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1

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

NASA Astrophysics Data System (ADS)

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

Stamp, Clifford Francis Joseph

2

Energy Levels of Hydrogen and Deuterium  

National Institute of Standards and Technology Data Gateway

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

3

Removal of deuterium from carbon-based codeposits by hydrogen isotope exchange  

NASA Astrophysics Data System (ADS)

The use of H2 gas soaks has been studied as a method of removing deuterium from DIII-D and ASDEX-Upgrade (ASDEX-U) codeposit specimens. The current experiments investigate the effectiveness of H2 gas soaks at 350-450 °C and 33 Pa-70 kPa for up to 100 h exposure time on codeposits with varying B impurity content. The range of parameters studied thus includes conditions relevant to the ITER divertor. Results show strong temperature dependence but little pressure dependence of D removal at the test conditions for DIII-D codeposits. At 350 °C and H2 pressures ranging from 33 Pa to 70 kPa, ˜50% of D in DIII-D codeposits was removed in 10-15 h. At 450 °C and similar pressures, ˜84% was removed in 6 h. In contrast, D removal for ASDEX-U codeposits shows little temperature dependence at the test conditions, with 76-80% of D removed after 6 h at 350-450 °C, 20 kPa.

Finlay, T. J.; Davis, J. W.; Haasz, A. A.

2013-11-01

4

Hydrogen and deuterium diffusion in lithium hydride  

NASA Astrophysics Data System (ADS)

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

Dologlou, Elisabeth

2010-04-01

5

Temperature dependent deuterium quadrupole coupling constants of short hydrogen bonds  

E-print Network

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

Barsegov, Valeri

6

Exchange of bonded hydrogen in amorphous silicon by deuterium  

SciTech Connect

We show that bonded hydrogen in a-Si:H is readily exchanged by atomic deuterium when exposed to a deuterium plasma discharge. The effective diffusion coefficient for the D,H exchange 10/sup -14/ cm/sup 2//sec at 160/sup 0/C, is comparable to that of interstitial hydrogen in c-Si.

Abeles, B.; Yang, L.; Leta, D.P.; Majkrzak, C.F.

1986-12-01

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

Observations of interstellar hydrogen and deuterium toward Alpha Centauri A  

NASA Technical Reports Server (NTRS)

A composite profile is presented of the Ly-alpha emission line of Alpha Cen A, obtained from 10 individual spectra with the high-resolution spectrograph aboard the International Ultraviolet Explorer (IUE) satellite. There is excellent overall agreement with two previous Copernicus observations. Interstellar deuterium is detected, and a lower limit is set on the deuterium to hydrogen ratio of nDI/nHI greater than 8 x 10 to the -6th. In addition, the deuterium bulk velocity appears blueshifted by 8 + or - 2 km/s with respect to interstellar hydrogen, suggesting a nonuniform medium along the line of sight.

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

1984-01-01

9

ELECTRON CYCLOTRON RESONANCE DISCHARGE AS A SOURCE FOR HYDROGEN AND DEUTERIUM IONS PRODUCTION  

E-print Network

beams of negative hydrogen ions is provoked predominantly by international and national programs1 ELECTRON CYCLOTRON RESONANCE DISCHARGE AS A SOURCE FOR HYDROGEN AND DEUTERIUM IONS PRODUCTION electrons and thermoelectrons in negative hydrogen and deuterium ion production. The obtained data

Boyer, Edmond

10

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

11

Permeability of hydrogen and deuterium of Hastelloy XR  

Microsoft Academic Search

Permeation of hydrogen isotope through a high-temperature alloy used as heat exchanger and steam reformer pipes is an important problem in the hydrogen production system connected to be a high-temperature engineering test reactor (HTTR). An experiment of hydrogen (H2) and deuterium (D2) permeation was performed to obtain permeability of H2 and D2 of Hastelloy XR, which is adopted as heat

Tetsuaki Takeda; Jin Iwatsuki; Yoshiyuki Inagaki

2004-01-01

12

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

E-print Network

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 $(3.02 \\pm 0.27 (stat.) \\pm 0.31 (syst.)) \\times 10^{-5}$ for hydrogen and $(1.42 \\pm ^{0.09}_{0.12} (stat.) \\pm 0.11 (syst.)) \\times 10^{-5}$ for deuterium, and relative branching ratios of double radiative capture to single radiative capture of $(7.68 \\pm 0.69(stat.) \\pm 0.79(syst.)) \\times 10^{-5}$ for hydrogen and $(5.44 \\pm^{0.34}_{0.46}(stat.) \\pm 0.42(syst.)) \\times 10^{-5}$ 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 $\\pi^-$ on the $\\pi^+$ 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.

S. Tripathi; D. S. Armstrong; M. E. Christy; J. H. D. Clark; T. P. Gorringe; M. D. Hasinoff; M. A. Kovash; D. H. Wright; P. A. Zolnierczuk

2007-01-02

13

Atomic deuterium (hydrogen) adsorption on thin silver films  

NASA Astrophysics Data System (ADS)

Atomic deuterium and hydrogen adsorption on thin silver films deposited under UHV conditions on Pyrex glass was studied by means of measurements of the resistance changes ? R combined with thermal desorption mass spectrometry (TDMS). The roughness factor of thin Ag films of known geometry, textured as a result of sintering, was determined by means of the BET method (xenon adsorption), while their preferential crystallographic orientation (1 1 1) was estimated on the basis of XRD data. ? R measurements were performed during various exposures of the films maintained at a constant temperature (78 or 89 K) to the flux of atomic deuterium (hydrogen) of known concentration generated on a hot tungsten filament. Every adsorption run was followed by thermal desorption. This gives a link between the ? R measured directly in the course of adsorption and the coverage ? determined on the basis of TDMS data, together with the BET and XRD results. It was found that at 78 K the rate of atomic deuterium (hydrogen) adsorption and recombination on the surface of sintered thin Ag films fits the Eley-Rideal (ER) mechanism, while at 89 K its overlapping with the Langmuir-Hinshelwood (LH) recombination starts to play a role. The initial sticking probability reaches 0.41 and 0.65 for D and H atoms, respectively, while the corresponding probabilities for recombination are 0.04 and 0.07. The activation energies for associative desorption of deuterium and hydrogen are 36 and 29 kJ/mol, respectively.

Du?, Ryszard; Nowicka, Ewa

2003-12-01

14

Ordered ground states of metallic hydrogen and deuterium  

NASA Technical Reports Server (NTRS)

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

Ashcroft, N. W.

1981-01-01

15

Laser-driven polarized sources of hydrogen and deuterium  

SciTech Connect

A novel laser-driven polarized source of hydrogen and deuterium which operates on the principle of spin exchange optical pumping is described. The advantages of this method over conventional polarized sources for internal target experiments are presented. Technological difficulties which prevent ideal source operation are outlined along with proposed solutions. At present, the laser-driven polarized hydrogen source delivers 8 /times/ 10/sup 16/ atoms/s with a polarization (P/sub z/) of 24%. 9 refs., 2 figs.

Young, L.; Holt, R.J.; Green, M.C.; Kowalczyk, R.S.

1988-01-01

16

Hydrogen and deuterium trapping in iron  

SciTech Connect

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

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

1981-02-01

17

The pion nucleon scattering lengths from pionic hydrogen and deuterium  

NASA Astrophysics Data System (ADS)

This is the final publication of the ETH Zurich Neuchâtel PSI collaboration on the pionic hydrogen and deuterium precision X-ray experiments. We describe the recent hydrogen 3 p 1 s measurement, report on the determination of the Doppler effect correction to the transition line width, analyze the deuterium shift measurement and discuss implications of the combined hydrogen and deuterium results. From the pionic hydrogen 3 p 1 s transition experiments we obtain the strong-interaction energy level shift \\varepsilon_{1s} = -7.108±0.013 (stat.)±0.034 (syst.) eV and the total decay width ?_{1s} = 0.868±0.040 (stat.)±0.038 (syst.) eV of the 1s state. Taking into account the electromagnetic corrections we find the hadronic ? N s-wave scattering amplitude a_{?-prightarrow?-p} = 0.0883±0.0008 m_{?}^{-1} for elastic scattering and a_{?-prightarrow?0n} = -0.128±0.006 m_{?} ^{-1} for single charge exchange, respectively. We then combine the pionic hydrogen results with the 1 s level shift measurement on pionic deuterium and test isospin symmetry of the strong interaction: our data are still compatible with isospin symmetry. The isoscalar and isovector ? N scattering lengths (within the framework of isospin symmetry) are found to be b_0 = -0.0001^{+0.0009}_{-0.0021} m_{?}^{-1} and b1 = -0.0885^{+0.0010}_{-0.0021} m_{?} ^{-1}, respectively. Using the GMO sum rule, we obtain from b_1 a new value of the ? N coupling constant (g_{? N} = 13.21_{-0.05}^{+0.11}) from which follows the Goldberger Treiman discrepancy ?_{{GT}} =0.027_{-0.008}^{+0.012}. The new values of b_0 and g_{? N} imply an increase of the nucleon sigma term by at least 9 MeV.

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

2001-07-01

18

Theory of muonic hydrogen - muonic deuterium isotope shift  

E-print Network

We calculate the corrections of orders alpha^3, alpha^4 and alpha^5 to the Lamb shift of the 1S and 2S energy levels of muonic hydrogen (mu p) and muonic deuterium (mu d). The nuclear structure effects are taken into account in terms of the proton r_p and deuteron r_d charge radii for the one-photon interaction and by means of the proton and deuteron electromagnetic form factors in the case of one-loop amplitudes. The obtained numerical value of the isotope shift (mu d) - (mu p) for the splitting (1S-2S) 101003.3495 meV can be considered as a reliable estimation for corresponding experiment with the accuracy 10^{-6}. The fine structure interval E(1S)-8E(2S) in muonic hydrogen and muonic deuterium are calculated.

A. P. Martynenko

2004-12-17

19

Excessive hydrogen and deuterium Balmer lines broadening in a hollow cathode glow discharges  

Microsoft Academic Search

Results of a Doppler spectroscopy study of hydrogen and deuterium Balmer lines in the stainless steel and copper hollow cathode glow discharge, operated in pure hydrogen, deuterium and mixtures of inert gases with hydrogen, are reported. For all gases and gas mixtures plasma observations perpendicular to electric field revealed the excessively large Doppler broadening. By changing mode of glow discharge

N. M. Sisovic; G. Lj. Majstorovic; N. Konjevic

2005-01-01

20

Diffusion of hydrogen, deuterium, and tritium in niobium  

SciTech Connect

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

Matusiewicz, Gerald Robert

1981-01-01

21

Doppler spectroscopy of hydrogen and deuterium Balmer alpha line in an abnormal glow discharge  

Microsoft Academic Search

The results of hydrogen and deuterium Balmer alpha line shapes and line intensities study in an abnormal glow discharge are reported and analyzed. The Doppler shifts along line wings are used to determine energies of excited hydrogen and deuterium atoms. For 12 different cathodes, intensity and shape of line wings are examined and dependence upon cathode material is determined. Tentative

M. R. Gemisic Adamov; Bratislav M. Obradovic; Milorad M. Kuraica; N. Konjevic

2003-01-01

22

CATALYTIC EXCHANGE OF HYDROGEN SULPHIDE AND OF HYDROGEN WITH DEUTERIUM ON DISULPHIDES OF MOLYBDENUM AND TUNGSTEN  

Microsoft Academic Search

The exchange reaction between hydrogen sulfide and deuterium was ; followed in the temperature range l50 to 200 deg C on a molybdenum disulfide ; catalyst and in the range 40 to 100 deg C on a sample of tungsten disulfide, the ; latter having a substantially greater surface area than the former. Studies were ; also made on the

R. L. Wilson; C. Kemball; A. K. Galwey

1962-01-01

23

Dynamics of hydrogen-deuterium exchange in Chlamydomonas centrin.  

PubMed

Chlamydomonas reinhardtii centrin is a 169-amino acid residue calcium binding protein belonging to the EF-hand protein superfamily. Centrin is associated with the microtubule organizing center (MTOC) in all eukaryotes, and in Chlamydomonas, centrin is a component of the flagellar basal body apparatus. Recombinant full-length centrin, calmodulin, and terminal domain fragments [Ccen-N (residues 1-94) and Ccen-C (residues 99-169)] were used to examine hydrogen-deuterium (H --> D) exchange dynamics using combined attenuated total reflectance (ATR) Fourier transform-infrared (FT-IR) spectroscopy, curve fit, and two-dimensional correlation analysis. Analysis of the Ccen-N and Ccen-C fragments allowed separation of domain specific solvent exchange events and together with analysis of the full-length proteins provides novel insight into domain accessibility to the aqueous environment and the internal dynamics of the protein. PMID:15709753

Ortiz, Mildred; Sanoguet, Zuleika; Hu, Haitao; Chazin, Walter J; McMurray, Cynthia T; McMurray, Cynthia; Salisbury, Jeffrey L; Pastrana-Rios, Belinda

2005-02-22

24

Excessive hydrogen and deuterium Balmer lines broadening in a hollow cathode glow discharges  

Microsoft Academic Search

.  Results of a Doppler spectroscopy study of hydrogen and deuterium \\u000aBalmer lines in the stainless steel and copper hollow cathode glow \\u000adischarge, operated in pure hydrogen, deuterium and mixtures of inert gases \\u000awith hydrogen, are reported. For all gases and gas mixtures plasma \\u000aobservations perpendicular to electric field revealed the excessively large \\u000aDoppler broadening. By changing mode of glow discharge

N. M. Šišovi?; G. Lj. Majstorovi?; N. Konjevi?

2005-01-01

25

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

SciTech Connect

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

Smith, M.F.

1981-10-01

26

SAIDE: A Semi-Automated Interface for Hydrogen/Deuterium Exchange Mass Spectrometry  

PubMed Central

Deuterium/hydrogen exchange in combination with mass spectrometry (DH MS) is a sensitive technique for detection of changes in protein conformation and dynamics. Since temperature, pH and timing control are the key elements for reliable and efficient measurement of hydrogen/deuterium content in proteins and peptides, we have developed a small, semiautomatic interface for deuterium exchange that interfaces the HPLC pumps with a mass spectrometer. This interface is relatively inexpensive to build, and provides efficient temperature and timing control in all stages of enzyme digestion, HPLC separation and mass analysis of the resulting peptides. We have tested this system with a series of standard tryptic peptides reconstituted in a solvent containing increasing concentration of deuterium. Our results demonstrate the use of this interface results in minimal loss of deuterium due to back exchange during HPLC desalting and separation. For peptides reconstituted in a buffer containing 100% deuterium, and assuming that all amide linkages have exchanged hydrogen with deuterium, the maximum loss of deuterium content is only 17% of the label, indicating the loss of only one deuterium molecule per peptide.

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

2011-01-01

27

Phonon localization by mass disorder in dense hydrogen-deuterium binary alloy.  

PubMed

Using a combination of the Raman spectroscopy and density functional theory calculations on dense hydrogen-deuterium mixtures of various concentrations, we demonstrate that, at 300 K and above 200 GPa, they transform into phase IV, forming a disordered binary alloy with six highly localized intramolecular vibrational (vibrons) and four delocalized low-frequency (<1200??cm^{-1}) modes. Hydrogen-deuterium mixtures are unique in showing a purely mass-induced localization effect in the quantum solid: chemical bonding is isotope-independent while the mass varies by a factor of 2. PMID:25379921

Howie, Ross T; Magd?u, Ioan B; Goncharov, Alexander F; Ackland, Graeme J; Gregoryanz, Eugene

2014-10-24

28

Phonon Localization by Mass Disorder in Dense Hydrogen-Deuterium Binary Alloy  

NASA Astrophysics Data System (ADS)

Using a combination of the Raman spectroscopy and density functional theory calculations on dense hydrogen-deuterium mixtures of various concentrations, we demonstrate that, at 300 K and above 200 GPa, they transform into phase IV, forming a disordered binary alloy with six highly localized intramolecular vibrational (vibrons) and four delocalized low-frequency (<1200 cm-1) modes. Hydrogen-deuterium mixtures are unique in showing a purely mass-induced localization effect in the quantum solid: chemical bonding is isotope-independent while the mass varies by a factor of 2.

Howie, Ross T.; Magd?u, Ioan B.; Goncharov, Alexander F.; Ackland, Graeme J.; Gregoryanz, Eugene

2014-10-01

29

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

SciTech Connect

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

David Gaskell

2001-05-01

30

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

PubMed

Lamb-shift polarimeters are used to measure the nuclear polarization of protons and deuterons at energies of a few keV. In combination with an ionizer, the polarization of hydrogen and deuterium atoms was determined after taking into account the loss of polarization during the ionization process. The present work shows that the nuclear polarization of hydrogen or deuterium molecules can be measured as well, by ionizing the molecules and injecting the H2 (+) (or D2 (+)) ions into the Lamb-shift polarimeter. PMID:25362391

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

2014-10-01

31

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

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

32

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

PubMed

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

Nagy, Kornél; Redeuil, Karine; Rezzi, Serge

2009-11-15

33

Temperature measurements and dissociation of shock-compressed liquid deuterium and hydrogen  

Microsoft Academic Search

Temperatures of shock compressed liquid deuterium and hydrogen up to 5200 K were measured at pressures up to 83 GPa (830 kbar). The measurements are in excellent agreement with earlier calculations to about 20 GPa and show evidence for dissociation above 20 GPa. At the highest measured temperatures and pressures current theories break down and a revised theory is proposed.

N. C. Holmes; M. Ross; W. J. Nellis

1995-01-01

34

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

ERIC Educational Resources Information Center

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

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

2014-01-01

35

Mean charged multiplicities in charged-current neutrino scattering on hydrogen and deuterium  

NASA Astrophysics Data System (ADS)

Available experimental data are analyzed to derive simple parametrizations for the mean charged-hadron multiplicities in charged-current neutrino and antineutrino interactions with hydrogen and deuterium targets. The obtained results can be used in the (anti)neutrino-induced hadronic shower modeling.

Kuzmin, Konstantin S.; Naumov, Vadim A.

2013-12-01

36

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

E-print Network

changes. Allosterically sensitive amide hydrogens located at near amino acid resolution help to confirm­4). For relatively small proteins, HX can be measured at an amino acid resolved level by NMR methods. For larger An automated high-throughput, high-resolution deuterium ex- change HPLC-MS method (DXMS) was used to extend

Englander, S. Walter

37

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

38

Quantifying hydrogen-deuterium exchange of meteoritic dicarboxylic acids during aqueous extraction  

NASA Astrophysics Data System (ADS)

Hydrogen isotope ratios of organic compounds in carbonaceous chondrites provide critical information about their origins and evolutionary history. However, because many of these compounds are obtained by aqueous extraction, the degree of hydrogen-deuterium (H/D) exchange that occurs during the process needs to be quantitatively evaluated. This study uses compound- specific hydrogen isotopic analysis to quantify the H/D exchange during aqueous extraction. Three common meteoritic dicarboxylic acids (succinic, glutaric, and 2-methyl glutaric acids) were refluxed under conditions simulating the extraction process. Changes in D values of the dicarboxylic acids were measured following the reflux experiments. A pseudo-first order rate law was used to model the H/D exchange rates which were then used to calculate the isotope exchange resulting from aqueous extraction. The degree of H/D exchange varies as a result of differences in molecular structure, the alkalinity of the extraction solution and presence/absence of meteorite powder. However, our model indicates that succinic, glutaric, and 2-methyl glutaric acids with a D of 1800 would experience isotope changes of 38, 10, and 6, respectively during the extraction process. Therefore, the overall change in D values of the dicarboxylic acids during the aqueous extraction process is negligible. We also demonstrate that H/D exchange occurs on the chiral -carbon in 2-methyl glutaric acid. The results suggest that the racemic mixture of 2-methyl glutaric acid in the Tagish Lake meteorite could result from post-synthesis aqueous alteration. The approach employed in this study can also be used to quantify H/D exchange for other important meteoritic compounds such as amino acids.

Fuller, M.; Huang, Y.

2003-03-01

39

Trapping behaviour of deuterium ions implanted into tungsten simultaneously with carbon ions  

NASA Astrophysics Data System (ADS)

The trapping behaviour of deuterium ions implanted into tungsten simultaneously with carbon ions was investigated by thermal desorption spectroscopy (TDS) and x-ray photoelectron spectroscopy (XPS). The D2 TDS spectrum consisted of three desorption stages, namely desorption of deuterium trapped by intrinsic defects, ion-induced defects and carbon with the formation of the C-D bond. Although the deuterium retention trapped by intrinsic defects was almost constant, that by ion-induced defects increased as the ion fluence increased. The retention of deuterium with the formation of the C-D bond was saturated at an ion fluence of 0.5×1022 D+ m-2, where the major process was changed from the sputtering of tungsten with the formation of a W-C mixture to the formation of a C-C layer, and deuterium retention as the C-D bond decreased. It was concluded that the C-C layer would enhance the chemical sputtering of carbon with deuterium with the formation of CDx and the chemical state of carbon would control the deuterium retention in tungsten under C+-D2+ implantation.

Kobayashi, Makoto; Suzuki, Sachiko; Wang, Wanjing; Kurata, Rie; Kida, Katsuya; Ashikawa, Naoko; Sagara, Akio; Yoshida, Naoaki; Oya, Yasuhisa; Okuno, Kenji

2009-12-01

40

Growth of redeposited carbon and its impact on isotope retention properties on tungsten in a high flux deuterium plasma  

NASA Astrophysics Data System (ADS)

Experiments were performed in a linear magnetized plasma facility (PISCES-B) to simulate carbon re-deposition in the divertor of a fusion reactor such as the International Thermonuclear Experimental Reactor (ITER). The average ion energies are about 100 eV and the ion flux is 2 × 10 22 m -2 s -1. Tungsten discs and foils were exposed to deuterium plasma for a period of 45-120 min at various substrate temperatures. Carbon impurities were introduced either using graphite sample holder or downstream CD 4 puffing near the targets. In-situ XPS measurements showed a shifting of the binding energy of the carbon in the interlayer between the carbon film and the tungsten surface. Based on AES depth profile, the ratio of tungsten to carbon in the interlayer is about 1.9 : 1. Scanning electron microscopy of plasma-exposed tungsten revealed bubble and pits formation on uncontaminated surfaces. Raman measurements on deposited carbon films were also performed. Deuterium retention measurements were done using Thermal Desorption Spectrometry (TDS). The dominant factor that influences the hydrogen isotope retention is substrate temperature. Measurements indicated a transition from D 2 dominant retention at low temperature exposure to D dominant retention at high temperature exposure. Carbon-contaminated tungsten substrates also showed similar, but a moderate, transition. Total deuterium retention decreases as the exposed temperature increases. The threshold of the carbon impurity concentration in the plasma, under which carbon starts to be deposited on the tungsten surface, is about 0.75% at 850 K. Keeping the impurity concentration at 1%, the temperature threshold is about 750 K.

Sze, Fan C.; Chousal, Leo; Doerner, Russ P.; Luckhardt, Stan

41

Kinetic isotope effect in hydrogen abstraction from 2-propanol by hydrogen and deuterium radicals. A pulse radiolysis Fourier transform electron spin resonance study  

Microsoft Academic Search

Using FT-ESR coupled with pulse radiolysis the kinetics of hydrogen abstraction from 2-propanol by hydrogen and deuterium radicals were studied in aqueous solution. The rate constants were determined from the effective spin–spin relaxation times of the free induction decay of hydrogen or deuterium ESR lines by variation of the 2-propanol concentration. The rate constants kHH and kDH for H(D)+2-propanol-h8 and

J. Geimer; D. Beckert; A. Jenichen

1997-01-01

42

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

PubMed

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

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

2014-10-21

43

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

44

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

SciTech Connect

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

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

2005-12-01

45

Biogeochemistry of the Stable Isotopes of Hydrogen and Carbon in Salt Marsh Biota 1  

PubMed Central

Deuterium to hydrogen ratios of 14 plant species from a salt marsh and lagoon were 55‰ depleted in deuterium relative to the environmental water. Carbon tetrachloride-extractable material from these plants was another 92‰ depleted in deuterium. This gave a fractionation factor from water to CCl4 extract of 1.147. This over-all fractionation was remarkably constant for all species analyzed. Plants also discriminate against 13C, particularly in the lipid fraction. Data suggest that different mechanisms for carbon fixation result in different fractionations of the carbon isotopes. Herbivore tissues reflected the isotopic ratios of plants ingested. Apparently different metabolic processes are responsible for the different degrees of fractionation observed for hydrogen and carbon isotopes. PMID:16657539

Smith, Bruce N.; Epstein, Samuel

1970-01-01

46

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

47

Measurements of the Deuterium to Hydrogen Ratio in QSO Absorption Systems  

NASA Astrophysics Data System (ADS)

Observational constraints on the primordial deuterium-to-hydrogen ratio (D/H) can test theories of the early universe and provide constraints on models of Big Bang nucleosynthesis (BBN). We measure deuterium absorption in high-redshift, metal-poor QSO absorption systems and directly infer the value of primordial D/H. We present two measurements of D/H, and find D/H = 3.2±0.3×10-5 at z=3.572 towards QSO 1937-1009 and D/H = 4.0-0.8+0.6×10-5 at z=2.504 towards QSO 1009+2956. Both measurements use multiple-component Voigt profile analysis of high resolution, high signal-to-noise spectra and determinations of the Lyman continuum optical depth in low resolution spectra to constrain the column densities of deuterium and hydrogen. The measurements are consistent with a single primordial value of D/H = 3.4±0.3×10-5. This is a relatively low value, which supports homogeneous models of BBN and standard models of galactic chemical evolution. Using models of standard BBN, we find a cosmological baryon-to-photon ratio, ?=5.1±0.4×10-10, and a present-day baryon density in units of the critical density, ?b/ h1002=0.019±0.002. These values are consistent with high abundance measurements of 4He in extragalactic H II regions, and estimates of 7Li in warm, metal-poor halo stars.

Burles, Scott Michael

48

Indirect use of deuterium in solution NMR studies of protein structure and hydrogen bonding.  

PubMed

A description of the utility of deuteration in protein NMR is provided with an emphasis on quantitative evaluation of the effects of deuteration on a number of NMR parameters of proteins: (1) chemical shifts, (2) scalar coupling constants, (3) relaxation properties (R1 and R2 rates) of nuclei directly attached to one or more deuterons as well as protons of methyl groups in a highly deuterated environment, (4) scalar relaxation of 15N and 13C nuclei in 15N-D and 13C-D spin systems as a measure of hydrogen bonding strength, and (5) NOE-based applications of deuteration in NMR studies of protein structure. The discussion is restricted to the 'indirect' use of deuterium in the sense that the description of NMR parameters and properties of the nuclei affected by nearby deuterons (15N, 13C, 1H) is provided rather than those of deuterium itself. PMID:24411830

Tugarinov, Vitali

2014-02-01

49

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

PubMed Central

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

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

2014-01-01

50

Experimental investigations of electron capture from atomic hydrogen and deuterium by alpha particles  

NASA Astrophysics Data System (ADS)

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(++) 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.

51

Experimental investigations of electron capture from atomic hydrogen and deuterium by alpha particles  

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.

1992-01-01

52

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

E-print Network

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

Hosszu, Laszlo

53

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

E-print Network

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

54

Transport of negative hydrogen and deuterium ions in RF-driven ion sources  

NASA Astrophysics Data System (ADS)

Negative hydrogen ion sources are major components of neutral beam injection systems for plasma heating in future large-scale fusion experiments such as ITER. In order to fulfill the requirements of the ITER neutral beam injection, a high-performance, large-area RF-driven ion source for negative ions is being developed at the MPI für Plasmaphysik. Negative hydrogen ions are mainly generated on a converter surface by impinging neutral particles and positive ions under the influence of magnetic fields and the plasma sheath potential. The 3D transport code TrajAn has been applied in order to obtain the total and spatially resolved extraction probabilities for H- and D- ions under identical plasma parameters and the realistic magnetic field topology of the ion source. A comparison of the isotopes shows a lower total extraction probability in the case of deuterium ions, caused by a different transport effect. The transport calculation shows that distortions of the spatial distributions of ion birth and extraction by the magnetic electron suppression field are present for both negative hydrogen and deuterium ions.

Gutser, R.; Wünderlich, D.; Fantz, U.; NNBI-Team

2010-04-01

55

Carbon Aerogels for Hydrogen Storage  

SciTech Connect

This effort is focused on the design of new nanostructured carbon-based materials that meet the DOE 2010 targets for on-board vehicle hydrogen storage. Carbon aerogels (CAs) are a unique class of porous materials that possess a number of desirable structural features for the storage of hydrogen, including high surface areas (over 3000 m{sup 2}/g), continuous and tunable porosities, and variable densities. In addition, the flexibility associated with CA synthesis allows for the incorporation of modifiers or catalysts into the carbon matrix in order to alter hydrogen sorption enthalpies in these materials. Since the properties of the doped CAs can be systematically modified (i.e. amount/type of dopant, surface area, porosity), novel materials can be fabricated that exhibit enhanced hydrogen storage properties. We are using this approach to design new H{sub 2} sorbent materials that can storage appreciable amounts of hydrogen at room temperature through a process known as hydrogen spillover. The spillover process involves the dissociative chemisorption of molecular hydrogen on a supported metal catalyst surface (e.g. platinum or nickel), followed by the diffusion of atomic hydrogen onto the surface of the support material. Due to the enhanced interaction between atomic hydrogen and the carbon support, hydrogen can be stored in the support material at more reasonable operating temperatures. While the spillover process has been shown to increase the reversible hydrogen storage capacities at room temperature in metal-loaded carbon nanostructures, a number of issues still exist with this approach, including slow kinetics of H{sub 2} uptake and capacities ({approx} 1.2 wt% on carbon) below the DOE targets. The ability to tailor different structural aspects of the spillover system (i.e. the size/shape of the catalyst particle, the catalyst-support interface and the support morphology) should provide valuable mechanistic information regarding the critical aspects of the spillover process (i.e. kinetics of hydrogen dissociation, diffusion and recombination) and allow for optimization of these materials to meet the DOE targets for hydrogen storage. In a parallel effort, we are also designing CA materials as nanoporous scaffolds for metal hydride systems. Recent work by others has demonstrated that nanostructured metal hydrides show enhanced kinetics for reversible hydrogen storage relative to the bulk materials. This effect is diminished, however, after several hydriding/dehydriding cycles, as the material structure coarsens. Incorporation of the metal hydride into a porous scaffolding material can potentially limit coarsening and, therefore, preserve the enhanced kinetics and improved cycling behavior of the nanostructured metal hydride. Success implementation of this approach, however, requires the design of nanoporous solids with large accessible pore volumes (> 4 cm{sup 3}/g) to minimize the gravimetric and volumetric capacity penalties associated with the use of the scaffold. In addition, these scaffold materials should be capable of managing thermal changes associated with the cycling of the incorporated metal hydride. CAs are promising candidates for the design of such porous scaffolds due to the large pore volumes and tunable porosity of aerogel framework. This research is a joint effort with HRL Laboratories, a member of the DOE Metal Hydride Center of Excellence. LLNL's efforts have focused on the design of new CA materials that can meet the scaffolding requirements, while metal hydride incorporation into the scaffold and evaluation of the kinetics and cycling performance of these composites is performed at HRL.

Baumann, T F; Worsley, M; Satcher, J H

2008-08-11

56

QSO 0130-4021: A Third QSO Showing a Low Deuterium-to-Hydrogen Abundance Ratio  

Microsoft Academic Search

We have discovered a third quasar absorption system which is consistent with a low deuterium-to-hydrogen abundance ratio, D\\/H=3.4x10-5. The zabs~2.8 partial Lyman limit system toward Q0130-4021 provides the strongest evidence to date against large D\\/H ratios because the H I absorption, which consists of a single high column density component with unsaturated high-order Lyman series lines, is readily modeled-a task

David Kirkman; David Tytler; Scott Burles; Dan Lubin; John M. O'Meara

2000-01-01

57

Determination of hydrogen/deuterium ratio with neutron measurements on MASTa)  

NASA Astrophysics Data System (ADS)

On MAST, compressional Alfvén eigenmodes can be destabilized by the presence of a sufficiently large population of energetic particles in the plasma. This dependence was studied in a series of very similar discharges in which increasing amounts of hydrogen were puffed into a deuterium plasma. A simple method to estimate the isotopic ratio nH/nD using neutron emission measurements is here described. The inferred isotopic ratio ranged from 0.0 to 0.6 and no experimental indication of changes in radial profile of nH/nD were observed. These findings are confirmed by TRANSP/NUBEAM simulations of the neutron emission.

Klimek, I.; Cecconello, M.; Sharapov, S. E.; Harrison, J.; Ericsson, G.

2014-11-01

58

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

PubMed Central

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

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

2014-01-01

59

Analysis of overlapped and noisy hydrogen/deuterium exchange mass spectra.  

PubMed

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. PMID:24018862

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

2013-12-01

60

Analysis of Overlapped and Noisy Hydrogen/Deuterium Exchange Mass Spectra  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

61

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 (60 cm) and colder (˜70 K) storage cell. A maximal target thickness of 1.2 (1.1)±0.1×10 14 nuclei/ cm2 was achieved with deuterium (hydrogen). With typical beam currents of 110 mA, this corresponds to a luminosity of about 8.4 (7.8)±0.8×10 31e- nuclei cm -2 s-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 720 MeV 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

62

QSO 0130-4021: A Third QSO Showing a Low Deuterium-to-Hydrogen Abundance Ratio  

NASA Astrophysics Data System (ADS)

We have discovered a third quasar absorption system which is consistent with a low deuterium-to-hydrogen abundance ratio, D/H=3.4×10-5. The zabs~2.8 partial Lyman limit system toward Q0130-4021 provides the strongest evidence to date against large D/H ratios because the H I absorption, which consists of a single high column density component with unsaturated high-order Lyman series lines, is readily modeled--a task which is more complex in other D/H systems. We have obtained 22 hr of spectra from the High-Resolution Echelle Spectrograph on the W. M. Keck Telescope, which allow a detailed description of the hydrogen. We see excess absorption on the blue wing of the H I Ly? line, near the expected position of deuterium. However, we find that deuterium cannot explain all of the excess absorption, and hence there must be contamination by additional absorption, probably H I. This extra H I can account for most or all of the absorption at the D position, and hence D/H=0 is allowed. We find an upper limit of D/H<=6.7×10-5 in this system, consistent with the value of D/H~=3.4×10-5 deduced toward QSO 1009+2956 and QSO 1937-1009 by Burles and Tytler. This absorption system shows only weak metal-line absorption, and we estimate [Si/H]<=-2.6, indicating that the D/H ratio of the system is likely primordial. All four of the known high-redshift absorption-line systems simple enough to provide useful limits on D are consistent with D/H=3.4+/-0.25×10-5. Conversely, this QSO provides the third case which is inconsistent with much larger values.

Kirkman, David; Tytler, David; Burles, Scott; Lubin, Dan; O'Meara, John M.

2000-02-01

63

Detection of deuterium and hydrogen using laser-induced helium gas plasma at atmospheric pressure  

SciTech Connect

An experimental study on gas analysis by means of laser-induced breakdown spectroscopy was conducted using a Nd-yttrium aluminum garnet laser (1,064 nm, 120 mJ, 8 ns) and helium host gas at atmospheric pressure on a sample of mixed water (H{sub 2}O) and heavy water (D{sub 2}O) in vapor form. It was shown that completely resolved hydrogen (H{sub {alpha}}) and deuterium (D{sub {alpha}}) emission lines that are separated by only 0.179 nm could be obtained at a properly delayed detection time when the charged particles responsible for the strong Stark broadening effect in the plasma have mostly disappeared. It is argued that the helium metastable excited state plays an important role in the hydrogen excitation process.

Kurniawan, Koo Hendrik; Lie, Tjung Jie; Suliyanti, Maria Margaretha; Hedwig, Rinda; Abdulmadjid, Syahrun Nur; Pardede, Marincan; Idris, Nasrullah; Kobayashi, Takao; Kusumoto, Yoshihumi; Kagawa, Kiichiro; Tjia, May On [Research Center of Maju Makmur Mandiri Foundation, 40 Srengseng Raya, Kembangan, Jakarta Barat 11630 (Indonesia); Department of Fiber Amenity, Graduate School of Engineering, Fukui University, 9-1 Bunkyo 3-chome, Fukui 910 (Japan); Department of Chemistry and Bio-Science, Faculty of Science, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065 (Japan); Department of Physics, Faculty of Education and Regional Studies, 9-1 Bunkyo 3-chome, Fukui 910 (Japan); Department of Physics, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, 10 Ganesha, Bandung 40132 (Indonesia)

2005-11-01

64

Sequence-Specific Conformational Flexibility of SNARE Transmembrane Helices Probed by Hydrogen/Deuterium Exchange  

PubMed Central

SNARE proteins mediate fusion of intracellular eukaryotic membranes and their ?-helical transmembrane domains are known to contribute to lipid bilayer mixing. Synthetic transmembrane domain peptides were previously shown to mimic the function of SNARE proteins in that they trigger liposome fusion in a sequence-specific fashion. Here, we performed a detailed investigation of the conformational dynamics of the transmembrane helices of the presynaptic SNAREs synaptobrevin II and syntaxin 1a. To this end, we recorded deuterium/hydrogen-exchange kinetics in isotropic solution as well as in the membrane-embedded state. In solution, the exchange kinetics of each peptide can be described by three different classes of amide deuteriums that exchange with different rate constants. These are likely to originate from exchange at different domains of the helices. Interestingly, the rate constants of each class vary with the TMD sequence. Thus, the exchange rate is position-specific and sequence-specific. Further, the rate constants correlate with the previously determined membrane fusogenicities. In membranes, exchange is retarded and a significant proportion of amide hydrogens are protected from exchange. We conclude that the conformational dynamics of SNARE TMD helices is mechanistically linked to their ability to drive lipid mixing. PMID:18456822

Stelzer, Walter; Poschner, Bernhard C.; Stalz, Holger; Heck, Albert J.; Langosch, Dieter

2008-01-01

65

Longitudinal-Transverse Separations of Deep-Inelastic Structure Functions at Low Q{sup 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 Laboratory Hall C spanning the four-momentum transfer range 0.06hydrogen and deuterium.

Tvaskis, V.; Blok, H. P. [Vrije Universiteit, 1081 HV Amsterdam (Netherlands); National Instituut voor Kernfysica en Hoge-Energiefysica (NIKHEF), 1009 DB Amsterdam (Netherlands); Christy, M. E.; Baker, O. K.; Cochran, A.; Cole, L.; Gasparian, A.; Nazaryan, V.; Sato, Y.; Uzzle, A. [Hampton University, Hampton, Virginia 23668 (United States); Arrington, J.; Jackson, H. E.; Potterveld, D. H. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Asaturyan, R.; Mkrtchyan, H.; Stepanyan, S.; Tadevosian, V. [Yerevan Physics Institute, 375036, Yerevan (Armenia); Bosted, P.; Ent, R.; Fenker, H. C. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)] (and others)

2007-04-06

66

A third QSO absorption system with a low Deuterium/Hydrogen ratio  

NASA Astrophysics Data System (ADS)

We present high signal-to-noise ratio data on an extremely simple zabs ~ 3 partial Lyman limit absorption system. This absorber has only a single major velocity component, and unsaturated high order H I Lyman series lines. Hence, the parameters which describe the Hydrogen absorption are very well determined. We find excess absorption on the blue wing of the H I Lyalpha line, near to the expected position of deuterium absorption. The excess absorption is slight, allowing us to set a firm upper limit to the amount of deuterium absorption in this absorber, D/H < 6 x 10(-5) . However, the expected deuterium line is at the wrong wavelength to explain all of the excess absorption on the blue wing of the H I Lyalpha line, and hence there must be contamination by additional H I interloper absorption. Because the parameters of the H I interloper and the D line will be somewhat degenerate, we can not place a lower limit on D/H in this absorption system. We show that this system probably has a very low metallicity, [C/H] < -2, so that our upper limit of D/H < 6 x 10(-5) should be representative of primordial D/H. All four of the known high redshift absorption line systems simple enough to provide useful limits on D are consistent with the low value of D/H = 3.4 +/- 0.5 x 10(-5) measured towards QSO 1009+2956 and QSO 1937-1009 by Burles and Tytler (1998a, 1998b). Conversely, three of the four D/H limits are inconsistent with high D/H value proposed by Webb et al. (1997a, 1997b) towards QSO 1718+4807.

Kirkman, D.; Tytler, D.; Burles, S.; Lubin, D.; Omeara, J.

1999-05-01

67

Structural Insights into Fibrinogen Dynamics Using Amide Hydrogen/Deuterium Exchange Mass Spectrometry  

PubMed Central

We determined the amide hydrogen/deuterium exchange profile of native human fibrinogen under physiologic conditions. After optimization of the quench and proteolysis conditions, more than 1,200 peptides were identified by mass spectrometry, spanning more than 90% of the constituent A?, B?, and ? chain amino acid sequences. The compact central and distal globular regions of fibrinogen were well protected from deuterium exchange, with the exception of the unfolded amino-terminal segments of the A? and B? chains extending from the central region, and the short ? chain “tail” extending from each distal globular region. The triple-helical coiled-coil regions, which bridge the central region to each distal region, were also well protected with the exception of a moderately fast-exchanging area in the middle of each coiled coil adjacent to the ? chain carbohydrate attachment site. These dynamic regions appear to provide flexibility to the fibrinogen molecule. The ? chain “out loop” contained within each coiled-coil also exchanged rapidly. The ?C domain (A? 392–610) exchanged rapidly, with the exception of a short segment sandwiched between a conserved disulfide linkage in the N-terminal ?C subdomain. This latter finding is consistent with a mostly disordered structure for the ?C domain in native fibrinogen. Analysis of the dysfibrinogen B? 235 Pro/Leu, which exhibits abnormal fibrin structure, revealed enhanced deuterium exchange surrounding the Pro/Leu substitution site as well as in the vicinity of the high affinity calcium binding site and the A knob polymerization pocket within the ?C domain. The implication of these changes with respect to fibrin structure is discussed. PMID:23875785

Marsh, James J.; Guan, Henry S.; Li, Sheng; Chiles, Peter G.; Tran, Danny; Morris, Timothy A.

2013-01-01

68

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

SciTech Connect

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

Lee, B.K.; Steckl, A.J. [Univ. of Cincinnati, OH (United States). Nanoelectronics Lab.; Zavada, J.M. [Army Research Office, Research Triangle Park, NC (United States); Wilson, R.G. [Hughes Research Labs., Malibu, CA (United States)

1998-12-31

69

Deuterium to hydrogen towards QSO 1009+2956 from a mesoturbulent model  

E-print Network

We present a new analysis of the deuterium absorption at z = 2.504 towards the quasar Q1009+2956 using the mesoturbulent model which accounts for possible correlations in the large scale velocity field. We obtain a slightly higher deuterium-to-hydrogen ratio D/H = (3.5 - 5.0)*10^{-5} as compared with the recent measurement D/H = (3.3 - 4.5)*10^{-5} (68% C.L.) performed by Burles & Tytler (1998b) using the usual microturbulent approximation which assumes that the velocity field is uncorrelated. Other mesoturbulent calculations of the D-abundances at z = 3.572 towards Q1937--1009 and at z = 0.701 towards Q1718+4807 (the systems showing `low' and possibly `high' D/H values, respectively, in the microturbulent approaches) agree with the present one within the errors of measurements. Thus, the mesoturbulent analysis does not reveal any spatial variations of D/H and supports the standard homogeneous model of big bang nucleosynthesis.

Levshakov, S A; Burles, S M; Levshakov, Sergei A.; Tytler, David; Burles, Scott

1998-01-01

70

Deuterium to hydrogen towards QSO 1009+2956 from a mesoturbulent model  

E-print Network

We present a new analysis of the deuterium absorption at z = 2.504 towards the quasar Q1009+2956 using the mesoturbulent model which accounts for possible correlations in the large scale velocity field. We obtain a slightly higher deuterium-to-hydrogen ratio D/H = (3.5 - 5.0)*10^{-5} as compared with the recent measurement D/H = (3.3 - 4.5)*10^{-5} (68% C.L.) performed by Burles & Tytler (1998b) using the usual microturbulent approximation which assumes that the velocity field is uncorrelated. Other mesoturbulent calculations of the D-abundances at z = 3.572 towards Q1937--1009 and at z = 0.701 towards Q1718+4807 (the systems showing `low' and possibly `high' D/H values, respectively, in the microturbulent approaches) agree with the present one within the errors of measurements. Thus, the mesoturbulent analysis does not reveal any spatial variations of D/H and supports the standard homogeneous model of big bang nucleosynthesis.

Sergei A. Levshakov; David Tytler; Scott Burles

1998-12-06

71

Deuterium to hydrogen towards QSO 1009 2956 from a mesoturbulent model  

NASA Astrophysics Data System (ADS)

We present a new analysis of the deuterium absorption at z = 2.504 towards the quasar Q1009+2956 using the mesoturbulent model which accounts for possible correlations in the large-scale velocity field. We obtain a slightly higher deuterium-to-hydrogen ratio D/H (3.5-5.0) × 10-5 as compared with the recent measurement D/H (3.3-4.5) × 10-5 (68% C.L.) performed by Burles and Tytler (1998b) using the usual microturbulent approximation which assumes that the velocity field is uncorrelated. Other mesoturbulent calculations of the D-abundances at z = 3.572 towards Q1937-1009 and at z = 0.701 towards Q1718+4807 (the systems showing 'low' and possibly 'high' D/H values, respectively, in the microturbulent approaches) agree with the present one with the errors of measurements. Thus, the mesoturbulent analysis does not reveal any spatial variations of D/H and supports the standard homogeneous model of big bang nucleosynthesis.

Levshakov, S. A.; Tytler, D.; Burles, S.

72

Hydrogen/deuterium exchange of cross-linkable ?-amino acid derivatives in deuterated triflic acid.  

PubMed

In this paper we report here a hydrogen/deuterium exchange (H/D exchange) of cross-linkable ?-amino acid derivatives with deuterated trifluoromethanesulfonic acid (TfOD). H/D exchange with TfOD was easily applied to o-catechol containing phenylalanine (DOPA) within an hour. A partial H/D exchange was observed for trifluoromethyldiazirinyl (TFMD) phenylalanine derivatives. N-Acetyl-protected natural aromatic ?-amino acids (Tyr and Trp) were more effective in H/D exchange than unprotected ones. The N-acetylated TFMD phenylalanine derivative afforded slightly higher H/D exchange than unprotected derivatives. An effective post-deuteration method for cross-linkable ?-amino acid derivatives will be useful for the analysis of biological functions of bioactive peptides and proteins by mass spectrometry. PMID:25229846

Wang, Lei; Murai, Yuta; Yoshida, Takuma; Okamoto, Masashi; Masuda, Katsuyoshi; Sakihama, Yasuko; Hashidoko, Yasuyuki; Hatanaka, Yasumaru; Hashimoto, Makoto

2014-07-01

73

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

74

Development of a hydrogen and deuterium polarized gas target for application in storage rings  

SciTech Connect

Polarized gas targets of atomic hydrogen and deuterium have significant advantages over conventional polarized targets, e.g. chemical and isotopic purity, large polarization including deuteron tensor polarization, absence of strong magnetic fields, rapid polarization reversal. While in principle the beam of polarized atoms from an atomic beam source (Stern-Gerlach spin separation) can be used as a polarized target, the target thickness achieved is too small for most applications. We propose to increase the target thickness by injecting the polarized atoms into a storage cell. Provided the atoms survive several hundred wall collisions without losing their polarization, it will be possible to achieve a target thickness of 10{sup 13} to 10{sup 14} atoms/cm{sup 2} by injection of polarized atoms from an atomic-beam source into suitable cells. Such targets are very attractive as internal targets in storage rings.

Haeberli, W.

1992-02-01

75

Development of a hydrogen and deuterium polarized gas target for application in storage rings. Progress report  

SciTech Connect

Polarized gas targets of atomic hydrogen and deuterium have significant advantages over conventional polarized targets, e.g. chemical and isotopic purity, large polarization including deuteron tensor polarization, absence of strong magnetic fields, rapid polarization reversal. While in principle the beam of polarized atoms from an atomic beam source (Stern-Gerlach spin separation) can be used as a polarized target, the target thickness achieved is too small for most applications. We propose to increase the target thickness by injecting the polarized atoms into a storage cell. Provided the atoms survive several hundred wall collisions without losing their polarization, it will be possible to achieve a target thickness of 10{sup 13} to 10{sup 14} atoms/cm{sup 2} by injection of polarized atoms from an atomic-beam source into suitable cells. Such targets are very attractive as internal targets in storage rings.

Haeberli, W.

1992-02-01

76

HDXFinder: automated analysis and data reporting of deuterium/hydrogen exchange mass spectrometry.  

PubMed

Hydrogen/deuterium exchange in combination with mass spectrometry (H/D MS) is a sensitive technique for detection of changes in protein conformation and dynamics. However, wide application of H/D MS has been hindered, in part, by the lack of computational tools necessary for efficient analysis of the large data sets associated with this technique. We report a novel web-based application for automatic analysis of H/D MS experimental data. This application relies on the high resolution of mass spectrometers to extract all isotopic envelopes before correlating these envelopes with individual peptides. Although a fully automatic analysis is possible, a variety of graphical tools are included to aid in the verification of correlations and rankings of the isotopic peptide envelopes. As a demonstration, the rate constants for H/D exchange of peptides from rabbit muscle pyruvate kinase are mapped onto the structure of this protein. PMID:22083588

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

2012-02-01

77

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

E-print Network

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

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

2014-10-10

78

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

PubMed

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

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

2014-11-01

79

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

80

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

81

Recombination and Relaxation Mechanisms of Atomic Hydrogen and Deuterium at Low Temperatures and in AN Esr Spectrometer  

NASA Astrophysics Data System (ADS)

The recombination and relaxation mechanisms of atomic hydrogen and atomic deuterium have been examined in an ESR spectrometer at temperatures between T = .5 to .7 K and a magnetic field of 3 kilogauss. The electronic relaxation time (T(,1)) is weakly dependent on the density and temperature and is felt to be dominated by atomic hydrogen hitting a wall covered with superfluid helium and flipping its spin via an interaction with the ferromagnetic impurities on the microwave cavity wall. From a measurement of the low temperature flux of atomic deuterium and the known sensitivity of the ESR spectrometer, the assumption that recombination is dominated by the surface leads to a wall recombination coefficient of greater than 5 x 10('-11) cm('3)/sec. Using the accepted value for the adsorption energy of 2.5 K for atomic deuterium on a superfluid surface, the wall recombination cross length is greater than 200 (ANGSTROM). This value is two to three orders of magnitude larger than the value for atomic hydrogen. Other loss mechanisms for atomic deuterium are examined.

Mayer, Rulon Richard

82

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

NASA Astrophysics Data System (ADS)

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

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

83

Measurements and monitoring of the hydrogen and deuterium contents in the plasma of the L-2M stellarator  

NASA Astrophysics Data System (ADS)

The program of experiments on ITER includes a sequential change of the plasma isotopic composition from pure hydrogen plasma in the initial stage of research to deuterium and, then, deuterium-tritium plasma with a gradual increase in the tritium content. In this context, the influence of the plasma isotopic composition on the processes of plasma heating and confinement are being actively studied on the existing tokamaks and stellarators. The plasma isotopic composition also depends on the composition of the gas desorbed from the vacuum chamber wall in the course of recycling. Therefore, the rate of change of the plasma isotopic composition after altering the injected gas also depends on the rate of change of the isotopic composition of the gas absorbed in the wall. These effects were studied in the experiments carried out on the L-2M stellarator in which the working gas was changed from hydrogen to deuterium. Spectral measurements of the intensity ratio between the H ? and D ? lines made it possible to monitor the isotopic composition of the plasma in the course of cleaning of the chamber wall from earlier absorbed hydrogen and its replacement with deuterium. After returning to hydrogen, the rate of cleaning of the wall from deuterium was also determined. The results of these experiments show that the plasma isotopic composition varies exponentially with the number N of shots after transition to another isotope, ˜exp(- N/47). Hence, the isotopic composition can be changed almost completely over 2 to 3 working days. This allows one to study the influence of the plasma isotopic composition on plasma confinement during the same experimental session.

Voronov, G. S.; Berezhetskii, M. S.

2012-04-01

84

Measurements and monitoring of the hydrogen and deuterium contents in the plasma of the L-2M stellarator  

SciTech Connect

The program of experiments on ITER includes a sequential change of the plasma isotopic composition from pure hydrogen plasma in the initial stage of research to deuterium and, then, deuterium-tritium plasma with a gradual increase in the tritium content. In this context, the influence of the plasma isotopic composition on the processes of plasma heating and confinement are being actively studied on the existing tokamaks and stellarators. The plasma isotopic composition also depends on the composition of the gas desorbed from the vacuum chamber wall in the course of recycling. Therefore, the rate of change of the plasma isotopic composition after altering the injected gas also depends on the rate of change of the isotopic composition of the gas absorbed in the wall. These effects were studied in the experiments carried out on the L-2M stellarator in which the working gas was changed from hydrogen to deuterium. Spectral measurements of the intensity ratio between the H{sub {alpha}} and D{sub {alpha}} lines made it possible to monitor the isotopic composition of the plasma in the course of cleaning of the chamber wall from earlier absorbed hydrogen and its replacement with deuterium. After returning to hydrogen, the rate of cleaning of the wall from deuterium was also determined. The results of these experiments show that the plasma isotopic composition varies exponentially with the number N of shots after transition to another isotope, {approx}exp(-N/47). Hence, the isotopic composition can be changed almost completely over 2 to 3 working days. This allows one to study the influence of the plasma isotopic composition on plasma confinement during the same experimental session.

Voronov, G. S.; Berezhetskii, M. S. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)

2012-04-15

85

Deuterium-hydrogen exchange and scrambling reactions in the pyrolysis of labeled cyclopentene. A radical mechanism  

SciTech Connect

Inter- and intraradical mechanisms that promote deuterium-hydrogen scrambling in labeled cyclopentene-d/sub 1/ are investigated at 800 and 1200 K. Rate constants are estimated for each step and for possible competing side reactions. The fast radical bimolecular exchange at 800 K and unimolecular scrambling at 1200 K of labeled cyclopentene are shown to be faster than the Woodward-Hoffman allowed 1,4 concerted molecular elimination of hydrogen. The low-energy estimate of 8.0 kcal/mol by Lewis of the difference between the allowed 1,4 and disallowed 1,2 channels can thus be explained. No conclusions can be drawn concerning the 1,2 channel. The estimated rates of radical reactions are in agreement with experiments on the addition of D/sub 2/ to cyclopentadiene at 300/sup 0/C which shows only cis, 3 to 5 addition and with pyrolysis experiments at 500 +- 20/sup 0/C which show about 5% contribution of a higher than first-order radical reaction. The mechanism of this radical decomposition is given and its steps are explicitly evaluated. 2 tables.

Kosnik, K.G.; Benson, S.W.

1983-07-21

86

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

PubMed Central

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

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

2013-01-01

87

Platform Dependencies in Bottom-up Hydrogen/Deuterium Exchange Mass Spectrometry*  

PubMed Central

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.

2013-01-01

88

Deuterium and selenium-77 NMR study of the condensed phases of hydrogen selenide  

SciTech Connect

Hydrogen selenide has been studied by /sup 2/H and /sup 77/Se NMR between 57 and 273 K, in order to characterize the molecular motions. In solid III the molecules are essentially rigid at approx. 77 K, but there is evidence for the onset of a slow motion just before the transition to phase II. The III equivalent to II phase transition shows hysteresis. At 77 K the /sup 77/Se rigid lattice shielding tensor components were found to be sigma/sub xx/ = - 240.7, sigma/sub yy/ = -9.5, and sigma/sub zz/ = 250.2 ppm relative to sigma/sub isotropic/. The /sup 2/H line shape at 77 K indicated a quadrupole coupling constant (e/sup 2/qQ/h) = 102.6 kHz and asymmetry parameter eta = 0.113, whereas in phase II at 120 K(e/sup 2/qQ/h) = 56.9 kHz, eta = 0 and in supercooled phase II at 85 K eta = 0.059. In the plastic crystalline phase I both /sup 2/H and /sup 77/Se line shapes are completely averaged by rapid overall rotations. Apparent activation energies of 3.5 kJ mol/sup -1/ (solid I) and 3.4 kJ mol/sup -1/ (liquid) were obtained from /sup 2/H T/sub 1/ measurements, and 4.3 kJ mol/sup -1/ (solid I) and 5.7 kJ mol/sup -1/ (liquid) were obtained from /sup 77/Se T/sub 1/ measurements. The /sup 77/Se spectra show a large deuterium isotope shift of 7 ppm per deuterium, and the chemical shift also shows large discontinuities at the gas-liquid-solid I phase transitions. 45 references, 6 figures, 4 tables.

Facey, G.; Wasylishen, R.E.; Collins, M.J.; Ratcliffe, C.I.; Ripmeester, J.A.

1986-05-08

89

Inelastic {J}/{?} production in deep inelastic scattering from hydrogen and deuterium and the gluon distribution of free nucleons  

NASA Astrophysics Data System (ADS)

We present results on inelastic J/? production from muon interactions with hydrogen and deuterium at an incident muon energy of 280 GeV. The measured cross section ratio per nucleon for muon-induced {J}/{?} production in deuterium and hydrogen was found to be R(D 2/H 2) = 1.01±0.15. The colour singlet model is shown to provide a good description of the observed differential cross section apart from a normalisation factor. The comparison between the observed cross section and the colour singlet model prediction allows the extraction of the gluon structure function G( x) of the nucleon. The momentum fraction x of the nucleon carried by the gluon is measured in the range of x = [0.02, 0.30]. The normalised gluon distribution of free nucleons thus found can be parametrised as xG(x) = {1}/{2} (?+1) (1-x) ?, with?=5+-9( sta.) .

Allasia, D.; Amaudruz, P.; Arneodo, M.; Arvidson, A.; Badelek, B.; Baum, G.; Beaufays, J.; Bird, I. G.; Botje, M.; Broggini, C.; Brückner, W.; Brüll, A.; Burger, W. J.; Ciborowski, J.; Crittenden, R.; van Dantzig, R.; Döbbeling, H.; Domingo, J.; Drinkard, J.; Dzierba, A.; Engelien, H.; Ferrero, M. I.; Fluri, L.; Grafstrom, P.; Hagberg, E.; von Harrach, D.; van der Heijden, M.; Heusch, C.; Ingram, Q.; Jacholkowska, A.; Janson, K.; de Jong, M.; Kabu?, E. M.; Kaiser, R.; Ketel, T. J.; Klein, F.; Korzen, B.; Krüner, U.; Kullander, S.; Landgraf, U.; Lettenström, F.; Lindqvist, T.; Mallot, G. K.; Mariotti, C.; van Middelkoop, G.; Mizuno, Y.; Nassalski, J.; Nowotny, D.; Pavel, N.; Peschel, H.; Peroni, C.; Pietrzyk, U.; Povh, B.; Rieger, R.; Rith, K.; Röhrich, K.; Rondio, E.; Ropelewski, L.; Sandacz, A.; Scholz, C.; Schumacher, R.; Sennhausser, U.; Sever, F.; Shibata, T.-A.; Siebler, M.; Simon, A.; Staiano, A.; Taylor, G.; Treichel, M.; Vuilleumier, J. L.; Walcher, T.; Welch, K.; Windmolders, R.; New Muon Collaboration (NMC)

1991-04-01

90

Kinetics, kinetic deuterium isotope effects, and mechanism of nitrous oxide reaction with hydrogen on supported precious-metal catalysts  

Microsoft Academic Search

The kinetics and kinetic deuterium isotope effects have been precisely measured for the reaction of nitrous oxide with hydrogen on Ru\\/AlâOâ, Rh\\/AlâOâ, Ir\\/AlâOâ, and Pt\\/AlâOâ catalysts. The reaction apparently proceeds through the two following elementary steps: NâO + M ..-->.. Nâ + M=O (reaction 1) and M=O + Hâ ..-->.. M + HâO (reaction 2). In reaction 1, an NâO

A. Mlyamoto; Shigeo Baba; Mitsushi Mori; Yuichi Murakami

1981-01-01

91

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

92

Carbon-hydrogen bonding in near-frictionless carbon  

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

93

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

94

Protein Conformation in Amorphous Solids by FTIR and by Hydrogen/Deuterium Exchange with Mass Spectrometry  

PubMed Central

Solid-state hydrogen/deuterium exchange (ssHDX) with electrospray ionization mass spectrometry (ESI-MS) and Fourier transform infrared (FTIR) spectroscopy were used to assess protein conformation in amorphous solids. Myoglobin, lysozyme, ?-lactoglobulin, ribonuclease A, E-cadherin 5, and concanavalin A were co-lyophilized with carbohydrates (trehalose, raffinose, and dextran 5000), linear polymers (polyvinyl alcohol and polyvinyl pyrrolidone) or guanidine hydrochloride (negative control). For ssHDX, samples were exposed to D2O vapor at 33% relative humidity and room temperature, and then reconstituted at low temperature (4°C) and pH 2.5 and analyzed by ESI-MS. Peptic digestion of selected proteins was used to provide region-specific information on exchange. FTIR spectra were acquired using attenuated total reflectance. FTIR and ssHDX of intact proteins showed preservation of structure by raffinose and trehalose, as indicated by FTIR band intensity and protection from exchange. ssHDX of peptic digests further indicated that these protective effects were not exerted uniformly along the protein sequence but were observed primarily in ?-helical regions, a level of structural resolution not afforded by FTIR. The results thus demonstrate the utility of HDX with ESI-MS for analyzing protein conformation in amorphous solid samples. PMID:18835903

Sinha, Sandipan; Li, Yunsong; Williams, Todd D.; Topp, Elizabeth M.

2008-01-01

95

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

PubMed Central

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

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

2011-01-01

96

Hydrogen attack - Influence of hydrogen sulfide. [on carbon steel  

NASA Technical Reports Server (NTRS)

An experimental study is conducted on 12.5-mm-thick SAE 1020 steel (plain carbon steel) plate to assess hydrogen attack at room temperature after specimen exposure at 525 C to hydrogen and a blend of hydrogen sulfide and hydrogen at a pressure of 3.5 MN/sq m for exposure times up to 240 hr. The results are discussed in terms of tensile properties, fissure formation, and surface scales. It is shown that hydrogen attack from a high-purity hydrogen environment is severe, with the formation of numerous methane fissures and bubbles along with a significant reduction in the room-temperature tensile yield and ultimate strengths. However, no hydrogen attack is observed in the hydrogen/hydrogen sulfide blend environment, i.e. no fissure or bubble formation occurred and the room-temperature tensile properties remained unchanged. It is suggested that the observed porous discontinuous scale of FeS acts as a barrier to hydrogen entry, thus reducing its effective equilibrium solubility in the iron lattice. Therefore, hydrogen attack should not occur in pressure-vessel steels used in many coal gasification processes.

Eliezer, D.; Nelson, H. G.

1978-01-01

97

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

98

Desorption of hydrogen trapped in carbon and graphite  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

99

Nuclear Quadrupole Double Resonance Investigation of the Anomalous Temperature Coefficients of the Strong Hydrogen Bonds in Sodium and Potassium Deuterium Diacetate.  

NASA Astrophysics Data System (ADS)

This thesis was directed at learning more about the unusual electronic environment near hydrogen within strong hydrogen bonds. "Strong" hydrogen bonds are unique in that the hydrogen atom is symmetrically located, or nearly so, between two electronegative atoms; the bond energies are relatively large. In a "normal" hydrogen bond the hydrogen atom is bonded to, and thus physically closer to, a parent atom, and only weakly attracted to another electronegative atom; bond energies are typically small. To examine these bonds, deuterium was substituted for hydrogen and the electric quadrupole coupling constant (QCC) of deuterium was measured using field cycling nuclear magnetic resonance. The electric quadrupole moment of deuterium is sensitive to changes in the surrounding electric field gradient, and is thus a good probe of the immediate electronic structure. The results show that the temperature dependence of the QCC is opposite to, and much larger than, what one would normally expect to observe for deuterium. The QCC is found to decrease strongly with decreasing temperature. This project was the first to study in detail the temperature dependence of deuterium QCCs in strong hydrogen bonds. The magnitude of the deuterium QCCs for the diacetates was found to be strongly depressed relative to typical values for deuterium. These results parallel large shifts in the infrared vibrational frequencies observed in many molecules which contain strong hydrogen bonds. The asymmetry parameter, which is a measure of the departure from axial symmetry of the electric field gradient (EFG) at deuterium, was found to be unusually large for what are known to be linear, or nearly linear, three-center bonds. Based on ab initio Hartree-Fock calculations aimed at determining the EFG at H in the archetypal bifluoride ion, F-H-F^-, the electronic charge density is drastically depleted at H. It is believed that the large reduction in the charge density allows the deuterium EFG to be highly sensitive to the shape of the charge distribution on the atoms to which deuterium is bonded. If these atoms are at points of low crystallographic symmetry, the polarization of these adjacent atoms by other nearby atoms may cause the EFG to depart substantially from being axially symmetric. Also obtained from the molecular orbital calculations for bifluoride ion were the total electronic energy and the electric field gradient at H. From these calculations potential function models for the asymmetric stretch and the bend were constructed. An attempt was made to correlate the predictions made by these models for the temperature dependence of the deuteron quadrupole coupling constant in bifluoride ion with the experimentally observed results for the diacetates.

Shaw, Eric Max

100

A critical compilation of experimental data on spectral lines and energy levels of hydrogen, deuterium, and tritium  

SciTech Connect

For more than 50 years, Charlotte Moore's compilation of atomic energy levels and its subsequent revisions have been the standard source of reference data for the spectra of hydrogen and its isotopes. In those publications, theoretical data based on quantum-electrodynamic calculations have been given. This reflects the fact that the theory of the hydrogen spectrum has been perfected to an extent far exceeding the capabilities of the best measurements. However, rapid advances in the techniques of laser spectroscopy and optical frequency metrology have recently put experiments on a par with theory in terms of precision. This calls for construction of new comprehensive data sets for H, D, and T that summarize the latest experimental work and can be directly compared with the modern theoretical reference data. The present work compiles several tens of recent measurements of the hydrogen, deuterium, and tritium fine and hyperfine structure intervals and presents sets of energy levels and Ritz wavelengths derived from those measurements. Data exist for the fine structure of energy levels of hydrogen and deuterium up to principal quantum number n = 12. For higher lying levels, there are many observed lines with unresolved fine structure. From those observations, level centers (centers of the fine structure) are derived by a least-squares optimization, and Ritz wavelengths of series with upper levels up to n = 40 are obtained. For tritium, the n = 2 and 3 energy level intervals are derived from experimental observations.

Kramida, A.E., E-mail: Alexander.kramida@nist.go [Atomic Physics Division, National Institute of Standards and Technology, 100 Bureau Dr., MS 8422, Gaithersburg, MD 20899 (United States)

2010-11-15

101

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

PubMed Central

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

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

2008-01-01

102

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

103

Methods for the Analysis of High Precision Differential Hydrogen Deuterium Exchange Data.  

PubMed

Hydrogen/deuterium exchange (HDX) mass spectrometry has been widely applied to the characterization of protein dynamics. More recently, differential HDX has been shown to be effective for the characterization of ligand binding. Previously we have described a fully automated HDX system for use as a ligand screening platform. Here we describe and validate the required data analysis workflow to facilitate the use of HDX as a robust approach for ligand screening. Following acquisition of HDX data at a single on-exchange time point (n ? 3), one way analysis of variance in conjunction with the Tukey multiple comparison procedure is used to establish the significance of any measured difference. Analysis results are graphed with respect to a single peptide, ligand or group of ligands, or displayed as an overview within a heat map. For the heat map display, only ?%D values with a Tukey-adjusted P value less than 0.05 are colored. Hierarchical clustering is used to bin compounds with highly similar HDX signatures. The workflow is evaluated with a small data set showing the ligand binding domain (LDB) of the nuclear receptor peroxisome proliferator-activated receptor gamma (PPAR?) screened against 10 functionally selective ligands. More significantly, data for the vitamin D receptor (VDR) in complex with 87 ligands are presented. To highlight the robustness and precision of our automated HDX platform we analyzed the data from 4191 replicate HDX measurements acquired over an eight month timeframe. Ninety six percent of these measurements were within 10 percent of the mean value. Work has begun to integrate these analysis and graphing components within our HDX software suite. PMID:21528013

Chalmers, Michael J; Pascal, Bruce D; Willis, Scooter; Zhang, Jun; Iturria, Stephen J; Dodge, Jeffery A; Griffin, Patrick R

2011-04-30

104

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

105

The Cosmological Baryon Density from the Deuterium-to-Hydrogen Ratio in QSO Absorption Systems: D\\/H toward Q1243+3047  

Microsoft Academic Search

We report the detection of deuterium absorption at redshift 2.525659 toward Q1243+3047. We describe improved methods to estimate the deuterium to hydrogen abundance ratio (D\\/H) in absorption systems, including improved modeling of the continuum level, the Lyalpha forest, and the velocity structure of the absorption. Together with improved relative flux calibration, these methods give D\\/H=2.42+0.35-0.25×10-5 from our Keck I HIRES

David Kirkman; David Tytler; Nao Suzuki; John M. O'Meara; Dan Lubin

2003-01-01

106

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

107

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

PubMed Central

PEGylation is the covalent attachment of polyethylene glycol to proteins, and it can be used to alter immunogenicity, circulating half life and other properties of therapeutic proteins. To determine the impact of PEGylation on protein conformation, we applied hydrogen/deuterium exchange mass spectrometry (HDX MS) to analyze Granulocyte Colony Stimulating Factor (G-CSF) upon PEGylation as a model system. The combined use of HDX automation technology and data analysis software allowed reproducible and robust measurements of the deuterium incorporation levels for peptic peptides of both PEGylated and non-PEGylated G-CSF. The results indicated that significant differences in deuterium incorporation were induced by PEGylation of G-CSF, although the overall changes observed were quite small. PEGylation did not result in gross conformational rearrangement of G-CSF. The data complexity often encountered in HDX MS measurements was greatly reduced though a data processing and presentation format designed to facilitate the comparison process. This study demonstrates the practical utility of HDX MS for comparability studies, process monitoring and protein therapeutic characterization in the biopharmaceutical industry. PMID:22227798

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

2012-01-01

108

Using hydrogen/deuterium exchange mass spectrometry to study conformational changes in granulocyte colony stimulating factor upon PEGylation.  

PubMed

PEGylation is the covalent attachment of polyethylene glycol to proteins, and it can be used to alter immunogenicity, circulating half life and other properties of therapeutic proteins. To determine the impact of PEGylation on protein conformation, we applied hydrogen/deuterium exchange mass spectrometry (HDX MS) to analyze granulocyte colony stimulating factor (G-CSF) upon PEGylation as a model system. The combined use of HDX automation technology and data analysis software allowed reproducible and robust measurements of the deuterium incorporation levels for peptic peptides of both PEGylated and non-PEGylated G-CSF. The results indicated that significant differences in deuterium incorporation were induced by PEGylation of G-CSF, although the overall changes observed were quite small. PEGylation did not result in gross conformational rearrangement of G-CSF. The data complexity often encountered in HDX MS measurements was greatly reduced through a data processing and presentation format designed to facilitate the comparison process. This study demonstrates the practical utility of HDX MS for comparability studies, process monitoring, and protein therapeutic characterization in the biopharmaceutical industry. PMID:22227798

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

2012-03-01

109

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

110

Fourier transform mass spectrometry to monitor hyaluronan-protein interactions: use of hydrogen/deuterium amide exchange  

PubMed Central

The use of Fourier transform mass spectrometry (FTMS) to monitor noncovalent complex formation in the gas phase under native conditions between the Link module from human tumor necrosis factor stimulated gene-6 (Link_TSG6) and hyaluronan (HA) oligosaccharides is reported. In particular, a titration experiment with increasing concentrations of octasaccharide (HA8) to protein produced a noncovalent complex with 1:1 stoichiometry when the oligosaccharide was in molar excess. However, in the presence of a molar excess of tetrasaccharide (HA4) nearly all proteins and oligosaccharides were observed in their unbound charge states. These results are consistent with solution-phase properties for this interaction in which HA8, but not HA4, supports high affinity Link_TSG6 binding. Hydrogen/deuterium amide exchange mass spectrometry (H/D-EX MS) was also utilized to investigate the level of global deuterium incorporation, over time, for Link_TSG6 in both the absence and presence of HA8. After dilution into quenching conditions, deuterium incorporation reached limiting asymptotic values of 37 and 26 deuterons for the free and bound protein at 240 and 480 min, respectively, indicating that the oligosaccharide interferes with amide exchange on binding. To detect sequence-specific deuterium incorporation, pepsin digestion of Link_TSG6 in both the absence and presence of HA8 was performed. A level of deuterium incorporation of 10–30% was observed for peptides analyzed in free Link_TSG6. Interestingly, HA8 blocked some sites of proteolysis in Link_TSG6 compared to the free protein. Molecular modeling indicated that amino acids proximal to the ligand correlated with regions of the protein that were resistant to enzymatic digestion. Of the peptides that could be analyzed by H/D-EX MS in the presence of the ligand, a 30–60% reduction in deuterium incorporation, relative to the free protein, was observed, even for those sequences not directly involved in HA binding. These results support the utility of FTMS as a method for the characterization of protein–carbohydrate interactions. PMID:17154353

Seyfried, Nicholas T.; Atwood, James A.; Yongye, Austin; Almond, Andrew; Day, Anthony J.; Orlando, Ron; Woods, Robert J.

2014-01-01

111

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

SciTech Connect

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

Lingyan Zhu

2004-02-28

112

Investigation of atomic deuterium (hydrogen) emission from the surface of some transition metal deuterides (hydrides)  

NASA Astrophysics Data System (ADS)

Deuterium desorption from the surface of decomposing palladium deuteride was studied while monitoring the atomic component of the desorbing gas by means of an adsorption method. A thin gold film was applied as an adsorbent active for D adsorption, but inert against interaction with D 2. The deuterium deposit thereby collected on the Au surface was analysed by means of thermal desorption mass spectrometry (TDMS). The atomic component of deuterium arising by desorption from decomposing PdD y was clearly detected. The experimental results obtained for PdD y are compared with those observed during the decomposition of PdH x, as well as the decomposition of other hydrides including TiH z and VH u.

Nowicka, E.; Wolfram, Z.; Lisowski, W.; Du?, R.

1996-01-01

113

Irradiated interplanetary dust particles as a possible solution for the deuterium/hydrogen paradox of Earth's oceans  

NASA Technical Reports Server (NTRS)

Determining the source of Earth's oceans is a longstanding problem in planetary science. Possible sources of water include water ice or water of hydration of silicate minerals in the original material from which the bulk Earth accreted and water brought in by late-arriving planetesimals during the heavy bombardment period (4.5-3.8 Gyr ago) [Chyba, 1989, 1991]. Comets are an attractive source of water because their origin in the outer solar system is consistent with the long timescale for heavy bombardment. However, the high deuterium/hydrogen (D/H) ratio of the three comets that have been studied, Halley, Hyakutake, and Hale-Bopp, indicates that Earth must have had a source with a low-D/H ratio as well. Here we suggest that solar wind-implanted hydrogen on interplanetary dust particles (IDPs) provided the necessary low-D/H component of Earth's water inventory.

Pavlov, A. A.; Pavlov, A. K.; Kasting, J. F.

1999-01-01

114

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

E-print Network

A deuterium-tritium (DT) nuclear pulse propulsion concept for fast interplanetary transport is proposed utilizing almost all the energy for thrust and without the need for a large radiator: 1. By letting the thermonuclear micro-explosion take place in the center of a liquid hydrogen sphere with the radius of the sphere large enough to slow down and absorb the neutrons of the DT fusion reaction, heating the hydrogen to a fully ionized plasma at a temperature of ~ 105 K. 2. By using the entire spacecraft as a magnetically insulated gigavolt capacitor, igniting the DT micro-explosion with an intense GeV ion beam discharging the gigavolt capacitor, possible if the space craft has the topology of a torus.

Winterberg, Friedwardt

2012-01-01

115

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

E-print Network

A deuterium-tritium (DT) nuclear pulse propulsion concept for fast interplanetary transport is proposed utilizing almost all the energy for thrust and without the need for a large radiator: 1. By letting the thermonuclear micro-explosion take place in the center of a liquid hydrogen sphere with the radius of the sphere large enough to slow down and absorb the neutrons of the DT fusion reaction, heating the hydrogen to a fully ionized plasma at a temperature of ~ 105 K. 2. By using the entire spacecraft as a magnetically insulated gigavolt capacitor, igniting the DT micro-explosion with an intense GeV ion beam discharging the gigavolt capacitor, possible if the space craft has the topology of a torus.

Friedwardt Winterberg

2012-07-31

116

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

SciTech Connect

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

117

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

NASA Technical Reports Server (NTRS)

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

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

1969-01-01

118

Proton magnetic resonance studies of glutamate-alanine transaminase-catalyzed deuterium exchange. Evidence for proton conservation during prototropic transfer from the alpha carbon of L-alanine to the C4-position of pyridoxal 5'-phosphate.  

PubMed

Pulsed Fourier transform proton magnetic resonance spectroscopy was used to study the glutamate-alanine transaminase-catalyzed incorporation of deuterium from solvent deuterium oxide into the alpha and beta positions of L-alanine. It was found that the beta proton resonance signal initially disappears slightly faster than the signal due to the alpha proton, but whereas the alpha proton signal decays exponentially, that due to the beta proton signal does not. Eventually, the rate of decrease of the alpha proton signal becomes greater than that for the beta proton. This change in the relative rates is ascribed to a deuterium isotope effect upon substitution of an alpha proton by a deuteron. Furthermore, as deuterium begins to replace hydrogen, two classes of alanine become distinguishable, i.e. alanine which contains deuterium in the alpha position and hydrogen in the beta position, and alanine which contains hydrogen in the alpha position and deuterium in the beta position. Thus, removal of all 3 beta protons is not contingent upon loss of an alpha proton from the same molecule. The two classes of deuterated alanine may conceivably arise by a scrambling mechanism in which protons are transferred from the alpha to the beta position and vice versa. Present evidence excludes this scramblong mechanism and leads to the conclusion that deuterium incorporation into L-alanine involves, (a) the reversible enzymatic conversion of the classical ketimine enzymes intermediate to an enaminetype structure, and (b) considerable conservation of label during the prototropic shift from the alpha carbon of L-alanine to the C4-position of pyridoxal 5'-phosphate. It is also postulated that alanine binds at the active site in such a way as to bring the beta protons into close contact with a basic group on the enzyme surface. This group is distinct from that used in abstraction of an alpha proton. The beta protons of glutamate are not enzymatically removed; presumably glutamate binds in such a way that the beta protons cannot effectively interact with an enzyme base. Similar studies were carried out on soluble glutamate-aspartate transaminase; no evidence was found for significant enzyme-catalyzed deuterium incorporation into the beta position of L-glutamate, L-aspartate, and L-alanine. PMID:1249068

Cooper, A J

1976-02-25

119

Stoichiometry: Elemental Analysis of Carbon and Hydrogen  

NSDL National Science Digital Library

This site provides a useful tutorial for applying principles of stoichiometry to determine the per cent composition by weight of carbon and hydrogen in unknown compounds. This information is then used to determine the empirical formulas of the unknowns. The empirical formula and molecular weight of the unknown compounds are then employed to determine the molecular formula.

Blauch, David N.

120

Modeling the selectivity of activated carbons for efficient separation of hydrogen and carbon dioxide  

E-print Network

the separation of hydrogen and carbon dioxide via adsorption in activated carbons. In the simulations, both hydrogen and carbon dioxide molecules are modeled as Lennard-Jones spheres, and the activated carbons essentially no preference over the two gases and the selectivity of carbon dioxide relative to hydrogen falls

Wu, Jianzhong

121

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

DOEpatents

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

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

2011-03-08

122

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

123

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

PubMed

The gas-phase conformations of electrosprayed ions of the model peptide KKDDDDIIKIIK have been examined by ion mobility spectrometry (IMS) and hydrogen deuterium exchange (HDX)-tandem mass spectrometry (MS/MS) techniques. [M+4H](4+) ions exhibit two conformers with collision cross sections of 418 Å(2) and 471 Å(2). [M+3H](3+) ions exhibit a predominant conformer with a collision cross section of 340 Å(2) as well as an unresolved conformer (shoulder) with a collision cross section of ~367 Å(2). Maximum HDX levels for the more compact [M+4H](4+) ions and the compact and partially-folded [M+3H](3+) ions are ~12.9, ~15.5, and ~14.9, respectively. Ion structures obtained from molecular dynamics simulations (MDS) suggest that this ordering of HDX level results from increased charge-site/exchange-site density for the more compact ions of lower charge. Additionally, a new model that includes two distance calculations (charge site to carbonyl group and carbonyl group to exchange site) for the computer-generated structures is shown to better correlate to the experimentally determined per-residue deuterium uptake. Future comparisons of IMS-HDX-MS data with structures obtained from MDS are discussed with respect to novel experiments that will reveal the HDX rates of individual residues. PMID:25267084

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

2014-12-01

124

Solubilization of coal with hydrogen sulfide and carbon monoxide  

SciTech Connect

Conversion of coal to products soluble in common solvents and conversion of coal tar to products of lower molecular weight, effected in liquid or fused reaction medium using a hydrogenating reactant, are carried out employing hydrogen sulfide and carbon monoxide as the sole or major hydrogenating reactant, without need of elemental hydrogen or a hydrogen donor solvent.

Abdel-baset, M.B.; Ratcliffe, C.T.

1980-11-25

125

Transfer of (pi)(sup -) from hydrogen to deuterium in H(sub 2)O + D(sub 2)O mixtures.  

National Technical Information Service (NTIS)

The transfer of stopping (pi)(sup -) mesons from hydrogen to deuterium has been investigated in mixtures of H(sub 2)O+D(sub 2)O as a function of D(sub 2)O concentration. The concentration dependence of the transfer probability is similar to that observed ...

S. Stanislaus, D. F. Measday, D. Vetterli, P. Weber, K. A. Aniol

1989-01-01

126

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

127

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

128

An On-Line, High-Pressure Digestion System for Protein Characterization by Hydrogen/Deuterium Exchange and Mass Spectrometry  

PubMed Central

The rapid and complete digestion of proteins is important when protein characterization by hydrogen deuterium exchange (HDX) is coupled with mass spectrometry. We developed a single-pump, on-line, high pressure digestion system that relies on UPLC technology to aid in the digestion of proteins. Two model proteins, A?1–42 and NBSA, were used to demonstrate the efficacy of the high pressure system. Both model proteins readily aggregate and are difficult to digest under normal conditions. Our high pressure system successfully digests these proteins into small, overlapping peptides. The extra information afforded by overlapping peptides allows us to pinpoint HDX protection to protein segments smaller than the digested peptide. The calculated average segment length (ASL) for both model proteins decreased by 2-fold for high pressure digestion compared to digestion at ambient pressure. PMID:20095571

Jones, Lisa M.; Zhang, Hao; Vidavsky, Ilan; Gross, Michael L.

2010-01-01

129

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

PubMed

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

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

2000-01-01

130

Carbon dioxide separation from hydrogen and nitrogen  

Microsoft Academic Search

CO2-selective membranes that obtain high CO2 permeabilities accompanied with high CO2\\/H2 and CO2\\/N2 separation factors at industrial temperatures and pressures are applicable to fuel cell operations and flue gas purification. This paper describes the separation of carbon dioxide from a mixed gas stream of hydrogen and nitrogen by a chitosan membrane containing 40wt% sodium arginate. Continuous membrane separations were done

Louei A. El-Azzami; Eric A. Grulke

2009-01-01

131

HYDROGEN CRYOSORPTION ON MULTI WALLED CARBON NANOTUBES  

Microsoft Academic Search

We present a Temperature Programmed Desorption (TPD) study on H2 adsorption on multiwalled carbon nanotubes (MWNT) at very low pressure (<10-6 Torr) and temperature (12-30 K). Our results show a hydrogen take up limit in the range of 10 -8 mol per gram depending on the adsorption temperature. We compare the MWNT cryosorption capacity with that of commonly used activated

F. Xu; M. Barberio; R. Vasta; P. Barone; A. Oliva; L. Papagno; V. Pirronello

132

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

PubMed

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

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

2014-08-27

133

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

134

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

135

Nano Structured Activated Carbon for Hydrogen Storge  

SciTech Connect

Development of a nanostructured synthetic carbons materials that have been synthesized by thermal-decomposition of aromatic rich polyether such as poly(ether ether ketone) (PEEK) is reported. These polymers based nanostructured carbons efficacious for gas adsorption and storage and have Brunauer-Emmett-Teller (BET) surface area of more than 3000 m2/g, and with average pore diameter of < 2nm. Surface-area, pore characteristics, and other critical variables for selecting porous materials of high gas adsorption capacities are presented. Analysis of the fragments evolved under various carbonization temperatures, and the correlation between the activation and carbonization temperatures provides a mechanistic perspective of the pore evolution during activation. Correlations between gas (N2 and H2) adsorption capacity and porous texture of the materials have been established. The materials possess excellent hydrogen storage properties, with hydrogen storage capacity up to 7.4 wt% (gravimetric) and ~ 45 g H2 L-1 (volumetric) at -196oC and 6.0 MPa.

Israel Cabasso; Youxin Yuan

2013-02-27

136

Thermochemical generation of hydrogen and carbon dioxide  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

137

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

138

Nickel\\/Chromium oxide\\/Zirconium oxide Catalysts for Hydrogen\\/Deuterium Isotopic Exchange  

Microsoft Academic Search

Catalysts composed of nickel and promoted with different metal oxides proved to be suitable for H\\/D isotropic exchange between hydrogen and water vapour. They loss their activity due to water condensation on their surfaces. Several nickel\\/chromium oxide\\/zirconium oxide catalysts of different composition were prepared by the coprecipitation technique. The liquid phase activity of these catalysts were followed using the hydrogen

M. M. Abdel-Badei; A. El-Sharkawi; M. Abdel-Khalik; F. Abou El-Nour

1990-01-01

139

Solution NMR Characterization of Hydrogen Bonds in a Protein by Indirect Measurement of Deuterium Quadrupole Couplings  

Microsoft Academic Search

Hydrogen bonds stabilize protein and nucleic acid structure, but little direct spectroscopic data have been available for characterizing these critical interactions in biological macromolecules. It is demonstrated that the electric field gradient at the nucleus of an amide hydrogen can be determined residue-specific by measurement of15N NMR relaxation times in proteins dissolved in D2O, and uniformly enriched with13C and15N. In

Andy C. LiWang; Ad Bax

1997-01-01

140

ORIGINAL RESEARCH Hydrogen and carbon isotope fractionation during  

E-print Network

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

Paris-Sud XI, Université de

141

Ultracold hydrogen and deuterium production via Doppler-cooled Feshbach molecules  

E-print Network

A counterintuitive scheme to produce ultracold hydrogen via fragmentation of laser cooled diatomic hydrides is presented where the final atomic H temperature is inversely proportional to the mass of the molecular parent. In addition, the critical density for formation of a Bose-Einstein Condensate (BEC) at a fixed temperature is reduced by a factor ratio hydrogen mass: parent mass raised to power 3/2 over directly cooled hydrogen atoms. The narrow Feshbach resonances between a singlet S atom and hydrogen are well suited to a tiny center of mass energy release necessary during fragmentation. With the support of ab initio quantum chemistry, it is demonstrated that BaH is an ideal diatomic precursor that can be laser cooled to a Doppler temperature of ~37 microKelvin with just two rovibronic transitions, the simplest molecular cooling scheme identified to date. Preparation of a hydrogen atom gas below the critical BEC temperature Tc is feasible with present cooling technology, with optical pulse control of the c...

Lane, Ian

2013-01-01

142

Solution NMR Characterization of Hydrogen Bonds in a Protein by Indirect Measurement of Deuterium Quadrupole Couplings  

NASA Astrophysics Data System (ADS)

Hydrogen bonds stabilize protein and nucleic acid structure, but little direct spectroscopic data have been available for characterizing these critical interactions in biological macromolecules. It is demonstrated that the electric field gradient at the nucleus of an amide hydrogen can be determined residue-specific by measurement of 15N NMR relaxation times in proteins dissolved in D 2O, and uniformly enriched with 13C and 15N. In D 2O, all backbone amide protons can be exchanged with solvent deuterons, and the T1relaxation rate of a deuteron is dominated by its quadrupole coupling constant (QCC), which is directly proportional to the electric field gradient at the nucleus. 2H NT 1relaxation can be measured quantitatively through its effect on the T2relaxation of its directly attached 15N. QCC values calculated from 2H NT 1and previously reported spectral densities correlate with the inverse cube of the X-ray crystal structure-derived hydrogen bond lengths: QCC = 228 + ? i130 cos ? i/ ri3kHz, where ? is the N-H···O iangle and ris the backbone-backbone (N-)H···O i(=C) hydrogen bond distance in ångstroms.

Liwang, Andy C.; Bax, Ad

1997-07-01

143

Solution NMR characterization of hydrogen bonds in a protein by indirect measurement of deuterium quadrupole couplings.  

PubMed

Hydrogen bonds stabilize protein and nucleic acid structure, but little direct spectroscopic data have been available for characterizing these critical interactions in biological macromolecules. It is demonstrated that the electric field gradient at the nucleus of an amide hydrogen can be determined residue-specific by measurement of 15N NMR relaxation times in proteins dissolved in D2O, and uniformly enriched with 13C and 15N. In D2O, all backbone amide protons can be exchanged with solvent deuterons, and the T1 relaxation rate of a deuteron is dominated by its quadrupole coupling constant (QCC), which is directly proportional to the electric field gradient at the nucleus. 2HN T1 relaxation can be measured quantitatively through its effect on the T2 relaxation of its directly attached 15N. QCC values calculated from 2HN T1 and previously reported spectral densities correlate with the inverse cube of the X-ray crystal structure-derived hydrogen bond lengths: QCC = 228 + Sigmai 130 cos alphai/ri3 kHz, where alpha is the N-H...Oi angle and r is the backbone-backbone (N-)H...Oi(=C) hydrogen bond distance in ângstroms. PMID:9245630

Liwang, A C; Bax, A

1997-07-01

144

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

145

Carbon-neutral economy with fossil fuel-based hydrogen energy and carbon materials  

Microsoft Academic Search

Hydrocarbon fossil fuels can be considered as hydrogen ores for CO2-free energy, and carbon ores for carbonaceous construction materials. Hydrogen fuel can be extracted from fossil fuels by decarbonization, and used as an energy resource. The carbon byproduct can be used as a versatile construction material. Carbon materials would sequester carbon, and replace CO2-generating steel and concrete. Approximate comparison of

John W. Halloran

2007-01-01

146

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

147

Characterization of stress-exposed granulocyte colony stimulating factor using ELISA and hydrogen/deuterium exchange mass spectrometry.  

PubMed

Information on the higher-order structure is important in the development of biopharmaceutical drugs. Recently, hydrogen/deuterium exchange coupled with mass spectrometry (HDX-MS) has been widely used as a tool to evaluate protein conformation, and unique automated systems for HDX-MS are now commercially available. To investigate the potential of this technique for the prediction of the activity of biopharmaceuticals, granulocyte colony stimulating factor (G-CSF), which had been subjected to three different stress types, was analyzed using HDX-MS and through comparison with receptor-binding activity. It was found that HDX-MS, in combination with ion mobility separation, was able to identify conformational changes in G-CSF induced by stress, and a good correlation with the receptor-binding activity was demonstrated, which cannot be completely determined by conventional peptide mapping alone. The direct evaluation of biological activity using bioassay is absolutely imperative in biopharmaceutical development, but HDX-MS can provide the alternative information in a short time on the extent and location of the structural damage caused by stresses. Furthermore, the present study suggests the possibility of this system being a versatile evaluation method for the preservation stability of biopharmaceuticals. PMID:25070584

Tsuchida, Daisuke; Yamazaki, Katsuyoshi; Akashi, Satoko

2014-10-01

148

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

149

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

PubMed

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

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

2014-07-01

150

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

NASA Astrophysics Data System (ADS)

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

Tsuchida, Daisuke; Yamazaki, Katsuyoshi; Akashi, Satoko

2014-10-01

151

Structural stability and internal motions of Escherichia coli ribonuclease HI: 15N relaxation and hydrogen-deuterium exchange analyses.  

PubMed

The relationship between the structural stability and the internal motions of proteins was investigated through measurements of 15N relaxation and hydrogen-deuterium exchange rates of ribonuclease HI from Escherichia coli and its thermostable quintuple mutant (Gly23-->Ala, His62-->Pro, Val74-->Leu, Lys95-->Gly, and Asp134-->His), which has a higher melting temperature by 20.2 degreesC. For most of the residues, the generalized order parameters (S2) obtained from 15N relaxation analyses as well as the localized hydrogen-bond-breaking motions (local breathing) observed as fast H-D exchange rates were largely unaffected by the mutations, indicating no global mutational effect on the internal motions. Several local mutational effects were observed for residues close to the mutation sites as follows. The S2 value significantly increased for Lys96 and Val98, which indicated that motions on the pico- to nanosecond time-scale became restricted within a protruding region including the Lys95-->Gly mutation site. In contrast, slight decreases in S2, and drastic increases in the chemical exchange motion on the micro- to millisecond time-scale (Deltaex), were observed for residues located in the joining region between the protrusion and the major domain of the protein. These changes may be caused by the elimination of the bulky Lys95 side-chain at the center of the protrusion. Deltaex observed for residues in alpha-helix I of the wild-type protein was reduced for the mutant, probably because a cavity in the hydrophobic core is filled by the Val74-->Leu mutation. The local breathing at position 134 was restricted by the Asp134-->His mutation, probably because the reduction of the negative charge repulsion contributes to the stability of the native major conformation relative to the breathing conformations around position 134. PMID:9533889

Yamasaki, K; Akasako-Furukawa, A; Kanaya, S

1998-04-01

152

Deuterium retention in codeposited layers and carbon materials exposed to high flux D-plasma  

NASA Astrophysics Data System (ADS)

A ceramic BCN target with samples of dense RG-Ti-91 without boron, RG-Ti-B with boron (0.1 at.%) and porous POCO AXF-5Q graphites was exposed in a stationary D-plasma of the `Lenta' device with an ion energy of 200 eV and an ion flux of (3 - 6) × 10 17 D/cm 2s at 1040 and 1400 K to a fluence of ˜1 × 10 22 D/cm 2. Codeposited layers were obtained for comparison on the target surface. Thermal desorption spectroscopy (TDS) showed that the amount of deuterium in RG-Ti after exposure at 1040 K was more than an order of magnitude higher than in POCO (9 × 10 17 and 7 × 10 16 D/cm 2, respectively). The retention took place preferentially in a surface layer about 100 ?m thick. The bulk deuterium concentration in both RG-Ti and POCO was lower than 1 appm. The irradiated RG-Ti surface was subjected to strong erosion and consisted of `columnar' grains covered with TiC at their tips. The deuterium in RG-Ti irradiated at 1400 K was located in the surface layer (1.5 × 10 16 D/cm 2). The value of the bulk concentration did not exceed 0.1 appm while in POCO it was equal to about 20 appm. TDS for deuterium in RG-Ti demonstrated a spectrum similar to that for codeposited layers on a target surface. The differences in deuterium retention in the graphites are explained on the basis of structural differences. Considering tritium inventory assessment for ITER, dense graphites like RG-Ti are preferred for working divertor plates at high temperatures.

Arkhipov, I. I.; Gorodetsky, A. E.; Zalavutdinov, R. Kh; Zakharov, A. P.; Burtseva, T. A.; Mazul, I. V.; Khripunov, B. I.; Shapkin, V. V.; Petrov, V. B.

153

Trapping and replacement of 1-14 keV hydrogen and deuterium in 316 stainless steel  

Microsoft Academic Search

Trapping of deuterium with energies between one and 14 keV implanted into 316 stainless steel has been studied as a function of implant energy at a target temperature of 150 K; replacement behavior occurring after saturation also receives attention. The replacement of trapped deuterium atoms in the saturated stainless steel lattice is investigated by switching the implant beam from D(+)

R. S. Blewer; R. Behrisch; B. M. U. Scherzer; R. Schulz

1978-01-01

154

Carbonate thermochemical cycle for the production of hydrogen  

DOEpatents

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

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

2010-02-23

155

Hydrogen Storage on Metal-Doped Ordered Mesoporous Carbons  

E-print Network

Meeting, May 18, 2010 #12;Outline · Research group · Hydrogen storage: background and status · SynthesisHydrogen Storage on Metal-Doped Ordered Mesoporous Carbons Shuguang Deng New Mexico State of pure and metal-doped OMC · Characterization of metal-doped OMC · Hydrogen adsorption equilibrium

Johnson, Eric E.

156

Hydrogen storage in carbon nanomaterials: Investigation of fiber structure, metal content, and hydrogen spillover  

NASA Astrophysics Data System (ADS)

Hydrogen storage in carbon nanomaterials was enhanced through hydrogen spillover. Carbon nanomaterials, including multi-wall nanotubes (MWNTs), single-wall nanotubes (SWNTs), and graphite nanofibers (GNFs), were synthesized via catalytic methods and tested for hydrogen uptake through volumetric and thermogravimetric experiments designed to reduce common experimental artifacts. A desorption activation energy of 96.9 kJ/mol and in situ carbon formation supported a hydrogen spillover hypothesis: hydrogen dissociates on a catalytic site then migrates to the carbon surface. This catalytic hydrogen spillover could be induced through residual metal oxide catalysts, controlled metal doping, or the formation of carbon defects. Further, the chemical and physical nature of the carbon structure determined the enhancement of hydrogen storage via hydrogen spillover and could be controlled through judicious selection of synthesis conditions, synthesis catalyst, and pretreatment. To understand and optimize the effects of carbon structure and metal content on hydrogen uptake, characterization included electron microscopy, chemical titration, surface area determinations, temperature-programmed studies, elemental analysis, x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). After saturation at a pressure of 69 bar, a desorbable hydrogen yield of 3.7% was observed for a MWNT/NiMgO composite and up to 3.8% for GNF synthesized from a Ni-Cu catalyst.

Lueking, Angela Dawn

2003-10-01

157

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

158

Sticking coefficient of hydrogen and deuterium on silicates under interstellar conditions  

E-print Network

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

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

2012-01-01

159

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

E-print Network

Effects of hydrogen adsorption on single-wall carbon nanotubes: Metallic hydrogen decoration O. Gu of carbon nanotubes undergo dramatic changes with hydrogen chemisorption from first principle calculations other isomers can be insulating. For both zigzag and armchair nanotubes, hydrogenation of each carbon

Yildirim, Taner

160

Kinetic hydrogen/deuterium effects in the direct hydrogenation of ketones catalyzed by a well-defined ruthenium diphosphine diamine complex.  

PubMed

The trans-dihydride complex trans-RuH(2)(NH(2)CMe(2)CMe(2)NH(2))((R)-binap) (1) is an active catalyst for the homogeneous hydrogenation of ketones in benzene under pressure of H(2) gas. The mechanism of the catalysis is proposed to occur through a rapid transfer of a hydride from the ruthenium and a proton from the amine on 1 to the carbonyl of the ketone to give the product alcohol and a hydrido-amido intermediate RuH(NHCMe(2)CMe(2)NH(2))((R)-binap) (2). The dihydride is then regenerated by the turnover-limiting heterolytic splitting of dihydrogen by complex 2. In this work the kinetic isotope effect (KIE) is measured to be 2.0 (+/-0.1) for the reduction of acetophenone to 1-phenylethanol catalyzed by 1 using 8.0 atm of H(2) versus D(2) gas. DFT calculations predict a KIE of 2.1 for the described mechanism using the simplified catalyst RuH(NHCH(2)CH(2)NH(2))(PH(3))(2) with H(2) or the catalyst RuD(NDCH(2)CH(2)ND(2))(PH(3))(2) with D(2). This supports the observation that deuterium scrambles into the catalyst when a pressure of D(2) is used. We discuss the significance of these results relative to the KIE of 2 that was reported by Sandoval et al. (J. Am. Chem. Soc. 2003 125, 13490) for the hydrogenation/deuteriation of acetophenone catalyzed by trans-RuH(eta(1)-BH(4))((S)-tolbinap)((S,S)-dpen) in basic isopropanol/isopropanol-d(8). PMID:19606863

Zimmer-De Iuliis, Marco; Morris, Robert H

2009-08-12

161

Hydrogen-Deuterium Exchange and Mass Spectrometry Reveal the pH-Dependent Conformational Changes of Diphtheria Toxin T Domain.  

PubMed

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

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

2014-11-01

162

Hydrogen storage: a comparison of hydrogen uptake values in carbon nanotubes and modified charcoals  

Microsoft Academic Search

We compared the hydrogen uptake weight percentages (wt.%) of different carbonized materials, before and after modification, for their application in hydrogen storage at room temperature. The Sievert's method [T.P. Blach, E. Mac, A. Gray, J. Alloys Compd. 446-447, 692 (2007)] was used to measure hydrogen uptake values on: (1) Taiwan bamboo charcoal (TBC), (2) white charcoal (WC), (3) single-walled carbon

H.-Y. Miao; G. R. Chen; D. Y. Chen; J. T. Lue; M. S. Yu

2010-01-01

163

HYDROGEN STORAGE IN CARBON NANOTUBES JOHN E. FISCHER  

E-print Network

* PHYSISORPTION vs. CHEMISORPTION * MOLECULAR vs. ATOMIC HYDROGEN * CONCLUSIONS #12;Allotropes of Carbon DENSITIESHYDROGEN STORAGE IN CARBON NANOTUBES JOHN E. FISCHER UNIVERSITY OF PENNSYLVANIA * SOME BASIC surface channels or "groove sites" INCLUSION COMPOUNDS OF CARBON HOST MATERIALS #12;OCTANE: C8H18 - 15

164

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

165

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

166

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

167

ETD in a traveling wave ion guide at tuned Z-spray ion source conditions allows for site-specific hydrogen/deuterium exchange measurements.  

PubMed

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

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

2011-10-01

168

Enzymatic functionalization of carbon-hydrogen bonds.  

PubMed

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

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

2011-04-01

169

Difference in fibril core stability between two tau four-repeat domain proteins: a hydrogen-deuterium exchange coupled to mass spectrometry study.  

PubMed

One of the signatures of Alzheimer's disease and tauopathies is fibrillization of the microtubule-associated protein tau. The purpose of this study was to compare the high-resolution structure of fibrils formed by two different tau four-repeat domain constructs, tau4RD and tauK18, using hydrogen-deuterium exchange coupled to mass spectrometry as a tool. While the two fibrils are found to be constructed on similar structural principles, the tauK18 fibril has a slightly more stable core. This difference in fibril core stability appears to be reflective of the mechanistic differences in the aggregation pathways of the two proteins. PMID:24256615

Ramachandran, Gayathri; Udgaonkar, Jayant B

2013-12-10

170

Using Hydrogen/Deuterium Exchange Mass Spectrometry to Define the Specific Interactions of the Phospholipase A2 Superfamily with Lipid Substrates, Inhibitors, and Membranes*  

PubMed Central

The phospholipase A2 (PLA2) superfamily consists of 16 groups and many subgroups and constitutes a diverse set of enzymes that have a common catalytic activity due to convergent evolution. However, different PLA2 types have unique three-dimensional structures and catalytic residues as well as specific tissue localization and distinct biological functions. Understanding how the different PLA2 enzymes associate with phospholipid membranes, specific phospholipid substrate molecules, and inhibitors on a molecular basis has advanced in recent years due to the introduction of hydrogen/deuterium exchange mass spectrometry. Its theory, practical considerations, and application to understanding PLA2/membrane interactions are addressed. PMID:23209293

Cao, Jian; Burke, John E.; Dennis, Edward A.

2013-01-01

171

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

PubMed

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

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

2014-08-26

172

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

173

Study on the influence of isotope exchange of hydrogen with deuterium on the vibrational spectrum of lysozyme by inelastic neutron scattering  

SciTech Connect

The influence of isotope exchange of hydrogen with deuterium on the lysozyme dynamics was studied by incoherent inelastic neutron scattering. The generalized vibrational densities of states G({omega}) were constructed from experimental results for protonated and deuterated protein samples at 200, 280, and 311 K. The major isotope effect was observed in G({omega}) in the frequency region higher than 100 cm{sup -1}. At all temperatures, both the Debye mode and the region of G({omega}), whose spectral dimension corresponds to the fracton mode, are observed in the low-frequency region of the densities of states of both protonated and deuterated lysozyme. The influence of the hydrogen isotope exchange on the low-frequency region of G({omega}) is insignificant.

Svanidze, A. V., E-mail: svanidze@mail.ioffe.ru; Lushnikov, S. G. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Sashin, I. L. [Joint Institute for Nuclear Research (Russian Federation); Gvasaliya, S. N. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

2007-09-15

174

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

PubMed

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

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

2006-01-01

175

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

NASA Astrophysics Data System (ADS)

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

Winterberg, F.

2013-08-01

176

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

2012-03-28

177

The interaction of perfluoro-polyether lubricant with hydrogenated carbon  

Microsoft Academic Search

The incorporation of a limited amount of hydrogen in the amorphous carbon (a-C:H) overcoat improves the CSS durability of thin film media lubricated with perfluoropolyether (PFPE). A mechanism is proposed to explain this phenomenon. With increasing H content in C, the likely bonding sites for the lubricant such as the carboxyl end groups and dangling bonds decrease in the carbon

Run-Han Wang; Richard L. White; Steven W. Meeks; B. G. Min; Andrew Kellock; Andy Homola; D. Yoon

1996-01-01

178

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

179

Electrochemical behaviour of single walled carbon nanotubes – Hydrogen storage and hydrogen evolution reaction  

Microsoft Academic Search

The electrochemical behaviour of single walled carbon nanotubes (SWCNT) related to the mechanism involved in the hydrogen electrode reaction applying electrochemical and spectroscopic techniques is studied. Cyclic voltammetry applied to electrodes containing different percentages of SWCNT demonstrates that this material can behave as efficient capacitor and that the hydrogen electrode reaction develops through the H-electrosorption followed by the formation of

P. S. Fernández; E. B. Castro; S. G. Real; M. E. Martins

2009-01-01

180

TENSILE TESTING OF CARBON STEEL IN HIGH PRESSURE HYDROGEN  

SciTech Connect

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

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

2007-05-02

181

Hydrogen storage: a comparison of hydrogen uptake values in carbon nanotubes and modified charcoals  

NASA Astrophysics Data System (ADS)

We compared the hydrogen uptake weight percentages (wt.%) of different carbonized materials, before and after modification, for their application in hydrogen storage at room temperature. The Sievert's method [T.P. Blach, E. Mac, A. Gray, J. Alloys Compd. 446-447, 692 (2007)] was used to measure hydrogen uptake values on: (1) Taiwan bamboo charcoal (TBC), (2) white charcoal (WC), (3) single-walled carbon nanotubes (SWCNTs) bought from CBT Inc. and (4) homemade multi-walled carbon nanotubes (MWCNTs) grown on TBC. Modified samples were coated with a metal catalyst by dipping in KOH solutions of different concentrations and then activated in a high temperature oven (800 °C) under the atmospheric pressure of inert gas. The results showed that unmodified SWCNTs had superior uptake but that Taiwan bamboo charcoal, after modification, showed enhanced uptake comparable to the SWCNTs. Due to TBC's low cost and high mass production rate, they will be the key candidate for future hydrogen storage applications.

Miao, H.-Y.; Chen, G. R.; Chen, D. Y.; Lue, J. T.; Yu, M. S.

2010-11-01

182

Ionic imbalance due to hydrogen carbonate from Asian dust  

NASA Astrophysics Data System (ADS)

In an attempt to identify the ionic imbalance, hydrogen carbonate, HCO 3- (bicarbonate), was determined together with the commonly determined nine major ions because the imbalance was frequently encountered in the chemical analysis of samples with high pHs. Titration method was applied for the determination of the samples with pH higher than 5.6. These samples amounted to 102 of the 1536 samples collected in Hokkaido, Northern Japan, from April 1998 to December 2002. Of the 102 samples, 74 (Group A) showed an acceptable ion balance without including HCO 3-. In the other 28 (Group B), however, inclusion of HCO 3- successfully improved the ion balance. These results suggested that hydrogen carbonate was a potential candidate for explaining the imbalance. The hydrogen carbonate concentrations showed a strong correlation with the corresponding non-sea salt calcium (nss-Ca 2+) concentrations, which implied that hydrogen carbonate was derived from calcium carbonate particles incorporated into falling raindrops or cloud droplets. For Group A, the relationship between hydrogen carbonate and the nss-calcium ion concentration was very similar to that for commonly suspended particles in Hokkaido. On the other hand, Group B exhibited a stronger but significantly different correlation. To the samples of Group B, a back-trajectory analysis was applied to demonstrate that the samples were associated with aerosol travelling from Northern China or Mongolia, which indicated that alkaline aerosol affected the chemistry. In consideration of these findings, the current standard of the ion balance should be critically reviewed for modification in regard to the contribution of hydrogen carbonate not only in source areas but also in receptor areas of alkaline aerosol.

Noguchi, Izumi; Hara, Hiroshi

183

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

184

Predicting protein aggregation during storage in lyophilized solids using solid state amide hydrogen/deuterium exchange with mass spectrometric analysis (ssHDX-MS).  

PubMed

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

Moorthy, Balakrishnan S; Schultz, Steven G; Kim, Sherry G; Topp, Elizabeth M

2014-06-01

185

Hydrogen Confinement in Carbon Nanopores: Extreme Densification at Ambient Temperature  

SciTech Connect

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

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

2011-01-01

186

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

187

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

188

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

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

189

Material processing with hydrogen and carbon monoxide on Mars  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

190

Why Alkali Metal Doped Carbon Nanotubes Poses High Hydrogen Uptake?  

NASA Astrophysics Data System (ADS)

The nature of the molecular hydrogen adsorption in pure and alkali metal doped single-walled carbon nanotubes (SWNTs) is investigated by a mixed Quantum Mechanics / Molecular Mechanics (QM/MM) model. For the QM part the B3LYP (DFT) functional is used while for the MM we employ the universal force field (UFF). Our results demonstrate that the charge transfer from the alkali metal to the tube polarizes the hydrogen molecule and this charge induced dipole interaction is responsible for the higher hydrogen uptake of the doped tube.

Froudakis, George

2002-03-01

191

Investigation of Kp- and Kd-atom formation and their collisional processes with hydrogen and deuterium targets by the classical-trajectory Monte Carlo method  

SciTech Connect

The classical-trajectory Monte Carlo method has been used to study the capture of negative kaons by hydrogen and deuterium atoms; subsequently, the elastic scattering, Stark mixing, and Coulomb deexcitation cross sections of Kp and Kd atoms have been determined. The results for kaonic atom formation confirm the initial conditions that have been parametrically applied by most atomic cascade models. Our results show that Coulomb deexcitation in Kp and Kd atoms with {Delta}n>1 is important in addition to n=1. We have shown that the contribution of molecular structure effects to the cross sections of the collisional processes is larger than the isotopic effects of the targets. We have also compared our results with the semiclassical approaches.

Raeisi, G. M. [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Department of Physics, Shahrekord University, Shahrekord 115 (Iran, Islamic Republic of); Kalantari, S. Z. [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

2010-10-15

192

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

193

Production of hydrogen from carbon monoxide and water  

SciTech Connect

An improved process is described for producing hydrogen from carbon monoxide and water in which carbon monoxide is contacted under homogeneous conditions with an alkaline aqueous liquid phase containing a soluble rhodium-containing catalyst at a reaction temperature from about 100 to 300/sup 0/C and at a reaction pressure from about 1 to 300 atmospheres in the presence of a saturated paraffinic water-soluble alcohol.

Anderson, L.R.; Novotny, M.

1980-09-16

194

Hydrogen evolution from water using solid carbon and light energy  

Microsoft Academic Search

Hydrogen production in the light-mediated decomposition of water vapor in the presence of solid carbon is reported. Three mg of active carbon, together with 30 mg of TiO2 and 10 mg of RuO2 powder were illuminated in the presence of water vapor by a 500-W mercury lamp. Mass spectrometer analysis of the gas evolved reveals the production a nonflammable mixture

Tomoji Kawai; Tadayoshi Sakata

1979-01-01

195

[Microbial synthesis of deuterium labelled L-phenylalanine with different levels of isotopic enrichment by facultative methylotrophic bacterium Brevibacterium methylicum with RMP assimilation of carbon].  

PubMed

The preparative microbial synthesis of amino acids labelled with stable isotopes, including deuterium ( 2 H), suitable for biomedical applications by methylotrophic bacteria was studied using L-phenylalanine as example. This amino acid is secreted by Gram-negative aerobic facultative methylotrophic bacteria Brevibacterium methylicum, assimilating methanol via ribulose-5-monophosphate (RMP) cycle of assimilation of carbon, The data on adaptation of L-phenylalanine secreted by methylotrophic bacterium ?. methylicum to the maximal concentration of deuterium in the growth medium with 98% 2 ? 2 O and 2% [ 2 ?]methanol, and biosynthesis of deuterium labelled L-phenylalanine With different levels of enrichment are presented. The strain was adapted by means of plating initial cells on firm (2% agarose) minimal growth media with an increasing gradient of 2 ? 2 O concentration from 0; 24.5; 49.0; 73.5 up to 98% 2 ? 2 O followed by subsequent selection of separate colonies stable to the action of 2 ? 2 O. These colonies were capable to produce L-phenylalanine. L-phenylalanine was extracted from growth medium by extraction with isopropanol with the subsequent crystallization in ethanol (output 0.65 g/l). The developed method of microbial synthesis allows to obtain deuterium labelled L-phenylalanine with different levels of isotopic enrichment, depending on concentration of 2 ? 2 O in growth media, from 17% (on growth medium with 24,5% 2 ? 2 O) up to 75% (on growth medium with 98% 2 ? 2 O) of deuterium in the molecule that is confirmed with the data of the electron impact (EI) mass- spectrometry analysis of methyl ethers of N-dimethylamino(naphthalene)-5-sulfochloride (dansyl) phenylalanine in these experimental conditions. PMID:25249528

Mosin, O V; Shvets, V I; Skladnev, D A; Ignatov, I

2014-01-01

196

Selective reduction of radiotracer trapping by deuterium substitution: Comparison of carbon-11-L-deprenyl and carbon-11-deprenyl-D2 for MAO B mapping  

SciTech Connect

Recent human PET studies with the monoamine oxidase B (MAO B) tracer [{sup 11}C]L-deprenyl show that the rapid rate of radiotracer trapping relative to transport reduces the sensitivity of the tracer in regions of high MAO B concentration. This study investigates the use of dueterium substituted L-deprenyl ([{sup 11}C]L-deprenyl-D2) to reduce the rate of trapping in tissue and to improve sensitivity. Five normal subjects (43-64 yr) were studied with [{sup 11}C]L-deprenyl and [{sup 11}C]L-deprenyl-D2 on the same day. Time-activity data from different brain regions and the arterial plasma were analyzed using a three-compartment model as well as graphical analysis for irreversible systems. For both tracers, maximum radioactivity accumulation occurred at about 5 min. For [{sup 11}C]-deprenyl, {sup 11}C concentration peaked at 5 min and remained constant throughout the study. With [{sup 11}C]L-deprenyl-D2, peak {sup 11}C concentration also occurred at about 5 min but was followed by an initial washout. Carbon-11 concentration generally plateaued from 30 to 60 min. The plateau for [{sup 11}C]L-deprenyl was higher than the plateau for [{sup 11}C]L-deprenyl-D2. Data analysis by a three-compartment model and by graphical analysis showed that deuterium substitution: (a) does not affect plasma to tissue transport (K{sub 1}); (b) reduces the rate of trapping of {sup 11}C in all brain regions; (c) facilitates the separation of model terms related to radiotracer delivery from radiotracer trapping in tissue; and (d) improves tracer sensitivity. This study demonstrates that deuterium substitution causes a significant reduction in the rate of trapping of labeled deprenyl, providing a direct link between radiotracer uptake and MAO B in the human brain and enhancing tracer sensitivity to changes in MAO B concentration. 38 refs., 8 figs., 2 tabs.

Fowler, J.S.; Wang, G.J.; Logan, J. [Brookhaven National Lab., Upton, NY (United States)]|[State Univ. of New York, Stony Brook, NY (United States)] [and others

1995-07-01

197

Crucial Role of Perfringolysin O D1 Domain in Orchestrating Structural Transitions Leading to Membrane-perforating Pores: A HYDROGEN-DEUTERIUM EXCHANGE STUDY.  

PubMed

Perfringolysin O (PFO) is a toxic protein that binds to cholesterol-containing membranes, oligomerizes, and forms a ?-barrel transmembrane pore, leading to cell lysis. Previous studies have uncovered the sequence of events in this multistage structural transition to a considerable detail, but the underlying molecular mechanisms are not yet fully understood. By measuring hydrogen-deuterium exchange patterns of peptide bond amide protons monitored by mass spectrometry (MS), we have mapped structural changes in PFO and its variant bearing a point mutation during incorporation to the lipid environment. We have defined all regions that undergo structural changes caused by the interaction with the lipid environment both in wild-type PFO, thus providing new experimental constraints for molecular modeling of the pore formation process, and in a point mutant, W165T, for which the pore formation process is known to be inefficient. We have demonstrated that point mutation W165T causes destabilization of protein solution structure, strongest for domain D1, which interrupts the pathway of structural transitions in other domains necessary for proper oligomerization in the membrane. In PFO, the strongest changes accompanying binding to the membrane focus in D1; the C-terminal part of D4; and strands ?1, ?4, and ?5 of D3. These changes were much weaker for PFO(W165T) lipo where substantial stabilization was observed only in D4 domain. In this study, the application of hydrogen-deuterium exchange analysis monitored by MS provided new insight into conformational changes of PFO associated with the membrane binding, oligomerization, and lytic pore formation. PMID:25164812

Kacprzyk-Stokowiec, Aleksandra; Kulma, Magdalena; Traczyk, Gabriela; Kwiatkowska, Katarzyna; Sobota, Andrzej; Dadlez, Micha?

2014-10-10

198

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

Code of Federal Regulations, 2012 CFR

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

2012-07-01

199

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

Code of Federal Regulations, 2011 CFR

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

2011-07-01

200

Material processing with hydrogen and carbon monoxide on Mars  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

201

Mean excitation energy for molecules of hydrogen and carbon  

NASA Technical Reports Server (NTRS)

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

Wilson, J. W.; Kamaratos, E.

1981-01-01

202

Comparing hardness and wear data for tetrahedral amorphous carbon and hydrogenated amorphous carbon thin films  

Microsoft Academic Search

We compared nanoindentation and nanoscratch testing of 10 and 50nm thick tetrahedral amorphous carbon (ta-C) and hydrogenated amorphous carbon (a-C:H). Raman spectroscopy shows the expected spectral features for the two carbon forms, however, luminescence from the ceramic substrate can alter the spectra. We find that hard ta-C films can blunt the diamond tip and hence use a tip area function

P. Lemoine; J. P. Quinn; P. Maguire; J. A. McLaughlin

2004-01-01

203

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

PubMed

We utilized gas phase hydrogen/deuterium (H/D) exchange reactions and ab initio calculations to investigate the complexation between a model peptide (Arg-Gly-Asp[triple bond]RGD) with various alkali metal ions. The peptide conformation is drastically altered upon alkali metal ion complexation. The associated conformational changes depend on both the number and type of complexing alkali metal ions. Sodium has a smaller ionic diameter and prefers a multidentate interaction that involves all three amino acids of the peptide. Conversely, potassium and cesium form different types of complexes with the RGD. The [RGD + 2Cs - H]+ species exhibit the slowest H/D exchange reactivity (reaction rate constant of approximately 6 x 10(-13) cm3molecule(-1)s(-1) for the fastest exchanging labile hydrogen with ND3). The reaction rate constant of the protonated RGD is two orders of magnitude faster than that of the [RGD + 2Cs - H]+. Addition of the first cesium to the RGD reduces the H/D exchange reaction rate constant (i.e., D0) by a factor of seven whereas sodium reduces this value by a factor of thirty. Conversely, addition of the second alkali metal ions has the opposite effect; the rate of D0 disappearance for all [RGD + 2Met - H]+ species (Met[triple bond]Na, K, and Cs) decreases with the alkali metal ion size. PMID:11766754

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

2001-12-01

204

Method for Measuring Enriched Levels of Deuterium in Soil Water.  

National Technical Information Service (NTIS)

This report describes procedures for analyzing hydrogen isotope ratios. Hydrogen is separated from liquid water or soil water by reacting the water with heated uranium. An isotope-ratio mass spectrometer determines the atom % deuterium in the hydrogen to ...

J. L. Oliphant, T. F. Jenkins, A. R. Tice

1982-01-01

205

Kinetic and mechanistic studies of carbon-to-metal hydrogen atom transfer involving Os-centered radicals: evidence for tunneling.  

PubMed

We have investigated the kinetics of novel carbon-to-metal hydrogen atom transfer reactions, in which homolytic cleavage of a C-H bond is accomplished by a single metal-centered radical. Time-resolved IR spectroscopic measurements revealed efficient hydrogen atom transfer from xanthene, 9,10-dihydroanthracene, and 1,4-cyclohexadiene to Cp(CO)2Os(•) and (?(5)-(i)Pr4C5H)(CO)2Os(•) radicals, formed by photoinduced homolysis of the corresponding osmium dimers. The rate constants for hydrogen abstraction from these hydrocarbons are in the range 1.5 × 10(5) M(-1) s(-1) to 1.7 × 10(7) M(-1) s(-1) at 25 °C. For the first time, kinetic isotope effects for carbon-to-metal hydrogen atom transfer were determined. Large primary deuterium kinetic isotope effects of 13.4 ± 1.0 and 16.8 ± 1.4 were observed for the hydrogen abstraction from xanthene to form Cp(CO)2OsH and (?(5)-(i)Pr4C5H)(CO)2OsH, respectively, at 25 °C. Temperature-dependent measurements of the kinetic isotope effects over a 60 °C temperature range were carried out to obtain the difference in activation energies (E(D) - E(H)) and the pre-exponential factor ratio (A(H)/A(D)). For hydrogen atom transfer from xanthene to (?(5)-(i)Pr4C5H)(CO)2Os(•), the (E(D) - E(H)) = 3.3 ± 0.2 kcal mol(-1) and A(H)/A(D) = 0.06 ± 0.02 values suggest a quantum mechanical tunneling mechanism. PMID:24498925

Lewandowska-Andralojc, Anna; Grills, David C; Zhang, Jie; Bullock, R Morris; Miyazawa, Akira; Kawanishi, Yuji; Fujita, Etsuko

2014-03-01

206

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

NASA Astrophysics Data System (ADS)

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

Adibhatla, Anasuya

207

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

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

208

Amorphous carbon enhancement of hydrogen penetration into UO2  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

209

Behavior of luminous clouds surrounding evaporating hydrogen and carbon pellets  

SciTech Connect

The technique of tokamak magnetic field shear determination using the tilt of evaporating-pellet produced luminous clouds is described. Some differences in the techniques, involving either hydrogen or carbon pellets, are discussed. Two experimental methods of obtaining the safety factor profile are compared. The first of them involved luminous cloud tilt measurements, while the second one was based on injected carbon pellets toroidal acceleration. The safety factor measurements of both kinds were carried out within the same tokamak shot. The experimental results were also compared with theoretical calculations of the safety factor, based on an experimentally measured temperature profile and the assumption of Spitzer plasma conductivity. 8 refs., 2 figs.

Egorov, S.M.; Kuteev, B.V.; Miroshnikov, I.V.; Polyakov, D.V.; Sergeev, V.Yu. [St. Petersburg State Technical Univ. (Russian Federation)

1994-12-31

210

Hydrogenated 5-carbon compound and method of making  

DOEpatents

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

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

1999-03-16

211

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

212

Carbon-Oxygen Hydrogen Bonding in Biological Structure and Function  

PubMed Central

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

Horowitz, Scott; Trievel, Raymond C.

2012-01-01

213

Hydrogen Storage in Carbon SWNTs: Atomic or Molecular?  

NASA Astrophysics Data System (ADS)

The atomistic nature of hydrogen storage in carbon SWNTs has been investigated by thermal desorption spectroscopy utilizing mass spectrometry. The partial pressures of desorbed H2, D2 and HD have been simultaneously recorded after sample loading with a 1:1 mixture of H2 and D2 gases. The amount of desorbed HD molecules approaches the ratio 2:1:1 for HD:H2:D2 in the case of atomic storage. In the case of molecular storage the concentration of HD approaches the background level. It was found that hydrogen isotopes are stored as atoms in SWNT samples containing transition metals from either sample production (Ni, Fe, …) and/or activation (opening) process (Ni, Fe, Ti, …). Purified SWNTs store hydrogen in the molecular state, if any.

Haluska, M.; Hirscher, M.; Becher, M.; Dettlaff-Weglikowska, U.; Chen, X.; Roth, S.

2002-10-01

214

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

215

Direct observation of hydrogen spillover on carbon-supported platinum and its influence on the hydrogenation of benzene  

Microsoft Academic Search

A study on the presence of hydrogen spillover on carbon-supported platinum catalysts was conducted. CO and H[sub 2] uptakes were determined at ambient temperature on Pt\\/C catalyst variously dilute with carbon. The effect of H[sub 2] spillover on benzene hydrogenation over Pt\\/C and dilute Pt\\/C was studied. From chemisorption results a direct observation of hydrogen spillover at room temperature was

S. T. Srinivas; P. K. Rao

1994-01-01

216

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

SciTech Connect

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

Blostein, J. J.; Palomino, L. A. Rodriguez; Dawidowski, J. [Consejo Nacional de Investigaciones Cientificas y Tecnicas, Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica, Universidad Nacional de Cuyo, (8400) Bariloche (Argentina)

2009-03-06

217

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

218

Hydrogen storage reactions on titanium decorated carbon nanocones theoretical study  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

219

Investigation of the effect of intra-molecular interactions on the gas-phase conformation of peptides as probed by ion mobility-mass spectrometry, gas-phase hydrogen/deuterium exchange, and molecular mechanics  

E-print Network

SAWYER Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY December 2004 Major Subject: Chemistry INVESTIGATION... OF THE EFFECT OF INTRA-MOLECULAR INTERACTIONS ON THE GAS-PHASE CONFORMATION OF PEPTIDES AS PROBED BY ION MOBILITY-MASS SPECTROMETRY, GAS-PHASE HYDROGEN/DEUTERIUM EXCHANGE, AND MOLECULAR MECHANICS A Dissertation by HOLLY ANN SAWYER Submitted to Texas A...

Sawyer, Holly Ann

2006-04-12

220

Atomic hydrogen interactions with amorphous carbon thin films Bhavin N. Jariwala,1  

E-print Network

Atomic hydrogen interactions with amorphous carbon thin films Bhavin N. Jariwala,1 Cristian V-scale interactions of H atoms with hydrogenated amorphous carbon a-C:H films were identified using molecular dynamics through a detailed analysis of the MD trajectories. The MD simulations showed that hydrogenation occurs

Ciobanu, Cristian

221

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

Microsoft Academic Search

Carbon nanotube films produced on a Si(100) substrate without any metal catalyst were used as electrodes in galvanic cells. The electrochemical mechanism of hydrogen evolution, storage and oxidation was studied using cyclic voltammetry and galvanostatic polarisation. Cyclic voltammetry showed that hydrogen is easily produced on the carbon nanotube surface, but a significant overvoltage was observed for hydrogen oxidation. The kinetics

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

2003-01-01

222

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

PubMed Central

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

2012-01-01

223

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

PubMed Central

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

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

2010-01-01

224

Mass spectrometric approaches using electrospray ionization charge states and hydrogen-deuterium exchange for determining protein structures and their conformational changes.  

PubMed

Electrospray ionization (ESI) mass spectrometry (MS) is a powerful analytical tool for elucidating structural details of proteins in solution especially when coupled with amide hydrogen/deuterium (H/D) exchange analysis. ESI charge-state distributions and the envelopes of charges they form from proteins can provide an abundance of information on solution conformations that is not readily available through other biophysical techniques such as near ultraviolet circular dichroism (CD) and tryptophan fluorescence. The most compelling reason for the use of ESI-MS over nuclear magnetic resonance (NMR) for measuring H/D after exchange is that larger proteins and lesser amounts of samples can be studied. In addition, MS can provide structural details on transient or folding intermediates that may not be accessible by CD, fluorescence, and NMR because these techniques measure the average properties of large populations of proteins in solution. Correlations between measured H/D and calculated parameters that are often available from crystallographic data can be used to extend the range of structural details obtained on proteins. Molecular dynamics and energy minimization by simulation techniques such as assisted model building with energy refinement (AMBER) force field can be very useful in providing structural models of proteins that rationalize the experimental H/D exchange results. Charge-state envelopes and H/D exchange information from ESI-MS data used complementarily with NMR and CD data provides the most powerful approach available to understanding the structures and dynamics of proteins in solution. PMID:14623985

Yan, Xuguang; Watson, Jeffrey; Ho, P Shing; Deinzer, Max L

2004-01-01

225

Goddard high-resolution spectrograph observations of the local interstellar medium and the deuterium/hydrogen ratio along the line of sight toward Capella  

NASA Technical Reports Server (NTRS)

HST Goddard High-Resolution Spectrograph observations of the 1216, 2600, and 2800 A spectral regions are analyzed for the spectroscopic binary system Capella, obtained at orbital phase 0.26 with 3.27-3.57 km/s resolution and high SNR. The column densities of H I, D I, Mg II, and Fe II for the local interstellar medium along this 12.5 pc line of sight, together with estimates of the temperature and turbulent velocity are inferred. It is inferred that the atomic deuterium/hydrogen ratio by number is 1.65(+0.07, -0.18) x 10 exp -5 for this line of sight. Galactic evolution calculations indicate that the primordial D/H ratio probably lies in the range of (1.5-3) x (D/H)LISM. If H0 = 80 km/s Mpc, as recent evidence suggests, then the baryonic density in units of the Einstein-de Sitter closure density is 0.023-0.031. Thus the universe is argued to expand forever, unless nonbaryonic matter greatly exceeds the amount of baryonic matter.

Linsky, Jeffrey L.; Brown, Alexander; Gayley, Ken; Diplas, Athanassios; Savage, Blair D.; Ayres, Thomas R.; Landsman, Wayne; Shore, Steven N.; Heap, Sara R.

1993-01-01

226

Separability of hydrogen from hydrogen–carbon dioxide mixture across silica–silicalite-1 film  

Microsoft Academic Search

Colloidal silica particles, grown on a mesoporous silica layer using macroporous alumina substrate as a support, were used to separate hydrogen from carbon dioxide. The particles transformed into rectangular interlocking silicalite-1 structures with size approximately 8×4×4?m, oriented epitaxially with film thickness of ca. 22?m. The silicalite-1 particles grew in size due to the effect of structure directing agent (SDA), Oswald

M. R. Othman; S. C. Tan; S. Bhatia; W. J. N. Fernando

2011-01-01

227

Was Venus wet? Deuterium reconsidered  

NASA Technical Reports Server (NTRS)

The ratio of deuterium to hydrogen on Venus has been accepted as proof of a wetter, more earth-like part on that planet. However, the present-day water abundance and the nonthermal hydrogen escape flux on Venus imply that hydrogen is in a steady state and that a hydrogen source, most likely cometary infall, is present. An alternative interpretation of the D/H ratio is offered, in which the measured value is consistent with a steady-state evolution over the age of the solar system. No past water excess is required to explain the isotopic data.

Grinspoon, David H.

1987-01-01

228

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

229

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

Microsoft Academic Search

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

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

230

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

2011-03-22

231

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

232

Effect of hydrogen on catalyst nanoparticles in carbon nanotube growth  

NASA Astrophysics Data System (ADS)

The structures of carbon nanotubes grown from catalytic nanoparticles via plasma-enhanced chemical vapor deposition in CH4/H2 mixtures show a strong dependence on the H2-to-CH4 ratio in the feed gas. A suite of characterization techniques, including optical emission, infrared, and Raman spectroscopies combined with convergent-beam and selected-area electron diffraction, and high-resolution (scanning) transmission electron microscopy imaging were used to systematically investigate the interrelation among plasma gas phase composition, catalysts morphology, catalyst structure, and carbon nanotube structure. Hydrogen plays a critical role in determining the final carbon nanotube structure through its effect on the catalyst crystal structure and morphology. At low H2-to-CH4 ratios (˜1), iron catalyst nanoparticles are converted to Fe3C and well-graphitized nanotubes grow from elongated Fe3C crystals. High (>5) H2-to-CH4 ratios in the feed gas result in high hydrogen concentrations in the plasma and strongly reducing conditions, which prevents conversion of Fe to Fe3C. In the latter case, poorly-graphitized nanofibers grow from ductile bcc iron nanocrystals that are easily deformed into tapered nanocrystals that yield nanotubes with thick walls.

Behr, Michael J.; Gaulding, E. Ashley; Mkhoyan, K. Andre; Aydil, Eray S.

2010-09-01

233

Adsorption of hydrogen in boron-substituted nanoporous carbons  

NASA Astrophysics Data System (ADS)

Nanoporous carbons are promising for hydrogen storage. However, the heat of physisorption is low (4.5-8 kJ/mol), which limits the total amount of hydrogen adsorbed at room temperature to ˜2 wt.% at 100 bar. To enhance sorption the surface must be modified by substitution or doping/intercalation of some atoms in the carbon skeleton by other elements. Here we present coupled ab initio calculations and Monte Carlo simulations showing that partial substitution of carbon atoms in nanoporous matrix with boron increases significantly the adsorption energy (up to 10-13.5 kJ/mol) and storage capacity (˜5 wt.% at 298 K, 100 bar), even for relatively low substitution ratios (5-10%). Although substitution causes both energetic and structural heterogeneity of the adsorbent, at room temperature the delivery of the stored gas during adsorption-desorption cycle is almost complete (˜97 %). We analyze whether the location of substituted atoms (within the graphene plane or between two adjacent planes) and randomness of its distribution modify either the adsorption mechanism or/and storage parameters. In particular the heterogeneity of energy landscape is discussed in a context of optimization of system delivery.

Firlej, L.; Kuchta, B.; Roszak, S.; Pfeifer, P.; Wexler, C.

2010-03-01

234

Voltammetric detection of hydrogen peroxide at carbon fiber microelectrodes.  

PubMed

Hydrogen peroxide is a reactive oxygen species that is implicated in a number of neurological disease states and that serves a critical role in normal cell function. It is commonly exploited as a reporter molecule enabling the electrochemical detection of nonelectroactive molecules at electrodes modified with substrate-specific oxidative enzymes. We present the first voltammetric characterization of rapid hydrogen peroxide fluctuations at an uncoated carbon fiber microelectrode, demonstrating unprecedented chemical and spatial resolution. The carbon surface was electrochemically conditioned on the anodic scan and the irreversible oxidation of peroxide was detected on the cathodic scan. The oxidation potential was dependent on scan rate, occurring at +1.2 V versus Ag/AgCl at a scan rate of 400 V.s(-1). The relationship between peak oxidation current and concentration was linear across the physiological range tested, with deviation from linearity above 2 mM and a detection limit of 2 muM. Peroxide was distinguished from multiple interferents, both in vitro and in brain slices. The enzymatic degradation of peroxide was monitored, as was peroxide evolution in response to glucose at a glucose oxidase modified carbon fiber electrode. This novel approach provides the requisite sensitivity, selectivity, spatial and temporal resolution to study dynamic peroxide fluctuations in discrete biological locations. PMID:20503997

Sanford, Audrey L; Morton, Stephen W; Whitehouse, Kelsey L; Oara, Hannah M; Lugo-Morales, Leyda Z; Roberts, James G; Sombers, Leslie A

2010-06-15

235

Gas phase hydrogen permeation in alpha titanium and carbon steels  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

236

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

237

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

238

Atomic hydrogen maser measurements with wall surfaces of carbon tetrafluoride  

NASA Technical Reports Server (NTRS)

The principal objectives of the Smithsonian Astrophysical Observatory cold maser research programs are given. This work is aimed principally at understanding more about the interaction of hydrogen atoms with wall coatings of fluorinated ethylene propylene (Dupont Teflon FEP-120 co-polymer) and of carbon tetrafluoride (CE4). The principal measured quantity in these experiments is the wall shift of the maser's output frequency. The wall shift per atomic collision was calculated from the measured wall frequency shift. This assumes that the wall surface area is smooth on a molecular scale.

Vessot, R. F. C.; Mattison, E. M.; Imbier, E. A.; Zhai, Z. C.

1984-01-01

239

Hydrogen/deuterium exchange mass spectrometry reveals specific changes in the local flexibility of plasminogen activator inhibitor 1 upon binding to the somatomedin B domain of vitronectin.  

PubMed

The native fold of plasminogen activator inhibitor 1 (PAI-1) represents an active metastable conformation that spontaneously converts to an inactive latent form. Binding of the somatomedin B domain (SMB) of the endogenous cofactor vitronectin to PAI-1 delays the transition to the latent state and increases the thermal stability of the protein dramatically. We have used hydrogen/deuterium exchange mass spectrometry to assess the inherent structural flexibility of PAI-1 and to monitor the changes induced by SMB binding. Our data show that the PAI-1 core consisting of ?-sheet B is rather protected against exchange with the solvent, while the remainder of the molecule is more dynamic. SMB binding causes a pronounced and widespread stabilization of PAI-1 that is not confined to the binding interface with SMB. We further explored the local structural flexibility in a mutationally stabilized PAI-1 variant (14-1B) as well as the effect of stabilizing antibody Mab-1 on wild-type PAI-1. The three modes of stabilizing PAI-1 (SMB, Mab-1, and the mutations in 14-1B) all cause a delayed latency transition, and this effect was accompanied by unique signatures on the flexibility of PAI-1. Reduced flexibility in the region around helices B, C, and I was seen in all three cases, which suggests an involvement of this region in mediating structural flexibility necessary for the latency transition. These data therefore add considerable depth to our current understanding of the local structural flexibility in PAI-1 and provide novel indications of regions that may affect the functional stability of PAI-1. PMID:22957734

Trelle, Morten Beck; Hirschberg, Daniel; Jansson, Anna; Ploug, Michael; Roepstorff, Peter; Andreasen, Peter A; Jørgensen, Thomas J D

2012-10-16

240

Unfolding and aggregation of a glycosylated monoclonal antibody on a cation exchange column. Part II. Protein structure effects by hydrogen deuterium exchange mass spectrometry.  

PubMed

Hydrogen-deuterium exchange mass spectrometry (HX-MS) with proteolytic fragmentation is used to determine patterns of unfolding, as measured by increased solvent exposure, with peptide-level resolution for a glycosylated monoclonal antibody both when eluted from a tentacle-type cation exchange column (Fractogel EMD SO3-) and while bound to the resin. Two peaks are obtained when the bound protein is eluted with either a NaCl gradient or with two NaCl steps at increasing concentration. The first, early eluting peak contains only monomeric species whose structure is consistent with the native monomer. The second, late eluting peak contains a mixture of monomeric and aggregated species. The monomeric species in this mixture is also found to have a structure consistent with that of the native mAb, showing no evidence of increased solvent exposure. The aggregated species show instead significant unfolding in areas of the protein structure contained within the Fc region. The same peptides that exhibit the greatest level of solvent exposure in the aggregated species are also found in the fraction of protein that elutes from the resin only at high salt concentration, indicating that the aggregates are formed when the strongly-bound unfolded intermediate is desorbed at high salt. There is no evidence that the unfolded intermediate, formed while the protein is bound on the resin, is present in any of the eluted fractions indicating that, upon desorption from the resin, the intermediate either quickly refolds or forms aggregates which end-up co-eluting with the refolded protein at high salt concentrations. PMID:25011681

Guo, Jing; Carta, Giorgio

2014-08-22

241

Deuterium trapping in deep traps of differently oriented pyrolytic graphite exposed to D 2 gas at 1473 K  

NASA Astrophysics Data System (ADS)

Due to their importance for tritium inventories in future DT fueled fusion machines, experimental data on H isotope diffusion, absorption and retention in deep traps ( Eb ? 4.3 eV) of graphites exposed to hydrogen at elevated temperatures have been reviewed. Deuterium retention was studied in edge- and basal-oriented pyrolytic graphite (PG) and polycrystalline RG-Ti-91 damaged by irradiation with 200 keV carbon ions. Deuterium loading was done by soaking in D 2 gas at 1473 K, and the resulting D retention was measured by nuclear reaction analysis. The microstructure was studied by cross-sectional TEM, SEM and microprofilometry. The concentration of strong traps created by irradiation and estimated by the amount of accumulated deuterium was shown to saturate with the damage above ?1 dpa at about 1000 appm. In non-damaged and damaged graphites deuterium diffuses via porous grain boundaries and along basal planes within crystallites, while its migration through the graphite lattice along the c direction was found to be negligible. Radiation modifications of PG retard deuterium diffusion and decrease the rate of its chemical erosion by a factor of five. The amount of deuterium accumulated in strong traps in graphites is mainly influenced by their macro- and microstructure, while the degree of graphitization seems to be less important. Derivations are made of the susceptibility of damaged graphites, in particular, CFCs to the retention of hydrogen isotopes in deep traps.

Chernikov, V. N.; Wampler, W. R.; Zakharov, A. P.; Gorodetsky, A. E.

1999-01-01

242

Magnetic Carbon Supported Palladium Nanoparticles: An Efficient and Sustainable Catalyst for Hydrogenation Reactions  

EPA Science Inventory

Magnetic carbon supported Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; the catalyst can be used for the hydrogenation of alkenes and reduction of aryl nitro compounds....

243

Combustion characteristics of hydrogen. Carbon monoxide based gaseous fuels  

NASA Astrophysics Data System (ADS)

An experimental rig program was conducted with the objective of evaluating the combuston performance of a family of fuel gases based on a mixture of hydrogen and carbon monoxide. These gases, in addition to being members of a family, were also representative of those secondary fuels that could be produced from coal by various gasification schemes. In particular, simulated Winkler, Lurgi, and Blue-water low and medium energy content gases were used as fuels in the experimental combustor rig. The combustor used was originally designed as a low NOx rich-lean system for burning liquid fuels with high bound nitrogen levels. When used with the above gaseous fuels this combustor was operated in a lean-lean mode with ultra long residence times. The Blue-water gas was also operated in a rich-lean mode. The results of these tests indicate the possibility of the existence of an 'optimum' gas turbine hydrogen - carbon monoxide based secondary fuel. Such a fuel would exhibit NOx and high efficiency over the entire engine operating range. It would also have sufficient stability range to allow normal light-off and engine acceleration. Solar Turbines Incorporated would like to emphasize that the results presented here have been obtained with experimental rig combustors. The technologies generated could, however, be utilized in future commercial gas turbines.

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

1981-10-01

244

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

SciTech Connect

The objective of the project was to develop a novel complementary membrane reactor process that can consolidate two or more downstream unit operations of a coal gasification system into a single module for production of a pure stream of hydrogen and a pure stream of carbon dioxide. The overall goals were to achieve higher hydrogen production efficiencies, lower capital costs and a smaller overall footprint than what could be achieved by utilizing separate components for each required unit process/operation in conventional coal-to-hydrogen systems. Specifically, this project was to develop a novel membrane reactor process that combines hydrogen sulfide removal, hydrogen separation, carbon dioxide separation and water-gas shift reaction into a single membrane configuration. The carbon monoxide conversion of the water-gas-shift reaction from the coal-derived syngas stream is enhanced by the complementary use of two membranes within a single reactor to separate hydrogen and carbon dioxide. Consequently, hydrogen production efficiency is increased. The single membrane reactor configuration produces a pure H{sub 2} product and a pure CO{sub 2} permeate stream that is ready for sequestration. This project focused on developing a new class of CO{sub 2}-selective membranes for this new process concept. Several approaches to make CO{sub 2}-selective membranes for high-temperature applications have been tested. Membrane disks using the technique of powder pressing and high temperature sintering were successfully fabricated. The powders were either metal oxide or metal carbonate materials. Experiments on CO{sub 2} permeation testing were also performed in the temperature range of 790 to 940 C for the metal carbonate membrane disks. However, no CO{sub 2} permeation rate could be measured, probably due to very slow CO{sub 2} diffusion in the solid state carbonates. To improve the permeation of CO{sub 2}, one approach is to make membranes containing liquid or molten carbonates. Several different types of dual-phase membranes were fabricated and tested for their CO{sub 2} permeation in reducing conditions without the presence of oxygen. Although the flux was quite low, on the order of 0.01-0.001 cc STP/cm{sup 2}/min, the selectivity of CO{sub 2}/He was almost infinite at temperatures of about 800 C. A different type of dual-phase membrane prepared by Arizona State University (ASU) was also tested at GTI for CO{sub 2} permeation. The measured CO{sub 2} fluxes were 0.015 and 0.02 cc STP/cm{sup 2}/min at 750 and 830 C, respectively. These fluxes were higher than the previous flux obtained ({approx}0.01 cc STP/cm{sup 2}/min) using the dual-phase membranes prepared by GTI. Further development in membrane development should be conducted to improve the CO{sub 2} flux. ASU has also focused on high temperature permeation/separation experiments to confirm the carbon dioxide separation capabilities of the dual-phase membranes with La{sup 0.6}Sr{sub 0.4}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} (LSCF6482) supports infiltrated with a Li/Na/K molten carbonate mixture (42.5/32.5/25.0 mole %). The permeation experiments indicated that the addition of O{sub 2} does improve the permeance of CO{sub 2} through the membrane. A simplified membrane reactor model was developed to evaluate the performance of the process. However, the simplified model did not allow the estimation of membrane transport area, an important parameter for evaluating the feasibility of the proposed membrane reactor technology. As a result, an improved model was developed. Results of the improved membrane reactor model show that the membrane shift reaction has promise as a means to simplify the production of a clean stream of hydrogen and a clean stream of carbon dioxide. The focus of additional development work should address the large area required for the CO{sub 2} membrane as identified in the modeling calculations. Also, a more detailed process flow diagram should be developed that includes integration of cooling and preheating feed streams as well as particulate removal so that stea

Micheal Roberts; Robert Zabransky; Shain Doong; Jerry Lin

2008-05-31

245

Hydrogen Storage in Carbon Nanotubes For the purposes of pollution free vehicular fuel cells and secondary batteries  

Microsoft Academic Search

Herein are discussed briefly the mechanisms theorized and supported by experiments or calculations pertaining the adsorption of hydrogen into carbon nanotubes. Affects of tube size, pressure, and temperature on hydrogen uptake in carbon nanotubes are also discussed. In particular, single-walled carbon nanotubes are discussed because of their promising hydrogen adsorption characteristics. Also, alkali-doping of carbon nanotubes and its benefits are

Brian Riestenberg

246

Study of the carbon-13 and deuterium kinetic isotope effects in the Cl and OH reactions of CH4 and CH3Cl.  

PubMed

Relative rate experiments have been carried out for three isotopologues of chloromethane and their reactions with Cl atoms and OH radicals. The OH and Cl reaction rates of CH2DCl and CHD2Cl were measured by long-path FTIR spectroscopy relative to CH3Cl at 298+/-2 K and 1013+/-10 hPa in purified air. The FTIR spectra were fitted using a nonlinear least squares spectral fitting method including measured high-resolution infrared spectra as references. The relative reaction rates defined by alpha=klight/kheavy were determined to be kOH+CH3Cl/kOH+CH2DCl=1.41+/-0.05, kOH+CH3Cl/kOH+CHD2Cl=2.03+/-0.05, kCl+CH3Cl/kCl+CH2DCl=1.42+/-0.04, and kCl+CH3Cl/kCl+CHD2Cl=2.27+/-0.04. The carbon-13 and deuterium kinetic isotope effects in the OH and Cl reactions of CH3Cl were investigated further using variational transition state theory, and the results were compared to similar calculations performed for the CH4+OH/Cl reaction systems. The calculations show that the order of magnitude difference for the carbon-13 kinetic isotope effect in the OH reaction of CH3Cl compared to CH4 reported by Gola et al. (Atmos. Chem. Phys. 2005, 5, 2395) can be explained by the lower barrier to internal rotation of the OH radical in the transition state of the CH4+OH reaction than in the CH3Cl+OH reaction. The deuterium kinetic isotope effects can be explained in terms of combined variational effects and tunneling. PMID:16392849

Sellevåg, Stig R; Nyman, Gunnar; Nielsen, Claus J

2006-01-12

247

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

248

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

249

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

EPA Science Inventory

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

250

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

251

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

E-print Network

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

Goddard III, William A.

252

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

Microsoft Academic Search

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

Mariusz Stolarski

2008-01-01

253

Production of carbon monoxide-free hydrogen and helium from a high-purity source  

DOEpatents

The invention provides vacuum swing adsorption processes that produce an essentially carbon monoxide-free hydrogen or helium gas stream from, respectively, a high-purity (e.g., pipeline grade) hydrogen or helium gas stream using one or two adsorber beds. By using physical adsorbents with high heats of nitrogen adsorption, intermediate heats of carbon monoxide adsorption, and low heats of hydrogen and helium adsorption, and by using vacuum purging and high feed stream pressures (e.g., pressures of as high as around 1,000 bar), pipeline grade hydrogen or helium can purified to produce essentially carbon monoxide -free hydrogen and helium, or carbon monoxide, nitrogen, and methane-free hydrogen and helium.

Golden, Timothy Christopher (Allentown, PA); Farris, Thomas Stephen (Bethlehem, PA)

2008-11-18

254

Hydrogen behavior in carbon-based materials and its neutron irradiation effect  

NASA Astrophysics Data System (ADS)

Hydrogen retention in graphites and CFCs (carbon fiber/carbon composites) has been studied with the crystallographic data obtained by the X-ray diffraction (XRD) technique. The amounts of retained hydrogen vary substantially among the samples by a factor of up to 16. After neutron irradiation at 1.9 × 10 24 n/m 2(˜ 0.2 dpa), the hydrogen retained becomes 20-50 times a larger than that of unirradiated samples. A strong correlation is observed between the values of hydrogen retention and the lattice constant c0. The size of crystallite also has a good correlation with the hydrogen retention. Hydrogen atoms will be trapped at dangling carbon bonds at edge surfaces of crystallite which are thermally stable even at high temperatures above 1000°C. Differences among the desorbed amount of hydrogen gas from graphite materials can be also explained well by this model.

Atsumi, Hisao; Iseki, Michio; Shikama, Tatsuo

1996-10-01

255

Sustainable production of green feed from carbon dioxide and hydrogen.  

PubMed

Carbon dioxide hydrogenation to form hydrocarbons was conducted on two iron-based catalysts, prepared according to procedures described in the literature, and on a new iron spinel catalyst. The CO2 conversion measured in a packed-bed reactor was limited to about 60% because of excessive amounts of water produced in this process. Switching to a system of three packed-bed reactors in series with interim removal of water and condensed hydrocarbons increased CO2 conversion to as much as 89%. The pure spinel catalyst displayed a significantly higher activity and selectivity than those of the other iron catalysts. This process produces a product called green feed, which is similar in composition to the product of a high-temperature, iron-based Fischer–Tropsch process from syngas. The green feed can be readily converted into renewable fuels by well-established technologies. PMID:24678062

Landau, Miron V; Vidruk, Roxana; Herskowitz, Moti

2014-03-01

256

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

NASA Technical Reports Server (NTRS)

We will demonstrate that carbon particles consisting of large cages can be produced without catalytic metal. The carbon particles were produced in CO gas as well as by introduction of 5% methane gas into the CO gas. The gas-produced carbon particles were able to absorb approximately 16.2 wt% of hydrogen. This value is 2.5 times higher than the 6.5 wt% goal for the vehicular hydrogen storage proposed by the Department of Energy in the USA. Therefore, we believe that this carbon particle is an excellent candidate for hydrogen storage for fuel cells.

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

2005-01-01

257

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

258

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

NASA Astrophysics Data System (ADS)

High-strength carbon steels of 1200 MPa strength level with different microalloying were tensile tested at constant extension rate and constant load under continuous electrochemical hydrogen charging. The results show that hydrogen markedly reduces elongation and time to fracture of all the studied steels. Fractography of the steels shows that nonmetallic inclusions (NMIs) play the major role in crack initiation in hydrogen-charged specimens. The role of NMIs in the hydrogen-induced fracture of steels is discussed.

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

2014-10-01

259

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

260

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

PubMed Central

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

Clausen, Dane J.

2012-01-01

261

Carbon nano-fiber growth on the anode during hydrogen DC arc-discharge  

Microsoft Academic Search

A carbon nano-fiber with a diameter of 25-100 nm and 98.4 percent purity was produced on the heated anode surface in hydrogen DC arc-discharge [1]. Hydrogen arc plasma was generated between the graphite cathode and the carbon\\/metal composite anode (Fe\\/Co\\/Ni\\/FeS). X-ray diffraction analysis revealed that the carbon nano-fiber had a turbostratic structure with a (002) interlayer spacing of 0.346nm. Three

Hisashi Kajiura; Houjin Huang; Shigemitsu Tsutsui; Yousuke Murakami; Mitsuaki Miyakoshi

2003-01-01

262

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

E-print Network

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

Nordlund, Kai

263

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

264

Concomitant Production of High Purity Hydrogen and Sequestration Ready Carbon Dioxide From Coal  

Microsoft Academic Search

A novel process on the production of a high purity stream of hydrogen from gasification products with concomitant generation of sequestration-ready carbon dioxide stream is presented. The central theme of the process lies in the sequential use of a) an oxygen transfer compound (OTC) to oxidize carbon monoxide present in syngas and b) capture of CO2 using an appropriate carbon

Kanchan Mondal; Krzysztof Piotrowski; Tomasz Wiltowski

265

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

Microsoft Academic Search

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

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

2006-01-01

266

PERGAMON Carbon 38 (2000) 17571765 High temperature hydrogen sulfide adsorption on activated  

E-print Network

temperature was examined as a2 function of carbon surface chemistry (oxidation, thermal desorption, and metalPERGAMON Carbon 38 (2000) 1757­1765 High temperature hydrogen sulfide adsorption on activated gas stream2 at a temperature of 5508C. The ability of activated carbon to remove H S at elevated

Cal, Mark P.

267

PERGAMON Carbon 38 (2000) 17671774 High temperature hydrogen sulfide adsorption on activated  

E-print Network

PERGAMON Carbon 38 (2000) 1767­1774 High temperature hydrogen sulfide adsorption on activated carbon II. Effects of gas temperature, gas pressure and sorbent regeneration 1 2 3 *M.P. Cal , B of activated carbon sorbents were evaluated for removal of H S at high temperatures (400­6008C) in an2

Cal, Mark P.

268

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

E-print Network

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

Harilal, S. S.

269

Optimal Design of a Fossil Fuel-Based Hydrogen Infrastructure with Carbon Capture and Sequestration: Case Study in Ohio  

Microsoft Academic Search

Presented at the National Hydrogen Association Annual Hydrogen Conference (NHA 2005), Washington, DC, March 29 - April 1, 2005 The use of hydrogen as a light-duty transportation fuel requires the development of a widespread regional hydrogen infrastructure, including production facilities, a distribution network, and refueling stations. In the case of fossil-based hydrogen production with carbon capture and sequestration, additional infrastructure

Nils Johnson; Christopher Yang; Jason Ni; Joshua Johnson; Zhenhong Lin; Joan M Ogden

2005-01-01

270

Evolution mechanism of nanocrystalline tungsten-carbon and effects on tungsten implanted amorphous hydrogenated carbon  

SciTech Connect

Tungsten doped amorphous carbon films are prepared on silicon (100) by postimplantation of tungsten ions into pure amorphous hydrogenated carbon using the plasma immersion ion implantation technique. The peak concentration of tungsten reaches 27 at. % and W-C nanocrystallites with largest diameters of {approx}5 nm are formed in the near surface region. Both the quantity and size of these nanocrystallites are observed to undergo unique transformation with increasing depths, enabling gradual release of the compressive stress and subsequently leading to better adhesion between the film and substrate. The film structures are evaluated by x-ray photoelectron spectroscopy and glancing angle x-ray diffraction, and high-resolution transmission microscopy is employed to investigate the structural transformation. The mechanical properties of the films including adhesion strength and hardness are determined by nanoindentation and nanoscratch tests. The formation of the nanocrystalline structures can be explained by ion implantation induced damage, chemical effects, and thermodynamics.

Xu Ming; Zhang Wei; Wu Zhengwei; Pu Shihao; Li Liuhe; Chu, Paul K. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China) and 702 Department, Mechanical Engineering School, Beijing University of Aeronautic and Astronautic, Beijing 100083 (China); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)

2007-12-01

271

Cometary deuterium.  

PubMed

Deuterium fractionations in cometary ices provide important clues to the origin and evolution of comets. Mass spectrometers aboard spaceprobe Giotto revealed the first accurate D/H ratios in the water of Comet 1P/Halley. Ground-based observations of HDO in Comets C/1996 B2 (Hyakutake) and C/1995 O1 (Hale-Bopp), the detection of DCN in Comet Hale-Bopp, and upper limits for several other D-bearing molecules complement our limited sample of D/H measurements. On the basis of this data set all Oort cloud comets seem to exhibit a similar (D/H)H2O ratio in H2O, enriched by about a factor of two relative to terrestrial water and approximately one order of magnitude relative to the protosolar value. Oort cloud comets, and by inference also classical short-period comets derived from the Kuiper Belt cannot be the only source for the Earth's oceans. The cometary O/C ratio and dynamical reasons make it difficult to defend an early influx of icy planetesimals from the Jupiter zone to the early Earth. D/H measurements of OH groups in phyllosilicate rich meteorites suggest a mixture of cometary water and water adsorbed from the nebula by the rocky grains that formed the bulk of the Earth may be responsible for the terrestrial D/H. The D/H ratio in cometary HCN is 7 times higher than the value in cometary H2O. Species-dependent D-fractionations occur at low temperatures and low gas densities via ion-molecule or grain-surface reactions and cannot be explained by a pure solar nebula chemistry. It is plausible that cometary volatiles preserved the interstellar D fractionation. The observed D abundances set a lower limit to the formation temperature of (30 +/- 10) K. Similar numbers can he derived from the ortho-to-para ratio in cometary water, from the absence of neon in cometary ices and the presence of S2. Noble gases on Earth and Mars, and the relative abundance of cometary hydrocarbons place the comet formation temperature near 50 K. So far all cometary D/H measurements refer to bulk compositions, and it is conceivable that significant departures from the mean value could occur at the grain-size level. Strong isotope effects as a result of coma chemistry can be excluded for molecules H2O and HCN. A comparison of the cometary (D/H)H2O ratio with values found in the atmospheres of the outer planets is consistent with the long-held idea that the gas planets formed around icy cores with a high cometary D/H ratio and subsequently accumulated significant amounts of H2 from the solar nebula with a low protosolar D/H. PMID:11543290

Meier, R; Owen, T C

1999-01-01

272

Interstellar deuterium chemistry  

Microsoft Academic Search

Possible improvements of gas-phase chemical models regarding processes in interstellar space are considered. It is pointed out that previous studies have not included deuterium in their reaction schemes. A consideration of deuterium is important in connection with the establishment of the cosmic deuterium abundance as an important indicator of the nature of the universe. Other deficiencies in current models are

R. D. Brown; E. Rice; J. Brooks

1981-01-01

273

Molten metal reactor and method of forming hydrogen, carbon monoxide and carbon dioxide using the molten alkaline metal reactor  

DOEpatents

A molten metal reactor for converting a carbon material and steam into a gas comprising hydrogen, carbon monoxide, and carbon dioxide is disclosed. The reactor includes an interior crucible having a portion contained within an exterior crucible. The interior crucible includes an inlet and an outlet; the outlet leads to the exterior crucible and may comprise a diffuser. The exterior crucible may contain a molten alkaline metal compound. Contained between the exterior crucible and the interior crucible is at least one baffle.

Bingham, Dennis N.; Klingler, Kerry M.; Turner, Terry D.; Wilding, Bruce M.

2012-11-13

274

Minimisation of carbon monoxide in a hydrogen stream for fuel cell application  

Microsoft Academic Search

Means of minimising carbon monoxide in a hydrogen stream for fuel cell operation are reviewed. Reduction of carbon monoxide to an acceptable level of 10–50ppm involves high temperature and low temperature water gas shift, followed by selective oxidation of residual carbon monoxide. Methanation of very small amounts of carbon monoxide may be an alternative final step.A new range of promoted

D. L. Trimm

2005-01-01

275

Molecular dynamics calculation of carbon\\/hydrocarbon reflection coefficients on a hydrogenated graphite surface  

Microsoft Academic Search

Reflection coefficients for carbon atoms and hydrocarbon molecules on a carbon surface are critically needed for plasma–surface interaction analysis of carbon surfaces. These coefficients have been calculated with a molecular dynamics code using the Brenner hydrocarbon potential. The surface was prepared by bombarding a pure graphite lattice with energetic hydrogen, until a saturation was reached at ?0.42 H:C. Carbon atoms

Darren A. Alman; D.N. Ruzic

2003-01-01

276

Chromogenic signaling of hydrogen carbonate anion with pyrylium-containing polymers.  

PubMed

Polymeric films containing pyrylium derivatives showing a selective color modulation from yellow to red in the presence of the poorly coordinating hydrogen carbonate anion in water at neutral pH have been developed. PMID:17518473

García-Acosta, Beatriz; García, Félix; García, Jose Miguel; Martínez-Mañez, Ramón; Sancenón, Félix; San-José, Noelia; Soto, Juan

2007-06-21

277

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...

278

Cosmological Deuterium Abundance and the Baryon Density of the Universe  

Microsoft Academic Search

Standard big bang nucleosynthesis (BBNS) promises accurate predictions of the primordial abundances of deuterium, helium-3, helium-4 and lithium-7 as a function of a single parameter. Previous measurements have nearly always been interpreted as confirmation of the model (Copi, Schramm & Turner 1995). Here we present a measurement of the deuterium to hydrogen ratio (D\\/H) in a newly discovered high redshift

Scott Burles; David Tytler

1996-01-01

279

Carbon dioxide separation from hydrogen and nitrogen by fixed facilitated transport in swollen chitosan membranes  

Microsoft Academic Search

The separation of carbon dioxide from hydrogen and nitrogen at high temperatures would be valuable to fuel cell, flue gas purification, and ammonia processes. A feed gas mixture of carbon dioxide, hydrogen and nitrogen (10% CO2, 10% H2, and 80% N2) was used to evaluate water-swollen chitosan as a facilitated transport membrane for these applications. The amino group of the

Louei A. El-Azzami; Eric A. Grulke

2008-01-01

280

Desulfurization of gaseous fuels using activated carbons as catalysts for the selective oxidation of hydrogen sulfide  

Microsoft Academic Search

The removal of low concentrations of hydrogen sulfide (HâS) from hydrogen-rich gaseous fuels by selective catalytic oxidation, using activated carbon as the catalyst, was studied. The capacities of four activated carbons for reducing the HâS concentration down to the parts per billion (ppb) level were determined to be strongly related to their microstructures and impurities, even though their activity and

Xianxian Wu; Viviane Schwartz; Steven H. Overbury; Timothy R. Armstrong

2005-01-01

281

The solubility of elemental sulfur in methane, carbon dioxide and hydrogen sulfide gas  

E-print Network

THE SOLUBILITY OF ELEMENTAL SULFUR IN METHANE, CARBON DIOXIDE AND HYDROGEN SULFIDE GAS By Denton R. Wieland A Dissertation Submitted to the Graduate School of The Agricultural and Mechanical College of Texas in partial fulfillment... of the requirements for the degree of DOCTOR OF PHILOSOPHY January 1958 Major Subject: Petroleum Engineering THE SOLUBILITY OF ELEMENTAL SULFUR IN METHANE, CARBON DIOXIDE AND HYDROGEN SULFIDE GAS A Dissertation By DENTON R. WlELAND Library A * "COLLEGE...

Wieland, Denton R.

2013-10-04

282

Robust, high reactivity and enhanced capacity carbon dioxide removal agents for hydrogen production applications  

Microsoft Academic Search

The first step of forming hydrogen from carbonaceous solid fuels (coal, biomass) is gasification, followed by water gas shift reaction and separation of the carbon dioxide and hydrogen. Several processes, such as the HyP-RING process, reaction swing methodology by SIU (Southern Illinois University), chemical looping processes, etc., have been developed for hydrogen production involving the use of CaO as the

D. Dasgupta; K. Mondal; T. Wiltowski

2008-01-01

283

Removal of the hydrogen sulfide contained in a gas of high carbon dioxide content  

Microsoft Academic Search

A process is described for removing hydrogen sulfide from a gas containing hydrogen sulfide mixed with a large amount of carbon dioxide. It comprises the successive steps of contacting the gas with an aqueous solution of ammonium sulfite so as to form ammonium thiosulfate; decomposing the ammonium thiosulfate to sulfur, ammonia, sulfur dioxide, and water; and recovering the sulfur and

P. Renault; A. Deschamps; C. Dezael

1974-01-01

284

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

285

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

286

Nature of the Bound States of Molecular Hydrogen in Carbon Nanohorns  

NASA Astrophysics Data System (ADS)

The effects of confining molecular hydrogen within carbon nanohorns are studied via high-resolution quasielastic and inelastic neutron spectroscopies. Both sets of data are remarkably different from those obtained in bulk samples in the liquid and crystalline states. At temperatures where bulk hydrogen is liquid, the spectra of the confined sample show an elastic component indicating a significant proportion of immobile molecules as well as distinctly narrower quasielastic line widths and a strong distortion of the line shape of the para?ortho rotational transition. The results show that hydrogen interacts far more strongly with such carbonous structures than it does to carbon nanotubes, suggesting that nanohorns and related nanostructures may offer significantly better prospects as lightweight media for hydrogen storage applications.

Fernandez-Alonso, F.; Bermejo, F. J.; Cabrillo, C.; Loutfy, R. O.; Leon, V.; Saboungi, M. L.

2007-05-01

287

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. PMID:16600964

Frego, Lee; Davidson, Walter

2006-01-01

288

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

289

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

290

Carbide-Derived Carbons with Tunable Porosity Optimized for Hydrogen Storage  

SciTech Connect

On-board hydrogen storage is a key requirement for fuel cell-powered cars and trucks. Porous carbon-based materials can in principle adsorb more hydrogen per unit weight at room temperature than liquid hydrogen at -176 oC. Achieving this goal requires interconnected pores with very high internal surface area, and binding energies between hydrogen and carbon significantly enhanced relative to H2 on graphite. In this project a systematic study of carbide-derived carbons, a novel form of porous carbon, was carried out to discover a high-performance hydrogen sorption material to meet the goal. In the event we were unable to improve on the state of the art in terms of stored hydrogen per unit weight, having encountered the same fundamental limit of all porous carbons: the very weak interaction between H2 and the carbon surface. On the other hand we did discover several strategies to improve storage capacity on a volume basis, which should be applicable to other forms of porous carbon. Further discoveries with potentially broader impacts include • Proof that storage performance is not directly related to pore surface area, as had been previously claimed. Small pores (< 1.5 nm) are much more effective in storing hydrogen than larger ones, such that many materials with large total surface areas are sub-par performers. • Established that the distribution of pore sizes can be controlled during CDC synthesis, which opens the possibility of developing high performance materials within a common family while targeting widely disparate applications. Examples being actively pursued with other funding sources include methane storage, electrode materials for batteries and supercapacitors with record high specific capacitance, and perm-selective membranes which bind cytokines for control of infections and possibly hemodialysis filters.

Fisher, John E.; Gogotsi, Yury; Yildirim, Taner

2010-01-07

291

Synthesis of Sulfur-Containing Heterocycles through Oxidative Carbon-Hydrogen Bond Functionalization  

PubMed Central

Vinyl sulfides react rapidly and efficiently with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to form ?,?-unsaturated thiocarbenium ions through oxidative carbon–hydrogen bond cleavage. These electrophiles couple with appended ?-nucleophiles to yield sulfur-containing heterocycles through carbon–carbon bond formation. Several nucleophiles are compatible with the procedure and the reactions generally proceed through readily-predictable transition states. PMID:22420412

Cui, Yubo; Floreancig, Paul E.

2012-01-01

292

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

293

Coulometric determination of dissolved hydrogen with a multielectrolytic modified carbon felt electrode-based sensor.  

PubMed

A multielectrolytic modified carbon electrode (MEMCE) was fabricated by the electrolytic-oxidation/reduction processes. First, the functional groups containing nitrogen atoms such as amino group were introduced by the electrode oxidation of carbon felt electrode in an ammonium carbamate aqueous solution, and next, this electrode was electroreduced in sulfuric acid. The redox waves between hydrogen ion and hydrogen molecule at highly positive potential range appeared in the cyclic voltammogram obtained by MEMCE. A coulometric cell using MEMCE with a catalytic activity of electrooxidation of hydrogen molecule was constructed and was used for the measurement of dissolved hydrogen. The typical current vs. time curve was obtained by the repetitive measurement of the dissolved hydrogen. These curves indicated that the measurement of dissolved hydrogen was finished completely in a very short time (ca. 10 sec). A linear relationship was obtained between the electrical charge needed for the electrooxidation process of hydrogen molecule and dissolved hydrogen concentration. This indicates that the developed coulometric method can be used for the determination of the dissolved hydrogen concentration. PMID:24191595

Matsuura, Hiroaki; Yamawaki, Yosuke; Sasaki, Kosuke; Uchiyama, Shunichi

2013-06-01

294

Preparation and characterization of ordered porous carbons for increasing hydrogen storage behaviors  

SciTech Connect

We prepared ordered porous carbons (PCs) by using a replication method that had well-organized mesoporous silica as a template with various carbonization temperatures in order to investigate the possibility of energy storage materials. The microstructure and morphologies of the samples are characterized by XRD, TEM, and FT-Raman spectroscopy. N{sub 2} adsorption isotherms are analyzed by the t-plot method, as well as the BET and the H-K method in order to characterize the specific surface area, pore volume, and pore size distribution of the samples, respectively. The capacity of the hydrogen adsorption of the samples is evaluated by BEL-HP at 77 K and 1 bar. From the results, we are able to confirm that the synthesis of the samples can be accurately governed by the carbonization temperature, which is one of the effective parameters for developing the textural properties of the carbon materials, which affects the behaviors of the hydrogen storage. - Graphical abstract: It is described that the considerable long-range ordering and the presence of mono-dimensional aligned channels between the two aligned nanorods of the porous framework from the SBA-15 was retained in the T-950 sample during the carbonization process. Highlights: > Ordered porous carbons (PCs) are synthesized with various carbonization temperatures by using a replication method. > Carbonization temperature plays an important role in shrinking the micropores during the carbonization process of PCs. > The textural and structural properties of the PCs are good parameters for enhancing the hydrogen storage capacity.

Lee, Seul-Yi [Department of Chemistry, Inha University, 253 Nam-gu, Incheon 402-751 (Korea, Republic of); Park, Soo-Jin, E-mail: sjpark@inha.ac.kr [Department of Chemistry, Inha University, 253 Nam-gu, Incheon 402-751 (Korea, Republic of)

2011-10-15

295

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

296

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

SciTech Connect

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

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

1992-06-01

297

Hydrogen Storage Property of Nanoporous Carbon Materials Prepared from Rice Husks  

NASA Astrophysics Data System (ADS)

Nanoporous carbon materials for use as hydrogen storage materials were fabricated from rice husks. Rice husks from agricultural waste changed to porous carbon materials by heat treating and KOH activation. The specific surface area of the porous carbon materials increased from 11 to 2061 m2/g as the KOH weight ratio increased. The pore volume of the materials also increased from 0.01 to 0.88 cm3/g by KOH activation. The pore sizes of the activated porous carbon materials were distributed around 0.6 and 1.2 nm at micro-pore ranges. These results suggested porous carbon material have micro-pore structure. The hydrogen storage capacity of the porous carbon materials showed a 0.62 wt.% at 298 K under 12 MPa. The fabrication of hydrogen storage materials from agricultural waste rice husks was achieved. The results indicate that porous carbon materials synthesized from rice husks have micro-pore structures which influence their hydrogen storage capabilities.

Toda, Ikumi; Ono, Hiroki; Takahata, Tomokazu; Ohshio, Shigeo; Akasaka, Hiroki; Himeno, Syuuji; Kokubu, Toshinori; Saitoh, Hidetoshi

298

Compound-Specific Carbon, Nitrogen, and Hydrogen Isotopic Ratios for Amino Acids in CM and CR Chondrites and their use in Evaluating Potential Formation Pathways  

NASA Technical Reports Server (NTRS)

Stable hydrogen, carbon, and nitrogen isotopic ratios (oD, 013C, and olSN) of organic compounds can revcal information about their origin and formation pathways. Several formation mechanisms and environments have been postulated for the amino acids detected in carbonaceous chondrites. As each proposed mechanism utilizes different precursor molecules, the isotopic signatures of the resulting amino acids may indicate the most likely of these pathways. We have applied gas chromatography with mass spectrometry and combustion isotope ratio mass spectrometry to measure the compound-specific C, N, and H stable isotopic ratios of amino acids from seven CM and CR carbonaceous chondrites: CM1I2 Allan Hills (ALH) 83100, CM2 Murchison, CM2 Lewis Cliff (LEW) 90500, CM2 Lonewolf Nunataks (LON) 94101, CRZ Graves Nunataks (GRA) 95229, CRZ Elephant Moraine (EET) 92042, and CR3 Queen Alexandra Range (QUE) 99177. We compare the isotopic compositions of amino acids in these meteorites with predictions of expected isotopic enrichments from potential formation pathways. We observe trends of decreasing ODC and increasing oD with increasing carbon number in the aH, (l-NH2 amino acids that correspond to predictions made for formation via Streckercyanohydrin synthesis. We also observe light ODC signatures for -alanine, which may indicate either formation via Michael addition or via a pathway that forms primarily small, straight-chain, amine-terminal amino acids (n-ro-amino acids). Higher deuterium enrichments are observed in amethyl amino acids, indicating formation of these amino acids or their precursors in cold interstellar or nebular environments. Finally, individual amino acids are more enriched in deuterium in CR chondrites than CM chondrites, reflecting different parent-body chemistry.

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

2012-01-01

299

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

NASA Astrophysics Data System (ADS)

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 °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 °C. The wear rate of the films decreased sharply when annealed at 200 or 300 °C. Structural analysis shows that annealing at 300 °C improved tribological properties originated from the volume increase in the fullerenelike microstructure, and further annealing at 600 °C improved mechanical properties originated from the transformation of nanosized curved sp2 to sp3 clusters.

Wang, Qi; He, Deyan; Wang, Chengbing; Wang, Zhou; Zhang, Junyan

2008-08-01

300

Surface hardness increasing of iron alloys by nitrogen-deuterium ion implanting  

NASA Astrophysics Data System (ADS)

In situ x-ray photoemission spectroscopy is used to study the deuterium and hydrogen oxygen etching effect in nitrogen-implanted iron alloys. A suitable deuterium-nitrogen mixture can increase the surface original steel hardness up to ˜40%. In similar conditions, hydrogen-nitrogen mixtures improves the hardness by ˜10%. On deuteration, the main change is the reduction of the zero-point energy of the hydrides bond. Due to this, the lower scission energy of hydrogen-metal bonds as compared with deuterium-metal bonds determines the favorable effect of deuterium on the nitriding process.

Figueroa, C. A.; Alvarez, F.

2004-12-01

301

Analysis of diffential absorption lidar technique for measurements of anhydrous hydrogen chloride from solid rocket motors using a deuterium fluoride laser  

NASA Technical Reports Server (NTRS)

An active optical technique (differential absorption lidar (DIAL)) for detecting, ranging, and quantifying the concentration of anhydrous HCl contained in the ground cloud emitted by solid rocket motors (SRM) is evaluated. Results are presented of an experiment in which absorption coefficients of HCl were measured for several deuterium fluoride (DF) laser transitions demonstrating for the first time that a close overlap exists between the 2-1 P(3) vibrational transition of the DF laser and the 1-0 P(6) absorption line of HCl, with an absorption coefficient of 5.64 (atm-cm) to the -1 power. These measurements show that the DF laser can be an appropriate radiation source for detecting HCl in a DIAL technique. Development of a mathematical computer model to predict the sensitivity of DIAL for detecting anhydrous HCl in the ground cloud is outlined, and results that assume a commercially available DF laser as the radiation source are presented.

Bair, C. H.; Allario, F.

1977-01-01

302

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

303

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

NASA Technical Reports Server (NTRS)

Metastable fragments produced by electron impact excitation of CH4 have been investigated for incident electron energies from threshold to 300 eV. Only metastable hydrogen and carbon atoms were observed. Onset energies for the production of metastable hydrogen atoms were observed at electron impact energies of 22.0 + or - .5 eV, 25.5 + or - .6 eV, 36.7 + or - .6 eV and 66 + or - 3 eV, and at 26.6 + or - .6 eV for the production of metastable carbon atoms. Most of the fragments appear to have been formed in high-lying Rydberg states. The total metastable hydrogen cross section reaches a maximum value of approximately 1 X 10 to the minus 18th power sq cm at 100 eV. At the same energy, the metastable carbon cross section is 2 x 10 to the minus 19th power sq cm.

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

1974-01-01

304

Substrate Bias Effect on Amorphous Hydrogenated Carbon Films Deposited by Filtered Cathodic Arc Deposition  

NASA Astrophysics Data System (ADS)

In the present study, we briefly describe the 45° angle magnetic filtered arc deposition (FAD) process and investigate the effect of substrate bias on the hardness of amorphous carbon (a-C) films. An attempt is made to correlate the microstructure, chemical composition and chemical bonding states with the hardness of the corresponding films. After deposition, the film properties were analyzed by Raman spectroscopy and nanoindentation system (NIS). It was found that amorphous carbon films possess highest hardness when deposited at substrate biases ranging from -50 V to -100 V@. The hardness values do not show good correlation with Raman I(D)/I(G) ratio. Hydrogen additions to the system help prevent the nucleation of the graphite phase, and stabilize the sp3 bonding of amorphous hydrogenated carbon films. Hydrogen affected on the small graphitic crystalline growth. Films have higher hardness when they have higher fraction of sp3 content.

Li, Yan-Way; Chen, Chia-Fu; Shue, Yew-Bin; Yu, Teng-Chien; Chang, Jack Jyh-Kau

2001-11-01

305

HST Observations of Carbon and Hydrogen in Hot DB White Dwarfs  

NASA Astrophysics Data System (ADS)

We present GHRS observations centered at 1215 and 1335 { Angstroms} of the hot helium white dwarfs PG0112+104 and GD190. We detect hydrogen and carbon in both objects, raising the number of hot DBs with known traces of these elements to three (including GD 358). We calculate hydrogen and carbon surface abundances and corresponding mass fractions using the stellar atmospheres program Tlusty and the convection calculations of Althaus & Benvenuto (1996). The hydrogen mass fraction is {MH~ 10(-17}M_{*}) in all three objects. This disturbing number is nearly two orders of magnitude below the predictions of chemical evolution. If the carbon originates from convective dredge-up of the underlying core, the process is initiated at temperatures much higher than expected.

Provencal, J. L.; Shipman, H. L.

1998-12-01

306

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

Microsoft Academic Search

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

Krishan Kumar Bhatia; Chao-Yang Wang

2004-01-01

307

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

NASA Technical Reports Server (NTRS)

The relation of hydrogen and methane to carbon monoxide in the exhaust gases from internal-combustion engines operating on standard-grade aviation gasoline, fighting-grade aviation gasoline, hydrogenated safety fuel, laboratory diesel fuel, and auto diesel fuel was determined by analysis of the exhaust gases. Two liquid-cooled single-cylinder spark-ignition, one 9-cylinder radial air-cooled spark-ignition, and two liquid-cooled single-cylinder compression-ignition engines were used.

Gerrish, Harold C; Tessmann, Arthur M

1935-01-01

308

Automotive hydrogen storage system using cryo-adsorption on activated carbon  

Microsoft Academic Search

An integrated model of a sorbent-based cryogenic compressed hydrogen system is used to assess the prospect of meeting the near-term targets of 36kg-H2\\/m3 volumetric and 4.5wt% gravimetric capacity for hydrogen-fueled vehicles. The model includes the thermodynamics of H2 sorption, heat transfer during adsorption and desorption, sorption dynamics, energetics of cryogenic tank cooling, and containment of H2 in geodesically wound carbon

R. K. Ahluwalia; J. K. Peng

2009-01-01

309

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

DOEpatents

Methods and compositions for reactions of hydrogen over a Re-containing catalyst with compositions containing a 5-carbon sugar, sugar alcohol, or lactic acid are described. It has been surprisingly discovered that reaction with hydrogen over a Re-containing multimetallic catalyst resulted in superior conversion and selectivity to desired products such as propylene glycol. A process for the synthesis of PG from lactate or lactic acid is also described.

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

2002-11-12

310

Hydrogenolysis Of 5-Carbon Sugars, Sugar Alcohols And Compositions For Reactions Involving Hydrogen  

DOEpatents

Methods and compositions for reactions of hydrogen over a Re-containing catalyst with compositions containing a 5-carbon sugar, sugar alcohol, or lactic acid are described. It has been surprisingly discovered that reaction with hydrogen over a Re-containing multimetallic catalyst resulted in superior conversion and selectivity to desired products such as propylene glycol. A process for the synthesis of PG from lactate or lactic acid is also described.

Werpy, Todd A. (West Richland, WA); Frye, Jr., John G. (Richland, WA); Zacher, Alan H. (Kennewick, WA); Miller, Dennis J. (Okemos, MI)

2004-01-13

311

Operating Characteristics, Absorptivity/Reflectivity Measurements, and Pulse System Design of the NPS (Naval Postgraduate School) Hydrogen Fluoride/Deuterium Fluoride Laser.  

National Technical Information Service (NTIS)

The Hydrogen Fluoride/Deterium Fluoride Laser is a fast flow electrical discharge operated chemical laser. Refitting of the subsystems of the laser was completed and lasing was observed utilizing a 100 percent reflectance mirror and a 95 percent reflectan...

E. L. Garcia

1984-01-01

312

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

SciTech Connect

In this study, we investigated the friction and wear performance of diamondlike carbon films (DLC) derived from increasingly hydrogenated methane plasmas. The films were deposited on steel substrates by a plasma-enhanced chemical vapor deposition process at room temperature and the tribological tests were performed in dry nitrogen. Tests results revealed a close correlation between the hydrogen in source gas plasma and the friction and wear coefficients of the DLC films. Specifically, films grown in plasmas with higher hydrogen-to-carbon ratios had much lower friction coefficients and wear rates than did films derived from source gases with lower hydrogen-to-carbon ratios. The lowest friction coefficient (0.003) was achieved with a film derived from 25% methane--75% hydrogen, while a coefficient of 0.015 was found for films derived from pure methane. Similar correlations were observed for wear rates. Films derived from hydrogen-rich plasmas had the least wear, while films derived from pure methane suffered the highest wear. We used a combination of surface analytical methods to characterize the structure and chemistry of the DLC films and worn surfaces.

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

2000-10-13

313

Optimizing the Binding Energy of Hydrogen on Nanostructured Carbon Materials through Structure Control and Chemical Doping  

SciTech Connect

The DOE Hydrogen Sorption Center of Excellence (HSCoE) was formed in 2005 to develop materials for hydrogen storage systems to be used in light-duty vehicles. The HSCoE and two related centers of excellence were created as follow-on activities to the DOE Office of Energy Efficiency and Renewable Energy’s (EERE’s) Hydrogen Storage Grand Challenge Solicitation issued in FY 2003. The Hydrogen Sorption Center of Excellence (HSCoE) focuses on developing high-capacity sorbents with the goal to operate at temperatures and pressures approaching ambient and be efficiently and quickly charged in the tank with minimal energy requirements and penalties to the hydrogen fuel infrastructure. The work was directed at overcoming barriers to achieving DOE system goals and identifying pathways to meet the hydrogen storage system targets. To ensure that the development activities were performed as efficiently as possible, the HSCoE formed complementary, focused development clusters based on the following four sorption-based hydrogen storage mechanisms: 1. Physisorption on high specific surface area and nominally single element materials 2. Enhanced H2 binding in Substituted/heterogeneous materials 3. Strong and/or multiple H2 binding from coordinated but electronically unsatruated metal centers 4. Weak Chemisorption/Spillover. As a member of the team, our group at Duke studied the synthesis of various carbon-based materials, including carbon nanotubes and microporous carbon materials with controlled porosity. We worked closely with other team members to study the effect of pore size on the binding energy of hydrogen to the carbon –based materials. Our initial project focus was on the synthesis and purification of small diameter, single-walled carbon nanotubes (SWNTs) with well-controlled diameters for the study of their hydrogen storage properties as a function of diameters. We developed a chemical vapor deposition method that synthesized gram quantities of carbon nanotubes with average diameter size at less than 1 nm. However, initial tests performed at our collaborator’s lab at the National Renewable Energy Laboratory (NREL) did not indicate improved hydrogen sorption properties for the smaller-diameter nanotubes (compared with other types of nanotubes). As work continued, the difficulties in purification, large-scale synthesis, and stability of small diameter SWNTs became a major concern. In 2008, the Department of Energy (DOE) made a no-go decision on future applied R&D investment in pure, undoped, single-walled carbon nanotubes for vehicular hydrogen storage.2 The second phase of the project involved developing a low-cost and scalable approach for the synthesis of microporous carbon materials with well-controlled pore sizes that would be suitable for hydrogen storage. The team studied several approaches, including the use of different zeolites as a template, the use of organic micelle structures as a template, and the slow oxidation of polymer precursors. Among them, the slow activation of Polyether ether ketone (PEEK) under either CO2 environment or H2O vapor produced microporous carbon with an average pore size of less than 2 nm. Initial testing at 77K at both NREL and the California Institute of Technology (CalTech) showed that these materials can store ~5.1 wt% hydrogen (excess) at 40 bar and 77K. The main feature to note with this material is that while the excess gravimetric capacities (>5 wt% at 77K) and specific surface areas (>3100 m2/g) are similar to AX-21 and other “super activated” commercial carbon sorbents at the same temperatures and pressures, due to the smaller pore sizes, bulk densities greater than 0.7 g/ml can be achieved, enabling excess volumetric capacities greater than 35 g/L; more than double that of AX-21.

Jie Liu

2011-02-01

314

Contrasting H-mode behaviour with deuterium fuelling and nitrogen seeding in the all-carbon and metallic versions of JET  

NASA Astrophysics Data System (ADS)

The former all-carbon wall on JET has been replaced with beryllium in the main torus and tungsten in the divertor to mimic the surface materials envisaged for ITER. Comparisons are presented between type I H-mode characteristics in each design by examining respective scans over deuterium fuelling and impurity seeding, required to ameliorate exhaust loads both in JET at full capability and in ITER. Attention is focused upon a common high-triangularity, single-null divertor configuration at 2.5 MA, q95 ? 3.5 yielding the most robust all-C performance. Contrasting results between the alternative linings are found firstly in unseeded plasmas, for which purity is improved and intrinsic radiation reduced in the ITER-like wall (ILW) but normalized energy confinement is ?30% lower than in all-C counterparts, owing to a commensurately lower (electron) pedestal temperature. Divertor recycling is also radically altered, with slower, inboard-outboard asymmetric transients at ELMs and spontaneous oscillations in between them. Secondly, nitrogen seeding elicits opposite responses in the ILW to all-C experience, tending to raise plasma density, reduce ELM frequency, and above all to recover (electron) pedestal pressure, hence global confinement, almost back to previous levels. A hitherto unrecognized role of light impurities in pedestal stability and dynamics is consequently suggested. Thirdly, while heat loads on the divertor outboard target between ELMs are successfully reduced in proportion to the radiative cooling and ELM frequency effects of N in both wall environments, more surprisingly, average power ejected by ELMs also declines in the same proportion for the ILW. Detachment between transients is simultaneously promoted. Finally, inter-ELM W sources in the ILW divertor tend to fall with N input, although core accumulation possibly due to increased particle confinement still leads to significantly less steady conditions than in all-C plasmas. This limitation of ILW H-modes so far will be readdressed in future campaigns to continue progress towards a fully integrated scenario suitable for D-T experiments on JET and for ‘baseline’ operation on ITER. The diverse changes in behaviour between all-C and ILW contexts demonstrate essentially the strong impact which boundary conditions and intrinsic impurities can have on tokamak-plasma states.

Maddison, G. P.; Giroud, C.; Alper, B.; Arnoux, G.; Balboa, I.; Beurskens, M. N. A.; Boboc, A.; Brezinsek, S.; Brix, M.; Clever, M.; Coelho, R.; Coenen, J. W.; Coffey, I.; da Silva Aresta Belo, P. C.; Devaux, S.; Devynck, P.; Eich, T.; Felton, R. C.; Flanagan, J.; Frassinetti, L.; Garzotti, L.; Groth, M.; Jachmich, S.; Järvinen, A.; Joffrin, E.; Kempenaars, M. A. H.; Kruezi, U.; Lawson, K. D.; Lehnen, M.; Leyland, M. J.; Liu, Y.; Lomas, P. J.; Lowry, C. G.; Marsen, S.; Matthews, G. F.; McCormick, G. K.; Meigs, A. G.; Morris, A. W.; Neu, R.; Nunes, I. M.; Oberkofler, M.; Rimini, F. G.; Saarelma, S.; Sieglin, B.; Sips, A. C. C.; Sirinelli, A.; Stamp, M. F.; van Rooij, G. J.; Ward, D. J.; Wischmeier, M.; EFDA Contributors, JET

2014-07-01

315

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

NASA Technical Reports Server (NTRS)

A fairly fool-proof method to ensure that the compounds isolated from meteorites are truly part of the meteorites and not an artifact introduced by exposure to the terrestrial environment, storage, or handling is presented. The stable carbon and hydrogen isotope ratios in several of the chemical compounds extracted from the Murchison meteorite were measured. The results obtained by studying the amino acids in this meteorite gave very unusual hydrogen and carbon isotope ratios. The technique was extended to the different classes of hydrocarbons and the hydrocarbons were isolated using a variety of separation techniques. The results and methods used in this investigation are described in this two page paper.

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

1991-01-01

316

Semiempirical study of hydrogen addition to single-walled carbon nanotubes  

SciTech Connect

Single-walled carbon nanotube models have been constructed by insertion of 10-carbon bracelets into C{sub 70} to form C{sub 90} and C{sub 120}. Semiempirical heats of vicinal hydrogenation along the sides of the tubes are {approximately}40 kcal/mol more endothermic (less stable) than addition to the endcaps. Based on the similarity of the endcaps to C{sub 60}, hydrogenation of nanotubes is estimated to be approximately thermoneutral; therefore, only relatively high energy dienes or other species are likely to yield stable addended products.

Cahill, P.A.

1995-07-01

317

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

Microsoft Academic Search

The hydrogen and carbon kinetic isotope effects (KIEs) 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 alphasoilD=k(CH4)\\/k(CH3D)=1.099+\\/-0.030 and 1.066+\\/-0.007 for the grassland and forest, respectively. The carbon KIE of alphasoilC=k(12CH4)\\/k(13CH4)=1.0173+\\/-0.0010 and 1.0181+\\/-0.0004 for the grassland and

Amy K. Snover; Paul D. Quay

2000-01-01

318

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

PubMed

The feasibility of renewable energy technology, hydrogen production by water electrolysis, depends on the design of efficient and durable electrocatalyst composed of earth-abundant elements. Herein, a highly active and stable nonmetallic electrocatalyst, nitrogen doped hexagonal carbon (NHC), was developed for hydrogen production. It exhibited high activity for hydrogen evolution with a low overpotential of only 65?mV, an apparent exchange current density of 5.7 × 10(-2)?mA cm(-2) and a high hydrogen production rate of 20.8?mL cm(-2) h(-1) at -0.35?V. The superior hydrogen evolution activity of NHC stemmed from the intrinsic electrocatalytic property of hexagonal nanodiamond, the rapid charge transfer and abundance of electrocatalytic sites after nitrogen doping. Moreover, NHC was stable in a corrosive acidic solution during electrolysis under high current density. PMID:25354806

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

2014-01-01

319

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

PubMed Central

The feasibility of renewable energy technology, hydrogen production by water electrolysis, depends on the design of efficient and durable electrocatalyst composed of earth-abundant elements. Herein, a highly active and stable nonmetallic electrocatalyst, nitrogen doped hexagonal carbon (NHC), was developed for hydrogen production. It exhibited high activity for hydrogen evolution with a low overpotential of only 65?mV, an apparent exchange current density of 5.7 × 10?2?mA cm?2 and a high hydrogen production rate of 20.8?mL cm?2 h?1 at ?0.35?V. The superior hydrogen evolution activity of NHC stemmed from the intrinsic electrocatalytic property of hexagonal nanodiamond, the rapid charge transfer and abundance of electrocatalytic sites after nitrogen doping. Moreover, NHC was stable in a corrosive acidic solution during electrolysis under high current density. PMID:25354806

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

2014-01-01

320

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

NASA Astrophysics Data System (ADS)

The feasibility of renewable energy technology, hydrogen production by water electrolysis, depends on the design of efficient and durable electrocatalyst composed of earth-abundant elements. Herein, a highly active and stable nonmetallic electrocatalyst, nitrogen doped hexagonal carbon (NHC), was developed for hydrogen production. It exhibited high activity for hydrogen evolution with a low overpotential of only 65 mV, an apparent exchange current density of 5.7 × 10-2 mA cm-2 and a high hydrogen production rate of 20.8 mL cm-2 h-1 at -0.35 V. The superior hydrogen evolution activity of NHC stemmed from the intrinsic electrocatalytic property of hexagonal nanodiamond, the rapid charge transfer and abundance of electrocatalytic sites after nitrogen doping. Moreover, NHC was stable in a corrosive acidic solution during electrolysis under high current density.

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

2014-10-01

321

Unmodified versus caustics-impregnated carbons for control of hydrogen sulfide emissions from sewage treatment plants  

SciTech Connect

Unmodified and caustic-impregnated carbons were compared as adsorbents for hydrogen sulfide in the North River Water Pollution Control Plant in New York City over a period of 2 years. The carbons were characterized using accelerated H{sub 2}S breakthrough capacity tests, sorption of nitrogen, potentiometric titration, and thermal analysis. The accelerated laboratory tests indicate that the initial capacity of caustic-impregnated carbons exceeds that of unmodified carbon, but the nature of real-life challenge streams, particularly their lower H{sub 2}S concentrations, nullifies this advantage. As the caustic content of the impregnated carbon is consumed, the situation reverses, and the unmodified carbon becomes more effective. When the concentration of H{sub 2}S is low, the developed surface area and pore volume along with the affinity to retain water create a favorable environment for dissociative adsorption of hydrogen sulfide and its oxidation to elemental sulfur, S{sup 4+}, and S{sup 6+}. In the case of the caustic carbon, the catalytic impact of the carbon surface is limited, and its good performance lasts only while active base is present. The results also show the significant differences in performance of unmodified carbons due to combined effects of their porosity and surface chemistry.

Bandosz, T.J.; Bagreev, A.; Adib, F.; Turk, A.

2000-03-15

322

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

SciTech Connect

Abstract The hydrogen economy presents an appealing energy future but its implementation must solve numerous problems ranging from low-cost sustainable production, high-density storage, costly infrastructure, to eliminating safety concern. The use of renewable carbohydrate as a high-density hydrogen carrier and energy source for hydrogen production is possible due to emerging cell-free synthetic biology technology called cell-free synthetic pathway biotransformation (SyPaB). Assembly of numerous enzymes and co-enzymes in vitro can create complicated set of biological reactions or pathways that microorganisms cannot complete, for example, C6H10O5 (aq) + 7 H2O (l) 12 H2 (g) + 6 CO2 (g) (PLoS One 2007, 2:e456). Thanks to 100% selectivity of enzymes, modest reaction conditions, and high-purity of generated hydrogen, carbohydrate is a promising hydrogen carrier for end users. Gravimetric density of carbohydrate is 14.8 H2 mass% if water can be recycled from PEM fuel cells or 8.33% H2 mass% without water recycling. Renewable carbohydrate can be isolated from plant biomass or would be produced from a combination of solar electricity/hydrogen and carbon dioxide fixation mediated by high-efficiency artificial photosynthesis mediated by SyPaB. The construction of this carbon-neutral carbohydrate economy would address numerous sustainability challenges, such as electricity and hydrogen storage, CO2 fixation and long-term storage, water conservation, transportation fuel production, plus feed and food production.

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

2011-01-01

323

Migration Mechanism for Atomic Hydrogen in Porous Carbon Materials  

SciTech Connect

To explain the fast kinetics of H in porous carbon, we propose that the migration relies on H hopping from a carbon nanotube (CNT) to another. Using density functional theory, we have found that the barrier for H hopping becomes smaller than that for diffusion along a tube for certain CNT separations, decreasting to less than 0.5 eV for separations of -3.1 {angstrom}. Such significant reduction occurs irrespective of radius, chirality, registry, and orientation of the two CNTs: the diffusion is thus facilitated by the porous nature of the material itself. The mechanism proposed is applicable for any porous carbon-based nanomaterials.

Narayanan, B.; Zhao, Y. F.; Ciobanu, C. V.

2012-05-14

324

From methane to hydrogen, carbon black and water  

Microsoft Academic Search

Most of the total world production of hydrogen comes from vapor cracking of methane. Even though methane is the least carbogen of all hydrocarbons, steam conversion of one ton of methane is accompanied by the emission of about four tons of CO2 into the atmosphere. Simple thermolysis of methane being no more endothermic than the vapor cracking reaction, cracking methane

L. Fulcheri; Y. Schwob

1995-01-01

325

Hydrogen Retention in and Release from Carbon Materials  

Microsoft Academic Search

Results of hydrogen retention, as a function of incident ion energy, ion fluence, graphite structure and temperature, are presented, and their implication for ITER is discussed. During H + irradiation of graphite, once the near surface is saturated, essentially all of the incident H + is re-emitted from the surface – except for the small fraction that diffuses into the

A. A. Haasz; J. W. Davis

326

Doped Carbon Nanotubes for Hydrogen Storage Ragaiy Zidan  

E-print Network

River Site Aiken, SC 29808 In Collaboration with: Apparao M. Rao Department of Physics Clemson can give rise to polarization and condensation inside the tubes. We believe that introducing nano to introduce transition metals and hydrogen bonding clusters inside tubes. Our approach is aimed at producing

327

Hydrogenation of ortho-nitrochlorobenzene on activated carbon supported platinum catalysts  

PubMed Central

Platinum/carbon catalyst is one of the most important catalysts in hydrogenation of ortho-nitrochlorobenzene to 2,2?-dichlorohydrazobenzene. The preparation process and the supports of catalysts are studied in this paper. Raw materials and preparation procedure of the activated carbon have great influences on the compositions and surface structure of platinum/carbon catalysts. Platinum catalysts supported on activated carbon with high purity, high surface area, large pore volume and appropriate pore structure usually exhibit higher activities for hydrogenation of ortho-nitrochlorobenzene to 2,2?-dichlorohydrazobenzene. The catalyst prepared from H2PtCl6 with pH=3 shows greater catalytic performance than those prepared under other conditions. PMID:15822151

Jiang, Cheng-jun; Yin, Hong; Chen, Zhi-rong

2005-01-01

328

Provocative Questions for the Deuterium Session  

NASA Astrophysics Data System (ADS)

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

Linsky, Jeffrey L.

2009-05-01

329

Separation of Bulk Carbon Dioxide-Hydrogen Mixtures by Selective Surface Flow Membrane  

Microsoft Academic Search

The separation performance of carbon dioxide-hydrogen mixtures by a nanoporous carbon membrane called selective surface flow membrane is described. The membrane selectively permeates CO2 from H2 and a H2 enriched gas is produced at the feed gas pressure. Extensive experimental data for the separation using feed gas pressures from 0.24 to 1.13 MPa and CO2 compositions from 5 to 75

M. Paranjape; P. F. Clarke; B. B. Pruden; D. J. Parrillo; C. Thaeron; S. Sircar

1998-01-01

330

Microwave-assisted catalytic decomposition of methane over activated carbon for CO 2 -free hydrogen production  

Microsoft Academic Search

The aim of this work was to combine microwave heating with the use of low-cost granular activated carbon as a catalyst for the production of CO2-free hydrogen by methane decomposition in a fixed bed quartz-tube flow reactor. In order to compare the results achieved, conventional heating was also applied to the catalytic decomposition reaction of methane over the activated carbon.

A. Domínguez; B. Fidalgo; Y. Fernández; J. J. Pis; J. A. Menéndez

2007-01-01

331

Exfoliated graphitic carbon nitride nanosheets as efficient catalysts for hydrogen evolution under visible light.  

PubMed

Graphitic carbon nitride nanosheets are extracted, produced via simple liquid-phase exfoliation of a layered bulk material, g-C3N4. The resulting nanosheets, having ?2 nm thickness and N/C atomic ratio of 1.31, show an optical bandgap of 2.65 eV. The carbon nitride nanosheets are demonstrated to exhibit excellent photocatalytic activity for hydrogen evolution under visible light. PMID:23450777

Yang, Shubin; Gong, Yongji; Zhang, Jinshui; Zhan, Liang; Ma, Lulu; Fang, Zheyu; Vajtai, Robert; Wang, Xinchen; Ajayan, Pulickel M

2013-05-01

332

Hydrogenation of PAH molecules through interaction with hydrogenated carbonaceous grains.  

PubMed

Carbonaceous materials contribute to a significant proportion of the interstellar dust inventory. Reactions on such grain surfaces are thought to play important roles in interstellar chemical networks. Of particular importance are reactions involving hydrogen atoms, and pathways to the formation of the most abundant molecular species, H2. Polycyclic aromatic hydrocarbons (PAHs) are an additional carbon reservoir, accounting for around 10% of the galactic carbon budget. Using thermal desorption and mass spectrometric techniques, we have investigated the interaction between PAH molecules and carbonaceous grain surfaces. We demonstrate that deuterium atoms adsorbed on graphite can react with adsorbed PAH molecules, forming superhydrogenated PAH species. Furthermore, by considering the number of D-atoms remaining bound to the graphite surface and the additional D-atoms in the observed superhydrogenated species, we see evidence for a significant release of deuterium from the graphite surface. We suggest that further reactive processes may be responsible for part of this deuterium loss, indicating that PAHs adsorbed on hydrogenated carbonaceous grains in warm interstellar environments may serve as a route to release H2 as well as forming superhydrogenated PAH species. PMID:24270708

Thrower, John D; Friis, Emil E; Skov, Anders L; Jørgensen, Bjarke; Hornekær, Liv

2014-02-28

333

Iron powder, graphite and activated carbon as catalysts for the oxidation of 4-chlorophenol with hydrogen peroxide in aqueous solution  

Microsoft Academic Search

Solid materials as iron powder, graphite and activated carbon were tested for their catalytic properties for the oxidation of 4-chlorophenol in aqueous solution with hydrogen peroxide. Batch tests were performed at 30°C, and continuous tests with granular activated carbon under ambient conditions (20°C). Iron powder was shown to act as a catalyst for the activation of hydrogen peroxide and owing

F Lücking; H Köser; M Jank; A Ritter

1998-01-01

334

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

Microsoft Academic Search

The deuterium concentrations ( D vs SMOW) of biogenic methanes from world-wide occurrences range from -180 to -280%. and were found to be depleted in deuterium by approx. 160%. compared to the deuterium concentration of their associated waters. Theoretical considerations support this relationship to be the result of bacterial transformation of CO 2 to methane and is therefore indicative of

Martin Schoell

1980-01-01

335

Absolute total cross sections for electron-stimulated desorption of hydrogen and deuterium from silicon,,111... measured by second harmonic generation  

E-print Network

are approximately a factor of 10 smaller than those found by Fuse T. Fuse et al., Surf. Sci. 420, 81 1999 on the Si are consistent with the multihole desorption model. Comparison to calculated ionization cross sec- tions suggests Hydrogen plays a critical role in silicon semiconductor technology. It mediates chemical vapor deposition

Tolk, Norman H.

336

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

E-print Network

to which extent these modifications can be accompanied by a hydrogen isotope fractionation process tetra- and pentacyclic derivatives) are systematically D-depleted when compared to their biochemical triterpenoids; ii) a microbial or photochemical degradation that is accompanied by fractionation; iii

Paris-Sud XI, Université de

337

Hydrogenation of Carbon Dioxide by Water: Alkali-Promoted Synthesis of Formate  

Microsoft Academic Search

Conversion of carbon dioxide utilizing protons from water decomposition is likely to provide a sustainable source of fuels and chemicals in the future. We present here a time-evolved infrared reflection absorption spectroscopy (IRAS) and temperature-programmed desorption (TPD) study of the reaction of CO + HO in thin potassium layers. Reaction at temperatures below 200 K results in the hydrogenation of

J. Hrbek; F. M. Hoffmann; Y. Yang; J. Paul; M. G. White

2010-01-01

338

Using steam reforming to produce hydrogen with carbon dioxide capture by chemical-looping combustion  

Microsoft Academic Search

In this paper, a novel process for hydrogen production by steam reforming of natural gas with inherent capture of carbon dioxide by chemical-looping combustion is proposed. The process resembles a conventional circulating fluidized bed combustor with reforming taking place in reactor tubes located inside a bubbling fluidized bed. Energy for the endothermic reforming reactions is provided by indirect combustion that

Magnus Rydén; Anders Lyngfelt

2006-01-01

339

Organometallics1994,13, 385-396 386 Functionalization of Benzylic Carbon-Hydrogen Bonds.  

E-print Network

Organometallics1994,13, 385-396 386 Functionalization of Benzylic Carbon-Hydrogen Bonds. Mechanism. Jones* Department of Chemistry, University of Rochester, Rochester, New York 14627 Received August 9 oxidativeaddition of the o-methylC-H bond. Competitive isotope effect studies using do- and a,a,a,a',a',a',3,5-dg

Jones, William D.

340

Olefin Cyclopropanation and Carbon-Hydrogen Amination via Carbene and Nitrene  

E-print Network

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

Winfree, Erik

341

Performance of allotropic forms of carbon in hydrogen at high temperatures  

Microsoft Academic Search

There is considerable evidence that at temperatures near 3000°K the mass loss of many graphites in at least pressure (1 atm) hydrogen cannot be accounted for by the formation of methane, acetylene, or other hydrocarbons. Although some data indicate that some graphitic carbons exhibit particulate mass loss in vacuum and inert gas, there is sufficient data comparing mass loss in

D. G. Schweitzer; C. Sastre

1991-01-01

342

Energetics of Homogeneous Intermolecular Vinyl and Allyl Carbon-Hydrogen Bond Activation by the  

E-print Network

Energetics of Homogeneous Intermolecular Vinyl and Allyl Carbon-Hydrogen Bond Activation by the 16 to devel- oping homogeneous transition-metal catalysts that ac- tivate and functionalize C-H bonds to the development of a viable homogeneous catalyst is a thorough understanding of the origin of the selectivities

Jones, William D.

343

Production of hydrogen and carbon black by methane decomposition using DC-RF hybrid thermal plasmas  

Microsoft Academic Search

A continuous production of carbon black and hydrogen has been investigated by thermal decomposition of methane using a prototype processing system of direct current (dc)-radio frequency (RF) hybrid thermal plasma, which has great advantage over other thermal sources like combustion or dc plasma torches in synthesizing new nanostructured materials by providing high-temperature environment and longer residence time for reactant gases

Keun Su Kim; Jun Ho Seo; Jun Seok Nam; Won Tae Ju; Sang Hee Hong

2005-01-01

344

Probing the Room Temperature Spatial Distribution of Hydrogen in Nanoporous Carbon by Use of Small-Angle Neutron Scattering  

SciTech Connect

The spatial distribution of hydrogen physically adsorbed in a nanoporous carbon at room temperature (RT) as a function of H2 gas pressure is investigated for the first time using small-angle neutron scattering (SANS). A hierarchical pore structure consisting of micropores and a fractal mesopore network of the used activated carbon is also studied to correlate the relationship between the spatial distribution of hydrogen and the pore confinement. The cylinder-like cluster of aggregated hydrogen is formed and is confined in the disklike micropore. The evolution of spatial structures of adsorbed hydrogen with hydrogen pressure is elucidated. A direct experimental observation of the spatial distribution and the behavior of hydrogen adsorbed in the porous materials at RT is still scarce to date. The analysis results obtained by SANS provide new information for the future investigations of the RT storage mechanism of hydrogen in the nanoporous materials developed for the purpose of on-board hydrogen storage.

Tsao, Cheng-Si [Massachusetts Institute of Technology (MIT); Li, Mingda [ORNL; Zhang, Yang [ORNL; Leao, Juscelino B [ORNL; Chiang, Wei-Shan [ORNL; Chung, Tsui-Yun [Institute of Nuclear Energy Research, Taiwan; Tzeng, Yi-Ren [Institute of Nuclear Energy Research, Taiwan; Chen, Sow-hsin H [ORNL

2010-01-01

345

Carbon-based nanoreporters designed for subsurface hydrogen sulfide detection.  

PubMed

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

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

2014-05-28

346

Enhanced room-temperature hydrogen storage in super-activated carbons: The role of porosity development by activation  

NASA Astrophysics Data System (ADS)

Efficient hydrogen storage with a high density under near-ambient temperature remains a key technical obstacle for a hydrogen economy. Here we demonstrate the enhanced room-temperature hydrogen storage in super-activated carbon materials, which were prepared by carbon dioxide activation of templated porous carbons. These carbon materials possess high specific surface areas of up to 2829 m2/g, large pore volumes of up to 2.34 cm3/g, and hierarchical pore structures consisting of primary micropores with median size in the range of 0.7-1.3 nm and secondary mesopores with the size of 2-4 nm. One of the super-activated carbons exhibits a high hydrogen uptake of 0.95 wt% at 298 K and 80 bar, which is among the highest data reported for the porous carbon materials at room temperature and moderate pressure. The role of porosity development caused by activation in improving the hydrogen storage properties of the carbon materials has been investigated. A close relationship between hydrogen storage capacities and micropore volumes has been found. The microporosity development, especially the rapid increase of narrow pores with the diameters around 1.2 nm, appears to be essential for the enhanced room-temperature hydrogen storage in the super-activated carbons.

Xia, Kaisheng; Hu, Juan; Jiang, Jinhua

2014-10-01

347

Reversible Storage of Hydrogen and Natural Gas in Nanospace-Engineered Activated Carbons  

NASA Astrophysics Data System (ADS)

An overview is given of the development of advanced nanoporous carbons as storage materials for natural gas (methane) and molecular hydrogen in on-board fuel tanks for next-generation clean automobiles. High specific surface areas, porosities, and sub-nm/supra-nm pore volumes are quantitatively selected by controlling the degree of carbon consumption and metallic potassium intercalation into the carbon lattice during the activation process. Tunable bimodal pore-size distributions of sub-nm and supra-nm pores are established by subcritical nitrogen adsorption. Optimal pore structures for gravimetric and volumetric gas storage, respectively, are presented. Methane and hydrogen adsorption isotherms up to 250 bar on monolithic and powdered activated carbons are reported and validated, using several gravimetric and volumetric instruments. Current best gravimetric and volumetric storage capacities are: 256 g CH4/kg carbon and 132 g CH4/liter carbon at 293 K and 35 bar; 26, 44, and 107 g H2/kg carbon at 303, 194, and 77 K respectively and 100 bar. Adsorbed film density, specific surface area, and binding energy are analyzed separately using the Clausius-Clapeyron equation, Langmuir model, and lattice gas models.

Romanos, Jimmy; Beckner, Matt; Rash, Tyler; Yu, Ping; Suppes, Galen; Pfeifer, Peter

2012-02-01

348

Fractionation of carbon and hydrogen isotopes by methane-oxidizing bacteria  

USGS Publications Warehouse

Carbon isotopic analysis of methane has become a popular technique in the exploration for oil and gas because it can be used to differentiate between thermogenic and microbial gas and can sometimes be used for gas-source rock correlations. Methane-oxidizing bacteria, however, can significantly change the carbon isotopic composition of methane; the origin of gas that has been partially oxidized by these bacteria could therefore be misinterpreted. We cultured methane-oxidizing bacteria at two different temperatures and monitored the carbon and hydrogen isotopic compositions of the residual methane. The residual methane was enriched in both 13C and D. For both isotopic species, the enrichment at equivalent levels of conversion was greater at 26??C than at 11.5??C. The change in ??D relative to the change in ??13C was independent of temperature within the range studied. One culture exhibited a change in the fractionation pattern for carbon (but not for hydrogen) midway through the experiment, suggesting that bacterial oxidation of methane may occur via more than one pathway. The change in the ??D value for the residual methane was from 8 to 14 times greater than the change in the ??13C value, indicating that combined carbon and hydrogen isotopic analysis may be an effective way of identifying methane which has been subjected to partial oxidation by bacteria. ?? 1981.

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

1981-01-01

349

Confident methods for the evaluation of the hydrogen content in nanoporous carbon microfibers  

NASA Astrophysics Data System (ADS)

Nanoporous carbon microfibers were grown by chemical vapor deposition in the vapor-liquid solid mode using different fluid hydrocarbons as precursors in different proportions. The as-grown samples were further treated in argon and hydrogen atmospheres at different pressure conditions and annealed at several temperatures in order to deduce the best conditions for the incorporation and re-incorporation of hydrogen into the microfibers through the nanopores. Since there are some discrepancies in the results on the hydrogen content obtained under vacuum conditions, in this work, we have measured the hydrogen content in the microfibers using several analytical methods in ambient conditions: surface tension, mass density, and Raman measurements. A discussion on the validity of the results obtained through the correlation between them is the purpose of the present work.

Culebras, Mario; Madroñero, Antonio; Cantarero, Andres; Amo, José Maria; Domingo, Concepción; López, Antonio

2012-10-01

350

Confident methods for the evaluation of the hydrogen content in nanoporous carbon microfibers  

PubMed Central

Nanoporous carbon microfibers were grown by chemical vapor deposition in the vapor-liquid solid mode using different fluid hydrocarbons as precursors in different proportions. The as-grown samples were further treated in argon and hydrogen atmospheres at different pressure conditions and annealed at several temperatures in order to deduce the best conditions for the incorporation and re-incorporation of hydrogen into the microfibers through the nanopores. Since there are some discrepancies in the results on the hydrogen content obtained under vacuum conditions, in this work, we have measured the hydrogen content in the microfibers using several analytical methods in ambient conditions: surface tension, mass density, and Raman measurements. A discussion on the validity of the results obtained through the correlation between them is the purpose of the present work. PMID:23095321

2012-01-01

351

Nanoporous carbons derived from binary carbides and their optimization for hydrogen storage  

NASA Astrophysics Data System (ADS)

On-board hydrogen storage is one of the major hurdles for success of hydrogen economy. Hydrogen storage using physisorption technique demands highly porous materials. Carbide derived carbons (CDC), a new class of porous carbons produced by thermo chemical etching of metal atoms from carbides were selected as a method for producing highly porous material for hydrogen storage. In order to synthesize tunable nanoporous carbon and to establish a structure-property relation between initial metal carbide and resultant nanoporous carbon, CDCs were synthesized from four metal carbides, two that have uniform carbon to carbon distance in the lattice structure (ZrC, TiC and SiC) and one that has a non-uniform carbon distribution in the lattice (B4C). It was shown that a uniform distribution of carbon atoms in the carbide is important for obtaining a narrow pore size distribution (PSD). CDC derived from B 4C had a relatively broad PSD and contained mesopores even at the lowest synthesis temperature, while the CDC produced from SiC maintained a narrow PSD even at the synthesis temperature of 1200°C. CDC produced from ZrC and TiC has a narrow PSD at low synthesis temperature and pores gets wider at higher temperatures. Comparison of CDCs produced from ZrC, TiC and B 4C shows that CDCs produced from ZrC and TiC show a lower degree of ordering than that from B4C at high temperatures. Unlike CDCs produced from ZrC and TiC, the PSD of CDCs from B4C does not change appreciably in the 600-1200°C range. CDCs produced from ZrC and TiC can have both narrowly distributed micropores (pores smaller than 2 nm) and mesopores (pores larger than 2 nm), depending on synthesis temperature. In this work, it is demonstrated that porosity of CDC can be fine tuned with a high accuracy by using different starting carbides and varying the synthesis temperatures. This is very important in many applications of porous carbon, especially for gas storage. CDC from ZrC, TiC, B4C and SiC resulted in a family of high surface area nanoporous carbons (300 to 2300 m2/g) of average pore size ranging from 0.5 to 1.4 nm, A systematic study on hydrogen storage capacity of CDCs and comparison with other materials including metal organic framework (MOF-5), single (SWCNT) and multi-walled carbon nanotubes (MWCNT) dispelled the popular myth that hydrogen physisorption is directly proportional to SSA, and provided guidance for optimal design by showing that a large volume of small open pores is the key to high hydrogen uptake at cryogenic temperatures and ambient pressure. Values up to 3 wt.% and 30 kg/m3 have been demonstrated in CDCs; these are twice what can be stored in MOF-5 and several times higher than has been achieved in SWCNT or MWCNT at 77 K and atmospheric pressure. The isosteric heat of hydrogen adsorption up to 11 kJ/mole of CDCs is higher than that reported for activated carbon, CNT and MOF.

Dash, Ranjan Kumar

352

The Deuterium Abundance toward Q1937-1009  

Microsoft Academic Search

We present a new measurement of the deuterium-to-hydrogen ratio (D\\/H) in the Lyman limit absorption system at z = 3.572 toward Q1937-1009. Tytler, Fan & Burles (TFB) made the first extragalactic detection of deuterium in this absorption system, which remains the best location for a high-accuracy measurement of primordial D\\/H. Their detailed analysis of Keck spectra gave a low value

Scott Burles; David Tytler

1998-01-01

353

The deuterium content of water in some volcanic glasses  

Microsoft Academic Search

The deuterium-hydrogen composition (relative to Lake Michigan WATER = 0.0) of water extractsd from coexisting perlite and obsidian from eleven different localities was determined. The water content of the obsidians is generally from 0.09 to 0.29 per cent by weight, though two samples from near Olancha, California, contain about 0.92 per cent. The relative deuterium concentration is from -4.6 to

Irving Friedman; Robert L. Smith

1958-01-01

354

ENHANCED HYDROGEN ECONOMICS VIA COPRODUCTION OF FUELS AND CARBON PRODUCTS  

SciTech Connect

This Department of Energy National Energy Technology Laboratory sponsored research effort to develop environmentally cleaner projects as a spin-off of the FutureGen project, which seeks to reduce or eliminate emissions from plants that utilize coal for power or hydrogen production. New clean coal conversion processes were designed and tested for coproducing clean pitches and cokes used in the metals industry as well as a heavy crude oil. These new processes were based on direct liquefaction and pyrolysis techniques that liberate volatile liquids from coal without the need for high pressure or on-site gaseous hydrogen. As a result of the research, a commercial scale plant for the production of synthetic foundry coke has broken ground near Wise, Virginia under the auspices of Carbonite Inc. This plant will produce foundry coke by pyrolyzing a blend of steam coal feedstocks. A second plant is planned by Quantex Energy Inc (in Texas) which will use solvent extraction to coproduce a coke residue as well as crude oil. A third plant is being actively considered for Kingsport, Tennessee, pending a favorable resolution of regulatory issues.

Kennel, Elliot B; Bhagavatula, Abhijit; Dadyburjor, Dady; Dixit, Santhoshi; Garlapalli, Ravinder; Magean, Liviu; Mukkha, Mayuri; Olajide, Olufemi A; Stiller, Alfred H; Yurchick, Christopher L

2011-03-31

355

Is the pre-Tg DSC endotherm observed with solid state proteins associated with the protein internal dynamics? Investigation of bovine serum albumin by solid state hydrogen/deuterium exchange.  

PubMed

DSC thermograms of solid state pure proteins often show a distinct endotherm at a temperature far below the glass transition temperature of the system (Tg). We hypothesized this endotherm represents enthalpy recovery associated with an internal mobility transition of the protein molecule. Although the existence of an internal transition has been postulated, whether this endotherm is associated with such a transition has not previously been discussed. The purpose of this study was to investigate the origin of the pre-Tg endotherm in lyophilized bovine serum albumin (BSA). Due to strong glass behavior, the system Tg was determined by extrapolating Tg data of disaccharide/BSA formulations to zero saccharide. A small pre-Tg endotherm around 40-60 °C was observed in amorphous BSA equilibrated at 11%RH. The apparent activation energy suggested the endotherm was "?-mobility"-related. A solid state hydrogen/deuterium exchange study using FTIR was conducted over a temperature range spanning the endotherm. We found a fast phase, followed by essentially a plateau level which is highly temperature dependent in the 40-60 °C range, suggesting enhanced internal protein motion as the system passes through the temperature range of the endotherm. These results suggest the pre-Tg endotherm is associated with a protein internal mobility transition. PMID:23669417

Mizuno, Masayasu; Pikal, Michael J

2013-10-01

356

(Carbon and hydrogen metabolism of green algae in light and dark)  

SciTech Connect

The focus of this project was the elucidation of anaerobic metabolism in ecuaryotic green algae, chlamydomonas reinhardii. Chlamydomonas is a versatile organism that can grow under disparate conditions such as fresh water lakes and sewage ponds. The cell an photoassimilate CO{sub 2} aerobically and anaerobically, the latter after adaptation'' to a hydrogen metabolism. It can recall the knallgas or oxyhydrogen reaction and utilize hydrogen the simplest of all reducing agents for the dark assimilation of CO{sub 2} by the photosynthetic carbon reduction cycle. The dark reduction with hydrogen lies on the border line between autotrophic and heterotrophic carbon assimilation. Both autotrophic and heterotrophic bacteria are known in which molecular hydrogen can replace either inorganic or organic hydrogen donors. Here the dark reduction of CO{sub 2} acquires a particular importance since it occurs in the same cell that carries on photoreduction and photosynthesis. We will demonstrate here that the alga chloroplast possesses a respiratory capacity. It seems likely that Chlamydomonas may have retained the chloroplastic respiratory pathway because of the selective advantage provided to the algae under a wide range of environmental conditions that the cells experience in nature. The ability to cycle electrons and poise the reduction level of the photosynthetic apparatus under aerobic and microaerobic conditions could allow more efficient CO{sub 2} fixation and enhanced growth under unfavorable conditions or survival under more severe conditions.

Not Available

1990-01-01

357

Effect of changes in the deuterium content of drinking water on the hydrogen isotope ratio of urinary steroids in the context of sports drug testing.  

PubMed

The hydrogen isotope ratio (HIR) of body water and, therefore, of all endogenously synthesized compounds in humans, is mainly affected by the HIR of ingested drinking water. As a consequence, the entire organism and all of its synthesized substrates will reflect alterations in the isotope ratio of drinking water, which depends on the duration of exposure. To investigate the effect of this change on endogenous urinary steroids relevant to doping-control analysis the hydrogen isotope composition of potable water was suddenly enriched from -50 to 200 ‰ and maintained at this level for two weeks for two individuals. The steroids under investigation were 5?-pregnane-3?,20?-diol, 5?-androst-16-en-3?-ol, 3?-hydroxy-5?-androstan-17-one (ANDRO), 3?-hydroxy-5?-androstan-17-one (ETIO), 5?-androstane-3?,17?-diol, and 5?-androstane-3?,17?-diol (excreted as glucuronides) and ETIO, ANDRO and 3?-hydroxyandrost-5-en-17-one (excreted as sulfates). The HIR of body water was estimated by determination of the HIR of total native urine, to trace the induced changes. The hydrogen in steroids is partly derived from the total amount of body water and cholesterol-enrichment could be calculated by use of these data. Although the sum of changes in the isotopic composition of body water was 150 ‰, shifts of approximately 30 ‰ were observed for urinary steroids. Parallel enrichment in their HIR was observed for most of the steroids, and none of the differences between the HIR of individual steroids was elevated beyond recently established thresholds. This finding is important to sports drug testing because it supports the intended use of this novel and complementary methodology even in cases where athletes have drunk water of different HIR, a plausible and, presumably, inevitable scenario while traveling. PMID:23128907

Piper, Thomas; Degenhardt, Karoline; Federherr, Eugen; Thomas, Andreas; Thevis, Mario; Saugy, Martial

2013-03-01

358

Toward New Candidates for Hydrogen Storage: High Surface Area Carbon Aerogels  

SciTech Connect

We report the hydrogen surface excess sorption saturation value of 5.3 wt% at 30 bar pressure at 77 K, from an activated carbon aerogel with a surface area of 3200 m{sup 2}/g as measured by Brunauer-Emmett-Teller (BET) analysis. This sorption value is one of the highest we have measured in a material of this type, comparable to values obtained in high surface area activated carbons. We also report, for the first time, the surface area dependence of hydrogen surface excess sorption isotherms of carbon aerogels at 77 K. Activated carbon aerogels with surface areas ranging from 1460 to 3200 m{sup 2}/g are evaluated and we find a linear dependence of the saturation of the gravimetric density with BET surface area for carbon aerogels up to 2550 m{sup 2}/g, in agreement with data from other types of carbons reported in the literature. Our measurements show these materials to have a differential enthalpy of adsorption at zero coverage of {approx}5 to 7 kJ/mole. We also show that the introduction of metal nanoparticles of nickel improves the sorption capacity while cobalt additions have no effect.

Kabbour, H; Baumann, T F; Satcher, J H; Saulnier, A; Ahn, C C

2007-02-05

359

Anthraquinonedisulfonate electrochemistry:? a comparison of glassy carbon, hydrogenated glassy carbon, highly oriented pyrolytic graphite, and diamond electrodes.  

PubMed

The electrochemistry of anthraquinone-2,6-disulfonate (2,6-AQDS) at glassy carbon (GC), hydrogenated glassy carbon (HGC), the basal plane of highly oriented pyrolytic graphite (HOPG), and boron-doped diamond was investigated by cyclic voltammetry and chronocoulometry. Quantitative determination of the surface coverage and qualitative assessment of the physisorption strength of 2,6-AQDS adsorption on each of these electrodes were done. The diamond and HGC surfaces are nonpolar and relatively oxygen-free, with the surface carbon atoms terminated by hydrogen. The polar 2,6-AQDS does not adsorb on these surfaces, and the electrolysis proceeds by a diffusion-controlled reaction. Conversely, the GC and HOPG surfaces are polar, with the exposed defect sites terminated by carbon-oxygen functionalities. 2,6-AQDS strongly physisorbs on both of these surfaces at near monolayer or greater coverages, such that the electrolysis proceeds through a surface-confined state. Less than 40% of the initial surface coverage can be removed by rinsing and solution replacement, reflective of strong physisorption. The results show the important role of the surface carbon-oxygen functionalities in promoting strong dipole-dipole and ion-dipole interactions with polar and ionic molecules such as 2,6-AQDS. The results also support the theory that diamond electrodes may be less subject to fouling by polar adsorbates, as compared to GC, leading to improved response stability in electroanalytical measurements. The relationship between the 2,6-AQDS surface coverage, the double-layer capacitance, and the heterogeneous electron-transfer rate constant for Fe(CN)(6)(3)(-)(/4)(-) for these four carbon electrodes is presented. PMID:21644653

Xu, J; Chen, Q; Swain, G M

1998-08-01

360

Hydrogenated silicon carbon films prepared by hot wire chemical vapor deposition using monomethylsilane  

Microsoft Academic Search

Hydrogenated microcrystalline silicon carbon (\\/spl mu\\/c-Si\\/sub 1-x\\/C\\/sub x\\/:H) films were deposited by hot wire chemical vapor deposition (HWCVD) using a gas mixture of silane, hydrogen and monomethylsilane. We could successfully deposited both \\/spl mu\\/c-Si\\/sub 1-x\\/C\\/sub x\\/:H film whose body was Si microcrystallites embedded in a-Si\\/sub 1-x\\/C\\/sub x\\/:H and \\/spl mu\\/c-3C-SiC:H film whose body was 3C-SiC microcrystallites embedded in a-Si\\/sub 1-x\\/C\\/sub

Shinsuke Miyajima; Akira Yamada; Makoto Konagai

2003-01-01

361

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

NASA Astrophysics Data System (ADS)

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

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

362

Hydrogen and oxygen trapping and retention in stainless steel and graphite materials irradiated in plasma  

NASA Astrophysics Data System (ADS)

The paper presents the results of experimental investigation of energy and flux dependences of hydrogen isotopes and oxygen trapping in carbon materials (carbon fiber composite and pyrolitic graphite), and metals (stainless steel and nickel) under irradiation in the deuterium gas discharge plasma with and without oxygen addition. The dependence of hydrogen trapping on ion energy, ion current density, oxygen addition in deuterium plasma are presented and analyzed. The sorbed molecules, containing hydrogen atoms from the residual gas and deuterium atoms of the working gas are shown to be the important source of hydrogen trapping in both carbon based materials and stainless steel. Irradiation of the SS vacuum vessel with the neutrals or/and ions of (D2 + O2) plasma initiate the hydrogen diffusion from the vessel wall and H2, HD, D2O, HDO, H2O molecule formation on the wall surface. Trapping of the low energy plasma particles and the particles from the sorbed molecules as well as modification of working gas composition are considered as the processes provided at the expense of the potential energy of plasma particles with respect to the surface and occurred through their inelastic collisions with the surface. The hydrogen trapping occurred due to “potential” processes was named as “potential”, and in contrast the trapping of fast particles due to their kinetic energy was labeled as “kinetic”.

Begrambekov, L.; Ayrapetov, A.; Ermakov, V.; Kaplevsky, A.; Sadovsky, Ya.; Shigin, P.

2013-11-01

363

Hydrogen  

NSDL National Science Digital Library

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

Project, Iowa P.

2004-01-01

364

Multi-walled carbon nanotube-doped tungsten oxide thin films for hydrogen gas sensing.  

PubMed

In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO(3)) thin films by means of the powder mixing and electron beam (E-beam) evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO(3) thin film exhibits high sensitivity and selectivity to hydrogen. Thus, MWCNT doping based on E-beam co-evaporation was shown to be an effective means of preparing hydrogen gas sensors with enhanced sensing and reduced operating temperatures. Creation of nanochannels and formation of p-n heterojunctions were proposed as the sensing mechanism underlying the enhanced hydrogen sensitivity of this hybridized gas sensor. To our best knowledge, this is the first report on a MWCNT-doped WO(3) hydrogen sensor prepared by the E-beam method. PMID:22163623

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

2010-01-01

365

Production of activated carbon and its catalytic application for oxidation of hydrogen sulphide  

NASA Astrophysics Data System (ADS)

Hydrogen sulphide is an environmentally hazardous gas which is present in many gas streams associated with oil and gas industry. Oxidation of H 2S to sulphur in air produces no bulky or waste material and requires no further purification. Activated carbon is known as a catalyst for this reaction. In this research, a coal-based precursor (luscar char) and a biomass-based precursor (biochar) were used for production of activated carbons by two common methods of activation: physical and chemical activation in which steam and potassium hydroxide (KOH), respectively, were used. Experiments were designed by the statistical central composite design method. Two models were developed for the BET surface area and reaction yield of each activation process. These models showed the effects of operating conditions, such as activation temperature, mass ratio of activating agent to precursor, activation time, and nitrogen flowrate on the BET surface area and reaction yield for each activation method for each precursor. The optimum operating conditions were calculated using these models to produce activated carbons with relatively large BET surface area (> 500 m2/g) and high reaction yield (> 50 wt %). The BET surface area and reaction yield for activated carbons produced at optimum operating conditions showed maximum 7 and 7.4% difference, respectively, comparing to the values predicted by models. The activated carbons produced at optimum operating conditions were used as the base catalysts for the direct oxidation of 1 mol % hydrogen sulphide in nitrogen to sulphur at the temperature range of 160-205°C and pressure of 700 kPa. Originally activated carbons showed a good potential for oxidation of hydrogen sulphide by their selectivity for sulphur product and low amount of sulphur dioxide production. To improve the performance of steam-activated carbons, the catalysts were modified by acid-treatment followed by thermal desorption. This method increased the break-through times for coal-based and biomass-based catalysts to 115 and 141 minutes, respectively. The average amounts of sulphur dioxide produced during the reaction time were 0.14 and 0.03% (as % of hydrogen sulphide fed to the reactor) for modified activated carbons prepared from biochar and luscar char, respectively. The effects of porous structure, surface chemistry, and ash content on the performances of these activated carbon catalysts were investigated for the direct oxidation reaction of hydrogen sulphide. The acid-treatment followed by thermal desorption of activated carbons developed the porosity which produced more surface area for active sites and in addition, provided more space for sulphur product storage resulting in higher life time for catalyst. Boehm titration and temperature program desorption showed that the modification method increased basic character of carbon surface after thermal desorption in comparison to acid-treated sample. In addition, the effects of impregnating agents (potassium iodide and manganese nitrate) and two solvents for impregnation process were studied on the performance of the activated carbon catalysts for the direct oxidation of H2S to sulphur. Sulphur L-edge X-ray near edge structure (XANES) showed that the elemental sulphur was the dominant sulphur species in the product. The kinetic study for oxidation reaction of H2S over LusAC-O-D(650) was performed for temperature range of 160-190°C, oxygen to hydrogen sulphide molar ratio of 1-3, and H2S concentration of 6000-10000 ppm at 200 kPa. The values of activation energy were 26.6 and 29.3 kJ.gmol-1 for Eley-Rideal and Langmuir-Hinshelwood mechanisms, respectively.

Azargohar, Ramin

366

Octagraphene as a versatile carbon atomic sheet for novel nanotubes, unconventional fullerenes, and hydrogen storage  

NASA Astrophysics Data System (ADS)

We study a versatile structurally favorable periodic sp2-bonded carbon atomic planar sheet with C4v symmetry by means of the first-principles calculations. This carbon allotrope is composed of carbon octagons and squares with two bond lengths and is thus dubbed as octagraphene. It is a semimetal with the Fermi surface consisting of one hole and one electron pocket, whose low-energy physics can be well described by a tight-binding model of ?-electrons. Its Young's modulus, breaking strength, and Poisson's ratio are obtained to be 306 N/m, 34.4 N/m, and 0.13, respectively, which are close to those of graphene. The novel sawtooth and armchair carbon nanotubes as well as unconventional fullerenes can also be constructed from octagraphene. It is found that the Ti-absorbed octagraphene can be allowed for hydrogen storage with capacity around 7.76 wt. %.

Sheng, Xian-Lei; Cui, Hui-Juan; Ye, Fei; Yan, Qing-Bo; Zheng, Qing-Rong; Su, Gang

2012-10-01

367

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

PubMed

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

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

2013-04-01

368

Hydrogen in semiconductors and metals  

SciTech Connect

Major highlights of the conference include further understanding of the structure of extended hydrogen clusters in semiconductors, switchable optical properties of metal-hydride films, reversible changes in the magnetic coupling in metallic superlattices, and increased lifetime of integrated circuits due to deuterium device passivation. Continued progress has also been achieved in understanding hydrogenation of defects in compound semiconductors and on surfaces. Total energy calculations in semiconductors have progressed sufficiently to predict energetics and vibration frequencies as measured by experiment. Similarly, electronic structure calculations of hydrogen-metal systems provide a deeper understanding of stability, bonding, and phase changes. Various nuclear techniques have been refined to yield important information regarding the concentration and transport of hydrogen in condensed matter. Finally, the interaction of hydrogen to create thermal donors has been used to create deep p-n junctions without the need for deep diffusion of dopants. The volume has been organized along the order of presentation within the conference. Similar methods and subjects have been grouped together. The authors have attempted to keep similar metal and semiconductor papers together in order to further promote cross-fertilization between the fields. Major categories include hydrogen on surfaces, theory and thermodynamics, hydrogen transport phenomena, nuclear characterization techniques, compound semiconductors, metal bulk, devices and applications, bulk silicon, and carbon and carbon-like materials. Separate abstracts were prepared for most papers.

Nickel, N.H. [ed.] [Hahn-Meitner-Inst., Berlin (Germany); Jackson, W.B. [ed.] [Xerox Palo Alto Research Center, CA (United States); Bowman, R.C. [ed.] [Jet Propulsion Lab., Pasadena, CA (United States); Leisure, R.G. [ed.] [Colorado State Univ., Fort Collins, CO (United States)

1998-12-31

369

Plasma-deposited amorphous hydrogenated carbon films and their tribological properties  

NASA Technical Reports Server (NTRS)

Recent work on the properties of diamondlike carbon films and their dependence on preparation conditions are reviewed. The results of the study indicate that plasma deposition enables one to deposit a variety of amorphous hydrogenated carbon (a-C:H ) films exhibiting more diamondlike behavior to more graphitic behavior. The plasma-deposited a-C:H can be effectively used as hard, wear-resistant, and protective lubricating films on ceramic materials such as Si(sub 3)N(sub 4) under a variety of environmental conditions such as moist air, dry nitrogrn, and vacuum.

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

1989-01-01

370

Hydrogen-induced slow crack growth of a plain carbon pipeline steel under conditions of cyclic loading  

NASA Technical Reports Server (NTRS)

The investigation described was aimed at establishing the degree of compatibility between a plain carbon pipeline-type steel and hydrogen and also hydrogen-rich environments containing small additions of H2S, O2, H2O, CO, CO2, CH4, and natural gas at pressures near 1 atm. Test were carried out under conditions of static and cyclic loading; the subcritical crack growth was monitored. The rates of crack growth observed in the hydrogen and hydrogen-rich environments are compared with the crack rate observed in a natural gas environment to determine the compatibility of the present natural gas transmission system with gaseous hydrogen transport.

Nelson, H. G.

1976-01-01

371

Influence of the pore size in multi-walled carbon nanotubes on the hydrogen storage behaviors  

SciTech Connect

Activated multi-walled carbon nanotubes (A-MWCNTs) were prepared using a chemical activation method to obtain well-developed pore structures for use as hydrogen storage materials. The microstructure and crystallinity of the A-MWCNTs were evaluated by X-ray diffraction and Fourier transform Raman spectroscopy. The textural properties of the A-MWCNTs were investigated by nitrogen gas sorption analysis at 77 K. The hydrogen storage capacity of the A-MWCNTs was evaluated at 77 K and 1 bar. The results showed that the specific surface area of the MWCNTs increased from 327 to 495 m{sup 2}/g as the activation temperature was increased. The highest hydrogen storage capacity was observed in the A-MWCNTs sample activated at 900 Degree-Sign C (0.54 wt%). This was attributed to it having the narrowest microporosity, which is a factor closely related to the hydrogen storage capacity. This shows that the hydrogen storage behaviors depend on the pore volume. Although a high pore volume is desirable for hydrogen storage, it is also severely affected if the pore size in the A-MWCNTs for the hydrogen molecules is suitable for creating the activation process. Highlights: Black-Right-Pointing-Pointer The AT-800 and AT-900 samples were prepared by a chemical activation method at activation temperature of 800 and 900 Degree-Sign C, respectively. Black-Right-Pointing-Pointer The AT-900 sample has the narrowest peak in comparison with the AT-800 sample, resulting from the overlap of the two peaks (Peak I and Peak II). Black-Right-Pointing-Pointer This overlapping effect is due to the newly created micropores or shrinkages of pores in Peak II. So, these determining characteristics are essential for designing materials that are suitable for molecular hydrogen storage.

Lee, Seul-Yi [Department of Chemistry, Inha University, 253, Nam-gu, Incheon 402-751 (Korea, Republic of)] [Department of Chemistry, Inha University, 253, Nam-gu, Incheon 402-751 (Korea, Republic of); Park, Soo-Jin, E-mail: sjpark@inha.ac.kr [Department of Chemistry, Inha University, 253, Nam-gu, Incheon 402-751 (Korea, Republic of)] [Department of Chemistry, Inha University, 253, Nam-gu, Incheon 402-751 (Korea, Republic of)

2012-10-15

372

Self-assembled multiwalled carbon nanotube films assisted by ureidopyrimidinone-based multiple hydrogen bonds.  

PubMed

Self-assembled functionalized multiwalled carbon nanotube (MWNT) films were successfully constructed, linked by a kind of strong binding strength from the self-complementary hydrogen-bonding array of ureidopyrimidinone-based modules (UPM) attached. Employing the feasible reaction of isocyanate containing ureidopyrimidinone with amine modified MWNTs, the UPMs composed of ureidopyrimidinone and ureido were attached to MWNTs with the content as low as 0.6 mmol/g MWNTs. Upon multiple hydrogen-bonding interactions from incorporation of the AADD (A, hydrogen-bonding acceptor; D, hydrogen-bonding donor) quadruple hydrogen bonds of ureidopyrimidinone and the double hydrogen bonds of ureido group, UPM functionalized MWNTs (MWNT-UPM) can be well dispersed in the polar solvent of N,N-dimethylformamide (DMF), while they tend to self-assemble to give a self-supported film in the apolar solvent of CHCl3. In addition, by using the multiple hydrogen-bonding interactions as the driving force, the layer-by-layer (LBL) MWNT-UPM films with high coverage on solid slides can be processed. Because of the self-association of MWNT-UPM in apolar solvent, it was found that the LBL assembly of MWNT-UPM was more favorable in the polar solvent of DMF than in the apolar solvent of CHCl3. Moreover, the hydrogen-bonding linked MWNT-UPM films showed good stability upon soaking in different solvents. Furthermore, the as-prepared LBL films showed electrochemical active behaviors, exhibiting a remarkable catalytic effect on the reduction of nifedipine. PMID:25296167

Wang, Sumin; Guo, Hao; Wang, Xiaomin; Wang, Qiguan; Li, Jinhua; Wang, Xinhai

2014-11-01

373

Appendix A: Radiation HYDROGEN ATOM  

E-print Network

. People are exposed to naturally occurring radiation constantly. For example, cosmic radiation; radonAppendix A: Radiation #12;P P P E E E N NN HYDROGEN ATOM DEUTERIUM ATOM TRITIUM ATOM HYDROGEN DEUTERIUM TRITIUM PROTONS NEUTRONS 1 1 1 0 1 2 ORNL-DWG 94M-5236 Appendix A: Radiation A-3 Fig. A.1

Pennycook, Steve

374

Appendix G: Radiation HYDROGEN ATOM  

E-print Network

. People are exposed to naturally occurring radiation constantly. For example, cosmic radiation; radonAppendix G: Radiation #12;#12;P P P E E E N NN HYDROGEN ATOM DEUTERIUM ATOM TRITIUM ATOM HYDROGEN DEUTERIUM TRITIUM PROTONS NEUTRONS 1 1 1 0 1 2 ORNL-DWG 94M-5236 Appendix G: Radiation G-3 Fig. G.1

Pennycook, Steve

375

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

Microsoft Academic Search

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

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

2011-01-01

376

Production of activated carbon and its catalytic application for oxidation of hydrogen sulphide  

Microsoft Academic Search

Hydrogen sulphide is an environmentally hazardous gas which is present in many gas streams associated with oil and gas industry. Oxidation of H 2S to sulphur in air produces no bulky or waste material and requires no further purification. Activated carbon is known as a catalyst for this reaction. In this research, a coal-based precursor (luscar char) and a biomass-based

Ramin Azargohar

2009-01-01

377

Hydrogen peroxide sensor based on glassy carbon electrode modified with ?-manganese dioxide nanorods  

Microsoft Academic Search

A novel sensor for hydrogen peroxide (H2O2) was fabricated using ?-MnO2 nanorods on a glassy carbon electrode (GCE). The nanorods were obtained by a hydrothermal method and characterized by scanning\\u000a electron microscopy and X-ray diffraction. Cyclic voltammetry was used to evaluate the electrochemical performance of the\\u000a modified GCE. The sensor exhibits excellent catalytic activity toward the oxidation of H2O2 and

Ai-Jun Wang; Pei-Pei Zhang; Yong-Fang Li; Jiu-Ju Feng; Wen-Ju Dong; Xue-Yan Liu

378

Carbon monoxide removal from hydrogen-rich fuel cell feedstreams by selective catalytic oxidation  

Microsoft Academic Search

Indirect methanol fuel cells currently being investigated at General Motors for transportation applications require removal of carbon monoxide from the hydrogen-rich gas stream produced by the fuel processing section. A variety of catalytic materials, including noble metals (Pt, Pd, Rh, and Ru) and base metals (Co\\/Cu, Ni\\/Co\\/Fe, Ag, Cr, Fe, and Mn), were evaluated in a laboratory reactor feedstream containing

Se. H. Oh; R. M. Sinkevitch

1993-01-01

379

A novel microelectronic gas sensor utilizing carbon nanotubes for hydrogen gas detection  

Microsoft Academic Search

A novel microelectronic gas sensor utilizing carbon nanotubes (CNTs) in a thin-layered Pd\\/CNTs\\/n+-Si structure for hydrogen detection has been achieved. The sensor is fabricated on an n-type silicon wafer, which is needed as an ohmic supporting substrate. Multiwalled CNTs were grown selectively on the substrate via catalytic activation with microwave plasma enhanced chemical vapor deposition. The I–V characteristics of the

Y. M. Wong; W. P. Kang; J. L. Davidson; A. Wisitsora-at; K. L. Soh

2003-01-01

380

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

PubMed

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

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

2012-01-01

381

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

NASA Astrophysics Data System (ADS)

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

Liu, Peng

382

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

NASA Astrophysics Data System (ADS)

Titanium/silicon codoped hydrogenated carbon film was deposited on the n-Si (100) substrates by reactive magnetron sputtering Ti80Si20 target in a mixture of argon and methane. Microstructure of the film was investigated using x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and attenuated total reflectance Fourier transform infrared spectroscopy. The investigations have revealed that the film has an amorphous structure and consists of high sp2 hybridized carbon atoms and bonding hydrogen atoms. The mechanical and tribological properties were evaluated using a nanoindentor and a ball-on-disk tribometer, respectively. The film exhibits hardness of 9.6 GPa, high elastic recovery of 73.0% and high H /E ratio of 0.156. Most significant, the superlow friction (? <0.01) and special low wear rate (2.4×10-7 mm3 N-1 m-1) was observed in ambient air with 40% relative humidity. Combining the results of scanning electron microscopy and Raman analyses of the worn surface, it is concluded that some mechanisms, e.g., transfer films, friction-induced graphitization, hydrogen-terminated carbon surface, tribochemical reaction, etc., could be together responsible for this superlow friction in the ambient air.

Jiang, Jinlong; Hao, Junying; Wang, Peng; Liu, Weimin

2010-08-01

383

Carbon and hydrogen isotope fractionation of benzene and toluene during hydrophobic sorption in multistep batch experiments.  

PubMed

The application of compound-specific stable isotope analysis (CSIA) for evaluating degradation of organic pollutants in the field implies that other processes affecting pollutant concentration are minor with respect to isotope fractionation. Sorption is associated with minor isotope fractionation and pollutants may undergo successive sorption-desorption steps during their migration in aquifers. However, little is known about isotope fractionation of BTEX compounds after consecutive sorption steps. Here, we show that partitioning of benzene and toluene between water and organic sorbents (i.e. 1-octanol, dichloromethane, cyclohexane, hexanoic acid and Amberlite XAD-2) generally exhibits very small carbon and hydrogen isotope effects in multistep batch experiments. However, carbon and hydrogen isotope fractionation was observed for the benzene-octanol pair after several sorption steps (??(13)C=1.6 ± 0.3‰ and ??(2)H=88 ± 3‰), yielding isotope fractionation factors of ?C=1.0030 ± 0.0005 and ?H=1.195 ± 0.026. Our results indicate that the cumulative effect of successive hydrophobic partitioning steps in an aquifer generally results in insignificant isotope fractionation for benzene and toluene. However, significant carbon and hydrogen isotope fractionation cannot be excluded for specific sorbate-sorbent pairs, such as sorbates with ?-electrons and sorbents with OH-groups. Consequently, functional groups of sedimentary organic matter (SOM) may specifically interact with BTEX compounds migrating in an aquifer, thereby resulting in potentially relevant isotope fractionation. PMID:24726480

Imfeld, G; Kopinke, F-D; Fischer, A; Richnow, H-H

2014-07-01

384

The deuterium content of water in some volcanic glasses  

USGS Publications Warehouse

The deuterium-hydrogen composition (relative to Lake Michigan water = 0.0) of water extractsd from coexisting perlite and obsidian from eleven different localities was determined. The water content of the obsidians is generally from 0.09 to 0.29 per cent by weight, though two samples from near Olancha, California, contain about 0.92 per cent. The relative deuterium concentration is from -4.6 to -12.3 per cent. The coexisting perlite contains from 2.0 to 3.8 per cent of water with a relative deuterium concentration of -3.1 to -16.6 per cent. The deuterium concentration in the perlites is not related to that in the enclosed obsidian. The deuterium concentration in the perlite water is related to the deuterium concentration of the modern meteoric water and the perlite water contains approximately 4 per cent less deuterium than does the groundwater of the area in which the perlites occur. The above relations hold true for perlites from northern New Mexico, east slope of the Sierra Nevada. California Coast Range, Yellowstone Park, Wyoming, and New Zealand. As the water in the obsidian is unrelated to meteoric water, but the enclosing perlite water is related, we believe that this is evidence for the secondary hydration of obsidian to form high water content perlitic glass. ?? 1958.

Friedman, I.; Smith, R. L.

1958-01-01

385

The Determination of Deuterium and Tritium in Effluent Wastewater by Pulsed Nuclear Magnetic Resonance Spectroscopy  

SciTech Connect

A pulsed nuclear magnetic resonance (NMR) procedure was developed for the quantitative determination of deuterium and tritium in radioactive, effluent, wastewater to aid in the design of an efficient combined electrolytic/catalytic exchange system for the recovery of these hydrogen isotopes. The deuterium and tritium NMR signals were observed at 9.210 and 45.7 MHz, respectively. Ten different effluent water samples were analyzed for deuterium and tritium to establish base-line data for the preparation of standard reference samples. The hydrogen isotope concentrations ranged from 0.11 to 2.40 g deuterium and from 2.0 to 21.0 mg tritium per liter of processed sample. The standard deviation of the hydrogen isotope determinations is +- 0.017 g deuterium and +- 0.06 mg tritium per liter of processed effluent water. In the future, the effectiveness of specially prepared and analyzed (calorimetry) effluent samples as tritium standards will be investigated.

Attalla, A.; Birkbeck, J. C.

1985-04-01

386

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

SciTech Connect

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

None

2010-07-12

387

Hydrogen yield from a hydrogenase in Frankia R43 at different levels of the carbon source propionate.  

PubMed

Fermentative hydrogen yield was investigated in the Frankia strain R43, which was grown in different amounts of the carbon source propionate. In relation to hydrogen yield, the hydrogenase enzyme was characterized by use of Western blot. A bioreactor study revealed a 10-fold increase in growth within 50 h. The study showed that there is an active anaerobic hydrogen production in Frankia R43 and that this hydrogenase is immunologically related to the subunit HoxU of Ralstonia eutropha. PMID:21276650

Chatchai, Kosawang; Lasanthi, Kudahettige Rasika; Lars, Resman; Anita, Sellstedt

2012-03-01

388

The effect of carbon monoxide and steam on the hydrogen permeability of a Pd\\/stainless steel membrane  

Microsoft Academic Search

Measurements of the hydrogen permeation rate through a Pd\\/stainless steel membrane have been carried out in the presence of carbon monoxide and steam and with mixtures of these two additives. Significant reductions in hydrogen permeability were observed, the extent of the reduction being dependent on the amount of CO or steam added. At low concentrations of additive (high feed flux),

A Li; W Liang; R Hughes

2000-01-01

389

The effect of hydrogen bonds on diffusion mechanism of water inside single-walled carbon nanotubes.  

PubMed

Nanopores can serve as a molecule channel for transport of fluid, where water diffusion differs remarkably from that of simple particles. Hydrogen bonds play an essential role in the diffusion anomaly. Detailed investigations are carried out on the systems of rigid (6, 6), (7, 7), (8, 8), (9, 9), and (10, 10) armchair carbon nanotubes, solvated with Lennard-Jones water fluids. The role of hydrogen bonds is examined by diffusivity statistics and animation snapshots. It is found that in small (6,6) CNT, hydrogen bonds tend to aggregate water into a wire and lead to rapid collective drift. Confinement can stabilize the hydrogen bond of water molecules and enhance its lifetime. In relatively smaller CNTs, the diffusion mechanism could be altered by the temperature. Moreover, in larger nanotubes hydrogen bonding network allows the water to form regional concentrated clusters. This allows water fluid in extremely low density exhibit rather slow self-diffusion motion. This fundamental study attempts to provide insights in understanding nanoscale delivery system in aqueous solution. PMID:24908026

Chen, Qu; Wang, Qi; Liu, Ying-Chun; Wu, Tao

2014-06-01

390

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

PubMed Central

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

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

2010-01-01

391

The effect of hydrogen bonds on diffusion mechanism of water inside single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Nanopores can serve as a molecule channel for transport of fluid, where water diffusion differs remarkably from that of simple particles. Hydrogen bonds play an essential role in the diffusion anomaly. Detailed investigations are carried out on the systems of rigid (6, 6), (7, 7), (8, 8), (9, 9), and (10, 10) armchair carbon nanotubes, solvated with Lennard-Jones water fluids. The role of hydrogen bonds is examined by diffusivity statistics and animation snapshots. It is found that in small (6,6) CNT, hydrogen bonds tend to aggregate water into a wire and lead to rapid collective drift. Confinement can stabilize the hydrogen bond of water molecules and enhance its lifetime. In relatively smaller CNTs, the diffusion mechanism could be altered by the temperature. Moreover, in larger nanotubes hydrogen bonding network allows the water to form regional concentrated clusters. This allows water fluid in extremely low density exhibit rather slow self-diffusion motion. This fundamental study attempts to provide insights in understanding nanoscale delivery system in aqueous solution.

Chen, Qu; Wang, Qi; Liu, Ying-Chun; Wu, Tao

2014-06-01

392

The inhibition of mitochondrial cytochrome oxidase by the gases carbon monoxide, nitric oxide, hydrogen cyanide and hydrogen sulfide: chemical mechanism and physiological significance  

Microsoft Academic Search

The four gases, nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H2S) and hydrogen cyanide (HCN) all readily inhibit oxygen consumption by mitochondrial cytochrome oxidase. This inhibition\\u000a is responsible for much of their toxicity when they are applied externally to the body. However, recently these gases have\\u000a all been implicated, to greater or lesser extents, in normal cellular signalling events.

Chris E. Cooper; Guy C. Brown

2008-01-01

393

Determining the transition-state structure for different SN2 reactions using experimental nucleophile carbon and secondary alpha-deuterium kinetic isotope effects and theory.  

PubMed

Nucleophile (11)C/ (14)C [ k (11)/ k (14)] and secondary alpha-deuterium [( k H/ k D) alpha] kinetic isotope effects (KIEs) were measured for the S N2 reactions between tetrabutylammonium cyanide and ethyl iodide, bromide, chloride, and tosylate in anhydrous DMSO at 20 degrees C to determine whether these isotope effects can be used to determine the structure of S N2 transition states. Interpreting the experimental KIEs in the usual fashion (i.e., that a smaller nucleophile KIE indicates the Nu-C alpha transition state bond is shorter and a smaller ( k H/ k D) alpha is found when the Nu-LG distance in the transition state is shorter) suggests that the transition state is tighter with a slightly shorter NC-C alpha bond and a much shorter C alpha-LG bond when the substrate has a poorer halogen leaving group. Theoretical calculations at the B3LYP/aug-cc-pVDZ level of theory support this conclusion. The results show that the experimental nucleophile (11)C/ (14)C KIEs can be used to determine transition-state structure in different reactions and that the usual method of interpreting these KIEs is correct. The magnitude of the experimental secondary alpha-deuterium KIE is related to the nucleophile-leaving group distance in the S N2 transition state ( R TS) for reactions with a halogen leaving group. Unfortunately, the calculated and experimental ( k H/ k D) alpha's change oppositely with leaving group ability. However, the calculated ( k H/ k D) alpha's duplicate both the trend in the KIE with leaving group ability and the magnitude of the ( k H/ k D) alpha's for the ethyl halide reactions when different scale factors are used for the high and the low energy vibrations. This suggests it is critical that different scaling factors for the low and high energy vibrations be used if one wishes to duplicate experimental ( k H/ k D) alpha's. Finally, neither the experimental nor the theoretical secondary alpha-deuterium KIEs for the ethyl tosylate reaction fit the trend found for the reactions with a halogen leaving group. This presumably is found because of the bulky (sterically hindered) leaving group in the tosylate reaction. From every prospective, the tosylate reaction is too different from the halogen reactions to be compared. PMID:18816038

Westaway, Kenneth C; Fang, Yao-ren; MacMillar, Susanna; Matsson, Olle; Poirier, Raymond A; Islam, Shahidul M

2008-10-16

394

Composition and performance of hydrogenated carbon overcoats on magnetic storage discs  

NASA Astrophysics Data System (ADS)

Magnetic storage discs overcoated under different conditions with sputtered carbon in the presence of hydrogen were analyzed for hydrogen/carbon content by nuclear reaction analysis (NRH:C), for thickness and optical absorption by ellipsometry, for carbon structure (D and G bands) by fast micro-Raman spectrophotometry, and for C-H bonds by polarized reflection Fourier transform infrared (FTIR) spectrophotometry. CSS wear performances were compared with the analytical data. It was observed that wear performance improved with increases of D and G Raman band frequencies, D/G Raman intensity ratios, integrated CH2 band intensity in the FTIR spectrum, and optical absorptivity, but with decreases of NRAH:C, up to a limiting value. A structural model is proposed to account for the observations. The divergence in the trends of infrared surface C-H and bulk NRAH:C with friction and wear indicates the presence of a relatively inert surface coating on a hard amorphous carbon substrate. Representative spectra are shown.

Lauer, J. L.; Blanchet, T. A.; Ng, Quock

1994-07-01

395

Nickel-supported metal-carbon nanocomposites: New catalysts of hydrogenation of phenylacetylene  

NASA Astrophysics Data System (ADS)

Nickel-containing metal-carbon nanocomposites (Ni@C) synthesized by levitation melting in a flow of an inert gas-hydrocarbon mixture were used as catalysts of the hydrogenation of phenylacetylene (PA). The nanocomposites were characterized by X-ray photoelectron spectroscopy, simultaneous thermal analysis, and temperature-programmed reduction. The nickel-carbon nanocomposites were stable on storage in air, with only 13% of the total amount of nickel oxidized after 3.5 years of storage. In addition to nanoparticles completely covered with carbon, the composites contained partially coated metal particles, which are readily oxidized in air. Both types of particles exhibited the catalytic activity in phenylacetylene hydrogenation. At higher contents of nickel partially coated with carbon, the activity increased and the selectivity of styrene formation decreased. The minimum half-conversion temperature (75°C) was determined for a specially prepared Ni@C sample with an increased content of oxidized nickel (28%). The maximum selectivity of styrene formation (˜75% at 150°C) was recorded in the presence of the sample with the smallest amount of oxidized nickel (less than 4%).

Erokhin, A. V.; Lokteva, E. S.; Golubina, E. V.; Maslakov, K. I.; Yermakov, A. Ye.; Uimin, M. A.; Lunin, V. V.

2014-01-01

396

Deuterium content of the Venus atmosphere  

NASA Technical Reports Server (NTRS)

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 which was inferred a D/H ratio of less than 0.002-0.005. This is smaller by a factor of 3-8 than the D/H ratio derived from measurements by the Pioneer Venus Large Probe, and may indicate either a stratification of D/H ratio with altitude or a smaller overall ratio than previously thought.

Bertaux, Jean-Loup; Clarke, John T.

1989-01-01

397

Graphitic Mesoporous Carbon as a Support of Promoted Rh Catalysts for Hydrogenation of Carbon Monoxide to Ethanol  

SciTech Connect

Graphitic mesoporous carbon (GMC), prepared through high-temperature graphitization of soft-templated amorphous mesoporous carbon (AMC), was used as the support for Mn, Li, and Fe triple-promoted Rh catalysts for CO hydrogenation to ethanol. The use of GMC results in C{sub 2}H{sub 5}OH selectivity and formation rate comparable to nonporous SiO{sub 2} support along with a significant inhibition on the formation of undesired CH{sub 4} and light hydrocarbons at the expense of appreciable amounts of CO{sub 2} produced. The better catalytic performance of promoted-Rh/GMC than those supported on other carbon allotropes (AMC and non-porous graphitic carbon black) seems to be associated with the specific graphitic structure and mesoporosity of GMC. The surface modification of GMC by wet oxidation leads to considerable increases in C{sub 2}H{sub 5}OH selectivity and formation rate. The modified GMC as a support shows substantially greater CO{sub 2}-free selectivity for C{sub 2}H{sub 5}OH than the SiO{sub 2}.

Chai, Songhai [ORNL; Howe, Jane Y [ORNL; Wang, Xiqing [ORNL; Kidder, Michelle [ORNL; Schwartz, Viviane [ORNL; Golden, Melissa L [ORNL; Overbury, Steven {Steve} H [ORNL; Dai, Sheng [ORNL; Jiang, Deen [ORNL

2012-01-01

398

Deuterium-tritium concentration measurements in the divertor of a tokamak via a modified Penning gauge  

Microsoft Academic Search

The measurement of the relative concentrations of hydrogen, deuterium, tritium and helium is an important task in the nuclear fusion research area. Control of the deuterium-tritium (D-T) isotropic ratio and limiting the helium ash content in a fusion plasma are the key to optimizing the fuel burn in a fusion reactor such as ITER. A diagnostic technique has been developed

D. L Hillis; C. C Klepper; M Von Hellermann; J Ehrenberg; K. H Finken; G Mank

1997-01-01

399

Amorphous carbon supported MoS2 nanosheets as effective catalysts for electrocatalytic hydrogen evolution  

NASA Astrophysics Data System (ADS)

Amorphous carbon supported MoS2, which was elaborately prepared by using a facile hydrothermal method followed by annealing, is first employed as a catalyst for the hydrogen evolution reaction (HER). Herein, we demonstrate a preparation strategy, by which MoS2 and carbon materials could be formed in situ and simultaneously. The MoS2 nanosheets are vertically formed on the carbon nanosphere, as illustrated in the scanning electron micrograph. The unique morphology can expose abundant edges of the MoS2 layer as active sites for the HER, while the underlying amorphous carbon effectively improves the conductivity. By means of employing amorphous carbon as a substrate, an optimized catalyst was developed, which exhibited enhanced catalytic activity for the electrocatalytic HER with an onset potential as low as 80 mV, extremely large cathodic current density and excellent stability. Notably, a Tafel slope of 40 mV per decade was measured, which exceeds by far the activity of previous MoS2 catalysts and suggests the Volmer-Heyrovsky-mechanism for the MoS2-catalyzed HER.Amorphous carbon supported MoS2, which was elaborately prepared by using a facile hydrothermal method followed by annealing, is first employed as a catalyst for the hydrogen evolution reaction (HER). Herein, we demonstrate a preparation strategy, by which MoS2 and carbon materials could be formed in situ and simultaneously. The MoS2 nanosheets are vertically formed on the carbon nanosphere, as illustrated in the scanning electron micrograph. The unique morphology can expose abundant edges of the MoS2 layer as active sites for the HER, while the underlying amorphous carbon effectively improves the conductivity. By means of employing amorphous carbon as a substrate, an optimized catalyst was developed, which exhibited enhanced catalytic activity for the electrocatalytic HER with an onset potential as low as 80 mV, extremely large cathodic current density and excellent stability. Notably, a Tafel slope of 40 mV per decade was measured, which exceeds by far the activity of previous MoS2 catalysts and suggests the Volmer-Heyrovsky-mechanism for the MoS2-catalyzed HER. Electronic supplementary information (ESI) available: Experimental details, additional data and discussions. See DOI: 10.1039/c4nr01885k

Zhao, Xue; Zhu, Hui; Yang, Xiurong

2014-08-01

400

Performance of carbon-based hot frit substrates. 2, Coating performance studies in hydrogen at atmospheric pressure  

SciTech Connect

Erosion tests were conducted on coated graphite and 2D, 3D carbon- carbons in 1 atm hydrogen at high temperatures. Refractory NbC, TaC coatings were used. It was found that the most effective combination of coating and substrate was TaC deposited by chemical vapor reaction method on AXF-5QI graphite.

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

1993-07-01

401

Deposition of hydrogenated diamond-like carbon films under the impact of energetic hydrocarbon ions  

NASA Astrophysics Data System (ADS)

In this article we studied the influence of bombardment energy of hydrocarbon ions on the properties of hydrogenated diamond-like carbon (DLC) films using x-ray reflectivity, Raman spectroscopy, and Fourier-transform infrared. The DLC films were prepared with an electron cyclotron resonance system using H2 and CH4 gases and the ion energy was tunable through a rf-induced dc bias voltage. It was observed that the surface roughness is increased and C-H bonded hydrogen concentration is decreased with increased ion energy, whereas the mass density, hardness, and sp3/sp2 ratio exhibited optimum values. A thin SiC layer was found to form between the DLC films and silicon substrates. Two proposed carbon deposition mechanisms, i.e., the shallow implantation (subplantation) model and the adsorbed layer model, are examined based on the results obtained in this study. Our results indicate that ion bombardment energy is a critical factor in determining the film properties and the ion subplantation could be an important deposition process even for hydrogenated DLC films.

Zhang, Qing; Yoon, S. F.; Rusli, Ahn, J.; Yang, H.; Bahr, D.

1998-11-01

402

Henry Cavendish (1731-1810): hydrogen, carbon dioxide, water, and weighing the world.  

PubMed

Henry Cavendish (1731-1810) was an outstanding chemist and physicist. Although he was not a major figure in the history of respiratory physiology he made important discoveries concerning hydrogen, carbon dioxide, atmospheric air, and water. Hydrogen had been prepared earlier by Boyle but its properties had not been recognized; Cavendish described these in detail, including the density of the gas. Carbon dioxide had also previously been studied by Black, but Cavendish clarified its properties and measured its density. He was the first person to accurately analyze atmospheric air and reported an oxygen concentration very close to the currently accepted value. When he removed all the oxygen and nitrogen from an air sample, he found that there was a residual portion of about 0.8% that he could not characterize. Later this was shown to be argon. He produced large amounts of water by burning hydrogen in oxygen and recognized that these were its only constituents. Cavendish also worked on electricity and heat. However, his main contribution outside chemistry was an audacious experiment to measure the density of the earth, which he referred to as "weighing the world." This involved determining the gravitational attraction between lead spheres in a specially constructed building. Although this was a simple experiment in principle, there were numerous complexities that he overcame with meticulous attention to experimental details. His result was very close to the modern accepted value. The Cavendish Experiment, as it is called, assures his place in the history of science. PMID:24793169

West, John B

2014-07-01

403

Hydrogen and carbon isotope fractionation during degradation of chloromethane by methylotrophic bacteria.  

PubMed

Chloromethane (CH3 Cl) is a widely studied volatile halocarbon involved in the destruction of ozone in the stratosphere. Nevertheless, its global budget still remains debated. Stable isotope analysis is a powerful tool to constrain fluxes of chloromethane between various environmental compartments which involve a multiplicity of sources and sinks, and both biotic and abiotic processes. In this study, we measured hydrogen and carbon isotope fractionation of the remaining untransformed chloromethane following its degradation by methylotrophic bacterial strains Methylobacterium extorquens CM4 and Hyphomicrobium sp. MC1, which belong to different genera but both use the cmu pathway, the only pathway for bacterial degradation of chloromethane characterized so far. Hydrogen isotope fractionation for degradation of chloromethane was determined for the first time, and yielded enrichment factors (?) of -29‰ and -27‰ for strains CM4 and MC1, respectively. In agreement with previous studies, enrichment in (13) C of untransformed CH3 Cl was also observed, and similar isotope enrichment factors (?) of -41‰ and -38‰ were obtained for degradation of chloromethane by strains CM4 and MC1, respectively. These combined hydrogen and carbon isotopic data for bacterial degradation of chloromethane will contribute to refine models of the global atmospheric budget of chloromethane. PMID:24019296

Nadalig, Thierry; Greule, Markus; Bringel, Françoise; Vuilleumier, Stéphane; Keppler, Frank

2013-12-01

404

Hydrogen production using solid oxide membrane electrolyzer with solid carbon reductant in liquid metal anode  

SciTech Connect

A laboratory-scale solid oxide membrane (SOM) steam electrolyzer that can potentially utilize the energy value of coal or any hydrocarbon reductant to produce high purity hydrogen has been fabricated and evaluated. The SOM electrolyzer consists of an oxygen-ion-conducting yttria-stabilized zirconia (YSZ) electrolyte with a Ni-YSZ cermet cathode coated on one side and liquid tin anode on the other side. Hydrogen production using the SOM electrolyzer was successfully demonstrated between 900 and 1000{sup o}C by feeding a steam-rich gas to the Ni-YSZ cermet cathode and solid carbon reductant into the liquid tin anode. It was confirmed that the energy required for hydrogen production can be effectively lowered by feeding a solid carbon reductant in the liquid tin anode. A polarization model for the SOM electrolyzer was developed. The experimental data obtained under different operating conditions were curve fitted into the model to identify the various polarization losses. Based on the results of this study, work needed toward increasing the electrochemical performance of the SOM electrolyzer is discussed.

Pati, S.; Yoon, K.J.; Gopalan, S.; Pal, U.B. [Boston University, Boston, MA (United States). Dept. of Mechanical Engineering

2009-07-01

405

CARBON NANOMATERIALS AS CATALYSTS FOR HYDROGEN UPTAKE AND RELEASE IN NAALH4  

SciTech Connect

A synergistic approach involving experiment and first-principles theory not only shows that carbon nanostructures can be used as catalysts for hydrogen uptake and release in complex metal hydrides such as sodium alanate, NaAlH{sub 4}, but also provides an unambiguous understanding of how the catalysts work. The stability of NaAlH{sub 4} originates from the charge transfer from Na to the AlH{sub 4} moiety, resulting in an ionic bond between Na{sup +} and AlH{sub 4}{sup -} and a covalent bond between Al and H. Interaction of NaAlH{sub 4} with an electro-negative substrate such as carbon fullerene or nanotube affects the ability of Na to donate its charge to AlH{sub 4}, consequently weakening the Al-H bond and causing hydrogen to desorb at lower temperatures as well as facilitating the absorption of H{sub 2} to reverse the dehydrogenation reaction. Ab initio molecular dynamics simulation further reveals the time evolution of the charge transfer process with hydrogen desorption occurring when the charge transfer is complete.

Berseth, P; Ragaiy Zidan, R; Andrew Harter, A

2008-06-19

406

Deuterium microbomb rocket propulsion  

E-print Network

Large scale manned space flight within the solar system is still confronted with the solution of two problems: 1. A propulsion system to transport large payloads with short transit times between different planetary orbits. 2. A cost effective lifting of large payloads into earth orbit. For the solution of the first problem a deuterium fusion bomb propulsion system is proposed where a thermonuclear detonation wave is ignited in a small cylindrical assembly of deuterium with a gigavolt-multimegampere proton beam, drawn from the magnetically insulated spacecraft acting in the ultrahigh vacuum of space as a gigavolt capacitor. For the solution of the second problem, the ignition is done by argon ion lasers driven by high explosives, with the lasers destroyed in the fusion explosion and becoming part of the exhaust.

Friedwardt Winterberg

2008-12-02

407

Deuterium microbomb rocket propulsion  

E-print Network

Large scale manned space flight within the solar system is still confronted with the solution of two problems: 1. A propulsion system to transport large payloads with short transit times between different planetary orbits. 2. A cost effective lifting of large payloads into earth orbit. For the solution of the first problem a deuterium fusion bomb propulsion system is proposed where a thermonuclear detonation wave is ignited in a small cylindrical assembly of deuterium with a gigavolt-multimegampere proton beam, drawn from the magnetically insulated spacecraft acting in the ultrahigh vacuum of space as a gigavolt capacitor. For the solution of the second problem, the ignition is done by argon ion lasers driven by high explosives, with the lasers destroyed in the fusion explosion and becoming part of the exhaust.

Winterberg, Friedwardt

2008-01-01

408

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

NASA Technical Reports Server (NTRS)

Results are reported for an experimental study of the microscopic fracture processes associated with hydrogen attack of a commercially produced plain carbon steel in a well-controlled high-temperature hydrogen environment of high purity. In the experiments, sheet samples were exposed to laboratory-grade hydrogen at a pressure of 3.5 MN/sq m and a temperature of 575 C. The fractography of gas-filled fissures and failed tension specimens is analyzed in an effort to identify any predominant microstructural defect associated with fissure formation, the prevalent modes of fracture, and the contribution of gas-filled fissures to the overall failure process. It is found that the tensile properties of the examined steel were significantly degraded after as few as 136 hr of exposure to a high-purity hydrogen atmosphere at 575 C; that the yield strength, ultimate strength, and elongation at fracture were all reduced progressively with increasing exposure time; and that the yield and ultimate strengths were reduced more than 40% after 408 hr while elongation was reduced to less than 2%.

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

1976-01-01

409

Effects of volatilization on carbon and hydrogen isotope ratios of MTBE.  

PubMed

Contaminant attenuation studies utilizing CSIA (compound-specific isotope analysis) routinely assume that isotope effects (IEs) result only from degradation. Experimental results on MTBE behavior in diffusive volatilization and dynamic vapor extraction show measurable changes in the isotope ratios of the MTBE remaining in the aqueous or nonaqueous phase liquid (NAPL) matrix. A conceptual model for interpretation of those IEs is proposed, based on the physics of liquid-air partitioning. Normal or inverse IEs were observed for different volatilization scenarios. The range of carbon enrichment factors (epsilon) was from +0.7 per thousand (gasoline vapor extraction) to -1 per thousand (diffusive volatilization of MTBE from gasoline), the range of hydrogen epsilon was from +7 per thousand (gasoline vapor extraction) to -12 per thousand (air sparging of aqueous MTBE). The observed IEs are lower than those associated with MTBE degradation. However, under a realistic scenario for MTBE vapor removal, their magnitude is within the detection limits of CSIA. The potential for interference of those IEs is primarily in confusing the interpretation of samples with a small extent of fractionation and where only carbon CSIA data are available. The IEs resulting from volatilization and biodegradation, respectively, can be separated by combined carbon and hydrogen 2D-CSIA. PMID:19368169

Kuder, Tomasz; Philp, Paul; Allen, Jon

2009-03-15

410

Decorating multi-walled carbon nanotubes with nickel nanoparticles for selective hydrogenation of citral  

SciTech Connect

The nanocomposites of multi-walled carbon nanotubes (MWNTs) decorated with nickel nanoparticles were conveniently prepared by a chemical reduction of nickel salt in the present of poly(acrylic acid) grafted MWNTs (PAA-g-MWNTs). Due to the strong interaction between Ni{sup 2+} and -COOH, PAA-g-MWNTs became an excellent supporting material for Ni nanoparticles. The morphology and distribution of Ni nanoparticles on the surface of MWNTs were greatly influenced by the reduction temperatures, the experimental results also showed that the distribution of Ni nanoparticles was greatly improved while the MWNTs were modified by poly(acrylic acid) (PAA). The hydrogenation activity and selectivity of MWNTs decorated with Ni nanoparticles (Ni-MWNTs) for alpha, beta-unsaturated aldehyde (citral) were also studied, and the experimental results showed that the citronellal, an important raw material for flavoring and perfumery industries, is the favorable product with a percentage as high as 86.9%, which is 7 times higher than that of catalyst by Ni-supported active carbon (Ni-AC). - Abstract: Nickel nanoparticles decorated multi-walled carbon nanotubes (Ni-MWNTs) nanocomposites were conveniently prepared by a chemical reduction of nickel salt in the present of poly(acrylic acid) grafted MWNTs (PAA-g-MWNTs). These nanocomposites possessed excellent catalytic activity and selectivity for hydrogenation of citral.

Tang Yuechao; Yang Dong [Key Laboratory of Molecular Engineering of Polymers (Ministry of Education), Department of Macromolecular Science and Advanced Materials Laboratory, Fudan University, Shanghai 200433 (China); Qin Feng [Department of Chemistry, Fudan University, Shanghai 200433 (China); Hu Jianhua [Key Laboratory of Molecular Engineering of Polymers (Ministry of Education), Department of Macromolecular Science and Advanced Materials Laboratory, Fudan University, Shanghai 200433 (China); Wang Changchun, E-mail: ccwang@fudan.edu.c [Key Laboratory of Molecular Engineering of Polymers (Ministry of Education), Department of Macromolecular Science and Advanced Materials Laboratory, Fudan University, Shanghai 200433 (China); Xu Hualong [Department of Chemistry, Fudan University, Shanghai 200433 (China)

2009-08-15

411

Novel applications of piezoresistive thin film systems based on hydrogenated carbon  

NASA Astrophysics Data System (ADS)

Thin film sensor systems based on hydrogenated carbon have the advantage to combine two very important characteristics. They show a piezoresistive behaviour and also a tribological stability caused by a high hardness and wear resistance. Therefore they can be applied on the surface of machine parts or used for building up universal insertable sensor systems like sensory washers. A real challenge is the deposition of a whole sensory layer system on technical components like a spindle, which have a length of 480 mm and an outer diameter of about 90 mm. The functions of the layer system directly applied in the contact zone between spindle shaft and tool holder are the measurement of the clamping force of the tool holder, the imbalance of the used tool and the process forces during machining. For this application a self-contained thin film sensor system is investigated. Directly in the spindle shaft an insulating alumina layer is deposited in a thickness of about 4 ?m followed by electrode structures out of 200 nm thin chromium coating. On top of this the piezoresistive hydrogenated carbon layer in a thickness of about 1 ?m is deposited, covered by a wear resistant and insulating top coating. Therefore a silicon and oxygen modified carbon layer in a thickness of about 2 ?m is used. The piezoresistive sensor layer and also the top layer are part of the diamond like carbon layer family [1,2,3,4]. Another very important application is the sensory washer. The thin film sensor system, consisting out of the piezoresistive sensor layer deposited directly on the washer surface, the electrode structures out of chromium for the local detection of the load distribution in the washer system and the insulating layer as top layer out of the silicon and oxygen modified carbon layer, has a thickness in the range of 9 ?m. In the latest investigations this layer system is connected with a RFID-chip for contactless data transmission.

Biehl, Saskia; Rumposch, Christian; Recknagel, Christian

2013-05-01

412

Aggregation of carbon in an atmosphere of molecular hydrogen investigated by ReaxFF-molecular dynamics simulations  

Microsoft Academic Search

The formation of carbon and hydrocarbon molecules by aggregation of carbon in a H2 atmosphere was investigated by molecular dynamics simulations based on the Reax force field (ReaxFF). Systems of 500 carbon atoms and 1000 hydrogen molecules were simulated at different densities and temperatures from 1000K to 2000K. The majority of hydrocarbons formed during 4ns of simulation time consist of

N. Lümmen

2010-01-01

413

The influence of potassium doping on hydrogen adsorption on carbon nanocone material studied by thermal desorption and photoemission  

NASA Astrophysics Data System (ADS)

Hydrogen adsorption/desorption on potassium doped carbon nanocones was studied by temperature programmed desorption (TPD), X-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy. TPD shows that the hydrogen storage was enhanced by up to 40% after potassium doping. Hydrogen adsorption on K-modified carbon nanocone material seems more stable than that on the undoped material. The XPS results indicate that there is charge transfer from potassium to carbon. The C 1s binding energy increases with increased potassium doping and the peak becomes wider. These binding energy shifts may be explained by work function changes related to potassium doping. The K 2p spectra indicate that there are two different local environments for potassium on the carbon cone material.

Yu, Xiaofeng; Raaen, Steinar

2013-04-01

414

Field emission characteristics of screen-printed carbon nanotubes cold cathode by hydrogen plasma treatment  

NASA Astrophysics Data System (ADS)

Selective plasma etching and hydrogen plasma treatment were introduced in turn to improve field emission characteristics of screen-printed carbon nanotubes (CNTs) cold cathode, which was prepared by using slurry of mixture of multi-wall CNTs, organic vehicles and inorganic binder, i.e. silicon dioxide sol. The results show that selective plasma etching process could effectively remove parts of surface inorganic vehicle (SiO 2) layer and expose more smooth and clean CNTs on cathode surface, which could significantly decrease the operating field of CNTs cathode. There are some nanoparticles emerging on the out of CNTs wall after hydrogen plasma treatment, which are equivalent to increase field emission point of cathode. At the same time, these nanoparticles can increase the local electric field of CNTs, which can decrease operating voltage of CNTs cathode and improve uniformity field emission.

Yu, Jun; Chen, Jun; Deng, S. Z.; Xu, N. S.

2011-11-01

415

Ammonia, hydrogen sulfide, carbon dioxide and particulate matter emissions from California high-rise layer houses  

NASA Astrophysics Data System (ADS)

Ammonia and hydrogen sulfide are hazardous substances that are regulated by the U.S. Environmental Protection Agency through community right-to-know legislation (EPCRA, EPA, 2011). The emissions of ammonia and hydrogen sulfide from large commercial layer facilities are of concern to legislators and nearby neighbors. Particulate matter (PM 10 and PM 2.5) released from layer houses are two of seven criteria pollutants for which EPA has set National Ambient Air Quality Standards as required by the Clean Air Act. Therefore, it is important to quantify the baseline emissions of these pollutants. The emissions of ammonia, hydrogen sulfide, carbon dioxide and PM from two California high-rise layer houses were monitored for two years from October 2007 to October 2009. Each house had 32,500 caged laying hens. The monitoring site was setup in compliance with a U.S. EPA-approved quality assurance project plan. The results showed the average daily mean emission rates of ammonia, hydrogen sulfide and carbon dioxide were 0.95 ± 0.67 (standard deviation) g d -1 bird -1, 1.27 ± 0.78 mg d -1 bird -1 and 91.4 ± 16.5 g d -1 bird -1, respectively. The average daily mean emission rates of PM 2.5, PM 10 and total suspended particulate (TSP) were 5.9 ± 12.6, 33.4 ± 27.4, and 78.0 ± 42.7 mg d -1 bird -1, respectively. It was observed that ammonia emission rates in summer were lower than in winter because the high airflow stabilized the manure by drying it. The reductions due to lower moisture content were greater than the increases due to higher temperature. However, PM 10 emission rates in summer were higher than in winter because the drier conditions coupled with higher internal air velocities increased PM 10 release from feathers, feed and manure.

Lin, X.-J.; Cortus, E. L.; Zhang, R.; Jiang, S.; Heber, A. J.

2012-01-01