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Sample records for dependent deuterium fractionation

  1. Deuterium fractionation mechanisms in interstellar clouds

    SciTech Connect

    Dalgarno, A.; Lepp, S.

    1984-12-01

    The theory of the fractionation of deuterated molecules is extended to include reactions with atomic deuterium. With the recognition that dissociative recombination of H/sup +//sub 3/ is not rapid, observational data can be used in conjunction with the theory to derive upper and lower bounds to the cosmic deuterium-hydrogen abundance ratio. We find that (D)/(H) is at least 3.4 x 10/sup -6/ and at most 4.0 x 10/sup -5/ with a probable value of 1 x 10/sup -5/. Because of the reaction HCO/sup +/+D..-->..DCO/sup +/+H, upper limits can be derived for the fractional ionization which depend only weakly on the cosmic ray flux, zeta. In four clouds, the upper limits to the fractional ionization lie between 1.1 x 10/sup -6/ and 1.5 x 10/sup -6/ if zeta = 10/sup -7/ s/sup -1/ and between 3.1 x 10/sup -6/ and 1.8 x 10/sup -6/ if zeta = 10/sup -16/ s/sup -1/.

  2. Deuterium fractionation in the Ophiuchus molecular cloud

    NASA Astrophysics Data System (ADS)

    Punanova, A.; Caselli, P.; Pon, A.; Belloche, A.; André, Ph.

    2016-03-01

    Context. In cold (T< 25 K) and dense (nH> 104 cm-3) interstellar clouds, molecules such as CO are significantly frozen onto dust grain surfaces. Deuterium fractionation is known to be very efficient in these conditions as CO limits the abundance of H3+, which is the starting point of deuterium chemistry. In particular, N2D+ is an excellent tracer of dense and cold gas in star-forming regions. Aims: We measure the deuterium fraction, RD, and the CO depletion factor, fd, towards a number of starless and protostellar cores in the L1688 region of the Ophiuchus molecular cloud complex and search for variations based upon environmental differences across L1688. The kinematic properties of the dense gas traced by the N2H+ and N2D+ (1-0) lines are also discussed. Methods: Deuterium fraction has been measured via observations of the J = 1-0 transition of N2H+ and N2D+ towards 33 dense cores in different regions of L1688. We estimated the CO depletion factor using C17O(1-0) and 850 μm dust continuum emission from the SCUBA survey. We carried out all line observations with the IRAM 30 m antenna. Results: The dense cores show large (≃2-40%) deuterium fractions with significant variations between the sub-regions of L1688. The CO depletion factor also varies from one region to another (between ≃1 and 7). Two different correlations are found between deuterium fraction and CO depletion factor: cores in regions A, B2, and I show increasing RD with increasing fd, similar to previous studies of deuterium fraction in pre-stellar cores; cores in regions B1, B1B2, C, E, F, and H show a steeper RD - fd correlation with large deuterium fractions occurring in fairly quiescent gas with relatively low CO freeze-out factors. These are probably recently formed, centrally concentrated starless cores, which have not yet started the contraction phase towards protostellar formation. We also find that the deuterium fraction is affected by the amount of turbulence, dust temperature, and

  3. Isotopic Anomalies in Primitive Solar System Matter: Spin-State-Dependent Fractionation of Nitrogen and Deuterium in Interstellar Clouds

    NASA Technical Reports Server (NTRS)

    Wirstrom, Eva S.; Charnley, Steven B.; Cordiner, Martin A.; Milam, Stefanie N.

    2012-01-01

    Organic material found in meteorites and interplanetary dust particles is enriched in D and N-15. This is consistent with the idea that the functional groups carrying these isotopic anomalies, nitriles and amines, were formed by ion-molecule chemistry in the protosolar nebula, Theoretical models of interstellar fractionation at low temperatures predict large enrichments in both D and N-15 and can account for the largest isotopic enrichments measured in carbonaceous meteorites. However, more recent measurements have shown that, in some primitive samples, a large N-15 enrichment does not correlate with one in D, and that some D-enriched primitive material displays little, if any, N-15 enrichment. By considering the spin-state dependence in ion-molecule reactions involving the ortho and para forms of H2, we show that ammonia and related molecules can exhibit such a wide range of fractionation for both N-15 and D in dense cloud cores. We also show that while the nitriles, HCN and HNC, contain the greatest N=15 enrichment, this is not expected to correlate with extreme D enrichment. These calculations therefore support the view that solar system N-15 and D isotopic anomalies have an interstellar heritage. We also compare our results to existing astronomical observations and briefly discuss future tests of this model.

  4. ISOTOPIC ANOMALIES IN PRIMITIVE SOLAR SYSTEM MATTER: SPIN-STATE-DEPENDENT FRACTIONATION OF NITROGEN AND DEUTERIUM IN INTERSTELLAR CLOUDS

    SciTech Connect

    Wirstroem, Eva S.; Cordiner, Martin A.; Charnley, Steven B.; Milam, Stefanie N.

    2012-09-20

    Organic material found in meteorites and interplanetary dust particles is enriched in D and {sup 15}N. This is consistent with the idea that the functional groups carrying these isotopic anomalies, nitriles and amines, were formed by ion-molecule chemistry in the protosolar nebula. Theoretical models of interstellar fractionation at low temperatures predict large enrichments in both D and {sup 15}N and can account for the largest isotopic enrichments measured in carbonaceous meteorites. However, more recent measurements have shown that, in some primitive samples, a large {sup 15}N enrichment does not correlate with one in D, and that some D-enriched primitive material displays little, if any, {sup 15}N enrichment. By considering the spin-state dependence in ion-molecule reactions involving the ortho and para forms of H{sub 2}, we show that ammonia and related molecules can exhibit such a wide range of fractionation for both {sup 15}N and D in dense cloud cores. We also show that while the nitriles, HCN and HNC, contain the greatest {sup 15}N enrichment, this is not expected to correlate with extreme D enrichment. These calculations therefore support the view that solar system {sup 15}N and D isotopic anomalies have an interstellar heritage. We also compare our results to existing astronomical observations and briefly discuss future tests of this model.

  5. Isotopic Anomalies in Primitive Solar System Matter: Spin-State Dependent Fractionation of Nitrogen and Deuterium in Interstellar Clouds

    NASA Technical Reports Server (NTRS)

    Wirstrom, Eva S.; Charnley, Steven B.; Cordiner, Martin A.; Milan, Stefanie N.

    2012-01-01

    Organic material found in meteorites and interplanetary dust particles is enriched in D and N-15, This is consistent with the idea that the functional groups carrying these isotopic anomalies, nitriles and amines, were formed by ion-molecule chemistry in the protosolar core. Theoretical models of interstellar fractionation at low temperatures predict large enrichments in both D and N-15 and can account for the largest isotop c enrichments measured in carbonaceous meteorites, However, more recent measurements have shown that, in some primitive samples, a large N-15 enrichment does not correlate with one in D, and that some D-enriched primitive material displays little, if any, N-15 enrichment. By considering the spin-state dependence in ion-molecule reactions involving the ortho and para forms of H2, we show that ammonia and related molecules can exhibit such a wide range of fractionation for both N-15 and D in dense cloud cores, We also show that while the nitriles, HCN and HNC, contain the greatest N-15 enrichment, this is not expected to correlate with extreme D emichment. These calculations therefore support the view that Solar System N-15 and D isotopic anomalies have an interstellar heritage, We also compare our results to existing astronomical observations and briefly discuss future tests of this model.

  6. Calculations of ion-molecule deuterium fractionation reactions involving HD

    NASA Technical Reports Server (NTRS)

    Maluendes, Sergio A.; Mclean, A. D.; Herbst, Eric

    1992-01-01

    Gas-phase chemical models of deuterium fractionation in dense interstellar clouds utilize a small number of exothermic reactions to achieve fractionation. Although HD is a major repository of deuterium, it appears not to exchange deuterium with many molecular ions. Useful semiquantitative reasons have been given for the unusual lack of reactivity of exothermic ion-HD deuterium exchange systems, but quantum chemical studies are needed to understand these ideas in more detail and to determine if the lack of reactivity pertains at very low temperatures not studied in the laboratory, or whether tunneling can drive the reactions. Accordingly, the potential energy surfaces of three representative ion-molecule exchange reactions involving protonated ions and HD have been investigated with ab initio quantum chemical techniques. Our results generally confirm the semiquantitative picture as to which reactions are likely to occur and show that tunneling at low temperatures is unlikely to alter this picture.

  7. Fluence dependence of deuterium retention in oxidized SS-316

    NASA Astrophysics Data System (ADS)

    Oya, Yasuhisa; Suzuki, Sachiko; Matsuyama, Masao; Hayashi, Takumi; Yamanishi, Toshihiko; Asakura, Yamato; Okuno, Kenji

    2011-10-01

    The ion fluence dependence of deuterium retention in SS-316 during oxidation at a temperature of 673 K was studied to evaluate the dynamics of deuterium retention in the oxide layer of SS-316. The correlation between the chemical state of stainless steel and deuterium retention was evaluated using XPS and TDS. It was found that the major deuterium desorption temperatures were located at around 660 K and 935 K, which correspond to the desorption of deuterium trapped as hydroxide. The deuterium retention increased with increasing deuterium ion fluence, since the deuterium retention as hydroxide increased significantly. However, retention saturated at an ion fluence of ˜2.5 × 10 21 D + m -2. The XPS result showed that FeOOD was formed on the surface, although pure Fe also remained in the oxide layer. These facts indicate the nature of the oxide layer have a key role in deuterium trapping behavior.

  8. The Gas-Phase Deuterium Fractionation of Formaldehyde

    NASA Astrophysics Data System (ADS)

    Osamura, Yoshihiro; Roberts, Helen; Herbst, Eric

    2005-03-01

    The dominant mechanism for the deuteration of formaldehyde in the gas phase of low-temperature interstellar cloud cores occurs via reaction with the deuterating ions H2D+, HD+2, and D+3. Until now, it has been assumed that deuteration leads to an ion that, on recombination with electrons, can produce a deuterated neutral species with a statistical branching fraction. Quantum chemical calculations reported here, however, show an entirely different picture, in which the deuteration of formaldehyde leads to the molecular ion H2COD+, where the deuterium binds only on the oxygen side of the molecule. The structure is quite stable, while an alternative structure, H2DCO+, cannot be produced in a straightforward manner. Dissociative recombination of H2COD+ to reproduce a formaldehyde structure then removes the deuteration if the dissociation is direct, i.e., it occurs without change of structure. There are several possible indirect mechanisms by which dissociative recombination can lead to HDCO, however. For example, if the direct products are HCOD+H, it is possible that subsequent isomerization to HDCO can occur, although this involved process is unlikely. Another possibility is isomerization during the actual dissociation of the H2COD intermediate. Models of deuterium fractionation in which dissociative recombination is predominantly direct are presented, and it is found that the deuterium fractionation of formaldehyde to form both HDCO and D2CO can still occur via other mechanisms, although with less efficiency than previously obtained. If the dissociative recombination is half indirect, however, then we can recover the previously calculated efficiency.

  9. CORRELATING INFALL WITH DEUTERIUM FRACTIONATION IN DENSE CORES

    SciTech Connect

    Schnee, Scott; Brunetti, Nathan; Friesen, Rachel; Di Francesco, James; Johnstone, Doug; Pon, Andy; Caselli, Paola

    2013-11-10

    We present a survey of HCO{sup +} (3-2) observations pointed toward dense cores with previous measurements of N(N{sub 2}D{sup +})/N(N{sub 2}H{sup +}). Of the 26 cores in this survey, 5 show the spectroscopic signature of outward motion, 9 exhibit neither inward nor outward motion, 11 appear to be infalling, and 1 is not detected. We compare the degree of deuterium fractionation with infall velocities calculated from the HCO{sup +} spectra and find that those cores with [D]/[H] > 0.1 are more likely to have the signature of inward motions than cores with smaller [D]/[H] ratios. Infall motions are also much more common in cores with masses exceeding their thermal Jeans masses. The fastest infall velocity measured belongs to one of the two protostellar cores in our survey, L1521F, and the observed motions are typically on the order of the sound speed.

  10. AN ANALYSIS OF THE DEUTERIUM FRACTIONATION OF STAR-FORMING CORES IN THE PERSEUS MOLECULAR CLOUD

    SciTech Connect

    Friesen, R. K.; Kirk, H. M.; Shirley, Y. L.

    2013-03-01

    We have performed a pointed survey of N{sub 2}D{sup +} 2-1 and N{sub 2}D{sup +} 3-2 emission toward 64 N{sub 2}H{sup +}-bright starless and protostellar cores in the Perseus molecular cloud using the Arizona Radio Observatory Submillimeter Telescope and Kitt Peak 12 m telescope. We find a mean deuterium fractionation in N{sub 2}H{sup +}, R{sub D} = N(N{sub 2}D{sup +})/N(N{sub 2}H{sup +}), of 0.08, with a maximum R{sub D} = 0.2. In detected sources, we find no significant difference in the deuterium fractionation between starless and protostellar cores, nor between cores in clustered or isolated environments. We compare the deuterium fraction in N{sub 2}H{sup +} with parameters linked to advanced core evolution. We only find significant correlations between the deuterium fraction and increased H{sub 2} column density, as well as with increased central core density, for all cores. Toward protostellar sources, we additionally find a significant anticorrelation between R{sub D} and bolometric temperature. We show that the Perseus cores are characterized by low CO depletion values relative to previous studies of star-forming cores, similar to recent results in the Ophiuchus molecular cloud. We suggest that the low average CO depletion is the dominant mechanism that constrains the average deuterium fractionation in the Perseus cores to small values. While current equilibrium and dynamic chemical models are able to reproduce the range of deuterium fractionation values we find in Perseus, reproducing the scatter across the cores requires variation in parameters such as the ionization fraction or the ortho-to-para-H{sub 2} ratio across the cloud, or a range in core evolution timescales.

  11. An Analysis of the Deuterium Fractionation of Star-forming Cores in the Perseus Molecular Cloud

    NASA Astrophysics Data System (ADS)

    Friesen, R. K.; Kirk, H. M.; Shirley, Y. L.

    2013-03-01

    We have performed a pointed survey of N2D+ 2-1 and N2D+ 3-2 emission toward 64 N2H+-bright starless and protostellar cores in the Perseus molecular cloud using the Arizona Radio Observatory Submillimeter Telescope and Kitt Peak 12 m telescope. We find a mean deuterium fractionation in N2H+, RD = N(N2D+)/N(N2H+), of 0.08, with a maximum RD = 0.2. In detected sources, we find no significant difference in the deuterium fractionation between starless and protostellar cores, nor between cores in clustered or isolated environments. We compare the deuterium fraction in N2H+ with parameters linked to advanced core evolution. We only find significant correlations between the deuterium fraction and increased H2 column density, as well as with increased central core density, for all cores. Toward protostellar sources, we additionally find a significant anticorrelation between RD and bolometric temperature. We show that the Perseus cores are characterized by low CO depletion values relative to previous studies of star-forming cores, similar to recent results in the Ophiuchus molecular cloud. We suggest that the low average CO depletion is the dominant mechanism that constrains the average deuterium fractionation in the Perseus cores to small values. While current equilibrium and dynamic chemical models are able to reproduce the range of deuterium fractionation values we find in Perseus, reproducing the scatter across the cores requires variation in parameters such as the ionization fraction or the ortho-to-para-H2 ratio across the cloud, or a range in core evolution timescales.

  12. Deuterium fractionation of water in the Solar nebula

    NASA Astrophysics Data System (ADS)

    Albertsson, Tobias; Semenov, Dmitry; Henning, Thomas

    2013-07-01

    Water evaporates in the inner regions of protoplanetary disks and is frozen onto grains in the outer regions. Therefore its presence in vast quantities on Earth is puzzling. Subsequent delivery through bombardment by primitive bodies formed in the outer icy regions is the favored mechanism. By studying water D/H ratios one hopes to understand whether the water was mainly delivered by comets or asteroids. Using an extended deuterium chemistry network coupled to a 2D chemo-dynamical disk model, we investigate the evolution of the D/H ratio of water in the young Solar nebula. We find that both the laminar and mixing Solar nebula models show the Earth's ocean water D/H ratio at 2-3 AU. In addition, the 2D-mixing model explains better the water D/H values observed in the Oort- and Jupiter-family comets.

  13. Deuterium Fractionation on Mars and Evolutionary Implications for Water

    NASA Astrophysics Data System (ADS)

    Pathare, A. V.; Paige, D. A.

    1998-09-01

    Deuterium/Hydrogen (D/H) in the Martian atmosphere is enriched relative to terrestrial Standard Mean Ocean Water (SMOW) by a factor of 5.5. Yung et al. (1) photochemically modeled the escape efficiency (R) of D relative to H and obtained 0.32. Such high R implies that Mars experienced massive water loss early in its history, and cannot have significantly exchanged with juvenile water since. But Yung et al. (1) did not consider solar cycle related variations in both exospheric temperature and ionospheric chemistry, and when we accounted for changes in solar activity we obtained R = 0.17, which as we discussed last year is consistent with episodic juvenile water resupply. However, earlier this year Krasnopolsky et al. (2) obtained an even lower R = 0.02, based on spectroscopic measurements of deuterium which they could only reproduce by assuming that the ratio of (HD/H2) / (HDO/H2O) at the 80 km base of the exosphere was less than 10 based on Yung et al. (1). To explain this significant deviation, Krasnopolsky et al. (2) argued that partitioning of D into HD and HDO is controlled not kinetically but rather thermodynamically. However, as pointed out by Yung and Kass (3), this explanation would require an isotopic exchange rate coefficient over 10 orders of magnitude larger than that measured for this thermodynamic reaction in the laboratory. Therefore, we explore within the confines of the more likely applicable kinetic photochemical theory whether less extreme variations in exospheric and/or lower atmospheric reaction rate constants could result in a resolution to this dilemma. For example, variations in the vertical distribution of D could allow higher densities of HD at 80 km to be consistent with the new spectroscopic observations, or changes in the tropospheric conversion of HDO into HD could lessen the predicted amount of HD at 80 km. In addition, we examine the new climatological implications of R < 0.32 upon the evolution of Martian water, as massive

  14. Deuterium Fractionation in Analogs of Interstellar Ices: Laboratory Measurements

    NASA Technical Reports Server (NTRS)

    Sandford, Scott A.; DeVincenzi, Donald L. (Technical Monitor)

    2001-01-01

    A question of key interest in the field of Astrobiology is the extent to which organic compounds made in space may play a role in the origin of life in planetary systems. In general, the best proof that at least some interstellar materials survive incorporation into forming stellar/planetary systems is their identification in extraterrestrial samples through detection of the isotopic anomalies they may carry. In the case of organic compounds, the chief isotopic anomalies that might be expected are the enrichment of D and 15N. and such enrichments are seen in primitive extraterrestrial materials, for example, in the organics in carbonaceous chondrites and interplanetary dust particles. In my talk I will review the various astrochemical processes by which deuterium can become enriched in organic compounds and will discuss some recent laboratory experiments that examine one of these processes in particular. name]y the UV photolysis of interstellar ices. Finally, I will review the current state of our knowledge of D enrichments in primitive solar system materials and discuss the constraints these data place on the relative importance of the various possible interstellar D enrichment processes.

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

    NASA Astrophysics Data System (ADS)

    Gurwell, M. A.; Yung, Y. L.

    1993-02-01

    The collisional ejection process for hydrogen on Venus is reanalyzed. Improved values for the efficiency of H and D escape as a function of the ionospheric temperature are reported. It is proposed that the reduction of the hydrogen flux for collisional ejection be reduced from 8 to 3.5 x 10 exp 6/sq cm/s, and a revised D/H fractional factor of 0.47 due to collisional ejection is suggested. The resulting deuterium flux is 3.1 x 10 exp 4/sq cm/s, roughly six times the flux due to charge exchange, making collisional ejection the dominant escape mechanism for deuterium on Venus.

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

    NASA Technical Reports Server (NTRS)

    Gurwell, Mark A.; Yung, Yuk L.

    1993-01-01

    The collisional ejection process for hydrogen on Venus is reanalyzed. Improved values for the efficiency of H and D escape as a function of the ionospheric temperature are reported. It is proposed that the reduction of the hydrogen flux for collisional ejection be reduced from 8 to 3.5 x 10 exp 6/sq cm/s, and a revised D/H fractional factor of 0.47 due to collisional ejection is suggested. The resulting deuterium flux is 3.1 x 10 exp 4/sq cm/s, roughly six times the flux due to charge exchange, making collisional ejection the dominant escape mechanism for deuterium on Venus.

  17. Deuterium Fractionation and Ionization Degree in Massive Protostellar/cluster Cores

    NASA Astrophysics Data System (ADS)

    Chen, Huei-Ru; Liu, Sheng-Yuan; Su, Yu-Nung

    2013-03-01

    We have conducted a survey of deuterium fractionation of N2H+, RD (N2H+) ≡ N(N2D+)/N(N2H+), with the Arizona Radio Observatory (ARO) Submillimeter Telescope (SMT) to assess the use of RD (N2H+) as an evolutionary tracer among massive protostellar/cluster cores in early stages. Our sample includes 32 dense cores in various evolutionary stages, from high-mass starless cores (HMSCs), high-mass protostellar objects (HMPOs), to ultra-compact (UC) HII regions, in infrared dark clouds (IRDCs) and high infrared extinction clouds. The results show a decreasing trend in deuterium fractionation with evolutionary stage traced by gas temperature and line width (Fig. 1). A moderate increasing trend of deuterium fractionation with the CO depletion factor is also found among cores in IRDCs and HMSCs. These suggest a general chemical behavior of deuterated species in low- and high-mass protostellar candidates. Upper limits to the ionization degree are also estimated to be in the range of 4 × 10-8 - 5 × 10-6.

  18. Temperature dependence of deuterium retention in tungsten deposits by deuterium ion irradiation

    NASA Astrophysics Data System (ADS)

    Katayama, K.; Uehara, K.; Date, H.; Fukada, S.; Watanabe, H.

    2015-08-01

    Tungsten (W) deposits were formed by hydrogen plasma sputtering and blisters were observed on the surface. The W deposits and W foils were exposed to deuterium ions with 2 keV-D2+ to doses of 1.0 × 1021 D2+/m2 at 294 and 773 K in addition to 573 K in the present authors' previous work. Hydrogen isotopes release behaviors from the W deposits and W foils were observed by the thermal desorption spectroscopy method. The amount of deuterium released from the W deposit was considerably larger than that from W foil. The obtained deuterium retention in D/m2 was in the range of deuterium retention in polycrystalline tungsten. Not only implanted deuterium but also hydrogen, which was incorporated during the sputtering-deposition process, were released from the W deposits. A hydrogen release peak at around 1100 K was observed for the W deposits. This is considered to be due to the rupture of the blisters.

  19. NEW EXTENDED DEUTERIUM FRACTIONATION MODEL: ASSESSMENT AT DENSE ISM CONDITIONS AND SENSITIVITY ANALYSIS

    SciTech Connect

    Albertsson, T.; Semenov, D. A.; Henning, Th.; Vasyunin, A. I.; Herbst, E.

    2013-08-15

    Observations of deuterated species are useful in probing the temperature, ionization level, evolutionary stage, chemistry, and thermal history of astrophysical environments. The analysis of data from the Atacama Large Millimeter Array and other new telescopes requires an elaborate model of deuterium fractionation. This paper presents a publicly available chemical network with multi-deuterated species and an extended, up-to-date set of gas-phase and surface reactions. To test this network, we simulate deuterium fractionation in diverse interstellar sources. Two cases of initial abundances are considered: (1) atomic except for H{sub 2} and HD, and (2) molecular from a prestellar core. We reproduce the observed D/H ratios of many deuterated molecules, and sort the species according to their sensitivity to temperature gradients and initial abundances. We find that many multiply deuterated species produced at 10 K retain enhanced D/H ratios at temperatures {approx}< 100 K. We study how recent updates to reaction rates affect calculated D/H ratios, and perform a detailed sensitivity analysis of the uncertainties of the gas-phase reaction rates in the network. We find that uncertainties are generally lower in dark cloud environments than in warm infrared dark clouds and that uncertainties increase with the size of the molecule and number of D-atoms. A set of the most problematic reactions is presented. We list potentially observable deuterated species predicted to be abundant in low- and high-mass star-formation regions.

  20. New Extended Deuterium Fractionation Model: Assessment at Dense ISM Conditions and Sensitivity Analysis

    NASA Astrophysics Data System (ADS)

    Albertsson, T.; Semenov, D. A.; Vasyunin, A. I.; Henning, Th.; Herbst, E.

    2013-08-01

    Observations of deuterated species are useful in probing the temperature, ionization level, evolutionary stage, chemistry, and thermal history of astrophysical environments. The analysis of data from the Atacama Large Millimeter Array and other new telescopes requires an elaborate model of deuterium fractionation. This paper presents a publicly available chemical network with multi-deuterated species and an extended, up-to-date set of gas-phase and surface reactions. To test this network, we simulate deuterium fractionation in diverse interstellar sources. Two cases of initial abundances are considered: (1) atomic except for H2 and HD, and (2) molecular from a prestellar core. We reproduce the observed D/H ratios of many deuterated molecules, and sort the species according to their sensitivity to temperature gradients and initial abundances. We find that many multiply deuterated species produced at 10 K retain enhanced D/H ratios at temperatures <~ 100 K. We study how recent updates to reaction rates affect calculated D/H ratios, and perform a detailed sensitivity analysis of the uncertainties of the gas-phase reaction rates in the network. We find that uncertainties are generally lower in dark cloud environments than in warm infrared dark clouds and that uncertainties increase with the size of the molecule and number of D-atoms. A set of the most problematic reactions is presented. We list potentially observable deuterated species predicted to be abundant in low- and high-mass star-formation regions.

  1. Hydrated fractions of cellulosics probed by infrared spectroscopy coupled with dynamics of deuterium exchange.

    PubMed

    Driemeier, Carlos; Mendes, Fernanda M; Ling, Liu Yi

    2015-08-20

    This article presents a novel method to selectively probe the non-crystalline, hydrated fractions of cellulosic biomass. The method is based on time-resolved infrared spectra analyzed to provide information on spectral and dynamical features of deuterium exchange (OH → OD) in D2O atmosphere. We assign deuterium exchange spectral regions (700-3800 cm(-1)) and explore changes due to relative humidity, different cellulosic samples, and infrared polarization. Here, two results are highlighted. First, a wide range of celluloses isolated from plants show remarkable spectral similarities whatever the relative amounts of cellulose and xylan. This result supports an inherent type of hydrated disorder which is mostly insensitive to the molecular identities of the associated polysaccharides. Second, polarized infrared analysis of cotton reveals hydrated cellulose having chains preferentially aligned with those of crystals, while the hydroxyls of hydrated cellulose present much more randomized orientation. Our results provide new insights on molecular and group orientation and on hydrogen bonding in hydrated fractions of cellulosic biomass. PMID:25965468

  2. Deuterium Fractionation: The Ariadne's Thread from the Precollapse Phase to Meteorites and Comets Today

    NASA Astrophysics Data System (ADS)

    Ceccarelli, C.; Caselli, P.; Bockelée-Morvan, D.; Mousis, O.; Pizzarello, S.; Robert, F.; Semenov, D.

    The solar system formed about 4.6 billion years (b.y.) ago from condensation of matter inside a molecular cloud. Trying to reconstruct what happened is the goal of this chapter. For that, we combine our understanding of Galactic objects that will eventually form new suns and planetary systems with our knowledge on comets, meteorites, and small bodies of the solar system today. The specific tool we are using is molecular deuteration, namely the amount of deuterium with respect to hydrogen in molecules. This is the Ariadne’s thread that helps us to find the way out from a labyrinth of possible histories of our solar system. The chapter reviews the observations and theories of the deuterium fractionation in prestellar cores, protostars, protoplanetary disks (PPDs), comets, interplanetary dust particles (IDPs), and meteorites and links them together to build up a coherent picture of the history of the solar system formation. We emphasize the interdisciplinary nature of this chapter, which gathers together researchers from different communities with the common goal of understanding solar system history.

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

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

    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

  4. DEUTERIUM FRACTIONATION AS AN EVOLUTIONARY PROBE IN MASSIVE PROTOSTELLAR/CLUSTER CORES

    SciTech Connect

    Chen, Huei-Ru; Wang, Mei-Yan; Liu, Sheng-Yuan; Su, Yu-Nung

    2011-12-20

    Clouds of high infrared extinction are promising sites of massive star/cluster formation. A large number of cloud cores discovered in recent years allow for the investigation of a possible evolutionary sequence among cores in early phases. We have conducted a survey of deuterium fractionation toward 15 dense cores in various evolutionary stages, from high-mass starless cores to ultracompact H II regions, in the massive star-forming clouds of high extinction, G34.43+0.24, IRAS 18151-1208, and IRAS 18223-1243, with the Submillimeter Telescope. Spectra of N{sub 2}H{sup +} (3-2), N{sub 2}D{sup +} (3-2), and C{sup 18}O (2-1) were observed to derive the deuterium fractionation of N{sub 2}H{sup +}, D{sub frac} {identical_to} N(N{sub 2}D{sup +})/N(N{sub 2}H{sup +}), as well as the CO depletion factor for every selected core. Our results show a decreasing trend in D{sub frac} with both gas temperature and line width. Since colder and quiescent gas is likely to be associated with less evolved cores, larger D{sub frac} appears to correlate with early phases of core evolution. Such decreasing trend resembles the behavior of D{sub frac} in the low-mass protostellar cores and is consistent with several earlier studies in high-mass protostellar cores. We also find a moderate increasing trend of D{sub frac} with the CO depletion factor, suggesting that sublimation of ice mantles alters the competition in the chemical reactions and reduces D{sub frac}. Our findings suggest a general chemical behavior of deuterated species in both low- and high-mass protostellar candidates at early stages. In addition, upper limits to the ionization degree are estimated to be within 2 Multiplication-Sign 10{sup -7} and 5 Multiplication-Sign 10{sup -6}. The four quiescent cores have marginal field-neutral coupling and perhaps favor turbulent cooling flows.

  5. Deuterium Fractionation during Amino Acid Formation by Photolysis of Interstellar Ice Analogs Containing Deuterated Methanol

    NASA Astrophysics Data System (ADS)

    Oba, Yasuhiro; Takano, Yoshinori; Watanabe, Naoki; Kouchi, Akira

    2016-08-01

    Deuterium (D) atoms in interstellar deuterated methanol might be distributed into complex organic molecules through molecular evolution by photochemical reactions in interstellar grains. In this study, we use a state-of-the-art high-resolution mass spectrometer coupled with a high-performance liquid chromatography system to quantitatively analyze amino acids and their deuterated isotopologues formed by the photolysis of interstellar ice analogs containing singly deuterated methanol CH2DOH at 10 K. Five amino acids (glycine, α-alanine, β-alanine, sarcosine, and serine) and their deuterated isotopologues whose D atoms are bound to carbon atoms are detected in organic residues formed by photolysis followed by warming up to room temperature. The abundances of singly deuterated amino acids are in the range of 0.3–1.1 relative to each nondeuterated counterpart, and the relative abundances of doubly and triply deuterated species decrease with an increasing number of D atoms in a molecule. The abundances of amino acids increase by a factor of more than five upon the hydrolysis of the organic residues, leading to decreases in the relative abundances of deuterated species for α-alanine and β-alanine. On the other hand, the relative abundances of the deuterated isotopologues of the other three amino acids did not decrease upon hydrolysis, indicating different formation mechanisms of these two groups upon hydrolysis. The present study facilitates both qualitative and quantitative evaluations of D fractionation during molecular evolution in the interstellar medium.

  6. Water deuterium fractionation in the low-mass protostar NGC1333-IRAS2A

    NASA Astrophysics Data System (ADS)

    Liu, F.-C.; Parise, B.; Kristensen, L.; Visser, R.; van Dishoeck, E. F.; Güsten, R.

    2011-03-01

    Context. Although deuterium enrichment of water may provide an essential piece of information in the understanding of the formation of comets and protoplanetary systems, only a few studies up to now have aimed at deriving the HDO/H2O ratio in low-mass star forming regions. Previous studies of the molecular deuteration toward the solar-type class 0 protostar, IRAS 16293-2422, have shown that the D/H ratio of water is significantly lower than other grain-surface-formed molecules. It is not clear if this property is general or particular to this source. Aims: In order to see if the results toward IRAS 16293-2422 are particular, we aimed at studying water deuterium fractionation in a second low-mass solar-type protostar, NGC1333-IRAS2A. Methods: Using the 1-D radiative transfer code RATRAN, we analyzed five HDO transitions observed with the IRAM 30 m, JCMT, and APEX telescopes. We assumed that the abundance profile of HDO in the envelope is a step function, with two different values in the inner warm (T > 100 K) and outer cold (T < 100 K) regions of the protostellar envelope. Results: The inner and outer abundance of HDO is found to be well constrained at the 3σ level. The obtained HDO inner and outer fractional abundances are xHDO_in = 6.6 × 10-8-1.0 × 10-7(3σ) and x^{HDO}out=9×10-11= 9 × 10-11-1.0-1.8 × 10-9(3σ). These values are close to those in IRAS 16293-2422, which suggests that HDO may be formed by the same mechanisms in these two solar-type protostars. Taking into account the (rather poorly onstrained) H2O abundance profile deduced from Herschel observations, the derived HDO/H2O in the inner envelope is ≥1% and in the outer envelope it is 0.9%-18%. These values are more than one order of magnitude higher than what is measured in comets. If the same ratios apply to the protosolar nebula, this would imply that there is some efficient reprocessing of the material between the protostellar and cometary phases. Conclusions: The H2O inner fractional

  7. Dynamics, CO depletion, and deuterium fractionation of the dense condensations within the fragmented prestellar core Orion B9-SMM 6

    NASA Astrophysics Data System (ADS)

    Miettinen, O.; Offner, S. S. R.

    2013-07-01

    Context. Low-mass prestellar cores are rarely found to be fragmented into smaller condensations, but studying any substructure, where present, is essential for understanding the origin of multiple stellar systems. Aims: We attempt to better understand the kinematics and dynamics of the subfragments inside the prestellar core SMM 6 in Orion B9. Another goal of the present study is to constrain the evolutionary stage of the condensations by investigating the levels of CO depletion and deuterium fractionation. Methods: We used the APEX telescope to observe the molecular lines C17O(2-1), N2H+(3-2), and N2D+(3-2) towards the condensations. We used the line data in conjunction with our previous SABOCA 350-μm dust continuum map of the source. Results: The condensations are characterised by subsonic internal non-thermal motions (σNT ≃ 0.5cs), and most of them appear to be gravitationally bound. The dispersion of the N2H+ velocity centroids among the condensations is very low (0.02 km s-1). The CO depletion factors we derive, fD = 0.8 ± 0.4-3.6 ± 1.5, do not suggest any significant CO freeze-out, but this may be due to the canonical CO abundance we adopt. The fractional abundances of N2H+ and N2D+ with respect to H2 are found to be ~0.9-2.3 × 10-9 and ~4.9-9.9 × 10-10, respectively. The deuterium fractionation of N2H+ lies in the range 0.30 ± 0.07-0.43 ± 0.09. Conclusions: The detected substructure inside SMM 6 is most likely the result of cylindrical Jeans-type gravitational fragmentation. We estimate the timescale for this fragmentation to be ~1.8 × 105 yr. The condensations are unlikely to be able to interact with one another and coalesce before local gravitational collapse ensues. Moreover, significant mass growth of the condensations via competitive-like accretion from the parent core seems unfeasible. The high level of molecular deuteration in the condensations suggests that gas-phase CO should be strongly depleted. It also points towards an advanced stage

  8. Isotopic fractionation through water vapor condensation: The Deuteropause, a cold trap for deuterium in the atmosphere of Mars

    NASA Astrophysics Data System (ADS)

    Bertaux, Jean-Loup; Montmessin, Franck

    2001-12-01

    Recent observations of deuterium atoms at Lyman alpha with the Hubble Space Telescope have shown the puzzling result of a D/H ratio in the upper atmosphere of Mars to be 11 times samller than the D/H ratio in HDO and H2O of the lower atmosphere [Krasnopolsky et al., 1998]. One factor to explain this vertical variation was proposed: the photo-induced fractionation effect (PHIFE), due to a lower absorption cross section of solar UV of HDO compared to H2O [Cheng et al., 1999]. Here we suggest that in addition to PHIFE, this vertical variation of D/H ratio is also the result of preferred condensation of HDO in rising air, a process already documented in the Earth's upper stratosphere. Results of a cloud model, including condensation, sedimentation, and sublimation of icy particles in the atmosphere of Mars, are presented, supporting the efficiency of the condensation/evaporation fractionation effect (CEFE) as an important factor controlling the D/H ratio in the upper atmosphere of Mars. For a typical H2O profile, PHIFE provides a depletion factor of 2.5, while CEFE induces a factor of 3.5. The combined effects of PHIFE and CEFE (depletion factor of 9.5) can explain the paucity of D atoms in the upper atmosphere of Mars, implying a very low escape rate of deuterium at present and in the past and, correspondingly, a smaller quantity of H2O in the past.

  9. THE INITIAL CONDITIONS OF CLUSTERED STAR FORMATION. III. THE DEUTERIUM FRACTIONATION OF THE OPHIUCHUS B2 CORE

    SciTech Connect

    Friesen, R. K.; Di Francesco, J.; Myers, P. C.; Bourke, T. L.; Belloche, A.; Shirley, Y. L.; Andre, P.

    2010-08-01

    We present N{sub 2}D{sup +} 3-2 (IRAM), and H{sub 2}D{sup +} 1{sub 11}-1{sub 10} and N{sub 2}H{sup +} 4-3 (JCMT) maps of the small cluster-forming Ophiuchus B2 core in the nearby Ophiuchus molecular cloud. In conjunction with previously published N{sub 2}H{sup +} 1-0 observations, the N{sub 2}D{sup +} data reveal the deuterium fractionation in the high-density gas across Oph B2. The average deuterium fractionation R{sub D} = N(N{sub 2}D{sup +})/N(N{sub 2}H{sup +}) {approx} 0.03 over Oph B2, with several small scale R{sub D} peaks and a maximum R{sub D} = 0.1. The mean R{sub D} is consistent with previous results in isolated starless and protostellar cores. The column density distributions of both H{sub 2}D{sup +} and N{sub 2}D{sup +} show no correlation with total H{sub 2} column density. We find, however, an anticorrelation in deuterium fractionation with proximity to the embedded protostars in Oph B2 to distances {approx}>0.04 pc. Destruction mechanisms for deuterated molecules require gas temperatures greater than those previously determined through NH{sub 3} observations of Oph B2 to proceed. We present temperatures calculated for the dense core gas through the equating of non-thermal line widths for molecules (i.e., N{sub 2}D{sup +} and H{sub 2}D{sup +}) expected to trace the same core regions, but the observed complex line structures in B2 preclude finding a reasonable result in many locations. This method may, however, work well in isolated cores with less complicated velocity structures. Finally, we use R{sub D} and the H{sub 2}D{sup +} column density across Oph B2 to set a lower limit on the ionization fraction across the core, finding a mean x{sub e,lim} {approx}> few x 10{sup -8}. Our results show that care must be taken when using deuterated species as a probe of the physical conditions of dense gas in star-forming regions.

  10. Vapor Pressure Isotope Fractionation Effects in Planetary Atmospheres: Application to Deuterium

    NASA Astrophysics Data System (ADS)

    Fouchet, Thierry; Lellouch, Emmanuel

    2000-03-01

    The impact of the vapor pressure difference between deuterated and nondeuterated condensing molecules in planetary atmospheres is quantitatively assessed. This difference results in a loss of deuterium in the vapor phase above the condensation level. In Titan, Uranus, and Neptune, the effect on CH 3D is too subtle to alter current D/H ratio determinations. In Mars, the effect can induce a large depletion of HDO, starting about one scale height above the condensation level. Although the current infrared measurements of the D/H ratio appear to be almost unaffected, the intensity of disk-averaged millimetric HDO lines can be modified by about 10%. The effect is much stronger in limb sounding and can be easily detected from orbiter observations.

  11. Deuterium fractionation in the presolar nebula - Kinetic limitations on surface catalysis

    NASA Technical Reports Server (NTRS)

    Grinspoon, David H.; Lewis, John S.

    1987-01-01

    A quantitative test is presented for the possibility that grain-based catalysis could shorten the equilibration times of low temperature equilibrium fractionation sufficiently to account for the D/H ratio values of the solar system even at nebular temperatures. It is found that under the highly idealized conditions in which the full cosmic abundance of Ni is available for catalysis in pure, 5-micron grains, the equilibration time constant becomes greater than the nebular lifetime at temperatures below 560 K. This lower limit is not, however, sufficiently low to permit strong fractionation.

  12. Warm water deuterium fractionation in IRAS 16293-2422. The high-resolution ALMA and SMA view

    NASA Astrophysics Data System (ADS)

    Persson, M. V.; Jørgensen, J. K.; van Dishoeck, E. F.

    2013-01-01

    Context. Measuring the water deuterium fractionation in the inner warm regions of low-mass protostars has so far been hampered by poor angular resolution obtainable with single-dish ground- and space-based telescopes. Observations of water isotopologues using (sub)millimeter wavelength interferometers have the potential to shed light on this matter. Aims: To measure the water deuterium fractionation in the warm gas of the deeply-embedded protostellar binary IRAS 16293-2422. Methods: Observations toward IRAS 16293-2422 of the 53,2 - 44,1 transition of H218O at 692.07914 GHz from Atacama Large Millimeter/submillimeter Array (ALMA) as well as the 31,3 - 22,0 of H218O at 203.40752 GHz and the 31,2 - 22,1 transition of HDO at 225.89672 GHz from the Submillimeter Array (SMA) are presented. Results: The 692 GHz H218O line is seen toward both components of the binary protostar. Toward one of the components, "source B", the line is seen in absorption toward the continuum, slightly red-shifted from the systemic velocity, whereas emission is seen off-source at the systemic velocity. Toward the other component, "source A", the two HDO and H218O lines are detected as well with the SMA. From the H218O transitions the excitation temperature is estimated at 124 ± 12 K. The calculated HDO/H2O ratio is (9.2 ± 2.6) × 10-4 - significantly lower than previous estimates in the warm gas close to the source. It is also lower by a factor of ~5 than the ratio deduced in the outer envelope. Conclusions: Our observations reveal the physical and chemical structure of water vapor close to the protostars on solar-system scales. The red-shifted absorption detected toward source B is indicative of infall. The excitation temperature is consistent with the picture of water ice evaporation close to the protostar. The low HDO/H2O ratio deduced here suggests that the differences between the inner regions of the protostars and the Earth's oceans and comets are smaller than previously thought

  13. Deuterium excess in the Rayleigh model

    NASA Astrophysics Data System (ADS)

    Dütsch, Marina; Pfahl, Stephan; Sodemann, Harald

    2016-04-01

    The deuterium excess is a useful quantity for measuring nonequilibrium effects of isotopic fractionation, and can therefore provide information about the meteorological conditions in evaporation regions (e.g., relative humidity over the ocean or the fraction of plant transpiration over land). In addition to nonequilibrium fractionation, there are two other effects that can change the deuterium excess during phase transitions. The first is the dependence of the equilibrium fractionation factors on temperature, the second is the nonlinearity of the delta scale, on which the deuterium excess is defined. We tested the impact of these three effects (nonequilibrium, temperature and delta scale) in a simple Rayleigh condensation model simulating the isotopic composition of an air parcel during a moist adiabatic ascent. The delta scale effect is important especially for depleted air parcels where it can change the sign of the deuterium excess in the remaining vapour from negative to positive. In this case the deuterium excess to a large extent reflects an artefact of its own definition, which overwrites both the nonequilibrium and the temperature effect. This problem can be solved by an alternative definition for the deuterium excess that is not based on the delta scale.

  14. WATER DEUTERIUM FRACTIONATION IN THE INNER REGIONS OF TWO SOLAR-TYPE PROTOSTARS

    SciTech Connect

    Taquet, V.; Lopez-Sepulcre, A.; Ceccarelli, C.; Kahane, C.; Coutens, A.; Vastel, C.

    2013-05-10

    The [HDO]/[H{sub 2}O] ratio is a crucial parameter for probing the history of water formation. So far, it has been measured for only three solar-type protostars and yielded different results, possibly pointing to a substantially different history in their formation. In the present work, we report new interferometric observations of the HDO 4{sub 2,2}-4{sub 2,3} line for two solar-type protostars, IRAS2A and IRAS4A, located in the NGC 1333 region. In both sources, the detected HDO emission originates from a central compact unresolved region. A comparison with previously published interferometric observations of the H{sub 2}{sup 18}O 3{sub 1,3}-2{sub 2,0} line shows that the HDO and H{sub 2}O lines mostly come from the same region. A non-LTE large velocity gradient analysis of the HDO and H{sub 2}{sup 18}O line emissions, combined with published observations, provides an [HDO]/[H{sub 2}O] ratio of 0.3%-8% in IRAS2A and 0.5%-3% in IRAS4A. First, the water fractionation is lower than that of other molecules such as formaldehyde and methanol in the same sources. Second, it is similar to that measured in the solar-type protostar prototype, IRAS16293-2422, and, surprisingly enough, larger than that measured in NGC 1333 IRAS4B. The comparison of the measured values toward IRAS2A and IRAS4A with the predictions of our gas-grain model GRAINOBLE gives similar conclusions to those for IRAS 16293, arguing that these protostars share a similar chemical history, although they are located in different clouds.

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

    NASA Astrophysics Data System (ADS)

    Lu, Yong; Zhang, Ping

    2013-05-01

    We report the prediction of temperature-dependent diffusion coefficients of interstitial hydrogen, deuterium, and tritium atoms in α-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.

  16. The Mass-Dependence of Cadmium Isotope Fractionation During Evaporation

    NASA Astrophysics Data System (ADS)

    Rehkamper, M.; Wombacher, F.; Mezger, K.; Wiechert, U.

    2002-12-01

    Isotope fractionation laws relate the isotope fractionation factor αA of one isotope ratio to the fractionation factor αB of a second isotope ratio of the same element with a fractionation exponent β, such that αA = αBβ. In a recent paper, Young et al. (GCA 66, 1095-1104 (2002)) inferred that kinetic and equilibrium isotope fractionations are characterized by different mass functions, such that βkin is not equal to βeq. As a consequence, kinetic isotope fractionation is expected to produce fractionation lines in three isotope space that are different from those generated by equilibrium fractionation processes. Young et al. furthermore stated that the variability in mass-dependent fractionation laws may be sufficient to account for the negative Δ17O of tropospheric O2 and the Δ17O anomalies of minerals in SNC meteorites. Such variations have otherwise been interpreted as evidence of non-mass dependant isotope fractionations (Luz et al., Nature 400, 547-550 (1999); Farquhar et al., Science 280, 1589-1582 (1998)). In the present study, we investigated the mass-dependence of isotope fractionation by evaluating the results of evaporation experiments that produced very large differences in Cd isotope compositions (up to about 100‰ ). In these experiments, liquid Cd was evaporated into a vacuum at a temperature of about 200°C. The metal residues remaining after evaporation were analyzed for their Cd isotope composition by multiple-collector inductively coupled plasma-mass spectrometry (MC-ICPMS) relative to the unfractionated starting material. The precision of the measurements is sufficient to clearly distinguish between different fractionation mechanisms. In linearized three-isotope space, the residual Cd metals plot on fractionation lines (e.g., with a slope β = 2.049 +/- 2 for 106}Cd/{114Cd vs. 110}Cd/{114Cd) that are intermediate between the kinetic (β = 2.036) and the equilibrium (β = 2.075) fractionation lines. This can be explained by an

  17. Cometary deuterium.

    PubMed

    Meier, R; Owen, T C

    1999-01-01

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

  18. Cometary Deuterium

    NASA Astrophysics Data System (ADS)

    Meier, Roland; Owen, Tobias C.

    1999-10-01

    Deuterium fractionations in cometary ices provide important clues to the origin and evolution of comets. Mass spectrometers aboard spaceprobe Giotto revealed the first accurate D/H ratios in the water of Comet 1P/Halley. Ground-based observations of HDO in Comets C/1996 B2 (Hyakutake) and C/1995 O1 (Hale-Bopp), the detection of DCN in Comet Hale-Bopp, and upper limits for several other D-bearing molecules complement our limited sample of D/H measurements. On the basis of this data set all Oort cloud comets seem to exhibit a similar ( {{{D} {{D {H}}} H}} )_{H}_{2} {O}} 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 be 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

  19. Velocity-dependent isotope fractionation in secondary-ion emission

    SciTech Connect

    Gnaser, H.; Hutcheon, I.D.

    1987-01-15

    The formation of secondary ions is subject to isotopic fractionation (differing ionization probabilities for two isotopes) that depends linearly on the inverse velocity of the ejected ions. Theoretically, such a correlation follows directly from an exponential dependence of the ionization probability P on v/sup -1/, Pproportionalexp(-v/sub 0//v). The parameter v/sub 0/, derived from the experiment, amounts to --2 x 10/sup 6/ cm/sec for B, Si, and Ca ions.

  20. FROM PRESTELLAR TO PROTOSTELLAR CORES. II. TIME DEPENDENCE AND DEUTERIUM FRACTIONATION

    SciTech Connect

    Aikawa, Y.; Wakelam, V.; Hersant, F.; Garrod, R. T.; Herbst, E.

    2012-11-20

    We investigate the molecular evolution and D/H abundance ratios that develop as star formation proceeds from a dense molecular cloud core to a protostellar core, by solving a gas-grain reaction network applied to a one-dimensional radiative hydrodynamic model with infalling fluid parcels. Spatial distributions of gas and ice-mantle species are calculated at the first-core stage, and at times after the birth of a protostar. Gas-phase methanol and methane are more abundant than CO at radii r {approx}< 100 AU in the first-core stage, but gradually decrease with time, while abundances of larger organic species increase. The warm-up phase, when complex organic molecules are efficiently formed, is longer-lived for those fluid parcels infalling at later stages. The formation of unsaturated carbon chains (warm carbon-chain chemistry) is also more effective in later stages; C{sup +}, which reacts with CH{sub 4} to form carbon chains, increases in abundance as the envelope density decreases. The large organic molecules and carbon chains are strongly deuterated, mainly due to high D/H ratios in the parent molecules, determined in the cold phase. We also extend our model to simulate simply the chemistry in circumstellar disks, by suspending the one-dimensional infall of a fluid parcel at constant disk radii. The species CH{sub 3}OCH{sub 3} and HCOOCH{sub 3} increase in abundance in 10{sup 4}-10{sup 5} yr at the fixed warm temperature; both also have high D/H ratios.

  1. Temperature Dependence of Carbon Isotope Fractionation in CAM Plants.

    PubMed

    Deleens, E; Treichel, I; O'leary, M H

    1985-09-01

    The carbon isotope fractionation associated with nocturnal malic acid synthesis in Kalanchoë daigremontiana and Bryophyllum tubiflorum was calculated from the isotopic composition of carbon-4 of malic acid, after appropriate corrections. In the lowest temperature treatment (17 degrees C nights, 23 degrees C days), the isotope fractionation for both plants is -4 per thousand (that is, malate is enriched in (13)C relative to the atmosphere). For K. daigremontiana, the isotope fractionation decreases with increasing temperature, becoming approximately 0 per thousand at 27 degrees C/33 degrees C. Detailed analysis of temperature effects on the isotope fractionation indicates that stomatal aperture decreases with increasing temperature and carboxylation capacity increases. For B. tubiflorum, the temperature dependence of the isotope fractionation is smaller and is principally attributed to the normal temperature dependences of the rates of diffusion and carboxylation steps. The small change in the isotopic composition of remaining malic acid in both species which is observed during deacidification indicates that malate release, rather than decarboxylation, is rate limiting in the deacidification process. PMID:16664371

  2. Does the obscured AGN fraction really depend on luminosity?

    NASA Astrophysics Data System (ADS)

    Sazonov, S.; Churazov, E.; Krivonos, R.

    2015-12-01

    We use a sample of 151 local non-blazar active galactic nuclei (AGN) selected from the INTEGRAL all-sky hard X-ray survey to investigate if the observed declining trend of the fraction of obscured (i.e. showing X-ray absorption) AGN with increasing luminosity is mostly an intrinsic or selection effect. Using a torus-obscuration model, we demonstrate that in addition to negative bias, due to absorption in the torus, in finding obscured AGN in hard X-ray flux-limited surveys, there is also positive bias in finding unobscured AGN, due to Compton reflection in the torus. These biases can be even stronger taking into account plausible intrinsic collimation of hard X-ray emission along the axis of the obscuring torus. Given the AGN luminosity function, which steepens at high luminosities, these observational biases lead to a decreasing observed fraction of obscured AGN with increasing luminosity even if this fraction has no intrinsic luminosity dependence. We find that if the central hard X-ray source in AGN is isotropic, the intrinsic (i.e. corrected for biases) obscured AGN fraction still shows a declining trend with luminosity, although the intrinsic obscured fraction is significantly larger than the observed one: the actual fraction is larger than ˜85 per cent at L ≲ 1042.5 erg s-1 (17-60 keV), and decreases to ≲60 per cent at L ≳ 1044 erg s-1. In terms of the half-opening angle θ of an obscuring torus, this implies that θ ≲ 30° in lower luminosity AGN, and θ ≳ 45° in higher luminosity ones. If, however, the emission from the central supermassive black hole is collimated as dL/dΩ ∝ cos α, the intrinsic dependence of the obscured AGN fraction is consistent with a luminosity-independent torus half-opening angle θ ˜ 30°.

  3. Microbial mass-dependent fractionation of chromium isotopes

    USGS Publications Warehouse

    Sikora, E.R.; Johnson, T.M.; Bullen, T.D.

    2008-01-01

    Mass-dependent fractionation of Cr isotopes occurs during dissimilatory Cr(VI) reduction by Shewanella oneidensis strain MR-1. Cells suspended in a simple buffer solution, with various concentrations of lactate or formate added as electron donor, reduced 5 or 10 ??M Cr(VI) to Cr(III) over days to weeks. In all nine batch experiments, 53Cr/52Cr ratios of the unreacted Cr(VI) increased as reduction proceeded. In eight experiments covering a range of added donor concentrations up to 100 ??M, isotopic fractionation factors were nearly invariant, ranging from 1.0040 to 1.0045, with a mean value somewhat larger than that previously reported for abiotic Cr(VI) reduction (1.0034). One experiment containing much greater donor concentration (10 mM lactate) reduced Cr(VI) much faster and exhibited a lesser fractionation factor (1.0018). These results indicate that 53Cr/52Cr measurements should be effective as indicators of Cr(VI) reduction, either bacterial or abiotic. However, variability in the fractionation factor is poorly constrained and should be studied for a variety of microbial and abiotic reduction pathways. ?? 2008 Elsevier Ltd.

  4. Nuclear Volume-Dependent Fractionation of Uranium Isotopes

    NASA Astrophysics Data System (ADS)

    Weyer, S.; Schauble, E. A.; Anbar, A. D.

    2007-12-01

    fractionation in these sediments is opposite in direction to what would be expected from mass-dependent equilibrium or kinetic/diffusive isotope fractionation. Instead, heavy U isotope compositions of reduced U species are expected from first-principles quantum chemical modeling of fractionation driven by nuclear volume. Our modeling results predict that equilibrium nuclear volume and mass-dependent isotope fractionation operate in opposite directions for U, and that the volume effect is of greater magnitude. Combining our observations on natural samples with the results of theoretical modeling strongly indicates that nuclear volume-, rather than mass-dependent isotope fractionation is the dominant process that fractionates the isotope composition of some very heavy elements, such as U, in nature.

  5. Alpha-tocopherol disappearance rates from plasma depend on lipid concentrations: Studies using deuterium labeled collard greens in younger and older adults

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Little is known about alpha-tocopherol's bioavailability as a constituent of food or its dependence on a subject's age. To evaluate the alpha-tocopherol bioavailability from food, we used collard greens grown in deuterated water (2H collard greens) as a source of deuterium-labeled (2H) alpha-tocophe...

  6. THE DEUTERIUM-BURNING MASS LIMIT FOR BROWN DWARFS AND GIANT PLANETS

    SciTech Connect

    Spiegel, David S.; Burrows, Adam; Milsom, John A. E-mail: burrows@astro.princeton.edu

    2011-01-20

    There is no universally acknowledged criterion to distinguish brown dwarfs from planets. Numerous studies have used or suggested a definition based on an object's mass, taking the {approx}13 Jupiter mass (M{sub J} ) limit for the ignition of deuterium. Here, we investigate various deuterium-burning masses for a range of models. We find that, while 13 M{sub J} is generally a reasonable rule of thumb, the deuterium fusion mass depends on the helium abundance, the initial deuterium abundance, the metallicity of the model, and on what fraction of an object's initial deuterium abundance must combust in order for the object to qualify as having burned deuterium. Even though, for most proto-brown dwarf conditions, 50% of the initial deuterium will burn if the object's mass is {approx}(13.0 {+-} 0.8) M{sub J} , the full range of possibilities is significantly broader. For models ranging from zero-metallicity to more than three times solar metallicity, the deuterium-burning mass ranges from {approx}11.0 M{sub J} (for three times solar metallicity, 10% of initial deuterium burned) to {approx}16.3 M{sub J} ( for zero metallicity, 90% of initial deuterium burned).

  7. Tokamak power reactor ignition and time dependent fractional power operation

    SciTech Connect

    Vold, E.L.; Mau, T.K.; Conn, R.W.

    1986-06-01

    A flexible time-dependent and zero-dimensional plasma burn code with radial profiles was developed and employed to study the fractional power operation and the thermal burn control options for an INTOR-sized tokamak reactor. The code includes alpha thermalization and a time-dependent transport loss which can be represented by any one of several currently popular scaling laws for energy confinement time. Ignition parameters were found to vary widely in density-temperature (n-T) space for the range of scaling laws examined. Critical ignition issues were found to include the extent of confinement time degradation by alpha heating, the ratio of ion to electron transport power loss, and effect of auxiliary heating on confinement. Feedback control of the auxiliary power and ion fuel sources are shown to provide thermal stability near the ignition curve.

  8. Species-dependent silicon isotope fractionation by marine diatoms

    NASA Astrophysics Data System (ADS)

    Sutton, Jill N.; Varela, Diana E.; Brzezinski, Mark A.; Beucher, Charlotte P.

    2013-03-01

    Fractionation of silicon (Si) isotopes was measured in seven species (nine strains) of polar and sub-polar marine diatoms grown in semi-continuous unialgal cultures under optimal irradiance and temperature for each diatom strain. Results from this work provide the first evidence that Si isotope fractionation by diatoms is species-dependent. The greatest difference in the Si isotope fractionation factor (ɛ) was observed between two Southern Ocean diatoms, Fragilariopsis kerguelensis (-0.54‰, average for two strains) and Chaetoceros brevis (-2.09‰). The ɛ for the other species, both polar and sub-polar, ranged from -0.72‰ to -1.21‰. The two remaining polar diatoms had ɛ values of -0.74 ± 0.05‰ for Thalassiosira antarctica, and -1.21 ± 0.04‰ for Thalassiosira nordenskioeldii, while the sub-polar species had ɛ values of -0.72 ± 0.04‰ for Thalassiosira weissflogii, -0.88 ± 0.06‰ for Thalassiosira pseudonana (CCCM58), -0.97 ± 0.14‰ for Thalassiosira pseudonana (CCMP1014), and -1.15 ± 0.03‰ for Porosira glacialis. The range in ɛ for the diatoms evaluated in this study may be large enough to significantly impact the Si isotope composition measured in diatom opal (δ30Si-bSiO2) from marine sediments and its subsequent interpretation. To test the influence of diatom taxonomic composition on δ30Si-bSiO2, we developed a model that considered the relative abundance of diatom species and the ɛ values (from this study) for each species present within the sediment core (i.e. weighted-average ɛ). The model was applied to records from a Southern Ocean sediment core (TN057-13) where both diatom abundance and δ30Si-bSiO2 data were available. The analysis indicated that 67% of the variation in δ30Si-bSiO2 could be explained by species-dependent Si isotope fractionation. We suggest that future work should assess phytoplankton taxonomic composition when using δ30Si-bSiO2 as a proxy for Si utilization.

  9. In situ deuterium observation in deuterium-implanted tungsten

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

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

    PubMed Central

    2015-01-01

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

  11. Pressure dependence of the deuterium isotope effect in the photolysis of formaldehyde by ultraviolet light

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

    The pressure dependence of the relative photolysis rate of HCHO vs. HCDO has been investigated for the first time, using a photochemical reactor at the University of Copenhagen. The dissociation of HCHO vs. HCDO using a UVA lamp was measured at total bath gas pressures of 50, 200, 400, 600 and 1030 mbar. The products of formaldehyde photodissociation are either H2 + CO (molecular channel) or HCO + H (radical channel), and a photolysis lamp was chosen to emit light at wavelengths that greatly favor the molecular channel. The isotope effect in the dissociation, kHCHO/kHCDO, was found to depend strongly on pressure, varying from 1.1 + 0.15/-0.1 at 50 mbar to 1.75±0.10 at 1030 mbar. The results can be corrected for radical channel contribution to yield the kinetic isotope effect for the molecular channel; i.e. the KIE in the production of molecular hydrogen. This is done and the results at 1030 mbar are discussed in relation to previous studies at ambient pressure. In the atmosphere the relative importance of the two product channels changes with altitude as a result of changes in pressure and actinic flux. The study demonstrates that the δD of photochemical hydrogen produced from formaldehyde will increase substantially as pressure decreases.

  12. Deuterium isotope effect on femtosecond solvation dynamics in an ionic liquid microemulsion: an excitation wavelength dependence study.

    PubMed

    Sasmal, Dibyendu Kumar; Mojumdar, Supratik Sen; Adhikari, Aniruddha; Bhattacharyya, Kankan

    2010-04-01

    The deuterium isotope effect on the solvation dynamics and the anisotropy decay of coumarin 480 (C480) in a room temperature ionic liquid (RTIL) microemulsion is studied by femtosecond up-conversion. The microemulsion consists of the RTIL 1-pentyl-3-methyl-imidazolium tetra-fluoroborate ([pmim][BF(4)]) in triton X-100 (TX-100)/benzene. Replacement of H(2)O by D(2)O in the microemulsion causes retardation of solvation dynamics. The average solvation time of C480 (tau(s)) in RTIL microemulsion with 5 wt % D(2)O is approximately 1.5-1.7 times slower compared to that in the H(2)O containing RTIL microemulsion. This suggests that the main species in the microemulsion responsible for solvation is the water molecules. In both D(2)O and H(2)O containing RTIL microemulsion, the solvation dynamics exhibits marked dependence on the excitation wavelength (lambda(ex)) and becomes about 15 times faster as lambda(ex) increases from 375 to 435 nm. This is ascribed to the structural heterogeneity in the RTIL microemulsion. For lambda(ex) = 375 nm, the region near the TX-100 surfactant is probed where bound water molecules cause slow solvation dynamics. At 435 nm, the RTIL pool is selected where the water molecules are more mobile and hence gives rise to faster solvation. The average time constant of anisotropy decay shows opposite dependence on lambda(ex) and increases about 2.5-fold from 180 ps at lambda(ex) = 375 nm to 500 ps at lambda(ex) = 435 nm for D(2)O containing RTIL microemulsion. The slower anisotropy decay at lambda(ex) = 435 nm is ascribed to the higher viscosity of RTIL which causes greater friction at the core. PMID:20235504

  13. DEPENDENCE OF BARRED GALAXY FRACTION ON GALAXY PROPERTIES AND ENVIRONMENT

    SciTech Connect

    Lee, Gwang-Ho; Lee, Myung Gyoon; Park, Changbom; Choi, Yun-Young E-mail: mglee@astro.snu.ac.kr E-mail: yy.choi@khu.ac.kr

    2012-02-01

    We investigate the dependence of the occurrence of bars in galaxies on galaxy properties and environment. We use a volume-limited sample of 33,391 galaxies brighter than M{sub r} = -19.5 + 5logh at 0.02 {<=} z {<=} 0.05489, drawn from the Sloan Digital Sky Survey Data Release 7. We classify the galaxies into early and late types, and identify bars by visual inspection. Among 10,674 late-type galaxies with axis ratio b/a > 0.60, we find 3240 barred galaxies (f{sub bar} = 30.4%) which divide into 2542 strong bars (f{sub SB1} = 23.8%) and 698 weak bars (f{sub SB2} = 6.5%). We find that f{sub SB1} increases as u - r color becomes redder and that it has a maximum value at intermediate velocity dispersion ({sigma} {approx_equal}150 km s{sup -1}). This trend suggests that strong bars are dominantly hosted by intermediate-mass systems. Weak bars prefer bluer galaxies with lower mass and lower concentration. In the case of strong bars, their dependence on the concentration index appears only for massive galaxies with {sigma} > 150 km s{sup -1}. We also find that f{sub bar} does not directly depend on the large-scale background density when other physical parameters (u - r color or {sigma}) are fixed. We discover that f{sub SB1} decreases as the separation to the nearest neighbor galaxy becomes smaller than 0.1 times the virial radius of the neighbor regardless of neighbor's morphology. These results imply that strong bars are likely to be destroyed during strong tidal interactions and that the mechanism for this phenomenon is gravitational and not hydrodynamical. The fraction of weak bars has no correlation with environmental parameters. We do not find any direct evidence for environmental stimulation of bar formation.

  14. α-Tocopherol disappearance rates from plasma depend on lipid concentrations: studies using deuterium-labeled collard greens in younger and older adults1234

    PubMed Central

    Traber, Maret G; Leonard, Scott W; Bobe, Gerd; Fu, Xueyan; Saltzman, Edward; Grusak, Michael A; Booth, Sarah L

    2015-01-01

    Background: Little is known about α-tocopherol’s bioavailability as a constituent of food or its dependence on a subject’s age. Objective: To evaluate the α-tocopherol bioavailability from food, we used collard greens grown in deuterated water (2H collard greens) as a source of deuterium-labeled (2H) α-tocopherol consumed by younger and older adults in a post hoc analysis of a vitamin K study. Design: Younger (mean ± SD age: 32 ± 7 y; n = 12 women and 9 men) and older (aged 67 ± 8 y; n = 8 women and 12 men) adults consumed a test breakfast that included 120 g 2H collard greens (1.2 ± 0.1 mg 2H-α-tocopherol). Plasma unlabeled α-tocopherol and 2H-α-tocopherol were measured by using liquid chromatography–mass spectrometry from fasting (>12 h) blood samples drawn before breakfast (0 h) and at 24, 48, and 72 h and from postprandial samples collected at 4, 5, 6, 7, 9, 12, and 16 h. Results: Times (12.6 ± 2.5 h) of maximum plasma 2H-α-tocopherol concentrations (0.82% ± 0.59% total α-tocopherol), fractional disappearance rates (0.63 ± 0.26 pools/d), half-lives (30 ± 11 h), and the minimum estimated 2H-α-tocopherol absorbed (24% ± 16%) did not vary between age groups or sexes (n = 41). Unlabeled α-tocopherol concentrations were higher in older adults (26.4 ± 8.6 μmol/L) than in younger adults (19.3 ± 4.2 μmol/L; P = 0.0019) and correlated with serum lipids (r = 0.4938, P = 0.0012). In addition, 2H-α-tocopherol half-lives were correlated with lipids (r = 0.4361, P = 0.0044). Conclusions: Paradoxically, α-tocopherol remained in circulation longer in participants with higher serum lipids, but the 2H-α-tocopherol absorbed was not dependent on the plasma lipid status. Neither variable was dependent on age. These data suggest that plasma α-tocopherol concentrations are more dependent on mechanisms that control circulating lipids rather than those related to its absorption and initial incorporation into plasma. This trial was registered at

  15. Chemodynamical deuterium fractionation in the early solar nebula: The origin of water on earth and in asteroids and comets

    SciTech Connect

    Albertsson, T.; Semenov, D.; Henning, Th.

    2014-03-20

    Formation and evolution of water in the solar system and the origin of water on Earth constitute one of the most interesting questions in astronomy. The prevailing hypothesis for the origin of water on Earth is by delivery through water-rich small solar system bodies. In this paper, the isotopic and chemical evolution of water during the early history of the solar nebula, before the onset of planetesimal formation, is studied. A gas-grain chemical model that includes multiply deuterated species and nuclear spin-states is combined with a steady-state solar nebula model. To calculate initial abundances, we simulated 1 Myr of evolution of a cold and dark TMC-1-like prestellar core. Two time-dependent chemical models of the solar nebula are calculated over 1 Myr: (1) a laminar model and (2) a model with two-dimensional (2D) turbulent mixing. We find that the radial outward increase of the H{sub 2}O D/H ratio is shallower in the chemodynamical nebular model than in the laminar model. This is related to more efficient defractionation of HDO via rapid gas-phase processes because the 2D mixing model allows the water ice to be transported either inward and thermally evaporated or upward and photodesorbed. The laminar model shows the Earth water D/H ratio at r ≲ 2.5 AU, whereas for the 2D chemodynamical model this zone is larger, r ≲ 9 AU. Similarly, the water D/H ratios representative of the Oort-family comets, ∼2.5-10 × 10{sup –4}, are achieved within ∼2-6 AU and ∼2-20 AU in the laminar and the 2D model, respectively. We find that with regards to the water isotopic composition and the origin of the comets, the mixing model seems to be favored over the laminar model.

  16. Chemodynamical Deuterium Fractionation in the Early Solar Nebula: The Origin of Water on Earth and in Asteroids and Comets

    NASA Astrophysics Data System (ADS)

    Albertsson, T.; Semenov, D.; Henning, Th.

    2014-03-01

    Formation and evolution of water in the solar system and the origin of water on Earth constitute one of the most interesting questions in astronomy. The prevailing hypothesis for the origin of water on Earth is by delivery through water-rich small solar system bodies. In this paper, the isotopic and chemical evolution of water during the early history of the solar nebula, before the onset of planetesimal formation, is studied. A gas-grain chemical model that includes multiply deuterated species and nuclear spin-states is combined with a steady-state solar nebula model. To calculate initial abundances, we simulated 1 Myr of evolution of a cold and dark TMC-1-like prestellar core. Two time-dependent chemical models of the solar nebula are calculated over 1 Myr: (1) a laminar model and (2) a model with two-dimensional (2D) turbulent mixing. We find that the radial outward increase of the H2O D/H ratio is shallower in the chemodynamical nebular model than in the laminar model. This is related to more efficient defractionation of HDO via rapid gas-phase processes because the 2D mixing model allows the water ice to be transported either inward and thermally evaporated or upward and photodesorbed. The laminar model shows the Earth water D/H ratio at r <~ 2.5 AU, whereas for the 2D chemodynamical model this zone is larger, r <~ 9 AU. Similarly, the water D/H ratios representative of the Oort-family comets, ~2.5-10 × 10-4, are achieved within ~2-6 AU and ~2-20 AU in the laminar and the 2D model, respectively. We find that with regards to the water isotopic composition and the origin of the comets, the mixing model seems to be favored over the laminar model.

  17. Water deuterium fractionation in the high-mass star-forming region G34.26+0.15 based on Herschel/HIFI data

    NASA Astrophysics Data System (ADS)

    Coutens, A.; Vastel, C.; Hincelin, U.; Herbst, E.; Lis, D. C.; Chavarría, L.; Gérin, M.; van der Tak, F. F. S.; Persson, C. M.; Goldsmith, P. F.; Caux, E.

    2014-12-01

    Understanding water deuterium fractionation is important for constraining the mechanisms of water formation in interstellar clouds. Observations of HDO and H_2^{18}O transitions were carried out towards the high-mass star-forming region G34.26+0.15 with the Heterodyne Instrument for the Far-Infrared (HIFI) instrument onboard the Herschel Space Observatory, as well as with ground-based single-dish telescopes. 10 HDO lines and three H_2^{18}O lines covering a broad range of upper energy levels (22-204 K) were detected. We used a non-local thermal equilibrium 1D analysis to determine the HDO/H2O ratio as a function of radius in the envelope. Models with different water abundance distributions were considered in order to reproduce the observed line profiles. The HDO/H2O ratio is found to be lower in the hot core (˜3.5 × 10-4-7.5 × 10-4) than in the colder envelope (˜1.0 × 10-3-2.2 × 10-3). This is the first time that a radial variation of the HDO/H2O ratio has been found to occur in a high-mass source. The chemical evolution of this source was modelled as a function of its radius and the observations are relatively well reproduced. The comparison between the chemical model and the observations leads to an age of ˜105 yr after the infrared dark cloud stage.

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

    SciTech Connect

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

    1984-07-19

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

  19. THE ENVIRONMENTAL DEPENDENCE OF THE EVOLVING S0 FRACTION

    SciTech Connect

    Just, Dennis W.; Zaritsky, Dennis; Sand, David J.; Desai, Vandana; Rudnick, Gregory

    2010-03-01

    We re-investigate the dramatic rise in the S0 fraction, f{sub S0}, within clusters since z {approx} 0.5. In particular, we focus on the role of the global galaxy environment on f{sub S0} by compiling, either from our own observations or the literature, robust line-of-sight velocity dispersions, sigma's, for a sample of galaxy groups and clusters at 0.1 < z < 0.8 that have uniformly determined, published morphological fractions. We find that the trend of f{sub S0} with redshift is twice as strong for sigma < 750 km s{sup -1} groups/poor clusters than for higher-sigma, rich clusters. From this result, we infer that over this redshift range galaxy-galaxy interactions, which are more effective in lower-sigma environments, are more responsible for transforming spiral galaxies into S0's than galaxy-environment processes, which are more effective in higher-sigma environments. The rapid, recent growth of the S0 population in groups and poor clusters implies that large numbers of progenitors exist in low-sigma systems at modest redshifts ({approx}0.5), where morphologies and internal kinematics are within the measurement range of current technology.

  20. Experimental investigation of mass-dependent and mass-independent fractionation of mercury isotopes

    NASA Astrophysics Data System (ADS)

    Bergquist, B. A.; Blum, J. D.; Marcus, J. W.; Biswas, A.

    2006-12-01

    Mercury is a globally distributed and highly toxic pollutant, the mobility and bioaccumulation of which is highly dependent on its redox cycling. With seven isotopes (including two odd-mass isotopes) and a relative mass difference of 4%, stable isotope fractionation of Hg could be a powerful tool to track and understand Hg cycling in the environment. Ongoing studies of natural mercury isotope variations in ore deposits, hydrothermal fluids, sediments, soils, fish tissues and bacterial cultures have documented a measurable range in Hg isotopes of up to ~5‰ in the ^{202}Hg/^{198}Hg ratio with most samples displaying mass-dependent fractionation. A small, but growing, body of data also suggests that natural samples display mass-independent fractionation of Hg isotopes. In this study, we explore mechanisms that lead to both mass- dependent and mass-independent fractionation of Hg isotopes. Isotope ratios were measured by continuous- flow cold-vapor generation coupled to MC-ICPMS with an external precision of ±0.1‰ (2SD). We observe three distinct types of isotope fractionation for Hg: (1) mass-dependent fractionation, (2) mass- independent fractionation of odd isotopes concurrent with mass-dependent fractionation of even isotopes, and (3) mass-independent fractionation of all Hg isotopes. Reduction of Hg species to Hg(0) vapor is an important mechanism for removal of Hg from aqueous systems into the atmosphere. Reduction of Hg occurs through numerous pathways including photoreduction, abiotic organic reduction, and biological reduction. We find that photoreduction of Hg(II) by natural sunlight leads to mass-independent fractionation of the odd isotopes (^{201}Hg, ^{199}Hg) with several permil deviations from predicted mass dependence, and mass- dependent fractionation of the even isotopes. In contrast, both biological reduction (Kritee et al., 2006) and dark abiotic organically mediated reduction follow mass-dependent fractionation of even and odd isotopes

  1. Astration of cosmological deuterium

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.

    1985-01-01

    Attention is given to the degree of primordial deuterium's astration through the continuous galactic processes of star formation and chemical evolution. Exact analytic solutions are given for galactic chemical evolution when infall of constant composition occurs at a rate, f(t), which is presently defined. Solutions are given for the linear model with instantaneous recycling and with constant return fraction R. The results suggest that big bang D/H was at least three times larger than the largest values observed in today's solar neighborhood, and even larger if matter falling into the disk is already astrated.

  2. Pressure-dependent boron isotopic fractionation observed by column chromatography

    NASA Astrophysics Data System (ADS)

    Musashi, M.; Oi, T.; Matsuo, M.; Nomura, M.

    2007-12-01

    Boron isotopic fractionation factor ( S ) between boron taken up in strongly basic anion exchange resin and boron in aqueous solution was determined by breakthrough column chromatography at 5 and 17 MPa at 25°C, using 0.1 mmol/L boric acid solution as feed solution. The S values obtained were 1.018 and 1.012, respectively, which were smaller than the value reported by using the same chromatographic method at atmospheric pressure at 25°C with the boron concentration of 10 mmol/L, but were larger than the values at the same condition with much higher concentration of 100 and 501 mmol/L, indicating that borate-polymerization reducing the isotopic fractionation was negligible. However, calculations based on the theory of isotope distribution between two phases estimated that 21% (5MPa) and 47% (17MPa) of boron taken up in the resin phase was in the three-coordinated B(OH)3-form, instead of in the four-coordinated B(OH)4--form, at high pressures even with the very diluted solution. We discussed this discrepancy by introducing (1) hydration or (2) a partial molar volume difference between isotopic molecules. It was inferred that borate ions were partially dehydrated upon transfer from the solution phase to the resin phase at high pressures, which resulted in smaller S values compared with those at the atmospheric pressure. Alternatively, it was likely that the S value decreased with increasing pressure, because the difference of the partial isotopic molar volumes between 10B(OH)3 and 11B(OH)3 was larger than that between 10B(OH)4- and 11B(OH)4-. If either will be the case, the influence of a pressure upon the isotope effect may not be negligible for boron isotopic exchange equilibrium. This knowledge is crucial for the principle of the boron isotopic pH-metry reconstructing a chemical variation at the paleo-deep oceanic environment where the early life may have been evolved.

  3. Deuterium enrichment of interstellar dusts

    NASA Astrophysics Data System (ADS)

    Das, Ankan; Chakrabarti, Sandip Kumar; Majumdar, Liton; Sahu, Dipen

    2016-07-01

    High abundance of some abundant and simple interstellar species could be explained by considering the chemistry that occurs on interstellar dusts. Because of its simplicity, the rate equation method is widely used to study the surface chemistry. However, because the recombination efficiency for the formation of any surface species is highly dependent on various physical and chemical parameters, the Monte Carlo method is best suited for addressing the randomness of the processes. We carry out Monte-Carlo simulation to study deuterium enrichment of interstellar grain mantle under various physical conditions. Based on the physical properties, various types of clouds are considered. We find that in diffuse cloud regions, very strong radiation fields persists and hardly a few layers of surface species are formed. In translucent cloud regions with a moderate radiation field, significant number of layers would be produced and surface coverage is mainly dominated by photo-dissociation products such as, C, CH_3, CH_2D, OH and OD. In the intermediate dense cloud regions (having number density of total hydrogen nuclei in all forms ˜2 × 10^4 cm^{-3}), water and methanol along with their deuterated derivatives are efficiently formed. For much higher density regions (˜10^6 cm^{-3}), water and methanol productions are suppressed but surface coverage of CO, CO_2, O_2, O_3 are dramatically increased. We find a very high degree of fractionation of water and methanol. Observational results support a high fractionation of methanol but surprisingly water fractionation is found to be low. This is in contradiction with our model results indicating alternative routes for de-fractionation of water.

  4. State-dependent switching control of switched positive fractional-order systems.

    PubMed

    Zhao, Xudong; Yin, Yunfei; Zheng, Xiaolong

    2016-05-01

    In this paper, the problem of switching stabilization for a class of continuous-time switched positive fractional-order systems is studied by using state-dependent switching. First, the asymptotic stability condition of switched positive fractional-order systems with state-dependent switching is given, which is based on the fractional co-positive Lyapunov method. Moreover, by the sliding sector method, the stability condition of switched positive fractional-order systems whose subsystems are possibly all unstable is obtained. A variable structure (VS) switching law with sliding sector is also proposed to guarantee the switched positive fractional-order system to be asymptotically stable. Finally, two numerical examples are given to demonstrate the advantages and effectiveness of our developed results. PMID:26922493

  5. Mass-dependent and -independent fractionation of isotopes in Ni and Pb chelate complex formation reactions

    NASA Astrophysics Data System (ADS)

    Nomura, Masao; Kudo, Takashi; Adachi, Atsuhiko; Aida, Masao; Fujii, Yasuhiko

    2013-11-01

    Mass independent fractionation (MIF) has been a very interesting topic in the field of inorganic isotope chemistry, in particular, geo- and cosmo- chemistry. In the present work, we studied the isotope fractionation of Ni(II) and Pb(II) ions in complex formation with chelating reagent EDTA. To obtain clear results on the mass dependence of the isotope fractionation, we have conducted long-distance ion exchange chromatography of Ni(II) and Pb(II), using chelate complex reagent EDTA. The results apparently show that the isotope fractionation in Ni complex formation system is governed by the mass dependent rule. On the other hand the isotope fractionation in the Pb complex system is governed by the mass independent rule or the nuclear volume effect.

  6. Mass-dependent and -independent fractionation of isotopes in Ni and Pb chelate complex formation reactions

    SciTech Connect

    Nomura, Masao; Kudo, Takashi; Adachi, Atsuhiko; Aida, Masao; Fujii, Yasuhiko

    2013-11-13

    Mass independent fractionation (MIF) has been a very interesting topic in the field of inorganic isotope chemistry, in particular, geo- and cosmo- chemistry. In the present work, we studied the isotope fractionation of Ni(II) and Pb(II) ions in complex formation with chelating reagent EDTA. To obtain clear results on the mass dependence of the isotope fractionation, we have conducted long-distance ion exchange chromatography of Ni(II) and Pb(II), using chelate complex reagent EDTA. The results apparently show that the isotope fractionation in Ni complex formation system is governed by the mass dependent rule. On the other hand the isotope fractionation in the Pb complex system is governed by the mass independent rule or the nuclear volume effect.

  7. Volume fraction dependent magnetic behaviour of ferrofluids for rotating seal applications

    NASA Astrophysics Data System (ADS)

    Schinteie, G.; Palade, P.; Vekas, L.; Iacob, N.; Bartha, C.; Kuncser, V.

    2013-10-01

    Ferrofluid samples consisting of magnetite nanoparticles (NPs) coated with oleic acid and dispersed in a non-polar organic solvent have been synthesized by chemical routes. Different volume fractions, φ, of magnetic NPs were considered. The overall structural characterization of NPs has been performed by x-ray diffractometry, with lattice parameters and average coherence lengths evaluated via Rietveld refinements. The magnetic properties of different samples have been analysed by SQUID magnetometry and temperature-dependent Mössbauer spectroscopy and finally explained by adequate magnetic relaxation mechanisms. Zero field cooling-field cooling protocols provided useful information about specific volume fraction dependent magnetic relaxation and de-freezing processes, the lack of the Verwey transition and stronger dipolar interactions at higher volume fractions. Anisotropy energies as obtained by both temperature dependent Mössbauer spectroscopy and magnetometry data are compared and a new procedure for a quantitative characterization of the dipolar interactions is proposed.

  8. Simulating transient dynamics of the time-dependent time fractional Fokker-Planck systems

    NASA Astrophysics Data System (ADS)

    Kang, Yan-Mei

    2016-09-01

    For a physically realistic type of time-dependent time fractional Fokker-Planck (FP) equation, derived as the continuous limit of the continuous time random walk with time-modulated Boltzmann jumping weight, a semi-analytic iteration scheme based on the truncated (generalized) Fourier series is presented to simulate the resultant transient dynamics when the external time modulation is a piece-wise constant signal. At first, the iteration scheme is demonstrated with a simple time-dependent time fractional FP equation on finite interval with two absorbing boundaries, and then it is generalized to the more general time-dependent Smoluchowski-type time fractional Fokker-Planck equation. The numerical examples verify the efficiency and accuracy of the iteration method, and some novel dynamical phenomena including polarized motion orientations and periodic response death are discussed.

  9. Equilibrium uranium isotope fractionation by nuclear volume and mass-dependent processes

    NASA Astrophysics Data System (ADS)

    Schauble, E. A.

    2006-12-01

    Uranium serves as a geochemical tracer of oxidation near the Earth's surface, and is also the basis for several isotopic geochronometers. It is thus important to understand possible non-radiogenic and non-radioactive isotopic fractionation of uranium in natural systems. This study presents theoretical estimates of equilibrium uranium isotope fractionations in U-bearing molecules and complexes, calculated using first-principles computational chemistry. Ion-exchange experiments (1,2) have indicated that mass-dependent mechanisms, alone, cannot explain 238U/234U and 238U/^{235}U fractionations, so nuclear volume (i.e., field shift) fractionation effects are also considered in theoretical calculations. The results indicate that equilibrium isotopic fractionation is likely when U4+ and U6+ species equilibrate. Nuclear volume fractionation leads to higher 238U/^{235}U in U4+-bearing species, overwhelming a smaller mass- dependent fractionation in the opposite direction. The calculated net fractionation between U(H2O)_94+ and UO2Cl3(H2O)_2^- is approximately 1 per mil at 20-150°C, in agreement with earlier experiments. These results also reproduce the apparent non mass-dependent signature observed in 238U/234U relative to 238U/^{235}U. In addition to redox reactions, significant fractionation is expected between different U6+-bearing uranyl complexes (e.g., UO2(H2O)_52+, UO2(NO3)_3^-, UO2(CO3)(H2O)3). These results suggest that U-isotope composition could be used as a proxy for the oxidation state and speciation of natural waters, and that U-isotope ratios are not constant in materials formed or equilibrated at low temperatures. More generally, nuclear volume fractionations are expected to partially cancel or reverse mass-dependent fractionations caused by redox transitions among the high oxidation states (≥+2) of lanthanides, actinides, and heavy transition elements. References: 1. Nomura, Higuchi and Fujii, 1996, J. Am. Chem. Soc., v. 118, p. 9127-9130. 2. Bigeleisen

  10. Mass dependent isotope fractionation during impacts induced the Archaean mass-independent fractionation of sulphur: Evidence against Great Oxidation Event

    NASA Astrophysics Data System (ADS)

    Huang, H.

    2010-12-01

    A prevailing hypothesis, low-oxygen level of the Archaean atmosphere, relies strongly on the presence of strong mass-independent fractionation (MIF) of the sulfur isotopes in sulfide- and sulfate-bearing minerals older than 2.4 billion years. Actually, there is “a broad overlap between MIF signals observed within Archaean sedimentary sequences and periods of enhanced asteroid impacts represented by impact ejecta/fallout units”(Glikson 2010) (Fig. 1). Moreover, usually MIF- related sulphur occurs in the Archaean sedimentary rocks as pyrite (FeS2) which has been found in the K-T boundary clay beds and in several identified impact craters, which is an independent argument in favor of pyrites could be the product of impact. Impact processes (vaporization and condensation) are sufficient to explain the MIF signals following the principle: the earlier the condensed material, the more enriched in lighter isotopes (Huang 2010). The nature of the MIF of the sulfur isotopes is that the fractionation of isotope is still mass dependent during impacts, which means the measured nonzero Δ33S values of Archean sulfide- and sulfate-bearing minerals indicate that their different condensation sequences. Another important line of evidence that support the impact-generated MIF of the sulfur isotopes comes from the various iron isotope values of the pyrites especially those with iron isotope heterogeneity at grain scale. Thus, it is clear that the signals are the markers of impact rather than O2 poor atmosphere. Furthermore, this can also account for the lack of MIF-S in several Archaean units before 2.4 billion years. Figure 1 Plot of mass-independent fractionation of sulphur and asteroid impact events with age. Modified from Glikson (2010)

  11. Correcting the initialization of models with fractional derivatives via history-dependent conditions

    NASA Astrophysics Data System (ADS)

    Du, Maolin; Wang, Zaihua

    2016-04-01

    Fractional differential equations are more and more used in modeling memory (history-dependent, non-local, or hereditary) phenomena. Conventional initial values of fractional differential equations are defined at a point, while recent works define initial conditions over histories. We prove that the conventional initialization of fractional differential equations with a Riemann-Liouville derivative is wrong with a simple counter-example. The initial values were assumed to be arbitrarily given for a typical fractional differential equation, but we find one of these values can only be zero. We show that fractional differential equations are of infinite dimensions, and the initial conditions, initial histories, are defined as functions over intervals. We obtain the equivalent integral equation for Caputo case. With a simple fractional model of materials, we illustrate that the recovery behavior is correct with the initial creep history, but is wrong with initial values at the starting point of the recovery. We demonstrate the application of initial history by solving a forced fractional Lorenz system numerically.

  12. Correcting the initialization of models with fractional derivatives via history-dependent conditions

    NASA Astrophysics Data System (ADS)

    Du, Maolin; Wang, Zaihua

    2015-08-01

    Fractional differential equations are more and more used in modeling memory (history-dependent, non-local, or hereditary) phenomena. Conventional initial values of fractional differential equations are defined at a point, while recent works define initial conditions over histories. We prove that the conventional initialization of fractional differential equations with a Riemann-Liouville derivative is wrong with a simple counter-example. The initial values were assumed to be arbitrarily given for a typical fractional differential equation, but we find one of these values can only be zero. We show that fractional differential equations are of infinite dimensions, and the initial conditions, initial histories, are defined as functions over intervals. We obtain the equivalent integral equation for Caputo case. With a simple fractional model of materials, we illustrate that the recovery behavior is correct with the initial creep history, but is wrong with initial values at the starting point of the recovery. We demonstrate the application of initial history by solving a forced fractional Lorenz system numerically.

  13. Molecular weight dependence of segmental alignment in a sheared polymer melt: A deuterium nuclear magnetic resonance investigation

    NASA Astrophysics Data System (ADS)

    Cormier, Ryan J.; Callaghan, Paul T.

    2002-06-01

    2H NMR quadrupole interaction spectroscopy has been used to measure the molecular weight dependence of poly(dimethylsiloxane) chain deformation under shear in a cylindrical Couette cell while NMR velocimetry has been used to directly measure shear rates. The signals were acquired from a perdeuterated benzene probe molecule, which provides a motionally averaged sampling of the entire segmental ensemble. We have measured the dependence on shear rate of the SXX (velocity), SYY (velocity gradient), and SZZ (vorticity) elements of the segmented alignment tensor, fitting the data using the standard Doi-Edwards theory and modified to allow for convected constraint release. Our results suggest that the tube disengagement times scale as molecular weight to the power 3.5±0.1, consistent with the usual 3.4 power law. Our velocimetry measurements indicate a reproducible and consistent slip occurring at high molecular weights (>1 M Dalton), a phenomenon which is independently observed in a lower than expected chain deformation.

  14. Hydrogen/Deuterium Exchange Kinetics Demonstrate Long Range Allosteric Effects of Thumb Site 2 Inhibitors of Hepatitis C Viral RNA-dependent RNA Polymerase.

    PubMed

    Deredge, Daniel; Li, Jiawen; Johnson, Kenneth A; Wintrode, Patrick L

    2016-05-01

    New nonnucleoside analogs are being developed as part of a multi-drug regimen to treat hepatitis C viral infections. Particularly promising are inhibitors that bind to the surface of the thumb domain of the viral RNA-dependent RNA polymerase (NS5B). Numerous crystal structures have been solved showing small molecule non-nucleoside inhibitors bound to the hepatitis C viral polymerase, but these structures alone do not define the mechanism of inhibition. Our prior kinetic analysis showed that nonnucleoside inhibitors binding to thumb site-2 (NNI2) do not block initiation or elongation of RNA synthesis; rather, they block the transition from the initiation to elongation, which is thought to proceed with significant structural rearrangement of the enzyme-RNA complex. Here we have mapped the effect of three NNI2 inhibitors on the conformational dynamics of the enzyme using hydrogen/deuterium exchange kinetics. All three inhibitors rigidify an extensive allosteric network extending >40 Å from the binding site, thus providing a structural rationale for the observed disruption of the transition from distributive initiation to processive elongation. The two more potent inhibitors also suppress slow cooperative unfolding in the fingers extension-thumb interface and primer grip, which may contribute their stronger inhibition. These results establish that NNI2 inhibitors act through long range allosteric effects, reveal important conformational changes underlying normal polymerase function, and point the way to the design of more effective allosteric inhibitors that exploit this new information. PMID:27006396

  15. A strong redshift dependence of the broad absorption line quasar fraction

    NASA Astrophysics Data System (ADS)

    Allen, James T.; Hewett, Paul C.; Maddox, Natasha; Richards, Gordon T.; Belokurov, Vasily

    2011-01-01

    We describe the application of non-negative matrix factorization to generate compact reconstructions of quasar spectra from the Sloan Digital Sky Survey (SDSS), with particular reference to broad absorption line quasars (BALQSOs). BAL properties are measured for Si IVλ1400, C IVλ1550, Al IIIλ1860 and Mg IIλ2800, resulting in a catalogue of 3547 BALQSOs. Two corrections, based on extensive testing of synthetic BALQSO spectra, are applied in order to estimate the intrinsic fraction of C IV BALQSOs. First, the probability of an observed BALQSO spectrum being identified as such by our algorithm is calculated as a function of redshift, signal-to-noise ratio and BAL properties. Secondly, the different completenesses of the SDSS target selection algorithm for BALQSOs and non-BAL quasars are quantified. Combining the detection probabilities with an intrinsic E(B-V) distribution capable of reproducing the observed increase in mean E(B-V) with increasing redshift, the intrinsic C IV BALQSO fraction is 41 ± 5 per cent. Our analysis of the selection effects allows us to measure the dependence of the intrinsic C IV BALQSO fraction on luminosity and redshift. We find a factor of 3.5 ± 0.4 decrease in the intrinsic fraction from the highest redshifts, z≃ 4.0, down to z≃ 2.0. The redshift dependence implies that an orientation effect alone is not sufficient to explain the presence of BAL troughs in some but not all quasar spectra. Our results are consistent with the intrinsic BALQSO fraction having no strong luminosity dependence, although with 3σ limits on the rate of change of the intrinsic fraction with luminosity of -6.9 and 7.0 per cent dex-1 we are unable to rule out such a dependence.

  16. Fractional Green's Function for the Time-Dependent Scattering Problem in the Space-Time-Fractional Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Dong, Jianping

    2014-12-01

    Integral form of the space-time-fractional Schrödinger equation for the scattering problem in the fractional quantum mechanics is studied in this paper. We define the fractional Green's function for the space-time fractional Schrödinger equation and express it in terms of Fox's H-function and in a computable series form. The asymptotic formula of the Green's function for large argument is also obtained, and applied to study the fractional quantum scattering problem. We get the approximate scattering wave function with correction of every order.

  17. Use and Abuse of a Fractional Fokker-Planck Dynamics for Time-Dependent Driving

    NASA Astrophysics Data System (ADS)

    Heinsalu, E.; Patriarca, M.; Goychuk, I.; Hänggi, P.

    2007-09-01

    We investigate a subdiffusive, fractional Fokker-Planck dynamics occurring in time-varying potential landscapes and thereby disclose the failure of the fractional Fokker-Planck equation (FFPE) in its commonly used form when generalized in an ad hoc manner to time-dependent forces. A modified FFPE (MFFPE) is rigorously derived, being valid for a family of dichotomously alternating force fields. This MFFPE is numerically validated for a rectangular time-dependent force with zero average bias. For this case, subdiffusion is shown to become enhanced as compared to the force free case. We question, however, the existence of any physically valid FFPE for arbitrary varying time-dependent fields that differ from this dichotomous varying family.

  18. Mass-Dependent and -Independent Fractionation of Hg Isotopes by Photoreduction in Aquatic Systems

    NASA Astrophysics Data System (ADS)

    Bergquist, Bridget A.; Blum, Joel D.

    2007-10-01

    Mercury (Hg) isotopes can be used as tracers of Hg biogeochemical pathways in the environment. The photochemical reduction of aqueous Hg species by natural sunlight leads to both mass-dependent fractionation (MDF) of Hg isotopes and mass-independent fractionation (MIF) of the odd-mass isotopes, with the relation between the MIF for the two odd isotopes being distinct for different photoreduction pathways. Large variations in MDF and MIF are observed in fish and provide new insights into the sources and bioaccumulation of Hg in food webs. MIF in fish can also be used to estimate the loss of methylmercury via photoreduction in aquatic ecosytems.

  19. Approximating a Giving Up Smoking Dynamic on Adolescent Nicotine Dependence in Fractional Order

    PubMed Central

    2016-01-01

    In this work, we consider giving up smoking dynamic on adolescent nicotine dependence. First, we use the Caputo derivative to develop the model in fractional order. Then we apply two different numerical methods to compute accurate approximate solutions of this new model in fractional order and compare their results. In order to do this, we consider the generalized Euler method (GEM) and multi-step generalized differential transform method (MSGDTM). We also show the unique positive solution for this model and present numerical results graphically. PMID:27105426

  20. Approximating a Giving Up Smoking Dynamic on Adolescent Nicotine Dependence in Fractional Order.

    PubMed

    Zeb, Anwar; Zaman, Gul; Erturk, Vedat Suat; Alzalg, Baha; Yousafzai, Faisal; Khan, Madad

    2016-01-01

    In this work, we consider giving up smoking dynamic on adolescent nicotine dependence. First, we use the Caputo derivative to develop the model in fractional order. Then we apply two different numerical methods to compute accurate approximate solutions of this new model in fractional order and compare their results. In order to do this, we consider the generalized Euler method (GEM) and multi-step generalized differential transform method (MSGDTM). We also show the unique positive solution for this model and present numerical results graphically. PMID:27105426

  1. Deuterium incorporation into Escherichia coli proteins. A neutron-scattering study of DNA-dependent RNA polymerase.

    PubMed

    Lederer, H; May, R P; Kjems, J K; Schaefer, W; Crespi, H L; Heumann, H

    1986-05-01

    Neutron small-angle scattering studies of single protein subunits in a protein-DNA complex require the adjustment of the neutron scattering-length densities of protein and DNA, which is attainable by specific deuteration of the protein. The neutron scattering densities of unlabelled DNA and DNA-dependent RNA polymerase of Escherichia coli match when RNA polymerase is isolated from cells grown in a medium containing 46% D2O and unlabelled glucose as carbon source. Their contrasts vanish simultaneously in a dialysis buffer containing 65% D2O. An expression was evaluated which allows the calculation of the degree of deuteration and match point of any E. coli protein from the D2O content of the growth medium, taking the 2H incorporation into RNA polymerase amino acids to be representative for all amino acids in E. coli proteins. The small-angle scattering results, on which the calculation of the degree of deuteration is based, were confirmed by mass spectrometric measurements. PMID:3516697

  2. Thermal conductivity of simple liquids: Temperature and packing-fraction dependence

    NASA Astrophysics Data System (ADS)

    Ohtori, Norikazu; Ishii, Yoshiki; Togawa, Yoshinori; Oono, Takuya; Takase, Keiichi

    2014-02-01

    The thermal conductivity of rare gases in liquid and dense fluid states has been evaluated using molecular dynamics simulation with the Lennard-Jones (LJ) potentials and the Green-Kubo (GK) formula. All the calculated thermal conductivities are in very good agreement with experimental results for a wide range of temperature and density. Special attention was paid to temperature and packing-fraction dependence which is nontrivial from dimensional analysis on the LJ potentials and the GK formula. First, the temperature dependence of T1/4 was determined from the calculations at constant densities. Secondly, in order to obtain the dependence on packing fraction from that on number density separately, a scaling method of particle and/or cell size was introduced. The number density dependence of (N/V)2/3 which is expected from the dimensional analysis of the GK formulas was confirmed and the packing-fraction dependence of η3/2 was determined by using the scaling method. It turned out that the summarized functional form of m-1/2(N/V)2/3η3/2T1/4 can well express both the calculated and experimental thermal conductivities for Ar, Kr, and Xe, where m is the atomic mass. The scaling method has also been applied to molten NaCl and KCl so that it has been found that the thermal conductivity has the packing-fraction dependence of η2/3 which is much weaker than that of the simple LJ liquids.

  3. Thermal conductivity of simple liquids: temperature and packing-fraction dependence.

    PubMed

    Ohtori, Norikazu; Ishii, Yoshiki; Togawa, Yoshinori; Oono, Takuya; Takase, Keiichi

    2014-02-01

    The thermal conductivity of rare gases in liquid and dense fluid states has been evaluated using molecular dynamics simulation with the Lennard-Jones (LJ) potentials and the Green-Kubo (GK) formula. All the calculated thermal conductivities are in very good agreement with experimental results for a wide range of temperature and density. Special attention was paid to temperature and packing-fraction dependence which is nontrivial from dimensional analysis on the LJ potentials and the GK formula. First, the temperature dependence of T(1/4) was determined from the calculations at constant densities. Secondly, in order to obtain the dependence on packing fraction from that on number density separately, a scaling method of particle and/or cell size was introduced. The number density dependence of (N/V)(2/3) which is expected from the dimensional analysis of the GK formulas was confirmed and the packing-fraction dependence of η(3/2) was determined by using the scaling method. It turned out that the summarized functional form of m(-1/2)(N/V)(2/3)η(3/2)T(1/4) can well express both the calculated and experimental thermal conductivities for Ar, Kr, and Xe, where m is the atomic mass. The scaling method has also been applied to molten NaCl and KCl so that it has been found that the thermal conductivity has the packing-fraction dependence of η(2/3) which is much weaker than that of the simple LJ liquids. PMID:25353444

  4. Oxygen isotope fractionation in the vacuum ultraviolet photodissociation of carbon monoxide: Wavelength, pressure and temperature dependency.

    SciTech Connect

    Chakraborty, Subrata; Davis, Ryan; Ahmed, Musahid; Jackson, Teresa L.; Thiemens, Mark H.

    2012-01-03

    Several absorption bands exist in the VUV region of Carbon monoxide (CO). Emission spectra indicate that these bands are all predissociative. An experimental investigation of CO photodissociation by vacuum ultraviolet photons (90 to 108 nm; ~13 to 11 eV) from the Advanced Light Source Synchrotron and direct measurement of the associated oxygen isotopic composition of the products are presented here. A wavelength dependency of the oxygen isotopic composition in the photodissociation product was observed. Slope values (δ'{sup 18}O/ δ'{sup 17}O) ranging from 0.76 to 1.32 were observed in oxygen three-isotope space (δ'{sup 18}O vs. δ'{sup 17}O) which correlated with increasing synchrotron photon energy, and indicate a dependency of the upper electronic state specific dissociation dynamics (e.g., perturbation and coupling associated with a particular state). An unprecedented magnitude in isotope separation was observed for photodissociation at the 105 and 107 nm synchrotron bands and are found to be associated with accidental predissociation of the vibrational states ({nu} = 0 and 1) of the upper electronic state E{sup 1}Π. For each synchrotron band, a large (few hundred per mil) extent of isotopic fractionation was observed and the range of fractionation is a combination of column density and exposure time. A significant temperature dependency in oxygen isotopic fractionation was observed, indicating a rotational level dependency in the predissociation process.

  5. Diffusion of spherical solutes: A fractional molecular-hydrodynamic study of solvent dependence

    NASA Astrophysics Data System (ADS)

    Chan, T. C.; Li, K. Y.; Li, H. T.

    2016-04-01

    Diffusivities of tetramethyltin, tetraethyltin, tetraethyllead, and 2,2-dichloropropane in methanol as well as tetraethyltin and tetraethyllead in ethanol were measured and combined with other literature data of spherical solutes in various solvents to study the effects of solvent on diffusivity. A new fractional molecular-hydrodynamic relation is found to well represent the solvent dependence for the diffusivities of carbon tetrachloride, tetramethyltin, tetraethyltin, tetrapropyltin, and tetrabutyltin at diverse temperatures. The relation consists of two components: one is a function of the hydrodynamic viscosity and the other associated with the molecular properties of solvent. Each has a fractional exponent dependent on solute size. The results here indicate that the relative importance of the viscosity component consistently increases with solute size, but that the trend for the molecular component is reversed. Comparison with other diffusion relations reveals that the newly developed model is more applicable and accurate for expressing the effects of solvent on diffusivity.

  6. Thermal conductivity of simple liquids: Origin of temperature and packing fraction dependences

    NASA Astrophysics Data System (ADS)

    Ishii, Yoshiki; Sato, Keisuke; Salanne, Mathieu; Madden, Paul A.; Ohtori, Norikazu

    2014-03-01

    The origin of both weak temperature dependence and packing fraction dependence of T1/4η3/2 in the thermal conductivity of the simple Lennard-Jones (LJ) liquid is explored. In order to discuss the relative contributions from attractive or repulsive part of the interaction potential separately, the thermal conductivity of a series of Weeks-Chandler-Anderson (WCA) fluids is calculated by molecular dynamics simulations. The results show that the repulsive part plays the main role in the heat conduction, while the attractive part has no direct effect on the thermal conductivity for a given packing fraction. By investigating WCA fluids with potentials of varying softness, we explain the difference observed between the LJ liquids such as argon and Coulombic liquids such as NaCl.

  7. Deuterium in Iceland waters

    USGS Publications Warehouse

    Friedman, I.; Sigurgeirsson, T.; Gardarsson, O.

    1963-01-01

    From the deuterium analysis of 159 samples of water collected in Iceland from hot-water boreholes, cold and hot springs, rivers and rain, the geographical distribution of deuterium in surface waters is plotted. On the basis of the deuterium analysis, the water from boreholes near Reykjavik does not originate from local precipitation. The variation of deuterium content of these water wells with time suggests that these data can be used to determine the time of travel of recharge water to the various boreholes, as well as the surface recharge area. ?? 1963.

  8. Mass dependent stable isotope fractionation of mercury during mer mediated microbial degradation of monomethylmercury

    NASA Astrophysics Data System (ADS)

    Kritee, K.; Barkay, Tamar; Blum, Joel D.

    2009-03-01

    Controlling bioaccumulation of toxic monomethylmercury (MMHg) in aquatic food chains requires differentiation between biotic and abiotic pathways that lead to its production and degradation. Recent mercury (Hg) stable isotope measurements of natural samples suggest that Hg isotope ratios can be a powerful proxy for tracing dominant Hg transforming pathways in aquatic ecosystems. Specifically, it has been shown that photo-degradation of MMHg causes both mass dependent (MDF) and mass independent fractionation (MIF) of Hg isotopes. Because the extent of MDF and MIF observed in natural samples (e.g., fish, soil and sediments) can potentially be used to determine the relative importance of pathways leading to MMHg accumulation, it is important to determine the potential role of microbial pathways in contributing to the fractionation, especially MIF, observed in these samples. This study reports the extent of fractionation of Hg stable isotopes during degradation of MMHg to volatile elemental Hg and methane via the microbial Hg resistance ( mer) pathway in Escherichia coli carrying a mercury resistance ( mer) genetic system on a multi-copy plasmid. During experimental microbial degradation of MMHg, MMHg remaining in reactors became progressively heavier (increasing δ202Hg) with time and underwent mass dependent Rayleigh fractionation with a fractionation factor α202/198 = 1.0004 ± 0.0002 (2SD). However, MIF was not observed in any of the microbial MMHg degradation experiments indicating that the isotopic signature left by mer mediated MMHg degradation is significantly different from fractionation observed during DOC mediated photo-degradation of MMHg. Additionally, a clear suppression of Hg isotope fractionation, both during reduction of Hg(II) and degradation of MMHg, was observed when the cell densities increased, possibly due to a reduction in substrate bioavailability. We propose a multi-step framework for understanding the extent of fractionation seen in our MMHg

  9. Size-dependent geometrically nonlinear free vibration analysis of fractional viscoelastic nanobeams based on the nonlocal elasticity theory

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Faraji Oskouie, M.; Gholami, R.

    2016-01-01

    In recent decades, mathematical modeling and engineering applications of fractional-order calculus have been extensively utilized to provide efficient simulation tools in the field of solid mechanics. In this paper, a nonlinear fractional nonlocal Euler-Bernoulli beam model is established using the concept of fractional derivative and nonlocal elasticity theory to investigate the size-dependent geometrically nonlinear free vibration of fractional viscoelastic nanobeams. The non-classical fractional integro-differential Euler-Bernoulli beam model contains the nonlocal parameter, viscoelasticity coefficient and order of the fractional derivative to interpret the size effect, viscoelastic material and fractional behavior in the nanoscale fractional viscoelastic structures, respectively. In the solution procedure, the Galerkin method is employed to reduce the fractional integro-partial differential governing equation to a fractional ordinary differential equation in the time domain. Afterwards, the predictor-corrector method is used to solve the nonlinear fractional time-dependent equation. Finally, the influences of nonlocal parameter, order of fractional derivative and viscoelasticity coefficient on the nonlinear time response of fractional viscoelastic nanobeams are discussed in detail. Moreover, comparisons are made between the time responses of linear and nonlinear models.

  10. THE ENVIRONMENTAL DEPENDENCE OF THE FRACTION OF 'UNCONVENTIONAL' GALAXIES: RED LATE TYPES AND BLUE EARLY TYPES

    SciTech Connect

    Deng Xinfa; He Jizhou; Wu Ping; Ding Yingping

    2009-07-10

    From the Main galaxy sample of the Sloan Digital Sky Survey Data Release 6, we construct two volume-limited samples with the luminosity -20.0 {<=} M{sub r} {<=} -18.5 and -22.40 {<=} M{sub r} {<=} -20.16, respectively, to explore the environmental dependence of the fraction of 'unconventional' galaxies: red late types and blue early types. We use the density estimator within the distance to the fifth nearest neighbor, and construct two samples at both extremes of density and perform comparative studies between them for each volume-limited sample. Results of two volume-limited samples show the same conclusions: the fraction of red late-type galaxies rises considerably with increasing local density, and that one of the blue early-type galaxies declines substantially with increasing local density. In addition, we note that bluer galaxies preferentially are late types, but the red galaxies are not dominated by early types.

  11. Reporting and measurement of mass-dependent and mass-independent fractionation of mercury isotopes

    NASA Astrophysics Data System (ADS)

    Bergquist, B. A.; Blum, J. D.

    2007-12-01

    Hg isotope analysis by MC-ICP-MS is an important new approach for fingerprinting Hg sources and monitoring Hg redox reactions and bioaccumulation, especially with the recent discovery of mass independent Hg isotope fractionation. Unfortunately research groups have adopted different standards, definitions of delta values, and methods of isotopic measurement. We suggest that a single standard, NIST SRM 3133, be adopted for reporting the isotopic variability of Hg isotopes. Isotope ratios should be determined by sample-standard bracketing (SSB) during analysis and reported as permil (‰) deviation from SRM 3133. For the highest precision and accuracy, a Tl internal standard along with SSB should be used to correct instrumental mass bias. Measurement routines should also include on-peak zero corrections and matching of concentration and matrix between the samples and bracketing standard. For samples that display mass-dependent fractionation (MDF), only one delta value needs to be reported (δ202/198Hg). Mass-independent fractionation (MIF) (Jackson et al., 2006; Bergquist et al., 2006; Bergquist and Blum, submitted) requires additional nomenclature, and we suggest reporting MIF as the deviation in isotope ratios from the theoretical mass dependent kinetic isotope fractionation (Δxxx/198Hg)¬. External reproducibility should be monitored by analysis of secondary standards. For studies of MDF, we use an in-house secondary standard solution made from metallic Hg mined from Almaden Spain and obtain a δ202Hg of -0.55 ±0.06‰ (2SD). For studies of MIF, we use NRCC CRM DORM-2 (dogfish muscle) and obtain a mean value of δ202Hg of +0.19 ±0.13‰ (2SD), Δ201Hg of +0.89 ±0.07‰ (2SD) , and Δ199Hg of +1.07 ±0.08‰ (2SD).

  12. Deuterium permeation through copper with trapping impurities

    NASA Astrophysics Data System (ADS)

    Mitchell, D. J.; Harris, J. M.; Patrick, R. C.; Boespflug, E. P.; Beavis, L. C.

    1982-02-01

    The time dependence of the deuterium permeation rate through impurity-doped copper membranes was measured in the temperature range 300-700 °C. Copper membranes that were doped with Er, Zr, and Ti all exhibited permeabilities that were nearly equal to pure copper, but the apparent diffusivities were smaller than those for pure copper by factors of 10-100 over the experimental temperature range. The permeation characteristics of these alloys appear to be altered from those for pure copper due to trapping of deuterium at sites that are associated with the impurity atoms. It is shown that the deuterium permeation rate through the copper alloys can be expressed in an analytical form that is analogous to that for pure copper, except that the apparent diffusivity takes on a value which depends on the trap concentration and binding energy for deuterium. The binding energies that are calculated for the alloys are used to determine the lag time which is required for deuterium or hydrogen to permeate through initially evacuated membranes. The lag times for copper alloys containing about 1% Er, Zr, or Ti are many orders of magnitude longer than for pure copper at room temperature. Copper alloys containing Cr do not appear to exhibit deuterium trapping. Nuclear reaction and backscattering analyses were used to help determine the effect or surface oxides on the permeation measurements.

  13. ORIGINS OF NON-MASS-DEPENDENT FRACTIONATION OF EXTRA-TERRESTRIAL OXYGEN

    SciTech Connect

    Barcena, Homar; Connolly, Harold C.

    2012-08-01

    The distribution of oxygen isotopes in meteorites and within the earliest solids that formed in the solar system hints that the precursors of these materials must have undergone a mass-independent process. The mass-independent process is specifically one that fractionates {sup 16}O from {sup 17}O and {sup 18}O. This chemical signature is indicative of non-equilibrium processing, which bear resemblance to some unusual terrestrial phenomenon such as fractionation of ozone in the upper Earth atmosphere. That the mass-independent fractionation of oxygen isotopes is preserved within petrological records presents planetary scientists interesting clues to the events that may have occurred during the formation of the solar system. Currently, there are several hypotheses on the origins of the oxygen isotope distribution within primitive planetary materials, which include both thermal and photochemical models. We present a new model based on a physico-chemical hypothesis for the origin of non-mass-dependent O-isotope distribution in oxygen-bearing extra-terrestrial materials, which originated from the disproportionation of CO in dark molecular clouds to create CO{sub 2} reservoirs. The disproportionation created a reservoir of heavy oxygen isotopes and could have occurred throughout the evolution of the disk. The CO{sub 2} was a carrier of the isotope anomaly in the solar nebula and we propose that non-steady-state mixing of these reservoirs with the early rock-forming materials during their formation corresponds with the birth and evolution of the solar system.

  14. Bulk retention of deuterium in graphites exposed to deuterium plasma at high temperature

    NASA Astrophysics Data System (ADS)

    Arkhipov, I. I.; Gorodetsky, A. E.; Zakharov, A. P.; Khripunov, B. I.; Shapkin, V. V.; Petrov, V. B.; Pistunovich, V. I.; Negodaev, M. A.; Bagulya, A. V.

    1996-10-01

    A highly ionized deuterium plasma with a low residual gas pressure and a high intensity D 2+-ion beam were used for the study of deuterium retention in RG-Ti-91 and POCO AXF-5Q graphites. Deuterium retention in the samples was estimated by TDS during heating to 2000 K. Mechanical removal of a surface layer 100 μm thick was used to distinguish bulk and surface fractions of retained deuterium. The samples of RG-Ti and POCO graphites were exposed to a plasma with an ion flux of 3 × 10 17 D/cm 2 · s in the 'Lenta' plasma device for 10 to 10 4 s at residual deuterium pressure of 0.04 Pa at 1400 K. Under plasma exposure deuterium capture in RG-Ti graphite reached the saturation level at a fluence of 4 × 10 20 D/cm 2 while the bulk inventory was negligible. As for POCO graphite, deuterium retention increased with fluence and was equal to 18 appm in the bulk for a fluence of 7 × 10 21 D/cm 2. The same amount of deuterium in the bulk was obtained after gas exposure of POCO at an effective pressure of 0.8 Pa (1400 K, 6 h). With this result, the tritium concentration in the plasma-facing graphite materials can reach 1500 appm or 380 grams of tritium per ton of graphite. To understand the role of ion flux in generation of effective pressure, POCO was irradiated with 16 keV D 2+-ions at 1400 K for 4 h to 8 × 10 20 D/cm 2 (ion flux was 6 × 10 16 D/cm 2 · s, residual deuterium pressure was 0.004 Pa). The results are discussed on the basis of structural differences for POCO and RG-Ti graphites.

  15. Inelastic dark matter with spin-dependent couplings to protons and large modulation fractions in DAMA

    NASA Astrophysics Data System (ADS)

    Scopel, Stefano; Yoon, Kook-Hyun

    2016-02-01

    We discuss a scenario where the DAMA modulation effect is explained by a Weakly Interacting Massive Particle (WIMP) which upscatters inelastically to a heavier state and predominantly couples to the spin of protons. In this scenario constraints from xenon and germanium targets are evaded dynamically, due to the suppression of the WIMP coupling to neutrons, while those from fluorine targets are evaded kinematically, because the minimal WIMP incoming speed required to trigger upscatters off fluorine exceeds the maximal WIMP velocity in the Galaxy, or is very close to it. In this scenario WIMP scatterings off sodium are usually sensitive to the large-speed tail of the WIMP velocity distribution and modulated fractions of the signal close to unity arise in a natural way. On the other hand, a halo-independent analysis with more conservative assumptions about the WIMP velocity distribution allows to extend the viable parameter space to configurations where large modulated fractions are not strictly necessary. We discuss large modulated fractions in the Maxwellian case showing that they imply a departure from the usual cosine time dependence of the expected signal in DAMA. However we explicitly show that the DAMA data is not sensitive to this distortion, both in time and frequency space, even in the extreme case of a 100 % modulated fraction. Moreover the same scenario provides an explanation of the maximum in the energy spectrum of the modulation amplitude detected by DAMA in terms of WIMPs whose minimal incoming speed matches the kinematic threshold for inelastic upscatters. For the elastic case the detection of such maximum suggests an inversion of the modulation phase below the present DAMA energy threshold, while this is not expected for inelastic scattering. This may allow to discriminate between the two scenarios in a future low-threshold analysis of the DAMA data.

  16. An inverse time-dependent source problem for a time-fractional diffusion equation

    NASA Astrophysics Data System (ADS)

    Wei, T.; Li, X. L.; Li, Y. S.

    2016-08-01

    This paper is devoted to identifying a time-dependent source term in a multi-dimensional time-fractional diffusion equation from boundary Cauchy data. The existence and uniqueness of a strong solution for the corresponding direct problem with homogeneous Neumann boundary condition are firstly proved. We provide the uniqueness and a stability estimate for the inverse time-dependent source problem. Then we use the Tikhonov regularization method to solve the inverse source problem and propose a conjugate gradient algorithm to find a good approximation to the minimizer of the Tikhonov regularization functional. Numerical examples in one-dimensional and two-dimensional cases are provided to show the effectiveness of the proposed method. This paper was supported by the NSF of China (11371181) and the Fundamental Research Funds for the Central Universities (lzujbky-2013-k02).

  17. Deuterium in the daytime thermosphere

    NASA Technical Reports Server (NTRS)

    Breig, E. L.; Sanatani, S.; Hanson, W. B.

    1987-01-01

    Ion concentration measurements for H(+) and D(+) from the magnetic ion mass spectrometer on the Atmosphere Explorer C satellite are used, in conjunction with other atmospheric data, to determine the concentrations of H and D in the nonpolar daytime thermosphere. The ratio of the observed D(+) to H(+) concentrations has essentially the same height dependence in the 300 to 800-km region as expected for their neutral counterparts, even in the presence of ion temperature gradients and probable large vertical ion fluxes. Rapid charge exchange with atomic oxygen ensures that D/H is about equal to D(+)/H(+) at the lower altitudes where the derived D to H concentration ratio is a factor of about 6 larger than its sea level value, for an exospheric temperature of 930 K. This relative enhancement of deuterium arises from the fact that hydrogen more readily escapes the earth, and a large vertical gradient in the H concentration relative to its diffusive equilibrium value is necessary to drive this upward flux through the lower thermosphere. If these planetary losses of hydrogen are much greater than those associated with evaporative escape, as is the current view, then correspondingly larger deuterium loss rates are also likely in order that the thermospheric D/H ratio not increase well above the observed value. The absolute winter daytime concentration of deuterium at 300 km is found to be 210 + or - 50 atoms/cu cm.

  18. Deuterium surface segregation in titanium alloys

    NASA Astrophysics Data System (ADS)

    Adler, Philip N.; Schulte, Robert L.; Margolin, Harold

    1990-07-01

    Deuterium surface segregation has been investigated in α, α + β, and β-phase titanium that were deuterium charged over the range of 2 to approximately 300 wppm. Surface segregation was observed in samples that were essentially α-phase materials, i.e., high-purity commercial α-Ti, Ti-6A1, and Ti-3A1-2.5V, whereas Ti-6A1-4V had slight enrichment and β-Ti-13Mn had no detectable segregation. Nuclear reaction analysis (NRA) techniques were used to measure the near-surface deuterium concentration, and the segregation has been localized to within 50 nm of the surface. The time-dependent increase of deuterium at the surface is consistent with deuterium diffusion from the bulk to the surface and a room-temperature diffusivity of approximately 3 × 10-9 cm2/s. Surface enrichment in excess of 30 times the bulk concentration was observed in charged samples and in excess of 60 times for samples that had been charged and then vacuum annealed. Polishing was found to be of importance in causing segregation. The presence of deuterides or a surface defect state is suggested to explain the deuterium surface enrichment.

  19. Interstellar Deuterium Chemistry

    NASA Technical Reports Server (NTRS)

    Sandford, S. A.

    2003-01-01

    The presence of isotopic anomalies is the most unequivocal demonstration that meteoritic material contains circumstellar or interstellar components. In the case of organic compounds in meteorites and interplanetary dust particles (IDPs), the most useful isotopic tracer of interstellar components has been deuterium (D) excesses. In some cases these enrichments are seen in bulk meteoritic materials, but D enrichments have also been observed in meteoritic subfractions and even within specific classes of molecular species, such as amino and carboxylic acids. These anomalies are not thought to be the result of nucleosynthetic processes, but are instead ascribed to chemical and physical processes occurring in the interstellar medium (ISM). The traditional explanation of these D excesses has been to invoke the presence of materials made in the ISM by low temperature gas phase ion-molecule reactions. Indeed, the DM ratios seen in the simple interstellar gas phase molecules in cold dense clouds amenable to measurement using radio spectral techniques are generally considerably higher than the values seen in enriched Solar System materials. However, the true linkage between the DM ratios in interstellar and meteoritic materials is obscured by several effects. First, current observations of D enrichment in the ISM have been made of only a few simple molecules, molecules that are not the main carriers of D in Solar System materials. Second, some of the interstellar D enrichment is likely to reside on labile moieties that will have exchanged to some degree with more isotopically normal material during incorporation into the warm protosolar nebula, parent body processing, delivery, recovery, and analysis. Third, ion-molecule reactions represent only one of at least four processes that can produce strong D-H fractionation in the ISM.

  20. Photochemical self-shielding as a source of non-mass-dependent isotope fractionation

    NASA Astrophysics Data System (ADS)

    Lyons, James; Stark, Glenn; Blackie, Doug; Pickering, Juliet; Heays, Alan

    2010-05-01

    Very large isotopic enrichments occur in the photolysis products of molecules that have line-type absorption spectra. Abundance-dependent line saturation, a process termed photochemical self-shielding, yields large non-mass-dependent (NMD) isotope effects, and has been proposed to have occurred in CO in the solar nebula (Clayton 2002) and SO2 in the early Earth atmosphere (Lyons 2007). The NMD signatures derived from photolysis of CO and SO2 are believed to be recorded in primitive meteorites inclusions (CAIs) and in Archean/Paleoproterozoic sulfur sediments, respectively. Comparison of theory and experiment can be used to distinguish self-shielding from other NMD processes. Recent low-resolution (~10 cm^-1) measurements of isotopic SO2 cross sections (Danielache et al. 2008) exhibit NMD effects when included in photoechemical models (Ueno et al. 2009), but not as a result of self-shielding. Higher resolution measurements (1-0.2 cm^-1) of isotopic cross sections are in progress at Imperial College. Inclusion of preliminary 1 cm^-1 resolution cross sections in a photochemical model for Earth's early atmosphere clearly demonstrates that isotopic self-shielding is present, yielding d33S>0 and d34S>0 in photoproduct SO. However, uncertainties in the measured cross sections also introduce NMD signatures. We are presently working to remove these uncertainties. Recent experiments on CO photodissociation at wavelengths ~91-108 nm show very large NMD effects in oxygen (Chakraborty et al. 2008). Because the measured NMD signatures are wavelength dependent, and differ in delta-values (i.e., d17O/d18O not equal unity), Chakraborty et al. claim that their experiments rule out CO self-shielding as the mechanism for the meteorite CAI slope-1 line. Here we show via model simulation of the experiments that the non-unity d17O/d18O values result primarily from self-shielding effects in both C16O and C18O. Also, model results indicate that the non-unity d17O/d18O values only arise for

  1. EVIDENCE FOR MULTIPLE PATHWAYS TO DEUTERIUM ENHANCEMENTS IN PROTOPLANETARY DISKS

    SciTech Connect

    Oeberg, Karin I.; Qi, Chunhua; Wilner, David J.; Hogerheijde, Michiel R.

    2012-04-20

    The distributions of deuterated molecules in protoplanetary disks are expected to depend on the molecular formation pathways. We use observations of spatially resolved DCN emission from the disk around TW Hya, acquired during ALMA science verification with a {approx}3'' synthesized beam, together with comparable DCO{sup +} observations from the Submillimeter Array, to investigate differences in the radial distributions of these species and hence differences in their formation chemistry. In contrast to DCO{sup +}, which shows an increasing column density with radius, DCN is better fit by a model that is centrally peaked. We infer that DCN forms at a smaller radii and thus at higher temperatures than DCO{sup +}. This is consistent with chemical network model predictions of DCO{sup +} formation from H{sub 2}D{sup +} at T < 30 K and DCN formation from additional pathways involving CH{sub 2}D{sup +} at higher temperatures. We estimate a DCN/HCN abundance ratio of {approx}0.017, similar to the DCO{sup +}/HCO{sup +} abundance ratio. Deuterium fractionation appears to be efficient at a range of temperatures in this protoplanetary disk. These results suggest caution in interpreting the range of deuterium fractions observed in solar system bodies, as multiple formation pathways should be taken into account.

  2. Fractional photo-current dependence of graphene quantum dots prepared from carbon nanotubes.

    PubMed

    Kundu, Sumana; Ghosh, Sujoy; Fralaide, Michael; Narayanan, T N; Pillai, Vijayamohanan K; Talapatra, Saikat

    2015-10-14

    We report on the photo-conductivity studies of chemically synthesized graphene quantum dots (GQDs) of average size 12 nm obtained by the oxidative acid treatment of MWCNTs. The dependence of photocurrent Iph (Iph = Iill - Idark) on the laser intensity P under a wide range of laser intensities (5 mW ≤ P ≤ 60 mW) shows a fractional power dependence of Iph on light intensity. The temperature dependence (300 K < T < 50 K) of Iph observed in thin films of these GQDs indicates that in the higher temperature region (T > ∼100 K), as the temperature increases, the number of thermally generated carriers increase resulting in increased Iph. At sufficiently low temperatures (T ≤ 100 K), a constant Iph is observed, indicating a constant photo-carrier density. Such a behavior is typically observed in many photoactive disordered semiconductors, which are often used in a variety of applications. We believe that the investigations presented here will enhance our understanding of the photocurrent generation phenomenon in chemically obtained GQDs. PMID:26351706

  3. Mass-Dependent and -Independent Fractionation of Mercury Isotopes in Aquatic Systems

    NASA Astrophysics Data System (ADS)

    Bergquist, B. A.; Joel, B. D.; Jude, D. J.

    2008-12-01

    Mercury is a globally distributed and highly toxic pollutant. Although Hg is a proven health risk, much of the natural cycle of Hg is not well understood and new approaches are needed to track Hg and the chemical transformations it undergoes in the environment. Recently, we demonstrated that Hg isotopes exhibit two types of isotope fractionation: (1) mass dependent fractionation (MDF) and (2) mass independent fractionation (MIF) of only the odd isotopes (Bergquist and Blum, 2007). The observation of large MIF of Hg isotopes (up to 5 permil) is exciting because only a few other isotopic systems have been documented to display large MIF, the most notable of which are oxygen and sulfur. In both cases, the application of MIF has proven very useful in a variety of fields including cosmochemistry, paleoclimatology, physical chemistry, atmospheric chemistry, and biogeochemistry. Both MDF and MIF isotopic signatures are observed in natural samples, and together they open the door to a new method for tracing Hg pollution and for investigating Hg behavior in the environment. For example, fish record MDF that appears to be related to size and age. Additionally, fish display MIF signatures that are consistent with the photo-reduction of methylmercury (Bergquist and Blum, 2007). If the MDF and MIF in ecosystems can be understood, the signatures in fish could inform us about the sources and processes transforming Hg and why there are differences in the bioaccumulation of Hg in differing ecosystems and populations of fish. This requires sampling of a variety of ecosystems, the sampling of many components of the ecosystems, and the use of other tracers such as carbon and nitrogen isotopes. We have expanded our studies of aquatic ecosystems to include several lakes in North America. Similar to other isotopic systems used to study food web dynamics and structure (i.e., C and N), the MDF of Hg in fish appears to be related to size and age. The MDF recorded in fish likely reflects

  4. The Deuterium Chemistry of the Early Universe

    SciTech Connect

    Stancil, P.C.; Lepp, S.; Dalgarno, A.

    1998-12-01

    The chemistry of deuterium, as well as that of hydrogen and helium, in the postrecombination era of the expanding early universe is presented. A thorough survey of all potentially important gas-phase reactions involving the primordial elements produced in the Big Bang, with a particular emphasis on deuterium, is given. The reaction set, consisting of 144 processes, is used in a nonequilibrium chemistry model to follow the production of primordial molecules in the postrecombination era. It is found that significant deuterium fractionation occurs for HD{sup +}, HD, and H{sub 2}D{sup +}, while the abundance of D{sup +} is reduced compared to the proton abundance. Even with the enhanced fractionation of H{sub 2}D{sup +}, its abundance is predicted to be too small to cause any interesting cosmological consequences, such as possible attenuation of spatial anisotropies in the cosmic background radiation field, detections of the epochs of reionization and reheating, or constraints on the primordial deuterium abundance. HD, being the second most abundant primordial molecule after H{sub 2}, may play a role in subsequent structure formation because of its cooling radiation. {copyright} {ital {copyright} 1998.} {ital The American Astronomical Society}

  5. Blister formation and deuterium retention on tungsten exposed to low energy and high flux deuterium plasma

    NASA Astrophysics Data System (ADS)

    Tokunaga, K.; Baldwin, M. J.; Doerner, R. P.; Noda, N.; Kubota, Y.; Yoshida, N.; Sogabe, T.; Kato, T.; Schedler, B.

    2005-03-01

    Deuterium ion irradiation on tungsten has been carried out with incident energies of 100 eV and flux of 1 × 10 22 D + m -2 s -1 at a temperature in range between 333 K and 1130 K up to a dose of 1 × 10 26 D + m -2. Three kinds of tungsten used are pure tungsten made by powder metallurgy tungsten (PM-W), vacuum plasma spray tungsten (VPS-W) and single crystal tungsten (SC-W). Surface morphology before and after the irradiation is observed with an SEM. In addition, retention property of deuterium after the irradiation is also examined with a TDS. Behavior of blister formation depends on the kind of the samples and the irradiation temperatures. TDS measurement also shows that deuterium is not retained in sample, which the blisters are not formed. The behavior of the blister formation and deuterium retention is influenced by the manufacturing process and the sample history of tungsten.

  6. Tritium catalyzed deuterium tokamaks

    SciTech Connect

    Greenspan, E.; Miley, G.H.; Jung, J.; Gilligan, J.

    1984-04-01

    A preliminary assessment of the promise of the Tritium Catalyzed Deuterium (TCD) tokamak power reactors relative to that of deuterium-tritium (D-T) and catalyzed deuterium (Cat-D) tokamaks is undertaken. The TCD mode of operation is arrived at by converting the /sup 3/He from the D(D,n)/sup 3/He reaction into tritium, by neutron capture in the blanket; the tritium thus produced is fed into the plasma. There are three main parts to the assessment: blanket study, reactor design and economic analysis and an assessment of the prospects for improvements in the performance of TCD reactors (and in the promise of the TCD mode of operation, in general).

  7. Distinction of tris(diimine)ruthenium(II) enantiomers chiral by virtue of helical chirality: temperature-dependent deuterium NMR spectroscopy in partially oriented phases.

    PubMed

    Szalontai, Gábor; Kovács, Margit

    2006-11-01

    2H NMR spectra of perdeuterated tris(diimine)ruthenium(II) complexes have been recorded in lyotropic liquid crystalline phase formed by the chiral polypeptide, poly-gamma-benzyl-L-glutamate (PBLG) and co-solvents. It is demonstrated that the left- and right-rotation isomers of these octahedral metal complexes with D3 symmetry can be distinguished. The effects of temperature and ligand size on spectral resolution were also studied. Although in the case of free bipyridine ligands excellent optical resolution could be obtained at room temperature in the complexes studied, the increase in ligand size has a detrimental effect on the resolution. This can be compensated to some extent by elevating the sample temperature and decreasing the deuterium relaxation rates, but the available temperature range and therefore the applicability of the technique are limited. PMID:16958156

  8. Diffusion in heterogeneous media: An iterative scheme for finding approximate solutions to fractional differential equations with time-dependent coefficients

    NASA Astrophysics Data System (ADS)

    Bologna, Mauro; Svenkeson, Adam; West, Bruce J.; Grigolini, Paolo

    2015-07-01

    Diffusion processes in heterogeneous media, and biological systems in particular, are riddled with the difficult theoretical issue of whether the true origin of anomalous behavior is renewal or memory, or a special combination of the two. Accounting for the possible mixture of renewal and memory sources of subdiffusion is challenging from a computational point of view as well. This problem is exacerbated by the limited number of techniques available for solving fractional diffusion equations with time-dependent coefficients. We propose an iterative scheme for solving fractional differential equations with time-dependent coefficients that is based on a parametric expansion in the fractional index. We demonstrate how this method can be used to predict the long-time behavior of nonautonomous fractional differential equations by studying the anomalous diffusion process arising from a mixture of renewal and memory sources.

  9. Analytical solutions to the fractional advection-diffusion equation with time-dependent pulses on the boundary

    NASA Astrophysics Data System (ADS)

    Rubbab, Qammar; Mirza, Itrat Abbas; Qureshi, M. Zubair Akbar

    2016-07-01

    The time-fractional advection-diffusion equation with Caputo-Fabrizio fractional derivatives (fractional derivatives without singular kernel) is considered under the time-dependent emissions on the boundary and the first order chemical reaction. The non-dimensional problem is formulated by using suitable dimensionless variables and the fundamental solutions to the Dirichlet problem for the fractional advection-diffusion equation are determined using the integral transforms technique. The fundamental solutions for the ordinary advection-diffusion equation, fractional and ordinary diffusion equation are obtained as limiting cases of the previous model. Using Duhamel's principle, the analytical solutions to the Dirichlet problem with time-dependent boundary pulses have been obtained. The influence of the fractional parameter and of the drift parameter on the solute concentration in various spatial positions was analyzed by numerical calculations. It is found that the variation of the fractional parameter has a significant effect on the solute concentration, namely, the memory effects lead to the retardation of the mass transport.

  10. An update on the Thermal Gradient Induced Non -Mass-Dependent Isotope Fractionation

    NASA Astrophysics Data System (ADS)

    Sun, T.; Niles, P. B.; Bao, H.; Socki, R. A.

    2012-12-01

    Mass flow and compositional gradient (elemental and isotope separation) occur when fluid(s) or gas(es) in an enclosure is subjected to a thermal gradient, and the phenomenon is named thermal diffusion. Gas phase thermal diffusion has been experimentally and theoretically investigated for more than a century, although there has not been a satisfactory theory to date. Nevertheless, theories predict that when dealing with a multi-isotope system, such as O16-O17-O18, S32-S33-S34-S36, or Ne20-Ne21-Ne22, the mass difference is the only term in the thermal diffusion separation factors that distinguish one isotope pair from another. Thus a mass dependent relationship is expected. For O-bearing molecules the α17O/ α 18O is expected to be at 0.5 to 0.515, and for S-bearing molecules the α33S/ α 34S at 0.5 to 0.508, where α is isotope fractionation factor between cold and warm reservoirs. We recently reported that thermal diffusion generates non-mass dependent (NMD) isotope fractionation for low-pressure O2 and SF6 gases. The observed NMD phenomenon in the simple thermal-diffusion experiments demands quantitative validation and theoretical explanation. It was suggested that additional (not mass related) terms need to be theoretically considered in the order to account for the observations. In addition to the pressure and temperature dependency illustrated in our earlier report, the role of turbulence, batch gas effects, and whether it is only a transient, non-equilibrium effect have been examined in this study. We report here new results on low-pressure O2 gas thermal diffusion. (1) In a purely diffusive vertical two-bulb setting with colder reservoir at lower position, time course experiments showed that the NMD effect persists after the system reaches isotopic steady state between warmer and colder compartments, suggesting that the effect is not a transient one. (2) When the average temperature approaching condensation point for O2, the 17O switches to migrating

  11. Nucleation and growth of micellar polycrystals under time-dependent volume fraction conditions

    NASA Astrophysics Data System (ADS)

    Louhichi, Ameur; Tamborini, Elisa; Ghofraniha, Neda; Caton, François; Roux, Denis; Oberdisse, Julian; Cipelletti, Luca; Ramos, Laurence

    2013-03-01

    We study the freezing kinetics of colloidal polycrystals made of micelles of Pluronic F108, a thermosensitive copolymer, to which a small amount of silica nanoparticles of a size comparable to that of the micelles are added. We use rheology and calorimetry to measure Tc, the crystallization temperature, and find that Tc increases with the heating rate Ṫ used to crystallize the sample. To rationalize our results, we first use viscosity measurements to establish a linear mapping between temperature T and the effective volume fraction, φ, of the micelles, treated as hard spheres. Next, we reproduce the experimental Ṫ dependence of the crystallization temperature with numerical calculations based on standard models for the nucleation and growth of hard-sphere crystals, classical nucleation theory and the Johnson-Mehl-Avrami-Kolmogorov theory. The models have been adapted to account for the peculiarities of our experiments: the presence of nanoparticles that are expelled in the grain boundaries and the steady increase of T and, hence, φ during the experiment. We moreover show that the polycrystal grain size obtained from the calculations is in good agreement with light microscopy data. Finally, we find that the φ dependence of the nucleation rate for the micellar polycrystal is in remarkable quantitative agreement with that found in previous experiments on colloidal hard spheres. These results suggests that deep analogies exist between hard-sphere colloidal crystals and Pluronics micellar crystals, in spite of the difference in particle softness. More generally, our results demonstrate that crystallization processes can be quantitatively probed using standard rheometry.

  12. Time-dependence of sea-ice concentration and multiyear ice fraction in the Arctic Basin

    USGS Publications Warehouse

    Gloersen, P.; Zwally, H.J.; Chang, A.T.C.; Hall, D.K.; Campbell, W.J.; Ramseier, R.O.

    1978-01-01

    The time variation of the sea-ice concentration and multiyear ice fraction within the pack ice in the Arctic Basin is examined, using microwave images of sea ice recently acquired by the Nimbus-5 spacecraft and the NASA CV-990 airborne laboratory. The images used for these studies were constructed from data acquired from the Electrically Scanned Microwave Radiometer (ESMR) which records radiation from earth and its atmosphere at a wavelength of 1.55 cm. Data are analyzed for four seasons during 1973-1975 to illustrate some basic differences in the properties of the sea ice during those times. Spacecraft data are compared with corresponding NASA CV-990 airborne laboratory data obtained over wide areas in the Arctic Basin during the Main Arctic Ice Dynamics Joint Experiment (1975) to illustrate the applicability of passive-microwave remote sensing for monitoring the time dependence of sea-ice concentration (divergence). These observations indicate significant variations in the sea-ice concentration in the spring, late fall and early winter. In addition, deep in the interior of the Arctic polar sea-ice pack, heretofore unobserved large areas, several hundred kilometers in extent, of sea-ice concentrations as low as 50% are indicated. ?? 1978 D. Reidel Publishing Company.

  13. Integration by parts and Pohozaev identities for space-dependent fractional-order operators

    NASA Astrophysics Data System (ADS)

    Grubb, Gerd

    2016-08-01

    Consider a classical elliptic pseudodifferential operator P on Rn of order 2a (0 < a < 1) with even symbol. For example, P = A(x , D)a where A (x , D) is a second-order strongly elliptic differential operator; the fractional Laplacian (- Δ)a is a particular case. For solutions u of the Dirichlet problem on a bounded smooth subset Ω ⊂Rn, we show an integration-by-parts formula with a boundary integral involving (d-a u)|∂Ω, where d (x) = dist (x , ∂ Ω). This extends recent results of Ros-Oton, Serra and Valdinoci, to operators that are x-dependent, nonsymmetric, and have lower-order parts. We also generalize their formula of Pohozaev-type, that can be used to prove unique continuation properties, and nonexistence of nontrivial solutions of semilinear problems. An illustration is given with P =(- Δ +m2)a. The basic step in our analysis is a factorization of P, P ∼P-P+, where we set up a calculus for the generalized pseudodifferential operators P± that come out of the construction.

  14. Development of a time-dependent incompressible Navier-Stokes solver based on a fractional-step method

    NASA Technical Reports Server (NTRS)

    Rosenfeld, Moshe

    1990-01-01

    The development, validation and application of a fractional step solution method of the time-dependent incompressible Navier-Stokes equations in generalized coordinate systems are discussed. A solution method that combines a finite-volume discretization with a novel choice of the dependent variables and a fractional step splitting to obtain accurate solutions in arbitrary geometries was previously developed for fixed-grids. In the present research effort, this solution method is extended to include more general situations, including cases with moving grids. The numerical techniques are enhanced to gain efficiency and generality.

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-03-01

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

  17. Fractionation of humic acids according to their hydrophobicity, size, and charge-dependent mobility by the salting-out method

    NASA Astrophysics Data System (ADS)

    Zavarzina, A. G.; Vanifatova, N. G.; Stepanov, A. A.

    2008-12-01

    Humic acids (HAs) represent heterogeneous and polydisperse mixture of molecules that differ in their chemical structure, composition, and functional properties. Fractionation of HAs is of key importance for understanding their interactions with various organic and inorganic compounds, for studying their physiological activity, and for predicting their behavior in natural environments and agroecosystems. Existing fractionation methods are rather laborious and time consuming, which limits their application in fundamental science and industry. It is shown that fractionation of humic acids with ammonium sulfate ensures their preparative separation with respect to (a) hydrophobicity, (b) molecular size, and (c) charge dependent on the amount of functional groups. Salting out at the lowest and highest degrees of saturation with ammonium sulfate, upon which precipitation of the molecules occurs, makes it possible to separate humic acids into functionally different high-molecular-weight/hydrophobic and low-molecular-weight/hydrophilic fractions. The first fraction is characterized by a lower electrophoretic mobility than the second fraction. The weight percentage of the components coagulated at the lowest degree of salt saturation can be used as a quantitative parameter for comparing hydrophobic properties of humic acids. Salting out is recommended as a fast, simple, and cheap alternative to chromatographic methods for preparative separation of humic acids if large amounts of functionally different fractions need to be obtained.

  18. Deuterium trapping in tungsten

    NASA Astrophysics Data System (ADS)

    Poon, Michael

    Tungsten is one of the primary material candidates being investigated for use in the first-wall of a magnetic confinement fusion reactor. An ion accelerator was used to simulate the type of ion interaction that may occur at a plasma-facing material. Thermal desorption spectroscopy (TDS) was the primary tool used to analyze the effects of the irradiation. Secondary ion mass spectroscopy (SIMS) was used to determine the distribution of trapped D in the tungsten specimen. The tritium migration analysis program (TMAP) was used to simulate thermal desorption profiles from the D depth distributions. Fitting of the simulated thermal desorption profiles with the measured TDS results provided values of the D trap energies. Deuterium trapping in single crystal tungsten was studied as a function of the incident ion fluence, ion flux, irradiation temperature, irradiation history, and surface impurity levels during irradiation. The results show that deuterium was trapped at vacancies and voids. Two deuterium atoms could be trapped at a tungsten vacancy, with trapping energies of 1.4 eV and 1.2 eV for the first and second D atoms, respectively. In a tungsten void, D is trapped as atoms adsorbed on the inner walls of the void with a trap energy of 2.1 eV, or as D2 molecules inside the void with a trap energy of 1.2 eV. Deuterium trapping in polycrystalline tungsten was also studied as a function of the incident fluence, irradiation temperature, and irradiation history. Deuterium trapping in polycrystalline tungsten also occurs primarily at vacancies and voids with the same trap energies as in single crystal tungsten; however, the presence of grain boundaries promotes the formation of large surface blisters with high fluence irradiations at 500 K. In general, D trapping is greater in polycrystalline tungsten than in single crystal tungsten. To simulate mixed materials comprising of carbon (C) and tungsten, tungsten specimens were pre-irradiated with carbon ions prior to D

  19. Photo-induced isotopic fractionation

    NASA Astrophysics Data System (ADS)

    Miller, Charles E.; Yung, Yuk L.

    2000-12-01

    This paper presents a systematic method for the analysis of photo-induced isotopic fractionation. The physical basis for this fractionation mechanism centers on the fact that isotopic substitution alters the energy levels, molecular symmetries, spin statistical weights and other fundamental molecular properties, producing spectroscopic signatures distinguishable from that of the parent isotopomer. These mass-dependent physical properties are identical to those invoked by Urey to explain stable isotope fractionation in chemical systems subject to thermodynamic equilibrium. Photo-induced isotopic fractionation is a completely general phenomenon and should be observable in virtually all gas phase photochemical systems. Water photo-induced isotopic fractionation has been examined in detail using experimental and theoretical data. These results illustrate the salient features of this fractionation mechanism for molecules possessing continuous UV absorption spectra and unit photodissociation quantum yields. Using the photo-induced isotopic fractionation methodology in conjunction with standard photochemical models, we predict substantial deuterium enrichment of water vapor in the planetary atmospheres of Earth and Mars.

  20. Injection of deuterium pellets

    SciTech Connect

    Sorensen, H.; Andersen, P.; Andersen, S.A.; Andersen, V.; Nordskov-Nielsen, A.; Sass, B.; Weisberg, K.V.

    1984-09-01

    A discussion is given of the work done at Riso National Laboratory on the design and construction of deuterium pellet injectors. A pellet injection system made for the TFR tokamak at Fontenay-aux-Roses, Paris is described. 0.12-mg pellets are injected with velocities of around 600-700 m/s through a 5-m long guide tube. Next some of the details of a new light gas gun are given; with this gun, hydrogen pellets are accelerated to velocities above 1400 m/s, deuterium pellets to velocities above 1300 m/s and neon pellets to velocities above 550 m/s. Finally, a new acceleration method where a pellet should be accelerated by means of a magnetically stabilised electrical discharge is discussed, and a set up for measuring of the pellet size by means of a microwave cavity is outlined.

  1. Kaon Electroproduction on Deuterium

    SciTech Connect

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

    1998-08-01

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

  2. Coil fraction-dependent phase behaviour of a model globular protein-polymer diblock copolymer.

    PubMed

    Thomas, Carla S; Olsen, Bradley D

    2014-05-01

    The self-assembly of the model globular protein-polymer block copolymer mCherry-b-poly(N-isopropyl acrylamide) is explored across a range of polymer coil fractions from 0.21 to 0.82 to produce a phase diagram for these materials as a function of molecular composition. Overall, four types of morphologies were observed: hexagonally packed cylinders, perforated lamellae, lamellae, and disordered nanostructures. Across all coil fractions and morphologies, a lyotropic re-entrant order-disorder transition in water was observed, with disordered structures below 30 wt% and above 70 wt% and well-ordered morphologies at intermediate concentrations. Solid state samples prepared by solvent evaporation show moderately ordered structures similar to those observed in 60 wt% solutions, suggesting that bulk structures result from kinetic trapping of morphologies which appear at lower concentrations. While highly ordered cylindrical nanostructures are observed around a bioconjugate polymer volume fraction of 0.3 and well-ordered lamellae are seen near a volume fraction of 0.6, materials at lower or higher coil fractions become increasingly disordered. Notable differences between the phase behaviour of globular protein-polymer block copolymers and coil-coil diblock copolymers include the lack of spherical nanostructures at either high or low polymer coil fractions as well as shifted phase boundaries between morphologies which result in an asymmetric phase diagram. PMID:24695642

  3. Coil fraction-dependent phase behaviour of a model globular protein–polymer diblock copolymer

    SciTech Connect

    Thomas, Carla S.; Olsen, Bradley D.

    2014-01-01

    The self-assembly of the model globular protein–polymer block copolymer mCherry-b-poly(N-isopropyl acrylamide) is explored across a range of polymer coil fractions from 0.21 to 0.82 to produce a phase diagram for these materials as a function of molecular composition. Overall, four types of morphologies were observed: hexagonally packed cylinders, perforated lamellae, lamellae, and disordered nanostructures. Across all coil fractions and morphologies, a lyotropic re-entrant order–disorder transition in water was observed, with disordered structures below 30 wt% and above 70 wt% and well-ordered morphologies at intermediate concentrations. Solid state samples prepared by solvent evaporation show moderately ordered structures similar to those observed in 60 wt% solutions, suggesting that bulk structures result from kinetic trapping of morphologies which appear at lower concentrations. While highly ordered cylindrical nanostructures are observed around a bioconjugate polymer volume fraction of 0.3 and well-ordered lamellae are seen near a volume fraction of 0.6, materials at lower or higher coil fractions become increasingly disordered. Notable differences between the phase behaviour of globular protein–polymer block copolymers and coil–coil diblock copolymers include the lack of spherical nanostructures at either high or low polymer coil fractions as well as shifted phase boundaries between morphologies which result in an asymmetric phase diagram.

  4. A molecular dynamic model for analyzing concentrations of electrolytes: Fractional molar dependences of microstructure properties

    NASA Astrophysics Data System (ADS)

    Khalansky, D.; Popova, E.; Gladyshev, P.; Dushanov, E.; Kholmurodov, Kh.

    2014-12-01

    Aqueous electrolyte solutions play an important role in many electrophysical and chemical processes in aerospace technology and industrial applications. As noncovalent interactions, the interactions between ions are crucially important for biomolecular structures as well (protein structure folding, molecular level processes followed by ionic pair correlations, the formation of flexible hydrate shells, and so on). Specifically, ions (cations and anions with the same valence charges) can form stable pairs if their sizes match. The formation of ionic pairs can substantially affect the thermodynamic stabilities of proteins in the alkali salts physiologically present in the human body. Research aims and problems impose severe demands on readjustments of the ionic force fields and potential parameters developed to describe aqueous solutions and electrolytic systems. Ionic solutions and their interaction with biomolecules have been observed for over 100 years [1], but the behavior of such solutions remains poorly studied today. New data obtained in this work deals with parameterization strategies and adjustments for the ionic force fields of the alkali cations and halide anions that should be helpful in biomolecular research. Using molecular dynamics (MD) models, four electrolytic systems (HCl-H2O, LiCl-H2O, NaCl-H2O, and KCl-H2O) are investigated as binary mixtures of water and cations and anions, respectively. The intermolecular interaction parameters are varied for two of the four model electrolytes (HCl-H2O and NaCl-H2O) to simulate the possibility of different ionic shells forming during interaction with water. It is found that varying the potential parameters strongly affects the dynamic and structural characteristics of electrolyte systems. MD simulations are performed in the temperature range of 300 to 600 K with a step of 50 K. MD simulations for all electrolyte models (HCl-H2O, LiCl-H2O, NaCl-H2O, KCl-H2O) are also conducted for different molar fractions of

  5. Dynamics of deuterium implanted in boron coating film for wall conditioning

    NASA Astrophysics Data System (ADS)

    Nakahata, Toshihiko; Yoshikawa, Akira; Oyaidzu, Makoto; Oya, Yasuhisa; Ishimoto, Yuki; Kizu, Kaname; Yagyu, Jyunichi; Ashikawa, Naoko; Nishimura, Kiyohiko; Miya, Naoyuki; Okuno, Kenji

    2007-08-01

    Retention and desorption behavior of deuterium implanted into pure boron films has been studied by means of the secondary ion mass spectroscopy. It was found that the process controlling deuterium desorption depended on the temperature. At stage 1, below 573 K, the desorption of deuterium from B-D-B bonds dominated and its diffusion was the rate-determining process. Above 573 K, deuterium was mainly desorbed from B-D bonds, and recombination was the rate-determining process. The effective molecular recombination rate constant of deuterium bound to boron associated with B-D bond was determined by an isothermal annealing experiment.

  6. Effects of deuterium oxide on cell growth and vesicle speed in RBL-2H3 cells

    PubMed Central

    Triplett, Ashley R.

    2014-01-01

    For the first time we show the effects of deuterium oxide on cell growth and vesicle transport in rat basophilic leukemia (RBL-2H3) cells. RBL-2H3 cells cultured with 15 moles/L deuterium showed decreased cell growth which was attributed to cells not doubling their DNA content. Experimental observations also showed an increase in vesicle speed for cells cultured in deuterium oxide. This increase in vesicle speed was not observed in deuterium oxide cultures treated with a microtubule-destabilizing drug, suggesting that deuterium oxide affects microtubule-dependent vesicle transport. PMID:25237603

  7. Lamb shift in muonic deuterium

    SciTech Connect

    Gorchtein, Mikhail; Vanderhaeghen, Marc; Carlson, Carl E.

    2013-11-07

    We consider the two-photon exchange contribution to the 2P-2S Lamb shift in muonic deuterium in the framework of forward dispersion relations. The dispersion integrals are evaluated with minimal model dependence using experimental data on elastic deuteron form factors and inelastic electron-deuteron scattering, both in the quasielastic and hadronic range. The subtraction constant that is required to ensure convergence of the dispersion relation for the forward Compton amplitude T{sub 1} (ν,Q{sup 2}) is related to the deuteron magnetic polarizability β(Q{sup 2}) and represents the main source of uncertainty in our analysis. We obtain for the Lamb shift ΔE{sub 2P-2S} = 1.620±0.190 meV and discuss ways to further reduce this uncertainty.

  8. Mass Dependence of Iron Isotope Fractionation in Fe(II)-Fe(III) Electron Exchange Equilibration

    NASA Astrophysics Data System (ADS)

    Fujii, Yasuhiko; Kim, Sang-Ho; Nomura, Masao; Kawakami, Fumiaki

    2013-02-01

    A one hundred meter long ion-exchange chromatograph was used to establish rigorously the mass effects in the iron isotope fractionation in the Fe(II)-Fe(III) electron exchange equilibration.We used a highly porous, strongly basic anion exchange resin packed in glass columns. The abundance ratios of all natural iron isotopes, 54Fe, 56Fe, 57Fe, and 58Fe, in the effluent at the iron adsorption band boundary were measured with a mass spectrometer. The enrichment correlations among these isotopes were analyzed by three-isotope plots. The results clearly showed that the isotope fractionation of Fe(II)-Fe(III) is governed by the normal mass effect; the iron isotope fractionation is not proportional to the nuclear size, but proportional to the reduced mass difference of the pair of iron isotopes.

  9. Hydrogen and deuterium diffusion in vanadium-titanium alloys

    NASA Astrophysics Data System (ADS)

    Peterson, D. T.; Herro, H. M.

    1987-02-01

    Hydrogen and deuterium diffusion coefficients were measured in vanadium-titanium alloys, containing up to 30 at. pct Ti, by Boltzmann-Matano techniques. Hydrogen and deuterium diffusivity decreased rapidly with titanium concentration. The diffusion coefficients showed an Arrhenius temperature dependence in each alloy between 230 and 473 K with activation energies that increased with titanium concentration. The diffusion coefficient decreased linearly with hydrogen concentration in all alloys. The terminal solid solubilities increased markedly with titanium concentration with deuterium showing a larger terminal solid solubility than hydrogen below ten percent titanium. The diffusion results do not fit a localized deep trapping of hydrogen by the titanium atoms.

  10. Measurement of gluconeogenesis using glucose fragments and mass spectrometry after ingestion of deuterium oxide.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We report a new method to measure the fraction of glucose derived from gluconeogenesis using gas chromatography-mass spectrometry and positive chemical ionization. After ingestion of deuterium oxide by subjects, glucose derived from gluconeogenesis is labeled with deuterium. Our calculations of gluc...

  11. More than just halo mass: modelling how the red galaxy fraction depends on multiscale density in an HOD framework

    NASA Astrophysics Data System (ADS)

    Phleps, S.; Wilman, D. J.; Zibetti, S.; Budavári, T.

    2014-03-01

    The fraction of galaxies with red colours depends sensitively on environment, and on the way in which environment is measured. To distinguish competing theories for the quenching of star formation, a robust and complete description of environment is required, to be applied to a large sample of galaxies. The environment of galaxies can be described using the density field of neighbours on multiple scales - the multiscale density field. We are using the Millennium simulation and a simple halo occupation distribution (HOD) prescription which describes the multiscale density field of Sloan Digital Sky Survey DR7 galaxies to investigate the dependence of the fraction of red galaxies on the environment. Using a volume-limited sample, where we have sufficient galaxies in narrow density bins, we have more dynamic range in halo mass and density for satellite galaxies than for central galaxies. Therefore, we model the red fraction of central galaxies as a constant while we use a functional form to describe the red fraction of satellites as a function of halo mass which allows us to distinguish a sharp from a gradual transition. While it is clear that the data can only be explained by a gradual transition, an analysis of the multiscale density field on different scales suggests that colour segregation within the haloes is needed to explain the results. We also rule out a sharp transition for central galaxies, within the halo mass range sampled.

  12. Trapping deuterium atoms

    SciTech Connect

    Wiederkehr, A. W.; Hogan, S. D.; Lambillotte, B.; Andrist, M.; Schmutz, H.; Agner, J.; Salathe, Y.; Merkt, F.

    2010-02-15

    Cold deuterium atoms in a supersonic beam have been decelerated from an initial velocity of 475 m/s to zero velocity in the laboratory frame using a 24-stage Zeeman decelerator. The atoms have been loaded in a magnetic quadrupole trap at a temperature of {approx}100 mK and an initial density of {approx}10{sup 6} cm{sup -3}. Efficient deceleration was achieved by pulsing the magnetic fields in the decelerator solenoids using irregular sequences of phase angles. Trap loading was optimized by monitoring and suppressing the observed reflection of the atoms by the field gradient of the back solenoid of the trap.

  13. Dependence of the Broad Absorption Line Quasar Fraction on Radio Luminosity

    NASA Astrophysics Data System (ADS)

    Shankar, Francesco; Dai, Xinyu; Sivakoff, Gregory R.

    2008-11-01

    We find that the fraction of classical broad absorption line quasars (BALQSOs) among the FIRST radio sources in the Sloan Data Release 3, is 20.5+ 7.3-5.9% at the faintest radio powers detected (L1.4 GHz ~ 1032 erg s-1), and rapidly drops to lesssim8% at L1.4 GHz ~ 3 × 1033 erg s-1. Similarly, adopting the broader absorption index (AI) definition of Trump et al., we find the fraction of radio BALQSOs to be 44+ 8.1-7.8%, reducing to 23.1+ 7.3-6.1% at high luminosities. While the high fraction at low radio power is consistent with the recent near-IR estimates by Dai et al., the lower fraction at high radio powers is intriguing and confirms previous claims based on smaller samples. The trend is independent of the redshift range, the optical and radio flux selection limits, or the exact definition of a radio match. We also find that at fixed optical magnitude, the highest bins of radio luminosity are preferentially populated by non-BALQSOs, consistent with the overall trend. We do find, however, that those quasars identified as AI-BALQSOs but not under the classical definition do not show a significant drop in their fraction as a function of radio power, further supporting independent claims that these sources, characterized by lower equivalent width, may represent an independent class from the classical BALQSOs. We find the balnicity index, a measure of the absorption trough in BALQSOs, and the mean maximum wind velocity to be roughly constant at all radio powers. We discuss several plausible physical models which may explain the observed fast drop in the fraction of the classical BALQSOs with increasing radio power, although none is entirely satisfactory. A strictly evolutionary model for the BALQSO and radio emission phases requires a strong fine-tuning to work, while a simple geometric model, although still not capable of explaining polar BALQSOs and the paucity of FRII BALQSOs, is statistically successful in matching the data if part of the apparent radio

  14. The extent, time course, and fraction size dependence of mouse spinal cord recovery from radiation injury

    SciTech Connect

    Lavey, R.S.; Taylor, M.G.; Tward, J.D.

    1994-10-15

    This experiment was designed to assess: (a) the influence of fraction size and time interval between fractions on the tolerance of the spinal cord to high cumulative doses of radiation; and (b) the influence of the long-term recovery process on the tolerance of the spinal cord to reirradiation. The T10-L2 level of the spinal cord of C3Hf mice was irradiated using a conventionally fractionated regimen of 2.0 Gy once daily, a prolonged fractionated regimen of 1.2 Gy once daily, a hyperfractionated regimen of 1.2 Gy twice daily, or a single dose of 12 Gy followed 0-190 days later by a second dose of 5-20 Gy. Mice in the multifractionated regimen groups were given a single 15 Gy top-up- dose 24 h after reaching a cumulative fractionated dose of 24-70 Gy. Hind limb strength was measured weekly for 2 years after the completion of irradiation. Paralysis occurred in a bimodal time distribution, with peaks at 5-10 months and 15-23 months after the completion of irradiation. The cumulative radiation dose was directly associated with the incidence of paralysis in each radiation schedule (p<0.0001) and inversely associated with the time to onset of paralysis in the 1.2 Gy b.i.d. (p = 0.0001) and 2.0 Gy q.d. schedules (p = 0.03). The median latency of paralysis in each group was inversely associated with the incidence of paralysis in that group (p =<0.001). Decreasing the fraction size from 2.0 to 1.2 Gy once daily markedly increased the radiation tolerance of the spinal cord (p <0.0001), consistent with a very small alpha-beta value of -0.30 Gy ({approximately}95% confidence interval -0.72, +0.18) in the linear-quadratic model. Decreasing the time interval from 24 h to alternating 8 and 16 h periods produced an offsetting diminuation in cord tolerance (p <0.0001). 36 refs., 5 figs., 6 tabs.

  15. Temperature Dependence and Recoil-free Fraction Effects in Olivines Across the Mg-Fe Solid Solution

    NASA Technical Reports Server (NTRS)

    Sklute, E. C.; Rothstein, Y.; Dyar, M. D.; Schaefer, M. W.; Menzies, O. N.; Bland, P. A.; Berry, F. J.

    2005-01-01

    Olivine and pyroxene are the major ferromagnesian minerals in most meteorite types and in mafic igneous rocks that are dominant at the surface of the Earth. It is probable that they are the major mineralogical components at the surface of any planetary body that has undergone differentiation processes. In situ mineralogical studies of the rocks and soils on Mars suggest that olivine is a widespread mineral on that planet s surface (particularly at the Gusev site) and that it has been relatively unaffected by alteration. Thus an understanding of the characteristics of Mossbauer spectra of olivine is of great importance in interpreting MER results. However, variable temperature Mossbauer spectra of olivine, which are needed to quantify recoil-free fraction effects and to understand the temperature dependence of olivine spectra, are lacking in the literature. Thus, we present here a study of the temperature dependence and recoil-free fraction of a series of synthetic olivines.

  16. Dependence of the hybridization parameter on nitrogen molar fraction in nitrogen-containing GaPN solid solutions

    NASA Astrophysics Data System (ADS)

    Nikitina, E. V.; Sobolev, M. S.; Pirogov, E. V.; Egorov, A. Yu.

    2013-12-01

    Heterostructures with GaP1 - x N x layers synthesized by molecular beam epitaxy on GaP(001) substrates have been studied by photoluminescence and X-ray diffraction measurement. The results are compared to parameters calculated using the band anticrossing (BAC) model. Results of this comparative study lead to the conclusion that the hybridization parameter of GaP1 - x N x depends on the molar fraction of nitrogen in the solid solution.

  17. Time-Dependent Regional Myocardial Strains in Patients with Heart Failure with a Preserved Ejection Fraction

    PubMed Central

    Smith, Shane P.; Secomb, Timothy W.; Hong, Brian D.; Moulton, Michael J.

    2016-01-01

    Objectives. To better understand the etiology of HFpEF in a controlled human population, regional time-varying strains were computed using echocardiography speckle tracking in patients with heart failure with a preserved ejection fraction and normal subjects. Methods. Eleven normal volunteers and ten patients with echo-graded diastolic dysfunction and symptoms of heart failure were imaged with echocardiography and longitudinal, circumferential, and rotational strains were determined using speckle-tracking. Diastolic strain rate was also determined. Patient demographics and echo-derived flows, volumes, and pressures were recorded. Results. Peak longitudinal and circumferential strain was globally reduced in patients (p < 0.001), when compared to controls. The patients attained peak longitudinal and circumferential strain at a consistently later point in systole than controls. Rotational strains were not different in most LV regions. Early diastolic strain rate was significantly reduced in the patients (p < 0.001). LV mass and wall thickness were significantly increased in the patients; however ejection fraction was preserved and stroke volume was diminished (p < 0.001). Conclusions. This study shows that patients with HFpEF have reduced early diastolic strain rate and reduced peak strain that is regionally homogeneous and that they also utilize a longer fraction of systole to achieve peak axial strains. PMID:27042673

  18. Hydrogen and deuterium diffusion in vanadium alloys

    SciTech Connect

    Herro, H.M.

    1982-01-01

    Hydrogen and deuterium diffusion coefficients were measured between 473 and 230 K in alloys of vanadium containing titanium or niobium. Boltzmann-Matano techniques allowed the measurement of the hydrogen concentration dependence of the diffusion coefficient. In addition, one of these techniques permitted a determination of the terminal hydrogen solid solubility which was greatly increased by alloying. Both the hydrogen and deuterium diffusion coefficients were found to decrease with hydrogen isotope concentration in all alloys at all temperatures. The effect of niobium additions was to markedly reduce the rate of hydrogen migration to a minimum in the 75 at. pct. Nb alloy. The rate of hydrogen migration decreased with titanium concentration up to 30 at. pct. Ti, the highest concentration examined in that alloy system. The diffusion coefficients exhibited an Arrhenius temperature dependence and the resulting diffusion activation energy and D/sub o/ values both increased with titanium and with niobium concentration to a maximum of 75 at. pct. Nb. Deuterium diffusion activation energies were larger than corresponding hydrogen values in all alloys. The diffusion behavior found in these alloys is not well represented by current local deep trapping models.

  19. Reading skill-fractional anisotropy relationships in visuospatial tracts diverge depending on socioeconomic status.

    PubMed

    Gullick, Margaret M; Demir-Lira, Özlem Ece; Booth, James R

    2016-07-01

    Low socioeconomic status (SES) has been repeatedly linked with decreased academic achievement, including lower reading outcomes. Some lower SES children do show skills and scores commensurate with those of their higher SES peers, but whether their abilities stem from the same systems as high SES children or are based on divergent strategies is unknown. We here investigated a potential interactive relationship between SES and real-word reading skill in the white matter in 42 typically developing children. SES was determined based on parental education; reading skill and age were not significantly related to SES. There was a significant neural interaction: Clusters in the bilateral inferior longitudinal fasciculus (ILF), left superior longitudinal fasciculus, and left corticospinal tract demonstrated interactive skill-SES relationships in fractional anisotropy. Follow-up analyses demonstrated that higher SES children showed a positive relationship between fractional anisotropy, reflecting tract coherence, and reading skill in left hemisphere tract clusters, whereas lower SES children showed a positive relationship in the right hemisphere homologues. Broadly, the ILF has been demonstrated to support orthographic skill on the left and more general visuospatial processing on the right, so high reading achievement in lower SES children may rely on supplementary visuospatial processing more than for higher SES readers. This pattern is consistent with previous work reporting low SES children's environments to include less rich verbal experience, which may lead them to disproportionately draw on visuospatial skills for success. Further, these results indicate that group SES differences may be best described by an adaptive, not a deficit, model. PMID:27412229

  20. Empirical equations for the temperature dependence of calcite-water oxygen isotope fractionation from 10 to 70°C.

    PubMed

    Demény, Attila; Kele, Sándor; Siklósy, Zoltán

    2010-12-30

    Although the temperature dependence of calcite-water oxygen isotope fractionation seems to have been well established by numerous empirical, experimental and theoretical studies, it is still being discussed, especially due to the demand for increased accuracy of paleotemperature calculations. Experimentally determined equations are available and have been verified by theoretical calculations (considered as representative of isotopic equilibrium); however, many natural formations do not seem to follow these relationships implying either that existing fractionation equations should be revised, or that carbonate deposits are seriously affected by kinetic and solution chemistry effects, or late-stage alterations. In order to test if existing fractionation-temperature relationships can be used for natural deposits, we have studied calcite formations precipitated in various environments by means of stable isotope mass spectrometry: travertines (freshwater limestones) precipitating from hot and warm waters in open-air or quasi-closed environments, as well as cave deposits formed in closed systems. Physical and chemical parameters as well as oxygen isotope composition of water were monitored for all the investigated sites. Measuring precipitation temperatures along with oxygen isotope compositions of waters and calcites yielded empirical environment-specific fractionation-temperature equations: [1] 1000 · lnα = 17599/T - 29.64 [for travertines with a temperature range of 30 to 70°C] and [2] 1000 · lnα = 17500/T - 29.89 [for cave deposits for the range 10 to 25°C]. Finally, based on the comparison of literature data and our results, the use of distinct calcite-water oxygen isotopic fractionation relationships and application strategies to obtain the most reliable paleoclimate information are evaluated. PMID:21080503

  1. Isotope fractionation of water during evaporation without condensation.

    PubMed

    Cappa, Christopher D; Drisdell, Walter S; Smith, Jared D; Saykally, Richard J; Cohen, Ronald C

    2005-12-29

    The microscopic events engendering liquid water evaporation have received much attention over the last century, but remain incompletely understood. We present measurements of isotope fractionation occurring during free molecular evaporation from liquid microjets and show that the isotope ratios of evaporating molecules exhibit dramatic differences from equilibrium vapor values, strong variations with the solution deuterium mole fraction, and a clear temperature dependence. These results indicate the existence of an energetic barrier to evaporation and that the evaporation coefficient of water is less than unity. These new insights into water evaporation promise to advance our understanding of the processes that control the formation and lifetime of clouds in the atmosphere. PMID:16375440

  2. Deuterium inventory in Tore Supra: Coupled carbon-deuterium balance

    NASA Astrophysics Data System (ADS)

    Pégourié, B.; Panayotis, S.; Languille, P.; Martin, C.; Dittmar, T.; Gauthier, E.; Hatchressian, J.-C.; Pascal, J.-Y.; Roubin, P.; Ruffe, R.; Tsitrone, E.; Vartanian, S.; Wang, H.; Beauté, A.; Bouvet, J.; Brosset, C.; Bucalossi, J.; Cabié, M.; Caprin, E.; Courtois, X.; Dachicourt, R.; Delchambre, E.; Dominici, C.; Douai, D.; Ekedahl, A.; Gunn, J. P.; Hakola, A.; Jacob, W.; Khodja, H.; Likonen, J.; Linez, F.; Litnovsky, A.; Marandet, Y.; Markelj, S.; Martinez, A.; Mayer, M.; Meyer, O.; Monier-Garbet, P.; Moreau, P.; Negrier, V.; Oddon, P.; Pardanaud, C.; Pasquet, B.; Pelicon, P.; Petersson, P.; Philipps, V.; Possnert, G.; Reiter, D.; Roth, J.; Roure, I.; Rubel, M.; Saint-Laurent, F.; Samaille, F.; Vavpetič, P.

    2013-07-01

    This paper presents an analysis of the carbon-deuterium circulation and the resulting balance in Tore Supra over the period 2002-2007. Carbon balance combines the estimation of carbon gross erosion from spectroscopy, net erosion and deposition using confocal microscopy, lock-in thermography and SEM, and a measure of the amount of deposits collected in the vacuum chamber. Fuel retention is determined from post-mortem (PM) analyses and gas balance (GB) measurements. Special attention was paid to the deuterium outgassed during the nights and weekends of the experimental campaign (vessel under vacuum, Plasma Facing Components at 120 °C) and during vents (vessel at atmospheric pressure, PFCs at room temperature). It is shown that this outgassing is the main process reconciling the PM and GB estimations of fuel retention, closing the coupled carbon-deuterium balance. In particular, it explains why the deuterium concentration in deposits decreases with increasing depth.

  3. Deuterium-tritium experiments on TFTR

    NASA Astrophysics Data System (ADS)

    Bretz, N. L.; Adler, H.; Alling, P.; Ancher, C.; Anderson, H.; Anderson, J. W.; Arunasalam, V.; Ascione, G.; Barnes, C. W.; Barnes, G.; Batha, S.; Bateman, G.; Beer, M.; Bell, M. G.; Bell, R.; Bitter, M.; Blanchard, W.; Brunkhorst, C.; Budny, R.; Bush, C. E.; Camp, R.; Caorlin, M.; Carnevale, H.; Cauffman, S.; Chang, Z.; Cheng, C.; Chrzanowski, J.; Collins, J.; Coward, G.; Cropper, M.; Darrow, D. S.; Daugert, R.; DeLooper, J.; Dorland, W.; Dudek, L.; Duong, H.; Durst, R.; Efthimion, P. C.; Ernst, D.; Evensen, H.; Fisch, N.; Fisher, R.; Fonck, R. J.; Fredd, E.; Fredrickson, E.; Fromm, R.; Fu, G.; Fujita, T.; Furth, H. P.; Garzotto, V.; Gentile, C.; Gilbert, J.; Giola, J.; Gorelenkov, N.; Grek, B.; Grisham, L. R.; Hammett, G.; Hanson, G. R.; Hawryluk, R. J.; Heidbrink, W.; Herrmann, H. W.; Hill, K. W.; Hosea, J.; Hsuan, H.; Hughes, M.; Hulse, R.; Janos, A.; Jassby, D. L.; Jobes, F. C.; Johnson, D. W.; Johnson, L. C.; Kalish, M.; Kamperschroer, J.; Kesner, J.; Kugel, H.; Labik, G.; Lam, N. T.; LaMarche, P. H.; Lawson, E.; LeBlanc, B.; Levine, J.; Levinton, F. M.; Loesser, D.; Long, D.; Loughlin, M. J.; Machuzak, J.; Majeski, R.; Mansfield, D. K.; Marmar, E.; Marsala, R.; Martin, A.; Martin, G.; Mauel, M.; Mazzucato, E.; McCarthy, M. P.; McChesney, J.; McCormack, B.; McCune, D. C.; McGuire, K. M.; McKee, G.; Meade, D. M.; Medley, S. S.; Mikkelsen, D. R.; Mirnov, S. V.; Mueller, D.; Murakami, M.; Murphy, J. A.; Nagy, A.; Navratil, G. A.; Nazikian, R.; Newman, R.; Norris, M.; O'Connor, T.; Oldaker, M.; Ongena, J.; Osakabe, M.; Owens, D. K.; Park, H.; Park, W.; Parks, P.; Paul, S. F.; Pearson, G.; Perry, E.; Persing, R.; Petrov, M.; Phillips, C. K.; Phillips, M.; Pitcher, S.; Pysher, R.; Qualls, A. L.; Raftapoulos, S.; Ramakrishnan, S.; Ramsey, A.; Rasmunsen, D. A.; Redi, M. H.; Renda, G.; Rewoldt, G.; Roberts, D.; Rogers, J.; Rossmassler, R.; Roquemore, A. L.; Ruskov, E.; Sabbaugh, S. A.; Sasao, M.; Schilling, G.; Schivell, J.; Schmidt, G. L.; Scillia, R.; Scott, S. D.; Semenov, I.; Senko, T.; Sesnic, S.; Sissingh, R.; Skinner, C. H.; Snipes, J.; Stencel, J.; Stevens, J.; Stevenson, T.; Stodiek, W.; Strachan, J. D.; Stratton, B. C.; Swanson, J.; Synakowski, E.; Takahashi, H.; Tang, W.; Taylor, G.; Terry, J.; Thompson, M. E.; Tighe, W.; Timberlake, J. R.; Tobita, K.; Towner, H. H.; Tuszewski, M.; Von Halle, A.; Vannoy, C.; Viola, M.; Goeler, S. von; Voorhees, D.; Walters, R. T.; Wester, R.; White, R.; Wieland, R.; Wilgen, J. B.; Williams, M.; Wilson, J. R.; Winston, J.; Wright, K.; Wong, K.-L.; Woskov, P.; Wurden, G. A.; Yamada, M.; Yoshikawa, S.; Young, K. M.; Zarnstorff, M. C.; Zavereev, V.; Zweben, S. J.

    1995-09-01

    A peak fusion power production of 9.3±0.7 MW has been achieved on the Tokamak Fusion Test Reactor (TFTR) in deuterium plasmas heated by co and counter injected deuterium and tritium neutral beams with a total power of 33.7 MW. The ratio of fusion power output to heating power input is 0.27. At the time of the highest neutron flux the plasma conditions are: Te(0)=11.5 keV, Ti(0)=44 keV, ne(0)=8.5×1019 m-3, and =2.2 giving τE=0.24 s. These conditions are similar to those found in the highest confinement deuterium plasmas. The measured D-T neutron yield is within 7% of computer code estimates based on profile measurements and within experimental uncertainties. These plasmas have an inferred central fusion alpha fraction of 0.2% and central fusion power density of 2 MW/m3 similar to that expected in a fusion reactor. Even though the alpha velocity exceeds the Alfven velocity throughout the time of high neutron output in most high power plasmas, MHD activity is not substantially different from that in comparable deuterium plasmas and Alfven wave activity is low. The measured loss rate of energetic alpha particles is about 3% of the total as expected from alphas which are born on unconfined orbits. Compared to pure deuterium plasmas with similar externally applied conditions, the stored energy in electrons and ions is about 25% higher indicating improvements in confinement associated with D-T plasmas and consistent with modest electron heating expected from alpha particles. ICRF heating of D-T plasmas using up to 5.5 MW has resulted in 10 keV increases in central ion and 2.5 keV increases in central electron temperatures in relatively good agreement with code predictions. In these cases heating on the magnetic axis at 2ΩT gave up to 80% of the ICRF energy to ions.

  4. Growth phase dependent hydrogen isotopic fractionation in alkenone-producing haptophytes

    NASA Astrophysics Data System (ADS)

    Wolhowe, M. D.; Prahl, F. G.; Probert, I.; Maldonado, M.

    2009-08-01

    Recent works have investigated use of the hydrogen isotopic composition of C37 alkenones (δDK37s, lipid biomarkers of certain haptophyte microalgae, as an independent paleosalinity proxy. We discuss herein the factors impeding the success of such an application and identify the potential alternative use of δDK37s measurements as a proxy for non-thermal, physiological stress impacts on the U37K' paleotemperature index. Batch-culture experiments with the haptophyte Emiliania huxleyi (CCMP 1742) were conducted to determine the magnitude and variability of the isotopic contrasts between individual C37 alkenones. Further experiments were conducted with Emiliania huxleyi (CCMP 1742) andGephyrocapsa oceanica (PZ3-1) to determine whether, and to what extent, δDK37s varies between the physiological extremes of nutrient-replete exponential growth and nutrient-depleted senescence. Emiliania huxleyi was observed to exhibit an isotopic contrast between di- and tri-unsaturated C37 alkenones (αK37:3-K37:2≈0.97) that is nearly identical to that reported recently by others for environmental samples. Furthermore, this contrast appears to be constant with growth stage. The consistency of the offset across different growth stages suggests that a single, well-defined value for αK37:3-K37:2 may exist and that its use in an isotope mass-balance will allow accurate determination of δD values for individual alkenones without having to rely on time- and labor-intensive chemical separations. The isotopic fractionation between growth medium and C37 alkenones was observed to increase dramatically upon the onset of nutrient-depletion-induced senescence, suggesting that δDK37s may serve as an objective tool for recognizing and potentially correcting, at least semi-quantitatively, for the effects of nutrient stress on U37K' temperature records.

  5. Deuterium Enrichment of PAHs by VUV Irradiation of Interstellar Ices

    NASA Technical Reports Server (NTRS)

    Bernstein, Max P.; Sandford, Scott A.; Allamandola, Louis J.; Gillette, J. Seb; Zare, Richard N.; DeVincenzi, Donald (Technical Monitor)

    1998-01-01

    Laboratory results demonstrate that polycyclic aromatic hydrocarbons (PAHs) rapidly exchange their hydrogen atoms with those of nearby molecules when they are frozen into low-temperature ices and exposed to vacuum ultraviolet radiation. As a result, PAHs quickly become deuterium-enriched when VUV irradiated in D-containing ices. This mechanism has important consequences for several astrophysical issues owing to the ubiquitous nature of PAHs in the interstellar medium. For example, this process may explain the deuterium enrichments found in PAHs in meteorites and interplanetary dust particles. These results also provide general predictions about the molecular siting of the deuterium on aromatic materials in meteorites if this process produced a significant fraction of their D-enrichment.

  6. An Update on the Non-Mass-Dependent Isotope Fractionation under Thermal Gradient

    NASA Technical Reports Server (NTRS)

    Sun, Tao; Niles, Paul; Bao, Huiming; Socki, Richard; Liu, Yun

    2013-01-01

    Mass flow and compositional gradient (elemental and isotope separation) occurs when flu-id(s) or gas(es) in an enclosure is subjected to a thermal gradient, and the phenomenon is named thermal diffusion. Gas phase thermal diffusion has been theoretically and experimentally studied for more than a century, although there has not been a satisfactory theory to date. Nevertheless, for isotopic system, the Chapman-Enskog theory predicts that the mass difference is the only term in the thermal diffusion separation factors that differs one isotope pair to another,with the assumptions that the molecules are spherical and systematic (monoatomic-like structure) and the particle collision is elastic. Our previous report indicates factors may be playing a role because the Non-Mass Dependent (NMD) effect is found for both symmetric and asymmetric, linear and spherical polyatomic molecules over a wide range of temperature (-196C to +237C). The observed NMD phenomenon in the simple thermal-diffusion experiments demands quantitative validation and theoretical explanation. Besides the pressure and temperature dependency illustrated in our previous reports, efforts are made in this study to address issues such as the role of convection or molecular structure and whether it is a transient, non-equilibrium effect only.

  7. Culture-Dependent and -Independent Methods Capture Different Microbial Community Fractions in Hydrocarbon-Contaminated Soils

    PubMed Central

    Stefani, Franck O. P.; Bell, Terrence H.; Marchand, Charlotte; de la Providencia, Ivan E.; El Yassimi, Abdel; St-Arnaud, Marc; Hijri, Mohamed

    2015-01-01

    Bioremediation is a cost-effective and sustainable approach for treating polluted soils, but our ability to improve on current bioremediation strategies depends on our ability to isolate microorganisms from these soils. Although culturing is widely used in bioremediation research and applications, it is unknown whether the composition of cultured isolates closely mirrors the indigenous microbial community from contaminated soils. To assess this, we paired culture-independent (454-pyrosequencing of total soil DNA) with culture-dependent (isolation using seven different growth media) techniques to analyse the bacterial and fungal communities from hydrocarbon-contaminated soils. Although bacterial and fungal rarefaction curves were saturated for both methods, only 2.4% and 8.2% of the bacterial and fungal OTUs, respectively, were shared between datasets. Isolated taxa increased the total recovered species richness by only 2% for bacteria and 5% for fungi. Interestingly, none of the bacteria that we isolated were representative of the major bacterial OTUs recovered by 454-pyrosequencing. Isolation of fungi was moderately more effective at capturing the dominant OTUs observed by culture-independent analysis, as 3 of 31 cultured fungal strains ranked among the 20 most abundant fungal OTUs in the 454-pyrosequencing dataset. This study is one of the most comprehensive comparisons of microbial communities from hydrocarbon-contaminated soils using both isolation and high-throughput sequencing methods. PMID:26053848

  8. Determination of mass-dependent isotopic fractionation of cerium and neodymium in geochemical samples by MC-ICPMS.

    PubMed

    Ohno, Takeshi; Hirata, Takafumi

    2013-01-01

    We have developed a new analytical method to determine the mass-dependent isotopic fractionations on Ce and Nd in geochemical samples. Mass discrimination effects on Ce and Nd were externally corrected by normalizing (149)Sm/(147)Sm and (153)Eu/(151)Eu, being 0.92124 and 1.0916, respectively based on an exponential law. The reproducibility of the isotopic ratio measurements on (142)Ce/(140)Ce, (146)Nd/(144)Nd and (148)Nd/(144)Nd were 0.08‰ (2SD, n = 25), 0.06‰ (2SD, n = 39) and 0.12‰ (2SD, n = 39), respectively. The present technique was applied to determine the variations of the Ce and Nd isotopic ratios for five geochemical reference materials (igneous rocks, JB-1a and JA-2; sedimentary rocks, JMn-1, JCh-1 and JDo-1). The resulting ratios for two igneous rocks (JB-1a and JA-2) and two sedimentary rocks (JMn-1 and JCh-1) did not vary significantly among the samples, whereas the Ce and Nd isotope ratios for the carbonate samples (JDo-1) were significantly higher than those for igneous and sedimentary rock samples. The 1:1 simple correlation between δ(142)Ce and δ(146)Nd indicates that there were no significant difference in the degree of isotopic fractionation between the Ce and Nd. This suggests that the isotopic fractionation for Ce found in the JDo-1 could be induced by geochemical or physicochemical processes without changing the oxidation status of Ce, since the redox-reaction can produce larger isotopic fractionation than the reactions without changing the oxidation state. The variations in the Ce and Nd isotope ratios for geochemical samples could provide new information concerning the physico-chemical processes of the sample formation. PMID:23303084

  9. Shock compression of precompressed deuterium

    SciTech Connect

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

    2011-07-31

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

  10. Growth phase dependent hydrogen isotopic fractionation in alkenone-producing haptophytes

    NASA Astrophysics Data System (ADS)

    Wolhowe, M. D.; Prahl, F. G.; Probert, I.; Maldonado, M.

    2009-04-01

    Several recent works have investigated use of the hydrogen isotopic composition of C37 alkenones (δDK37s), lipid biomarkers of certain haptophyte microalgae, as an independent paleosalinity proxy. We discuss herein the factors impeding the success of such an application and identify the potential alternative use of δDK37s measurements as a proxy for non-thermal, physiological stress impacts on the U37K' paleotemperature index. Batch-culture experiments with the haptophyte Emiliania huxleyi (CCMP 1742) were conducted to determine the magnitude and variability of the isotopic contrasts between individual C37 alkenones, an analytical impediment to the use of δDK37s in any paleoceanographic context. Further experiments were conducted with Emiliania huxleyi (CCMP 1742) and Gephyrocapsa oceanica (PZ3-1) to determine whether, and to what extent, δDK37s varies between the physiological extremes of nutrient-replete exponential growth and nutrient-depleted senescence, the basis for our proposed use of the measurement as an indicator of stress. Emiliania huxleyi exhibited an isotopic contrast between di- and tri-unsaturated C37 alkenones (αK37:3-K37:2≈0.97) that is nearly identical to that reported recently by others for environmental samples. Furthermore, this contrast appears to be constant with growth stage. The consistency of the offset across different growth stages suggests that a single, well-defined value for αK37:3-K37:2 exists and that its use in an isotope mass-balance will allow accurate determination of δD values for individual alkenones without having to rely on time- and labor-intensive chemical separations. The isotopic fractionation between growth medium and C37 alkenones was observed to increase dramatically upon the onset of nutrient-depletion-induced senescence, suggesting that δDK37s may serve as an objective tool for recognizing and potentially correcting, at least semi-quantitatively, for the effects of nutrient stress on U37K' temperature

  11. There is no temperature dependence of net biochemical fractionation of hydrogen and oxygen isotopes in tree-ring cellulose.

    PubMed

    Roden, J S; Ehleringer, J R

    2000-01-01

    The isotopic composition of tree-ring cellulose was obtained over a two-year period from small diameter, riparian zone trees along an elevational transect in Big Cottonwood Canyon, Utah, USA to test for a possible temperature dependence of net biological fractionation during cellulose synthesis. The isotope ratios of stream water varied by only 3.6% and 0.2% in deltaD and delta18O, respectively, over an elevation change of 810m. The similarity in stream water and macroenvironment over the short (13km) transect produced nearly constant stem and leaf water deltaD and delta18O values. In addition, what few seasonal variations observed in the isotopic composition of source water and atmospheric water vapor or in leaf water evaporative enrichment were experienced equally by all sites along the elevational transect. The temperature at each site along the transect spanned a range of > or = 5 degrees C as calculated using the adiabatic lapse rate. Since the deltaD and delta18O values of stem and leaf water varied little for these trees over this elevation/temperature transect, any differences in tree-ring cellulose deltaD and delta18O values should have been associated with temperature effects on net biological fractionation. However, the slopes of the regressions of elevation versus the deltaD and delta18O values of tree-ring cellulose were not significantly different from zero indicating little or no temperature dependence of net biological fractionation. Therefore, cross-site climatic reconstruction studies using the isotope ratios of cellulose need not be concerned that temperatures during the growing season have influenced results. PMID:11501707

  12. Laser-driven polarized hydrogen and deuterium internal targets

    SciTech Connect

    Jones, C.E.; Fedchak, J.A.; Kowalczyk, R.S.

    1995-08-01

    After completing comprehensive tests of the performance of the source with both hydrogen and deuterium gas, we began tests of a realistic polarized deuterium internal target. These tests involve characterizing the atomic polarization and dissociation fraction of atoms in a storage cell as a function of flow and magnetic field, and making direct measurements of the average nuclear tensor polarization of deuterium atoms in the storage cell. Transfer of polarization from the atomic electron to the nucleus as a result of D-D spin-exchange collisions was observed in deuterium, verifying calculations suggesting that high vector polarization in both hydrogen and deuterium can be obtained in a gas in spin temperature equilibrium without inducing RF transitions between the magnetic substates. In order to improve the durability of the system, the source glassware was redesigned to simplify construction and installation and eliminate stress points that led to frequent breakage. Improvements made to the nuclear polarimeter, which used the low energy {sup 3}H(d,n){sup 4}He reaction to analyze the tensor polarization of the deuterium, included installing acceleration lenses constructed of wire mesh to improve pumping conductance, construction of a new holding field coil, and elimination of the Wien filter from the setup. These changes substantially simplified operation of the polarimeter and should have reduced depolarization in collisions with the wall. However, when a number of tests failed to show an improvement of the nuclear polarization, it was discovered that extended operation of the system with a section of teflon as a getter for potassium caused the dissociation fraction to decline with time under realistic operating conditions, suggesting that teflon may not be a suitable material to eliminate potassium from the target. We are replacing the teflon surfaces with drifilm-coated ones and plan to continue tests of the polarized internal target in this configuration.

  13. Studies of quaternary saline lakes-I. Hydrogen isotope fractionation in saline minerals

    USGS Publications Warehouse

    Matsuo, S.; Friedman, I.; Smith, G.I.

    1972-01-01

    Borax, gaylussite, nahcolite and trona were synthesized in aqueous solution at temperatures ranging from 8?? to 35??C. Except for borax, deuterium was always depleted in these hydrated minerals relative to the solutions from which they were crystallized. In borax, no significant fractionation was found. The fractionation factor of D H for the trona-water system exhibited a marked temperature dependence. By combining the deuterium contents of trona and the solution from which trona was crystallized, the following thermometer scale was obtained: In ( D H) trona ( D H)water = 1.420 ?? 104 T2 + 23.56 T (1). An attempt to establish a geothermometer based on C13 C12 fractionation between carbonate minerals and carbonate ions in aqueous solution was not successful. ?? 1972.

  14. Mechanistic deductions from multiple kinetic and solvent deuterium isotope effects and pH studies of pyridoxal phosphate dependent carbon-carbon lyases: escherichia coli tryptophan indole-lyase

    SciTech Connect

    Kiick, D.M.; Phillips, R.S.

    1988-09-20

    Analysis of the pH dependence of the kinetic parameters and competitive inhibitor Ki values for tryptophan indole-lyase suggests two enzymic groups must be unprotonated in order to facilitate binding and catalysis of tryptophan. The V/K for tryptophan and the pKi for oxindolyl-L-alanine, a putative transition state analogue and competitive inhibitor, decrease below two pK values of 7.6 and 6.0, while the Ki for L-alanine, also a competitive inhibitor, is 3300-fold larger (20 mM) than that for oxindolyl-L-alanine and increases below a single pK of 7.6. A single pK of 7.6 is also observed in the V/K profile for the alternate substrate, S-methyl-L-cysteine. Therefore, the enzymic group with a pK of 7.6 is responsible for proton abstraction at the 2-position of tryptophan, while the enzymic group with a pK of 6.0 interacts with the indole portion of tryptophan and probably catalyzes formation of the indolenine tautomer of tryptophan (in concert with proton transfer to C-3 of indole from the group with pK 7.6) to facilitate carbon-carbon bond cleavage and elimination of indole. The pH variation of the primary deuterium isotope effects for proton abstraction at the 2-position of tryptophan (DV = 2.5 and D(V/Ktrp) = 2.8) are pH independent, while the Vmax for tryptophan or S-methyl-L-cysteine is the same and also pH independent. Thus, substrates bind only to the correctly protonated form of the enzyme. Further, tryptophan is not sticky, and the pK values observed in both V/K profiles are the correct ones.

  15. Deuterium retention and surface modifications of nanocrystalline tungsten films exposed to high-flux plasma

    NASA Astrophysics Data System (ADS)

    `t Hoen, M. H. J.; Dellasega, D.; Pezzoli, A.; Passoni, M.; Kleyn, A. W.; Zeijlmans van Emmichoven, P. A.

    2015-08-01

    Deuterium retention studies are presented for nanostructured tungsten films exposed to high-flux deuterium plasmas. Thin tungsten films of ∼1 μm thickness were deposited with pulsed laser deposition (PLD) on bulk tungsten. Surface modifications were studied with scanning electron microscopy and deuterium retention with thermal desorption spectroscopy. Three types of PLD films with different densities and crystallinity were studied after exposure to deuterium plasmas. The surface temperature ranged from about 460 K at the periphery to about 520 K in the centre of the targets. The films withstand the intense plasma exposure well and maintain their overall integrity. An increase of deuterium retention is observed with decreasing tungsten density and crystallite size. We found that the filling of these thin films with deuterium is significantly faster than for pre-damaged polycrystalline tungsten. We observed formation of micrometer-sized blisters as well as structures on the nanometer scale, both depending on the layer type.

  16. Influence of Deuterium Treatments on the Polysilicon-Based Metal-Semiconductor-Metal Photodetector.

    PubMed

    Lee, Jae-Sung

    2016-06-01

    The electrical behavior of metal-semiconductor-metal (MSM) Schottky barrier photodetector structure, depending on deuterium treatment, is analyzed by means of the dark current and the photocurrent measurements. Al/Ti bilayer was used as Schottky metal. The deuterium incorporation into the absorption layer, undoped polysilicon, was achieved with annealing process and with ion implantation process, respectively. In the photocurrent-to-dark current ratio measurement, deuterium-ion-implanted photodetector shows over hundred higher than the control device. It means that the heightening of the Schottky barrier and the passivation of grain boundary trap were achieved effectively through the deuterium ion implantation process. PMID:27427689

  17. Mercury (Hg) in meteorites: Variations in abundance, thermal release profile, mass-dependent and mass-independent isotopic fractionation

    NASA Astrophysics Data System (ADS)

    Meier, Matthias M. M.; Cloquet, Christophe; Marty, Bernard

    2016-06-01

    We have measured the concentration, isotopic composition and thermal release profiles of Mercury (Hg) in a suite of meteorites, including both chondrites and achondrites. We find large variations in Hg concentration between different meteorites (ca. 10 ppb to 14,000 ppb), with the highest concentration orders of magnitude above the expected bulk solar system silicates value. From the presence of several different Hg carrier phases in thermal release profiles (150-650 °C), we argue that these variations are unlikely to be mainly due to terrestrial contamination. The Hg abundance of meteorites shows no correlation with petrographic type, or mass-dependent fractionation of Hg isotopes. Most carbonaceous chondrites show mass-independent enrichments in the odd-numbered isotopes 199Hg and 201Hg. We show that the enrichments are not nucleosynthetic, as we do not find corresponding nucleosynthetic deficits of 196Hg. Instead, they can partially be explained by Hg evaporation and redeposition during heating of asteroids from primordial radionuclides and late-stage impact heating. Non-carbonaceous chondrites, most achondrites and the Earth do not show these enrichments in vapor-phase Hg. All meteorites studied here have however isotopically light Hg (δ202Hg = ∼-7 to -1) relative to the Earth's average crustal values, which could suggest that the Earth has lost a significant fraction of its primordial Hg. However, the late accretion of carbonaceous chondritic material on the order of ∼2%, which has been suggested to account for the water, carbon, nitrogen and noble gas inventories of the Earth, can also contribute most or all of the Earth's current Hg budget. In this case, the isotopically heavy Hg of the Earth's crust would have to be the result of isotopic fractionation between surface and deep-Earth reservoirs.

  18. Mass-dependent and mass-independent fractionation of mercury isotopes in precipitation from Guiyang, SW China

    NASA Astrophysics Data System (ADS)

    Wang, Zhuhong; Chen, Jiubin; Feng, Xinbin; Hintelmann, Holger; Yuan, Shengliu; Cai, Hongming; Huang, Qiang; Wang, Shuxiao; Wang, Fengyang

    2015-11-01

    The isotopic composition of mercury (Hg) is increasingly used to constrain the sources and pathways of this metal in the atmosphere. Though China has the highest Hg production, consumption and emission in the world, Hg isotope ratios are rarely reported for Chinese wet deposition. In this study, we examined, for the first time outside North America, both mass-dependent fractionation (MDF, expressed as δ202Hg) and mass-independent fractionation of odd (odd-MIF, Δ199Hg) and even (even-MIF, Δ200Hg) Hg isotopes in 15 precipitation samples collected from September 2012 to August 2013 in Guiyang (SW China). All samples displayed significant negative δ202Hg (-0.44 ∼ -4.27‰), positive Δ199Hg (+0.19 to +1.16‰) and slightly positive Δ200Hg (-0.01‰ to +0.20‰). Potential sources of Hg in precipitation were identified by coupling both MDF and MIF of Hg isotopes with a back-trajectory model. The results showed that local emission from coal-fired power plants and cement plants and western long-range transportation are two main contributing sources, while the contribution of Hg from south wind events would be very limited on an annual basis. The relatively lower Δ200Hg values in Guiyang precipitation may indicate a dilution effect by local sources and/or insignificant even-MIF in the tropopause contribution of this subtropical region. Our study demonstrates the usefulness of isotope fractionation, especially MIF for tracing sources and pathways of Hg in the atmosphere.

  19. Deuterated H3+ as a probe of isotope fractionation in star-forming regions.

    PubMed

    Roberts, Helen; Millar, T J

    2006-11-15

    Observations of molecular D/H ratios in the interstellar medium are used to probe the physical conditions, such as temperature, ionization fraction and the importance of gas-grain reactions. In cold, dense regions, such as cores which are collapsing to form stars, the level of deuterium fractionation depends on the conversion of H3+ into its deuterated isotopologues (H2D+, D2H+ and D3+). The relative abundances of these molecules uniquely probe the centres of these cores where other, heavier, species have frozen onto dust grains. We present models of the deuterium chemistry close to the centre of a pre-stellar core, in the last stage before the star forms, showing the dependence of the observable molecular D/H ratios on the physical parameters and rate coefficients that are assumed. We compare model predictions with the latest observations of these regions. PMID:17015383

  20. Experimental determination of the strain and strain rate dependence of the fraction of plastic work converted to heat

    SciTech Connect

    Hodowany, J.; Ravichandran, G.; Rosakis, A.J.

    1995-12-31

    When metals are deformed dynamically, there is insufficient time for heat generated by plastic deformation to be conducted to the surroundings. Thus, the conversion of plastic work into heat at high strain rates can result in significant temperature increases, which contribute to thermal softening, thereby altering a material`s constitutive response. The fraction of plastic work converted to heat represents the strength of the coupling term between temperature and mechanical fields in thermalmechanical problems involving plastic flow. The experimental determination of this constitutive function is important since it is an integral part of the formulation of coupled thermomechanical field equations. This fraction also plays an important role in failure mode characterization for metals deforming at high rates of strain, such as the formation of adiabatic shear bands. This investigation systematically examines the rate of conversion of plastic work to heat in metals under dynamic loading. Temperature was measured in-situ using an array of high speed In-Sb infrared detectors. The plastic work rate and the heat generation rate were determined directly from experimental data. The ratio of heat generation rate to plastic work rate, i.e., the relative rate at which plastic work is converted to heat, was calculated from this data. The functional dependence of this quantity upon strain and strain rate is reported for 1020 steel, 2024 aluminum, Ti-6Al-4V titanium alloy, and C300 maraging steel.

  1. Deuterium in North Atlantic storm tops

    NASA Technical Reports Server (NTRS)

    Smith, Ronald B.

    1992-01-01

    During the ERICA project in 1989, ice crystals were collected from the tops of two winter storms and one broad cirrus cloud. Deuterium concentration in the storm ice samples, together with a model of isotope fractionation, are used to determine the temperature where the ice was formed. Knowledge of the ice formation temperature allows us to determine whether the ice has fallen or been lofted to the altitude of collection. In both storms, the estimated fall distance decreases upward. In the 21 January storm, the fall distance decreases to zero at the cloud top. In the 23 January storm, the fall distance decreases to zero at a point 2 km below the cloud top and appears to become negative above, indicating lofted ice. Cloud particle data from the cloud tops show an ice-to-vapor ratio greater than one and indicate the presence of particles with small terminal velocities; both observations support the idea of ice lofting. The satellite-derived cloud tops lie well below the actual cloud top (e.g., 2.5 km below on 23 January), indicating that the lofted ice in winter storms may not be detectable from space using IR radiance techniques. A comparison of deuterium in cloud-top ice and clear-air vapor suggests that even in winter, when vertical air motions are relatively weak, lofted ice crystals are the dominant source of water vapor in the upper troposphere.

  2. Deuterium enrichment of the interstellar grain mantle

    NASA Astrophysics Data System (ADS)

    Das, Ankan; Sahu, Dipen; Majumdar, Liton; Chakrabarti, Sandip K.

    2016-01-01

    We carry out Monte Carlo simulation to study deuterium enrichments of interstellar grain mantles under various physical conditions. Based on the physical properties, various types of clouds are considered. We find that in diffuse cloud regions, very strong radiation fields persists and hardly a few layers of surface species are formed. In translucent cloud regions with a moderate radiation field, significant number of layers would be produced and surface coverage is mainly dominated by photo-dissociation products such as, C, CH3, CH2D, OH and OD. In the intermediate dense cloud regions (having number density of total hydrogen nuclei in all forms ˜2 × 104 cm-3), water and methanol along with their deuterated derivatives are efficiently formed. For much higher density regions (˜106 cm-3), water and methanol productions are suppressed but surface coverages of CO, CO2, O2 and O3 are dramatically increased. We find a very high degree of fractionation of water and methanol. Observational results support a high fractionation of methanol but surprisingly water fractionation is found to be low. This is in contradiction with our model results indicating alternative routes for de-fractionation of water. Effects of various types of energy barriers are also studied. Moreover, we allow grain mantles to interact with various charged particles (such as H+, Fe+, S+ and C+) to study the stopping power and projected range of these charged particles on various target ices.

  3. Deuterium Retention and Physical Sputtering of Low Activation Ferritic Steel

    NASA Astrophysics Data System (ADS)

    T, Hino; K, Yamaguchi; Y, Yamauchi; Y, Hirohata; K, Tsuzuki; Y, Kusama

    2005-04-01

    Low activation materials have to be developed toward fusion demonstration reactors. Ferritic steel, vanadium alloy and SiC/SiC composite are candidate materials of the first wall, vacuum vessel and blanket components, respectively. Although changes of mechanical-thermal properties owing to neutron irradiation have been investigated so far, there is little data for the plasma material interactions, such as fuel hydrogen retention and erosion. In the present study, deuterium retention and physical sputtering of low activation ferritic steel, F82H, were investigated by using deuterium ion irradiation apparatus. After a ferritic steel sample was irradiated by 1.7 keV D+ ions, the weight loss was measured to obtain the physical sputtering yield. The sputtering yield was 0.04, comparable to that of stainless steel. In order to obtain the retained amount of deuterium, technique of thermal desorption spectroscopy (TDS) was employed to the irradiated sample. The retained deuterium desorbed at temperature ranging from 450 K to 700 K, in the forms of DHO, D2, D2O and hydrocarbons. Hence, the deuterium retained can be reduced by baking with a relatively low temperature. The fluence dependence of retained amount of deuterium was measured by changing the ion fluence. In the ferritic steel without mechanical polish, the retained amount was large even when the fluence was low. In such a case, a large amount of deuterium was trapped in the surface oxide layer containing O and C. When the fluence was large, the thickness of surface oxide layer was reduced by the ion sputtering, and then the retained amount in the oxide layer decreased. In the case of a high fluence, the retained amount of deuterium became comparable to that of ferritic steel with mechanical polish or SS 316L, and one order of magnitude smaller than that of graphite. When the ferritic steel is used, it is required to remove the surface oxide layer for reduction of fuel hydrogen retention. Ferritic steel sample was

  4. Mass Dependent and Mass Independent Fractionation of Hg Isotopes and Estimation of Photochemical Loss of Hg in Aquatic Systems

    NASA Astrophysics Data System (ADS)

    Bergquist, B. A.; Blum, J. D.

    2007-12-01

    Mercury is a globally distributed and highly toxic pollutant, the mobility and bioaccumulation of which is dependent on its redox cycling. Hg isotope analysis is an important new tool for identifying Hg sources and tracking Hg transformations in the environment. Most natural samples analyzed for Hg isotopes display mass-dependent isotope fractionation (MDF), but a small body of data suggests that some natural samples also display mass- independent isotope fractionation (MIF) of the odd Hg isotopes. Here we document MIF of Hg isotopes during an important natural process, constrain the potential mechanism of isotope fractionation, and apply the MIF observed in natural samples to quantify the photochemical reduction of Hg species in the environment. Reduction of Hg species to Hg0 vapor is an important pathway for removal of Hg from aqueous systems into the atmosphere and occurs by abiotic and biotic mechanisms. In laboratory experiments, we find that photochemical reduction Hg species by natural sunlight leads to large MIF of the odd isotopes. Also, the relationship between MIF for the two odd isotopes of Hg is significantly different for different photo-reduction pathways. In contrast, both biological reduction (Kritee et al., 2006) and dark abiotic organically-mediated reduction follow MDF. Natural samples from aquatic ecosystems preserve both MDF and MIF. In fish, MDF increases with the size and Hg concentration of fish suggesting MDF may be useful in understanding Hg bioaccumulation. Fish also display a large range in MIF (4‰), and the relationship between the MIF of the two odd isotopes in fish has a similar slope to the slope found for photo-reduction of CH3Hg+. Since fish bioaccumulate CH3Hg+, fish may be recording the extent to which CH3Hg+ is lost via photochemical reduction in an aquatic ecosystem. Fish populations from different locations have different MIF values, but mostly display similar MIF within a given locale. This suggests that MIF is preserved

  5. Mass Dependency of Isotope Fractionation of Gases Under Thermal Gradient and Its Possible Implications for Planetary Atmosphere Escaping Process

    NASA Technical Reports Server (NTRS)

    Sun, Tao; Niles, Paul; Bao, Huiming; Socki, Richard

    2014-01-01

    Physical processes that unmix elements/isotopes of gas molecules involve phase changes, diffusion (chemical or thermal), effusion and gravitational settling. Some of those play significant roles for the evolution of chemical and isotopic compositions of gases in planetary bodies which lead to better understanding of surface paleoclimatic conditions, e.g. gas bubbles in Antarctic ice, and planetary evolution, e.g. the solar-wind erosion induced gas escaping from exosphere on terrestrial planets.. A mass dependent relationship is always expected for the kinetic isotope fractionations during these simple physical processes, according to the kinetic theory of gases by Chapman, Enskog and others [3-5]. For O-bearing (O16, -O17, -O18) molecules the alpha O-17/ alpha O-18 is expected at 0.5 to 0.515, and for S-bearing (S32,-S33. -S34, -S36) molecules, the alpha S-33/ alpha S-34 is expected at 0.5 to 0.508, where alpha is the isotope fractionation factor associated with unmixing processes. Thus, one isotope pair is generally proxied to yield all the information for the physical history of the gases. However, we recently] reported the violation of mass law for isotope fractionation among isotope pairs of multiple isotope system during gas diffusion or convection under thermal gradient (Thermal Gradient Induced Non-Mass Dependent effect, TGI-NMD). The mechanism(s) that is responsible to such striking observation remains unanswered. In our past studies, we investigated polyatomic molecules, O2 and SF6, and we suggested that nuclear spin effect could be responsible to the observed NMD effect in a way of changing diffusion coefficients of certain molecules, owing to the fact of negligible delta S-36 anomaly for SF6.. On the other hand, our results also showed that for both diffusion and convection under thermal gradient, this NMD effect is increased by lower gas pressure, bigger temperature gradient and lower average temperature, which indicate that the nuclear spin effect may

  6. NOTE: On the Deuterium Abundance on Mars and Some Related Problems

    NASA Astrophysics Data System (ADS)

    Krasnopolsky, Vladimir

    2000-12-01

    Strong fractionation of deuterium in photolysis of H 2O and above the hygropause reduces the production of HD relative to H 2 on Mars by a factor of 3.7 total. The model by Y. L. Yung et al. (1988, Icarus76, 146-159) for deuterium fractionation in chemical reactions on Mars corrected for this factor results in (HD/H 2)/(HDO/H 2O)=0.43. This value may fit the deuterium abundance observed by V. A. Krasnopolsky et al. (1998, Science 280, 1576-1580) if the eddy diffusion coefficient does not depend on solar activity: K=1.4×10 13n-1/2 cm 2 s -1 (model 2). The Mariner 9 observations show very low variability of atomic oxygen at the 1.2 n bar pressure level (h˜125 km) with solar activity. This requires eddy diffusion to be proportional to the solar activity index F10.7: K=( F10.7 cm/30)×10 13n-1/2 cm 2 s -1 (model 1). The fractionation factor for escape of hydrogen isotopes is equal to 0.016 and 0.135 for models 1 and 2. These values have been averaged over the solar cycle. The three-reservoir model for hydrogen isotope fractionation suggested by Krasnopolsky et al. (1998) involves a reservoir composed primarily of water ice in the polar caps that isotopically interacts with the atmosphere. Assuming that water ice is half of the total volume of the polar caps and the polar-layered deposits, the total loss of water from Mars is equal to 65 and 120 m for models 1 and 2, respectively. Along with thermal and nonthermal escape, these values may include the loss of water by oxidation of regolith, if the released hydrogen escaped with isotopic fractionation. Although the solar-wind α particles are the main source of He on Mars, capture of the solar-wind H + and D + ions by Mars has a negligible effect on the thermospheric abundances of H and D. Improved observations of minor components in Mars' thermosphere may resolve the problem of eddy diffusion at various solar activity and choosing between the models.

  7. Channeling effect in polycrystalline deuterium-saturated CVD diamond target bombarded by deuterium ion beam

    NASA Astrophysics Data System (ADS)

    Bagulya, A. V.; Dalkarov, O. D.; Negodaev, M. A.; Rusetskii, A. S.; Chubenko, A. P.; Ralchenko, V. G.; Bolshakov, A. P.

    2015-07-01

    At the ion accelerator HELIS at LPI, the neutron yield is investigated in DD reactions within a strongly textured polycrystalline deuterium-saturated CVD diamond under irradiation by a deuterium ion beam with the energy of less than 30 keV. The measurements of the neutron flux in the beam direction are performed using a multichannel detector based on 3He counters, in dependence on the target angle, β, with respect to the beam axis. A significant anisotropy in the neutron yield is observed. At β = 0° the yield is higher by a factor of 3 as compared to that at β = ±45°. The possible reasons for the anisotropy, including ion channeling, are discussed.

  8. Release of deuterium from irradiation damage in Fe-9Cr-2W ferritic alloy irradiated with deuterium ions

    NASA Astrophysics Data System (ADS)

    Ono, K.; Miyamoto, M.; Kudo, F.

    2014-09-01

    The release profile of deuterium from an Fe-9Cr-2W ferritic alloy irradiated with low-energy deuterium ions was studied by thermal desorption spectroscopy (TDS) and in situ transmission electron microscopy (TEM). It was found that one sharp TDS peak appeared at a temperature around 410 K depending on the heating rate that ranged from 1.5 to 20 K/min. The TDS peak height increased with increasing fluence from 2 × 1019 to 2 × 1021 D+/m2 with no shift of the peak temperature. A close correlation between these TDS peaks and the disappearance of dislocation loops formed by the irradiation was observed. The effects of tiny bubbles on TDS were small. These results suggest that most of the deuterium was trapped by dislocation loops, which affected the thermal stability of dislocation loops in the alloy. The dependence of TDS peak temperature on the heating rate yielded an activation energy of 0.63 ± 0.02 eV for deuterium de-trapping from dislocation loops. The retention properties of the total amount of deuterium exhibited a tendency of saturation at values on the order of 1020 D+/m2, which corresponded to a saturation tendency of the loop density.

  9. Diffusion, trapping, and isotope exchange of plasma implanted deuterium in ion beam damaged tungsten

    NASA Astrophysics Data System (ADS)

    Barton, Joseph Lincoln

    Tritium accumulation in nuclear fusion reactor materials is a major concern for practical and safe fusion energy. This work examines hydrogen isotope exchange as a tritium removal technique, analyzes the effects of neutron damage using high energy copper ion beams, and introduces a diffusion coefficient that is a function of the concentration of trapped atoms. Tungsten samples were irradiated with high energy (0.5 - 5 MeV) copper ions for controlled levels of damage - 10-3 to 10-1 displacements per atom (dpa) - at room temperature. Samples were then exposed to deuterium plasma at constant temperature (˜ 380 K) to a high fluence of 1024 ions/m2, where retention is at is maximized (i.e. saturated). By then subsequently exposing these samples to fractions of this fluence with hydrogen plasma, isotope exchange rates were observed. The resulting deuterium still trapped in the tungsten is then measured post mortem. Nuclear reaction analysis (NRA) gives the depth resolved deuterium retention profile with the 3He(D,p) 4He reaction, and thermal desorption spectroscopy (TDS) gives the total amount of deuterium trapped in the tungsten by heating a sample in vacuum up to 1200 K and measuring the evaporated gas molecules with a residual gas analyzer. Isotope exchange data show that hydrogen atoms can displace trapped deuterium atoms efficiently only up to the first few microns, but does not affect the atoms trapped at greater depths. In ion damaged tungsten, measurements showed a significant increase in retention in the damage region proportional to dpa 0.66, which results in a significant spike in total retention, and isotope exchange in damaged samples is still ineffective at depths greater than a few microns. Thus, isotope exchange is not an affective tritium removal technique; however, these experiments have shown that trapping in material defects greatly affects diffusion. These experiments lead to a simplified diffusion model with defect densities as the only free

  10. [Consideration of the deuterium-free water supply to an expedition to Mars].

    PubMed

    Siniak, Iu E; Turusov, V S; Grigor'ev, A I; Zaridze, D G; Gaĭdadymov, V B; Gus'kova, E I; Antoshina, E E; Gor'kova, T G; Trukhanova, L S

    2003-01-01

    Interplanetary missions, including to Mars, will put crews into severe radiation conditions. Search for methods of reducing the risk of radiation-induced cancer is of the top priority in preparation for the mission to Mars. One of the options is designing life support systems that will generate water with low content of the stable hydrogen isotope (deuterium) to be consumed by crewmembers. Preliminary investigations have shown that a decrease of the deuterium fraction by 65% does impart to water certain anti-cancer properties. Therefore, drinking deuterium-free water has the potential to reduce the risk of cancer consequent to the extreme radiation exposure of the Martian crew. PMID:14959623

  11. Detection of atomic deuterium in the upper atmosphere of Mars

    NASA Technical Reports Server (NTRS)

    Krasnopolsky, V. A.; Mumma, M. J.; Gladstone, G. R.

    1998-01-01

    High-resolution spectroscopy of Mars' atmosphere with the Hubble Space Telescope revealed the deuterium Lyman alpha line at an intensity of 23 +/- 6 rayleighs. This measured intensity corresponds to HD/H2 = 1.5 +/- 0.6 x 10(-4), which is smaller by a factor of 11 than HDO/H2O. This indicates that fractionation of HD/H2 relative to that of HDO/H2O is not kinetically controlled by the rates of formation and destruction of H2 and HD but is thermodynamically controlled by the isotope exchange HD + H2O left and right arrow HDO + H2. Molecular hydrogen is strongly depleted in deuterium relative to water on Mars because of the very long lifetime of H2 (1200 years). The derived isotope fractionation corresponds to an estimate of a planetwide reservoir of water ice about 5 meters thick that is exchangeable with the atmosphere.

  12. Detection of atomic deuterium in the upper atmosphere of Mars.

    PubMed

    Krasnopolsky, V A; Mumma, M J; Gladstone, G R

    1998-06-01

    High-resolution spectroscopy of Mars' atmosphere with the Hubble Space Telescope revealed the deuterium Lyman alpha line at an intensity of 23 +/- 6 rayleighs. This measured intensity corresponds to HD/H2 = 1.5 +/- 0.6 x 10(-4), which is smaller by a factor of 11 than HDO/H2O. This indicates that fractionation of HD/H2 relative to that of HDO/H2O is not kinetically controlled by the rates of formation and destruction of H2 and HD but is thermodynamically controlled by the isotope exchange HD + H2O left and right arrow HDO + H2. Molecular hydrogen is strongly depleted in deuterium relative to water on Mars because of the very long lifetime of H2 (1200 years). The derived isotope fractionation corresponds to an estimate of a planetwide reservoir of water ice about 5 meters thick that is exchangeable with the atmosphere. PMID:9616115

  13. Power-law dependence of the melting temperature of ubiquitin on the volume fraction of macromolecular crowders

    NASA Astrophysics Data System (ADS)

    Waegele, Matthias M.; Gai, Feng

    2011-03-01

    The dependence of the melting temperature increase (ΔTm) of the protein ubiquitin on the volume fraction (φ) of several commonly used macromolecular crowding agents (dextran 6, 40, and 70 and ficoll 70) was quantitatively examined and compared to a recently developed theoretical crowding model, i.e., ΔTm ˜ (Rg/Rc)αφα/3. We found that in the current case this model correctly predicts the power-law dependence of ΔTm on φ but significantly overestimates the role of the size (i.e., Rc) of the crowding agent. In addition, we found that for ubiquitin the exponent α is in the range of 4.1-6.5, suggesting that the relation of α = 3/(3ν - 1) is a better choice for estimating α based on the Flory coefficient (ν) of the polypeptide chain. Taken together these findings highlight the importance of improving our knowledge and theoretical treatment of the microcompartmentalization of the commonly used model crowding agents.

  14. Nucleon structure at large x: nuclear effects in deuterium

    SciTech Connect

    Wally Melnitchouk

    2010-07-01

    I review quark momentum distributions in the nucleon at large momentum fractions x. Particular attention is paid to the impact of nuclear effects in deuterium on the d/u quark distribution ratio as x -> 1. A new global study of parton distributions, using less restrictive kinematic cuts in Q^2 and W^2, finds strong suppression of the d quark distribution once nuclear corrections are accounted for.

  15. The CALYMHA survey: Lyα escape fraction and its dependence on galaxy properties at z = 2.23

    NASA Astrophysics Data System (ADS)

    Matthee, Jorryt; Sobral, David; Oteo, Iván; Best, Philip; Smail, Ian; Röttgering, Huub; Paulino-Afonso, Ana

    2016-05-01

    We present the first results from our CAlibrating LYMan α with Hα (CALYMHA) pilot survey at the Isaac Newton Telescope. We measure Lyα emission for 488 Hα selected galaxies at z = 2.23 from High-z Emission Line Survey in the COSMOS and UDS fields with a specially designed narrow-band filter (λc = 3918 Å, Δλ = 52 Å). We find 17 dual Hα-Lyα emitters [fLyα > 5 × 10-17 erg s-1 cm-2, of which five are X-ray active galactic nuclei (AGN)]. For star-forming galaxies, we find a range of Lyα escape fractions (fesc, measured with 3 arcsec apertures) from 2 to 30 per cent. These galaxies have masses from 3 × 108 M⊙ to 1011 M⊙ and dust attenuations E(B - V) = 0-0.5. Using stacking, we measure a median escape fraction of 1.6 ± 0.5 per cent (4.0 ± 1.0 per cent without correcting Hα for dust), but show that this depends on galaxy properties. The stacked fesc tends to decrease with increasing star formation rate and dust attenuation. However, at the highest masses and dust attenuations, we detect individual galaxies with fesc much higher than the typical values from stacking, indicating significant scatter in the values of fesc. Relations between fesc and UV slope are bimodal, with high fesc for either the bluest or reddest galaxies. We speculate that this bimodality and large scatter in the values of fesc is due to additional physical mechanisms such as outflows facilitating fesc for dusty/massive systems. Lyα is significantly more extended than Hα and the UV. fesc continues to increase up to at least 20 kpc (3σ, 40 kpc [2σ]) for typical star-forming galaxies and thus the aperture is the most important predictor of fesc.

  16. Spectral irradiance standard for the ultraviolet - The deuterium lamp

    NASA Technical Reports Server (NTRS)

    Saunders, R. D.; Ott, W. R.; Bridges, J. M.

    1978-01-01

    A set of deuterium lamps is calibrated as spectral irradiance standards in the 200-350-nm spectral region utilizing both a high accuracy tungsten spectral irradiance standard and a newly developed argon mini-arc spectral radiance standard. The method which enables a transfer from a spectral radiance to a spectral irradiance standard is described. The following characteristics of the deuterium lamp irradiance standard are determined: sensitivity to alignment; dependence on input power and solid angle; reproducibility; and stability. The absolute spectral radiance is also measured in the 167-330-nm region. Based upon these measurements, values of the spectral irradiance below 200 nm are obtained through extrapolation.

  17. Transport of Recycled Deuterium to the Plasma Core in TFTR

    SciTech Connect

    Bell, M.G.; Budny, R.V.; Jassby, D.L.; Park, H.; Skinner, C.H.; et al

    1997-10-01

    We report a study of the fueling of the plasma core by recycling in the Tokamak Fusion Test Reactor (TFTR) [Phys. Plasmas 2, 2176 (1995)]. We have analyzed discharges fueled by deuterium recycled from the limiter and tritium-only neutral beam injection. In these plasmas, the DT neutron rate provides a measure of the deuterium influx into the core plasma. We find a reduced influx with plasmas using lithium pellet conditioning and with plasmas of reduced major (and minor) radius. Modeling with the DEGAS neutrals code shows that the dependence on radius can be related to the penetration of neutrals through the scrape-off layer.

  18. Transport of recycled deuterium to the plasma core in TFTR

    SciTech Connect

    Skinner, C.H.; Bell, M.G.; Budny, R.V.; Jassby, D.L.; Park, H.; Ramsey, A.T.; Stotler, D.P.; Strachan, J.D.

    1997-10-01

    The authors report a study of the fueling of the plasma core by recycling in the Tokamak Fusion Test Reactor (TFTR). They have analyzed discharges fueled by deuterium recycled from the limiter and tritium-only neutral beam injection. In these plasmas, the DT neutron rate provides a measure of the deuterium influx into the core plasma. They find a reduced influx with plasmas using lithium pellet conditioning and with plasmas of reduced major (and minor) radius. Modeling with the DEGAS neutrals code shows that the dependence on radius can be related to the penetration of neutrals through the scrape-off layer.

  19. Hydrogen and deuterium diffusion in vanadium-titanium alloys

    SciTech Connect

    Peterson, D.T.; Herro, H.M.

    1987-02-01

    Hydrogen and deuterium diffusion coefficients were measured in vanadium-titanium alloys, containing up to 30 at. pct Ti, by Boltzmann-Matano techniques. Hydrogen and deutrium diffusivity decreased rapidly with titanium concentration. The diffusion coefficients showed an Arrhenius temperature dependence in each alloy between 230 and 473 K with activation energies that increased with titanium concentration. The diffusion coefficient decreased linearly with hydrogen concentration in all alloys. The terminal solid solubilities increased markedly with titanium concentration with deuterium showing a larger terminal solid solubility than hydrogen below ten percent titanium. The diffusion results do not fit a localized deep trapping of hydrogen by the titanium atoms.

  20. Branching fraction and time-dependent CP asymmetry in neutral B decays to psi and a neutral pion

    NASA Astrophysics Data System (ADS)

    Soha, Aron Lucas

    The invariance of physical laws under the combination of exchange of particles with antiparticles (charge conjugation, C) and reversal of coordinates (parity, P) is called CP symmetry. The violation of CP symmetry was first discovered in 1964 in the neutral kaon system, and is in general one of the great puzzles of particle physics. The recent observation of CP violation in the B meson system has been a simultaneous success for model predictions and experiment. The opportunity now exists to probe details of the underlying mechanisms. This thesis presents measurements of the branching fraction and time-dependent CP-violating asymmetry in neutral B decays to J/ y pi0. The decay amplitude for this channel features both tree and penguin diagram contributions, the interference of which can yield a result for the asymmetry differing from that found in the "golden mode" B0 → J/ yK0S . Using the measured branching fraction and CP asymmetry, constraints are placed on the ratio of penguin to tree amplitudes in B0 → J/ y pi0. In addition, the impact on the CP asymmetry measurement in B0 → J/ yK0S is discussed. The results are presented for e+ e- annihilation data collected with the BABAR detector on the Upsilon(4S) resonance at the PEP-II asymmetric-energy B Factory at SLAC. The measurement of the branching fraction, based on about 23 million BB¯ pairs collected between October 1999 and October 2000, yields BF(B0 → J/ y pi0) = (2.0 +/- 0.6 (stat) +/- 0.2 (syst)) x 10-5. With about 88 million BB¯ pairs collected during the years 1999--2002, our results for the coefficients of the cosine and sine terms of the CP asymmetry are CJ/ y pi0 = 0.38 +/- 0.41 (stat) +/- 0.09 (syst) and SJ/ y pi0 = 0.05 +/- 0.49 (stat) +/- 0.16 (syst).

  1. Study of ion-irradiated tungsten in deuterium plasma

    NASA Astrophysics Data System (ADS)

    Khripunov, B. I.; Gureev, V. M.; Koidan, V. S.; Kornienko, S. N.; Latushkin, S. T.; Petrov, V. B.; Ryazanov, A. I.; Semenov, E. V.; Stolyarova, V. G.; Danelyan, L. S.; Kulikauskas, V. S.; Zatekin, V. V.; Unezhev, V. N.

    2013-07-01

    Experimental study aimed at investigation of neutron induced damage influence on fusion reactor plasma facing materials is reported. Displacement damage was produced in tungsten by high-energy helium and carbon ions at 3-10 MeV. The reached level of displacement damage ranged from several dpa to 600 dpa. The properties of the irradiated tungsten were studied in steady-state deuterium plasma on the LENTA linear divertor simulator. Plasma exposures were made at 250 eV of ion energy to fluence 1021-1022 ion/сm2. Erosion dynamics of the damaged layer and deuterium retention were observed. Surface microstructure modifications and important damage of the 5 μm layer shown. Deuterium retention in helium-damaged tungsten (ERD) showed its complex behavior (increase or decrease) depending on implanted helium quantity and the structure of the surface layer.

  2. Deuterium chemistry in protoplanetary disks

    NASA Astrophysics Data System (ADS)

    Albertsson, T.; Semenov, D.; Henning, T.

    2011-05-01

    We have generated a extensive chemical network that includes reactions with multi-deuterated species, in which the most recent information deuterium chemistry is implemented. By implementing this chemical network with our sophisticated model, we study in detail the chemical evolution of protoplanetary disks, and compare our results with observations.

  3. Solid deuterium centrifuge pellet injector

    SciTech Connect

    Foster, C.A.

    1982-01-01

    Pellet injectors are needed to fuel long pulse tokamak plasmas and other magnetic confinement devices. For this purpose, an apparatus has been developed that forms 1.3-mm-diam pellets of frozen deuterium at a rate of 40 pellets per second and accelerates them to a speed of 1 km/s. Pellets are formed by extruding a billet of solidified deuterium through a 1.3-mm-diam nozzle at a speed of 5 cm/s. The extruding deuterium is chopped with a razor knife, forming 1.3-mm right circular cylinders of solid deuterium. The pellets are accelerated by synchronously injecting them into a high speed rotating arbor containing a guide track, which carries them from a point near the center of rotation to the periphery. The pellets leave the wheel after 150/sup 0/ of rotation at double the tip speed. The centrifuge is formed in the shape of a centrifugal catenary and is constructed of high strength KEVLAR/epoxy composite. This arbon has been spin-tested to a tip speed of 1 km/s.

  4. Solid deuterium centrifuge pellet injector

    SciTech Connect

    Foster, C.A.

    1983-04-01

    Pellet injectors are needed to fuel long pulse tokamak plasmas and other magnetic confinement devices. For this purpose, an apparatus has been developed that forms 1.3-mm-diam pellets of frozen deuterium at a rate of 40 pellets per second and accelerates them to a speed of 1 km/s. Pellets are formed by extruding a billet of solidified deuterium through a 1.3-mm-diam nozzle at a speed of 5 cm/s. The extruding deuterium is chopped with a razor knife, forming 1.3-mm right circular cylinders of solid deuterium. The pellets are accelerated by synchronously injecting them into a high speed rotating arbor containing a guide track, which carries them from a point near the center of rotation to the periphery. The pellets leave the wheel after 150/sup 0/ of rotation at double the tip speed. The centrifuge is formed in the shape of a centrifugal catenary and is constructed of high strength Kevlar/epoxy composite. This arbor has been spin-tested to a tip speed of 1 km/s.

  5. Deuterium pellet injector gun design

    SciTech Connect

    Lunsford, R.V.; Wysor, R.B.; Bryan, W.E.; Shipley, W.D.; Combs, S.K.; Foust, C.R.; Milora, S.L.; Fisher, P.W.

    1985-01-01

    The Deuterium Pellet Injector (DPI), an eight-pellet pneumatic injector, is being designed and fabricated for the Tokamak Fusion Test Reactor (TFTR). It will accelerate eight pellets, 4 by 4 mm maximum, to greater than 1500 m/s. It utilizes a unique pellet-forming mechanism, a cooled pellet storage wheel, and improved propellant gas scavenging.

  6. Exposure of Equal-Channel Angular Extruded Tungsten to Deuterium Plasma

    NASA Astrophysics Data System (ADS)

    Liu, Feng; Xu, Yuping; Zhou, Haishan; Zhao, Sixiang; Li, Bo; Lyu, Guanghong; Yuan, Yue; Hao, Ting; Luo, Guangnan

    2015-07-01

    Surface morphology and deuterium retention in ultrafine-grained tungsten fabricated by equal-channel angular pressing (ECAP) have been examined after exposure to a low energy, high-flux deuterium (D) plasma at fluences of 3×1024 D/m2 and 1×1025 D/m2 in a temperature range of 100°C-150°C. The methods used were scanning electron microscopy (SEM) and thermal desorption spectroscopy (TDS). Sparse and small blisters (∼0.1 μm) were observed by SEM after D plasma irradiation on every irradiated surface; yet they did not exhibit significant structure or plasma fluence dependence. Larger blisters or protrusions appeared after subsequent TDS heating up to 1000°C. The TDS results showed a single D desorption peak at ∼220°C for all samples and the D retention increased with increasing numbers of extrusion passes, i.e., the decrease of grain sizes. The increased D retention in this low temperature range should be attributed to the faster diffusion of D along the larger volume fraction of grain boundaries introduced by ECAP. supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2013GB105001, 2013GB105002, 2015GB109001), National Natural Science Foundation of China (Nos. 11305213, 11405201), Technological Development Grant of Hefei Science Center of CAS (No. 2014TDG-HSC003), and China National Funds for Distinguished Young Scientists (No. 51325103)

  7. Thermal desorption of deuterium implanted into beryllium

    SciTech Connect

    Markin, A.V.; Chernikov, V.N.; Zakharov, A.P.

    1995-09-01

    By means of TDS measurements it is shown that the desorption of deuterium from Be implanted with 5 keV D ions to fluences, {Phi}, from 1x10{sup 20} D/m{sup 2} to 1x10{sup 21} D/m{sup 2} proceeds in one high temperature stage B, while at {Phi} {ge} 1.2x10{sup 21}D/m{sup 2} one more stage A is added. The desorption maximum A is narrow and consists of two peaks A{sub 1} and A{sub 2} at about 460 K and 490 K, respectively. Peak A{sub 1} is attributed to the desorption of deuterium from the walls of opened channels formed under D ion implantation. Peak {sub A}2 is a consequence of the opening of a part of closed bubbles/channels to the outer surface. The position of maximum B shifts noticeably and nonsteadily on the fluence in a range from 850 to 1050 K. The origin of this maximum is the liberation of D atoms bound at vacancy complexes discussed previously by Wampler. The dependence of Tm(B) on the fluence is governed by the interaction of freely migrating D atoms with partly opened or fully closed gas cavity arrangements which are created under temperature ramping, but differently in specimens implanted with D ions to different fluences.

  8. The diffusion of muonic deuterium atoms in deuterium gas

    SciTech Connect

    Kraiman, J.B.

    1989-01-01

    Negative muons were brought to rest in a target array consisting of 30-50 parallel plastic foils coated with Au which were separated by a few mm. The interstitial volumes between the foils were filled with deuterium gas at pressures from 0.094 bar to 1.52 bar. Muons which stopped in the deuterium formed {mu}d atoms, which subsequently diffused through the gas until either the muon decayed or the {mu}d atom struck a foil surface. For {mu}d atoms impinging upon the Au layer, the muon would transfer to an Au atom, resulting in the formation of a {mu}Au atom in a highly excited state. De-excitation to the 1S ground state resulted in emission of characteristic muonic Au x rays, and after the muon was absorbed by the Au nucleus, the emission of Pt {gamma} rays. These transfer photons were detected by one of four germanium x-ray detectors adjacent to the target vessel. Analysis of the time distributions formed by collecting delayed transfer events for several sets of experimental conditions yielded information on the diffusion process of {mu}d atoms in deuterium gas.

  9. Community N and O isotope fractionation by sulfide-dependent denitrification and anammox in a stratified lacustrine water column

    NASA Astrophysics Data System (ADS)

    Wenk, Christine B.; Zopfi, Jakob; Blees, Jan; Veronesi, Mauro; Niemann, Helge; Lehmann, Moritz F.

    2014-01-01

    We investigated the community nitrogen (N) and oxygen (O) isotope effects of fixed N loss in the northern basin of Lake Lugano, where sulfide-dependent denitrification and anammox are the main drivers of suboxic N2 production. A decrease in nitrate (NO3-) concentration toward the redox transition zone (RTZ) at mid-water depth was paralleled by an increase in δ15N and δ18O from approximately 5‰ to >20‰ and from 0‰ to >10‰, respectively. Ammonium (NH4+) concentrations were highest in the near-bottom water and decreased toward the RTZ concomitant with an increase in δ15N-NH4+ from ∼7‰ to >15‰. A diffusion-reaction model yielded N and O isotope enrichment factors that are significantly smaller than isotope effects reported previously for microbial NO3- reduction and NH4+ oxidation (15εNO3 ≈ 10‰, 18εNO3 ≈ 7‰, and 15εNH4 ≈ 10-12‰). For the Lake Lugano north basin, we constrain the apparent under-expression of the N isotope effects to: (1) environmental conditions (e.g., substrate limitation, low cell specific N transformation rates), or (2) low process-specific (chemolithotrophic denitrification and anammox) isotope fractionation. Our results have confirmed the robust nature of the co-linearity between N and O isotope enrichment during microbial denitrification beyond its organotrophic mode. However, the ratio of 18O to 15N enrichment (18εNO3:15εNO3) associated with NO3- reduction in the RTZ was ∼0.89, which is lower than observed in marine environments and in most culture experiments. We propose that chemolithotrophic NO3- reduction in the Lake Lugano north basin was partly catalyzed by the periplasmic dissimilatory nitrate reductase (Nap) (rather than the membrane-bound dissimilatory Nar), which is known to express comparably low 18εNO3:15εNO3 ratios in the ambient NO3- pool. However, NO2- re-oxidation, e.g., during anammox or microaerobic nitrification, could have contributed to the lowered 18O to 15N enrichment ratios. Although

  10. Laser spectroscopy of muonic deuterium

    NASA Astrophysics Data System (ADS)

    Pohl, Randolf; Nez, François; Fernandes, Luis M. P.; Amaro, Fernando D.; Biraben, François; Cardoso, João M. R.; Covita, Daniel S.; Dax, Andreas; Dhawan, Satish; Diepold, Marc; Giesen, Adolf; Gouvea, Andrea L.; Graf, Thomas; Hänsch, Theodor W.; Indelicato, Paul; Julien, Lucile; 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; Rabinowitz, Paul; dos Santos, Joaquim M. F.; Schaller, Lukas A.; Schuhmann, Karsten; Schwob, Catherine; Taqqu, David; Veloso, João F. C. A.; Antognini, Aldo

    2016-08-01

    The deuteron is the simplest compound nucleus, composed of one proton and one neutron. Deuteron properties such as the root-mean-square charge radius rd and the polarizability serve as important benchmarks for understanding the nuclear forces and structure. Muonic deuterium μd is the exotic atom formed by a deuteron and a negative muon μ–. We measured three 2S-2P transitions in μd and obtain rd = 2.12562(78) fm, which is 2.7 times more accurate but 7.5σ smaller than the CODATA-2010 value rd = 2.1424(21) fm. The μd value is also 3.5σ smaller than the rd value from electronic deuterium spectroscopy. The smaller rd, when combined with the electronic isotope shift, yields a “small” proton radius rp, similar to the one from muonic hydrogen, amplifying the proton radius puzzle.

  11. Laser spectroscopy of muonic deuterium.

    PubMed

    Pohl, Randolf; Nez, François; Fernandes, Luis M P; Amaro, Fernando D; Biraben, François; Cardoso, João M R; Covita, Daniel S; Dax, Andreas; Dhawan, Satish; Diepold, Marc; Giesen, Adolf; Gouvea, Andrea L; Graf, Thomas; Hänsch, Theodor W; Indelicato, Paul; Julien, Lucile; 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; Rabinowitz, Paul; dos Santos, Joaquim M F; Schaller, Lukas A; Schuhmann, Karsten; Schwob, Catherine; Taqqu, David; Veloso, João F C A; Antognini, Aldo

    2016-08-12

    The deuteron is the simplest compound nucleus, composed of one proton and one neutron. Deuteron properties such as the root-mean-square charge radius rd and the polarizability serve as important benchmarks for understanding the nuclear forces and structure. Muonic deuterium μd is the exotic atom formed by a deuteron and a negative muon μ(-). We measured three 2S-2P transitions in μd and obtain r(d) = 2.12562(78) fm, which is 2.7 times more accurate but 7.5σ smaller than the CODATA-2010 value r(d) = 2.1424(21) fm. The μd value is also 3.5σ smaller than the r(d) value from electronic deuterium spectroscopy. The smaller r(d), when combined with the electronic isotope shift, yields a "small" proton radius r(p), similar to the one from muonic hydrogen, amplifying the proton radius puzzle. PMID:27516595

  12. Conditional dependence of evaporative fraction on surface and root-zone soil moisture and its application to soil moisture retrieval

    NASA Astrophysics Data System (ADS)

    Ryu, D.; Akuraju, V.

    2013-12-01

    Thermal infrared (TIR) or evapotranspiration (ET) estimates from space have been gaining growing attention as an input to retrieve root-zone soil moisture. The rationale behind the approach is that i) there exists a strong causal link between the evapotranspiration and the vegetation canopy temperature and ii) under water-limited conditions soil water available for transpiration controls the evaporative fraction (EF) or the actual evapotranspiration (AET) to potential evapotranspiration (PET) ratio of vegetated surfaces. In this work, we examine the relationship between EF and surface to root-zone soil moisture content collected from two study sites (wheat and pasture fields) at the Dookie research farm site in Victoria, Australia. EF estimated from the eddy covariance system is compared with soil moisture content under various ranges of soil depths (5 depths from surface to 120 cm), net radiation, soil wetness and biomass. In both wheat and pasture fields, EF is highly correlated with surface (0-8 cm) soil moisture when the soil surface is bare-to-lightly vegetated, but the correlation decreases as vegetation grows or as the net radiation decreases. On the other hand, EF shows strong correlation with root-zone soil moisture during the growing seasons of the fields. Under similar ranges of soil moisture and net radiation, EF can have different ranges depending on the vegetation height and density. These results indicate the importance of biophysical parameters and processes in estimating surface and root-zone soil moisture contents using surface energy flux. We propose an exponential and a spherical model to fit EF versus soil moisture and show how their uncertainty changes with biophysical parameters.

  13. Depletion of GSH in human blood plasma and cytosolic fraction during cadmium toxicity is temperature and pH dependent.

    PubMed

    Ullah, Hashmat; Khan, Muhammad Farid; Jan, Syed Umer; Hashmat, Farwa

    2016-01-01

    Toxicities of heavy metals is a burning issue and a topic of interest among the toxicologists throughout the world. Metals are always in use of man since long but in recent years the use of cadmium has increased in the form of various cadmium compounds such as cadmium compounds as stabilizers in plastic pipe industries and in the preparations of different alloys etc. Cadmium is even used in phosphate fertilizers and thus comes directly or indirectly in contact with human eatables like crops, vegetables and fruits. Once it is absorbed it affects almost all the organs and systems of human body especially blood components and kidneys. Always the chemical reactions of different chemicals are dependent on some influential factors, among these factors the effect of pH and temperature of the media in which these chemicals interact with each other are very much important. Keeping in view this fact we have evaluated the effect of cadmium nitrate tetra hydrate on GSH of human plasma and cytosolic fraction. Estimation of thiol was done by Ellman's modified method and was found that the interaction of cadmium nitrate tetra hydrate and GSH of these blood components was more at a pH and temperature, which were near to physiological pH and temperature of human body. This fact was proved as the estimated thiol concentration left after the interaction of cadmium nitrate tetra hydrate and thiol of these blood components was minimum at pH and temperature near to human blood pH and temperature. We concluded that the possible reason for depletion of GSH of these blood components was conversion of GSH into Cd(SG) (2) and/or GSSG formation. PMID:26826820

  14. Geographic origin determination of heroin and cocaine using site-specific isotopic ratio deuterium NMR

    PubMed

    Hays; Remaud; Jamin; Martin

    2000-05-01

    SNIF-NMR (Site-specific natural isotopic fractionation measured by deuterium NMR) was employed on 36 heroin samples from seven different known origins, and two cocaine samples from two different known origins. Heroin has two "synthetic" deuterium labeled sites (the two acetyls from acetic anhydride, each representing three equivalent nuclei) and 15 "natural" deuterium labeled sites (originating from the morphine produced in the opium plant). The "natural" sites have the potential for determining geographic location of the original opium plant, while the "synthetic" sites could assist in giving information about the commercial source of acetic anhydride used to convert morphine to heroin. Cocaine has 15 "natural" deuterium labeled sites. This study shows that SNIF-NMR has some use in determining the geographic origin of heroin and also has good potential for determining the geographical origin of cocaine. PMID:10855958

  15. Deuterium gas-puff Z-pinch implosions on the Z accelerator

    SciTech Connect

    Coverdale, C. A.; Deeney, C.; Ruiz, C. L.; Velikovich, A. L.; Davis, J.; Clark, R. W.; Chong, Y. K.; Apruzese, J. P.; Chittenden, J.; Chantrenne, S.; Franklin, J.; LePell, P. D.; Cooper, G. W.; Nelson, A. J.; Levine, J.; Banister, J.

    2007-05-15

    Experiments on the Z accelerator with deuterium gas-puff implosions have produced up to 3.7x10{sup 13} ({+-}20%) neutrons at 2.34 MeV ({+-}0.10 MeV). Although the mechanism for generating these neutrons was not definitively identified, this neutron output is 100 times more than previously observed from neutron-producing experiments at Z. Dopant gases in the deuterium (argon and chlorine) were used to study implosion characteristics and stagnated plasma conditions through x-ray yield measurements and spectroscopy. Magnetohydrodynamic (MHD) calculations have suggested that the dopants improved the neutron output through better plasma compression, which has been studied in experiments increasing the dopant fraction. Scaling these experiments, and additional MHD calculations, suggest that {approx}5x10{sup 14} deuterium-deuterium (DD) neutrons could be generated at the 26-MA refurbished Z facility.

  16. Single crystal diamond detector measurements of deuterium-deuterium and deuterium-tritium neutrons in Joint European Torus fusion plasmas

    SciTech Connect

    Cazzaniga, C. Gorini, G.; Nocente, M.; Sundén, E. Andersson; Binda, F.; Ericsson, G.; Croci, G.; Grosso, G.; Cippo, E. Perelli; Tardocchi, M.; Giacomelli, L.; Rebai, M.; Griesmayer, E.; Kaveney, G.; Syme, B.; Collaboration: JET-EFDA Contributors

    2014-04-15

    First simultaneous measurements of deuterium-deuterium (DD) and deuterium-tritium neutrons from deuterium plasmas using a Single crystal Diamond Detector are presented in this paper. The measurements were performed at JET with a dedicated electronic chain that combined high count rate capabilities and high energy resolution. The deposited energy spectrum from DD neutrons was successfully reproduced by means of Monte Carlo calculations of the detector response function and simulations of neutron emission from the plasma, including background contributions. The reported results are of relevance for the development of compact neutron detectors with spectroscopy capabilities for installation in camera systems of present and future high power fusion experiments.

  17. Single crystal diamond detector measurements of deuterium-deuterium and deuterium-tritium neutrons in Joint European Torus fusion plasmas

    NASA Astrophysics Data System (ADS)

    Cazzaniga, C.; Sundén, E. Andersson; Binda, F.; Croci, G.; Ericsson, G.; Giacomelli, L.; Gorini, G.; Griesmayer, E.; Grosso, G.; Kaveney, G.; Nocente, M.; Cippo, E. Perelli; Rebai, M.; Syme, B.; Tardocchi, M.

    2014-04-01

    First simultaneous measurements of deuterium-deuterium (DD) and deuterium-tritium neutrons from deuterium plasmas using a Single crystal Diamond Detector are presented in this paper. The measurements were performed at JET with a dedicated electronic chain that combined high count rate capabilities and high energy resolution. The deposited energy spectrum from DD neutrons was successfully reproduced by means of Monte Carlo calculations of the detector response function and simulations of neutron emission from the plasma, including background contributions. The reported results are of relevance for the development of compact neutron detectors with spectroscopy capabilities for installation in camera systems of present and future high power fusion experiments.

  18. Deuterium Abundance in Consciousness and Current Cosmology

    NASA Astrophysics Data System (ADS)

    Rauscher, Elizabeth A.

    We utilize the deuterium-hydrogen abundances and their role in setting limits on the mass and other conditions of cosmogenesis and cosmological evolution. We calculate the dependence of a set of physical variables such as density, temperature, energy mass, entropy and other physical variable parameters through the evolution of the universe under the Schwarzschild conditions as a function from early to present time. Reconciliation with the 3°K and missing mass is made. We first examine the Schwarzschild condition; second, the geometrical constraints of a multidimensional Cartesian space on closed cosmologies, and third we will consider the cosmogenesis and evolution of the universe in a multidimensional Cartesian space, obeying the Schwarzschild condition. Implications of this model for matter creation are made. We also examine experimental evidence for closed versus open cosmologies; x-ray detection of the "missing mass" density. Also the interstellar deuterium abundance, along with the value of the Hubble constant set a general criterion on the value of the curvature constant, k. Once the value of the Hubble constant, H is determined, the deuterium abundance sets stringent restrictions on the value of the curvature constant k by an detailed discussion is presented. The experimental evidences for the determination of H and the primary set of coupled equations to determine D abundance is given. 'The value of k for an open, closed, or flat universe will be discussed in terms of the D abundance which will affect the interpretation of the Schwarzschild, black hole universe. We determine cosmology solutions to Einstein's field obeying the Schwarzschild solutions condition. With this model, we can form a reconciliation of the black hole, from galactic to cosmological scale. Continuous creation occurs at the dynamic blackhole plasma field. We term this new model the multiple big bang or "little whimper model". We utilize the deuteriumhydrogen abundances and their role in

  19. Mass-dependent sulfur isotope fractionation during reoxidative sulfur cycling: A case study from Mangrove Lake, Bermuda

    NASA Astrophysics Data System (ADS)

    Pellerin, André; Bui, Thi Hao; Rough, Mikaella; Mucci, Alfonso; Canfield, Donald E.; Wing, Boswell A.

    2015-01-01

    The multiple sulfur isotope composition of porewater sulfate from the anoxic marine sapropel of Mangrove Lake, Bermuda was measured in order to establish how multiple sulfur isotopes are fractionated during reoxidative sulfur cycling. The porewater-sulfate δ34S and Δ33S dataset exhibits the distinct isotopic signatures of microbial sulfate reduction and sulfur reoxidation. We reproduced the measurements with a simple diagenetic model that yielded fractionation factors for net sulfate removal of between -29.2‰ and -32.5‰. A new approach to isotopic modeling of the sulfate profiles, informed by the chemistry of sulfur intermediate compounds in Mangrove Lake, reveals that sulfate reduction produces a relatively small intrinsic fractionation and that an active reoxidative sulfur cycle increases the fractionation of the measured values. Based on the model results, the reoxidative cycle of Mangrove Lake appears to include sulfide oxidation to elemental sulfur followed by the disproportionation of the elemental sulfur to sulfate and sulfide. This model also indicates that the reoxidative sulfur cycle of Mangrove Lake turns over from 50 to 80% of the sulfide produced by microbial sulfate reduction. The Mangrove Lake case study shows how sulfur isotope fractionations can be separated into three different "domains" in Δ33S-δ34S space based on their ability to resolve reductive and reoxidative sulfur transformations. The first domain that differentiates reductive and reoxidative sulfur cycling is well illustrated by previous studies and requires 34S-32S fractionations more negative than ≈-70‰, beyond the fractionation limit of microbial sulfate reduction at earth surface temperatures. The second domain that distinguishes reductive and reoxidative processes is between 34S-32S fractionations of -40‰ and 0‰, where the 33S-32S fractionations of sulfate reduction and reoxidation are significantly different. In the remaining domain (between 34S-32S fractionations

  20. Low deuterium content of Lake Vanda, Antarctica

    USGS Publications Warehouse

    Ragotzkie, R.A.; Friedman, I.

    1965-01-01

    Lake Vanda in Victoria Land, Antarctica, is permanently ice-covered and permanently stratified, with warm, salty water near the bottom. Deuterium analyses of lake water from several levels indicate that the lake has a low deuterium content, and that it is stratified with respect to this isotope. This low deuterium content supports the evidence from the lake's ionic content that the saline layer is not of marine origin, and it indicates that evaporation from the ice surface has taken place. The stratification of the lake with respect to deuterium suggests that the upper and lower layers of water were formed at different times from different sources of glacial melt water.

  1. Mass dependent fractionation of stable chromium isotopes in mare basalts: Implications for the formation and the differentiation of the Moon

    NASA Astrophysics Data System (ADS)

    Bonnand, Pierre; Parkinson, Ian J.; Anand, Mahesh

    2016-02-01

    We present the first stable chromium isotopic data from mare basalts in order to investigate the similarity between the Moon and the Earth's mantle. A double spike technique coupled with MC-ICP-MS measurements was used to analyse 19 mare basalts, comprising high-Ti, low-Ti and KREEP-rich varieties. Chromium isotope ratios (δ53Cr) for mare basalts are positively correlated with indices of magmatic differentiation such as Mg# and Cr concentration which suggests that Cr isotopes were fractionated during magmatic differentiation. Modelling of the results provides evidence that spinel and pyroxene are the main phases controlling the Cr isotopic composition during fractional crystallisation. The most evolved samples have the lightest isotopic compositions, complemented by cumulates that are isotopically heavy. Two hypotheses are proposed to explain this fractionation: (i) equilibrium fractionation where heavy isotopes are preferentially incorporated into the spinel lattice and (ii) a difference in isotopic composition between Cr2+ and Cr3+ in the melt. However, both processes require magmatic temperatures below 1200 °C for appreciable Cr3+ to be present at the low oxygen fugacities found in the Moon (IW -1 to -2 log units). There is no isotopic difference between the most primitive high-Ti, low-Ti and KREEP basalts, which suggest that the sources of these basalts were homogeneous in terms of stable Cr isotopes. The least differentiated sample in our sample set is the low-Ti basalt 12016, characterised by a Cr isotopic composition of -0.222 ± 0.025‰, which is within error of the current BSE value (-0.124 ± 0.101‰). The similarity between the mantles of the Moon and Earth is consistent with a terrestrial origin for a major fraction of the lunar Cr. This similarity also suggests that Cr isotopes were not fractionated by core formation on the Moon.

  2. Deuterium accelerator experiments for APT.

    SciTech Connect

    Causey, Rion A. (Sandia National Laboratories, Livermore, CA); Hertz, Kristin L. (Sandia National Laboratories, Livermore, CA); Cowgill, Donald F. (Sandia National Laboratories, Livermore, CA)

    2005-08-01

    Sandia National Laboratories in California initiated an experimental program to determine whether tritium retention in the tube walls and permeation through the tubes into the surrounding coolant water would be a problem for the Accelerator Production of Tritium (APT), and to find ways to mitigate the problem, if it existed. Significant holdup in the tube walls would limit the ability of APT to meet its production goals, and high levels of permeation would require a costly cleanup system for the cooling water. To simulate tritium implantation, a 200 keV accelerator was used to implant deuterium into Al 6061-T and SS3 16L samples at temperatures and particle fluxes appropriate for APT, for times varying between one week and five months. The implanted samples were characterized to determine the deuterium retention and Permeation. During the implantation, the D(d,p)T nuclear reaction was used to monitor the build-up of deuterium in the implant region of the samples. These experiments increased in sophistication, from mono-energetic deuteron implants to multi-energetic deuteron and proton implants, to more accurately reproduce the conditions expected in APT. Micron-thick copper, nickel, and anodized aluminum coatings were applied to the front surface of the samples (inside of the APT walls) in an attempt to lower retention and permeation. The reduction in both retention and permeation produced by the nickel coatings, and the ability to apply them to the inside of the APT tubes, indicate that both nickel-coated Al 6061-T6 and nickel-coated SS3 16L tubes would be effective for use in APT. The results of this work were submitted to the Accelerator Production of Tritium project in document number TPO-E29-Z-TNS-X-00050, APT-MP-01-17.

  3. Was Venus wet? Deuterium reconsidered

    NASA Technical Reports Server (NTRS)

    Grinspoon, David H.

    1987-01-01

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

  4. Retention behavior in tungsten and molybdenum exposed to high fluences of deuterium ions in TPE

    SciTech Connect

    J.P. Sharpe; R.D. Kolasinski; M. Shimada; P. Calderoni; R.A. Causey

    2009-06-01

    The Tritium Plasma Experiment (TPE) has been used to investigate deuterium fuel retention behavior in tungsten and molybdenum– materials utilized for plasma-facing surfaces in some existing tokamak plasma devices and under consideration for future devices. Although several studies have been performed over the past several years on these metals, many issues remain unresolved, including for example blister formation mechanisms and correlation to surface conditions. In this study we expose several metal samples to deuterium ion fluences up to 1026 ions/m2 and measure retention behavior with thermal desportion spectroscopy. Fractional retention of up to 2.0×10-5 is found for W at 600 K, and Mo similarly retains deuterium at a fraction of 1.5×10-5 at 600 K. Blistering was found for W samples exposed at temperatures above 453 K, whereas blistering was not observed for Mo samples at any experiment temperature.

  5. Ion-induced deuterium retention in tungsten coatings on carbon substrate

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    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 μm 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 μm thickness produced by combined magnetron-sputtering and ion implantation technique is higher compared to physical vapour deposited W coating of 4-5 μm thickness and 200 μm thickness plasma-sprayed W coating for all investigated energies and sample temperatures up to 650 K.

  6. Fundamental aspects of deuterium retention in tungsten at high flux plasma exposure

    SciTech Connect

    Ogorodnikova, O. V.

    2015-08-21

    An effect of enhanced trapping of deuterium in tungsten at high flux was discovered. It was shown analytically and confirmed experimentally that the deuterium trapping in a presence of high density of defects in tungsten (W) depends on the ion energy and ion flux. Newly developed analytical model explains experimentally observed discrepancy of deuterium trapping at radiation-induced defects in tungsten at different ion fluxes that significantly improves a prediction of hydrogen isotope accumulation in different plasma devices, including ITER and DEMO. The developed model can be used for many system of hydrogen in a metal in both normal and extreme environments (high fluxes, elevated temperatures, neutron irradiation, etc.). This new model allows, for the first time, to validate density function theory (DFT) predictions of multiple occupation of a defect with deuterium against experimental data that bridge the gap in length and time scale between DFT calculations and experiments. By comparing first-principle calculations based on DFT and semi-empirical “adsorption model,” it was proved that the mechanism of hydrogen isotope trapping in a vacancy cluster is similar to a chemisorption on a surface. Binding energies of deuterium with different types of defects in W were defined. Moreover, the surface barrier of deuterium to be chemisorbed on a clean W surface was found to be less than 1 eV and kinetics of deuterium release is limited by de-trapping from defects rather than to be limited by surface effects.

  7. Deuterium chemistry in the Orion Bar PDR. ``Warm'' chemistry starring CH{2}D^+

    NASA Astrophysics Data System (ADS)

    Parise, B.; Leurini, S.; Schilke, P.; Roueff, E.; Thorwirth, S.; Lis, D. C.

    2009-12-01

    Context: High levels of deuterium fractionation in gas-phase molecules are usually associated with cold regions, such as prestellar cores. Significant fractionation ratios are also observed in hot environments such as hot cores or hot corinos, where they are believed to be produced by the evaporation of the icy mantles surrounding dust grains, and are thus remnants of a previous cold (either gas-phase or grain surface) chemistry. The recent detection of DCN towards the Orion Bar, in a clump at a characteristic temperature of 70 K, has shown that high deuterium fractionation can also be detected in PDRs. The Orion Bar clumps thus appear to be a good environment for the observational study of deuterium fractionation in luke warm gas, allowing us to validate chemistry models for a different temperature range, where dominating fractionation processes are predicted to differ from those in cold gas (<20 K). Aims: We aimed to study observationally in detail the chemistry at work in the Orion Bar PDR, to understand whether DCN is either produced by ice mantle evaporation or is the result of warm gas-phase chemistry, involving the CH2D+ precursor ion (which survives higher temperatures than the usual H2D+ precursor). Methods: Using the APEX and the IRAM 30 m telescopes, we targeted selected deuterated species towards two clumps in the Orion Bar. Results: We confirmed the detection of DCN and detected two new deuterated molecules (DCO+ and HDCO) towards one clump in the Orion Bar PDR. Significant deuterium fractionations are found for HCN and H2CO, but we measured a low fractionation in HCO^+. We also provide upper limits to other molecules relevant to deuterium chemistry. Conclusions: We argue that grain evaporation in the clumps is unlikely to be a dominant process, and we find that the observed deuterium fractionation ratios are consistent with predictions of pure gas-phase chemistry models at warm temperatures (T ~ 50 K). We show evidence that warm deuterium chemistry

  8. Vanadium hydride deuterium-tritium generator

    DOEpatents

    Christensen, Leslie D.

    1982-01-01

    A pressure controlled vanadium hydride gas generator to provide deuterium-tritium gas in a series of pressure increments. A high pressure chamber filled with vanadium-deuterium-tritium hydride is surrounded by a heater which controls the hydride temperature. The heater is actuated by a power controller which responds to the difference signal between the actual pressure signal and a programmed pressure signal.

  9. Measurement of time-dependent CP asymmetries and the CP-odd fraction in the decay B0-->D(*+)D(*-).

    PubMed

    Aubert, B; Barate, R; Boutigny, D; Gaillard, J-M; Hicheur, A; Karyotakis, Y; Lees, J P; Robbe, P; Tisserand, V; Zghiche, A; Palano, A; Pompili, A; Chen, J C; Qi, N D; Rong, G; Wang, P; Zhu, Y S; Eigen, G; Ofte, I; Stugu, B; Abrams, G S; Borgland, A W; Breon, A B; Brown, D N; Button-Shafer, J; Cahn, R N; Charles, E; Day, C T; Gill, M S; Gritsan, A V; Groysman, Y; Jacobsen, R G; Kadel, R W; Kadyk, J; Kerth, L T; Kolomensky, Yu G; Kral, J F; Kukartsev, G; LeClerc, C; Levi, M E; Lynch, G; Mir, L M; Oddone, P J; Orimoto, T J; Pripstein, M; Roe, N A; Romosan, A; Ronan, M T; Shelkov, V G; Telnov, A V; Wenzel, W A; Ford, K; Harrison, T J; Hawkes, C M; Knowles, D J; Morgan, S E; Penny, R C; Watson, A T; Watson, N K; Deppermann, T; Goetzen, K; Koch, H; Lewandowski, B; Pelizaeus, M; Peters, K; Schmuecker, H; Steinke, M; Barlow, N R; Boyd, J T; Chevalier, N; Cottingham, W N; Kelly, M P; Latham, T E; Mackay, C; Wilson, F F; Abe, K; Cuhadar-Donszelmann, T; Hearty, C; Mattison, T S; McKenna, J A; Thiessen, D; Kyberd, P; McKemey, A K; Blinov, V E; Bukin, A D; Golubev, V B; Ivanchenko, V N; Kravchenko, E A; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Yushkov, A N; Best, D; Chao, M; Kirkby, D; Lankford, A J; Mandelkern, M; McMahon, S; Mommsen, R K; Roethel, W; Stoker, D P; Buchanan, C; del Re, D; Hadavand, H K; Hill, E J; MacFarlane, D B; Paar, H P; Rahatlou, Sh; Schwanke, U; Sharma, V; Berryhill, J W; Campagnari, C; Dahmes, B; Kuznetsova, N; Levy, S L; Long, O; Lu, A; Mazur, M A; Richman, J D; Verkerke, W; Beck, T W; Beringer, J; Eisner, A M; Heusch, C A; Lockman, W S; Schalk, T; Schmitz, R E; Schumm, B A; Seiden, A; Turri, M; Walkowiak, W; Williams, D C; Wilson, M G; Albert, J; Chen, E; Dubois-Felsmann, G P; Dvoretskii, A; Hitlin, D G; Narsky, I; Porter, F C; Ryd, A; Samuel, A; Yang, S; Jayatilleke, S; Mancinelli, G; Meadows, B T; Sokoloff, M D; Abe, T; Barillari, T; Blanc, F; Bloom, P; Chen, S; Clark, P J; Ford, W T; Nauenberg, U; Olivas, A; Rankin, P; Roy, J; Smith, J G; van Hoek, W C; Zhang, L; Harton, J L; Hu, T; Soffer, A; Toki, W H; Wilson, R J; Zhang, J; Altenburg, D; Brandt, T; Brose, J; Colberg, T; Dickopp, M; Dubitzky, R S; Hauke, A; Lacker, H M; Maly, E; Müller-Pfefferkorn, R; Nogowski, R; Otto, S; Schubert, K R; Schwierz, R; Spaan, B; Wilden, L; Bernard, D; Bonneaud, G R; Brochard, F; Cohen-Tanugi, J; Thiebaux, Ch; Vasileiadis, G; Verderi, M; Khan, A; Lavin, D; Muheim, F; Playfer, S; Swain, J E; Tinslay, J; Andreotti, M; Azzolini, V; Bettoni, D; Bozzi, C; Calabrese, R; Cibinetto, G; Luppi, E; Negrini, M; Piemontese, L; Sarti, A; Treadwell, E; Anulli, F; Baldini-Ferroli, R; Calcaterra, A; de Sangro, R; Falciai, D; Finocchiaro, G; Patteri, P; Peruzzi, I M; Piccolo, M; Zallo, A; Buzzo, A; Contri, R; Crosetti, G; Lo Vetere, M; Macri, M; Monge, M R; Passaggio, S; Pastore, F C; Patrignani, C; Robutti, E; Santroni, A; Tosi, S; Bailey, S; Morii, M; Bhimji, W; Bowerman, D A; Dauncey, P D; Egede, U; Eschrich, I; Gaillard, J R; Morton, G W; Nash, J A; Sanders, P; Taylor, G P; Grenier, G J; Lee, S-J; Mallik, U; Cochran, J; Crawley, H B; Lamsa, J; Meyer, W T; Prell, S; Rosenberg, E I; Yi, J; Davier, M; Grosdidier, G; Höcker, A; Laplace, S; Le Diberder, F; Lepeltier, V; Lutz, A M; Petersen, T C; Plaszczynski, S; Schune, M H; Tantot, L; Wormser, G; Brigljević, V; Cheng, C H; Lange, D J; Wright, D M; Bevan, A J; Coleman, J P; Fry, J R; Gabathuler, E; Gamet, R; Kay, M; Parry, R J; Payne, D J; Sloane, R J; Touramanis, C; Back, J J; Harrison, P F; Shorthouse, H W; Strother, P; Vidal, P B; Brown, C L; Cowan, G; Flack, R L; Flaecher, H U; George, S; Green, M G; Kurup, A; Marker, C E; McMahon, T R; Ricciardi, S; Salvatore, F; Vaitsas, G; Winter, M A; Brown, D; Davis, C L; Allison, J; Barlow, R J; Hart, P A; Forti, A C; Jackson, F; Lafferty, G D; Lyon, A J; Weatherall, J H; Williams, J C; Farbin, A; Jawahery, A; Kovalskyi, D; Lae, C K; Lillard, V; Roberts, D A; Blaylock, G; Dallapiccola, C; Flood, K T; Hertzbach, S S; Kofler, R; Koptchev, V B; Moore, T B; Saremi, S; Staengle, H; Willocq, S; Cowan, R; Sciolla, G; Taylor, F; Yamamoto, R K; Mangeol, D J J; Milek, M; Patel, P M; Lazzaro, A; Palombo, F; Bauer, J M; Cremaldi, L; Eschenburg, V; Godang, R; Kroeger, R; Reidy, J; Sanders, D A; Summers, D J; Zhao, H W; Hast, C; Taras, P; Nicholson, H; Cartaro, C; Cavallo, N; De Nardo, G; Fabozzi, F; Gatto, C; Lista, L; Paolucci, P; Piccolo, D; Sciacca, C; Baak, M A; Raven, G; LoSecco, J M; Gabriel, T A; Brau, B; Pulliam, T; Wong, Q K; Brau, J; Frey, R; Potter, C T; Sinev, N B; Strom, D; Torrence, E; Colecchia, F; Dorigo, A; Galeazzi, F; Margoni, M; Morandin, M; Posocco, M; Rotondo, M; Simonetto, F; Stroili, R; Tiozzo, G; Voci, C; Benayoun, M; Briand, H; Chauveau, J; David, P; de la Vaissière, Ch; Del Buono, L; Hamon, O; John, M J J; Leruste, Ph; Ocariz, J; Pivk, M; Roos, L; Stark, J; T'Jampens, S; Therin, G; Manfredi, P F; Re, V; Gladney, L; Guo, Q H; Panetta, J; Angelini, C; Batignani, G; Bettarini, S; Bondioli, M; Bucci, F; Calderini, G; Carpinelli, M; Forti, F; Giorgi, M A; Lusiani, A; Marchiori, G; Martinez-Vidal, F; Morganti, M; Neri, N; Paoloni, E; Rama, M; Rizzo, G; Sandrelli, F; Walsh, J; Haire, M; Judd, D; Paick, K; Wagoner, D E; Danielson, N; Elmer, P; Lu, C; Miftakov, V; Olsen, J; Smith, A J S; Tanaka, H A; Varnes, E W; Bellini, F; Cavoto, G; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Mazzoni, M A; Morganti, S; Pierini, M; Piredda, G; Safai Tehrani, F; Voena, C; Christ, S; Wagner, G; Waldi, R; Adye, T; De Groot, N; Franek, B; Geddes, N I; Gopal, G P; Olaiya, E O; Xella, S M; Aleksan, R; Emery, S; Gaidot, A; Ganzhur, S F; Giraud, P-F; Hamel de Monchenault, G; Kozanecki, W; Langer, M; London, G W; Mayer, B; Schott, G; Vasseur, G; Yeche, Ch; Zito, M; Purohit, M V; Weidemann, A W; Yumiceva, F X; Aston, D; Bartoldus, R; Berger, N; Boyarski, A M; Buchmueller, O L; Convery, M R; Coupal, D P; Dong, D; Dorfan, J; Dujmic, D; Dunwoodie, W; Field, R C; Glanzman, T; Gowdy, S J; Grauges-Pous, E; Hadig, T; Halyo, V; Hryn'ova, T; Innes, W R; Jessop, C P; Kelsey, M H; Kim, P; Kocian, M L; Langenegger, U; Leith, D W G S; Luitz, S; Luth, V; Lynch, H L; Marsiske, H; Menke, S; Messner, R; Muller, D R; O'Grady, C P; Ozcan, V E; Perazzo, A; Perl, M; Petrak, S; Ratcliff, B N; Robertson, S H; Roodman, A; Salnikov, A A; Schindler, R H; Schwiening, J; Simi, G; Snyder, A; Soha, A; Stelzer, J; Su, D; Sullivan, M K; Va'vra, J; Wagner, S R; Weaver, M; Weinstein, A J R; Wisniewski, W J; Wright, D H; Young, C C; Burchat, P R; Edwards, A J; Meyer, T I; Roat, C; Ahmed, S; Alam, M S; Ernst, J A; Saleem, M; Wappler, F R; Bugg, W; Krishnamurthy, M; Spanier, S M; Eckmann, R; Kim, H; Ritchie, J L; Schwitters, R F; Izen, J M; Kitayama, I; Lou, X C; Ye, S; Bianchi, F; Bona, M; Gallo, F; Gamba, D; Borean, C; Bosisio, L; Della Ricca, G; Dittongo, S; Grancagnolo, S; Lanceri, L; Poropat, P; Vitale, L; Vuagnin, G; Panvini, R S; Banerjee, Sw; Brown, C M; Fortin, D; Jackson, P D; Kowalewski, R; Roney, J M; Band, H R; Dasu, S; Datta, M; Eichenbaum, A M; Hu, H; Johnson, J R; Kutter, P E; Li, H; Liu, R; Di Lodovico, F; Mihalyi, A; Mohapatra, A K; Pan, Y; Prepost, R; Sekula, S J; von Wimmersperg-Toeller, J H; Wu, J; Wu, S L; Yu, Z; Neal, H

    2003-09-26

    We present a measurement of time-dependent CP asymmetries and an updated determination of the CP-odd fraction in the decay B0-->D(*+)D(*-) using a data sample of 88x10(6)BB pairs collected by the BABAR detector at the PEP-II B Factory at SLAC. We determine the CP-odd fraction to be 0.063+/-0.055(stat)+/-0.009(syst). The time-dependent CP asymmetry parameters Im(lambda(+)) and /lambda(+)/ are determined to be 0.05+/-0.29(stat)+/-0.10(syst) and 0.75+/-0.19(stat)+/-0.02(syst), respectively. The standard model predicts these parameters to be -sin(2beta and 1, respectively, in the absence of penguin diagram contributions. PMID:14525298

  10. Measurement of time-dependent CP asymmetries and the CP-odd fraction in the decay B0-->D*+D*-.

    PubMed

    Aubert, B; Barate, R; Boutigny, D; Couderc, F; Karyotakis, Y; Lees, J P; Poireau, V; Tisserand, V; Zghiche, A; Grauges, E; Palano, A; Pappagallo, M; Pompili, A; Chen, J C; Qi, N D; Rong, G; Wang, P; Zhu, Y S; Eigen, G; Ofte, I; Stugu, B; Abrams, G S; Battaglia, M; Breon, A B; Brown, D N; Button-Shafer, J; Cahn, R N; Charles, E; Day, C T; Gill, M S; Gritsan, A V; Groysman, Y; Jacobsen, R G; Kadel, R W; Kadyk, J; Kerth, L T; Kolomensky, Yu G; Kukartsev, G; Lynch, G; Mir, L M; Oddone, P J; Orimoto, T J; Pripstein, M; Roe, N A; Ronan, M T; Wenzel, W A; Barrett, M; Ford, K E; Harrison, T J; Hart, A J; Hawkes, C M; Morgan, S E; Watson, A T; Fritsch, M; Goetzen, K; Held, T; Koch, H; Lewandowski, B; Pelizaeus, M; Peters, K; Schroeder, T; Steinke, M; Boyd, J T; Burke, J P; Chevalier, N; Cottingham, W N; Kelly, M P; Cuhadar-Donszelmann, T; Fulsom, B G; Hearty, C; Knecht, N S; Mattison, T S; McKenna, J A; Khan, A; Kyberd, P; Saleem, M; Teodorescu, L; Blinov, A E; Blinov, V E; Bukin, A D; Druzhinin, V P; Golubev, V B; Kravchenko, E A; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Yushkov, A N; Best, D; Bondioli, M; Bruinsma, M; Chao, M; Eschrich, I; Kirkby, D; Lankford, A J; Mandelkern, M; Mommsen, R K; Roethel, W; Stoker, D P; Buchanan, C; Hartfiel, B L; Weinstein, A J R; Foulkes, S D; Gary, J W; Long, O; Shen, B C; Wang, K; Zhang, L; Del Re, D; Hadavand, H K; Hill, E J; Macfarlane, D B; Paar, H P; Rahatlou, S; Sharma, V; Berryhill, J W; Campagnari, C; Cunha, A; Dahmes, B; Hong, T M; Mazur, M A; Richman, J D; Verkerke, W; Beck, T W; Eisner, A M; Flacco, C J; Heusch, C A; Kroseberg, J; Lockman, W S; Nesom, G; Schalk, T; Schumm, B A; Seiden, A; Spradlin, P; Williams, D C; Wilson, M G; Albert, J; Chen, E; Dubois-Felsmann, G P; Dvoretskii, A; Hitlin, D G; Narsky, I; Piatenko, T; Porter, F C; Ryd, A; Samuel, A; Andreassen, R; Jayatilleke, S; Mancinelli, G; Meadows, B T; Sokoloff, M D; Blanc, F; Bloom, P; Chen, S; Ford, W T; Nauenberg, U; Olivas, A; Rankin, P; Ruddick, W O; Smith, J G; Ulmer, K A; Wagner, S R; Zhang, J; Chen, A; Eckhart, E A; Soffer, A; Toki, W H; Wilson, R J; Zeng, Q; Altenburg, D; Feltresi, E; Hauke, A; Spaan, B; Brandt, T; Brose, J; Dickopp, M; Klose, V; Lacker, H M; Nogowski, R; Otto, S; Petzold, A; Schott, G; Schubert, J; Schubert, K R; Schwierz, R; Sundermann, J E; Bernard, D; Bonneaud, G R; Grenier, P; Schrenk, S; Thiebaux, Ch; Vasileiadis, G; Verderi, M; Bard, D J; Clark, P J; Gradl, W; Muheim, F; Playfer, S; Xie, Y; Andreotti, M; Azzolini, V; Bettoni, D; Bozzi, C; Calabrese, R; Cibinetto, G; Luppi, E; Negrini, M; Piemontese, L; Anulli, F; Baldini-Ferroli, R; Calcaterra, A; de Sangro, R; Finocchiaro, G; Patteri, P; Peruzzi, I M; Piccolo, M; Zallo, A; Buzzo, A; Capra, R; Contri, R; Lo Vetere, M; Macri, M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Santroni, A; Tosi, S; Bailey, S; Brandenburg, G; Chaisanguanthum, K S; Morii, M; Won, E; Wu, J; Dubitzky, R S; Langenegger, U; Marks, J; Schenk, S; Uwer, U; Bhimji, W; Bowerman, D A; Dauncey, P D; Egede, U; Flack, R L; Gaillard, J R; Morton, G W; Nash, J A; Nikolich, M B; Taylor, G P; Vazquez, W P; Charles, M J; Mader, W F; Mallik, U; Mohapatra, A K; Cochran, J; Crawley, H B; Eyges, V; Meyer, W T; Prell, S; Rosenberg, E I; Rubin, A E; Yi, J; Arnaud, N; Davier, M; Giroux, X; Grosdidier, G; Höcker, A; Le Diberder, F; Lepeltier, V; Lutz, A M; Oyanguren, A; Petersen, T C; Pierini, M; Plaszczynski, S; Rodier, S; Roudeau, P; Schune, M H; Stocchi, A; Wormser, G; Cheng, C H; Lange, D J; Simani, M C; Wright, D M; Bevan, A J; Chavez, C A; Coleman, J P; Forster, I J; Fry, J R; Gabathuler, E; Gamet, R; George, K A; Hutchcroft, D E; Parry, R J; Payne, D J; Schofield, K C; Touramanis, C; Cormack, C M; Di Lodovico, F; Sacco, R; Brown, C L; Cowan, G; Flaecher, H U; Green, M G; Hopkins, D A; Jackson, P S; McMahon, T R; Ricciardi, S; Salvatore, F; Brown, D; Davis, C L; Allison, J; Barlow, N R; Barlow, R J; Hodgkinson, M C; Lafferty, G D; Naisbit, M T; Williams, J C; Chen, C; Farbin, A; Hulsbergen, W D; Jawahery, A; Kovalskyi, D; Lae, C K; Lillard, V; Roberts, D A; Simi, G; Blaylock, G; Dallapiccola, C; Hertzbach, S S; Kofler, R; Koptchev, V B; Li, X; Moore, T B; Saremi, S; Staengle, H; Willocq, S; Cowan, R; Koeneke, K; Sciolla, G; Sekula, S J; Spitznagel, M; Taylor, F; Yamamoto, R K; Kim, H; Patel, P M; Robertson, S H; Lazzaro, A; Lombardo, V; Palombo, F; Bauer, J M; Cremaldi, L; Eschenburg, V; Godang, R; Kroeger, R; Reidy, J; Sanders, D A; Summers, D J; Zhao, H W; Brunet, S; Côté, D; Taras, P; Viaud, B; Nicholson, H; Cavallo, N; De Nardo, G; Fabozzi, F; Gatto, C; Lista, L; Monorchio, D; Paolucci, P; Piccolo, D; Sciacca, C; Baak, M; Bulten, H; Raven, G; Snoek, H L; Wilden, L; Jessop, C P; Losecco, J M; Allmendinger, T; Benelli, G; Gan, K K; Honscheid, K; Hufnagel, D; Jackson, P D; Kagan, H; Kass, R; Pulliam, T; Rahimi, A M; Ter-Antonyan, R; Wong, Q K; Brau, J; Frey, R; Igonkina, O; Lu, M; Potter, C T; Sinev, N B; Strom, D; Strube, J; Torrence, E; Dorigo, A; Galeazzi, F; Margoni, M; Morandin, M; Posocco, M; Rotondo, M; Simonetto, F; Stroili, R; Voci, C; Benayoun, M; Briand, H; Chauveau, J; David, P; Del Buono, L; de la Vaissière, Ch; Hamon, O; John, M J J; Leruste, Ph; Malclès, J; Ocariz, J; Roos, L; Therin, G; Behera, P K; Gladney, L; Guo, Q H; Panetta, J; Biasini, M; Covarelli, R; Pacetti, S; Pioppi, M; Angelini, C; Batignani, G; Bettarini, S; Bucci, F; Calderini, G; Carpinelli, M; Cenci, R; Forti, F; Giorgi, M A; Lusiani, A; Marchiori, G; Morganti, M; Neri, N; Paoloni, E; Rama, M; Rizzo, G; Walsh, J; Haire, M; Judd, D; Wagoner, D E; Biesiada, J; Danielson, N; Elmer, P; Lau, Y P; Lu, C; Olsen, J; Smith, A J S; Telnov, A V; Bellini, F; Cavoto, G; D'Orazio, A; Di Marco, E; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Li Gioi, L; Mazzoni, M A; Morganti, S; Piredda, G; Polci, F; Tehrani, F Safai; Voena, C; Schröder, H; Wagner, G; Waldi, R; Adye, T; De Groot, N; Franek, B; Gopal, G P; Olaiya, E O; Wilson, F F; Aleksan, R; Emery, S; Gaidot, A; Ganzhur, S F; Giraud, P-F; Graziani, G; Hamel de Monchenault, G; Kozanecki, W; Legendre, M; London, G W; Mayer, B; Vasseur, G; Yèche, Ch; Zito, M; Purohit, M V; Weidemann, A W; Wilson, J R; Yumiceva, F X; Abe, T; Allen, M T; Aston, D; Bartoldus, R; Berger, N; Boyarski, A M; Buchmueller, O L; Claus, R; Convery, M R; Cristinziani, M; Dingfelder, J C; Dong, D; Dorfan, J; Dujmic, D; Dunwoodie, W; Fan, S; Field, R C; Glanzman, T; Gowdy, S J; Hadig, T; Halyo, V; Hast, C; Hryn'ova, T; Innes, W R; Kelsey, M H; Kim, P; Kocian, M L; Leith, D W G S; Libby, J; Luitz, S; Luth, V; Lynch, H L; Marsiske, H; Messner, R; Muller, D R; O'grady, C P; Ozcan, V E; Perazzo, A; Perl, M; Ratcliff, B N; Roodman, A; Salnikov, A A; Schindler, R H; Schwiening, J; Snyder, A; Stelzer, J; Su, D; Sullivan, M K; Suzuki, K; Swain, S; Thompson, J M; Va'vra, J; Weaver, M; Wisniewski, W J; Wittgen, M; Wright, D H; Yarritu, A K; Yi, K; Young, C C; Burchat, P R; Edwards, A J; Majewski, S A; Petersen, B A; Roat, C; Ahmed, M; Ahmed, S; Alam, M S; Ernst, J A; Saeed, M A; Wappler, F R; Zain, S B; Bugg, W; Krishnamurthy, M; Spanier, S M; Eckmann, R; Ritchie, J L; Satpathy, A; Schwitters, R F; Izen, J M; Kitayama, I; Lou, X C; Ye, S; Bianchi, F; Bona, M; Gallo, F; Gamba, D; Bomben, M; Bosisio, L; Cartaro, C; Cossutti, F; Della Ricca, G; Dittongo, S; Grancagnolo, S; Lanceri, L; Vitale, L; Martinez-Vidal, F; Panvini, R S; Banerjee, Sw; Bhuyan, B; Brown, C M; Fortin, D; Hamano, K; Kowalewski, R; Roney, J M; Sobie, R J; Back, J J; Harrison, P F; Latham, T E; Mohanty, G B; Band, H R; Chen, X; Cheng, B; Dasu, S; Datta, M; Eichenbaum, A M; Flood, K T; Graham, M; Hollar, J J; Johnson, J R; Kutter, P E; Li, H; Liu, R; Mellado, B; Mihalyi, A; Pan, Y; Prepost, R; Tan, P; von Wimmersperg-Toeller, J H; Wu, S L; Yu, Z; Neal, H

    2005-10-01

    We present an updated measurement of time-dependent CP asymmetries and the CP-odd fraction in the decay B0-->D*+D*- using 232x10(6)BB pairs collected by the BABAR detector at the SLAC PEP-II B factory. We determine the CP-odd fraction to be 0.125+/-0.044(stat)+/-0.007(syst). The time-dependent CP asymmetry parameters C+ and S+ are determined to be 0.06+/-0.17(stat)+/-0.03(syst) and -0.75+/-0.25(stat)+/-0.03(syst), respectively. The standard model predicts these parameters to be 0 and -sin2beta, respectively, in the absence of penguin amplitude contributions. PMID:16241717

  11. Measurement of Time-Dependent CP Asymmetries and the CP-Odd Fraction in the Decay B0->D*+D*-

    SciTech Connect

    Aubert, B.; Barate, R.; Boutigny, D.; Couderc, F.; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Tisserand, V.; Zghiche, A.; Grauges, E.; Palano, A.; Pappagallo, M.; Pompili, A.; Chen, J.C.; Qi, N.D.; Rong, G.; Wang, P.; Zhu, Y.S.; Eigen, G.; Ofte, I.; Stugu, B. /Bergen U. /LBL, Berkeley /UC, Berkeley /Birmingham U. /Ruhr U., Bochum /Bristol U. /British Columbia U. /Brunel U. /Novosibirsk, IYF /UC, Irvine /UCLA /UC, Riverside /UC, San Diego /UC, Santa Barbara /UC, Santa Cruz /Caltech /Cincinnati U. /Colorado U. /Colorado State U. /Dortmund U. /Dresden, Tech. U. /Ecole Polytechnique /Edinburgh U. /Ferrara U. /INFN, Ferrara /Frascati /Genoa U. /INFN, Genoa /Harvard U. /Heidelberg U. /Imperial Coll., London /Iowa U. /Iowa State U. /Orsay, LAL /LLNL, Livermore /Liverpool U. /Queen Mary, U. of London /Royal Holloway, U. of London /Louisville U. /Manchester U. /Maryland U. /Massachusetts U., Amherst /MIT, LNS /McGill U. /Milan U. /INFN, Milan /Mississippi U. /Montreal U. /Mt. Holyoke Coll. /Naples U. /INFN, Naples /NIKHEF, Amsterdam /Notre Dame U. /Ohio State U. /Oregon U. /Padua U. /INFN, Padua /Paris U., VI-VII /Pennsylvania U. /Perugia U. /INFN, Perugia /Pisa U. /INFN, Pisa /Prairie View A-M /Princeton U. /Rome U. /INFN, Rome /Rostock U. /Rutherford /DAPNIA, Saclay /South Carolina U. /SLAC /Stanford U., Phys. Dept. /SUNY, Stony Brook /Tennessee U. /Texas U. /Texas U., Dallas /Turin U. /INFN, Turin /Trieste U. /INFN, Trieste /Valencia U., IFIC /Vanderbilt U. /Victoria U. /Warwick U. /Wisconsin U., Madison /Yale U.

    2005-07-06

    We present an updated measurement of time-dependent CP asymmetries and the CP-odd fraction in the decay B{sup 0} D*{sup +}D*{sup -} using 232 x 10{sup 6} B{bar B} pairs collected by the BABAR detector at the PEP-II B factory. We determine the CP-odd fraction to be 0.125 {+-} 0.044(stat) {+-} 0.007(syst). The time-dependent CP asymmetry parameters C{sub +} and S{sub +} are determined to be 0.06 {+-} 0.17(stat) {+-} 0.03(syst) and -0.75 {+-} 0.25(stat) {+-} 0.03(syst), respectively. The Standard Model predicts these parameters to be 0 and -sin2{beta}, respectively, in the absence of penguin amplitude contributions.

  12. High-dose total-body irradiation and autologous marrow reconstitution in dogs: dose-rate-related acute toxicity and fractionation-dependent long-term survival

    SciTech Connect

    Deeg, H.J.; Storb, R.; Weiden, P.L.; Schumacher, D.; Shulman, H.; Graham, T.; Thomas, E.D.

    1981-11-01

    Beagle dogs treated by total-body irradiation (TBI) were given autologous marrow grafts in order to avoid death from marrow toxicity. Acute and delayed non-marrow toxicities of high single-dose (27 dogs) and fractionated TBI (20 dogs) delivered at 0.05 or 0.1 Gy/min were compared. Fractionated TBI was given in increments of 2 Gy every 6 hr for three increments per day. Acute toxicity and early mortality (<1 month) at identical total irradiation doses were comparable for dogs given fractionated or single-dose TBI. With single-dose TBI, 14, 16, and 18 Gy, respectively, given at 0.05 Gy/min, 0/5, 5/5, and 2/2 dogs died from acute toxicity; with 10, 12, and 14 Gy, respectively, given at 0.1 Gy/min, 1/5, 4/5, and 5/5 dogs died acutely. With fractionated TBI, 14 and 16 Gy, respectively, given at 0.1 Gy/min, 1/5, 4/5, and 2/2 dogs died auctely. Early deaths were due to radiation enteritis with or without associated septicemia (29 dogs; less than or equal to Day 10). Three dogs given 10 Gy of TBI at 0.1 Gy/min died from bacterial pneumonia; one (Day 18) had been given fractionated and two (Days 14, 22) single-dose TBI. Fifteen dogs survived beyond 1 month; eight of these had single-dose TBI (10-14 Gy) and all died within 7 months of irradiation from a syndrome consisting of hepatic damage, pancreatic fibrosis, malnutrition, wasting, and anemia. Seven of the 15 had fractionated TBI, and only one (14 Gy) died on Day 33 from hepatic failure, whereas 6 (10-14 Gy) are alive and well 250 to 500 days after irradiation. In conclusion, fractionated TBI did not offer advantages over single-dose TBI with regard to acute toxicity and early mortality; rather, these were dependent upon the total dose of TBI. The total acutely tolerated dose was dependent upon the exposure rate; however, only dogs given fractionated TBI became healthy long-term survivors.

  13. Theoretical study of the voltage and concentration dependence of the anomalous mole fraction effect in single calcium channels. New insights into the characterization of multi-ion channels.

    PubMed Central

    Campbell, D L; Rasmusson, R L; Strauss, H C

    1988-01-01

    Several recent independent studies on macroscopic Ca currents have demonstrated the anomalous mole fraction effect in mixtures of Ca and Ba at concentrations of 10 mM or less. Recently, Hess and Tsien (1984; Nature 309) proposed a dual binding site model, based upon Eyring rate theory, to account for this effect in L-type cardiac Ca channels. This model predicts that the anomalous mole fraction effect can be accounted for solely in terms of open single channel permeation properties; it was able to adequately reproduce the effect for macroscopic Ca currents recorded in 10 mM solutions. However, the electrochemical gradients under which single Ca channel current recordings are routinely made with the patch clamp technique vary dramatically from those used for macroscopic Ca currents. To properly assess the general validity of the Hess and Tsien model at the single Ca channel level, the effects of both large electrical potentials and elevated divalent concentrations must be understood. Computer simulations were therefore carried out using the original parameters used by Hess and Tsien under conditions designed to mimic those used in patch clamp studies. The permeation behavior generated by this model is quite complex. In particular, hyperpolarization and increased divalent concentration combine to reduce and ultimately abolish the anomalous mole fraction effect. It may therefore be very difficult to observe the anomalous mole fraction effect at the single Ca channel level; the dual-site model displays a relationship between current and mole fraction generally associated with a single-site model under the conditions frequently employed to resolve single Ca channel activity. Nonetheless, analysis of such monotonic mole fraction behavior can still be used as a test for the general validity of the dual-site model. Apparent Kms for Ca and Ba can be extracted from such monotonic behavior, and may not only be functions of membrane potential but may also depend upon the total

  14. A study of the substance dependence effect of the ethanolic extract and iridoid-rich fraction from Valeriana jatamansi Jones in mice

    PubMed Central

    Yu, Lin; Ke-ke, Xu; Chao-yong, Chen; Rui-tong, Zhang; Ming, Lan; Shao-hua, Li; Ling-zhen, Pan; Tian-e, Zhang; Zhi-yong, Yan

    2015-01-01

    Background: Recently we found the ethanolic extract and iridoid-rich fraction from Valeriana jatamansi Jones, which is a traditional Chinese medicine exhibited anxiolytic properties. Objective: This study aims to the substance dependence effect of the ethanolic extract and iridoid-rich fraction. Materials and Methods: The study included two experiments: Mice were given orally with ethanolic extract for 12 weeks or iridoid-rich fraction for 16 weeks in experiment I and experiment II, respectively. Diazepam was used as a control drug and the normal mice groups were administered with 0.5% carboxymethyl cellulose Na in both experiments. All groups were administered twice daily. Natural withdrawal symptoms, withdrawal-induced body weight change, audiogenic tail-erection test (in experiment I), and pentylenetetrazol (PTZ)-induced convulsion test (in experiment II) were measured. Results: (1) Compared to normal group in both experiments, the diazepam-treated group exhibited obvious withdrawal symptoms of tail-erection, irritability, teeth chattering, etc; the body weight of them after withdrawal had a period of significant loss (P < 0.05 or P < 0.01); and the ratios of tail-erection and seizure in two experiments were improved significantly when mice were induced by mixer noise ringtone (experiment I) or PTZ (experiment II) (P < 0.05 or P < 0.01).(2) In experiment I and II, there were no significant differences between mice that received ethanolic extract or iridoid-rich fraction and normal group in terms of natural withdrawal symptoms and withdrawal-induced body weight change (P > 0.05); in audiogenic tail-erection test, it found that the significant difference compared with normal group was just in ethanolic extract 900 mg/kg dose group on week 8 (P < 0.05); in PTZ-induced convulsion test, mice in iridoid-rich fraction groups had a slightly tail-erection and seizure, all results of them were with no significant difference compare to normal mice (P > 0.05), while

  15. Ignition of a Deuterium Micro-Detonation with a Gigavolt Super Marx Generator

    NASA Astrophysics Data System (ADS)

    Winterberg, Friedwardt

    2009-09-01

    The Centurion-Halite experiment demonstrated the feasibility of igniting a deuterium-tritium micro-explosion with an energy of not more than a few megajoule, and the Mike test, the feasibility of a pure deuterium explosion with an energy of more than 106 MJ. In both cases the ignition energy was supplied by a fission bomb explosive. While an energy of a few megajoule, to be released in the time required of less than 10-9 s, can be supplied by lasers and intense particle beams, this is not enough to ignite a pure deuterium explosion. Because the deuterium-tritium reaction depends on the availability of lithium, the non-fission ignition of a pure deuterium fusion reaction would be highly desirable. It is shown that this goal can conceivably be reached with a "Super Marx Generator", where a large number of "ordinary" Marx generators charge (magnetically insulated) fast high voltage capacitors of a second stage Marx generator, called a "Super Marx Generator", ultimately reaching gigavolt potentials with an energy output in excess of 100 MJ. An intense 107 Ampere-GeV proton beam drawn from a "Super Marx Generator" can ignite a deuterium thermonuclear detonation wave in a compressed deuterium cylinder, where the strong magnetic field of the proton beam entraps the charged fusion reaction products inside the cylinder. In solving the stand-off problem, the stiffness of a GeV proton beam permits to place the deuterium target at a comparatively large distance from the wall of a cavity confining the deuterium micro-explosion.

  16. A fraction from Dojuksan 30% ethanol extract exerts its anti-inflammatory effects through Nrf2-dependent heme oxygenase-1 expression.

    PubMed

    Lee, Dong-Sung; Kim, Kyoung-Su; Ko, Wonmin; Bae, Gi-Sang; Park, Sung-Joo; Jang, Jun-Hyeog; Oh, Hyuncheol; Kim, Youn-Chul

    2016-02-01

    Dojuksan is a traditional herbal medicine used in Korea and China to treat urinary diseases. In the present study, we aimed to examine the anti-inflammatory effects of an ethanol solvent extract of Dojuksan and a fraction (by bioassay-guided fractionation) derived from this extract, and to elucidate the specific mechanisms involved. The Dojuksan 30% ethanol extract (DEE) had a more significant and potent anti-inflammatory effect than the Dojuksan water extract (DWE). DEE markedly inhibited the production of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), nitric oxide (NO), prostaglandin E2 (PGE2), tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), as well as nuclear factor-κB (NF-κB) binding activity. We found that the anti-inflammatory effects of DEE were mediated by the induction of nuclear factor E2-related factor 2 (Nrf2)-dependent heme oxygenase-1 (HO-1). To further explore the anti-inflammatory effects of DEE, we generated 6 different fractions of DEE. Of these, DEE-5 decreased the production of NO more significantly than the other fractions. DEE-5 also significantly decreased the expression of iNOS and COX-2, and the production of NO, PGE2, TNF-α and IL-1β. In addition, DEE-5 also significantly increased HO-1 levels; HO-1 significanlty contributed to the inhibitory effects of DEE-5 on the production of pro-inflammatory mediators. In this study, we determined whether the choice of extraction solvent affects the biological activity of Dojuksan, a traditional herbal formula. Our findings demonstrate that DEE and a fraction derived from this extract exerts anti-inflammatory effects through Nrf2‑dependent HO-1 expression, and that DEE may thus have greater potential therapeutic application than DWE. PMID:26647788

  17. Investigations of chemical erosion of carbon materials in hydrogen and deuterium low pressure plasmas

    NASA Astrophysics Data System (ADS)

    Starke, P.; Fantz, U.; Balden, M.

    2005-03-01

    Investigations on chemical erosion of pure and carbide-doped graphite materials were carried out in inductively coupled RF plasmas containing hydrogen, deuterium or a mixture of both in helium. For extrapolations of erosion yields to future fusion devices the relevant particle fluxes have to be known precisely. This was done by several diagnostic techniques. In particular the ion fluxes are determined by an energy mass analyzer. An isotope effect of the ion composition is measured resulting in an enhanced erosion of graphite in deuterium plasmas. Since in fusion plasmas a mixture of deuterium and tritium will interact with the surface, a mixture of hydrogen and deuterium on graphite was investigated as well. In order to reduce erosion yields doping of carbon is under discussion. Therefore, fluence dependent erosion yields of several W-, Ti-, V- and Zr-doped graphite materials are measured and compared with pure graphite.

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

    PubMed

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

    2010-04-15

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

  19. Impact-induced devolatilization and hydrogen isotopic fractionation of serpentine: Implications for planetary accretion

    NASA Technical Reports Server (NTRS)

    Tyburczy, James A.; Krishnamurthy, R. V.; Epstein, Samuel; Ahrens, Thomas J.

    1988-01-01

    Impact-induced devolatilization of porous serpentine was investigated using two independent experimental methods, the gas recovery and the solid recovery method, each yielding nearly identical results. For shock pressures near incipient devolatilization, the hydrogen isotopic composition of the evolved H2O is very close to that of the starting material. For shock pressures at which up to 12 percent impact-induced devolatilization occurs, the bulk evolved gas is significantly lower in deuterium than the starting material. There is also significant reduction of H2O to H2 in gases recovered at these higher shock pressures, probably caused by reaction of evolved H2O with the metal gas recovery fixture. Gaseous H2O-H2 isotopic fractionation suggests high temperature isotopic equilibrium between the gaseous species, indicating initiation of devolatilization at sites of greater than average energy deposition. Bulk gas-residual solid isotopic fractionations indicate nonequilibrium, kinetic control of gas-solid isotopic ratios. Impact-induced hydrogen isotopic fractionation of hydrous silicates during accretion can strongly affect the long-term planetary isotopic ratios of planetary bodies, leaving the interiors enriched in deuterium. Depending on the model used for extrapolation of the isotopic fractionation to devolatilization fractions greater than those investigated experimentally can result from this process.

  20. Deuterium gas puff Z-pinch at currents of 2 to 3 mega-ampere

    NASA Astrophysics Data System (ADS)

    Klir, D.; Shishlov, A. V.; Kubes, P.; Rezac, K.; Fursov, F. I.; Kokshenev, V. A.; Kovalchuk, B. M.; Kravarik, J.; Kurmaev, N. E.; Labetsky, A. Yu.; Ratakhin, N. A.

    2012-03-01

    Deuterium gas-puff experiments have been carried out on the GIT-12 generator at the Institute of High Current Electronics in Tomsk. The emphasis was put on the study of plasma dynamics and neutron production in double shell gas puffs. A linear mass density of deuterium (D2) varied between 50 and 85 μg/cm. Somewhat problematic was a spread of the D2 gas at a large diameter in the central anode-cathode region. The generator operated in two regimes, with and without a plasma opening switch (POS). When the POS was used, a current reached a peak of 2.7 MA with a 200 ns rise time. Without the POS, a current rise time approached 1500 ns. The influence of different current rise times on neutron production was researched. Obtained results were important for comparison of fast deuterium Z-pinches with plasma foci. Average DD neutron yields with and without the POS were about 1011. The neutron yield seems to be dependent on a peak voltage at the Z-pinch load. In all shots, the neutron emission started during stagnation. At the beginning of the neutron production, the neutron emission correlated with soft x-rays and a significant fraction of neutrons could be explained by the thermonuclear mechanism. Nevertheless, a peak of the neutron emission occurred 40 ns after a soft x-ray peak. At this very moment, hard x-rays above 1 MeV were detected and a rapid expansion with a velocity of 3×105 m/s was observed. In the case of the POS, 1 MeV widths of radial neutron spectra implied that there are deuterons with the energy above 200 keV moving in the radial direction. On the basis of D2 gas puff experiments in the 0.3-17 MA region, the neutron yield dependence on a current as Y∝I3.0±0.2 was proposed.

  1. Deuterium and the stellar birthline

    NASA Technical Reports Server (NTRS)

    Stahler, Steven W.

    1988-01-01

    A series of simplified evolutionary calculations are used to show that deuterium burning acts as an effective thermostat in low-mass protostars over a plausible range of initial conditions and mass accretion rates. The thermostat keeps the central temperature of the accreting hydrostatic core close to 10 to the 6th K, and thereby tightly constrains the core's mass-radius relation. This relation, when combined with premain-sequence evolutionary tracks, yields a theoretical birthline or upper envelope for young stars in the H-R diagram which maintains excellent agreement with observations of T Tauri stars in nearby molecular cloud complexes. This derivation of the birthline helps to explain its insensitivity to protostellar collapse conditions. The calculations indicate that the birthline will be little affected by the inclusion of rotation as long as the newly visible stars have lost most of their accreted angular momentum.

  2. Muon transfer from hydrogen and deuterium atoms to neon

    SciTech Connect

    Jacot-Guillarmod, R. )

    1995-03-01

    The muon exchange reactions from the ground state of muonic protium and deuterium atoms to neon are studied. Measurements have been performed in binary gas mixtures at room temperature. The transfer rate from thermalized muonic deuterium is found to exceed by about an order of magnitude the one from muonic protium. On the other hand, an energy dependence of the rate from [mu][ital d] is revealed, while none is observed from [mu][ital p]. The intensity patterns of the muonic Lyman series of neon resulting from the muon exchange differ from one hydrogen isotope to the other, the most obvious discrepancy being the presence of the muonic Ne(7-1) line after transfer from [mu][ital d], whereas this line is absent by transfer from [mu][ital p]. This indicates that the muon is transferred to the level [ital n][sub [ital p

  3. First observation of muonic hyperfine effects in pure deuterium

    SciTech Connect

    Kammel, P.; Breunlich, W.H.; Cargnelli, M.; Mahler, H.G.; Zmeskal, J.; Bertl, W.H.; Petitjean, C.

    1983-11-01

    We discovered a strong hyperfine dependence of the resonant formation process of d..mu..d mesomolecules, while detecting neutrons from muon-catalyzed fusion in pure deuterium gas at 34 K. This new effect enabled us to observe directly transitions between hyperfine states of the ..mu..d atom for the first time and to determine an accurate experimental value for this transition rate. Our analysis demonstrates the importance of hyperfine effects for the quantitative understanding of the mechanism of resonant d..mu..d formation. Moreover, this experiment indicates that the resonant formation process is a powerful tool for a refined spectroscopy of d..mu..d bound states. Finally, the detailed knowledge about mesoatomic and mesomolecular processes obtained in this work provides valuable information for the analysis of experiments on the elementary muon-capture process in deuterium.

  4. CO2-dependent fractional crystallization of alkaline silicate magmas and unmixing of carbonatites within the intrusive complexes of Brava Island (Cape Verde)

    NASA Astrophysics Data System (ADS)

    Weidendorfer, D.; Schmidt, M. W.; Mattsson, H. B.

    2014-12-01

    Intrusive carbonatites often occur in intimate association with SiO2-undersaturated rocks such as melilitites, nephelinites, syenites and phonolites. The occurrence of carbonatites on five of the 10 main islands of the Cape Verde hotspot argues for a CO2-enriched mantle source. Whether alkali-poor carbonatites on the Cape Verdes directly represent small mantle melt fractions or form by extreme fractionation and/or liquid immiscibility from a CO2-rich silicate magma remains a matter of debate. This study focuses on the pyroxenites, nephelinites, ijolites, syenites, phonolites and carbonatites of the intrusive unit of Brava Island. This relative complete series allows for the deduction of a CO2-dependent fractionation pathway from the most primitive basanitic dikes towards phonolitic compositions through an ijolitic series. Major and trace element whole rock and mineral composition trends can be reproduced by fractionating a sequence of olivine, augite, perovskite, biotite, apatite, sodalite and FeTi-oxides, present as phenocrysts in the rocks corresponding to their fractionation interval. To reproduce the observed chemistry of the alkaline silicate rocks a total fractionation of ~87% is required. The melts evolve towards the carbonatite-silicate miscibility gap, an initial CO2 of 0.5 wt% would be sufficient to maintain CO2-saturation in the more evolved compositions. The modelled carbonatite compositions, conjugate to nepheline-syenites to phonolites, correspond well to the observed ones except for an alkali-enrichment with respect to the natural samples. The alkali-depleted nature of the small carbonatite intrusions and dikes on Brava is likely a consequence of fluid-release to the surrounding wall-rocks during crystallization, where fenitization can be observed. The trace element chemistry of primary carbonates and also cpx within both, the carbonatites and the associated silicate rocks, substantiates our fractionation model. Furthermore, carbonatite and silicate

  5. Simultaneous determination of labile proton fraction ratio and exchange rate with irradiation radio frequency (RF) power dependent quantitative CEST MRI analysis

    PubMed Central

    Sun, Phillip Zhe; Wang, Yu; Xiao, Gang; Wu, Renhua

    2014-01-01

    Chemical exchange saturation transfer (CEST) imaging is sensitive to dilute proteins/peptides and microenvironmental properties, and has been increasingly evaluated for molecular imaging and in vivo applications. However, the experimentally measured CEST effect depends on the CEST agent concentration, exchange rate and relaxation time. In addition, there may be non-negligible direct radio-frequency (RF) saturation effects, particularly severe for diamagnetic CEST (DIACEST) agents due to their relatively small chemical shift difference from that of the bulk water resonance. As such, the commonly used asymmetry analysis only provides CEST-weighted information. Recently, it has been shown with numerical simulation that both labile proton concentration and exchange rate can be determined by evaluating the RF power dependence of DIACEST effect. To validate the simulation results, we prepared and imaged two CEST phantoms: a pH phantom of serially titrated pH at a fixed creatine concentration and a concentration phantom of serially varied creatine concentration titrated to the same pH, and solved the labile proton fraction ratio and exchange rate per-pixel. For the concentration phantom, we showed that the labile proton fraction ratio is proportional to the CEST agent concentration with negligible change in the exchange rate. Additionally, we found the exchange rate of the pH phantom is dominantly base-catalyzed with little difference in the labile proton fraction ratio. In summary, our study demonstrated quantitative DIACEST MRI, which remains promising to augment the conventional CEST-weighted MRI analysis. PMID:23606428

  6. Simultaneous experimental determination of labile proton fraction ratio and exchange rate with irradiation radio frequency power-dependent quantitative CEST MRI analysis.

    PubMed

    Sun, Phillip Zhe; Wang, Yu; Xiao, Gang; Wu, Renhua

    2013-01-01

    Chemical exchange saturation transfer (CEST) imaging is sensitive to dilute proteins/peptides and microenvironmental properties, and has been increasingly evaluated for molecular imaging and in vivo applications. However, the experimentally measured CEST effect depends on the CEST agent concentration, exchange rate and relaxation time. In addition, there may be non-negligible direct radio-frequency (RF) saturation effects, particularly severe for diamagnetic CEST (DIACEST) agents owing to their relatively small chemical shift difference from that of the bulk water resonance. As such, the commonly used asymmetry analysis only provides CEST-weighted information. Recently, it has been shown with numerical simulation that both labile proton concentration and exchange rate can be determined by evaluating the RF power dependence of DIACEST effect. To validate the simulation results, we prepared and imaged two CEST phantoms: a pH phantom of serially titrated pH at a fixed creatine concentration and a concentration phantom of serially varied creatine concentration titrated to the same pH, and solved the labile proton fraction ratio and exchange rate per-pixel. For the concentration phantom, we showed that the labile proton fraction ratio is proportional to the CEST agent concentration with negligible change in the exchange rate. Additionally, we found the exchange rate of the pH phantom is dominantly base-catalyzed with little difference in the labile proton fraction ratio. In summary, our study demonstrated quantitative DIACEST MRI, which remains promising to augment the conventional CEST-weighted MRI analysis. PMID:23606428

  7. Isolation of CA1 nuclear enriched fractions from hippocampal slices to study activity-dependent nuclear import of synapto-nuclear messenger proteins.

    PubMed

    Yuanxiang, Pingan; Bera, Sujoy; Karpova, Anna; Kreutz, Michael R; Mikhaylova, Marina

    2014-01-01

    Studying activity dependent protein expression, subcellular translocation, or phosphorylation is essential to understand the underlying cellular mechanisms of synaptic plasticity. Long-term potentiation (LTP) and long-term depression (LTD) induced in acute hippocampal slices are widely accepted as cellular models of learning and memory. There are numerous studies that use live cell imaging or immunohistochemistry approaches to visualize activity dependent protein dynamics. However these methods rely on the suitability of antibodies for immunocytochemistry or overexpression of fluorescence-tagged proteins in single neurons. Immunoblotting of proteins is an alternative method providing independent confirmation of the findings. The first limiting factor in preparation of subcellular fractions from individual tetanized hippocampal slices is the low amount of material. Second, the handling procedure is crucial because even very short and minor manipulations of living slices might induce activation of certain signaling cascades. Here we describe an optimized workflow in order to obtain sufficient quantity of nuclear enriched fraction of sufficient purity from the CA1 region of acute hippocampal slices from rat brain. As a representative example we show that the ERK1/2 phosphorylated form of the synapto-nuclear protein messenger Jacob actively translocates to the nucleus upon induction of LTP and can be detected in a nuclear enriched fraction from CA1 neurons. PMID:25145907

  8. The effect of propylene glycol on the P450-dependent metabolism of acetaminophen and other chemicals in subcellular fractions of mouse liver

    SciTech Connect

    Snawder, J.E.; Benson, R.W.; Leakey, J.E.A.; Roberts, D.W. )

    1993-01-01

    Propylene glycol (PG) decreases the hepatotoxicity of acetominophen (APAP). To elucidate the mechanism for this response, the authors measured the effect of PG on the in vitro metabolism of APAP by subcellular liver fractions from 6-10 week-old male B6C3F1 mice. The fractions were assayed for their ability to bioactivate APAP to N-acetyl-p-benzoquinone imine, which was trapped as APAP-glutathione conjugates or APAP-protein adducts, and for dimethyl-nitrosamine-N-demethylase (DMN), 4-nitrophenol hydroxylase (4-NPOH), and phenacetin-O-deethylase (PAD) activities. Activity in the crude mitochondrial-rich (10,000 [times] g pellet) fraction was low and PG had no effect. PG inhibited DMN and 4-NPOH, indicators of IIE1-dependent activity, and the formation of APAP-glutathione conjugates and APAP-protein adducts in both heavy (15,000 [times] g pellet) and light (100,000 [times] g pellet) microsomes. PAD, a measure of IA2-dependent activity, was not inhibited. These data demonstrate that PG selectively inhibits IIE1 activity, including the bioactivation of APAP, and implicates this as the mechanism for PG-mediated protection of APAP hepatotoxicity in mice. 27 refs., 1 fig., 1 tab.

  9. Measurements of the Branching Fraction and Time-Dependent CP Asymmetries of B0 to J/Psi pi0 Decays

    SciTech Connect

    George, K

    2006-03-10

    We present measurements of the branching fraction and time-dependent CP asymmetries in B{sup 0} {yields} J/{psi}{pi}{sup 0} decays based on (231.8 {+-} 2.6) x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. We obtain a branching fraction {Beta}(B{sup 0} {yields} J/{psi}{pi}{sup 0}) = (1.94 {+-} 0.22 (stat) {+-} 0.17 (syst)) x 10{sup -5}. We also measure the CP asymmetry parameters C = -0.21 {+-} 0.26 (stat) {+-} 0.06 (syst) and S = -0.68 {+-} 0.30 (stat) {+-} 0.04 (syst).

  10. Measurements of the Branching Fraction and Time-Dependent CP Asymmetries of B0 to J/Psi pi0 Decays.

    SciTech Connect

    Aubert, B.

    2005-08-04

    The authors present measurements of the branching fraction and time-dependent CP asymmetries in B{sup 0} {yields} J/{psi} {pi}{sup 0} decays based on (231.8 {+-} 2.6) x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC during the years 1999-2004. We obtain a branching fraction {Beta}(B{sup 0} {yields} J/{psi}{pi}{sup 0}) = (1.94 {+-} 0.22 (stat) {+-} 0.17 (syst)) x 10{sup -5}. They also measure the CP asymmetry parameters C = -0.21 {+-} 0.26 (stat) {+-} 0.09 (syst) and S = -0.68 {+-} 0.30 (stat) {+-} 0.04 (syst). All results presented in this paper are preliminary.

  11. Density dependent stopping power and muon sticking in muon catalyzed D-T fusion

    SciTech Connect

    Rafelski, H.E.; Mueller, B.

    1988-12-27

    The origin of the experimentally observed (1) density dependence of the muon alpha sticking fraction ..omega../sub s/ in muon catalyzed deuterium- tritium fusion is investigated. We show that the reactivation probability depends sensitively on the target stopping power at low ion velocities. The density dependence of the stopping power for a singly charged projectile in liquid heavy hydrogen is parametrized to simulate possible screening effects and a density dependent effective ionization potential. We find that, in principle, a description of the measured density dependence is possible, but the required parameters appear too large. Also, the discrepancy with observed (He..mu..) X-ray data widens.

  12. Water cluster-deuterium oxide collisions: An experimental glimpse

    SciTech Connect

    Kaiser, D.W.

    1993-01-01

    The wealth of cluster research now found in the literature is just beginning to bridge the gap between the study of molecule, surface, and condensed matter physics. Recent advances in experimental technology have opened up new windows into the world of cluster-molecule collision dynamics. This thesis is an attempt to present a glimpse into the collision dynamics of the water cluster-deuterium oxide system. An analysis of the potential reaction channels is presented and the cluster size dependence of the reaction cross section is detailed. An interpretation of this cluster size dependence is proposed.

  13. Deuterium nuclear magnetic resonance unambiguously quantifies pore and collagen-bound water in cortical bone

    PubMed Central

    Ong, Henry H.; Wright, Alexander C.; Wehrli, Felix W.

    2012-01-01

    Bone water (BW) plays a pivotal role in nutrient transport and conferring bone with its viscoelastic mechanical properties. BW is partitioned between the pore spaces of the Haversian and lacuno-canalicular system, and water predominantly bound to the matrix proteins (essentially collagen). The general model of BW is that the former predominantly experiences fast isotropic molecular reorientation, whereas water in the bone matrix undergoes slower anisotropic rotational diffusion. Here, we provide direct evidence for the correctness of this model and show that unambiguous quantification in situ of these two functionally and dynamically different BW fractions is possible. The approach chosen relies on nuclear magnetic resonance (NMR) of deuterium (2H) that unambiguously separates and quantifies the two fractions on the basis of their distinguishing microdynamic properties. Twenty-four specimens of the human tibial cortex from six donors (3 male, 3 female, ages 27-83 years) were cored and 2H spectra recorded at 62 MHz (9.4 Tesla) on a Bruker Instruments DMX 400 spectrometer after exchange of native BW with 2H2O. Spectra consisted of a doublet signal resulting from quadrupole interaction of water bound to collagen. Doublet splittings were found to depend on the orientation of the osteonal axis with respect to the magnetic field direction (8.2 and 4.3 kHz for parallel and perpendicular orientation, respectively). In contrast, the isotropically reorienting pore-resident water yielded a single resonance line superimposed on the doublet. Nulling of the singlet resonance allowed separation of the two fractions. The results indicate that in human cortical bone 60-80% of detectable BW is collagen-bound. Porosity determined as the difference between total BW and collagen bound water fraction was found to strongly parallel μCT based measurements (R2 = 0.91). Our method provides means for direct validation of emerging relaxation-based measurements of cortical bone porosity by

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

    PubMed

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

    2003-04-01

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

  15. Deuterium desorption temperature of Mg-Ti composites prepared by the method of atom-by-atom component mixing

    NASA Astrophysics Data System (ADS)

    Morozov, O. M.; Kulish, V. G.; Zhurba, V. I.; Neklyudov, I. M.; Progolaieva, V. O.; Kuprin, A. S.; Lomino, N. S.; Ovcharenko, V. D.; Kolodiy, I. V.; Galitskiy, O. G.

    2013-12-01

    The plasma evaporation-sputtering method has been applied to obtain composite materials of the Mg-Ti system. Variations in the temperature of the ion-implanted deuterium desorption as a function of the component concentration are studied. It has been established, that introduction of titanium into magnesium leads to the significant decrease of deuterium desorption temperature, namely, to 400-450 K as compared to ~800 K in the case of deuterium release (desorption) from magnesium. The step-like shape of the deuterium desorption temperature curve evidences on the existence of two different structural states of the Mg-Ti composite depending on the ratio of components. The deuterium temperature drop can be caused by filamentary inclusions composed of titanium atoms in magnesium (insoluble component in magnesium) produced in the process of composite formation and providing the deuterium release from the sample at lower temperature (channels for deuterium diffusion and desorption through the surface barrier). The deuterium desorption data obtained on the example of Mg-Ti composites provide a support for further research into hydrogen storage materials containing not readily soluble chemical elements in the alloy components.

  16. Characterization of deuterium clusters mixed with helium gas for an application in beam-target-fusion experiments

    DOE PAGESBeta

    Bang, W.; Quevedo, H. J.; Bernstein, A. C.; Dyer, G.; Ihn, Y. S.; Cortez, J.; Aymond, F.; Gaul, E.; Donovan, M. E.; Barbui, M.; et al

    2014-12-10

    We measured the average deuterium cluster size within a mixture of deuterium clusters and helium gas by detecting Rayleigh scattering signals. The average cluster size from the gas mixture was comparable to that from a pure deuterium gas when the total backing pressure and temperature of the gas mixture were the same as those of the pure deuterium gas. According to these measurements, the average size of deuterium clusters depends on the total pressure and not the partial pressure of deuterium in the gas mixture. To characterize the cluster source size further, a Faraday cup was used to measure themore » average kinetic energy of the ions resulting from Coulomb explosion of deuterium clusters upon irradiation by an intense ultrashort pulse. The deuterium ions indeed acquired a similar amount of energy from the mixture target, corroborating our measurements of the average cluster size. As the addition of helium atoms did not reduce the resulting ion kinetic energies, the reported results confirm the utility of using a known cluster source for beam-target-fusion experiments by introducing a secondary target gas.« less

  17. Characterization of deuterium clusters mixed with helium gas for an application in beam-target-fusion experiments

    SciTech Connect

    Bang, W.; Quevedo, H. J.; Bernstein, A. C.; Dyer, G.; Ihn, Y. S.; Cortez, J.; Aymond, F.; Gaul, E.; Donovan, M. E.; Barbui, M.; Bonasera, A.; Natowitz, J. B.; Albright, B. J.; Fernández, J. C.; Ditmire, T.

    2014-12-10

    We measured the average deuterium cluster size within a mixture of deuterium clusters and helium gas by detecting Rayleigh scattering signals. The average cluster size from the gas mixture was comparable to that from a pure deuterium gas when the total backing pressure and temperature of the gas mixture were the same as those of the pure deuterium gas. According to these measurements, the average size of deuterium clusters depends on the total pressure and not the partial pressure of deuterium in the gas mixture. To characterize the cluster source size further, a Faraday cup was used to measure the average kinetic energy of the ions resulting from Coulomb explosion of deuterium clusters upon irradiation by an intense ultrashort pulse. The deuterium ions indeed acquired a similar amount of energy from the mixture target, corroborating our measurements of the average cluster size. As the addition of helium atoms did not reduce the resulting ion kinetic energies, the reported results confirm the utility of using a known cluster source for beam-target-fusion experiments by introducing a secondary target gas.

  18. Sulfur and oxygen isotope fractionation during sulfate reduction coupled to anaerobic oxidation of methane is dependent on methane concentration

    NASA Astrophysics Data System (ADS)

    Deusner, Christian; Holler, Thomas; Arnold, Gail L.; Bernasconi, Stefano M.; Formolo, Michael J.; Brunner, Benjamin

    2014-08-01

    to induce very large sulfur isotope fractionation between sulfate and sulfide (i.e. >60‰) and will drive the oxygen isotope composition of sulfate towards the sulfate-water oxygen isotope equilibrium value. Sulfur isotope fractionation by AOM-SR at gas seeps, where methane fluxes are high, will be much smaller (i.e. 20 to 40‰).

  19. Dose-dependent suppression of serum cholesterol by tocotrienol-rich fraction (TRF25) of rice bran in hypercholesterolemic humans.

    PubMed

    Qureshi, Asaf A; Sami, Saeed A; Salser, Winston A; Khan, Farooq A

    2002-03-01

    Tocotrienols are effective in lowering serum total and LDL-cholesterol levels by inhibiting the hepatic enzymic activity of beta-hydroxy-beta-methylglutaryl coenzymeA (HMG-CoA) reductase through the post-transcriptional mechanism. alpha-Tocopherol, however, has an opposite effect (induces) on this enzyme activity. Since tocotrienols are also converted to tocopherols in vivo, it is necessary not to exceed a certain dose, as this would be counter-productive. The present study demonstrates the effects of various doses of a tocotrienol-rich fraction (TRF25) of stabilized and heated rice bran in hypercholesterolemic human subjects on serum lipid parameters. Ninety (18/group) hypercholesterolemic human subjects participated in this study, which comprised three phases of 35 days each. The subjects were initially placed on the American Heart Association (AHA) Step-1 diet and the effects noted. They were then administered 25, 50, 100, and 200 mg/day of TRF25 while on the restricted (AHA) diet. The results show that a dose of 100 mg/day of TRF25 produce maximum decreases of 20, 25, 14 (P<0.05) and 12%, respectively, in serum total cholesterol, LDL-cholesterol, apolipoprotein B and triglycerides compared with the baseline values, suggesting that a dose of 100 mg/day TRF25 plus AHA Step-1 diet may be the optimal dose for controlling the risk of coronary heart disease in hypercholesterolemic human subjects. PMID:11882333

  20. 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.

  1. Vanadium hydride deuterium-tritium generator

    DOEpatents

    Christensen, L.D.

    1980-03-13

    A pressure controlled vanadium hydride gas generator was designed to provide deuterium-tritium gas in a series of pressure increments. A high pressure chamber filled with vanadium-deuterium-tritium hydride is surrounded by a heater which controls the hydride temperature. The heater is actuated by a power controller which responds to the difference signal between the actual pressure signal and a programmed pressure signal.

  2. Tempered fractional calculus

    NASA Astrophysics Data System (ADS)

    Sabzikar, Farzad; Meerschaert, Mark M.; Chen, Jinghua

    2015-07-01

    Fractional derivatives and integrals are convolutions with a power law. Multiplying by an exponential factor leads to tempered fractional derivatives and integrals. Tempered fractional diffusion equations, where the usual second derivative in space is replaced by a tempered fractional derivative, govern the limits of random walk models with an exponentially tempered power law jump distribution. The limiting tempered stable probability densities exhibit semi-heavy tails, which are commonly observed in finance. Tempered power law waiting times lead to tempered fractional time derivatives, which have proven useful in geophysics. The tempered fractional derivative or integral of a Brownian motion, called a tempered fractional Brownian motion, can exhibit semi-long range dependence. The increments of this process, called tempered fractional Gaussian noise, provide a useful new stochastic model for wind speed data. A tempered fractional difference forms the basis for numerical methods to solve tempered fractional diffusion equations, and it also provides a useful new correlation model in time series.

  3. Tempered fractional calculus

    SciTech Connect

    Sabzikar, Farzad; Meerschaert, Mark M.; Chen, Jinghua

    2015-07-15

    Fractional derivatives and integrals are convolutions with a power law. Multiplying by an exponential factor leads to tempered fractional derivatives and integrals. Tempered fractional diffusion equations, where the usual second derivative in space is replaced by a tempered fractional derivative, govern the limits of random walk models with an exponentially tempered power law jump distribution. The limiting tempered stable probability densities exhibit semi-heavy tails, which are commonly observed in finance. Tempered power law waiting times lead to tempered fractional time derivatives, which have proven useful in geophysics. The tempered fractional derivative or integral of a Brownian motion, called a tempered fractional Brownian motion, can exhibit semi-long range dependence. The increments of this process, called tempered fractional Gaussian noise, provide a useful new stochastic model for wind speed data. A tempered fractional difference forms the basis for numerical methods to solve tempered fractional diffusion equations, and it also provides a useful new correlation model in time series.

  4. Radio observations of D I and fractionation

    NASA Technical Reports Server (NTRS)

    Heiles, Carl; Mccullough, Peter R.; Glassgold, Alfred E.

    1993-01-01

    We report observations to detect the 327 MHz line of atomic deuterium in the primarily molecular clouds towards Cas A and Sgr A, making appropriate choices of spectral and spatial resolution. Our best results for Cas A, based on 1253 hr of observing with the 85 foot (26 m) Hat Creek telescope and 45 hr with the very large array (VLA), yield an upper limit for the fraction of deuterium in atomic form, D I, of 0.14. We present an approximate analytical analysis of deuterium fractionation in translucent clouds, which shows that gas-phase ion-molecule reactions, assisted by dust and HD line self-shielding, are efficient in converting deuterium to HD. We conclude that little atomic deuterium is present in the molecular clumps in the Cas A clouds and that much higher sensitivity observations would be required to detect 327 MHz line in molecular clouds. We have also attempted to detect the 72 GHz line of DCO(+) toward Cas A. The observed upper limit to the DCO(+)/HCO(+) ratio of approximately 0.03 is not much larger than our theoretical estimate, and the DCO(+) line should be detectable with existing instrumentation, unless the temperature of these clouds is much larger than usually assumed.

  5. Transcription of fractionated mammalian chromatin by mammalian ribonucleic acid polymerase. Demonstration of temperature-dependent rifampicin-resistant initiation sites in euchromatin deoxyribonucleic acid

    PubMed Central

    Chesterton, C. James; Coupar, Barbara E. H.; Butterworth, Peter H. W.

    1974-01-01

    The chromatin fractionation method of Frenster et al. (1963) as modified by Leake et al. (1972) was used to prepare fragments of euchromatin from rat liver nuclei. These remain soluble in 5mm-MgCl2, and contain DNA of maximum mol.wt. 1×106–2×106. The fragments were separated from condensable chromatin on a sucrose gradient. Euchromatin contains endogenous DNA-dependent RNA polymerase, and most of the nascent RNA labelled in vivo or in vitro. Euchromatin fragments allow initiation of transcription by added purified rat liver form-B RNA polymerase and contain temperature-dependent rifampicin-resistant initiation sites for the form-B enzyme. These findings indicate that transcription of the euchromatin regions of interphase chromosomes is not initiated in condensed chromatin, but is initiated within the euchromatin stretches. Condensable chromatin also contains most of these activities, but is not associated with nascent RNA. PMID:4464858

  6. Anomalous density dependence of the activation gap of ν = 5/2 fractional quantum Hall state at extremely large Landau level mixing

    NASA Astrophysics Data System (ADS)

    Samkharadze, Nodar; Manfra, Michael; Pfeiffer, Loren; West, Ken; Csathy, Gabor

    2013-03-01

    We have conducted a study of the density dependence of ν = 5/2 fractional quantum Hall state (FQHS) in the regime of extremely low densities, down to n =4.9x10⌃10 cm⌃-2. In the density range accessed in our sample, the Landau level mixing parameter κ spans the so far unexplored range 2.52< κ<2.82. Here we observe an anomalous dependence of the activation gap of ν = 5/2 FQHS on the carrier density. We discuss the possible origins of this unexpected behavior. N.S. and G.C. were supported by the NSF grant DMR-0907172 and DMR-1207375. K. West and L. Pfeiffer acknowledge the support of the Princeton NSF-MRSEC and the Moore Foundation.

  7. Gas swelling and deuterium distribution in beryllium implanted with deuterium ions

    SciTech Connect

    Chernikov, V.N.; Alimov, V.Kh.; Zakharov, A.P.

    1995-09-01

    An extensive TEM study of the microstructure of Be TIP-30 irradiated with 3 and 10 keV D ions up to fluences, {Phi}, in the range from 3 x 10{sup 20} to 8 x 10{sup 21} D/m{sup 2} at temperatures T{sub irr} = 300 K, 500 K and 700 K has been carried out. Depth distributions of deuterium in the form of separate D atoms and D{sub 2} molecules have been investigated by means of SIMS and RGA methods, correspondingly. D ion irradiation is accompanied by blistering and gives rise to different kind of destructions depending mainly on the irradiation temperature. Irradiation with D ions at 300 K leads to the formation of tiny highly pressurized D{sub 2} bubbles reminiscent of He bubbles in Be. Under 3 keV D ion irradiation D{sub 2} bubbles ({bar r}{sub b} {approx} 0.7 nm) appear at a fluence as low as 3x10{sup 20} D/m{sup 2}. Irradiation at 500 K results in the development, along with relatively small facetted bubbles, of larger oblate gas-filled cavities accumulating most of injected D atoms and providing for much higher gas swelling values as compared to irradiation at 300 K. The increase of D and/or T{sub irr}, to 700 K causes the further coarsening of large cavities which are transformed into sub-surface labyrinth structures. D and He ion implantation leads to the enhanced growth of porous microcrystalline layers of c.p.h.-BeO oxide with a microstructure which differs considerably from that of oxide layers on electropolished surfaces of Be. Based on the analysis of experimental data questions of deuterium reemission, thermal desorption and trapping in Be have been discussed in detail.

  8. Controlling the Neutron Yield from a Small Dense Plasma Focus using Deuterium-Inert Gas Mixtures

    SciTech Connect

    Bures, B. L.; Krishnan, M.; Eshaq, Y.

    2009-01-21

    The dense plasma focus (DPF) is a well known source of neutrons when operating with deuterium. The DPF is demonstrated to scale from 10{sup 4} n/pulse at 40 kA to >10{sup 12} n/pulse at 2 MA by non-linear current scaling as described in [1], which is itself based on the simple yet elegant model developed by Lee [2]. In addition to the peak current, the gas pressure controls the neutron yield. Recent published results suggest that mixing 1-5% mass fractions of Krypton increase the neutron yield per pulse by more than 10x. In this paper we present results obtained by mixing deuterium with Helium, Neon and Argon in a 500 J dense plasma focus operating at 140 kA with a 600 ns rise time. The mass density was held constant in these experiments at the optimum (pure) deuterium mass density for producing neutrons. A typical neutron yield for a pure deuterium gas charge is 2x10{sup 6}{+-}15% n/pulse. Neutron yields in excess of 10{sup 7}{+-}10% n/pulse were observed with low mass fractions of inert gas. Time integrated optical images of the pinch, soft x-ray measurements and optical emission spectroscopy where used to examine the pinch in addition to the neutron yield monitor and the fast scintillation detector. Work supported by Domestic Nuclear Detection Office under contract HSHQDC-08-C-00020.

  9. TEMPERED FRACTIONAL CALCULUS

    PubMed Central

    MEERSCHAERT, MARK M.; SABZIKAR, FARZAD; CHEN, JINGHUA

    2014-01-01

    Fractional derivatives and integrals are convolutions with a power law. Multiplying by an exponential factor leads to tempered fractional derivatives and integrals. Tempered fractional diffusion equations, where the usual second derivative in space is replaced by a tempered fractional derivative, govern the limits of random walk models with an exponentially tempered power law jump distribution. The limiting tempered stable probability densities exhibit semi-heavy tails, which are commonly observed in finance. Tempered power law waiting times lead to tempered fractional time derivatives, which have proven useful in geophysics. The tempered fractional derivative or integral of a Brownian motion, called a tempered fractional Brownian motion, can exhibit semi-long range dependence. The increments of this process, called tempered fractional Gaussian noise, provide a useful new stochastic model for wind speed data. A tempered difference forms the basis for numerical methods to solve tempered fractional diffusion equations, and it also provides a useful new correlation model in time series. PMID:26085690

  10. Determination of degradation rates of organic substances in the unsaturated soil zone depending on the grain size fractions of various soil types

    NASA Astrophysics Data System (ADS)

    Fichtner, Thomas; Stefan, Catalin; Goersmeyer, Nora

    2015-04-01

    Rate and extent of the biological degradation of organic substances during transport through the unsaturated soil zone is decisively influenced by the chemical and physical properties of the pollutants such as water solubility, toxicity and molecular structure. Furthermore microbial degradation processes are also influenced by soil-specific properties. An important parameter is the soil grain size distribution on which the pore volume and the pore size depends. Changes lead to changes in air and water circulation as well as preferred flow paths. Transport capacity of water inclusive nutrients is lower in existing bad-drainable fine pores in soils with small grain size fractions than in well-drainable coarse pores in a soil with bigger grain size fractions. Because fine pores are saturated with water for a longer time than the coarse pores and oxygen diffusion in water is ten thousand times slower than in air, oxygen is replenished much slower in soils with small grain size fractions. As a result life and growth conditions of the microorganisms are negatively affected. This leads to less biological activity, restricted degradation/mineralization of pollutants or altered microbial processes. The aim of conducted laboratory column experiments was to study the correlation between the grain size fractions respectively pore sizes, the oxygen content and the biodegradation rate of infiltrated organic substances. Therefore two columns (active + sterile control) were filled with different grain size fractions (0,063-0,125 mm, 0,2-0,63 mm and 1-2 mm) of soils. The sterile soil was inoculated with a defined amount of a special bacteria culture (sphingobium yanoikuae). A solution with organic substances glucose, oxalic acid, sinaphylic alcohol and nutrients was infiltrated from the top in intervals. The degradation of organic substances was controlled by the measurement of dissolved organic carbon in the in- and outflow of the column. The control of different pore volumes