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1

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

USGS Publications Warehouse

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

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

1970-01-01

2

Flame Structure and Flame Reaction Kinetics. VII. Reactions of Traces of Heavy Water, Deuterium and Carbon Dioxide Added to Rich Hydrogen + Nitrogen + Oxygen Flames  

Microsoft Academic Search

The overall reactions of traces of heavy water, deuterium and carbon dioxide added to some fuel-rich hydrogen + nitrogen + oxygen flames have been examined both experimentally and theoretically. The mechanism and most of the controlling rate constants for the flames both without and with the additives are now sufficiently firmly established for computation of the detailed flame profiles to

G. Dixon-Lewis

1972-01-01

3

95 MeV neutron scattering on hydrogen, deuterium, carbon, and oxygen  

SciTech Connect

Three neutron-deuteron scattering experiments at 95 MeV have been performed recently at The Svedberg Laboratory in Uppsala. Subsets of the results of these experiments have been reported in two short articles, showing clear evidence for three-nucleon force effects. In this paper, we present a more detailed description of the experimental methods as well as further discussion of the results. In addition to neutron-deuteron scattering data, neutron-proton and {sup 12}C(n,n) elastic scattering data have been measured for normalization purposes, and {sup 16}O(n,n) data have been obtained for the first time at this energy. It was possible to extract {sup 12}C(n,n{sup '}) and {sup 16}O(n,n{sup '}) inelastic scattering cross sections to excited states below 12 MeV excitation energy. The inelastic scattering data (for both carbon and oxygen) are shown to have a significant impact on the determination of nuclear recoil kerma coefficients.

Mermod, P.; Blomgren, J.; Johansson, C. [Department of Neutron Research, Uppsala University, Box 525, S-75120 Uppsala (Sweden) and Department of Radiation Sciences, Uppsala University (Sweden); Institute of Nuclear and Hadron Physics, Forschungszentrum Rossendorf, Dresden (Germany)] (and others)

2006-11-15

4

Hyperpolarization transfer from parahydrogen to deuterium via carbon-13  

NASA Astrophysics Data System (ADS)

Hyperpolarization arising from para-hydrogen (p-H2) can be transferred via carbon-13 to deuterium after hydrogenation of a perdeuterated substrate. The model compound is acetylene-d2, hydrogenated to yield ethylene-d2. Transfer to deuterium occurs in ALTADENA experiments (the hydrogenation reaction being performed outside the magnet of the NMR spectrometer prior to the insertion of the sample tube into the NMR probe). The proposed theory, limited to the case where the two p-H2 protons remain isochronous (same chemical shift), is based on the concept of a steady-state density operator which prevails subsequently to the hydrogenation reaction. The outcome quantity is the carbon-deuterium longitudinal spin order, denoted as IzCIzD. Calculations simply involve commutators of all relevant spin quantities with the J-coupling Hamiltonian (denoted as HJ). In particular, it is shown that the necessary condition for polarization transfer toward deuterium via carbon-13 is that IzCIzD does not commute with HJ. The structure of HJ is thus of prime importance and it appears that transfer to carbon-13 occurs for both types of experiments, ALTADENA and PASADENA (hydrogenation reaction in the presence of the NMR spectrometer magnetic field). Conversely, transfer toward deuterium via carbon-13 is possible only with ALTADENA experiments.

Aime, Silvio; Gobetto, Roberto; Reineri, Francesca; Canet, Daniel

2003-11-01

5

Stabilization of Atomic Hydrogen and Deuterium.  

National Technical Information Service (NTIS)

This thesis deals with the first of a series of experiments done at the University of Amsterdam to study the properties of spin polarized atomic hydrogen (spa H) and deuterium (spa D) at very low temperatures (T approximately 0.3 K) and in high magnetic f...

J. T. M. Walraven

1982-01-01

6

Deuterium Enrichment in Stratospheric Molecular Hydrogen  

NASA Astrophysics Data System (ADS)

Molecular hydrogen (H2) is the second most abundant reduced gas in the atmosphere (after methane) with a globally averaged mixing ratio of ~ 530 ppbv. Its largest source is believed to be photochemical oxidation of methane (C H4) and non-methane hydrocarbons (NMHCs); other recognized sources include biomass burning, fossil fuel burning, nitrogen fixation, and ocean degassing. As with other atmospheric trace gases, the stable isotopic content of H2 has the potential to help quantify various aspects of its production and destruction. The average deuterium content of H2 (expressed as ?DH2) is enriched by ~110 ‰ relative to Vienna Standard Mean Ocean Water while CH4 in the troposphere, the precursor for photochemical H2 production, is depleted by ~ 90 ‰ relative to V-SMOW and similar values are expected for NMHCs. Both natural and anthropogenic combustion sources of H2 have been shown to be depleted in deuterium by 200 to 300 ‰ (Gerst and Quay, 2001; Rahn et al., 2002), and the ocean and N2 fixation sources are expected to be in near thermodynamic equilibrium with local H2O and should have deuterium levels of ~-700 ‰ (Rahn et al., 2002). In order to offset these deuterium depleted sources and account for the observed tropospheric ?DH2, the balancing loss processes must discriminate against reaction with HD and/or the total fractionation associated with CH4 oxidation and the subsequent reactions leading to H2 must favor production of deuterated H2. We have analyzed a suite of stratospheric air samples in order to investigate the photochemical processes influencing the deuterium content of H2. While the mixing ratio of H2 is nearly constant, the deuterium content increases such that ?D=440 ‰ in samples with a stratospheric mean age of ~6 years. The constant mixing ratio results from the fact that production due to CH4 oxidation and loss due to H2 oxidation are approximately equal. The observed trend in ?D of stratospheric H2 can only be accounted for by an enrichment in the ratio of D to H of H2 relative to that in precursor CH4 in addition to the enrichment due to the slower oxidation of deuterated H2. We calculate the fractionation associated with this enrichment to be ?Total=1.54. As with other trace gases, in situ photochemical processes and the return flux of air from the stratosphere must be accounted for to explain tropospheric observations. Gerst, S., and P. Quay, J. Geophys. Res., 106, 5021-5031, 2001. Rahn, T., N. Kitchen, and J. M. Eiler, Geochim. Cosmochim. Acta, 66, 2475-2481, 2002.

Rahn, T.; Eiler, J.; McCarthy, M. C.; Boering, K. A.; Wennberg, P.; Atlas, E.; Donnelly, S.; Schauffler, S.

2002-12-01

7

Carbon Nanotube Based Deuterium Ion Source for Improved Neutron Generators  

SciTech Connect

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

Fink, R. L.; Jiang, N.; Thuesen, L. [Applied Nanotech, Inc., 3006 Longhorn Blvd., Ste 107, Austin, TX 78758 (United States); Leung, K. N. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Antolak, A. J. [Sandia National Laboratories, Livermore, CA 94550 (United States)

2009-03-10

8

Hydrogen-deuterium exchange in bulk LiBH4.  

PubMed

Because of its apparent simplicity, diffusion of hydrogen in solids can be regarded as a general model system for diffusion. However, only rudimentary knowledge exists for the dynamics of hydrogen in complex hydrides. Insight into the specific diffusion process is given by hydrogen-deuterium exchange experiments. Thermogravimetry and Raman spectroscopy are used to measure the hydrogen-deuterium exchange during the decomposition of LiBH4. At a temperature of 523 K the self-diffusion constant of deuterium in LiBH4 is estimated to be D approximately 7 x 10(-14) m(2) s(-1). A careful analysis of the Raman spectra shows that hydrogen is statistically exchanged by deuterium in LiBH4; i.e., the diffusing species is assumed to be the single hydrogen atom. PMID:18461915

Borgschulte, A; Züttel, A; Hug, P; Racu, A-M; Schoenes, J

2008-05-08

9

Cryocondensation Pumping of Thick Films of Hydrogen and Deuterium.  

National Technical Information Service (NTIS)

In order to obtain engineering data for design of large capacity cryopumps for hydrogen, deuterium and tritium, an apparatus was built where pumping speeds and sticking coefficients can be studied as a function of surface coverage for different leak rates...

H. J. Halams J. A. Bamberger

1975-01-01

10

Cryogenic Source of Polarized Atoms of Hydrogen and Deuterium.  

National Technical Information Service (NTIS)

An apparatus producing electron spin polarized atomic beams of deuterium and hydrogen is described. A cryopumping system, a superconducting sextupole magnet and liquid nitrogen cooled dissociator with a r.f. discharge are used. A possibility of developing...

A. A. Belushkina V. P. Vadeev A. I. Valevich G. I. Gai E. D. Donets

1975-01-01

11

Probing backbone dynamics with hydrogen/deuterium exchange mass spectrometry.  

PubMed

Protein dynamics can be probed by the solution technique amide hydrogen/deuterium exchange. The exchange rate of hydrogen for deuterium along a peptide backbone is dependent on the extent of hydrogen bonding from secondary structure, accessibility by D2O, and protein motions. Both global and local conformational changes that alter bonding or structure will lead to changes in the amount of deuterium incorporated. The deuterium can be localized via pepsin digestion of the protein and quantified by electrospray ionization mass spectrometry through the mass shifts of the resulting peptides. The technique is emerging as an essential tool to study protein structure in solution due to the exceptional capability of examining both dynamic and structural changes related to protein function. PMID:24061917

Singh, Harsimran; Busenlehner, Laura S

2014-01-01

12

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

13

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

SciTech Connect

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, Predrag S. [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Allain, J. P. [Purdue University; Taylor, C. N. [Purdue University; Dadras, J. [UTK/Univ. California, Los Angeles; Maeda, S. [Kyoto University, Fukui Institute for Fundamental Chemistry, Japan; Morokuma, K. [Kyoto University, Fukui Institute for Fundamental Chemistry, Japan; Jakowski, J. [National Inst. Computational Sciences, UTK; Allouche, A. [PIM/CNRS/Aix-Marseille University, Marseille, France; Baylor, Larry R [ORNL; Skinner, C. H. [Princeton Plasma Physics Laboratory (PPPL)

2013-01-01

14

Double radiative pion capture on hydrogen and deuterium and the nucleon's pion cloud  

SciTech Connect

We report measurements of double radiative capture in pionic hydrogen and pionic deuterium. The measurements were performed with the RMC spectrometer at the TRIUMF cyclotron by recording photon pairs from pion stops in liquid hydrogen and deuterium targets. We obtained absolute branching ratios of [3.02{+-}0.27(stat.){+-}0.31(syst.)]x10{sup -5} for hydrogen and [1.42{+-}{sub 0.12}{sup 0.09}(stat.){+-}0.11(syst.)]x10{sup -5} for deuterium and relative branching ratios of double radiative capture to single radiative capture of [7.68{+-}0.69(stat.){+-}0.79(syst.)]x10{sup -5} for hydrogen and [5.44{+-}{sub 0.46}{sup 0.34}(stat.){+-}0.42(syst.)]x10{sup -5} for deuterium. For hydrogen, the measured branching ratio and photon energy-angle distributions are in fair agreement with a reaction mechanism involving the annihilation of the incident {pi}{sup -} on the {pi}{sup +} cloud of the target proton. For deuterium, the measured branching ratio and energy-angle distributions are qualitatively consistent with simple arguments for the expected role of the spectator neutron. A comparison between our hydrogen and deuterium data and earlier beryllium and carbon data reveals substantial changes in the relative branching ratios and the energy-angle distributions and is in agreement with the expected evolution of the reaction dynamics from an annihilation process in S-state capture to a bremsstrahlung process in P-state capture. Lastly, we comment on the relevance of the double radiative process to the investigation of the charged pion polarizability and the in-medium pion field.

Tripathi, S.; Christy, M. E.; Gorringe, T. P.; Kovash, M. A.; Zolnierczuk, P. A. [Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506 (United States); Armstrong, D. S.; Clark, J. H. D. [Department of Physics, College of William and Mary, Williamsburg, Virginia 23187 (United States); Hasinoff, M. D.; Wright, D. H. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1 (Canada)

2007-06-15

15

Cryocondensation pumping of thick films of hydrogen and deuterium  

Microsoft Academic Search

In order to obtain engineering data for design of large capacity ; cryopumps for hydrogen, deuterium and tritium, an apparatus was built where ; pumping speeds and sticking coefficients can be studied as a function of surface ; coverage for different leak rates. In addition, thermal conductivity and thermal ; absorption of these frozen gases can be inferred from the

H. J. Halams; J. A. Bamberger

1975-01-01

16

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

17

Rydberg States of Triatomic Hydrogen and Deuterium  

NASA Astrophysics Data System (ADS)

The triatomic hydrogen ion (H3+) has spurred tremendous interest in astrophysics in recent decades, and Rydberg states of H3 have also maintained an important role for understanding H3+ experiments. In a previous study (J. Chem. Phys. 2010, 133, 234302), radiative transitions between neutral H3 Rydberg states were calculated at wavelengths near 7 -m and could be compared with mid-infrared laser lines observed in hydrogen/rare gas discharges. The present study extends the investigation to wavelengths near 10-13 -m. Rydberg states of D3 are also treated.

Wang, Jia; Greene, Chris H.

2013-10-01

18

The Blast Experiment:. Polarized Electron Scattering from Hydrogen and Deuterium  

NASA Astrophysics Data System (ADS)

At the MIT-Bates Linear Accelerator Center, the nucleon form factors have been measured by scattering polarized electrons from vector-polarized hydrogen and deuterium. The experiment used the longitudinally polarized electron beam stored in the MIT-Bates South Hall Ring along with an isotopically pure, highly vector-polarized internal atomic hydrogen and deuterium target provided by an atomic beam source. The measurements were carried out with the symmetric Bates Large Acceptance Spectrometer Toroid (BLAST). Results are presented for the proton form factor ratio, ? p GEp/G_M^p, and for the charge form factor of the neutron, GEn. Both results are more precise than previous data in the corresponding Q2 ranges.

Alarcon, R.

19

Azimuthal asymmetries in DVCS on unpolarized hydrogen and deuterium targets  

SciTech Connect

We report the latest results of azimuthal asymmetries in the DVCS process measured at the HERMES experiment on unpolarized hydrogen and deuterium targets. Exploiting the ability of HERA to provide lepton beams with both charges and spin orientations, it is possible to extract simultaneously asymmetry amplitudes attributed to the pure DVCS process and to the interference between the Bethe-Heitler and DVCS processes. The results are compared to the theoretical calculations.

Marukyan, H. [Yerevan Physics Institute, Alikhanian Brs. St. 2, Yerevan, 375036 (Armenia)

2009-08-04

20

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

21

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

22

Hydrogen-deuterium exchange in KD2PO4  

NASA Astrophysics Data System (ADS)

Depth profiles of 1H and 2D in rapidly grown KD2xH2(1-x)PO4 single crystals are studied by elastic recoil detection analysis. Results show that, under ambient conditions, deuteration in the first ~500 nm from the sample surface significantly decreases within the first several days after D2O surface polishing. This effect is attributed to deuterium-hydrogen exchange. The effective diffusion coefficient of this process is strongly dependent on both the degree of deuteration and the sample growth conditions. Physical mechanisms of D/H exchange are discussed.

Kucheyev, S. O.; Felter, T. E.; Siekhaus, W. J.; Nelson, A. J.; Hamza, A. V.

2004-02-01

23

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

24

Deuterium permeation through carbon-coated tungsten during ion bombardment  

Microsoft Academic Search

Deuterium permeation during ion bombardment through tungsten membranes coated by amorphous carbon films was investigated and compared with the permeation through bare tungsten. The membrane was bombarded by D3+ ions with energies of 200 and 1200 eV\\/D at a temperature of 873 K. The thickness of the amorphous carbon film was 120–170 nm. Detailed characterization of the carbon films were

Yu. Gasparyan; M. Mayer; A. Pisarev; A. Wiltner; C. Adelhelm; F. Koch; M. Rasinski; J. Roth

2011-01-01

25

Infrared spectroscopy of solid hydrogen sulfide and deuterium sulfide.  

PubMed

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

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

2006-09-21

26

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

SciTech Connect

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

Alekseev, I.; Fedorchenko, O.; Kravtsov, P.; Vasilyev, A.; Vznuzdaev, M. [Petersburg Nuclear Physics Inst., Leningrad district, Gatchina, 188300 (Russian Federation)

2008-07-15

27

rho^0- and psi^0Meson Photoproduction from Hydrogen and Deuterium  

Microsoft Academic Search

The rho^0- and psi^0-meson photoproduction from hydrogen and deuterium is studied. In the relation between cross sections on hydrogen and deuterium target it is found that the deuteron form factor plays an important role. Effects of isoscalar part of photon and the Glauber correction are also discussed.

M. Kawaguchi; H. Sakai; Y. Sumi

1970-01-01

28

Sono implantation of hydrogen and deuterium from water into metallic fine powders  

NASA Astrophysics Data System (ADS)

We observed the production of hydrogenated/deuterated metallic fine powders when various metals (Pd, Ag, Ta, Pt, and Au) were irradiated in normal and heavy water by ultrasonic waves. Mass analyses of remnant metal powders revealed substantial amounts of sono-implanted hydrogen and deuterium. The deuterium implantation (D implantation) in D2O was found to be much stronger than the hydrogen implantation (H implantation) in H2O.

Arata, Yoshiaki; Zhang, Yue-Chang

2000-04-01

29

Energy confinement of hydrogen and deuterium H-mode plasmas in JT-60U  

NASA Astrophysics Data System (ADS)

Energy confinement properties for hydrogen and deuterium H-mode plasmas are investigated. The thermal energy confinement time becomes longer in deuterium by a factor of ˜1.4 than in hydrogen at a given absorbed power. When the absorbed power is fixed, the values of electron temperature Te and ion temperature Ti become explicitly higher in deuterium than in hydrogen across the whole range of minor radius while the profiles of electron density ne are almost the same. Accordingly, the effective heat diffusivity becomes relatively lower in deuterium than in hydrogen. Despite almost the same power crossing the separatrix, type-I ELM frequency for hydrogen becomes approximately double that of deuterium. When the stored energy is fixed, the spatial profiles of ne, Te and Ti become identical for both cases while higher heating power is required in the hydrogen case. The pedestal pressure is about twice as high in deuterium as that in hydrogen at a given absorbed power. The increase of the pedestal temperature is more significant for the deuterium case while the pedestal density is not changed. The poloidal beta at the H-mode pedestal \\beta_p^ped is increased linearly with the increased total poloidal beta \\beta_p^TOT for both cases. The relation between \\beta_p^TOT and \\beta_p^ped is almost identical regardless of the difference of the isotope species.

Urano, H.; Takizuka, T.; Fujita, T.; Kamada, Y.; Nakano, T.; Oyama, N.; the JT-60 Team

2012-11-01

30

Bubble formation with electron irradiation in SiC implanted with hydrogen or deuterium  

Microsoft Academic Search

The bubbles were formed and grew when SiC implanted with high fluence of hydrogen ion was irradiated with electron. In this study we tried to inspect the supposition that the energy deposition of the electron beam to hydrogen caused the migration of hydrogen and gave rise to bubble formation and growth. We used hydrogen (H) or deuterium (D) as implanted

J. Aihara; K. Hojou; S. Furuno; M. Ishihara

2002-01-01

31

Hydrogenated Amorphous Carbon Films  

Microsoft Academic Search

\\u000a Hydrogenated amorphous carbon (a-C:H) thin film is one of the most studied materials due to its unique features. The a-C:H\\u000a thin film is a remarkable material because of its novel optical, mechanical and electrical properties and its similarities\\u000a to diamond. In this chapter we reviewed the structural and optical properties of hydrogenated amorphous carbon (a-C:H) thin\\u000a films prepared in a

Suriani Abu Bakar; Azira Abdul Aziz; Putut Marwoto; Samsudi Sakrani; Mohamad Rusop

32

Probing protein ensemble rigidity and hydrogen–deuterium exchange  

NASA Astrophysics Data System (ADS)

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

Sljoka, Adnan; Wilson, Derek

2013-10-01

33

Precise Calculation of Transition Frequencies of Hydrogen and Deuterium Based on a Least-Squares Analysis  

SciTech Connect

We combine a limited number of accurately measured transition frequencies in hydrogen and deuterium, recent quantum electrodynamics (QED) calculations, and, as an essential additional ingredient, a generalized least-squares analysis, to obtain precise and optimal predictions for hydrogen and deuterium transition frequencies. Some of the predicted transition frequencies have relative uncertainties more than an order of magnitude smaller than that of the g factor of the electron, which was previously the most accurate prediction of QED.

Jentschura, Ulrich D. [National Institute of Standards and Technology, Mail Stop 8401, Gaithersburg, Maryland 20899-8401 (United States); Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); Kotochigova, Svetlana; Mohr, Peter J.; Taylor, Barry N. [National Institute of Standards and Technology, Mail Stop 8401, Gaithersburg, Maryland 20899-8401 (United States); Le Bigot, Eric-Olivier [National Institute of Standards and Technology, Mail Stop 8401, Gaithersburg, Maryland 20899-8401 (United States); Laboratoire Kastler Brossel, Ecole Normale Superieure et Universite Pierre et Marie Curie, Case 74, 4 place Jussieu, 75005 Paris (France)

2005-10-14

34

Deuterium-depleted hydrogen in acid-insoluble residues of the Efremovka chondrite  

NASA Astrophysics Data System (ADS)

The paper presents results of an analysis of the isotope composition of hydrogen in three acid-insoluble residues of the Efremovka carbonaceous chondrite. The magnitude of deuterium depletion in two of these residue samples is similar to that observed in ordinary and enstatitic chondrites, suggesting that a single reservoir of hydrogen with D/H = 0.0001 existed in the early solar system. This reservoir might have been formed as the result of mixing of interstellar hydrogen with hydrogen released during the vaporization of deuterium-enriched interstellar dust.

Fisenko, A. V.; Devirts, A. L.; Lagutina, E. P.; Semenova, L. F.; Lavrukhina, A. K.

35

Electronic Structure of Palladium-Hydrogen and Palladium-Deuterium Rom Dehaas-van Alphen Experiments.  

National Technical Information Service (NTIS)

The electronic structure of a transition metal-hydrogen interstitial alloy was studied. Data on the Fermi surface and on the electron scattering rates of palladium-hydrogen and palladium-deuterium are obtained from de Haas-van Alphen experiments using a t...

W. J. Venema

1980-01-01

36

Venus was wet: a measurement of the ratio of deuterium to hydrogen  

Microsoft Academic Search

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 (1.6 +- 0.2) x 10⁻². The hundredfold enrichment of deuterium means that at least 0.3% of a terrestrial ocean was outgassed on Venus, but is consistent with a

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

1982-01-01

37

Calculation of carbon-14, chlorine-37, and deuterium kinetic isotope effects in the solvolysis of tert-butyl chloride  

Microsoft Academic Search

In the solvolysis of tert-butyl chloride, satisfactory ..cap alpha..-carbon-14, ..beta..-deuterium, and chlorine kinetic isotope effects (KIE) may be calculated for a productlike transition state characterized by bond orders n\\/sub C Cl\\/ = 0.2, n\\/sub C C\\/ = 1.18, and n\\/sub C H\\/ = 0.94, employing a diagonal valence force field, provided that allowance is made for hydrogen-bonded solvation of the

Graham W. Burton; Leslie B. Sims; Joe C. Wilson; Arthur Fry

1977-01-01

38

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

SciTech Connect

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

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

1984-02-01

39

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

40

Deuterium isotope exchange reaction between hydrogen and water over polyester-supported platinum catalysts  

SciTech Connect

Deuterium transfer between hydrogen and water over polyester-supported platinum has been found to follow a two-step process, namely, an initial fast step followed by a slower one. The faster exchange step was more susceptible to water poisoning while the other step continued to be active for H/D exchange reaction during prolonged contact with liquid water. The results are in agreement with the existence of heterogeneous metal sites with varying degrees of catalytic activity and support the mechanism whereby the chemisorption of both the water and hydrogen molecules at metal sites leads to the deuterium exchange process.

Gupta, N.M.; Mishra, K.; Belapurkar, A.D.; Rama Rao, K.V.S.; Iyer, R.M. (Bhabha Atomic Research Centre, Bombay (India))

1990-02-01

41

Effects of chemical states of carbon on deuterium retention in carbon-containing materials  

Microsoft Academic Search

Deuterium retention behavior in highly oriented pyrolytic graphite (HOPG), poly-crystalline diamond, poly-crystalline SiC, sintered WC, and converted B4C were investigated to reveal tritium behavior in re-deposition and co-deposition layers. Such layers would contain carbon, when the first wall and\\/or divertor were made of graphite or carbon-containing materials. Furthermore, the employment of other materials such as tungsten, and first wall conditioning

Makoto Oyaidzu; Hiromi Kimura; Toshihiko Nakahata; Yusuke Nishikawa; Masayuki Tokitani; Yasuhisa Oya; Hirotomo Iwakiri; Naoaki Yoshida; Kenji Okuno

2007-01-01

42

Dilute solution of hydrogen and deuterium in (C-15) TiCr/sub 1/ /sub 8/  

SciTech Connect

The dilute solution of hydrogen (and deuterium) in the intermetallic compound TiCr/sub 1/ /sub 8/ differs significantly from the behavior exhibited by hydrogen in pure metals and in random binary alloys. Specifically, (1) the solution of hydrogen in TiCr/sub 1/ /sub 8/ exhibits pronounced positive deviation from Sieverts' Law; (2) the partial molar enthalpy at infinite dilution is significantly more exothermic than the enthalpy of hydride formation; (3) the relative partial molar enthalpy of solution of hydrogen increases with increasing hydrogen content; and (4) the excess free energy of hydrogen solution increases with hydrogen content. These results parallel the behavior of hydrogen in the intermetallic LaNi/sub 5/, and suggest the intriguing possibility that such behavior is common to the solution of hydrogen in all intermetallic compounds. A comparison of the solubility of hydrogen and deuterium in TiCr/sub 1/ /sub 8/ allows an estimation of the hydrogen vibrational frequency, ..nu../sub H/ = 1530 cm/sup -1/. X-ray diffraction data reveal that the partial molar volume of hydrogen in TiCr/sub 1/ /sub 8/ = (1.01 cm/sup 3/) is about 30% smaller than the value generally observed in pure metals or random binary alloys.

Lynch, J.F.; Johnson, J.R.; Reilly, J.J.

1979-01-01

43

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.

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

2013-11-01

44

Isomeric Differentiation of Green Tea Catechins using Gas-Phase Hydrogen/Deuterium Exchange Reactions  

PubMed Central

Hydrogen/deuterium exchange reactions in a quadrupole ion trap mass spectrometer are used to differentiate galloylated catechin stereoisomers (catechin gallate and epicatechin gallate; gallocatechin gallate and epigallocatechin gallate) and the non-galloylated analogs (catechin and epicatechin, gallocatechin and epigallocatechin). Significant differences in the hydrogen/deuterium exchange behavior of the four pairs of deprotonated catechin stereoisomers are observed upon reaction with D2O. Interestingly, the non-galloylated catechins undergo H/D exchange to a much greater extent than the galloylated species, incorporating deuterium at both aromatic/allylic and active phenolic sites. Non-galloylated catechin isomers are virtually indistinguishable by their H/D exchange kinetics over a wide range of reaction times (0.05 to 10 s). Our experimental results are explained using high-level ab initio calculations to elucidate the subtle structural variations in the catechin stereoisomers that lead to their differing H/D exchange kinetics.

Niemeyer, Emily D.; Brodbelt, Jennifer S.

2007-01-01

45

Hydrogen (deuterium) vibron frequency as a pressure comparison gauge at multi-Mbar pressures  

NASA Astrophysics Data System (ADS)

The Raman spectra of compressed hydrogen (deuterium) have been measured in the multi-Mbar pressure range in the diamond anvil cell using the position of the stressed first-order Raman diamond edge (DE) to estimate pressure. We find that the Raman spectra are very consistent in repeated experiments for the critical frequencies of the hydrogen (deuterium) bands at the phase transition pressure-temperature (P-T) points. However, measurements of pressure determined from the DE in different experiments vary substantially with virtually identical Raman spectra of H2 (D2), giving in some cases a pressure variation as high as 20 GPa. These variations do not only depend on sample and sample chamber geometry but also on the P-T path taken, thus making the DE pressure determination uncertain. Therefore, we propose in experiments on hydrogen (deuterium) to use the Raman frequency of the intramolecular vibration (vibron) of H2(D2) as a pressure sensor. By comparing the vibron frequencies and considering the geometrical changes of the sample chamber caused by very high pressures, we propose an alternative explanation to the recent claims of a transformation to a metallic liquid state of hydrogen (deuterium).

Howie, Ross T.; Gregoryanz, Eugene; Goncharov, Alexander F.

2013-08-01

46

The Effect of Inhibitors on the Hydrogen-Deuterium Exchange Reaction  

Microsoft Academic Search

The exchange reaction between hydrogen and deuterium in silica vessels at temperatures in the region of 560 degrees C has been studied, the rate of formation of HD being determined by mass-spectrometer analysis. Nitric oxide and propylene are effective inhibitors of the reaction: both reduce the rate to the same limit. The fully inhibited reaction is approximately of the first

M. J. Stephen; C. J. Danby

1955-01-01

47

OLIGOSACCHARIDE STRUCTURES STUDIED BY HYDROGEN-DEUTERIUM EXCHANGE (HX) AND MALDI-TOF MASS SPECTROMETRY  

Technology Transfer Automated Retrieval System (TEKTRAN)

Hydrogen-deuterium exchange matrix-assisted laser desorption/ionization - time-of-flight mass spectrometry (HX-MALDI-TOF MS) is reported for the first time for the determination of exchangeable protons in diverse oligosaccharide and glycoconjugate structures. The method is generally analogous to th...

48

A STUDY OF EMBRITTLEMENT OF HIGH STRENGTH STEELS BY HYDROGEN ISOTOPES. II. A COMPARISON OF GAS CONTENTS AND HYDROGEN OR DEUTERIUM EMBRITTLEMENT RESULTING FROM ELECTROPLATING PROCESSES  

Microsoft Academic Search

Plating processes introduce more deuterium into steel from heavy water ; solutions than hydrogen from ordinary water solutions, yet hydrogen embrittles ; steel more than deuterium. No simple relation between the total gas content and ; embrittlement was found. Embrittlement appears to be dependent on factors other ; than the total gas content. The difference in the chemical affinity of

Wood

1963-01-01

49

Deep penetration of deuterium in carbon based substrates exposed to the PISCES-A plasma  

Microsoft Academic Search

Carbon based substrates were exposed to the PISCES-A high flux deuterium plasma, i.e. pyrolytic graphite, a carbon fibre material, the same material coated with a layer of SiC, and a graphite composite containing 30% SiC. The sides of the samples facing the plasma were again analysed after 1½ years of storage. In both analyses, the same amount of retained deuterium

B. Emmoth; M. Rubel; E. Franconi

1990-01-01

50

Hydrogen incorporation in tungsten deposits growing by deuterium plasma sputtering  

Microsoft Academic Search

Tungsten deposits were produced by sputtering method using hydrogen isotope RF plasma, and the density and the incorporated components in the deposits were investigated. The density changed in the range from 14.2g\\/cm3 to 6.1g\\/cm3, and hydrogen isotope retention changed in the range from 0.25 to 0.05 as (H+D)\\/W by the difference of deposition conditions. Both the density and hydrogen isotope

Kazunari Katayama; Sanshiro Kasahara; Shinichiro Ishikawa; Satoshi Fukada; Masabumi Nishikawa

2011-01-01

51

Effects of hydrogen/deuterium absorption on the magnetic properties of Co/Pd multilayers  

NASA Astrophysics Data System (ADS)

The effects of hydrogen and deuterium absorption were studied in two Co/Pd multilayers with perpendicular magnetic anisotropy using Polarized Neutron Reflectivity (PNR). PNR measurements were performed with the field in the plane of the sample with the magnetization M saturated at H = 6.0 T and unsaturated at 0.65 T. The nominal thicknesses of the Co/Pd layers were 2.5 å/21 å. Therefore, the actual layer chemical composition, thickness, and interface width parameters were defined from the nuclear scattering length density (SLD) profile obtained from both x-ray reflectivity (XRR) and PNR and their derivatives. The nuclear PNR SLD profile showed that although deuterium absorption occurred throughout the sample, the multilayer stack did not expand. The magnetic SLD showed that M in both the Pd and Co layers was affected. At saturation, M decreased, while at H = 0.65 T M increased upon deuterium exposure. Magnetization measurements confirmed hydrogen absorption decreased the total M at saturation and increased the component of M parallel to the field when not at saturation. These results indicate that hydrogen or deuterium absorption decreases both the perpendicular anisotropy and total magnetization of the samples.

Munbodh, Kineshma; Perez, Felio; Keenan, Cameron; Lederman, David; Zhernenkov, Mikhail; Fitzsimmons, Michael

2011-03-01

52

Deuterium concentration of co-deposited carbon layer produced at gap of wall tiles  

NASA Astrophysics Data System (ADS)

Tritium retention of a carbon layer deposited in the gap of plasma-facing materials is a primary concern for next step fusion devices. In this study, deuterium concentration and carbon deposition profile in a gap were investigated for carbon layers prepared by using deuterium arc discharge with carbon electrodes. The deuterium retention was measured with thermal desorption spectroscopy (TDS). The discharge pressure was varied from 0.8 to 36 Pa. The amount of deposited carbon into the gap decreased exponentially with the increase of the depth. The atomic ratios of D/C of the carbon layers prepared at 0.8 and 36 Pa were approximately 0.1 and 1.0, respectively. For the carbon layer prepared at 0.8 Pa, most of retained deuterium was released in the form of D2 and HD. On the other hand, at 36 Pa, approximately a half of retained deuterium was desorbed in the form of hydrocarbon, CD4 and C2D4.

Nobuta, Y.; Yokoyama, K.; Kanazawa, J.; Yamauchi, Y.; Hino, T.; Suzuki, S.; Ezato, K.; Enoeda, M.; Akiba, M.

2011-10-01

53

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

54

Fractionation of hydrogen and deuterium on Venus due to collisional ejection.  

PubMed

The fractionation factor f is important for interpreting the current escape fluxes of H and D on Venus and how the D/H ratio has evolved. The escape flux is currently governed by the two processes of charge exchange and collisional ejection by fast oxygen atoms. Using a best-fit parameterized equation for the O-H scattering angle phase function, more accurate branching ratios for the oxygen ion dissociation and including the effects of the initial energy and momentum of the ions and electrons, as well as for the hydrogen and deuterium gas, we have reanalyzed the collisional ejection process. Our analysis produces improved values for the efficiency of H and D escape as a function of the ionospheric temperature. From our results we propose the reduction of the hydrogen flux for collisional ejection from 8 to 3.5 x 10(6) cm-2 s-1. Assuming that collisions leading to escape occur mostly in the region between 200 and 400 km, the revised D/H fractionation factor due to collisional ejection is 0.47, where previously the process had been considered completely discriminating against deuterium escape (or f approximately 0.) The resulting deuterium flux is 3.1 x 10(4) cm-2 s-1, roughly 6 times the flux due to charge exchange, making collisional ejection the dominant escape mechanism for deuterium on Venus. PMID:11537633

Gurwell, M A; Yung, Y L

1993-02-01

55

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

56

Collisions of deuterium and tritium atoms with single-wall carbon nanotube: adsorption, encapsulation, and healing  

Microsoft Academic Search

Molecular dynamics simulations (MDSs) are used to study the collisions of deuterium (D) and tritium (T) atoms with single-wall carbon nanotube (SWNT) in the incident energy range of 1–33 eV. The MDSs show the scattering, encapsulation of deuterium and tritium, and the formation of exohedral D-SWNT, T-SWNT complexes. The hole on the sidewall induced by energetic atoms can be healed in

Yuchen Ma; Yueyuan Xia; Mingwen Zhao; M. Ying; Xiangdong Liu; Pijun Liu

2001-01-01

57

In electrospray ionization source hydrogen\\/deuterium exchange LCMS and LCMS\\/MS for characterization of metabolites  

Microsoft Academic Search

A new method is described for performing hydrogen\\/deuterium (H\\/D) exchange in an electrospray ionization (ESI) source. The\\u000a use of liquid chromatography (LC)-mass spectrometer equipped with an ESI source and deuterium oxide (D2O) as the sheath liquid allows H\\/D exchange experiments to be performed on-line. This directly provides information for determining\\u000a the number and position of exchangeable hydrogens, aiding in the

Wing Lam; Ragu Ramanathan

2002-01-01

58

Proton spin-lattice relaxation in solutions of hydrogen chloride and deuterium chloride  

Microsoft Academic Search

Proton spin-lattice relaxation times T1 for anhydrous solutions of hydrogen chloride and deuterium chloride have been measured at 20.8 Mc\\/s by a 90°-tau-90° pulse method. The measurements have been made, for most solutions, from the supercooled liquid (-116 °c) up to the liquid-vapour critical temperature (51.4 °c) and a little above. These T1 results for the HCl-DCl liquid solutions have

K. Krynicki; J. G. Powles

1965-01-01

59

CATALYTIC REACTIONS ON SEMICONDUCTORS: HYDROGEN-DEUTERIUM EXCHANGE AND FORMIC ACID DECOMPOSITION ON CHEMICALLY DOPED GERMANIUM  

Microsoft Academic Search

Hydrogen--deuterium exchange and the decomposition of formic acid were ; studied from 100 to 400 deg over samples of germanium doped with 10¹⁶ to ; 10²° atoms per cc. of n- and p-type impurities. Over these wide ranges of ; electronic chemical potentials (Fermi level) and temperature the rate and ; activation energy of the exchange reaction varied definitely with

George E. Moore; Hilton A. Smith; Ellison H. Taylor

1962-01-01

60

Hydrogen Adsorption in Carbon nanoparticles  

NASA Astrophysics Data System (ADS)

We have studied hydrogen adsorption in carbon nanoparticles using a quartz crystal microbalance. The carbon nanoparticles were synthesized from a thermal plasma jet at different pressure (15 -- 263 torr) of the reactants and different current (50 -- 250 A) to generate the plasma. The as-prepared carbon nanoparticles were directly deposited on top of the gold electrode of a quartz crystal and we monitored in-situ the changes in resonance frequency while the chamber was pressurized at different hydrogen pressures. These changes enabled determination of absorbed hydrogen mass in order to get H/C mass ratio curves as a function of H2 pressure. Adsorption curves obtained in some carbon nanoparticles indicated the formation of hydrogen monolayer inside the pores of the carbon nanoparticles. Using the value of the jump due to the formation of a H2monolayer, a surface area was estimated between 40-60 m^2/g for hydrogen adsorption. In other carbon samples, hydrogen uptake curves indicated that H2 was filling the sample's pores when pore volume was large. These observations will be discussed in detail for several carbon nanoparticles samples.

Cabrera, A. L.; Rojas, S.; Dias-Droguett, D. E.; Bhuyan, H.; Aomoa, N.; Kakati, M.

2013-03-01

61

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

NASA Astrophysics Data System (ADS)

A number of o-hydroxyacetylnitrobenzenes have been synthesized and their structures (X-ray and/or ab initio DFT calculations) have been determined. The intramolecular hydrogen bonds show correlations between the distances: O?O, O H, CO and O?H for both hydrogen bonds to acetyl and nitro groups. Rather short O?O distances and strong hydrogen bonds are obtained in a number of compounds, e.g. 1,3-diacetyl-5-nitro-2,4,6-trihydroxybenzene. Deuterium isotope effects on 1H and 13C chemical shifts have been determined. 2?C(OD) isotope effects correlate well with O?O distances, whereas 4?CO(OD) isotope effects do not. The latter become unusually large in 3,5-dinitro substituted derivatives. Deuterium isotope effects on 13C chemical shifts especially 2?C(OD), 5?CH3(OD) and 4?CO(OD) are used to evaluate steric and electronic contributions to resonance assisted hydrogen bonds. The effects are analysed using principal component analysis (PCA) techniques. Direct transmission of isotope effects via hydrogen bonds is demonstrated. DFT calculated NMR chemical shifts are shown to be useful in choosing between possible rotameric structures. X-ray analysis is used to determine structures in the solid. ‘Bond localization’ is shown to be important in understanding the effects of substituents. Intra molecular hydrogen bonds with acetyl or nitro groups as acceptors and OH groups as donors are compared. They are structurally similar but hydrogen bonds involving nitro groups are weaker for similar compounds. An unusual hydrogen bond pattern is observed in 1-acetyl-3,5-dinitro-2,4,6-trihydroxybenzene (two OH groups forms hydrogen bonds to the same nitro group). OH chemical shifts correlate with calculated Mulliken charges of OH for both hydrogen bonds to acetyl and nitro groups.

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

2006-05-01

62

CARBON DIOXIDE UPTAKE STUDIES IN ALGAE GROWN IN WATER AND DEUTERIUM OXIDE  

Microsoft Academic Search

A procedure is described for studying carbon dioxide uptake in algae ; using C¹⁴-labeled sodium bicarbonate as the source of carbon dioxide, ; Actively dividing, water grown and deuterium oxide adapted, Scenedesmus obliquus ; and Chlorella vulgaris were employed in the studies. Uptake comparisons were ; made over pH range 6 to 9 using appropriate buffer systems. Uptake was fairly

Martin I. Blake; Arlene S. Kaganove; Joseph J. Katz

1962-01-01

63

Protein structure change studied by hydrogen-deuterium exchange, functional labeling, and mass spectrometry  

PubMed Central

An automated high-throughput, high-resolution deuterium exchange HPLC-MS method (DXMS) was used to extend previous hydrogen exchange studies on the position and energetic role of regulatory structure changes in hemoglobin. The results match earlier highly accurate but much more limited tritium exchange results, extend the analysis to the entire sequence of both hemoglobin subunits, and identify some energetically important changes. Allosterically sensitive amide hydrogens located at near amino acid resolution help to confirm the reality of local unfolding reactions and their use to evaluate resolved structure changes in terms of allosteric free energy.

Englander, Joan J.; Del Mar, Charyl; Li, Will; Englander, S. Walter; Kim, Jack S.; Stranz, David D.; Hamuro, Yoshitomo; Woods, Virgil L.

2003-01-01

64

Tracking hydrogen/deuterium exchange at glycan sites in glycoproteins by mass spectrometry  

PubMed Central

Hydrogen deuterium exchange coupled to mass spectrometry (HDX-MS) has emerged as a technique for studying glycoproteins, which are often refractory to classical methods. Glycan chains are generally assumed to exchange protons very rapidly making them invisible to this technique. Here we show that under conditions commonly used for HDX-MS, acetamido groups within glycan chains retain a significant amount of deuterium. Using mono and polysaccharide standards along with glycopeptides from a panel of glycoproteins, we demonstrate that N-acetyl hexosamines, along with modified Asn sidechains are responsible for this effect. Model compounds for sialic acid also displayed similar exchange kinetics, but terminal sialic acids in the context of an entire glycan chain did not contribute to deuterium retention. Furthermore, the presence of sialic acid appears to enhance the exchange rate of the nearby N-acetyl glucosamines. The ability to detect deuterium exchange at the glycan level opens the possibility of applying HDX-MS to monitor glycan interactions and dynamics.

Guttman, M.; Scian, M.; Lee, K.K.

2011-01-01

65

Ion-induced deuterium retention in tungsten coatings on carbon substrate  

NASA Astrophysics Data System (ADS)

Deuterium retention in different tungsten (W) coatings on carbon substrates was investigated for various incident ion energies ranging from 20 to 200 eV per deuterium atom and fluences ranging from 1 × 1023 m-2 to 2 × 1025 m-2. The targets were irradiated by deuterium ions at the IPP laboratory with a mass-separated ion beam with a flux of 1019 D/m2 s and with a deuterium plasma providing a flux of 1020 D/m2 s. Irradiation has been done at different sample temperatures ranging from 320 to 650 K. The depth profile of deuterium in the W coatings was measured up to 6 ?m depth by nuclear reaction analysis (NRA) and the total retained amount was determined by thermal desorption spectroscopy. It is shown that deuterium retention significantly depends on the microstructure of each W coating. The deuterium retention in W coating of 7 ?m thickness produced by combined magnetron-sputtering and ion implantation technique is higher compared to physical vapour deposited W coating of 4-5 ?m thickness and 200 ?m thickness plasma-sprayed W coating for all investigated energies and sample temperatures up to 650 K.

Ogorodnikova, O. V.; Sugiyama, K.; Schwarz-Selinger, T.; Dürbeck, T.; Balden, M.

2011-12-01

66

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

67

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

NASA Astrophysics Data System (ADS)

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 PuH2). The heats of solution for PuHS and PuDS 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, S.; Bridgewater, J. S.; Ward, J. W.; Allen, T. H.

2010-03-01

68

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

69

Kinetic Method for Hydrogen-Deuterium-Tritium Mixture Distillation Simulation  

SciTech Connect

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

Sazonov, A.B.; Kagramanov, Z.G.; Magomedbekov, E.P. [Mendeleyev University of Chemical Technology of Russia (Russian Federation)

2005-07-15

70

Effects of lithium-implantation on the hydrogen retention in both aC:H and aSiC:H materials submitted to deuterium bombardment  

Microsoft Academic Search

The hydrogen release in plasma facing materials is a challenging problem for the hydrogen recycling. The hydrogen desorption from the a-C:H and a-SiC:H materials induced by deuterium bombardment has been investigated. Prior to the deuterium bombardment, both materials were implanted with different fluences of lithium ions. Before and after each irradiation, depth profiles of H, Li and deuterium were determined

G. Barbier; G. G. Ross; M. A. El Khakani; N. Chevarier; A. Chevarier

1997-01-01

71

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.

2013-09-01

72

Studies of negative ions by collision-induced decomposition and hydrogen-deuterium exchange techniques.  

PubMed Central

Development of two new techniques for studying the gas phase chemistry of negative ions is reported. Collision induced dissociation (CID) of (M-1)- ions has been accomplished in a newly constructed triple stage quadrupole mass spectrometer. This instrument was assembled by adding two additional Finnigan quadrupole mass filters to a Finnigan Model 3200 CI mass spectrometer. Generation of (M-1)- ions is accomplished by allowing OH- and sample to react under CI conditions in the ion source. The first quadrupole mass filter, Q1, is then employed to selectively pass the (M-1)- ion into a second quadrupole filter containing argon or neon at 10(-3) torr. On collision with the inert gas the (M-1)- ions dissociate into fragments which are then mass analyzed in the third quadrupole filter, CID spectra of (M-1)- ions from twelve carbonyl compounds are presented in this paper. Ion molecule isotope exchange reactions in the CI ion source can be used to count the number of hydrogen atoms in many different chemical environments. Collisions between sample (M-1)- ions and deuterium-labeled reagent gases (ND3, D2O, EtOD) facilitate incorporation of deuterium into the negative ion if the basicities of the sample and reagent anions are similar. Thus it is possible to selectively incorporate deuterium into many organic samples by controlling the exothermicity of the acid base, ion-molecule chemistry.

Hunt, D F; Sethi, S K; Shabanowitz, J

1980-01-01

73

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

74

Performance of a hydrogen/deuterium polarized gas target in a storage ring  

NASA Astrophysics Data System (ADS)

The performance of a high-density polarized hydrogen/deuterium gas target internal to a medium-energy electron storage ring is presented. Compared to our previous electron scattering experiments with tensor-polarized deuterium at NIKHEF (Zhou et al., Nucl. Instr. and Meth. A 378 /(1996) 40; Ferro-Luzzi et al., Phys. Rev. Lett. 77 /(1996) 2630; Van den Brand et al., Phys. Rev. Lett. 78 /(1997) 1235; Bouwhuis et al., Phys. Rev. Lett. 82 /(1999) 687; Zhou et al., Phys. Rev. Lett. 82 /(1999) 687) the target figure of merit, (polarization)2×luminosity, was improved by more than an order of magnitude. The target density was increased by upgrading the flux of nuclear-polarized atoms injected into the storage cell and by using a longer (60cm) and colder (~70K) storage cell. A maximal target thickness of 1.2(1.1)+/-0.1×1014nuclei/cm2 was achieved with deuterium (hydrogen). With typical beam currents of 110mA, this corresponds to a luminosity of about 8.4(7.8)+/-0.8×1031e-nucleicm- 2s-1. By reducing the molecular background and using a stronger target guide field, a higher polarization was achieved. The target was used in combination with a 720MeV polarized electron beam stored in the AmPS ring (NIKHEF) to measure spin observables in electron-proton and electron-deuteron scattering. Scattered electrons were detected in a large acceptance magnetic spectrometer. Ejected hadrons were detected in a single time-of-flight scintillator array. The product of beam and target vector polarization, PePt, was determined from the known spin-correlation parameters of /e'p quasi-elastic (or elastic) scattering. With the deuterium (hydrogen) target, values up to PePt=0.49+/-0.03 /(0.32+/-0.03) were obtained with an electron beam polarization of Pe=0.62+/-0.04 /(0.56+/-0.03) as measured with a Compton backscattering polarimeter (Passchier et al., Nucl. Instr. and Meth. A 414 /(1998) 4988). From this, we deduce a cell-averaged target polarization of Pt=0.78+/-0.07 (/0.58+/-0.07), including the dilution by unpolarized molecules.

van Buuren, L. D.; Szczerba, D.; van den Brand, J. F. J.; Bulten, H. J.; Ferro-Luzzi, M.; Klous, S.; Kolster, H.; Lang, J.; Mul, F. A.; Poolman, H. R.; Simani, M. C.

2001-12-01

75

Improved protein hydrogen/deuterium exchange mass spectrometry platform with fully automated data processing.  

PubMed

Protein hydrogen/deuterium exchange (HDX) followed by protease digestion and mass spectrometric (MS) analysis is accepted as a standard method for studying protein conformation and conformational dynamics. In this article, an improved HDX MS platform with fully automated data processing is described. The platform significantly reduces systematic and random errors in the measurement by introducing two types of corrections in HDX data analysis. First, a mixture of short peptides with fast HDX rates is introduced as internal standards to adjust the variations in the extent of back exchange from run to run. Second, a designed unique peptide (PPPI) with slow intrinsic HDX rate is employed as another internal standard to reflect the possible differences in protein intrinsic HDX rates when protein conformations at different solution conditions are compared. HDX data processing is achieved with a comprehensive HDX model to simulate the deuterium labeling and back exchange process. The HDX model is implemented into the in-house developed software MassAnalyzer and enables fully unattended analysis of the entire protein HDX MS data set starting from ion detection and peptide identification to final processed HDX output, typically within 1 day. The final output of the automated data processing is a set (or the average) of the most possible protection factors for each backbone amide hydrogen. The utility of the HDX MS platform is demonstrated by exploring the conformational transition of a monoclonal antibody by increasing concentrations of guanidine. PMID:22571272

Zhang, Zhongqi; Zhang, Aming; Xiao, Gang

2012-05-15

76

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

PubMed

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 Cu(2+) 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

2013-08-19

77

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

78

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

NASA Astrophysics Data System (ADS)

Hydrogen and deuterium incorporation into nitrided and non-nitrided hafnium silicate films on Si during thermal annealing in 1H- and 2H-containing atmospheres was investigated. 1H profiling was accessed by means of nuclear resonant reaction profiling, whereas 2H incorporation was quantified by nuclear reaction analysis. The effects of preannealing in different atmospheres and temperatures were determined, as well as the losses of 1H and 2H from these structures during postannealing in vacuum. The results reveal a rather uniform depth distribution of incorporated 1H, 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.

2004-10-01

79

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

SciTech Connect

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

Fitch, M.W.; Koros, W.J. (Univ. of Texas, Austin (United States)); Nolen, R.L.; Carnes, J.R. (Los Alamos National Lab., NM (United States))

1993-02-10

80

Hydrogen-deuterium exchange experiments to probe the decomposition reaction of sodium alanate.  

PubMed

NaAlH(4) is the archetypical complex hydride for hydrogen storage. The extraordinary effect of dopants on the sorption kinetics triggered the investigation of this empirical finding. In this paper, a short review of the state of the art is given. To gain further understanding of the mechanisms involved we label the interacting species during the sorption process. This was experimentally realized by hydrogen-deuterium exchange measurements during the decomposition of NaAlH(4) followed by thermogravimetry, Raman spectroscopy and mass spectrometry. By these experiments we are able to obtain specific information on the diffusing species and formation of intermediates. The activation energy of tracer diffusion in NaAlH(4) is found to be 0.28 eV. The results are evidence for a vacancy-mediated desorption process of NaAlH(4). PMID:18597019

Borgschulte, A; Züttel, A; Hug, P; Barkhordarian, G; Eigen, N; Dornheim, M; Bormann, R; Ramirez-Cuesta, A J

2008-05-29

81

Deuterium-hydrogen exchange in olivine: Implications for point defects and electrical conductivity  

NASA Astrophysics Data System (ADS)

Knowledge about hydrogen self diffusion (DH) is critical for determining mantle hydrogen distribution and understanding point defects. Also, chemical diffusion of hydrogen in olivine, such as redox exchange with polarons (DRedox), depends on DH. In this study deuterium 2H was exchanged into hydrogen 1H saturated single crystals of San Carlos olivine between 750 and 900°C at 2 GPa. We measured and fit the resulting 2H profiles to obtain DH,[100] = 10(-4.9±1.4)*e(-140±30kJ/mol)/(RT) m2/s, which is ˜1 log unit lower than DRedox,[100], with similar activation enthalpy Ha. By comparing these two diffusion coefficients, we estimate the small polaron diffusion coefficient. Additionally, we estimate DH in the [010] and [001] orientations, demonstrating that DH is highly anisotropic in olivine. These DHvalues were used with the Nernst-Einstein relation to estimate the electrical conductivity by hydrogen in olivine (?H = 101.1*e(-130kJ/mol)/(RT) S/m for 10-2 wt % H2O) that is lower in magnitude than previous measurements. Our results suggest that hydrogen alone cannot account for high electrical conductivity anomalies observed at asthenospheric depths (˜10-2 to ˜10-1 S/m). The maximum anisotropic variation of DH and ?Hin olivine is ˜2 log units between 750 and 900°C and increases when extrapolated to higher temperature (˜3.3 at 1400°C). Anisotropy observed in the mantle may indicate substantial amounts of hydrogen in olivine with lattice-preferred orientation.

Du Frane, Wyatt L.; Tyburczy, James A.

2012-03-01

82

Deuterium retention in carbon and tungsten–carbon mixed films deposited by magnetron sputtering in D 2 atmosphere  

Microsoft Academic Search

Deuterium (D) retention in carbon (C) and tungsten–carbon (W–C) mixed films deposited by reactive magnetron sputtering in D2 atmosphere has been investigated by means of secondary ion mass spectrometry and residual gas analysis measurements. In the C and W–C films, D is distributed homogeneously throughout the film thickness. With the deposition temperature increase, the D concentration in the C films

V. Kh. Alimov; D. A. Komarov

2003-01-01

83

Comparative study of hydrogenated diamondlike carbon film and hard hydrogenated graphitelike carbon film  

NASA Astrophysics Data System (ADS)

The structure, mechanical properties, and friction properties of hydrogenated graphitelike carbon film and typical hydrogenated diamondlike carbon film were investigated comparatively that the hydrogenated graphitelike carbon film has relatively high sp2 content and low bonded hydrogen content and possessed high hardness and elasticity. It was attributed to the curved graphene microstructure, which is able to form three-dimensional covalently bonded network. Furthermore, in comparison with the hydrogenated diamondlike carbon film, the hydrogenated graphitelike carbon film demonstrated excellent friction behavior probably due to the extraordinary structure of hydrogenated graphitelike carbon film.

Wang, Chengbing; Yang, Shengrong; Wang, Qi; Wang, Zhou; Zhang, Junyan

2008-06-01

84

Localized hydration in lyophilized myoglobin by hydrogen-deuterium exchange mass spectrometry. 2. Exchange kinetics.  

PubMed

Solid-state hydrogen-deuterium exchange with mass spectrometric analysis (ssHDX) is a promising method for characterizing proteins in amorphous solids. Though analysis of HDX kinetics is informative and well-established in solution, application of these methods to solid samples is complicated by possible heterogeneities in the solid. The studies reported here provide a detailed analysis of the kinetics of hydration and ssHDX for equine myoglobin (Mb) in solid matrices containing sucrose or mannitol. Water sorption was rapid relative to ssHDX, indicating that ssHDX kinetics was not limited by bulk water transport. Deuterium uptake in solids was well-characterized by a biexponential model; values for regression parameters provided insight into differences between the two solid matrices. Analysis of the widths of peptide mass envelopes revealed that, in solution, an apparent EX2 mechanism prevails, consistent with native conformation of the protein. In contrast, in mannitol-containing samples, a smaller non-native subpopulation exchanges by an EX1-like mechanism. Together, the results indicate that the analysis of ssHDX kinetic data and of the widths of peptide mass envelopes is useful in screening solid formulations of protein drugs for the presence of non-native species that cannot be detected by amide I FTIR. PMID:22352990

Sophocleous, Andreas M; Topp, Elizabeth M

2012-02-29

85

A STUDY OF CATALYTIC REACTIONS ON SEMICONDUCTORS: HYDROGEN-DEUTERIUM EXCHANGE AND FORMIC ACID DECOMPOSITION ON CHEMICALLYDOPED GERMANIUM  

Microsoft Academic Search

Rates and activation energies for the hydrogen-deuterium exchange and ; formic acid vapor decomposition were measured on a series of chemically doped ; germanium catalysts over the temperature range 100 to 400 deg C. The germanium ; catalysts were intriosic and n- or p-type extrinsic semiconductors; the position ; of the Fermi level of the solid was located suitably in

1962-01-01

86

Simultaneous quantitative determination of deuterium- and carbon-13-labeled essential fatty acids in rat plasma  

Microsoft Academic Search

This study reports methods for the quantitative determination of stable isotope-labeled essential fatty acids (EFAs) as well as an experiment in which deuterium-labeled linoleic acid (18:2n-6) and ? -linolenic acid (18:3n-3) were compared with those labeled with carbon-13 in rat plasma in vivo. Standard curves were constructed to compensate for concentration and plasma matrix effects. It was observed that endogenous

Yu Hong Lin; Robert J. Pawlosky; Norman Salem

2005-01-01

87

Global budget fo molecular hydrogen and its deuterium content: constraints from surface, aircraft, and oceanic cruise observations  

Microsoft Academic Search

To improve our understanding of the global budget of molecular hydrogen, we present a new simulation of molecular hydrogen and its deuterium component (deltaD) using the GEOS-CHEM three dimensional global model of tropospheric chemistry. The primary sources of H2 (fossil fuel, biofuel, and biomass burning) used in the model are based on the GEOS-CHEM CO emissions inventory, scaled with the

H. U. Price; L. Jaegle; P. Quay; A. Rice; P. Novelli

2006-01-01

88

Production of beam of negative hydrogen and deuterium ions from source with electron cyclotron resonance  

SciTech Connect

The GELIOS-H/sup /minus// ion source is described; it has electron cyclotron resonance and is designed for generation of negative hydrogen and deuterium ions. The source consumes up to 100 W of microwave power at a frequency of 2.4 GHz and provides a stationary beam of H/sup /minus// ions of up to 1.5 mA and D/sup /minus// ions of up to 1.0 mA for an exit-aperture diameter of 6.2 mm and an extraction voltage of 4.5 kV. The life of the source is limited only by the life of the microwave generator.

Golovanivskii, K.S.; Dzhayamanna, K.; Dugar-Zhabon, V.D.

1988-09-01

89

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

90

Oligomerization Interface of RAGE Receptor Revealed by MS-Monitored Hydrogen Deuterium Exchange.  

PubMed

Activation of the receptor for advanced glycation end products (RAGE) leads to a chronic proinflammatory signal, affecting patients with a variety of diseases. Potentially beneficial modification of RAGE activity requires understanding the signal transduction mechanism at the molecular level. The ligand binding domain is structurally uncoupled from the cytoplasmic domain, suggesting receptor oligomerization is a requirement for receptor activation. In this study, we used hydrogen-deuterium exchange and mass spectrometry to map structural differences between the monomeric and oligomeric forms of RAGE. Our results indicated the presence of a region shielded from exchange in the oligomeric form of RAGE and led to the identification of a new oligomerization interface localized at the linker region between domains C1 and C2. Based on this finding, a model of a RAGE dimer and higher oligomeric state was constructed. PMID:24098480

Sitkiewicz, Ewa; Tarnowski, Krzysztof; Pozna?ski, Jaros?aw; Kulma, Magdalena; Dadlez, Michal

2013-10-01

91

Hydrogen/Deuterium Exchange Analysis of HIV-1 Capsid Assembly and Maturation  

PubMed Central

Summary Following budding, HIV-1 virions undergo a maturation process where the gag polyprotein in the immature virus is cleaved by the viral protease and rearranges to form the mature, infectious virion. Despite the wealth of structures of isolated capsid domains and an in vitro assembled mature lattice, models of the immature lattice do not provide an unambiguous model of capsid molecule orientation and no structural information is available for the capsid maturation pathway. Here we have applied hydrogen/deuterium exchange mass spectrometry to immature, mature and mutant gag particles (CA5) blocked at the final gag cleavage event to examine the molecular basis of capsid assembly and maturation. Capsid packing arrangements were very similar for all virions while immature and CA5 virions contained an additional intermolecular interaction at the hexameric, three-fold axis. Additionally, the N-terminal ?-hairpin was observed to form as a result of capsid-SP1 cleavage rather than driving maturation as previously postulated.

Monroe, Eric B.; Kang, Sebyung; Kyere, Sampson K.; Li, Rui; Prevelige, Peter E.

2010-01-01

92

Oligomerization Interface of RAGE Receptor Revealed by MS-Monitored Hydrogen Deuterium Exchange  

PubMed Central

Activation of the receptor for advanced glycation end products (RAGE) leads to a chronic proinflammatory signal, affecting patients with a variety of diseases. Potentially beneficial modification of RAGE activity requires understanding the signal transduction mechanism at the molecular level. The ligand binding domain is structurally uncoupled from the cytoplasmic domain, suggesting receptor oligomerization is a requirement for receptor activation. In this study, we used hydrogen-deuterium exchange and mass spectrometry to map structural differences between the monomeric and oligomeric forms of RAGE. Our results indicated the presence of a region shielded from exchange in the oligomeric form of RAGE and led to the identification of a new oligomerization interface localized at the linker region between domains C1 and C2. Based on this finding, a model of a RAGE dimer and higher oligomeric state was constructed.

Poznanski, Jaroslaw; Kulma, Magdalena; Dadlez, Michal

2013-01-01

93

Deuterium-Hydrogen Interdiffusion in Olivine: Implications for Point Defects and Electrical Conductivity  

NASA Astrophysics Data System (ADS)

Knowledge about hydrogen diffusivity in mantle minerals is critical for determining mantle hydrogen distribution, and additionally for understanding point defects. Chemical diffusion of hydrogen in olivine depends on self diffusion and concentration of hydrogen and other point defects, such as small polarons and metal vacancies. In this study we measured hydrogen self diffusion in olivine, and we compare these values to those previously reported for chemical 1-H redox exchange DExch. Deuterium 2-H was interdiffused into hydrogen 1-H saturated single crystals of San Carlos olivine between 750-900 °C at 2 GPa. We measured and fit the resulting 2-H and 1-H profiles to obtain the interdiffusion coefficient DH,[100] = 10^(-5.04+/-1.43)*e(-137+/-31kJ/mol)/(RT) m^2/s. This is ~1 log unit lower than DExch,[100], with similar activation energy Ea,[100]. DH is anisotropic with DH,[001] = 10^(-12.0+/-0.2) m^2/s at 900 °C and 2 GPa; only upper bound estimates for DH,[010] could be determined from our experiments. We use DH,[100] and DExch,[100] to calculate the small polaron diffusion coefficient associated with redox exchange Dh,[100] = 10^-3.90*e(-142kJ/mol)/(RT) m^2/s. Dh,[100] is combined with reported values for DExch,[010] and DExch,[010] to calculate values for DH,[010] and DH,[001] that are consistent with our upper bound estimates. These DH values, both measured and derived, are used with the Nernst-Einstein relation to calculate the electrical conductivity ? by hydrogen in olivine ?H. We calculate ?H = 10^1.63*e(-126kJ/mol)/(RT) S/m, which is similar in magnitude to the lower range of reported ? measurements. This similarly suggests that hydrogen alone cannot account for high ? anomalies observed at asthenospheric depths (~10^-2 to ~10^-1 S/m). The Ea for hydrogen mobility/diffusion we calculate are higher (~40% for 100 ppmw H2O) than those derived from previous ? measurements. This work supported by NSF EAR 0739050 to J. A. Tyburczy and R. Hervig. The SIMS data were obtained at the ASU National SIMS Facility, supported by NSF EAR 0622775 to R. Hervig & P.Williams. Piston cylinder experiments were conducted in the ASU OmniPressure lab. Prepared by LLNL under Contract DE-AC52-158 07NA27344.

Tyburczy, J. A.; Du Frane, W. L.

2011-12-01

94

Deuterium-induced chemical erosion of carbon-metal layers  

Microsoft Academic Search

Magnetron-sputtered layers consisting of carbon and metal (W, Ti, V) were produced with 0–20at.% metal concentration. The mixed layers were characterised by RBS, SEM, XRD and XPS, and exposed to D3+ ions of 30eV\\/D at temperatures between 77 and 1100K. The chemical erosion yield was investigated by mass spectrometry and RBS. Above RT (?300K), the CD4 production yield for pure

M. Balden; E. de Juan Pardo; I. Quintana; B. Cieciwa; J. Roth

2005-01-01

95

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

96

Conformational stability of ribonuclease T1 determined by hydrogen-deuterium exchange.  

PubMed Central

The hydrogen-deuterium exchange kinetics of 37 backbone amide residues in RNase T1 have been monitored at 25, 40, 45, and 50 degrees C at pD 5.6 and at 40 and 45 degrees C at pD 6.6. The hydrogen exchange rate constants of the hydrogen-bonded residues varied over eight orders of magnitude at 25 degrees C with 13 residues showing exchange rates consistent with exchange occurring as a result of global unfolding. These residues are located in strands 2-4 of the central beta-pleated sheet. The residues located in the alpha-helix and the remaining strands of the beta-sheet exhibited exchange behaviors consistent with exchange occurring due to local structural fluctuations. For several residues at 25 degrees C, the global free energy change calculated from the hydrogen exchange data was over 2 kcal/mol greater than the free energy of unfolding determined from urea denaturation experiments. The number of residues showing this unexpected behavior was found to increase with temperature. This apparent inconsistency can be explained quantitatively if the cis-trans isomerization of the two cis prolines, Pro-39 and Pro-55, is taken into account. The cis-trans isomerization equilibrium calculated from kinetic data indicates the free energy of the unfolded state will be 2.6 kcal/mol higher at 25 degrees C when the two prolines are cis rather than trans (Mayr LM, Odefey CO, Schutkowski M, Schmid FX. 1996. Kinetic analysis of the unfolding and refolding of ribonuclease T1 by a stopped-flow double-mixing technique. Biochemistry 35: 5550-5561). The hydrogen exchange results are consistent with the most slowly exchanging hydrogens exchanging from a globally higher free energy unfolded state in which Pro-55 and Pro-39 are still predominantly in the cis conformation. When the conformational stabilities determined by hydrogen exchange are corrected for the proline isomerization equilibrium, the results are in excellent agreement with those from an analysis of urea denaturation curves.

Mullins, L. S.; Pace, C. N.; Raushel, F. M.

1997-01-01

97

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

98

Transitions between Elongated Conformations of Ubiquitin [M+11H]11+ Enhance Hydrogen/Deuterium Exchange  

PubMed Central

Hydrogen/deuterium (H/D) exchange reactions between different elongated conformations of [M+11H]11+ ions of ubiquitin and D2O are studied by a combination of ion mobility spectrometry (IMS) and mass spectrometry techniques. Three conformers (B, C, and D), resolved in the IMS separation, each exchange ~27 hydrogens upon exposure to 0.06 torr of D2O vapor for ~35 to 40 ms. However, a region of the IMS spectrum that appears between the C and D states (corresponding to ions that undergo a structural transition during the mobility separation) undergoes substantially more exchanges (~39 total sites, 44% more than the B, C, and D states). Selection and activation of the individual B, C, and D states reveals that the increased H/D exchange occurs during the transition between structures. Overall, these studies suggest a key process in establishing the maximum exchange levels involves structural transitions, which allow protected sites to be exposed for some fraction of the reaction time. Analysis of changes in exchange levels upon structural transitions can provide insight about common regions of structure that exist in the B, C, and D conformations.

Bohrer, Brian C.; Atlasevich, Natalya; Clemmer, David E.

2011-01-01

99

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

NASA Astrophysics Data System (ADS)

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

Iliescu, M.

2005-06-01

100

Hydrogen/Deuterium Exchange Study of Subtilisin Carlsberg During Prolonged Exposure to Organic Solvents  

PubMed Central

It has been previously reported that prolonged exposure of an enzyme to organic solvents leads to substantial decrease of activity. This effect was found to be unrelated to the catalysts’ structure or their possible aggregation in organic solvents, and up to the present day the cause for activity loss remains unclear. In the present work, the structural dynamics of the serine protease subtilisin Carlsberg (SC) have been investigated during prolonged exposure to two organic solvents by following hydrogen/deuterium (H/D) exchange of mobile protons. The enzyme, after lyophilization, was incubated in organic solvents at controlled deuteriated water activity for different times and the H/D exchange was allowed to take place. The amount of deuterium exchanged was evaluated by 2H NMR, which in turn gave us a picture of the changing dynamics of our model enzyme during incubation and under different experimental conditions. Our results show that the flexibility of SC decreases during prolonged storage in 1,4-dioxane (Diox) and acetonitrile (ACN) as indicated by the observed 3- to 10-fold decrease in the apparent rate constants of exchange (k) of fast exchangeable protons (FEP) and slow exchangeable protons (SEP) in the protein. Our study also shows that SC is more flexible in ACN than in Diox (k 3?20 times higher in ACN for the FEP and SEP), suggesting that enzyme dynamics are affected by solvent physicochemical properties. Additionally, the enzyme dynamics are also affected by the method of preparation: decreased flexibility (k decreases 3- to 10-fold for FEP and SEP) is observed when the enzyme is chemically modified with poly ethylene glycol (PEGylated) or colyophilized with crown ethers. A possible relationship between activity, enantioselectivity (E), and structural dynamics is discussed, demonstrating that direct correlations, as have been attempted in the past, are hampered by the multi-variable nature and complexity of the system.

Fasoli, Ezio; Ferrer, Amaris; Barletta, Gabriel L.

2009-01-01

101

Platform dependencies in bottom-up hydrogen/deuterium exchange mass spectrometry.  

PubMed

Hydrogen-deuterium exchange mass spectrometry is an important method for protein structure-function analysis. The bottom-up approach uses protein digestion to localize deuteration to higher resolution, and the essential measurement involves centroid mass determinations on a very large set of peptides. In the course of evaluating systems for various projects, we established two (HDX-MS) platforms that consisted of a FT-MS and a high-resolution QTOF mass spectrometer, each with matched front-end fluidic systems. Digests of proteins spanning a 20-110 kDa range were deuterated to equilibrium, and figures-of-merit for a typical bottom-up (HDX-MS) experiment were compared for each platform. The Orbitrap Velos identified 64% more peptides than the 5600 QTOF, with a 42% overlap between the two systems, independent of protein size. Precision in deuterium measurements using the Orbitrap marginally exceeded that of the QTOF, depending on the Orbitrap resolution setting. However, the unique nature of FT-MS data generates situations where deuteration measurements can be inaccurate, because of destructive interference arising from mismatches in elemental mass defects. This is shown through the analysis of the peptides common to both platforms, where deuteration values can be as low as 35% of the expected values, depending on FT-MS resolution, peptide length and charge state. These findings are supported by simulations of Orbitrap transients, and highlight that caution should be exercised in deriving centroid mass values from FT transients that do not support baseline separation of the full isotopic composition. PMID:23197788

Burns, Kyle M; Rey, Martial; Baker, Charles A H; Schriemer, David C

2012-11-28

102

Sodium-proton exchanger isoform-1: synthesis of a potent inhibitor labeled with deuterium and carbon-14.  

PubMed

Sodium-proton exchangers, NHEs are plasma membrane proteins that are essential in the regulation of intracellular pH of the myocardium. There are nine known variously expressed isoforms of NHEs with NHE-1 being the predominant isoform in the heart. N-[4-(1-acetyl-piperidin-4-yl)-3-trifluoromethyl-benzoyl]-guanidine (1) is a potent NHE 1-inhibitor with good pharmacokinetics. It was prepared labeled with deuterium and carbon-14 to aid in drug metabolism, pharmacokinetics, and other studies. The combination of Comins' reaction and reduction under deuterium gas was used to access deuterium labeled (1) starting from deuterium labeled pyridine. Carbon-14 labeled zinc cyanide was used to prepare [(14)C]-(1) in three steps, with a specific activity of 55.6 mCi/mmol. PMID:23256768

Latli, Bachir; Haddad, Nizar; Hrapchak, Matt; Wei, Xudong; Tang, Wenjun; Song, Jinhua J; Senanayake, Chris H

2013-03-01

103

Substrate binding and conformational changes of Clostridium glutamicum diaminopimelate dehydrogenase revealed by hydrogen/deuterium exchange and electrospray mass spectrometry.  

PubMed Central

C. glutamicum meso-diaminopimelate dehydrogenase is an enzyme of the L-lysine biosynthetic pathway in bacteria. The binding of NADPH and diaminopimelate to the recombinant, overexpressed enzyme has been analyzed using hydrogen/deuterium exchange and electrospray ionization/mass spectrometry. NADPH binding reduces the extent of deuterium exchange, as does the binding of diaminopimelate. Pepsin digestion of the deuterated enzyme and enzyme-substrate complexes coupled with liquid chromatography/mass spectrometry have allowed the identification of eight peptides whose deuterium exchange slows considerably upon the binding of the substrates. These peptides represent regions known or thought to bind NADPH and diaminopimelate. One of these peptides is located at the interdomain hinge region and is proposed to be exchangeable in the "open," catalytically inactive, conformation but nonexchangeable in the "closed," catalytically active conformation formed after NADPH and diaminopimelate binding and domain closure. Furthermore, the dimerization region has been localized by this method, and this study provides an example of detecting protein-protein interface regions using hydrogen/deuterium exchange and electrospray ionization.

Wang, F.; Scapin, G.; Blanchard, J. S.; Angeletti, R. H.

1998-01-01

104

Compilation of erosion yields of metal-doped carbon materials by deuterium impact from ion beam and low temperature plasma  

Microsoft Academic Search

The erosion yield by deuterium impact was determined for various doped carbon-based materials. Ion beam bombardment with 30 and 200eV at elevated temperatures (600–850K) and low temperature plasma exposure with 30eV ion energy (?7×1020ions\\/m2s) and about 170 times higher thermal atomic deuterium flux at 300K and 630K were performed. The total yield of fine-grain graphites doped with 4at.% Ti and

M. Balden; P. Starke; C. García-Rosales; C. Adelhelm; P. A. Sauter; I. López-Galilea; N. Ordas; J. M. Ramos Fernández; M. Martínez Escandell

2011-01-01

105

Infrared spectroscopic study of photoreceptor membrane and purple membrane. Protein secondary structure and hydrogen deuterium exchange  

SciTech Connect

Infrared spectroscopy in the interval from 1800 to 1300 cm-1 has been used to investigate the secondary structure and the hydrogen/deuterium exchange behavior of bacteriorhodopsin and bovine rhodopsin in their respective native membranes. The amide I' and amide II' regions from spectra of membrane suspensions in D2O were decomposed into constituent bands by use of a curve-fitting procedure. The amide I' bands could be fit with a minimum of three theoretical components having peak positions at 1664, 1638, and 1625 cm-1 for bacteriorhodopsin and 1657, 1639, and 1625 cm-1 for rhodopsin. For both of these membrane proteins, the amide I' spectrum suggests that alpha-helix is the predominant form of peptide chain secondary structure, but that a substantial amount of beta-sheet conformation is present as well. The shape of the amide I' band was pH-sensitive for photoreceptor membranes, but not for purple membrane, indicating that membrane-bound rhodopsin undergoes a conformation change at acidic pH. Peptide hydrogen exchange of bacteriorhodopsin and rhodopsin was monitored by observing the change in the ratio of integrated absorbance (Aamide II'/Aamide I') during the interval from 1.5 to 25 h after membranes were introduced into buffered D2O. The fraction of peptide groups in a very slowly exchanging secondary structure was estimated to be 0.71 for bacteriorhodopsin at pD 7. The corresponding fraction in vertebrate rhodopsin was estimated to be less than or equal to 0.60. These findings are discussed in relationship to previous studies of hydrogen exchange behavior and to structural models for both proteins.

Downer, N.W.; Bruchman, T.J.; Hazzard, J.H.

1986-03-15

106

Precision Measurement of the Rydberg Constant by Laser Saturation Spectroscopy of the Balmer alpha Line in Hydrogen and Deuterium  

Microsoft Academic Search

We have determined a new Rydberg value, R?=109737.3143(10) cm-1, with an order of magnitude improvement in precision, by measuring the absolute wavelengths of resolved fine-structure components of the Balmer alpha line in hydrogen and deuterium, excited in a dc gas discharge. Doppler broadening was eliminated by saturation spectroscopy with a pulsed dye laser. An iodine-stabilized He-Ne laser was the wavelength

T. W. Hänsch; M. H. Nayfeh; S. A. Lee; S. M. Curry; I. S. Shahin

1974-01-01

107

Frequency measurement of the 2S-12D transitions in hydrogen and deuterium. New determination of the Rydberg constant  

Microsoft Academic Search

We have performed the first pure frequency measurement of the 2S-12D two-photon transitions in atomic hydrogen and deuterium. These frequencies are compared to two optical standards, the CO2 laser stabilized on the OsO4 molecule and the optical rubidium laser standard (LD\\/Rb) (namely a laser diode at 778 nm stabilized on the 5S1\\/2-5D5\\/2 two-photon transition of rubidium). We have built a

C. Schwob; L. Jozefowski; O. Acef; L. Hilico; B. de Beauvoir; F. Nez; L. Julien; A. Clairon; F. Biraben

1998-01-01

108

Optical Frequency Measurement of the 2S-12D Transitions in Hydrogen and Deuterium: Rydberg Constant and Lamb Shift Determinations  

Microsoft Academic Search

We have performed a pure optical frequency measurement of the 2S-12D two-photon transitions in atomic hydrogen and deuterium. From a complete analysis taking into account this result and all other precise measurements (by ourselves and other authors), we deduce optimized values for the Rydberg constant, R? = 109 737.315 685 16\\\\(84\\\\) cm-1 (relative uncertainty of 7.7×10-12) and for the 1S

C. Schwob; L. Jozefowski; B. de Beauvoir; L. Hilico; F. Nez; L. Julien; F. Biraben; O. Acef; A. Clairon

1999-01-01

109

Frequency measurement of the 2S-12D transitions in hydrogen and deuterium, new determination of the Rydberg constant  

Microsoft Academic Search

We have performed the first pure frequency measurement of the 2S-12D two-photon transitions in atomic hydrogen and deuterium. These frequencies are compared to two optical standards, the CO2 laser stabilized on the OsO4 molecule and the optical rubidium laser standard (LD\\/Rb) (namely, a laser diode at 778 nm stabilized on the 5S1\\/2-5D5\\/2 two-photon transition of rubidium). The main part of

C. Schwob; L. Jozefowski; O. Acef; L. Hilico; B. de Beauvoir; F. Nez; L. Julien; A. Clairon; F. Biraben

1999-01-01

110

Global budget of molecular hydrogen and its deuterium content: Constraints from ground station, cruise, and aircraft observations  

Microsoft Academic Search

The distribution and atmospheric budgets for molecular hydrogen and its deuterium component ?D are simulated with the GEOS-Chem global chemical transport model and constrained by observations of H2 from the NOAA Climate Monitoring and Diagnostics Laboratory network and ?D observations from ship and ground stations. Our simulation includes a primary H2 source of 38.8 Tg a?1 (22.7 Tg a?1 from

Heather Price; Lyatt Jaeglé; Andrew Rice; Paul Quay; Paul C. Novelli; Richard Gammon

2007-01-01

111

Global budget of molecular hydrogen and its deuterium content: Constraints from ground station, cruise, and aircraft observations  

Microsoft Academic Search

The distribution and atmospheric budgets for molecular hydrogen and its deuterium component deltaD are simulated with the GEOS-Chem global chemical transport model and constrained by observations of H2 from the NOAA Climate Monitoring and Diagnostics Laboratory network and deltaD observations from ship and ground stations. Our simulation includes a primary H2 source of 38.8 Tg a-1 (22.7 Tg a-1 from

Heather Price; Lyatt Jaeglé; Andrew Rice; Paul Quay; Paul C. Novelli; Richard Gammon

2007-01-01

112

Defining the Interacting Regions between Apomyoglobin and Lipid Membrane by Hydrogen\\/Deuterium Exchange Coupled to Mass Spectrometry  

Microsoft Academic Search

Sperm whale myoglobin can be considered as the model protein of the globin family. The pH-dependence of the interactions of apomyoglobin with lipid bilayers shares some similarities with the behavior of pore-forming domains of bacterial toxins belonging also to the globin family. Two different states of apomyoglobin bound to a lipid bilayer have been characterized by using hydrogen\\/deuterium exchange experiments

Petr Man; Caroline Montagner; Grégory Vernier; Bernard Dublet; Alexandre Chenal; Eric Forest; Vincent Forge

2007-01-01

113

Temperature and site dependence of the rate of hydrogen and deuterium abstraction by methyl radicals in methanol glasses  

SciTech Connect

Rate constants are reported for hydrogen and deuterium abstraction by methyl radicals in CH/sub 3/OH and CD/sub 3/OD glasses in the ranges 5-89 and 77-97 K, respectively. At each temperature, they show a distribution due to a variation of radical trapping sites. The rate constants of this distribution are analyzed theoretically to yield a quantitative relation between tunneling rate and equilibrium tunneling distance. 20 references, 2 figures.

Doba, T.; Ingold, K.U.; Siebrand, W.; Wildman, T.A.

1984-07-19

114

Microscopic self dynamics in liquid hydrogen and in its mixtures with deuterium and neon: a neutron scattering study  

Microsoft Academic Search

No Heading By means of inelastic neutron scattering measurements, we have extracted the incoherent scattering function of liquid para-hydrogen, pure and mixed with deuterium or neon, in various thermodynamic conditions. The low-energy parts of the neutron spectra recorded in forward scattering on TOSCA-II were analyzed in the framework of the Gaussian approximation and filled through a Levesque-Vertet model for the

M. Celli; D. Colognesi; M. Zoppi; A. J. Ramirez-Cuesta

2005-01-01

115

Fourier transform ion cyclotron resonance investigation of the deuterium isotope effect on gas phase ion\\/molecule hydrogen bonding interactions in alcohol--fluoride adduct ions  

Microsoft Academic Search

Fourier transform ion cyclotron resonance measurements of the deuterium isotope effect have been used to probe the nature of the potential describing the motion of the hydrogen in gas phase ion\\/molecule hydrogen bond interactions. The hydrogen bonding system studied is fluoride ion solvated by one molecule of aliphatic alcohol, ROH · F-. No variation of the isotope effect with alcohol

F. E. Wilkinson; J. E. Szulejko; C. E. Allison; T. B. McMahon

1992-01-01

116

Nanoengineered Carbon Scaffolds for Hydrogen Storage  

Microsoft Academic Search

Single-walled carbon nanotube (SWCNT) fibers were engineered to become a scaffold for the storage of hydrogen. Carbon nanotube fibers were swollen in oleum (fuming sulfuric acid), and organic spacer groups were covalently linked between the nanotubes using diazonium functionalization chemistry to provide 3-dimensional (3-D) frameworks for the adsorption of hydrogen molecules. These 3-D nanoengineered fibers physisorb twice as much hydrogen

Ashley D. Leonard; Jared L. Hudson; Hua Fan; Richard Booker; Lin J. Simpson; K. J. ONeill; Philip A. Parilla; Michael J. Heben; Matteo Pasquali; Carter Kittrell; James M. Tour

2009-01-01

117

Hydrogen/deuterium exchange of mass-selected peptide ions with ND3 in a tandem sector mass spectrometer  

NASA Astrophysics Data System (ADS)

Hydrogen/deuterium exchange of mass-selected protonated peptide ions with ND3 is investigated in a four sector tandem mass spectrometer equipped with a high-pressure collision cell. The dependence of H/D exchange on the pressure of ND3, on collision energy and on proton affinities (PAs) of the peptides is examined. For leucine enkephalin, a peptide without strongly basic residues, the maximum number of H/D exchanges observed can correspond to the maximum number of active hydrogen atoms in the ions. In peptides with basic residues such as arginine, the H/D exchange proceeds more slowly and more selectively. H/D exchange is observed for renin substrate whose PA is estimated to be higher than ND3 by more than 50 kcal mol-. The pattern of H/D exchange of leucine enkephalin shows discrepancy with the number of hydrogen atoms in the peptide ion expected to undergo fast H/D exchange, thus indicating possible conformational effects. When protonated leucine enkephalin is reacted with ND3 under predominantly single-collision conditions, the incorporation of deuterium into fragment ions is found to vary, depending on the type of fragment ion. This differential incorporation of deuterium may be informative about the nature of the processes leading to the formation of fragment ions.

Cheng, Xueheng; Fenselau, Catherine

1992-12-01

118

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.

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

2011-01-01

119

Cooperative alpha-helix unfolding in a protein-DNA complex from hydrogen-deuterium exchange.  

PubMed

We present experimental evidence for a cooperative unfolding transition of an alpha-helix in the lac repressor headpiece bound to a symmetric variant of the lac operator, as inferred from hydrogen-deuterium (H-D) exchange experiments monitored by NMR spectroscopy. In the EX1 limit, observed exchange rates become pH-independent and exclusively sensitive to local structure fluctuations that expose the amide proton HN to exchange. Close to this regime, we measured decay rates of individual backbone HN signals in D2O, and of their mutual HN-HN NOE by time-resolved two-dimensional (2D) NMR experiments. The data revealed correlated exchange at the center of the lac headpiece recognition helix, Val20-Val23, and suggested that the correlation breaks down at Val24, at the C terminus of the helix. A lower degree of correlation was observed for the exchange of Val9 and Ala10 at the center of helix 1, while no correlation was observed for Val38 and Glu39 at the center of helix 3. We conclude that HN exchange in the recognition helix and, to some extent, in helix 1 is a cooperative event involving the unfolding of these helices, whereas the HN exchange in helix 3 is dominated by random local structure fluctuations. PMID:16751603

Salinas, Roberto K; Diercks, Tammo; Kaptein, Robert; Boelens, Rolf

2006-06-02

120

The Utility of Hydrogen/Deuterium Exchange Mass Spectrometry in Biopharmaceutical Comparability Studies  

PubMed Central

The function, efficacy, and safety of protein biopharmaceuticals are tied to their three-dimensional structure. The analysis and verification of this higher-order structure are critical in demonstrating manufacturing consistency and in establishing the absence of structural changes in response to changes in production. It is, therefore, essential to have reliable, high-resolution and high sensitivity biophysical tools capable of interrogating protein structure and conformation. Here, we demonstrate the use of hydrogen/deuterium exchange mass spectrometry (H/DX-MS) in biopharmaceutical comparability studies. H/DX-MS measurements can be conducted with good precision, consume only picomoles of protein, interrogate nearly the entire molecule with peptide level resolution, and can be completed in a few days. Structural comparability or lack of comparability was monitored for different preparations of interferon-?-1a. We present specific graphical formats for the display of H/DX-MS data that aid in rapidly making both the qualitative (visual) and quantitative assessment of comparability. H/DX-MS is capable of making significant contributions in biopharmaceutical characterization by providing more informative and confident comparability assessments of protein higher order structure than are currently available within the biopharmaceutical industry.

Houde, Damian; Berkowitz, Steven A.; Engen, John R.

2011-01-01

121

Pulsed hydrogen/deuterium exchange mass spectrometry for time-resolved membrane protein folding studies.  

PubMed

Kinetic folding experiments by pulsed hydrogen/deuterium exchange (HDX) mass spectrometry (MS) are a well-established tool for water-soluble proteins. To the best of our knowledge, the current study is the first that applies this approach to an integral membrane protein. The native state of bacteriorhodopsin (BR) comprises seven transmembrane helices and a covalently bound retinal cofactor. BR exposure to sodium dodecyl sulfate (SDS) induces partial unfolding and retinal loss. We employ a custom-built three-stage mixing device for pulsed-HDX/MS investigations of BR refolding. The reaction is triggered by mixing SDS-denatured protein with bicelles. After a variable folding time (10?ms to 24?h), the protein is exposed to excess D(2) O buffer under rapid exchange conditions. The HDX pulse is terminated by acid quenching after 24?ms. Subsequent off-line analysis is performed by size exclusion chromatography and electrospray MS. These measurements yield the number of protected backbone N-H sites as a function of folding time, reflecting the recovery of secondary structure. Our results indicate that much of the BR secondary structure is formed quite late during the reaction, on a time scale of 10?s and beyond. It is hoped that in the future it will be possible to extend the pulsed-HDX/MS approach employed here to membrane proteins other than BR. PMID:23280751

Khanal, Anil; Pan, Yan; Brown, Leonid S; Konermann, Lars

2012-12-01

122

Carbon-hydrogen bonding in near-frictionless carbon  

SciTech Connect

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

Johnson, Jackie A. [University of Tennessee Space Institute; Woodford, John B [Argonne National Laboratory (ANL); Rajput, Deepak [University of Tennessee Space Institute; Kolesnikov, Alexander I [ORNL; Schleuter, John A [Argonne National Laboratory (ANL); Eryilmaz, Osman L [Argonne National Laboratory (ANL); Erdemir, Ali [Argonne National Laboratory (ANL)

2008-01-01

123

Carbon-hydrogen bonding in near-frictionless carbon.  

SciTech Connect

The uniquely low friction behavior of near-frictionless carbon (NFC) as compared to conventional diamondlike carbon (DLC) is determined by the bonding within the film. Inelastic neutron scattering (INS) and Fourier transform infrared (FTIR) spectroscopy were used to probe the bonding environment of carbon and hydrogen; both INS and FTIR can probe the whole sample. Previous work has focused on surface studies; the present results show that in the film as a whole the majority of the hydrogen is adjacent to sp{sup 3}-bonded carbon. In addition this work has determined the absence of any molecular hydrogen in NFC.

Johnson, J. A.; Woodford, J. B.; Rajput, D.; Kolesnikov, A. I.; Schleuter, J. A.; Eryilmaz, O. L.; Erdemir, A.; Univ. of Tennessee Space Inst.; ORNL

2008-01-01

124

Hydrogen storage in engineered carbon nanospaces  

Microsoft Academic Search

It is shown how appropriately engineered nanoporous carbons provide materials for reversible hydrogen storage, based on physisorption, with exceptional storage capacities (~80 g H2\\/kg carbon, ~50 g H2\\/liter carbon, at 50 bar and 77 K). Nanopores generate high storage capacities (a) by having high surface area to volume ratios, and (b) by hosting deep potential wells through overlapping substrate potentials

Jacob Burress; Michael Kraus; Matt Beckner; Raina Cepel; Galen Suppes; Carlos Wexler; Peter Pfeifer

2009-01-01

125

Hydrogen/deuterium exchange-LC-MS approach to characterize the action of heparan sulfate C5-epimerase.  

PubMed

Heparan sulfate (HS) proteoglycans regulate a number of biological functions in many systems. Most of the functions of HS are attributed to its unique structure, consisting of sulfated and non-sulfated domains, arising from the differential presence of iduronyl and glucuronyl residues along the polysaccharide chain. A single glucuronyl C5-epimerase enzyme acts on HS precursors, converts glucuronyl residues into iduronyl residues, and modulates subsequent biosynthetic steps in vivo. Previously, the ratios of non-sulfated epimers within the polysaccharide chain have been calculated by resolving radiolabeled GlcA-(A)Man(R) and IdoA-(A)Man(R) disaccharides using a tedious paper chromatography technique. This radioactive assay, based on measuring either the release or incorporation of (3)H at C5 carbon of uronyl residues of (3)H-labeled HS precursor substrate, has been in use over three decades to characterize the action of HS C5-epimerase. We have developed a non-radioactive assay to estimate the epimerase activity through resolving GlcA-(A)Man(R) and IdoA-(A)Man(R) disaccharides on high-performance liquid chromatography in conjunction with hydrogen/deuterium exchange upon epimerization protocol-liquid chromatography mass spectrometry (DEEP-LC-MS). Utilizing this new, non-radioactive-based assay, DEEP-LC-MS, we were able to determine the extent of both forward and reverse reactions on the same substrate catalyzed by C5-epimerase. The results from this study also provide insights into the action of C5-epimerase and provide an opportunity to delineate snapshots of biosynthetic events that occur during the HSPG assembly in the Golgi. PMID:21573838

Babu, Ponnusamy; Victor, Xylophone V; Nelsen, Emily; Nguyen, Thao Kim Nu; Raman, Karthik; Kuberan, Balagurunathan

2011-05-15

126

Hydrogen/Deuterium Exchange-LC-MS Approach to Characterize the Action of Heparan Sulfate C5-Epimerase  

PubMed Central

Heparan sulfate (HS) proteoglycans regulate a number of biological functions in many systems. Most of the functions of HS are attributed to its unique structure, consisting of sulfated and non-sulfated domains, arising from the differential presence of iduronyl and glucuronyl residues along the polysaccharide chain. A single glucuronyl C5-epimerase enzyme acts on heparan sulfate precursor, converts glucuronyl residues into iduronyl residues and modulates subsequent biosynthetic steps in vivo. The ratios of non-sulfated epimers within the polysaccharide chain have been calculated by resolving radiolabeled GlcA-AManR and IdoA-AManR disaccharides using a tedious paper chromatography technique. Radioactive assay, based on measuring either the release or incorporation of 3H at C5 carbon of uronyl residues of 3H-labeled HS precursor substrate, has been in use over three decades to characterize the action of HS C5-epimerase. We have developed a non-radioactive assay to estimate the epimerase activity through resolving GlcA-AManR and IdoA-AManR disaccharides on HPLC in conjunction with hydrogen/deuterium exchange upon epimerization protocol-liquid chromatography mass spectrometry (DEEP-LC-MS). Utilizing this new, non-radioactive based assay, DEEP-LC-MS, we were able to determine the extent of both forward and reverse reaction on the same substrate catalyzed by C5-epimerase. Results from this study also provide insights into the action of C5-epimerase and provide an opportunity to delineate snapshots of biosynthetic events that occur during the HSPG assembly in the Golgi.

Babu, Ponnusamy; Victor, Xylophone V.; Nelsen, Emily; Nguyen, Thao Kim Nu; Raman, Karthik; Kuberan, Balagurunathan

2011-01-01

127

Equation of state of solid hydrogen and deuterium from single-crystal x-ray diffraction to 26. 5 GPa  

SciTech Connect

Pressure-volume equations of state of solid normal hydrogen and deuterium are determined from single-crystal x-ray diffraction measurements to maximum pressures of 26.5 GPa (265 kbar) at 300 K. Experimental data for deuterium are presented and used with the previously reported results for hydrogen. The measurements for deuterium indicate that the structure remains hexagonal closed packed to at least 14.2 GPa at 300 K. The {ital P}-{ital V} data are analyzed with both phenomenological equation-of-state formalisms and pair-potential models. The thermal contributions are calculated from a Mie-Gruneisen model and from lattice-dynamics calculations using effective potentials. A {ital P}-{ital V} equation of state is determined that accurately describes both the high-pressure diffraction data (to {ital V}/{ital V}{sub 0}=0.2) and previous low-pressure compression results ({ital V}/{ital V}{sub 0}=1.0 to 0.4). There is a significant softening of the equation of state relative to the predictions of lattice-dynamics calculations using previously reported pair potentials, and several effective potentials are examined. Possible corrections to the equation of state at higher pressures, above the range of the present experiments, include effects associated with order-disorder transitions, vibron softening, and band overlap.

Hemley, R.J.; Mao, H.K.; Finger, L.W.; Jephcoat, A.P.; Hazen, R.M.; Zha, C.S. (Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road, N.W., Washington, D.C. (USA))

1990-10-01

128

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

NASA Astrophysics Data System (ADS)

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

Ahmed, Arif; Kim, Sunghwan

2013-09-01

129

High-temperature diffusion of hydrogen and deuterium in titanium and Ti{sub 3}Al  

SciTech Connect

Diffusion coefficients (D{sub H} and D{sub D}) of hydrogen (H) and deuterium (D) in {beta}-titanium (Ti) and {beta}-Ti{sub 3}Al have been obtained from the rates of gaseous H and D absorption by samples in the temperature ranges of 1,173 to 1,473 K for {beta}-Ti and 1,423 to 1,523 K for {beta}-Ti{sub 3}Al. Activation energies for diffusion ({epsilon}{sub d}) are found to be 0.26 eV in {beta}-Ti and 0.39 eV in {beta}-Ti{sub 3}Al, which are smaller than those corresponding to {alpha}-Ti and {alpha}-Ti{sub 3}Al. Ratios D{sub D}/D{sub H} in {beta}-Ti and {beta}-Ti{sub 3}Al are found to be larger than the classical value, 1/{radical}2, and those in {alpha}-Ti and {alpha}-Ti{sub 3}Al. The observed smaller {epsilon}{sub d} in {beta}-Ti than in {alpha}-Ti is due to the difference between the body-centered cubic structure of {beta}-Ti and the hexagonal close-packed structure of {alpha}-Ti and the observed larger D{sub D}/D{sub H} in {beta}-Ti than in {alpha}-Ti due to phonon-assisted jumps of diffusing H atoms in {beta}-Ti. The observed distribution of aluminum atoms in it, and the larger D{sub D}/D{sub H} in {beta}-Ti{sub 3}Al than in {alpha}-Ti, {alpha}-Ti{sub 3}Al, and {beta}-Ti by the presence of aluminum atoms as well as by the phonon-assisted H-atom jumps.

Naito, Shizuo; Yamamoto, Masahiro [Kyoto Univ. (Japan). Inst. of Advance Energy; Doi, Minoru [Nagoya Inst. of Tech. (Japan). Dept. of Materials Science and Engineering; Kimura, Masao [Nippon Steel Corp., Kawasaki (Japan). Advanced Technology Research Labs.

1998-07-01

130

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

131

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

PubMed Central

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

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

2009-01-01

132

Hydrogen/deuterium exchange of hydrophobic peptides in model membranes by electrospray ionization mass spectrometry.  

PubMed

We demonstrate here that the hydrogen/deuterium solvent exchange (HDX) properties of the transmembrane fragment of the M2 protein of Influenza A (M2-TM) incorporated into lipid vesicles or detergent micelles can be studied with straightforward electrospray (ESI) and nanospray mass spectrometry (MS) configurations provided that key factors, including sample preparation techniques, are optimized. Small unilamellar vesicle preparations were obtained by solubilizing dimyristoyl phosphatidylcholine (DMPC) and the M2-TM peptide in aqueous solution with n-octyl-beta-D-glycopyranoside, followed by dialysis to remove the detergent. Electron microscopy experiments revealed that subsequent concentration by centrifugation introduced large multilamellar aggregates that were not compatible with ESI-MS. By contrast, a lyophilization-based concentration procedure, followed by thawing above the liquid crystal transition temperature of the lipid component, maintained the liposome size profile and yielded excellent ion fluxes in both ESI-MS and nano-ESI-MS. Using these methods the global HDX profile of M2-TM in aqueous DMPC vesicles was compared with that in methanol, demonstrating that several amide sites were protected from exchange by the lipid membrane. We also show that hydrophobic peptides can be detected by ESI-MS in the presence of a large molar excess of the detergent Triton X-100. The rate of HDX of M2-TM in Triton X-100 micelles was faster than that in DMPC vesicles but slower than when the peptide had been denatured in methanol. These results indicate that the accessibility of backbone amide sites to the solvent can be profoundly affected by membrane protein structure and dynamics, as well as the properties of model bilayer systems. PMID:12484457

Hansen, Raino K; Broadhurst, R William; Skelton, Paul C; Arkin, Isaiah T

2002-12-01

133

Carbon-hydrogen bonding in near-frictionless carbon  

Microsoft Academic Search

The uniquely low friction behavior of near-frictionless carbon (NFC) as compared to conventional diamondlike carbon (DLC) is determined by the bonding within the film. Inelastic neutron scattering (INS) and Fourier transform infrared (FTIR) spectroscopy were used to probe the bonding environment of carbon and hydrogen; both INS and FTIR can probe the whole sample. Previous work has focused on surface

Jackie A. Johnson; John B Woodford; Deepak Rajput; Alexander I Kolesnikov; John A Schleuter; Osman L Eryilmaz; Ali Erdemir

2008-01-01

134

Nanoengineered Carbon Scaffolds for Hydrogen Storage  

SciTech Connect

Single-walled carbon nanotube (SWCNT) fibers were engineered to become a scaffold for the storage of hydrogen. Carbon nanotube fibers were swollen in oleum (fuming sulfuric acid), and organic spacer groups were covalently linked between the nanotubes using diazonium functionalization chemistry to provide 3-dimensional (3-D) frameworks for the adsorption of hydrogen molecules. These 3-D nanoengineered fibers physisorb twice as much hydrogen per unit surface area as do typical macroporous carbon materials. These fiber-based systems can have high density, and combined with the outstanding thermal conductivity of carbon nanotubes, this points a way toward solving the volumetric and heat-transfer constraints that limit some other hydrogen-storage supports.

Leonard, A. D.; Hudson, J. L.; Fan, H.; Booker, R.; Simpson, L. J.; O'Neill, K. J.; Parilla, P. A.; Heben, M. J.; Pasquali, M.; Kittrell, C.; Tour, J. M.

2009-01-01

135

CARBON NANOTUBE MATERIALS FOR HYDROGEN STORAGE  

Microsoft Academic Search

Carbon single-wall nanotubes (SWNTs) are essentially elongated pores of molecular dimensions and are capable of adsorbing hydrogen at relatively high temperatures and low pressures. This behavior is unique to these materials and indicates that SWNTs are the ideal building block for constructing safe, efficient, and high energy density adsorbents for hydrogen storage applications. In past work we developed methods for

A. C. Dillon; T. Gennett; J. L. Alleman; K. M. Jones; P. A. Parilla

136

Photobiological hydrogen production and carbon dioxide sequestration  

Microsoft Academic Search

Photobiological hydrogen production is an alternative to thermochemical and electrolytic technologies with the advantage of carbon dioxide sequestration. However, it suffers from low solar to hydrogen energy conversion efficiency due to limited light transfer, mass transfer, and nutrient medium composition. The present study aims at addressing these limitations and can be divided in three parts: (1) experimental measurements of the

Halil Berberoglu

2008-01-01

137

A Membrane Cell for On-line Hydrogen/Deuterium Exchange to Study Protein Folding and Protein-Protein Interactions by Mass Spectrometry*  

PubMed Central

A membrane cell for hydrogen and deuterium exchange on-line with mass spectrometry has been developed to monitor protein-protein interactions and protein conformations. It consists of two channels separated by a semipermeable membrane, where one channel carries the protein sample and the other deuterium oxide. The membrane allows transfer of deuterium oxide into the sample flow. The labeling time is controlled via the flow rate in the sample channel. This cell was validated against three models commonly used in hydrogen-deuterium exchange mass spectrometry: monitoring of folded and unfolded states in a protein, mapping the protein secondary structure at the peptide level, and detection of protein and antibody interactions. The system avoids the conventionally used sample dilution and handling, allowing for potential automation.

Astorga-Wells, Juan; Landreh, Michael; Johansson, Jan; Bergman, Tomas; Jornvall, Hans

2011-01-01

138

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

USGS Publications Warehouse

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

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

1981-01-01

139

Variability of Deuterium Fractionation Associated With Soil Uptake of Atmospheric Molecular Hydrogen  

NASA Astrophysics Data System (ADS)

Molecular hydrogen (H2) is the second most abundant reduced gas in the atmosphere (after methane) with a globally averaged mixing ratio of ~530 nmol/mol. Its largest sources are photochemical oxidation of methane and non-methane hydrocarbons with other recognized sources that include biomass burning, fossil fuel burning, nitrogen fixation, and ocean degassing. These sources are balanced by reaction of H2 with hydroxyl radicals (~25%) in the atmosphere and by deposition at the terrestrial soil surface (~75%). As with other atmospheric trace gases, the stable isotopic content of H2 has the potential to help quantify the various aspects of its production and destruction. The average deuterium content of H2 is dDH2 = ~130 ‰ relative to Standard Mean Ocean Water. While recent studies have begun to elucidate the deuterium content of the individual sources of H2 and the fractionation associated with hydroxyl oxidation has been well established in the laboratory, there are still few data documenting the fractionation associated with soil uptake. We measured the fractionation associated with soil uptake in May, June and August of 2002 in three upland ecosystems that were part of an Alaskan fire chronosequence. Fire occurred at these sites in 1999, 1987, and ~1920. Grasses and herbaceous vegetation establish initially after fire and are gradually replaced by deciduous trees and finally by evergreen trees and moss. All three sites were in interior Alaska near the town of Delta Junction (63° 54'N, 145° 40'W). Fluxes were measured with a Plexiglas flux chamber (8 liter volume) with a manifold of four ~400 ml double-valved glass flasks in parallel and a diaphragm pump for circulation (5 SLPM). Flasks were continuously flushed by the circulating system and isolated sequentially; they were then returned to the laboratory at Caltech for subsequent analysis. In the field, the chamber was seated on Plexiglas collars that were installed prior to initiating the study and left in place for the duration of the study. Permanent collars insured that placement of the chamber/collar system did not cause any localized disturbance and unintentionally perturb the H2 flux and that sampling locations could be reoccupied to investigate seasonal differences. Prior to field deployment the entire system was tested on a plain sheet of Plexiglas to ensure that no H2 was produced or consumed by the diaphragm pump or any of the system parts. While earlier studies have measured HD/HH deposition velocities with a ratio of ~0.96, results of our Alaskan study show deposition velocity ratios of 0.89 ± 0.03 (n=17). Furthermore, sorting of data by season reveals no significant variability in this ratio but sorting by location over all seasons reveals the greatest fractionation at the most recent burn, 0.87 ± 0.02 (n=8) and the least fractionation at the mature spruce forest, 0.93 ± 0.01 (n=3) with fractionation at the intermediate burn site being 0.90 ± 0.02 (n=6). While not statistically conclusive, our results suggest that soil/ecosystem variability may affect fractionation associated with soil uptake of H2, adding further complication to modeling efforts that until now have assumed this parameter to be a constant value.

Rahn, T.; Randerson, J. T.; Eiler, J.

2005-12-01

140

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

Microsoft Academic Search

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 SiO2 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.

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

1998-01-01

141

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); Julien, L.; Biraben, F. [Laboratoire Kastler Brossel, Universite Pierre et Marie Curie, 75230 Paris Cedex 05 (France)

1995-10-01

142

Conformational analysis of dynorphin A (1-13) using hydrogen-deuterium exchange and tandem mass spectrometry.  

PubMed

Trifluoroethanol (TFE)-induced conformational changes in dynorphin A (1-13) were investigated using charge-state distribution (CSD) and hydrogen-deuterium exchange (HDX), combined with electrospray ionization (ESI) mass spectrometry (MS). Individual amino acids involved in secondary structural elements were identified by collision-induced dissociation-tandem mass spectrometry (MS/MS). It was observed that dynorphin A (1-13) largely exists in an unfolded conformation and a folded structure in increasing concentrations of TFE. In 50% TFE, it forms an alpha-helix that encompasses residues 1-9 and remains flexible from residues 10 to 13. PMID:18417761

Cai, Xianmei; Dass, Chhabil

2007-01-01

143

Carbon-Hydrogen Bond Strengths in Methane  

Microsoft Academic Search

Earlier formulas for the electron-pair bonding energies of methane, and radicals derivable from methane, are combined with recent data on the energy levels of the carbon atom, the heat of sublimation of carbon, the energy for removal of the first hydrogen, and the dissociation energy of CH to obtain the energies of CH3 and CH2. A consistent set of values

H. H. Voge

1948-01-01

144

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

145

Displacement and helium-induced enhancement of hydrogen and deuterium retention in ion-irradiated 18Cr10NiTi stainless steel  

NASA Astrophysics Data System (ADS)

There is strong interest in the accelerator-driven transmutation technology community on the synergistic effects of displacement damage and co-generated helium and hydrogen on property changes such as void swelling, irradiation creep, hardening, and possibly on corrosion and cracking. Substituting deuterium for protium offers advantages in experimental studies of the helium hydrogen-damage synergisms. The influence of preimplanted helium and self-ion induced damage on deuterium trapping in 18Cr10NiTi stainless steel was studied using thermal desorption spectrometry, the nuclear reactions 3He(D, p)4He and D(3He, p)4He, and transmission electron microcopy. Reemission, retention and evolution of depth distribution profiles of deuterium in 18Cr10NiTi SS were studied for 10 keV D2+ and 10 keV He+ implantation at room temperature followed by annealing at 300 1500 K. The amounts of trapped and released deuterium and helium atoms were measured as a function of implantation dose at various temperatures. It was found that retention of hydrogen and deuterium is strongly enhanced by the presence of large amounts of helium and also strongly enhanced by damage introduced by 2 MeV Cr3+ ions. These results are consistent with recent observations of hydrogen storage in stainless steels after irradiation in LANSCE with high energy protons and neutrons and also after irradiation in light water reactors.

Tolstolutskaya, G. D.; Ruzhytskiy, V. V.; Kopanets, I. E.; Karpov, S. A.; Bryk, V. V.; Voyevodin, V. N.; Garner, F. A.

2006-09-01

146

Deuterium isotope effects on gas phase ion-molecule hydrogen-bonding interactions: Alcohol-alkoxide and alcohol-chloride adduct ions  

Microsoft Academic Search

Fourier Transform Ion Cyclotron Resonance (FT-ICR) and High Pressure Mass Spectrometric (HPMS) measurements of the deuterium isotope effect and kinetics of adduct ion formation have been used to probe the nature of the potential describing the motion of the hydrogen in gas phase ion-molecule hydrogen-bonding interactions. Hydrogen-bonding systems reported in this paper are alkoxide ion and chloride ion solvated by

F. E. Wilkinson; M. Peschke; J. E. Szulejko; T. B. McMahon

1998-01-01

147

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

148

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

SciTech Connect

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

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

1980-09-01

149

Hydrogen uptake by carbon nanotubes  

Microsoft Academic Search

Multi-wall carbon nanotubes were synthesised from the catalytic decomposition of CO and CH4 on powder Co\\/La2O3 catalysts. TEM and HR-TEM, XRD, and TGA were used to characterise carbon nanotubes. It was found that by adjusting the composition of the catalysts, the size of the nanotubes was controllable and by annealing, the crystallinity could be improved. The carbon nanotubes produced from

X. B. Wu; P. Chen; J. Lin; K. L. Tan

2000-01-01

150

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

151

Hydrogen adsorption on modified activated carbon  

Microsoft Academic Search

The aim of this work is to investigate hydrogen adsorption on prepared super activated carbon (AC). Litchi trunk was activated by potassium hydroxide under N2 or CO2 atmosphere. Nanoparticles of palladium were impregnated in the prepared-AC. Hydrogen adsorption was accurately measured by a volumetric adsorption apparatus at 77, 87, 90 and 303K, up to 5MPa. Experimental results revealed that specific

Chen-Chia Huang; Hsiu-Mei Chen; Chien-Hung Chen

2010-01-01

152

Isotopic multiplets in the carbon-13 NMR spectra of aniline derivatives and nucleosides with partially deuterated amino groups: effects of intra- and intermolecular hydrogen bonding  

SciTech Connect

In aniline derivatives, the carbon-13 resonances of atoms bearing partially deuterated amino groups, as well as the resonances of vicinal carbon atoms, appear as multiplets. This phenomenon, which is due to upfield deuterium isotope effects on carbon-13 chemical shifts, is observed under conditions of slow hydrogen exchange (e.g., in Me/sub 2/SO solutions). The effects are larger for groups engaged in intramolecular hydrogen bonds. Empirical expressions are presented that relate isotope effects with amino proton chemical shifts and hydrogen bond energies. Isotopic multiplets are also observed in the carbon-13 NMR spectra of partially deuterated nucleosides. The multiplet structure is altered upon formation of base pairs. These results are interpreted in terms of hydrogen exchange reactions involving uridine (or thymidine) hydrogen-bonded dimers or changes in hydrogen bond energies upon formation of guanosine-cytidine complexes. Estimates are given for the energies of individual hydrogen bonds in Watson-Crick base pairs.

Reuben, J.

1987-01-21

153

Method for direct production of carbon disulfide and hydrogen from hydrocarbons and hydrogen sulfide feedstock  

DOEpatents

A method for converting hydrocarbons and hydrogen sulfide to carbon disulfide and hydrogen is provided comprising contacting the hydrocarbons and hydrogen sulfide to a bi-functional catalyst residing in a controlled atmosphere for a time and at a temperature sufficient to produce carbon disulfide and hydrogen. Also provided is a catalyst for converting carbon sulfides and hydrogen sulfides to gasoline range hydrocarbons comprising a mixture containing a zeolite catalyst and a hydrogenating catalyst.

Miao, Frank Q.; Erekson, Erek James

1998-12-01

154

Mechanism of hydrogen spillover and its role in deuterium exchange on PtY zeolite  

SciTech Connect

The exchange of the surface hydroxyl groups of HNaY zeolite with D/sub 2/ takes place in the presence of platinum much faster than in the absence of platinum. To cause this effect, it is sufficient to arrange the platinum at a distance of a few millimeters from the HNaY zeolite. The transport of the activated deuterium to the OH groups of the HNaY zeolite, i.e., its spillover, does not occur through the gas phase but on the surface of whatever solid is situated between the platinum and the HNaY zeolite. The transport of the activated deuterium takes place on oxide materials at the same rate, independent of their chemical nature, but it occurs only very slowly on the surface of stainless steel. It is proposed that the mechanism of spillover probably involves the participation of lattice oxygen of the solid surface.

Dmitriev, R.V. (Inst. of Organic Chemistry, Moscow); Steinberg, K.H.; Detjuk, A.N.; Hofmann, F.; Bremer, H.; Minachev, Kh.M.

1980-09-01

155

Physisorption of Hydrogen on Microporous Carbon and Carbon Nanotubes  

Microsoft Academic Search

A safe, effective, and cheap storage system is crucial for the future utilization of hydrogen as a pollution-free energy carrier. Besides the established techniques (liquid hydrogen, compressed gas), the storage in a solid-state matrix (e.g., metal hydride) has the advantage of being safe, but fails for most materials with respect to the total weight of the tank system. Therefore carbon

M. Rzepka; P. Lamp; M. A. de la Casa-Lillo

1998-01-01

156

Simulation of hydrogen adsorption in carbon nanotubes  

NASA Astrophysics Data System (ADS)

Computer simulations are reported of hydrogen adsorption in multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs). The gas-solid interaction was modelled both as pure dispersion forces and also with a hypothetical model for chemisorption introduced in a previous paper (CRACKNELL, R., F., 2001, Phys. Chem. chem. Phys. , 3 , 2091). A two-centre model for hydrogen was employed and the grand canonical Monte Carlo methodology was used throughout. Uptake of hydrogen in the internal space of a carbon nanotube is predicted to be lower than in the optimal graphitic nanofibre with slitlike pores (provided the gas-solid potential is consistent). Part of the difference arises from the assumption of pore surface area used in converting the raw simulation data to gravimetric adsorption; however, the majority of the differences can be attributed to the curvature of the pore. This reduces the uptake of hydrogen (on a gravimetric basis) in spite of deepening the potential minimum inside the pore associated with dispersion forces. It is concluded that for the uptake of hydrogen in SWNTs of 5-10% reported by Heben (DILLON, A. C., JONES, K. M., BEKKEDAHL, T. A., KIANG, C. H., BETHUNE, D. S., AND HEBEN, M. J., 1997, Nature , 386 , 377), gas-solid forces other than dispersion forces are required and most of the adsorption must occur in the interstices between SWNTs.

Cracknell, Roger F.

157

Pharmacokinetic and deuterium isotope effect studies on the metabolism of formaldehyde and formate to carbon dioxide in rats in vivo  

SciTech Connect

The effect of deuterium substitution on the metabolism of formaldehyde and formate to carbon dioxide in vivo was examined. Four groups of male Sprague-Dawley rats were injected ip with carbon-14-labeled formaldehyde, formaldehyde-d2, sodium formate, or sodium formate-d at doses of 0.67 mmol/kg. Similar rates of labeled carbon dioxide exhalation were observed for the four groups of animals, the cumulative excretion of /sup 14/CO/sub 2/ in breath reaching 68-71% of the theoretical value 12 hr after injection in all cases. Plots of amount remaining to be excreted showed that the metabolism was biexponential, with half-lives of approximately 0.4 and 3 hr for the two phases for each of the four compounds. Competitive experiments in which equimolar mixtures of CH/sub 2/O with CD/sub 2/O or HCO/sub 2/- with DCO/sub 2/- were injected also failed to reveal a substantial isotope effect, although the cumulative conversion of formate to carbon dioxide was significantly higher than that of its deuterated analog at four time points in the middle of the 8-hr mixed-isotope experiment. The data indicate that deuterium substitution has little or no effect on the rates and extents of in vivo oxidation of these 1-carbon species to carbon dioxide, although a small decrease of up to 10% in reactivity under the conditions employed cannot be excluded. The results support the use of carbon dioxide exhalation data in the measurement of deuterium isotope effects on oxidative demethylation reactions such as those that occur in the activation of the carcinogen, N-nitrosodimethylamine.

Keefer, L.K.; Streeter, A.J.; Leung, L.Y.; Perry, W.C.; Hu, H.S.; Baillie, T.A.

1987-05-01

158

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.

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

2009-01-01

159

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.

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

2009-01-01

160

Deuterium content of water vapour and hydrogen in volcanic gas at Surtsey, Iceland  

Microsoft Academic Search

The D \\/ H ratio has been measured in the water vapour and hydrogen gas emerging from the oceanic volcano Surtsey. The measurements have given D = -55.3%. relative to SMOW in total hydrogen contained in the volcanic gases.

Bragi Árnason; Thorbjörn Sigurgeirsson

1968-01-01

161

Usefulness of the hydrogen–deuterium exchange method in the study of drug metabolism using liquid chromatography-tandem mass spectrometry  

Microsoft Academic Search

The usefulness of the hydrogen–deuterium (H-D) exchange method in the study of drug metabolism was investigated. Metabolite samples of denopamine and promethazine prepared in vitro were introduced to a triple stage quadrupole tandem mass spectrometer via a high performance liquid chromatography (HPLC) system using a deuterated mobile phase. Mass spectra by various ionization modes and collisionally induced dissociation (CID) mass

Noriko Ohashi; Satoshi Furuuchi; Masayoshi Yoshikawa

1998-01-01

162

Laser spectroscopy of the 1 S -2 S transition in hydrogen and deuterium: Determination of the 1 S Lamb shift and the Rydberg constant  

Microsoft Academic Search

We have observed the narrow 1{ital S}-2{ital S} transition in hydrogen and deuterium with high resolution using Doppler-free two-photon absorption of continuous-wave 243-nm light. The transition frequencies were measured by direct comparison with accurately calibrated lines in the spectrum of the ¹³°Teâ molecule. We find the 1{ital S}-2{ital S} interval to be 2 466 061 414.1(8) MHz in hydrogen and

M. G. Boshier; P. E. G. Baird; C. J. Foot; E. A. Hinds; M. D. Plimmer; D. N. Stacey; J. B. Swan; D. A. Tate; D. M. Warrington; G. K. Woodgate

1989-01-01

163

Laser spectroscopy of the 1S-2S transition in hydrogen and deuterium: Determination of the 1S Lamb shift and the Rydberg constant  

Microsoft Academic Search

We have observed the narrow 1S-2S transition in hydrogen and deuterium with high resolution using Doppler-free two-photon absorption of continuous-wave 243-nm light. The transition frequencies were measured by direct comparison with accurately calibrated lines in the spectrum of the 130Te2 molecule. We find the 1S-2S interval to be 2 466 061 414.1(8) MHz in hydrogen and 2 466 732 408.5(7)

M. G. Boshier; P. E. G. Baird; C. J. Foot; E. A. Hinds; M. D. Plimmer; D. N. Stacey; J. B. Swan; D. A. Tate; D. M. Warrington; G. K. Woodgate

1989-01-01

164

Hydrogen atom vs electron transfer in catecholase-mimetic oxidations by superoxometal complexes. Deuterium kinetic isotope effects.  

PubMed

Dioximato-cobalt(II), -iron(II) and -manganese(II) complexes (1)-(6), acting as functional catecholase and phenoxazinone synthase models, exhibit a deuterium kinetic isotope effect predicted by theory (k4H/k4D < or = 3) in the catalytic oxidative dehydrogenation of 3,5-di-tert-butylcatechol and 2-aminophenol by O2. KIEs in the range of (k4H/k4D approximately 1.79-3.51) are observed with (1) and (2) as catalysts, pointing to hydrogen atom transfer in the rate-determining step from the substrate hydroxy group to the metal-bound superoxo ligand. Less significant KIEs (1.06-1.20) are exhibited by catalysts systems (3)-(6), indicating that proton-coupled electron transfer is the preferred route in those cases. PMID:15616728

Simándi, Tatiana M; May, Zoltán; Szigyártó, Imola Cs; Simándi, László I

2004-12-06

165

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

166

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

PubMed

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

Resetca, Diana; Wilson, Derek J

2013-06-11

167

Deuterium retention in the carbon co-deposition layers deposited by magnetron sputtering in D2/He atmosphere  

NASA Astrophysics Data System (ADS)

Carbon was deposited on Si and W substrates using a D2/He plasma in a radio frequency magnetron sputtering system. The deposited layers were examined with ion beam analysis (IBA), Raman spectra analysis (RS) and scanning electron microscopy (SEM). The growth rate of the layers deposited at 2.5 Pa total pressure and 300 K decreased with increasing He fraction in the D2/He gas mixture. The deuterium concentration in the layers deposited on the Si substrate increased from 14% to 28% when the flow rate of the He gas relative to the D2 gas was varied from 0.125 to 0.5, but the deuterium concentration in the layers on a W substrate decreased from 24% to 14%. Deuterium or helium retention and the layer thickness all significantly decreased when the substrate temperature was increased from 423 K to 773 K. Raman analysis showed that the deposited layers were amorphous deuterated-carbon layers (named a-C: D layer) and the extent of bond disorder increased dramatically with the increasing helium content in the film. Blisters and bubbles occurred in the films for high helium content in the films, and surface cracking and exfoliation were also observed.

Tang, X. H.; Shi, L. Q.; Qi, Q.; Zhang, B.; Zhang, W. Y.; Hu, J. S.; O'Connor, D. J.; King, B.

2013-05-01

168

The reactions of carbon in a hydrogen plasma  

SciTech Connect

Acetylene can be directly produced by coal pyrolysis in hydrogen plasma. A key factor affecting acetylene yield is whether the residue solid carbon is able to react with hydrogen to form acetylene after volatile matters released from coal powders pyrolyzed in hydrogen plasma. Reactions of carbon in hydrogen plasma are studied in this article. The study showed that solid carbon could hardly react with hydrogen at temperatures below the sublimation point, while sublimated carbon could easily react with hydrogen at temperatures above sublimation point, and mainly acetylene and other hydrocarbons can be obtained after quenching process.

Li, M.; Fan, Y.; Bao, W.; Guan, Y.; Li, S. [Tsing Hua University, Beijing (China)

2006-07-01

169

Gas-phase hydrogen\\/deuterium exchange of 5?- and 3?-mononucleotides in a quadrupole ion trap: Exploring the role of conformation and system energy  

Microsoft Academic Search

Gas-phase hydrogen\\/deuterium (H\\/D) exchange reactions for deprotonated 2?-deoxy-5?-monophosphate and 2?-deoxy-3?-monophosphate\\u000a nucleotides with D2O were performed in a quadrupole ion trap mass spectrometer. To augment these experiments, molecular modeling was also conducted\\u000a to identify likely deprotonation sites and potential gas-phase conformations of the anions. A majority of the 5?-monophosphates\\u000a exchanged extensively with several of the compounds completely incorporating deuterium in place

Joseph E. Chipuk; Jennifer S. Brodbelt

2007-01-01

170

NEW INVESTIGATIONS ON THE PRESENCE OF NEGATIVE DEUTERIUM IONS IN HYDROGEN  

Microsoft Academic Search

The energy absorption of negative hydrogen ions produced in the Faraday ; region at the interior of a tube crossed by a continuous current is studied. The ; frequencies studied are between 400 and 1940 cm. It is shown experimentally that ; there are characteristic frequencies of negative hydrogen ions. These ; frequencies are shown either by the energy absorption

T. Ionescu; V. P. Mihu

1952-01-01

171

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

172

Effects of collisions on Raman line profiles of hydrogen and deuterium gas  

Microsoft Academic Search

Vibrational Raman lines of hydrogen gas show very small collision broadening. As a result the collision narrowing of the Doppler profile which occurs when the mean-free path of a radiating molecule becomes comparable to the wavelength of the radiation is very easily observed in hydrogen. This paper presents measurements of the narrowing effect and of collision broadening and shift of

J. R. Murray; A. Javan

1972-01-01

173

Carbon-deuterium vibrational probes of peptide conformation: Alanine dipeptide and glycine dipeptide  

NASA Astrophysics Data System (ADS)

The utility of ?-carbon deuterium-labeled bonds (C?-D) as infrared reporters of local peptide conformation was investigated for two model dipeptide compounds: C?-D labeled alanine dipeptide (Adp-d1) and C?-D2 labeled glycine dipeptide (Gdp-d2). These model compounds adopt structures that are analogous to the motifs found in larger peptides and proteins. For both Adp-d1 and Gdp-d2, we systematically mapped the entire conformational landscape in the gas phase by optimizing the geometry of the molecule with the values of ? and ?, the two dihedral angles that are typically used to characterize the backbone structure of peptides and proteins, held fixed on a uniform grid with 7.5° spacing. Since the conformations were not generally stationary states in the gas phase, we then calculated anharmonic C?-D and C?-D2 stretch transition frequencies for each structure. For Adp-d1 the C?-D stretch frequency exhibited a maximum variability of 39.4 cm-1 between the six stable structures identified in the gas phase. The C?-D2 frequencies of Gdp-d2 show an even more substantial difference between its three stable conformations: there is a 40.7 cm-1 maximum difference in the symmetric C?-D2 stretch frequencies and an 81.3 cm-1 maximum difference in the asymmetric C?-D2 stretch frequencies. Moreover, the splitting between the symmetric and asymmetric C?-D2 stretch frequencies of Gdp-d2 is remarkably sensitive to its conformation.

Miller, C. S.; Ploetz, E. A.; Cremeens, M. E.; Corcelli, S. A.

2009-03-01

174

Enhanced hydrogen adsorption in ordered mesoporous carbon through clathrate formation  

Microsoft Academic Search

Ordered mesoporous carbons were synthesized with a soft-template approach and modified with a water and tetrahydrofuran mixture having a H2O\\/THF molar ratio of 17:1 as potential adsorbent media for hydrogen storage. Hydrogen adsorption equilibrium on the carbon adsorbents was measured gravimetrically at 270K and hydrogen pressures up to 163bar. Enhanced hydrogen adsorption was observed on the carbon adsorbents doped with

Dipendu Saha; Shuguang Deng

2009-01-01

175

Catalytic carbon membranes for hydrogen production  

SciTech Connect

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

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

1992-01-01

176

Hydrogen storage in engineered carbon nanospaces  

NASA Astrophysics Data System (ADS)

It is shown how appropriately engineered nanoporous carbons provide materials for reversible hydrogen storage, based on physisorption, with exceptional storage capacities (~80 g H2/kg carbon, ~50 g H2/liter carbon, at 50 bar and 77 K). Nanopores generate high storage capacities (a) by having high surface area to volume ratios, and (b) by hosting deep potential wells through overlapping substrate potentials from opposite pore walls, giving rise to a binding energy nearly twice the binding energy in wide pores. Experimental case studies are presented with surface areas as high as 3100 m2 g-1, in which 40% of all surface sites reside in pores of width ~0.7 nm and binding energy ~9 kJ mol-1, and 60% of sites in pores of width>1.0 nm and binding energy ~5 kJ mol-1. The findings, including the prevalence of just two distinct binding energies, are in excellent agreement with results from molecular dynamics simulations. It is also shown, from statistical mechanical models, that one can experimentally distinguish between the situation in which molecules do (mobile adsorption) and do not (localized adsorption) move parallel to the surface, how such lateral dynamics affects the hydrogen storage capacity, and how the two situations are controlled by the vibrational frequencies of adsorbed hydrogen molecules parallel and perpendicular to the surface: in the samples presented, adsorption is mobile at 293 K, and localized at 77 K. These findings make a strong case for it being possible to significantly increase hydrogen storage capacities in nanoporous carbons by suitable engineering of the nanopore space.

Burress, Jacob; Kraus, Michael; Beckner, Matt; Cepel, Raina; Suppes, Galen; Wexler, Carlos; Pfeifer, Peter

2009-05-01

177

Cryogenic ultra-high vacuum scanning tunneling microscopy of electron-stimulated desorption of hydrogen and deuterium from silicon  

NASA Astrophysics Data System (ADS)

A cryogenic ultra-high vacuum (UHV) scanning tunneling microscope (STM) has been developed. This design utilizes a novel vibration isolation scheme which provides excellent thermal coupling to a cooling source. The cooling scheme departs from other cryogenic UHV STMs where vibration isolation and cooling compete with each other. Variable temperature operation from 11 K to 300 K has been demonstrated. Future improvements will enable operation down to 1.5 K. This system has been used to perform low temperature desorption studies of hydrogen and deuterium from Si(100) surfaces. Comparing these results to previous room temperature studies indicates that there is no temperature dependence to the desorption in the high voltage field emission regime. However, in the low voltage vibrational heating regime a strong temperature dependence is observed, with the desorption yield for hydrogen at 11 K being 300 times greater than at 300 K. In the context of Avouris' vibrational heating model, these data are consistent with an increase in the Si-H vibrational lifetime from 10 ns at 300 K to 19 ns at 11 K. By similar analysis, the Si-D vibrational lifetime increases from 0.25 ns at 300 K to 0.85 ns at 11 K.

Foley, Edward Thomas

1997-12-01

178

Reactions of saturated hydrocarbons with hydrogen and deuterium on epitaxially oriented (111) Pd and Pd-Au alloy films  

SciTech Connect

The reactions of neopentane, n-butane, propane, and n-pentane in the presence of an excess of hydrogen have been studied on evaporated Pd/Au-on-mica films. The characterization of films showed that they were predominantly (111) oriented. The selectivity in hydrogenolysis of all hydrocarbons decreased markedly with an increase in the content in Au. The catalytic activity for isomerization of neopentane and n-butane was higher for ca. 10 at. % Au alloys than for pure Pd. This finding appears to support the mechanism involving 1,2-bond shift isomerization at one metal site proposed by McKervey et al. Additional experiments with CH/sub 4//D/sub 2/ and neopentane/D/sub 2/ exchange over Pd-Au(111) alloys at higher temperatures showed considerable difficulties in forming carbene adspecies which could be responsible for another isomerization route. The isotopic exchange between cyclopentane and deuterium over (111) oriented Pd-Au alloys showed that the rate of multiple exchange goes through a gentle maximum for ca. 10 at. % Au. At the same time no special catalytic role of the surface sites of a low coordination number is seen. It is speculated that the rollover process may involve similar intermediate species as in alkene hydrogenation. The relative importance of ensemble size vs electronic effects in the Pd-Au alloys for various reactions is discussed.

Karpinski, Z.

1982-09-01

179

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

180

Hydrogen-Deuterium Changeover Experiments in a Plasma-Wall Interaction Simulator.  

National Technical Information Service (NTIS)

Hydrogen recycling from walls and limiters of tokamaks constitutes the major source of plasma particles after the initial few milliseconds of a plasma pulse. The physical processes involved in recycling are thus very important to the control of plasma den...

R. E. Clausing L. Heatherly L. C. Emerson

1981-01-01

181

Photobiological hydrogen production and carbon dioxide sequestration  

NASA Astrophysics Data System (ADS)

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

Berberoglu, Halil

182

Functionalized carbon nanostructures for hydrogen catalysis  

NASA Astrophysics Data System (ADS)

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

Hu, Lung-Hao

183

FeTiMn alloy granulate in a pressure container for storage of hydrogen and deuterium  

Microsoft Academic Search

Oxygen is incorporated into an FeTiMn granulate in an amount sufficient to form double oxides of titanium and manganese therein, but insufficient to form oxides containing iron. As the result, the granules are embrittled, favoring the formation of microcracks to such an extent that activation of the granules by hydrogen takes place, after initial evacuation, at room temperature, after which

K. Klatt; H. Wenzl

1982-01-01

184

Absolute Frequency Measurement of the 2S-8S\\/D Transitions in Hydrogen and Deuterium: New Determination of the Rydberg Constant  

Microsoft Academic Search

We have performed a pure optical frequency measurement of the 2S-8S\\/D two-photon transitions in atomic hydrogen and deuterium. These frequencies are directly compared to a new frequency standard, a diode laser stabilized to a two-photon transition at 778 nm in rubidium. We deduce a new value for the Rydberg constant, R? = 109 737.315 685 9\\\\(10\\\\) cm-1 with an uncertainty

B. de Beauvoir; F. Nez; L. Julien; B. Cagnac; F. Biraben; D. Touahri; L. Hilico; O. Acef; A. Clairon; J. J. Zondy

1997-01-01

185

Gas phase hydrogen deuterium exchange reactions of a model peptide: FT-ICR and computational analyses of metal induced conformational mutations  

Microsoft Academic Search

We utilized gas phase hydrogen\\/deuterium (H\\/D) exchange reactions and ab initio calculations to investigate the complexation\\u000a between a model peptide (Arg-Gly-Asp?RGD) with various alkali metal ions. The peptide conformation is drastically altered\\u000a upon alkali metal ion complexation. The associated conformational changes depend on both the number and type of complexing\\u000a alkali metal ions. Sodium has a smaller ionic diameter and

T. Solouki; R. C. Fort; A. Alomary; A. Fattahi

2001-01-01

186

Characterization of Low-Salt and High-Salt Conformation of Poly(dI-dC) by Hydrogen-Deuterium Exchange Kinetics: A Classical Raman Spectroscopy Study  

Microsoft Academic Search

Poly(dI-dC) in H2O and D2O solution can undergo different equilibrium geometries which strongly depend on the salt nature and concentration. These structures were studied by classical Raman spectroscopy in order to monitor a hydrogen-deuterium exchange kinetics in 8- CH group in inosine. Spectral and isotopic exchange rate changes depending on NaCl concentration were observed and interpreted on the basis of

G. Fabriciova; P. Miskovsky; D. Jancura; V. Lisy

1998-01-01

187

The Roles of Subsurface Carbon and Hydrogen in Palladium-Catalyzed Alkyne Hydrogenation  

Microsoft Academic Search

Alkynes can be selectively hydrogenated into alkenes on solid palladium catalysts. This process requires a strong modification of the near-surface region of palladium, in which carbon (from fragmented feed molecules) occupies interstitial lattice sites. In situ x-ray photoelectron spectroscopic measurements under reaction conditions indicated that much less carbon was dissolved in palladium during unselective, total hydrogenation. Additional studies of hydrogen

Detre Teschner; János Borsodi; Attila Wootsch; Zsolt Révay; Michael Hävecker; Axel Knop-Gericke; S. David Jackson; Robert Schlögl

2008-01-01

188

Evidence for site-specific intra-ionic hydrogen/deuterium exchange in the low-energy collision-induced dissociation product ion spectra of protonated small molecules generated by electrospray ionisation.  

PubMed

The experimental investigation of site-specific intra-ionic hydrogen/deuterium (H/D) exchange in the low-energy collision-induced dissociation (CID) product ion spectra of protonated small molecules generated by electrospray ionisation (ESI) is presented. The observation of intra-ionic H/D exchange in such ions under low-energy CID conditions has hitherto been rarely reported. The data suggest that the intra-ionic H/D exchange takes place in a site-specific manner between the ionising deuteron, localised at either a tertiary amine or a tertiary amine-N-oxide, and a gamma-hydrogen relative to the nitrogen atom. Nuclear magnetic resonance (NMR) spectroscopy measurements showed that no H/D exchange takes place in solution, indicating that the reaction occurs in the gas phase. The compounds analysed in this study suggested that electron-withdrawing groups bonded to the carbon atom bearing the gamma-hydrogen can preclude exchange. The effect of the electron-withdrawing group appears dependent upon its electronegativity, with lower chi value groups still allowing exchange to take place. However, the limited dataset available in this study prevented robust conclusions being drawn regarding the effect of the electron-withdrawing group. The observation of site-specific intra-ionic H/D exchange has application in the area of structural elucidation, where it could be used to introduce an isotopic label into the carbon skeleton of a molecule containing specific structural features. This could increase the throughput, and minimise the cost, of such studies due to the obviation of the need to produce a deuterium-labelled analogue by synthetic means. PMID:20069530

Holman, Stephen W; Wright, Patricia; Wells, Neil J; Langley, G John

2010-04-01

189

Defining the interacting regions between apomyoglobin and lipid membrane by hydrogen/deuterium exchange coupled to mass spectrometry.  

PubMed

Sperm whale myoglobin can be considered as the model protein of the globin family. The pH-dependence of the interactions of apomyoglobin with lipid bilayers shares some similarities with the behavior of pore-forming domains of bacterial toxins belonging also to the globin family. Two different states of apomyoglobin bound to a lipid bilayer have been characterized by using hydrogen/deuterium exchange experiments and mass spectrometry. When bound to the membrane at pH 5.5, apomyoglobin remains mostly native-like and interacts through alpha-helix A. At pH 4, the binding is related to the stabilization of a partially folded state. In that case, alpha-helices A and G are involved in the interaction. At this pH, alpha-helix G, which is the most hydrophobic region of apomyoglobin, is available for interaction with the lipid bilayer because of the loss of the tertiary structure. Our results show the feasibility of such experiments and their potential for the characterization of various membrane-bound states of amphitropic proteins such as pore-forming domains of bacterial toxins. This is not possible with other high-resolution methods, because these proteins are usually in partially folded states when interacting with membranes. PMID:17346745

Man, Petr; Montagner, Caroline; Vernier, Grégory; Dublet, Bernard; Chenal, Alexandre; Forest, Eric; Forge, Vincent

2007-02-13

190

A two-stage differential hydrogen deuterium exchange method for the rapid characterization of protein/ligand interactions.  

PubMed

The peroxisome proliferator-activated receptor is a member of the nuclear receptor superfamily of transcriptional regulators. Regulation of the nuclear receptors occurs through changes to the structure and dynamics of the ligand-binding domain. Therefore, the need has arisen for a rapid method capable of detecting changes in the dynamics of nuclear receptors following ligand binding. We recently described how solution-phase amide hydrogen/deuterium exchange (HDX) provides a biophysical technique for probing changes in protein dynamics induced by ligand interaction. Building from this platform, we have optimized the robustness of the differential HDX experiment by minimizing systematic errors, and have increased the efficiency of the chromatographic separation through the use of high-pressure liquid chromatography. Using knowledge gained previously from comprehensive HDX experiments of PPARgamma, a modest throughput method to probe changes in the dynamics of key regions of the receptor was developed. A collection of ten synthetic and endogenous PPARgamma ligands were characterized with this new method requiring approximately 24 h of analysis. This is a dramatic improvement over the 10 d of analysis that would have been required with our previous approach for comprehensive differential HDX analysis. In addition to demonstrating the utility of this approach, the study presented here is the first to measure changes to the dynamics of PPARgamma upon the binding of putative endogenous ligands. PMID:17916792

Chalmers, Michael J; Busby, Scott A; Pascal, Bruce D; Southern, Mark R; Griffin, Patrick R

2007-09-01

191

Polarized Fourier transform infrared spectroscopy of bacteriorhodopsin. Transmembrane alpha helices are resistant to hydrogen/deuterium exchange.  

PubMed Central

The secondary structure of bacteriorhodopsin has been investigated by polarized Fourier transform infrared spectroscopy combined with hydrogen/deuterium exchange, isotope labeling and resolution enhancement methods. Oriented films of purple membrane were measured at low temperature after exposure to H2O or D2O. Resolution enhancement techniques and isotopic labeling of the Schiff base were used to assign peaks in the amide I region of the spectrum. alpha-helical structure, which exhibits strong infrared dichroism, undergoes little H/D exchange, even after 48 h of D2O exposure. In contrast, non-alpha-helical structure, which exhibits little dichroism, undergoes rapid H/D exchange. A band at 1,640 cm-1, which has previously been assigned to beta-sheet structure, is found to be due in part to the C = N stretching vibration of protonated Schiff base of the retinylidene chromophore. We conclude that the membrane spanning regions of bR consist predominantly of alpha-helical structure whereas most beta-type structure is located in surface regions directly accessible to water.

Earnest, T N; Herzfeld, J; Rothschild, K J

1990-01-01

192

Ultra performance liquid chromatography (UPLC) further improves hydrogen\\/deuterium exchange mass spectrometry  

Microsoft Academic Search

Ultra performance liquid chromatography (UPLC) employs particles smaller than 2 µm in diameter to achieve superior resolution,\\u000a speed, and sensitivity compared with high-performance liquid chromatography (HPLC). We have tested the suitability of UPLC\\u000a for the analysis of deuterated peptides in hydrogen exchange mass spectrometry experiments. Superior resolution and sample\\u000a throughput were obtained with UPLC versus HPLC. For highly deuterated model

Yan Wu; John R. Engen; William B. Hobbins

2006-01-01

193

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

194

Histidine Hydrogen-Deuterium Exchange Mass Spectrometry for Probing the Microenvironment of Histidine Residues in Dihydrofolate Reductase  

PubMed Central

Background Histidine Hydrogen-Deuterium Exchange Mass Spectrometry (His-HDX-MS) determines the HDX rates at the imidazole C2-hydrogen of histidine residues. This method provides not only the HDX rates but also the pKa values of histidine imidazole rings. His-HDX-MS was used to probe the microenvironment of histidine residues of E. coli dihydrofolate reductase (DHFR), an enzyme proposed to undergo multiple conformational changes during catalysis. Methodology/Principal Findings Using His-HDX-MS, the pKa values and the half-lives (t1/2) of HDX reactions of five histidine residues of apo-DHFR, DHFR in complex with methotrexate (DHFR-MTX), DHFR in complex with MTX and NADPH (DHFR-MTX-NADPH), and DHFR in complex with folate and NADP+ (DHFR-folate-NADP+) were determined. The results showed that the two parameters (pKa and t1/2) are sensitive to the changes of the microenvironment around the histidine residues. Although four of the five histidine residues are located far from the active site, ligand binding affected their pKa, t1/2 or both. This is consistent with previous observations of ligand binding-induced distal conformational changes on DHFR. Most of the observed pKa and t1/2 changes could be rationalized using the X-ray structures of apo-DHFR, DHFR-MTX-NADPH, and DHFR-folate-NADP+. The availability of the neutron diffraction structure of DHFR-MTX enabled us to compare the protonation states of histidine imidazole rings. Conclusions/Significance Our results demonstrate the usefulness of His-HDX-MS in probing the microenvironments of histidine residues within proteins.

Ahmad, Md. Faiz; Gokulrangan, Giridharan; Tomechko, Sara E.; Bennett, Brad; Dealwis, Chris

2011-01-01

195

Structural Dynamics of Soluble Chloride Intracellular Channel Protein CLIC1 Examined by Amide Hydrogen-Deuterium Exchange Mass Spectrometry (DXMS)†  

PubMed Central

Chloride intracellular channel protein 1 (CLIC1) functions as an anion channel in plasma and nuclear membranes when its soluble monomeric form converts to an integral-membrane form. The transmembrane region of CLIC1 is located in its thioredoxin-like domain 1 but the mechanism whereby the protein converts to its membrane conformation has yet to be determined. Since channel formation in membranes is enhanced at low pH (5 to 5.5), a condition that is found at the surface of membranes, the structural dynamics of soluble CLIC1 was studied at pH 7 and at pH 5.5 in the absence of membranes by amide hydrogen-deuterium exchange mass spectrometry (DXMS). Rapid hydrogen exchange data indicate that CLIC1 displays a similar core structure at these pH values. Domain 1 is less stable than the all-helical domain 2 and, while the structure of domain 1 remains intact, its conformational flexibility is further increased in an acidic environment (pH 5.5). In the absence of membrane, an acidic environment appears to prime the solution structure of CLIC1 by destabilising domain 1 in order to lower the activation energy barrier for its conversion to the membrane-insertion conformation. The significantly enhanced H/D-exchange rates at pH 5.5 displayed by two segments (peptides 11-31 and 68-82) could be due to the protonation of acidic residues in salt bridges. One of these segments (peptide 11-31) includes part of the transmembrane region which, in the solution structure, consists of helix ?1. This helix is intrinsically stable and is most likely retained in the membrane conformation. Strand ?2, another element of the transmembrane region, displays a propensity to form a helical structure and has putative N- and C-capping motifs, suggesting that it too most likely forms a helix in a lipid bilayer.

Stoychev, Stoyan H.; Nathaniel, Christos; Fanucchi, Sylvia; Brock, Melissa; Li, Sheng; Asmus, Kyle; Woods, Virgil L.; Dirr, Heini W.

2009-01-01

196

Molecular hydrogen and spiltover hydrogen storage on high surface area carbon sorbents  

Microsoft Academic Search

A series of templated carbons with various high surface areas (2033–3798m2\\/g) have been prepared using various microporous zeolites as hard templates. Molecular hydrogen storage and spiltover hydrogen storage on these templated carbons were investigated and compared with superactivated carbon AX-21 and other reported porous carbon sorbents at 298K and 100atm. Two relationships between the surface areas of these carbons and

Lifeng Wang; Ralph T. Yang

197

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

198

Metrology of the hydrogen and deuterium atoms: Determination of the Rydberg constant and Lamb shifts  

Microsoft Academic Search

:   We present a detailed description of several experiments which have been previously reported in several letters: the determination\\u000a of the 1S Lamb shift in hydrogen by a comparison of the frequencies of the 1S-3S and 2S-6S or 2S-6D two-photon transitions,\\u000a and the measurement of the 2S-8S\\/D and 2S-12D optical frequencies. Following a complete study of the lineshape of the

B. de Beauvoir; C. Schwob; O. Acef; L. Jozefowski; L. Hilico; F. Nez; L. Julien; A. Clairon; F. Biraben

2000-01-01

199

Annealing amorphous carbon nanotubes for their application in hydrogen storage  

Microsoft Academic Search

Carbon nanotubes with poor crystallization degree were mass-produced by the floating catalyst method, and their crystallizing procedure at high annealing temperatures were investigated. The crystallization behavior is different from that of bulk amorphous carbons due to the finite dimensions and tube-like shape of the as-grown carbon nanotubes. Further hydrogen adsorption experiments showed that the as-grown carbon nanotubes have poor hydrogen

Lijie Ci; Hongwei Zhu; Bingqing Wei; Cailu Xu; Dehai Wu

2003-01-01

200

Hydrogen storage properties of Pd nanoparticle\\/carbon template composites  

Microsoft Academic Search

Theoretical studies predict improved hydrogenation properties for hybrid carbon\\/metal composites. The hydrogen storage capacity of ordered porous carbon containing Pd clusters was measured. The C\\/Pd composite was obtained by chemical impregnation of an ordered porous carbon template (CT) with a H2PdCl4 solution followed by a reduction treatment. 10wt.% of palladium clusters were introduced in the carbon porosity; the Pd clusters

R. Campesi; F. Cuevas; R. Gadiou; E. Leroy; M. Hirscher; C. Vix-Guterl; M. Latroche

2008-01-01

201

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

202

Pressure dependent deuterium fractionation in the formation of molecular hydrogen in formaldehyde photolysis  

NASA Astrophysics Data System (ADS)

The pressure dependence of the relative photolysis rates of HCHO and HCDO has been investigated using a new photochemical reactor at the University of Copenhagen. The relative photolysis rate of HCHO vs. HCDO under UVA lamp irradiation was measured at total pressures of 50, 200, 400, 600 and 1030 mbar. The relative dissociation rate kHCHO/kHCDO was found to depend strongly on pressure, varying from 1.1±0.1 at 50 mbar to 1.75±0.10 at 1030 mbar. The products of formaldehyde photodissociation are either H2+CO (molecular channel) or HCO+H (radical channel). The partitioning between the channels has been estimated using available values for the absorption cross section and quantum yield. As a result of the change in pressure with altitude the isotope effect for production of molecular hydrogen is found to change from a value of kH/kD=1.8±0.2 at the surface to unity at 50 km. The relative importance of the two product channels changes with altitude as a result of changes in both pressure and actinic flux. The study concludes that the ?D of photochemical hydrogen produced in situ will increase substantially with altitude.

Nilsson, E. J. K.; Andersen, V. F.; Skov, H.; Johnson, M. S.

2009-11-01

203

Deuterium Retention in Liquid Lithium  

NASA Astrophysics Data System (ADS)

Flowing liquid Li as a plasma-facing material in a tokamak offers potential advantages over solid materials. The high-thermal conductivity of Li allows heat loads to be effectively removed and erosion lifetime is no longer a significant concern as a flowing liquid surface is self-repairing. In addition to this, it has also been demonstrated that lithium surfaces are effective in providing low-recycling boundaries. Oxygen, carbon and hydrogen are readily gettered by lithium and it is expected that fuel control should also be possible though the retention of deuterium. However, it is not clear that Li, in its liquid state, offers the same low-recycling properties. As part of the liquid-metals research effort being undertaken at the UCSD, we are examining the practicality of fuel control through studies of the retention of deuterium in liquid Li. Samples of solid and liquid Li have been exposed to deuterium plasma in the UCSD PISCES B linear plasma facility and characterized using secondary-ion mass spectrometry (SIMS), x-ray-photoelectron spectroscopy (XPS) and thermal-desorption mass spectrometry (TDS). Results will be presented and discussed at the meeting.

Baldwin, M. J.; Doerner, R. P.; Luckhardt, S. C.; Conn, R. W.; Seraydarian, R.; Whyte, D. G.

2000-10-01

204

Thermodynamic and neutron scattering study of hydrogen adsorption in two mesoporous ordered carbons.  

PubMed

Two mesoporous ordered carbon materials (MOCs) have been synthesized from silica templates by using sucrose as the carbon precursor. The textural characterization using Ar, N2, and CO2 adsorption combined with neutron diffraction showed that the two samples exhibit a significant microporous volume close to 0.5 cm3/g and an ordered network of mesopores. For both MCM48 and SBA15 templated carbons, adsorption first proceeds with the filling of micropores and then by the filling of mesopores with an adsorption energy close to the enthalpy of vaporization of bulk hydrogen. The hydrogen isosteric heat of adsorption in the micropores (6-8 kJ/mol) is significantly larger than that on the graphite surface (approximately 4 kJ/mol) but still too small for a reasonable use of these MOCs as hydrogen adsorbents for storage at room temperature. The neutron scattering study showed that the structure at 10 K of the adsorbed deuterium phase is poorly organized; it exhibits short and medium range orders of about 13 angstroms in micropores and about 20 angstroms in mesopores, respectively. The average distance between adsorbed molecules decreases with coverage by about 10%. In the mesopores, the diffracted line is consistent with a pseudohexagonal packing. PMID:16649772

Roussel, T; Pellenq, R J-M; Bienfait, M; Vix-Guterl, C; Gadiou, R; Béguin, F; Johnson, M

2006-05-01

205

Dynamics of Cleft Closure of the GluA2 Ligand-binding Domain in the Presence of Full and Partial Agonists Revealed by Hydrogen-Deuterium Exchange.  

PubMed

The majority of excitatory neurotransmission in the CNS is mediated by tetrameric AMPA receptors. Channel activation begins with a series of interactions with an agonist that binds to the cleft between the two lobes of the ligand-binding domain of each subunit. Binding leads to a series of conformational transitions, including the closure of the two lobes of the binding domain around the ligand, culminating in ion channel opening. Although a great deal has been learned from crystal structures, determining the molecular details of channel activation, deactivation, and desensitization requires measures of dynamics and stabilities of hydrogen bonds that stabilize cleft closure. The use of hydrogen-deuterium exchange at low pH provides a measure of the variation of stability of specific hydrogen bonds among agonists of different efficacy. Here, we used NMR measurements of hydrogen-deuterium exchange to determine the stability of hydrogen bonds in the GluA2 (AMPA receptor) ligand-binding domain in the presence of several full and partial agonists. The results suggest that the stabilization of hydrogen bonds between the two lobes of the binding domain is weaker for partial than for full agonists, and efficacy is correlated with the stability of these hydrogen bonds. The closure of the lobes around the agonists leads to a destabilization of the hydrogen bonding in another portion of the lobe interface, and removing an electrostatic interaction in Lobe 2 can relieve the strain. These results provide new details of transitions in the binding domain that are associated with channel activation and desensitization. PMID:23940029

Ahmed, Ahmed H; Ptak, Christopher P; Fenwick, Michael K; Hsieh, Ching-Lin; Weiland, Gregory A; Oswald, Robert E

2013-08-12

206

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

2010-02-23

207

Review of hydrogen storage by adsorption in carbon nanotubes  

Microsoft Academic Search

This work deals with hydrogen adsorption in carbon nanotube materials over a wide range of pressure and temperature in order to establish the reliability of this phenomenon as a valuable storage technique of hydrogen. Our purpose is to give, discuss and compare the different results published comprising our works. Both experimental and simulation adsorption data concerning the hydrogen gas within

F. Lamari Darkrim; P. Malbrunot; G. P. Tartaglia

2002-01-01

208

Absolute Frequency Measurement of the 2{ital S}-8{ital S}/{ital D} Transitions in Hydrogen and Deuterium: New Determination of the Rydberg Constant  

SciTech Connect

We have performed a pure optical frequency measurement of the 2S-8S/D two-photon transitions in atomic hydrogen and deuterium. These frequencies are directly compared to a new frequency standard, a diode laser stabilized to a two-photon transition at 778nm in rubidium. We deduce a new value for the Rydberg constant, R{sub {infinity}}=109737.3156859(10)cm{sup -1} with an uncertainty of 9{times}10{sup -12}. From the isotope shift, we derive a precise value of the 2S Lamb shift in deuterium [L{sub 2S-2P}=1059.230(9)MHz] and the difference of the quadratic charge radii of deuteron and proton. {copyright} {ital 1997} {ital The American Physical Society}

de Beauvoir, B.; Nez, F.; Julien, L.; Cagnac, B.; Biraben, F. [Laboratoire Kastler Brossel, Ecole Normale Superieure Universite Pierre et Marie Curie, Laboratoire associe au CNRS URA18, 4 place Jussieu, Tour 12 E01, 75252 Paris Cedex 05 (France); Touahri, D.; Hilico, L.; Acef, O.; Clairon, A.; Zondy, J. [Laboratoire Primaire du Temps et des Frequences, Bureau National de Metrologie-Observatoire de Paris, 61 avenue de l`Observatoire, 75014 Paris (France)

1997-01-01

209

Dissecting the mechanism of Epac activation by hydrogen/deuterium exchange FT-IR and structural modeling*  

PubMed Central

Exchange proteins directly activated by cAMP (Epac) is a family of cAMP-binding domain containing proteins that play important roles in mediating the effects of cAMP through the activation of down-stream small GTPases, Ras-proximate proteins. To delineate the mechanism of Epac activation, we probed the conformation and structural dynamics of Epac using amide hydrogen/deuterium (H/D) exchange coupled with Fourier transform infrared spectroscopy (FT-IR) and structural modeling. Our studies show that unlike that of cAMP-dependent protein kinase (PKA), the classic intracellular cAMP receptor, binding of cAMP to Epac does not induce significant changes in overall secondary structure and structural dynamics, as measured by FT-IR and the rate of H/D exchange, respectively. These results suggest that Epac activation does not involve significant changes in the amount of exposed surface areas as in the case of PKA activation and conformational changes induced by cAMP in Epac are most likely confined to small local regions. Homology modeling and comparative structural analyses of the CBDs of Epac and PKA lead us to propose a model of Epac activation. Based on our model, Epac activation by cAMP employs the same underlying structural principal utilized by PKA although the detailed structural and conformational changes associated with Epac and PKA activation are significantly different. In addition, we predict that during Epac activation the first ? strand of the switchboard switches conformation to a ?-helix, which folds back to the ? barrel core of the CBD and interacts directly with cAMP to form the base of the cAMP-binding pocket.

Yu, Shaoning; Fan, Fenghui; Flores, Samuel C.; Mei, Fang; Cheng, Xiaodong

2008-01-01

210

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

2013-05-01

211

Dynamic motions of free and bound O29 scaffolding protein identified by hydrogen deuterium exchange mass spectrometry.  

PubMed

In the double-stranded DNA containing bacteriophages, hundreds of copies of capsid protein subunits polymerize to form icosahedral shells, called procapsids, into which the viral genome is subsequently packaged to form infectious virions. High assembly fidelity requires the assistance of scaffolding protein molecules, which interact with the capsid proteins to insure proper geometrical incorporation of subunits into the growing icosahedral lattices. The interactions between the scaffolding and capsid proteins are transient and are subsequently disrupted during DNA packaging. Removal of scaffolding protein is achieved either by proteolysis or alternatively by some form of conformational switch that allows it to dissociate from the capsid. To identify the switch controlling scaffolding protein association and release, hydrogen deuterium exchange was applied to Bacillus subtilis phage Ø29 scaffolding protein gp7 in both free and procapsid-bound forms. The H/D exchange experiments revealed highly dynamic and cooperative opening motions of scaffolding molecules in the N-terminal helix-loop-helix (H-L-H) region. The motions can be promoted by destabilizing the hydrophobic contact between two helices. At low temperature where high energy motions were damped, or in a mutant in which the helices were tethered through the introduction of a disulfide bond, this region displayed restricted cooperative opening motions as demonstrated by a switch in the exchange kinetics from correlated EX1 exchange to uncorrelated EX2 exchange. The cooperative opening rate was increased in the procapsid-bound form, suggesting this region might interact with the capsid protein. Its dynamic nature might play a role in the assembly and release mechanism. PMID:16522798

Fu, Chi-Yu; Prevelige, Peter E

2006-03-07

212

Optical and strucutral properties of hydrogen implanted silicon carbon alloys  

Microsoft Academic Search

The hydrogen effects on the optical and structural properties of amorphous silicon carbon alloys are investigated for different hydrogen concentration (0–20 at.%) and a fixed silicon to carbon concentration ratio (?Si?c = 1). Hydrogen was introduced into a preamorphized SiC sample by ion implantation of H ions with energies in the range 5–20 keV and fluences in the range 1017?5

G. Compagnini; L. Calcagno; G. Foti

1995-01-01

213

Adsorptive hydrogen storage in carbon and porous materials  

Microsoft Academic Search

The hydrogen adsorption and desorption isotherms of a highly pure single-walled carbon nanotube sample (SWCNT), a corresponding nitric acid-treated sample (A-SWCNT), two zeolites, and several kinds of activated carbon fibers (ACFs) were measured at 77 and 303K over the hydrogen pressure range 0–3.5MPa by using the high-pressure adsorption apparatus with sufficient accuracy. The amount of adsorbed hydrogen by weight depended

H. Takagi; H. Hatori; Y. Soneda; N. Yoshizawa; Y. Yamada

2004-01-01

214

Carbon-Deuterium Bonds as Non-perturbative Infrared Probes of Protein Dynamics, Electrostatics, Heterogeneity, and Folding.  

PubMed

Vibrational spectroscopy is uniquely able to characterize protein dynamics and microenvironmental heterogeneity because it possesses an inherently high temporal resolution and employs probes of ultimately high structural resolution-the bonds themselves. The use of carbon-deuterium (C-D) bonds as vibrational labels circumvents the spectral congestion that otherwise precludes the use of vibrational spectroscopy to proteins and makes the observation of single vibrations within a protein possible while being wholly non-perturbative. Thus, C-D probes can be used to site-specifically characterize conformational heterogeneity and thermodynamic stability. C-D probes are also uniquely useful in characterizing the electrostatic microenvironment experienced by a specific residue side chain or backbone due to its effect on the C-D absorption frequency. In this chapter we describe the experimental procedures required to use C-D bonds and FT IR spectroscopy to characterize protein dynamics, structural and electrostatic heterogeneity, ligand binding, and folding. PMID:24061918

Zimmermann, Jörg; Romesberg, Floyd E

2014-01-01

215

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

216

Hydrogen storage in nickel catalysts supported on activated carbon  

Microsoft Academic Search

We have studied hydrogen storage in a commercial activated carbon impregnated with nickel. High-pressure (20–30bars) hydrogen uptake at room temperature was assessed using a high-pressure volumetric adsorption–desorption system. The properties of the prepared materials were studied by means of N2 physisorption, X-ray diffraction, transmission electron microscopy, metal surface area, hydrogen temperature programmed reduction and hydrogen temperature programmed desorption. Various factors

M. Zieli?ski; R. Wojcieszak; S. Monteverdi; M. Mercy; M. M. Bettahar

2007-01-01

217

The influence of textural properties on the hydrogen adsorption on ordered mesoporous carbons and activated carbons  

Microsoft Academic Search

Microporosity is one of the key parameters which influences the physisorption of hydrogen on carbon materials. Ordered mesoporous carbons (OMC) which are synthetized by templating procedures have numerous interresting properties such as a large microporous volume, and a three dimensional mesoporous network. The aim of this study was to determine the hydrogen adsorption capacity for ordered mesoporous carbons and for

A. Didion; R. Gadiou; T. Piquero; P. David; C. Vix-Guterl

218

Experimental investigations of electron capture from atomic hydrogen and deuterium by alpha particles. Annual progress report, 15 September 1991--14 September 1992  

SciTech Connect

We report progress made during the period 15 September 1991--14 September 1992 on the project ``Experimental Investigations of Electron Capture from Atomic Hydrogen and Deuterium by Alpha Particles``. In the past year we have developed reliable, narrow energy spread, high-current sources of He{sup ++} based on direct-current magentron and electron-cyclotron resonance discharges. These sources have been proven on our test bench accelerator which has been upgraded to also allow us to test atomic hydrogen effusive targets. We have thus made substantial progress toward our goal of studying single electron capture from atomic hydrogen by doubly-ionized helium. A research plan for the upcoming year is also presented.

Gay, T.J.; Park, J.T.

1992-11-01

219

Small-angle neutron scattering measurements of hydrogen and deuterium trapping at dislocations in deformed single-crystalline Pd at low temperature  

NASA Astrophysics Data System (ADS)

Small-angle neutron scattering (SANS) measurements of hydrogen and deuterium trapped at dislocation defects in deformed single-crystalline Pd have been performed at 15, 100, and 200 K at total interstitial solute concentrations of order 10-3. This work supports recent incoherent inelastic neutron scattering measurements of the vibrational density of states of trapped hydrogen under similar concentration-temperature conditions [Heuser , Phys. Rev. BPLRBAQ1098-012110.1103/PhysRevB.78.214101 78, 214101 (2008)]. The measured net absolute macroscopic differential scattering cross sections have been fitted with a cylindrical form factor representing solute-decorated dislocation line segments. Generally, very little difference in the measured cross sections was observed with temperature for a given solute type, while a significant change was observed between hydrogen- and deuterium-loaded samples. The latter difference is understood within a cross-section model that takes into account the local lattice dilatation associated with solute segregation at dislocations. The application of the model cross section to the net PdH0.0013 SANS response yields an effective trapping radius of R ˜ 10 Å and dislocation density of ?d~1010 cm-2. Analysis of the SANS response allowed the local trapped solute concentration (˜0.5 [H]/[Pd]) and volumetric dilatation (??/? ˜ 1.1) to be determined with the constraint that the system locally satisfies the known lattice expansion of Pd hydride (i.e., Vegard's law).

Heuser, Brent J.; Ju, Hyunsu

2011-03-01

220

Small-angle neutron scattering measurements of hydrogen and deuterium trapping at dislocations in deformed single-crystalline Pd at low temperature  

SciTech Connect

Small-angle neutron scattering (SANS) measurements of hydrogen and deuterium trapped at dislocation defects in deformed single-crystalline Pd have been performed at 15, 100, and 200 K at total interstitial solute concentrations of order 10 3. This work supports recent incoherent inelastic neutron scattering measurements of the vibrational density of states of trapped hydrogen under similar concentration-temperature conditions [Heuser et al., Phys. Rev. B 78, 214101 (2008)]. The measured net absolute macroscopic differential scattering cross sections have been fitted with a cylindrical form factor representing solute-decorated dislocation line segments. Generally, very little difference in the measured cross sections was observed with temperature for a given solute type, while a significant change was observed between hydrogen- and deuterium-loaded samples. The latter difference is understood within a cross-section model that takes into account the local lattice dilatation associated with solute segregation at dislocations. The application of the model cross section to the net PdH0.0013 SANS response yields an effective trapping radius of R 10 A and dislocation density of d 1010 cm 2. Analysis of the SANS response allowed the local trapped solute concentration ( 0.5 [H]/[Pd]) and volumetric dilatation (/ 1.1) to be determined with the constraint that the system locally satisfies the known lattice expansion of Pd hydride (i.e., Vegard s law).

Heuser, Brent J. [University of Illinois, Urbana-Champaign; JU, H. S. [University of Illinois, Urbana-Champaign

2011-01-01

221

Separation and identification of structural isomers by quadrupole collision-induced dissociation-hydrogen\\/deuterium exchange-infrared multiphoton dissociation (QCID-HDX-IRMPD)  

Microsoft Academic Search

A new approach that uses a hybrid Q-FTICR instrument and combines quadrupole collision-induced dissociation, hydrogen-deuterium\\u000a exchange, and infrared multiphoton dissociation (QCID-HDX-IRMPD) has been shown to effectively separate and differentiate\\u000a isomeric fragment ion structures present at the same m\\/z. This method was used to study protonated YAGFL-OH (free acid), YAGFL-NH2 (amide), cyclic YAGFL, and YAGFL-OCH3 (methyl ester). QCID-HDX of m\\/z 552.28

Ashley C. Gucinski; Árpád Somogyi; Julia Chamot-Rooke; Vicki H. Wysocki

2010-01-01

222

Absolute Frequency Measurement of the 2{ital S}-8{ital S}\\/{ital D} Transitions in Hydrogen and Deuterium: New Determination of the Rydberg Constant  

Microsoft Academic Search

We have performed a pure optical frequency measurement of the 2S-8S\\/D two-photon transitions in atomic hydrogen and deuterium. These frequencies are directly compared to a new frequency standard, a diode laser stabilized to a two-photon transition at 778nm in rubidium. We deduce a new value for the Rydberg constant, R{sub â}=109737.3156859(10)cm⁻¹ with an uncertainty of 9Ã10⁻¹². From the isotope shift,

B. de Beauvoir; F. Nez; L. Julien; B. Cagnac; F. Biraben; D. Touahri; L. Hilico; O. Acef; A. Clairon; J. Zondy

1997-01-01

223

Gas-phase noncovalent interactions between vancomycin-group antibiotics and bacterial cell-wall precursor peptides probed by hydrogen\\/deuterium exchange  

Microsoft Academic Search

Gas-phase structures of noncovalent complexes between the glycopeptide antibiotics vancomycin, eremomycin, ristocetin, and\\u000a pseudo aglyco-ristocetin and the cell-wall mimicking peptides N-acetyl-D-Alanyl-D-Alanine, N-acetyl-Glycyl-D-Alanine, and\\u000a N,N?-di-acetyl L-Lysyl-D-Alanyl-D-Alanine have been probed by hydrogen\\/deuterium (H\\/D) exchange using ND3 as reagent gas. The noncovalent complexes were transferred from solution to the vacuum using electrospray ionization. The\\u000a H\\/D exchange of the solvent-free ions was studied in

Albert J. R. Heck; Thomas J. D. Jørgensen; Mary O’Sullivan; Markus von Raumer; Peter J. Derrick

1998-01-01

224

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

225

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

PubMed

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 (13)C in groundwater pollutants in aquifers. It is also suggested that deuterium shifts are expected to be higher, especially for strongly sorbing pollutants. PMID:22055158

Höhener, Patrick; Yu, Xianjing

2011-09-29

226

Single riser fluidized catalytic cracking process utilizing hydrogen and carbon-hydrogen contributing fragments  

Microsoft Academic Search

A riser catalytic cracking process is described which comprises (a) generating at least one of hydrogen species and carbon-hydrogen fragments by cracking in the base of the riser a hydrogen-rich hydrocarbon feed containing 12 to 25 weight-percent hydrogen, in the presence of a mixture of cracking catalysts of comprising (1) at least one member of the group selected from amorphous

J. A. Herbst; H. Owen; P. H. Schipper

1989-01-01

227

Preparation and characterization of highly porous carbons for hydrogen storage.  

PubMed

In this work, Porous Carbons (PCs) were prepared by using a chemical acid treatment, and the hydrogen storage behaviors of PCs doped by Pt nanoparticles were investigated. The hydrogen storage capacities of the Pt-doped carbons with a platinum content of 0.2-1.5 wt% were evaluated by a volumetric adsorption method at 298 K and 10 MPa. The microstructures of samples were examined by XRD and SEM. It was found that the hydrogen storage capacities of the PCs dramatically increased, but the amount of hydrogen stored from the samples began to decrease after 0.6 wt% of Pt content due to the pore blocking. These results indicate that a suitable amount of supported catalysts and layer intervals of carbons had a very important impact on hydrogen storage behaviors. PMID:21446562

Kim, Byung-Joo; An, Kay Hyeok; Park, Soo-Jin

2011-01-01

228

Measurements of Hydrogen Spillover in Platinum-Doped Superactivated Carbon  

NASA Astrophysics Data System (ADS)

Hydrogen uptake was measured of platinum doped superactivated carbon at 296 K where hydrogen spillover was expected to occur. High pressure adsorption measurements using a Sieverts apparatus did not show an increase in gravimetric storage capacity over the unmodified superactivated carbon. Measurements of small samples (0.2 g) over long equilibration times, consistent with reported procedure, showed significant scatter and were not well above instrument background. In larger samples (3.2 g) the hydrogen uptake was significantly above background but did not show enhancement due to spillover; total uptake scaled with the available surface area of the superactivated carbon. Any hydrogen spillover sorption was thus below the detection limit of standard volumetric gas adsorption measurements. Due to the additional mass of the catalyst nanoparticles and decreased surface area in the platinum doped system, the net effect of spillover sorption is detrimental for gravimetric density of hydrogen.

Stadie, Nicholas; Ahn, Channing; Fultz, Brent

2010-03-01

229

Pt NANOCLUSTERS ON CARBON NANOMATERIALS FOR HYDROGEN FUEL CELLS  

Microsoft Academic Search

The detailed study of carbon nanomaterials constitution with allowance for of reduction conversions Pt (II, IV) allows to\\u000a realize directional looking up of methods of preparation of platinum catalysts for redox reactions in hydrogen fuel cells.

N. S. KUYUNKO; S. D. KUSHCH; V. E. MURADYAN; A. A. VOLODIN; V. I. TORBOV; B. P. TARASOV

230

Investigation of the role of the micro-porous layer in polymer electrolyte fuel cells with hydrogen deuterium contrast neutron radiography.  

PubMed

In this study, the high resolution hydrogen-deuterium contrast radiography method was applied to elucidate the impact of the micro-porous layer (MPL) on water distribution in the porous fuel cell media. At the steady state, deuterium replaced hydrogen in the anode stream, and the large difference in neutron attenuation of the D(2)O produced at the cathode was used to track the produced water. It was found that the water content peaked in the cathode-side diffusion media (DM) for the cell without MPL, but with an MPL on the anode and cathode DM, the peak water amount was pushed toward the anode, resulting in a relatively flattened water profile through components and demonstrating a liquid barrier effect. Additionally, the dynamic water behavior in diffusion media was analyzed to understand the effect of a MPL and operating conditions. The water content in the DM changed with applied current, although there is a significant amount of residual liquid content that does not appear to be part of capillary channels. The effect of the MPL on irreducible saturation in DM and cell performance was also investigated. PMID:22337210

Cho, Kyu Taek; Mench, Matthew M

2012-02-15

231

Modification of single wall carbon nanotubes (SWNT) for hydrogen storage  

Microsoft Academic Search

Due to unique structural, mechanical and electrical properties of single wall carbon nanotubes, SWNTs, they have been proposed as promising hydrogen storage materials especially in automotive industries. This research deals with investing of CNT’s and some activated carbons hydrogen storage capacity. The CNT’s were prepared through natural gas decomposition at a temperature of 900?C over cobalt-molybdenum nanoparticles supported by nanoporous magnesium

A. M. Rashidi; A. Nouralishahi; A. A. Khodadadi; Y. Mortazavi; A. Karimi; K. Kashefi

2010-01-01

232

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

233

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

SciTech Connect

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

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

2001-04-01

234

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

235

Material Processing with Hydrogen and Carbon Monoxide on MARS.  

National Technical Information Service (NTIS)

Several novel proposals are examined for propellant production from carbon dioxide and monoxide and hydrogen. Potential uses were also examined of CO as a fuel or as a reducing agent in metal oxide processing as obtained or further reduced to carbon. Hydr...

A. F. Hepp G. A. Landis D. L. Linne

1991-01-01

236

Electron spin resonance of carbon nanotubes under hydrogen adsorption  

Microsoft Academic Search

Carbon nanotubes provided by different manufacturers and synthesized by a variety of methods were subjected to the same oxidative purification procedure. Electron spin resonance (ESR) was used to investigate changes in the electronic structure before and after purification and exposure to hydrogen gas at a pressure of 136 kPa. The ESR signal in single-wall carbon nanotubes was due to paramagnetic

K. Shen; D. L. Tierney; T. Pietraß

2003-01-01

237

Hydrogenated amorphous silicon carbon alloys for solar cells  

Microsoft Academic Search

Hydrogenated amorphous silicon carbon films were grown by PECVD from silane\\/methane gas mixtures by fixing the methane ratio in the gas phase and by changing the rf power and pressure. The effects of the discharge parameters on the optical, electrical and structural properties were investigated. These effects were attributed to the variation of carbon content in the film. The analyses

Giuseppina Ambrosone; Ubaldo Coscia; Stefano Lettieri; Pasqualino Maddalena; Carlo Privato; Sergio Ferrero

2002-01-01

238

Characteristics of electron spin resonance in hydrogenated amorphous silicon-carbon\\/hydrogenated amorphous silicon heterojunctions  

Microsoft Academic Search

The characteristics of light soaking and equilibrium electron spin resonance (ESR) in p-hydrogenated amorphous silicon-carbon\\/i-hydrogenated amorphous silicon heterojunction are investigated. The influence of the carbon content in the p layer on ESR is also studied in this letter. We find that the light-induced silicon dangling bond defects mainly originate from the i layer and the increased spin density can be

Guanghua Chen; Guosheng Sun; Fangqing Zhang

1989-01-01

239

Recombination of atomic oxygen and hydrogen on amorphous carbon  

NASA Astrophysics Data System (ADS)

Deposit buildup and fuel entrapment due to amorphous carbon are relevant issues in fusion devices with carbon based plasma facing components. Neutral atomic species play a significant role - atomic hydrogen facilitates the formation of amorphous carbon while atomic oxygen could be used to remove carbon deposits. The kinetics of either reaction depends on the density of neutral species, which in turn is influenced by recombination on the vessel walls. In this work, we measured the probability of heterogeneous recombination of atomic hydrogen and oxygen on amorphous carbon deposits. The recombination coefficients were determined by observing density profiles of atomic species in a closed side-arm of a plasma vessel with amorphous carbon deposit-lined walls. Density profiles were measured with fiber optics catalytic probes. The source of atomic species was inductively coupled radiofrequency plasma. The measured recombination coefficient values were of the order of 10-3 for both species.

Drenik, A.; Vesel, A.; Mozeti?, M.; Panjan, P.

2013-11-01

240

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

Microsoft Academic Search

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

Micheal Roberts; Robert Zabransky; Shain Doong; Jerry Lin

2008-01-01

241

Hydrogen and carbon kinetic isotope effects during soil uptake of atmospheric methane  

NASA Astrophysics Data System (ADS)

The hydrogen and carbon kinetic isotope effects (KJEs) occurring during uptake of atmospheric methane (CH4) by soils were measured using in situ static flux chambers in a native grassland and a temperate forest in Washington State. The hydrogen KIE was ?Dsoil =k(CH4)/k(CH3D) = 1.099 ± 0.030 and 1.066 ± 0.007 for the grassland and forest, respectively. The carbon KIE of ?Csoil =k(12CH4)/k(13CH4) = 1.0173 ± 0.0010 and 1.0181 ± 0.0004 for the grassland and forest, respectively, compares well to previous determinations in other ecosystems. Local spatial variability in ?soil was as large as the between-ecosystem variability. The dependence of ?soil on ?ox and the KIE during diffusion is described. The apparent KIE associated with microbial oxidation, ?ox, was determined from ?soil and the relative rates of CH4 oxidation and diffusion in the soil column, derived from observed steady state profiles of soil air CH4 concentration. The apparent ?ox ranged from 1.094 to 1.209 for ?Dox and from 1.0121 to 1.0183 for ?Cox. These are the first determinations of the hydrogen KIEs during soil uptake of atmospheric CH4 and during aerobic microbial oxidation of CH4 at or below atmospheric concentrations. The KIE during uptake of atmospheric CH4 by soils is significantly different than the KIEs associated with the other sinks of atmospheric CH4. The interhemispheric asymmetry in the strength of the soil sink of atmospheric CH4 suggests a difference of ˜6‰ between the overall hydrogen KIEs in the two hemispheres. Modeling studies of the global atmospheric CH4 budget using deuterium as a tracer must therefore include ?Dsoil.

Snover, Amy K.; Quay, Paul D.

2000-03-01

242

The preparation and characterization of porous carbons for hydrogen storage  

Microsoft Academic Search

Porous carbon materials with a cylindrical pore structure were prepared using ordered mesoporous silica as a removable template.\\u000a To investigate the effect of the structural and textural properties of the products on hydrogen adsorption capacity, different\\u000a carbon precursors and synthetic methods were used in their preparation. All of the carbon materials prepared showed a well-defined\\u000a pore structure with a high

Wooyoung Kim; Pil Kim; Ji Bong Joo; Hyun Khil Shin; Kwang S. Jung; Jongheop Yi

2006-01-01

243

Hydrogen evolution reaction of low carbon steel electrode in hydrochloric acid as a source for hydrogen production  

Microsoft Academic Search

The hydrogen evolution reaction (HER) (cathodic reaction) of low carbon steel electrode immersed in hydrochloric acid was investigated as a source for hydrogen production. Corrosion rate, hydrogen evolution rate, and current density increase with the increase of HCl concentration. Theoretically and practically, every 1g of iron produces about 0.036g of hydrogen. Therefore, the hydrogen production efficiency over the immersion period

A. A. El-Meligi; N. Ismail

2009-01-01

244

Hydrogen Adsorption on Activated Carbon an Carbon Nanotubes Using Volumetric Differential Pressure Technique  

Microsoft Academic Search

A simple hydrogen adsorption measurement system utilizing the volumetri differential pressure technique has been designed, fabricated and calibrated. Hydroge adsorption measurements have been carried out at temperatures 298 K and 77 K on activate carbon and carbon nanotubes with different surface areas. The adsorption data obtained will b helpful in understanding the adsorption property of the studied carbon materials using

S. M. Sanip; M. A. R. Saidin; M. Aziz; A. F. Ismail

2010-01-01

245

Proton and deuteron nuclear magnetic resonance studies of amorphous hydrogenated silicon, carbon, and carbon alloys  

Microsoft Academic Search

Despite the profound influence of semiconductors and the changes they have produced, many fundamental questions remain unanswered. We have used proton and deuteron nuclear magnetic resonance (NMR) to explore the role of hydrogens in amorphous silicon and amorphous carbon and carbon alloy films. In the carbon films, dipolar filtering techniques reveal a two-component shifted lineshape in the proton NMR spectra

Mary Jane Wurth Kernan

1997-01-01

246

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

247

Hydrogen component fugacities in binary mixtures with carbon dioxide  

NASA Astrophysics Data System (ADS)

The fugacity coefficients of hydrogen in binary mixtures with carbon dioxide were measured using a physical equilibrium technique. This technique involves the use of an experimental chamber which is divided into two regions by a semipermeable membrane. Hydrogen can penetrate and pass through the membrane, while the other component (in this case carbon dioxide) cannot. At equilibrium, pure hydrogen will permeate into one “compartment” of the chamber, while the binary mixture occupies the other compartment. Thus, the pressure of pure hydrogen on one side of the membrane approaches the partial pressure of hydrogen in the mixture on the other side of the membrane. This allows the direct measurement of the hydrogen component fugacity at a given mixture mole fraction. In this study, results are reported for measurements made on the hydrogen+carbon dioxide binary at 80°C (353 K), 130°C (403 K), 160°C (433 K), and 190°C (463 K), each at a total mixture pressure of 3.45 MPa. The experimental results are compared with predictions from the Redlich-Kwong, Peng-Robinson, and extended corresponding-states models.

Bruno, T. J.; Hume, G. L.

1986-09-01

248

ISOTHERMS OF GASEOUS ADSORPTION ON BAU COAL AT LOW TEMPERATURES AND 10$sup - 9$ TO 10⁻² mm Hg PRESSURES. I. ISOTHERMS OF DEUTERIUM AND HYDROGEN ADSORPTION  

Microsoft Academic Search

Descriptions are given of the installation, method, and results obtained ; in determiring the equilibrium hydrogen -deuterium pressure over BAU coal at 4.2, ; 20.4, and 80 deg K at 10⁻⁹ to 10⁻² mm Hg pressure. (R.V.J.);

Fedorova

1963-01-01

249

Kaon Electroproduction on Deuterium  

SciTech Connect

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

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

1998-08-01

250

MECHANICAL TESTING OF CARBON STEEL IN HIGH PRESSURE HYDROGEN  

SciTech Connect

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

Duncan, A

2006-05-11

251

An electrospray ms-coupled microfluidic device for sub-second hydrogen/deuterium exchange pulse-labelling reveals allosteric effects in enzyme inhibition.  

PubMed

In this work, we introduce an integrated, electrospray mass spectrometry-coupled microfluidic chip that supports the complete workflow for 'bottom up' hydrogen/deuterium exchange (HDX) pulse labelling experiments. HDX pulse labelling is used to measure structural changes in proteins that occur after the initiation of a reaction, most commonly folding. In the present case, we demonstrate the device on the ?-lactamase enzyme TEM-1, identifying active site changes that occur upon acylation by a covalent inhibitor and subtle changes in conformational dynamics that occur away from the active site over a period of several second after the inhibitor is bound. Our results demonstrate the power of microfluidics-enabled sub-second HDX pulse labelling as a tool for studying allostery and show some intriguing correlations with mutagenesis studies. PMID:23426018

Rob, Tamanna; Gill, Preet Kamal; Golemi-Kotra, Dasantila; Wilson, Derek J

2013-02-21

252

Effect of substitution of hydrogen oxide by deuterium oxide on thermotropic transition between the interdigitated gel phase and the ripple phase of dihexadecylphosphatidylcholine  

SciTech Connect

Thermotropic transitions of dihexadecylphosphatidylcholine (DHPC) dispersions in hydrogen oxide (1H2O) and deuterium oxide (2H2O) were investigated by differential scanning calorimetry (DSC). In DHPC dispersions, transition temperature between interdigitated gel phase (L beta I) and ripple phase (P beta') is lower in 2H2O than in 1H2O, and transition between the ripple phase (P beta') and fluid phase (L alpha) in 2H2O occurs at a temperature slightly higher than in 1H2O. In dipalmitoylphosphatidylcholine (DPPC) dispersions, on the other hand, transition temperature between lamellar gel phase (L beta') and ripple phase is higher in 2H2O than in 1H2O. These results suggest that the interdigitated gel phase is more stable in 1H2O than in 2H2O. To account for the shift of transition temperature by the water substitution, difference of interfacial energies between these aqueous environments is discussed.

Ohki, K. (Nagoya Univ. (Japan))

1991-01-15

253

Carbon-carbon bond activation in cyclopropane by energetic forms of hydrogen on the Ni(100) surface  

Microsoft Academic Search

Carbon-carbon bond activation is important in catalytic processes, and is observed here at a low temperature during reactions of adsorbed cyclopropane with both gas phase atomic hydrogen and bulk hydrogen in the presence of surface hydrogen on the Ni(100) surface. The large energies possessed by gas phase atomic hydrogen may allow substantial activation barriers to be overcome in the absence

Kyung-Ah Son; John L. Gland

1995-01-01

254

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

PubMed

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

Cho, Yunju; Ahmed, Arif; Kim, Sunghwan

2013-09-30

255

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

256

Plasma Pyrolysis of Methane to Hydrogen and Carbon Black  

SciTech Connect

The plasma-driven gas-phase thermal decomposition of methane yielding hydrogen and solid-phase carbon has been suggested as an environmentally friendly alternative to conventional methods of producing hydrogen from natural gas. The advantage of the process is that hydrogen is obtained directly from methane without producing CO2 as a byproduct. The process was experimentally examined using a modified version of a dc plasma reactor originally developed for the conversion of methane to acetylene. Carbon yields of 30%, a factor of 6 increase, with a corresponding decrease in acetylene yield were obtained by simply increasing the residence or reaction time. A detailed kinetic model that includes the reaction mechanisms resulting in the formation of acetylene and heavier hydrocarbons through benzene is described. A model for solid carbon nucleation and growth is included. The model is compared to experimental results and is used to examine process optimization.

Fincke, James Russell; Anderson, Raymond Paul; Hyde, Timothy Allen; Detering, Brent Alan

2002-02-01

257

Carbon nanotubes in hydrogen fuel cells  

Microsoft Academic Search

Carbon nanotubes possess exceptional mechanical and electrical properties such as high tensile strength, great resilience, high thermal and electrical conductivity, high specific surface area, and high temperature stability. The coexistence of these desirable properties in one material makes carbon nanotubes a fascinating candidate for incorporation into a fuel cell to improve its performance and decrease the thickness of the fuel

Jason Ming-Young Tang

2007-01-01

258

Palladium Nanoparticles Decorated Single-Walled Carbon Nanotube Hydrogen Sensor  

Microsoft Academic Search

We developed a simple and cost-effective fabrication technique to construct a hydrogen nanosensor by decorating single-walled carbon nanotubes with Pd nanoparticles. By varying the sensor's synthesis conditions (e.g., Pd electrodeposition charge, deposition potential, and initial baseline resistance of the SWNT network), the sensing performance was optimized. The optimized sensor showed excellent sensing properties toward hydrogen (¢R\\/R of 0.42%\\/ppm) with a

Syed Mubeen; Ting Zhang; Bongyoung Yoo; Marc A. Deshusses; Nosang V. Myung

2007-01-01

259

Hydrogen Reflection in Low-Energy Collisions with Amorphous Carbon  

SciTech Connect

Reflection and sticking of hydrogen atoms at amorphous carbon surfaces is studied at impact energies ranging from 0.1 to 50 eV using molecular dynamics simulations. We show that the reflection coefficient at the lowest energies is large and is very sensitive to both the many-body potential used in the simulations and the degree of hydrogen enrichment of the surfaces.

Reinhold, Carlos O [ORNL; Krstic, Predrag S [ORNL; Stuart, S. J. [Clemson University

2009-01-01

260

Itinerant flat-band magnetism in hydrogenated carbon nanotubes.  

PubMed

We investigate the electronic and magnetic properties of hydrogenated carbon nanotubes using ab initio spin-polarized calculations within both the local density approximation (LDA) and the generalized gradient approximation (GGA). We find that the combination of charge transfer and carbon network distortion makes the spin-polarized flat-band appear in the tube's energy gap. Various spin-dependent ground state properties are predicted with the changes of the radii, the chiralities of the tubes, and the concentration of hydrogen. It is found that strain or external electric field can effectively modulate the flat-band spin-splitting and even induce an insulator-metal transition. PMID:19548640

Yang, Xiaoping; Wu, Gang

2009-06-23

261

Process for producing hydrogen and carbonyl sulfide from hydrogen sulfide and carbon monoxide using a heteropolyanionic metal complex catalyst  

SciTech Connect

Hydrogen and carbonyl sulfide are produced by a process comprising contracting gaseous hydrogen sulfide with gaseous carbon monoxide in the presence of a heteropolymolybdate or tungstate complex. Use of these catalysts reduce the amount of by-product carbon dioxide and methane formation and thus enhance the make of hydrogen and carbonyl sulfide.

Kuch, Ph. L.

1984-12-18

262

Hydrogen storage in boron substituted carbon nanotubes  

Microsoft Academic Search

Template assisted synthesis of boron substituted carbon nanotubes was carried out by the carbonization of hydroborane polymer in alumina membrane template. The nanotubes were characterized by electron microscopic analysis, FT-Raman, FT-IR, XRD, X-ray photoelectron spectroscopy (XPS) and 13C &11B MAS NMR techniques. The presence of boron in different chemical environment has been visualized by XPS and 11B MAS NMR. The

M. Sankaran; B. Viswanathan

2007-01-01

263

Laser annealing of hydrogenated amorphous silicon–carbon films  

Microsoft Academic Search

Hydrogenated amorphous silicon–carbon films with carbon content, x=C\\/(C+Si), ranging from 0.08 to 0.28 have been irradiated by excimer (KrF) laser varying the incident energy density, ?, from 64 to 242 mJ\\/cm2. The crystallization of the silicon phase is induced in all the samples, independently of the alloy composition and the average Si crystallite size increases with the laser energy density.

U. Coscia; G. Ambrosone; C. Minarini; V. Parisi; S. Schutzmann; A. Tebano; S. Restello; V. Rigato

2004-01-01

264

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

NASA Astrophysics Data System (ADS)

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

Wang, Qinyu; Johnson, J. Karl

1999-01-01

265

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

NASA Astrophysics Data System (ADS)

Retention and enrichment of a model system for mixed layers, tungsten-containing carbon films (a-C:W), were investigated with respect to the interaction with D ions. a-C:W was exposed to a mass-separated, mono-energetic D beam (200 eV/D, 1.2 × 1015 D cm?2 s?1). The W concentration in the films (0–7.5 at.%), the specimen temperature during D beam exposure (300–1300 K) and the fluence (?) of incident D (1015–1020 D cm?2) were varied. Analysis of retention and enrichment were performed by nuclear reaction analysis and Rutherford backscattering spectrometry, respectively. At 300 K and fluences up to 1019 D cm?2, the increase of the D inventory with fluence in a-C:W cannot be distinguished from a-C and pyrolytic graphite, e.g., above ˜1017 D cm?2 the D inventory increases with fluence according to ?x (x = 0.1). Above a fluence of 1019 D cm?2, however, the D inventory depends strongly on the W concentration. At a fluence of 1020 D cm?2 the D inventory is increased to the 1.5-fold of the D inventory of pyrolytic graphite for 1% and 2.5% a-C:W and it is decreased to the half value of the D inventory of pyrolytic graphite for 7.5% a-C:W. At temperatures above 300 K, following trends are observed: With increasing temperature, the D inventory increases more strongly with fluence and D reaches depths far beyond the width of the ion range. However, the D inventory does not increase with fluence according to ?x, especially at fluences above 1019 D cm?2.

Sauter, P. A.; Balden, M.

2013-09-01

266

Isotopic effect on the vibrational lifetime of the carbon-deuterium stretch excitation on graphene  

NASA Astrophysics Data System (ADS)

The relaxation of vibrational energy in the H and D stretch modes has been studied on the graphene surface using ab initio calculations. The dissipation of the vibrational energy stored in the stretching modes proceeds through vibration-phonon coupling, while the dissipation through electronic excitations makes only minor contributions. Recently, we reported the fast relaxation of the H stretch energy on graphene [S. Sakong and P. Kratzer, J. Chem. Phys. 133, 054505 (2010)]. Interestingly, we predict the lifetime of the D stretch to be markedly longer compared to the relaxation of the H stretch. This is unexpected since the vibrational amplitudes at carbon atoms in the joint C-D vibrational modes are larger than in the joint C-H modes, due to the mass ratio mD/mC > mH/mC. However, the vibrational relaxation rate for the D stretch is smaller than for the H stretch, because the energy is dissipated to an acoustic phonon of graphene in the case of C-D rather than an optical phonon as is the case in C-H, and hence, the corresponding phonon density of states is lower in the C-D case. To rationalize our findings, we propose a general scheme for estimating vibrational lifetimes of adsorbates based on four factors: the density of states of the phonons that mediates the transitions, the vibration-phonon coupling strength, the anharmonic coupling between local modes, and the number of quanta involved in the transitions. Mainly the first two of these factors are responsible for the differences in the lifetimes of the C-H and C-D stretches. The possible role of the other factors is illustrated in the context of vibrational lifetimes in other recently studied systems.

Sakong, Sung; Kratzer, Peter

2011-09-01

267

Ultradense Deuterium  

Microsoft Academic Search

An attempt is made to explain the recently reported occurrence of ultradense deuterium as an isothermal transition of Rydberg matter into a high density phase by quantum mechanical exchange forces. It is conjectured that the transition is made possible by the formation of vortices in a Cooper pair electron fluid, separating the electrons from the deuterons, with the deuterons undergoing

F. Winterberg

2009-01-01

268

Hydrogen adsorption in defected carbon nanotubes  

Microsoft Academic Search

Recently there has been lot of interest in the development of hydrogen storage in various systems for the large-scale application\\u000a of fuel cells, mobiles and for automotive uses. Hectic materials research is going on throughout the world with various adsorption\\u000a mechanisms to increase the storage capacity. It was observed that physisorption proves to be an effective way for this purpose.

V. Gayathri; R. Geetha

2007-01-01

269

Simultaneous microdetermination of carbon, hydrogen and lead in organolead compounds  

Microsoft Academic Search

The straight emtpy-tube method of Korshun and Klimova has been successfully extended to the simultaneous microdetermination of carbon, hydrogen and lead in organolead compounds. In all cases, the lead content was calculated from the weight of the plumbous oxide residue left behind in the fused-silica capsule used to hold the sample. Sulphur could also be determined in the same analysis.

Hassan N. A. Hassan; Mohamed E. M. Hassouna; Youssef A. Gawargious

1992-01-01

270

Storage of hydrogen in single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Pores of molecular dimensions can adsorb large quantities of gases owing to the enhanced density of the adsorbed material inside the pores1, a consequence of the attractive potential of the pore walls. Pederson and Broughton have suggested2 that carbon nanotubes, which have diameters of typically a few nanometres, should be able to draw up liquids by capillarity, and this effect has been seen for low-surface-tension liquids in large-diameter, multi-walled nanotubes3. Here we show that a gas can condense to high density inside narrow, single-walled nanotubes (SWNTs). Temperature-programmed desorption spectrosocopy shows that hydrogen will condense inside SWNTs under conditions that do not induce adsorption within a standard mesoporous activated carbon. The very high hydrogen uptake in these materials suggests that they might be effective as a hydrogen-storage material for fuel-cell electric vehicles.

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

1997-03-01

271

In Situ Electrical Study on Primary Hydrogen Spillover from Nanocatalysts to Amorphous Carbon Support  

SciTech Connect

Primary hydrogen spillover has been studied using a unique electrical method. We observed that at ambient temperature, when a discontinuous nanogranular Pd film is on the top of an amorphous carbon film, the electrical conductance of the carbon film decreases in pressurized hydrogen. In comparison, in the absence of this Pd layer, the conductance of the carbon film remains unchanged in pressurized hydrogen. The observed decrease in the current in the Pd/carbon structure is ascribed to the hydrogenation of the dangling carbon bonds and sp{sup 2}-sp{sup 3} transition in the amorphous carbon by the primary spillover hydrogen atoms from Pd nanoclusters.

Lin, C.; Yang, Z.; Xu, T.; Zhao, Y.

2008-01-01

272

Carbon Nanotube Films for Hydrogen Sensing.  

National Technical Information Service (NTIS)

A multi-layer H.sub.2 sensor includes a carbon nanotube layer, and a ultra-thin metal or metal alloy layer in contact with the nanotube layer. The ultra-thin metal or metal alloy layer is preferably from 10 to 50 angstroms thick. An electrical resistance ...

A. G. Rinzler B. S. Kang F. Ren H. T. Wang J. A. Sippel-Oakley

2005-01-01

273

Stable hydrogen and carbon isotope fractionation during microbial toluene degradation: mechanistic and environmental aspects.  

PubMed

Primary features of hydrogen and carbon isotope fractionation during toluene degradation were studied to evaluate if analysis of isotope signatures can be used as a tool to monitor biodegradation in contaminated aquifers. D/H hydrogen isotope fractionation during microbial degradation of toluene was measured by gas chromatography. Per-deuterated toluene-d(8) and nonlabeled toluene were supplied in equal amounts as growth substrates, and kinetic isotope fractionation was calculated from the shift of the molar ratios of toluene-d(8) and nondeuterated toluene. The D/H isotope fractionation varied slightly for sulfate-reducing strain TRM1 (slope of curve [b] = -1.219), Desulfobacterium cetonicum (b = -1.196), Thauera aromatica (b = -0.816), and Geobacter metallireducens (b = -1.004) and was greater for the aerobic bacterium Pseudomonas putida mt-2 (b = -2.667). The D/H isotope fractionation was 3 orders of magnitude greater than the (13)C/(12)C carbon isotope fractionation reported previously. Hydrogen isotope fractionation with nonlabeled toluene was 1.7 and 6 times less than isotope fractionation with per-deuterated toluene-d(8) and nonlabeled toluene for sulfate-reducing strain TRM1 (b = -0.728) and D. cetonicum (b = -0.198), respectively. Carbon and hydrogen isotope fractionation during toluene degradation by D. cetonicum remained constant over a growth temperature range of 15 to 37 degrees C but varied slightly during degradation by P. putida mt-2, which showed maximum hydrogen isotope fractionation at 20 degrees C (b = -4.086) and minimum fractionation at 35 degrees C (b = -2.138). D/H isotope fractionation was observed only if the deuterium label was located at the methyl group of the toluene molecule which is the site of the initial enzymatic attack on the substrate by the bacterial strains investigated in this study. Use of ring-labeled toluene-d(5) in combination with nondeuterated toluene did not lead to significant D/H isotope fractionation. The activity of the first enzyme in the anaerobic toluene degradation pathway, benzylsuccinate synthase, was measured in cell extracts of D. cetonicum with an initial activity of 3.63 mU (mg of protein)(-1). The D/H isotope fractionation (b = -1.580) was 30% greater than that in growth experiments with D. cetonicum. Mass spectroscopic analysis of the product benzylsuccinate showed that H atoms abstracted from the toluene molecules by the enzyme were retained in the same molecules after the product was released. Our findings revealed that the use of deuterium-labeled toluene was appropriate for studying basic features of D/H isotope fractionation. Similar D/H fractionation factors for toluene degradation by anaerobic bacteria, the lack of significant temperature dependence, and the strong fractionation suggest that analysis of D/H fractionation can be used as a sensitive tool to assess degradation activities. Identification of the first enzyme reaction in the pathway as the major fractionating step provides a basis for linking observed isotope fractionation to biochemical reactions. PMID:11571192

Morasch, B; Richnow, H H; Schink, B; Meckenstock, R U

2001-10-01

274

Nitrogen-containing carbon nanotubes as a possible hydrogen storage medium  

Microsoft Academic Search

Nitrogen containing carbon nanotubes have been synthesized using a variety of templates. The hydrogen absorption capacity of these materials has been evaluated. The study shows that it is necessary to stabilize nitrogen in the carbon nanotube framework for reproducible hydrogen uptake. The role of nitrogen is to activate gaseous molecular hydrogen and its subsequent transport to the carbon surface by

M Sankaran; B Viswanathan

275

A comparative study of hydrogen adsorption on superactivated carbon versus carbon nanotubes  

Microsoft Academic Search

Adsorption isotherms of hydrogen on activated carbon and multiwalled carbon nanotubes (MWNT) were collected using volumetric method for the range of 233–298K and pressures up to 11Mpa. The same shape of isotherms revealed a common mechanism of adsorption. However, the amount of H2 adsorbed on MWNT is 3–5 times less than on activated carbon, but the surface concentration of H2

Li Zhou; Yaping Zhou; Yan Sun

2004-01-01

276

Ultradense Deuterium  

Microsoft Academic Search

An attempt is made to explain the recently reported occurrence of ultradense deuterium as an isothermal transition of Rydberg\\u000a matter into a high density phase by quantum mechanical exchange forces. It is conjectured that the transition is made possible\\u000a by the formation of vortices in a Cooper pair electron fluid, separating the electrons from the deuterons, with the deuterons\\u000a undergoing

F. Winterberg

2010-01-01

277

Restricted dynamics of molecular hydrogen confined in activated carbon nanopores  

SciTech Connect

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

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

2012-01-01

278

Effects of hydrogen adsorption on single-wall carbon nanotubes: Metallic hydrogen decoration  

Microsoft Academic Search

We show that the electronic and atomic structure of carbon nanotubes undergo dramatic changes with hydrogen chemisorption from first principle calculations. Upon uniform exohydrogenation at half coverage, the cross sections of zigzag nanotubes become literally square or rectangular, and they are metallic with very high density of states at the Fermi level, while other isomers can be insulating. For both

O. Gülseren; T. Yildirim; S. Ciraci

2002-01-01

279

Simulation of chemical adsorption of hydrogen by carbon nanotubes  

NASA Astrophysics Data System (ADS)

The hydrogen chemical adsorption on a single-walled carbon nanotube (6, 6) has been studied by quantum-chemical computer simulation. Different variants of hydrogen coverage of the nanotube have been considered, and the dependences of the adsorption energy and the nanotube strain energy on the coverage density have been found. In addition, the adsorption has been considered on both the outer and inner surfaces of the nanotube wall. It has been established that some adsorption conformations are unstable, which leads to fracture of the nanotubes.

Bogdanova, D. A.; Bulyarskii, S. V.

2013-03-01

280

Study on crystallization of hydrogenated nanocrystalline silicon carbon films  

Microsoft Academic Search

Hydrogenated nanocrystalline silicon carbon (nc-SiCx:H) films were prepared by RF glow discharge of gas mixture of silane (SiH4) and ethene (C2H4) diluted heavily by hydrogen (H2). The effect of the gas volume ratio of (SiH4 + C2H4)\\/H2 (Xg) and C2H4\\/(SiH4 + C2H4) (Xc) on the crystallization and composition of films are described in the paper. When the Xg increases from

Weiqiang Han; Shoushan Fan; Binglin Gu

1996-01-01

281

Mechanism of enhanced hydrogen adsorption on palladium-doped nanoporous carbon fibers  

SciTech Connect

Recent work at Oak Ridge National Laboratory was directed towards adsorptive storage of hydrogen in nanoporous carbon fibers in which palladium was incorporated prior to spinning and carbonization/activation of the fibers. Palladium doped carbon fibers exhibited enhanced hydrogen uptake compared to the corresponding palladium-free nanoporous carbon fibers (at room temperature and 2 MPa pressure). However, the mechanism responsible for the enhanced hydrogen uptake is not fully understood. New findings are presented in this paper in support of a mechanism that encompasses both hydrogen spillover on palladium metal sites and hydrogen physisorption on nanostructured carbon sites.

Contescu, Cristian I [ORNL; Gallego, Nidia C [ORNL; Wu, Xianxian [ORNL; Tekinalp, Halil [Clemson University; Edie, Dan [Clemson University; Thies, Mark C [ORNL; Baker, Frederick S [ORNL

2007-01-01

282

Biocatalytic deuterium- and hydrogen-transfer using over-expressed ADH-'A': enhanced stereoselectivity and 2H-labeled chiral alcohols.  

PubMed

Employing the over-expressed highly organic solvent tolerant alcohol dehydrogenase ADH-'A' from Rhodococcus ruber DSM 44541, versatile building blocks, which were not accessible by the wild type catalyst, were obtained in > 99% e.e.; furthermore, employing d8-2-propanol as deuterium source, stereoselective biocatalytic deuterium transfer was made feasible to furnish enantiopure deuterium labeled sec-alcohols on a preparative scale employing a single enzyme. PMID:16733594

Edegger, Klaus; Gruber, Christian C; Poessl, Tina M; Wallner, Sabine R; Lavandera, Iván; Faber, Kurt; Niehaus, Frank; Eck, Juergen; Oehrlein, Reinhold; Hafner, Andreas; Kroutil, Wolfgang

2006-04-11

283

Pion Electroproduction from Deuterium at BLAST  

NASA Astrophysics Data System (ADS)

The latest pion electroproduction results from the BLAST (Bates Large Acceptance Spectrometer Toroid) experiment at the MIT-Bates Linear Accelerator Center are presented. The experiment used the BLAST detector, a longitudinally polarized electron beam at 850 MeV, and internal targets of polarized hydrogen and vector and tensor polarized deuterium. Event selection and particle identification will be discussed. The measured asymmetries for exclusive pion electroproduction from deuterium will be presented and compared with results obtained from hydrogen and available theoretical predictions.

Shinozaki, Aki

2007-04-01

284

Studies of chemical vapor deposition of diamond films in carbon/hydrogen and carbon/hydrogen/halogen systems  

SciTech Connect

Experiments employing molecular beams of atomic hydrogen and a hydrocarbon precursor were carried out in an attempt to deposit diamond films at the pressure of 10{sup {minus}4} torr. No diamond films were deposited using methane, methyl iodide or di-tert-butyl peroxide as carbon sources. Only amorphous carbon films were deposited under some circumstances. By using a carbon-13 labeling technique, it was found that chloromethanes contribute to diamond growth via a new growth precursor(s) in the form of chlorocarbon radicals in addition to the methyl radical pathway in a hot filament reactor. On the other hand, fluoromethanes, bromomethane and iodomethane yield diamond through the methyl radical mechanism. It was argued that the drastically different behaviors among halocarbons in diamond CVD systems are attributable to the differences in their thermodynamic properties and kinetic parameters of the reactions of halocarbons with atomic hydrogen. It was demonstrated that low temperature deposition of diamond films can be achieved by either using chlorocarbons as carbon sources or adding HCl to a methane/hydrogen system. The major function of HCl under diamond CVD conditions is to generate chlorine atoms. These chlorine atoms in turn activate the hydrogenated diamond surface via a more efficient pathway, i.e., chlorine abstraction reaction of surface-adsorbed hydrogen atoms at low temperatures. As a result, diamond films were deposited by using methyl chloride at substrate temperatures as low as 300{degrees}C. Studies of the dependence of the growth rate on the substrate temperature revealed the existence of two growth regions. The transition temperature was found to be around 730{degrees}C and 570{degrees}C for the CH{sub 4}/H{sub 2} and CCl{sub 4}/H{sub 2} systems respectively. It was also found that adding HCl to the CH{sub 4}H{sub 2} deposition system yielded an increase in growth rates of diamond films at low temperatures.

Bai, Jianmin

1993-12-31

285

CRYOGENIC ADSORPTION OF HYDROGEN ISOTOPES OVER NANO-STRUCTURED MATERIALS  

Microsoft Academic Search

Porous materials such as zeolites, activated carbon, silica gels, alumina and a number of industrial catalysts are compared and ranked for hydrogen and deuterium adsorption at liquid nitrogen temperature. All samples show higher D adsorption than that of H, in which a HY sample has the greatest isotopic effect while 13X has the highest hydrogen uptake capacity. Material's moisture content

S. Xiao; L. Heung

2010-01-01

286

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

USGS Publications Warehouse

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

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

1989-01-01

287

EPR study of carbon and silicon related defects in carbon-rich hydrogenated amorphous silicon-carbon films  

Microsoft Academic Search

Three paramagnetic defects were revealed in amorphous hydrogenated carbon-rich silicon-carbon alloy films (a-Si0.3C0.7:H) . Two of them were attributed to silicon (Si) dangling bonds (Si DBs) and carbon-related defects (CRDs). The third defect, based on its g -value and linewidth, was tentatively attributed to a bulk Si DB defect bonded with nitrogen atoms in Si-N2Si configuration. The effect of thermal

E. N. Kalabukhova; S. N. Lukin; D. V. Savchenko; B. D. Shanina; A. V. Vasin; V. S. Lysenko; A. N. Nazarov; A. V. Rusavsky; J. Hoentsch; Y. Koshka

2010-01-01

288

Transport and Magnetism in Template Synthesized Hydrogenated Multiwalled Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

In this work, we synthesize highly disordered carbon nanotubes by CVD in porous alumina templates. We show that, due to the disorder in the nanotubes, they can easily be made to uptake hydrogen by annealing. We show that this induces ferromagnetism in the nanotubes, and we perform a magnetic study. We also measure the transport properties of the nanotubes. First, we find a rate dependent hysteretic magnetoresistance. We explain the rate dependence through strong magneto-viscosity effects, and we attribute the hysteresis to anisotropic magnetoresistance. We also discover a magnetic field-driven temperature dependent transition from positive to negative magnetoresistance in the ferromagnetic nanotubes that is not observed in similarly disordered un-hydrogenated carbon nanotubes. We attempt to explain this behavior by considering it an order-disorder transition described by the Bright model due to several scattering pathways, that are present in the ferromagnetic nanotubes that are not present in the non-ferromagnetic tubes.

Friedman, Adam; Chun, Hyunkyung; Heiman, Donald; Jung, Yung Joon; Menon, Latika

2009-03-01

289

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

2013-09-25

290

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.

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

2013-01-01

291

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.

Elliott, Douglas C. (Richland, WA); Frye, John G. (Richland, WA)

1999-01-01

292

Catalytic carbon membranes for hydrogen production. Final report  

SciTech Connect

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

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

1992-01-01

293

Hydrogen-deuterium isotope shift: From the 1S-2S-transition frequency to the proton-deuteron charge-radius difference  

SciTech Connect

We analyze and review the theory of the hydrogen-deuterium isotope shift for the 1S-2S transition, which is one of the most accurately measured isotope shifts in any atomic system, in view of a recently improved experiment. A tabulation of all physical effects that contribute to the isotope shift is given. These include the Dirac binding energy, quantum electrodynamic effects, including recoil corrections, and the nuclear-size effect, including the pertaining relativistic and radiative corrections. From a comparison of the theoretical result {Delta}f{sub th}=670 999 566.90(66)(60) kHz (exclusive of the nonrelativistic nuclear-finite-size correction) and the experimental result {Delta}f{sub expt}=670 994 334 605(15) Hz, we infer the deuteron-proton charge-radius difference {sub d}-{sub p}=3.820 07(65) fm{sup 2} and the deuteron structure radius r{sub str}=1.975 07(78) fm.

Jentschura, U.D. [Department of Physics, Missouri University of Science and Technology, Rolla, Missouri 65409-0640 (United States); Matveev, A.; Parthey, C.G.; Alnis, J.; Pohl, R.; Udem, Th.; Kolachevsky, N.; Haensch, T.W. [Max-Planck-Institut fuer Quantenoptik, DE-85748 Garching (Germany)

2011-04-15

294

Hydrogen/Deuterium Exchange Mass Spectrometry and Site-Directed Disulfide Cross-Linking Suggest an Important Dynamic Interface between the Two Lysostaphin Domains  

PubMed Central

Lysostaphin is a peptidoglycan hydrolase secreted by Staphylococcus simulans. It can specifically lyse Staphylococcus aureus and is being tested as a novel antibacterial agent. The protein contains an N-terminal catalytic domain and a C-terminal cell wall targeting domain. Although the two domains from homologous enzymes were structurally determined, the structural organization of lysostaphin domains remains unknown. We used hydrogen/deuterium exchange mass spectrometry (H/DX-MS) and site-directed disulfide cross-linking to probe the interface between the lysostaphin catalytic and targeting domains. H/DX-MS-mediated comparison of peptides from full-length lysostaphin and the separated domains identified four peptides of lower solvent accessibility in the full-length protein. Cross-linking analysis using cysteine pair substitutions within those peptides showed that two pairs of cysteines can form disulfide bonds, supporting the domain association role of the targeted peptides. The cross-linked mutant exhibited a binding capacity to S. aureus that was similar to that of the wild-type protein but reduced bacteriolytic activity probably because of restraint in conformation. The diminished activity was further reduced with increasing NaCl concentrations that can cause contractions of bacterial peptidoglycan. The lytic activity, however, could be fully recovered by reducing the disulfide bonds. These results suggest that lysostaphin may require dynamic association of the two domains for coordinating substrate binding and target cleavage on the elastic peptidoglycan. Our study will help develop site-specific PEGylated lysostaphin to treat systemic S. aureus infections.

Lu, Hai-Rong; Gu, Mei-Gang; Huang, Qiang; Huang, Jin-Jiang; Lu, Wan-Ying; Lu, Hong

2013-01-01

295

Polymorphic Triple ?-Sheet Structures Contribute to Amide Hydrogen/Deuterium (H/D) Exchange Protection in the Alzheimer Amyloid ?42 Peptide*  

PubMed Central

Characterization of the polymorphic structural range of A? oligomers is important to the understanding of the mechanisms of toxicity. Yet for highly polymorphic ensembles, experimental structural elucidation is difficult. Here, we use a combination of NMR solvent protection experiments and computational structural screening to identify major species in the amyloid conformational ensemble. We examined the polymorphic pentamer and fibril seeds of A?42 and its mutants and compared the theoretical backbone amide protection obtained from simulations with experimental hydrogen/deuterium (H/D) exchange protection ratio. We observed that highly flexible pentamers do not share structural similarities with fibril seed oligomers, except the turn regions. We found that a novel amyloid structural motif of a triple ?-sheet, with the N-terminal residues interacting with the core (Lys17–Glu22) ?-sheet region, correlates with H/D exchange protection. The triple ?-sheet A?42 oligomer has a minimal exposure of hydrophobic residues and is further stabilized by the E22Q (Dutch) mutation in Alzheimer disease. The experimental H/D exchange solvent protection ratio implies that triple ?-sheet fibrils and globulomers could coexist in the A?42 ensemble, pointing to a broad heterogeneous aggregate population. Our results suggest that an approach that combines computational modeling with NMR protection data can be a useful strategy for obtaining clues to the preferred conformational species of the assemblies in solution and help in alleviating experimental difficulties and consequently possible errors in the exchange data for A?42 fibrils.

Ma, Buyong; Nussinov, Ruth

2011-01-01

296

Conformational dynamics of the bovine mitochondrial ADP/ATP carrier isoform 1 revealed by hydrogen/deuterium exchange coupled to mass spectrometry.  

PubMed

The mitochondrial adenine nucleotide carrier (Ancp) catalyzes the transport of ADP and ATP across the mitochondrial inner membrane, thus playing an essential role in cellular energy metabolism. During the transport mechanism the carrier switches between two different conformations that can be blocked by two toxins: carboxyatractyloside (CATR) and bongkrekic acid. Therefore, our understanding of the nucleotide transport mechanism can be improved by analyzing structural differences of the individual inhibited states. We have solved the three-dimensional structure of bovine carrier isoform 1 (bAnc1p) in a complex with CATR, but the structure of the carrier-bongkrekic acid complex, and thus, the detailed mechanism of transport remains unknown. Improvements in sample processing in the hydrogen/deuterium exchange technique coupled to mass spectrometry (HDX-MS) have allowed us to gain novel insights into the conformational changes undergone by bAnc1p. This paper describes the first study of bAnc1p using HDX-MS. Results obtained with the CATR-bAnc1p complex were fully in agreement with published results, thus, validating our approach. On the other hand, the HDX kinetics of the two complexes displays marked differences. The bongkrekic acid-bAnc1p complex exhibits greater accessibility to the solvent on the matrix side, whereas the CATR-bAnc1p complex is more accessible on the intermembrane side. These results are discussed with respect to the structural and biochemical data available on Ancp. PMID:20805227

Rey, Martial; Man, Petr; Clémençon, Benjamin; Trézéguet, Véronique; Brandolin, Gérard; Forest, Eric; Pelosi, Ludovic

2010-08-30

297

Hydrogen and carbon nanotube production via catalytic decomposition of methane  

NASA Astrophysics Data System (ADS)

The future energy demand is expected to increase significantly due to an increasing world population and demands for higher standards of living and better air quality. Hydrogen is considered as an energy carrier because of its high conversion efficiency and low pollutant emissions. It can be produced from various sources and transformed into electricity and other energy forms with a low pollution. The catalytic decomposition of hydrocarbon has been seen as a really useful method for production of pure hydrogen and for the environmental concern. The objective of this study was to assess the impact of catalyst composition and processing parameters on COx-free hydrogen production and to produce an available solid form of co-product carbon as carbon nanotubes via catalytic decomposition of methane. The optimum experimental conditions for methane decomposition have been investigated. Fe, Co and Ni are used as catalysts (nano materials) over different substrates as SiO2 and MgO to produce hydrogen at optimum temperatures.

Deniz, Cansu; Karatepe, Nilgün

2013-09-01

298

Towards efficient solar hydrogen production by intercalated carbon nitride photocatalyst.  

PubMed

The development of efficient photocatalytic material for converting solar energy to hydrogen energy as viable alternatives to fossil-fuel technologies is expected to revolutionize energy shortage and environment issues. However, to date, the low quantum yield for solar hydrogen production over photocatalysts has hindered advances in the practical applications of photocatalysis. Here, we show that a carbon nitride intercalation compound (CNIC) synthesized by a simple molten salt route is an efficient polymer photocatalyst with a high quantum yield. We found that coordinating the alkali metals into the C-N plane of carbon nitride will induce the un-uniform spatial charge distribution. The electrons are confined in the intercalated region while the holes are in the far intercalated region, which promoted efficient separation of photogenerated carriers. The donor-type alkali metal ions coordinating into the nitrogen pots of carbon nitrides increase the free carrier concentration and lead to the formation of novel nonradiative paths. This should favor improved transport of the photogenerated electron and hole and decrease the electron-hole recombination rate. As a result, the CNIC exhibits a quantum yield as high as 21.2% under 420 nm light irradiation for solar hydrogen production. Such high quantum yield opens up new opportunities for using cheap semiconducting polymers as energy transducers. PMID:24061109

Gao, Honglin; Yan, Shicheng; Wang, Jiajia; Huang, Yu An; Wang, Peng; Li, Zhaosheng; Zou, Zhigang

2013-10-01

299

Hydrogen Isotopic Exchange Rates Between Deuterium-rich Sources (UV Irradiated Molecular Hydrogen and Liquid Water) and an Organic Molecule: Implications for the Conditions of Formation of the Insoluble Organic Matter in the Early Solar System  

NASA Astrophysics Data System (ADS)

The rate of deuterium exchange between the C-H bonds of the insoluble organic matter (IOM) and H3+ confirm the interpretation according to which IOM could get its deuterium in the dense and UV irradiated protosolar disk.

Thomen, A.; Robert, F.; Derenne, S.

2008-03-01

300

Superconductivity in the Niobium-Deuterium and Palladium-Hydrogen Systems in Relation to Their Phase Diagrams.  

NASA Astrophysics Data System (ADS)

In Part A of this thesis the concentration dependence of the superconducting transition temperature for the NbD(,x) alloys over the concentration range 0 (LESSTHEQ) X = D/Nb (LESSTHEQ) 0.75 was examined. An a.c. susceptibility method was used for locating the transition and the change in susceptibility per unit volume of the NbD(,x) alloys as a function of D/Nb was determined. The results are consistent with the residence of the superconductivity in the (alpha)-phase of the Nb-D(H) system (essentially pure Nb at low temperatures) as the deuterium concentration is increased. A comparison with previous work on the superconducting transition in NbH(,x) alloys reveals that there is no significant isotope effect on the superconducting transition temperature as was indicated by Welter and Johnen (21). In Part B measurements have been made of the superconducting transition temperature, together with the bulk magnetization as a function of applied field, for superconducting PdH(,x) alloys over the concentration range 0.82(, )<(, )X = H/Pd(, )<(, )0.91. The observed magnetization behaviour is consistent with the presence of two superconducting forms of PdH(,x) in the concentration range 0.84(, )<(, )X(, )<(, )0.91 which can be regarded as a mixed phase region giving superconducting behaviour similar to that which has been observed for mixed phase regions in some other alloy systems. Specific heat measurements near T(,c) were also performed for two D/Pd values. The results of these measurements clearly confirm the presence of two superconducting phases of PdH(,x)(D(,x)) in the sample each having a slightly different transition temperature. The relative concentration for these phases and the H concentration of each phase depends on the cooling rate of the PdH(,x)(D(,x)) sample; this implies that experimental T(,c)(X) data can no longer be used with confidence as one of the means of testing theories of superconductivity in PdH(,x) unless the exact relative abundance for, and the H concentration of, the two phases is known. Also the present work shows that in the concentration range investigated, PdH(,x) alloys are type II, strong coupling superconductors.

Balbaa, Ibrahim Sabri Lotfi

301

Effects of hydrogen and amorphous carbon on the microwave absorption of carbon nanotubes  

NASA Astrophysics Data System (ADS)

Plans for experiments studying the effects of hydrogen on the microwave absorption of carbon nanotubes are described, including details concerning the construction of experimental apparatus. Previous studies have shown that carbon nanotubes emit infrared, visible, and ultraviolet radiation under microwave fields. Theoretical studies of this phenomenon have suggested that either vibrational resonances or interactions of the microwaves with metal catalysts are responsible for the observed radiation emission. Our plans involve comparing the emission spectra for unpurified carbon nanotubes synthesized via arc-discharge using nickel and cobalt catalysts with single-walled carbon nanotubes synthesized via chemical vapor deposition using iron catalyst. Additionally, the emission spectra of samples that have undergone hydrogen absorption will be compared to samples that have not as part of an effort to help understand the mechanism(s) responsible for the exothermic reactions observed when nanotubes are irradiated with microwaves.

Sayavedra, C. R.; Gonzales, D.; Cavness, B. S.; Williams, S.

2012-03-01

302

Laser induced crystallization of hydrogenated amorphous silicon-carbon alloys  

SciTech Connect

Laser induced crystallization of hydrogenated amorphous silicon carbon alloy (a-Si{sub 1-x}C{sub x}:H) films has been investigated by means of synchrotron x-ray diffraction. The a-Si{sub 1-x}C{sub x}:H films were deposited on (100) silicon wafers by very high frequency plasma enhanced chemical vapor deposition at 100 MHz in hydrogen diluted silane-methane gas mixtures. The substrate was kept at 250 deg. C or 350 deg. C and the stoichiometry was changed from x=0.20 to 0.63. The structural characterization of the as-grown films has been carried out by Rutherford backscattering (hydrogen concentration) and infrared spectroscopy (film ordering). The films were irradiated by a KrF excimer laser (248 nm) with varying energy density and number of pulses. After irradiation, the formation of SiC crystallites has been revealed by synchrotron x-ray diffraction. Besides SiC nanocrystals, the formation of crystalline Si and graphite is observed for under- (x<0.50) and over-stoichiometric (x>0.50) samples, respectively. The essential role played by hydrogen concentration and hydrogen bonding configuration in determining the melting threshold and the consequent SiC grain formation is highlighted.

Summonte, C.; Rizzoli, R.; Servidori, M.; Milita, S.; Nicoletti, S.; Bianconi, M.; Desalvo, A.; Iencinella, D. [CNR-IMM Section of Bologna, Via Gobetti 101, I-40129 Bologna (Italy); DICASM, University of Bologna, Viale Risorgimento 2, I-40136 Bologna (Italy)

2004-10-01

303

Hetero-atoms as activation centers for hydrogen absorption in carbon nanotubes  

Microsoft Academic Search

Carbon materials should have specific centers for hydrogen adsorption\\/absorption. The role of heteroatom substitution in carbon nanotubes as an activator has been identified by Density Functional Theory. The effect of various hetero-atoms like nitrogen, phosphorus, sulphur and boron for hydrogen activation and their geometrical positions has been recognized as the one of the possible reasons for easy hydrogenation. Experimentally, nitrogen

B. Viswanathan; M. Sankaran

2009-01-01

304

The influence of textural properties on the adsorption of hydrogen on ordered nanostructured carbons  

Microsoft Academic Search

The design of an efficient hydrogen storage device is a major key point for the development of this fuel in mobile applications. Hydrogen physisorption on porous carbon materials is one among the different technologies which could be used. Although numerous types of carbon materials have been tested, the hydrogen adsorption capacities measured are far from reaching the goal proposed by

Roger Gadiou; Seif-Eddine Saadallah; Thierry Piquero; Patrick David; Julien Parmentier; Cathie Vix-Guterl

2005-01-01

305

Determination of the gamma-ray asymmetry in the capture of polarized neutrons on hydrogen and deuterium.  

SciTech Connect

The n+p{yields}d+{gamma} experiment measures the parity-violating directional gamma-ray asymmetry, A{gamma}, with uncertainties of 0.5x10{sup -8} when cold polarized neutrons are captured by para-hydrogen. This precision measurement will determine the long-range pion-nucleon weak coupling constant, H{sub {pi}}{sup 1}, with a precision of 10% of its predicted value, and thus will help to clarify our understanding of the weak interaction between nucleons. The n+p{yields}d+{gamma} experiment on the SNS beamline 14B is designed to take advantage of the high intensity of the source and its pulsed nature. The experiment requires a 30-Hz pulsed beam for optimal performance. In three months of run time the experiment will achieve a statistical uncertainty of 0.5x10{sup -8}.

Bowman, J. D. (J. David); Greene, G. L. (Geoff L.); Knudson, J. N. (James N.); Lamoreaux, Steve Keith; Mitchell, G. S. (Gregory S.); Morgan, G. L. (George Lake); Wilburn, W. S. (Wesley S.); Yuan, V. W. (Vincent W.); Penttila, S. I. (Seppo I.)

2001-01-01

306

Facile synthesis of hydrogenated carbon nanospheres with a graphite-like ordered carbon structure.  

PubMed

We report a synthesis of hydrogenated carbon nanospheres (HCNSs) via a facile solvothermal route at low temperatures (60-100 °C), using CHCl3 as the carbon source and potassium (K) as the reductant. Selective cleavage of the relatively lower stable C-Cl bonds (compared to C-H bonds) of the carbon precursor (CHCl3) by K metal results in the growth of HCNSs. The diameter of HCNSs ranges from 40 to 90 nm. The HCNSs have a graphite-like ordered carbon structure in spite of their high degree of hydrogenation. The HCNSs exhibit an average Brunauer-Emmett-Teller (BET) surface area of 43 m(2) g(-1), containing a small amount of mesopores and macropores in the structure. The nanospheres' sample as an anode material for lithium ion batteries (LIBs) has been studied. It exhibits a high discharge capacity (3539 mA h g(-1) in the first cycle, 978 mA h g(-1) after 50 cycles) and good cycling stability, demonstrating advantages as a promising candidate for anode materials in LIBs. The high capacity of the HCNSs is due to their unique nanostructures and high percentage hydrogenation, as well as hydrogenation induced structural defects. PMID:24096808

Xiao, Junping; Yao, Mingguang; Zhu, Kai; Zhang, Dong; Zhao, Shijia; Lu, Shuangchen; Liu, Bo; Cui, Wen; Liu, Bingbing

2013-10-04

307

Hydrogenation of carbon–carbon multiple bonds: chemo-, regio- and stereo-selectivity  

Microsoft Academic Search

Results of the last decade with respect to the selective hydrogenation of hydrocarbons with multiple unsaturation (dienes and alkynes) over heterogeneous palladium catalysts are reviewed. Factors such as metal dispersion, carbon deposits, and the use of promoters and additives controlling catalytic activities and chemo-, regio- and stereo-selectivity are discussed. A detailed treatment of the status of the selective removal of

Árpád Molnár; Antal Sárkány; Mónika Varga

2001-01-01

308

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

PubMed

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

Laurenczy, Gábor

2011-01-01

309

Pionic Deuterium  

NASA Astrophysics Data System (ADS)

The strong interaction shift ?1s?D and broadening ?1s?D in pionic deuterium have been remeasured with high statistics by means of the ?D(3p - 1s) X-ray transition using the cyclotron trap and a high-resolution crystal ?D ?D spectrometer. Preliminary results are ?1s?D = (-2325 ± 31) meV (repulsive) and ?1s?D(1171+23-49) meV which yields for the ?D scattering length a?D = [-(24.8 ± 0.3) + i (6.3-0.3+0.1)] · 10-3 m?-1. From the imaginary part the threshold parameter for pion production is determined to be ? = (252-11+15) µb.

Strauch, Th.; Amaro, F. D.; Anagnostopoulos, D. F.; Bühler, P.; Covita, D. S.; Gorke, H.; Gotta, D.; Gruber, A.; Hirtl, A.; Indelicato, P.; Le Bigot, E.-O.; Nekipelov, M.; Dos Santos, J. M. F.; Schmid, Ph.; Schlesser, S.; Simons, L. M.; Trassinelli, M.; Veloso, J. F. C. A.; Zmeskal, J.

2010-04-01

310

Hydrogen Storage in Carbon Nanostructures: Possibilities and Challenges for Fundamental Molecular Simulations  

Microsoft Academic Search

This paper discusses the potential for hydrogen storage in carbon nanostructures through a better understanding at the fundamental molecular level. The use of hydrogen as a fuel is limited in large part because of lack of progress in developing suitable storage and delivery systems. Materials that adsorb significant quantities of hydrogen are therefore urgently needed. The special hydrogen adsorbing characteristics

Soumik Banerjee; Sohail Murad; Ishwar K. Puri

2006-01-01

311

Kinetic effect of Pd additions on the hydrogen uptake of chemically activated, ultramicroporous carbon  

SciTech Connect

The effect of mixing chemically-activated ultramicroporous carbon (UMC) with Pd nanopowder is investigated. Results show that Pd addition doubles the rate of hydrogen uptake, but does not enhance the hydrogen capacity or improve desorption kinetics. The effect of Pd on the rate of hydrogen adsorption supports the occurrence of the hydrogen spillover mechanism in the Pd - UMC system.

Bhat, Vinay V [ORNL; Contescu, Cristian I [ORNL; Gallego, Nidia C [ORNL

2010-01-01

312

Laser annealing study of PECVD deposited hydrogenated amorphous silicon carbon alloy films  

Microsoft Academic Search

The influence of carbon content on the crystallization process has been investigated for the excimer laser annealed hydrogenated amorphous silicon carbon alloy films deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD) technique, using silane methane gas mixture diluted in helium, as well as for the hydrogenated microcrystalline silicon carbon alloy films prepared by PECVD from silane methane gas mixture highly

U. Coscia; G. Ambrosone; F. Gesuele; V. Grossi; V. Parisi; S. Schutzmann; D. K. Basa

2007-01-01

313

The Influence of Microporosity on the Hydrogen Storage Capacity of Ordered Mesoporous Carbons  

Microsoft Academic Search

The adsorption of hydrogen on nanostructured carbons prepared by templating of mesoporous silicas has been studied at 77 K and between 0.1 and 1 MPa. The maximum capacity was obtained with a carbon synthetized by a sucrose liquid infiltration process in MCM-48 silica. It was observed that the hydrogen weight percentage which can be adsorbed on a carbon can be

Roger Gadiou; Nathalie Texier-Mandoki; Thierry Piquero; Seif-Eddine Saadallah; Julien Parmentier; Joël Patarin; Patrick David; Cathie Vix-Guterl

2005-01-01

314

Deuteration of triborane(7) adducts with anhydrous deuterium chloride  

Microsoft Academic Search

A hydrogen-deuterium exchange reaction between triborane(7) adducts and deuterium chloride is reported which involves all the hydrogen atoms in the BâHâ moiety and proceeds rapidly even at low temperatures. The exchange reaction is reported to proceed much faster in dichloromethane solution than in tetrahydrofuran. (BLM)

Alan R. Dodds; Goji. Kodama

1977-01-01

315

Hydrogen sensing with diameter- and chirality-sorted carbon nanotubes.  

PubMed

The work function of palladium is known to be sensitive to hydrogen by the formation of a surface dipole layer or Pd hydride. One approach to detect such a change in the work function can be based on the formation of a Schottky barrier between the palladium metal and a semiconductor. Here, we study the hydrogen sensitivity of Schottky barrier field-effect transistors made for the first time from diameter- and chirality-sorted semiconducting single-walled carbon nanotubes (s-SWNTs) in contact with Pd electrodes. We observe an unrivaled 100-fold change in the on-state conductance at 100 ppm H2 compared to air for devices with s-SWNT and diameters between 1 and 1.6 nm. Hydrogen sensing is not observed for devices of Pd-contacted few-layer graphene (FLG), as expected due to the absence of a significant Schottky barrier. Unexpectedly, we observe also a vanishing sensitivity for small-diameter SWNTs. We explain this observation by changes in the nanotube work function caused by spillover and chemisorption of atomic hydrogen onto small-diameter nanotubes. We also observe that long-term sensing stability is only achieved if the gate voltage is inverted periodically. Under constant gate bias, the sensitivity reduces with time, which we relate to gate screening by accumulated charges in the substrate. PMID:21341751

Ganzhorn, Marc; Vijayaraghavan, Aravind; Dehm, Simone; Hennrich, Frank; Green, Alexander A; Fichtner, Maximilian; Voigt, Achim; Rapp, Michael; von Löhneysen, Hilbert; Hersam, Mark C; Kappes, Manfred M; Krupke, Ralph

2011-02-22

316

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

SciTech Connect

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

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

1995-04-01

317

A reverse Monte Carlo modelling study of amorphous hydrogenated carbon  

NASA Astrophysics Data System (ADS)

The results of a Reverse Monte Carlo (RMC) modelling of amorphous hydrogenated carbon (a-C:H) are presented. The RMC method has been implemented with the introduction of maximum co-ordination number and "triplet" constraints, whilst fitting both neutron and x-ray diffraction data. The positions of 5000 "atoms" in a box, with full periodicity, are altered until the associated model structure factor, S(Q), and pair distribution function, G(r), agree with the analogous experimental data within the errors. Once the data has been fitted, it is possible to generate model partial pair distribution functions (i.e. those associated with C-C, C-H and H-H), bond angle distributions, co-ordination number distributions, etc. X-ray data is used to provide information on the carbon-carbon network, whilst neutrons are also sensitive to the cross-terms involving hydrogen. The fitting of both types of data simultaneously therefore provides sufficient information to generate a viable "physical" model for the structure of these materials. The effects of increasing the number density inside the box have also been investigated.

Walters, J. K.; Rigden, J. S.; Newport, R. J.

1995-01-01

318

Carbon Erosion and Dust Formation under Heavy Atomic Hydrogen Irradiation  

NASA Astrophysics Data System (ADS)

Experiments on erosion and dust formation on graphite materials have been performed using high power induction plasmas containing high atomic hydrogen flux (˜1024 m-2 s-1 ). Chemical sputtering by atomic hydrogen irradiation with an incident energy below 1 eV eroded the graphite targets significantly, and the sputtering yield was roughly estimated to be 0.002-0.005, which is as high as that obtained by ion beam experiments. The transport of the released hydrocarbon along the gas flow results in carbon dust formation on the eroded graphite target and also on the silicon and graphite targets located at the remote position. The dust structure strongly depends on the target surface temperature, and the graphite dust turns into diamond crystals when the surface temperature rises to 1100 K.

Takeguchi, Yuji; Kyo, Masaaki; Uesugi, Yoshihiko; Tanaka, Yasunori; Masuzaki, Suguru

319

Interrupted hydrogen/deuterium exchange reveals the stable core of the remarkably helical molten globule of alpha-beta parallel protein flavodoxin.  

PubMed

Kinetic intermediates that appear early during protein folding often resemble the relatively stable molten globule intermediates formed by several proteins under mildly denaturing conditions. Molten globules have a substantial amount of secondary structure but lack virtually all tertiary side-chain packing characteristics of natively folded proteins. Due to exposed hydrophobic groups, molten globules are prone to aggregation, which can have detrimental effects on organisms. The molten globule that is observed during folding of alpha-beta parallel flavodoxin from Azotobacter vinelandii is a remarkably non-native species. This folding intermediate is helical and contains no beta-sheet and is kinetically off-pathway to the native state. It can be trapped under native-like conditions by substituting residue Phe(44) for Tyr(44). To characterize this species at the residue level, in this study, use is made of interrupted hydrogen/deuterium exchange detected by NMR spectroscopy. In the molten globule of flavodoxin, the helical region comprising residues Leu(110)-Val(125) is shown to be better protected against exchange than the other ordered parts of the folding intermediate. This helical region is better buried than the other helices, causing its context-dependent stabilization against unfolding. Residues Leu(110)-Val(125) thus form the stable core of the helical molten globule of alpha-beta parallel flavodoxin, which is almost entirely structured. Non-native docking of helices in the molten globule of flavodoxin prevents formation of the parallel beta-sheet of native flavodoxin. Hence, to produce native alpha-beta parallel protein molecules, the off-pathway species needs to unfold. PMID:19959481

Nabuurs, Sanne M; van Mierlo, Carlo P M

2009-12-03

320

Hydrogen/deuterium exchange mass spectrometry and site-directed disulfide cross-linking suggest an important dynamic interface between the two lysostaphin domains.  

PubMed

Lysostaphin is a peptidoglycan hydrolase secreted by Staphylococcus simulans. It can specifically lyse Staphylococcus aureus and is being tested as a novel antibacterial agent. The protein contains an N-terminal catalytic domain and a C-terminal cell wall targeting domain. Although the two domains from homologous enzymes were structurally determined, the structural organization of lysostaphin domains remains unknown. We used hydrogen/deuterium exchange mass spectrometry (H/DX-MS) and site-directed disulfide cross-linking to probe the interface between the lysostaphin catalytic and targeting domains. H/DX-MS-mediated comparison of peptides from full-length lysostaphin and the separated domains identified four peptides of lower solvent accessibility in the full-length protein. Cross-linking analysis using cysteine pair substitutions within those peptides showed that two pairs of cysteines can form disulfide bonds, supporting the domain association role of the targeted peptides. The cross-linked mutant exhibited a binding capacity to S. aureus that was similar to that of the wild-type protein but reduced bacteriolytic activity probably because of restraint in conformation. The diminished activity was further reduced with increasing NaCl concentrations that can cause contractions of bacterial peptidoglycan. The lytic activity, however, could be fully recovered by reducing the disulfide bonds. These results suggest that lysostaphin may require dynamic association of the two domains for coordinating substrate binding and target cleavage on the elastic peptidoglycan. Our study will help develop site-specific PEGylated lysostaphin to treat systemic S. aureus infections. PMID:23380729

Lu, Hai-Rong; Gu, Mei-Gang; Huang, Qiang; Huang, Jin-jiang; Lu, Wan-Ying; Lu, Hong; Huang, Qing-Shan

2013-02-04

321

Distinct interaction modes of an AKAP bound to two regulatory subunit isoforms of protein kinase A revealed by amide hydrogen/deuterium exchange.  

PubMed

The structure of an AKAP docked to the dimerization/docking (D/D) domain of the type II (RIIalpha) isoform of protein kinase A (PKA) has been well characterized, but there currently is no detailed structural information of an AKAP docked to the type I (RIalpha) isoform. Dual-specific AKAP2 (D-AKAP2) binds in the nanomolar range to both isoforms and provided us with an opportunity to characterize the isoform-selective nature of AKAP binding using a common docked ligand. Hydrogen/deuterium (H/D) exchange combined with mass spectrometry (DXMS) was used to probe backbone structural changes of an alpha-helical A-kinase binding (AKB) motif from D-AKAP2 docked to both RIalpha and RIIalpha D/D domains. The region of protection upon complex formation and the magnitude of protection from H/D exchange were determined for both interacting partners in each complex. The backbone of the AKB ligand was more protected when bound to RIalpha compared to RIIalpha, suggesting an increased helical stabilization of the docked AKB ligand. This combined with a broader region of backbone protection induced by the AKAP on the docking surface of RIalpha indicated that there were more binding constraints for the AKB ligand when bound to RIalpha. This was in contrast to RIIalpha, which has a preformed, localized binding surface. These distinct modes of AKAP binding may contribute to the more discriminating nature of the RIalpha AKAP-docking surface. DXMS provides valuable structural information for understanding binding specificity in the absence of a high-resolution structure, and can readily be applied to other protein-ligand and protein-protein interactions. PMID:16260760

Burns-Hamuro, Lora L; Hamuro, Yoshitomo; Kim, Jack S; Sigala, Paul; Fayos, Rosa; Stranz, David D; Jennings, Patricia A; Taylor, Susan S; Woods, Virgil L

2005-10-31

322

Distinct interaction modes of an AKAP bound to two regulatory subunit isoforms of protein kinase A revealed by amide hydrogen/deuterium exchange  

PubMed Central

The structure of an AKAP docked to the dimerization/docking (D/D) domain of the type II (RII?) isoform of protein kinase A (PKA) has been well characterized, but there currently is no detailed structural information of an AKAP docked to the type I (RI?) isoform. Dual-specific AKAP2 (D-AKAP2) binds in the nanomolar range to both isoforms and provided us with an opportunity to characterize the isoform-selective nature of AKAP binding using a common docked ligand. Hydrogen/deuterium (H/D) exchange combined with mass spectrometry (DXMS) was used to probe backbone structural changes of an ?-helical A-kinase binding (AKB) motif from D-AKAP2 docked to both RI? and RII? D/D domains. The region of protection upon complex formation and the magnitude of protection from H/D exchange were determined for both interacting partners in each complex. The backbone of the AKB ligand was more protected when bound to RI? compared to RII?, suggesting an increased helical stabilization of the docked AKB ligand. This combined with a broader region of backbone protection induced by the AKAP on the docking surface of RI? indicated that there were more binding constraints for the AKB ligand when bound to RI?. This was in contrast to RII?, which has a preformed, localized binding surface. These distinct modes of AKAP binding may contribute to the more discriminating nature of the RI? AKAP-docking surface. DXMS provides valuable structural information for understanding binding specificity in the absence of a high-resolution structure, and can readily be applied to other protein–ligand and protein–protein interactions.

Burns-Hamuro, Lora L.; Hamuro, Yoshitomo; Kim, Jack S.; Sigala, Paul; Fayos, Rosa; Stranz, David D.; Jennings, Patricia A.; Taylor, Susan S.; Woods, Virgil L.

2005-01-01

323

Role of Calcium in the Conformational Dynamics of Factor XIII Activation Examined by Hydrogen/Deuterium Exchange Coupled with MALDI-TOF MS  

PubMed Central

Factor XIII catalyzes formation of ?-glutamyl-?-lysyl crosslinks within fibrin clots. FXIII A2 can be activated proteolytically with thrombin and low mM Ca2+ or nonproteolytically with high monovalent/divalent cations along with low mM Ca2+. Physiologically, FXIII A2 is poised to respond to transient influxes of Ca2+ in a Na+ containing environment. A successful strategy to monitor FXIII conformational events is hydrogen-deuterium exchange (HDX) coupled with mass spectrometry. FXIII A2 was examined in the presence of different cations (Ca2+, Mg2+, Ba2+, Cu2+, Na+, TMAC+, and EDA2+) ranging from 1–2 mM, physiological Ca2+ concentration, to 50–500mM for nonproteolytic activation. Increases in FXIII solvent exposure could already be observed at 1 mM Ca2+ 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 Ca2+ is insufficient for FXIII activation. The metals 1mM Mg2+, 1mM Ba2+, and 1mM Cu2+ each led to conformational changes, many in the same FXIII regions as Ca2+. FXIII could also be activated nonproteolytically with 500mM tetramethylammonium chloride (TMAC+) and 500mM ethylenediamine (EDA2+), both with 2mM Ca2+. These different HDX studies help reveal the first FXIII segments that respond to physiological Ca2+ levels.

Woofter, Ricky T.; Maurer, Muriel C.

2011-01-01

324

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

2011-05-26

325

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

SciTech Connect

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

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

1987-07-28

326

Hydrogen storage for carbon nanotubes synthesized by the pyrolysis method using lanthanum nickel alloy as catalyst  

Microsoft Academic Search

We have investigated the adsorption of hydrogen of multiwall carbon nanotubes synthesized by the pyrolysis method using a lanthanum nickel hydrogen storage alloy as a catalyst. The mechanism of carbon nanotubes synthesized using a La-Ni alloy catalyst is discussed. In the hydrogen atmosphere and high-temperature process of carbon nanotube preparation, the LaNi5 alloy particle may be changed into an intermetallic

Haiyan Zhang; Yimin Chen; Shunhua Li; Xiaojuan Fu; Yanjuan Zhu; Shuangping Yi; Xinmin Xue; Yanyang He; Yulian Chen

2003-01-01

327

Microwave attenuation of hydrogen plasma in carbon nanotubes  

SciTech Connect

The attenuation (ATT) of hydrogen plasma in carbon nanotubes, grown by iron-catalyzed high-pressure carbon monoxide disproportionate process, is investigated. The effects of the incident wave, the electron density, the collision frequency, the thermal frequency, and the cyclotron frequency on the ATT of the microwave are discussed. Moreover, the impacts of thermal frequency and cyclotron frequency on the ATT are investigated separately. Numerical results indicate that position of the ATT peak and the ATT level depend on the incident frequency, the electron density, the collision frequency, the thermal frequency, and the cyclotron frequency. The results show that the cyclotron frequency highly influences the ATT level. In contrast, the shift frequency is more affected by the thermal frequency. The ATT is more sensitive at the middle band of incident frequency.

Babaei, S.; Solari, M. Sh. [Department of Physics, Amirkabir University of Technology, Tehran 15875-4413 (Iran, Islamic Republic of) and Amirkabir Nanotechnology Research Institute (NTRI), Tehran 15914 (Iran, Islamic Republic of)

2008-12-15

328

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

329

Effect of carbon\\/noncarbon addition on hydrogen storage behaviors of magnesium hydride  

Microsoft Academic Search

Various Mg\\/carbon and Mg\\/noncarbon composite systems were prepared by mechanical milling and their hydrogen storage behaviors were investigated. It was found that all the carbon additives exhibited prominent advantage over the noncarbon additives, such as BN nanotubes (BNNTs) or asbestos in improving the hydrogen capacity and dehydriding\\/hydriding kinetics of Mg. And among the various carbon additives, purified single-walled carbon nanotubes

C. Z. Wu; P. Wang; X. Yao; C. Liu; D. M. Chen; G. Q. Lu; H. M. Cheng

2006-01-01

330

Isotopic exchange of carbon-bound hydrogen over geologic timescales  

NASA Astrophysics Data System (ADS)

The increasing popularity of compound-specific hydrogen isotope (D/H) analyses for investigating sedimentary organic matter raises numerous questions about the exchange of carbon-bound hydrogen over geologic timescales. Important questions include the rates of isotopic exchange, methods for diagnosing exchange in ancient samples, and the isotopic consequences of that exchange. This article provides a review of relevant literature data along with new data from several pilot studies to investigate such issues. Published experimental estimates of exchange rates between organic hydrogen and water indicate that at warm temperatures (50-100°C) exchange likely occurs on timescales of 10 4 to 10 8 yr. Incubation experiments using organic compounds and D-enriched water, combined with compound-specific D/H analyses, provide a new and highly sensitive method for measuring exchange at low temperatures. Comparison of ?D values for isoprenoid and n-alkyl carbon skeletons in sedimentary organic matter provides no evidence for exchange in young (<1 Ma), cool sediments, but strong evidence for exchange in ancient (>350 Ma) rocks. Specific rates of exchange are probably influenced by the nature and abundance of organic matter, pore-water chemistry, the presence of catalytic mineral surfaces, and perhaps even enzymatic activity. Estimates of equilibrium fractionation factors between organic H and water indicate that typical lipids will be depleted in D relative to water by ˜75 to 140‰ at equilibrium (30°C). Thus large differences in ?D between organic molecules and water cannot be unambiguously interpreted as evidence against hydrogen exchange. A better approach may be to use changes in stereochemistry as a proxy for hydrogen exchange. For example, estimated rates of H exchange in pristane are similar to predicted rates for stereochemical inversion in steranes and hopanes. The isotopic consequences of this exchange remain in question. Incubations of cholestene with D 2O indicate that the number of D atoms incorporated during structural rearrangements can be far less than the number of C-H bonds that are broken. Sample calculations indicate that, for steranes in immature sediments, the D/H ratio imparted by biosynthesis may be largely preserved in spite of significant structural changes.

Sessions, Alex L.; Sylva, Sean P.; Summons, Roger E.; Hayes, John M.

2004-04-01

331

HYBRID HETEROGENEOUS CATALYSTS FOR HYDROGENATION OF CARBON DIOXIDE  

SciTech Connect

HYBRID HETEROGENEOUS CATALYSTS FOR HYDROGENATION OF CARBON DIOXIDE Lucia M. Petkovic, Harry W. Rollins, Daniel M. Ginosar, and Kyle C. Burch Idaho National Laboratory P.O. Box 1625 Idaho Falls, ID 83415-2208 Introduction Anthropogenic emissions of carbon dioxide, a gas often associated with global warming, have increased considerably since the beginning of the industrial age.1 In the U.S., stationary CO2 sources, such as electricity generation plants, produce about one-third of the anthropogenic CO2 generation. Reports2 indicate that the power required to recover 90% of the CO2 from an integrated coal-fired power-plant is about 10% of the power-plant capacity. This energy requirement can be reduced to less than 1% if the recovered CO2 is applied to the production of synthetic fuels. However, the lack of efficient catalysts along with the costs of energy and hydrogen has prevented the development of technologies for direct hydrogenation of CO2.3 Although the cost of hydrogen for hydrogenating CO2 is not economically attractive at present, the future production of hydrogen by nuclear power sources could completely change this scenario.2 Still, an efficient catalyst will be essential for commercial application of those processes. The objective of the work presented here was the development of hybrid catalysts for one-step carbon dioxide hydrogenation to liquid fuels. The hybrid catalysts, which were prepared by two novel techniques, included a copper/zinc oxide catalytic function distributed within an acidic zeolitic matrix. Results of catalyst activity and selectivity studies at atmospheric pressure are presented in this contribution. Experimental Catalysts were prepared by two novel techniques and under several different conditions to produce copper/zinc oxide/zeolite materials. Once synthesized, samples were pelletized and the fraction between 40-60 mesh was utilized for the experiments. Two hundred milligrams of catalyst were loaded in a U-tube stainless steel reactor and a flow of 100 cm3/min of a 10:90 H2:Ar mixture was passed through the catalyst bed while the temperature was increased from room temperature to 513 K at 1.8 K/min and held at 513 K for 15 h. A reactant gas mixture composed by 10 cm3/min of CO2 and 30 cm3/min of H2 was then passed through the catalyst bed and the reaction products monitored by on-line gas chromatographic analyses using an SRI Multiple Gas Analyzer #2 equipped with 3 columns (MoleSieve 13X, Hayesep-D, and MXT-1) and 3 detectors (TCD, FID, and FID-methanizer). This GC system allowed for quantification of inert gases, CO, CO2, methanol, dimethylether, higher alcohols, water, and hydrocarbons up to C20. One hundred milligrams of a commercial syngas-to-methanol catalyst along with the same amount of a commercial zeolite catalyst was utilized under the same reaction conditions for comparison purposes. These catalysts were utilized either in two-layers (Com1) or mixed together (Com2). Results and Discussion Under the conditions applied in this study, the main reaction products were CO, CH3OH, CH3OCH3, and H2O. Methanol and dimethylether production rates and selectivities with respect to CO formation are presented in Figures 1 and 2, respectively. Although the activity of the synthesized catalysts did not surpass the commercial catalysts, the selectivity to oxygenates with respect to CO on most of the synthesized catalysts were better than on the commercial catalysts. For example, cat

Licia M. Petkovic; Harry W. Rollins; Daniel M. Ginosar; Kyle C. Burch

2006-09-01

332

Deuterium Content of Naturally Occurring Water  

Microsoft Academic Search

THE deuterium content of naturally occurring water has so far been determined by two methods-from the mass-spectrogram of the hydrogen derived from it; and from the specific gravity of deuterium-free water. The former method1 gave for the abundance ratio H\\/D the value 5000 +\\/-500, while two discrepant values2,3 have been obtained by the latter, namely 9000 and 5750+\\/-250.

A. J. Edwards; R. P. Bell; J. H. Wolfenden

1935-01-01

333

Deuterium content of the Venus atmosphere  

Microsoft Academic Search

The abundance of deuterium in the atmosphere of Venus is an important clue to the role of water in the planet's history, because ordinary and deuterated water escape the atmosphere at different rates. The high-resolution mode of the IUE was used to measure hydrogen Lyman-alpha emission from Venus, but only an upper limit on deuterium Lyman-alpha emission was found, from

J.-L. Bertaux; J. T. Clarke

1989-01-01

334

Hydrogen Adsorption on Activated Carbon an Carbon Nanotubes Using Volumetric Differential Pressure Technique  

SciTech Connect

A simple hydrogen adsorption measurement system utilizing the volumetric differential pressure technique has been designed, fabricated and calibrated. Hydrogen adsorption measurements have been carried out at temperatures 298 K and 77 K on activate carbon and carbon nanotubes with different surface areas. The adsorption data obtained will be helpful in understanding the adsorption property of the studied carbon materials using the fundamentals of adsorption theory. The principle of the system follows the Sievert-type method. The system measures a change in pressure between the reference cell, R1 and the sample cell S1, S2, S3 over a certain temperature range, R1, S1, S2, and S3 having known fixed volume. The sample temperatures will be monitored by thermocouple TC while the pressures in R1 an S1, S2, S3 will be measured using a digital pressure transducer. The maximum operating pressure of the pressure transducer is 20 bar and calibrated with an accuracy of +-0.01 bar. High purity hydrogen is being used in the system and the amount of samples for the study is between 1.0-2.0 grams. The system was calibrated using helium gas without any samples in S1, S2 an S3. This will provide a correction factor during the adsorption process providing an adsorption free reference point when using hydrogen gas resulting in a more accurate reading of the adsorption process by eliminating the errors caused by temperature expansion effects and other non-adsorption related phenomena. The ideal gas equation of state is applied to calculate the hydrogen adsorption capacity based on the differential pressure measurements. Activated carbon with a surface area of 644.87 m{sup 2}/g showed a larger amount of adsorption as compared to multiwalled nanotubes (commercial) with a surface area of 119.68 m{sup 2}/g. This study als indicated that there is a direct correlation between the amounts of hydrogen adsorbed an surface area of the carbon materials under the conditions studied and that the adsorption significant at 77 K.

Sanip, S. M.; Saidin, M. A. R.; Aziz, M.; Ismail, A. F. [Membrane Research Unit, Faculty of Chemical and Natural Resources Engineering, Universiti Teknologi Malaysia, 81310, Skudai, Johor (Malaysia)

2010-03-11

335

Hypothetical high-surface-area carbons with exceptional hydrogen storage capacities: open carbon frameworks.  

PubMed

A class of high-surface-area carbon hypothetical structures has been investigated that goes beyond the traditional model of parallel graphene sheets hosting layers of physisorbed hydrogen in slit-shaped pores of variable width. The investigation focuses on structures with locally planar units (unbounded or bounded fragments of graphene sheets), and variable ratios of in-plane to edge atoms. Adsorption of molecular hydrogen on these structures was studied by performing grand canonical Monte Carlo simulations with appropriately chosen adsorbent-adsorbate interaction potentials. The interaction models were tested by comparing simulated adsorption isotherms with experimental isotherms on a high-performance activated carbon with well-defined pore structure (approximately bimodal pore-size distribution), and remarkable agreement between computed and experimental isotherms was obtained, both for gravimetric excess adsorption and for gravimetric storage capacity. From this analysis and the simulations performed on the new structures, a rich spectrum of relationships between structural characteristics of carbons and ensuing hydrogen adsorption (structure-function relationships) emerges: (i) Storage capacities higher than in slit-shaped pores can be obtained by fragmentation/truncation of graphene sheets, which creates surface areas exceeding of 2600 m(2)/g, the maximum surface area for infinite graphene sheets, carried mainly by edge sites; we call the resulting structures open carbon frameworks (OCF). (ii) For OCFs with a ratio of in-plane to edge sites ?1 and surface areas 3800-6500 m(2)/g, we found record maximum excess adsorption of 75-85 g of H(2)/kg of C at 77 K and record storage capacity of 100-260 g of H(2)/kg of C at 77 K and 100 bar. (iii) The adsorption in structures having large specific surface area built from small polycyclic aromatic hydrocarbons cannot be further increased because their energy of adsorption is low. (iv) Additional increase of hydrogen uptake could potentially be achieved by chemical substitution and/or intercalation of OCF structures, in order to increase the energy of adsorption. We conclude that OCF structures, if synthesized, will give hydrogen uptake at the level required for mobile applications. The conclusions define the physical limits of hydrogen adsorption in carbon-based porous structures. PMID:22897685

Kuchta, Bogdan; Firlej, Lucyna; Mohammadhosseini, Ali; Boulet, Pascal; Beckner, Matthew; Romanos, Jimmy; Pfeifer, Peter

2012-08-30

336

Morphological and chemical features of nano and macroscale carbons affecting hydrogen peroxide decomposition in aqueous media  

Microsoft Academic Search

Chemical and structural factors of carbon materials affect their activity in adsorption and surface reactions in aqueous media. Decomposition of hydrogen peroxide studied is a probe reaction for exploring parameters of carbons that might be involved, such as specific surface area, nitrogen and oxygen doping and conformational changes. To date, a detailed comparison of the behavior of carbon nanoscale (Carbon

Kateryna V. Voitko; Raymond L. D. Whitby; Vladimir M. Gun’ko; Olga M. Bakalinska; Mykola T. Kartel; Krisztina Laszlo; Andrew B. Cundy; Sergey V. Mikhalovsky

2011-01-01

337

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

SciTech Connect

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

338

Pionic deuterium  

NASA Astrophysics Data System (ADS)

Data taking of the PIONIC HYDROGEN project has been completed with a high statistics study of the strong-interaction effects in ?D by measuring the K? X-radiation for three different target densities with a high resolution Bragg crystal spectrometer. The ?D hadronic shift will provide a constraint for the ?N isospin scattering lengths extracted from the ?H measurement. The hadronic width is directly related to pion production at threshold.

Strauch, Th.; Amaro, F. D.; Anagnostopoulos, D. F.; Bühler, P.; Covita, D. S.; Gorke, H.; Gotta, D.; Gruber, A.; Hirtl, A.; Indelicato, P.; Le Bigot, E.-O.; Marton, J.; Nekipelov, M.; Dos Santos, J. M. F.; Schmid, Ph.; Schlesser, S.; Simons, L. M.; Veloso, J. F. C. A.; Zmeskal, J.

2009-09-01

339

Feasibility of hydrogen production in a steam-carbon electrochemical cell  

Microsoft Academic Search

A high temperature electrochemical cell with a bed of solid carbon at the anode and steam at the cathode is proposed for carbon-assisted hydrogen production. This scheme eliminates the uphill potential barrier and provides a significant reduction in the required electrical work input to produce hydrogen from steam. The electrochemical cell is made of an yttria stabilized zirconia electrolyte with

Andrew C. Lee; Reginald E. Mitchell; Turgut M. Gür

2011-01-01

340

Alkaline fuel cell: carbon nanobeads coated with metal catalyst over porous ceramic for hydrogen electrode  

Microsoft Academic Search

The development of a hydrogen electrode using a porous ceramic coated with carbon nanobeads for an alkaline fuel cell (AFC) is reported. This electrode can provide necessary strength and porosity to enable hydrogen to diffuse without allowing electrolyte to percolate inside the electrode. Various catalysts (Pt, Ni, Co and Fe) are electrochemically dispersed over the carbon nanobeads to examine their

A. K Chatterjee; Maheshwar Sharon; Rangan Banerjee

2003-01-01

341

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

342

Quantitative analysis of hydrogenated diamondlike carbon films by visible Raman spectroscopy  

Microsoft Academic Search

The correlations between properties of hydrogenated diamondlike carbon films and their Raman spectra have been investigated. The films are prepared by plasma deposition technique, keeping different hydrogen to methane ratios during the growth process. The hydrogen concentration, sp3 content, hardness, and optical Tauc gap of the materials have been estimated from a detailed analysis of their Raman spectra. We have

Achintya Singha; Aditi Ghosh; Anushree Roy; Nihar Ranjan Ray

2006-01-01

343

Ab initio study of hydrogen interaction with pure and nitrogen-doped carbon nanotubes  

Microsoft Academic Search

Detailed studies of mechanisms for hydrogen dissociative adsorption and diffusion on pure and nitrogen-doped (8, 0) carbon nanotubes are carried out using the first-principles density functional theory method. (1) For pure carbon nanotubes, we have identified the energetically most favorable dissociative pathway for hydrogen adsorption, with a barrier height of 1.3eV . We also found that the adsorbed hydrogen atoms

Zhiyong Zhang; Kyeongjae Cho

2007-01-01

344

Deuterium tracer studies on hydrotreating catalysts-isotopic exchange between hydrogen and hydrogen sulfide on sulfided NiMo/Al{sub 2}O{sub 3}  

SciTech Connect

The H-D isotopic exchange between H{sub 2} and D{sub 2} and between H{sub 2} (D{sub 2}) and D{sub 2}S (H{sub 2}S) was studied at 80{degree}C in a recycling reactor under a pressure of 2 bar in the presence of a sulfided NiMo/Al{sub 2}O{sub 3} catalyst and by means of gas chromatography. From the H{sub 2}-D{sub 2} exchange an amount of three exchangeable surface hydrogen atoms retained by the catalyst per Mo atom was estimated after sulfiding the catalyst by 10% H{sub 2}S in H{sub 2} at 400{degree}C and sweeping it by helium at 80{degree}C H-D isotope exchange occurred between H{sub 2}(D{sub 2}) and D{sub 2}S(H{sub 2}S). As expected under the reaction conditions, H{sub 2}S(D{sub 2}S) did not produced H{sub 2}(D{sub 2}). The isotope exchange between H{sub 2} and D{sub 2} was about six times faster than the exchange between H{sub 2}(D{sub 2}) and D{sub 2}S(H{sub 2}S). However, it was shown that H{sub 2}S competed with H{sub 2} for adsorption: H{sub 2}S inhibited the exchange between H{sub 2} and D{sub 2}. It is proposed that H{sub 2}(D{sub 2}) and H{sub 2}S(D{sub 2}S) dissociate heterolytically on the same sites, involving both a sulfur vacancy and a sulfur atom. Furthermore, it is suggested that the isotope exchange could occur by dissociation of both reactants on one single center provided that this center possesses at least two coordinative unsaturations. 47 refs., 8 figs., 2 tabs.

Thomas, C.; Vivier, L.; Lemberton, J.L. [Universite de Poitiers (France)] [and others

1997-04-01

345

Kinetic modelling of molecular hydrogen transport in microporous carbon materials.  

PubMed

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(2)/D(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(2) transport is dramatically favored over H(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(2)/D(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. PMID:21442120

Hankel, Marlies; Zhang, Hong; Nguyen, Thanh X; Bhatia, Suresh K; Gray, Stephen K; Smith, Sean C

2011-03-28

346

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

347

40 CFR 415.330 - Applicability; description of the carbon monoxide and by-product hydrogen production subcategory.  

Code of Federal Regulations, 2010 CFR

...carbon monoxide and by-product hydrogen production subcategory. 415.330...Monoxide and By-Product Hydrogen Production Subcategory § 415.330...monoxide and by-product hydrogen production subcategory. The...

2010-07-01

348

40 CFR 415.330 - Applicability; description of the carbon monoxide and by-product hydrogen production subcategory.  

Code of Federal Regulations, 2010 CFR

...carbon monoxide and by-product hydrogen production subcategory. 415.330...Monoxide and By-Product Hydrogen Production Subcategory § 415.330...monoxide and by-product hydrogen production subcategory. The...

2009-07-01

349

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

350

Gas-phase ion\\/molecule isotope-exchange reactions: methodology for counting hydrogen atoms in specific organic structural environments by chemical ionization mass spectrometry  

Microsoft Academic Search

Ion\\/molecule reactions are described which facilitate exchange of hydrogens for deuteriums in a variety of different chemical environments. Aromatic hydrogens in alkylbenzenes, oxygenated benzenes, m-toluidine, m-phenylenediamine, thiophene, and several polycyclic aromatic hydrocarbons and metallocenes are exchanged under positive ion CI conditions by using either DâO, EtOD, or NDâ as the reagent gas. Aromatic hydrogens, benzylic hydrogens, and hydrogens on carbon

Donald F. Hunt; Satinder K. Sethi

1980-01-01

351

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

352

Post-synthesis modifications of SBA15 carbon replicas: Improving hydrogen storage by increasing microporous volume  

Microsoft Academic Search

SBA-15 carbon replicas were synthesized with a sucrose solution as carbon source, carrying out carbonization at two different temperatures (800 and 1000°C). Carbon pyrolised at 800°C showed higher BET surface area and was chosen for further post-synthesis activation treatments (physical via CO2 or chemical via KOH), with the aim of improving hydrogen adsorption capacity. For comparison, an amorphous carbon was

M. Armandi; B. Bonelli; E. I. Karaindrou; C. Otero Areán; E. Garrone

2008-01-01

353

Piezoresistive Silicon Microresonator for Measurements of Hydrogen Adsorption in Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

In this paper, the mass detection of hydrogen adsorption using a piezoresistive resonant silicon microresonator is presented. The working principle relies on the resonant frequency shifts of the cantilevered resonator with a sample due to hydrogen adsorption. The mass of adsorbed hydrogen in carbon nanotubes (CNTs) grown on the resonator is measured experimentally after exposing to high pressure hydrogen. The mass of CNTs on the resonator is measured from resonant frequency change after the removal. According to masses of the adsorbed hydrogen and CNTs, we obtain the adsorption capacity of hydrogen into CNTs.

An, Zhonglie; Esashi, Masayoshi; Ono, Takahito

2012-11-01

354

Deposition of hydrogenated amorphous carbon and silicon-carbon thin films in low energy RF magnetron plasmas  

Microsoft Academic Search

Studies have been made of the room temperature deposition of hydrogenated amorphous carbon and hydrogenated amorphous silicon-carbon in a magnetron discharge system at low ion energy (Ei approximately 30 eV), high density (ne approximately 1011 cm-3) and low pressure ( approximately 5 mTorr) with CH4\\/Ar and CH4\\/SiH4\\/Ar gas mixtures respectively. A gas flow rate modulation technique was introduced to investigate

Lin I; Ming-Shing Wu

1992-01-01

355

Deuterium recombination coefficients on tungsten exposed to RF plasma  

NASA Astrophysics Data System (ADS)

Deuterium recombination coefficients on pure tungsten have been experimentally studied. Tungsten samples were continuously exposed to deuterium RF plasma and, simultaneously, deuterium surface densities and bulk concentrations were observed by using a nuclear reaction analysis. From consideration of deuterium particle balance between surface and bulk, the recombination coefficient on the plasma-exposed surface, ku = 4.5 × 10-25 exp(-0.78 eV/kT) m4 s-1, was obtained at temperature range of 426-654 K. A potential energy diagram for hydrogen (deuterium) near tungsten surface was proposed based on the results. The diagram indicates that tungsten hardly absorbs hydrogen molecules and hydrogen atoms once entering into tungsten are not easily desorbed due to a high potential barrier between surface and vacuum.

Takagi, I.; Imade, R.; Ikegami, Y.; Akiyoshi, M.; Moritani, K.; Sasaki, T.; Moriyama, H.

2011-10-01

356

Transferrin--interactions of lactoferrin with hydrogen carbonate.  

PubMed

The interaction of apolactoferrin with hydrogen carbonate (bicarbonate) has been investigated in the pH range 6.5-9.2. In the absence of bicarbonate apolactoferrin loses a single proton with pK1a of 8.10. This proton loss is independent of the interaction with the synergistic anion. The C-site of apolactoferrin interacts with bicarbonate with a very low affinity (K(-1)C = 3.2 M(-1)). This process is accompanied by a proton loss, which is probably provided by the bicarbonate in interaction with the protein. This proton loss can possibly be the result of a shift in the proton dissociation constant, pKa, of the bicarbonate/carbonate acid/base equilibrium, which would decrease from pKa 10.35 to pK2a 6.90 in the bicarbonate-lactoferrin adduct. The N-site of the protein interacts with bicarbonate with an extremely low affinity, which excludes the presence of the N-site-synergistic anion adduct in neutral physiological media. Contrary to serum transferrin, the concentration of the apolactoferrin in interaction with bicarbonate is pH dependent. Between pH 7.4 and pH 9 with [HCO3-] about 20 mM, the concentration of the serum transferrin-bicarbonate adduct is always about 30%, whereas that of the apolactoferrin-synergistic anion adduct varies from 25% at pH 7.5 to 90% at pH 9. This implies that, despite an affinity for bicarbonate two orders of magnitude lower than that of serum transferrin, lactoferrin interacts better with the synergistic anion. This can be explained by the possible interaction of lactoferrin with carbonate in neutral media, whereas transferrin only interacts with bicarbonate. PMID:9363766

Pakdaman, R; El Hage Chahine, J M

1997-10-01

357

Purification of single-walled carbon nanotubes synthesized by the hydrogen arc-discharge method  

Microsoft Academic Search

A simple procedure for the purification of the single-walled carbon nanotube (SWNT) product synthesized by the hydrogen arc-discharge method was proposed and discussed. The procedure involves ultrasonication in alcohol, oxidation in fixed air, and soaking in hydrochloric acid. Most of the amorphous carbon and carbon nanoparticles as well as metal particles in the product was successfully removed, according to the

Pengxiang Hou; Chang Liu; Yu Tong; Shitao Xu; Min Liu; Huiming Cheng

2001-01-01

358

Tribological behavior and gas-surface interactions of hydrogenated carbon films  

Microsoft Academic Search

Diamond-like carbon films are used as tribological coatings for surfaces of devices that see relative motion. One class of highly hydrogenated diamond-like carbon coatings, termed near frictionless carbon (NFC), have experimentally shown extremely low friction coefficients and wear rates when used in a dry or inert environment. The tribological properties of NFC films are influenced by the surrounding environment and

Pamela Laurie Dickrell

2005-01-01

359

CO 2 activation of ordered porous carbon CMK-1 for hydrogen storage  

Microsoft Academic Search

Porous carbons with large surface areas and pore volumes, as well as relatively uniform micropore texture were prepared by CO2 activation of ordered porous carbon CMK-1 for hydrogen storage. Both activation temperature and time were studied. The structure and texture changes in the carbons were investigated by using XRD and nitrogen sorption. Under the optimum condition that treating with CO2

Kaisheng Xia; Qiuming Gao; Shuqing Song; Chundong Wu; Jinhua Jiang; Juan Hu; Lu Gao

2008-01-01

360

Structure and hydrogen adsorption properties in low density nanoporous carbons from simulations  

SciTech Connect

We systematically model the hydrogen adsorption in nanoporous carbons over a wide range of carbon bulk densities (0.6 - 2.4 g/cm3) by using tight binding molecular dynamics simulations for the carbon structures and thermodynamics calculations of the hydrogen adsorption. The resulting structures are in good agreement with the experimental data of ultra-microporous carbon (UMC), a wood-based activated carbon, as indicated by comparisons of the microstructure at atomic level, pair distribution function, and pore size distribution. The hydrogen adsorption calculations in carbon structures demonstrate both a promising hydrogen storage capacity (excess uptake of 1.33 wt% at 298K and 5 MPa, for carbon structures at the lower range of densities) and a reasonable heat of adsorption (12-22 kJ/mol). This work demonstrates that increasing the heat of adsorption does not necessarily increase the hydrogen uptake. In fact, the available adsorption volume is as important as the isosteric heat of adsorption for hydrogen storage in nanoporous carbons.

Peng, L. [University of Tennessee, Knoxville (UTK); Morris, James R [ORNL

2012-01-01

361

TCAD simulation of hydrogenated amorphous silicon-carbon\\/microcrystalline-silicon\\/hydrogenated amorphous silicon-germanium PIN solar cells  

Microsoft Academic Search

This study investigates the device performance of hydrogenated amorphous silicon-carbon (a-SiC:H)\\/microcrystalline-silicon (?c-Si)\\/hydrogenated amorphous silicon-germanium (a-SiGe:H) PIN thin film solar cells using Technology Computer Aided Design (TCAD) simulations. The physical parameters used in the TCAD simulations are calibrated to reproduce experimental data. The influence of the density of states (DOS) and intrinsic layer (I-layer) thickness on the performance of thin film

S. T. Chang; M. Tang; R. Y. He; W.-C. Wang; Z. Pei; C.-Y. Kung

2010-01-01

362

Hydrogenated amorphous carbon films having embedded nanoparticles deposited by cathodic jet carbon arc technique  

NASA Astrophysics Data System (ADS)

This paper reports the formation and properties of hydrogenated amorphous carbon (a-C: H) films having embedded nanoparticles deposited by cathodic jet carbon arc (CJCA) technique in absence of magnetic field. The films have been characterized by XRD, HRTEM, XPS, dark conductivity, activation energy, optical band gap, residual stress, hardness, elastic modulus and plastic index parameter. The properties evaluated of a-C: H films having embedded particles have been compared with that of undoped and nitrogen doped a-C films having embedded nanoparticles deposited by CJCA technique. All the properties of a- C films studied are found to depend on the gaseous environment used during the deposition of the films. These a-C films having embedded nanoparticles act as hard coating materials.

Panwar, O. S.; Ishpal, .; tripathi, R. K.; Srivastava, A. K.; Kumar, Sushil

2012-10-01

363

Hydrogen storage in high surface area carbons: experimental demonstration of the effects of nitrogen doping.  

PubMed

The influence of nitrogen doping on the hydrogen uptake and storage capacity of high surface area carbon materials is presented in this report. To generate suitable study materials, we have exploited the relationship between synthesis conditions and textural properties of zeolite-templated carbons to generate a range of high surface area carbons with similar pore size distribution but which are either N-doped or N-free. For N-doped carbons, the nitrogen content was kept within a narrow range of between 4.7 and 7.7 wt %. The carbon materials, irrespective of whether they were doped or not, exhibited high surface area (1900-3700 m(2)/g) and pore volume (0.99 and 1.88 cm(3)/g), a micropore surface area of 1500-2800 m(2)/g, and a micropore volume of 0.65-1.24 cm(3)/g. The hydrogen uptake varied between 4.1 and 6.9 wt %. We present experimental data that indicates that the effect of N-doping on hydrogen uptake is only apparent when related to the surface area and pore volume associated with micropores rather than total porosity. Furthermore, by considering the isosteric heat of hydrogen adsorption and excess hydrogen uptake on N-free or N-doped carbons, it is shown that N-doping can be beneficial at lower coverage (low hydrogen uptake) but is detrimental at higher coverage (higher hydrogen uptake). The findings are consistent with previous theoretical predictions on the effect of N-doping of carbon on hydrogen uptake. The findings, therefore, add new insights that are useful for the development of carbon materials with enhanced hydrogen storage capacity. PMID:19852461

Xia, Yongde; Walker, Gavin S; Grant, David M; Mokaya, Robert

2009-11-18

364

Fluorine-induced suppression of disorder effects of carbon in the hydrogenated amorphous silicon-carbon alloy thin films  

Microsoft Academic Search

We report here the Raman scattering studies of modifications in the structural disorder due to fluorine incorporation in the hydrogenated amorphous silicon-carbon (a-Si(1-x)C(x):H) alloys. The structural disorder in the unfluorinated a-Si(1-x)C(x):H alloys has been observed to increase continuously with the increasing carbon content, whereas the incorporation of fluorine appears to substantially suppress disordering effects of carbon, irrespective of its concentration

D. M. Bhusari; A. S. Kumbhar; S. T. Kshirsagar

1995-01-01

365

Fluorine-induced suppression of disorder effects of carbon in the hydrogenated amorphous silicon-carbon alloy thin films  

Microsoft Academic Search

We report here the Raman scattering studies of modifications in the structural disorder due to fluorine incorporation in the hydrogenated amorphous silicon-carbon (a-Si1?xCx:H) alloys. The structural disorder in the unfluorinated a-Si1?xCx:H alloys has been observed to increase continuously with the increasing carbon content, whereas the incorporation of fluorine appears to substantially suppress disordering effects of carbon, irrespective of its concentration

D. M. Bhusari; A. S. Kumbhar; S. T. Kshirsagar

1995-01-01

366

Hydrogen storage capacity of carbon nanotubes, filaments, and vapor-grown fibers  

Microsoft Academic Search

We have studied the sorption of hydrogen by nine different carbon materials at pressures up to 11 MPa (1600 psi) and temperatures from ?80 to +500°C. Our samples include graphite particles, activated carbon, graphitized PYROGRAF vapor-grown carbon fibers (VGCF), CO2 and air-etched PYROGRAF fibers, Showa-Denko VGCF, carbon filaments grown from a FeNiCu alloy, and nanotubes from MER Corp. and Rice

Gary G Tibbetts; Gregory P Meisner; Charles H Olk

2001-01-01

367

Hydrogen production by catalytic decomposition of methane over carbon catalysts in a fluidized bed  

Microsoft Academic Search

A fluidized bed reactor made of quartz tube with an I.D. of 0.055 m and a height of 1.0 m was employed for the thermocatalytic\\u000a decomposition of methane to produce CO2 — free hydrogen. The fluidized bed was used for continuous withdrawal of the carbon products from the reactor. Two kinds\\u000a of carbon catalysts — activated carbon and carbon black

Jae Uk Jung; Wooseok Nam; Ki June Yoon; Gui Young Han

2007-01-01

368

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

369

Enzymatic Functionalization of Carbon-Hydrogen Bonds1  

PubMed Central

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.

Lewis, Jared C.; Coelho, Pedro S.

2010-01-01

370

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...

371

Temperature and Water Vapor Pressure Effects on the Friction Coefficient of Hydrogenated Diamondlike Carbon Films.  

National Technical Information Service (NTIS)

Microtribological measurements of a hydrogenated diamondlike carbon film in controlled gaseous environments show that water vapor plays a significant role in the friction coefficient. These experiments reveal an initial high friction transient behavior th...

A. Erdemir N. Argibay O. L. Eryilmaz P. L. Dickrell W. G. Sawyer

2009-01-01

372

Effects of Hydrogen and Carbon on Thermally Activated Deformation in Nickel.  

National Technical Information Service (NTIS)

Deformation experiments were performed to determine the effects of hydrogen and carbon on the activation parameters for dislocation slip in nickel. The techniques used were isothermal stress relaxation and differential temperature measurements. These meth...

E. Sirois H. K. Birnham

1991-01-01

373

Irradiation Effects on the Reaction of Mixture of Carbon Monoxide and Hydrogen, 1.  

National Technical Information Service (NTIS)

Whether or not a radiation chemical method is useful for obtaining chemical raw materials from carbon monoxide and hydrogen in future chemical industries has been studied. the experimental results of the radiation chemistry studies of the above gas mixtur...

S. Sugimoto M. Nishii T. Sugiura

1978-01-01

374

Effect of metal Additions on the Hydrogen Uptake of Microporous Carbon at Near-Ambient Temperature  

SciTech Connect

Enhancing the hydrogen sorption capacity of microporous carbon materials at near-ambient temperature continue to be a challenge and the subject of intense research. Physisorption alone on microporous carbons is not strong enough to provide the desired levels of hydrogen uptake. Modifying carbons with small amounts of metals has been proven effective to increase the amounts adsorbed. However, very different mechanisms may be involved when the promoters are transition metals or alkali metals. In this presentation we compare the effect of additions of palladium and/or alkali metals on the hydrogen uptake of microporous carbons, in an attempt to differentiate between the possible mechanisms leading to enhanced hydrogen capacity and fast kinetics.

Contescu, Cristian I [ORNL; Gallego, Nidia C [ORNL; Bhat, Vinay V [ORNL

2010-01-01

375

Modeling of adsorption storage of hydrogen on activated carbons  

Microsoft Academic Search

The storage of hydrogen on board vehicles is one of the most critical issues for the transition towards an hydrogen-based transportation system. An electric vehicle powered by a typical gasoline tank will require 3.1kg of hydrogen (H2) to achieve a range of 500km. Compared to a typical gasoline tank, this would correspond to a hydrogen density of 65kg\\/m3 (including the

Pierre Bénard; R. Chahine

2001-01-01

376

Collision of hydrogen atom with single-walled carbon nanotube: Adsorption, insertion, and healing  

Microsoft Academic Search

Interaction of hydrogen atom with (5, 5) single-walled carbon nanotube (SWNT) has been studied over the collision energy range from 1 to 30 eV using a molecular dynamics simulation method. In the energy interval of 1-3 eV, the hydrogen atom can be chemisorbed on the outer wall of the SWNT, provided the impact point is near a vertex carbon atom

Yuchen Ma; Yueyuan Xia; Mingwen Zhao; Minju Ying; Xiangdong Liu; Pijun Liu

2001-01-01

377

Decreased carbon centered and hydrogen radicals in skeletal muscle of vitamin E supplemented rats.  

PubMed

Carbon centered and hydrogen radicals were examined using electron spin resonance techniques with 5,5 dimethyl-2-pyrroline-1-oxide in the skeletal muscle of rats fed with a control diet and a vitamin E supplemented diet containing alpha tocopherol. Carbon centered and hydrogen radical levels in the white and red muscles and the soleus of these vitamin E treated muscle fibers were decreased. These results suggest that vitamin E directly quenches these free radicals. PMID:1654902

Hiramatsu, M; Velasco, R D; Packer, L

1991-09-16

378

Hydrogen adsorption of open-tipped insufficiently graphitized multiwalled carbon nanotubes  

Microsoft Academic Search

Open-tipped carbon nanotubes with a large amount of subnanopores and open ends on the tube wall were conveniently prepared by an improved anodized aluminum oxide template growth. The hydrogen storage was measured based on a volumetric method. Adsorptions of 6.46 and 1.12 wt % were achieved at 77 K and room temperature, respectively. Compared to hydrogen adsorption of other carbon

Han Gao; Xiao Bin Wu; Ji Tao Li; Guo Tao Wu; Jian Yi Lin; Kai Wu; Dong Sheng Xu

2003-01-01

379

Hydrogen storage capacities of nanoporous carbon calculated by density functional and Møller-Plesset methods  

NASA Astrophysics Data System (ADS)

The hydrogen storage capacities of nanoporous carbons, simulated as flat graphene slit pores, have been calculated using a quantum-thermodynamical model. The model is applied for several interaction potentials between the hydrogen molecules and the graphitic walls that have been generated from density functional theory (DFT) and second-order Møller-Plesset (MP2) calculations. The hydrogen storage properties of the pores can be correlated with the features of the potential. It is shown that the storage capacity increases with the depth of the potential, De . Moreover, the optimal pore widths, yielding the maximum hydrogen storage capacities, are close to twice the equilibrium distance of the hydrogen molecule to one graphene layer. The experimental hydrogen storage capacities of several nanoporous carbons such as activated carbons (ACs) and carbide-derived carbons (CDCs) are well reproduced within the slit pore model considering pore widths of about 4.9-5.1Å for the DFT potential and slightly larger pore widths (5.3-5.9Å) for the MP2 potentials. The calculations predict that nanoporous carbons made of slit pores with average widths of 5.8-6.5Å would yield the highest hydrogen storage capacities at 300 K and 10 MPa.

Cabria, I.; López, M. J.; Alonso, J. A.

2008-08-01

380

Coherent Carbon Cryogel-Ammonia Borane Nanocomposites for Improved Hydrogen Storage  

SciTech Connect

Ammonia borane has been adsorbed into mesoporous carbon cryogels in an effort to manipulate the hydrogen release properties. TEM studies showed that ammonia borane was incorporated into the cyrogel structure. Thermochemical analysis of the dehydrogenation indicated that the hydrogen release properties of ammonia borane were enhanced when incorporated into cryogels. Dehydrogenation occured at lower temperatures and the non-hydrogen volatile products were controlled, liimiting borazine formation.

Feaver, Aaron M.; Sepehri, Saghar; Shamberger, Patrick J.; Stowe, Ashley C.; Autrey, Thomas; Cao, Guozhong

2007-07-15

381

Carbon\\/nitrogen-ratio effect on fermentative hydrogen production by mixed microflora  

Microsoft Academic Search

Anaerobic sewage sludge acclimated with sucrose was used as the seed in a batch experiment to investigate the carbon\\/nitrogen (C\\/N)-ratio effects on biological hydrogen production from sucrose. Experimental results indicated that the hydrogen production ability of the anaerobic microflora (dominated by Clostridium pasteurianum) in the sewage sludge was dependent on the influent C\\/N-ratio. At a C\\/N-ratio of 47, the hydrogen

C. Y Lin; C. H Lay

2004-01-01

382

Transitioning Towards a Low-Carbon Hydrogen Economy in the United States: Role of Transition Management  

Microsoft Academic Search

This paper describes the process of transitioning to a low-carbon hydrogen economy in the United States and the role of transition management (TM) in this process. Focusing on the transition process for hydrogen-based energy and transport systems in the United States, especially California, this study outlines the key characteristics of TM that have been employed in managing the transition. Several

Jacqueline C. K. Lam; Peter Hills; Esther C. T. Wong

2012-01-01

383

Optical study of disorder and defects in hydrogenated amorphous silicon carbon alloys  

Microsoft Academic Search

We have studied the defect density and disorder in hydrogenated amorphous silicon carbon alloys produced by rf glow discharge of silane-methane-hydrogen mixtures, by combining spectroscopic ellipsometry and photothermal deflection spectroscopy measurements. Increasing the methane flow rate leads to a widening of the optical gap and to an increase of the apparent disorder, deduced from the standard analysis of the exponential

Th. Nguyen-Tran; V. Suendo; P. Roca I Cabarrocas

2005-01-01

384

The study of controlling pore size on electrospun carbon nanofibers for hydrogen adsorption  

Microsoft Academic Search

Polyacrylonitrile (PAN)-based carbon nanofibers (CNFs) were prepared by using electrospinning method and heat treatment to get the media for hydrogen adsorption storage. Potassium hydroxide and zinc chloride activations were conducted to increase specific surface area and pore volume of CNFs. To investigate the relation between pore structure and the capacity of hydrogen adsorption, textural properties of activated CNFs were studied

Ji Sun Im; Soo-Jin Park; Tae Jin Kim; Young Ho Kim; Young-Seak Lee

2008-01-01

385

Conformational changes of the glucocorticoid receptor ligand binding domain induced by ligand and cofactor binding, and the location of cofactor binding sites determined by hydrogen/deuterium exchange mass spectrometry  

PubMed Central

HXMS (hydrogen/deuterium exchange mass spectrometry) of the glucocorticoid receptor ligand-binding domain (GR LBD) complexed with the agonist dexamethasone and the antagonist RU-486 is described. Variations in the rates of exchange were observed in regions consistent with the published crystal structures of GR LBD complexed with RU-486 when compared with the GR dexamethasone complex. We also report the HXMS results for agonist-bound GR LBD with the coactivator transcriptional intermediary factor 2 (TIF2) and anatagonist-bound GR LBD with nuclear receptor corepressor (NCoR). Alterations in exchange rates observed for agonist-bound GR LBD with TIF2 present were consistent with the published crystal structural contacts for the complex. Alterations in exchange rates observed for antagonist-bound GR LBD with NCoR were a subset of those observed with TIF2 binding, suggesting a common or overlapping binding site for coactivator and corepressor.

Frego, Lee; Davidson, Walter

2006-01-01

386

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

387

The effect of hydrogen on the electronic and bonding properties of amorphous carbon  

NASA Astrophysics Data System (ADS)

A series of amorphous carbon and hydrogen-containing amorphous carbon structures has been generated, by using classical Monte Carlo and molecular dynamics simulation techniques, respectively. The Brenner empirical bond order potential is used to generate hydrogenated amorphous carbon while that by Tersoff is used for amorphous carbon. The resulting structures are relaxed further using the density functional theory approach. Structures containing 15 at.% hydrogen are generated for various mass densities in order to investigate the effect of pressure changes on the properties of the hydrogenated amorphous carbon. The structures are analysed in terms of their sp3/sp2 ratio. The density of states (DOS), energy-loss near-edge structure (ELNES) and x-ray photoelectron spectroscopy (XPS) calculations are performed within the first-principles methodology on the generated carbon systems. The ELNES and the C 1s energy calculations are performed taking into account the core-hole effect. Our calculations show that depending on the density ?, hydrogenated amorphous carbon can be classified into three categories: polymeric at low densities (?<=2.0 g cm-3), graphitic at intermediate densities (2.0 g cm-32.4 g cm-3).

Titantah, J. T.; Lamoen, D.; Neyts, E.; Bogaerts, A.

2006-12-01

388

Influence of the source gas ratio on the hydrogen and deuterium content of a-C:H and a-C:D films: Plasma-enhanced CVD with CH4/H2, CH4/D2, CD4/H2 and CD4/D2  

NASA Astrophysics Data System (ADS)

Amorphous hydrogenated carbon (a-C:H) and amorphous deuterated carbon (a-C:D) films were prepared using plasma-enhanced chemical vapor deposition (PECVD) from CD4, H2, CD4 and D2 source gases. Fourteen different samples were prepared by changing the source gas ratios of CH4/H2, CH4/D2, CD4/H2, and CD4/D2. The concentrations of hydrogen (H) and deuterium (D) relative to carbon (C) in the films were determined by elastic recoil detection analysis (ERDA) and Rutherford backscattering spectroscopy (RBS). The sp2/(sp2 + sp3) ratios of the films were analyzed by near-edge X-ray absorption fine structure (NEXAFS) measurements. Hardness and mass density of the films were measured using a nanoindenter and X-ray reflectivity (XRR), respectively. For all combinations of source gas, the H and D concentrations varied by only 4.0 at.%. For the CH4/D2 source gas, the D concentration in the film increased from 0 at.% with the D2/(CH4 + D2) source gas combination to 11.2 at.% for the 80% D2/(CH4 + D2) source gas combination. The increase in D concentration exceeded the increase in total H and D concentration (3.4 at.%). For CH4/D2 source gas, the H concentration decreased as the D concentration increased. For the CD4/H2 source gas, we observed the opposite tendency. Additionally, an isotope effect between the a-C:H films and the a-C:D films was observed, with preferential incorporation of H over D. From the NEXAFS measurements, the sp2/(sp2 + sp3) ratios in all of the samples were between 38.8% and 40.8%. A correlation between the sp2/(sp2 + sp3) ratio and the H2 or D2 gas source ratio was not observed. The hardness and density of the films decreased when the H2 or D2 source gas ratio increased. Even though the H concentration in the a-C:H films was higher than the D concentration in the a-C:D films, the a-C:D films had lower hardness and mass density values. These findings suggest that information concerning the voids, nanostructures, sp2/sp3 ratios and H concentrations of hydrogenated amorphous carbon films is crucial for evaluation of their mechanical properties.

Ozeki, K.; Sekiba, D.; Suzuki, T.; Kanda, K.; Niibe, M.; Hirakuri, K. K.; Masuzawa, T.

2013-01-01

389

Hydrogenated amorphous carbon as protective coating for a forming tool  

NASA Astrophysics Data System (ADS)

This paper investigates the performance of hydrogenated amorphous carbon (a-C:H) films as protective coatings for a forming tool made from AISI M2 steel coated with a titanium nitride (TiN) PVD commercial layer. The samples were initially cleaned in ultrasonic baths and subsequently in a plasma ablation procedure. Films were then deposited by plasma immersion ion implantation using 91% of acetylene and 9% of argon at a total pressure of 5.5 Pa. Samples were biased with high voltage negative pulses, P (T = 3.33 ms, pulse on-time: 0.03 ms, pulse off-time: 3.30 ms and application rate: 299 Hz) with amplitudes varying from 1.000 to 4.000 V. The chemical structure and composition of the films were evaluated by infrared spectroscopy. The roughness was determined by profilometry while the surface topography and morphology were investigated by atomic force microscopy and scanning electron microscopy, respectively. The friction coefficient was determined by the ball on disk technique. A decrease in the proportion of C-H and O-H groups was observed while the concentration of dangling bonds enhanced with increasing P. Sharp structures were detected on the film surface affecting roughness in two different ways: it increased with enhancing pulse magnitude in the smoothest substrate (AISI M2) and decreased in the roughest one (AISI M2-TiN). The best tribological result was found for the sample deposited with 3.600 V of bias onto TiN-AISI M2 steel.

Martinatti, J. F.; Santos, L. V.; Cruz, N. C.; Rangel, E. C.

2011-11-01

390

Hydrogen and elemental carbon production from natural gas and other hydrocarbons  

DOEpatents

Diatomic hydrogen and unsaturated hydrocarbons are produced as reactor gases in a fast quench reactor. During the fast quench, the unsaturated hydrocarbons are further decomposed by reheating the reactor gases. More diatomic hydrogen is produced, along with elemental carbon. Other gas may be added at different stages in the process to form a desired end product and prevent back reactions. The product is a substantially clean-burning hydrogen fuel that leaves no greenhouse gas emissions, and elemental carbon that may be used in powder form as a commodity for several processes.

Detering, Brent A. (Idaho Falls, ID); Kong, Peter C. (Idaho Falls, ID)

2002-01-01

391

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

392

A vertically aligned carbon nanotube\\/fiber based electrode for economic hydrogen production by water electrolysis  

Microsoft Academic Search

This paper presents a novel approach to maximize the current density of electrodes modified by carbon nanotubes for high efficiency hydrogen production. Multiwalled carbon nanotubes (MWNTs), due to their unique electrical conductivity and mechanical properties, have led to our interest in their application of MWNTs for water splitting purposes. The motivation for this work is to provide a platform which

Xiaozhi Wang; Hang Zhou; Peng Li; Wenmiao Shu; G. Amaratunga; W. Milne

2010-01-01

393

Study on the microstructural and overall disorder in hydrogenated amorphous silicon carbon films  

Microsoft Academic Search

Hydrogenated amorphous silicon carbon alloy films of different carbon compositions were prepared by plasma enhanced chemical vapor deposition system using silane and methane with helium dilution and were characterized by structural and optical techniques to understand the microstructural and overall disorder in amorphous semiconductors. The study demonstrates that the increase of the microstructural disorder results in an increase in the

G. Ambrosone; D. K. Basa; U. Coscia; M. Fathallah

2008-01-01

394

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

Microsoft Academic Search

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

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

2011-01-01

395

Preparation of activated rectangular polyaniline-based carbon tubes and their application in hydrogen adsorption  

Microsoft Academic Search

Porous materials, especially porous carbon materials, have the most potential as hydrogen adsorbents. In this research, a series of novel rectangular polyaniline tubes (RPTs) are synthesized using hollow carbon nanosphere (HCNS) templates. By changing mass ratios of ammonium persulfate to HCNSs, the sizes of RPTs can be controlled. Chemical activation with KOH gives rise to a large specific surface area

Yuanzhen Chen; Haiyan Zhu; Yongning Liu

2011-01-01

396

Prediction of deuterium abundance in comets  

SciTech Connect

Using a chemical scheme based on ion-molecule reactions in cool interstellar clouds, the possibility of a deuterium enrichment of volatile material in comets is discussed. It is assumed that the hydrogen-containing molecules are deuterated before accretion and condensation on the core-mantle dust particles from which the cometesimals are formed. The D/H ratio in comets may be enhanced in respect to the average value by a factor of 100. Therefore comets are not promising objects for testing the primordial deuterium abundance. 16 references.

Vanysek, V.; Vanysek, P.

1985-01-01

397

Bimetallic ruthenium-copper nanoparticles embedded in mesoporous carbon as an effective hydrogenation catalyst.  

PubMed

Bimetallic ruthenium-copper nanoparticles embedded in the pore walls of mesoporous carbon were prepared via a template route and evaluated in terms of catalytic properties in d-glucose hydrogenation. The existence of bimetallic entities was supported by Ru L3-edge and Cu K-edge X-ray absorption results. The hydrogen spillover effect of the bimetallic catalyst on the hydrogenation reaction was evidenced by the results of both hydrogen and carbon monoxide chemisorptions. The bimetallic catalyst displayed a higher catalytic activity than the single-metal catalysts prepared using the same approach, namely ruthenium or copper nanoparticles embedded in the pore walls of mesoporous carbon. This improvement was due to the changes in the geometric and electronic structures of the bimetallic catalyst because of the presence of the second metal. PMID:24072134

Liu, Jiajia; Zhang, Li Li; Zhang, Jiatao; Liu, Tao; Zhao, X S

2013-09-26

398

Analysis of hydrogen sorption characteristics of boron-doped activated carbons  

NASA Astrophysics Data System (ADS)

There is significant interest in the properties of boron-doped activated carbons for their potential to improve hydrogen storage.ootnotetextSee http://all-craft.missouri.edu Boron-doped activated carbons have been produced using a novel process involving the pyrolysis of a boron containing compound and subsequent high-temperature annealing. In this talk we will present a systematic study of the effect of different boron doping processes on the samples' surface area, micropore structure, and hydrogen sorption. Experimental results include boron content from prompt gamma neutron activation analysis, boron-carbon chemistry from Fourier transform infrared spectroscopy (FTIR), nitrogen subcritical adsorption, and 80K and 90K hydrogen adsorption isotherms which allow us to evaluate the hydrogen binding energy for each sorptive material.

Beckner, M.; Romanos, J.; Stalla, D.; Dohnke, E.; Singh, A.; Lee, M.; Suppes, G.; Hawthorne, M. F.; Yu, P.; Wexler, C.; Pfeifer, P.

2011-03-01

399

Measurement of retained hydrogen by laser thermal desorption for carbon exposed to sub-eV atomic deuterium  

SciTech Connect

Retention levels for sub-eV D/sup 0/ atoms in single crystal and pyrolytic graphite were measured using a newly-developed Laser Thermal Desorption (LTD) technique. Retention levels for single crystals were approx. 3 x 10/sup 13/ D/sup 0//cm/sup 2/ for incident fluences of approx. 10/sup 19/D/sup 0//cm/sup 2/. This is about two orders of magnitude lower than D/sup 0/ retention in pyrolytic graphite, and correlates very well with the differences in effective surface areas. The D(/sup 3/He,p)/sup 4/H/sub e/ Nuclear Reaction Analysis (NRA) was used to confirm retention levels as measured by the LTD technique. A further finding was the influence of a small layer of evaporated tungsten on the sample surface. Such W impurity resulted in an increase of D/sup 0/ retention of up to a factor of ten.

Davis, J.W.; Haasz, A.A.; Auciello, O.; Stangeby, P.C.; Doyle, B.L.

1984-01-01

400

Effects of hydrogen on carbon steels at the Multi-Function Waste Tank Facility  

SciTech Connect

Concern has been expressed that hydrogen produced by corrosion, radiolysis, and decomposition of the waste could cause embrittlement of the carbon steel waste tanks at Hanford. The concern centers on the supposition that the hydrogen evolved in many of the existing tanks might penetrate the steel wall of the tank and cause embrittlement that might lead to catastrophic failure. This document reviews literature on the effects of hydrogen on the carbon steel proposed for use in the Multi-Function Waste Tank Facility for the time periods before and during construction as well as for the operational life of the tanks. The document draws several conclusions about these effects. Molecular hydrogen is not a concern because it is not capable of entering the steel tank wall. Nascent hydrogen produced by corrosion reactions will not embrittle the steel because the mild steel used in tank construction is not hard enough to be susceptible to hydrogen stress cracking and the corrosion product hydrogen is not produced at a rate sufficient to cause either loss in tensile ductility or blistering. If the steel intended for use in the tanks is produced to current technology, fabricated in accordance with good construction practice, postweld heat treated, and operated within the operating limits defined, hydrogen will not adversely affect the carbon steel tanks during their 50-year design life. 26 refs.

Carlos, W.C.

1995-02-08

401

Adsorption model of atomic hydrogen on the surfaces of carbon nanotubes  

NASA Astrophysics Data System (ADS)

A model for the adsorption of atomic hydrogen on the surfaces of single-walled zig-zag and armchair carbon nanotubes is constructed on the basis of the single-impurity periodic Anderson model. Features of the bands caused by the adsorption of hydrogen atoms in the structure of carbon nanotubes are studied. A reduction in the forbidden gap as a result of adsorption is revealed, and its dependence on the diameter of the semiconducting nanotubes is established. It is concluded that the model can be used to study the adsorption of other monovalent atoms on the surfaces of carbon particles.

Pak, A. V.; Lebedev, N. G.

2013-06-01

402

Association of hydrogen metabolism with unitrophic or mixotrophic growth of Methanosarcina barkeri on carbon monoxide  

SciTech Connect

Methanosarcina barkeri was adapted to grow on carbon monoxide by sequential transfer of the culture in medium that contained CO (100% of culture headspace). These experiments document the ability of the organism to grow slowly (65-h doubling time) and to produce methane and CO/sub 2/ either on CO as the sole carbon and energy source or by the simultaneous consumption of methanol and CO. During growth on CO as carbon and energy source, net hydrogen formation occurred when the CO partial pressure in the culture headspace was greater than 20% CO, but hydrogen was consumed when the CO concentration was below this value.

O'Brien, J.M.; Wolkin, R.H.; Moench, T.T.; Morgan, J.B.; Zeikus, J.G.

1984-04-01

403

Interlayer Carbon Bond Formation Induced by Hydrogen Adsorption in Few-Layer Supported Graphene  

NASA Astrophysics Data System (ADS)

We report on the hydrogen adsorption induced phase transition of a few layer graphene (1 to 4 layers) to a diamondlike structure on Pt(111) based on core level x-ray spectroscopy, temperature programed desorption, infrared spectroscopy, and density functional theory total energy calculations. The surface adsorption of hydrogen induces a hybridization change of carbon from the sp2 to the sp3 bond symmetry, which propagates through the graphene layers, resulting in interlayer carbon bond formation. The structure is stabilized through the termination of interfacial sp3 carbon atoms by the substrate. The structural transformation occurs as a consequence of high adsorption energy.

Rajasekaran, Srivats; Abild-Pedersen, Frank; Ogasawara, Hirohito; Nilsson, Anders; Kaya, Sarp

2013-08-01

404

Microchannel development and hydrogen adsorption properties in templated microporous carbons containing platinum nanoparticles  

Microsoft Academic Search

Ordered microporous carbons containing dispersed platinum nanoparticles were fabricated and chosen as suitable models to investigate micro-structure development and hydrogen transport properties of zeolite-templated carbons. X-ray photoelectron spectroscopy analysis revealed that the enhanced heat of adsorption is related to the narrow micro-channels templated from the zeolite and the presence of certain CO groups on the carbon. The lack of a

Yunxia Yang; Craig M. Brown; Chunxia Zhao; Alan L. Chaffee; Burke Nick; Dongyuan Zhao; Paul A. Webley; Jacob Schalch; Jason M. Simmons; Yun Liu; Jae-Hyuk Her; C. E. Buckley; Drew A. Sheppard

2011-01-01

405

Carbon nanomaterials synthesized using liquid petroleum gas: Analysis toward applications in hydrogen storage and production  

Microsoft Academic Search

A chemical vapor deposition (CVD) technique was developed to synthesize carbon nanomaterials using liquid petroleum gas (LPG) as the carbon source. Multi-walled carbon nanotubes (CNTs) were produced using commercial hydrogen storage materials (LaNi5 and TiFe) powders as the catalyst. Nickel micro-wire arrays were synthesized using a template technique, and were subsequently used to synthesize a CNT mat. Nanomaterials were thoroughly

P. Ndungu; A. Nechaev; L. Khotseng; N. Onyegebule; W. Davids; R. Mohammed; G. Vaivars; B. Bladegroen; V. Linkov

2008-01-01

406

Carbon, Hydrogen, and Oxygen Isotope Ratios of Cellulose from Plants Having Intermediary Photosynthetic Modes 1  

PubMed Central

Carbon and hydrogen isotope ratios of cellulose nitrate and oxygen isotope ratios of cellulose from species of greenhouse plants having different photosynthetic modes were determined. When hydrogen isotope ratios are plotted against carbon isotope ratios, four clusters of points are discernible, each representing different photosynthetic modes: C3 plants, C4 plants, CAM plants, and C3 plants that can shift to CAM or show the phenomenon referred to as CAM-cycling. The combination of oxygen and carbon isotope ratios does not distinguish among the different photosynthetic modes. Analysis of the carbon and hydrogen isotope ratios of cellulose nitrate should prove useful for screening different photosynthetic modes in field specimens that grew near one another. This method will be particularly useful for detection of plants which show CAM-cycling.

Sternberg, Leonel O'Reilly; Deniro, Michael J.; Ting, Irwin P.

1984-01-01

407

Nanoconfinement in activated mesoporous carbon of calcium borohydride for improved reversible hydrogen storage  

NASA Astrophysics Data System (ADS)

Mesoporous carbon frameworks were synthesized using the soft-template method. Ca(BH4)2 was incorporated into activated mesoporous carbon by the incipient wetness method. The activation of mesoporous carbon was necessary to optimize the surface area and pore size. Thermal programmed absorption measurements showed that the confinement of this borohydride into carbon nanoscaffolds improved its reversible capacity (relative to the reactive portion) and performance of hydrogen storage compared to unsupported borohydride. Hydrogen release from the supported hydride started at a temperature as low as 100?°C and the dehydrogenation rate was fast compared to the bulk borohydride. In addition, the hydrogen pressure necessary to regenerate the borohydride from the dehydrogenation products was reduced.

Com?nescu, Cezar; Capurso, Giovanni; Maddalena, Amedeo

2012-09-01

408

Performance of Carbon Hydrogen Storage Materials as a Function of Post-Production Thermal Treatment  

NASA Astrophysics Data System (ADS)

High-surface-area activated carbons for hydrogen storage were investigated as a function of post-synthesis surface treatment. Thermal treatment of the initial carbon in high vacuum at temperatures 200-1000 C leads to materials with significantly different surface chemistries and hydrogen storage capacities. Results from nitrogen pore-structure analyses, FT-IR spectroscopy before and after the treatment, and thermogravimetric analysis and mass spectroscopy of volatile reaction products during treatment, are reported. For treatment at 600 C, excess hydrogen adsorption at 80 K and 303 K is found to be 20-30% higher than for the untreated sample. At temperatures below 450 C, volatiles are mostly water and air; volatiles above 450 C are mostly carbon dioxide and carbon monoxide. The results are interpreted as that high-temperature treatment produces materials with a large fraction of high-binding-energy sites.

Dohnke, E.; Romanos, J.; Beckner, M.; Burress, J. W.; Yu, P.; Pfeifer, P.

2012-02-01

409

Nanoconfinement in activated mesoporous carbon of calcium borohydride for improved reversible hydrogen storage.  

PubMed

Mesoporous carbon frameworks were synthesized using the soft-template method. Ca(BH(4))(2) was incorporated into activated mesoporous carbon by the incipient wetness method. The activation of mesoporous carbon was necessary to optimize the surface area and pore size. Thermal programmed absorption measurements showed that the confinement of this borohydride into carbon nanoscaffolds improved its reversible capacity (relative to the reactive portion) and performance of hydrogen storage compared to unsupported borohydride. Hydrogen release from the supported hydride started at a temperature as low as 100 °C and the dehydrogenation rate was fast compared to the bulk borohydride. In addition, the hydrogen pressure necessary to regenerate the borohydride from the dehydrogenation products was reduced. PMID:22948563

Com?nescu, Cezar; Capurso, Giovanni; Maddalena, Amedeo

2012-09-05

410

A solar hydrogen hybrid system with activated carbon storage  

Microsoft Academic Search

A solar hydrogen hybrid system has been developed to convert, store and use energy from renewable energy sources. The theoretical model has been implemented in a dynamic model-based software environment and applied to real data. A photovoltaic sub-system drives a residential load and, if a surplus of energy is available, an electrolyzer to produce hydrogen which is stored in a

Gabriele Zini; Riccardo Marazzi; Simone Pedrazzi; Paolo Tartarini

2010-01-01

411

Asymmetric catalytic hydrogenation reactions in supercritical carbon dioxide  

Microsoft Academic Search

We demonstrate that asymmetric catalytic hydrogenation reactions can be conducted in supercritical COâ and that, in some cases, higher enantioselectivities can be achieved in this solvent relative to conventional solvents. These preliminary studies effectively demonstrate the feasibility of conducting highly enantioselective hydrogenation reactions in supercritical COâ. Importantly, we have shown that higher enantioselectivities may be achieved in supercritical COâ relative

Mark J. Burk; M. F. Gross; S. Feng; William Tumas

1995-01-01

412

Hydrogenated K4 carbon: A new stable cubic gauche structure of carbon hydride  

NASA Astrophysics Data System (ADS)

The structural and electronic properties of hydrogenated K4 carbon as a new cubic gauche structure in I213 symmetry are investigated using first-principles calculations. The total energy for this carbon hydride (labeled by K4-CH) is 0.47 eV per CH unit lower than that of solid molecular cubane, suggesting its energetic stability. Based on the calculated phonon dispersion curves and electronic band structure obtained by hybrid density functional method, we find that K4-CH is dynamically stable and exhibits as an insulator with an indirect band gap of 6.07 eV, which is close to 6.10 eV of cubic gauche nitrogen (cg-N). To study the doping effect of nitrogen, we have also investigated N-doped K4-CH with a composition of C4H4N4 in P213 symmetry. The phonon and electronic band structures show that it is dynamically stable and behaves as an insulator with an indirect band gap of 5.39 eV, smaller than that of both K4-CH and cg-N. These results broaden our understanding of the cubic gauche structure.

Lian, Chao-Sheng; Wang, Xin-Quan; Wang, Jian-Tao

2013-01-01

413

Hydrogen Diffusion and Trapping Effects in Low and Medium Carbon Steels for Subsurface Reinforcement in the Proposed Yucca Mountain Repository  

NASA Astrophysics Data System (ADS)

The electrochemical hydrogen permeation method was used to investigate hydrogen transport, trapping characteristics of low (0.08 pct C) and medium carbon (0.44 pct C) steels proposed for the Yucca Mountain (YM) repository environment. The presence of relatively high amounts of C, Mn, and S increased the density of trapping sites in medium carbon steel. The measured diffusivity of medium carbon steel was lower than that of the low carbon steel due to increased trapping of hydrogen at irreversible sites in the medium carbon steel. Hydrogen concentration values obtained for low carbon steels in YM ground water electrolytes indicate that increased ionic concentration decreases the uptake of hydrogen. The decrease in hydrogen permeation were due the formation of CaCO3 corrosion products on the surface of steels.

Lamb, Joshua; Arjunan, Venugopal; Deodeshmukh, Vinay; Chandra, Dhanesh; Daemen, Jaak; Rebak, Raúl B.

2007-02-01

414

Spatial Variability in the Ratio of Interstellar Atomic Deuterium to Hydrogen. I. Observations toward delta Orionis by the Interstellar Medium Absorption Profile Spectrograph  

NASA Astrophysics Data System (ADS)

Studies of the abundances of deuterium in different astrophysical sites are of fundamental importance to answering the question about how much deuterium was produced during big bang nucleosynthesis and what fraction of it was destroyed later. With this in mind, we used the Interstellar Medium Absorption Profile Spectrograph (IMAPS) on the ORFEUS-SPAS II mission to observe at a wavelength resolution of 4 km s^-1 (FWHM) the Lydelta and Lyepsilon absorption features produced by interstellar atomic deuterium in the spectrum of delta Ori A. A chi^2 analysis indicated that 0.96

Jenkins, Edward B.; Tripp, Todd M.; Wo?niak, Przemys?aw R.; Sofia, Ulysses J.; Sonneborn, George

1999-07-01

415

Role of microporosity in hydrogen adsorption on templated nanoporous carbons  

Microsoft Academic Search

Casting of inorganic templates is a viable method for obtaining porous carbons with tailored properties and with potential applications in gas adsorption and storage. One of the most used inorganic templates is mesoporous SBA-15 silica, which presents a honeycomb structure, with microporous channels interconnecting mesopores, this three-dimensional structure allowing facile pores filling by the carbon source. In this work, carbon

M. Armandi; B. Bonelli; C. Otero Areán; E. Garrone

2008-01-01

416

Characterisation of hydrogenated silicon–carbon alloy filters with different carbon composition for on-chip fluorescence detection of biomolecules  

Microsoft Academic Search

Absorption filters based on hydrogenated amorphous silicon–carbon alloys are developed for application as fluorescence filters in microarray and lab-on-a-chip systems. The carbon content of the thin film is varied by changing the amount of ethylene added to the ethylene\\/silane gas mixture during plasma-enhanced chemical vapour deposition. The optical properties of the films are characterised by transmittance measurements to obtain the

B. Lipovšek; A. Jóskowiak; J. Kr?; M. Topi?; D. M. F. Prazeres; V. Chu; J. P. Conde

2010-01-01

417

Biotechnical sulphate reduction using gas-lift reactors fed with hydrogen and carbon dioxide as energy and carbon source  

Microsoft Academic Search

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,

Houten van R. T; Look W. Hulshoff Pol; Gatze Lettinga

1994-01-01

418

Transition metal activation and functionalization of carbon-hydrogen bonds  

SciTech Connect

We are investigating the fundamental thermodynamic and kinetic factors that influence carbon-hydrogen bond activation at homogeneous transition metal centers and the conversion of hydrocarbons into functionalized products of potential use to the chemical industry. Advances have been made in both understanding the interactions of hydrocarbons with metals and in the functionalization of hydrocarbons. We have found that RhCl(PR{sub 3}){sub 2}(CNR) complexes can catalyze the insertion of isonitriles into the C-H bonds or arenes upon photolysis. The mechanism of these reactions was found to proceed by way of initial phosphine dissociation, followed by C-H activation and isonitrile insertion. We have also examined reactions of a series of arenes with (C{sub 5}Me{sub 5})Rh(PMe{sub 3})PhH and begun to map out the kinetic and thermodynamic preferences for arene coordination. The effects of resonance, specifically the differences in the Hueckel energies of the bound vs free ligand, are now believed to fully control the C-H activation/{eta}{sup 2}-coordination equilibria. We have begun to examine the reactions of rhodium isonitrile pyrazolylborates for alkane and arene C-H bond activation. A new, labile, carbodiimide precursor has been developed for these studies. We have completed studies of the reactions of (C{sub 5}Me{sub 5})Rh(PMe{sub 3})H{sub 2} with D{sub 2} and PMe{sub 3} that indicate that both {eta}{sup 5} {yields} {eta}{sup 3} ring slippage and metal to ring hydride migration occur more facilely than thermal reductive elimination of H{sub 2}. We have examined the reactions of heterocycles with (C{sub 5}Me{sub 5})Rh(PMe{sub 3})PhH and found that pyrrole and furan undergo C-H or N-H activation. Thiophene, however, undergoes C-S bond oxidative addition, and the mechanism of activation has been shown to proceed through sulfur coordination prior to C-S insertion.

Jones, W.D.

1992-06-01

419

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

420

Hydrogen Adsorption by High Surface Area Micro- porous Carbon Synthesized from Phenol-Formaldehyde  

NASA Astrophysics Data System (ADS)

A high surface area microporous carbon material can be synthesized by mixing the activation reagent potassium hydroxide into a carbon precursor solution of phenol-formaldehyde oligomers. Some polymerization of the carbon precursor occurs during the initial mixing, and further polymerization is completed by heating to 160^oC. Carbonization and activation is accomplished by heating to 500^oC - 900^oC in an inert atmosphere. The porosity and surface area of the resulting carbon material depends predominantly on the amount of activation reagent added to the carbon precursor solution and on the carbonization/activation temperature and time. Optimized synthesis conditions yield a microporous carbon with a very high BET specific surface area of nearly 3000 m^2/g and a narrow pore size distribution. This new synthesis approach yields surface areas dramatically larger than those typically obtained by traditional chemical activation methods for porous carbon where solid carbon precursors are soaked in activation reagent solutions. Hydrogen absorption up to 5.75 wt% at 77 K and above 20 bars hydrogen pressure is observed for this new microporous carbon material.

Hu, Qingyuan; Meisner, Gregory P.

2009-03-01

421

Studies of the coadsorption of deuterium and carbon monoxide with silver on rhodium and the adsorption of 2,4,6-trinitrotoluene on clean and carbon covered platinum  

SciTech Connect

Ag adsorbed on Rh(100) is presented as a model of the corresponding bimetallic catalyst. Ag overlayer growth follows the Frank-Van der Merwe growth mechanism at 300 K and the Stranski-Krastanov growth mechanism at 640 K. Ag(3d) binding energies are found to track the vacuum level rather than the Fermi level. The results of D/sub 2/ and CO adsorption studies on Ag/Rh(100) show that adsorbed Ag does not significantly alter the properties of adjacent D/sub 2/ or CO adsorption sites on the Rh(100) surface. The desorption and decomposition of 2,4,6-trinitrotoluene (TNT) on clean and carbon covered Pt(111) is also reported. No evidence for TNT decomposition on the carbon covered surface is found. Molecular TNT desorption kinetics at low coverage are first order, yielding an activation energy of 16.7 +/- 1 Kcal/mol and a preexponential factor of 2.3 x 10/sup 11/ (x e/sup - + 0.5/) sec/sup -1/. TNT adsorbed on the clean Pt(111) surface at submonolayer coverages undergoes almost complete decomposition during heating. The major decomposition products are H/sub 2/O, NO, CO/sub 2/, CO, HCN, and a carbon residue left on the surface. TNT adsorbed in the second and higher monolayers desorbs molecularly. The significance of these results in understanding the performance of a commercial explosive vapor preconcentrator is discussed.

Peebles, H.C.

1983-01-01

422

Carbon–carbon double bonds can be catalytically hydrogenated on hydrated alumina  

Microsoft Academic Search

We use inelastic electron tunneling spectroscopy to study catalytically induced hydrogenation of several unsaturated dicarboxylates chemisorbed on undried, hydrated alumina. Using isotope substitution we estabilish that hydroxyl groups on the alumina are the source of hydrogen. Fumarate and maleate hydrogenate completely at room temperature forming a succinate species. Gutaconate, hydromuconate, and muconate hydrogenate in a way that is exponentially temperature

James T. Hall; Duncan E. McBride

1981-01-01

423

Selective Catalytic Oxidation of Hydrogen Sulfide on Activated Carbons Impregnated with Sodium Hydroxide  

SciTech Connect

Two activated carbons of different origin were impregnated with the solution of sodium hydroxide (NaOH) of various concentrations up to 10 wt %, and the effect of impregnation on the catalytic performance of the carbons was evaluated. The catalytic activity was analyzed in terms of the capacity of carbons for hydrogen sulfide (H2S) conversion and removal from hydrogen-rich fuel streams and the emission times of H2S and the products of its oxidation [e.g., sulfur dioxide (SO2) and carbonyl sulfide (COS)]. The results of impregnation showed a significant improvement in the catalytic activity of both carbons proportional to the amount of NaOH introduced. NaOH introduces hydroxyl groups (OH-) on the surface of the activated carbon that increase its surface reactivity and its interaction with sulfur-containing compounds.

Schwartz, Viviane [ORNL; Baskova, Svetlana [ORNL; Armstrong, Timothy R. [ORNL

2009-01-01

424

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

425

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

National Technical Information Service (NTIS)

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 car...

J. R. Mielenz Y. P. Zhang

2011-01-01

426

SPITZER OBSERVATIONS OF SHOCK-EXCITED HYDROGEN DEUTERIDE IN IC 443C, HH 7, AND HH 54: PROBING THE GAS-PHASE DEUTERIUM ABUNDANCE IN THE DENSE INTERSTELLAR MEDIUM  

SciTech Connect

We present and analyze observations-carried out using the Infrared Spectrograph (IRS) on the Spitzer Space Telescope-of the R(3) and R(4) pure rotational lines of hydrogen deuteride (HD) detected from shock-heated material associated with the supernova remnant IC 443C and with the Herbig-Haro objects HH 7 and HH 54. Assuming a continuous temperature distribution for gas observed along the sight lines, we have constrained the gas density to be in the {approx}10{sup 3}-10{sup 4} cm{sup -3} range, using both spectroscopic data for H{sub 2}, HD, and CO from IRS and from the Infrared Space Observatory (ISO), as well as photometric data from Spitzer's Infrared Array Camera. The derived HD abundance relative to H{sub 2} is quite sensitive to the assumed excitation conditions in the emitting gas. Assuming that HD accounts for all gas-phase deuterium in the emitting material, and using all the available spectroscopic data to constrain the excitation conditions, we obtained gas-phase deuterium abundances [D/H]{sub gas} of 0.95{sup +0.54}{sub -0.27} Multiplication-Sign 10{sup -5} and 0.87{sup +0.31}{sub -0.27} Multiplication-Sign 10{sup -5} (statistical errors only) for IC 443C and HH 54, respectively. The uncertainties in the HD abundance are dominated by systematic effects related to the poorly known excitation conditions, and more accurate estimates of the HD abundance in shocked molecular clouds will require measurements of the emission in additional HD rotational transitions.

Yuan Yuan; Neufeld, David A. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Sonnentrucker, Paule [Space Telescope Science Institute, 3700 San Martin Dr, Baltimore, MD 21218 (United States); Melnick, Gary J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Watson, Dan M. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States)

2012-07-10

427

Metal-Assisted Hydrogen Storage on Pt-Decorated Single-Walled Carbon Nanohorns  

SciTech Connect

The catalytic dissociation of hydrogen molecules by metal nanoparticles and spillover of atomic hydrogen onto various supports is a well-established phenomenon in catalysis. However, the mechanisms by which metal catalyst nanoparticles can assist in enhanced hydrogen storage on high-surface area supports are still under debate. Experimental measurements of metal-assisted hydrogen storage have been hampered by inaccurate estimation of atomically stored hydrogen deduced from comparative measurements between metal-decorated and undecorated samples. Here we report a temperature cycling technique combined with inelastic neutron scattering (INS) measurements of quantum rotational transitions of molecular H2 to more accurately quantify adsorbed hydrogen aided by catalytic particles using single samples. Temperature cycling measurements on single-wall carbon nanohorns (SWCNHs) decorated with 2-3 nm Pt nanoparticles showed 0.17 % mass fraction of metal-assisted hydrogen storage (at 0.5 MPa) at room temperature. Temperature cycling of Pt-decorated SWCNHs using a Sievert s apparatus also indicated metal-assisted hydrogen adsorption of 0.08 % mass fraction at 5 MPa at room temperature. No additional metal-assisted hydrogen storage was observed in SWCNH samples without Pt nanoparticles cycled to room temperature, or in Pt-SWCNHs when the temperature was cycled to less than 150K. The possible formation of C-H bonds due to spilled-over atomic hydrogen was also investigated using both INS and density functional theory calculations.

Liu, Yun [National Institute of Standards and Technology (NIST); Brown, Craig [National Institute of Standards and Technology (NIST); Neumann, Dan [National Institute of Standards and Technology (NIST); Geohegan, David B [ORNL; Puretzky, Alexander A [ORNL; Rouleau, Christopher M [ORNL; Hu, Hui [ORNL; Styers-Barnett, David J [ORNL; Krasnov, Pavel O. [Rice University; Yakobson, Boris I. [Rice University

2012-01-01

428

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

429

Single Pd atoms in activated carbon fibers and their contribution to hydrogen storage  

SciTech Connect

Palladium-modified activated carbon fibers (Pd-ACF) were synthesized by meltspinning, carbonization and activation of an isotropic pitch carbon precursor premixed with an organometallic Pd compound. The hydrogen uptake at 25 oC and 20 bar on Pd- ACF exceeded the expected capacity based solely on Pd hydride formation and hydrogen physisorption on the microporous carbon support. Aberration-corrected scanning transmission electron microscopy (STEM) with sub- ngstrom spatial resolution provided unambiguous identification of isolated Pd atoms occurring in the carbon matrix that coexist with larger Pd particles. First principles calculations revealed that each single Pd atom can form Kubas-type complexes by binding up to three H2 molecules in the pressure range of adsorption measurements. Based on Pd atom concentration determined from STEM images, the contribution of various mechanisms to the excess hydrogen uptake measured experimentally was evaluated. With consideration of Kubas binding as a viable mechanism (along with hydride formation and physisorption to carbon support) the role of hydrogen spillover in this system may be smaller than previously thought.

Contescu, Cristian I [ORNL; van Benthem, Klaus [ORNL; Li, Sa [Virginia Commonwealth University, Richland; Bonifacio, Cecile S [University of California, Davis; Pennycook, Stephen J [ORNL; Jena, Puru [Virginia Commonwealth University, Richland; Gallego, Nidia C [ORNL

2011-01-01

430

Hydrogen adsorption in transition metal carbon nano-structures  

Microsoft Academic Search

Templated microporous carbons were synthesized from metal impregnated zeolite Y templates. Scanning Electron Microscopy (SEM)\\u000a and Transmission Electron Microscopy (TEM) were employed to characterize morphology and structure of the generated carbon\\u000a materials. The surface area, micro- and meso-pore volumes, as well as the pore size distribution of all the carbon materials\\u000a were determined by N2 adsorption at 77 K and

Yun Xia Yang; Ranjeet K. Singh; Paul A. Webley

2008-01-01

431

Molecular dynamics simulation of the formation of sp3 hybridized bonds in hydrogenated diamondlike carbon deposition processes  

NASA Astrophysics Data System (ADS)

The formation process of sp3 hybridized carbon networks (i.e., diamondlike structures) in hydrogenated diamondlike carbon (DLC) films has been studied with the use of molecular-dynamics simulations. The processes simulated in this study are injections of hydrocarbon ( CH3 and CH) beams into amorphous carbon (a-C) substrates. It has been shown that diamondlike sp3 structures are formed predominantly at a subsurface level when the beam energy is relatively high, as in the “subplantation” process for hydrogen-free DLC deposition. However, for hydrogenated DLC deposition, the presence of abundant hydrogen at subsurface levels, together with thermal spikes caused by energetic ion injections, substantially enhances the formation of carbon-to-carbon sp3 bonds. Therefore, the sp3 bond formation process for hydrogenated DLC films essentially differs from that for hydrogen-free DLC films.

Murakami, Yasuo; Horiguchi, Seishi; Hamaguchi, Satoshi

2010-04-01

432

Deuterium Formation and Abundance.  

National Technical Information Service (NTIS)

The importance of deuterium (and helium) in interstellar space is underlined. Formed during the early universe nucleosynthesis, it represents one of the few available cosmological probes. Observational methods are mentioned. An average D/H value in the in...

A. Vidal-madjar

1987-01-01

433

Catalytic reactions of mixtures of carbon dioxide, ethene, and hydrogen on cobalt surfaces  

SciTech Connect

Using a plug-flow and a batch reactor the hydrogenation of mixtures of carbon dioxide and ethene over unsupported cobalt has been studied. The results show that the hydrogenation of carbon dioxide is totally blocked as long as ethene is present in the gas phase. In contrast carbon dioxide does not at all influence the hydrogenation of ethene, which leads to a complex mixture of hydrocarbons. This reaction can be explained as a copolymerization proceeding via two different monomers (C{sub 1} and C{sub 2} fragments). The