage media  

SciTech Connect

We report on hydrogen desorption mechanisms in the nanopores of multiwalled carbon nanotubes (MWCNTs). The as-grown MWCNTs show continuous walls that do not provide sites for hydrogen storage under ambient conditions. However, after treating the nanotubes with oxygen plasma to create nanopores in the MWCNTs, we observed the appearance of a new hydrogen desorption peak in the 300-350 K range. Furthermore, the calculations of density functional theory and molecular dynamics simulations confirmed that this peak could be attributed to the hydrogen that is physically adsorbed inside nanopores whose diameter is approximately 1 nm. Thus, we demonstrated that 1 nm nanopores in MWCNTs offer a promising route to hydrogen storage media for onboard practical applications.

Han, Sang Soo; Kim, Hyun Seok; Han, Kyu Sung; Lee, Jai Young; Lee, Hyuck Mo; Kang, Jeung Ku; Woo, Seong Ihl; Duin, Adri C.T. van; Goddard, William A. III [Department of Materials Science and Engineering, KAIST, Daejeon 305-701 (Korea, Republic of); Department of Chemical and Biomolecular Engineering, KAIST, Daejeon 305-701 (Korea, Republic of); Materials and Process Simulation Center, California Institute of Technology, California 91125 (United States)

2005-11-21

182

METHOD FOR PRODUCING DEUTERIUM WHEN SYNTHESIZING AMMONIA  

Microsoft Academic Search

Deuterium can be produced by means of hydrogen exchange reactions ; between the hydrogen molecules and ammonia in the presence of a catalyst or by ; means of distillation. The method described is for producing a base material for ; this process which is already enriched in deuterium. It comprises the steps of ; separating ammonia, nitrogen, and inert gases

G. Schaurer; A. Heinzel

1963-01-01

183

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)

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.

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

2012-04-01

184

Activated carbon fiber composites for ammonia, methane and hydrogen adsorption  

Microsoft Academic Search

Complex compound material (activated carbon fiber, saturated with salts, or metal hydrides) was developed as an efficient gas (ammonia, methane, hydrogen) adsorbent for new gas storage and transportation system application. To enhance the performance and thermodynamic efficiency of the gas storage vessels a heat pipe thermal control system was suggested. Copyright , Manchester University Press.

L. L. Vasiliev; L. E. Kanonchik; A. G. Kulakov; D. A. Mishkinis; A. M. Safonova; N. K. Luneva

2006-01-01

185

Carbon phases versus hydrogen phases: neutral gas in nearby galaxies  

NASA Astrophysics Data System (ADS)

Due to its lower-than-hydrogen first ionization energy, atomic carbon is ionized throughout the diffuse ISM, tracing both regions of ioinized and neutral hydrogen gas. On the other hand, carbon monoxide (CO) exists and emits exclusively where hydrogen is in molecular form. Neutral atomic carbon is predicted to exist in between these phases, but recent evidence in our Galaxy and from simulations show it may be closely tied to the molecular gas than previously thought. Here, we investigate the gas in various carbon stages (evidenced through emission in [CII], [CI] and CO) compared to hydrogen stages (through ?CO-corrected CO for H2 and HI emission). The observations are based upon the Beyond the Peak sample of 22 galaxies with data from the Herschel Space Observatory SPIRE FTS instrument, as well as relying on ground-based CO and HI observations. Based on these comparisons, [CI] does trace CO well and thus may provide a good way to trace molecular gas in external galaxies as well as in molecular clouds in the Milky Way.

Crocker, Alison Faye; Pellegrini, Eric; Smith, John-David T.; Beyond the Peak Team

2015-01-01

186

OXYGEN, CARBON, AND HYDROGEN ISOTOPE STUDIES CONTACT METAMORPHISM  

E-print Network

OXYGEN, CARBON, AND HYDROGEN ISOTOPE STUDIES OF CONTACT METAMORPHISM Thesis by Yuch-Ning Shieh. Hugh P. Taylor, Jr. for encouragement and guidance throughout the course of this research. I om wife, Tiee-leou, for her encouragement and assistance during this study. This research was supported

Winfree, Erik

187

Hydrogen Storage in Carbon Nanotubes Through the Formation of Stable C-H Bonds  

SciTech Connect

To determine if carbon-based materials can be used for hydrogen storage, we have studied hydrogen chemisorption in single-walled carbon nanotubes. Using atomic hydrogen as the hydrogenation agent, we demonstrated that maximal degree of nanotube hydrogenation depends on the nanotube diameter, and for the diameter values around 2.0 nm nanotube-hydrogen complexes with close to 100% hydrogenation exist and are stable at room temperature. This means that specific carbon nanotubes can have a hydrogen storage capacity of more than 7 wt % through the formation of reversible C-H bonds.

Nikitin, A.; Li, X.L.; Zhang, Z.Y.; Ogasawara, H.; Dai, H.J.; Nilsson, A.; /SLAC, SSRL /Stanford U., Chem. Dept. /Stockholm U.

2009-04-30

188

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

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. A 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

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

2014-09-01

189

Hydrogen Bonds Involved in Binding the Qi-site Semiquinone in the bc1 Complex, Identified through Deuterium Exchange  

E-print Network

Hydrogen Bonds Involved in Binding the Qi-site Semiquinone in the bc1 Complex, Identified through them. The strength of interactions indicates that the protons are involved in hydrogen bonds with SQ. The hyperfine cou- plings differ from values typical for in-plane hydrogen bonds previously observed in model

Crofts, Antony R.

190

Negative-ion production on carbon materials in hydrogen plasma: Influence of the carbon hybridization state and the hydrogen content on H-  

E-print Network

1 Negative-ion production on carbon materials in hydrogen plasma: Influence of the carbon, The Netherlands Key words: Negative-ions, hydrogen plasma, mass spectrometer, carbon materials, Negative-ion H- ions due to bombardment of positive ions from the plasma are measured by an energy analyzer cum

Boyer, Edmond

191

Hydrogenation of Single-Wall Carbon Nanotubes Using Polyamine Reagents: Combined Experimental and  

E-print Network

oxidation of SWNTs using some combination of sulfuric acid, nitric acid, and occasionally hydrogen peroxide9Hydrogenation of Single-Wall Carbon Nanotubes Using Polyamine Reagents: Combined Experimental hydrogenation of single-wall carbon nanotubes using high boiling polyamines as hydrogenation reagents. Our

192

Nucleotide- and activator-dependent structural and dynamic changes of Arp2/3 complex monitored by hydrogen/deuterium exchange and mass spectrometry  

PubMed Central

Arp2/3 complex plays a central role in the de novo nucleation of filamentous actin as branches on existing filaments. To form a new actin filament the complex must bind ATP, protein activators (e.g. Wiskott-Aldrich syndrome proteins, WASp) and the side of an actin filament. Amide Hydrogen/Deuterium exchange (HDX) coupled with mass spectrometry (MS) was used to examine the structural and dynamic properties of the mammalian Arp2/3 complex in the presence of both ATP and the activating peptide segment from WASp. Changes in the rate of hydrogen exchange indicate that ATP binding causes conformational rearrangements of Arp2 and Arp3 that are transmitted allosterically to the ArpC1, ArpC2, ArpC4 and ArpC5 subunits. These data are consistent with the closure of nucleotide-binding cleft of Arp3 upon ATP binding, resulting in structural rearrangements that propagate throughout the complex. Binding of the VCA domain of WASp to ATP-Arp2/3 further modulates the rates of hydrogen exchange in these subunits, indicating that a global conformational reorganization is occurring. These effects may include the direct binding of activators to Arp3, Arp2 and ARPC1; alterations in the relative orientations of Arp2 and Arp3; and the long-range transmission of activator-dependent signals to segments proposed to be involved in binding the F-actin mother filament. PMID:19298826

Zencheck, Wendy D.; Xiao, Hui; Nolen, Bradley J.; Angeletti, Ruth; Pollard, Thomas D.; Almo, Steven C.

2010-01-01

193

Shock compression of precompressed deuterium  

SciTech Connect

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.

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

2011-07-31

194

Selective Removal of Hydrogen Sulfide from Gases Containing Hydrogen Sulfide and Carbon Dioxide Using Diethanolamine  

Microsoft Academic Search

It is sometimes necessary to selectively remove hydrogen sulfide from gases containing carbon dioxide. This may be the case for example in the production of sulfur using the Claus process. When two gases are simultaneously absorbed into a solution containing a reactant with which each gas can react, the rate of absorption of each component is affected by the presence

N. Haimour; O. C. Sandall

1983-01-01

195

Microwave absorption of magnetized hydrogen plasma in carbon nanotubes  

SciTech Connect

A simple model to describe the microwave absorption of magnetized hydrogen plasma embedded inside the carbon nanotubes (CNTs), which were grown by iron-catalyzed high-pressure disproportionation (HiPco), is proposed and analyzed. By using Maxwell equations in conjunction with a general expression of the complex permittivity of magnetized hydrogen plasma in HiPco CNTs, known as the Appleton-Hartree formula, the absorption coefficients of the system for right-hand circularly wave propagation along and across the static magnetic field are obtained. The effects of the continuously changing the electron density, the collision frequency, and the cyclotron frequency on the absorption of the microwave are discussed.

Moradi, Afshin [Department of Nano Science, Kermanshah University of Technology, Kermanshah (Iran, Islamic Republic of) and Department of Nano Science, Institute for Studies in Theoretical Physics and Mathematics (IPM), Tehran (Iran, Islamic Republic of)

2009-11-15

196

Amorphous carbon enhancement of hydrogen penetration into UO2  

NASA Astrophysics Data System (ADS)

The interaction of D2 and H2O (humidity) with amorphous carbon covered UO2 vs. clean UO2 was studied using Secondary Ion Mass Spectrometry (SIMS) and X-ray Photoelectron Spectroscopy (XPS). It was found that SIMS depth profiles of the carbon covered side vs. the bare oxide, show significant higher intensities of H- and D- for the first, through the carbon layer and beneath it. The presence of a thin carbon layer on a UO2 surface caused a significant buildup of hydroxyl, probably adsorbed on the carbon, but maybe also beneath the layer, in the presence of atmospheric humidity. Exposure of the carbon covered oxide to D2 on a UHV annealed surface also caused a growth of the hydroxyl. It is concluded that the carbon surface strongly enhances the dissociation of water vapor as well as that of hydrogen and the penetration of the dissociation products to the oxide, as compared to the bare UO2 surface. The contribution of the latter, beneath the carbon, should be verified or ruled out by further experiments.

Zalkind, S.; Shamir, N.; Gouder, T.; Akhvlediani, R.; Hoffman, A.

2014-06-01

197

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

E-print Network

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 carbon containing molecules. Aims. We want to check the underlying hypothesis that the 13C/ 12C ratio of nitriles and isonitriles is equal to the elemental value via a chemical time dependent gas phase chemical model. Methods. We have built a chemical network containing 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 2 different physical conditions corresponding respectively to a moderately dense cloud in an early evolutionary stage and a dense depleted pre-stellar core tend to show that ammonia and its singly deuterated form are somewhat enriched in 15N, in agreement with observations. The 14N/ 15N ratio in N2H+ is found to be close to the elemental v...

Roueff, E; Hickson, K M

2015-01-01

198

Renewable hydrogen and carbon nanotubes from biodiesel waste glycerol.  

PubMed

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

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

2013-01-01

199

Renewable hydrogen and carbon nanotubes from biodiesel waste glycerol  

PubMed Central

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

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

2013-01-01

200

Selective removal of hydrogen sulfide from gases containing hydrogen sulfide and carbon dioxide using diethanolamine  

SciTech Connect

It is sometimes necessary to selectively remove hydrogen sulfide from gases containing carbon dioxide. This may be the case for example in the production of sulfur using the Claus process. When two gases are simultaneously absorbed into a solution containing a reactant with which each gas can react, the rate of absorption of each component is affected by the presence of the other gas. For the absorption of hydrogen sulfide into primary and secondary amines, the reaction which occurs can usually be considered to be instantaneous. An instantaneous reaction is diffusion-limited since the reaction occurs so rapidly that the liquid phase reactant and the absorbed gas cannot coexist in the same region of the liquid. For primary and secondary amines used for the gas treatment, the reaction with carbon dioxide is much slower than for hydrogen sulfide and can often be considered to be second order. In this work the simultaneous absorption of two gases into a liquid containing a reactant with which both gases can react is modeled using penetration theory. It is assumed that one gas reacts instantaneously and the other gas undergoes a second order reaction. Parameters used in the calculations are those available in the literature corresponding to the absorption of hydrogen sulfide and carbon dioxide in diethanolamine.

Haimour, N.; Sandall, O.C.

1983-01-01

201

Carbon-Oxygen Hydrogen Bonding in Biological Structure and Function  

PubMed Central

Carbon-oxygen (CH···O) hydrogen bonding represents an unusual category of molecular interactions first documented in biological structures over 4 decades ago. Although CH···O hydrogen bonding has remained generally underappreciated in the biochemical literature, studies over the last 15 years have begun to yield direct evidence of these interactions in biological systems. In this minireview, we provide a historical context of biological CH···O hydrogen bonding and summarize some major advancements from experimental studies over the past several years that have elucidated the importance, prevalence, and functions of these interactions. In particular, we examine the impact of CH···O bonds on protein and nucleic acid structure, molecular recognition, and enzyme catalysis and conclude by exploring overarching themes and unresolved questions regarding unconventional interactions in biomolecular structure. PMID:23048026

Horowitz, Scott; Trievel, Raymond C.

2012-01-01

202

Hydrogenated 5-carbon compound and method of making  

DOEpatents

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.

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

1999-03-16

203

Sulfur and Hydrogen Isotope Anomalies in Meteorite Sulfonic Acids  

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

204

Hydrogen storage reactions on titanium decorated carbon nanocones theoretical study  

NASA Astrophysics Data System (ADS)

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).

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

2014-12-01

205

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

NASA Technical Reports Server (NTRS)

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.

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

1976-01-01

206

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

NASA Astrophysics Data System (ADS)

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.

Adibhatla, Anasuya

207

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

PubMed

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

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

2014-03-01

208

Electrochemical Removal of Carbon Monoxide in Reformate Hydrogen for Fueling Proton Exchange Membrane  

E-print Network

Electrochemical Removal of Carbon Monoxide in Reformate Hydrogen for Fueling Proton Exchange, Austria, Meeting of the Society, October 4­9, 2009. Carbon monoxide CO in hydrogen reformed from carbon by poisoning the anode active sites, as shown in Reaction 1 1-4 Pt + CO Pt­CO 1 To mitigate the detrimental

Weidner, John W.

209

Finite element model for charge and discharge cycle of activated carbon hydrogen storage  

Microsoft Academic Search

One of the main challenges to introduce hydrogen on the energy market is to improve on-board hydrogen storage and develop more efficient distribution technologies to increase the amount of stored gas while lowering the storage pressure. The physisorption of hydrogen on activated carbons (AC) is being investigated as a possible route for hydrogen storage. The objective of this work is

Jinsheng Xiao; Jijuan Wang; Daniel Cossement; Pierre Bénard; Richard Chahine

210

High-resolution mass spectrometry and hydrogen/deuterium exchange study of mitorubrin azaphilones and nitrogenized analogues.  

PubMed

Azaphilones represent numerous groups of wild fungal secondary metabolites that exhibit exceptional tendency to bind to nitrogen atoms in various molecules, especially those containing the amine group. Nitrogenized analogues of mitorubrin azaphilones, natural secondary metabolites of Hypoxylon fragiforme fungus, have been detected in the fungal methanol extract in very low concentrations. Positive electrospray ionization interfaced with high-resolution mass spectrometry was applied for confirmation of the elemental composition of protonated species. Collision-induced dissociation (CID) experiments have been performed, and fragmentation mechanisms have been proposed. Additional information regarding both secondary metabolite analogue families has been reached by application of gas-phase proton/deuterium (H/D) exchanges performed in the collision cell of a triple quadrupole mass spectrometer. An incomplete H/D exchange with one proton less than expected was observed for both protonated mitorubrin azaphilones and their nitrogenized analogues. By means of the density functional theory, an appropriate explanation of this behavior was provided, and it revealed some information concerning gas-phase H/D exchange mechanism and protonation sites. PMID:22899505

Svilar, Ljubica; Stankov-Jovanovic, Vesna; Lesage, Denis; Dossmann, Héloïse; Tabet, Jean-Claude

2012-08-01

211

Gas phase hydrogen permeation in alpha titanium and carbon steels  

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

212

Hydrogen Storage in Single-Walled Carbon Nanotubes at Room Temperature  

Microsoft Academic Search

Masses of single-walled carbon nanotubes (SWNTs) with a large mean diameter of about 1.85 nanometers, synthesized by a semicontinuous hydrogen arc discharge method, were employed for hydrogen adsorption experiments in their as-prepared and pretreated states. A hydrogen storage capacity of 4.2 weight percent, or a hydrogen to carbon atom ratio of 0.52, was achieved reproducibly at room temperature under a

C. Liu; Y. Y. Fan; M. Liu; H. T. Cong; H. M. Cheng; M. S. Dresselhaus

1999-01-01

213

Sites involved in intra- and interdomain allostery associated with the activation of factor viia pinpointed by hydrogen-deuterium exchange and electron transfer dissociation mass spectrometry.  

PubMed

Factor VIIa (FVIIa) is a trypsin-like protease that plays an important role in initiating blood coagulation. Very limited structural information is available for the free, inactive form of FVIIa that circulates in the blood prior to vascular injury and the molecular details of its activity enhancement remain elusive. Here we have applied hydrogen/deuterium exchange mass spectrometry coupled to electron transfer dissociation to pinpoint individual residues in the heavy chain of FVIIa whose conformation and/or local interaction pattern changes when the enzyme transitions to the active form, as induced either by its cofactor tissue factor or a covalent active site inhibitor. Identified regulatory residues are situated at key sites across one continuous surface of the protease domain spanning the TF-binding helix across the activation pocket to the calcium binding site and are embedded in elements of secondary structure and at the base of flexible loops. Thus these residues are optimally positioned to mediate crosstalk between functional sites in FVIIa, particularly the cofactor binding site and the active site. Our results unambiguously show that the conformational allosteric activation signal extends to the EGF1 domain in the light chain of FVIIa, underscoring a remarkable intra- and interdomain allosteric regulation of this trypsin-like protease. PMID:25344622

Song, Hongjian; Olsen, Ole H; Persson, Egon; Rand, Kasper D

2014-12-19

214

Fluoroketone inhibition of Ca(2+)-independent phospholipase A2 through binding pocket association defined by hydrogen/deuterium exchange and molecular dynamics.  

PubMed

The mechanism of inhibition of group VIA Ca(2+)-independent phospholipase A(2) (iPLA(2)) by fluoroketone (FK) ligands is examined by a combination of deuterium exchange mass spectrometry (DXMS) and molecular dynamics (MD). Models for iPLA(2) 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 iPLA(2) should greatly improve our ability to design new inhibitors with higher potency and selectivity. PMID:23256506

Hsu, Yuan-Hao; Bucher, Denis; Cao, Jian; Li, Sheng; Yang, Sheng-Wei; Kokotos, George; Woods, Virgil L; McCammon, J Andrew; Dennis, Edward A

2013-01-30

215

Identification of Pharmacological Chaperones for Gaucher Disease and Characterization of Their Effects on ?-Glucocerebrosidase by Hydrogen/Deuterium Exchange Mass Spectrometry  

PubMed Central

Point mutations in ?-glucocerebrosidase (GCase) can result in a deficiency of both GCase activity and protein in lysosomes thereby causing Gaucher Disease (GD). Enzyme inhibitors such as isofagomine, acting as pharmacological chaperones (PCs), increase these levels by binding and stabilizing the native form of the enzyme in the endoplasmic reticulum (ER), and allow increased lysosomal transport of the enzyme. A high-throughput screen of the 50 000-compound Maybridge library identified two, non-carbohydrate-based inhibitory molecules, a 2,4-diamino-5-substituted quinazoline (IC50 5 ?M) and a 5-substituted pyridinyl-2-furamide (IC50 8 ?M). They raised the levels of functional GCase 1.5–2.5-fold in N370S or F213I GD fibroblasts. Immunofluorescence confirmed that treated GD fibroblasts had decreased levels of GCase in their ER and increased levels in lysosomes. Changes in protein dynamics, monitored by hydrogen/deuterium-exchange mass spectrometry, identified a domain III active-site loop (residues 243–249) as being significantly stabilized upon binding of isofagomine or either of these two new compounds; this suggests a common mechanism for PC enhancement of intracellular transport. PMID:18972510

Tropak, Michael B.; Kornhaber, Gregory J.; Rigat, Brigitte A.; Maegawa, Gustavo H.; Buttner, Justin D.; Blanchard, Jan E.; Murphy, Cecilia; Tuske, Steven J.; Coales, Stephen J.; Hamuro, Yoshitomo; Brown, Eric D.

2010-01-01

216

PAS Domain Allostery and Light-Induced Conformational Changes in Photoactive Yellow Protein upon I2 Intermediate Formation, Probed with Enhanced Hydrogen/Deuterium Exchange Mass Spectrometry  

PubMed Central

Photoactive yellow protein (PYP) is a small bacterial photoreceptor that undergoes a light-activated reaction cycle. PYP is also the prototypical PAS (Per-Arnt-Sim) domain. PAS domains, found in diverse multi-domain proteins from bacteria to humans, mediate protein-protein interactions and function as sensors and signal transducers. Here, we investigate conformational and dynamic changes in solution in wild-type PYP upon formation of the long-lived putative signaling intermediate I2 with enhanced hydrogen/deuterium exchange mass spectrometry (DXMS). The DXMS results showed that the central ?-sheet remains stable but specific external protein segments become strongly deprotected. Light-induced disruption of the dark-state hydrogen-bonding network in I2 produces increased flexibility and opening of PAS core helices ?3 and ?4, releases the ?4-?5 hairpin, and propagates conformational changes to the central ?-sheet. Surprisingly, the first ~10 N-terminal residues, which are essential for fast dark state recovery from I2, become more protected. By combining the DXMS results with our crystallographic structures, which reveal detailed changes near the chromophore, but limited protein conformational change, we propose a mechanism for I2 state formation. This mechanism integrates the results from diverse biophysical studies of PYP, and links an allosteric T- to R-state conformational transition to three pathways for signal propagation within the PYP fold. Based upon the observed changes in PYP plus commonalities shared among PAS domain proteins, we further propose that PAS domains share this conformational mechanism, which explains the versatile signal transduction properties of the structurally conserved PYP/PAS module by framework-encoded allostery. PMID:16952373

Brudler, Ronald; Gessner, Chris R.; Li, Sheng; Tyndall, Sammy; Getzoff, Elizabeth D.; Woods, Virgil L.

2008-01-01

217

Simultaneous deuterium implantation and ion beam microanalyses in CFC NB31: Understanding the in-bulk migration  

NASA Astrophysics Data System (ADS)

Understanding the dynamic of in-depth migration and retention of hydrogen in Carbon Fiber Composites (CFCs) used as plasma facing material has for long time been complicated by the lack on in situ analyzing tools. A dedicated experimental setup coupling an ECR ion source to the Saclay nuclear microprobe was developed to expose CFC samples to deuterium implantation at 200-300 eV and fluences from 1022 to 1024 D/m2, and then to perform in situ ?NRA analysis for 3D deuterium profiles. Once the technique proven as non perturbative, we observed that while we have a homogeneous, fluence-independent deuterium concentration at the surface, the in-bulk deuterium is concentrated in the porosities and increases with the incident fluence, up to very large depth (500 ?m). For the first time, it was evidenced that these two distinct mechanisms are simultaneous to the implantation. D profiles evolve very little with in-vacuum storage time.

Bernard, E.; Khodja, H.; Chêne, J.; Pégourié, B.; Martin, C.; Pardanaud, C.

2013-07-01

218

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....

219

Performance of carbon-based hot frit substrates: I, Low pressure helium and hydrogen testing  

SciTech Connect

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.

Barletta, R.; Adams, J.; Svandrlik, J.; Powell, J.R.

1993-07-01

220

Membrane-based systems for carbon capture and hydrogen purification  

SciTech Connect

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.

Berchtold, Kathryn A [Los Alamos National Laboratory

2010-11-24

221

Combustion characteristics of hydrogen. Carbon monoxide based gaseous fuels  

NASA Technical Reports Server (NTRS)

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.

Notardonato, J. J.; White, D. J.; Kubasco, A. J.; Lecren, R. T.

1981-01-01

222

Novel role of boron on carbon-based hydrogen storage  

NASA Astrophysics Data System (ADS)

Carbon materials such as fullerenes and nanotubes are one of the promising materials for hydrogen storage. To increase H intake, however, a lot remains to be done. First principles calculations show that in such materials, substitutional boron can greatly increase the binding between hydrogen molecules and the carbon hosts, via a non-classical chemical binding mechanism in which the two un-dissociated H atoms in the molecule and the B atom form a three-body center, sharing two common electrons. The calculated binding energy can be as large as 0.4 eV, versus the typical van der Waals energy of 0.08 eV, per H2. Our analysis further reveals that the enhanced binding is a result of strong exchange-correlation interaction among the s electrons shared by the Hs and B. Noticeable level splitting and shift are observed for the B s state but not for the B p states. By maximizing the B concentration, the calculated upper limit on the H storage in these systems is 4.17 wt %. Supported by the U. S. DOE/EERE and BES under contract No. DE-AC36-99GO10337.

Kim, Yong-Hyun; Zhao, Yufeng; Zhang, S. B.

2004-03-01

223

Gas-driven hydrogen isotopes permeation through different carbon materials  

NASA Astrophysics Data System (ADS)

Hydrogen gas driven permeation through the fine-grain graphites MPG-8 and R5710, and through CFC NB31 in two main directions has been investigated for sample thicknesses of 1-7 mm and pressures from 10 -2-10 Pa. The gas driven permeation occurs through the carbon-base materials by the hydrogen molecular gas flow through the internal porosity network rather than hydrogen atom diffusion through the graphite lattice. The permeabilities of MPG-8 and Nb31 are of the same order, while the permeability of R5710 is two orders of magnitude less. The specific bulk conductivity is about 5 × 10 15 molecules s -1 m -1 Pa -1 for MPG-8; 8 × 10 13 molecules s -1 m -1 Pa -1 for R5710; 1 × 10 16 molecules s -1 m -1 Pa -1 for Nb31 along ex-pitch ( x) fibers after taking into account the perforated surface layer and 0.8 × 10 16 molecules s -1 m -1 Pa -1 for Nb31 along needled ( z) fibers.

Spitsyn, A. V.; Golubeva, A. V.; Mayer, M.; Skovoroda, A. A.

2009-06-01

224

Single Membrane Reactor Configuration for Separation of Hydrogen, Carbon Dioxide and Hydrogen Sulfide  

SciTech Connect

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 stea

Micheal Roberts; Robert Zabransky; Shain Doong; Jerry Lin

2008-05-31

225

Study on reaction rates for methanol synthesis from carbon monoxide, carbon dioxide, and hydrogen  

Microsoft Academic Search

The reaction rates for methanol synthesis from carbon monoxide, carbon dioxide, and hydrogen over a copper-zinc-based catalyst were measured under the following conditions: temperature, 210-300°C; pressure, 4-10 MPa, feed gas composition Hâ\\/CO 2.7-720, Hâ\\/COâ, 4.3-120, COâ\\/CO, 0.05-180 (in moles). It was concluded that direct methanol production from COâ takes place under the above conditions in addition to the two well-known

M. Takagawa; M. Ohsugi

1987-01-01

226

Cleaner pathways of hydrogen, carbon nano-materials and metals production via solar thermal processing  

Microsoft Academic Search

This paper describes various solar thermochemical processes for the production of hydrogen, carbon nano particles, industrial grade carbon black, and metals with substantially reduced CO2 emission footprint. The paper introduces an innovative approach of a three-dimensional volumetric production of carbon nano particles via thermal cracking of methane gained by carbon seeding as an alternative to the existing two dimensional modes.

Nesrin Ozalp; Michael Epstein; Abraham Kogan

2010-01-01

227

Modulated hydrogen beam study of adsorption-induced desorption of deuterium from Si(100)-3×1:D surfaces  

NASA Astrophysics Data System (ADS)

We have studied the kinetic mechanism of the adsorption-induced-desorption (AID) reaction, H+D/Si(100)?D2. Using a modulated atomic hydrogen beam, two different types of AID reaction are revealed: one is the fast AID reaction occurring only at the beam on-cycles and the other the slow AID reaction occurring even at the beam off-cycles. Both the fast and slow AID reactions show the different dependence on surface temperature Ts, suggesting that their kinetic mechanisms are different. The fast AID reaction overwhelms the slow one in the desorption yield for 300 K?Ts?650 K. It proceeds along a first-order kinetics with respect to the incident H flux. Based on the experimental results, both two AID reactions are suggested to occur only on the 3×1 dihydride phase accumulated during surface exposure to H atoms. Possible mechanisms for the AID reactions are discussed.

Rahman, F.; Kuroda, M.; Kiyonaga, T.; Khanom, F.; Tsurumaki, H.; Inanaga, S.; Namiki, A.

2004-08-01

228

Thermocatalytic process for CO.sub.2-free production of hydrogen and carbon from hydrocarbons  

DOEpatents

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.

Muradov, Nazim Z. (Melbourne, FL)

2011-08-23

229

Low-molecular-weight carbon nitrides for solar hydrogen evolution.  

PubMed

This work focuses on the control of the polymerization process for melon ("graphitic carbon nitride"), with the aim of improving its photocatalytic activity intrinsically. We demonstrate here that reduction of the synthesis temperature leads to a mixture of the monomer melem and its higher condensates. We show that this mixture can be separated and provide evidence that the higher condensates are isolated oligomers of melem. On evaluating their photocatalytic activity for hydrogen evolution, the oligomers were found to be the most active species, having up to twice the activity of the monomer/oligomer mixture of the as-synthesized material, which in turn has 3 times the activity of the polymer melon, the literature benchmark. These results highlight the role of "defects", i.e., chain terminations, in increasing the catalytic activity of carbon nitrides and at the same time point to the ample potential of intrinsically improving the photocatalytic activity of "carbon nitride", especially through the selective synthesis of the active phase. PMID:25537611

Lau, Vincent Wing-Hei; Mesch, Maria B; Duppel, Viola; Blum, Volker; Senker, Jürgen; Lotsch, Bettina V

2015-01-28

230

CONTENT OF CARBON, HYDROGEN AND SULPHUR IN BIOMASS OF SOME SHRUB WILLOW SPECIES  

Microsoft Academic Search

Carbon, hydrogen and sulphur were determined in biomass (shoots and roots) of five species of shrub willow: Salix viminalis, Salix dasyclados, Salix triandra, Salix purpurea and Salix alba. Samples of the biomass collected from a strict experiment were dried to constant weight at 105oC. The content of carbon, hydrogen and sulphur was determined in an automatic determinator ELTRA CHS 500.

Mariusz Stolarski

2008-01-01

231

Development of Affordable, Low-Carbon Hydrogen Supplies at an Industrial Scale  

ERIC Educational Resources Information Center

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…

Roddy, Dermot J.

2008-01-01

232

Transition-State Charge Transfer Reveals Electrophilic, Ambiphilic, and Nucleophilic Carbon-Hydrogen Bond Activation  

E-print Network

@scripps.edu To capture the powerful potential of metal-mediated carbon- hydrogen (C-H) bond activation, it is essentialTransition-State Charge Transfer Reveals Electrophilic, Ambiphilic, and Nucleophilic Carbon-Hydrogen Bond Activation Daniel H. Ess,*,, Robert J. Nielsen, William A. Goddard III,*, and Roy A. Periana

Goddard III, William A.

233

A STUDY TO EVALUATE CARBON MONOXIDE AND HYDROGEN SULFIDE CONTINUOUS EMISSION MONITORS AT AN OIL REFINERY  

EPA Science Inventory

An eleven month field evaluation was done on five hydrogen sulfide and four carbon monoxide monitors located at an oil refinery. The hydrogen sulfide monitors sampled a fuel gas feed line and the carbon monoxide monitors sampled the emissions from a fluid cat cracker (FCC). Two o...

234

Hydrogen induced redox mechanism in amorphous carbon resistive random access memory  

PubMed Central

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

2014-01-01

235

Industrial Scale Measurements of Hydrogen Uptake and Delivery in KOH Activated Carbons  

NASA Astrophysics Data System (ADS)

The Alliance for Collaborative Research in Alternative Fuel Technologies (ALL-CRAFT) has been producing high surface area activated carbons. Here we will investigate the hydrogen adsorption characteristics of these activated carbons using a custom built 10 liter hydrogen adsorption apparatus filled with 4 kg of activated carbon. We will discuss problems and solutions specific to filling and delivering hydrogen from industrial scale systems. Results show that activated carbons can produce a significant but surmountable, amount of impedance to hydrogen flow. The 10 liter hydrogen storage system measures adsorption at temperatures between -78 Celsius and 100 Celsius and at pressures between zero and 100 bar. The 10 liter hydrogen adsorption uptakes are compared against results obtained with the Hiden Isochema HTP1 volumetric gas analyzer.

Rash, Tyler; Stalla, Dave; Beckner, Matt; Romanos, Jimmy; Suppes, G.; Tekeei, A.; Buckley, P.; Doynov, P.; Pfeifer, Peter

2012-02-01

236

Assessment of differences in the conformational flexibility of hepatitis B virus core-antigen and e-antigen by hydrogen deuterium exchange-mass spectrometry.  

PubMed

Hepatitis B virus core-antigen (capsid protein) and e-antigen (an immune regulator) have almost complete sequence identity, yet the dimeric proteins (termed Cp149d and Cp(-10)149d , respectively) adopt quite distinct quaternary structures. Here we use hydrogen deuterium exchange-mass spectrometry (HDX-MS) to study their structural properties. We detect many regions that differ substantially in their HDX dynamics. Significantly, whilst all regions in Cp(-10)149d exchange by EX2-type kinetics, a number of regions in Cp149d were shown to exhibit a mixture of EX2- and EX1-type kinetics, hinting at conformational heterogeneity in these regions. Comparison of the HDX of the free Cp149d with that in assembled capsids (Cp149c ) indicated increased resistance to exchange at the C-terminus where the inter-dimer contacts occur. Furthermore, evidence of mixed exchange kinetics were not observed in Cp149c , implying a reduction in flexibility upon capsid formation. Cp(-10)149d undergoes a drastic structural change when the intermolecular disulphide bridge is reduced, adopting a Cp149d -like structure, as evidenced by the detected HDX dynamics being more consistent with Cp149d in many, albeit not all, regions. These results demonstrate the highly dynamic nature of these similar proteins. To probe the effect of these structural differences on the resulting antigenicity, we investigated binding of the antibody fragment (Fab E1) that is known to bind a conformational epitope on the four-helix bundle. Whilst Fab E1 binds to Cp149c and Cp149d , it does not bind non-reduced and reduced Cp(-10)149d , despite unhindered access to the epitope. These results imply a remarkable sensitivity of this epitope to its structural context. PMID:24715628

Bereszczak, Jessica Z; Watts, Norman R; Wingfield, Paul T; Steven, Alasdair C; Heck, Albert J R

2014-07-01

237

Role of calcium in the conformational dynamics of factor XIII activation examined by hydrogen-deuterium exchange coupled with MALDI-TOF MS.  

PubMed

Factor XIII catalyzes formation of ?-glutamyl-?-lysyl crosslinks within fibrin clots. FXIII A(2) can be activated proteolytically with thrombin and low mM Ca(2+) or nonproteolytically with high monovalent/divalent cations along with low mM Ca(2+). Physiologically, FXIII A(2) is poised to respond to transient influxes of Ca(2+) in a Na(+) containing environment. A successful strategy to monitor FXIII conformational events is hydrogen-deuterium exchange (HDX) coupled with mass spectrometry. FXIII A(2) was examined in the presence of different cations (Ca(2+), Mg(2+), Ba(2+), Cu(2+), Na(+), TMAC(+), and EDA(2+)) ranging from 1 to 2mM, physiological Ca(2+) concentration, to 50-500mM for nonproteolytic activation. Increases in FXIII solvent exposure could already be observed at 1mM Ca(2+) for the dimer interface, the catalytic site, and glutamine substrate regions. By contrast, solvent protection was observed at the secondary cleavage site. These events occurred even though 1mM Ca(2+) is insufficient for FXIII activation. The metals 1mM Mg(2+), 1mM Ba(2+), and 1mM Cu(2+) each led to conformational changes, many in the same FXIII regions as Ca(2+). FXIII could also be activated nonproteolytically with 500mM tetramethylammonium chloride (TMAC(+)) and 500mM ethylenediamine (EDA(2+)), both with 2mM Ca(2+). These different HDX studies help reveal the first FXIII segments that respond to physiological Ca(2+) levels. PMID:21640701

Woofter, Ricky T; Maurer, Muriel C

2011-08-01

238

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

PubMed

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

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

2014-04-01

239

Catalytic Metal Free Production of Large Cage Structure Carbon Particles: A Candidate for Hydrogen Storage  

NASA Technical Reports Server (NTRS)

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.

Kimura, Yuki; Nuth, Joseph A., III; Ferguson, Frank T.

2005-01-01

240

Apparatus for hydrogen and carbon production via carbon aerosol-catalyzed dissociation of hydrocarbons  

NASA Technical Reports Server (NTRS)

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.

Muradov, Nazim Z. (Inventor); Smith, Franklyn (Inventor); Tabatabaie-Raissi, Ali (Inventor)

2012-01-01

241

Alignment of nematic LCs on surface of amorphous hydrogenated carbon  

NASA Astrophysics Data System (ADS)

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.

Konshina, Elena A.

1996-01-01

242

Kinetic modelling of molecular hydrogen transport in microporous carbon materials.  

SciTech Connect

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.

Hankel, M.; Zhang, H.; Nguyen, T. X.; Bhatia, S. K.; Gray, S. K.; Smith, S. C. (Center for Nanoscale Materials); (The Univ. of Queensland)

2011-01-01

243

Synthesis and characterization of double-walled carbon nanotubes from multi-walled carbon nanotubes by hydrogen-arc discharge  

Microsoft Academic Search

Double-walled carbon nanotubes (DWNTs) were synthesized in a large scale by a hydrogen arc discharge method using graphite powders or multi-walled carbon nanotubes\\/carbon nanofibers (MWNTs\\/CNFs) as carbon feedstock. The yield of DWNTs reached about 4g\\/h. We found that the DWNT product synthesized from MWNTs\\/CNFs has higher purity than that from graphite powders. The results from high-resolution transmission electron microscopy observations

Lixiang Li; Feng Li; Chang Liu; Hui-Ming Cheng

2005-01-01

244

The eVect of a nitrogen-rich surface layer on the sub-surface deuterium (hydrogen) concentration distribution in titanium  

Microsoft Academic Search

Deuterium and nitrogen depth profiles in Ti with modified surfaces have been measured with Auger electron spectroscopy, secondary ion mass spectroscopy, and D(3He,p)4He nuclear reaction analysis. Nitrogen-rich surfaces layers of varying thicknesses were created on Ti by exposure to N 2 gas at 650°C. Deuterium loading was performed by exposure to 1 Torr of D 2 gas at 500°C. The

Corneliu I. Costescu; Brent J. Heuser

245

Hydrogen storage system based on novel carbon materials and heat pipe heat exchanger  

Microsoft Academic Search

Adsorbed hydrogen is being considered as a potential energy carrier for vehicular applications to replace compressed gas due to its high energy density capability. A new design of hydrogen storage vessel using novel carbon sorbents and heat pipes thermal control is the subject of research program oriented on 5–10 kg of hydrogen be stored on-board. Porous structure and hydrogen-sorption capacities

L. L. Vasiliev; L. E. Kanonchik; A. G. Kulakov; V. A. Babenko

2007-01-01

246

Role of Nonmetallic Inclusions in Hydrogen Embrittlement of High-Strength Carbon Steels with Different Microalloying  

NASA Astrophysics Data System (ADS)

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.

Todoshchenko, Olga Madelen Ingrid; Yagodzinskyy, Yuriy; Saukkonen, Tapio; Hänninen, Hannu

2014-10-01

247

Aromatic Cations from Oxidative Carbon–Hydrogen Bond Cleavage in Bimolecular Carbon–Carbon Bond Forming Reactions  

PubMed Central

Chromenes and isochromenes react quickly with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to form persistent aromatic oxocarbenium ions through oxidative carbon–hydrogen cleavage. This process is tolerant of electron-donating and electron-withdrawing groups on the benzene ring and additional substitution on the pyran ring. A variety of nucleophiles can be added to these cations to generate a diverse set of structures. PMID:22780559

Clausen, Dane J.

2012-01-01

248

Suppression of carbon erosion by hydrogen shielding during high-flux hydrogen bombardment E. Salonen, K. Nordlund, J. Tarus, T. Ahlgren, and J. Keinonen  

E-print Network

Suppression of carbon erosion by hydrogen shielding during high-flux hydrogen bombardment E Garching bei Mu¨nchen, Germany Received 3 August 1999 The erosion of carbon by intensive hydrogen cannot be explained by standard sputtering or erosion mod- els, yet understanding it is central

Nordlund, Kai

249

Improved hydrogen storage properties of LiBH4 destabilized by carbon  

NASA Astrophysics Data System (ADS)

The hydrogen storage properties of LiBH4 ball milled with various ratios of carbon nanotubes (Cnano) were investigated. The LiBH4/Cnano mixtures showed superior dehydrogenation, hydrogen desorption starting at 250°C, and the majority of hydrogen being released below 600°C. The rehydrogenation results revealed that the Li2C2, formed during the dehydrogenation, could be reversed to LiH, in which the hydrogen capacity corresponds to 1/4 of the original hydrogen content of LiBH4, and C at 10MPa hydrogen pressure and 400°C.

Yu, X. B.; Wu, Z.; Chen, Q. R.; Li, Z. L.; Weng, B. C.; Huang, T. S.

2007-01-01

250

Thermodynamic analysis of Glycerol Steam Reforming for hydrogen production with in situ hydrogen and carbon dioxide separation  

NASA Astrophysics Data System (ADS)

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.

Silva, Joel M.; Soria, M. A.; Madeira, Luis M.

2015-01-01

251

Deuterium enrichment by selective photo-induced dissociation of an organic carbonyl compound  

DOEpatents

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.

Marling, John B. (Livermore, CA)

1981-01-01

252

Ammonium and caesium carbonate peroxosolvates: supramolecular networks formed by hydrogen bonds.  

PubMed

Diammonium carbonate hydrogen peroxide monosolvate, 2NH(4)(+)·CO(3)(2-)·H(2)O(2), (I), and dicaesium carbonate hydrogen peroxide trisolvate, 2Cs(+)·CO(3)(2-)·3H(2)O(2), (II), were crystallized from 98% hydrogen peroxide. In (I), the carbonate anions and peroxide solvent molecules are arranged on twofold axes. The peroxide molecules act as donors in only two hydrogen bonds with carbonate groups, forming chains along the a and c axes. In the structure of (II), there are three independent Cs(+) ions, two of them residing on twofold axes, as are two of the four peroxide molecules, one of which is disordered. Both structures comprise complicated three-dimensional hydrogen-bonded networks. PMID:22382531

Medvedev, Alexander G; Mikhaylov, Alexey A; Churakov, Andrei V; Prikhodchenko, Petr V; Lev, Ovadia

2012-03-01

253

Study of Hydrogen Adsorption by Spiral Carbon Nano Fibers Synthesized From Acetylene  

Microsoft Academic Search

A spiral carbon nanofiber of 30 to 40 nm diam and 20 µm average lengths has been synthesized by catalyst chemical vapor deposition method using Ni or Fe?Ni alloy as catalyst. The purpose of synthesis of carbon nano fibers was to use it for hydrogen adsorption. Catalysts used affected the morphology of carbon nano material (CNM) where as purification and ball milling

Sandesh V. Jaybhaye; Maheshwar Sharon; Madhuri Sharon; L. N. Singh

2006-01-01

254

Sputtering and codeposition of silicon carbide with deuterium  

NASA Astrophysics Data System (ADS)

Due to its excellent thermal properties, silicon carbide is being considered as a possible plasma-facing material for fusion devices. If used as a plasma-facing material, the energetic hydrogen isotope ions and charge-exchanged neutrals escaping from the plasma will sputter the silicon carbide. To assess the tritium inventory problems that will be generated by the use of this material, it is necessary that we know the codeposition properties of the redeposited silicon carbide. To determine the codeposition properties, the deuterium plasma experiment at Sandia National Laboratories in Livermore, California has been used to directly compare the deuterium sputtering and codeposition of silicon carbide with that of graphite. A Penning discharge at a flux of 6×10 19 D/m 2 and an energy of ?300 eV was used to sputter silicon and carbon from a pair of 0.05 m diameter silicon carbide disks. The removal rate of deuterium gas from the fixed volume of the system isolated from all other sources and sinks was used to measure the codeposition probability (probability that a hydrogen isotope atom will be removed through codeposition per ion striking the sample surface). A small catcher plate used to capture a fraction of the codeposited film was analyzed using Auger spectroscopy. This analysis showed the film to begin with a high carbon to silicon ratio due to preferential sputtering of the carbon. As the film became thicker, the ratio of the depositing material changed over to the (1:1) value that must eventually be attained.

Causey, Rion A.

2003-03-01

255

Report on the evening discussion: ``Hydrogen storage in carbon materials''  

Microsoft Academic Search

Hydrogen may be the most important energy carrier of the future as soon as the problem of hydrogen storage is solved. Storing of hydrogen under high pressure or as liquid costs much energy. Furthermore, a high pressure or liquid hydrogen tank in a fuel cell driven vehicle would be much larger and heavier compared to a typical gasoline tank. In

Andrea Quintel

2000-01-01

256

Study of depth profile of hydrogen in hydrogenated diamond like carbon thin film using ion beam analysis techniques  

NASA Astrophysics Data System (ADS)

The Hydrogenated Diamond Like Carbon (HDLC) thin films are deposited on Silicon substrate at room temperature using asymmetric capacitively coupled RF plasma with varying flow rates of methane. These films are undergone annealing at high vacuum (˜10-7 torr) and high temperature (750 and 1050 °C) furnace. The as-prepared and annealed HDLC films have been depth profiled for hydrogen using the resonance at 6.44 MeV in 1H(19F,??)16O nuclear reaction. The as prepared films exhibit non-uniform depth distribution of hydrogen: it decreases with depth. Annealing in vacuum brings about is a significant desorption of hydrogen from the films. Loss of hydrogen, albeit in much lower proportions, is also induced by the bombarding beam. The films also experience a mild loss of carbon, as shown by proton backscattering spectrometry, during high vacuum annealing. The depth profiles of hydrogen in the annealed films are indicative of the prevalence of graphitic carbon near film-substrate interface.

Datta, J.; Biswas, H. S.; Rao, P.; Reddy, G. L. N.; Kumar, S.; Ray, N. R.; Chowdhury, D. P.; Reddy, A. V. R.

2014-06-01

257

The Effect of Carbon Monoxide on the Hydrogen Permeability of a Palladium Membrane  

NASA Astrophysics Data System (ADS)

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.

Katoh, Masahiro; Nishihara, Katsunori; Kinouchi, Koji; Chohama, Koichi; Horikawa, Toshihide; Tomida, Tahei; Sotowa, Ken-Ichiro

258

Ellipsometric and optical study of amorphous hydrogenated carbon films  

NASA Astrophysics Data System (ADS)

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).

Alterovitz, S. A.; Warner, J. D.; Liu, D. C.; Pouch, J. J.

1986-11-01

259

Simultaneous determination of hydrogen, methane and carbon dioxide of breath using gas-solid chromatography.  

PubMed

The analysis of respiratory hydrogen and methane was estimated as a useful index of intestinal fermentation of undigestible carbohydrate. A simultaneous and precious analysis of these gases as well as carbon dioxide was studied. A gas-impermeable multi-laminated film bag metalized by aluminum vapor was fitted to use as a storage bag; its impermeability was verified by measuring the residual rate of hydrogen after 3 months' storage. Hydrogen, methane and carbon dioxide of the breath gas even at 1 ppm could be determined simultaneously by using a gas-solid chromatography installed with a photoionization detector and active carbon column. To observe the genesis of hydrogen and methane after carbohydrate ingestion, pectin, a typical water-soluble dietary fiber, was fed to healthy volunteers. Increasing excretion of pulmonary hydrogen or methane showed the sign of intestinal fermentation as the results of carbohydrate malabsorption. PMID:1629782

Tsuji, K; Shimizu, M; Nishimura, Y; Nakagawa, Y; Ichikawa, T

1992-02-01

260

Combined hydrogenation of carbon oxides on catalysts bearing iron and nickel nanoparticles  

NASA Astrophysics Data System (ADS)

The reaction of the hydrogenation of a mixture of carbon oxides on ultradisperse powder (UDP) catalysts containing Fe and Ni nanoparticles and their bimetallic mechanical mixtures was investigated. It was established that the main reaction product on UDP Ni is methane, while the main products on the bimetallic systems are methane and ethylene. A synergetic effect was observed on the bimetallic catalyst under investigation. It was revealed that the hydrogenation of a mixture of carbon oxides proceeds through the stage of dissociative adsorption of both components, CO and CO2. The olefin selectivity of the process was explained by the participation of different forms of adsorbed hydrogen (HI: HII) at the catalyst surface. It is assumed that the hydrogenation of carbon oxides on iron-nickel catalysts proceeds either through the jumpover effect or via hydrogen spillover.

Sheshko, T. F.; Serov, Yu. M.

2011-01-01

261

SEASONAL VARIATIONS OF STABLE HYDROGEN AND CARBON ISOTOPE RATIOS OF METHANE IN SUBTROPICAL FRESHWATER SEDIMENTS  

EPA Science Inventory

Stable hydrogen (D) and carbon (13C) isotope ratios of sedimentary methane from five subtropical Florida freshwater sites exhibited smaller, less distinct seasonal variations than previously observed in temperate sediments, apparently due to the smaller range of temperatures forc...

262

Molecular dynamics simulation of erosion and surface evolution of tungsten due to bombardment with deuterium and carbon in  

E-print Network

Molecular dynamics simulation of erosion and surface evolution of tungsten due to bombardment dynamics simulation. Tungsten erosion and surface evolution is simulated during irradiation by carbon irradiation on crystal tungsten reveals that tungsten erosion is enhanced at high substrate temperatures

Harilal, S. S.

263

Tribological studies of amorphous hydrogenated carbon films in a vacuum, spacelike environment  

NASA Technical Reports Server (NTRS)

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.

Miyoshi, Kazuhisa

1991-01-01

264

Multi-walled carbon nanotubes produced by hydrogen DC arc discharge at elevated environment temperature  

Microsoft Academic Search

Multi-walled carbon nanotubes (MWCNTs) were synthesized by hydrogen DC arc discharge at elevated environment temperature. The sample collected from the soot on the inner wall of the arc discharge furnace was investigated using TEM, HRTEM and X-ray diffraction. The results show that environment temperature has a significant effect on the formation of MWCNTs in the soot in hydrogen atmosphere as

Xiaolong Song; Yongning Liu; Jiewu Zhu

2007-01-01

265

Hydrogen isotope retention and impurity deposition of carbon based components used in JT-60U  

NASA Astrophysics Data System (ADS)

Various types of carbon based components, such as isotropic graphite, carbon fiber composite (CFC-2D felt type) and B 4C-overlaid CFC/graphite were used for divertor and first wall tiles in JT-60U. Surface analysis of tiles exposed to discharge shots in JT-60U, was performed using MeV region ion beam. The retention of deuterium for each tile was distributed between ˜ 6 × 10 20 and ˜ 6 × 10 21 m -2. Highest deuterium retention was observed on the outboard, lower part of first wall tiles. Metallic impurity measurement was performed by X-PIXE. The dominant species were Fe, Cr, Ni, Cu, Mo and Zn of which total concentration as high as 10 21 m -2. This value is one order of magnitude smaller than that of JT-60. Highest oxygen concentration examined by RBS was observed on the B 4C converted graphite tile. Carbon tile containing B 4C is shown to be useful for oxygen gettering compared with an other.

Amemiya, S.; Masuda, T.; Ando, T.; Kodama, K.; Masaki, K.

1995-04-01

266

Structure, hydrogen bonding and thermal expansion of ammonium carbonate monohydrate.  

PubMed

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) [?calc = 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

Fortes, A Dominic; Wood, Ian G; Alfè, Dario; Hernández, Eduardo R; Gutmann, Matthias J; Sparkes, Hazel A

2014-12-01

267

Biofiltration for control of carbon disulfide and hydrogen sulfide vapors  

SciTech Connect

A full-scale biofiltration system has been installed to control carbon disulfide (CS{sub 2}) and hydrogen sulfide (H{sub 2}S) vapor emissions at Nylonge Corporation (Nylonge), a cellulose sponge manufacturing facility in Elyria, Ohio. Both CS{sub 2} and H{sub 2}S are toxic and odorous. In addition, the US Environmental Protection Agency (EPA) has classified CS{sub 2} as one of the 189 hazardous air pollutants listed under Title 3 of the 1990 Clean Air Act Amendments. Nylonge evaluated several technologies to control CS{sub 2} and H{sub 2}S vapor emissions. After careful consideration of both removal efficiency requirements and cost, Nylonge selected biological treatment as the best overall technology for their application. A biological based technology has been developed to effectively degrade CS{sub 2} and H{sub 2}S vapors. Biofiltration is a process that aerobically converts particular vapor phase compounds into CO{sub 2}, biomass, and water vapor. In this process, microorganisms, in the form of a moistened biofilm layer, immobilized on an organic packing material, such as compost, peat, wood chips, etc., are used to catalyze beneficial chemical reactions. As a contaminated vapor stream passes through the biofilter bed, the contaminants are transferred to the biofilm and are degraded by the microorganisms. This paper describes the CS{sub 2} and H{sub 2}S biofiltration process and the full-scale biofilter system installed at Nylonge`s facility. The system was started in October of 1995, and is designed to treat a 30,000 CFM exhaust stream contaminated with CS{sub 2} and H{sub 2}S vapors.

Fucich, W.J.; Yang, Y.; Togna, A.P. [Envirogen, Inc., Lawrenceville, NJ (United States); Alibeckoff, D. [Nylonge Corp., Elyria, OH (United States)

1997-12-31

268

Design and Development of New Carbon-Based Sorbent Systems for an Effective Containment of Hydrogen  

SciTech Connect

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.

Alan C. Cooper

2012-05-03

269

Hydrogen Storage in Metal-Modified Single-Walled Carbon Nanotubes (start 9/15/01)  

E-print Network

Hydrogen Storage in Metal-Modified Single-Walled Carbon Nanotubes (start 9/15/01) Channing Ahn, PI Intercalation of carbons Characterization of intercalated single walled nanotubes Gravimetric and volumetric-metal) additions to single-walled nanotubes on H2 adsorption. Potassium intercalated graphite long known to absorb

270

On the adsorption/oxidation of hydrogen sulfide on activated carbons at ambient temperatures.  

PubMed

Activated carbons of various origins (bituminous coal, wood, coconut shells, and peat) were studied as adsorbents of hydrogen sulfide. Before the experiments the surface of the adsorbents was characterized by using the sorption of nitrogen, Boehm and potentiometric titrations, thermal analysis, and FTIR. The adsorbents were chosen to differ in their surface areas, pore volumes, and surface acidities. To broaden the spectrum of surface acidity, carbons were oxidized by using nitric acid and ammonium persulfate. After hydrogen sulfide adsorption the species present on the surface were analyzed using thermal analysis, ion chromatography, and elemental analysis. The H(2)S breakthrough capacity tests showed that the performances of different carbons differ significantly. For a good performance of carbons as hydrogen sulfide adsorbents a proper combination of surface chemistry of carbon and porosity is needed. It was demonstrated that a more acidic environment promotes the formation of sulfur oxides and sulfuric acid despite yielding small H(2)S removal capacities. On the other hand, a basic environment favors the formation of elemental sulfur (sulfur radicals) and yields high capacities. The presence of a sufficient amount of water preadsorbed on the carbon surface to facilitate dissociation also plays an important role in the process of H(2)S adsorption/oxidation. The results showed that there is a critical value in carbon surface acidity, which when exceeded results in a negligible hydrogen sulfide breakthrough capacity. This is consistent with the mechanism of H(2)S adsorption on unmodified carbons, where the rate-limiting step is the reaction of adsorbed hydrogen sulfide ion with dissociatively adsorbed oxygen. When the acidity is expressed as pH, its value should be higher than 5 to ensure the effective removal of hydrogen sulfide from the gas phase. Study of carbon regeneration using water washing and heat treatment showed that the adsorbents can be regenerated to about 40% of their initial capacity. PMID:16290378

Bandosz, Teresa J

2002-02-01

271

Cometary deuterium.  

PubMed

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

Meier, R; Owen, T C

1999-01-01

272

Experiment on first-wall carbon coating: Focusing hydrogen concentration  

Microsoft Academic Search

As a back-up experiment for investigations on first-wall carbon coatings of toroidal machines, we constructed the RIKEN ECR-2 device and carried out simulation experiments. By electron cyclotron resonance discharges we obtain an amorphous, hard, and dense carbon film. It is possible to decrease the atomic H\\/C ratio of carbon films by high-energy ion bombardment. Harmful carbon films deposited on observation

Y. Sakamoto; H. Amemiya; Y. Ishibe; S. Kato; K. Okazaki; H. Oyama; K. Yano; K. Akaishi; N. Noda; T. Masuda; Y. Tsurita; S. Amemiya; H. Minagawa; T. Hino; T. Yamashina

1987-01-01

273

Sulfur-resistant carbon-supported iridium catalysts: Cyclohexane dehydrogenation and benzene hydrogenation  

SciTech Connect

Carbon-supported iridium catalysts, with different metal loadings, were prepared by impregnation of a high-purity activated carbon. The dispersion of the metallic phase was studied by hydrogen and carbon monoxide chemisorption and transmission electron microscopy (TEM). The hydrogen chemisorption on the iridium crystallites supported on activated carbon was quite different from the chemisorption on an Ir/alumina catalyst. TEM observations of the catalysts show metal particles as spheres in the former case and as rafts in the latter. The cyclohexane dehydrogenation and the benzene hydrogenation were studied for both catalyst types. Both reactions are insensitive to the iridium dispersion and to the support. The thiotolerance level of the cyclohexane dehydrogenation, the thiotolerance level is affected neither by the support (activated carbon versus alumina) not by the metallic dispersion of the Ir/carbon catalysts. However, in the benzene hydrogenation the carbon-supported iridium catalysts are more resistant toward the poisoning than the Ir/alumina counterpart. This behavior is interpreted as due to the different metallic microstructures produced on the two supports.

Rodriguez-Ramos, I. (Campus Univ. Autonoma, Madrid (Spain)); Guerrero-Ruiz, A. (UNED, Madrid (Spain))

1992-06-01

274

Shock Compression of Deuterium and the Interiors of Jupiter and Saturn  

Microsoft Academic Search

Recently, deuterium has been the focus of a high level of experimental and theoretical activity, sparked by a disagreement on the experimental value of the maximum compression along the principal Hugoniot. The behavior of deuterium at megabar pressures is not well understood. It is of great interest to understand how the current uncertainty on the hydrogen\\/deuterium equation of state (EOS)

D. Saumon; T. Guillot

2004-01-01

275

Hydrogen and carbon in solid solution in oxides and silicates  

NASA Astrophysics Data System (ADS)

The dissolution of H2O and CO2 in structurally dense, nominally anhydrous and non-carbonate oxide matrices such as MgO and CaO is reviewed. H2O and CO2 are treated as gaseous oxide components which enter into solid solution with the refractory oxide hosts. They form anion complexes associated with cation vacancy sites. Evidence is presented that OH- pairs which derive from the dissolution of H2O are subject to a charge transfer (CT) conversion into peroxy moieties and molecular hydrogen, O{2/2-}... H2. Because the O{2/2-}moiety is small (O--O- distance ? 1.5 Å) high pressure probably favors the CT conversion. Mass spectroscopic studies show that molecular H2 may be lost from the solid which retains excess oxygen in the form of O{2/2-}, leading to the release of atomic O. The dissociation of O{2/2-}moieties into a vacancy-bound O- state and an unbound O- state can be followed by measuring the internal redox reactions involving transition metal impurities, the transient paramagnetism of the O- and their effect on the d.c. conductivity. Evidence is presented that CO2 molecules dissolve dissociatively in the structurally dense oxide matrix, as if they were first to dissociate into CO+O and then to form separate solute moieties CO{2/2-}and O{2/2-}, both associated with cation vacancy sites. In the CO{2/2-}moiety (C-O- distance 1.2 1.3 Å, OCO angle ? 130°) the C atom probably sits off center. The transition of the C atom into interstitial sites is accompanied by dissociation of the CO{2/2-}moiety into CO- and O-. This transition can be followed by infrared spectroscopy, using OH- as local probes. Further support derives from magnetic susceptibility, thermal expansion, low frequency dielectric loss and low temperature deformation measurements. The recently observed emission of O and Mg atoms besides a variety of molecules such as CO, CO2, CH4, HCN and other hydrocarbons during impact fracture of MgO single crystals is presented and discussed in the light of the other experimental data.

Freund, Friedemann

1987-10-01

276

HYDROGEN ISOTOPE PROFILE OF METHYL GROUPS IN MILIACIN (OLEAN-18-EN-3OL ME) BY NATURAL ABUNDANCE DEUTERIUM 2D-NMR  

E-print Network

.lesot@u-psud.fr; jeremy.jacob@univ-orleans.fr Compound-specific hydrogen isotope analyses are gaining increasing interestHYDROGEN ISOTOPE PROFILE OF METHYL GROUPS IN MILIACIN (OLEAN- 18-EN-3OL ME) BY NATURAL ABUNDANCE to which extent these modifications can be accompanied by a hydrogen isotope fractionation process

Paris-Sud XI, Université de

277

Effects of Microstructure of Carbon Nanofibers for Amperometric Detection of Hydrogen Peroxide  

SciTech Connect

Carbon nanofibers (CNFs) with different microstructures, including platelet-carbon nanofibers (PCNFs), fish-bone-carbon nanofibers (FCNFs), and tube-carbon nanofibers (TCNFs), were synthesized, characterized, and evaluated for electrochemical sensing of hydrogen peroxide. The CNFs studied here can show several microstructures in which various stacked morphologies and their sizes and graphite-layer ordering can be well controlled. Glassy carbon (GC) electrodes modified by CNFs were fabricated and compared for amperometric detection of hydrogen peroxide. Sensors of PCNFs/GC, FCNFs/GC, and TCNFs/GC were used in the amperometric detection of H2O2 in a solution of 0.05 M phosphate buffered saline solution (pH 7.4).

Li, Zhizhou; Cui, Xiaoli; Zheng, Junsheng; Wang, Qingfei; Lin, Yuehe

2007-08-10

278

Nonrelativistic contributions of order {alpha}{sup 5}m{sub {mu}c}{sup 2} to the Lamb shift in muonic hydrogen and deuterium, and in the muonic helium ion  

SciTech Connect

Contributions to the energy levels in light muonic atoms and, in particular, to the Lamb shift fall into a few well-distinguished classes. The related diagrams are calculated using different approaches. In particular, there is a specific type of nonrelativistic (NR) contribution. Here, we consider such corrections to the Lamb shift of order {alpha}{sup 5}m{sub {mu}.} These contributions are due to free vacuum-polarization loops as well as to various effects of light-by-light scattering. The closed loop in the related diagrams is an electronic one, which allows an NR consideration of the muon. Both types of contributions have been known for some time, however, the results obtained to date are only partial results. We complete a calculation of the {alpha}{sup 5}m{sub {mu}}contributions for muonic hydrogen. The results are also adjusted for muonic deuterium atom and helium ion.

Karshenboim, S. G.; Ivanov, V. G.; Korzinin, E. Yu.; Shelyuto, V. A. [D. I. Mendeleev Institute for Metrology, St. Petersburg RU-190005 (Russian Federation) and Max-Planck-Institut fuer Quantenoptik, Garching D-85748 (Germany); Pulkovo Observatory, St. Petersburg RU-196140 (Russian Federation) and D. I. Mendeleev Institute for Metrology, St. Petersburg RU-190005 (Russian Federation); D. I. Mendeleev Institute for Metrology, St. Petersburg RU-190005 (Russian Federation)

2010-06-15

279

Process for producing methane from gas streams containing carbon monoxide and hydrogen  

DOEpatents

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.

Frost, Albert C. (Congers, NY)

1980-01-01

280

The evolution of the structure and mechanical properties of fullerenelike hydrogenated amorphous carbon films upon annealing  

SciTech Connect

Hydrogenated amorphous carbon films were deposited on Si (100) substrates using dc-pulse plasma chemical vapor deposition. Structurally, the as-deposited carbon films could be considered as nanocomposite thin films with fullerenelike microstructure in diamondlike carbon matrix based on our previous result [Q. Wang et al., Appl. Phys. Lett. 91, 141902 (2007)]. In this paper, the evolution of the structure and the mechanical properties of hydrogenated carbon films with fullerenelike microstructure on the annealing in vacuum was investigated. The fullerenelike hydrogenated carbon films annealed at 500 deg. C showed higher hardness (16.9% harder) and higher elastic recovery (11.2% higher) than the as-deposited films. The friction coefficient of fullerenelike hydrogenated carbon films in air with 40% relative humidity remained constant at about 0.037 when annealed at 600 deg. C. The wear rate of the films decreased sharply when annealed at 200 or 300 deg. C. Structural analysis shows that annealing at 300 deg. C improved tribological properties originated from the volume increase in the fullerenelike microstructure, and further annealing at 600 deg. C improved mechanical properties originated from the transformation of nanosized curved sp{sup 2} to sp{sup 3} clusters.

Wang Qi [Department of Physics, Lanzhou University, Lanzhou 730000 (China); State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); He Deyan [Department of Physics, Lanzhou University, Lanzhou 730000 (China); Wang Chengbing; Wang Zhou; Zhang Junyan [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

2008-08-15

281

Electrospun polyacrylonitrile-based carbon nanofibers and their hydrogen storages  

Microsoft Academic Search

Electrospun polyacrylonitrile (PAN) nanofibers were carbonized with or without iron (III) acetylacetonate to induce catalytic\\u000a graphitization within the range of 900–1,500 °C, resulting in ultrafine carbon fibers with a diameter of about 90–300 nm.\\u000a Their structural properties and morphologies were investigated. The carbon nanofibers (CNF) prepared without a catalyst showed\\u000a amorphous structures and very low surface areas of 22–31 m2\\/g.

Dong-Kyu Kim; Sun Ho Park; Byung Chul Kim; Byung Doo Chin; Seong Mu Jo; Dong Young Kim

2005-01-01

282

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)

Stable hydrogen, carbon, and nitrogen isotopic ratios (?D, ?13C, and ?15N) 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 ?13C and increasing ?D with increasing carbon number in the ?-H, ?-NH2 amino acids that correspond to predictions made for formation via Strecker-cyanohydrin synthesis. We also observe light ?13C 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-?-amino acids). Higher deuterium enrichments are observed in ?-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.

Elsila, Jamie E.; Charnley, Steven B.; Burton, Aaron S.; Glavin, Daniel P.; Dworkin, Jason P.

2012-09-01

283

Hydrogen-bond acidic functionalized carbon nanotubes (CNTs) with covalently-bound hexafluoroisopropanol groups  

SciTech Connect

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.

Fifield, Leonard S.; Grate, Jay W.

2010-06-01

284

Electrodeposition and characterization of Pd nanoparticles doped amorphous hydrogenated carbon films  

NASA Astrophysics Data System (ADS)

Palladium (0) nanoparticles incorporated hydrogenated amorphous carbon (Pd/a-C:H) films were synthesized on single crystal silicon (100) substrates by electrochemical deposition route using methanol and camphor as carbon source, and Pd nanoparticles as dopant. The characterization results indicate that Pd nanocrystalline particles with diameter in the range of 1-5 nm dispersed in the amorphous carbon matrix. Compared with pure a-C:H films, the introduction of Pd nanoparticles didn't change the structure of carbon films. At the end, the growth mechanism of the Pd/a-C:H composite films was discussed.

Yu, Yuanlie; Zhang, Junyan

2009-11-01

285

Dissociation of CH4 by electron impact: Production of metastable hydrogen and carbon fragments  

NASA Technical Reports Server (NTRS)

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.

Finn, T. G.; Carnahan, B. L.; Zipf, E. C.

1974-01-01

286

Enhancement of electrical conductivity and electrochemical activity of hydrogenated amorphous carbon by incorporating boron atoms  

NASA Astrophysics Data System (ADS)

Conductive boron-doped hydrogenated amorphous carbon (B-DLC) thin films were successfully synthesized with RF plasma-enhanced CVD method. By incorporating boron atoms in amorphous carbon, conduction types were changed from n- to p-type, and volume resistivity was decreased from 30.4 (non-doped) to 6.36 × 10-2 ? cm (B/C = 2.500 atom%). B-DLC film with sp2/(sp2 + sp3) carbons of 75 atom% exhibited high resistance to electrochemically-induced corrosion in strong acid solution. Furthermore, it was clarified that boron atoms in DLC could enhance kinetics of hydrogen evolution during water electrolysis at B-DLC surface. B-DLC is, therefore, a promising electrode material for hydrogen production by increasing the concentration of boron atoms in B-DLC and enhancing the reactivity of H2 evolution.

Naragino, Hiroshi; Yoshinaga, Kohsuke; Nakahara, Akira; Tanaka, Sakuya; Honda, Kensuke

2013-06-01

287

“Green” path from fossil-based to hydrogen economy: An overview of carbon-neutral technologies  

Microsoft Academic Search

While the dominant role of hydrogen in a sustainable energy future is widely accepted, the strategies for the transition from fossil-based to hydrogen economy are still actively debated. This paper emphasizes the role of carbon-neutral technologies and fuels during the transition period. To satisfy the world's growing appetite for energy and keep our planet healthy, at least 10TW (or terawatt)

Nazim Z. Muradov; T. Nejat Veziro?lu

2008-01-01

288

Hydrogenolysis of 5-carbon sugars, sugar alcohols, and other methods and compositions for reactions involving hydrogen  

DOEpatents

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.

Werpy, Todd A [West Richland, WA; Zacher, Alan H [Kennewick, WA

2002-11-12

289

Relation of Hydrogen and Methane to Carbon Monoxide in Exhaust Gases from Internal-Combustion Engines  

NASA Technical Reports Server (NTRS)

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.

Gerrish, Harold C; Tessmann, Arthur M

1935-01-01

290

Transient carbon monoxide poisoning of a polymer electrolyte fuel cell operating on diluted hydrogen feed  

Microsoft Academic Search

The transient behavior of a 50cm2 PEM fuel cell fed on simulated reformate containing diluted hydrogen and trace quantities of carbon monoxide (CO) was experimentally investigated. It was found that the overall cell performance throughout the CO poisoning process can be described with a lumped model of hydrogen and CO adsorption, desorption, and electro-oxidation coupled with a current–voltage relationship for

Krishan Kumar Bhatia; Chao-Yang Wang

2004-01-01

291

Synthesis of superlow friction carbon films from highly hydrogenated methane plasmas.  

SciTech Connect

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.

Erdemir, A.; Eryilmaz, O. L.; Nilufer, I. B.; Fenske, G. R.

2000-10-13

292

Stereo- and regioselective direct multi-deuterium-labeling methods for sugars.  

PubMed

Deuterium-labeled sugars can be utilized as powerful tools for the architectural analyses of high-sugar-containing molecules represented by the nucleic acids and glycoproteins, and chiral building blocks for the syntheses of new drug candidates (heavy drugs) due to their potential characteristics, such as simplifying the (1)H?NMR spectra and the stability of C-D bonds compared with C-H bonds. We have established a direct and efficient synthetic method of deuterated sugars from non-labeled sugars by using the heterogeneous Ru/C-catalyzed H-D exchange reaction in D(2)O under a hydrogen atmosphere with perfect chemo- and stereoselectivities. The direct H-D exchange reaction can selectively proceed on carbons adjacent to the free hydroxyl groups, and the deuterium labeling of various pyranosides (such as glucose and disaccharides), as well as furanosides, represented by ribose and deoxyribose was realized. Furthermore, the desired number of deuterium atoms can be freely incorporated into selected positions by the site-selective protection of the hydroxyl groups using acetal-type protective groups because the deuterium exchange reaction never proceeds on positions adjacent to the protected hydroxyl groups. PMID:23150471

Sawama, Yoshinari; Yabe, Yuki; Iwata, Hiroki; Fujiwara, Yuta; Monguchi, Yasunari; Sajiki, Hironao

2012-12-14

293

Stable hydrogen and carbon isotope ratios of extractable hydrocarbons in the Murchison meteorite  

NASA Technical Reports Server (NTRS)

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.

Krishnamurthy, R. V.; Epstein, S.; Pizzarello, S.; Cronin, J. R.; Yuen, G. U.

1991-01-01

294

Hydrogenated carbon nanotubes: x-ray absorption spectroscopy and ab initio simulation analysis  

NASA Astrophysics Data System (ADS)

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.

Brzhezinskaya, M.; Yalovega, G.; Shmatko, V.; Klyushin, A.; Bogoslavskaya, E.; Krestinin, A.; Bashkin, I.

2013-04-01

295

New Pathways and Metrics for Enhanced, Reversible Hydrogen Storage in Boron-Doped Carbon Nanospaces  

SciTech Connect

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.

Pfeifer, Peter [University of Missouri; Wexler, Carlos [University of Missouri; Hawthorne, M. Frederick [University of Missouri; Lee, Mark W. [University of Missouri; Jalistegi, Satish S. [University of Missouri

2014-08-14

296

Deuterium-incorporated gate oxide of MOS devices fabricated by using deuterium ion implantation  

NASA Astrophysics Data System (ADS)

In the aspect of metal-oxide-semiconductor (MOS) device reliability, deuterium-incorporated gate oxide could be utilized to suppress the wear-out that is combined with oxide trap generation. An alternative deuterium process for the passivation of oxide traps or defects in the gate oxide of MOS devices has been suggested in this study. The deuterium ion is delivered to the location where the gate oxide resides by using an implantation process and subsequent N2 annealing process at the back-end of metallization process. A conventional MOS field-effect transistor (MOSFET) with a 3-nm-thick gate oxide and poly-to-ploy capacitor sandwiched with 20-nm-thick SiO2 were fabricated in order to demonstrate the deuterium effect in our process. An optimum condition of ion implantation was necessary to account for the topography of the overlaying layers in the device structure and to minimize the physical damage due to the energy of the implanted ion. Device parameter variations, the gate leakage current, and the dielectric breakdown phenomenon were investigated in the deuterium-ion-implanted devices. We found the isotope effect between hydrogen- and deuterium-implanted devices and an improved electrical reliability in the deuterated gate oxide. This implies that deuterium bonds are generated effectively at the Si/SiO2 interface and in the SiO2 bulk.

Lee, Jae-Sung; Lear, Kevin L.

2012-04-01

297

LITERATURE SURVEY OF GASEOUS HYDROGEN EFFECTS ON THE MECHANICAL PROPERTIES OF CARBON AND LOW ALLOY STEELS  

SciTech Connect

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).

Lam, P; Andrew Duncan, A; Robert Sindelar, R; Thad Adams, T

2009-04-27

298

LITERATURE SURVEY OF GASEOUS HYDROGEN EFFECTS ON THE MECHANICAL PROPERTIES OF CARBON AND LOW ALLOY STEELS  

SciTech Connect

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).

Lam, P; Robert Sindelar, R; Thad Adams, T

2007-04-18

299

Efficient and durable hydrogen evolution electrocatalyst based on nonmetallic nitrogen doped hexagonal carbon  

NASA Astrophysics Data System (ADS)

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.

Liu, Yanming; Yu, Hongtao; Quan, Xie; Chen, Shuo; Zhao, Huimin; Zhang, Yaobin

2014-10-01

300

Efficient and durable hydrogen evolution electrocatalyst based on nonmetallic nitrogen doped hexagonal carbon.  

PubMed

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

Liu, Yanming; Yu, Hongtao; Quan, Xie; Chen, Shuo; Zhao, Huimin; Zhang, Yaobin

2014-01-01

301

Efficient and durable hydrogen evolution electrocatalyst based on nonmetallic nitrogen doped hexagonal carbon  

PubMed Central

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

Liu, Yanming; Yu, Hongtao; Quan, Xie; Chen, Shuo; Zhao, Huimin; Zhang, Yaobin

2014-01-01

302

Renewable Hydrogen Carrier Carbohydrate: Constructing the Carbon-Neutral Carbohydrate Economy  

SciTech Connect

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.

Zhang, Y.-H. Percival [Virginia Polytechnic Institute and State University (Virginia Tech); Mielenz, Jonathan R [ORNL

2011-01-01

303

N-doped carbon networks: alternative materials tracing new routes for activating molecular hydrogen.  

PubMed

The fragmentation of molecular hydrogen on N-doped carbon networks was investigated by using molecular (polyaromatic macrocycles) as well as truncated and periodic (carbon nanotubes) models. The computational study was focused on the ergonicity analysis of the reaction and on the properties of the transition states involved when constellations of three or four pyridinic nitrogen atom defects are present in the carbon network. Calculations show that whenever N-defects are embedded in species characterized by large conjugated ?-systems, either in polyaromatic macrocycles or carbon nanotubes, the corresponding H2 bond cleavage is largely exergonic. The fragmentation Gibbs free energy is affected by the final arrangement of the hydrogen atoms on the defect and by the extension of the ?-electron cloud, but it is not influenced by the curvature of the system. PMID:25614208

Cortese, Remedios; Ferrante, Francesco; Roggan, Stefan; Duca, Dario

2015-02-23

304

Ultrananopores in Carbons by Boron-neutron Capture and Their Effect on Hydrogen Storage  

NASA Astrophysics Data System (ADS)

The Alliance for Collaborative Research in Alternative Fuel Technology (ALL-CRAFT) has been optimizing high surface area activated carbon nanospaces for high capacity hydrogen storage. Boron doped samples have been prepared by vapor deposition of decaborane. Neutron irradiation of Boron doped activated carbon was done at the University of Missouri Research Reactor (MURR). Ultrananopores created by alpha particle fission tracks from Boron-neutron capture alter the surface and the adsorption properties of activated Carbons. A detailed theoretical model of the creation and the structure of defects on graphene sheets was developed. BET surface areas, porosity, and pores size distributions of modified activated carbons were measured using sub-critical nitrogen isotherms. Hydrogen adsorption isotherms of irradiated samples were indicative of record fraction of high binding energies and record fraction of sub-nm pores compared to their unirradiated parent samples.

Romanos, J.; Robertson, D.; Beckner, M.; Kraus, M.; Kuchta, B.; Firlej, L.; Pfeifer, P.

2010-03-01

305

Simulation of quantum separation of binary hydrogen isotope mixtures in carbon slit pores  

Microsoft Academic Search

The carbon slit pore has been investigated as a medium for low temperature hydrogen isotope mixture separation. It is shown that the path integral formalism with Silvera–Goldman potential provides the most accurate results for the adsorption simulations. At 40 K, an operating pressure of 1.0 bar and carbon slit width of 0.56 nm is found to be optimal for efficient quantum separation. Simulations

Yang Wang; Suresh K. Bhatia

2009-01-01

306

Carbon nanofiber mesoporous films: efficient platforms for bio-hydrogen oxidation in biofuel cells.  

PubMed

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

de Poulpiquet, Anne; Marques-Knopf, Helena; Wernert, Véronique; Giudici-Orticoni, Marie Thérèse; Gadiou, Roger; Lojou, Elisabeth

2014-01-28

307

Determination of concentrated hydrogen peroxide at single-walled carbon nanohorn paste electrode  

Microsoft Academic Search

Single-walled carbon nanohorn (SWCNH) paste electrode was used for amperometric determination of concentrated hydrogen peroxide, and was compared with other carbon electrodes. The calibration plots are linear from 0.5 to 100mM at activated SWCNH paste electrode and edge plane graphite (EPG) electrode. In contrast, the calibration plots are linear only at concentrations lower than 45mM at graphite paste electrode, multi-walled

Shuyun Zhu; Lishuang Fan; Xiaoqing Liu; Lihong Shi; Haijuan Li; Shuang Han; Guobao Xu

2008-01-01

308

On the control of carbon nanostructures for hydrogen storage applications  

E-print Network

as for graphite nanofibers at 293 K and 10 MPa. The amount of hydrogen uptake strongly depends on the porosity within the nanostructure network where optimal arrangements give rise to the formation of a well-walled nanotube bundles was modeled by disseminating atomic particles, characterized by a highly attractive

Rochefort, Alain

309

Measuring the primordial deuterium abundance during the cosmic dark ages.  

PubMed

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

Sigurdson, Kris; Furlanetto, Steven R

2006-09-01

310

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...

311

Stable Isotope (delta OXYGEN-18, Delta Deuterium, Delta CARBON-13) Dendroclimatological Studies in the Waterloo Region of Southern Ontario, Canada, Between AD 1610 and 1990.  

NASA Astrophysics Data System (ADS)

Oxygen (delta^{18} O), hydrogen (delta^2H) and carbon (delta^{13}C) isotopes were measured in wood cellulose from elm, white pine and maple trees that grew in southwestern Ontario, Canada. The measured oxygen and hydrogen isotopic data were used for model-based reconstructions of delta^{18}{O}_{meteoric water}, mean annual temperature (MAT) and relative humidity for a period, AD 1610 to 1880, that precedes instrumental records of climate. The carbon isotope measurements were compared with the Cellulose Model inferred climate data to reveal additional environmental information. Modifications made to the Cellulose Model focused on the dynamics of oxygen and hydrogen isotopic fractionation in plants during evapotranspiration and photosynthetic assimilation. For instance, kinetic fractionation of ^{18}O was found to be predictable from theoretical considerations of leaf energy balance and boundary layer dynamics. Kinetic fractionation during evapotranspiration is sensitive to the nature of the boundary layer, which is controlled by leaf size and morphology. Generally, plants with small segmented leaves have a lower component of turbidity in the leaf boundary layer, which results in higher kinetic fractionation values, than do plants having large simple leaves and more turbulent boundary layers. Kinetic ^2H enrichment in plant leaf water can also be rationalized in terms of leaf size and morphology when an apparent temperature-dependent isotope effect, acting in opposition to evaporative enrichment, is taken into account. Accounting for this temperature -dependent isotope effect helps to: (1) reconcile hydrogen kinetic fractionation inconsistencies for different leaves; (2) explain a temperature effect previously attributed to variable biochemical fractionation during cellulose synthesis, and; (3) verify hydrogen biochemical effects in plants. This improved characterization of the oxygen and hydrogen isotopic effects in plants, using the modified Cellulose Model, helped to constrain the paleoclimate interpretations from three species of trees that grew in different hydrologic settings. The inferred climate data, integrated with the hydrological setting of the trees and various climate modifying factors in the Great Lakes basin, generated an independent interpretation of summer and winter conditions in southwestern Ontario for the past 380 years. The inferred evidence indicates that conditions in southwestern Ontario between 1610 and 1750 typified those of "Little Ice Age" Europe by being cooler and drier than present. This probably resulted from a southerly positioning of the Polar Front, with respect to southwestern Ontario, which allowed sub-polar airmasses to dominantly influence this region. A subsequent retreat of the Polar Front north after 1750 allowed for a predominance of sub -tropical airmasses that resulted in warm-moist conditions and an increase in winter precipitation in this area between 1750 and 1850. Another advance of the Polar Front position south, sometime after 1850, renewed cool-dry conditions and reduced winter precipitation amounts in southwestern Ontario until the early twentieth century, after which time, climate ameliorated progressively. Typical of the findings in previous studies, a significant correlation between climate parameters and delta^{13}C_ {cellulose} values is observed for a tree (maple) from a groundwater recharge setting. The correlation is best between MAT and delta^ {13}C_{cellulose} values between 1610 and 1850. The breakdown of this correlation after 1850, due to enriched delta ^{13}C_{cellulose} values, could indicate that the tree is responding to an alteration in soil chemistry occurring due to the fallout of anthropogenically produced atmospheric pollutants. This is because the effects of depleted soil nutrients and/or leached phytotoxins on delta^ {13}C_{cellulose} values in wood cellulose, are similar to ones seen in trees that regularly experience drought stress.

Buhay, William Mark

312

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)

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.

Bair, C. H.; Allario, F.

1977-01-01

313

Mechanism for high hydrogen storage capacity on metal-coated carbon nanotubes: A first principle analysis  

SciTech Connect

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.

Lu, Jinlian; Xiao, Hong [Department of Physics and Institute for nanophysics and Rare-earth Luminescence, Xiangtan University, Xiangtan, Hunan Province 411105 (China)] [Department of Physics and Institute for nanophysics and Rare-earth Luminescence, Xiangtan University, Xiangtan, Hunan Province 411105 (China); Cao, Juexian, E-mail: jxcao@xtu.edu.cn [Department of Physics and Institute for nanophysics and Rare-earth Luminescence, Xiangtan University, Xiangtan, Hunan Province 411105 (China)] [Department of Physics and Institute for nanophysics and Rare-earth Luminescence, Xiangtan University, Xiangtan, Hunan Province 411105 (China)

2012-12-15

314

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

Microsoft Academic Search

The deuterium concentrations ( D 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

Martin Schoell

1980-01-01

315

Hydrogen production from coal by separating carbon dioxide during gasification  

Microsoft Academic Search

Hydrogen generation during the reaction of a coal\\/CaO mixture with high pressure steam was investigated using a flow-type reactor. Coal, CaO and CO reactions with steam, and CO2 absorption by Ca(OH)2 or CaO occurred simultaneously in the experiment. It was found that H2 was the primary resultant gas, comprising about 85% of the reaction products. CO2 was fixed into CaCO3

Shiying Lin; Michiaki Harada; Yoshizo Suzuki; Hiroyuki Hatano

2002-01-01

316

Different types of methane monooxygenases produce similar carbon and hydrogen isotope fractionation patterns during methane oxidation  

Microsoft Academic Search

We determined the stable carbon and hydrogen isotope fractionation factors for methane oxidation under oxic conditions using strains with known degradation pathways. The aerobic oxidation of methane can be initiated by two different forms of enzymes known as methane monooxygenases (MMO). The expression of these enzymes is type-specific and dependent upon the adjusted copper concentration in the medium (or environment).

Stefan Feisthauer; Carsten Vogt; Jakub Modrzynski; Maurycy Szlenkier; Martin Krüger; Michael Siegert; Hans-Hermann Richnow

2011-01-01

317

Kinetics of the Homogeneous Catalytic Hydrogenation of Olefins in Supercritical Carbon Dioxide Using a Fluoroacrylate Copolymer  

E-print Network

Kinetics of the Homogeneous Catalytic Hydrogenation of Olefins in Supercritical Carbon Dioxide. The reactions were investigated at temperatures between 50 and 120 °C, and pressures ranging from 172 to 241 bar in conventional solvents. It was proposed that two hydride catalytic species are formed during the kinetic cycle

Abdou, Hanan E.

318

Olefin Cyclopropanation and Carbon-Hydrogen Amination via Carbene and Nitrene  

E-print Network

Olefin Cyclopropanation and Carbon- Hydrogen Amination via Carbene and Nitrene Transfers Catalyzed ACKNOWLEDGEMENTS To my mentor and role model, Frances Arnold, whose career is proof that novel and useful research stages of this research project. To my parents and my brothers for their unconditional support. To Renata

Winfree, Erik

319

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...

320

The Role of Hydrogen in Small Amorphous Carbon Grains: The IR Spectrum  

NASA Technical Reports Server (NTRS)

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.

Mennella, V.; Colangeli, L.; Pestellini, C. Cecchi; Palomba, E.; Palumbo, P.; Rotundi, A.; Bussoletti, E.

1996-01-01

321

The effect of KOH:C and activation temperature on hydrogen storage capacities of activated carbons  

NASA Astrophysics Data System (ADS)

The Alliance for Collaborative Research in Alternative Fuel Technologies (ALL-CRAFTootnotetextSee http://all-craft.missouri.edu) has been producing high surface area activated carbons. Here we will investigate the effect of the ratio of activating agent to carbon and activation temperature on hydrogen sorption characteristics and sample structure. Results show that a ratio of 3:1 KOH:C and an activation temperature of 790 C are the ideal activation conditions for hydrogen storage applications. Hydrogen sorption measurements are completed using a volumetric instrument that operates at pressures up to 100 bar and at temperatures of 80 K, the sublimation temperature of dry ice (-78.5 C), and room temperature. Specific surface area and pore size distributions are measured using subcritical nitrogen isotherms.

Rash, Tyler; Beckner, Matt; Romanos, Jimmy; Leimkuehler, Eric; Takeei, Ali; Suppes, Galen; Wexler, Carlos; Pfeifer, Peter

2011-03-01

322

Direct synthesis of formic acid from carbon dioxide by hydrogenation in acidic media  

PubMed Central

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

Moret, Séverine; Dyson, Paul J.; Laurenczy, Gábor

2014-01-01

323

Direct synthesis of formic acid from carbon dioxide by hydrogenation in acidic media.  

PubMed

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

Moret, Séverine; Dyson, Paul J; Laurenczy, Gábor

2014-01-01

324

The deuterium inventory in ASDEX Upgrade  

Microsoft Academic Search

The deuterium inventory in ASDEX Upgrade was determined by quantitative ion beam analysis techniques and SIMS for different discharge campaigns between the years 2002 and 2005. ASDEX Upgrade was a carbon dominated machine during this phase. Full poloidal sections of the lower and upper divertor tile surfaces, limiter tiles, gaps between divertor tiles, gaps between inner heat shield tiles and

M. Mayer; V. Rohde; G. Ramos; E. Vainonen-Ahlgren; J. Likonen; A. Herrmann; R. Neu

2007-01-01

325

Record Hydrogen Storage Capacities in Advanced Carbon Storage Materials  

NASA Astrophysics Data System (ADS)

Carbons can be engineered to achieve exceptional storage capacities: the ALL-CRAFT (www.all-craft.missouri.edu) nanoporous carbon achieves gravimetric excess adsorption of 0.073 kg H2/kg C, gravimetric storage capacity of 0.106 kg H2/kg C, and volumetric storage capacity of 0.040 kg H2/l C (80 K, 100 bar). The nanopores generate high storage capacity by having: high surface area (2,600 m^2/g); high H2-wall interaction; and multi-layer H2 adsorption (cryogenic). We we show how the experimental characteristics of the ALL-CRAFT carbon correlate to the observed H2 storage, with help from theoretical considerations and GCMC simulations. The ALL-CRAFT carbon is composed of a large variety of pore sizes which generates substantial heterogeneity. We explain most features observed by considering superpositions of low- and high-binding energy sites (9 kJ and 5 kJ/mol), corresponding to wide and narrow (< 1 nm) pores. We further explain: exceptional low-temperature storage (in excess of the usual Chahine's rule); and absence of an excess adsorption peak (for 0 < P < 100 bar).

Wexler, C.; Beckner, M.; Romanos, J.; Burress, J.; Kraus, M.; Olsen, R.; Dohnke, E.; Carter, S.; Casteel, G.; Kuchta, B.; Firlej, L.; Leimkuehler, E.; Tekeei, A.; Suppes, G.; Pfeifer, P.

2010-03-01

326

Carbon-based nanoreporters designed for subsurface hydrogen sulfide detection.  

PubMed

Polyvinyl alcohol functionalized carbon black with H2S-sensor moieties can be pumped through oil and water in porous rock and the H2S content can be determined based on the fluorescent enhancement of the H2S-sensor addends. PMID:24735429

Hwang, Chih-Chau; Ruan, Gedeng; Wang, Lu; Zheng, Haiyan; Samuel, Errol L G; Xiang, Changsheng; Lu, Wei; Kasper, William; Huang, Kewei; Peng, Zhiwei; Schaefer, Zachary; Kan, Amy T; Martí, Angel A; Wong, Michael S; Tomson, Mason B; Tour, James M

2014-05-28

327

Chemisorption and associative adsorption of hydrogen in carbon nanostructures synthesized on zeolites  

NASA Astrophysics Data System (ADS)

The chemisorptive and adsorptive interactions of hydrogen accumulated in cylindrical and planar graphene nanostructures (CPGNSes) formed on TsVM and TsVN zeolites with chemical compounds of these zeolites are studied for the first time. CPGNSes are synthesized at a temperature of 800°C using methane as a pyrolyzed reagent and saturated with hydrogen under pressures of 9.2-12.2 MPa. Using thermogravimetric analysis (TGA) in combination with mass spectrometry, it is determined that hydrogen is desorbed from the CPGNSes at temperatures of 250 and 450°C, indicating two mechanisms of hydrogen adsorption. It is shown that at temperatures of 200 and 240°C, chemical structures with m/ e = 15 and 31 undergo desorption at the same time as the removal of H2 by the first mechanism. Using IR spectroscopy, it is shown that carbon atoms can react with zeolites at a temperature of 800°C to form carbonate structures during the formation of CPGNSes. Our study of hydrogen adsorption in CPGNSes showed that the above mechanisms may be considered associative and are characterized by the formation of new structures close to superacid sites and a chemisorptive mechanism attributable to the strong coordination of the hydrogen molecule on the C=O bonds of carbonate groups. A quantitative estimate of hydrogen adsorption in CPGNSes synthesized on TsVM and TsVN is made. It is found that the total adsorption (by the first and second mechanisms) is ˜70 cm3/g in the first case; this value is slightly higher than the one for CPGNSes on TsVN (˜65 cm3/g), while the magnitude of adsorption by the first mechanism is ˜2.5 times higher than for the second.

Soldatov, A. P.; Bondarenko, G. N.; Sorokina, E. Yu.

2015-02-01

328

Fractionation of carbon and hydrogen isotopes by methane-oxidizing bacteria  

USGS Publications Warehouse

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.

Coleman, D.D.; Risatti, J.B.; Schoell, M.

1981-01-01

329

Diffusion of carbon atoms in hydrogenated amorphous silicon carbide into hydrogenated amorphous silicon through the interface  

Microsoft Academic Search

The depth distribution and the chemical states of the carbon atoms in a-SiC:H and a-Si:H films are observed by Auger electron spectroscopy and X-ray photoelectron spectroscopy. It is found that carbon atoms in a-SiC:H films diffuse into a-Si:H film through the a-SiC:H\\/a-Si:H interface. It is believed that the drastic degradation in the lifetime and the diffusion coefficient of photoexcited carriers

Y. Aoyagi; Y. Segawa; S. Namba; A. Masuyama; H. Okamoto; Y. Hamakawa; S. Komuro

1984-01-01

330

Effects of heavy ion irradiation on amorphous hydrogenated (diamondlike) carbon films  

NASA Astrophysics Data System (ADS)

Energetic ion-beam irradiation of diamondlike carbon thin films induces a decrease of 5-6 orders of magnitude in the resistivity of the films from their as-grown value of 107 ? cm. Diagnostics used to characterize the nature of the transformation included optical absorption measurements (band gap), Raman spectroscopy (microcrystalline structure), Rutherford backscattering spectroscopy (hydrogen content of the films), and measurements of the temperature dependence of the conductivity (electronic structure). It was found that the initial decrease in resistivity with an increasing ion dose is due to the loss of hydrogen from the films, with a concomitant decrease in the optical band gap. Heating the films during the irradiation greatly accelerates the rate of hydrogen loss as a function of dose. Once the hydrogen removal is complete, further irradiation increases the film conductivity by inducing the growth of microcrystallites of graphite.

Prawer, S.; Kalish, R.; Adel, M.; Richter, V.

1987-05-01

331

Provocative Questions for the Deuterium Session  

NASA Astrophysics Data System (ADS)

Analyses of spectra obtained with the Far Ultraviolet Spectrograph Explorer (FUSE) satellite, together with spectra from the Copernicus, Hubble Space Telescope (HST), and Interstellar Medium Absorption Profile Spectrograph (IMAPS) instruments reveal a very wide range in the observed deuterium/hydrogen (D/H) ratios for interstellar gas in the Galactic disk beyond the Local Bubble. For gas located beyond the Local Bubble but within several hundred parsecs, the observed D/H ratios differ by a factor of 4-5. A critically important question is what value or values of D/H in the local region of our Galaxy should be compared with chemical evolution models of the Galaxy and with the primordial deuterium abundance. Linsky et al. [Astrophys. J. 647, 1106 (2006)] argued that spatial variations in the depletion of deuterium onto dust grains can explain these local variations in the observed gas-phase D/H ratios. In this provacative introduction to the deuterium session, I ask six questions concerning analysis techniques and proposed results from the FUSE D/H program in the hope that the speakers and participants in this conference will give serious thought to the robustness of our present understanding of this important topic. In particular, is the deuterium depletion model valid? Is it only part of the explanation?

Linsky, Jeffrey L.

2009-05-01

332

ENHANCED HYDROGEN ECONOMICS VIA COPRODUCTION OF FUELS AND CARBON PRODUCTS  

SciTech Connect

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.

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

333

Probing lactate dehydrogenase activity in tumors by measuring hydrogen/deuterium exchange in hyperpolarized l-[1-(13)C,U-(2)H]lactate.  

PubMed

(13)C magnetic resonance spectroscopy and spectroscopic imaging measurements of hyperpolarized (13)C label exchange between exogenously administered [1-(13)C]pyruvate and endogenous lactate, catalyzed by lactate dehydrogenase (LDH), has proved to be a powerful approach for probing tissue metabolism in vivo. This experiment has clinical potential, particularly in oncology, where it could be used to assess tumor grade and response to treatment. A limitation of the method is that pyruvate must be administered in vivo at supra-physiological concentrations. This problem can be avoided by using hyperpolarized [1-(13)C]lactate, which can be used at physiological concentrations. However, sensitivity is limited in this case by the relatively small pyruvate pool size, which would result in only low levels of labeled pyruvate being observed even if there was complete label equilibration between the lactate and pyruvate pools. We demonstrate here a more sensitive method in which a doubly labeled lactate species can be used to measure LDH-catalyzed exchange in vivo. In this experiment exchange of the C2 deuterium label between injected hyperpolarized l-[1-(13)C,U-(2)H]lactate and endogenous unlabeled lactate is observed indirectly by monitoring phase modulation of the spin-coupled hyperpolarized (13)C signal in a heteronuclear (1)H/(13)C spin-echo experiment. PMID:22316419

Kennedy, Brett W C; Kettunen, Mikko I; Hu, De-En; Brindle, Kevin M

2012-03-14

334

Characterization of reduced natural garnierite and its catalytic activity for carbon monoxide hydrogenation  

SciTech Connect

The reaction of 3:1 hydrogen/carbon monoxide at 500/sup 0/-573/sup 0/K and 0.101 Mnewton/sq m pressure over reduced natural garnierite from New Caledonia yielded only methane in a reaction that was 1.8 order in hydrogen, approx. -0.45 order in carbon monoxide, had an activation energy of approx. 100 kj/mole, and had a turnover number lower than the ones reported by Vannice for other supports at 548/sup 0/K At a hydrogen/carbon monoxide ratio of 1.5:1 and higher pressures (1.5-2.13 Mnewton/sq m) higher hydrocarbons were obtained in concentrations which were correctly predicted by the Schulz-Flory equation, even for the products of low carbon number. The catalyst, which consisted of a nickel-containing mixture of talc-like and serpentine-like phases, and its reduction behavior, were characterized by X-ray diffraction, thermal analyses, electron microscopy and microprobe analyses, and adsorption studies. An optimum catalyst reduction temperature existed which was associated with the redispersion nickel in the serpentine fiber phase.

Jacobs, P.A; Nijs, H.H.; Poncelet, G.

1980-08-01

335

Monodispersed Pd-nanoparticles on carbon fiber fabrics as structured catalyst for selective hydrogenation  

Microsoft Academic Search

Monodispersed Pd-nanoparticles (?8nm) prepared via a modified microemulsion method were deposited on active carbon fibers (ACF) fabrics and studied in a semi-batch 1-hexyne liquid-phase hydrogenation. The catalyst Pd(0.45wt%)\\/ACF demonstrated >96% selectivity to 1-hexene up to 90% of conversion. Initial activity at 303K, 1.3MPa pressure, in n-heptane as a solvent was 0.14kmolH2kgPd-1s-1. Assuming a Langmuir–Hinshelwood kinetics with a weak hydrogen adsorption

N. Semagina; A. Renken; L. Kiwi-Minsker

2007-01-01

336

Breakdown of diameter selectivity in a reductive hydrogenation reaction of single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Reductive hydrogenation was applied to two types of single-walled carbon nanotubes with different diameter range. Alkali metal intercalation, followed by reaction with methanol, led to hydrogenated products. Both yield and selectivity of this reaction showed strong dependence on diameter, contrary to expectation based on simple curvature effects. The observed yield, as detected by thermogravimetry-mass spectrometry and 1H NMR, is drastically reduced in small-diameter tubes where the alkali dopant does not reach the inside of the bundles. Wide range optical transmission measurements were employed to determine the selectivity and indicate that besides higher yield, lower diameter selectivity occurs above a critical diameter.

Nemeth, Katalin; Jakab, Emma; Borondics, Ferenc; Tóháti, Hajnalka M.; Pekker, Áron; Bokor, Mónika; Verebélyi, Tamás; Tompa, Kálmán; Pekker, Sándor; Kamarás, Katalin

2015-01-01

337

Effect of carbon monoxide on the electrooxidation of hydrogen by tungsten carbide  

NASA Astrophysics Data System (ADS)

The effect of carbon monoxide (CO) on the anodic oxidation of hydrogen by tungsten carbide (WC) electrocatalysts is described. CO poisoning of these base electrocatalysts is small, with reductions of ?6% of the hydrogen current. Tests of the anodic oxidation of CO alone on these catalysts show the reaction to be very slow. The low degree of poisoning is quite reversible and ascribed to weak adsorption of CO on WC surfaces. The experiments have been conducted on a variety of WCs synthesised from several different routes, all showing similar results.

McIntyre, D. R.; Burstein, G. T.; Vossen, A.

338

Technoeconomical analysis of the co-production of hydrogen energy and carbon materials  

NASA Astrophysics Data System (ADS)

HECAM (Hydrogen Energy and Carbon Materials) is a new energy production strategy. The main paradigm of HECAM is that energy extracted from the carbon in hydrocarbon fuels is not worth the production of carbon dioxide. The hydrocarbon fuel is heated in an oxygen free environment and it is chemically decomposed by the heat into gases (mostly hydrogen and methane), small quantities of liquid (light oil and tar), and a solid residue containing carbon and ash (char or coke). More quantities of hydrocarbons will need to be used, but less carbon dioxide will be produced. HECAM is going to compete with steam methane reforming (SMR) to produce hydrogen. HECAM with thermocatalytic decomposition of methane and efficient sensible heat recovery has a production cost per gigajoule of hydrogen about 9% higher than SMR, but will produce about half the carbon dioxide emissions that SMR produces. If HECAM with efficient sensible heat recovery is used to produce electricity in a power plant, it will have a comparable electricity production cost and carbon dioxide emissions to a natural gas combined cycle (NGCC) power plant. The byproduct coke is not a waste residue, but a valuable co-product. Uses for the byproduct coke material may be carbon sequestration, mine land restoration, additive to enhance agricultural soils, low sulfur and mercury content heating fuel for power plants, new construction materials, or carbon-base industrial materials. This study investigated the use of byproduct coke for new construction materials. HECAM concrete substitute (HCS) materials will have a comparable cost with concrete when the cost of the raw materials is $65 per metric ton of HCS produced. HECAM brick substitute (HBS) materials will have 20% higher cost per brick than clay bricks. If the HECAM byproduct coke can be formed into bricks as a product of the HECAM process, the manufacture of HBS bricks will be cheaper and may be cost competitive with clay bricks. The results of this analysis are conservative because the model for the HECAM process is an approximated model, base on a metallurgical coke plant.

Guerra, Zuimdie

339

Palladium Nanoparticles Decorated Single-Walled Carbon Nanotube Hydrogen Sensor Syed Mubeen, Ting Zhang, Bongyoung Yoo, Marc A. Deshusses,* and Nosang V. Myung*  

E-print Network

Palladium Nanoparticles Decorated Single-Walled Carbon Nanotube Hydrogen Sensor Syed Mubeen, Ting-effective fabrication technique to construct a hydrogen nanosensor by decorating single-walled carbon nanotubes with Pd or semiconductive, depending on their helicity.12 Further, since all carbon atoms in a single-walled carbon nanotube

340

An amperometric hydrogen peroxide biosensor based on Co3O4 nanoparticles and multiwalled carbon nanotube modified glassy carbon electrode  

NASA Astrophysics Data System (ADS)

In this work a new type of hydrogen peroxide biosensor was fabricated based on the immobilization of horseradish peroxidase (HRP) by cross-linking on a glassy carbon electrode (GCE) modified with Co3O4 nanoparticles, multiwall carbon nanotubes (MWCNTs) and gelatin. The introduction of MWCNTs and Co3O4 nanoparticles not only enhanced the surface area of the modified electrode for enzyme immobilization but also facilitated the electron transfer rate, resulting in a high sensitivity of the biosensor. The fabrication process of the sensing surface was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Amperometric detection of hydrogen peroxide was investigated by holding the modified electrode at -0.30 V (vs. Ag/AgCl). The biosensor showed optimum response within 5 s at pH 7.0. The optimized biosensor showed linear response range of 7.4 × 10-7-1.9 × 10-5 M with a detection limit of 7.4 × 10-7. The applicability of the purposed biosensor was tested by detecting hydrogen peroxide in disinfector samples. The average recovery was calculated as 100.78 ± 0.89.

Kaçar, Ceren; Dalkiran, Berna; Erden, P?nar Esra; Kiliç, Esma

2014-08-01

341

Multi-Walled Carbon Nanotube-Doped Tungsten Oxide Thin Films for Hydrogen Gas Sensing  

PubMed Central

In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO3) thin films by means of the powder mixing and electron beam (E-beam) evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO3 thin film exhibits high sensitivity and selectivity to hydrogen. Thus, MWCNT doping based on E-beam co-evaporation was shown to be an effective means of preparing hydrogen gas sensors with enhanced sensing and reduced operating temperatures. Creation of nanochannels and formation of p-n heterojunctions were proposed as the sensing mechanism underlying the enhanced hydrogen sensitivity of this hybridized gas sensor. To our best knowledge, this is the first report on a MWCNT-doped WO3 hydrogen sensor prepared by the E-beam method. PMID:22163623

Wongchoosuk, Chatchawal; Wisitsoraat, Anurat; Phokharatkul, Ditsayut; Tuantranont, Adisorn; Kerdcharoen, Teerakiat

2010-01-01

342

Effect of p-type multi-walled carbon nanotubes for improving hydrogen storage behaviors  

SciTech Connect

In this study, the hydrogen storage behaviors of p-type multi-walled carbon nanotubes (MWNTs) were investigated through the surface modification of MWNTs by immersing them in sulfuric acid (H{sub 2}SO{sub 4}) and hydrogen peroxide (H{sub 2}O{sub 2}) at various ratios. The presence of acceptor-functional groups on the p-type MWNT surfaces was confirmed by X-ray photoelectron spectroscopy. Measurement of the zeta-potential determined the surface charge transfer and dispersion of the p-type MWMTs, and the hydrogen storage capacity was evaluated at 77 K and 1 bar. From the results obtained, it was found that acceptor-functional groups were introduced onto the MWNT surfaces, and the dispersion of MWNTs could be improved depending on the acid-mixed treatment conditions. The hydrogen storage was increased by acid-mixed treatments of up to 0.36 wt% in the p-type MWNTs, compared with 0.18 wt% in the As-received MWNTs. Consequently, the hydrogen storage capacities were greatly influenced by the acceptor-functional groups of p-type MWNT surfaces, resulting in increased electron acceptor–donor interaction at the interfaces. - Graphical abstract: Hydrogen storage behaviors of the p-type MWNTs with the acid-mixed treatments are described. Display Omitted Display Omitted.

Lee, Seul-Yi [Department of Chemistry, Inha University, 253, Nam-gu, Incheon 402-751 (Korea, Republic of); Yop Rhee, Kyong [Industrial Liaison Research Institute, Department of Mechanical Engineering, College of Engineering, Kyung Hee University, 446-701 Yongin (Korea, Republic of); Nahm, Seung-Hoon [Center for New and Renewable Energy Measurement, Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of); Park, Soo-Jin, E-mail: sjpark@inha.ac.kr [Department of Chemistry, Inha University, 253, Nam-gu, Incheon 402-751 (Korea, Republic of)

2014-02-15

343

The deuterium inventory in ASDEX Upgrade  

NASA Astrophysics Data System (ADS)

The deuterium inventory in ASDEX Upgrade was determined by quantitative ion beam analysis techniques and SIMS for different discharge campaigns between the years 2002 and 2005. ASDEX Upgrade was a carbon dominated machine during this phase. Full poloidal sections of the lower and upper divertor tile surfaces, limiter tiles, gaps between divertor tiles, gaps between inner heat shield tiles and samples from remote areas below the roof baffle and in pump ducts were analysed, thus offering an exhaustive survey of all relevant areas in ASDEX Upgrade. Deuterium is mainly trapped on plasma-exposed surfaces of inner divertor tiles, where about 70% of the retained deuterium inventory is found. About 20% of the inventory is retained at or below the divertor roof baffle, and about 10% is observed in other areas, such as the outer divertor and in gaps between tiles. The long term deuterium retention is 3-4% of the total deuterium input. The obtained results are compared with gas balance measurements, and conclusions about tritium retention in ITER are made.

Mayer, M.; Rohde, V.; Ramos, G.; Vainonen-Ahlgren, E.; Likonen, J.; Herrmann, A.; Neu, R.; ASDEX Upgrade Team

2007-11-01

344

Exploiting microbial hyperthermophilicity to produce an industrial chemical, using hydrogen and carbon dioxide  

PubMed Central

Microorganisms can be engineered to produce useful products, including chemicals and fuels from sugars derived from renewable feedstocks, such as plant biomass. An alternative method is to use low potential reducing power from nonbiomass sources, such as hydrogen gas or electricity, to reduce carbon dioxide directly into products. This approach circumvents the overall low efficiency of photosynthesis and the production of sugar intermediates. Although significant advances have been made in manipulating microorganisms to produce useful products from organic substrates, engineering them to use carbon dioxide and hydrogen gas has not been reported. Herein, we describe a unique temperature-dependent approach that confers on a microorganism (the archaeon Pyrococcus furiosus, which grows optimally on carbohydrates at 100°C) the capacity to use carbon dioxide, a reaction that it does not accomplish naturally. This was achieved by the heterologous expression of five genes of the carbon fixation cycle of the archaeon Metallosphaera sedula, which grows autotrophically at 73°C. The engineered P. furiosus strain is able to use hydrogen gas and incorporate carbon dioxide into 3-hydroxypropionic acid, one of the top 12 industrial chemical building blocks. The reaction can be accomplished by cell-free extracts and by whole cells of the recombinant P. furiosus strain. Moreover, it is carried out some 30°C below the optimal growth temperature of the organism in conditions that support only minimal growth but maintain sufficient metabolic activity to sustain the production of 3-hydroxypropionate. The approach described here can be expanded to produce important organic chemicals, all through biological activation of carbon dioxide. PMID:23530213

Keller, Matthew W.; Schut, Gerrit J.; Lipscomb, Gina L.; Menon, Angeli L.; Iwuchukwu, Ifeyinwa J.; Leuko, Therese T.; Thorgersen, Michael P.; Nixon, William J.; Hawkins, Aaron S.; Kelly, Robert M.; Adams, Michael W. W.

2013-01-01

345

Hydrogen  

NSDL National Science Digital Library

This article explores the possibilities of using hydrogen as a renewable energy source, pointing out that hydrogen fuel and hydrogen fuel cells are two options for generating power from hydrogen. The article gives an overview of the three methods used to isolate hydrogen for energy-production purposes: steam reforming, electrolysis, and burning. Information is also offered about the uses, limitations, and benefits of hydrogen as an energy source. Supporting web links are provided, including links to an article about fuel cell buses and to animations that demonstrate how hydrogen fuel cells operate.

Project, Iowa P.

2004-01-01

346

Lanthanum-hexaboride carbon composition for use in corrosive hydrogen-fluorine environments  

DOEpatents

The present invention relates to a structural composition useful in corrosive hydrogen-fluorine environments at temperatures in excess of 1400/sup 0/K. The composition is formed of a isostatically pressed and sintered or a hot-pressed mixture of lanthanum hexaboride particles and about 10 to 30 vol% carbon. The lanthanum-hexaboride reacts with the high-temperature fluorine-containing gases to form an adherent layer of corrosion-inhibiting lanthanum trifluoride on exposed surfaces of the composition. The carbon in the composite significantly strengthens the composite, enhances thermal shock resistance, and significantly facilitates the machining of the composition.

Holcombe, C.E. Jr.; Kovach, L.; Taylor, A.J.

1980-01-22

347

Lanthanum-hexaboride carbon composition for use in corrosive hydrogen-fluorine environments  

DOEpatents

The present invention relates to a structural composition useful in corrosive hydrogen-fluorine environments at temperatures in excess of 1400.degree. K. The composition is formed of a isostatically pressed and sintered or a hot-pressed mixture of lanthanum hexaboride particles and about 10-30 vol. % carbon. The lanthanum-hexaboride reacts with the high-temperature fluorine-containing bases to form an adherent layer of corrosion-inhibiting lanthanum trifluoride on exposed surfaces of the composition. The carbon in the composite significantly strengthens the composite, enhances thermal shock resistance, and significantly facilitates the machining of the composition.

Holcombe, Cressie E. (Knoxville, TN); Kovach, Louis (Oak Ridge, TN); Taylor, Albert J. (Ten Mile, TN)

1981-01-01

348

Preparation of activated carbons previously treated with hydrogen peroxide: Study of their porous texture  

NASA Astrophysics Data System (ADS)

Cedar wood was used as raw material for the preparation of activated carbons by treatment with hydrogen peroxide of different concentrations. The samples were next carbonised and activated under CO 2 atmosphere. The activated carbons were characterised by means of the adsorption isotherms of N 2 at 77 K, as well as by applying the Density Functional Theory (DFT) method and mercury porosimetry. The experimental results corresponding to the activated samples indicate a more remarkable porous development as a consequence of the treatment with hydrogen peroxide, probably due to the elimination of surface complexes produced during the activation step. The DFT diagrams point out that the activating treatment favours the development of medium and narrow-size micropores whereas the carbonisation process leads to the development of wide micropores of size close to that corresponding to mesopores.

López de Letona Sánchez, M.; Macías-García, A.; Díaz-Díez, M. A.; Cuerda-Correa, E. M.; Gañán-Gómez, J.; Nadal-Gisbert, A.

2006-06-01

349

First principles studies on hydrogen storage in single-walled carbon nanotube functionalized with TiO2  

NASA Astrophysics Data System (ADS)

In this first principles study, hydrogen storage capacity of armchair single-walled carbon nanotube (10, 10) functionalized with TiO2 has been investigated. The functionalized TiO2 molecules are found to be chemisorbed on CNT (10, 10) with the binding energy of 3.54 eV. The functionalized CNT binds up to six hydrogen molecules. The first hydrogen adsorption is dissociative with the binding energy of 1.51 eV and the further adsorbed hydrogen are weakly chemisorbed on the functionalized system with the elongated bond length of hydrogen. The storage capacity of functionalized SWCNT, desorption temperature and binding energy of hydrogen molecules are evaluated. The system exhibits a maximum storage capacity of 3.64 wt%. The band structure, density of states (DOS) and partial density of states (PDOS) are calculated for the functionalized and hydrogenated SWCNTs. DOS studies reveal that, functionalization and hydrogenation does not affect the metallic nature of CNT.

Kanmani, M.; Lavanya, R.; Silambarasan, D.; Iyakutti, K.; Vasu, V.; Kawazoe, Y.

2014-04-01

350

Bio-inspired carbon nanotube-polymer composite yarns with hydrogen bond-mediated lateral interactions.  

PubMed

Polymer composite yarns containing a high loading of double-walled carbon nanotubes (DWNTs) have been developed in which the inherent acrylate-based organic coating on the surface of the DWNT bundles interacts strongly with poly(vinyl alcohol) (PVA) through an extensive hydrogen-bond network. This design takes advantage of a toughening mechanism seen in spider silk and collagen, which contain an abundance of hydrogen bonds that can break and reform, allowing for large deformation while maintaining structural stability. Similar to that observed in natural materials, unfolding of the polymeric matrix at large deformations increases ductility without sacrificing stiffness. As the PVA content in the composite increases, the stiffness and energy to failure of the composite also increases up to an optimal point, beyond which mechanical performance in tension decreases. Molecular dynamics (MD) simulations confirm this trend, showing the dominance of nonproductive hydrogen bonding between PVA molecules at high PVA contents, which lubricates the interface between DWNTs. PMID:23548065

Beese, Allison M; Sarkar, Sourangsu; Nair, Arun; Naraghi, Mohammad; An, Zhi; Moravsky, Alexander; Loutfy, Raouf O; Buehler, Markus J; Nguyen, SonBinh T; Espinosa, Horacio D

2013-04-23

351

Hydrogen storage properties of nano-structural carbon and metal hydrides composites  

NASA Astrophysics Data System (ADS)

Thermodynamic and structural properties of some ball-milled mixtures composed of the hydrogenated nanostructural carbon (C nanoH x) and metal hydride (MH; M=Li, Na, Mg and Ca) were examined from thermal desoroption mass spectroscopy and powder X-ray diffraction, respectively. The results showed that the hydrogen desorption temperatures are significantly lowered from those of each hydride (C nanoH x, MH) in the composites. This indicates that a new type of interaction exists between C nanoH x and MH, which destabilizes C-H and/or M-H bonding as well. Therefore, the above Metal-C-H system would be recognized as a new family of hydrogen storage materials.

Miyaoka, Hiroki; Ichikawa, Takayuki; Isobe, Shigehito; Fujii, Hironobu

2006-08-01

352

Electrochemical hydrogen storage behaviors of CVD, AD and LA grown carbon nanotubes in KOH medium  

Microsoft Academic Search

Carbon nanotubes (CNTs) were synthesized catalytically by both chemical vapor deposition (CVD) method in C2H2\\/H2 atmosphere at 600°C and arc-discharge (AD) method under helium atmosphere. The structure and morphology of CNTs was determined employing scanning electron microscopy (SEM) and FT-Raman spectroscopy. Hydrogen storage capacities were electrochemically measured for undoped and alkali metal (Li, Na and K) doped CVD, AD and

A. K. M. Fazle Kibria; Y. H. Mo; K. S. Park; K. S. Nahm; M. H. Yun

2001-01-01

353

Formate stability and carbonate hydrogenation on strained Cu overlayers on Pt(1 1 1)  

Microsoft Academic Search

Formate (HCOO) synthesis, decomposition and the hydrogenation of carbonate (CO3) on Cu overlayers deposited on a Pt(111) single crystal are investigated to examine the reactivity of a Cu surface under tensile strain with defects present.Formate is synthesized from a 0.5bar mixture of 70% CO2 and 30% H2 at varying temperatures, and the evolution is followed with polarization modulation infrared reflection

N. Schumacher; K. J. Andersson; J. Nerlov; I. Chorkendorff

2008-01-01

354

Formate stability and carbonate hydrogenation on strained Cu overlayers on Pt(1 1 1)  

NASA Astrophysics Data System (ADS)

Formate (HCOO) synthesis, decomposition and the hydrogenation of carbonate (CO 3) on Cu overlayers deposited on a Pt(1 1 1) single crystal are investigated to examine the reactivity of a Cu surface under tensile strain with defects present. Formate is synthesized from a 0.5 bar mixture of 70% CO 2 and 30% H 2 at varying temperatures, and the evolution is followed with polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS). Subsequent TPD reveals decomposition of the formate species into CO 2 and H 2 at 420 ± 5 K for strained Cu at sub-monolayer to monolayer coverages. This is a significantly lower decomposition temperature than obtained earlier on pristine Cu(1 1 1) (˜460 K), as well as for thicker Cu layers where we assign an observed decomposition peak at 440 ± 5 K to relaxed, but defect-rich Cu(1 1 1). However, the thermal stability of formate on strained and defect-rich Cu is similar to previous results obtained for supported, and lattice-strained, Cu nanoparticles. The hydrogenation of carbonate produced by 0.3 bar CO 2 exposure at room temperature was monitored with XPS and TPD showing a significant loss of carbonate when subjected to 0.2 bar H 2 at room temperature. However, the presence of formate on the surface, or any other hydrogenation product, could not be established during or after H 2 exposure by PM-IRRAS, EELS or TPD. Even so, the results suggest that carbonate and its hydrogenation may constitute a relevant pathway to methanol production.

Schumacher, N.; Andersson, K. J.; Nerlov, J.; Chorkendorff, I.

2008-08-01

355

STABLE HYDROGEN PAIR TRAPPED AT CARBON IMPURITIES IN SILICON B. Hourahine,1,  

E-print Network

trigonal defects found in carbon rich Si into which H had been in-diffused. Isotopic shifts with D and 13 C in comparison with separated Cs and H2 in Si and may represent aggregation sites for hydrogen. PACS numbers: 61 of the spectra are indicated. All the samples were treated in H(D) gas ambient at 1350 C for 30 min with a gas

Jones, Robert

356

Selective hydrogenation of citral with transition metal complexes in supercritical carbon dioxide  

Microsoft Academic Search

The activity and selectivity of the transition metal complexes formed from Ru, Rh, Pd and Ni with triphenylphosphine (TPP) have been investigated for hydrogenation of citral in supercritical carbon dioxide (scCO2). High activities are obtained with Ru\\/TPP and Pd\\/TPP catalysts, and the overall activity is in the order of Pd?Ru>Rh>Ni. The Ru\\/TPP complex is highly selective to the formation of

Ruixia Liu; Fengyu Zhao; Shin-ichiro Fujita; Masahiko Arai

2007-01-01

357

Ion beam deposition of amorphous hydrogenated carbon films on amorphous silicon interlayer: Experiment and simulation  

Microsoft Academic Search

A thick layer of amorphous silicon (a-Si) was deposited on industrial grade crystalline n-Si <111>substrate by means of electron beam evaporation. On top of a-Si layer, amorphous hydrogenated carbon (a-C:H) film was grown by direct ion beam deposition from acetylene precursor gas. In order to study on atomic level the a-C:H film growth on amorphous silicon, a theoretical model was

A. Ibenskas; A. Galdikas; Š. Meškinis; M. Andrulevi?ius; S. Tamulevi?ius

2011-01-01

358

Micromachined sol–gel carbon nanotube\\/SnO 2 nanocomposite hydrogen sensor  

Microsoft Academic Search

A novel micromachined single wall carbon nanotube (SWCNT) reinforced nanocrystalline tin dioxide gas sensor has been developed. The presence of SWCNT in SnO2 matrix was realized by a spin-on sol–gel process. The SWCNT\\/SnO2 sensor's sensitivity for hydrogen detection has greatly increased by a factor of three, in comparison to that of pure SnO2 sensor. The novel sensor also lowers the

Jianwei Gong; Jianren Sun; Quanfang Chen

2008-01-01

359

Thermocatalytic hydrogen production from the methane in a fluidized bed with activated carbon catalyst  

Microsoft Academic Search

A fluidized bed reactor made of quartz with 0.055m i.d. and 0.65m in height was employed for the thermocatalytic decomposition of methane to produce CO2 free hydrogen. The fluidized bed reactor was proposed in order to overcome the reactor plugging problem due to carbon deposition, which was resulted in the shut-down of the fixed bed reactor system. Several kinds of

Kang Kyu Lee; Gui Young Han; Ki June Yoon; Byung Kwon Lee

2004-01-01

360

Efficient catalytic addition of aromatic carbon-hydrogen bonds to olefins  

Microsoft Academic Search

The selective cleavage of carbon-hydrogen bonds in organic compounds is a critical step in many organic syntheses, and is particularly important in the conversion of hydrocarbons to useful organic compounds. An organometallic ruthenium complex can cleave C-H bonds in a variety of aromatic systems, leading to addition to alkenes by C-C bond formation. The catalyst operates with a degree of

Shinji Murai; Fumitoshi Kakiuchi; Shinya Sekine; Yasuo Tanaka; Asayuki Kamatani; Motohiro Sonoda; Naoto Chatani

1993-01-01

361

Activated carbon nanotubes: a highly-active metal-free electrocatalyst for hydrogen evolution reaction.  

PubMed

In this communication, for the first time, we report on the development and utilization of activated carbon nanotubes (CNTs) as a highly-active metal-free electrocatalyst for the hydrogen evolution reaction (HER) with good durability in acidic electrolytes. This catalyst shows an onset overpotential and an exchange current density of 100 mV and 16.0 × 10(-3) mA cm(-2), respectively. The possible catalytic mechanism for the HER is also proposed. PMID:25000967

Cui, Wei; Liu, Qian; Cheng, Ningyan; Asiri, Abdullah M; Sun, Xuping

2014-08-25

362

A Comprehensive Reaction Mechanism For Carbon Monoxide\\/Hydrogen\\/Oxygen Kinetics  

Microsoft Academic Search

A comprehensive reaction mechanism for the oxidation of carbon monoxide in the presence of hydrogen is described. Model predictions are compared with experimental data over wide ranges of physical conditions. The data, obtained from shock tube experiments and various types of reactor experiments, encompassed a combined temperature range of 823-2870 K, fuel-oxidizer equivalence ratios between 0.0005 and 6.0, C\\/H ratios between

R. A. YETTER; F. L. DRYER; H. RABITZ

1991-01-01

363

Tests of carbon targets for 12C+12C reactions at astrophysical energies  

NASA Astrophysics Data System (ADS)

As a preliminary step towards measurements of the 12C +12 C reactions at astrophysical energies, we investigate the behaviour of targets under beam bombardment, specifically the quantitative relation between hydrogen and deuterium content of different carbon targets and target temperature. Experiments have taken place at the CIRCE accelerator in Caserta, Italy and preliminary results are presented here.

Morales-Gallegos, L.; Aliotta, M.; Di Leva, A.; Gialanella, L.; Schürmann, D.; De Cesare, M.; Davinson, T.; Imbriani, G.; Romano, M.; Romoli, M.

2015-01-01

364

Weak Carbon-Hydrogen-Nitrogen Interactions Affect the Heterocyclic Ligand Bonding Modes in Barium Complexes Containing 2-Tetrazolato  

E-print Network

Weak Carbon-Hydrogen-Nitrogen Interactions Affect the Heterocyclic Ligand Bonding Modes in Barium calculations of barium complexes of the formula Ba- (azolate)2(18-crown-6). With dimethylaminotetrazolate [CN4

Schlegel, H. Bernhard

365

Carbon dioxide alters the Hoffmann reflex independent of hydrogen ions.  

PubMed

The purpose of this study was to examine the effect of changes in capillary blood pH on the resting soleus Hoffmann (H) reflex in the intact human. H-max size, H-wave at 20% of H-max, M-max and H-reflex latency were recorded in 10 subjects (apparently healthy, ages 19-36) before and after exposure to 3 hours of NaHCO(3), CaCO(3), NH(4)Cl (all at 0.3 g/kg) or 10 minutes 7% Carbon dioxide (CO(2)) administration. NaHCO(3) increased capillary blood pH, CaCO(3) did not change capillary blood pH, and NH(4)Cl and 7% CO(2) decreased capillary blood pH. H-max and H-wave at 20% of M-max size were significantly decreased with no change in M-max, and H-reflex latency significantly increased during 7% CO(2) administration only. No other changes in H-maximum size or H-reflex latency in response to dry chemical administration were observed. Seven percent CO(2) administration reduces the size and increases the latency of the H-maximum size as previously found, but other chemicals which alter capillary blood pH do not. CO(2) modulates afferent nerve function, and does so, it appears, independent of changes in capillary blood pH. PMID:24134189

Beekley, Matthew D

2014-07-01

366

Fractography of the high temperature hydrogen attack of a medium carbon steel  

NASA Technical Reports Server (NTRS)

Microscopic fracture processes were studied which are associated with hydrogen attack of a medium carbon steel in a well-controlled, high-temperature, high-purity hydrogen environment. Exposure to a hydrogen pressure and temperature of 3.5 MN/m2 and 575 C was found to degrade room temperature tensile properties with increasing exposure time. After 408 hr, yield and ultimate strengths were reduced by more than 40 percent and elongation was reduced to less than 2 percent. Initial fissure formation was found to be associated with manganese rich particles, most probably manganese oxide, aligned in the microstructure during the rolling operation. Fissure growth was found to be associated with a reduction in carbide content of the microstructure and was inhibited by the depletion of carbon. The interior surfaces of sectioned fissures or bubbles exhibit both primary and secondary cracking by intergranular separation. The grain surfaces were rough and rounded, suggesting a diffusion-associated separation process. Specimens that failed at room temperature after exposure to hydrogen were found to exhibit mixed mode fracture having varying amounts of intergranular separation, dimple formation, and cleavage, depending on exposure time.

Melson, H. G.; Moorhead, R. D.

1975-01-01

367

Insights into hydrogen bond donor promoted fixation of carbon dioxide with epoxides catalyzed by ionic liquids.  

PubMed

Catalytic coupling of carbon dioxide with epoxides to obtain cyclic carbonates is an important reaction that has been receiving renewed interest. In this contribution, the cycloaddition reaction in the presence of various hydrogen bond donors (HBDs) catalyzed by hydroxyl/carboxyl task-specific ionic liquids (ILs) is studied in detail. It was found that the activity of ILs could be significantly enhanced in the presence of ethylene glycol (EG), and EG/HEBimBr were the most efficient catalysts for the CO2 cycloaddition to propylene oxide. Moreover, the binary catalysts were also efficiently versatile for the CO2 cycloaddition to less active epoxides such as styrene oxide and cyclohexene oxide. Besides, the minimum energy paths for this hydrogen bond-promoted catalytic reaction were calculated using the density functional theory (DFT) method. The DFT results suggested that the ring-closing reaction was the rate-determining step in the HEBimBr-catalyzed cycloaddition reaction but the EG addition could remarkably reduce its energy barrier as the formation of a hydrogen bond between EG and the oxygen atom of epoxides led this process along the standard SN2 mechanism. As a result, the ring-opening reaction became the rate-determining step in the EG/HEBimBr-catalyzed cycloaddition reaction. The work reported herein helped the understanding and design of catalysts for efficient fixation of CO2 to epoxides via hydrogen bond activation. PMID:25639733

Liu, Mengshuai; Gao, Kunqi; Liang, Lin; Wang, Fangxiao; Shi, Lei; Sheng, Li; Sun, Jianmin

2015-02-10

368

Non-syngas direct steam reforming of methanol to hydrogen and carbon dioxide at low temperature.  

PubMed

A non-syngas direct steam reforming route is investigated for the conversion of methanol to hydrogen and carbon dioxide over a CuZnGaO(x) catalyst at 150-200 °C. This route is in marked contrast with the conventional complex route involving steam reformation to syngas (CO/H2) at high temperature, followed by water gas shift and CO cleanup stages for hydrogen production. Here we report that high quality hydrogen and carbon dioxide can be produced in a single-step reaction over the catalyst, with no detectable CO (below detection limit of 1 ppm). This can be used to supply proton exchange membrane fuel cells for mobile applications without invoking any CO shift and cleanup stages. The working catalyst contains, on average, 3-4 nm copper particles, alongside extremely small size of copper clusters stabilized on a defective ZnGa2O4 spinel oxide surface, providing hydrogen productivity of 393.6 ml g(-1)-cat h(-1) at 150 °C. PMID:23187630

Yu, Kai Man Kerry; Tong, Weiyi; West, Adam; Cheung, Kevin; Li, Tong; Smith, George; Guo, Yanglong; Tsang, Shik Chi Edman

2012-01-01

369

Fundamental studies of hydrogen attack in carbon-0.5molybdenum steel and weldments applied in petroelum and petrochemical industries  

NASA Astrophysics Data System (ADS)

High temperature hydrogen attack (HTHA) is a form of surface decarburization, internal decarburization, and/or intergranular cracking in steels exposed to high temperature (>400°F) and high hydrogen pressure. Hydrogen attack is an irreversible process which can cause permanent damage resulting in degradation of mechanical properties and failures such as leakage, bursting, fire, and/or explosion. The continuous progression of hydrogen attack in C-0.5Mo steel and weldments below the C-0.5Mo Nelson Curve has caused a significant concern for the integrity and serviceability of C-0.5Mo steel utilized for pressure vessels and piping in the petroleum refinery and petrochemical industries. A state-of-the-art literature review was implemented to provide a comprehensive overview of the published research efforts on hydrogen attack studies. The evolution of "Nelson Curves" for carbon steel, C-0.5Mo, and Cr-Mo steels was historically reviewed in regard to design applications and limitations. Testing techniques for hydrogen attack assessment were summarized under the categories of hydrogen exposure testing, mechanical evaluation, and dilatometric swelling testing. In accord with the demands of these industries, fundamental studies of hydrogen attack in C-0.5Mo steel and weldments were accomplished in terms of quantitative methodologies for hydrogen damage evaluation; hydrogen damage assessment of service exposed weldments and autoclave exposed materials; effects of carbon and alloying elements, heat treatments, hot and cold working, welding processes and postweld heat treatment (PWHT) on hydrogen attack susceptibility; development of continuous cooling transformation (CCT) diagrams for C-0.5Mo base metals and the coarse grained heat-affected zone (CGHAZ); carbide evaluation for the C-0.5Mo steel after service exposure and heat treatment; methane evolution by the reaction of hydrogen and carbides; hydrogen diffusion and methane pressure through the wall thickness of one-sided hydrogen exposure assembly; hydrogen attack mechanism and hydrogen attack limit modeling.

Liu, Peng

370

Superlow friction of titanium/silicon codoped hydrogenated amorphous carbon film in the ambient air  

SciTech Connect

Titanium/silicon codoped hydrogenated carbon film was deposited on the n-Si (100) substrates by reactive magnetron sputtering Ti80Si20 target in a mixture of argon and methane. Microstructure of the film was investigated using x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and attenuated total reflectance Fourier transform infrared spectroscopy. The investigations have revealed that the film has an amorphous structure and consists of high sp{sup 2} hybridized carbon atoms and bonding hydrogen atoms. The mechanical and tribological properties were evaluated using a nanoindentor and a ball-on-disk tribometer, respectively. The film exhibits hardness of 9.6 GPa, high elastic recovery of 73.0% and high H/E ratio of 0.156. Most significant, the superlow friction ({mu}<0.01) and special low wear rate (2.4x10{sup -7} mm{sup 3} N{sup -1} m{sup -1}) was observed in ambient air with 40% relative humidity. Combining the results of scanning electron microscopy and Raman analyses of the worn surface, it is concluded that some mechanisms, e.g., transfer films, friction-induced graphitization, hydrogen-terminated carbon surface, tribochemical reaction, etc., could be together responsible for this superlow friction in the ambient air.

Jiang Jinlong [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Department of Physics, Lanzhou University of Technology, Lanzhou 730050 (China); Graduate University of the Chinese Academy of Sciences, Beijing 100049 (China); Hao Junying; Wang Peng; Liu Weimin [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

2010-08-15

371

Efficient hydrogenation of organic carbonates, carbamates and formates indicates alternative routes to methanol based on CO2 and CO  

NASA Astrophysics Data System (ADS)

Catalytic hydrogenation of organic carbonates, carbamates and formates is of significant interest both conceptually and practically, because these compounds can be produced from CO2 and CO, and their mild hydrogenation can provide alternative, mild approaches to the indirect hydrogenation of CO2 and CO to methanol, an important fuel and synthetic building block. Here, we report for the first time catalytic hydrogenation of organic carbonates to alcohols, and carbamates to alcohols and amines. Unprecedented homogeneously catalysed hydrogenation of organic formates to methanol has also been accomplished. The reactions are efficiently catalysed by dearomatized PNN Ru(II) pincer complexes derived from pyridine- and bipyridine-based tridentate ligands. These atom-economical reactions proceed under neutral, homogeneous conditions, at mild temperatures and under mild hydrogen pressures, and can operate in the absence of solvent with no generation of waste, representing the ultimate ‘green’ reactions. A possible mechanism involves metal-ligand cooperation by aromatization-dearomatization of the heteroaromatic pincer core.

Balaraman, Ekambaram; Gunanathan, Chidambaram; Zhang, Jing; Shimon, Linda J. W.; Milstein, David

2011-08-01

372

Molecular dynamics simulations of hydrogen adsorption\\/desorption by palladium decorated single-walled carbon nanotube bundle  

Microsoft Academic Search

Utilising molecular dynamics simulations, the hydrogen molecules adsorption isotherms of the (8,?0) palladium decorated single-walled carbon nanotube (SWNT) were obtained. The hydrogen adsorption was studied on the external, interstial and internal surfaces of the SWNT bundle at several temperatures ranging from 77 to 400?K. The results were compared with the bare single-walled carbon nanotube bundle under the same conditions. The

Seifollah Jalili; Arezou Jaberi; Mohammad Ghasem Mahjani; Majid Jafarian

2012-01-01

373

Engineering Bacteria for Efficient Fuel Production: Novel Biological Conversion of Hydrogen and Carbon Dioxide Directly into Free Fatty Acids  

SciTech Connect

Electrofuels Project: OPX Biotechnologies is engineering a microorganism currently used in industrial biotechnology to directly produce a liquid fuel from hydrogen and carbon dioxide (CO2). The microorganism has the natural ability to use hydrogen and CO2 for growth. OPX Biotechnologies is modifying the microorganism to divert energy and carbon away from growth and towards the production of liquid fuels in larger, commercially viable quantities. The microbial system will produce a fuel precursor that can be chemically upgraded to various hydrocarbon fuels.

None

2010-07-12

374

Passive colorimetric dosimeter tubes for ammonia, carbon monoxide, carbon dioxide, hydrogen sulfide, nitrogen dioxide, and sulfur dioxide  

SciTech Connect

Colorimetric, stain length, personal dosimeters operating by gas diffusion have been developed to determine worker exposure for up to an 8-h period for several inorganic airborne contaminants in the range of their threshold limit values. Length of stain, colorimetric dosimeters have been made for the detection of ammonia (NH/sub 3/), carbon monoxide (CO), carbon dioxide (CO/sub 2/), hydrogen sulfide (H/sub 2/S), nitrogen dioxide (NO/sub 2/), and sulfur dioxide (SO/sub 2/) in air. For each gas detection system, the sampler depends on the transfer of the gas by diffusion into a glass tube containing a colorimetric length of stain indicator. The stain length developed in a given period of time is compared to a calibration chart to determine, on the spot, the average gas concentration to which the dosimeter has been exposed. These dosimeters are known by the trade name Vapor Gard.

McKee, E.S.; Pritts, I.M.

1981-08-01

375

Passive colorimetric dosimeter tubes for ammonia, carbon monoxide, carbon dioxide, hydrogen sulfide, nitrogen dioxide and sulfur dioxide  

SciTech Connect

Colorimetric, stain length, personal dosimeters operating by gas diffusion have been developed to determine worker exposure for up to an eight-hour period for several inorganic airborne contaminants in the range of their Threshold Limit Values. Length of stain, colorimetric dosimeters have been made for the detection of ammonia (NH/sub 3/), carbon monoxide (CO), carbon dioxide (CO/sub 2/), hydrogen sulfide (H/sub 2/S), nitrogen dioxide (NO/sub 2/), and sulfur dioxide (SO/sub 2/) in air. For each gas detection system, the sampler depends on the transfer of the gas by diffusion into a glass tube containing a colorimetric length of stain indicator. The stain length developed in a given period of time is compared to a calibration chart to determine, on the spot, the average gas concentration to which the dosimeter has been exposed. These dosimeters are known by the trade name Vapor Gard.

McConnaughey, P.W.; McKee, E.S.; Pritts, I.M.

1985-07-01

376

Biological sulfate reduction using gas-lift reactors fed with hydrogen and carbon dioxide as energy and carbon source  

SciTech Connect

Feasibility and engineering aspects of biological sulfate reduction in gas-lift reactors were studied. Hydrogen and carbon dioxide were used as energy and carbon source. Attention was paid to biofilm formation, sulfide toxicity, sulfate conversion rate optimization, and gas-liquid mass transfer limitations. Sulfate-reducing bacteria formed stable biofilms on pumice particles. Biofilm formation was not observed when basalt particles were used. However, use of basalt particles led to the formation of granules of sulfate-reducing biomass. The sulfate-reducing bacteria, grown on pumice, easily adapted to free H[sub 2]S concentrations up to 450 mg/L. Biofilm growth rate then equilibrated biomass loss rate. These high free H[sub 2]S concentrations caused reversible inhibition rather than acute toxicity. When free H[sub 2]S concentrations were kept below 450 mg/L, a maximum sulfate conversion rate of 30 g SO[sub 4][sup 2[minus

Houten, R.T. van; Hulshoff Pol, L.W.; Lettinga, G. (Wageningen Agricultural Univ. (Netherlands). Dept. of Environmental Technology)

1994-08-20

377

Kinetic deuterium isotope effects in the combustion of nitramine propellants. Final report, October 1986-July 1988. [HMX and RDX  

SciTech Connect

The deuterium isotope effect was used to investigate the rate-limiting process in the combustion of nitramine propellants. Model propellant formulations containing either octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), or their deuteriated analogues were pressed into pellets and burned under nitrogen pressure in a window bomb. The magnitudes of the observed deuterium isotope effects indicate that the HMX and RDX exert significant control over the burning process of the studied propellants. Furthermore, assuming a consistent mechanism between decomposition and combustion, the observed isotope effects suggest that a carbon-hydrogen bond rupture in HMX and RDX is the rate-controlling process in the combustion of the model nitramine propellants.

Trulove, P.C.

1988-07-01

378

Effect of p-type multi-walled carbon nanotubes for improving hydrogen storage behaviors  

NASA Astrophysics Data System (ADS)

In this study, the hydrogen storage behaviors of p-type multi-walled carbon nanotubes (MWNTs) were investigated through the surface modification of MWNTs by immersing them in sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) at various ratios. The presence of acceptor-functional groups on the p-type MWNT surfaces was confirmed by X-ray photoelectron spectroscopy. Measurement of the zeta-potential determined the surface charge transfer and dispersion of the p-type MWMTs, and the hydrogen storage capacity was evaluated at 77 K and 1 bar. From the results obtained, it was found that acceptor-functional groups were introduced onto the MWNT surfaces, and the dispersion of MWNTs could be improved depending on the acid-mixed treatment conditions. The hydrogen storage was increased by acid-mixed treatments of up to 0.36 wt% in the p-type MWNTs, compared with 0.18 wt% in the As-received MWNTs. Consequently, the hydrogen storage capacities were greatly influenced by the acceptor-functional groups of p-type MWNT surfaces, resulting in increased electron acceptor-donor interaction at the interfaces.

Lee, Seul-Yi; Yop Rhee, Kyong; Nahm, Seung-Hoon; Park, Soo-Jin

2014-02-01

379

GASEOUS HYDROGEN EFFECTS ON THE MECHANICAL PROPERTIES OF CARBON AND LOW ALLOY STEELS (U)  

SciTech Connect

This report is a compendium of sets of mechanical properties of carbon and low alloy steels following the short-term effects of hydrogen exposure. The property sets include the following: Yield Strength; Ultimate Tensile Strength; Uniform Elongation; Reduction of Area; Threshold Cracking, K{sub H} or K{sub th}; Fracture Toughness (K{sub IC}, J{sub IC}, and/or J-R Curve); and Fatigue Crack Growth (da/dN). 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).

Lam, P

2006-06-08

380

Hydrogen storage in carbon nanofibers as being studied by Northeastern University. Technical evaluation report  

SciTech Connect

As part of the current technical evaluation effort, the author was tasked with going to Northeastern, interviewing Dr. Baker and his team, seeing a demonstration of the storage process, and making an assessment of the validity of the claim and the soundness of the research. Dr. Baker and his group have a process that, if proven to work, could be the breakthrough that is needed in the area of on-board hydrogen storage. One of the biggest problems may be the fact that the results look so good, that even if they are real, they will be viewed with skepticism by many. The chemisorption value of 5.8 liters of hydrogen per gram of carbon that Dr. Baker claimed at the time of his proposal has now been surpassed many times. Dr. Baker has reported reproducible hydrogen take-up levels as high as 30 liters per gram, depending on fiber structure. The fibers are loaded with hydrogen at ambient temperature using a pressurized feed at levels of about 600--900 psi. The hydrogen will be retained at pressure, but can apparently be essentially totally recovered upon pressure release. This paper reports the findings from the trip to Northeastern.

Skolnik, E.G. [Energetics, Inc., Columbia, MD (United States)

1997-06-01

381

Redox Control and Hydrogen Production in Sediment Caps Using Carbon Cloth Electrodes  

PubMed Central

Sediment caps that degrade contaminants can improve their ability to contain contaminants relative to sand and sorbent-amended caps, but few methods to enhance contaminant degradation in sediment caps are available. The objective of this study was to determine if, carbon electrodes emplaced within a sediment cap at poised potential could create a redox gradient and provide electron donor for the potential degradation of contaminants. In a simulated sediment cap overlying sediment from the Anacostia River (Washington, DC), electrochemically induced redox gradients were developed within 3 days and maintained over the period of the test (~100 days). Hydrogen and oxygen were produced by water electrolysis at the electrode surfaces and may serve as electron donor and acceptor for contaminant degradation. Electrochemical and geochemical factors that may influence hydrogen production were studied. Hydrogen production displayed zero order kinetics with ~75% coulombic efficiency and rates were proportional to the applied potential between 2.5V to 5V and not greatly affected by pH. Hydrogen production was promoted by increasing ionic strength and in the presence of natural organic matter. Graphite electrode-stimulated degradation of tetrachlorobenzene in a batch reactor was dependent on applied voltage and production of hydrogen to a concentration above the threshold for biological dechlorination. These findings suggest that electrochemical reactive capping can potentially be used to create “reactive” sediments caps capable of promoting chemical or biological transformations of contaminants within the cap. PMID:20879761

Sun, Mei; Yan, Fei; Zhang, Ruiling; Reible, Danny D.; Lowry, Gregory V.; Gregory, Kelvin B.

2010-01-01

382

Photoelectron spectroscopy study of metallic nanocluster arrangement at the surface of reactively sputtered amorphous hydrogenated carbon  

SciTech Connect

We report on the results of the arrangement of isolated surface metallic nanoclusters embedded in amorphous hydrogenated carbon (a-C:H) thin films, studied by photoelectron spectroscopy. As a model system we used gold-containing amorphous hydrogenated carbon (a-C:H/Au), due to the lack of reactivity between carbon and gold. The a-C:H/Au samples are obtained by simultaneous magnetron sputtering of Au target by argon and plasma-enhanced chemical vapor deposition of methane. Photoelectron spectroscopy with x-ray and ultraviolet excitation has been employed for surface studies that comprise as-deposited sample spectra recordings, measurements at off-normal takeoff angle, in situ in-depth profiling by Ar{sup +} ion etching, and thiophene adsorption at the sample surface. The results of these extended studies firmly support previously drawn conclusions [I. R. Videnovic, V. Thommen, P. Oelhafen, D. Mathys, M. Dueggelin, and R. Guggenheim, Appl. Phys. Lett 80, 2863 (2002)] that by deposition on electrically grounded substrates one obtains samples with topmost Au clusters covered with a thin layer of a-C:H. Introducing a dc substrate bias voltage results in bald Au clusters on the surface and increased sp{sup 2}/sp{sup 3} coordinated carbon ratio in the a-C:H matrix.

Videnovic, Ivan R.; Oelhafen, Peter [Institut fuer Physik, Universitaet Basel, Klingelbergstr. 82, CH-4056 Basel (Switzerland)

2005-04-01

383

Deuterium isotope effects during HMX combustion: Chemical kinetic burn-rate control mechanism verified  

SciTech Connect

The appearance of a significant deuterium isotope effect during the combustion of the solid HMX compound verifies that the chemical reaction kinetics is a major contributor in determining the experimentally observed or global burn rate. Burn rate comparison of HMX and its deuterium labeled HMX-d(8) analogue reveals a primary kinetic deuterium isotope effect (1 deg. KDIE) at 500 psig (3.55 MPa) and 1000 psig (6.99 MPa) pressure and selectively identifies covalent carbon-hydrogen bond rupture as the mechanistic step which ultimately controls the further HMX burn rate under the static combustion conditions of this experiment. The 1 deg. KDIE value further suggests the rate-limiting C-H bond rupture occurs during the solid state HMX decomposition/deflagration portion of the overall combustion event and is supported by other independently published studies. A possible anomalous KDIE result at 1500 psig (10.4 MPa) is addressed. This condensed phase KDIE approach illustrates a direct link between lower temperature/pressure thermal decomposition and deflagration processes and their potential applicability to the combustion regime. Most importantly, a new general method is demonstrated for mechanistic combustion investigations which selectively permits an in-situ identification of the compound's burn rate-controlling step.

Shackelford, S.A.; Goshgarian, B.B.; Chapman, R.D.; Askins, R.E.; Flanigan, D.A.

1989-01-01

384

Dissolution of Irradiated Commercial UO2 Fuels in Ammonium Carbonate and Hydrogen Peroxide  

SciTech Connect

We propose and test a disposition path for irradiated nuclear fuel using ammonium carbonate and hydrogen peroxide media. We demonstrate on a 13 g scale that >98% of the irradiated fuel dissolves. Subsequent expulsion of carbonate from the dissolver solution precipitates >95% of the plutonium, americium, curium, and substantial amounts of fission products, effectively partitioning the fuel at the dissolution step. Uranium can be easily recovered from solution by any of several means, such as ion exchange, solvent extraction, or direct precipitation. Ammonium carbonate can be evaporated from solution and recovered for re-use, leaving an extremely compact volume of fission products, transactinides, and uranium. Stack emissions are predicted to be less toxic, less radioactive, chemically simpler, and simpler to treat than those from the conventional PUREX process.

Soderquist, Chuck Z.; Johnsen, Amanda M.; McNamara, Bruce K.; Hanson, Brady D.; Chenault, Jeffrey W.; Carson, Katharine J.; Peper, Shane M.

2011-01-18

385

Hydrogen sulfide and ammonia removal on activated carbon fiber cloth-supported metal oxides.  

PubMed

The present investigation attempts to provide mechanisms for the influence of metal catalysts on carbon supports in odorous gas removal. For this purpose, an activated carbon fiber cloth (ACFC) was subjected to successive metal impregnation to modify its surface properties and so increase its treatment capacity. The carbon fiber cloth adsorbent was prepared by classical incipient wetness impregnation followed by calcination in order to obtain metal oxide phases. Different impregnation parameters (type of metal, level of impregnation, calcination temperature) in the removal of hydrogen sulfide and ammonia were studied. Adsorption kinetics and capacities were carried out in a batch reactor at room temperature. It was found that removal activity depended on metal loading as well as on the order of the metal addition and calcination phase. The capacity of ACFC-supported metal oxides to adsorb both pollutants showed great improvement compared to the virgin adsorbent. PMID:16335599

Le Leuch, L M; Subrenat, A; Le Cloirec, P

2005-11-01

386

Stereospecific deuterium substitution at the alpha-carbon position of dopamine and its effect on oxidative deamination catalyzed by MAO-A and MAO-B from different tissues.  

PubMed

Stereospecific replacement of deuterium in the alpha-carbon side chain position of dopamine (DA) was achieved by decarboxylation of L-3,4-dihydroxyphenylalanine (L-dopa) using hog kidney aromatic aminoacid decarboxylase. The S[alpha-2H1]DA enantiomer was obtained by decarboxylation of L-[alpha-2H1]dopa in H2O, while the R[alpha-2H1]DA enantiomer was obtained by decarboxylation of unsubstituted L-dopa in 2H2O. An inverse solvent isotope effect of L-dopa decarboxylation was observed in 2H2O. The deaminated aldehyde products of the four DA analogues, i.e. undeuterated DA, [alpha, alpha-2H2] DA, R[alpha-2H1]DA and S[alpha-2H1]DA, have been analyzed by the gas chromatography-mass spectrometry (GC-MS) method. It is evident that monoamine oxidase (MAO) catalyzes the stereochemical removal of only R-deuterium and that S-deuterium was maintained at the alpha-carbon atom of 3,4-dihydroxyphenylacetaldehyde. The steady-state kinetics of the oxidative deamination of undeuterated, [alpha, alpha-2H2], R[alpha-2H1], and S[alpha-2H1] dopamine were assessed by determination of the aldehyde products directly by high performance liquid chromatography (HPLC) using electrochemical detection (ECD). MAO-A from rat liver mitochondria (deprenyl-treated) and from human placenta, as well as MAO-B from rat liver (clorgyline-treated) and from human platelet were used in this study. The apparent isotope effects, i.e. (V/K)H/(V/K)D ratios of [alpha, alpha-2H2]DA and R[alpha-2H1]DA, were quite similar (2.34 and 3.13) with respect to both MAO-A and MAO-B. S[alpha-2H1]DA exhibited a slight secondary isotope effect. Formula: see text. PMID:3954792

Yu, P H; Bailey, B A; Durden, D A; Boulton, A A

1986-03-15

387

Hydrogen storage in carbon nitride nanobells X. D. Bai, Dingyong Zhong, G. Y. Zhang, X. C. Ma, Shuang Liu, and E. G. Wanga)  

E-print Network

Hydrogen storage in carbon nitride nanobells X. D. Bai, Dingyong Zhong, G. Y. Zhang, X. C. Ma as hydrogen adsorbent. A hydrogen storage capacity up to 8 wt % was achieved reproducibly under ambient pressure and at temperature of 300 °C. The high hydrogen storage capacity under the moderate conditions

Zhang, Guangyu

388

Hydrogen production using solid oxide membrane electrolyzer with solid carbon reductant in liquid metal anode  

SciTech Connect

A laboratory-scale solid oxide membrane (SOM) steam electrolyzer that can potentially utilize the energy value of coal or any hydrocarbon reductant to produce high purity hydrogen has been fabricated and evaluated. The SOM electrolyzer consists of an oxygen-ion-conducting yttria-stabilized zirconia (YSZ) electrolyte with a Ni-YSZ cermet cathode coated on one side and liquid tin anode on the other side. Hydrogen production using the SOM electrolyzer was successfully demonstrated between 900 and 1000{sup o}C by feeding a steam-rich gas to the Ni-YSZ cermet cathode and solid carbon reductant into the liquid tin anode. It was confirmed that the energy required for hydrogen production can be effectively lowered by feeding a solid carbon reductant in the liquid tin anode. A polarization model for the SOM electrolyzer was developed. The experimental data obtained under different operating conditions were curve fitted into the model to identify the various polarization losses. Based on the results of this study, work needed toward increasing the electrochemical performance of the SOM electrolyzer is discussed.

Pati, S.; Yoon, K.J.; Gopalan, S.; Pal, U.B. [Boston University, Boston, MA (United States). Dept. of Mechanical Engineering

2009-07-01

389

Aggregation of carbon in an atmosphere of molecular hydrogen investigated by ReaxFF-molecular dynamics simulations  

Microsoft Academic Search

The formation of carbon and hydrocarbon molecules by aggregation of carbon in a H2 atmosphere was investigated by molecular dynamics simulations based on the Reax force field (ReaxFF). Systems of 500 carbon atoms and 1000 hydrogen molecules were simulated at different densities and temperatures from 1000K to 2000K. The majority of hydrocarbons formed during 4ns of simulation time consist of

N. Lümmen

2010-01-01

390

Hydrogen adsorption on single-walled carbon nanotubes studied by core-level photoelectron spectroscopy and Raman spectroscopy  

Microsoft Academic Search

We have investigated the adsorption of atomic hydrogen on vertically aligned carbon nanotube (CNT) films using in situ synchrotron-radiation-based core-level (CL) photoelectron spectroscopy and Raman spectroscopy. From C 1s CL spectra, we identified a CL peak component due to C–H bonds of carbon atoms in single-walled carbon nanotubes (SWCNTs). We also found the suppression of ?-plasmon excitation, indicating that the

A. Tokura; F. Maeda; Y. Teraoka; A. Yoshigoe; D. Takagi; Y. Homma; Y. Watanabe; Y. Kobayashi

2008-01-01

391

Is Deuterium Nuclear Fusion Catalyzed by Antineutrinos?  

NASA Astrophysics Data System (ADS)

The hypothesis of Fischbach and Jenkins that neutrinos emitted from the sun accelerate radioactive decay is noted. It is thought that neutrinos accelerate beta decay by reacting with neutron-rich nuclides to form a beta particle and a daughter product, with no antineutrino emitted. Conversely, it is proposed that antineutrinos can react with proton-rich nuclides to cause positron decay, with no neutrino emitted. It is also proposed that the nuclear fusion of the hydrogen bomb is triggered not only by the energy of the igniting fission bomb, but by the antineutrinos created by the rapid beta decay of the daughter products in the fission process. The contemplated mechanism for antineutrino initiated fusion is the following: 1. The antineutrinos from the fission daughter products cause positron decay of deuterium by the process outlined above. 2. In a later fusion step, these positrons subsequently react with neutrons in deuterium to create antineutrinos. Electrons are unavailable to annihilate positrons in the plasma of the hydrogen bomb. 3. These antineutrinos thereafter react with more deuterium to form positrons, thereby propagating a chain reaction. )

Shomer, Isaac

2010-02-01

392

Decorating multi-walled carbon nanotubes with nickel nanoparticles for selective hydrogenation of citral  

SciTech Connect

The nanocomposites of multi-walled carbon nanotubes (MWNTs) decorated with nickel nanoparticles were conveniently prepared by a chemical reduction of nickel salt in the present of poly(acrylic acid) grafted MWNTs (PAA-g-MWNTs). Due to the strong interaction between Ni{sup 2+} and -COOH, PAA-g-MWNTs became an excellent supporting material for Ni nanoparticles. The morphology and distribution of Ni nanoparticles on the surface of MWNTs were greatly influenced by the reduction temperatures, the experimental results also showed that the distribution of Ni nanoparticles was greatly improved while the MWNTs were modified by poly(acrylic acid) (PAA). The hydrogenation activity and selectivity of MWNTs decorated with Ni nanoparticles (Ni-MWNTs) for alpha, beta-unsaturated aldehyde (citral) were also studied, and the experimental results showed that the citronellal, an important raw material for flavoring and perfumery industries, is the favorable product with a percentage as high as 86.9%, which is 7 times higher than that of catalyst by Ni-supported active carbon (Ni-AC). - Abstract: Nickel nanoparticles decorated multi-walled carbon nanotubes (Ni-MWNTs) nanocomposites were conveniently prepared by a chemical reduction of nickel salt in the present of poly(acrylic acid) grafted MWNTs (PAA-g-MWNTs). These nanocomposites possessed excellent catalytic activity and selectivity for hydrogenation of citral.

Tang Yuechao; Yang Dong [Key Laboratory of Molecular Engineering of Polymers (Ministry of Education), Department of Macromolecular Science and Advanced Materials Laboratory, Fudan University, Shanghai 200433 (China); Qin Feng [Department of Chemistry, Fudan University, Shanghai 200433 (China); Hu Jianhua [Key Laboratory of Molecular Engineering of Polymers (Ministry of Education), Department of Macromolecular Science and Advanced Materials Laboratory, Fudan University, Shanghai 200433 (China); Wang Changchun, E-mail: ccwang@fudan.edu.c [Key Laboratory of Molecular Engineering of Polymers (Ministry of Education), Department of Macromolecular Science and Advanced Materials Laboratory, Fudan University, Shanghai 200433 (China); Xu Hualong [Department of Chemistry, Fudan University, Shanghai 200433 (China)

2009-08-15

393

Influence of quantum effects on the physisorption of molecular hydrogen in model carbon foams  

NASA Astrophysics Data System (ADS)

The physisorption of molecular hydrogen in model carbon foams has been investigated from 50 K to room temperature. The study is carried out within the framework of the density functional theory for quantum liquids at finite temperatures. Calculations are performed in the grand canonical ensemble, i.e., the adsorbed fluid is assumed to be in equilibrium with an external gas of hydrogen molecules with concentrations ranging from 8 × 10^{-4} kg m^{-3} to n=71 kg {{m}}^{-3}. It is shown that, while strong zero-point energy effects are present even at room temperature, the adsorption isotherms exhibit only a weak dependence on the explicit incorporation of the bosonic exchange symmetry of hydrogen molecules. The increase of the average particle density prevents the deviations from the Maxwell-Boltzmann statistics to become noticeable if the system is cooled down. The volumetric storage capacity of these materials at low temperatures is about one half of the U. S. Department of Energy goal, while the gravimetric capacity is still far from the standards required by mobile applications. The relation between the microscopic structure of the hydrogen fluid and the calculated adsorption properties is also addressed.

Martínez-Mesa, A.; Yurchenko, S. N.; Patchkovskii, S.; Heine, T.; Seifert, G.

2011-12-01

394

Amorphous carbon supported MoS? nanosheets as effective catalysts for electrocatalytic hydrogen evolution.  

PubMed

Amorphous carbon supported MoS?, which was elaborately prepared by using a facile hydrothermal method followed by annealing, is first employed as a catalyst for the hydrogen evolution reaction (HER). Herein, we demonstrate a preparation strategy, by which MoS? and carbon materials could be formed in situ and simultaneously. The MoS? nanosheets are vertically formed on the carbon nanosphere, as illustrated in the scanning electron micrograph. The unique morphology can expose abundant edges of the MoS? layer as active sites for the HER, while the underlying amorphous carbon effectively improves the conductivity. By means of employing amorphous carbon as a substrate, an optimized catalyst was developed, which exhibited enhanced catalytic activity for the electrocatalytic HER with an onset potential as low as 80 mV, extremely large cathodic current density and excellent stability. Notably, a Tafel slope of 40 mV per decade was measured, which exceeds by far the activity of previous MoS? catalysts and suggests the Volmer-Heyrovsky-mechanism for the MoS?-catalyzed HER. PMID:25089653

Zhao, Xue; Zhu, Hui; Yang, Xiurong

2014-09-21

395

Hydrogen exchange in some coal-related reactions at 400/sup 0/C  

SciTech Connect

Data are available for kinetics of the transfer of hydrogen from tetralin and other hydrogen-rich solvents, but not much is known about the detailed mechanism involving individual linkages or groups in coal. In order to obtain some of this information, we have chosen to work with the pure compounds, 1,2-diphenylethane (bibenzyl), and diphenylmethane as models for certain linkages in coal. Because the thermolysis of the compound gives some different products when heated alone or when heated in the presence of a good hydrogen donor, such as tetralin, it was of interest to know where the cleavage fragments derive their hydrogen to give the final product. While the source of hydrogen needed to cap off the thermolysis fragments is obvious when bibenzyl is heated alone, its origin is ambiguous when tetralin is present. In order to resolve this aspect of the reaction, we prepared bibenzyl completely deuterated (99.8%) in the dimethylene linkage, and pyrolyzed it in the presence of ordinary tetralin. The products were isolated and their hydrogen and deuterium content were determined. From the data we conclude that the benzyl radical, formed by cleavage of bibenzyl, gives toluene by abstracting hydrogen from tetralin. The product after 1 percent conversion was PhCD/sub 2/H. Further, it was observed that, upon heating the mixture for eight hours, deuterium appeared in all the compounds. A considerable amount of deuterium exchange had taken place. In fact, in this mixture, tetralin-bibenzyl-d/sub 4/ at 400/sup 0/C, deuterium is lost from bibenzyl by exchange 3 to 4 times faster than it undergoes carbon-carbon bond scission. Thus, the chemistry of bibenzyl at 400/sup 0/ is dominated by hydrogen exchange reactions.

Benjamin, B.M.; Michalczyk, M.J.; Woody, M.C.

1980-01-01

396

Numerical simulation by a random particle method of Deuterium-Tritium fusion reactions in a plasma.  

E-print Network

Reactor is to obtain fusion reactions between two isotopes of hydrogen in a confined plasma. We study hereNumerical simulation by a random particle method of Deuterium-Tritium fusion reactions in a plasma that models the fusion reaction between a deuterium ion and a tritium ion, and giving an particle

397

Metal-oxide-silicon diodes on deuterium-implanted silicon substrate and R. K. Jarwal  

E-print Network

PROOF COPY 047021APL Metal-oxide-silicon diodes on deuterium-implanted silicon substrate D. Misraa implantation was used to incorporate deuterium at the Si­SiO2 interface. Polycrystalline silicon gate metal-oxide0003-6951 00 04721-5 Role of hydrogen in metal-oxide-semiconductor MOS device stability and reliability

Misra, Durgamadhab "Durga"

398

Covalent immobilization of protein onto a functionalized hydrogenated diamond-like carbon substrate.  

PubMed

Hydrogenated diamond-like carbon (HDLC) has an atomically smooth surface that can be deposited on high-surface area substrata and functionalized with reactive chemical groups, providing an ideal substrate for protein immobilization. A synthetic sequence is described involving deposition and hydrogenation of DLC followed by chemical functionalization. These functional groups are reacted with amines on proteins causing covalent immobilization on contact. Raman measurements confirm the presence of these surface functional groups, and Fourier transform infrared spectroscopy (FTIR) confirms covalent protein immobilization. Atomic force microscopy (AFM) of immobilized proteins is reproducible because proteins do not move as a result of interactions with the AFM probe-tip, thus providing an advantage over mica substrata typically used in AFM studies of protein. HDLC offers many of the same technical advantages as oxidized graphene but also allows for coating large surface areas of biomaterials relevant to the fabrication of medical/biosensor devices. PMID:20949913

Biswas, Hari Shankar; Datta, Jagannath; Chowdhury, D P; Reddy, A V R; Ghosh, Uday Chand; Srivastava, Arvind Kumar; Ray, Nihar Ranjan

2010-11-16

399

Applications of functional carbon nanomaterials from hydrogen storage to drug delivery  

NASA Astrophysics Data System (ADS)

This dissertation describes the modification and functionalization of single-walled carbon nanotubes (SWCNTs). These SWCNTs were then investigated for their use in medical applications and for the storage of hydrogen. A technique was developed that leads to highly customized, individually suspended aqueous solutions of SWCNTs. These newly generated water-soluble SWCNTs were then functionalized further in water, thereby permitting the second functionalization addends to be chemically sensitive functional groups, for example drugs, that would not withstand the strongly acidic conditions of the first functionalization. The radical scavenging properties of nanovectors derived from SWCNTs were investigated and it was found that even the poorest SWCNT nanovector studied was nearly 40 times more effective at scavenging radicals than dendrite-fullerene DF-1, which has been shown to be a radioprotective to zebrafish via an antioxidant niechanism. This was used as the base to investigate using SWCNTs as protectors and mitigators of radiation exposure. SWCNTs were then explored for their use as drug delivery agents, in particular, the water insoluble chemotherapy drug, paclitaxel. SWCNTs showed promising in vivo and in vitro efficacy in the delivery of paclitaxel. Toxicity and biodistribution studies of the SWCNTs as drug delivery agents were performed in vivo using SWCNTs functionalized with radiolabeled indium. It was found that SWCNTs could be used for hydrogen storage by chemically crosslinking 3-dimensional frameworks of SWCNT fibers. These frameworks were shown to physisorb twice as much hydrogen, at low pressures, with respect to their surface areas, than typical macroporous carbon materials. This makes these SWCNT frameworks attractive materials for the development of a hydrogen vehicle fuel tank.

Leonard, Ashley Dawn

400

A Powerful Remote Source of O Atoms for the Removal of Hydrogenated Carbon Deposits  

NASA Astrophysics Data System (ADS)

We describe a system to deliver a large flux of O atoms for the removal of hydrogenated carbon films from surfaces in remote areas of tokamaks with carbon divertors. The oxygen plasma is generated via electrode-less radiofrequency discharge in a discharge chamber connected to a remote chamber by a 2 m long complex-shaped glass tube 4 cm in diameter. The density of O atoms in the remote chamber was measured with a nickel catalytic probe and its variation with discharge power obtained. The density was close to the detection limit of the probe (around 1 × 1019 m-3) as long as the vacuum system was pumped with a rotary pump at a nominal pumping speed of 80 m3 h-1. The density increased well over 1020 m-3 when a Roots pump was added. The effective pumping speed at the current setup was up to 200 m3 h-1. At such conditions, the maximal O-atom density at 2 m from the source was up to 3 × 1020 m-3. The density depended on the pressure as well as the discharge power. The behavior of O-atom density far away from the source was explained by gas phase and surface phenomena. The effective pumping speed was found to be of crucial importance. The setup was used for removal of model hydrogenated carbon films. Experiments were performed at sample temperatures up to 600 K and etching rates up to 50 nm/s were obtained. We found that the experimental setup is suitable for removal of hydrogenated atoms on a large scale.

Zaplotnik, R.; Vesel, A.; Mozetic, M.

2013-02-01

401

Fluence dependence of deuterium trapping in graphite  

NASA Astrophysics Data System (ADS)

The trapping of ˜ 1 keV D in graphite at 300 K has been studied by thermal desorption spectroscopy, as a function of fluence, for fluences up to ˜ 4 × 10 24 D/m 2. In pyrolytic (HPG99) and fine grain (EK98) graphite, the amount of retained deuterium was found to increase with increasing D + fluence over the entire range studied. In a pseudo-monocrystal sample, however, the amount of retained deuterium did not increase significantly beyond the saturation concentration of ˜ 2 × 10 21 D/m 2. The difference in retention properties is attributed to the crystal structure of the graphite. The more porous structure of pyrolytic and fine-grain graphites allows the migration of thermalized D atoms beyond the implantation zone, where they may be trapped, adding to the total hydrogen inventory.

Haasz, A. A.; Davis, J. W.

1994-04-01

402

Simultaneous determination of stable carbon, oxygen, and hydrogen isotopes in cellulose.  

PubMed

A technological development is described through which the stable carbon-, oxygen-, and nonexchangeable hydrogen-isotopic ratios (?(13)C, ?(18)O, ?(2)H) are determined on a single carbohydrate (cellulose) sample with precision equivalent to conventional techniques (?(13)C 0.15‰, ?(18)O 0.30‰, ?(2)H 3.0‰). This triple-isotope approach offers significant new research opportunities, most notably in physiology and medicine, isotope biogeochemistry, forensic science, and palaeoclimatology, when isotopic analysis of a common sample is desirable or when sample material is limited. PMID:25495958

Loader, N J; Street-Perrott, F A; Daley, T J; Hughes, P D M; Kimak, A; Levani?, T; Mallon, G; Mauquoy, D; Robertson, I; Roland, T P; van Bellen, S; Ziehmer, M M; Leuenberger, M

2015-01-01

403

Instability of hydrogenated amorphous carbon films towards defect creation at high disorder  

NASA Astrophysics Data System (ADS)

We report a complete characterization of hydrogenated amorphous carbon (a-C:H) thin films through Raman spectroscopy, photothermal deflection spectroscopy, and mechanical studies. The interpretation of the optical absorption data within the Dasgupta's model offers an estimate of the disorder intensity through a characteristic energy scale of the model. The vibrational data (Raman spectra) and the stress data together with the optical absorption data give strong evidence for a sharp transition between a low disorder state dominated by aromatic rings and a strong disorder state likely in keeping with the creation of some topological defects, such as odd rings.

Lejeune, M.; Bouzerar, R.; Benlahsen, M.; Durand-Drouhin, O.; Zeinert, A.

2001-11-01

404

Distribution of Hydrogen Peroxide, Carbon Dioxide, and Sulfuric Acid in Europa's Icy Crust  

NASA Technical Reports Server (NTRS)

Galileo's Near Infrared Mapping Spectrometer (NIMS) detected hydrogen peroxide, carbon dioxide and a hydrated material on Europa's surface, the latter interpreted as hydrated sulfuric acid (H2SO4*nH2O) or hydrated salts. Related compounds are molecular oxygen, sulfur dioxide, and two chromophores, one that is dark in the ultraviolet(UV) and concentrated on the trailing side, the other brighter in the UV and preferentially distributed in the leading hemisphere. The UV-dark material has been suggested to be sulfur.

Carlson, R. W.

2004-01-01

405

A regenerative process for carbon dioxide removal and hydrogen production in IGCC  

NASA Astrophysics Data System (ADS)

Advanced power generation technologies, such as Integrated Gasification-Combined Cycles (IGCC) processes, are among the leading contenders for power generation conversion because of their significantly higher efficiencies and potential environmental advantages, compared to conventional coal combustion processes. Although the increased in efficiency in the IGCC processes will reduce the emissions of carbon dioxide per unit of power generated, further reduction in CO2 emissions is crucial due to enforcement of green house gases (GHG) regulations. In IGCC processes to avoid efficiency losses, it is desirable to remove CO2 in the temperature range of 300° to 500°C, which makes regenerable MgO-based sorbents ideal for such operations. In this temperature range, CO2 removal results in the shifting of the water-gas shift (WGS) reaction towards significant reduction in carbon monoxide (CO), and enhancement in hydrogen production. However, regenerable, reactive and attrition resistant sorbents are required for such application. In this work, a highly reactive and attrition resistant regenerable MgO-based sorbent is prepared through dolomite modification, which can simultaneously remove carbon dioxide and enhance hydrogen production in a single reactor. The results of the experimental tests conducted in High-Pressure Thermogravimetric Analyzer (HP-TGA) and high-pressure packed-bed units indicate that in the temperature range of 300° to 500°C at 20 atm more than 95 molar percent of CO2 can be removed from the simulated coal gas, and the hydrogen concentration can be increased to above 70 percent. However, a declining trend is observed in the capacity of the sorbent exposed to long-term durability analysis, which appears to level off after about 20 cycles. Based on the physical and chemical analysis of the sorbent, a two-zone expanding grain model was applied to obtain an excellent fit to the carbonation reaction rate data at various operating conditions. The modeling results indicate that more than 90 percent purification of hydrogen is achievable, either by increasing the activity of the sorbent towards water-gas shift reaction or by mixing the sorbent bed with a commercialized water-gas shift catalyst. The preliminary economical evaluation of the MgO-based process indicates that this process can be economically viable compared to the commercially available WGS/Selexol(TM) processes.

Hassanzadeh Khayyat, Armin

406

Solubility of mixtures of hydrogen sulfide and carbon dioxide in aqueous N-methyldiethanolamine solutions  

SciTech Connect

Aqueous solutions of alkanolamines are commonly used to strip acid gases (H[sub 2]S and CO[sub 2]) from streams contaminated with these components. The two most widely used amines are monoethanolamine (MEA) and diethanolamine (DEA). The solubilities of mixtures of hydrogen sulfide and carbon dioxide in a 35 wt% (3.04 kmol/m[sup 3]) aqueous solution of N-methyldiethanolamine at 40 and 100C have been measured. Partial pressures of the acid gases ranged from 0.006 to 101 kPa at 40C and from 4 to 530 kPa at 100C.

Jou, Fang Yuan; Carroll, J.J.; Mather, A.E.; Otto, F.D. (Univ. of Alberta, Edmonton, Alberta (Canada). Dept. of Chemical Engineering)

1993-01-01

407

Biocatalytic methanation of hydrogen and carbon dioxide in an anaerobic three-phase system.  

PubMed

A new type of anaerobic trickle-bed reactor was used for biocatalytic methanation of hydrogen and carbon dioxide under mesophilic temperatures and ambient pressure in a continuous process. The conversion of gaseous substrates through immobilized hydrogenotrophic methanogenic archaea in a biofilm is a unique feature of this type of reactor. Due to the formation of a three-phase system on the carrier surface and operation as a plug flow reactor without gas recirculation, a complete reaction could be observed. With a methane concentration higher than [Formula: see text] , the product gas exhibits a very high quality. A specific methane production of [Formula: see text] was achieved at a hydraulic loading rate of [Formula: see text] . The relation between trickle flow through the reactor and productivity could be shown. An application for methane enrichment in combination with biogas facilities as a source of carbon dioxide has also been positively proven. PMID:25193088

Burkhardt, M; Koschack, T; Busch, G

2015-02-01

408

Influence of hydrogen-oxidizing bacteria on the corrosion of low carbon steel: Local electrochemical investigations.  

PubMed

Low carbon steel has been considered a suitable material for component of the multi-barrier system employed on the geological disposal of high-level radioactive waste (HLW). A non negligible amount of dihydrogen (H2) is expected to be produced over the years within the geological repository due to the anoxic corrosion of metallic materials and also to the water radiolysis. The influence of the activity of hydrogen-oxidizing bacteria (HOB) and iron-reducing bacteria (IRB) on carbon steel corrosion is considered in this study because of the high availability of energetic nutriments (H2, iron oxides and hydroxides) produced in anoxic disposal conditions. Local electrochemical techniques were used for investigating the activity of IRB as a promoter of local corrosion in the presence of H2 as electron donor. A local consumption of H2 by the bacteria has been evidenced and impedance measurements indicate the formation of a thick layer of corrosion products. PMID:24177135

Moreira, Rebeca; Schütz, Marta K; Libert, Marie; Tribollet, Bernard; Vivier, Vincent

2014-06-01

409

Hydrogen depolarized carbon dioxide concentrator performance improvements and cell pair structural tests. [for manned space station  

NASA Technical Reports Server (NTRS)

The investigations and testing associated with the CO2 removal efficiency and voltage degradation of a hydrogen depolarized carbon oxide concentrator are reported. Also discussed is the vibration testing of a water vapor electrolysis cell pair. Performance testing of various HDC cell pairs with Cs2CO3 electrolyte provided sufficient parametric and endurance data to size a six man space station prototype CO2 removal system as having 36 HDC cell pairs, and to verify a life capability exceeding six moths. Testing also demonstrated that tetramethylammonium carbonate is an acceptable HDC electrolyte for operating over the relative humidity range of 30 to 90 percent and over a temperature range of 50 to 80 F.

Huddleston, J. D.; Aylward, J. R.

1973-01-01

410

Decontamination of adsorbed chemical warfare agents on activated carbon using hydrogen peroxide solutions.  

PubMed

Mild treatment with hydrogen peroxide solutions (3-30%) efficiently decomposes adsorbed chemical warfare agents (CWAs) on microporous activated carbons used in protective garments and air filters. Better than 95% decomposition of adsorbed sulfur mustard (HD), sarin, and VX was achieved at ambient temperatures within 1-24 h, depending on the H2O2 concentration. HD was oxidized to the nontoxic HD-sulfoxide. The nerve agents were perhydrolyzed to the respective nontoxic methylphosphonic acids. The relative rapidity of the oxidation and perhydrolysis under these conditions is attributed to the microenvironment of the micropores. Apparently, the reactions are favored due to basic sites on the carbon surface. Our findings suggest a potential environmentally friendly route for decontamination of adsorbed CWAs, using H2O2 without the need of cosolvents or activators. PMID:25133545

Osovsky, Ruth; Kaplan, Doron; Nir, Ido; Rotter, Hadar; Elisha, Shmuel; Columbus, Ishay

2014-09-16

411

Catalytic hydrogenation of carbon monoxide. Progress report, December 15, 1991--December 14, 1992  

SciTech Connect

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.

Wayland, B.B.

1992-12-01

412

Hydrogen oxidation on gas diffusion electrodes for phosphoric acid fuel cells in the presence of carbon monoxide and oxygen  

SciTech Connect

Hydrogen oxidation has been studied on a carbon-supported platinum gas diffusion electrode in a phosphoric acid electrolyte in the presence of carbon monoxide and oxygen in the feed gas. The poisoning effect of carbon monoxide present in the feed gas was measured in the temperature range from 80 to 150 C. It was found that throughout the temperature range, the potential loss due to the CO poisoning can be reduced to a great extent by the injection of small amounts of gaseous oxygen into the hydrogen gas containing carbon monoxide. By adding 5 volume percent (v/o) oxygen, an almost CO-free performance can be obtained for carbon monoxide concentrations up to 0.5 v/o CO at 130 C, 0.2 v/o CO at 100 C, and 0.1 v/o CO at 80 C, respectively.

Gang, X.; Qingfeng, L.; Hjuler, H.A.; Bjerrum, N.J. [Technical Univ. of Denmark, Lyngby (Denmark)

1995-09-01

413

Hydrogen-Stimulated Carbon Acquisition and Conservation in Salmonella enterica Serovar Typhimurium ? §  

PubMed Central

Salmonella enterica serovar Typhimurium can utilize molecular hydrogen for growth and amino acid transport during anaerobic growth. Via microarray we identified H2 gas-affected gene expression changes in Salmonella. The addition of H2 caused altered expression of 597 genes, of which 176 genes were upregulated and 421 were downregulated. The significantly H2-upregulated genes include those that encode proteins involved in the transport of iron, manganese, amino acids, nucleosides, and sugars. Genes encoding isocitrate lyase (aceA) and malate synthase (aceB), both involved in the carbon conserving glyoxylate pathway, and genes encoding the enzymes of the d-glucarate and d-glycerate pathways (gudT, gudD, garR, garL, garK) are significantly upregulated by H2. Cells grown with H2 showed markedly increased AceA enzyme activity compared to cells without H2. Mutant strains with deletion of either aceA or aceB had reduced H2-dependent growth rates. Genes encoding the glutamine-specific transporters (glnH, glnP, glnQ) were upregulated by H2, and cells grown with H2 showed increased [14C]glutamine uptake. Similarly, the mannose uptake system genes (manX, manY) were upregulated by H2, and cells grown with H2 showed about 2.0-fold-increased [14C]d-mannose uptake compared to the cells grown without H2. Hydrogen stimulates the expression of genes involved in nutrient and carbon acquisition and carbon-conserving pathways, linking carbon and energy metabolism to sustain H2-dependent growth. PMID:21856852

Lamichhane-Khadka, Reena; Frye, Jonathan G.; Porwollik, Steffen; McClelland, Michael; Maier, Robert J.

2011-01-01

414

Reorganization of graphite surfaces into carbon micro- and nanoparticles under high flux hydrogen plasma bombardment  

SciTech Connect

Fine-grain graphite samples were exposed to high density low temperature (n{sub e}{approx}10{sup 20} m{sup -3}, T{sub e}{approx}1 eV) hydrogen plasmas in the Pilot-PSI linear plasma generator. Redeposition of eroded carbon is so strong that no external precursor gas injection is necessary for deposits to form on the exposed surface during the bombardment. In fact, up to 90% of carbon is redeposited, most noticeably in the region of the highest particle flux. The redeposits appear in the form of carbon microparticles of various sizes and structures. Discharge parameters influence the efficiency of the redeposition processes and the particle growth rate. Under favorable conditions, the growth rate reaches 0.15 {mu}m/s. The authors used high resolution scanning electron microscopy and transmission electron microscopy to study the particle growth mode. The columnar structure of some of the large particles points toward surface growth, while observation of the spherical carbon nanoparticles indicates growth in the plasma phase. Multiple nanoparticles can agglomerate and form bigger particles. The spherical shape of the agglomerates suggests that nanoparticles coalesce in the gas phase. The erosion and redeposition patterns on the samples are likely determined by the gradients in plasma flux density and surface temperature across the surface.

Bystrov, Kirill; Vegt, Lenze van der; De Temmerman, Gregory; Arnas, Cecile; Marot, Laurent [FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM, Partner in the Trilateral Euregio Cluster, P.O. Box 1207, NL-3430 BE Nieuwegein (Netherlands); Laboratoire de Physique des Interactions Ioniques et Moleculaires (PIIM), CNRS/Aix-Marseille Universite, F-13397 Marseille (France); Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)

2013-01-15

415

Dispersion of multi walled carbon nanotubes in a hydrogen bonded liquid crystal  

NASA Astrophysics Data System (ADS)

In a newly synthesized self assembled system, namely, hydrogen bonded liquid crystal, multi walled carbon nanotubes (MWCNTs) are dispersed. This self assembly system of liquid crystal is realized by formation of hydrogen bond between levo tartaric acid and undecyloxy benzoic acid. The proposed structure is confirmed by FTIR and P-NMR studies. Thermal and electrical properties of this system dispersed with MWCNT are studied. Alignment of carbon nanotubes in the nematic phase of the self assembled system is responsible for the observation of bistable electrical states namely ON and OFF. Optical textural observations of these two states are recorded and the light intensity complexly decays and unwinding of the helix with the application of external field indicates an optical shuttering action. It is interesting to note that a small threshold value of 3.5 V/?m is sufficient to realize an optical shutter. DSC studied reveals that the enthalpy values pertaining to liquid crystal dispersed with MWCNT is approximately two fold to that of the pure liquid crystal. Results of conductance relating to the liquid crystal with MWCNT dispersion are discussed.

Vijayakumar, V. N.; Madhu Mohan, M. L. N.

2010-11-01

416

Imidazolium hydrogen carbonates versus imidazolium carboxylates as organic precatalysts for N-heterocyclic carbene catalyzed reactions.  

PubMed

Imidazolium-2-carboxylates (NHC-CO(2) adducts, 3) and (benz)imidazolium hydrogen carbonates ([NHC(H)][HCO(3)], 4) were independently employed as organic precatalysts for various molecular N-heterocyclic carbene (NHC) catalyzed reactions. NHC-CO(2) adducts were obtained by carboxylation in THF of related free NHCs (2), while the synthesis of [NHC(H)][HCO(3)] precursors was directly achieved by anion metathesis of imidazolium halides (1) using potassium hydrogen carbonate (KHCO(3)) in methanolic solution, without the need for the prior preparation of free carbenes. Thermogravimetric analysis (TGA) and TGA coupled with mass spectrometry (TGA-MS) of most [NHC(H)][HCO(3)] precursors 4 showed a degradation profile in stages, with either a concomitant or a stepwise release of H(2)O and CO(2), between 108 and 280 °C, depending on the nature of the azolium and substituents. In solution, NHC generation from both [NHC(H)][HCO(3)] salts and NHC-CO(2) adducts could be achieved at room temperature, most likely by a simple solvation effect. Both types of precursors proved efficient for organocatalyzed molecular reactions, including cyanosilylation, benzoin condensation, and transesterification reactions. The catalytic efficiencies of NHC-CO(2) adducts 3 were found to be approximately 3 times higher than those of their [NHC(H)][HCO(3)] counterparts 4. PMID:23092332

Fèvre, Maréva; Coupillaud, Paul; Miqueu, Karinne; Sotiropoulos, Jean-Marc; Vignolle, Joan; Taton, Daniel

2012-11-16

417

Diamond and Hydrogenated Carbons for Advanced Batteries and Fuel Cells: Fundamental Studies and Applications.  

SciTech Connect

The original funding under this project number was awarded for a period 12/1999 until 12/2002 under the project title Diamond and Hydrogenated Carbons for Advanced Batteries and Fuel Cells: Fundamental Studies and Applications. The project was extended until 06/2003 at which time a renewal proposal was awarded for a period 06/2003 until 06/2008 under the project title Metal/Diamond Composite Thin-Film Electrodes: New Carbon Supported Catalytic Electrodes. The work under DE-FG02-01ER15120 was initiated about the time the PI moved his research group from the Department of Chemistry at Utah State University to the Department of Chemistry at Michigan State University. This DOE-funded research was focused on (i) understanding structure-function relationships at boron-doped diamond thin-film electrodes, (ii) understanding metal phase formation on diamond thin films and developing electrochemical approaches for producing highly dispersed electrocatalyst particles (e.g., Pt) of small nominal particle size, (iii) studying the electrochemical activity of the electrocatalytic electrodes for hydrogen oxidation and oxygen reduction and (iv) conducting the initial synthesis of high surface area diamond powders and evaluating their electrical and electrochemical properties when mixed with a Teflon binder.

Swain; Greg M.

2009-04-13

418

Method for converting hydrocarbon fuel into hydrogen gas and carbon dioxide  

DOEpatents

A method for converting hydrocarbon fuel into hydrogen gas and carbon dioxide within a reformer 10 is disclosed. According to the method, a stream including an oxygen-containing gas is directed adjacent to a first vessel 18 and the oxygen-containing gas is heated. A stream including unburned fuel is introduced into the oxygen-containing gas stream to form a mixture including oxygen-containing gas and fuel. The mixture of oxygen-containing gas and unburned fuel is directed tangentially into a partial oxidation reaction zone 24 within the first vessel 18. The mixture of oxygen-containing gas and fuel is further directed through the partial oxidation reaction zone 24 to produce a heated reformate stream including hydrogen gas and carbon monoxide. Steam may also be mixed with the oxygen-containing gas and fuel, and the reformate stream from the partial oxidation reaction zone 24 directed into a steam reforming zone 26. High- and low-temperature shift reaction zones 64,76 may be employed for further fuel processing.

Clawson, Lawrence G. (Dover, MA); Mitchell, William L. (Belmont, MA); Bentley, Jeffrey M. (Westford, MA); Thijssen, Johannes H. J. (Cambridge, MA)

2000-01-01

419

Determination of vibrational energy relaxation rates of CH,D,T stretching modes on hydrogen, deuterium, and tritium-terminated H,D,T\\/C(111) and H,D,T\\/C(110) diamond surfaces using molecular dynamics simulation: Thermal effect  

Microsoft Academic Search

Molecular dynamics simulations were carried out to determine the vibrational energy relaxation rates for C-H,D,T stretches on hydrogen-, deuterium-, and tritium-terminated H,D,T\\/C(111) and H,D,T\\/C(110) diamond surfaces at high temperatures based on the Bloch-Redfield theory and the calculated power spectra of fluctuating force along C-H,D,T stretches. The lifetime of C-H stretches on H\\/(110) surfaces at room temperature was found to be

Hsiu-Feng Lu; Ming-Shun Ho; Sho-Ching Hong; Ai-Hsin Liu; Pei-Fang Wu; Ying-Chieh Sun

1998-01-01

420

Hydrogen isotope separation in carbon nanotubes: calculation of coupled rotational and translational States at high densities.  

PubMed

The effect of the quantized rotational degrees of freedom of hydrogen on the adsorption and sieving properties in carbon nanotubes is studied using computer simulations. We have developed a highly efficient multiple timestep algorithm for hybrid Monte Carlo sampling of quantized rotor configurations and extended the grand canonical Boltzmann bias method to rigid linear molecules. These new computational tools allow us to calculate accurately the quantum sieving selectivities for cases of extreme two-dimensional confinement as a function of pressure. The para-T2/para-H2 selectivity at 20 K is analyzed as a function of the tube diameter and the density of adsorbed hydrogen. Extraordinarily high selectivities, up to 2.6 x 10(8), are observed in the narrowest nanotube. The quantized nature of the rotational degrees of freedom is found to dramatically affect adsorption and selectivity for hydrogen isotopes adsorbed in very narrow nanotubes. The T2/H2 zero-pressure selectivity increases from 2.4 x 10(4) to 1.7 x 10(8) in the (3,6) nanotube at 20 K when quantum rotations are accounted for. The isotopic selectivity is found to increase with pressure, tending to a constant value at saturation. A simplified mean-field model is used to discuss the origin of this behavior. PMID:20146443

Garberoglio, Giovanni; Johnson, J Karl

2010-03-23

421

Recoverable solution reaction of HiPco carbon nanotubes with hydrogen peroxide.  

PubMed

There is increasing interest in developing single-walled carbon nanotubes (SWNTs)-based optical biosensors for remote or in vitro and in vivo sensing because the near-IR optical properties of SWNTs are very sensitive to surrounding environmental changes. Many enzyme-catalyzed reactions yield hydrogen peroxide (H(2)O(2)) as a product. To our knowledge, there is no report on the interaction of H(2)O(2) with SWNTs from the optical sensing point of view. Here, we study the reaction of H(2)O(2) with an aqueous suspension of water-soluble (ws) HiPco SWNTs encased in the surfactant sodium dodecyl sulfate (SDS). The SWNTs are optically sensitive to hydrogen peroxide in pH 6.0 buffer solutions through suppression of the near-IR absorption band intensity. Interestingly, the suppressed spectral intensity of the nanotubes recovers by increasing the pH, by decomposing the H(2)O(2) into H(2)O and O(2) with the enzyme catalase, and by dialytically removing H(2)O(2). Preliminary studies on the mechanisms suggest that H(2)O(2) withdraws electrons from the SWNT valence band by charge transfer, which suppresses the nanotube spectral intensity. The findings suggest possible enzyme-assisted molecular recognition applications by selective optical detection of biological species whose enzyme-catalyzed products include hydrogen peroxide. PMID:16853809

Song, Chulho; Pehrsson, Pehr E; Zhao, Wei

2005-11-24

422

Deuterium microbomb rocket propulsion  

E-print Network

Large scale manned space flight within the solar system is still confronted with the solution of two problems: 1. A propulsion system to transport large payloads with short transit times between different planetary orbits. 2. A cost effective lifting of large payloads into earth orbit. For the solution of the first problem a deuterium fusion bomb propulsion system is proposed where a thermonuclear detonation wave is ignited in a small cylindrical assembly of deuterium with a gigavolt-multimegampere proton beam, drawn from the magnetically insulated spacecraft acting in the ultrahigh vacuum of space as a gigavolt capacitor. For the solution of the second problem, the ignition is done by argon ion lasers driven by high explosives, with the lasers destroyed in the fusion explosion and becoming part of the exhaust.

Friedwardt Winterberg

2008-12-02

423

The ebullition of hydrogen, carbon monoxide, methane, carbon dioxide and total gaseous mercury from the Cornwall Area of Concern.  

PubMed

This paper reports the first ebullitive fluxes of hydrogen (H2), carbon monoxide (CO), methane (CH4), carbon dioxide (CO2) and total gaseous mercury (TGM) from the Cornwall Area of Concern (CAC). Although sediments were contaminated with mercury, bubbling was a negligible source of mercury for the global atmosphere. Indeed, the average emission of TGM through ebullition was 0.04 pg m(-2) h(-1). Measurements of H2, CO, CH4 and CO2 trapped gas concentrations and fluxes were used as indicators of diagenesis processes. The CAC represented a significant regional source of CH4 since the estimated ebullitive fluxes (3.5 mg m(-2) h(-1)) were similar to the CH4 emissions measured above typical flooded freshwater wetlands. As molecular diffusion is known as the main pathway of CO2 transport from water to the atmosphere, CO2 ebullitive fluxes were weak (0.39 mg m(-2) h(-1)). Bubbling of CO (1.6 microg m(-2) h(-1)) was 10 folds less important than CO fluxes measured over flooded freshwater wetlands. Finally, H2 emissions (0.001 microg m(-2) h(-1)) were negligible since the level of this trace gas is tightly regulated by microorganisms in anaerobic environments. PMID:17499842

Poissant, Laurier; Constant, Philippe; Pilote, Martin; Canário, João; O'Driscoll, Nelson; Ridal, Jeff; Lean, David

2007-08-01

424

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

SciTech Connect

Laboratory experiments have been used to investigate the fundamental interactions responsible for deuterium retention in lithiated graphite. Oxygen was found to be present and play a key role in experiments that simulated NSTX lithium conditioning, where the atomic surface concentration can increase to >40% when deuterium retention chemistry is observed. Quantum-classical molecular dynamic simulations elucidated this oxygen-deuterium effect and showed that oxygen retains significantly more deuterium than lithium in a simulated matrix with 20% lithium, 20% oxygen, and 60% carbon. Simulations further show that deuterium retention is even higher when lithium is removed from the matrix. Experiments artificially increased the oxygen content in graphite to ?16% and then bombarded with deuterium. X-ray photoelectron spectroscopy showed depletion of the oxygen and no enhanced deuterium retention, thus demonstrating that lithium is essential in retaining the oxygen that thereby retains deuterium.

Taylor, C. N. [Fusion Safety Program, Idaho National Laboratory, P.O. Box 1625-7113, Idaho Falls, Idaho 83415 (United States) [Fusion Safety Program, Idaho National Laboratory, P.O. Box 1625-7113, Idaho Falls, Idaho 83415 (United States); School of Nuclear Engineering, Purdue University, 400 Central Drive, West Lafayette, Indiana 47907 (United States); Allain, J. P. [School of Nuclear Engineering, Purdue University, 400 Central Drive, West Lafayette, Indiana 47907 (United States) [School of Nuclear Engineering, Purdue University, 400 Central Drive, West Lafayette, Indiana 47907 (United States); Department of Nuclear, Plasma and Radiological Engineering, University of Illinois at Urbana-Champaign, Illinois 61801 (United States); Luitjohan, K. E. [School of Nuclear Engineering, Purdue University, 400 Central Drive, West Lafayette, Indiana 47907 (United States)] [School of Nuclear Engineering, Purdue University, 400 Central Drive, West Lafayette, Indiana 47907 (United States); Krstic, P. S. [Institute for Advanced Computational Science, Stony Brook University, New York 11794 (United States) [Institute for Advanced Computational Science, Stony Brook University, New York 11794 (United States); Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996 (United States); TheoretiK, Knoxville, Tennessee 379XX (United States); Dadras, J. [Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996 (United States) [Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996 (United States); Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095 (United States); Skinner, C. H. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2014-05-15

425

Deuterium isotope effects on 15N, 13C and 1H chemical shifts of proton sponges  

NASA Astrophysics Data System (ADS)

Deuterium isotope effects on 15N, 13C and 1H chemical shifts have been measured in the protonated forms of DMAN, 4-bromo, 4-picryl, 4-nitro and 2- and 2,7-chloro derivatives. Structures have been geometry optimised using BPW91/6-31(d)G density functional theory (DFT) methods and show good correspondence to experimental X-ray data. 15N, 13C and 1H chemical shifts are calculated using GIAO/DFT methods. Chemical shifts for the two tautomers are calculated. Equilibrium constants are determined from 1J(N,H) coupling constants. A comparison of 1J(N,H) and 1J(N,D) couplings for the non-symmetrical derivatives show that upon deuteriation the equilibrium is shifted towards the dominant form. The experimental deuterium isotope effect on chemical shifts of DMANH + shows only small values despite the apparently strong intramolecular hydrogen bonds as judged from primary isotope effects. The counter ion has little effect on the one-bond isotope effect. Secondary isotope effects on 15N and 13C chemical shifts for the non-symmetrical derivatives are divided into intrinsic and equilibrium contributions. The one-bond deuterium intrinsic isotope effect on 15N chemical shifts is close to 0.3 ppm and is related to charge delocalisation and the close proximity of the positive charge. The equilibrium contributions to the isotope effects at the nitrogens and at carbons are seen to increase throughout the series in parallel with the increase of the equilibrium constant. For 1H resonances only equilibrium contributions are found at the aromatic hydrogens. An important feature in the analysis of the protonated DMANs is the multi-isotope effect approach.

Grech, E.; Klimkiewicz, J.; Nowicka-Scheibe, J.; Pietrzak, M.; Schilf, W.; Pozharski, A. F.; Ozeryanskii, V. A.; Bolvig, S.; Abildgaard, J.; Hansen, P. E.

2002-09-01

426

Anomalous aggregation state of deuterium molecules in the nanoscale pores of a metal organic framework  

NASA Astrophysics Data System (ADS)

The behavior of hydrogen molecules adsorbed onto the nanospace of porous materials is of great interest but is poorly understood. Here we show direct visualization of deuterium molecules adsorbed on isoreticular metal organic frameworks (IRMOF-1) at 77 K using reverse Monte Carlo simulation based on first principle molecular dynamics simulation and neutron diffraction. Results show that the two types of adsorption sites around a ZnO4 cluster are almost fully occupied by the deuterium molecules but that other sites are not fully occupied. Moreover an interesting information about the aggregation state of deuterium molecules was directly obtained from the deuterium-deuterium partial pair distribution function. Namely, the average distance of deuterium molecules adsorbed onto IRMOF-1 is slightly longer than that in a solid state but much shorter than that in the corresponding gas state.

Kanoya, Izuru; Furuta, Terumi; Sakamoto, Ryogo; Hosoe, Mitsuya; Ichikawa, Masao; Itoh, Keiji; Fukunaga, Toshiharu

2010-10-01

427

Carbon sequestration in soybean crop soils: the role of hydrogen-coupled CO2 fixation  

NASA Astrophysics Data System (ADS)

Conversion of native vegetation to agricultural land in order to support the world's growing population is a key factor contributing to global climate change. However, the extent to which agricultural activities contribute to greenhouse gas emissions compared to carbon storage is difficult to ascertain, especially for legume crops, such as soybeans. Soybean establishment often leads to an increase in N2O emissions because N-fixation leads to increased soil available N during decomposition of the low C:N legume biomass. However, soybean establishment may also reduce net greenhouse gas emissions by increasing soil fertility, plant growth, and soil carbon storage. The mechanism behind increased carbon storage, however, remains unclear. One explanation points to hydrogen coupled CO2 fixation; the process by which nitrogen fixation releases H2 into the soil system, thereby promoting chemoautotrophic carbon fixation by soil microbes. We used 13CO2 as a tracer to track the amount and fate of carbon fixed by hydrogen coupled CO2 fixation during one-year field and laboratory incubations. The objectives of the research are to 1) quantify rates of 13CO2 fixation in soil collected from a field used for long-term soybean production 2) examine the impact of H2 gas concentration on rates of 13CO2 fixation, and 3) measure changes in ?13C signature over time in 3 soil fractions: microbial biomass, light fraction, and acid stable fraction. If this newly-fixed carbon is incorporated into the acid-stable soil C fraction,