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1

Adsorption of nitrogen, hydrogen, and deuterium on carbon nanotubes bundles  

NASA Astrophysics Data System (ADS)

Adsorption isotherm measurements on bundles of closed ends carbon nanotubes will be reported, for temperatures between 77K and 96K for N2, H2, and D2, and between 28K and 40K for H2 and D2. Results show the two broad coverage vs. pressure steps reported by Migone's group [S.E.Weber et al., Phys. Rev. B61, 13150 (2000)] and Bienfait's group [M.Muris et al., Langmuir 16, 7019 (2000)] for other adsorbates using similar substrates. The calculated isosteric heat from the lower coverage step is about twice the isosteric heat of the higher coverage step for each of the molecules, with this higher step having somewhat smaller binding energy than the same molecules on graphite.

Vilches, Oscar E.; Tyburski, Adam; Wilson, Tate; Depies, Matt; Becquet, Daphne; Bienfait, Michel

2001-03-01

2

Intramolecular hydrogen bonding as reflected in the deuterium isotope effects on carbon-13 chemical shifts. Correlation with hydrogen bond energies  

SciTech Connect

The carbon-13 resonances of atoms bearing phenolic or enolic hydroxyl groups, that are engaged in intramolecular hydrogen bonds, experience large (/sup 2/..delta.. may exceed 1 ppm) upfield deuterium isotope effects. The magnitude of the two-bond isotope effect, /sup 2/..delta.., correlates with the hydrogen bond energy as obtained from the hydroxyl proton chemical shift. In the conjugated systems investigated in this work, the isotope effects extend over several (up to six) chemical bonds. The signs and magnitudes of the long-range isotope effects are related to molecular structure.

Reuben, J.

1986-04-16

3

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

USGS Publications Warehouse

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

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

1970-01-01

4

Hydrogen-deuterium exchange of weak carbon acids under phase-transfer catalysis conditions  

SciTech Connect

A practical method for hydrogen-deuterium exchange is obtained via extractive hydroxide ion initiated phase-transfer catalysis. The reaction of NaOD/D/sub 2/O system allows the easy production of compounds that otherwise would require very strong bases and aprotic solvents. The strong basicity of OD/sup -/ anion is attributable to its relative freedom from water molecules when OD/sup -/ is extracted into the depth of the organic layer. 22 references, 1 table.

Feldman, D.; Halpern, M.; Rabinovitz, M.

1985-05-17

5

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.

6

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

7

In situ measurement of deuterium retention in graphite under successive exposure to deuterium and hydrogen plasmas  

NASA Astrophysics Data System (ADS)

The time evolution of deuterium retention in isotropic graphite has been investigated under successive deuterium and hydrogen plasma exposure using a ‘plasma surface dynamics with ion beam analysis’ device. Deuterium retention was decreased exponentially in time by hydrogen plasma exposure, and the decay time of deuterium retention was inversely proportional to hydrogen ion flux.

Ohno, N.; Nakamura, Y.; Yamagiwa, M.; Kaneko, T.; Matsunami, N.; Kajita, S.; Takagi, M.

2014-04-01

8

Stabilization of Atomic Hydrogen and Deuterium.  

National Technical Information Service (NTIS)

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

J. T. M. Walraven

1982-01-01

9

The deuterium content of atmospheric molecular hydrogen  

Microsoft Academic Search

A new technique for the separation of molecular hydrogen (H2) from air and the determination of its deuterium (D) content is presented. A high-pressure air sample in an aluminum cylinder is condensed at -196°C, whereby H2 contained in the air sample is enriched in the gaseous headspace above the liquefied air. The H2-enriched headspace is bled into a vacuum extraction

Steven Gregory Gerst

2000-01-01

10

Laser-driven polarized targets of hydrogen and deuterium  

SciTech Connect

An optical pumping technique used in a laser-driven source of polarized hydrogen or deuterium is described and measurements of the achievable polarization as a function of flow for both hydrogen and deuterium are presented. Ongoing tests of the feasibility of using a laser-driven polarized deuterium source coupled to a storage cell as a polarized internal target, including direct measurements of the nuclear polarization, are discussed.

Jones, C.E.; Coulter, K.P.; Holt, R.J.; Kowalczyk, R.S.; O`Neill, T.G.; Poelker, M.; Zeidman, B.

1994-08-01

11

Omegatron mass spectrometer in a hydrogen/deuterium detached plasma  

NASA Astrophysics Data System (ADS)

Diagnostics of the relative concentrations of the atomic and molecular ions were carried out in hydrogen/deuterium plasma with hydrogen/deuterium gas puff in the linear plasma device, TPD-SheetIV. An omegatron ion mass spectrometer is used for analyzing ion species.

Tonegawa, A.; Nishijima, T.; Ishioka, H.; Nakanowatari, A.; Kawamura, K.

2008-03-01

12

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

13

Influence of Murchison or Allende minerals on hydrogen-deuterium exchange of amino acids.  

PubMed

Deuterium-enriched amino acids occur in the Murchison carbonaceous chrondrite. This meteorite underwent a period of aqueous alteration with isotopically light water. With the objective of setting limits on the conditions of aqueous alteration, the exchange of the carbon-bonded hydrogen atoms of amino acids with D2O has been studied from 295 to 380 K as a function of time and meteorite/heavy water ratio. The amount of Murchison or Allende dust present has a significant effect on the rate and amount of hydrogen-deuterium exchange observed. At elevated temperatures, the alpha-hydrogens of all the amino acids studied were found to exchange with deuterium. In glycine and aspartic acid, this process resulted in total exchange of the carbon-bonded hydrogen. A completely deuterated isotopomer of alanine was produced in significant quantities only when the rock/water ratio was greater than 0.5. No exchange of carbon-bonded hydrogens was observed in the case of amino acids which do not possess an alpha-hydrogen atom. The rates of H/D exchange for amino acids observed here did not correspond to deuterium enrichment of the amino acids in the Murchison meteorite. These results suggest that H/D exchange with water had a negligible effect on the observed deuterium enrichment of amino acids found in Murchison and that the temperature at which the amino acids were exposed to liquid water was close to 273 K. PMID:11540046

Lerner, N R

1995-04-01

14

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

15

Probing backbone dynamics with hydrogen/deuterium exchange mass spectrometry.  

PubMed

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

Singh, Harsimran; Busenlehner, Laura S

2014-01-01

16

The deuterium content of atmospheric molecular hydrogen  

NASA Astrophysics Data System (ADS)

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

Gerst, Steven Gregory

2000-09-01

17

Deuterium and hydrogen in the local interstellar medium  

NASA Technical Reports Server (NTRS)

Densities of neutral hydrogen and deuterium are found from observation with the Copernicus satellite of the Ly-alpha line toward two nearby stars. The hydrogen density is 0.03 + or - 0.01 per cu cm toward Alpha Aur (Capella) and 0.20 + or - 0.05 per cu cm in the direction of Alpha Cen A, values indicating that the nearby (less than 14 pc) interstellar medium is inhomogeneous and can be of low density in certain directions. The ratios of deuterium to hydrogen - 3.9 (+5.7, -1.7) by 10 to the -5th power and 0.24 (+0.12, -0.07) by 10 to the -5th power for Alpha Aur and Alpha Cen A, respectively - suggest that variations in the deuterium abundance may exist.

Dupree, A. K.; Baliunas, S. L.; Shipman, H. L.

1977-01-01

18

Proton tunneling in phase IV of hydrogen and deuterium  

NASA Astrophysics Data System (ADS)

Using in situ optical spectroscopy we have investigated the temperature stability of the mixed atomic and molecular phases IV of dense deuterium and hydrogen. Through a series of low-temperature experiments at high pressures, we observe phase III-to-IV transformation, imposing constraints on the P-T phase diagrams. The spectral features of the phase IV-III transition and differences in appearances of the isotopes Raman spectra strongly indicate the presence of proton tunneling in phase IV. No differences between isotopes were observed in absorption spectroscopic studies, resulting in identical values for the band gap. The extrapolation of the combined band gap yields 375 GPa as the minimum transition pressure to the metallic state of hydrogen (deuterium). The minute changes in optical spectra above 275 GPa might suggest the presence of a new solid modification of hydrogen (deuterium), closely related structurally to phase IV.

Howie, Ross T.; Scheler, Thomas; Guillaume, Christophe L.; Gregoryanz, Eugene

2012-12-01

19

Experiments with Slow K Mesons in Deuterium and Hydrogen  

Microsoft Academic Search

It is pointed out that the following useful information can be obtained from experiments on K mesons in deuterium and hydrogen: (a) an indication of the K-particle spin; (b) a test of isotopic spin conservation in reactions involving strange particles; (c) a measurement of the Sigma0 mass.

K. M. Case; Robert Karplus; C. N. Yang

1956-01-01

20

Hydrogen and deuterium solubility in aluminum with voids  

NASA Astrophysics Data System (ADS)

Hydrogen and deuterium concentrations in aluminum were measured at 600°C in the pressure range from 0.2 to 1.0 atm, by means of a desorption technique which was an outgassing study from thermally gas-charged cylindrical samples with various amounts of voids. The relation between the pressure of hydrogen or deuterium and the equilibrium concentration in a void-free sample was observed to follow Sieverts' law. In the sample with voids, an apparent hydrogen or deuterium concentration was given by the sum of the gas solved in the lattice and that held in the voids in the molecular state thermally equilibrated with the gas pressure of the atmosphere. In the as-cast sample with blowing hydrogen gas through the melt, the average hydrogen pressure in the voids was calculated to be about 7.3 atm at room temperature (about 23 atm at 660°C), and the apparent hydrogen diffusion coefficient decreased with increasing amount of voids.

Ichimura, Minoru; Katsuta, Hiroji; Sasajima, Yasusi; Imabayashi, Mamoru

21

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

22

Equations of state for hydrogen and deuterium.  

SciTech Connect

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

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

2003-12-01

23

Rydberg States of Triatomic Hydrogen and Deuterium  

NASA Astrophysics Data System (ADS)

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

Wang, Jia; Greene, Chris H.

2013-10-01

24

Mid-infrared lasers in hydrogen and deuterium  

SciTech Connect

New laser lines at 3.71 and 3.84 ..mu..m in hydrogen and lines at 4.52, 4.60, and 4.71 ..mu..m in deuterium excited by a pulsed electrical discharge have been obtained. The lines in hydrogen are assigned to the a /sup 3/..sigma../sup +//sub g/ ..-->.. c /sup 3/Pi/sub u/ triplet band, but the lines in deuterium have not yet been assigned. Direct electronic excitation from the ground state to the a /sup 3/..sigma../sup +//sub g/ state is believed to be the excitation mechanism, and indicates that an excimer-type laser from the a /sup 3/..sigma../sup +//sub g/ upper state to the dissociative b /sup 3/..sigma../sup +//sub u/ state may be possible.

Barr, T.A. Jr.; McKnight, W.B.

1982-07-15

25

Hydrogen and deuterium in the local interstellar medium  

SciTech Connect

This work reports on the results of a series of IUE observations of interstellar HI and DI Ly..cap alpha.. absorption against the chromospheric Ly..cap alpha.. emission of the nearby late-type stars ..cap alpha.. Cen B(1.3 pc), epsilon Eri (3.3 pc), Procyon (3.5 pc), Altair (5.1 pc), Capella (13.2 pc), and HR 1099 (33 pc). The density, velocity dispersion, and bulk velocity of the neutral hydrogen along the line of sight to each of these stars was derived. Lower limits were placed on the deuterium-to-hydrogen (D/H) ratio towards the same stars. These IUE results are generally consistent with previous observations of the same stars with the Copernicus satellite showing that this modeling procedure is independent of stellar variations over a period of several years. The HI absorption profile towards Altair shows a broad saturated core and steep line wings, consistent with a multicomponent interstellar medium in that direction. The bulk velocities towards the other stars are consistent with a bulk flow from the approximate direction of the galactic center but do show local variations from a uniform flow, possibly indicating a complicated velocity structure even in the solar neighborhood. Interstellar deuterium is detected towards every star except Altair and the derived values for the D/H ratio are consistent with those previously found with Copernicus.

Murthy, J.N.

1987-01-01

26

Hydrogen/deuterium exchange in interstellar ice analogs  

NASA Astrophysics Data System (ADS)

Context: For several reasons, methanol is believed to be formed on grain surfaces and, in warm environments, released in the gas phase. In the past, multiply deuterated isotopologues of methanol have been detected in gas phase around several low-mass protostars. In all these sources, there is significantly more CH2DOH than CH3OD. Various hypotheses have been suggested to explain this anomaly, but none is fully convincing. Aims: In this work, we test a new hypothesis experimentally: the spontaneous exchange between hydrogen and deuterium atoms in water ice as responsible for the deficiency of CH3OD with respect to CH2DOH. Methods: We follow the temperature dependence of the composition of interstellar ice analogs initially composed of CD3OD and H2O. To this aim, thin films of intimate H2O:CD3OD ice mixtures, condensed at low temperature (<110 K), are monitored by Fourier transform infrared (FTIR) spectroscopy up to the complete evaporation of CD3OD (~170 K). Results: Rapid hydrogen/deuterium (H/D) exchange is observed, at 120 K and above, through the growth of the ?_OD stretching mode of HDO at ~2425 cm-1. It is also shown that H/D exchange occurs i) on the hydroxyl functional group of methanol, i.e through hydrogen bonds, and ii) before the completion of crystallization. Conclusions: The present results suggest that the much lower abundance of CH3OD compared to CH2DOH in low-mass protostars could reflect H/D exchanges in water ice either prior to or definitely during the grain mantle sublimation. This solid-state depletion mechanism, so far neglected in the astronomical literature, might affect other deuterated molecules with hydrogen bonds.

Ratajczak, A.; Quirico, E.; Faure, A.; Schmitt, B.; Ceccarelli, C.

2009-03-01

27

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

28

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

29

Deuterium depth profiling in graphite tiles not exposed to hydrogen discharges before air ventilation of JT-60U  

NASA Astrophysics Data System (ADS)

Depth profiles of deuterium trapped in graphite tiles not exposed to hydrogen discharges just before air ventilation of JT-60U were determined based on the D( 3He,p) 4He resonant nuclear reaction analysis. The samples were taken from the W-shaped divertor. The maximum depth of analysis is about 1.4 × 10 24 carbon atoms/m 2, corresponding to a linear depth of 16 ?m for the density of 1.7 × 10 3 kg/m 3. The highest concentration (19 at.%) was found at the surface of the inner divertor area, which was significantly higher than that exposed to H discharges at the same location. However in the deeper region, the deuterium concentrations without H discharges were lower than those with H discharges in 3 of 4 samples. These results indicate that hydrogen discharges can remove deuterium trapped only in the shallow region.

Hayashi, T.; Sugiyama, K.; Mayer, M.; Krieger, K.; Masaki, K.; Tanabe, T.; Sato, M.

2009-06-01

30

Modeling the Extreme Deuterium Enrichment in Stratospheric Hydrogen  

NASA Astrophysics Data System (ADS)

Observations of the isotopic composition of molecular hydrogen in whole air samples collected by the NASA ER-2 aircraft showed extreme enrichment in deuterium of up to 440 per mil on the V-SMOW isotope scale [Rahn et al., Nature, 2003]. In this study, we use the Lawrence Livermore National Laboratory 2D model to investigate the extreme deuterium enrichment in stratospheric H2 and find that kinetic isotope effects (KIEs) in the oxidation of H2 in the stratosphere account for over 60% of the enrichment while production of heavy H2 from CH4 oxidation accounts for the remainder. The sensitivity of the H2 isotopic composition to uncertainties in the CH4 oxidation pathway branching ratios, formaldehyde oxidation KIEs, formaldehyde photolysis isotope effects, and the H2 oxidation KIEs is explored, and recommendations for needed laboratory and field measurements based on these model sensitivities are given. Finally, we investigate the global H2 isotope budget using model estimates of ? D-H2 produced from CH4 oxidation in both the stratosphere and troposphere.

McCarthy, M. C.; Connell, P.; Boering, K. A.

2003-12-01

31

A source of polarized negative hydrogen ions with deuterium plasma ionizer  

NASA Astrophysics Data System (ADS)

An atomic beam-type source of polarized negative hydrogen ions with deuterium plasma ionizer has been developed. A charge-exchange reaction between thermal polarized hydrogen atoms and negative deuterium ions is used for production of polarized hydrogen negative ions. A polarized beam with peak current up to 150 ?A and pulse duration 100 ?s has been obtained from the source at repetition rate 5 Hz. The results of experimental test of the source developed and polarized beam emittance measurement are presented.

Belov, A. S.; Kuzik, V. E.; Nechaeva, L. P.; Vasil'Ev, G. A.; Plokhinski, Yu. V.; Yakushev, V. P.; Dudnikov, V. G.

1993-12-01

32

A source of polarized negative hydrogen ions with deuterium plasma ionizer  

NASA Astrophysics Data System (ADS)

An atomic beam-type source of polarized negative hydrogen ions with deuterium plasma ionizer has been developed. A charge-exchange reaction between thermal polarized hydrogen atoms and negative deuterium ions is used for production of polarized hydrogen negative ions. A polarized beam with a peak current up to 150 ?A and a pulse duration 100 ?s has been obtained from the source at repetition rate 5 Hz. The results of experimental test of the source developed are presented.

Belov, A. S.; Dudnikov, V. G.; Kuzik, V. E.; Plokhinsky, Yu. V.; Yakushev, V. P.

1993-09-01

33

A comparison of hydrogen and deuterium plasmas in the IPP prototype ion source for fusion  

NASA Astrophysics Data System (ADS)

Negative hydrogen ion sources for fusion are based on the surface conversion process and operate with both cesium seeded hydrogen and deuterium plasmas. Although the required extracted negative ion densities are achieved, the source performance is limited at present by the amount of co-extracted electrons, which is much higher in deuterium than in hydrogen for up to now unknown reasons. Systematic Langmuir probe measurements combined with emission spectroscopy have been carried out in the ITER prototype source. They show very similar electron densities and temperatures in the plasma generation region, the ``driver'', but the degree of dissociation is clearly higher in deuterium than in hydrogen. The filter field in the expansion region generates a plasma drift which is more pronounced in hydrogen. Consequently, for deuterium, more electrons are present in front of the plasma grid. Close to the extraction, a recombining plasma evolves where the Balmer line emission is higher in deuterium due the relevance of the dissociative recombination process and thus more molecular ions. Throughout the source the plasma potential is higher in deuterium. It is concluded that the transport across the filter field plays a crucial role in the differences obtained for particle densities and coextracted electrons in hydrogen and deuterium operation.

Fantz, U.; Schiesko, L.; Wünderlich, D.; NNBI Team

2013-02-01

34

Probing protein ensemble rigidity and hydrogen-deuterium exchange  

NASA Astrophysics Data System (ADS)

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

Sljoka, Adnan; Wilson, Derek

2013-10-01

35

Probing protein ensemble rigidity and hydrogen-deuterium exchange.  

PubMed

Protein rigidity and flexibility can be analyzed accurately and efficiently using the program floppy inclusion and rigid substructure topography (FIRST). Previous studies using FIRST were designed to analyze the rigidity and flexibility of proteins using a single static (snapshot) structure. It is however well known that proteins can undergo spontaneous sub-molecular unfolding and refolding, or conformational dynamics, even under conditions that strongly favor a well-defined native structure. These (local) unfolding events result in a large number of conformers that differ from each other very slightly. In this context, proteins are better represented as a thermodynamic ensemble of 'native-like' structures, and not just as a single static low-energy structure. Working with this notion, we introduce a novel FIRST-based approach for predicting rigidity/flexibility of the protein ensemble by (i) averaging the hydrogen bonding strengths from the entire ensemble and (ii) by refining the mathematical model of hydrogen bonds. Furthermore, we combine our FIRST-ensemble rigidity predictions with the ensemble solvent accessibility data of the backbone amides and propose a novel computational method which uses both rigidity and solvent accessibility for predicting hydrogen-deuterium exchange (HDX). To validate our predictions, we report a novel site specific HDX experiment which characterizes the native structural ensemble of Acylphosphatase from hyperthermophile Sulfolobus solfataricus (Sso AcP). The sub-structural conformational dynamics that is observed by HDX data, is closely matched with the FIRST-ensemble rigidity predictions, which could not be attained using the traditional single 'snapshot' rigidity analysis. Moreover, the computational predictions of regions that are protected from HDX and those that undergo exchange are in very good agreement with the experimental HDX profile of Sso AcP. PMID:24104456

Sljoka, Adnan; Wilson, Derek

2013-10-01

36

Photoactivation of Rhodopsin Causes an Increased Hydrogen-Deuterium Exchange of Buried Peptide Groups  

Microsoft Academic Search

A key step in visual transduction is the light-induced conformational changes of rhodopsin that lead to binding and activation of the G-protein transducin. In order to explore the nature of these conformational changes, time-resolved Fourier transform infrared spectroscopy was used to measure the kinetics of hydrogen\\/deuterium exchange in rhodopsin upon photoexcitation. The extent of hydrogen\\/deuterium exchange of backbone peptide groups

Parshuram Rath; Willem J. DeGrip; Kenneth J. Rothschild

1998-01-01

37

Hydrogen and deuterium in shock wave experiments, ab initio simulations and chemical picture modeling  

NASA Astrophysics Data System (ADS)

We present equation of state data of shock compressed hydrogen and deuterium. These have been calculated in the physical picture by using ab initio molecular dynamics simulations based on finite temperature density functional theory as well as in the chemical picture via the Saha-D model. The results are compared in detail with data of shock wave experiments obtained for condensed and gaseous precompressed hydrogen and deuterium targets in a wide range of shock compressions from low pressures up to megabars.

Holst, B.; Redmer, R.; Gryaznov, V. K.; Fortov, V. E.; Iosilevskiy, I. L.

2012-04-01

38

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

SciTech Connect

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

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

2005-10-14

39

Deuterium/protium fractionation factors for polyfunctional organic molecules: direct determination by carbon-13 NMR spectroscopy  

SciTech Connect

The isotope exchange processes between water and readily exchangeable groups (e.g., OH, NH, and SH) are of interest in studying reaction mechanisms and elucidating the structural dynamics of biological macromolecules. A knowledge of the equilibrium partitioning of deuterium and protium between the different types of exchangeable hydrogens is needed for a detailed interpretation of kinetic and equilibrium data and for the understanding of these processes. This paper describes a method for the direct determination of fractionation factors from the integrated intensities of the carbon-13 resonances of deuterio and protio species under conditions of slow chemical exchange.

Reuben, J.

1986-03-05

40

Amorphous Hydrogenated Carbon Nanofilm  

Microsoft Academic Search

Amorphous hydrogenated carbon (a-C:H) nanofilm is a metastable form of amorphous carbon with significant sp3 bonding. a-C:H\\u000a is a semiconductor with a high mechanical hardness, chemical inertness, and optical transparency. This chapter will describe\\u000a the deposition methods, deposition mechanisms, characterization methods, electronic structure, gap states, defects, doping,\\u000a luminescence, field emission, mechanical properties, and some applications of a-C:H. The films have

Dechun Ba; Zeng Lin

41

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

NASA Astrophysics Data System (ADS)

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

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

42

Deuterium and Hydrogen Tunneling in the Hydrogenation of 4-Oxocyclohexa-2,5-dienylidene.  

PubMed

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

Henkel, Stefan; Ertelt, Melanie; Sander, Wolfram

2014-06-16

43

Hydrogen/deuterium isotope effects in water and aqueous solutions of organic molecules and proteins  

NASA Astrophysics Data System (ADS)

It is pointed out that hydrogen/deuterium substitution, frequently used in neutron scattering studies of the structure and dynamics of hydrogenous samples, can have significant effects on structure, phase behavior and protein stability. The effects must be kept in mind in the interpretation of such experiments. In suitable cases, these effects can be mitigated by an appropriate choice of experimental conditions.

Price, David L.; Fu, Ling; Bermejo, F. Javier; Fernandez-Alonso, Felix; Saboungi, Marie-Louise

2013-10-01

44

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

45

Trans-hydrogen bond deuterium isotope effects of A:T base pairs in DNA  

Microsoft Academic Search

The chemical shifts of 13C2 of adenosine residues of DNA were observed to experience a through-space or trans-hydrogen bond isotope effect as a result of deuterium substitution at the imino hydrogen site of base-paired thymidine residues. NMR measurements of several self-complementary DNA duplexes at natural abundance 13C in 50% H2O, 50% D2O solvent mixtures yielded an average trans-hydrogen bond isotope

Ioannis Vakonakis; Andy C. LiWang

2004-01-01

46

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

SciTech Connect

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

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

1984-02-01

47

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

SciTech Connect

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

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

2006-11-20

48

Precision Measurement of the Hydrogen-Deuterium 1S-2S Isotope Shift  

SciTech Connect

Measuring the hydrogen-deuterium isotope shift via two-photon spectroscopy of the 1S-2S transition, we obtain 670 994 334 606(15) Hz. This is a 10-times improvement over the previous best measurement [A. Huber et al., Phys. Rev. Lett. 80, 468 (1998)] confirming its frequency value. A calculation of the difference of the mean square charge radii of deuterium and hydrogen results in {sub d}-{sub p}=3.820 07(65) fm{sup 2}, a more than twofold improvement compared to the former value.

Parthey, Christian G.; Matveev, Arthur; Alnis, Janis; Pohl, Randolf; Udem, Thomas; Kolachevsky, Nikolai; Haensch, Theodor W. [Max-Planck-Institut fuer Quantenoptik, 85748 Garching (Germany); Jentschura, Ulrich D. [Department of Physics, Missouri University of Science and Technology, Rolla, Missouri 65409 (United States)

2010-06-11

49

High Pressure Apparatus for Gaseous Hydrogen and Deuterium up to 25 Kilobars and Temperature Range ?50 to 100°C  

Microsoft Academic Search

A high pressure device for gaseous hydrogen and deuterium in form of a double piston-cylinder system is described. Any contact between gaseous volume and the pressure transmitting liquid is avoided. The device has 15 electrical leads from gaseous volume to the outside of the apparatus. Resistance data for palladium under hydrogen and deuterium pressures are presented.

Roland Wis´niewski

1970-01-01

50

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

51

Deuterium depth profiling in graphite tiles not exposed to hydrogen discharges before air ventilation of JT-60U  

Microsoft Academic Search

Depth profiles of deuterium trapped in graphite tiles not exposed to hydrogen discharges just before air ventilation of JT-60U were determined based on the D(3He,p)4He resonant nuclear reaction analysis. The samples were taken from the W-shaped divertor. The maximum depth of analysis is about 1.4×1024 carbon atoms\\/m2, corresponding to a linear depth of 16?m for the density of 1.7×103kg\\/m3. The

T. Hayashi; K. Sugiyama; M. Mayer; K. Krieger; K. Masaki; T. Tanabe; M. Sato

2009-01-01

52

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

53

Coverage dependence of quantum tunneling diffusion of hydrogen and deuterium on Ni(111)  

NASA Astrophysics Data System (ADS)

We measured the diffusion rate of deuterium on Ni(111) as a function of temperature at atomic coverage of ?=0.3 and 0.05. In both cases, the crossovers from classical over-barrier hopping to under-barrier tunneling occurred at around T=125 K. At T=110 K, we measured the tunneling diffusion rates Dtunnel(?) for both deuterium and hydrogen in the coverage range from ?=0.05 to 0.45 and found that (1) Dtunnel(?) varied by less than a factor of 3; (2) the overall features of Dtunnel(?) for the two isotopes were similar; (3) Dtunnel(?) weakly peaked at around ?=0.25 and 0.5. Our results mostly agree with an early report by Lin and Gomer. Based on these results, we discuss the effect of the hydrogen-hydrogen interaction on hydrogen tunneling diffusion on Ni(111).

Wong, A.; Lee, A.; Zhu, X. D.

1995-02-01

54

IUE observations of neutral hydrogen and deuterium in the local interstellar medium  

NASA Technical Reports Server (NTRS)

Small-aperture, high-dispersion IUE spectra have been obtained of seven late-type stars that, in general, confirm previous Copernicus results concerning the distribution of hydrogen and deuterium in the local interstellar medium. In addition, the IUE Ly Alpha spectra of Altair, and of the Alpha Cen components, suggest that multiple velocity components exist in these two directions.

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

1986-01-01

55

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

56

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

57

In-ESI source hydrogen/deuterium exchange of carbohydrate ions.  

PubMed

We present the investigation of hydrogen/deuterium (H/D) exchange of carbohydrates ions occurring in the electrospray ion source. The shape of the deuterium distribution was observed to be considerably dependent on the temperature of the ion transfer tube and the solvent used. If deuterated alcohol (EtOD or MeOD) or D2O/deuterated alcohol is used as an electrospray solvent, then for high temperatures (>350 °C), intensive back exchange is observed, resulting in ?30% depth of the deuterium exchange. At low temperatures (<150 °C), the back exchange is weaker and the depth of the deuterium exchange is ?70%. In the intermediate temperature region (?250 °C), the deuterium distribution is unusually wide for methanol and bimodal for ethanol. The addition of 1% formic acid results in low (?30%) depth of the deuterium exchange for any temperature in the operating region. The bimodal distribution for the ethanol can be possibly explained by the presence of differently folded gas-phase ions of carbohydrates. PMID:24499243

Kostyukevich, Yury; Kononikhin, Alexey; Popov, Igor; Nikolaev, Eugene

2014-03-01

58

Hydrogen and deuterium in Pd25 pct Ag alloy: Permeation, diffusion, solubilization, and surface reaction  

Microsoft Academic Search

In this work, the hydrogen and deuterium transport parameters such as permeability, diffusivity, and solubility in a Pd-25\\u000a pct Ag alloy are studied, using a permeation gas phase technique and, additionally, a computer-controlled microbalance system.\\u000a In the region in which Sieverts' law is valid, the hydrogen solubilities found using both techniques are in very good agreement.\\u000a From permeation measurements, the

E. Serra; M. Kemali; A. Perujo; D. K. Ross

1998-01-01

59

Deuterium Tracer Experiments Prove the Thiophenic Hydrogen Involvement During the Initial Step of Thiophene Hydrodesulfurization  

Microsoft Academic Search

\\u000a Abstract  We reassess literature data and demonstrate that the intermolecular hydrogen transfer occur likely during the primary catalytic\\u000a interaction between thiophene molecules, rendering it the credible thiophene hydrodesulfurization (HDS) pathway. Deuterium\\u000a tracer experiments prove that thiophenic hydrogen plays a part in direct C–S cleavage, in the initial step of thiophene HDS.\\u000a Hypothetical surface intermediates for thiophene exchange do not precede, i.e.

Gregory Y. Katsapov; Artur Braun

2010-01-01

60

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

61

Hydrogen and deuterium internal friction behavior in vanadium-niobium alloys  

SciTech Connect

Internal friction behavior of hydrogen in vanadium-niobium alloys containing from 40 at. pct. niobium to 100 at. pct. niobium as a function of hydrogen concentrations was investigated. The internal friction measurements were performed in an electrostatic drive and detection apparatus for rods in flexural vibration in the temperature range from 30/degree/K to 290/degree/K. An internal friction peak due to hydrogen was found in all the vanadium-niobium alloys. The peak was considered to be due to the jumps of hydrogen atoms in solid solution. The peak moved toward lower temperatures with increasing hydrogen concentration. In other words, the activation energies of the hydrogen motion responsible for the internal friction peaks decreased with increasing hydrogen concentration. The activation energies and /tau//sub 0/ values for the hydrogen internal friction processes obtained from the present study were compared to those obtained from long range diffusion experiments. In order to examine the isotope effect, internal friction of deuterium in the same alloys were measured and compared to those of hydrogen. Effects of oxygen on the internal friction behavior of hydrogen and deuterium were also investigated. 45 refs., 23 figs., 9 tabs.

Kim, Seon Jin

1988-07-01

62

A combined deuterium NMR and quantum chemical investigation of inequivalent hydrogen bonds in organic solids.  

PubMed

Deuterium magic angle spinning (MAS) NMR spectroscopy and quantum chemical calculations are used to investigate organic solids in which inequivalent hydrogen bonds are present. The use of (2)H MAS allows one to measure the chemical shift, ?, quadrupolar coupling constant, C(Q), and asymmetry in the quadrupolar interaction, ?(Q), for each type of hydrogen bond present in the system. Quantum chemical calculations of the magnetic shielding (?, which can be related to ?) and the electric field gradient (EFG, which can be related to C(Q)) are compared to the experimental results and are discussed with respect to the relative strengths of the hydrogen bonds within each system. PMID:22883448

Webber, Renee; Penner, Glenn H

2012-01-01

63

Functionalization of Carbon Nanotubes using Atomic Hydrogen  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

64

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

65

Tests of a polarized source of hydrogen and deuterium based on spin-exchange optical pumping and a storage cell for polarized deuterium  

SciTech Connect

A novel laser-driven polarized source of hydrogen and deuterium which is based on the principle of spin-exchange optical pumping has been developed at Argonne. The advantages of this method over conventional polarized sources for internal target experiments is discussed. At present, the laser-driven polarized source delivers hydrogen 8 x 10 W atoms/s with a polarization of 24% and deuterium at 6 x 10 W atoms/s with a polarization of 25%. A passive storage cell for polarized deuterium was tested in the VEPP-3 electron storage ring. The storage cell was found to increase the target thickness by approximately a factor of three and no loss in polarization was observed. 10 refs., 4 figs., 2 tabs.

Holt, R.J.; Gilman, R.; Kinney, E.R.; Kowalczyk, R.S.; Napolitano, J.; Young, L.; Mishnev, S.I.; Nikolenko, D.M.; Popov, S.G.; Rachek, I.A.

1988-01-01

66

Kinetics study of two-channel hydrogen and deuterium atom reactions with interhalogen molecules  

SciTech Connect

Rate constants and the ratio of rates of two available reaction channels (branching ratios) for the reaction of hydrogen and deuterium atoms with FCl, ICl, and BrF molecules were measured using a fast-flow reactor with RF discharge as source of atoms and with syperheterodyne ESR spectrometer as detector. For the reaction with FCl a substantial difference was found in branching ratios when substituting hydrogen atoms with deuterium ones: {Gamma}{sub D+FCl}/{Gamma}{sub H+FCl}=3.3{plus_minus}0.2. The results are compared with the known experimental data and theoretical calculations; in particular, the possible influence of light atom (H or D) migration in collision complex on reaction mechanism is discussed.

Bykhalo, I.B.; Filatov, V.V.; Gordon, E.B. [Institute of Energy Problems of Chemical Physics, Moscow (Russian Federation)] [and others

1994-10-01

67

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

68

First-principles study of temperature-dependent diffusion coefficients: Hydrogen, deuterium, and tritium in ?-Ti  

NASA Astrophysics Data System (ADS)

We report the prediction of temperature-dependent diffusion coefficients of interstitial hydrogen, deuterium, and tritium atoms in ?-Ti using transition state theory. The microscopic parameters in the pre-factor and activation energy of the impurity diffusion coefficients are obtained from first-principles total energy and phonon calculations including the full coupling between the vibrational modes of the diffusing atom with the host lattice. The dual occupancy case of impurity atom in the hcp matrix is considered, and four diffusion paths are combined to obtain the final diffusion coefficients. The calculated diffusion parameters show good agreement with experiments. Our numerical results indicate that the diffusions of deuterium and tritium atoms are slower than that of the hydrogen atom at temperatures above 425 K and 390 K, respectively.

Lu, Yong; Zhang, Ping

2013-05-01

69

IUE observations of hydrogen and deuterium in the local interstellar medium  

NASA Technical Reports Server (NTRS)

High-resolution Ly-alpha spectra of the late-type stars Epsilon Eri, Procyon, Altair, Capella, and HR 1099 taken with the short-wavelength camera on IUE are presented. The density, velocity dispersion, and bulk velocity of the interstellar H I toward each of the stars is derived from the spectra. Lower limits on the deuterium-to-hydrogen ratio toward these stars are obtained.

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

1987-01-01

70

IUE observations of hydrogen and deuterium in the local interstellar medium  

SciTech Connect

High-resolution Ly-alpha spectra of the late-type stars Epsilon Eri, Procyon, Altair, Capella, and HR 1099 taken with the short-wavelength camera on IUE are presented. The density, velocity dispersion, and bulk velocity of the interstellar H I toward each of the stars is derived from the spectra. Lower limits on the deuterium-to-hydrogen ratio toward these stars are obtained. 40 references.

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

1987-04-01

71

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

Microsoft Academic Search

We demonstrate here that the hydrogen\\/deuterium solvent exchange (HDX) properties of the transmembrane fragment of the M2\\u000a protein of Influenza A (M2-TM) incorporated into lipid vesicles or detergent micelles can be studied with straightforward electrospray (ESI) and\\u000a nanospray mass spectrometry (MS) configurations provided that key factors, including sample preparation techniques, are optimized.\\u000a Small unilamellar vesicle preparations were obtained by solubilizing

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

2002-01-01

72

Gas phase hydrogen\\/deuterium exchange of proteins in an ion trap mass spectrometer  

Microsoft Academic Search

Electrospray ionization ion trap mass spectrometry (ESI-ITMS) coupled with gas phase hydrogen\\/deuterium (H\\/D) exchange is demonstrated to be a useful tool to investigate the gas phase conformations of proteins when coupled with a mechanistic understanding of exchange. We have investigated the H\\/D exchange of multiple charge states of lysozyme, cytochrome c, ubiquitin, insulin, thioredoxin and melittin with deuterated methanol in

Sarah E. Evans; Nathan Lueck; Elaine M. Marzluff

2003-01-01

73

Equation of state of molecular hydrogen and deuterium from shock-wave experiments to 760 kbar  

SciTech Connect

We have carried out single-shock experiments with liquid deuterium to 210 kbar (Troughly-equal4800 K) and reflected experiments to 760 kbar (Troughly-equal7000 K) as well as single-shock experiments with liquid hydrogen to 100 kbar (Troughly-equal3300 K). These data enable us to determine a theoretical spherically symmetric, effective intermolecular pair potential. Calculated solid isotherms are compared with recent static measurements.

Nellis, W.J.; Ross, M.; Mitchell, A.C.; van Thiel, M.; Young, D.A.; Ree, F.H.; Trainor, R.J.

1983-01-01

74

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

Microsoft Academic Search

Hydrogen and deuterium incorporation into nitrided and non-nitrided hafnium silicate films on Si during thermal annealing in 1H- and 2H-containing atmospheres was investigated. 1H profiling was accessed by means of nuclear resonant reaction profiling, whereas 2H incorporation was quantified by nuclear reaction analysis. The effects of preannealing in different atmospheres and temperatures were determined, as well as the losses of

R. P. Pezzi; L. Miotti; K. P. Bastos; G. V. Soares; C. Driemeier; I. J. R. Baumvol; P. Punchaipetch; G. Pant; B. E. Gnade; R. M. Wallace; A. Rotondaro; J. M. Visokay; J. J. Chambers; L. Colombo

2004-01-01

75

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

76

Modification of tungsten coated carbon by low energy and high flux deuterium irradiation  

Microsoft Academic Search

Plasma sprayed tungsten coated carbon fiber composites (VPS-W\\/CX-2002U) and powder metallurgy tungsten (PM-W) have been exposed to a high deuterium flux (?1022 m?2s?1) with low energy (100 eV) in a range from 708 to 843 K. Surface modification and deuterium retention after the exposure have been investigated to prove the suitability of such materials in fusion devices. Blisters are formed

K. Tokunaga; R. P. Doerner; R. Seraydarian; N. Noda; N. Yoshida; T. Sogabe; T. Kato; B. Schedler

2002-01-01

77

Ion-induced deuterium retention in tungsten coatings on carbon substrate  

NASA Astrophysics Data System (ADS)

Deuterium retention in different tungsten (W) coatings on carbon substrates was investigated for various incident ion energies ranging from 20 to 200 eV per deuterium atom and fluences ranging from 1 × 10 23 m -2 to 2 × 10 25 m -2. The targets were irradiated by deuterium ions at the IPP laboratory with a mass-separated ion beam with a flux of 10 19 D/m 2 s and with a deuterium plasma providing a flux of 10 20 D/m 2 s. Irradiation has been done at different sample temperatures ranging from 320 to 650 K. The depth profile of deuterium in the W coatings was measured up to 6 ?m depth by nuclear reaction analysis (NRA) and the total retained amount was determined by thermal desorption spectroscopy. It is shown that deuterium retention significantly depends on the microstructure of each W coating. The deuterium retention in W coating of 7 ?m thickness produced by combined magnetron-sputtering and ion implantation technique is higher compared to physical vapour deposited W coating of 4-5 ?m thickness and 200 ?m thickness plasma-sprayed W coating for all investigated energies and sample temperatures up to 650 K.

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

2011-12-01

78

Kinetic Method for Hydrogen-Deuterium-Tritium Mixture Distillation Simulation  

SciTech Connect

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

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

2005-07-15

79

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

NASA Astrophysics Data System (ADS)

Pressure-Composition-Temperature (PCT) data are presented for the plutonium-hydrogen (Pu-H) and plutonium-deuterium (Pu-D) systems in the solubility region up to terminal solubility (precipitation of PuH2). The heats of solution for PuHS and PuDS are determined from PCT data in the ranges 350-625°C for gallium alloyed Pu and 400-575°C for unalloyed Pu. The solubility of high purity plutonium alloyed with 2 at.% gallium is compared to high purity unalloyed plutonium. Significant differences are found in hydrogen solubility for unalloyed Pu versus gallium alloyed Pu. Differences in hydrogen solubility due to an apparent phase change are observable in the alloyed and unalloyed solubilities. The effect of iron impurities on Pu-Ga alloyed Pu is shown via hydrogen solubility data as preventing complete homogenization.

Richmond, S.; Bridgewater, J. S.; Ward, J. W.; Allen, T. H.

2010-03-01

80

Deuterium diffusion and retention in a tungsten–carbon multilayer system  

NASA Astrophysics Data System (ADS)

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

Wang, P.; Jacob, W.

2014-06-01

81

Helium doped hydrogen or deuterium beam as cost effective and simple tool for plasma spectroscopy  

NASA Astrophysics Data System (ADS)

Energetic neutral particles from neutral beam heating systems are widely used for active spectroscopic measurements of key plasma parameters in fusion experiments. Both the plasma discharges and the neutral beam systems are normally operated with hydrogen or deuterium. Helium beams are used in dedicated diagnostic beam lines as they offer deeper penetration and are subject to less background radiation and enable resonant double charge exchange with alpha particles. Neutral beam systems using pure helium either require specialized helium gas pumping with a pumping speed in excess of 1000 m3/h or are restricted to short pulses (normally less than 1 s). A doped hydrogen/helium beam combines the requirements for plasma heating and diagnostics without the need for sophisticated helium pumping. A small flow of helium gas is injected into the plasma source for the time helium particles are required. The helium current is typically 10% of the total extracted current. The reduction in heating power of the doped beam can be kept below 5%. The small amount of helium gas does not cause an excessive pressure rise along the beam line and does not reduce the reliability of the beam heating system. Doped deuterium/helium beams have been successfully tested and routinely used at JET. The Hel beam emission spectra obtained with a doped deuterium/helium beam produce sufficiently strong visible lines for spectroscopic applications. Furthermore, the simultaneous availability of helium and hydrogenic particles in the beam allows us to extend spectroscopic measurements to another atomic system and hence cross-check results from helium beams with those from hydrogenic beams. The only investment required is an additional helium gas inlet system into the ion source.

Falter, H. D.; Proschek, M.; Menhart, S.; Aumayr, F.; Winter, Hp.; Ciric, D.; Cox, S.; Dines, A.; Godden, D.; Hawkes, N.; Jones, T. T. C.

2000-10-01

82

Effects of lithium-implantation on the hydrogen retention in both a-C:H and a-Si C:H materials submitted to deuterium bombardment.  

National Technical Information Service (NTIS)

The hydrogen release in plasma facing materials is a challenging problem for the hydrogen recycling. The hydrogen desorption from a-C:H and a-SiC:H materials induced by deuterium bombardment has been investigated. Prior to the deuterium bombardment, both ...

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

1996-01-01

83

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

84

Identifying Zn-bound histidine residues in metalloproteins using hydrogen-deuterium exchange mass spectrometry.  

PubMed

In this work, we have developed a method that uses hydrogen-deuterium exchange (HDX) of C2-hydrogens of histidines coupled with mass spectrometry (MS) to identify Zn-bound histidines in metalloproteins. This method relies on differences in HDX reaction rates of Zn-bound and Zn-free His residues. Using several model peptides and proteins, we find that all Zn-bound His residues have substantially lower HDX reaction rates in the presence of the metal. The vast majority of non-Zn-binding His residues undergo no significant changes in HDX reaction rates when their reactivity is compared in the presence and absence of Zn. Using this new approach, we then determined the Zn binding site of ?-2-microglobulin, a protein associated with metal-induced amyloidosis. Together, these results suggest that HDX-MS of His C2-hydrogens is a promising new method for identifying Zn-bound histidines in metalloproteins. PMID:24313328

Dong, Jia; Callahan, Katie L; Borotto, Nicholas B; Vachet, Richard W

2014-01-01

85

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

PubMed

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

2014-04-01

86

Hydrogen electrode in molten carbonate  

Microsoft Academic Search

Open-circuit potentials are reported for the hydrogen (Au) electrode in molten carbonate at 650°C. The data, with few exceptions, agree with thermodynamic values calculated assuming simultaneous equilibrium of the shift and the methane reactions. The exceptions are those instances where methane has to be oxidized almost completely to reach equilibrium, and those where carbon can form during preheating of the

W. M. Vogel; C. D. Iacovangelo

1977-01-01

87

Deuterium isotope effects and fractionation factors of hydrogen-bonded A:T base pairs of DNA  

Microsoft Academic Search

Deuterium isotope effects and fractionation factors of N1...H3–N3 hydrogen bonded Watson–Crick A:T base pairs of two DNA dodecamers are presented here. Specifically, two-bond deuterium isotope effects on the chemical shifts of 13C2 and 13C4, 2?13C2 and 2?13C4, and equilibrium deuterium\\/protium fractionation factors of H3, F, were measured and seen to correlate with the chemical shift of the corresponding imino proton,

Ioannis Vakonakis; Miguel Salazar; Mijeong Kang; Kim R. Dunbar; Andy C. LiWang

2003-01-01

88

Time-resolved measurements of hydrogen and deuterium fluxes in the ASDEX plasma boundary  

SciTech Connect

Hydrogen and deuterium fluxes parallel to the toroidal magnetic field were measured in the plasma boundary of ASDEX using graphite collector probes. Time resolution of the order of 100 ms can be obtained by rotating the cylindrical probes behind an aperture during the discharge. The trapped amount of hydrogen was determined by subsequent thermal desorption; in the analyses of deuterium the D(/sup 3/He,p)/sup 4/He nuclear reaction was used. Both methods yield quantitative results. Measurements were done for limiter and divertor discharges in the range of 4 to 20 cm outside the limiter or separatrix. The time distributions show a maximum flux at the beginning and the end of the discharge. The relatively lower flux during the plateau phase of the discharge is in the range 10/sup 15/ to 2 x 10/sup 17/ cm/sup -2/ sec/sup -1/, depending on the radial probe position; the maximum values are higher by a factor of 5 to 50. During neutral hydrogen injection, an additional maximum can be observed. The radial l/e-decay length is about 0.9 cm in front and 0.4 cm behind the fixed limiter. The results are compared with independent measurements in ASDEX and other plasma machines.

Roth, J.; Varga, P.; Martinelli, A.P.; Scherzer, B.M.U.; Chen, C.K.; Wampler, W.R.; Taglauer, E.

1982-01-01

89

Anomalously deep penetration of hydrogen and deuterium in assemblies from Nb foils and deuterated polyethylene (CD2) n under the pulse high temperature hydrogen plasma  

NASA Astrophysics Data System (ADS)

Studies of the storage and redistribution of hydrogen atoms under pulse high temperature hydrogen plasma that was obtained using a PF-4 Plasma Focus facility in a multilayered structure (sandwich) which consists of two high-purity niobium foils and a deuterium polyethylene film pressed between them have been carried out using the method for elastic recoil detection (ERD). It was established that, with an increase in pulses of the PF-4 facility, the redistribution of implanted hydrogen atoms for large depths occurs in the two Nb foils and deuterated polyethylene. The depths substantially exceed the projective range of paths of hydrogen ions (at their maximum velocity of ˜108 cm/s). A maximum hydrogen concentration of 45 at % is reached in the nearest surface of the second Nb foil to the PF-4 at 20 pulses of hydrogen plasma. An X-ray diffraction analysis showed the presence of a niobium hydride phase in both Nb foils. The redistribution of deuterium atoms from the bound state of deuterated polyethylene into the near-surface layer and the bulk material of the second Nb foil was detected as well. This phenomenon can be attributed to the transfer of implanted hydrogen atoms through the foil assembly and the transfer of deuterium from deuterated polyethylene into the near-surface layer of the second foil under the effect of powerful shock waves that are created by pulse hydrogen plasma and by acceleration in the diffusion of hydrogen and deuterium in the strain field induced by the shock wave.

Didyk, A. Yu.

2012-03-01

90

Gas phase atomic hydrogen induced carbon-carbon bond activation in cyclopropane on the Ni(100) surface  

SciTech Connect

Carbon-carbon activation in adsorbed cyclopropane is observed following exposure to gas phase atomic hydrogen on the Ni(100) surface for temperatures as low as 100 K. Exposure to either gas phase atomic hydrogen or deuterium results in formation of adsorbed propyl. In both cases subsequent reaction between adsorbed propyl and coadsorbed hydrogen/deuterium produces propane at 121 K. The activation of a single C-C bond in adsorbed cyclopropane dominates as indicated by the fact that propane is the only product observed. No multiple C-C bond activation which would result in methane or ethane formation was ever observed. These reactions and their mechanisms have been investigated using temperature-programmed reaction and vibrational spectroscopy using high-resolution electron energy loss spectroscopy. The results obtained clearly indicate that C-C bond activation occurs during exposure to gas phase atomic hydrogen. Isotopic labeling studies reveal that the adsorbed propyl intermediate is hydrogenated by labelled surface hydrogen. Carbon-carbon bond activation in adsorbed cyclopropane has never been observed during adsorption on a surface with preadsorbed hydrogen nor during exposure to nascent hydrogen formed by dissociating molecular hydrogen. A detailed potential energy diagram for the reactions of adsorbed cyclopropane on the Ni(100) surface is developed based on results from these experiments and the literature. 68 refs., 11 figs., 1 tab.

Son, K.A.; Gland, J.L. [Univ. of Michigan, Ann Arbor, MI (United States)] [Univ. of Michigan, Ann Arbor, MI (United States)

1996-10-30

91

Temperature and spectroscopic characteristics of homogeneous co-deposited carbon–deuterium films produced in the T-10 tokamak  

Microsoft Academic Search

Homogeneous carbon–deuterium (C? D) films with a high [D]\\/[C] ratio, redeposited on deuterium-plasma discharge in the T-10 tokamak, have been studied by means of thermogravimetric analysis, spectroscopy based on electron paramagnetic resonance, Fourier-transform infrared spectroscopy and photoluminescence spectroscopy. Deuterium was found to be accumulated only in the C? D2, 3 sp vibrational modes, including 633 and 1090 cm deformation modes, and

N. Yu. Svechnikov; V. G. Stankevich; A. M. Lebedev; K. A. Menshikov; B. N. Kolbasov; M. I. Guseva; L. N. Khimchenko; D. Rajarathnam; Yu. Yu. Kostetsky

2006-01-01

92

Characterization of isotopically labeled coal liquefaction solvents and products by deuterium and carbon-13 nuclear magnetic resonance spectrometry  

SciTech Connect

Primary and secondary deuterium isotope shifts are observed in the carbon-13 NMR spectrum of partially deuterated tetralin and naphthalene. These shifts are used to quantitate the extent of deuteration at each carbon site. Deuterium exchange at the tetralin ..cap alpha.. position is faster than coal liquefaction. A deuterium NMR method, using the natural abundance signal of the solvent as an internal standard, shows not only the relative distribution of deuterium in coal liquid products produced from deuterated tetralin as the donor solvent but also the absolute amount of deuterium in nonvolatile products. Some carbon-carbon coupling constants are reported for (1-/sup 13/C)tetralin, (1-/sup 13/C)octahydrophenathrene, and (4-/sup 13/C)-2,6-dimethyltetralin. The carbon-13 compounds verify that thermal ring opening is a negligible process under coal liquefaction conditions unless a catalyst is present. Ring contraction remains constant at about 5% of the thermal products with or without a catalyst. Deuterium NMR is used to follow the deuterium exchange between partially deuterated tetralin and mestylene. The deuterium label goes to the mesitylene methyls as expected. 13 references, 8 figures, 6 tables.

Young, D.C.; McNeil, R.I.; Cronauer, D.C.; Ruberto, R.G.; Galya, L.G.

1984-03-01

93

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

SciTech Connect

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

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

1993-02-10

94

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

SciTech Connect

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

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

2004-10-18

95

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

96

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

PubMed

Probing the conformational changes of amyloid beta (A?) peptide aggregation is challenging owing to the vast heterogeneity of the resulting soluble aggregates. To investigate the formation of these aggregates in solution, we designed an MS-based biophysical approach and applied it to the formation of soluble aggregates of the A?42 peptide, the proposed causative agent in Alzheimer's disease. The approach incorporates pulsed hydrogen-deuterium exchange coupled with MS analysis. The combined approach provides evidence for a self-catalyzed aggregation with a lag phase, as observed previously by fluorescence methods. Unlike those approaches, pulsed hydrogen-deuterium exchange does not require modified A?42 (e.g., labeling with a fluorophore). Furthermore, the approach reveals that the center region of A?42 is first to aggregate, followed by the C and N termini. We also found that the lag phase in the aggregation of soluble species is affected by temperature and Cu(2+) ions. This MS approach has sufficient structural resolution to allow interrogation of A? aggregation in physiologically relevant environments. This platform should be generally useful for investigating the aggregation of other amyloid-forming proteins and neurotoxic soluble peptide aggregates. PMID:23959898

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

2013-09-01

97

Investigation of hydrogen/deuterium isotope effects in coal-conversion processes  

SciTech Connect

This paper reports on the investigation of hydrogen/deuterium isotope effects in catalytic coal char gasification experiments been conducted to obtain information about the mechanisms of hydrogasification and steam gasification reactions. Hydrogasification and steam gasification experiments were conducted with or without K/sub 2/CO/sub 3/ catalyst (K/C atomic ratio 0.04) using H/sub 2/ or D/sub 2/ for hydrogasification and H/sub 2/O or D/sub 2/O for steam gasification. Three pairs of hydrogasification experiments have been made to investigate the deuterium isotope effect: one pair with noncatalyzed char and two pairs with K/sub 2/CO/sub 3/-catalyzed char. The K/C atomic ratio in both catalyzed chars was 0.04. In the case of the noncatalyzed char, little, if any, isotope effect was observed. In contrast, a strong reverse isotope effect was found for the K/sub 2/CO/sub 3/-catalyzed char, at both 750 and 850/sup 0/C. The value of the rate (D/sub 2/)/rate (H/sub 2/) ratio was 2.5 at 750/sup 0/C and 2.2 at 850/sup 0/C, read at around the midpoint of the rate versus weight loss curve (at 33% weight loss). Noncatalyzed hydrogasification of char in hydrogen to form methane can be described by a two-step mechanism according to Blackwood and coworkers. Chemisorption of hydrogen takes place at active centers on the char surface in the first step; the surface complex formed by chemisorption reacts with hydrogen to form methane in the second step. A refinement of this mechanism was also proposed, postulating a stepwise formation of the surface complex G(H)/sub 2/.

Heredy, L.A.; McCoy, L.R.; Goldberg, I.B.

1983-01-01

98

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

99

Longitudinal-transverse separations of deep-inelastic structure functions at low Q2 for hydrogen and deuterium.  

PubMed

We report on a study of the longitudinal to transverse cross section ratio, R=sigmaL/sigmaT, at low values of x and Q2, 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. PMID:17501267

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

2007-04-01

100

Subzero temperature chromatography for reduced back-exchange and improved dynamic range in amide hydrogen/deuterium exchange mass spectrometry.  

PubMed

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

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

2012-11-01

101

Deuterium isotope effects on the carbon-13 chemical shifts of carbocations  

SciTech Connect

The deuterium isotope effect on the carbon-13 NMR spectrum of several carbocations and neutral molecules have been examined. The carbon-13 resonance of the cationic carbon atom in the heavy isotopomer of the carbocations was found to be shifted upfield, to be unaffected, or to be shifted downfield, upon ..beta..-deuteration from the corresponding carbon in the nondeuterated compound. These effects ranged from -2.5 ppm to +1.6 ppm and were found to be consistent with previous work of Servis and Shue. The two bond chemical shift isotope effects determined for 2-methyl-2-norbornyl cation and for 2-(3,5-bis-(trifluoromethyl)-phenyl)-2-norbornyl cation provide evidence for partial delocalization of positive charge away from C2 into a three-center two-electron bond. The deuterium isotope effects determined for the 2-(p-fluorophenyl)-2-norbornyl cation and the 2-phenyl-2-norbornyl cation provide evidence about the stereochemical dependence of the two bond chemical shift isotope effect. The effect of exo C3 deuterium substitution on the C2-resonance in the carbon-13 NMR spectrum of the 2-(p-fluorophenyl)-2-norbornyl cation and the 2-phenyl-2-norbornyl cation is small and positive while the effect of endo C3 deuterium substitution is small and negative. This is the first case reported in which stereochemically distinct isotope effects at the same carbon are of opposite sign. The two bond chemical shift isotope effects determined for 2,3-dimethyl-2-butene bromonium ion and for 2,3-dimethyl-2-butene mercurinium ion permit the elucidation of the electronic structure of these cations.

Domenick, R.L.

1985-01-01

102

Advantages of isotopic depletion of proteins for hydrogen/deuterium exchange experiments monitored by mass spectrometry.  

PubMed

Solution-phase hydrogen/deuterium exchange (HDX) monitored by mass spectrometry is an excellent tool to study protein-protein interactions and conformational changes in biological systems, especially when traditional methods such as X-ray crystallography or nuclear magnetic resonance are not feasible. Peak overlap among the dozens of proteolytic fragments (including those from autolysis of the protease) can be severe, due to high protein molecular weight(s) and the broad isotopic distributions due to multiple deuterations of many peptides. In addition, different subunits of a protein complex can yield isomeric proteolytic fragments. Here, we show that depletion of (13)C and/or (15)N for one or more protein subunits of a complex can greatly simplify the mass spectra, increase the signal-to-noise ratio of the depleted fragment ions, and remove ambiguity in assignment of the m/z values to the correct isomeric peptides. Specifically, it becomes possible to monitor the exchange progress for two isobaric fragments originating from two or more different subunits within the complex, without having to resort to tandem mass spectrometry techniques that can lead to deuterium scrambling in the gas phase. Finally, because the isotopic distribution for a small to medium-size peptide is essentially just the monoisotopic species ((12)C(c)(1)H(h)(14)N(n)(16)O(o)(32)S(s)), it is not necessary to deconvolve the natural abundance distribution for each partially deuterated peptide during HDX data reduction. PMID:20337424

Bou-Assaf, George M; Chamoun, Jean E; Emmett, Mark R; Fajer, Piotr G; Marshall, Alan G

2010-04-15

103

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

SciTech Connect

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

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

2012-07-15

104

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

Microsoft Academic Search

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

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

2006-01-01

105

Surface phonons of clean, hydrogen- and deuterium-terminated Si(0 0 1) surfaces  

NASA Astrophysics Data System (ADS)

We present a comprehensive vibrational study of the clean and hydrogen- or deuterium-terminated silicon (0 0 1) surface. The modes related to the clean as well as to the H:Si, D:Si, and 2H:Si, 2D:Si surfaces are studied by means of high resolution electron energy loss spectroscopy (HREELS). We pay special attention to the modification of the phonon modes by the surface treatments and compare the data with reported experimental and theoretical results. The analysis of the relative phonon intensities of the clean, mono- and dihydride surfaces yields the assignment of the modes related to the dimer bonds. The isotopic shifts of vibrons related to the Si-H and Si-D bonds and to the surface phonon are discussed and applied to the characterisation of the surface excitations.

Eremtchenko, M.; Tautz, F. S.; Öttking, R.; Schaefer, J. A.

2006-09-01

106

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

PubMed Central

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

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

2012-01-01

107

Activation of AMP-activated protein kinase revealed by hydrogen/deuterium exchange mass spectrometry.  

PubMed

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

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

2013-11-01

108

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

SciTech Connect

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

Malinowski, M.E.

1985-05-01

109

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

110

Carbon and hydrogen isotope fractionation by moderately thermophilic methanogens  

NASA Astrophysics Data System (ADS)

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

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

2004-04-01

111

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

PubMed

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

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

2013-02-01

112

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

SciTech Connect

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

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

1986-03-15

113

Thermally induced evolution of hydrogenated amorphous carbon  

NASA Astrophysics Data System (ADS)

The thermally induced structural evolution of hydrogenated amorphous carbon (a-C:H) films was investigated in situ by X-ray photoelectron spectroscopy for annealing temperatures up to 500 °C. A model for the conversion of sp3- to sp2-hybridized carbon in a-C:H vs. temperature and time was developed and applied to determine the ranges of activation energies for the thermally activated processes occurring. The energies are consistent with ordering and clustering of sp2 carbon, scission of sp3 carbon-hydrogen bonds and formation of sp2 carbon, and direct transformation of sp3- to sp2-hybridized carbon.

Mangolini, Filippo; Rose, Franck; Hilbert, James; Carpick, Robert W.

2013-10-01

114

Investigation of detached recombining deuterium plasma and carbon chemical erosion in the toroidal divertor simulator NAGDIS-T  

NASA Astrophysics Data System (ADS)

Detached deuterium recombining plasma has been generated in the toroidal divertor simulator. The electron temperature (0.1-0.4 eV) and density (˜10 18 m -3) in the detached plasmas were evaluated with a spectroscopic method using a series of deuterium Balmer line emission from highly excited levels and the Stark broadening of D(2-12). We have investigated the role of volume plasma recombination through Electron-Ion Recombination (EIR) and Molecular Activated Recombination (MAR) processes. Moreover, the carbon erosion in the detached deuterium plasma has been studied with a weight loss method. It is found that deuterium neutrals generated by EIR process could have strong influence on the carbon chemical erosion.

Yada, K.; Matsui, N.; Ohno, N.; Kajita, S.; Takamura, S.; Takagi, M.

2009-06-01

115

Hydrogen storage capacity on different carbon materials  

NASA Astrophysics Data System (ADS)

The hydrogen adsorption capacity of various carbon structures including activated carbon (AC) and carbon nanofibers (CNFs) has been measured as a function of pressure and temperature. Results have shown the correlation between hydrogen storage capacity and specific micropore surface area and also explain the hysteresis in H 2 uptake observed at 273 and 299 K principally with CNFs materials. The highest H 2 storage value (2.02 wt%) was obtained with AC at 10 bar and 77 K.

Jiménez, Vicente; Sánchez, Paula; Díaz, José Antonio; Valverde, José Luis; Romero, Amaya

2010-01-01

116

Hydrogen storage in carbon nitride nanobells  

NASA Astrophysics Data System (ADS)

Aligned carbon nitride (C-N) nanobells in polymer form, prepared by microwave plasma-assisted chemical vapor deposition, were used as hydrogen adsorbent. A hydrogen storage capacity up to 8 wt % was achieved reproducibly under ambient pressure and at temperature of 300 °C. The high hydrogen storage capacity under the moderate conditions was mainly derived from the short nanobell structure with openended graphitic layers, as well as the nitrogen in the nanobells, which acts as an active site for hydrogen adsorption. The high hydrogen uptake and the simple adsorption-desorption process suggest that a C-N nanobell is promising as a hydrogen storage material.

Bai, X. D.; Zhong, Dingyong; Zhang, G. Y.; Ma, X. C.; Liu, Shuang; Wang, E. G.; Chen, Yan; Shaw, David T.

2001-09-01

117

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

Microsoft Academic Search

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

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

2007-01-01

118

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

Microsoft Academic Search

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

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

2007-01-01

119

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

Microsoft Academic Search

The secondary structure of bacteriorhodopsin has been investigated by polarized Fourier transform infrared spectroscopy combined with hydrogen\\/deuterium exchange, isotope labeling and resolution enhancement methods. Oriented films of purple membrane were measured at low temperature after exposure to H2O or D2O. Resolution enhancement techniques and isotopic labeling of the Schiff base were used to assign peaks in the amide I region

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

1990-01-01

120

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

Microsoft Academic Search

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

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

1999-01-01

121

Conformational analysis of recombinant monoclonal antibodies with hydrogen/deuterium exchange mass spectrometry.  

PubMed

Understanding the conformation of antibodies, especially those of therapeutic value, is of great interest. Many of the current analytical methods used to probe protein conformation face issues in the analysis of antibodies, either due to the nature of the antibody itself or due to the limitations of the method. One method that has recently been utilized for conformational analysis of antibodies is hydrogen/deuterium exchange mass spectrometry (H/DX MS). H/DX MS can be used to probe the conformation and dynamics of proteins in solution, requires small sample quantities, is compatible with many buffer systems, and provides peptide-level resolution. The application of H/DX MS to immunoglobulin gamma 1 (IgG1) recombinant monoclonal antibodies can provide information about IgG1 conformation, dynamics, and changes to conformation as a result of protein modification(s), changes in storage conditions, purification procedures, formulation, and many other parameters. In this article we provide a comprehensive H/DX MS protocol for the analysis of an antibody. PMID:23475726

Houde, Damian; Engen, John R

2013-01-01

122

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

123

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.

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

2008-01-01

124

A new method to produce cold atomic hydrogen and deuterium beams  

SciTech Connect

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

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

1998-01-20

125

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

SciTech Connect

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

Colognesi, D.; Celli, M.; Zoppi, M. [Consiglio Nazionale delle Ricerche, Istituto dei Sistemi Complessi, Via Madonna del Piano, 50019 Sesto Fiorentino, FI (Italy); Neumann, M. [Institut fuer Experimentalphysik, Universitaet Wien, Strudlhofgasse 4, 1090 Vienna (Austria)

2004-12-01

126

A new method to produce cold atomic hydrogen and deuterium beams  

NASA Astrophysics Data System (ADS)

A new method to produce cold atomic hydrogen and deuterium beams is described. This technique can be applied to development of internal polarized targets. The proposed scheme is to combine the low density beam of atoms from a dissociator of a conventional atomic-beam source with a supersonic carrier gas jet formed by a circular converging-diverging Laval nozzle surrounding the central one. A computer code for a realistic description of the formation of the atomic beam inside the supersonic carrier gas jet has been developed and applied for computer simulations of different nozzle geometries, various combinations of gas and carrier gas, and different mixtures of partly dissociated gas, like H-H2 and D-D2. The calculations indicate that with a carrier gas flow of about six times higher than the inner atomic beam, the central beam is confined, which should result in a better forward intensity and much lower beam temperature. An experimental study of this new method is in progress.

Varentsov, Victor L.; Ignatiev, Alexei A.; Steffens, Erhard; Koch, Norbert

1998-01-01

127

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

NASA Astrophysics Data System (ADS)

To improve our understanding of the global budget of molecular hydrogen, we present a new simulation of molecular hydrogen and its deuterium component (?D) using the GEOS-CHEM three dimensional global model of tropospheric chemistry. The primary sources of H2 (fossil fuel, biofuel, and biomass burning) used in the model are based on the GEOS-CHEM CO emissions inventory, scaled with the appropriate emission factors. Secondary sources from photochemical production arise from the photolysis of formaldehyde (resulting from oxidation of methane and biogenic volatile organic compounds, BVOCs) and account for an estimated 45% of the H2 source. There is considerable uncertainty in the source of H2 from formaldehyde, because of poor understanding of BVOC sources and chemistry. We also include a seasonally varying ocean source, based on a simulation of ocean nitrogen fixation. The main tropospheric sink, accounting for ~80% of the total, is uptake by enzymes in soils, a process which is poorly understood. The remainder loss is through oxidation by the hydroxyl radical (OH). The observed deuterium component of tropospheric H2 (expressed as ?D) is enriched by ~130‰ relative to Vienna Standard Mean Ocean Water [Gerst and Quay, 2000]. The combustion and ocean sources of H2 are isotopically depleted, while the photochemical sources are thought to be isotopically enriched [Gerst and Quay, 2001]. The soil sink for H2 shows little fractionation, while the OH sink shows considerable fractionation. Furthermore, stratosphere-troposphere exchange is believed to isotopically enrich H2 [Röckmann et al. 2003; Rahn et al. 2002]. We use H2 observations from the CMDL network (seasonal cycle, latitudinal and longitudinal gradients, aircraft observations) to constrain the budget of H2 in the atmosphere, in particular, the sink by soil uptake, the photochemical source, and ocean emissions. At the same time, we use observations of ?D from ocean cruises, aircraft, and ground sites to further constrain the budget of H2 and provide new isotopic constraints on the enrichment due to the photochemical source and stratosphere-troposphere exchange. Gerst S. and P. Quay, The deuterium content of atmospheric molecular hydrogen: Methods and initial measurements, J. Geosphy. Res., 105, 26,433-26,445, 2000. Gerst S. and P. Quay, Deuterium component of the global molecular hydrogen cycle, J. Geophys. Res., 106, 5021-5031, 2001. Rahn, T. et al., Extreme deuterium enrichment in the stratospheric hydrogen and the global atmospheric budget of H2, Nature, 424, 2003. Röckmann T., T. Rhee, and A. Engel, Heavy hydrogen in the stratosphere, Atmos. Chem. Phys., 3, 2015-2023, 2003.

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

2006-05-01

128

Nanostructural activated carbons for hydrogen storage  

NASA Astrophysics Data System (ADS)

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

Li, Suoding

129

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

130

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

131

Carbon-hydrogen bonding in near-frictionless carbon  

SciTech Connect

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

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

2008-01-01

132

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

133

Impurity coverage and deuterium inventory of beryllium and carbon first wall components after beryllium operation in JET  

NASA Astrophysics Data System (ADS)

During 1989, following a brief all carbon phase, JET was operated with an evaporated beryllium film on all the plasma facing surfaces and then, in a third phase, with bulk beryllium used for the belt limiters and one set of antenna protection tiles. Subsequent analysis of wall components and long term samples (LTS) using Beta Backscatter and Ion Beam Analysis has been conducted to determine the condition of the First Wall and its deuterium inventory after beryllium operation. Ex-situ analysis of components where deposition occurs during operation shows mixed carbon and beryllium layers with an approximate ratio 1:1 and some localised higher Z components. The deuterium inventory situation is littled changed by the introduction of beryllium. Similar surface levels of deuterium, ~1 × 10 22 atoms m -2, have been seen for both carbon and beryllium belt limiter tiles.

Peacock, A. T.; Coad, J. P.; Lama, F.; Behrisch, R.; Martinelli, A. P.; Mills, B. E.; Pick, M.; Partridge, J.; Simpson, J. C. B.; Zhu, Y. K.

1990-12-01

134

Carbon-hydrogen bonding in near-frictionless carbon  

Microsoft Academic Search

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

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

2008-01-01

135

The frequency dependence of internal friction caused by hydrogen and deuterium in iron-nickel Invar alloy  

SciTech Connect

A hydrogen peak of internal friction has been investigated in detail for various kinds of fcc Fe-Ni alloys, including such engineering materials as Permalloy and Invar alloy. Its activation energy is closely related to that for hydrogen diffusion. For an Fe-36%Ni Invar alloy, a deuterium peak has also been found, located at a temperature 2 - 3 K higher than the hydrogen peak which appears around 250 K at audio frequencies. Such an isotope shift of the peak position can be interpreted in terms of the isotope effect of hydrogen diffusion. This suggests that the hydrogen peak is attributed to a Snoek-type relaxation caused by dissolved hydrogen in the fcc lattice. In all the above studies, internal friction has been measured by the free-decay method in resonant vibrations and obtained as a function of temperature at nearly constant frequencies. This conventional method, providing the data on the temperature dependence of internal friction, is known to introduce a very low background and suppress a scatter of the data points. However, for fcc Fe-Ni alloys which occlude only a small quantity of hydrogen, the hydrogen peak can only be detected under large supersaturations of hydrogen.

Nishino, Y.; Tamaoka, S.; Asano, S.

1989-02-01

136

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

PubMed

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

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

2013-11-19

137

Designing Microporus Carbons for Hydrogen Storage Systems  

SciTech Connect

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

Alan C. Cooper

2012-05-02

138

Hydrogen-deuterium exchange studies of the rat thyroid transcription factor 1 homeodomain.  

PubMed

The 1H NMR solution structure of the rat thyroid transcription factor 1 homeodomain (TTF-1 HD) showed that the molecule folds like classical homeodomains. The C-terminal extension of helix III (fragment 51-59) appeared to adopt a helical geometry, albeit not as rigid as the preceding portion, but the hydrogen-deuterium exchange of backbone amides and the NOE data provided evidence of a discontinuity between the two moieties of helix III at the highly conserved fragment Asn51-His52-Arg53. Analysis of quantitative measurements of isotope exchange rates allows one to recognize the general occurrence, in that region of HD motifs, of opposite effects to helix III stability. Asparagine, histidine and arginine residues occur most frequently at the beginning and end of protein helices. In TTF-1 HD a local fluctuation is observed in the fragment 51-53 which either kinks or tightens the alpha-helix. A search through the protein structure database reveals that the three most common variants of HD fragments 51-53 are often involved in helices and, frequently, in helix initiation or termination. For homeodomains in general, the nature of the fragment 51-53 may be related to the conformational dynamics of their DNA-recognition helix (helix III). Besides the specific results on fragment 51-53, the complete isotope exchange analysis of TTF-1 HD data shows that the partially solvent-exposed recognition helix is stabilized by hydrophobic interactions, like most of the structured regions of the molecule. Hydrophobic stabilization of the contacting regions meets the requirements of a DNA-interaction mechanism which, as shown with other DNA-protein complexes, should entail negative heat capacity variations due to changes in solvent exposure of the nonpolar protein surface. PMID:9255944

Esposito, G; Fogolari, F; Damante, G; Formisano, S; Tell, G; Leonardi, A; Di Lauro, R; Viglino, P

1997-06-01

139

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.

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

140

Meridional distribution of molecular hydrogen and its deuterium content in the atmosphere  

NASA Astrophysics Data System (ADS)

The atmospheric molecular hydrogen concentration and its deuterium abundance were measured in remote air samples collected onboard six Pacific Ocean ship transects between 37°N and 77°S during years 2001 through 2005. The data reveal a year-round interhemispheric gradient in H2 concentration and isotopic composition with the extratropical Northern Hemisphere lower in H2 concentration by 17 ± 11 ppb and ?D of H2 by 16 ± 12‰ than the Southern Hemisphere (95% confidence). On the basis of these snapshots, the interhemispheric gradient in ?D was observed to be smallest in September through November, a time that experiences the largest gradient in concentration, and the largest in April, a time that has a small gradient in concentration. A simple hemispheric box model of the atmosphere indicates that, while the hemispheric asymmetry in soil sink of H2 is primarily responsible for the observed interhemispheric gradient in H2 concentration, the hemispheric difference in the ?D of the H2 sources and sinks are equally responsible for the observed interhemispheric gradient in ?D. Both the inverse correlation between interhemispheric H2 and ?D gradients and their seasonal changes point to the importance of the H2 produced by photochemical sources. Comparisons with a three-dimensional chemical transport model shows reasonable agreement with mean behavior in both variables and provides an accounting for H2 sources and sinks within ±15% without a dramatic change in the H2 budget. Anomalous H2 concentrations and ?D in tropics and low-latitude regions observed during the November-December 2001 meridional H2 and ?D snapshot is thought to be a result of H2 emissions from biomass burning, possibly from continental Africa.

Rice, Andrew; Quay, Paul; Stutsman, Johnny; Gammon, Richard; Price, Heather; Jaeglé, Lyatt

2010-06-01

141

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

142

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

NASA Astrophysics Data System (ADS)

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

Ahmed, Arif; Kim, Sunghwan

2013-12-01

143

Effects of protein-ligand interactions on hydrogen/deuterium exchange kinetics: canonical and noncanonical scenarios.  

PubMed

Hydrogen/deuterium exchange (HDX) methods are widely used for monitoring protein-ligand interactions. This approach relies on the fact that ligand binding can modulate the extent of protein structural fluctuations that transiently disrupt hydrogen bonds and expose backbone amides to the solvent. It is commonly observed that ligand binding causes a reduction of HDX rates. This reduction can be restricted to elements adjacent to the binding site, but other regions can be affected as well. Qualitatively, ligand-induced HDX protection can be rationalized on the basis of two-state models that equate structural dynamics with global unfolding/refolding. Unfortunately, such models tend to be unrealistic because the dynamics of native proteins are dominated by subglobal transitions and local fluctuations. Ligand binding lowers the ground-state free energy. It is not obvious why this should necessarily be accompanied by a depletion of excited-state occupancies, which would be required for a reduction of HDX rates. Here, we propose a framework that implies that ligand binding can either slow or accelerate amide deuteration throughout the protein. These scenarios are referred to as "type 1" and "type 2", respectively. Evidence for type 1 binding is abundant in the literature, whereas the viability of type 2 interactions is less clear. Using HDX mass spectrometry (MS), we demonstrate that the oxygenation of hemoglobin (Hb) provides a dramatic example of a type 2 scenario. The observed behavior is consistent with cooperative T ? R switching, where part of the intrinsic O2 binding energy is reinvested for destabilization of the ground state. This destabilization increases the Boltzmann occupancy of unfolded conformers, thereby enhancing HDX rates. Surprisingly, O2 binding to myoglobin (Mb) also induces elevated HDX rates. These Mb data reveal that type 2 behavior is not limited to cooperative multisubunit systems. Although enhanced protection from deuteration is widely considered to be a hallmark of protein-ligand interactions, this work establishes that an overall deuteration increase also represents a viable outcome. HDX-based ligand screening assays, therefore, have to allow for canonical as well as noncanonical effects. PMID:24904985

Sowole, Modupeola A; Konermann, Lars

2014-07-01

144

Hydrogen storage on activated carbon. Final report  

SciTech Connect

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

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

1994-11-01

145

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

146

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

NASA Astrophysics Data System (ADS)

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

Lee, Anthony Story

147

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

148

Resolving isotopic fine structure to detect and quantify natural abundance- and hydrogen/deuterium exchange-derived isotopomers.  

PubMed

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

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

2014-01-01

149

Hydrogen/deuterium exchange in parallel with acid/base induced protein conformational change in electrospray droplets.  

PubMed

The exposure of electrospray droplets to vapors of deuterating reagents during droplet desolvation in the interface of a mass spectrometer results in hydrogen/deuterium exchange (HDX) on the sub-millisecond time scale. Deuterated water is used to label ubiquitin and cytochrome c with minimal effect on the observed charge state distribution (CSD), suggesting that the protein conformation is not being altered. However, the introduction of deuterated versions of various acids (e.g., CD3 COOD and DCl) and bases (ND3 ) induces unfolding or refolding of the protein while also labeling these newly formed conformations. The extent of HDX within a protein CSD associated with a particular conformation is essentially constant, whereas the extent of HDX can differ significantly for CSDs associated with different conformations from the same protein. In some cases, multiple HDX distributions can be observed within a given charge state (as is demonstrated with cytochrome c) suggesting that the extent of HDX and CSDs share a degree of complementarity in their sensitivities for protein conformation. The CSD is established late in the evolution of ions in electrospray whereas the HDX process presumably takes place in the bulk of the droplet throughout the electrospray process. Back exchange is also performed in which proteins are prepared in deuterated solvents prior to ionization and exposed to undeuterated vapors to exchange deuteriums for hydrogens. The degree of deuterium uptake is easily controlled by varying the identity and partial pressure of the reagent introduced into the interface. Since the exchange occurs on the sub-millisecond time scale, the use of deuterated acids or bases allows for transient species to be generated and labeled for subsequent mass analysis. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24913396

Kharlamova, Anastasia; Fisher, Christine M; McLuckey, Scott A

2014-06-01

150

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

151

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

PubMed

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. PMID:11543198

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

1999-12-25

152

Rapid Annealing Of Amorphous Hydrogenated Carbon  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

153

Equilibrium carbon and hydrogen isotope fractionation in iron  

NASA Astrophysics Data System (ADS)

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

Schauble, E. A.

2009-12-01

154

Parametric studies of carbon erosion mitigation dynamics in beryllium seeded deuterium plasmas  

NASA Astrophysics Data System (ADS)

The characteristic time of protective beryllium layer formation on a graphite target, ?Be/C, has been investigated as a function of surface temperature, Ts, ion energy, Ei, ion flux, ?i, and beryllium ion concentration, cBe, in beryllium seeded deuterium plasma. ?Be/C is found to be strongly decreased with increasing Ts in the range of 550-970 K. This is thought to be associated with the more efficient formation of beryllium carbide (Be 2C). By scanning the parameters, a scaling expression for ?Be/C has been derived as ?[s]=1.0×10-7cBe-1.9±0.1Ei0.9±0.3?i-0.6±0.3exp((4.8±0.5)×103/T), where cBe is dimensionless, Ei in eV, ?i in 10 22 m -2 s -1 and Ts in K. Should this scaling extend to an ITER scenario, carbon erosion of the divertor strike point region may be reduced with characteristic time of ˜6 ms. This is much shorter than the time between predicted ITER type I ELMs (˜1 s), and suggests that protective beryllium layers can be formed in between ELMs, and mitigate carbon erosion.

Nishijima, D.; Baldwin, M. J.; Doerner, R. P.; Seraydarian, R.

2007-06-01

155

Affinity capture of biotinylated proteins at acidic conditions to facilitate hydrogen/deuterium exchange mass spectrometry analysis of multimeric protein complexes.  

PubMed

Characterization of conformational and dynamic changes associated with protein interactions can be done by hydrogen/deuterium exchange mass spectrometry (HDX-MS) by comparing the deuterium uptake in the bound and unbound state of the proteins. Investigation of local hydrogen/deuterium exchange in heteromultimeric protein complexes poses a challenge for the method due to the increased complexity of the mixture of peptides originating from all interaction partners in the complex. Previously, interference of peptides from one interaction partner has been removed by immobilizing the intact protein on beads prior to the HDX-MS experiment. However, when studying protein complexes of more than two proteins, immobilization can possibly introduce steric limitations to the interactions. Here, we present a method based on the high affinity biotin-streptavidin interaction that allows selective capture of biotinylated proteins even under the extreme conditions for hydrogen/deuterium exchange quenching i.e. pH 2.5 and 0 °C. This biotin-streptavidin capture strategy allows hydrogen/deuterium exchange to occur in proteins in solution and enables characterization of specific proteins in heteromultimeric protein complexes without interference of peptides originating from other interaction partners in the complex. The biotin-streptavidin strategy has been successfully implemented in a model system with two recombinant monoclonal antibodies that target nonoverlapping epitopes on the human epidermal growth factor receptor (EGFR). We present a workflow for biotinylation and characterization of recombinant antibodies and demonstrate affinity capture of biotinylated antibodies under hydrogen/deuterium exchange quench conditions by the biotin-streptavidin strategy. PMID:23534402

Jensen, Pernille Foged; Jørgensen, Thomas J D; Koefoed, Klaus; Nygaard, Frank; Sen, Jette Wagtberg

2013-08-01

156

Simulation of hydrogen adsorption in carbon nanotubes  

NASA Astrophysics Data System (ADS)

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

Cracknell, Roger F.

157

Hydrogenation catalyst based on modified carbon nanofibers  

NASA Astrophysics Data System (ADS)

The aim of this work was to study the palladium-carboxylated carbon nanofibers (CNF) as a catalyst for the hydrogenation of nitrobenzene model reaction. It is shown that the efficiency of the catalyst obtained more than 6 times higher than that of the industrial counterpart (Pd/C).

Osipov, N. N.; Klyuev, M. V.

2012-02-01

158

Anomalous NMR Line Shapes in Solid Ordered OrthoHydrogen and Para-Deuterium  

Microsoft Academic Search

Some highly anomalous features have been observed in the low-temperature NMR spectrum of high-purity (> 99% J=1), solid para-deuterium. The intensity of the low-frequency side of the Pake doublet is enhanced and that of the high-frequency side reduced, sometimes becoming negative, corresponding to an emission of power. The anomaly is particularly pronounced and of the opposite sign for the I=2

Walter N. Hardy; A. John Berlinsky

1973-01-01

159

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

160

Computational and Empirical Trans-hydrogen Bond Deuterium Isotope Shifts Suggest that N1–N3 A:U Hydrogen Bonds of RNA are Shorter than those of A:T Hydrogen Bonds of DNA  

Microsoft Academic Search

Density functional theory calculations of isolated Watson–Crick A:U and A:T base pairs predict that adenine 13C2 trans-hydrogen bond deuterium isotope shifts due to isotopic substitution at the pyrimidine H3, 2h?13C2, are sensitive to the hydrogen-bond distance between the N1 of adenine and the N3 of uracil or thymine, which supports\\u000a the notion that 2h?13C2 is sensitive to hydrogen-bond strength. Calculated

Yong-Ick Kim; Marlon N. Manalo; Lisa M. Peréz; Andy LiWang

2006-01-01

161

Methods for the Synthesis of L-Leucine Selectively Labelled with Carbon13 or Deuterium in either Diastereotopic Methyl Group  

Microsoft Academic Search

A versatile approach is described for the enantioselective synthesis of isotopically labelled L-leucine involving the preparation of 2-oxo-4-methylpentanoic acid labelled selectively with carbon-13 or deuterium in either the pro-R or pro-S methyl group followed by a reductive amination of the ketone catalysed by leucine dehydrogenase. This strategy is applied to the total synthesis of (2S.4R)-[5.5.5-D3]-leucine using CD3I as the source

Nicholas M. Kelly; R. Gordon Reid; Christine L. Willis; Peter L. Winton

1995-01-01

162

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

163

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

164

Wave Packet Molecular Dynamics Simulations of the Equation of State of Hydrogen and Deuterium Under Extreme Conditions  

NASA Astrophysics Data System (ADS)

Recent laser shock-wave experiments by Da Silva et al.1 with deuterium in a regime where a plasma phase-trasition has been predicted5 are a topic of many current discussions (e.g.2,3,4,12,13). In this paper we apply "Wave Packet Molecular Dynamics" (WPMD) simulations to the equation of state of hydrogen at constant temperature T = 300 K and of deuterium at constant hugoniot E - E0 +(1)/(2)(V - V0)(p + p0) = 0 and compare them with experiments and several theoretical approaches. The WPMD method was originally used by Heller for a description of the scattering of composite particles like simple atoms and molecules7; later it was applied to Coulomb systems by Klakow et al.8,9. In the present version of our model the protons are treated as classical point-particles, whereas the electrons are represented by a completely anti-symmetrized Slater-sum of periodic Gaussian wavepackets.

Knaup, M.; Reinhard, P.-G.; Toepffer, C.

2001-09-01

165

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

PubMed Central

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

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

2009-01-01

166

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

167

Hydrogen and deuterium permeation in copper alloys, copper--gold brazing alloys, gold, and the in situ growth of stable oxide permeation barriers  

Microsoft Academic Search

The deuterium permeation through several copper alloys has been measured over a temperature range of 550 to 830 K using the membrane technique. In some cases, the hydrogen permeability was also measured. The results were divided into three categories: common alloys, gold alloys, and stable oxide forming alloys. Common alloys which showed typical bulk metallic diffusion with litle change in

David R. Begeal

1978-01-01

168

Top-down mass spectrometry and hydrogen/deuterium exchange for comprehensive structural characterization of interferons: implications for biosimilars.  

PubMed

Rapid development in biopharmaceuticals has put high demands on analytical tools that can provide accurate and comprehensive characterization of protein drugs, including biosimilars. Although the enzyme digestion based "bottom-up" approach is usually the method of choice for this purpose, it only gives peptide-level information and sequence coverage is often incomplete. In this work, we used top-down MS with electron capture dissociation (ECD) to characterize both the primary and higher order structures of a therapeutic protein interferon and its variants. Accurate mass measurement at the intact protein level combined with top-down ECD fragmentation enabled unambiguous protein sequence confirmation and identification of all PTMs. Combining hydrogen/deuterium exchange and rapid disulfide reduction with top-down ECD on the LC time scale, we have investigated the differences in higher order structure between the protein variants, as well as the impact of PTMs on protein conformation. PMID:24574185

Pan, Jingxi; Borchers, Christoph H

2014-05-01

169

Low-temperature phases of dense hydrogen and deuterium by first-principles path-integral molecular dynamics  

NASA Astrophysics Data System (ADS)

The low-temperature phases of dense hydrogen and deuterium have been investigated using first-principles path-integral molecular dynamics, a technique that we have recently implemented in the ABINIT code and that allows to account for the quantum fluctuations of atomic nuclei. A massively parallelized scheme is applied to produce trajectories of several tens of thousands steps using a 64-atom supercell and a Trotter number of 64. The so-called phases I, II and III are studied and compared to the structures proposed in the literature. The quantum fluctuations produce configurational disorder and are shown to systematically enhance the symmetry of the system: a continuous gain of symmetry in the angular density of probability of the molecules is found from classical particles to quantum D2 and finally to quantum H2. Particular emphasis is made on the ``broken-symmetry'' phase (phase II).

Torrent, Marc; Geneste, Gregory

2012-02-01

170

Infrared, Raman, and coherent anti-Stokes Raman spectroscopy of the hydrogen/deuterium isotopomers of nitromethane  

SciTech Connect

The vibrational spectroscopy of the four hydrogen/deuterium isotopomers of nitromethane was investigated. Infrared, Raman, and coherent anti-Stokes Raman spectroscopy (CARS) of the isotopomers were used to determine vibrational frequencies for each isotopomer. Results for the d{sub 0}, d{sub 2}, and d{sub 3} isotopomers agree well with literature values. Gas- and liquid-phase spectra for the d{sub 1} isotopomer are presented, and the measured vibrational frequencies compare well with a theoretical prediction. In addition, high-resolution Raman spectra of the CN stretch mode were used to analyze the elements of the anharmonic coupling matrix involving this mode. Finally, the relative differential Raman scattering cross section of the Cn stretch mode of each isotopomer was determined.

Hill, J.R.; Moore, D.S.; Schmidt, S.C.; Storm, C.B. (Los Alamos National Lab., NM (United States))

1991-04-18

171

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

172

Analysis of hydrogen and deuterium by secondary ion mass spectrometry as applied to fusion technology  

SciTech Connect

This paper will focus on hydrogen detection using secondary ion mass spectrometry (SIMS), an established technique that has been used relatively infrequently for hydrogen analysis in fusion research. Fusion technology-related examples will be shown of hydrogen detection using SIMS. These include flux and energy measurements of H and D in the edge plasma, H and D isotope saturation and exchange studies; and species-mix determination for H and D in neutral beams from high power injectors.

Magee, C.W.

1983-04-01

173

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

Microsoft Academic Search

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

B. B. Dayton

1948-01-01

174

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

NASA Astrophysics Data System (ADS)

The erosion yield by deuterium impact was determined for various doped carbon-based materials. Ion beam bombardment with 30 and 200 eV at elevated temperatures (600-850 K) and low temperature plasma exposure with 30 eV ion energy (˜7 × 10 20 ions/m 2s) and about 170 times higher thermal atomic deuterium flux at 300 K and 630 K were performed. The total yield of fine-grain graphites doped with 4 at.% Ti and Zr is reduced by a factor of 4 for 30 and 200 eV D impact at elevated temperatures at D fluences above 10 24 m -2 compared to undoped graphite. Extensive carbide particle loss can be excluded up to fluences of ˜10 25 m -2.

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

2011-10-01

175

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

NASA Astrophysics Data System (ADS)

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

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

1997-01-01

176

Hydrogenated amorphous carbon grains in Comet Halley  

SciTech Connect

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

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

1990-01-01

177

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

178

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

179

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

180

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

PubMed

Hydrogen-deuterium exchange (HDX) experiments analyzed by mass spectrometry (MS) provide information about the dynamics and the solvent accessibility of protein backbone amide hydrogen atoms. Continuous improvement of MS instrumentation has contributed to the increasing popularity of this method; however, comprehensive automated data analysis is only beginning to mature. We present Hexicon 2, an automated pipeline for data analysis and visualization based on the previously published program Hexicon (Lou et al. 2010). Hexicon 2 employs the sensitive NITPICK peak detection algorithm of its predecessor in a divide-and-conquer strategy and adds new features, such as chromatogram alignment and improved peptide sequence assignment. The unique feature of deuteration distribution estimation was retained in Hexicon 2 and improved using an iterative deconvolution algorithm that is robust even to noisy data. In addition, Hexicon 2 provides a data browser that facilitates quality control and provides convenient access to common data visualization tasks. Analysis of a benchmark dataset demonstrates superior performance of Hexicon 2 compared with its predecessor in terms of deuteration centroid recovery and deuteration distribution estimation. Hexicon 2 greatly reduces data analysis time compared with manual analysis, whereas the increased number of peptides provides redundant coverage of the entire protein sequence. Hexicon 2 is a standalone application available free of charge under http://hx2.mpimf-heidelberg.mpg.de . PMID:24676893

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

2014-06-01

181

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

182

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

SciTech Connect

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

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

2009-04-22

183

Study of order and dynamics in liquid crystalline materials by carbon-13 and deuterium NMR spectroscopy  

NASA Astrophysics Data System (ADS)

This dissertation investigates the phase structures, molecular structures and diffusion motions in some recently discovered liquid crystals using 1D and 2D carbon-13 and deuterium NMR spectroscopy. Two classes of liquid crystals are involved: chiral rod-like liquid crystals and banana mesogens. Our investigations of these new materials were divided into five main sections. The ordering and structures of banana liquid crystals and chiral rod-like mesogens were extracted from solid-state 13C NMR experiments including Separated-Local-Field study based on Lee-Goldberg Cross-Polarization (LGCP-SLF) and temperature dependent chemical shifts. The principal values of CSA tensor were measured using Separation of Undistorted CSA Powder patterns by Effortless Recoupling (SUPER) experiment. Some ID and 2D pulse experiments were performed for the assignment of carbon peaks, such as Cross-Polarization Polarization-Inversion (CPPI), HECTOR and so on. The soliton-like distortion of the helicoidal structure in the chiral smectic C phase (SmC*) of 8BEF5 liquid crystal was observed by the angular dependent DNMR patterns, and quantitatively interpreted based on Landau theory. The distortion was induced by the NMR magnetic field. The phase structure and interlayer diffusion in anticlinic Sm C* phases (Sm C*A , Sm C*Fi1 and Sm C*Fi2 ) of 10B1M7 liquid crystal were measured using angular dependent DNMR lineshapes and echo intensities. This work represents the first study of ferrielectric smectic phases by means of NMR. Measurements of the interlayer diffusion in synclinic and anticlinic SmC* phases (SmC*, Sm C*Fi1 and Sm C*Fi2 ) of 10B1M7 were carried out using 2H NMR exchange experiments. The phase structures of anticlinic SmC* phases were also determined using the same technique. A 'deformed clock model' was found to be appropriate for these phases. Molecular structures and dynamics were investigated in an exotic B 2 phase of a banana liquid crystal Pbis11BB by means of CP-MAS 13C NMR, MAS 2D 13C NMR exchange and LGCP-SLF (with MAS) experiments. These experiments showed that the molecules have asymmetric conformation in the solid state and carry on much slower motions in solid and liquid states compared to banana molecules in the same homologous series.

Xu, Jiadi

184

Functionalized carbon nanostructures for hydrogen catalysis  

NASA Astrophysics Data System (ADS)

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

Hu, Lung-Hao

185

Hydrogen adsorption\\/desorption properties of mechanically milled activated carbon  

Microsoft Academic Search

We investigated the hydrogen adsorption\\/desorption properties of activated carbon that was prepared by mechanical milling in a hydrogen atmosphere at an ambient temperature. Although the hydrogen concentration estimated by inert gas fusion-thermal conductivity method increased with milling time up to 10 h, samples milled for longer than 10 h showed little dependence on milling time. Ultimately, the hydrogen concentration reached

K. Shindo; T. Kondo; M. Arakawa; Y. Sakurai

2003-01-01

186

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

NASA Astrophysics Data System (ADS)

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

Smith, Kyle K. G.; Poulsen, Jens Aage; Cunsolo, A.; Rossky, Peter J.

2014-01-01

187

Carbon dioxide hydrogenation on Ni(110).  

PubMed

We demonstrate that the key step for the reaction of CO 2 with hydrogen on Ni(110) is a change of the activated molecule coordination to the metal surface. At 90 K, CO 2 is negatively charged and chemically bonded via the carbon atom. When the temperature is increased and H approaches, the H-CO 2 complex flips and binds to the surface through the two oxygen atoms, while H binds to the carbon atom, thus yielding formate. We provide the atomic-level description of this process by means of conventional ultrahigh vacuum surface science techniques combined with density functional theory calculations and corroborated by high pressure reactivity tests. Knowledge about the details of the mechanisms involved in this reaction can yield a deeper comprehension of heterogeneous catalytic organic synthesis processes involving carbon dioxide as a reactant. We show why on Ni the CO 2 hydrogenation barrier is remarkably smaller than that on the common Cu metal-based catalyst. Our results provide a possible interpretation of the observed high catalytic activity of NiCu alloys. PMID:18665600

Vesselli, Erik; De Rogatis, Loredana; Ding, Xunlei; Baraldi, Alessandro; Savio, Letizia; Vattuone, Luca; Rocca, Mario; Fornasiero, Paolo; Peressi, Maria; Baldereschi, Alfonso; Rosei, Renzo; Comelli, Giovanni

2008-08-27

188

Damages of Carbon-Tungsten Samples under Influence of Deuterium Ions and Dense Plasma Streams within Plasma-Focus Facility  

SciTech Connect

The paper reports on experimental studies of processes of the interaction of pulsed streams of fast deuterium ions (E{sub i}{approx}100 keV) and dense deuterium plasma (v{sub pl}>10{sup 7} cm/s) with samples made of carbon and tungsten. Experiments were performed in the large PF-1000 plasma-focus facility with the charging energy of 481 kJ and with the pure deuterium filling. Power flux density of plasma/ions streams was q = 10{sup 7}-10{sup 10} W/cm{sup 2} and the pulse length was from 10{sup -7} s to 10{sup -6} s, whereas the duration of heat pulses (due to a secondary plasma at the target's surface) was 10{sup -4} s. The stainless steel, tungsten and carbon-tungsten samples were placed in the zone of their strong melting and evaporation or in the zone without their melting. Each sample was exposed to 1 through 10 discharges, and the irradiated samples were investigated with optical-, electron- and atomic-force-microscopes. The interaction of intense plasma-ion pulses with the carbon-tungsten samples caused the formation of a wave-like relief on sample surfaces, the evident erosion of the sample material, and the creation of numerous micro-cracks. It was also found that about 200-nm-thick layer of the irradiated tungsten sample contained many melted fragments of nm-dimensions. The results might be useful for estimations of tungsten behavior in extreme situations (e.g. disruptions) expected in fusion reactors with magnetic plasma confinement.

Gribkov, V. A. [A.I. Alikhanov Institute of Theoretical and Experimental Physics, 117218 Moscow (Russian Federation); Institute of Plasma Physics and Laser Microfusion, 23 Hery St. 00-908 Warsaw (Poland); Grebenschikova, Ye. S.; Dubrovsky, A. V.; Makeev, O. N.; Rogozhkin, S. V.; Zaluzhnij, A. G. [A.I. Alikhanov Institute of Theoretical and Experimental Physics, 117218 Moscow (Russian Federation); Demina, Ye. V.; Kovtun, A. V.; Maslayev, S. A.; Pimenov, V. N. [A.A. Baykov Institute of Metallurgy and Material Science, 119991 Moscow (Russian Federation); Malinowski, K.; Skladnik-Sadowska, E. [A. Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk n. Warsaw (Poland); Paduch, M.; Scholz, M. [Institute of Plasma Physics and Laser Microfusion, 23 Hery St. 00-908 Warsaw (Poland); Sadowski, M. J. [Institute of Plasma Physics and Laser Microfusion, 23 Hery St. 00-908 Warsaw (Poland); A. Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk n. Warsaw (Poland)

2008-03-19

189

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

PubMed Central

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

Engen, John R.

2009-01-01

190

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

191

Carbon assisted water electrolysis for hydrogen generation  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

192

Computational investigation and hydrogen\\/deuterium exchange of the fixed charge derivative tris(2,4,6-Trimethoxyphenyl) phosphonium: Implications for the aspartic acid cleavage mechanism  

Microsoft Academic Search

Aspartic acid (Asp)-containing peptides with the fixed charge derivative tris(2,4,6trimethoxyphenyl) phosphonium (tTMP-P+) were explored computationally and experimentally by hydrogen\\/deuterium (H\\/D) exchange and by fragmentation studies to probe\\u000a the phenomenon of selective cleavage C-terminal to Asp in the absence of a “mobile” proton. Ab initio modeling of the tTMP-P+ electrostatic potential shows that the positive charge is distributed on the phosphonium

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

2005-01-01

193

Mass Spectrometric Approaches Using Electrospray Ionization Charge States and Hydrogen-Deuterium Exchange for Determining Protein Structures and Their Conformational Changes  

Microsoft Academic Search

Electrospray ionization (ESI) mass spectrometry (MS) is a powerful analytical tool for elucidating structural details of proteins in solution especially when coupled with am- ide 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

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

2003-01-01

194

Study of a polarized hydrogen ion source with deuterium plasma ionizer  

SciTech Connect

A description of the atomic beam polarized hydrogen ion source developed at the INR in Moscow is given. It is capable of producing polarized 100 {mu}sec long H{sup +} beams with currents up to 6 {mu}A. The beam is 85% polarized and has a normal emittance of 2{pi} mm mrad. Additionally polarized H{sup {minus}} beams have currents up to 200 {mu}A and normalized emittance 2.2 {pi} mm mrad. (AIP)

Belov, A.S. [Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, 117312, Russian Federation (Russian Federation); Derevyankin, G.E.; Dudnikov, V.G. [Budker Institute for Nuclear Physics of the Russian Academy of Sciences, Novosibirsk, 630090, Russian Federation (Russian Federation); Klenov, V.S.; Nechaeva, L.P.; Plohinsky, Y.V.; Vasil`ev, G.A.; Yakushev, V.P. [Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, 117312, Russian Federation (Russian Federation)

1995-07-15

195

Study of a polarized hydrogen ion source with deuterium plasma ionizer  

NASA Astrophysics Data System (ADS)

A description of the atomic beam polarized hydrogen ion source developed at the INR in Moscow is given. It is capable of producing polarized 100 ?sec long H+ beams with currents up to 6 ?A. The beam is 85% polarized and has a normal emittance of 2? mm mrad. Additionally polarized H- beams have currents up to 200 ?A and normalized emittance 2.2 ? mm mrad. (AIP)

Belov, A. S.; Derevyankin, G. E.; Dudnikov, V. G.; Klenov, V. S.; Nechaeva, L. P.; Plohinsky, Yu. V.; Vasil'ev, G. A.; Yakushev, V. P.

1995-07-01

196

The deuterium content of atmospheric molecular hydrogen: Method and initial measurements  

Microsoft Academic Search

A new technique for determining the deltaD of atmospheric molecular hydrogen (H2) at background mixing ratios is described in detail. An air sample is compressed into a high-pressure cylinder, after which the cylinder is cooled to -196°C to condense the air and generate a headspace greatly enriched in H2. The H2-enriched headspace is collected and admitted into a high-vacuum extraction

Steve Gerst; Paul Quay

2000-01-01

197

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

198

Direct evidence for a two-state protein unfolding transition from hydrogen-deuterium exchange, mass spectrometry, and NMR.  

PubMed

We use mass spectrometry in conjunction with hydrogen-deuterium exchange and NMR to characterize the conformational dynamics of the 62-residue IgG binding domain of protein L under conditions in which the native state is marginally stable. Mass spectra of protein L after short incubations in D2O reveal the presence of two distinct populations containing different numbers of protected protons. NMR experiments indicate that protons in the hydrophobic core are protected in one population, whereas all protons are exchanged for deuterons in the other. As the exchange period is increased, molecules are transferred from the former population to the latter. The absence of molecules with a subset of the core protons protected suggests that exchange occurs in part via a highly concerted transition to an excited state in which all protons exchange rapidly with deuterons. A steady increase in the molecular weight of the population with protected protons, and variation in the exchange rates of the individual protected protons indicates the presence of an additional exchange mechanism. A simple model in which exchange results from rapid (> 10(5)/s) local fluctuations around the native state superimposed upon transitions to an unfolded excited state at approximately 0.06/s is supported by qualitative agreement between the observed mass spectra and the mass spectra simulated according to the model using NMR-derived estimates of the proton exchange rates. PMID:8762137

Yi, Q; Baker, D

1996-06-01

199

Lattice vibrations of para-hydrogen impurities in a solid deuterium matrix: An inelastic neutron scattering study  

NASA Astrophysics Data System (ADS)

In the present study, we report inelastic neutron scattering measurements from para-hydrogen defects in solid normal deuterium at three different concentrations (between 3% and 11%) using the time-of-flight spectrometer TOSCA-II. The measured double-differential cross sections give access to the self-inelastic structure factors for the H2 centers of mass. Corrected experimental data, analyzed through the Young-Koppel model and the Gaussian approximation, are transformed into defect densities of phonon states, which come out to be broad, structured, and nearly concentration independent. Two experimentally determined Bose-corrected spectral moments are found to be in agreement with independent estimates, providing a strong validation of our data reduction procedure. Subsequently, experimental phonon spectra are compared to three calculations, namely, a simple harmonic model at infinite dilution, a more advanced harmonic model with concentration effects, and finally a lattice dynamics simulation based on self-consistent phonon and coherent potential approximations. However, while the first part of the defect spectral density, attributed to the propagating modes, turns out to be roughly explained, the localized part is properly described by none of these models, except for its mean frequency position. The large overall width appears so far impossible to be reproduced, representing a challenge for the physicists involved in quantum dynamics simulations.

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

2007-11-01

200

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

SciTech Connect

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

Earnest, T.N.; Herzfeld, J.; Rothschild, K.J. (Boston Univ., MA (USA))

1990-12-01

201

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

202

Interrupted Hydrogen/Deuterium Exchange Reveals the Stable Core of the Remarkably Helical Molten Globule of ?-? Parallel Protein Flavodoxin  

PubMed Central

Kinetic intermediates that appear early during protein folding often resemble the relatively stable molten globule intermediates formed by several proteins under mildly denaturing conditions. Molten globules have a substantial amount of secondary structure but lack virtually all tertiary side-chain packing characteristics of natively folded proteins. Due to exposed hydrophobic groups, molten globules are prone to aggregation, which can have detrimental effects on organisms. The molten globule that is observed during folding of ?-? parallel flavodoxin from Azotobacter vinelandii is a remarkably non-native species. This folding intermediate is helical and contains no ?-sheet and is kinetically off-pathway to the native state. It can be trapped under native-like conditions by substituting residue Phe44 for Tyr44. To characterize this species at the residue level, in this study, use is made of interrupted hydrogen/deuterium exchange detected by NMR spectroscopy. In the molten globule of flavodoxin, the helical region comprising residues Leu110-Val125 is shown to be better protected against exchange than the other ordered parts of the folding intermediate. This helical region is better buried than the other helices, causing its context-dependent stabilization against unfolding. Residues Leu110–Val125 thus form the stable core of the helical molten globule of ?-? parallel flavodoxin, which is almost entirely structured. Non-native docking of helices in the molten globule of flavodoxin prevents formation of the parallel ?-sheet of native flavodoxin. Hence, to produce native ?-? parallel protein molecules, the off-pathway species needs to unfold.

Nabuurs, Sanne M.; van Mierlo, Carlo P. M.

2010-01-01

203

Changes in the Factor VIII C2 domain upon membrane binding determined by hydrogen-deuterium exchange MS.  

PubMed

Factor VIII enhances the catalytic activity of Factor IXa in a membrane-bound enzyme complex and both proteins are necessary to prevent haemophilia. Tandem lectin-like C domains mediate the membrane binding of Factor VIII and membrane-interactive residues have been identified. However, the available data provide little insight into the dynamic changes that occur upon membrane binding. We used time-based hydrogen-deuterium exchange MS to evaluate the dynamics of FVIII-C2 (Factor VIII C2 domain) alone and when membrane bound. The results confirm the participation of previously identified membrane-interactive loops in the binding mechanism. In addition, they indicate that a long peptide segment, encompassing a membrane-interactive loop and strands of the ?-barrel core, is remarkably dynamic prior to membrane binding. The flexibility is reduced following membrane binding. In addition, regions that interact with the A1 and C1 domains have reduced solvent exchange. Thus the isolated C2 domain has extensive flexibility that is subject to stabilization and could be related to interactions between domains as well as between Factor VIII and Factor IXa or Factor X. These results confirm that the proposed membrane-binding loops of the FVIII-C2 interact with the membrane in a manner that leads to protection from solvent exposure. PMID:24814520

Pantazatos, Dionysios; Gessner, Christopher R; Woods, Virgil L; Gilbert, Gary E

2014-08-01

204

NMR-Based Amide Hydrogen-Deuterium Exchange Measurements for Complex Membrane Proteins: Development and Critical Evaluation  

NASA Astrophysics Data System (ADS)

A method for measuring site-specific amide hydrogen-deuterium exchange rates for membrane proteins in bilayers is reported and evaluated. This method represents an adaptation and extension of the approach of Dempsey and co-workers ( Biophys. J. 70, 1777-1788 (1996)) and is based on reconstituting 15N-labeled membrane proteins into phospholipid bilayers, followed by lyophilization and rehydration with D 2O or H 2O (control). Following incubation for a time t under hydrated conditions, samples are again lyophilized and then solubilized in an organic solvent system, where 1H- 15N HSQC spectra are recorded. Comparison of spectra from D 2O-exposed samples to spectra from control samples yields the extent of the H-D exchange which occurred in the bilayers during time t. Measurements are site specific if specific 15N labeling is used. The first part of this paper deals with the search for a suitable solvent system in which to solubilize complex membrane proteins in an amide "exchange-trapped" form for NMR quantitation of amide peak intensities. The second portion of the paper documents application of the overall procedure to measuring site-specific amide exchange rates in diacylglycerol kinase, a representative integral membrane protein. Both the potential usefulness and the significant limitations of the new method are documented.

Czerski, Lech; Vinogradova, Olga; Sanders, Charles R.

2000-01-01

205

Confinement of hydrogen at high pressure in carbon nanotubes  

DOEpatents

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

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

2011-12-13

206

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

PubMed Central

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

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

2009-01-01

207

Deuterium Retention in the Co-Deposition Carbon Layers Deposited by Radio-Frequency Magnetron Sputtering in D2 Atmosphere  

NASA Astrophysics Data System (ADS)

Carbon is deposited on C and Si substrates by rf magnetron plasma sputtering in a D2 atmosphere. The deposited layers are examined with ion beam analysis and thermal desorption spectroscopy (TDS). The growth rates of the layers deposited on Si decrease with increasing substrate temperature, while increase significantly with the increase of D2 pressure. Meanwhile, the deuterium concentrations in the layers deposited on the Si substrates decrease from 30% to 2% and from 31% to 1% on the C substrates, respectively, when the substrate temperature varies from 350K to 900 K. Similarly, the D concentration in the layer on the Si substrates increases from 3.4% to 47%, and from 8% to 35% on the C substrates when the D2 pressure increases from 0.3Pa to 8.0Pa. D desorption characterized by TDS is mainly in the forms of D2, HD, HDO, CD4, and C2D4, and a similar release peak occurs at 645 K. The release peak of D2 molecules at 960K can be attributed to the escaped gas from the thin co-deposited deuterium-rich carbon layer in the form of C–D bonding.

Zhang, Wei-Yuan; Shi, Li-Qun; Zhang, Bin; Hu, Jian-Sheng

2014-05-01

208

The solubility of hydrogen and deuterium in crystalline Pd{sub 9}Si{sub 2}  

SciTech Connect

Isotherms have been measured for H(D){sub 2}(g) solution in crystalline Pd{sub 9}Si{sub 2} in the temperature range from 235 to 373 K. The solubilities are significant, e.g., at 1.0 MPa (298 K), (H/Pd) = 0.052 or Pd{sub 9}Si{sub 2}H{sub 0.47}, however, there is no indication of hydride phase formation even down to 235 K at 1.0 MPa. The thermodynamic values for hydrogen solutions at infinite dilution of hydrogen are {Delta}H{degrees}{sub H}= -11.9 kJ/mole {1/2}H{sub 2} and {Delta}S{degrees}{sub H} = -50 J/K mole {1/2}H{sub 2}. The former is more negative than for Pd-H{sub 2} and the latter is somewhat more positive; but generally the values are not that different from Pd-H{sub 2}. The isotope effect is similar to that found for Pd-H(D){sub 2}.

Flanagan, T.B.; Noh, H.; Craft, A. [Univ. of Vermont, Burlington, VT (United States)] [Univ. of Vermont, Burlington, VT (United States); Andersson, Y. [Univ. of Uppsala (Sweden)] [Univ. of Uppsala (Sweden)

1995-11-15

209

Determination of the charge on carbon in a bridging methylene iron dimer with solid-state deuterium NMR spectroscopy  

SciTech Connect

The chemistry of bridging methylene metal dimers and the value of the /sup 13/C NMR chemical shifts have been interpreted as due to a partial negative charge on the carbon atom. PES yields a C/sub 1s/ binding energy indicative of -0.5 e charge. However, for (..mu..-CH/sub 2/)(MnCp(CO)/sub 2/)/sub 2/, a high-resolution x-ray diffraction electron density map shows no excess charge buildup. The authors are attempting to resolve the dilemma by using solid-state deuterium NMR techniques. In the results for cis-(..mu..-C/sup 2/H/sub 2/)(..sigma..-CO)(FeCp/sup d/(CO))/sub 2/ (Cp/sup d/ and 5% deuteriated cyclopentadienyl) presented here, the authors find no evidence for an excess negative charge on the bridging methylene carbon atom.

Altbach, M.I.; Hiyama, Y.; Gerson, D.J.; Butler, L.G.

1987-09-02

210

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

PubMed

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

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

2006-05-01

211

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

212

Material processing with hydrogen and carbon monoxide on Mars  

Microsoft Academic Search

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,

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

1991-01-01

213

Process and catalyst for hydrogenation of carbon oxides  

US Patent & Trademark Office Database

A process for hydrogenation of carbon oxides comprising contacting a gas mixture containing carbon oxides and of hydrogen with a catalyst comprising bimetallic iron-nickel or iron-cobalt alloys as the active catalytic material supported on a carrier of an oxide. The carrier is preferably formed to have a surface area greater than 20 m.sup.2/g.

2010-09-07

214

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

NASA Astrophysics Data System (ADS)

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

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

1983-09-01

215

Process for producing carbon monoxide and hydrogen from methanol  

SciTech Connect

A process is described for producing carbon monoxide and hydrogen which comprises contacting methanol vapor at a temperature of 200 degrees to 300 degrees C with an indirectly heated zinc containing catalyst to obtain an effluent gas in which the components of carbon monoxide and hydrogen constitute at least 90% by volume of said gas. At least a part of the impurities from said effluent gas are removed and said effluent gas is deparated into its carbon monoxide and hydrogen components by adsorption. The effluent gas can be separated into its carbon monoxide and hydrogen components by use of a plurality of adsorbers containing zeolite-type molecular sieve material where the zeolite is substantially permeable to hydrogen but sorbs carbon monoxide.

Jockel, H.; Marschner, F.; Moller, F.W.; Mortel, H.

1982-02-23

216

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

PubMed

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

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

2003-08-21

217

The deuterium content of atmospheric molecular hydrogen: Method and initial measurements  

NASA Astrophysics Data System (ADS)

A new technique for determining the ?D of atmospheric molecular hydrogen (H2) at background mixing ratios is described in detail. An air sample is compressed into a high-pressure cylinder, after which the cylinder is cooled to -196°C to condense the air and generate a headspace greatly enriched in H2. The H2-enriched headspace is collected and admitted into a high-vacuum extraction line, where the H2 is separated from the headspace gases by combustion to water followed by cryogenic collection. The H2-derived water is then reduced back to H2 for measurement of its D/H content via isotope-ratio mass spectrometry. The primary limitation of the method is contamination during compressor collection and subsequent storage of air samples in high-pressure cylinders. The ?D of atmospheric H2 was measured on air samples collected between 46°N and 72°S during a research cruise in the Pacific Ocean during 1998 and at Cheeka Peak, Washington (48°N), during 1997-1999 and Point Barrow, Alaska (71°N), during 1996-1997. These measurements yield a global average ?D of atmospheric H2 of +130+/-4‰ and average Northern and Southern Hemispheric ?D values of +123+/-3‰ and +138+/-8‰, respectively (versus Vienna standard mean ocean water).

Gerst, Steve; Quay, Paul

2000-11-01

218

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

NASA Astrophysics Data System (ADS)

The distribution and atmospheric budgets for molecular hydrogen and its deuterium component ?D are simulated with the GEOS-Chem global chemical transport model and constrained by observations of H2 from the NOAA Climate Monitoring and Diagnostics Laboratory network and ?D observations from ship and ground stations. Our simulation includes a primary H2 source of 38.8 Tg a-1 (22.7 Tg a-1 from fossil and biofuels, 10.1 Tg a-1 from biomass burning, 6.0 Tg a-1 from the ocean) (where a is years) and a secondary photochemical source from photolysis of formaldehyde of 34.3 Tg a-1. The simulated global tropospheric mean H2 is 525 ppbv, with a tropospheric burden of 141 Tg and tropospheric lifetime of 1.9 a. Uptake by enzymes in soils accounts for 75% of the H2 sink, with the remainder due to reaction with OH. The model captures the observed latitudinal, vertical, and seasonal variations of H2. For ?D we find that a photochemical source signature from methane and biogenic volatile organic compound oxidation of 162‰ yields a global mean atmospheric ?D of 130‰, consistent with atmospheric observations. The model captures the observed latitudinal gradient in ?D, simulating a 21‰ greater enrichment in the Southern Hemisphere because of the predominance of isotopically depleted fossil fuel emissions in the Northern Hemisphere. We find that stratospheric-tropospheric exchange results in 37‰ enrichment of tropospheric ?D. Our simulation provides new simultaneous constraints on the H2 soil sink (55 ± 8 Tg a-1), the ocean source (6 ± 3 Tg a-1), and the isotopic signature for photochemical production (162 ± 57‰).

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

2007-11-01

219

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

PubMed

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), specifically Group VIIA PLA(2), is a member of the phospholipase A(2) superfamily and is found mainly associated with LDL and HDL in human plasma. Lp-PLA(2) is considered as a risk factor, a potential biomarker, a target for therapy in the treatment of cardiovascular disease, and evidence suggests that the level of Lp-PLA(2) in plasma is associated with the risk of future cardiovascular and stroke events. The differential location of the enzyme in LDL/HDL lipoproteins has been suggested to affect Lp-PLA(2) function and/or its physiological role and an abnormal distribution of the enzyme may correlate with diseases. Although a mutagenesis study suggested that a surface helix (residues 362-369) mediates the association between Lp-PLA(2) and HDL, the molecular details and mechanism of association has remained unknown. We have now employed hydrogen deuterium exchange mass spectrometry to characterize the interaction between recombinant human Lp-PLA(2) and human HDL. We have found that specific residues 113-120, 192-204, and 360-368 likely mediate HDL binding. In a previous study, we showed that residues 113-120 are important for Lp-PLA(2)-liposome interactions. We now find that residues 192-204 show a decreased deuteration level when Lp-PLA(2) is exposed to apoA-I, but not apoA-II, the most abundant apoproteins in HDL, and additionally, residues 360-368 are only affected by HDL.The results suggest that apoA-I and phospholipid membranes play crucial roles in Lp-PLA(2) localization to HDL. PMID:23089916

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

2013-01-01

220

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

NASA Astrophysics Data System (ADS)

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

Jiang, Qian

221

Hydrogen Permeation of Carbon Steel in Weak Alkaline Solution Containing Hydrogen Sulfide and Cyanide Ion  

Microsoft Academic Search

The hydrogen permeation behavior of carbon steel (CS) was investigated electrochemically in weak alkaline solutions containing hydrogen sulfide (HâS) with various cyanide ion (CN⁻) concentrations under open-circuit conditions. Anodic and cathodic polarization behaviors of CS also were investigated under the same environmental conditions. Little hydrogen content (Câ) was detected in alkaline solutions without CN⁻. However, when a small amount of

K. Yamakawa; R. Nishimura

1999-01-01

222

Hydrogenation, purification, and unzipping of carbon nanotubes by reaction with molecular hydrogen: road to graphane nanoribbons.  

PubMed

Reaction of single-walled carbon nanotubes (SWNTs) with hydrogen gas was studied in a temperature interval of 400-550 °C and at hydrogen pressure of 50 bar. Hydrogenation of nanotubes was observed for samples treated at 400-450 °C with about 1/3 of carbon atoms forming covalent C-H bonds, whereas hydrogen treatment at higher temperatures (550 °C) occurs as an etching. Unzipping of some SWNTs into graphene nanoribbons is observed as a result of hydrogenation at 400-550 °C. Annealing in hydrogen gas at elevated conditions for prolonged periods of time (72 h) is demonstrated to result also in nanotube opening, purification of nanotubes from amorphous carbon, and removal of carbon coatings from Fe catalyst particles, which allows their complete elimination by acid treatment. PMID:21504190

Talyzin, Alexandr V; Luzan, Serhiy; Anoshkin, Ilya V; Nasibulin, Albert G; Jiang, Hua; Kauppinen, Esko I; Mikoushkin, Valery M; Shnitov, Vladimir V; Marchenko, Dmitry E; Noréus, Dag

2011-06-28

223

Structural dynamics of soluble chloride intracellular channel protein CLIC1 examined by amide hydrogen-deuterium exchange mass spectrometry.  

PubMed

Chloride intracellular channel protein 1 (CLIC1) functions as an anion channel in plasma and nuclear membranes when its soluble monomeric form converts to an integral-membrane form. The transmembrane region of CLIC1 is located in its thioredoxin-like domain 1, but the mechanism whereby the protein converts to its membrane conformation has yet to be determined. Since channel formation in membranes is enhanced at low pH (5 to 5.5), a condition that is found at the surface of membranes, the structural dynamics of soluble CLIC1 was studied at pH 7 and at pH 5.5 in the absence of membranes by amide hydrogen-deuterium exchange mass spectrometry (DXMS). Rapid hydrogen exchange data indicate that CLIC1 displays a similar core structure at these pH values. Domain 1 is less stable than the all-helical domain 2, and, while the structure of domain 1 remains intact, its conformational flexibility is further increased in an acidic environment (pH 5.5). In the absence of membrane, an acidic environment appears to prime the solution structure of CLIC1 by destabilizing domain 1 in order to lower the activation energy barrier for its conversion to the membrane-insertion conformation. The significantly enhanced H/D-exchange rates at pH 5.5 displayed by two segments (peptides 11-31 and 68-82) could be due to the protonation of acidic residues in salt bridges. One of these segments (peptide 11-31) includes part of the transmembrane region which, in the solution structure, consists of helix alpha1. This helix is intrinsically stable and is most likely retained in the membrane conformation. Strand beta2, another element of the transmembrane region, displays a propensity to form a helical structure and has putative N- and C-capping motifs, suggesting that it too most likely forms a helix in a lipid bilayer. PMID:19650640

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

2009-09-01

224

Sticking coefficient of hydrogen and deuterium on silicates under interstellar conditions  

NASA Astrophysics Data System (ADS)

Context. 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. Isotopic properties of the sticking can have an incidence on the observed HD molecule. Aims: 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. Methods: 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 coefficients of H2 and D2 molecules on a silicate surface and estimated the sticking coefficient of atoms by a single measurement of atomic recombination and propose an extrapolation. Results: Sticking of H, D, HD, H2, and D2 on silicates grains behaves the same as on icy dust grains. The sticking decreases with the gas temperature, and is dependent on the mass of the impactor. The sticking coefficient for both surfaces and impactors can be modeled by an analytical formulae S(T) = S0(1 + ?T/T0)/(1 + T/T0)?, which describes both the experiments and the thermal distribution expected in an astrophysical context. The parameters S0 and T0 are summarized in a table. Conclusions: Previous estimates for the sticking coefficient of H atoms are close to the new estimation; however, we find that, when isotopic effects are taken into account, the sticking coefficient variations can be as much as a factor of 2 at T = 100 K.

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

2012-02-01

225

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

NASA Astrophysics Data System (ADS)

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

Taran, Y.

2009-05-01

226

Sulfur and Hydrogen Isotope Anomalies in Meteorite Sulfonic Acids.  

National Technical Information Service (NTIS)

Intramolecular carbon, hydrogen, and sulfur isotope ratios were measured on a homologous series of organic sulfonic acids discovered in the Murchison meteorite. Mass-independent sulfur isotope fractionations were observed along with high deuterium/hydroge...

G. W. Cooper M. H. Thiemens S. Chang T. L. Jackson

1997-01-01

227

Carbon-deuterium bonds as non-perturbative infrared probes of protein dynamics, electrostatics, heterogeneity, and folding.  

PubMed

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

Zimmermann, Jörg; Romesberg, Floyd E

2014-01-01

228

Synthesis of selectively labeled histidine and its methylderivatives with deuterium, tritium, and carbon-14.  

PubMed

Isotopologues of l-histidine and its N-methylderivatives labeled with deuterium and tritium at the 5-position in the imidazole ring were obtained using the isotope exchange method. The deuterium-labeled isotopologues [5-(2)H]-l-histidine, [5-(2)H]-N(?) -methyl-l-histidine, [5-(2)H]-N(?) -methyl-l-histidine, and [2,5-(2)H(2)]-l-histidine were synthesized by isotope exchange method carried out in a fully deuterated medium with. The same reaction conditions were applied to synthesize [5-(3)H]-N(?) -methyl-l-histidine, [5-(3)H]-N(?) -methyl-l-histidine, and [5-(3)H]-l-histidine with specific activity of 2.0, 5.0, and 2.6?MBq/mmol, respectively. The N(?) -[methyl-(14)C]-histamine was obtained with specific activity of 0.23?MBq/mmol in a one-step reaction by the direct methylation of histamine by [(14)C]iodomethane. PMID:24285411

Šamonina-Kosicka, J; Ka?ska, M

2013-05-30

229

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

230

Deuterium-labeling experiments relevant to the mechanism of platinum-catalyzed hydrogenation of (diolefin)dialkylplatinum(II) complexes: evidence for isotopic exchange via platinum surface hydrogen. The stereochemistry of reduction  

SciTech Connect

Reduction of (diolefin)dialkylplatinum(II) complexes with dihydrogen over a platinum black catalyst is accompanied by interchange of hydrogen among the organic groups and gaseous dihydrogen. Exchange of hydrogens between an alkane solvent and these organic groups also occurs during the reaction, but only relatively slowly. An examination of the stereochemistry of reduction of (norbornadiene)dimethylplatinum(II) with D/sub 2/ indicates that the deuterium atoms add predominantly to the same (endo) face of the olefins as that coordinated to the dimethylplatinum moiety. Reduction of uncomplicated norbornadiene under the same conditions yields norbornane having primarily exo C-D bonds. These experiments are compatible with a mechanism for the reduction involving adsorption of the (diolefin)dialkylplatinum(II) complex on the surface of the platinum catalyst via its platinum atom, conversion of the organic moieties of the soluble (diolefin)dialkylplatinum complex to platinum-surface alkyls, and interchange of hydrogen atoms between these surface alkyls via a mobile pool of platinum-surface hydrogen atoms. Combination of the surface alkyls with surface hydrogen yields alkanes in a final irreversible step. Comparison of the evidence from deuterium-interchange experiments conducted under mass transport limited and reaction rate limited conditions is consistent with the hypothesis that the concentrations of hydrogen on the platinum surface is lower under mass transport limited conditions.

Miller, T.M.; McCarthy, T.J.; Whitesides, G.M.

1988-05-11

231

Evidence for a bound water molecule next to the retinal Schiff base in bacteriorhodopsin and rhodopsin: a resonance Raman study of the Schiff base hydrogen/deuterium exchange.  

PubMed Central

The retinal chromophores of both rhodopsin and bacteriorhodopsin are bound to their apoproteins via a protonated Schiff base. We have employed continuous-flow resonance Raman experiments on both pigments to determine that the exchange of a deuteron on the Schiff base with a proton is very fast, with half-times of 6.9 +/- 0.9 and 1.3 +/- 0.3 ms for rhodopsin and bacteriorhodopsin, respectively. When these results are analyzed using standard hydrogen-deuteron exchange mechanisms, i.e., acid-, base-, or water-catalyzed schemes, it is found that none of these can explain the experimental results. Because the exchange rates are found to be independent of pH, the deuterium-hydrogen exchange can not be hydroxyl (or acid-)-catalyzed. Moreover, the deuterium-hydrogen exchange of the retinal Schiff base cannot be catalyzed by water acting as a base because in that case the estimated exchange rate is predicted to be orders of magnitude slower than that observed. The relatively slow calculated exchange rates are essentially due to the high pKa values of the Schiff base in both rhodopsin (pKa > 17) and bacteriorhodopsin (pKa approximately 13.5). We have also measured the deuterium-hydrogen exchange of a protonated Schiff base model compound in aqueous solution. Its exchange characteristics, in contrast to the Schiff bases of the pigments, is pH-dependent and consistent with the standard base-catalyzed schemes. Remarkably, the water-catalyzed exchange, which has a half-time of 16 +/- 2 ms and which dominates at pH 3.0 and below, is slower than the exchange rate of the Schiff base in rhodopsin and bacteriorhodopsin. Thus, there are two anomalous results, the inconsistency of the observed hydrogen exchange rates of retinal Schiff base in the two pigments with those predicted from the standard exchange schemes and the enhancement of the rate of hydrogen exchange in the two proteins over the model Schiff base in aqueous solution. We suggest that these results are explained by the presence of a structural water molecule (or molecules) at the retinal binding sites of the two pigments, quite close, probably-hydrogen bonded, to the Schiff base proton. In this case, the rate of exchange can be faster than that found for the model compound due to an "effective water concentration" near the Schiff base that is increased from that found in aqueous solution.

Deng, H.; Huang, L.; Callender, R.; Ebrey, T.

1994-01-01

232

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

PubMed

Linear free energy relationships (LFERs) were established which relate equilibrium vapor-liquid isotope effects to stable carbon and hydrogen isotope enrichment factors for equilibrium sorption to geosorbents. The LFERs were established for normal, cyclic or branched alkanes, monoaromatic hydrocarbons, and chloroethenes. These LFERs predict that isotopic light compounds sorb more strongly than their heavy counterparts. Defining fractionation as in classical literature by "heavy divided by light", carbon enrichment factors for equilibrium sorption were derived which ranged from -0.13±0.04‰ (benzene) to -0.52±0.19‰ (trichloroethene at 5-15 °C). Hydrogen enrichment factors for sorption of 14 different compounds were between -2.4 and -9.2‰. For perdeuterated hydrocarbons the predicted enrichment factors ranged from -19±5.4‰ (benzene) to -64±30‰ (cyclohexane). Equilibrium sorption experiments with a soil and activated carbon as sorbents were performed in the laboratory for perdeuterocyclohexane and perdeuterotoluene. The measured D/H enrichments agreed with the LFER prediction for both compounds and both sorbents within the uncertainty estimate of the prediction. The results of this work suggest that equilibrium sorption does create only very small isotope shifts for (13)C in groundwater pollutants in aquifers. It is also suggested that deuterium shifts are expected to be higher, especially for strongly sorbing pollutants. PMID:22055158

Höhener, Patrick; Yu, Xianjing

2012-03-15

233

Hydrogen bonds in ionic liquids revisited: (35/37)Cl NMR studies of deuterium isotope effects in 1-n-butyl-3-methylimidazolium chloride.  

PubMed

Detailed knowledge of the structure, dynamics, and interionic interactions of ionic liquids (ILs) is critical to understand their physicochemical properties. In this letter, we show that deuterium isotope effects on the chloride ion 35/37Cl NMR signal represent a useful tool in the study of interionic hydrogen bonds in imidazolium chloride ILs. Sizable Delta35/37Cl(H,D) values obtained for the model system 1-n-butyl-3-methylimidazolium chloride ([C4mim]Cl) upon deuteriation of the imidazolium C-2 and C-2,4,5 positions, of nearly 1 and 2 ppm, respectively, show that the approach can readily identify and differentiate Cl...H hydrogen bonds between the anion and cation. Our study is one of a few examples in which hydrogen-bonding in ILs has been investigated using deuterium isotope effects and, to our knowledge, the only one employing 35/37Cl NMR to detect these interactions. The methodology described could be easily extended to the study of other systems bearing NMR-active nuclei. PMID:17887671

Remsing, Richard C; Wildin, Jayme L; Rapp, Ashleigh L; Moyna, Guillermo

2007-10-11

234

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

PubMed Central

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.

2012-01-01

235

Characterization of hydrogenated and deuterated thin carbon films deposited by magnetron sputtering  

NASA Astrophysics Data System (ADS)

Thin films of C layers were deposited by radiofrequency magnetron sputtering on silicon substrates using three gaseous atmospheres: pure Ar, Ar + H2 and Ar + D2 mixtures. Scanning Electron Microscopy investigations showed that addition of D2 or H2 to main sputtering gas (Ar) leads to the enhancement of the deposition rate while the layer morphology remained columnar. Fourier Transform Infrared Spectroscopy measurements revealed the presence of D-C or H-C chemical bonds in the samples. Ion beam analysis measurements performed by simultaneous recording of the recoiled H and D ions, and of backscattered 4He confirmed the incorporation of hydrogen and deuterium in the deposited carbon thin films.

Pantelica, D.; Ionescu, P.; Petrascu, H.; Nita, C. R.; Matei, E.; Rasoga, O.; Acsente, T.; Dinescu, G.

2014-07-01

236

Oxazolone versus macrocycle structures for leu-enkephalin b 2 –b 4 : Insights from infrared multiple-photon dissociation spectroscopy and gas-phase hydrogen\\/deuterium exchange  

Microsoft Academic Search

The collision-induced dissociation (CID) products b2-b4 from Leu-enkephalin are examined with infrared multiple-photon dissociation (IR-MPD) spectroscopy and gas-phase hydrogen\\/deuterium\\u000a exchange (HDX). Infrared spectroscopy reveals that b2 exclusively adopts oxazolone structures, protonated at the N-terminus and at the oxazolone ring N, based on the presence\\u000a and absence of diagnostic infrared vibrations. This is correlated with the presence of a single HDX

Xian Chen; Jeffrey D. Steill; Jos Oomens; Nick C. Polfer

2010-01-01

237

Hydrogen\\/Deuterium Exchange and Aggregation of a Polyvaline and a Polyleucine Helix Investigated by Matrix-assisted Laser Desorption Ionization Mass Spectrometry  

Microsoft Academic Search

The membrane-associated pulmonary surfactant protein C (SP-C), containing a polyvaline -helix, and a synthetic SP-C analogue with a polyleucine helix (SP-C(Leu)) were studied by hydrogen\\/deuterium exchange matrix-assisted laser desorption ionization (MALDI) mass spectrometry. SP-C, but not SP-C(Leu), formed abundant amyloid fibrils under experimental conditions. In CD3OD\\/D2O, 91:9 (v\\/v), containing 2 mM ammonium acetate, SP-C(Leu) and SP-C exchanged 40% of their

Waltteri Hosia; Jan Johansson; William J. Griffiths

238

High-field fourier transform ion cyclotron resonance mass spectrometry for simultaneous trapping and gas-phase hydrogen\\/deuterium exchange of peptide ions  

Microsoft Academic Search

Gas-phase hydrogen\\/deuterium exchange of D2O with [M+H]+ ions of angiotensin II, angiotensin I, [Sar1]-angiotensin II, bradykinin, des-Arg1-bradykinin, des-Arg9-bradykinin, luteinizing hormone releasing hormone (LH-RH), and substance P has been examined by Fourier transform ion cyclotron\\u000a resonance mass spectrometry at 9.4 tesla. Because the FTICR dynamic range increases quadratically with magnetic field, parent\\u000a ions from a mixture of several peptides may be

Michael A. Freitas; Christopher L. Hendrickson; Mark R. Emmett; Alan G. Marshall

1998-01-01

239

Characterization of the Hydrogen-Deuterium Exchange Activities of the Energy-Transducing HupSL Hydrogenase and H2Signaling HupUV Hydrogenase in Rhodobacter capsulatus  

Microsoft Academic Search

Rhodobacter capsulatus synthesizes two homologous protein complexes capable of activating molecular H2 ,a membrane-bound (NiFe) hydrogenase (HupSL) linked to the respiratory chain, and an H2 sensor encoded by the hupUV genes. The activities of hydrogen-deuterium (H-D) exchange catalyzed by the hupSL-encoded and the hupUV-encoded enzymes in the presence of D2 and H2O were studied comparatively. Whereas HupSL is in the

PAULETTE M. VIGNAIS; BERNARD DIMON; NIKOLAY A. ZORIN; MASAMITSU TOMIYAMA; ANNETTE COLBEAU

2000-01-01

240

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.

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

2013-01-01

241

Numerical Analysis of Hydrogen Storage in Carbon Nanopores  

Microsoft Academic Search

Carbon-based materials, due to their low cost and weight, have long been considered as suitable physisorption substrates for the reversible storage of hydrogen. Nanoporous carbons can be engineered to achieve exceptional storage capacities: gravimetric excess adsorption of 0.073 ± 0.003 kg H2\\/kg carbon, gravimetric storage capacity of 0.106 ± 0.005 kg H2\\/kg carbon, and volumetric storage capacity of 0.040 ±

Carlos Wexler; Raina Olsen; Peter Pfeifer; Bogdan Kuctha; Lucyna Firlej; Sztepan Roszak

2010-01-01

242

Modified carbon nanostructures as materials for hydrogen storage  

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

243

Hydrogen bond and halogen bond inside the carbon nanotube  

NASA Astrophysics Data System (ADS)

The hydrogen bond and halogen bond inside the open-ended single-walled carbon nanotubes have been investigated theoretically employing the newly developed density functional M06 with the suitable basis set and the natural bond orbital analysis. Comparing with the hydrogen or halogen bond in the gas phase, we find that the strength of the hydrogen or halogen bond inside the carbon nanotube will become weaker if there is a larger intramolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom donor to the antibonding orbital of the X-H or X-Hal bond involved in the formation of the hydrogen or halogen bond and will become stronger if there is a larger intermolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom acceptor to the antibonding orbital of the X-H or X-Hal bond. According to the analysis of the molecular electrostatic potential of the carbon nanotube, the driving force for the electron-density transfer is found to be the negative electric field formed in the carbon nanotube inner phase. Our results also show that the X-H bond involved in the formation of the hydrogen bond and the X-Hal bond involved in the formation of the halogen bond are all elongated when encapsulating the hydrogen bond and halogen bond within the carbon nanotube, so the carbon nanotube confinement may change the blue-shifting hydrogen bond and the blue-shifting halogen bond into the red-shifting hydrogen bond and the red-shifting halogen bond. The possibility to replace the all electron nanotube-confined calculation by the simple polarizable continuum model is also evaluated.

Wang, Weizhou; Wang, Donglai; Zhang, Yu; Ji, Baoming; Tian, Anmin

2011-02-01

244

Physisorption of molecular hydrogen on carbon nanotube with vacant defects  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

245

Physisorption of molecular hydrogen on carbon nanotube with vacant defects.  

PubMed

Physisorption of molecular hydrogen on single-walled carbon nanotubes (SWCNTs) is important for its engineering applications and hydrogen energy storage. Using molecular dynamics simulation, we study the physisorption of molecular hydrogen on a SWCNT with a vacant defect, focusing on the effect of the vacant defect size and external parameters such as temperature and pressure. We find that hydrogen can be physisorbed inside a SWCNT through a vacant defect when the defect size is above a threshold. By controlling the size of the defects, we are able to extract hydrogen molecules from a gas mixture and store them inside the SWCNT. We also find that external parameters, such as low temperature and high pressure, enhance the physisorption of hydrogen molecules inside the SWCNT. In addition, the storage efficiency can be improved by introducing more defects, i.e., reducing the number of carbon atoms on the SWCNT. PMID:24880316

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

2014-05-28

246

Interaction of hydrogen plasma with carbon–tungsten composite layer  

Microsoft Academic Search

Interaction of neutral hydrogen atoms with the layer of hydrogenated carbon–tungsten composite was studied. A 1?m thick layer was prepared by sputter deposition from C and WC-targets in Ar\\/C2–H2 gas mixture. After deposition the samples were treated in weakly ionized highly dissociated hydrogen plasma created in a microwave discharge at a power of 1kW. The gas flow was 13l\\/h and

Alenka Vesel; Miran Mozetic; Peter Panjan; Hauptman; M. Klanjsek-Gunde; Marianne Balat-Pichelin

2011-01-01

247

Hydrogen storage in ni nanoparticle-dispersed multiwalled carbon nanotubes.  

PubMed

Hydrogen storage properties of mutiwalled carbon nanotubes (MWCNTs) with Ni nanoparticles were investigated. The metal nanoparticles were dispersed on MWCNTs surfaces using an incipient wetness impregnation procedure. Ni catalysts have been known to effectively dissociate hydrogen molecules in gas phase, providing atomic hydrogen possible to form chemical bonding with the surfaces of MWCNTs. Hydrogen desorption spectra of MWCNTs with 6 wt % of Ni nanoparticles showed that approximately 2.8 wt % hydrogen was released in the range of 340-520 K. In Kissinger's plot to evaluate the nature of interaction between hydrogen and MWCNTs with Ni nanoparticles, the hydrogen desorption activation energy was measured to be as high as approximately 31 kJ/mol.H(2), which is much higher than the estimates of pristine SWNTs. C-H(n)() stretching vibrations after hydrogenation in FTIR further supported that hydrogen molecules were dissociated when bound to the surfaces of MWCNTs. During cyclic hydrogen absorption/desorption, there was observed no significant decay in hydrogen desorption amount. The hydrogen chemisorption process facilitated by Ni nanopaticles could be suggested as an effective reversible hydrogen storage method. PMID:16852070

Kim, Hyun-Seok; Lee, Ho; Han, Kyu-Sung; Kim, Jin-Ho; Song, Min-Sang; Park, Min-Sik; Lee, Jai-Young; Kang, Jeung-Ku

2005-05-12

248

Metal-Containing Organic and Carbon Aerogels for Hydrogen Storage  

SciTech Connect

This document and the accompanying manuscript summarize the technical accomplishments of our one-year LDRD-ER effort. Hydrogen storage and hydrogen fuel cells are important components of the 2003 Hydrogen Fuel Initiative focused on the reduction of America's dependence on oil. To compete with oil as an energy source, however, one must be able to transport and utilize hydrogen at or above the target set by DOE (6 wt.% H{sub 2}) for the transportation sector. Other than liquid hydrogen, current technology falls well short of this DOE target. As a result, a variety of materials have recently been investigated to address this issue. Carbon nanostructures have received significant attention as hydrogen storage materials due to their low molecular weight, tunable microporosity and high specific surface areas. For example, the National Renewable Energy Laboratory (NREL) achieved 5 to 10 wt.% H{sub 2} storage using metal-doped carbon nanotubes. That study showed that the intimate mix of metal nanoparticles with graphitic carbon resulted in the unanticipated hydrogen adsorption at near ambient conditions. The focus of our LDRD effort was the investigation of metal-doped carbon aerogels (MDCAs) as hydrogen storage materials. In addition to their low mass densities, continuous porosities and high surface areas, these materials are promising candidates for hydrogen storage because MDCAs contain a nanometric mix of metal nanoparticles and graphitic nanostructures. For FY04, our goals were to: (1) prepare a variety of metal-doped CAs (where the metal is cobalt, nickel or iron) at different densities and carbonization temperatures, (2) characterize the microstructure of these materials and (3) initiate hydrogen adsorption/desorption studies to determine H2 storage properties of these materials. Since the start of this effort, we have successfully prepared and characterized Ni- and Co-doped carbon aerogels at different densities and carbonization temperatures. The bulk of this work is described in the attached manuscript entitled 'Formation of Carbon Nanostructures in Cobalt- and Nickel- Doped Carbon Aerogels'. This one-year effort has lead to our incorporation into the DOE Carbon-based Hydrogen Storage Center of Excellence at NREL, with funding from DOE's Energy Efficiency and Renewable Energy (EERE) Program starting in FY05.

Satcher, Jr., J H; Baumann, T F; Herberg, J L

2005-01-10

249

Deuterium abundances  

NASA Astrophysics Data System (ADS)

We discuss the measurements of deuterium abundances in high redshift quasar absorbers, in the solar system and in the interstellar medium. We present new results that indicate spatial variations of the deuterium abundance in the interstellar medium at the level of ˜50% over scales possibly as small as ˜10 pc, and discuss plausible causes for the origin of these variations.

Lemoine, Martin; Audouze, Jean; Ben Jaffel, Lotfi; Feldman, Paul; Ferlet, Roger; Hébrard, Guillaume; Jenkins, Edward B.; Mallouris, Christoforos; Moos, Warren; Sembach, Kenneth; Sonneborn, George; Vidal-Madjar, Alfred; York, Donald G.

1999-07-01

250

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

NASA Astrophysics Data System (ADS)

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(?) 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(?) in the frequency region higher than 100 cm-1. At all temperatures, both the Debye mode and the region of G(?), 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(?) is insignificant.

Svanidze, A. V.; Lushnikov, S. G.; Sashin, I. L.; Gvasaliya, S. N.

2007-09-01

251

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

252

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

253

Material Processing with Hydrogen and Carbon Monoxide on MARS.  

National Technical Information Service (NTIS)

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

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

1991-01-01

254

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

255

Hydrogen-deficient atmospheres for cool carbon stars  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

256

Movement of hydrogen molecules in pristine, hydrogenated and nitrogen-doped single-walled carbon nanotubes  

Microsoft Academic Search

Carbon nanotubes (CNT) are considered promising nano-scale materials because of their unique structural, mechanical and electronic properties. Due to their long seamless cylindrical shaped structures they could be applied as effective nano-channels for mass transfer and relevant storages for hydrogen molecules. We study hydrogen transport mechanisms in CNTs for various chiral indices and different peculiarities, using the molecular dynamics simulation

Kyung Su Oh; Dong Hyun Kim; Seungho Park; Joon Sik Lee; Ohmyoung Kwon; Young Ki Choi

2008-01-01

257

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

NASA Astrophysics Data System (ADS)

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

Hey, J. D.

2012-03-01

258

Controlled carbon nitride growth on surfaces for hydrogen evolution electrodes.  

PubMed

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

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

2014-04-01

259

Hydrogenation of chloronitrobenzenes over filamentous carbon stabilized nickel nanoparticles  

Microsoft Academic Search

Ni nanoparticles and filamentous carbon were generated simultaneously by decomposing methane over Raney nickel catalyst. Nickel nanoparticles were stabilized by filamentous carbon. The Ni–filamentous carbon composite materials were tested as catalysts for the hydrogenation of ortho- and para-chloronitrobenzene, producing chloroanilines selectively (99% yield). The catalysts exclusively reduce the nitro group in chloronitrobenzenes, leaving the C–Cl bond untouched. A possible explanation

N. Mahata; A. F. Cunha; J. J. M. Órfão; J. L. Figueiredo

2009-01-01

260

Determination of site-specific (deuterium/hydrogen) ratios in vanillin by 2H-nuclear magnetic resonance spectrometry: collaborative study.  

PubMed

The results of collaborative study are reported for a method that determines the site-specific isotope ratios of deuterium/hydrogen (D/H)i in vanillin by deuterium-nuclear magnetic resonance (2H-NMR) spectrometry. This method allows characterization of all the main commercial sources of commercial vanillin and detection of undeclared mixtures. It is based on the fact that the amounts of deuterium at various positions in the vanillin molecule are significantly different from one source to another. Vanillin is dissolved in acetonitrile and analyzed with a high-field NMR spectrometer fitted with a deuterium probe and a fluorine lock. The proportions of isotopomers monodeuterated at each hydrogen position of the molecule are recorded, and the corresponding (D/H) ratios are determined by using a calibrated reference. Nine laboratories analyzed 5 materials supplied as blind duplicates (1 natural vanillin from vanilla beans, 2 synthetic vanillins from guaiacol, 1 semisynthetic vanillin from lignin, and a mixture of natural and synthetic vanillins). The precision of the method for measuring site-specific ratios was as follows: for (D/H)1 the within-laboratory standard deviation (Sr) values ranged from 2.2 to 5.8 ppm, and the among-laboratories standard deviation (sR) values ranged from 3.6 to 5.1 ppm; for (D/H)3 the Sr values ranged from 1.7 to 3.2 ppm, and the SR values ranged from 2.4 to 3.7 ppm; for (D/H)4 the Sr values ranged from 2.3 to 6.2 ppm, and the SR values ranged from 2.4 to 6.4 ppm; for (D/H)5 the Sr values ranged from 0.8 to 2.7 ppm, and the SR values ranged from 0.9 to 2.3 ppm. It was shown that these values allow a satisfactory discrimination between vanillin sources. Therefore, the Study Director recommends the method for adoption as a First Action Official Method by AOAC INTERNATIONAL. PMID:17373451

Jamin, Eric; Martin, Frédérique; Martin, Gilles G

2007-01-01

261

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

262

Flow-injection analysis of hydrogen peroxide based on carbon nanospheres catalyzed hydrogen carbonate-hydrogen peroxide chemiluminescent reaction.  

PubMed

A flow-injection chemiluminescence (CL) system with high sensitivity, selectivity, rapidity, and reproducibility is proposed for the determination of hydrogen peroxide (H(2)O(2)) in water samples. The system is based on the reaction of hydrogen peroxide and hydrogen carbonate solution. Carbon nanospheres (CNSs) prepared from aqueous glucose solution are used to enhance the weak CL. The CL intensity was found to be directly proportional to the concentration of H(2)O(2) present in the sample solutions. The effects upon the CL of several physicochemical parameters, including the concentration of the reagents, the mixing order of the reagents, flow rate, pH, particle size of CNSs and other relevant variables, were studied and optimized. The proposed method exhibited advantages in a larger linear range of 5.0 × 10(-8) to 3.0 × 10(-6) mol L(-1) and a lower limit of detection of 1.0 × 10(-9) mol L(-1) (S/N = 3). This method has been successfully applied to the evaluation of H(2)O(2) in tap water and snow water with recoveries from 80 to 110%. The relative standard deviation (RSD) was less than 8% for intra- and inter-assay precision. Based on the kinetic curve, the CL spectrum, fluorescence spectrum, UV-visible spectrum, and electron spin resonance (ESR) spectrum of NaHCO(3)-H(2)O(2)-CNSs system, a possible CL mechanism was proposed. Superoxide ion radical (?O(2)(-)) and hydroxide radical (?OH) were generated during the reaction of NaHCO(3) and H(2)O(2). They were the key intermediates for the production of hole-injected and electron-injected CNSs in the CL process. PMID:21384016

Chen, Hui; Lin, Ling; Lin, Zhen; Lu, Chao; Guo, Guangsheng; Lin, Jin-Ming

2011-05-01

263

NMR studies of nucleic acids. Deuterium isotope effects on sup 13 C chemical shifts in hydrogen-bonded complexes of pyrimidines and purines  

SciTech Connect

{sup 13}C NMR spectra were recorded for chloroform solutions of 2',3'-O-isopropylidene-5'-O-acetyladenosine (1), 2',3',5'-O-tribenzoyluridine (2), 2',3'-O-isopropylidene-5'-O-acetyluridine (2a), 2',3'-O-isopropylidene-5'-O-(tert-butyldimethylsilyl)guanosine (3), and 2',3'-O-isopropylidene-5'-O-(tert-butyldimethylsilyl)cytidine (4) in which the imino hydrogens were partially exchanged with deuterium. Upfield two-bond deuterium isotope effects (DIE) on {sup 13}C chemical shifts were detected under conditions of slow exchange as multiple peaks for the appropriate resonances and ranged in magnitude from 40 ppB for the amino interaction with C2 in guanosine to 217 ppB for the imino interaction with C4 in the uridine self-association dimer. {sup 13}C chemical shifts and DIEs for 2 were measured at 12 different concentrations from 219 to 231 K. The data were used in an iterative procedure to estimate chemical shifts at C2 and C4 for monomeric and dimeric forms of 2, equilibrium constants and enthalpies for self-association, and the distribution of isomeric self-association dimers. Enthalpies for formation of hydrogen bonds to C2 and C4 in 2 were similar, {Delta}H = {minus}1.8 kcal/mol. DIEs at C2 and C4 increased upon formation of a hydrogen bond to the carbonyl oxygens. The maximal increase for each center was estimated to be 90 ppB. Small increases were also observed in DIEs when nucleosides 1-4 were mixed with their complementary bases. 38 refs., 3 figs., 7 tabs.

Gmeiner, W.H.; Poulter, C.D.

1988-11-09

264

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

PubMed Central

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.

2013-01-01

265

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

266

Cosmic deuterium.  

NASA Astrophysics Data System (ADS)

In this short review the author tried to demonstate the importance of accurately measuring the cosmic abundance of deuterium. Chemical evolution of the D-abundance is presented, together with new observational data which cast a shadow onto seemingly shining picture of the Big Bang nucleosynthesis. Link between deuterium astration and metal production is emphasized as the key to the solution of the puzzle, and confusing observational evidence is briefly discussed.

?irkovi?, M. M.

267

Deuterium Gas Analysis by Residual Gas Analyzer  

NASA Astrophysics Data System (ADS)

Hydrogen gas is generated by electrolysis method in a compact hydrogen generator. A simple procedure reduces handling and storage of hydrogen cylinders for laboratory applications. In such a system, we are producing deuterium gas from heavy water by electrolysis method. After production of the deuterium gas, we have checked the purity level of the outgoing deuterium from the electrolyser. The test was carried out in a high vacuum system in which one residual gas analyser (RGA) was mounted. The deuterium gas was inserted by one manual gas leak valve in to the vacuum system. In this study, the effect of the emission current of the RGA on the detection of the deuterium was performed. In this paper, we will discuss the detail analysis of the deuterium gas and the effect of the emission current on the partial pressure measurement.

Das, B. K.; Shukla, R.; Das, R.; Shyam, A.; Rao, A. D. P.

2012-11-01

268

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

269

Design of tailored carbon nanostructures for hydrogen storage  

NASA Astrophysics Data System (ADS)

In a time of increasing scarcity of fossil fuel resources worldwide, hydrogen is widely regarded as a potential cost-effective, renewable and clean energy alternative to petroleum, especially in the transportation sector. However, storage of hydrogen has revealed to be particularly challenging so far. In the present work, we report our progress on the computational study of functionalized carbon nanostructures for hydrogen storage. Structures and properties of these nanostructures consisting of single-walled carbon nanotubes constrained by spacers were calculated using the density functional theory (GGA, PW91). Particular emphasis was given to understanding the role of the chirality and diameter of small single-walled carbon nanotubes on the overall thermal stability and storage capacity of such nano-frameworks.

Weck, Philippe F.; Kim, Eunja; Balakrishnan, Naduvalath; Cheng, Hansong

2007-03-01

270

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

271

Dissecting the effect of RNA aptamer binding on the dynamics of plasminogen activator inhibitor 1 using hydrogen/deuterium exchange mass spectrometry.  

PubMed

RNA aptamers, selected from large synthetic libraries, are attracting increasing interest as protein ligands, with potential uses as prototype pharmaceuticals, conformational probes, and reagents for specific quantification of protein levels in biological samples. Very little is known, however, about their effects on protein conformation and dynamics. We have employed hydrogen/deuterium exchange (HDX) mass spectrometry to study the effect of RNA aptamers on the structural flexibility of the serpin plasminogen activator inhibitor-1 (PAI-1). The aptamers have characteristic effects on the biochemical properties of PAI-1. In particular, they are potent inhibitors of the structural transition of PAI-1 from the active state to the inactive, so-called latent state. This transition is one of the largest conformational changes of a folded protein domain without covalent modification. Binding of the aptamers to PAI-1 is associated with substantial and widespread protection against deuterium uptake in PAI-1. The aptamers induce protection against exchange with the solvent both in the protein-aptamer interface as well as in other specific areas. Interestingly, the aptamers induce substantial protection against exchange in ?-helices B, C and I. This observation substantiates the relevance of structural instability in this region for transition to the latent state and argues for involvement of flexibility in regions not commonly associated with regulation of latency transition in serpins. PMID:24138169

Trelle, Morten B; Dupont, Daniel M; Madsen, Jeppe B; Andreasen, Peter A; Jørgensen, Thomas J D

2014-01-17

272

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

PubMed

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

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

2014-09-01

273

Exfoliated single-walled carbon nanotube-based hydrogen sensor  

Microsoft Academic Search

The paper presents a simple and inexpensive method for the preparation of an efficient hydrogen gas sensor based on exfoliated Pd-decorated single-walled carbon nanotubes (SWNTs). SWNTs were synthesized by catalytic chemical vapor deposition of methane using a fixed-bed catalytic reactor over hydrides of Mm0.2Tb0.8Co2 obtained through hydrogen decrepitation technique. Purified and chemically treated SWNTs were functionalized with Pd, resulting in

M. Krishna Kumar; A. Leela Mohana Reddy; S. Ramaprabhu

2008-01-01

274

Carbon gasification in a hydrogen glow-discharge plasma  

Microsoft Academic Search

1.A study has been made of the gasifications of carbon in hydrogen plasmas at temperatures ranging from 550 to 900°C. The kinetic curves covering this temperature range are anomolous, the reaction rate decreasing as the temperature rises.2.Diamond does not react with the hydrogen plasma at 3.2 torr pressure and temperatures up to 500°C. The depth of penetration of the graphite

D. V. Fedoseev; Yu. N. Tolmachev

1979-01-01

275

Material processing with hydrogen and carbon monoxide on Mars  

NASA Astrophysics Data System (ADS)

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.

276

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

277

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

SciTech Connect

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

Kuch, Ph. L.

1984-12-18

278

Solidification and crystal growth of highly compressed hydrogen and deuterium: Time-resolved study under ramp compression in dynamic-diamond anvil cell  

NASA Astrophysics Data System (ADS)

Solidification of hydrogen and deuterium has been studied under dynamic compression using dynamic-diamond anvil cell, time-resolved Raman spectroscopy, and fast micro-photography. Liquid H2 or D2 solidifies into a grain boundary free crystal grown from the outer edge of the sample chamber in 1-30 ms depending on the compression rate. The time scale of solidification agrees well with that of the discontinuous Raman shift across the liquid/solid phase boundary, underscoring a compression rate dependence of the solidification process. The crystal growth rates were measured to be 0.12-0.80 cm/s for H2 and 0.13-1.27 cm/s for D2, varying linearly with the compression rate.

Tomasino, Dane; Yoo, Choong-Shik

2013-08-01

279

Hydrogen-deuterium exchange in vivo to measure turnover of an ALS-associated mutant SOD1 protein in spinal cord of mice.  

PubMed

Mutations of cytosolic Cu/Zn superoxide dismutase 1 (SOD1) in humans and overexpression of mutant human SOD1 genes in transgenic mice are associated with the motor neuron degenerative condition known as amyotrophic lateral sclerosis (ALS; Lou Gehrig's disease). Gain-of-function toxicity from the mutant protein expressed in motor neurons, associated with its misfolding and aggregation, leads to dysfunction and cell death, associated with paralyzing disease. Here, using hydrogen-deuterium exchange in intact mice in vivo, we have addressed whether an ALS-associated mutant protein, G85R SOD1-YFP, is subject to the same rate of turnover in spinal cord both early in the course of the disease and later. We find that the mutant protein turns over about 10-fold faster than a similarly expressed wild-type fusion and that there is no significant change in the rate of turnover as animals age and disease progresses. PMID:21780215

Farr, George W; Ying, Zheng; Fenton, Wayne A; Horwich, Arthur L

2011-10-01

280

Kaon electroproduction on deuterium.  

SciTech Connect

Kaon electroproduction on deuterium and hydrogen targets has been measured at beam energies of 3.245 and 2.445 GeV and momentum transfer Q{sup 2}=0.38 and 0.5 GeV{sup 2}. Associated {Lambda} production off a proton in the deuteron exhibits a quasifree production mechanism. The production of {Sigma}{sup {minus}} off the neutron could be extracted for the first time with reasonable errors.

Reinhold, J.

1998-01-12

281

Kaon Electroproduction on Deuterium  

SciTech Connect

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

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

1998-08-01

282

Palladium-doped Nanoporous Carbon Fibers for Hydrogen Storage  

SciTech Connect

Pd-free and Pd-containing activated carbon fibers (Pd-ACF) were synthesized from isotropic pitch as a carbon precursor. The source of Pd was a palladium salt that was premixed with pitch before carbonization. Hydrogen adsorption was measured at near-ambient temperatures (5 to 80 oC) and moderate pressures (up to 20 bar). It was found that adsorption on Pd-ACF is always higher than that on corresponding ACF, and in excess of what it would be expected based solely on formation of Pd hydride. This fact can be explained based on the mechanism of hydrogen spillover. It was also found that temperature and pressure have opposite effects on physisorption and spillover. It was hypothesized that a narrow temperature range exists, where the kinetic advantage of H2 spillover in Pd-ACF overlaps synergistically with the thermodynamic advantage of physisorption, thus contributing to enhanced uptakes compared with the Pd-free carbons.

Gallego, Nidia C [ORNL; Contescu, Cristian I [ORNL; Bhat, Vinay V [ORNL; van Benthem, Klaus [ORNL; Tekinalp, Halil [Clemson University; Edie, Dan [Clemson University

2008-01-01

283

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

PubMed

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

Cho, Yunju; Ahmed, Arif; Kim, Sunghwan

2013-10-15

284

Calcium-Decorated Carbon Nanotubes for Hydrogen Storage  

Microsoft Academic Search

Using the first-principles pseudopotential density-functional method, we carry out a systematic search for high-capacity hydrogen storage media based on individually dispersed calcium atoms on carbon nanotubes (CNTs). We find that Ca clustering is suppressed on boron-doped and defective carbon nanotubes and that up to six H2 molecules can bind to a Ca atom with a binding energy of ˜0.2 eV\\/H2.

Hoonkyung Lee; Jisoon Ihm; Marvin L. Cohen; Steven G. Louie

2009-01-01

285

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

NASA Astrophysics Data System (ADS)

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

Wang, Qinyu; Johnson, J. Karl

1999-01-01

286

Material processing with hydrogen and carbon monoxide on Mars  

NASA Astrophysics Data System (ADS)

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.

287

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

288

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

289

High capacity carbon anode materials: Structure, hydrogen effect, and stability  

Microsoft Academic Search

The local structure of several disordered carbons, obtained from radial distribution function analysis of elastic neutron scattering data, consists of small isolated graphene fragments. The effect of residual hydrogen which presumably saturates the dangling bonds in low-temperature pyrolyzed materials was studied by inelastic neutron vibrational spectroscopy and computer modelling of lithiated polyaromatic hydrocarbons. We discuss the possibility of exploiting the

P. Zhou; P. Papanek; C. Bindra; R. Lee; J. E. Fischer

1997-01-01

290

Carbon-Hydrogen Insertion Reaction of Dichlorocarbene with Polycyclic Hydrocarbons. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

The factors influencing the carbon-hydrogen insertion reaction of dichlorocarbene into tertiary carbon-hydrogen bonds are investigated. Both steric matters and alignment with adjacent bonds appear to be important in the insertion of dichlorocarbene into t...

I. R. Likhotvorik K. Yuan D. W. Brown P. A. Krasutsky N. Smyth

1992-01-01

291

Hydrogen storage in nanoporous carbon materials: myth and facts.  

PubMed

We used Grand canonical Monte Carlo simulation to model the hydrogen storage in the primitive, gyroid, diamond, and quasi-periodic icosahedral nanoporous carbon materials and in carbon nanotubes. We found that none of the investigated nanoporous carbon materials satisfy the US Department of Energy goal of volumetric density and mass storage for automotive application (6 wt% and 45 kg H(2) m(-3)) at considered storage condition. Our calculations indicate that quasi-periodic icosahedral nanoporous carbon material can reach the 6 wt% at 3.8 MPa and 77 K, but the volumetric density does not exceed 24 kg H(2) m(-3). The bundle of single-walled carbon nanotubes can store only up to 4.5 wt%, but with high volumetric density of 42 kg H(2) m(-3). All investigated nanoporous carbon materials are not effective against compression above 20 MPa at 77 K because the adsorbed density approaches the density of the bulk fluid. It follows from this work that geometry of carbon surfaces can enhance the storage capacity only to a limited extent. Only a combination of the most effective structure with appropriate additives (metals) can provide an efficient storage medium for hydrogen in the quest for a source of "clean" energy. PMID:17415489

Kowalczyk, Piotr; Ho?yst, Robert; Terrones, Mauricio; Terrones, Humberto

2007-04-21

292

An in situ electrical study on primary hydrogen spillover from nanocatalysts to amorphous carbon support  

NASA Astrophysics Data System (ADS)

Primary hydrogen spillover has been studied using a unique electrical method. We observed that at ambient temperature, when a discontinuous nanogranular Pd film is on the top of an amorphous carbon film, the electrical conductance of the carbon film decreases in pressurized hydrogen. In comparison, in the absence of this Pd layer, the conductance of the carbon film remains unchanged in pressurized hydrogen. The observed decrease in the current in the Pd/carbon structure is ascribed to the hydrogenation of the dangling carbon bonds and sp2-sp3 transition in the amorphous carbon by the primary spillover hydrogen atoms from Pd nanoclusters.

Lin, Chikai; Yang, Zhenzhen; Xu, Tao; Zhao, Yufeng

2008-12-01

293

Atypical Hydrogen Uptake on Chemically Activated, Ultramicroporous Carbon  

SciTech Connect

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

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

2010-01-01

294

Carbon-13 and deuterium isotope effects on the catalytic reactions of biotin carboxylase  

SciTech Connect

/sup 13/C and /sup 2/H kinetic isotope effects have been used to investigate the mechanism of enzymic biotin carboxylation. /sup D/(V/K) is 0.50 in 80% D/sub 2/O at pD 8.0 for the forward reaction and 0.57 at pD 8.5 for the phosphorylation of ADP by carbamoyl phosphate. These values approach the theoretical maximum limit for a reaction in which a proton is transferred from a sulfhydryl to a nitrogen or oxygen base. Therefore, it appears that this portion of the reaction is at or near equilibrium. /sup 13/(V/K) at pH 8 is 1.007; the small magnitude of this number suggests that the reaction is almost fully committed by the time the carbon-sensitive steps are reached. There does not appear to be a reverse commitment to the reaction under the conditions in which /sup 13/(V/K) was determined. A large forward commitment is consistent with the failure to observe positional isotope exchange from the ..beta gamma..-bridge position to the ..beta..-nonbridge position in (/sup 18/O/sub 4/)ATP or washout of /sup 18/O from the ..gamma..-nonbridge positions. Transfer of /sup 18/O from bicarbonate to inorganic phosphate in the forward reaction was clearly observed, however. These observations suggest that biotin carboxylase exists in two distinct forms which differ in the protonation states of the two active-site bases, one of which is a sulfhydryl. Only when the sulfhydryl is ionized and the second base protonated can catalysis take place. Carboxylation of biotin is postulated to occur via a pathway in which carboxyphosphate is formed by nucleophilic attack of bicarbonate on ATP. Decarboxylation of carboxyphosphate in the active site generates CO/sub 2/, which serves to carboxylate the isourea tautomer of biotin that is generated by the removal of the proton on N1' by the ionized sulfhydryl.

Tipton, P.A.; Cleland, W.W.

1988-06-14

295

Procees for low temperature carbonization of hydrogenation residues  

SciTech Connect

The residues obtained in the hydrogenation of oil, especially heavy oil, or of coal are subjected to low temperature carbonization in a drum, preferably a rotary drum, at temperatures between approximately 400/sup 0/ C. and approximately 600/sup 0/ C., by means of a carbonization gas after the separation of the condensable portions and heating to temperatures between approximately 600/sup 0/ C. and approximately 950/sup 0/ C. which is introduced into the low temperature carbonization drum. The gas is heated to tepmeratures between approximately 600/sup 0/ C. and approximately 950/sup 0/ C. indirectly by flue gases arising from the combustion of oil or gas, for example, of excess carbonization gas. The residue to be carbonized at low temperature is introduced into the hot gas in a finely dispersed state and preferably atomized.

Escher, G.; Holighaus, R.; Wenning, H. P.

1985-04-23

296

Nitrogen-containing carbon nanotubes as a possible hydrogen storage medium  

Microsoft Academic Search

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

M Sankaran; B Viswanathan

297

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

NASA Astrophysics Data System (ADS)

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

Sauter, P. A.; Balden, M.

2013-09-01

298

Hydrogen Storage in Novel Carbon-based Nanostructured Materials  

NASA Astrophysics Data System (ADS)

One of the biggest challenges facing a future hydrogen economy is that of onboard vehicular hydrogen storage, for which novel carbon-based nanostructured materials have emerged as potential candidates. Towards this end, we present the synthesis and characterization of ``bucky dumbbell,'' a new organometallic compound comprised of two buckyballs complexed to a central iron atom. This new compound has been characterized using both ^13C solid-state NMR and Raman spectroscopy, and electron spin paramagnetic resonance spectroscopy reveals the presence of Fe^3+. Temperature-programmed desorption has revealed a new hydrogen binding site via the appearance of a peak centered at approximately -50 C, indicating the hydrogen is stabilized at a temperature significantly above that expected for physisorption but still lower than that of C-H bond formation. Comparison with C60 under the same hydrogen exposure and heating conditions shows almost no hydrogen adsorption, and the exact binding energy (or desorption activation energy, Ed) for the bucky dumbbell shows an enhanced value of ˜6.2 kJ/mol. Initial volumetric analyses conducted at 77K and 3 bar show a storage capacity of ˜0.4 wt%. The synthesis and analysis of other novel fullerene-based organometallic hydrogen complexes will also be discussed.

Whitney, Erin; Curtis, Calvin; Engtrakul, Chaiwat; Davis, Mark; Jones, Kim; Parilla, Philip; Simpson, Lin; Dillon, Anne

2007-03-01

299

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

300

Electron impact dissociation of molecular Hydrogen and Deuterium: Isotope effect on the emission cross section of H* AND D* ( n=3,4,5)  

NASA Astrophysics Data System (ADS)

The Balmer aB, y lines of the excited hydrogen atoms ( n=3,4,5) produced in e-H 2 and D 2 collisions have beeen measured at high resolutions. The isotope effects for the formation of the slow and the fast groups of excited hydrogen and deuterium atoms are obtained separately from an analysis of the Doppler line shapes. The observed values of ? D/ ? H for the slow group are 0.68±0.10, 0.49 ±0.09 and 0.25 ±0.06 for n = 3. 4 and 5, respectively, and are independent of the electron energy (25- 100 eV). These results indicate that the wider Franck-Condon region and the smaller reduced mass of H 2, are favorable for dissociation, and that the contribution of predissociation becomes small with increasing n. An isotope effect for the fast group seems to be present. The emission cross sections and their electron energy dependence have been estimated for both groups.

Higo, Morihide; Kamata, Satsuo; Ogawa, Teiichiro

1982-12-01

301

Enhanced Digestion Efficiency, Peptide Ionization Efficiency, and Sequence Resolution for Protein Hydrogen/Deuterium Exchange Monitored by FT-ICR Mass Spectrometry  

PubMed Central

Solution-phase hydrogen/deuterium exchange (HDX) monitored by high-resolution FT-ICR mass spectrometry offers a rapid method to study protein conformations and protein-protein interactions. Pepsin is usually used to digest proteins in HDX and is known as lack of cleavage specificity. To improve digestion efficiency and specificity, we have optimized digestion conditions and cleavage preferences for pepsin and protease type XIII from Aspergillus saitoi. A dilution series of the proteases was used to determine the digestion efficiency for several test proteins. Protease type XIII prefers to cleave on the C-terminal end of basic amino acids and produced the highest number of fragments and the best sequence coverage compared to pepsin or protease type XVIII from Rhizhopus. Furthermore, protease type XIII exhibited much less self-digestion than pepsin, and thus is superior for HDX experiments. Many highly overlapped segments from protease type XIII and pepsin digestion, combined with high-resolution FT-ICR mass spectrometry, provide high sequence resolution (to as few as one or two amino acids) for the assignment of amide hydrogen exchange rate. Our H/D exchange results correlate well with the secondary and tertiary structure of myoglobin. Such assignments of highly overlapped fragments promise to greatly enhance the accuracy and sequence resolution for determining conformational differences resulting from ligand binding or protein-protein interactions.

Zhang, Hui-Min; Kazazic, Sasa; Schaub, Tanner M.; Tipton, Jeremiah D.; Emmett, Mark R.; Marshall, Alan G.

2009-01-01

302

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

303

Restricted dynamics of molecular hydrogen confined in activated carbon nanopores  

SciTech Connect

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

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

2012-01-01

304

Hydrogen uptake in single-walled carbon nanotubes synthesized by the hydrogen arc plasma jet method.  

NASA Astrophysics Data System (ADS)

Carbon nanotubes were synthesized by a modified electric arc discharge method under hydrogen atmosphere using a catalytic mixture of powders with composition C/Ni/Co/Fe/FeS. The samples were characterized with transmission and scanning electron microscopy, Raman spectroscopy and thermo-gravimetric analysis. Unpurified samples contain 20 wt% of carbon nanotubes, 2 wt% of other forms of carbon and 78 wt% of catalytic metals. Adsorption/desorption of hydrogen in unpurified samples at atmospheric pressure measured with gravimetric methods was of the order of 2 wt%. Samples for these measurements were prepared with a three-step treatment: (i) oxidation in air for 30 min at 500 ^oC, (ii) ball- milling for 1 hr, and (iii) second oxidation in air for 30 min at 500 ^oC. This treatment was applied to eliminate other forms of carbon as well as to shorten the tubes and open their caps. Hydrogen desorption was also measured in degassed samples (400 ^oC for 20 min in vacuum) which adsorbed H2 while cooling to room temperature. Desorption in degassed/hydrogenated samples is a two-step process which we attribute to distinct desorption characteristics of nanotubes and of residual oxidized metal catalysts.

Moreno-Ruiz, L. A.; Ortiz-Lopez, J.; de Ita de La Torre, A.; Arellano-Peraza, J. S.; Flores-Díaz, G.

2006-03-01

305

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

306

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

307

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

308

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

309

Effects of reactive admixtures on the near-IR emission spectra of hydrogen and deuterium oxidation flames  

Microsoft Academic Search

The emission spectra of hydrogen-oxygen and hydrogen-air flames at 0.1–1 atm exhibit a system of bands between 852 and 880\\u000a nm, which is assigned to the H2O2 molecule vibrationally excited into the overtone region. This molecule results from the reaction HO\\u000a 2\\u000a \\u000a + HO\\u000a 2\\u000a \\u000a ? H2O\\u000a 2\\u000a v\\u000a + O2. The overtone region also contains bands at 670 and

N. M. Rubtsov; G. I. Tsvetkov; V. I. Chernysh; V. V. Azatyan

2007-01-01

310

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

SciTech Connect

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

Bai, Jianmin

1993-12-31

311

Renewable hydrogen and carbon nanotubes from biodiesel waste glycerol  

PubMed Central

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

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

2013-01-01

312

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

313

Hydrogenated 5-carbon compound and method of making  

SciTech Connect

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

314

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.

Horowitz, Scott; Trievel, Raymond C.

2012-01-01

315

Path integral Monte Carlo calculations of helium and hydrogen–helium plasma thermodynamics and of the deuterium shock Hugoniot  

Microsoft Academic Search

In this work, we calculate the thermodynamic properties of hydrogen–helium plasmas with different mass fractions of helium by the direct path integral Monte Carlo method. To avoid unphysical approximations, we use the path integral representation of the density matrix. We pay special attention to the region of weak coupling and degeneracy and compare the results of simulation with a model

P. R. Levashov; V. S. Filinov; M. Bonitz; V. E. Fortov

2006-01-01

316

Path integral Monte Carlo calculations of helium and hydrogen helium plasma thermodynamics and of the deuterium shock Hugoniot  

Microsoft Academic Search

In this work, we calculate the thermodynamic properties of hydrogen-helium plasmas with different mass fractions of helium by the direct path integral Monte Carlo method. To avoid unphysical approximations, we use the path integral representation of the density matrix. We pay special attention to the region of weak coupling and degeneracy and compare the results of simulation with a model

P. R. Levashov; V. S. Filinov; M. Bonitz; V. E. Fortov

2006-01-01

317

Multilayer Adsorption of Neon, Hydrogens, and Carbon Monoxide on Graphite  

Microsoft Academic Search

Multilayer adsorption of neon, hydrogens (H _2, HD, and D_2), and carbon monoxide on graphite have been investigated using ellipsometric-coverage vapor-pressure isotherm measurements. Chemical potentials at layer condensations and widths of the layer condensation steps were tabulated, and layer critical points were determined from the temperature dependence of the widths for all five adsorbates. In Ne we do not find

Hong Wu

1995-01-01

318

Spin density in hydrogenated amorphous carbon films—different originations  

Microsoft Academic Search

Hydrogenated amorphous carbon (a-C:H) films were deposited on glass in a plasma-enhanced chemical vapor deposition (PECVD) system using methane as a source gas. The characteristics of the films were studied by electron spin resonance (ESR), Raman, and Fourier transform infrared (FT-IR) spectroscopy. In particular, the relationship between the variation of ESR spin density and the structural change in the a-C:H

Y. O. Cho; J. M. Cho; W. J. Yun; O. H. Cha; E.-K. Suh; K. H. Yu; S.-C. Yu; J.-K. Lee

2002-01-01

319

Optimization of Nano-Carbon Materials for Hydrogen Sorption  

SciTech Connect

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

Yakobson, Boris I [Rice University

2013-08-02

320

Substrate effects on the microstructure of hydrogenated amorphous carbon films  

Microsoft Academic Search

In this work, plasma enhanced chemical vapour deposition was used to prepare hydrogenated amorphous carbon films (a-C:H) on different substrates over a wide range of thickness. In order to observe clear substrate effect the films were produced under identical growth conditions. Raman and near edge X-ray absorption fine structure (NEXAFS) spectroscopies were employed to probe the chemical bonding of the

I. Ahmad; S. S. Roy; T. I. T. Okpalugo; P. D. Maguire; J. A. McLaughlin

2009-01-01

321

Hydrogenated amorphous carbon as protective coating for a forming tool  

Microsoft Academic Search

This paper investigates the performance of hydrogenated amorphous carbon (a-C:H) films as protective coatings for a forming tool made from AISI M2 steel coated with a titanium nitride (TiN) PVD commercial layer. The samples were initially cleaned in ultrasonic baths and subsequently in a plasma ablation procedure. Films were then deposited by plasma immersion ion implantation using 91% of acetylene

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

2011-01-01

322

Carbon nanofiber supported Ni catalysts for the hydrogenation of chloronitrobenzenes  

Microsoft Academic Search

Carbon nanofiber (CNF) supported nickel catalysts for hydrogenation of o-chloronitrobenzene were prepared by deposition precipitation method in ethylene glycol. It has been found that the precipitation temperature affected both the particle size and the catalytic performance of the CNF-supported catalysts. The Ni\\/CNFs catalyst prepared at 80°C showed the best catalytic activity. For all of the Ni\\/CNFs catalysts prepared in ethylene

Chuang Wang; Jieshan Qiu; Changhai Liang; Li Xing; Xiaomin Yang

2008-01-01

323

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

PubMed

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

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

2006-06-14

324

Sulfur and Hydrogen Isotope Anomalies in Meteorite Sulfonic Acids  

NASA Astrophysics Data System (ADS)

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

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

1997-08-01

325

Sulfur and hydrogen isotope anomalies in meteorite sulfonic acids.  

PubMed

Intramolecular carbon, hydrogen, and sulfur isotope ratios were measured on a homologous series of organic sulfonic acids discovered in the Murchison meteorite. Mass-independent sulfur isotope fractionations were observed along with high deuterium/hydrogen ratios. The deuterium enrichments indicate formation of the hydrocarbon portion of these compounds in a low-temperature environment that is consistent with that of interstellar clouds. Sulfur-33 enrichments observed in methanesulfonic acid could have resulted from gas-phase ultraviolet irradiation of a precursor, carbon disulfide. The source of the sulfonic acid precursors may have been the reactive interstellar molecule carbon monosulfide. PMID:9262469

Cooper, G W; Thiemens, M H; Jackson, T L; Chang, S

1997-08-22

326

Sulfur and Hydrogen Isotope Anomalies in Meteorite Sulfonic Acids  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

327

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

328

Identification of the degradation product of ezlopitant, a non-peptidic substance p antagonist receptor, by hydrogen deuterium exchange, electrospray ionization tandem mass spectrometry (ESI\\/MS\\/MS) and nuclear magnetic resonance (NMR) spectroscopy  

Microsoft Academic Search

The degradation product of ezlopitant was isolated from low specific activity material and identified by solution phase hydrogen\\/deuterium (H\\/D) exchange and electrospray ionization tandem mass spectrometry (ESI\\/MS\\/MS) to be an isopropyl peroxide analog of ezlopitant. The structure of the degradant was further confirmed by nuclear magnetic resonance (NMR) spectroscopy utilizing complete 1H and 13C assignments. Studies were also performed to

Amin M Kamel; Kathleen S Zandi; Walter W Massefski

2003-01-01

329

Hydrogen-Bond Detection, Configuration Assignment, and Rotamer Correction of Side-Chain Amides in Large Proteins by NMR through Protium/Deuterium Isotope Effects  

PubMed Central

In this study, the configuration and hydrogen-bonding network of side-chain amides in a 35 kDa protein are determined via measuring differential and across-hydrogen-bond H/D isotope effects by the IS-TROSY technique, which leads to a reliable recognition and correction of erroneous rotamers frequently found in protein structures. First, the differential two-bond isotope effects on carbonyl 13C? shifts, defined as ?2?13C? (ND) = 2?13C? (NDE) ? 2?13C? (NDZ), provide a reliable means for the configuration assignment for side-chain amides, as environmental effects (hydrogen bonds and charges etc.) are greatly attenuated over the two bonds separating the carbon and hydrogen atoms and the isotope effects fall into a narrow range of positive values. Second and more importantly, the significant variations in the differential one-bond isotope effects on 15N chemical shifts, defined as ?1?15N(D) = 1?15N(DE) ? 1?15N(DZ), can be correlated with hydrogen-bonding interactions, particularly those involving charged acceptors. The differential one-bond isotope effects are additive with major contributions from intrinsic differential conjugative interactions between the E and Z configurations, H-bonding interactions, and charge effects. Furthermore, the pattern of across-H-bond H/D isotope effects can be mapped onto more complicated hydrogen-bonding networks involving bifurcated hydrogen-bonds. Third, the correlations between ?1?15N(D) and hydrogen-bonding interactions afford an effective means for the correction of erroneous rotamer assignments of side-chain amides. The rotamer correction via differential isotope effects is not only robust but simple and can be applied to large proteins.

Liu, Aizhuo; Wang, Jifeng; Lu, Zhenwei; Yao, Lishan; Li, Yue; Yan, Honggao

2010-01-01

330

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.

2012-01-01

331

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

332

External reflection FTIR of peptide monolayer films in situ at the air/water interface: experimental design, spectra-structure correlations, and effects of hydrogen-deuterium exchange.  

PubMed Central

A Fourier transform infrared spectrometer has been interfaced with a surface balance and a new external reflection infrared sampling accessory, which permits the acquisition of spectra from protein monolayers in situ at the air/water interface. The accessory, a sample shuttle that permits the collection of spectra in alternating fashion from sample and background troughs, reduces interference from water vapor rotation-vibration bands in the amide I and amide II regions of protein spectra (1520-1690 cm-1) by nearly an order of magnitude. Residual interference from water vapor absorbance ranges from 50 to 200 microabsorbance units. The performance of the device is demonstrated through spectra of synthetic peptides designed to adopt alpha-helical, antiparallel beta-sheet, mixed beta-sheet/beta-turn, and unordered conformations at the air/water interface. The extent of exchange on the surface can be monitored from the relative intensities of the amide II and amide I modes. Hydrogen-deuterium exchange may lower the amide I frequency by as much as 11-12 cm-1 for helical secondary structures. This shifts the vibrational mode into a region normally associated with unordered structures and leads to uncertainties in the application of algorithms commonly used for determination of secondary structure from amide I contours of proteins in D2O solution.

Flach, C R; Brauner, J W; Taylor, J W; Baldwin, R C; Mendelsohn, R

1994-01-01

333

The pH dependence of hydrogen-deuterium exchange in trp repressor: the exchange rate of amide protons in proteins reflects tertiary interactions, not only secondary structure.  

PubMed Central

The pH dependence of amide proton exchange rates have been measured for trp-repressor. One class of protons exchanges too fast to be measured in these experiments. Among the protons that have measurable hydrogen-deuterium exchange rates, two additional classes may be distinguished. The second class of protons are in elements of secondary structure that are mostly on the surface of the protein, and exchange linearly with increasing base concentration (log kex versus pH). The third class of amide protons is characterized by much higher protection against exchange at higher pH. These protons are located in the core of the protein, in helices B and C. The exchange rate in the core region does not increase linearly with pH, but rather goes through a minimum around pH 6. The mechanism of exchange for the slowly exchanging core protons is interpreted in terms of the two-process model of Hilton and Woodward (1979, Biochemistry 18:5834-5841), i.e., exchange through both a local mechanism that does not require unfolding of the protein, and a mechanism involving global unfolding of the protein. The increase in exchange rates at low pH is attributed to a partial unfolding of the repressor. It is concluded that the formation of secondary structure alone is insufficient to account for the high protection factors seen in the core of native proteins at higher pH, and that tertiary interactions are essential to stabilize the structure.

Finucane, M. D.; Jardetzky, O.

1996-01-01

334

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

PubMed Central

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

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

2013-01-01

335

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

SciTech Connect

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

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

2011-04-15

336

Local Conformational Stability of HIV-1 gp120 in Unliganded and CD4-Bound States as Defined by Amide Hydrogen/Deuterium Exchange? †  

PubMed Central

The binding reaction of the HIV-1 gp120 envelope glycoprotein to the CD4 receptor involves exceptional changes in enthalpy and entropy. Crystal structures of gp120 in unliganded and various ligand-bound states, meanwhile, reveal an inner domain able to fold into diverse conformations, a structurally invariant outer domain, and, in the CD4-bound state, a bridging sheet minidomain. These studies, however, provide only hints as to the flexibility of each state. Here we use amide hydrogen/deuterium exchange coupled to mass spectrometry to provide quantifications of local conformational stability for HIV-1 gp120 in unliganded and CD4-bound states. On average, unliganded core gp120 displayed >10,000-fold slower exchange of backbone-amide hydrogens than a theoretically unstructured protein of the same composition, with binding by CD4 reducing the rate of gp120 amide exchange a further 10-fold. For the structurally constant CD4, alterations in exchange correlated well with alterations in binding surface (P value = 0.0004). For the structurally variable gp120, however, reductions in flexibility extended outside the binding surface, and regions of expected high structural diversity (inner domain/bridging sheet) displayed roughly 20-fold more rapid exchange in the unliganded state than regions of low diversity (outer domain). Thus, despite an extraordinary reduction in entropy, neither unliganded gp120 nor free CD4 was substantially unstructured, suggesting that most of the diverse conformations that make up the gp120 unliganded state are reasonably ordered. The results provide a framework for understanding how local conformational stability influences entropic change, conformational diversity, and structural rearrangements in the gp120-CD4 binding reaction.

Kong, Leopold; Huang, Chih-chin; Coales, Stephen J.; Molnar, Kathleen S.; Skinner, Jeff; Hamuro, Yoshitomo; Kwong, Peter D.

2010-01-01

337

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

PubMed Central

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

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

2008-01-01

338

Was venus wet? Deuterium reconsidered.  

PubMed

The ratio of deuterium to hydrogen on Venus has been accepted as proof of a wetter, more Earth-like past 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. PMID:17737672

Grinspoon, D H

1987-12-18

339

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

PubMed

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

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

2014-03-01

340

Numerical Analysis of Hydrogen Storage in Carbon Nanopores  

NASA Astrophysics Data System (ADS)

Carbon-based materials, due to their low cost and weight, have long been considered as suitable physisorption substrates for the reversible storage of hydrogen. Nanoporous carbons can be engineered to achieve exceptional storage capacities: gravimetric excess adsorption of 0.073 ± 0.003 kg H2/kg carbon, gravimetric storage capacity of 0.106 ± 0.005 kg H2/kg carbon, and volumetric storage capacity of 0.040 ± 0.002 kg H2/liter carbon, at 80 K and 50 bar. The nanopores generage high storage capacity by having a very high surface are, by generating a high H2-wall interaction potential, and by allowing multi-layer adsorption of H2 (at cryogenic temperatures). In this paper we show how the experimental adsorption isotherms can be understood from basic theoretical considerations and computational simulations of the adsorption in a bimodal distribution of narrow and wide pore spaces. We also analyze the possibility of multi-layer adsorption, and the effects of hypothetical larger adsorption energies. Finally, we present the results of coupled ab initio calculations and Monte Carlo simulations showing that partial substitution of carbon atoms in nanoporous matrix with boron results in significant increases of the adsorption energy and storage capacity.

Wexler, Carlos; Olsen, Raina; Pfeifer, Peter; Kuctha, Bogdan; Firlej, Lucyna; Roszak, Sztepan

341

Numerical Analysis of Hydrogen Storage in Carbon Nanopores  

NASA Astrophysics Data System (ADS)

Carbon-based materials, due to their low cost and weight, have long been considered as suitable physisorption substrates for the reversible storage of hydrogen. Nanoporous carbons can be engineered to achieve exceptional storage capacities: gravimetric excess adsorption of 0.073 ± 0.003 kg H2/kg carbon, gravimetric storage capacity of 0.106 ± 0.005 kg H2/kg carbon, and volumetric storage capacity of 0.040 ± 0.002 kg H2/liter carbon, at 80 K and 50 bar. The nanopores generage high storage capacity by having a very high surface are, by generating a high H2-wall interaction potential, and by allowing multi-layer adsorption of H2 (at cryogenic temperatures). In this paper we show how the experimental adsorption isotherms can be understood from basic theoretical considerations and computational simulations of the adsorption in a bimodal distribution of narrow and wide pore spaces. We also analyze the possibility of multi-layer adsorption, and the effects of hypothetical larger adsorption energies. Finally, we present the results of coupled ab initio calculations and Monte Carlo simulations showing that partial substitution of carbon atoms in nanoporous matrix with boron results in significant increases of the adsorption energy and storage capacity.

Wexler, Carlos; Olsen, Raina; Pfeifer, Peter; Kuctha, Bogdan; Firlej, Lucyna; Roszak, Sztepan

2011-03-01

342

Effect of the Surface Temperature on Net Carbon Deposition and Deuterium Codeposition in DIII-D Divertor  

Microsoft Academic Search

We report a strong effect of a moderately elevated surface temperature on net C deposition and D co-deposition in DIII-D divertor under detached conditions. A DiMES sample with a gap 2 mm wide and 15 mm deep was exposed to L-mode plasmas first at room temperature then at 200^oC. At the elevated temperature deuterium co-deposition in the gap was reduced

D. L. Rudakov; R. Bastasz; J. Brooks; N. H. Brooks; W. Jacob; A. Litnovsky; A. G. McLean

2005-01-01

343

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

PubMed

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

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

2013-11-21

344

The determination of hydrogen and deuterium in Zr 2.5Nb material by hot vacuum extraction mass spectrometry  

NASA Astrophysics Data System (ADS)

An analysis method for the determination of H and D concentrations in Zr-2.5Nb material has been established based on hot vacuum extraction and isotope dilution mass spectrometry. Hot vacuum extraction enables complete removal of the hydrogen isotopes from the sample. The isotope dilution technique is used to determine quantitatively the amount of hydrogen isotopes in the extracted gas. Methods for preparing standards of H, D or H and D in Zr-2.5Nb have also been established. These 'in-house' standards are used to assess the performance of the analysis method. The analysis uncertainty, based on the determined content relative to the dosed H or D isotope content of each standard, is 1% (at a level of confidence of 95%) for samples containing greater than ˜5 ?moles H or D. The uncertainty increases to 5% as the sample content decreases to 0.5 ?moles H or D. The uncertainty of this analysis method is well within the requirements for surveillance examinations of CANDU ® reactors and post-irradiation examinations of reactor components.

Bickel, G. A.; Green, L. W.; James, M. W. D.; Lamarche, T. G.; Leeson, P. K.; Michel, H.

2002-11-01

345

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

SciTech Connect

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

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

2010-01-01

346

Triboelectromagnetic phenomena in a diamond\\/hydrogenated-carbon-film tribosystem under perfluoropolyether fluid lubrication  

Microsoft Academic Search

Triboelectromagnetic phenomena of an emission of negatively and positively charged particles were measured during sliding of a diamond on a carbon film with various hydrogen contents under perfluoropolyether (PFPE) fluid lubrication. This tribosystem simulates the material combination of a head slider coated with a diamond-like carbon film and the magnetic recording disk coated with hydrogenated carbon films under PFPE lubrication.

Keiji Nakayama; Stephanie Nguyen

2000-01-01

347

Hydrogenated carbon layers produced by ion beam irradiation of PMMA and polystyrene films  

Microsoft Academic Search

The dissociation of the polymeric structure, which results from ion beam irradiation, leads to the formation of hydrogenated carbon layers exhibiting new optical and conducting properties at high fluence. The properties of these hydrogenated carbon layers have been compared to the properties of diamond-like carbon films prepared by plasma techniques: we discuss the modifications induced by ion beams in PMMA,

J. Davenas; P. Thevenard; G. Boiteux; M. Fallavier; X. L. Lu

1990-01-01

348

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

349

Voltammetric Detection of Hydrogen Peroxide at Carbon Fiber Microelectrodes  

PubMed Central

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 non-electroactive 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 vs. Ag/AgCl at a scan rate of 400 V·sec-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 ?M. 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.

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

2010-01-01

350

Hydrogen sensors based on Pd-functionalized Single-walled carbon nanotubes  

Microsoft Academic Search

We have demonstrated properties for hydrogen sensing by single-walled carbon nanotubes (SWNTs) with Pd nanoparticles functionalized on dendrimer. In conclusion, fabricated SWNTs with Pd nanoparticles functionalized on dendrimers can expect outstanding ability as hydrogen sensor.

J. M. Lee; Seonghwa Ju; Y. Jung; Sung-Jin Kim; Wooyoung Lee

2010-01-01

351

Long-lived electron capture dissociation product ions experience radical migration via hydrogen abstraction  

Microsoft Academic Search

To explore the mechanism of electron capture dissociation (ECD) of linear peptides, a set of 16-mer peptides were synthesized\\u000a with deuterium labeled on the ?-carbon position of four glycines. The ECD spectra of these peptides showed that such peptides\\u000a exhibit a preference for the radical to migrate to the ?-carbon position on glycine via hydrogen (or deuterium) abstraction\\u000a before the

Peter B. O’Connor; Cheng Lin; Jason J. Cournoyer; Jason L. Pittman; Marina Belyayev; Bogdan A. Budnik

2006-01-01

352

Polarizability calculations on water, hydrogen, oxygen, and carbon dioxide  

NASA Technical Reports Server (NTRS)

A semiclassical model of damped oscillators is used as a basis for the calculation of the dispersion of the refractive index, polarizability, and dielectric permeability in water, hydrogen, and oxygen in liquid and gaseous states, and in gaseous carbon dioxide. The absorption coefficient and the imaginary part of the refractive index are also calculated at corresponding wavelengths. A good agreement is obtained between the observed and calculated values of refractive indices, and between those of absorption coefficients in the region of absorption bands. The calculated values of oscillator strengths and damping factors are also discussed. The value of the polarizability of liquid water was about 2.8 times that of previous calculations.

Nir, S.; Adams, S.; Rein, R.

1973-01-01

353

Synthesis of carbon black/carbon nitride intercalation compound composite for efficient hydrogen production.  

PubMed

The photoactivity of g-C3N4 is greatly limited by its high recombination rate of photogenerated carriers. Coupling g-C3N4 with other materials has been demonstrated to be an effective way to facilitate the separation and transport of charge carriers. Herein we report a composite of conductive carbon black and carbon nitride intercalation compound synthesized through facile one-step molten salt method. The as-prepared carbon black/carbon nitride intercalation compound composite was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), UV-vis absorption spectrum and photoluminescence spectroscopy (PL). The carbon black nanoparticles, homogeneously dispersed on the surface of carbon nitride intercalation compound, efficiently enhanced separation and transport of photogenerated carriers, thus improving the visible-light photocatalytic activity. The composite of 0.5 wt% carbon black and carbon nitride intercalation compound exhibited a H2 production rate of 68.9 ?mol h(-1), which is about 3.2 times higher than hydrogen production on pristine carbon nitride intercalation compound. PMID:24975427

Wu, Zhaochun; Gao, Honglin; Yan, Shicheng; Zou, Zhigang

2014-07-15

354

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

355

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

356

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

PubMed Central

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

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

2013-01-01

357

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

PubMed

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

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

2014-07-01

358

Cyclic deformation behavior and low cycle fatigue life of normalized medium carbon steel with hydrogen charging  

Microsoft Academic Search

The effects of hydrogen on low cycle fatigue properties have been fundamentally examined using normalized JIS S45C steel. With the aid of hydrogen thermal desorption analysis, the influence of the increase in carbon content has been discussed. The S45C steel easily pick-up hydrogen. But it is relatively insensitive to hydrogen absorption. This increased amount of hydrogen pick-up is firstly caused

Y. Tsuchida; T. Watanabe; G. Suzuki; H. Yano

2011-01-01

359

Combustion characteristics of hydrogen. Carbon monoxide based gaseous fuels  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

360

Hydrogenation of carbon monoxide over nanostructured systems: A mechanochemical approach  

NASA Astrophysics Data System (ADS)

In this study we investigated the mechanochemical hydrogenation of carbon monoxide over nanostructured FeCo- and Mg 2Ni-based catalysts. To this aim powdered materials, prepared by mechanical alloying, were subjected to mechanical treatment under CO + H 2 atmosphere. A methodology to evaluate the activity of the solid catalysts on an absolute basis was developed. Conversion data were, indeed, expressed as turnover frequency, TOF, and related to the occurrence of ball to powder collision events through the mechanochemical turnover frequency parameter, MTOF. Differences in the catalytic activity and selectivity were observed for the two FeCo-based studied systems, the solid solution Fe 50Co 50 and its dispersion on TiO 2 support. As for the Mg 2Ni system, we explored the possibility to estimate the specific role of hydrogen pre-activation step. The catalytic properties of the mechanically alloyed Mg 2Ni system were compared with the conversion data shown by the same system pre-hydrogenated and subsequently milled under CO atmosphere.

Mulas, Gabriele; Campesi, Renato; Garroni, Sebastiano; Delogu, Francesco; Milanese, Chiara

2011-07-01

361

HYBRID HETEROGENEOUS CATALYSTS FOR HYDROGENATION OF CARBON DIOXIDE  

SciTech Connect

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

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

2006-09-01

362

Interaction of carbon monoxide and hydrogen with the (1010) face of ruthenium  

SciTech Connect

The interaction was studied at 23.5, 200, and -135/sup 0/C with low energy electron diffraction (LEED) and Auger electron spectroscopy. (AES). Carbon monoxide adsorbs associatively at 23.5/sup 0/C, but is apparently dissociated by the LEED beam and hydrogen adsorbed from the ambient after a few minutes for less than 10 Langmuirs of carbon monoxide. For large doses of carbon monoxide at 23.5/sup 0/C, 10 Langmuirs or more, the LEED beam does not disociate carbon monoxide, but carbon monoxide and hydrogen adsorbed from the ambient do appear to be removed from the surface by the LEED beam. Carbon monoxide and hydrogen on the surface together will react and form surface complexes with distinctive LEED patterns at 23.5/sup 0/C though some of the interactions appear to be LEED beam induced. If sufficient hydrogen is present, some of these complexes are lost from the surface probably as methane and water. Carbon monoxide will react with itself and hydrogen at 23.5/sup 0/C with carbon being lost from the surface probably as carbon dioxide. At 200/sup 0/C, neither carbon monoxide nor hydrogen will absorb on Ru (1010) in significant amounts at the low dose pressures used. However, if the Ru(1010) crystal is allowed to cool below 70/sup 0/C, ambient carbon monoxide and hydrogen will adsorb on Ru (1010) and form LEED patterns like those formed at 23.5/sup 0/C. At -135/sup 0/C, carbon monoxide will react with itself and hydrogen readily most of the time producing surface complexes with distinctive LEED paterns. If a moderate amount of hydrogen is present, some of these complexes are lost from the surface, probably as methane. If a large amount of hydrogen is present, some of these complexes are lost from the surface probably as carbon dioxdie. 17 figures, 8 tables.

Tomcsik, T.L.

1979-01-01

363

High electric field deuterium ion sources for neutron generators  

NASA Astrophysics Data System (ADS)

Active interrogation systems for highly enriched uranium require improved fieldable neutron sources. The target technology for deuterium-tritium neutron generators is well understood and the most significant improvement can be achieved by improving the deuterium ion source through increased output and, in some cases, lifetime of the ion source. We are developing a new approach to a deuterium ion sources based upon the field desorption/evaporation of deuterium from the surfaces of metal tips. Electrostatic field desorption (EFD) desorbs previously adsorbed deuterium as ions under the influence of high electric fields (several V/A), without removing tip material. Single etched wire tip experiments have been performed and have shown that this is difficult but can be achieved with molybdenum and tungsten tips. Electrostatic field evaporation (EFE) evaporates ultra thin deuterated titanium films as ions. It has been shown that several 10s of atomic layers can be removed within a few nanoseconds from etched tungsten tips. In the course of these studies titanium deposition and deuteration methods were studied and new detection methods developed. Space charge effects resulting from the large ion currents were identified to be the most likely cause of some unusual ion emission characteristics. In addition, on W < 110 > oriented substrates a surprising body-centered cubic crystal structure of the titanium film was found and studied. The ion currents required for neutron generator applications can be achieved by microfabrication of metal tip arrays. Field desorption studies of microfabricated field emitter tip arrays have been conducted for the first time. Maximum fields of 3 V/A have been applied to the array tip surfaces to date, although fields of ˜ 2 V/A to ˜ 2.5 V/A are more typical. Desorption of atomic deuterium ions has been observed at fields of roughly 2 V/A at room temperature. The desorption of common surface adsorbates, such as hydrogen, carbon, water, and carbon monoxide is observed at fields exceeding ˜1 V/A. In vacuo heating of the arrays to temperatures of the order of 800°C can be effective in removing many of the surface contaminants observed. For both the field desorption and the field evaporation approaches further improvements to array design and fabrication are required if arrays are to provide sufficient deuterium ion currents to produce 109 to 1010 n/cm2 of tip array area for the detection systems.

Reichenbach, Birk

364

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

Microsoft Academic Search

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

M. Takagawa; M. Ohsugi

1987-01-01

365

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

366

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

Microsoft Academic Search

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

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

2011-01-01

367

Role of Surface Hydrogen Bonds in Determining the Friction Behaviors of Hydrogenated Diamond-like Carbon Films  

NASA Astrophysics Data System (ADS)

Friction behaviors of hydrogenated diamond-like carbon (H-DLC) films are investigated on a ball-on-disk type tribometer in dry N2 and dry vacuum. The result shows that the friction behaviors of the H-DLC films are very sensitive to the testing environment, the H-DLC films exhibit a very low friction coefficient of 0.016 in dry N2, and similarly in an inert gas the friction coefficient increases to about 0.063 in dry vacuum. Combining the testing conditions, friction results, SEM and XPS investigation, it is concluded that the friction behaviors of the hydrogenated DLC films are associated with surface hydrogen of the H-DLC films and are dictated by whether or not hydrogen bonds are formed between the transfer films/H-DLC films at the sliding interface. A hydrogen-induced hydrogen bond model is proposed to interpret the friction behaviors of hydrogenated DLC films in different environments.

Wang, Cheng-Bing; Shi, Jing; Geng, Zhong-Rong; Zhang, Jun-Yan

2012-05-01

368

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

369

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...

370

Physical solubility of hydrogen sulfide and carbon dioxide in alkanolamine solutions  

Microsoft Academic Search

The study was undertaken to develop a method that would make direct measurements of acid gases, hydrogen sulfide and carbon dioxide, physical solubilities in aqueous alkanolamine solutions possible. Hydrogen sulfide and carbon dioxide physical solubilities in 20, 35, and 50% by weight diethanolamine aqueous solutions were measured. The solubility measurements were made at acid gas partial pressure up to 1000

Abu-Arabi

1988-01-01

371

Extreme hydrogen, oxygen and carbon isotope anomalies in the pore waters and carbonates of the sediments and basalts from the Norwegian Sea: Methane and hydrogen from the mantle  

SciTech Connect

D/H ratios in the pore waters of the sediments from the Norwegian Sea decrease as a function of depth to values as low as {minus}14{per thousand}. Oxygen isotope ratios in the pore waters and carbon and oxygen isotope ratios in carbonates both in the sediments and basalts are low. Extensive alteration of basalt has been given as the explanation for the low oxygen isotope ratios. Material balance calculations suggest that alteration of volcanic material and oxidation of organic matter cannot explain the hydrogen and carbon isotope anomalies. Arguments are presented suggesting that methane and hydrogen from the mantle are oxidized to carbon dioxide and water by sulfate and ferric iron in the basaltic crust to yield the low hydrogen and carbon isotope ratios.

Lawrence, J.R. (Univ. of Houston, University Park, TX (USA)); Taviani, M. (Instituto di Geologia Marina, del C.N.R., Bologna (Italy))

1988-08-01

372

Carbon doped boron nitride cages as competitive candidates for hydrogen storage materials.  

PubMed

By the incorporation of C atoms into (BN)(12) fullerene, our theoretical investigation shows that carbon doped boron nitride cages (BNC) can achieve a high hydrogen storage amount of 7.43 wt%, and dehydrogenation of the corresponding BNC hydrides (BNC(H)) is thermodynamically favored for practical applications of hydrogen energy, making BNC competitive candidates for hydrogen storage materials. PMID:20107638

Wu, H Y; Fan, X F; Kuo, Jer-Lai; Deng, Wei-Qiao

2010-02-14

373

Content of hydrogen in boron-, carbon-, nitrogen-, oxygen-, fluorine- and neon-implanted titanium  

Microsoft Academic Search

Commercially available pure titanium contains a significant amount of hydrogen. Ion implantation into pure titanium samples distorts the lattice causing the hydrogen to diffuse into the implantation region and can thus affect the formation of phases (defects, vacancies). In this work, the effects of hydrogen content were examined for ion-implanted titanium samples. The implantation of boron, carbon, nitrogen, oxygen and

M Soltani-Farshi; H Baumann; D Rück; E Richter; U Kreissig; K Bethge

1998-01-01

374

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

375

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

376

Hydrogen concentration of co-deposited carbon film produced in the vicinity of LHD divertor tiles  

NASA Astrophysics Data System (ADS)

In order to investigate the hydrogen retention and desorption behavior in co-deposited carbon film, a unique sample holder was mounted on the plasma-facing wall close to the graphite divertor tiles in the LHD during the 13th experimental campaign. The amount of deposited carbon for the sample with a large visual angle against the divertor tile was much larger than that with a small visual angle. The amount of retained hydrogen increased with the film thickness, but not proportional to the thickness. The carbon films contained boron caused by boronization and the retained hydrogen was trapped mainly by C-H and B-H bonds. Hydrogen concentration for the carbon film with a large visual angle against the graphite tile was much smaller than that with a small visual angle, possibly owing to the difference of the ratio of hydrogen influx to carbon influx.

Nobuta, Y.; Fukayama, K.; Ashikawa, N.; Yamauchi, Y.; Hino, T.; Sagara, A.; LHD Experimental Group

2013-07-01

377

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

378

Platelet adhesion on silicon modified hydrogenated amorphous carbon films.  

PubMed

We have investigated the effect of changes in microstructure, surface energy, surface charge condition and electronic conduction on the interaction of human platelets with silicon modified hydrogenated amorphous carbon films (a-C:H:Si or Si-DLC). Results based on Raman spectroscopy, Scanning electron microscopy, X-ray photo-electron spectroscopy, surface energy measurements, electrical resistivity, contact potential difference, and thermal annealing indicates a correlation between some of the measured values and the interaction of the films with human blood platelets. Statistical analysis of platelet aggregation on the films using the Student's t-test indicated differences between platelet aggregation on the modified films compared to the as-deposited film at a p-value of <0.05. PMID:14585711

Okpalugo, T I T; Ogwu, A A; Maguire, P D; McLaughlin, J A D

2004-01-01

379

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

NASA Technical Reports Server (NTRS)

A novel process and apparatus is disclosed for sustainable, continuous production of hydrogen and carbon by catalytic dissociation or decomposition of hydrocarbons at elevated temperatures using in-situ generated carbon particles. Carbon particles are produced by decomposition of carbonaceous materials in response to an energy input. The energy input can be provided by at least one of a non-oxidative and oxidative means. The non-oxidative means of the energy input includes a high temperature source, or different types of plasma, such as, thermal, non-thermal, microwave, corona discharge, glow discharge, dielectric barrier discharge, or radiation sources, such as, electron beam, gamma, ultraviolet (UV). The oxidative means of the energy input includes oxygen, air, ozone, nitrous oxide (NO.sub.2) and other oxidizing agents. The method, apparatus and process of the present invention is applicable to any gaseous or liquid hydrocarbon fuel and it produces no or significantly less CO.sub.2 emissions compared to conventional processes.

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

2012-01-01

380

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

Microsoft Academic Search

Hydrogen-bond acidic fluoroalcohol groups are directly attached to the backbone of single walled carbon nanotubes (SWCNTs) via carbon–carbon bonds without the introduction of intermediate heteroatoms. Hexafluoroisopropanol functional groups are exceptionally strong hydrogen-bond acids, and are added to the nanotube surface (via the substituted benzene para position) as 2-phenyl-1,1,1,3,3,3-hexafluoro-2-propanol (i.e., –(p-C6H4)C(CF3)2OH) using the aryl diazonium approach to create hydrogen-bond acidic carbon

Leonard S. Fifield; Jay W. Grate

2010-01-01

381

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

382

Characterization of the hydrogen-deuterium exchange activities of the energy-transducing HupSL hydrogenase and H(2)-signaling HupUV hydrogenase in Rhodobacter capsulatus.  

PubMed

Rhodobacter capsulatus synthesizes two homologous protein complexes capable of activating molecular H(2), a membrane-bound [NiFe] hydrogenase (HupSL) linked to the respiratory chain, and an H(2) sensor encoded by the hupUV genes. The activities of hydrogen-deuterium (H-D) exchange catalyzed by the hupSL-encoded and the hupUV-encoded enzymes in the presence of D(2) and H(2)O were studied comparatively. Whereas HupSL is in the membranes, HupUV activity was localized in the soluble cytoplasmic fraction. Since the hydrogenase gene cluster of R. capsulatus contains a gene homologous to hoxH, which encodes the large subunit of NAD-linked tetrameric soluble hydrogenases, the chromosomal hoxH gene was inactivated and hoxH mutants were used to demonstrate the H-D exchange activity of the cytoplasmic HupUV protein complex. The H-D exchange reaction catalyzed by HupSL hydrogenase was maximal at pH 4. 5 and inhibited by acetylene and oxygen, whereas the H-D exchange catalyzed by the HupUV protein complex was insensitive to acetylene and oxygen and did not vary significantly between pH 4 and pH 11. Based on these properties, the product of the accessory hypD gene was shown to be necessary for the synthesis of active HupUV enzyme. The kinetics of HD and H(2) formed in exchange with D(2) by HupUV point to a restricted access of protons and gasses to the active site. Measurement of concentration changes in D(2), HD, and H(2) by mass spectrometry showed that, besides the H-D exchange reaction, HupUV oxidized H(2) with benzyl viologen, produced H(2) with reduced methyl viologen, and demonstrated true hydrogenase activity. Therefore, not only with respect to its H(2) signaling function in the cell, but also to its catalytic properties, the HupUV enzyme represents a distinct class of hydrogenases. PMID:11029418

Vignais, P M; Dimon, B; Zorin, N A; Tomiyama, M; Colbeau, A

2000-11-01

383

Ab initio investigation of molecular hydrogen physisorption on graphene and carbon nanotubes  

NASA Astrophysics Data System (ADS)

Density-functional theory is used to investigate hydrogen physisorption on a graphene layer and on single wall carbon nanotubes. Both external and internal adsorption sites of (9, 0) and (10, 0) carbon nanotubes have been studied with the hydrogen molecular axis oriented parallel or perpendicular to the nanotube wall. A range of hydrogen molecule binding sites has been examined and it is found that hydrogen binds weakly to each of the graphitic structures and at all adsorption sites examined. Calculations using different functionals reveal that the binding energies are a factor of 2 larger for hydrogen bound inside the nanotubes than for adsorption outside the nanotubes or on the graphene layer. Furthermore, configurations of the hydrogen molecular axis parallel to the nanotube wall or graphene layer bind more effectively than configurations where the axis is normal to the carbon nanostructures. The differing behavior between the carbon nanostructures is attributed to the curvature of the structure and the hydrogen-carbon electron interactions, where analysis of the electron density reveals evidence of charge redistribution with little charge transfer. The potential of hydrogen physisorption to carbon nanostructures for hydrogen storage and delivery is also discussed.

Henwood, D.; Carey, J. David

2007-06-01

384

Spreading of PFPE lubricants on carbon surfaces: effect of hydrogen and nitrogen content  

Microsoft Academic Search

The spreading of OH-terminated perfluoropolyalkylether (PFPE), Zdol, on amorphous carbon surfaces was studied as a function\\u000a of hydrogen or nitrogen content in the carbon film, using scanning micro-ellipsometry. A layered structure of the thickness\\u000a profiles was observed, which remained qualitatively the same for all carbon types. The sharpness of the second layer was gradually\\u000a eroded as either hydrogen or nitrogen

Xiaoding Ma; Jing Gui; Kevin J. Grannen; Laura A. Smoliar; Bruno Marchon; Myung S. Jhon; Charles L. Bauer

1999-01-01

385

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

SciTech Connect

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 made. Activity data suggest that benzene hydrogenation occurs both on Pt/C and carbon diluent due to hydrogen spillover. The specific activity increased to a dilution level beyond which it became constant. This fact was further confirmed by H[sub 2] uptake measurements. Arrhenius plots of various diluted samples show an equal slope resulting in a uniform value for activation energy. The mechanism of benzene hydrogenation due to spilled over hydrogen on Pt/C appears to be same as on Pt/[gamma]-Al[sub 2]O[sub 3]. 73 refs., 5 figs., 1 tab.

Srinivas, S.T.; Rao, P.K. (Indian Institute of Chemical Technology, Hyderabad (India))

1994-08-01

386

Comparison of metal and carbon catalysts for hydrogen production by methane decomposition  

Microsoft Academic Search

The COx-free hydrogen production by decomposition of methane was carried out over metal-free carbons and bulk and supported metal catalysts. Catalysts based on Ni or Fe (oxides, spinels and ex-hydrotalcite mixed oxides) and carbon-catalysts of different types (carbon black, activated carbon, carbon nanotubes and graphite) have been used and the performance of both different kinds of catalyst compared in the

R. Guil-Lopez; J. A. Botas; J. L. G. Fierro; D. P. Serrano

2011-01-01

387

Deep inelastic structure functions from electron scattering on hydrogen, deuterium, and iron at 0. 6 GeV sup 2 le Q sup 2 le 30. 0 GeV sup 2  

SciTech Connect

We report the final results from experiment E140, a recent deep inelastic electron-deuterium and electron-iron scattering experiment at SLAC. In addition, we present the results of a combined global analysis of all SLAC deep inelastic electron-hydrogen and electron-deuterium cross section measurements between 1970 and 1983. Data from seven earlier experiments are re-radiatively corrected and normalized to experiment E140. We report extractions of R(x,Q{sup 2}) and F{sub 2}(x,Q{sup 2}) for hydrogen and deuterium over the entire SLAC kinematic range: .06{le} x {le}.90 and 0.6{le} Q{sup 2} {le}30.0 (GeV{sup 2}). We fine that R{sup p} = R{sup d}, as expected by QCD. Extracted values of R(x,Q{sup 2}) are significantly larger than predictions based on QCD and on QCD with the inclusion of kinematic target mass terms. This difference indicates that dynamical higher twist effects may be important in the SLAC kinematic range. A best fit empirical model of R(x,Q{sup 2}) is used to extract F{sub 2} from each cross section measurement. These F{sub 2} extractions are compared with F{sub 2} data from EMC and BCDMS. Agreement is observed with EMC when the EMC data are multiplied by 1.07. Agreement is observed with BCDMS over a limited range in x. The ratios of F{sub 2}{sup d}/F{sub 2}{sup p} are examined for Q{sup 2} dependence. We observe a significant negative slope for x {le} .6, and a significant positive slope above x > .7, in excellent agreement with predictions based on QCD with the inclusion of kinematic target mass terms. 111 refs., 40 figs., 34 tabs.

Whitlow, L.W.

1990-03-01

388

Tribological behavior and gas-surface interactions of hydrogenated carbon films  

Microsoft Academic Search

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

Pamela Laurie Dickrell

2005-01-01

389

Synthesis of deuterium-labeled fluphenazine  

SciTech Connect

The propylpiperazine side chain of fluphenazine has been labeled with two, four, and six deuterium atoms by lithium aluminum deuteride reduction of the appropriate ester or imide. The gamma-carbon of the propyl group was labeled with two deuterium atoms by reduction of 10- (2-methoxycarbonylethyl) -2-trifluoromethyl-10H-phenothiazine, while four deuterium atoms were incorporated into the piperazine ring by reduction of 10-(3-(3,5-dioxo-1-piperazinyl)propyl)-2-trifluoromethyl-10H-pheno thiazine. The latter reduction gave the d4-labeled N-deshydroxyethyl metabolite of fluphenazine.

Shetty, H.U.; Hawes, E.M.; Midha, K.K.

1984-01-01

390

Extreme deuterium enrichment of organic radicals in the Orgueil meteorite: Revisiting the interstellar interpretation?  

NASA Astrophysics Data System (ADS)

The insoluble organic matter of the carbonaceous meteorites contains radicals having a polyaromatic structure and a heterogeneous distribution. By using Hyperfine Sublevel Correlation spectroscopy (HYSCORE) in pulsed Electron Paramagnetic Resonance (pulsed-EPR), whereby nuclear frequencies of magnetic nuclei and their hyperfine interaction with electron spin of radicals are detected with high resolution, the radicals are shown to be considerably enriched in deuterium in the Orgueil meteorite, with a D/H ratio of 1.5 ± 0.5 × 10 -2. These radicals hold 3.6 ± 1.2 × 10 -3 H relative to total organic H. Analysis of hydrogen and deuterium hyperfine interactions indicates that the deuterium atoms are localized in the benzylic position, on aliphatic carbons bonded to aromatic radical moieties. This type of C-H bond exhibits one of the smallest bond energy, reinforcing the recent finding that the lower the C-H bond energy the higher the deuterium-enrichment (Remusat L., Palhol F., Robert F., Derenne S. and France-Lanord C. (2006) Enrichment of deuterium in insoluble organic matter from primitive meteorites: a solar system origin? Earth Planet. Sci. Lett.243, 15-25). Such a behavior is difficult to reconcile with the usual interpretation according to which high D/H ratios represent survivals of interstellar grains. More likely, the deuterium-enrichment process took place after the formation of organic grains whose initial isotopic compositions was close to the protosolar D/H ratio. These grains were possibly loaded at the surface of the protosolar disk where they exposed to the intense solar UV irradiation, triggering an isotopic exchange with deuterium-rich highly reactive ions.

Gourier, Didier; Robert, Francois; Delpoux, Olivier; Binet, Laurent; Vezin, Herve; Moissette, Alain; Derenne, Sylvie

2008-04-01

391

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

392

Hydrogen adsorption in bundles of well-aligned carbon nanotubes at room temperature  

NASA Astrophysics Data System (ADS)

Bundles of well-aligned and randomly-ordered carbon nanotubes were produced by catalytic pyrolysis of a carbon source with quartz glass as a substrate. Their morphologies and pore structures were analyzed by N 2 adsorption at 77 K and by SEM and TEM. According to N 2 adsorption, the bundles of aligned carbon nanotubes have a narrow pore distribution mainly in micro- and meso-pores, which is favorable for hydrogen uptake. In hydrogen adsorption measurements at room temperature under moderate pressure (3-10 MPa), we found that the well-aligned carbon nanotube bundles have a hydrogen storage capacity of over 3 wt.%. This suggests that multi-walled carbon nanotubes are a promising material for hydrogen storage.

Zhu, Hongwei; Cao, Anyuan; Li, Xuesong; Xu, Cailu; Mao, Zongqiang; Ruan, Dianbo; Liang, Ji; Wu, Dehai

2001-07-01

393

Inverse kinetic isotope effects and deuterium enrichment as a function of carbon number during formation of C–C bonds in cobalt catalyzed Fischer–Tropsch synthesis  

Microsoft Academic Search

How the deuterium is enriched in hydrocarbons produced by Fischer–Tropsch (FT) synthesis is of broad scientific interest, particularly to those studying the mechanism of the FT reaction and the formation of hydrocarbons in the Earth's crust or in the nebula. In order to determine whether there is an inverse isotope effect and whether there exists the deuterium enrichment in hydrocarbons

Buchang Shi; Chunfen Jin

2011-01-01

394

Effect of Hydrogen Content on Threshold Stress Intensity Factor in Carbon Steel in Hydrogen-Assisted Cracking Environments  

Microsoft Academic Search

Crack propagation of carbon steel (CS) caused by hydrogen in an overprotective buffer solution environment was investigated to determine the threshold stress intensity factor (K{sub IH}) for hydrogen assisted-cracking (HAC) using a wedge open-load (WOL) specimen. The K-value decreasing-type testing method was adopted as the experimental method. The possibility of crack propagation by cathodic protection (CP) in the soil environment

Y. Yamaguchi; K. Yamakawa; H. Nonaka

1997-01-01

395

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

396

Hydrogen storage in different carbon materials: Influence of the porosity development by chemical activation  

NASA Astrophysics Data System (ADS)

The hydrogen adsorption capacity of different types of carbon nanofibers (platelet, fishbone and ribbon) and amorphous carbon have been measured as a function of pressure and temperature. The results showed that the more graphitic carbon materials adsorbed less hydrogen than more amorphous materials. After a chemical activation process, the hydrogen storage capacities of the carbon materials increased markedly in comparison with the non-activated ones. BET surface area of amorphous carbon increased by a factor of 3.5 and the ultramicropore volume doubled, thus increasing the hydrogen adsorption by a factor of 2. However, BET surface area in platelet CNFs increased by a factor of 3 and the ultramicropore volume by a factor of 6, thus increasing the hydrogen storage by a factor of 4.5. The dependency of hydrogen storage capacity of carbon materials on the BET surface area was evaluated using both a condensation model and experimental results. Comparison of data suggests that the hydrogen adsorption capacity clearly depends on the pore structure and so, on the accessibility to the internal surface.

Jiménez, Vicente; Ramírez-Lucas, Ana; Sánchez, Paula; Valverde, José Luís; Romero, Amaya

2012-01-01

397

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

398

Multilayer Adsorption of Neon, Hydrogens, and Carbon Monoxide on Graphite.  

NASA Astrophysics Data System (ADS)

Multilayer adsorption of neon, hydrogens (H _2, HD, and D_2), and carbon monoxide on graphite have been investigated using ellipsometric-coverage vapor-pressure isotherm measurements. Chemical potentials at layer condensations and widths of the layer condensation steps were tabulated, and layer critical points were determined from the temperature dependence of the widths for all five adsorbates. In Ne we do not find evidence for reentrant first -order layering, which was previously found in Ar, Kr, and Xe. The adsorption behavior on graphite of H_2, HD, and D_2 is very similar. We observed temperature-dependent splitting and hysteresis in the fourth, fifth, and sixth layers in all three adsorbates. This may suggest structure changes, possibly between face-centered cubic and hexagonal closed-packed stacking, in these layers. In CO, below the bulk alpha- beta transition temperature, we have seen incomplete wetting with a series of layer-appearance transitions from the third to the tenth layer. Above the alpha-beta transition temperature, the thickness of the film remains around 11 layers. We observed reentrant first-order layering in the condensation of the fourth layer in CO. But the broadening feature is much weaker compared to Ar, Kr, and Xe, and is not observed at all in the higher layers.

Wu, Hong

399

Behavior of carbon, oxygen, and sulfur during hydrogen blowing of liquid steel  

NASA Astrophysics Data System (ADS)

The decarburization of liquid steel during hydrogen blowing has been studied. The decarburization is caused by the interaction of carbon with oxygen dissolved in the metal. As the melt is blown with hydrogen, the decarburization is enhanced owing to hydrogen bubbles, which increase the effect of mixing of a metal bath and substantially increase the melt-gas phase interface. As a result, the rate and completeness of decarburization increase significantly. It is experimentally shown that hydrogen blowing of a melt substantially decreases the sulfur concentration in the metal because of the interaction of hydrogen with sulfur.

Makarov, M. A.; Aleksandrov, A. A.; Dashevskii, V. Ya.

2009-04-01

400

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

Microsoft Academic Search

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

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

2007-01-01

401

Determination of the charge on carbon in a bridging methylene iron dimer with solid-state deuterium NMR spectroscopy  

Microsoft Academic Search

The chemistry of bridging methylene metal dimers and the value of the ¹³C NMR chemical shifts have been interpreted as due to a partial negative charge on the carbon atom. PES yields a C\\/sub 1s\\/ binding energy indicative of -0.5 e charge. However, for (..mu..-CHâ)(MnCp(CO)â)â, a high-resolution x-ray diffraction electron density map shows no excess charge buildup. The authors are

Maria I. Altbach; Yukio Hiyama; Dennis J. Gerson; Leslie G. Butler

1987-01-01

402

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

403

The Friction Property of Hydrogenated Carbon with Fullerene Microstructure after Annealing  

Microsoft Academic Search

\\u000a Hydrogenated amorphous carbon films were deposited on Si (100) substrates by dc-pulse plasma chemical vapor deposition. Structurally,\\u000a the as-deposited carbon films could be considered as nanocomposite thin films with fullerene-like microstructure in diamond-like\\u000a carbon matrix based on our previous result. Here, the evolution of the structure and tribological properties of hydrogenated\\u000a carbon film with fullerene-like microstructure on the annealing in

Qi Wang; Zhou Wang; Chengbing Wang; Junyan Zhang

404

Mechanism and kinetics of dehydrogenation of higher n-paraffins on promoted platinum catalysts. I. Hydrogen/deuterium isotope exchange in n-decane  

SciTech Connect

To clarify the mechanism of the dehydrogenation reaction of n-decane on promoted platinum-alumina catalysts, we have examined the kinetics of deuterium isotope exchange with n-decane and its reaction products and measured the kinetic isotope effects. The reaction of n-decane proceeds via slow stages of desorption of olefins and dienes and of decatriene formation, while the aromatic products are rapidly desorbed. The reaction is mainly stepwise.

Krylova, T.L.; Nekrasov, N.V.; Gudkov, B.S.; Gurevich, V.R.; Kiperman, S.L.

1981-06-01

405

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

National Technical Information Service (NTIS)

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

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

2009-01-01

406

Liquid-Vapor Equilibria of the Hydrogen-Carbon Dioxide System.  

National Technical Information Service (NTIS)

An experimental investigation was conducted to determine the liquid-vapor phase equilibria of the hydrogen-carbon dioxide system. The experimental apparatus used in the investigation was a vapor recirculation type flow system provided with facilities for ...

P. L. Barrick C. K. Heck J. O. Spano

1966-01-01

407

Hydrogen Depolarized Carbon Dioxide Concentrator Performance Improvements and Cell Pair Structural Tests.  

National Technical Information Service (NTIS)

The investigations and testing associated with the CO2 removal efficiency and voltage degradation of a hydrogen depolarized carbon oxide concentrator are reported. Also discussed is the vibration testing of a water vapor electrolysis cell pair. Performanc...

J. D. Huddleston J. R. Aylward

1973-01-01

408

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

NASA Technical Reports Server (NTRS)

Recent work on the adhesion and friction properties of plasma-deposited amorphous hydrogenated carbon films and their dependence on preparation conditions are reviewed. The results of the study indicate that plasma deposition enables one to deposit a variety of amorphous hydrogenated carbon (a-C:H) exhibiting diamondlike friction behavior. The plasma-deposited a-C:H films can be effectively used as hard lubricating films on ceramic materials such as silicon nitride in vacuum.

Miyoshi, Kazuhisa

1991-01-01

409

Hydrogenation of isophorone with noble metal catalysts in supercritical carbon dioxide  

Microsoft Academic Search

Catalytic hydrogenation of 3,3,5-trimethyl-2-cyclohexen-1-one (isophorone) was examined over several supported noble metal catalysts in supercritical carbon dioxide. Charcoal supported rhodium and platinum catalysts were found to be active for the isophorone hydrogenation to 3,3,5-trimethylcyclohexanone (dihydroisophorone), but undesirable successive hydrogenation to 3,3,5-trimethylcyclohexanol also proceeded. Supported palladium catalysts were less active than the supported rhodium and platinum catalysts, but were highly selective

Takafumi Sato; Chandrashekhar V. Rode; Osamu Sato; Masayuki Shirai

2004-01-01

410

Hydrogen degradation of 21-6-9 and medium carbon steel by disc pressure test  

NASA Astrophysics Data System (ADS)

This paper reports the method of disc pressure test and the results for 21-6-9 stainless steel and medium carbon steel in hydrogen gas with different pressures and time of storage. The results show the hydrogen induced degradation of these two kinds of steel. An attempt was made to establish an index which uses variation of area of deformed disc to determine the degradation of ductility in a hydrogen environment.

Zhou, D. H.; Zhou, W. X.; Xu, Z. L.

1986-11-01

411

Carbon Nanotube-Based Hydrogen Gas Sensor Electrochemically Functionalized with Palladium  

Microsoft Academic Search

Palladium (Pd) has been widely employed for conventional hydrogen sensors due to the catalytic nature. Pd has been incorporated also with carbon nanotube (CNT) gas sensors for hydrogen sensing. In this study, a liquid-phase electrochemical reaction was proposed to realize a simple and inexpensive fabrication method of a Pd-functionalized CNT hydrogen sensor. The single-walled CNTs were trapped onto a microelectrode

Junya Suehiro; Shinji Yamane; Kiminobu Imasaka

2007-01-01

412

Coherent Carbon Cryogel-Ammonia Borane Nanocomposites for Improved Hydrogen Storage  

SciTech Connect

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

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

2007-07-15

413

A theoretical study of the dissociative chemisorption of hydrogen on carbon nanotubes  

Microsoft Academic Search

Potential profiles were obtained for the chemisorption of hydrogen on ( n, n) and ( n, 0) carbon nanotubes. The energy barriers and rate constants for hydrogen molecule sorption on and desorption from various nanotubes were determined. The constants for sorption and desorption were used to calculate sorption-desorption equilibrium constants. Sorption on outside nanotube surfaces was found to be more

A. A. Kuzubov; M. N. Popov; A. S. Fedorov; T. A. Kozhevnikova

2008-01-01

414

Selective replacement of hydrogen at a saturated carbon atom under the action of oxidising agents  

NASA Astrophysics Data System (ADS)

Data have been correlated for the heterolytic substitution reaction of hydrogen atoms in saturated hydrocarbons and also in some ethers and esters under the action of oxidising agents, viz. halogens, nitronium salts, halogen fluorides and ozone. Alternative schemes of electrophilic and nucleophilic substitution of hydrogen at an sp3-hybrid carbon atom are considered. The bibliography contains 79 references.

Boguslavskaya, L. S.; Kartashov, A. V.; Chuvatkin, N. N.

1990-06-01

415

Hydrogen degradation of 21-6-9 and medium carbon steel by disc pressure test  

Microsoft Academic Search

This paper reports the method of disc pressure test and the results for 21-6-9 stainless steel and medium carbon steel in hydrogen gas with different pressures and time of storage. The results show the hydrogen induced degradation of these two kinds of steel. An attempt was made to establish an index which uses variation of area of deformed disc to

D. H. Zhou; W. X. Zhou; Z. L. Xu

1986-01-01

416

Hydrogen production from solar energy powered supercritical cycle using carbon dioxide  

Microsoft Academic Search

A hydrogen production method is proposed, which utilizes solar energy powered thermodynamic cycle using supercritical carbon dioxide (CO2) as working fluid for the combined production of hydrogen and thermal energy. The proposed system consists of evacuated solar collectors, power generating turbine, water electrolysis, heat recovery system, and feed pump. In the present study, an experimental prototype has been designed and

Xin-Rong Zhang; Hiroshi Yamaguchi; Yuhui Cao

2010-01-01

417

Merging allylic carbon-hydrogen and selective carbon-carbon bond activation  

NASA Astrophysics Data System (ADS)

Since the nineteenth century, many synthetic organic chemists have focused on developing new strategies to regio-, diastereo- and enantioselectively build carbon-carbon and carbon-heteroatom bonds in a predictable and efficient manner. Ideal syntheses should use the least number of synthetic steps, with few or no functional group transformations and by-products, and maximum atom efficiency. One potentially attractive method for the synthesis of molecular skeletons that are difficult to prepare would be through the selective activation of C-H and C-C bonds, instead of the conventional construction of new C-C bonds. Here we present an approach that exploits the multifold reactivity of easily accessible substrates with a single organometallic species to furnish complex molecular scaffolds through the merging of otherwise difficult transformations: allylic C-H and selective C-C bond activations. The resulting bifunctional nucleophilic species, all of which have an all-carbon quaternary stereogenic centre, can then be selectively derivatized by the addition of two different electrophiles to obtain more complex molecular architecture from these easily available starting materials.

Masarwa, Ahmad; Didier, Dorian; Zabrodski, Tamar; Schinkel, Marvin; Ackermann, Lutz; Marek, Ilan

2014-01-01

418

Shock Compression of Deuterium and the Interiors of Jupiter and Saturn  

Microsoft Academic Search

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